Document:

<PAGE>

                                                                   EXHIBIT 10.12

              CONFIDENTIAL TREATMENT HAS BEEN REQUESTED FOR CERTAIN
               PORTIONS OF THIS DOCUMENT. SUCH PORTIONS HAVE BEEN
                REDACTED AND MARKED WITH ASTERISKS (**). THE NON-
               REDACTED VERSION OF THIS DOCUMENT HAS BEEN SENT TO
               THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO
                   AN APPLICATION FOR CONFIDENTIAL TREATMENT.

                 DEVELOPMENT AND SUPPLY AGREEMENT (PRAECIS-149)

BETWEEN     UCB-BIOPRODUCTS S.A., with registered office at Avenue Louise
            326, B-1050 Brussels, Belguim, (Facsimile No. 32.2/386.29.90)
            ("UCB")
                                                on the one hand,

AND         PRAECIS PHARMACEUTICALS INCORPORATED with its
            principal office at One Hampshire Street, 5th Floor, Cambridge,
            Massachusetts, 02139, USA (Facsimile No. 617/494.8414)
            ("PRAECIS")
                                                on the other hand,

WHEREAS, PRAECIS holds exclusive worldwide rights, as licensee, to a compound
identified as "PPI-149", USAN name "Abarelix" (the "Product"), and is interested
in development and marketing on a worldwide basis pharmaceutical compositions
containing the Product for the treatment of prostate cancer and other diseases
as used by the end user (the "Finished Product"); and

WHEREAS, UCB has suitable premises, equipment and expertise in the development
and production of pharmaceutical grade bulk peptides; and

WHEREAS, PRAECIS wishes UCB, as a preferred supplier, to produce and supply it
with quantities of the Product for development and commercial purposes, upon the
terms and subject to the conditions set forth in this Agreement; and

WHEREAS, UCB is willing to manufacture and supply Product upon the terms and
subject to the conditions set forth in this Agreement;
<PAGE>

NOW, THEREFORE, IN CONSIDERATION OF THE FOREGOING, AND THE REPRESENTATIONS,
WARRANTIES, COVENANTS AND AGREEMENTS CONTAINED HEREIN, THE PARTIES AGREE AS
FOLLOWS:

SECTION 1 - DEFINITIONS

When used herein, the following terms, used with initial capital letters, shall
have the following respective meanings and the singular shall include the plural
and vice-versa:

1.1   "Affiliates" shall mean with respect to either party, any person,
      corporation, company, partnership, joint venture or other entity
      controlling, controlled by or under common control with such party. For
      such purpose the term "control" means the holding of 50% or more of the
      common voting stock or ordinary shares in, or the right to appoint 50% or
      more of the directors of, or the right to share in 50% or more of the
      profits of, the said corporation, company, partnership, joint venture, or
      entity.

1.2   "Confidential Information" shall mean any UCB or PRAECIS trade secret or
      other information of a confidential and/or proprietary nature which is
      disclosed by one party ("Disclosing Party") to the other party ("Receiving
      Party"), excluding such trade secret or other information which (i) is
      published or otherwise becomes a matter of public knowledge by any means
      other than through the breach of this Agreement by the Receiving Party,
      (ii) was known by the Receiving Party at the time of such disclosure, as
      evidenced by the Receiving Party's written records predating such
      disclosure and maintained in the ordinary course of business, or (iii) was
      disclosed to the Receiving Party by any Third Party (as defined below) who
      has the right to disclose the same. For the purposes of this Section 1.2,
      information shall not be deemed to be public knowledge or known to PRAECIS
      solely because: (i) the general principal is public knowledge or known to
      PRAECIS, if the particular practice is not itself public knowledge or so
      known, or (ii) it constitutes a combination of information which is public
      knowledge or known to PRAECIS unless the combination itself and the
      principle and mode of operation of such combination is also public
      knowledge or known to PRAECIS.

1.3   "Development Period" shall mean the period of time from the Effective Date
      until Launch Date (as defined below).

                                       2
<PAGE>

1.4   "Development Plan" shall have the meaning set forth in Section 2.1 of this
      Agreement.

1.5   "Effective Date" shall mean the date on which this Agreement is signed by
      the latter of the parties to sign this Agreement.

1.6   "Finished Product" shall have the meaning set forth in the preamble to
      this Agreement.

1.7   "Forecast" shall have the meaning set forth in Section 4.2.

1.8   "Initial Product Orders" shall have the meaning set forth in Section 4.3.

1.9   "Launch Date" shall mean the first date that the Finished Product is sold
      commercially by PRAECIS, its Affiliates, Partners, licensee(s),
      sublicensee(s) or distributors to a wholesaler or end user.

1.10  "LHRH Antagonist" shall mean any compound which exhibits Lutenizing
      Hormone Releasing Hormone (LHRH) antagonist activity.

1.11  "Manufacturing Standards" shall have the meaning set forth in Section 3.2
      of this Agreement.

1.12  "Net Sales" shall mean with respect to all Finished Product sold by
      PRAECIS, any PARTNER, and their respective Affiliates, licensee(s),
      sublicensee(s) or distributors, the total gross invoices for such Finished
      Product less (i) quantity and/or cash discounts actually allowed and
      taken, (ii) customs duties and sales and income taxes, if any, related to
      the sale of the Finished Product, and (iii) amounts allowed by reason of
      rejections and return of goods.

1.13  "Partner" shall mean ROCHE PRODUCTS INC. and SYNTHELABO, and their
      respective Affiliates, as long as their respective Agreements dated May
      13, 1997 and August 21, 1997 (or in the case of the August 21st Agreement,
      the definitive agreement to be entered into upon the exercise of the
      option provided for in such August 21st Agreement), respectively, with
      PRAECIS remain in force.

1.14  "Product" shall have the meaning set forth in the preambles to this
      Agreement.

                                       3
<PAGE>

1.15  "Specifications" shall have the meaning set forth in Section 2.1.

1.16  "Supplied Entities" shall have the meaning set forth in Section 3.1.

1.17  "Third Party" shall mean any natural person, corporation, firm, trust,
      joint venture, company, partnership or other business organization which
      is not a party hereto or an Affiliate of any party hereto.

1.18  "UCB Manufacturing Capacity" shall mean the aggregate amount of Product
      which UCB and its Affiliates can manufacture over the applicable time
      period.

1.19  "UCB Technical Information" shall mean any and all know-how, trade
      secrets, formulations, process, vendor or supplies information, raw
      material, peptide or intermediate specifications, methods and the like,
      whether or not patented or patentable, including without limitation,
      pre-clinical, pharmacological, toxicological, chemical, physical and
      analytical, safety, quality control or other proprietary data and
      information relating to the development, testing, use, manufacture or
      marketing of peptides (including the Product) which UCB or any of its
      Affiliates has now (which is fully set forth in Annex F, with respect to
      UCB strategy of synthesis and purification) or may conceive, develop,
      acquire or have the ability to license or sublicensee (under licenses from
      others or otherwise) during the term of or in the performance of this
      Agreement, provided that any of the foregoing (including that set forth in
      Annex F) which would otherwise constitute UCB Technical Information (i)
      shall not be deemed to be UCB Technical Information unless it constitutes
      Confidential Information and (ii) shall not be deemed to be UCB Technical
      Information, but information owned jointly, to the extent it was jointly
      conceived, discovered or developed by PRAECIS or its Affiliates and UCB or
      its Affiliates.

SECTION 2 - DEVELOPMENT OF THE PROCESS, SPECIFICATIONS

2.1   Development Plan. UCB, in liaison with PRAECIS, shall develop a method of
      assembly, synthesis and purification of the Product, using specifications
      of the Product established by PRAECIS which, upon PRAECIS' approval, will
      be the contractual specifications hereunder and will be attached hereto as
      Annex A to this Agreement (the "Specifications"), prepare the drug master
      file ("DMF"), develop the analytical procedures and supply stability
      batches and validation batches, all in accordance with the plan to be
      agreed upon by the parties, as amended from time to time in accordance
      with the terms hereof

                                       4
<PAGE>

      (the "Development Plan"), and the other terms and conditions of this
      Agreement. An outline of the Development Plan is attached hereto as Annex
      B. Alternatively, at the request of PRAECIS, in lieu of submission of a
      DMF, the information and data which would be contained therein will be
      included in the Chemistry Manufacturing and Controls section of the
      applicable regulatory submission. The Development Plan may be amended or
      updated from time to time by written agreement of the parties, as
      development proceeds and results are obtained. In the Development Period,
      it is understood that Specifications are tentative; therefore PRAECIS may
      propose changes to the Specifications, including as required by a
      regulatory agency, it being understood that if any such changes would
      cause an increase in UCB manufacturing costs, acceptance of the new
      Specifications by UCB shall be conditional on a mutually agreeable
      revision of the prices at which Product is delivered hereunder based on
      such increased costs, and if applicable, taking into account any material
      change in percentage margin. UCB may also request changes to the
      Specifications, which may be implemented upon approval by PRAECIS.
      PRAECIS, any Partners, and their respective Affiliates, shall have the
      right to review any manufacturing and regulatory documents, under secrecy
      obligation.

2.2   Reports. UCB shall issue PRAECIS written development reports on a mutually
      agreed upon schedule during the Development Period. Such development
      reports shall describe the work performed during the period concerned in
      connection with the Development Plan. The parties shall each designate
      responsible members of their respective organizations to meet at least
      quarterly to discuss the progress of the foregoing work.

SECTION 3 - SUPPLY OF THE PRODUCT

3.1   Product Requirements. Subject to the terms and conditions of this
      Agreement (i) UCB shall manufacture and supply to PRAECIS, and PRAECIS
      shall purchase from UCB, the full amount of Product ordered by PRAECIS
      pursuant to the Initial Product Orders, provided that if PRAECIS, the
      Partners and the respective Affiliates, licensee(s) and sublicensee(s)
      of PRAECIS, the Partners and such Affiliates (collectively, the
      "Supplied Entities"), have requirements for Product during the
      Development Period in addition to the

                                       5
<PAGE>

      quantities supplied and purchased pursuant to the Initial Product Orders,
      then (A) UCB shall manufacture and supply to PRAECIS all of such
      requirements up to ***% of the then current UCB Manufacturing Capacity and
      (B) PRAECIS shall purchase from UCB at least ***% of such requirements for
      Product and (ii) after the Development Period until the expiration or
      termination of this Agreement, with respect to the Supplied Entities'
      total requirements for Product in addition to the quantities supplied and
      purchased pursuant to clause (i) above, UCB shall manufacture and supply
      to PRAECIS, and PRAECIS shall purchase from UCB, the lesser of (A) such
      applicable percentage of such requirements for Product of the Supplied
      Entities as set forth in Annex G (which percentage for any twelve-month
      period after the Launch Date may be increased up to *** by notice to such
      effect from PRAECIS to UCB given at least twelve (12) months prior to the
      time such increased percentage takes effect), or (B) up to *** (***%) of
      the then current UCB Manufacturing Capacity; provided however that such
      obligation to supply by UCB and to purchase by PRAECIS shall be without
      prejudice to PRAECIS' right to make quantities of Product itself or to
      purchase quantities of Product from either the Partners or any Affiliate
      thereof or an alternative Third Party manufacturer/supplier (i) to the
      extent UCB fails or is unwilling (A) to meet PRAECIS' specific or excess
      requirements for Product, as provided under Sections 3.2 and 4.2
      respectively, or (B) to fulfill its obligations to supply, as provided
      under Section 4.6, (ii) to the extent such quantities of Product exceed
      the quantities of Product required by this Section 3.1 to be purchased
      from UCB, or (iii) in the event that at any time after the Development
      Period a Third Party manufacturer/supplier is able to provide a ***% or
      greater discount from the per unit amount then being charged by UCB
      hereunder for similarly qualified materials and the Third Party
      manufacturer/supplier is willing to enter into a supply contract of at
      least two years at such a ***% or greater discount.

3.2   Compliance with Specifications and Manufacturing Standards. UCB shall
      manufacture Product for approval and ongoing product supply hereunder in
      accordance with the Specifications, under current Good Manufacturing
      Practices ("cGMP") as applicable in the European Union, USA and Japan
      (collectively, the "Manufacturing Standards").

      In the event any regulatory authority in any country requires cGMP
      deviating from the Manufacturing Standards or the Specifications, PRAECIS
      and UCB shall discuss and reach agreement with respect to such modified
      cGMP or such modified Specification. If such conformance of the Product to
      such modified cGMP or such modified Specification would cause UCB
      substantial

                                       6
<PAGE>

      costs, UCB will so notify PRAECIS and the parties will negotiate in good
      faith the possible adaptation/expansion of the UCB Manufacturing Capacity
      and the costs thereof. If UCB determines in good faith that it is
      commercially impracticable to adapt/expand the UCB Manufacturing Capacity
      as required to meet such modified cGMP or such modified Specifications,
      PRAECIS shall be free to have the excess demand satisfied by itself or by
      a Third Party supplier/manufacturer and PRAECIS shall be permitted to
      grant sublicenses under the UCB Technical Information for this sole
      purpose, to the extent provided in Section 7. UCB and PRAECIS will
      establish an effective cGMP change control system, and UCB will not make
      any material change in the manufacturing process without PRAECIS' prior
      written consent.

