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ImmunoGen
Annual Report 2010

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FY2010 Annual Report · ImmunoGen
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ImmunoGen, Inc. 

830 Winter Street 

Waltham, MA 02451 

781-895-0600 

www.immunogen.com 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Our Targeted Antibody Payload (TAP) technology uses tumor-targeting antibodies to 
deliver one of our potent cancer-cell killing agents specifically to tumor cells. Multiple 
TAP compounds are in clinical testing today, with 3-4 more expected to enter the clinic 
by the end of 2011.    

    Clinical-Stage Pipeline Today 

Compound 

Partner 

Indication 

Stage 

3rd-line in advanced HER2+ 
breast cancer  

Phase II  
(completed) 

2nd-line in advanced HER2+ 
breast cancer  

Phase III 

Trastuzumab-DM1 
(T-DM1) 

Genentech/ 
Roche 

1st-line in advanced HER2+ 
breast cancer  

Phase III 

Adjuvant use in HER2+  
breast cancer 

Phase II expected  
to start 4Q10 

Use in combination with other 
anticancer agents 

Multiple trials 

Merkel cell carcinoma 

Decision in 4Q10 about 
initiating pivotal testing 

Small-cell lung cancer (SCLC) 
– combination 

Phase I/II expected  
to start 4Q10 

Lorvotuzumab 
mertansine 
(IMGN901) 

Wholly  
owned 

SCLC, Merkel cell carcinoma, 
ovarian cancer – single agent 

Phase I 

Multiple myeloma  
– single agent 

Multiple myeloma  
– combination 

Phase I 

Phase I 

IMGN388 

Wholly 
owned* 

Solid tumors – single agent 

Phase I 

SAR3419 

sanofi-aventis 

Non-Hodgkin’s lymphoma  
– single agent 

BT-062 

Biotest* 

BIIB015 

Biogen Idec 

Multiple myeloma  
– single agent 

Cripto+ solid tumors  
– single agent 

SAR650984** 

sanofi-aventis 

Hematologic malignancies  
– single agent 

SAR566658 

sanofi-aventis 

CA6+ solid tumors 
– single agent 

Phase I 

Phase I 

Phase I 

Phase I 

Phase I 

Corporate Information 

Directors 

Chairman of the Board 

Stephen C. McCluski 

Former Senior Vice President 

and Chief Financial Officer, 

Baush & Lomb, Inc. 

David W. Carter 

Former Chairman and 

Chief Executive Officer, 

Xenogen Corporation 

Daniel M. Junius 

President and  

Chief Executive Officer, 

ImmunoGen, Inc. 

Nicole Onetto, M.D. 

Deputy Director, 

Ontario Institute for Cancer 

Research 

Howard Pien 

Former Chairman of the Board  

and Chief Executive Officer, 

Medarex, Inc. 

Mitchel Sayare, Ph.D. 

Former President and  

Chief Executive Officer, 

ImmunoGen, Inc. 

Mark Skaletsky 

Chairman and  

Chief Executive Officer, 

Fenway Pharmaceuticals 

Joseph J. Villafranca, Ph.D. 

Senior Vice President, 

Life Sciences, 

Business Development, 

Tunnell Consulting 

Richard J. Wallace 

Former Senior Vice President, 

Research and Development, 

GlaxoSmithKline plc. 

Executive Management

Corporate Headquarters 

Daniel M. Junius 

President and  

Chief Executive Officer 

John M. Lambert, Ph.D. 

Executive Vice President and  

Chief Scientific Officer 

Gregory D. Perry 

Senior Vice President and 

Chief Financial Officer 

Craig Barrows 

and Secretary 

James J. O’Leary, M.D. 

Vice President and  

Chief Medical Officer 

Peter J. Williams 

Vice President, 

Business Development 

Vice President, General Counsel  

Stock Transfer Agent and  

ImmunoGen, Inc. 

830 Winter Street 

Waltham, MA 02451 

781.895.0600 

www.immunogen.com 

Annual Meeting 

11:00 AM on November 16, 2010 

at the offices of the Company 

830 Winter Street 

Waltham, MA  02451 

Registrar 

BNY Mellon Shareowner Services 

Newport Office Center VII 

480 Washington Boulevard 

Jersey City, NJ 07310 

www.bnymellon.com/shareowners/ 

Toll-Free Number: 888.810.7458 

isd

Auditors 

Ernst & Young LLP 

Boston, Massachusetts 

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. 

This annual report includes forward-looking statements based on management’s current expectations. These statements include, 

but are not limited to, ImmunoGen’s expectations related to the advancement of new Company and partner compounds into clinical 

testing, the initiation of new clinical trials, the timing of go/no go clinical decisions, and the timing and occurrence of the

presentation of new preclinical and clinical data, of potential business development events, and of potential future regulatory

submissions. For these statements, ImmunoGen claims the protection of the safe harbor for forward-looking statements provided 

by the Private Securities Litigation Reform Act of 1995. 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 annual report. Factors that could cause future results to 

differ materially from such expectations include, but are not limited to: the timing and outcome of ImmunoGen’s and the Company’s 

partners’ research and clinical development processes; the difficulties inherent in the development of novel pharmaceuticals, 

including uncertainties as to the timing, expense and results of preclinical studies, clinical trials and regulatory processes;

ImmunoGen’s ability to financially support its product programs; ImmunoGen’s dependence on collaborative partners; industry 

merger and acquisition activity; and other factors more fully described in ImmunoGen’s Annual Report on Form 10-K for the fiscal

year ended June 30, 2010 and other reports filed with the Securities and Exchange Commission.  

  *Centocor Ortho Biotech (J&J) has opt-in rights to IMGN388; ImmunoGen has opt-in rights to BT-062 
**Therapeutic antibody (non-TAP) compound 

Revlimid® is a registered trademark of Celgene Corporation. 

 
 
  
  
 
  Dear Fellow Shareholders, 

ImmunoGen today has a growing and 
expanding product pipeline as well as a 
significant technology. Eight compounds 
are in clinical testing through our own 
programs and those of our partners, and 
we expect this to increase to as many as 
twelve by the end of 2011.    

Of particular importance, we’ve increased 
the support we’re putting behind 
advancing our own compounds to value-
inflection points. We envision that – over 
time – ImmunoGen will become known for 
the targeted anticancer products we 
develop, complementing the leadership 
position of our TAP technology in the field 
of antibody-drug conjugates.  

Driving this increased support behind our 
own compounds is – first and foremost – 
the validation of our TAP technology in the 
clinic. While we are disappointed with the 
FDA’s refuse-to-file decision on the first 
marketing application for trastuzumab-
DM1 (T-DM1) that was announced in late 
August, there is no question that the 
clinical findings reported to date with this 
product candidate are impressive – both in 
efficacy and tolerability – and support the 
continued comprehensive evaluation of 
the compound that Roche is pursuing. 
Encouraging findings are being reported 
with other TAP compounds in earlier 
stages of clinical testing, and we expect 
the support behind our technology will 
continue to expand as we go forward. 

We’re implementing an aggressive clinical 
program with our lead wholly owned 
compound, lorvotuzumab mertansine 
(IMGN901); are making solid progress 
with our second compound, IMGN388; 
and expect to advance our third compound 
into the clinic in 2011. At the same time, 
our partners also are making meaningful 
progress, and we’re seeing an 

unprecedented level of interest from other 
companies in our TAP technology. 

Our Lead Wholly Owned Compound: 
Lorvotuzumab Mertansine  

This TAP compound targets an antigen, 
CD56, found on an array of cancers with 
limited treatment options today. Up until 
quite recently, lorvotuzumab mertansine 
was still just being assessed in early stage 
dose-escalation trials, used as a single 
agent.  

In late 2009, we started our first trial that 
evaluates this agent used as part of a 
combination regimen, since that is how 
cancer generally is treated. That study 
assesses lorvotuzumab mertansine used 
together with Revlimid® (lenalidomide) 
and dexamethasone in patients with 
relapsed multiple myeloma. While patient 
enrollment in this study is still in early 
stages, we’re encouraged by the findings 
to date. 

In late 2009, we also advanced to the 
expansion phase of our Study 002, which 
previously had been assessing alternative 
doses of lorvotuzumab mertansine for 
CD56+ solid tumors. We narrowed the 
enrollment criteria of this trial to focus on 
metastatic cancers of particular interest – 
ovarian cancer, small-cell lung cancer 
(SCLC), and Merkel cell carcinoma (MCC) 
– to inform our next steps with the 
compound for these cancers. We chose 
ovarian cancer and SCLC due to the size 
of these markets, their unmet need, and 
the preclinical and clinical data available.  

Our interest in MCC, a rare cancer, came 
from the notable findings seen with 
lorvotuzumab mertansine in the first six 
MCC patients treated: one patient had 
complete remission, another has had 
marked, sustained tumor shrinkage, and a 

 
 
 
 
 
 
third had stable disease. As metastatic 
MCC today has a median survival of less 
than seven months and no approved 
therapies, development of lorvotuzumab 
mertansine for this use is potentially one of 
its fastest routes to market. We plan to 
decide by the end of 2010 whether we 
should initiate a pivotal trial with the 
compound in MCC.  

Study 002 assesses lorvotuzumab 
mertansine in patients previously treated 
with other agents. We believe it is 
important to assess the compound used 
1st-line in SCLC, as this is a very 
aggressive cancer. Thus, we’re preparing 
to initiate a trial that assesses 
lorvotuzumab mertansine, used in 
combination with standard care, as a 1st-
line treatment for SCLC. We expect to 
start this trial in the fourth quarter of 2010. 

We believe lorvotuzumab mertansine is a 
promising product candidate for a number 
of cancers that have poor outcomes today. 
We’re implementing an aggressive clinical 
program designed to establish the value of 
this compound, with an eye to eventually 
partnering it. 

Our Earlier-Stage Compounds 

We’re also making solid progress with 
IMGN388, our second clinical-stage 
compound, which is in development for the 
treatment of solid tumors. We reported the 
first IMGN388 clinical data at the American 
Society of Clinical Oncology (ASCO) 
meeting in June. We’ve since completed 
the dose-escalation process in our 
evaluation of it when administered every 
three weeks, and we’ll report updated 
findings at the EORTC-AACR-NCI 
conference in November. The initial 
findings with IMGN388 are encouraging, 
and we’re evaluating the next steps in its 
development. 

About two years ago, our scientists 
resumed developing product candidates 

for our proprietary product pipeline upon 
the completion of our research and 
development obligations to our 
collaborator, sanofi-aventis. Since then, 
our team has been aggressively creating 
and advancing targeted anticancer 
compounds. We expect to submit an IND 
for the first of these new product 
candidates, IMGN529, in mid-2011 and to 
submit an IND for another new compound 
in 2012.  

Our goal is to have an ongoing stream of 
new antibody-based anticancer agents 
entering the clinic. While we plan to take 
many of these forward ourselves, we also 
have the option of selectively partnering 
one or more product candidate(s), as 
appropriate, to accelerate development 
without overextending our human and 
financial resources.  

Partner Product Candidates 

There are currently six compounds in 
clinical testing through our collaborations 
with other companies, and we expect 
another 2-3 partner compounds to enter 
the clinic in 2011.  

The most advanced partner compound, 
T-DM1, is in global development by Roche 
under a licensing agreement between 
ImmunoGen and Genentech, a member of 
the Roche Group. T-DM1 is being 
assessed for 2nd-line treatment of 
advanced HER2+ breast cancer in a 
Phase III trial, EMILIA, that started in early 
2009. Roche expects to apply in 2012 for 
marketing approval of T-DM1 in the US 
and Europe for 2nd-line and later treatment 
of advanced HER2+ breast cancer.  

T-DM1 also is being assessed for 1st-line 
treatment of this cancer in a separate 
Phase III trial, MARIANNE, that began 
earlier this summer. Roche intends to use 
MARIANNE to apply for marketing 
approval of T-DM1 for 1st-line treatment of 
HER2+ breast cancer. Roche projects this 

 
 
 
 
 
 
regulatory submission could occur 
sometime after 2013, since this trial has 
only recently begun.  

Additionally, Roche is now preparing to 
start a Phase II trial assessing T-DM1 
used in the adjuvant setting that we hope 
will lead to the compound being evaluated 
for this use in a registration trial.  

Initial findings from a Phase II trial 
assessing T-DM1 for 1st-line treatment of 
advanced HER2+ breast cancer will be 
reported at the European Society of 
Medical Oncology (ESMO) meeting taking 
place in Milan next month. We’re 
particularly interested in seeing these 
data, as they will be the first findings with a 
compound utilizing our TAP technology for 
1st-line treatment of an advanced cancer.  

In 2003-2008, we were in a collaboration 
with sanofi-aventis in which we agreed to 
generate novel antibody-based 
compounds for its pipeline in exchange for 
meaningful research support funding. 
Three compounds are now in clinical 
testing as a result of this collaboration: 
SAR3419, SAR650984, and SAR566658. 
While we’re no longer developing 
compounds for sanofi-aventis, we continue 
to be entitled to receive milestone 
payments on the advancement of 
collaboration compounds and royalties on 
their sales, if any.  

SAR3419 uses our TAP technology with 
an ImmunoGen antibody that binds to 
CD19, a target found on non-Hodgkin’s 
lymphoma and other B-cell malignancies. 
Sanofi-aventis is planning to further 
expand its Phase I evaluation of SAR3419 
with an intent to promptly start its Phase II 
program in the second half of 2011. We 
expect the full Phase I findings to be 
reported at ASH in late 2011. 

While ImmunoGen is known for our TAP 
technology, we have full antibody 
development capabilities. Some of the 

antibodies we create are for use in TAP 
compounds, such as the one we 
developed for SAR3419. Others are 
designed for use as therapeutic antibodies 
– antibody compounds that do not utilize a 
payload. We developed both types of 
antibody-based compounds for sanofi-
aventis, and the SAR650984 compound 
now in the clinic is a therapeutic antibody 
for the treatment of hematological 
malignancies.  

Additionally, we can identify promising 
targets and use antibodies created by 
others to develop TAP compounds. 
SAR566658 uses an antibody from one of 
our academic collaborators to a target 
found on a number of types of solid 
tumors, including ovarian, breast and lung 
cancers. We humanized this antibody 
using our proprietary technology and 
created the SAR566658 TAP compound 
with it. 

In addition to the compounds in the clinic 
through our collaborations with Genentech 
and sanofi-aventis, BT-062 and BIIB015 
are in clinical testing through our partners 
Biotest and Biogen Idec, respectively. 

Continued Commitment to Our TAP 
Technology 

We continue to invest in our TAP 
technology – further expanding our 
portfolio of linkers and cell-killing agents – 
to maintain our leadership position in 
antibody-drug conjugates (ADCs). For 
example, today certain cancers can be 
highly problematic because they have 
intrinsic multi-drug resistance (MDR). 
ImmunoGen scientists have created a 
family of linkers for use in TAP compounds 
for cancers with MDR, to enable the 
achievement of the necessary efficacy 
while retaining the tolerability benefits of 
our targeted approach. A compound 
incorporating one of these linkers is now in 
preclinical development.  

 
 
 
 
 
 
 
Business Development 

We’re seeing an unprecedented level of 
interest in licensing access to our 
technology by major healthcare 
companies. We believe our technology is 
worth considerably more today than it was 
before it had been validated in the clinic 
and that its value will only increase over 
time. This, combined with our solid 
financial position, means that we can be 
much more selective – and more 
demanding – in entering into new licenses 
to our technology. Business development 
will continue to be an important source of 
non-dilutive funding for ImmunoGen and a 
means to more broadly advance our 
technology than we could accomplish on 
our own. 

Thank You 

As we have since our inception, we remain 
committed to the development of novel 
anticancer compounds that make a real 
difference for patients with cancer. What 
has changed is that we are putting more 
support behind the aggressive 
advancement of our own compounds to 
value-inflection points and being more 
selective in entering into new 
collaborations than in the past.  

I thank our Directors for their guidance and 
encouragement and our employees for 
their scientific insights, teamwork, and 
unrelenting commitment in helping us 
reach this new stage for ImmunoGen. 
And, I particularly wish to thank you, our 
shareholders, for your support of our 
progress. 

Sincerely,  

Daniel M. Junius 
President and Chief Executive Officer 

September 21, 2010 

 
 
 
 
 
 
 
 
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

(cid:2) ANNUAL  REPORT PURSUANT TO  SECTION 13  OR 15(d) OF  THE

SECURITIES EXCHANGE ACT OF 1934

(cid:3)

For the fiscal year ended June 30, 2010
OR

TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)  OF THE
SECURITIES EXCHANGE ACT OF 1934
For the transition 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

Name of Each Exchange on Which Registered

Common Stock, $.01  par value

NASDAQ Global Market

Indicate by  check mark if the registrant  is a  well-known seasoned issuer, as defined in Rule 405 of the Securities

Act. (cid:3)  Yes (cid:2) 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. (cid:3)  Yes (cid:2) 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. (cid:2) Yes (cid:3) No

Indicate by  check mark whether the registrant has submitted electronically and posted on its corporate Website, if any,

every Interactive  Data  File  required  to  be  submitted and posted 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 and post such
files). (cid:3)  Yes (cid:3)  No

Indicate by  check mark if disclosure  of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405 of this chapter)

is not  contained herein, and will not  be  contained,  to the best of registrant’s knowledge, in definitive proxy or information
statements incorporated by reference  in  Part  III  of  this Form 10-K or any amendment to this Form 10-K. (cid:3)

Indicate by  check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a
smaller reporting  company. See  definitions  of  ‘‘large accelerated filer,’’ ‘‘accelerated filer,’’ and ‘‘smaller reporting company’’ in
Rule  12b-2 of the Exchange Act.  (Check  one):
Large accelerated  filer (cid:3)

Smaller reporting company (cid:3)

Accelerated filer (cid:2)

Non-accelerated filer (cid:3)
(Do  not check if  a smaller
reporting company)

Indicate by  check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange

Act). (cid:3)  Yes (cid:2) No

Aggregate market value,  based upon the closing sale price of the shares as reported by the NASDAQ Global Market, of

voting stock held by non-affiliates at  December  31,  2009: $444,794,248 (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 August 24, 2010: 67,949,840 shares.

Portions of the definitive Proxy Statement to be delivered to shareholders in connection with the Annual Meeting of

Shareholders to be  held  on November  16, 2010  are  incorporated by reference into Part III.

DOCUMENTS INCORPORATED BY REFERENCE

ImmunoGen, Inc.

Form 10-K

TABLE OF CONTENTS

Item

1.
1A.
1B.
2.
3.
3.1
4.

5.

6.
7.

7A.
8.
9.

9A.
9B.

10.
11.
12.

13.
14.

15.

Part I
Business . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Risk Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unresolved Staff Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Legal Proceedings
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Executive Officers of the Registrant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part II
Market for the Registrant’s Common Equity, Related  Stockholder Matters and Issuer

Purchases of Equity Securities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selected Financial Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Management’s Discussion and Analysis of  Financial Condition and Results

of Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Quantitative and Qualitative Disclosures  About Market Risk . . . . . . . . . . . . . . . . . . .
Financial Statements and Supplementary Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Changes in and Disagreements  with Accountants  on Accounting and Financial

Disclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Controls and Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part III
Directors, Executive Officers  and  Corporate Governance . . . . . . . . . . . . . . . . . . . . . .
Executive Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Security Ownership of Certain  Beneficial  Owners and  Management and Related

Stockholder Matters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Certain Relationships and Related Transactions, and  Director Independence . . . . . . . .
Principal Accounting Fees and Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part IV
Exhibits, Financial Statement Schedules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page
Number

3
24
38
39
39
39
40

41
43

43
58
59

95
95
97

98
98

98
98
98

99

100

2

Item 1. Business

In this Annual Report on Form 10-K, ImmunoGen, Inc.  (ImmunoGen,  Inc., together with its

subsidiaries, is referred to in this document as ‘‘we’’, ‘‘us’’, ‘‘ImmunoGen’’, or the  ‘‘Company’’),
incorporates by reference certain information from  parts of other documents filed with  the Securities
and Exchange Commission. The Securities and Exchange  Commission allows us to disclose important
information by referring to it in that manner.  Please  refer to all such  information when reading this
Annual Report on Form 10-K. All information is as of June 30,  2010 unless  otherwise indicated.  For  a
description of the risk factors affecting or applicable to our business, see  ‘‘Risk  Factors,’’ below.

The Company

We  develop novel, targeted therapeutics for  the treatment  of cancer using our expertise  in cancer

biology, the development of monoclonal  antibodies,  the creation of highly potent  cytotoxic,  or
cell-killing, agents, and the engineering  of linkers used to attach  our cell-killing  agents to antibodies.

Most of the product candidates being developed by us and  through our collaborations  with others
utilize our Targeted Antibody Payload, or TAP, technology. A TAP compound consists of a monoclonal
antibody  that binds specifically to an antigen target found  on cancer cells with one of  our highly potent
cytotoxic agents attached using one of our  linkers. Our  linkers are engineered to keep  the cytotoxic
agent stably attached to the antibody  while the TAP compound is in the  blood stream and then release
it in a fully active form after delivery  to  a cancer cell. Six  TAP compounds and  one therapeutic
antibody  are in clinical testing through our own  programs  and  those of our partners, with  more
expected to enter the clinic in 2010 and  2011.

We  develop targeted, antibody-based  anticancer compounds  for  our own proprietary  pipeline. Our
most advanced wholly owned product candidate  is lorvotuzumab mertansine (also known as IMGN901).
This TAP compound is a potential treatment for cancers that  express CD56, which include small-cell
lung  cancer, Merkel cell carcinoma, ovarian cancer,  and  multiple myeloma. We  have several clinical
trials underway with lorvotuzumab mertansine and  expect to initiate additional  trials going forward.
Our second most advanced compound, IMGN388, is a  potential  treatment for solid tumors including
melanomas, sarcomas and many carcinomas. IMGN388 also is a  clinical-stage TAP compound. We  have
three TAP compounds currently in or  positioned  to  begin preclinical toxicology  studies. One of these
compounds, IMGN529, is being developed for the  treatment of  certain  liquid tumors and  we expect to
submit an investigational new drug, or IND,  application to the FDA  for this product candidate in  2011.
We  expect to submit an IND for another  of  these  in 2012. In addition to our product  programs, we
continue to invest in our TAP technology, including the development of additional cytotoxic agents and
linkers, to maintain a leadership position in our field.

Part of our business model is to establish collaborations with other  companies in order to provide
us with cash and revenue short term and potential  significant value long term. The collaborations  also
expand the utilization of our TAP technology. The most  advanced TAP compound, Trastuzumab-DM1
or T-DM1, is in development through  our collaboration with Genentech,  a member of the Roche
Group, and it is in Phase III testing for  two  indications. SAR3419 and SAR650984 are  in clinical
testing through a collaboration with sanofi-aventis. BIIB015 and BT-062 are  in clinical development
through our collaborations with Biogen Idec and Biotest,  respectively.  Companies with  licenses to
develop TAP compounds to other targets include Amgen, Bayer  Schering Pharma, Genentech, and
sanofi-aventis.

We  were organized as a Massachusetts corporation in 1981.  Our principal offices are located  at
830 Winter Street, Waltham, Massachusetts (MA)  02451, and  our telephone  number is (781)  895-0600.
We  maintain a website at www.immunogen.com, where certain information about  us is available. Please
note that information contained on the  website is  not a part of this document. Our Annual Reports on
Form 10-K, Quarterly Reports on Form 10-Q,  Current Reports on Form 8-K, and any  amendments to

3

those reports are available free of charge through the ‘‘Investor Information’’ 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. We have adopted a Code of Corporate Conduct that applies
to all our directors, officers and employees and  a Senior Officer and Financial  Personnel Code of
Ethics that applies to our senior officers  and  financial personnel.  Our Code of  Corporate Conduct and
Senior Officer and Financial Personnel  Code of Ethics are available free  of charge  through the
‘‘Investor Information’’ section of our website.

Product  Candidates

The following table summarizes the status for  compounds in development  by  us  and our
collaborators. The results from preclinical testing and early clinical trials  may not be predictive of
results obtained in subsequent clinical  trials and  there can be no  assurance that our or our

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collaborators’ clinical trials will demonstrate  the level  of  safety and efficacy of any product candidates
necessary to obtain regulatory approval.

Product Candidate

Trastuzumab-DM1

Development Stage

Collaborative
Partner, if any

(T-DM1) . . . . . . . . For advanced HER2+  breast cancer:

Genentech/Roche

(cid:129) 2nd-line use—Phase III trial underway
(cid:129) 1st-line use—Phase III trial underway
(cid:129) Adjuvant use—described as being  under

consideration

Lorvotuzumab
mertansine
(IMGN901) . . . . . . For CD56+ solid tumors:

Proprietary to ImmunoGen

(cid:129) Merkel  cell carcinoma—patients  with  advanced
disease being enrolled  into expansion phase
of  a  Phase I  trial; Go/no go decision to
be made regarding initiation  of pivotal  testing
(cid:129) Small-cell lung cancer—patients with  advanced
disease being enrolled  into expansion phase
of  a  Phase I  elial;  Phase  I/II trial
in  1st-line use expected to start
by  late  2010

(cid:129) Ovarian cancer—patients  with  advanced  disease

being recruited into  expansion  phase of a
Phase I trial; next  steps to  be  determined

For  CD56+ multiple  myeloma:
(cid:129) Use as monotherapy in advanced disease—

patients being  enrolled into expansion
phase of a  Phase I trial

(cid:129) Use in  combination in  advanced

disease—patients being enrolled into
Phase I trial

SAR3419 . . . . . . . . . . For advanced CD19+ non-Hodgkin’s

sanofi-aventis

lymphoma—Phase  I

IMGN388 . . . . . . . . . For advanced solid  tumors—Phase  I

Centocor Ortho  Biotech has
opt-in rights

BIIB015 . . . . . . . . . . For advanced solid tumors—Phase I

Biogen  Idec

BT-062 . . . . . . . . . . . For advanced multiple myeloma—Phase  I

Biotest; ImmunoGen has
opt-in rights

SAR650984(1) . . . . . . . For advanced hematological  malignancies—Phase I

sanofi-aventis

SAR566658 . . . . . . . . For advanced solid tumors—Preclinical

sanofi-aventis

Other compounds

. . . Research/preclinical

ImmunoGen/collaborators

(1) Therapeutic antibody; the  rest of the product  candidates are TAP  compounds.

Trastuzumab-DM1 (T-DM1)

The most advanced compound in our  pipeline  is T-DM1, which is in global development by Roche

for the treatment of advanced HER2+ breast  cancer.  T-DM1 consists  of our DM1  cell-killing  agent
attached to trastuzumab, which is the active  component  of  the marketed anticancer compound,

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Herceptin(cid:4). T-DM1 was created under  a  HER2-specific license agreement established in 2000  between
ImmunoGen and Genentech.

To date, we have earned $13.5 million of a  potential $44 million in milestone payments  with

Genentech/Roche’s advancement of T-DM1:  $2 million when  the IND became effective  in January
2006, $5 million when T-DM1 entered  Phase II clinical testing in  July  2007, and  $6.5 million when it
began Phase III evaluation in February 2009. Genentech retained  us to develop a commercial-scale
manufacturing process for T-DM1 in  May 2006 and we have completed and  transferred this process.

In early July 2010, Roche announced the submission of a Biologics License Application, or BLA,

to the FDA to gain U.S. marketing approval for use of T-DM1 to treat  patients with advanced HER2+
breast cancer who had previously received multiple chemotherapies and HER2-targeted medicines; this
is also known as 3rd-line use. The basis of the submission is  the single-arm Phase II  clinical  trial  that
was reported at the San Antonio Breast Cancer  Symposium in December 2009.  In August 2010,  Roche
announced that the FDA issued a Refuse to File  letter for this BLA. Roche  will  continue to work  with
the FDA and expects to submit a new BLA in mid 2012 based  on  results  of the ongoing EMILIA  trial
described below.

In February 2009, patient dosing began in a Phase III trial,  EMILIA, being conducted by Roche to

assess T-DM1 for 2nd-line use in advanced HER2+ breast cancer. EMILIA compares T-DM1, used
alone, against the  marketed anticancer agents,  lapatinib and capecitabine, used together. Roche has
noted that, if successful, this trial would be used to apply in  2012 for marketing  approval of T-DM1  for
2nd-line  use in the U.S. It would also be used to apply in  2012 for marketing approval  in Europe.

In July 2010, patient dosing began in a Phase III  trial, MARIANNE, being conducted by Roche to
assess T-DM1 for 1st-line use in advanced HER2+ breast  cancer.  MARIANNE compares T-DM1, used
alone, against the  marketed agent, trastuzumab, used together  with a taxane, in patients not previously
treated for metastatic disease. This trial also includes comparison to T-DM1  used  with Roche’s
experimental agent, pertuzumab. Roche has noted  that, if successful, MARIANNE would be used to
apply some time after 2013 for marketing approval of T-DM1  for 1st-line use in the U.S. and Europe.

The first findings with T-DM1 used for 1st-line treatment of advanced HER2+ breast cancer  are
expected to be reported at a medical meeting in October 2010. These data would be from  a Phase II
trial.

Roche also is assessing T-DM1 used  in combination  with several approved and experimental
agents, and reported the first data on  T-DM1  used  together with pertuzumab at  a medical meeting in
June 2010. It expects to report additional data at a medical meeting in December 2010.

Lorvotuzumab mertansine

Our most advanced wholly owned compound is lorvotuzumab mertansine, also known as

IMGN901. The target for this TAP compound,  CD56,  is found on  a number of tumor  types, including
small-cell lung cancer, ovarian cancer, Merkel cell carcinoma, and the  liquid tumor, multiple myeloma.
We  believe lorvotuzumab mertansine  has the potential to be the first effective antibody-based therapy
for the treatment of these cancers.

There is a need for better therapies for  a number of CD56+ cancers.  For  example, patients with

advanced small-cell lung cancer can respond to their first  treatment regimen, but typically their disease
then recurs fairly quickly and, at that stage, patients usually survive for less than 6 months. There are
no approved therapies for metastatic Merkel cell carcinoma,  and  patients  with advanced  disease
typically survive for less than 7 months. In  recent years, several new therapies have become  available to
treat multiple myeloma; however, patients  still die from this disease and  we believe there is a  need for
a treatment, such as lorvotuzumab mertansine, that has  a different mechanism of action  from the
approved therapies.

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We  are evaluating lorvotuzumab mertansine for the treatment of CD56+ cancers, focusing initially

on small-cell lung cancer, Merkel cell carcinoma, ovarian cancer, and multiple  myeloma:

Small-cell lung cancer, or SCLC—Patients  with recurrent SCLC  were  enrolled in the  first
lorvotuzumab mertansine Phase I trial conducted, which has been completed, and  are being
enrolled in the expansion phase of a  second  Phase I trial, which is  in progress. To assess
lorvotuzumab mertansine for 1st-line treatment of SCLC, we plan to commence a  Phase I/II trial
by late 2010 assessing it used in combination with etoposide/carboplatin, the  standard 1st-line
treatment for this cancer. We have applied  for orphan drug designation in SCLC in the  U.S. and
Europe and are awaiting the decision.

Merkel cell carcinoma, or MCC—A limited number  of  patients  with advanced  MCC received
lorvotuzumab mertansine in the ongoing Phase I trial referenced  previously. Additional patients
with advanced MCC are being enrolled  in the expansion phase of this  trial to gain more
experience with lorvotuzumab mertansine in  the treatment of this disease. These  findings—along
with other clinical data and input gained from regulatory  agencies—will  be  used  to  determine
whether or not we will initiate a pivotal Phase  II trial for this use during 2011.  We have received
orphan drug designation in MCC in the  U.S. and Europe.

Ovarian  cancer—To gain experience  with  lorvotuzumab mertansine in this disease, patients with
CD56+ ovarian cancer are being recruited  to  the expansion phase  of the ongoing Phase  I trial
referenced previously.

Multiple myeloma, or MM—Two Phase I trials  are underway  in this indication. One evaluates
lorvotuzumab mertansine when used  as a single agent and is currently  in its expansion phase. The
other evaluates the compound used in combination with the  standard treatment  for this cancer,
lenalidomide plus dexamethasone. We expect  to  report interim data from one or  both of these
trials at the ASH annual meeting in December 2010.  The  findings from these trials will inform the
future development of lorvotuzumab mertansine for MM.

SAR3419

We  created this TAP compound for the treatment  of non-Hodgkin’s lymphoma and  other  B-cell

malignancies and licensed it to sanofi-aventis as part of a  broader research collaboration. We  earned a
$1 million milestone payment from sanofi-aventis in  October 2007 with the its advancement into clinical
testing. SAR3419 is currently in Phase I  testing for the  treatment  of  non-Hodgkin’s lymphoma.
Encouraging findings from the first Phase I trial  conducted were  reported at  a medical meeting in
December 2009. Sanofi-aventis is evaluating  the compound using  a different dosing schedule in a
second  Phase I trial, and SAR3419 is expected to advance into Phase  II testing  in the second half of
2011. Like Genentech for T-DM1, sanofi-aventis retained  us to develop a commercial-scale
manufacturing process for the compound. We  have completed and transferred this  process.

