UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES

EXCHANGE ACT OF 1934

For the quarterly period ended December 31, 2006

OR

o 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.

128 Sidney Street, Cambridge, MA 02139

(Address of principal executive offices, including zip code)

(617) 995-2500

(Registrant’s telephone number, including area code)

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.      xYes o No

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check one):

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

o Yes    x No

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date.

Shares of common stock, par value $.01 per share:  41,641,450 shares outstanding as of February 5, 2007.

IMMUNOGEN, INC.
TABLE OF CONTENTS

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IMMUNOGEN, INC.

CONSOLIDATED BALANCE SHEETS

(UNAUDITED)

In thousands, except per share amounts

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

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IMMUNOGEN, INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

(UNAUDITED)

In thousands, except per share amounts

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

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IMMUNOGEN, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

(UNAUDITED)

In thousands, except per share amounts

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

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IMMUNOGEN, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

December 31, 2006

A. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements at December 31, 2006 and June 30, 2006 and for the three and six months ended December 31, 2006, and 2005 include the accounts of ImmunoGen, Inc. (the “Company”) and its wholly-owned subsidiaries, ImmunoGen Securities Corp. and ImmunoGen Europe Limited. Although the consolidated financial statements are unaudited, they include all of the adjustments, consisting only of normal recurring adjustments, which management considers necessary for a fair presentation of the Company’s financial position in accordance with accounting principles generally accepted in the U.S. for interim financial information. Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. The preparation of interim financial statements requires the use of management’s estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the interim financial statements and the reported amounts of revenues and expenditures during the reported period. The results of the interim periods are not necessarily indicative of the results for the entire year. Accordingly, the interim financial statements should be read in conjunction with the audited financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended June 30, 2006.

Revenue Recognition

The Company enters into out-licensing and development agreements with collaborative partners for the development of monoclonal antibody-based cancer therapeutics. The Company follows the provisions of the Securities and Exchange Commission’s Staff Accounting Bulletin No. 104 (SAB No. 104), Revenue Recognition, and Emerging Issues Task Force 00-21 Accounting for Revenue Arrangements with Multiple Elements (EITF 00-21). In accordance with SAB No. 104 and EITF 00-21, the Company recognizes collaboration 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 Company recognizes revenue on preclinical and clinical materials when the materials have passed all quality testing required for collaborator acceptance and title has transferred to the collaborator. The terms of the Company’s agreements contain multiple revenue elements, which typically include non-refundable license fees, payments for research activities and clinical material manufacturing obligations, payments based upon the achievement of certain milestones, and royalties on product sales. The Company evaluates such elements of its agreements to determine if the deliverables are separable into units of accounting and then applies applicable revenue recognition criteria to each unit of accounting.

At December 31, 2006, the Company had the following four types of collaborative contracts with the counterparties identified below:

· License to a single target antigen (single-target license):

Biogen Idec, Inc.

Biotest AG

Boehringer Ingelheim International GmbH

Centocor, Inc., a wholly-owned subsidiary of Johnson & Johnson

Genentech, Inc. (multiple single-target licenses)

Millennium Pharmaceuticals, Inc.

· Broad option agreements to acquire rights to a limited number of targets over a specified time period (broad license):

Amgen, Inc. (formerly Abgenix, Inc.)

Genentech, Inc.

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Millennium Pharmaceuticals, Inc.

· A broad agreement to discover, develop and commercialize antibody-based anticancer products:

sanofi-aventis

· Non exclusive license to humanization technology

sanofi-aventis

Generally, the forgoing collaboration agreements provide that the Company will (i) at the collaborator’s request, manufacture preclinical and clinical materials at the Company’s cost, or, in some cases, cost plus a margin, (ii) receive payments upon the collaborators’ achievements of certain milestones and (iii) receive royalty payments, generally until the later of the last applicable patent expiration or 12 years after product launch. 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. ImmunoGen 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 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. At each reporting period, the Company analyzes individual product facts and circumstances and reviews the estimated period of its substantial involvement to determine whether a significant change in its estimates has occurred and adjusts the deferral period accordingly. We do not believe that the change in the estimated period of substantial involvement during the three and six months ended December 31, 2006, had a material impact on net loss or license and milestone fees for the periods. 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.

The Company defers upfront payments received from its broad licenses over the period during which the collaborator may elect to receive a license. These periods are specific to each collaboration agreement, but are between seven 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 license 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 that 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 pre-clinical activity on another product candidate and the Company’s remaining period of substantial involvement can be estimated.

The Company’s discovery, development and commercialization agreement with sanofi-aventis included an upfront payment of $12.0 million that sanofi-aventis paid to ImmunoGen in August 2003. The Company deferred the upfront payment and is recognizing it ratably over the period of the Company’s substantial involvement of five years, which includes the term of the collaborative research program of three years and two 12-month extensions that sanofi-aventis has exercised. The discovery, development and commercialization agreement also provides that ImmunoGen receive committed research funding totaling $79.3 million over the full five years of the research collaboration, which includes the initial three-year period and the two 12-month extensions. The committed research funding is based upon resources that ImmunoGen is required to contribute to the collaboration. The Company records the research funding as it is earned based upon its actual resources utilized in the collaboration. In August 2005, sanofi-aventis exercised the first of the two 12-month extensions. This extension is providing the Company with $18.2 million in additional committed funding over the twelve months beginning September 1, 2006. In August 2006, sanofi-aventis exercised its remaining option to extend the term of its research collaboration with the Company for an additional year. The Company is to receive a minimum of $10.4 million in committed research support funding from sanofi-aventis over the twelve-month period beginning September 1, 2007.

At the conclusion of the second sanofi-aventis research program year on August 31, 2005, a review of research activities during this period was conducted. This review identified $1.1 million in billable research activities performed under the program during the fiscal year ended June 30, 2005, which had not been billed or recorded as revenue. Accordingly, the Company has included this additional $1.1 million of research and support revenue in the accompanying consolidated statement of operations for the six months ended December 31, 2005. The Company does not believe such previously unrecorded revenue was material to the results of operations or the financial position of the Company for any interim period of fiscal 2005 or for the three or six months ended

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December 31, 2005.

When milestone fees are specifically tied to a separate earnings process and are deemed to be substantive, revenue is recognized when such milestones are achieved. In addition, when appropriate, the Company recognizes revenue from certain research payments based upon the level of research services performed during the period of the research contract. Deferred revenue 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 some of its collaborators. The Company is reimbursed for its fully burdened cost to produce clinical materials and, in some cases, fully burdened cost plus a profit margin. The Company recognizes revenue on preclinical and clinical materials when the materials have passed all quality testing required for collaborator acceptance and title has 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 its fully burdened cost of producing these materials or providing these services. The Company records the amounts received for the materials produced or services performed as a component of research and development support.

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 fair value. Unrealized gains and losses, if any, are reported as accumulated other comprehensive income (loss) within stockholders’ 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 interest income. Realized gains and losses on available-for-sale securities are included in net realized gains (losses) on investments. The cost of securities sold is based on the specific identification method. Interest and dividends are included in interest income.

Unbilled Revenue

The majority of the Company’s unbilled revenue at December 31, 2006 and June 30, 2006 represents (i) committed research funding to be earned based on actual resources utilized under the Company’s discovery, development and commercialization agreement with sanofi-aventis; and (ii) research funding to be earned based on actual resources utilized under the Company’s development and license agreements with Biogen Idec, Biotest, Centocor, and Genentech.

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 December 31, 2006 and June 30, 2006 is summarized below (in thousands):

Inventory at December 31, 2006 and June 30, 2006 is stated net of write-downs of $2.1 million and $2.9 million, respectively. The write-downs represent the cost of DM1, DM4 and ansamitocin P3 that the Company considers to be in excess of a 12-month supply based on current collaborator firm, fixed orders and projections

All Tumor-Activated Prodrug (TAP) product candidates currently in preclinical and clinical testing include either DM1 or DM4

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as a cell-killing agent, and these agents are the subject of the Company’s collaborations. DM1 and DM4 (collectively referred to as DMx) are both manufactured from a precursor, ansamitocin P3.

Due to yield fluctuations, the actual amount of ansamitocin P3 and DMx that will be produced in future periods under supply agreements is highly uncertain. As such, the amount of ansamitocin P3 and/or DMx produced could be more than is required to support the development of the Company’s and its collaborators’ products. Such excess product, as determined under the Company’s inventory reserve policy, is charged to cost of clinical materials reimbursed.

The Company produces preclinical and clinical materials for its collaborators either in anticipation of or in support of 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 on-going clinical trials for which the Company is producing clinical material for itself and its collaborators, the speed of enrollment in those trials and the dosage schedule of each clinical trial. 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 DMx and ansamitocin P3 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 contractually required to reimburse the Company the full cost of the conjugate and any agreed margin thereon, even if the collaborator subsequently cancels the manufacturing run.

The Company accounts for the DMx and ansamitocin P3 inventory as follows:

a)              That portion of the DMx and/or ansamitocin P3 that the Company intends to use in the production of its own products is expensed upon receipt of the materials;

b)             To the extent that the Company has collaborator projections for up to twelve months of firm, fixed orders and/or projections, the Company capitalizes the value of DMx and ansamitocin P3 that will be used in the production of conjugate subject to these firm, fixed orders and/or projections;

c)              The Company considers more than twelve month supply of ansamitocin P3 and/or DMx that is not supported by collaborators’ firm, fixed orders or projections to be excess. The Company establishes a reserve to reduce to zero the value of any such excess ansamitocin P3 or DMx inventory with a corresponding charge to cost of clinical materials reimbursed; and

d)             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 DMx and ansamitocin P3 inventory at each reporting period.

The Company did not record any cost of clinical materials reimbursement expense related to excess inventory during the three and six months ended December 31, 2006.  However, in the three and six months ended December 31, 2005, the Company recorded $26,000 and $153,000, respectively, to write down certain batches of ansamitocin P3 and DMx and certain work-in-process amounts to their net realizable value. If the Company increases its on-hand supply of DMx or ansamitocin P3, a corresponding change to the Company’s collaborators’ projections could result in significant changes in the Company’s estimate of the net realizable value of DMx and ansamitocin P3 inventory. Reductions in collaborators’ projections could indicate that the Company has additional excess DMx and/or ansamitocin P3 inventory and the Company would then evaluate the need to record further write-downs, included as charges to cost of clinical materials reimbursed.

Computation of Net Loss Per Common Share

Basic net loss per common share is calculated based upon the weighted average number of common shares outstanding during the period. Diluted net loss per common share incorporates the dilutive effect of stock options and warrants. The total number of options and warrants convertible into ImmunoGen Common Stock and the resulting ImmunoGen Common Stock equivalents, as calculated in accordance with the treasury-stock accounting method, are included in the following table (in thousands):

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ImmunoGen Common Stock equivalents have not been included in the calculations of dilutive net loss per common share calculations for the three and six months ended December 31, 2006 and 2005 because their effect is anti-dilutive due to the Company’s net loss position.

Comprehensive Loss

The Company presents comprehensive income (loss) in accordance with Statement of Financial Accounting Standards (SFAS) No. 130, “Reporting Comprehensive Income.” For the three and six months ended December 31, 2006, total comprehensive loss equaled $3.1 million and $9.1 million, respectively. For the three and six months ended December 31, 2005, total comprehensive loss equaled $3.5 million and $8.2 million, respectively. Comprehensive loss was comprised entirely of the Company’s net loss and the change in its unrealized gains and losses on its available-for-sale marketable securities for all periods presented.

