TABLE OF CONTENTS

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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 . &