IMGN388

We  are developing IMGN388 for the treatment  of solid tumors. It includes an integrin-targeting

antibody  developed by Centocor Ortho  Biotech, previously Centocor. IMGN388’s  target occurs  on
many  types of solid tumors and also on  vascular endothelial  cells in the  process of  forming new blood
vessels, a process that needs to occur  for solid tumors  to  grow. IMGN388 is in Phase I testing  and
clinical data from this trial were presented at a medical meeting in June 2010. Centocor  Ortho Biotech
has opt-in rights for this compound.

7

Other  Compounds in Development by Us

In addition to lorvotuzumab mertansine and IMGN388, we  have a  number of product candidates
at earlier stages in our pipeline. We expect to submit an IND for  our third compound,  IMGN529,  in
2011, and an IND for our fourth compound  in 2012. These are both  TAP  compounds. IMGN529 is  a
potential treatment for certain types  of liquid tumors.

We  also continue to invest in our TAP  technology, including the development of additional

cytotoxic agents and linkers, to maintain  our leadership position  in our field.

Other  Compounds in Development by Our Partners

In addition to T-DM1 and SAR3419, other compounds  in clinical testing through  our

collaborations with other companies are BT-062, BIIB015, and SAR650984. We  expect 3 - 4 additional
TAP compounds to advance into clinical  testing  during 2010 and 2011  through  our  existing
collaborative partnerships. Companies with licenses to develop TAP compounds other  than those
already in the clinic include Amgen, Bayer Schering Pharma,  Genentech, and sanofi-aventis.

Incidence of Relevant Cancers

Cancer remains a leading cause of death worldwide, and is the  second leading cause of death  in

the U.S.  Based on American Cancer  Society estimates,  we believe  approximately  1.5 million new cases
of cancer will be diagnosed in the U.S. in 2010 and that approximately 570,000 people will  die from
various cancers. The total number of  people living with  cancer  significantly exceeds the number of
patients diagnosed with cancer in a given year  as patients can live with cancer for  a year or longer.
Additionally, the potential market for anticancer drugs exceeds the number of patients treated as  many
types of cancer typically are treated with  multiple compounds at the same  time. Additionally, patients
often receive multiple drug regimens sequentially, either to  treat or help prevent  recurrence  of the
disease. In recent years, several antibody-based  anticancer drugs have  enjoyed considerable commercial
success, as have other targeted anticancer agents.

T-DM1—Based on American Cancer Society and  Roche estimates,  we  believe  approximately
42,000-50,000 new cases of HER2+ breast cancer  will be diagnosed in 2010. These include diagnoses
for both localized disease and advanced,  or metastatic, disease. The first approvals of T-DM1 are
expected to be for advanced disease.  Roche has estimated the 2nd-line and later patient population in
the U.S.  to be approximately 13,700 patients.

Lorvotuzumab mertansine—We are assessing this compound for the treatment of  CD56+ solid
tumors, including small-cell lung cancer, ovarian cancer  and Merkel  cell  carcinoma, as well  as the liquid
tumor, multiple myeloma. Based on our  own studies and scientific literature, we  believe that CD56 is
expressed on approximately 100% of small-cell lung  cancer and Merkel cell carcinoma cases,  70% of
multiple myeloma cases, and 58% of  ovarian cancer cases. Based on American  Cancer Society
estimates and other sources, we believe that approximately 28,000  new cases  of small-cell lung  cancer
will be diagnosed in the U.S. in 2010.  Based on American  Cancer Society estimates, we  also believe
that approximately 22,000 new cases of ovarian cancer  and 20,000  new cases  of  multiple myeloma  will
be diagnosed in the U.S. in 2010. Based  on other published  data, we believe  approximately 1,900 new
cases of Merkel cell carcinoma will be diagnosed in the U.S. in  2010.

We  are assessing our IMGN388 compound for the  treatment  of  solid  tumors.  Cancers of particular

interest include melanoma, lung, breast, and ovarian cancers. Based on American  Cancer Society
estimates, we believe approximately 522,000 new  cases of these cancers will be diagnosed in the  U.S. in
2010.

8

Out-licenses and Collaborations

As part of our business strategy to expand  the use of and financial return from our TAP
technology, we enter into license agreements  with third parties where we grant the other  party the
exclusive right to use our TAP technology with  their antibodies  to  specific antigen  targets. We also  had
a research collaboration with sanofi-aventis that provided them access to compounds in our preclinical
pipeline. As part of these agreements, we are entitled to receive upfront fees, potential milestone
payments and royalties on the sales of  any resulting products.  Our principal out-licenses and
collaborative agreements are described below.

Genentech (a member of the Roche Group)

In May 2000, we entered into two separate  agreements with Genentech. The first agreement  grants
Genentech an exclusive license to our maytansinoid  TAP  technology for use  with antibodies that target
HER2, such as trastuzumab. Under the  terms of this agreement, Genentech has exclusive worldwide
rights to develop and commercialize  maytansinoid TAP  compounds with antibodies  that  target  HER2.
Genentech is responsible for the manufacturing, product  development and  marketing  of  any products
resulting from the agreement. We are reimbursed for any preclinical and clinical materials that we
manufacture under the agreement. We  received  a $2 million non-refundable  payment from  Genentech
upon execution of the agreement. We  also are  entitled to receive up to $44 million in  milestone
payments from Genentech under this agreement, as  amended in  May  2006, in addition to royalties  on
the net sales of any resulting products.  Genentech and  Roche began Phase  III  evaluation of T-DM1 in
February 2009, which triggered a $6.5 million  milestone payment  to  us. Through June  30, 2010, we
have received a total of $13.5 million in  milestone  payments.

In May 2000 we also entered into a ‘‘right-to-test’’ agreement with  Genentech. This agreement

provided Genentech with the right to test our maytansinoid  TAP technology with antibodies to a
defined number of targets on an exclusive  basis for specified option periods and to take  exclusive
licenses to use our maytansinoid TAP  technology  to  develop  products directed to individual targets  on
agreed-upon terms. We received non-refundable  technology access  fees  totaling $5 million for the
eight-year term of the agreement. Genentech no  longer has the right  to  designate new targets  under
this  ‘‘right-to-test’’ agreement.

Under this agreement, Genentech licensed  exclusive  rights to use  our maytansinoid TAP

technology with antibodies to four undisclosed targets.  The most recent license was taken in December
2008. Under the terms defined in the  2000 ‘‘right-to-test’’  agreement, for  each license  we received a
$1 million license fee and may receive  up to $38 million  in milestone payments. We  are also entitled to
receive royalties on the sales of any resulting products.  Genentech is responsible  for the  development,
manufacturing, and marketing of any  products resulting from these licenses.

Amgen

In September 2000, we entered into a  ten-year ‘‘right-to-test’’ agreement  with Abgenix, Inc.,  which

was later acquired by Amgen. The agreement provides  Amgen with  the right to test our maytansinoid
TAP technology with antibodies to a defined number  of targets on either an  exclusive  and non-exclusive
basis for specified option periods and  to  take exclusive or non-exclusive licenses to use our
maytansinoid TAP technology to develop products for individual targets on agreed-upon  terms. We
received a $5 million technology access  fee in  September 2000. Under the agreement,  in September
2009 and November 2009, we entered  into  two  development and license  agreements with Amgen and
received a $1 million upfront payment with  each license  taken. In addition to the $1 million  upfront
payment, we are entitled to earn milestone  payments potentially  totaling $34 million per target for each
compound developed under the ‘‘right-to-test’’  agreement, as well as royalties  on the commercial  sales
of any resulting products. In March 2010,  we granted  Amgen a non-exclusive option to test our  TAP

9

technology with antibodies to a specific target, for which  Amgen paid  us a  nominal  fee. Under this
‘‘right-to-test’’ agreement, there can be option  periods in effect that extend  beyond the expiration  of
the agreement in September 2010.

sanofi-aventis

In July 2003, we entered into a broad collaboration agreement  with sanofi-aventis to discover,

develop and commercialize antibody-based anticancer therapeutics.

The agreement provides sanofi-aventis with worldwide commercialization rights  to  new anticancer
therapeutics developed to targets that were included  in the collaboration,  including the  right to use  our
TAP technology and our humanization technology in the  creation of therapeutics  to  these  targets. The
product  candidates (targets) currently in  the collaboration include  SAR3419 (CD19), SAR650984
(CD38), SAR566658 (CA6) and additional compounds  at earlier stages of development  that  have yet to
be disclosed.

The collaboration  agreement entitles us  to  receive milestone payments potentially totaling

$21.5 million for each therapeutic now  included in  the collaboration agreement.  Through  June  30, 2010,
we have earned a total of $4 million  in milestone payments  related to the three  product candidates
noted above and one target not yet disclosed.  We also  earned an aggregate  of  $8 million of milestone
payments related to two product candidates  previously  in the collaboration  that  have been returned to
us along with the rights to the respective targets.

The agreement also entitles us to royalties on the commercial  sales  of  any resulting products  if  and

when such sales commence. Sanofi-aventis  is responsible for the cost of the development,
manufacturing and marketing of any products created through  the collaboration. We are reimbursed for
any preclinical and clinical materials that  we make under the agreement. The  collaboration  agreement
also provides us an option to certain co-promotion rights in the  U.S.  on a product-by-product basis.
The terms of the collaboration agreement allow sanofi-aventis  to  terminate our co-promotion rights if
there is a change of control of our company.

The overall term of the agreement extends to the  later of  the latest patent to expire or twelve
years after the latest launch of any product  discovered,  developed and/or commercialized under  the
agreement. Sanofi-aventis paid us an upfront  fee of $12.0 million in August 2003.  Inclusive  of  all  of its
allowed extensions, the agreement enabled us to receive committed research  funding  totaling
$79.3 million over the five years of the  research collaboration.  The  two companies subsequently agreed
to extend the date of research funding through October  31, 2008 to enable  completion  of  previously
agreed-upon research. We recorded the  research funding as it  was earned based upon  its actual
resources utilized in the collaboration.  We earned $81.5  million  of committed funding over  the duration
of the research program and are now  compensated for research performed for sanofi-aventis on a
mutually agreed-upon basis.

In October 2006, sanofi-aventis licensed non-exclusive rights to use our proprietary resurfacing
technology to humanize antibodies to targets not included in the collaboration,  including antibodies  for
non-cancer applications. This license  provides sanofi-aventis with the non-exclusive right to use our
proprietary humanization technology  through August  31, 2011 with the right  to  extend for one or more
additional periods of three years each by providing  us  with written notice prior  to  expiration of the
then-current license term. Under the terms  of  the license,  we are entitled to a  $1 million license  fee,
half of which was paid upon contract  signing  and the  second half  was paid in August 2008,  and in
addition, we are entitled to receive milestone payments potentially totaling $4.5  million  for each
antibody  humanized under this agreement and also royalties on commercial sales, if any.

In August 2008, sanofi-aventis exercised  its  option under a 2006 agreement for  expanded access to

our  TAP technology. The exercise of  this option enables sanofi-aventis  to evaluate, with certain

10

restrictions, our maytansinoid TAP technology with  antibodies to targets that were not included  in the
research collaboration between the companies and to license  the  exclusive  right to use  the technology
to develop products to specific targets based  on the  terms in  the 2006 agreement.  We are entitled to
earn upfront and milestone payments potentially totaling $32 million per target for each compound
developed under the 2006 agreement,  as well as royalties  on the  commercial sales of any  resulting
products. We are also entitled to manufacturing payments  for any  materials  made on behalf of sanofi-
aventis. We received $500,000 in December 2006  with the  signing of the  option agreement  and we
received $3.5 million with the exercise  of this  option in August 2008. The agreement has a three-year
term from the date of the exercise of the option and can  be  renewed  by sanofi-aventis  for one
additional three-year term by payment of a $2  million  fee.

Biogen Idec

In October 2004, we entered into a development and license agreement with Biogen Idec. The
agreement grants Biogen Idec exclusive rights to use  our maytansinoid TAP technology to develop and
commercialize therapeutic compounds  to  the target Cripto.  Biogen  Idec  is responsible for the research,
development, manufacturing, and marketing  of  any  products resulting  from the license. We received a
$1 million upfront payment upon execution  of the agreement.  In January 2008, Biogen Idec  submitted
an IND to the FDA for BIIB015, which  was created under  this agreement. This  event triggered a
$1.5 million milestone payment to us.  Assuming  all  benchmarks are met, we could receive up  to
$42 million in milestone payments under  this agreement. We  are also  entitled to receive royalties on
net sales of resulting products. We also  receive  compensation  from  Biogen Idec for any  product
development research done on its behalf,  as well as  for the production of preclinical and clinical
materials.

Biotest

In July 2006, we entered into a development and license agreement with Biotest.  The agreement
grants Biotest exclusive rights to use our  maytansinoid TAP technology to develop and  commercialize
therapeutic compounds directed to the  target CD138. We received a $1 million upfront  payment upon
execution of the agreement. In September 2008, Biotest began Phase  I  evaluation of BT-062, which was
created under this agreement. This event triggered a  $500,000 milestone payment to us. Assuming all
benchmarks are met under this agreement, we  could receive up  to  $35.5 million  in milestone payments.
We  are also entitled to receive royalties on net sales of any resulting  products. We receive payments for
manufacturing any preclinical and clinical materials made at the request of Biotest.

The agreement also provides us with  the right to elect, at specific stages during the clinical

evaluation of any compound created under this agreement, to participate  in the U.S. development and
commercialization of that compound  in  lieu of receiving  royalties on U.S.  sales and the milestone
payments not yet earned. We can exercise  this  right by making a payment to Biotest of an agreed-upon
fee of $5 million or $15 million, depending on the stage of development. Upon exercise of this right,
we would share equally with Biotest the associated  costs of product development and commercialization
in the U.S. along with the profit, if any, from U.S. product sales.

Bayer Schering Pharma

In October 2008, we entered into a development and license agreement with Bayer  Schering
Pharma AG. The agreement grants Bayer Schering Pharma exclusive rights  to  use our maytansinoid
TAP technology to develop and commercialize therapeutic compounds directed  to  a specific  target.
Bayer Schering Pharma is responsible for the research,  development, manufacturing  and marketing of
any products resulting from the license. We received a  $4 million  upfront payment  upon execution  of
the agreement, and—for each compound  developed  and  marketed by  Bayer Schering  Pharma  under
this  collaboration—we could potentially  receive up to $170.5 million  in milestone  payments;

11

additionally, we are entitled to receive royalties on the net sales of any resulting  products. In
September 2009, Bayer Schering Pharma  reached  a preclinical milestone  which triggered  a $1 million
payment to us. We also are entitled to receive payments for manufacturing any preclinical and clinical
materials at the request of Bayer Schering Pharma as well as for any related process development
activities.

In-Licenses

From time to time we may in-license certain rights to targets or technologies for use  in conjunction
with our internal efforts to develop both TAP and naked-antibody products and related  technologies. In
exchange, we may be obligated to pay upfront  fees,  potential  milestone payments and royalties on any
product  sales.

Centocor Ortho Biotech

In December 2004, we entered into a development and license agreement with a predecessor to
Centocor Ortho Biotech, a wholly owned  subsidiary of Johnson & Johnson. Under  the terms of  this
agreement, Centocor was granted exclusive  worldwide rights to develop and commercialize  anticancer
therapeutics that consist of our maytansinoid cell-killing agent  attached  to an (cid:2)v integrin-targeting
antibody  that was developed by Centocor. Under the terms of the agreement, we received an upfront
payment of $1 million upon execution  of  the agreement.

In December 2007, we licensed from Centocor the exclusive, worldwide right to develop and

commercialize a TAP compound, IMGN388, that  consists of  an (cid:2)v integrin-targeting  antibody
developed by them and one of our maytansinoid  cell-killing agents. This license  reallocates the  parties’
respective responsibilities and financial obligations from the license  referenced above.  Centocor has the
right to opt-in on future development  and commercialization of IMGN388  at an agreed-upon stage in
early clinical testing. Should Centocor not exercise this right,  Centocor would be entitled to receive
milestone payments potentially totaling $30  million,  with the first payment due upon the completion of
a successful Phase III trial, and also royalties on  IMGN388  sales, if any. In this event, ImmunoGen  has
the right to obtain a new partner for IMGN388,  with certain restrictions.  Should Centocor exercise  its
opt-in right, ImmunoGen would receive an opt-in fee and  be released from its obligation to pay
Centocor any milestone payments or  royalties  on sales. Both companies would contribute  to  the costs
of developing the compound. The two companies  would share  equally any profits on the  sales  of  the
compound in the U.S. and ImmunoGen would receive royalties on any international sales. The
companies have agreed to share certain  third-party payments. In  June  2008, the FDA  approved the
IND application for IMGN388. This  event triggered  a $1 million milestone payment to a third-party,
half of which was paid by ImmunoGen.  As of June 30,  2010, the maximum  amount  that  may be
payable in the future to such third-parties  under this agreement  is $11  million.

Other  Licenses

We  also have licenses with third parties,  including other  companies  and academic institutions,  to
gain access to techniques and materials  for drug  discovery and product  development and  the rights to
use those techniques and materials to  make  our product candidates. These licenses include rights to
certain antibodies.

Patents, Trademarks and Trade Secrets

Our intellectual property strategy centers  on obtaining  patent  protection for our proprietary

technologies and product candidates.  As  of  June  30, 2010, our  patent portfolio had a total  of  299 issued
patents worldwide and 463 pending patent applications worldwide that we own or license from third
parties. We seek to protect our TAP  technology and our product candidates through a multi-pronged

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approach. In this regard, we have patents and patent applications covering antibodies and other
cell-binding agents, linkers, maytansinoid and other cell-killing agents, and complete antibody-drug
conjugates, or immunoconjugates, comprising these components  and methods  of making and using each
of the above. Typically, multiple issued  patents and pending patent applications cover various aspects  of
each  product candidate.

We  consider our maytansinoid technology  to  be  a key component of our overall corporate  strategy.
We  currently own 21 issued U.S. patents covering various embodiments of  our  maytansinoid technology
including claims directed to certain maytansinoids, antibody-maytansinoid  conjugates and  other
cell-binding agents used with maytansinoids, and methods of making and  using the same.  In all cases,
we have received or are applying for  comparable  patents  in other  jurisdictions  including Europe and
Japan. We have issued patents that cover  numerous aspects of the  manufacture of both our DM1  and
DM4 cell-killing agents. These issued  patents remain  in force  until various times between 2020 and
2026. We also have a composition of  matter patent on our DM4 cell-killing agent that is  expected to
remain in force until 2024.

Our intellectual property strategy also includes  pursuing patents directed to linkers, antibodies,

conjugation methods, immunoconjugate formulations and the use of specific  antibodies  and
immunoconjugates to treat certain diseases. In this regard, we have  issued patents and  pending  patent
applications related to many of our linker technologies.  These issued patents, expiring  in 2021-2023,
and any patents which may issue from the patent applications, cover antibody-maytansinoid conjugates
using these linkers. We also have issued  U.S. patents and  pending  patent  applications  covering methods
of assembling immunoconjugates from their constituent antibody, linker and cell-killing agent moieties.
These issued patents will expire in 2021,  while  any patents that may issue from  pending  patent
applications also covering various aspects of these technologies will, if issued, expire between 2021 and
2030. We also have issued patents and  pending patent applications related to monoclonal antibodies
that may be a component of a TAP compound or may  be  developed  as a therapeutic, or ‘‘naked,’’
antibody  anticancer compound. Among  these  patents is an issued U.S. patent claiming a method of
humanizing murine antibodies to avoid  their detection by the human immune system.  We have received
patents in other jurisdictions, including Europe and Japan, that correspond to our antibody
humanization U.S. patent. These patents will expire between  2013 and  2014.

We  expect our continued work in each of these areas  will  lead to other patent applications. In all
such cases, we will either be the assignee or  owner of such patents  or have  an exclusive license  to  the
technology covered by the patents. For  example, we also  own issued patents covering proprietary
derivatives of non-maytansinoid cell-killing molecules. However, we  do not currently consider  these
additional patent families to be material  to our business.

As described elsewhere in this annual  report on  Form 10-K under the heading ‘‘In-Licenses—

Centocor Ortho Biotech,’’ we have in-licensed certain  technology from Centocor  Ortho Biotech in
connection with the development of our IMGN388  product candidate. In  addition,  we have in-licensed
intellectual property relating to our lorvotuzumab mertansine product  candidate from Dana-Farber
Cancer Institute. We do not believe that the  terms of this license  are  material to our business or
prospects.

We  cannot provide assurance that the  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,  Inc.
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.

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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, Pfizer, Seattle  Genetics, and
Bristol Myers Squibb have programs  to  attach a  proprietary  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 and in
recruiting highly qualified scientific personnel.  Many  competitors and  potential competitors  have
substantially greater scientific, research and product development capabilities, as  well as greater
financial, marketing and human resources than we  do.  In addition, many specialized biotechnology
firms have formed 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:

(cid:129) the safety and efficacy of products;

(cid:129) the timing of regulatory approval and commercial  introduction;

(cid:129) special regulatory designation of products,  such as  Orphan Drug designation; and

(cid:129) the effectiveness of marketing, sales, and reimbursement efforts.

Our competitive position depends on our ability to develop effective proprietary products,

implement clinical development programs,  production plans and marketing plans,  including
collaborations with other companies with greater marketing resources than ours, and  to  obtain  patent
protection and secure sufficient capital  resources.

Continuing 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. In addition, antibodies  developed by certain  of these  companies have been
approved for use as cancer therapeutics.  In the  future, additional antibodies may  compete with our
product  candidates. In addition, 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.

Because of the acceptance of combination therapy  for  the treatment of cancer and  the variety  of

genes and targets implicated in cancer  incidence and progression, we believe that products resulting
from applications of new technologies may be complementary to our own.

Such new technologies include, but are not limited to:

(cid:129) the use of genomics technology to identify new  gene-based targets for the development of

anticancer drugs;

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(cid:129) the use of high-throughput screening to identify  and optimize  lead compounds;

(cid:129) the use of gene therapy to deliver  genes to regulate gene  function; and

(cid:129) the use of therapeutic vaccines.

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  products such as those we are developing. 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,  or FDCA,

and in the case of biologics, also under the Public  Health Service  Act, or PHSA, and  implementing
regulations. The process of obtaining regulatory approvals and the subsequent compliance with
appropriate federal, state, local, and foreign 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 administrative or judicial  sanctions.  These sanctions 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 agency or
judicial enforcement action could have a  material adverse effect on us.  The process required  by  the
FDA before a drug or biologic may be  marketed in  the U.S. generally involves the following:

(cid:129) completion of preclinical laboratory tests,  animal studies and formulation studies  according to

Good Laboratory Practices or other applicable regulations;

(cid:129) submission to the FDA of an IND which must become effective  before  human clinical trials may

begin;

(cid:129) performance of adequate and well-controlled  human clinical trials according  to  Good Clinical

Practices to establish the safety and efficacy of the  proposed drug for its intended  use;

(cid:129) submission to the FDA of an NDA or BLA;

(cid:129) 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, or cGMP,
to assure that the facilities, methods and controls are adequate to preserve the  drug’s identity,
strength, quality and purity; and

(cid:129) FDA review and approval of the NDA  or BLA.

The testing and approval process requires substantial  time, effort and financial resources,  and we
cannot be certain that any approvals  for our product candidates will  be  granted  on a  timely  basis, if at
all.

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

15

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 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 preclinical testing may continue even after the
IND is submitted. 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 studies  due  to  safety
concerns or non-compliance.

All clinical trials must be conducted  under the supervision of one or more qualified investigators in

accordance with good clinical practice regulations. These regulations  include the requirement that all
research subjects provide informed consent. Further,  an institutional  review  board, or  IRB,  must  review
and approve the plan for any clinical trial before it commences at any institution. An IRB  considers,
among other things, whether the risks  to  individuals  participating in the trials are  minimized  and are
reasonable in relation to anticipated  benefits. The  IRB also approves the information regarding  the
trial and the consent form that must be provided to each trial subject or his  or her legal representative
and must monitor the study until completed.

Each  new clinical protocol must be submitted to the FDA for  its review, and  to  the IRBs for
approval. Protocols detail, among other things, the  objectives of the study, dosing  procedures,  subject
selection and exclusion criteria, and the parameters to be used  to  monitor subject  safety.

Human clinical trials are typically conducted  in three  sequential phases that may overlap or be

combined:

(cid:129) Phase I: The drug is initially introduced into healthy human subjects  and tested for safety,
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.

(cid:129) Phase II: Involves studies 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.

(cid:129) Phase III: Clinical trials are undertaken to further evaluate dosage, clinical  efficacy and safety  in
an expanded patient population at geographically  dispersed clinical study sites. These  studies are
intended to establish the overall risk-benefit ratio of the  product and provide, if appropriate, an
adequate basis for product labeling.

Progress reports detailing the results  of the  clinical trials  must  be  submitted at  least  annually  to  the

FDA and safety reports must be submitted to the FDA  and  the  investigators for  serious and
unexpected adverse events. Phase I, Phase  II, and  Phase III testing may not be completed successfully
within any specified period, if at all. 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 serious  harm to patients.

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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.

U.S. Review and Approval Processes

The results of product development, preclinical 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.

In addition, under the Pediatric Research  Equity Act of 2007, or PREA, an  NDA, BLA and

certain types of supplements to an NDA  or BLA must  contain data to assess the  safety and
effectiveness of the drug for the claimed indications in  all relevant pediatric  subpopulations and to
support dosing and administration for  each pediatric subpopulation for which the drug is  safe and
effective. The FDA may grant deferrals  for  submission  of  data or full or partial waivers. Unless
otherwise required by regulation, PREA does  not  apply to any  drug for  an indication for  which orphan
designation has been granted. PREA  sunsets on October  1, 2012.

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 a NDA or BLA for  filing. In this event, the  NDA 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.
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 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 is 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  interpret data  differently than we interpret the  same data. The
FDA may issue a complete response letter, which  may require additional  clinical  or other data or
impose other conditions that must be  met in order to secure  final approval  of  the NDA or  BLA, or an
approved letter following satisfactory completion of all aspects  of the review process. 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, the FDA will inspect the facility or  facilities where the product is manufactured.

NDAs or BLAs receive either standard or priority  review. A drug representing a significant
improvement in treatment, prevention or  diagnosis of disease may  receive priority review.  In  addition,
products studied for their safety and effectiveness in treating  serious or  life-threatening illnesses and
that provide meaningful therapeutic  benefit over existing treatments may  receive accelerated approval
and may be approved on the basis of  adequate and well-controlled clinical trials establishing  that  the

17

drug product has an effect on a surrogate endpoint that is  reasonably likely  to  predict clinical  benefit
or on the basis of an effect on a clinical endpoint  other  than  survival or  irreversible morbidity. As a
condition of approval, the FDA may require  that a sponsor of a drug receiving accelerated  approval
perform adequate and well-controlled  post-marketing clinical trials.  Priority  review and  accelerated
approval do  not change the standards  for approval, but may expedite the  approval process.

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  us 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.

Patent Term Restoration and Marketing  Exclusivity

Depending upon the timing, duration and specifics of FDA  approval of the  use 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 United States 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 or  BLA.

Market exclusivity provisions under the FDCA  also can delay the submission or the approval  of

certain applications. The FDCA provides  a five-year period of non-patent marketing exclusivity  within
the U.S.  to the first applicant to gain  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, or ANDA,
or a 505(b)(2) NDA submitted by another company for  another version of such  drug 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. The FDCA also  provides three years of  marketing  exclusivity for  an
NDA,  505(b)(2) NDA or supplement  to  an existing  NDA if new clinical investigations, other than
bioavailability studies, that were conducted or sponsored by the applicant are deemed  by  FDA to be
essential to the approval of the application,  for example, for new indications, dosages, or strengths  of
an existing drug. This three-year exclusivity covers only the conditions associated with the  new clinical
investigations and does not prohibit the FDA from approving 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 exclusivity in the U.S. Pediatric exclusivity, if granted,
provides an additional six months to  an  existing exclusivity  or  statutory delay  in approval resulting from

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a patent certification. This six-month  exclusivity, which runs from the end  of other exclusivity protection
or patent delay, may be granted based on the voluntary  completion of a pediatric study  in accordance
with an FDA-issued ‘‘Written Request’’ for  such a  study. The current  pediatric  exclusivity provision  will
sunset on October 1, 2012.

Biologics Price Competition and Innovation Act of 2009

On March 23, 2010, President Obama signed  into  law  the Patient Protection and Affordable Care

Act which included the Biologics Price Competition and Innovation  Act of 2009,  or BPCIA. The
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 exclusivity
period for the first approved biological product, or reference product, against which  a biosimilar  or
interchangeable application is evaluated. 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 may be substituted for the  reference product 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  studies 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; however  if  pediatric studies are  performed  and
accepted by  the FDA, the twelve-year exclusivity period will be extended for an additional six  months.
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.

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 are disclosed  publicly by the FDA.
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  orphan product  exclusivity, which
means that the FDA may not approve  any other applications  to  market  the  same drug for the same
indication, except in very limited circumstances,  for seven years. Orphan drug exclusivity,  however, also
could block the approval of one of our  products for seven years if a competitor obtains approval of the

19

same drug as defined by the FDA or if  our product  candidate is  determined to be contained within  the
competitor’s product for the same indication or disease.

The FDA also administers a clinical research grants program, whereby  researchers may compete
for funding to conduct clinical trials to  support the approval  of drugs, biologics, medical devices, and
medical foods for rare diseases and conditions. A product  does not have  to  be  designated as an orphan
drug to be eligible for the grant program. An application for  an orphan grant should propose one
discrete  clinical study to facilitate FDA approval of  the product  for a  rare  disease  or condition. The
study may address an unapproved new  product  or an unapproved new use  for a  product already on the
market.

In March 2010 and August 2010, the  FDA granted Orphan Drug designation to our  lorvotuzumab

mertansine compound when used for  the treatment of Merkel cell carcinoma  (MCC) and small-cell
lung  cancer (SCLC), respectively. Orphan drug designation provides  ImmunoGen  with seven years of
market exclusivity that begins once lorvotuzumab mertansine receives  FDA marketing approval  for the
use for which the orphan drug status  was granted. Through  a  separate  process,  lorvotuzumab
mertansine has been granted orphan  medicinal product designation for the treatment  of  MCC in the
European Union. The European Medicines  Agency Committee for Orphan Medicinal Products
rendered a positive opinion in July 2010  on also granting lorvotuzumab mertansine orphan medicinal
product  status for SCLC, and finalization of  that designation  is expected in 2010.  Orphan medicinal
product  designation provides ImmunoGen with  ten years of market exclusivity that begins once
lorvotuzumab mertansine receives European  approval for the use  for which it was granted. We may
pursue these designations for other indications for  lorvotuzumab mertansine, and for other product
candidates intended for qualifying patient  populations.

New Drugs for Serious or Life Threatening  Illnesses

The FDA Modernization Act allows  the  designation  of ‘‘Fast Track’’ status to expedite

development of new drugs, including  review and approvals, and is  intended to speed the availability of
new therapies to desperately ill patients.  ‘‘Fast Track’’ procedures permit  early consultation and
commitment from the FDA regarding preclinical studies and clinical trials necessary to gain marketing
approval. We may seek ‘‘Fast Track’’ status for some,  or all,  of our product  candidates.

‘‘Fast Track’’ status also incorporates initiatives  announced by the President of the  U.S. and the
FDA Commissioner in March 1996 intended  to  provide cancer patients  with faster access to new  cancer
therapies. One of these initiatives states  that the initial  basis for approval of  anticancer agents to treat
refractory, hard-to-treat cancer may be  objective evidence  of response, rather than  statistically improved
disease-free and/or overall survival, as had  been common practice.  The  sponsor  of a product  approved
under this accelerated mechanism is required to follow up with further studies on clinical safety and
effectiveness in larger groups of patients.

Post-Approval Requirements

Once an approval is granted, the FDA may  withdraw the 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  may result  in restrictions  on the  product or even
complete withdrawal of the product from the  market.  After approval,  some types  of changes to the
approved product, such as adding new indications,  manufacturing  changes and  additional labeling
claims, 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. We rely, and expect  to  continue
to rely, on third parties for the production  of  clinical and commercial quantities of our products.  Future

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FDA and state inspections may identify  compliance  issues  at the facilities of  our contract manufacturers
that may disrupt production or distribution,  or require substantial resources to correct.

Any drug products manufactured or  distributed  by us  pursuant  to  FDA approvals  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  FDA promotion and advertising requirements.  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.

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. For example,  on September 27, 2007,  the Food and  Drug  Administration
Amendments Act of 2007, or FDAAA,  gave the FDA enhanced postmarket authority, including the
authority to require postmarket studies and clinical trials,  labeling changes  based on new safety
information, and compliance with a risk evaluation and mitigation  strategy approved by the FDA.
Failure to comply with any requirements under the new  law may result in significant penalties.  The  new
law also authorizes significant civil money  penalties  for the  dissemination of false  or misleading
direct-to-consumer advertisements. Additionally,  the new law expands  the clinical  trial  registry so  that
sponsors of all clinical trials, except for  Phase I trials,  are required to submit certain clinical  trial
information for inclusion in the clinical  trial registry data bank,  including summary adverse effect
information. In addition, FDA regulations and guidance are often revised or reinterpreted by the
agency in ways that may significantly  affect our business and our products.  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.

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 FDA approval for a product, we  must obtain approval  of a product  by  the comparable
regulatory authorities of foreign countries  before  we can commence clinical trials or marketing of the
product  in those countries. The approval  process varies from country  to  country  and the  time may  be
longer or shorter than that required for  FDA  approval. The requirements governing the conduct of
clinical trials, product licensing, pricing and reimbursement  vary  greatly from country to country.

