Arena Pharmaceuticals
Annual Report 2017

Plain-text annual report

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 FORM 10-K ☒☒ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934For the fiscal year ended December 31, 2017or☐☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934For the transition period from to COMMISSION FILE NUMBER 000-31161 ARENA PHARMACEUTICALS, INC.(Exact name of registrant as specified in its charter) Delaware 23-2908305(State or other jurisdiction ofincorporation or organization) (I.R.S. EmployerIdentification No.) 6154 Nancy Ridge Drive, San Diego, CA 92121(Address of principal executive offices) (Zip Code)858.453.7200(Registrant’s telephone number, including area code)Securities registered pursuant to 12(b) of the Act: Title of each class Name of each exchange on which registeredCommon Stock, par value $0.0001 per share The Nasdaq Global Select MarketSecurities registered pursuant to 12(g) of the Act: None Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No ☒Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ☐ No ☒Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during thepreceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past90 days. Yes ☒ No ☐Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submittedand posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submitand post such files). Yes ☒ No ☐Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405 of this chapter) is not contained herein, and will not becontained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to thisForm 10-K. ☒Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growthcompany. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act. Large accelerated filer ☐ Accelerated filer ☒Non-accelerated filer ☐(Do not check if a smaller reporting company) Smaller reporting company ☐ Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revisedfinancial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒The aggregate market value of the voting and non-voting common equity held by non-affiliates of the registrant was approximately $536.0 million as of June 30, 2017,based on the last sale price of the registrant’s common stock as reported on the Nasdaq Global Select Market on such date. For purposes of this calculation, shares of theregistrant’s common stock held by directors and executive officers have been excluded. This number is provided only for purposes of this Annual Report on Form 10-K and doesnot represent an admission that any particular person or entity is an affiliate of the registrant.As of March 9, 2018, there were 39,401,783 shares of the registrant’s common stock outstanding.DOCUMENTS INCORPORATED BY REFERENCECertain information required by Part III of this Annual Report on Form 10-K is incorporated by reference from the Registrant’s Definitive Proxy Statement for the AnnualMeeting of Stockholders to be held in June 2018, which will be filed with the Securities and Exchange Commission on or before April 30, 2018. ARENA PHARMACEUTICALS, INC.FORM 10-K – ANNUAL REPORTFor the Fiscal Year Ended December 31, 2017Table of Contents PagePART IItem 1.Business2Item 1A.Risk Factors19Item 1B.Unresolved Staff Comments41Item 2.Properties42Item 3.Legal Proceedings42Item 4.Mine Safety Disclosures44 PART IIItem 5.Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities45Item 6.Selected Financial Data47Item 7.Management’s Discussion and Analysis of Financial Condition and Results of Operations48Item 7A.Quantitative and Qualitative Disclosures About Market Risk63Item 8.Financial Statements and Supplementary Data64Item 9.Changes in and Disagreements with Accountants on Accounting and Financial Disclosure94Item 9A.Controls and Procedures94Item 9B.Other Information97 PART IIIItem 10.Directors, Executive Officers and Corporate Governance98Item 11.Executive Compensation98Item 12.Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters98Item 13.Certain Relationships and Related Transactions, and Director Independence99Item 14.Principal Accountant Fees and Services99 PART IVItem 15.Exhibits, Financial Statement Schedules99 iINFORMATION RELATING TO FORWARD-LOOKING STATEMENTSThis Annual Report on Form 10-K, or Annual Report, includes forward-looking statements, which involve a number of risks and uncertainties. Theseforward-looking statements can generally be identified as such because the context of the statement will include words such as “may,” “will,” “intend,”“plan,” “believe,” “anticipate,” “expect,” “estimate,” “predict,” “potential,” “continue,” “likely,” or “opportunity,” the negative of these words or othersimilar words. Similarly, statements that describe our future plans, strategies, intentions, expectations, objectives, goals or prospects and other statements thatare not historical facts are also forward-looking statements. Discussions containing these forward-looking statements may be found, among other places, in“Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in this Annual Report. For such statements, weclaim the protection of the Private Securities Litigation Reform Act of 1995. Readers of this Annual Report are cautioned not to place undue reliance onthese forward-looking statements, which speak only as of the time this Annual Report was filed with the Securities and Exchange Commission, or SEC. Theseforward-looking statements are based largely on our expectations and projections about future events and future trends affecting our business and are subjectto risks and uncertainties that could cause actual results to differ materially from those anticipated in the forward-looking statements. These risks anduncertainties include, without limitation, those discussed in “Business”, “Risk Factors” and “Management’s Discussion and Analysis of Financial Conditionand Results of Operations” of this Annual Report. In addition, past financial or operating performance is not necessarily a reliable indicator of futureperformance, and you should not use our historical performance to anticipate results or future period trends. We can give no assurances that any of the eventsanticipated by the forward-looking statements will occur or, if any of them do, what impact they will have on our results of operations and financialcondition. In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are basedupon information available to us as of the date of this Annual Report, and while we believe such information forms a reasonable basis for such statements,such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, orreview of, all potentially available relevant information. These statements are inherently uncertain and you are cautioned not to unduly rely upon thesestatements. Except as required by law, we undertake no obligation to update publicly or revise our forward-looking statements to reflect events orcircumstances that arise after the filing of this Annual Report or documents incorporated by reference herein that include forward-looking statements.TRADEMARKS AND CERTAIN TERMSArena Pharmaceuticals ® and Arena ® are registered service marks of Arena. Any other brand names or trademarks appearing in this Annual Report arethe property of their respective holders.In this Annual Report, “Arena Pharmaceuticals,” “Arena,” “we,” “us” and “our” refer to Arena Pharmaceuticals, Inc., and our wholly ownedsubsidiaries on a consolidated basis, unless the context otherwise provides. “APD” is an abbreviation for Arena Pharmaceuticals Development. 1PART IItem 1. BusinessOverviewWe are a biopharmaceutical company focused on developing novel, small molecule drugs with optimized receptor pharmacology designed to deliverclinical utility across therapeutic areas. Our proprietary, internally-developed pipeline includes multiple potentially first- or best-in-class programs.Our three most advanced investigational clinical programs are: ralinepag (APD811), which we are currently preparing for a Phase 3 program forpulmonary arterial hypertension, or PAH; etrasimod (APD334), which is being studied in Phase 2 trials for immune and inflammatory conditions with aninitial focus on ulcerative colitis and hepatic conditions; and APD371 for visceral pain conditions and which is being studied in a Phase 2 trial for treatmentof pain associated with Crohn's disease, or CD.In addition, we have collaborations with the following pharmaceutical companies: Everest Medicines Limited (ralinepag and etrasimod in GreaterChina and select countries in Asia), Axovant Sciences GmbH (nelotanserin - Phase 2), Boehringer Ingelheim International GmbH (undisclosed target -preclinical), and Eisai Co., Ltd. and Eisai Inc., collectively, Eisai (BELVIQ®/BELVIQ XR® - marketed products).Our StrategyThe primary elements of our strategic focus are to: •Develop ralinepag – a next-generation, potent, highly selective oral IP receptor agonist intended for the treatment of PAH •Develop etrasimod – a modulator of the sphingosine 1-phosphate, or S1P, receptor intended for the treatment of a broad range of immune andinflammatory conditions •Develop APD371 – an agonist of the cannabinoid-2, or CB2, receptor intended for the treatment of a range of visceral pain conditions •Develop our pipeline by efficiently managing our cash and development timelines, which may include entering strategic collaborations forcertain clinical and preclinical programs •Progress additional pipeline programs over time in select therapeutic areas •Build a streamlined, high-performing and high-energy organizationArena Pharmaceuticals, Inc., incorporated in the state of Delaware in April 1997, is located in San Diego, California. Our development operations arelocated in San Diego and Zug, Switzerland. We also have manufacturing operations in Zofingen, Switzerland, which are subject to a pending sale under anasset purchase agreement described elsewhere in this Annual Report.2Pipeline of Development Programs and Commercial ProductsBelow is a summary of our internally developed, proprietary portfolio:In addition, we have several other partnered programs. We discovered and developed lorcaserin (BELVIQ and BELVIQ XR), which is currentlymarketed by Eisai or its distributors in the United States, or US, and certain other countries for weight loss. Lorcaserin is also being tested in an ongoingcardiovascular outcomes trial, or CVOT, for the reduction of major cardiovascular events and progression to type 2 diabetes. We also discovered nelotanserinwhich is partnered with Axovant Sciences and currently in Phase 2 development for various neurologic disorders. We also maintain a preclinicalcollaboration with Boehringer Ingelheim for undisclosed orphan targets in central nervous system disorders.We also own and have rights to other clinical and preclinical stage compounds that were internally discovered by us.Ralinepag ProgramRalinepag is a next, generation potent, highly selective oral IP receptor agonist intended for the treatment of pulmonary arterial hypertension (PAH).Ralinepag was designed by us to deliver intravenous prostacyclin-like potency and pharmacokinetics in an oral tablet. In non-clinical experiments, ralinepagdemonstrated potentially best-in-class activation of the IP receptor resulting in vasodilation, inhibition of smooth muscle cell proliferation and inhibition ofplatelet aggregation. Additionally, early stage studies of ralinepag pharmacokinetics in humans revealed an approximately 24-hour half-life and a low peak-to-trough ratio supporting therapeutic blood levels with once daily dosing. In September 2014, ralinepag was granted orphan drug status for the treatment of PAH by the US Food and Drug Administration, or FDA.PAH is a progressive, life-threatening disorder characterized by increased pressure in the pulmonary arteries that carry blood from the heart to thelungs. PAH occurs when the pulmonary arteries thicken or grow rigid. This makes blood flow more difficult. The heart must work harder to push bloodthrough the arteries, and the arteries are unable to carry adequate blood to the lungs. The increased pressure strains the heart, which can limit physicalactivity, result in heart failure and reduce life expectancy. PAH will continue to worsen over time, even with proper treatment. Based on data from theRegistry to EValuate Early And Long-term PAH disease management, or REVEAL, of patients in the US, there is an estimated five-year survival rate of 57%from diagnosis. The reported prevalence of PAH varies widely. One estimate is 15-50 cases/million with a higher female preponderance (approximately 3:1).More recently, the prevalence of PAH in the US among the privately insured (under age 65) and Medicare (age 65 and over) populations was estimated usingadministrative claims data in accordance with the current clinical classification of PAH. This analysis suggests PAH prevalence was 109 (71–146)cases/million among the under age 65 population, and 451 (384–519) cases/million for age 65 and over population or Medicare patients. Another estimate isthat PAH affects about 500,000 individuals worldwide. A recent report characterizes the global market sales of PAH therapies as $5.8 billion in 2015, whichare expected to increase to $6.7 billion by 2025.PAH involves several interrelated mechanisms, with prostacyclin and thromboxane A2 playing a major role in maintaining pulmonary vascular tonethrough their balanced activity. Prostacyclin, released by endothelial cells, promotes vasodilation and inhibits platelet aggregation. Prostacyclin also hasantiproliferative effects on vascular smooth muscle. Despite treatment guidelines, targeting the prostacyclin pathway has been primarily reserved for patientswith advanced disease due to limitations of currently available options including parenteral prostacyclins which are the only PAH treatment that havedemonstrated a mortality benefit. 3Ralinepag DevelopmentWe are currently preparing for a Phase 3 program for ralinepag.In 2017, we announced topline results from a 22-week, randomized, double-blind, placebo-controlled Phase 2 trial evaluating the effectiveness inreducing pulmonary vascular resistance, or PVR, improving exercise capacity, tolerability and safety of ralinepag. In this trial, 40 patients with PAH receivedralinepag and 21 received placebo. Topline results showed statistically significant improvement of both absolute and percentage change from baseline inPVR. Ralinepag also demonstrated numerical improvement in six-minute walk distance, or 6MWD, but as the study was not powered to show a difference in6MWD from placebo, this was a not a statistically-significant finding. The safety and tolerability profiles were in line with other oral prostacyclins.In 2013, we announced topline results from a multiple-dose, randomized, double-blind and placebo-controlled Phase 1 clinical trial evaluatingmultiple-ascending doses of ralinepag in healthy volunteers. In this trial, 40 healthy volunteers received ralinepag and 15 received placebo. The safetyprofile of ralinepag in this trial was characteristic of IP receptor agonists: the most frequent treatment-emergent adverse events were headache, nausea and jawpain. One serious adverse event, transient atrial fibrillation, occurred in a single subject, and the study investigator considered it to be possibly treatmentrelated. Further review revealed that the subject had multiple characteristics predisposing the patient to atrial fibrillation, including cardiac abnormalitiesprior to study start.In 2011, we announced topline results of a Phase 1 clinical trial to evaluate the safety, tolerability and pharmacokinetics of single-ascending doses ofralinepag. The randomized, double-blind and placebo-controlled trial evaluated 32 healthy volunteers in four cohorts of eight participants each, with sixrandomized to ralinepag and two to placebo. Ralinepag was rapidly absorbed and demonstrated dose-proportional pharmacokinetic exposure over the testeddose range. Consistent with the expected pharmacology of ralinepag, the most common adverse events were headache, vomiting, nausea, jaw pain andflushing.Ralinepag intellectual propertyAs of March 2, 2018, we owned issued patents covering compositions of matter for ralinepag and related compounds and methods of treatmentutilizing ralinepag and related compounds, synthetic routes, and various solid state forms of ralinepag in 61 jurisdictions, including the United States, China,Japan, Germany, France, Italy, the United Kingdom, Spain, Canada, Russia, South Korea and Australia, and we had applications pending in three otherjurisdictions, of which the ones with the largest pharmaceutical markets were Brazil and India. The patent on ralinepag issued by the US Patent andTrademark Office has serial number US 8,895,776, while the corresponding patent granted by the European Patent Office has serial number EP 2280696 B2.We also own issued patents and/or pending applications directed to synthetic processes and dosage regimens of ralinepag. The earliest priority date for thepatents on ralinepag is 2008. The terms of these patents are capable of continuing into 2029 in most jurisdictions without taking into account any patentterm adjustment or extension regimes of any country or any additional term of exclusivity we might obtain by virtue of the later filed patent applications.Etrasimod ProgramEtrasimod (APD334), is an oral, next generation, selective sphingosine 1-phosphate, or S1P, receptor modulator, discovered by Arena, designed toprovide systemic and local cell modulation by selectively targeting S1P receptor subtypes 1, 4 and 5, while avoiding subtypes 2 and 3. In early stage studies,etrasimod exhibited potentially best-in-class pharmacokinetics and pharmacodynamics with rapid onset of action and rapid recovery of T lymphocytes.Selective binding with S1P receptor subtype 1 is believed to inhibit a specific subset of activated lymphocytes from migrating to sites of inflammation. Theresult is a reduction of circulating T and B lymphocytes that leads to anti-inflammatory activity and immune surveillance is maintained. The receptor4subtypes 4 and 5 exhibit similar activity on additional proliferating immune cell types. Optimized pharmacology and pharmacokinetics may allow improvedclinical utility across a broad range of immune-inflammatory conditions.Ulcerative ColitisInflammatory bowel diseases, or IBD, like ulcerative colitis, or UC, and Crohn’s disease, or CD, are chronic inflammatory conditions of thegastrointestinal tract that affect approximately 1.6 million people in the US alone. The prevalence of UC and CD in the US are currently estimated at 914,000and 684,000 patients, respectively. The prevalence of IBD in European Union, or EU, is estimated at 2.6 million with 1.1 million persons with CD and 1.5million persons with UC. Both conditions have a significant impact on the patient’s quality of life and can in many cases be very aggressive and disabling.UC is characterized by mucosal inflammation limited to the colon which involves the rectum in about 95% of cases and may extend to involve partsor all of the large intestine. In contrast, CD is characterized by full thickness inflammation that can occur anywhere in the gastrointestinal, or GI, tract butmost typically involves the terminal ileum and colon; and causes fistulation and scarring. Symptoms for UC and CD can vary, depending on the location andseverity of inflammation, but some of the most common are diarrhea, abdominal cramps, and rectal bleeding.Important goals of therapy for UC are to induce and maintain remission while improving the patient’s quality of life. Currently available treatmentoptions have limitations in terms of long-term efficacy and side effects, have complicated administration regimens, and often fail to induce or maintainremission. Therefore, we believe a significant unmet need remains for differentiated oral agents that are efficacious for induction and maintenance therapywith a favorable side effect profile. We believe that the oral once-daily dosing, selectivity, mechanism of action, and emerging clinical profile of etrasimodmay represent a significant opportunity to provide patients with an effective treatment for UC with an improved safety and dosing profile over currenttherapies.Primary Biliary CholangitisPrimary biliary cholangitis, or PBC (previously referred to as primary biliary cirrhosis), is a chronic liver disease which is classified as a rare disease.The prevalence in the US is approximately 40 cases per 100,000 inhabitants. The incidence and prevalence of PBC in European countries are similar to thoseseen in the US.Progressive bile-duct injury from portal and periportal inflammation could result in progressive fibrosis, cholangitis and eventually cirrhosis.Evidence to date suggests that immunological and genetic factors might cause the disease. Current treatment attempts to slow the progression rate of thedisease and to alleviate the symptoms. Currently liver transplantation appears to be the only life-saving procedure for PBC patients.Inflammation, the underlying cause of PBC, is believed to be T lymphocyte mediated. In research models with etrasimod, we have demonstratedmodulation of the specific subtypes of T lymphocytes believed to be implicated in PBC.Pyoderma GangrenosumPyoderma gangrenosum, or PG, is a rare inflammatory skin disease characterized by painful recurrent ulcerations. Lesions may occur either in theabsence of any apparent underlying disorder or in association with other diseases, such as UC, CD, and other conditions. The clinical course can be mild ormalignant, and chronic or relapsing.The etiology of PG has not yet been clearly determined, although it is suspected to be an autoimmune disease caused by dysregulation of the immunesystem. Approximately 50% of cases of PG are associated with other disorders, especially UC or CD.Based upon the US Department of Health and Human Services' National Institutes of Health's Office of Rare Disease Research, the incidence of PGeach year in the US has been estimated to be 1 person per 100,000 people.Treatment is challenging, and the prognosis of PG remains unpredictable. Current treatments involve wound care and the use of anti-inflammatoryagents, including antibiotics, corticosteroids, immune-suppressants and biologics, and attempts to target a broad spectrum of immunologic mediators andinflammatory cells, including T lymphocytes shown to be involved in PG. We believe reduction of lymphocytes by S1P receptor modulators such asetrasimod may represent a novel therapeutic approach in PG.5Etrasimod DevelopmentUlcerative ColitisWe are conducting a dose finding 12-week randomized, double-blind, placebo-controlled multinational Phase 2 clinical trial of etrasimod in moderateto severe UC. The aim of the trial includes investigating a clear dose response and establishing a clinically meaningful signal for the active arm(s) fromplacebo. The trial is expected to evaluate the effects of etrasimod at 1mg and 2mg versus placebo on multiple efficacy measures including a three-componentpartial Mayo Clinic Score, clinical remission, clinical response, and endoscopic improvement in up to 160 patients. Patients from this study have thepossibility to continue after the initial 12-week study in an open-label extension study for up to 46 weeks with the focus on safety and maintenance oftherapeutic effect.Primary Biliary CholangitisWe are conducting a 24-week open-label multinational Phase 2 trial of etrasimod in PBC. The aim of the study is to evaluate the safety andtolerability of etrasimod in this patient population as well as evaluate the effect of etrasimod on alkaline phosphatase, a key diagnostic marker of PBC, aswell as other laboratory parameters.Pyoderma GangrenosumWe are conducting a Phase 2, proof of concept, open-label study to evaluate the efficacy and safety of etrasimod in patients with PG. The objective isto evaluate the efficacy, safety and tolerability of etrasimod in patients with PG over a 12-week treatment period. The study includes patients with diagnosedPG independent of IBD as a background disease.Dermatologic Extraintestinal Manifestations of IBDIn March 2017, we initiated a Phase 2, proof of concept, open-label study evaluating the efficacy and safety of etrasimod in IBD patients with activedermatologic extraintestinal manifestations, or EIM. In November 2017, we announced that we decided to conclude the study since the UC study alsoincludes patients with dermatological manifestations. We intend to assess the impact of etrasimod on EIMs of IBD in a combined data set from the two trials.Prior DevelopmentIn January 2015, we announced top-line results from a Phase 1b multiple-ascending dose clinical trial for etrasimod. In the trial, etrasimoddemonstrated a dose-dependent effect on lymphocyte count lowering in blood, with mean decreases from baseline of up to 69%. Lymphocyte counts, onaverage, recovered to baseline within one week of conclusion of dosing. There was a modest impact on heart rate, but none of the changes were classified bythe investigator as clinically significant. There were also no findings with respect to pulmonary function or liver enzyme tests that were classified by theinvestigator as clinically significant. The most common treatment-emergent adverse events were mild or moderate contact dermatitis, headache, constipationand diarrhea, with none being clearly drug related. There were no discontinuations for adverse events, and no serious adverse events were observed.The randomized, double-blind, placebo-controlled Phase 1b clinical trial evaluated the safety, tolerability, pharmacodynamics and pharmacokineticsof multiple-ascending doses of etrasimod. In five different dosing cohorts, 50 healthy volunteers received etrasimod and 10 healthy volunteers receivedplacebo for 21 days.Prior to commencing the Phase 1b multiple-ascending dose clinical trial for etrasimod, we completed a Phase 1 single-ascending dose clinical trial ofthe compound. This randomized, double-blind and placebo-controlled trial evaluated the safety, tolerability and pharmacokinetics of single-ascending dosesof etrasimod in 40 healthy adult volunteers. In the trial, etrasimod demonstrated favorable pharmacokinetic and pharmacodynamic effects, a dose-responsivereduction in blood lymphocyte count and a slowing of heart rate that appears comparable to other S1P receptor modulators. The terminal half-life wasapproximately 35 hours.Etrasimod intellectual propertyAs of March 2, 2018, we owned issued patents that cover compositions of matter for etrasimod and related compounds, methods of treatment utilizingetrasimod and related compounds, and various salts of etrasimod and crystalline forms thereof in 61 jurisdictions, including the United States, China, Japan,Germany, France, Italy, the United Kingdom, Spain, Canada, India, Russia, South Korea and Australia, and had applications pending in one otherjurisdiction (Brazil). The patents on etrasimod issued by the US Patent and Trademark Office have serial numbers US 8,580,841 and US 9,126,932, while thecorresponding patent granted by the European Patent Office has serial number EP 2326621 B2. We also own issued patents and/or pending applicationsdirected to solid-state forms of etrasimod, dosage regimens for etrasimod and synthetic routes and intermediates useful in the manufacturing of etrasimod. Theearliest priority date for the patents on etrasimod is 2008. The terms of these patents are capable of continuing into62029 in most jurisdictions without taking into account any patent term adjustment or extension regimes of any country or any additional term of exclusivitywe might obtain by virtue of the later filed patent applications.APD371 Program APD371, an orally available, potent, peripherally restricted, highly selective, full agonist of the CB2 receptor, is an internally discoveredinvestigational drug candidate we are exploring for the treatment of visceral pain, specifically pain associated with CD.Visceral pain is defined as pain that originates within muscle, pleura, connective tissue, nervous system or solid organs within the abdomen orperitoneum. It is distinct from somatic or neuropathic pain, and is perceived as stretching, pulling and distention, rather than by cutting, crushing, or burningmore commonly associated with neuropathic pain. Visceral pain is one of the most common types of pain. For example, abdominal pain affectsapproximately 20% of the general population. Visceral pain may be caused by a diverse set of organic causes, such as inflammation (e.g., IBD (including CDand UC), pancreatitis, prostatitis, and vaginitis), obstruction (e.g., bowel obstruction, and nephrolithiasis), ischemia, and malignancy, among others. Visceralpain may also be caused by functional disorders such as interstitial cystitis, dyspepsia, irritable bowel syndrome (IBS), and vulvodynia.A specific type of visceral pain, pain associated with CD, affects a significant portion of patients with underlying CD. CD affects approximately684,000 patients in the US, and 20% of patients suffer from residual pain even while in remission.Common treatments for visceral pain range from non-invasive, conservative approaches (e.g., physical therapy or acupuncture), to pharmacologic(e.g., tricyclic antidepressants acting as neurotransmitter reuptake inhibitors), and invasive interventions (e.g., bowel resection). Potent analgesics, such asopioids, can adversely affect GI function. Other commonly prescribed analgesics are often not potent enough and may lead to other GI side effects such asbleeding. Apart from linaclotide and lubiprostone, prescribed for IBS, no visceral-specific analgesics are available. Approximately one in eight CD patients ischronically treated with opioids.The CB2 receptor is expressed in the GI nervous system, and in many tissues and organs of the abdomen. CB2 receptors are found peripherally onimmune cells but also on microglia, terminal neurons, dorsal root ganglia, and on visceral sensory neurons. We believe selectively targeting the CB2 receptormay provide therapeutic benefit for visceral pain without the potential for dependence, abuse, and GI and cardiovascular side effects associated with opiatesor nonsteroidal anti-inflammatory drugs, or NSAIDs, which are among the most common pain relievers. In addition to analgesic effects, APD371 may haveanti-inflammatory properties.APD371 is designed to be a peripherally restricted and selective CB2 receptor agonist, and is intended to provide pain relief without the unwantedside effects associated with CB1 receptor activation.APD371 DevelopmentWe are conducting a Phase 2a clinical trial to evaluate APD371 in pain associated with CD. This exploratory study is an open‑label investigation toevaluate safety and tolerability of APD371 in this patient population and to gain initial insights into its efficacy via a pain visual analog scale, or VAS.In April 2016, we announced favorable results from a Phase 1b multiple-ascending dose clinical trial of APD371. This randomized, double-blind,placebo-controlled Phase 1b clinical trial enrolled 36 healthy adults to evaluate the safety, tolerability and pharmacokinetics of multiple-ascending doses ofAPD371. Cohorts of 12 subjects (9 active, 3 placebo) were administered doses of 50 mg, 100 mg, or 200 mg of APD371 or placebo three times daily for 10days and, in connection with the pharmacokinetic evaluation, one time on the 11th day. The most common adverse events were headache and nausea. Alladverse events were classified as mild, and there were no serious adverse events reported. There was one discontinuation in the high-dose group due to anadverse event of mild thirst and somnolence. Reductions in blood pressure and heart rate were observed, but none were symptomatic or resulted in an adverseevent. Drug levels at all doses tested in the trial, including the lowest dose, were well above those believed to be needed to stimulate the CB2 receptor.In April 2015, we announced favorable top-line results from a Phase 1 single-ascending dose clinical trial of APD371. The randomized, double-blindand placebo-controlled trial enrolled 56 healthy adults to evaluate the safety, tolerability and pharmacokinetics of single-ascending doses of APD371. Dose-responsive exposure was observed over the explored dose range of 10-400 mg with good tolerability at all doses administered.APD371 intellectual propertyAs of March 2, 2018, we owned issued patents covering compositions of matter for APD371 and related compounds in 21 jurisdictions, including theUnited States, China, Japan, Canada, Russia, South Korea and Australia, and we had applications pending in 10 other jurisdictions, of which the ones withthe largest pharmaceutical markets were Europe, Venezuela, Brazil and India. The7patent on APD371 issued by the US Patent and Trademark Office has serial number US 8,778,950. We also own issued patents and/or pending applicationsdirected to various solid-state forms of APD371. The earliest priority date for the patents on APD371 is 2009. The terms of these patents are capable ofcontinuing into 2030 in most jurisdictions without taking into account any patent term adjustment or extension regimes of any country or any additionalterm of exclusivity we might obtain by virtue of the later filed patent applications.Additional Internal Preclinical and Clinical ProgramsWe have additional clinical and preclinical assets, including temanogrel and APD597, which we are evaluating for future development. We are alsoevaluating additional delivery forms of the products in our pipeline to extend clinical utility or improve the product profile.CollaborationsIn addition to our primary focus on internally developing our clinical pipeline, we have entered into strategic collaborations with pharmaceuticalcompanies, including Everest Medicines Limited, or Everest, Axovant Sciences GmbH, or Axovant, Boehringer Ingelheim International GmbH, orBoehringer Ingelheim, Beacon Discovery, Inc., or Beacon, and Eisai.Everest CollaborationIn December 2017, we entered into a Collaboration and License Agreement, or the Everest Agreement, with Everest.Under the Everest Agreement, we granted Everest an exclusive, royalty-bearing license to develop, manufacture and commercialize two of our productcandidates, ralinepag (in any formulation) and etrasimod (in oral formulations only), in China, Taiwan, Hong Kong, Macau and South Korea, or the EverestTerritories.Everest will be responsible for all development, manufacture and commercialization of the licensed products in the Everest Territories, and mayparticipate in the portion of our global clinical trials that is conducted in the Everest Territories.In addition to an upfront payment of $12.0 million, we are eligible to receive development, regulatory and commercial milestone payments fromEverest of up to $212.0 million for both licensed products, as well as tiered royalties on net sales ranging from the high single digits to low double digits.Following an initial royalty term, we are eligible to receive a lower trademark royalty if Everest continues to use our licensed product-related trademarks.Nelotanserin CollaborationNelotanserin, an orally available potent and selective inverse agonist of the 5-HT2A receptor, is an investigational drug candidate that has beenimplicated in the pathophysiology underlying psychosis. Nelotanserin was discovered by Arena, and we previously completed Phase 1 trials in healthyvolunteers and Phase 2 trials in subjects with insomnia before development was discontinued for that indication.Development, Marketing, and Supply AgreementIn May 2015, we entered into a Development, Marketing and Supply Agreement with Roivant Sciences Ltd., or Roivant, for nelotanserin. Roivantsubsequently assigned all of its rights to develop and commercialize nelotanserin to its subsidiary, Axovant. Under our collaboration, Axovant has exclusiveworldwide rights to develop and commercialize nelotanserin, and we are required to manufacture or have manufactured clinical supply and commercialproduct to sell to Axovant. We received a $4.0 million upfront payment and are eligible to receive $41.5 million in regulatory and development milestonepayments. We are also eligible to receive 15% of net sales of nelotanserin in exchange for the manufacture and supply of finished commercial drug product,and up to a total of $60.0 million in one-time purchase price adjustment payments tied to certain commercial sales milestones.Axovant has agreed to indemnify us for losses resulting from certain third-party claims, including for (i) Axovant’s negligence, willful misconduct orviolation of law, (ii) Axovant’s breach of the development, marketing and supply agreement or related agreements, (iii) any product liability claim, (iv)certain uses or misuses of nelotanserin, (v) certain infringement of intellectual property rights, and (vi) product manufactured according to the productwarranty. We have agreed to indemnify Axovant for losses resulting from certain third-party claims, including for our negligence, willful misconduct orviolation of law, and for losses resulting from our breach of the agreement or related agreements.8Axovant has the right to terminate the agreement on a compound-by-compound basis or in its entirety upon 90 days’ prior written notice to us. Wehave the right to terminate the agreement upon certain intellectual property concerns. Either party has the right to terminate the agreement early in certaincircumstances, including if the other party is in material breach.Nelotanserin developmentUnder our Development, Marketing and Supply Agreement, Axovant will be responsible for funding the development and commercialization ofnelotanserin. In January 2018, Axovant reported results for a pilot Phase 2 Visual Hallucination study of nelotanserin in patients with Lewy body dementia.Additionally, Axovant is studying nelotanserin in patients with dementia with Lewy Bodies or Parkinson’s disease dementia who are experiencing rapid eyemovement, or REM, sleep behavior disorder. Axovant will determine the overall development strategy for nelotanserin once its ongoing clinical, regulatoryand commercial review is completed.Orphan GPCR CollaborationIn December 2015, we entered into an exclusive agreement with Boehringer Ingelheim, to conduct joint research to identify drug candidates targetinga GPCR that belongs to a group of orphan central nervous system, or CNS, receptors. An “orphan receptor” is structurally related to a family of proteins thatare known to act as functional cell-surface receptors but whose ligand has not yet been identified.We contracted with Beacon to perform our research obligations under the Boehringer Ingelheim collaboration. In exchange, we agreed to share limitednear term milestones with Beacon as well as the full-time equivalent funding paid to us by Boehringer Ingelheim. We have retained the longer-term successmilestones and all royalties.Beacon Discovery AgreementsIn September 2016, we entered into a series of agreements with Beacon. Beacon was founded and is owned by several of our former employees.We entered into a License and Collaboration Agreement with Beacon, pursuant to which we granted Beacon a non-exclusive, non-assignable and non-sublicensable license to certain database information relating to compounds, receptors and pharmacology, and transferred certain equipment toBeacon. Beacon will seek to engage global partners to facilitate discovery and development. Beacon has agreed to assign to us any intellectual propertyrelating to our existing research and development programs developed in the course of performing research for us, and grant us a non-exclusive license to anyintellectual property developed outside the course of performing work for us that is reasonably necessary or useful for developing or commercializing theproducts under our research and development programs. We are also entitled to rights of negotiation and rights of first refusal to potentially obtain licenses tocertain compounds discovered and developed by Beacon. In addition, we are entitled to receive (i) a percentage of any revenue received by Beacon on orafter the second anniversary of the effective date of the agreement from any third party pursuant to a third-party license, including upfront payments,milestone payments and royalties; (ii) single-digit royalties on the aggregate net sales of any related products sold by Beacon and its affiliates; and (iii) in theevent that Beacon is sold, a percentage of the consideration for such sale transaction.We also entered a Master Services Agreement with Beacon, pursuant to which Beacon performs certain research services for us relating to ourproprietary pipeline, as well as a services agreement to support our research obligations under our collaboration with Boehringer Ingelheim.BELVIQ (lorcaserin) CollaborationLorcaserin is approved for marketing in the United States, South Korea, Brazil, Mexico, Israel, and Taiwan for the indication of weight management,and is being commercialized by Eisai or its distributors in the United States, South Korea, Israel, and Taiwan. BELVIQ was made available by prescription inthe United States in June 2013 and in South Korea in February 2015. Eisai also has launched of a once-daily formulation of lorcaserin in the United States,which is marketed under the brand name BELVIQ XR. Lorcaserin has not yet been launched in Brazil or Mexico. In December 2016, we entered into aTransaction Agreement and a Supply Agreement with Eisai, which replaced our prior marketing and supply agreement with Eisai for lorcaserin.Transaction AgreementPursuant to the Transaction Agreement, we granted Eisai an exclusive, royalty-bearing license, or transferred intellectual property, to develop,manufacture and commercialize lorcaserin in all countries and territories of the world. In consideration for the9rights granted to Eisai under the Transaction Agreement, Eisai has agreed to make tiered royalty payments to us on the net sales of lorcaserin. The royaltyrates range from 9.5% on annual global net sales less than or equal to $175.0 million, 13.5% on annual global net sales greater than $175.0 million but lessthan or equal to $500.0 million and 18.5% on annual global net sales greater than $500.0 million.We are eligible to receive a milestone payment of $25.0 million upon the achievement of global net sales of lorcaserin for a calendar year firstexceeding $250.0 million.Eisai is solely responsible for all costs and expenses in connection with the development of lorcaserin, and our wholly owned subsidiary, ArenaPharmaceuticals GmbH, or Arena GmbH, was relieved of its obligation under the former marketing and supply agreement to pay for its share of developmentcosts for lorcaserin. Eisai has the exclusive right and responsibility to plan and implement all research and development of lorcaserin at its own cost andexpense, including conducting all regulatory activities and all clinical and development activities. Additionally, Eisai has agreed to (i) conduct all studiesrequired by the FDA as a condition of obtaining and maintaining regulatory approval of lorcaserin in the United States (otherwise known as thecardiovascular outcomes trial, or CVOT), (ii) continue the current study assessing whether lorcaserin reduces the incidence of major cardiovascular events,(iii) continue the current study assessing whether lorcaserin reduces the incidence of conversion to Type 2 diabetes mellitus, and (iv) use commerciallyreasonable efforts to develop and seek regulatory approval of lorcaserin in each of China, Japan and the European Union.Eisai is solely responsible, and has the exclusive rights, for commercializing lorcaserin and is responsible for manufacturing lorcaserin, except for anymanufacturing to be conducted by Arena GmbH under the Supply Agreement. Eisai is responsible for using commercially reasonable efforts to commercializelorcaserin products in the United States, the European Union, China and Japan (collectively, the Major Markets) after regulatory approval in the applicablemarket.We and Eisai will each bear 50% of losses arising from any alleged defective manufacturing of lorcaserin by Arena GmbH under the SupplyAgreement, and Eisai will be solely responsible for any expenses and losses associated with other product liability claims.The Transaction Agreement will remain in effect until terminated by us or Eisai with respect to all countries in the world. We may terminate theTransaction Agreement with respect to a Major Market if Eisai permanently ceases development and commercialization of lorcaserin products in such MajorMarket, or in its entirety if Eisai permanently ceases development and commercialization of lorcaserin products in the world. We may also terminate theTransaction Agreement if Eisai challenges any patent controlled by us related to lorcaserin as of the effective date of the Transaction Agreement, or LicensedPatents, if Eisai is debarred under the US Federal Food, Drug, and Cosmetic Act, or if Eisai is in material breach of the standstill provisions. Eisai mayterminate the Transaction Agreement if as a result of its change of control, it would be in breach of certain competition restrictions.In the event the Transaction Agreement is terminated by us due to Eisai’s failure to develop and commercialize lorcaserin products, Eisai’schallenging of any of the Licensed Patents or Eisai’s debarment or material breach of the standstill provisions, or by Eisai after a change of control that wouldresult in Eisai being in breach of certain competition restrictions, Eisai will grant Arena an exclusive, royalty-free license to certain patent rights and know-how necessary or useful for the development and commercialization of lorcaserin products, re-assign the assets purchased by Eisai under the TransactionAgreement and Supply Agreement, and provide certain other transition assistance.Supply AgreementUnder the Supply Agreement, Arena GmbH agreed to manufacture and supply, and Eisai agreed to purchase, all of Eisai’s requirements (or specifiedminimum quantities if such quantities are greater than Eisai’s requirements), subject to certain exceptions, for BELVIQ and BELVIQ XR for the developmentand commercial use of such products in all countries and territories of the world for an initial two-year period, which initial period may be extended by Eisaifor an additional payment. Eisai will pay Arena GmbH agreed upon prices to deliver finished drug product during this time. Additionally, Eisai agreed to payup to CHF 13.0 million in payments to Arena GmbH to support the maintenance of Arena GmbH’s manufacturing facility in Switzerland during the initialtwo-year supply period, and an additional amount during the extension period, if any.Pursuant to the Supply Agreement, Arena GmbH agreed to transfer to Eisai all know-how and materials necessary for Eisai to manufacture BELVIQ atthe facility in accordance with Arena GmbH’s manufacturing processes used at the effective date of the Supply Agreement or 24 months prior. Arena GmbHalso assigned its agreements with distributors in South Korea, Taiwan and Israel to Eisai, and Eisai agreed to assume responsibilities under such agreements.10On the effective date of the Supply Agreement, Eisai purchased Arena GmbH’s entire inventory of the precursor materials for manufacturing lorcaserinthen in Arena GmbH’s possession. In exchange for these materials Eisai made a one-time payment to Arena GmbH of $10.0 million.Absent early termination, the Supply Agreement will remain in effect until (i) the last day of the initial two-year supply period, or the last day of thesix-month extension period (if any), or up to two weeks thereafter if so requested by Eisai, or (ii) in the event of an acquisition of Arena or Arena GmbH by athird party, or of an assignment of the Supply Agreement by Arena GmbH to a third party, five years after the effective date of the Supply Agreement. Afterthe initial two-year period of the Supply Agreement, either Arena GmbH or Eisai may terminate the Supply Agreement upon the other party’s material breachthat remains uncured 60 days after receiving written notice thereof. The Supply Agreement will also terminate automatically upon termination of theTransaction Agreement.On March 9, 2018, we entered into an Asset Purchase Agreement, or Sale Agreement, with Siegfried Pharma AG and Siegfried AG (collectively andindividually, Siegfried). Under the Sale Agreement, we agreed to sell and assign to Siegfried, and Siegfried agreed to purchase and assume from Arena GmbH,certain drug product finishing facility assets and know-how, including fixtures, equipment, other personal property and real estate assets located in Zofingen,Switzerland, related contracts and certain related liabilities after the closing as well as to the transfer of all of Arena GmbH’s approximately 50 currentemployees, or collectively, Manufacturing Operations. We refer to this transaction as Siegfried Transaction. Under the Sale Agreement, at the closing, ArenaGmbH will assign to Siegfried Pharma the Supply Agreement.Intellectual PropertyOur success depends in large part on our ability to protect our compounds and information, and to operate without infringing the proprietary rights ofthird parties. We rely on a combination of patent, trade secret, copyright, and trademark laws, as well as confidentiality, licensing and other agreements, toestablish and protect our proprietary rights. We seek patent protection for our key inventions, including drug candidates we identify, routes for chemicalsynthesis, pharmaceutical formulations and methods of treatment.There is no assurance that any of our patent applications will issue, or that any of the patents will be enforceable or will cover a drug or othercommercially significant product or method. In addition, we regularly review our patent portfolio to identify patents and patent applications for potentialabandonment that we deem to have relatively low value to our ongoing business operations. There is also no assurance that we will correctly identify whichof our patents and patent applications should be maintained and which should be abandoned. The term of most of our other current patents commenced, andmost of our future patents, if any, will commence, on the date of issuance and terminate 20 years from the earliest effective filing date of the patentapplication. Because any marketing and regulatory approval for a drug often occurs several years after the related patent application is filed, the resultingmarket exclusivity afforded by any patent on our drug candidates will likely be substantially less than 20 years.In the United States, patent term adjustment is available for certain delays in patent office proceedings. In addition, under the Drug Price Competitionand Patent Term Restoration Act of 1984, or the Hatch-Waxman Act, the term of a patent that covers an FDA-approved drug may be eligible for patent termextension, or PTE. PTE permits patent term restoration of a US patent as compensation for the patent term lost during product development and the FDAregulatory review process. The Hatch-Waxman Act permits a PTE of up to five years beyond the expiration of the patent. This period is generally one-half thetime between the effective date of an Investigational New Drug, or IND (falling after issuance of the patent), and the submission date of an NDA, plus the timebetween the submission date of an NDA and the approval of that application, provided the sponsor acted with diligence. The Improving RegulatoryTransparency for New Medical Therapies Act was signed into law in 2015 to prevent the loss of PTE (and market exclusivity) for drugs for which the FDArecommends scheduling under the Controlled Substances Act. A PTE cannot extend the remaining term of a patent beyond a total of 14 years from the date ofproduct approval and only one patent applicable to an approved drug may be extended. The application for PTE is subject to approval by the PTO inconjunction with the FDA.Outside of the United States, similar provisions may be available in the European Union, Japan, South Korea and some other jurisdictions to extendthe term of a patent that covers an approved drug. The length of any such extension would vary by country. Our European patents may be eligible forsupplemental protection certificates of up to five years in one or more countries.Due to the specific requirements for obtaining these extensions, there is no assurance that our patents will be afforded extensions even if we encountersignificant delays in patent office proceedings or marketing and regulatory approval.In addition to patent protection, we rely on trade secrets, proprietary know-how and continuing technological advances to develop and maintain ourcompetitive position. To maintain the confidentiality of our trade secrets and proprietary information, all of our employees are required to enter into andadhere to an employee confidentiality and invention assignment agreement, and invention disclosure procedures as a condition of employment.Additionally, our employee confidentiality and invention assignment agreements11require that our employees not bring to us, or use without proper authorization, any third-party proprietary technology. We also generally require ourconsultants and collaborators that have access to proprietary property and information to execute confidentiality and invention rights agreements in ourfavor before beginning their relationship with us. While such arrangements are intended to enable us to better control the use and disclosure of ourproprietary property and provide for our ownership of proprietary technology developed on our behalf, they may not provide us with meaningful protectionfor such property and technology in the event of unauthorized use or disclosure.CompetitionThe biotechnology and pharmaceutical industries are highly competitive and are subject to rapid and significant change. We face significantcompetition from many organizations with drugs or drug candidates that do or may compete drug candidates we are developing. We may not be able tocompete successfully against these organizations, which include many large, well-financed and experienced pharmaceutical and biotechnology companies,as well as academic and research institutions and government agencies. Developments by others may render our drug candidates obsolete or noncompetitive,and we or our collaborators may not be successful in developing either first or best in class drugs.Many of our existing and potential competitors have substantially greater drug development capabilities and financial, scientific and marketingresources than we do. Additional consolidation in the pharmaceutical industry may result in even more resources being concentrated with our competitors. Asa result, our competitors may be able to devote greater resources than we can to the research, development, marketing and promotion of therapeutic productsor drug discovery techniques, or to adapt more readily to technological advances than we can. Accordingly, our competitors may succeed in obtaining patentprotection, receiving regulatory approval or commercializing drugs before we do.We expect to encounter significant competition in the therapeutic areas targeted by our principal drug candidates. Companies that complete clinicaltrials, obtain regulatory approvals and commence commercial sales of their drug candidates before us may achieve a significant competitive advantage.Furthermore, we may be competing against companies with substantially greater manufacturing, marketing, distribution and selling capabilities, and anydrug candidate that we successfully develop may compete with existing therapies that have longer histories of safe and effective use.We may rely on collaborators for support of development programs and for the manufacturing and marketing of drug candidates. Such collaboratorsmay be conducting multiple drug development efforts within the same disease areas that are the subject of their agreements with us, which may negativelyimpact the development of drugs that are subject to our agreements. In addition, we face and will continue to face intense competition from other companiesfor such collaboration arrangements, and technological and other developments by others may make it more difficult for us to establish such relationships.Government RegulationWe and our collaborators are subject to significant governmental regulation. The FDA and comparable regulatory agencies in state and localjurisdictions and in foreign countries impose substantial requirements upon the preclinical and clinical development, pre-market approval, manufacture,import, export, marketing and distribution of pharmaceutical products. These agencies and other regulatory agencies regulate research and developmentactivities and the testing, approval, manufacture, quality control, safety, effectiveness, labeling, storage, tracking, recordkeeping, advertising, pricing andpromotion of drug candidates and commercialized drugs. Failure to comply with applicable FDA or other regulatory requirements may result in inspectionalnotices of violation, warning letters, civil or criminal penalties, suspension or delays in clinical development, recall or seizure of products, partial or totalsuspension of production, withdrawal of a product from the market or other negative consequences.In the United StatesIn the United States, the FDA regulates drug products under the Federal Food, Drug, and Cosmetic Act, or FD&C Act, and its implementingregulations. The process required by the FDA before drug candidates may be marketed in the United States generally involves the following: •completion of extensive preclinical laboratory tests and preclinical animal studies, many of which are required to be performed in accordancewith the FDA’s Good Laboratory Practice, or GLP, regulations; •submission to the FDA of an IND, which must become effective before human clinical trials may begin and be updated annually; •performance of adequate and well-controlled human clinical trials to establish the safety and efficacy of the drug candidate for each proposedindication;12 •submission to the FDA of a New Drug Application, or NDA, after completion of adequate and well-controlled human clinical trials, generallyaccompanied by payment of a substantial user fee to the FDA; •a determination by the FDA within 60 days of its receipt of the NDA to file the NDA for review; •satisfactory completion of an FDA pre-approval inspection of the manufacturing facilities at which the active pharmaceutical ingredient andfinished drug product are produced and tested to assess compliance with Current Good Manufacturing Practices, or cGMP, regulations; •FDA review and approval of the NDA prior to any commercial marketing or sale of the drug in the United States; and •Prior to commercialization, centrally acting drugs may be subject to review and potential scheduling by the DEA.The development and approval process requires substantial expertise, time, effort and financial resources, and we cannot be certain that any approvalsfor our drug candidates will be granted on a timely basis, if at all.The results of preclinical tests (which include laboratory evaluation as well as GLP studies to evaluate toxicity in animals) for a particular drugcandidate, together with related manufacturing information and analytical data, are submitted as part of an IND to the FDA. The IND automatically becomeseffective 30 days after receipt by the FDA. During the 30-day time period the FDA may require additional information. The FDA may institute a clinical holdat the 30-day time period if any questions are not fully addressed or because of other concerns about the conduct of the clinical trial, including concerns thathuman research subjects will be exposed to unreasonable health risks. In such a case, the IND sponsor and the FDA must resolve any outstanding concernsbefore the clinical trial can begin. The FDA may place an IND on partial or full clinical hold at any time during a product candidate’s development. Aseparate submission to an existing IND must also be made for each successive clinical trial conducted during product development. Further, an independentinstitutional review board, or IRB, for each medical center proposing to conduct the clinical trial must review and approve the plan for any clinical trialbefore it commences at that center and it must monitor the study until completed. The FDA, the IRB or the sponsor may suspend a clinical trial at any time onvarious grounds, including a finding that the subjects or patients are being exposed to an unacceptable health risk. Clinical testing also must satisfyextensive Good Clinical Practice, or GCP, regulations and regulations for informed consent and privacy of individually identifiable information.Clinical trials. For purposes of NDA submission and approval, clinical trials are typically conducted in the following sequential phases, which mayoverlap: •Phase 1 clinical trials. Studies are initially conducted in a limited population to test the drug candidate for safety, dose tolerance, absorption,metabolism, distribution and excretion, typically in healthy volunteers, but in some cases in patients. •Phase 2 clinical trials. Studies are generally conducted in a limited patient population to identify possible adverse effects and safety risks,explore the initial efficacy of the product for specific targeted indications and to determine dose range or pharmacodynamics. Multiple Phase 2clinical trials may be conducted by the sponsor to obtain information prior to beginning larger and more expensive Phase 3 clinical trials. •Phase 3 clinical trials. These are commonly referred to as pivotal studies or adequate and well-controlled studies. When Phase 2 evaluationsdemonstrate that a dose range of the product is effective and has an acceptable safety profile, Phase 3 clinical trials are undertaken in largepatient populations to further evaluate dosage, provide substantial evidence of clinical efficacy and further test for safety in an expanded anddiverse patient population at multiple, geographically dispersed clinical trial centers. •Phase 4 clinical trials. The FDA may approve an NDA for a drug candidate, but require that the sponsor conduct additional clinical trials tofurther assess the drug after NDA approval under a post-approval commitment. In addition, a sponsor may decide to conduct additional clinicaltrials after the FDA has approved an NDA. Post-approval trials are typically referred to as Phase 4 clinical trials.New drug applications. The results of drug development, preclinical studies and clinical trials are submitted to the FDA as part of an NDA. NDAs alsomust contain extensive chemistry, manufacturing and control, or CMC, information. An NDA is usually accompanied by a significant user fee. The FDAreviews all NDAs submitted to ensure that they are sufficiently complete for substantive review before it accepts them for filing, which occurs, if at all, 60days after submission by the NDA sponsor. Once the submission has been accepted for filing, the FDA’s goal is to review applications within 10 months fromits acceptance of the filing or, if the application relates to an unmet medical need in a serious or life-threatening indication, six months from its acceptance ofthe filing. The review process can be significantly extended by FDA requests for additional information or clarification. The FDA may refer the application toan advisory committee for review, evaluation and recommendation as to whether the application should be approved. The FDA is not bound by therecommendation of an advisory committee. The FDA may deny approval of an NDA by issuing a Complete Response Letter, or CRL, if the applicableregulatory criteria are not satisfied. A CRL may require additional13clinical data and/or an additional pivotal Phase 3 clinical trial(s), and/or other significant, expensive and time-consuming requirements related to clinicaltrials, preclinical studies or manufacturing. Data are not always conclusive and the FDA may interpret data differently than we or our collaborators interpretdata. Approval may occur with Risk Evaluation and Mitigation Strategies, or REMS, that may limit the labeling, distribution or promotion of a drug product.Once issued, the FDA may withdraw product approval if ongoing regulatory requirements are not met or if safety problems occur after the product reaches themarket. In addition, the FDA may require testing, including Phase 4 clinical trials, and surveillance programs to monitor the safety effects of approvedproducts which have been commercialized, and the FDA has the power to prevent or limit further marketing of a product based on the results of thesepostmarketing programs or other information.Other US regulatory requirements. Products manufactured or distributed pursuant to FDA approvals are subject to continuing regulation by theFDA, including recordkeeping, annual product quality review and reporting requirements. Adverse event experience with the product must be reported to theFDA in a timely fashion and pharmacovigilance programs to proactively look for these adverse events are mandated by the FDA. Drug manufacturers andtheir subcontractors are required to register their establishments with the FDA and certain state agencies, and are subject to periodic inspections (which maybe unannounced) by the FDA and certain state agencies for compliance with ongoing regulatory requirements, including cGMP regulations, which imposecertain procedural and documentation requirements upon us and our third-party manufacturers. Following such inspections, the FDA may issue notices onForm FDA 483 and warning letters that could cause us to modify certain activities. A Form FDA 483 notice, if issued at the conclusion of an FDA inspectionor after the appropriate FDA office review of the Establishment Inspection Report prepared by the investigator, can list conditions the FDA believes may haveviolated cGMP or other FDA regulations. FDA guidelines specify that a warning letter be issued for violations of “regulatory significance,” also known asOfficial Action Indicated, or OAI. Failure to adequately and promptly correct the observation(s) can result in regulatory action. In addition to Form FDA 483notices and warning letters, failure to comply with the statutory and regulatory requirements can subject a manufacturer to possible legal or regulatory action,such as suspension of manufacturing, recall of product, seizure of product, injunctive action or possible civil or criminal penalties.The FDA closely regulates the post-approval marketing and promotion of drugs, including standards and regulations for healthcare professionalmarketing activities and materials, direct-to-consumer advertising, dissemination of off-label information, industry-sponsored scientific and educationalactivities and promotional activities involving the Internet. Drugs may be marketed only for their approved indications and in accordance with theprovisions of the confines of the pivotal studies and the approved label. Further, we may be required to develop additional data or conduct additionalpreclinical studies and clinical trials, and we may be required to submit and obtain FDA approval of a new or supplemental NDA for changes to, among otherthings, the indications, labeling, or manufacturing processes or facilities of a drug. Failure to comply with these requirements can subject a manufacturer topossible legal or regulatory action, such as warning letters, corrective advertising, suspension of manufacturing, seizure of product, injunctive action orpotential civil and criminal penalties.Physicians may prescribe legally available drugs for uses that are not described in the product’s labeling and that differ from those tested by us andapproved by the FDA, if in their professional medical judgment, the physicians deem such use to be appropriate. Such off-label uses are common acrosscertain medical specialties. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, impose stringentrestrictions on manufacturers’ communications regarding off-label use.To distribute products commercially, we or our collaborators, as applicable, must comply with state laws that require the registration of manufacturersand wholesale distributors of pharmaceutical products in a state, including, in certain states, manufacturers and distributors who ship products into the stateeven if such manufacturers or distributors have no place of business within the state. Some states also impose requirements on manufacturers and distributorsto establish the pedigree of product in the chain of distribution.Drug Enforcement Administration regulation. The DEA regulates drugs that are controlled substances. Controlled substances are those drugs thatappear on one of the five schedules promulgated and administered by the DEA under the Controlled Substances Act, or CSA. The CSA governs, among otherthings, the inventory, distribution, recordkeeping, handling, security and disposal of controlled substances. Any drug that acts on the central nervous systemhas the potential to become a controlled substance based on an evaluation of its abuse potential, and scheduling by the DEA is a separate process that maydelay the commercial launch of a drug even after FDA approval of the NDA. Companies with a scheduled drug are subject to periodic and ongoinginspections by the DEA and similar state drug enforcement authorities to assess ongoing compliance with the DEA’s regulations. Any failure to comply withthese regulations could lead to a variety of sanctions, including the revocation or a denial of renewal of any DEA registration, injunctions, or civil or criminalpenalties.14Outside of the United StatesOutside of the United States, the ability to market a product is contingent upon obtaining marketing authorization from the appropriate regulatoryauthorities. The requirements governing marketing authorization, pricing and reimbursement vary widely from country to country. Whether or not we obtainFDA approval for a product candidate, we must obtain the requisite approvals from regulatory authorities in foreign jurisdictions prior to the commencementof clinical studies or marketing and sale of the product in those countries. Approval in the United States does not guarantee approval in other countries andvice-versa.Hatch-Waxman Exclusivity. Market exclusivity provisions of the Hatch-Waxman Act can delay the submission or approval of applications seekingto rely upon the FDA’s findings of safety and effectiveness for a previously approved NDA. A new chemical entity, or NCE, subject to an NDA is entitled to afive-year period of non-patent marketing exclusivity in the United States. A drug is an NCE if the FDA has not previously approved any other new drugcontaining the same active moiety, which is the molecule or ion responsible for the action of the drug substance. During the exclusivity period, the FDA maynot accept for review an abbreviated new drug application, or ANDA, or a 505(b)(2) NDA submitted by another company for another version of such drugwhere the applicant does not own or have a legal right of reference to all the data required for approval. However, such an application may be submitted afterfour years if it contains a certification of patent invalidity or non-infringement of patents listed with the FDA by the NDA holder. The Hatch-Waxman Actalso provides three years of marketing exclusivity for an NDA, or supplement to an existing NDA, if new clinical investigations, other than bioavailabilitystudies, that were conducted or sponsored by the applicant are deemed by the FDA to be essential to the approval of the application. This three-yearexclusivity covers only the conditions of use associated with the new clinical investigations and does not prohibit the FDA from approving ANDAs for drugscontaining the original active ingredient. Five-year and three-year exclusivity will not delay the submission or approval of a full NDA. However, an applicantsubmitting a full NDA would be required to conduct or obtain a right of reference to all of the preclinical studies and adequate and well-controlled clinicaltrials necessary to demonstrate safety and effectiveness.Orphan drug designation and exclusivity. Under the Orphan Drug Act, the FDA may designate a drug product as an “orphan drug” if it is intended totreat a rare disease or condition (generally meaning that it affects fewer than 200,000 individuals in the United States, or more in cases in which there is noreasonable expectation that the cost of developing and making a drug product available in the United States for treatment of the disease or condition will berecovered from sales of the product). A company must request orphan product designation before submitting an NDA. If the request is granted, the FDA willdisclose the identity of the therapeutic agent and its potential use. Orphan product designation does not convey any advantage in or shorten the duration ofthe regulatory review and approval process.If a product with orphan status receives the first FDA approval for the disease or condition for which it has such designation or for a select indicationor use within the rare disease or condition for which it was designated, the product generally will receive orphan product exclusivity. Orphan productexclusivity means that the FDA may not approve any other applications for the same product for the same indication for seven years, except in certain limitedcircumstances. Competitors may receive approval of different products for the indication for which the orphan product has exclusivity and may obtainapproval for the same product but for a different indication or the same product for the same indication if demonstrated to be clinically superior. If a drug ordrug product designated as an orphan product ultimately receives marketing approval for an indication broader than what was designated in its orphanproduct application, it may not be entitled to exclusivity.Drug product manufacturing. Our Swiss subsidiary, Arena GmbH operates a drug product manufacturing facility in Zofingen, Switzerland.Swissmedic, a public service organization of the Swiss federal government, is the central Swiss agency for the authorization and supervision of therapeuticproducts. Our Swiss manufacturing facility has been inspected by the competent regional authorities (Regionales Heilmittelinspektorat der Nordwestschweiz,Basel, Switzerland), acting on behalf of Swissmedic, which issued GMP and production licenses to Arena GmbH for the production of drugs.Prescription drug reimbursement. In the United States and markets in other countries, sales of prescription drug products depend in part on theavailability of reimbursement from third-party payers. Third-party payers include government health administrative authorities, managed care organizations,private health insurers and other organizations. The process for determining whether a payer will provide coverage for a drug product may be separate fromthe process for setting the price or reimbursement rate that the payer will pay for the drug product. Third-party payers may limit coverage to specific drugproducts on an approved list, or formulary, which might not include all of the FDA-approved drug products for a particular indication. Third-party payers areincreasingly challenging the price and examining the medical necessity and cost-effectiveness of medical products and services, in addition to their safetyand efficacy. We may need to conduct expensive pharmacoeconomic studies to demonstrate the cost-effectiveness of our products. A payer’s decision toprovide coverage for a drug product does not imply that an adequate reimbursement rate will be approved. Adequate third-party reimbursement may not beavailable to enable us to maintain price levels sufficient to realize an appropriate return on our investment in product development. Patients who areprescribed medications for the treatment of their conditions, and their prescribing physicians, generally rely on third-party payers to reimburse all or part ofthe costs associated with their prescription drugs. Patients are less likely to use our products unless coverage is provided and reimbursement is15adequate to cover a significant portion of the cost of our products. Therefore, coverage and adequate reimbursement are important to new product acceptance.If a drug is reimbursed by Medicare or Medicaid, pricing and rebate programs must comply with, as applicable, the Medicare Prescription Drug,Improvement, and Modernization Act of 2003 as well as the Medicaid rebate requirements of the Omnibus Budget Reconciliation Act of 1990 and theVeterans Health Care Act of 1992, or VHCA, each as amended. If products are made available to authorized users of the Federal Supply Schedule of theGeneral Services Administration, additional laws and requirements apply. Under the VHCA, drug companies are required to offer certain drugs at a reducedprice to a number of federal agencies including US Department of Veterans Affairs and US Department of Defense, the Public Health Service and certainprivate Public Health Service designated entities in order to participate in other federal funding programs including Medicare and Medicaid. Participationunder the VHCA requires submission of pricing data and calculation of discounts and rebates pursuant to complex statutory formulas, as well as entry intogovernment procurement contracts governed by the Federal Acquisition Regulations.The containment of healthcare costs has become a priority of federal, state and foreign governments, and the prices of drugs have been a focus in thiseffort, which has resulted in several recent congressional inquiries and proposed and enacted federal and state legislation designed to, among other things,bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government programreimbursement methodologies for products. In addition, emphasis on managed care in the United States has increased and we expect will continue to increasethe pressure on drug pricing. Coverage policies, third-party reimbursement rates and drug pricing regulation may change at any time. In particular, the PatientProtection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, or collectively the ACA, was enacted in theUnited States in March 2010 and contains provisions that may reduce the profitability of drug products, including, for example, increased rebates for drugssold to Medicaid programs, extension of Medicaid rebates to Medicaid managed care plans, mandatory discounts for certain Medicare Part D beneficiariesand annual fees based on pharmaceutical companies’ share of sales to federal healthcare programs. There have been judicial and Congressional challenges tocertain aspects of the ACA. For example, since January 2017, President Trump has signed two Executive Orders and other directives designed to delay theimplementation of certain provisions of the ACA or otherwise circumvent some of the requirements for health insurance mandated by the ACA. Concurrently,Congress has considered legislation that would repeal or repeal and replace all or part of the ACA. While Congress has not passed comprehensive repeallegislation, two bills affecting the implementation of certain taxes under the ACA have been signed into law. The Tax Cuts and Jobs Act of 2017 includes aprovision repealing, effective January 1, 2019, the tax-based shared responsibility payment imposed by the ACA on certain individuals who fail to maintainqualifying health coverage for all or part of a year that is commonly referred to as the “individual mandate”. Additionally, on January 22, 2018, PresidentTrump signed a continuing resolution on appropriations for fiscal year 2018 that delayed the implementation of certain ACA-mandated fees, including theso-called “Cadillac” tax on certain high cost employer-sponsored insurance plans, the annual fee imposed on certain health insurance providers based onmarket share, and the medical device excise tax on non-exempt medical devices. Further, the Bipartisan Budget Act of 2018, or the BBA, among other things,amends the ACA, effective January 1, 2019, to increase from 50 percent to 70 percent the point-of-sale discount that is owed by pharmaceuticalmanufacturers who participate in Medicare Part D and to close the coverage gap in most Medicare drug plans, commonly referred to as the “donut hole”. Theextent to which any of these, or additional, changes to the ACA may impact our business remains uncertain, but it is clear that concrete steps are being takenby Congress and the Trump administration to further repeal and replace certain aspects of the ACA. Even if favorable coverage and reimbursement status isattained for our products, less favorable coverage policies and reimbursement rates may be implemented in the future. In the case of BELVIQ, Medicareexplicitly excludes coverage of drugs for weight loss.In countries outside the United States, pricing of pharmaceutical products may be subject to governmental control. Evaluation criteria used by manygovernment agencies for the purposes of pricing and reimbursement typically focus on a product’s degree of innovation and its ability to meet a clinical needunfulfilled by currently available therapies. Some countries operate positive and negative list systems under which products may only be marketed once areimbursement price has been agreed. To obtain reimbursement or pricing approval, some of these countries may require the completion of clinical trials thatcompare the cost-effectiveness of a particular drug candidate to currently available therapies. Other countries allow companies to fix their own prices formedicines, but monitor and control company profits. In addition, in some countries, cross-border imports from low-priced markets exert a commercial pressureon pricing within a country. There can be no assurance that any country that has price controls or reimbursement limitations for drug products will allowfavorable reimbursement and pricing arrangements for any of our products.Healthcare fraud and abuse. Pharmaceutical companies are subject to various federal and state laws pertaining to healthcare fraud and abuse,including, but not limited to, anti-kickback and false claims laws.The Federal Anti-Kickback Statute makes it illegal for any person or entity, including a prescription drug manufacturer, or a party acting on its behalf,to knowingly and willfully solicit, offer, receive or provide any remuneration, directly or indirectly, in exchange for, or to induce, the referral of business,including the purchase, order, lease of any good, facility, service or item, including the prescription of a particular drug, for which payment may be madeunder federal healthcare programs such as Medicare and16Medicaid. Some of the state prohibitions are broader in scope and apply to referral of patients for healthcare services reimbursed by any source, not only theMedicare and Medicaid programs.In the course of practicing medicine, physicians may legally prescribe FDA-approved drugs for an indication that has not been approved by the FDAand which, therefore, is not described in the product’s approved labeling, so-called “off-label use” or “the practice of medicine,” if deemed appropriate in thephysicians’ professional medical judgment. The FDA does not ordinarily regulate the behavior of physicians in their choice of treatments. The FDA and othergovernment agencies do, however, restrict communications on the subject of off-label use by a manufacturer or those acting on behalf of a manufacturer.Companies may not promote FDA-approved drugs for off-label uses. The FDA and other governmental agencies do permit a manufacturer (and those actingon its behalf) to engage in some limited, non-misleading, non-promotional exchanges of scientific information regarding unapproved indications.There are numerous federal false claims laws and civil monetary penalty laws that forbid, among other things, anyone from knowingly presenting, orcausing to be presented for payment to third-party payers (including Medicare and Medicaid) claims for reimbursed drugs or services that are false orfraudulent, claims for items or services not provided as claimed or claims for medically unnecessary items or services.Violations of fraud and abuse laws may be punishable by criminal, civil and/or administrative sanctions, including individual imprisonment,disgorgement, criminal fines and civil monetary penalties, possible exclusion from federal healthcare programs (including Medicare and Medicaid), andintegrity oversight and reporting obligations to resolve allegations of non-compliance with these laws. In addition, under certain healthcare fraud and abuselaws, there is an ability for private individuals to bring similar actions. Additionally, many states have analogous fraud and abuse laws, some of which may bebroader in scope. Further, there are an increasing number of state laws that require pharmaceutical companies to establish marketing compliance programs,file periodic reports with the state, make periodic public disclosures on sales, marketing, pricing, clinical trials and other activities, or register their salesrepresentatives, as well as prohibiting certain other sales and marketing practices. The federal transparency requirements under the ACA require certainmanufacturers of drugs, devices, biologics and medical supplies to annually report to the Department of Health and Human Services information related topayments and other transfers of value to physicians and teaching hospitals and physician ownership and investment interests. Additionally, recent federallegislation imposes additional obligations on certain pharmaceutical manufacturers, among others, regarding drug product tracking and tracing.Our activities are also potentially subject to federal and state consumer protection and unfair competition laws. We are also subject to the US ForeignCorrupt Practices Act, or the FCPA, which prohibits companies and individuals from engaging in specified activities to obtain or retain business or toinfluence a person working in an official capacity. Under the FCPA, it is illegal to pay, offer to pay, or authorize the payment of anything of value to anyforeign government official, governmental staff members, political party or political candidate in an attempt to obtain or retain business or to otherwiseinfluence a person working in an official capacity.Healthcare privacy and security laws. The Health Insurance Portability and Accountability Act of 1996, or HIPAA, as amended by the HealthInformation Technology for Economic and Clinical Health Act and its implementing regulations, imposes obligations, including mandatory contractualterms, with respect to safeguarding the privacy, security and transmission of individually identifiable health information. In addition, many state laws applyto the use and disclosure of health information. We may be subject to, or our collaborators’ marketing activities may be limited by, HIPAA and itsimplementing regulations. In addition, the European Union has established its own data security and privacy legal framework, including but not limited toDirective 95/46/EC, or the Data Protection Directive. The Data Protection Directive will be replaced starting in May 2018 with the recentlyadopted European General Data Protection Regulation, or GDPR, which contains new provisions specifically directed at the processing of health information,higher sanctions and extra-territoriality measures intended to bring non-EU companies under the regulation. We may in the future expand our businessoperations to include additional operations in the EU, including potentially conducting preclinical and clinical trials. With such expansion, we would besubject to increased governmental regulation, including the GDPR, in the EU countries in which operate.Manufacturing, Revenues from External Customers, Sources and Availability of Materials, and Long-Lived AssetsWe have certain drug product facility assets, including manufacturing facility production licenses, fixtures, equipment, other personal property andreal estate assets in Zofingen, Switzerland. We are using this facility to manufacture and package BELVIQ as well as for toll manufacturing of certain drugproducts for Siegfried and other customers. Under the Sale Agreement with Siegfried, we expect to transfer such manufacturing facility and related assets toSiegfried, subject to the satisfaction or waiver of certain customary closing conditions specified in the Sale Agreement.Our revenues of $21.3 million for the year ended December 31, 2017, included $12.0 million, or 56.2%, from Everest, $5.1 or 23.8%, from BoehringerIngelheim and $1.7 million, or 8.0%, from Eisai. Our revenues of $92.2 million for the year ended December1731, 2016, included $78.4 million, or 85.1%, from Eisai, $5.1 million, or 5.5%, from Boehringer Ingelheim and $4.2 million, or 4.6%, from Ildong. Ourrevenues of $13.4 million for the year ended December 31, 2015, included $8.6 million, or 64.0%, from Eisai, $3.4 million, or 25.0%, from Ildong and $1.1million, or 8.5%, from Axovant. This information excludes revenue activity reported within discontinued operations. See Note 5 to our consolidatedfinancial statements included in this Annual Report for additional information.We purchase raw materials, starting materials, intermediates, active pharmaceutical ingredients, excipients and other materials from commercialsources. To decrease the risk of an interruption to our supply, when we believe it is reasonable for us to do so, we source these materials from multiplesuppliers so that, in general, the loss of any one source of supply would not have a material adverse effect on commercial production. However, currently wehave only one or a limited number of suppliers for some of these materials. The loss of a primary source of supply would potentially delay our production.Our facility in Zofingen, Switzerland is currently the only manufacturer of finished drug product for BELVIQ. The carrying value of long-lived assets located in the United States and Switzerland were $30.1 million and $8.7 million, respectively, at December31, 2017. The carrying value of long-lived assets located in the United States and Switzerland were $35.1 million and $11.1 million, respectively, atDecember 31, 2016. The carrying value of long-lived assets located in the United States and Switzerland were $41.5 million and $38.1 million, respectively,at December 31, 2015. As of December 31, 2017, the long-lived assets located in Switzerland are reported under assets of disposal group held for sale in ourconsolidated financial statements included in this Annual Report.Compliance with Environmental RegulationsOur research and development programs involve the controlled use of hazardous materials, chemicals, biological materials and various radioactivecompounds. In the United States, we are subject to regulation under the Occupational Safety and Health Act, the Environmental Protection Act, the USEnvironmental Protection Agency, the California Environmental Protection Agency, the Toxic Substances Control Act, the Resource Conservation andRecovery Act, the CSA and other federal, state or local regulations.With regard to Arena GmbH’s drug product manufacturing facility, Arena GmbH has contracted with Siegfried to provide certain safety, health andenvironmental services. Arena GmbH is subject to regulation under the Environmental Protection Act (Umweltschutzgesetz, USG), the Chemicals Act(Chemikaliengesetz, ChemG), and the Federal Act on the Protection of Waters (Gewässerschutzgesetz, GSchG), which refer to several ordinances such as theOrdinance on Air Pollution Control (Luftreinhalte-Verordnung, LRV), the Ordinance on Incentive Taxes on Volatile Organic Compounds (Verordnung überdie Lenkungsabgabe auf flüchtigen organischen Verbindungen, VOCV), the Water Protection Ordinance (Gewässerschutzverordnung, GSchV), the Ordinanceof the Handling of Wastes (Verordnung über den Verkehr mit Abfällen, VeVA), the Chemicals Ordinance (Chemikalienverordnung, ChemV), the ChemicalRisk Reduction Ordinance (Chemikalien-Risikoreduktions-Verordnung, ChemRRV) and the Ordinance on Protection against Major Accidents(Störfallverordnung, StFV). The competent authorities in Switzerland for the implementation of environmental regulations are BAFU (Bundesamt für Umwelt/ Federal Office for the Environment), which is the Swiss federal agency for the environment, and the respective authorities of the Canton of Aargau(Abteilung für Umwelt, AfU). Furthermore, the BAFU and the BAG (Bundesamt für Gesundheit / Federal Office of Public Health) share authorities with regardto the implementation and, together with the respective authority of the Canton of Aargau (Amt für Verbraucherschutz), the supervision of compliance withthe laws and regulations related to chemicals. Occupational health and safety is regulated, in particular, by the EKAS (EidgenössischeKoordinationskommission für Arbeitssicherheit) guideline No. 6508 (ASA), governing the evaluation of worker safety and the reporting to the relevantauthorities. The competent authority for the implementation of occupational health and safety regulations is the Canton of Aargau (Amt für Wirtschaft undArbeit), whereby exposure limits are set by SUVA (Schweizerische Unfallversicherungsanstalt), which is the Swiss Accident Insurance Fund.We may be subject to further such regulations in the future. Although we believe that our operations comply in all material respects with theapplicable environmental laws and regulations, the risk of accidental contamination or injury from these materials cannot be eliminated. In the event of suchan accident, we could be held liable for any damages that result, and the extent of that liability could exceed our resources. Our compliance with these lawsand regulations has not had, and is not expected to have, a material effect upon our capital expenditures, results of operations or competitive position.Research and Development ExpensesResearch and development activities are the primary source of our expenses. Our research and development expenses include personnel costs, facilityand equipment costs, clinical and preclinical study fees, research supplies, and manufacturing costs for non-commercial products. Such expenses totaled$71.0 million, $63.8 million, and $83.2 million for the years ended December 31, 2017, 2016, and 2015, respectively. For research and developmentsponsored by collaborators for which we initially incur the costs, we record the costs within research and development expenses and record thereimbursements we receive from the collaborators for these18costs within revenues; these expenses and revenues totaled $2.9 million, $2.8 million, and $1.2 million for the years ended December 31, 2017, 2016, and2015, respectively.EmployeesAs of March 9, 2018, we had a total of 159 employees, including 122 in research, development and manufacturing and 37 in administration, whichincludes finance, legal, facilities, information technology and other general support areas. This includes the approximately 50 employees that we expect willbe transferred to Siegfried as part of the sale of our manufacturing operations in Switzerland.Available InformationOur annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and all amendments to those reports filed or furnishedpursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, or the Exchange Act, are available free of charge on our website(www.arenapharm.com) as soon as reasonably practicable after they are electronically filed with, or furnished to, the SEC. Item 1A. Risk FactorsInvestment in our stock involves a high degree of risk. You should consider carefully the risks described below, together with other information inthis Annual Report on Form 10-K and other public filings, before making investment decisions regarding our stock. If any of the following events actuallyoccur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of ourcommon stock to decline and you may lose all or part of your investment. Moreover, the risks described below are not the only ones that we face. Additionalrisks not presently known to us or that we currently deem immaterial may also affect our business, operating results, prospects or financial condition.The risks described below include risks relating to continuing to operate our manufacturing facility in Switzerland, which we expect to divestpursuant to an asset purchase agreement, as discussed in other portions of this Annual Report on Form 10-K.Risks Relating to Our BusinessWe will need to obtain additional funds or enter into collaboration agreements to execute on our corporate strategy, and we may not be able to do so atall or on terms you view as favorable; your ownership may be substantially diluted if we do obtain additional funds; you may not agree with the mannerin which we allocate our available resources; and we may not be profitable.It takes many years and potentially hundreds of millions of dollars to successfully develop a compound into a marketed drug. We have accumulated alarge deficit that has primarily resulted from the significant expenditures we have made in research and development since our inception. We expect that ourlosses and operating expenses will continue to be substantial.All of our current active development programs are in the development stage, and we currently do not have, and we may not have in the future,adequate funds to develop any of our compounds into marketed drugs.We may seek to obtain additional funding through the capital markets or other financing sources. Additional funding may not be available to us ormay not be available on terms we or others believe are favorable. Our ability to obtain additional funding may depend on many factors, including thoseoutside our control. Should we obtain additional funding, your ownership interest may be diluted or otherwise negatively impacted.We may enter into collaboration or other agreements with other entities to continue to develop and, if successful, commercialize one or more of ourdrug candidates. We may not be able to enter into any such agreements on terms that we or third parties, including investors or analysts, view as favorable, ifat all. Our ability to enter into any such agreement for any of our programs or drug candidates depends on many factors, potentially including the outcomesof additional testing (including clinical trial results) or regulatory applications for marketing approval, and we do not control these outcomes.We may allocate our resources in ways that do not improve our results of operations or enhance the value of our assets, and our stockholders andothers may also not agree with the manner in which we choose to allocate our resources or obtain additional funding. We may also eliminate, scale back ordelay some or all of our research and development programs, and any such reductions or failure to apply our resources effectively or to obtain additionalfunding could narrow, slow or otherwise adversely impact the development and commercialization of one or more of our drug candidates, which could reduceour opportunities for success and have a material adverse effect on our business, our prospects and the market price of our common stock.19In addition, we cannot assure you that we will be profitable or, if we are profitable for any particular time period, that we will be profitable in thefuture.Drug development programs are expensive, time consuming, uncertain and susceptible to change, interruption, delay or termination.Drug development programs are very expensive, time consuming and difficult to design and implement. Our drug candidates are in various stages ofclinical and preclinical development and are prone to the risks of failure inherent in research and development. Clinical trials and preclinical studies areneeded to demonstrate that drug candidates are safe and effective to the satisfaction of the FDA, and similar non-US regulatory authorities, and the FDA orother regulatory authority may require us to, or we or others may decide to, conduct additional research and development even after a drug is approved. Thecommencement or completion of our clinical trials or preclinical studies could be substantially delayed or prevented by several factors, including thefollowing: •limited number of, and competition for, suitable patients required for enrollment in our clinical trials or animals to conduct our preclinicalstudies; •limited number of, and competition for, suitable sites to conduct our clinical trials or preclinical studies; •delay or failure to obtain approval or agreement from the applicable regulatory authority to commence a clinical trial or approval of a studyprotocol; •delay or failure to obtain sufficient supplies of drug candidates, drugs or other materials for the trial or study; •delay or failure to reach agreement on acceptable agreement terms or protocols; and •delay or failure to obtain institutional review board, or IRB, approval to conduct a clinical trial at a prospective site.For example, recruitment for ulcerative colitis studies is competitive and challenging, and led us to make changes to our internal staffing, externalvendors and trial design relating to our etrasimod program. It is not known how such changes, or any future changes we may implement, will impact clinicaltrials for our drug candidates, and it is difficult to predict when ongoing trials will be fully enrolled or when data will be available. Recruitment for trials forother indications, such as a Phase 3 ralinepag trial for PAH, can also be competitive and challenging.In addition, the FDA, other regulatory authorities, collaborators, or we may suspend, delay or terminate our development programs at any time forvarious reasons, including those listed above affecting the commencement or completion of trials and the following: •lack of effectiveness of any drug candidate during clinical trials; •side effects experienced by study participants or other safety issues; •slower than expected rates of patient recruitment and enrollment or lower than expected patient retention rates; •inadequacy of or changes in our manufacturing process or compound formulation; •delays in obtaining regulatory approvals to commence a study, or “clinical holds,” or delays requiring suspension or termination of a study bya regulatory authority, such as the FDA, after a study is commenced; •changes in applicable regulatory policies and regulations; •delays in identifying and reaching agreement on acceptable terms with prospective clinical trial sites; •uncertainty regarding proper dosing; •unfavorable results from ongoing clinical trials or preclinical studies; •failure of our clinical research organizations to comply with all regulatory and contractual requirements or otherwise perform their services in atimely or acceptable manner; •scheduling conflicts with participating clinicians and clinical institutions; •failure to design appropriate clinical trial protocols; •insufficient data to support regulatory approval; •termination of clinical trials at one or more clinical trial sites; •inability or unwillingness of medical investigators to follow our clinical protocols; •difficulty in maintaining contact with subjects during or after treatment, which may result in incomplete data;20 •lack of sufficient funding to continue clinical trials or preclinical studies; or •changes in business priorities or perceptions of the value of the program.There is typically a high rate of attrition from the failure of drug candidates proceeding through clinical trials, and many companies have experiencedsignificant setbacks in advanced development programs even after promising results in earlier studies or trials. We have experienced setbacks in our internaland partnered development programs and expect to experience additional setbacks from time to time in the future. In addition, even if the earlier-stage resultsof our development programs are favorable, these programs may take significantly longer than expected to complete or may not be completed at all. If we orour collaborators abandon or are delayed in our development efforts related to any drug or drug candidate, we may not be able to generate sufficient revenuesto continue our operations at the current level or be profitable, our reputation in the industry and in the investment community would likely be significantlydamaged, additional funding may not be available to us or may not be available on terms we or others believe are favorable, and our stock price may decreasesignificantly.We may not be successful in initiating or completing our studies or trials or advancing our programs on our projected timetable, if at all. Any failure toinitiate or delays in our studies, trials or development programs, or unfavorable results or decisions or negative perceptions regarding any of our programs,could cause our stock price to decline significantly. This is particularly the case with respect to our clinical programs.Our business may be negatively impacted based on the clinical trials and preclinical studies of, and decisions affecting, one or more of our drugcandidates.The results and timing of clinical trials and preclinical studies, as well as related decisions by us, collaborators and regulators, can affect our stockprice. Results of clinical trials and preclinical studies are uncertain and subject to different interpretations by regulatory agencies, us or others. The design ofthese trials and studies (which may change significantly and be more expensive than anticipated depending on results and regulatory decisions), as well asrelated analyses of such results, including adverse effects, may not be viewed favorably by us or third parties, including investors, analysts, current orpotential collaborators, the academic and medical communities, and regulators, which could adversely impact the development and opportunities forregulatory approval of drug candidates and commercialization (and even result in withdrawal from the market) of approved drugs. The same may be true ofdecisions regarding the focus and prioritization of our research and development efforts. Stock prices of companies in our industry have declinedsignificantly when such results and decisions were unfavorable or perceived negatively or when a drug candidate or product did not otherwise meetexpectations.The development, approval or commercialization of any of our drug candidates could be negatively affected by circumstances related to other drugcandidates or approved products.Information on our drug candidates in clinical development is preliminary and incomplete, and for such drug candidates, particularly in the earlierstages of development, information on approved products in the same or related drug classes may indicate potential risks related to the development of ourdrug candidates. For example, etrasimod is an orally available modulator of the S1P receptors. An approved drug that is also an orally available modulator ofthe S1P receptors, Gilenya, is associated with risks such as adverse cardiovascular effects, including lowering of the heart rate and heart blocks, infection,macular edema, respiratory effects, fetal risk, a rare brain infection, and elevations in liver enzymes. These adverse reactions and risks may be associated withS1P receptor modulation and could be found to be associated with the use of etrasimod. Such adverse reactions and risks, either actual or perceived, couldnegatively impact its development, approval or commercialization, or our ability to enter into a collaboration on acceptable terms.Topline data may not accurately reflect the complete results of a particular study or trial.We may publicly disclose topline or interim data from time to time, which are based on a preliminary analysis of then-available efficacy and safetydata, and the results and related findings and conclusions are subject to change following a more comprehensive review of the data related to the particularstudy or trial.We also make assumptions, estimations, calculations and conclusions as part of our analyses of data, and others, including regulatory agencies, maynot accept or agree with our assumptions, estimations, calculations, conclusions or analyses or may interpret or weigh the importance of data differently,which could impact the value of the particular program, the approvability or commercialization of the particular drug candidate or drug and our company ingeneral. In addition, the information we may publicly disclose regarding a particular study or clinical trial is based on what is typically extensiveinformation, and you or others may not agree with what we determine is the material or otherwise appropriate information to include in our disclosure, andany information we determine not to disclose may ultimately be deemed significant with respect to future decisions, conclusions, views, activities orotherwise regarding a particular drug, drug candidate or our business.21Our hypothesis that selectively targeting receptors can lead to more efficacious or safer drugs may not be correct.In general, we have designed and optimized our drug candidates (including etrasimod, ralinepag and APD371) to selectively target certain receptorsfound on cells in humans. Our hypothesis is that selectivity may allow our drug candidates to address diseases more efficaciously or without some of thenegative effects associated with less selective drugs. In certain cases, we believe early research and, if available, early clinical testing, provides preliminarysupport for our hypothesis. However, our hypothesis may not be correct, early research and early phase clinical testing may not be predictive of efficacy orsafety in later trials, and our drug candidates may not be approved or, if approved, have the desired efficacy or safety profile.The results of preclinical studies and completed clinical trials are not necessarily predictive of future results, and our current drug candidates or anyapproved drugs may not be further developed or have favorable results in later studies or trials.Preclinical studies and Phase 1 and Phase 2 clinical trials are not primarily designed to test the efficacy of a drug candidate, but rather to test safety, tostudy pharmacokinetics and pharmacodynamics, and to understand the drug candidate’s side effects at various doses and schedules. Favorable results in earlystudies or trials may not be confirmed in later studies or trials, including preclinical studies that continue or that are initiated after earlier clinical trials andlarge-scale clinical trials, and our drug candidates or drugs in subsequent trials or studies may fail to show desired safety and efficacy despite havingprogressed through earlier-stage trials. For example, we recently announced positive topline Phase 2 results for ralinepag in patients with PAH, but theseresults may not be confirmed in any subsequent Phase 3 study. By way of another example, the impact of etrasimod on heart rate that was observed incompleted clinical trials may not be observed in subsequent trials, and it could be viewed negatively by the FDA or other regulatory agencies.Unfavorable results from clinical trials or preclinical studies could result in delays, modifications or abandonment of ongoing or future clinical trials,or abandonment of a program. Clinical and preclinical results are frequently susceptible to varying interpretations that may delay, limit or prevent regulatoryapprovals or commercialization. Negative or inconclusive results or adverse medical events during such trials or studies could cause a clinical trial to bedelayed, repeated or terminated; a program to be abandoned; or negatively impact a related marketed drug, which could have a material adverse effect on ourbusiness, financial condition and results of operations.Drug discovery and development is intensely competitive in the therapeutic areas on which we focus. If the number of our competitors increase or theydevelop treatments that are approved faster, marketed better, less expensive or demonstrated to be more effective or safer than our drugs or drugcandidates, our commercial opportunities will be reduced or eliminated.Many of the drugs we or our collaborators are attempting or may attempt to discover and develop may compete with existing therapies in the UnitedStates and other territories. In addition, many companies are pursuing the development of new drugs that target the same diseases and conditions that wetarget.For example, with regard to etrasimod, there are other drugs that have a similar mechanism of action already in Phase 3 clinical development for thesame indications that we are pursuing, such as ulcerative colitis. By way of another example, with regard to ralinepag, a competitor with the same mechanismof action, selexipag, is already currently approved in the United States, Europe and other countries. Our competitors, particularly large pharmaceuticalcompanies, may have substantially greater research, development and marketing and sales capabilities and greater financial, scientific and human resourcesthan we do. Companies that complete clinical trials, obtain required regulatory agency approvals and commence commercial sale of their drugs before we dofor the same indication may achieve a significant competitive advantage, including certain patent and marketing exclusivity rights. In addition, ourcompetitors’ drugs may have fewer side effects, more desirable characteristics (such as efficacy, route of administration or frequency of dosing), or be viewedmore favorably by patients, healthcare providers, healthcare payers, the medical community, the media or others than our drug candidates or drugs, if any, forthe same indication. Our competitors may also market generic or other drugs that compete with our drugs at a lower price than our drugs, which maynegatively impact our drug sales, if any. Any results from our research and development efforts, or from our joint efforts with our existing or any futurecollaborators, may not compete successfully with existing or newly discovered products or therapies.Our revenues in the future will be substantially dependent on the success of our or our collaborators’ marketing of drugs we have discovered ordeveloped. To the extent such drugs are not commercially successful, our business, financial condition and results of operations may be materiallyadversely affected and the price of our common stock may decline.We believe our revenues will be substantially dependent on the success of the drugs we or our collaborators successfully develop. We do not knowwhether or when such drug candidates will be approved by regulatory authorities for sale or commercialized. Even if approved and commercialization begins,we do not know if such commercialization will be successful or otherwise meet our, your, analysts’ or others’ expectations, and the market price of ourcommon stock could decline significantly. For example, sales of lorcaserin to date have been less than we and others initially anticipated, and, becauselorcaserin is the only22approved and marketed drug in which we have a financial interest, our revenue for the near-term is substantially dependent on our Transaction Agreementwith Eisai and sales of lorcaserin.We cannot guarantee future product sales or achievement of any other milestones. In addition, our Transaction Agreement with Eisai for lorcaserin,and any of our other collaborations, may be terminated early in certain circumstances, which may result in us not receiving additional milestone or otherpayments under the terminated agreement.The degree of market acceptance and commercial success of a drug will depend on a number of factors, including the following, as well as risksidentified in other risk factors: •the number of patients treated with the drug and their results; •market acceptance and use of the drug, which may depend on the public’s view of the drug, economic changes, national and world events,potentially seasonal and other fluctuations in demand, the timing and impact of current or new competition, and the drug’s perceivedadvantages or disadvantages over alternative treatments (including relative convenience, ease of administration, and prevalence and severity ofany adverse events, including any unexpected adverse events); •the actual and perceived safety and efficacy of the drug on both a short- and long-term basis among actual or potential patients, healthcareproviders and others in the medical community, regulatory agencies and insurers and other payers, including related decisions by any suchentity or individual; •incidence and severity of any side effects, including as a result of off-label use or in combination with one or more drugs; •new data relating to the drug, including as a result of additional studies, trials or analyses of the drug or related drugs or drug candidates; •the willingness of physicians to prescribe and of patients to use the drug; •the claims, limitations, warnings and other information in the drug’s current or future labeling; •any current or future scheduling designation for the drug by the US Drug Enforcement Administration, or DEA, or any comparable foreignauthorities; •our or our collaborators’ maintenance of an effective sales force, marketing team, strategy and program, and medical affairs group and relatedfunctions, as well as its sales, marketing and other representatives accurately describing the drug consistent with its approved labeling; •the price and perceived cost-effectiveness of the drug, including as compared to possible alternatives; •the ability of patients and physicians and other providers to obtain and maintain coverage and adequate reimbursement, if any, by third-partypayers, including government payers; •the ability and desire of group purchasing organizations, or GPOs, including distributors and other network providers, to sell the drug to theirconstituencies; •introduction of counterfeit or unauthorized versions of the drug; •to the extent the drug is approved and marketed in a jurisdiction with a significantly lower price than in another jurisdiction, the impact of thelower pricing in the higher-priced territory, including on the pricing of reimbursement, if available, and by the diversion of the lower-priceddrug into the higher-priced territory; and •the availability of adequate commercial manufacturing and supply chain for the drug.Our drugs may not be commercially successful if not widely covered and adequately reimbursed by third-party payers, and we may depend on others toobtain and maintain third-party payer access; inadequate third-party coverage and reimbursement could make entering into agreements withpharmaceutical companies to collaborate or commercialize our drugs more difficult and diminish our revenues.Our and our collaborators’ ability to successfully commercialize any of our drugs that have been or may be approved will depend, in part, ongovernment regulation and the availability of coverage and adequate reimbursement from third-party payers, including private health insurers andgovernment payers, such as the Medicaid and Medicare programs, increases in government-run, single-payer health insurance plans and compulsory licensesof drugs. We expect government and third-party payers will continue their efforts to contain healthcare costs by limiting coverage and reimbursement levelsfor new drugs. In addition, many countries outside of the United States have nationalized healthcare systems in which the government pays for all suchproducts and services and23must approve product pricing. A government or third-party payer decision not to approve pricing, or provide adequate coverage and reimbursements, for ourdrugs, if any, could limit market acceptance of and demand for our drugs.It is increasingly difficult to obtain coverage and adequate reimbursement levels from third-party payers, and significant uncertainty exists as to thecoverage and reimbursement of newly approved prescription drug products. We or our collaborators also face competition in negotiating for coverage frompharmaceutical companies and others with competitive drugs or other treatment, and these competitors may have significantly more negotiating leverage orsuccess with respect to individual payers than we or our collaborators may have.Federal and state healthcare reform measures that have been or may be implemented in the future, may result in more rigorous coverage criteria, morelimited coverage and downward pressure on the price that we may receive for any approved product, which could seriously decrease our future revenues. ThePatient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, or collectively the ACA, which wasenacted in 2010, is one such healthcare reform measure that has made a number of substantial changes in the way healthcare is financed by bothgovernmental and private insurers. In the years since its enactment, there have been, and continue to be, significant developments in, and continuedlegislative activity around, attempts to repeal or