ImmunoGen
Annual Report 2022

R E P O RT 2 0 2 2
A N N UA L
Nasdaq: IMGN

MESSAGE TO OUR SHAREHOLDERS
2
022 was a landmark year for ImmunoGen as 
we transitioned to a commercial oncology 
company following the approval and launch of 
ELAHERE™ (mirvetuximab soravtansine-gynx). As 
the first and only antibody-drug conjugate (ADC) 
approved in ovarian cancer, and the first new drug 
indicated specifically for platinum-resistant disease 
since 2014, the addition of ELAHERE as a biomarker-
defined treatment option was a major advance for 
women living with this devastating condition. 
Beyond our first product launch, we successfully 
executed towards our strategic priorities across the 
business. As we look to establish ELAHERE as the 
standard of care for folate receptor alpha (FRα)-
positive ovarian cancer, we completed enrollment 
in our confirmatory MIRASOL trial to support full 
approval of ELAHERE and advanced our broader 
development program, which targets a large 
portion of the recurrent disease market. In addition, 
we progressed the rest of our pipeline with 
encouraging data for our second pivotal program, 
pivekimab sunirine (PVEK) in blastic plasmacytoid 
dendritic cell neoplasm (BPDCN) and acute myeloid 
leukemia (AML), and clinical milestones for both of 
our earlier stage assets, IMGC936 and IMGN151. 
Positioning us for the year ahead, we strengthened 
our leadership team with the recent appointments 
of Dr. Michael Vasconcelles as Head of Research, 
Development, and Medical Affairs, Daniel Char as 
Chief Legal Officer, and Isabel Kalofonos as Chief 
Commercial Officer. With the momentum generated 
over the last 12 months, we look forward to a 
productive year ahead as we grow our business, 
drive value for shareholders, and deliver more good 
days for patients.
APPROVAL AND LAUNCH OF ELAHERE
On November 14, 2022, we received accelerated 
approval of ELAHERE from the US Food and Drug 
Administration (FDA) for the treatment of FRα-
positive platinum-resistant ovarian cancer (PROC).
STRONG MARKET ENTRY  
In 2022, we built best-in-class commercial and 
medical affairs organizations to deliver ELAHERE 
to eligible patients upon approval and, on 
December 1, the first patient was treated in the 
community setting. Since then, we have seen strong 
performance across each of the key imperatives we 
set for the business. 
• Uptake has been broad and deep. We generated 
$2.6 million in net ELAHERE sales in the fourth 
quarter of 2022, nearly all of which came in 
December. Through the end of 2022, ~70% of 
our orders came from nonacademic settings, 
and ~75% of our orders were from accounts with 
no prior ELAHERE experience – an important 
indicator of the level of adoption. In the new year, 
revenue growth has accelerated as we are seeing 
a significant percentage of accounts with repeat 
orders complementing new patient starts.
• Strong demand continues for the VENTANA 
FOLR1 RxDx Assay, the companion diagnostic 
to identify patients eligible for treatment with 
ELAHERE. We estimate that ~1,500 tests were 
performed through the end of 2022 and volume 
has since substantially increased. We believe a 
significant percentage of these tests are being 
ordered for newly diagnosed patients, and while 
these patients are not eligible for treatment with 
ELAHERE today, this will enable oncologists to 
rapidly incorporate ELAHERE into their future 
treatment decisions.
• A growing number of payers are including 
ELAHERE in coverage policies aligned to its label. 
At the start of the year, 18% of Medicare and 25% 
of commercial lives were covered; driven by the 
efforts of our access team, coverage has rapidly 
increased during the first and second quarters 
of 2023. In addition, ELAHERE is included in the 
National Comprehensive Cancer Network (NCCN) 
Clinical Practice Guidelines as monotherapy and 
in combination with bevacizumab.
• Finally, our highly active customer-facing teams 
connected with 70% of their priority targets 
through the end of December, and these numbers 
are continuing to rise. Our teams continue 
to leverage field insights to ensure positive 
physician and patient experiences with ELAHERE.
We’ve made a strong start in the early months of 
launch and are excited to carry this momentum 
through the rest of the year.
EXPANDING ELAHERE’S LABEL 
ELAHERE’s broad label, for PROC patients 
regardless of prior treatment with bevacizumab, 
reflects the strength of the SORAYA data and 
reinforces our belief in ELAHERE’s potential to 
become the new standard of care for patients with 
FRα-positive disease. Building upon this foundation, 
our development program is designed to move 
ELAHERE into platinum-sensitive ovarian cancer 
(PSOC) and position this innovative therapy as the 
combination agent of choice. 
MIRASOL is our Phase 3 confirmatory trial 
evaluating ELAHERE compared to single-agent 
chemotherapy in patients with FRα-high PROC. 
MIRASOL is designed to support full approval in this 
population in the US and EU. Patient enrollment was 
completed in mid-2022 and we expect to report 
top-line data in early May 2023.
PICCOLO is our single-arm Phase 2 trial that 
expands the evaluation of ELAHERE monotherapy 
into FRα-high PSOC. Patient enrollment was 
completed in January 2023 and we expect to report 
data on the primary endpoint of objective response 
rate (ORR) before the end of this year.
GLORIOSA is our randomized Phase 3 trial of 
ELAHERE with bevacizumab maintenance in FRα-
high PSOC. This trial is open in the US, and we are 
actively working to open sites around the globe.
TRIAL 0420 is our single-arm Phase 2 trial of 
ELAHERE plus carboplatin followed by ELAHERE 
continuation in PSOC patients with FRα-low, 
medium, and high expression, designed to inform 
a registrational path in recurrent PSOC. This trial is 
open in the US, and we are actively working to open 
sites in Europe.
PROGRESSING PVEK, OUR SECOND  
PIVOTAL PROGRAM
We advanced PVEK, our CD123-targeting ADC, 
in BPDCN and AML. PVEK has demonstrated 
encouraging safety and efficacy as a monotherapy 
in BPDCN and in combination regimens for AML.
CADENZA is our registrational trial in frontline 
BPDCN. We shared initial data demonstrating 
encouraging activity and favorable tolerability in 
both de novo patients and those with a prior or 
concomitant hematologic malignancy (PCHM). 
Following alignment with FDA in 2022 on an 
efficacy evaluable population of de novo patients, 
we expect to complete enrollment in this pivotal 
cohort in 2023 and report top-line data next year. 
Additionally, we continue to enroll PCHM patients to 
further evaluate PVEK’s benefit in this population.
STUDY 802 is our Phase 1b/2 trial of PVEK in 
combination with venetoclax and azacitidine in 
AML, which we refer to as the “triplet.” We shared 
encouraging data evaluating the triplet in relapsed/
refractory (R/R) and frontline AML at the 2022 ASH 
Annual Meeting and are moving forward with two 
expansion cohorts in frontline AML to evaluate 
the optimal duration of venetoclax dosing in the 
triplet. Tolerability and efficacy outcomes from 
these cohorts will guide development of the triplet 
in pivotal trials in frontline AML. We also expect 
to initiate an additional cohort, as part of our 
collaboration with Gilead, of PVEK in combination 
with magrolimab in R/R AML during the second half 
of this year.
ADVANCING OUR EARLIER-STAGE PORTFOLIO
We completed dose escalation in our Phase 1 
trial of IMGC936 in multiple solid tumor types, 
identified the recommended Phase 2 dose, and 
initiated expansion cohorts in non-small cell lung 
cancer (NSCLC) and triple-negative breast cancer 
(TNBC). We expect to share data from the Phase 1 
dose escalation and our initial experience from the 
expansion cohorts in the second quarter of this year.
With the enrollment of the first patient in our Phase 
1 trial of IMGN151, our next-generation anti-FRα ADC, 
we now have four assets in the clinic as we look to 
provide an option for patients with tumors across 
the range of FRα expression and build upon the 
success of ELAHERE.
PARTNERING TO MAXIMIZE OUR PIPELINE  
AND TECHNOLOGY 
Partnering is a core element of our strategy, 
allowing us to lever complementary technologies 
and expertise to expand our pipeline, while 
providing an additional source of revenue for the 
Company. In addition to our existing partnership 
with Huadong Medicine to bring ELAHERE to 
patients in Greater China and our co-development 
agreement with MacroGenics for IMGC936, over 
the past 12 months, we established a research 
collaboration with Oxford BioTherapeutics, multi-
target license agreements with Lilly and Vertex, and 
a clinical collaboration with Gilead. 
OUR NEXT CHAPTER AS A FULLY-INTEGRATED 
ONCOLOGY COMPANY
With strong momentum across all areas of the 
business, a clear strategy for commercial execution, 
key regulatory and data milestones on the horizon, 
and ongoing investment in our pipeline, we look 
forward to another exciting and productive year  
in 2023. 
We would not be in this position without the 
remarkable efforts of our team, whose steadfast 
commitment and drive to deliver more good 
days to patients inspire me each and every day. 
I would also like to recognize our board and 
shareholders for their continued support. Finally, I 
thank the patients, caregivers, physicians, nurses, 
and scientific and clinical partners, who enable us 
to unlock the potential of our science to deliver 
improved outcomes for people living with cancer.
Sincerely, 
Mark J. Enyedy

 
UNITED STATES 
SECURITIES AND EXCHANGE COMMISSION 
Washington, D.C. 20549 
Form 10-K 
 
 
☒ 
ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES 
EXCHANGE ACT OF 1934 
 
For the year ended December 31, 2022 
 
 
 
OR 
☐ 
TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES 
EXCHANGE ACT OF 1934 
 
For the period from        to      
Commission file number 0-17999 
ImmunoGen, Inc. 
Massachusetts 
(State or other jurisdiction 
of incorporation or organization) 
04-2726691 
(I.R.S. Employer 
Identification No.) 
830 Winter Street, Waltham, MA 02451 
(Address of principal executive offices, including zip code) 
(781) 895-0600 
(Registrant’s telephone number, including area code) 
 
Securities registered pursuant to Section 12(b) of the Act: 
Title of Each Class 
 
Trading Symbol(s) 
     
Name of Each Exchange on Which Registered 
Common Stock, $0.01 par value 
 
IMGN 
 
Nasdaq Global Select Market 
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 the preceding 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 past 90 days. ☒ Yes   ☐ No 
Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to 
Rule 405 of Regulation S-T (§229.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to 
submit such files). ☒ Yes   ☐ No 
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 growth company. See 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 ☐ 
 
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 revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐ 
Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its 
internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm 
that prepared or issued its audit report.   ☒   
If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant 
included in the filing reflect the correction of an error to previously issued financial statements. ☐ 
Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive‐based 
compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D‐1(b). ☐ 
Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). ☐ Yes   ☒ No 
Aggregate market value, based upon the closing sale price of the shares as reported by the Nasdaq Global Select Market, of common stock 
held by non-affiliates at June 30, 2022: $989,665,866 (excludes shares held by executive officers and directors). Exclusion of shares held by any 
person should not be construed to indicate that such person possesses the power, direct or indirect, to direct or cause the direction of management or 
policies of the registrant, or that such person is controlled by or under common control with the registrant. Common stock outstanding at February 
21, 2023: 226,046,108 shares. 
DOCUMENTS INCORPORATED BY REFERENCE 
Portions of the definitive Proxy Statement on Schedule 14A to be delivered to shareholders in connection with the Annual Meeting of 
Shareholders to be held on June 14, 2023 are incorporated by reference into Part III of this report. 
 

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ImmunoGen, Inc. 
Form 10-K 
TABLE OF CONTENTS 
Item 
 
Page 
Number 
 
Part I 
1. 
Business . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
4
1A. 
Risk Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
22
1B. 
Unresolved Staff Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
43
2. 
Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
44
3. 
Legal Proceedings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
44
4. 
Mine Safety Disclosures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
44
 
Part II 
5. 
Market for Registrant’s Common Equity, Related Stockholder Matters, and Issuer Purchases of Equity 
Securities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
44
6. 
Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
45
7. 
Management’s Discussion and Analysis of Financial Condition and Results of Operations . . . . . . . . . . . .  
45
7A. 
Quantitative and Qualitative Disclosures About Market Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
53
8. 
Financial Statements and Supplementary Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
54
9. 
Changes in and Disagreements with Accountants on Accounting and Financial Disclosure . . . . . . . . . . . .  
86
9A. 
Controls and Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
86
9B. 
Other Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
88
9C. 
Disclosure Regarding Foreign Jurisdictions that Prevent Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
88
 
Part III 
10. 
Directors, Executive Officers, and Corporate Governance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
88
11. 
Executive Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
88
12. 
Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters . .  
88
13. 
Certain Relationships and Related Transactions, and Director Independence . . . . . . . . . . . . . . . . . . . . . . .  
88
14. 
Principal Accounting Fees and Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
88
 
Part IV 
15. 
Exhibits, Financial Statement Schedules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
88
16. 
Form 10-K Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
91
 
Signatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
92
 
 
 
 

3 
Forward-looking statements 
The Annual Report on Form 10-K includes forward-looking statements. Forward-looking statements are neither 
historical facts nor assurances of future performance. Instead, these forward-looking statements relate to analyses and 
other information that are based on beliefs, expectations, assumptions, and forecasts of future results and estimates of 
amounts that are not yet determinable. These statements also relate to our prospects, future developments, product 
candidates, and business strategies. 
These forward-looking statements are identified by their use of terms and phrases, such as “anticipate,” 
“believe,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “predict,” “project,” “will,” and other similar terms 
and phrases, including references to assumptions.  
The forward-looking statements in this Annual Report on Form 10-K include, but are not limited to, statements 
about: 
• 
the initiation, cost, timing, progress and results of our current and future research and development activities, 
preclinical studies, and clinical trials;  
• 
the timing of, and our ability to obtain, regulatory approvals for our current and future product candidates, 
including full marketing approval of ELAHERE™ in the U.S., as well as for additional indications and 
additional geographies;  
• 
our ability to advance any product candidates into, and successfully complete, clinical trials; 
• 
the timing of our release of future data; 
• 
the potential benefits of our product candidates;  
• 
the potential benefits of our licensing arrangements; 
• 
our expected sources of future revenues, including from product revenue and licensing arrangements; 
• 
our estimates regarding expenses, capital requirements, the sufficiency of our current and expected cash 
resources, and our need for additional financing; 
• 
the effect of the novel coronavirus (COVID-19) pandemic on the economy generally and on our business and 
operations specifically, including our research and development efforts, our clinical trials, and our employees, 
and the potential disruptions in supply chains and to our third-party manufacturers, including the availability of 
materials and equipment; and 
• 
our commercialization, marketing, and manufacturing capabilities and strategy. 
We may not actually achieve the plans, intentions, or expectations disclosed in our forward-looking statements, 
and investors should not place undue reliance on our forward-looking statements. Additionally, these forward-looking 
statements involve known and unknown risks, uncertainties, and other factors that may cause actual results to be 
materially different from those contemplated by our forward-looking statements. These known and unknown risks, 
uncertainties, and other factors are described in detail in the “Risk Factors” section and in other sections of this report.  
The forward-looking statements contained herein represent our views as of the date of this Annual Report on 
Form 10-K. Except as required by law, we disclaim any intention or obligation to update or revise any forward-looking 
statements, whether as a result of new information, future events, or otherwise.  
Risk Factors Summary 
Our business is subject to varying degrees of risk and uncertainty. Investors should consider the risks and 
uncertainties summarized below, as well as the risks and uncertainties discussed further in Part I, Item 1A, “Risk 
Factors” of this Annual Report on Form 10-K. 
Our business is subject to the following principal risks and uncertainties: 
• 
We have a history of operating losses, expect to incur significant additional operating losses, and may never be 
profitable. 
• 
There is substantial doubt about our ability to continue as a going concern. 
 
 

4 
• 
If we are unable to obtain additional funding when needed, we may have to delay or scale back some of our 
programs or grant rights to third parties to develop and market ELAHERE or our product candidates. 
• 
Our prospects are highly dependent on the success of our only approved product, ELAHERE, which received 
FDA approval under an accelerated approval pathway. If we are unable to maintain approval for, or 
successfully commercialize, ELAHERE, our business, financial condition, results of operations, as well as our 
prospects, could be adversely affected. 
• 
If our Antibody-Drug Conjugate technology does not produce safe, effective, and commercially viable products 
or if such products fail to obtain or maintain FDA approval, our business will be severely harmed. 
• 
Clinical trials for ELAHERE, our product candidates, and those of our collaborators will be lengthy and 
expensive, and their outcome is uncertain. 
• 
Interim, top-line, or preliminary data from our clinical trials that we announce may change as more patient data 
become available and are subject to audit and verification procedures that could result in material changes in the 
final data. 
• 
We may be unable to compete successfully. 
• 
If we are unable to protect our intellectual property rights adequately, the value of our technology and our 
product candidates could be diminished. 
• 
We rely on a third-party to develop, manufacture, and commercialize the companion diagnostic for ELAHERE, 
and any delay or interruption in supply could negatively impact our commercial activities. 
• 
Side effects, serious adverse events, or other undesirable properties associated with ELAHERE or our product 
candidates could delay or halt clinical trials, affect our ability to obtain or maintain regulatory approval, limit 
the commercial profile reflected in product labeling, or negatively affect market acceptance and commercial 
sales. 
• 
We have received orphan drug designation for ELAHERE and other product candidates for specified 
indications; we may seek additional orphan drug designation for additional indications and for our other drug 
candidates. However, we may be unsuccessful in obtaining or may be unable to maintain the benefits associated 
with orphan drug designation, including the potential for market exclusivity. 
• 
As our business grows, we will become subject to additional healthcare regulation and enforcement by various 
government entities, and our failure to strictly adhere to these regulatory regimes could have a detrimental 
impact on our business. 
• 
We depend on our key personnel, and we must continue to attract and retain key employees and consultants. 
• 
Our stock price may be volatile and fluctuate significantly and results announced by us and our collaborators or 
competitors could cause our stock price to decline. 
Note Regarding Third-Party Trademarks 
KADCYLA® is a registered trademark of Genentech, Inc. PROBODY™ is a trademark of CytomX. 
ELZONRIS® is a registered trademark of Menarini Group. Any other trademarks referred to in this Annual Report on 
Form 10-K are the property of their respective owners. 
PART I 
Item 1.    Business 
We are a commercial-stage biotechnology company focused on developing and commercializing the next 
generation of antibody-drug conjugates (ADCs) to improve outcomes for cancer patients. By generating targeted 
therapies with enhanced anti-tumor activity and favorable tolerability profiles, we aim to disrupt the progression of 
cancer and offer patients more good days. We call this our commitment to “target a better now.” 
An ADC with our proprietary technology comprises an antibody that binds to a target found on tumor cells and 
is conjugated to one of our potent anti-cancer agents as a “payload” to kill the tumor cell once the ADC has bound to its 
target. ADCs are an expanding class of anticancer therapeutics, with twelve approved products and the number of agents 
in development growing significantly in recent years. 
 

5 
We have established a leadership position in ADCs with a portfolio of differentiated product candidates to 
address both solid tumors and hematologic malignancies. We have set four strategic priorities for the business: 
• 
execute the commercial launch for ELAHERE™ (mirvetuximab soravtansine-gynx) (ELAHERE);  
• 
expand the ELAHERE label by moving into platinum-sensitive ovarian cancer; 
• 
advance our clinical pipeline of novel ADCs for hematologic and solid tumors; and 
• 
strengthen and expand our pipeline through both internal discovery and external partnerships. 
We believe that sound execution of these prioritized activities will create substantial short-and long-term value 
for shareholders, employees, patients, and other stakeholders in the Company.  
ELAHERE (Mirvetuximab Soravtansine) 
Approval and Launch 
ELAHERE is a first-in-class ADC targeting folate receptor alpha (FRα), a cell-surface protein over-expressed 
in a number of epithelial tumors, including ovarian, endometrial, and non-small-cell lung cancers. On November 14, 
2022, the U.S. Food and Drug Administration (FDA) granted accelerated approval for ELAHERE for the treatment of 
adult patients with FRα positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who 
have received one to three prior systemic treatment regimens. The accelerated approval of ELAHERE was based on 
efficacy and safety outcomes from SORAYA, a single-arm trial of ELAHERE in patients with platinum-resistant 
ovarian cancer whose tumors express high levels of FRα. Continued approval may be contingent upon verification and 
description of clinical benefit in a confirmatory trial. Patients eligible for treatment with ELAHERE are selected by the 
VENTANA FOLR1 (FOLR1-2.1) RxDx Assay developed by Roche Tissue Diagnostics (RTD), which was also 
approved by the FDA on November 14, 2022. We completed the build out of our U.S. commercial infrastructure in 2022 
and initiated sales in the U.S. in November 2022. 
Ongoing Development 
In addition to SORAYA, we are conducting MIRASOL, a randomized Phase 3 clinical trial designed to support 
full approval of ELAHERE. In July of 2022, we completed enrollment in MIRASOL and expect to report top-line data 
from this trial in the second quarter of 2023. If MIRASOL is successful, we plan to submit a marketing authorisation 
application, or MAA, for approval of ELAHERE for the treatment of adult patients with FRα positive, platinum-resistant 
epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to three prior systemic treatment 
regimens with the European Medicines Agency, or EMA, in the second half of 2023. Additionally, our partner, Huadong 
Medicine, expects to submit a biologics license application to the National Medical Products Administration (NMPA) of 
China for ELAHERE in the same indication in the second half of 2023 to support potential approval and launch of 
ELAHERE in Greater China in 2024.  
Beyond platinum-resistant ovarian cancer, our strategy is to move ELAHERE into platinum- sensitive disease, 
and to position the product as the combination agent of choice in ovarian cancer. To this end, in January 2023, we 
completed patient enrollment in PICCOLO, a single-arm trial of ELAHERE monotherapy in later-line FRα positive 
platinum-sensitive patients, and plan to report on the primary endpoint before the end of 2023. We have also generated 
encouraging data in recurrent platinum-sensitive disease with the combination of ELAHERE plus carboplatin and are 
supporting investigator sponsored trials (ISTs) with this combination in a single arm trial in the neoadjuvant setting and 
in a randomized trial comparing ELAHERE combined with carboplatin to standard of care in patients with recurrent 
platinum-sensitive disease. We also initiated a single-arm Phase 2 trial (0420) of this combination followed by 
ELAHERE continuation in FRα-low, medium, and high patients with platinum-sensitive disease. Results from this trial 
and our ongoing ISTs will inform a path to the potential registration for ELAHERE plus carboplatin and, in parallel, 
could support compendia listing for this combination. Finally, we have initiated GLORIOSA, a randomized Phase 3 trial 
of ELAHERE plus bevacizumab maintenance in FRα-high recurrent platinum-sensitive disease that we believe could 
support label expansion. 
Pivekimab Sunirine 
Pivekimab sunirine (PVEK), formerly known as IMGN632, is an ADC comprised of a high-affinity antibody 
designed to target CD123 with site-specific conjugation to a DNA-alkylating payload of the novel IGN 
(indolinobenzodiazepine pseudodimer) class. Our IGNs are designed to alkylate DNA without cross-linking, which has 
provided a broad therapeutic index in preclinical models. We are advancing PVEK in clinical trials for patients with 

6 
blastic plasmacytoid dendritic cell neoplasm (BPDCN) and acute myeloid leukemia (AML).  
BPDCN is a rare form of blood cancer, with an annual incidence of between 500 and 1,000 patients in the US. 
In October 2020, the FDA granted Breakthrough Therapy designation for PVEK for the treatment of patients with 
relapsed or refractory BPDCN. Based on feedback from the FDA, we amended our ongoing 801 Phase 2 trial, known as 
CADENZA, to include a new cohort of up to 20 frontline BPDCN patients. 
Initial enrollment in CADENZA did not distinguish between de novo BPDCN patients and those who presented 
with a prior or concomitant hematologic malignancy (PCHM). Although complete responses have been observed in 
BPDCN patients who present with PCHM, most will not achieve full hematologic recovery due to the impact of their 
prior or concomitant malignancy. For these patients, we believe that achieving a complete response with partial 
hematological recovery (CRh) is a potentially important measure of clinical benefit. 
In data from the first ten patients in the pivotal CADENZA frontline cohort, we observed: 2 of 4 de novo 
patients achieved CR (complete response)/CRc (clinical complete response); and 4 of 6 PCHM patients achieved 
CR/CRc/CRh. In addition, in three frontline patients (2 de novo, 1 PCHM) enrolled prior to the opening of the pivotal 
cohort, all three patients achieved CR/CRc.  
A Type B meeting was held in August 2022 regarding these initial data from the CADENZA trial. Based on 
FDA feedback on trial design provided in this meeting, the efficacy analysis will be conducted in de novo BPDCN 
patients with CR/CRc as the primary endpoint and the key secondary endpoint of duration of CR/CRc. We will enroll up 
to 20 de novo patients for purposes of the efficacy analysis. We will also continue to enroll PCHM patients in 
CADENZA to further evaluate PVEK in this population. The Company expects to report top-line data on the primary 
and key secondary endpoints in 2024. 
We are also conducting our 802 trial for PVEK, which is a Phase 1b/2 trial designed to determine the safety, 
tolerability, and preliminary antileukemia activity of PVEK when administered in combination with azacytidine and 
venetoclax to patients with relapsed and frontline CD123-positive AML. Having identified the recommended Phase 2 
dose for the triplet, patients are accruing in both expansion cohorts. In December 2022, safety and efficacy findings in 
relapsed refractory AML and initial data in frontline AML was presented at the American Society of Hematology 
Annual Meeting. In the first 10 frontline patients enrolled, 5/10 (50%) patients achieved a CR and 3/4 (75%) patients 
tested had a minimal residual disease (MRD)-negative CR. Based upon these results, the Company will continue 
enrollment in two frontline AML expansion cohorts to optimize the duration of venetoclax therapy. In addition, in 
December 2022, the Company announced a clinical collaboration with Gilead Sciences, Inc. to study PVEK in 
combination with magrolimab in relapsed refractory AML and expects to initiate this cohort under the 802 trial in the 
second half of 2023.  
Other Pipeline Programs 
We continue to advance our earlier-stage pipeline programs. IMGC936 is an ADC in development with 
MacroGenics, Inc. that is designed to target ADAM9, an enzyme over-expressed in a range of solid tumors and 
implicated in tumor progression and metastasis. IMGC936 incorporates a number of innovations, including antibody 
engineering to extend half-life, site-specific conjugation with a fixed drug-antibody ratio to enable higher dosing, and a 
next-generation linker and payload designed for improved stability and bystander activity. Phase 1 dose escalation was 
completed and expansion cohorts in non–small cell lung cancer and triple-negative breast cancer initiated in the second 
half of 2022. We expect to provide initial data from these cohorts in the second quarter of 2023.  
IMGN151 is our next generation anti-FRα product candidate in development. This ADC integrates innovation 
in each of its components, which we believe may enable IMGN151 to address patient populations with lower levels of 
FRα expression, including tumor types outside of ovarian cancer. We began enrollment in a Phase I clinical trial 
evaluating IMGN151 in patients with recurrent endometrial cancer and recurrent, high-grade serous epithelial ovarian, 
primary peritoneal, or fallopian tube cancers in January 2023.  
Collaborations and Out-Licenses   
Over the last 40 years, we believe ImmunoGen has assembled the most comprehensive ‘‘toolbox’’ in the ADC 
field. Our platform technology combines advanced chemistry and biochemistry with innovative approaches to antibody 
optimization, with a focus on increasing the diversity and potency of our payload agents, advancing antibody-payload 
linkage and release technologies, and integration of novel approaches to antibody engineering. These capabilities have 
enabled us to generate a pipeline of novel candidates with potent anti-tumor activity and favorable safety profiles that we 
can develop as monotherapies and in combination with existing and novel therapies. 
Collaborating on ADC development with other companies allows us to enhance our capabilities, extend the 
reach of our proprietary platform, mitigate expenses, and generate revenue. We have selectively licensed restricted 

7 
access to our ADC platform technology to other companies to expand the use of our technology and to provide us with 
cash to fund our own product programs. These agreements typically provide the licensee with rights to use our ADC 
platform technology with its antibodies or related targeting vehicles to a defined target to develop products. The licensee 
is generally responsible for the development, clinical testing, manufacturing, registration, and commercialization of any 
resulting product candidate. As part of these agreements, we are generally entitled to receive upfront fees, potential 
milestone payments, royalties on the sales of any resulting products, and research and development funding based on 
activities performed at our collaborative partner’s request.   
Below is a table setting forth our current licensed ADC partnerships and status of the most advanced program in 
each partnership:  
Partner 
    Licensed targets/compounds 
    Status of Most Advanced Program 
 
Roche . . . . . . . . . . . . . . . . . . . .   HER2, 4 other1 . . . . . . . . . . . . . . . . . . . . . . .   Marketed 
 
Huadong . . . . . . . . . . . . . . . . . .   ELAHERE – Greater China . . . . . . . . . . . .   Phase 3 
 
Viridian . . . . . . . . . . . . . . . . . .   IGF-1R non-cancer radiopharmaceuticals .   Phase 3 
 
CytomX . . . . . . . . . . . . . . . . . .   CD166, EpCAM . . . . . . . . . . . . . . . . . . . . .   Phase 2 
 
Debiopharm . . . . . . . . . . . . . . .   CD372 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Phase 2 
 
Bayer . . . . . . . . . . . . . . . . . . . .   Mesothelin . . . . . . . . . . . . . . . . . . . . . . . . . .   Phase 1 
 
Novartis . . . . . . . . . . . . . . . . . .   CCR7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Phase 1 
 
Oxford 
BioTherapeutics/Menarini . .   CD2053 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   Phase 1 
 
Fusion . . . . . . . . . . . . . . . . . . . .   Undisclosed . . . . . . . . . . . . . . . . . . . . . . . . .   Phase 1 
 
Lilly  . . . . . . . . . . . . . . . . . . . . .   Undisclosed . . . . . . . . . . . . . . . . . . . . . . . . .   Preclinical 
 
Magenta . . . . . . . . . . . . . . . . . .   Undisclosed . . . . . . . . . . . . . . . . . . . . . . . . .   Preclinical 
 
1 Undisclosed. 
2 Debiopharm has an exclusive license for Debio 1562 (formerly known as IMGN529). 
3 Oxford BioTherapeutics and Menarini are developing MEN 1309, an ADC targeting CD205 and utilizing our DM4 
payload, pursuant to a sublicense from Amgen, which in turn licensed our maytansinoid ADC technology to develop and 
commercialize ADCs targeting CD205. 
Below is a brief description of material business relationships underlying certain of the foregoing programs. For 
more information concerning these relationships with partners, including their ongoing financial and accounting impact 
on our business, please read Note C, Collaboration and License Agreements, to our audited consolidated financial 
statements included in this Annual Report on Form 10-K. 
Huadong 
In October 2020, we entered into a collaboration and license agreement with Hangzhou Zhongmei Huadong 
Pharmaceutical Co., Ltd. (Huadong) a subsidiary of Huadong Medicine Co., Ltd., under which Huadong will exclusively 
develop and commercialize ELAHERE in the People’s Republic of China, Hong Kong, Macau, and Taiwan, which we 
refer to as Greater China. Under the terms of the collaboration and license agreement, we received a non-refundable 
upfront payment of $40 million and are eligible to receive additional payments of up to $265.0 million as certain 
development, regulatory, and net sales milestones are achieved. We are also eligible to receive tiered low double digit to 
high teen royalties as a percentage of ELAHERE commercial sales by Huadong in Greater China. Through December 
31, 2022, the Company had received an aggregate of $15.0 million in milestone payments under this agreement. 
Although we hold the MAA, Huadong is responsible for the development and commercialization of ELAHERE in 
Greater China except in limited circumstances. In addition, we granted Huadong a right of first negotiation if we 
determine to enter into an agreement to grant a third party rights in Greater China to develop or commercialize a product, 
other than ELAHERE, that specifically binds to FRα. We retain all rights to ELAHERE in the rest of the world. The 
standard termination provisions discussed below apply to this license. 
 
 

8 
Lilly 
In February 2022, we entered into a license agreement with Eli Lilly and Company (Lilly), pursuant to which 
we granted Lilly worldwide exclusive rights to research, develop, and commercialize antibody-drug conjugates based on 
the Company’s novel camptothecin technology. Under the terms of the license agreement, we received a non-refundable 
upfront payment of $13.0 million, reflecting initial targets selected by Lilly. During 2022, pursuant to the terms of the 
agreement, Lilly selected additional targets for which we received an additional $13.0 million in non-refundable 
payments. Lilly may select a pre-specified number of additional targets, with the Company eligible to receive an 
additional $19.5 million in exercise fees if Lilly licenses the full number of remaining additional targets over a specified 
period following the effective date of the license agreement, with the potential for up to $1.7 billion in development and 
sales-based milestone payments if all targets are selected and all milestones are realized. In addition, we are entitled to 
receive tiered royalties, on a product-by-product basis, as a percentage of worldwide annual net sales by Lilly, based on 
certain net sales thresholds. Lilly is responsible for all costs associated with the research, development, and 
commercialization of any ensuing products. The standard termination provisions discussed below apply to this license. 
Standard Termination Provisions 
Standard termination provisions in our license agreements state that the partner may terminate the agreement 
for convenience at any time upon prior written notice to us. The agreement may also be terminated by either party for a 
material breach by the other, subject to notice and cure provisions. We may also terminate certain of these agreements 
upon the occurrence of specified events. Upon termination, the partner’s rights to our intellectual property with respect 
to the applicable target are canceled and could then be used by us or re-licensed for that target. Unless earlier terminated, 
each agreement will continue in effect until the expiration of partner’s royalty obligations, which are determined on a 
product-by-product and country-by-country basis. For each product and country, royalty obligations commence upon 
first commercial sale of that product in that country and extend until the later of either the expiration of the last-to-expire 
ImmunoGen patent covering that product in that country or the expiration for that country of the minimum royalty 
period specified in the agreement. 
Patents, Trademarks and Trade Secrets 
ImmunoGen has a substantial and robust intellectual property portfolio comprising over 1,800 issued patents 
and over 700 pending patent applications on a worldwide basis. Our intellectual property strategy centers on obtaining 
high quality patent protection directed to various embodiments of our proprietary technologies and product candidates. 
Using this strategy, our ADC technology and our product candidates are protected through a multi-layered approach. In 
this regard, we have patents and patent applications covering antibodies and other cell binding agents, linkers, cytotoxic 
payload agents (e.g., tubulin-acting maytansinoids, DNA-alkylating IGNs, and DNA-acting camptothecins), conjugation 
methodologies and complete ADCs, comprising one or more of these components, as well as methods of making and 
using each of the above. Typically, multiple issued patents and pending patent applications cover various embodiments 
of each of ImmunoGen’s and our licensees’ product candidates. 
We consider our tubulin-acting maytansinoid, DNA-alkylating IGN, and DNA-acting camptothecin cytotoxic 
payload agent technologies to be key components of our overall patent strategy. With regard to our tubulin-acting 
maytansinoid cytotoxic payload agents, we currently own 22 issued U.S. patents covering various embodiments of our 
maytansinoid technology including those with claims directed to certain maytansinoids, including DM4 and DM21, and 
methods of manufacturing DM1, DM4, and DM21, as well as methods of using the same. These issued patents are 
expected to remain in force until various times between 2023 and 2038. With regard to our IGN payload agents, we have 
39 issued U.S. patents covering various aspects of our DNA-acting cytotoxic payload agents, which will expire at 
various times between 2030 and 2038. With regard to our camptothecin agents, we have an issued U.S. patent covering 
various aspects of our camptothecin cytotoxic payload agents, which expires in 2040. In addition, we have received or 
are applying for comparable patent protection in other major commercial and manufacturing jurisdictions, including 
Europe, Japan, and China. In nearly all cases for our maytansinoid, IGN, and camptothecin patent portfolios, we have 
additional pending patent applications disclosing and claiming many other related and strategically important 
embodiments of these technologies which, upon issuance or grant, will extend our patent protection term over these 
technologies by several additional years. 
Our intellectual property strategy also includes pursuing patents directed to linkers, antibodies, conjugation 
methods, ADC formulations and the use of specific antibodies and ADCs to treat certain diseases. In this regard, we 
have 22 issued patents related to many of our linker technologies, as well as additional pending patent applications 
disclosing and claiming many other related and strategically important embodiments of these linker technologies, 
including methods of making the linkers and antibody maytansinoid conjugates comprising these linkers. These issued 
patents are expected to remain in force until various times between 2023 and 2034. We also have 23 issued U.S. patents 

9 
covering methods of assembling ADCs from their constituent antibody, linker, and cytotoxic payload agent moieties. 
These issued patents will expire between 2026 and 2039. In nearly all instances for both our linker and conjugation 
patent portfolios, we have additional pending patent applications disclosing and claiming many other related and 
strategically important embodiments of these technologies which, upon issuance or grant, would extend our patent 
protection term over these technologies by several additional years. In addition, we have received or are applying for 
comparable patents in other major commercial and manufacturing jurisdictions including Europe, Japan, and China.   
We also file, prosecute, and maintain a substantial portfolio of patents and patent applications specifically 
directed to ImmunoGen’s and our licensees’ ADC candidates. In this regard, we craft a detailed patent protection 
strategy for each ADC as it approaches clinical evaluation. Such strategies make use of the patents and patent 
applications described in the preceding paragraphs, as well as ADC-specific filings, to create a multi-layered and multi-
jurisdictional patent protection approach for each ADC as it enters the clinic. These ADC-specific patent strategies are 
intended to provide the exclusivity basis for revenue and royalties arising from commercial development of each of 
ImmunoGen’s and our licensees’ ADCs. In addition to the platform patent strategy described above and specific to 
ELAHERE, we have 21 issued U.S. patents and 15 pending U.S. applications covering various embodiments of the 
composition of matter and methods of treatment using ELAHERE, expiring at various times between 2031 and 2043. 
We have filed 5 applications for patent term extension of patents covering various aspects of ELAHERE with the U.S. 
Patent and Trademark Office. We expect the U.S. Patent and Trademark Office to deem one or more of these patent term 
extension applications allowable. We will elect to have the term of one of the patents underlying the patent term 
extension applications extended for the period of time set forth in the application for patent term extension. With respect 
to PVEK, we have 6 issued U.S. patents and 5 pending U.S. applications covering various embodiments of the 
composition of matter and methods of treatment using PVEK, expiring at various times between 2036 and 2043. 
We expect our continued independent and collaborative work in each of these areas will lead to other patent 
applications. We will be the owner of all patents covering our independently generated inventions. In all other instances, 
we expect to either be the sole owner or co-owner of any patents covering collaboratively generated inventions insofar as 
they relate to co-developed products or our ADC platform technology, or otherwise have an exclusive or non-exclusive 
license to the technology covered by such patents. 
We cannot provide assurance that pending patent applications will issue as patents or that any patents, if issued, 
will provide us with adequate protection against competitors with respect to the covered products, technologies, or 
processes. Defining the scope and term of patent protection involves complex legal and factual analyses and, at any 
given time, the result of such analyses may be uncertain. In addition, other parties may challenge our patents in litigation 
or administrative proceedings resulting in a partial or complete loss of certain patent rights owned or controlled by 
ImmunoGen. Furthermore, as a patent does not confer any specific freedom to operate, other parties may have patents 
that may block or otherwise hinder the development and commercialization of our technology. 
In addition, many of the processes and much of the know-how that are important to us depend upon the skills, 
knowledge, and experience of our key scientific and technical personnel, which skills, knowledge, and experience are 
not patentable. To protect our rights in these areas, we require that all employees, consultants, advisors, and 
collaborators enter into confidentiality agreements with us. Further, we require that all employees enter into assignment 
of invention agreements as a condition of employment. We cannot provide assurance, however, that these agreements 
will provide adequate or any meaningful protection for our trade secrets, know-how, or other proprietary information in 
the event of any unauthorized use or disclosure of such trade secrets, know-how, or proprietary information. Further, in 
the absence of patent protection, we may be exposed to competitors who independently develop substantially equivalent 
technology or otherwise gain access to our trade secrets, know-how, or other proprietary information. 
Competition 
We focus on highly competitive areas of product development. Our competitors include major pharmaceutical 
companies and other biotechnology firms. For example, Mersana Therapeutics, Eisai, and Sutro BioPharma have 
clinical-stage ADCs targeting platinum resistant ovarian cancer, and Pfizer, Seattle Genetics, Roche, Astellas, 
AstraZeneca, Daiichi Sankyo, GlaxoSmithKline, AbbVie, and the Menarini Group have programs to attach a cell-killing 
small molecule to an antibody for targeted delivery to cancer cells. Pharmaceutical and biotechnology companies, as 
well as other institutions, also compete with us for promising targets for antibody-based therapeutics, for obtaining 
licenses and collaboration agreements with other companies to develop targets for antibody-based therapeutics, and in 
recruiting highly qualified scientific personnel. Additionally, there are non-ADC therapies available and/or in 
development for the cancer types we and our partners are targeting. Many competitors and potential competitors have 
substantially greater scientific, research, and product development capabilities, as well as greater financial, sales, 
marketing, and human resources than we do. In addition, many specialized biotechnology firms have formed 

10 
collaborations with large, established companies to support the research, development, and commercialization of 
products that may be competitive with ours. 
In particular, competitive factors within the antibody and cancer therapeutic market include: 
• 
the safety, efficacy, and convenience of products; 
• 
the timing of regulatory approvals and commercial introductions; 
• 
special regulatory designation of products, such as orphan drug and breakthrough therapy designations; and 
• 
the effectiveness of marketing, sales, and reimbursement efforts. 
Our competitive position depends on a combination of factors. These include effectively pursuing the 
development of proprietary products, the implementation of clinical development programs, the ability to appropriately 
manufacture, sell, and market our products, and the procurement of patent protection for our products. In addition, we 
must secure sufficient capital resources to accomplish all of the previously mentioned activities. 
Continued development of conventional and targeted chemotherapeutics by large pharmaceutical companies 
and biotechnology companies may result in new compounds that may compete with our product candidates. Antibodies 
developed by certain of these companies have been approved for use as cancer therapeutics. In the future, new antibodies 
or other targeted therapies may compete with our product candidates. Other companies have created or have programs to 
create potent cell-killing agents for attachment to antibodies. These companies may compete with us for technology 
out-license arrangements. 
Managing the Impact of the COVID-19 Pandemic 
Since the first quarter of 2020, although we have experienced some delays or disruptions due to the COVID-19 
pandemic, we have successfully continued to move our clinical trials forward while adapting to meet the evolving 
challenges of the pandemic. We implemented business continuity plans in March 2020 that enabled our workforce to 
remain productive while working from home until mid-September 2021, at which time our workforce returned to the 
office. From a regulatory perspective, since the beginning of the pandemic, we have received timely reviews of our 
submissions to the FDA and other health authorities covering our clinical trial applications. From a manufacturing and 
supply chain perspective, we believe we have sufficient inventory on hand for all of our ongoing and near-term clinical 
trials and to support the launch and continued commercialization of ELAHERE. COVID-19 may impact our commercial 
activities for ELAHERE, including patient access to testing and identification, but we will conduct commercial and 
medical affairs field activities in virtual formats where in-person interactions are not feasible. 
Regulatory Matters 
Government Regulation and Product Approval 
Government authorities in the U.S., at the federal, state, and local level, and other countries extensively 
regulate, among other things, the research, development, testing, manufacture, quality control, approval, labeling, 
packaging, storage, record-keeping, promotion, advertising, distribution, marketing, and export and import of drug 
products. A new drug must be approved by the FDA through the new drug application, or NDA, process and a new 
biologic must be approved by the FDA through the biologics license application, or BLA, process before it may be 
legally marketed in the U.S. 
U.S. Drug Development Process 
In the U.S., the FDA regulates drugs under the federal Food, Drug, and Cosmetic Act (FDCA) and in the case 
of biologics, also under the Public Health Service Act (PHSA) and implementing regulations. The process of obtaining 
regulatory approvals and the subsequent compliance with applicable federal, state, and local statutes and regulations 
require the expenditure of substantial time and financial resources. Failure to comply with the applicable U.S. 
requirements at any time during the product development process, approval process, or after approval, may subject an 
applicant to adverse administrative or judicial actions. These actions could include the FDA’s refusal to approve pending 
applications, withdrawal of an approval, a clinical hold, warning letters, product recalls, product seizures, total or partial 
suspension of production or distribution, injunctions, fines, refusals of government contracts, restitution, disgorgement, 
or civil or criminal penalties. Any such administrative or judicial action could have a material adverse effect on our 
business.  