Under European Union regulatory systems, we  may submit  marketing authorization applications

either under a centralized or decentralized procedure.  The  centralized  procedure, which  is compulsory
for medicines produced by certain biotechnological processes,  orphan drugs  and products containing a
new active substance intended for treatment of specific conditions/illnesses including cancer, provides
for the grant of a single marketing authorization that is valid for all  European Union member states. If
a drug does not fall within a mandatory category, it may still  be  submitted to the centralized procedure
if it  contains a new active substance and constitutes  a significant  therapeutic,  scientific or  technical
innovation. Other new drugs without  approval  in any Member  State,  will  follow the  decentralized
procedure which provides for approval by  one or more  other, or concerned,  Member States of  an
assessment of an application performed by one  Member State, known as the reference  Member State.
Under this procedure, an applicant submits an  application,  or dossier,  and related materials (draft
summary of product characteristics, draft labeling  and  package leaflet) to the  reference Member State
and concerned Member States. The reference  Member State prepares  a draft assessment and drafts of
the related materials within 120 days  after receipt  of a valid  application. Within 90 days of receiving the
reference Member State’s assessment  report, each concerned Member State must decide whether to

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approve the  assessment report and related materials.  If a Member State cannot approve the  assessment
report and related materials on the grounds of potential serious risk to public health, the  disputed
points may eventually be referred to the  European  Commission, whose decision is  binding  on all
Member States.

Reimbursement

Sales of pharmaceutical products depend in  significant part on the availability  of  third-party
reimbursement. Third-party payors include  government  healthcare programs, managed care  providers,
private  health insurers and other organizations. We  anticipate third-party payors  will provide
reimbursement for our products. However, these third-party payors are increasingly challenging  the
price and examining the cost-effectiveness of  medical products and  services. In addition, significant
uncertainty exists as to the reimbursement status  of newly approved  healthcare products. We may need
to conduct expensive pharmacoeconomic studies  in order to demonstrate  the cost-effectiveness of our
products. Our product candidates may  not be considered cost-effective. It is  time consuming  and
expensive for us to seek reimbursement from third-party payors.  Reimbursement may not be available
or sufficient to allow us to sell our products on  a competitive and profitable basis.

The Medicare Prescription Drug, Improvement,  and Modernization Act of  2003, or the  MMA,

imposed new requirements for the distribution and pricing of prescription drugs  for Medicare
beneficiaries, and included a major expansion of  the prescription drug benefit  under Medicare Part D.
Under Part D, Medicare beneficiaries  may enroll in prescription  drug plans  offered by private entities
which  provide coverage of outpatient prescription drugs.  Part D plans include both stand-alone
prescription  drug benefit plans and prescription drug coverage as  a supplement to Medicare  Advantage
plans. Unlike Medicare Part A and B,  Part D coverage is  not standardized.  Part D prescription drug
plan  sponsors are not required to pay  for all covered Part  D drugs, and each drug plan can develop its
own drug formulary that identifies which  drugs  it  will cover and at  what tier or level. However, Part D
prescription  drug formularies must include drugs within each therapeutic  category and class  of covered
Part D drugs, though not necessarily all the drugs in each category or class. Any formulary used by a
Part D prescription drug plan must be developed and reviewed by a pharmacy and  therapeutic
committee.

It  is not clear what effect the MMA  will have on  the prices  paid  for currently approved drugs and

the pricing options for future approved drugs. Government payment for some of the costs of
prescription  drugs may increase demand for  products for which we receive marketing approval.
However, any negotiated prices for our products covered  by  a Part D prescription  drug plan will likely
be lower than the  prices we might otherwise obtain. Moreover, while  the MMA applies only to drug
benefits for Medicare beneficiaries, private payors  often  follow  Medicare coverage policy and payment
limitations in setting their own payment  rates. Any reduction in  payment that results from the MMA
may result in a similar reduction in payments from non-governmental payors.

We  expect that there will continue to  be  a number of federal  and state proposals  to  implement

governmental pricing controls and limit the growth of healthcare costs, including the cost of
prescription  drugs. For example, in March 2010,  President  Obama signed one of the most significant
health care reform measures in decades,  the  Patient  Protection and Affordable Care Act,  as amended
by the Health Care and Education Affordability Reconciliation Act, collectively referred to as the
PPACA. The PPACA will significantly impact  the pharmaceutical industry. The PPACA will require
discounts under the Medicare drug benefit  program and increased rebates  on drugs  covered by
Medicaid. In addition, the PPACA imposes an annual fee, which will increase annually, on sales  by
branded pharmaceutical manufacturers starting in 2011.  The  financial  impact of these discounts,
increased rebates and fees and the other provisions of the PPACA on our business is  unclear.

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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.

Research and Development Spending

During  each of the three years ended June 30, 2010,  2009 and  2008, we spent approximately

$50.3 million, $45.9 million and $60.0  million, respectively,  on research  and development activities.
During  the year ended June 30, 2010,  approximately  1% of our full-time  equivalent research and
development personnel were dedicated to our  sanofi-aventis collaboration  compared to 14% and 36%
during the years ended June 30, 2009  and  2008, respectively.

Raw Materials and Manufacturing

We  procure certain raw material components of finished conjugate,  including antibodies,  DM1,
DM4, and linker, for ourselves and on  behalf of our  collaborators. In  order to meet  our  commitments
to our collaborators as well as our own  needs, we  are required to enter into  agreements with third
parties to produce these components well in  advance of our production needs. Our principal  suppliers
for these components include Cytovance  Biologics LLC, SAFC, Inc. and Societ`a Italiana
Corticosteroidi S.r.l.

In addition, we operate a conjugate manufacturing facility. A portion  of  the cost  of operating this
facility, including the cost of manufacturing  personnel, is reimbursed by our  collaborators  based on  the
number of batches of preclinical and  clinical materials produced on  their behalf. Over the past few
years, we have expanded and upgraded  the capabilities of  our manufacturing facility.

Employees

As of June 30, 2010, we had 211 full-time  employees, of whom 178 were  engaged  in research and

development activities. Seventy-seven  research  and  development employees  hold  post-graduate degrees,
of which 41 hold Ph.D. degrees and  four  hold M.D.  degrees. We  consider our relations with  our
employees to be good. None of our employees is covered by  a  collective bargaining  agreement.

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.

Third-Party Trademarks

Herceptin is a registered trademark of  Genentech.

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Item 1A. Risk Factors

THE RISKS AND UNCERTAINTIES DESCRIBED BELOW ARE THOSE THAT WE  CURRENTLY
BELIEVE MAY MATERIALLY AFFECT OUR  COMPANY. ADDITIONAL RISKS AND
UNCERTAINTIES THAT WE ARE UNAWARE OF OR THAT  WE CURRENTLY DEEM
IMMATERIAL ALSO MAY BECOME IMPORTANT FACTORS THAT AFFECT OUR COMPANY.

We have a history of operating losses and expect to incur significant  additional operating losses.

We  have generated operating losses since our inception. As  of June 30, 2010,  we had an

accumulated deficit of $372.4 million.  For  the years ended June 30, 2010,  2009, and 2008, we generated
losses of $50.9 million, $31.9 million  and $32.0  million,  respectively. We may never be profitable. We
expect to incur substantial additional  operating expenses over the  next several years as  our research,
development, preclinical testing, clinical trials and collaborator support activities continue. We intend to
continue to invest significantly in our  product candidates.  Further, we expect to invest significant
resources supporting our existing collaborators  as they  work  to  develop, test and commercialize TAP
and other antibody compounds. We or  our  collaborators  may encounter technological or regulatory
difficulties as part  of this development and  commercialization process that we  cannot overcome  or
remedy. We may also incur substantial  marketing and other costs in the future if we decide to establish
marketing and sales capabilities to commercialize  our  product candidates.  None of our or our
collaborators’ product candidates has  generated any commercial  revenue and our only revenues  to  date
have been primarily from upfront and  milestone payments, research and development support  and
clinical materials reimbursement from  our collaborative partners. We do  not expect  to  generate
revenues from the  commercial sale of  our internal product  candidates in the  near future,  and we may
never generate revenues from the commercial sale of internal products. Even  if  we do successfully
develop products that can be marketed and sold commercially, we  will need  to  generate significant
revenues from those products 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.

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 our  product candidates.

We  will continue to expend substantial  resources developing new and existing  product candidates,

including costs associated with research  and development, acquiring new technologies,  conducting
preclinical studies and clinical trials, obtaining regulatory approvals and manufacturing products as well
as providing certain support to our collaborators  in the development of their  products. We  believe that
our  current working capital and expected  future payments from our collaboration arrangements  will  be
sufficient to meet our current and projected  operating and capital requirements for fiscal year 2011 and
approximately the first half of fiscal 2012. However, we may need additional  financing sooner due to a
number of factors  including:

(cid:129) 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;

(cid:129) lower revenues than expected under our  collaboration agreements; or

(cid:129) acquisition of technologies and other  business opportunities that  require financial commitments.

Additional funding may not be available to us on favorable terms, or  at all. We may  raise

additional funds through public or private  financings, collaborative arrangements or other
arrangements. Debt financing, if available, may involve covenants that could restrict our business
activities. If we are unable to raise additional funds through equity or  debt financing when needed, we
may be required to delay, scale back or eliminate expenditures for some of our development  programs
or grant rights to develop and market  product candidates  that we would  otherwise prefer to internally

24

develop and market. If we are required  to  grant such rights, the ultimate value  of  these  product
candidates to us may be reduced.

If our TAP technology does not produce safe, effective and  commercially viable  products,  our business
will be severely harmed.

Our TAP technology yields novel product candidates for the treatment of cancer. To date, no  TAP

product  candidate has obtained regulatory  approval and the most advanced TAP product candidate is
in Phase III clinical testing. Our TAP  product candidates  and/or our collaborators’ TAP product
candidates may not prove to be safe, effective or commercially viable treatments for  cancer and  our
TAP technology may not result in any  future meaningful benefits  to  us or for our  current or potential
collaborative partners. Furthermore,  we  are  aware of only one compound  that  is a conjugate  of  an
antibody  and a cytotoxic small molecule  that has  obtained approval by the FDA and  is based  on
technology similar to our TAP technology. This  product was recently taken off the market by its owner
due to toxicity concerns. If our TAP  technology  fails to generate product candidates that are  safe,
effective and commercially viable treatments for cancer, or  fails  to  obtain FDA approval, our business
will be severely harmed.

Clinical trials for our and our collaborative partners’ product  candidates will be lengthy  and expensive
and their outcome is uncertain.

Before obtaining regulatory approval  for the  commercial sale  of  any product candidates,  we and
our  collaborative partners must demonstrate  through clinical testing that our product candidates  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. The most advanced product  candidate
incorporating our TAP technology is  in Phase III clinical testing. 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. At any time during the clinical  trials, we, our collaborative partners, or the  FDA might delay
or halt any clinical trials of our product candidates  for various reasons,  including:

(cid:129) occurrence of unacceptable toxicities or side effects;

ineffectiveness of the product candidate;

(cid:129) insufficient drug supply;

(cid:129) negative or inconclusive results from the clinical trials,  or  results that necessitate  additional

studies  or clinical trials;

(cid:129) delays in obtaining or maintaining required approvals from institutions,  review boards  or other

reviewing entities at clinical sites;

(cid:129) delays in patient enrollment;

(cid:129) insufficient funding or a reprioritization of financial or  other resources; or

(cid:129) other reasons that are internal to the businesses of our collaborative partners, which  they may

not share with us.

Any failure or substantial delay in successfully completing  clinical  trials  and  obtaining  regulatory
approval for our product candidates or  our collaborative partners’ product candidates could severely
harm our business.

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We and our collaborative partners are  subject to  extensive government regulations and  we and  our
collaborative partners may not be able  to  obtain necessary regulatory approvals.

We  and our collaborative partners may not receive  the regulatory  approvals necessary to

commercialize our product candidates, which would cause  our business to be severely harmed.
Pharmaceutical product candidates, including those in development  by us  and our collaborative
partners, 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  our  potential  products or
our  collaborators’ potential products are marketed  abroad, they will also  be  subject to extensive
regulation by foreign governments. None  of our product candidates has been  approved for sale in the
U.S. or any foreign market. The regulatory  review and approval process, which includes preclinical
studies and clinical trials of each product  candidate, is  lengthy, complex, expensive  and uncertain.
Securing FDA approval requires the submission of extensive preclinical  and  clinical data and supporting
information to the FDA for each indication to establish  the product candidate’s safety and efficacy.
Data obtained from preclinical 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-marketing studies. In  light of the  limited  regulatory
history of monoclonal antibody-based  therapeutics, regulatory  approvals for our or our collaborative
partners’ product candidates may not  be  obtained without lengthy  delays, if at  all.  Any  FDA or other
regulatory approvals of our or our collaborative  partners’  product candidates,  once obtained, may be
withdrawn. The effect of government regulation may be to:

(cid:129) delay marketing of potential products for a considerable period of time;

(cid:129) limit the indicated uses for which potential products  may  be  marketed;

(cid:129) impose costly requirements on our activities; and

(cid:129) 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  FDA policy during
the period of product development, clinical trials and  FDA regulatory review. Failure to comply with
FDA or other 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 product candidates or  us. Outside the  U.S., our ability to market a
product  is contingent upon receiving clearances  from the appropriate regulatory authorities. The
foreign regulatory  approval process includes similar  risks to those associated with the FDA  approval
process. 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.

Our and our collaborative partners’ product candidates will remain subject  to ongoing regulatory
review even if they receive marketing  approval. If we  or our  collaborative partners fail to comply with
continuing regulations, we could lose  these approvals and the sale of  our products could  be suspended.

Even if we or our collaborative partners receive  regulatory approval to market  a particular product

candidate, the approval could be conditioned  on us  or our  collaborative  partners conducting  costly
post-approval studies 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

26

collaborative partners to withdraw it from the  market  or impede  or  delay our or  our collaborative
partners’ ability to obtain regulatory  approvals in  additional countries.  In addition, the  manufacturer of
the product and its facilities will continue  to  be  subject to FDA  review and periodic inspections  to
ensure adherence to applicable regulations. After  receiving marketing approval, the manufacturing,
labeling, packaging, adverse event reporting,  storage, advertising, promotion and  record-keeping related
to the product remain subject to extensive regulatory  requirements.  We or our collaborative partners
may be slow to adapt, or we or our collaborative partners may never adapt,  to  changes in existing
regulatory requirements or adoption  of  new regulatory requirements.

If we  or our collaborative partners 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:

(cid:129) restrictions on the products, manufacturers or manufacturing  processes;

(cid:129) warning letters;

(cid:129) civil or criminal penalties;

(cid:129) fines;

(cid:129) injunctions;

(cid:129) product seizures or detentions;

(cid:129) import bans;

(cid:129) voluntary or mandatory product recalls and publicity requirements;

(cid:129) suspension or withdrawal of regulatory approvals;

(cid:129) total or partial suspension of production;  and

(cid:129) 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.

If our collaborative partners fail to perform their obligations under our agreements with them,  or
determine not to continue with clinical trials for  particular product candidates, our business  could be
severely impacted.

Our strategy for the development and commercialization of our product candidates depends, in
large part, upon the formation and maintenance of collaborative arrangements. Collaborations provide
an opportunity for us to:

(cid:129) generate cash flow and revenue;

(cid:129) fund some of the costs associated with our internal research and development,  preclinical

testing, clinical trials and manufacturing;

(cid:129) seek and obtain regulatory approvals  faster than we  could  on our own;

(cid:129) successfully commercialize existing and future  product candidates; and

(cid:129) 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

27

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 collaborative partners may  devote to our product candidates. Our  collaborative partners
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 not known to us, to discontinue  development of product candidates under our agreements  with
them. Any of our collaborative partners  may  slow or discontinue the  development of a product
candidate covered by a collaborative arrangement for reasons that  can include, but are not limited to:

(cid:129) a change in the collaborative partner’s strategic focus as a  result of merger, management

changes, adverse business events, or other causes;

(cid:129) a change in the priority of the product candidate relative to other programs in the collaborator’s

pipeline;

(cid:129) a reassessment of the patent situation related to the compound  or  its target;

(cid:129) a change in the anticipated competition for the product  candidate;

(cid:129) preclinical studies and clinical trial results; and

(cid:129) a reduction in the financial resources  the collaborator can  or  is willing to apply to the

development of new compounds.

Even if our collaborative partners continue  their  collaborative arrangements with  us, they  may

nevertheless determine not to actively  pursue the  development or commercialization of any resulting
products. Also, our collaborative partners may fail to perform their obligations under  the collaborative
agreements or may be slow in performing their obligations. Our collaborative partners can terminate
our  collaborative agreements under certain conditions. The decision to advance a  product that is
covered by a collaborative agreement through clinical trials and ultimately to commercialization is in
the discretion of our collaborative partners. 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 from  the
development and commercialization of the  products would  be  severely limited. 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 TAP compounds,  our business prospects would  be  severely
harmed.

We depend on a small number of collaborators for a substantial portion  of our revenue.  The  loss of, or
a material reduction in activity by, any  one  of these collaborators could result  in a  substantial decline
in our revenue.

We  have and will continue to have collaborations  with a limited  number of companies. As a  result,

our  financial performance depends on the efforts and overall success of these companies. Also, the
failure of any one of our collaborative  partners  to  perform its obligations  under its agreement with us,
including making any royalty, milestone or  other payments to us,  could have an adverse effect on our
financial condition. Further, any material  reduction by any one of our collaborative partners in  its  level
of commitment of resources, funding, personnel,  and  interest in continued development under its
agreement with us could have an adverse effect  on our financial condition. To  date, we have recorded
$13.5 million in milestone payments with the advancement  of  T-DM1.  Our agreement with Genentech,
a member of the Roche Group, entitles us to receive up to $44  million  in milestone payments and also
royalties on commercial sales, if any.  Failure  of Genentech  and Roche to continue to advance T-DM1

28

would have an adverse effect on our  financial  outlook. Also, if consolidation trends in the healthcare
industry continue, the number of our  potential collaborators  could decrease, which  could  have an
adverse impact on our development efforts. If a  present  collaborator  or future  collaborator of  ours
were to be involved in a business combination, the collaborator’s continued pursuit  and emphasis on
our  product development program could  be delayed,  diminished or terminated.

If our collaborative partners’ requirements for  clinical  materials to be manufactured by us are
significantly lower than we have estimated, our financial results  and  condition  could be  adversely
affected.

We  procure certain components of finished conjugate, including DM1,  DM4, and linker, on  behalf
of our collaborators. In order to meet our commitments  to our collaborative  partners,  we are  required
to enter into agreements with third parties  to  produce these components  well in advance of our
production of clinical materials on behalf  of our collaborative partners. If our collaborative partners do
not require as much clinical material  as we have contracted to produce, we may  not  be  able to recover
our  investment in these components and we may suffer significant losses. Collaborators have
discontinued development of product candidates in the past and  in the periods subsequent to these
discontinuations, we had significantly reduced demand  for  conjugated material which  adversely
impacted our financial results.

In addition, we operate a conjugate manufacturing facility. A portion  of  the cost  of operating this
facility, including the cost of manufacturing personnel, is reimbursed by our  collaborators  based on  the
number of batches of preclinical and  clinical materials produced on  their behalf. If we produce  fewer
batches  of clinical materials for our collaborators, a  smaller amount  of the cost  of  operating the
conjugate manufacturing facility will  be  charged to our collaborative partners and our financial
condition could be adversely affected.

If our antibody requirements for clinical  materials  to be manufactured are significantly higher than we
estimated, the inability to procure additional  antibody in a timely manner could impair our ability to
initiate or advance our clinical trials.

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 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.  There can  be  no assurance
that we will not have supply problems  that  could  delay or  stop our clinical trials or otherwise could
have a material adverse effect on our  business.

We currently rely on one third-party manufacturer with commercial production  experience  to produce
our cell-killing agents, DM1 and DM4.

We  rely on third-party suppliers to manufacture materials used to make TAP compounds. Our

cell-killing agents DM1 and DM4, collectively  DMx, are manufactured from a precursor, ansamitocin
P3. As part of preparing to produce  TAP compounds for later-stage  clinical trials  and
commercialization, we have transitioned  from  our original supplier of ansamitocin  P3, as well  as our
single supplier that converts ansamitocin  P3  to  DMx,  to  one  larger company with  more commercial
production experience. Any delay or interruption in our supply  of  DMx could lead  to  a delay or
interruption in our manufacturing operations, preclinical  studies and clinical trials of our product
candidates and our collaborators’ product candidates, which could  negatively affect  our business.

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We may be unable to establish the manufacturing capabilities  necessary to develop and commercialize
our and  our collaborative partners’ potential products.

Currently, we have only one conjugate manufacturing facility that  we use  to  manufacture
conjugated compounds for us and our  collaborative partners  for  preclinical studies  and early-stage
clinical testing. Two of our partners have  contracted for separate, large-scale manufacturing  capacity to
make materials to support potential future commercialization of their TAP compounds. We do not
currently have the manufacturing capacity needed to make our product candidates for commercial sale.
In addition, our manufacturing capacity may be insufficient to complete all clinical trials contemplated
by us and our collaborative partners over time.  We intend to rely in part on third-party contract
manufacturers to produce sufficiently  large quantities of drug materials  that are and  will be needed  for
later-stage clinical trials and commercialization of our potential products. We are currently  in the
process of developing relationships with third-party manufacturers that we believe  will  be  necessary  to
continue the development of our product  candidates. 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 clinical trials may  be  delayed, thereby delaying
the submission of product candidates  for regulatory approval  and the market introduction and
subsequent commercialization of our  potential products. Any such  delays may  lower our revenues  and
potential profitability.

In addition to the outsourcing of manufacturing, we  may  develop our  manufacturing capacity  in
part by expanding our current facilities. This  activity would require substantial additional funds and we
would need to hire and train significant numbers of employees to staff  these  facilities.  We may not be
able to develop manufacturing facilities that are sufficient to produce drug materials for later-stage
clinical trials or commercial use. We  and  any  third-party manufacturers that  we may use must
continually adhere to current good manufacturing practice,  or  cGMP, regulations  enforced by the  FDA
through its facilities inspection program.  If our  facilities or the facilities of third-party manufacturers
cannot pass a pre-approval plant inspection, the  FDA will not grant  approval to our product
candidates. In complying with these cGMP regulations and  foreign regulatory requirements, we and any
of our third-party manufacturers will be obligated to expend time, money and effort on production,
record-keeping and quality control to assure  that our  potential products  meet  applicable specifications
and other requirements. If we or any  third-party manufacturer with whom we may  contract fail to
maintain regulatory compliance, we or  the third party may be subject to fines  and/or manufacturing
operations may be suspended.

We have only one conjugate manufacturing facility and any  prolonged  and significant  disruption  at
that facility could impair our ability to manufacture our  and our collaborative  partners’  product
candidates for clinical testing.

Currently, in certain cases, we are contractually obligated to manufacture  Phase I and non-pivotal
Phase II clinical products for companies licensing  our TAP  technology. We manufacture  this material,
as well as material for our own product  candidates, in  our conjugate manufacturing  facility.  We have
only one such manufacturing facility in  which we can  manufacture clinical products.  Our current
manufacturing facility contains highly specialized  equipment and utilizes complicated  production
processes developed over a number of  years  that would be difficult, time-consuming and costly to
duplicate. Any prolonged disruption in  the operations of our  manufacturing facility would  have a
significant negative impact on our ability to manufacture  products  for clinical testing on our own  and
would cause us to seek additional third-party manufacturing contracts, thereby increasing our
development costs. Even though we carry business interruption insurance policies, we may  suffer losses
as a result of business interruptions that  exceed the  coverage available  or any losses may  be  excluded
under our insurance policies. Certain  events,  such as natural disasters, fire,  political disturbances,

30

sabotage or business accidents, which could impact our current or future facilities, could have a
significant negative impact on our operations by disrupting our product  development efforts until such
time as we are able to repair our facility or put in  place third-party  contract manufacturers to assume
this  manufacturing role.

Unfavorable pricing regulations, third-party reimbursement practices or healthcare  reform initiatives
applicable to our product candidates could limit our potential product revenue.

Antibody-based anticancer products are often much more costly to produce than traditional
chemotherapeutics and tend to have significantly higher prices. Factors  that  help justify the  price
include the high mortality associated with many types  of  cancer and the need for  more and  better
treatment options.

Regulations governing drug pricing and reimbursement vary widely  from  country to country. Some

countries require approval of the sales price of a  drug before  it can be marketed. Some countries
restrict the physicians that can authorize the  use of more  expensive medications.  Some  countries
establish treatment guidelines to help  limit the  use of more  expensive  therapeutics and  the pool of
patients that receive them. In some countries, including  the U.S., third-party payers  frequently  seek
discounts from list prices and are increasingly challenging the  prices charged  for medical products.
Because our product candidates are  in  the development stage, we do not know the level of
reimbursement, if any, we will receive  for  any products that we are able to successfully develop. If  the
reimbursement for any of our product candidates is inadequate in light of our development and other
costs, our ability to achieve profitability would be affected.

We  believe that the efforts of governments and third-party  payors to contain or reduce the cost  of

healthcare will continue to affect the  business and financial condition of pharmaceutical and
biopharmaceutical companies. A number  of  legislative  and regulatory proposals to change the
healthcare system in the U.S. and other major  healthcare markets have  been proposed and  adopted in
recent years. For example, the U.S. Congress enacted  a limited prescription drug benefit  for Medicare
recipients as part of the Medicare Prescription Drug, Improvement and Modernization  Act of 2003.
While the program established by this  statute may  increase demand for any products  that  we are  able
to successfully develop, if we participate in this program, our  prices will be  negotiated with drug
procurement organizations for Medicare  beneficiaries and are likely  to  be lower than prices we might
otherwise obtain. Non-Medicare third-party  drug procurement organizations  may also base the  price
they are willing to pay on the rate paid  by drug procurement organizations for  Medicare beneficiaries.
Also, in March 2010, President Obama signed  one of the most significant  health  care reform measures
in decades, the Patient Protection and  Affordable Care Act, as  amended by the Health  Care and
Education Affordability Reconciliation Act, collectively  referred  to  herein as the PPACA.  The PPACA
will significantly impact the pharmaceutical industry.  The PPACA will require discounts under  the
Medicare drug benefit program and increased rebates on  drugs  covered  by  Medicaid.  In  addition, the
PPACA imposes an annual fee, which  will  increase annually, on  sales by branded pharmaceutical
manufacturers starting in 2011. The financial  impact  of these discounts,  increased rebates and  fees  and
the other provisions of the PPACA on our business is  unclear and there can be no  assurance that our
business will not be materially adversely affected  by  the PPACA. In addition, ongoing initiatives in the
U.S. have increased and will continue  to  increase pressure on drug pricing. The announcement or
adoption of any such initiative could have an adverse effect on potential  revenues from any product
candidate that we may successfully develop.

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We may be unable to establish sales  and  marketing  capabilities  necessary  to successfully
commercialize our potential products.

We  currently have no direct sales or marketing capabilities. We anticipate  relying  on third parties
to market and sell most of our primary product candidates or we may outlicense these products  prior
to the time when these capabilities are  needed.  If we  decide to market our potential products through
a direct sales force, we would need either  to  hire a sales force with  expertise in  pharmaceutical sales or
to contract with a third party to provide a sales force  which meets  our needs.  We may be unable  to
establish marketing, sales and distribution capabilities necessary to commercialize and gain market
acceptance for our potential products and be competitive. In addition, co-promotion  or other marketing
arrangements with third parties to commercialize potential products could significantly limit the
revenues we derive from these potential  products, and these  third parties may fail to commercialize our
compounds successfully.

If our product candidates or those of  our  collaborative partners  do not gain market acceptance, our
business  will suffer.

Even if clinical trials demonstrate the safety and efficacy  of  our and  our collaborative partners’

product  candidates and the necessary  regulatory approvals are obtained, our and our collaborative
partners’ product candidates may not  gain market acceptance  among  physicians, patients,  healthcare
payors and other members of the medical  community. The degree of market acceptance of any product
candidates that we or our collaborative partners develop will depend on a  number of  factors, including:

(cid:129) their degree of clinical efficacy and  safety;

(cid:129) their advantage over alternative treatment  methods;

(cid:129) our/the marketer’s and our collaborative partners’ ability to gain acceptable  reimbursement and

the reimbursement policies of government and third-party  payors; and

(cid:129) the quality of the distribution capabilities for product  candidates, both ours and our collaborative

partners.

Physicians may not prescribe any of our  future products until such time as clinical  data  or other
factors demonstrate the safety and efficacy  of those  products as compared to conventional drug and
other treatments. Even if the clinical  safety and efficacy of therapies using our products is  established,
physicians may elect not to recommend  the therapies for any number of other reasons,  including
whether the mode of administration of our  products is effective for certain conditions, and whether the
physicians are already using competing products  that satisfy their  treatment objectives. Physicians,
patients, third-party payors and the medical  community may not accept and use any  product candidates
that we, or our collaborative partners,  develop. 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.

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 pricing reductions, reduced gross margins and failure to achieve market
acceptance for our potential products. Our competitors include research  institutions, pharmaceutical
companies and biotechnology companies,  such  as Pfizer,  Seattle Genetics and Bristol-Meyers  Squibb.
Many of these organizations have substantially  more experience and more capital, research and
development, regulatory, manufacturing,  human and  other resources than we  do.  As a  result, they may:

(cid:129) develop products that are safer or  more effective  than  our product candidates;

32

(cid:129) obtain FDA and other regulatory approvals or  reach  the market with their products more

rapidly than we can, reducing the potential sales of our product  candidates;

(cid:129) devote greater resources to market or sell their  products;

(cid:129) adapt more quickly to new technologies and scientific  advances;

(cid:129) initiate or withstand substantial price competition more  successfully than we can;

(cid:129) have greater success in recruiting skilled scientific workers from  the  limited pool of available

talent;

(cid:129) more effectively negotiate third-party licensing  and collaboration  arrangements;  and

(cid:129) take advantage of acquisition 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.

Our product candidates, if approved and  commercialized,  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, if our product
candidates are approved and commercialized, we  may  face competition from generic  products if the
product  candidate is a small molecule  drug, or biosimilars if  the product candidate is  a biologic. The
route to market for generic versions of small molecule drugs was  established  with the passage of the
Hatch-Waxman Amendments in 1984  and for biosimilars  with the  passage of the PPACA in March
2010. The PPACA establishes a pathway  for the FDA approval of follow-on biologics and provides
twelve years exclusivity for reference products and an additional  six months exclusivity period if
pediatric studies are conducted. In Europe, the  European  Medicines  Agency  has issued guidelines for
approving products through an abbreviated pathway,  and biosimilars have been approved  in Europe. If
a biosimilar version of one of our potential products were approved in  the United States  or Europe,  it
could have a negative effect on sales  and gross profits of the  potential  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  product  candidates obsolete or noncompetitive or  result in
treatments or cures superior to any therapy  developed by us.

If we are unable to protect our intellectual property rights adequately,  the value of  our  technology  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. 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. 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.

33

Also, patents and applications owned  or licensed by us may  become the subject  of  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  or priority of invention,  which could result  in
substantial cost to us. An adverse decision  in such a  proceeding may result in our loss of rights  under a
patent or patent application. It is unclear how much protection, if any, will  be  given to 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. In addition, the cost of litigation or interference 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 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.

In recent years, policymakers have also proposed  reforming U.S. patent laws and regulations. For

example, in March 2010, the Senate Judiciary Committee released the  Patent Reform Act  of  2010.
Although it has not yet been approved by both houses, in  general,  the proposed legislation  attempts  to
address issues surrounding the enforceability of patents and the increase in patent litigation by, among
other things, changing the way damages  for patent infringement are determined, moving to a first-
inventor-to-file system, establishing new procedures for  challenging  patents and  establishing different
methods for invalidating patents. While  we cannot  predict what  form  any  new patent reform  laws  or
regulations ultimately may take, final legislation could introduce new substantive rules  and procedures
for challenging patents, and certain reforms that make it easier for  competitors to challenge our
patents could have a material adverse effect  on our business and prospects.

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 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.

Any inability to license from third parties their proprietary technologies or processes which we  use in
connection with the development and manufacture of 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 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  our potential  products.  Any  necessary licenses may  not  be
available on commercially acceptable terms, if at  all.  If we  do not obtain required  licenses,  we may not
be able to market our potential products at all or we may encounter significant delays in product
development while we redesign products or  methods that are found to infringe on  the patents held by
others.

34

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, 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 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 potential 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 potential  products that may
block or  compete with our products  or processes.  In  addition, we sometimes undertake research and
development with respect to potential  products even  when we are aware of third-party patents  that  may
be relevant to our potential products, on the basis that  such patents may be challenged or  licensed by
us. If our subsequent challenge to such  patents were not to prevail,  we may not be able to
commercialize our potential 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 royalty or 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
potential products or may have to cease  some of our business operations, which could severely harm
our  business.

We use hazardous materials in our business, and any claims relating  to  improper  handling, storage or
disposal of these materials could harm  our business.

Our research and development and manufacturing activities  involve the controlled use of
hazardous materials, chemicals, biological  materials and  radioactive compounds.  We are subject  to
federal, state and local laws and regulations governing the  use, manufacture,  storage,  handling and
disposal of these materials and certain waste products. Although  we  believe  that  our  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. Failure  to  comply with these laws could result  in fines  and the  revocation
of permits, which could prevent us from  conducting our business.