      UCB shall also be responsible for adherence to appropriate health
      standards for its employees and furthermore will operate under guidelines
      provided by PPI's MSDS, which shall be updated from time to time (such
      guidelines in effect on the date hereof are given in Annex H).

3.3   Certificate of Analysis. UCB shall include, with each shipment of Product
      hereunder, a certificate of analysis certifying that such shipment meets
      the Specifications and was manufactured in compliance with the
      Manufacturing Standards. PRAECIS, the Partners, and the respective
      Affiliates of PRAECIS and the Partners, shall have the opportunity to
      review at UCB's premises all batch records, in process batch data, and
      other appropriate documents associated with manufacture.

3.4   Audit. In order to ascertain compliance by PRAECIS with the purchase
      obligation set forth in Section 3.1, PRAECIS shall, within sixty (60) days
      after the end of each calendar year during the period of time in which UCB
      supplies PRAECIS with Product under this Agreement, provide written
      reports to UCB specifying the amount of Product manufactured by PRAECIS
      and purchased by PRAECIS from suppliers other than UCB during the prior
      calendar year. If UCB does not object to such written reports within sixty
      (60) days, then UCB shall waive the right to audit PRAECIS' books and
      records relating to the information contained in such reports. However, if
      in a subsequent year it is determined in accordance with the provisions of
      this Section 3.4 that PRAECIS breached its purchase obligation set forth
      in Section 3.1, then UCB shall have the right to audit PRAECIS' books and
      records relating to the information contained in such reports for the
      previous three (3) years. If UCB timely notifies PRAECIS of its intention
      to audit PRAECIS's books and records, UCB may designate an auditor
      reasonably acceptable to PRAECIS. PRAECIS shall make available to such
      auditor such

                                       7
<PAGE>

      books and records as may be required to audit such information and such
      books and records shall be deemed Confidential Information for purposes of
      Section 8. Such audit shall be completed within ninety (90) days after the
      date on which UCB notified PRAECIS that it desired to audit such
      information. UCB shall promptly deliver a copy of the report of such audit
      to PRAECIS. If PRAECIS disagrees with the conclusions of such report, it
      shall notify UCB and the parties shall attempt to resolve the
      disagreement. If the parties fail to agree on the conclusions in the
      report, such disagreement shall be resolved in accordance with Section 15.
      Each such audit shall be at UCB's expense; provided, that if it is finally
      determined that in any calendar year PRAECIS violated its purchase
      obligation set forth in Section 3.1, then PRAECIS shall pay the costs of
      such audit and PRAECIS shall compensate for or purchase an additional
      quantity of Product from UCB in an amount which, if it had been purchased
      in the prior calendar year, would have resulted in PRAECIS' compliance
      with such obligation.

3.5   Inspection. In order to ascertain compliance by UCB with the quality
      requirements provided in Section 3.2, PRAECIS, the Partners, and the
      respective Affiliates of PRAECIS and the Partners, shall have the right,
      during regular business hours and on reasonable prior notice to UCB, to
      inspect and take samples from such facilities at which UCB manufactures,
      tests, sources and/or stores raw materials or Product. UCB shall use its
      best efforts to enable PRAECIS and its Affiliates to inspect and sample
      raw materials from all UCB suppliers. Such inspections and sampling shall,
      to the extent reasonably practicable, be conducted in a manner which does
      not interrupt or impair in any significant manner the manufacturing
      operations of such facilities.

3.6   Inventory Management. The parties will meet periodically to discuss
      inventory management and address efficiencies with respect thereto.

3.7   Non-Competition. Neither UCB nor any of its Affiliates shall, during the
      term of this Agreement and, unless this Agreement is terminated by UCB
      pursuant to and in accordance with Section 10.2, for a period of
      twenty-four (24) months thereafter (except that such period shall be ten
      (10) years with respect to any generic version of the Product), directly
      or indirectly engage in development activities with respect to, or
      produce, any LHRH Antagonist other than, during the term of this
      Agreement, Product; provided that this

                                       8
<PAGE>

      Section 3.7 shall not apply after the applicable date set forth on Annex D
      if PRAECIS has not, by, or within 30 days after, such date, submitted the
      Initial Product Order(s) in substantially at least the amount set forth on
      Annex D with respect to such date; and provided further that in any event
      this Section 3.7 shall again apply in accordance with its terms from and
      after the Launch Date as long as PRAECIS or the Supplied Entities orders
      at least 35 kg of Product per year; it being understood and agreed that
      this Section 3.7 shall apply in accordance with its terms after
      termination of this Agreement (without any minimum purchase requirement)
      if this Section 3.7 was applicable at the time of such termination.

SECTION 4 - FORECASTS AND ORDERS FOR THE PRODUCT

4.1   Five-year plan. During the term of this Agreement, PRAECIS shall provide
      UCB with a non-binding 5-year plan of Product needs, which plan shall,
      during the term of this Agreement, be updated annually before year-end,
      for planning purposes. The first plan covering the years 1998 up to 2002
      is attached hereto as Annex C.

4.2   Forecasts. Beginning as of the date the first *** of Product have been
      ordered, and each calendar quarter thereafter so long this Agreement shall
      remain in effect, PRAECIS shall provide UCB at least *** in advance of the
      relevant *** period with a forecast (each, a "Forecast") specifying
      PRAECIS' requirements for Product in respect of each of the *** during the
      *** period covered by such Forecast (each such *** period being referred
      to as a "Forecast Period"). The delivery by PRAECIS of each Forecast as
      required by this Section 4.2 shall constitute PRAECIS' irrevocable
      agreement to order and purchase from UCB during such Forecast Period in
      accordance with this Agreement (i) at least *** (***%) of the quantity of
      Product specified in such Forecast in respect of the *** of such Forecast
      Period and (ii) at least *** of the quantity of Product specified in such
      Forecast in respect of the *** of such Forecast Period, provided that such
      quantities do not exceed the UCB Manufacturing Capacity for such ***. UCB
      shall supply the Product so ordered, provided, however, that UCB shall not
      be obligated (but shall use its diligent efforts) to supply Product
      ordered during a *** to the extent the quantities of Product so ordered
      exceed *** (***%) of the quantities of Product in respect of such ***
      specified in the Forecast delivered *** prior to such ***, nor to supply
      quantities of Product in excess of the then current UCB Manufacturing
      Capacity.

                                       9
<PAGE>

      It is expressly understood and agreed that if the quantities of Product
      specified in a Forecast exceed the UCB Manufacturing Capacity, the
      delivery of such Forecast shall not constitute PRAECIS' irrevocable
      agreement to order and purchase that quantity of Product which exceeds the
      UCB Manufacturing Capacity. If UCB notifies PRAECIS that the quantities of
      Product specified in a Forecast exceed the UCB Manufacturing Capacity, the
      parties will negotiate in good faith the possible expansion of the UCB
      Manufacturing Capacity and the estimated costs thereof. If UCB or PRAECIS
      determines that it is commercially impracticable to expand the UCB
      Manufacturing Capacity to supply the quantities of Product specified in a
      Forecast which exceed the then current UCB Manufacturing Capacity, PRAECIS
      shall be free to have such excess quantities of Product manufactured
      and/or supplied by itself or by a Third Party supplier/manufacturer and
      PRAECIS shall be permitted to sublicense under the UCB Technical
      information to the extent set forth in Section 7.

4.3   Timing of Product Orders and Product Delivery. Subject to Section 4.2, UCB
      will deliver Product ordered by PRAECIS hereunder pursuant to a firm
      purchase order on or before the delivery date set forth in such purchase
      order, provided that, except as set forth in the next succeeding sentence,
      such purchase order is submitted at least *** (***) days prior to such
      requested delivery date for orders placed on or prior to the date which is
      two (2) years after the Launch Date, and at least *** (***) days prior to
      such requested delivery date for orders placed thereafter. UCB agrees that
      with respect to each order for Product listed on Annex D hereto
      (collectively, the "Initial Product Orders"), if PRAECIS places (and makes
      the prepayment with respect to) such Initial Product Order by the date
      specified in Annex D, UCB will deliver to PRAECIS the quantity of Product
      reflected in each such Initial Product Order on or before the applicable
      Delivery Date therefor set forth on such Annex D.

      At UCB's request, PRAECIS shall use commercially reasonable efforts to
      reschedule its purchase orders in order to spread the supply more evenly
      over the quarter concerned to reflect UCB's production rate, provided that
      for this purpose reasonable efforts shall not require PRAECIS to incur
      additional costs or to risk breach of any agreement between PRAECIS or any
      of its Affiliates and any Third Party.

4.4   UCB Manufacturing Capacity
      (a) UCB covenants and agrees with PRAECIS that (i) if PRAECIS places (and
      makes the prepayment with respect to) the first Initial Purchase Order

                                       10
<PAGE>

      (for *** of Product) on or before the date specified in Annex D, then on
      or before the last delivery date with respect to such Initial Purchase
      Order as set forth on Annex D, the UCB Manufacturing Capacity will be at
      least *** of Product per six-month period, (ii) if PRAECIS places (and
      makes the prepayment with respect to) the third Initial Purchase Order
      (for *** of Product) on or before the date specified in Annex D, then on
      or before the last delivery date with respect to such Initial Purchase
      Order as set forth on Annex D, the UCB Manufacturing Capacity will be at
      least *** of Product per six-month period.

      (b) After the first *** of Product have been ordered, UCB will maintain
      for *** a minimum annual UCB Manufacturing Capacity equal to the greater
      of (i) ***/year and (ii) the amount of Product supplied by UCB in the
      immediately preceding year. After such ***, UCB will maintain a minimum
      annual UCB Manufacturing Capacity equal to the amount of Product supplied
      by UCB in the immediately preceding year; provided that in any *** period
      after the first *** have been ordered, if PRAECIS orders an amount of
      Product equal to at least the UCB Manufacturing Capacity as of the
      commencement of such *** period, the minimum annual UCB Manufacturing
      Capacity for the following *** will be at least such UCB Manufacturing
      Capacity as of the commencement of such *** period.

4.5   Product Delivery.  Product ordered hereunder shall be delivered by UCB
      FOB, Belgium, express courier selected by PRAECIS (ICC Incoterms 1990).

4.6   Inability or failure to supply. In the event UCB is unable to supply
      Product in accordance with the terms hereof, UCB shall promptly notify
      PRAECIS in writing of such inability, which notice shall include a
      reasonably detailed explanation of the reasons for such inability (a "UCB
      Product Supply Deficiency Notice"). Upon PRAECIS' receipt of a Product
      Supply Deficiency Notice, or upon any material failure by UCB to meet its
      supply obligations hereunder and UCB's receipt from PRAECIS of a notice
      reasonably describing such material failure by UCB (a "PRAECIS Default
      Notice"), if UCB's inability or material failure to supply Product in
      accordance with the terms hereof is reasonably likely to continue for at
      least ninety (90) days (or such shorter period not shorter than thirty
      (30) days if such inability or failure would materially jeopardize
      PRAECIS' commercial relationships with respect to Product or Finished
      Product, or would present PRAECIS with a significant risk of contractual
      damages to Third Parties), PRAECIS shall have the right to sublicense one
      or more other suppliers under the UCB Technical Information to the extent
      provided in Section 7, and in such event UCB shall

                                       11
<PAGE>

      promptly provide to such other supplier(s) such technical information
      (including without limitation UCB Technical Information) as may be
      necessary for such supplier(s) to qualify with relevant regulatory
      authorities. Except in the case of force majeure, in which case the
      provisions of Section 14 shall apply, UCB shall be liable to PRAECIS for
      all costs and expenses incurred by PRAECIS in connection with qualifying
      one or more alternative suppliers of Product with the relevant regulatory
      authorities (such costs and expenses will not be considered as
      consequential losses as defined in Section 9.6), including any advance
      payments (other than those described on Annex D except to the extent set
      forth below) made in respect of the quantities of Product not so supplied;
      provided however that (i) PRAECIS shall act in a commercially reasonable
      manner with respect to obtaining an alternative supply of Product as
      contemplated above, and (ii) UCB shall not be required to reimburse
      PRAECIS for any advance payment described in Annex D unless (A) UCB shall
      have failed to apply such advance payments (or part thereof) to the
      purchase or construction of such plant and equipment as is reasonably
      intended to enable it to meet its supply obligations hereunder or shall
      have so applied such advance payments but shall have failed to utilize
      such plant and equipment for such purpose or (B) UCB's inability or
      failure to supply constitutes an intentional breach of this Agreement or
      arises from UCB's gross negligence or willful misconduct. If within ninety
      (90) days (extended to one hundred and eighty (180) days during the
      Development Period) after PRAECIS' receipt of a UCB Product Supply
      Deficiency Notice or PRAECIS' delivery to UCB of a PRAECIS Default Notice,
      as applicable, UCB provides PRAECIS with evidence reasonably satisfactory
      to PRAECIS that UCB is able to and will meet its supply obligations
      hereunder ("Cure Evidence"), then, unless this Agreement has been
      terminated in accordance with Section 10, within sixty (60) days of
      receiving such Cure Evidence PRAECIS shall resume purchasing Product from
      UCB in accordance with the terms of this Agreement (subject to again
      ceasing such purchasing as contemplated by this Section 4.6), provided
      that PRAECIS shall be allowed to fulfill any outstanding obligations to
      other suppliers that were incurred by PRAECIS due to UCB's failure or
      inability to supply Product to PRAECIS.

