OPTION AND LICENSE AGREEMENT

Exhibit 10.2

Execution Copy

OPTION AND LICENSE AGREEMENT

This Option and License Agreement (this "Agreement") is made effective as of December 21, 2006 (the "Effective Date") by and between ImmunoGen, Inc., a Massachusetts corporation with 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, sanofi-aventis is the owner of or otherwise Controls certain Patent Rights and Technology relating to certain proprietary Antibodies; and

WHEREAS, ImmunoGen is the owner of or otherwise Controls certain proprietary Patent Rights and Technology relating to or otherwise useful in the conjugation of certain maytansine compounds to Antibodies; and

WHEREAS, ImmunoGen has entered into agreements based on the so-called "Revolving-Door" structure with a number of Third Parties whereby such Third Parties are obligated to grant back to ImmunoGen the right to such Third Parties’ improvements to Technology and Patent Rights, and pursuant to which ImmunoGen has the right to grant access to such Third Party Improvements to sanofi-aventis; and

WHEREAS, sanofi-aventis desires to have access to such Technology, Patent Rights and Improvements for research, discovery and development of Ab-MAY Products (as defined below); and

WHEREAS, in connection therewith, sanofi-aventis desires to receive, and ImmunoGen desires to grant, Options to obtain one or more licenses to Licensed Technology having the terms set forth in one or more License Agreements to be executed by the Parties.

NOW, THEREFORE, in consideration of the mutual covenants contained herein, and for other good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, the Parties hereby agree as follows:

1.              DEFINITIONS

Whenever used in this Agreement with an initial capital letter, the terms defined in this Section 1 shall have the meanings specified below.

1.1            " Ab-MAY Product " means any product containing a conjugate of a Sanofi-aventis Antibody with a MAY Compound in which the Sanofi-aventis Antibody is directed against a Target that is not an Excluded Target.

1.2            " 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%)

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.

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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.

1.3            " 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            " Antibody-MAY Compound Conjugate " means any compound containing a conjugate of an Antibody with a MAY Compound.

1.5            " 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.

1.6            " Business Day " means a day on which banking institutions in New York, New York are open for business.

1.7            " Confidential Information " means (a) with respect to ImmunoGen, all tangible embodiments of Licensed Technology and Licensed Patent Rights; (b) with respect to sanofi-aventis, the identification by sanofi-aventis of a Proposed Target and the exercise by sanofi-aventis of any Option with respect to an Optioned Target; and (c) 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.

1.8            " Control " or " Controlled " means (a) 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 and (b) with

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respect to any Antibody, the possession by a Party of the right to supply such Antibody to the other Party as provided herein without the payment of additional consideration to, and without violating the terms of any agreement or arrangement with, any Third Party.

1.9            " Designated Senior Officer " means, with respect to a Party, the senior officer of such Party or an Affiliate designated by such Party to have final decision making authority over disputed matters.

1.10          " Field " means all human therapeutic, prophylactic and diagnostic uses.

1.11          " ImmunoGen Antibody " means any Antibody Controlled, owned or made available by ImmunoGen.

1.12          " Improvement " means any enhancement, improvement or modification to the Licensed Technology or the Licensed Patent Rights.

1.13          " License Agreement " means a written license agreement executed by the Parties upon exercise of any Option pursuant to Section 2.2.2 in substantially the form set forth in Appendix A attached hereto.

1.14          " Licensed Patent Rights " means any of the patents and patent applications described in Schedule 1 attached hereto, and any divisionals, continuations, continuations-in-part (to the extent that any continuations-in-part are entitled to the priority date of an initial patent or patent application which is the subject of this Agreement), reissues, reexaminations, confirmations, revalidations, registrations, patents of addition, renewals, extensions or substitutes thereof, or any patents issuing therefrom or any supplementary protection certificates related thereto, including any Improvement related thereto that is conceived or reduced to practice by ImmunoGen or its Third Party collaborators, that are Controlled by ImmunoGen and that include one or more claims that cover Licensed Technology.

1.15          " Licensed Target " means an Optioned Target following exercise of an Option as set forth in Section 2.2.2 and which is the subject of a License Agreement between the Parties.

1.16          " Licensed Technology " means any Technology Controlled by ImmunoGen as of the Effective Dateorthat is Controlled by ImmunoGen at any time during the Term including, without limitation, any Improvement related thereto that is conceived or reduced to practice by ImmunoGen or its Third Party collaborators and that is, in any case, necessary or useful for sanofi-aventis to practice the research licenses set forth in Section 2.3.

1.17          " Manufacturing Cost " means, with respect to any Preclinical Materials manufactured by ImmunoGen, ImmunoGen’s fully-burdened costs (including the costs associated with product testing and release activities) of producing and packaging such Preclinical Materials, including the sum of the following components: (a) direct costs, including (1) materials directly used in producing and packaging such Preclinical Materials and (2) with respect to any Preclinical Materials obtained by ImmunoGen from a Third Party and supplied to sanofi-aventis without modification, the amount paid by ImmunoGen to such Third Party for the same; (b) manufacturing overhead costs attributable to the cost of goods under the foregoing clause(a)(1), including manufacturing and quality labor and manufacturing and quality

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supervisory services, operating and administrative costs of the manufacturing and quality departments and occupancy costs which are allocable to company departments based on space occupied or headcount or another reasonable activity-based method; for the purpose of clarity, any cost allocation shall be (i) in any case, applied in accordance with GAAP, and (ii) applied consistently by ImmunoGen in relation to all other Third Parties for which ImmunoGen manufactures comparable materials; (c) any other reasonable and customary out-of-pocket costs borne by ImmunoGen for the testing, transport, customs clearance, duty, insurance and/or storage of such Preclinical Materials; and (d) ImmunoGen’s general and administrative costs, including purchasing, human resources, payroll, information system and accounting, which are directly attributable or reasonably allocable to company departments based on space occupied or headcount.

1.18          " MAY Compound " means any and all maytansinoid compounds (including, without limitation, maytansinol, ansamitocins, DM1 and DM4), whether produced by a botanical source, natural fermentation, chemical synthesis or otherwise, and shall include, without limitation, all variants, fragments or derivatives of any of the foregoing, in each case Controlled by ImmunoGen.

1.19          " Option Agreement " means the Option Agreement between the Parties dated as of August 31, 2006.

1.20          " Option Grant Date " means, with respect to a Proposed Target that is not an Excluded Target, the date of the Option Response provided by ImmunoGen.

