<PAGE>

SECTION A

THIS AGREEMENT (the "Agreement") is made this 22nd day of December 1999 (the
"Effective Date") by and between GENZYME TRANSGENICS CORPORATION ("GTC"), with
offices at 175 Crossing Boulevard, Framingham, Massachusetts 01702-9322 U.S.A.
and Alexion Pharmaceuticals Inc. ("Alexion") located at 25 Science Park, New
Haven, Connecticut 06511.

1.   BACKGROUND. Alexion is a biopharmaceutical company actively involved in
the development of [***] (the "Product"). Alexion is interested in GTC
producing Product in the milk of transgenic goats (the "Project"). GTC is
willing to perform the Project, subject to the terms and conditions of this
Agreement, including the Project Work Plan set forth herein.

2.   EXPRESSION TECHNOLOGY. "Expression Technology" means GTC's proprietary
technology, which GTC shall use to generate and propagate transgenic animal
founder lines for Product.

3.   PERFORMANCE OF THE PROJECT. The Project will be performed by GTC in
accordance with the Project Work Plan, which may be amended from time to time by
written agreement of the parties.

GTC shall conduct the Project in conformance with the Good Laboratory Practice
requirements of the United States Food and Drug Administration ("FDA") and
otherwise in compliance with all laws, ordinances, and governmental rules or
regulations pertaining thereto.

GTC will have met the success criteria of the Project and the Project will be
concluded upon demonstration that founder females produce in the ordinary course
milk containing fully processed, functional Product and delivery of reasonable
quantities of samples to Alexion, provided that GTC uses commercially reasonable
and diligent efforts to achieve such criteria within the timeline as hereinafter
provided. GTC makes no guarantee that such success criteria can be attained.

4.      RECORDS.

        4.1    GTC will keep accurate records of the status and progress of the
               Project. GTC will not destroy such records without giving Alexion
               prior written notice and the opportunity to further store such
               records.

        4.2    Alexion's personnel shall have the right to review such records
               at GTC's facilities during regular business hours on 5 days'
               written notice.
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5.      REPORTS.

        5.1    PROJECT UPDATES. GTC will keep Alexion advised of the status of
               the Project through regular telephone conversations and meetings.

        5.2    FINAL REPORT. GTC will complete a final report of the Project
               within sixty (60) days of its completion. If performance of the
               Project is suspended or terminated prior to completion, GTC will
               promptly provide Alexion with a final report of the results of
               the Project through the date of suspension or termination.
               Alexion is and shall at all times remain the sole owner of the
               reports prepared by GTC.

6.      COMPENSATION. Alexion agrees to pay GTC for the Project as
               follows:

        6.1    Alexion will pay GTC a Start-up fee of [***], payable on
               execution of this Agreement by both parties;

        6.2    Alexion will pay GTC a fee of [***] upon completion of the
               microinjection of a suitable number of goat embryos which would
               normally be expected to yield [***], and transfer of such
               embryos to recipient females;

        6.3    Alexion will pay GTC a fee of [***] upon the birth of the
               first F0 goat transgenic for Product;

        6.4    Alexion will pay GTC a success fee for expression of Product as
               follows:

               a.      [***]

               b.      [***]

               For avoidance of doubt, Alexion will only pay a maximum amount
               equal to [***] for the successful expression of Product.

               c.      In the event GTC is not successful in obtaining either a
                       male or female founder animal with induced and/or natural
                       expression of approximately [***], as per (a)



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                       and (b) above, and the DNA provided by Alexion is
                       verified correct, GTC will conduct a second round of
                       microinjections [***].

        6.5    Alexion will pay GTC a fee of [***] upon delivery of an amount
               of clarified intermediate product which yields at least
               [***] of pre-pivotal clinical grade Product, as
               produced by a development scale purification process consistent
               with industry standards, for comparability testing.

        6.6    Should Alexion at its sole discretion elect to enter into a
               Clinical Development and/or Commercial Supply Agreement pursuant
               to Section 10.4 below, Alexion will pay GTC a commercial fee of
               [***].