SECTION 5 - QUALITY AND DEFICIENCY CLAIMS

5.1   Limited warranty - Inspection and claim. UCB's only warranty, with respect
      to the Product, is that the Product will conform to the Specifications and
      will be manufactured in accordance with the Manufacturing Standards.
      Without express or implied, is expressly excluded. PRAECIS shall be
      responsible for performing all necessary inspections to detect obvious
      damage (shortages,

                                       12
<PAGE>

      breakage, damage, etc.) and non-conformity of Product to Specifications,
      within sixty (60) days of receipt of Product. PRAECIS shall notify UCB in
      writing of any defective shipment and shall set forth the lot, date of
      delivery and date of the failure. At PRAECIS' option, UCB shall promptly
      replace, or reimburse or give credit with respect to any payment for, any
      defective shipment. Unless such notification is timely provided, subject
      to and without limitation of Section 5.2(b), the Product shall be deemed
      to be delivered and accepted by PRAECIS. PRAECIS shall hold any allegedly
      defective shipment of Product for inspection by UCB or, at UCB's request
      and expense, shall return such shipment or part thereof to UCB.

5.2   Remedy. (a) In the event that it is determined in accordance with this
      Section 5.2 that all or any portion of a shipment of Product does not meet
      the Specifications or was not manufactured in accordance with the
      Manufacturing Standards, UCB, at PRAECIS' option but after consultation of
      UCB, shall either replace or rework such rejected shipment or portion
      thereof or reimburse or give credit for such payment to PRAECIS, and,
      without limitation of Section 4.6, UCB shall have no other liability to
      PRAECIS therefor except as provided in Section 4.5. In the event that the
      parties disagree over whether a shipment of Product fails to comply with
      the Specifications or was not manufactured in accordance with the
      Manufacturing Standards, the parties shall make every attempt to resolve
      the disagreement first between themselves and, failing that, by referring
      the matter to a mutually-agreeable Third Party specializing in the
      analysis of such products. If these methods fail to resolve the
      disagreement, the matter shall be resolved pursuant to Section 15. UCB and
      PRAECIS shall develop a qualified rework procedure. At PRAECIS' request,
      unsatisfactory material shall be reworked at UCB's expense.

      (b) Hidden defects not revealed by the inspections specified under Section
      5.1 shall be brought to UCB's attention promptly upon discovery. In such
      event, the parties shall in good faith discuss and agree upon procedures
      and business terms for addressing such defects to the reasonable
      satisfaction of PRAECIS and UCB.

SECTION 6 - PRICE AND PAYMENT TERMS

6.1   Prices. Product supplied pursuant to the Initial Purchase Orders will be
      supplied at the prices, which shall not exceed *** peptide weight with
      respect to each Initial Purchase Order (subject to PRAECIS having placed
      such Initial Purchase Order for an amount of Product and substantially by
      the dates

                                       13
<PAGE>

      set out in Annex D). All other Product quantities will be supplied at the
      prices (expressed *** peptide weight) and/or according to the price
      formula/system out in Annex E hereto.

      All prices referred to in Annexes D and E are exclusive of any taxes and
      duties, such as sales, export, import, value added tax, excise duty, which
      shall be added to such prices as appropriate.

6.2   Payment terms. Payment of the price for Product shall be in USD net thirty
      (30) days from invoice and shipment. Any amount not received at its due
      date shall automatically and without further notice bear an interest on
      overdue payment at the rate of three percent (3%) above LIBOR (3 months)
      as in effect on the date such payment was due.

6.3   Exchange rate fluctuations. The prices set out in Section 6.1 shall be
      adjusted each calendar quarter to reflect exchange rate fluctuations, as
      follows.

      In the event at the date for such an adjustment the average of the
      exchange rate of US Dollars into Belgian francs (BEF), as reported in the
      Wall Street Journal (Eastern Edition), for the 10 business day period
      immediately preceding that date varies by more than ten (10) percent
      compared to 37.79 USD (which is the rate of exchange as applicable at the
      day of signature of this Agreement) or the date of the last price
      adjustment, then the purchase prices set out in Section 6.1, as theretofor
      adjusted, shall be adjusted to reflect 50% of such change.

SECTION 7 - INTELLECTUAL PROPERTY RIGHTS

7.1   No Intellectual Property Rights in the Product. UCB expressly acknowledges
      that it has no ownership or intellectual property rights of any kind in or
      to the Product, by virtue of this Agreement or otherwise, and will not
      acquire any such rights as a result of its or PRAECIS' performance of
      their respective obligations hereunder.

7.2   UCB License Grant During Term of Agreement.  (a) During the term of this
      Agreement and subject to its terms, UCB hereby grants to PRAECIS and its

      Affiliates an exclusive worldwide royalty-free right and license, with the
      right to grant sublicenses, under the UCB Technical Information (i) to use
      or incorporate quantities of Product supplied by UCB in connection with
      the manufacture, use or sale of the Finished Product and (ii) to make or
      have

                                       14
<PAGE>

      made quantities of Product for incorporation in the Finished Product in an
      amount up to 100% of the worldwide requirements of the Supplied Entities
      in the case of UCB's unwillingness or inability (A) to meet PRAECIS'
      specific or excess requirements for Product as provided under Section 3.2
      and 4.2 or (B) to fulfill its obligations to supply, as provided under
      Section 4.6, and to use or incorporate Product so made in connection with
      the manufacture, use or sale of Finished Product.

      (b) During the term of this Agreement and subject to its terms, UCB hereby
      grants to PRAECIS and its Affiliates an exclusive worldwide right and
      license, with the right to grant sublicenses, under the UCB Technical
      Information, (i) to make or have made quantities of Product which exceed
      the requirements reserved to UCB as provided in Section 3.1 and Annex G
      and (ii) to use or incorporate quantities of Product made and supplied by
      PRAECIS, its Affiliates or any Third Party, as contemplated by clause (i)
      of this subparagraph (b) in connection with the manufacture, use or sale
      of Finished Product.

7.3   UCB License Grant Upon Termination of Agreement. Upon termination of this
      Agreement (other than a termination by UCB pursuant to and in accordance
      with Section 10.2 or a termination by UCB or PRAECIS pursuant to Section
      10.3, in which event no license, and thus no ability to grant sublicenses,
      shall be granted by UCB to PRAECIS upon such termination), UCB shall, and
      hereby does, grant to PRAECIS and its Affiliates an exclusive perpetual
      worldwide right and license, with the right to grant sublicenses, under
      the UCB Technical Information, to make or have made quantities of Product
      for incorporation in the Finished Product, and to use or incorporate
      Product so made in connection with the manufacture, use or sale of
      Finished Product.

7.4   Royalties in Respect of Licenses and Sublicenses. The license granted to
      PRAECIS and its Affiliates, and any sublicenses, hereunder shall be ***,
      except that (i) during the term of this Agreement, (A) any sublicense
      granted to make or have made quantities of Product which exceed the
      requirements reserved to UCB as provided in Section 3.1 and Annex G, or
      (B) any sublicense granted pursuant to Section 3.2 or Section 4.2, shall
      be royalty-bearing at the rate and for the period set forth in this
      Section 7.4, (ii) if this Agreement is terminated by PRAECIS pursuant to
      and in accordance with Section 10.1, such license and any such sublicenses
      shall be royalty-bearing at the rate and for the period set forth in this
      Section 7.4, (iii) if this Agreement is terminated by UCB pursuant to and
      in accordance with Section 10.1,

                                       15
<PAGE>

      any such sublicense (other than to a Partner) shall be royalty-bearing at
      the rate and for the period set forth in this Section 7.4. If under this
      Section 7.4 the license or any sublicense granted pursuant to this Section
      7 for the term of this Agreement and upon the termination hereof is
      royalty-bearing, such royalty shall apply until the termination of this
      Agreement and for a period of five years thereafter. If under this Section
      7.4 the license or any sublicense granted pursuant to this Section 7 upon
      the termination hereof if royalty-bearing, such royalty shall apply for a
      period of five years after such termination. In each case such royalty
      shall be payable by PRAECIS to UCB. With respect to a royalty-bearing
      sublicense referred to in clause (i) (B) or clause (iii) of this Section
      7.4, such royalty shall be at a rate of ***% percent, and with respect to
      any other royalty bearing license or sublicense referred to in this
      Section 7.4 such royalty shall be at a rate of ***%, on the Net Sales of
      Finished Product containing Product manufactured or supplied by any Third
      Party and which incorporates or uses any part of the UCB Technical
      Information, provided that in any event the applicable royalty shall be
      payable only once with respect to the sale of any Finished Product.

7.5   Royalties. Royalties shall be payable in USD on a calendar quarterly basis
      within thirty (30) days of the end of each calendar quarter. The exchange
      rate of the due date shall apply. Each payment shall be accompanied by a
      report stating the Net Sales and the amount of royalties payable to UCB,
      as well as computation hereof.

      The audit provisions contained in Section 3.4 shall apply mutatis mutandis
      to the royalty payments provided by this Section and payment of any
      shortfall in royalty shall be made forthwith after its determination
      increased by an interest of 3 percentage points over LIBOR (3 months )
      interest rate.

7.6   Grant-back license. PRAECIS hereby grants to UCB and UCB's Affiliates (i)
      during the term of this Agreement, a non-exclusive royalty-free license to
      use any technical information and data relating to the development,
      testing, use or manufacture of the Product (other than relating to
      formulations) which PRAECIS or its Affiliates have not or may conceive,
      develop, acquire or have the ability to license or sublicense during the
      term of this Agreement solely to make Product for PRAECIS, as provided
      under this Agreement and (ii) during the term of this Agreement and
      thereafter (except in the case of termination of this Agreement by PRAECIS
      pursuant to and in accordance with Section 10.2, in which event the
      license granted under this Section 7.6 shall automatically terminate), a
      perpetual, irrevocable non-exclusive, fully paid-up license, with the
      right to grant sublicenses to use said information

                                       16
<PAGE>

      and data solely to make and have made peptides other than Product and
      other than any other LHRH Antagonists.

7.7   Disclosure of technical and regulatory information. In accordance with
      Sections 3.1, 3.2, 4.2, 4.6 and 6.1, as it may become necessary for
      PRAECIS or a Third Party to undertake the manufacture of the Product, UCB
      shall promptly supply to PRAECIS or such Third Party such technical
      information (including without limitation UCB Technical Information) in
      its possession as may be necessary for PRAECIS or such Third Party to
      manufacture the Product in accordance with the Specifications and
      Manufacturing Standards, including without limitation the Product's
      current Drug Master, the SOPs and master batch records.

7.8   UCB Representations and Indemnity as to UCB Technical Information. UCB
      represents and warrants to PRAECIS that (i) UCB is the sole and exclusive
      owner of the UCB Technical Information, and has the full right, power and
      authority to grant the licenses to PRAECIS pursuant to this Section 7, and
      (ii) such grant, and UCB's performance of its obligations hereunder
      (including its use of UCB Technical Information in connection with such
      performance), do not and will not violate or infringe upon the
      intellectual property or other rights of any Third Party. UCB shall
      indemnify and hold PRAECIS harmless with respect to all liabilities,
      claims, demands, actions, suits, losses, costs, damages and expenses
      (including attorneys fees) arising out of or in connection with any claim
      that the use by any Supplied Entities of the UCB Technical Information
      pursuant to and in accordance with any license or sublicense granted under
      this Section 7 violates or infringes upon the rights of any Third Party.

SECTION 8 - CONFIDENTIAL INFORMATION

8.1   Mutual confidentiality undertaking. From time to time during the term of
      this Agreement, the parties will disclose or make available to each other
      Confidential Information in connection with the activities contemplated
      hereunder.

      Each party hereby agrees that it will use Confidential Information
      belonging to the other solely for the purpose(s) for which it was
      disclosed hereunder; and that it will not disclose Confidential
      Information belonging to the other to any Third Party (other than its
      employees and/or consultants reasonably requiring such Confidential
      Information for purposes of this Agreement who are bound by obligations of
      non disclosure and limited use at least as stringent as those contained
      herein) without the express prior written consent of

                                       17
<PAGE>

      the other party, except to regulatory authorities to the extent required
      by law or by applicable regulations.