1.21          " Optioned Target " means any Proposed Target that is not an Excluded Target and becomes the subject of an Option granted by ImmunoGen pursuant to Section 2.2.1.

1.22          " Patent Rights " means the rights and interests in and to issued patents and pending patent applications (including inventor’s certificates and utility models) in any country or jurisdiction within the Territory, including all provisionals, substitutions, continuations, continuations-in-part, divisionals, supplementary protection certificates, renewals, all letters patent granted thereon, and all reissues, reexaminations, extensions, confirmations, revalidations, registrations, patents of addition thereof, PCTs and foreign counterparts.

1.23          " Preclinical Materials " means any materials (including without limitation any supplies of MAY Compound or Ab-MAY Product) manufactured by ImmunoGen for sanofi-aventis pursuant to this Agreement and in accordance with Applicable Laws and all applicable specifications for use in preclinical testing.

1.24          " Sanofi-aventis Antibody " means any Antibody and other binding proteins Controlled by, owned by or made available to sanofi-aventis.

1.25            " Sanofi-aventis Improvement " means any Improvement that is conceived or first reduced to practice by sanofi-aventis in connection with the exercise by sanofi-aventis of the licenses set forth in Section 2.3.

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1.26          " Target " means any particular antigen (whether a protein, carbohydrate, etc.) that is bound by a particular Antibody used to create an Ab-MAY Product, and all epitopes of such particular antigen.

1.27          " 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).

1.28          " Territory " means all countries of the world.

1.29          " Third Party " means any person or entity other than ImmunoGen, sanofi-aventis and their respective Affiliates.

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

2.              GRANT OF RIGHTS

2.1            Option to Initiate Research Term .  ImmunoGen hereby grants sanofi-aventis an option (the "Research Term Option"), at sanofi-aventis’ sole discretion, to initiate the Research

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Term by providing written notice of election to ImmunoGen and paying the Research Term Exercise Fee on, or prior to, August 31, 2008 (the date of such election, the "Research Term Exercise Date").

2.2            Exclusive Target Options .

2.2.1         Option Request and Grant .  Sanofi-aventis may from time to time during the Research Term provide written notice to ImmunoGen requesting the grant by ImmunoGen of an exclusive option (each such option, an "Option") (the "Option Request") to obtain an exclusive license in the Territory under the Licensed Technology and Licensed Patent Rights, with respect to any Target specified in the Option Request (each, a "Proposed Target"), for the sole purpose of researching, making and having made, Ab-MAY Products directed to such Proposed Target, for any and all uses within the Field.  ImmunoGen shall provide a written response (the "Option Response") to sanofi-aventis within [***] ([***]) Business Days of any Option Request specifying whether or not the Proposed Target is available to be the subject of an Option and, if unavailable, the reasons for such unavailability as set forth in this Section 2.2.1 (it being understood that the foregoing disclosure shall be subject to any confidentiality obligations ImmunoGen may have with any Third Party), provided, that, ImmunoGen hereby acknowledges and agrees that it may only treat a Proposed Target that is identified in an Option Request as unavailable (each, an "Excluded Target") if, on the date of the Option Request, (a) ImmunoGen is pursuing an internal development or commercialization program with a MAY Compoundconjugated with an ImmunoGen Antibody that is directed against such Proposed Target; (b) ImmunoGen has, with respect to the Proposed Target, granted an exclusive option or license to a Third Party under any Patent Rights Controlled by ImmunoGen that are necessary or useful for the development, manufacture, use or sale of Antibody-MAY Compound Conjugates (a "Third Party Right"); or (c) ImmunoGen is in discussions with a Third Party relating to a potential grant of a Third Party Right.  Upon the grant of an Option to a Proposed Target to sanofi-aventis as provided in this Section 2.2.1, the Proposed Target shall be deemed to be an Optioned Target for purposes of this Agreement and, for the duration of the Option Period, (i) sanofi-aventis shall have the rights granted in Section 2.3.2 and (ii) ImmunoGen shall not initiate or engage in discussions with any Third Party concerning a Third Party Right with respect to the Optioned Target, or pursue internally any development or commercialization program concerning an Antibody-MAY Compound Conjugate directed against the Optioned Target.  Notwithstanding anything to the contrary set forth in this Agreement, the Parties hereby agree that sanofi-aventis shall have the right to select and maintain no more than [***] ([***]) Optioned Targets at any given time during the Term, provided, that, Expired Options and Terminated Options shall not count as Optioned Targets for purposes of this limitation.

2.2.2         Exercise of Options .   Sanofi-aventis shall have the right to exercise any Option at any time during the period commencing on the Option Grant Date and continuing for a period of [***] ([***]) months thereafter (as such period may be extended as provided in Section 2.2.5 below, the "Option Period"), by (a) delivering written notice of exercise thereof, which notice shall specify the Optioned Target and (b) executing a License Agreement in the form of Appendix A attached hereto.  Upon exercise of an Option covering an Optioned Target as provided in this Section 2.2.2, such Optioned Target shall become a Licensed Target and the Licensed Patent Rights and Licensed Technology (as defined in the License Agreement) shall be

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exclusively licensed with respect to such Licensed Target to sanofi-aventis on the terms and subject to the conditions set forth in the relevant License Agreement.

2.2.3         Option Expiration .  In the event that sanofi-aventis fails to exercise any Option during the applicable Option Period (each, an "Expired Option"), all rights granted by ImmunoGen to sanofi-aventis pursuant to Section 2.2.1 applicable to such Expired Option shall terminate as of such expiration date; provided, that, if the Option becomes an Expired Option prior to expiration of the Research Term, the non-exclusive research license granted pursuant to Section 2.3.1 below for the Optioned Target that is the subject of such Expired Option shall again be in effect and shall survive, and such non-exclusive license will continue until the date on which ImmunoGen provides written notice to sanofi-aventis that such Target has become an Excluded Target.  Notwithstanding the foregoing, following the expiration of any Option Period with respect to an Optioned Target, (a) ImmunoGen shall have the right to initiate or engage in discussions with any Third Party concerning a Third Party Right or pursue internally any project concerning, any rights regarding an Antibody-MAY Compound Conjugate directed to the Target covered by such Expired Option; (b) during the period commencing on the date of expiration of the Option Period and continuing for a period of [***] ([***]) months (the "Expired Option Tail Period"), sanofi-aventis may not provide an Option Request to ImmunoGen with respect to the Target that is the subject of the Expired Option; and (c) on and after the Expired Option Tail Period but prior to the expiration of the Research Term, and subject to notice, availability and limitations pursuant to this Section 2.2, sanofi-aventis shall have the right, upon written request, to provide an Option Request to ImmunoGen with respect to the Target covered by such Expired Option.