        6.7    Alexion will pay GTC a fee in the amount of [***] in the
               event that Alexion decides these activities are required.

        6.8    Alexion will reimburse GTC for costs incurred as a result of
               GTC's assistance with Alexion's collaboration with a third-party
               to develop and scale-up a downstream purification process for
               Product, [***].

               Fully Burdened Costs means GTC's direct labor and materials
               costs, plus allocable indirect overhead expenses and allocable
               selling, general and administrative expenses, determined in
               accordance with generally accepted accounting principles,
               consistently applied.

        6.9    Except for under the conditions set forth in Section 6.4(c),
               Alexion also agrees to pay for transgenic animal maintenance
               costs at [***] GTC's FBC during any period of delay in
               the Project where GTC is not funded by Alexion to conduct
               activities on the Project, until such time as the Project is
               terminated, provided that such delay is not caused by the acts or
               omissions of GTC. A minimum of thirty (30) days termination
               notice applies to these costs.

7.      CONFIDENTIALITY.

        7.1    For a period of [***] years from the termination of this
               Agreement, any Confidential Information (as defined below)
               disclosed by the disclosing party hereunder, directly or
               indirectly, to the receiving party hereunder, shall be deemed
               confidential, and shall not be disclosed by the receiving party
               to third parties, except as set forth below. Access to such
               Confidential Information will be limited to employees, agents,
               Affiliates (as defined



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               below), consultants or contractors of the receiving party who
               reasonably require such Confidential Information and who are
               bound to the receiving party by similar obligations in respect of
               confidentiality and use. The receiving party will use such
               Confidential Information only to carry out its obligations or to
               exercise its rights hereunder and will not use such Confidential
               Information for its own benefit or for the benefit of others or
               in any way inconsistent with this Agreement.

        7.2    Nothing contained herein will in any way restrict or impair each
               party's right to use, disclose or otherwise deal with any
               Confidential Information which:

               i)  at the time of disclosure, is in the public knowledge;

               ii) after disclosure, becomes part of the public knowledge by
               publication or otherwise, except by breach of this Agreement by
               the receiving party;

               iii) was demonstrably in the receiving party's possession at the
               time of such disclosure, and which was not acquired, directly or
               indirectly, from the disclosing party;

               iv) the receiving party receives from third parties, provided
               such Confidential Information was not obtained by such third
               parties, directly or indirectly, from the disclosing party on a
               confidential basis;

               v) results from research and development of the receiving party
               demonstrably independent of such disclosure;

               vi) is required to be disclosed by legal process; provided,
               however, in each case the party so disclosing Confidential
               Information timely informs the other party and uses its
               reasonable efforts to limit the disclosure and maintain
               confidentiality to the extent possible and permits the other
               party to attempt by appropriate legal means to limit such
               disclosure; and

               vii) the disclosing party identifies in writing as being for
               public disclosure.

        7.3    For purposes of this Agreement, the term "Confidential
               Information" shall mean all of the data, information, technology,
               samples, DNA, specimens, materials and any other information
               affecting the business operations of the disclosing party
               received by the receiving party from the disclosing party
               hereunder.

        7.4    For purposes of this Agreement, the term "Affiliate" shall mean
               any corporation which controls, is controlled by or is under
               common control with a party hereto. A corporation shall be
               regarded as in control of another corporation if it owns or
               directly



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               or indirectly controls at least fifty percent (50%) of the voting
               stock of the other corporation, or in the absence of the
               ownership of at least fifty percent (50%) of the voting stock, if
               it possesses, directly or indirectly, the power to direct or
               cause the direction of the management and policies of the
               corporation.

        7.5    In addition, neither party shall originate any written publicity,
               news release or other public announcement or statement relating
               to this Agreement or to the performance hereunder or the
               existence of an arrangement between the parties without prior
               review and written approval of the other party. Notwithstanding
               the foregoing, either party may make a public written disclosure
               if required by applicable law provided that prior to making such
               written disclosure, the disclosing party shall provide the other
               party with a copy of, and reasonable opportunity to review, the
               materials to be disclosed. To the extent that the non-disclosing
               party requests that any information in the proposed disclosure be
               deleted, the disclosing party shall request confidential
               treatment of such information pursuant to applicable law, so that
               there be omitted from the materials that are publicly filed any
               information that the non-disclosing party requests to be deleted.

8.      RIGHTS AND DEVELOPMENTS.

        8.1    DEFINITION. "Rights and Developments" include, without
               limitation, ideas, concepts, discoveries, inventions,
               developments, know-how, patent rights, trade secrets, techniques,
               methodologies, innovations, improvements, writings,
               documentation, data and other rights (whether or not protectable
               under state, federal, or foreign patent, trademark, copyright or
               similar laws) that are conceived, discovered, invented,
               developed, created, made or reduced to practice by GTC, alone or
               jointly with others, in performance of the Project.

        8.2    OWNERSHIP.

               a.      All Rights and Developments relating to Alexion's Product
                       or its use shall be solely owned by Alexion, regardless
                       of the designation of inventorship between the parties
                       and their employees.

                       GTC shall promptly notify Alexion of all such Rights and
                       Developments and shall transfer and assign to Alexion all
                       rights, title and interest in the Rights and
                       Developments, and Alexion, in its sole discretion, may
                       apply for patents and other intellectual property rights
                       relating to the Rights and Developments. GTC shall, at
                       Alexion's request, execute such declarations, assignments
                       and other documents required by Alexion to effect such
                       transfer and assignment and any intellectual property
                       applications.



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               b.      All Rights and Developments relating to the Expression
                       Technology shall be solely owned by GTC, regardless of
                       the designation of inventorship between the parties and
                       their employees.

                       Alexion shall promptly notify GTC of all such Rights and
                       Developments and shall transfer and assign to GTC all
                       rights, title and interest in the Rights and
                       Developments, and GTC, in its sole discretion, may apply
                       for patents and other intellectual property rights
                       relating to the Rights and Developments. Alexion shall,
                       at GTC's request, execute such declarations, assignments
                       and other documents required by GTC to effect such
                       transfer and assignment and any intellectual property
                       applications.

               c.      All transgenic animals expressing Alexion's Product which
                       are generated by GTC as part of the Project performed
                       under this Agreement shall be solely owned by Alexion,
                       regardless of the designation of inventorship between the
                       parties and their employees, [***].

                       In the case where Alexion uses the animals to make at
                       least a portion of Alexion's commercial Product and where
                       GTC does not manufacture all of Alexion's commercial
                       Product, [***] from the commercial manufacture of
                       transgenic Product on Alexion's behalf.

               d.      All other Rights and Developments shall be jointly owned
                       by the parties, regardless of the designation of
                       inventorship between the parties and their employees.

        8.3    PATENT RIGHTS. Any patent applications covering Rights and
               Developments owned by Alexion will be prepared and filed by
               Alexion, with expenses paid [***]. Any patent applications
               covering Rights and Developments owned by GTC or jointly owned by
               the parties will be prepared and filed by GTC, [***].
               If either party elects not to file or maintain an application
               or patent covering any jointly owned Rights and Developments,
               that party shall promptly notify the other party, which shall



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               have the right to file or maintain such applications or patents,
               at its expense. Inventorship will be determined according to U.S.
               patent law.

        8.4    INFRINGEMENT OF THIRD PARTY PATENTS.

               a.      GTC warrants that it shall not knowingly infringe any
                       existing third-party patents or other intellectual
                       property rights of any third party relating to the
                       transgenic expression vectors, clarification and other
                       processes used in connection with the Project.

               b.      Alexion warrants that it shall not knowingly infringe any
                       existing thirdparty patents or other intellectual
                       property rights of any third party relating to the DNA
                       supplied by Alexion to GTC hereunder and used in
                       connection with the Project.

9.   INDEMNIFICATION. Alexion and GTC shall each defend, indemnify and hold the
other and it's affiliates and the respective directors, officers, employees and
agents and affiliates, harmless from and against any and all losses, damages,
liabilities, claims, demands, judgements, settlements, costs and expenses
(including, without limitation, reasonable attorneys' fees and other costs of
defense) arising out of, relating to or resulting from the breach of any of
their respective representations, warranties and covenants contained within this
Agreement or their respective negligence or willful misconduct.

10.  TERM AND TERMINATION.

        10.1   TERM. The term of this Agreement shall commence on the Effective
               Date. Unless earlier terminated in accordance with the provisions
               of this Agreement, the Project shall terminate upon GTC's making
               available for delivery to Alexion:

               a.      the Final Report in a form reasonably satisfactory to
                       Alexion,

               b.      any transgenic founder animals generated for Alexion's
                       Product, and

               c.      samples of deliverable Product as indicated in the
                       Project Work Plan.

        10.2   TERMINATION BY EITHER PARTY. This Agreement may be terminated by
               either party in the event of a material breach by the other party
               of the terms hereof; provided, however, the nondefaulting party
               shall first give to the defaulting party written notice of the
               proposed termination of this Agreement, specifying the grounds
               therefore, and the defaulting party shall have thirty (30) days
               after such notice is given to cure the breach. If not so cured,
               this Agreement shall terminate at the expiration of such thirty
               (30) days.



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               Upon termination, neither party will have any further obligations
               under this Agreement, except (a) the liabilities accrued through
               the date of termination and (b) the obligations which by their
               terms survive termination shall survive. Upon termination, GTC
               will return to Alexion or dispose of any of Alexion's Product and
               any transgenic animals generated by GTC pursuant to the Project
               in accordance with Alexion's instructions.

        10.3   CONTINUING OBLIGATION. The termination or expiration of this
               Agreement shall not relieve either party of its obligations to
               the other party in respect of (a) the confidentiality or use of
               Confidential Information and, (b) any publication or presentation
               relating to the Project, or (c) indemnification as provided in
               Section 9.

        10.4   FURTHER CLINICAL DEVELOPMENT AND COMMERCIAL SUPPLY AGREEMENT. In
               the event that the parties decide to enter into an agreement for
               the supply of Product for clinical and/or commercial use, GTC
               agrees to scale up the transgenic production herd, develop and
               scale up a primary recovery step (Tangential Flow Filtration,
               "TFF"), and assist Alexion [***]. The parties agree to commence
               good faith negotiations in an effort to reach agreement on the
               terms of such an agreement, such negotiations to ensure an
               efficient transition from development to clinical and/or
               commercial activities and not to unnecessarily delay the
               development of transgenically-produced Product.

               In the event of an agreement to produce Product for clinical
               studies, GTC will provide the required Product at [***].

               In the event of entering into a Development and Commercial
               Agreement, the key compensation elements will be as follows:

               a.      Within a Development and Commercial Agreement constructed
                       under industry standard terms and conditions, GTC will
                       provide Product for commercial activities at [***]
                       at a commercially relevant scale for Alexion.
                       [***] TFF stage Product. This would result in an
                       effective transfer price to Alexion of [***] of TFF
                       stage Product). In the event GTC is able to lower its
                       costs, GTC and Alexion will share equally in the
                       benefits;


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<PAGE>

               b.      [***] will pay the capital costs associated with herd
                       scale up and the construction of a dedicated barn, dairy
                       and primary recovery (TFF) suite as agreed to by the
                       parties;

               c.      Alexion will pay GTC a royalty of [***].

11.  ASSIGNABILITY. This Agreement, and the rights and obligations hereunder,
may not be assigned or transferred by either party without the prior written
consent of the other party, such consent not to be unreasonably withheld, except
that GTC or Alexion may assign this Agreement to an affiliated company or in
connection with the merger, consolidation or sale of all or substantially all of
it assets.

12.  PUBLICATION. Any publication or presentation relating to the Project must
first be approved in writing by both parties, such approval not to be
unreasonably withheld. Each party agrees to submit, for review, any proposed
publication (including any writing to be presented orally) relating to the
Project at least forty-five (45) days prior to submission for publication or
presentation. If either party requests a delay in publication or presentation,
the other party agrees to delay the publication or presentation, for a period of
ninety (90) days from the date of such request. Such period may be extended, if
necessary, for an additional period mutually acceptable to the parties.
Notwithstanding the foregoing, both parties agree that no publication or
presentation shall contain Confidential Information with respect to which it has
confidentiality obligations pursuant to Section 7 hereof.

13.  GOVERNING LAW AND ENTIRETY. The validity, interpretation and performance of
this Agreement shall be governed and construed in accordance with the laws of
the State of Massachusetts, U.S.A. This document along with any Confidentiality
Agreement, constitutes the full understanding of the parties with respect to the
subject matter hereof, and a complete and exclusive statement of the terms of
their agreement, and no terms, conditions, understanding or agreement purporting
to modify or vary the terms of this Agreement shall be binding unless made in
writing and signed by the party to be bound.

14.  NO WAIVER. No waiver of any term or condition of this Agreement shall be
valid or binding on either party unless agreed in writing by the party to be
charged. The failure of either party to enforce at any time any of the
provisions of this Agreement, or the failure to require at any time performance
by the other party of any of the provisions of this Agreement, shall in no way
be construed to be a present or future waiver of such provisions, nor in any way
affect the validity of either party to enforce each and every such provision
thereafter.

15.  COUNTERPARTS. This Agreement may be executed in two counterparts, each of
which shall be deemed an original and both of which together shall constitute
one instrument.

16.  INDEPENDENT CONTRACTORS. The relationship of Alexion and GTC established by
this Agreement is that of independent contractors, and nothing contained in this
Agreement shall be



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construed to: (a) give either party the power to direct or control the
day-to-day activities of the other, (b) constitute the parties as partners,
joint venturers, co-owners or otherwise as participants in a joint or common
undertaking; or (c) allow a party to create or assume any obligation on behalf
of the other party for any purpose whatsoever. Nothing in this Agreement will
give rise to the creation of any labor relation by and between either party and
any employees of the other party.



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        IN WITNESS WHEREOF, duly-authorized representatives of the parties have
        signed this Agreement as a document under seal of the Effective Date.

ALEXION PHARMACEUTICALS INC.                GENZYME TRANSGENICS
                                            CORPORATION

By:     /s/ David W. Keiser                     By:     /s/ Michael W. Young
   -------------------------------             ---------------------------------
Print Name: David W. Keiser                 Print Name: Michael W. Young

Title: Exec. Vice-President and COO         Title: Vice-President, Commercial
         Duly Authorized                           Development Duly Authorized



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SECTION B

                                PROJECT WORK PLAN

WORK PLAN OBJECTIVES:

1.      Generate founder goats transgenic for Product

2.      Evaluate transgenic technology for the manufacture of Product for
        clinical use at a scale of [***].

3.      Provide Product samples for in vitro testing

4.      Deliver to Alexion an amount of clarified intermediate Product which
        yields [***], as produced by a development scale purification process
        consistent with industry standards.

WORK PLAN ACTIVITIES:

1.      [***]

2.      [***]

3.      [***]

4.      [***]

5.      [***]

6.      [***]

7.      [***]

8.      [***]

9.      [***]

10.     [***]

11.     [***]

12.     [***]


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FROM GTC

GTC agrees to conduct the Project as described below. GTC shall provide
personnel, facilities and resources as required to perform the Project.

[***]

A provisional timeline is set forth below:

        TIME                    ACTIVITY

[***]                   [***]

[***]                   [***]

[***]                   [***]

[***]                   [***]

[***]                   [***]

[***]                   [***]

[***]                   [***]


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FROM ALEXION

In connection with the Project, Alexion shall supply GTC with the following:

        (a)    [***];

        (b)    [***];

        (c)    [***];

        (d)    [***].


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