      Any Confidential Information reasonably classifiable as a trade secret
      shall, as between the parties and their employees, remain a trade secret
      and be fully protected as such in spite of any failure by the disclosing
      party to constantly admonish the receiving party of the trade secret
      nature of the information disclosed or because of any failure of the
      disclosing party to pursue an active course of conduct designed to inform
      the receiving party or its employees that the secrets and information are
      to remain confidential.

8.2   Publicity. The parties further agree that except as otherwise expressly
      required by law, they will not publicly announce or otherwise disclose any
      of the terms and conditions of this Agreement without the express prior
      written consent of the other; provided that the foregoing shall not
      prohibit or restrict in any manner, and no consent shall be required, for
      any such public announcement or disclosure by a party in connection with
      any financing, strategic transaction, acquisition or disposition involving
      such party. Neither party will use the names of the other or any of its
      employees in any advertising, promotional or sales materials relating to
      Product or otherwise, except as required by law or regulatory authorities,
      without the express prior written consent of the other.

SECTION 9 - INDEMNIFICATION

9.1   UCB Indemnity. UCB shall at all times during the term of this Agreement
      and thereafter defend, indemnify and hold PRAECIS and its Affiliates and
      their respective officers, directors, agents, employees and permitted
      assigns, harmless from and against any and all third party claims, suits
      (whether or not groundless), damages, liabilities, costs and expenses
      (whether based on tort, breach of contract, patent infringement, product
      liability or otherwise), including, but not limited to court costs and
      reasonable attorneys fees, arising out of or based on a material breach by
      UCB of any representation, warranty or obligation under this Agreement,
      subject to any limitations set forth in this Agreement.

9.2   PRAECIS Indemnity. PRAECIS shall at all times during the term of this
      Agreement and thereafter defend, indemnify and hold UCB and its Affiliates
      and their respective officers, directors, agents, employees and permitted
      assigns, harmless from and against any and all third party claims, suits
      (whether or not groundless), damages, liabilities, costs and expenses
      (whether

                                       18
<PAGE>

      based on tort, breach of contract, patent infringement, product liability
      or otherwise), including, but not limited to court costs and reasonable
      attorneys fees, (i) arising out of or based on a material breach by
      PRAECIS of any representation, warranty or obligation under this
      Agreement, subject to any limitations set forth in this Agreement or (ii)
      arising out of any sale or use of pharmaceutical compositions containing
      the Product, except, in the case of clause (ii), to the extent determined
      by a court as being attributable to UCB's gross negligence or reckless or
      willful misconduct.

9.3   Third Party Claims. Either party (the "Notifying Party") shall promptly
      notify the other party (the "Indemnifying Party") of the existence of any
      Third Party claim, demand or other action giving rise to a claim for
      indemnification under this Agreement (a "Third Party Claim") and shall
      give the Indemnifying Party a reasonable opportunity to defend the same at
      its own expense and with its own counsel, provided that the Notifying
      Party shall at all times have the right to participate in such defense at
      its own expense. If, within a reasonable time after receipt of notice of a
      Third Party Claim the Indemnifying Party shall fail to so defend, the
      Notifying Party shall have the right, but not the obligation, to defend
      and, with the Indemnifying Party's written consent (not to be unreasonably
      withheld) to compromise or settle (exercising reasonable business
      judgment) the Third Party Claim for the account and at the risk and
      expense of the Indemnifying Party. Each party shall make available to the
      other, at the other's expense, such information and assistance as the
      other shall reasonably request in connection with the defense of a Third
      Party Claim.

9.5   Assistance with Claims. Subject to Sections 9.1 through 9.4 above, each
      party shall, at the request and expense of the other, furnish such
      reasonable assistance as may be required to enable the other party to
      defend itself against Third Party Claims threatened or filed in connection
      with any activities conducted hereunder.

9.6   Consequential losses. Notwithstanding any other provision hereof to the
      contrary, neither party shall be liable to the other party for any
      special, incidental, indirect or consequential damages, such as loss of
      reputation or loss of revenue, profit, downtime costs, and claims of
      customers or others for such damages.

SECTION 10 - TERM AND TERMINATION

                                       19
<PAGE>

10.1  Term. This Agreement shall be in full force and effect as from its
      signature and shall remain in force for an initial period expiring seven
      (7) years from the Launch Date, except that it will be automatically
      renewed for consecutive two (2) year periods, unless terminated by either
      party by written notice given at the latest twenty-four (24) months before
      the expiration of the initial period or any renewal period.

10.2  Earlier termination. This Agreement may be terminated by either party by
      written notice of termination to the other party (i) if the other party
      commits a material and substantial breach or default in the performance of
      any of the provisions of this Agreement and such breach or default is not
      cured within ninety (90) days after the giving of notice (a "Section 10.2
      Default Notice") by the other party specifying such breach or default;
      provided that, subject to the next succeeding proviso, PRAECIS may not
      give a Section 10.2 Default Notice in respect of such a breach or default
      by UCB consisting of a failure to supply Product in accordance with the
      terms hereof until the expiration, without UCB having delivered the Cure
      Evidence, of the ninety (90) day period (extended to one hundred and
      eighty (180) days during the Development Period) referred to in the last
      sentence of Section 4.6; provided further that PRAECIS may give a Section
      10.2 Default Notice prior to the expiration of such ninety (90) day
      period, whether or not UCB has delivered the Cure Evidence prior to such
      expiration, in respect of such a breach or default by UCB consisting of a
      failure to supply Product in accordance with the terms hereof if such a
      breach or default has occurred more than once within any twenty-four month
      period after the Development Period, (ii) forthwith if the other party
      institutes or is the subject of bankruptcy, liquidation or any other
      similar proceedings or (iii) forthwith if a situation of Force Majeure as
      provided by Section 14 continues for more than one hundred and twenty
      (120) days.

10.3  Additional Termination Rights. PRAECIS and UCB shall have the right upon
      written notice thereof to the other to terminate this Agreement if PRAECIS
      either (i) determines that the pharmaceutical formulation of the Product
      is unsafe or not efficacious, or (ii) determines not to commercialize or
      continue to commercialize the Product. PRAECIS shall promptly notify UCB
      if PRAECIS makes the determination referred to in clause (i) or (ii) of
      this Section 10.3.

SECTION 11 - EFFECT OF TERMINATION

                                       20
<PAGE>

11.1  Effects of Termination. In the event of the termination of this Agreement
      for any reason, other than termination by PRAECIS pursuant to Section
      10.2, PRAECIS shall purchase from UCB (i) all inventories of Product
      meeting Specifications and Manufacturing Standards, manufactured by UCB
      based on the forecasted quantities of Product for the first two quarters
      contained in the most recent Forecast preceding such termination and/or
      Purchase Orders delivered by PRAECIS to UCB prior to such termination, at
      the then current price, (ii) all inventories of quality control released
      process intermediates manufactured by UCB based on the forecasted
      quantities of Product for the first two quarters contained in the most
      recent Forecast preceding such termination at a price equal to their
      proportionate part of the price of Product and (iii) all raw materials
      previously purchased by UCB to meet the forecasted quantities of Product
      for the first two quarters contained in the most recent Forecast preceding
      such termination, delivered by PRAECIS to UCB, at UCB's purchase cost.

11.2  Survival. Upon termination of this Agreement, all rights, licenses and
      obligations of the parties hereunder shall immediately cease, except (i)
      for Section 3.7 and Sections 7 through 12 which shall survive, (ii) for
      Sections 6 and 13 through 19 (to the extent applicable to such surviving
      sections referred to in clause (i)), and (iii) that termination of this
      Agreement shall not release a party from any liability for breach of this
      Agreement or from any liability or obligation that arose prior to such
      termination.

11.3  Return of Confidential Information upon termination. Upon termination of
      this Agreement, each party shall promptly return to the other, at the
      other's request, any and all Confidential Information of the other then in
      its possession or under its control, except if such information is covered
      under surviving license rights.

SECTION 12 - REPORTS AND RECORDS

12.1  Notice of certain events. Each party shall promptly notify the other upon
      becoming aware of any of the following events: any confirmed or
      unconfirmed information concerning adverse, serious or unexpected
      occurrences associated with the safety, handling or use of Product;
      unauthorized disclosure of any Confidential Information of the other; any
      alleged infringement of Third Party proprietary rights in connection with
      actions taken hereunder; liability claims relating to Product; and any
      other event that might reasonably be expected to have a material adverse
      effect upon the development, production, sale or distribution of Product.

                                       21
<PAGE>

12.2  Quality Control records. UCB shall maintain records relating to Product in
      accordance with the Manufacturing Standards and shall retain such records
      for not less than ten (10) years after shipment to PRAECIS of the Product
      to which such records relate, and thereafter such records will be
      transferred to PRAECIS if requested. 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 UCB.

                                       22
<PAGE>

SECTION 13 - ASSIGNMENT AND DELEGATION

Neither this Agreement nor any rights hereunder may be assigned or licensed by
either party, without the prior written consent of the other party, except for
(i) assignments or sublicenses to Affiliates which shall occur freely by simple
notice to the other party (provided that no such assignment or sublicense shall
relieve a party from liability for its obligations hereunder), (ii) as provided
in Section 7 and (iii) any such assignment to an entity which acquires control
of the entire business of such party or that part of its business to which this
Agreement relates, whether pursuant to a merger, consolidation, stock purchase
recapitalization, asset sale or otherwise, unless, with respect to this clause
(iii), (A) in the case of such an acquisition of the business (or such part
thereof) of UCB, the acquiring entity is, at the time of such acquisition,
engaged, directly or indirectly, in the business of commercializing and/or
manufacturing products containing any LHRH antagonist or LHRH agonist and is a
direct or substantial competitor of PRAECIS with respect to such business or (B)
in the case of such an acquisition of the business (or such part thereof) of
PRAECIS, the acquiring entity is, at the time of such acquisition, engaged,
directly or indirectly, in the business of the contract manufacture of peptides
and is a direct and substantial competitor of UCB with respect to such business.

SECTION 14 - FORCE MAJEURE

Neither party hereto shall be liable for damages, nor shall this Agreement be
terminable or cancelable (except as provided in Section 10.2) by reason of any
delay or default in such party's performance hereunder if such default or delay
is caused by events beyond such party's reasonable control ("force majeure")
including, but not limited to, acts of God, regulation or law or other action of
any government or agency thereof, war or insurrection, civil commotion
destruction of production facilities or materials by earthquake, fire, flood or
storm, labor disturbances, epidemics, or failure of suppliers (except to the
extent reasonably foreseeable or attributable to such party, public utilities or
common carriers).

Each party shall endeavor to resume its performance hereunder as soon as
reasonably possible if such performance is delayed or interrupted by reason of
force majeure.

SECTION 15 - APPLICABLE LAW - ARBITRATION

This Agreement shall be governed by and interpreted in accordance with the laws
of the state of New York without reference to its conflicts of law principles.
Any dispute arising under this Agreement which cannot be settled amicably shall
be submitted to binding arbitration in accordance with the International Chamber
of

                                       23
<PAGE>

Commerce Rules, by an arbitration panel composed of three members selected in
accordance with such rules, and the decision or award of such panel will be
binding upon the parties without the right of appeal, and may be enforced in any
court of competent jurisdiction. The place of arbitration shall be Atlanta,
Georgia and the language of arbitration shall be English.

Within thirty (30) days after selection of the arbitrators, each party shall
submit to the arbitrators a proposed resolution of the dispute and the reasons
for proposing the resolution. Should either party desire, a joint meeting before
the arbitrators shall be held within thirty (30) days after the end of the above
resolution submission period. Within thirty (30) days after the later of (i) the
end of the above resolution submission period or (ii) the holding of the joint
meeting, the arbitrators shall decide the matter by selecting only one of such
resolutions, and shall have no authority to modify its proposed terms.

SECTION 16 - SEVERABILITY

Should any part of this Agreement be held unenforceable or in conflict with the
applicable laws or regulations of any jurisdiction, the invalid or unenforceable
part or provisions shall be replaced with a provision which accomplishes, to the
extent possible, the original business purpose of such part or provision in a
valid and enforceable manner, and the remainder of this Agreement shall remain
binding upon the parties hereto.

SECTION 17 - NOTICES

Any notice required or permitted to be given under the terms of this Agreement
shall be in writing and shall be sufficiently given if mailed by first class
postage prepaid or given by telefax or delivery to the party for whom is
intended at the address indicated in the preamble or to such other address as
either party hereto may from time to time advise the other party by notice in
writing to the addresses (or facsimile number) first above given. Any notice
given as aforesaid shall be deemed to have been given on the day on which it was
delivered or sent by telefax (with "answer-back" confirmation), if delivered or
sent by telefax, or on the seventh business day excluding Saturday, Sunday and
statutory holidays, following the date on which it was mailed, if mailed,
provided that if there is a postal interruption due to strike, slow down or
other causes, notice shall be given by delivery or telefax only. Any party
hereto may change its address for service from time to time by notice given in
accordance with the foregoing.