2.2.4         Termination of Options .  Sanofi-aventis may terminate any Option that is not an Expired Option at any time on and after [***] ([***]) months from the Option Grant Date by providing written notice of termination to ImmunoGen, which notice shall identify the Optioned Target to be terminated (each, a "Terminated Option").  Upon termination of an Option as provided in this Section 2.2.4, sanofi-aventis shall have the rights set forth in Section 2.2.3 above, as if the Terminated Option were an Expired Option (subject to notice, availability and other limitations set forth in this Section 2.2), and at such time or thereafter sanofi-aventis may select and be granted another Option to replace the Terminated Option, subject to limitations on the number of Options set forth in Section 2.2.1.

2.2.5         Non-Optioned Target: Request for Exclusive License .  Notwithstanding anything to the contrary in this Agreement, sanofi-aventis may at any time during the Research Term request the grant by ImmunoGen of an exclusive license to any Target that is not an Optioned Target by giving written notice to ImmunoGen (the "License Request"), which License Request shall specify in reasonable detail the Target.  ImmunoGen shall provide a written response (the "License Response") to sanofi-aventis within [***] ([***]) Business Days of any License Request specifying whether or not the Target specified in the License Request is available to be the subject of an exclusive license and, if unavailable, the reasons for such unavailability as set forth in Section 2.2.1.  As promptly as possible following the issuance by ImmunoGen of a License Response indicating that the Target is available to be the subject of an exclusive license (a) the Parties shall execute a License Agreement in the form of Appendix A attached hereto.  Upon execution of such License Agreement, such Target shall become a Licensed Target and the Licensed Patent Rights and Licensed Technology (as defined in the

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License Agreement) shall be exclusively licensed with respect to such Licensed Target to sanofi-aventis on the terms and subject to the conditions set forth in the relevant License Agreement.

2.2.6         Discussions Regarding Targets .   ImmunoGen agrees, upon the request of sanofi-aventis, to confer with sanofi-aventis on whether ImmunoGen reasonably expects any Target identified by sanofi-aventis will remain available to become an Optioned Target and/or Licensed Target, provided, that under no circumstances shall any such discussions be deemed by sanofi-aventis to be a commitment by ImmunoGen with respect to any such Target.

2.3            Non-Exclusive Research License; Option for Exclusive Research License .

2.3.1         Non-Exclusive Research License .  ImmunoGen hereby grants sanofi-aventis a non-exclusive, royalty-free license during the Research Term, without the right to grant sublicenses, under the Licensed Technology and Licensed Patent Rights with respect to any Target that is not an Optioned Target or a Licensed Target (including any Optioned Target that is the subject of an Expired Option and/or Terminated Option), to (a) conduct safety and other preclinical studies in vitro and toxicity studies in vivo in any non-human species with any Ab-MAY Product directed at such Target, (b) to manufacture Ab-MAY Product solely for use in such studies and (c) to manufacture and conjugate MAY Compounds that do not comprise an Ab-MAY Product solely for use as a control for any Ab-MAY Product that is directed at an Optioned Target.  For purposes of clarity, sanofi-aventis shall have no right under the license described in this Section 2.3.1 to conduct in vivo efficacy studies of any Ab-MAY Product to any Target that is not an Optioned Target or Licensed Target.

2.3.2         Exclusive Research License .  ImmunoGen hereby grants sanofi-aventis an exclusive, royalty-free license during the Research Term, without the right to grant sublicenses, with respect to any Optioned Target, to (a) conduct any and all preclinical studies (including without limitation in vivo efficacy studies) on any Ab-MAY Product directed at such Optioned Target; and (b) manufacture Ab-MAY Product solely for use in such studies.

2.3.3         Use of Subcontractors; bona fide Collaborators .  Sanofi-aventis shall have the right to engage one or more Third Party subcontractors to perform designated functions, or participate in bona fide collaborations, related to the conduct of the activities described in Section 2.3.1 and 2.3.2, provided , that (i) sanofi-aventis shall remain responsible for the satisfactory accomplishment of such activities in accordance with the terms and conditions of this Agreement; and (ii) each such Third Party subcontractor or bona fide collaborator shall be bound to the same extent that sanofi-aventis is obligated to ImmunoGen under this Agreement.

2.3.4         Research Records .   Sanofi-aventis shall maintain records of access to and use of the Licensed Technology and Licensed Patent Rights.  Such records shall be made available to ImmunoGen upon reasonable request during business hours and provided that ImmunoGen shall make such request no more than once per Calendar Year.

2.3.5         Research Term .   Subject to the payment of the Research Term Exercise Fee as provided in Section 3.2 below and to the extension as provided in Section 2.3.6 below, the research term shall commence on the Research Term Exercise Date and continue until August 31, 2011 (the "Research Term"), unless this Agreement is earlier terminated by either Party

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pursuant to the provisions of Section 8.  Unless otherwise provided in a License Agreement or otherwise set forth in this Agreement, upon termination or expiration of the Research Term, sanofi-aventis shall discontinue use of the Licensed Technology and Licensed Patent Rights and destroy all portions and copies of the Licensed Technology and Licensed Patent Rights, provided, however, that sanofi-aventis shall have the right to retain one (1) copy for its legal files.

2.3.6         Extension of Research Term .   Sanofi-aventis may extend the Research Term for one additional three (3) year period (ending on August 31, 2014) by providing written notice and by paying ImmunoGen a non-refundable, non-creditable fee in the amount of [***] [***] dollars (US $[***]) by wire transfer of immediately available funds at any time prior to the expiration of the Research Term.