repeal and replace the ACA, which leads to uncertainty regarding the future of the ACA, and its impact onour business and operations. Further, there has been heightened governmental scrutiny in the United States of pharmaceutical pricing practices in light of therising cost of prescription drugs and biologics. Such scrutiny has resulted in several recent congressional inquiries and proposed and enacted federal and statelegislation designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patientprograms, and reform government program reimbursement methodologies for products. Any reduction in reimbursement from Medicare, Medicaid or othergovernment programs may result in a similar reduction in payments from private payers. For example, reimbursement has been challenging for BELVIQ,including because Medicare explicitly excludes coverage for drugs for weight loss. The implementation of additional cost containment measures or otherhealthcare reforms may also limit our commercial opportunities by reducing the amount a potential collaborator is willing to pay to license our programs ordrug candidates in the future, which may prevent us from being able to generate revenue, attain profitability, commercialize our products or establish andmaintain collaborations. There have been judicial and Congressional challenges to certain aspects of the ACA, as well as recent efforts by the Trumpadministration to repeal and replace certain aspects of the ACA, and we expect such challenges to continue. Since January 2017, President Trump has signedtwo Executive Orders and other directives designed to delay the implementation of certain provisions of the ACA or otherwise circumvent some of therequirements for health insurance mandated by the ACA. Concurrently, Congress has considered legislation that would repeal or repeal and replace all or partof the ACA. While Congress has not passed comprehensive repeal legislation, two bills affecting the implementation of certain taxes under the ACA havebeen enacted. The Tax Cuts and Jobs Act of 2017 includes a provision repealing, effective January 1, 2019, the tax-based shared responsibility paymentimposed by the ACA on certain individuals who fail to maintain qualifying health coverage for all or part of a year that is commonly referred to as the“individual mandate”. Additionally, on January 22, 2018, President Trump signed a continuing resolution on appropriations for fiscal year 2018 that delayedthe implementation of certain fees mandated by the ACA, including the so-called “Cadillac” tax on certain high cost employer-sponsored insurance plansand the annual fee imposed on certain health insurance providers based on market share. Further, the Bipartisan Budget Act of 2018, or the BBA, amongother things, amends the ACA, effective January 1, 2019, to close the coverage gap in most Medicare drug plans, and also increases in 2019 the percentagethat a drug manufacturer must discount the cost of prescription drugs from 50 percent under current law to 70 percent. Congress also could consideradditional legislation to repeal or repeal and replace other elements of the ACA. At this time, the full effect that the ACA will have on our business in thefuture remains unclear.There have also been several recent US Congressional inquiries and proposed and enacted federal and state legislation designed to, among otherthings, bring more transparency to drug pricing, review the relationship between pricing and manufacturer patient programs, reduce the cost of drugs underMedicare, and reform government program reimbursement methodologies for drugs. For example, the Trump administration’s budget proposal for fiscal year2019 contains additional drug price control measures that could be enacted during the 2019 budget process or in other future legislation, including, forexample, measures to permit Medicare Part D plans to negotiate the price of certain drugs under Medicare Part B, to allow some states to negotiate drug pricesunder Medicaid and to eliminate cost sharing for generic drugs for low-income patients. Cost control measures legislation has been enacted at the state level.Any reduction in reimbursement from Medicare or other government programs may result in a similar reduction in payments from private payors. Theimplementation of cost containment measures or other healthcare reforms may prevent us from being able to generate revenue, attain profitability, orcommercialize our products.24Forecasting potential sales for drugs will be difficult, and if our projections are inaccurate, our business may be harmed and our stock price may beadversely affected.Our business planning requires us to forecast or make assumptions regarding demand and revenues for our drugs if they are approved, despitenumerous uncertainties. These uncertainties may be increased if we rely on our collaborators to conduct commercial activities and provide us with accurateand timely information. Actual results may deviate materially from projected results for various reasons, including the following, as well as risks identified inother risk factors: •the rate of adoption in the particular market, including fluctuations in demand for various reasons, such as fluctuations related to economicchanges, national and world events, holidays and seasonal changes; •pricing (including discounting or other promotions), reimbursement, product returns or recalls, competition, labeling, DEA scheduling, adverseevents and other items that impact commercialization; •lack of patient and physician familiarity with the drug; •lack of patient use and physician prescribing history; •lack of commercialization experience with the drug; •actual sales to patients may significantly differ from expectations based on sales to wholesalers; and •uncertainty relating to when the drug may become commercially available to patients and rate of adoption in other territories.Revenues from drug sales may be based in part on estimates, judgment and accounting policies, and incorrect estimates or regulators’ or others’disagreement regarding such estimates or accounting policies may result in changes to guidance, projections or previously reported results. Expected andactual product sales and quarterly and other results may greatly fluctuate, including in the near-term for lorcaserin, and such fluctuations can adversely affectthe market price of our common stock, perceptions of our ability to forecast demand and revenues, and our ability to maintain and fund our operations.Our efforts will be seriously jeopardized if we are unable to retain and attract key and other employees.Our success depends on the continued contributions of our principal management, development and scientific personnel, and the ability to hire andretain key and other personnel. We face competition for such personnel, and we believe that risks and uncertainties related to our business may impact ourability to hire and retain key and other personnel. If we do not recruit and retain effective management and other key employees, particularly our executiveofficers, our operations, our ability to generate or raise additional capital, and our business in general may be adversely impacted. For example, to execute ourclinical programs, our strategy is to maintain a sufficient and robust clinical expertise and program management function. We are in the process of modifyingand building this function, and we may not be able to establish the function we believe necessary to support our clinical goals and meet our corporateobjectives.We may need to expand our organization and may experience difficulties in managing this growth, which could disrupt our operations.As of March 9, 2018, we employed approximately 159 employees. In the future we may expand our employee base to increase our managerial,scientific, operational, manufacturing, commercial, financial and other resources and to hire more consultants and contractors. Future growth would imposesignificant additional responsibilities on our management, including the need to identify, recruit, maintain, motivate and integrate additional employees,consultants and contractors. Also, our management may need to divert attention away from our day-to-day activities and devote a substantial amount of timeto managing these growth activities. We may not be able to effectively manage the expansion of our operations, which may result in weaknesses in ourinfrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. Ourfuture growth could require significant capital expenditures and may divert financial resources from other projects, such as the development of additionalproduct candidates. Moreover, if our management is unable to effectively manage our growth, our expenses may increase more than expected, our ability togenerate and/or grow revenues could be reduced, and we may not be able to implement our business strategy. Our future financial performance and our abilityto commercialize any approved products and compete effectively will depend, in part, on our ability to effectively manage any future growth.Data generated or analyzed with respect to product use in the market or required postmarketing or other studies or trials may result in decreaseddemand, lower sales, product recall, regulatory action or litigation.An NDA holder (or the equivalent outside the United States) is responsible for assessing and monitoring the safety of a drug that has been approved formarketing, including reviewing reports of adverse safety events. In addition, NDA holders often conduct25additional studies or trials or analyze new or previous data related to an approved drug, including with respect to required postmarketing studies and inconnection with seeking additional regulatory approvals in new territories.For example, as a condition to obtaining FDA approval of lorcaserin, the FDA required the conduct of postmarketing studies, including evaluation ofthe effect of long-term treatment with lorcaserin on the incidence of major adverse cardiovascular events, or MACE (non-fatal myocardial infarction, non-fatal stroke and cardiovascular death), in overweight and obese subjects with cardiovascular disease or multiple cardiovascular risk factors (otherwise knownas CVOT). The FDA-required portion of the trial is designed to evaluate lorcaserin’s effect on the incidence of major adverse cardiovascular events comparedto placebo, with a non-inferiority margin for the hazard ratio of 1.4. The trial also includes FDA-required echocardiographic assessments. Along with theFDA-required portion of the trial, we expect that the trial will include the non-FDA required evaluation of whether lorcaserin reduces the incidence ofconversion to type 2 diabetes in patients without type 2 diabetes at baseline and the incidence of MACE+ (MACE or hospitalization for unstable angina orheart failure, or any coronary revascularization), both as compared to placebo. We expect that the trial (including the non-FDA required portion) will run forup to several more years, but the duration could be longer or shorter depending on the actual number of events observed. New data relating to lorcaserin,including from adverse event reports or required postmarketing, registration or other studies or trials, may result in label changes, may adversely affect salesor development, result in withdrawal of lorcaserin from the market, or result in litigation. In addition, analyses of previous data can have similar risks. Weexpect Eisai to continue to generate data from new studies and trials, as well as to continue analyzing existing data from previously conducted studies andtrials, including for potential use in applications for the marketing approval of lorcaserin. Regulatory agencies may consider the new data or analyses inreviewing marketing applications for lorcaserin in their territories or impose post-approval requirements that require significant additional expenditures.Furthermore, the discovery of significant problems with a product or class of products similar to lorcaserin could have an adverse effect on the lorcaserinprogram, including commercialization.The commercialization and continuing development of lorcaserin may be adversely impacted by cardiovascular side effects associated with drugs usedfor the treatment of obesity.We developed lorcaserin to more selectively stimulate the serotonin 2C receptor than did fenfluramine or dexfenfluramine because we believe thismay avoid the cardiovascular side effects associated with fenfluramine and dexfenfluramine (often used in combination with phentermine, the combinationof which was commonly referred to as “fen-phen”). These two drugs were serotonin-releasing agents and non-selective serotonin receptor agonists and werewithdrawn from the market in 1997 after reported incidences of heart valve disease and pulmonary hypertension associated with their usage. In in vitrostudies examining affinity, activity and serotonin receptor subtype specificity, lorcaserin demonstrated affinity for, and activity at, serotonin 2A, 2B and 2Creceptors, but demonstrated greater affinity, activity and selectivity for the serotonin 2C receptor than for the serotonin 2A and 2B receptors. Activation ofthe latter two receptors has been associated with undesirable effects. Activation of the 2A receptor has been associated with CNS effects, including alteredperception, mood and abuse potential, and activation of the 2B receptor has been associated with cardiac valvulopathy.We may not be correct in our belief that more selectively stimulating the serotonin 2C receptor will avoid these undesired side effects, or lorcaserin’sselectivity profile may not be adequate to avoid these side effects. Lorcaserin’s selectivity profile and the potential relationship between the activity oflorcaserin and the activity of fenfluramine and dexfenfluramine may result in increased regulatory scrutiny of the safety of lorcaserin, may raise potentialadverse publicity and may affect product sales or result in litigation.If we license or otherwise partner our drugs, our failure to maintain such agreements or poor performance under such agreements could negativelyimpact our business.Our collaborators may have primary responsibility for the regulatory approval and, ultimately, marketing and distribution of our drug candidate in theterritory or territories under the applicable collaboration. We may have limited or no control over the amount and timing of resources that any of thesecollaborators will dedicate to such activities. This is the case for our ralinepag and etrasimod license agreement with Everest and for our lorcaserinTransaction Agreement with Eisai.When we enter collaboration agreements, we are subject to a number of other risks, including: •our collaborators may not comply with applicable regulatory guidelines, which could adversely impact the commercialization or developmentof the drug candidate; •there could be disagreements regarding the agreements or the study or development that delay or terminate the commercialization, research,study or development, delay or eliminate potential payments under the agreements or increase our costs under or outside of the agreements; •our collaborators may not effectively allocate adequate resources or may have limited experience in a particular territory; and26 •our collaborators may not perform as expected, including with regard to making any required payments, and the agreements may not provideadequate protection or may not be effectively enforced.We or our collaborators might terminate our agreements in certain circumstances or amend the terms of our agreement, and investors and analysts may notview any termination or amendments as favorable.We are currently responsible for manufacturing lorcaserin and certain other drugs. We also rely on other companies, including third-partymanufacturers and sole-source suppliers, and we or such other companies may encounter failures or difficulties or not receive or provide adequatesupply, which could adversely affect development or commercialization.Our drug product manufacturing facility in Switzerland is currently the only source for finished drug product of lorcaserin. If the sale of theManufacturing Operations is completed, we expect that the purchaser will become the only current source for finished drug product of lorcaserin.In addition, we do not own or operate manufacturing facilities that can produce active pharmaceutical ingredient, or API, intermediates and othermaterial required to make our drug candidates or lorcaserin. Instead, we currently contract with other companies to supply API, intermediates and othermaterials. Certain of these materials are available from only one or a small number of suppliers, and using a new supplier, if available, could result insubstantial delay and greater cost. Our dependence on single or limited sources of materials may adversely affect our ability to develop and deliver drugproducts on a timely and competitive basis, or at all.Any performance failure on the part of us or a third-party manufacturer could result in a product recall or seizure, delay or otherwise adversely affectsales of an approved product or the clinical development or regulatory approval of lorcaserin or one or more of our other drug candidates. We or third-partymanufacturers may encounter difficulties involving production yields, regulatory compliance, lot release, quality control and quality assurance, as well asshortages of qualified personnel. For example, in December 2014, Eisai and we discovered that a small number of bottles of lorcaserin in a limited number oflots had a missing or incomplete label, and, as a precautionary measure, Eisai voluntarily initiated a recall from wholesalers of the involved lots forinspection.The ability to adequately and timely manufacture and supply drug product is dependent on the uninterrupted and efficient operation of themanufacturing facilities, which is impacted by many manufacturing variables, including: •availability or contamination of raw materials and components used in the manufacturing process, particularly those for which we have noother source or supplier; •capacity of our facilities or those of our contract manufacturers; •having the ability to adjust to changes in actual or anticipated use of the facility, including with respect to having sufficient capacity and asufficient number of qualified personnel; •facility contamination by microorganisms or viruses or cross contamination; •compliance with regulatory requirements, including inspectional notices of violation and warning letters; •maintenance and renewal of any required licenses or certifications; •changes in actual or forecasted demand; •timing and number of production runs; •production success rates and bulk drug yields; and •timing and outcome of product quality testing.In addition, we or our third-party manufacturers may encounter delays and problems in manufacturing our drug candidates or drugs for a variety ofreasons, including accidents during operation, failure of equipment, delays in receiving materials, natural or other disasters, political or governmental unrestor changes, social unrest, intentional misconduct or other factors inherent in operating complex manufacturing facilities. Commercially available startingmaterials, reagents and excipients may be or become scarce or more expensive to procure, and we may not be able to obtain favorable terms in agreementswith subcontractors. We or our third-party manufacturers may not be able to operate our respective manufacturing facilities in a cost-effective manner or in atime frame that is consistent with our expected future manufacturing needs. If we or our third-party manufacturers cease or interrupt production or if our third-party manufacturers and other service providers fail to supply materials, products or services to us for any reason, such interruption could delay progress onour programs, or interrupt the commercial supply, with the potential for additional costs and lost revenues. If this were to occur, we may also need to seekalternative means to fulfill our manufacturing needs.27We may not be able to enter into or maintain agreements with manufacturers whose facilities and procedures comply with applicable law.Manufacturers are subject to ongoing periodic inspection (which may be unannounced) by the FDA, the DEA, corresponding state and foreign authoritiesand other regulatory authorities to ensure strict compliance with Current Good Manufacturing Practices, or cGMPs, regulations and other applicablegovernment regulations and corresponding foreign standards. We do not have control over a third-party manufacturer’s compliance with these regulationsand standards. In addition, we have contracted with Siegfried to provide to us certain business and technical services, including safety, health andenvironmental services. We are, therefore, relying at least in part on Siegfried’s judgment, experience and expertise. We intend to reduce or eliminate ourdependence on Siegfried for such business and technical services, and any changes may result in increased cost, additional risk or otherwise negativelyimpact our operations. If we or one of our manufacturers or other company in the supply chain fail to maintain compliance or otherwise experience setbacks,we or they could be subject to civil or criminal penalties, the production of one or more of our drug candidates or lorcaserin could be interrupted orsuspended, or our product could be recalled or withdrawn, resulting in delays, additional costs and potentially lost revenues.Our drug candidates are subject to extensive regulation, and we may not receive required regulatory approvals, or timely approvals, for any of ourdrug candidates.Preclinical and clinical development, manufacturing, labeling, packaging, storage, recordkeeping, advertising, promotion, export, marketing anddistribution, and other activities relating to developing and manufacturing drugs are subject to extensive regulation by the FDA and other regulatoryagencies. We are subject to periodic inspections (which may be unannounced) by the FDA, the DEA and other regulatory agencies, including inspections atour Swiss manufacturing facility. Failure to comply with applicable regulatory requirements may, either before or after product approval, subject us toadministrative or judicially imposed sanctions that may negatively impact research and development or commercialization, or otherwise negatively impactour business. Regulatory agencies have in the past inspected certain aspects of our business in the United States and Switzerland, and we were provided withobservations of objectionable conditions or practices with respect to our business in the United States. There is no assurance that regulatory agencies will notprovide us with observations in future inspections or that we satisfactorily addressed observations provided to us in past inspections.Regulatory approval of a drug candidate is not guaranteed, and our business and reputation may be harmed by any failure or significant delay inreceiving regulatory approval. The number and types of preclinical studies and clinical trials that will be required for FDA approval varies depending on thedrug candidate, the disease or condition that the drug candidate is designed to target and the regulations applicable to any particular drug candidate. Despitethe time and expense exerted in preclinical and clinical studies, failure can occur at any stage, and we could encounter problems that cause us to abandonclinical trials or to repeat or perform additional preclinical studies and clinical trials.We cannot predict when or whether, or assure you that, our collaborators’ or our past or any future regulatory submissions or responses will besufficient to the applicable regulatory authority or others, that the applicable regulatory authority or others will consider data or our analyses, interpretationsor procedures related to any of our drug candidates as sufficient or persuasive, or that any regulatory authority will ever approve any of our drug candidates inthe future.To market any drugs outside of the United States, we and our current or future collaborators must comply with numerous and varying regulatoryrequirements of other countries. Approval procedures vary among countries and can involve additional product testing and additional administrative reviewperiods. The time required to obtain approval in other countries might differ from that required to obtain FDA approval. The regulatory approval process inother countries may include all of the risks associated with FDA approval as well as additional risks, some of which may be unanticipated. The approval bythe FDA or any other regulatory authority does not assure or predict with any certainty that any other regulatory authority will approve the drug.In addition, existing regulatory policies and laws may change. We cannot predict the likelihood, nature or extent of new government regulation, eitherin the United States or in other countries, or the impact on our drug candidates or drugs. For example, new FDA regulation could delay or prevent marketingapprovals, increase the cost of research and development, and result in narrower product labeling and expensive post-marketing requirements.Our activities and drugs will still be subject to extensive postmarketing regulation if approved.Following regulatory approval of any of our drug candidates, we and our collaborators will be subject to ongoing obligations and continuedregulatory review from the FDA and other applicable regulatory agencies, such as continued adverse event reporting requirements. There may also beadditional postmarketing obligations imposed by the FDA or other regulatory agencies. These obligations may result in significant expense and limit theability to commercialize such drugs.The FDA or other regulatory agencies may also require that the sponsor of the NDA or foreign equivalent, as applicable, conduct additional clinicaltrials to further assess approved drugs after approval under a post-approval commitment. Such additional studies may be costly and may impact thecommercialization of the drug. For example, as part of the approval of BELVIQ, the FDA required the conduct of the CVOT described above as well aspostmarketing studies to assess the safety and efficacy of BELVIQ for28weight management in obese pediatric and adolescent patients. Along with being costly and time consuming, a delay or unfavorable results from these trialscould negatively impact market acceptance of BELVIQ; limit the revenues we generate from sales; result in BELVIQ’s withdrawal from the market;negatively impact the potential approval of lorcaserin in other territories for weight management, for other indications, in combination with other agents orusing different formulations; and result in litigation.The FDA or other regulatory agencies may also impose significant restrictions on the indicated uses for which a drug may be marketed. Additionally,the FDA may require a Risk Evaluation and Mitigation Strategies, or REMS, study, including in connection with a drug’s approval, to help ensure that thebenefits of the drug outweigh its risks. A REMS may be required to include various elements, such as a medication guide or patient package insert, acommunication plan to educate healthcare providers of the drug’s risks, limitations on who may prescribe or dispense the drug, requirements that patientsenroll in a registry or undergo certain health evaluations or other measures that the FDA deems necessary to ensure the safe use of the drug.With regard to any of drug that receives regulatory approval, the labeling, packaging, adverse event reporting, storage, advertising and promotion forthe drug will be subject to extensive regulatory requirements. We and the manufacturers of our products are also required to comply with cGMP regulations,which include requirements relating to quality control and quality assurance, as well as the corresponding maintenance of records and documentation.Further, regulatory agencies must approve these manufacturing facilities before they can be used to manufacture our products, and these facilities are subjectto ongoing regulatory inspections. In addition, regulatory agencies subject a drug, its manufacturer and the manufacturer’s facilities to continual review andinspections. The subsequent discovery of previously unknown problems with a drug, including adverse events of unanticipated severity or frequency, orproblems with the facility where the drug is manufactured, may result in restrictions on the marketing of that drug, up to and including withdrawal of the drugfrom the market. In the United States, the DEA and comparable state-level agencies also heavily regulate the manufacturing, holding, processing, security,recordkeeping and distribution of drugs that are considered controlled substances, and the DEA periodically inspects facilities for compliance with its rulesand regulations.Our ability to generate revenues from any of our drugs that receive regulatory approval will be subject to a variety of risks, many of which are out ofour control.Any drug that may be approved for marketing may not gain market acceptance among patients, healthcare providers, healthcare payers or the medicalcommunity. We believe that the degree of market acceptance and our ability to generate revenues from such products will depend on a number of factors,including: •timing of market introduction of our drugs and competitive drugs and alternative treatments; •actual and perceived efficacy and safety of our drugs; •incidence and severity of any side effects; •potential or perceived advantages or disadvantages as compared to alternative treatments; •effectiveness of sales, marketing and distribution support; •price of our future products, both in absolute terms and relative to alternative treatments; •the general marketplace for the particular drug; •the effect of current and future healthcare laws on our drug candidates; •availability of coverage and adequate reimbursement from government and other third-party payers; and •product labeling or product insert requirements of the FDA or other regulatory authorities.If our approved drugs fail to achieve market acceptance, we may not be able to generate significant revenues to be profitable.Collaboration relationships may lead to disputes and delays in drug development and commercialization, and we may not realize the full commercialpotential of our drug candidates or drugs.We may have conflicts with our prospective, current or past collaborators, such as conflicts concerning rights and obligations under our agreements,the interpretation of preclinical or clinical data, the achievement of milestone or other payments, the ownership of intellectual property, or research anddevelopment, regulatory, commercialization or other strategy. Collaborators may stop supporting our drug candidates or drugs, including if they no longerview the program as in their best financial or other interests or they develop or obtain rights to competing drug candidates or drugs. In addition, collaboratorsmay fail to effectively develop, obtain approval for or commercialize our drugs, which may result in us not realizing their full commercial potential. If anyconflicts arise with any of our current, past or prospective collaborators, the other party may act in a manner that is adverse to our interests. Any such29disagreement could result in one or more of the following, each of which could delay, or lead to termination of, development or commercialization of ourdrug candidates or drugs, and in turn prevent us from generating revenues: •unwillingness on the part of a collaborator to pay for studies or other research, milestones, royalties or other payments that we believe are dueto us under a collaboration; •uncertainty regarding ownership of intellectual property rights arising from our collaboration activities, which could prevent us from enteringinto additional collaborations; •unwillingness on the part of a collaborator to keep us informed regarding the progress of its development, regulatory, commercialization,pharmacovigilance or other activities or to permit public disclosure of the results of those activities; •slowing or cessation of a collaborator’s research, development, regulatory or commercialization efforts with respect to our drug candidates ordrugs; or •litigation or arbitration.We have obtained orphan drug designation from the FDA for ralinepag for the treatment of PAH, but we may be unable to maintain the benefitsassociated with orphan drug designation, including the potential for market exclusivity.Under the Orphan Drug Act, the FDA may grant orphan drug designation to a drug intended to treat a rare disease or condition, which is defined as oneoccurring in a patient population of fewer than 200,000 in the United States, or a patient population greater than 200,000 in the United States where there isno reasonable expectation that the cost of developing the drug will be recovered from sales in the United States. In the United States, orphan drugdesignation entitles a party to financial incentives such as opportunities for grant funding towards clinical trial costs, tax advantages and user-fee waivers. Inaddition, if a drug that has orphan drug designation subsequently receives the first FDA approval for the disease for which it has such designation, the drug isentitled to orphan drug exclusivity, which means that the FDA may not approve any other applications to market the same drug for the same indication forseven years, except in limited circumstances, such as a showing of clinical superiority to the drug with orphan drug exclusivity or where the manufacturer isunable to assure sufficient drug quantity.Even though ralinepag has been granted orphan drug status for the treatment of PAH, exclusive marketing rights in the United States may be limited ifwe seek approval for an indication broader than the orphan-designated indication or may be lost if the FDA later determines that the request for designationwas materially defective or if the manufacturer is unable to assure sufficient quantities of the drug to meet the needs of patients with the rare disease orcondition. Further, even if we obtain orphan drug exclusivity for a drug, that exclusivity may not effectively protect the drug from competition becausedifferent drugs with different active moieties (which is the molecule or ion responsible for the action of the drug substance) can be approved for the samecondition. Even after an orphan drug is approved, the FDA can subsequently approve the same drug with the same active moiety for the same condition if theFDA concludes that the later drug is safer, more effective, or makes a major contribution to patient care. Orphan drug designation neither shortens thedevelopment time or regulatory review time of a drug nor gives the drug any advantage in the regulatory review or approval process.Setbacks and consolidation in the pharmaceutical and biotechnology industries could make entering into agreements with pharmaceutical companies tocollaborate or commercialize our drugs more difficult and diminish our revenues.Setbacks in the pharmaceutical and biotechnology industries, such as those caused by safety concerns relating to drugs or drug candidates, as well ascompetition from generic drugs, litigation and industry consolidation, may have an adverse effect on us, including by making it more difficult to enter intoagreements with pharmaceutical companies to collaborate or commercialize our drugs and diminishing our revenues. For example, the FDA may be morecautious in approving our drug candidates based on safety concerns relating to these or other drugs or drug candidates, or pharmaceutical companies may beless willing to enter into new collaborations or continue existing collaborations if they are integrating a new operation as a result of a merger or acquisition orif their therapeutic areas of focus change following a merger.We and our collaborators may from time to time rely on third parties to conduct clinical trials and preclinical studies. If those parties do not complywith regulatory and contractual requirements, successfully carry out their contractual obligations or meet expected deadlines, our drug candidatesmay not advance in a timely manner or at all.In the course of our discovery, preclinical testing and clinical trials, we and our collaborators may from time to time rely on third parties, includinglaboratories, investigators, clinical research organizations and manufacturers, to perform critical services. For example, we rely on third parties to conduct ourclinical trials and many of our preclinical studies. Clinical research organizations are responsible for many aspects of the trials, including finding andenrolling subjects for testing and administering the trials. Although we rely on these third parties to conduct our clinical trials, we are responsible forensuring that each of our clinical trials is conducted in accordance with its investigational plan and protocol. Moreover, the FDA and foreign regulatoryauthorities require us to comply30with regulations and standards, commonly referred to as Good Clinical Practices, or GCPs, for conducting, monitoring, recording and reporting the results ofclinical trials to ensure that the data and results are scientifically credible and accurate and that the trial subjects are adequately informed of the potentialrisks of participating in clinical trials. Our reliance on third parties does not relieve us of these responsibilities and requirements. These third parties may notbe available when we need them or, if they are available, may not comply with all regulatory and contractual requirements or may not otherwise perform theirservices in a timely or acceptable manner, and we may need to enter into new arrangements with alternative third parties and our preclinical studies or clinicaltrials may be extended, delayed or terminated. These independent third parties may also have relationships with other commercial entities, some of whichmay compete with us. In addition, if such third parties fail to perform their obligations in compliance with regulatory requirements and our protocols, ourpreclinical studies or clinical trials may not meet regulatory requirements or may need to be repeated. As a result of our dependence on third parties, we mayface delays or failures outside of our direct control. These risks also apply to the development activities of collaborators, and we do not control their researchand development, clinical trial or regulatory activities.We may participate in new strategic transactions that could impact our liquidity, increase our expenses, present significant distractions to ourmanagement and be viewed as unfavorable.From time to time we consider strategic transactions, such as out-licensing or in-licensing of compounds or technologies, acquisitions of companiesand asset purchases. Additional potential transactions we may consider include a variety of different business arrangements, such as strategic collaborations,joint ventures, spin-offs, restructurings, divestitures, business combinations and investments. In addition, another entity may pursue us as an acquisitiontarget. Any such transaction may be viewed as unfavorable by our stockholders or others and may require us to incur non-recurring or other charges, maycreate potential liabilities, may increase our near- and long-term expenditures and may pose significant integration challenges, require additional expertise ordisrupt our management or business, which could harm our operations and financial results.As part of an effort to enter into significant transactions, we conduct business, legal and financial due diligence with the goal of identifying andevaluating material risks involved in the transaction. Despite our efforts, we ultimately may be unsuccessful in ascertaining or evaluating all such risks and,as a result, might not realize the intended advantages of the transaction. If we fail to realize the expected benefits from any transaction we may consummate,whether as a result of unidentified risks, integration difficulties, regulatory setbacks or other events, our business, results of operations and financialcondition could be adversely affected.We may incur substantial liabilities for any product liability claims or otherwise as a drug product manufacturer.We develop, test, manufacture and expect to commercialize drugs for use by humans. We face an inherent risk of product liability exposure related tothe testing of our drug candidates in clinical trials, and an even greater risk with the commercialization of lorcaserin as well as any other drug that may beapproved for marketing. In addition, under our agreement with Eisai, Arena GmbH and Eisai will, for a limited period of time, in general share in lossesresulting from third-party product liability claims relating to lorcaserin, with certain limited exceptions.Whether or not we are ultimately successful in any product liability or related litigation, such litigation would consume substantial amounts of ourfinancial and managerial resources, and might result in adverse publicity, all of which would impair our business. In addition, damages awarded in a productliability action could be substantial and could have a negative impact on our financial condition.An individual may bring a liability claim against us if one of our drugs or drug candidates causes, or merely appears to have caused, an injury.Regardless of merit or eventual outcome, liability claims may result in: •decreased demand for our drug; •injury to our reputation; •increased difficulty to attract, or withdrawal of, clinical trial subjects; •costs of related litigation; •substantial monetary awards to subjects or other claimants; •loss of revenues; and •the inability to commercialize our drug candidates.We have limited product liability insurance that covers our clinical trials and products. We may not be able to maintain or obtain insurance coverageat a reasonable cost, and we may not have insurance coverage that will be adequate to satisfy any liability that may arise, which could have an adverse effecton our results of operations and financial condition.31Arena GmbH manufactures BELVIQ and other products for commercialization, and lorcaserin and other drug candidates for clinical trials or otherstudies and potentially commercialization. Arena GmbH is subject to liability for non-performance, product recalls and breaches of the agreements with ourcollaborators and other third parties. We expect that even if the sale of its Manufacturing Operations to Siegfried is completed, Arena GmbH will retainliability for its actions and omissions that precede the closing of the sale.We have significant contractual obligations that may adversely affect our cash flow, cash position and stock price.We have long-term leases on real properties and other contractual obligations. If we are unable to generate cash from operations sufficient to meet ourfinancial obligations, we will need to obtain additional funds from other sources, which may include one or more financings. However, we may be unable toobtain sufficient additional funds when we need them on favorable terms or at all. The sale of equity or convertible debt securities or other financingtransaction in the future may be dilutive to our stockholders, and some financing arrangements may require us to enter into covenants that would furtherrestrict certain business activities or our ability to incur additional indebtedness or conduct other financing transactions, and may contain other terms that arenot favorable to our stockholders or us.Also, if we are unable to generate cash from operations or obtain additional funds from other sources sufficient to meet our contractual obligations, orwe need to use existing cash to fund our contractual obligations, we may have to delay or curtail some or all of our development and commercializationprograms, sell or license some or all of our assets on terms that you or others may view as unfavorable, or default under our agreements. Our contractualobligations could have significant additional negative consequences, including, without limitation: •increasing our vulnerability to general adverse economic conditions; •limiting our ability to obtain additional funds; •placing us at a possible competitive disadvantage to less leveraged competitors and competitors that have better access to capital resources;and •litigation or other disagreements.We may be subject, directly or indirectly, to federal and state healthcare laws, including but not limited to fraud and abuse and false claims laws. If weare unable to comply, or have not fully complied, with such laws, we could face substantial penalties and prosecution.In the United States, drug manufacturers and marketers are subject to various state and federal fraud and abuse laws, including, without limitation, theFederal Anti-Kickback Statute and Federal False Claims Act. There are similar laws in other countries. These laws may impact, among other things, theresearch, manufacturing, sales, marketing and education programs for our drugs.The Federal Anti-Kickback Statute prohibits persons and entities from knowingly and willingly soliciting, offering, receiving or providing anyremuneration, directly or indirectly, in exchange for or to induce either the referral of an individual, or the purchase, lease, order or the furnishing or arrangingfor, a good, item, facility or service, for which payment may be made, in whole or in part, under a federal healthcare program such as the Medicare andMedicaid programs. Several courts have interpreted the statute’s intent requirement to mean that if any one purpose of an arrangement involvingremuneration is to induce referrals of federal healthcare covered business, the statute has been violated. The Federal Anti-Kickback Statute is broad and,despite a series of narrow statutory exceptions and regulatory safe harbors, prohibits many arrangements and practices that are lawful in businesses outside ofthe healthcare industry. Moreover, the ACA, among other things, amended the intent requirement of the Federal Anti-Kickback Statute and certain criminalhealthcare fraud statutes. A person or entity no longer needs to have actual knowledge of these statutes or specific intent to violate them. The ACA alsoprovides that the government may assert that a claim including items or services resulting from a violation of the Federal Anti-Kickback Statute constitutes afalse or fraudulent claim for purposes of the Federal Civil False Claims Act. Many states have also adopted laws similar to the Federal Anti-Kickback Statute,some of which apply to the referral of patients for healthcare items or services reimbursed by any source, not only the Medicare and Medicaid programs.The Federal Civil False Claims Act prohibits, among other things, persons or entities from knowingly presenting, or causing to be presented, a falseclaim to, or the knowing use of false statements to obtain payment from the federal government. Suits filed under the Federal Civil False Claims Act can bebrought by any individual on behalf of the government, known as “qui tam” actions, and such individuals, commonly known as “whistleblowers,” may sharein any amounts paid by the entity to the government in fines or settlement. The filing of qui tam actions has caused a number of pharmaceutical, medicaldevice and other healthcare companies to have to defend a Federal Civil False Claims Act action. When an entity is determined to have violated the FederalCivil False Claims Act, it may be required to pay up to three times the actual damages sustained by the government, plus civil penalties for each separatefalse claim, in addition to other penalties that may apply. Various states have also enacted laws modeled after the Federal Civil False Claims Act, some ofwhich are broader in scope and may apply regardless of payer.32The Federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, created federal criminal statutes that prohibit, among otheractions, knowingly and willfully executing, or attempting to execute, a scheme to defraud any healthcare benefit program, including private third-partypayers, knowingly and willfully embezzling or stealing from a healthcare benefit program, willfully obstructing a criminal investigation of a healthcareoffense, and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false, fictitious or fraudulent statement inconnection with the delivery of or payment for healthcare benefits, items or services. Additionally, the civil monetary penalties statute imposes penaltiesagainst any person or entity that, among other things, is determined to have presented or caused to be presented a claim to a federal health program that theperson knows or should know is for an item or service that was not provided as claimed or is false or fraudulent. The Federal Physician Payments Sunshine Act, created under the ACA, and its implementing regulations requires certain manufacturers of drugs,devices, biologicals and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program (with certainexceptions) to report annually to the US Department of Health and Human Services, or HHS, information related to payments or other transfers of value madeto physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors) and teaching hospitals, as well as ownership and investmentinterests held by physicians and their immediate family members.We may be subject to data privacy and security regulation by both the federal government and the states in which we conduct our business. HIPAA, asamended by the Health Information Technology for Economic and Clinical Health Act, or HITECH, and their respective implementing regulations, imposespecified requirements relating to the privacy, security and transmission of individually identifiable health information. Further, we may also be subject tostate health information privacy and data breach notification laws which govern the collection, use, disclosure, and protection of health-related and otherpersonal information, many of which differ from each other in significant ways and often are not pre-empted by HIPAA, thus requiring additional complianceefforts.Additionally, the Drug Supply Chain Security Act imposes obligations on manufacturers of pharmaceutical products, among others, related to producttracking and tracing. Among the requirements, manufacturers will be required to provide certain information regarding the drug product to individuals andentities to which product ownership is transferred, label drug product with a product identifier, and keep certain records regarding the drug product. Thetransfer of information to subsequent product owners by manufacturers will eventually be required to be done electronically. Manufacturers will also berequired to verify that purchasers of the manufacturers’ products are appropriately licensed. Further, manufacturers will have drug product investigation,quarantine, disposition, and notification responsibilities related to counterfeit, diverted, stolen, and intentionally adulterated products, as well as productsthat are the subject of fraudulent transactions or which are otherwise unfit for distribution such that they would be reasonably likely to result in serious healthconsequences or death.We are unable to predict whether we could be subject to actions under any of these fraud and abuse or other laws, or the impact of such actions. If weare found to be in violation of any of the laws described above and other applicable state and federal fraud and abuse laws, we may be subject to penalties,including civil, criminal and/or administrative penalties, damages, fines, individual imprisonment, disgorgement, possible exclusion from governmenthealthcare reimbursement programs, integrity oversight and reporting obligations to resolve allegations of non-compliance with these laws, and thecurtailment or restructuring of our operations, all of which could have a material adverse effect on our business and results of operations.We may not be able to effectively integrate, manage or maintain our international operations, and such difficulty could adversely affect our businessoperations, financial condition, results of operations and stock price.The headquarters of our operations outside of the United States is in Switzerland. Activities conducted in Switzerland include clinical operations andregulatory, manufacturing, quality control, quality assurance, development of manufacturing processes, qualifying suppliers and otherwise managing aspectsof the supply chain, regulatory compliance, distribution of finished products, alliance management, and strategic planning and development. We also havedrug candidates in clinical trials outside of the United States. There are significant risks associated with foreign operations, including, but not limited to,compliance with local laws and regulations, the protection of our intellectual property, the ability to integrate our corporate culture with local customs andcultures, the distraction to our management, foreign currency exchange rates and the impact of shifts in the United States and local economies on those rates,and integration of our policies and procedures, including disclosure controls and procedures and internal control over financial reporting, with ourinternational operations.With respect to local laws and regulations, the European Union, Switzerland and certain other foreign territories have restrictions on the transfer, useand maintenance of certain personal data, including providing that transfers of personal data outside of their territories may only take place if the country towhich the personal data is transferred ensures an “adequate” level of privacy protection. The European Commission has previously found that the UnitedStates did not provide adequate levels of protection. In addition, the European Commission has approved a data protection regulation, known as the GeneralData Protection Regulation, or GDPR, which is scheduled to become effective in May 2018. The GDPR contains new provisions specifically directed at theprocessing of health information, higher sanctions and extra-territoriality measures intended to bring non-EU companies under the regulation. In the futurewe may expand our business operations to include additional operations in the EU, including potentially33conducting preclinical and clinical trials. With such expansion, we would be subject to increased governmental regulation, including the GDPR, in the EUcountries in which we operate, including restrictions on data transfers that may negatively impact our ability and increase our costs to maintain internationaloperations.In 2015 and 2016, we initiated measures to reduce our expenditures and streamline our operations in Switzerland, including changes with respect tothe staffing, process, procedures and strategy relating to our Swiss manufacturing facility and our ongoing Phase 2 clinical trials. These staffing and otherchanges may increase risks related to our international operations as well as our operations in general.We use biological materials, hazardous materials, chemicals and radioactive compounds.Our activities involve the use of potentially harmful biological materials, as well as materials, chemicals and various radioactive compounds thatcould be hazardous to human health and safety or the environment. These materials and various wastes resulting from their use are stored at our facilitypending ultimate use and disposal. We cannot completely eliminate the risk of contamination, which could cause: •interruption of our development or manufacturing efforts; •injury to our employees and others; •environmental damage resulting in costly clean up; and •liabilities under domestic or foreign laws and regulations governing the use, storage, handling and disposal of these materials and specifiedwaste products.In such an event, we may be held liable for any resulting damages, and any such liability could exceed our resources. Although we carry insurance inamounts and type that we consider commercially reasonable, we cannot be certain that the coverage or coverage limits of our insurance policies will beadequate, and we do not have insurance coverage for losses relating to an interruption of our research and development efforts caused by contamination.Our business and operations might be adversely affected by business disruptions and security breaches, including any cybersecurity incidents.Our US operations are located in a business park in San Diego, and our clinical operations outside the US are located in single building in Zug,Switzerland. We also have a drug product manufacturing facility in Zofingen, Switzerland, and we expect that, at least for the near-term, this facility will bethe sole location for the manufacturing of lorcaserin finished drug product, whether or not the sale of such Manufacturing Operations to Siegfried iscompleted. We depend on our facilities and on collaborators, contractors and vendors for the continued operation of our business, some of whom are locatedin Europe and Asia. Natural disasters or other catastrophic events, including interruptions in the supply of natural resources, political and governmentalchanges, disruption in transportation networks or delivery services, severe weather conditions, wildfires and other fires, explosions, actions of animal rightsactivists, terrorist attacks, earthquakes and wars could disrupt our operations or those of our collaborators, contractors and vendors.We depend on the efficient and uninterrupted operation of our computer and communications systems, which we use for, among other things, sensitivecompany data, including our financial data, intellectual property and other proprietary business information.While certain of our operations have business continuity and disaster recovery plans and other security measures intended to prevent and minimizethe impact of IT-related interruptions, our IT infrastructure and the IT infrastructure of our current and any future collaborators, contractors and vendors arevulnerable to damage from cyberattacks, computer viruses, unauthorized access, electrical failures and natural disasters or other catastrophic events. Wecould experience failures in our information systems and computer servers, which could result in an interruption of our normal business operations andrequire substantial expenditure of financial and administrative resources to remedy. System failures, accidents or security breaches can cause interruptions inour operations and can result in a material disruption of our research and development programs, manufacturing or commercialization activities and otherbusiness operations. The loss of data from completed or future studies or clinical trials could result in delays in our research, development or regulatoryapproval efforts and significantly increase our costs to recover or reproduce the data. Similarly, we rely on third parties to conduct studies and clinical trialsof our drug candidates, supply materials for the manufacture of our drug candidates and lorcaserin, and warehouse, market and distribute lorcaserin, andsimilar events relating to these third parties’ computer systems could also have a material adverse effect on our business. To the extent that any disruption orsecurity breach were to result in a loss of, or damage to, our data or applications, or inappropriate disclosure of confidential or proprietary information, wecould incur liabilities and the development of any of our other drug candidates and the commercialization of drugs could be delayed or otherwise adverselyaffected.34Even though we believe we carry commercially reasonable business interruption and liability insurance, and our contractors may carry liabilityinsurance that protect us in certain events, we might suffer losses as a result of business interruptions that exceed the coverage available under our and ourcontractors’ insurance policies or for which we or our contractors do not have coverage. For example, we are not insured against a terrorist attack. Any naturaldisaster or catastrophic event could have a significant negative impact on our operations and financial results. Moreover, any such event could delay ourresearch and development programs and adversely affect, which may include stopping, our commercial production.We and certain of our current and former employees and directors have been named as defendants in litigation