Document:

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                                                                   Exhibit 10.17

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                           COMMERCIAL SUPPLY AGREEMENT

This Commercial Supply Agreement (this "Agreement") is entered into on Dec. 4,
2002 (the "Signing Date"), effective as of the 1st day of June, 2002 (the
"Effective Date") by and between BAXTER PHARMACEUTICAL SOLUTIONS LLC ("BAXTER"),
a Delaware limited liability company having a place of business at 927 South
Curry Pike, Bloomington, Indiana 47403, and PRAECIS PHARMACEUTICALS INCORPORATED
("PRAECIS"), a Delaware corporation having a principal place of business at 830
Winter Street, Waltham, Massachusetts 02451.

                                    RECITALS

     1.     PRAECIS is engaged in the development, bulk production, formulation,
            sale and distribution of pharmaceutical products;

     2.     BAXTER is engaged in the filling, labeling and packaging of
            pharmaceutical products;

     3.     PRAECIS and BAXTER desire to have BAXTER fill, package, inspect,
            label, and test pharmaceutical products for distribution and sale by
            PRAECIS;

     4.     In order to induce PRAECIS to enter into this Agreement, Baxter
            Healthcare Corporation, the parent company of BAXTER, has agreed to
            guarantee the performance of BAXTER hereunder as set forth herein.

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, the parties agree as follows:

ARTICLE 1, DEFINITIONS

     As used in this Agreement, the following words and phrases shall have the
following meanings:

     1.1    "AFFILIATE" of a party hereto shall mean any entity that controls or
            is controlled by such party, or is under common control with such
            party. For purposes of this definition, an entity shall be deemed to
            control another entity if it owns or controls, directly or
            indirectly, at least fifty percent (50%) of the voting equity of

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            another entity (or other comparable ownership interest for an entity
            other than a corporation).

     1.2    "ANDA" shall mean the FDA-required Abbreviated New Drug Application.

     1.3    "ANNUAL OBLIGATION" shall be defined in Section 4.1.3(c).

     1.4    "BATCH" shall mean a specific quantity of a Product comprising a
            number of units mutually agreed upon between PRAECIS and BAXTER (as
            set forth in the Product Master Plan), and that is intended to have
            uniform character and quality within specified limits.

     1.5    "BAXTER QUALITY ASSURANCE RELEASE" shall mean approval of Produced
            Product by the BAXTER Quality Assurance team based on the Product's
            conformance to the Product Requirements.

     1.6    "BAXTER SOPS" shall mean BAXTER's Standard Operating Procedures,
            which PRAECIS shall have the right to access and inspect during
            annual audits; provided, however, specific BAXTER SOPs can be
            requested and reviewed by PRAECIS on an individual basis at any
            time.

     1.7    "CANCELLATION FEES" shall mean the fees payable by PRAECIS for
            modification or cancellation of a Firm Purchase Order, if any, as
            set forth in the Product Master Plan.

     1.8    "COMPONENTS" shall mean all materials, including without limitation
            packaging materials, used by BAXTER in the Production of Product
            under this Agreement. Components are listed in the Product Master
            Plan. Such Components are identified as Components supplied by
            PRAECIS ("PRAECIS Supplied Components") or Components supplied by
            BAXTER ("BAXTER Supplied Components").

     1.9    "COMPONENT SPECIFICATIONS" shall mean the specifications and testing
            to be performed for the Components, as set forth in the Product
            Master Plan.

     1.10   "CONFIDENTIAL INFORMATION" shall have the meaning set forth in the
            Confidentiality Agreement dated as of December 4, 2001 by and
            between Baxter Healthcare Corporation and PRAECIS.

     1.11   "CURRENT GOOD MANUFACTURING PRACTICES" or "CGMP" shall mean: (a) the
            good manufacturing practices required by the FDA and set forth in
            the FD&C Act or FDA Regulations (including without limitation 21 CFR
            210 and 211), policies or guidelines, in effect at any time during
            the Term of this Agreement, for the Production and testing of
            pharmaceutical materials as applied solely to Products, and (b) the
            corresponding requirements of each applicable Regulatory Authority.

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     1.12   "DELIVERY DATE" with respect to a Batch of Product shall mean the
            date of BAXTER's Quality Assurance Release of such Batch of Product.

     1.13   "DRUG PRODUCT INTERMEDIATE" shall mean the intermediate formulated
            Abarelix used as the raw material in the Production of Product.

     1.14   "EFFECTIVE DATE" shall mean the date on which this Agreement first
            comes into effect, as set forth above.

     1.15   "FDA" shall mean the United States Food and Drug Administration or
            any successor organization thereto.

     1.16   "FD&C ACT" shall mean the United States Federal Food, Drug and
            Cosmetic Act, as may be amended from time to time.

     1.17   "LONG RANGE FORECAST" shall be defined in Section 4.1.1.

     1.18   "MASTER BATCH RECORD" shall mean, with respect to each Presentation
            of Product to be Produced hereunder, a formal set of instructions
            for the Production of each Presentation of such Product. Each Master
            Batch Record shall be developed by BAXTER and subject to the written
            approval of PRAECIS.

     1.19   "NDA" shall mean the FDA-required New Drug Application.

     1.20   "PRAECIS TRADEMARKS" shall mean the proprietary mark(s) for Product
            owned by PRAECIS as stated in a Project Plan.

     1.21   "PRESENTATION" shall mean the specific formula and Components of a
            Product.

     1.22   "PRODUCE" or "PRODUCTION" shall mean BAXTER's filling and inspecting
            of the Drug Product Intermediate in unlabeled vials, reviewing the
            Released Executed Batch Record (including without limitation
            reviewing the irradiation documentation following the irradiation of
            the Drug Product Intermediate) and testing of the resulting Product,
            all in accordance with the Product Master Plan and the Project Plan.
            Details of the Production process shall be included in the Master
            Batch Record.

     1.23   "PRODUCT" shall mean the resulting Drug Product Intermediate in
            unlabeled vials following Production by BAXTER in accordance with
            the Product Master Plan and the Project Plan.

     1.24   "PRODUCT MASTER PLAN" shall mean an addendum to this Agreement for
            each Product Produced hereunder, which may include, without
            limitation, the Product, Product Specifications, Components,
            Component Specifications, Regulatory Authorities and BAXTER SOPs
            related to the Production of the Product, the countries where such
            Product will be sold, Presentations, Cancellation Fees and pricing
            for such Product Produced under this Agreement, developed as
            described

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            in Section 2.1. The Product Master Plan for the first Product to be
            Produced under this Agreement is set forth in Exhibit 1.

     1.25   "PRODUCT REQUIREMENTS" shall be defined in Section 7.1.

     1.26   "PRODUCT SPECIFICATIONS" shall mean, with respect to each Product,
            the specifications and testing procedures developed by PRAECIS and
            BAXTER to be performed for the Drug Product Intermediate, the
            Product, and/or the stability program that are set forth in the
            BAXTER SOPs and the Master Batch Records. The Product Specifications
            include, without limitation, all tests that BAXTER is required to
            conduct or cause to be conducted as specified in the Product Master
            Plan and Project Plan. The Product Specifications may be modified
            from time to time only by the written agreement of PRAECIS and
            BAXTER.

     1.27   "PROJECT PLAN" shall mean the manual containing the parameters for
            the Production of each Presentation of Product, including without
            limitation the Testing Standards and Procedures for each
            Presentation of Product under this Agreement, developed as described
            in Section 2.2.

     1.28   "PURCHASE ORDER" shall mean written orders from PRAECIS to BAXTER
            which shall specify key production information with respect to the
            ordered Product including, without limitation: (a) the quantity of
            Product ordered, (b) delivery and shipping instructions, both with
            respect to the final Product and with respect to work-in-process
            during Production, (c) the scheduled date for PRAECIS' delivery of
            Drug Product Intermediate to BAXTER, (d) the scheduled date of
            filling, and (e) the proposed Delivery Date.

     1.29   "PURCHASE PRICE" shall be defined in Section 5.1

     1.30   "QUALITY ASSURANCE DISPOSITION" shall mean the document issued by
            PRAECIS pursuant to Section 7.1 to indicate PRAECIS' determination
            that a Batch released by BAXTER conforms to the Product
            Requirements.

     1.31   "REGULATORY APPROVAL" shall mean all authorizations by the
            appropriate Regulatory Authority necessary for commercial sale in a
            jurisdiction, including without limitation, approval of labeling,
            price, reimbursement and Production.

     1.32   "REGULATORY AUTHORITY" shall mean those agencies or authorities
            responsible for regulation of the Product in the United States and
            overseas (which shall include, without limitation, the U.S.
            Pharmacopoeia and European Pharmacopoeia, if applicable), as
            specified in the Product Master Plan. BAXTER shall have no
            obligation to Produce Product in compliance with the requirements of
            a Regulatory Authority not specified in the applicable Product
            Master Plan, Project Plan or Regulatory Plan.

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     1.33   "REGULATORY PLAN" shall mean the manual describing the regulatory
            services and support to be provided by BAXTER for the development
            and maintenance of regulatory submissions and supporting
            documentation as set forth in Section 2.3.

     1.34   "RELEASED EXECUTED BATCH RECORD" shall mean the completed batch
            record and associated deviation reports, investigation reports and
            certificates of analysis created by BAXTER for each Batch released
            by BAXTER. The Released Executed Batch Record shall be sent to
            PRAECIS in accordance with Section 9.3. The Released Executed Batch
            Record shall be in a format as agreed between the parties and shall
            contain at a minimum the information set forth in Exhibit 2 to this
            Agreement.

     1.35   "ROLLING FORECAST" shall be defined in Section 4.1.2.

     1.36   "SATELLITE SAMPLE" shall mean a prepared quantity of the Drug
            Product Intermediate representing the Drug Product Intermediate that
            will be used by BAXTER for Production. BAXTER shall use the
            Satellite Sample to conduct quality control tests of the Drug
            Product Intermediate prior to commencing Production of the relevant
            Batch, in accordance with Exhibit D1 of the Product Master Plan.

     1.37   "TERM" shall be defined in Section 8.1.

     1.38   "TESTING STANDARDS AND PROCEDURES" shall mean, with respect to each
            Product Produced hereunder, the written standards and procedures for
            evaluating compliance with the applicable Product Specifications, as
            mutually agreed upon in writing by PRAECIS and BAXTER, and
            incorporated in the applicable Project Plan.

ARTICLE 2, PROJECT AND REGULATORY PLANS

     2.1    PRODUCT MASTER PLAN. From time to time during the Term of the
            Agreement, PRAECIS may request that BAXTER Produce a Product for
            PRAECIS hereunder. For each Product to be Produced by BAXTER
            hereunder, the parties shall agree in writing upon a Product Master
            Plan. PRAECIS shall deliver to BAXTER the information that BAXTER
            and PRAECIS agree in writing is necessary for BAXTER to prepare each
            Product Master Plan. BAXTER then shall deliver two (2) copies of
            each Product Master Plan to PRAECIS within three (3) weeks of
            receipt of PRAECIS' information. PRAECIS shall either sign such
            Product Master Plan and return one (1) copy to BAXTER or shall
            return an amended Product Master Plan acceptable to PRAECIS, in each
            case within ten (10) business days of receipt of such Product Master
            Plan from BAXTER. If such amended Product Master Plan is not
            acceptable to BAXTER, then BAXTER shall so notify PRAECIS within ten
            (10) business days of BAXTER's receipt of such amended Product
            Master Plan, and the parties shall promptly meet in order to resolve
            in good faith any outstanding disagreements with respect to such
            amended

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            Product Master Plan. In no event shall BAXTER be required to
            schedule the Production of any Product until a Product Master Plan
            for such Product has been approved in writing by both BAXTER and
            PRAECIS.

     2.2    PROJECT PLAN. For each Presentation of Product to be Produced
            hereunder, the parties shall agree in writing upon a Project Plan.
            BAXTER shall deliver two (2) copies of each Project Plan to PRAECIS
            at least   ***   prior to the commencement of Production of the
            applicable Presentation of Product. PRAECIS shall either sign such
            Project Plan and return one (1) copy to BAXTER or shall return an
            amended Project Plan acceptable to PRAECIS, in each case within ten
            (10) business days of receipt of such Project Plan from BAXTER. If
            such amended Project Plan is not acceptable to BAXTER, then BAXTER
            shall so notify PRAECIS within ten (10) business days of BAXTER's
            receipt of such amended Project Plan, and the parties shall promptly
            meet in order to resolve in good faith any outstanding disagreements
            with respect to such amended Project Plan. In no event shall BAXTER
            be required to schedule or commence the Production of the
            Presentation of the applicable Product until a Project Plan for such
            Presentation of Product has been approved in writing by both BAXTER
            and PRAECIS.

     2.3    REGULATORY PLAN. If requested by PRAECIS, BAXTER shall provide
            regulatory services in connection with obtaining Regulatory Approval
            for a Product. BAXTER shall deliver to PRAECIS two (2) copies of the
            Regulatory Plan for each Product requested by PRAECIS at least
            fourteen (14) calendar days after such PRAECIS request and prior to
            the date that BAXTER is to initiate Production of the registration
            Batches of the applicable Product. PRAECIS shall either sign such
            Regulatory Plan and return one (1) copy to BAXTER or shall return an
            amended Regulatory Plan acceptable to PRAECIS, in each case within
            ten (10) business days of receipt of such Regulatory Plan from
            BAXTER. If such amended Regulatory Plan is not acceptable to BAXTER,
            then BAXTER shall so notify PRAECIS within ten (10) business days of
            BAXTER's receipt of such amended Regulatory Plan, and the parties
            shall promptly meet in order to resolve in good faith any
            outstanding disagreements with respect to such amended Regulatory
            Plan. BAXTER shall have no obligation to conduct regulatory services
            for a Product until the Regulatory Plan for such Product has been
            agreed upon by the parties.

     2.4    AMENDMENT OF PLANS. Each Project Plan, Regulatory Plan and Product
            Master Plan may be amended from time to time only upon mutual
            written agreement of PRAECIS and BAXTER.

     2.5    NO AMENDMENT OF AGREEMENT. No Project Plan, Regulatory Plan or
            Product Master Plan shall be deemed to amend this Agreement. In the
            event that the terms of any Project Plan, Regulatory Plan or Product
            Master Plan are inconsistent with the terms of this Agreement, this
            Agreement shall control, unless otherwise

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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            explicitly agreed to in a writing by the parties, expressly
            indicating an intent by the parties to amend this Agreement in
            accordance with Article 26. Upon approval in writing by both BAXTER
            and PRAECIS of any Project Plan, Regulatory Plan or Product Master
            Plan, such Project Plan, Regulatory Plan or Product Master Plan
            shall be deemed to be incorporated herein by reference and made a
            part of this Agreement.

     2.6    EFFECT OF FAILURE TO EXECUTE PLANS OR ADDENDUM. No failure to
            execute a Project Plan, Product Master Plan or Regulatory Plan with
            respect to a particular Product will relieve either party of any
            obligation that has accrued with respect to such Product. Provided,
            however, that PRAECIS shall not be liable for any such accrued costs
            or expenses incurred by BAXTER in connection with such Product
            unless such costs or expenses had been expressly approved in writing
            by PRAECIS prior to such costs or expenses having been incurred.