2.4            Grant of Improvement License to ImmunoGen .  Sanofi-aventis hereby grants ImmunoGen a non-exclusive, worldwide, fully-paid, irrevocable, royalty-free license of perpetual duration, with the right to grant sublicenses as described below, under sanofi-aventis’ interest in any Sanofi-aventis Improvements (a) to manufacture Preclinical Materials pursuant to the terms of this Agreement; (b) to develop, make, have made, use, sell, have sold, offer for sale, import, have imported, export and have exported any product that is not otherwise restricted by an agreement by and between sanofi-aventis and ImmunoGen; and (c) to otherwise exploit such Sanofi-aventis Improvements for all uses within the Field that are not otherwise restricted by an agreement by and between sanofi-aventis and ImmunoGen, provided, that, (i) any grant by ImmunoGen of a sublicense is only made in connection with the grant of a license to Technology and/or Patent Rights Controlled by ImmunoGen and used in the conjugation of MAY Compounds to binding proteins; and (ii) the right of ImmunoGen to grant any such sublicense is subject to sanofi-aventis obtaining a grant back of a non-exclusive, fully paid, irrevocable, royalty-free license, under that sublicensee’s improvements, enhancements or modifications to Technology Controlled by ImmunoGen to conduct research in the Field and in the Territory in accordance with Sections 2.3.1 and/or 2.3.2 of this Agreement.

2.5            Notice of Improvements.  Sanofi-aventis shall promptly notify ImmunoGen of the conception or reduction to practice of any such Sanofi-aventis Improvement. ImmunoGen shall promptly notify sanofi-aventis of (a) the conception or reduction to practice by ImmunoGen of any Improvement or (b) its receipt of written notice from any of its Third Party collaborators of its conception or reduction to practice of any Improvement.

2.6            Manufacture of Research and/or Preclinical Materials .  Subject to this Section 2.6, Sanofi-aventis shall have the sole right, at its sole cost and discretion, for the manufacture of all materials (including without limitation any Ab-MAY Products and/or MAY Compounds) necessary for sanofi-aventis to practice the licenses granted to it under Sections 2.3.1 and/or 2.3.2.  In the event that, during the Term, sanofi-aventis desires ImmunoGen to supply sanofi-aventis with quantities of Preclinical Materials, sanofi-aventis shall provide ImmunoGen with written notice of same.  ImmunoGen shall manufacture all ordered amounts of Preclinical Materials at ImmunoGen’s Cambridge, Massachusetts facility or its Norwood, Massachusetts facility and deliver such ordered amounts in accordance with forecasting parameters, advance ordering timeframes and delivery timeframes to be agreed upon by the Parties.  Sanofi-aventis may [***], at its sole discretion, the [***] [***] [***] ImmunoGen will supply the requested

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Preclinical Materials.  In connection with any ordering of Preclinical Materials by sanofi-aventis, (a) ImmunoGen shall provide sanofi-aventis with ImmunoGen’s good faith estimate of the Manufacturing Cost for manufacture and supply of such Preclinical Materials; (b) ImmunoGen’s price to supply Preclinical Materials to sanofi-aventis manufactured at ImmunoGen’s Cambridge, Massachusetts facility shall equal [***]% of ImmunoGen’s Manufacturing Cost for such Preclinical Materials; and (c) ImmunoGen’s price to supply Preclinical Materials manufactured at ImmunoGen’s Norwood, Massachusetts facility shall equal [***]% of ImmunoGen’s Manufacturing Cost for such Preclinical Materials; provided, that, nothing in this Section 2.6 shall preclude sanofi-aventis from making its own arrangements for manufacture and supply of Preclinical Materials on its own or with Third Parties, subject to the licenses granted hereunder.

3.              FINANCIAL TERMS

3.1            Up-Front Fee .  In consideration of the rights granted to sanofi-aventis under this Agreement, sanofi-aventis agrees to pay ImmunoGen a non-refundable, non-creditable up-front fee in the amount of five hundred thousand dollars ($500,000), payable in immediately available funds within [***] ([***]) days of the Effective Date.

3.2            Research Term Exercise Fee In consideration of the rights granted to sanofi-aventis under this Agreement, sanofi-aventis agrees to pay ImmunoGen a non-refundable, non-creditable exercise fee in the amount of [***] [***] [***] [***] [***] dollars ($[***]) (the "Research Term Exercise Fee"), payable in immediately available funds within [***] ([***]) Business Days of the Research Term Exercise Date.

4.              TREATMENT OF CONFIDENTIAL INFORMATION

4.1            Confidentiality .

4.1.1         Confidentiality Obligations .   ImmunoGen and sanofi-aventis each recognizes that the other Party’s Confidential Information constitutes highly valuable assets of such other Party.  ImmunoGen and sanofi-aventis each agrees that, subject to Section 4.1.2, (a) during the Term and for an additional [***] ([***]) years thereafter it will not disclose, and will cause its Affiliates and Sublicensees not to disclose, any Confidential Information of the other Party and (b) during and after the Term, it will not use, and will cause its Affiliates not to use, any Confidential Information of the other Party, in either case, except as expressly permitted hereunder.  Without limiting the generality of the foregoing, each Party shall take such action, and shall cause its Affiliates and sublicensees to take such action, to preserve the confidentiality of the other Party’s Confidential Information as such Party would customarily take to preserve the confidentiality of its own Confidential Information and shall, in any event, use at least reasonable care to preserve the confidentiality of the other Party’s Confidential Information.

4.1.2         Limited Disclosure .  ImmunoGen and sanofi-aventis each agrees that disclosure of its Confidential Information may be made by the other Party to any employee, consultant or Affiliate of such other Party to enable such other Party to exercise its rights or to carry out its responsibilities under this Agreement, provided that any such disclosure or transfer shall only be made to Persons who are bound by written obligations as described in Section 4.1.3.

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In addition, ImmunoGen and sanofi-aventis each agrees that the other Party may disclose its Confidential Information (a) on a need-to-know basis to such other Party’s legal and financial advisors and (b) as reasonably necessary in connection with an actual or potential (i) permitted sublicense of such other Party’s rights hereunder, (ii) debt or equity financing of such other Party or (iii) purchase by any Third Party of all of the capital stock or all or substantially all of the assets of such other Party or any merger or consolidation involving such other Party; if, in each case, the Person receiving such Confidential Information of the other Party agrees in writing to maintain the confidentiality of such Confidential Information of the other Party with terms at least as restrictive as those contained in Section 4.1.1.  In addition, each Party agrees that the other Party may disclose such Party’s Confidential Information (A) as reasonably necessary to file, prosecute or maintain patents or patent applications, or to file, prosecute or defend litigation related to patents or patent applications, in accordance with this Agreement; or (B) as required by Applicable Laws, provided that, in the case of any disclosure under this clause (B), the disclosing Party shall (1) if practicable, provide the other Party with reasonable advance notice of and an opportunity to comment on any such required disclosure, (2) if requested by the other Party, cooperate in all reasonable respects with the other Party’s efforts to obtain confidential treatment or a protective order with respect to any such disclosure, at the other Party’s expense and (3) use good faith efforts to incorporate the comments of such other Party in any such disclosure or request for confidential treatment or a protective order.