We face product liability risks and may  not be able to  obtain adequate insurance.

While we secure waivers from all participants in our clinical  trials, the use of 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:

(cid:129) decreased demand for our product;

(cid:129) injury to our reputation and significant negative media  attention;

(cid:129) withdrawal of clinical trial volunteers;

35

(cid:129) costs of litigation;

(cid:129) distraction of management; and

(cid:129) substantial monetary awards to plaintiffs.

We  may not have sufficient resources to satisfy any liability  resulting from these  claims. We
currently have $5 million of product liability insurance  for products which  are in clinical testing. This
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  or obtain general product liability
insurance on reasonable terms and at  an acceptable cost  if we or our collaborative partners begin
commercial production of our proposed product candidates. This insurance, even  if  we can obtain and
maintain it, may not be sufficient to provide us  with adequate coverage against potential liabilities.

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 of our current and future  product  candidates depends largely  on retaining the services of
our  existing personnel and hiring additional qualified scientific personnel to perform research and
development. We will also need to hire  personnel with  expertise in  clinical testing, government
regulation, manufacturing, marketing  and finance.  Attracting  and retaining qualified  personnel will be
critical to our success. We may not be able to attract and retain 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 delay the development of
our  product candidates and harm our  business.

Our stock price can fluctuate significantly and  results announced by us and  our collaborators  can
cause our stock price to decline.

Our stock price can fluctuate significantly due to business developments  announced by us and by

our  collaborators, as a result of market trends and daily trading volume. The business developments
that could impact our stock price include disclosures  related to clinical findings with compounds that
make use of our TAP technology, new collaborations and clinical advancement or discontinuation of
product  candidates that make use of  our TAP technology. Our stock price can  also fluctuate
significantly with the level of overall investment  interest  in small-cap biotechnology stocks.

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 collaborative partners  with  respect to our agreements with them,  reimbursement for
manufacturing services, 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 collaborations. 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.

36

The potential sale  of additional shares  of our common stock may cause our stock price  to decline.

On April 9, 2010, we filed a Registration Statement  on Form S-3 with the Securities and Exchange

Commission. The Securities and Exchange Commission declared the Registration Statement effective
on April 22, 2010. Subject to our ongoing obligations  under the Securities Act of 1933,  as amended,
and the Securities Exchange Act of 1934, as  amended, the Registration Statement permits us to offer
and sell up to an aggregate of $125 million  of  our  common stock. Pursuant to the  shelf registration
statement, on May 6, 2010, we sold 10,350,000 shares of our common stock at  $8.00 per share  in a
public offering resulting in gross proceeds  of  $82.8 million. Additionally, pursuant  to  a shelf registration
statement filed on July 11, 2007, on June 23,  2009, we sold 5,750,000 shares  of our  common stock at
$7.00 per share in a public offering resulting  in gross proceeds of $40.3  million and, on June  20, 2008, a
private  investor purchased 7,812,500 shares  of our common stock at  $3.20 per share resulting in  gross
proceeds of $25 million. The potential  sale of additional shares of our  common  stock may be dilutive to
our  shares outstanding and may cause  our  stock price to decrease.

We do not intend to pay cash dividends  on our common stock.

We  have not paid cash dividends since  our  inception and do not intend to  pay cash  dividends  in
the foreseeable future. Therefore, shareholders will have to rely on appreciation in  our stock  price, if
any, in order to achieve a gain on an investment.

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A WARNING ABOUT FORWARD-LOOKING STATEMENTS

This report includes forward-looking statements  within the meaning  of the Private Securities
Litigation Reform Act of 1995. These statements relate to analyses and other information  which are
based on  forecasts of future results and estimates of amounts that are not yet  determinable. These
statements also relate to our future prospects,  developments 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.  These statements are
contained in the ‘‘Business,’’ ‘‘Risk Factors’’ and ‘‘Management’s  Discussion and Analysis of Financial
Condition and Results of Operations’’  sections, as well as other sections of this  Annual  Report on
Form 10-K.

Forward-looking statements in this report  include, but are not limited to:

(cid:129) successfully finding and managing the relationships  with collaborative partners;

(cid:129) the uncertainty as to whether our TAP compounds or those of  our collaborators will succeed in

entering human clinical trials and uncertainty  as to the  results of such trials;

(cid:129) the risk that we and/or our collaborators may not  be  able to obtain regulatory  approvals

necessary to commercialize product candidates;

(cid:129) the potential development of competing products and technologies; uncertainty  whether  our

TAP technology will produce safe, effective and commercially  viable products;

(cid:129) our ability to successfully protect our intellectual property;

(cid:129) our reliance on third-party manufacturers to achieve supplies of our  maytansinoid cell-killing

agents, DM1 and DM4;

(cid:129) the risk that we may be unable to  establish the  manufacturing  capabilities necessary to develop

and  commercialize our potential products;

(cid:129) the adequacy of our liquidity and capital resources;

(cid:129) government regulation of our activities,  facilities, products  and personnel; the dependence  on

key  personnel;

(cid:129) uncertainties as to the extent of reimbursement for the  costs  of  our potential products  and
related  treatments by government and private health insurers and other organizations; the
potential adverse impact of government-directed health care reform;  and

(cid:129) the risk of product liability claims; and economic conditions, both generally and  those specifically

related  to the biotechnology industry.

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 Annual Report on  Form 10-K. 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.

Item 1B. Unresolved Staff Comments

None.

38

Item 2. Properties

We  lease approximately 89,000 square  feet of laboratory and office  space in a  building located at

830 Winter Street, Waltham, MA. The  initial term of the 830 Winter Street lease  expires on March 31,
2020, with an option for us to extend the lease  for  two additional five-year terms.  In  December 2009,
we entered into a  sublease for 14,100 square feet  of our office and laboratory space at  830 Winter
Street, Waltham, MA through January  2015. We  also lease approximately 43,850  square feet of space in
Norwood, MA, which serves as our conjugate  manufacturing  facility and office space.  The  Norwood
lease expires on June 30, 2011, with an option  for us  to  extend  the lease for an additional five-year
term.

We  also lease approximately 15,000 square feet of  laboratory and office  space  in a building  located

at 148 Sidney Street, Cambridge, MA, which we vacated in March 2008  when we relocated all our
Cambridge operations to Waltham, MA.  The 148  Sidney  Street lease term  was to expire on October  30,
2010. In May 2008, we entered into a  sub-sublease for this  entire  space for the remainder  of the lease
term. Both the lease and sub-sublease  for 148 Sidney Street were  terminated as of  July 31,  2010.

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 3.1. Executive Officers of the Registrant

ImmunoGen’s executive officers are  appointed  by the  Board of Directors at  the first meeting of
the Board following the annual meeting  of shareholders or  at other Board meetings as appropriate, and
hold office until the first Board meeting following the next annual meeting of  shareholders and  until a
successor is chosen, subject to prior death, resignation or removal. Information regarding our executive
officers is presented below.

Daniel M. Junius, age 58, joined ImmunoGen in  2005, and has served as  our  President  and Chief

Executive Officer since January 2009.  Prior to that he served as our President and  Chief Operating
Officer and Acting Chief Financial Officer  from July  2008 to December  2008, as  our  Executive Vice
President and Chief Financial Officer  from 2006  to  July 2008, and as our Senior Vice President  and
Chief Financial Officer from 2005 to 2006. Prior to joining ImmunoGen in  2005, he served as Executive
Vice President and Chief Financial Officer of  New England Business  Service, Inc. (NEBS), a  supplier
of business products and services to small businesses, from  2002 to 2004, and as  Senior Vice President
and Chief Financial Officer of NEBS  from 1998  to  2002. Mr. Junius  holds  a Masters of Management
from Northwestern University’s Kellogg  School of  Management.

John M. Lambert, Ph.D., age 59, joined ImmunoGen  in 1987, and has  served  as our Executive

Vice President, Research and Development and  Chief  Scientific Officer  since July 2008. Prior to that
he served as our Senior Vice President,  Research and Development and Chief Scientific Officer from
early 2008 to July 2008, as our Senior  Vice  President,  Pharmaceutical  Development, from 2000  to  early
2008, as our Vice President, Research  and  Development,  from 1994  to  2000, and  as our Senior Director
of Research from 1987 to 1994. Prior  to  joining ImmunoGen, Dr. Lambert was  an assistant professor at
Harvard Medical School working at the Dana-Farber  Cancer Institute.  Dr.  Lambert  holds  a Ph.D. in
Biochemistry from University of Cambridge in England, and completed his  postdoctoral work at  the
University of California at Davis and  at  Glasgow  University in Scotland.

James J. O’Leary, MD, age 46, joined ImmunoGen in  2008, and  has served as our  Vice President
and Chief Medical Officer since that date. Prior to joining  ImmunoGen, Dr. O’Leary  served  as Senior
Medical Director Clinical Oncology of Bayer Corporation, a  pharmaceutical company,  from 2006 to
2008. Prior to that he served as Medical  Director  Clinical  Oncology  of  Pfizer Global Research and

39

Development, a pharmaceutical company, from 2003 to 2006, and as  Assistant Medical Director
Clinical Oncology of Pfizer from 2000  to  2003. Prior to that he served as  a Medical Reviewer, Division
of Oncology Drug Products at the U.S. Food and Drug Administration  from 1998 to 2000.  Dr. O’Leary
has a Doctor of Medicine degree from  the State University of New York–Health Science Center  at
Brooklyn.

Gregory D. Perry, age 50, joined ImmunoGen in January 2009, and  has served as our Senior Vice
President and Chief Financial Officer  since that  date. Prior to joining ImmunoGen, he served as Chief
Financial Officer of Elixir Pharmaceuticals,  Inc., a pharmaceutical company,  from 2007 to 2008.  Prior
to that he served as Chief Financial Officer for  Domantis  Ltd., a biopharmaceutical company,  in 2006,
as Senior Vice President, Finance and  Chief Financial Officer  of  Transkaryotic Therapies,  Inc., a
biopharmaceutical company, from 2003 to 2005.

Peter J. Williams, age 56, joined ImmunoGen  in August 2009, and has served as our  Vice

President, Business Development since that date.  Prior  to  joining ImmunoGen, he served as  a Senior
Director of Business Development at Alnylam Pharmaceuticals, Inc., a biopharmaceutical company,
from 2006 to August 2009. Prior to that  he  served as Vice President of Business Development of  Link
Medicine Corporation, a drug development company, from 2005 to 2006.  Prior  to  that  he  acted  as an
independent business development consultant from 2003  to 2006.  Prior to that he served as a  Senior
Director of Business Development at Millennium Pharmaceuticals, Inc., a biopharmaceutical  company,
from 1998 to 2003.

Item 4. Reserved

40

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  Market  under  the symbol  ‘‘IMGN.’’  The
table  below sets forth the high and low closing  price per share of our common stock  as reported by
NASDAQ:

First  Quarter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Second Quarter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Third Quarter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fourth Quarter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$10.13
$ 9.55
$ 8.34
$10.90

$6.88
$6.44
$6.25
$7.69

$5.80
$4.89
$7.19
$8.83

High

Low

High

Low

$2.95
$2.47
$3.85
$6.49

Fiscal Year 2010

Fiscal Year 2009

As of August 11, 2010, the closing price per share of our common stock  was  $8.93, as reported  by

NASDAQ, and we had approximately 503 holders of record of  our common stock and,  according to
our  estimates, approximately 18,342 beneficial  owners 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.

41

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 June 30,  2005 through June 30,  2010
(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 Stock Market  Index  (U.S.)  and the  NASDAQ
Pharmaceutical Stocks Total Return 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. This
graph is not ‘‘soliciting material,’’ is not  deemed  filed  with the Commission  and is not to be
incorporated by reference in any of our  filings under  the Securities Act of 1933, as amended, or the
Securities Exchange Act of 1934, as amended, whether  made before or after the date  hereof and
irrespective of any general incorporation  language  in any  such filing. Information used  on the graph for
the NASDAQ Pharmaceutical Stocks Total Return Index and  the NASDAQ Stock  Market Index (U.S.)
was prepared by the Center for Research in Security Prices, a source believed to be reliable, but  we are
not responsible for any errors or omissions  in such information.

IMMUNOGEN INC

NASDAQ STOCK MARKET INDEX (U.S.)

NASDAQ PHARMACEUTICAL STOCKS TOTAL RETURN INDEX

)
s
r
a

l
l

o
D

.

.

S
U
n
I
(

s

i

s
a
B

$180.00

$160.00

$140.00

$120.00

$100.00

$80.00

$60.00

$40.00

$20.00

$0.00

2005

2006

2007

2008

2009

17AUG201018231515
2010

IMMUNOGEN, INC. . . . . . . . . . . . . . . . . . . . . .

$100.00

$ 54.05

$ 95.85

$ 52.84

$148.85

$160.07

NASDAQ STOCK MARKET INDEX  (U.S.) . . . . .

$100.00

$106.33

$126.75

$110.83

$ 71.44

$ 88.54

NASDAQ PHARMACEUTICAL STOCKS TOTAL
RETURN INDEX  * . . . . . . . . . . . . . . . . . . . .

$100.00

$110.01

$119.75

$119.32

$116.61

$120.30

2005

2006

2007

2008

2009

2010

*

This index represents a group of  peer issuers  compiled  by the  Center for Research in  Security  Prices.

The above graph and table assume $100 invested on  June  30, 2005 with all dividends reinvested,

in each of our common stock, the NASDAQ Stock  Market Index (U.S.) and the NASDAQ
Pharmaceutical Stocks Total Return Index. Upon written request by any  shareholder, we  will  promptly
provide a list of the companies comprising  the NASDAQ Pharmaceutical Stocks  Total Return Index.

42

 
 
 
Recent  Sales of Unregistered Securities; Uses of Proceeds from Registered Securities; Issuer
Repurchases of Equity Securities

None.

Item 6. Selected Financial Data

The following table (in thousands, except per share  data) sets  forth our  consolidated financial data
for each  of our five fiscal years through our fiscal  year  ended June  30, 2010. The  information set  forth
below should be read in conjunction  with ‘‘Management’s Discussion and Analysis of Financial
Condition and Results of Operations’’  and the consolidated financial  statements and related notes
included elsewhere in this Annual Report  on Form 10-K.

Year Ended June 30,

2010

2009

2008

2007

2006

Consolidated Statement of Operations  Data:
Total revenues . . . . . . . . . . . . . . . . . . . . . . . . .
Total operating expenses . . . . . . . . . . . . . . . . .
Other income (expense), net . . . . . . . . . . . . . .
(Benefit) provision for income taxes . . . . . . . . .

$ 13,943
65,178
58
(265)

$ 27,988
59,804
(221)
(100)

$ 40,249
74,361
2,119
27

$ 38,212
60,438
3,274
35

$ 32,088
53,474
3,569
17

Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ (50,912) $ (31,937) $(32,020) $(18,987) $(17,834)

Basic and diluted net loss per common  share . .

$

(0.87) $

(0.63) $ (0.75) $ (0.45) $ (0.43)

Basic and diluted weighted average common

shares outstanding . . . . . . . . . . . . . . . . . . . .

58,845

51,068

42,969

41,759

41,184

Consolidated Balance Sheet Data:
Cash, cash equivalents and marketable

securities . . . . . . . . . . . . . . . . . . . . . . . . . . .
Total assets . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shareholders’ equity . . . . . . . . . . . . . . . . . . . .

$110,298
137,208
102,048

$ 71,125
100,704
66,857

$ 47,871
83,338
55,299

$ 59,700
80,421
58,401

$ 75,023
94,128
72,350

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of  Operations

Overview

Since our inception, we have been principally engaged in the development of novel, targeted
therapeutics for the treatment of cancer using our expertise  in cancer biology, monoclonal antibodies,
highly potent cytotoxic, or cell-killing,  agents,  and  the design of linkers that enable  these agents to be
stably attached to the antibodies while  in  the  blood stream and released in their fully active form after
delivery to a cancer cell. An anticancer  compound made using our Targeted Antibody Payload, or TAP,
technology consists of a monoclonal antibody  that binds specifically to an antigen target found on
cancer cells with multiple copies of one of our proprietary cell-killing agents attached using one of our
engineered linkers. Its antibody component enables a  TAP compound to bind  specifically to cancer  cells
that express a particular target antigen, the  highly potent  cytotoxic agent serves to kill the cancer  cell,
and the engineered linker controls the release and activation of the cytotoxic agent inside the  cancer
cell. Our TAP technology is designed to enable the creation of highly effective, well-tolerated
anticancer products. All of our and our collaborative  partners’ TAP compounds currently in preclinical
and clinical testing contain either DM1  or DM4 as the cytotoxic agent. Both DM1 and DM4,
collectively DMx, are our proprietary derivatives of  a naturally occurring substance called maytansine.
We  also use our expertise in antibodies  and cancer biology to develop ‘‘naked,’’ or non-conjugated,
antibody  anticancer product candidates.

43

We  have entered into collaborative agreements that enable companies to  use  our  TAP  technology
to develop commercial product candidates to specified targets.  We have also  used our  proprietary TAP
technology in conjunction with our in-house antibody expertise  to  develop our  own anticancer product
candidates. Under the terms of our collaborative agreements, we are  generally entitled to upfront  fees,
milestone payments, and royalties on  any  commercial  product sales. In addition, under  certain
agreements we are entitled to research and development funding based on activities  performed  at our
collaborative partner’s request. We are  reimbursed for our direct and a portion of overhead costs to
manufacture preclinical and clinical materials and, under  certain collaborative agreements, the
reimbursement includes a profit margin.  Currently,  our  collaborative partners include Amgen,  Bayer
Schering Pharma, Biogen Idec, Biotest,  Genentech (a member of the Roche  Group)  and sanofi-aventis.
We  expect that substantially all of our  revenue for  the foreseeable future  will result from payments
under our collaborative arrangements.  Details for some of our major  and recent collaborative
agreements can be found in this 10-K under Item  1, Business.

To date, we have not generated revenues  from commercial product  sales  and we expect to incur

significant operating losses for the foreseeable future. As  of  June 30, 2010,  we had approximately
$110.3 million in cash and marketable securities  compared to $71.1 million in  cash and marketable
securities as of June 30, 2009.

We  anticipate that future cash expenditures will  be  partially offset by collaboration-derived

proceeds, including milestone payments,  royalties  and upfront  fees.  Accordingly, period-to-period
operational results may fluctuate dramatically based  upon the  timing of receipt of  the proceeds.  We
believe that our established collaborative  agreements, while subject  to  specified milestone achievements,
will provide funding to assist us in meeting  obligations under  our collaborative agreements while also
assisting in providing funding for the  development of  internal  product candidates  and technologies.
However, we can give no assurances that  such collaborative agreement  funding  will,  in fact, be realized
in the time frames we expect, or at all.  Should we or our partners not meet some or all of the  terms
and conditions of our various collaboration  agreements, we  may  be  required  to  secure alternative
financing arrangements and/or defer or  limit some or all of our research,  development and/or clinical
projects. However, we cannot provide assurance that  any such  opportunities presented by additional
strategic partners or alternative financing  arrangements will  be  entirely available to us, if at all.

Critical Accounting Policies

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
estimates and judgments that affect the reported amounts of assets, liabilities, revenues  and expenses
and related disclosure of contingent assets and liabilities. On  an on-going  basis, we evaluate our
estimates, including those related to our  collaborative agreements and inventory.  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 these estimates.

We  believe the following critical accounting policies affect our more  significant judgments and

estimates used in the preparation of our consolidated  financial  statements.

Revenue Recognition

We  enter into licensing and development agreements with collaborative partners for  the

development of monoclonal antibody-based  anticancer therapeutics.  We follow the provisions of FASB’s
Accounting Standards Codification (ASC) Topic 605, Revenue Recognition. Accordingly, we recognize
revenue related to research activities  as  they  are performed, as long as there is persuasive evidence of
an arrangement, the fee is fixed or determinable, and collection of the related receivable  is probable.
The terms of our agreements contain  multiple  elements which typically include non-refundable license

44

fees, payments based upon the achievement of  certain milestones and royalties  on product sales.  We
evaluate  such arrangements to determine  if the deliverables are separable  into  units of accounting  and
then apply applicable revenue recognition criteria  to  each unit of accounting. Agreements containing
multiple elements are divided into separate units of  accounting if  certain criteria are met, including
whether the delivered element has stand-alone  value to the  collaborator  and whether  there is objective
and reliable evidence of the fair value  of the  undelivered obligation(s).  The consideration received is
allocated among the separate units either on the  basis of each  unit’s fair  value or  using  the residual
method, and the applicable revenue recognition criteria are  applied  to  each of the separate units.

In October 2009 a new accounting standard for the recognition of revenue arrangements  with
multiple deliverables was issued. This  standard provides accounting principles and application guidance
on whether multiple deliverables exist, how the  arrangement should be separated, and  how the
consideration should be allocated. This  new approach is effective prospectively for revenue
arrangements entered into or materially modified in fiscal years beginning on  or after June 15, 2010
(our  fiscal year 2011). While we do not  expect the adoption of this  standard  to  have a material impact
on our financial position and results of  operations, this  standard may impact us in the  event we
complete future transactions or modify existing collaborative relationships. Refer to Note B, Recent
Accounting Pronouncements, to our Consolidated Financial Statements for additional  discussion of this
standard and its impact on us.

At June 30, 2010, we had the following three types of collaborative contracts with  the parties

identified below:

(cid:129) Exclusive license to use our TAP technology and/or certain  other  intellectual  property to develop

compounds to a single target antigen:

Amgen (multiple single-target licenses)

Bayer Schering Pharma (single-target license)

Biogen Idec (single-target license)

Biotest (single-target license)

Genentech (multiple single-target licenses)

sanofi-aventis (license to multiple individual targets)

(cid:129) Option agreement for a defined period of time to secure licenses to use  our TAP technology to

develop anticancer compounds to a limited number  of  targets on  established terms  (broad
option agreement):

Amgen
sanofi-aventis

(cid:129) Non-exclusive license to our humanization technology:

sanofi-aventis

Generally, the foregoing collaboration agreements provide that we will  (i) at  the collaborator’s
request, manufacture and provide to them preclinical and clinical materials which  are reimbursed  at
our  cost, or, in some cases, cost plus a margin,  (ii) earn payments  upon the collaborators’ achievements
of certain milestones and (iii) earn royalty payments, generally  until the later of the last applicable
patent expiration or 10 to 12 years after product  launch.  Royalty rates may vary over the  royalty term
depending on our intellectual property  rights. We provide technical training and share any process
improvements and know-how with our  collaborators during the research term  of  the collaboration
agreements.

45

Generally, upfront payments on single-target licenses  are deferred  over the  period of our

substantial involvement during development. The determination of the length of this period  is subject
to judgment and estimation and can  have an impact  on the  amount  of  revenue  recognized in  a given
period. Our employees are available to assist  our  collaborators during the development  of  their
products. We estimate this development phase to begin at the inception of the  collaboration  agreement
and conclude at the end of non-pivotal  Phase II testing.  We believe  this period of involvement is,
depending on the nature of the license,  on  average six  and one-half years. Quarterly, we reassess our
periods of substantial involvement over  which we  amortize  our upfront license  fees  and we make
adjustments as appropriate. In the event  that  a single-target  license were  to be terminated,  we would
recognize as revenue any portion of  the upfront fee that had not previously been recorded  as revenue,
but was classified as deferred revenue  at the date of such termination.

We  defer upfront payments received from our broad option  agreements over the  period during

which  the collaborator may elect to receive a license. These  periods are specific to each collaboration
agreement, but are between three and  12 years. If a collaborator  selects an option  to  acquire a license
under these agreements, any option fee  is deferred and is recorded  over the life of  the option,
generally 12 to 18  months. If a collaborator exercises an option and we  grant a single-target  license to
the collaborator, we defer the license  fee and account  for the  fee as we  would an upfront  payment on a
single-target license, as discussed above. Upon exercise of an option to acquire  a license,  we would
recognize any remaining deferred option  fee over  the period of  our substantial involvement  under the
license acquired. In the event a broad  option agreement were  to  be  terminated, we would recognize  as
revenue any portion of the upfront fee that  had not previously been  recorded as revenue, but  was
classified as deferred revenue at the date of such termination. In  the event a  collaborator elects to
discontinue development of a specific  product candidate under a single- target license,  but retains its
right to use our technology to develop  an  alternative  product candidate to  the same target or  a target
substitute, we would cease amortization  of any remaining portion of the upfront fee until there  is
substantial preclinical activity on another  product  candidate and our  remaining  period of substantial
involvement can be estimated.

When milestone fees are specifically tied to a separate earnings  process and are deemed to be

substantive and at risk, revenue is recognized when  such milestones are achieved. In  addition,  we
recognize research and development  support revenue from  certain  collaboration and  development
agreements based upon the level of research services  performed during  the period  of  the research
agreement. Deferred revenue substantially represents amounts received under collaborative agreements
and not yet earned pursuant to these policies.  Where we  have no  continuing  involvement, we  will
record non-refundable license fees as  revenue upon receipt and will record revenue upon achievement
of milestones by our collaborative partners.

We  produce preclinical and clinical materials for  our  collaborators. We are  reimbursed for our
direct costs and a portion of our overhead costs  to  produce clinical materials. We  recognize revenue on
preclinical and clinical materials when the  materials  have passed all quality  testing required for
collaborator acceptance and title and  risk  of  loss have  transferred to the collaborator.

We  also produce research material for potential  collaborators  under material transfer agreements.

Additionally, we perform research activities, including developing antibody-specific conjugation
processes, on behalf of our collaborators  and potential collaborators during the  early evaluation  and
preclinical testing stages of drug development.  Generally, we  are reimbursed  for certain  of  our  direct
and overhead costs of producing these  materials  or providing these services. We record the  amounts
received for the preclinical materials  produced or services  performed as a component of  research  and
development support. We also develop  conjugation processes for  materials  for later stage testing and
commercialization for certain collaborators. We  are reimbursed for  certain  of our  direct and overhead
costs and may receive milestone payments  for developing  these  processes  which are  recorded as a
component of research and development  support.

46

Inventory

We  review our estimates of the net realizable value of our inventory  at each reporting  period. Our
estimate of the net realizable value of our inventory  is subject  to  judgment and estimation. The actual
net realizable value of our inventory  could vary significantly  from  our estimates. We  consider quantities
of raw materials in excess of twelve-month projected usage  that are not supported  by  firm,  fixed
collaborator orders and projections at the  time of  the assessment to be excess. During fiscal 2008,  we
obtained additional amounts of DMx  from a new supplier. Due  to  the need to evaluate the  process
which  was developed to prepare such material from  this new  supplier  across multiple batches,  we had
committed to a level of production which yielded  more  material  than  would be required by our
collaborators over the next twelve months. As a result, during the year ended June 30,  2008, we
recorded  a $2.1 million charge to research and development  expense related to raw material inventory
identified as excess. We also recorded $1.6 million  to  write down the  raw material inventory purchased
during the fiscal year 2008 to its net  realizable value, which  is also included in  research  and
development expense for the year ended June 30, 2008.  During  fiscal 2010, we  obtained  additional
amounts of DMx from our supplier which  yielded more  material than would be required  by  our
collaborators over the next twelve months and as a  result, we  recorded $900,000  of  charges  to  research
and development expense related to raw  material inventory identified as  excess. We also  recorded
$28,000 to write down certain raw material inventory to its net realizable value,  which is  also included
in research and development expense  for the year ended June 30, 2010. No  similar costs  were recorded
during the year ended June 30, 2009. Our  collaborators’  estimates  of  their clinical material
requirements are based upon expectations of their clinical trials,  including the  timing, size, dosing
schedule and the maximum tolerated dose  likely  to  be  reached  for the  compound being evaluated. Our
collaborators’ actual requirements for clinical  materials  may  vary  significantly from their projections.
Significant differences between our collaborators’  actual manufacturing orders and their  projections
could result in our actual twelve-month  usage of raw materials varying significantly from our estimated
usage at an earlier reporting period.  Reductions in collaborators’  projections could indicate that we
have additional excess raw material inventory and we would  then evaluate  the need  to  record further
write-downs, which would be included  as  charges  to  research  and development expense.

Stock-based Compensation

As of June 30, 2010, the Company is authorized to grant future awards under one share-based
compensation plan, which is the ImmunoGen, Inc. 2006  Employee,  Director and Consultant Equity
Incentive Plan. The stock-based awards are accounted  for under ASC Topic 718,  ‘‘Compensation—
Stock Compensation,’’ using the modified prospective transition  method. Under this methodology, the
estimated fair value of awards is charged  to the statement of operations over the requisite service
period, which is the vesting period. Such amounts have been reduced by our estimate  of forfeitures of
all unvested  awards.

The fair value of each stock option is estimated on  the date  of grant using the  Black-Scholes
option-pricing model. Expected volatility  is based exclusively on  historical volatility data of  our 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  we  do not  expect substantially  different
exercise or post-vesting termination behavior amongst our 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. Estimated forfeitures are  based on  historical data  as well as  current trends.  Stock
compensation cost incurred during the years ended  June 30, 2010, 2009  and 2008  was $4.2 million,
$4.0 million and $2.9 million, respectively.  During  fiscal  year  2009, we recorded approximately $843,000
of stock compensation cost related to the  modification  of  certain outstanding  common stock options in
accordance with the former Chief Executive  Officer’s succession  plan.

47

Investment in Marketable Securities

We  invest in marketable securities of highly rated financial institutions and investment-grade  debt

instruments and limit the amount of credit exposure with  any  one  entity.  We have classified our
marketable securities as ‘‘available-for-sale’’ and, accordingly, carry such  securities at aggregate fair
value. In accounting for investments, we evaluate if a  decline  in the fair  value  of a marketable security
below our cost basis is other-than-temporary, and if  so, we record an  impairment  charge related to any
credit loss in our consolidated statement of  operations. The  factors that we consider  in our evaluation
include the fair market value of the security, the  duration and magnitude of the security’s decline, and
our  intent to sell or whether we would more likely than not to be required to sell the security  before
the expected recovery of the amortized  cost  basis. The determination of  whether  a loss  is other than
temporary is highly judgmental and can have a material  impact  on our results. During the fiscal years
ended June 30, 2009 and 2008, we recorded approximately $516,000 and $535,000, respectively, in
other-than-temporary impairment charges.  No similar  charges were recorded in the fiscal  year ended
June 30, 2010. We adopted certain provisions of  ASC Topic  320, ‘‘Investments—Debt and  Equity
Securities,’’ on April 1, 2009. As a result of the adoption of these provisions, during fiscal  year 2009 we
reclassified $54,000 of previously recognized other-than-temporary impairment charges to other
comprehensive loss as a cumulative effect adjustment.

Fair Value of Financial Instruments

As of July 1, 2008, we partially adopted the provisions of ASC Topic 820,  ‘‘Fair  Value
Measurements and Disclosures,’’ for financial  assets and liabilities recognized at fair value  on a
recurring basis. ASC Topic 820 defines  fair value, establishes a framework for measuring  fair value in
accordance with accounting principles  generally  accepted in the  U.S.,  and expands disclosures  about fair
value measurements. Certain provisions of ASC Topic 820 related to other non-financial assets  and
liabilities were adopted by us on July  1,  2009 and did  not  have a material impact on our financial
position or results of operations upon adoption; however, this standard may impact us in  subsequent
periods and require additional disclosures.

Fair value is defined under ASC Topic 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 fair value 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. This standard is applicable to all assets and  liabilities (i.e. financial and
non-financial) and requires enhanced  disclosures, including interim and annual  disclosure of the input
and valuation techniques (or changes in techniques) used to measure  fair value  and the  defining  of  the
major security types comprising debt  and  equity  securities held based  upon the  nature and risk  of  the
security. The fair value of our investments is  generally  determined from market prices  based upon
either quoted prices from active markets  or other significant observable market  transactions at  fair
value.

48

Results of Operations

Revenues

Our total revenues for the year ended  June  30, 2010 were $13.9  million compared with

$28.0 million and $40.2 million for the  years ended June 30,  2009 and 2008, respectively. The
$14.1 million decrease in revenues in fiscal year 2010 from fiscal year  2009 is primarily  attributable to
lower revenues from research and development support,  license and milestone fees and clinical
materials reimbursement, as discussed below. The  $12.2 million decrease in  revenues in  fiscal year  2009
from fiscal year 2008 is primarily attributable to lower  revenues  from  research  and development
support and clinical materials reimbursement, partially offset  by higher revenues from license and
milestone fees, as discussed below.