Stock-Based Compensation

As of December 31, 2006, the Company has one share-based compensation plan, which is the ImmunoGen, Inc. 2006 Employee, Director and Consultant Equity Incentive Plan (the “Plan”). The Plan was approved by the Company’s Board of Directors and the stockholders of the Company on November 14, 2006, and replaced the previous stock option plan, the ImmunoGen, Inc. Restated Stock Option Plan, as amended (the “Former Plan”).  The Plan provides for the issuance of Stock Grants, the grant of Options and the grant of Stock-Based Awards for up to 2,500,000 shares of Common Stock of the Company, as well as any shares of Common Stock that are represented by awards granted under the Former Plan that are forfeited, expire or are cancelled without delivery of shares of Common Stock or which result in the forfeiture of shares of Common Stock back to the Company on or after November 13, 2006, or the equivalent of such number of shares after the Administrator, in its sole discretion, has interpreted the effect of any stock split, stock dividend, combination, recapitalization or similar transaction in accordance with the Plan; 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.

Effective July 1, 2005, the Company adopted the fair value recognition provisions of Financial Accounting Standards Board (FASB) Statement 123(R), Share-Based Payment(Statement 123(R)), using the modified-prospective-transition method. Under that transition method, compensation cost recognized includes: (a) compensation cost for all share-based payments granted, but not yet vested as of July 1, 2005, based on the grant-date fair value estimated in accordance with the original provisions of Statement 123 (as defined below), and (b) compensation cost for all share-based payments granted subsequent to July 1, 2005, based on the grant-date fair value estimated in accordance with the provisions of Statement 123(R). Such amounts have been reduced by the Company’s estimate of forfeitures of all unvested awards. For stock options granted to non-employees, the Company recognizes compensation expense in accordance with the requirements of Statement of Financial Accounting Standards (SFAS) No. 123, “Accounting for Stock Based Compensation” (Statement 123). Statement 123 requires that companies recognize compensation expense based on the estimated fair value of options granted to non-employees over their vesting period, which is generally the period during which services are rendered by such non-employees.

The fair value of each stock option is estimated on the date of grant using the Black-Scholes option-pricing model that uses the assumptions noted in the following table. 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 among 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. The following table includes the assumptions used in calculating our stock-based compensation for the three and six month periods ended December 31, 2006 and 2005:

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Using the Black-Scholes option-pricing model, the weighted average grant date fair value of options granted during the three months ended December 31, 2006 and 2005 was $3.13 and $4.17, respectively, and $2.72 and $4.72 for options granted during the six months ended December 31, 2006 and 2005, respectively.

As of December 31, 2006, the estimated fair value of unvested employee awards was $4.1 million net of estimated forfeitures. The weighted-average remaining vesting period for these awards is approximately two and one-half years.

During the six months ended December 31, 2006, holders of options issued under the Plan exercised their rights to acquire an aggregate of 167,495 shares of common stock at prices ranging from $0.84 to $3.95 per share.  The total proceeds to the Company from these option exercises were approximately $257,000.

Derivatives

Derivative instruments include a portfolio of short duration foreign currency forward contracts intended to mitigate the risk of exchange fluctuations for manufacturing/development contracts to be paid in Euros and Swedish Krona. Derivatives are estimated at fair value and classified as other current assets or liabilities in the accompanying Consolidated Balance Sheets. The fair value of these instruments represent 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.

We do 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 we enter into forward contracts only as an economic hedge, any gain or loss on the underlying foreign-denominated balance would be offset by the loss or gain on the forward contract.  Net gains on forward contracts for the period are $13,000 and are included in the Consolidated Statement of Operations as other income (expense).  As of December 31, 2006, we had outstanding forward contracts with notional amounts equivalent to approximately $4.1 million (2.6 million in Euros and 4.8 million in Swedish Krona), all maturing on or before June 29, 2007. As of December 31, 2005, there were no foreign currency contracts outstanding.

Reclassifications

Prior year treasury stock balances have been reclassified to common stock and additional paid-in capital in order to conform to the current year presentation.

Segment Information

During the three and six months ended December 31, 2006, the Company continued to operate in one reportable business segment under the management approach of SFAS No. 131, “Disclosures about Segments of an Enterprise and Related Information,” which is the business of discovery of monoclonal antibody-based cancer therapeutics.

Revenues from sanofi-aventis accounted for approximately 67% and 79% of total revenues for the three and six months ended December 31, 2006 and 2005, respectively. Revenues from Genentech accounted for 18% and 7% of total revenues for the three months ended December 31, 2006 and 2005, respectively, and 21% and 8% for the six months ended December 31, 2006 and 2005, respectively. There were no other individually significant customers in the three and six months ended December 31, 2006 and 2005.

Recent Accounting Pronouncements

In September 2006, the FASB issued SFAS No. 157, “Fair Value Measurements,” or SFAS 157, which is effective for fiscal years beginning after November 15, 2007. SFAS 157 defines fair value, establishes a framework for measuring fair value in accordance with Generally Accepted Accounting Principles, and expands disclosures about fair value measurements. The Statement codifies the definition of fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The standard clarifies the principle that fair value should be based on the assumptions market participants would use when pricing the asset or liability and establishes a fair value hierarchy that prioritizes the information used to develop those assumptions. We have not completed our evaluation of the effects of adopting this standard, however, we do not believe the adoption will have a material impact on the Company’s financial statements.

In September 2006, the SEC staff issued Staff Accounting Bulletin Topic 1N (SAB 108), “Financial Statements — Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements,” or SAB 108 which is effective for fiscal years ending after November 15, 2006. SAB 108 provides guidance on how prior year misstatements should be taken into consideration when quantifying misstatements in current year financial statements for purposes of determining whether the financial statements are materially misstated. Under this guidance, companies should take into account both the effect of a misstatement on the current year balance sheet as well as the impact upon the current year income statement in assessing the materiality of a current year misstatement. Once a current year misstatement has been quantified, the guidance in SAB Topic 1M,

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“Financial Statements — Materiality,” or SAB 99, should be applied to determine whether the misstatement is material. The implementation of SAB 108 has not had a material impact on the Company’s financial statements.

In July 2006, the FASB issued Financial Interpretation No. (FIN) 48, Accounting for Uncertainty in Income Taxes, which applies to all tax positions related to income taxes subject to No. 109 (SFAS 109), Accounting for Income Taxes. This includes tax positions considered to be “routine” as well as those with a high degree of uncertainty. FIN 48 utilizes a two-step approach for evaluating tax positions. Recognition (step one) occurs when an enterprise concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustained upon examination. Measurement (step two) is only addressed if step one has been satisfied (i.e., the position is more-likely-than-not to be sustained). Under step two, the tax benefit is measured as the largest amount of benefit, determined on a cumulative probability basis that is more-likely-than-not to be realized upon ultimate settlement. FIN 48’s use of the term “more-likely-than-not” in steps one and two is consistent with how that term is used in SFAS 109 (i.e., a likelihood of occurrence greater than 50 percent).

Those tax positions failing to qualify for initial recognition are recognized in the first subsequent interim period they meet the more-likely-than-not standard, or are resolved through negotiation or litigation with the taxing authority, or upon expiration of the statute of limitations. Derecognition of a tax position that was previously recognized would occur when a company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained. FIN 48 specifically prohibits the use of a valuation allowance as a substitute for derecognition of tax positions. Additionally, FIN 48 requires expanded disclosure requirements, which include a tabular rollforward of the beginning and ending aggregate unrecognized tax benefits as well as specific detail related to tax uncertainties for which it is reasonably possible the amount of unrecognized tax benefit will significantly increase or decrease within twelve months. These disclosures are required at each annual reporting period unless a significant change occurs in an interim period. FIN 48 is effective for fiscal years beginning after December 15, 2006 (our fiscal year 2008). We have not completed our evaluation of the effects of adopting this standard, however, we do not believe the adoption will have material impact on our results of operation or financial position.

B. Agreements

Biotest AG

In July 2006, the Company entered into a development and license agreement with Biotest AG. The agreement grants Biotest AG exclusive rights to use the Company’s TAP technology with antibodies to a target found on multiple myeloma cells to create anticancer therapeutics. Under the agreement, the Company received a $1 million upfront payment, and is entitled to receive up to $35.5 million in milestone payments plus royalties on the sales of any resulting products. The Company will receive manufacturing payments for any preclinical and clinical materials made at the request of Biotest. The agreement also provides ImmunoGen with the right to elect to participate, at specific stages during the clinical evaluation of any compound created under this agreement, 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 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, ImmunoGen and Biotest would share equally the associated costs of product development and commercialization in the United States along with the profit, if any, from U.S. product sales.

sanofi-aventis

In August 2006, sanofi-aventis exercised its remaining option to extend the term of the research collaboration with the Company for another year, and committed to pay the Company a minimum of $10.4 million in research support over the twelve months beginning September 1, 2007. Additionally, effective September 1, 2006, ImmunoGen is no longer obligated to present new targets for antibody-based anticancer therapeutics to sanofi-aventis, enabling the Company to use such targets in the development of its own proprietary products.

In October 2006, sanofi-aventis informed the Company that the clinical testing of AVE1642 began, triggering a $2 million milestone payment to the Company. This milestone is included in license and milestone fee revenue for the three and six month period ended December 31, 2006. Additionally, in October 2006, sanofi-aventis licensed non-exclusive rights to use ImmunoGen’s proprietary resurfacing technology to humanize antibodies. This technology was developed to enable antibodies initially of murine origin to appear to be human to the human immune system. This license provides sanofi-aventis with the non-exclusive right to use ImmunoGen’s proprietary humanization technology through August 31, 2011, and can be extended thereafter. Under the terms of the license, ImmunoGen will receive a $1 million license fee, half of which was paid upon contract signing and the second half is due on August 31, 2008, and in addition, ImmunoGen is entitled to receive milestone payments potentially totaling $4.5 million plus royalties on sales for each compound humanized under this agreement.  The Company has deferred the $500,000 portion of the upfront payment already received and will recognize this amount as revenue over the estimated period of substantial involvement.

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In December 2006, sanofi-aventis entered into an option agreement with the Company that provides it the right to gain expanded and extended access to the Company’s TAP technology. The option agreement provides sanofi-aventis with the right to enter into a multi-target agreement with the Company prior to or on August 31, 2008 by payment of an agreed-upon option exercise fee. The multi-target agreement would allow sanofi-aventis to evaluate the Company’s TAP technology with antibodies to targets not included in the existing research collaboration between the companies-with certain restrictions- and to license the right to use the technology to develop products for such targets on agreed-upon terms. The Company received payment of $500,000 with the signing of this option agreement, which the Company has deferred and will recognize over the option period.

The Company has agreements with other companies with respect to its compounds, as described elsewhere in this Quarterly Report and in its 2006 Annual Report on Form 10-K.

C. Capital Stock

The Company recorded approximately $32,000 and $42,000 in compensation expense during the three and six months ended December 31, 2006, respectively, related to stock units outstanding under the Company’s 2001 Non-Employee Director Stock Plan. During the three and six months ended December 31, 2005, the Company recaptured approximately $52,800 and $15,800, respectively, of previously recorded compensation expense. The value of the stock units is adjusted to market value at each reporting period.

Under the Company’s 2004 Non-Employee Director Compensation and Deferred Share Unit Plan, the Company issued 35,047 deferred share units during the six months ended December 31, 2006. The Company recorded approximately $67,000 and $121,000 in compensation expense related to deferred share units outstanding under the 2004 Plan during the three and six months ended December 31, 2006, respectively. The Company recorded approximately $(8,300) and $47,500 in compensation expense or (expense reduction) related to the issuance of 13,817 stock units for director services rendered during the three and six months ended December 31, 2005, respectively. The 2004 Non-Employee Director Compensation and Deferred Share Unit Plan was amended on September 5, 2006. Per the terms of the amended 2004 Non-Employee Director Compensation and Deferred Share Unit Plan, upon approval of the 2006 Employee, Director and Consultant Equity Plan, the redemption amount for deferred share units will be paid in shares of Common Stock of the Company in lieu of cash.  The 2006 Employee, Director and Consultant Equity Plan was approved by the Company’s Board of Directors on September 6, 2006, subject to approval by the Company’s stockholders, which was received on November 14, 2006. 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 in the amount of $175,000 and the total value of the awards, as calculated on the modification date, is being 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.  Additionally, under the amended 2004 Non-Employee Director Compensation and Deferred Share Unit Plan, the Company issued 15,552 deferred share units during the six months ended December 31, 2006.