4.1.3         Employees and Consultants .   ImmunoGen and sanofi-aventis each hereby represents that all of its employees and consultants, and all of the employees and consultants of its Affiliates, who participate in the activities contemplated by this Agreement or have access to Confidential Information of the other Party are or will, prior to their participation or access, be bound by written obligations to maintain such Confidential Information in confidence and not to use such information except as expressly permitted hereunder.  Each Party agrees to use, and to cause its Affiliates to use, reasonable efforts to enforce such obligations.

4.2            Publicity .   The Parties acknowledge that the terms of this Agreement constitute Confidential Information of each Party and may not be disclosed except as permitted by Section 4.1.2.  Notwithstanding anything to the contrary in Section 4.1, the Parties, upon the execution of this Agreement, shall mutually agree to a press release with respect to this Agreement and either Party may make subsequent public disclosure of the contents of such press release without further approval of the other Party.  After issuance of such press release, except as required by Applicable Laws, neither Party shall issue a press or news release or make any similar public announcement (other than publication in scientific journals, in advertising materials and brochures, or presentation at scientific conferences and meetings and the like that are intended to be covered by, and are issued in compliance with, Section 4.3) related to events arising under this Agreement without the prior written consent of the other Party, provided that notwithstanding the foregoing, ImmunoGen shall be expressly permitted to publicly announce the exercise of an Option under Section 2.1.3, provided, however, that the text of such announcement shall be mutually agreed to by the Parties.

4.3            Publications and Presentations .   The Parties acknowledge that scientific publications and presentations must be strictly monitored to prevent any adverse effect from premature publication or dissemination of results of the activities hereunder.  Each Party agrees that, except as required by Applicable Laws, it shall not publish or present, or permit to be

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published or presented, the results of the research conducted by sanofi-aventis under or pursuant to this Agreement to the extent such results refer to or otherwise relate to the Licensed Technology or Licensed Patent Rights (the "Covered Results") without the prior review by and approval of the other Party.  Each Party shall provide to the other Party the opportunity to review each of the submitting Party’s proposed abstracts, manuscripts or presentations (including, without limitation, information to be presented verbally) that relate to the Covered Results at least [***] ([***]) days prior to its intended presentation or submission for publication, and such submitting Party agrees, upon written request from the other Party given within such [***]-[***] period, not to submit such abstract or manuscript for publication or to make such presentation until the other Party is given up to [***] ([***]) days from the date of such written request to seek appropriate patent protection for any Covered Rights in such publication or presentation that it reasonably believes may be patentable.  Once such abstracts, manuscripts or presentations have been reviewed and approved by each Party, the same abstracts, manuscripts or presentations do not have to be provided again to the other Party for review for a later submission for publication.  Each Party also shall have the right to require that any of its Confidential Information that is disclosed in any such proposed publication or presentation be deleted prior to such publication or presentation.  In any permitted publication or presentation by a Party, the other Party’s contribution shall be duly recognized, and co-authorship shall be determined in accordance with customary industry standards.

5.              INTELLECTUAL PROPERTY RIGHTS

Except as otherwise expressly provided herein, all inventions and discoveries governed by this Agreement shall be owned based on inventorship, as inventorship is determined in accordance with United States patent law.  Notwithstanding anything to the contrary in this Agreement, Sanofi-aventis Improvements shall be solely owned by sanofi-aventis, and Licensed Technology and Licensed Patent Rights shall be solely owned by ImmunoGen.

6.              PROVISIONS CONCERNING THE FILING, PROSECUTION AND MAINTENANCE OF PATENT RIGHTS

6.1            Applicability .  The provisions of this Section 6 shall be applicable to all patents covering Licensed Technology and Licensed Patent Rights unless and until they become subject to a License Agreement, whereupon the License Agreement will govern the rights of the Parties with respect to the subject matter thereof.

6.2            Patent Filing .

6.2.1         Licensed Technology .   ImmunoGen, acting through patent counsel or agents of its choice, shall be responsible, at its sole cost and expense, for the preparation, filing, prosecution and maintenance of all Licensed Patent Rights.  All costs and expenses incurred by ImmunoGen in connection with the preparation, filing, prosecution and maintenance of Licensed Patent Rights shall be the sole responsibility of ImmunoGen.  At ImmunoGen’s request, sanofi-aventis shall cooperate with ImmunoGen in all reasonable respects in connection with such preparation, filing, prosecution and maintenance of Licensed Patent Rights.

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6.2.2         Sanofi-aventis Improvements.  Sanofi-aventis, acting through patent counsel or agents of its choice, shall be responsible, at its sole cost and expense, for the preparation, filing, prosecution and maintenance of patent applications and patents constituting Patent Rights claiming Sanofi-aventis Improvements.  Sanofi-aventis (i) will provide ImmunoGen with a copy of any such proposed patent application for review and comment reasonably in advance of filing, and (ii) will keep ImmunoGen reasonably informed of the status of such filing, prosecution and maintenance, including, without limitation, (A) by providing ImmunoGen with copies of all communications received from or filed in patent office(s) with respect to such filing, and (B) by providing ImmunoGen a reasonable time prior to taking or failing to take any action that would affect the scope or validity of any such filing (including the substantially narrowing, cancellation or abandonment of any claim(s) without retaining the right to pursue such subject matter in a separate application, or the failure to file or perfect the filing of any claim(s) in any country), with prior written notice of such proposed action or inaction so that ImmunoGen has a reasonable opportunity to review and comment.  If sanofi-aventis fails to undertake the filing(s) of any such patent application with respect to any such invention within [***] ([***]) days after receipt of written notice from ImmunoGen that ImmunoGen believes filing(s) of such an application by sanofi-aventis is appropriate, ImmunoGen may undertake such filing(s) at its own expense, in which case sanofi-aventis will assign all of its rights to such Improvements to ImmunoGen and any subsequently issued patent thereon will be owned solely by ImmunoGen.

6.2.3         Cooperation .   Each Party agrees to cooperate reasonably with the other Party in the preparation, filing, and prosecution of any patent applications pursuant to this Section 6.2.  Such cooperation includes, but is not limited to, executing all papers and instruments, or requiring its employees or agents to execute such papers and instruments, so as to effectuate the ownership of such patent applications and any patents thereon and to enable the filing and prosecution of applications in any country.