11 
The process required by the FDA before a drug or biologic may be marketed in the U.S. generally involves the 
following: 
• 
completion of preclinical and other nonclinical laboratory tests, animal studies, and formulation studies 
according to current Good Laboratory Practices (cGLP) or other applicable regulations; 
• 
submission to the FDA of an IND, which must become effective before human clinical trials may begin; 
• 
performance of adequate and well-controlled human clinical trials according to current Good Clinical 
Practices (cGCP) to establish the safety and efficacy of the proposed drug for its intended use; 
• 
development and approval of a companion diagnostic if the FDA or the sponsor believes that its use is 
essential for the safe and effective use of a corresponding product; 
• 
submission to the FDA of an NDA or BLA; 
• 
satisfactory completion of an FDA inspection of the manufacturing facility or facilities at which the drug is 
produced to assess compliance with current Good Manufacturing Practice (cGMP) to assure that the 
facilities, methods, and controls are adequate to preserve the drug’s identity, strength, quality, and purity; 
and 
• 
the FDA’s review and approval of the NDA or BLA. 
Once a pharmaceutical candidate is identified for development, it enters the preclinical testing stage. Preclinical 
tests include laboratory evaluations of product chemistry, toxicity, and formulation, as well as animal studies. An IND 
sponsor must submit the results of the preclinical tests, together with manufacturing information and analytical data, to 
the FDA as part of the IND. The sponsor will also include a clinical protocol detailing, among other things, the 
objectives of the first phase of the clinical trial, the parameters to be used in monitoring safety, and the effectiveness 
criteria to be evaluated, if the first phase lends itself to an efficacy evaluation. Some nonclinical testing may continue 
even after the IND is submitted and clinical trials have begun. The IND automatically becomes effective 30 days after 
receipt by the FDA, unless the FDA, within the 30-day time period, places the clinical trial on a clinical hold. In such a 
case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. Clinical 
holds also may be imposed by the FDA at any time before or during clinical trials due to safety concerns about ongoing 
or proposed clinical trials or non-compliance with specific FDA requirements, and the trials may not begin or continue 
until the sponsor submits additional information that alleviates the FDA’s concerns, and the FDA notifies the sponsor 
that the hold has been lifted. 
Each clinical trial must be conducted under the supervision of one or more qualified investigators in accordance 
with cGCP requirements in accordance with a protocol for each phase of the clinical trial included as part of the IND, 
and timely safety reports must be submitted to the FDA and the investigators for serious and unexpected adverse events. 
A local or central institutional review board (IRB) acting on behalf of each institution participating in the clinical trial 
must review and approve each protocol before a clinical trial commences at that institution and must also approve the 
information regarding the trial and the consent form that must be provided to each trial subject or his or her legal 
representative, monitor the trial until completed, and otherwise comply with IRB regulations. 
Human clinical trials are typically conducted in three sequential phases that may overlap or be combined: 
• 
Phase 1:  The product candidate is initially introduced into healthy human subjects and tested for safety 
and dosage tolerance, absorption, metabolism, distribution, and excretion. In the case of some products for 
severe or life-threatening diseases, such as cancer, especially when the product may be too inherently toxic 
to ethically administer to healthy volunteers, the initial human testing is often conducted in patients. 
• 
Phase 2:  This phase involves clinical trials in a limited patient population to identify possible adverse 
effects and safety risks, to preliminarily evaluate the efficacy of the product for specific targeted diseases 
and to determine dosage tolerance and optimal dosage. 
• 
Phase 3:  These trials are undertaken to further evaluate dosage, clinical efficacy, and safety in an 
expanded patient population at geographically dispersed clinical trial sites and to establish the overall 
risk-benefit ratio of the product candidate and provide, if appropriate, an adequate basis for product 
labeling. 

12 
Post-approval trials, sometimes referred to as Phase 4, may be conducted after initial marketing approval. These 
trials are used to gain additional information about the use of the approved drug in the treatment of patients in the 
intended therapeutic indication. In certain instances, the FDA may mandate the performance of post-approval trials as a 
condition of approval of an NDA or BLA. 
The FDA or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the 
research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or 
terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the 
IRB’s requirements or if the drug has been associated with unexpected or serious patient reactions. Additionally, some 
clinical trials are overseen by an independent group of qualified experts organized by the sponsor, known as a data safety 
monitoring board or committee. Depending on its charter, this group may determine whether a trial may move forward at 
designated check points based on access to certain data from the trial. Phase 1, Phase 2, and Phase 3 testing may not be 
completed successfully within any specified period, if at all. 
During the development of a new drug, sponsors may request meetings with the FDA to share information 
about the data gathered to date, for the FDA to provide advice, and for the sponsor and the FDA to reach agreement on 
the next phase of development.  
Concurrent with clinical trials, companies usually complete additional animal studies and must also develop 
additional information about the chemistry and physical characteristics of the drug and finalize a process for 
manufacturing the product in commercial quantities in accordance with cGMP requirements. The manufacturing process 
must be capable of consistently producing quality batches of the product candidate and, among other things, the 
manufacturer must develop methods for testing the identity, strength, quality, and purity of the final drug. Additionally, 
appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the 
product candidate does not undergo unacceptable deterioration over its shelf life. 
While the IND is active, progress reports summarizing the results of the clinical trials and nonclinical studies 
performed since the last progress report must be submitted at least annually to the FDA, and written IND safety reports 
must be submitted to the FDA and investigators for serious and unexpected suspected adverse events, findings from 
other studies suggesting a significant risk to humans exposed to the same or similar drugs, findings from animal or in 
vitro testing suggesting a significant risk to humans, and any clinically important increased incidence of a serious 
suspected adverse reaction compared to that listed in the protocol or investigator brochure. 
There are also requirements governing the reporting of ongoing clinical trials and completed trial results to 
public registries. Most sponsors of clinical trials of FDA-regulated products are required to register and disclose 
specified clinical trial information, which is publicly available at www.clinicaltrials.gov. Information related to the 
product, patient population, phase of investigation, trial sites and investigators, and other aspects of the clinical trial is 
then made public as part of the registration. Sponsors are also obligated to disclose the results of their clinical trials after 
completion. Disclosure of the results of these trials can be delayed until the new product or new indication being studied 
has been approved. However, there are evolving rules and increasing requirements for publication of all trial-related 
information, and it is possible that data and other information from trials involving drugs that never garner approval 
could require disclosure in the future. 
Companion Diagnostics 
For ELAHERE, (and potentially other of our product candidates), we work with collaborators to develop or 
obtain access to in vitro companion diagnostic tests to identify appropriate patients for these targeted therapies. For 
example, we partnered with RTD to develop a companion diagnostic device for ELAHERE. In conjunction with the 
FDA’s approval of ELAHERE, the agency also approved the VENTANA FOLR1 RxDx Assay as a companion 
diagnostic device to select patients eligible for treatment with ELAHERE. 
If the FDA believes that a diagnostic test is essential for the safe and effective use of a corresponding 
therapeutic product, the FDA may require the sponsor to develop, and obtain contemporaneous clearance or approval for 
a companion diagnostic. Companion diagnostics can be used to identify patients likely to be more responsive to a 
particular therapy or at increased risk for serious side effects as a result of treatment with a particular therapeutic 
product. They may also be useful for monitoring the response to treatment for the purpose of adjusting treatment or 
doses to achieve improved safety or effectiveness. 
Companion diagnostics are regulated by the FDA as medical devices. The FDA applies a risk-based approach 
to determine the regulatory pathway for companion diagnostics. This means that the regulatory pathway will depend on 
the level of risk to patients, based on the intended use of the companion diagnostic device and the controls necessary to 
provide a reasonable assurance of safety and effectiveness. The two primary types of marketing pathways for medical 

13 
devices are clearance of a premarket notification under Section 510(k) of the FDCA, or 510(k), and approval of a 
premarket approval application (PMA). We expect that any companion diagnostic developed for use with our drug 
candidates will utilize the PMA pathway. If the diagnostic test and the therapeutic drug are studied together to support 
their respective approvals, the clinical trial must meet both the IND requirements and the FDA’s companion diagnostic 
requirements that apply to clinical trials of significant risk devices. 
The FDA expects that the therapeutic sponsor will address the need for a companion diagnostic device in its 
therapeutic product development plan and that, in most cases, the therapeutic product and its corresponding companion 
diagnostic device will be developed contemporaneously.  
PMAs must be supported by valid scientific evidence, which typically requires extensive data, including 
technical, preclinical, clinical, and manufacturing data, to demonstrate to the FDA’s satisfaction the safety and 
effectiveness of the device. For diagnostic tests, a PMA typically includes data regarding analytical and clinical 
validation studies. As part of its review of the PMA, the FDA will conduct a pre-approval inspection of the 
manufacturing facility or facilities to ensure compliance with the Quality System Regulation (QSR) which requires 
manufacturers to follow design, testing, control, documentation, and other quality assurance procedures. The FDA’s 
review of an initial PMA may require several years to complete. 
After approval, the use of a companion diagnostic device with a therapeutic product will be stipulated in the 
instructions for use in the labeling of both the diagnostic device and the corresponding therapeutic product. In addition, a 
diagnostic test that was approved through the PMA process or one that was cleared through the 510(k) process and 
placed on the market will be subject to ongoing regulatory requirements, including requirements related to device 
labeling and promotion, registration and listing, QSR, and medical device reporting. 
U.S. Review and Approval Processes 
The results of product development, preclinical and other non-clinical studies, and clinical trials, along with 
descriptions of the manufacturing process, analytical tests conducted on the chemistry of the drug, proposed labeling, 
and other relevant information are submitted to the FDA as part of an NDA or BLA requesting approval to market the 
product. The submission of an NDA or BLA is subject to the payment of user fees; a waiver of such fees may be 
obtained under certain limited circumstances. The FDA reviews all NDAs and BLAs submitted to ensure that they are 
sufficiently complete for substantive review before it accepts them for filing. The FDA may request additional 
information rather than accept an NDA or BLA for filing. In this event, the NDA or BLA must be resubmitted with the 
additional information. The resubmitted application also is subject to review before the FDA accepts it for filing. Once 
the submission is accepted for filing, the FDA begins an in-depth substantive review. The FDA may refer the NDA or 
BLA to an advisory committee for review, evaluation, and recommendation as to whether the application should be 
approved and under what conditions. The FDA is not bound by the recommendation of an advisory committee, but it 
generally follows such recommendations. The approval process is lengthy and often difficult, and the FDA may refuse to 
approve an NDA or BLA if the applicable regulatory criteria are not satisfied or may require additional clinical or other 
data and information. Even if such data and information are submitted, the FDA may ultimately decide that the NDA or 
BLA does not satisfy the criteria for approval. Data obtained from clinical trials are not always conclusive and the FDA 
may analyze and interpret data differently than we analyze and interpret the same data. The FDA reviews an NDA to 
determine, among other things, whether a product is safe and effective for its intended use and whether its manufacturing 
is cGMP-compliant to assure and preserve the product’s identity, strength, quality, and purity. The FDA reviews a BLA 
to determine, among other things whether the product is safe, pure, and potent and the facility in which it is 
manufactured, processed, packed, or held meets standards designed to assure the product’s continued safety, purity, and 
potency. Before approving an NDA or BLA, the FDA will inspect the facility or facilities where the product is 
manufactured to assure compliance with cGMPs and may also inspect clinical trial sites to assure compliance with 
GCPs. 
NDAs or BLAs receive either standard or priority review. Priority review, which is requested at the time of 
BLA or NDA submission, is designed to expedite the review for drugs that provide meaningful therapeutic benefit to 
patients over existing treatments. Priority review for an NDA for a new molecular entity and original BLAs will be 
6 months from the date that the NDA or BLA is filed, compared to 10 months under standard review. Although the 
FDA’s goal is to take action on priority review applications within 6 months, the agency does not always meet this goal 
and the review process may be significantly extended by requests for additional information or clarification from the 
FDA. Priority review does not change the standards for approval, but may expedite the approval process. 
After the FDA evaluates an NDA or BLA, it will issue an approval letter or a complete response letter. An 
approval letter authorizes commercial marketing of the drug with prescribing information for specific indications. A 
complete response letter indicates that the review cycle of the application is complete, and the application will not be 

14 
approved in its present form. A complete response letter usually describes the specific deficiencies in the NDA or BLA 
identified by the FDA and may require additional clinical data, such as an additional Phase 3 trial or other significant and 
time-consuming requirements related to clinical trials, nonclinical studies, or manufacturing. If a complete response 
letter is issued, the sponsor has one year to resubmit the NDA or BLA, addressing all of the deficiencies identified in the 
letter, or withdraw the application. Even if such data and information are submitted, the FDA may decide that the NDA 
or BLA does not satisfy the criteria for approval. 
If a product receives regulatory approval, the approval may be significantly limited to specific diseases and 
dosages or the indications for use may otherwise be limited, which could restrict the commercial value of the product. In 
addition, the FDA may require a sponsor to conduct Phase IV testing which involves clinical trials designed to further 
assess a drug’s safety and effectiveness after NDA or BLA approval and may require testing and surveillance programs 
to monitor the safety of approved products which have been commercialized. The FDA may also place other conditions 
on approval including the requirement for a risk evaluation and mitigation strategy (REMS) to assure the safe use of the 
drug. If the FDA concludes a REMS is needed, the sponsor of the NDA or BLA must submit a proposed REMS. The 
FDA will not approve the NDA or BLA without an approved REMS, if  one is required. A REMS could include 
medication guides, physician communication plans, or other elements to assure safe use, such as restricted distribution 
methods, patient registries, and other risk minimization tools. Any of these limitations on approval or marketing could 
restrict the commercial promotion, distribution, prescription, or dispensing of products. Marketing approval may be 
withdrawn for non-compliance with regulatory requirements or if problems occur following initial marketing. 
The Pediatric Research Equity Act (PREA) requires a sponsor to conduct pediatric clinical trials for most drugs 
and biologics, for a new active ingredient, new indication, new dosage form, new dosing regimen, or new route of 
administration. Under PREA, original NDAs, BLAs, and supplements thereto, must contain a pediatric assessment 
unless the sponsor has received a deferral or waiver. The required assessment must evaluate the safety and effectiveness 
of the product for the claimed indications in all relevant pediatric subpopulations and support dosing and administration 
for each pediatric subpopulation for which the product is safe and effective. The sponsor or the FDA may request a 
deferral of pediatric clinical trials for some or all of the pediatric subpopulations. A deferral may be granted for several 
reasons, including a finding that the drug or biologic is ready for approval for use in adults before pediatric clinical trials 
are complete or that additional safety or effectiveness data need to be collected before the pediatric clinical trials begin. 
Orphan disease indications are exempt from PREA. The FDA must send a non-compliance letter to any sponsor that fails 
to submit the required assessment, keep a deferral current, submit a request for approval of a pediatric formulation. 
Patent Term Restoration and Marketing Exclusivity 
Depending upon the timing, duration, and specifics of the FDA’s approval of our drugs, some of our U.S. 
patents may be eligible for limited patent term extension under the Drug Price Competition and Patent Term Restoration 
Act of 1984, referred to as the Hatch-Waxman Amendments. The Hatch-Waxman Amendments permit a patent 
restoration term of up to five years as compensation for patent term lost during product development and the FDA 
regulatory review process. However, patent term restoration cannot extend the remaining term of a patent beyond a total 
of 14 years from the product’s approval date. The patent term restoration period is generally one-half the time between 
the effective date of an IND, and the submission date of an NDA or BLA, plus the time between the submission date of 
an NDA or BLA and the approval of that application. Only one patent applicable to an approved drug is eligible for the 
extension, and the extension must be applied for prior to expiration of the patent. The U.S. Patent and Trademark Office, 
in consultation with the FDA, reviews and approves the application for any patent term extension or restoration. In the 
future, we intend to apply for restorations of patent term for some of our currently owned or licensed patents to add 
patent life beyond their current expiration date, depending on the expected length of clinical trials and other factors 
involved in the filing of the relevant NDA. 
The FDCA provides a five-year period of marketing exclusivity within the United States to the first applicant to 
obtain approval of an NDA for a new chemical entity. A drug is a new chemical entity if the FDA has not previously 
approved any other new drug containing the same active moiety, which is the molecule or ion responsible for the action 
of the drug substance. During the exclusivity period, the FDA may not accept for review an abbreviated new drug 
application (ANDA) or 505(b)(2) NDA for another drug that contains the same active moiety where the applicant does 
not own or have a legal right of reference to all the data required for approval. However, an application may be 
submitted after four years if it contains a certification of patent invalidity or non-infringement to one of the patents listed 
with the FDA by the fist applicant.  
The FDCA also provides three years of data exclusivity for an NDA or 505(b)(2) NDA (or supplement thereto) 
that contains reports of new clinical investigations, other than bioavailability studies, that were conducted or sponsored 
by the applicant and are deemed by the FDA to be essential to the approval of the application, such as clinical 

15 
investigations for new indications, strength, or routes of administration. This three-year exclusivity covers only the 
conditions of use associated with the new clinical investigations and does not prohibit the FDA from approving 
505(b)(2) NDAs or ANDAs for drugs containing the original active agent.  
Five-year and three-year exclusivity will not delay the submission or approval of a full NDA. However, an 
applicant submitting 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 clinical trials necessary to demonstrate safety and effectiveness. 
Pediatric exclusivity is another type of marketing exclusivity available in the U.S. Under the Best 
Pharmaceuticals for Children Act (BPCA) an additional six months of marketing exclusivity may be available if a 
sponsor conducts clinical trials in children in response to a written request from the FDA (Written Request). If the 
Written Request does not include clinical trials in neonates, the FDA is required to include its rationale for not 
requesting those clinical trials. The FDA may request studies on approved or unapproved indications in separate Written 
Requests. The issuance of a Written Request does not require the sponsor to undertake the described clinical trials. To 
date, we have not received any Written Requests. 
Biologics Price Competition and Innovation Act of 2009 
The Patient Protection and Affordable Care Act, which included the Biologics Price Competition and 
Innovation Act of 2009 (BPCIA), amended the PHSA to create an abbreviated approval pathway for two types of 
“generic” biologics—biosimilars and interchangeable biologic products, and provides for a twelve-year data exclusivity 
period for the first approved biological product, or reference product, against which a biosimilar or interchangeable 
application is evaluated; however if pediatric clinical trials are performed and accepted by the FDA, the twelve-year data 
exclusivity period will be extended for an additional six months. A biosimilar product is defined as one that is highly 
similar to a reference product notwithstanding minor differences in clinically inactive components and for which there 
are no clinically meaningful differences between the biological product and the reference product in terms of the safety, 
purity, and potency of the product. An interchangeable product is a biosimilar product that meets additional requirements 
that show, among other things, that the product will produce the same clinical result as the reference product in any 
given patient. In addition, for products administered to a patient more than once, the effects of switching back and forth 
between the interchangeable product and a reference product on safety and efficacy will have to be evaluated. An 
interchangeable product may be substituted for the reference product by the pharmacy without the intervention of the 
health care provider who prescribed the reference product. 
The biosimilar applicant must demonstrate that the product is biosimilar based on data from (1) analytical 
studies showing that the biosimilar product is highly similar to the reference product; (2) animal studies (including 
toxicity); and (3) one or more clinical trials to demonstrate safety, purity, and potency in one or more appropriate 
conditions of use for which the reference product is approved. In addition, the applicant must show that the biosimilar 
and reference products have the same mechanism of action for the conditions of use on the label, route of administration, 
dosage, and strength, and the production facility must meet standards designed to assure product safety, purity, and 
potency. 
An application for a biosimilar product may not be submitted until four years after the date on which the 
reference product was first approved. The first approved interchangeable biologic product will be granted an exclusivity 
period of up to one year after it is first commercially marketed, but the exclusivity period may be shortened under certain 
circumstances. 
The FDA has issued a number of final and draft guidance documents in order to implement the law and will 
likely continue to publish new guidance as new issues relating to biosimilars and interchangeability are identified. The 
guidance documents provide the FDA’s current thinking on approaches to demonstrating that a proposed biological 
product is biosimilar to or interchangeable with, a reference product. Although the FDA intends to issue additional 
guidance documents in the future, the absence of final guidance documents covering all issues does not prevent a 
sponsor from seeking licensure of a biosimilar or interchangeable product under the BPCIA, as evidenced by the 
products already approved by the FDA. 
Orphan Drug Designation 
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 generally a disease or condition that affects fewer than 200,000 individuals in the U.S., or 
more than 200,000 individuals in the U.S. and for which there is no reasonable expectation that the cost of developing 
and making available in the U.S. a drug for this type of disease or condition will be recovered from sales in the U.S. for 
that drug. Orphan drug designation must be requested before submitting an NDA or BLA. After the FDA grants orphan 
drug designation, the identity of the therapeutic agent and its potential orphan use will be disclosed publicly by the FDA; 

16 
the posting will also indicate whether a drug is no longer designated as an orphan drug. More than one product candidate 
may receive an orphan drug designation for the same indication. Orphan drug designation does not convey any 
advantage in or shorten the duration of the regulatory review and approval process. 
If a product that has orphan drug designation subsequently receives the first FDA approval for the disease for 
which it has such designation, the product is entitled to seven years of orphan drug exclusivity. Orphan drug exclusivity 
means that the FDA cannot approve another sponsor’s marketing application for the same product for the same 
indication, except in very limited circumstances. For example, the FDA may approve a subsequent application for the 
same product in the same indication if the product is clinically superior to the previously approved drug. Additionally, 
orphan drug exclusivity may be lost if the FDA later determines that the request for designation was materially defective 
or if the manufacturer is unable to assure sufficient quantities of the product to meet the needs of patients with the rare 
disease or condition. Orphan drug exclusivity does not prevent the FDA from approving a different drug for the same 
disease or condition, or the same drug for a different disease or condition. A designated orphan drug may not receive 
orphan drug exclusivity if it is approved for a use that is broader than the indication for which it received orphan 
designation. 
Expedited Review and Approval; Breakthrough Therapy Designation 
The FDA has various programs, including Fast Track and accelerated approval, that are intended to expedite or 
simplify the process for reviewing drugs and/or provide for approval on the basis of surrogate endpoints. Even if a drug 
qualifies for one or more of these programs, the FDA may later decide that the drug no longer meets the conditions for 
qualification or that the time period for the FDA’s review or approval will not be shortened. Generally, drugs that may 
be eligible for these programs are those for serious or life-threatening conditions, those with the potential to address 
unmet medical needs, and those that offer meaningful benefits over existing treatments. For example, Fast Track is a 
process designed to facilitate the development, and expedite the review, of drugs to treat serious diseases and fill an 
unmet medical need. The request may be made at the time of IND submission and generally no later than the pre-BLA or 
pre-NDA meeting. The FDA will respond within 60 days of receipt of the request. Although Fast Track does not affect 
the standards for approval, the FDA will attempt to facilitate early and frequent meetings with a sponsor of a Fast Track 
designated drug. 
Breakthrough Therapy designation is designed to expedite the development and review of drugs that are 
intended to treat a serious condition where preliminary clinical evidence indicates that the drug may demonstrate 
substantial improvement over available therapy on a clinically significant endpoint(s). A sponsor may request 
Breakthrough Therapy designation at the time that the IND is submitted, or no later than at the end-of-Phase 2 meeting. 
The FDA will respond to a Breakthrough Therapy designation request within sixty days of receipt of the request. A drug 
that receives Breakthrough Therapy designation is eligible for all Fast-Track designation features, intensive guidance on 
an efficient drug development program, beginning as early as Phase I, and commitment from the FDA involving senior 
managers. In October 2020, we announced that the FDA granted Breakthrough Therapy designation for pivekimab for 
the treatment of patients with relapsed or refractory BPDCN. 
Accelerated approval provides an earlier approval of drugs to treat serious diseases, and that fill an unmet 
medical need based on a surrogate endpoint that is reasonably likely to predict clinical benefit. The FDA may grant 
accelerated approval to a product designed to treat a serious or life-threatening condition that demonstrates an effect on a 
surrogate endpoint, such as a laboratory measurement, radiographic image, physical sign, or other measure that is 
thought to predict clinical benefit, but is not itself a measure of clinical benefit or on an intermediate clinical endpoint 
that is reasonably likely to predict an effect on irreversible morbidity, mortality, or other clinical benefit. Discussions with 
the FDA about the feasibility of an accelerated approval typically begin early in the development of the drug in order to 
identify, among other things, an appropriate endpoint. Accelerated approval does not change the standards for approval, 
but may expedite the approval process. As a condition of approval, the FDA may require that a sponsor of a drug 
receiving accelerated approval perform post-approval clinical trials to confirm the appropriateness of the surrogate 
marker trial. Failure to conduct required post-approval trials, confirm a clinical benefit during post-approval trials, or 
dissemination of false or misleading promotional materials would allow the FDA to withdraw the product from the 
market on an expedited basis. All promotional materials for therapeutic candidates approved under accelerated 
regulations are subject to prior review by the FDA. ELAHERE was granted accelerated approval based on the results of 
the SORAYA trial and we plan to seek full approval on the basis of the confirmatory Phase 3 MIRASOL trial. 
Post-Approval Requirements 
Once an approval is granted, the sponsor will be required to comply with all post-approval regulatory 
requirements as well as any specific post-approval commitments that the sponsor has undertaken as part of the approval 
process. After approval, some types of changes to the approved product, such as adding new indications, certain 

17 
manufacturing changes, additional labeling claims, and required additional testing are subject to further FDA review and 
approval. Drug manufacturers and other entities involved in the manufacture and distribution of approved drugs are 
required to register their establishments with the FDA and certain state agencies and are subject to periodic unannounced 
inspections by the FDA and certain state agencies for compliance with cGMP and other laws and regulations. We rely, 
and expect to continue to rely, on third parties for the production of clinical and commercial quantities of our products. 
Future inspections by the FDA and other regulatory agencies may identify compliance issues at the facilities of our 
contract manufacturers that may disrupt production or distribution or require substantial resources to correct. In addition, 
the discovery of conditions that violate these rules, including failure to conform to cGMPs, could result in regulatory or 
enforcement actions. 
Approved drug products, such as ELAHERE, are subject to continuing regulation by the FDA, including, 
among other things, record-keeping requirements, reporting of adverse experiences with the drug, providing the FDA 
with updated safety and efficacy information, drug sampling and distribution requirements, complying with certain 
electronic records and signature requirements, and complying with the FDA’s promotion and advertising requirements. 
Compliance with these requirements will require us to expend significant time, money, and effort.  
The FDA strictly regulates labeling, advertising, promotion, and other types of information on products that are 
placed on the market. Drugs may be promoted only for the approved indications and in accordance with the provisions 
of the approved label. If a company, including any agent of the company or anyone speaking on behalf of the company, 
is found to have promoted the drug for an indication that is not in the approved label, the company may become subject 
to adverse public relations and administrative and judicial enforcement by the FDA, the Department of Justice, or the 
Office of the Inspector General of the Department of Health and Human Services, as well as state authorities. This could 
subject a company to a range of penalties that could have a significant commercial impact, including civil and criminal 
fines and agreements that materially restrict the manner in which a company promotes or distributes drug products. The 
federal government has levied large civil and criminal fines against companies for alleged improper promotion and has 
also requested that companies enter into consent decrees or permanent injunctions under which specified promotional 
conduct is changed or curtailed. 
The FDA may withdraw an approval if compliance with regulatory standards is not maintained or if problems 
occur after the product reaches the market. Later discovery of previously unknown problems with a product, including 
adverse events of unanticipated severity or frequency, or with manufacturing processes, may result in revisions to the 
approved labeling to add new safety information, requirements to conduct post-approval studies or clinical trials to 
assess new safety risks, or imposition of distribution or other restrictions under a REMS. Other potential consequences 
include, among other things: 
• 
restrictions on the marketing or manufacturing of the product, complete withdrawal of the product from the 
market, or product recalls; 
• 
the issuance of safety alerts, Dear Healthcare Provider letters, press releases or other communications 
containing warnings or other safety information about the product; 
• 
fines, warning letters or holds on post-approval clinical trials; 
• 
refusal of the FDA to approve applications or supplements to approved applications, or suspension or 
revocation of product approvals; 
• 
product seizure or detention, or refusal to permit the import or export of products; 
• 
injunctions or the imposition of civil or criminal penalties;  
• 
consent decrees, corporate integrity agreements, debarment or exclusion from federal healthcare programs; 
and  
• 
mandated modification of promotional materials and labeling and issuance of corrective information. 
From time to time, legislation is drafted, introduced, and passed in Congress that could significantly change the 
statutory provisions governing the approval, manufacturing, and marketing of products regulated by the FDA. It is 
impossible to predict whether further legislative changes will be enacted, or FDA regulations, guidance, or 
interpretations changed, or what the impact of such changes, if any, may be. 
Other Healthcare Laws  
In the U.S., activities of pharmaceutical manufacturers are subject to numerous other federal, state, and local 
laws designed to, for example, prevent fraud and abuse; promote transparency in interactions with others in the 
healthcare industry; protect the privacy of individual information; and ensure integrity of research or protect human 
subjects involved in research. These laws are enforced by various federal and the state enforcement authorities and non-

18 
compliance, or alleged non-compliance, with such laws could adversely affect our reputation, our business and our 
financial results.  See “Risk Factors – Risks Related to Government Regulation.” 
We may be subject to various federal and state laws pertaining to health care “fraud and abuse,” including anti-
kickback laws (which typically prohibit soliciting, offering, receiving, or paying anything of value to generate healthcare 
business reimbursable by third party payors, including Medicare and Medicaid), and false claims laws (which generally 
prohibit anyone from knowingly and willingly presenting, or causing to be presented, any false or fraudulent claims for 
payment for reimbursed drugs or services to third-party payors, including Medicare and Medicaid). Although the 
specific provisions of these laws vary, their scope is generally broad and there may not be regulations, guidance, or court 
decisions that apply the laws to particular industry practices. 
Laws and regulations have also been enacted by the federal government and various states to regulate the sales 
and marketing practices of pharmaceutical manufacturers, including laws that require manufacturers to adopt certain 
compliance standards; disclose financial interactions with health care providers to the government and public; or report 
pricing information or marketing expenditures. Many of these laws and regulations contain ambiguous requirements or 
require administrative guidance for implementation. Given the lack of clarity in laws and their implementation, our 
activities could be subject to challenge. 
We may need to obtain and maintain licenses for our manufacturing and distribution activities in the states in 
which we operate or distribute our products. 
We are subject to federal laws, including the Medicaid Drug Rebate Program, that require pharmaceutical 
manufacturers to report certain calculated product prices to the government or provide certain discounts or rebates to 
government authorities or private entities, often as a condition of reimbursement under government healthcare programs.  
Reporting requirements are complex and, in some instances, require reporting manufacturers to make reasonable 
assumptions in interpreting their obligations.  
We may be subject to privacy and security laws in the various jurisdictions in which we operate, obtain, or store 
personally identifiable information. Numerous U.S. federal and state laws govern the collection, use, disclosure, and 
storage of personal information. See “Risk Factors - Risks Related to Our Business and Industry.” 
If our operations are found to be in violation of any of such laws or any other governmental regulations that 
apply to us, we may be subject to penalties, including, without limitation, administrative, civil and criminal penalties, 
damages, fines, disgorgement, the curtailment or restructuring of our operations, exclusion from participation in federal 
and state healthcare programs, and imprisonment, any of which could adversely affect our ability to operate our business 
and our financial results.  
Foreign Regulation 
In addition to regulations in the U.S., we will be subject to a variety of foreign regulations governing clinical 
trials and commercial sales and distribution of our products. Whether or not we obtain the FDA’s approval for a product, 
we must obtain approval by the comparable regulatory authorities of foreign countries or economic areas, such as the 
European Union, before we may commence clinical trials or market products in those countries or areas. The approval 
process and requirements governing the conduct of clinical trials, product licensing, pricing, and reimbursement vary 
greatly from place to place, and the time to obtain these approvals may be longer or shorter than that required for the 
FDA’s approval. 
Under the European Union regulatory regime, a company may submit marketing authorization applications 
under a centralized, decentralized, or mutual recognition procedure. Where the product is intended to be marketed in one 
EU member state, a national application for a marketing authorization is filed. The centralized procedure is compulsory 
for medicinal products produced by biotechnology, designated orphan medicines, advanced-therapy medicines such as 
gene-therapies, and those medicinal products containing new active substances for specific indications such as the 
treatment of HIV, AIDS and immune dysfunctions, cancer, neurodegenerative diseases, diabetes, and viral diseases, and 
is optional for other medicines, which are highly innovative. Under the centralized procedure, a single marketing 
authorization application is submitted to the European Medicines Agency (EMA) where it will be evaluated by the 
CHMP. A favorable CHMP opinion typically results in a single marketing authorization granted by the European 
Commission in an implementing decision, known as a centralized marketing authorization. A centralized marketing 
authorization is valid for all European Union member states and, by extension (after taking the corresponding national 
implementing measures), in Norway, Iceland, and Liechtenstein. In general, the initial marketing authorization is valid 
for five years, but once renewed is usually valid for an unlimited period. Under the centralized procedure, the maximum 
timeframe for the evaluation of a marketing authorization application by the EMA is 210 days, excluding clock-stops. 
Clock-stops allow the applicant the necessary time to provide additional information in response to questions raised by 

19 
the CHMP. The clock-stops considerably extend the time taken by the CHMP to complete the evaluation of a marketing 
authorization application. Ordinarily, within 67 days of receipt of the positive scientific opinion provided by the EMA, 
the European Commission will issue a binding decision on the marketing authorization application. 
The decentralized procedure allows marketing authorization applications to be submitted simultaneously in two 
or more EU member states, whereas the mutual recognition procedure must be used if the product has been authorized in 
at least one EU member state on a national basis, and the applicant seeks approval progressively of the same medicinal 
product in one or more EU member state(s). Both the decentralized and mutual recognition procedures provide for 
approval by one or more “concerned” member state(s) based on an assessment of an application performed by one 
“reference” member state. Under the decentralized approval procedure, an applicant submits an application, or dossier, 
and related materials to the reference member state and concerned member state(s). The reference member state prepares 
a draft assessment and drafts of the related materials within 120 days of the receipt of a valid application. Within 90 days 
of receiving the reference member state’s positive assessment report, each concerned member state must approve the 
assessment report and related materials, unless they identify a potential serious risk to public health. Under the mutual 
recognition procedure, the concerned member state(s) have the same 90-day period to recognize the marketing 
authorization in the reference member state. The decentralized procedure contemplates a single clock-stop at day 105, 
which may extend the process for completing the assessment procedure. In either case, if there is a disagreement 
between member states during the assessment of the submitted data based on concerns about serious risks to public 
health, the Coordination Group for Mutual Recognition and Decentralised Procedures will consider the matter and seek 
to reach a conclusion within 60 days. If this is not possible, the reference member state can escalate the issue to the EMA 
for arbitration. The purely national procedure results in a marketing authorization in a single EU member state.  
In relation to the United Kingdom, high quality marketing authorization applications can be submitted for an 
expedited 150-day assessment to be initiated. At least 90 days prior to the intended marketing authorization application 
submission date, applicants should request a pre-submission meeting from the Medicines and Healthcare products 
Regulatory Agency (MHRA). At this meeting, the applicant will provide a short summary of the dossier and, if 
necessary, request input on specific issues, such as consideration for an orphan marketing authorization, conditional 
marketing authorization or marketing authorization under exceptional circumstances. When the marketing authorization 
applications is submitted to the MHRA, the clock will start when the application is validated for completeness of dossier 
for the regulatory review to commence. The assessment process involves two phases which are separated by a ‘clock-
off’. At Day 80 constituting the Phase 1 of the assessment procedure, matters requiring clarification will be raised with 
the applicant as a letter requesting further information (RFI). Applicants must address these matters within 60 days. 
Phase 2 of the marketing authorization assessment process begins as soon as the MHRA receives the applicant’s 
responses to the RFIs. By day 150, the MHRA will provide a decision on approvability of the product. If the MHRA 
proposes to refuse the grant of the marketing authorization, the applicant can request a review of the decision. 
In the European Union, orphan designations are assessed by the EMA’s Committee for Orphan Medicinal 
Products for binding decisions to be issued by the European Commission to promote the development of medicinal 
products that are intended for the diagnosis, prevention or treatment of life-threatening or chronically debilitating 
conditions which either affect not more than five in 10,000 persons in the EU, or where it is unlikely that the marketing 
of the medicinal product in the EU would generate sufficient return to justify the necessary investment in its 
development. In each case, there can be no satisfactory method of diagnosis, prevention or treatment of the condition 
already authorized (or, if such a method exists, the product would be a significant benefit to those affected by the 
condition). 
If the European Commission grants an orphan designation, the developer will be entitled to financial incentives 
such as reduction of fees or fee waivers. If orphan status is maintained when the marketing authorization is granted, the 
medicinal product will benefit from certain economic and marketing benefits, including up to 10 years of market 
exclusivity for the approved indication unless another “similar medicinal product” applicant can show that its product is 
safer, more effective, or otherwise clinically superior to the orphan-designated product. The 10-year market exclusivity 
can also be broken by another company developing a similar medicinal product if the marketing authorization holder is 
unable to supply sufficient quantities of the marketed orphan medicinal product. A “similar medicinal product” is 
defined as a medicinal product containing a similar active substance or substances as contained in an authorized orphan 
medicinal product, and which is intended for the same therapeutic indication. The period of market exclusivity can be 
reduced if the medicinal product no longer meets the orphan drug designation criteria at the end of the fifth year, 
including where it is shown that the product is sufficiently profitable not to justify maintenance of market exclusivity. 
Orphan designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval 
process. As in the U.S., we may apply for designation of a product as an orphan drug for the treatment of a specific 
indication in the European Union before the application for marketing authorization is made. Orphan drugs in Europe 

20 
enjoy economic and marketing benefits, including up to 10 years of market exclusivity for the approved indication 
unless another applicant can show that its product is safer, more effective, or otherwise clinically superior to the 
orphan-designated product. 
An equivalent regime is in place in the United Kingdom. Under the United Kingdom’s regime, there is no pre-
authorization orphan designation and instead a decision is made at the point of the marketing authorization grant. 
Reimbursement 
Significant uncertainty exists regarding the coverage and reimbursement status of products approved by the 
FDA and other government authorities. Sales of ELAHERE and any other products for which we may obtain approval 
depend, in part, on the availability of coverage and the adequacy of reimbursement from third-party payors.  
Within the U.S., third-party payors include government authorities or government healthcare programs, such as 
Medicare and Medicaid (which provides prescription drug benefits to low-income individuals), and private entities, such 
as managed care organizations, private health insurers and other organizations. Third-party payors may limit coverage of 
certain drug products or may manage utilization of a particular product (e.g., by requiring pre-approval (known as “prior 
authorization”) for coverage of particular prescriptions (to allow the payor to assess medical necessity)). A third-party 
payor's decision to provide coverage for a drug product does not mean that an adequate reimbursement rate will be 
approved. Adequate third-party reimbursement may not be available to enable us to maintain net price levels sufficient 
to realize an appropriate return on our investment in product development. Additionally, coverage and reimbursement 
for drug products can differ significantly from payor to payor. One third-party payor’s decision to cover a particular drug 
product or service does not ensure that other payors will also provide coverage for the medical product or service or will 
provide coverage at an adequate reimbursement rate.  
Third-party payors are increasingly challenging the price and examining the cost-effectiveness of new products 
and services in addition to their safety and efficacy. To obtain or maintain coverage and reimbursement for any approved 
drug product, we may need to collect real-world evidence and conduct pharmacoeconomic studies to demonstrate the 
medical necessity and cost-effectiveness of our product. These studies will be in addition to the studies required to obtain 
or maintain regulatory approvals. If third-party payors do not consider a product to be cost-effective compared to other 
available therapies, they may not cover the product or, if they do, the level of payment may not be sufficient to allow 
sales of a product at a profit. Thus, obtaining and maintaining reimbursement status is complex and costly. 
Within the U.S., we may be required to provide discounts or rebates under government healthcare programs or 
to certain government and private purchasers in order to obtain coverage under federal healthcare programs such as 
Medicare and Medicaid or to sell products to government purchasers. 
In the U.S., there have been ongoing efforts by federal and state governments to reform delivery of, or payment 
for, health care, which include initiatives to reduce the cost of healthcare generally and drugs specifically. See “Risk 
Factors – Risks Related to Government Regulation.” Healthcare reform efforts or any future legislation or regulatory 
actions aimed at controlling and reducing healthcare costs, including through measures designed to limit reimbursement, 
restrict access, or impose unfavorable pricing modifications on pharmaceutical products, could impact our ability to 
obtain or maintain coverage and adequate reimbursement for any approved products which could materially harm our 
business and financial results. 
In addition, in some foreign countries, the proposed pricing for a drug must be approved before it may be 
lawfully marketed. The requirements governing drug pricing vary widely from country to country. For example, the 
European Union provides options for its member states to restrict the range of medicinal products for which their 
national health insurance systems provide reimbursement and to control the prices of medicinal products for human use. 
A member state may approve a specific price for the medicinal product, or it may instead adopt a system of direct or 
indirect controls on the profitability of the company placing the medicinal product on the market. There can be no 
assurance that any country that has price controls or reimbursement limitations for pharmaceutical products will allow 
favorable reimbursement and pricing arrangements for any of our products. Historically, products launched in the 
European Union do not follow price structures of the U.S. and prices generally tend to be significantly lower. 
Companion Diagnostics 
Under the EU regulatory regime, namely Regulation (EU) 2017/746 (IVDR) on in vitro diagnostic medical 
devices (IVD), companion diagnostics (CDx) are classified as Class C devices, the second highest risk level of IVD. In 
order to place a CDx on the EU market, the general safety and performance of the CDx must be subject to a conformity 
assessment, which involves a notified body, an independent body designated by a regulatory authority in an EU Member 
State to assess the conformity with the regulatory requirements under the IVDR.  