ARTICLE 3, PURCHASE AND SUPPLY OF PRODUCT

     3.1    AGREEMENT TO PURCHASE AND SUPPLY. Pursuant to the terms and
            conditions of this Agreement, BAXTER shall Produce and deliver to
            PRAECIS the amounts of Product ordered by PRAECIS in accordance with
            Section 4.2.

     3.2    REPRODUCTION, REWORK OR REPROCESSING. Any reprocessing, rework,
            reproduction or change required during Production in order to meet
            the Product Requirements must be approved in writing by PRAECIS
            prior to implementation. BAXTER shall conduct such reprocessing,
            rework, reproduction or change in compliance with cGMPs and the NDA
            or ANDA, unless otherwise specifically agreed in writing by PRAECIS.
            PRAECIS shall be responsible for all costs and expenses incurred in
            connection with such reprocessing, rework, reproduction or change
            unless such reprocessing, rework, reproduction or change is required
            solely as a result of: (a) the negligence or willful misconduct of
            BAXTER, its officers, directors, employees or agents; (b) breach by
            BAXTER of its representations, warranties, covenants or other
            obligations under this Agreement; or (c) failure of any BAXTER
            Supplied Component to conform to the relevant Component
            Specifications, in which case (whether (a), (b) and/or (c)) BAXTER
            shall be responsible for such costs and expenses.

     3.3    DRUG PRODUCT INTERMEDIATE AND PRAECIS SUPPLIED COMPONENTS DELIVERY.
            PRAECIS, at its expense, shall deliver or cause to be delivered to
            BAXTER: (a) a reasonably sufficient amount of Drug Product
            Intermediate and applicable certificate of analysis therefor and (b)
            all other PRAECIS Supplied Components, in each case either (i) at
            least   ***   before BAXTER's scheduled date of   ***   for the
            Product (such date provided by BAXTER to PRAECIS as set forth in
            Section 4.2) if the Drug Product Intermediate is accompanied by a
            Satellite Sample, or (ii) at least   ***   before BAXTER's scheduled
            date of   ***   for the Product if the Drug Product Intermediate is
            not accompanied by a Satellite

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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            Sample. Drug Product Intermediate and PRAECIS Supplied Components
            shall be delivered to BAXTER DDP Bloomington, IN (INCOTERMS 2000).
            All PRAECIS Supplied Components shall conform in all respects to the
            relevant Component Specifications.

     3.4    MATERIAL SAFETY DATA SHEET. PRAECIS shall provide BAXTER a Material
            Safety Data Sheet for Drug Product Intermediate and for each
            Product. BAXTER shall immediately notify PRAECIS of any unusual
            health or environmental occurrence relating to Production or the
            Product, including, but not limited to, any claim or complaint by
            any employee of BAXTER or any of its Affiliates or third party that
            the operations of BAXTER pursuant to this Agreement have resulted in
            any adverse health or safety effect on an employee or third party.
            BAXTER agrees to advise PRAECIS immediately of any safety or
            toxicity problems of which it becomes aware regarding Production or
            the Product.

     3.5    VENDOR AND SUPPLIER AUDIT AND CERTIFICATION. BAXTER shall not use
            any vendor or supplier, other than the vendors and suppliers
            specified in the applicable Product Master Plan or Project Plan,
            without the prior written consent of PRAECIS. BAXTER and PRAECIS
            shall work together to conduct audits and PRAECIS shall approve all
            Product-related vendors and suppliers, at PRAECIS' expense. BAXTER
            shall keep PRAECIS informed of all actions taken by BAXTER in
            connection with any such audits and all expenses in connection with
            the same shall be submitted to PRAECIS for prior written approval.
            Upon PRAECIS' approval of such vendors and suppliers, BAXTER shall
            add such vendors and suppliers to BAXTER's list of audited vendors
            and suppliers, as specified in the Product Master Plan.

     3.6    BAXTER SUPPLIED COMPONENTS. BAXTER will purchase, at BAXTER's
            expense, the BAXTER Supplied Components, including without
            limitation all packaging materials listed in the applicable Product
            Master Plan and Project Plan, all primary container Components and
            all secondary packaging materials, required to Produce the Product
            in quantities sufficient to meet PRAECIS' Purchase Orders for such
            Product consistent with Article 4, at no additional cost to PRAECIS.
            All BAXTER Supplied Components shall conform in all respects to the
            relevant Component Specifications and BAXTER shall control and
            maintain inventory of all BAXTER Supplied Components. BAXTER shall
            not initiate any changes to any BAXTER Supplied Components without
            the prior written consent of PRAECIS.

     3.7    IMPORTER OF RECORD. In the event any material or equipment to be
            supplied by PRAECIS, including, without limitation, PRAECIS Supplied
            Components and Drug Product Intermediate, is imported into the
            United States for delivery to BAXTER ("Imported Goods"), such
            Imported Goods shall be imported DDP Bloomington, IN (INCOTERMS
            2000). PRAECIS shall be the "Importer of Record" of such Imported
            Goods. As the Importer of Record, PRAECIS shall be

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            responsible for all aspects of the Imported Goods including, without
            limitation: (a) customs and other regulatory clearance of Imported
            Goods; (b) payment of all tariffs, duties, customs, fees, expenses
            and charges payable in connection with the importation and delivery
            of the Imported Goods; and (c) keeping all records, documents,
            correspondence and tracking information required by applicable laws,
            rules and regulations arising out of or in connection with the
            importation or delivery of the Imported Goods.

     3.8    STORAGE.

            3.8.1   DRUG PRODUCT INTERMEDIATE AND COMPONENT STORAGE. In no event
                    shall BAXTER be required to store more than a   ***   supply
                    of Drug Product Intermediate and Components, as calculated
                    using the Rolling Forecast, without the prior written
                    consent of BAXTER and PRAECIS' agreement to reimburse BAXTER
                    for all costs incurred in connection with such storage.

            3.8.2   THIRD PARTY STORAGE. BAXTER shall be permitted to store
                    Components (but not Drug Product Intermediate or Product) in
                    third party storage facilities approved in writing by
                    PRAECIS; provided, however, that: (a) BAXTER shall provide
                    PRAECIS with no less than thirty (30) days' written notice
                    prior to storing Components at any such third party
                    facilities, and (b) any such storage at third party
                    facilities shall in no way release BAXTER for any liability
                    for such stored Components and BAXTER shall remain fully
                    liable therefor in accordance with the terms of this
                    Agreement.

ARTICLE 4, FORECASTS, ORDERS AND CAPACITY

     4.1    FORECASTS AND COMMITMENTS.

            4.1.1   LONG RANGE FORECAST. Within   ***   from the Signing Date,
                    and prior to   ***   , 2003, and   ***   of each
                    subsequent year thereafter, PRAECIS will provide to BAXTER
                    in writing an annual forecast for each calendar year during
                    the remainder of the Term (up to five (5) forecasted years)
                    of PRAECIS' estimated Purchase Order quantities of vials of
                    Product to be Produced and delivered to PRAECIS (the "Long
                    Range Forecast"). BAXTER specifically agrees that the Long
                    Range Forecasts submitted by PRAECIS will be for general
                    planning purposes only, and shall not be binding on PRAECIS
                    or BAXTER except as provided in Section 4.1.3(c).

            4.1.2   ROLLING FORECAST. Within thirty (30) days from the Signing
                    Date, and prior to the tenth (10th) day of each April, July,
                    October and January thereafter, PRAECIS will provide BAXTER
                    in writing a quarterly rolling forecast of PRAECIS'
                    estimated Purchase Order quantities for Product

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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                    (the "Rolling Forecast") for the following four (4) calendar
                    quarters. BAXTER specifically agrees that the Rolling
                    Forecasts submitted by PRAECIS will be for general planning
                    purposes only, and shall not be binding on PRAECIS or
                    BAXTER.

            4.1.3   PURCHASE AND SUPPLY COMMITMENTS.

                    (a)  BAXTER shall supply PRAECIS with the quantity of
                    Product ordered by PRAECIS, unless the overall quantity
                    ordered for a calendar quarter   ***   of the quantity of
                    Product forecasted in the immediately preceding Rolling
                    Forecast for such calendar quarter, in which case BAXTER
                    shall use all commercially reasonable efforts to supply
                    quantities   ***   of such quantity forecasted by PRAECIS
                    in the immediately preceding Rolling Forecast for such
                    calendar quarter.

                    (b)  From the Effective Date through the first anniversary
                    of the Delivery Date of the first Batch shipped by or on
                    behalf of PRAECIS to third parties for commercial use in the
                    United States (the "Initial Annual Minimums Period"),
                    PRAECIS shall order and purchase in any calendar year no
                    less than three hundred seventy five thousand dollars
                    ($375,000) of Product (the "Initial Annual Minimum"). The
                    Initial Annual Minimum shall be prorated for any period
                    covered by the Initial Annual Minimums Period that does not
                    constitute a full calendar year. In the event PRAECIS orders
                    and purchases less than the Initial Annual Minimum in any
                    calendar year, then, at the end of such calendar year,
                    BAXTER may invoice PRAECIS for the difference between the
                    Purchase Price of Product actually ordered and purchased and
                    the Initial Annual Minimum and PRAECIS shall pay such amount
                    within thirty (30) days from the date of invoice.

                    (c)  After the Initial Annual Minimums Period, the first
                    calendar year of each Long Range Forecast will be used to
                    determine the minimum quantity that PRAECIS shall purchase
                    from BAXTER for such calendar year (the "Annual
                    Obligation"). The Annual Obligation will be calculated as
                    ***   of the forecasted quantity for the first year of the
                    Long Range Forecast (for purposes of calculating the first
                    such Annual Obligation, using the Long Range Forecast whose
                    first calendar year includes the date on which the Initial
                    Annual Minimums Period expired, and prorating such Annual
                    Obligation based on the months remaining in such calendar
                    year); provided, however, in no event shall the Annual
                    Obligation be a quantity which would generate an aggregate
                    Purchase Price of Product less than six hundred fifty
                    thousand dollars ($650,000). The Annual Obligation shall be
                    applicable only when BAXTER is not in breach of its
                    obligations under this Agreement and all Firm Purchase
                    Orders (as defined in Section 4.2)

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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                    have been filled in accordance with the terms and conditions
                    of this Agreement.

     4.2    PURCHASE ORDERS. In order to purchase Product under this Agreement,
            PRAECIS shall submit Purchase Orders to BAXTER. PRAECIS shall not,
            without the written consent of BAXTER, propose a Delivery Date in a
            Purchase Order earlier than   ***   from the date PRAECIS submits
            the Purchase Order; provided, however, that for Purchase Orders that
            PRAECIS designates are for audit dose Batches, such proposed
            Delivery Date shall not be earlier than   ***   from the date
            PRAECIS submits the Purchase Order. No later than ten (10) days
            after receipt by BAXTER of a Purchase Order, BAXTER shall provide a
            confirmation of receipt of such Purchase Order confirming the
            Delivery Date of the Product, BAXTER's scheduled date of filling for
            the Product, and the scheduled date for PRAECIS delivery of the Drug
            Product Intermediate for the Product ordered thereunder. Upon
            PRAECIS' receipt of the confirmation, such Purchase Order shall
            become a "Firm Purchase Order" and the Delivery Date set forth
            therein shall be a "Firm Delivery Date" binding upon BAXTER. In the
            event that PRAECIS cancels a Firm Purchase Order without BAXTER's
            written consent, PRAECIS shall pay the Cancellation Fees, if any, as
            set forth in the Product Master Plan as may be modified by each
            Project Plan; provided, however, that PRAECIS shall be entitled to
            postpone a Firm Delivery Date for up to   ***   without penalty upon
            written notice to BAXTER, which written notice shall not be given
            ***   prior to the scheduled date of filling for the Product (such
            date provided by BAXTER to PRAECIS as set forth in Section 4.2). To
            the extent of any conflict between Purchase Orders submitted by
            PRAECIS and this Agreement, this Agreement shall control.

     4.3    DELIVERY DELAYS.

            4.3.1   FAILURE TO MEET FIRM DELIVERY DATE. If BAXTER is unable to
                    meet the Firm Delivery Date, then BAXTER shall so notify
                    PRAECIS promptly upon becoming aware thereof and shall
                    provide to PRAECIS an alternative delivery date which shall
                    not be more than   ***   later than the Firm Delivery Date
                    (or such later date as may be agreed by both parties);
                    provided, however that: (a) BAXTER shall use commercially
                    reasonable efforts to make delivery earlier than the
                    alternative delivery date and as close as possible to the
                    Firm Delivery Date; and (b) unless otherwise agreed by both
                    parties, such alternative delivery date may not subsequently
                    be extended again pursuant to this sentence. In the event
                    that BAXTER's failure to meet the Firm Delivery Date, or any
                    alternative delivery date, is   ***   APPROXIMATELY 5 LINES
                    OMITTED   ***   , then, in addition to any other rights and
                    remedies that may be available to PRAECIS,   ***   .
                    BAXTER's failure to meet a Firm Delivery Date, or any
                    alternative delivery date,   ***   shall constitute a
                    material breach of

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       11
<Page>

                    this Agreement if such failures were   ***   APPROXIMATELY 5
                    LINES OMITTED   ***   .

            4.3.2   DELAYS IN DRUG PRODUCT INTERMEDIATE AND PRAECIS SUPPLIED
                    COMPONENTS. BAXTER shall have no responsibility for delays
                    in delivery of Product caused solely by delays in receipt of
                    Drug Product Intermediate or PRAECIS Supplied Components.
                    Notwithstanding anything in this Agreement or any Firm
                    Purchase Order to the contrary, in the event that BAXTER
                    receives the Drug Product Intermediate for the Production of
                    Product from PRAECIS outside of the timeframe specified in
                    Section 3.3, BAXTER shall   ***   and BAXTER shall Produce
                    such Product as per the original schedule. BAXTER shall
                    invoice PRAECIS for such fee and PRAECIS shall pay such fee
                    within thirty (30) days from the date of invoice.
                    Notwithstanding the foregoing, in the event BAXTER receives
                    the Drug Product Intermediate for Production of Product from
                    PRAECIS less than   ***   prior to the scheduled date of
                    ***   for such Product, BAXTER may cancel Production of such
                    Product and invoice PRAECIS the Cancellation Fees as set
                    forth in the Product Master Plan and PRAECIS shall pay such
                    fees within thirty (30) days from the date of the invoice.

ARTICLE 5, PRICE

     5.1    PRODUCT PURCHASE PRICE. The price to be paid by PRAECIS for Product
            ("Purchase Price") shall initially be as set forth in the Product
            Master Plan, and may be adjusted as provided in Section 5.3 and
            modified by each Project Plan or an amendment to the Product Master
            Plan.

     5.2    REGULATORY SERVICES PRICE. The price to be paid by PRAECIS for
            regulatory services shall be set forth in the Regulatory Plan.