6.3            Infringement .

6.3.1         Sanofi-aventis Improvements .   Sanofi-aventis shall have all rights, at its own expense, to bring suit (or other appropriate legal action) against any actual or suspected infringement of Patent Rights claiming Sanofi-aventis Improvements.

6.3.2         ImmunoGen Technology .   ImmunoGen shall have all rights, at its own expense, to bring suit (or other appropriate legal action) against any actual or suspected infringement of the Licensed Patent Rights.

6.4            Cooperation .  Each Party shall give notice to the other Party of any potential infringement or actual infringement by a Third Party of any Patents Rights covering Licensed Technology and shall execute all papers and perform such other acts (other than monetary) as may be reasonably required to maintain any infringement suit brought in accordance with Section 6.3 above (including giving legal consent for bringing such suit, and agreeing to be named as a plaintiff or otherwise joined in such suit), and at its option and expense, may be represented in such suit by counsel of its choice.  In addition, the Parties shall reasonably cooperate with each other in obtaining patent term restoration or supplemental protection

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certificates or their equivalents in any country in the Territory where applicable to Licensed Patent Rights.

6.5            No Obligation .  No Party shall have any obligation to the other Party under this Agreement to pay any fees or costs: (i) for that Party’s bringing a lawsuit or other action to enforce any Licensed Patent Rights, or any other patent owned by a Party against an actual or suspected infringement or (ii) for any other Party to obtain for its own benefit independent business or legal advice concerning any of the patent rights set forth in clause (i) hereof.

7.              TERM AND TERMINATION

7.1            Term .  Unless earlier terminated as provided in this Section 7, the term of this Agreement shall expire upon the later of the expiration of the Research Term or the last to expire of the Option Periods (the "Term").

7.2            Termination .  This Agreement and the rights and options granted herein may be terminated by either Party upon any material breach by the other Party of any material obligation or condition, effective [***] ([***]) days after giving written notice to the breaching Party of such termination in the case of a payment breach and [***] ([***]) days after giving written notice to the breaching Party of such termination in the case of any other breach, which notice shall describe such breach in reasonable detail.  The foregoing notwithstanding, if such default or breach is cured or shown to be non-existent within the aforesaid [***] ([***]) or [***] ([***]) day period, the notice shall be automatically withdrawn and of no effect.  However, prior to giving any notice for breach, the Parties shall first attempt to resolve any disputes as to the existence of any breach as set forth in Section 8.14.  Additionally, until such time as sanofi-aventis has exercised the Research Term Option, sanofi-aventis shall have the further right to terminate this Agreement upon providing not less than [***] ([***]) days’ written notice to ImmunoGen of such termination.

7.3            Remedies .  If either Party shall fail to perform or observe or otherwise breaches any of its material obligations under this Agreement, in addition to any right to terminate this Agreement, the non-defaulting Party may elect to obtain other relief and remedies available under law.

7.4            Surviving Provisions .  Notwithstanding any provision herein to the contrary, the rights and obligations set forth in Sections 2.3.6, 4, 5, 6.2, 7.4, 8.4, 8.5, 8.6, 8.16 and 8.17 hereof shall survive the expiration of the Term or the termination of this Agreement.  All other rights and licenses of the Parties set forth in this Agreement shall terminate.

8.              REPRESENTATIONS, WARRANTIES AND COVENANTS

8.1            Mutual Representations and Warranties .  ImmunoGen and sanofi-aventis each represents and warrants to the other, as of the Effective Date, as follows:

8.1.1         Organization .  It is a corporation duly organized, validly existing and in good standing under the laws of the jurisdiction of its organization, and has all requisite power and authority, corporate or otherwise, to execute, deliver and perform this Agreement.

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8.1.2         Authorization .  The execution and delivery of this Agreement and the performance by it of the transactionscontemplated hereby have been duly authorized by all necessary corporate action and will not violate (a) such Party’s certificate of incorporation or bylaws, (b) any agreement, instrument or contractual obligation to which such Party is bound in any material respect, (c) any requirement of any Applicable Law, or (d) any order, writ, judgment, injunction, decree, determination or award of any court or governmental agency presently in effect applicable to such Party.

8.1.3         Binding Agreement .   This Agreement is a legal, valid and binding obligation of such Party enforceable against it in accordance with its terms and conditions.

8.1.4         No Inconsistent Obligation .   It is not under any obligation, contractual or otherwise, to any Person that conflicts with or is inconsistent in any respect with the terms of this Agreement or that would impede the diligent and complete fulfillment of its obligations hereunder.

8.2            Additional Representations of ImmunoGen .  ImmunoGen further represents and warrants to sanofi-aventis, as of the Effective Date, as follows:

8.2.1         Licensed Patent Rights .  All Licensed Patent Rights existing as of the Effective Date are existing and, to ImmunoGen’s knowledge, no such Licensed Patent Rights are invalid or unenforceable.

8.2.2         Claims or Judgments .  There are no claims, judgment or settlements against ImmunoGen pending, or to ImmunoGen’s knowledge, threatened, that invalidate or seek to invalidate the Licensed Patent Rights existing as of the Effective Date.

8.2.3         Right to Technology .   ImmunoGen has the right to (a) use the Licensed Technology and Licensed Patent Rights existing as of the Effective Date as is necessary to fulfill its obligations under this Agreement; and (b) grant the licenses under the Licensed Patent Rights granted pursuant to this Agreement.

8.2.4         No Infringement .   To ImmunoGen’s knowledge, no Third Party is infringing, or threatening to infringe, the Licensed Patent Rights.

8.2.5         No Litigation .   To ImmunoGen’s knowledge, there is no pending or threatened litigation that alleges that ImmunoGen’s proposed activities under this Agreement would infringe or misappropriate any intellectual property rights of any Third Party.

8.3            Covenant .   ImmunoGen agrees to use commercially reasonable efforts to maintain the right, to (a) use the Licensed Technology and Licensed Patent Rights existing as of the Effective Date as is necessary to fulfill its obligations under this Agreement; and (b) grant the licenses under the Licensed Patent Rights granted pursuant to this Agreement.