21 
As part of the conformity assessment procedure, the notified body will seek a scientific opinion on the 
suitability of the CDx with the corresponding medicinal product from either a competent authority of an EU member 
state or the EMA. Where the CDX is to be used exclusively with a medicinal product that falls within the mandatory 
scope of the centralized procedure, then the EMA must be consulted. If the corresponding medicinal product has already 
been authorized, the notified body will consult the competent authority responsible for the authorization. 
To initiate this process the notified body will provide an “intention-to-submit-letter” to the EMA at least 
3 months prior to the planned submission date of request for a scientific opinion on suitability. This letter also triggers 
the timely appointment of the rapporteur by the CHMP or, in the case of advanced therapy medicinal products, a 
Committee for Advanced Therapies (CAT) rapporteur will be appointed and the CHMP coordinator will work closely 
with them.  
After the EMA’s acceptance of the “intention-to-submit-letter”, the notified body can submit questions 
concerning timing, regulatory or procedural aspects to the EMA within 2 months of the planned submission and request 
a pre-submission meeting with the EMA and relevant stakeholders. 
The IVDR requires the EMA’s consultation to be based on the draft summary of safety and performance and 
draft instructions for use of the device as submitted by the notified body. Aspects including the scientific validity of a 
biomarker, analytical performance and clinical performance are assessed whereas the technical documentation dossier 
for the device, including the adequacy of the analytical measures used to assess these aspects is assessed by the notified 
body as part of the conformity assessment.  
The EMA will provide its opinion within 60 days of the start of its scientific assessment, with a maximum 
extension of a further 60 days on justified grounds. If further clarification is required by the CHMP/CAT, a list of 
questions may be issued to the notified body within this 60-day extension. The CHMP will then issue a scientific opinion 
to the notified body on the suitability of the device in relation to the corresponding medicinal product by, at the latest, 
the end of this extension period. The notified body will then give due consideration to this opinion when issuing its 
decision and will convey a final decision to the EMA in the form of a formal notification to the EMA.  
Manufacturing 
We contract with third-party contract manufacturers (CMOs) for the manufacture of our product candidates for 
both our clinical and potential commercial needs. Our CMO network manufactures antibody, linker, and payload, and 
conjugates the foregoing to create bulk drug substance of our product candidates and processes the bulk drug substance 
into vialed and labeled drug product for use in humans. Although we are reliant on third parties to manufacture our 
product candidates, we have personnel with extensive manufacturing experience to oversee the relationships with our 
CMOs. 
CMOs are subject to extensive governmental regulations, and we depend on them to manufacture our product 
candidates in accordance with cGMP. We have an established quality assurance program designed to ensure that the 
CMOs involved in the manufacture of product candidates do so in accordance with cGMP and other applicable U.S. and 
foreign regulations. We believe that our current CMO network complies with such regulations. 
Human Capital Resources 
As of December 31, 2022, we had 277 full-time employees, of whom 155 were engaged in research and 
development activities. Of the 155 research and development employees, 116 employees hold post-graduate degrees, of 
which 44 hold Ph.D. degrees and 12 hold M.D. degrees. We consider our relations with our employees to be good. None 
of our employees are covered by a collective bargaining agreement. We believe our employee relations are good. 
We have entered into confidentiality agreements with all of our employees, members of our board of directors, 
and consultants. Further, we have entered into assignment of invention agreements with all of our employees. 
Our key human capital management objectives are to attract, retain, and develop the highest quality talent. 
These objectives are critical to our success and our ability to increase the value we provide for patients, shareholders, 
and stakeholders. We have several initiatives in place that support these objectives: 
• 
Enhancement of our culture through efforts aimed at making the workplace more engaging and inclusive, such 
as team events, service days, and wellbeing programs. 
• 
Commitment to diversity, equity, and inclusion across all aspects of our organization, including in our hiring, 
promotion, and development practices. At ImmunoGen, we are an equal opportunity employer where prejudice, 
racism, and intolerance are unacceptable.  
 
 

22 
• 
Development of employees through trainings and mentorship opportunities to prepare them for critical roles 
and leadership positions for the future. 
• 
Reward and support our employees through robust compensation packages, including competitive base pay, 
incentive compensation and equity programs, and provide a range of benefits, including 401(k) plan, healthcare 
and insurance benefits, paid time off, flexible work schedules, paid family and medical leave, and health and 
wellbeing programs. 
Through the company mission and these initiatives, we want to inspire our employees to build their careers with 
us and reward those who exemplify our values. 
Corporate Responsibility 
At ImmunoGen, how we do our jobs is just as important as what we do. Our culture is about putting people 
first, innovation, accountability, and teamwork. Living these values means managing our environmental, social, and 
governance (ESG) impacts effectively.   
We are currently laying the foundation for our ESG strategy. Over the last two years, we formalized board 
oversight over our ESG strategy and recently begun to assess our material ESG issues. This materiality assessment 
considers ESG topics from a wide range of stakeholders and global reporting frameworks. In the coming months, we 
will narrow our focus to a few priority areas that are most material for our business. We are committed to 
operationalizing these ESG topics through a top-down approach and maintaining consistent stakeholder engagement to 
continue to evolve our strategy.  
Corporate Information 
We were organized as a Massachusetts corporation in March 1981. Our principal offices are located at 
830 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (781) 895-0600. Our internet address 
is www.immunogen.com. Our annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on 
Form 8-K, and all amendments to those reports, are available to you free of charge through the “Investors & Media – 
Financials & Filings - SEC Filings” section of our website as soon as reasonably practicable after those materials have 
been electronically filed with, or furnished to, the Securities and Exchange Commission. Please note that the information 
contained on the web site is not a part of this Annual Report on Form 10-K. 
Item 1A.    Risk Factors 
INVESTING IN OUR COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. BEFORE DECIDING WHETHER 
TO INVEST IN OUR COMMON STOCK, YOU SHOULD CAREFULLY CONSIDER THE RISKS DESCRIBED BELOW, 
TOGETHER WITH THE OTHER INFORMATION CONTAINED IN THIS ANNUAL REPORT ON FORM 10-K, 
INCLUDING OUR CONSOLIDATED FINANCIAL STATEMENTS AND RELATED NOTES. THE RISKS AND 
UNCERTAINTIES DESCRIBED BELOW ARE THOSE THAT WE CURRENTLY BELIEVE MAY MATERIALLY 
AFFECT OUR COMPANY AND IF ANY OF THESE RISKS ACTUALLY OCCURS, OUR BUSINESS, FINANCIAL 
CONDITION, RESULTS OF OPERATIONS, OR CASH FLOW COULD BE SERIOUSLY HARMED. ADDITIONAL 
RISKS AND UNCERTAINTIES THAT WE ARE UNAWARE OF OR THAT WE CURRENTLY DEEM IMMATERIAL 
ALSO MAY BECOME IMPORTANT FACTORS THAT AFFECT OUR COMPANY AND MAY MATERIALLY IMPAIR 
OUR BUSINESS. 
Risks Related to our Financial Condition 
We have a history of operating losses, expect to incur significant additional operating losses, and may never be 
profitable. 
We have generated operating losses since our inception. As of December 31, 2022, we had an accumulated 
deficit of $1.7 billion. We may never be profitable. We expect to incur substantial additional operating losses for at least 
the near term as our development, preclinical testing, clinical trials, and commercialization of ELAHERE continue. We 
intend to continue to invest significantly in ELAHERE and our product candidates. We may encounter technological, 
regulatory, or marketing difficulties as part of this development and commercialization process that we cannot overcome 
or remedy. Our revenues to date have been primarily from upfront and milestone payments, research and development 
support, clinical materials reimbursement from our collaborators, and from royalties received from the commercial sales 
 
 
 

23 
of KADCYLA (to which we have sold our cash rights). We received approval of our first product, ELAHERE, in the 
fourth quarter of 2022, and have started generating revenue from product sales. Because of the numerous risks and 
uncertainties associated with developing and commercializing pharmaceutical drugs, we are unable to predict the extent 
of any future losses or when we will become profitable, if at all. In addition, our expenses could increase beyond 
expectations as we expand our commercial activities for ELAHERE and continue our ongoing trials with ELAHERE 
and our product candidates. Even with the approval and commercialization of ELAHERE, we will need to generate 
significant revenues from ELAHERE to achieve and maintain profitability. Even if we do become profitable, we may 
not be able to sustain or increase profitability on a quarterly or annual basis. Our failure to become and remain profitable 
would decrease the value of the company and could impair our ability to raise capital, maintain our development efforts, 
expand our business, or continue our operations and may require us to raise additional capital that would dilute your 
ownership interest. A decline in the value of our company could also cause you to lose all or part of your investment. 
There is substantial doubt about our ability to continue as a going concern. 
 
At December 31, 2022, we had $275.1 million of cash and cash equivalents on hand. Our current level of cash 
and cash equivalents is not sufficient to meet our current operating plans for the next twelve months following the 
issuance of the financial statements appearing in this Annual Report on Form 10-K. As a result, substantial doubt is 
deemed to exist regarding our ability to continue as a going concern for a period of one year from the issuance of these 
financial statements. We plan to meet our operating cash flow requirements with our current cash and cash equivalents, 
cash generated from commercial sales of ELAHERE, milestone payments from new or existing collaborations, and 
additional funds accessed through equity, debt, or other financings such as royalty financing transactions, as well as cash 
preservation activities. Such activities may not succeed. The failure of the Company to obtain sufficient funds on 
acceptable terms could have a material adverse effect on the Company’s business, results of operations, and financial 
condition and require the Company to defer or limit some or all of its research, development, clinical, and/or commercial 
projects, including trials to support potential label expansion of ELAHERE, and may materially and adversely affect our 
share price.  
 
If we are unable to obtain additional funding when needed, we may have to delay or scale back some of our 
programs or grant rights to third parties to develop and market ELAHERE or our product candidates. 
We will continue to expend substantial resources developing and commercializing ELAHERE and our product 
candidates, including costs associated with research and development, acquiring new technologies, conducting 
preclinical studies and clinical trials, obtaining regulatory approvals, manufacturing products, establishing marketing and 
sales capabilities to commercialize ELAHERE, as well as providing certain support to our collaborators in the 
development of their products. Conducting preclinical studies and clinical trials is a time-consuming, expensive, and 
uncertain process that can take years to complete, and we may never generate the necessary data or results required to 
obtain marketing approval for ELAHERE in additional indications or for our product candidates. In addition, ELAHERE 
or any of our product candidates that may receive marketing approval may not achieve commercial success. 
Accordingly, we may need to continue to rely on additional financing to achieve our business objectives. 
In addition, we cannot provide assurance that anticipated collaborator payments will, in fact, be received. 
Should such future collaborator payments not be received, we expect we could seek additional funding from other 
sources. We may elect or need to seek additional financing sooner due to a number of other factors as well, including: 
• 
if either we incur higher than expected costs or we or any of our collaborators experience slower than expected 
progress in developing product candidates and obtaining regulatory approvals; and 
• 
the acquisition of technologies and other business opportunities that require financial commitments. 
 
Additional funding may not be available to us in sufficient amounts, on favorable terms, or at all. We may raise 
additional funds through public or private financings, collaborative arrangements, or other arrangements such as royalty 
financing transactions. Any additional fundraising efforts may divert our management from their day-to-day activities, 
which may adversely affect our ability to develop and commercialize ELAHERE or our product candidates. Volatility in 
the financial markets has generally made equity and debt financing more difficult to obtain and may have a material 
adverse effect on our ability to meet our fundraising needs. Moreover, the terms of any financing may adversely affect 
the holdings or the rights of our shareholders and the issuance of additional securities, whether equity or debt, by us, or 
the possibility of such issuance, may cause the market price of our shares to decline. Debt and debt-like financing, if 
available, may involve covenants that could restrict our business activities. If we are unable to raise additional funds 
through equity, royalty, or debt financing when needed, we may be required to delay, scale back, or eliminate 

24 
expenditures for some of our commercialization activities and development programs, including restructuring our 
operations, or grant rights to develop and market ELAHERE or our product candidates that we would otherwise prefer to 
internally develop and market. If we are required to grant such rights, the ultimate value of ELAHERE or our product 
candidates to us may be reduced. 
Our ability to use our net operating loss carryforwards and certain other tax attributes to offset future taxable 
income may be limited. 
Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, a corporation that undergoes 
an “ownership change,” is subject to limitations on its ability to use its pre-change net operating loss carryforwards 
(NOLs), and other pre-change tax attributes (such as research tax credits) to offset its post-change income or taxes. For 
these purposes, an ownership change generally occurs where the equity ownership of one or more shareholders or groups 
of shareholders who own at least 5% of a corporation’s stock increases its ownership by more than 50 percentage points 
over its lowest ownership percentage within a three-year period. We may have experienced such ownership changes in 
the past, and we may experience shifts in our stock ownership, some of which are outside our control. These ownership 
changes may subject our existing NOLs or credits to substantial limitations under Sections 382 and 383. Accordingly, 
we may not be able to utilize a material portion of our NOLs or credits. As of December 31, 2022, we had federal NOLs 
of $443.3 million available to reduce federal taxable income, if any, that can be carried forward indefinitely. As of 
December 31, 2022, we also had $85.6 million of federal credit carryforwards that will begin to expire in 2027. 
Limitations on our ability to utilize those NOLs to offset U.S. federal taxable income could potentially result in 
increased future tax liability to us. In addition, at the state level, there may be periods during which the use of NOLs is 
suspended or otherwise limited, which could accelerate or permanently increase state taxes owed. 
Risks Related to Our Business and Industry 
Our prospects are highly dependent on the success of our only approved product, ELAHERE, which received 
FDA approval under an accelerated approval pathway. If we are unable to maintain approval for, or successfully 
commercialize, ELAHERE, our business, financial condition, results of operations, as well as our prospects, could 
be adversely affected. 
We obtained FDA approval for ELAHERE for the treatment of adult patients with FRα positive, platinum-
resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to three prior systemic 
treatment regimens. We have not obtained any other marketing approvals for ELAHERE or our product candidates. We 
first commercialized ELAHERE in the U.S. in the fourth quarter of 2022 and therefore do not have a long history 
operating as a commercial company. 
The FDA approved ELAHERE under the accelerated approval pathway and continued approval may be 
contingent upon verification and description of clinical benefit in a confirmatory trial. Our intent is for our ongoing 
Phase 3 MIRASOL trial to serve as our confirmatory trial and, if successful, to support full approval of ELAHERE. If 
the MIRASOL trial is unsuccessful, the FDA could require us to conduct additional trials to remain on the market, could 
require updates to our label, or could ultimately seek to withdraw marketing approval for ELAHERE. Separate from the 
confirmatory trial, ELAHERE is subject to additional post-approval requirements and commitments, including post-
approval requirements to conduct a randomized clinical trial to evaluate the safety of the recommended dose of 
ELAHERE and alternative dosing schedules, conduct a dose escalation trial to determine the appropriate starting dose in 
patients with moderate hepatic impairment, and conduct a clinical trial or revise existing trials to incorporate 
prospectively scheduled ophthalmologic assessments to characterize the incidence and severity of ocular events and 
evaluate risk mitigation strategies. We are also subject to other post-approval requirements, including submission to the 
FDA of all promotional materials 30-120 days prior to their dissemination. 
Failure to meet any of our post-approval requirements or commitments may result in adverse regulatory actions. 
Products that receive accelerated approval may be subject to expedited withdrawal procedures if post-approval trials fail 
to verify the predicted clinical benefit. The FDA could seek to withdraw accelerated approval for multiple reasons, 
including if we fail to conduct any required post-approval trial, other evidence shows that the product is not safe or 
effective under the conditions of use, or we disseminate promotional materials that are found by the FDA to be false or 
misleading. 
Our long-term viability, growth, and ability to generate revenue depend heavily on successfully 
commercializing and obtaining full regulatory approval for ELAHERE. ELAHERE will be our first commercial launch, 

25 
and its successful commercialization and our receipt of full regulatory approval in the United States are subject to many 
risks. 
If ELAHERE or our product candidates or those of our collaborators do not gain market acceptance, our 
business will suffer. 
ELAHERE may not gain market acceptance among physicians, patients, healthcare payors, and other members 
of the medical community. The degree of market acceptance of ELAHERE, or other products we may develop, will 
depend on a number of factors, including: 
• 
their level of clinical efficacy and safety; 
• 
the clinical indications for which they are approved; 
• 
the prevalence and severity of any adverse events and their overall safety profile; 
• 
the willingness of physicians to include FRα testing as part of routine patient care; 
• 
their advantage over alternative treatment methods; 
• 
our/the marketer’s and our collaborators’ ability to gain acceptable reimbursement and the reimbursement 
policies of government and other third-party payors; and 
• 
the quality of the distribution capabilities of the party(ies) responsible to market and distribute the product(s). 
 
Physicians may elect not to recommend the therapies for any number of other reasons, including whether the 
physicians are already using competing products that satisfy their treatment objectives. If our products do not achieve 
significant market acceptance and use, we will not be able to recover the significant investment we have made in 
developing such products and our business will be severely harmed. 
ELAHERE has received FDA approval as a monotherapy in a limited patient population, and additional 
successful clinical trials and regulatory approvals may be needed to expand its indications.  Such trials may fail, 
or we may fail to obtain such regulatory approvals, either of which could adversely affect our business and 
prospects. 
The FDA granted accelerated approval of ELAHERE as a monotherapy for the treatment of patients with FRα-
positive platinum-resistant epithelial ovarian cancer, fallopian tube, or primary peritoneal cancer who have been 
previously treated with one to three prior systemic treatments. We do not anticipate obtaining regulatory approval for 
ELAHERE in additional patient populations or as a combination therapy without additional clinical data. Such additional 
clinical trials are ongoing and will require time and expense, and these trials may fail to generate results that support 
additional indications. If we are unable to expand the indications for use of ELAHERE, our business and prospects could 
be adversely affected. 
We currently do not have the direct sales, marketing, or distribution capabilities necessary to successfully 
commercialize our products on a global scale and may rely on third parties to support development and 
commercialization activities. 
We are commercializing ELAHERE in the United States and currently intend to commercialize ELAHERE in 
the European Union and UK if we receive marketing approval in these territories. We may choose to rely on third parties 
to market and sell ELAHERE outside of the United States, the European Union, and the UK, either through distributor 
or out-licensing arrangements. For example, in October 2020, we entered into a collaboration and license agreement with 
Huadong under which Huadong will exclusively develop and commercialize ELAHERE in Greater China. We retain all 
rights to ELAHERE in the rest of the world. In addition, arrangements with third parties to develop and commercialize 
ELAHERE or other future products could significantly limit the revenues we derive from these compounds, and these 
third parties, including Huadong, may fail to commercialize our compounds successfully. 
If our ADC technology does not produce safe, effective, and commercially viable products or if such products fail 
to obtain or maintain FDA approval, our business will be severely harmed. 
Our ADC technology yields novel product candidates for the treatment of cancer. To date, only two ADCs 
using our technology, KADCYLA and ELAHERE, have obtained marketing approval. Our ADC product candidates 
and/or those of our collaborators’ may not prove to be safe, effective, or commercially viable treatments for cancer and 
as a result, our ADC technology may not result in any future meaningful benefits to us or for our current or potential 

26 
collaborators. Furthermore, we are aware of only a limited number of other compounds that are based on technology 
similar to our ADC technology that have obtained marketing approval by the FDA. If our ADC technology fails to 
generate additional product candidates that are safe, effective, and commercially viable treatments for cancer or such 
product candidates fail to obtain or maintain FDA and foreign regulatory authorities approval, our business will be 
severely harmed. 
Clinical trials for ELAHERE, our product candidates, and those of our collaborators will be lengthy and 
expensive, and their outcome is uncertain. 
Before we can convert our accelerated approval for ELAHERE to full approval, obtain regulatory approval for 
ELAHERE in additional indications, or obtain regulatory approval for our product candidates, we must demonstrate 
through clinical testing that our products are safe and effective for use in humans. Conducting clinical trials is a time-
consuming, expensive, and uncertain process and typically requires years to complete. In our industry, the results from 
preclinical studies and early clinical trials often are not predictive of results obtained in later-stage clinical trials. Some 
compounds that have shown promising results in preclinical studies or early clinical trials subsequently fail to establish 
sufficient safety and efficacy data necessary to obtain regulatory approval. For example, despite encouraging results 
from earlier clinical trials of ELAHERE, our FORWARD I Phase 3 clinical trial evaluating ELAHERE compared to 
chemotherapy in women with FRα-positive, platinum-resistant ovarian cancer, did not meet the primary endpoint in 
either the entire treatment population or the pre-specified high FRα expression population. Based on post hoc 
exploratory analyses of the FORWARD I results and consultations with the FDA, we implemented two new trials of 
ELAHERE, SORAYA and MIRASOL. We reported positive results from our SORAYA trial, which served as the basis 
for ELAHERE’s accelerated approval, but results from our ongoing MIRASOL trial may not show positive results 
consistent with our SORAYA trial, which would cause significant harm to our business and future prospects. 
Before we can commence clinical trials for a therapeutic candidate, we must conduct extensive preclinical 
testing and studies and submit an IND to the FDA and foreign regulatory authorities. We cannot be sure that submission 
of an IND will result in the FDA and/or foreign regulatory authorities allowing our clinical trials to begin on the 
timelines we expect, if at all, as the FDA and/or foreign regulatory authorities may require additional preclinical, 
toxicology, or other in vivo or in vitro data to support the IND. Additionally, at any time during the clinical trials, we, 
our collaborators, or the FDA or other regulatory authority might delay or halt any clinical trials of our products for 
various reasons, including: 
• 
occurrence of unacceptable toxicities or side effects; 
• 
ineffectiveness of the product; 
• 
insufficient drug supply, including delays in obtaining supplies/materials necessary for manufacturing such 
drugs; 
• 
negative or inconclusive results from the clinical trials, or results that necessitate additional nonclinical studies 
or clinical trials; 
• 
delays in obtaining or maintaining required approvals from institutions, review boards, or other reviewing 
entities at clinical sites; 
• 
delays in patient enrollment; 
• 
insufficient funding or a reprioritization of financial or other resources; 
• 
our or our collaborators’ inability to develop and obtain approval for any companion in vitro diagnostic devices 
that the FDA or other regulatory authority may conclude must be used with such drug to ensure its safe use; or 
• 
other reasons that are internal to the businesses of our collaborators and third-party suppliers, which they may 
not share with us. 
If we are required by the FDA, or foreign regulatory agencies, to perform studies and clinical trials in addition 
to those that we currently anticipate, or if there are any delays in our or our partners completing clinical trials or the 
development of any of ELAHERE or our product candidates, our expenses could increase beyond expectations. Any 
failure or substantial delay in successfully completing clinical trials and obtaining additional regulatory approvals for 
ELAHERE or our product candidates could severely harm our business. 

27 
Interim, top-line, or preliminary data from our clinical trials that we announce may change as more patient data 
become available and are subject to audit and verification procedures that could result in material changes in the 
final data. 
From time to time, we have publicly disclosed, and in the future will disclose, preliminary or top-line data from 
our preclinical studies and clinical trials, which are based on preliminary analyses of then- available data, and the results 
and related findings and conclusions are subject to change following a more comprehensive review of the data related to 
the particular study or trial. We also make assumptions, estimations, calculations, and conclusions as part of our analyses 
of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. Therefore, final 
results from the trials may differ from the top-line results initially reported, and the final results may indicate different 
conclusions once additional data have been evaluated. As such, top-line data should be viewed with caution until the 
final data are available. 
From time to time, we may also disclose interim data from our preclinical studies and clinical trials. Interim 
data from clinical trials that we may complete are subject to the risk that one or more of the outcomes may materially 
change as patient enrollment continues and more data become available. Adverse differences between top-line, 
preliminary, or interim data, on the one hand, and final data, on the other, could significantly harm our business 
prospects. Further, disclosure of interim data by us or by our competitors could result in volatility in the price of our 
common stock. 
Further, others, including regulatory agencies, may not accept or agree with our assumptions, estimates, 
calculations, conclusions, or analyses, or may interpret or weigh the importance of data differently, which could 
negatively affect the approvability or commercialization of the particular product. 
In addition, the information we choose to publicly disclose regarding a particular study or clinical trial is based 
on what is typically extensive information, and you or others may not agree with what we determine is material or 
otherwise appropriate information to include in our disclosure. If the final results differ from the interim, top-line, or 
preliminary data, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to 
obtain or maintain approval for, and to commercialize, ELAHERE or our product candidates may be harmed, which may 
negatively affect our business, financial condition, results of operations, and prospects. 
We face product liability risks and may not be able to obtain adequate insurance. 
The use of ELAHERE or our product candidates during testing or after approval entails an inherent risk of 
adverse effects, which could expose us to product liability claims. Regardless of their merit or eventual outcome, product 
liability claims may result in: 
• 
decreased demand for our product; 
• 
injury to our reputation and significant negative media attention; 
• 
withdrawal of clinical trial volunteers; 
• 
costs of litigation; 
• 
distraction of management; and 
• 
substantial monetary awards to plaintiffs. 
 
We may not have sufficient resources to satisfy any liability resulting from these claims. While we currently 
have product liability insurance for the use of ELAHERE and products that are in clinical testing, our coverage may not 
be adequate in scope to protect us in the event of a successful product liability claim. Further, we may not be able to 
maintain our current insurance, increase our insurance coverage as may be needed, or obtain general product liability 
insurance on reasonable terms and at an acceptable cost as we expand commercial activities for ELAHERE. This 
insurance, even if we can obtain and maintain it, may not be sufficient to provide us with adequate coverage against 
potential liabilities. If we are unable to maintain sufficient insurance coverage at an acceptable cost or to otherwise 
protect against potential product liability claims, it could prevent or inhibit the development and commercial production 
and sale of ELAHERE or our product candidates, which could severely harm our business. 
 
 

28 
We may be unable to compete successfully. 
The markets in which we compete are well-established and intensely competitive. We may be unable to 
compete successfully against our current and future competitors. Our failure to compete successfully may result in lower 
volume sold, pricing reductions, reduced gross margins, and failure to achieve market acceptance for ELAHERE or any 
of our product candidates that may receive marketing approval. Our competitors include research institutions, 
pharmaceutical companies, and biotechnology companies, such as Pfizer, Seattle Genetics, Roche, Astellas, 
AstraZeneca, Daiichi Sankyo, GlaxoSmithKline, AbbVie, Mersana Therapeutics, Eisai, Sutro BioPharma, and the 
Menarini Group. For example, pivekimab is in development for the treatment of BPDCN and, if approved, would 
compete with the Menarini Group’s ELZONRIS® (tagraxofusp), which is approved by the FDA for sale in the United 
States and by the EMA for sale in the European Union for the treatment of BPDCN. Many of our competitors have 
substantially more experience and more capital, research and development, regulatory, manufacturing, human, and other 
resources than we do. As a result, they may: 
• 
develop products that are safer or more effective than ELAHERE or our product candidates; 
• 
obtain FDA and other regulatory approvals or reach the market with their products more rapidly than we can, 
reducing the sales or potential sales of ELAHERE or any of our product candidates that may receive marketing 
approval; 
• 
devote greater resources to market or sell their products; 
• 
adapt more quickly to new technologies and scientific advances; 
• 
initiate or withstand substantial price competition more successfully than we can; 
• 
have greater success in recruiting skilled scientific workers from the limited pool of available talent; 
• 
more effectively negotiate third-party licensing and collaboration arrangements; and 
• 
take advantage of acquisitions or other opportunities more readily than we can. 
 
A number of pharmaceutical and biotechnology companies are currently developing products targeting the 
same types of cancer that we target, and some of our competitors’ products have entered clinical trials or already are 
commercially available. 
ELAHERE and any of our product candidates that may receive marketing approval will also compete against 
well-established, existing therapeutic products that are currently reimbursed by government healthcare programs, private 
health insurers, and health maintenance organizations. In addition, ELAHERE and our product candidates, if approved 
and commercialized, may face competition from biosimilars. The ACA, which included the BPCIA, amended the Public 
Health Service Act to create an abbreviated approval pathway for two types of “generic” biologics-biosimilars and 
interchangeable biologic products. The BPCIA establishes a pathway for the FDA approval of follow-on biologics and 
provides twelve years data exclusivity for reference products and an additional six-month exclusivity period if pediatric 
trials are conducted. In Europe, the EMA has issued guidelines for approving products through an abbreviated pathway, 
and biosimilars have been approved in Europe. If a biosimilar version of ELAHERE or one of our product candidates 
was approved in the United States or Europe, it could have a negative effect on sales and gross profits of the product and 
our financial condition. 
We face and will continue to face intense competition from other companies for collaborative arrangements 
with pharmaceutical and biotechnology companies, for relationships with academic and research institutions, and for 
licenses to proprietary technology. In addition, we anticipate that we will face increased competition in the future as new 
companies enter our markets and as scientific developments surrounding antibody-based therapeutics for cancer continue 
to accelerate. While we will seek to expand our technological capabilities to remain competitive, research and 
development by others may render our technology or ELAHERE or our product candidates obsolete or noncompetitive 
or result in treatments or cures superior to any therapy developed by us. 
Unfavorable global economic conditions, as well as regional conflicts, could adversely affect our business, 
financial condition, and results of operations. 
Our results of operations could be adversely affected by general conditions in the global economy and in the 
global financial markets. For example, the global economy has experienced extreme volatility and disruptions, including 
significant volatility in commodity and market prices, declines in consumer confidence, declines in economic growth, 
supply chain interruptions, uncertainty about economic stability, and inflation. Unfavorable economic conditions could 
result in a variety of risks to our business, including demand and pricing for our products, difficulty in forecasting our 

29 
financial results, and our ability to raise additional capital when needed and on acceptable terms. A weak or declining 
economy could also strain our suppliers, possibly resulting in supply chain disruptions. These and other economic 
factors or regional conflicts could adversely affect our business and results of operations. 
A pandemic, epidemic, or outbreak of an infectious disease, such as the COVID-19 pandemic, may materially and 
adversely affect our business and our financial results. 
The spread of COVID-19 has affected the global economy, our operations, clinical trial activities, and supply 
chain and may continue to do so. Even with the approval of vaccines for COVID-19, the COVID-19 pandemic is still 
evolving. In the recent past, the pandemic resulted in the implementation of various responses, including government-
imposed quarantines, travel restrictions, and other public health safety measures, as well as reported adverse impacts on 
healthcare resources, facilities, and providers across the United States, and in other countries worldwide. The continued 
impact of COVID-19 may result in a period of business disruption, including delays in our clinical trials or delays or 
disruptions in our supply chain. For example, COVID-19 slowed site activation and patient enrollment for both 
SORAYA and MIRASOL, which resulted in a limited delay in patient accrual for each of these trials. The pandemic 
may further delay enrollment in trials due to prioritization of hospital resources toward the pandemic, the resumption of 
restrictions on travel, and some patients may be unwilling to enroll in our trials or be unable to comply with clinical trial 
protocols if quarantines or travel restrictions impede patient movement or interrupt healthcare services, which would 
delay our ability to conduct clinical trials or release clinical trial results. COVID-19 may also affect employees of third-
party contract research organizations that we rely upon to carry out our clinical trials or the operations at our third-party 
manufacturers, which could result in delays or disruptions in our trials or in product supply. 
We cannot presently predict the scope and severity of any additional potential business shutdowns or 
disruptions as a result of the COVID-19 pandemic, including due to new variants of COVID-19. If we or any of the third 
parties with whom we engage, however, were to experience further shutdowns or other business disruptions, our ability 
to conduct our business in the manner and on the timelines presently planned could be materially and negatively 
affected, which could have a material adverse impact on our business and our results of operation and financial 
condition. 
Risks Related to Our Dependence on Third Parties 
If our collaborators fail to perform their obligations under our agreements with them or determine not to 
continue with clinical trials, our business could be severely affected. 
The development and commercialization of ELAHERE and our product candidates depends, in part, upon the 
formation and maintenance of collaborative arrangements. Collaborations provide an opportunity for us to: 
• 
generate cash flow and revenue; 
• 
fund some of the costs associated with our internal research and development, preclinical testing, clinical trials, 
and manufacturing; 
• 
seek and obtain regulatory approvals faster than we could on our own; 
• 
successfully commercialize ELAHERE and our product candidates; and 
• 
secure access to targets which, due to intellectual property restrictions, would otherwise be unavailable to our 
technology. 
 
If we fail to secure or maintain successful collaborative arrangements, the development and marketing of 
compounds that use our technology may be delayed, scaled back, or otherwise may not occur. In addition, we may be 
unable to negotiate other collaborative arrangements or, if necessary, modify our existing arrangements on acceptable 
terms. We cannot control the amount and timing of resources our collaborators may devote to ELAHERE or our product 
candidates. Our collaborators may separately pursue competing product candidates, therapeutic approaches, or 
technologies to develop treatments for the diseases targeted by us or our collaborative efforts, or may decide, for reasons 
that may not be known to us or with which we may disagree, to discontinue development of our products under our 
agreements with them. Any of our collaborators may slow or discontinue the development of a product covered by a 
collaborative arrangement for reasons that include, but are not limited to: 

30 
• 
a change in the collaborative partner’s strategic focus as a result of merger, management changes, adverse 
business events, or other causes; 
• 
a change in the priority of the product relative to other programs in the collaborator’s pipeline; 
• 
a reassessment of the patent situation related to the compound or its target; 
• 
a change in the anticipated competition for the product candidate; 
• 
preclinical studies and clinical trial results; and 
• 
a reduction in the financial resources the collaborator can or is willing to apply to the development of new 
compounds. 
 
Even if our collaborators continue their collaborative arrangements with us, they may nevertheless determine 
not to actively pursue the development or commercialization of any resulting product candidates. Also, our collaborators 
may fail to perform their obligations under the collaborative agreements or may be slow in performing their obligations. 
Our collaborators can terminate our collaborative agreements under certain conditions. The decision to advance a 
product candidate that is covered by a collaborative agreement through clinical trials and ultimately to 
commercialization is, in some cases, at the discretion of our collaborators. If any collaborative partner were to terminate 
or breach our agreements, fail to complete its obligations to us in a timely manner, or decide to discontinue its 
development of a product candidate, our anticipated revenue from the agreement and the development and 
commercialization of the product candidates could be severely limited or eliminated. If we are not able to establish 
additional collaborations or any or all of our existing collaborations are terminated and we are not able to enter into 
alternative collaborations on acceptable terms, or at all, our continued development, manufacture, and commercialization 
of our product candidates could be delayed or scaled back as we may not have the funds or capability to continue these 
activities. If our collaborators fail to successfully develop and commercialize ADC compounds, our business prospects 
could be harmed. 
If our product requirements for clinical trials or commercialization are significantly higher than we estimated, 
the inability to procure additional antibody production, conjugation, or fill/finish services in a timely manner 
could impair our ability to initiate or advance our clinical trials or commercialization of ELAHERE or our 
product candidates. 
We rely on third-party suppliers to manufacture antibodies used in our own proprietary compounds. Due to the 
specific nature of the antibody and availability of production capacity, there is significant lead time required by these 
suppliers to provide us with the needed materials. If our antibody requirements for clinical or commercial materials to be 
manufactured are significantly higher than we estimated, we may not be able to readily procure additional antibody 
which would impair our ability to advance our clinical trials currently in process or initiate additional trials or 
commercialize ELAHERE or our product candidates. We also rely on third parties to manufacture bulk drug substance 
and convert it into filled and finished vials of drug product for clinical use and commercial sales. If our product 
requirements are significantly higher than we estimated, we may not be able to readily procure slots to manufacture bulk 
drug substance or to convert drug substance into filled and finished vials of drug product for clinical or commercial use. 
There can be no assurance that we will not have supply problems that could delay or stop our clinical trials, hinder our 
commercialization efforts, or otherwise could have a material adverse effect on our business. 
We are currently contractually required to obtain DM4 used in ELAHERE from a single third-party 
manufacturer, and any delay or interruption in such manufacturer’s operations could impair our ability to 
advance preclinical and clinical trials and commercialization of ELAHERE. 
We rely on a sole third-party supplier, Società Italiana Corticosteroidi S.r.l, to manufacture the DM4 used in 
ELAHERE. Any delay or interruption in the operations of our sole third-party supplier and/or our supply of DM4 could 
lead to a delay or interruption in our manufacturing operations, preclinical studies, clinical trials, and commercialization 
of ELAHERE, which could negatively affect our business. 
We currently rely on, and expect to continue to rely on, third-party manufacturers to produce our antibodies, 
linkers, payloads, drug substance, and drug product for ELAHERE and our product candidates and any delay or 
interruption in such manufacturers’ operations could impair our ability to advance clinical trials and 
commercialization. 
We rely on third-party contract manufacturers to produce sufficiently large quantities of drug materials that are 
and will be needed for clinical trials and commercialization of ELAHERE and our product candidates.  We have 

31 
established relationships with third-party manufacturers to provide clinical and commercial supply, but these third-party 
manufacturers may not be able to meet our needs with respect to timing, quantity, or quality of materials. If we are 
unable to contract for a sufficient supply of needed materials on acceptable terms, or if we should encounter delays or 
difficulties in our relationships with manufacturers, our ability to commercialize ELAHERE may be adversely affected.  
Additionally, our clinical trials may be delayed, thereby delaying the submission of applications for regulatory approval 
and the market introduction and subsequent commercialization of our product candidates. Any such delays may lower 
our revenues and potential profitability. 
The facilities used to manufacture ELAHERE and our product candidates (drug substance and drug product) are 
subject to periodic inspection by the FDA and similar regulatory authorities.  These facilities generally must be inspected 
by the FDA (and other similar regulatory agencies outside the United States depending on where marketing 
authorizations are filed) before marketing authorizations are approved. In the United States, if we want to change 
manufacturers or add additional manufacturers following product approval, the FDA must approve the use of these 
manufacturers through a supplemental BLA. We are completely dependent on our contract manufacturers for 
compliance with cGMPs in connection with the manufacture of ELAHERE and our product candidates. If our contract 
manufacturers cannot successfully manufacture material that conforms to our specifications and the regulatory 
requirements of the FDA or others, we will not be able to use the products produced at their manufacturing facilities. In 
addition, we have no control over the ability of our contract manufacturers to maintain adequate quality control, quality 
assurance, and qualified personnel. If the FDA or a comparable foreign regulatory authority finds that these facilities do 
not comply with cGMP, we may need to find alternative manufacturing facilities, which would significantly impact our 
ability to successfully develop and commercialize ELAHERE and our product candidates and could result in inventory 
write-offs that adversely affect our results of operations. Further, our failure, or the failure of our third-party 
manufacturers, to comply with these or other applicable regulations could result in sanctions being imposed on us, 
including clinical holds, fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, license 
revocation, seizures or recalls of ELAHERE or our product candidates, operating restrictions and criminal prosecutions, 
any of which could significantly and adversely affect our business and product supplies. 
We rely on a third-party to develop, manufacture, and commercialize the companion diagnostic for ELAHERE, 
and any delay or interruption in supply could negatively impact our commercial activities. 
We rely on RTD for the design, development, manufacture, and commercialization of a companion diagnostic 
for ELAHERE. Roche has received FDA approval for the VENTANA FOLR1 RxDx Assay, a companion diagnostic 
that measures FRα tumor expression to select patients eligible for treatment with ELAHERE. Risks related to the 
development, manufacture, and commercialization of companion diagnostics are similar to the risks we face with respect 
to our drug products, including risks related to manufacturing sufficient supply, compliance with manufacturing 
standards and other regulatory requirements, and gaining market acceptance. Any delays or difficulties in the 
manufacture or commercialization of the companion diagnostic, could impact our commercialization of ELAHERE. For 
example, a manufacturing delay might result in a shortage of the companion diagnostic being supplied to the testing 
laboratories, which might impede their ability to deliver test results promptly and impact our commercialization of 
ELAHERE. In addition, if Roche decides to discontinue selling or manufacturing the companion diagnostic or our 
relationship otherwise terminates, we may not be able to enter into arrangements with another diagnostic company to 
obtain supplies of an alternative diagnostic test for use with ELAHERE or do so on commercially reasonable terms, 
which could adversely affect commercialization. 
The FDA, the EMA, or comparable foreign regulatory authorities could require the clearance or approval of 
additional companion diagnostics as a condition of approval for our product candidates, which would require substantial 
financial resources and could delay regulatory approval. We would be dependent on the sustained cooperation and effort 
of third-party collaborators to develop these companion diagnostics, and our collaborators may encounter difficulties in 
developing such tests, including issues relating to the selectivity and/or specificity of the diagnostic, analytical 
validation, reproducibility, or clinical validation, or in obtaining regulatory clearance or approval for such companion 
diagnostic. Any delay or failure by our collaborators to develop or obtain regulatory clearance or approval of such 
companion diagnostics, if necessary, could delay or prevent approval of our product candidates. 