SECTION 18 - ENTIRE AGREEMENT

                                       24
<PAGE>

This Agreement (including the Annexes hereto) constitutes the entire
understanding between the parties with respect to the subject matter hereof and
supersedes all prior agreements, negotiations, understandings, representations,
statements and writings relating to it ir any part thereof.

No modification, alteration, waiver or change in any terms of this Agreement
shall be valid or binding upon the parties hereto unless made in writing.

SECTION 19 - ANTITRUST COMPLIANCE

In the event that a governmental authority of competent jurisdiction advises
either of the parties in writing that one or more of the provisions of this
Agreement violate any applicable competition or antitrust law of the USA or the
EU, UCB and PRAECIS agree to amend this agreement to the minimum extent
necessary to render it compatible with such provisions.

SECTION 20 - REPRESENTATIONS AND WARRANTIES

Each party represents and warrants to the other that (i) the execution, delivery
and performance by such party of this Agreement has been duly authorized by all
requisite corporate action on the part of such party, and (ii) this Agreement
has been duly executed and delivered by such party and constitutes the valid and
binding agreement of such party, enforceable against such party in accordance
with is terms.

                                       25
<PAGE>

Done as of this March 12, 1998 (date), in Brussels (place), in two original
copies, each party having received its copy.

UCB-BIOPRODUCTS S.A.                PRAECIS PHARMACEUTICALS
                                    INCORPORATED

/s/ E. Croufer                      /s/ Marc A. Silver
--------------------                ----------------------------
By: E. Croufer                      By: Marc A. Silver
Title: Director                     Title: Vice President,
                                           Corporate Development

/s/ Ph. Proost
--------------------                ----------------------------
By: /s/ Ph. Proost                  By:
Title: Director                     Title:

                                       26
<PAGE>

                                 LIST OF ANNEXES

to the Development and Supply Agreement between UCB-BIOPRODUCTS S.A. and PRAECIS
PHARMACEUTICALS, INC, signed on March 12, 1998.

            ANNEX A           Specifications

            ANNEX B           Development Plan

            ANNEX C           5-year plan (1997-2001)

            ANNEX D           First orders (stability and validations lots)

            ANNEX E           Prices (formula or mode)

            ANNEX F           UCB strategy of synthesis

            ANNEX G           Product requirements allocated to UCB

            ANNEX H           Guidelines provided by PRAECIS' MSDS

                                       27
<PAGE>

                                                                         ANNEX A

PRAECIS
PHARMACEUTICALS
INCORPORATED

                 PPI-149 Drug Substance Tentative Specifications

--------------------------------------------------------------------------------
Parameter                  ***                        Tentative Specification
--------------------------------------------------------------------------------
Appearance                 ***                        White to off-white powder
--------------------------------------------------------------------------------
Identification

o     HPLC                 ***                        ***

o     Mass Spectrometry    ***                        ***

o     Amino acid analysis  ***                        ***
--------------------------------------------------------------------------------
***                        ***                        ***
--------------------------------------------------------------------------------
***                        ***                        ***
--------------------------------------------------------------------------------
Water content              ***                        ***
--------------------------------------------------------------------------------
Specific rotation          ***                        ***
--------------------------------------------------------------------------------
***                        ***                        ***
--------------------------------------------------------------------------------
Residual solvents:         ***                        ***
***
--------------------------------------------------------------------------------
HPLC purity                ***                        ***
- Total impurities
- Individual impurity
--------------------------------------------------------------------------------
Microbial limits           ***                        ***
--------------------------------------------------------------------------------
Bacterial endotoxins       ***                        ***
(LAL)
--------------------------------------------------------------------------------
Peptide content            ***                        ***
--------------------------------------------------------------------------------

Note: The tightening of current tentative specifications is envisioned,
      according to batch analysis data, as part of the NDA process.

              1 Hampshire Street Cambridge Massachusetts 02139-1572
                        Tel 617/494-8400 Fax 617/494-8414

                                       28
<PAGE>

                                                                         ANNEX B

                      OUTLINE OF UCB DEVELOPMENT/WORK PLAN
                             PPI-149 DRUG SUBSTANCE

In synergy with PRAECIS:
1.    Develop and Supply both clinical and commercial quantities of PPI-149 Drug
      Substance prepared according to cGMP and other international quality
      standards.
2.    Prepare/assist in preparation of CMC drug substance filings (US NDA Dec.,
      98) European Filings estimated 2Q99.
3.    Develop, maintain and provide documentation to support approval and
      ongoing commercial supply of drug substance.
      o     Batch Production records
      o     Certificates of Analysis
      o     Development reports
      o     Facilities and instrumentation IQ/QQ/ and PQ
      o     Facilities Drug Master Files, to be included in CMC/DMF
      o     SOP's
      o     Change control
      o     Validation documentation - strategy, plan, protocol, report
      o     CMC section for NDA filing
      o     Stability programs and reports (development and commercial)
4.    Prepare and qualify reference standards
5.    Determine and qualify impurity profile including preparation of impurity
      standards as required.
6.    Supply representative pre-launch material.
7.    Source, secure, and qualify appropriate production facilities for
      commercial volumes and expedite scale up in a timely manner.
8.    Qualify raw material suppliers, dual supply to minimize risk, as
      appropriate.
9.    Outsource qualified intermediates as appropriate
10.   Develop suitable recycle strategy for the filing
11.   Develop/assist in developing a supplemental commercial strategy which
      favorably impacts cycle time and cost of goods.
12.   Maintain regulatory filing with appropriate updates (CBE's, AR's)
13.   Provide comprehensive regulatory support for international approvals and
      commercializations.
14.   Expediently work to correct/improve any findings documented or questions
      generated by regulatory agencies or other quality assessments.

                                       29
<PAGE>

Annex C - 5 Yr. Plan (1998-2002)

                       Year                     Quantity (***)
                       ----                     --------
                       1998                        ***
                       1999                        ***
                       2000                        ***
                       2001                        ***
                       2002                        ***

                                       30
<PAGE>

ANNEX D

to the Development & Supply Agreement between UCB-Bioproducts S.A. and PRAECIS
PHARMACEUTICALS Inc.

Annex D is a part of the above mentioned Agreement.

                          ORDERS & DELIVERIES SCHEDULE
                          DURING THE DEVELOPMENT PERIOD

Reference to Article 4.4 & Article 6.1

o     *** orders for a total amount of *** will be issued at the following
      dates:

1.    P.O. of *** will be issued *** and not later than ***
2.    P.O. of *** will be issued not later than ***
3.    P.O. of *** will be issued not later than ***

These orders are ***

o     Advanced payments: each P.O. will be accompanied by an advanced payment at
      the corresponding date of the P.O. according to the following schedule:

1.    ***: *** USD
2.    ***: *** USD
3.    ***: *** USD

o     Delivery schedule: delivery schedule for the *** is as follows:

1.    ***: deliveries not later than ***;
2.    ***: deliveries not later than ***;
3.    ***:  deliveries not later than ***.

o     Modifications in the dates of issuing P.O. may significantly affect the
      delivery schedule which would be revisited by UCB-Bioproducts should such
      modifications occur.

o     The prices for the *** is ***

                                       31
<PAGE>

ANNEX E

to the Development & Supply Agreement between UCB-Bioproducts S.A. and PRAECIS
PHARMACEUTICALS Inc.

Annex E is part of the above mentioned Agreement.

         ORDERS & DELIVERIES SCHEDULE AFTER DELIVERY OF THE FIRST 112 Kg

Reference to Article 6.1

Pricing structure:  the price structure is defined taking into account ***.

o     For minimum orders of ***:  ***
o     For orders between***: ***
o     For orders above ***: ***

                                       32
<PAGE>

                                                                         ANNEX F

UCB-BIOPRODUCTS S.A.
--------------------------------------------------------------------------------

                          ----------------------------
                          Praecis Pharmaceuticals Inc.

                          UCB Strategy of Syntheses
                          ----------------------------

1.    INTRODUCTION AND OVERVIEW

The manufacturing strategy developed by UCB-Bioproducts for PPI-149 is outlined
on the following chart:

                               ***Chart Omitted***

*** Approximately 10 lines omitted ***

2.    SEQUENCE ASSEMBLY

*** Approximately 18 lines omitted ***

3.    DEPROTECTION

*** Approximately 7 lines omitted ***

4.    PURIFICATION

*** Approximately 15 lines omitted ***

--------------------------------------------------------------------------------
UCB-Bioproducts S.A.          Page 1 of 4                Confidential

                                       33
<PAGE>

                                                                         ANNEX F

5.    ISOLATION

*** Approximately 7 lines omitted ***

6.    PROCESS CONTROLS

*** Approximately 8 lines omitted ***

7.    FLOW CHART

An actual flow chart for a preferred manufacturing strategy is given hereafter,
to illustrate the current process.

      (a)   General Flow Chart
      (b)   Assembly Flow Chart
      (c)   Deprotection Flow Chart
      (d)   Purification Flow Chart

--------------------------------------------------------------------------------
UCB-Bioproducts S.A.          Page 2 of 4                Confidential

                                       34
<PAGE>

UCB-BIOPRODUCTS S.A.
--------------------------------------------------------------------------------

                               Flow Chart Omitted

                                       35
<PAGE>

                                                                         ANNEX G

                 to the supply agreement between PRAECIS and UCB

                PERCENTAGE OF PRODUCT REQUIREMENTS (article 3.1.)

Launch year             ***

first                   ***

second                  ***

third                   ***

fourth                  ***

fifth and following     ***

                                       36
<PAGE>

                                                                         ANNEX H

                           Material Safety Data Sheet

PPI-149-Depot (abarelix Depot)           PRAECIS Pharmaceuticals, Incorporated
                                         One Hampshire St., 5th Floor
                                         Cambridge, MA  02139
                                         617-894-8400

Section I: Identification

Trade Name: abarelix or abarelix depot
Synonyms:   PPI-149, R3827,
CAS#:       None
M.W.        ***
MF:         ***

Section II: Hazardous Ingredients

None

Section III: Physical Data

Appearance: White to Off white powder
Odor:       Odorless
Solubility: ***

Section IV: Fire and Explosion Information

Not considered to be a fire or explosion hazard.
Use any means suitable for extinguishing surrounding fire.
In the event of a fire, wear protective clothing and NIOSH-approved
      self-contained breathing apparatus.

Section V: Health Hazards

*** Approximately 12 lines omitted ***

Toxicity -
      ***

First Aid -
      If swallowed, wash out mouth with water provided person is conscious
      Call a Physician

                                       37
<PAGE>

      In case of skin contact, flush with copious amounts of water for at least
            15 minutes, remove contaminated clothing and call a Physician.
      If inhaled, remove to fresh air. If breathing becomes difficult, call a
            physician.
      In case of contact with eyes, flush with copious amounts of water for at
            least 15 minutes. Call a physician.

Section VI: Reactivity Data

Stability:
      Stable under ordinary storage conditions.
      Preferably store cool and dry.
Hazardous combustion or decomposition products:
      toxic fumes of carbon monoxide, carbon dioxide, nitrogen oxides
Hazardous polymerization
      will not occur.

Section VII: Spill or Leak Procedures

Steps to be taken if material is released or spilled -
      Wear Respirator, chemical safety goggles, rubber boots and rubber gloves.
      Sweep up, place in a bag and hold for disposal.
            ventilate area and wash spill after pickup is complete.
Waste Disposal Method -
      Dissolve or mix in a combustible solvent and burn in a chemical
            incinerator equipped with an afterburner and scrubber.
      Observe all Federal, State, and Local Laws.

Section VIII: Precautions to be Taken in Handling and Storage

NIOSH/MSHA approved respirator
Mechanical exhaust
Chemical resistant gloves
Chemical safety Goggles

Caution: The Chemical, Physical and Toxicological properties of this molecule
      have not been thoroughly investigated.
Exercise Due Care.
Target Organs:  ***

The above information is believed to be correct but does not purport to be all
inclusive and are offered as a guide for your consideration, investigation, and
verification. PRAECIS makes no guarantee of the accuracy or the completeness of
the data and shall not be held liable for any damage resulting from handling or
from direct contact with the above product.

Section IX: Special Precautions

None

                                       38<PAGE>

                                                                   EXHIBIT 10.13

              CONFIDENTIAL TREATMENT HAS BEEN REQUESTED FOR CERTAIN
               PORTIONS OF THIS DOCUMENT. SUCH PORTIONS HAVE BEEN
                REDACTED AND MARKED WITH ASTERISKS (**). THE NON-
               REDACTED VERSION OF THIS DOCUMENT HAS BEEN SENT TO
               THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO
                   AN APPLICATION FOR CONFIDENTIAL TREATMENT.