     5.3    PURCHASE PRICE ADJUSTMENT. Upon the first anniversary of the
            Effective Date and on each anniversary thereafter, the Purchase
            Price of the Product may be adjusted to reflect changes in the cost
            of materials provided by BAXTER and labor costs paid by BAXTER
            directly in connection with the Production of Product. BAXTER shall
            provide PRAECIS with no less than   ***   written notice of any such
            Purchase Price adjustment, which notice shall set forth the amount
            of such Purchase Price adjustment and the effective date of such
            Purchase Price adjustment. Any Purchase Price increase may not
            exceed the average percentage increase in the   ***   over the
            preceding   ***   period plus   ***   . Any change in the Purchase
            Price in accordance with the foregoing shall be effective for all
            such Product ordered after the effective date of the applicable
            Purchase Price adjustment.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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<Page>

ARTICLE 6, SHIPMENT AND INVOICING

     6.1    DELIVERY TERMS. All deliveries by BAXTER under this Agreement,
            including final Product and work-in-process during Production, shall
            be delivered to the location designated by PRAECIS in the Purchase
            Order, EXW (INCOTERMS, 2000) BAXTER's facility in Bloomington,
            Indiana freight collect, by a common carrier designated by PRAECIS
            in the Purchase Order, at PRAECIS' expense; provided, however,
            BAXTER shall be responsible for the loading of the Product (or
            work-in-process during Production) on departure and shall bear risk
            of loss and all costs of such loading. PRAECIS shall procure, at its
            cost, insurance covering damage or loss to the Product (or
            work-in-process during Production) during shipping.

     6.2    EXPORTER OF RECORD. PRAECIS shall be the exporter of record for any
            Product shipped out of the United States. PRAECIS warrants that all
            shipments of Product exported from the United States will be made in
            material compliance with all applicable United States export laws
            and regulations and all applicable import laws and regulations into
            the country of importation. PRAECIS shall be responsible for
            obtaining and paying for any licenses or other governmental
            authorization(s) necessary for exportation of Product Produced by
            BAXTER hereunder from the United States. PRAECIS shall select and
            pay the freight forwarder who shall solely be PRAECIS' agent.
            PRAECIS and its freight forwarder shall be solely responsible for
            preparing and filing the Shipper's Export Declaration and any other
            documentation required for the export of Product Produced by BAXTER
            hereunder.

     6.3    FOREIGN CORRUPT PRACTICES ACT. PRAECIS acknowledges it is not the
            agent of BAXTER and represents and warrants that it has not, and
            covenants that it will not, pay anything of value to any government
            employee in connection with the resale of the Product.

     6.4    INVOICING AND PAYMENT FOR PRODUCT. The following invoicing and
            payment terms shall apply to all Product shipped to PRAECIS in
            accordance with Section 6.1 hereof:

<Table>
<Caption>
                STATUS          INVOICE DATE            PAYMENT DUE
                ------          ------------            -----------
                <S>             <C>                   <C>
                Production            ***             Invoice Date + 30 days

                Regulatory      As set forth in       Invoice Date + 30 days
                Services        Regulatory Plan

                Termination of        ***             Invoice Date + 30 days
                Agreement
</Table>

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       13
<Page>

     6.5    GENERAL PAYMENT TERMS. All payments to be made by one party to the
            other under this Agreement shall be made in U.S. Dollars by check
            delivered to the receiving party by overnight delivery with a
            reputable overnight delivery service. Any payment due under this
            Agreement not received within the times noted herein shall bear
            interest, compounded monthly, at the lesser of   ***   .

     6.6    DEFAULT IN PRAECIS PAYMENT OBLIGATIONS. In addition to all other
            remedies available to BAXTER in the event of a PRAECIS default,  ***
            APPROXIMATELY 5 LINES OMITTED   ***   .

ARTICLE 7, ACCEPTANCE OF PRODUCT

     7.1    CONFORMITY REVIEW. Within   ***   (the "Document Review Period")
            from the date the Released Executed Batch Record with respect to a
            Batch of Product is delivered to PRAECIS, PRAECIS shall deliver to
            BAXTER a Quality Assurance Disposition or a written notice of
            nonconformance ("Notice of Nonconformance") indicating that such
            Batch does not conform to cGMPs, Product Specifications, Master
            Batch Record or BAXTER SOPs (collectively the "Product
            Requirements"). Notwithstanding the foregoing, in the event that
            upon receipt of the Released Executed Batch Record PRAECIS discovers
            minor issues, inconsistencies or deviations in such Released
            Executed Batch Record, then PRAECIS shall notify BAXTER promptly and
            BAXTER shall have   ***   from the date of notification to address
            and correct such minor issues, inconsistencies or deviations and
            resubmit the Released Executed Batch Record to PRAECIS. Upon receipt
            of the resubmitted Released Executed Batch Record, PRAECIS shall
            have   ***   to: (a) issue a Quality Assurance Disposition; (b)
            issue a Notice of Nonconformance; or (c) extend the time period for
            correction of the outstanding issues, not to exceed an additional
            ***   unless otherwise agreed to by the parties.

     7.2    NOTICE OF NONCONFORMANCE. If PRAECIS delivers a Notice of
            Nonconformance to BAXTER indicating that a Batch does not conform to
            the Product Requirements, then BAXTER will investigate such alleged
            non-conformity, and: (a) if BAXTER agrees such Batch is
            non-conforming, deliver to PRAECIS a corrective action plan within
            ***   after receipt of PRAECIS' Notice of Nonconformance, or such
            additional time as is reasonably required if such investigation or
            plan requires data from sources other than PRAECIS or BAXTER; or (b)
            if BAXTER disagrees with PRAECIS' determination that the Batch is
            non-conforming, then BAXTER shall so notify PRAECIS by telephone
            within the   ***   period and confirm such notice in writing by
            overnight delivery.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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<Page>

     7.3    REMEDIES FOR NON-CONFORMING PRODUCT.

            7.3.1   RESOLUTION OF DISPUTES. If the parties dispute whether a
                    Batch is conforming or non-conforming,   ***   , then
                    samples or documents from the Batch will be submitted to a
                    mutually acceptable third party laboratory or consultant for
                    resolution, whose determination of conformity or
                    non-conformity, and the cause thereof, shall be binding upon
                    the parties. The non-prevailing party shall bear the costs
                    of such laboratory or consultant.

            7.3.2   REPLACEMENT PRODUCT. In the event BAXTER agrees that the
                    Batch is non-conforming or the laboratory or consultant
                    determines that the Batch is non-conforming pursuant to
                    Section 7.3.1, BAXTER shall replace such non-conforming
                    Batch within the later of: (a)   ***   from receipt of
                    replacement Drug Product Intermediate from PRAECIS, or (b)
                    ***   from the date of determination by the laboratory or
                    consultant of non-conformity or agreement by BAXTER of such
                    non-conformity, and such replaced Batch again shall be
                    subject to the acceptance procedures of this Article 7.

            7.3.3   PRAECIS COSTS FOR REPLACEMENT PRODUCT. PRAECIS shall pay for
                    all Product, including replacement Product and the cost of
                    Drug Product Intermediate therefor, except as specifically
                    set forth in Section 7.3.4.

            7.3.4   BAXTER COSTS FOR REPLACEMENT PRODUCT. In the event BAXTER
                    agrees, or the laboratory or consultant determines, that a
                    Batch is non-conforming,   ***   as a result of:   ***
                    APPROXIMATELY 4 LINES OMITTED   ***   , then BAXTER shall
                    incur the cost of Production of the replacement Batch, shall
                    reimburse PRAECIS for its actual cost of the Drug Product
                    Intermediate for the replacement Batch which cost shall not
                    exceed the amount set forth in the Product Master Plan, and
                    shall reimburse PRAECIS for its actual cost of the PRAECIS
                    Supplied Components for the replacement Batch, as specified
                    in the Product Master Plan.

            7.3.5   SOLE REMEDIES AND LIMITATION OF LIABILITY. Except as
                    provided in Section 7.4, Section 9.4 and Section 14.2, this
                    Section 7.3 sets forth BAXTER's entire liability and
                    PRAECIS' sole and exclusive remedies for delivery of
                    non-conforming Product.

     7.4    DRUG PRODUCT INTERMEDIATE YIELD ACCOUNTABILITY.

            7.4.1   GUARANTEED YIELD The Purchase Price is based upon a
                    guaranteed yield, expressed as a percentage, of conforming
                    vials of Product in each Batch (the "Guaranteed Yield").
                    Starting on the date of the   ***   of commercial Product to
                    PRAECIS (not including process validation

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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<Page>

                    Batches), within   ***   after the end of each   ***
                    period thereafter BAXTER shall provide PRAECIS with a
                    written report showing the actual yield of conforming vials
                    of Product in each Batch during such   ***   period (the
                    "Yield") calculated as set forth in the Product Master Plan.
                    If the average Yield, expressed as a percentage, for all
                    such Batches during such   ***   period (the "Average
                    Yield") is less than the Guaranteed Yield (as determined
                    pursuant to Section 7.4.2), then BAXTER shall credit PRAECIS
                    with a dollar amount equal to the product of: (a) the cost
                    to PRAECIS of the Drug Product Intermediate contained   ***
                    in the Batch, multiplied by (b) the difference between the
                    Guaranteed Yield and the Average Yield, expressed as a
                    percentage, multiplied by (c) the number of vials filled in
                    connection with such Batches, calculated as specified in the
                    Product Master Plan; provided, however, that such dollar
                    amount shall not exceed the amount set forth in the Product
                    Master Plan. BAXTER at all times shall endeavor in good
                    faith to achieve the highest practical Yield on all Batches.

            7.4.2   SETTING THE GUARANTEED YIELD. The Guaranteed Yield for the
                    first   ***   Batches (not including process validation
                    Batches) (the "Initial Guaranteed Yield") shall be the
                    average yield of conforming vials in the process validation
                    Batches, which shall be agreed in writing by the parties no
                    later than the date of the   ***   non-process validation
                    shipment of commercial Product to PRAECIS and shall remain
                    in effect through the   ***   Batch (not including process
                    validation Batches). The Guaranteed Yield for the   ***
                    commercial Batch (not including process validation Batches)
                    and subsequent Batches shall be the average yield of
                    conforming vials in the first   ***   Batches (not including
                    process validation Batches) which shall be agreed in writing
                    by the parties no later than the date of shipment of such
                    Batch to PRAECIS and shall remain in effect through the  ***
                    period following the shipment of such Batch. At the end of
                    such   ***   period, and every subsequent   ***   period
                    thereafter, BAXTER and PRAECIS shall review the Average
                    Yield for all Batches of such Product accepted by PRAECIS
                    during such   ***   period. If such Average Yield has been
                    consistently higher or lower than the Guaranteed Yield
                    during the course of such period, then the Guaranteed Yield
                    may be revised by the mutual agreement of the parties in
                    writing. In addition, the Guaranteed Yield may be revised by
                    mutual agreement of the parties in writing whenever
                    significant changes are made to the Production process.

     7.5    NON-CONFORMING DRUG PRODUCT INTERMEDIATE. If Product is rejected by
            PRAECIS and such Product's failure to meet the Product Requirements
            is determined in accordance with Section 7.3.1 to be the result of
            the failure at the time delivered to BAXTER of Drug Product
            Intermediate to meet the Component

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       16
<Page>

            Specifications for such Drug Product Intermediate, then PRAECIS
            shall be solely responsible for such non-conformity and such
            non-conformity shall not be deemed to be non-conforming solely as a
            result of the negligence or willful misconduct of BAXTER.

     7.6    PRODUCT COMPLAINTS. PRAECIS will promptly notify BAXTER of any
            Product complaints received by PRAECIS which may be related to
            Production by BAXTER and will supply to BAXTER any samples of
            Product which are the subject of such complaint. BAXTER will notify
            PRAECIS promptly of any Product complaints received by BAXTER which
            relate to the Product or the Production. Each party shall provide
            reasonable details of the complaint along with the notification.
            Upon BAXTER's receipt of any such notification from PRAECIS, BAXTER
            promptly shall investigate the complaint and shall provide PRAECIS
            with a written report of such investigation, including a review of
            the BAXTER SOPs related to such complaint, within thirty (30)
            calendar days of BAXTER's receipt of PRAECIS' written notification
            unless additional time is required for investigation. In the event
            that the parties dispute the cause of or corrective action plan
            required to address the complaint, the matter shall be handled in
            accordance with Section 7.3.1.

ARTICLE 8, TERM AND TERMINATION

     8.1    TERM AND EXTENSIONS.

            8.1.1   INITIAL TERM. This Agreement shall be effective as of the
                    Effective Date and shall continue for sixty (60) months
                    thereafter (the "Initial Term"), unless earlier terminated
                    at any time by: (a) mutual agreement of the parties hereto,
                    (b) PRAECIS after giving at least   ***   prior written
                    notice to BAXTER, or (c) otherwise in accordance with the
                    terms of this Agreement.

            8.1.2   EXTENSIONS. This Agreement will be renewed automatically for
                    ***   periods commencing, respectively, at the expiration of
                    the Initial Term (in the case of extension for such  ***  )
                    and at the expiration of such first extension (in the case
                    of extension for   ***   ), unless PRAECIS terminates the
                    Agreement by giving written notice to BAXTER at least   ***
                    prior to the expiration of the Initial Term or of the first
                    such extension, as applicable.

            8.1.3   DEFINITION OF TERM. The Initial Term, as it may be extended
                    pursuant to this Section 8.1, or earlier terminated whether
                    before or after any such extension, is referred to herein as
                    the "Term."

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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<Page>

     8.2    TERMINATION FOR BREACH. Either party may terminate this Agreement
            upon the material breach of any provision of this Agreement by the
            other party, effective   ***   after notice of termination is given
            if such breach is not cured by the breaching party within such   ***
            period, in the case of payment defaults, and effective   ***   after
            notice of termination is given if such breach is not cured by the
            breaching party within such   ***   period (or such additional
            period as the non-breaching party may reasonably provide if the
            breaching party has commenced a cure within the   ***   period and
            is actively pursuing completion of such cure) for non-monetary
            defaults. At the option of the non-breaching party, such termination
            may be with respect to the entire Agreement, or only with respect to
            the Product that is the subject of the breach.

     8.3    TERMINATION FOR FINANCIAL MATTERS. This Agreement may be terminated
            immediately by either party by giving the other party written notice
            thereof in the event such other party makes a general assignment for
            the benefit of its creditors, or proceedings of a case are commenced
            in any court of competent jurisdiction by or against such party
            seeking: (a) such party's reorganization, liquidation, dissolution,
            arrangement or winding up, or the composition or readjustment of its
            debts; (b) the appointment of a receiver or trustee for or over such
            party's property; or (c) similar relief in respect of such party
            under any law relating to bankruptcy, insolvency, reorganization,
            winding up or composition or adjustment of debt, and (in the case of
            (a), (b) or (c)) such proceedings shall continue undismissed, or an
            order for relief with respect to the foregoing shall be entered and
            continue unstayed, for a period of more than   ***   .