that could result in substantial costs anddivert management’s attention.Beginning in September 2010, a number of lawsuits were filed against us and certain of our employees and directors on behalf of certain purchasers ofour common stock. The lawsuits in general include allegations that we and certain of our employees and directors violated laws by making materially falseand misleading statements regarding our BELVIQ trials, thereby artificially inflating the price of our common stock. The plaintiffs are seeking monetarydamages and other relief.We have reached a tentative settlement agreement regarding these lawsuits. Under the terms of the settlement agreement, and in exchange for a releaseof all claims by class members and a dismissal of the consolidated class action with prejudice, we have agreed (i) our insurers will pay class members and theirattorneys a total of approximately $12.025 million and (ii) we will pay class members and their attorneys approximately $11.975 million in either shares ofour common stock or cash at our election. The terms of the settlement agreement remain subject to final approval by the US District Court for the SouthernDistrict of California.There is no guarantee that the settlement will become final or that we will be successful in defending these lawsuits. Also, our insurance coverage maybe insufficient, our assets may be insufficient to cover any amounts that exceed our insurance coverage, and we may have to pay damage awards or otherwisemay enter into settlement arrangements in connection with such claims. A settlement of any of these lawsuits could involve the issuance of common stock orother equity, which may dilute your ownership interest. Any payments or settlement arrangements could have material adverse effects on our business,operating results, financial condition or your ownership interest. Even if the plaintiffs’ claims are not successful, this litigation could result in substantialcosts and significantly and adversely impact our reputation and divert management’s attention and resources, which could have a material adverse effect onour business, operating results or financial condition. In addition, such lawsuits may make it more difficult to finance our operations, obtain certain types ofinsurance (including directors’ and officers’ liability insurance), and attract and retain qualified executive officers, other employees and directors.Negative US and global economic conditions may pose challenges to our business strategy, which relies on funding from collaborators or the financialmarkets, and creates other financial risks for us.Negative conditions in the US or global economy, including financial markets, may adversely affect our business and the business of our current andprospective collaborators, distributors and licensees, which we sometimes refer to generally as our collaborators, and others with which we do or may conductbusiness. The duration and severity of these conditions is uncertain. If negative economic conditions persist or worsen, we may be unable to secure fundingto sustain our operations or to find suitable collaborators to advance our internal programs, even if we achieve positive results from our research anddevelopment or business development efforts. Such negative conditions could also impact commercialization of BELVIQ or any other drugs we develop aswell as our financial condition.From time to time, we may maintain a portfolio of investments in marketable debt securities, which are recorded at fair value. Although we haveestablished investment guidelines relative to diversification and maturity with the objectives of maintaining safety of principal and liquidity, we rely oncredit rating agencies to help evaluate the riskiness of investments, and such agencies may not accurately predict such risk. In addition, such agencies mayreduce the credit quality of our individual holdings, which could adversely affect their value. Lower credit quality and other market events, such as changesin interest rates and further deterioration in the credit markets, may have an adverse effect on the fair value of our investment holdings and cash position.Currency fluctuations may negatively affect our financial condition.We primarily spend and generate cash in US dollars and present our consolidated financial statements in US dollars. However, a portion of ourexpected and potential payments and receipts under our agreements are in foreign currencies, including Swiss francs. For example, payments and receiptsunder our agreements with Siegfried are required to be paid in Swiss francs. A fluctuation of the exchange rates of foreign currencies versus the US dollar maythus adversely affect our financial results, including cash balances, expenses and revenues. We may in the future enter into hedging transactions to try toreduce our foreign currency exposure, but there is no assurance that such transactions will occur or be successful.35Laws, rules and regulations relating to public companies may be costly and impact our ability to attract and retain directors and executive officers; ourdisclosure controls and procedures and our internal control over financial reporting may not prevent potential errors and fraud.Laws and regulations affecting public companies, including rules adopted by the SEC and by Nasdaq, as well as the laws and regulations of foreigngovernments, may result in increased costs to us, particularly as we continue to develop the required capabilities in the United States and abroad tocommercialize our products. These laws, rules and regulations could make it more difficult or costly for us to obtain certain types of insurance, includingdirectors’ and officers’ liability insurance, and we may be forced to accept reduced policy limits and coverage or incur substantially higher costs to obtain thesame or similar coverage. These laws, rules and regulations could also make it more difficult for us to attract and retain qualified persons to serve on our boardof directors, on our board committees or as executive officers. We cannot estimate accurately the amount or timing of additional costs we may incur torespond to these laws, rules and regulations.Our management does not expect that our disclosure controls and procedures or our internal control over financial reporting will prevent all potentialerrors and fraud. A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of thecontrol system are met. There are inherent limitations in all control systems, and no system of controls can provide absolute assurance that all control issuesand instances of fraud, if any, or misstatements due to error, if any, within the company have been detected. While we believe that our disclosure controls andprocedures and internal control over financial reporting are and have been effective at the reasonable assurance level, we intend to continue to examine andrefine our disclosure controls and procedures and internal control over financial reporting and to monitor ongoing developments in these areas.The recently passed comprehensive tax reform bill could adversely affect our business and financial condition. On December 22, 2017, President Trump signed into law new legislation that significantly revises the Internal Revenue Code of 1986, asamended. The newly enacted federal income tax law, among other things, contains significant changes to corporate taxation, including reduction of thecorporate tax rate from a top marginal rate of 35% to a flat rate of 21%, limitation of the tax deduction for interest expense to 30% of adjusted earnings(except for certain small businesses), limitation of the deduction for net operating losses to 80% of current year taxable income and elimination of netoperating loss carrybacks, one time taxation of offshore earnings at reduced rates regardless of whether they are repatriated, immediate deductions for certainnew investments instead of deductions for depreciation expense over time, and modifying or repealing many business deductions and credits (includingreducing the business tax credit for certain clinical testing expenses incurred in the testing of certain drugs for rare diseases or conditions). Notwithstandingthe reduction in the corporate income tax rate, the overall impact of the new federal tax law is uncertain and our business and financial condition could beadversely affected. In addition, it is uncertain if and to what extent various states will conform to the newly enacted federal tax law.Our ability to use net operating losses to offset future taxable income may be subject to limitations.As of December 31, 2017, we had federal and state net operating loss carryforwards of $1,120.0 million. Our federal net operating losscarryforwards ($721.4 million) will begin to expire, if not utilized, beginning in 2023, and our state net operating loss carryforwards ($398.6 million) beginexpiring in 2028. These net operating loss carryforwards could expire unused and be unavailable to offset future income tax liabilities. Under the newlyenacted federal income tax law, federal net operating losses incurred in 2018 and in future years may be carried forward indefinitely, but the deductibility ofsuch federal net operating losses is limited. It is uncertain if and to what extent various states will conform to the newly enacted federal tax law. In addition,under Section 382 of the Internal Revenue Code of 1986, as amended, and corresponding provisions of state law, if a corporation undergoes an “ownershipchange,” which is generally defined as a greater than 50% change, by value, in its equity ownership over a three-year period, the corporation’s ability to useits pre-change net operating loss carryforwards and other pre-change tax attributes to offset its post-change income or taxes may be limited. We haveexperienced ownership changes in the past and we may experience additional ownership changes in the future as a result of subsequent shifts in our stockownership, some of which may be outside of our control. If an ownership change occurs and our ability to use our net operating loss carryforwards ismaterially limited, it would harm our future operating results by effectively increasing our future tax obligations.Changes or modifications in financial accounting standards, including those related to revenue recognition, may harm our results of operations. From time to time, the Financial Accounting Standards Board, or FASB, either alone or jointly with other organizations, promulgates new accountingprinciples that could have an adverse impact on our financial position, results of operations or reported cash flows. In May 2014, the FASB issuedAccounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize the amount ofrevenue when promised goods or services are transferred to customers. The standard requires a company to recognize revenue to depict the transfer of goodsor services to customers in the36amount that reflects the consideration it expects to be entitled to receive in exchange for those goods or services. In August 2015, the FASB issued ASU2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delayed the effective date of the new standard fromJanuary 1, 2017 to January 1, 2018. The FASB also agreed to allow entities to choose to adopt the standard as of the original effective date. In March 2016,the FASB issued additional ASUs which clarified certain aspects of the new guidance. We are in the process of reviewing our revenue arrangements, which weexpect to include product sales, manufacturing support payments, royalty payments, other collaboration payments and toll manufacturing payments, and arenot yet able to estimate the anticipated impact to our consolidated financial statements from the implementation of the new standard as we continue tointerpret the principles of the new standard. Any difficulties in implementing this standard, or in adopting or implementing any other new accountingstandard, and to update or modify our internal controls as needed on a timely basis, could result in our failure to meet our financial reporting obligations,which could result in regulatory discipline and harm investors’ confidence in us. Finally, if we were to change our critical accounting estimates, includingthose related to the recognition of product or collaboration revenue, our operating results could be significantly affected.Risks Relating to Our Intellectual PropertyOur success is dependent on intellectual property rights held by us and third parties and our interest in these rights is complex and uncertain.Our success will depend on our own and on current or future collaborators’ abilities to obtain, maintain and defend patents. In particular, the patentsdirected to our drug candidates and drugs are important to developing and commercializing drugs and our revenue. We have numerous US and foreignpatents issued and patent applications pending for our technologies. There is no assurance that any of our patent applications will issue, or that any of thepatents will be enforceable or will cover a drug or other commercially significant technology or method, or that the patents will be held to be valid for theirexpected terms.The procedures for obtaining a patent are complex. These procedures require an analysis of the scientific technology related to the invention andmany sophisticated legal issues. Obtaining patent rights outside the United States often requires the translation of highly technical documents and animproper translation may jeopardize our patent protection. Ensuring adequate quality of translators and foreign patent attorneys is often very challenging.Consequently, the process for having our pending patent applications issue as patents will be difficult, complex and time consuming. Our patent position isvery uncertain and we do not know when, or if, we will obtain additional patents, or if the scope of the patents obtained will be sufficient to protect our drugs,or be considered sufficient by parties reviewing our patent positions pursuant to a potential marketing, licensing or financing transaction.In addition, other entities may challenge the validity or enforceability of our patents in litigation or administrative proceedings. We cannot makeassurances as to how much protection, if any, our patents will provide if we attempt to enforce them or they are challenged. It is possible that a competitor or ageneric pharmaceutical provider may successfully challenge our patents and those challenges may result in reduction or elimination of our patent coverage.We also rely on confidentiality agreements and trade secrets to protect our technologies. However, such information is difficult to protect. We requireour employees to contractually agree not to improperly use our confidential information or disclose it to others, but we may be unable to determine if ouremployees have conformed or will conform to their legal obligations under these agreements. We also enter into confidentiality agreements with prospectivecollaborators, collaborators, service providers and consultants, but we may not be able to adequately protect our trade secrets or other proprietary informationin the event of any unauthorized use or disclosure or the lawful development by others of this information. Many of our employees and consultants were, andmany of them may currently be, parties to confidentiality agreements with other pharmaceutical and biotechnology companies, and the use of ourtechnologies could violate these agreements. In addition, third parties may independently discover our trade secrets or other proprietary information.Some of our research and development collaborators and scientific consultants have rights to publish data and information to which we have rights.We generally seek to prevent our collaborators and consultants from disclosing scientific discoveries before we have the opportunity to file patentapplications on such discoveries. In some of our collaborations, we do not control our collaborators’ ability to disclose their own discoveries under thecollaboration and in some of our academic relationships we are limited to relatively short periods to review a proposed publication and file a patentapplication. If we cannot maintain confidentiality in connection with our collaborations and relationships, our ability to receive patent protection or protectour proprietary information will be impaired.We believe that the United States is by far the largest single market for pharmaceuticals in the world. Because of the critical nature of patent rights toour industry, changes in US patent laws could have a profound effect on our future profits, if any. It is unknown which, if any, patent laws will change, howchanges to the patent laws will ultimately be enforced by the courts and how it would impact our business.37A dispute regarding the infringement or misappropriation of our proprietary rights or the proprietary rights of others could be costly and result indelays or termination of our future research, development, manufacturing and sales activities.Our commercial success depends upon our ability to develop and manufacture our drugs and drug candidates, market and sell drugs, and conduct ourresearch and development activities without infringing or misappropriating the proprietary rights of others. There are many issued patents and pending patentapplications owned by others relating to research and development programs that could be determined to be similar, identical or superior to ours or ourlicensors or collaborators. We may be exposed to future litigation by others based on claims that our drugs, drug candidates, technologies or activitiesinfringe the intellectual property rights of others. Numerous issued patents and pending patent applications owned by others exist in the areas of our researchand development, including some which purport to allow the patent holder to control the use of all drugs that modulate a particular drug target regardless ofwhether the infringing drug bears any structural resemblance to a chemical compound known to the patent holder at the time of patent filing. Numerousissued patents and pending patent applications owned by others also exist in the therapeutic areas in which we are developing drugs. There are also numerousissued patents and pending patent applications owned by others that are directed to chemical compounds or synthetic processes that may be necessary oruseful to use in our research, development, manufacturing or commercialization activities. These could materially affect our ability to develop our drugcandidates or manufacture, import or sell drugs, and our activities, or those of our licensors or collaborators, could be determined to infringe these patents.Because patent applications can take many years to issue, there may be currently pending applications, unknown to us, which may later result in issuedpatents that our drugs, drug candidates or technologies may infringe. There also may be existing patents owned by others, of which we are not aware, that ourdrug candidates or technologies may infringe. Further, there may be issued patents or pending patent applications owned by others in fields relevant to ourbusiness, of which we are or may become aware, that we believe (i) are invalid, unenforceable, or we do not infringe; (ii) relate to immaterial portions of ouroverall research and development, manufacturing and commercialization efforts; or (iii) in the case of pending patent applications, the resulting patent wouldnot be granted or, if granted, would not likely be enforced in a manner that would materially impact such efforts. We cannot assure you that others holdingany of these patents or patent applications will not assert infringement claims against us and seek damages or enjoinment of our activities. We also cannotassure you that, in the event of litigation, we will be able to successfully assert non-infringement, unenforceability, invalidity or immateriality, or that anyinfringement claims will be resolved in our favor.In addition, others may infringe or misappropriate our proprietary rights. We may have to institute costly legal action to protect our intellectualproperty rights or may not be able to afford the costs of enforcing or defending our intellectual property rights.There could be significant litigation and other administrative proceedings in our industry that affect us regarding patent and other intellectualproperty rights. Any legal action or administrative action against us, or our collaborators, claiming damages or seeking to enjoin commercial activitiesrelating to our research and development, manufacturing and commercialization activities could: •require us, or our collaborators, to obtain a license which may not be available on commercially reasonable terms, if at all; •prevent us from importing, making, using, selling or offering to sell the subject matter claimed in patents held by others and subject us topotential liability for damages; •consume a substantial portion of our managerial, scientific and financial resources; or •be costly, regardless of the outcome.Furthermore, because of the substantial amount of pre-trial document and witness discovery required in connection with intellectual propertylitigation, there is a risk that some of our confidential information could be compromised. In addition, during the course of intellectual property litigation,there could be public announcements of the results of hearings, motions or other interim proceedings or developments. If securities analysts or investorsperceive these results to be negative, it could have a substantial adverse effect on the trading price of our common stock.We are aware of third-party patents, as well as third-party patent applications, that could adversely affect the potential commercialization of etrasimod.For example, we are aware of a third-party patent, as well as third-party patent applications, with broad claims to administering an S1P modulators by startingwith a lower dose and then increasing to a higher, standard daily dose. While we do not believe that any such claims that would cover the potentialcommercialization of etrasimod are valid and enforceable, we may be incorrect in this belief. In addition, other patents may issue from third-party patentapplications with respect to certain dosing regimens, which could also adversely affect the potential commercialization of etrasimod, if etrasimod isapproved with a specific dosing regimen.We have been contacted from time to time by third parties regarding their intellectual property rights, sometimes asserting that we may need a licenseto use their technologies. For example, a third party has communicated that it believes its issued US patents (one of which has subsequently expired) includepatent claims that cover lorcaserin or its use. If we fail to obtain any required licenses38or make any necessary changes to our technologies, we may become involved in expensive and time-consuming litigation or we may be unable to develop orcommercialize some or all of our drugs or drug candidates.We and Eisai have filed patent infringement lawsuits against ANDA filers relating to “Paragraph IV certifications.” While we intend to vigorouslyenforce our intellectual property rights relating to lorcaserin, we cannot predict the outcome of any litigation matter. For example, our existing patents couldbe invalidated, found unenforceable or found not to cover a generic form of lorcaserin. If an ANDA filer were to prevail in patent litigation and/or receiveapproval to sell a generic version of lorcaserin, lorcaserin would become subject to increased competition and our revenue would be adversely affected.We cannot protect our intellectual property rights throughout the world.Filing, prosecuting, defending and enforcing patents on all of our drug candidates throughout the world would be prohibitively expensive. The lawsof some foreign countries do not protect intellectual property rights to the same extent as the laws of the United States, and many companies haveencountered significant problems in protecting and defending such rights in foreign jurisdictions. Many countries, including certain countries in Europe,have compulsory licensing laws under which a patent owner may be compelled to grant licenses to third parties (for example, the patent owner has failed to“work” the invention in that country or the third party has patented improvements). In addition, many countries limit the enforceability of patents againstgovernment agencies or government contractors. In these countries, the patent owner may have limited remedies, which could materially diminish the valueof the patent. Compulsory licensing of life-saving drugs is also becoming increasingly popular in developing countries either through direct legislation orinternational initiatives. Such compulsory licenses could be extended to include some of our drug candidates, which could limit our potential revenueopportunities. Moreover, the legal systems of certain countries, particularly certain developing countries, do not favor the aggressive enforcement of patentsand other intellectual property protection, particularly those relating to pharmaceuticals, which makes it difficult for us to stop the infringement of ourpatents. Proceedings to enforce our patent rights in foreign jurisdictions could result in substantial cost and divert our efforts and attention from other aspectsof our business.Risks Relating to Our SecuritiesOur stock price will likely be volatile, and your investment in our stock could decline in value.Our stock price has fluctuated historically. From January 1, 2016, to March 9, 2018, the market price of our stock was as low as $11.30 per share and ashigh as $44.50 per share.Very few drug candidates being tested will ultimately receive regulatory approval, and companies in our industry sometimes experience significantvolatility in their stock price. Our stock price may fluctuate significantly depending on a variety of factors, including: •results or decisions affecting the development or commercialization of any of our drug candidates or drugs, including the results of studies,trials and other analyses; •the success, failure or setbacks of our or a perceived competitor’s drugs or drug candidates; •the timing of the development of our drug candidates; •discussions or recommendations affecting our drugs or drug candidates by the FDA or other reviewers of preclinical or clinical data or otherinformation related to our drug candidates or drugs; •regulatory actions or decisions or legislation affecting drugs or drug candidates, including ours and those of our competitors; •the commercial availability and success or failure of any of our drug candidates or lorcaserin; •the development and implementation of our continuing development and research plans, including outcome studies for lorcaserin; •the entrance into, or failure to enter into, a new collaboration or the modification or termination of an existing collaboration or other materialtransaction; •the timing and receipt by us of milestone and other payments or failing to achieve and receive the same; •fluctuation in prescriptions, sales or financial results (including with respect to revenue recognition) or inaccurate sales or cash forecasting; •accounting restatements and changes; •supply chain or manufacturing issues;39 •changes in our research and development budget or the research and development budgets of our existing or potential collaborators; •the introduction, development or withdrawal of drug candidates or drugs by others that target the same diseases and conditions that we or ourcollaborators target or the introduction of new drug discovery techniques; •expenses related to, and the results of, litigation, other disputes and other proceedings; •financing strategy or decisions; •the allocation of our resources; •our ability, or the perception by investors of our ability, to continue to meet all applicable requirements for continued listing of our commonstock on The Nasdaq Stock Market, and the possible delisting of our common stock if we are unable to do so; •developments in intellectual property rights or related announcements; and •capital market conditions.We are not able to control many of these factors. If our financial or scientific results in a particular period do not meet stockholders’ or analysts’expectations, our stock price may decline and such decline could be significant.We may be unable to comply with the applicable continued listing requirements of the Nasdaq Global Select Market.Our common stock is currently listed on the Nasdaq Global Select Market, or Nasdaq. In order to maintain this listing, we must satisfy minimumfinancial and other continued listing requirements and standards. There can be no assurance that we will be able to comply with the applicable listingstandards. If we were not able to comply with applicable listing standards, our shares of common stock would be subject to delisting. In the event that ourcommon stock is delisted from Nasdaq and is not eligible for quotation or listing on another market or exchange, trading of our common stock could beconducted only in the over-the-counter market or on an electronic bulletin board established for unlisted securities such as the Pink Sheets or the OTCBulletin Board. In such event, it could become more difficult to dispose of, or obtain accurate price quotations for, our common stock, and there would likelyalso be a reduction in our coverage by securities analysts and the news media, which could cause the price of our common stock to decline further.Any future equity or debt issuances or other financing transactions may have dilutive or adverse effects on our existing stockholders.We have been opportunistic in our efforts to obtain cash, and we expect to continue to evaluate various funding alternatives from time to time. Wehave primarily financed our operations, and we may continue to finance our operations, by issuing and selling our common stock or securities convertibleinto or exercisable for shares of our common stock. We may issue additional shares of common stock or convertible securities that could dilute yourownership in our company and may include terms that give new investors rights that are superior to yours. We have effective registration statements to sellshares of our common stock and certain other securities, and we may elect to sell shares pursuant to such registration from time to time, including pursuant toan Equity Distribution Agreement that we put in place in January 2017 with Citigroup Global Markets Inc. During the period from February through April2017, we sold 489,023 shares for aggregate gross proceeds of $7.4 million under the Equity Distribution Agreement, which permits total sales of up to $50.0million in the aggregate.Moreover, any issuances by us of equity securities may be at or below the prevailing market price of our common stock and in any event may have adilutive impact on your ownership interest, which could cause the market price of our common stock to decline. In addition, we may also raise additionalfunds through the incurrence of debt or other financing transaction, and the investors may have rights superior to your rights in the event we are notsuccessful and are forced to seek the protection of bankruptcy laws or the transaction may otherwise adversely affect our business prospects and existingstockholders.Our executive officers and directors may sell shares of their stock, and these sales could adversely affect our stock price.Sales of our stock by our executive officers and directors, or the perception that such sales may occur, could adversely affect the market price of ourstock. Our executive officers and directors may sell stock in the future, either as part, or outside, of trading plans under Rule 10b5-1 of the SEC.40There are a substantial number of shares of our common stock that may become eligible for future sale in the public market, and the sale of ourcommon stock could cause the market price of our common stock to fall.As of March 9, 2018, there were (i) options to purchase 5,716,398 shares of our common stock outstanding under our equity incentive plans at aweighted-average exercise price of $25.52 per share, (ii) 21,220 restricted stock unit awards outstanding under our equity incentive plans, and (iii) 937,739additional shares of common stock remaining issuable under our 2017 Long-Term Incentive Plan.Once issued, the shares described above will be available for immediate resale in the public market. The market price of our common stock coulddecline as a result of such resales due to the increased number of shares available for sale in the market. As of March 9, 2018, there were 39,401,783 shares ofour common stock outstanding.The holders of our common stock and other securities may take actions that are contrary to your interests, including selling their stock.A small number of stockholders may hold or acquire a significant amount of our outstanding stock. From time to time, there is a large short interest inour stock. These holders of such stock or positions may seek control of us, support transactions that we or you do not believe are favorable, and have intereststhat are different from yours. In addition, sales of a large number of shares of our stock by these large stockholders or other stockholders within a short periodof time could adversely affect our stock price.We may also be involved in disagreements with the holders of our stock, warrants or other securities in the future. Such disagreements may lead toproxy contests or litigation, which may be expensive and consume management’s time, involve settlements, the terms of which may not be favorable to us, orresult in other negative consequences to our business.Certain of our agreements, provisions in our charter documents, possible future agreements and Delaware law could delay or prevent a change inmanagement or a takeover attempt that you may consider to be in your best interests.There is a standstill provision in our marketing and supply agreement with Eisai, and we may enter into agreements with similar provisions. Inaddition, we may in the future adopt a stockholders’ rights agreement, which would cause substantial dilution to any person who attempts to acquire us in amanner or on terms not approved by our board of directors. These provisions or agreements, as well as other provisions in our certificate of incorporation andbylaws and under Delaware law, could delay or prevent the removal of directors and other management and could make more difficult a merger, tender offeror proxy contest involving us that you may consider to be in your best interests. For example, our charter provisions: •allow our board of directors to issue preferred stock without stockholder approval; •limit who can call a special meeting of stockholders; •eliminate stockholder action by written consent; and •establish advance notice requirements for nomination for election to the board of directors or for proposing matters to be acted upon atstockholders’ meetings. Item 1B. Unresolved Staff CommentsNone.41Item 2. PropertiesAs set forth in the table below, we lease approximately 336,000 square feet of research, development, warehouse and office space located at variousaddresses in the same business park in San Diego, California and own or lease approximately 153,000 square feet of laboratory, manufacturing, warehouseand office space located in the same business park in Zofingen, Switzerland. Location Own/ Lease Description6114 Nancy Ridge Drive, SanDiego, California Lease This chemical development facility consists of approximately 40,000 square feet(which includes approximately 18,000 of internal square feet and approximately22,000 square feet of integrated external space), of which approximately 5,000square feet is office space. We sublease this facility to a third party.6118 Nancy Ridge Drive, SanDiego, California Lease This facility of approximately 30,000 square feet consists of approximately 30%laboratory space and 70% office space. We sublease approximately 15,000 squarefeet of this space to Beacon and the rest is substantially unoccupied.6122-6124-6126 NancyRidge Drive, San Diego,California Lease This facility of approximately 68,000 square feet consists of approximately 28,500square feet of laboratory space, 37,500 square feet of office space and 2,000 squarefeet of warehouse space. We sublease this facility to a third party.6138-6150 Nancy RidgeDrive, San Diego, California Lease This facility of approximately 55,000 square feet consists of approximately 33,000square feet of laboratory space and 22,000 square feet of office space, which issubstantially unoccupied.6154 Nancy Ridge Drive, SanDiego, California Lease This facility of approximately 143,000 square feet consists of approximately131,000 square feet of office space and 12,000 square feet of warehouse space, whichis partially unoccupied.Zofingen, Switzerland Own This facility of approximately 134,000 square feet includes approximately 76,000square feet we occupy of which 39,000 square feet is manufacturing space, 30,000square feet is warehouse space and 7,000 square feet is office space. We lease theremaining 58,000 square feet of warehouse space to Siegfried.Zofingen, Switzerland Lease We lease from Siegfried a total of approximately 19,000 square feet, consisting ofapproximately 11,000 square feet of office space, 5,000 square feet of warehousespace and 3,000 square feet of laboratory space, in various facilities.Zug, Switzerland Lease We lease a total of approximately 4,500 square feet of office space. Under the Siegfried Transaction, we expect to transfer our owned and leased facilities in Zofingen, Switzerland to Siegfried, subject to the satisfactionor waiver of certain customary closing conditions specified in the Sale Agreement with Siegfried. We expect the remaining facilities to be sufficient for ourneeds for at least the near term. We have significantly more space in San Diego than we expect to need for the foreseeable future, and we have subleasedcertain of our space and are exploring subleasing additional unused space to reduce our expenses.Item 3. Legal ProceedingsBeginning on September 20, 2010, a number of complaints were filed in the US District Court for the Southern District of California, or District Court,against us and certain of our current and former employees and directors on behalf of certain purchasers of our common stock. The complaints were broughtas purported stockholder class actions, and, in general, include allegations that we and certain of our current and former employees and directors violatedfederal securities laws by making materially false and misleading statements regarding our BELVIQ program, thereby artificially inflating the price of ourcommon stock. The plaintiffs sought unspecified monetary damages and other relief. On August 8, 2011, the District Court consolidated the actions andappointed a lead plaintiff and lead counsel. On November 1, 2011, the lead plaintiff filed a consolidated amended complaint. On March 28, 2013, the DistrictCourt dismissed the consolidated amended complaint without prejudice. On May 13, 2013, the lead plaintiff filed a second consolidated amended complaint.On November 5, 2013, the District Court dismissed the second consolidated amended complaint without prejudice as to all parties except for Robert E.Hoffman, who was dismissed from the action with prejudice. On November 27, 2013, the lead plaintiff filed a motion for leave to amend the secondconsolidated amended complaint. On March 20, 2014, the District Court denied plaintiff’s motion and dismissed the second consolidated amendedcomplaint with prejudice. On April 18, 2014, the lead plaintiff filed a notice of appeal, and on August 27, 2014, the lead plaintiff filed his appellate brief inthe US Court of Appeals for the Ninth Circuit, or Ninth Circuit. On October 24, 2014, we filed our answering brief in response to the lead plaintiff’s appeal.On December 5, 2014, the lead plaintiff filed his reply brief. A panel of the Ninth Circuit heard oral argument on the appeal on May 4,422016. On October 26, 2016, the Ninth Circuit panel reversed the District Court’s dismissal of the second consolidated amended complaint and remanded thecase back to the District Court for further proceedings. On January 25, 2017, the District Court permitted us to submit a renewed motion to dismiss thesecond consolidated amended complaint. On February 2, 2017, we filed the renewed motion to dismiss. On February 23, 2017, the lead plaintiff filed hisopposition, and on March 2, 2017, we filed our reply. On April 28, 2017, the District Court denied our renewed motion to dismiss. On November 3, 2017, weand the lead plaintiff signed a stipulation and agreement of settlement, or Stipulation, to resolve the consolidated class action. Under the terms of theStipulation, and in exchange for a release of all claims by class members and a dismissal of the consolidated class action with prejudice, we have agreed (i)our insurers will pay class members and their attorneys a total of approximately $12.025 million and (ii) Arena will pay class members and their attorneysapproximately $11.975 million in either shares of our common stock or cash at our election. On November 30, 2017, the District Court preliminary approvedthe settlement and the form of notice to potential class members of the proposed settlement and the procedure by which they can become class members. OnMarch 8, 2018, the lead plaintiff filed motions for final approval of the settlement, the plan of allocation and award of attorney fees. The settlement and therelated matters remain subject to final approval by the District Court.On September 30, 2016, we and Eisai Inc. filed a patent infringement lawsuit against Lupin Limited and Lupin Pharmaceuticals, Inc. (collectively,Lupin) in the U.S. District Court for the District of Delaware. The lawsuit relates to a “Paragraph IV certification” notification that we and Eisai Inc. receivedregarding an abbreviated new drug application, or ANDA, submitted to the FDA by Lupin requesting approval to engage in the commercial manufacture, use,importation, offer for sale or sale of a generic version of BELVIQ (lorcaserin hydrochloride tablets, 10 mg). In its notification, Lupin alleged that no valid,enforceable claim of any of the patents that are listed in the FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, or Orange Book, forBELVIQ will be infringed by Lupin’s manufacture, importation, use, sale or offer for sale of the product described in its ANDA for 10 mg lorcaserinhydrochloride tablets. Lupin is accused of infringing U.S. Patent Nos. 6,953,787; 7,514,422; 7,977,329; 8,207,158 and 8,273,734. In accordance with theHatch-Waxman Act, as a result of filing a patent infringement lawsuit within 45 days of receipt of Lupin’s notification, the FDA cannot approve Lupin’sANDA any earlier than 7.5 years from NDA approval unless a District Court finds that all of the asserted claims of the patents-in-suit are invalid,unenforceable or not infringed. On January 11, 2017, Lupin filed an answer, defenses and counterclaims to the September 30, 2016 complaint. We and EisaiInc. filed an answer to Lupin’s counterclaims on February 1, 2017. We and Eisai Inc. are seeking a determination from the court that, among other things,Lupin has infringed our patents, Lupin’s ANDA for 10 mg lorcaserin hydrochloride tablets should not be approved until the expiration date of our patents,and Lupin should be enjoined from commercializing a product that infringes our patents. Trial is currently scheduled for April 15, 2019. The parties arecurrently in the fact discovery phase of the case. We cannot predict the ultimate outcome of any proceeding.On March 6, 2017, we and Eisai Inc. filed a patent infringement lawsuit against Teva Pharmaceuticals USA, Inc. and Teva Pharmaceutical IndustriesLtd. (collectively, Teva) in the U.S. District Court for the District of Delaware. The lawsuit also relates to a “Paragraph IV certification” notification that weand Eisai Inc. received regarding an ANDA submitted to the FDA by Teva requesting approval to engage in the commercial manufacture, use, importation,offer for sale or sale of a generic version of BELVIQ XR (lorcaserin hydrochloride extended-release tablets, 20 mg). In its notification, Teva alleged that novalid, enforceable claim of any of the patents that are listed in the Orange Book for BELVIQ XR will be infringed by Teva’s manufacture, importation, use,sale or offer for sale of the product described in its ANDA. Teva is accused of infringing U.S. Patent Nos. 6,953,787; 7,514,422; 7,977,329; 8,207,158 and8,273,734. In accordance with the Hatch-Waxman Act, as a result of filing a patent infringement lawsuit within 45 days of receipt of Teva’s notification, theFDA cannot approve Teva’s ANDA any earlier than 7.5 years from NDA approval unless a District Court finds that all of the asserted claims of the patents-in-suit are invalid, unenforceable or not infringed. On April 18, 2017, Teva filed an amended answer, defenses and counterclaims to the March 6, 2017complaint. We and Eisai Inc. are seeking a determination from the court that, among other things, Teva has infringed our patents, Teva’s ANDA should not beapproved until the expiration date of our patents, and Teva should be enjoined from commercializing a product that infringes our patents. On May 1, 2017,the Teva and Lupin actions were consolidated for all purposes and will follow the case schedule that was previously entered in the Lupin action. We andEisai Inc. filed an answer to Teva’s amended counterclaims on May 3, 2017. On or about October 16, 2017, we and Eisai Inc. received a “Paragraph IVcertification” notification from Teva alleging that no valid, enforceable claim of U.S. Patent No. 9,770,455, which was listed in the Orange Book forBELVIQ and BELVIQ XR after the patent issued on September 26, 2017, will be infringed by Teva’s manufacture, importation, use, offer for sale or sale ofthe product described in its ANDA. On October 25, 2017, we and Eisai Inc. filed a first amended complaint against Lupin and Teva, adding infringement ofU.S. Patent No. 9,770,455 by their respective ANDA products to the consolidated lawsuit. On or about November 6, 2017, we and Eisai Inc. received a“Paragraph IV certification” notification from Lupin alleging that no valid, enforceable claim of U.S. Patent No. 9,770,455 will be infringed by Lupin’smanufacture, importation, use, offer for sale or sale of the product described in its ANDA for 10 mg lorcaserin hydrochloride tablets. We cannot predict theultimate outcome of any proceeding.We and Eisai Inc. also received a “Paragraph IV certification” notification from Lupin alleging that no valid, enforceable claim of any of the patentsthat are listed in the Orange Book for BELVIQ and BELVIQ XR will be infringed by Lupin’s manufacture, importation, use, sale or offer for sale of theproduct described in its ANDA for 20 mg lorcaserin hydrochloride extended-release tablets. Because Lupin is not the first applicant to submit a substantiallycomplete application containing a Paragraph IV certification43for approval of a generic equivalent of BELVIQ XR, absent extenuating circumstances, Lupin would not be able to launch its 20 mg lorcaserin hydrochlorideextended-release tablets before Teva was able to launch its respective product.Item 4. Mine Safety DisclosuresNot applicable. 44PART IIItem 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity SecuritiesMarket informationOur common stock is listed on the Nasdaq Global Select Market under the symbol “ARNA.” The following table sets forth, for the periods indicated,the high and low sale prices for our common stock as reported by the Nasdaq Global Select Market. All figures have been adjusted to give retrospective effectto the June 2017 reverse split of our common stock. High Low Year ended December 31, 2017 First quarter $17.00 $13.40 Second quarter 17.75 11.30 Third quarter 27.86 16.95 Fourth quarter 35.09 24.33 High Low Year ended December 31, 2016 First quarter $20.50 $13.00 Second quarter 21.60 14.80 Third quarter 18.30 14.70 Fourth quarter 19.20 13.50 HoldersAs of March 9, 2018, there were approximately 102 stockholders of record of our common stock, one of which is Cede & Co., a nominee forDepository Trust Company, or DTC. Shares of common stock that are held by financial institutions as nominees for beneficial owners are deposited intoparticipant accounts at DTC and are considered to be held of record by Cede & Co. as one stockholder.DividendsWe have never paid cash dividends on our capital stock. We anticipate that we will retain earnings, if any, to support operations and finance thegrowth and development of our business and, therefore, do not expect to pay cash dividends in the foreseeable future.Securities authorized for issuance under equity compensation plansInformation on securities authorized for issuance under our equity compensation plans is set forth in Item 12 of Part III of this Annual Report onForm 10-K.Performance graphThe graph below compares the cumulative five-year total return on our common stock from December 31, 2012, through December 31, 2017, to thecumulative total return over such period for (i) the Nasdaq Composite Index and (ii) the Nasdaq Biotechnology Index. The graph assumes the investment of$100 on December 31, 2012, with the reinvestment of dividends, although dividends have not been declared on our common stock, and is calculatedaccording to the Securities and Exchange Commission’s methodology. We caution that the stock price performance shown in the graph may not beindicative of future stock price performance. The graph, including each of the graph lines, was provided by Research Data Group, Inc.45This information, including the graph below, is not deemed to be “soliciting material” or to be “filed” with the Securities and ExchangeCommission, or subject to the Securities and Exchange Commission’s proxy rules, other than as provided in such rules, or to the liabilities of Section 18 ofthe Securities Exchange Act of 1934, and shall not be deemed incorporated by reference into any prior or subsequent filing by us under the Securities Act of1933 or the Securities Exchange Act of 1934, except to the extent that we specifically incorporate it by reference into any such filing. 46Item 6. Selected Financial DataThe following Selected Financial Data should be read in conjunction with “Item 7. Management’s Discussion and Analysis of Financial Conditionand Results of Operations” and “Item 8. Financial Statements and Supplementary Data” included below in this Annual Report on Form 10-K.The following amounts related to earnings per share and shares outstanding have been adjusted for all periods reported for the 1-for-10 reverse stocksplit that we effected in June 2017. Years ended December 31, 2017 2016 2015 2014 2013 (In thousands, except per share data) Consolidated Statement of Operations Data: Revenues Collaboration revenue $19,632 $92,163 $13,398 $18,582 $71,900 Royalty revenue 1,705 — — — — Total revenues 21,337 92,163 13,398 18,582 71,900 Operating Costs and Expenses Research and development 70,988 63,782 83,283 89,815 58,798 General and administrative 30,341 27,529 30,281 28,985 26,526 Litigation settlement expense, net 11,975 — — — — Restructuring charges — 6,115 3,346 — — Total operating costs and expenses 113,304 97,426 116,910 118,800 85,324 Interest and other income (expense), net (3,887) (7,037) (7,195) 47,006 3,230 Loss from continuing operations (95,854) (12,300) (110,707) (53,212) (10,194)Income (loss) from discontinued operations 3,122 (10,596) 2,728 (7,296) (9,241)Net loss (92,732) (22,896) (107,979) (60,508) (19,435)Less net loss attributable to noncontrolling interest in consolidated variable interest entity 1,325 380 — — — Net loss allocable to common stockholders $(91,407) $(22,516) $(107,979) $(60,508) $(19,435) Amounts attributable to stockholders of Arena: Loss from continuing operations $(94,529) $(11,920) $(110,707) $(53,212) $(10,194)Income (loss) from discontinued operations 3,122 (10,596) 2,728 (7,296) (9,241) $(91,407) $(22,516) $(107,979) $(60,508) $(19,435) Net income (loss) attributable to stockholders of Arena per share, basic and diluted: Continuing operations $(2.87) $(0.49) $(4.60) $(2.42) $(0.47)Discontinued operations 0.10 (0.44) 0.11 (0.33) (0.42) $(2.77) $(0.93) $(4.49) $(2.75) $(0.89) Shares used in calculating net income (loss) per share allocable to common stockholders, basic and diluted 32,990 24,313 24,067 21,973 21,810 As of December 31, 2017 2016 2015 2014 2013 (In thousands) Consolidated Balance Sheet Data: Cash and cash equivalents $158,837 $90,712 $156,184 $163,209 $221,878 Total available-for-sale securities 112,482 — — — — Total assets 339,275 169,010 256,792 276,385 339,807 Total lease financing obligations 61,748 65,266 68,245 70,737 72,794 Total derivative liabilities — — — 474 4,892 Accumulated deficit (1,490,187) (1,398,736) (1,376,220) (1,268,241) (1,207,733)Total equity 207,144 40,395 53,542 47,345 91,857 47Item 7. Management’s Discussion and Analysis of Financial Condition and Results of OperationsYou should read the following discussion and analysis in conjunction with “Item 8. Financial Statements and Supplementary Data” included below inthis Annual Report on Form 10-K, or Annual Report. Operating results are not necessarily indicative of results that may occur in future periods.This discussion and analysis contains forward-looking statements that involve a number of risks, uncertainties and assumptions. Actual events orresults may differ materially from our expectations. Important factors that could cause actual results to differ materially from those stated or implied by ourforward-looking statements include, but are not limited to, those set forth in “Item 1A. Risk Factors” in this Annual Report. All forward-looking statementsincluded in this Annual Report are based on information available to us as of the time we file this Annual Report and, except as required by law, weundertake no obligation to update publicly or revise any forward-looking statements. In addition, statements that “we believe” and similar statements reflectour beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this Annual Report, and whilewe believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not beread to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements areinherently uncertain.OVERVIEW AND RECENT DEVELOPMENTSWe are a biopharmaceutical company focused on developing novel, small molecule drugs with optimized receptor pharmacology designed to deliverclinical utility across multiple therapeutic areas. Our proprietary, internally-developed pipeline includes potentially first- or best-in-class programs.Our three most advanced investigational clinical programs include: •Ralinepag, which we are preparing for a Phase 3 program for pulmonary arterial hypertension, or PAH, •Etrasimod, which is being studied in Phase 2 trials for a broad range of immune and inflammatory conditions, and •APD371 for a broad range of visceral pain conditions and which is being studied in a Phase 2 trial for treatment of pain associated with Crohn'sdisease, or CD.We continue to explore additional indications for all of our clinical-stage programs. Additionally, we have collaborations with the followingpharmaceutical companies: •Everest Medicines Limited, or Everest, in their efforts with respect to ralinepag and etrasimod in Greater China and select Asian countries, •Eisai Co., Ltd. and Eisai Inc., or collectively, Eisai, in their efforts with respect to BELVIQ/BELVIQ XR, which are marketed products, •Axovant Sciences GmbH, or Axovant, in its efforts with respect to nelotanserin, an orally available inverse agonist of the serotonin 2A receptor,which is in development for various neurological disorders, and •Boehringer Ingelheim International GmbH, or Boehringer Ingelheim, targeting a G protein-coupled receptor that belongs to the group oforphan central nervous system receptors, which is in preclinical development stage.During 2017, we reported positive topline Phase 2 results for ralinepag in patients with PAH and raised $236.4 million through completion of twounderwritten public offerings of shares of our common stock. We also made changes to the composition of our board of directors and hired a new chiefmedical officer.On March 9, 2018, we entered into an Asset Purchase Agreement, or Sale Agreement, with Siegfried Pharma AG and Siegfried AG (collectively andindividually, Siegfried). Under the Sale Agreement, we agreed to sell and assign to Siegfried, and Siegfried agreed to purchase and assume from Arena GmbH,certain drug product finishing facility assets and know-how, including fixtures, equipment, other personal property and real estate assets located in Zofingen,Switzerland, related contracts and certain related liabilities after the closing as well as to the transfer of all of Arena GmbH’s approximately 50 currentemployees, or collectively, Manufacturing Operations. We refer to this transaction as Siegfried Transaction. The Siegfried Transaction is expected to close onor about March 31, 2018, subject to satisfaction or waiver of certain customary closing conditions. As a result of the Siegfried Transaction, we have excludedfrom our continuing operations for all periods presented in this report revenues and expenses associated with our manufacturing operations to be divested,which are reported as discontinued operations. See Note 5 to our consolidated financial statements included in this Annual Report for additional informationregarding the Manufacturing Operations.In December 2017, we entered into a Collaboration and License Agreement, or the Everest Agreement, with Everest. Under the Everest Agreement, wegranted Everest an exclusive, royalty-bearing license to develop, manufacture and commercialize two of our48product candidates, ralinepag (in any formulation) and etrasimod (in oral formulations only), in China, Taiwan, Hong Kong, Macau and South Korea, or theEverest Territories. Everest will be responsible for all development, manufacture and commercialization of the licensed products in the Everest Territories,and may participate in the portion of our global clinical trials that is conducted in the Everest Territories. In addition to an upfront payment of $12.0 millionwhich we collected in December 2017, we are eligible to receive development, regulatory and commercial milestone payments from Everest of up to $212.0million for both licensed products, as well as tiered royalties on net sales ranging from the high single digits to low double digits. Following an initial royaltyterm, we are eligible to receive a lower trademark royalty if Everest continues to use our licensed product-related trademarks.Since 2010, a number of complaints were filed in the US District Court for the Southern District of California, or District Court, against us and certainof our current and former employees and directors on behalf of certain purchasers of our common stock. The complaints were brought as purportedstockholder class actions, and, in general, include allegations that we and certain of our current and former employees and directors violated federal securitieslaws by making materially false and misleading statements regarding our BELVIQ program, thereby artificially inflating the price of our common stock. InNovember 2017, we and the lead plaintiff signed a stipulation and agreement of settlement, or Stipulation, to resolve the consolidated class action. Under theterms of the Stipulation, and in exchange for a release of all claims by class members and a dismissal of the consolidated class action with prejudice, we haveagreed (i) our insurers will pay class members and their attorneys a total of approximately $12.025 million and (ii) Arena will pay class members and theirattorneys approximately $11.975 million in either shares of our common stock or cash at our election. The terms of the settlement remain subject topreliminary approval by the District Court. If the settlement is preliminarily approved by the District Court, potential class members will be notified of theproposed settlement and the procedure by which they can become class members. The settlement will then be subject to final approval by the District Court.In June 2017, we filed a certificate of amendment to our certificate of incorporation with the Secretary of State of the state of Delaware to effect a one-for-ten