ITEM 2.   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 targeted antibody-based anticancer therapeutics. The combination of our expertise in antibodies and cancer biology has resulted in the development of both proprietary product candidates and technologies. Our Tumor-Activated Prodrug, or TAP, technology relates to the attachment of one of our proprietary, extremely potent small molecule cytotoxic (cell-killing) agents to monoclonal antibodies that bind specifically to cancer cells. The antibody serves to target the cytotoxic agent specifically to cancers cells and the cytotoxic agent serves to kill the cells. Our TAP technology is designed to selectively kill cancer cells with limited damage to healthy tissue. The cytotoxic agents used in TAP compounds currently in preclinical and clinical testing are DM1 and DM4, our proprietary derivatives of a naturally occurring substance called maytansine. We also use our expertise in antibodies and cancer biology to develop naked-antibody anticancer product candidates.

We have entered into collaborative agreements that enable companies to use our TAP technology to develop commercial product candidates containing their antibodies. 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 entitled to upfront fees, milestone payments, and royalties on any commercial product sales. We are reimbursed for our fully burdened costs to manufacture preclinical and clinical materials and, under certain collaborative agreements, the reimbursement includes a profit margin. Currently, our collaborative partners include Amgen, Inc. (formerly Abgenix, Inc.), Biogen Idec, Biotest AG, Boehringer Ingelheim International GmbH, Centocor, Inc. (a wholly-owned subsidiary of Johnson & Johnson), Genentech, Inc., Millennium Pharmaceuticals, Inc., and sanofi-aventis. We expect that substantially all of our revenue for the foreseeable future will result from payments under our collaborative arrangements.

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In July 2003, we announced a discovery, development and commercialization collaboration with Aventis Pharmaceuticals, Inc. (now sanofi-aventis).  Under the terms of this agreement, in consideration of an upfront payment of $12 million, sanofi-aventis gained commercialization rights to three of the then-most-advanced product candidates in our preclinical pipeline, and the commercialization rights to new product candidates developed within the collaboration during its research program. This collaboration allows us to benefit from sanofi-aventis’ clinical development and commercialization capabilities. Under the terms of the sanofi-aventis agreement, we also are entitled to receive committed research funding totaling approximately $79.3 million over the full five years of the research collaboration, which includes the initial three-year term of the research program ending August 31, 2006 plus the two 12-month extensions beginning September 1, 2006.

In August 2005, sanofi-aventis exercised its contractual right to extend the term of its research program with us and committed to fund $18.2 million in research support over the twelve months beginning September 1, 2006. In August 2006, sanofi-aventis exercised its remaining option to extend the term of the research collaboration with us for an additional year, and committed to pay ImmunoGen a minimum of $10.4 million in research support over the twelve months beginning September 1, 2007. Additionally, effective September 1, 2006, we are no longer obligated to present new targets for antibody-based anticancer therapeutics to sanofi-aventis, enabling us to be able to use such targets in the development of our own proprietary products. After August 2008, sanofi-aventis will need to license the right to use our maytansinoid TAP technology with antibodies to targets that were not part of the research collaboration between us and sanofi-aventis.

In December 2006, sanofi-aventis entered into an option agreement with us that enables them to gain expanded access to our TAP technology. The option agreement provides sanofi-aventis with the right to enter into a multi-target agreement with us prior to or on August 31, 2008 by payment of an agreed-upon option exercise fee. The multi-target agreement would allow sanofi-aventis to evaluate our TAP technology with antibodies to targets not included in the existing research collaboration between the companies-with certain restrictions-and to license the right to use the technology to develop products for such targets on agreed-upon terms. We received payment of $500,000 with the signing of this option agreement, which we have deferred and will recognize over the option period.

In October 2006, sanofi-aventis informed us that clinical testing of AVE1642 had begun, triggering a $2 million milestone payment to us. This milestone is included in license and milestone fees revenue for the three and six months ending December 31, 2006. Additionally, in October 2006, sanofi-aventis licensed non-exclusive rights to use our proprietary resurfacing technology to humanize antibodies. This technology was developed to enable antibodies initially of murine origin to appear to be human to the human immune system. This license provides sanofi-aventis with the non-exclusive right to use our proprietary humanization technology through August 31, 2011, and can be extended thereafter. Under the terms of the license, ImmunoGen is due a $1 million license fee, half of which was paid upon contract signing and the second half is due on August 31, 2008, and in addition, ImmunoGen is entitled to receive milestone payments potentially totaling $4.5 million plus royalties on sales for each compound humanized under this agreement. We have deferred the $500,000 portion of the upfront payment already received and will recognize this amount as revenue over the estimated period of substantial involvement.

On January 27, 2006, Genentech notified us that the trastuzumab-MCC-DM1 Investigational New Drug (IND) application submitted by Genentech to the FDA had become effective. Under the terms of our May 2000 license agreement with Genentech that granted Genentech exclusive rights to use our TAP technology with antibodies to HER2, this event triggered a $2.0 million milestone payment to us. Trastuzumab-MCC-DM1 comprises Genentech’s HER2-targeting antibody, trastuzumab, and our DM1 cell-killing agent. On December 15, 2006 we announced the presentation of initial findings from a trastuzumab-MCC-DM1 clinical study at a medical conference. The findings presented were from an ongoing Phase I trial evaluating the compound in patients with HER2-positive metastatic breast cancer that had progressed while being treated with a chemotherapy regimen that included trastuzumab (Herceptin(R)). This study is designed to assess the safety, tolerability, and pharmacokinetics of trastuzumab-MCC-DM1; evidence of anticancer activity also was reported. The patient who had received the greatest amount of trastuzumab-MCC-DM1 at the time of the conference had an objective partial response by RECIST criteria. Dose limiting but rapidly reversible thrombocytopenia was observed in this patient. At the time of the symposium, the maximum tolerated dose had not yet been defined and patient enrollment was ongoing.

On January 25, 2006, Millennium Pharmaceuticals, Inc. notified us that, as part of its ongoing portfolio management process and based on the evaluation of clinical data in the context of other opportunities in its pipeline, Millennium had decided not to continue the development of its MLN2704 compound. Millennium retains its right to use our maytansinoid TAP technology with antibodies targeting PSMA.

On March 27, 2006, Millennium paid us a fee of $250,000 to extend the agreement that provides Millennium with certain rights to test our TAP technology with antibodies to specific targets and to license the right to use the technology to develop products on the terms defined in the agreement. This agreement was scheduled to expire on March 30, 2006, it is now scheduled to expire on March 30, 2007.

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In August 2003, Vernalis completed its acquisition of British Biotech. In connection with this acquisition, the merged company, called Vernalis plc, announced that it intended to review its merged product candidate portfolio, including its collaboration with ImmunoGen on huN901-DM1. After discussion with Vernalis, in January 2004 we announced that we would take over further development of the product candidate. Pursuant to the terms of the termination agreement executed on January 7, 2004, Vernalis retained responsibility for the conduct and expense of the study it initiated in the United States (Study 001) until June 30, 2004, and the study it had started in the United Kingdom (Study 002) through completion. We took over responsibility for Study 001 on July 1, 2004 and, in September 2005, we announced the initiation of our own clinical trial with huN901-DM1 in multiple myeloma (Study 003). On December 15, 2005, we executed an agreement to amend the residual obligation terms of the January 7, 2004 termination agreement with Vernalis. Under the terms of the amendment, we assumed responsibility for Study 002 as of December 15, 2005, including the cost of its completion. Under the amendment, Vernalis paid us $365,000 in consideration of the expected cost of the obligations assumed by us with the amendment.

On November 10, 2006, we announced the presentation of clinical data from Study 002 at the 18th EORTC-NCI-AACR International Conference on Molecular Targets and Cancer Therapeutics (EORTC) in Prague. This ongoing Phase I dose-escalation trial is designed to assess the safety and tolerability of huN901-DM1in patients with CD56-expressing solid tumors. At the time of the conference, the maximum tolerated dose of the compound had not yet been established. Evidence of anticancer activity was reported. A patient with Merkel cell cancer had a complete response following treatment with huN901-DM1 and had been in remission for 21 months at the time of the conference. A patient with relapsed small-cell lung cancer had an unconfirmed partial response and another thirteen patients had stable disease following treatment with huN901-DM1. In December 2006, the first findings from Study 003 were reported at the American Society of Hematology (ASH) annual meeting.  While this ongoing Phase I trial is designed to evaluate the safety and tolerability of huN901-DM1 in patients with relapsed multiple myeloma, evidence of anticancer activity also was reported.  Among the three patients receiving the higher of the two dose levels evaluated to date, one had an objective response and the other two had stable disease. The maximum tolerated dose had not yet been established in this study.

On January 8, 2004, we announced that we intended to advance cantuzumab mertansine (huC242-DM1), or an improved version of the compound, into human testing to assess the clinical utility of the compound in certain indications. In October 2004, we announced that we decided to move huC242-DM4 into clinical trials instead of cantuzumab mertansine. We initiated a Phase I clinical trial with huC242-DM4 in June 2005. On November 8, 2006 we announced the presentation of initial clinical data from this ongoing study at EORTC. This trial is designed as a dose-escalation study, in which increasingly higher doses of the compound are evaluated in new cohorts of patients until dose-limiting toxicity is observed. In a trial of this design, the occurrence of potential dose-limiting toxicity is typically assessed prior to defining the maximum tolerated dose. Eight huC242-DM4 dose levels have been evaluated in this study. We have encountered some toxicity, which is being assessed and may be addressable with patient pretreatment. The maximum tolerated dose of the compound has not been established.

Based upon the results of our clinical trials, if and when they are completed, we will evaluate whether to continue clinical development of huN901-DM1 and huC242-DM4, and, if so, whether we will seek a collaborative partner or partners to continue the clinical development and commercialization of either or both of these compounds.

To date, we have not generated revenues from commercial product sales and we expect to incur significant operating losses for the foreseeable future. We do not anticipate that we will have a commercially approved product within the near future. Research and development expenses and cash expenditures are expected to increase significantly in the near term as we continue our development efforts, including an expanded clinical trial program and development of commercial-scale production capabilities at third-party suppliers. As of December 31, 2006, we had approximately $66.7 million in cash and marketable securities. We anticipate that our current capital resources and future collaboration payments, including the committed research funding due us under the sanofi-aventis collaboration over the remainder of the research program, will enable us to meet our operational expenses and capital expenditures for at least the current and next one to two fiscal years.

We anticipate that the increase in total cash expenditures will be partially offset by collaboration-derived proceeds, including milestone payments and the committed research funding to which we are entitled pursuant to the sanofi-aventis collaboration. 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 pursue additional strategic partners, secure alternative financing arrangements, and/or defer or limit some or all of our research, development and/or clinical projects.

Critical Accounting Policies

We prepare our consolidated financial statements in accordance with accounting principles generally accepted in the United

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States. 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 estimate the period of our significant involvement during development for each of our collaborative agreements. We recognize any upfront fees received from our collaborators ratably over this estimated period of significant involvement. We generally believe our period of significant involvement occurs between the date we sign a collaboration agreement and completion of Phase II testing of our collaborator’s product that is the subject of the collaboration agreement. We estimate that this time period is generally six and one-half years, depending on the characteristics of the license. The actual period of our involvement could differ significantly based upon the results of our collaborators’ preclinical and clinical trials, competitive products that are introduced into the market and the general uncertainties surrounding drug development. Any difference between our estimated period of involvement during development and our actual period of involvement could have a material effect upon our results of operations. We assess our period of significant involvement with each collaboration on a quarterly basis and adjust the period of involvement prospectively, as appropriate.

We are recognizing the $12.0 million upfront fee we received from sanofi-aventis ratably over our estimated period of significant involvement of five years. This estimated period includes the initial three-year term of the collaborative research program and the two 12-month extensions sanofi-aventis exercised in August 2005 and 2006.