9.              INDEMNIFICATION

9.1            Indemnification of sanofi-aventis by ImmunoGen .  ImmunoGen shall indemnify, defend and hold harmless sanofi-aventis, its Affiliates, their respective directors,

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officers, employees and agents, and their respective successors, heirs and assigns (collectively, the "sanofi-aventis Indemnitees"), against all liabilities, damages, losses and expenses (including, without limitation, reasonable attorneys’ fees and expenses of litigation) (collectively, "Losses") incurred by or imposed upon the sanofi-aventis Indemnitees, or any one of them, as a direct result of claims, suits, actions, demands or judgments of Third Parties, including without limitation personal injury and product liability claims and claims of suppliers and ImmunoGen employees (collectively, "Claims"), arising out of the material breach by ImmunoGen of this Agreement, except with respect to any Claim or Losses that result from a material breach of this Agreement by, or the gross negligence or willful misconduct of, sanofi-aventis, provided that, with respect to any Claim for which ImmunoGen has an obligation to any sanofi-aventis Indemnitee pursuant to this Section 9.1 and sanofi-aventis has an obligation to any ImmunoGen Indemnitee pursuant to Section 9.2, each Party shall indemnify each of the other Party’s Indemnitees for its Losses to the extent of its responsibility, relative to the other Party, for the facts underlying the Claim.

9.2            Indemnification of ImmunoGen by sanofi-aventis .  Sanofi-aventis shall indemnify, defend and hold harmless ImmunoGen, its Affiliates, their respective directors, officers, employees and agents, and their respective successors, heirs and assigns (the "ImmunoGen Indemnitees"), against any Losses incurred by or imposed upon the ImmunoGen Indemnitees, or any one of them, as a direct result of Claims arising out of (a) the material breach by sanofi-aventis of this Agreement; (b) the development or commercialization (including, without limitation, the production, manufacture, promotion, import, sale or use by any Person) of any MAY Compound or Ab-MAY Product by sanofi-aventis or any of its Affiliates, Sublicensees, distributors or agents, except with respect to any Claim or Losses that result from a breach of this Agreement by, or the gross negligence or willful misconduct of, ImmunoGen, provided that with respect to any Claim for which ImmunoGen has an obligation to any sanofi-aventis Indemnitee pursuant to Section 9.1 and sanofi-aventis has an obligation to any ImmunoGen Indemnitee pursuant to this Section 9.2, each Party shall indemnify each of the other Party’s Indemnitees for its Losses to the extent of its responsibility, relative to the other Party, for the facts underlying the Claim.

9.3            Conditions to Indemnification .  A Person seeking recovery under Sections 9.1 or 9.2(the "Indemnified Party") in respect of a Claim shall give prompt notice of such Claim to the Party from which recovery is sought (the "Indemnifying Party") and, provided that the Indemnifying Party is not contesting its obligation under Sections 9.1 or 9.2, shall permit the Indemnifying Party to control any litigation relating to such Claim and the disposition of such Claim, provided that the Indemnifying Party shall (a) act reasonably and in good faith with respect to all matters relating to the settlement or disposition of such Claim as the settlement or disposition relates to such Indemnified Party and (b) not settle or otherwise resolve such claim without the prior written consent of such Indemnified Party (which consent shall not be unreasonably withheld, conditioned or delayed).  Each Indemnified Party shall cooperate with the Indemnifying Party in its defense of any such Claim in all reasonable respectsand shall have the right to be present in person or through counsel at all legal proceedings with respect to such Claim.

9.4            Warranty Disclaimer .  EXCEPT AS OTHERWISE EXPRESSLY PROVIDED IN THIS AGREEMENT, NEITHER PARTY MAKES ANY WARRANTY WITH RESPECT

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TO ANY TECHNOLOGY, GOODS, SERVICES, RIGHTS OR OTHER SUBJECT MATTER OF THIS AGREEMENT AND EACH PARTY HEREBY DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

9.5            Limited Liability .  NOTWITHSTANDING ANYTHING TO THE CONTRARY IN THIS AGREEMENT, NEITHER PARTY SHALL BE LIABLE TO THE OTHER PARTY OR ANY OF ITS AFFILIATES FOR (I) ANY SPECIAL, PUNITIVE, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION LOST PROFITS OR LOST REVENUES, OR (II) COST OF PROCUREMENT OF SUBSTITUTE GOODS, TECHNOLOGY OR SERVICES, WHETHER UNDER ANY CONTRACT, WARRANTY, NEGLIGENCE, STRICT LIABILITY OR OTHER LEGAL OR EQUITABLE THEORY.

10.           MISCELLANEOUS

10.1          Notices .  Any notices, requests, deliveries, approvals or consents required or permitted to be given under this Agreement to sanofi-aventis or ImmunoGen shall be in writing and shall be effective on receipt when delivered to the applicable address specified below (or to such other address as may be specified in writing to the other Party hereto):

Except as otherwise expressly provided in this Agreement or mutually agreed in writing, any notice, communication or document (excluding payment) required to be given or made shall be deemed given or made and effective upon actual receipt or, if earlier, (a) three (3) business days after deposit with an internationally-recognized overnight express courier with changes prepaid, or (b) five (5) business days after mailed by certified, registered or regular mail, postage prepaid, in each case addressed to a Parties at its address stated above or to such other address as such Party may designate by written notice given in accordance with this Section 10.1.

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10.2          Governing Law .  This Agreement will be construed, interpreted and applied in accordance with the laws of the State of Delaware (excluding its body of law controlling conflicts of law).

10.3          Limitations .  Except as set forth elsewhere in this Agreement, neither Party grants to the other Party any right or license to any of its intellectual property.

10.4          Entire Agreement .  This is the entire Agreement between the Parties with respect to the subject matter hereof and supersedes all prior representations, understandings and agreements between the Parties with respect to the subject matter hereof, including without limitation the Option Agreement.  No modification shall be effective unless in writing with specific reference to this Agreement and signed by the Parties.

10.5          Waiver .  The terms or conditions of this Agreement may be waived only by a written instrument executed by the Party waiving compliance.  The failure of either Party at any time or times to require performance of any provision hereof shall in no manner affect its rights at a later time to enforce the same.  No waiver by either Party of any condition or term shall be deemed as a continuing waiver of such condition or term or of another condition or term.

10.6          Headings .  Section and subsection headings are inserted for convenience of reference only and do not form part of this Agreement.