     8.4    NON-CANCELABLE COSTS AND EXPENSES. Upon termination of this
            Agreement in its entirety in accordance with its terms for any
            reason, BAXTER immediately shall cease all work under this
            Agreement, any Product Master Plan, Project Plans and Regulatory
            Plans (other than work-in-process at the time notice of termination
            is given, which shall be completed, tested and delivered in
            accordance with this Agreement) and shall pay to PRAECIS any credits
            due PRAECIS under Section 7.4.1 and any other amounts due to PRAECIS
            hereunder, reduced by any amounts due to BAXTER hereunder. In the
            event of the termination of this Agreement in accordance with its
            terms, except by PRAECIS pursuant to Section 8.2, Section 8.3 or
            Article 19, PRAECIS shall: (a) reimburse BAXTER for all BAXTER
            Supplied Components ordered prior to notice of termination pursuant
            to a Product Master Plan and not cancelable at no cost to BAXTER;
            and (b) pay BAXTER the Cancellation Fees as set forth in the Product
            Master Plan, if any, as may be modified by each Project Plan. In
            addition, in the event of termination of this Agreement in
            accordance with its terms for any reason, PRAECIS shall pay prices
            described in Article 5 for: (i) all work-in-process commenced by
            BAXTER pursuant to a Purchase Order prior to notice of termination,
            and (ii) all final Product Produced in accordance with a Purchase
            Order prior to notice of termination. Subject at all times to
            Article 7, BAXTER shall ship to PRAECIS

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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<Page>

            pursuant to Section 6.1 all BAXTER Supplied Components for which
            PRAECIS is liable for payment under this Section 8.4, all
            work-in-process and all final Product, as applicable. PRAECIS shall
            make payment for all expenses described in this Section 8.4 within
            thirty (30) calendar days from the invoice date therefor; which
            invoice shall be generated upon shipment of such material to
            PRAECIS.

     8.5    TERMINATION DAMAGES. In addition to the costs and expenses payable
            pursuant to Section 8.4, in the event of termination of this
            Agreement in accordance with its terms, except by PRAECIS: (a)
            pursuant to Section 8.2; or (b) pursuant to Sections 8.1.2, 8.3,
            9.9.2, 9.10 or Article 19, then PRAECIS shall pay BAXTER:   ***
            the difference between the Purchase Price of Product actually
            ordered and purchased by PRAECIS in the calendar year in which
            termination occurs and the Purchase Price of the Annual Obligation
            in such calendar year   ***   APPROXIMATELY 3 LINES OMITTED   ***  .

     8.6    EFFECT OF EXPIRATION OR TERMINATION; SURVIVAL. Upon expiration or
            termination of this Agreement in its entirety in accordance with its
            terms, this Agreement shall immediately be without further force or
            effect, provided that termination, expiration, cancellation or
            abandonment of this Agreement through any means or for any reason
            shall be without prejudice to the rights and remedies of either
            party with respect to any antecedent breach of any of the provisions
            of this Agreement, and, subject to Section 13.1, expiration or
            termination of this Agreement for any reason shall not relieve any
            party of any obligations accruing hereunder prior to such expiration
            or termination. The provisions of Articles 11, 12, 13, 14, 15, 16,
            17, 18, 28 and 29 hereof, together with Sections 8.4, 8.5, 8.6,
            9.2.6, 9.2.7, 9.11.1 and 9.11.4, shall survive expiration or
            termination of this Agreement, except that the representations set
            forth in Sections 12.2 and 12.4 shall survive only until the one (1)
            year anniversary of the expiration or termination date of this
            Agreement.

ARTICLE 9, PRODUCTION OF PRODUCT

     9.1    PRODUCTION. BAXTER shall Produce each Presentation of Product in
            accordance with the Product Requirements, the Product Master Plan
            and the Project Plan, as well as in accordance with cGMP or any
            other applicable local, state, federal or foreign laws or
            regulations as set forth in Product Master Plan as may be modified
            by each Project Plan. Subject to compliance with reasonable rules
            and regulations of BAXTER, PRAECIS shall have the right to be
            present during Production. Production deviations and investigations
            which occur during Production of Product that do not cause the
            Production to be non-compliant with cGMP shall not be deemed to
            cause such Product to be non-conforming.

     9.2    INSPECTIONS AND AUDITS.

            9.2.1   RIGHT TO INSPECT AND AUDIT. PRAECIS and its third party
                    designees, provided such designees are subject to
                    confidentiality agreements with

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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                    BAXTER, shall have the right to inspect and audit BAXTER's
                    facilities to determine compliance with: (a) cGMP; and (b)
                    applicable local state, federal and foreign laws,
                    regulations and rules. Such inspections and audits shall be
                    scheduled at mutually agreeable times upon reasonable
                    advance written notice to BAXTER, shall be at PRAECIS'
                    expense, and shall not occur more than   ***   per calendar
                    year unless: (i) PRAECIS reasonably believes that Product is
                    not being Produced in accordance with the Master Batch
                    Record, the Product Master Plan, the Regulatory Plan, the
                    Project Plans or cGMPs; or (ii)   ***   APPROXIMATELY 3
                    LINES OMITTED   ***   .

            9.2.2   COSTS OF INSPECTIONS AND AUDITS. Except for the annual
                    audits noted above and any other inspection and audit
                    conducted pursuant to the last sentence of Section 9.2.1, if
                    PRAECIS requests additional audits, then PRAECIS will incur
                    fees as reasonably determined by BAXTER to cover BAXTER's
                    direct costs resulting therefrom. BAXTER shall invoice
                    PRAECIS for such fees, including documentation supporting
                    such fees together with such invoice, and PRAECIS shall pay
                    such fees within thirty (30) calendar days from the date of
                    invoice.

            9.2.3   SAMPLE TESTING. In order to ascertain compliance by BAXTER
                    with the quality requirements contained in this Agreement,
                    PRAECIS and its third party designees also shall have the
                    right to request BAXTER to, and upon such request BAXTER
                    shall, sample raw materials for PRAECIS' evaluation, and
                    PRAECIS and its designees shall be entitled to observe such
                    sampling according to a mutually-agreed schedule.

            9.2.4   COMPLIANCE WITH RULES. In connection with performing such
                    inspections and audits, PRAECIS and its third party
                    designees shall comply with all reasonable rules and
                    regulations promulgated by BAXTER and generally applicable
                    to all BAXTER customers and made known to PRAECIS reasonably
                    in advance of an inspection or audit. All information
                    disclosed or reviewed in such inspections and audits shall
                    be treated in accordance with Article 18 hereof.

            9.2.5   REPORT FINDINGS. PRAECIS may provide BAXTER with a written
                    report summarizing its findings within   ***   after the
                    conclusion of an inspection or audit. If such a report is
                    provided by PRAECIS, BAXTER shall provide PRAECIS with a
                    written response to such report within   ***   after its
                    receipt thereof. Such response shall include a plan for
                    corrective action designed to address reasonable concerns
                    and shortcomings documented in the audit report.

            9.2.6   RETENTION OF RECORDS. BAXTER shall maintain, at its own
                    expense, records relating to the Production in accordance
                    with cGMP (and other

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

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                    regulatory requirements) and shall retain such records for
                    not less than   ***   beyond the expiration date of the
                    relevant Product and thereafter such records will be
                    transferred to PRAECIS at PRAECIS' prior request and expense
                    or such records will be disposed; provided, however, that
                    BAXTER will notify PRAECIS prior to any such disposal.
                    PRAECIS shall be entitled to inspect such records at its own
                    expense and at such times and intervals as PRAECIS shall
                    reasonably request upon prior written notice to BAXTER
                    pursuant to PRAECIS' audit rights under this Article 9.

            9.2.7   RETENTION SAMPLES. BAXTER shall collect and maintain, at its
                    own expense, appropriate cGMP-compliant Product samples for
                    retention throughout the earlier of the Term of this
                    Agreement or   ***   beyond the expiration date of the
                    relevant Product and thereafter such samples will be
                    transferred to PRAECIS at PRAECIS' prior request and expense
                    or such samples will be disposed; provided, however, that
                    BAXTER will notify PRAECIS prior to any such disposal. The
                    samples shall include   ***   the quantity of Product
                    necessary for all tests required to meet the specifications
                    for BAXTER Quality Assurance Release, with the exception of
                    sterility and pyrogen testing.

     9.3    TESTING. BAXTER shall test, or cause to be tested by third party
            testing facilities audited by BAXTER, in accordance with the Testing
            Standards and Procedures, each Batch of Product Produced pursuant to
            this Agreement before delivery to PRAECIS to test conformity of the
            Batch with the requirements as contained in the Product Master Plan,
            Project Plan, Regulatory Plan and Product Specifications. A
            certificate of analysis for each Batch Produced and delivered to
            PRAECIS shall set forth the items tested by BAXTER, specifications
            and test results. BAXTER shall send, or cause to be sent, to PRAECIS
            such certificates along with one (1) copy of the Released Executed
            Batch Record as soon as such documents are prepared and BAXTER shall
            use commercially reasonable efforts to send such documents no later
            than   ***   from the date of   ***   for a Batch, unless: (a) any
            such Batch requires investigation pursuant to Section 7.2, in which
            case BAXTER shall send such documents promptly following such
            investigation; or (b) such Batch is designated by PRAECIS in a
            Purchase Order as   ***   , in which case BAXTER shall use
            commercially reasonable efforts to send such documents no later than
            ***   from the date of   ***   for such Batch. In no event shall the
            Released Executed Batch Record be sent to PRAECIS later than ***
            from the date of the BAXTER Quality Assurance Release of such Batch.

     9.4    STERILITY TESTING. BAXTER shall conduct sterility testing of the
            Product in accordance with the Testing Standards and Procedures to
            determine if the Product is sterile in accordance with the relevant
            Regulatory Authority guidelines. Following such testing, BAXTER
            shall review: (a) the sterility test results in

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       21
<Page>

            accordance with the relevant BAXTER SOPs, and (b) the Certificate of
            Irradiation as prepared by the third party irradiator chosen by
            PRAECIS. The sterility test results will be included in the BAXTER
            certificate of analysis delivered to PRAECIS by BAXTER as part of
            the Released Executed Batch Record for such Batch. In the event that
            the results of the sterility testing show that the Product is not
            sterile, BAXTER promptly will conduct an investigation and provide
            PRAECIS a written report of such investigation, including a review
            of the Testing Standards and Procedures and any relevant BAXTER
            SOPs. In the event that the investigation determines that the
            sterility testing was not performed accurately or in accordance with
            the Testing Standards and Procedures or any relevant BAXTER SOP,
            then BAXTER shall again conduct the sterility testing of the Product
            at no cost to PRAECIS until performed accurately and in accordance
            with the Testing Standards and Procedures and all relevant BAXTER
            SOPs and resubmit the results to PRAECIS.   ***   APPROXIMATELY 7
            LINES OMITTED   ***   .

     9.5    STABILITY TESTING. The stability protocol for Product Produced
            hereunder must comply with the applicable NDA, ICH Guidelines and
            BAXTER SOPs. At PRAECIS' cost and expense, PRAECIS or a party
            selected by PRAECIS (which may be BAXTER) shall perform the
            stability testing on Production Batches of Product as set forth in
            the NDA. If performed by BAXTER, such stability testing shall be
            performed in accordance with the procedures set out in the
            Product-specific BAXTER SOPs for the stability protocol and the
            relevant Project Plan and at the price set forth in such Project
            Plan.

     9.6    PERMITS AND LICENSES. PRAECIS shall have sole responsibility, at its
            expense, for obtaining all permits, licenses and other
            authorizations necessary or required for the sale, marketing and
            commercialization of each Presentation of Product Produced by BAXTER
            hereunder. BAXTER shall have sole responsibility, at its expense, to
            obtain and maintain all permits, licenses and other authorizations
            required for it to carry out its development, regulatory and
            Production obligations hereunder in respect of each Presentation of
            Product Produced hereunder.

     9.7    REGULATORY REQUIREMENTS. Each party shall notify the other promptly
            of new regulatory requirements of which it becomes aware which are
            relevant to the Production of a Product under this Agreement and
            which are required by the FDA, any other applicable Regulatory
            Authority or other applicable laws or governmental regulations, and
            shall confer with each other with respect to the best means to
            comply with such requirements.

     9.8    DRUG MASTER FILE. BAXTER shall: (a) file the appropriate Drug Master
            File ("DMF") and related reference applications for its Production
            of each Product hereunder in accordance with 21 CFR 314.420, as may
            be amended from time to time, at BAXTER's expense; and (b) update
            the appropriate DMF to include all Product and Production-related
            manufacturing information prior to the submission

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       22
<Page>

            by PRAECIS of the NDA for the Product and thereafter on an annual
            basis during the Term hereof.

     9.9    CHANGES IN MANUFACTURING.

            9.9.1   CHANGES TO MASTER BATCH RECORDS AND PRODUCT SPECIFICATIONS.
                    PRAECIS agrees to inform BAXTER within   ***   of the result
                    of any regulatory development or any additions or changes
                    that materially affect the Production of or Presentation for
                    Product. BAXTER agrees to inform PRAECIS within   ***   of
                    the result of any regulatory development or any additions or
                    changes to BAXTER SOPs that materially affect the Production
                    or Presentation of a Product. Each party shall notify the
                    other of any proposed changes to Master Batch Records,
                    Product Specifications or other Production changes with
                    respect to a Product prior to the Production of subsequent
                    Batches of such Product and shall require written approval
                    from the other prior to implementation of any such changes.

            9.9.2   PRODUCT-SPECIFIC CHANGES. If, after the Effective Date,
                    either party determines that facility, equipment, process or
                    system changes are required as a result of changes in
                    requirements set forth by the FDA or any other Regulatory
                    Authority, and such regulatory changes apply primarily to
                    the Production and supply of one or more Products, then
                    PRAECIS and BAXTER jointly will review and discuss such
                    requirements. If the parties agree in writing that such
                    changes are mandated by the change in Regulatory Authority
                    requirements, then PRAECIS shall have the option to: (a)
                    ***   of the reasonable costs of those changes that apply
                    primarily to the Production and supply of one or more
                    Products; or (b) terminate this Agreement, in whole, or in
                    part as it relates to the applicable Product, upon   ***
                    written notice to BAXTER.

     9.10   EQUIPMENT EXPENSES. If BAXTER is required to obtain specialized
            equipment in order to Produce Product for PRAECIS, then the costs of
            such equipment and all spare parts and replacement parts shall be
            paid by PRAECIS. BAXTER shall advise PRAECIS of the specialized
            equipment required and the estimated costs associated with the
            purchase and installation of such equipment prior to any such
            equipment purchase. If PRAECIS, in its sole discretion, determines
            that it does not desire to pay the costs for such equipment, then
            PRAECIS shall have the right to terminate this Agreement only with
            respect to such Product for which such equipment is required, upon
            ***   prior written notice to BAXTER. PRAECIS shall be invoiced for
            all approved equipment and spare part costs after installation and
            acceptance of such equipment by BAXTER, and PRAECIS shall make
            payments promptly thereafter.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       23
<Page>

     9.11   OWNERSHIP OF EQUIPMENT.

            9.11.1  SOLE OWNERSHIP. PRAECIS shall retain sole ownership of, and
                    title to, any and all equipment purchased by PRAECIS on,
                    before or after the date hereof for use in the Production,
                    or for which BAXTER is reimbursed by PRAECIS pursuant to
                    Section 9.10, (collectively, the "Equipment") and BAXTER
                    shall store, label or otherwise mark any such Equipment
                    maintained at its facilities in a manner that facilitates
                    the identification of such Equipment. BAXTER shall be solely
                    responsible for the security of all Equipment. BAXTER and
                    PRAECIS shall enter into maintenance contracts with third
                    parties for the upkeep and maintenance of the Equipment.
                    Throughout the Term, PRAECIS shall be responsible for the
                    payment of all maintenance fees under such third party
                    maintenance contracts and BAXTER shall include all Equipment
                    in BAXTER's standard equipment preventative maintenance
                    programs and shall be responsible to notify the third party
                    maintenance providers promptly of any maintenance or
                    preventive maintenance services to be performed under such
                    contracts and to otherwise provide the third party
                    maintenance providers with all notices and information in
                    respect of the maintenance services to be provided under
                    such maintenance contracts.