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 DM1 and DM4, collectively referred to as DMx, and ansamitocin P3 in excess of twelve-month projected usage that is not supported by collaborators’ firm, fixed orders and projections to be excess. To date, we have fully reserved any such material identified as excess with a corresponding charge to cost of clinical materials reimbursed. Our collaborators’ estimates of their clinical material requirements are based upon expectations of their clinical trials, including the timing, size, dosing schedule and maximum tolerated dose of each clinical trial. Our collaborators’ actual requirements for clinical materials may vary significantly from their projections. Sizeable differences between our collaborators’ actual manufacturing orders and their projections could result in our actual twelve-month usage of DMx and ansamitocin P3 varying significantly from our estimated usage at an earlier reporting period.

Stock Based Compensation

As of December 31, 2006, the Company has one share-based compensation plan, which is the ImmunoGen, Inc. 2006 Employee, Director and Consultant Equity Incentive Plan. Effective July 1, 2005, we adopted the fair value recognition provisions of Financial Accounting Standards Board (FASB) Statement 123(R), Share-Based Payment (Statement 123(R)), using the modified-prospective-transition method. Under that transition method, compensation cost includes: (a) compensation cost for all share-based payments granted, but not yet vested as of July 1, 2005, based on the grant-date fair value estimated in accordance with the original provisions of Statement 123 (as defined below), and (b) compensation cost for all share-based payments granted subsequent to July 1, 2005, based on the grant-date fair value estimated in accordance with the provisions of Statement 123(R). Such amounts have been reduced by the Company’s 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 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 among 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. The compensation cost that has been incurred during the three and six months ended December 31, 2006 is $589,000 and $1.2 million, respectively. As of December 31, 2006, the estimated fair value of unvested employee awards was $4.1 million net of estimated forfeitures. The weighted-average remaining vesting period for these awards is approximately two and one-half years.

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Derivatives

Derivative instruments include a portfolio of short duration foreign currency forward contracts intended to mitigate the risk of exchange fluctuations for manufacturing/development contracts to be paid in Euros and Swedish Krona. Derivatives are estimated at fair value and classified as other current assets or liabilities in the accompanying Consolidated Balance Sheets. The fair value of these instruments represent 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.

We do 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 we enter into forward contracts only as an economic hedge, any gain or loss on the underlying foreign-denominated balance would be offset by the loss or gain on the forward contract.  Net gains on forward contracts for the period are $13,000 and are included in the Consolidated Statement of Operations as other income (expense).  As of December 31, 2006, we had outstanding forward contracts with notional amounts equivalent to approximately $4.1 million (2.6 million in Euros and 4.8 million in Swedish Krona), all maturing on or before June 29, 2007. As of December 31, 2005, there were no foreign currency contracts outstanding.

RESULTS OF OPERATIONS

Comparison of Three Months ended December 31, 2006 and 2005

Our total revenues for each of the three months ended December 31, 2006 and 2005 were $12.1 million and $6.6 million, respectively. The $5.5 million increase in revenues in the three months ended December 31, 2006 compared to the same period in the prior year due to an increase in license and milestone fees, clinical materials reimbursement revenue, and research and development support revenue.

Research and development support was $6.6 million for the three months ended December 31, 2006 compared with $5.2 million for the three months ended December 31, 2005. These amounts primarily represent committed research funding earned based on actual resources utilized under our discovery, development and commercialization agreement with sanofi-aventis, as well as amounts earned for resources utilized under our development and license agreements with Biogen Idec, Biotest, Centocor, and Genentech. Also included in research and development support revenue are fees related to samples of research-grade material shipped to collaborators. To date, our development fees represent the fully burdened reimbursement of costs incurred in producing research-grade materials and 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’ compounds 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.

Revenues from license and milestone fees for the three months ended December 31, 2006 increased $2.2 million to $3.4 million from $1.3 million in the same period ended December 31, 2005. Total revenue from license and milestone fees recognized from each of our collaborative partners in the three-month periods ended December 31, 2006 and 2005 is included in the following table (in thousands):

Deferred revenue of $15.1 million as of December 31, 2006 primarily represents payments received from our collaborators pursuant to our license and supply agreements, which we have yet to earn pursuant to our revenue recognition policy.

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Clinical materials reimbursement increased by approximately $2.0 million in the three months ended December 31, 2006, to nearly $2.1 million from $81,000 in the three months ended December 31, 2005. During the three months ended December 31, 2006, we shipped clinical materials in support of the AVE9633 clinical trials and trastuzumab-DM1 clinical trials, as well as preclinical materials in support of the development efforts of certain other collaborators. During the three months ended December 31, 2005, we shipped preclinical materials in support of the development efforts of certain other collaborators. Under certain collaborative agreements, we are reimbursed for our fully burdened cost to produce clinical materials plus a profit margin. The amount of clinical materials reimbursement we earn, and the related cost of clinical materials reimbursed, is directly related to (i) the number of on-going clinical trials our collaborators 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 the clinical materials, and (ii) our production of clinical-grade material on behalf of our collaborators, either in anticipation of clinical trials, or for process development and analytical purposes. As such, the amount of clinical materials reimbursement and the related cost of clinical materials reimbursed may vary significantly from quarter to quarter and year to year.

Research and Development Expenses

We report research and development expense net of certain reimbursements we receive from our collaborators. Our research and development expenses relate to (i) research to identify and evaluate new targets and to develop and evaluate new antibodies and cytotoxic drugs, (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:

·                  activities pursuant to our discovery, development and commercialization agreement with sanofi-aventis;

·                  activities related to the preclinical and clinical development of huN901-DM1 and huC242-DM4;

·                  process development related to production of the huN901 antibody and huN901-DM1 conjugate for clinical materials;

·                  process development related to production of the huC242 antibody and huC242-DM4 conjugate for clinical materials;

·                  process improvements related to the production of DM1, DM4 and strain development of their precursor, ansamitocin P3;

·                  funded development activities with contract manufacturers for the huN901 antibody, the huC242 antibody, and DM1, DM4 and their precursor, ansamitocin P3;

·                  operation and maintenance of our conjugate manufacturing plant;

·                  process improvements to our TAP technology;

·                  identification and evaluation of potential antigen targets;

·                  evaluation of internally developed and/or in-licensed product candidates and technologies; and

·                  development and evaluation of additional cytotoxic agents.

DM1 and DM4 are the cytotoxic agents that we currently use in the manufacture of our two TAP product candidates in clinical testing. We have also investigated the viability of other maytansinoid effector molecules, which, collectively with DM1 and DM4, we refer to as DMx. In order to make commercial manufacture of DMx conjugates viable, we have devoted substantial resources to improving the strain of the microorganism that produces ansamitocin P3, the precursor to DMx, to enhance manufacturing yields. We also continue to devote considerable resources to improve other DMx manufacturing processes.

On January 8, 2004, we announced that pursuant to the terms and conditions of a termination agreement between us and Vernalis, Vernalis relinquished its rights to develop and commercialize huN901-DM1. As a result, we regained the rights to develop and commercialize huN901-DM1. Under the terms of this termination agreement with Vernalis, we assumed responsibility for one of the studies underway with the compound (Study 001) on July 1, 2004. Since then, we have expanded this study based upon the data from the initial patients enrolled. Additionally, we initiated a Phase I clinical trial with huN901-DM1 in CD56-positive multiple myeloma (Study 003) in September 2005. On December 15, 2005, we executed an amendment to this termination agreement with Vernalis. Under the terms of the amendment, we assumed responsibility as of December 15, 2005, at our own expense, to complete the huN901-DM1 clinical study (Study 002) that had been initiated in the United Kingdom. Vernalis paid us $365,000 in consideration of the

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expected cost of the obligations assumed by us under the amendment. We intend to evaluate whether to out-license all or part of the development and commercial rights to this compound as we move through the clinical trial process.

In January 2004, we announced that we planned to advance cantuzumab mertansine, or an improved version of the compound, into a clinical trial that we would manage. In October 2004, we decided to move forward in developing a modified version of cantuzumab mertansine which we call huC242-DM4. Patient dosing was initiated for the Phase I study of huC242-DM4 in June 2005. We intend to evaluate whether to out-license all or part of the development and commercial rights to this compound as we move through the clinical trial process for this compound.

In July 2003, under the terms of our discovery, development and commercialization collaboration, we licensed a number of compounds to sanofi-aventis, including the three then-most advanced product candidates in our preclinical portfolio. These three product candidates were an anti-CD33 TAP compound for acute myeloid leukemia (AVE9633), an anti-IGF-1R antibody (AVE1642), and an anti-CD19 TAP compound (SAR 3419) for certain B-cell malignancies, including non-Hodgkin’s lymphoma.  Over the original, three-year term of the collaboration and two agreed-upon one-year extensions, we will receive a minimum of $79.3 million of committed research funding and will devote a significant amount of our internal research and development resources to advancing the research program. Under the terms of the agreement, we may advance any TAP or antibody products that sanofi-aventis has elected not to either initially include or later advance in the research program.  Additionally, as of September 1, 2006 we are no longer obligated to present new targets for antibody-based anticancer therapeutics to sanofi-aventis, enabling us to be able to use such targets in the development of our own proprietary products.  In December, 2006, sanofi-aventis entered into an option agreement that enables them to gain expanded access to the Company’s TAP technology.

Sanofi-aventis initiated Phase I testing of AVE9633 in March 2005. An abstract with findings from the first Phase I study was published in December 2006. A separate Phase I study is underway in Europe. In October 2006, clinical testing of AVE1642, a therapeutic antibody that binds to the Insulin-like Growth Factor 1 Receptor (IGF-1R), was initiated. SAR3419 is in preclinical development. Additional compounds also are in various stages of research and development.

Our agreement with sanofi-aventis required us to present for inclusion in the collaborative research program certain antibodies or antibody targets that we believe will have utility in oncology, with the exception of those antibodies or antibody targets that are the subject of our pre-existing or future collaboration and license agreements. Sanofi-aventis then had the right to either include in or exclude from the collaborative research program these proposed antibodies and antibody targets. If sanofi-aventis elected to exclude any antibodies or antibody targets, we could elect to develop the compounds for our own pipeline. Effective September 1, 2006, we are no longer obligated to present new targets for antibody-based anticancer therapeutics to sanofi-aventis, enabling us to use such targets in the development of our own proprietary products.

The potential product candidates that have been or that may eventually be excluded from the sanofi-aventis collaboration are in an early stage of discovery research and we are unable to accurately estimate which potential products, 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 research 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 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 dosing schedule 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 ineffective or cause harmful 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 impracticable 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.

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Research and development expense for the three months ended December 31, 2006 increased $3.0 million to $11.8 million from $8.8 million for the three months ended December 31, 2005. The number of research and development personnel increased to 162 at December 31, 2006 compared to 146 at December 31, 2005. Research and development salaries and related expenses increased by $618,000 in the three months ended December 31, 2006 compared to the three months ended December 31, 2005. Contract service expense increased by $2.6 million in the three months ended December 31, 2006 compared to the same period ended December 31, 2005. This increase is primarily related to the manufacturing and material costs for our compounds currently in clinical trials, as well as development costs with contract manufacturing organizations for the potential production of later-stage materials. Partially offsetting these increases, overhead utilization from the manufacture of clinical materials on behalf of our collaborators increased by $349,000 in the three months ended December 31, 2006 compared to the three months ended December 31, 2005.

We expect future research and development expenses to increase as we expand our clinical trial activity. We do not track our research and development costs by project. Since we use our research and development resources across multiple research and development projects, we manage our research and development expenses within each of the categories listed in the following table and described in more detail below (in thousands):

Research:   Research includes expenses associated with activities to identify and evaluate new targets and to develop and evaluate new antibodies 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 for the three months ended December 31, 2006 increased $366,000 to $3.8 million from $3.5 million for the three months ended December 31, 2005. The increase in research expenses was primarily the result of an increase in salaries and related expense.