reverse stock split of our issued and outstanding common stock. The consolidated financial statements and notes thereto included in this AnnualReport give retrospective effect to the reverse stock split for all periods presented. All issued and outstanding common stock, options exercisable for commonstock, restricted stock units, performance restricted stock units, and per share amounts contained in this Annual Report have been retrospectively adjusted toreflect this reverse stock split for all periods presented. Concurrent with the reverse stock split we effected a reduction in the number of authorized shares ofcommon stock from 367,500,000 shares to 73,500,000 shares.In general, developing drugs and obtaining marketing approval is a long, uncertain and expensive process, and our ability to execute on our plans andachieve our goals depends on numerous factors, many of which we do not control. To date, we have generated limited revenues. We expect to continue toincur substantial net losses for at least the short term as we advance our clinical development programs, and support our collaborators.We plan to raise additional cash from outside sources in order to carry out our operational strategy and advance our clinical pipeline.There is no guarantee that adequate funds will be available when needed from additional debt or equity financing, development andcommercialization partnerships or from other sources, or on terms acceptable to us. If our efforts to obtain sufficient additional funds are notsuccessful, we would be required to delay, scale back, or eliminate some or all of our research or development, manufacturing operations,administrative operations, and clinical or regulatory activities, which could negatively affect our ability to achieve certain corporate goals. Webelieve our cash resources are sufficient to allow us to continue operations for at least the next twelve months from the date this Annual Report isfiled with the SEC.See the above “Business” section for a more complete discussion of our business.49RESULTS OF OPERATIONSWe are providing the following summary of our revenues, research and development expenses and general and administrative expenses to supplementthe more detailed discussion below. This summary excludes our revenues, research and development expenses and general and administrative expensesassociated with our Manufacturing Operations, which are reported within income (loss) from discontinued operations. The dollar values in the followingtables are in millions.Revenues Years ended December 31, % change from % change from Source of revenue 2017 2016 2015 2016 to 2017 2015 to 2016 Collaboration agreement with Everest $12.0 $— $— * —%Collaboration agreement with Boehringer Ingelheim 5.1 5.1 — 0.5% * Collaboration agreement with Axovant 2.2 2.1 1.1 6.3% 85.3%Royalty revenue 1.7 — — * —%Collaboration agreement with Eisai — 78.4 8.6 (100.0)% * Other collaboration revenue 0.3 6.6 3.7 (95.2)% 78.6%Total revenues $21.3 $92.2 $13.4 (76.8)% * *The change is more than 100%. Research and development expenses Years ended December 31, % change from % change from Type of expense 2017 2016 2015 2016 to 2017 2015 to 2016 External clinical and preclinical study fees and internal non-commercial manufacturing costs $43.4 $29.5 $29.1 47.2% 1.2%Salary and other personnel costs (excluding non-cash share-based compensation) 15.9 17.2 29.1 (7.5)% (40.9)%Facility and equipment costs 5.3 8.0 10.0 (34.2)% (20.5)%Non-cash share-based compensation 1.9 5.6 7.5 (65.2)% (25.5)%Research supply costs 0.8 2.3 6.2 (66.4)% (63.1)%Other 3.7 1.2 1.4 * 4.6%Total research and development expenses $71.0 $63.8 $83.3 11.3% (23.4)% *The change is more than 100%. General and administrative expenses Years ended December 31, % change from % change from Type of expense 2017 2016 2015 2016 to 2017 2015 to 2016 Salary and other personnel costs (excluding non-cash share-based compensation) $9.6 $9.2 $11.7 5.0% (21.4)%Legal, accounting and other professional fees 8.7 8.3 7.2 3.6% 15.7%Non-cash share-based compensation 5.9 4.4 6.5 33.2% (31.1)%Facility and equipment costs 4.7 4.3 3.7 11.1% 13.6%Other 1.4 1.3 1.2 8.0% 9.4%Total general and administrative expenses $30.3 $27.5 $30.3 10.2% (9.1)% YEAR ENDED DECEMBER 31, 2017, COMPARED TO YEAR ENDED DECEMBER 31, 2016Revenues. In December 2016, we amended and restated the terms of the marketing and supply agreement for lorcaserin with Eisai by entering into anew Transaction Agreement and a new Supply Agreement (collectively, the Eisai Agreement) with Eisai. Under the Eisai Agreement, Eisai acquired globalcommercialization and manufacturing rights to lorcaserin, including in the territories retained by us under the prior agreement, with control over globaldevelopment and commercialization decisions. Eisai is responsible for all lorcaserin development expenses going forward. We also assigned to Eisai ourrights under the commercial lorcaserin distribution agreements with Ildong Pharmaceutical Co., Ltd., or Ildong, for South Korea; CY Biotech CompanyLimited, or CYB, for Taiwan; and Teva Pharmaceuticals Ltd.’s Israeli subsidiary, Abic Marketing Limited, or Teva, for Israel.50Prior to the Eisai Agreement, we received from Eisai, Ildong, CYB and Teva total upfront payments of $122.5 million. Revenues from these upfrontpayments were previously deferred, as we determined that the exclusive rights did not have standalone value without our ongoing development andregulatory activities. Accordingly, these payments were recognized ratably as revenue over the periods in which we expected the services to be rendered. TheEisai Agreement eliminated our obligation to continue performing the development and regulatory activities required in the prior agreements. Therefore, onDecember 28, 2016, $64.0 million of deferred revenues from these upfront payments was allocated to the rights delivered by us to Eisai pursuant to the EisaiAgreement and recognized as revenue in 2016.We recognized revenues of $21.3 million for the year ended December 31, 2017, compared to $92.2 million for the year ended December 31, 2016.This decrease was primarily due to $66.0 million of revenue recorded in 2016 from upfront payments for lorcaserin collaborations received from Eisai in prioryears, and $5.7 million of revenue recorded in 2016 from upfront payments for other lorcaserin collaborations received from Ildong and CYB in prior yearswith no similar revenue in 2017 and a total of $12.3 million of milestones from Eisai and Ildong that we earned during 2016 primarily from the approval ofthe once-daily formulation of lorcaserin in the United States (branded as BELVIQ XR), the approval of the twice-daily formulation of lorcaserin in Mexico(branded as VENESPRI), and the approval of BELVIQ in Brazil. These decreases were partially offset by $12.0 million revenue in 2017 related to an upfrontpayment pursuant to a collaboration agreement with Everest entered into in December 2017 and $1.7 million of royalty revenue recorded in 2017 under theEisai Agreement.Absent any new collaborations, we expect our 2018 revenues will primarily consist of (i) royalty payments from Eisai based upon Eisai’s sales ofBELVIQ to its distributors, (ii) amortization of upfront payments we have received from our collaborators and (iii) reimbursements from collaborators forresearch funding.Revenues from royalties based on sales of BELVIQ are difficult to predict, and our overall revenues will likely vary from quarter to quarter and year toyear. In the short term, we expect the amount of BELVIQ-related revenue we earn to fluctuate significantly due to the terms of the Eisai Agreement.Research and development expenses. Research and development expenses, which account for the majority of our expenses, consist primarily ofsalaries and other personnel costs, clinical trial costs (including payments to contract research organizations, or CROs), preclinical study fees, manufacturingcosts for non-commercial products, research supply costs and facility and equipment costs. We expense research and development costs as they are incurredwhen these expenditures have no alternative future uses. We generally do not track our earlier-stage, internal research and development expenses by project;rather, we track such expenses by the type of cost incurred.Research and development expenses increased by $7.2 million to $71.0 million for the year ended December 31, 2017, from $63.8 million for the yearended December 31, 2016. This increase was primarily due to an increase of $13.9 million in external clinical and preclinical study fees and internal non-commercial manufacturing costs partially offset by decreases of $3.7 million in non-cash, share-based compensation expense, $2.7 million in facility andequipment costs, $1.5 million in research supply costs and $1.3 million in salary and other personnel costs, primarily due to the workforce reductions in2016.We expect to incur substantial research and development expenses in 2018 and for the aggregate amount in 2018 to be potentially greater than theamount incurred in 2017. We expect our internal costs to be higher primarily due to increasing headcount related to advancing the ralinepag and etrasimodprograms and we also expect to incur higher external clinical trial costs in connection with Phase 3 clinical trials for ralinepag, including patient enrollment.Our actual expenses may be higher or lower than anticipated due to various factors, including our progress and results. For example, patient enrollment in ourPhase 3 clinical program for ralinepag is expected to be competitive and challenging, and could take longer than originally projected, which may result inour related external expenses being lower in 2018 than anticipated (but which might increase the overall costs for completing this multi-year program).Included in the $43.4 million of total external clinical and preclinical study fees and internal non-commercial manufacturing costs noted in the tableabove in this section for the year ended December 31, 2017, were the following: •$28.7 million related to etrasimod, •$9.7 million related to ralinepag, and51 •$2.8 million related to APD371.Included in the $29.5 million of total external clinical and preclinical study fees and internal non-commercial manufacturing costs noted in the tableabove in this section for the year ended December 31, 2016, were the following: •$17.6 million related to etrasimod, •$4.7 million related to ralinepag, •$4.2 million related to lorcaserin, and •$1.1 million related to APD371.Cumulatively from our inception through December 31, 2017, we have recognized (i) external clinical and preclinical study fees of $307.7 million forlorcaserin, $62.2 million for etrasimod, $43.8 million for nelotanserin, $30.8 million for ralinepag and $10.3 million for APD371 and (ii) $53.0 million fornon-commercial manufacturing and other development costs for lorcaserin and, to a lesser extent, nelotanserin.While expenditures on current and future clinical development programs are expected to be substantial, they are subject to many uncertainties,including whether we have adequate funds and develop our drug candidates with one or more collaborators or independently. As a result of suchuncertainties, we cannot predict with any significant degree of certainty the duration and completion costs of our research and development projects orwhether, when and to what extent we will generate revenues from the commercialization and sale of any of our drug candidates. The duration and cost ofclinical trials may vary significantly over the life of a project as a result of unanticipated events arising during clinical development and a variety of factors,including: •the nature and number of trials and studies in a clinical program; •the potential therapeutic indication; •the number of patients who participate in the trials; •the number and location of sites included in the trials; •the rates of patient recruitment, enrollment and withdrawal; •the duration of patient treatment and follow-up; •the costs of manufacturing drug candidates; and •the costs, requirements, timing of, and the ability to secure and maintain regulatory approvals.General and administrative expenses. General and administrative expenses increased by $2.8 million to $30.3 million for the year ended December31, 2017, from $27.5 million for the year ended December 31, 2016. This increase was primarily due to increases of $1.5 million in non-cash, share-basedcompensation expense, and $0.4 million in salary and other personnel costs, both primarily due to the increase in hiring activity in the latter half of 2017, anincrease of $0.4 million in facility and equipment costs, and an increase of $0.4 million in legal, accounting and other professional fees. We expect that our2018 general and administrative expenses will be higher than in 2017.Litigation settlement expense, net. Litigation settlement expense, net was $11.975 million for the year ended December 31, 2017. This expenserelated to a stipulation and agreement of settlement we entered into in November 2017 in connection with a stockholder class action. The accrued amountrepresents the allocated value of the settlement that we will pay either in shares of our common stock or in cash, at our election. We expect this amount willbe settled during the second quarter of 2018.Restructuring charges. We recognized $6.1 million of restructuring charges for the year ended December 31, 2016, in connection with employeetermination costs, including severance and other benefits, related to the reduction of our US workforce in 2016. We incurred no similar charges in 2017.Interest and other expense, net. Interest and other expense, net, decreased by $3.1 million to $3.9 million for the year ended December 31, 2017, from$7.0 million for the year ended December 31, 2016. This decrease was primarily due to (i) $0.4 million in gain on sale and disposal of equipment for the yearended December 31, 2017, compared to $1.3 million in net loss on sale and disposal of equipment for the year ended December 31, 2016, (ii) an increase of$1.0 million in rental income from additional sublease activity in 2017, and (iii) a decrease of $0.4 million in interest expense.Discontinued operations. On March 9, 2018, Arena GmbH entered into the Sale Agreement with Siegfried to divest our Manufacturing Operations.The Siegfried Transaction is expected to close on or about March 31, 2018, subject to satisfaction or52waiver of certain customary closing conditions. As a result of the Siegfried Transaction, we have excluded from our continuing operations for all periodspresented in this report revenues and expenses associated with our manufacturing operations to be divested, or Manufacturing Operations, which are reportedas discontinued operations. For the year ended December 31, 2017, income from discontinued operations was $3.1 million. For the year ended December 31,2016, loss from discontinued operations was $10.6 million. See Note 5 to our consolidated financial statements included in this Annual Report for additionalinformation regarding the Manufacturing Operations.YEAR ENDED DECEMBER 31, 2016, COMPARED TO YEAR ENDED DECEMBER 31, 2015Revenues. We recognized revenues of $92.2 million for the year ended December 31, 2016, compared to $13.4 million for the year endedDecember 31, 2015. This increase was primarily due to (i) $66.0 million of revenue recorded in 2016 from upfront payments for lorcaserin collaborationsreceived from Eisai, compared to $7.5 million in 2015, (ii) $5.7 million of revenue recorded in 2016 from upfront payments for other lorcaserincollaborations received from Ildong and CYB, compared to $0.5 million in 2015, (iii) a total of $12.3 million of milestones from Eisai and Ildong that weearned during 2016 primarily from the approval of the once-daily formulation of lorcaserin in the United States (branded as BELVIQ XR), the approval of thetwice-daily formulation of lorcaserin in Mexico (branded as VENESPRI), and the approval of BELVIQ in Brazil, compared to $3.0 million of milestones fromIldong that we earned in February 2015 for the approval of BELVIQ in South Korea and (iv) $5.1 million earned in the year ended December 31, 2016, underour collaboration agreement with Boehringer Ingelheim, or Boehringer Ingelheim Agreement, which commenced in December 2015.Research and development expenses. Research and development expenses decreased by $19.5 million to $63.8 million for the year ended December31, 2016, from $83.3 million for the year ended December 31, 2015. This decrease was primarily due to decreases of $11.9 million in salary and otherpersonnel costs, $3.9 million in research supply costs, $2.0 million in facility and equipment costs, and $1.9 million in non-cash, share-based compensationexpense, primarily due to the reduction in the number of our research and development employees in 2016.Included in the $29.5 million of total external clinical and preclinical study fees and internal non-commercial manufacturing costs noted in the tableabove in this section for the year ended December 31, 2016, were the following: •$17.6 million related to etrasimod, •$4.7 million related to ralinepag, •$4.2 million related to lorcaserin, and •$1.1 million related to APD371.Included in the $29.1 million of total external clinical and preclinical study fees and internal non-commercial manufacturing costs noted in the tableabove in this section for the year ended December 31, 2015, were the following: •$10.8 million related to lorcaserin, •$8.7 million related to etrasimod, •$5.1 million related to ralinepag, and •$3.5 million related to APD371.General and administrative expenses. General and administrative expenses decreased by $2.8 million to $27.5 million for the year ended December31, 2016, from $30.3 million for the year ended December 31, 2015. This decrease was primarily due to decreases of $2.5 million in salary and otherpersonnel costs and $2.1 million in non-cash, share-based compensation expense, primarily due to reductions in the number of our employees in 2016 and2015. These decreases were partially offset by an increase of $1.1 million in legal, accounting and other professional fees and an increase of $0.6 million infacility and equipment costs.Restructuring charges. We recognized $6.1 million of restructuring charges for the year ended December 31, 2016, in connection with employeetermination costs, including severance and other benefits, related to the reduction of our US workforce to which we committed in June 2016. We recognized$3.3 million of restructuring charges for the year ended December 31, 2015, in connection with employee termination costs, including severance and otherbenefits, related to the workforce reductions to which we committed in the fourth quarter of 2015.Interest and other expense, net. Interest and other expense, net, decreased by $0.2 million to $7.0 million for the year ended December 31, 2016, from$7.2 million for the year ended December 31, 2015.53Discontinued operations. For the year ended December 31, 2016, loss from discontinued operations was $10.6 million. For the year ended December31, 2015, income from discontinued operations was $2.7 million. See Note 5 to our consolidated financial statements included in this Annual Report foradditional information regarding the Manufacturing Operations.LIQUIDITY AND CAPITAL RESOURCESWe have accumulated a large deficit since inception that has primarily resulted from the significant research and development expenditures we havemade in seeking to identify and develop compounds that could become marketed drugs. We expect to continue to incur substantial losses for at least theshort term.To date, we have obtained cash and funded our operations to date primarily through the sale of common and preferred stock, the issuance of debt andrelated financial instruments, payments from collaborators and customers and sale leaseback transactions. From our inception through December 31, 2017, wehave generated $2.3 billion in cash from these sources, of which $1.6 billion was through sales of equity, $560.5 million was through payments fromcollaborators and customers, $96.9 million was through the issuance of debt and related financial instruments and $77.1 million was from sale and leasebacktransactions.Short term liquidity.At December 31, 2017, we had $271.3 million in cash and cash equivalents, and available-for-sale investments. In addition to payments expected fromEisai for royalties, our other potential sources of liquidity in the short term include (i) milestone and other payments from collaborators, (ii) entering into newcollaboration, licensing or commercial agreements for one or more of our drug candidates or programs, (iii) the sale or lease of our facilities or other assets and(iv) sale of equity, issuance of debt or other transactions.Long term liquidity.It will require substantial cash to achieve our objectives of discovering, developing and commercializing drugs, and this process typically takes manyyears and potentially several hundreds of millions of dollars for an individual drug. We may not have adequate available cash, or assets that could be readilyturned into cash, to meet these objectives in the long term. We will need to obtain significant funds under our existing collaborations, under newcollaboration, licensing or other commercial agreements for one or more of our drug candidates and programs or patent portfolios, or from other potentialsources of liquidity, which may include the sale of equity, issuance of debt or other transactions.In addition to potential payments from our current collaborators, as well as funds from public and private financial markets, potential sources ofliquidity in the long term include (i) upfront, milestone, royalty and other payments from any future collaborators or licensees and (ii) revenues from sales ofany drugs we obtain regulatory approval to commercialize on our own. The length of time that our current cash and cash equivalents and any availableborrowings will sustain our operations will be based on, among other things, the rate of adoption and commercial success of BELVIQ and any other drug weor our collaborators obtain regulatory approval to market, regulatory decisions affecting our and our collaborator’s drug candidates, prioritization decisionsregarding funding for our programs, progress in our clinical and earlier-stage programs, the time and costs related to current and future clinical trials andnonclinical studies, our research, development, manufacturing and commercialization costs (including personnel costs), our progress in any programs undercollaborations, costs associated with intellectual property, our capital expenditures, and costs associated with securing any in-licensing opportunities. Anysignificant shortfall in funding may result in us reducing our development and/or research activities, which, in turn, would affect our development pipelineand ability to obtain cash in the future.We evaluate from time to time potential acquisitions, in-licensing and other opportunities. Any such transaction may impact our liquidity as well asaffect our expenses if, for example, our operating expenses increase as a result of such acquisition or license or we use our cash to finance the acquisition orlicense.Sources and uses of our cash.Net cash used in operating activities increased by $4.5 million to $66.6 million in the year ended December 31, 2017, compared to $62.1 million inthe year ended December 31, 2016. This increase was primarily due to (i) an increase of $13.7 million in payments made for external clinical study fees, (ii)the $10.0 million payment we received from Eisai in December 2016 in connection of the sale of bulk inventory under the Eisai Agreement, while we did notreceive any similar payment in the year ended December 31, 2017, and (iii) the $7.5 million payment we received from Boehringer Ingelheim in February2016 upon entering into the Boehringer Ingelheim Agreement. These increases in net cash used in operating activities were partially offset by (i) the $12.0million we received from Everest in December 2017 upon entering into the collaboration agreement with Everest, (ii) an increase of $5.9 million in netpayments we received from Eisai and other BELVIQ distributors, from $9.3 million in the year ended December 31, 2016, to $15.254million (primarily consisting of $7.2 million of manufacturing support payments related to the Eisai Agreement and $5.2 million in net settlement paymentsrelated to the prior agreements) in the year ended December 31, 2017, and (iii) decreased cash expenditures of approximately $10.7 million for personnelcosts primarily resulting from the workforce reductions payments in 2016.Net cash used in operating activities during the year ended December 31, 2016 decreased by $36.0 million to $62.1 million, compared to $98.1million in the year ended December 31, 2015. This decrease was primarily due to (i) the $10.0 million we received from Eisai in December 2016 pursuant toentering the Eisai Agreement, (ii) a decrease of $9.6 million in payments made for external clinical and preclinical study fees, (iii) reduced cash expendituresof approximately $9.4 million for personnel costs primarily resulting from the workforce reductions we effected at the end of 2015, in June 2016, and in July2016, (iv) the $7.5 million payment we received from Boehringer Ingelheim, less $1.2 million of withholding taxes (which was refunded to us in October2016), in February 2016 upon entering into the Boehringer Ingelheim Agreement, while we did not receive any similar upfront payments in the year endedDecember 31, 2015, and (v) reduced cash expenditures for research supply costs and facility and equipment costs primarily resulting from the workforcereductions. These decreases in net cash used in operations were partially offset by (i) the $3.0 million milestone payment we received from Ildong, lesswithholding taxes, in March 2015 for the marketing approval of BELVIQ in South Korea, while we did not receive any similar milestone payment in the yearDecember 31, 2016, and (ii) net payments of $7.6 million we received for shipments of BELVIQ to Eisai and Ildong in the year ended December 31, 2016,compared to $10.4 million in the year ended December 31, 2015.Net cash used in investing activities increased by $111.6 million to $112.4 million in the year ended December 31, 2017, compared to $0.8 million inthe year ended December 31, 2016. This increase was primarily due to $112.6 million in net purchases of available-for-sale investments in the year endedDecember 31, 2017, while there was no similar investing activity in the year ended December 31, 2016.Net cash used in investing activities was $0.8 million in the year ended December 31, 2016, compared to $8.2 million in the year ended December 31,2015. This decrease was primarily due to $1.0 million in purchases of property and equipment in the year ended December 31, 2016, compared to $11.0million in the year ended December 31, 2015 including the investing activities classified as discontinued operations, partially offset by (i) a $1.3 milliondecrease in net proceeds from the sale of equipment and (ii) a $0.8 million increase in deposits and restricted cash in the year ended December 31, 2016,compared to a $0.6 million decrease in deposits and restricted cash in the year ended December 31, 2015.Net cash of $245.3 million was provided by financing activities in the year ended December 31, 2017, as a result of net proceeds of $236.4 millionfrom our April 2017 and July 2017 offerings of our common stock, net proceeds of $7.0 million from the sale of our common stock under our ATM facilityand net proceeds of $5.4 million from stock option exercises, partially offset by $3.5 million of principal payments on our lease financing obligations. Netcash of $2.3 million was used in financing activities in the year ended December 31, 2016, as a result of $3.0 million of principal payments on our leasefinancing obligations, partially offset by net proceeds of $0.4 million from stock option exercises and purchases under our employee stock purchase plan anda $0.3 million security deposit received from a sublessee. Net cash of $101.1 million was provided by financing activities in the year ended December 31,2015, as a result of net proceeds of $100.7 million from our January 2015 offering of 2,100,000 shares of common stock and net proceeds of $3.0 millionfrom stock option exercises and purchases under our employee stock purchase plan, which were partially offset by $2.5 million for principal payments on ourlease financing obligations.Contractual ObligationsThe following table summarizes our contractual obligations at December 31, 2017, in thousands: Payments due by period Contractual Obligations Total Less than 1year 1-3years 3-5years More than 5years Financing obligations $83,309 $8,930 $16,307 $17,133 $40,939 Operating leases 10,675 1,299 2,676 1,976 4,724 Total $93,984 $10,229 $18,983 $19,109 $45,663 Our “financing obligations” relate to sale and leaseback transactions for certain of our properties. We have applied the financing method to these saleand leaseback transactions, which requires that the book value of the properties and related accumulated depreciation remain on our balance sheet with nosale recognized. The sales price of the properties is recorded as a financing obligation and a portion of each lease payment is recorded as interest expense. AtDecember 31, 2017, we expect interest expense over the remaining term of these leases to total $31.6 million. Other of our properties are under operatingleases and are included under “operating leases” above.55Off-balance sheet arrangements.We do not have and did not have at December 31, 2017, any off-balance sheet arrangements that have or are reasonably likely to have a current orfuture material effect on our financial condition, results of operations, liquidity, capital expenditures or capital resources.COLLABORATIONSEverest.In December 2017, we and Everest entered into an exclusive agreement to conduct joint development for the ralinepag and etrasimod programs. Underthis agreement, we granted Everest an exclusive, royalty-bearing license to develop and commercialize ralinepag (in any formulation) and etrasimod (in oralformulations), in mainland China, Taiwan, Hong Kong, Macau and South Korea, or collectively, the Territories. Everest is generally responsible fordevelopment and commercialization of the licensed products in the Territories, and may participate in the portion of our global clinical trials that isconducted in the Territories.We received from Everest an upfront payment of $12.0 million in December 2017. Revenues from this upfront payment were recognized in December2017 as we determined (i) that the license is a deliverable with standalone value to Everest and (ii) the upfront payment represents consideration to beallocated to the delivered license.We are also eligible to receive up to an aggregate of $212.0 million in success milestones in case of full commercial success of multiple drug products.Of these payments, six development milestones totaling $49.5 million are substantive, nine regulatory milestones totaling $22.5 million are substantive andsix commercial milestones totaling $140.0 million are non-substantive. We are further eligible to receive tiered royalties on net sales of ralinepag andetrasimod products in the Territories.Eisai.In July 2010, we granted Eisai exclusive commercialization rights for lorcaserin (marketed as BELVIQ® / BELVIQ XR®) solely in the United Statesand its territories and possessions. In May 2012, we and Eisai entered into the first amended and restated agreement, which expanded Eisai’s exclusivecommercialization rights to include most of North and South America. In November 2013, we and Eisai entered into the second amended and restatedagreement, or Second Amended Agreement, which expanded Eisai’s exclusive commercialization rights for lorcaserin to all of the countries in the world,except for South Korea, Taiwan, Australia, New Zealand and Israel.56In December 2016, we and Eisai amended and restated the terms of marketing and supply agreement for lorcaserin with Eisai by entering into aTransaction Agreement and a Supply Agreement (collectively, the Eisai Agreement) with Eisai. Under the Transaction Agreement, Eisai acquired anexclusive royalty-bearing license or transfer of intellectual property to global commercialization and manufacturing rights to lorcaserin, including in theterritories retained by us under the prior agreement, with control over global development and commercialization decisions. Eisai is responsible for alllorcaserin development expenses going forward. We also assigned to Eisai our rights under the commercial lorcaserin distribution agreements with IldongPharmaceutical Co., Ltd., or Ildong, for South Korea; CY Biotech Company Limited, or CYB, for Taiwan; and Teva Pharmaceuticals Ltd.’s Israeli subsidiary,Abic Marketing Limited, or Teva, for Israel. This is collectively referred to as License Deliverable.Under the Supply Agreement, Eisai paid us $10.0 million to acquire our entire on-hand inventory of bulk lorcaserin and the precursor material formanufacturing lorcaserin, which is referred to as Inventory Deliverable. Eisai is also paying us for finished drug product plus up to CHF 13.0 million inmanufacturing support payments over an initial two-year supply period.We manufacture lorcaserin at our facility in Zofingen, Switzerland. Revenues earned for (i) lorcaserin sold by us to Eisai under the manufacturing andsupply commitment within the Supply Agreement, or Manufacturing and Supply Commitment Deliverable, and formerly sold by us to Eisai, Ildong, CYBand Teva for commercial or development purposes under the prior lorcaserin collaboration agreements and (ii) the manufacturing support payments areclassified within discontinued operations as part of the Manufacturing Operations on the consolidated statements of operations (see Note 5). All otherrevenues earned under the Transaction Agreement and the prior lorcaserin collaboration agreements, such as royalties, licenses, milestones and developmentexpense reimbursements, are classified within continuing operations on the consolidated statements of operations.Royalty payments.Pursuant to the Transaction Agreement, we are eligible to receive royalty payments from Eisai based on the global net sales of lorcaserin. The royaltyrates are as follows: •9.5% on annual net sales less than or equal to $175.0 million •13.5% on annual net sales greater than $175.0 million but less than or equal to $500.0 million •18.5% of annual net sales greater than $500.0 millionWe record revenues from the royalty payments in the period in which the net sales upon which the royalties are calculated occur as reported to us byEisai. For the year ended December 31, 2017, we recognized royalty revenue of $1.7 million under the Eisai Agreement.Upfront payments.Prior to the Transaction Agreement, we received from Eisai total upfront payments of $115.0 million under prior lorcaserin collaboration agreements.Revenues from these upfront payments were previously deferred, as we determined that the exclusive rights did not have standalone value without ourongoing development and regulatory activities. Accordingly, these payments were recognized ratably as revenue over the periods in which we expected theservices to be rendered. The Transaction Agreement effectively eliminated our obligation to continue performing the development and regulatory activitiesrequired in the original agreement, which resulted in acceleration of upfront payment revenue recognition in 2016. For the years ended December 31, 2016,and 2015, we recognized revenue of $66.0 million and $7.5 million, respectively, related to these upfront payments.Milestone payments.In July 2016, the US Food and Drug Administration, or FDA, approved the New Drug Application for BELVIQ XR. We earned from Eisai a $10.0million substantive milestone payment from this achievement. In October 2016, Eisai announced the commercial launch of BELVIQ XR in the United States.In July 2016, the Federal Commission for the Protection Against Sanitary Risk approved the Marketing Authorization Application in Mexico for ourtwice-daily formulation of lorcaserin for chronic weight management. We earned from Eisai a $1.0 million substantive milestone payment from thisachievement.In December 2016, the Brazilian Health Surveillance Agency provided regulatory approval in Brazil for BELVIQ. We earned from Eisai a $1.0 millionsubstantive milestone payment from this achievement.We are eligible to receive an additional substantive commercial milestone of $25.0 million upon the achievement of global net sales of lorcaserin for acalendar year first exceeding $250.0 million.57Product purchase price and inventory purchase.We manufacture lorcaserin at our facility in Zofingen, Switzerland. Under the Eisai Agreement, we have agreed to manufacture and supply, and Eisaihas agreed to purchase from us, all of Eisai’s requirements (or specified minimum quantities if such quantities are greater than Eisai’s requirements), subject tocertain exceptions, for lorcaserin for development and commercial use for an initial two-year period. The initial period may be extended by Eisai for anadditional six months upon payment of an extension fee of CHF 2.0 million. Eisai will pay us agreed upon prices to deliver finished drug product during thistime. Additionally, Eisai has agreed to pay up to CHF 13.0 million in manufacturing support payments during the initial two-year period supply period, andpay up to CHF 6.0 million in manufacturing support payments during the six-month extension period, if the extension option is exercised by Eisai.Under the Second Amended Agreement, we sold lorcaserin to Eisai for Eisai’s commercialization in the United States for a purchase price of 31.5% ofEisai’s aggregate annual net product sales (which are the gross invoiced sales less certain deductions described in the Second Amended Agreement), or theProduct Purchase Price. The amount that Eisai paid us for lorcaserin product supply was based on Eisai’s estimated price at the time the order was shipped,which was Eisai’s estimate of the Eisai Product Purchase Price, and was subject to change on April 1 and October 1 of each year. The Eisai Product PurchasePrice for the product Eisai sold under the Second Amended Agreement was lower than the estimated price that Eisai paid us for such product, primarily due toan increase in deductions from savings cards and returns, partially offset by a decrease in vouchers. At the end of Eisai’s fiscal year (March 31), the estimatedprice paid to us for product that Eisai sold to its distributors was compared to the Eisai Product Purchase Price of such product, and the difference wasrefunded back to Eisai for the overpayments. The $9.1 million classified as Payable to Eisai within the total liabilities of disposal group held for sale atDecember 31, 2016, relates to product sold by Eisai to its distributors from April 1, 2015, through March 31, 2016. Under the Eisai Agreement, we were notrequired to refund to Eisai any net overpayment which would have been otherwise due to Eisai under the Second Amended Agreement for product we sold toEisai under the Second Amended Agreement which Eisai did not sell to its distributors on or before March 31, 2016. For product which Eisai sold to itsdistributors from April 1, 2016, through December 28, 2016, we recognized the net overpayment which would have been otherwise due to Eisai under theSecond Amended Agreement of $2.0 million as revenues and included this amount in net product sales for the year ended December 31, 2016, which is acomponent of discontinued operations in the consolidated statement of operations.Prior to December 2016, we deferred recognition of revenue and the related cost at the time we sold lorcaserin to Eisai because we did not have theability to estimate the amount of product that could have been returned to us and thus recognized revenues and the related costs from net product sales whenEisai shipped BELVIQ to its distributors. Pursuant to a change in the terms of the Eisai Agreement, we determined that we achieved the ability to reasonablyestimate the amount of product returns and recognize revenue and the related cost from product sales when we ship BELVIQ to Eisai. On December 28, 2016,we recognized revenues of $6.7 million and costs of $1.9 million on net product sales which had been previously deferred, which is a component ofdiscontinued operations in the consolidated statement of operations.Allocation of Eisai Agreement arrangement consideration to the units of accounting.The total arrangement consideration of $115.6 million primarily consists of (i) the December 28, 2016, balances of deferred revenues from the upfrontpayments received under the prior Eisai agreements and the distribution agreements with Ildong, CYB and Teva; (ii) the $10.0 million payment receivedfrom Eisai on December 28, 2016; and (iii) the product purchase payments and manufacturing support payments we expect to receive from Eisai for the initialtwo-year manufacturing and supply commitment period.All of the deliverables were determined to have standalone value and to meet the criteria to be accounted for as separate units of accounting. Factorsconsidered in the determination included, among other things, for the license, the manufacturing experience and capabilities of Eisai and their sublicenserights, and for the remaining deliverables the fact that they are not proprietary and can be provided by other vendors. The total arrangement considerationwas allocated to the units of accounting on the basis of their relative estimated selling prices as follows: •$64.0 million was allocated to the License Deliverable. As the License Deliverable was delivered on December 28, 2016, this amount wasrecognized as collaboration revenue of continuing operations for the year ended December 31, 2016. •$30.8 million was allocated to the Inventory Deliverable. Title to this entire inventory passed to Eisai on December 28, 2016. However, none ofthis inventory was physically transferred from the manufacturing facility on that date. There is no fixed schedule for delivery given a portionhas been and will be delivered on a continuous basis as we perform under the manufacturing commitment, another portion has been and will bephysically transferred to Eisai upon request by Eisai and the rest is expected to be physically transferred at the end of the manufacturing andsupply commitment period. Also, the risks of ownership for this inventory did not pass to Eisai in 2016 as we have financial responsibility forloss, damage or destruction which occurs while in our possession. Therefore, none of the arrangement consideration allocated to thisdeliverable was recognized as revenue and none of the carrying value of this inventory was recognized as cost of product sales for the yearended December 31, 2016. For the year ended December 31, 2017, we recognized $6.4 million as58 revenue of discontinued operations related to this deliverable and $0.9 million of the carrying value of this inventory as cost of product sales ofdiscontinued operations. •$20.8 million was allocated to the Manufacturing and Supply Commitment Deliverable. This deliverable is being provided over 2017 and2018 as product is shipped to Eisai. Therefore, none of the arrangement consideration allocated to this deliverable was recognized as revenuefor the year ended December 31, 2016. For the year ended December 31, 2017, we recognized $9.5 million as revenue of discontinuedoperations related to this deliverable. The estimated selling price represents the price at which we would contract if the deliverable was sold regularly on a standalone basis. The estimatedselling price for each unit of accounting was determined as follows: •The estimated selling price for the License Deliverable was determined using an income approach that estimates the net present value ofroyalties Eisai is expected to earn under the Eisai Agreement as compared to the Second Amended Agreement, net of the development costs weare no longer obligated to spend. This model includes several assumptions, including the potential market for lorcaserin in each relevantjurisdiction, probabilities of obtaining regulatory approval in additional jurisdictions, the impact of competition, the potential impact ofEisai’s ongoing development and regulatory activities related to lorcaserin, and the appropriate discount rate. •The estimated selling price for the Inventory Deliverable was determined by considering the historical cost of the precursor materials, adjustedfor any changes in market condition and supplier relationships. We believe that the Eisai Agreement pricing represents pricing that would becharged if it were sold on a standalone basis. •The estimated selling price for the Manufacturing and Supply Commitment Deliverable was determined to be the aggregate product purchasepayments we expect to receive from Eisai for the initial two-year manufacturing and supply commitment period. As noted above, we believethat the Eisai Agreement pricing represents pricing that would be charged if it were sold on a standalone basis. Development payments.As part of the US approval of BELVIQ, the FDA, is requiring the evaluation of the effect of long-term treatment with BELVIQ on the incidence ofmajor adverse cardiovascular events, or MACE, in overweight and obese patients with cardiovascular disease or multiple cardiovascular risk factors (which isthe FDA-required portion of the cardiovascular outcomes trial), as well as the conduct of postmarketing studies to assess the safety and efficacy of BELVIQfor weight management in obese pediatric and adolescent patients. Under the Second Amended Agreement, Eisai and we were responsible for 90% and 10%,respectively, of the cost for the FDA-required portion of the cardiovascular outcomes trial, or CVOT, 50% and 50%, respectively, of the non-FDA portion ofthe studies and we were also obligated to share the cost of FDA-required studies in obese pediatric patients and for additional clinical studies in otherterritories.Under the Eisai Agreement, Eisai is solely responsible for all costs and expenses in connection with further development of lorcaserin from and afterJuly 1, 2016, and we were relieved of any obligations under the Second Amended Agreement to pay our share of future development costs of lorcaserin.Accordingly, on December 28, 2016, we recorded a reduction of research and development expenses which would have been otherwise due to Eisai under theSecond Amended Agreement of $3.7 million for the period from July 1, 2016, through December 28, 2016.December 31, 2016, and 2015, we recognized expenses of $4.2 million, and $10.8 million, respectively, for external clinical study fees related tolorcaserin, which are included in continuing operations. There were no such expenses in 2017. Additionally, for the years ended December 31, 2017, 2016,and 2015 we recognized expenses of $1.4 million, $3.1 million, and $5.4 million, respectively for internal non-commercial manufacturing costs primarilyrelated to lorcaserin, which are included in discontinued operations.Ildong Pharmaceutical Co., Ltd.In November 2012, we and Ildong entered into the Marketing and Supply Agreement, or Ildong Agreement. Under this agreement, we granted Ildongexclusive rights to commercialize BELVIQ in South Korea for weight loss or weight management in obese and overweight patients. We also provided certainservices and manufacture and sold BELVIQ to Ildong. As noted above, the Ildong Agreement was assigned to Eisai pursuant to the Eisai Agreement onDecember 28, 2016.In connection with entering into the Ildong Agreement, we received from Ildong an upfront payment of $5.0 million, less withholding taxes.Revenues from this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoingdevelopment and regulatory activities. Accordingly, this payment was recognized ratably as revenue over the period in which we expected the services to berendered. The assignment of the Ildong Agreement pursuant to the59Eisai Agreement effectively eliminated our obligation to continue performing the development and regulatory activities required in the Ildong Agreement.Therefore, on December 28, 2016, the $3.5 million of deferred revenues from this upfront payment was allocated to the value of the License provided to Eisaiand recognized as revenue in 2016.In February 2015, we earned a substantive milestone payment of $3.0 million upon the approval of BELVIQ for marketing in South Korea for weightmanagement. We received the payment, less withholding taxes, in March 2015.Under the Ildong Agreement, we manufactured BELVIQ at our facility in Zofingen, Switzerland, and sold BELVIQ to Ildong for a purchase pricestarting at the higher of the defined minimum amount or 35% of Ildong’s annual net product sales (which are the gross invoiced sales less certain deductionsdescribed in the Ildong Agreement), or the Ildong Product Purchase Price. The Ildong Product Purchase Price increased on a tiered basis up to the higher ofthe defined minimum amount or 45% on the portion of annual net product sales exceeding $15.0 million. Since the inception of commercial sales of BELVIQin South Korea in 2015, the Ildong Product Purchase Price equaled the defined minimum amount (which exceeded the amounts calculated using theapplicable percentages for the applicable tiers of Ildong’s annual net product sales).Prior to December 2016, we deferred recognition of revenue and the related cost at the time we sold BELVIQ to Ildong because we did not have theability to estimate the amount of product that could have been returned to us and thus recognized revenues and the related costs from net product sales whenIldong shipped BELVIQ to its distributors. In December 2016, we determined that we achieved the ability to reasonably estimate product returns under theIldong Agreement. Accordingly, we recognized revenues of $2.0 million and costs of $0.7 million in December 2016 on net product sales which had beenpreviously deferred, which is a component of discontinued operations in the consolidated statement of operations.For the years ended December 31, 2016 and 2015, we recognized revenues of $11.4 million and $8.9 million, respectively, under the Ildongagreement, of which $7.2 million and $5.5 million, respectively are included in discontinued operations. No revenues were recognized during the year endedDecember 31, 2017 under this agreement.CY Biotech Company Limited.In July 2013, we entered into the CYB Agreement. Under this agreement, we granted CYB exclusive rights to commercialize BELVIQ in Taiwan forweight loss or weight management in obese and overweight patients, subject to regulatory approval of BELVIQ by the Taiwan Food and DrugAdministration, or TFDA. The CYB Agreement provided for us to perform certain services and to manufacture and sell BELVIQ to CYB. As noted above, theCYB Agreement was assigned to Eisai pursuant to the Eisai Agreement on December 28, 2016.In connection with entering into the CYB agreement, we received from CYB an upfront payment of $2.0 million, less withholding taxes. Revenuesfrom this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoing development andregulatory activities. Accordingly, this payment was recognized ratably as revenue over the period in which we expected the services to be rendered. Theassignment of the CYB Agreement pursuant to the Eisai Agreement effectively eliminated our obligation to continue performing the development andregulatory activities required in the CYB Agreement. Therefore, on December 28, 2016, the $1.7 million of deferred revenues from this upfront payment wasallocated to the value of the License provided to Eisai and recognized as revenue in 2016.For the years ended December 31, 2016 and 2015, we recognized revenues of $1.8 million and $0.2 million, respectively, under this agreement. Norevenues were recognized during the year ended December 31, 2017 under this agreement.Axovant Sciences GmbH.In May 2015, we entered into a Development, Marketing and Supply Agreement with Roivant Sciences Ltd., or Roivant. In October 2015, Roivant,assigned the exclusive rights to develop and commercialize nelotanserin to its subsidiary, Axovant. Under this agreement, Axovant has exclusive worldwiderights to develop and commercialize nelotanserin, subject to regulatory approval. We also provide certain services and will manufacture and sell nelotanserinto Axovant.We received an upfront payment of $4.0 million, which was recorded as deferred revenues and is being recognized as revenue ratably overapproximately five years, which is the period in which we expect to provide services under the arrangement. We are entitled to receive payments from sales ofnelotanserin under the agreement and are eligible to receive purchase price adjustment payments based on Axovant’s annual net product sales. We are alsoeligible to receive up to an aggregate of $41.5 million in success milestones in case of full development and regulatory success of nelotanserin. Of thesepayments, two development milestones totaling $4.0 million are substantive and four regulatory milestones totaling $37.5 million are substantive.60For the years ended December 31, 2017, 2016, and 2015, and we recognized revenues of $2.2 million, $2.1 million and $1.1 million, respectively,under this agreement.Boehringer Ingelheim International GmbH.In December 2015, we and Boehringer Ingelheim entered into an exclusive agreement, under which we and Boehringer Ingelheim conduct jointresearch to identify drug candidates targeting an undisclosed G protein-coupled receptor, or GPCR, that belongs to the group of orphan central nervoussystem, or CNS, receptors. Under this agreement, we granted Boehringer Ingelheim exclusive rights to our internally discovered, novel compounds andintellectual property for an orphan CNS receptor. We jointly conduct research with Boehringer Ingelheim to identify additional drug candidates that aresuitable for continued research and development as therapeutic compounds for various disease indications, with the initial focus expected to be psychiatricdiseases such as schizophrenia. The agreement grants Boehringer Ingelheim exclusive worldwide rights to develop, manufacture and commercialize productsresulting from the collaboration.In part consideration of the rights to our intellectual property necessary or useful to conduct the joint research under the agreement, we received fromBoehringer Ingelheim an upfront payment of $7.5 million in January 2016, less $1.2 million of withholding taxes which was refunded to us in October 2016.Revenues from this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoingparticipation in the joint research, and are being recognized ratably as revenues over the period in which we expect the services to be rendered, which isapproximately two years.We are also eligible to receive up to an aggregate of $251.0 million (of which up to $12.0 million is payable to Beacon) in success milestones in caseof full commercial success of multiple drug products. Of these payments, three development milestones totaling $7.0 million are substantive, threedevelopment milestones totaling $30.0 million are non-substantive, nine regulatory milestones totaling $84.0 million are non-substantive and fourcommercial milestones totaling $130.0 million are non-substantive.For the years ended December 31, 2017, and 2016, we recognized revenues of $5.1 million and $5.1 million, respectively under this agreement. Wedid not recognize any revenues under this agreement during the year ended December 31, 2015.CRITICAL ACCOUNTING POLICIES AND MANAGEMENT ESTIMATESThe SEC defines critical accounting policies as those that are, in management’s view, important to the portrayal of our financial condition and resultsof operations and demanding of management’s judgment. Our discussion and analysis of financial condition and results of operations is based on ourconsolidated financial statements, which have been prepared in accordance with the US generally accepted accounting principles, or GAAP. The preparationof these financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses andrelated disclosures. We base our estimates on historical experience and on various assumptions that we believe are reasonable under the circumstances, theresults of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actualresults may differ significantly from those estimates.While our significant accounting policies are described in more detail in Note 1 to our consolidated financial statements included in this AnnualReport, we believe the following accounting policies are critical in the preparation of our financial statements:Revenue recognition. Our revenues to date have been generated primarily through collaboration agreements. Our collaboration agreements maycontain multiple elements including commercialization rights, services (joint steering committee and research and development services) and manufacturedproducts. Consideration we receive under these arrangements may include upfront payments, research and development funding, cost reimbursements,milestone payments, payments for product sales and royalty payments. We recognize revenue when (i) persuasive evidence of an arrangement exists,(ii) delivery has occurred and title has passed, (iii) the price is fixed or determinable and (iv) collectability is reasonably assured. Any advance payments wereceive in excess of amounts earned are classified as deferred revenues.We evaluate deliverables in a multiple-element arrangement to determine whether each deliverable represents a separate unit of accounting. Adeliverable constitutes a separate unit of accounting when it has standalone value to the customer. If the delivered element does not have standalone valuewithout one of the undelivered elements in the arrangement, we combine such elements and account for them as a single unit of accounting. The arrangementconsideration that is fixed or determinable at the inception of the arrangement is allocated to each unit of accounting at the inception of the arrangementbased on the relative selling price. Determining whether a deliverable is a separate unit of accounting as well as estimating the selling prices of such unit ofaccounting requires the use of significant judgment. A change in such judgment could result in a significant change in the period in which revenue isrecognized.To determine the selling price of a separate deliverable, we use the hierarchy as prescribed in Accounting Standards Codification Topic 605-25 based on vendor-specific objective evidence, or VSOE, third-party evidence, or TPE, or best estimate of61selling price, or BESP. VSOE is based on the price charged when the element is sold separately and is the price actually charged for thatdeliverable. TPE is determined based on third-party evidence for a similar deliverable when sold separately. BESP is the estimated selling price atwhich we would transact a sale if the elements of collaboration and license arrangements were sold on a stand-alone basis to the buyer. We maynot be able to establish VSOE or TPE for the deliverables within collaboration and license arrangements, as we may not have a history of enteringinto such arrangements or selling the individual deliverables within such arrangements separately. In addition, there may be significantdifferentiation in these arrangements, which indicates that comparable third-party pricing may not be available. We may determine that the sellingprice for the deliverables within collaboration and license arrangements should be determined using BESP. The process for determining BESPinvolves significant judgment and includes consideration of multiple factors such as estimated revenues, market size, and development risk,among other factors contemplated in negotiating the arrangement with the customer.Non-refundable upfront payments received under our collaboration agreements for commercialization rights are deferred if such rights are not deemedto have standalone value without ongoing services which may be required under the agreement. If deferred, such amounts are recognized as revenues on astraight-line basis over the period in which we expect to perform the services. In December 2016, we recognized a portion of the previously unrecognizednon-refundable upfront