10.7          Assignment .  Neither this Agreement nor any obligation of a Party hereunder may be assigned by either Party without the consent of the other which shall not be unreasonably withheld, except that each Party may assign this Agreement and the rights, obligations and interests of such Party, in whole or in part, to any of its Affiliates, and to any Third Party purchaser of all of the capital stock of such Party or all or substantially all of its assets in the line of business to which this Agreement pertains or to any successor corporation resulting from any merger or consolidation of such Party with or into such corporation.

10.8          Force Majeure .  Neither Party shall be liable for failure of or delay in performing obligations set forth in this Agreement, and neither shall be deemed in breach of its obligations, if such failure or delay is due to natural disasters or any causes beyond the reasonable control of such Party.  In the event of such force majeure, the Party affected thereby shall use reasonable efforts to cure or overcome the same and resume performance of its obligations hereunder.

10.9          Construction .  The Parties hereto acknowledge and agree that each Party and its counsel reviewed and negotiated the terms and provisions of this Agreement and have contributed to its revision.

10.10        Severability .  If any provision(s) of this Agreement are or become invalid, are ruled illegal by any court of competent jurisdiction or are deemed unenforceable under then current applicable law from time to time in effect during the Term hereof, it is the intention of the Parties that the remainder of this Agreement shall not be affected thereby provided that a Party’s rights under this Agreement are not materially affected.  The Parties hereto covenant and agree to renegotiate any such term, covenant or application thereof in good faith in order to provide a reasonably acceptable alternative to the term, covenant or condition of this Agreement

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or the application thereof that is invalid, illegal or unenforceable, it being the intent of the Parties that the basic purposes of this Agreement are to be effectuated.

10.11        Status .  Nothing in this Agreement is intended or shall be deemed to constitute a partner, agency, employer-employee, or joint venture relationship between the Parties.

10.12        Section 365(n) .  All licenses granted under this Agreement are deemed to be, for purposes of Section 365(n) of the U.S. Bankruptcy Code, licenses of right to "intellectual property" as defined in Section 101 of such Code.  The Parties agree that the licensee may fully exercise all of its rights and elections under the U.S. Bankruptcy Code, regardless of whether either Party files for bankruptcy in the United States or other jurisdiction.  The Parties further agree that, in the event a licensee elects to retain its rights as a licensee under such Code, the licensee shall be entitled to complete access to any technology licensed to it hereunder and all embodiments of such technology.  Such embodiments of the technology shall be delivered to the licensee not later than (a) the commencement of bankruptcy proceedings against the licensor, upon written request, unless the licensor elects to perform its obligations under the Agreement, or (b) if not delivered under Section 10.12(a) above, upon the rejection of this Agreement by or on behalf of the licensor, upon written request.

10.13        Further Assurances .  Each Party agrees to execute, acknowledge and deliver such further instructions, and to do all such other acts, as may be necessary or appropriate in order to carry out the purposes and intent of this Agreement.

10.14        Counterparts .  This Agreement may be executed simultaneously in one or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

[Remainder of page intentionally left blank.]

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IN WITNESS WHEREOF, the Parties have caused this Agreement to be executed by their duly authorized representative in two (2) originals.

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APPENDIX A

FORM OF EXCLUSIVE LICENSE AGREEMENT

This EXCLUSIVE LICENSE AGREEMENT (this "Agreement") is entered into as of                  ,         , 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, the Parties executed an Option and License Agreement (as hereinafter defined) pursuant to which ImmunoGen granted sanofi-aventis certain options to license certain Technology Controlled by ImmunoGen; and

WHEREAS, ImmunoGen has entered into agreements based on the so-called "Revolving-Door" structure with a number of Third Parties whereby such Third Parties are obligated to grant back to ImmunoGen the right to such Third Parties’ improvements to Technology and Patent Rights, and pursuant to which ImmunoGen has the right to grant access to such Third Party Improvements to sanofi-aventis; and

WHEREAS, sanofi-aventis exercised an Option (as hereinafter defined) pursuant to the Option and License Agreement, pursuant to which the Parties have agreed to enter into this Agreement in accordance with the terms thereof.

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

Whenever used in this Agreement with an initial capital letter, the terms defined in this Section 1 shall have the meanings specified.

1.1            " Ab-MAY Product " means any product containing a conjugate of a Sanofi-aventis Antibody with a MAY Compound.

1.2            " 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.

1.3            " Annual Net Sales " means the aggregate Net Sales during a particular Calendar Year.

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1.4            " 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.

1.5            " Antibody-MAY Compound Conjugate " means any compound containing a conjugate of an Antibody with a MAY Compound.

1.6            " 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.

1.7            " Business Day " means a day on which banking institutions in New York, New York are open for business.

1.8            " 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.

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

1.10          " Clinical Materials " means any supplies of MAY Compound or Licensed Product manufactured by ImmunoGen in accordance with all Applicable Laws (including GMP) and applicable Specifications for use in human clinical testing up to and including non-pivotal Phase IIB Studies.

1.11          " Collaboration Agreement " means that certain Collaboration and License Agreement dated as of July 30, 2003, as amended, by and between ImmunoGen and Aventis Pharmaceuticals, Inc., the predecessor in interest to sanofi-aventis.

1.12          " 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.

1.13          " Commercially Reasonable Efforts " means, with respect to sanofi-aventis, the efforts at least equal to those customarily 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

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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.

1.14        " 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.

1.15        " Comparable Product " means a product, other than any product being marketed and/or sold as of the Effective Date, that (a) incorporates or is comprised of an Antibody-drug conjugate, (b) is directed against the same Target as a Licensed Product and (c) is marketed and sold by a Third Party for use in the Field.

1.16        " Confidential Information " means (a) with respect to ImmunoGen, all tangible embodiments of Licensed Technology and Licensed Patent; (b) with respect to sanofi-aventis, all information and Technology related to the sanofi-aventis Antibody and otherwise included in any Regulatory Filings made, and Regulatory Approvals received, by sanofi-aventis with respect to Licensed Products; and (c) 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.

1.17        " 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.

1.18        " Derived " means obtained, developed, created, synthesized, designed, derived or resulting or generated from, based upon, or otherwise containing (whether directly or indirectly, or in whole or in part).

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1.19        " Designated Senior Officer " means, with respect to a Party, the senior officer of such Party or its Affiliate designated by such Party to have final decision making authority over Disputed Matters.

1.20        " 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.

1.21        " 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.

1.22        " Effective Date " means the date first set forth above in the introductory paragraph to this Agreement.

1.23        " FDA " means the United States Food and Drug Administrati