                                SUPPLY AGREEMENT

      THIS AGREEMENT (the "Agreement") dated as of this twenty-third (23) day of
July, 1998, by and between PRAECIS PHARMACEUTICALS INCORPORATED, a Delaware
corporation, of 1 Hampshire Street, Cambridge, MA 02139-1572 ("PRAECIS") and
Salsbury Chemicals, Inc., an Iowa corporation of 1205 Eleventh Street, Charles
City, Iowa 50616-3466 ("SALSBURY").

                                   WITNESSETH:

      WHEREAS, PRAECIS is in the business of developing and commercializing
pharmaceutical chemicals and has submitted information regarding PPI-149 peptide
(the "Peptide") in a PPI-149-CMC formulation ("CMC") to the Federal Food and
Drug Administration ("FDA") for testing and approval; and

      WHEREAS, PRAECIS and SALSBURY have entered into a letter agreement dated
November 28, 1997 (the "Letter Agreement") which provides, among other things,
for SALSBURY to manufacture and supply PRAECIS, and for PRAECIS to purchase from
SALSBURY, certain qualification batches of CMC using the Peptide supplied by
PRAECIS as a raw ingredient, and for the parties to negotiate and execute a
mutually agreeable Supply Agreement with respect to CMC; and

      WHEREAS, SALSBURY owns and operates a pilot plant pharmaceutical
manufacturing facility (the "Facility") in Charles City, Iowa, meeting cGMP
requirements. SALSBURY will be required to design, engineer, install and qualify
additional equipment and facility which will enable SALSBURY to produce
commercial quantities of CMC; and

      WHEREAS, the parties have reached agreement as set forth herein with
respect to the terms of the Supply Agreement contemplated by the Letter
Agreement.
<PAGE>

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

1. MANUFACTURE

A. Subject to the terms and conditions set forth herein, during the Term (as
hereinafter defined), SALSBURY shall manufacture for and supply to PRAECIS, and
PRAECIS shall purchase from SALSBURY, PRAECIS's requirements of CMC.

B. Not withstanding Section 1A. above, PRAECIS retains the right, at its sole
option, to qualify one or more alternative suppliers at any time during the
Term. Upon completion of such qualification, PRAECIS may order up to ** (**%) of
its annual requirements for CMC from such alternative suppliers; provided that,
without limitation of its other remedies, PRAECIS may order a greater percent
(up to 100%) of such requirements from such alternative suppliers if SALSBURY is
unable to meet is supply obligations hereunder.

2. TERM

Subject to earlier termination as provided in Section 20 below or extension as
provided in this Section 2, this Agreement shall commence on the date hereof and
shall continue for a period of seven (7) years (the "Original Term"); provided
that commencing with the seventh anniversary of the date hereof and on each
subsequent anniversary, the term of this Agreement shall automatically be
extended for an additional twelve months from the then current expiration date,
unless either party provides written notice to the other party electing not to
extend the term of this Agreement, such notice to be provided at least twelve
(12) months prior to the applicable anniversary date (the term of this
Agreement, as so extended or earlier terminated, being referred so as the
"Term").

3. CONFIDENTIALITY

The parties hereto have entered into a Non-Disclosure Agreement dated as of
September 2, 1997 (the "Non-Disclosure Agreement") relating to the Technical
Information (as hereinafter defined) and such agreement is attached hereto as
Exhibit A and is incorporated herein and made part hereof. The parties agree
that all Technical or Confidential Information disclosed by either party to the
other shall be covered under the terms of the Non-Disclosure Agreement and,
notwithstanding any provision of the Non-Disclosure Agreement, shall be held
confidential as provided in the Non-Disclosure Agreement from time of disclosure
until ten (10) years after the end of the Term.

                                       2
<PAGE>

4. PRODUCTION UNIT AND EQUIPMENT

A. The parties recognize that additional equipment must be installed at the
Facility to permit SALSBURY to produce CMC in the required commercial
quantities. SALSBURY shall be responsible for the design, engineering,
installation and qualification of the additional equipment and facility for the
CMC Production Facility (the "Production Facility"), and PRAECIS shall be
responsible for the capital and other costs incurred by SALSBURY associated with
constructing and completing the Production Facility (the "Costs"). The costs
shall be recovered by SALSBURY in monthly payments by PRAECIS (on an invoice
pass through basis) over the length of the engineering, construction and
commission phase of the project. SALSBURY shall provide the project management
team and the Costs shall be capped at Four Million Nine Hundred Thousand Dollars
($4,900.00). The Production Facility shall be dedicated to PRAECIS over the
Original Term of this Agreement. SALSBURY shall make best efforts to commission
the Production Facility in April 1999. Although the Costs shall be paid for by
PRAECIS, SALSBURY shall own the Production Facility and all installed equipment
and PRAECIS shall have no claim thereon whatsoever.

B. Upon signing of this Agreement, PRAECIS shall execute a binding Purchase
Order for ** of CMC at a price of ** ($**) **, F.O.B. Charles City, Iowa, for
delivery as soon as practical after completion and commissioning of the
Production Facility. SALSBURY's obligation to complete the Production Facility
shall be subject to PRAECIS's execution, not later than October 1, 1998, of a
binding Purchase Order for at least an additional ** (**) ** of CMC at a price
of ** ($**) **, for delivery in calendar year 1999.

C. In the event that PRAECIS does not proceed with the commercialization of CMC,
either because of its inability to obtain the requisite regulatory approvals or
for any other reason including its inability to provide SALSBURY with Peptide
and other raw materials necessary to fill such order, PRAECIS may instead pay to
SALSBURY the amount which it would have been required to pay (at time it would
have been required to make such payment) under Section 4(B) above had PRAECIS
actually received both shipments of CMC.

D. All CMC will be billed at the time the product successfully passes Quality
Control and Quality Assurance. Payment is required 30 days from invoice date.
Ownership and risk of loss passes to PRAECIS at the time of invoicing.

5. FORECASTING

                                       3
<PAGE>

A. Thirty (30) days prior to the start of each calendar quarter during the Term,
PRAECIS will provide SALSBURY with a written non-binding four quarter rolling
forecast estimating PRAECIS's CMC requirements for the next four quarters or for
each remaining quarter if the remainder of the Term is less than four quarters
and, without limitation of SALSBURY's supply obligations under Section 1 hereof,
SALSBURY may use such orders as the basis to schedule production.

B. At least thirty (30) days prior to the start of each month during the Term
PRAECIS shall give SALSBURY firm purchase orders for its CMC requirements during
the next month. SALSBURY shall deliver CMC to PRAECIS not later than
thirty-seven (37) days from the date of SALSBURY's receipt of a firm Purchase
Order, the Peptide and other raw materials.

C. If PRAECIS's actual requirements in any calendar quarter exceed the most
recent forecast for that quarter by more than ** (**%), without limitation of
SALSBURY's supply obligations under Section 1 with respect to an amount of CMC
equal to ** (**%) of such forecasted amount (the "**% Amount"), SALSBURY shall
only be required to use best efforts to meet PRAECIS' requirements in excess of
the **% Amount.

6. PRICE

A. Following FDA (or equivalent foreign regulatory) approval of the Peptide in a
CMC formulation, the base price per kilogram for quantities up to ** (**) ** per
calendar year shall be ** ($**) **, and ** ($**) ** for any quantities in excess
of ** (**) ** in any calendar year. All prices are F.O.B. Charles City, Iowa.
CMC will be billed at the time the CMC successfully passes Quality Control and
Quality Assurance. Payment is required thirty (30) days from invoice date.
Ownership and risk of loss passes to PRAECIS at the time of invoicing.

B. Following FDA (or equivalent foreign regulatory) approval of the Peptide in a
CMC formulation, the base price will be adjusted annually by SALSBURY by an
amount not to exceed the change in the published Produce Price Index for
Chemicals and Allied Products (PPI), as published by the Bureau of Labor
Statistics of the U.S. Department of Labor. The parties agree that the PPI
factor adjustment will begin at the average for June 1998 at 144.9.

C. SALSBURY shall use best efforts to maximize the concentration of active
Peptide in CMC and to maximize the conversion of Peptide to CMC, consistent with
the In-Process Limits (as defined herein).

                                       4
<PAGE>

D. The parties shall seek to establish a mutually agreed program to reduce
manufacturing costs and improvement yields in the CMC process (the "Program").
Any cost savings or yield improvements resulting from the Program shall be ** by
the parties and will be reflected in annual price adjustments. For yield
improvements, if Yield is defined as the mole of CMC produce per mole of peptide
reacted, and if Yield becomes higher, the sales price of CMC is adjusted upward
as follows:

         Adjusted Price = **

         Yield #1 is the Average Yield of the 3-kilogram validation lots
         Yield #2 is a future Yield

E. Each party shall bear its own costs in the Program, provided that PRAECIS
shall bear the costs of any raw material losses in the Program with the
exception of raw material losses due to negligence or willful misconduct by
SALSBURY which shall be borne entirely by SALSBURY. In the event new capital is
required to implement a cost savings program both parties will share the cost
equally.

7. RAW MATERIALS, SHIPPING AND WAREHOUSING

A. PRAECIS will provide, at PRAECIS's sole risk and expense, all Peptide and
other raw materials (except WFI water which will be supplied by SALSBURY),
freight prepaid, to the Production Facility, in such amounts and at such times
as shall be jointly determined by SALSBURY and PRAECIS to be required for
manufacture ofCMCordered by PRAECIS; provided that with respect to any purchase
order, PRAECIS shall not be required to supply SALSBURY with Peptide and other
raw materials required to fill such order more than fifteen (15) days prior to
submission to SALSBURY of such purchase order. Risk of loss of Peptide and the
other raw materials delivered by PRAECIS shall pass to SALSBURY when safely
delivered at the Production Facility.

B. PRAECIS will provide a Certificate of Analysis ("CA") for each lot of Peptide
delivered to SALSBURY for use in producing CMC. SALSBURY will perform a cGMP
identity test upon receipt of Peptide. Any cost of loss resulting from
SALSBURY's use of off-spec material in reliance on PRAECIS's CA shall be
PRAECIS's sole responsibility unless such off-spec condition shall be the fault
of SALSBURY who shall then bear such risk. SALSBURY shall be responsible for any
rework or loss rising from actions or omissions of SALSBURY, including any costs
to rework or replace PRAECIS-supplied materials.

C. Upon completion of manufacture, SALSBURY will arrange for shipment of CMC to
PRAECIS designated locations, F.O.B. the Facility. CMC will be billed at

                                       5
<PAGE>

the time the product successfully passes Quality Control and Quality Assurance
as evidenced by receipt of a CA. Payment is required 30 days from invoice date.
Ownership and risk of loss passes to PRAECIS at the time of invoicing.

8. ANALYTICAL SERVICES

A. PRAECIS desires to have SALSBURY provided a CA for each lot of CMC
manufactured at SALSBURY's facility according to the in-process limits attached
hereto as Exhibit B (the "In-Process Limits"). A CA will accompany each lot of
CMC shipped.

B. SALSBURY and PRAECIS agree to jointly establish a release procedure for CMC
manufactured by SALSBURY. SALSBURY shall obtain prior written approval from
PRAECIS for any exemption in the In-Process Limits. If, at any time, CMC
produced for PRAECIS fails to meet the In-Process Limits, PRAECIS and SALSBURY
agree to work together in good faith to attempt to resolve any such problem
through rework of the CMC, as appropriate, and SALSBURY will perform a failure
investigation and report results to PRAECIS.

C. Any changes to the In-Process Limits must be approved and signed by
authorized representatives of both parties as may be designated from time to
time.

D. SALSBURY will maintain retention samples no greater than 0.5 gram of each lot
of CMCproduced for a period of (1) year from the date of shipment. Such samples
will be returned to PRAECIS or it's designate upon request by PRAECIS.

E. Analytical methods will be validated and reports will be provided to PRAECIS.
As necessary, cross-validation will be performed with other parties.

9. INVOICING AND INVENTORIES

SALSBURY shall invoice PRAECIS immediately following completion of CMC
manufacture, packaging and Quality Control and Quality Assurance approval.
Payment shall be due from PRAECIS within thirty (30) days of date of SALSBURY's
invoice. Ownership and risk of loss passes to PRAECIS as the time of invoicing.
Bill of Lading for each shipment will accompany the shipment. Within ten (10)
days following the end of each month during the Term, SALSBURY shall submit the
following to PRAECIS.

A. Inventory of CMC at the end of each calendar month and a listing of each
shipment of CMC made during such calendar month showing truck or car numbers,
date, weight and number of containers; and

                                       6
<PAGE>

B. Inventory of Peptide supplied by PRAECIS at the end of each calendar month;
and

C. Total amount of Peptide used in the processing of CMC during such calendar
month.

10. CHANGE IN MATERIAL, PROCESS OR PROCEDURE.

SALSBURY shall obtain prior written approval of PRAECIS for any change in
materials or methods of manufacture or analysis employed in producing CMC
hereunder, and SALSBURY shall promptly notify PRAECIS of and implement any
changes advised by any appropriate regulatory agency or other authority.