payments received from Eisai and other BELVIQ distributors as revenues in the amount of arrangement consideration allocated to theunit of accounting delivered to Eisai under the Eisai Agreement.Amounts we receive as reimbursement for our research and development expenditures are recognized as revenue as the services are performed.Under the milestone method, we recognize revenue that is contingent upon the achievement of a substantive milestone in its entirety in the period inwhich the milestone is achieved. A milestone is an event (i) that can be achieved in whole or in part on either our performance or on the occurrence of aspecific outcome resulting from our performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event willbe achieved and (iii) that would result in additional payments being due us. A milestone payment is considered substantive when the consideration payableto us for each milestone (a) is consistent with our performance necessary to achieve the milestone or the increase in value to the collaboration resulting fromour performance, (b) relates solely to our past performance and (c) is reasonable relative to all of the other deliverables and payments under the arrangement.In making this assessment, we consider all facts and circumstances relevant to the arrangement, including factors such as the scientific, regulatory,commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respectivemilestone and whether any portion of the milestone consideration is related to future performance or deliverables. Other contingent-based payments receivedare recognized when earned.Clinical trial expenses. We accrue clinical trial expenses based on work performed. In determining the amount to accrue, we rely on estimates of totalcosts incurred based on enrollment, the completion of trials and other events. We follow this method because we believe reasonably dependable estimates ofthe costs applicable to various stages of a clinical trial can be made. However, the actual costs and timing of clinical trials are uncertain, subject to risks andmay change depending on a number of factors. Differences between the actual clinical trial costs and the estimated clinical trial costs that we have accrued inany prior period are recognized in the subsequent period in which the actual costs become known. Historically, these differences have not been material;however, material differences could occur in the future.Accounting for long-lived assets. We assess the impairment of long-lived assets, consisting of property and equipment, and finite-lived intangibleassets, whenever events or circumstances indicate that the carry value may not be recoverable. Examples of such circumstances include: (1) loss of legalownership or title to an asset; (2) significant changes in our strategic business objectives and utilization of the assets; and (3) the impact of significantnegative industry or economic trends. If a change were to occur in any of the above-mentioned factors the likelihood of a material change in our net losswould increase.If such assets are considered impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceedsthe fair value of the assets. In addition, we base useful lives and amortization or depreciation expense on our subjective estimate of the period that the assetswill generate revenue or otherwise be used by us. The estimated fair value of the asset group is based on an estimate of the net proceeds we would receiveupon disposition of the asset group to a market participant. As the estimates used are based on the best information available at the time of the estimates,additional impairment charges may be required in the future as additional facts and information become available.Share-based compensation. We grant equity-based awards under our share-based compensation plan and, from time to time, under inducement awardsoutside of our share-based compensation plan. We estimate the fair value of stock option awards using the Black-Scholes option pricing model. This fairvalue is then amortized over the requisite service periods of the awards. The Black-Scholes option pricing model requires the input of subjectiveassumptions, including price volatility of the underlying stock, risk-free interest rate, dividend yield, and expected life of the option. We estimate the fairvalue of restricted stock unit awards based on the closing price of our common stock at the date of grant. Prior to 2017, we estimated forfeitures at the time ofgrant and revised our62estimate in subsequent periods if actual forfeitures differed from those estimates. Beginning January 1, 2017, in accordance with ASU No. 2016-09,Improvements to Employee Share-Based Payment Accounting, we account for the forfeitures at the time they occur. Changes in assumptions used under theBlack-Scholes option pricing model could materially affect our net loss and net loss per share.Income taxes. Significant judgment is required by management to determine our provision for income taxes, our deferred tax assets and liabilities, andthe valuation allowance to record against our net deferred tax assets, which are based on complex and evolving tax regulations throughout the world. Our taxcalculation is impacted by tax rates in the jurisdictions in which we are subject to tax and the relative amount of income earned in each jurisdiction. Ourdeferred tax assets and liabilities are determined using the enacted tax rates expected to be in effect for the years in which those tax assets are expected to berealized.The effect of an uncertain income tax position is recognized at the largest amount that is “more-likely-than-not” to be sustained under audit by thetaxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained.The realization of our deferred tax assets is dependent upon our ability to generate sufficient future taxable income. We establish a valuationallowance when it is more-likely-than-not that the future realization of all or some of the deferred tax assets will not be achieved. The evaluation of the needfor a valuation allowance is performed on a jurisdiction-by-jurisdiction basis, and includes a review of all available evidence, both positive and negative. AtDecember 31, 2017, we concluded that it was more-likely-than-not that our deferred tax assets would not be realized.The above listing is not intended to be a comprehensive list of all of our accounting policies. In many cases, the accounting treatment of a particulartransaction is specifically dictated by GAAP. See our audited consolidated financial statements and notes thereto included elsewhere in this Annual Report,which contain additional accounting policies and other disclosures required by GAAP.Item 7A. Quantitative and Qualitative Disclosures About Market RiskInterest Rate RiskWe invest our excess cash in investment-grade, interest-bearing securities. The primary objective of our investment activities is to preserve principaland liquidity. To achieve this objective, we invest in a money market fund, US Treasury notes, and high quality marketable debt instruments of corporationsand government sponsored enterprises with contractual maturity dates of generally less than two years. All investment securities have a credit rating of atleast A or better, as determined by Moody’s Investors Service, Standard & Poor’s or Fitch Ratings. If a 10% change in interest rates were to have occurred onDecember 31, 2017, this change would not have had a material effect on the fair value of our investment portfolio as of that date.Foreign Currency Exchange RiskWe have two wholly owned subsidiaries in Switzerland, which exposes us to foreign currency exchange risk. The functional currency of oursubsidiaries in Switzerland is the Swiss franc. Accordingly, all assets and liabilities of our subsidiaries are translated to US dollars based on the applicableexchange rate on the balance sheet date. Revenue and expense components are translated to US dollars at weighted-average exchange rates in effect duringthe period. Gains and losses resulting from foreign currency translation are reported as a separate component of accumulated other comprehensive gain (loss)in the equity section of our consolidated balance sheets.Foreign currency transaction gains and losses recorded in continuing operations are insignificant. If a 10% change in the US dollar-to-Swiss francexchange rate were to have occurred on December 31, 2017, this change would not have had a material effect on our results of continuing operations.We have not hedged exposures denominated in foreign currencies, but may do so in the future.63Item 8. Financial Statements and Supplementary DataARENA PHARMACEUTICALS, INC.INDEX TO CONSOLIDATED FINANCIAL STATEMENTS Page Report of Independent Registered Public Accounting Firm65Consolidated Balance Sheets66Consolidated Statements of Operations and Comprehensive Loss67Consolidated Statements of Equity68Consolidated Statements of Cash Flows69Notes to Consolidated Financial Statements70 64Report of Independent Registered Public Accounting FirmThe Stockholders and Board of DirectorsArena Pharmaceuticals, Inc.: Opinion on the Consolidated Financial StatementsWe have audited the accompanying consolidated balance sheets of Arena Pharmaceuticals, Inc. and subsidiaries (the Company) as of December 31, 2017 and2016, the related consolidated statements of operations and comprehensive loss, equity, and cash flows for each of the years in the three‑year period endedDecember 31, 2017, and the related notes (collectively, the “consolidated financial statements”). In our opinion, the consolidated financial statementspresent fairly, in all material respects, the financial position of the Company as of December 31, 2017 and 2016, and the results of its operations and its cashflows for each of the years in the three‑year period ended December 31, 2017, in conformity with U.S. generally accepted accounting principles.We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’sinternal control over financial reporting as of December 31, 2017, based on criteria established in Internal Control – Integrated Framework (2013) issued bythe Committee of Sponsoring Organizations of the Treadway Commission, and our report dated March 14, 2018 expressed an unqualified opinion on theeffectiveness of the Company’s internal control over financial reporting.Basis for OpinionThese consolidated financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on theseconsolidated financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent withrespect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and ExchangeCommission and the PCAOB.We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonableassurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud. Our audits included performingprocedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures thatrespond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financialstatements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating theoverall presentation of the consolidated financial statements. We believe that our audits provide a reasonable basis for our opinion./s/ KPMG LLP We have served as the Company’s auditor since 2010.San Diego, CaliforniaMarch 14, 2018 65ARENA PHARMACEUTICALS, INC.Consolidated Balance Sheets(In thousands, except share and per share data) December 31, 2017 2016 Assets Current assets: Cash and cash equivalents $158,837 $90,712 Short-term investments, available-for-sale 88,240 — Accounts receivable 2,357 573 Insurance recovery receivable 12,025 — Prepaid expenses and other current assets 2,681 2,169 Assets of disposal group held for sale 17,140 26,435 Total current assets 281,280 119,889 Investments, available-for-sale 24,242 — Land, property and equipment, net 30,131 35,109 Assets of disposal group held for sale, non-current — 11,171 Other non-current assets 3,622 2,841 Total assets $339,275 $169,010 Liabilities and Equity Current liabilities: Accounts payable and other accrued liabilities $7,916 $5,676 Accrued clinical and preclinical study fees 7,706 3,883 Accrued litigation settlement 24,000 — Current portion of deferred revenues 1,110 4,410 Current portion of lease financing obligations 4,000 3,518 Liabilities of disposal group held for sale 27,595 46,392 Total current liabilities 72,327 63,879 Other long-term liabilities 989 821 Deferred revenues, less current portion 1,067 2,167 Lease financing obligations, less current portion 57,748 61,748 Commitments and contingencies Equity: Preferred stock, $0.0001 par value, 7,500,000 shares authorized, no shares issued and outstanding at December 31, 2017, and 2016 — — Common stock, $0.0001 par value, 73,500,000 shares authorized at December 31, 2017, and 367,500,000 shares authorized at December 31, 2016; 39,280,687 shares issued and outstanding at December 31, 2017; 24,340,080 shares issued and outstanding at December 31, 2016 4 2 Additional paid-in capital 1,698,543 1,441,737 Accumulated other comprehensive loss (1,216) (3,099)Accumulated deficit (1,490,187) (1,398,736)Total equity attributable to stockholders of Arena 207,144 39,904 Equity attributable to noncontrolling interest in consolidated variable interest entity — 491 Total equity 207,144 40,395 Total liabilities and equity $339,275 $169,010 See accompanying notes to consolidated financial statements. 66ARENA PHARMACEUTICALS, INC.Consolidated Statements of Operations and Comprehensive Loss(In thousands, except per share data) Years ended December 31, 2017 2016 2015 Revenues Collaboration and other revenue $19,632 $92,163 $13,398 Royalty revenue 1,705 — — Total revenues 21,337 92,163 13,398 Operating costs and expenses Research and development 70,988 63,782 83,283 General and administrative 30,341 27,529 30,281 Litigation settlement expense, net 11,975 — — Restructuring charges — 6,115 3,346 Total operating costs and expenses 113,304 97,426 116,910 Loss from operations (91,967) (5,263) (103,512)Interest and other income (expense) Interest income 492 290 158 Interest expense (6,119) (6,512) (6,828)Gain from valuation of derivative liabilities — — 474 Other income (expense) 1,740 (815) (999)Total interest and other expense, net (3,887) (7,037) (7,195)Loss from continuing operations (95,854) (12,300) (110,707)Income (loss) from discontinued operations 3,122 (10,596) 2,728 Net loss (92,732) (22,896) (107,979)Less net loss attributable to noncontrolling interest in consolidated variable interest entity 1,325 380 — Net loss attributable to stockholders of Arena $(91,407) $(22,516) $(107,979) Amounts attributable to stockholders of Arena: Loss from continuing operations $(94,529) $(11,920) $(110,707)Income (loss) from discontinued operations 3,122 (10,596) 2,728 $(91,407) $(22,516) $(107,979) Net income (loss) attributable to stockholders of Arena per share, basic and diluted: Continuing operations $(2.87) $(0.49) $(4.60)Discontinued operations 0.10 (0.44) 0.11 $(2.77) $(0.93) $(4.49) Shares used in calculating net income (loss) attributable to stockholders of Arena per share, basic and diluted 32,990 24,313 24,067 Comprehensive Loss: Net loss $(92,732) $(22,896) $(107,979)Foreign currency translation adjustment 2,016 (1,920) (4,087)Unrealized loss on available-for-sale investments (133) — — Comprehensive loss (90,849) (24,816) (112,066)Less comprehensive loss attributable to noncontrolling interest in consolidated variable interest entity 1,325 380 — Comprehensive loss attributable to stockholders of Arena $(89,524) $(24,436) $(112,066) See accompanying notes to consolidated financial statements. 67ARENA PHARMACEUTICALS, INC.Consolidated Statements of Equity(In thousands, except share data) Common Stock AdditionalPaid-InCapital AccumulatedOtherComprehensiveIncome (Loss) AccumulatedDeficit Total EquityAttributabletoStockholdersofArena Equity AttributabletoNoncontrollingInterestin ConsolidatedVariable InterestEntity TotalEquity Shares Amount TotalEquity Balance at December 31, 2014 22,032,165 $2 $1,312,676 $2,908 $(1,268,241)$47,345 $— $47,345 Issuance of common stock tounderwriters, net 2,100,000 — 100,658 — — 100,658 — 100,658 Issuance of common stock upon exerciseof options 115,408 — 2,211 — — 2,211 — 2,211 Issuance of common stock underemployee stock purchase plan 32,795 — 758 — — 758 — 758 Issuance of common stock upon vestingof restricted stock unit awards 6,750 — — — — — — — Share-based compensation expense, net of forfeitures — — 14,463 — — 14,463 — 14,463 Share-based compensation expensecapitalized — — 173 — — 173 — 173 Translation loss — — — (4,087) (4,087) — (4,087)Net loss — — — — (107,979) (107,979) — (107,979)Balance at December 31, 2015 24,287,118 2 1,430,939 (1,179) (1,376,220) 53,542 — 53,542 Issuance of common stock upon exerciseof options 11,556 — 179 — — 179 — 179 Issuance of common stock underemployee stock purchase plan 14,140 — 203 — — 203 — 203 Issuance of common stock upon vestingof restricted stock unit awards 27,266 — — — — — — — Share-based compensation expense, net of forfeitures — — 11,117 — — 11,117 — 11,117 Share-based compensation expensecapitalized — — 170 — — 170 — 170 Contribution to variable interest entity — — (871) — — (871) 871 — Translation loss — — — (1,920) — (1,920) — (1,920)Net loss — — — — (22,516) (22,516) (380) (22,896)Balance at December 31, 2016 24,340,080 2 1,441,737 (3,099) (1,398,736) 39,904 491 40,395 Adoption of ASU No. 2016-09 — — 44 — (44) — — — Issuance of common stock tounderwriters, net 14,087,500 2 236,386 — — 236,388 — 236,388 Issuance of common stock under the ATMfacility, net 489,023 — 6,987 — — 6,987 — 6,987 Issuance of common stock upon exerciseof options 323,431 — 5,404 — — 5,404 — 5,404 Issuance of common stock underemployee stock purchase plan and upon vesting ofrestricted stock unit awards 40,653 — 12 — — 12 — 12 Share-based compensation expense — — 7,973 — — 7,973 17 7,990 Unrealized loss on available-for-saleinvestments — — — (133) — (133) — (133)Translation gain — — — 2,016 — 2,016 — 2,016 Net loss — — — — (91,407) (91,407) (1,325) (92,732)Deconsolidation of variable interest entity — — — — — — 817 817 Balance at December 31, 2017 39,280,687 $4 $1,698,543 $(1,216)$(1,490,187)$207,144 $— $207,144 See accompanying notes to consolidated financial statements. 68ARENA PHARMACEUTICALS, INC.Consolidated Statements of Cash Flows(In thousands) Years ended December 31, 2017 2016 2015 Operating activities: Net loss $(92,732) $(22,896) $(107,979)Adjustments to reconcile net loss to net cash used in operating activities: (Income) loss from discontinued operations (3,122) 10,596 (2,728)Depreciation and amortization 4,278 4,994 5,430 Share-based compensation 7,855 11,075 14,112 Gain from valuation of derivative liabilities — — (474)Litigation settlement expense, net 11,975 — — Amortization of prepaid financing costs 136 136 136 Loss (gain) on disposal of equipment (379) 1,270 1,007 Changes in operating assets and liabilities: Accounts receivable 10,787 (12,246) 781 Prepaid expenses and other assets 585 1,753 (641)Payables and accrued liabilities 1,803 2,410 (2,092)Deferred revenues (4,401) (69,078) (4,647)Other long-term liabilities (577) 30 101 Net cash used in operating activities - continuing operations (63,792) (71,956) (96,994)Net cash provided by (used in) operating activities - discontinued operations (2,850) 9,817 (1,119)Net cash used in operating activities (66,642) (62,139) (98,113)Investing activities: Purchases of available-for-sale securities, net (112,615) — — Deconsolidation of variable interest entity (406) — — Purchases of land, property and equipment (113) (814) (1,119)Proceeds from sale of equipment 789 954 2,232 Other non-current assets (5) (654) 609 Net cash provided by (used in) investing activities - continuing operations (112,350) (514) 1,722 Net cash used in investing activities - discontinued operations (40) (236) (9,873)Net cash used in investing activities (112,390) (750) (8,151)Financing activities: Principal payments on lease financing obligations (3,518) (2,979) (2,492)Proceeds from issuance of common stock 248,805 370 103,628 Other financing activities — 320 — Net cash provided by (used in) financing activities 245,287 (2,289) 101,136 Effect of exchange rate changes on cash 1,870 (294) (1,897)Net decrease in cash and cash equivalents 68,125 (65,472) (7,025)Cash and cash equivalents at beginning of year 90,712 156,184 163,209 Cash and cash equivalents at end of year $158,837 $90,712 $156,184 Supplemental disclosure of cash flow information: Interest paid $5,967 $6,303 $6,562 See accompanying notes to consolidated financial statements. 69ARENA PHARMACEUTICALS, INC.Notes to Consolidated Financial Statements 1. The Company and Summary of Significant Accounting PoliciesThe CompanyArena Pharmaceuticals, Inc., or Arena, was incorporated on April 14, 1997, and commenced operations in July 1997. We are a biopharmaceuticalcompany focused on developing novel, small molecule drugs with optimized receptor pharmacology designed to deliver broad clinical utility acrossmultiple therapeutic areas. Our proprietary pipeline includes potentially first or best in class programs for which we own global commercial rights.Our three most advanced investigational clinical programs are ralinepag in preparation of Phase 3 program for pulmonary arterial hypertension, orPAH, etrasimod in late Phase 2 evaluation for multiple inflammatory indications, and APD371 in Phase 2 evaluation for the treatment of pain associated withCrohn's disease.Additionally, we have collaborations with the following pharmaceutical companies: Everest Medicines Limited, or Everest, (ralinepag and etrasimodin Greater China and select Asian countries), Axovant Sciences GmbH, or Axovant, (nelotanserin - Phase 2), Boehringer Ingelheim International GmbH, orBoehringer Ingelheim, (undisclosed target - preclinical) and Eisai Co., Ltd. and Eisai Inc. (collectively, Eisai) (BELVIQ® / BELVIQ XR® - marketedproduct).We operate in one business segment. Our primary clinical operations are conducted in San Diego, California and in Zug, Switzerland by ArenaPharmaceuticals Development GmbH, or APD GmbH, our wholly-owned subsidiary. Our commercial and development manufacturing operations areconducted by Arena GmbH, our wholly-owned subsidiary located in Zofingen, Switzerland.In order to further focus our efforts and resources on our strategic objectives of developing our pipeline drug candidates, on March 9, 2018, we enteredinto an Asset Purchase Agreement, or Sale Agreement, with Siegfried Pharma AG and Siegfried AG, (collectively and individually, Siegfried). Under the SaleAgreement, we agreed to sell and assign to Siegfried, and Siegfried agreed to purchase and assume from Arena GmbH, certain drug product finishing facilityassets and know-how, including fixtures, equipment, other personal property and real estate assets located in Zofingen, Switzerland and related contracts andcertain related liabilities after the closing, or collectively, Manufacturing Operations. We refer to this transaction as the Siegfried Transaction. In connectionwith the Siegfried Transaction, all of Arena GmbH’s approximately 50 current employees are expected to transfer to Siegfried. The Siegfried Transaction isexpected to close on or about March 31, 2018, subject to satisfaction or waiver of certain customary closing conditions. We have excluded from ourcontinuing operations for all periods presented in this report revenues and expenses associated with our Manufacturing Operations, which are reported asdiscontinued operations. See Note 5 for additional information on the Manufacturing Operations.Basis of PresentationThe accompanying consolidated financial statements have been prepared in accordance with the US generally accepted accounting principles, orGAAP, and reflect all of our activities, including those of our wholly owned subsidiaries. All material intercompany accounts and transactions have beeneliminated in consolidation. The accompanying consolidated financial statements also include the activity of Beacon, a variable interest entity in which wehad a controlling financial interest until December 2017 at which point we deconsolidated Beacon (see Note 15). The results of operations andcomprehensive loss attributable to the noncontrolling interest in Beacon are presented as separate components from the results of operations andcomprehensive loss attributable to the stockholders of Arena in the consolidated statements of operations and comprehensive loss.On June 14, 2017, we filed a certificate of amendment to our certificate of incorporation with the Secretary of State of the State of Delaware to effect aone-for-ten reverse split of our issued and outstanding common stock. The accompanying consolidated financial statements and notes thereto giveretrospective effect to the reverse stock split for all periods presented. All issued and outstanding common stock, options exercisable for common stock,restricted stock units, performance restricted stock units, and per share amounts contained in the consolidated financial statements have been retrospectivelyadjusted to reflect this reverse stock split for all periods presented. Concurrent with the reverse stock split we effected a reduction in the number of authorizedshares of common stock from 367,500,000 shares to 73,500,000 shares.70As a result of the anticipated divestiture of our Manufacturing Operations, we have retrospectively revised the consolidated statements of operationsand cash flows for the years ended December 31, 2016 and 2015 and the consolidated balance sheet as of December 31, 2016, to reflect the operations andcash flows of the Manufacturing Operations as discontinued operations and the related assets and liabilities as held for sale.LiquidityAs of December 31, 2017, we had cash and cash equivalents and available-for-sale investments of approximately $271.3 million. We believe our cashand cash equivalents and investments will be sufficient to fund our operations for at least the next 12 months from the date these consolidated financialstatements are issued.We will require substantial cash to achieve our objectives of discovering, developing and commercializing drugs, as this process typically takesmany years and potentially hundreds of millions of dollars for an individual drug. We may not have adequate available cash, or assets that could be readilyturned into cash, to meet these objectives in the long term. We will need to obtain significant funds under our existing collaborations, under newcollaboration, licensing or other commercial agreements for one or more of our drug candidates and programs or patent portfolios, or from other potentialsources of liquidity, which may include the sale of equity, issuance of debt or other transactions.Recent Accounting PronouncementsRevenue recognition.In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2014-09, Revenue fromContracts with Customers. ASU No. 2014-09 supersedes most current revenue recognition guidance and establishes a comprehensive revenue recognitionmodel with a broad principle that would require an entity to recognize revenue to depict the transfer of promised goods or services to customers in an amountthat reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this principle, an entity identifiesthe contract with a customer, identifies the separate performance obligations in the contract, determines the transaction price, allocates the transaction priceto the separate performance obligations and recognizes revenue when each separate performance obligation is satisfied. FASB has subsequently issuedadditional ASUs to clarify certain elements of the new revenue recognition guidance.The new guidance allows for two methods of adoption: (a) “full retrospective” adoption, meaning the standard is applied to all periods presented, or(b) “modified retrospective” adoption, meaning the cumulative effect of applying the new guidance is recognized as an adjustment to the opening retainedearnings balance for the year of implementation. We will adopt the new revenue standard effective January 1, 2018, using the modified retrospective methodwith the cumulative effect of the change reflected in retained earnings as of January 1, 2018.As of December 31, 2017, we have completed our assessment of the new revenue standard and its impact to our consolidated financial statements andrelated disclosures, except for the impact related to our contracts with Eisai. We have completed an analysis of existing contracts with our other customersand assessed the differences in accounting for such contracts under ASU No. 2014-09 compared with current revenue accounting standards. In the future, wemay recognize revenue related to potential future milestones earlier than under the current standard. Currently, we defer recognition of milestones until themilestone is achieved. Under the new revenue standard, the receipt of such milestones will be accounted for as variable consideration, which may result inrevenue being recognized earlier provided it is probable that a significant reversal in revenue will not occur when the uncertainty associated with themilestone is resolved. Adoption of the new revenue standard will also result in additional revenue-related disclosures in the footnotes to our consolidatedfinancial statements.With the exception of our contracts with Eisai, we do not expect the adoption of ASU No. 2014-09 to have a material impact on our consolidatedfinancial statements. Regarding our contracts with Eisai, we are in the process of analyzing previous contract modifications and their impact on theidentification of satisfied and unsatisfied performance obligations, the determination of the transaction price, and the allocation of the transaction price to thesatisfied and unsatisfied performance obligations. Accordingly, we are not yet able to estimate the impact the adoption of ASU No. 2014-09 will have on ourconsolidated financial statements.Other.In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. ASU No. 2016-01supersedes and amends the guidance to classify equity securities with readily determinable fair values into different categories (that is, trading or available-for-sale) and require equity securities to be measured at fair value with changes in the fair value recognized through net income. The amendments allowequity investments that do not have readily determinable fair values to be remeasured at fair value either upon the occurrence of an observable price changeor upon identification of an71impairment. The amendments also require enhanced disclosures about those investments. ASU No. 2016-01 is effective for annual reporting beginning afterDecember 15, 2017, including interim periods within the year of adoption, and calls for prospective application, with early application permitted. We do notexpect the adoption of ASU No. 2016-01 to have a material impact on our consolidated financial statements.In February 2016, the FASB issued ASU No. 2016-02, Leases. ASU No. 2016-02 amends the accounting guidance for leases. The amendments containprinciples that will require lessees to recognize most leases on the balance sheet by recording a right-of-use asset and a lease liability, unless the lease is ashort-term lease that has an accounting lease term of 12 months or less. The amendments also contain other changes to the current lease guidance that mayresult in changes to how entities determine which contractual arrangements qualify as a lease, the accounting for executory costs (such as property taxes andinsurance), as well as which lease origination costs will be capitalizable. The new standard also requires expanded quantitative and qualitative disclosures.ASU No. 2016-02 is effective for annual reporting periods, and interim periods within those periods, beginning after December 15, 2018, with early adoptionpermitted. ASU No. 2016-02 requires the use of the modified retrospective transition method, whereby the new guidance will be applied at the beginning ofthe earliest period presented in the financial statements of the period of adoption. We are currently evaluating the impact of ASU No. 2016-02 on ourconsolidated financial statements.In November 2016, the FASB issued ASU No. 2016-18, Restricted Cash. ASU No. 2016-18 requires that restricted cash be included with cash and cashequivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU No. 2016-18 is effectivefor annual reporting periods beginning after December 15, 2017, including interim periods within the year of adoption, and calls for retrospective applicationto each period presented. We do not expect the adoption of ASU No. 2016-18 to have a material impact on our consolidated financial statements.In May 2017, the FASB issued ASU No. 2017-09, Scope of Modification Accounting. ASU No. 2017-09 clarifies which changes to the terms orconditions of a share-based payment award require an entity to apply modification accounting. This guidance is to be applied prospectively to awardsmodified on or after the adoption date and is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, with earlyadoption permitted. We do not expect the adoption of ASU 2017-09 to have a material impact on our consolidated financial statements unless there aresignificant changes to our outstanding share-based payment awards at which time we would assess the impact of the standard.Use of EstimatesThe preparation of financial statements in conformity with GAAP requires our management to make estimates and assumptions that affect the reportedamounts (including assets, liabilities, revenues and expenses) and related disclosures. The amounts reported could differ under different estimates andassumptions.Cash and Cash EquivalentsCash and cash equivalents consist of cash and highly liquid investments with remaining maturities of three months or less when purchased.Available-for-Sale InvestmentsWe define investments as income-yielding securities that can be readily converted to cash, and classify such investments as available-for-sale. Wecarry these securities at fair value, and report unrealized gains and losses as a separate component of accumulated other comprehensive income or loss. Thecost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interestincome. Realized gains and losses and declines in securities judged to be other than temporary are included in other income or expense. The cost of securitiessold is based on the specific identification method. Interest and dividends on available-for-sale securities are included in interest income.Concentrations of RiskFinancial instruments, which potentially subject us to concentrations of credit risk, consist primarily of cash and cash equivalents and available-for-sale investments. We limit our exposure to credit loss by holding our cash primarily in US dollars or, from time to time, placing our cash and investments inUS government, agency or government-sponsored enterprise obligations and in corporate debt instruments that are rated investment grade, in accordancewith an investment policy approved by our Board of Directors.Our customers are typically other biopharmaceutical companies to which we license our intellectual property, or sell research and developmentservices or other services under licensing or collaboration agreements. For the year ended December 31,722017, Everest, Boehringer Ingelheim and Axovant accounted for 56.2%, 23.8%, and 10.5%, respectively, of our total revenues. For the yearsended December 31, 2016, and 2015, more than 90% of our annual revenue was from Eisai and other BELVIQ distributors.As of December 31, 2017, Eisai, Axovant and Boehringer Ingelheim accounted for 61.1%, 17.6%, and 14.8%, respectively of our accounts receivable.As of December 31, 2016, Boehringer Ingelheim and Axovant accounted for 50.4% and 48.9%, respectively of our accounts receivable. We monitor ourcustomers' financial credit worthiness in order to assess and respond to any changes in their credit profile. During the years ended December 31, 2017, 2016,and 2015, we did not record any write-offs or reserves against accounts receivable.Property and EquipmentProperty and equipment are stated at cost and depreciated over the estimated useful lives of the assets (generally 3 to 15 years) using the straight-linemethod. Buildings are stated at cost and depreciated over an estimated useful life of approximately 20 years using the straight-line method. Leaseholdimprovements are stated at cost and amortized over the shorter of the estimated useful lives of the assets or the lease term using the straight-line method.Capital improvements are stated at cost and amortized over the estimated useful lives of the underlying assets using the straight-line method.Long-lived AssetsIf indicators of impairment exist, we assess the recoverability of the affected long-lived assets by determining whether the carrying value of such assetscan be recovered through undiscounted cash flows. If impairment is indicated, we measure the impairment loss by comparing the fair value to the carryingvalue of the asset.Deferred RentFor financial reporting purposes, rent expense and rental income are recognized on a straight-line basis over the term of the underlying lease orsublease. The difference between rent expense or rental income and amounts paid under lease agreements is recorded as an asset or a liability in ourconsolidated balance sheets.Foreign CurrencyThe functional currency of our wholly owned subsidiaries in Switzerland, Arena GmbH and APD GmbH is the Swiss franc. Accordingly, all assets andliabilities of these subsidiaries are translated to US dollars based on the applicable exchange rate on the balance sheet date. Revenue and expensecomponents are translated to US dollars at weighted-average exchange rates in effect during the period. Gains and losses resulting from foreign currencytranslation are reported as a separate component of accumulated other comprehensive income or loss in the equity section of our consolidated balance sheets.Foreign currency transaction gains and losses are primarily the result of remeasuring US dollar-denominated receivables and payables at Arena GmbH.Foreign currency transaction gains and losses recorded by Arena GmbH are included in net income (loss) from discontinued operations.Share-based CompensationOur share-based awards are measured at fair value and recognized over the requisite service or performance period. The fair value of each stock optionis estimated on the date of grant using the Black-Scholes option pricing model, based on the market price of the underlying common stock, expected life,expected stock price volatility and expected risk-free interest rate. Expected volatility is computed using a combination of historical volatility for a periodequal to the expected term and implied volatilities from traded options to buy our common stock, with historical volatility being weighted at 75%. Theexpected life of options is determined based on historical experience of similar awards, giving consideration to the contractual terms of the share-basedawards, vesting schedules and post-vesting terminations. The risk-free interest rates are based on the US Treasury yield curve, with a remaining termapproximately equal to the expected term used in the option pricing model. The fair value of each restricted stock unit award is estimated based on themarket price of the underlying common stock on the date of the grant. The fair value of restricted stock unit awards that include market-based performanceconditions is estimated on the date of grant using a Monte Carlo simulation model, based on the market price of the underlying common stock, expectedperformance measurement period, expected stock price volatility and expected risk-free interest rate.Prior to 2017, we estimated forfeitures at the time of grant and revised our estimate in subsequent periods if actual forfeitures differed from thoseestimates. Beginning January 1, 2017, in accordance with ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting, we account forthe forfeitures at the time they occur. The adoption of ASU No. 2016-09 resulted in a $44,000 cumulative-effect adjustment to increase our accumulateddeficit and additional paid-in capital as of January 1, 2017.73Revenue RecognitionOur revenues to date have been generated primarily through collaboration agreements. Our collaboration agreements may contain multiple elementsincluding commercialization rights, services (joint steering committee and research and development services) and manufactured products. Consideration wereceive under these arrangements may include upfront payments, research and development funding, cost reimbursements, milestone payments, payments forproduct sales and royalty payments. We recognize revenue when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred and title haspassed, (iii) the price is fixed or determinable and (iv) collectability is reasonably assured. Any advance payments we receive in excess of amounts earned areclassified as deferred revenues.We evaluate deliverables in a multiple-element arrangement to determine whether each deliverable represents a separate unit of accounting. Adeliverable constitutes a separate unit of accounting when it has standalone value to the customer. If the delivered element does not have standalone valuewithout one of the undelivered elements in the arrangement, we combine such elements and account for them as a single unit of accounting. We allocate theconsideration to each unit of accounting at the inception of the arrangement based on the relative selling price.To determine the selling price of a separate deliverable, we use the hierarchy as prescribed in Accounting Standards Codification Topic 605-25 based on vendor-specific objective evidence, or VSOE, third-party evidence, or TPE, or best estimate of selling price, or BESP. VSOE isbased on the price charged when the element is sold separately and is the price actually charged for that deliverable. TPE is determined based onthird-party evidence for a similar deliverable when sold separately. BESP is the estimated selling price at which we would transact a sale if theelements of collaboration and license arrangements were sold on a stand-alone basis to the buyer.Non-refundable upfront payments received under our collaboration agreements for commercialization rights are deferred if such rights are not deemedto have standalone value without ongoing services which may be required under the agreement. If deferred, such amounts are recognized as revenues on astraight-line basis over the period in which we expect to perform the services.Amounts we receive as reimbursement for our research and development expenditures are recognized as revenue as the services are performed.Under the milestone method, we recognize revenue that is contingent upon the achievement of a substantive milestone in its entirety in the period inwhich the milestone is achieved. A milestone is an event (i) that can be achieved in whole or in part on either our performance or on the occurrence of aspecific outcome resulting from our performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event willbe achieved and (iii) that would result in additional payments being due us. A milestone payment is considered substantive when the consideration payableto us for each milestone (a) is consistent with our performance necessary to achieve the milestone or the increase in value to the collaboration resulting fromour performance, (b) relates solely to our past performance and (c) is reasonable relative to all of the other deliverables and payments under the arrangement.In making this assessment, we consider all facts and circumstances relevant to the arrangement, including factors such as the scientific, regulatory,commercial and other risks that must be overcome to achieve the respective milestone, the level of effort and investment required to achieve the respectivemilestone and whether any portion of the milestone consideration is related to future performance or deliverables. Other contingent-based payments receivedare recognized when earned.Research and Development ExpensesResearch and development expenses, which consist primarily of salaries and other personnel costs, clinical trial costs and preclinical study fees,manufacturing costs for non-commercial products, and the development of earlier-stage programs and technologies, are expensed as incurred when theseexpenditures have no alternative future uses.We accrue clinical trial expenses based on work performed. In determining the amount to accrue, we rely on estimates of total costs incurred based onenrollment, the completion of trials and other events. We follow this method because we believe reasonably dependable estimates of the costs applicable tovarious stages of a clinical trial can be made. However, the actual costs and timing of clinical trials are uncertain, subject to risks and may change dependingon a number of factors. Differences between the actual clinical trial costs and the estimated clinical trial costs that we have accrued in any prior period arerecognized in the subsequent period in which the actual costs become known. Historically, these differences have not been material; however, materialdifferences could occur in the future. Payments made to reimburse collaborators for our share of their research and development activities are recorded asresearch and development expenses, and are recognized as the work is performed.74Comprehensive LossComprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources.We report components of comprehensive loss in the period in which they are recognized. For the year ended December 31, 2017, comprehensive lossconsisted of net loss, foreign currency translation gains and losses, and unrealized gains and losses related to available-for-sale investments. For the yearsended 2016, and 2015, comprehensive loss consisted of net loss and foreign currency translation gains and losses.Income (Loss) Per ShareWe calculate basic and diluted loss from continuing operations, income (loss) from discontinued operations and net loss per share using the weighted-average number of shares of common stock outstanding during the period.We have a loss from continuing operations for the years ended December 31, 2017, 2016, and 2015, in addition to excluding potentially dilutive out-of-the money securities, we have excluded from our calculation of income (loss) per share all potentially dilutive in-the-money (i) stock options, (ii) restrictedstock unit awards, or RSUs, (iii) Total Stockholder Return, or TSR, performance restricted stock unit, or PRSU, awards, (iv) unvested restricted stock in ourdeferred compensation plan and (v) our previously outstanding warrants, and our diluted net loss per share is the same as our basic net loss per share. Thetable below presents the weighted-average number of potentially dilutive securities that were excluded from our calculation of diluted income (loss) per sharefor the years presented, in thousands. Years ended December 31, 2017 2016 2015 Stock options 3,664 2,495 1,703 Warrants — — 2 RSUs and unvested restricted stock 3 21 55 Total 3,667 2,516 1,760 Because the market condition for the PRSUs was not satisfied at December 31, 2017, 2016, and 2015, such securities are excluded from the tableabove.Income TaxesWe use the asset and liability method of accounting for income taxes. Deferred tax assets and liabilities are recognized for the estimated future taxconsequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Ourdeferred tax assets and liabilities are determined using the enacted tax rates expected to be in effect for the years in which those tax assets are expected to berealized.The realization of our deferred tax assets is dependent upon our ability to generate sufficient future taxable income. We establish a valuationallowance when it is more-likely-than-not the future realization of all or some of the deferred tax assets will not be achieved. The evaluation of the need for avaluation allowance is performed on a jurisdiction-by-jurisdiction basis, and includes a review of all available evidence, both positive and negative.The impact of an uncertain income tax position is recognized at the largest amount that is more-likely-than-not to be sustained upon audit by therelevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. 2. Fair Value DisclosuresWe measure our financial assets and liabilities at fair value, which is defined as the exit price, or the amount that would be received from selling anasset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.We use the following three-level valuation hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs tovalue our financial assets and liabilities: Level 1 - Observable inputs such as unadjusted quoted prices in active markets for identical instruments.75Level 2 - Quoted prices for similar instruments in active markets or inputs that are observable for the asset or liability, either directlyor indirectly.Level 3 - Significant unobservable inputs based on our assumptions.The following tables present our valuation hierarchy for our financial assets and liabilities that are measured at fair value on a recurring basis, inthousands: Fair Value Measurements at December 31, 2017 Balance Quoted Prices inActive Markets(Level 1) Significant OtherObservableInputs(Level 2) SignificantUnobservable Inputs(Level 3) Assets: Money market funds(1) $48,750 $48,750 $— $— US government and government agency notes(2) 50,335 50,335 — — Corporate debt instruments(2) 94,639 — 94,639 — Fair Value Measurements at December 31, 2016 Balance Quoted Prices inActive Markets(Level 1) Significant OtherObservableInputs(Level 2) SignificantUnobservable Inputs(Level 3) Assets: Money market funds(1) $46,371 $46,371 $— $— (1)Included in cash and cash equivalents in the accompanying consolidated balance sheets. (2)Included in either cash and cash equivalents or available-for-sale investments in the accompanying consolidated balance sheet. 3. Investments, Available-for-SaleInvestments, available-for-sale, consisted of the following at December 31, 2017, in thousands: Maturityin years AmortizedCost GrossUnrealized Gains GrossUnrealized Losses EstimatedFair Value US government and government agency notes Less than 1 $34,873 $— $(8) $34,865 Corporate debt securities Less than 1 53,438 — (63) 53,375 Short-term investments, available-for-sale $88,311 $— $(71) $88,240 US government and government agency notes 1 - 5 $— $— $— $— Corporate debt securities 1 - 5 24,304 — (62) 24,242 Investments, available-for-sale $24,304 $— $(62) $24,242 764. Balance Sheet DetailsLand, property and equipment, net consisted of the following, in thousands: December 31, 2017 2016 Land $7,650 $7,650 Building and capital improvements 54,584 54,584 Leasehold improvements 17,769 17,769 Machinery and equipment 1,737 13,181 Computers and software 4,890 4,890 Furniture and office equipment 1,614 1,563 88,244 99,637 Less accumulated depreciation and amortization (58,113) (64,528)Land, property and equipment, net $30,131 $35,109Substantially all of our long-lived assets, other than those held for sale, are located in the United States.Accounts payable and other accrued liabilities consisted of the following, in thousands: December 31, 2017 2016 Accounts payable $1,599 $1,295 Accrued compensation 5,255 3,703 Other accrued liabilities 1,062 678 Total accounts payable and other accrued liabilities $7,916 $5,676 5. Manufacturing Operations Held for SaleOn March 9, 2018, Arena GmbH entered into the Sale Agreement with Siegfried to divest our Manufacturing Operations. The Siegfried Transaction isexpected to close on or about March 31, 2018, subject to satisfaction or waiver of certain customary closing conditions. The total sales price for theTransferred Assets and assignment of certain liabilities by Arena GmbH is expected to be approximately CHF 4 million in cash. In the event Siegfried agreesto sell or transfer some or all of the Transferred Assets to certain third parties on or prior to December 31, 2018, for a consideration in excess of a specifiedamount, Arena GmbH will be entitled to percentage of such excess amount.We have retrospectively revised the consolidated statements of operations and cash flows for the years ended December 31, 2016 and 2015 and theconsolidated balance sheet as of December 31, 2016 to reflect the operations and cash flows of the Manufacturing Operations as discontinued operations andthe related assets and liabilities as held for sale.The following table summarizes the results of discontinued operations for the periods presented in the consolidated statements of operations for theyears ended December 31, 2017, 2016, and 2015, in thousands:77 Years ended December 31, Revenues 2017 2016 2015 Net product sales $9,189 $26,349 $19,726 Other collaboration revenue 6,671 1,334 952 Toll manufacturing 3,179 4,129 4,250 Total revenues 19,039 31,812 24,928 Operating costs and expenses Cost of product sales 7,472 9,297 8,590 Cost of toll manufacturing 4,756 6,044 4,585 Research and development 643 2,643 5,128 General and administrative 1,672 3,714 5,685 Impairment of long-lived assets — 21,766 — Restructuring charges — 231 626 Total operating costs and expenses 14,543 43,695 24,614 Income (loss) from operations 4,496 (11,883) 314 Other income (expense), net (1,374) 1,287 2,414 Income (loss) from discontinued operations $3,122 $(10,596) $2,728 The following table summarizes the assets and liabilities of the Manufacturing Operations which are classified as held for sale as of December 31,2017 and 2016, in thousands: December 31, 2017 2016 Assets Current assets: Accounts receivable $813 $19,589 Inventories 6,949 6,708 Prepaid expenses and other current assets 634 138 Total current assets(1) 26,435 Land, property and equipment, net 7,511 8,719 Intangible assets, net 1,233 2,357 Other assets — 95 Total non-current assets(1) 11,171 Total assets of disposal group held for sale $17,140 $37,606 Liabilities Current liabilities: Accounts payable and other accrued liabilities $2,145 $6,440 Payable to Eisai — 9,074 Deferred revenues 25,450 30,878 Total liabilities of disposal group held for sale (all current) $27,595 $46,392 (1)The assets and liabilities of the Manufacturing Operations classified as held for sale are classified as current in the consolidated balance sheet atDecember 31, 2017, because it is probable that the sale will occur and proceeds will be collected within one year. 6. Derivative LiabilitiesIn August 2008, we issued seven-year warrants, which we refer to as the Series B Warrants, to purchase 110,634 shares of our common stock at anexercise price of $77.10 per share. As a result of the warrants’ anti-dilution provision and certain of our subsequent equity issuances, the number of sharesissuable upon exercise of the warrants increased and the exercise price decreased.In August 2015, the August 2008 Series B Warrant, which was recorded as a current derivative liability of $0.5 million in our consolidated balancesheet at December 31, 2014, expired pursuant to its terms. Therefore, we recorded a gain in our consolidated statement of operations and comprehensive lossfor the year ended December 31, 2015.The warrants were revalued on each balance sheet date, with changes in the fair value between reporting periods recorded in the interest and otherincome (expense) section of our consolidated statements of operations and comprehensive loss.78 7. CommitmentsWe have four properties in California under sale and leaseback agreements. The terms of these leases stipulate annual increases in monthly rentalpayments of 2.5%. We accounted for our sale and leaseback transactions using the financing method. Under the financing method, the book value of theproperties and related accumulated depreciation remain on our balance sheet and no sale is recognized. The sales price of the properties is recorded as afinancing obligation, and a portion of each lease payment is recorded as interest expense. We recorded interest expense of $6.1 million, $6.4 million, and$6.7 million for the years ended December 31, 2017, 2016, and 2015, respectively, related to these leases. We expect interest expense related to our facilitiesto total $31.6 million from December 31, 2017, through the remaining terms of the leases in fiscal year 2027. At December 31, 2017, the total financingobligation for these facilities was $61.7 million. The aggregate residual value of the facilities at the end of the lease terms is $10.0 million.We lease an additional property in California under an operating lease, which expires in May 2027, and contains a purchase option and stipulatesannual increases in monthly rental payments of 2.5%. We also lease office space in Zug, Switzerland under an operating lease which expires in September2020. Additionally, we also lease space in various facilities in Zofingen, Switzerland pertaining to the Manufacturing Operations.In accordance with the lease terms for certain of our properties, we are required to maintain deposits for the benefit of the landlord throughout the termof the leases. A total of $0.7 million and $0.7 million were recorded in other non-current assets in our consolidated balance sheets at December 31, 2017, and2016, respectively, related to such leases.We recognize rent expense on a straight-line basis over the term of each lease. Rent expense of $1.5 million, $1.2 million and $1.1 million wasrecognized for the years ended December 31, 2017, 2016, and 2015, respectively.At December 31, 2017, the future minimum lease payments under our existing financing and operating lease obligations are as follows, in thousands: Year ending December 31, FinancingObligations OperatingLeases 2018 $8,930 $1,299 2019 8,053 1,396 2020 8,254 1,280 2021 8,461 976 2022 8,672 1,000 Thereafter 40,939 4,724 Total minimum lease payments 83,309 $10,675 Less amounts representing interest (31,551) Add amounts representing residual value 9,990 Lease financing obligations 61,748 Less current portion (4,000) $57,748 In May 2016, we entered into an agreement to sublease one of our other California properties to a third party. This sublease commenced in August2016 and expires in May 2027. The terms of the sublease stipulate annual increases in monthly rental payments of 3.19%.In September 2016, we entered into an agreement to sublease one of our California properties to Beacon, which commenced in September 2016 andexpires in August 2021. The monthly rental payments are fixed for the terms of this sublease.In April 2017, we entered into an agreement to sublease another of our California properties, which commenced in July 2017 and expires in May2027. The terms of the sublease stipulate annual increases in monthly rental payments of 3.00%.We recognize rent income on a straight-line basis over the term of the subleases. Expected minimum rental payments to be received under the subleaseare as follows:79 Year ending December 31, 2018 $1,205 2019 1,526 2020 1,567 2021 1,551 2022 1,476 Thereafter 7,076 Total $14,401 8. Stockholders’ EquityIn January 2017, we entered into an Equity Distribution Agreement, or ATM, with Citigroup Global Markets, Inc., or the Sales Agent, under which wemay offer and sell common stock having an aggregate offering price of up to $50.0 million from time to time though our Sales Agent. Sales of the sharesunder the ATM were made in transactions that are deemed to be “at‑the‑market” equity offerings as defined in Rule 415 under the Securities Act of 1933, asamended, including sales made by means of ordinary brokers’ transactions, including on the Nasdaq Stock Market. During the period from February throughApril 2017, we sold 489,023 shares of our common stock at an average market price of $15.05 per share under the ATM for aggregate net proceeds ofapproximately $7.0 million after deducting commissions and expenses.In April 2017, we completed the sale of an aggregate of 6,900,000 shares of our common stock under an underwritten public offering. Net proceedsfrom the offering were approximately $74.4 million after deducting underwriting discounts and commissions, and offering expenses payable by us. In July 2017, we completed the sale of an additional 7,187,500 shares of our common stock under an underwritten public offering. Net proceeds fromthe offering were $162.0 million after deducting underwriting discounts and commissions, and offering expenses payable by us.Equity Compensation Plans.On June 13, 2017, our stockholders approved our 2017 Long-Term Incentive Plan, or 2017 LTIP. Upon such approval, our 2013 Long-Term IncentivePlan, or 2013 LTIP, was