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, 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 for the three months ended December 31, 2006 increased $316,000 to $2.2 million compared to $1.9 million for the three months ended December 31 2005. This increase is primarily due to an increase in salaries and related expense, as well as an increase in contract service expense resulting from increased costs associated with preclinical studies.

Process and Product Development:  Process and product development expenses include costs for development of clinical and commercial manufacturing processes. Such expenses include the costs of personnel, contract services and facility expenses. For the three months ended December 31, 2006, total development expenses increased $144,000 to $1.4 million, compared to $1.2 million for the three months ended December 31, 2005.  The increase is primarily due to an increase in salaries and related expense, partially offset by a decrease in contract service expense.

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Manufacturing Operations: Manufacturing operations expense includes costs to scale-up the manufacture of preclinical and clinical materials for our own product candidates and costs to support the operation and maintenance of our conjugate manufacturing plant. Such expenses include personnel, raw materials for our preclinical and clinical trials, development costs with contract manufacturing organizations, manufacturing supplies, and facilities expense. Manufacturing costs related to the production of material for our collaborators are recorded as cost of clinical material reimbursed in our statement of operations. For the three months ended December 31, 2006, manufacturing operations expense increased $2.2 million to $4.3 million compared to $2.2 million in the same period last year. The increase in the three months ended December 31, 2006 as compared to the three months ended December 31, 2005 was primarily the result of (i) an increase in contract service expense substantially due to higher antibody purchases as well as development costs with contract manufacturing organizations for the potential production of later-stage materials and (ii) and increase in salaries and related expense. Partially offsetting these increases was higher overhead utilization from the manufacture of clinical materials on behalf of our collaborators during the three months ended December 31, 2006 as compared to the same period ended December 31, 2005.

General and Administrative Expenses

General and administrative expenses for the three months ended December 31, 2006 increased $234,000 to $2.6 million compared to $2.3 million for the three months ended December 31 2005. The increase is primarily due to an increase in director compensation, and to a lesser extent, consulting fees.

Interest Income

Interest income for the three months ended December 31, 2006 increased $116,000 to $874,000 from $758,000 for the three months ended December 31, 2005. The increase in interest income is primarily the result of higher rates of return resulting from higher yields on investments.

Net Realized Gains (Losses) on Investments

Net realized gains on investments were $5,000 for the three months ended December 31, 2006 as compared to net realized losses on investments of $22,000 for the three months ended December 31, 2005. The difference is attributable to the timing of investment sales.

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Comparison of Six Months ended December 31, 2006 and 2005

Our total revenues for each of the six months ended December 31, 2006 and 2005 were $19.8 million and $14.4 million, respectively. The $5.5 million increase in revenues in the six months ended December 31, 2006 compared to the same period in the prior year is attributable to an increase in license and milestone fees, clinical materials reimbursement revenue, and research and development support revenue.

Research and development support was $12.1 million for the six months ended December 31, 2006 compared with $10.9 million for the six months ended December 31, 2005. These amounts primarily represent committed research funding earned based on actual resources utilized under our discovery, development and commercialization agreement with sanofi-aventis, as well as amounts earned for resources utilized under our development and license agreements with Biogen Idec, Biotest, Centocor, and Genentech. Of the $10.9 million reported in the six months ended December 31, 2005, $1.1 million represents funding related to research and development efforts performed during the Company’s 2005 fiscal year under the sanofi-aventis collaboration but billed and recognized in fiscal 2006.  Also included in research and development support revenue are fees related to samples of research-grade material shipped to collaborators. To date, our development fees represent the fully burdened reimbursement of costs incurred in producing research-grade materials and 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’ compounds 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.

Revenues from license and milestone fees for the six months ended December 31, 2006 increased $2.3 million to $4.8 million from $2.5 million in the same period ended December 31, 2005. Total revenue from license and milestone fees recognized from each of our collaborative partners in the six-month periods ended December 31, 2006 and 2005 is included in the following table (in thousands):

Clinical materials reimbursement increased by approximately $2.0 million to $2.9 million in the six months ended December 31, 2006, compared to $912,000 in the six months ended December 31, 2005. During the six months ended December 31, 2006, we shipped clinical materials in support of the AVE9633 clinical trials and trastuzumab-DM1 clinical trials, as well as preclinical materials in support of the development efforts of certain other collaborators. During the six months ended December 31, 2005, we shipped clinical materials in support of the AVE9633 clinical trials and in the anticipation of the clinical trials to be conducted by our partners, as well as preclinical materials in support of the development efforts of certain other collaborators. We are reimbursed for our fully burdened cost to produce clinical materials plus under certain collaborative agreements, a profit margin. The amount of

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clinical materials reimbursement we earn, and the related cost of clinical materials reimbursed, is directly related to (i) the number of on-going clinical trials our collaborators 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 the clinical materials, and (ii) our production of clinical-grade material on behalf of our collaborators, either in anticipation of clinical trials, or for process development and analytical purposes. As such, the amount of clinical materials reimbursement and the related cost of clinical materials reimbursed may vary significantly from quarter to quarter and year to year.

Research and Development Expenses

Research and development expense for the six months ended December 31, 2006 increased $4.9 million to $23.2 million from $18.3 million for the six months ended December 31, 2005. The number of research and development personnel increased to 162 at December 31, 2006 compared to 146 at December 31, 2005. Research and development salaries and related expenses increased by $1.1 million in the six months ended December 31, 2006 compared to the six months ended December 31, 2005. Contract service expense increased by $4.4 million in the six months ended December 31, 2006 compared to the same period ended December 31, 2005. This increase is primarily related to the manufacturing and material costs for our compounds currently in clinical trials, as well as development costs with contract manufacturing organizations for the potential production of later-stage materials. Partially offsetting these increases, overhead utilization from the manufacture of clinical materials on behalf of our collaborators increased by $1.2 million in the six months ended December 31, 2006 compared to the six months ended December 31, 2005.

We expect future research and development expenses to increase as we expand our clinical trial activity. We do not track our research and development costs by project. Since we use our research and development resources across multiple research and development projects, we manage our research and development expenses within each of the categories listed in the following table and described in more detail below (in thousands):

Research:   Research includes expenses associated with activities to identify and evaluate new targets and to develop and evaluate new antibodies 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 for the six months ended December 31, 2006 increased $531,000 to $7.5 million from $7.0 million for the six months ended December 31, 2005. The increase in research expenses was primarily the result of an increase in salaries and related expense, and to a lesser extent, facilities expense.

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, 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 for the six months ended December 31, 2006 increased $552,000 to $4.1 million compared to $3.6 million for the six months ended December 31, 2005. This increase is primarily the result of (i) an increase in salaries and related expense; (ii) an increase in contract service expense resulting from increased costs associated with preclinical studies, and (iii) an increase in clinical trial costs resulting from the advancement of our clinical trials.

Process and Product Development:  Process and product development expenses include costs for development of clinical and commercial manufacturing processes. Such expenses include the costs of personnel, contract services and facility expenses. For the six months ended December 31, 2006, total development expenses increased $86,000 to $2.7 million, compared to $2.6 million for the six months ended December 31, 2005.  The increase is primarily due to an increase in salaries and related expense and facilities expense, partially offset by an decrease in contract service expense.

Manufacturing Operations:Manufacturing operations expense includes costs to manufacture preclinical and clinical materials for our own product candidates and costs to support the operation and maintenance of our conjugate manufacturing plant. Such expenses include personnel, raw materials for our preclinical and clinical trials, development costs with contract manufacturing

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organizations, manufacturing supplies, and facilities expense. Manufacturing costs related to the production of material for our collaborators are recorded as cost of clinical material reimbursed in our statement of operations. For the six months ended December 31, 2006, manufacturing operations expense increased $3.8 million to $8.8 million compared to $5.1 million in the same period last year. The increase in the six months ended December 31, 2006 as compared to the same period ended December 31, 2005 was primarily the result of (i) an increase in contract service expense substantially due to higher antibody purchases as well as development costs with contract manufacturing organizations for the potential production of later-stage materials and (ii) and an increase in the cost of disposable materials. Partially offsetting these increases was higher overhead utilization from the manufacture of clinical materials on behalf of our collaborators during the six months ended December 31, 2006 as compared to the same period ended December 31, 2005.

General and Administrative Expenses

General and administrative expenses for the six months ended December 31, 2006 increased $238,000 to $5.4 million compared to $5.1 million for the six months ended December 31, 2005. The increase is primarily due to an increase in patent expense, recruiting fees, and director compensation, partially offset by a decrease in facilities expense. Patent costs rose primarily due to increased patents filed in additional countries, resulting in additional fees. The decrease in facilities expense was due to an adjustment made during the six months ended December 31, 2006 to reverse an incorrect accrual recorded in fiscal 2006 of $195,000 related to operating expenses and real estate taxes associated with the 64 Sidney Street office. The Company does not believe such previously recorded expense was material to the results of operations or the financial position of the Company for fiscal year 2006 or for the six months ended December 31, 2006.

Interest Income

Interest income for the six months ended December 31, 2006 increased $263,000 to $1.7 million from $1.5 million for the six months ended December 31, 2005. The increase in interest income is primarily the result of higher rates of return resulting from higher yields on investments.

Net Realized Gains (Losses) on Investments

Net realized gains on investments were $5,000 for the six months ended December 31, 2006 as compared to net realized losses on investments of $26,000 for the six months ended December 31, 2005. The difference is attributable to the timing of investment sales.

LIQUIDITY AND CAPITAL RESOURCES

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 and research funding. As of December 31, 2006, we had approximately $66.7 million in cash and marketable securities.  Net cash used for operations during the six months ended December 31, 2006 was $7.9 million compared to $4.6 million during the six months ended December 31, 2005. The principal use of cash in operating activities for all periods presented was to fund our net loss. The increase in cash used in operations during the first half of fiscal 2007 compared to the first half of fiscal 2006 is principally due to the increased net loss.

Net cash provided by investing activities during the six months ended December 31, 2006 was $8.0 million compared to $7.6 million during the six months ended December 31, 2005. The variance primarily relates to a decrease in capital expenditures. Capital expenditures, primarily for the purchase of new equipment, were $920,000 and $1.2 million for the six-month periods ended December 31, 2006 and 2005, respectively.

Net cash provided by financing activities was $257,000 for the six months ended December 31, 2006 compared to net cash provided by financing activities of $266,000 for the six months ended December 31, 2005. For the six months ended December 31, 2006, net cash provided by financing activities reflects the proceeds to us from the exercise of 167,495 stock options under our Restated Stock Option Plan, at prices ranging from $0.84 to $3.95 per share. For the six months ended December 31, 2005, net cash provided by financing activities reflects the proceeds to us from the exercise of 61,138 stock options under the Company’s Restated Stock Option Plan, at prices ranging from $1.94 to $6.27 per share.

We anticipate that our current capital resources and future collaborator payments, including committed research funding that we expect to receive from sanofi-aventis pursuant to the terms of our collaboration agreement, will enable us to meet our operational expenses and capital expenditures for at least the current and the next one to two fiscal years. We believe that our existing capital resources in addition to our established collaborative agreements will provide funding sufficient to allow us to meet our obligations under all collaborative agreements while also allowing us to develop product candidates and technologies not covered by collaborative agreements. However, we cannot provide assurance that such collaborative agreement funding will, in fact, be received. Should we

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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.

Recent Accounting Pronouncements

In September 2006, the FASB issued SFAS No. 157, “Fair Value Measurements,” or SFAS 157, which is effective for fiscal years beginning after November 15, 2007 (our fiscal year 2009). SFAS 157 defines fair value, establishes a framework for measuring fair value in accordance with Generally Accepted Accounting Principles, and expands disclosures about fair value measurements. The Statement codifies the definition of fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The standard clarifies the principle that fair value should be based on the assumptions market participants would use when pricing the asset or liability and establishes a fair value hierarchy that prioritizes the information used to develop those assumptions. We have not completed our evaluation of the effects of adopting this standard, however, we do not believe the adoption will have a material impact on our results of operation or financial position.