32 
Risks Related to Our Intellectual Property 
If we are unable to protect our intellectual property rights adequately, the value of our technology, ELAHERE, 
and our product candidates could be diminished. 
Our success depends in part on obtaining, maintaining, and enforcing our patents and other proprietary rights 
and our ability to avoid infringing the proprietary rights of others. We seek to protect our proprietary position by filing 
patent applications in the United States and in foreign countries that cover ELAHERE, our other novel product 
candidates and their uses, pharmaceutical formulations and dosages, and processes for the manufacture of them. Our 
patent portfolio currently includes both patents and patent applications. Patent law relating to the scope of claims in the 
biotechnology field in which we operate is still evolving, is surrounded by a great deal of uncertainty, and involves 
complex legal, scientific, and factual questions. To date, no consistent policy has emerged regarding the breadth of 
claims allowed in biotechnology patents. Accordingly, our pending patent applications may not result in issued patents 
or in patent claims as broad as in the original applications. Although we own numerous patents, the issuance of a patent 
is not conclusive as to its validity or enforceability. Through litigation, a third party may challenge the validity or 
enforceability of a patent after its issuance. In addition, the patent prosecution process is expensive and time-consuming. 
We may not be able to file and prosecute all necessary or desirable patent applications at a reasonable cost or in a timely 
manner. We may choose not to seek patent protection for certain innovations and may choose not to pursue patent 
protection in certain jurisdictions. Under the laws of certain jurisdictions, patents or other intellectual property rights 
may be unavailable or limited in scope. It is also possible that we will fail to identify patentable aspects of our research 
and development before it is too late to obtain patent protection. 
Following approval of ELAHERE in the U.S., we timely filed five applications for patent term extension. If one 
or more of the applications for patent term extension are deemed to be allowable by the U.S. Patent and Trademark 
Office, we will be able to designate one to proceed to grant, and thereby extend the term of one U.S. patent covering 
ELAHERE. Even if an extension is granted, any such extension may be shorter than what we seek or may otherwise fail 
to provide meaningful protection for ELAHERE.  
Patents and patent applications owned or licensed by us may become the subject of inter partes review, post-
grant review, ex parte reexamination, interference, opposition, nullity, or other proceedings in a court or patent office in 
the United States or in a foreign jurisdiction to determine validity, enforceability, patentability, or priority of invention, 
which could result in substantial cost to us. An adverse decision in such a proceeding may result in our inability to gain 
issuance of a patent from a pending patent application or our loss of rights under a patent or patent application. It is 
unclear how much protection, if any, will result from our patents if we attempt to enforce them or if they are challenged 
in court or in other proceedings. A competitor may successfully invalidate our patents, or a challenge could result in 
limitations of the patents’ coverage. The courts continue to interpret various aspects of patent-related laws and related 
agency rules in ways that we cannot predict, potentially making it easier for competitors and other interested parties to 
challenge our patents, which, if successful, could have a material adverse effect on our business and prospects. In 
addition, the cost of litigation or patent office proceedings to uphold the validity of patents can be substantial. If we are 
unsuccessful in these proceedings, third parties may be able to use our patented technology and may be able to do so 
without paying us licensing fees or royalties. Moreover, competitors may infringe our patents or successfully avoid them 
through design innovation. To prevent infringement or unauthorized use, we may need to file infringement claims, which 
are expensive and time-consuming. In an infringement proceeding, a court may decide that a patent of ours is not valid. 
Even if the validity of our patents were upheld, a court may refuse to stop the other party from using the technology at 
issue on the ground that its activities are not covered by our patents or that the facts surrounding the other party’s use of 
our technology do not satisfy the legal requirements to grant such an injunction. 
Policing unauthorized use of our intellectual property is difficult, and we may not be able to prevent 
misappropriation of our proprietary rights, particularly in countries where the laws may not protect such rights as fully as 
in the United States. 
In addition to our patent rights, we also rely on unpatented technology, trade secrets, know-how, and 
confidential information. Third parties may independently develop substantially equivalent information and techniques 
or otherwise gain access to or disclose our technology. We may not be able to effectively protect our rights in unpatented 
technology, trade secrets, know-how, and confidential information. We require each of our employees, consultants, and 
corporate partners to execute a confidentiality agreement at the commencement of an employment, consulting, or 
collaborative relationship with us. Further, we require that all employees enter into assignment of invention agreements 

33 
as a condition of employment. However, these agreements may not provide effective protection of our information, or, in 
the event of unauthorized use or disclosure, they may not provide adequate remedies. If we are unable to prevent 
material disclosure of the trade secrets and other intellectual property related to our technologies to third parties, we may 
not be able to establish or maintain the competitive advantage that we believe is provided by such intellectual property, 
adversely affecting our market position and business and operational results. 
We may incur substantial costs as a result of litigation or other proceedings relating to patent and other 
intellectual property rights held by third parties and we may be unable to protect our rights to, or to 
commercialize, ELAHERE or our product candidates. 
Patent litigation is very common in the biotechnology and pharmaceutical industries. Third parties may assert 
patent or other intellectual property infringement claims against us with respect to our technologies, products, or other 
matters. From time to time, we have received correspondence from third parties alleging that, or inquiring whether, we 
infringe their intellectual property rights. Any claims that might be brought against us alleging infringement of patents 
may cause us to incur significant expenses and, if successfully asserted against us, may cause us to pay substantial 
damages and limit our ability to use the intellectual property subject to these claims. Even if we were to prevail, any 
litigation would be costly and time-consuming and could divert the attention of our management and key personnel from 
our business operations. Furthermore, as a result of a patent infringement suit, we may be forced to stop or delay 
developing, manufacturing, or selling products that incorporate the challenged intellectual property unless we enter into 
royalty or license agreements. There may be third-party patents, patent applications, and other intellectual property 
relevant to our products that may block or compete with our products or processes of which we are currently unaware 
with claims that cover the use or manufacture of our drug candidates or the practice of our related methods. Because 
patent applications can take many years to issue, there may be currently pending patent applications that may later result 
in issued patents that our drug candidates may infringe. In addition, we sometimes undertake research and development 
with respect to products even when we are aware of third-party patents that may be relevant to our products, on the basis 
that such patents may be challenged or licensed by us or that the Safe Harbor under 35 U.S.C. 271(e) applies. If our 
subsequent challenge to such patents were not to prevail, we may not be able to commercialize our products after having 
already incurred significant expenditures unless we are able to license the intellectual property on commercially 
reasonable terms. We may not be able to obtain such license agreements on terms acceptable to us, if at all. Even if we 
were able to obtain licenses to such technology, some licenses may be non-exclusive, thereby giving our competitors 
access to the same technologies licensed to us. Ultimately, we may be unable to commercialize some of our products or 
may have to cease some of our business operations, which could severely harm our business. 
Any inability to license proprietary technologies or processes from third parties that we use in connection with 
the development and manufacture of ELAHERE or our product candidates may impair our business. 
Other companies, universities, and research institutions have or may obtain patents that could limit our ability 
to use, manufacture, market, or sell ELAHERE or our product candidates or impair our competitive position. As a result, 
we would have to obtain licenses from other parties before we could continue using, manufacturing, marketing, or 
selling ELAHERE or our potential candidates. Any necessary licenses may not be available on commercially acceptable 
terms, if at all. If we do not obtain the required licenses, we may not be able to market our products at all or we may 
encounter significant delays in product development while we redesign products or methods that are found to infringe 
the patents held by others. 
Risks Related to Government Regulation 
Side effects, serious adverse events, or other undesirable properties associated with ELAHERE or our product 
candidates could delay or halt clinical trials, affect our ability to obtain or maintain regulatory approval, limit the 
commercial profile reflected in product labeling, or negatively affect market acceptance and commercial sales. 
The prescribing information for ELAHERE includes a boxed warning related to the risk of severe ocular 
toxicities, including visual impairment, keratopathy, dry eye, photophobia, eye pain, and uveitis, as well as other 
warnings and precautions for various toxicities and reactions, including pneumonitis, peripheral neuropathy, and 
embryo-fetal toxicity. Side effects and toxicities associated with ELAHERE, as well as the warnings, precautions, and 
requirements listed in the prescribing information, could affect the willingness of physicians to prescribe, and patients to 
use, ELAHERE and negatively affect market acceptance and commercial sales. Patients receiving ELAHERE may 
experience serious adverse events in the future, whether the serious adverse events are disclosed in the prescribing 

34 
information or are newly reported. Further, patients receiving our products with co-morbid diseases not previously 
studied may experience new or different serious adverse events. Reports of adverse events or new safety concerns 
involving ELAHERE, including from our ongoing and recently completed trials, could result in the limitation or 
withdrawal of regulatory approval, implementation of a risk evaluation mitigation strategy or the inclusion of 
unfavorable information in our product labeling, such as additional boxed warnings, limitations of use, contraindications, 
and warnings and precautions. 
Additionally, undesirable side effects or serious adverse events caused by ELAHERE or our product candidates 
could cause us or regulatory authorities to interrupt, delay, or halt clinical trials and could result in a restrictive label or 
the delay, denial, or withdrawal of regulatory approval by the FDA or other comparable foreign regulatory authorities. 
Any related drug-side effects or serious adverse events in our clinical trials could affect clinical trial patient 
recruitment or the ability of enrolled patients to complete the clinical trial or result in potential product liability claims. 
If we or others identify undesirable side effects or serious adverse events caused by ELAHERE or any of our 
product candidates that may receive marketing approval, a number of potentially significant negative consequences 
could result, including: 
• 
we may suspend or be forced to suspend marketing; 
• 
we may be obliged to conduct a product recall or withdrawal; 
• 
regulatory authorities may suspend, vary, or withdraw their approvals; 
• 
regulatory authorities may order the seizure of product; 
• 
regulatory authorities may require additional warnings on the label or a risk evaluation and mitigation strategy 
(REMS) that could diminish the usage or otherwise limit commercial success; 
• 
we may be required to conduct post-approval trials; 
• 
we could be sued and held liable for harm caused to patients; 
• 
we could be required to pay fines and face other administrative, civil, and criminal penalties; and 
• 
our reputation may suffer. 
 
Any of these events could prevent us from achieving or maintaining market acceptance of ELAHERE or any of 
our product candidates that may receive marketing approval. 
We have received orphan drug designation for ELAHERE and our product candidates for specified indications; 
we may seek additional orphan drug designation for additional indications and for our other product candidates. 
However, we may be unsuccessful in obtaining or may be unable to maintain the benefits associated with orphan 
drug designation, including the potential for market exclusivity. 
ELAHERE has been granted orphan drug designation by the FDA in the United States, and orphan medicinal 
product status by the EMA in the European Union for the treatment of ovarian cancer. Pivekimab has been granted 
orphan drug designation by the FDA for the treatment of AML and for the treatment of BPDCN, and by the EMA for the 
treatment of BPDCN. As part of our business strategy, we may seek orphan drug designation for our other product 
candidates; however, we may be unsuccessful. 
Generally, if a product with an orphan drug designation subsequently receives the first marketing approval for 
the indication for which it has such designation, the product is entitled to a period of marketing exclusivity, which 
precludes the EMA or the FDA from approving another marketing application for the same drug or biologic for the 
indication for that time period. Even if we obtain orphan drug exclusivity for a drug, that exclusivity may not effectively 
protect the designated drug from competition because different drugs can be approved for the same condition. Even after 
an orphan drug is approved, the FDA can subsequently approve another product that meets the definition of a “same 
drug” under 21 C.F.R. 316.3 for the same condition if the FDA concludes that the later product is clinically superior by 
evidence that it is safer, more effective, or makes a major contribution to patient care. In addition, a designated orphan 
drug may not receive orphan drug exclusivity if it is approved for a use that is broader than the indication for which it 
received orphan drug designation. Moreover, orphan drug exclusive marketing rights in the United States may be lost if 
the FDA later determines that the request for designation was materially defective or if the manufacturer is unable to 
assure sufficient quantity of the drug to meet the needs of patients with the rare disease or condition. Orphan drug 
designation neither shortens the development time or regulatory review time of a drug nor gives the drug any advantage 

35 
in the regulatory review or approval process. While we intend to seek additional orphan drug designation for our other 
product candidates, we may never receive such designations. Even if we receive orphan drug designation, there is no 
guarantee that we will enjoy the benefits of those designations or obtain orphan drug exclusivity. 
We and our collaborators are subject to extensive government regulations and we and our collaborators may not 
be able to obtain or maintain necessary regulatory approvals. 
We and our collaborators may not obtain or maintain the regulatory approvals necessary to commercialize our 
product candidates, which would cause our business to be severely harmed. Pharmaceutical products, including 
ELAHERE and our product candidates, are subject to extensive and rigorous government regulation. The FDA regulates, 
among other things, the development, testing, manufacture, safety, record-keeping, labeling, storage, approval, 
advertising, promotion, sale, and distribution of pharmaceutical products. If ELAHERE or our product candidates are 
marketed outside of the United States, they will also be subject to extensive regulation by foreign governments. The 
regulatory review and approval process, which includes preclinical studies and clinical trials of each product, is lengthy, 
complex, expensive, and uncertain. Securing regulatory approval requires the submission of extensive preclinical and 
clinical data and supporting information to the authorities for each indication to establish the product’s safety and 
efficacy. Data obtained from preclinical and other nonclinical studies and clinical trials are susceptible to varying 
interpretation, which may delay, limit, or prevent regulatory approval. The approval process may take many years to 
complete and may involve ongoing requirements for post-approval trials. The FDA may approve our product candidate 
for indications that are significantly more limited than what we apply for or require labeling statements that limit the use 
of our products, such as a boxed warning or warnings, contra-indications, or precaution statements. The FDA may also 
require a REMS, which could include physician communication plans or restricted distribution methods, such as 
training, certification, or other requirements for prescribers, pharmacies, or patients. Any FDA or other regulatory 
approvals, once obtained, may be withdrawn or limited. Any of these actions could diminish the usage of the product or 
otherwise limit the commercial success of our product candidates. The effect of government regulation may be to: 
• 
delay marketing of product candidates for a considerable period of time; 
• 
limit the indicated uses for which product candidates may be marketed; 
• 
impose costly requirements on our activities; and 
• 
place us at a competitive disadvantage to other pharmaceutical and biotechnology companies. 
 
We may encounter delays or rejections in the regulatory approval process because of additional government 
regulation from future legislation or administrative action or changes in regulatory policy during the period of product 
development, clinical trials, and regulatory review. Failure to comply with applicable regulatory requirements may result 
in criminal prosecution, civil penalties, recall or seizure of products, total or partial suspension of production or 
injunction, as well as other regulatory action against our products or us. In addition, we are, or may become, subject to 
various federal, state, and local laws, regulations, and recommendations relating to safe working conditions, laboratory 
and manufacturing practices, the experimental use of animals, and the use and disposal of hazardous substances, 
including radioactive compounds and infectious disease agents, used in connection with our research work. If we fail to 
comply with the laws and regulations pertaining to our business, we may be subject to sanctions, including the 
temporary or permanent suspension of operations, product recalls, marketing restrictions, and civil and criminal 
penalties. 
We remain subject to ongoing regulatory requirements and review. If we or our collaborators fail to comply with 
regulations applicable to approved products, these approvals could be lost and the sale of our or our 
collaborators’ products could be suspended. 
ELAHERE and any of our product candidates that may receive marketing approval will continue to be subject 
to extensive regulatory requirements related to product manufacturing, labeling, packaging, storage, record-keeping, 
advertising, promotion, registration and listing, and reporting of adverse events and other post-market information.  The 
approval of a product could be conditioned on us or our collaborators conducting costly post-approval trials or could 
limit the indicated uses included in product labeling. Moreover, the product may later cause adverse effects that limit or 
prevent its widespread use, force us or our collaborators to withdraw it from the market, or impede or delay our or our 
collaborators’ ability to obtain regulatory approvals in additional countries. In addition, the manufacturer of the product 
and its facilities will continue to be subject to regulatory review and periodic inspections to ensure adherence to 
applicable regulations. We may be unable or slow to comply with existing regulations, including changes in existing 
regulatory requirements, or new regulations. Furthermore, our collaborators may be slow to adapt, or may never adapt, 

36 
to changes in existing regulatory requirements or adoption of new regulatory requirements pertaining to products that 
have already received approval. 
The FDA closely regulates the post-approval marketing and promotion of drugs and biologics to ensure they are 
marketed only for the approved indications and in accordance with the provisions of the approved labeling. If we market 
our products outside of their approved indications, we may be subject to enforcement action for off-label promotion. 
Violations of the FDA’s restrictions relating to the promotion of prescription drugs may also lead to investigations 
alleging violations of federal and state health care fraud and abuse laws, as well as state consumer protection laws. 
If we or our collaborators fail to comply with the regulatory requirements of the FDA and other applicable U.S. 
and foreign regulatory authorities, or if previously unknown problems with our or our partners’ products, manufacturers, 
or manufacturing processes are discovered, we could be subject to administrative or judicially imposed sanctions, 
including: 
• 
restrictions on the products, manufacturers, or manufacturing processes; 
• 
warning or untitled letters; 
• 
civil or criminal penalties; 
• 
fines; 
• 
injunctions; 
• 
product seizures or detentions; 
• 
import bans; 
• 
voluntary or mandatory product recalls and publicity requirements; 
• 
suspension or withdrawal of regulatory approvals; 
• 
total or partial suspension of production; and 
• 
refusal to approve pending applications for marketing approval of new drugs or supplements to approved 
applications. 
 
Any one of these could have a material adverse effect on our business or financial condition. 
Adequate coverage and reimbursement from third-party payors may not be available for our products and we 
may be unable to successfully contract for coverage from third-party payors; conversely, to secure coverage from 
third-party payors, we may be required to pay rebates or other discounts; and we may confront other restrictions 
to reimbursement, any of which could diminish our sales or adversely affect our ability to sell our products 
profitably. 
Our ability to successfully commercialize and achieve market acceptance of our products depends in significant 
part on adequate financial coverage and reimbursement from third-party payors, including government healthcare 
programs, such as the Medicare and Medicaid programs within the U.S., and private entities, such as managed care 
organizations and private health insurers. Moreover, a third-party payor’s decision to provide coverage for a product 
does not mean that an adequate reimbursement rate will be approved. We may be required to provide discounts or 
rebates to certain purchasers to obtain coverage under federal healthcare programs, or to sell products to government 
purchasers. Adequate third-party reimbursement may not be available to enable us to maintain net price levels sufficient 
to realize an appropriate return on our investment in product development. Additionally, coverage and reimbursement 
for drug products can differ significantly from payor to payor. One third-party payor’s decision to cover a particular drug 
product or service does not ensure that other payors will also provide coverage for the medical product or service or will 
provide coverage at an adequate reimbursement rate. The demand for, and the profitability of, our products could be 
materially harmed if state Medicaid programs, the Medicare program, other government healthcare programs, or third-
party commercial payors deny reimbursement for our products, limit the indications for which our products will be 
reimbursed, or provide reimbursement only on unfavorable terms. 
Third-party payors are increasingly challenging the price and examining the cost-effectiveness of new products 
and services in addition to their safety and efficacy. To obtain or maintain coverage and reimbursement for any approved 
drug product, we may need to collect real-world evidence and conduct pharmacoeconomic studies to demonstrate the 
medical necessity and cost-effectiveness of our product. These studies will be in addition to the studies required to obtain 
or maintain regulatory approvals. If third-party payors do not consider a product to be cost-effective compared to other 
available therapies, they may not cover the product or, if they do, the level of payment may not be sufficient to allow 
sale of a product at a profit. Thus, obtaining and maintaining reimbursement status is complex and costly. 

37 
As part of the overall trend toward cost containment, third-party payors, directly or through pharmacy benefit 
managers, or PBMs, may seek to restrict coverage or control utilization of certain drug products.  Third-party PBMs and 
third-party payors can limit coverage to specific products on an approved list, or formulary, which might not include all 
of the approved products for a particular indication and can exclude drugs from their formularies in favor of competitor 
drugs or alternative treatments. We cannot guarantee that we will be able to agree to coverage terms with all PBMs and 
third-party payors. Payors could decide to exclude our products from formulary coverage lists, impose step edits that 
require patients to try alternative, including generic, treatments before authorizing payment for our products, limit the 
types of diagnoses for which coverage will be provided, require pre-approval (known as “prior authorization”) for 
coverage of a prescription for each patient (to allow the payor to assess medical necessity) or impose a moratorium on 
coverage for products while the payor makes a coverage decision. An inability to maintain adequate access, including 
through formulary positions, could increase patient cost-sharing for our products and cause some patients to determine 
not to use our products.  
Healthcare reform efforts, future legislation, and regulatory actions aimed at reducing healthcare costs could 
impact our ability to obtain or maintain coverage and adequate reimbursement. This could materially harm our business 
and financial result. See “Regulatory Matters - Reimbursement”. See also, “Risks Related to Government Regulation - 
Healthcare reform initiatives and other legislative action applicable to our product candidates could limit our potential 
product revenue.” 
We may never receive approval to commercialize ELAHERE or our product candidates outside of the U.S. 
We are not permitted to market or sell ELAHERE in the EU or in any other foreign countries on a commercial 
basis until we receive the requisite approval from such country’s regulatory authorities. Obtaining and maintaining 
marketing approval, or pricing and reimbursement approval, of ELAHERE or our product candidates in one jurisdiction 
does not guarantee that we will be able to obtain or maintain equivalent approvals in any other jurisdiction, but a failure 
or delay in obtaining regulatory approval in one jurisdiction may have a negative effect on the regulatory approval 
process in others. Approval procedures vary among jurisdictions and can involve requirements and administrative review 
periods different from those in the United States, including additional preclinical studies or clinical trials, as clinical 
trials conducted in one jurisdiction may not be accepted by regulatory authorities in other jurisdictions. The process for 
obtaining marketing approval in a foreign country is an extensive, lengthy, expensive, and uncertain process and the 
regulatory authority may reject a filing or delay, limit, or deny marketing approval for many reasons. In many 
jurisdictions outside the United States, a product must be approved for reimbursement before it can be approved for sale. 
Failure to obtain marketing approval in other countries or any delay or setback in obtaining such approval would impair 
our ability to develop foreign markets for ELAHERE and could adversely affect our business and financial condition. 
Any such complications may reduce our target market and delay or limit the full commercial potential of ELAHERE. 
Government pricing requirements, such as those under the Medicaid Drug Rebate Program, other federal 
government programs, and state price transparency laws, and their related reporting and payment obligations 
require strict adherence; our failure to adhere to such requirements could subject us to penalties, sanctions, and 
fines that could have a material adverse effect on our business, financial condition, results of operations, and 
growth prospects. 
We participate in the Medicaid Drug Rebate Program, the 340B program, the U.S. Department of Veterans 
Affairs, Federal Supply Schedule, or FSS, pricing program, and the Tricare Retail Pharmacy program, and have 
obligations to report the average sales price for certain drug products to the Medicare program. Pricing and rebate 
calculations vary across products and programs, are complex, and are often subject to interpretation by us, governmental 
or regulatory agencies, and the courts, which can change and evolve over time. Requirements are subject to change. For 
example, as of January 1, 2022, all manufacturers must report the average sales price for drugs under the Medicare 
program regardless of whether they are enrolled in the Medicaid Drug Rebate Program. 
If we become aware that our reporting for a prior quarter or other time period was incorrect or has changed as a 
result of recalculation of pricing data, we generally are obligated to resubmit the corrected data and provide refunds or 
other reconciliations.  Price recalculations may affect the ceiling price at which we are required to offer our products to 
certain customers under the 340B program and increase our general costs. 
Civil monetary penalties can be applied if we are found to have knowingly submitted any false price or product 
information to the government, if we are found to have made a misrepresentation in the reporting of our average sales 

38 
price, if we fail to submit the required price data on a timely basis, or if we are found to have charged certain customers 
more than the statutorily mandated ceiling price. The Centers for Medicare & Medicaid Services, or CMS, also could 
decide to terminate our Medicaid Drug Rebate agreement. Our failure to comply with our reporting and payment 
obligations under the Medicaid Drug Rebate Program and other governmental programs could negatively impact our 
financial results. 
Several states have passed or are considering legislation that requires or purports to require companies to report 
pricing information, including proprietary pricing information. Such reporting requirements are not always clearly 
defined and failure to appropriately disclose in accordance with these requirements may lead to the imposition of 
penalties. 
Healthcare reform initiatives and other legislative action applicable to our product candidates could limit our 
potential product revenue. 
In the U.S., federal and state governments continue to propose and pass legislation designed to reform delivery 
of, or payment for, health care, which include initiatives to reduce the cost of healthcare generally and drugs specifically.  
For example, in March 2010, the U.S. Congress enacted the Patient Protection and Affordable Care Act and the Health 
Care and Education Reconciliation Act (the “ACA”), which expanded health care coverage through Medicaid expansion 
and the implementation of the individual mandate for health insurance coverage and which included changes to the 
coverage and reimbursement of drug products under government healthcare programs. Since its enactment, there have 
been and likely will be judicial, administrative, executive, and legislative challenges to certain aspects of the ACA. For 
example, tax reform legislation was enacted at the end of 2017 that eliminates the tax penalty for individuals who do not 
maintain sufficient health insurance coverage beginning in 2019 (the so-called “individual mandate”).  In 2021, the U.S. 
Supreme Court dismissed the latest judicial challenge to the ACA brought by several states without specifically ruling on 
the constitutionality of the ACA. Changes resulting from any successful challenges or other future modifications may 
have a material impact on our business. 
Beyond the ACA, there are ongoing and widespread health care reform efforts, a number of which have focused 
on regulation of prices or payment for drug products. Drug pricing and payment reform was a focus of the Trump 
Administration and has been a focus of the Biden Administration. For example, federal legislation enacted in 2021 
eliminates a statutory cap on Medicaid drug rebate program rebates effective January 1, 2024. As another example, the 
Inflation Reduction Act (IRA) of 2022 contains various drug price negotiation, inflationary rebate, and pricing 
provisions. Among other provisions, the IRA imposes penalties if drug prices are increased at a rate faster than inflation, 
redesigns Medicare Part D benefits to shift a greater portion of the costs to manufacturers, and allows for the U.S. 
government to set prices for certain drugs in Medicare. More specifically, the IRA creates a drug price negotiation 
program under which the prices for Medicare units of certain high Medicare spend drugs and biologicals without generic 
or biosimilar competition will be limited by a cap that is defined by reference to, among other things, a specified non-
federal average manufacturer price, starting in 2026 for certain products. It is not yet clear which products the 
government will select and subject to the cap, but if one of our products is subject to the government-established price, 
there could be a significant impact to our business. Further, failure to comply with requirements under the drug price 
negotiation program can result in an excise tax and/or a civil monetary penalty. The impact of the IRA on our business 
and the broader pharmaceutical industry remains uncertain, as the federal government has yet to make various IRA 
implementation decisions. This or any other legislative change could affect the market conditions for our products. We 
expect continued scrutiny on drug pricing and government price reporting from Congress, agencies, and other bodies. 
Individual states in the United States have also become increasingly active in passing legislation and 
implementing regulations designed to control pharmaceutical product pricing, including price constraints, restrictions on 
copayment assistance by pharmaceutical manufacturers, value-based pricing, marketing cost disclosure and transparency 
measures, and, in some cases, measures designed to encourage importation from other countries and bulk purchasing. 
Healthcare reform efforts have been and may continue to be subject to scrutiny and legal challenge. For 
example, revisions to regulations under the federal anti-kickback statute would remove protection for traditional 
Medicare Part D discounts offered by pharmaceutical manufacturers to pharmacy benefit managers and health plans. 
Pursuant to court order, the removal was delayed, and the IRA further delayed implementation of the rule until 
January 1, 2032. 

39 
Health care reform at the federal or state level could affect demand for, or pricing of, our product candidates if 
approved for sale. We cannot, however, predict the ultimate content, timing, or effect of any federal and state reform 
efforts. There is no assurance that federal or state health care reform will not adversely affect our future business and 
financial results. 
In addition, other broader legislative changes have been adopted that could have an adverse effect upon, and 
could prevent, our products’ commercial success. For example, the Budget Control Act of 2011, as amended, resulted in 
the imposition of reductions in Medicare (but not Medicaid) payments to providers in 2013 and remains in effect through 
2031 (except May 1, 2020 to March 31, 2022) unless additional Congressional action is taken. Any significant spending 
reductions affecting Medicare, Medicaid or other publicly funded or subsidized health programs that may be 
implemented and/or any significant taxes or fees that may be imposed on us could have an adverse impact on our results 
of operations. 
As our business grows, we will become increasingly subject to additional healthcare regulation and enforcement 
by various government entities, and our failure to strictly adhere to these regulatory regimes could have a 
detrimental impact on our business. 
In the United States, pharmaceutical manufacturers and their products are subject to extensive federal and state 
regulation, including laws intended to prevent fraud and abuse in the healthcare industry. These laws subject us to 
regulations by regional, national, state and local agencies, including, but not limited to the DOJ, the Office of Inspector 
General of the U.S. Department of Health and Human Services, or OIG, and other regulatory bodies. These laws include: 
• 
federal false claims, false statements, and civil monetary penalties laws prohibiting, among other things, any 
person from knowingly presenting, or causing to be presented, a false claim for payment of government funds 
or knowingly making, or causing to be made, a false statement to get a false claim paid; 
• 
the federal anti-kickback law, which prohibits, among other things, persons from offering, soliciting, receiving, 
or providing remuneration, directly or indirectly, to induce either the referral of an individual for, or the 
purchasing or ordering of, a good or service for which payment may be made under federal healthcare programs 
such as Medicare and Medicaid; 
• 
the federal Health Insurance Portability and Accountability Act of 1996 (HIPAA), which, in addition to privacy 
protections applicable to healthcare providers and other entities, prohibits executing a scheme to defraud any 
healthcare benefit program or making false statements relating to healthcare matters; 
• 
FDCA, which among other things, strictly regulates drug marketing, prohibits manufacturers from marketing 
products prior to approval or for off-label use, and regulates the distribution of samples; 
• 
federal laws that require pharmaceutical manufacturers to report certain calculated product prices to the 
government or provide certain discounts or rebates to government authorities or private entities, often as a 
condition of reimbursement under government healthcare programs; 
• 
the federal Open Payments (or federal “sunshine” law), which requires pharmaceutical and medical device 
companies to monitor and report certain financial interactions with certain healthcare providers to the Center for 
Medicare & Medicaid Services within the U.S. Department of Health and Human Services for re-disclosure to 
the public, as well as ownership and investment interests held by physicians and their immediate family 
members; 
• 
federal consumer protection and unfair competition laws, which broadly regulate marketplace activities and 
activities that potentially harm consumers; 
• 
analogous state laws and regulations, including state anti-kickback and false claims laws and state laws 
governing privacy, security, and breaches of health information in certain circumstances, many of 
• 
which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating 
compliance efforts; and 
• 
state laws that require pharmaceutical companies to comply with specific compliance standards, restrict 
financial interactions between pharmaceutical companies and healthcare providers, report drug product pricing 
information, financial interactions with health care providers, or marketing expenditures and/or require the 
registration of pharmaceutical sales representatives. 
 
Ensuring compliance is time-consuming and costly. Given the breadth of the laws and regulations, limited 
guidance for certain laws and regulations, and evolving government interpretations of the laws and regulations, 
governmental authorities may possibly conclude that our business practices are non- compliant. If our operations are 
found to be in violation of any of the laws described above or any other government regulations that apply to us, we may 

40 
be subject to penalties, including civil and criminal penalties, damages, fines, exclusion from participation in 
government health care programs, such as Medicare and Medicaid, imprisonment, and the curtailment or restructuring of 
our operations, any of which could adversely affect our business, financial condition, results of operations, and 
prospects. 
If we fail to comply with environmental, health, and safety laws and regulations that apply to us, we could become 
subject to fines or penalties or incur costs that could harm our business. 
We are subject to numerous federal, state, and local environmental, health, and safety laws and regulations, 
including those governing the manufacture and transportation of hazardous materials and pharmaceutical compounds. 
Although we believe that our contracted research, development, and manufacturing safety procedures for handling and 
disposing of these materials comply with the standards prescribed by applicable laws and regulations, we cannot 
completely eliminate the risk of accidental contamination or injury from these materials. In the event of such an 
accident, we could be held liable for any resulting damages, and any liability could exceed our resources. We may be 
required to incur significant costs to comply with these laws in the future, including civil or criminal fines and penalties, 
which we may not be able to afford. 
In addition, we may incur substantial costs in order to comply with current or future environmental, health, and 
safety laws and regulations applicable to us. These current or future laws and regulations may impair our research, 
development, or production efforts or impact the research activities we pursue, particularly with respect to research 
involving human subjects or animal testing. Our failure to comply with these laws and regulations also may result in 
substantial fines, penalties, or other sanctions, which could cause our financial condition to suffer. 
Failure to comply with the Foreign Corrupt Practices Act and other similar anti-corruption laws and anti-money 
laundering laws, as well as export control laws, customs laws, sanctions laws, and other laws governing our 
operations could subject us to significant penalties and damage our reputation. 
We are subject to the Foreign Corrupt Practices Act (FCPA), which generally prohibits U.S. companies and 
intermediaries acting on their behalf from offering or making payments to “foreign officials” for the purpose of 
obtaining or retaining business or securing an improper business advantage. The FCPA also requires companies whose 
securities are publicly listed in the United States to maintain accurate books and records and to maintain adequate 
internal accounting controls. We are also subject to other similar anti-corruption laws and anti-money laundering laws, 
as well as export control laws, customs laws, sanctions laws, and other laws that apply to our activities in the countries 
where we operate. Certain of the jurisdictions in which we conduct or expect to conduct business have heightened risks 
for public corruption, extortion, bribery, pay-offs, theft, and other fraudulent practices. In many countries, health care 
professionals who serve as investigators in our clinical trials or may prescribe or purchase ELAHERE or any of our 
product candidates if they are approved, are employed by a government or an entity owned or controlled by a 
government. Dealings with these investigators, prescribers, and purchasers are subject to regulation under the FCPA. 
Under these laws and regulations, as well as other anti-corruption laws, anti-money-laundering laws, export control laws, 
customs laws, sanctions laws, and other laws governing our operations, various government agencies may require export 
licenses, may seek to impose modifications to business practices, including cessation of business activities in sanctioned 
countries or with sanctioned persons or entities and modifications to compliance programs, which may increase 
compliance costs, and may subject us to fines, penalties, and other sanctions. 
Inadequate funding for the FDA, the Securities and Exchange Commission, and other government agencies could 
hinder their ability to hire and retain key leadership and other personnel, prevent new products and services 
from being developed or commercialized in a timely manner, or otherwise prevent those agencies from 
performing normal business functions, which could negatively affect our business. 
The ability of the FDA to review and approve new products can be affected by a variety of factors, including 
government budget and funding levels, ability to hire and retain key personnel and accept the payment of user fees, and 
statutory, regulatory, and policy changes. Average review times at the agency have fluctuated in recent years as a result. 
In addition, government funding of the U.S. Securities and Exchange Commission (SEC) and other government agencies 
on which our operations may rely, including those that fund research and development activities is subject to the political 
process, which is inherently fluid and unpredictable. 

41 
Disruptions at the FDA and other agencies may also slow the time required for new drugs to be reviewed and/or 
approved by necessary government agencies, which would adversely affect our business. For example, the U.S. 
government has shut down several times, including December 22, 2018 to January 25, 2019, and certain regulatory 
agencies, such as the FDA and the SEC, have had to furlough employees and stop critical activities. If a prolonged 
government shutdown or a series of shutdowns occurs, it could significantly affect the ability of the FDA to timely 
review and process our regulatory submissions, which could have a material adverse effect on our business. Further, 
future government shutdowns could impact our ability to gain access to the public markets and obtain necessary capital 
in order to properly capitalize and continue our operations. 
We may be subject to, or may in the future become subject to, U.S. federal and state and foreign laws and 
regulations imposing obligations on how we collect, use, disclose, store, and process personal information. Our 
actual or perceived failure to comply with such obligations could result in liability or reputational harm and 
adversely affect our business. Ensuring compliance with such laws and regulations could also impair our efforts 
to maintain and expand our customer base, and thereby decrease our revenue. 
In many activities, including the conduct of clinical trials, we are subject to laws and regulations governing data 
privacy and the protection of health-related and other personal information. These laws and regulations govern our 
processing of personal data, including the collection, access, use, analysis, modification, storage, transfer, destruction, 
and disposal of personal data. They also impose requirements with respect to notification and remediation of security 
breaches involving personal data. We must comply with laws and regulations associated with the international transfer of 
personal data based on the location in which the personal data originates and the location in which such data are 
processed. There is also heightened sensitivity around certain types of health data, which may be subject to additional 
protections. While we strive to comply with all applicable privacy and security laws and regulations, legal standards for 
privacy continue to evolve and any failure or perceived failure to comply may result in proceedings or actions against us 
by government entities or others, or could cause reputational harm, which could have a material adverse effect on our 
business. 
The legislative and regulatory landscape for privacy and data security continues to evolve. For example, the EU 
General Data Protection Regulation (GDPR), which was effective as of May 25, 2018, introduced new data protection 
requirements in the European Union relating to the consent of the individuals to whom the personal data relate, the 
information provided to the individuals, the documentation we must retain, the security and confidentiality of the 
personal data, data breach notification, and the use of third-party processors in connection with the processing of 
personal data. The GDPR has increased our responsibility and potential liability in relation to personal data that we 
process, and we may be required to put in place additional mechanisms to ensure compliance with the GDPR. However, 
our ongoing efforts related to compliance with the GDPR may not be successful and could increase our cost of doing 
business. In addition, data protection authorities of the different EU member states may interpret the GDPR differently, 
and guidance on implementation and compliance practices are often updated or otherwise revised, which adds to the 
complexity of processing personal data in the European Union. 
In the United States, numerous federal and state data protection laws govern our collection, use and disclosure 
of personal information. For example, the California Consumer Privacy Act of 2018 as amended and expanded by the 
California Privacy Rights Act of 2020 (together, the CCPA), mirrors a number of the key provisions of the EU GDPR 
and applies to a broad range of information deemed to be personal information. The CCPA establishes data privacy 
rights for consumers in the State of California, imposing special rules on the collection of consumer data from minors, 
requires additional disclosures and transparency, and requires us to allow consumers to opt-out of certain online 
disclosures.  The CCPA also creates potentially significant statutory damages framework for violations of the CCPA and 
for businesses that fail to implement reasonable security procedures and practices to prevent data breaches.  Other 
similar laws will go into operation in 2023 or are under consideration in additional states and abroad in jurisdictions 
worldwide.  Additionally, laws in all 50 states require businesses to provide notice to individuals whose personally 
identifiable information has been disclosed as a result of a data breach. The laws are not consistent, and compliance in 
the event of a widespread data breach is costly.  
Any such additional legislation, if enacted, may add additional complexity, variation in requirements, 
restrictions and potential legal risk, and may require additional investment of resources in compliance programs, impact 
strategies, reduce the availability of previously useful data and result in increased compliance costs and/or changes in 
business practices and policies. 

42 
Risks Related to Our Key Personnel and Other Service Providers 
We depend on our key personnel, and we must continue to attract and retain key employees and consultants. 
We depend on our key scientific and management personnel. Our ability to pursue the development and 
commercialization of ELAHERE and our product candidates depends largely on retaining the services of our existing 
personnel and hiring additional qualified personnel to perform research, development, and commercialization activities. 
Although we have entered into employment agreements with our executive officers, each of them may terminate their 
employment with us at any time. We do not maintain “key person” insurance for any of our executives or other 
employees. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in 
formulating our research and development and commercialization strategy. Our consultants and advisors may be 
employed by employers other than us and may have commitments under consulting or advisory contracts with other 
entities that may limit their availability to us. If we are unable to continue to attract and retain high-quality personnel, 
our ability to pursue our growth strategy will be limited. Attracting and retaining qualified personnel will be critical to 
our success. We may not be able to attract and retain personnel, or, in the event key personnel leave, suitable 
replacements for such personnel, on acceptable terms given the competition for such personnel among biotechnology, 
pharmaceutical, and healthcare companies, universities, and non-profit research institutions. Failure to retain our existing 
key management and scientific personnel or to attract additional highly qualified personnel could harm our business. 
Our employees, independent contractors, principal investigators, CROs, consultants, and collaborators may 
engage in misconduct or other improper activities, including noncompliance with regulatory standards and 
requirements and insider trading. 
We are exposed to the risk that our employees, independent contractors, principal investigators, third-party 
contract research organizations (CROs), consultants, and collaborators may engage in fraudulent conduct or other illegal 
activity. Misconduct by these parties could include intentional, reckless and/or negligent conduct or unauthorized 
activities that violate: (1) laws or regulations in jurisdictions where we are performing activities in relation to ELAHERE 
or our product candidates, including those laws requiring the reporting of true, complete, and accurate information to 
such authorities; (2) manufacturing regulations and standards; (3) applicable laws prohibiting the promotion of a medical 
product for a use that has not been cleared or approved; (4) fraud and abuse, anti-corruption, and anti-money laundering 
laws, as well as similar laws and regulations and other laws; or (5) laws that require the reporting of true and accurate 
financial information and data. In particular, sales, marketing, and business arrangements in the healthcare industry are 
subject to laws intended to prevent fraud, bias, misconduct, kickbacks, self-dealing, and other abusive practices, and 
these laws may differ substantially from country to country. Misconduct by these parties could also include the improper 
use of information obtained in the course of clinical trials or performing other services, which could result in 
investigations, sanctions, and serious harm to their or our reputation. It is not always possible to identify and deter 
misconduct by these parties, and the precautions and procedures we currently take or may establish in the future as our 
operations and employee, CRO, consultant, and collaborator base expands to detect and prevent this type of activity may 
not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental 
investigations or other actions or lawsuits stemming from a failure by these parties to comply with such laws or 
regulations. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting 
our rights, those actions could have a significant impact on our business and results of operations, including the 
imposition of significant fines or other sanctions.  
Risks Related to Our Technology Systems 
Our business and operations could suffer in the event of system failures. 
We utilize information technology systems and networks to process, transmit, and store electronic information 
in connection with our business activities. As use of digital technologies has increased, cyber incidents, including 
deliberate attacks and attempts to gain unauthorized access to computer systems and networks, have increased in 
frequency and sophistication. These threats pose a risk to the security of our systems and networks and the 
confidentiality, availability, and integrity of our data. There can be no assurance that we will be successful in preventing 
cyber-attacks or successfully mitigating their effects. 
Despite the implementation of security measures, our internal computer systems, and those of our CROs and 
other contractors and consultants, are vulnerable to damage from cyber-attack, computer viruses, unauthorized access, 

43 
natural disasters, terrorism, war, and telecommunication and electrical failures. Furthermore, we have little or no control 
over the security measures and computer systems of our third-party CROs and other contractors and consultants. While 
we have not experienced any such system failure, accident, or security breach to date, if such an event were to occur and 
cause interruptions in our operations, it could result in a material disruption of our programs. For example, the loss of 
clinical trial data for our product candidates could result in delays in our marketing approval efforts and significantly 
increase our costs to recover or reproduce the data. To the extent that any disruption or security breach results in a loss of 
or damage to our data or applications or other data or applications relating to our technology or product candidates, or 
inappropriate disclosure of confidential or proprietary information, we could incur liabilities and the further development 
of our product candidates could be delayed. 
Risks Related to the Ownership of Our Common Stock 
Our stock price may be volatile and fluctuate significantly and results announced by us and our collaborators or 
competitors could cause our stock price to decline. 
Our stock price could fluctuate significantly due to the risks listed in this section, business developments 
announced by us and by our collaborators and competitors, or as a result of market trends and daily trading volume. The 
business developments that could affect our stock price include disclosures related to clinical findings with compounds 
that make use of our ADC technology, new collaborations, clinical advancement, or discontinuation of product 
candidates that make use of our ADC technology or product candidates that compete with our compounds or those of our 
collaborators, and regulatory approvals for our product candidates or product candidates that compete with our 
compounds or those of our collaborators. Our stock price could also fluctuate significantly with the level of overall 
investment interest in small-cap biotechnology stocks or for other reasons unrelated to our business. 
Our operating results have fluctuated in the past and are likely to continue to do so in the future. Our revenue is 
unpredictable and may fluctuate due to the timing of non-recurring licensing fees, decisions of our collaborators with 
respect to our agreements with them, and the achievement of milestones and our receipt of the related milestone 
payments under new and existing licensing and collaboration agreements. Revenue historically recognized under our 
prior collaboration agreements may not be an indicator of revenue from any future collaboration. In addition, our 
expenses are unpredictable and may fluctuate from quarter to quarter due to the timing of expenses, which may include 
obligations to manufacture or supply product or payments owed by us under licensing or collaboration agreements. It is 
possible that our quarterly and/or annual operating results will not meet the expectations of securities analysts or 
investors, causing the market price of our common stock to decline. We believe that quarter-to-quarter and year-to-year 
comparisons of our operating results are not good indicators of our future performance and should not be relied upon to 
predict the future performance of our stock price. 
The potential sale of additional shares of our common stock may cause our stock price to decline. 
We may seek additional capital due to market conditions or strategic considerations even if we believe we have 
sufficient funds for our current or future operating plans through a variety of means, including through private and public 
equity offerings and debt financings. To the extent that we raise additional capital through the sale of equity or 
convertible debt securities, ownership interest of existing shareholders will be diluted, and the price of our stock may 
decline. The price of our common stock may also decline if the market expects us to raise additional capital through the 
sale of equity or convertible debt securities whether or not we actually plan to do so. 
We do not intend to declare or pay cash dividends on our common stock in the foreseeable future. 
We have not declared or paid cash dividends on our common stock since our inception and do not intend to 
declare or pay cash dividends in the foreseeable future. We currently intend to retain all of our future earnings, if any, to 
finance the growth and development of our business. Therefore, shareholders will have to rely solely on appreciation in 
our stock price, if any, in order to achieve a gain on an investment. 
Item 1B.    Unresolved Staff Comments 
None. 