terminated. However, notwithstanding such termination or the previous termination of our 2012 Long-Term Incentive Plan, 2009Long-Term Incentive Plan, and 2006 Long-Term Incentive Plan, as amended, or, together with the 2013 LTIP, the Prior Plans, all outstanding awards underthe Prior Plans will continue to be governed under the terms of the Prior Plans. The number of shares of common stock authorized for issuance under the 2017LTIP may be increased by the number of shares subject to any stock awards under the Prior Plans that are forfeited, expire or otherwise terminate without theissuance of such shares and would otherwise be returned to the share reserve under the Prior Plans but for their termination and as otherwise provided in the2017 LTIP.The 2017 LTIP provides for the grant of a total of 3.1 million shares of our common stock (subject to adjustment for certain corporate events), as(i) decreased for grants made under the 2013 LTIP between March 30, 2017, and the approval of the 2017 LTIP and (ii) increased by the number of sharessubject to any stock awards under the Prior Plans that, between March 30, 2017, and the approval of the 2017 LTIP, were forfeited, expired or settled for cashand as otherwise provided in the 2017 LTIP.Shares under the 2017 LTIP may be granted as incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards,restricted stock unit awards and performance awards. Subject to certain limited exceptions, stock options and stock appreciation rights granted under the2017 LTIP reduce the available number of shares by one share for every share issued while awards other than stock options and stock appreciation rightsgranted under the 2017 LTIP reduce the available number of shares by 1.6 shares for every share issued. In addition, shares that are released from awardsgranted under the Prior Plans or the 2017 LTIP because the awards expire, are forfeited or are settled for cash will increase the number of shares availableunder the 2017 LTIP by one share for each share released from a stock option or stock appreciation right and by 1.6 shares for each share released from arestricted stock award or restricted stock unit.Stock options granted under the 2017 LTIP generally vest over four years with 25% of the shares subject to each option vesting on the firstanniversary of the grant date and the remainder of the shares vesting monthly over the following three years in equal installments and are exercisable for upto seven years from the date of grant. The recipient of a restricted stock award has all rights of a stockholder at the date of grant, subject to certain restrictionson transferability and a risk of forfeiture. Restricted stock unit awards generally vest over one or four years from the date of grant. The minimum performanceperiod under a performance award is 12 months. Neither the exercise price of an option nor the grant price of a stock appreciation right may be less than100% of the fair80market value of the common stock on the date such equity award is granted, except in specified situations. The 2017 LTIP prohibits option and stockappreciation right repricings (other than to reflect stock splits, spin-offs or certain other corporate events) without stockholder approval.The following table summarizes our stock option activity under the Prior Plans and the 2017 LTIP, or collectively, our Equity Compensation Plans,for the year ended December 31, 2017, in thousands (except per share data): Options Weighted-AverageExercise Price Weighted-AverageRemainingContractualTerm (in years) AggregateIntrinsicValue Outstanding at December 31, 2016 2,520 $30.30 Granted 2,241 $16.53 Exercised (323) $16.71 Forfeited/cancelled/expired (683) $47.24 Outstanding at December 31, 2017 3,755 $20.00 5.46 $60,003 Vested and expected to vest at December 31, 2017 3,755 $20.00 5.46 $60,003 Vested and exercisable at December 31, 2017 1,094 $27.35 4.01 $14,385 The aggregate intrinsic value in the above table is calculated as the difference between the closing price of our common stock at December 31, 2017,of $33.97 per share and the exercise price of stock options that had strike prices below the closing price. The intrinsic value of all stock options exercisedduring the years ended December 31, 2017, 2016, and 2015, was $2.8 million, $0.1 million, and $2.2 million, respectively. During the year endedDecember 31, 2017, cash of $5.4 million was received from stock option exercises. There is no tax impact related to share-based compensation or stockoption exercises because we are in a net operating loss position with a full valuation allowance on our deferred tax assets. Subsequent to December 31, 2017,we granted an additional 2,088,625 stock options to our employees and directors under the 2017 LTIP.In March 2015, March 2014 and March 2013, we granted our executive officers PRSU awards. The PRSUs may be earned and converted intooutstanding shares of our common stock based on the TSR of our common stock relative to the TSR over a three-year performance period beginning March 1of the year granted of the Nasdaq Biotechnology Index. In the aggregate, the target number of shares of common stock that could be earned under the PRSUsgranted in March 2015, March 2014 and March 2013 were originally 74,500, 69,500 and 78,000, respectively; however, the actual number of shares thatcould be earned ranges from 0% to 200% of such amounts. In addition, there is a cap on the number of shares that could be earned under the PRSUs equal tosix times the grant-date fair value of each award, and funding is capped at 100% if the absolute 3-year TSR is negative even if performance is above themedian. As these awards contain a market condition, we used a Monte Carlo simulation model to estimate the grant-date fair value, which totaled $3.4million, $5.0 million and $5.9 million for the March 2015, 2014 and March 2013 grants, respectively. The grant-date fair value is recognized ascompensation expense over the performance period as service is provided; no compensation expense is recognized for service not provided in case ofseparation from the Company. There is no adjustment of compensation expense recognized for service performed regardless of the number of PRSUs, if any,that ultimately vest.In February 2016, the remaining PRSUs granted in March 2013 were forfeited without any earnout based on the TSR of our common stock relative tothe TSR of the Nasdaq Biotechnology Index over the three-year performance period that began on March 1, 2013. In February 2017, the remaining PRSUsgranted in March 2014 were forfeited without any earnout based on the TSR of our common stock relative to the TSR Nasdaq Biotechnology Index over thethree-year performance period that began on March 1, 2014. In March 2018, 32,322 shares were issued to the holders of the remaining PRSUs granted inMarch 2015 based on the TSR of our common stock relative to the TSR Nasdaq Biotechnology Index over the three-year performance period that began onMarch 1, 2015.Employee Stock Purchase Plan.In June 2015, our stockholders approved our 2009 Employee Stock Purchase Plan, as amended, or 2009 ESPP. Under the 2009 ESPP substantially allemployees could choose to have up to 15% of their annual compensation withheld to purchase up to 625 shares of our common stock per purchase period,subject to certain limitations. The shares of our common stock could be purchased over an offering period with a maximum duration of 24 months and at aprice of not less than 85% of the lesser of the fair market value of the common stock on (i) the first trading day of the applicable offering period or (ii) the lasttrading day of the applicable three-month purchase period. Under applicable accounting guidance, the 2009 ESPP was considered a compensatory plan. The2009 ESPP was terminated in June 2017.During the years ended December 31, 2017, 2016, and 2015, a total of 2,236, 14,140, and 32,795 shares, respectively, were purchased by ouremployees under the 2009 ESPP.81Share-based Compensation.We estimate the grant-date fair value of all of our share-based awards in determining our share-based compensation expense. Our share-based awardsinclude stock options, options to purchase stock granted under our employee stock purchase plan, RSUs, and PRSU awards. The table below sets forth the weighted-average assumptions and estimated fair value of stock options we granted under our Equity CompensationPlans during the years presented: Years ended December 31, 2017 2016 2015 Risk-free interest rate 1.9% 1.4% 1.8%Dividend yield 0% 0% 0%Expected volatility 69% 79% 80%Expected life (years) 4.58 4.81 6.08 Weighted-average estimated fair value per share of stock options granted $9.17 $10.17 $25.48 We recognized share-based compensation expense as follows for the years presented, in thousands, except per share data: Years ended December 31, 2017 2016 2015 Research and development $1,945 $5,596 $7,512 General and administrative 5,925 4,447 6,458 Restructuring charges — 1,032 142 Discontinued operations 120 42 351 Total share-based compensation expense $7,990 $11,117 $14,463 Impact on net loss per share, basic and diluted $0.24 $0.46 $0.60The table below sets forth our total unrecognized estimated compensation expense at December 31, 2017, by type of award and the weighted-averageremaining requisite service period over which such expense is expected to be recognized: UnrecognizedExpense (inthousands) RemainingWeighted-AverageRecognitionPeriod (in years) Unvested stock options $20,311 2.89 PRSUs 55 0.16 RSUs 22 0.96 Common Stock Reserved for Future Issuance.A total of 6,813,713 shares of our common stock are reserved for future issuance at December 31, 2017, pursuant to our Equity Compensation Plans. 9. CollaborationsEverest.In December 2017, we and Everest entered into an exclusive agreement to conduct joint development for the ralinepag and etrasimod programs. Underthis agreement, we granted Everest an exclusive, royalty-bearing license to develop and commercialize ralinepag (in any formulation) and etrasimod (in oralformulations), in mainland China, Taiwan, Hong Kong, Macau and South Korea, or collectively, the Territories. Everest is generally responsible fordevelopment and commercialization of the licensed products in the Territories, and may participate in the portion of our global clinical trials that isconducted in the Territories.We received from Everest an upfront payment of $12.0 million in December 2017. Revenues from this upfront payment were recognized in December2017 as we determined (i) that the license is a deliverable with standalone value to Everest and (ii) the upfront payment represents consideration to beallocated to the delivered license.82We are also eligible to receive up to an aggregate of $212.0 million in success milestones in case of full commercial success of multiple drug products.Of these payments, six development milestones totaling $49.5 million are substantive, nine regulatory milestones totaling $22.5 million are substantive andsix commercial milestones totaling $140.0 million are non-substantive. We are further eligible to receive tiered royalties on net sales of ralinepag andetrasimod products in the Territories.Eisai.In July 2010, we granted Eisai exclusive commercialization rights for lorcaserin (marketed as BELVIQ® / BELVIQ XR®) solely in the United Statesand its territories and possessions. In May 2012, we and Eisai entered into the first amended and restated agreement, which expanded Eisai’s exclusivecommercialization rights to include most of North and South America. In November 2013, we and Eisai entered into the second amended and restatedagreement, or Second Amended Agreement, which expanded Eisai’s exclusive commercialization rights for lorcaserin to all of the countries in the world,except for South Korea, Taiwan, Australia, New Zealand and Israel.In December 2016, we and Eisai amended and restated the terms of marketing and supply agreement for lorcaserin with Eisai by entering into aTransaction Agreement and a Supply Agreement (collectively, the Eisai Agreement) with Eisai. Under the Transaction Agreement, Eisai acquired anexclusive royalty-bearing license or transfer of intellectual property to global commercialization and manufacturing rights to lorcaserin, including in theterritories retained by us under the prior agreement, with control over global development and commercialization decisions. Eisai is responsible for alllorcaserin development expenses going forward. We also assigned to Eisai our rights under the commercial lorcaserin distribution agreements with IldongPharmaceutical Co., Ltd., or Ildong, for South Korea; CY Biotech Company Limited, or CYB, for Taiwan; and Teva Pharmaceuticals Ltd.’s Israeli subsidiary,Abic Marketing Limited, or Teva, for Israel. This is collectively referred to as License Deliverable.Under the Supply Agreement, Eisai paid us $10.0 million to acquire our entire on-hand inventory of bulk lorcaserin and the precursor material formanufacturing lorcaserin, which is referred to as Inventory Deliverable. Eisai is also paying us for finished drug product plus up to CHF 13.0 million inmanufacturing support payments over an initial two-year supply period.We manufacture lorcaserin at our facility in Zofingen, Switzerland. Revenues earned for (i) lorcaserin sold by us to Eisai under the manufacturing andsupply commitment within the Supply Agreement, or Manufacturing and Supply Commitment Deliverable, and formerly sold by us to Eisai, Ildong, CYBand Teva for commercial or development purposes under the prior lorcaserin collaboration agreements and (ii) the manufacturing support payments areclassified within discontinued operations as part of the Manufacturing Operations on the consolidated statements of operations (see Note 5). All otherrevenues earned under the Transaction Agreement and the prior lorcaserin collaboration agreements, such as royalties, licenses, milestones and developmentexpense reimbursements, are classified within continuing operations on the consolidated statements of operations.Royalty payments.Pursuant to the Transaction Agreement, we are eligible to receive royalty payments from Eisai based on the global net sales of lorcaserin. The royaltyrates are as follows: •9.5% on annual net sales less than or equal to $175.0 million •13.5% on annual net sales greater than $175.0 million but less than or equal to $500.0 million •18.5% of annual net sales greater than $500.0 millionWe record revenues from the royalty payments in the period in which the net sales upon which the royalties are calculated occur as reported to us byEisai. For the year ended December 31, 2017, we recognized royalty revenue of $1.7 million under the Eisai Agreement.Upfront payments.Prior to the Transaction Agreement, we received from Eisai total upfront payments of $115.0 million under prior lorcaserin collaboration agreements.Revenues from these upfront payments were previously deferred, as we determined that the exclusive rights did not have standalone value without ourongoing development and regulatory activities. Accordingly, these payments were recognized ratably as revenue over the periods in which we expected theservices to be rendered. The Transaction Agreement effectively eliminated our obligation to continue performing the development and regulatory activitiesrequired in the original agreement, which resulted in acceleration of upfront payment revenue recognition in 2016. For the years ended December 31, 2016,and 2015, we recognized revenue of $66.0 million and $7.5 million, respectively, related to these upfront payments.83Milestone payments.In July 2016, the US Food and Drug Administration, or FDA, approved the New Drug Application for BELVIQ XR. We earned from Eisai a $10.0million substantive milestone payment from this achievement. In October 2016, Eisai announced the commercial launch of BELVIQ XR in the United States.In July 2016, the Federal Commission for the Protection Against Sanitary Risk approved the Marketing Authorization Application in Mexico for ourtwice-daily formulation of lorcaserin for chronic weight management. We earned from Eisai a $1.0 million substantive milestone payment from thisachievement.In December 2016, the Brazilian Health Surveillance Agency provided regulatory approval in Brazil for BELVIQ. We earned from Eisai a $1.0 millionsubstantive milestone payment from this achievement.We are eligible to receive an additional substantive commercial milestone of $25.0 million upon the achievement of global net sales of lorcaserin for acalendar year first exceeding $250.0 million.Product purchase price and inventory purchase.We manufacture lorcaserin at our facility in Zofingen, Switzerland. Under the Eisai Agreement, we have agreed to manufacture and supply, and Eisaihas agreed to purchase from us, all of Eisai’s requirements (or specified minimum quantities if such quantities are greater than Eisai’s requirements), subject tocertain exceptions, for lorcaserin for development and commercial use for an initial two-year period. The initial period may be extended by Eisai for anadditional six months upon payment of an extension fee of CHF 2.0 million. Eisai will pay us agreed upon prices to deliver finished drug product during thistime. Additionally, Eisai has agreed to pay up to CHF 13.0 million in manufacturing support payments during the initial two-year period supply period, andpay up to CHF 6.0 million in manufacturing support payments during the six-month extension period, if the extension option is exercised by Eisai.Under the Second Amended Agreement, we sold lorcaserin to Eisai for Eisai’s commercialization in the United States for a purchase price of 31.5% ofEisai’s aggregate annual net product sales (which are the gross invoiced sales less certain deductions described in the Second Amended Agreement), or theProduct Purchase Price. The amount that Eisai paid us for lorcaserin product supply was based on Eisai’s estimated price at the time the order was shipped,which was Eisai’s estimate of the Eisai Product Purchase Price, and was subject to change on April 1 and October 1 of each year. The Eisai Product PurchasePrice for the product Eisai sold under the Second Amended Agreement was lower than the estimated price that Eisai paid us for such product, primarily due toan increase in deductions from savings cards and returns, partially offset by a decrease in vouchers. At the end of Eisai’s fiscal year (March 31), the estimatedprice paid to us for product that Eisai sold to its distributors was compared to the Eisai Product Purchase Price of such product, and the difference wasrefunded back to Eisai for the overpayments. The $9.1 million classified as Payable to Eisai within the total liabilities of disposal group held for sale atDecember 31, 2016, relates to product sold by Eisai to its distributors from April 1, 2015, through March 31, 2016. Under the Eisai Agreement, we were notrequired to refund to Eisai any net overpayment which would have been otherwise due to Eisai under the Second Amended Agreement for product we sold toEisai under the Second Amended Agreement which Eisai did not sell to its distributors on or before March 31, 2016. For product which Eisai sold to itsdistributors from April 1, 2016, through December 28, 2016, we recognized the net overpayment which would have been otherwise due to Eisai under theSecond Amended Agreement of $2.0 million as revenues and included this amount in net product sales for the year ended December 31, 2016, which is acomponent of discontinued operations in the consolidated statement of operations.Prior to December 2016, we deferred recognition of revenue and the related cost at the time we sold lorcaserin to Eisai because we did not have theability to estimate the amount of product that could have been returned to us and thus recognized revenues and the related costs from net product sales whenEisai shipped BELVIQ to its distributors. Pursuant to a change in the terms of the Eisai Agreement, we determined that we achieved the ability to reasonablyestimate the amount of product returns and recognize revenue and the related cost from product sales when we ship BELVIQ to Eisai. On December 28, 2016,we recognized revenues of $6.7 million and costs of $1.9 million on net product sales which had been previously deferred, which is a component ofdiscontinued operations in the consolidated statement of operations.Allocation of Eisai Agreement arrangement consideration to the units of accounting.The total arrangement consideration of $115.6 million primarily consists of (i) the December 28, 2016, balances of deferred revenues from the upfrontpayments received under the prior Eisai agreements and the distribution agreements with Ildong, CYB and Teva; (ii) the $10.0 million payment receivedfrom Eisai on December 28, 2016; and (iii) the product purchase payments and manufacturing support payments we expect to receive from Eisai for the initialtwo-year manufacturing and supply commitment period.84All of the deliverables were determined to have standalone value and to meet the criteria to be accounted for as separate units of accounting. Factorsconsidered in the determination included, among other things, for the license, the manufacturing experience and capabilities of Eisai and their sublicenserights, and for the remaining deliverables the fact that they are not proprietary and can be provided by other vendors. The total arrangement considerationwas allocated to the units of accounting on the basis of their relative estimated selling prices as follows: •$64.0 million was allocated to the License Deliverable. As the License Deliverable was delivered on December 28, 2016, this amount wasrecognized as collaboration revenue of continuing operations for the year ended December 31, 2016. •$30.8 million was allocated to the Inventory Deliverable. Title to this entire inventory passed to Eisai on December 28, 2016. However, none ofthis inventory was physically transferred from the manufacturing facility on that date. There is no fixed schedule for delivery given a portionhas been and will be delivered on a continuous basis as we perform under the manufacturing commitment, another portion has been and will bephysically transferred to Eisai upon request by Eisai and the rest is expected to be physically transferred at the end of the manufacturing andsupply commitment period. Also, the risks of ownership for this inventory did not pass to Eisai in 2016 as we have financial responsibility forloss, damage or destruction which occurs while in our possession. Therefore, none of the arrangement consideration allocated to thisdeliverable was recognized as revenue and none of the carrying value of this inventory was recognized as cost of product sales for the yearended December 31, 2016. For the year ended December 31, 2017, we recognized $6.4 million as revenue of discontinued operations related tothis deliverable and $0.9 million of the carrying value of this inventory as cost of product sales of discontinued operations. •$20.8 million was allocated to the Manufacturing and Supply Commitment Deliverable. This deliverable is being provided over 2017 and2018 as product is shipped to Eisai. Therefore, none of the arrangement consideration allocated to this deliverable was recognized as revenuefor the year ended December 31, 2016. For the year ended December 31, 2017, we recognized $9.5 million as revenue of discontinuedoperations related to this deliverable. The estimated selling price represents the price at which we would contract if the deliverable was sold regularly on a standalone basis. The estimatedselling price for each unit of accounting was determined as follows: •The estimated selling price for the License Deliverable was determined using an income approach that estimates the net present value ofroyalties Eisai is expected to earn under the Eisai Agreement as compared to the Second Amended Agreement, net of the development costs weare no longer obligated to spend. This model includes several assumptions, including the potential market for lorcaserin in each relevantjurisdiction, probabilities of obtaining regulatory approval in additional jurisdictions, the impact of competition, the potential impact ofEisai’s ongoing development and regulatory activities related to lorcaserin, and the appropriate discount rate. •The estimated selling price for the Inventory Deliverable was determined by considering the historical cost of the precursor materials, adjustedfor any changes in market condition and supplier relationships. We believe that the Eisai Agreement pricing represents pricing that would becharged if it were sold on a standalone basis. •The estimated selling price for the Manufacturing and Supply Commitment Deliverable was determined to be the aggregate product purchasepayments we expect to receive from Eisai for the initial two-year manufacturing and supply commitment period. As noted above, we believethat the Eisai Agreement pricing represents pricing that would be charged if it were sold on a standalone basis. Development payments.As part of the US approval of BELVIQ, the FDA, is requiring the evaluation of the effect of long-term treatment with BELVIQ on the incidence ofmajor adverse cardiovascular events, or MACE, in overweight and obese patients with cardiovascular disease or multiple cardiovascular risk factors (which isthe FDA-required portion of the cardiovascular outcomes trial), as well as the conduct of postmarketing studies to assess the safety and efficacy of BELVIQfor weight management in obese pediatric and adolescent patients. Under the Second Amended Agreement, Eisai and we were responsible for 90% and 10%,respectively, of the cost for the FDA-required portion of the cardiovascular outcomes trial, or CVOT, 50% and 50%, respectively, of the non-FDA portion ofthe studies and we were also obligated to share the cost of FDA-required studies in obese pediatric patients and for additional clinical studies in otherterritories.Under the Eisai Agreement, Eisai is solely responsible for all costs and expenses in connection with further development of lorcaserin from and afterJuly 1, 2016, and we were relieved of any obligations under the Second Amended Agreement to pay our share of future development costs of lorcaserin.Accordingly, on December 28, 2016, we recorded a reduction of research and development expenses which would have been otherwise due to Eisai under theSecond Amended Agreement of $3.7 million for the period from July 1, 2016, through December 28, 2016.85For the years ended December 31, 2016, and 2015, we recognized expenses of $4.2 million, and $10.8 million, respectively, for external clinicalstudy fees related to lorcaserin, which are included in continuing operations. There were no such expenses in 2017. Additionally, for the years endedDecember 31, 2017, 2016, and 2015 we recognized expenses of $1.4 million, $3.1 million, and $5.4 million, respectively for internal non-commercialmanufacturing costs primarily related to lorcaserin, which are included in discontinued operations.Ildong Pharmaceutical Co., Ltd.In November 2012, we and Ildong entered into the Marketing and Supply Agreement, or Ildong Agreement. Under this agreement, we granted Ildongexclusive rights to commercialize BELVIQ in South Korea for weight loss or weight management in obese and overweight patients. We also provided certainservices and manufacture and sold BELVIQ to Ildong. As noted above, the Ildong Agreement was assigned to Eisai pursuant to the Eisai Agreement onDecember 28, 2016.In connection with entering into the Ildong Agreement, we received from Ildong an upfront payment of $5.0 million, less withholding taxes.Revenues from this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoingdevelopment and regulatory activities. Accordingly, this payment was recognized ratably as revenue over the period in which we expected the services to berendered. The assignment of the Ildong Agreement pursuant to the Eisai Agreement effectively eliminated our obligation to continue performing thedevelopment and regulatory activities required in the Ildong Agreement. Therefore, on December 28, 2016, the $3.5 million of deferred revenues from thisupfront payment was allocated to the value of the License provided to Eisai and recognized as revenue in 2016.In February 2015, we earned a substantive milestone payment of $3.0 million upon the approval of BELVIQ for marketing in South Korea for weightmanagement. We received the payment, less withholding taxes, in March 2015.Under the Ildong Agreement, we manufactured BELVIQ at our facility in Zofingen, Switzerland, and sold BELVIQ to Ildong for a purchase pricestarting at the higher of the defined minimum amount or 35% of Ildong’s annual net product sales (which are the gross invoiced sales less certain deductionsdescribed in the Ildong Agreement), or the Ildong Product Purchase Price. The Ildong Product Purchase Price increased on a tiered basis up to the higher ofthe defined minimum amount or 45% on the portion of annual net product sales exceeding $15.0 million. Since the inception of commercial sales of BELVIQin South Korea in 2015, the Ildong Product Purchase Price equaled the defined minimum amount (which exceeded the amounts calculated using theapplicable percentages for the applicable tiers of Ildong’s annual net product sales).Prior to December 2016, we deferred recognition of revenue and the related cost at the time we sold BELVIQ to Ildong because we did not have theability to estimate the amount of product that could have been returned to us and thus recognized revenues and the related costs from net product sales whenIldong shipped BELVIQ to its distributors. In December 2016, we determined that we achieved the ability to reasonably estimate product returns under theIldong Agreement. Accordingly, we recognized revenues of $2.0 million and costs of $0.7 million in December 2016 on net product sales which had beenpreviously deferred, of which is a component of discontinued operations in the consolidated statement of operations.For the years ended December 31, 2016 and 2015, we recognized revenues of $11.4 million and $8.9 million, respectively, under the Ildongagreement, of which $7.2 million and $5.5 million, respectively are included in discontinued operations. No revenues were recognized during the year endedDecember 31, 2017 under this agreement.CY Biotech Company Limited.In July 2013, we entered into the CYB Agreement. Under this agreement, we granted CYB exclusive rights to commercialize BELVIQ in Taiwan forweight loss or weight management in obese and overweight patients, subject to regulatory approval of BELVIQ by the Taiwan Food and DrugAdministration, or TFDA. The CYB Agreement provided for us to perform certain services and to manufacture and sell BELVIQ to CYB. As noted above, theCYB Agreement was assigned to Eisai pursuant to the Eisai Agreement on December 28, 2016.In connection with entering into the CYB agreement, we received from CYB an upfront payment of $2.0 million, less withholding taxes. Revenuesfrom this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoing development andregulatory activities. Accordingly, this payment was recognized ratably as revenue over the period in which we expected the services to be rendered. Theassignment of the CYB Agreement pursuant to the Eisai Agreement effectively eliminated our obligation to continue performing the development andregulatory activities required in the CYB Agreement. Therefore, on December 28, 2016, the $1.7 million of deferred revenues from this upfront payment wasallocated to the value of the License provided to Eisai and recognized as revenue in 2016.86For the years ended December 31, 2016 and 2015, we recognized revenues of $1.8 million and $0.2 million, respectively, under this agreement. Norevenues were recognized during the year ended December 31, 2017 under this agreement.Axovant Sciences GmbH.In May 2015, we entered into a Development, Marketing and Supply Agreement with Roivant Sciences Ltd., or Roivant. In October 2015, Roivant,assigned the exclusive rights to develop and commercialize nelotanserin to its subsidiary, Axovant. Under this agreement, Axovant has exclusive worldwiderights to develop and commercialize nelotanserin, subject to regulatory approval. We also provide certain services and will manufacture and sell nelotanserinto Axovant.We received an upfront payment of $4.0 million, which was recorded as deferred revenues and is being recognized as revenue ratably overapproximately five years, which is the period in which we expect to provide services under the arrangement. We are entitled to receive payments from sales ofnelotanserin under the agreement and are eligible to receive purchase price adjustment payments based on Axovant’s annual net product sales. We are alsoeligible to receive up to an aggregate of $41.5 million in success milestones in case of full development and regulatory success of nelotanserin. Of thesepayments, two development milestones totaling $4.0 million are substantive and four regulatory milestones totaling $37.5 million are substantive.For the years ended December 31, 2017, 2016, and 2015, and we recognized revenues of $2.2 million, $2.1 million and $1.1 million, respectively,under this agreement.Boehringer Ingelheim International GmbH.In December 2015, we and Boehringer Ingelheim entered into an exclusive agreement, under which we and Boehringer Ingelheim conduct jointresearch to identify drug candidates targeting an undisclosed G protein-coupled receptor, or GPCR, that belongs to the group of orphan central nervoussystem, or CNS, receptors. Under this agreement, we granted Boehringer Ingelheim exclusive rights to our internally discovered, novel compounds andintellectual property for an orphan CNS receptor. We jointly conduct research with Boehringer Ingelheim to identify additional drug candidates that aresuitable for continued research and development as therapeutic compounds for various disease indications, with the initial focus expected to be psychiatricdiseases such as schizophrenia. The agreement grants Boehringer Ingelheim exclusive worldwide rights to develop, manufacture and commercialize productsresulting from the collaboration.In part consideration of the rights to our intellectual property necessary or useful to conduct the joint research under the agreement, we received fromBoehringer Ingelheim an upfront payment of $7.5 million in January 2016, less $1.2 million of withholding taxes which was refunded to us in October 2016.Revenues from this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoingparticipation in the joint research, and are being recognized ratably as revenues over the period in which we expect the services to be rendered, which isapproximately two years.We are also eligible to receive up to an aggregate of $251.0 million (of which up to $12.0 million is payable to Beacon) in success milestones in caseof full commercial success of multiple drug products. Of these payments, three development milestones totaling $7.0 million are substantive, threedevelopment milestones totaling $30.0 million are non-substantive, nine regulatory milestones totaling $84.0 million are non-substantive and fourcommercial milestones totaling $130.0 million are non-substantive.For the years ended December 31, 2017, and 2016, we recognized revenues of $5.1 million and $5.1 million, respectively under this agreement. Wedid not recognize any revenues under this agreement during the year ended December 31, 2015. 10. Employee Benefit Plans401(k) Plan.All of our US employees are eligible to participate in our defined contribution retirement plan that complies with Section 401(k) of the InternalRevenue Code, or IRC. We match 100% of each participant’s voluntary contributions, subject to a maximum of 6% of the participant’s eligiblecompensation. Our matching portion, which totaled $0.5 million, $1.0 million, and $1.7 million for the years ended December 31, 2017, 2016, and 2015,respectively, vests over a five-year period from the date of hire.Pension Plan.Arena GmbH contributes to a multiemployer defined benefit pension plan, established under an affiliated group of employers, for the purpose ofproviding mandatory occupational pension benefits for its employees. The risks of participating in a multiemployer plan are different from a single-employerplan in that (i) assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers,(ii) if a participating employer stops contributing to the plan, the87unfunded obligations of the plan may be borne by the remaining participating employers, (iii) if Arena GmbH elects to stop participating in themultiemployer plan, Arena GmbH may be required to pay the plan an amount based on the underfunded status of the plan, referred to as a withdrawalliability, and (iv) Arena GmbH has no involvement in the management of the multiemployer plan’s investments. We currently have no intention ofwithdrawing from the multiemployer plan.Our contributions to the multiemployer plan were $0.5 million, $0.8 million and $0.7 million for the years ended December 31, 2017, 2016, and 2015,respectively.APD GmbH contributes to a single employer defined contribution pension plan. Our contributions to the multiemployer plan were $0.2 million for theyear ended December 31, 2017. There were no such contributions in 2016 and 2015. 11. Income TaxesThe following table summarizes our loss attributable to stockholders of Arena before benefit for income taxes by region for the years presented, inthousands: Years ended December 31, 2017 2016 2015 United States $(62,109) $(10,268) $(64,109)Foreign (29,298) (12,248) (43,870)Total loss attributable to stockholders of Arena before income taxes $(91,407) $(22,516) $(107,979) We have not recorded a benefit for income taxes for the years ended December 31, 2017, 2016, and 2015, because we have a full valuation allowance.Our effective income tax rate differs from the statutory federal rate of 34% for the years presented due to the following, in thousands: Years ended December 31, 2017 2016 2015 Benefit for income taxes at statutory federal rate $(32,140) $(4,053) $(37,641)Change in valuation allowance due to tax reform 96,333 — — Change in federal and foreign valuation allowance (68,604) (3,867) 22,240 Permanent differences and other (782) 3,412 2,349 Share-based compensation expense 7,071 4,001 1,820 Foreign losses at lower effective rates 1,428 3,944 15,041 Research and development and Orphan Drug credits (3,306) (3,437) (3,647)Gain from valuation of derivative liabilities — — (162)Benefit for income taxes $— $— $— 88The components of our net deferred tax assets are as follows, in thousands: December 31, 2017 2016 Deferred tax assets: Federal and California NOL carryforwards $179,323 $255,317 Federal and California research and development credit carryforwards 61,272 53,059 Foreign NOL carryforwards 15,425 4,238 Share-based compensation expense 4,884 10,395 Depreciation 3,896 5,441 Deferred revenues 3,554 9,357 Other, net 5,758 5,164 Total deferred tax assets 274,112 342,971 Deferred tax liabilities — — Net deferred tax assets 274,112 342,971 Valuation allowance (274,112) (342,971)Net deferred tax liabilities $— $— A valuation allowance is recorded against all of our deferred tax assets, as realization of such assets is not more-likely-than-not. The realization of ourdeferred tax assets is dependent upon future taxable income. Our ability to generate taxable income is analyzed regularly on a jurisdiction-by-jurisdictionbasis. At such time as it is more-likely-than-not that we will generate taxable income in a jurisdiction, we will reduce or remove the valuation allowance. Thevaluation allowance decreased by $69.5 million from December 31, 2016, to December 31, 2017.On December 22, 2017, H.R. 1/Public Law No. 115-97 known as the Tax Cuts and Jobs Act, or the Tax Act, was signed into law. The effects of thisnew federal legislation are recognized upon enactment, which is the date a bill is signed into law. The Act includes numerous changes in existing tax law,including a permanent reduction in the federal corporate income tax rate from 35% to 21%. The rate reduction takes effect on January 1, 2018. As a result ofthe Tax Act, we have revalued our net deferred tax assets as of December 31, 2017 to reflect the rate reduction. Based on currently available information, werecorded a reduction in our net deferred tax assets of $96.3 million in the fourth quarter of 2017 related to the revaluation of our net deferred tax assets as aresult of the Tax Act; however, the revaluation does not result in any additional net income tax expense as our net deferred tax assets are fully offset by thevaluation allowance.At December 31, 2017, we had federal NOL carryforwards of $721.4 million that will begin to expire in 2023 unless previously utilized. At the samedate, we had California NOL carryforwards of $398.6 million, which begin expiring in 2028 and foreign NOL carryforwards of $184.8 million, which beginexpiring in 2018. At December 31, 2017, we also had federal and California research and development tax credit carryforwards, net of reserves, of $31.7million and $23.8 million, respectively. At December 31, 2017, we had a Federal Orphan Drug Credit carryforward, net of reserves, of $10.1 million. Federalcredit carryforwards will begin to expire after 2026 unless previously utilized. The California research and development credit carries forward indefinitely.Sections 382 and 383 of the IRC limit the utilization of tax attribute carryforwards that arise prior to certain cumulative changes in a corporation’sownership. We have completed an IRC Section 382/383 analysis through 2015 and identified ownership changes that limit our utilization of tax attributecarryforwards. We reduced deferred tax assets associated with such tax attribute carryforwards to remove deferred tax assets that will expire prior toutilization. Pursuant to IRC Section 382 and 383, use of the Company’s net operating loss and research and development income tax credit carryforwardsmay be limited in the event of cumulative changes in ownership subsequent to 2015 of more than 50% within a three-year period.In accordance with authoritative guidance, the impact of an uncertain income tax position on the income tax return must be recognized at the largestamount that is more-likely-than-not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if ithas less than a 50% likelihood of being sustained.89The following table reconciles the beginning and ending amount of unrecognized tax benefits for the years presented, in thousands: Years ended December 31, 2017 2016 2015 Gross unrecognized tax benefits at the beginning of the year $5,906 $5,619 $5,214 Additions from tax positions taken in the current year 1,133 287 405 Additions from tax positions taken in prior years 723 — — Reductions from tax positions taken in prior years — — — Tax settlements — — — Gross unrecognized tax benefits at end of the year $7,762 $5,906 $5,619 Of our total unrecognized tax benefits at December 31, 2017, $6.2 million will impact our effective tax rate in the event the valuation allowance isremoved. We do not anticipate that there will be a substantial change in unrecognized tax benefits within the next 12 months.Our practice is to recognize interest and/or penalties related to income tax matters in income tax expense. Because we have incurred net losses sinceour inception, we did not have any accrued interest or penalties included in our consolidated balance sheets at December 31, 2017, or 2016, and did notrecognize any interest and/or penalties in our consolidated statements of operations and comprehensive loss for the years ended December 31, 2017, 2016,and 2015.We are subject to income taxation in the United States at the Federal and state levels. All tax years are subject to examination by US and California taxauthorities due to the carryforward of unutilized NOLs and tax credits. We are also subject to foreign income taxes in the countries in which we operate. Toour knowledge, we are not currently under examination by any taxing authorities.At December 31, 2017, no foreign subsidiaries have accumulated earnings and, as such, there are no unrepatriated earnings.Our Swiss subsidiary, Arena GmbH, has been granted a conditional incentive tax holiday by the Canton of Aargau for its operations in Switzerland.Without a tax holiday or other tax incentives, the standard effective tax rate of a company located in Aargau is approximately 19%. As a result of the taxholiday and other tax incentives, we expect the effective tax rate for Arena GmbH to be approximately half of such rate. The tax holiday came into effect onJanuary 1, 2013, and will continue for a period of up to 10 years, not to extend beyond December 31, 2022. As a result of foreign losses and a full valuationallowance, no net tax benefit was derived for the years ended December 31, 2017, 2016, and 2015, as a result of the tax holiday. 12. Legal ProceedingsBeginning on September 20, 2010, a number of complaints were filed in the US District Court for the Southern District of California, or District Court,against us and certain of our current and former employees and directors on behalf of certain purchasers of our common stock. The complaints were broughtas purported stockholder class actions, and, in general, include allegations that we and certain of our current and former employees and directors violatedfederal securities laws by making materially false and misleading statements regarding our BELVIQ program, thereby artificially inflating the price of ourcommon stock. The plaintiffs sought unspecified monetary damages and other relief. On August 8, 2011, the District Court consolidated the actions andappointed a lead plaintiff and lead counsel. On November 1, 2011, the lead plaintiff filed a consolidated amended complaint. On March 28, 2013, the DistrictCourt dismissed the consolidated amended complaint without prejudice. On May 13, 2013, the lead plaintiff filed a second consolidated amended complaint.On November 5, 2013, the District Court dismissed the second consolidated amended complaint without prejudice as to all parties except for Robert E.Hoffman, who was dismissed from the action with prejudice. On November 27, 2013, the lead plaintiff filed a motion for leave to amend the secondconsolidated amended complaint. On March 20, 2014, the District Court denied plaintiff’s motion and dismissed the second consolidated amendedcomplaint with prejudice. On April 18, 2014, the lead plaintiff filed a notice of appeal, and on August 27, 2014, the lead plaintiff filed his appellate brief inthe US Court of Appeals for the Ninth Circuit, or Ninth Circuit. On October 24, 2014, we filed our answering brief in response to the lead plaintiff’s appeal.On December 5, 2014, the lead plaintiff filed his reply brief. A panel of the Ninth Circuit heard oral argument on the appeal on May 4, 2016. On October 26,2016, the Ninth Circuit panel reversed the District Court’s dismissal of the second consolidated amended complaint and remanded the case back to theDistrict Court for further proceedings. On January 25, 2017, the District Court permitted us to submit a renewed motion to dismiss the second consolidatedamended complaint. On February 2, 2017, we filed the renewed motion to dismiss. On February 23, 2017, the lead plaintiff filed his opposition, and on March2, 2017, we filed our reply. On April 28, 2017, the District Court denied our renewed motion to dismiss. On November 3, 2017, we and the Lead Plaintiffsigned a stipulation and agreement of settlement, or Stipulation, to resolve the consolidated class action. Under the terms of the Stipulation, and in exchangefor a release of all claims by class members and a dismissal of the consolidated class action with prejudice, we have agreed (i) our insurers will pay classmembers and their attorneys a total of approximately $12.025 million and (ii) Arena will pay90class members and their attorneys approximately $11.975 million in either shares of our common stock or cash at our election. On November 30, 2017, theDistrict Court preliminary approved the settlement and the form of notice to potential class members of the proposed settlement and the procedure by whichthey can become class members. On March 8, 2018, the lead plaintiff filed motions for final approval of the settlement, the plan of allocation and award ofattorney fees. The settlement and related matters remain subject to final approval by the District Court. We recognized $11.975 million of net expense for theportion of the settlement that we will pay in either common stock or cash in the consolidated statements of operations for the year ended December 31, 2017,and $24.0 million as a current liability in the consolidated balance sheet as of December 31, 2017 for the gross settlement liability, with a corresponding$12.025 million insurance recovery receivable.On September 30, 2016, we and Eisai Inc. filed a patent infringement lawsuit against Lupin Limited and Lupin Pharmaceuticals, Inc. (collectively,Lupin) in the U.S. District Court for the District of Delaware. The lawsuit relates to a “Paragraph IV certification” notification that we and Eisai Inc. receivedregarding an abbreviated new drug application, or ANDA, submitted to the FDA by Lupin requesting approval to engage in the commercial manufacture, use,importation, offer for sale or sale of a generic version of BELVIQ (lorcaserin hydrochloride tablets, 10 mg). In its notification, Lupin alleged that no valid,enforceable claim of any of the patents that are listed in the FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, or Orange Book, forBELVIQ will be infringed by Lupin’s manufacture, importation, use, sale or offer for sale of the product described in its ANDA for 10 mg lorcaserinhydrochloride tablets. Lupin is accused of infringing U.S. Patent Nos. 6,953,787; 7,514,422; 7,977,329; 8,207,158 and 8,273,734. In accordance with theHatch-Waxman Act, as a result of filing a patent infringement lawsuit within 45 days of receipt of Lupin’s notification, the FDA cannot approve Lupin’sANDA any earlier than 7.5 years from NDA approval unless a District Court finds that all of the asserted claims of the patents-in-suit are invalid,unenforceable or not infringed. On January 11, 2017, Lupin filed an answer, defenses and counterclaims to the September 30, 2016 complaint. We and EisaiInc. filed an answer to Lupin’s counterclaims on February 1, 2017. We and Eisai Inc. are seeking a determination from the court that, among other things,Lupin has infringed our patents, Lupin’s ANDA for 10 mg lorcaserin hydrochloride tablets should not be approved until the expiration date of our patents,and Lupin should be enjoined from commercializing a product that infringes our patents. Trial is currently scheduled for April 15, 2019. The parties arecurrently in the fact discovery phase of the case. We cannot predict the ultimate outcome of any proceeding.On March 6, 2017, we and Eisai Inc. filed a patent infringement lawsuit against Teva Pharmaceuticals USA, Inc. and Teva Pharmaceutical IndustriesLtd. (collectively, Teva) in the U.S. District Court for the District of Delaware. The lawsuit also relates to a “Paragraph IV certification” notification that weand Eisai Inc. received regarding an ANDA submitted to the FDA by Teva requesting approval to engage in the commercial manufacture, use, importation,offer for sale or sale of a generic version of BELVIQ XR (lorcaserin hydrochloride extended-release tablets, 20 mg). In its notification, Teva alleged that novalid, enforceable claim of any of the patents that are listed in the Orange Book for BELVIQ XR will be infringed by Teva’s manufacture, importation, use,sale or offer for sale of the product described in its ANDA. Teva is accused of infringing U.S. Patent Nos. 6,953,787; 7,514,422; 7,977,329; 8,207,158 and8,273,734. In accordance with the Hatch-Waxman Act, as a result of filing a patent infringement lawsuit within 45 days of receipt of Teva’s notification, theFDA cannot approve Teva’s ANDA any earlier than 7.5 years from NDA approval unless a District Court finds that all of the asserted claims of the patents-in-suit are invalid, unenforceable or not infringed. On April 18, 2017, Teva filed an amended answer, defenses and counterclaims to the March 6, 2017complaint. We and Eisai Inc. are seeking a determination from the court that, among other things, Teva has infringed our patents, Teva’s ANDA should not beapproved until the expiration date of our patents, and Teva should be enjoined from commercializing a product that infringes our patents. On May 1, 2017,the Teva and Lupin actions were consolidated for all purposes and will follow the case schedule that was previously entered in the Lupin action. We andEisai Inc. filed an answer to Teva’s amended counterclaims on May 3, 2017. On or about October 16, 2017, we and Eisai Inc. received a “Paragraph IVcertification” notification from Teva alleging that no valid, enforceable claim of U.S. Patent No. 9,770,455, which was listed in the Orange Book forBELVIQ and BELVIQ XR after the patent issued on September 26, 2017, will be infringed by Teva’s manufacture, importation, use, offer for sale or sale ofthe product described in its ANDA. On October 25, 2017, we and Eisai Inc. filed a first amended complaint against Lupin and Teva, adding infringement ofU.S. Patent No. 9,770,455 by their respective ANDA products to the consolidated lawsuit. On or about November 6, 2017, we and Eisai Inc. received a“Paragraph IV certification” notification from Lupin alleging that no valid, enforceable claim of U.S. Patent No. 9,770,455 will be infringed by Lupin’smanufacture, importation, use, offer for sale or sale of the product described in its ANDA for 10 mg lorcaserin hydrochloride tablets. We cannot predict theultimate outcome of any proceeding.We and Eisai Inc. also received a “Paragraph IV certification” notification from Lupin alleging that no valid, enforceable claim of any of the patentsthat are listed in the Orange Book for BELVIQ and BELVIQ XR will be infringed by Lupin’s manufacture, importation, use, sale or offer for sale of theproduct described in its ANDA for 20 mg lorcaserin hydrochloride extended-release tablets. Because Lupin is not the first applicant to submit a substantiallycomplete application containing a Paragraph IV certification for approval of a generic equivalent of BELVIQ XR, absent extenuating circumstances, Lupinwould not be able to launch its 20 mg lorcaserin hydrochloride extended-release tablets before Teva was able to launch its respective product. 