Research and development support was $5.4 million for the  year ended June  30, 2010, $7.6 million

for the year ended June 30, 2009, and $15.0 million  for  the year ended June 30, 2008.  These amounts
primarily represent research funding  earned based  on actual resources utilized under our agreements
with our collaborators as shown in the table below. The decreased  research and  development support
fees in fiscal years 2010 and 2009 compared to fiscal year 2008 is primarily due to a reduction in the
amount earned from sanofi-aventis with the  conclusion of its committed funding  obligations in the first
half of fiscal 2009. Also included in research and development support revenue are development fees
charged for reimbursement of our direct and overhead costs  incurred  in producing and delivering
research-grade materials to our collaborators and for  developing  antibody-specific conjugation processes
on behalf of our collaborators and potential  collaborators during the early evaluation and preclinical
testing stages of drug development. The amount of development fees we  earn is directly  related to the
number of our collaborators and potential collaborators, the  stage of development of  our collaborators’
product  candidates and the resources our collaborators allocate  to  the  development effort. As  such, the
amount of development fees may vary widely from quarter to quarter  and year to year. Total revenue
recognized from research and development support from each  of our  collaborative  partners  in the years
ended June 30, 2010, 2009 and 2008  is  included in  the following table (in thousands):

Research and Development Support

Collaborative Partner:

Year Ended June 30,

2010

2009

2008

Amgen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bayer Schering Pharma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biogen Idec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biotest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Centocor Ortho Biotech . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
Genentech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
sanofi-aventis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$3,470
96
186
1,041
—
424
148
—

$

8
227
621
1,361
—
238
4,861
250

$

5
88
336
1,648
466
741
11,697
54

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$5,365

$7,566

$15,035

Revenue from license and milestone  fees  for  the year  ended June 30, 2010  decreased

approximately $9.4 million to $5.7 million from $15.1 million in the year ended June 30,  2009. Revenue
from license and milestone fees for the  year ended June 30,  2008 was $13.2  million. Included  in license
and milestone fees for the year ended  June 30,  2010 were $1 million and  $500,000 of preclinical
milestones earned pursuant to our agreements with  Bayer and sanofi-aventis, respectively,  as well as a
$1 million milestone related to the initiation  of Phase  I clinical testing of  SAR650984  by  sanofi-aventis.
Included in license and milestone fees  for the year ended June 30,  2009 was a $6.5 million  milestone
related to the initiation of Phase III clinical testing of  trastuzumab-DM1, or T-DM1, by Genentech, a
$4 million milestone related to the initiation  of Phase  II clinical testing of  AVE1642 by sanofi-aventis

49

and a $500,000 milestone related to the initiation of Phase  I  clinical  testing of BT-062 by Biotest. Also
during the year ended June 30, 2009, Millennium  Pharmaceuticals and  Boehringer  Ingelheim agreed to
terminate their licenses with us that were no longer being  used  to  develop  products and as  a result, we
recognized as license and milestone fees  $361,000 and $486,000, respectively, of upfront fees previously
deferred. Included in license and milestone fees for  the year  ended June 30, 2008 was $5 million
related to the achievement of a milestone under the Genentech agreement from the  initiation of
Phase II clinical testing of T-DM1, $1.5  million related  to  the achievement  of a milestone  under the
Biogen Idec agreement from the submission of the IND application  for  BIIB015,  $2 million related  to
the achievement of milestones under the  sanofi-aventis agreement from the  initiation of clinical  testing
of SAR3419 and certain preclinical milestones. Total  revenue recognized from  license and milestone
fees from each of our collaborative partners in the years ended June 30,  2010, 2009 and 2008 is
included in the following table (in thousands):

License and Milestone Fees

Collaborative Partner:

Year Ended June 30,

2010

2009

2008

Amgen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bayer Schering Pharma . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biogen Idec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biotest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Boehringer Ingelheim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Centocor Ortho Biotech . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Genentech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Millennium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
sanofi-aventis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 689
1,616
157
149
—
114
38
—
2,935

$

511
410
228
669
486
138
6,651
361
5,663

$

433
—
1,684
169
—
69
5,991
—
4,810

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$5,698

$15,117

$13,156

Deferred revenue of $11.7 million at June 30, 2010  represents payments  received from  our
collaborators pursuant to our license and  supply  agreements  with them which  we have  yet to earn
pursuant to our revenue recognition policy.

Clinical materials reimbursement decreased by  approximately  $2.4 million to $2.9 million in the
year ended June 30, 2010 compared to $5.3 million in the  year ended June 30, 2009.  We earned clinical
materials reimbursement of $12.1 million  during  the year ended June 30, 2008. During  the years ended
June 30, 2010, 2009 and 2008, we shipped  clinical materials in support of  a number  of  clinical trials
including, for certain of these years, those of T-DM1, AVE9633, SAR3419, SAR566658, BIIB015,
BT-062, as well as preclinical materials  in  support of the development  efforts of certain other
collaborators and DMx shipments to certain collaborators in support  of  development and
manufacturing efforts. The decrease in clinical materials reimbursement in  fiscal  year  2010 as compared
to fiscal year 2009 is primarily related  to  less clinical  material  shipped in  support of two of our
collaborators’ trials due to various factors, including the dosage schedule  and speed  of  enrollment
within the trials. The decrease in clinical materials reimbursement in  fiscal  year  2009 as compared to
fiscal year 2008 is  primarily related to  $5.0 million in  revenue recognized from  supplying DMx to a
collaborator in fiscal year 2008, along with the  transfer of T-DM1  to  commercial-scale production at a
third-party contract manufacturing organization in  fiscal year 2009. During fiscal year 2009,  sanofi-
aventis discontinued clinical trial activity for AVE9633. We are reimbursed for certain of our direct and
overhead costs to produce clinical materials plus, for  certain programs,  a profit  margin. The amount of
clinical materials reimbursement we earn, and the related cost of clinical  materials charged  to  research
and development expense, is directly  related to the  number of clinical trials our  collaborators  are
preparing or have underway, the speed  of enrollment in those trials, the dosage schedule of each
clinical trial and the time period, if any, during which  patients in the trial  receive clinical benefit from

50

the clinical materials, and the supply of clinical- grade material to our  collaborators  for process
development and analytical purposes. As  such, the amount of clinical materials  reimbursement revenue
and the related cost of clinical materials  charged to research  and  development  expense may  vary
significantly from quarter to quarter  and  year to year.

Research and Development Expenses

Our net  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  and (iv)  manufacturing
operations. Our research and development efforts have been  primarily  focused in the  following areas:

(cid:129) activities pursuant to our discovery, development and commercialization  agreement with sanofi-

aventis;

(cid:129) activities pursuant to our development  and license agreements with various  other  collaborators;

(cid:129) activities related to the preclinical  and clinical development  of lorvotuzumab mertansine,

IMGN388 and IMGN529;

(cid:129) process development related to production of the  lorvotuzumab antibody  and lorvotuzumab

mertansine conjugate for clinical materials;

(cid:129) process development related to production of IMGN388 conjugate for clinical  materials;

(cid:129) process improvements related to the production of DM1,  DM4 and  strain  development of their

precursor, ansamitocin P3;

(cid:129) funded development activities with contract  manufacturers  for the antibody component of

IMGN529, the lorvotuzumab antibody,  and DM1, DM4 and their precursor, ansamitocin P3;

(cid:129) production costs for the supply of the lorvotuzumab antibody;

(cid:129) production costs for the supply of DMx  for  our  and our partners’ preclinical  and clinical

activities;

(cid:129) operation and maintenance of our conjugate manufacturing facility, including production of our

own and our collaborators’ clinical materials;

(cid:129) process improvements to our TAP  technology;

(cid:129) evaluation of potential antigen targets;

(cid:129) evaluation of internally developed and/or  in-licensed  product candidates  and technologies; and

(cid:129) development and evaluation of additional cytotoxic agents and  linkers.

Research and development expense for the  year  ended June  30, 2010 increased $4.4  million  to
$50.3 million from $45.9 million for the  year ended June 30, 2009.  Research  and development expense
was $60.0 million for the year ended June 30,  2008. Research and development salaries and  related
expenses increased by $1.8 million in  the year ended June 30, 2010 compared to the year ended
June 30, 2009 and increased by $1.4  million in the  year ended June 30, 2009  compared to the year
ended June 30, 2008. Included in salaries  and related expenses  for  the year  ended June 30, 2010  is
$2.7 million of stock compensation costs compared to $1.7  million  and  $1.6 million  of stock
compensation costs for fiscal years 2009 and 2008, respectively.  The higher stock compensation  costs in
fiscal 2010 are driven by higher stock prices and increases  in the number of annual options  granted.
Clinical trial costs increased $1.1 million during  fiscal  year  2010 compared  to  fiscal  year  2009 and
increased $523,000 in fiscal year 2009 compared to fiscal year  2008. Additionally, overhead utilization

51

from the manufacture of clinical materials on behalf of our collaborators decreased $1.8 million during
fiscal year 2010 compared to fiscal year  2009 and decreased  by $1.3 million in fiscal year 2009
compared to fiscal year 2008.

Included in research and development expenses for the year ended June 30,  2010 is $900,000
related to raw material inventory identified  as excess, as well as $28,000 to  write down certain raw
material inventory to its net realizable  value. Included  in research and  development expenses for  the
year ended June 30, 2008 is a $2.1 million  charge related to raw material inventory identified as excess
and a $1.6 million charge to write down raw material purchased  during that year to its net realizable
value. No similar costs were recorded  during fiscal  year 2009. Reserve requirements  for excess
quantities of DMx are principally determined based  on our collaborators’ forecasted demand compared
to our inventory position. The DMx  purchased during fiscal year  2008 was produced by a  supplier in
conjunction with process scale-up, resulting in the  purchase  of  quantities  of material exceeding
anticipated collaborator demand in the  next  twelve  months. Due to lead times required  to  secure
material, process development and the changing  requirements of our  collaborators, expenses to
recognize excess quantities have fluctuated from period to period and we expect  that  these period
fluctuations will continue in the future.  See ‘‘Inventory’’  within our Critical Accounting Policies above
for further discussion of our inventory  reserve policy.

We  are unable to accurately estimate which  potential  product candidates, if  any, will eventually
move into our internal preclinical research program. We are unable to reliably estimate  the costs  to
develop these products as a result of  the uncertainties related to discovery research efforts as  well as
preclinical and clinical testing. Our decision to move a  product candidate into the  clinical development
phase is  predicated upon the results  of  preclinical  tests.  We  cannot accurately  predict which, if any, of
the discovery stage product candidates will  advance from preclinical testing and move into our internal
clinical development program. The 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 not ever  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 would
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. As a result of  these uncertainties  surrounding  the timing and outcome of our
clinical trials, we are currently unable to estimate  when, if  ever, our product  candidates that have
advanced into clinical testing will generate  revenues and cash flows.

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

52

development expenses within each of the categories listed in the following table and described in more
detail below (in thousands):

Research and Development Expense

Year Ended June 30,

2010

2009

2008

Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preclinical and Clinical Testing . . . . . . . . . . . . . . . . . . . . . . . . .
Process and Product Development . . . . . . . . . . . . . . . . . . . . . .
Manufacturing Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$14,200
12,892
5,959
17,229

$13,965
9,762
6,037
16,140

$15,265
8,280
5,731
30,737

Total Research and Development Expense . . . . . . . . . . . . . . . .

$50,280

$45,904

$60,013

Research—Research includes expenses associated  with activities  to  evaluate  new targets and to

develop and evaluate new antibodies, linkers and cytotoxic  agents  for our  products and in  support of
our  collaborators. Such expenses primarily include personnel, fees to in-license certain technology,
facilities and lab supplies. Research expenses increased  $235,000 to $14.2 million in  fiscal year  2010
from fiscal year 2009 and decreased $1.3 million to $14.0  million in fiscal year 2009 from fiscal  year
2008. The increase in fiscal year 2010  was  principally the  result of an  increase in stock compensation
costs. The decrease in research expense in fiscal  year 2009 was principally  the result of a  decrease in
salaries and related expenses due to  a reorganization of departments  in March 2008 and July 2008,
resulting in lower personnel costs included in research  expense for the period.

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, and the cost of our own clinical trials.  Such expenses include personnel, patient enrollment at
our  clinical testing sites, consultant fees, contract  services,  and facility expenses. Preclinical and clinical
testing expenses increased $3.1 million  to $12.9 million in  fiscal  year 2010 from fiscal  2009 and
$1.5 million to $9.8 million in fiscal year  2009 from fiscal  year 2008.  The increase in fiscal year 2010 is
primarily the result of an increase in  clinical  trial  costs, an  increase in consulting fees for regulatory
assistance and preclinical studies conducted, and an increase  in salaries and related  expenses due to the
addition of two executive officers and higher salary  levels. The increase  in fiscal year 2009  was primarily
due to an increase in salaries and related expenses due to a reorganization of departments  in March
2008 and July 2008, as well as an increase  in clinical trials costs.

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, contract services and facility expenses.  Total
development expenses decreased $78,000  to  $6.0 million in fiscal year 2010 from fiscal year 2009 and
expenses increased $306,000 to $6.0 million in fiscal year 2009  from fiscal year 2008. The  increase in
fiscal year 2009 was primarily the result of the reorganization of departments in July  2008.

Manufacturing Operations—Manufacturing  operations  expense includes costs to manufacture
preclinical and clinical materials for our  own and  our  collaborators’ product candidates, quality control
and quality assurance activities and costs to support  the operation  and maintenance of our conjugate
manufacturing facility. Such expenses include personnel, raw materials for  our  and our collaborators’
preclinical studies and clinical trials, development  costs with  contract manufacturing organizations,
manufacturing supplies, and facilities  expense. Manufacturing operations expense  increased $1.1 million
to $17.2 million in fiscal year 2010 from fiscal year 2009 and  decreased $14.6  million to $16.1 million in
fiscal year 2009 from fiscal year 2008. The increase  in fiscal year 2010 was  primarily  the result of (i) a
decrease in overhead utilization from the  manufacture of clinical materials on behalf of our
collaborators; (ii) an increase in antibody supply and development expenses; and (iii) an increase in
stock compensation costs. Partially offsetting these increases, contract  service  expense decreased and

53

cost of clinical materials reimbursed decreased.  The  decrease in fiscal year 2009 was primarily the
result of (i) a decrease in supply of DMx  and clinical materials to our  collaborators;  (ii) a decrease in
antibody  supply and development expenses; (iii)  a decrease in contract  service expenses;  and (iv) a
significant decrease in charges incurred related  to  the write  down of raw material inventory.  Partially
offsetting these decreases, salaries and  related expenses  increased, depreciation and amortization
increased, and overhead utilization from the  manufacture of clinical materials on  behalf of our
collaborators decreased.

Antibody expense in anticipation of potential future clinical  trials, as  well as our ongoing trials, was

$1.1 million in fiscal year 2010, $503,000 in  fiscal  year  2009, and  $7.4 million in fiscal  year 2008. The
process of antibody production is lengthy as is 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 and  we expect  these cost fluctuations to continue in the future.

General and Administrative Expenses

General and administrative expenses  for the  year ended June 30, 2010  increased $998,000 to
$14.9 million from $13.9 million for the  year ended June 30, 2009.  General and administrative expenses
for the year ended June 30, 2008 were  $14.3 million.  The increase in  fiscal year  2010 as compared to
fiscal year 2009 was primarily due to  an increase in patent expenses, an increase  in consulting fees, an
increase in directors’ fees and an increase in other  general corporate expenses, partially offset by a
decrease in salaries and related expenses.  During  fiscal year 2009, the Company recognized  a total of
$1.6 million in stock compensation expense and other compensation costs related to the  former Chief
Executive Officer’s succession plan and a  termination  of an executive. The decrease  in fiscal year 2009
as compared to fiscal year 2008 was primarily the result of a decrease  in rent expense  and move-related
expenses, partially offset by greater salaries and related  expenses. During fiscal year 2008,  the Company
recognized $1.5 million of expense related to the rental of laboratory  and office  space in Waltham  prior
to occupying the space in late March 2008, as well as $799,000  of  move-related  expenses, classifying
such as general and administrative expenses.

Other Income (Expense), net

Other income (expense), net for the  years ended June 30,  2010, 2009, and 2008  is included in the

following table (in thousands):

Other Income (Expense), net

Year Ended June 30,

2010

2009

2008

Investment Income . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Net Realized (Losses) Gains on Investments . . . . . . . . . . . . . . . . . .
Other-Than-Temporary Impairment . . . . . . . . . . . . . . . . . . . . . . . . .
Other (Expense) Income, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 583
$ 176
—
(33)
— (516)
(255)

(118)

$2,152
39
(535)
463

Total Other Income (Expense), net . . . . . . . . . . . . . . . . . . . . . . . . .

$ 58

$(221) $2,119

Investment Income, net

Investment income for the years ended June 30, 2010,  2009 and 2008 was $176,000,  $583,000 and

$2.2 million, respectively. The decrease  in investment  income in fiscal year 2010 and fiscal year 2009
from fiscal year 2008 is primarily the  result  of  lower yields on  investments reflecting lower market rates
and lower average investable balances.

54

Net Realized (Losses) Gains on Investments

Net realized (losses) gains on investments were  ($33,000)  and $39,000, for the  years  ended
June 30, 2009 and 2008, respectively. There  were no gains or losses recognized during the year ended
June 30, 2010.

Other than Temporary Impairment

During  the years ended June 30, 2009 and 2008, we  recognized $516,000  and  $535,000,

respectively, in charges for the impairment of available-for-sale securities that were determined to be
other-than-temporary following a decline in value. No similar charges were recognized  during the year
ended June 30, 2010.

Other (Expense) Income, net

Other (expense) income, net for the  years ended June 30,  2010, 2009 and 2008  was  $(118,000),

($255,000) and $463,000, respectively. During the years ended  June  30, 2010, 2009  and 2008, we
recorded  net (losses) gains on forward  contracts of  $(219,000), $(234,000) and $699,000, respectively.
We  incurred $104,000, $(29,000) and  $(243,000) in  foreign currency translation income (expenses)
related to obligations with non-U.S. dollar-based suppliers during the  years  ended June 30, 2010,  2009
and 2008, respectively.

Liquidity and Capital Resources

June 30,

2010

2009

(In thousands)

Cash, cash equivalents and marketable securities . . . . . . . . . . . . . . . . .
Working capital
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shareholders’ equity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cash used for operating activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cash (used for) provided by investing activities . . . . . . . . . . . . . . . . . . .
Cash provided by financing activities . . . . . . . . . . . . . . . . . . . . . . . . . .

$110,298
103,296
102,048
(40,584)
(882)
80,983

$ 71,125
65,738
66,857
(13,334)
11,995
39,359

Cash Flows

We  require cash to fund our operating  expenses, including the advancement  of our  own clinical

programs, and to make capital expenditures. Historically,  we  have funded our  cash requirements
primarily through equity financings in public  markets and payments from  our collaborators, including
equity investments, license fees, milestones  and research funding.  As of June 30,  2010, we  had
approximately $110.3 million in cash, cash  equivalents and marketable  securities. Net  cash used for
operations was $40.6 million, $13.3 million and $20.1 million during the  years  ended June 30, 2010,
2009 and 2008, respectively. The principal use  of cash  in operating  activities for all periods presented
was to fund our net loss.

Net cash (used for) provided by investing  activities was $(882,000), $12.0 million and $15.2 million
for the years ended June 30, 2010, 2009  and 2008, respectively, and  substantially represents cash inflows
from the sales and maturities of marketable securities partially  offset by capital expenditures. Capital
expenditures were $1.5 million, $1.9 million  and $18.0  million  for the  fiscal years ended June 30, 2010,
2009 and 2008, respectively. The significant capital expenditures for fiscal 2008 were primarily leasehold
improvements made to our Waltham, MA  facility related to the construction allowance received from
the landlord to build out laboratory and  office space to our specifications, as  well as expansion and
improvements of our manufacturing plant in Norwood, MA.  The  leasehold  improvements made to the
Waltham, MA facility were paid by the  landlord, with  such reimbursement  recorded as a benefit to cash

55

used in operations. Capital expenditures for the years ended June 30,  2010 and  2009 consisted  primarily
of laboratory equipment and computer software applications.

Net cash provided by financing activities was  $81.0 million,  $39.4 million and  $26.0 million for  the
years ended June 30, 2010, 2009 and  2008, respectively, which includes  the proceeds  from the exercise
of 634,000, 416,000 and 619,000 stock options, respectively. Also, in May 2010,  pursuant to a public
offering, we issued and sold 10,350,000  shares of our common stock  resulting in net  proceeds of
$77.5 million. The shares of common  stock offered were registered under our  existing shelf  registration
statement on Form S-3 which was filed with the  Securities and  Exchange Commission in April 2010.  In
June 2009, pursuant to a public offering,  we  issued and sold 5,750,000 shares  of  our  common stock
resulting in net proceeds of $38 million. In June  2008, pursuant to a securities purchase agreement with
a private investor, we issued and sold 7,812,500  shares of  our common  stock resulting in  net proceeds
of $24.9 million.

We  anticipate that our current capital resources and expected  future collaborator payments will

enable us to meet our operational expenses and capital  expenditures for fiscal year 2011  and
approximately the first half of fiscal 2012. However, we cannot provide  assurance that such
collaborative agreement funding will, in fact, be received. Should  we  or  our partners not meet some or
all of the terms and conditions of our various collaboration  agreements, we may be required to pursue
additional strategic partners, secure alternative financing  arrangements, and/or  defer  or limit some or
all of our research, development and/or  clinical projects.

As mentioned above, on April 9, 2010, we  filed a  Registration Statement on Form S-3
(Registration No. 333-144488) with the Securities and Exchange Commission. The  Securities  and
Exchange Commission declared the Registration Statement  effective  on  April 22, 2010. Subject  to  our
ongoing obligations under the Securities  Act of 1933, as amended, and the Securities Exchange Act of
1934, as amended, the Registration Statement permits us to offer and sell up to an aggregate of
$125 million of our common stock, $82.8 million  of which we sold in  the transaction discussed above.

Contractual Obligations

Below is a table that presents our contractual  obligations  and commercial  commitments  as of

June 30, 2010 (in thousands):

Payments Due by Period

Total

Less than
One Year

1-3
Years

4-5
Years

More than
5 Years

Waltham lease obligation(1) . . . . . . . . . . . . .
Other operating lease obligations(2)
. . . . . . .

$49,263
1,198

$4,631
1,198

$9,662
—

$9,996
—

$24,974
—

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$50,461

$5,829

$9,662

$9,996

$24,974

(1) Lease agreement was signed on July 27, 2007. In  December  2009, we entered into a sublease for
14,100 square feet of our office and laboratory space at 830  Winter Street,  Waltham, MA through
January 2015. We will receive approximately $2.8  million  in minimum rental payments over the
remaining term of the sublease, which is not  included in  the table above.

(2) The Company entered into a sub-sublease  in May  2008 for the entire space at 148 Sidney Street,
Cambridge, MA through October 2010, the remainder of the sublease. Both the sublease and
sub-sublease for the 148 Sidney Street facility were terminated  as of July 31, 2010.  Included in the
table above is $233,000 in minimum  rental payments owed by the Company through October 2010,
however, only approximately $58,000 was paid by the  Company for the  month of July 2010. The
Company was reimbursed this amount pursuant  to  the sub-sublease.

56

In addition to the above table, we are  contractually obligated to make potential future success-

based regulatory milestone payments  in  conjunction with certain  collaborative  agreements. These
payments are contingent upon the occurrence of certain future events and, given the nature of  these
events, it is unclear when, if ever, we  may  be  required  to  pay  such amounts. As a result,  these
contingent payments have not been included in  the table above  or recorded  in our consolidated
financial statements. Further, the timing  of any future payment is  not reasonably estimable. As of
June 30, 2010, the  maximum amount  that may be payable in the  future under such arrangements is
approximately $43.2 million.

Recent  Accounting Pronouncements

In October 2009, the FASB issued Accounting Standards  Update (ASU) No.  2009-13, Multiple-

Deliverable Revenue Arrangements (ASU No. 2009-13). ASU No. 2009-13,  which amends existing
revenue recognition accounting pronouncements and provides  accounting principles and  application
guidance on whether multiple deliverables  exist, how the arrangement should be separated, and the
consideration allocated. This guidance eliminates the requirement to establish the fair value  of
undelivered products and services and instead provides for separate revenue recognition  based upon
management’s estimate of the selling  price for an  undelivered item when there is no other means to
determine the fair value of that undelivered item. Previous accounting principles required  that  the fair
value of the undelivered item be the price of the item either sold in a separate transaction between
unrelated third parties or the price charged  for each  item when the item  is sold separately  by  the
vendor. This was difficult to determine when the product was not individually  sold because of its
unique  features. If the fair value of all  of the elements in the  arrangement was not determinable, then
revenue was deferred until all of the items  were  delivered or fair value was determined.  This new
approach is effective prospectively for revenue arrangements entered into or  materially modified in
fiscal years beginning on or after June  15, 2010 (our fiscal year 2011). While we do  not  expect the
adoption of this standard to have a material impact on  our financial position and results of operations,
this  standard may impact us in the event  we complete future transactions or  modify existing
collaborative relationships.

The provisions of ASC Topic 810, ‘‘Consolidation’’,  related to the  changes to how a  reporting
entity determines when an entity that is insufficiently capitalized or is  not controlled through voting  (or
similar rights) should be consolidated will  be  effective for fiscal years beginning after November 15,
2009 (our fiscal year 2011). Early application is not permitted.  We do not expect the adoption of these
provisions to have a significant impact on  our  financial position or results of operations.

In March 2010, the FASB issued guidance related to the milestone method of revenue  recognition,
which  will codify a method of revenue recognition that has  been common practice. Under this method,
contingent consideration from research and development activities that is earned upon the achievement
of a substantive milestone is recognized in its entirety in the period in which the milestone  is achieved.
This guidance is effective for annual  periods beginning on or after June 15, 2010 but may  be  adopted
as of  the beginning of an annual period.  Because our  current revenue recognition policy for  milestone
payments is consistent with the FASB’s guidance, we do not expect  the adoption of this standard  will
have a material effect on our consolidated financial position, results of operations and  cash flows.

Off-Balance Sheet Arrangements

None.

57

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. Although our  investments are subject to credit  risk, our
investment policy specifies credit quality standards for our investments  and limits the  amount  of credit
exposure from any single issue, issuer or type  of investment. Our investments are  also subject  to
interest rate risk and will decrease in  value  if  market  interest rates  increase. However,  due  to  the
conservative nature of our investments and relatively  short duration, interest rate risk  is mitigated.  We
do not own derivative financial instruments in our investment  portfolio. Accordingly, we  do  not  believe
that 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 forward contracts to manage the foreign currency
exposures that exist as part of our ongoing business operations. The contracts are denominated  in
Euros and have maturities of less than  one year. 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  concentrated
primarily in a portfolio of short duration  foreign currency  forward contracts. Generally, these contracts
provide that we receive certain foreign currencies and  pay U.S. dollars at specified exchange rates at
specified future dates. Although we are exposed to credit  and  market  risk in  the event of future
nonperformance by a counterparty, management  has no  reason to believe that such an  event will  occur.

58

Item 8. Financial Statements and Supplementary  Data

IMMUNOGEN, INC.
INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

Report of Independent Registered Public Accounting Firm . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Consolidated Financial Statements:

Consolidated Balance Sheets as of June 30,  2010 and 2009 . . . . . . . . . . . . . . . . . . . . . . . . .
Consolidated Statements of Operations for the Years Ended June 30, 2010,  2009,  and  2008 . . .
Consolidated Statements of Shareholders’ Equity for the Years Ended June 30, 2010,  2009,

and 2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Consolidated Statements of Cash Flows for the Years Ended June 30, 2010, 2009, and 2008 . .
Notes to Consolidated Financial Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page

60

61
62

63
64
65

59

Report of Independent Registered Public  Accounting Firm

The Board of Directors and Shareholders  of ImmunoGen, Inc.

We  have audited the accompanying consolidated balance sheets of ImmunoGen, Inc.  as of June 30,

2010 and 2009, and the related consolidated  statements  of operations,  shareholders’ equity,  and cash
flows for each of the three years in the period ended June 30,  2010. Our  audits  also included the
financial statement schedule listed in the  Index at Item  15.  These financial  statements and  schedule are
the responsibility of the Company’s management. Our  responsibility is to express an opinion on these
financial statements and schedule based  on our audits.

We  conducted our audits in accordance with the standards  of  the Public Company Accounting
Oversight Board (United States). Those  standards require that we  plan and perform the audit to obtain
reasonable assurance about whether  the  financial  statements are free  of material misstatement.  An
audit includes examining, on a test basis, evidence  supporting the amounts and disclosures  in the
financial statements. An audit also includes assessing the accounting  principles used  and significant
estimates made by management, as well as  evaluating the overall financial statement presentation. We
believe that our audits provide a reasonable  basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects,

the consolidated financial position of  ImmunoGen, Inc.  at June 30,  2010 and  2009, and the
consolidated results of its operations and its cash  flows  for  each  of the three years in the period ended
June 30, 2010, in conformity with U.S. generally accepted accounting principles.  Also, in our  opinion,
the related financial statement schedule, when considered  in relation to the basic financial statements
taken as a whole, presents fairly in all material  respects the information set forth  therein.

We  also have audited, in accordance with the standards of  the Public Company Accounting

Oversight Board (United States), the  effectiveness of ImmunoGen,  Inc.’s  internal control  over financial
reporting as of June 30, 2010, based on criteria established in Internal Control—Integrated Framework
issued by the Committee of Sponsoring  Organizations of the Treadway  Commission  and our report
dated August 27, 2010 expressed an unqualified opinion  thereon.

/s/ ERNST & YOUNG LLP

Boston, Massachusetts
August 27, 2010

60

IMMUNOGEN, INC.

CONSOLIDATED BALANCE SHEETS

AS OF JUNE 30, 2010 AND JUNE 30,  2009

In thousands, except per share amounts

ASSETS
Cash and cash equivalents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Marketable securities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accounts receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unbilled revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Restricted cash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Prepaid and other current assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total current assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Property and equipment, net of accumulated depreciation . . . . . . . . . . . . . . . .
Long-term restricted cash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

June 30,
2010

June 30,
2009

$ 109,156
1,142
1,795
1,595
1,242
574
1,614

117,118
16,326
3,568
196

$ 69,639
1,486
1,746
561
1,836
366
1,232

76,866
19,671
4,142
25

Total  assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 137,208

$ 100,704

LIABILITIES AND SHAREHOLDERS’ EQUITY
Accounts payable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accrued compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other accrued liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current portion of deferred lease incentive . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current portion of deferred revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$

Total current liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Deferred lease incentive, net of current  portion . . . . . . . . . . . . . . . . . . . . . . .
Deferred revenue, net of current portion . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other long-term liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Commitments and contingencies (Note  H)
Shareholders’ equity:
Preferred stock, $.01 par value; authorized 5,000 shares;  no  shares  issued and

3,064
4,201
2,404
979
3,174

13,822
8,562
8,488
4,288

35,160

$

1,244
4,140
1,566
979
3,199

11,128
9,540
9,543
3,636

33,847

outstanding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

—

—

Common stock, $.01 par value; authorized  100,000 shares; issued and
outstanding 67,931 and 56,947 shares as of June  30, 2010 and 2009,
respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additional paid-in capital
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accumulated deficit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accumulated other comprehensive income (loss) . . . . . . . . . . . . . . . . . . . . . . .

679
473,450
(372,363)
282

569
387,947
(321,451)
(208)

Total shareholders’ equity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

102,048

66,857

Total liabilities and shareholders’ equity . . . . . . . . . . . . . . . . . . . . . . . .

$ 137,208

$ 100,704

The accompanying notes are an integral part of the consolidated financial statements.

61

IMMUNOGEN, INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

In thousands, except per share amounts

Year Ended June 30,

2010

2009

2008

Revenues:

Research and development support . . . . . . . . . . . . . . . . . . . . . . . .
License and milestone fees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clinical materials reimbursement . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 5,365
5,698
2,880

$ 7,566
15,117
5,305

$ 15,035
13,156
12,058

Total revenues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13,943

27,988

40,249

Operating Expenses:

Research and development
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General and administrative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total operating expenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Loss from operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Investment income, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other-than-temporary impairment . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other (expense) income, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Loss before (benefit) provision for income taxes . . . . . . . . . . . . . . . . .
(Benefit) provision for income taxes . . . . . . . . . . . . . . . . . . . . . . . . .

50,280
14,898

65,178

(51,235)
176
—
(118)

(51,177)
(265)

45,904
13,900

59,804

(31,816)
583
(516)
(288)

(32,037)
(100)

60,013
14,348

74,361

(34,112)
2,191
(535)
463

(31,993)
27

Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$(50,912) $(31,937) $(32,020)

Basic and diluted net loss per common share . . . . . . . . . . . . . . . . . . .

$

(0.87) $ (0.63) $ (0.75)

Basic and diluted weighted average common  shares outstanding . . . . .

58,845

51,068

42,969

The accompanying notes are an integral part of the consolidated financial statements.

62

CONSOLIDATED STATEMENTS OF SHAREHOLDERS’  EQUITY

IMMUNOGEN, INC.

In thousands

Common Stock

Shares Amount

Additional
Paid-In
Capital

Accumulated
Other

Total

Accumulated Comprehensive Shareholders’ Comprehensive

Deficit

Income  (Loss)

Equity

(Loss)

Balance at June 30, 2007 . . . . . . . . . . . . . . . . . . 42,346
—
. . . . . . .
Unrealized losses on marketable securities
—
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . .
619
Stock options exercised . . . . . . . . . . . . . . . . . . .
—
Stock-based compensation expense . . . . . . . . . . . .
Directors’ stock-based compensation . . . . . . . . . . .
—
Issuance of common stock in a private  offering,  net of
financing costs . . . . . . . . . . . . . . . . . . . . . . .