44 
Item 2.    Properties 
We lease approximately 120,000 square feet of laboratory and office space in a building located at 830 Winter 
Street, Waltham, MA. The term of the 830 Winter Street lease expires on March 31, 2026, with an option for us to 
extend the lease for two additional five-year terms. We currently sublet approximately 37,000 square feet of this space 
through the remaining term of the initial lease, and we continue to use the remaining space.  
Item 3.   Legal Proceedings 
From time to time, we may be a party to various legal proceedings arising in the ordinary course of our 
business. We are not currently subject to any material legal proceedings. 
Item 4.    Mine Safety Disclosures 
None. 
PART II 
Item 5.   Market for Registrant’s Common Equity, Related Stockholder Matters, and Issuer Purchases of Equity 
Securities 
Market Price of Our Common Stock and Related Stockholder Matters 
Our common stock is quoted on the Nasdaq Global Select Market under the symbol “IMGN.” As of February 
21, 2023, we had 398 holders of record of our common stock. 
We have not paid any cash dividends on our common stock since our inception and do not intend to pay any 
cash dividends in the foreseeable future. 
Recent Sales of Unregistered Securities; Uses of Proceeds from Registered Securities; Issuer Repurchases of 
Equity Securities 
None. 
 
 

45 
Item 6.    Reserved 
Item 7.    Management’s Discussion and Analysis of Financial Condition and Results of Operations 
Overview 
We are a commercial-stage biotechnology company focused on developing and commercializing the next 
generation of antibody-drug conjugates (ADCs) to improve outcomes for cancer patients. By generating targeted 
therapies with enhanced anti-tumor activity and favorable tolerability profiles, we aim to disrupt the progression of 
cancer and offer patients more good days. We call this our commitment to “target a better now.” 
An ADC with our proprietary technology comprises an antibody that binds to a target found on tumor cells and 
is conjugated to one of our potent anti-cancer agents as a “payload” to kill the tumor cell once the ADC has bound to its 
target. ADCs are an expanding class of anticancer therapeutics, with twelve approved products and the number of agents 
in development growing significantly in recent years. 
We have established a leadership position in ADCs with a portfolio of differentiated product candidates to 
address both solid tumors and hematologic malignancies. We have set four strategic priorities for the business:  
• 
execute the commercial launch for ELAHERE; 
• 
expand the ELAHERE label by moving into platinum-sensitive ovarian cancer; 
• 
advance our clinical pipeline of novel ADCs for hematologic and solid tumors; and 
• 
strengthen and expand our pipeline through both internal discovery and external partnerships. 
We believe that sound execution of these prioritized activities will create substantial short-and long-term value 
for shareholders, employees, patients, and other stakeholders in the Company.  
ELAHERE (Mirvetuximab Soravtansine) 
Approval and Launch 
ELAHERE is a first-in-class ADC targeting folate receptor alpha (FRα), a cell-surface protein over-expressed 
in a number of epithelial tumors, including ovarian, endometrial, and non-small-cell lung cancers. On November 14, 
2022, the FDA granted accelerated approval for ELAHERE for the treatment of adult patients with FRα positive, 
platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to three prior 
systemic treatment regimens. The accelerated approval of ELAHERE was based on efficacy and safety outcomes from 
SORAYA, a single-arm trial of ELAHERE in patients with platinum-resistant ovarian cancer whose tumors express high 
levels of FRα. Continued approval may be contingent upon verification and description of clinical benefit in a 
confirmatory trial. Patients eligible for treatment with ELAHERE are selected by the VENTANA FOLR1 (FOLR1-2.1) 
RxDx Assay developed by RTD, which was also approved by the FDA on November 14, 2022. We completed the build 
out of our U.S. commercial infrastructure in 2022 and initiated sales in the U.S. in November 2022.  
Ongoing Development 
In addition to SORAYA, we are conducting MIRASOL, a randomized Phase 3 clinical trial designed to support 
full approval of ELAHERE. In July of 2022, we completed enrollment in MIRASOL and expect to report top-line data 
from this trial in the second quarter of 2023. If the MIRASOL trial is successful, we plan to submit a marketing 
authorisation application for approval of ELAHERE for the treatment of adult patients with FRα positive, platinum-
resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to three prior systemic 
treatment regimens with the EMA in the second half of 2023. Additionally, our partner, Huadong Medicine, expects to 
submit a biologics license application to the National Medical Products Administration (NMPA) of China for 
ELAHERE in the same indication in the second half of 2023 to support potential approval and launch of ELAHERE in 
Greater China in 2024.  
Beyond platinum-resistant ovarian cancer, our strategy is to move ELAHERE into platinum- sensitive disease, 
and to position the product as the combination agent of choice in ovarian cancer. To this end, in January 2023, we 
completed patient enrollment in PICCOLO, a single-arm trial of ELAHERE monotherapy in later-line FRα positive 
platinum-sensitive patients, and plan to report on the primary endpoint before the end of 2023. We have also generated 
encouraging data in recurrent platinum-sensitive disease with the combination of ELAHERE plus carboplatin and are 
supporting investigator sponsored trials (ISTs) with this combination in a single arm trial in the neoadjuvant setting and 
in a randomized trial comparing ELAHERE combined with carboplatin to standard of care in patients with recurrent 

46 
platinum-sensitive disease. We also initiated a single-arm Phase 2 trial (0420) of this combination followed by 
ELAHERE continuation in FRα-low, medium, and high patients with platinum-sensitive disease. Results from this trial 
and our ongoing ISTs will inform a path to the potential registration for ELAHERE plus carboplatin and, in parallel, 
could support compendia listing for this combination. Finally, we have initiated GLORIOSA, a randomized Phase 3 trial 
of ELAHERE plus bevacizumab maintenance in FRα-high recurrent platinum-sensitive disease that we believe could 
support label expansion. 
Pivekimab Sunirine 
Pivekimab sunirine (PVEK), formerly known as IMGN632, is an ADC comprised of a high-affinity antibody 
designed to target CD123 with site-specific conjugation to a DNA-alkylating payload of the novel IGN 
(indolinobenzodiazepine pseudodimer) class. Our IGNs are designed to alkylate DNA without cross-linking, which has 
provided a broad therapeutic index in preclinical models. We are advancing PVEK in clinical trials for patients with 
blastic plasmacytoid dendritic cell neoplasm (BPDCN) and acute myeloid leukemia (AML).  
BPDCN is a rare form of blood cancer, with an annual incidence of between 500 and 1,000 patients in the US. 
In October 2020, the FDA granted Breakthrough Therapy designation for PVEK for the treatment of patients with 
relapsed or refractory BPDCN. Based on feedback from the FDA, we amended our ongoing 801 Phase 2 trial, known as 
CADENZA, to include a new cohort of up to 20 frontline BPDCN patients. 
Initial enrollment in CADENZA did not distinguish between de novo BPDCN patients and those who presented 
with a prior or concomitant hematologic malignancy (PCHM). Although complete responses have been observed in 
BPDCN patients who present with PCHM, most will not achieve full hematologic recovery due to the impact of their 
prior or concomitant malignancy. For these patients, we believe that achieving a complete response with partial 
hematological recovery (CRh) is a potentially important measure of clinical benefit. 
A Type B meeting was held in August 2022 regarding the initial data from the CADENZA trial. Based on FDA 
feedback on trial design provided in this meeting, the efficacy analysis will be conducted in de novo BPDCN patients 
with CR/CRc as the primary endpoint and the key secondary endpoint of duration of CR/CRc. We will enroll up to 20 de 
novo patients for purposes of the efficacy analysis. We will also continue to enroll PCHM patients in CADENZA to 
further evaluate PVEK in this population. The Company expects to report top-line data on the primary and key 
secondary endpoints in 2024. 
We are also conducting our 802 trial for PVEK, which is a Phase 1b/2 trial designed to determine the safety, 
tolerability, and preliminary antileukemia activity of PVEK when administered in combination with azacytidine and 
venetoclax to patients with relapsed and frontline CD123-positive AML. Having identified the recommended Phase 2 
dose for the triplet, patients are accruing in both expansion cohorts. In December 2022, safety and efficacy findings in 
relapsed refractory AML and initial data in frontline AML was presented at the American Society of Hematology 
Annual Meeting. In the first 10 frontline patients enrolled, 5/10 (50%) patients achieved a CR and 3/4 (75%) patients 
tested had a minimal residual disease (MRD)-negative CR. Based upon these results, the Company will continue 
enrollment in two frontline AML expansion cohorts to optimize the duration of venetoclax therapy. In addition, in 
December 2022, the Company announced a clinical collaboration with Gilead Sciences, Inc. to study PVEK in 
combination with magrolimab in relapsed refractory AML and expects to initiate this cohort under the 802 trial in the 
second half of 2023.  
Other Pipeline Programs 
We continue to advance our earlier-stage pipeline programs. IMGC936 is an ADC in co- development with 
MacroGenics, Inc. that is designed to target ADAM9, an enzyme over-expressed in a range of solid tumors and 
implicated in tumor progression and metastasis. IMGC936 incorporates a number of innovations, including antibody 
engineering to extend half-life, site-specific conjugation with a fixed drug-antibody ratio to enable higher dosing, and a 
next-generation linker and payload designed for improved stability and bystander activity. Phase 1 dose escalation was 
completed and expansion cohorts in non–small cell lung cancer and triple-negative breast cancer initiated in the second 
half of 2022. We expect to provide initial data from these cohorts in the second quarter of 2023.  
IMGN151 is our next generation anti-FRα product candidate in development. This ADC integrates innovation 
in each of its components, which we believe may enable IMGN151 to address patient populations with lower levels of 
FRα expression, including tumor types outside of ovarian cancer. We began enrollment in a Phase I clinical trial 
evaluating IMGN151 in patients with recurrent endometrial cancer and recurrent, high-grade serous epithelial ovarian, 
primary peritoneal, or fallopian tube cancers in January 2023.  

47 
We have selectively licensed restricted access to our ADC platform technology to other companies to expand 
the use of our technology and to provide us with cash to fund our own product programs. These agreements typically 
provide the licensee with rights to use our ADC platform technology with its antibodies or related targeting vehicles to a 
defined target to develop products. The licensee is generally responsible for the development, clinical testing, 
manufacturing, registration, and commercialization of any resulting product candidate. As part of these agreements, we 
are generally entitled to receive upfront fees, potential milestone payments, and royalties on the sales of any resulting 
products. For more information concerning these relationships, including their ongoing financial and accounting impact 
on our business, please read Note C, “Significant Collaborative Agreements,” to our consolidated financial statements 
included in this report. 
We expect to continue to incur substantial operating losses for at least the near term as we incur significant 
operating expenses related to research and development and selling and marketing of ELAHERE. As of December 31, 
2022, we had $275.1 million in cash and cash equivalents compared to $478.8 million as of December 31, 2021.  
Critical Accounting Policies and Estimates 
We prepare our consolidated financial statements in accordance with accounting principles generally accepted 
in the U.S. The preparation of these financial statements requires us to make certain estimates and judgments that affect 
the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the 
consolidated financial statements, and the reported amounts of revenues and expenses during the reported periods. These 
items are monitored and analyzed by management for changes in facts and circumstances, and material changes in these 
estimates could occur in the future. Changes in estimates are reflected in reported results for the period in which the 
change occurs. We base our estimates on historical experience and various other assumptions that we believe to be 
reasonable under the circumstances. Actual results may differ from our estimates if past experience or other assumptions 
do not turn out to be substantially accurate. 
We believe that our application of the following accounting policies, each of which requires significant 
judgments and estimates on the part of management, are the most critical to aid in fully understanding and evaluating our 
reported financial results: 
• 
inventory capitalization; 
• 
revenue recognition; 
• 
clinical trial accruals; and 
• 
stock-based compensation. 
Our accounting policies are more fully described in the Notes to our consolidated financial statements, 
including Note B, “Summary of Significant Accounting Policies,” included in this Annual Report on Form 10-K. 
Managing the Impact of the COVID-19 Pandemic 
Since the first quarter of 2020, although we have experienced some delays or disruptions due to the COVID-19 
pandemic, we have successfully continued to move our clinical trials forward while adapting to meet the evolving 
challenges of the pandemic. We implemented business continuity plans in March 2020 that enabled our workforce to 
remain productive while working from home until mid-September 2021, at which time our workforce returned to the 
office. From a regulatory perspective, since the beginning of the pandemic, we have received timely reviews of our 
submissions to the FDA and other health authorities covering our clinical trial applications. From a manufacturing and 
supply chain perspective, we believe we have sufficient inventory on hand for all of our ongoing and near-term clinical 
trials and to support the launch of ELAHERE. COVID-19 may impact our commercial activities for ELAHERE, 
including patient access to testing and identification, but we will conduct commercial and medical affairs field activities 
in virtual formats where in-person interactions are not feasible. 
Results of Operations 
For a discussion related to the results of operations for 2021 compared to 2020, refer to Part II, Item 7, 
"Management's Discussion and Analysis of Financial Condition and Results of Operations – Results of Operations" in 
our Annual Report on Form 10–K for the year ended December 31, 2021 filed with the SEC on February 28, 2022. 
Revenues 
For 2022, our total revenues increased to $108.8 million compared to $69.9 million for 2021, driven by 
increases in license and milestone fees and ELAHERE net product revenue, partially offset by a decrease in non-cash 
royalty revenue, all of which are discussed further below.  

48 
Product revenue, net 
On November 14, 2022, the FDA granted accelerated approval for ELAHERE for the treatment of adult patients 
with FRα positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received 
one to three prior systemic treatment regimens. We recorded $2.6 million of net product revenue related to U.S. sales of 
ELAHERE in the fourth quarter of 2022. 
License and milestone fees 
The amount of license and milestone fees we earn is directly related to the number of our collaborators, the 
collaborators’ advancement of the product candidates, and the overall success in clinical trials of the product candidates. 
As such, the amount of license and milestone fees may vary widely from quarter to quarter and year to year. Total 
revenue recognized from license and milestone fees for the years ended December 31, 2022 and 2021 was $76.0 million 
and $22.7 million, respectively. Driving the increase, pursuant to our license agreement with Huadong executed in 
October 2020, upon delivery of clinical supply in 2022 and 2021, we recognized $25.4 million and $14.6 million, 
respectively, of the one-time upfront payment previously received pursuant to our license agreement. Additionally, 
pursuant to license agreements executed with Lilly and Magenta in 2022, we recognized $18.4 million and $6.0 million, 
respectively, of upfront payments received. We also recorded $23.2 million of revenue related to development and 
regulatory milestones achieved under various license and collaboration agreements in 2022 compared to $7.4 million in 
2021, and $2.8 million of deferred revenue related to upfront payments previously received pursuant to certain license 
agreements with Novartis that were terminated in 2022. 
Deferred revenue of $50.2 million as of December 31, 2022 includes $7.6 million related to the multi-target 
license agreement with Lilly and $41.2 million related to the sale of our residual rights to receive royalty payments on 
commercial sales of KADCYLA in 2019, with the remainder of the balance primarily representing consideration 
received from our other collaborators pursuant to our license agreements that we have yet to earn pursuant to our 
revenue recognition policy. 
Non-cash royalty revenue related to the sale of future royalties 
KADCYLA is a marketed ADC resulting from one of our development and commercialization licenses with 
Roche, through its Genentech unit. We receive royalty reports and payments related to sales of KADCYLA from Roche 
one quarter in arrears. We sold our rights to receive royalty payments on the net sales of KADCYLA through two 
separate transactions in 2015 and 2019. In accordance with our revenue recognition policy, $29.3 million and 
$46.8 million of non-cash royalties on net sales of KADCYLA were recorded and included in royalty revenue for 2022 
and 2021, respectively. The decrease in non-cash royalty revenue in 2022 compared to 2021 is a result of the aggregate 
royalty threshold, as outlined in the 2015 royalty purchase agreement, being met in the second quarter of 2021, 
effectively reducing the royalty payments under the 2015 transaction from 100% to 15% of KADCYLA royalty 
payments received over the remaining royalty term. See further details regarding these agreements in Note H, “Liability 
Related to Sale of Future Royalties,” of the Consolidated Financial Statements.  
Cost of Sales 
Our cost of sales includes the cost of producing and distributing inventories that are related to product revenue, 
including freight. In addition, shipping and handling costs for product shipments are recorded as incurred. Finally, cost 
of sales may also include costs related to excess or obsolete inventory adjustment charges. 
Prior to receiving FDA approval for ELAHERE in November 2022, we manufactured inventory to be sold upon 
commercialization and recorded the costs as research and development expense. As a result, the manufacturing costs 
related to the inventory build-up incurred before FDA approval were expensed in a prior period and are therefore 
excluded from the cost of goods sold for the year ended December 31, 2022. We estimate our cost of sales related to 
product revenue as a percentage of net product revenue will continue to be positively affected as we sell through certain 
inventory that was previously expensed prior to FDA approval. We expect to utilize zero and low-cost inventory for an 
extended period of time.  
Research and Development Expenses 
Our research and development expenses relate to (i) research to evaluate new targets and to develop and 
evaluate new antibodies, linkers, and cytotoxic agents, (ii) preclinical testing of our own and, in certain instances, our 
collaborators’ product candidates, and the cost of our own clinical trials, (iii) development related to clinical and 
commercial manufacturing processes, (iv) regulatory activities, (v) medical affairs activities, and (vi) external 
manufacturing operations. 

49 
Clinical trial and regulatory approval processes for our product candidates that have advanced or that we intend 
to advance to clinical testing are lengthy, expensive, and uncertain in both timing and outcome. As a result, the pace and 
timing of the clinical development of our product candidates is highly uncertain and may never result in approved 
products. Completion dates and development costs will vary significantly for each product candidate and are difficult to 
predict. A variety of factors, many of which are outside our control, could cause or contribute to the prevention or delay 
of the successful completion of our clinical trials, or delay or prevent our obtaining necessary regulatory approvals. The 
costs to take a product through clinical trials are dependent upon, among other factors, the clinical indications, the 
timing, size, and design of each clinical trial, the number of patients enrolled in each trial, and the speed at which 
patients are enrolled and treated. Product candidates may be found to be ineffective or to cause unacceptable side effects 
during clinical trials, may take longer to progress through clinical trials than anticipated, may fail to receive necessary 
regulatory approvals, or may prove impractical to manufacture in commercial quantities at reasonable cost or with 
acceptable quality. 
The lengthy process of securing FDA approvals for new drugs requires the expenditure of substantial resources. 
Any failure by us to obtain, or any delay in obtaining, regulatory approvals, could materially adversely affect our product 
development efforts and our business overall. Accordingly, we cannot currently estimate, with any degree of certainty, 
the amount of time or money that we will be required to expend in the future on our product candidates prior to their 
regulatory approval, if such approval is ever granted.  
Research and development expense was $213.4 million and $151.1 million for 2022 and 2021, respectively, 
with increased expenses related to personnel, third-party staffing costs, external manufacturing costs, clinical trial costs, 
and contract services, including medical affairs activities in support of advancing ELAHERE, which are discussed 
further below.  
We do not track our research and development costs by project. Since we use our research and development 
resources across multiple research and development projects, we manage our research and development expenses within 
each of the categories listed in the following table and described in more detail below (in thousands): 
 
 
Year Ended  
 
 
 
 
December 31,  
 
Increase/ 
Research and Development Expenses 
     
2022 
     
2021 
     
(Decrease) 
Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 8,913  $ 
 —  $ 
 8,913 
Preclinical and clinical testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 140,873 
 
 99,971   
 40,902 
Process and product development . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 7,499 
 
 7,010   
 489 
Manufacturing operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 56,085 
 
 44,136   
 11,949 
Total research and development expenses . . . . . . . . . . . . . . . . . . . . .   $ 
 213,370 
$ 
 151,117  $ 
 62,253 
 
Research 
Research includes expenses to evaluate new targets and to develop and evaluate new antibodies, linkers, and 
cytotoxic agents. Such expenses include third-party license fees, research funding payments, and contract services.  
Pursuant to a research collaboration agreement executed with Oxford BioTherapeutics in June 2022, we recognized 
$1.4 million of committed research costs in 2022, as well as a $7.5 million upfront license fee paid upon execution of the 
agreement. No similar expenses were recorded in 2021. 
Preclinical and clinical testing 
Preclinical and clinical testing includes expenses related to preclinical testing of our own, and, in certain 
instances, our collaborators’ product candidates, regulatory activities, the cost of clinical trials, and expenses related to 
medical affairs. Such expenses include those related to personnel, third-party staffing, patient enrollment at our clinical 
testing sites, consultant fees, contract services, and facility expenses. Preclinical and clinical testing expenses increased 
to $140.9 million for 2022 compared to $100.0 million for 2021. This increase is primarily the result of increases in 
personnel, third-party staffing costs, contract services driven by medical affairs’ activities in support of advancing 
ELAHERE, and clinical trial costs driven by our ELAHERE and PVEK trials.  
Process and product development 
Process and product development expenses include costs for development of clinical and commercial 
manufacturing processes for our own and collaborator compounds. Such expenses include the costs of personnel, third-
party staffing, contract services, and facility expenses. Process and product development expenses increased to 
$7.5 million for 2022 compared to $7.0 million for 2021, due primarily to increased personnel-related costs.  

50 
Manufacturing operations 
Manufacturing operations expense includes costs to have preclinical and clinical materials manufactured for our 
product candidates and quality control and quality assurance activities. Such expenses include personnel, third-party 
staffing, raw materials for our preclinical studies and clinical trials, non-pivotal and pivotal development costs with 
contract manufacturing organizations, and facility expenses. Manufacturing operations expense increased $11.9 million 
to $56.1 million for 2022 compared to 2021. The increase in 2022 is principally due to increases in personnel-related 
costs and external manufacturing activity across our programs.  
Manufacturing operations expense also includes antibody development and supply expense in support of 
commercial validation and in anticipation of potential future clinical trials, as well as our ongoing trials, of $18.9 million 
and $20.6 million for 2022 and 2021, respectively. The process of antibody production is lengthy due in part to the lead 
time to establish a satisfactory production process at a vendor. Accordingly, costs incurred related to antibody 
production and development have fluctuated from period to period. Additionally, antibody used in the manufacture and 
sale of ELAHERE produced subsequent to FDA accelerated approval is capitalized and, therefore, we expect to record 
lower antibody expense in 2023 as compared to 2022. 
Selling, General and Administrative Expenses 
Selling, general and administrative expenses consist primarily of personnel-related costs, including stock-based 
compensation, for commercial operations and for personnel in executive, finance, accounting, business development, 
information technology, legal, and human resources functions. Other significant costs include facility costs not otherwise 
included in research and development expenses, commercial development activities, legal fees related to intellectual 
property and corporate matters, and fees for accounting and consulting services. 
Selling, general and administrative expenses increased $72.3 million to $116.1 million for 2022 due primarily 
to building our commercial capabilities, including personnel-related costs and infrastructure as well as expenses related 
to sales and marketing activities, in support of the U.S. launch of ELAHERE in the fourth quarter of 2022. 
Investment Income, net 
Investment income for 2022 and 2021 was $4.3 million and $0.1 million, respectively. The increase in 2022 
was driven by a greater average cash balance and an increase in interest rates. 
Non-Cash Interest Expense on Liability Related to Sale of Future Royalty 
In 2015, IRH purchased our right to receive 100% of the royalty payments on commercial sales of KADCYLA 
arising under our development and commercialization license with Genentech, subject to a residual cap. In January 2019, 
OMERS purchased IRH’s right to the royalties the Company previously sold in 2015. As described in Note H, “Liability 
Related to Sale of Future Royalties,” to our Consolidated Financial Statements, this royalty sale transaction has been 
recorded as a liability that amortizes over the estimated royalty payment period as KADCYLA royalties are remitted 
directly to the purchaser. During 2022 and 2021, we recorded $4.2 million and $13.1 million, respectively, of non-cash 
interest expense, which includes amortization of deferred financing costs. The decrease in 2022 was a result of a lower 
average royalty liability balance for the year and the KADCYLA royalty threshold being met in the second quarter of 
2021, effectively reducing the royalty payments under the 2015 transaction from 100% to 15% of KADCYLA royalty 
payments received over the remaining royalty term.  
We record interest expense at the imputed interest rate, which we currently estimate to be 10.5%. There are a 
number of factors that could materially affect the estimated interest rate in the future, in particular, the estimated amount 
and timing of royalty payments from future net sales of KADCYLA. We assess this estimate on a periodic basis and any 
resulting change in interest rate will be adjusted prospectively. 
Other Expense, net 
Other expense, net for 2022 and 2021 was $1.0 million and $1.1 million, respectively, substantially consisting 
of foreign currency exchange losses related to obligations with non-U.S. dollar-based suppliers and Euro cash balances 
maintained to fulfill them during the respective periods.  
Income Tax Expense 
For the year ended December 31, 2022, we incurred a tax expense of $1.2 million, primarily related to a 
significant income inclusion for U.S. tax purposes resulting from the transfer of certain intellectual property rights to a 
newly formed Swiss subsidiary and the impact of R&E capitalization pursuant to Section 174 of the 2017 Tax Act in 
2022, partially offset by net operating loss carryforwards and credits. No similar expense was recorded in 2021. 

51 
Liquidity and Capital Resources  
 
For a discussion related to our cash flows for 2021 compared to 2020, refer to Part II, Item 7, "Management's 
Discussion and Analysis of Financial Condition and Results of Operations – Liquidity and Capital Resources" in our 
Annual Report on Form 10–K for the year ended December 31, 2021 filed with the SEC on February 28, 2022. 
 
The following tables show certain balance sheet and cash flow information as of and for the periods indicated 
(in thousands): 
 
 
As of December 31,  
 
     
2022 
     
2021 
Cash and cash equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  275,138  $  478,750 
Working capital . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 182,263     399,054 
Shareholders’ equity  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 155,826     325,586 
 
 
     
Year Ended December 31, 
 
  
2022 
     
2021 
Cash used for operating activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  (229,802) $  (169,416)
Cash used for investing activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (1,364)   
 (1,434)
Cash provided by financing activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 27,554    
 355,744 
Cash Flows 
We require cash to fund our operating expenses, including the advancement of our clinical programs, and to 
make capital expenditures. Historically, we have funded our cash requirements primarily through equity and convertible 
debt financings in private and public markets and payments from our collaborators, including license fees, milestones, 
research funding, and royalties. We also monetized our rights to receive royalties on KADCYLA for upfront 
consideration. As of December 31, 2022, we had $275.1 million in cash and cash equivalents. Net cash used for 
operating activities was $229.8 million and $169.4 million during 2022 and 2021, respectively. The principal use of cash 
in operating activities for these periods was to fund our net loss, adjusted for non-cash items, with 2022 benefiting from 
$32.0 million of upfront payments pursuant to license agreements with Lilly and Magenta.  
Net cash used for investing activities was $1.4 million for each of 2022 and 2021, consisting of cash outflows 
for capital expenditures in both periods, including leasehold improvements, computer and office equipment, and 
dedicated equipment at third-party manufacturing vendors.  
Net cash provided by financing activities was $27.6 million and $355.7 million for 2022 and 2021, respectively. 
During 2022 and 2021, we sold 5.2 million and 6.7 million shares, respectively, of our common stock under our Open 
Market Sale AgreementSM (Sale Agreement) with Jefferies, LLC as sales agent, dated December 18, 2020, generating 
net proceeds of $25.6 million and $45.8 million in 2022 and 2021, respectively. Pursuant to the Sale Agreement, we may 
offer and sell, from time to time, shares of our common stock having an aggregate offering price of up to $150.0 million. 
As of December 31, 2022, $76.3 million remains available under the Sale Agreement. In connection with entering into 
the Sale Agreement, we filed a prospectus supplement to the prospectus included in our registration statement on Form 
S-3 (No. 333-251502), which became effective upon filing on December 18, 2020, with the SEC relating to the offer and 
sale of the up to $150.0 million of our common stock under the Sale Agreement.  
In December 2021, pursuant to a public offering, we issued and sold 17.5 million shares of common stock and 
issued pre-funded warrants to purchase 27.4 million shares of common stock, resulting in aggregate net proceeds of 
$277.6 million. Additionally, in August 2021, pursuant to a Securities Purchase Agreement with RA Capital Healthcare 
Fund, L.P., we issued a pre-funded warrant to purchase up to approximately 5.4 million shares of common stock, 
resulting in net proceeds of $29.8 million.  
Net cash provided by financing activities for 2022 and 2021 also include proceeds from the exercise of stock 
options and sale of shares through our ESPP. 
Future Capital Requirements 
We have significant future capital requirements including: 
• 
significant expected operating expenses to commercialize ELAHERE;  
• 
significant expected operating expenses to conduct research and development activities and to 
 

52 
potentially commercialize additional product candidates from our portfolio; 
• 
noncancelable in-process and future manufacturing obligations, including commercial supply of 
ELAHERE; and  
• 
substantial facility lease obligations as described in Note K, “Leases,” included in this Annual Report 
on Form 10-K. 
Our current level of cash and cash equivalents is not sufficient to meet our current operating plans for the next 
twelve months following the issuance of these financial statements. We plan to meet our operating cash flow 
requirements with current cash and cash equivalents, cash generated from commercial sales of ELAHERE, milestone 
payments from new or existing collaborations, and additional funds accessed through equity, debt, or other financings 
such as royalty financing transactions, as well as cash preservation activities. Such activities may not succeed. The 
failure to obtain sufficient funds on acceptable terms could have a material adverse effect on our business, results of 
operations, and financial condition and require us to defer or limit some or all of our research, development, clinical 
and/or commercial projects, including trials to support potential label expansion of ELAHERE. 
Recent Accounting Pronouncements 
The information set forth under Note B to the consolidated financial statements under the caption “Recently 
Adopted Accounting Pronouncements” is incorporated herein by reference. 
 
 

53 
Item 7A.  Quantitative and Qualitative Disclosure About Market Risk 
We maintain an investment portfolio in accordance with our investment policy. The primary objectives of our 
investment policy are to preserve principal, maintain proper liquidity to meet operating needs, and maximize yields. Our 
investments are comprised of money market funds consisting principally of U.S. Government-issued securities and high 
quality, short-term commercial paper. We do not currently own derivative financial instruments in our investment 
portfolio. Accordingly, we do not believe there is any material market risk exposure with respect to derivative or other 
financial instruments that would require disclosure under this item. 
Our foreign currency hedging program uses either forward contracts or a Euro-denominated bank account to 
manage the foreign currency exposures that exist as part of our ongoing business operations. Our foreign currency risk 
management strategy is principally designed to mitigate the future potential financial impact of changes in the value of 
transactions, anticipated transactions, and balances denominated in foreign currency resulting from changes in foreign 
currency exchange rates. Our market risks associated with changes in foreign currency exchange rates are currently 
limited to a Euro-denominated bank account as we had no forward contracts at December 31, 2022. Accordingly, we do 
not believe there was any material market risk exposure with respect to foreign currency exposures that would require 
disclosure under this item. 
 
 

54 
Item 8.  Financial Statements and Supplementary Data 
IMMUNOGEN, INC. 
INDEX TO CONSOLIDATED FINANCIAL STATEMENTS 
 
Page 
Report of Independent Registered Public Accounting Firm (PCAOB ID 42) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  55 
Consolidated Financial Statements: 
 
Consolidated Balance Sheets as of December 31, 2022 and 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  57 
Consolidated Statements of Operations and Comprehensive Loss for the Years Ended December 31, 2022, 
2021, and 2020  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  58 
Consolidated Statements of Shareholders’ Equity (Deficit) for the Years Ended December 31, 2022, 2021, 
and 2020 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  59 
Consolidated Statements of Cash Flows for the Years Ended December 31, 2022, 2021, and 2020  . . . . . . . . . .  60 
Notes to Consolidated Financial Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  61 
 
 
 

55 
Report of Independent Registered Public Accounting Firm 
 
To the Shareholders and the Board of Directors of ImmunoGen, Inc. 
 
Opinion on the Financial Statements 
We have audited the accompanying consolidated balance sheets of ImmunoGen, Inc. (the Company) as of December 31, 
2022 and 2021, the related consolidated statements of operations and comprehensive loss, shareholders' equity (deficit) 
and cash flows for each of the three years in the period ended December 31, 2022, and the related notes (collectively 
referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present 
fairly, in all material respects, the financial position of the Company at December 31, 2022 and 2021, and the results of 
its operations and its cash flows for each of the three years in the period ended December 31, 2022 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's internal control over financial reporting as of December 31, 2022, based on criteria 
established in Internal Control-Integrated Framework issued by the Committee of Sponsoring Organizations of the 
Treadway Commission (2013 framework) and our report dated March 1, 2023 expressed an unqualified opinion thereon. 
 
The Company's Ability to Continue as a Going Concern 
The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a 
going concern. As discussed in Note A to the financial statements, the Company has suffered recurring losses from 
operations and has stated that substantial doubt exists about the Company’s ability to continue as a going concern. 
Management's evaluation of the events and conditions and management’s plans regarding these matters are also 
described in Note A. The consolidated financial statements do not include any adjustments that might result from the 
outcome of this uncertainty. 
 
Basis for Opinion 
These financial statements are the responsibility of the Company's management. Our responsibility is to express an 
opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the 
PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities 
laws and the applicable rules and regulations of the Securities and Exchange Commission 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 reasonable assurance about whether the financial statements are free of material 
misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material 
misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those 
risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the 
financial statements. Our audits also included evaluating the accounting principles used and significant estimates made 
by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits 
provide a reasonable basis for our opinion. 
 
Critical Audit Matter 
The critical audit matter communicated below is a matter arising from the current period audit of the financial statements 
that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or 
disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or 
complex judgments. The communication of the critical audit matter does not alter in any way our opinion on the 
consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, 
providing a separate opinion on the critical audit matter or on the account or disclosure to which it relates. 
 
 
 
Clinical Trial Accrual 
Description of the 
Matter 
As discussed in Note B to the consolidated financial statements, the Company estimates certain 
clinical trial expenses due to a lag in receiving information from third parties. Moreover, payments 
for these activities are based on the terms of the individual arrangements, which may differ from 
the pattern of costs incurred. The Company maintained a clinical trial accrual of $15.7 million at 
December 31, 2022 included as a component of other accrued liabilities. 
 

56 
Auditing the Company’s clinical trial accruals was especially subjective due to the management 
judgment used to estimate the patient-related costs incurred but not yet invoiced. While the 
Company’s estimates of patient-related costs incurred but not yet invoiced are primarily based on 
information received from its vendors related to each clinical trial, the Company may need to use 
assumptions such as estimates of patient enrollment, patient cycles incurred, clinical sites activated, 
and other pass-through costs in determining its accrual. Additionally, due to the duration of the 
clinical trials as well as the timing of invoices received from vendors, actual amounts incurred are 
not typically known at the time the financial statements are issued. 
 
 
How We 
Addressed the 
Matter in Our 
Audit 
We obtained an understanding, evaluated the design and tested the operating effectiveness of 
internal controls related to clinical trial accruals. For example, we tested management’s review 
controls over the accuracy and completeness of the underlying data and the assumptions used in the 
Company’s process for recording accrued patient-related costs. 
 
Our audit procedures to test clinical trial accruals included, among others, testing the accuracy and 
completeness of the underlying data used to estimate costs incurred but not yet invoiced as well as 
evaluating and testing the assumptions used by management. We inspected the contracts and any 
amendments to the contracts with third parties and assessed the pattern of historical invoicing 
activity and the associated billing lags. We also corroborated the progress of clinical trials and other 
research and development projects through discussion with the Company’s research and 
development personnel that oversee the clinical trials. In addition, we inspected information 
obtained by the Company directly from third-party vendors, which included the third-party 
vendors’ estimate of costs incurred to date. We also compared subsequent invoices received from 
third-party vendors to the amounts accrued. 
 
 /s/ Ernst & Young LLP  
We have served as the Company’s auditor since 2001. 
Boston, Massachusetts  
March 1, 2023    
 

57 
IMMUNOGEN, INC. 
CONSOLIDATED BALANCE SHEETS 
In thousands, except per share amounts 
 
 
 
 
 
 
 
 
     December 31,       December 31,  
 
 
2022 
 
2021 
ASSETS 
   
   
Cash and cash equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 275,138  $ 
 478,750 
Accounts receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 12,596    
 4,467 
Unbilled receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 1,531    
 2,345 
Contract assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 3,000 
Non-cash royalty receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 3,851   
 4,115 
Prepaid and other current assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 11,005    
 7,322 
Total current assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 304,121    
 499,999 
Property and equipment, net of accumulated depreciation . . . . . . . . . . . . . . . . . . . . . . . . . .     
 4,377    
 4,663 
Operating lease right-of-use assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 10,231   
 12,392 
Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 16,196   
 — 
Other assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 14,011    
 8,711 
Total assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 348,936  $ 
 525,765 
LIABILITIES AND SHAREHOLDERS’ EQUITY  
   
   
Accounts payable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 45,353  $ 
 18,434 
Accrued compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 11,111    
 5,469 
Other accrued liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 38,783    
 23,077 
Current portion of liability related to the sale of future royalties, net of deferred  
financing costs of $162 and $198, respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 8,659   
 6,077 
Current portion of operating lease liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 4,096   
 3,537 
Current portion of deferred revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 13,856    
 44,351 
Total current liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 121,858    
 100,945 
Deferred revenue, net of current portion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 36,355    
 47,717 
Operating lease liability, net of current portion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 11,148   
 15,244 
Liability related to the sale of future royalties, net of current portion and deferred 
financing costs of $205 and $381, respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 23,449   
 34,967 
Other long-term liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 300    
 1,306 
Total liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 193,110    
 200,179 
Commitments and contingencies (Note L) 
   
   
Shareholders’ equity: 
   
   
Preferred stock, $.01 par value; authorized 5,000 shares; no shares issued and 
outstanding as of each of December 31, 2022 and 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 —    
 — 
Common stock, $.01 par value; authorized 600,000 shares; 226,046 and 220,361  
shares issued and outstanding as of December 31, 2022 and 2021, respectively . . . . . . . .     
 2,260    
 2,204 
Additional paid-in capital . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      1,847,638     1,794,525 
Accumulated deficit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      (1,694,072)    (1,471,143)
Total shareholders’ equity  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 155,826    
 325,586 
Total liabilities and shareholders’ equity  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 348,936  $ 
 525,765 
The accompanying notes are an integral part of the consolidated financial statements. 
 
 

58 
IMMUNOGEN, INC. 
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS 
In thousands, except per share amounts 
 
 
 
 
 
 
 
 
 
 
 
 
Year Ended 
 
 
December 31,  
 
     
2022 
     
2021 
     
2020 
Revenues: 
   
   
   
License and milestone fees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 76,027  $
 22,650  $
 63,742 
Non-cash royalty revenue related to the sale of future royalties . . . . . .    
 29,261   
 46,808   
 68,529 
Product revenue, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 2,554   
 —   
 — 
Research and development support . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 940    
 398    
 28 
Total revenues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 108,782    
 69,856    
 132,299 
Cost and operating expenses: 
  
  
  
Cost of sales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 176   
 —   
 — 
Research and development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 213,370    
 151,117   
 114,592 
Selling, general and administrative . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 116,129    
 43,812   
 38,600 
Restructuring charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 —   
 1,487 
Total cost and operating expenses . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 329,675    
 194,929    
 154,679 
Loss from operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      (220,893)    (125,073)   
 (22,380)
Investment income, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 4,341    
 51   
 729 
Non-cash interest expense on liability related to the sale of future  
royalties and convertible senior notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (4,165)  
 (13,103)  
 (23,107)
Interest expense on convertible senior notes . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 (47)  
 (95)
Other (expense) income, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (994)   
 (1,131)  
 481 
Net loss before income taxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  (221,711) $  (139,303) $
 (44,372)
Income tax expense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 1,218   
 —   
 — 
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (222,929)  
 (139,303)  
 (44,372)
Basic and diluted net loss per common share . . . . . . . . . . . . . . . . . . . . . . .   $ 
(0.88) $
(0.68) $
(0.25)
Basic and diluted weighted-average common shares outstanding . . . . . . .     
 253,631    
 206,147   
 176,153 
Total comprehensive loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  (222,929) $  (139,303) $
 (44,372)
The accompanying notes are an integral part of the consolidated financial statements. 
 