            9.11.2  LEASE OF EQUIPMENT. Effective as of the date any Equipment
                    is delivered to BAXTER's facility, PRAECIS hereby leases any
                    such Equipment to BAXTER solely for use in connection with
                    the Production of Product hereunder, unless PRAECIS shall
                    otherwise agree in writing. Following receipt of such
                    Equipment by BAXTER, BAXTER agrees to cooperate with PRAECIS
                    in the execution and filing of a precautionary financing
                    statement (substituting PRAECIS, as lessor, for creditor and
                    BAXTER, as lessee, for debtor) in accordance with Article 9
                    of the Uniform Commercial Code. Such financing statement
                    shall specifically describe the Equipment and shall
                    otherwise be in a standard and customary form as agreed to
                    by BAXTER and PRAECIS. PRAECIS shall deliver a termination
                    statement to BAXTER at or prior to removal of the Equipment
                    from BAXTER's premises or at or prior to BAXTER's purchase
                    of such Equipment as provided herein.

            9.11.3  EQUIPMENT INSURANCE. PRAECIS shall procure and maintain, at
                    its expense, from, with respect to the Equipment described
                    in Section 9.10, the delivery date, and, with respect to
                    Equipment delivered prior to the date hereof, the date
                    hereof, through either the date such Equipment is removed
                    from BAXTER's facility by PRAECIS or the consummation of the
                    purchase of such Equipment by BAXTER pursuant to Section
                    9.11.4, insurance covering the Equipment of not less than
                    two and one half

                                       24
<Page>

                    million dollars ($2,500,000) for all such Equipment. Upon
                    the written request of BAXTER, PRAECIS promptly shall
                    deliver to BAXTER a certificate of insurance evidencing the
                    insurance required hereunder. If PRAECIS fails to furnish
                    such certificate within fifteen (15) calendar days after
                    BAXTER's written request, BAXTER, at its option, may obtain
                    the PRAECIS insurance and PRAECIS shall promptly reimburse
                    BAXTER for the direct cost of the same. Any deductible shall
                    be the sole responsibility of PRAECIS.

            9.11.4  REMOVAL OF EQUIPMENT. Within thirty (30) days from the date
                    of termination or expiration of this Agreement, PRAECIS, at
                    its option, shall either: (a) remove the Equipment from
                    BAXTER's facility at PRAECIS' expense; or (b) offer to sell
                    such Equipment (in whole or in part), in writing, to BAXTER
                    at a purchase price equal to the fair market value of such
                    Equipment; provided, that in no case shall the fair market
                    value of such Equipment be less than the then current book
                    value of such Equipment, calculating depreciation of such
                    Equipment in accordance with United States generally
                    accepted accounting principals. If PRAECIS offers to sell
                    such Equipment to BAXTER pursuant to the preceding sentence,
                    BAXTER must deliver its acceptance of such offer, in
                    writing, to PRAECIS within ten (10) days after receipt of
                    such offer. If the purchase and sale of such Equipment is
                    not completed within thirty (30) days after PRAECIS' receipt
                    of such acceptance, PRAECIS' obligation to sell, and
                    BAXTER's obligation to purchase, such Equipment shall be
                    null and void, unless the parties otherwise agree in
                    writing. In the event PRAECIS offers to sell the Equipment
                    to BAXTER and BAXTER declines or otherwise fails to purchase
                    such Equipment, PRAECIS shall submit to BAXTER a written
                    plan to remove such Equipment from BAXTER's facility no
                    later than thirty (30) days following the date that BAXTER
                    so declines or fails to purchase such Equipment and shall
                    complete removal of such Equipment from BAXTER's facility no
                    later than sixty (60) days following the date that BAXTER so
                    declines or fails to purchase such Equipment.

     9.12   ANNUAL PRODUCT REVIEW. BAXTER shall conduct an annual review of the
            commercial services performed by BAXTER under this Agreement which
            review shall include, but not be limited to, tracking and trending
            of all Batch records, stability and Production data. BAXTER and
            PRAECIS will determine, via a protocol, a mutually agreed upon date
            for completion of the review each year. BAXTER shall provide to
            PRAECIS a written report containing the results of such annual
            review according to the time line established in the protocol.

                                       25
<Page>

ARTICLE 10, REGULATORY

     10.1   REGULATORY APPROVALS. PRAECIS will diligently pursue Regulatory
            Approval of marketing licenses for each Product Produced by BAXTER
            hereunder. PRAECIS will advise BAXTER of document requirements in
            support of NDA and/or ANDA and similar applications required of
            foreign governments and agencies including amendments, license
            applications, supplements and maintenance of such. BAXTER will
            provide documents and assist PRAECIS in preparation of submissions
            to Regulatory Authorities (both U.S. and foreign) designated by
            PRAECIS in support of PRAECIS' NDAs, ANDAs, similar applications
            required by foreign governments and licenses. All regulatory
            submission preparation and maintenance to be performed by BAXTER for
            PRAECIS shall be specified in the Regulatory Plan. Prior to
            submission to the Regulatory Authority, PRAECIS will provide BAXTER
            with a copy of the CMC section of any NDA or ANDA for review and
            comment. A final copy of the CMC section will be provided by PRAECIS
            to BAXTER upon submission to the Regulatory Authority. Within   ***
            of Regulatory Approval, PRAECIS will notify BAXTER of such approval
            and the anticipated date of Product launch to the market.

     10.2   REGULATORY AUTHORITY INSPECTIONS. At PRAECIS' request, BAXTER will
            authorize Regulatory Authorities to review any of PRAECIS'
            applications on PRAECIS' behalf. BAXTER will notify PRAECIS within
            ***   of all contacts with Regulatory Authorities (both written and
            verbal) related to each Product. BAXTER shall permit PRAECIS to be
            on site at the BAXTER facility during any such inspection that
            directly affects the Production of Product. BAXTER shall inform
            PRAECIS of the result of any regulatory inspection that directly or
            indirectly affects the Production of a Product, including without
            limitation any notice of inspection, notice of violation or other
            similar notice received by BAXTER affecting Production, testing,
            storage or handling of a Product. In the event of an FDA inspection
            which directly involves the Production of a Product, PRAECIS shall
            be immediately informed by BAXTER of the issuance of the Notice of
            Inspection (FDA Form 482) and provided a copy thereof. In the event
            that there are Inspectional Observations (FDA Form 483) resulting
            from an inspection that directly involves the Product, PRAECIS shall
            be informed immediately by BAXTER and provided a copy thereof as
            promptly as possible. BAXTER shall provide PRAECIS the opportunity
            to participate in the preparation of BAXTER's responses to any
            Regulatory Authority directly concerning Production of Product;
            provided, however, that BAXTER shall have final authority as to the
            content of any such responses. In addition, BAXTER shall supply
            PRAECIS with any manufacturing, testing or in-process control data
            within   ***   , if requested as the result of a regulatory
            inspection, an annual audit by PRAECIS or a potential regulatory
            exposure such as a recall or significant complaint relating to the
            Product or the Production services.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       26
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ARTICLE 11, TRADEMARKS

     11.1   LIMITED LICENSE. During the Term of this Agreement, PRAECIS grants
            to BAXTER a non-exclusive, royalty free license, without the right
            to sublicense, to display the PRAECIS Trademarks for the sole
            purpose of allowing BAXTER to fulfill its express Production
            responsibilities under this Agreement in accordance with the
            relevant Master Batch Record and subject at all times to the
            trademark usage standards and policies provided by PRAECIS to BAXTER
            from time to time. Except as expressly provided in Section 21.1,
            such license shall not be assignable or transferable in whole or in
            part.

     11.2   USE OF TRADEMARKS. PRAECIS may at any time, in PRAECIS' sole and
            absolute discretion, and at PRAECIS' expense, require that BAXTER
            modify the display of the PRAECIS Trademarks, or substitute an
            alternative mark for any PRAECIS Trademark, and BAXTER shall comply
            with such requirement promptly. Title to and ownership of the
            PRAECIS Trademarks at all times shall remain with PRAECIS. All uses
            of the PRAECIS Trademarks will inure solely to PRAECIS and BAXTER
            hereby irrevocably assigns to PRAECIS all such right, title and
            interest, together with any goodwill or other benefits, if any, in
            any of the PRAECIS Trademarks accruing from BAXTER's use of the
            PRAECIS Trademarks hereunder. At no time during or after the Term of
            this Agreement shall BAXTER attempt to register or cause to be
            registered PRAECIS Trademarks or any trademarks, service marks or
            trade names confusingly similar to those of PRAECIS. BAXTER shall
            not form and use for itself any combination marks with the PRAECIS
            Trademarks.

     11.3   ENFORCEMENT OF TRADEMARKS. PRAECIS shall be solely responsible for
            selecting, registering and enforcing the PRAECIS Trademarks used to
            identify the Product (it being understood that PRAECIS shall
            determine in which jurisdictions such registration and/or
            enforcement is appropriate) and, except as set forth in Section
            11.1, BAXTER shall have no right, title or interest in or to PRAECIS
            Trademarks.

ARTICLE 12, REPRESENTATIONS, WARRANTIES AND COVENANTS

     12.1   MUTUAL REPRESENTATIONS AND WARRANTIES. Each party hereby represents
            and warrants to the other party that: (a) the person executing this
            Agreement is authorized to execute this Agreement on its behalf; (b)
            this Agreement is the legal, valid and binding obligation of such
            party, enforceable against such party in accordance with its terms,
            except as such enforcement may be limited by: (i) applicable
            bankruptcy, insolvency, fraudulent transfer, reorganization,
            moratorium or other similar local, state, federal or foreign laws,
            rules or regulations now or hereinafter in effect relating to or
            affecting creditors' rights

                                       27
<Page>

            generally; and (ii) general principles of equity (regardless of
            whether enforceability is considered in a proceeding in equity or at
            law); and (c) the execution, delivery and performance of this
            Agreement by such party does not conflict with any agreement,
            instrument or understanding, oral or written, to which such party is
            bound, nor violate any law or regulation of any court, governmental
            body or administrative or other agency having jurisdiction over it,
            wherein such violation would have a material effect on the
            performance by such party of its obligations hereunder.

     12.2   BAXTER REPRESENTATIONS, WARRANTIES AND COVENANTS. BAXTER represents,
            warrants and covenants that each Presentation of Product shall be
            Produced in accordance with the Master Batch Record, the Product
            Master Plan and the Project Plan, as well as in accordance with
            cGMPs. BAXTER represents and warrants that it has obtained (or will
            obtain prior to Producing Product), and covenants that it will
            remain in compliance with, during the Term of this Agreement, all
            permits, licenses and other authorizations (the "Permits") which are
            required under local, state, federal and foreign laws, rules and
            regulations applicable to the Production of Product as specified in
            Product Master Plan as may be modified by each Project Plan or
            Regulatory Plan; provided, however, BAXTER shall have no obligation
            to obtain Permits relating to the sale, marketing, distribution or
            use of Drug Product Intermediate or Product or with respect to the
            labeling of Product. BAXTER represents, warrants and covenants that
            BAXTER shall secure, store and handle all Drug Product Intermediate,
            PRAECIS Supplied Components and Product in accordance with industry
            standards. BAXTER makes no representation or warranty with respect
            to the sale, marketing, distribution or use of the Drug Product
            Intermediate or as to printed materials supplied by PRAECIS or its
            consignee. BAXTER further represents and warrants to PRAECIS that
            there have been no claims asserted or threatened against BAXTER that
            any BAXTER Supplied Components infringe upon any issued patent,
            trademark, copyright or other intellectual property or proprietary
            rights of any third party.

     12.3   DISCLAIMER OF WARRANTIES. Except for those warranties set forth in
            Sections 12.1 and 12.2, BAXTER makes no warranties, written, oral,
            express or implied, with respect to Product or the Production of
            Product. ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING,
            WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY,
            FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE HEREBY
            DISCLAIMED BY BAXTER. NO WARRANTIES OF BAXTER MAY BE CHANGED BY ANY
            REPRESENTATIVES OF BAXTER UNLESS EVIDENCED IN AN AMENDMENT TO THIS
            AGREEMENT IN ACCORDANCE WITH ARTICLE 26. PRAECIS ACCEPTS PRODUCT
            SUBJECT TO THE TERMS HEREOF.

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     12.4   PRAECIS REPRESENTATIONS AND WARRANTIES. PRAECIS represents and
            warrants that: (a) it has the right to give BAXTER any information
            provided by PRAECIS hereunder, and that BAXTER has the right to use
            such information for the Production of Product as specified
            hereunder; and (b) PRAECIS has no knowledge of any: (i) patents or
            other intellectual rights that would be infringed by BAXTER's
            Production of Product under this Agreement, or (ii) proprietary
            rights of third parties which would be violated by BAXTER's
            performance hereunder. PRAECIS further represents and warrants that
            the Drug Product Intermediate provided to BAXTER hereunder: (1) will
            conform to the Component Specifications for Drug Product
            Intermediate, and (2) will not be adulterated or misbranded within
            the meaning of the FD&C Act.

ARTICLE 13, LIMITATION OF LIABILITY AND WAIVER OF SUBROGATION

     13.1   LIMITATION OF LIABILITY. Neither party hereto shall be liable for
            loss of use or profits or other collateral, special or consequential
            damages, losses, or expenses,   ***   , except as specifically set
            forth in Article 16 or in Sections 14.1 and 14.2, in connection with
            or by reason of the Production and delivery of Product under this
            Agreement whether such claims are founded in tort or contract. All
            claims by either party for breach or default under this Agreement
            shall be brought within three (3) years after the cause of action
            accrued or shall be deemed waived.

     13.2   WAIVER OF SUBROGATION. All BAXTER Supplied Components and equipment
            used by BAXTER in the Production of Product, other than the
            Equipment described in Section 9.11.1 (collectively, "BAXTER
            Property") shall at all times remain the property of BAXTER and
            BAXTER assumes risk of loss for such property when at a BAXTER
            facility (including the facility of a BAXTER agent or subcontractor)
            until delivery of Product (or work-in-process during Production) to
            a common carrier as specified in Section 6.1. BAXTER hereby waives
            any and all rights of recovery against PRAECIS and its Affiliates,
            and against any of their respective directors, officers, employees,
            agents or representatives, for any loss or damage to BAXTER Property
            to the extent the loss or damage is covered by insurance carried by
            BAXTER (whether or not such insurance is described in this
            Agreement). Except as otherwise expressly provided in this
            Agreement, PRAECIS assumes all risk of loss for all Equipment
            described in Section 9.11.1, PRAECIS Supplied Components, Drug
            Product Intermediate supplied by PRAECIS, and Product (collectively,
            "PRAECIS Property"). PRAECIS hereby waives any and all rights of
            recovery against BAXTER and its Affiliates, and against any of their
            respective directors, officers, employees, agents or
            representatives, for any loss or damage to the PRAECIS Property to
            the extent the loss or damage (i) is not expressly assumed by BAXTER
            under this Agreement and (ii) is covered by insurance carried by
            PRAECIS (whether or not such insurance is described in this
            Agreement).