11. FACILITY INSPECTION

A. Upon reasonable prior notice, PRAECIS and its Licensees who agree to be bound
by the terms of Non-Disclosure Agreement shall have the right to inspect and
audit the Production Facility, provided that if PRAECIS requests an inspection
at a time when such inspection would not present a significant risk of
disclosure of confidential information of SALSBURY or a customer of SALSBURY
other than PRAECIS. SALSBURY will, if practical, arrange for the inspection to
take place within five (5) working days from the date of said request.

B. PRAECIS employees and Licensees who are present at the Production Facility
shall comply with all SALSBURY's rules, regulations and instructions from
SALSBURY's employees, and PRAECIS assumes all liability, costs and loss of
whatever kind directly resulting from the presence of PRAECIS's employees at the
Production Facility, provided that SALSBURY shall be responsible for its
negligence, recklessness or willful misconduct.

12. PACKAGING

The CMC supplied by SALSBURY hereunder shall be packaged in containers specified
by PRAECIS (but supplied by SALSBURY) and shall bear labels supplied by SALSBURY
using label copy supplied by PRAECIS. PRAECIS shall be solely responsible for
complying with any applicable laws, regulations, rules or ordinances (federal,
state or local) relating to the container and the contents of the labels. In
addition to the container specifications and labels, PRAECIS shall also provide
SALSBURY with all the packaging component specifications necessary to package
the CMC.

                                       7
<PAGE>

13. WASTE DISPOSAL

SALSBURY is responsible for all costs and liabilities associated with the
transport and approved disposal of waste streams generated by the manufacture of
CMC at the Facility. Upon request, SALSBURY will provide to PRAECIS copies of
all manifests for shipping CMC waste streams from the Production Facility. At
PRAECIS option and PRAECIS' expense, all waste will be shipped to PRAECIS or
it's designate.

14. SAFETY INFORMATION

PRAECIS will supply Material Safety Data Sheets ("MSDS") for Peptide and CMC.
SALSBURY will obtain from their raw material suppliers all other raw material
MSDS's utilized in the manufacture of the CMC before said manufacture will
begin.

15. REGULATORY APPROVALS

SALSBURY is responsible for securing and complying with the necessary worldwide
regulatory approvals for the manufacture and supply of CMCand any substitute
CMC's at the Facility, in the case where modifications to the manufacture and
supply of CMC are not required by regulatory agencies and PRAECIS requests
modifications to the manufacture and supply of CMC, PRAECIS shall reimburse
SALSBURY promptly for all increased approval and compliance costs. If PRAECIS
offers and SALSBURY accepts substitute or additional CMC's, PRAECIS shall be
responsible for all costs of regulatory compliance, and shall reimburse SALSBURY
promptly for all such approval and compliance costs. PRAECIS shall be solely
responsible for obtaining all regulatory approvals required for the sale of CMC
to PRAECIS's customers.

16. TECHNICAL INFORMATION

A. PRAECIS has developed and is the owner of certain technical information
required to produce CMC (the "Technical Information"), and except to the extent
provided in this Section 16A, SALSBURY shall have no rights of any kind with
respect to any Technical Information. PRAECIS hereby licenses the Technical
Information to SALSBURY on non-exclusive, royalty-free basis for the sole
purpose of producing CMC for PRAECIS during the Term.

B. Any and all improvements, discoveries and/or inventions, whether or not
patentable, which may be made or conceived by SALSBURY during the Term which is
based on or incorporates or uses any Technical Information, or otherwise arises
out

                                       8
<PAGE>

of SALSBURY's performance of its obligations hereunder shall be the sole and
exclusive property of PRAECIS. Process or equipment information or
recommendations provided by PRAECIS and/or inventions relating to such process
and/or equipment information or recommendations, which arise in whole or in part
out of such information shall also be the sole and exclusive property of
PRAECIS. SALSBURY shall provide full disclosure to PRAECIS of all such
improvements, discoveries, and/or inventions described above, and shall execute
or cause to be executed any and all applications, assignments, or other
instruments which PRAECIS shall deem necessary or useful in order to apply for,
obtain and protect Patents of the United States and all foreign countries with
respect to any and all such discoveries, improvements and/or inventions and
shall, and hereby does, assign and convey to PRAECIS the sole and exclusive
right, title, and interest in and to any and all such discoveries, improvements
and/or inventions and to all patent applications and patents thereon. PRAECIS
will bear the cost of preparation of all such patent applications and patents.
PRAECIS shall grant SALSBURY a royalty-free, perpetual, worldwide license under
any patent so obtained and agrees that SALSBURY can utilize any operational
knowledge in other areas of its business; provided that such license shall not
extend to, and SALSBURY shall not utilize any operational knowledge to provide,
products, services or processes which are competitive with the business of
PRAECIS.

17. WARRANTIES

A. SALSBURY warrants and represents:

      (i) that all CMC manufactured by SALSBURY hereunder will meet the
In-Process Limits and will be made in accordance with worldwide cGMP;

      (ii) that the Production Facility (and the operations thereof) is, and
shall remain during the term hereof, in substantial compliance with all
applicable laws, statutes, rules, regulations or ordinances (federal, state or
local) including but not limited to those enforced by the U.S. Environmental
Protection Agency and the Occupational Safety and Health Administration.

B. PRAECIS warrants and represents:

      (i) that all Peptide and other raw materials delivered to SALSBURY for use
in the manufacture of CMC hereunder shall meet the In-Process Limits shall be
suitable for use in the CMC;

                                       9
<PAGE>

      (ii) that it has the right to use the Technical Information and to grant
to SALSBURY the license granted pursuant to Section 18A. hereof;

18. INDEMNIFICATION

A. SALSBURY shall protect, defend, indemnify and hold harmless PRAECIS and its
affiliates, and their respective directors, officers, employees and agents, from
and against any and all actions, liability, loss, damage, cost or expense
(including reasonable attorney's fees) arising out of, incident to, or in any
way connected with, any breach by SALSBURY of this Agreement, including without
limitation any representations or warranties of SALSBURY set forth herein.
PRAECIS shall give SALSBURY prompt notice of any claim on which PRAECIS seeks
indemnification from SALSBURY under this Section.

B. (i) PRAECIS shall protect, defend, indemnify and hold harmless SALSBURY and
its affiliates, and their respective directors, officers, employees and agents,
from and against any and all actions, liability, loss, damage, cost or expense
(including reasonable attorney's fees) arising out of, incident to, or in any
way connected with, any breach by PRAECIS of this Agreement, including without
limitation any representations or warranties of PRAECIS set forth herein.
SALSBURY shall give PRAECIS prompt notice of any claim on which SALSBURY seeks
indemnification from PRAECIS under this Section.

      (ii) it is understood that SALSBURY has no control over the ultimate use
of the CMC once the CMC leaves the Facility, and SALSBURY shall have no
liability in connection with any use made of the CMC, except to the extent
attributable to SALSBURY's gross negligence, willful misconduct or breach of
this Agreement, including without limitation any breach of any representations
or warranties of SALSBURY set forth herein. PRAECIS shall protect, defend,
indemnify and hold harmless SALSBURY and its affiliates, and their respective
directors, officers, employees and agents, from and against any and all actions,
liability, loss, damage, cost or expense (including reasonable attorney's fees):

      (a)   arising out of or in connection with the sale or use of the CMC; or

      (b)   arising out of any claim that the CMC, the Technology or the
            manufacturing process furnished by PRAECIS infringes any patent or
            other intellectual property right of any third party or that the
            labels of the CMC infringe any patent, copyright or trademark of any
            third party; or

                                       10
<PAGE>

      (c)   otherwise arising out of the labeling or packaging of the CMC.
            Prompt notice of any such claim asserted against SALSBURY shall be
            given by SALSBURY to PRAECIS.

      (d)   notwithstanding the foregoing provisions of this paragraph (ii),
            PRAECIS shall have no indemnify obligation under this paragraph (ii)
            to the extent any action, liability, loss, damage, cost or expense
            (including reasonable attorney's fees) referred to in this paragraph
            (ii) is attributable to SALSBURY's gross negligence, willful
            misconduct or breach of this Agreement, including without limitation
            any breach of any representations or warranties of SALSBURY set
            forth herein.

19. INSURANCE

SALSBURY shall furnish to PRAECIS, at PRAECIS request, but not later than the
date of the commencement of manufacture of CMChereunder by SALSBURY, adequate
evidence of the fact (including amounts of coverage) of insurance coverage, more
particularly, worker's compensation, employer's liability and comprehensive
general liability insurance, provided that self-insurance shall be permitted.
SALSBURY shall carry (and provide evidence to PRAECIS of) appropriate insurance
to cover loss or damage to in-process CMCand in-process Peptide.

20. TERMINATION FOR CAUSE

Either party may terminate this Agreement (and upon any such termination the
Term shall automatically end), by giving the other party ninety (90) days
written notice thereof, in any of the following events:

A. the cessation of business activities by the other party, except as the result
of the merger or consolidation referred to in Section 26 hereof;

B. (i) the admission by the other party of its inability to pay its debts as
they mature;

      (ii) the filing of a petition for bankruptcy or similar proceedings by the
other party, but excluding a proceeding for reorganization pursuant to Chapter
11 of the Federal Bankruptcy Code by the other party providing that the party
continues in the operation of its business and further provided that the party
shall otherwise continue to perform its obligations under this Agreement; or

                                       11
<PAGE>

      (iii) a general assignment for the benefit of creditors or similar acts by
the other party.

C. In the event this Agreement is terminated during the Production Facility
construction phase, PRAECIS shall pay SALSBURY the Costs incurred or irrevocably
committed to through the date of termination.

D. In the event that Salsbury does not perform under the terms of the Agreement,
Salsbury will nevertheless use its best efforts to continue to supply Product
until PRAECIS has an alternate validated replacement reproduction facility on
line. Salsbury will assist PRAECIS with the Technology transfer. In no case will
Salsbury's best efforts obligation extend beyond the Original Term

E. Any act of material dishonesty or violation of laws or regulations by the
other party in relation to this Agreement which could affect that party's
ability to perform hereunder.

F. The parties agree that assignment or transfer of this Agreement as provided
in Section 24 might be an alternative to termination under this provision.

G. The material breach by the other party of this Agreement, including without
limitation any such other party's representations or warranties set forth
herein, which, if curable, continues uncured for a period of ninety (90) days
after notice thereof is given to such other party.

21. FORCE MAJEURE

A. Neither party shall be liable for failure or delay of performance, except
with respect to PRAECIS's obligations of payment under Section 6(A). hereunder,
by reason of any Acts of God, riots, insurrections, strikes, lockouts,
governmental action or regulation or any other cause beyond the reasonable
control of such party. In the event of any such occurrence, deliveries of any
order placed and accepted under this Agreement or the appropriate portion of
such delivery shall be suspended for the duration of the period during which
such cause continues, provided that no such act or occurrence shall relieve
PRAECIS from its obligations of payment hereunder.

B. In the event of partial failure or delay of performance hereunder by reason
of cause described in Section 21(A). above, unaffected portions of the Facility
may be allocated to perform hereunder on an equivalent basis, but only if such
allocation is determined by PRAECIS, prior to manufacture, to be in accordance
with cGMP.

                                       12
<PAGE>

22. ARBITRATION

A. Any dispute, controversy or claim arising out of or relating to this
Agreement, or the breach hereof shall be settled by arbitration in New Jersey in
accordance with the Rules of the American Arbitration Association and judgment
upon the award rendered by the Arbitrator(s) may be entered in any court having
jurisdiction thereof. Written notice of demand for arbitration shall be filed
with the other party to the Agreement and with the American Arbitration
Association within a reasonable time after the dispute, controversy or claim has
arisen.

B. In any such arbitration proceeding in which damages may be awarded to PRAECIS
based on SALSBURY's inability or failure to meet its supply obligations under
this Agreement, such damages may include reasonably foreseeable losses arising
from such inability or failure, including loss of sales and costs and expenses
to obtain an alternate supply (including qualification of an alternate
supplier), provided that damages consisting of loss of sales may not be awarded
based on SALSBURY's inability or failure to supply to the extent the cause of
such inability or failure is one or more force majeure events described in
Section 21A. above.

23. APPLICABLE LAW; ENTIRE AGREEMENT

This Agreement (including the Exhibits hereto), which shall be interpreted and
enforced in accordance with the laws of the State of Iowa, constitutes the
entire agreement between the parties, and it is expressly agreed that any and
all prior understandings or agreements relating to the subject matter of this
Agreement, whether oral or written, are automatically canceled by the execution
of this Agreement, except that the respective obligations of the parties set
forth in the Letter Agreement with respect to the manufacture, delivery and
payment for qualification lots of CMCshall remain in full force and effect. The
terms and conditions set forth herein may only be modified in a subsequent
writing signed by both parties.