 

59 
IMMUNOGEN, INC. 
CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY (DEFICIT) 
In thousands 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
Additional   
 
 
Total 
 
 
Common Stock  
Paid-In  Accumulated Shareholders’
 
    Shares     Amount     
Capital     
Deficit 
    
Equity  
Balance at December 31, 2019 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     150,136  $  1,501  $ 1,209,846  $  (1,287,468) $ 
 (76,121)
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 —   
 —   
 (44,372)   
 (44,372)
Issuance of common stock pursuant to the exercise of stock options and 
employee stock purchase plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 458   
 5   
 1,466   
 —    
 1,471 
Issuance of common stock, net of issuance costs . . . . . . . . . . . . . . . . . . . . . .   
 44,496   
 445   
 193,826   
 —   
 194,271 
Restricted stock units vested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 395   
 4   
 (4)  
 —   
 — 
Restricted stock award forfeitures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 (487)  
 (5)  
 5   
 —   
 — 
Stock option and restricted stock compensation expense . . . . . . . . . . . . . . . . .    
 —   
 —   
 13,978   
 —    
 13,978 
Directors’ deferred share unit compensation . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 —   
 343   
 —   
 343 
Balance at December 31, 2020 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     194,998  $  1,950  $ 1,419,460  $  (1,331,840) $ 
 89,570 
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 —   
 —   
 —   
 (139,303)   
 (139,303)
Issuance of common stock pursuant to the exercise of stock options and 
employee stock purchase plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 998   
 10   
 3,759   
 —    
 3,769 
Issuance of common stock, net of issuance costs . . . . . . . . . . . . . . . . . . . . . .   
 24,181   
 242   
 153,788   
 —   
 154,030 
Issuance of pre-funded warrants, net of issuance costs . . . . . . . . . . . . . . . . . .   
 —   
 —   
 199,045   
 —   
 199,045 
Conversion of convertible senior notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 239   
 3   
 997   
 —   
 1,000 
Restricted stock units vested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 2   
 —   
 —   
 —    
 — 
Restricted stock award forfeitures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 (57)  
 (1)  
 1   
 —   
 — 
Stock option and restricted stock compensation expense . . . . . . . . . . . . . . . . .   
 —   
 —   
 16,794   
 —   
 16,794 
Directors’ deferred share unit compensation . . . . . . . . . . . . . . . . . . . . . . . . . .   
 —   
 —   
 681   
 —   
 681 
Balance at December 31, 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    220,361  $  2,204  $ 1,794,525  $  (1,471,143) $ 
 325,586 
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 —   
 —   
 —   
 (222,929)  
 (222,929)
Issuance of common stock, net of issuance costs . . . . . . . . . . . . . . . . . . . . . .   
 5,167   
 51   
 25,598   
 —   
 25,649 
Issuance of common stock pursuant to the exercise of stock options and 
employee stock purchase plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 491   
 5   
 1,900   
 —   
 1,905 
Stock option and restricted stock compensation expense . . . . . . . . . . . . . . . . .   
 —   
 —   
 24,899   
 —   
 24,899 
Restricted stock units vested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 27   
 —   
 —   
 —   
 — 
Directors’ deferred share unit compensation . . . . . . . . . . . . . . . . . . . . . . . . . .   
 —   
 —   
 716   
 —   
 716 
Balance at December 31, 2022 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    226,046  $  2,260  $ 1,847,638  $  (1,694,072) $ 
 155,826 
The accompanying notes are an integral part of the consolidated financial statements. 
 
 

60 
IMMUNOGEN, INC. 
CONSOLIDATED STATEMENTS OF CASH FLOWS 
In thousands 
 
 
 
 
 
 
 
 
 
 
 
 
Year Ended 
 
 
December 31,  
 
     
2022 
     
2021 
     
2020 
 
 
 
 
  
 
 
 
 
Cash flows from operating activities: 
   
   
   
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ (222,929)
$ (139,303) $  (44,372)
Adjustments to reconcile net loss to net cash used for operating activities: 
  
 
  
Non-cash royalty revenue related to sale of future royalties . . . . . . . . . . . . . . .     (12,836)
  (39,155)   (68,529)
Non-cash interest expense on liability related to sale of future  
royalties and convertible senior notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 4,165 
 
 13,103    23,107 
Depreciation and amortization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 1,783 
  
 2,017    
 2,101 
Gain on sale/disposal of fixed assets and impairment charges . . . . . . . . . . . . .     
 — 
  
 —    
 (691)
Stock and deferred share unit compensation . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 25,615 
  
 17,475     14,321 
Change in operating assets and liabilities: 
  
 
  
Accounts receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (8,129)
  
 (4,432)   
 7,465 
Unbilled receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 814 
  
 (2,334)   
 990 
Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      (16,196)
  
 —    
 — 
Contract asset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 3,000 
 
 (3,000)  
 3,631 
Prepaid and other current assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (3,683)
  
 579     (2,476)
Operating lease right-of-use assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 2,161 
 
 1,680   
 1,515 
Other assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (5,300)
  
 2,275     (7,202)
Accounts payable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 26,735 
  
 9,148    
 (819)
Accrued compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 5,642 
  
 849     (4,100)
Other accrued liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 14,750 
  
 (7,261)    16,734 
Deferred revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      (41,857)
   (18,041)    (17,323)
Operating lease liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (3,537)
 
 (3,016)  
 (2,972)
Net cash used for operating activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      (229,802)
   (169,416)    (78,620)
Cash flows from investing activities: 
   
   
   
Proceeds from sale of equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 — 
  
 —    
 1,426 
Purchases of property and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (1,364)
  
 (1,434)  
 (917)
Net cash used for investing activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (1,364)
  
 (1,434)   
 509 
Cash flows from financing activities: 
   
   
   
Payments upon settlement of convertible senior notes . . . . . . . . . . . . . . . . . .    
 —   
 (1,100)  
 — 
Proceeds from issuance of common stock under stock plans . . . . . . . . . . . . .     
 1,905 
  
 3,769    
 1,471 
Proceeds from warrant issuance, net of $391 of transaction costs . . . . . . . . .    
 — 
  199,045   
 — 
Proceeds from common stock issuance, net of $373 and $701 of  
transaction costs, respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 25,649 
  154,030    194,271 
Net cash provided by financing activities . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 27,554 
   355,744     195,742 
Net change in cash and cash equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      (203,612)
   184,894     117,631 
Cash and cash equivalents, beginning of period . . . . . . . . . . . . . . . . . . . . . . . . . . .      478,750 
   293,856     176,225 
Cash and cash equivalents, end of period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  275,138 
$  478,750  $ 293,856 
Supplemental cash flow information: 
   
   
   
Cash paid during the year for interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 — 
$
 47  $ 
 95 
The accompanying notes are an integral part of the consolidated financial statements. 
 
 

61 
IMMUNOGEN, INC. 
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS 
A. 
Nature of Business and Plan of Operations 
ImmunoGen, Inc. (the Company) was incorporated in Massachusetts in 1981 and is focused on the development 
and commercialization of antibody-drug conjugates, or ADCs. On November 14, 2022, the U.S. Food and Drug 
Administration (FDA) granted accelerated approval for ELAHERE™ (mirvetuximab soravtansine-gynx) for the 
treatment of adult patients with folate receptor alpha (FRα)-positive, platinum-resistant epithelial ovarian, fallopian tube, 
or primary peritoneal cancer, who have received one to three prior systemic treatment regimens. ELAHERE was 
approved under FDA's accelerated approval program based on objective response rate (ORR), duration of response 
(DOR), and safety data from the pivotal SORAYA trial. Continued approval may be contingent upon verification and 
description of clinical benefit in a confirmatory trial. 
The Company has generally incurred operating losses and negative cash flows from operations since inception, 
incurred a net loss of $222.9 million during the year ended December 31, 2022, and had an accumulated deficit of 
approximately $1.7 billion as of December 31, 2022. The Company has primarily funded these losses through payments 
received from its collaborations and equity, convertible debt, and other financings such as royalty financing transactions. 
Until the Company can generate significant cash flows from sales of ELAHERE, management expects to continue to 
generate substantial operating losses for at least the near term as the Company incurs significant operating expenses 
related to research and development and selling and marketing of ELAHERE. 
At December 31, 2022, the Company had $275.1 million of cash and cash equivalents on hand. The Company’s 
current level of cash and cash equivalents is not sufficient to meet its current operating plans for the next twelve months 
following the issuance of these financial statements. As a result, substantial doubt is deemed to exist regarding the 
Company’s ability to continue as a going concern for a period of one year from the issuance of these financial 
statements.  
The Company plans to meet its operating cash flow requirements with its current cash and cash equivalents, 
cash generated from commercial sales of ELAHERE, milestone payments from new or existing collaborations, and 
additional funds accessed through equity, debt, or other financings such as royalty financing transactions, as well as cash 
preservation activities. Such activities may not succeed. The failure of the Company to obtain sufficient funds on 
acceptable terms could have a material adverse effect on the Company’s business, results of operations, and financial 
condition and require the Company to defer or limit some or all of its research, development, clinical and/or commercial 
projects, including trials to support potential label expansion of ELAHERE. 
The accompanying consolidated financial statements have been prepared on a going concern basis, which 
contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The consolidated 
financial statements do not include any adjustments relating to the recoverability and classification of recorded asset 
amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. 
The Company is subject to risks common to companies in the biotechnology industry including, but not limited 
to, the development by its competitors of new technological innovations, dependence on key personnel, protection of 
proprietary technology, manufacturing and marketing limitations, challenges entering into new collaborations, 
complexities associated with managing collaboration arrangements, third-party reimbursements, and compliance with 
governmental regulations. 
B. 
Summary of Significant Accounting Policies 
Principles of Consolidation 
The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, 
ImmunoGen Switzerland GmbH, ImmunoGen U.S. Holding, Inc., ImmunoGen Securities Corp., ImmunoGen Europe 
Limited, ImmunoGen BioPharma (Ireland) Limited, and Hurricane, LLC. All intercompany transactions and balances 
have been eliminated. 
Use of Estimates 
The preparation of financial statements in conformity with accounting principles generally accepted in the 
United States (U.S.) requires management to make estimates and assumptions that affect the reported amounts of assets 
and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported 
amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. 

62 
Subsequent Events 
The Company has evaluated all events or transactions that occurred after December 31, 2022 up through the 
date the Company issued these financial statements. On February 28, 2023, the Company and Vertex Pharmaceuticals 
Incorporated (“Vertex”) entered into a multi-target license and option agreement, pursuant to which the Company 
granted Vertex rights to the Company’s ADC technology to research and evaluate ADCs directed to specified targets, 
with an option to take exclusive development and commercialization licenses to a specified number of targets over a 
specified term. Under the terms of the agreement, the Company is entitled to receive an upfront payment of $15.0 
million. The Company did not have any other material subsequent events. 
 
Revenue Recognition  
Product Revenue 
The Company generates product revenue from sales of ELAHERE in the U.S. to a limited number of specialty 
distributors and specialty pharmacy providers. These customers subsequently resell the products or dispense the products 
directly to patients. In addition, the Company has entered into arrangements with payors that provide for government 
mandated rebates, discounts, and allowances with respect to the utilization of its products. 
Product revenue is recognized when the customer takes control of the product, typically upon delivery to the 
customer. Product revenue is recorded at the net sales price, or transaction price, which includes estimated reserves for 
variable consideration resulting from chargebacks, government rebates, trade discounts and allowances, product returns 
and other incentives that are offered within the contract with customers, healthcare providers, payors and other indirect 
customers relating to the sales of the Company’s product. Reserves are established based on the amounts earned or to be 
claimed on the related sales. Where appropriate, the Company utilizes the expected value method to determine the 
appropriate amount for estimates of variable consideration based on factors such as the Company’s current contractual 
and statutory requirements, specific known market events and trends, industry data and forecasted customer buying and 
payment patterns, the percentage of our products that are sold via these programs, and our product pricing. The amount 
of variable consideration that is included in the transaction price may be constrained and is included in net product 
revenues only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue 
recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the 
Company’s estimates. If actual results vary from the Company’s estimates, the Company adjusts these estimates, which 
would affect net product revenue and earnings in the period such variances become known. 
Chargebacks: Chargebacks for fees and discounts represent the estimated obligations resulting from contractual 
commitments to sell product to qualified healthcare providers and government agencies at prices lower than the list 
prices charged to the customers who directly purchase the product from the Company. The customers charge the 
Company for the difference between what they pay for the product and the ultimate contractually committed or 
government required lower selling price to the qualified healthcare providers. These reserves are estimated using the 
expected value method based upon a range of possible outcomes and are established in the same period that the related 
revenue is recognized, resulting in a reduction of product revenue. 
Government rebates: Government rebates consist of Medicare and Medicaid rebates, which were estimated 
using the expected value method, based upon a range of possible outcomes for the estimated payor mix. These reserves 
are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue. 
Trade discounts and allowances: The Company provides the customers with discounts that are explicitly stated 
in the contracts and recorded as a reduction of revenue in the period the related product revenue is recognized.  
Product returns: The Company estimates the amount of its product sales that may be returned by its customers 
and records this estimate as a reduction of revenue in the period the related product revenue is recognized. The Company 
currently estimates product return liabilities based on available industry data and its visibility into the inventory 
remaining in the distribution channel. 
Other deductions: Co-pay assistance relates to financial assistance provided to qualified patients, whereby the 
Company may assist them with prescription drug co-payments required by the patient’s insurance provider. Reserves for 
co-pay assistance are recorded in the same period the related revenue is recognized, resulting in a reduction of product 
revenue. 
The Company entered into a third-party logistics distribution agreement (the 3PL Agreement) to engage a 
logistics distribution agent (the 3PL Agent) to distribute the Company’s products to its customers. The 3PL Agent 
provides services to the Company that include storage, distribution, processing product returns, customer service 
support, logistics 

63 
support, electronic data interface and system access support. Revenue is recognized upon transfer of control of the 
product to the customer. 
As a practical expedient, sales commissions, which represent costs to obtain a contract, are expensed when 
incurred because the amortization period would have been one year or less. Sales commissions are recorded in selling, 
general and administrative expense and costs of sales, respectively, in the statements of operations and comprehensive 
loss. Additionally, as a practical expedient, the Company has elected to treat all shipping and handling fees related to 
delivery of product as fulfillment activities. 
License and Milestone Fee Revenue 
The Company enters into licensing and development agreements with collaborators for the development of 
ADCs. The terms of these agreements contain multiple promised goods and services which may include (i) licenses, or 
options to obtain licenses, to the Company’s ADC technology, (ii) rights to future technological improvements, (iii) 
technology transfer services and other activities to be performed on behalf of the collaborative partner, and (iv) delivery 
of cytotoxic agents and/or the manufacture of preclinical and clinical materials for the collaborative partner. Payments to 
the Company under these agreements may include upfront fees, option fees, exercise fees, payments for services, 
payments for preclinical or clinical materials, payments based upon the achievement of certain milestones, and royalties 
on product sales. The Company follows the provisions of ASC 606, Revenue from Contracts with Customers, in 
accounting for these agreements. 
Revenue is recognized when a customer obtains control of promised goods or services in an amount that 
reflects the consideration which the entity expects to receive in exchange for those goods or services. In determining the 
appropriate amount of revenue to be recognized as it fulfills its obligations under the agreements, the Company performs 
the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether 
the promised goods or services are performance obligations, including whether they are distinct in the context of the 
contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of 
the transaction price to the performance obligations; and (v) recognition of revenue when or as the Company satisfies 
each performance obligation.   
The Company only applies the five-step model to contracts when it is probable that the Company will collect 
the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. At contract 
inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or 
services promised within each contract and determines those that are performance obligations based on its assessment of 
whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the 
transaction price that is allocated to the respective performance obligation when or as the performance obligation is 
satisfied. 
The Company exercises judgment in assessing those promised goods and services that are distinct and thus 
representative of performance obligations. To the extent the Company identifies multiple performance obligations in a 
contract, the Company must develop assumptions that require judgment to determine the estimated standalone selling 
price for each performance obligation in order to allocate the transaction price among the identified performance 
obligations. These judgments and assumptions are discussed in further detail below. 
At December 31, 2022, the Company had the following types of agreements with the parties identified below: 
• 
Development and commercialization licenses, which provide the counterparty with the right to use the 
Company’s ADC technology and/or certain other intellectual property to develop and commercialize 
compounds to a specified antigen target: 
Bayer (one exclusive single-target license) 
CytomX (two exclusive single-target licenses) 
Debiopharm (one exclusive single-compound license) 
Eli Lilly and Company (multiple exclusive single-target licenses) 
Fusion Pharmaceuticals (one exclusive single-target license) 
Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd. (one territory-specific exclusive single-
compound license) 
Magenta Therapeutics (one exclusive single-target license) 

64 
Novartis (one exclusive single-target licenses) 
Oxford BioTherapeutics/Menarini (one exclusive single-target license sublicensed from Amgen) 
Roche, through its Genentech unit (five exclusive single-target licenses) 
Viridian (one exclusive single-target license) 
• 
Collaboration and license agreement to co-develop and co-commercialize a specified anticancer compound 
on established terms: 
MacroGenics 
During the year ended December 31, 2022, pursuant to notice received, certain exclusive development and 
commercialization licenses granted to Novartis were terminated. 
There are no performance, cancellation, termination, or refund provisions in any of the arrangements that 
contain material financial consequences to the Company. 
Development and Commercialization Licenses 
The obligations under a development and commercialization license agreement generally include the license to 
the Company’s ADC technology with respect to a specified antigen target or compound and may also include obligations 
related to rights to future technological improvements and other activities to be performed on behalf of the collaborative 
partner. 
 Generally, development and commercialization licenses contain non-refundable terms for payments and, 
depending on the terms of the agreement, provide that the Company will earn payments upon the achievement of certain 
milestones and royalty payments, generally until the later of the last applicable patent expiration or a fixed period of 
years after product launch. Royalty rates may vary over the royalty term depending on the Company’s intellectual 
property rights and/or the presence of comparable competing products. In certain instances, the Company may also 
provide cytotoxic agents and/or clinical materials or other services in addition to the development and commercialization 
licenses. For example, the Company may provide technology transfer services in connection with the out-licensing of 
product candidates initially developed by the Company and may also provide technical assistance and share any 
technology improvements with its collaborators during the term of the collaboration agreements. The Company does not 
directly control when or whether any collaborator will request certain services, achieve milestones, or become liable for 
royalty payments. 
In determining the performance obligations for these arrangements, management evaluates whether the license 
is distinct and has significant standalone functionality either alone or with other readily available resources based on the 
consideration of the relevant facts and circumstances for each arrangement. Factors considered in this determination 
include the research capabilities of the partner and the availability of ADC technology research expertise and ADC 
manufacturing capabilities in the general marketplace and whether technological improvements are required for the 
continued functionality of the license. If the license to the Company’s intellectual property is determined to be distinct, 
the Company recognizes revenues from non-refundable, upfront fees allocated to the license when the license is 
transferred to the customer and the customer is able to use and benefit from the license. If the license is not distinct, the 
license is combined with other goods or services into a single performance obligation and revenue is recognized over 
time. 
The Company estimates the standalone selling prices of the license and all other performance obligations based 
on market conditions, similar arrangements entered into by third parties, and entity-specific factors such as the terms of 
the Company’s previous collaborative agreements, recent preclinical and clinical testing results of therapeutic products 
that use the Company’s ADC technology, the Company’s pricing practices and pricing objectives, the likelihood that 
technological improvements will be made, and, if made, will be used by the Company’s collaborators, and the nature of 
the other services to be performed on behalf of its collaborators and market rates for similar services. 
The Company recognizes revenue related to technology transfer activities and other services as the services are 
performed. The Company is generally compensated for these activities at negotiated rates that are consistent with what 
other third parties would charge. The Company records amounts recognized for services performed as a component of 
research and development support revenue.  
The Company may also provide cytotoxic agents and/or preclinical and clinical materials (drug substance/drug 
product) to its collaborators at negotiated prices generally consistent with what other third parties would charge. The 

65 
Company recognizes revenue on cytotoxic agents and/or preclinical and clinical materials when control transfers to the 
collaborator as a component of research and development support revenue.  
The Company recognizes revenue related to the rights to future technological improvements over the estimated 
term of the applicable license. 
The Company’s development and commercialization license agreements have milestone payments which for 
reporting purposes are aggregated into two categories: (i) development and regulatory milestones, and (ii) sales 
milestones. Development milestones are typically payable when a product candidate initiates or advances into different 
clinical trial phases. Regulatory milestones are typically payable upon submission for marketing approval with the FDA 
or other countries’ regulatory authorities or on receipt of actual marketing approvals for the compound or for additional 
indications. Sales milestones are typically payable when annual sales reach certain levels. 
At the inception of each arrangement, the Company evaluates any development and regulatory milestone 
payments to determine whether the milestone is considered probable of being reached and estimates the amount to be 
included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal 
would not occur, the associated milestone value is included in the transaction price to be allocated; otherwise, such 
amounts are considered constrained and excluded from the transaction price. As part of its evaluation of the constraint, 
the Company considers numerous factors, including whether the achievement of the milestone is outside the control of 
the Company and contingent upon the future success of clinical trials, the collaborator’s efforts, or the receipt of 
regulatory approval. At the end of each subsequent reporting period, the Company re-evaluates the probability of 
achievement of such development or regulatory milestones and any related constraint, and if necessary, adjusts the 
estimate of the transaction price. In addition, the Company evaluates whether the achievement of each milestone 
specifically relates to the Company’s efforts to satisfy a performance obligation or transfer a distinct good or service 
within a performance obligation. If the achievement of a milestone is considered a direct result of the Company’s efforts 
to satisfy a performance obligation or transfer a distinct good or service and the receipt of the payment is based upon the 
achievement of the milestone, the associated milestone value is allocated to that distinct good or service. If the milestone 
payment is not specifically related to the Company’s effort to satisfy a performance obligation or transfer a distinct good 
or service, the amount is allocated to all performance obligations using the relative standalone selling price method. 
Amounts allocated to a satisfied performance obligation are recognized as revenue, or as a reduction of revenue, in the 
period in which the transaction price changes. 
For development and commercialization license agreements that include sales-based royalties, including 
milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the 
royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the 
performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied) in 
accordance with the royalty recognition constraint. Under the Company’s development and commercialization license 
agreements, the Company receives royalty payments based upon its licensees’ net sales of covered products. Generally, 
under the development and commercialization agreements, the Company receives royalty reports and payments from its 
licensees approximately one quarter in arrears. The Company estimates the amount of royalty revenue to be recognized 
based on historical and forecasted sales and/or sales information from its licensees if available.  
Collaboration and Option Agreements/Right-to-Test Agreements 
The Company’s right-to-test agreements provide collaborators the right to test the Company’s ADC technology 
for a defined period of time through a research, or right-to-test, license. Under both right-to-test agreements and 
collaboration and option agreements, collaborators may (a) “take” options, for a defined period of time, to specified 
targets and (b) upon exercise of those options, secure or “take” licenses to develop and commercialize products for the 
specified targets on established terms. Under these agreements, fees may be due to the Company (i) at the inception of 
the arrangement (referred to as “upfront” fees or payments), (ii) upon the opt-in to acquire a development and 
commercialization license(s) (referred to as exercise fees or payments earned, if any, when the development and 
commercialization license is “taken”), (iii) after providing services at the collaborator’s request at negotiated prices, 
which are generally consistent with what other third parties would charge, or (iv) upon some combination of all of these 
fees. 
The accounting for collaboration and option agreements and right-to-test agreements is dependent on the nature 
of the options granted to the collaborative partner. Options are considered distinct performance obligations if they 
provide a collaborator with a material right. Factors that are considered in evaluating whether options convey a material 
right include the overall objective of the arrangement, the benefit the collaborator might obtain from the agreement 
without exercising the options, the cost to exercise the options relative to the fair value of the licenses, and the additional 
financial commitments or economic penalties imposed on the collaborator as a result of exercising the options.  

66 
If the Company concludes that an option provides the customer a material right, and therefore is a separate 
performance obligation, the Company then determines the estimated standalone selling price of the option using the 
following inputs: (a) estimated fair value of the license underlying each option, (b) the amount the partner would pay to 
exercise the option to obtain the license, and (c) probability of exercise.  
The Company does not control when or if any collaborator will exercise its options for development and 
commercialization licenses. As a result, the Company cannot predict when or if it will recognize revenues in connection 
with any of the foregoing. 
Upfront payments on development and commercialization licenses may be recognized upon delivery of the 
license if facts and circumstances dictate that the license is distinct from the other promised goods and services. 
In determining whether a collaboration and option agreement is within the scope of ASC 808, Collaborative 
Arrangements, management evaluates the level of involvement of both companies in the development and 
commercialization of the products to determine if both parties are active participants and if both parties are exposed to 
risks and rewards dependent on the commercial success of the licensed products. If the agreement is determined to be 
within the scope of ASC 808 and not representative of a vendor-customer relationship, the Company segregates the 
research and development activities and the related cost sharing arrangement. Payments made by the Company for such 
activities are recorded as research and development expense and reimbursements received from the partner are 
recognized as an offset to research and development expense.  
Transaction Price Allocated to Remaining Performance Obligations 
Deferred revenue under ASC 606 represents the portion of the transaction price received under various 
contracts for which work has not been performed (or has been partially performed) and includes unexercised contract 
options that are considered material rights. As of December 31, 2022, the aggregate amount of the transaction price 
allocated to remaining performance obligations comprising deferred revenue was $50.2 million. The Company expects 
to recognize revenue on approximately 28%, 70%, and 2% of the remaining performance obligations over the next 
12 months, 13 to 60 months, and 61 to 120 months, respectively, however, it does not control when or if any collaborator 
will terminate existing development and commercialization licenses. 
Contract Balances from Contracts with Customers 
The following tables present changes in the Company’s contract assets and contract liabilities during the years 
ended December 31, 2022 and 2021 (in thousands): 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Balance at 
 
 
 
 
 
 
 
 
 
 
Balance at 
 
    December 31, 2021    Additions      Deductions     Impact of Netting     December 31, 2022
Contract asset . . . . . . . . . . . . . . . . . . . . . .   $ 
 3,000  $ 
 —  $
 (3,000) $ 
 —  $ 
 — 
Contract liabilities (deferred revenue) . .   $ 
 92,068  $ 
 7,605  $  (49,462) $ 
 —  $ 
 50,211 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Balance at 
   
   
   
 
Balance at 
 
    December 31, 2020    Additions      Deductions     Impact of Netting     December 31, 2021
Contract asset . . . . . . . . . . . . . . . . . . . . . .   $ 
 —  $ 
 5,500  $
 (2,500) $ 
 — 
 $ 
 3,000 
Contract liabilities (deferred revenue) . .   $ 
 110,109  $ 
 4,753  $  (22,794) $ 
 — 
 $ 
 92,068 
 
During the years ended December 31, 2022, 2021, and 2020 the Company recognized the following revenues as 
a result of changes in contract asset and contract liability balances in the respective periods (in thousands):  
 
 
 
 
 
 
 
 
 
 
 
 
Year Ended  
 
 
December 31,  
 
     
2022 
     
2021 
     
2020 
Revenue recognized in the period from: 
   
   
   
Amounts included in contract liabilities at the beginning of the period . .   $ 
 49,462  $ 
 22,765  $ 
 61,872 
Performance obligations satisfied in previous periods . . . . . . . . . . . . . . . .   $ 
 13,661 
$ 
 5,500  $ 
 — 
 

67 
The timing of revenue recognition, billings, and cash collections results in billed receivables, unbilled 
receivables, contract assets, and contract liabilities on the consolidated balance sheets. When consideration is received, 
or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer 
under the terms of a contract, a contract liability is recorded (under the caption deferred revenue). Contract liabilities are 
recognized as revenue after control of the products or services is transferred to the customer and all revenue recognition 
criteria have been met. 
The Company recorded the following during the year ended December 31, 2022: (i) pursuant to the Company’s 
license agreement with Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd. (Huadong), upon delivery of clinical 
materials in 2022, the Company recognized as license and milestone fee revenue the remaining $28.5 million of the 
deferred revenue balance as of December 31, 2021 related to the $45.0 million of upfront and development milestone 
payments previously received; (ii) pursuant to a license agreement executed with Eli Lilly and Company (Lilly) during 
2022, the Company received upfront payments of $26.0 million, of which $18.4 million was recognized as license and 
milestone fee revenue and the remainder deferred, further details of which can be found in Note C, “Agreements”; 
(iii) pursuant to a license agreement executed with Magenta Therapeutics in 2022, the Company recorded $6.0 million as 
license and milestone fee revenue, of which $1.6 million had been previously received and recorded as deferred revenue 
as of December 31, 2021; (iv) $16.4 million of previously deferred non-cash royalty revenue related to the sale of rights 
to KADCYLA royalties, further details of which can be found in Note H, “Liability Related to Sale of Future Royalties”; 
and (v) $2.9 million of license and milestone fee revenue related to numerous collaborators’ rights to technological 
improvements that had been previously deferred, which includes $2.8 million related to Novartis Institutes for 
BioMedical Research, Inc.’s (Novartis) termination of certain of the license agreements between the Company and 
Novartis in August 2022, further details of which can be found in Note C, “Agreements.” Lastly, during 2021, the 
Company recorded a contract asset of $3.0 million for a probable development milestone pursuant to its license 
agreement with Viridian Therapeutics, Inc. (Viridian), which was subsequently achieved in April 2022. 
Pursuant to the Company’s license agreement with Huadong, upon delivery of clinical materials in 2021, the 
Company recorded $14.6 million of the $40.0 million upfront payment received and deferred in 2020 as license and 
milestone fee revenue. Additionally, in December 2021, the Company received a $5.0 million payment for a 
development milestone achieved pursuant to its agreement with Huadong, of which $1.8 million was recorded as license 
and milestone fee revenue in 2021, with the remainder deferred and recorded as revenue upon delivery of clinical 
material in 2022 as noted above. Also, during 2021, pursuant to its license agreement with Viridian, the Company 
recorded $2.5 million as license and milestone fee revenue related to a development milestone achieved in October 2021 
and a contract asset of $3.0 million for a second probable development milestone which was subsequently achieved and 
paid in 2022 as discussed above. The Company also recorded $0.2 million as license and milestone fee revenue for 
delivery of certain materials to Viridian that had been previously deferred, $0.3 million of license and milestone fee 
revenue related to numerous collaborators’ rights to technological improvements that had been previously deferred, and 
recorded $7.7 million of previously deferred non-cash royalty revenue related to the sale of rights to KADCYLA 
royalties, further details of which can be found in Note H, “Liability Related to Sale of Future Royalties.”  Lastly, 
pursuant to a research agreement with Magenta, the Company received a $1.6 million upfront option fee that was 
included in deferred revenue at December 31, 2021. 
During 2020, the Company recognized $60.5 million of previously deferred license revenue upon Jazz’s opt-out 
of its right to the last remaining license under the agreement and $3.2 million of upfront fees previously received from 
other partners, of which $1.4 million was included in contract liabilities at the beginning of 2020. As noted above, a 
$40.0 million upfront payment received in 2020 pursuant to a license agreement executed with Huadong was recorded as 
deferred revenue and none of this amount was recognized as revenue during 2020. Additionally, a contract asset of $3.6 
million, net of $4.4 million in related contract liabilities, was recorded for two probable milestones in 2019 pursuant to 
license agreements with CytomX and Novartis, which were subsequently achieved and paid during 2020.  
Financial Instruments and Concentration of Credit Risk 
Cash and cash equivalents are primarily maintained with three financial institutions in the U.S. Deposits with 
banks may exceed the amount of insurance provided on such deposits. Generally, these deposits may be redeemed upon 
demand and, therefore, bear minimal risk. The Company’s cash equivalents consist of money market funds with 
underlying investments primarily being U.S. Government-issued securities and high quality, short-term commercial 
paper. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of 
cash, cash equivalents, and marketable securities. The Company held no marketable securities as of December 31, 2022 
and 2021. The Company’s investment policy, approved by the Board of Directors, limits the amount it may invest in any 
one type of investment, thereby reducing credit risk concentrations. 

68 
Cash and Cash Equivalents 
All highly liquid financial instruments with maturities of three months or less when purchased are considered 
cash equivalents. As of December 31, 2022 and 2021, the Company held $275.1 million and $478.8 million, 
respectively, in cash and money market funds consisting principally of U.S. Government-issued securities and high 
quality, short-term commercial paper which were classified as cash and cash equivalents.  
Non-cash Investing Activities 
The Company had $0.3 million and $0.2 million of accrued capital expenditures as of December 31, 2022 and 
2021, respectively, which have been treated as a non-cash investing activity and accordingly, are not reflected in the 
consolidated statement of cash flows.  
Fair Value of Financial Instruments 
ASC 820, Fair Value Measurement, defines fair value, establishes a framework for measuring fair value in 
accordance with accounting principles generally accepted in the U.S., and provides for disclosures about fair value 
measurements. Fair value is defined under ASC 820 as the exchange price that would be received for an asset or paid to 
transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly 
transaction between market participants on the measurement date. Valuation techniques used to measure fair value must 
maximize the use of observable inputs and minimize the use of unobservable inputs. The standard describes a hierarchy 
to measure fair value which is based on three levels of inputs, of which the first two are considered observable and the 
last unobservable, as follows: 
• 
Level 1—Quoted prices in active markets for identical assets or liabilities. 
• 
Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices 
for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are 
observable or can be corroborated by observable market data for substantially the full term of the assets or 
liabilities. 
• 
Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to 
the fair value of the assets or liabilities. 
As of December 31, 2022 and 2021, the Company held certain assets that are required to be measured at fair 
value on a recurring basis. The fair value of the Company’s cash equivalents is based on quoted prices from active 
markets (Level 1 inputs). The carrying amounts reflected in the consolidated balance sheets for accounts receivable, 
unbilled receivable, contract assets, non-cash royalty receivable, prepaid and other current assets, accounts payable, 
accrued compensation, and other accrued liabilities approximate fair value due to their short-term nature.  
Accounts Receivable  
Accounts receivable arise from product sales and amounts due from the Company’s collaboration partners. The 
amount from product sales represents amounts due from specialty distributors and specialty pharmacy providers in the 
U.S. The Company monitors economic conditions and the financial performance and credit worthiness of its 
counterparties to identify facts or circumstances that may indicate that its receivables are at risk of collection. The 
Company provides reserves against accounts receivable for estimated losses that may result from a customer’s inability 
to pay based on the composition of its accounts receivable, considering past events, current economic conditions, and 
reasonable and supportable forecasts about the future economic conditions. The contractual life of our accounts 
receivable is generally short-term. Amounts determined to be uncollectible are charged or written-off against the reserve. 
For the years ended December 31, 2022 and 2021, the Company did not record any expected credit losses related to 
outstanding accounts receivable. 
Unbilled Receivable 
Unbilled receivable primarily represents research funding earned based on actual resources utilized and external 
expenses incurred under certain of the Company’s collaborator agreements. 
Inventory 
Inventories are stated at the lower of cost or estimated net realizable value with cost based on the first-in first-
out method. Inventory that can be used in either the production of clinical or commercial products is expensed as 
research and development costs when identified for use in clinical trials. The Company classifies its inventory costs as 
long-term when it expects to utilize the inventory beyond its normal operating cycle based on forecasted levels of sales. 

69 
Prior to the regulatory approval of its drug candidates, the Company incurs expenses for the manufacture of 
drug product to support clinical development that could potentially be available to support the commercial launch of 
those drugs. Until the date at which regulatory approval has been received or is otherwise considered probable, the 
Company records all such costs as research and development expenses. Inventory used in clinical trials is also expensed 
as research and development expense, when selected for such use. 
The Company performs an assessment of the recoverability of capitalized inventories during each reporting 
period and writes down any excess and obsolete inventory to its net realizable value in the period in which the 
impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of sales 
in the consolidated statements of operations and comprehensive loss. The determination of whether inventory costs will 
be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected 
by management, additional write-downs of inventory may be required. 
Clinical Trial Accruals 
Clinical trial expenses are a significant component of research and development expenses, and the Company 
outsources a significant portion of these activities to third parties. Third-party clinical trial expenses include investigator 
fees, site costs (patient cost), clinical research organization costs, and costs for central laboratory testing and data 
management. The accrual for site and patient costs includes inputs such as estimates of patient enrollment, patient cycles 
incurred, clinical site activations, and other pass-through costs. These inputs are required to be estimated due to a lag in 
receiving the actual clinical information from third parties. Payments for these activities are based on the terms of the 
individual arrangements, which may differ from the pattern of costs incurred. Clinical trial costs are reflected on the 
consolidated balance sheets as prepaid assets (to the extent payments exceed costs incurred) or accrued clinical trial costs 
(to the extent costs incurred exceed payments). These third-party agreements are generally cancelable, and related costs 
are recorded as research and development expenses as incurred. Non-refundable advance clinical payments for goods or 
services that will be used or rendered for future R&D activities are recorded as a prepaid asset and recognized as 
expense as the related goods are delivered or the related services are performed. The Company also records accruals for 
estimated ongoing clinical research and development costs. When evaluating the adequacy of the accrued liabilities, the 
Company analyzes progress of the studies, including the phase or completion of events, invoices received, and 
contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any 
reporting period. Actual results could differ from the estimates made by the Company. The historical clinical accrual 
estimates made by the Company have not been materially different from the actual costs.  
Leases 
The Company determines if an arrangement is a lease at inception. Operating leases include right-of-use (ROU) 
assets and operating lease liabilities (current and non-current), which are recorded in the Company’s consolidated 
balance sheets. Single payment capital leases for equipment that are considered finance leases are included in property 
and equipment in the Company’s consolidated balance sheets. As the single payment obligations have all been made, 
there is no related liability recorded.   
ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities 
represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and 
liabilities are recognized at commencement date based on the present value of lease payments over the lease term. The 
Company uses the implicit rate when readily determinable. As a number of the Company’s leases do not provide an 
implicit rate, the Company uses an incremental borrowing rate applicable to the Company based on the information 
available at the commencement date in determining the present value of lease payments. As the Company has no 
existing or proposed collateralized borrowing arrangements, to determine a reasonable incremental borrowing rate, the 
Company considers collateral assumptions, the lease term, the Company’s current credit risk profile, and rates for 
existing borrowing arrangements for comparable peer companies. The Company accounts for the lease and fixed non-
lease components as a single lease component. The Company’s lease terms may include options to extend or terminate 
the lease when it is reasonably certain that the Company will exercise that option. Lease expense for operating lease 
payments is recognized on a straight-line basis over the lease term. 

70 
Other Accrued Liabilities 
Other accrued liabilities consisted of the following at December 31, 2022 and 2021 (in thousands): 
 
 
 
 
 
 
 
 
 
December 31,       December 31,  
 
     
2022 
 
2021 
Accrued contract payments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 15,971 
$ 
 5,558 
Accrued clinical trial costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 15,716 
  
 15,556 
Accrued professional services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 2,020 
  
 839 
Accrued employee benefits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 340 
  
 40 
Accrued public reporting charges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 265 
  
 309 
Accrued tax provision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 1,218   
 — 
Other current accrued liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 3,253 
  
 775 
Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 38,783 
$ 
 23,077 
Accrued contract payments included in the table above primarily relate to external manufacturing, regulatory, 
and quality-related services. The increase in the balance as of December 31, 2022 compared to prior year was driven by 
timing of external manufacturing expenses. 
Research and Development Expenses 
The Company’s research and development expenses are charged to expense as incurred and relate to 
(i) research to evaluate new targets and to develop and evaluate new antibodies, linkers, and cytotoxic agents, 
(ii) preclinical testing of its own and, in certain instances, its collaborators’ product candidates, and the cost of its own 
clinical trials, (iii) development related to clinical and commercial manufacturing processes, (iv) regulatory activities, 
(v) medical affairs activities, and (vi) external manufacturing operations. Payments made by the Company in advance for 
research and development services not yet provided and/or materials not yet delivered and accepted are recorded as 
prepaid expenses and are included in the accompanying consolidated balance sheets as prepaid and other current assets. 
Income Taxes 
The Company uses the liability method to account for income taxes. Deferred tax assets and liabilities are 
determined based on differences between the financial reporting and income tax basis of assets and liabilities, as well as 
net operating loss carry forwards and tax credits and are measured using the enacted tax rates and laws that will be in 
effect when the differences reverse. A valuation allowance against net deferred tax assets is recorded if, based on the 
available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. 
Property and Equipment 
Property and equipment are stated at cost. The Company provides for depreciation based upon expected useful 
lives using the straight-line method over the following estimated useful lives: 
Machinery and equipment . . . . . . . . . . . . . . . . . . . . . . . .       5 years 
 
Computer hardware and software . . . . . . . . . . . . . . . . . .    
3 years 
 
Furniture and fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
5 years 
 
Leasehold improvements . . . . . . . . . . . . . . . . . . . . . . . . .    
Shorter of remaining lease term or 7 years 
 
Equipment under capital leases is amortized over the lives of the respective leases or the estimated useful lives 
of the assets, whichever is shorter, and included in depreciation expense. Maintenance and repairs are charged to 
expense as incurred. Upon retirement or sale, the cost of disposed assets and the related accumulated depreciation are 
removed from the accounts and any resulting gain or loss is included in the statement of operations.  
Impairment of Long-Lived Assets 
The Company continually evaluates whether events or circumstances have occurred that indicate that the 
estimated remaining useful life of its long-lived assets may warrant revision or that the carrying value of these assets 
may be impaired if impairment indicators are present. The Company evaluates the realizability of its long-lived assets 
based on cash flow expectations for the related asset. Any write-downs to fair value are treated as permanent reductions 
in the carrying amount of the assets. Based on this evaluation, the Company believes that, as of each of the balance sheet 
dates presented, none of the Company’s long-lived assets were impaired. 