7,813

$423
—
—
6
—
—

$315,621
—
—
1,087
2,861
92

$(257,548)
—
(32,020)
—
—
—

$ (95)
(44)
—
—
—
—

$ 58,401
(44)
(32,020)
1,093
2,861
92

(44)
(32,020)
—
—
—

79

24,837

—

—

24,916

—

Balance at June 30, 2008 . . . . . . . . . . . . . . . . . . 50,778

$508

$344,498

$(289,568)

$(139)

$ 55,299

$(32,064)

(15)

(15)

—
(31,937)
—
—
—

—
—

$(31,952)

490
(50,912)
—
—

—
—

$(50,422)

Comprehensive loss . . . . . . . . . . . . . . . . . . . . .

. . . . . . .
Unrealized losses on marketable securities
Cumulative effect adjustment relating to the adoption
of ASC Topic 718 . . . . . . . . . . . . . . . . . . . . .
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stock options exercised . . . . . . . . . . . . . . . . . . .
Stock-based compensation expense . . . . . . . . . . . .
Restricted stock issued . . . . . . . . . . . . . . . . . . .
Issuance of common stock in a public offering,  net of
financing costs . . . . . . . . . . . . . . . . . . . . . . .
Directors’ stock-based compensation . . . . . . . . . . .

—

—
—
416
—
3

5,750
—

—

—
—
4
—
—

57
—

—

—

—
—
1,310
3,956
20

37,988
175

54
(31,937)
—
—
—

—
—

(15)

(54)
—
—
—
—

—
—

—
(31,937)
1,314
3,956
20

38,045
175

Balance at June 30, 2009 . . . . . . . . . . . . . . . . . . 56,947

$569

$387,947

$(321,451)

$(208)

$ 66,857

Comprehensive loss . . . . . . . . . . . . . . . . . . . . .

Unrealized gains on marketable securities . . . . . . . .
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stock options exercised . . . . . . . . . . . . . . . . . . .
Stock-based compensation expense . . . . . . . . . . . .
Issuance of common stock in a public offering,  net of

—
—
634
—

—
—
6
—

—
—
3,455
4,170

—
(50,912)
—
—

financing costs . . . . . . . . . . . . . . . . . . . . . . . 10,350
—

Directors’ stock-based compensation . . . . . . . . . . .

104
—

77,418
460

—
—

490
—
—
—

—
—

490
(50,912)
3,461
4,170

77,522
460

Balance at June 30, 2010 . . . . . . . . . . . . . . . . . . 67,931

$679

$473,450

$(372,363)

$ 282

$ 102,048

Comprehensive loss . . . . . . . . . . . . . . . . . . . . .

The accompanying notes are an integral part of the consolidated financial statements.

63

IMMUNOGEN, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

In thousands

Cash flows from operating activities:
Net loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adjustments to reconcile net loss to net  cash used for operating

activities:
Depreciation and amortization . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss on sale/disposal of fixed assets . . . . . . . . . . . . . . . . . . . . . . . .
Amortization of deferred lease incentive obligation . . . . . . . . . . . . .
Loss (gain) on sale of marketable securities . . . . . . . . . . . . . . . . . .
Other-than-temporary impairment of  investments . . . . . . . . . . . . . .
Loss (gain) on forward contracts . . . . . . . . . . . . . . . . . . . . . . . . . .
Stock and deferred share unit compensation . . . . . . . . . . . . . . . . . .
Deferred rent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Change in operating assets and liabilities:

Accounts receivable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unbilled revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Prepaid and other current assets . . . . . . . . . . . . . . . . . . . . . . . .
Restricted cash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accounts payable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accrued compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other accrued liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Deferred revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Proceeds from landlord for tenant improvements . . . . . . . . . . . .

Year Ended June 30,

2010

2009

2008

$ (50,912) $(31,937) $(32,020)

4,838
41
(979)
—
—
219
4,640
55

(49)
(1,034)
594
(386)
366
(171)
1,820
61
1,393
(1,080)
—

4,995
18
(975)
33
516
234
4,235
1,450

(1,350)
2,911
280
312
366
13
(167)
2,976
(2,871)
4,877
750

4,445
103
(512)
(39)
535
(699)
2,915
1,816

1,140
2,508
1,151
(241)
(4,511)
37
(815)
(49)
(44)
(5,910)
10,041

Net cash used for operating activities . . . . . . . . . . . . . . . . . . .

(40,584)

(13,334)

(20,149)

Cash flows from investing activities:

Proceeds from maturities or sales of  marketable securities . . . . . .
Purchases of marketable securities . . . . . . . . . . . . . . . . . . . . . . .
Reclassification of cash equivalent balance to marketable

securities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Purchases of property and equipment, net
. . . . . . . . . . . . . . . . .
Proceeds from settlement of forward contracts . . . . . . . . . . . . . .

834
—

14,227
(25)

45,908
—

—
(1,534)
(182)

— (13,605)
(17,995)
846

(1,896)
(311)

Net cash (used for) provided by investing  activities . . . . . . . . .

(882)

11,995

15,154

Cash flows from financing activities:

Proceeds from stock options exercised . . . . . . . . . . . . . . . . . . . .
Proceeds from common stock issuance,  net . . . . . . . . . . . . . . . . .

Net cash provided by financing activities . . . . . . . . . . . . . . . . .

Net change in cash and cash equivalents . . . . . . . . . . . . . . . . . . . . . .
Cash and cash equivalents, beginning  balance . . . . . . . . . . . . . . . . . .

3,462
77,521

80,983

39,517
69,639

1,314
38,045

39,359

38,020
31,619

1,093
24,916

26,009

21,014
10,605

Cash and cash equivalents, ending balance . . . . . . . . . . . . . . . . . . . .

$109,156

$ 69,639

$ 31,619

Supplemental disclosure:
Cash paid for income taxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$

1

$

1

$

27

The accompanying notes are an integral part of the consolidated financial statements.

64

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS

AS OF JUNE 30, 2010

A. Nature of Business and Plan of Operations

ImmunoGen, Inc. (the Company) was incorporated in Massachusetts in 1981 and is focused on the

development of antibody-based anticancer therapeutics.  The Company has  incurred operating losses
and negative cash flows from operations since inception, incurred a net loss of approximately
$50.9 million during the fiscal year ended  June 30, 2010, and has an accumulated deficit of
approximately $372.4 million as of June  30, 2010. The  Company has primarily funded these  losses
through payments received from its collaborations  and equity financings. To date, the Company has  no
product  revenue and management expects operating losses to continue for the foreseeable future. The
Company believes that its existing cash,  cash equivalents  and marketable securities as of June 30, 2010
together with milestone payments and research and development funding that the Company expects to
receive under its existing collaborations,  will be sufficient to allow it to fund its  current operating  plan
through approximately the first half of fiscal 2012.

The Company may raise additional funds  through  equity or debt financings or generate revenues
from collaborative partners through a combination of upfront license payments,  milestone payments,
research funding, and clinical material reimbursement.  There can  be  no assurance that the Company
will be able to obtain additional debt  or  equity financing  or generate revenues from collaborative
partners, on terms acceptable to the  Company,  or at  all. The failure of the Company to obtain
sufficient funds on acceptable terms  when needed 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 and/or clinical projects.

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, 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 Securities Corp. (established in December 1989), and ImmunoGen Europe
Limited (established in October 2005).  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.

65

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Subsequent Events

The Company has evaluated all events or transactions that  occurred after June 30, 2010 up

through the date the Company issued  these financial statements. In  July 2010, the Company sold
$1.1 million of the remaining securities in its investment portfolio, resulting in a  net realized gain of
$339,000. The Company did not have  any other  material recognizable or unrecognizable  subsequent
events during this period.

Revenue Recognition

The Company enters into licensing and development agreements with collaborative partners for

the development of monoclonal antibody-based anticancer therapeutics. The Company follows the
provisions of Financial Accounting Standards Board’s Accounting Standards Codification (ASC) Topic
605, ‘‘Revenue Recognition.’’ Accordingly, the Company recognizes revenue related to research
activities as they are performed, as long  as there is persuasive evidence of an arrangement, the  fee is
fixed or determinable, and collection  of the related receivable is probable. The terms  of the Company’s
agreements contain multiple elements  which typically include non-refundable license fees, payments
based upon the achievement of certain  milestones and royalties  on product sales. The Company
evaluates such arrangements to determine if the deliverables  are separable into units of accounting  and
then applies applicable revenue recognition criteria to each unit of accounting. Agreements containing
multiple elements are divided into separate units of accounting if  certain criteria are met, including
whether the delivered element has stand-alone value to the  collaborator  and whether there is objective
and reliable  evidence of the fair value  of the  undelivered obligation(s).  The consideration received is
allocated among the separate units either on the basis of each unit’s fair value or using  the residual
method, and the applicable revenue recognition criteria are  applied  to  each of the separate units.

In October 2009 a new accounting standard for the recognition of revenue arrangements  with
multiple deliverables was issued. This  standard provides accounting principles and application guidance
on whether multiple deliverables exist, how  the arrangement should be separated, and  how the
consideration should be allocated. This  new approach is effective prospectively for revenue
arrangements entered into or materially modified in fiscal years beginning on  or after June 15, 2010
(our  fiscal year 2011). While the Company does not  expect the  adoption of this standard to have a
material impact on its financial position  and results of operations, this standard  may impact the
Company in the event it completes future transactions or  modifies existing collaborative  relationships.
Refer to Note B, Recent Accounting Pronouncements  to  the Consolidated Financial Statements for
additional discussion of this standard  and its impact  on the Company.

66

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

At June  30, 2010, the Company had the following three types of collaborative contracts with the

parties identified below:

(cid:129) Exclusive license to use the Company’s TAP technology and/or certain other intellectual property

to develop compounds to a single antigen:

Amgen (multiple single-target licenses)

Bayer Schering Pharma (single-target license)

Biogen Idec (single-target license)

Biotest (single-target license)

Genentech, a member of the Roche  Group (multiple single-target licenses)

sanofi-aventis (license to multiple individual  targets)

(cid:129) Option agreement for a defined period of time  to  secure licenses to use the Company’s TAP

technology to develop anticancer compounds to a  limited  number of targets on established terms
(broad option agreement):

Amgen

sanofi-aventis

(cid:129) Non-exclusive license to the Company’s humanization technology:

sanofi-aventis

Generally, the foregoing collaboration agreements provide that the Company will (i) at the

collaborator’s request, manufacture and provide to them preclinical and clinical materials reimbursed at
the Company’s cost, or, in some cases,  cost plus a margin, (ii) earn payments upon the collaborators’
achievements of certain milestones and (iii) earn royalty payments, generally until the later  of the last
applicable patent expiration or 10 to 12 years after product launch. Royalty rates may vary over the
royalty term depending on certain intellectual property  rights. The Company is  required to provide
technical training and to share any process improvements  and know-how with its  collaborators during
the research term of the collaboration  agreements.

Generally, upfront payments on single-target licenses  are deferred  over the period of the

Company’s substantial involvement during development. The determination of the length of this period
is subject to judgment and estimation and can have an impact on the amount of revenue recognized in
a given period. The Company’s employees are  available to assist  the Company’s collaborators during
the development of their products. The  Company estimates this development phase to begin at the
inception of the collaboration agreement  and conclude at the  end of non-pivotal Phase II testing.  The
Company believes this period of involvement is,  depending on  the nature of the license, on average six
and one-half years. Quarterly, the Company reassesses its periods of substantial involvement over which
the Company amortizes its upfront license  fees  and  makes  adjustments as appropriate. In  the event that
a single-target license were to be terminated, the Company would recognize as revenue any  portion of
the upfront fee that had not previously been recorded  as  revenue, but was classified as deferred
revenue at the date of such termination.

67

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

The Company defers upfront payments received from its broad option agreements over the period

during which the collaborator may elect  to receive  a license. These periods are specific to each
collaboration agreement, but are between three and  12 years.  If a collaborator selects  an option  to
acquire a license under these agreements, any option fee  is  deferred and  recorded over the life of the
option, generally 12 to 18 months. If a  collaborator exercises an option and the Company  grants a
single-target license to the collaborator, the Company defers the license fee  and accounts for the fee  as
it would an upfront payment on a single-target license, as  discussed above. Upon exercise of an  option
to acquire a license, the Company would recognize any  remaining deferred option  fee over the period
of the Company’s substantial involvement under the license acquired. In the event that a broad option
agreement were to be terminated, the  Company would  recognize as revenue any  portion of the upfront
fee that had not previously been recorded as  revenue, but was classified as deferred revenue at the  date
of such termination. In the event a collaborator  elects to discontinue development  of a specific product
candidate under a single-target license,  but  retains  its right to use the  Company’s technology to develop
an alternative product candidate to the same target or a  target substitute, the Company would cease
amortization of any remaining portion of  the upfront fee until there  is substantial preclinical activity  on
another product candidate and the Company’s remaining period  of substantial  involvement can  be
estimated.

When milestone fees are specifically tied to a separate  earnings  process and are deemed to be

substantive and at risk, revenue is recognized when  such milestones are achieved. In  addition, the
Company recognizes research and development support revenue from  certain collaboration and
development agreements based upon the  level of research  services performed during the period of the
relevant research agreement. Deferred revenue  substantially represents amounts received under
collaborative agreements and not yet  earned pursuant to these policies.  Where the Company has no
continuing involvement, the Company will record non-refundable license fees as revenue upon receipt
and will record revenue upon achievement  of milestones by its collaborative partners.

The Company produces preclinical and clinical materials for its  collaborators. The Company is
reimbursed for its  direct costs and a  portion of its overhead costs to produce clinical materials. The
Company recognizes revenue on preclinical and clinical materials when the materials have passed all
quality testing required for collaborator acceptance  and  title and risk of loss have  transferred to the
collaborator.

The Company also produces research material  for potential collaborators under material transfer

agreements. Additionally, the Company performs research activities,  including  developing  antibody-
specific  conjugation processes, on behalf of its collaborators and potential collaborators  during the early
evaluation and preclinical testing stages  of drug development. Generally,  the Company is reimbursed
for certain of its direct and overhead costs of producing these materials or providing these services.
The Company records the amounts received for the preclinical materials produced or services
performed as a component of research  and  development support. The Company  also develops
conjugation processes for materials for later stage testing and commercialization for  certain
collaborators. The Company is reimbursed for certain of  its direct and  overhead costs  and may  receive
milestone payments for developing these  processes which are recorded as a component of research and
development support.

68

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Inventory

Inventory costs primarily relate to clinical trial materials being manufactured for sale  to  the

Company’s collaborators. Inventory is stated at  the lower of cost or market  as determined on a first-in,
first-out (FIFO) basis.

Inventory at June 30, 2010 and 2009  is  summarized below (in thousands):

Raw materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Work in process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$1,242
—

$ 952
884

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$1,242

$1,836

June 30,

2010

2009

Raw materials inventory consists entirely of DM1 or DM4 ,  our proprietary cell-killing agents,
which  are included in all Targeted Antibody Payload, or TAP, product candidates currently in preclinical
and clinical testing with our collaborators. All  raw  materials  inventory is  currently procured  from a
single supplier.

Inventory cost is stated net of write-downs of $939,000  and  $1.8 million  as of June 30, 2010  and

June 30, 2009, respectively. The write-downs represent the  cost of raw materials that the Company
considers to be in excess of a twelve-month supply  based on  firm, fixed orders and  projections from its
collaborators as of the respective balance sheet date.

Due to yield fluctuations, the actual amount of  raw materials that will  be  produced in future
periods under supply agreements is highly uncertain. As  such, the amount of raw materials produced
could be more than is required to support the development  of  the Company’s  and its collaborators’
product  candidates. Such excess supply, as determined  under the Company’s inventory reserve policy, is
charged to research and development  expense.

The Company produces preclinical and clinical materials for its  collaborators either in  anticipation

of or in support of preclinical studies  and  clinical trials, or for process  development and analytical
purposes. Under the terms of supply  agreements with its collaborators, the Company generally receives
rolling six-month firm, fixed orders for  conjugate  that the Company  is required  to  manufacture, and
rolling twelve-month manufacturing projections for  the quantity  of conjugate the  collaborator expects to
need in any given twelve-month period. The amount of clinical  material produced is  directly related to
the number of Company and collaborator anticipated  or on-going  clinical trials  for which the Company
is producing clinical material, the speed  of enrollment in those trials, the dosage schedule of each
clinical trial and the time period, if any, during which  patients in the trial  receive clinical benefit from
the clinical materials. Because these elements are difficult to estimate  over the course of a  trial,
substantial differences between collaborators’ actual  manufacturing  orders  and their projections could
result in usage of raw materials varying  significantly from estimated usage at  an earlier reporting
period. To the extent that a collaborator  has provided the Company  with a firm, fixed order, the
collaborator is required by contract to  reimburse  the Company the  full  cost of  the conjugate and any
agreed margin thereon, even if the collaborator  subsequently cancels the manufacturing  run.

69

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

The Company accounts for the raw material inventory  as follows:

a)

b)

c)

d)

raw material is capitalized as inventory upon  receipt of the materials. The portion of  the raw
material the Company uses in the production  of its  own products is recorded as research and
development expense as consumed;

to the extent that the Company  has up to twelve months of firm, fixed  orders  and/or
projections from its collaborators, the Company capitalizes the  value of raw materials that will
be used in the production of conjugate subject  to  these firm, fixed orders and/or  projections;

the Company  considers more than a  twelve  month supply of raw materials that is not
supported by firm, fixed orders or projections  from its collaborators  to  be  excess and
establishes a reserve to reduce to zero the value of any such excess raw material inventory
with a corresponding charge to research  and  development expense; and

the Company  also considers any other external factors and information of which it  becomes
aware and assesses the impact of such factors or information on  the net realizable value of the
raw material inventory at each reporting period.

During  the year ended June 30, 2008, the  Company  obtained additional amounts of DM1 and

DM4 from a new supplier. Due to the  need to evaluate the process which was developed to prepare
such material from this new supplier  across multiple batches, the Company had  committed to a  level of
production which yielded more material  than would be required by  its  collaborators over the next
twelve months. As a result, the Company  recorded  a $2.1 million charge to research and  development
expense related to excess inventory during the year  ended June  30, 2008. The Company also recorded
$1.6 million as research and development expense to write down  this material to its net  realizable
value. During fiscal 2010, we  obtained  additional  amounts of DMx from our  supplier which yielded
more material than would be required  by our collaborators over the next  twelve months and as a result,
we recorded $900,000 of charges to research and development expense related  to  raw material
inventory identified as excess. The Company  also recorded $28,000 as research and development
expense to write down certain raw material inventory to its net realizable value. No similar  costs were
recorded  during the year ended June 30,  2009. Increases in the Company’s on-hand supply  of raw
materials, or a reduction to the Company’s collaborators’ projections, could result  in significant  changes
in the Company’s estimate of the net  realizable  value of such raw material inventory. Reductions in
collaborators’ projections could indicate  that the Company  has additional excess raw  material  inventory
and the Company would then evaluate the  need  to  record further write-downs  as charges to research
and development expense.

Unbilled Revenue

The majority of the Company’s unbilled revenue at June 30, 2010 and 2009 represents research

funding earned based on actual resources utilized under the Company’s various collaborator
agreements.

70

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Restricted Cash

Restricted cash at June 30, 2010 and 2009 are cash  balances  securing irrevocable letters of credit
required for the Company to receive value added tax  reimbursements related to payments to foreign
vendors for activities performed in fiscal  2008 and 2007 and as security deposits for the Company’s
leased facilities.

Other Accrued Liabilities

Other accrued liabilities consisted of  the following at June 30, 2010 and 2009 (in thousands):

Accrued contract payments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accrued clinical trial costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accrued professional services . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accrued employee benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accrued public reporting charges . . . . . . . . . . . . . . . . . . . . . . . . .
Other current accrued liabilities . . . . . . . . . . . . . . . . . . . . . . . . . .

June 30,

2010

2009

$ 324
537
709
233
111
490

$ 130
160
722
306
113
135

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$2,404

$1,566

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 and (iv) manufacturing operations.

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.

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. Financial instruments  that
potentially subject the Company to concentrations  of credit  risk consist principally  of  marketable
securities. Marketable securities at June 30,  2010 generally consist of high-grade  corporate bonds and

71

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

asset-backed securities. 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.

Derivative instruments include a portfolio of short  duration foreign currency  forward contracts
intended to mitigate the risk of exchange fluctuations for existing or anticipated receivable  and payable
balances denominated in foreign currency. Derivatives are estimated at fair value and classified as  other
current assets or liabilities. The fair value  of these instruments represents  the present value  of
estimated future cash flows under the  contracts, which are a function of underlying interest rates,
currency rates, related volatility, counterparty creditworthiness and duration of the contracts. Changes
in these factors or a combination thereof  may affect the fair value of these instruments.

The Company does not designate foreign  currency forward contracts as hedges for accounting
purposes, and changes in the fair value of  these instruments are recognized in  earnings during the
period of change. Because the Company  enters into forward contracts  only as an economic hedge, any
gain or loss on the underlying foreign-denominated  existing or  anticipated  receivable or payable
balance would be offset by the loss or  gain on the forward contract.  Net (losses)  gains on  forward
contracts for the years ended June 30,  2010, 2009 and 2008 were ($219,000),  ($234,000) and $699,000,
respectively, and are included in the accompanying Consolidated Statement of Operations as other
(expense) income, net. As of June 30, 2010, we had outstanding forward contracts with amounts
equivalent to approximately $1.6 million (A1.3 million), all maturing on or before January 4, 2011. As
of June 30, 2009, we had outstanding forward contracts with amounts equivalent to approximately
$517,000 (A371,000). The Company does not anticipate using derivative instruments for any purpose
other than hedging exchange rate exposure.

Cash Equivalents

Cash equivalents consist principally of  money  market  funds and other investments with original

maturities of three months or less at  the  date of purchase.

Marketable Securities

The Company invests in marketable securities of highly  rated financial institutions  and investment-
grade debt instruments and limits the amount of credit exposure  with any one entity. The Company has
classified its marketable securities as ‘‘available-for-sale’’ and, accordingly, carries such securities  at
aggregate fair value. Unrealized gains  and losses, if any, are reported as other comprehensive income
(loss) in shareholders’ equity. The amortized  cost of debt securities in this category  is adjusted for
amortization of premiums and accretion of discounts  to  maturity. Such amortization and accretions are
included in investment income, net, as  well as  interest and  dividends. Realized gains and losses on
available-for-sale securities are also included  in other (expense) income, net. Charges for the
impairment of available-for-sale securities that were determined to be other-than-temporary and related
to a credit loss are included in the accompanying Consolidated Statement of Operations as
other-than-temporary impairment. The cost  of securities sold is based  on the specific identification
method.

72

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Other-than-Temporary Impairments

In April 2009, the Company implemented a newly issued accounting  standard which provides
guidance for the recognition, measurement and  presentation of other-than-temporary impairments.
Under this standard, an other-than-temporary  impairment must be recognized  through earnings if an
investor has the intent to sell the debt  security or if it is more likely than not that the investor will be
required to sell the debt security before recovery of its amortized cost basis.  In the event of a credit
loss, only the amount associated with  the  credit loss is recognized in net income (loss). The amount of
loss relating to other factors is recorded  in  accumulated other comprehensive income (loss). As a  result
of the adoption, $54,000 of previously  recognized  other-than-temporary impairment  charges was
reclassified to other comprehensive loss  as  a cumulative  effect adjustment.

The Company conducts periodic reviews to identify and  evaluate each investment that has an

unrealized loss, which exists when the  current  fair  value of an  individual security is less than its
amortized cost basis. Unrealized losses on available-for-sale securities that are determined to be
temporary, and not related to credit loss, are  recorded in  accumulated other  comprehensive loss.

For available-for-sale debt securities  with unrealized losses, management performs an analysis to

assess whether it intends to sell or whether it would more likely than not be required  to  sell the
security before the expected recovery of  the amortized cost  basis. Where the Company intends to sell a
security, or may be required to do so,  the security’s  decline in fair value is deemed to be
other-than-temporary and the full amount  of the unrealized loss is recorded in the statement of
operations as an other-than-temporary impairment charge.  When this is not the  case, the Company
performs additional analysis on all securities with unrealized losses  to  evaluate losses  associated with
the creditworthiness of the security. Credit losses are  identified where the Company does not expect to
receive cash flows, based on using a single best estimate, sufficient  to  recover the amortized cost basis
of a security and these are recognized  as other-than-temporary impairment.

Fair Value of Financial Instruments

As of July 1, 2008, the Company partially adopted the provisions of ASC Topic 820, ‘‘Fair  Value

Measurements and Disclosures,’’ for financial assets and liabilities recognized at fair value on a
recurring basis. ASC Topic 820 defines  fair value, establishes a framework for measuring  fair value in
accordance with accounting principles  generally accepted  in the  U.S., and expands disclosures  about fair
value measurements. Certain provisions of ASC  Topic 820 related to other non-financial assets  and
liabilities were adopted by the Company  on  July 1, 2009 and  did not have a material impact on its
financial position or results of operations  upon adoption; however, this standard  may impact the
Company in subsequent periods and  require  additional disclosures.

Fair value is defined under ASC Topic 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 fair value hierarchy to measure fair

73

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

value which is based on three levels of  inputs, of which  the first two are considered observable and  the
last unobservable, as follows:

(cid:129) Level 1—Quoted prices in active markets  for identical  assets  or liabilities.

(cid:129) 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.

(cid:129) 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 June 30, 2010, the Company held certain assets  that are required to be measured  at fair
value on  a recurring basis, including cash equivalents and marketable securities. The following table
represents the fair value hierarchy for the  Company’s financial assets measured at fair value on  a
recurring basis as of June 30, 2010 (in thousands):

Cash, cash equivalents and restricted cash .
Available-for-sale marketable securities . . .

Fair Value Measurements at June 30, 2010 Using

Quoted Prices in
Active Markets for
Identical Assets

Significant Other
Observable Inputs

Significant
Unobservable
Inputs

Total

$113,298
1,142

$114,440

(Level 1)

$113,298
—

$113,298

(Level 2)

(Level  3)

$ —
1,142

$1,142

$—
—

$—

The fair value of the Company’s investments is generally determined from  market prices based
upon either quoted prices from active  markets or other significant  observable market transactions  at
fair value.

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 . . . . . . . . . .
Computer hardware and software . . . . .
Furniture and fixtures . . . . . . . . . . . . .
Leasehold improvements . . . . . . . . . . .

5 years
3 years
5 years
Shorter of remaining lease term or 7 years

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.  The  Company recorded $41,000,
$18,000 and $103,000 of losses on the  sale/disposal of certain  furniture and equipment during the  years
ended June 30, 2010, 2009, and 2008,  respectively.

74

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Impairment of Long-Lived Assets

In accordance with ASC Topic 360, ‘‘Property, Plant, and Equipment,’’ 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. The Company evaluates the realizability  of its  long-lived assets  based on cash flow
expectations for the related asset. Any write-downs  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.

Computation of Net Loss Per Common Share

Basic and diluted net loss per common share is calculated based upon  the weighted average
number of common shares outstanding during  the period. The Company’s  common stock equivalents,
as calculated in accordance with the  treasury-stock  accounting method, are shown in the following table
(in thousands):

June 30,

2010

2009

2008

Options to purchase common stock . . . . . . . . . . . . . . . . . . .
Common stock equivalents under treasury stock method . . . .

6,065
1,853

5,529
848

5,678
483

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 June 30, 2010, the Company is authorized to grant future awards under one employee  share-

based compensation plan, which is the  ImmunoGen, Inc.  2006 Employee, Director and Consultant
Equity Incentive Plan, or the 2006 Plan.  At  the annual meeting of shareholders  on November 12, 2008,
an amendment to  the 2006 Plan was approved and an  additional 2,000,000  shares were authorized  for
issuance under this plan. As amended, the 2006  Plan  provides  for the issuance of Stock  Grants, the
grant of Options and the grant of Stock-Based Awards for up  to  4,500,000 shares  of the Company’s
common stock, as well as any shares of common stock that are represented by awards granted under
the previous stock option plan, the ImmunoGen,  Inc. Restated Stock Option Plan, or the  Former Plan,
that are forfeited, expire or are cancelled without delivery of shares of common  stock; provided,
however, that no more than 5,900,000 shares shall be added  to  the  Plan  from the Former Plan,
pursuant to this provision. Option awards 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.

The stock-based awards are accounted  for under ASC Topic  718, ‘‘Compensation—Stock
Compensation,’’ using the modified prospective transition method. Under this methodology,  the
estimated fair value of awards is charged  to the statement of operations over the requisite service
period, which is the vesting period. Such amounts have been reduced by our estimate  of forfeitures of
all unvested  awards. The fair value of  each stock option is estimated on the date of grant using  the

75

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Black-Scholes option-pricing model with the  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 data 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 June 30,

2010

2009

2008

Dividend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Volatility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Risk-free interest rate . . . . . . . . . . . . . . . . . . . . . . . . . .
Expected life (years) . . . . . . . . . . . . . . . . . . . . . . . . . . .

None

None

None
59.90% 63.11% 66.60%
3.19% 2.40% 3.72%
7.2
7.0

7.1

Using the Black-Scholes option-pricing  model, the  weighted average grant  date fair  values  of
options granted during fiscal 2010, 2009 and 2008 were $5.83, $2.73, and $2.38 per share, respectively.

A summary of option activity under the  Plan  as of June 30, 2010, and changes during the twelve

month period then ended is presented below (in thousands, except weighted-average data):

Number of
Stock
Options

Weighted- Weighted-
Average
Average
Remaining
Exercise
Life in Yrs
Price

Aggregate
Intrinsic
Value

Outstanding at June 30, 2009 . . . . . . . . .
Granted . . . . . . . . . . . . . . . . . . . . . . . .
Exercised . . . . . . . . . . . . . . . . . . . . . . .
Forfeited/Canceled . . . . . . . . . . . . . . . . .

5,529
1,461
(634)
(291)

Outstanding at June 30, 2010 . . . . . . . . .

6,065

Outstanding at June 30, 2010—vested or

unvested and expected to vest . . . . . . .

Exercisable at June 30, 2010 . . . . . . . . . .

5,483

4,011

$6.36
$9.46
$5.46
$8.66

$7.09

$7.14

$6.88

6.24

$20,014

5.99

4.96

$16,187

$15,678

As of June 30, 2010, the estimated fair value of  unvested employee awards was $5.1 million,  net of
estimated forfeitures. The weighted-average remaining vesting period  for these awards is approximately
three years.

76

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

A summary of option activity  for shares vested during  the fiscal years ended June 30, 2010, 2009

and 2008 is presented below (in thousands):

Year Ended June 30,

2010

2009

2008

Total fair value of shares vested . . . . . . . . . . . . . . . . . . . .
Total intrinsic value of options exercised . . . . . . . . . . . . .
Cash received for exercise of stock options . . . . . . . . . . . .

$2,410
1,888
3,461

$2,838
920
1,314

$2,817
1,749
1,093

During  the year ended June 30, 2009,  the Company  recorded approximately  $843,000 of stock-
based compensation expense related to certain  stock  options previously granted  to  the former Chief
Executive Officer of the Company that  were modified in accordance  with the  succession plan approved
by the Company’s Board of Directors  in  September 2008. No  similar charges were  recorded during the
years ended June 30, 2010 and 2008.

Comprehensive Loss

The Company presents comprehensive loss  in accordance with ASC Topic 220, Comprehensive
Income. Comprehensive loss is comprised  of the Company’s  net loss  for the  period and unrealized  gains
and losses recognized on available-for-sale marketable securities.

Segment Information

During  the three fiscal years ended June 30, 2010,  the Company continued to operate in  one
reportable business segment under the management approach of ASC  Topic  280, Segments Reporting,
which  is the business of discovery of monoclonal antibody-based anticancer therapeutics.

The percentages of revenues recognized from  significant customers of  the  Company in  the years

ended June 30, 2010, 2009 and 2008  are  included in  the following table:

Collaborative Partner:

Amgen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
sanofi-aventis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bayer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biogen Idec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biotest
Genentech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Year Ended
June 30,

2010

2009

2008

32% 2% 1%
28% 45% 48%
15% 2% —
13% 7% 8%
9% 13% 8%
3% 26% 34%

There were no other customers of the Company  with significant revenues  in the years ended

June 30, 2010, 2009 and 2008.

77

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

B. Summary of Significant Accounting Policies (Continued)

Recent Accounting Pronouncements

In October 2009, the FASB issued Accounting Standards  Update (ASU) No.  2009-13, ‘‘Multiple-

Deliverable Revenue Arrangements’’  (ASU No. 2009-13). ASU  No. 2009-13, which amends existing
revenue recognition accounting pronouncements and provides  accounting principles and  application
guidance on whether multiple deliverables exist, how the arrangement should be separated, and the
consideration allocated. This  guidance eliminates the requirement to establish the fair value of
undelivered products and services and instead provides for separate revenue recognition  based upon
management’s estimate of the selling  price for  an undelivered item when there is no other means to
determine the fair value of that undelivered item. Previous accounting principles required  that  the fair
value of the undelivered item be the price of the item either sold in a separate transaction between
unrelated third parties or the price charged  for each item  when the item  is sold separately by the
vendor. This was difficult to determine when the product was not individually  sold because of its
unique  features. If the fair value of all  of the elements in the arrangement was not determinable, then
revenue was deferred until all of the items  were delivered or fair value was determined.  This new
approach is effective prospectively for revenue arrangements entered into or  materially modified in
fiscal years beginning on or after June  15, 2010 (the Company’s fiscal year 2011). While the  Company
does not expect the adoption of this standard to have a material impact  on its financial position and
results of operations, this standard may  impact  the Company in the event it completes future
transactions  or modifies existing collaborative relationships.