9113. Restructuring ActivitiesIn the fourth quarter of 2015, we committed to a reduction in our US workforce of approximately 35%, or approximately 80 employees, which wesubstantially completed by the end of 2015. As a result of this workforce reduction, we recorded a restructuring charge in the fourth quarter of 2015 fortermination benefits, including severance and other benefits, of $3.3 million, which was paid by December 31, 2016.In the second quarter of 2016, we committed to a reduction in our US workforce of approximately 73%, or approximately 100 employees, which wesubstantially completed in the third quarter of 2016. As a result of this workforce reduction, we recorded a restructuring charge in the second quarter of 2016of $6.1 million for termination benefits, including severance and other benefits. Included within this amount is non-cash, share-based compensation expenseof $1.0 million related to the accelerated vesting of stock options and the extension of the exercise period of vested options for employees impacted by theworkforce reduction. At December 31, 2016, substantially all of this charge had been paid. 14. Quarterly Financial Data (Unaudited)The following tables present selected quarterly financial data for the years presented, in thousands, except per share data: 2017 Quarter endedDecember 31 Quarter endedSeptember 30 Quarter endedJune 30 Quarter endedMarch 31 Revenues $15,364 $2,415 $1,898 $1,660 Operating costs and expenses 28,964 36,626 24,850 22,864 Net income (loss): Loss from continuing operations $(14,270) $(35,270) $(23,763) $(22,551)Income from discontinued operations 315 2,606 147 54 $(13,955) $(32,664) $(23,616) $(22,497) Amounts attributable to stockholders of Arena: Loss from continuing operations $(13,999) $(34,959) $(23,464) $(22,107)Income from discontinued operations 315 2,606 147 54 $(13,684) $(32,353) $(23,317) $(22,053) Net income (loss) attributable to stockholders of Arena per share, basic and diluted: Continuing operations $(0.36) $(0.93) $(0.77) $(0.90)Discontinued operations 0.01 0.07 — — $(0.35) $(0.86) $(0.77) $(0.90) 922016 Quarter endedDecember 31 Quarter endedSeptember 30 Quarter endedJune 30 Quarter endedMarch 31 Revenues $69,224 $14,637 $4,219 $4,083 Operating costs and expenses 18,548 24,534 31,522 22,822 Net income (loss): Income (loss) from continuing operations $48,925 $(12,257) $(28,789) $(20,179)Income (loss) from discontinued operations (10,611) (222) 1,606 (1,369) $38,314 $(12,479) $(27,183) $(21,548) Amounts attributable to stockholders of Arena: Income (loss) from continuing operations $49,183 $(12,135) $(28,789) $(20,179)Income (loss) from discontinued operations (10,611) (222) 1,606 (1,369) $38,572 $(12,357) $(27,183) $(21,548) Net income (loss) attributable to stockholders of Arena per share, basic: Continuing operations $2.02 $(0.50) $(1.18) $(0.83)Discontinued operations (0.43) (0.01) 0.06 (0.06) $1.59 $(0.51) $(1.12) $(0.89) Net income (loss) attributable to stockholders of Arena per share, diluted: Continuing operations $2.02 $(0.50) $(1.18) $(0.83)Discontinued operations (0.44) (0.01) 0.06 (0.06) $1.58 $(0.51) $(1.12) $(0.89) 15. Beacon Discovery, Inc.On September 1, 2016, we entered into a series of agreements with Beacon. Beacon, a privately held drug discovery incubator which focuses onidentifying and advancing molecules targeting GCPRs, was founded and is owned by several of our former employees.We entered into an agreement, or License and Collaboration Agreement, with Beacon, pursuant to which we transferred certain equipment to Beaconand granted Beacon a non-exclusive, non-assignable and non-sublicensable license to certain database information relating to compounds, receptors andpharmacology, and transferred certain equipment to Beacon. Beacon will seek to engage global partners to facilitate discovery and development. Beacon hasagreed to assign to us any intellectual property relating to our existing research and development programs developed in the course of performing researchfor us, and grant us a non-exclusive license to any intellectual property developed outside the course of performing work for us that is reasonably necessaryor useful for developing or commercializing the products under our research and development programs. We are also entitled to rights of negotiation andrights of first refusal to potentially obtain licenses to compounds discovered and developed by Beacon. In addition, we are entitled to receive (i) a percentageof any revenue received by Beacon on or after the second anniversary of the effective date of the agreement from any third party pursuant to a third-partylicense, including upfront payments, milestone payments and royalties; (ii) single-digit royalties on the aggregate net sales of any related products sold byBeacon and its affiliates; and (iii) in the event that Beacon is sold, a percentage of the consideration for such sale transaction.We entered a services agreement with Beacon, or Master Services Agreement, pursuant to which Beacon performs certain research services for us.We also entered into a separate services agreement with Beacon, or Beacon Services Agreement, pursuant to which Beacon now performs our researchobligations under our December 2015 agreement with Boehringer Ingelheim. In consideration for performing these research obligations, Beacon is entitled toreceive the applicable FTE payments that are paid to us by Boehringer Ingelheim for the research services and certain milestone payments.We also entered into a sublease agreement, or Sublease, with Beacon, pursuant to which we sublease approximately 15,000 square feet of laboratory,office and meeting room space to Beacon until August 2021. Beacon can defer payments due to us under the Sublease by increasing the outstandingprincipal amount under a secured promissory note, or Note, we issued to Beacon. The outstanding principal amount and all accrued or unpaid interest thereon(calculated at a simple interest rate of 7% per annum) shall be93due and payable on the earlier of (i) August 31, 2022 or (ii) Beacon receiving cumulative cash proceeds of $10 million from the sale of equity, issuance ofdebt or third-party license revenue.As Beacon’s equity investment at risk is not sufficient to permit Beacon to finance its activities without subordinated financial support, Beacon isconsidered a variable interest entity in which we hold a significant variable interest pursuant to the License and Collaboration Agreement. We do not ownany equity interest in Beacon; however, as the agreements described above provided us the controlling financial interest in Beacon until December 2017, weconsolidated Beacon’s balances and activity within our consolidated financial statements until December 2017 as we were determined to be the primarybeneficiary of Beacon. Pursuant to a contract Beacon entered into with a third party in December 2017 which provided Beacon with a certain amount ofupfront funding, we determined we no longer held the controlling financial interest as of that date and, therefore, deconsolidated Beacon from ourconsolidated financial statements as we were no longer deemed to be the primary beneficiary. Our consolidated financial statements for the year endedDecember 31, 2017, includes Beacon’s results of operations and cash flows until the December 2017 deconsolidation. As of December 31, 2017, Beacon’stotal assets of $1.0 million, total liabilities of $1.8 million and total stockholders’ deficit of $0.8 million are excluded from our consolidated balance sheet.For the year ended December 31, 2017, Beacon recognized revenues of $2.7 million of which less than $0.1 million was earned from third parties andis included on our consolidated statement of operations. For the year ended December 31, 2017, Beacon incurred a net and comprehensive loss of $1.3million which is fully presented as net loss attributable to noncontrolling interest in consolidated variable interest entity in our consolidated statement ofoperations and comprehensive loss as we do not own any equity interest in Beacon.As of December 31, 2017, the following balances pertaining to our transactions with Beacon are included in our consolidated balance sheet, inthousands: DescriptionClassification Prepaid costs under the Master Services AgreementPrepaid expenses and other current assets $368 Receivable under the Sublease and the NoteOther non-current assets 477 Payable under the Beacon Services AgreementAccounts payable and other accrued liabilities 139 We believe that our maximum exposure to loss as a result of our involvement with Beacon is limited to the receivable due to us from Beacon under theSublease and the Note. 16. Subsequent EventsSee Notes 1 and 5 regarding the Sale Agreement with Siegfried to divest our Manufacturing Operations and Note 12 for the update to our legalproceedings, which occurred subsequent to December 31, 2017. Item 9. Changes in and Disagreements with Accountants on Accounting and Financial DisclosureNone.Item 9A. Controls and ProceduresConclusion Regarding the Effectiveness of Disclosure Controls and ProceduresWe maintain disclosure controls and procedures that are designed to ensure that information required to be disclosed in our periodic and currentreports that we file with the SEC is recorded, processed, summarized and reported within the time periods specified in the SEC’s rules and forms, and that suchinformation is accumulated and communicated to our management, including our principal executive officer and principal financial officer, as appropriate, toallow timely decisions regarding required disclosure.As of December 31, 2017, we conducted an evaluation, under the supervision and with the participation of our management, including our ChiefExecutive Officer and Chief Financial Officer, of our disclosure controls and procedures, as such term is defined under Rule 13a-15(e) promulgated under theSecurities Exchange Act of 1934, as amended, or the Exchange Act. Based on this evaluation, our Chief Executive Officer and Chief Financial Officerconcluded that our disclosure controls and procedures were effective at the reasonable assurance level as of the end of the period covered by this AnnualReport on Form 10-K.94Management’s Report on Internal Control Over Financial ReportingOur management is also responsible for establishing and maintaining for us adequate internal control over financial reporting, as such term is definedin Exchange Act Rule 13a-15(f). Under the supervision and with the participation of our management, including our Chief Executive Officer and ChiefFinancial Officer, we conducted an evaluation of the effectiveness of our internal control over financial reporting based on the Internal Control—IntegratedFramework (2013 framework) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on our evaluation under thisframework, our management concluded that our internal control over financial reporting was effective as of December 31, 2017.The registered public accounting firm that audited our financial statements as of and for the year ended December 31, 2017, included in this AnnualReport on Form 10-K, has issued an attestation report on our internal control over financial reporting, and such report is included below.Changes in Internal Control Over Financial ReportingAn evaluation was also performed under the supervision and with the participation of our management, including our Chief Executive Officer andChief Financial Officer, of any changes in our internal control over financial reporting that occurred during our last fiscal quarter and that has materiallyaffected, or is reasonably likely to materially affect, our internal control over financial reporting. That evaluation did not identify any change in our internalcontrol over financial reporting during the fourth quarter of the year ended December 31, 2017 that has materially affected, or is reasonably likely tomaterially affect, our internal control over financial reporting.95Report of Independent Registered Public Accounting FirmThe Stockholders and Board of DirectorsArena Pharmaceuticals, Inc.: Opinion on Internal Control over Financial Reporting We have audited Arena Pharmaceuticals, Inc. and subsidiaries’ (the Company) internal control over financial reporting as of December 31, 2017, based oncriteria established in Internal Control – Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission.In our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2017, based on criteriaestablished in Internal Control – Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidatedbalance sheets of the Company as of December 31, 2017 and 2016, the related consolidated statements of operations and comprehensive loss, equity, andcash flows for each of the years in the three-year period ended December 31, 2017, and the related notes (collectively, the “consolidated financialstatements”), and our report dated March 14, 2018 expressed an unqualified opinion on those consolidated financial statements. Basis for Opinion The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness ofinternal control over financial reporting, included in the accompanying Management’s Report on Internal Control over Financial Reporting. Ourresponsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. We are a public accounting firmregistered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and theapplicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonableassurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit of internal control over financialreporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing andevaluating the design and operating effectiveness of internal control based on the assessed risk. Our audit also included performing such other procedures aswe considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion. Definition and Limitations of Internal Control over Financial Reporting A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reportingand the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal controlover financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairlyreflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permitpreparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are beingmade only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention ortimely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements. Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation ofeffectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliancewith the policies or procedures may deteriorate. /s/ KPMG LLP San Diego, California March 14, 2018 96Item 9B. Other InformationNot applicable. 97PART IIIItem 10. Directors, Executive Officers and Corporate GovernanceWe have adopted a Code of Business Conduct and Ethics that applies to our directors and employees (including our principal executive officer,principal financial officer, principal accounting officer and controller), and have posted the text of the policy on our website (www.arenapharm.com) inconnection with “Investor” materials. In addition, we intend to promptly disclose on our website in the future (i) the date and nature of any amendment (otherthan technical, administrative or other non-substantive amendments) to the policy that applies to our principal executive officer, principal financial officer,principal accounting officer or controller, or persons performing similar functions and relates to any element of the code of ethics definition enumerated inItem 406(b) of Regulation S-K, and (ii) the nature of any waiver, including an implicit waiver, from a provision of the policy that is granted to one of thesespecified individuals that relates to one or more of the elements of the code of ethics definition enumerated in Item 406(b) of Regulation S-K, the name ofsuch person who is granted the waiver and the date of the waiver.The other information required by this item will be included under the captions “Election of Directors,” “Compensation and Other InformationConcerning Executive Officers, Directors and Certain Stockholders” and “Section 16(a) Beneficial Ownership Reporting Compliance” in our definitiveproxy statement for the annual meeting of stockholders to be held in June 2018 to be filed with the SEC on or before April 30, 2018, or the Proxy Statement,and is incorporated herein by reference.Item 11. Executive CompensationThe information required by this item will be included under the captions “Compensation and Other Information Concerning Executive Officers,Directors and Certain Stockholders” and “Compensation Committee Interlocks and Insider Participation” in the Proxy Statement and is incorporated hereinby reference.Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.The following table summarizes our compensation plans under which our equity securities are authorized for issuance at December 31, 2017: Plan category Number of securities to be issued uponexercise of outstanding options,warrants and rights Weighted-average exerciseprice of outstanding options,warrants and rights Number of securities remaining available forfuture issuance under equity compensation plans(excluding securities reflected in column (a)) (a) (b) (c) Equity compensation plans approved by security holders 3,184,801 *$20.20 2,934,785*** Equity compensation plans not approved by security holders 669,350 ** 16.08 — Total 3,854,151 $19.49 2,934,785*** *Includes stock options to purchase 3,085,693 shares of our common stock with a per share weighted-average exercise price of $20.85. Also includes (i)21,220 restricted stock unit awards with no exercise price and (ii) 38,944 performance restricted stock unit awards with no exercise price. In theaggregate, the target number of shares of common stock that may be earned under the performance restricted stock unit awards is 77,888; however, theactual number of shares that may be earned ranges from 0% to 200% of such amount, and this table reflects 200%.**Represents inducement stock options to purchase 669,350 shares of our common stock reserved for inducement awards.***Stock options and stock appreciation rights granted under our 2017 Long-Term Incentive Plan, or 2017 LTIP, reduce the available number of sharesunder our 2017 LTIP by 1 share for every share issued while awards other than stock options and stock appreciation rights granted under our 2017LTIP reduce the available number of shares by 1.6 shares for every share issued. In addition, shares that are released from awards granted under any ofour prior long-term incentive plans or the 2017 LTIP because the awards expire, are forfeited or are settled for cash will increase the number of sharesavailable under our 2017 LTIP by 1 share for each share released from a stock option or stock appreciation right and by 1.6 shares for each sharereleased from a restricted stock award or restricted stock unit award. Each share we withhold to satisfy any tax withholding obligation with respect toan award other than an option or stock appreciation right under any of our prior long-term incentive plans or the 2017 LTIP will increase the sharereserve by 1.6 shares. 98The other information required by this item will be included under the caption “Security Ownership of Certain Beneficial Owners and Management”in the Proxy Statement and is incorporated herein by reference.Item 13. Certain Relationships and Related Transactions, and Director IndependenceThe information required by this item will be included under the captions “Certain Relationships and Related Transactions” and “Election ofDirectors” in the Proxy Statement and is incorporated herein by reference.Item 14. Principal Accountant Fees and ServicesThe information required by this item will be included under the captions “Independent Auditors’ Fees” and “Pre-approval Policies and Procedures”in the Proxy Statement and is incorporated herein by reference. PART IVItem 15. Exhibits, Financial Statement Schedules.(a)1. FINANCIAL STATEMENTSReference is made to the Index to Financial Statements under Item 8, Part II hereof.2. FINANCIAL STATEMENT SCHEDULESThe financial statement schedules have been omitted either because they are not required or because the information has been included in theconsolidated financial statements or the notes thereto included in this annual report.3. EXHIBITS ExhibitNo. Exhibit Description 2.1* Agreement of Purchase and Sale, dated as of March 21, 2007, by and between Arena and BMR-6114-6154 Nancy Ridge Drive LLP (asassignee of BioMed Realty, L.P.) (incorporated by reference to Exhibit 2.1 to Arena’s current report on Form 8-K filed with the Securitiesand Exchange Commission on May 8, 2007, Commission File No. 000-31161) 3.1 Fifth Amended and Restated Certificate of Incorporation of Arena (incorporated by reference to Exhibit 3.1 to Arena’s quarterly report onForm 10-Q for the quarter ended June 30, 2002, filed with the Securities and Exchange Commission on August 14, 2002, CommissionFile No. 000-31161) 3.2 Certificate of Amendment of the Fifth Amended and Restated Certificate of Incorporation of Arena (incorporated by reference to Exhibit 4.2to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commission on June 28, 2006, CommissionFile No. 333-135398) 3.3 Certificate of Amendment No. 2 of the Fifth Amended and Restated Certificate of Incorporation of Arena, as amended (incorporated byreference to Exhibit 4.3 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commission on June 30, 2009,Commission File No. 333-160329) 3.4 Certificate of Amendment No. 3 of the Fifth Amended and Restated Certificate of Incorporation of Arena, as amended (incorporated byreference to Exhibit 3.4 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commission on June 20, 2012,Commission File No. 333-182238) 3.5 Certificate of Amendment No. 4 of the Fifth Amended and Restated Certificate of Incorporation of Arena, as amended (incorporated byreference to Exhibit 3.1 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 15, 2017,Commission File No. 000-31161) 3.6 Amended and Restated Bylaws of Arena (incorporated by reference to Exhibit 3.1 to Arena’s current report on Form 8-K filed with theSecurities and Exchange Commission on October 9, 2014, Commission File No. 000-31161) 4.1 Reference is made to Exhibits 3.1, 3.2, 3.3, 3.4, 3.5 and 3.6 4.2 Form of common stock certificate (incorporated by reference to Exhibit 4.7 to Arena’s registration statement on Form S-8, filed with theSecurities and Exchange Commission on June 22, 2017, Commission File No. 333-218905)99ExhibitNo. Exhibit Description 10.1 Lease Agreement, dated December 30, 2003, between Arena and ARE—Nancy Ridge No. 3, LLC (incorporated by reference to Exhibit 10.2to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on January 6, 2004, Commission File No. 000-31161) 10.2** 2006 Long-Term Incentive Plan, as amended (incorporated by reference to Exhibit 10.1 to Arena’s current report on Form 8-K filed with theSecurities and Exchange Commission on April 13, 2007, Commission File No. 000-31161) 10.3** Form of Stock Option Grant Agreement under the Arena 2006 Long-Term Incentive Plan, as amended (incorporated by reference toExhibit 10.1 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on August 1, 2006, Commission FileNo. 000-31161) 10.4** Form of Stock Option Grant Agreement—Director under the Arena 2006 Long-Term Incentive Plan, as amended (incorporated by referenceto Exhibit 10.2 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on August 1, 2006, CommissionFile No. 000-31161) 10.5** Form of Incentive Stock Option Grant Agreement under the Arena 2006 Long-Term Incentive Plan, as amended (incorporated by referenceto Exhibit 10.3 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on August 1, 2006, CommissionFile No. 000-31161) 10.6** Form of Indemnification Agreement between Arena and its directors (incorporated by reference to Exhibit 10.1 to Arena’s current report onForm 8-K filed with the Securities and Exchange Commission on June 18, 2007, Commission File No. 000-31161) 10.7** Form of Indemnification Agreement between Arena and its executive officers (incorporated by reference to Exhibit 10.2 to Arena’s currentreport on Form 8-K filed with the Securities and Exchange Commission on June 18, 2007, Commission File No. 000-31161) 10.8** Form of Indemnification Agreement between Arena and individuals serving as its directors and executive officers (incorporated by referenceto Exhibit 10.3 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 18, 2007, CommissionFile No. 000-31161) 10.9 Lease agreement between BMR-6114-6154 Nancy Ridge Drive LLC and Arena for 6114 Nancy Ridge Drive, San Diego, California(incorporated by reference to Exhibit 10.5 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2007, filed with theSecurities and Exchange Commission on August 9, 2007, Commission File No. 000-31161) 10.10 Lease agreement between BMR-6114-6154 Nancy Ridge Drive LLC and Arena for 6118 Nancy Ridge Drive, San Diego, California(incorporated by reference to Exhibit 10.6 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2007, filed with theSecurities and Exchange Commission on August 9, 2007, Commission File No. 000-31161) 10.11 Lease agreement between BMR-6114-6154 Nancy Ridge Drive LLC and Arena for 6122, 6124 and 6126 Nancy Ridge Drive, San Diego,California (incorporated by reference to Exhibit 10.7 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2007, filedwith the Securities and Exchange Commission on August 9, 2007, Commission File No. 000-31161) 10.12 Lease agreement between BMR-6114-6154 Nancy Ridge Drive LLC and Arena for 6154 Nancy Ridge Drive, San Diego, California(incorporated by reference to Exhibit 10.8 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2007, filed with theSecurities and Exchange Commission on August 9, 2007, Commission File No. 000-31161) 10.13** Form of Amended and Restated Termination Protection Agreement, dated December 30, 2008, by and between Arena and Mr. Spector(incorporated by reference to Exhibit 10.2 to Arena’s Form 8-K filed with the Securities and Exchange Commission on December 31, 2008,Commission File No. 000-31161) 10.14** Arena’s 2009 Long-Term Incentive Plan (incorporated by reference to Exhibit 99.1 to Arena’s registration statement on Form S-8 filed withthe Securities and Exchange Commission on June 30, 2009, Commission File No. 333-160329) 10.15** Form of Incentive Stock Option Grant Agreement for Employees under the Arena 2009 Long-Term Incentive Plan (incorporated by referenceto Exhibit 10.7 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2009, filed with the Securities and ExchangeCommission on August 7, 2009, Commission File No. 000-31161) 10.16** Form of Stock Option Grant Agreement for Employees or Consultants under the Arena 2009 Long-Term Incentive Plan (incorporated byreference to Exhibit 10.8 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2009, filed with the Securities andExchange Commission on August 7, 2009, Commission File No. 000-31161)100ExhibitNo. Exhibit Description 10.17** Form of Stock Option Grant Agreement for Non-Employee Directors under the Arena 2009 Long-Term Incentive Plan (incorporated byreference to Exhibit 10.9 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2009, filed with the Securities andExchange Commission on August 7, 2009, Commission File No. 000-31161) 10.18** Arena’s 2009 Employee Stock Purchase Plan, as amended (incorporated by reference to Exhibit 10.1 to Arena’s current report on Form 8-Kfiled with the Securities and Exchange Commission on June 16, 2015, Commission File No. 000-31161) 10.19** Arena’s 2012 Long-Term Incentive Plan (incorporated by reference to Exhibit 99.1 to Arena’s registration statement on Form S-8 filed withthe Securities and Exchange Commission on June 20, 2012, Commission File No. 333-182238) 10.20** Form of Incentive Stock Option Grant Agreement for Employees for grants prior to December 13, 2012, under the Arena 2012 Long-TermIncentive Plan (incorporated by reference to Exhibit 10.3 to Arena’s current report on Form 8-K filed with the Securities and ExchangeCommission on June 20, 2012, Commission File No. 000-31161) 10.21** Form of Stock Option Grant Agreement for Employees or Consultants for grants prior to December 13, 2012, under the Arena 2012 Long-Term Incentive Plan (incorporated by reference to Exhibit 10.4 to Arena’s current report on Form 8-K filed with the Securities and ExchangeCommission on June 20, 2012, Commission File No. 000-31161) 10.22** Form of Stock Option Grant Agreement for Non-Employee Directors under the Arena 2012 Long-Term Incentive Plan (incorporated byreference to Exhibit 10.5 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 20, 2012,Commission File No. 000-31161) 10.23** Form of Restricted Stock Grant Agreement under the Arena 2012 Long-Term Incentive Plan (incorporated by reference to Exhibit 10.6 toArena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 20, 2012, Commission File No. 000-31161) 10.24** Form of Incentive Stock Option Grant Agreement for Employees for grants beginning on December 13, 2012, under the Arena 2012 Long-Term Incentive Plan (incorporated by reference to Exhibit 10.45 to Arena’s annual report on Form 10-K for the year ended December 31,2012, filed with the Securities and Exchange Commission on March 1, 2013, Commission File No. 000-31161) 10.25** Form of Stock Option Grant Agreement for Employees or Consultants for grants beginning on December 13, 2012, under the Arena 2012Long-Term Incentive Plan (incorporated by reference to Exhibit 10.46 to Arena’s annual report on Form 10-K for the year endedDecember 31, 2012, filed with the Securities and Exchange Commission on March 1, 2013, Commission File No. 000-31161) 10.26** Form of Restricted Stock Unit Grant Agreement under the Arena 2012 Long-Term Incentive Plan (incorporated by reference to Exhibit 10.47to Arena’s annual report on Form 10-K for the year ended December 31, 2012, filed with the Securities and Exchange Commission onMarch 1, 2013, Commission File No. 000-31161) 10.27** Form of Performance Restricted Stock Unit Grant Agreement under the Arena 2012 Long-Term Incentive Plan (incorporated by reference toExhibit 10.2 to Arena’s quarterly report on Form 10-Q for the quarter ended March 31, 2013, filed with the Securities and ExchangeCommission on May 9, 2013, Commission File No. 000-31161) 10.28** Arena’s 2013 Long-Term Incentive Plan, as amended (incorporated by reference to Exhibit 10.3 to Arena’s quarterly report on Form 10-Q forthe quarter ended March 31, 2017, filed with the Securities and Exchange Commission on May 9, 2017, Commission File No. 000-31161) 10.29** Form of Stock Option Grant Agreement for Employees or Consultants under the Arena 2013 Long-Term Incentive Plan, as amended(incorporated by reference to Exhibit 10.3 to Arena’s quarterly report on Form 10-Q for the quarter ended June 30, 2016, filed with theSecurities and Exchange Commission on August 9, 2016, Commission File No. 000-31161) 10.30** Form of Incentive Stock Option Grant Agreement for Employees under the Arena 2013 Long-Term Incentive Plan (incorporated by referenceto Exhibit 10.3 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 14, 2013, CommissionFile No. 000-31161) 10.31** Form of Restricted Stock Unit Grant Agreement (other than for non-employee directors) under the Arena 2013 Long-Term Incentive Plan(incorporated by reference to Exhibit 10.4 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission onJune 14, 2013, Commission File No. 000-31161) 10.32** Form of Restricted Stock Unit Grant Agreement for Non-Employee Directors under the Arena 2013 Long-Term Incentive Plan (incorporatedby reference to Exhibit 10.5 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 14, 2013,Commission File No. 000-31161)101ExhibitNo. Exhibit Description 10.33** Form of Performance Restricted Stock Unit Grant Agreement under the Arena 2013 Long-Term Incentive Plan (incorporated by reference toExhibit 10.42 to Arena’s annual report on Form 10-K for the year ended December 31, 2015, filed with the Securities and ExchangeCommission on February 29, 2016, Commission File No. 000-31161) 10.34** Executive Employment Agreement, dated as of May 6, 2016, by and between Arena and Amit D. Munshi (incorporated by reference toExhibit 10.1 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on May 9, 2016, Commission FileNo. 000-31161) 10.35** Severance Agreement, dated as of May 6, 2016, by and between Arena and Amit D. Munshi (incorporated by reference to Exhibit 10.2 toArena’s current report on Form 8-K filed with the Securities and Exchange Commission on May 9, 2016, Commission File No. 000-31161) 10.36** Form of Amendment to Amended and Restated Termination Protection Agreement, dated May 9, 2016, by and between Arena and StevenW. Spector (incorporated by reference to Exhibit 10.3 to Arena’s current report on Form 8-K filed with the Securities and ExchangeCommission on May 9, 2016, Commission File No. 000-31161) 10.37** Amended and Restated Severance Benefit Plan, effective May 9, 2016, and providing benefits for certain of Arena’s executive officers(incorporated by reference to Exhibit 10.4 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission onMay 9, 2016, Commission File No. 000-31161) 10.38** Employment Agreement, dated as of June 14, 2016, by and between Arena and Kevin R. Lind (incorporated by reference to Exhibit 10.1 toArena’s current report on Form 8-K filed with the Securities and Exchange Commission on June 16, 2016, Commission File No. 000-31161) 10.39** Amendment No. 1, effective June 15, 2016, to Amended and Restated Severance Benefit Plan, effective May 9, 2016, and providing benefitsfor certain of Arena’s executive officers (incorporated by reference to Exhibit 10.2 to Arena’s current report on Form 8-K filed with theSecurities and Exchange Commission on June 16, 2016, Commission File No. 000-31161) 10.40** Summary of compensation for Arena’s non-employee directors, approved June 13, 2017 (incorporated by reference to Exhibit 10.7 toArena’s quarterly report on Form 10-Q for the quarter ended June 30, 2017, filed with the Securities and Exchange Commission on August 8,2017, Commission File No. 000-31161) 10.41** Annual Incentive Plan for Arena’s executive officers (incorporated by reference to Exhibit 10.11 to Arena’s quarterly report on Form 10-Qfor the quarter ended June 30, 2016, filed with the Securities and Exchange Commission on August 9, 2016, Commission File No. 000-31161) 10.42** Amendment No. 2, effective August 15, 2016, to Amended and Restated Severance Benefit Plan, effective May 9, 2016, and amended onJune 13, 2016, and, as amended, providing benefits for certain of Arena’s executive officers (incorporated by reference to Exhibit 10.2 toArena’s quarterly report on Form 10-Q for the quarter ended September 30, 2016, filed with the Securities and Exchange Commission onNovember 9, 2016, Commission File No. 000-31161) 10.43** Employment Agreement, dated as of August 9, 2016, by and between Arena and Vincent E. Aurentz (incorporated by reference to Exhibit10.3 to Arena’s quarterly report on Form 10-Q for the quarter ended September 30, 2016, filed with the Securities and Exchange Commissionon November 9, 2016, Commission File No. 000-31161) 10.44** Summary of housing allowance for Vincent E. Aurentz, effective February 2018 10.45+ Transaction Agreement, dated as of December 28, 2016, by and among 356 Royalty Inc., Eisai Inc. and Eisai Co., Ltd. (incorporated byreference to Exhibit 10.52 to Arena’s annual report on Form 10-K for the year ended December 31, 2016, filed with the Securities andExchange Commission on March 15, 2017, Commission File No. 000-31161) 10.46 Amendment No. 1 dated as of March 9, 2018, to Transaction Agreement, dated as of December 29, 2016, by and among 356 Royalty Inc.,Eisai Inc. and Eisai Co. Ltd. 10.47+ Supply Agreement, dated as of December 28, 2016, by and among Arena Pharmaceuticals GmbH, Eisai Inc. and Eisai Co., Ltd. (incorporatedby reference to Exhibit 10.53 to Arena’s annual report on Form 10-K for the year ended December 31, 2016, filed with the Securities andExchange Commission on March 15, 2017, Commission File No. 000-31161) 10.48 Amendment No. 1 dated as of March 9, 2018, to Supply Agreement, dated as of December 28, 2016, by and among Arena PharmaceuticalsGmbH, Eisai Inc. and Eisai Co., Ltd. 102ExhibitNo. Exhibit Description10.49 Equity Distribution Agreement, dated as of January 4, 2017, by and between Arena and Citigroup Global Markets Inc. (incorporated byreference to Exhibit 10.1 to Arena’s current report on Form 8-K filed with the Securities and Exchange Commission on January 4, 2017,Commission File No. 000-31161) 10.50** Letter Agreement, dated as of December 12, 2016, by and between Arena and Craig M. Audet, Ph.D. (incorporated by reference to Exhibit10.55 to Arena’s annual report on Form 10-K for the year ended December 31, 2016, filed with the Securities and Exchange Commission onMarch 15, 2017, Commission File No. 000-31161) 10.51** Employment Agreement, dated as of February 15, 2017, by and between Arena and Preston Klassen, M.D. (incorporated by reference toExhibit 10.1 to Arena’s quarterly report on Form 10-Q for the quarter ended March 31, 2017, filed with the Securities and ExchangeCommission on May 9, 2017, Commission File No. 000-31161) 10.52** Amendment No. 3, effective March 20, 2017, to Amended and Restated Severance Benefit Plan, effective May 9, 2016, and amended onJune 13, 2016 and August 15, 2016, and, as amended, providing benefits for certain of Arena’s executive officers (incorporated by referenceto Exhibit 10.2 to Arena’s quarterly report on Form 10-Q for the quarter ended March 31, 2017, filed with the Securities and ExchangeCommission on May 9, 2017, Commission File No. 000-31161) 10.53** Arena’s 2017 Long-Term Incentive Plan (incorporated by reference to Exhibit 99.1 to Arena’s registration statement on Form S-8 filed withthe Securities and Exchange Commission on June 22, 2017, Commission File No. 333-218905) 10.54** Form of Nonqualified Stock Option Grant Agreement for Employees and Consultants under the Arena 2017 Long-Term Incentive Plan(incorporated by reference to Exhibit 99.2 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commissionon June 22, 2017, Commission File No. 333-218905) 10.55** Form of Incentive Stock Option Grant Agreement under the Arena 2017 Long-Term Incentive Plan (incorporated by reference to Exhibit99.3 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commission on June 22, 2017, Commission FileNo. 333-218905) 10.56** Form of Restricted Stock Unit Grant Agreement (other than for non-employee directors) under the Arena 2017 Long-Term Incentive Plan(incorporated by reference to Exhibit 99.4 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commissionon June 22, 2017, Commission File No. 333-218905) 10.57** Form of Restricted Stock Unit Grant Agreement for Non-Employee Directors under the Arena 2017 Long-Term Incentive Plan (incorporatedby reference to Exhibit 99.5 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commission on June 22,2017, Commission File No. 333-218905) 10.58** Form of Nonqualified Stock Option Grant Agreement for Non-Employee Directors under the Arena 2017 Long-Term Incentive Plan(incorporated by reference to Exhibit 99.6 to Arena’s registration statement on Form S-8 filed with the Securities and Exchange Commissionon June 22, 2017, Commission File No. 333-218905) 21.1 Subsidiaries of the Registrant 23.1 Consent of Independent Registered Public Accounting Firm 31.1 Certification of principal executive officer pursuant to Rule 13a-14(A) promulgated under the Securities Exchange Act of 1934 31.2 Certification of principal financial and accounting officer pursuant to 18 U.S.C. Section 1350 and Rule 13a-14(B) promulgated under theSecurities Exchange Act of 1934 32.1 Certification of principal executive officer and principal financial and accounting officer pursuant to 18 U.S.C. Section 1350 and Rule 13a-14(B) promulgated under the Securities Exchange Act of 1934 101.INS XBRL Instance Document 101.SCH XBRL Taxonomy Extension Schema Document 101.CAL XBRL Taxonomy Extension Calculation Linkbase Document 101.DEF XBRL Taxonomy Extension Definition Linkbase Document 101.LAB XBRL Taxonomy Extension Label Linkbase Document 101.PRE XBRL Taxonomy Extension Presentation Linkbase Document 103+Confidential treatment has been requested or granted with respect to certain portions of this exhibit. Omitted portions have been filed separately withthe Securities and Exchange Commission.*Exhibits and schedules to this agreement have been omitted pursuant to the rules of the Securities and Exchange Commission. We will submit copiesof such exhibits and schedules to the Securities and Exchange Commission upon request.**Management contract or compensatory plan or arrangement.(b)EXHIBITSSee Item 15(a)(3) above.(c)FINANCIAL STATEMENT SCHEDULESSee Item 15(a)(2) above. 104SIGNATURESPursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed onits behalf by the undersigned, thereunto duly authorized. ARENA PHARMACEUTICALS, INC. Date: March 14, 2018By:/ S / AMIT D. MUNSHI Amit D. MunshiPresident and Chief Executive Officer(principal executive office) Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of theregistrant and in the capacities and on the dates indicated. Signatures Title Date By: / S / AMIT D. MUNSHI President and Chief Executive Officer and Director(principal executive officer) March 14, 2018 Amit D. Munshi By: / S / KEVIN R. LIND Executive Vice President and Chief Financial Officer(principal financial and accounting officer) March 14, 2018 Kevin R. Lind By: / S / SCOTT H. BICE Director March 14, 2018 Scott H. Bice By: / S / JAYSON DALLAS Director March 14, 2018 Jayson Dallas, M.D. By: / S / OLIVER FETZER Director March 14, 2018 Oliver Fetzer, Ph.D. By: / S / JENNIFER JARRETT Director March 14, 2018 Jennifer Jarrett By: / S / GARRY A. NEIL Director March 14, 2018 Garry A. Neil, M.D. By: / S / TINA S. NOVA Director March 14, 2018 Tina S. Nova, Ph.D. By: / S / PHILLIP M. SCHNEIDER Director March 14, 2018 Phillip M. Schneider By: / S / CHRISTINE A. WHITE Director March 14, 2018 Christine A. White, M.D. By: / S / RANDALL E. WOODS Director March 14, 2018 Randall E. Woods 105 Exhibit 10.44Arena Pharmaceuticals, Inc. Summary of Housing Allowance for Vincent E. Aurentz On January 19, 2018, the Compensation Committee of the Board of Directors of Arena Pharmaceuticals, Inc. (“Arena”)approved a housing allowance for Vincent Aurentz, Arena’s Executive Vice President and Chief Business Officer, from February 2018through February 2019 in the amount of $7,000.00 per month. The Compensation Committee also approved the reimbursement, on anafter-tax basis, of Mr. Aurentz’s airfare between North Carolina and San Diego during this same time period. Exhibit 10.46 AMENDMENT NO. 1 TOTRANSACTION AGREEMENT This Amendment No. 1 (this “Amendment”) is entered into as of March 9, 2018, and shall become effective as providedbelow, by and among 356 Royalty Inc., a company organized under the laws of Delaware having a principal place of business at 6154Nancy Ridge Drive, San Diego, CA 92121 (“Arena”), Eisai Inc., a company organized under the laws of Delaware, having a principalplace of business at 100 Tice Blvd., Woodcliff Lake, New Jersey 07677 (“ESI”), and Eisai Co., Ltd., a company organized under thelaws of Japan, having a principal place of business at 4-6-10 Koishikawa Bunkyo-ku, Tokyo, Japan, 112-88 (“ECL”). “Eisai” shallmean (a) ESI, with respect to all rights and obligations of Eisai under the Agreement (as defined below) with respect to the ESI Territory(as defined in the Agreement) and (b) ECL, with respect to all rights and obligations of Eisai under the Agreement with respect to theECL Territory (as defined in the Agreement). Each of Arena and Eisai may be referred to in this Amendment individually as a “Party”and collectively as the “Parties”. Capitalized terms used in this Amendment that are not otherwise defined shall have the meaningsascribed to such terms in the Agreement. Whereas A.Arena and Eisai previously entered into the Transaction Agreement dated December 28, 2016 (as may be amended inaccordance with its terms, the “Agreement”); B.Arena’s affiliate Arena Pharmaceuticals GmbH (“Arena GmbH”) and Eisai previously entered into the Supply Agreementdated December 28, 2016 (as may be amended in accordance with its terms, the “Supply Agreement”); C.Arena GmbH is pursuing a sale of all or substantially all of its business or assets to which the Supply Agreement relates toSiegfried Pharma AG or an affiliate thereof (“Siegfried”), which would include assignment to and assumption by Siegfriedof the Supply Agreement (the “Siegfried Transaction”). D.The Parties intend to amend the Transaction Agreement in certain respects as set forth in this Amendment, with suchamendments taking effect automatically upon (i) the execution by Siegfried and Arena GmbH of the acquisition agreementin respect of the Siegfried Transaction with respect to paragraphs 1 and 3 below and (ii) the closing of the SiegfriedTransaction with respect to paragraphs 2 and 4 below. Now, Therefore, in consideration of the foregoing premises and the mutual covenants herein contained, and for other goodand valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Arena and Eisai, intending to be legallybound, hereby agree as follows: 1.Section 1.15 of the Transaction Agreement shall be deleted and replaced in its entirety by the following: “1.15“Arena Manufacturing Defect Losses” means Product Liability Losses attributable to a Product LiabilityClaim to the extent alleging defective manufacturing of a Product where such Product was manufactured by Arena GmbH orany successor or assign of Arena GmbH under the Supply Agreement, but excluding Product manufactured by anysuccessor or assign of Arena GmbH under the Supply Agreement after the closing 1 of the transaction resulting in such Person becoming a successor or assign (a “Facility Acquisition”).” 2.Section 4.3(a) of the Transaction Agreement shall be deleted and replaced in its entirety by the following: “(a)Co-Promotion Partners, Sublicensees and Distributors. (i) Eisai shall have the right to appoint one or moreThird Parties as Co-Promotion Partners to co-promote or co-market Products with Eisai in the Territory, to grant one or moreSublicenses in the Territory, or to appoint one or more Third Parties as Distributors to market, promote, sell and distribute theProducts on Eisai’s behalf in the Territory; and (ii) each such Co-Promotion Partner shall have the right to appoint additionalCo-Promotion Partners, each such Distributor shall have the right to appoint additional Distributors, and each suchSublicensee or Affiliate shall have the right to grant further Sublicenses, in each case (i) and (ii), as and to the extent set forthbelow in this Section 4.3(a). Eisai shall have the right to appoint a Third Party as a Co-Promotion Partner in the Territory, togrant a Sublicense in any country in the Territory, and to appoint one or more Third Parties as Distributors in any country inthe Territory (which may include development work on a Product in such country), without Arena’s prior written consentbut on at least three Business Days prior written notice to Arena. In addition, any Co-Promotion Partner shall have the rightto appoint a Third Party as a Co-Promotion Partner in the Territory, any Distributor shall have the right to appoint a ThirdParty as a Distributor in the Territory, and any Sublicensee may grant further Sublicenses in the Territory, in each case on atleast three Business Days prior written notice to Arena. Any such Third Party described in this Section 4.3(a) shall be a“subcontractor” of Eisai for which Eisai shall be responsible as provided in Section 15.5(b).” 3.Notwithstanding anything to the contrary in the Agreement (as amended by this Amendment), the Parties hereby agree thatEisai does not owe any royalties for Products sold by Ildong Pharmaceutical Co., Ltd. or its Affiliates for which the purchaseprice for such Products was paid or due to Arena GmbH or its Affiliates by Ildong Pharmaceutical Co., Ltd. or its Affiliatespursuant to the Third Party Distributor Agreement with Ildong Pharmaceutical Co., Ltd. For the avoidance of doubt, nothingin this paragraph 3 modifies Eisai's obligations in the Agreement to pay royalties for Products sold by Ildong PharmaceuticalCo., Ltd. for which the purchase price for such Products was paid or due to Eisai or its Affiliates by Ildong PharmaceuticalCo., Ltd. pursuant to the Third Party Distributor Agreement with Ildong Pharmaceutical Co., Ltd. 4.The Parties hereby agree that the Siegfried Transaction shall constitute a Facility Acquisition. 5.This Amendment (other than paragraphs 1 and 3) shall become effective, and the Agreement shall be amended as set forthherein, upon the closing of the Siegfried Transaction if, and only if, the closing of the Siegfried Transaction occurs on orprior to June 30, 2018. Arena shall keep Eisai reasonably apprised of the status of the Siegfried Transaction and provideEisai written notice of the signing and the closing of the Siegfried Transaction, including the date of such execution bySiegfried and Arena GmbH of the acquisition agreement in respect of the Siegfried Transaction and the closing of theSiegfried Transaction. If Arena provides written notice to Eisai that the Siegfried Transaction has been terminated and willnot close, this Amendment (other than paragraphs 1 and 3) shall be null and void effective as of the date of such writtennotice. Paragraphs 1 and 3 of this Amendment shall become effective, and the Agreement shall be amended2  as set forth herein, upon the execution by Siegfried and Arena GmbH of the acquisition agreement in respect of the SiegfriedTransaction regardless of whether or not the Siegfried Transaction ever closes. 6.Unless otherwise specifically stated herein, all of the terms and conditions of the Agreement shall remain in full force andeffect in accordance with its terms. At the time this Amendment becomes effective as provided in paragraph 5, thisAmendment shall form a part of the Agreement for all purposes, each Party shall be bound hereby, and any reference to theAgreement shall be deemed a reference to the Agreement as amended hereby. 7.This Amendment may be executed in any number of counterparts each of which shall be deemed an original, and all ofwhich together shall constitute one and the same instrument. This Amendment may be executed by facsimile or otherelectronic signatures and such signatures shall be deemed to bind each Party as if they were original signatures. ThisAmendment and all questions regarding its existence, validity, interpretation, breach or performance, shall be governed by,and construed and enforced in accordance with, the laws of the State of New York, United States, without reference to itsconflicts of law principles with the exception of sections 5-1401 and 5-1402 of New York General Obligations Law. [Signature Pages Follow] 3 In Witness Whereof, the Parties have caused this Amendment to be executed by their duly authorized agents. 356 Royalty Inc. By: / s / Amit D. Munshi Name: Amit D. Munshi Title: President and Chief Executive Officer 6154 Nancy Ridge Drive San Diego, CA 92121 United States of America [Signature Page to Transaction Agreement Amendment] Eisai Inc. By:__/ s/ Shaji Procida ____________________Name: Shaji ProcidaTitle: President and Chief Operating Officer100 Tice Blvd.Woodcliff Lake, New Jersey 07677United States of America Eisai Co., Ltd. By:___/ s / Alexander Scott_________________Name: Alexander ScottTitle: Vice President, Chief Strategy Officer, Neurology Business Group4-6-10 Koishikawa Bunkyo-kuTokyo, Japan, 112-88 [Signature Page to Transaction Agreement Amendment]  Exhibit 10.48 AMENDMENT NO. 1 TOSUPPLY AGREEMENT This Amendment No. 1 (this “Amendment”) is entered into March 9, 2018, and shall become effective as provided below,by and among Arena Pharmaceuticals GmbH, a company organized under the laws of Switzerland, having a principal place of businessat Untere Brühlstrasse 4, 4800, Zofingen, Switzerland (“Arena”), Eisai Inc., a company organized under the laws of Delaware, having aprincipal place of business at 100 Tice Blvd., Woodcliff Lake, New Jersey 07677 (“ESI”), and Eisai Co., Ltd., a company organizedunder the laws of Japan, having a principal place of business at 4-6-10 Koishikawa Bunkyo-ku, Tokyo, Japan, 112-88 (“ECL”).“Eisai” shall mean (a) ESI, with respect to all rights and obligations of Eisai under the Agreement (as defined below) with respect toNorth America, South America, Central America and the Caribbean and (b) ECL, with respect to all rights and obligations of Eisaiunder the Agreement with respect to the world other than North America, South America, Central America and the Caribbean. Each ofArena and Eisai may be referred to in this Amendment individually as a “Party” and collectively as the “Parties”. Capitalized termsused in this Amendment that are not otherwise defined shall have the meanings ascribed to such terms in the Agreement. Whereas A.Arena and Eisai previously entered into the Supply Agreement dated December 28, 2016 (as may be amended in accordancewith its terms, the “Agreement”); B.Arena is pursuing a sale of all or substantially all of its business or assets to which the Agreement relates to Siegfried PharmaAG or an affiliate thereof (“Siegfried”) (the “Siegfried Transaction”). C.The Parties intend to amend the Agreement as set forth in this Amendment, with such amendments taking effect automaticallyupon the closing of the Siegfried Transaction. Now, Therefore, in consideration of the foregoing premises and the mutual covenants herein contained, and for other goodand valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Arena and Eisai, intending to be legallybound, hereby agree as follows: 1.The reference to “Section 16.3” in the second to last sentence of Section 2.1 of the Agreement shall be deleted and replacedwith “Section 17.3”. 2.Section 3.8 of the Agreement shall be deleted and replaced in its entirety by the following: “3.8.Sublicense Rights; Co-Promotion Partners and Distributors. (i) Eisai shall have the right to appoint one ormore Third Parties as Co-Promotion Partners to co-promote or co-market Products with Eisai in the Territory, to grant one ormore Sublicenses in the Territory, or to appoint one or more Third Parties as Distributors to market, promote, sell anddistribute the Products on Eisai’s behalf in the Territory; and (ii) each such Co-Promotion Partner shall have the right toappoint additional Co-Promotion Partners, each such Distributor shall have the right to appoint additional Distributors, andeach such Sublicensee or Affiliate shall have the right to grant further Sublicenses, in each case (i) and (ii), as and to theextent set forth in this Section 3.8. Eisai shall have the right to appoint a Third Party as a Co-Promotion Partner in theTerritory, to grant a Sublicense in any country in the Territory, and to appoint one or more Third Parties as Distributors in anycountry in the Territory (which may include development work on a Product in such country), without Arena’s prior writtenconsent but on at least three Business Days prior written notice to Arena. In addition, any Co-Promotion Partner shall havethe right to appoint a Third Party as a Co-Promotion Partner in the 1  Territory, any Distributor shall have the right to appoint a Third Party as a Distributor in the Territory, and any Sublicenseemay grant further Sublicenses in the Territory, in each case on at least three Business Days prior written notice to Arena. Anysuch Third Party described in this Section 3.8 shall be a “subcontractor” of Eisai for which Eisai shall be responsible asprovided in Section 2.4.” 3.Section 15.1 of the Agreement shall be deleted and replaced in its entirety by the following: “15.1.Term. The term of this Agreement (the “Term”) shall commence on the Effective Date and continue until fiveyears after the Effective Date (the “Initial Term”), unless terminated earlier under Section 15.2 or extended by mutual writtenagreement of the Parties.” 4.A new Section 15.2(d) shall be added to the Agreement as follows: “(d)Termination in Case of Low Product Demand. Each Party shall have the right, but not the obligation, toterminate this Agreement if the total amount of Products purchased by Eisai in any twelve-month period or forecasted byEisai for any twelve-month period falls below 75,000,000 tablets of Product by giving six months’ advance written notice oftermination to the other Party; provided, however, that no such termination notice may be given prior to June 28, 2018, andno such termination may be effective prior to December 28, 2018.” 5.This Amendment shall become effective, and the Agreement shall be amended as set forth herein, upon the closing of theSiegfried Transaction if, and only if, the closing of the Siegfried Transaction occurs on or prior to June 30, 2018. Only uponthe satisfaction of this condition precedent shall this Amendment take effect. Arena shall keep Eisai reasonably apprised ofthe status of the Siegfried Transaction and provide Eisai written notice of the closing of the Siegfried Transaction, includingthe date of such closing, which shall be the effective date of this Amendment. If Arena provides written notice to Eisai thatthe Siegfried Transaction has been terminated and will not close, this Amendment shall be null and void effective as of thedate of such written notice. 6.Unless otherwise specifically stated herein, all of the terms and conditions of the Agreement shall remain in full force andeffect. At the time this Amendment becomes effective as provided in paragraph 5, this Amendment shall form a part of theAgreement for all purposes, each Party shall be bound hereby, and any reference to the Agreement shall be deemed areference to the Agreement as amended hereby. 7.This Amendment may be executed in any number of counterparts each of which shall be deemed an original, and all ofwhich together shall constitute one and the same instrument. This Amendment may be executed by facsimile or otherelectronic signatures and such signatures shall be deemed to bind each Party as if they were original signatures. ThisAmendment and all questions regarding its existence, validity, interpretation, breach or performance shall be governed by,and construed and enforced in accordance with, the laws of the State of New York, United States, without reference to itsconflicts of law principles with the exception of sections 5-1401 and 5-1402 of New York General Obligations Law. [Signature Pages Follow] 2  In Witness Whereof, the Parties have caused this Amendment to be executed by their duly authorized agents. Arena Pharmaceuticals GmbH By:__/ s / Amit D. Munshi Name: Amit D. Munshi Title: Managing Director By:__ / s / Kevin R. Lind Name: Kevin R. Lind Title: Managing Director [Signature Page to Supply Agreement Amendment] Eisai Inc. By:____/ s / Shaji Procida _________Name: Shaji ProcidaTitle: President and Chief Operating Officer100 Tice Blvd.Woodcliff Lake, New Jersey 07677United States of America Eisai Co., Ltd. By:______ / s / Alexander Scott______Name: Alexander ScottTitle: Vice President, Chief Strategy Officer, Neurology Business Group4-6-10 Koishikawa Bunkyo-kuTokyo, Japan, 112-88 [Signature Page to Supply Agreement Amendment]Exhibit 21.1Subsidiaries of Arena Pharmaceuticals, Inc.As of December 31, 2017 125 Royalty Inc., a Delaware corporation356 Royalty Inc., a Delaware corporationArena Pharmaceuticals Development GmbH, a limited liability company organized under the laws of Switzerland and having its domicile in ZugArena Pharmaceuticals GmbH, a limited liability company organized under the laws of Switzerland and having its domicile in ZofingenAPI Development LTD, a company incorporated in the Cayman Islands with limited liability Exhibit 23.1 Consent of Independent Registered Public Accounting Firm The Board of DirectorsArena Pharmaceuticals, Inc.:We consent to the incorporation by reference in the registration statements (Nos. 333-45330, 333‑45332, 333-62894, 333-86350, 333-135398, 333-160329,333-182238, 333-189213, 333-204999, 333-212012, 333-214529, 333-217805, and 333-218905) on Form S-8 and (Nos. 333-112542, 333-136023, 333-160983, 333-167498, 333-212011, and 333-219237) on Form S-3 of Arena Pharmaceuticals, Inc. of our reports dated March 14, 2018, with respect to theconsolidated balance sheets of Arena Pharmaceuticals, Inc. and subsidiaries as of December 31, 2017 and 2016, and the related consolidated statements ofoperations and comprehensive loss, equity, and cash flows for each of the years in the three-year period ended December 31, 2017, and the related notes(collectively, the “consolidated financial statements”), and the effectiveness of internal control over financial reporting as of December 31, 2017, whichreports appear in the December 31, 2017 annual report on Form 10‑K of Arena Pharmaceuticals, Inc./s/ KPMG LLPSan Diego, CaliforniaMarch 14, 2018 Exhibit 31.1CERTIFICATIONI, Amit D. Munshi, certify that:1. I have reviewed this annual report on Form 10-K of Arena Pharmaceuticals, Inc.;2. Based on my knowledge, this annual report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make thestatements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this annualreport;3. Based on my knowledge, the financial statements, and other financial information included in this annual report, fairly present in all material respects thefinancial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this annual report;4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in ExchangeAct Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrantand have: a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, toensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within thoseentities, particularly during the period in which this annual report is being prepared; b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under oursupervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements forexternal purposes in accordance with generally accepted accounting principles; c)Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this annual report our conclusions about theeffectiveness of the disclosure controls and procedures, as of the end of the period covered by this annual report based on such evaluation; and d)Disclosed in this annual report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s mostrecent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting; and5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions): a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonablylikely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal controlover financial reporting. Date: March 14, 2018 /s/ Amit D. Munshi Amit D. Munshi, President and Chief Executive Officer (principal executive officer) Exhibit 31.2CERTIFICATIONI, Kevin R. Lind, certify that:1. I have reviewed this annual report on Form 10-K of Arena Pharmaceuticals, Inc.;2. Based on my knowledge, this annual report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make thestatements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this annualreport;3. Based on my knowledge, the financial statements, and other financial information included in this annual report, fairly present in all material respects thefinancial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this annual report;4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in ExchangeAct Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrantand have: a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, toensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within thoseentities, particularly during the period in which this annual report is being prepared; b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under oursupervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements forexternal purposes in accordance with generally accepted accounting principles; c)Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this annual report our conclusions about theeffectiveness of the disclosure controls and procedures, as of the end of the period covered by this annual report based on such evaluation; and d)Disclosed in this annual report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s mostrecent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting; and5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions): a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonablylikely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal controlover financial reporting. Date: March 14, 2018 /s/ Kevin R. Lind Kevin R. Lind, Executive Vice President and Chief Financial Officer (principal financial and accounting officer) Exhibit 32.1CERTIFICATION PURSUANT TO18 U.S.C. SECTION 1350,AS ADOPTED PURSUANT TOSECTION 906 OF THE SARBANES-OXLEY ACT OF 2002In connection with the Annual Report on Form 10-K of Arena Pharmaceuticals, Inc. (“the Company”) for the period ended December 31, 2017, as filedwith the Securities and Exchange Commission on the date hereof (the “Report”), Amit D. Munshi, as President and Chief Executive Officer (principal andfinancial officer) of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of2002, that to the best of his knowledge:1.the Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and2.the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. /s/ Amit D. Munshi Amit D. Munshi President and Chief Executive Officer (principal executive officer) Date: March 14, 2018 In connection with the Annual Report on Form 10-K of Arena Pharmaceuticals, Inc. (“the Company”) for the period ended December 31, 2017, as filedwith the Securities and Exchange Commission on the date hereof (the “Report”), Kevin R. Lind, as Executive Vice President and Chief Financial Officer(principal financial and accounting officer) of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of theSarbanes-Oxley Act of 2002, that to the best of his knowledge:1.the Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and2.the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. /s/ Kevin R. Lind Kevin R. Lind Executive Vice President and Chief Financial Officer (principal financial and accounting officer) Date: March 14, 2018 

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