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       29
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ARTICLE 14, INDEMNIFICATION

     14.1   PRAECIS INDEMNIFICATION. PRAECIS shall indemnify, defend and hold
            harmless BAXTER and its Affiliates and any of their respective
            directors, officers, managers, employees, subcontractors and agents
            (collectively the "BAXTER Indemnified Parties") from and against any
            and all liabilities, obligations, penalties, claims, judgments,
            demands, actions, disbursements of any kind and nature, suits,
            losses, damages, costs and expenses (including, without limitation,
            reasonable attorney's fees) (collectively, "Losses") arising out of
            or in connection with property damage or personal injury (including,
            without limitation, death) of third parties (collectively "Claims")
            in connection with or relating to: (a) PRAECIS' storage, promotion,
            labeling, marketing, distribution, use or sale of Drug Product
            Intermediate or Product; (b) PRAECIS' negligence or willful
            misconduct; (c) PRAECIS' breach of this Agreement; or (d) any claim
            that the use, sale, Production, marketing or distribution of Drug
            Product Intermediate or Product by BAXTER or PRAECIS violates the
            patent, trademark, copyright or other proprietary rights of any
            third party; except to the extent any of the foregoing (a) or (d) is
            caused solely by the negligence or willful misconduct of the BAXTER
            Indemnified Parties or solely by the breach by BAXTER of its
            representations, warranties, covenants or other obligations under
            this Agreement {for the avoidance of doubt, it being expressly
            acknowledged by PRAECIS that PRAECIS' indemnification obligation as
            provided in this Section 14.1 shall apply with respect to a Claim if
            such Claim (i) is caused partially by the negligence or willful
            misconduct of the BAXTER Indemnified Parties, (ii) is a Claim for
            which BAXTER could be held strictly liable (except if such Claim is
            caused solely by the negligence or willful misconduct of BAXTER or
            solely by the breach by BAXTER of its representations, warranties,
            covenants or other obligations under this Agreement), or (iii) is
            caused partially by the breach by BAXTER of its representations,
            warranties, covenants or other obligations under this Agreement}.

     14.2   BAXTER INDEMNIFICATION. BAXTER shall indemnify, defend and hold
            harmless PRAECIS and its Affiliates and any of their respective
            directors, officers, managers, employees, subcontractors and agents
            (the "PRAECIS Indemnified Parties") from and against any and all
            Losses resulting solely from: (a) the negligence or willful
            misconduct of a BAXTER Indemnified Party; or (b) a breach by BAXTER
            of its representations, warranties, covenants or other obligations
            under this Agreement.

     14.3   INDEMNITEE OBLIGATIONS. A party (the "Indemnitee") which intends to
            claim indemnification under this Article 14 shall promptly notify
            the other party (the "Indemnitor") in writing of any action, claim
            or other matter in respect of which the Indemnitee or any of its
            Affiliates, or any of their respective directors, officers,
            employees, subcontractors, or agents, intend to claim such
            indemnification; provided, however, that failure to provide such
            notice within a reasonable period of time shall not relieve the
            Indemnitor of any of its obligations

                                       30
<Page>

            hereunder except to the extent the Indemnitor is prejudiced by such
            failure. The Indemnitee shall permit, and shall cause its
            Affiliates, and their respective directors, officers, employees,
            subcontractors and agents to permit, the Indemnitor, at its
            discretion, to settle any such action, claim or other matter, and
            the Indemnitee agrees to the complete control of such defense or
            settlement by the Indemnitor. Notwithstanding the foregoing, the
            Indemnitor shall not enter into any settlement that would adversely
            affect the Indemnitee's rights hereunder, or impose any obligations
            on the Indemnitee in addition to those set forth herein, in order
            for it to exercise such rights, without Indemnitee's prior written
            consent, which shall not be unreasonably withheld, conditioned, or
            delayed. No such action, claim or other matter shall be settled
            without the prior written consent of the Indemnitor, which shall not
            be unreasonably withheld, conditioned or delayed. The Indemnitee,
            its Affiliates, and their respective directors, officers, employees,
            subcontractors and agents shall fully cooperate with the Indemnitor
            and its legal representatives in the investigation and defense of
            any action, claim or other matter covered by the indemnification
            obligations of this Article 14. The Indemnitee shall have the right,
            but not the obligation, to be represented in such defense by counsel
            of its own selection and at its own expense.

ARTICLE 15, INSURANCE

     15.1   PRAECIS INSURANCE. PRAECIS shall procure and maintain, during the
            Term of this Agreement and for a period one (1) year beyond the
            expiration date of Product, Commercial General Liability Insurance,
            including without limitation, Product Liability and Contractual
            Liability coverage (the "PRAECIS Insurance"). The PRAECIS Insurance
            shall cover amounts not less than fifteen million dollars
            ($15,000,000) combined single limit and shall be with an insurance
            carrier reasonably acceptable to BAXTER. BAXTER shall be named as an
            additional insured on the PRAECIS Insurance, unless otherwise agreed
            in the Product Master Plan. Upon the written request of BAXTER,
            PRAECIS promptly shall deliver to BAXTER a certificate of the
            PRAECIS Insurance evidencing such coverage and, if applicable, the
            endorsement of BAXTER as an additional insured. If PRAECIS fails to
            furnish such certificate within fifteen (15) calendar days after
            BAXTER's request, BAXTER, at its option, may obtain the PRAECIS
            Insurance and PRAECIS promptly shall reimburse BAXTER for the direct
            cost of the same. Any deductible and/or self insurance retention
            shall be the sole responsibility of PRAECIS.

     15.2   BAXTER INSURANCE. BAXTER is, and shall during the Term of this
            Agreement remain, self-insured for liabilities typically covered by
            Commercial General Liability policies, including contractual
            liability and liability related to bodily injury and property
            damage, in connection with the performance of its duties hereunder.

                                       31
<Page>

ARTICLE 16, RECALL OF PRODUCT

     In the event PRAECIS shall be required to recall any Product Produced
     hereunder because such Product may violate local, state or federal laws or
     regulations, the laws or regulations of any applicable foreign government
     or agency or the Product Specifications, or in the event that PRAECIS
     elects to institute a voluntary recall, PRAECIS shall be responsible for
     coordinating such recall. PRAECIS promptly shall notify BAXTER if any
     Product Produced hereunder is the subject of a recall and provide BAXTER
     with a copy of all documents relating to such recall. BAXTER shall
     cooperate with PRAECIS in connection with any such recall. PRAECIS shall be
     responsible for all of the costs and expenses of any such recall unless
     such recall is caused   ***   APPROXIMATELY 3 LINES OMITTED   ***   , in
     which case BAXTER will bear all reasonable costs associated with such
     recall, product withdrawal or field correction (including but not limited
     to costs associated with receiving and administering the recalled Product
     and notification of the recall to those persons whom PRAECIS deems
     appropriate); provided however that solely in respect of administrative and
     operating costs and expenses, BAXTER's liability for conducting the recall
     shall be in accordance with and up to a cumulative total maximum amount set
     forth in the chart below. Notwithstanding the foregoing, in no event shall
     BAXTER's liability for costs associated with such recall, product
     withdrawal or field correction exceed the Purchase Price for the Product
     which is the subject of such recall, product withdrawal or field
     correction.

<Table>
<Caption>
                                      ADMINISTRATIVE
           NUMBER OF                  COST CAPS BY
           CONSIGNEES                 RECALL CLASS
                          ---------------------------------------
                           I          II                  III
          -------------------------------------------------------
           <S>             <C>        <C>                 <C>
           ***             ***        ***                 ***

           ***             ***        ***                 ***

           ***             ***        ***                 ***

           ***             ***        ***                 ***

           ***             ***        ***                 ***
</Table>

ARTICLE 17, INTELLECTUAL PROPERTY

     17.1   INVENTIONS. All Inventions (as defined below) and all documents,
            computer documentation and other tangible materials related thereto,
            which are conceived, reduced to practice or created by BAXTER in the
            course of performing its obligations under this Agreement and which
            relate directly to the Product, Drug Product Intermediate or PRAECIS
            Supplied Components (the "PRAECIS

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       32
<Page>

            Inventions") are and shall be the sole and exclusive property of
            PRAECIS and shall be considered works for hire for United States
            copyright purposes. For the purposes of all matters other than
            United States copyright laws, and to the extent that the PRAECIS
            Inventions may not fall within the specifically enumerated works
            that constitute works made for hire under the United States
            copyright laws, BAXTER hereby assigns all copyrights, trademarks,
            trade secrets, patents or other proprietary rights and all other
            right, title and interest throughout the world and without further
            consideration in and to the PRAECIS Inventions to PRAECIS. For
            purposes of this Agreement, "Invention" shall mean information
            relating to any innovation, improvement, development, discovery,
            computer program, device, trade secret, method, know-how, process,
            technique or the like, whether or not written or otherwise fixed in
            any form or medium, regardless of the media on which contained and
            whether or not patentable or copyrightable.

     17.2   PATENT PROSECUTION. PRAECIS shall have the world wide right to
            control the drafting, filing, prosecution and maintenance of patents
            covering the PRAECIS Inventions or otherwise relating to its
            Intellectual Property (as defined in Section 17.3), including
            decisions about the countries in which to file patent applications.
            Patent costs associated with the patent activities described in this
            Section 17.2 shall be borne by PRAECIS. BAXTER will cooperate with
            PRAECIS, at PRAECIS' expense, in the filing and prosecution of
            patent applications. Such cooperation will include, but not be
            limited to, furnishing supporting data and affidavits for the
            prosecution of patent applications and completing and signing forms
            needed for the prosecution, assignment and maintenance of patent
            applications.

     17.3   RETENTION OF RIGHTS. Except as otherwise expressly provided herein,
            nothing contained in this Agreement shall be construed or
            interpreted, either expressly or by implication, estoppel or
            otherwise, as: (a) a grant, transfer or other conveyance by either
            party to the other of any right, title, license or other interest of
            any kind in any of its patents, trademarks, copyrights, trade
            secrets or other intellectual property or proprietary information
            (collectively, "Intellectual Property") and, except as otherwise
            expressly provided herein, each party shall retain all rights in its
            Intellectual Property without conferring any right, title or
            interest therein to the other party; (b) creating an obligation on
            the part of either party to make any such grant, transfer or other
            conveyance; or (c) requiring either party to participate with the
            other party in any cooperative development program or project of any
            kind or to continue with any such program or project. Without
            limiting the generality of the preceding sentence, PRAECIS shall
            retain all right, title and interest arising under the United States
            Patent Act, the United States Trademark Act, the United States
            Copyright Act and all other applicable laws, rules and regulations
            in and to all Products, Presentation methods, Drug Product
            Intermediate, PRAECIS Supplied Components, and all packaging,
            labeling and PRAECIS Trademarks associated therewith.

                                       33
<Page>

ARTICLE 18, CONFIDENTIAL INFORMATION, NONDISCLOSURE AND PUBLICITY

     18.1   CONFIDENTIALITY. It is contemplated that in the course of the
            performance of this Agreement each party may, from time to time,
            disclose Confidential Information to the other. Each party agrees to
            take all reasonable steps to prevent disclosure of Confidential
            Information to third parties. No provision of this Agreement shall
            be construed so as to preclude disclosure of Confidential
            Information as may be reasonably necessary to secure from any
            governmental agency necessary approvals or licenses or to file and
            prosecute applications for, or obtain, patents with respect to the
            Product.

     18.2   PRIOR CONFIDENTIALITY AGREEMENT. This Agreement, by reference,
            incorporates the Confidentiality Agreement dated December 4th, 2001
            (the "Confidentiality Agreement") by and between Baxter Healthcare
            Corporation and PRAECIS, and which was subsequently assigned by
            Baxter Healthcare Corporation to BAXTER on or about January 1, 2002,
            and such Confidentiality Agreement is made a part hereof as though
            fully set forth herein, as such Confidentiality Agreement may be
            modified by Sections 18.3 through 18.7 hereof.

     18.3   THIRD PARTY DISCLOSURE. BAXTER shall be permitted to disclose
            Product information to third party developmental and analytical
            services providers solely in connection with, and only to the extent
            reasonably necessary for, performance of its obligations hereunder;
            provided that such providers shall be subject to confidentiality
            agreements which protect the disclosure and use of any such Product
            information to the same extent as, or greater than, provided
            hereunder. Either party may disclose Confidential Information of the
            disclosing party to those Affiliates, agents, consultants and
            employees of the receiving party who need to know such information
            to accomplish the purposes of this Agreement (collectively,
            "Permitted Recipients"); provided that such Permitted Recipients are
            bound to maintain such Confidential Information in confidence in
            accordance with the terms herein.

     18.4   LITIGATION AND GOVERNMENTAL DISCLOSURE. Each party may disclose
            Confidential Information hereunder to the extent such disclosure is
            reasonably necessary for complying with applicable governmental
            regulations or conducting pre-clinical or clinical trials, provided
            that if a party is required by law or regulation to make any such
            disclosure of the other party's Confidential Information it will,
            except where impractical for necessary disclosures, for example in
            the event of a medical emergency, give reasonable advance notice to
            the other party of such disclosure requirement and will use good
            faith efforts to assist such other party to secure a protective
            order or confidential treatment of such Confidential Information
            required to be disclosed. Disclosure of Confidential Information in
            connection

                                       34
<Page>

            with any Legal Proceeding (as defined in the Confidentiality
            Agreement) shall be governed by Section 4 of the Confidentiality
            Agreement.

     18.5   PUBLICITY AND DISCLOSURE OF TERMS. The parties agree that the public
            announcement of the execution of this Agreement shall only be by one
            or more press releases mutually agreed to by the parties. The
            failure of a party to return a draft of a press release with its
            proposed amendments or modifications to such press release to the
            other party within five (5) days of such party's receipt of such
            press release shall be deemed as such party's approval of such press
            release as received by such party. Neither party shall disclose the
            terms of this Agreement without the prior written consent of the
            other party hereto, except: (a) as may be required by a court of
            competent jurisdiction, in which case the disclosing party shall
            immediately notify the non-disclosing party so that the
            non-disclosing party may seek a protective order or other remedy;
            provided that if no protective order or other remedy is obtained,
            then the disclosing party shall disclose only that portion of this
            Agreement which, in the opinion of the disclosing party's legal
            counsel, is required to be disclosed, and the disclosing party shall
            use commercially reasonable efforts to obtain an order or other
            reliable assurances that confidential treatment will be given to the
            disclosed portion of this Agreement; (b) as may be required by
            federal law or the regulations of Regulatory Authorities, including
            without limitation the United States Securities and Exchange
            Commission; or (c) if PRAECIS determines in good faith that such
            disclosure is necessary or appropriate in connection with any
            financing, strategic transaction, acquisition or disposition
            involving PRAECIS or any Affiliate of PRAECIS, provided, however,
            with respect to disclosures pursuant to this clause 18.5(c), in no
            event may such disclosure be made to any contract drug manufacturer
            or any Affiliate of a contract drug manufacturer unless such
            disclosures are subject to a confidentiality agreement that protects
            disclosure of and Confidential Information to the same extent, or
            greater than, provided hereunder.