71 
Common Stock Warrants  
The Company accounts for common stock warrants as either equity-classified or liability-classified instruments 
based on an assessment of the warrant’s specific terms and applicable authoritative guidance included in Financial 
Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 480, Distinguishing Liabilities 
from Equity (“ASC 480”) and ASC 815, Derivatives and Hedging (“ASC 815”). The assessment considers whether the 
warrants are freestanding financial instruments pursuant to ASC 480, whether the warrants meet the definition of a 
liability pursuant to ASC 480, and whether the warrants meet all of the requirements for equity classification under ASC 
815, including whether the warrants are indexed to the Company’s own common stock and whether the warrant holders 
could potentially require “net cash settlement” in a circumstance outside of the Company’s control, among other 
conditions for equity classification. This assessment, which requires the use of professional judgment, is conducted at the 
time of warrant issuance and as of each subsequent quarterly period end date while the warrants are outstanding. 
For issued or modified warrants that meet all of the criteria for equity classification, the warrants are required to 
be recorded as a component of additional paid-in capital at the time of issuance. For issued or modified warrants that do 
not meet all the criteria for equity classification, the warrants are required to be recorded at their initial fair value on the 
date of issuance and remeasured each balance sheet date thereafter. Changes in the estimated fair value of the liability-
classified warrants are recognized as a non-cash gain or loss in the accompanying consolidated statements of operations 
and comprehensive loss. 
Computation of Net Loss per Common Share 
Basic and diluted net loss per share is calculated based upon the weighted average number of shares of common 
stock outstanding during the period. Shares of the Company’s common stock underlying pre-funded warrants are 
included in the calculation of basic and diluted earnings per share. During periods of income, participating securities are 
allocated a proportional share of income determined by dividing total weighted average participating securities by the 
sum of the total weighted average common shares and participating securities (the “two-class method”). Shares of the 
Company’s restricted stock participate in any dividends that may be declared by the Company and are therefore 
considered to be participating securities. Participating securities have the effect of diluting both basic and diluted 
earnings per share during periods of income. During periods of loss, no loss is allocated to participating securities since 
they have no contractual obligation to share in the losses of the Company. Diluted loss per share is computed after giving 
consideration to the dilutive effect of stock options, convertible notes, and restricted stock that are outstanding during the 
period, except where such non-participating securities would be anti-dilutive. 
The Company’s common stock equivalents, as calculated in accordance with the treasury-stock method for 
options and unvested restricted stock and the if-converted method for the convertible notes, are shown in the following 
table (in thousands): 
 
 
 
 
 
 
 
 
 
Year Ended December 31, 
 
     
2022 
     
2021 
     
2020 
Options outstanding to purchase common stock, shares issuable under the 
employee stock purchase plan, and unvested restricted stock/units at end of 
period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 33,264 
 21,296 
 18,459 
Common stock equivalents under treasury stock method for options, shares 
issuable under the employee stock purchase plan, and unvested restricted 
stock/units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 1,596 
 2,546 
 1,301 
Shares issuable upon conversion of convertible notes at end of period . . . . . . . .   
 —  
 —  
 501 
Common stock equivalents under if-converted method for convertible notes . . .   
 —  
 —  
 501 
The Company’s common stock equivalents have not been included in the net loss per share calculation because 
their effect is anti-dilutive due to the Company’s net loss position. 
Stock-based Compensation 
As of December 31, 2022, the Company is authorized to grant future awards under three employee share-based 
compensation plans, which are the ImmunoGen, Inc. 2018 Employee, Director and Consultant Equity Incentive Plan, or 
the 2018 Plan, the Employee Stock Purchase Plan, or ESPP, and the ImmunoGen Inducement Equity Incentive Plan, or 
the Inducement Plan. At the annual meeting of shareholders on June 15, 2022, the 2018 Plan was amended to provide for 

72 
the issuance of stock grants, the grant of options, and the grant of stock-based awards for up to an additional 
13,000,000 shares of the Company’s common stock, as well as up to 28,742,013 shares of common stock, which 
represent the number of shares of common stock remaining under the 2018 Plan as of April 1, 2022, and awards 
previously granted under the 2018 Plan and the Company’s former stock-based plans, including the ImmunoGen, Inc. 
2016 and 2006 Employee, Director and Consultant Equity Incentive Plans, that forfeit, expire, or cancel without delivery 
of shares of common stock or which resulted in the forfeiture of shares of common stock back to the Company 
subsequent to April 1, 2022. The Inducement Plan was approved by the Board of Directors in December 2019, and 
pursuant to subsequent amendments, provides for the issuance of non-qualified option grants for up to 10,500,000 shares 
of the Company’s common stock. Options awarded under the two plans are granted with an exercise price equal to the 
market price of the Company’s stock at the date of grant. Options vest at various periods of up to four years and may be 
exercised within ten years of the date of grant under each of these plans.   
The stock-based awards are accounted for under ASC 718, “Compensation—Stock Compensation.” Pursuant to 
ASC 718, the estimated grant date fair value of awards is charged to the statement of operations over the requisite 
service period, which is the vesting period. The fair value of each stock option is estimated on the date of grant using the 
Black-Scholes option-pricing model with the weighted-average assumptions noted in the following table. As the 
Company has not paid dividends since inception, nor does it expect to pay any dividends for the foreseeable future, the 
expected dividend yield assumption is zero. Expected volatility is based exclusively on historical volatility of the 
Company’s stock. The expected term of stock options granted is based exclusively on historical data and represents the 
period of time that stock options granted are expected to be outstanding. The expected term is calculated for and applied 
to one group of stock options as the Company does not expect substantially different exercise or post-vesting termination 
behavior amongst its employee population. The risk-free rate of the stock options is based on the U.S. Treasury rate in 
effect at the time of grant for the expected term of the stock options. 
 
 
 
 
 
 
 
 
 
 
Year Ended 
 
 
December 31, 
 
     
2022 
     
2021 
     
2020 
Dividend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
None 
 
None 
 
None 
Volatility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
83.09%  
84.67%  
85.07% 
Risk-free interest rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
2.76% 
 
0.80% 
 
1.21% 
Expected life (years) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
5.9 
 
6.0 
 
6.0 
 
Using the Black-Scholes option-pricing model, the weighted-average grant date fair values of options granted 
during the years ended December 31, 2022, 2021, and 2020, were $3.62, $5.07, and $3.28 per share, respectively. 
A summary of option activity under the option plans for 2022 is presented below (in thousands, except 
weighted-average data): 
 
 
 
 
 
 
 
 
 
 
 
 
     
 
     
Weighted- 
     Weighted-       
 
 
 
Number 
 
Average 
 
Average 
 
Aggregate 
 
 
of Stock 
 
Exercise 
 
Remaining  
Intrinsic 
 
 
Options 
 
Price 
 
Life in Yrs.  
Value 
Outstanding at December 31, 2021 . . . . . . . . . . . . . . . . . . . .   
21,219  $ 
6.28  
  
Granted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
13,892   
5.11  
  
Exercised . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
(313)  
3.89  
  
Forfeited/Canceled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
(1,672)  
 7.40  
  
Outstanding at December 31, 2022 . . . . . . . . . . . . . . . . . . . .   
33,126  $ 
5.76  
7.71  $ 
 11,013 
Exercisable at December 31, 2022 . . . . . . . . . . . . . . . . . . . . .    
15,018  $ 
6.27  
6.14  $ 
 7,685 
Vested and expected to vest at December 31, 2022 . . . . . . .    
33,126  $ 
5.76  
7.71  $ 
 11,013 
In 2020, the Company issued 2.6 million performance-based stock options to certain employees that will vest 
upon the achievement of specified performance goals. Upon assessment of the performance-based stock option awards 
as of December 31, 2021, the Company determined the first performance goal to be probable of vesting and, as such, 
recorded $2.6 million of stock-based compensation expense for the year ended December 31, 2021. In May 2022, the 
first performance goal was achieved, resulting in the vesting of 25% of the 2.6 million performance-based stock options. 
In November 2022, the second performance goal was achieved, resulting in the vesting of 50% of the 2.6 million 
performance-based stock options and $5.2 million of stock-based compensation expense recorded for the year ended 
December 31, 2022. On December 31, 2022, 12.5% of the 2.6 million performance-based stock options forfeited. The 
fair value of the remaining unvested performance-based stock options that could be expensed in future periods is $1.3 
million. 

73 
 A summary of restricted stock and restricted stock unit activity under the option plans for 2022 is presented 
below (in thousands, except weighted-average data): 
 
 
 
 
 
 
 
 
 
Number of  
Weighted- 
 
 
Restricted  
Average Grant 
 
     Stock Shares      Date Fair Value 
Unvested at December 31, 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
77  $ 
5.59 
Granted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
138   
5.45 
Vested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (27)  
5.43 
Forfeited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 (50)  
5.68 
Unvested at December 31, 2022 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
138  $ 
5.45 
 
In June 2018, the Company's Board of Directors, with shareholder approval, adopted the Employee Stock 
Purchase Plan. Following the share increase on January 1, 2021 under the ESPP’s “evergreen” provision, an aggregate of 
2,000,000 shares of common stock have been reserved for issuance under the ESPP. Under the ESPP, eligible 
participants purchase shares of the Company's common stock at a price equal to 85% of the lesser of the closing price of 
the Company's common stock on the first business day and the final business day of the applicable plan purchase period. 
Plan purchase periods are six months and begin on January 1 and July 1 of each year, with purchase dates occurring on 
the final business day of the given purchase period. The fair value of each ESPP award is estimated on the first day of 
the offering period using the Black-Scholes option-pricing model. The Company recognizes share-based compensation 
expense equal to the fair value of the ESPP awards on a straight-line basis over the offering period. During 2022, 2021, 
and 2020, approximately 178,000, 126,000, and 122,000 shares, respectively, were issued to participating employees at 
fair values ranging from $1.72 to $2.37 per share.  
Stock compensation expense related to stock options and restricted stock awards granted under the option plans 
and the ESPP was $24.9 million, $16.8 million, and $14.0 million during the years ended December 31, 2022, 2021, and 
2020, respectively. The increase in stock compensation expense in 2022 was due primarily to the vesting of 
performance-based stock option awards as discussed above and an increase in the number of stock options granted in 
2022 driven by significant hiring in the year. As of December 31, 2022, the estimated fair value of unvested employee 
awards was $57.4 million. The weighted-average remaining vesting period for these awards is approximately three 
years. Also included in stock and deferred stock unit compensation expense in the consolidated statements of cash flows 
for the years ended December 31, 2022, 2021, and 2020 is $0.7 million, $0.7 million, and $0.3 million, respectively, of 
expense recorded for directors’ deferred share units, the details of which are discussed in Note J. 
A summary of option activity for options vested during the years ended December 31, 2022, 2021, and 2020 is 
presented below (in thousands): 
 
 
 
 
 
 
 
 
 
 
 
 
 
Year Ended December 31, 
 
 
     
2022 
     
2021 
     
2020 
 
Total fair value of options vested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 25,442  $ 
 15,839  $ 
 11,465  
Total intrinsic value of options exercised . . . . . . . . . . . . . . . . . . . . . . . . . .    
 451    
 3,322    
 746  
Cash received from the exercise of stock options and ESPP purchases . .    
 1,905    
 3,769    
 1,471  
Comprehensive Loss 
The Company presents comprehensive loss in accordance with ASC 220, Comprehensive Income. 
Comprehensive loss is comprised of the Company’s net loss for all periods presented. 
Segment Information 
During all periods presented, the Company continued to operate in one reportable business segment under the 
management approach of ASC 280, Segment Reporting, which is the business of the discovery and development of 
ADCs for the treatment of cancer. 

74 
The percentages of revenues recognized from significant customers of the Company in the years ended 
December 31, 2022, 2021, and 2020 are included in the following table: 
 
 
 
 
 
 
 
 
 
 
Year Ended December 31,  
Collaborative Partner: 
     
2022 
     
2021 
     
2020 
Huadong . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
37% 
 
24% 
 
-% 
Roche . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
28% 
 
67% 
 
53% 
Eli Lilly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
17% 
 
-% 
 
-% 
Viridian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
10% 
 
11% 
 
1% 
Jazz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
-% 
-% 
46% 
 
There were no other customers of the Company with significant revenues in the periods presented. 
Pending Accounting Pronouncements 
No recently issued or effective ASUs had, or are expected to have, a material effect on the Company's results of 
operations, financial condition, or liquidity. 
 
C. 
Collaboration and License Agreements 
The Company has numerous collaboration and license agreements with third parties. These agreements 
typically provide the licensee with rights to use the Company’s ADC platform technology with its antibodies or related 
targeting vehicles to a defined target to develop products. The licensee is generally responsible for the development, 
clinical testing, manufacturing, registration, and commercialization of any resulting product candidate. As part of these 
agreements, the Company is generally entitled to receive upfront fees, potential milestone payments, royalties on the 
sales of any resulting products, and research and development funding based on activities performed at our collaborative 
partner’s request. See below for details regarding the Company’s collaboration and license agreements with activity in 
the financial statement periods presented.    
Roche 
In 2000, the Company granted Genentech, now a unit of Roche, an exclusive development and 
commercialization license to use the Company’s maytansinoid ADC technology with antibodies, such as trastuzumab, or 
other proteins that target HER2. Under the terms of this agreement, Roche has exclusive worldwide rights to develop 
and commercialize maytansinoid ADC compounds targeting HER2. Pursuant to this agreement, Roche developed and 
received marketing approval for its HER2-targeting ADC, KADCYLA, in the U.S., Japan, the European Union, and 
numerous other countries. Roche is responsible for the manufacturing, product development, and marketing of any 
products resulting from the agreement. The Company received a $2.0 million non-refundable upfront payment from 
Roche upon execution of the agreement. The Company is also entitled to receive up to a total of $44.0 million in 
development and regulatory milestone payments, plus royalties on the commercial sales of KADCYLA or any other 
resulting products. Through December 31, 2022, the Company had received and recognized $39.0 million in milestone 
payments related to KADCYLA.  
The Company receives royalty reports and payments related to sales of KADCYLA from Roche one quarter in 
arrears. In accordance with the Company’s revenue recognition policy, $29.3 million, $46.8 million, and $68.5 million 
of non-cash royalties on net sales of KADCYLA were recorded and included in royalty revenue for the years ended 
December 31, 2022, 2021, and 2020, respectively. The Company sold its rights to receive royalty payments on the net 
sales of KADCYLA through two separate transactions in 2015 and 2019. Following the 2019 transaction, OMERS, the 
defined benefit pension plan for municipal employees in the Province of Ontario, Canada, is entitled to receive all of 
these royalties. 
Roche, through its Genentech unit, also has licenses for the exclusive right to use the Company’s maytansinoid 
ADC technology with antibodies to four undisclosed targets, which were granted under the terms of a separate, now 
expired, 2000 right-to-test agreement with Genentech. For each of these licenses, the Company received a $1.0 million 
license fee and is entitled to receive up to a total of $38.0 million in development, regulatory, and sales-based milestone 
payments plus royalties on the sales of any resulting products. The Company has not received any milestone payments 
from these agreements through December 31, 2022. Roche is responsible for the development, manufacturing, and 
marketing of any products resulting from these licenses.  

75 
Novartis 
The Company granted Novartis exclusive development and commercialization licenses to the Company’s 
maytansinoid and IGN ADC technology for use with antibodies to six specified targets under a now-expired right-to-test 
agreement established in 2010. The Company received a $45.0 million upfront payment in connection with the execution 
of the right-to-test agreement in 2010, $8.5 million in extension and amendment fees, and an exercise fee of $1.0 million 
for each of the six licenses taken. In May 2018, Novartis terminated one of its six licenses. In August 2022, Novartis 
terminated four of the remaining development and commercialization licenses. The Company had $2.8 million of 
deferred revenue associated with the terminated licenses related to the portion of the transaction price previously 
allocated to rights to future technological improvements. In consideration that no technological improvements would be 
provided to Novartis and, therefore, no unsatisfied obligations were remaining related to such licenses, the $2.8 million 
was recorded as revenue and is included in license and milestone fees for 2022. With respect to the remaining license, 
$0.8 million of deferred revenue related to the portion of the transaction price previously allocated to rights to future 
technological improvements continues to be amortized over the remaining estimated term of the license agreement, and 
we are entitled to receive up to a total of $199.5 million in potential milestone payments, of which $5.0 million has been 
received to date, plus royalties on the commercial sales of any resulting products. Novartis is responsible for the 
manufacturing, development, and marketing of any products resulting from these licenses. 
CytomX 
In 2016, the Company granted CytomX an exclusive development and commercialization license to the 
Company’s maytansinoid ADC technology for use with PROBODIES™ that target CD166 under a now expired 
reciprocal right-to-test agreement. The Company neither received nor made an upfront cash payment in connection with 
the execution of the right-to-test agreement or the license agreement. With respect to the development and 
commercialization license granted to CytomX, the Company is entitled to receive up to a total of $160.0 million in 
development, regulatory, and sales-based milestone payments plus royalties on the commercial sales of any resulting 
product. Through December 31, 2022, the Company had received and recognized an aggregate of $4.0 million in 
milestone payments under this agreement. 
In December 2019, the Company granted CytomX an exclusive development and commercialization license to 
maytansinoid and IGN ADC technology for use with PROBODIES™ that target EpCAM. Pursuant to the license 
agreement, in January 2020, the Company received a $7.5 million upfront payment. The Company is also entitled to 
receive up to a total of $355.0 million in development, regulatory, and sales-based milestone payments plus royalties on 
the commercial sales of any resulting product. The Company had not received any milestone payments under this 
agreement through December 31, 2022. CytomX is responsible for the manufacturing, product development, and 
marketing of any products resulting from these licenses.  
Viridian  
In October 2020, the Company entered into a license agreement with Viridian Therapeutics, Inc. pursuant to 
which the Company granted Viridian the exclusive right to develop and commercialize an insulin-like growth factor-1 
receptor (IGF-1R) antibody for all non-oncology indications that do not use radiopharmaceuticals in exchange for an 
upfront payment, with the potential to receive up to a total of $143.0 million in development, regulatory, and sales-based 
milestone payments plus royalties on the commercial sales of any resulting product. Through December 31, 2022, the 
Company had achieved an aggregate $15.5 million in development milestone payments under the agreement, of which 
$10.0 million and $5.5 million was included in license and milestone fee revenue for the years ended December 31, 2022 
and 2021, respectively. The $10.0 million milestone payment recorded in 2022 was included in accounts receivable as of 
December 31, 2022. Viridian is responsible for the manufacturing, development, and marketing of any products resulting 
from the license agreement.  
Huadong 
In October 2020, the Company entered into a collaboration and license agreement with Hangzhou Zhongmei 
Huadong Pharmaceutical Co., Ltd. (Huadong), a subsidiary of Huadong Medicine Co., Ltd. The collaboration and 
license agreement grants Huadong an exclusive, royalty-bearing, and sublicensable right to develop and commercialize 
ELAHERE (the Licensed Product) in the People’s Republic of China, Hong Kong, Macau, and Taiwan (collectively, 
Greater China). The Company retains exclusive rights to the Licensed Product outside of Greater China. Under the terms 
of the collaboration and license agreement, the Company received a non-refundable upfront payment of $40.0 million 
with the potential for approximately $265.0 million in development, regulatory, and sales-based milestone payments. In 
addition, the Company is entitled to receive tiered percentage royalties ranging from low double digits to high teens as a 
percentage of commercial sales of the Licensed Product, if approved, by Huadong in Greater China, subject to 

76 
adjustment in specified circumstances. In December 2022 and December 2021, the Company received milestone 
payments of $10.0 million and $5.0 million, respectively, upon achievement of development and regulatory milestones. 
The Company evaluated the agreement and determined it was within the scope of ASC 606. The Company 
determined the promised goods and services included the license to intellectual property and know-how and the clinical 
supply of the Licensed Product to Huadong for a specified period. The Company concluded that the license to 
intellectual property and know-how is not distinct from the clinical supply of the Licensed Product because the clinical 
supply is essential to the use of the license and an alternative source of clinical supply is not readily available in the 
marketplace. Accordingly, these two promised goods and services are considered a single combined performance 
obligation. The Company determined there were no options in the agreement that represented material rights.  
The transaction price was determined to consist of the upfront payment of $40.0 million and estimated 
payments to be received for clinical supply of the Licensed Product. At contract inception, future development and 
regulatory milestones were fully constrained. Any consideration related to sales-based milestones (including royalties) 
will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the 
license granted to Huadong. The Company re-evaluates the transaction price, including its estimated variable 
consideration included in the transaction price and all constrained amounts, at each reporting period and as uncertain 
events are resolved or other changes in circumstances occur. 
The Company determined that revenue related to the agreement would be recognized as the clinical supply of 
the Licensed Product is delivered to Huadong, estimated to be completed over approximately two years. Accordingly, 
based on clinical supply delivered to Huadong during 2022 and 2021, the Company recorded $28.5 million and $16.5 
million as license and milestone fee revenue in 2022 and 2021, respectively, related to $45.0 million of upfront and 
milestone payments previously received and deferred. The Company also recorded $10.0 million of license and 
milestone fee revenue related to a regulatory milestone achieved in 2022. 
Lilly 
In February 2022, the Company entered into a license agreement with Lilly, pursuant to which the Company 
granted Lilly worldwide exclusive rights to research, develop, and commercialize antibody-drug conjugates based on the 
Company’s novel camptothecin technology. Under the terms of the license agreement, the Company received a non-
refundable upfront payment of $13.0 million, reflecting initial targets selected by Lilly. During 2022, pursuant to the 
terms of the agreement, Lilly selected additional targets for which the Company received an additional $13.0 million in 
non-refundable payments. Lilly may select a pre-specified number of additional targets, with the Company eligible to 
receive an additional $19.5 million in exercise fees if Lilly licenses the full number of remaining additional targets over 
a specified period following the effective date of the license agreement, with the potential for up to $1.7 billion in 
development and sales-based milestone payments if all targets are selected and all milestones are realized. In addition, 
the Company is entitled to receive tiered royalties, on a product-by-product basis, as a percentage of worldwide annual 
net sales by Lilly, based on certain net sales thresholds. Lilly is responsible for all costs associated with the research, 
development, and commercialization of any ensuing products. 
The Company evaluated the agreement and determined it was within the scope of ASC 606. The Company 
determined the promised goods and services included an exclusive license to use the Company’s intellectual property 
and know-how to research, develop, and commercialize products related to each of the initial targets selected by Lilly. 
Each of these licenses is distinct, as Lilly can derive benefit from each license independent of any other initial target 
licenses. Accordingly, the license to each of the initial targets selected by Lilly represents a separate performance 
obligation. Lilly has the right to replace each of the initial licensed targets once during a specified term for no additional 
consideration. If Lilly fails to advance an initial or replacement target to a specified stage within a specified period from 
the date the target was selected, Lilly’s rights to the respective target will cease and will revert back to the Company. 
The Company determined Lilly’s right to a replacement target for each of the initial targets represented a material right. 
Each material right is therefore a separate performance obligation.  
Lilly’s right to select additional targets does not represent a material right as the target fee for each additional 
target is the same and is also consistent with the target fee for each of the initial targets selected by Lilly. Accordingly, 
each additional target selected by Lilly is accounted for as a separate arrangement.  
The transaction price related to the initial targets was determined to consist of the upfront payment of $13.0 
million. Future development milestones have been fully constrained. Any consideration related to sales-based milestones 
(including royalties) will be recognized when the related sales occur as these amounts have been determined to relate 
predominantly to the license granted to Lilly. The transaction price of $13.0 million was allocated to the performance 
obligations based on their relative stand-alone selling prices. In consideration of each target being at the same stage of 

77 
development at the time of the initial license or at the time of replacement and each target having approximately the 
same earnings potential, the Company allocated the $13.0 million transaction price equally across the initial target 
licenses and the corresponding material rights to obtain licenses to replacement targets, adjusted based on the probability 
that Lilly would exercise those rights. The Company considered pharmaceutical industry data of the probability of early-
stage assets to advance to clinical stage in determining the probability that Lilly would exercise its option to a 
replacement target. Accordingly, $9.2 million and $3.8 million of the total transaction price was allocated to the initial 
targets and the material rights to obtain licenses to replacement targets, respectively.  
The license terms and accounting outlined above are the same for the additional target licenses selected. 
Accordingly, $9.2 million and $3.8 million of the $13.0 million transaction price was allocated to the targets selected 
and the material right to obtain a license to replacement targets, respectively.  
The Company re-evaluates the transaction price for each arrangement, including its estimated variable 
consideration included in the transaction price and all constrained amounts, at each reporting period and as uncertain 
events are resolved or other changes in circumstances occur. 
The transfer of intellectual property and know-how to Lilly to allow for Lilly to derive benefit from the initial 
and additional target licenses was completed during the three months ended March 31, 2022. As such, during 2022, the 
Company recognized $18.4 million of license and milestone fee revenue related to the portion of the transaction price 
allocated to the initial and additional target licenses. The $7.6 million allocated to the material rights to obtain licenses to 
replacement targets is included in long-term deferred revenue as of December 31, 2022 and will be recognized when the 
right is either exercised or expires.  
Magenta 
In November 2022, the Company granted Magenta an exclusive development and commercialization license to 
the Company’s IGN ADC technology to a specified target and a non-exclusive license to use intellectual property and 
know-how resulting from the collaboration to research, develop, and commercialize products directed to the specified 
target. Under the terms of the license agreement, the Company received non-refundable upfront payments totaling $6.0 
million. The Company is also entitled to receive up to a total of $125.0 million in development, regulatory, and sales-
based milestone payments plus royalties on the commercial sales of any resulting product. 
The Company evaluated the agreement and determined it was within the scope of ASC 606. The Company 
determined there was a single, combined performance obligation consisting of the license to use the Company’s 
intellectual property and know-how and the non-exclusive license to use intellectual property and know-how resulting 
from the collaboration. The transaction price was determined to consist of the upfront payments totaling $6.0 million. 
Future development and regulatory milestones have been fully constrained. Any consideration related to sales-based 
milestones (including royalties) will be recognized when the related sales occur as these amounts have been determined 
to relate predominantly to the license granted to Magenta. The single, combined performance obligation was satisfied 
during 2022, and as such, the Company recognized $6.0 million of license and milestone fee revenue in 2022. 
In February 2023, Magenta announced its decision to halt further development of its programs and conduct a 
comprehensive review of strategic alternatives focusing on maximizing shareholder value. As part of this review 
process, Magenta will explore potential strategic alternatives that may include, but are not limited to, an acquisition, 
merger, business combination, or other transaction. 
Terminated Agreements 
Jazz Pharmaceuticals 
In August 2017, the Company entered into a Collaboration and Option Agreement with Jazz Pharmaceuticals 
Ireland Limited (Jazz), a subsidiary of Jazz Pharmaceuticals plc, granting Jazz exclusive, worldwide rights to opt into 
development and commercialization of two early-stage, hematology-related ADC programs, as well as an additional 
program to be designated during the term of the agreement. Pursuant to the agreement, Jazz made an upfront payment of 
$75.0 million to the Company. Additionally, Jazz had also agreed to pay the Company up to $100.0 million in 
development funding over seven years to support the three ADC programs.  
In October 2019 and December 2020, Jazz exercised certain opt-out rights under the agreement, thereby 
relinquishing its development and commercialization options and restoring all rights to the ADC programs to the 
Company. The non-refundable, upfront arrangement consideration of $75.0 million was allocated to the three license 
options. In conjunction with the opt-outs, the Company recognized $60.5 million of the remaining deferred upfront fee 
as license and milestone fee revenue in the year ended December 31, 2020.  

78 
Due to the involvement the Company and Jazz both had in the development and commercialization of the 
products, as well as both parties being part of the cost share agreement and exposed to significant risks and rewards 
dependent on the commercial success of the products, the arrangement was determined to be a collaborative arrangement 
within the scope of ASC 808. Accordingly, the Company separated the research and development activities and the 
related cost sharing arrangement with Jazz. Payments for such activities were recorded as research and development 
expense and reimbursements received from Jazz were recognized as an offset to research and development expense in 
the accompanying statement of operations during the development period. Included in research and development 
expense for each of the years ended December 31, 2021 and 2020 are $6.7 million of credits related to reimbursements 
from Jazz.  
D. 
Product Revenue Reserves and Allowances 
In November 2022, the FDA granted accelerated approval for ELAHERE for the treatment of adult patients with 
FRα positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who have received one to 
three prior systemic treatment regimens. The Company recorded net product revenue of $2.6 million from U.S. sales of 
ELAHERE through December 31, 2022. 
The following table summarizes activity in each of the product revenue allowance and reserve categories for the 
years ended December 31, 2022 and 2021 (in thousands): 
 
 
 
 
 
 
 
 
 
 
December 31,   
December 31,  
 
     
2022 
     
2021 
Beginning balance at January 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 —  $ 
 — 
Provision related to sales in the current period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 313   
 — 
Credits and payments made . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 — 
Ending balance at December 31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 313  $ 
 — 
 
E. 
Inventory 
Capitalized inventory consists of the following at December 31, 2022 and 2022 (in thousands): 
 
 
 
 
 
 
 
 
 
 
December 31,   
December 31,  
 
     
2022 
     
2021 
Raw materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 15,952  $ 
 — 
Work in process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 — 
Finished goods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 244   
 — 
Total Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 16,196  $ 
 — 
 
 
F. 
Property and Equipment 
Property and equipment consisted of the following at December 31, 2022 and 2021 (in thousands): 
 
 
 
 
 
 
 
 
 
 
December 31,   
December 31,   
 
     
2022 
     
2021 
 
Leasehold improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 22,867  $ 
 22,051  
Machinery and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 3,063    
 2,955  
Computer hardware and software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 6,248    
 5,846  
Furniture and fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 3,383    
 3,265  
Assets under construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 180    
 233  
 
 $ 
 35,741  $ 
 34,350  
Less accumulated depreciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (31,364)   
 (29,687) 
Property and equipment, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 4,377  $ 
 4,663  
Included in the table above are amounts capitalized for equipment under capital leases at December 31, 2022 
and 2021 totaling $2.2 million and $2.1 million, net of accumulated amortization of $1.8 million and $1.6 million, 
respectively. Depreciation expense was $1.8 million, $2.0 million, and $2.1 million for the years ended December 31, 
2022, 2021 and 2020, respectively. As a result of the restructuring in 2019, during the year ended December 31, 2020, 
the Company liquidated laboratory equipment and certain other fixed assets with an aggregate cost basis of $7.5 million 
and accumulated depreciation of $6.8 million for $1.4 million in payments to the Company. 

79 
G. 
Convertible 4.5% Senior Notes 
In 2016, the Company issued convertible notes with an aggregate principal amount of $100 million, of which 
$2.1 million remained outstanding as of December 31, 2020. In June 2021, $1.0 million of outstanding convertible notes 
were converted into 238,777 shares of the Company’s common stock and the remaining $1.1 million outstanding was 
repaid in full by a cash payment upon maturity on July 1, 2021. The convertible notes were senior unsecured obligations 
and bore interest at a rate of 4.5% per year, payable semi-annually in arrears on January 1 and July 1 of each year, 
commencing on January 1, 2017. The Company recorded $0.1 million of interest expense in each of the years ended 
December 31, 2021 and 2020. The Company analyzed the terms of the convertible notes and determined the notes were 
entirely accounted for as debt and none of the terms of the notes required separate accounting. 
H. 
Liability Related to Sale of Future Royalties 
In 2015, Immunity Royalty Holdings, L.P. (IRH) purchased the right to receive 100% of the royalty payments 
on commercial sales of KADCYLA arising under the Company’s development and commercialization license with 
Genentech, until IRH had received aggregate royalties equal to $235 million or $260 million, depending on when the 
aggregate royalties received by IRH reached a specified milestone. Once the applicable threshold was met, the Company 
would thereafter have received 85% and IRH would have received 15% of the KADCYLA royalties for the remaining 
royalty term. At consummation of the transaction, the Company received cash proceeds of $200 million. As part of this 
sale, the Company incurred $5.9 million of transaction costs, which are presented net of the liability in the 
accompanying consolidated balance sheet and are being amortized to interest expense over the estimated life of the 
royalty purchase agreement. Although the Company sold its rights to receive royalties from the sales of KADCYLA, as 
a result of its ongoing involvement in the cash flows related to these royalties, the Company continues to account for 
these royalties as revenue and recorded the $200 million in proceeds from this transaction as a liability related to sale of 
future royalties (Royalty Obligation) that is being amortized using the interest method over the estimated life of the 
royalty purchase agreement.   
In January 2019, the Company sold its residual rights to receive royalty payments on commercial sales of 
KADCYLA to OMERS, the defined benefit pension plan for municipal employees in the Province of Ontario, Canada, 
for a net payment of $65.2 million (amount is net of $1.5 million in broker fees). Simultaneously, OMERS purchased 
IRH’s right to the royalties the Company previously sold as described above, therefore obtaining the rights to 100% of 
the royalties received from that date on. Because the Company will not be involved with the cash flows related to the 
residual royalties, the $65.2 million of net proceeds received from the sale of its residual rights to receive royalty 
payments was recorded as deferred revenue and is being amortized as the royalty revenue related to the residual rights is 
earned using the units of revenue approach. During the second quarter of 2021, the aggregate royalty threshold was met 
and, in accordance with the Company’s revenue recognition policy, $16.4 million and $7.7 million of revenue related to 
the residual rights was recorded and is included in non-cash royalty revenue for the years ended December 31, 2022 and 
2021, respectively. Additionally, the purchase of IRH’s interest by OMERS did not result in an extinguishment or 
modification of the original instrument and, accordingly, the Company will continue to account for the remaining 
obligation as a liability as outlined above.   
The following table shows the activity within the liability account during the year ended December 31, 2022 
and the period from inception (in thousands): 
 
 
 
 
 
 
 
 
 
 
 
 
 
Period from 
 
 
 
Year Ended 
 
inception to 
 
 
    December 31, 2022     December 31, 2022 
Liability related to sale of future royalties, net — beginning balance . . . . . . . . . . . . .   $ 
 41,044 
 $ 
 — 
Proceeds from sale of future royalties, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
  
 — 
  
 194,135 
KADCYLA royalty payments received and paid . . . . . . . . . . . . . . . . . . . . . . . . . .  
  
 (13,101)   
 (276,958)
Non-cash interest expense recognized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
 
 4,165 
 
 114,931 
Liability related to sale of future royalties, net — ending balance . . . . . . . . . . . . . . .   $ 
 32,108 
 $ 
 32,108 
The Company receives royalty reports and royalty payments related to sales of KADCYLA from Roche one 
quarter in arrears. As royalties are remitted to OMERS, the balance of the Royalty Obligation will be effectively repaid 
over the life of the agreement. In order to determine the amortization of the Royalty Obligation, the Company is required 
to estimate the total amount of future royalty payments to be received and remitted as noted above over the life of the 
agreement. The sum of these amounts less the $200 million proceeds the Company received from IRH will be recorded 
as interest expense over the life of the Royalty Obligation. The Company’s estimate of this total interest expense has 
resulted in an imputed annual interest rate of 10.5% since inception and as of December 31, 2022. The Company 
periodically assesses the estimated royalty payments to IRH/OMERS and to the extent such payments are greater or less 

80 
than its initial estimates, or the timing of such payments is materially different than its original estimates, the Company 
will prospectively adjust the amortization of the Royalty Obligation. There are a number of factors that could materially 
affect the amount and timing of royalty payments from Genentech, most of which are not within the Company’s control. 
Such factors include, but are not limited to, changing standards of care, the introduction of competing products, 
manufacturing or other delays, biosimilar competition, patent protection, adverse events that result in governmental 
health authority imposed restrictions on the use of the drug products, significant changes in foreign exchange rates as the 
royalties are paid in U.S. dollars (USD) while significant portions of the underlying sales of KADCYLA are made in 
currencies other than USD, and other events or circumstances that could result in reduced royalty payments from 
KADCYLA, all of which would result in a reduction of non-cash royalty revenues and non-cash interest expense over 
the life of the Royalty Obligation. Conversely, if sales of KADCYLA are more than expected, the non-cash royalty 
revenues and the non-cash interest expense recorded by the Company would be greater over the term of the Royalty 
Obligation. 
I. 
Income Taxes 
For the years ended December 31, 2022, 2021 and 2020, the loss before provision for income taxes consist of 
the following (in thousands): 
 
 
 
 
 
 
 
 
 
 
 
 
 
Years Ended December 31, 
 
     
2022 
     
2021 
     
2020 
Domestic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $ 
 18,417  $  (139,303) $ 
 (44,372)
Foreign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      
 (240,128)  
 —   
 — 
Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  (221,711) $  (139,303) $ 
 (44,372)
 
For the year ended December 31, 2022, the Company’s total tax expense was all federal current expense. The 
difference between the Company’s expected tax benefit, as computed by applying the applicable U.S. federal corporate 
tax rate to loss before the benefit for income taxes, and actual tax is reconciled in the following table (in thousands): 
 
 
 
 
 
 
 
 
 
 
 
 
Years Ended December 31, 
 
     
2022 
     
2021 
     
2020 
Loss before income tax expense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $  (221,711) $  (139,303) $
 (44,372)
Expected tax benefit at 21% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 (46,559) $
 (29,254) $
 (9,318)
Permanent differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 454    
 606    
 157 
Intra-entity transfer of intangible assets . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 90,720   
 —   
 — 
Incentive stock options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 769   
 420   
 201 
State tax provision (benefit) net of federal benefit . . . . . . . . . . . . . . . . . . .     
 29,304    
 (7,376)   
 (2,250)
Change in valuation allowance, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (75,683)   
 46,987    
 15,175 
Federal research credit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 (2,030)   
 (575)   
 (228)
Federal orphan drug credit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (9,286)  
 (7,429)  
 (6,218)
Expired loss and credit carryforwards . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 —   
 345   
 419 
Withholding tax credit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (878)  
 (4,789)  
 — 
Stock option expirations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     
 —    
 1,065    
 2,062 
Foreign rate differential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 14,407   
 —   
 — 
Income tax expense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 1,218  $
 —  $
 — 
 
In 2017, the Tax Cuts and Jobs Act of 2017 (“2017 Tax Act”) was signed into law. Among other provisions, the 
2017 Tax Act requires taxpayers to capitalize and amortize research and experimental (R&E) expenditures under Section 
174 for tax years beginning after December 31, 2021. As such, the rule noted became effective for the Company during 
the year ended December 31, 2022 and resulted in the capitalization of certain R&E costs within its tax provision. The 
Company will amortize such costs for tax purposes over 5 years if the R&E was performed in the United States and over 
15 years if the R&E was performed outside the United States.  
During 2022, the Company transferred certain of its intellectual property rights to a newly formed Swiss 
subsidiary. This transfer resulted in a significant income inclusion for U.S. tax purposes which has been partially offset 
by utilization of a portion of the Company’s net operating loss (NOL) carryforwards that existed before the transaction. 
The income inclusion for state tax purposes was completely offset by NOL carryforwards. 
At December 31, 2022, the Company had NOL carryforwards of $443.3 million available to reduce federal 
taxable income, if any, that can be carried forward indefinitely. The Company has $251.1 million of NOL carryforwards  

81 
available to reduce state taxable income, if any, that expire in 2036 through 2042. The Company also has federal and 
state credit carryforwards of $85.6 million and $11.1 million, respectively, available to offset federal and state income 
taxes, which expire beginning in 2027 and foreign tax credits of $6.5 million that begin to expire in 2030. Due to the 
degree of uncertainty related to the ultimate use of the loss carryforwards and tax credits, the Company has established a 
valuation allowance to fully reserve these tax benefits.  
Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of 
assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant 
components of the Company’s deferred tax assets and liabilities as of December 31, 2022 and 2021 are as follows (in 
thousands): 
 
 
 
 
 
 
 
 
 
December 31,  
 
     
2022 
     
2021 
Deferred tax assets: 
  
 
  
 
Net operating loss carryforwards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 115,047  $
 264,773 
Research and development tax credit carryforwards . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 103,155    
 92,832 
Property and other intangible assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 1,452    
 1,150 
Deferred revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 14,561    
 25,153 
Stock-based compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 18,783    
 12,195 
Operating lease liability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 4,421    
 5,170 
Other liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 3,144    
 1,737 
Royalty sale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 8,393   
 10,247 
Sec 174 R&E capitalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 68,150   
 — 
Total deferred tax assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 337,106  $
 413,257 
 
  
  
Deferred tax liabilities: 
  
  
Operating lease right of use asset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (2,967)  
 (3,386)
Royalty sale transaction costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (107)  
 (158)
Total deferred tax liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 (3,074) $
 (3,544)
Valuation allowance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 (334,032)    (409,713)
Net deferred tax assets/(liabilities) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   $
 —  $
 — 
The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax 
assets. The Company has determined that it is not more-likely-than-not that the tax benefits related to the federal and 
state deferred tax assets will be realized for financial reporting purposes. Accordingly, the deferred tax assets have been 
fully reserved at December 31, 2022 and 2021. The valuation allowance decreased by $75.7 million during the year 
ended December 31, 2022. 
Utilization of the NOL and credit carryforwards may be subject to a substantial annual limitation due to 
ownership change limitations that have occurred previously or that could occur in the future as provided by Sections 382 
and 383 of the Internal Revenue Code of 1986, as well as similar state and foreign provisions. These ownership changes 
may limit the amount of NOL and credit carry forwards that can be utilized annually to offset future taxable income and 
tax, respectively. In general, an ownership change, as defined by Section 382, results from transactions increasing the 
ownership of certain shareholders or public groups in the stock of a corporation by more than 50 percentage points over 
a three-year period. Since the Company’s formation, it has raised capital through the issuance of capital stock on several 
occasions (both pre and post initial public offering) which, combined with the purchasing shareholders’ subsequent 
disposition of those shares, may have resulted in a change of control, as defined by Section 382, or could result in a 
change of control in the future upon subsequent disposition. The Company completed a study to assess whether a change 
of control has occurred or whether there have been multiple changes of control since its formation and determined no 
ownership change occurred under Section 382 as of December 31, 2022. The Company has not completed a detailed 
Research and Development Credit Study (including the Orphan Drug Credit); accordingly, a portion of the tax credit 
carryforward may not be available to offset future income.  
The Company accounts for uncertain tax positions under the recognition and measurement criteria of ASC 740-
10. For those tax positions for which it is more likely than not that a tax benefit will be sustained, the Company records 
the largest amount of tax benefit with a greater than 50% likelihood of being realized upon settlement with a taxing 
authority that has full knowledge of all relevant information. If the Company does not believe that it is not more likely 
than not that a tax benefit will be sustained, no tax benefit is recognized. As of December 31, 2022 and 2021, no 
uncertain tax positions have been recorded. Interest and penalties related to the settlement of uncertain tax positions, if 
any, will be reflected in income tax expense. The Company did not recognize any interest and penalties associated with 