24. ASSIGNMENT

This Agreement may not be assigned or transferred by either party without the
prior written consent of the other party, which consent shall not be
unreasonably withheld, except (i) that either party may assign its rights
hereunder to a subsidiary or controlled affiliated company, provided that no
such assignment shall release the assigning party from its obligation hereunder
and (ii) for any such assignment by PRAECIS to an entity which this Agreement
relates, whether pursuant to a merger, consolidation, stock purchase,
recapitalization, asset sale or otherwise.

                                       13
<PAGE>

25. INDEPENDENT CONTRACTOR

SALSBURY's status hereunder is that of an independent contractor. SALSBURY is
not, and shall not, represent itself to be PRAECIS's agent or representative.
SALSBURY shall not contact or communicate with PRAECIS's customers for the CMCin
any manner or for any reason unless PRAECIS shall have consented thereto in
advance.

26. NOTICES

A. All notices given pursuant to this Agreement shall be in writing and shall be
(i) hand delivered, or (ii) sent by (a) recognized overnight courier service,
(b) certified or registered mail, return receipt requested, or (c) facsimile,
addressed as follows:

          To PRAECIS:
                      PRAECIS PHARMACEUTICALS Inc.
                      1 Hampshire Street
                      Cambridge, MA 02139-1572
                      Attention: Vice President, Corporate Development
                      Facsimile No.: 617-494-8414

          To SALSBURY:
                      Salsbury Chemicals, Inc.
                      1205 Eleventh Street
                      Charles City, Iowa 50616
                      Attention: Vice President, Sales and Marketing
                      Facsimile No.: 515-257-1020

                 with a copy to:

                      Cambrex Corporation
                      One Meadowlands Plaza
                      East Rutherford, NJ 07073
                      Attention: Corporate Secretary
                      Facsimile No.: 201-804-9851

B. Notice shall be effective seven business days after the time of posting if
sent by mail (or on the date of delivery if hand delivered including by
overnight courier) and on the date sent (if sent by facsimile with receipt
confirmed), unless the notice relates to changing a party's address for purposes
of giving notice, in which event the notice shall be effective as of the time
received.

                                       14
<PAGE>

      IN WITNESS WHEREOF, the parties have executed this Agreement as of the day
and year first above written.

Witnesseth:                              PRAECIS PHARMACEUTICALS INC.

By:/s/ Kevin McLaughlin                  By:/s/ Marc A. Silver
       ------------------                ---------------------

  Name:Kevin McLaughlin                  Name:Marc A. Silver
  ---------------------                  -------------------

                                         Title:Vice President
                                         --------------------

                                         Date:  7/23/98
                                         --------------

Witnesseth:                              SALSBURY CHEMICALS, INC.

By:/s/ Nicholas P. Johnson               By:/s/ Dennis P. Bauer
   -----------------------                  -------------------

Name:Nicholas P. Johnson                 Name:Dennis P. Bauer
------------------------                 --------------------

                                         Title:Vice President, Sales & Marketing
                                               ---------------------------------

                                         Date:June 23, 1998
                                              ---------------

                                       15
<PAGE>

                                    EXHIBIT A
                        CONFIDENTIAL DISCLOSURE AGREEMENT

AGREEMENT dated of September 2, 1997, by and between PRAECIS Pharmaceuticals,
Inc. ("PRAECIS"), a Delaware corporation, having its principal place of business
at One Hampshire Street, Cambridge, Massachusetts 02139, and Salsbury Chemicals,
Inc., an Iowa corporation having its principal place of business at 1205 11th
Street, Charles City, Iowa, 50616-3466 ("CONFIDANT").

1.    Background

      PRAECIS and CONFIDANT intend to engage in discussions in order to evaluate
      a potential business relationship between the two parties. In the course
      of such discussions and negotiations, it is anticipated that the CONFIDANT
      may acquire PRAECIS's proprietary or confidential information
      ("CONFIDENTIAL INFORMATION") relating to PRAECIS's research and
      development programs including its LHRH and drug formulation programs,
      specifically; compound structures, compositions, formulation strategies,
      compound characteristics, methods of preparation, methods of testing, uses
      of, mechanisms of action, biologic activity, marketing research, clinical
      development and registration strategies, research and management
      personnel, technical and economic information, business concepts, proposed
      corporate partnership arrangements, and other information relating to
      PRAECIS business affairs and know how, for the purpose of enabling
      CONFIDANT to evaluate the feasibility of such business relationship.
      PRAECIS and CONFIDANT have entered into this Agreement in order to protect
      their rights with respect to any such information in accordance with the
      terms of this Agreement.

2.    Disclosure of CONFIDENTIAL INFORMATION.

      CONFIDANT shall hold in confidence and shall not disclose to any third
      party any CONFIDENTIAL INFORMATION disclosed to it by PRAECIS, except as
      expressly permitted under this Agreement. In order for such information to
      be subject to the obligations set forth herein, it must be disclosed in
      written or other tangible form, and clearly marked "confidential". If
      disclosed orally, such information must be reduced to written or tangible
      form within 30 days of initial disclosure, so marked and delivered to
      CONFIDANT. CONFIDANT shall use such CONFIDENTIAL INFORMATION only for the
      purpose for which it was disclosed and shall not exploit such CONFIDENTIAL
      INFORMATION for its own benefit or the benefit of another without the
      prior written consent of PRAECIS. CONFIDANT shall disclose CONFIDENTIAL
      INFORMATION of PRAECIS only to its employees and consul-

                                       16
<PAGE>

      tants who have need to know such CONFIDENTIAL INFORMATION in the course of
      the performance of their duties and who are legally bound to protect the
      confidentiality of such CONFIDENTIAL INFORMATION.

3.    Protection of CONFIDENTIAL INFORMATION.

      CONFIDANT shall protect PRAECIS's CONFIDENTIAL INFORMATION by using the
      same degree of care, but not less than a reasonable degree of care, to
      prevent the unauthorized use, dissemination, publication of, or access to,
      PRAECIS's CONFIDENTIAL INFORMATION as it uses to protect its own
      CONFIDENTIAL INFORMATION.

4.    Property Rights in CONFIDENTIAL INFORMATION.

      CONFIDENTIAL INFORMATION shall remain the property of PRAECIS
      notwithstanding disclosure hereunder. Disclosure of CONFIDENTIAL
      INFORMATION hereunder shall not be deemed to constitute a grant, by
      implication or otherwise, of a right or license to the CONFIDENTIAL
      INFORMATION or in any patents or patent applications of the PRAECIS.

5.    Limitation on Obligations.

      The obligations of each party specified in Section 3 above shall not apply
      to any CONFIDENTIAL INFORMATION which:

(a)   Is otherwise in the pubic domain at the time of disclosure, or becomes
      publicly known, in each case, through no breach of this Agreement by
      CONFIDANT (provided, however, that information shall not be disqualified
      as CONFIDENTIAL INFORMATION (i) merely because it is embraced by more
      general or generic information which is in the public domain or available
      from a third party, or (ii) if it can only be reconstructed from
      information taken from multiple sources, none of which individually shows
      or fairly suggests the whole combination (with matching degree of
      specificity), its principle of operation and/or the relevant use or method
      of use, as applicable;

(b)   Becomes known to CONFIDANT through disclosure by sources other than
      PRAECIS having the rights to disclose such CONFIDENTIAL INFORMATION:

(c)   Is generally disclosed to third parties by PRAECIS without similar
      restriction on such third parties;

(d)   Is approved for release by written authorization of an officer of PRAECIS;
      or

                                       17
<PAGE>

(e)   Is independently developed by employees or agents of CONFIDANT who have
      not utilized CONFIDENTIAL INFORMATION of PRAECIS's in such independent
      development.

6.    Return of Documents.

      CONFIDANT shall, upon the written request of PRAECIS, or upon termination
      of this Agreement, return to PRAECIS all CONFIDENTIAL INFORMATION received
      by CONFIDANT from PRAECIS pursuant to this Agreement (and all copies and
      reproductions thereof), except that one (1) copy thereof may be retained
      by CONFIDANT solely for the purpose of determining the extent of its
      obligations hereunder. CONFIDANT will retain copies of reports, data, and
      documentation, such as to remain in compliance with relevant regulatory
      agencies.

7.    Term

      Exchange of information hereunder shall occur within one year from the
      effective date of this agreement. This agreement shall remain in effect
      for ten years from the date of the signing or until the signing of a
      superseding agreement.

8.    General.

(a)   This Agreement and a party's rights, duties and obligations under this
      Agreement are not transferable or assignable by that party without express
      prior written consent of the other. Any attempt to transfer or assign this
      Agreement or any of the rights, duties or obligations under this Agreement
      without such consent is void

(b)   This Agreement can only be modified by written agreement duly signed by
      the persons authorized to sign agreements on behalf of the parties hereto,
      and variance from the terms or conditions of this Agreement will be of no
      effect.

(c)   If any provision or provisions of this Agreement shall be held to be
      invalid, illegal or unenforceable, the validity, legality and
      enforceability of the remaining provisions shall not in any way be
      affected or be impaired thereby.

(d)   This Agreement shall be governed and constructed in accordance with the
      laws of the State of Massachusetts.

                                       18
<PAGE>

(e)   This Agreement is the complete and exclusive statement of the agreement
      between the parties as to the subject matter hereof and supersedes all
      communications between the parties related to the subject matter of this
      Agreement.

(f)   A waiver of a breach or default under this Agreement shall not be a waiver
      of any other or subsequent breach or default. The failure or delay in
      enforcing compliance with any term or condition of this Agreement shall
      not constitute a waiver of such term or condition unless such term or
      condition is expressly waived in writing.

(g)   In the event of a breach or threatened breach by CONFIDANT of any of the
      provisions of this Agreement, PRAECIS, in addition to any other remedies
      available to it under law, shall be entitled to an injunction restraining
      CONFIDANT from the performance of acts which constitute breach of this
      Agreement.

(h)   This Agreement shall be binding upon the parties hereto and inure to the
      benefit of the parties hereto, their respective successors and permitted
      assigns.

                                       19
<PAGE>

IN WITNESS WHEREOF, the parties hereto have executed this Agreement effective
the day and year first above written.

PRAECIS Pharmaceuticals, Inc.              CONFIDANT - SALSBURY CHEMICALS, INC.
-----------------------------              ---------

By:/s/ N. Barker                           By:/s/ Rudi E. Moerck
   ---------------------------                ------------------

Name:N. Barker                             Name:Rudi E. Moerck
     -----------------------                    --------------

Title:V. P., Development                   Title:President
      ------------------                         ---------

                                           Date:September 9, 1997
                                                -----------------

                                       20
<PAGE>

                                    EXHIBIT B

SALSBURY CHEMICALS, INC.                                                 CPD 174

                        QUALITY ASSURANCE SPECIFICATIONS

CATEGORY:                            PRODUCT                        QC FLAG:  QC

CODE NO:                             2000300

NAME:                                PPI 149-CMC

SYNONYMS:                            ABARELIZ DEPOT

FORMULA:                             **

MOLECULAR WEIGHT:                    **

CAS NO:                              [183552-38-7]

DATE ISSUED:                         APRIL 24, 1998

REPLACES                             04/09/1998

**                                   **

                   DRUG PRODUCT INTERMEDIATE IN-PROCESS LIMITS

TEST ITEM                           LIMITS                          TEST METHOD
---------                           ------                          -----------

1.  Description                     White to off-white powder       **

2.  CMC Content                               **                              **
     (spectrophotometric)

3.  Moisture                                  **                              **

4.  HPLC ID (retention time)                  **                              **

5.  Assay                                     **                              **

6.  Impurities (HPLC)                         **                              **

7.  Particle Size                             **                              **
    **
    **
    **

8.  **                                        **                              **

9.**                                          **

10. Microbial Limits **                       **                              **

11. Endotoxin (LAL) ( per mg)                 **                              **

                                       21
<PAGE>

                                EXHIBIT B (cont.)

QUALITY ASSURANCE SPECIFICATION                                CODE NO.  2000300
PPI-149                                                        Revision No. 9804

APPROVALS:

ORIGINATOR                  /s/ Michael Tzarny                  Date:  4/22/98
                            --------------------------------           -------

QUALITY CONTROL             /s/ Michael Tzarny                  Date:  4/22/98
                            --------------------------------           -------
                                   Supervisor

QUALITY ASSURANCE           /s/ L.J. Frahm                      Date:  4/22/98
                            --------------------------------           -------
                                   Manager

CHEMICAL DEVELOPMENT        /s/ Eric Michalson                  Date:  4/22/98
                            --------------------------------           -------
                                   Manager

SALES & MARKETING           /s/ Shel Gelman                     Date:  4/22/98
                            --------------------------------           -------
                                 Director

OPERATIONS                  /s/ Donald Bertling                 Date:  4/22/98
                            ----------------------------------         -------
                                   Manager

CHANGES: 1. Correct Replace date and Revision Number.

                                       22

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00001-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00001-of-00352.parquet"}]]