The provisions of ASC Topic 810, ‘‘Consolidation’’, related to the changes to how a reporting
entity determines when an entity that is insufficiently  capitalized or is  not controlled through voting  (or
similar rights) should be consolidated will be effective  for fiscal years beginning after November 15,
2009 (our fiscal year 2011). Early application is not permitted. We do not expect the adoption of these
provisions to have a significant impact on our  financial position or results of operations.

In March 2010, the FASB issued guidance related to the milestone method of revenue recognition,
which  will codify a method of revenue recognition that  has  been common practice. Under this method,
contingent consideration from research and development activities that is earned upon the achievement
of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved.
This guidance is effective for annual  periods beginning on or after June 15, 2010 but may be adopted
as of  the beginning of an annual period.  Because the  Company’s current revenue recognition policy for
milestone payments is consistent with the FASB’s guidance, the Company does not expect the adoption
of this standard will have a material  effect on the  Company’s consolidated financial position, results of
operations and cash flows.

78

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

C. Agreements

Significant Collaborative Agreements

sanofi-aventis

In July 2003, the Company entered into a broad collaboration agreement  with sanofi-aventis to

discover, develop and commercialize antibody-based anticancer therapeutics.

The agreement provides sanofi-aventis with worldwide commercialization rights to new anticancer
therapeutics developed to targets that were included  in  the collaboration,  including the  right to use  the
Company’s TAP technology and humanization  technology  in the creation  of therapeutics to these
targets. The product candidates (targets)  as  of  June 30, 2010 in the collaboration  include SAR3419
(CD19), SAR566658 (CA6), SAR650984  (CD38) and additional compounds  at earlier  stages of
development that have yet to be disclosed.

The collaboration agreement entitles the  Company to receive milestone payments potentially
totaling $21.5 million for each therapeutic developed under the collaboration agreement. Through
June 30, 2010, the Company has earned  a  total  of $4 million  in milestone payments related to the three
product  candidates noted above and one target not yet  disclosed. The Company also earned an
aggregate of $8 million of milestone payments  related to two product candidates previously in the
collaboration that have been returned  to  us along with the rights to the respective  targets.

The agreement also entitles the Company to royalties on the commercial sales of any resulting

products if and when such sales commence. Sanofi-aventis is responsible for the cost of the
development, manufacturing and marketing of any  products created through the collaboration. The
Company is reimbursed for any preclinical and clinical materials that it makes  under the agreement.
The collaboration agreement also provides the Company an option to certain co-promotion rights in
the U.S.  on a product-by-product basis. The terms of the collaboration agreement allow sanofi-aventis
to terminate the Company’s co-promotion rights if  there is a  change of control of  the company.

The overall term of the agreement extends to the later of  the latest patent to expire or twelve
years after the latest launch of any product discovered, developed and/or commercialized under  the
agreement. Sanofi-aventis paid the Company  an upfront fee of $12  million in August 2003. Inclusive of
all of its allowed extensions, the agreement enabled the Company to receive committed research
funding totaling $79.3 million over the five years of the research collaboration.  The two companies
subsequently agreed to extend the date of research funding through  October 31, 2008 to enable
completion of previously agreed-upon  research. The Company recorded the research funding as  it was
earned based upon its actual resources  utilized  in the collaboration. The  Company earned $81.5 million
of committed funding over the duration of the research program, of which $2.7 million and
$10.8 million were recognized during  fiscal  years  2009  and  2008, respectively. The Company is now
compensated for research performed  for sanofi-aventis on a mutually agreed-upon basis.

In October 2006, sanofi-aventis licensed non-exclusive rights to use the Company’s proprietary

resurfacing technology to humanize antibodies to targets not included in the collaboration, including
antibodies for non-cancer applications. This license provides  sanofi-aventis with  the non-exclusive right
to use the Company’s proprietary humanization technology  through August 31, 2011 with the  right to
extend for one or more additional periods of three years each by providing the Company with written
notice prior to expiration of the then-current  license term. Under  the terms of the license, the

79

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

C. Agreements (Continued)

Company is entitled to a $1 million license  fee, half of which  was  paid upon contract signing and  the
second  half was paid in August 2008, and  in  addition, the Company is  entitled to receive milestone
payments potentially totaling $4.5 million for  each antibody humanized under this agreement and also
royalties on commercial sales, if any.

In August 2008, sanofi-aventis exercised  its  option under a 2006 agreement for expanded access to

ImmunoGen’s TAP technology. The exercise of this option enables sanofi-aventis to evaluate,  with
certain restrictions, the Company’s maytansinoid TAP technology with antibodies to targets that were
not included in the existing research  collaboration  between the companies and to license the exclusive
right to use the technology to develop  products to specific  targets on the terms in the 2006 agreement.
ImmunoGen is entitled to earn upfront  and  milestone payments potentially totaling $32 million per
target for each compound developed  under  the 2006 agreement,  as well as royalties on the commercial
sales of any resulting products. ImmunoGen also is entitled to manufacturing payments for any
materials made on behalf of sanofi-aventis. The Company received  $3.5 million with the  exercise of this
option in  August 2008, in addition to the  $500,000  ImmunoGen received in  December 2006 with the
signing of the option agreement. The agreement has  a three-year term from the date of the exercise of
the option and can be renewed by sanofi-aventis for  one additional three-year term by payment of a
$2 million fee.

Genentech

In May 2000, the Company entered into two separate agreements with Genentech. The first
agreement grants Genentech  an exclusive license to the Company’s maytansinoid TAP technology for
use with antibodies, such as trastuzumab, that target  HER2. Under the terms of this agreement,
Genentech has exclusive worldwide rights to develop and commercialize maytansinoid TAP compounds
with antibodies that target HER2. Genentech is responsible for the  manufacturing, product
development and marketing of any products resulting from the agreement. The Company received a
$2 million non-refundable payment from  Genentech upon  execution of the agreement. The  Company is
also entitled to up to $44 million in milestone payments from Genentech under this agreement,  as
amended in May 2006, in addition to  royalties  on the net sales of any resulting products. Genentech
began Phase II evaluation of T-DM1 in  July 2007 and the Company earned a $5 million  milestone
payment with this event, which is included in license and milestone fees for the fiscal year ended
June 30, 2008. Genentech and Roche  began Phase III evaluation of T-DM1 in February 2009 and the
company earned a $6.5 million milestone payment with this event. This milestone  is included in license
and milestone fees for the fiscal year  ended June 30,  2009. Through June 30, 2010, the Company  has
received $13.5 million in milestone payments.

In May 2000 the Company also entered into a ‘‘right-to-test’’ agreement with Genentech. This
agreement provided Genentech with the  right  to  test the  Company’s maytansinoid TAP technology with
Genentech antibodies to a defined number of targets on an exclusive basis for specified  option periods
and to take exclusive licenses  for individual targets on agreed-upon terms to use the Company’s
maytansinoid TAP technology to develop  products.  The Company received a non-refundable technology
access fee of $3 million when the Company entered into this five-year  agreement in May 2000, and an
additional technology access fee of $2  million when  Genentech renewed this agreement in April 2005
for the one additional three-year period allowed. The upfront fees were deferred and recognized

80

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

C. Agreements (Continued)

ratably over the period during which Genentech could elect to obtain product licenses.  Genentech no
longer has the right to designate new targets under this  ‘‘right-to-test’’ agreement.

Under this agreement, Genentech licensed exclusive rights to use  the Company’s maytansinoid

TAP technology with antibodies to four  undisclosed targets. The most recent license was taken in
December 2008. Under the terms defined  in  the 2000 ‘‘right-to-test’’ agreement, for each license the
Company received a $1 million license  fee and may  receive up to $38 million in milestone payments.
The Company is also entitled to receive  royalties on the  sales of  any resulting products.  Genentech is
responsible for the development, manufacturing, and marketing of any products resulting from these
licenses.

Biogen Idec

In October 2004, the Company entered  into  a development and license  agreement with  Biogen

Idec. The agreement grants Biogen Idec  exclusive rights  to use the Company’s maytansinoid TAP
technology to develop and commercialize therapeutic  compounds to the target Cripto. Biogen Idec is
responsible for the research, development,  manufacturing,  and  marketing of any products resulting
from the license. The Company received  a $1 million  upfront payment upon  execution of the
agreement. In January 2008, Biogen Idec  submitted an IND to the FDA for BIIB015, which was
created under this agreement. This event  triggered a  $1.5  million milestone payment to the Company.
Assuming all benchmarks are met, the  Company could receive up to $42 million in milestone payments
under this agreement. The Company  is also entitled to receive  royalties on net sales of resulting
products. The Company also receives compensation from  Biogen Idec for any product  development
research done on its behalf, as well as for  the production of preclinical and clinical  materials.

Biotest

In July 2006, the Company entered into a development and license agreement with Biotest  AG.

The agreement grants Biotest exclusive rights to use our  maytansinoid  TAP technology to develop and
commercialize therapeutic compounds  to  the target  CD138. The Company received a $1 million
upfront payment upon execution of the  agreement and  could potentially  receive up to $35.5 million in
milestone payments, as well as royalties on the sales of any resulting products. The Company receives
payments for manufacturing any preclinical  and clinical materials made at the  request of Biotest. In
September 2008, Biotest began Phase  I evaluation  of  BT062 which triggered a $500,000 milestone
payment to the Company. This milestone is included in  license and milestone fees for the fiscal  year
ended June 30, 2009.

The agreement also provides the Company with the right to elect at specific stages  during the

clinical evaluation of any compound  created  under this agreement, to participate in the U.S.
development and commercialization of that compound in  lieu of receiving  royalties on U.S. sales of
that product and the milestone payments not yet earned. The Company can exercise this right by
making a payment to Biotest of an agreed-upon fee of  $5 million or $15 million, depending on the
stage of development. Upon exercise of this  right, the Company would share equally with Biotest the
associated costs of product development  and commercialization in the U.S. along with the profit, if any,
from U.S. product sales.

81

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

C. Agreements (Continued)

Bayer Schering Pharma

In October 2008, the Company entered  into  a development and license  agreement with  Bayer

Schering Pharma AG. The agreement  grants Bayer Schering Pharma exclusive rights to use the
Company’s maytansinoid TAP technology to develop and commercialize therapeutic compounds  to  a
specific  target. Bayer Schering Pharma is responsible  for the research, development, manufacturing and
marketing of any products resulting from  the license. The Company received a $4 million upfront
payment upon execution of the agreement, and—for  each compound developed and marketed by Bayer
Schering Pharma under this collaboration—the Company  could potentially  receive up to $170.5 million
in milestone payments; additionally, the Company  is  entitled to receive royalties on the sales of any
resulting products. The Company will be compensated by Bayer Schering Pharma at a stipulated rate
for work performed on behalf of Bayer  Schering  Pharma under a mutually agreed-upon research plan
and budget which may be amended from time  to  time during the term  of the agreement. The Company
also is entitled to receive payments for manufacturing any preclinical and clinical materials at the
request of Bayer Schering Pharma as  well as for  any related  process development activities. The
Company has deferred the $4 million upfront payment and is  recognizing this amount as revenue
ratably over the estimated period of  substantial involvement. In September 2009,  Bayer Schering
Pharma reached a preclinical milestone  which triggered a  $1 million payment to the Company. This
milestone is included in license and milestone fees for the  fiscal  year ended June 30, 2010.

Amgen

In September 2009 and November 2009, the Company entered into two  development and license
agreements with Amgen Inc. granting  Amgen the exclusive right to use the Company’s maytansinoid
TAP technology to develop anticancer  therapeutics to specific targets. These licenses were taken under
an agreement established in 2000 between ImmunoGen and Abgenix, Inc., which  later was acquired by
Amgen. Under the terms of the licenses,  the Company received  a $1 million upfront payment with each
license taken. In addition to the $1 million upfront payment, the  Company is  entitled to earn milestone
payments potentially totaling $34 million  per target for each compound developed  under the
‘‘right-to-test’’ agreement, as well as royalties on  the commercial sales of any resulting products. The
Company has deferred the $1 million upfront payments  and is  recognizing these amounts as revenue
ratably over the estimated period of  substantial involvement.

Other Collaborative Agreements

In December 2004, the Company entered into a development and license agreement with  a
predecessor to Centocor Ortho Biotech,  a wholly  owned subsidiary of Johnson & Johnson. Under  the
terms of this agreement, Centocor was  granted exclusive worldwide rights to develop and commercialize
anticancer therapeutics that consist of the Company’s  maytansinoid cell-killing agent  attached to an (cid:2)v
integrin-targeting antibody that was developed by  Centocor. Under the terms of the  agreement, the
Company received an upfront payment  of $1 million upon execution of the agreement.

In December 2007, the Company licensed from Centocor  the exclusive, worldwide  right to develop

and commercialize a TAP compound,  IMGN388, that  consists of an  (cid:2)v integrin-targeting antibody
developed by them and one of the Company’s maytansinoid cell-killing  agents. This  license reallocates
the parties’ respective responsibilities  and financial obligations from the license referenced above.

82

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

C. Agreements (Continued)

Centocor has the right to opt-in on future development and commercialization of IMGN388 at an
agreed-upon stage in early clinical testing. Should Centocor not exercise this right, Centocor would be
entitled to receive milestone payments potentially  totaling $30  million, with the first payment due upon
the completion of a successful Phase  III trial,  and  also royalties on IMGN388 sales, if any. In  this
event, ImmunoGen has the right to obtain a new partner for IMGN388, with certain restrictions.
Should Centocor exercise its opt-in right,  ImmunoGen would receive an opt-in fee and be released
from its obligation to pay Centocor any milestone payments or  royalties on sales.  Both companies
would contribute to the costs of developing the  compound. The two companies  would share equally any
profits on the sales of the compound  in the  U.S. and ImmunoGen would receive royalties  on any
international sales. The companies have agreed  to  share certain third-party payments. In June 2008, the
FDA approved the IND application for IMGN388.  This event triggered  a $1 million milestone payment
to a third-party, half of which was paid by ImmunoGen. As of June 30, 2010, the maximum  amount
that may be payable in the future to such third-parties  under  this agreement is $11  million.

In July 2008, the Company received  notice  of  Millennium Pharmaceuticals Inc.’s  election to

terminate its exclusive license to the  Company’s TAP technology to develop and commercialize
antibody-based cytotoxic products directed to the  prostate  specific membrane  antigen (PSMA) target.
This license  was granted pursuant to  the Access, Option  and License Agreement between the Company
and Millennium dated March 30, 2001. As a result  of the termination, the Company recognized  the
remaining $361,000 of the $1 million  upfront  fee received from Millennium upon execution of the
license which had been previously deferred,  and  is included in license and milestone fees for  the fiscal
year ended June 30, 2009.

In August 2008, the Company received notice of  Boehringer Ingelheim’s election to terminate its
exclusive license to use the Company’s  technology to develop and  commercialize TAP compounds to
CD44 or the alternative target selected.  This license was granted pursuant to the Development and
License Agreement between the Company and  Boehringer Ingelheim dated November 27, 2001. As a
result of the termination, the Company recognized the remaining $486,000 of the $1 million upfront  fee
received from Boehringer Ingelheim  upon  execution of the license agreement which had been
previously deferred, and is included in license and milestone fees for the fiscal year ended June  30,
2009.

83

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

D. Marketable Securities

As of June 30, 2010, $109.2 million in  cash and  money  market funds were classified as cash and
cash equivalents. The Company’s cash,  cash equivalents and  marketable securities as of June 30,  2010
are as follows (in thousands):

Cash and money market funds . . . . . .
Asset-backed securities

Current . . . . . . . . . . . . . . . . . . . . .
Non-current . . . . . . . . . . . . . . . . . .

Corporate notes

Current . . . . . . . . . . . . . . . . . . . . .

Amortized
Cost

Gross
Unrealized
Gains

Gross
Unrealized
Losses

Estimated
Fair Value

$ 109,156

$ —

$ —

$ 109,156

25
810

25

8
291

—

—
(17)

—

33
1,084

25

Total

. . . . . . . . . . . . . . . . . . . . .

$ 110,016

$299

$(17)

$ 110,298

Less amounts classified as cash and

cash equivalents . . . . . . . . . . . . . . .

(109,156)

—

—

(109,156)

Total marketable securities . . . . .

$

860

$299

$(17)

$

1,142

As of June 30, 2009, $69.6 million in  cash and money market funds were classified as cash  and

cash equivalents. The Company’s cash,  cash equivalents and  marketable securities as of June 30,  2009
are as follows (in thousands):

Cash and money market funds . . . . . . . .
Asset-backed securities

. . . . . . . . . . . . . . . . . . . . . .
Current
Non-current . . . . . . . . . . . . . . . . . . .

Corporate notes

Current
. . . . . . . . . . . . . . . . . . . . . .
Non-current . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . .
Less amounts classified as cash and cash
equivalents . . . . . . . . . . . . . . . . . . . .

Amortized
Cost

Gross
Unrealized
Gains

Gross
Unrealized
Losses

Estimated
Fair Value

$ 69,639

$ —

$ — $ 69,639

395
1,024

250
25

25
201

—
1

(25)
(410)

—
—

395
815

250
26

$ 71,333

$227

$(435)

$ 71,125

(69,639)

—

—

(69,639)

Total marketable securities . . . . . . .

$ 1,694

$227

$(435)

$ 1,486

In 2010, the Company had no realized losses or gains. In 2009, the Company realized  losses of
$33,000 and had no realized gains. In 2008, the  Company realized losses of $42,000 and realized gains
of $3,000.

84

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

D. Marketable Securities (Continued)

As of June 30, 2010, the Company had 13 individual securities in its investment portfolio, of which
four  were in an unrealized loss position.  The aggregate fair  value of investments with  unrealized losses
was approximately $348,000 as of June 30, 2010, and all  of which had been in an  unrealized loss
position for a year or more, as of June 30, 2010. As of June 30, 2009, the Company  had 19 individual
securities in its investment portfolio, of which  seven  were in an unrealized loss  position. The  aggregate
fair value of investments with unrealized losses was approximately $705,000 as of  June 30, 2009, of
which  $332,000 had been in an unrealized loss position for more  than a year. See Note B
Other-than-Temporary Impairments. The Company reviewed its investments with unrealized losses and as
a result recorded $516,000 and $535,000, respectively, as an other-than-temporary impairment  charge
during the years ended June 30, 2009  and 2008. No similar charges were  incurred  during the fiscal year
ended June 30, 2010.

In July 2010, the Company sold the remaining securities in its investment  portfolio,  resulting in a

net realized gain of approximately $339,000.

E. Property and Equipment

Property and equipment consisted of the following at June 30, 2010 and 2009 (in thousands):

June 30,

2010

2009

Leasehold improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Machinery and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . .
Computer hardware and software . . . . . . . . . . . . . . . . . . . . . .
Furniture and fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Assets under construction . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 25,272
12,083
2,072
1,273
1,235

$ 25,189
11,910
1,635
1,361
766

Less accumulated depreciation . . . . . . . . . . . . . . . . . . . . . . . .

$ 41,935
(25,609)

$ 40,861
(21,190)

Property and equipment, net

. . . . . . . . . . . . . . . . . . . . . . . . .

$ 16,326

$ 19,671

Depreciation expense was approximately $4.8  million,  $5.0 million and $4.4  million for the years

ended June 30, 2010, 2009 and 2008,  respectively.

85

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

F.

Income Taxes

The difference between the Company’s expected tax benefit, as computed by applying the U.S.
federal corporate tax rate of 34% to loss  before the(benefit) provision for income taxes, and actual tax
is reconciled in the following chart (in  thousands):

Loss before income tax expense . . . . . . . . . . . . . . .

$(51,177) $(32,037) $(31,993)

Year Ended June 30,

2010

2009

2008

Expected tax benefit at 34% . . . . . . . . . . . . . . . . . .
State tax benefit net of federal benefit
. . . . . . . . . .
Increase in valuation allowance, net . . . . . . . . . . . .
Expired loss and credit carryforwards . . . . . . . . . . .
Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$(17,400) $(10,893) $(10,888)
(394)
4,538
6,235
536

(2,002)
11,991
6,858
288

(677)
1,531
7,924
2,015

(Benefit) provision for income taxes . . . . . . . . . . . .

$

(265) $

(100) $

27

At June 30, 2010, the Company has net operating loss carryforwards of approximately

$229.1 million available to reduce federal taxable income, if any, that expire in 2011  through 2030 and
$143.1 million available to reduce state taxable income, if any,  that expire  in fiscal 2011 through  fiscal
2015. A portion of such carryforwards  related to the exercise  of stock  options  and the  related tax
benefit will result in an increase in additional  paid-in  capital if and when realized. The Company also
has federal and state research tax credits of approximately $9.4 million available to offset federal  and
state income taxes, which expire beginning in fiscal  2011. 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 as  of June  30, 2010 and 2009
are as follows (in thousands):

June 30,

2010

2009

Net operating loss carryforwards . . . . . . . . . . . . . . . . . . . . . .
Research and development tax credit carryforwards . . . . . . . .
Property and other intangible assets . . . . . . . . . . . . . . . . . . .
Deferred revenue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stock-based compensation . . . . . . . . . . . . . . . . . . . . . . . . . .
Deferred lease incentive . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other liabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 85,459
7,986
197
4,581
1,510
3,747
2,444

$ 74,626
8,081
(745)
5,005
879
4,132
2,148

Total deferred tax assets . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Valuation allowance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 105,924
(105,924)

$ 94,126
(94,126)

Net deferred tax assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$

— $

—

86

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

F.

Income Taxes (Continued)

The valuation allowance increased by $11.8  million during  2010 due primarily to the greater net

loss recognized during the year compared to last and deferred revenue timing differences.

Utilization of the NOL and R&D 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 Section 382 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 R&D  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 has not currently completed  a study to assess whether a change of control
has occurred or whether there have been multiple changes of control since its  formation due to the
significant complexity and cost associated  with such study and the  possibility that there could be
additional changes in control in the future. If the Company  has experienced a change of control at any
time since its formation, utilization of  its  NOL or R&D credit carry forwards would be subject to an
annual limitation under Section 382 which  is  determined by  first multiplying the value of the
Company’s stock at the time of the ownership change  by the applicable long-term tax-exempt rate, and
then could be subject to additional adjustments, as required. Any limitation may result in expiration of
a portion of the NOL or R&D credit  carry forwards before utilization. Further, until a study is
completed and any limitation known,  no amounts are being presented  as an uncertain tax position. The
Company does not expect to have any  taxable income for at least the next several years.

The Company did not recognize any interest  and  penalties associated  with 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 our  unrecognized tax benefits will not impact our effective
tax rate. The Company’s loss carryforwards are  subject to adjustment by state and federal taxing
authorities, commencing when those  losses  are utilized to reduce taxable income.

G. Capital Stock

Sale of Common Stock

On April 9, 2010, the Company filed a  Registration Statement on Form  S-3 with the Securities and

Exchange Commission. The Securities and Exchange Commission declared the Registration Statement
effective on April 22, 2010. Subject to  the Company’s ongoing obligations under the Securities Act of
1933, as amended, and the Securities  Exchange Act of 1934, as amended, the Registration Statement
permits the Company to offer and sell  up to an aggregate  of $125 million of its common stock.
Pursuant to the shelf registration statement,  in May  2010, the Company issued  and sold 10,350,000
shares of its common stock at $8.00 per share through a  public offering resulting in gross proceeds of
$82.8 million.

87

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

G. Capital Stock (Continued)

On July 11, 2007, the Company filed a Registration  Statement on  Form S-3  with the Securities and

Exchange Commission. The Registration  Statement permitted the Company to offer and  sell up to an
aggregate of $75 million of its common  stock.  Pursuant to the shelf  registration statement, in June
2009, the Company issued and sold 5,750,000 shares of its common stock at $7.00 per share through  a
public offering resulting in gross proceeds  of  $40.3  million, and in June 2008, a  private investor
purchased 7,812,500 shares of its common stock at  $3.20 per share resulting  in gross proceeds of
$25 million.

Common Stock Reserved

At June  30, 2010, the Company has reserved 7.81  million  shares of authorized common stock for
the future issuance of shares under the 2006 Plan. See ‘‘Stock-Based  Compensation’’ in Note B for a
description of the 2006 Plan and the  Former  Plan.

Stock Options

As of June 30, 2010, the 2006 Plan was the  only employee share-based compensation plan of  the

Company. During the year ended June 30, 2010, holders of options issued under the 2006  Plan and the
Former Plan exercised their rights to acquire an  aggregate of 634,178 shares of  common stock at  prices
ranging from $2.03 to $8.57 per share. The total proceeds to the  Company from these option exercises
were approximately $3.5 million.

The Company has granted options at  the fair market value of the  common stock on the date of

such grant. The following options and  their  respective weighted-average exercise prices per share were
exercisable at June 30, 2010, 2009 and  2008:

Exercisable
(in thousands)

Weighted-
Average
Exercise Price

June 30, 2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
June 30, 2009 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
June 30, 2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4,011
3,906
3,430

$6.88
$7.25
$7.57

2001 Non-Employee Director Stock Plan

In November 2001, the Company’s shareholders approved the  establishment of the  2001

Non-Employee Director Stock Plan,  or the 2001  Director Plan, and  50,000 shares of common stock to
be reserved for grant thereunder. The 2001 Director Plan provided for  the  granting of awards to
Non-Employee Directors and, at the election of Non-Employee Directors, to have all or  a portion of
their awards in the form of cash, stock,  or stock  units. All stock  or  stock units are  immediately vested.
The number of stock or stock units issued was determined by  the market value  of  the Company’s
common stock on the last date of the  Company’s fiscal quarter for  which the services are  rendered.
The 2001 Director Plan was administered  by the Board  of  Directors which was authorized to interpret
the provisions of the 2001 Director Plan,  determine which  Non-Employee  Directors would  be  granted
awards, and determine the number of  shares of  stock  for  which a stock right will be granted. The 2001
Director Plan was replaced in 2004 by  the 2004  Non-Employee  Director Compensation and Deferred
Share Unit Plan.

88

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

G. Capital Stock (Continued)

During  the years ended June  30, 2010, 2009 and 2008, the  Company recorded approximately
$10,000, $84,000, and ($38,000) in compensation expense (expense reduction), respectively, related to
approximately 15,000 stock units outstanding  under  the 2001 Director  Plan. The value  of the stock units
is adjusted to market value at each reporting period.  No  stock units  have been issued under  the 2001
Plan subsequent to June 30, 2004.

2004 Non-Employee Director Compensation  and Deferred Share  Unit Plan

In June 2004, the Board of Directors approved  the establishment of the 2004 Non-Employee
Director Compensation and Deferred Share Unit Plan, or the 2004 Director  Plan. The  2004 Director
Plan provided for the compensation  to  Non-Employee Directors, awarding their annual retainers in the
form of deferred share units, and, at their  discretion, to have  all or a portion  of their  other
compensation such as meeting fees in the form of  cash or deferred share units. The deferred  share
units for annual retainers vested one-twelfth  monthly over  the next year  after the award; other deferred
share units vested immediately upon issuance. The  number of deferred share units issued was
determined by the market value of the Company’s common stock on the last  date of the  Company’s
fiscal year prior to the fiscal year for  which services were rendered. The deferred share  units were to be
paid out in cash to each non-employee director based upon the market value of the  Company’s
common stock on the date of such director’s retirement  from the Board  of Directors of  the Company.
The 2004 Director Plan was administered  by the Board  of  Directors.

The 2004 Director Plan was amended on  September 5, 2006. Under the terms of the amended

2004 Director Plan, the redemption amount of deferred  share units will  be  paid in shares of common
stock of the Company under the 2006  Plan  in lieu of cash. As a  result of the change  in payout
structure, the value of the vested awards was  transferred to  additional paid-in capital  as of the
modification date and the total value of  the awards,  as calculated on the modification date,  was
expensed over the remainder of the vesting period. Accordingly, the value of the  share units  is fixed
and will no longer be adjusted to market value  at each reporting period. In addition, the amended 2004
Director Plan changed the vesting for annual retainers to take  place quarterly over the three years after
the award and the number of deferred  share units awarded  for all compensation is now  based on the
market value of the Company’s common  stock on the  date of the award.

On September 16,  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 policy was  amended  on November  11, 2009 to provide that, whenever the
Board has a non-employee Chairman  in lieu of a Lead Director, the cash payment for the
non-employee Chairman of the Board shall be the same as the cash compensation that would otherwise
have been payable to the Lead Director.  Effective November 12, 2009, non-employee directors became
entitled to receive annual meeting fees  and committee fees under  the new policy. The new policy made
changes to the equity portion of the  non-employee director compensation, but left  the cash  portion
unchanged. Effective November 11, 2009, non-employee directors became entitled to receive deferred
stock units under the new policy as follows.

(cid:129) New non-employee directors will be initially awarded a number of deferred stock units having  an
aggregate market value of $65,000, based on the closing price of our common stock on the date
of their initial election to the Board. These  awards  will vest quarterly over three years from  the

89

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

G. Capital Stock (Continued)

date  of grant, contingent upon the individual remaining a director of ImmunoGen as of each
vesting date.

(cid:129) On the first anniversary of a non-employee director’s initial  election to the Board, such

non-employee director will be awarded a number  of deferred stock  units  having an aggregate
market value of $30,000, based on  the closing price  of our common stock on  such date of grant
and pro-rated based on the number of whole  months remaining between the first day of the
month in which such grant date occurs and  the first October 31 following the grant date. These
awards will generally vest quarterly over  approximately the period from the grant date  to  the
first November 1 following the grant  date, contingent upon the individual remaining a director
of ImmunoGen as of each vesting date.

(cid:129) Thereafter, non-employee directors  in general will  be  annually awarded a  number of deferred
stock units having an aggregate market value of $30,000, based on the closing price of our
common stock on the date of our annual meeting of shareholders. These  awards will vest
quarterly over approximately one year from the date of grant, contingent upon the individual
remaining a director of ImmunoGen  as of each vesting  date.

As with the 2004 Plan, 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 be settled in shares
of our common stock issued under our  2006 Plan 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. The new
policy provides that all unvested deferred stock units will automatically vest immediately prior to the
occurrence of a change of control, as defined in the 2006 Plan.

In connection with the adoption of the new  compensation policy, the Board also amended the

2004 Plan as follows:

(cid:129) All unvested deferred stock awards (other than any unvested initial  awards) were vested in full

on September 16, 2009 unless the date such deferred stock units were credited to the
non-employee director was less than  one  year prior  to  September 16, 2009, in which case such
unvested deferred stock units will vest  on the first  anniversary of the date such deferred  stock
units were credited to the non-employee director.

(cid:129) All unvested deferred stock awards will automatically vest immediately  prior to the  occurrence

of a change of control.

Pursuant to the Compensation Policy for Non-Employee Directors and the 2004 Director  Plan, as

amended, the Company recorded approximately $460,000 in  compensation  expense during the  year
ended June 30, 2010 related to the issuance of 42,000 deferred share units and  183,000 deferred  share
units previously issued under the 2004 Director Plan. Pursuant to the 2004 Director Plan, as amended,
the Company recorded approximately $175,000  in  compensation expense during  the year ended
June 30, 2009 related to the issuance  of 54,000 deferred share units and 129,000 deferred share  units
previously issued under the 2004 Director Plan. The Company recorded approximately $92,000 in
compensation expense during the year  ended June 30, 2008 related to the issuance of  49,000 deferred
share units and 108,000 deferred share  units  previously issued under the 2004  Director Plan.

90

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

H. Commitments and Contingencies

Leases

Effective July 27, 2007, the Company entered into a  lease agreement with Intercontinental Fund

III for the rental of approximately 89,000 square feet  of laboratory and office  space at 830 Winter
Street, Waltham, MA. The Company uses  this space  for its corporate headquarters  and other
operations. The initial term of the lease is for  twelve  years  with an  option for the Company to extend
the lease for two additional terms of five years. The Company is required to pay certain operating
expenses for the leased premises subject to escalation charges for certain expense increases over a base
amount. The Company entered into  a  sublease  in December 2009 for 14,100 square feet of this space
in Waltham through January 2015, with  the sublessee  having an option to extend the term for an
additional two years.

As part of the lease agreement, the Company received a construction  allowance of  up to

approximately $13.3 million to build out  laboratory and office space  to  the Company’s specifications.
After completion, the Company had  recorded $12.0 million of leasehold improvements under the
construction allowance. The Company received $10.8 million from the  landlord  and paid  out the same
amount towards these leasehold improvements. The remaining balance of the  improvements was paid
directly by the landlord. The lease term  began on October 1, 2007,  when the  Company obtained
physical control of the space in order  to  begin  construction.

Under the terms of the agreement, any remaining construction allowance was  to  be  applied evenly
as a credit to rent for the first year. The  final balance of the construction allowance was  determined in
August 2008, resulting in a credit of  $1.3 million to the Company  from the landlord during the  fiscal
year 2009 relating to the first  year of  occupancy.

At June  30, 2010, the Company also leases facilities  in Norwood and Cambridge, MA under
agreements through 2011. The Company is required to pay certain operating  expenses for the leased
premises subject to escalation charges  for certain expense increases over a base amount. The  Company
entered into a sub-sublease in May 2008  for the  entire space in Cambridge, MA  through October 2010,
the remainder of the sublease. Both the  lease and  sub-sublease  for the Cambridge facility were
terminated as of July 31, 2010.

Facilities rent expense, net of sublease income, was approximately $5.4 million, $5.0 million and

$5.3 million during fiscal years 2010,  2009 and 2008, respectively. During fiscal 2008, the Company
recorded  $1.8 million of rent expense related  to  the Waltham, MA facility for the period prior to
occupancy, which has been classified  as general and administrative expense in the accompanying
Consolidated Statement of Operations for the  year ended June 30, 2008.

91

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

H. Commitments and Contingencies (Continued)

As of June 30, 2010, the minimum rental commitments,  including real estate taxes and  other

expenses, for the next five fiscal years  and thereafter under the non-cancelable operating  lease
agreements discussed above are as follows  (in thousands):

2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2012 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2013 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2015 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thereafter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$ 5,829
4,831
4,831
4,898
5,098
24,974

Total minimum lease payments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Total minimum rental income from subleases . . . . . . . . . . . . . . . . . . . . . .

$50,461
(3,063)

Total minimum lease payments, net . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

$47,398

Collaborations

The Company is contractually obligated  to  make potential future  success-based regulatory
milestone payments in conjunction with certain collaborative agreements. These payments are
contingent upon the occurrence of certain future  events and, given  the nature of these events,  it is
unclear when, if ever, the Company may be required to pay such  amounts.  Further,  the timing of any
future payment is not reasonably estimable. As of June 30, 2010, the maximum amount that may be
payable in the future under such arrangements  is approximately $43.2  million.

Litigation

The Company is not party to any material  litigation.

I.

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. Effective  February 1, 2008, the Company
increased its matching contribution to  50% of  the first 6%  of  the eligible employees’ contributions,
compared to 20% of the first 7% of the eligible  employees’  contributions previously. In fiscal years
2010, 2009 and 2008, the Company’s contributions to the  401(k) Plan  totaled  approximately  $450,000,
$429,000, and $268,000, respectively.

92

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

J. Quarterly Financial Information  (Unaudited)

Fiscal Year 2010

First Quarter
Ended

Second Quarter
Ended

Third  Quarter
Ended

September 30, 2009 December 31, 2009 March 31, 2010

Fourth Quarter
Ended
June 30,  2010

(In thousands, except per share data)

Revenues:

Research and development support . . .
License and milestone fees . . . . . . . . .
Clinical materials reimbursement . . . .

Total revenues . . . . . . . . . . . . . . . .

$

782
1,831
486

3,099

Expenses:

Research and development . . . . . . . . .
General and administrative . . . . . . . .

Total expenses . . . . . . . . . . . . . . . .

Loss from operations . . . . . . . . . . . . . .
. . . . . . .

Other income (expense), net

Loss before income tax benefit

. . . . . . .
Income tax benefit . . . . . . . . . . . . . . .

12,188
3,592

15,780

(12,681)
144

(12,537)
(162)

$ 1,283
827
998

3,108

12,211
3,886

16,097

(12,989)
(19)

(13,008)
—

$ 1,805
1,266
243

3,314

12,091
3,447

15,538

(12,224)
(3)

(12,227)
(103)

$ 1,495
1,774
1,153

4,422

13,790
3,973

17,763

(13,341)
(64)

(13,405)
—

Net loss . . . . . . . . . . . . . . . . . . . . . . . .

$(12,375)

$(13,008)

$(12,124)

$(13,405)

Basic and diluted net loss per

common share . . . . . . . . . . . . . . . .

$

(0.22)

$

(0.23)

$

(0.21)

$ (0.21)

93

IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL  STATEMENTS (Continued)

AS OF JUNE 30, 2010

J. Quarterly Financial Information  (Unaudited) (Continued)

Fiscal Year 2009

First Quarter
Ended

Second Quarter
Ended

Ended

Third  Quarter Fourth Quarter

September 30, 2008 December 31, 2008 March 31, 2009

(In thousands, except per share data)

Revenues:

Research and development support . . . .
License and milestone fees . . . . . . . . . .
Clinical materials reimbursement . . . . . .

Total revenues . . . . . . . . . . . . . . . . .

Expenses:

Research and development . . . . . . . . . .
General and administrative . . . . . . . . . .

Total expenses . . . . . . . . . . . . . . . . .

Loss from operations . . . . . . . . . . . . . . . .
Other income (expense), net . . . . . . . . .

Loss before  income tax expense (benefit) .
Income tax expense (benefit) . . . . . . . .

$ 3,207
2,223
696

6,126

11,860
3,678

15,538

(9,412)
16

(9,396)
1

$ 2,283
4,766
2,285

9,334

12,888
3,521

16,409

(7,075)
(129)

(7,204)
(101)

$

908
7,314
4

8,226

9,493
3,243

12,736

(4,510)
(100)

(4,610)
—

Ended
June  30, 2009

$ 1,168
814
2,320

4,302

11,663
3,458

15,121

(10,819)
(8)

(10,827)
—

Net loss . . . . . . . . . . . . . . . . . . . . . . . . .

$ (9,397)

$ (7,103)

$ (4,610)

$(10,827)

Basic and diluted net loss per common

share . . . . . . . . . . . . . . . . . . . . . . . .

$ (0.19)

$ (0.14)

$ (0.09)

$ (0.21)

94

Item 9. Changes in and Disagreements with Accountants  on Accounting and Financial  Disclosure

None.

Item 9A. Controls and Procedures

1. Disclosure Controls and Procedures

The Company’s management, with the  participation of its principal executive officer and principal

financial officer, has evaluated the effectiveness  of the Company’s  disclosure controls and procedures
(as defined in Rules 13a-15(e) or 15d-15(e)  under the  Securities Exchange Act  of 1934, as  amended) as
of the end of the period covered by this  Annual Report on Form 10-K. Based on such evaluation,  the
Company’s principal executive officer  and principal financial officer have concluded  that,  as of the end
of such period, the Company’s 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

Management of the Company 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, the
Company’s principal executive and principal financial officers and  effected  by  the Company’s 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:

(cid:129) pertain to the maintenance of records that in reasonable detail accurately and fairly  reflect the

transactions and dispositions of the assets of  the Company;

(cid:129) 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

(cid:129) 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. 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 the Company’s internal control over financial reporting

as of  June 30, 2010. 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.

Based on this assessment, management has concluded that, as of  June  30, 2010 the  Company’s

internal control over financial reporting is  effective.

Ernst & Young LLP, the Company’s independent registered public accounting  firm,  has issued a
report on the effectiveness of the Company’s internal  control over  financial reporting,  as of June 30,
2010. This report appears immediately  below.

95

(b) Attestation Report of the Independent  Registered Public Accounting Firm

Report of Independent Registered Public  Accounting Firm

The Board of Directors and Shareholders  of ImmunoGen, Inc.

We  have audited ImmunoGen, Inc.’s  internal  control  over financial reporting  as of June 30, 2010,

based on criteria established in Internal Control—Integrated  Framework issued  by  the Committee of
Sponsoring Organizations of the Treadway  Commission (the COSO  criteria). ImmunoGen, Inc.’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  conducted our audit in accordance with the standards of  the Public Company Accounting
Oversight Board (United States). 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.

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.

In our opinion, ImmunoGen, Inc. maintained, in all material respects, effective internal control

over financial reporting as of June 30, 2010  based on the COSO criteria.

We  also have audited, in accordance with the standards of  the Public Company Accounting
Oversight Board (United States), the  consolidated balance sheets of ImmunoGen, Inc.  as of June 30,
2010 and 2009, and the related consolidated  statements  of operations,  shareholders’ equity,  and cash
flows for each of the three years in the period ended June 30,  2010 and our  report dated August 27,
2010 expressed an unqualified opinion thereon.

/s/ ERNST & YOUNG LLP

Boston, Massachusetts
August 27, 2010

96

(c) Changes in Internal Control Over Financial Reporting

There have not been any changes in the  Company’s 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 June 30, 2010 that have materially affected, or are reasonably likely to materially affect,  the
Company’s internal control over financial reporting.

3. Limitations on the Effectiveness of  Controls

The Company’s management, including  its principal  executive officer and  principal financial  officer,

does not expect that the Company’s 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.

97

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
2010 annual meeting of shareholders,  which will be filed  with the  Securities  and Exchange  Commission
not later than October 28, 2010 (120 days after the  end of the fiscal year covered by this Annual
Report on Form 10-K), except that information required  by Item  10 concerning  our executive officers
appears  in Part I, Item 3.1 of this Annual  Report on Form 10-K.

98

Item 15. Exhibits, Financial Statement Schedules

(a) Financial Statements:

PART IV

(1) See ‘‘Index to Consolidated Financial Statements’’  at Item  8 of this Annual  Report on

Form 10-K. 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.

(2) The following schedule is filed as part of this Annual Report  on Form  10-K:

Schedule II—Valuation and Qualifying Accounts for the years ended June 30,  2010, 2009 and 2008.

(3) See Exhibit Index following the  signature page  to  this  Annual  Report  on Form 10-K.

99

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.

SIGNATURES

IMMUNOGEN, INC.

By:

/s/ DANIEL M. JUNIUS

Daniel M. Junius
President and
Chief Executive Officer
(Principal Executive Officer)

Dated: August 27, 2010

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/ DANIEL M. JUNIUS

Daniel M. Junius

/s/ GREGORY D. PERRY

Gregory D. Perry

/s/ STEPHEN MCCLUSKI

Stephen McCluski

/s/ MITCHEL SAYARE

Mitchel Sayare

/s/ DAVID W. CARTER

David W. Carter

/s/ NICOLE ONETTO, M.D.

Nicole Onetto

/s/ MARK SKALETSKY

Mark Skaletsky

/s/ JOSEPH VILLAFRANCA

Joseph Villafranca

/s/ RICHARD WALLACE

Richard Wallace

/s/ HOWARD PIEN

Howard Pien

President, Chief Executive Officer and Director

(Principal Executive Officer)

August 27, 2010

Senior Vice President and
Chief Financial Officer
(Principal Financial and Accounting Officer)

August 27, 2010

Chairman of the Board of Directors

August 27, 2010

Director

Director

Director

Director

Director

Director

Director

100

August 27, 2010

August 27, 2010

August 27, 2010

August 27, 2010

August 27, 2010

August 27, 2010

August 27, 2010

EXHIBIT INDEX

Exhibit
Number

3.1

3.2

4.1

4.2

10.1

10.1(a)

10.1(b)

10.1(c)

10.1(d)

10.1(e)

10.1(f)

10.1(g)

10.1(h)

10.2

10.3

Exhibit Description

Restated Articles of Organization, as  amended

Amended and  Restated By-Laws

Article 4 of Restated Articles of Organization,  as
amended (see Exhibit 3.1)

Form of Common Stock certificate

Leases dated as of December 1,  1986  and  June  21,
1988 by and between James H.  Mitchell,  Trustee  of
New Providence Realty Trust, lessor,  and Charles
River Biotechnical Services,  Inc. (‘‘Lessee’’),
together with Assignment of Leases  dated  June  29,
1989 between Lessee and the Registrant

First Amendment to Lease  dated  May 9,  1991 by
and between James H. Mitchell, Trustee  of New
Providence Realty Trust, lessor, and the  Registrant

Confirmatory Second Amendment  to  Lease  dated
September 17, 1997 by and between  James  H.
Mitchell, Trustee of New Providence Realty Trust,
lessor, and the Registrant

Third Amendment  and Partial Termination  of  Lease
dated as of August 8, 2000 by and between  James
H. Mitchell, Trustee of New Providence Realty
Trust, lessor, and the Registrant

Fourth Amendment to Lease dated  as of  October 3,
2000 by and between James H.  Mitchell,  Trustee  of
New Providence Realty Trust, lessor,  and the
Registrant

Fifth Amendment to Lease dated  as  of  June 7, 2001
by and between James H. Mitchell, Trustee  of New
Providence Realty Trust, lessor, and the Registrant

Sixth Amendment to Lease dated as  of April 30,
2002 by and between Bobson 333 L.L.C.,  lessor, and
the Registrant

Seventh Amendment to Lease dated as  of
October 20, 2005 by and between  Bobson 333
L.L.C., lessor, and the Registrant

Eighth Amendment to Lease dated as of
February 21, 2007 by and between Bobson 333
L.L.C., lessor, and the Registrant

Lease Agreement, dated as  of July 27,  2007,  by and
between Intercontinental Fund III 830 Winter
Street LLC, landlord, and the Registrant

Research and License Agreement dated as  of
May 22, 1981 by and between  the  Registrant and
Sidney Farber Cancer Institute, Inc.  (now
Dana-Farber Cancer Institute, Inc.), with  addenda
dated as of August 13, 1987 and August  22, 1989

101

Filed
with this
Form 10-K Form

Incorporated by Reference

Filing Date
with SEC

Exhibit
Number

10-Q

8-K

April 30,  2010

April 6,  2007

S-1 November 15, 1989
(File No.  33-31219)

3.1

3.1

4.2

S-1 September 22, 1989
(File No. 33-31219)

10.10

S-1 November 6, 1991 10.10a

(File No.  33-43725)

10-K September 26, 1997

10.10

10-K September 2,  2008

10.1(c)

10-K September 2,  2008 10.1(d)

10-K September 2,  2008 10.1(e)

10-K September 2,  2008

10.1(f)

10-K September 2,  2008 10.1(g)

10-K September 2,  2008 10.1(h)

10-Q November 7, 2007

10.2

S-1 September 22, 1989
(File No.  33-31219)

10.1

Exhibit
Number

10.4*

10.4(a)

Exhibit Description

License Agreement dated as of  June  1,  1998 by  and
between the Registrant and Pharmacia  &  Upjohn
AB

Amendment to License Agreement  dated as of
October 23, 1998 by and between  the Registrant  and
Pharmacia & Upjohn AB

Filed
with this
Form 10-K Form

Incorporated by Reference

Filing Date
with SEC

Exhibit
Number

10-K September 29,  1998

10.48

10-K September 2,  2008 10.4(a)

10.5*

License Agreement dated effective May 2,  2000  by
and between the Registrant and Genentech, Inc.

10-K September 27, 2000

10.51

10.5(a)* Amendment to License Agreement for  Anti-HER2

10-K

August 28, 2006

10.32

10.6*

10.7*

10.8*

10.9*

10.10*

10.11*

Antibodies, dated as of May 3, 2006, between the
Registrant and Genentech, Inc.

License Agreement executed November  13, 2006,
effective as of July 22, 2005, between  the Registrant
and Genentech,  Inc.

License Agreement executed February 21, 2007,
effective as of April 27, 2005, between  the
Registrant and Genentech, Inc.

License Agreement executed February 21, 2007,
effective as of December 12, 2005, between  the
Registrant and Genentech, Inc.

Amendment to License Agreements made effective
as of March 11,  2009, between the  Registrant and
Genentech, Inc.

Option and License Agreement dated September  5,
2000 by and between the Registrant and Amgen Inc.
(as successor-in-interest to Abgenix, Inc.)

Collaboration and License  Agreement dated  as  of
July 30, 2003 by  and between the  Registrant and
sanofi-aventis U.S. LLC (as successor-in-interest  to
Aventis Pharmaceuticals Inc.)

10-Q

February 8,  2007

10.3

10-Q

May 9, 2007

10.1

10-Q

May 9, 2007

10.2

10-Q

May 7, 2009

10.1

8-K/A

October 10, 2000

10.1

10-Q November 14, 2003

10.1

10.11(a)* Amendment No. 1, dated  as of  August 31, 2006,  to
the Collaboration and License Agreement  between
the Registrant and sanofi-aventis U.S.  LLC

10-Q November 3, 2006

10.1

10.11(b)* Amendment No. 2, dated  as of  October 11,  2007,  to

10-Q

February 7,  2008

10.4

the Collaboration and License Agreement  between
the Registrant and sanofi-aventis U.S.  LLC

10.11(c)* Amendment No. 3, dated as  of August  31, 2008, to
the Collaboration and License Agreement  between
the Registrant and sanofi-aventis U.S.  LLC

10.12*

10.13*

10.14*

License Agreement dated as of  October  5, 2006  by
and between the Registrant and sanofi-aventis
U.S. LLC

Option and License Agreement dated as of
December 21, 2006  by and between the  Registrant
and sanofi-aventis U.S. LLC

Development  and  License Agreement  dated  as of
October 1, 2004 by and between the  Registrant and
Biogen Idec MA Inc.

102

10-Q

February 6,  2009

10.7

10-Q

February 8,  2007

10.1

10-Q

February 8,  2007

10.2

10-Q

February 9,  2005

10.1

Exhibit
Number

10.15*

Exhibit Description

Collaborative Development and License Agreement
dated as of July 7, 2006 by and between  the
Registrant and Biotest AG

Filed
with this
Form 10-K Form

Incorporated by Reference

Filing Date
with SEC

Exhibit
Number

10-Q November 3,  2006

10.2

10.15(a)* Amendment No. 1, dated  August  23,  2006, to

10-Q November 3, 2006

10.3

10.16

Collaborative Development and License Agreement
by and between the Registrant and Biotest  AG

Registration Rights Agreement  dated  as of  June  20,
2008 by and between the Registrant  and  Ziff  Asset
Management, L.P.

10.17†

Restated Stock Option Plan

10.17(a)† Form  of Incentive Stock Option  Agreement

10.17(b)† Form  of Non-Qualified Stock Option Agreement

10.18†

2006 Employee, Director and Consultant  Equity
Incentive Plan, as amended and restated through
November 12, 2008

8-K

June 23, 2008

10.2

8-K

8-K

8-K

February 7, 2006

February 7, 2006

February 7, 2006

8-K November 14,  2008

10.1

10.2

10.3

10.1

10.18(a)† Form of Incentive Stock Option  Agreement  for

S-8 November 15, 2006

99.4

Executives

10.18(b)† Form of Non-Qualified Stock Option Agreement  for

S-8 November 15, 2006

99.5

Executives

10.18(c)† Form of Non-Qualified Stock Option Agreement  for

S-8 November 15, 2006

99.6

Directors

10.18(d)† Form of Restricted Stock Agreement for  Executives

10.18(e)† Form of Restricted Stock Agreement  for Directors

10.19†

10.20†

10.21†

10.22†

10.23†

10.24†

10.25†

10.26†

10.27†

10.28†

10.29†

2001 Non-Employee Director  Stock  Plan

2004 Non-Employee Director  Compensation and
Deferred Stock Unit Plan, as amended through
September 16, 2009

Form of Proprietary Information, Inventions and
Competition Agreement between the Registrant  and
each of its executive officers

Amendment to Stock Option Agreements  dated as
of September 24, 2008 between the  Registrant  and
Mitchel Sayare

Severance Agreement dated as of  December  1, 2008
between the Registrant and Daniel M. Junius

Severance Agreement dated as of  December  1, 2008
between the Registrant and John  M.  Lambert

Severance Agreement dated as of  December  1, 2008
between the Registrant and James J. O’Leary

Severance Agreement dated as of  January 9,  2009
between the Registrant and Gregory  D.  Perry

Severance Agreement dated as of  August 17,  2009
between the Registrant and Peter  Williams

Employment offer letter between the  Registrant  and
Gregory D. Perry

Employment offer letter between  the Registrant and
James J. O’Leary

103

S-8 November 15, 2006

S-8 November 15, 2006

S-8 December 18,  2001

10-Q November 4,  2009

99.9

99.8

99

10.1

10-Q

February 8,  2007

10.15

10-Q

October 31, 2008

10.1

10-Q

February 6,  2009

10.1

10-Q

February 6,  2009

10.3

10-Q

February 6,  2009

10.4

10-Q

February 6,  2009

10.5

10-K

August 28, 2010

10.30

10-Q

February 6,  2009

10.6

10-K

August 28, 2010

10.32

Filed
with this
Form 10-K Form

Incorporated by Reference

Filing Date
with SEC

Exhibit
Number

10-Q

January 29,  2010

10.1

10-Q November 7, 2007

10-K

August 30, 2007

10.1

21

Exhibit
Number

10.30†

Exhibit Description

Compensation Policy for  Non-Employee  Directors,
as amended through November 11, 2009

10.31†

Summary of Annual Executive Bonus Program

21

23

31.1

31.2

32

Subsidiaries of the Registrant

Consent of  Ernst & Young  LLP

Certification of the Chief  Executive Officer pursuant
to Section 302 of the Sarbanes-Oxley  Act of 2002

Certification of the Chief  Financial  Officer  pursuant
to Section 302 of the Sarbanes-Oxley  Act of 2002

Certifications of Chief Executive Officer and Chief
Financial Officer pursuant to Section 906  of the
Sarbanes- Oxley Act of 2002

X

X

X

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.

Exhibit is a management contract or compensatory  plan,  contract  or  arrangement  required  to  be  filed  as  an
exhibit to the annual report on Form  10-K.

104

IMMUNOGEN, INC.

SCHEDULE II—VALUATION AND QUALIFYING ACCOUNTS

(In thousands)

COLUMN A—DESCRIPTION

Inventory Valuation Allowance

Year End June 30, 2010 . . . . . . . . . . . . . . . . . . .
Year End June 30, 2009 . . . . . . . . . . . . . . . . . . .
Year End June 30, 2008 . . . . . . . . . . . . . . . . . . .

COLUMN B

COLUMN C—
ADDITIONS

COLUMN D

COLUMN  E

Balance At
Beginning
of Period

$1,784
$2,534
$1,430

Charged
to Costs
and
Expenses

927
—
3,732

Use of
Zero
Value
Inventory

(1,772)
(750)
(2,628)

Balance  at
End of
Period

$ 939
$1,784
$2,534

105

EXHIBIT 31.1

CERTIFICATIONS UNDER SECTION 302

I, Daniel M. Junius, certify that:

1.

I have reviewed this Annual Report on Form 10-K of  ImmunoGen, Inc.;

2. Based on my knowledge, this report does  not  contain any untrue statement  of  a material fact or

omit to state a material fact necessary to make the statements made,  in light  of the circumstances
under which such statements were made, not misleading with respect to the period  covered by this
report;

3. Based on my knowledge, the financial statements, and  other financial  information included in  this
report, fairly present in all material respects the financial  condition, results of operations and  cash
flows of the registrant as of, and for, the periods presented in  this report;

4. The registrant’s other certifying  officer(s)  and  I are responsible for establishing and maintaining
disclosure controls and procedures (as defined in  Exchange  Act Rules 13a-15(e) and 15d-15(e))
and internal control over financial reporting  (as  defined in  Exchange Act  Rules 13a-15(f)  and
15d-15(f)) for the registrant and have:

a)

designed such disclosure controls  and procedures, or  caused such disclosure controls and
procedures to be designed under our supervision,  to  ensure that material  information relating
to the registrant, including its consolidated subsidiaries, is made  known to us by others within
those entities, particularly during the period in which  this  report is being prepared;

b) designed such internal control over financial  reporting, or caused such internal control over

financial reporting to be designed under  our  supervision, 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;

c)

evaluated the effectiveness of the registrant’s disclosure controls and  procedures and
presented in this report our conclusions about  the effectiveness of the disclosure controls and
procedures, as of the end of the period  covered by this report based on such evaluation; and

d) disclosed in this report any change in  the registrant’s internal control over  financial  reporting

that occurred during the registrant’s  most recent fiscal  quarter (the registrant’s fourth fiscal
quarter in the case of an annual report) that  has materially  affected, or is reasonably likely to
materially affect, the registrant’s internal control  over financial reporting; and

5. The registrant’s other certifying  officer(s)  and  I have disclosed,  based on our  most recent

evaluation of internal control over financial reporting,  to  the registrant’s auditors and the audit
committee of the registrant’s board of directors (or persons performing the equivalent functions):

a)

b)

all significant deficiencies and material  weaknesses in the design  or  operation  of internal
control over financial reporting which  are reasonably likely  to  adversely affect  the registrant’s
ability to record, process, summarize and report financial information; and

any fraud, whether or not material, that involves management  or other employees who have a
significant role in the registrant’s internal control over  financial  reporting.

Date: August 27, 2010

/s/ DANIEL M. JUNIUS

Daniel M. Junius
President and Chief Executive Officer
(Principal Executive Officer)

EXHIBIT 31.2

CERTIFICATIONS UNDER SECTION 302

I, Gregory D. Perry, certify that:

1.

I have reviewed this Annual Report on Form 10-K of  ImmunoGen, Inc.;

2. Based on my knowledge, this report does  not  contain any untrue statement  of  a material fact or

omit to state a material fact necessary to make the statements made,  in light  of the circumstances
under which such statements were made, not misleading with respect to the period  covered by this
report;

3. Based on my knowledge, the financial statements, and  other financial  information included in  this
report, fairly present in all material respects the financial  condition, results of operations and  cash
flows of the registrant as of, and for, the periods presented in  this report;

4. The registrant’s other certifying  officer(s)  and  I are responsible for establishing and maintaining
disclosure controls and procedures (as defined in  Exchange  Act Rules 13a-15(e) and 15d-15(e))
and internal control over financial reporting  (as  defined in  Exchange Act  Rules 13a-15(f)  and
15d-15(f)) for the registrant and have:

a)

designed such disclosure controls  and procedures, or  caused such disclosure controls and
procedures to be designed under our supervision,  to  ensure that material  information relating
to the registrant, including its consolidated subsidiaries, is made  known to us by others within
those entities, particularly during the period in which  this  report is being prepared;

b) designed such internal control over financial  reporting, or caused such internal control over

financial reporting to be designed under  our  supervision, 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;

c)

evaluated the effectiveness of the registrant’s disclosure controls and  procedures and
presented in this report our conclusions about  the effectiveness of the disclosure controls and
procedures, as of the end of the period  covered by this report based on such evaluation; and

d) disclosed in this report any change in  the registrant’s internal control over  financial  reporting

that occurred during the registrant’s  most recent fiscal  quarter (the registrant’s fourth fiscal
quarter in the case of an annual report) that  has materially  affected, or is reasonably likely to
materially affect, the registrant’s internal control  over financial reporting; and

5. The registrant’s other certifying  officer(s)  and  I have disclosed,  based on our  most recent

evaluation of internal control over financial reporting,  to  the registrant’s auditors and the audit
committee of the registrant’s board of directors (or persons performing the equivalent functions):

a)

b)

all significant deficiencies and material  weaknesses in the design  or  operation  of internal
control over financial reporting which  are reasonably likely  to  adversely affect  the registrant’s
ability to record, process, summarize and report financial information; and

any fraud, whether or not material, that involves management  or other employees who have a
significant role in the registrant’s internal control over  financial  reporting.

Date: August 27, 2010

/s/ GREGORY D. PERRY

Gregory D. Perry
Senior Vice President and Chief Financial  Officer
(Principal Financial and Accounting Officer)

EXHIBIT 32

CERTIFICATIONS UNDER SECTION 906

Pursuant to section 906 of the Sarbanes-Oxley Act of 2002  (subsections  (a) and  (b) of

section 1350, chapter 63 of title 18, United States Code), each of the undersigned officers of
ImmunoGen, Inc., a Massachusetts corporation (the ‘‘Company’’), does  hereby certify,  to  such officer’s
knowledge, that:

The Annual Report for the year ended June 30, 2010  (the  ‘‘Form 10-K’’) of  the Company fully

complies with the requirements of Section  13(a) or  15(d) of  the Securities Exchange Act  of 1934, and
the information contained in the Form 10-K fairly presents, in all material respects,  the financial
condition and results of operations of  the Company.

Dated: August 27, 2010

/s/ DANIEL M. JUNIUS

Daniel M. Junius
President and Chief Executive Officer
(Principal Executive Officer)

Dated: August 27, 2010

/s/ GREGORY D. PERRY

Gregory D. Perry
Senior Vice President and Chief Financial Officer
(Principal Financial and Accounting Officer)

A signed original of this written statement required  by  Section 906 has  been provided to the

Company and will be retained by the  Company and furnished to the  Securities and Exchange
Commission or its staff upon request.

Our Targeted Antibody Payload (TAP) technology uses tumor-targeting antibodies to 

deliver one of our potent cancer-cell killing agents specifically to tumor cells. Multiple 

TAP compounds are in clinical testing today, with 3-4 more expected to enter the clinic 

by the end of 2011.    

    Clinical-Stage Pipeline Today 

Compound 

Partner 

Indication 

Stage 

3rd-line in advanced HER2+ 

Phase II  

breast cancer  

(completed) 

2nd-line in advanced HER2+ 

breast cancer  

Phase III 

Trastuzumab-DM1 

(T-DM1) 

Genentech/ 

Roche 

1st-line in advanced HER2+ 

breast cancer  

Phase III 

Adjuvant use in HER2+  

breast cancer 

Phase II expected  

to start 4Q10 

Use in combination with other 

anticancer agents 

Multiple trials 

Merkel cell carcinoma 

Decision in 4Q10 about 

initiating pivotal testing 

Small-cell lung cancer (SCLC) 

Phase I/II expected  

– combination 

to start 4Q10 

Lorvotuzumab 

mertansine 

(IMGN901) 

Wholly  

owned 

SCLC, Merkel cell carcinoma, 

ovarian cancer – single agent 

Phase I 

Multiple myeloma  

– single agent 

Multiple myeloma  

– combination 

IMGN388 

Solid tumors – single agent 

Phase I 

Wholly 

owned* 

SAR3419 

sanofi-aventis 

Non-Hodgkin’s lymphoma  

– single agent 

BT-062 

Biotest* 

BIIB015 

Biogen Idec 

Multiple myeloma  

– single agent 

Cripto+ solid tumors  

– single agent 

SAR650984** 

sanofi-aventis 

Hematologic malignancies  

– single agent 

SAR566658 

sanofi-aventis 

CA6+ solid tumors 

– single agent 

Phase I 

Phase I 

Phase I 

Phase I 

Phase I 

Phase I 

Phase I 

Corporate Information 

Directors 

Chairman of the Board 
Stephen C. McCluski 
Former Senior Vice President 
and Chief Financial Officer, 
Baush & Lomb, Inc. 

David W. Carter 
Former Chairman and 
Chief Executive Officer, 
Xenogen Corporation 

Daniel M. Junius 
President and  
Chief Executive Officer, 
ImmunoGen, Inc. 

Nicole Onetto, M.D. 
Deputy Director, 
Ontario Institute for Cancer 
Research 

Howard Pien 
Former Chairman of the Board  
and Chief Executive Officer, 
Medarex, Inc. 

Mitchel Sayare, Ph.D. 
Former President and  
Chief Executive Officer, 
ImmunoGen, Inc. 

Mark Skaletsky 
Chairman and  
Chief Executive Officer, 
Fenway Pharmaceuticals 

Joseph J. Villafranca, Ph.D. 
Senior Vice President, 
Life Sciences, 
Business Development, 
Tunnell Consulting 

Richard J. Wallace 
Former Senior Vice President, 
Research and Development, 
GlaxoSmithKline plc. 

Executive Management

Corporate Headquarters 

Daniel M. Junius 
President and  
Chief Executive Officer 

John M. Lambert, Ph.D. 
Executive Vice President and  
Chief Scientific Officer 

Gregory D. Perry 
Senior Vice President and 
Chief Financial Officer 

Craig Barrows 
Vice President, General Counsel  
and Secretary 

James J. O’Leary, M.D. 
Vice President and  
Chief Medical Officer 

Peter J. Williams 
Vice President, 
Business Development 

ImmunoGen, Inc. 
830 Winter Street 
Waltham, MA 02451 
781.895.0600 
www.immunogen.com 

Annual Meeting 

11:00 AM on November 16, 2010 
at the offices of the Company 
830 Winter Street 
Waltham, MA  02451 

Stock Transfer Agent and  
Registrar 

BNY Mellon Shareowner Services 
Newport Office Center VII 
480 Washington Boulevard 
Jersey City, NJ 07310 
www.bnymellon.com/shareowners/ 
isd
Toll-Free Number: 888.810.7458 

Auditors 

Ernst & Young LLP 
Boston, Massachusetts 

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. 

This annual report includes forward-looking statements based on management’s current expectations. These statements include, 
but are not limited to, ImmunoGen’s expectations related to the advancement of new Company and partner compounds into clinical 
testing, the initiation of new clinical trials, the timing of go/no go clinical decisions, and the timing and occurrence of the
presentation of new preclinical and clinical data, of potential business development events, and of potential future regulatory
submissions. For these statements, ImmunoGen claims the protection of the safe harbor for forward-looking statements provided 
by the Private Securities Litigation Reform Act of 1995. 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 annual report. Factors that could cause future results to 
differ materially from such expectations include, but are not limited to: the timing and outcome of ImmunoGen’s and the Company’s 
partners’ research and clinical development processes; the difficulties inherent in the development of novel pharmaceuticals, 
including uncertainties as to the timing, expense and results of preclinical studies, clinical trials and regulatory processes;
ImmunoGen’s ability to financially support its product programs; ImmunoGen’s dependence on collaborative partners; industry 
merger and acquisition activity; and other factors more fully described in ImmunoGen’s Annual Report on Form 10-K for the fiscal
year ended June 30, 2010 and other reports filed with the Securities and Exchange Commission.  

  *Centocor Ortho Biotech (J&J) has opt-in rights to IMGN388; ImmunoGen has opt-in rights to BT-062 

**Therapeutic antibody (non-TAP) compound 

Revlimid® is a registered trademark of Celgene Corporation. 

 
 
  
  
 
ImmunoGen, Inc. 
830 Winter Street 
Waltham, MA 02451 
781-895-0600 
www.immunogen.com