82 
unrecognized tax benefits in the accompanying consolidated financial statements. The Company does not expect any 
material changes to the unrecognized benefits within 12 months of the reporting date. Due to existence of the valuation 
allowance, future changes in the Company’s unrecognized tax benefits will not impact its effective tax rate.  
The statute of limitations for assessment by the Internal Revenue Service, or IRS, and state tax authorities is 
open for tax years ending after December 31, 2018, although carryforward attributes that were generated prior to 
2018 may still be adjusted upon examination by the IRS or state tax authorities if they either have been or will be used in 
a future period.  
J. 
Capital Stock 
Common Stock Reserved 
At December 31, 2022, the Company had reserved 56.0 million shares of authorized common stock for the 
future issuance of shares under the 2018, ESPP, and Inducement Plans. See “Stock-Based Compensation” in Note B for 
a description of the 2018, ESPP, and Inducement Plans. Additionally, the Company has reserved 32.8 million shares of 
authorized common stock for future issuance pursuant to pre-funded warrant agreements, the details of which are 
discussed below. 
Pre-Funded Warrants 
In August 2021, the Company entered into a Securities Purchase Agreement (SPA) with RA Capital Healthcare 
Fund, L.P. (RA Capital), pursuant to which the Company agreed to sell to RA Capital a pre-funded warrant to purchase 
up to 5,434,782 shares of common stock for $5.51 per share of common stock underlying the pre-funded warrant. The 
per share exercise price of the pre-funded warrant is $0.01. The private placement resulted in aggregate gross proceeds 
of $29.9 million, before $0.2 million of transaction costs. 
In connection with a public offering in December 2021, the Company issued pre-funded warrants to purchase 
16,000,000 and 11,363,636 shares of common stock to RA Capital and Redmile Group, LLC, respectively, for $6.59 per 
share of common stock underlying the pre-funded warrants, which, together with the per share exercise price of $0.01, is 
equal to $6.60, the public offering price of the shares of common stock in the offering. RA Capital and Redmile Group, 
LLC are each considered related parties pursuant to ASC 850, Related Party Disclosures. 
The pre-funded warrants’ fundamental transaction provision does not provide the warrant holders with the 
option to settle any unexercised warrants for cash in the event of any fundamental transactions; rather, in all fundamental 
transaction scenarios, the warrant holder will only be entitled to receive from the Company or any successor entity the 
same type or form of consideration (and in the same proportion) that is being offered and paid to the shareholders of the 
Company in connection with the fundamental transaction, whether that consideration be in the form of cash, stock or any 
combination thereof. The pre-funded warrants also include a separate provision whereby the exercisability of the 
warrants may be limited if, upon exercise, the warrant holder or any of its affiliates would beneficially own more 
than 9.99% of the Company’s common stock. This threshold is subject to the holder’s rights under the pre-funded 
warrants to increase or decrease such percentage to any other percentage not in excess of 19.99% upon at least 61 days’ 
prior notice from the holder to the Company. 
The Company has assessed the pre-funded warrants for appropriate equity or liability classification pursuant to 
the Company’s accounting policy described in Note B, “Summary of Significant Accounting Policies.” During this 
assessment, the Company determined the pre-funded warrants are freestanding instruments that do not meet the 
definition of a liability pursuant to ASC 480 and do not meet the definition of a derivative pursuant to ASC 815. The 
pre-funded warrants are indexed to the Company’s common stock and meet all other conditions for equity classification 
under ASC 480 and ASC 815. Based on the results of this assessment, the Company concluded that the pre-funded 
warrants are freestanding equity-linked financial instruments that meet the criteria for equity classification under ASC 
480 and ASC 815. Accordingly, the pre-funded warrants are classified as equity and accounted for as a component of 
additional paid-in capital at the time of issuance. The Company also determined that the pre-funded warrants should be 
included in the determination of basic and diluted earnings per share in accordance with ASC 260, Earnings per Share. 
Stock Options 
As of December 31, 2022, the 2018 Plan and the Inducement Plan were the only employee share-based 
compensation plans of the Company under which grants can be made. During the year ended December 31, 2022, 
holders of options issued under the option plans exercised their rights to acquire an aggregate of 313,000 shares of 
common stock at prices ranging from $2.31 to $5.25 per share. The total proceeds to the Company from these option 

83 
exercises were $1.2 million. Additionally, during 2022 and pursuant to the Company’s ESPP, approximately 178,000 
shares of common stock were issued to participating employees generating $0.7 million of proceeds to the Company. 
2004 Non-Employee Director Compensation and Deferred Share Unit Plan 
Under the 2004 Non-Employee Director Compensation and Deferred Share Unit Plan, or the 2004 Director 
Plan, as amended, between 2004 and 2009 non-employee directors were paid their annual retainers in the form of 
deferred stock units, based on the fair market value of the Company’s common stock on the last date of the Company’s 
fiscal year prior to the year for which services were rendered, and in cash, with the option, at their discretion, to have all 
or a portion of the cash portion paid in additional deferred stock units. All deferred stock units awarded under the 2004 
Director Plan have vested and are redeemed on the date a director ceases to be a member of the Board, at which time 
such director’s deferred stock units will be settled in shares of common stock of the Company issued under the 2006 
Plan at a rate of one share for each vested unit. 
Compensation Policy for Non-Employee Directors 
In September 2009, the Board adopted a new Compensation Policy for Non-Employee Directors, which 
superseded the 2004 Plan and made certain changes to the compensation of its non-employee directors. The 
Compensation Policy for Non-Employee Directors, as amended as of December 2022, consists of three elements: cash 
compensation; deferred stock units; and stock options. 
Cash Compensation 
Each non-employee director receives annual meeting fees which are paid in quarterly installments in, at each 
director’s election, either cash or deferred stock units. 
Deferred Stock Units 
Pursuant to the Compensation Policy for Non-Employee Directors, as amended, non-employee directors receive 
deferred stock units upon initial election to the Board and annually thereafter. Vested deferred stock units are redeemed 
on the date a director ceases to be a member of the Board, at which time such director’s deferred stock units will 
generally be settled in shares of the Company’s common stock issued under our 2018 Plan (or its predecessor plans, 
depending on the grant date of the deferred stock units) at a rate of one share for each vested deferred stock unit then 
held. Any deferred stock units that remain unvested at that time will be forfeited.  
Pursuant to the Compensation Policy for Non-Employee Directors, as amended, the Company recorded: 
• 
$0.7 million in compensation expense during the year ended December 31, 2022 related to the grant of 
148,000 deferred share units and 100,000 deferred share units previously granted; 
• 
$0.7 million in compensation expense during the year ended December 31, 2021 related to the grant of 
166,000 deferred share units and 52,000 deferred share units previously granted; and 
• 
$0.3 million in compensation expense during the year ended December 31, 2020 related to the grant of 
127,000 deferred share units and 15,000 deferred share units previously granted. 
Effective 2023, non-employee directors will opt to receive deferred stock units, restricted stock units, 
and/or shares upon initial election and annually thereafter. 
Stock Options 
Pursuant to the Compensation Policy for Non-Employee Directors, as amended, non-employee directors also 
receive stock option awards upon initial election to the Board and annually thereafter. The directors received a total of 
321,622, 352,000, and 300,000 options in the years ended December 31, 2022, 2021, and 2020, and the related stock 
compensation expense is included in the amounts discussed in the “Stock-Based Compensation” section of footnote B 
above.  
K. 
Leases 
Leases 
The Company currently has one real estate lease with CRP/King 830 Winter L.L.C. for the rental of 
approximately 120,000 square feet of laboratory and office space at 830 Winter Street, Waltham, Massachusetts through 
March 2026. The Company uses this space for its corporate headquarters and other operations. The Company may 
extend the lease for two additional terms of five years and is required to pay certain operating expenses for the leased 

84 
premises subject to escalation charges for certain expense increases over a base amount. The Company also has a lease 
agreement through March 2027 for the rental of copier equipment. 
Lease expense for operating lease payments is recognized on a straight-line basis over the lease term, which for 
each of the years ended December 31, 2022, 2021, and 2020 was $4.0 million and is included in operating expenses in 
the consolidated income statements. Cash paid against operating lease liabilities in each of the years ended December 31, 
2022 and 2021 was $5.3 million. As of December 31, 2022, the Company’s ROU assets and lease liabilities for 
operating leases totaled $10.2 million and $15.2 million, respectively, and the weighted average remaining term of the 
operating leases is approximately 3.25 years. The weighted average discount rate for the operating lease liability is 
approximately 11%. A 100-basis point change in the incremental borrowing rate would result in less than a $1 million 
impact to the ROU assets and liabilities recorded. 
The maturities of operating lease liabilities discussed above are as follows (in thousands): 
2023 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     $ 
 5,503 
2024 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 5,522 
2025 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 5,543 
2026 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    
 1,429 
2027 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 13 
Total lease payments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 18,010 
Less imputed interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
 (2,766)
Total lease liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  $ 
 15,244 
In addition to the amounts in the table above, the Company is also responsible for variable operating costs and 
real estate taxes approximating $3.8 million per year through March 2026. 
Sublease Income 
In 2020, the Company executed four agreements to sublease a total of approximately 65,000 square feet of the 
Company’s leased space at 830 Winter Street, Waltham, Massachusetts through March 2026. During the years ended 
December 31, 2022 and 2021, the Company recorded $1.1 million and $4.9 million of sublease income, respectively, 
inclusive of the sublessees’ proportionate share of operating expenses and real estate taxes for the period. The decrease 
in the current year period is driven by amortization of the lease incentive discussed further below.  
In June 2022, in order to reclaim laboratory and office space, the Company modified one of its sublease 
agreements to terminate the sublease early. Pursuant to the amended sublease agreement, the Company is required to pay 
the sublessee $4.0 million as a lease incentive, of which $1.8 million was paid in June 2022 and the remainder was paid 
at the end of the sublease term in early January 2023. No other terms from the original sublease agreement were 
modified. In accordance with ASC 842, Leases, the $4.0 million lease incentive was recognized on a straight-line basis 
over the remaining sublease term. Additionally, in November 2022, the Company modified a separate sublease 
agreement to terminate the sublease on January 31, 2023. There was no lease incentive included and no other terms from 
the original sublease agreement were modified. As a result of the early termination of the two sublease agreements, the 
Company will forego $4.6 million in minimum future rental payments. The Company assessed the underlying right-of-
use asset and determined there was no impairment. 
One of the two remaining sublease agreements includes an early termination option after certain periods of time 
for an agreed-upon fee. Assuming no early termination option is exercised, the Company will receive $5.7 million in 
minimum rental payments over the remaining term of the subleases, which is not included in the operating lease liability 
table above. The sublessees are also responsible for their proportionate share of variable operating expenses and real 
estate taxes. 
L. 
Commitments and Contingencies 
Manufacturing Commitments 
As of December 31, 2022, the Company has noncancelable obligations under several agreements related to in-
process and future manufacturing of antibody and cytotoxic agents required for supply of the Company’s product 
candidates totaling $17.9 million, which will be paid in 2023. Additionally, pursuant to commercial agreements for 
future production of antibody, the Company’s noncancelable commitments total $43.7 million at December 31, 2022. 

85 
License Commitment 
In October 2021, as a result of a dispute regarding terms of a 2012 license agreement with a contract 
manufacturing vendor, the Company and vendor amended their agreement to replace certain annual fees and potential 
royalties payable by the Company on future sales of ELAHERE with capped development and sales-based milestone 
payments totaling $18.0 million, of which $6.0 million and $3.0 million was recorded as research and development 
expense during the years ended December 31, 2022 and 2021, respectively.  
Litigation 
The Company is not party to any material litigation. 
M. 
Related Party Transactions 
The Company’s chief executive officer has served as a director on the board of directors of Ergomed PLC since 
June 2021. During the year ended December 31, 2022, the Company executed agreements with Ergomed Clinical 
Research, Inc. and PrimeVigilance USA, Inc., subsidiaries of Ergomed PLC, for clinical trial and pharmacovigilance-
related services. Ergomed Clinical Research, Inc. and PrimeVigilance USA, Inc. are each considered related parties 
pursuant to ASC 850, Related Party Disclosures. In the year ended December 31, 2022, the Company made payments 
totaling $5.0 million to Ergomed Clinical Research, Inc. Payments made pursuant to the agreement with PrimeVigilance 
USA, Inc. during the year ended December 31, 2022 were not material to the Company’s consolidated statement of 
operations. 
The Company’s Executive Vice President of Research, Development, and Medical Affairs joined the Company 
on December 29, 2022. He has served as a director on the board of directors of Magenta Therapeutics since August 
2022. In 2020, the Company and Magenta executed a Material Transfer and Evaluation Agreement, and subsequently 
executed an exclusive development and commercialization license to the Company’s IGN ADC technology to a 
specified target in November 2022. Pursuant to the agreements, the Company received an aggregate $6.0 million in 
license fees during the years ended December 31, 2022 and 2021. 
N. 
Employee Benefit Plans 
The Company has a deferred compensation plan under Section 401(k) of the Internal Revenue Code (the 401(k) 
Plan). Under the 401(k) Plan, eligible employees are permitted to contribute, subject to certain limitations, up to 100% of 
their gross salary and the Company’s matching contribution is 50% of the first 6% of the eligible employees’ 
contributions. In the years ended December 31, 2022, 2021 and 2020, the Company’s contributions to the 401(k) Plan 
totaled $1.0 million, $0.5 million, and $0.4 million, respectively. 
 
 

86 
 
Item 9.  Changes in and Disagreements with Accountants on Accounting and Financial Disclosure 
None. 
Item 9A.  Controls and Procedures 
1. 
Disclosure Controls and Procedures 
Our management, with the participation of our principal executive officer and principal financial officer, has 
evaluated the effectiveness of our disclosure controls and procedures (as defined in Rules 13a-15(e) or 15d-15(e) under 
the Securities Exchange Act of 1934, as amended, or the Exchange Act) as of the end of the period covered by this 
Annual Report on Form 10-K. Based on such evaluation, our principal executive officer and principal financial officer 
have concluded that, as of the end of such period, our disclosure controls and procedures were adequate and effective. 
2. 
Internal Control Over Financial Reporting 
(a) 
Management’s Annual Report on Internal Control Over Financial Reporting 
Our management is responsible for establishing and maintaining adequate internal control over financial 
reporting. Internal control over financial reporting is defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act 
as a process designed by, or under the supervision of, our principal executive and principal financial officers and 
effected by our board of directors, management, and other personnel to provide reasonable assurance regarding the 
reliability of financial reporting and the preparation of financial statements for external purposes in accordance with 
generally accepted accounting principles in the U.S. and includes those policies and procedures that: 
• 
pertain to the maintenance of records that in reasonable detail accurately and fairly reflect our transactions 
and dispositions of our assets; 
• 
provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial 
statements in accordance with generally accepted accounting principles, and that our receipts and 
expenditures are being made only in accordance with authorizations of our management and directors; and 
• 
provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or 
disposition of our 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. Projections of any evaluation of effectiveness to future periods are subject to the risks that controls may 
become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures 
may deteriorate. 
Management assessed the effectiveness of our internal control over financial reporting as of December 31, 
2022. In making this assessment, management used the criteria established in Internal Control—Integrated Framework 
issued by the Committee of Sponsoring Organizations of the Treadway Commission, or COSO, in 2013. 
Based on this assessment, management has concluded that, as of December 31, 2022 our internal control over 
financial reporting is effective. 
Ernst & Young LLP, our independent registered public accounting firm, has issued a report on the effectiveness 
of our internal control over financial reporting as of December 31, 2022. This report appears immediately below. 
 
 

87 
(b) 
Attestation Report of the Independent Registered Public Accounting Firm 
Report of Independent Registered Public Accounting Firm 
To the Shareholders and the Board of Directors of ImmunoGen, Inc.  
Opinion on Internal Control over Financial Reporting 
We have audited ImmunoGen, Inc.’s internal control over financial reporting as of December 31, 2022, based on criteria 
established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the 
Treadway Commission (2013 framework) (the COSO criteria). In our opinion, ImmunoGen, Inc. (the Company) 
maintained, in all material respects, effective internal control over financial reporting as of December 31, 2022, based on 
the COSO criteria.  
We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United 
States) (PCAOB), the consolidated balance sheets of the Company as of December 31, 2022 and 2021, the related 
consolidated statements of operations and comprehensive loss, shareholders’ equity (deficit) and cash flows for each of 
the three years in the period ended December 31, 2022, and the related notes and our report dated March 1, 2023 
expressed an unqualified opinion thereon that included an explanatory paragraph regarding the Company’s ability to 
continue as a going concern. 
Basis for Opinion 
The Company’s management is responsible for maintaining effective internal control over financial reporting and for its 
assessment of the effectiveness of internal control over financial reporting included in the accompanying Management’s 
Annual Report on Internal Control Over Financial Reporting. Our responsibility is to express an opinion on the 
Company’s internal control over financial reporting based on our audit. We are a public accounting firm registered with 
the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal 
securities laws and the applicable 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 reasonable assurance about whether effective internal control over financial reporting was 
maintained in all material respects.  
Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a 
material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the 
assessed risk, and performing such other procedures as we 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 reporting and the preparation of financial statements for external purposes in accordance with 
generally accepted accounting principles. A company’s internal control over financial reporting includes those policies 
and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the 
transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are 
recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting 
principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of 
management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely 
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 of effectiveness to future periods are subject to the risk that controls may become 
inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may 
deteriorate. 
/s/ Ernst & Young LLP 
  
Boston, Massachusetts  
March 1, 2023 
 
 

88 
(c) 
Changes in Internal Control Over Financial Reporting 
During the three months ended December 31, 2022, we implemented certain internal controls in connection 
with our product launch. There were no other changes in our internal control over financial reporting (as such term is 
defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) during the quarter ended December 31, 2022 that 
have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting. 
3. 
Limitations on the Effectiveness of Controls 
Our management, including our principal executive officer and principal financial officer, does not expect that 
our disclosure controls and procedures or its internal control over financial reporting will prevent all error and all fraud. 
A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that 
the objectives of the control system are met. Further, the design of a control system must reflect the fact that there are 
resource constraints, and the benefits of controls must be considered relative to their costs. Because of the inherent 
limitations in all control systems, no evaluation of controls can provide absolute assurance that all control issues and 
instances of fraud, if any, within an organization have been detected. These inherent limitations include the realities that 
judgments in decision-making can be faulty, and that breakdowns can occur because of simple error or mistake. 
Additionally, controls can be circumvented by the individual acts of some persons, by collusion of two or more 
people, or by management override of the control. The design of any system of controls also is based in part upon certain 
assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in 
achieving our stated goals under all potential future conditions. Over time, controls may become inadequate because of 
changes in conditions, or the degree of compliance with the policies or procedures may deteriorate. Because of the 
inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be 
detected. 
Item 9B.  Other Information 
None 
Item 9C.  Disclosure Regarding Foreign Jurisdictions that Prevent Inspections 
Not applicable 
 
PART III 
The information called for by Part III of Form 10-K (Item 10—Directors, Executive Officers and Corporate 
Governance of the Registrant, Item 11—Executive Compensation, Item 12—Security Ownership of Certain Beneficial 
Owners and Management and Related Stockholder Matters, Item 13—Certain Relationships and Related Transactions, 
and Director Independence, and Item 14—Principal Accounting Fees and Services) is incorporated by reference from 
our proxy statement related to our 2022 annual meeting of shareholders, which will be filed with the Securities and 
Exchange Commission not later than May 2, 2022 (120 days after the end of the year covered by this report). 
 
PART IV 
Item 15.  Exhibits, Financial Statement Schedules 
(a) 
Documents filed as part of this Report: 
(1) 
See the financial statements of ImmunoGen, Inc. at Item 8 of this report.  
(2) 
Financial Statement Schedules: 
Schedules not included herein are omitted because they are not applicable, or the required 
information appears in the accompanying Consolidated Financial Statements or Notes thereto. 
(3) 
Exhibit Index 
 
 
 

89 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Filed 
 
Incorporated by Reference 
Exhibit 
Number     
Exhibit Description 
    
with this 
Form 10-K    
Form 
    
Filing Date 
with SEC 
    
Exhibit 
Number 
 3.1 
 Restated Articles of Organization, as amended 
  
 
10-Q 
 
August 5, 2020  
3.1 
 3.1(a) 
 Articles of Amendment 
  
 
10-Q 
 
January 30, 2013 
3.1 
 3.1(b) 
 Articles of Amendment 
  
 
10-Q 
 
August 4, 2017 
3.1 
 3.1(c) 
 Articles of Amendment 
  
 
10-Q 
 
August 5, 2020 
3.1(c) 
 3.1(d) 
 Articles of Amendment 
  
 
10-Q 
 
August 1, 2022 
3.1(d) 
 3.2 
 Amended and Restated By-Laws 
  
 
8-K 
 
June 20, 2016 
3.1 
 4.1 
 
Article 4 of Restated Articles of Organization, as 
amended (see Exhibit 3.1) 
  
 
 
  
 
 4.2 
 
Form of Common Stock certificate 
  
 
S-1 
 
November 15, 1989 
(File No. 33-31219) 
4.2 
 4.3 
 Description of Securities 
 
X 
 
 
 
 
 4.4 
 
Form of Pre-Funded Warrant issued August 12, 
2021 
  
 
8-K 
 
August 12, 2021 
  
4.1 
 4.5 
 
Form of Pre-Funded Warrant issued December 6, 
2021 
  
 
8-K 
 
December 3, 2021 
  
4.1 
10.1 
 
Lease Agreement, dated as of July 27, 2007, by 
and between Intercontinental Fund III 830 Winter 
Street LLC, landlord, and the Registrant 
  
 
10-Q 
 
November 7, 2007 
 
10.2 
10.1(a) 
 
First Amendment to Lease Agreement dated as of 
December 9, 2013, by and between 
Intercontinental Fund III 830 Winter Street LLC, 
landlord, and the Registrant 
  
 
10-Q 
 
February 5, 2014 
 
10.1 
10.1(b) 
 
Second Amendment to Lease Agreement dated as 
of April 28, 2014, by and between Intercontinental 
Fund III 830 Winter Street LLC, landlord, and the 
Registrant 
  
 
10-Q 
 
May 2, 2014 
 
10.1 
10.1(c) 
 
Third Amendment to Lease Agreement dated as of 
December 14, 2015 by and between CRP/King 
830 Winter, L.L.C., landlord, and the Registrant 
  
 
10-Q 
 
February 4, 2016  
 
10.1
10.1(d) 
 
Fourth Amendment to Lease Agreement dated as 
of April 6, 2018 by and between CRP/King 830 
Winter, L.L.C., landlord, and the Registrant 
  
 
10-Q 
 
May 9, 2018 
 
10.2
10.2** 
 
Collaboration and License Agreement effective as 
of October 19, 2020 by and between the registrant 
and Hangzhou Zhongmei Huadong 
Pharmaceutical Co., Ltd., a subsidiary of Huadong 
Medicine Co., Ltd.  
 
 
 
10-K 
 
March 1, 2021 
 
10.6
10.3** 
 
License Agreement as of February 14, 2022 by 
and between the Registrant and Eli Lilly and 
Company 
   
 
 
10-Q 
 
May 6, 2022 
 
10.1
10.10† 
 
2006 Employee, Director and Consultant Equity 
Incentive Plan, as amended and restated through 
November 11, 2014 
  
 
8-K 
 
November 13, 2014 
 
10.1 
10.10(a)† 
 
Form of Incentive Stock Option Agreement for 
Executives under 2006 Plan 
  
 
S-8 
 
November 15, 2006 
 
99.4 
10.10(b)† 
 
Form of Non-Qualified Stock Option Agreement 
for Executives under 2006 Plan 
  
 
S-8 
 
November 15, 2006 
 
99.5 
10.10(c)† 
 
Form of Non-Qualified Stock Option Agreement 
for Directors under 2006 Plan 
  
 
10-Q 
 
October 29, 2010 
 
10.1 
10.10(d)†  Form of Director Deferred Stock Unit Agreement   
 
10-Q 
 
October 29, 2010 
10.1 
10.10(e)† 
 
Form of Incentive Stock Option Agreement for all 
employees (including executives) 
  
 
10-K 
 
August 29, 2012 
 
10.14(g)
10.10(f)† 
 
Form of Non-Qualified Stock Option Agreement 
for all employees (including executives) 
  
 
10-K 
 
August 29, 2012 
 
10.14(h)
10.10(g)† 
 
Form of Non-Qualified Stock Option Agreement 
for Directors 
  
 
10-K 
 
August 29, 2012 
 
10.14(i)
10.10(h)† 
 
Form of Incentive Stock Option for all employees 
(including executives)  
  
 
8-K 
 
April 26, 2016 
 
10.1
10.10(i)† 
 
Form of Non-Qualified Stock Option Agreement 
for all employees (including executives)  
  
 
8-K 
 
April 26, 2016 
 
10.2

90 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Filed 
 
Incorporated by Reference 
Exhibit 
Number     
Exhibit Description 
    
with this 
Form 10-K    
Form 
    
Filing Date 
with SEC 
    
Exhibit 
Number 
10.11† 
 
2016 Employee, Director and Consultant Equity 
Incentive Plan, as amended and restated through 
June 13, 2017 
  
 
8-K 
 
June 16, 2017 
 
10.1
10.11(a)† 
 
Form of Incentive Stock Option Agreement under 
the 2016 Plan 
  
 
8-K 
 
December 13, 2016 
 
10.2
10.11(b)† 
 
Form of Non-Qualified Stock Option Agreement 
for Employees under the 2016 Plan 
  
 
8-K 
 
December 13, 2016 
 
10.3
10.11(c)† 
 
Form of Non-Qualified Stock Option Agreement 
for Non-Employee Directors  
  
 
8-K 
 
December 13, 2016 
 
10.4
10.11(d)† 
 
Form of Deferred Stock Unit Agreement for Non-
Employee Directors  
  
 
8-K 
 
December 13, 2016 
 
10.5
10.12† 
 
Amended and Restated 2018 Employee, Director 
and Consultant Equity Incentive Plan 
  
 
8-K 
 
June 17, 2022 
 
10.1 
10.12(a)† 
 
Form of Incentive Stock Option Agreement under 
the 2018 Plan 
  
 
8-K 
 
June 22, 2018 
 
10.2
10.12(b)† 
 
Form of Non-Qualified Stock Option Agreement 
for Employees under the 2018 Plan 
  
 
8-K 
 
June 22, 2018 
 
10.3
10.12(c)† 
 
Form of Restricted Stock Unit Agreement under 
the 2018 Plan, as amended February 3, 2023 
 
X 
 
 
 
 
 
10.12(d)† 
 
Form of Non-Qualified Stock Option Agreement 
for Non-Employee Directors, as amended 
December 15, 2022  
 
X 
 
 
 
 
 
10.12(e)† 
 
Form of Deferred Stock Unit Agreement for Non-
Employee Directors  
  
 
8-K 
 
June 22, 2018 
 
10.6
10.12(f)† 
 
Form of Restricted Stock Unit Agreement for 
Non-Employee Directors as of December 15, 2022 
X 
 
 
 
 
 
10.12(g)† 
 
Form of Performance-Based Stock Option 
Agreement dated February 7, 2020 
 
 
 
10-K 
 
March 11, 2020 
 
10.11(f)
10.13† 
 
Amended and Restated 2018 Employee Director 
and Consultant Equity Incentive Plan 
  
 
8-K 
 
June 17, 2021 
 
10.1
10.14† 
 
Employee Stock Purchase Plan, as amended 
through September 27, 2019  
  
 
10-Q 
 
November 5, 2019 
 
10.1
10.15† 
 
2004 Non-Employee Director Compensation and 
Deferred Stock Unit Plan, as amended and restated 
on December 15, 2022 
 
X 
 
 
 
 
 
10.16† 
 
Form of Proprietary Information, Inventions and 
Competition Agreement between the Registrant 
and each of its executive officers 
  
 
10-Q 
 
February 8, 2007 
 
10.15 
10.17† 
 
Change in Control Severance Agreement dated as 
of March 31, 2017 between the Registrant and 
Anna Berkenblit 
  
 
10-Q 
 
May 5, 2017 
 
10.3 
10.18† 
 
Change in Control Severance Agreement dated as 
of March 31, 2017 between the Registrant and 
Mark J. Enyedy 
  
 
10-Q 
 
May 5, 2017 
 
10.4 
10.19† 
 
Change in Control Severance Agreement dated as 
of January 5, 2021 between the Registrant and 
Renee Lentini 
 
X 
 
 
 
 
 
10.20† 
 
Change in Control Severance Agreement dated as 
of December 29, 2022 between the Registrant and 
Michael J. Vasconcelles 
 
X 
 
 
 
 
 
10.21† 
 
Change in Control Severance Agreement dated as 
of July 20, 2020 between the Registrant and Susan 
Altschuller, Ph.D. 
  
 
10-Q 
 
August 5, 2020 
 
10.4
10.22† 
 
Change in Control Severance Agreement dated as 
of June 1, 2020 between the Registrant and Stacy 
Coen 
 
 
 
10-K 
 
March 1, 2021 
 
10.19
10.23† 
 
Offer Letter dated as of December 29, 2022 
between the Registrant and Michael J. 
Vasconcelles 
 
X 
 
 
 
 
 
10.23(a)† 
 
First Amendment to Offer Letter dated as of 
December 29, 2022 between the Registrant and 
Michael J. Vasconcelles 
 
X 
 
 
 
 
 

91 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Filed 
 
Incorporated by Reference 
Exhibit 
Number     
Exhibit Description 
    
with this 
Form 10-K    
Form 
    
Filing Date 
with SEC 
    
Exhibit 
Number 
10.24† 
 
Compensation Policy for Non-Employee 
Directors, as amended through December 15, 2022 
X 
 
 
 
 
 
10.25† 
 
Severance Pay Plan for Vice Presidents and 
Higher, as amended through June 20, 2019 
 
 
 
10-Q 
 
August 7, 2019 
 
10.1
10.26† 
 Summary of ImmunoGen Incentive Bonus Plan 
 
 
 
8-K 
 
February 20, 2018 
10.1
10.27† 
 
Inducement Equity Incentive Plan, as amended 
December 15, 2022 
 
X 
 
 
 
 
 
10.27(a)† 
 
Form of Non-Qualified Stock Option Agreement 
under the Inducement Equity Incentive Plan 
 
 
 
8-K 
 
December 20, 2019 
 
10.2
10.27(b)† 
 
Form of Restricted Stock Unit Agreement 
(Inducement Plan), as amended February 3, 2023  
X 
 
 
 
 
 
    10.27(c)† 
 
Form of Performance-Based Stock Option 
Agreement (February 2020) under the Inducement 
Equity Incentive Plan 
 
 
 
10-Q 
 
August 5, 2020 
 
10.2
10.28 
 
Open Market Sale AgreementSM, dated December 
18, 2020, by and between the Registrant and 
Jeffries LLC 
  
 
8-K 
 
December 18, 2020 
 
10.1
21 
 Subsidiaries of the Registrant 
 
X 
 
 
 
 
23 
 Consent of Ernst & Young LLP 
 
X 
  
  
  
31.1 
 
Certification of the principal executive officer 
pursuant to Section 302 of the Sarbanes-Oxley Act 
of 2002 
 
X 
  
  
  
31.2 
 
Certification of the principal financial officer 
pursuant to Section 302 of the Sarbanes-Oxley Act 
of 2002 
 
X 
  
  
  
32 
 
Certifications of principal executive officer and 
principal financial officer pursuant to Section 906 
of the Sarbanes-Oxley Act of 2002 
 
X 
  
  
  
101 
 
Financial statements from the annual report on 
Form 10-K of ImmunoGen, Inc. for the year ended 
December 31, 2022 formatted in inline XBRL 
(eXtensible Business Reporting Language): (i) the 
Consolidated Balance Sheets; (ii) the Consolidated 
Statements of Operations and Comprehensive 
Loss; (iii) the Consolidated Statements of 
Shareholder’s Equity (Deficit); (iv) the 
Consolidated Statements of Cash Flows; and (v) 
the Notes to Consolidated Financial Statements 
 
X 
  
  
  
104 
 
Cover Page Interactive Data File (formatted as 
Inline XBRL and contained in Exhibit 101) 
 
X 
  
  
  
 
* 
Portions of this Exhibit were omitted, as indicated by [***], and have been filed separately with the Secretary of the 
Commission pursuant to the Registrant’s application requesting confidential treatment. 
** Certain confidential portions of this Exhibit were omitted by means of marking such portions with brackets [***] 
because the identified confidential portions (i) are not material and (ii) is the type of information the Registrant 
treats as private or confidential.  
† 
Exhibit is a management contract or compensatory plan, contract or arrangement required to be filed as an exhibit to 
this report on Form 10-K. 
Item 16. Form 10-K Summary 
None 
 
 

92 
SIGNATURES 
Pursuant 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 on its behalf by the undersigned, thereunto duly authorized. 
IMMUNOGEN, INC. 
 
 
By:
/s/Mark J. Enyedy 
 
Mark J. Enyedy 
President and 
Chief Executive Officer 
(Principal Executive Officer) 
Dated:   March 1, 2023 
Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the 
following persons on behalf of the Registrant in the capacities and on the dates indicated. 
Signature 
     
Title 
     
Date 
 
 
 
 
 
/s/ MARK J. ENYEDY 
Mark J. Enyedy 
 
President, Chief Executive Officer and Director 
(Principal Executive Officer) 
 
March 1, 2023 
 
 
 
 
 
/s/ RENEE LENTINI 
Renee Lentini 
 
Vice President - Finance, Chief Accounting Officer, 
and Interim Chief Financial Officer 
(Principal Accounting Officer and Principal Financial 
Officer) 
 
March 1, 2023 
 
 
 
 
 
/s/ STEPHEN C. MCCLUSKI 
Stephen C. McCluski 
 
Chairman of the Board of Directors 
 
March 1, 2023 
 
 
 
 
 
/s/ STUART A. ARBUCKLE 
Stuart A. Arbuckle 
 
Director 
 
March 1, 2023 
 
 
 
 
 
/s/ MARK GOLDBERG, M.D. 
Mark Goldberg, M.D. 
 
Director 
 
March 1, 2023 
 
 
 
 
 
/s/ TRACEY L. MCCAIN 
Tracey L. McCain 
 
Director 
 
March 1, 2023 
 
 
 
 
 
/s/ DEAN J. MITCHELL 
Dean J. Mitchell 
 
Director 
 
March 1, 2023 
 
 
 
 
 
/s/ KRISTINE PETERSON 
Kristine Peterson 
 
Director 
 
March 1, 2023 
 
 
 
 
 
/s/ HELEN THACKRAY, M.D. 
Helen Thackray, M.D. 
 
Director 
 
March 1, 2023 
 
 
 
 
 
/s/ RICHARD J. WALLACE 
Richard J. Wallace 
 
Director 
 
March 1, 2023 
 
 
 

93 
IMMUNOGEN, INC. 
Stock Price Performance Graph 
The graph and table below compare the annual percentage change in our cumulative total shareholder return on 
our common stock for the period from December 31, 2017 through December 31, 2022 (as measured by dividing (i) the 
sum of (A) the cumulative amount of dividends for the measurement period, assuming dividend reinvestment, and 
(B) the difference between our share price at the end and the beginning of the measurement period; by (ii) the share price 
at the beginning of the measurement period) with the total cumulative return of the NASDAQ US Benchmark TR Index 
and the NASDAQ Biotechnology TR Index during such period. We have not paid any dividends on our common stock, 
and no dividends are included in the representation of our performance. The stock price performance on the graph below 
is not necessarily indicative of future price performance.  
 
 
 
     Dec 2017    Dec 2018    Dec 2019     Dec 2020    Dec 2021    Dec 2022
IMMUNOGEN, INC. ...........................................................................................  $100.00  
$74.88 
   $79.64  $100.62  $115.75    $77.37 
NASDAQ US BENCHMARK TR INDEX .........................................................  $100.00  
$94.56 
 $124.03  $150.41  $189.36  $152.00 
NASDAQ BIOTECHNOLOGY TR INDEX ......................................................  $100.00  
$91.14 
 $114.02  $144.15  $144.18  $129.59 
 
The above graph and table assume $100 invested on December 31, 2017 with all dividends reinvested, in each 
of our common stock, the NASDAQ US Benchmark TR Index, and the NASDAQ Biotechnology TR Index.  

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ImmunoGen, Inc. | 830 Winter Street | Waltham, MA 02451 | 781–895–0600 | www.immunogen.com 
VIRTUAL ANNUAL MEETING
9:00 AM ET on June 14, 2023
www.virtualshareholdermeeting.com/ 
IMGN2023 
No in-person meeting will be held.
STOCK TRANSFER AGENT AND REGISTRAR 
Broadridge Corporate Issuer Solutions, Inc. 
P.O. Box 1342
Brentwood, NY 11717 
Phone: 855–697–4961 
Fax: 215–553–5402 
Email: shareholder@broadridge.com 
EXECUTIVES
Mark J. Enyedy 
President and Chief Executive Officer
Audrey M. Bergan 
Senior Vice President, Chief Human Resources Officer
Anna Berkenblit, MD, MMsC 
Senior Vice President, Chief Medical Officer
Daniel S. Char, JD
Senior Vice President, Chief Legal Officer
Stacy A. Coen
Senior Vice President, Chief Business Officer
Robert W. Herbst, PhD
Vice President, Technical Operations
Isabel Kalofonos
Senior Vice President, Chief Commercial Officer
Renee Lentini
Interim Chief Financial Officer, Chief Accounting 
Officer, and Vice President, Finance
Massimo Radaelli
Senior Vice President, General Manager 
International (Ex-US)
Mike J. Vasconcelles, MD
Executive Vice President, Research, Development, 
and Medical Affairs
Theresa G. Wingrove, PhD
Senior Vice President, Regulatory Affairs and Quality
DIRECTORS 
Stephen C. McCluski 
Chairman of the Board, Former Senior Vice President and 
Chief Financial Officer, Bausch & Lomb, Inc.
Stuart A. Arbuckle
Executive Vice President and Chief Operating Officer,  
Vertex Pharmaceuticals, Inc.
Mark J. Enyedy 
President and Chief Executive Officer, ImmunoGen, Inc.
Mark A. Goldberg, MD 
Former Executive Vice President, Medical and Regulatory 
Strategy, Synageva BioPharma Corp. 
Tracey L. McCain, Esq
Executive Vice President and Chief Legal and Compliance 
Officer, Blueprint Medicines Corporation
Dean J. Mitchell 
Former Executive Chairman of the Board,  
Covis Pharma Holdings S.a.r.l. 
Kristine Peterson 
Former Chief Executive Officer, Valeritas, Inc. 
Helen M. Thackray, MD
Chief Research and Development Officer,  
BioCryst Pharmaceuticals, Inc.
Richard J. Wallace
Former Senior Vice President Research and Development, 
GlaxoSmithKline plc
CORPORATE INFORMATION
AUDITORS 
Ernst & Young LLP 
Boston, MA
LEGAL COUNSEL 
Ropes & Gray, LLP
Boston, MA
SHAREHOLDER INQUIRIES 
Information about ImmunoGen can be found at 
www.immunogen.com. Inquiries related to the Company 
may be directed to the Investor Relations department at 
our headquarters. Communications related to stock and 
transfer requirements, including lost stock certificates and 
change of name or address, should be directed to the 
Transfer Agent. 

We extend our sincere gratitude to the patients, 
families, and medical professionals who participate 
in our clinical trials as we work to meaningfully 
improve the lives of people with cancer.
830 Winter Street
Waltham, MA 02451 
781–895–0600
www.immunogen.com 
We extend our sincere gratitude to the patients, 
families, and medical professionals who participate 
in our clinical trials as we work to meaningfully 
improve the lives of people with cancer.
830 Winter Street
Waltham, MA 02451 
781–895–0600
www.immunogen.com 
Nasdaq: IMGN
The enclosed message to our shareholders includes forward-looking statements regarding ImmunoGen’s current expectations related to the commercialization of ELAHERE; 
mirvetuximab soravtansine, pivekimab sunirine, IMGC936, and IMGN151 clinical trials, including the timing of initiating and receiving data from, as well as the likelihood of success 
of, the trials for these product candidates, including a trial that is intended to support full regulatory approval of ELAHERE; the potential of ELAHERE to become a standard of 
care; and the potential of ELAHERE to become a combination agent of choice. Various factors could cause ImmunoGen’s actual results to differ materially from those discussed 
or implied in the forward-looking statements, and you are cautioned not to place undue reliance on these forward-looking statements, which are current only as of the date of 
this presentation. We undertake no obligation to update or revise any of these forward-looking statements. Factors that could cause future results to differ materially from such 
expectations include, but are not limited to: that top-line data may change as more patient data become available and are subject to audit and verification procedures; the 
difficulties inherent in the development of novel biopharmaceuticals; the results of the ongoing MIRASOL trial may fail to support full approval of ELAHERE and, if so, additional 
studies may be required; the risks and uncertainties inherent in the Company’s development programs, including its preclinical and clinical studies and regulatory processes, their 
timing, expense, and results as well as the possibility that studies of the Company’s development programs fail to confirm the hypotheses suggested by exploratory analyses 
or fail to satisfy the requirements for approval by one or more regulatory agencies; the Company’s ability to financially support its development programs; additional market 
research and sources that may cause the Company’s expectations of future market opportunities for its development programs to change; the risk that we may not be able 
to obtain adequate reimbursement for any approved products, including the potential for delays or additional difficulties for ELAHERE in light of the FDA granting accelerated 
approval; and the risks and uncertainties associated with the scale and duration of the COVID19 pandemic and resulting impact on ImmunoGen’s industry and business. A review 
of these and other risks can be found in the “risk factors” set forth in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on 
March 1, 2023, and other reports filed with the SEC and available at www.sec.gov and on our website at www.ImmunoGen.com.