In September 2006, the SEC staff issued Staff Accounting Bulletin Topic 1N (SAB 108), “Financial Statements — Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements,” or SAB 108 which is effective for fiscal years ending after November 15, 2006. SAB 108 provides guidance on how prior year misstatements should be taken into consideration when quantifying misstatements in current year financial statements for purposes of determining whether the financial statements are materially misstated. Under this guidance, companies should take into account both the effect of a misstatement on the current year balance sheet as well as the impact upon the current year income statement in assessing the materiality of a current year misstatement. Once a current year misstatement has been quantified, the guidance in SAB Topic 1M, “Financial Statements — Materiality,” or SAB 99, should be applied to determine whether the misstatement is material. The implementation of SAB 108 has not had a material impact on the Company’s financial statements.

In July 2006, the FASB issued Financial Interpretation No. (FIN) 48, Accounting for Uncertainty in Income Taxes, which applies to all tax positions related to income taxes subject to No. 109 (SFAS 109), Accounting for Income Taxes. This includes tax positions considered to be “routine” as well as those with a high degree of uncertainty. FIN 48 utilizes a two-step approach for evaluating tax positions. Recognition (step one) occurs when an enterprise concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustained upon examination. Measurement (step two) is only addressed if step one has been satisfied (i.e., the position is more-likely-than-not to be sustained). Under step two, the tax benefit is measured as the largest amount of benefit, determined on a cumulative probability basis that is more-likely-than-not to be realized upon ultimate settlement. FIN 48’s use of the term “more-likely-than-not” in steps one and two is consistent with how that term is used in SFAS 109 (i.e., a likelihood of occurrence greater than 50 percent).

Those tax positions failing to qualify for initial recognition are recognized in the first subsequent interim period they meet the more-likely-than-not standard, or are resolved through negotiation or litigation with the taxing authority, or upon expiration of the statute of limitations. Derecognition of a tax position that was previously recognized would occur when a company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained. FIN 48 specifically prohibits the use of a valuation allowance as a substitute for derecognition of tax positions. Additionally, FIN 48 requires expanded disclosure requirements, which include a tabular rollforward of the beginning and ending aggregate unrecognized tax benefits as well as specific detail related to tax uncertainties for which it is reasonably possible the amount of unrecognized tax benefit will significantly increase or decrease within twelve months. These disclosures are required at each annual reporting period unless a significant change occurs in an interim period. FIN 48 is effective for fiscal years beginning after December 15, 2006 (our fiscal year 2008). We have not completed our evaluation of the effects of adopting this standard, however, we do not believe the adoption will have a material impact on our results of operation or financial position.

Forward-Looking Statements

Various statements in this Quarterly Report on Form 10-Q are forward-looking statements concerning our future products, revenues, expenses, liquidity and cash needs, as well as our plans and strategies. Forward-looking statements give management’s current expectations or forecasts of future events. You can identify these statements by the fact that they do not relate strictly to historic or current events. They use words such as “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” “should,” “may,” “will,” and other words and terms of similar meaning. These forward-looking statements are based upon current expectations and we assume no obligation to update this information. Any or all of our forward-looking statements in this Quarterly Report on Form 10-Q may turn out to be wrong. They can be affected by inaccurate assumptions we might make or by known or unknown risks or uncertainties. Consequently, no forward-looking statement can be guaranteed. Actual results may vary materially from those set forth in the forward-looking statements. Forward-looking statements, therefore, should be considered in light of all of the information included or referred to in this Quarterly Report on Form 10-Q, including the cautionary information set forth under Part II, Item 1A., Risk Factors.

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ITEM 3.          Quantitative and Qualitative Disclosures 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.

ITEM 4.                             Controls and Procedures

(a)          Evaluation of Disclosure Controls and Procedures

As of the end of the period covered by this report, the Company’s principal executive officer and principal financial officer evaluated the effectiveness of the Company’s disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and have concluded, based on such evaluation, that the design and operation of the Company’s disclosure controls and procedures were adequate and effective to ensure that material information relating to the Company, including its consolidated subsidiaries, was made known to them by others within those entities, particularly during the period in which this Quarterly Report on Form 10-Q was being prepared.

(b)         Changes in Internal Controls

There were no changes, identified in connection with the evaluation described above, in the Company’s internal controls over financial reporting or in other factors that could significantly affect those controls that have materially affected or are reasonably likely to materially affect, the Company’s internal control over financial reporting.

PART II. OTHER INFORMATION

ITEM 1.                             Legal Proceedings.

None.

ITEM 1A.                    Risk Factors.

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 December 31, 2006, we had an accumulated deficit of $247.9 million. For the six months ended December 31, 2006, and the fiscal years ended June 30, 2006, 2005, and 2004, we generated losses of $9.3 million, $17.8 million, $11.0 million and $5.9 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 studies and collaborator support activities increase. 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, and 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 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 product candidates for several years, and we may never generate revenues from the commercial sale of 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.

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Foreign currency exchange risk

ImmunoGen’s 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 ImmunoGen receive certain foreign currencies and pay U.S. dollars at specified exchange rates at specified future dates.

Our foreign currency risk management strategy is principally designed to mitigate the future potential financial impact of changes in the value of transactions and balances denominated in foreign currency, resulting from changes in foreign currency exchange rates.  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 primarily are denominated in European currencies and have maturities of less than six months.

In addition to the foregoing risk factors, for a complete set of risk factors, please refer to the section entitled “Risk Factors” in our Annual Report on Form 10-K for our fiscal year ended June 30, 2006, on file with the Securities and Exchange Commission.

ITEM 2.                             Unregistered Sales of Equity Securities and Use of Proceeds.

None.

ITEM 3.                             Defaults Upon Senior Securities.

None.

ITEM 4.  Submission of Matters to a Vote of Security Holders.

The 2006 Annual Meeting of Shareholders of the Company was held at 11:00 a.m., Boston time, on Tuesday, November 14, 2006. At the Annual Meeting, five members were elected to the Board of Directors, and the ImmunoGen, Inc. 2006 Employee, Director and Consultant Equity Incentive Plan was approved.

Subsequent to the shareholder vote, the following directors’ terms of office continued after the Annual Meeting: Mitchel Sayare, the Chairman of the Board, David W. Carter, Nicole Onetto, Mark Skaletsky, and Joseph J. Villafranca.

The ImmunoGen, Inc. 2006 Employee, Director and Consultant Equity Incentive Plan was approved as follows:

Fixing the number of Directors constituting the full Board of Directors of the Company at five (5) was approved as follows:

ITEM 5.                             Other Information.

None.

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ITEM 6.                             Exhibits.

(a)          Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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Exhibit 10.1

LICENSE AGREEMENT

between

IMMUNOGEN, INC.

and

SANOFI-AVENTIS U.S. LLC

October 5, 2006

Portions of this Exhibit were omitted and have been filed separately with the Secretary of the Commission pursuant to the Company’s application requesting confidential treatment under Rule 24b-2 of the Securities Exchange Act of 1934.

TABLE OF CONTENTS

i

ii

LICENSE AGREEMENT

This LICENSE AGREEMENT (this “Agreement”) is entered into as of October 5, 2006, by and between ImmunoGen, Inc., a Massachusetts corporation having a principal place of business at 128 Sidney Street, Cambridge, Massachusetts 02139 (“ImmunoGen”), and sanofi-aventis U.S. LLC, a limited liability company organized and existing under the laws of Delaware with offices at 1041 Rt.202-206, Bridgewater, NJ 08807 (“sanofi-aventis”).  Each of sanofi-aventis and ImmunoGen is sometimes referred to individually herein as a “Party” and collectively as the “Parties.”

WHEREAS, ImmunoGen and Aventis Pharmaceuticals, Inc., sanofi-aventis’ predecessor in interest (“Aventis”), entered into that certain Collaboration and License Agreement dated as of July 30, 2003 (the “Collaboration Agreement”) pursuant to which ImmunoGen and Aventis agreed to collaborate in the identification and validation of targets for use in the discovery of antibodies and antibody drug conjugates for the prevention, control and/or treatment in humans of precancerous and/or cancerous conditions; and

WHEREAS, ImmunoGen has developed certain proprietary technology related to antibody humanization; and

WHEREAS, sanofi-aventis desires to obtain from ImmunoGen, and ImmunoGen desires to grant to sanofi-aventis, a non-exclusive license to use such proprietary technology in the development of its proprietary Antibodies and the commercialization of Licensed Products resulting therefrom.

NOW, THEREFORE, in consideration of the mutual covenants contained herein, and for other good and valuable consideration, the Parties hereto, intending to be legally bound, hereby agree as follows:

1.             DEFINITIONS

Any reference to a defined term not specifically defined in this Agreement shall have the meaning set forth in the Collaboration Agreement.  Whenever used in this Agreement with an initial capital letter, the terms defined in this Section 1 shall have the meanings specified.

1.1   “Affiliate” means, with respect to any Party, any Person that, directly or through one or more Affiliates, controls, or is controlled by, or is under common control with, such Party. For purposes of this definition, “control” means (a) ownership of more than fifty percent (50%) of the shares of stock entitled to vote for the election of directors in the case of a corporation, or more than fifty percent (50%) of the equity interests in the case of any other type of legal entity, (b) status as a general partner in any partnership, or (c) any other arrangement whereby a Person controls or has the right to control the board of directors of a corporation or equivalent governing body of an entity other than a corporation.

1.2   “Annual Net Sales” means the aggregate Net Sales during a particular Calendar Year.

1.3   “Antibody” means a polyclonal or monoclonal antibody, whether multiple or single chain, recombinant or naturally occurring, whole or fragment, and any variants, derivatives or

constructs thereof, including but not limited to, antigen binding portions including Fab, Fab’, F(ab’)2, Fv, dAb and CDR fragments, single chain antibodies (scFv), chimeric antibodies, diabodies and polypeptides (including any humanized versions thereof) that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide.

1.4   “Applicable Laws” means Federal, state, local, national and supra-national laws, statutes, rules and regulations, including any rules, regulations, guidance, guidelines or requirements of Regulatory Authorities, national securities exchanges or securities listing organizations, that may be in effect from time to time during the Term and applicable to a particular activity hereunder.

1.5   “Calendar Quarter” means the period beginning on the Effective Date and ending on the last day of the calendar quarter in which the Effective Date falls, and thereafter each successive period of three (3) consecutive calendar months ending on March 31, June 30, September 30 or December 31.

1.6   “Calendar Year” means each successive period of twelve (12) months commencing on January 1 and ending on December 31.

1.7   “Collaboration Exclusions” means any research activities directed towards Targets or Antibodies being actively pursued in the Research Program pursuant to the Collaboration Agreement.

1.8   “Commercialization” or “Commercialize” means any and all activities directed to the commercialization of a Licensed Product, including pre-launch and launch activities, marketing, manufacturing for commercial sale, promoting, detailing, distributing, offering to sell and selling a Licensed Product, importing a Licensed Product for sale, conducting additional human clinical trials and interacting with Regulatory Authorities regarding the foregoing.  When used as a verb, “Commercializing” means to engage in Commercialization and “Commercialized” has a corresponding meaning.

1.9   “Commercially Reasonable Efforts” means, with respect to sanofi-aventis, the efforts at least equal to those normally used by sanofi-aventis with respect to a product or potential product of similar nature at a similar stage in its development or product life and of similar market potential, in view of conditions prevailing at the time, and evaluated taking into account all relevant factors, including without limitation, the mechanism of action, efficacy, safety, the anticipated regulatory authority approved labeling, the competitiveness of alternative products that are in the marketplace or under development, the patent and other proprietary position of the product, the likelihood of Regulatory Approval, the profitability of the product and other technical, scientific, legal, medical, marketing and competitive factors.