     18.6   LIMITATION OF DISCLOSURE. The parties agree that, except as
            expressly authorized in this Agreement or in the Confidentiality
            Agreement, no information concerning this Agreement and the
            transactions contemplated herein shall be made public by either
            party without the prior written consent of the other.

     18.7   DURATION OF CONFIDENTIALITY. All obligations of confidentiality and
            non-use imposed upon the parties under this Agreement and the
            Confidentiality Agreement shall expire ten (10) years after the
            expiration or earlier termination of this Agreement; provided,
            however, that Confidential Information which constitutes the trade
            secrets of a party shall be kept confidential indefinitely, subject
            to the limitations set forth in Sections 18.4 through 18.6.

                                       35
<Page>

ARTICLE 19, FORCE MAJEURE

     Any delay in the performance of any of the duties or obligations of either
     party hereto (except the payment of money) caused by an event outside the
     affected party's reasonable control shall not be considered a breach of
     this Agreement, and unless provided to the contrary herein, the time
     required for performance shall be extended for a period equal to the period
     of such delay. Such events shall include without limitation, acts of God;
     acts of public enemies; insurrections; riots; embargoes; labor disputes,
     including strikes, lockouts, job actions, or boycotts; fires; explosions;
     floods; shortages of material or energy; delays in the delivery of raw
     materials; acts or orders of any government or agency thereof or other
     unforeseeable causes beyond the reasonable control and without the fault or
     negligence of the party so affected. The party so affected shall give
     prompt notice to the other party of such cause and a good faith estimate of
     the continuing effect of the force majeure condition and duration of the
     affected party's nonperformance, and shall take whatever reasonable steps
     are appropriate to relieve the effect of such causes as rapidly as
     possible. If the period of nonperformance by BAXTER because of BAXTER force
     majeure conditions exceeds   ***   , then PRAECIS may terminate this
     Agreement by written notice to BAXTER. If the period of nonperformance by
     PRAECIS because of PRAECIS force majeure conditions exceeds   ***   , then
     BAXTER may terminate this Agreement by written notice to PRAECIS.
     Notwithstanding anything to the contrary in this Agreement or any Product
     Master Plan, termination of this Agreement by either party pursuant to this
     Article 19 shall not result in the imposition of Cancellation Fees, if any.

ARTICLE 20,  NOTICES

     All notices hereunder must be in writing and shall be delivered by
     facsimile (confirmed by overnight delivery), or by overnight delivery by a
     reputable overnight delivery service, to the following address of the
     respective parties:

            If to BAXTER:     Baxter Pharmaceutical Solutions LLC
                              927 South Curry Pike
                              Bloomington, Indiana 47403
                              Attn: Alisa K. Wright, Vice President of
                              Business Affairs

                              Telefax No.:   (812) 332-3079
                              Telephone No.: (812) 333-0887

            With a copy to:   Baxter Healthcare Corporation
                              One Baxter Parkway
                              Deerfield, Illinois 60015-4633
                              Attn: General Counsel
                              Telefax No.:   (847) 948-2450
                              Telephone No.: (847) 948-2600

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                       36
<Page>

            If to PRAECIS:    PRAECIS PHARMACEUTICALS INCORPORATED
                              830 Winter Street
                              Waltham, MA 02145
                              Attn: Kevin McLaughlin, Chief Financial Officer

                              Telefax No.:   (781) 890-7471
                              Telephone No.: (781) 795-4100

            With a copy to:   PRAECIS PHARMACEUTICALS INCORPORATED
                              830 Winter Street
                              Waltham, MA 02145
                              Attn: Vice President, Legal

                              Telefax No.:   (781) 890-7471
                              Telephone No.: (781) 795-4100

            Notices shall be effective on the day following the date of
            transmission if sent by facsimile, and on the first business day
            following the date of delivery to the overnight delivery service if
            sent by overnight delivery. A party may change its address listed
            above by notice to the other party given in accordance with this
            Article 20.

ARTICLE 21, ASSIGNMENT

     21.1   ASSIGNMENT. Neither party shall assign this Agreement or any part
            hereof or any interest herein to any third party (or use any
            subcontractor or otherwise transfer responsibility for any of its
            obligations hereunder to any third party) without the written
            approval of the other party; provided, however, that either party
            may, without such consent, assign this Agreement to an Affiliate;
            and further provided that in either case, no such assignment shall
            be valid unless the permitted assignee assumes all obligations of
            its assignor under this Agreement. In addition, PRAECIS may, without
            the consent of BAXTER, assign all of its rights, title and interest
            in this Agreement to a successor by way of merger, consolidation,
            reorganization, stock sale or similar corporate transaction, or by
            way of a sale of all or substantially all of its assets in which the
            transferee, assignee or successor in such asset sale agrees in
            writing to be fully bound by all of the provisions of this
            Agreement.

     21.2   BINDING EFFECT. Subject to Section 21.1, this Agreement shall be
            binding upon and shall inure to the benefit of the parties hereto,
            their successors and permitted assigns.

                                       37
<Page>

ARTICLE 22, ALLIANCES

     Notwithstanding anything to the contrary herein, BAXTER agrees that PRAECIS
     shall have the right to enter into alliances with third parties who may
     engage in joint (with PRAECIS) or unilateral marketing and promoting of the
     Product or any combination of products that includes the Product.

ARTICLE 23, TAXES

     PRAECIS shall pay all national, state, municipal or other sales, use,
     excise, import, property, value added, or other similar taxes, assessments
     or tariffs assessed upon or levied against the sale of Product to PRAECIS
     pursuant to this Agreement or the sale or distribution of Product by
     PRAECIS (or at PRAECIS' sole expense, defend against the imposition of such
     taxes and expenses). BAXTER shall notify PRAECIS of any such taxes that any
     governmental authority is seeking to collect from BAXTER, and PRAECIS may
     assume the defense thereof in BAXTER's name, if necessary, and BAXTER
     agrees to fully cooperate in such defense to the extent of the capacity of
     BAXTER, at PRAECIS' expense. BAXTER shall pay all national, state,
     municipal or other taxes on the income resulting from the sale by BAXTER of
     the Product to PRAECIS under this Agreement, including but not limited to,
     gross income, adjusted gross income, supplemental net income, gross
     receipts, excess profit taxes, or other similar taxes.

ARTICLE 24, ENTIRE AGREEMENT

     This Agreement and the Confidentiality Agreement constitute the entire
     agreement between the parties concerning the subject matter hereof,
     supersede all written or oral prior agreements or understandings with
     respect thereto and shall control the parties' relationship with respect to
     the subject matter hereof. The parties agree and acknowledge that the
     Letter of Intent between PRAECIS and Baxter Healthcare Corporation dated
     December 11, 2001, is terminated hereby, except that Paragraph 8 of such
     Letter of Intent shall survive. The parties intend to incorporate all
     project plans for Product developed and mutually agreed under the Letter of
     Intent into the Project Plans hereunder.

ARTICLE 25, SEVERABILITY

     If any term or provision of this Agreement shall for any reason be held
     invalid, illegal or unenforceable in any respect, such invalidity,
     illegality or unenforceability shall not affect any other term or provision
     hereof, and this Agreement shall be interpreted and construed as if such
     term or provision, to the extent the same shall have been held to be
     invalid, illegal or unenforceable, had never been contained herein.

                                       38
<Page>

ARTICLE 26, WAIVER AND MODIFICATION OF AGREEMENT

     No waiver or modification of any of the terms of this Agreement shall be
     valid unless in writing and signed by authorized representatives of both
     parties hereto. Failure by either party to enforce any rights under this
     Agreement shall not be construed as a waiver of such rights nor shall a
     waiver by either party in one or more instances be construed as
     constituting a continuing waiver or as a waiver in other instances.

ARTICLE 27, INDEPENDENT CONTRACTOR

     BAXTER shall act as an independent contractor for PRAECIS in providing the
     services required hereunder and shall not be considered an agent of, or
     joint venturer with, PRAECIS.

ARTICLE 28, ATTORNEY'S FEES

     The successful party in any litigation or other dispute resolution
     proceeding to enforce the terms and conditions of this Agreement shall be
     entitled to recover from the other party reasonable attorney's fees and
     related costs involved in connection with such litigation or dispute
     resolution proceeding.

ARTICLE 29, GUARANTY

     Baxter Healthcare Corporation (the "Guarantor") shall, and hereby does,
     absolutely and completely guarantee the payment and performance by BAXTER
     of the obligations of BAXTER hereunder; provided, however, that, except as
     provided below in this Article 29, this guaranty is contingent, and may be
     enforced against the Guarantor only, upon either: (a) recourse being taken
     first against BAXTER, final judgment obtained against BAXTER and execution
     thereon returned unsatisfied, or (b) if it is shown that BAXTER has
     insufficient assets available for the performance by BAXTER of BAXTER's
     obligations hereunder. The aforesaid guaranty by the Guarantor shall become
     the primary and independent obligation of the Guarantor and shall be
     enforceable directly against the Guarantor, following written notice and
     demand to Guarantor by PRAECIS, without the necessity of: (i) any suit or
     proceeding against BAXTER, (ii) any notice of nonperformance or
     nonobservance, or (iii) any notice of acceptance thereof, all of which the
     Guarantor hereby expressly and irrevocably waives, in the event that (1)
     BAXTER shall have filed a petition in bankruptcy or for any relief relating
     to reorganization, arrangement, readjustment of debt, dissolution or
     liquidation, or BAXTER shall have had any such petition filed against it in
     which an adjudication of bankruptcy or insolvency is made or an order for
     relief is entered, which remains undismissed for a period of sixty (60)
     days (or to which it shall have consented or acquiesced) or (2) BAXTER
     shall have had a receiver, custodian or trustee appointed for all or a
     substantial part of its property. The Guarantor's obligations under the
     aforesaid guaranty shall not be affected in any way

                                       39
<Page>

     by the reason of any amendment, renewal, supplement or modification of this
     Agreement. In the event that BAXTER assigns this Agreement to an Affiliate
     of BAXTER in accordance with Section 21.1, then the Guarantor's guarantee
     hereunder automatically shall continue in full force and effect with
     respect to the obligations of such BAXTER Affiliate hereunder. This
     guaranty shall be binding upon, and enforceable by PRAECIS against, the
     successors of the Guarantor.

                                       40
<Page>

     IN WITNESS WHEREOF, the parties have caused this Commercial Supply
Agreement to be signed by their duly authorized representatives as of the
Signing Date written above.

"BAXTER"                                "PRAECIS"

BAXTER PHARMACEUTICAL                   PRAECIS PHARMACEUTICALS
SOLUTIONS LLC                           INCORPORATED

By:   /s/ Alisa K. Wright               By: /s/ Kevin F. McLaughlin
    ------------------------------          -----------------------------
    Name: Alisa K. Wright                   Name:
    Title: VP, Business Affairs             Title: Sr. V.P. and C.F.O.

     For purposes of Article 29 hereof,

     BAXTER HEALTHCARE CORPORATION

     By:   /s/ Joel A. Tune
         -----------------------------
         Name:
         Title:

                                       41
<Page>

                                    EXHIBIT 1
                              PRODUCT MASTER PLAN 1

                              PRODUCT MASTER PLAN 1

     This Product Master Plan 1 is entered into pursuant to, and shall be
governed by the terms of, the Commercial Supply Agreement (including all
exhibits thereto) signed on Dec. 4, 2002, by and between Baxter Pharmaceutical
Solutions LLC ("BAXTER"), a Delaware limited liability company having a place of
business at 927 South Curry Pike, Bloomington, Indiana 47403, and PRAECIS
PHARMACEUTICALS INCORPORATED ("PRAECIS"), a Pennsylvania corporation having a
principal place of business at 830 Winter Street, Waltham, Massachusetts 02451.

                 "BAXTER"                                "PRAECIS"

BAXTER PHARMACEUTICAL                       PRAECIS PHARMACEUTICALS
SOLUTIONS LLC                               INCORPORATED

By:     /s/ Alisa K. Wright                 By:     /s/ Kevin F. McLaughlin
    --------------------------------------      ------------------------------

Name:   Alisa K. Wright                     Name:
      ------------------------------------        ----------------------------

Title:  Vice President, Business Affairs    Title:  Sr. V.P. and C.F.O.
       ---------------------------------           ---------------------------

Date:   11-25-02                            Date:   12/4/02
      ------------------------------------        ----------------------------

                                     1 OF 12
<Page>

                            EXHIBIT A - PRESENTATIONS

<Table>
<Caption>
PRAECIS   BAXTER
ID #      ID #           Product Description
------------------------------------------------------------------------------------------
<S>       <C>            <C>
N/A       ***            Abarelix for Injectable Suspension, 100 mg/Vial, US (Nude Vials)

N/A       ***            Abarelix for Injectable Suspension, 100 mg/Vial, US (Packaged for
                         Irradiation)
</Table>

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     2 OF 12
<Page>

                               EXHIBIT B - PRICING

BATCH SIZE

***
***

BASIC YIELD CALCULATION

a = Fill Weight Rejects from Manufacturing
b = Capping Rejects from Manufacturing
c = Inspection/Packaging Rejects

W = VIALS FILLED   (obtained from the Finished Product Accountability sheet
                   delivered by BAXTER to PRAECIS as part of the Released
                   Executed Batch Record)

X =  TOTAL REJECTS  ***
X(TO THE POWER OF 1) = PROCESS REJECTS  ***

Y =  YIELD          ***

  *** Approximately 4 lines omitted ***

Z = VIALS TO BILL  ***

PER UNIT PRICE

<Table>
<Caption>
Vials produced annually                 Price
-----------------------                 -----
<S>                                     <C>
***                                     ***

***                                     ***

***                                     ***
</Table>

PRAECIS will order complete Batches of Product on a single Purchase Order,
except when PRAECIS orders a Batch to be divided into sections, such as for
separate labeling. In such cases, PRAECIS will issue multiple Purchase Orders,
each with the same Delivery Date, and the sum of the quantities of Product
ordered on such multiple Purchase Orders shall equal one or more complete
Batches.   ***    APPROXIMATELY 2 LINES OMITTED   ***   .