1.10        “Commercialization Regulatory Approval” means, with respect to any Licensed Product, the granting of approval by a Regulatory Authority of (a) an NDA in the United States, or (b) the equivalent of an NDA required by Applicable Laws in any country or region in the Territory outside of the United States to sell such Licensed Product for use in the Field in such country or region.

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1.11        “Confidential Information” means (a) with respect to ImmunoGen, all tangible embodiments of Licensed Technology and Licensed Patents and (b) with respect to each Party, all information and Technology disclosed or provided by or on behalf of such Party (the “disclosing Party”) to the other Party (the “receiving Party”) or to any of the receiving Party’s employees, consultants, Affiliates or sublicensees; provided, that, none of the foregoing shall be Confidential Information if: (i) as of the date of disclosure, it is known to the receiving Party or its Affiliates as demonstrated by credible contemporaneous written documentation, other than by virtue of a prior confidential disclosure to such receiving Party; (ii) as of the date of disclosure it is in the public domain, or it subsequently enters the public domain through no fault of the receiving Party; (iii) it is obtained by the receiving Party from a Third Party having a lawful right to make such disclosure free from any obligation of confidentiality to the disclosing Party; or (iv) it is independently developed by or for the receiving Party without reference to or use of any Confidential Information of the disclosing Party as demonstrated by credible contemporaneous written documentation.  For purposes of clarity, the terms of this Agreement shall constitute Confidential Information of each Party.

1.12        “Control” or “Controlled” means with respect to Technology or Patent Rights, the possession by a Party of the right to grant a license or sublicense to such Technology or Patent Rights as provided herein without the payment of additional consideration to, and without violating the terms of any agreement or arrangement with, any Third Party.

1.13        “Designated Senior Officer” means, with respect to a Party, the senior officer designated by such Party to have final decision making authority over disputed matters.

1.14        “Development” or “Develop” means, with respect to each Licensed Product, all non-clinical and clinical activities required to obtain Regulatory Approval of such Licensed Product.  For purposes of clarity, these activities include, without limitation, test method development and stability testing, regulatory toxicology studies, formulation, process development, manufacturing, manufacturing scale-up, development-stage manufacturing, quality assurance/quality control development, statistical analysis and report writing, Clinical Trial design and operations, preparing and filing Drug Approval Applications, and all regulatory affairs related to the foregoing.  When used as a verb, “Developing” means to engage in Development and “Developed” has a corresponding meaning.

1.15        “Discover” or “Discovered” means, with respect to any Licensed Product (a) the invention, discovery or identification of such Licensed Product; (b) the identification of the function, utility or mode of action of such Licensed Product in the Field; or (c) the identification of a new method of synthesizing such Licensed Product.

1.16        “Drug Approval Application” means, with respect to a Licensed Product in a particular country or region, an application for Commercialization Regulatory Approval for such Licensed Product in such country or region, including without limitation: (a) an NDA or sNDA; (b) a counterpart of an NDA or sNDA, including any MAA, in any country or region in the Territory; and (c) all supplements and amendments to any of the foregoing.

1.17        “Effective Date” means the date first set forth above in the introductory paragraph to this Agreement.

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1.18        “FDA” means the United States Food and Drug Administration or any successor agency or authority thereto.

1.19        “FDCA”means the United States Federal Food, Drug, and Cosmetic Act, as amended.

1.20        “Field” means all human therapeutic and diagnostic uses of Licensed Products, provided, however, that during the Research Program Term the Field shall not include the Collaboration Exclusions.

1.21        “First Commercial Sale” means, with respect to a Licensed Product in any country in the Territory, the first sale, transfer or disposition for value or for end use or consumption of such Licensed Product in such country; provided, that, any sale to an Affiliate or Sublicensee will not constitute a First Commercial Sale unless the Affiliate or Sublicensee is the last entity in the distribution chain of the Licensed Product.

1.22        “Force Majeure” means any occurrence beyond the reasonable control of a Party that (a) prevents or substantially interferes with the performance by such Party of any of its obligations hereunder and (b) occurs by reason of any act of God, flood, fire, explosion, earthquake, strike, lockout, labor dispute, casualty or accident, or war, revolution, civil commotion, act of terrorism, blockage or embargo, or any injunction, law, order, proclamation, regulation, ordinance, demand or requirement of any government or of any subdivision, authority or representative of any such government.

1.23        “Hatch-Waxman Act” means the Drug Price Competition and Patent Term Restoration Act of 1984, as amended.

1.24        “IND” means: (a) an Investigational New Drug Application (as defined in the FDCA and regulations promulgated thereunder) or any successor application or procedure required to initiate clinical testing of a Licensed Product in humans in the United States; (b) a counterpart of an Investigational New Drug Application that is required in any other country or region in the Territory before beginning clinical testing of a Licensed Product in humans in such country or region; and (c) all supplements and amendments to any of the foregoing.

1.25        “Initiation” means, with respect to any Pivotal Clinical Trial, the first date that a human subject is dosed in such Pivotal Clinical Trial.

1.26        “Licensed Patent Rights” means any of the patents and patent applications described in Schedule 1 attached hereto, and any divisional, continuation, continuation-in-part (to the extent that the continuation-in-part is entitled to the priority date of an initial patent or patent application which is the subject of this Agreement), reissue, reexamination, confirmation, revalidation, registration, patent of addition, renewal, extension or substitute thereof, or any patent issuing therefrom or any supplementary protection certificates related thereto.

1.27        “Licensed Product” means any product (including any product that incorporates an Antibody) (a) the manufacture, use or sale of which would, absent the license granted to sanofi-aventis hereunder, infringe any Valid Claim included in the Licensed Patent Rights,

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(b) that is Discovered and/or Developed in whole or in part through the use of a process which is covered by a Valid Claim included in the Licensed Patent Rights, or (c) that is not covered by (a) or (b) but that is Discovered, Developed and/or manufactured as a result of the use of the Licensed Technology.

1.28        “Licensed Technology” means any Technology Controlled by ImmunoGen as of the Effective Dateorthat is Controlled by ImmunoGen at any time during the Term that is related to any patent or patent application included in the Licensed Patent Rights and is necessary for sanofi-aventis to exercise the license granted to it pursuant to Section 2.1.

1.29        “MAA” means any application filed with the relevant Regulatory Authority seeking Regulatory Approval to market and sell a Licensed Product outside the United States for a particular indication in the Field.

1.30        “NDA” means a New Drug Application, as defined in the FDCA and regulations promulgated thereunder, or any successor application or procedure required to sell a Licensed Product in the United States for a particular indication in the Field.

1.32        “Net Sales” means the gross amount invoiced by sanofi-aventis or its Affiliates or Sublicensees to Third Parties in each country in the Territory for sales of each Licensed Product in such country during the period in which royalties are payable hereunder with respect to sales of such Licensed Product in such country, less the following deductions from such gross amounts absorbed or accrued with respect to such gross amounts: (a) trade, cash and/or quantity discounts allowed and taken directly with respect to such sales, or reflected in the invoiced amount; (b) excise, sales and other consumption taxes (including VAT on the sale of Licensed Products and excluding taxes based on income) and custom duties imposed upon and paid directly by sanofi-aventis with respect to the Licensed Products, to the extent included in the invoice price; (c) freight, insurance and other transportation charges, to the extent included in the invoice price; (d) amounts repaid or credited by reason of returns, rejections, defects or recalls, chargebacks, retroactive price reductions, refunds and billing errors; and (e) compulsory payments and rebates directly related to the sale of Licensed Products, accrued, paid or deducted, pursuant to agreements (including, but not limited to, managed care agreements) or governmental regulations.

Use of Licensed Products for promotional or sampling purposes and for use in clinical trials contemplated under this Agreement shall not be considered in determining Net Sales.  In the case of any sale of a Licensed Products between or among sanofi-aventis and its Affiliates or Sublicensees for resale, Net Sales shall be calculated as above only on the first arm’s length sale thereafter to a Third Party.

In the event a Licensed Product is sold as a component of a combination or bundledproduct that consists of a Licensed Product together with another therapeutically active product for the same indication (a “Combination Product”), the Net Sales from the Combination Product, for the purposes of determining royalty payments, shall be determined by multiplying the Net Sales of the Combination Product (as defined in the standard Net Sales definition above), during the applicable royalty reporting period, by the fraction, A/A+B, where A is the average per unit sale price of the active ingredient contained in Licensed Product when sold separately in finished

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form in the country in which the Combination Product is sold during the same royalty reporting period in similar volumes and of the same class, purity and potency and B is the average per unit sale price of the active ingredient contained in other product(s) included in the Combination Product when sold separately in finished form in the country during the same royalty reporting period in similar volumes and of the same class, purity and potency in which the Combination Product is sold, in each case during the applicable royalty reporting period or, if sales of the Licensed Product alone did not occur in such period, then in the most recent royalty reporting period in which arms length fair market sales of such Licensed Product occurred.  In the event that such average sale price cannot be determined for the Licensed Product, on the one hand, and all other product(s) included in the Combination Product, on the other, Net Sales for the purposes of determining royalty payments shall be mutually agreed upon by the Parties based on the relative value contributed by each component, such agreement to be negotiated in good faith.

1.33        “Person” means an individual, sole proprietorship, partnership, limited partnership, limited liability partnership, corporation, limited liability company, business trust, joint stock company, trust, incorporated association, joint venture or similar entity or organization, including a government or political subdivision, department or agency of a government.

1.34        “Pivotal Clinical Trial” means, as to a particular Licensed Product for a particular indication, a controlled and lawful study in humans of the safety and efficacy of such Licensed Product for such indication, which is prospectively designed to demonstrate statistically whether such Licensed Product is safe and effective for use in such indication in a manner sufficient to file a Drug Approval Application for the indication under investigation in such study.

1.35        “Regulatory Approval” means, with respect to any country or region in the Territory, any approval, product and establishment license, registration or authorization of any Regulatory Authority required for the manufacture, use, storage, importation, exportation, transport or sale of a Licensed Product for use in the Field in such country or region.

1.36        “Regulatory Authority” means the FDA or any counterpart of the FDA outside the United States, or other national, supra-national, regional, state or local regulatory agency, department, bureau, commission, council or other governmental entity with authority over the distribution, importation, exportation, manufacture, production, use, storage, transport, clinical testing or sale of a Licensed Product.

1.37        “Regulatory Filings” means, collectively: (a) all INDs, NDAs, establishment license applications, drug master files, applications for designation as an “Orphan Product” under the Orphan Drug Act, for “Fast Track” status under Section 506 of the FDCA (21 U.S.C. § 356) or for a Special Protocol Assessment under Section 505(b)(4)(B) and (C) of the FDCA (21 U.S.C. § 355(b)(4)(B)) or all other similar filings (including CTNs, MAAs and, counterparts of any of the foregoing in any country or region in the Territory) as may be required by any Regulatory Authority for the Development or Commercialization of a Licensed Product in the Territory; (b) all supplements and amendments to any of the foregoing; and (c) all data and other information contained in, and correspondence relating to, any of the foregoing.

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1.38        “Reportable Event” means any occurrence in a patient or subject who is administered a Licensed Product to the extent attributable to a [***] [***] [***] [***].

1.39        “Research License Term” means the period beginning on the Effective Date and ending on the third anniversary of the termination or expiration of the Research Program Term, as such period may be extended pursuant to Section 2.1.2.

1.40        “Research Program Term” means the Research Program Term as defined pursuant to Section 2.1.2 of the Collaboration Agreement.

1.41        “Resurfaced Antibody” means any Antibody Controlled by sanofi-aventis that is resurfaced by ImmunoGen using the Licensed Patent Rights and/or Licensed Technology as part of its conduct of ImmunoGen activities pursuant to Section 2.5.4.

1.42        “Royalty Term” means, with respect to each Licensed Product in each country in the Territory, the period beginning on the date of First Commercial Sale of such Licensed Product in such country and continuing until the later of (a) the expiration of the last to expire Valid Claim in such country within the Licensed Patent Rights or (b) [***] ([***]) years from the date of the First Commercial Sale of such Licensed Product in such country.