GUARANTEED YIELDS OVER TIME
Definitions:

     Y(SUB IGY)   = Initial Guaranteed Yield = average yield for conforming
                  vials for the   ***   validation Batches.
     Y(SUB GY1)   = Guaranteed Yield = average yield for the   ***
                  (non-process validation) Batches.
     Y(SUB GYi)   = on-going Guaranteed Yield = average yield for all Batches in
                  every   ***   period, where i (starting with   ***   )
                  indicates the current period and i-1 indicates the previous
                  ***   period and i+1 indicates the next   ***   period.
     W(SUB i)     = total vials filled for all Batches during a   ***   period,
                  where i (starting with   ***   ) indicates the current period
                  and i-1 indicates the previous   ***   period and i+1
                  indicates the next   ***   period.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     3 OF 12
<Page>

In accordance with section 7.4.1 of the Commercial Supply Agreement BAXTER's
credit to PRAECIS, to be applied against subsequent BAXTER invoices, shall be
computed as follows:

     a) First   ***   Batches (non-process validation)
        if Y(SUB GY1) GREATER THAN OR EQUAL TO Y(IGY);
        no credit to PRAECIS, otherwise,
        Credit to PRAECIS =   ***   * (Y(SUB IGY) - Y(SUB GY1)) * W(SUB i)

     b)     ***   Batch until the end of first   ***   period;
        if Y(SUB GY2) GREATER THAN OR EQUAL TO Y(SUB GY1);
        no credit to PRAECIS, otherwise,
        Credit to PRAECIS =   ***   * (Y(SUB GY1) - Y(SUB GY2)) * W(SUB i)

     c) On-going  ***  period yield calculation;
        if Y(SUB GYi+1) GREATER THAN OR EQUAL TO Y(SUB GYi);
        no credit to PRAECIS, otherwise,
        Credit to PRAECIS =   ***   * (Y(SUB GYi) - Y(SUB GYi+1)) * W(SUB i)

     ***

     *** APPROXIMATELY 4 LINES OMITTED ***

STABILITY TESTING

Upon PRAECIS' request, BAXTER will perform stability testing of Product. The
testing protocol and pricing will be detailed in a Project Plan.

ANNUAL PRODUCT QUALITY REVIEW

BAXTER will prepare an annual Batch review/comparison summary for use by PRAECIS
regulatory at a charge of $   ***   per hour. Prior to commencement of work
BAXTER shall provide an estimate, for informational purposes only, of the number
of hours expected to consume.

QUALITY ASSURANCE AUDITS

Subject to Sections 9.2.1 and 9.2.2 of the Commercial Supply Agreement, a charge
of $   ***   per hour will be paid to BAXTER for quality assurance audits
requested by PRAECIS in excess of   ***   per year. The hours charged will
include preparation time, audit time by all BAXTER participants, and follow-up
time in preparing responses. Prior to commencement of work BAXTER shall provide
an estimate, for informational purposes only, of the number of hours expected to
consume.

QUALITY CONTROL SAMPLES

Subject to Section 9.2.3 of the Commercial Supply Agreement, BAXTER will provide
PRAECIS with Quality Control Samples of Product at PRAECIS' request. BAXTER will
supply samples within   ***   of PRAECIS' request at no cost to PRAECIS. In the
event PRAECIS requests samples for delivery in less than   ***   and BAXTER
delivers such samples in less than   ***   , then PRAECIS will pay BAXTER $  ***
for such expedited delivery.

BATCH RECORDS

In the event that PRAECIS requests that the information contained in the
Released Executed Batch Record for a Batch be modified more than   ***   in any
12-month period, then BAXTER shall charge PRAECIS $   ***   to incorporate such
revisions into the Released Executed Batch Record for such Batch and, if
requested by PRAECIS, for all subsequent Batches. Following the initial delivery
of a Released Executed Batch Record for a Batch, a charge of $

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     4 OF 12
<Page>

*** per record will be paid to BAXTER for distribution of additional Released
Executed Batch Records for such Batch. In the event that PRAECIS requests that
the information contained in the Master Batch Record be modified more than ***
in any 12-month period, then BAXTER shall charge PRAECIS $   ***   to
incorporate such revisions into the Master Batch Record

DELAYED RECEIPT DRUG PRODUCT INTERMEDIATE

Per Section 4.3 of the Commercial Supply Agreement, a charge of $   ***   per
occurrence will be paid to BAXTER if BAXTER receives the Drug Product
Intermediate for the Production of Product from PRAECIS not in accordance with
Section 3.3. In addition, in the event BAXTER receives the Drug Product
Intermediate for Production of Product from PRAECIS less than   ***   prior to
the scheduled date of filling for such Product, BAXTER may cancel Production of
such Product and invoice PRAECIS the Cancellation Fees as set forth in Exhibit
G.

STORAGE OF PRODUCT

A charge of $   ***   per pallet per month will be paid to BAXTER for the
storage of Product in excess of   ***   after the BAXTER Quality Assurance
Release for such Product.

DRUG PRODUCT INTERMEDIATE REIMBURSEMENT

For purposes of Section 7.4.1 of the Commercial Supply Agreement, BAXTER's
maximum liability for reimbursement of Drug Product Intermediate is   ***   per
Batch.

NO ADDITIONAL NAMED INSURED REQUIREMENT

In accordance with Section 15.1 of the Commercial Supply Agreement, BAXTER
confirms that PRAECIS shall not be obligated to name BAXTER as an additional
insured on the PRAECIS Insurance.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     5 OF 12
<Page>

                    EXHIBIT C - AUDITED VENDORS AND SUPPLIERS

     ***

     ***

Cambrex Charles City

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     6 OF 12
<Page>

                      EXHIBIT D - COMPONENT SPECIFICATIONS

              EXHIBIT D1 - DRUG PRODUCT INTERMEDIATE SPECIFICATIONS

DRUG PRODUCT INTERMEDIATE: ABARELIX CMC RELEASE
BAXTER PN: ***

<Table>
<Caption>
TESTS                               METHOD REFERENCE       SPECIFICATIONS
----------------------------------------------------------------------------------------------------
<S>                                 <C>                    <C>
Appearance                          ***                    White to Off-White Powder

CMC Content(HPLC)                   ***                    ***

Loss on Drying(Water Content)       ***                    ***

Identification (HPLC)               ***                    Meets SOP Requirements

Abarelix Assay (HPLC)               ***                    *** APPROXIMATELY 6 LINES OMITTED ***

Particle Size                       ***                    *** APPROXIMATELY 5 LINES OMITTED ***

Acetate Content (HPLC)              ***                    ***

Bacterial Endotoxins                ***                    ***
</Table>

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     7 OF 12
<Page>

              EXHIBIT D2 - BAXTER SUPPLIED COMPONENT SPECIFICATIONS

ITEM: VIAL, ***
BAXTER PN: ***

<Table>
<Caption>
TESTS                               METHOD REFERENCE       SPECIFICATIONS
--------------------------------------------------------------------------------
<S>                                 <C>                    <C>
Full USP Testing                    ***                    ***

Full EP Testing                     ***                    ***

Full SOP Testing                    ***                    ***
</Table>

ITEM: STOPPER ***
BAXTER PN: ***

<Table>
<Caption>
TESTS                               METHOD REFERENCE       SPECIFICATIONS
--------------------------------------------------------------------------------
<S>                                 <C>                    <C>
Elastomeric Testing                 ***                    ***
   a)  Specific Gravity                a)  ***                a)  ***
   b)  Ultraviolet Spectrum            b)  ***                b)  ***
   c)  Infrared Spectrum               c)  ***                c)  ***

Full USP Physiochemical Testing     ***                    ***

EP Testing                          ***                    ***

Full SOP Testing                    ***                    ***
</Table>

ITEM: SEAL, ***
BAXTER PN: ***

<Table>
<Caption>
TESTS                               METHOD REFERENCE       SPECIFICATIONS
--------------------------------------------------------------------------------
<S>                                 <C>                    <C>
Requirements as Described in SOP    ***                    ***
</Table>

The following BAXTER supplied items will under go no incoming release testing
but will be ordered to the dimentional specifications below.

ITEM: BOX ***
BAXTER PN: ***

DIMENSIONS

***

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     8 OF 12
<Page>

ITEM: DIVIDER ***
BAXTER PN: ***

DIMENSIONS

***

ITEM: PAD ***
BAXTER PN: ***

DIMENSIONS

***

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                     9 OF 12
<Page>

                       EXHIBIT E - PRODUCT SPECIFICATIONS

PRODUCT: ABARELIX FOR INJECTION SUSPENSION
BAXTER PN: ***

<Table>
<Caption>
TESTS                               METHOD REFERENCE       SPECIFICATIONS
--------------------------------------------------------------------------------------------------------
<S>                                 <C>                    <C>
Bacterial Endotoxin by Kinetic      ***                    ***
Turbidimetric

Appearance (Powder)                 ***                    White to Off-White Powder

Appearance     ***                  ***                    White to Off-White Suspension

Loss on Drying (Water Content)      ***                    ***

ID of CMC by HPLC                   ***                    Retention time conforms with retention time
                                                           of working standard

Assay by HPLC                       ***                    ***

ID by HPLC                          ***                    Retention time conforms with retention time
                                                           of working standard

ID by FTIR                          ***                    Abarelix IR spectrum conforms to standard
                                                           spectrum

Content Uniformity                  ***                    ***

Related Substances                  ***                    *** APPROXIMATELY 8 LINES OMITTED ***

pH      ***                         ***                    ***

Dose Delivered     ***              ***                    ***

Dissolution                         ***                    ***

Particle Size     ***               ***                    *** APPROXIMATELY 6 LINES OMITTED ***

Sterility                           ***                    Sterile
</Table>

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                    10 OF 12
<Page>

                       EXHIBIT F - REGULATORY AUTHORITIES

United States Federal Food and Drug Administration or any successor organization
thereto

                                    11 OF 12
<Page>

                          EXHIBIT G - CANCELLATION FEES

<Table>
<Caption>
                                     TIMING                                  CANCELLATION FEE
       ----------------------------------------------------------------------------------------
       <S>                                                                            <C>
       Cancellation of any lot within   ***   of the scheduled   ***   date           ***

       Cancellation of any lot within   ***   of the scheduled   ***   date           ***

       Cancellation of any lot within   ***   of the scheduled   ***   date           ***

</Table>

**   Notwithstanding the foregoing Cancellation Fees chart, PRAECIS shall be
entitled, at any time upon   ***   written notice to BAXTER, to postpone a Firm
Delivery Date for up to   ***   with no cancellation penalty or fee.
**   PRAECIS shall be entitled to cancel or delay any Firm Purchase Order more
than   ***   from the scheduled  ***  date with no cancellation penalty or fee.

           CONFIDENTIAL INFORMATION OMITTED AND FILED SEPARATELY WITH
                     THE SECURITIES AND EXCHANGE COMMISSION.
                      ASTERISKS (*) DENOTE SUCH OMISSIONS.

                                    12 OF 12
<Page>

                                    EXHIBIT 2
                         RELEASED EXECUTED BATCH RECORD

The Released Executed Batch Record for Product shall meet cGMP requirements and
shall, at a minimum, include the following information with respect to such
Batch:

     -    Written confirmation from BAXTER that all Production Batch records and
          supporting records have been reviewed and approved by BAXTER's Quality
          Assurance Group
     -    Certificate of Analysis
     -    Certificate of Irradiation
     -    Finished Product Accountability Sheet
     -    A certificate of compliance/conformance indicating that the final
          Product at the time of the BAXTER Quality Assurance Release for such
          Product has been manufactured under cGMPs and has met all established
          performance requirements related to the approved Product
          Specifications
     -    A detailed listing of all deviations, holds and investigations out of
          specification
     -    Manufacturing process data

                                     1 OF 1<Page>

                                                                   EXHIBIT 10.19

                    FIFTH AMENDMENT TO OFFICE LEASE AGREEMENT

     THIS FIFTH AMENDMENT TO OFFICE LEASE AGREEMENT (this "Fifth Amendment") is
made and entered into effective as of February 28, 2002, by and between Collins
Campbell Joint Venture ("Landlord") and telecom technologies, inc. ("Tenant").

                                    RECITALS

     WHEREAS, Landlord and Tenant entered into that certain Office Lease
Agreement, dated as of April 4, 1997, as amended by (i) that certain First
Amendment to Office Lease Agreement, dated as of November 1, 1997; (ii) those
certain Second and Third Amendments to Office Lease Agreement each dated as of
July 1, 1998; and (iii) that certain Fourth Amendment to Office Lease Agreement,
dated February 1, 1999 (collectively, the "Lease"), with respect to certain
Premises defined therein and commonly known as Suite 3000 at 1701 North Collins
Blvd., Richardson, Dallas County, Texas 75080, which Lease is incorporated
herein by reference;

     WHEREAS, Landlord and Tenant among others, have entered into the terms of a
certain global agreement of even date herewith (the "GLOBAL AGREEMENT"), and
Landlord and Tenant acknowledge and agree that the terms of the Global Agreement
shall be binding on the parties hereto;

     WHEREAS, Landlord and Tenant desire to further amend the Lease to reduce
the size of the Premises.

     NOW, THEREFORE, in consideration of the mutual agreements herein set forth,
the mutual agreements set forth in the Lease, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
Landlord and Tenant have agreed, and do hereby agree, to the above Recitals, and
as follows, subject to the occurrence of all of the events set forth in
Paragraph 1 of the Global Agreement:

     1.   All terms used herein and not specifically defined shall have the same
          meanings herein as is ascribed to them in the Lease.

     2.   The Premises are hereby reduced to approximately 20,227 square feet of
          rentable area by deleting approximately 17,789 square feet of rentable
          area on the second floor, such "Give Back Space" being described on
          Exhibit "A", attached hereto and incorporated herein for all purposes.

     3.   Basic rental is decreased from $3,909,279.04 to $3,475,939.00.

     4.   The monthly rental installment is decreased as set forth below:

          Monthly from March 1, 2002 through October 31, 2002 - $35,043.28
          Monthly from November 1, 2002 through April 30, 2003 - $35,397.25

     5.   Tenant's option to extend the term of the Lease set forth in Rider 101
          is hereby eliminated and of no further force or effect.

     6.   Except as herein provided to the contrary, Tenant's lease of the
          Premises from Landlord shall be on the same terms and conditions as
          those specified in the Lease.

     7.   The Lease (as amended by this Fifth Amendment) remains in full force
          and effect and is hereby ratified and affirmed.

<Page>

     8.   All notices required to be sent to the Tenant shall also be sent to
          Sonus Networks, Inc., 5 Carlisle Road, Westford, Massachusetts 01886:
          Attention: Chief Financial Officer.

     9.   The Global Agreement, and all of the terms therein, shall be
          incorporated herein for all purposes. To the extent that there is a
          conflict between the terms of this Fifth Amendment and the terms of
          the Global Agreement with respect to the relevant subject matter, the
          terms of this Fifth Amendment shall control.

     IN WITNESS WHEREOF, this Fifth Amendment is hereby executed as of the day
and year first set forth above.

                                    LANDLORD:

                                    COLLINS CAMPBELL JOINT VENTURE,
                                     a Texas general partnership

                                    By: Jaytex Properties, Ltd.,
                                         a Texas limited partnership

                                        By: JRS Management, Inc.

                                           By:  /s/ W.T. Field
                                               -----------------------------
                                                W.T. Field, President

                                    TENANT:

                                    telecom technologies, inc.,
                                      a Texas corporation

                                    By: /s/ G.M. Eastep
                                       ---------------------------------
                                    Name:   G.M. EASTEP
                                          ------------------------------
                                    Title:  COO
                                          ------------------------------

<Page>

[GRAPHIC DEPICTING 2ND LEVEL FLOOR PLAN]

     telecom technologies, inc

     Give Back Space: 17,789
     rentable square feet on
     the second floor of
     1701 N. Collins Blvd.
     Richardson, Texas 75080

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