1.43        “sNDA” means a Supplemental New Drug Application, as defined in the FDCA and applicable regulations promulgated thereunder.

1.44        “Sublicensee” means any Third Party (other than an Affiliate) to which sanofi-aventis grants a license or sublicense pursuant to Section 2.2.

1.45        “Technology” means, collectively, all inventions, discoveries, improvements, trade secrets and proprietary methods, whether or not patentable, including without limitation, macromolecular sequences, data, formulations, processes, techniques, know-how and results (including any negative results).

1.46        “Territory” meansall countries of the world.

1.47        “Third Party” means any Person other than sanofi-aventis and ImmunoGen and their respective Affiliates.

1.48        “Valid Claim” means any claim of a pending patent application or an issued unexpired patent within the Licensed Patent Rights that (a) has not been finally cancelled, withdrawn, abandoned or rejected by any administrative agency or other body of competent jurisdiction, (b) has not been permanently revoked, held invalid, or declared unpatentable or unenforceable in a decision of a court or other body of competent jurisdiction that is unappealable or unappealed within the time allowed for appeal, (c) has not been rendered unenforceable through disclaimer or otherwise, and (d) is not lost through an interference proceeding.

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Additional Definitions.  In addition, each of the following definitions shall have the respective meanings set forth in the section of this Agreement indicated below or in the section of the Collaboration Agreement indicated below:

2.             LICENSE GRANTS; TECHNOLOGY TRANSFER

2.1           License Grants.

2.1.1        License to sanofi-aventis.  Subject to the other terms of this Agreement, ImmunoGen hereby grants to sanofi-aventis and its Affiliates (a) a non-exclusive, royalty-free, license during the Research License Term, without right to grant sublicenses, to use Licensed Technology and Licensed Patent Rights with Antibodies Controlled by sanofi-aventis to Develop Licensed Products in the Field and in the Territory and (b) a non-exclusive, royalty-bearing license during the Term, including the right to grant sublicenses as provided in Section 2.2, under the Licensed Technology and Licensed Patent Rights, to Develop, have Developed, Commercialize and have Commercialized Licensed Products in the Field and in the Territory.

2.1.2        Extension of Research License Term.  Notwithstanding anything to the contrary in Section 2.1.1, sanofi-aventis shall have the right to extend the Research License Term for one or more additional periods of three (3) years each by providing ImmunoGen with written notice in accordance with Section 4.2 at any time on or before expiration of the then-current Research License Term (each such extension, a “Research License Term Extension”).  The Research License Term Extension Fee shall be paid as set forth in Section 4.2.

2.2           Right to Sublicense.  Sanofi-aventis and its Affiliates shall have the right to grant sublicenses under the license granted to it under Section 2.1.1(b)with respect to any Licensed Product to any Third Party; provided, that: (a) it shall be a condition of any such sublicense that such Sublicensee agrees to be bound by all terms of this Agreement applicable to the

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Development and Commercialization of Licensed Products in the Field in the Territory (including, without limitation, Sections 3.2, 3.3 and 3.4); (b) sanofi-aventis shall provide written notice to ImmunoGen of any such proposed sublicense at least [***] ([***]) days prior to such execution and provide redacted copies to ImmunoGen of each such sublicense within [***] ([***]) days of such execution; (c) sanofi-aventis shall be deemed to have guaranteed that each such Sublicensee will fulfill all of sanofi-aventis’ obligations under this Agreement applicable to the subject matter of such sublicense; and (d) sanofi-aventis shall not be relieved of its obligations pursuant to this Agreement as a result of any such sublicense.

2.3           Retained Rights of ImmunoGen  Subject to the other terms of this Agreement, ImmunoGen retains the right to use the Licensed Technology and practice the Licensed Patent Rights (a) to perform its obligations under this Agreement (including without limitation its obligation to perform ImmunoGen Activities in accordance with Section 2.6.4 of this Agreement), (b) to develop, have developed, make, have made, use, have used, sell, have sold, offer for sale, import, have imported, export and have exported any product that is not a Licensed Product, and (c) for any and all uses outside of the Field.

2.4           No Other Rights.  Sanofi-aventis shall have no rights to use or otherwise exploit any Technology Controlled by ImmunoGen except as expressly set forth herein.

2.5           Technology Transfer; ImmunoGen Activities.

2.5.1        Transfer of Licensed Technology. ImmunoGen shall (a) as soon as practicable after the Effective Date, transfer to sanofi-aventis all Licensed Technology (including any protocols) comprising and/or otherwise applicable to the Licensed Patent Rights not previously transferred to sanofi-aventis pursuant to the Collaboration Agreement and necessary for sanofi-aventis to perform in silico resurfacing as contemplated by this Agreement; and (b) during the Research License Term, provide updates to sanofi-aventis of any improvements and/or updates to the Licensed Technology or Licensed Patent Rights that are Controlled by ImmunoGen.

2.5.2        Use of Licensed Technology.  In connection with the transfer of the Licensed Technology contemplated by Section 2.5.1, sanofi-aventis hereby agrees that (a) it shall not use such Licensed Technology for any purpose other than exercising its rights or performing its obligations hereunder; (b) it shall use such Licensed Technology only in compliance with all Applicable Laws; (c) it shall not transfer any such Licensed Technology to any Third Party without the prior written consent of ImmunoGen, except as expressly permitted hereby; and (d) except for the rights expressly set forth herein, sanofi-aventis shall not acquire any other rights, title or interest in or to such Licensed Technology as a result of such transfer by ImmunoGen.

2.5.3        Training.  ImmunoGen shall use commercially reasonable efforts to provide sanofi-aventis with such training as may be reasonably necessary to enable sanofi-aventis to practice the Licensed Technology and Licensed Patent Rights to humanize Antibodies through conference calls [***] [***] [***] [***] to the [***] of sanofi-aventis or its Affiliates in the United States and Europe.  All such training calls [***] [***] shall be requested in advance

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in writing by sanofi-aventis and shall be scheduled by ImmunoGen at times mutually convenient to the Parties.

2.5.4        Additional Obligations of ImmunoGen.  Subject to the other terms of this Agreement (including without limitation Section 4.3), ImmunoGen shall use commercially reasonable efforts to conduct such activities in connection with a Resurfaced Antibody as sanofi-aventis may request in writing at any time during the Research License Term.

2.6           Compliance.  Sanofi-aventis shall perform its obligations to Develop Licensed Products in good scientific manner and in compliance in all material respects with all Applicable Laws; provided that, with respect to each activity so performed that will or would reasonably be expected to be submitted to a Regulatory Authority in support of a Regulatory Filing or Drug Approval Application, sanofi-aventis shall comply in all material respects with the regulations and guidance of the FDA that constitute Good Laboratory Practice or Good Manufacturing Practice (or, if and as appropriate under the circumstances, or other comparable regulation and guidance of any applicable Regulatory Authority in any country or region in the Territory).

2.7           Manufacture of Licensed Products for Development.  Sanofi-aventis shall have the sole responsibility and obligation, at its sole cost and expense, to manufacture all Licensed Products required for the conduct of Development activities under this Agreement (including without limitation the conduct of all necessary Clinical Trials in the Territory) and/or the making of all Regulatory Filings and obtaining of all Regulatory Approvals.

3.             DEVELOPMENT AND COMMERCIALIZATION OF LICENSED PRODUCTS

3.1           Responsibility for Development and Commercialization.  Except for the activities conducted by ImmunoGen in accordance with Section 2.5.4, sanofi-aventis shall have the sole right, at its sole expense, for all aspects of the Development and Commercialization of Licensed Products in the Field in the Territory, including, without limitation, the conduct of: (a) all IND-enabling non-clinical studies; (b) all activities related to human clinical trials; (c) all activities relating to the manufacture and supply of Licensed Products (including all required process development and scale up work with respect thereto); and (d) all pre-marketing, marketing, promotion, sales, distribution, import and export activities (including securing reimbursement, sales and marketing and conducting any post-marketing trials or databases and post-marketing safety surveillance).  Without limiting the generality of the foregoing, sanofi-aventis shall have the sole right, at its sole expense, for (i) making all Regulatory Filings for Licensed Products and filing all Drug Approval Applications and otherwise seeking all Regulatory Approvals for Licensed Products, as well as all correspondence and communications with Regulatory Authorities regarding such matters, and (ii) reporting of all adverse events to Regulatory Authorities if and to the extent required by Applicable Laws.

3.2           Diligence.  Sanofi-aventis shall use Commercially Reasonable Efforts in the conduct of all Commercialization activities it undertakes related to Licensed Products in the Field in the Territory.  For the purpose of clarity, sanofi-aventis shall have no diligence obligations of any kind related to the research and Development of Licensed Products.

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3.3           Reportable Events.  Sanofi-aventis shall promptly provide ImmunoGen with all information related to any Reportable Event as such information is compiled or prepared by sanofi-aventis in the normal course of business in connection with the Development and Commercialization of any Licensed Product and, in any event, within time frames consistent with any reporting obligations under Applicable Laws.

3.4           Manufacture of Licensed Products for Commercial Sale.  Unless otherwise agreed to by the Parties, sanofi-aventis shall have the sole obligation and responsibility, at its sole cost and expense, for the manufacture of all Licensed Products (including without limitation the active pharmaceutical ingredient in any Licensed Product) for commercial sale.

3.5           Product Recalls.  In the event that any Regulatory Authority issues or requests a recall or takes similar action in connection with a Licensed Product that sanofi-aventis reasonably believes is attributable to or otherwise relates to the Licensed Technology or Licensed Patent Rights, or in the event a Party reasonably believes that an event, incident or circumstance has occurred that may result in the need for such a recall, such Party shall promptly advise the other Party thereof by telephone or facsimile.  Following such notification, sanofi-aventis shall decide and have control of whether to conduct a recall or market withdrawal (except in the event of a recall or market withdrawal mandated by a Regulatory Authority, in which case it shall be required) or to take other corrective action in any country and the manner in which any such recall, market withdrawal or corrective action shall be conducted; provided that sanofi-aventis shall keep ImmunoGen regularly informed regarding any such recall, market withdrawal or corrective action.  sanofi-aventis shall bear all expenses of any such recall, market withdrawal or corrective action (including, without limitation, expenses for notification, destruction and return of the affected Licensed Product and any refund to customers of amounts paid for such Licensed Product).

4.             PAYMENTS

4.1           Upfront Fee.  Sanofi-aventis shall pay ImmunoGen an upfront fee in the amount of One Million Dollars (US $1,000,000), which amount shall be non-refundable and non-creditable, fifty percent (50%) of which shall be payable in immediately available funds within thirty (30) days of the Effective Date and fifty percent (50%) of which shall be payable in immediately available funds on the date of [***] or [***] of the [***] [***] [***].

4.2           Research License Term Extension Fee.  Upon the exercise by sanofi-aventis of each [***] ([***]) year Research License Term Extension as described in Section 2.1.2, sanofi-aventis shall pay ImmunoGen an extension fee (the “Research License Term Extension Fee”) in the amount of [***] [***] [***] Dollars (US $[***]) in immediately available funds within seven (7) days of the start of each such Research License Term Extension.

4.3           ImmunoGen Activity Payments.  In consideration of the conduct by ImmunoGen of the activities, if any, contemplated by Section 2.5.4, sanofi-aventis shall pay ImmunoGen [***] [***] [***] Dollars (US $[***]) upon delivery by ImmunoGen of each Resurfaced Antibody.  ImmunoGen shall provide sanofi-aventis with an invoice promptly upon delivery to sanofi-aventis of each Resurfaced Antibody and sanofi-aventis shall pay each such invoice within thirty (30) days of receipt.

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4.4           Milestone Payments.

4.4.1        Milestones.  Sanofi-aventis shall make the following nonrefundable, non-creditable milestone payments to ImmunoGen within [***] ([***]) days after the achievement by sanofi-aventis and/or sanofi-aventis’ Affiliates and Sublicensees of each event for each Licensed Product as set forth below: