<PAGE>   1
                                                                   EXHIBIT 10.23


                                    CONFIDENTIAL TREATMENT REQUESTED = [*]
                                    CERTAIN CONFIDENTIAL INFORMATION CONTAINED
                                    IN THIS DOCUMENT, MARKED BY BRACKETS, IS
                                    FILED WITH THE SECURITIES AND EXCHANGE
                                    COMMISSION PURSUANT TO RULE 24b-2 OF THE
                                    SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.



                               AMENDMENT NO. 1 TO
                         THE LONG TERM SUPPLY AGREEMENT
                         BETWEEN COR THERAPEUTICS, INC.
                                       AND
                                  SOLVAY, S. A.


         THIS AMENDMENT NO. 1 to the Long Term Supply Agreement (the
"Amendment") is entered into between COR Therapeutics, Inc. ("COR"), a Delaware
corporation, with its principal offices at 256 East Grand Avenue, South San
Francisco, California, USA 94080, and Solvay, Societe Anonyme ("Solvay"), a
Belgian corporation, with its principal offices at 33, rue du Prince Albert,
1050 Bruxelles, Belgium, each on behalf of itself and its Affiliates. This
Amendment shall be effective on April 1, 1997 (the "Amendment Effective Date").

                                    RECITALS

         WHEREAS, COR and Solvay entered into a License and Supply Agreement
dated 27 July 1994 (the "License and Supply Agreement") and a Long Term Supply
Agreement dated 28 September 1995 (the "Long Term Supply Agreement"), to provide
for the manufacture of a bulk peptide product and for the supply of that product
to COR for commercial and clinical use; and

         WHEREAS, the Long Term Supply Agreement provided, in Article 2.3, for
the establishment by Solvay of [*] New Production Suites before the beginning of
[*] and it is Solvay's present intention to increase its capacity through a
Facility Expansion according to the Expansion Plan; and

         WHEREAS, under this Amendment, the parties confirm their approval and
support of the Expansion Plan according to the terms herein.

         NOW, THEREFORE, in consideration of the foregoing and the covenants and
promises contained in this Amendment, COR and Solvay hereby amend the Long Term
Supply Agreement as follows.

         In this Amendment, capitalized terms shall have the meanings provided
herein or otherwise provided by the License and Supply Agreement or the Long
Term Supply Agreement. Headings are for the convenience of the Parties only, and
shall not be of any force or substance.



                                       1.

                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   2


1.       Article 1.3a shall be inserted after Article 1.3 as follows:

         1.3a     "DILIGENT EFFORTS" means the carrying out of activities in a
sustained manner consistent with the efforts a Party devotes to a product of
similar market potential, profit potential or other value resulting from its own
research efforts, based on conditions then prevailing. Diligent Efforts requires
that (i) the Party promptly assign responsibility for such activities to
specific employee(s) who are held accountable for progress and monitor such
progress on an ongoing basis, (ii) the Party set and consistently seek to
achieve specific and meaningful objectives for carrying out such obligations,
and (iii) the Party consistently make and implement decisions and allocate
resources designed to advance progress with respect to such objectives.

2.       Article 1.3b shall be inserted after Article 1.3a as follows:

         1.3b     "EXPANSION PLAN" shall refer to the plan and timeline for the
design, construction and validation of new Production Capacity, current as of
the Amendment Effective Date, provided to COR as the "Peptisyntha Facility
Expansion Summary Description Prepared for the [*] Meeting" dated [*] together
with the Amendment to that document attached hereto as Appendix H. The Expansion
Plan shall include the ordering, installation and validation of [*] identified
in that plan and specified in the Equipment List attached as Appendix E.

3.       Article 1.3c shall be inserted after Article 1.3b as follows:

         1.3c     "1997 FACILITY EXPANSION" shall refer to Solvay's new
Production Capacity established according to the Expansion Plan.

         4.       Article 1.4 shall be deleted and replaced with the following:

         1.4      "INTEGRILIN" shall refer to a specific peptide designated by
COR and known as INTEGRILIN(TM), which same peptide was known previously as
"Integrelin", the chemical structure of which is known to Solvay because of the
prior business relationship between COR and Solvay. Any references herein to
Integrelin shall be deemed to refer to Integrilin.





                                       2.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   3

5.       Article 1.11 shall be inserted after Article 1.10 as follows:

         1.11     "STEP ONE INTERMEDIATES" shall refer to those Bulk Product
Intermediates which exist upon completion of the manufacture of Bulk Product
through [*] as described in Appendix A, namely Bulk Product Intermediates [*].

6.       Article 2.3 shall be deleted in its entirety and shall be replaced with
the following:

         2.3      TIMING OF NEW PRODUCTION SUITE COMMITMENTS. On [*] and on [*]
during the term of this Agreement, COR may request that Solvay establish
additional New Production Suites capable of complete production of Bulk Product
therein [*] following the request. Within [*] from each [*] when such request
has been made, Solvay shall notify COR whether or not it will establish part or
all of the requested New Production Suites.

7.       Article 2.3a shall be inserted following Article 2.3 as follows:

         2.3a     1997 FACILITY EXPANSION. Solvay shall proceed with Diligent
Efforts to complete its planned 1997 Facility Expansion according to the
Expansion Plan and the timelines set forth therein. Solvay's progress on the
1997 Facility Expansion shall be monitored by [*] a [*] company having an
address at [*] in accordance with the provisions of the Confidentiality
Agreement between COR, Solvay and [*] has been retained by COR which shall be
solely responsible for compensation of [*] under this contract. [*] shall
monitor the 1997 Facility Expansion (including the design, construction and
validation plans) and report to COR and Solvay on an ongoing basis until the
1997 Facility Expansion is completed [*]. In the event [*] is not able or
willing to perform the tasks identified in this Article, COR shall have the
right to appoint another comparable firm to perform these tasks.

8.       Article 2.3b shall be inserted following Article 2.3a as follows:

         2.3b     APPLICATION OF FEES PAID FOR NEW PRODUCTION SUITES. The
Parties acknowledge the payment by COR to Solvay of [*] in [*] for the
facilitation of New Production Suites according to Article 2.4(a), and also [*]
in [*] for the 1997 Facility Expansion according to Article 2.3c(a). Upon
execution of this Amendment, Solvay may apply this money to its 1997 Facility
Expansion activities. The parties further acknowledge the accrued interest on
this payment, in the agreed amount of [*]. For their mutual convenience, the
parties hereby confirm



                                       3.

                                          CONFIDENTIAL TREATMENT REQUESTED = [*]

<PAGE>   4


that the credits available to COR according to Article 2.5 by reason of payments
made through the Amendment Effective Date consist of [*].

9.       Article 2.3c shall be inserted following Article 2.3b as follows:

         2.3c     FEE FOR FACILITATION OF 1997 FACILITY EXPANSION. In addition
to the payment referred to in Article 2.3b above, COR will facilitate the 1997
Facility Expansion with [*] additional milestone payments:

         (a)      [*] which was paid to Solvay in [*] upon receipt of
                  notification by Solvay of:

                  (i) delivery of all major equipment (list attached as Appendix
                  E to this Amendment), and

                  (ii) certification by Solvay of completion of the new
                  construction according to the Expansion Plan, including [*].
                  If there is a good faith dispute between the Parties about the
                  milestone being met, then the issues will be put before an
                  independent auditor agreeable to both COR and Solvay, and the
                  milestone payment will not be made unless the auditor finds
                  that it is due; and

         (b)      [*] to be paid for [*] according to the activities lists and
Plan provided to COR by [*] as the "Solvay Commissioning and Validation Schedule
Overall Project" dated [*] (Appendix I) as well as the Master Validation Plan
already agreed to by COR and Solvay [*] within [*] of Solvay's certification of
completion of [*] and [*] within [*] of Solvay's certification of completion of
all [*]. In the event COR does not agree with Solvay's certification of [*] and
provided that COR so notifies Solvay within [*] of COR's receipt of Solvay's
certification, COR shall pay the appropriate portion of this milestone payment
subject to return of such payment on demand forthwith in the event that an
independent auditor, agreeable to both COR and Solvay, finds that [*] was not
appropriately [*]. In the event COR's 1997 Purchase Order is [*] as a result of
the rescheduling procedure provided in Article 4.6 such that [*] of the 1997
Facility Expansion [*] using material manufactured under CORs 1997 Purchase
Order [*] then the payment provided in this Paragraph (b) of Article 2.3c shall
be made upon Solvay's certification of completion of all [*] subject to audit as
above.



                                       4.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   5

10.      Article 2.5 shall be deleted in its entirety and shall be replaced with
         the following:

         2.5      CREDIT FOR FEE PAYMENT. The fee payments made to Solvay
pursuant to Article 2.4 coincident with the establishment of New Production
Suites, if any, and pursuant to Article 2.3b and Paragraph (b) of Article 2.3c
coincident with the 1997 Facility Expansion, shall be credited against future
installment payments made pursuant to Article 8.3(c) for Bulk Product in an
amount equal to (i) [*] of the total purchase price of quantities of Bulk
Product produced in the New Production Suite or 1997 Facility Expansion up to
the first [*] per calendar year, and (ii) [*] of the total purchase price of
quantities of Bulk Product produced in the New Production Suite or 1997 Facility
Expansion over [*] per calendar year, until this Agreement is terminated. The
fee payments made to Solvay pursuant to Article 2.4 coincident with the
establishment of a New Production Suite, and pursuant to Articles 2.3b and 2.3c
coincident with the 1997 Facility Expansion, shall not be refundable to COR
except in the event of a material breach by Solvay of its obligations under this
Agreement to establish that particular New Production Suite or 1997 Facility
Expansion.

11.      Article 2.6 shall be deleted in its entirety and shall be replaced with
the following:

         2.6      RESERVATION OF PRODUCTION CAPACITY. Solvay shall reserve a
Production Capacity of [*] for 1997, in addition to the capacity required to
manufacture the quantity of Bulk Product already ordered for [*]. For 1998,
Solvay shall reserve a Production Capacity of [*] per year. For 1999 and
subsequent years, Solvay shall reserve a Production Capacity equal to [*](a)
the quantity of Bulk Product ordered for manufacture [*] Production Capacity of
the 1997 Facility Expansion [*], or (b)[*] Production Capacity of the 1997
Facility Expansion [*]. In the event that the reserved Production Capacity for
1999 or subsequent years is [*] Solvay may utilize the unreserved capacity for
manufacturing activities unrelated to this Agreement, so long as such activities
do not adversely effect the ability of Solvay to produce Bulk Product in the
amounts ordered by COR or the regulatory status of Integrilin(TM).

12.      Article 3.4 shall be inserted following article 3.3 as follows:

         3.4      PRODUCTION AND COMPLIANCE TEAM. The Parties acknowledge that
they have previously established and hereby agree to maintain a Production and
Compliance Team (PCT), composed of members appointed by COR and appointed by
Solvay. The role of the PCT will be to review Solvay and its subcontractors'
planned and actual manufacturing of Bulk Product



                                       5.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   6

Intermediates and Bulk Product, including, [*]. The PCT shall not have the
authority to amend this or any other Agreements between COR and Solvay.

13.      Section 3.5 shall be inserted after Section 3.4 as follows:

         3.5      PERSONNE DE CONFIANCE. Solvay agrees that COR may designate a
"Personne de confiance", who will be a COR employee or COR consultant. He or she
shall have the mission to improve communications between SOLVAY and COR and to
identify issues and facilitate their prompt resolution. Such mission shall
consist of the following activities:

     [*]

Any additional activity is subject to Solvay's approval.

Under appropriate confidentiality arrangements with Solvay, the Personne de
confiance will have access to the same information that could be communicated to
any other COR personnel, except technology transfer agents (also referred to by
the parties as TTAs). However, the Personne de confiance shall not have the
power to make contractual commitments on behalf of COR, amend this Amendment or
any other agreements between COR and Solvay or enter into any other agreements
on behalf of COR without specific written authorization from COR. COR may change
its designated Personne de confiance as necessary, provided he or she signs a
confidentiality agreement in substantially similar form to that signed by [*] (a
copy of which is attached hereto as Appendix F).

14.      Article 5.1a shall be inserted following Article 5.1 as follows:

         5.1a     AVAILABILITY OF PRODUCTION OF BULK PRODUCT INTERMEDIATES [*]
On an ongoing basis for each year during the term of this Long Term Supply
Agreement, Solvay guarantees the availability of the [*] for the production of
sufficient Bulk Product Intermediate [*] to satisfy all of Solvay's Bulk Product
production commitments, up to a level of each which is equivalent to that
quantity required to manufacture [*] of Bulk Product until the time when Solvay
has qualified (through [*]) and guarantees the availability of [*] having at
least the same capacity.

15.      Article 5.1b shall be inserted following Article 5.1 as follows:

         5.1b     AVAILABILITY OF PRODUCTION OF BULK PRODUCT INTERMEDIATE [*] On
an ongoing basis for each year during the term of this Long Term Supply
Agreement, Solvay guarantees the production of Bulk Product Intermediate [*] up
to a level equivalent to that quantity which is



                                       6.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   7

required to manufacture [*] of Bulk Product until the time when Solvay has
qualified (through [*]) and guarantees the availability of [*] having at least
the same capacity. In the event of a sale, merger or transfer of substantially
all of the stock or assets of the [*] Long Term Supply Agreement.

16.      Article 5.1c shall be inserted following Article 5.1 as follows:

         5.1c     Solvay commits to the establishment of [*] agreements with [*]
for the manufacture of sufficient quantities of the Bulk Product [*] to satisfy
[*] of Solvay's production commitments up to a maximum of [*] of Bulk Product
per year. Such agreements shall be entered into by the [*] the first product
regulatory approval from the U.S. Food and Drug Administration ("U.S. FDA") or
the European Agency for the Evaluation of Medicinal Products ("EMEA"). COR will
be given copies of all such supply agreements promptly [*].

17.      Article 5.2 shall be deleted in its entirety and shall be replaced with
         the following:

         5.2      INVENTORY OF BULK PRODUCT INTERMEDIATES. During the term of
this Agreement, Solvay will maintain in inventory Bulk Product Intermediates
manufactured up through certain manufacturing steps, as defined in Appendix A,
pursuant to Articles 4.6, 4.7 or 4.8. To the extent possible, such inventory
shall be rotated [*] with Bulk Product Intermediates subsequently manufactured
and scheduled for production through to final Bulk Product. Solvay shall retain
samples of lots of each Bulk Product Intermediate to be used in the manufacture
of Bulk Product until such Bulk Product has been manufactured, shipped to and
accepted by COR. COR will be informed by Solvay at least [*] on the level of
inventories of all Bulk Product Intermediates and on the scheduled production of
Bulk Product Intermediates.

18.      Article 5.2a shall be inserted following Article 5.2 as follows:

         5.2a     INVENTORY OF BULK PRODUCT INTERMEDIATES [*] In addition to the
provisions of Article 5.2, commencing [*] the first regulatory approval from the
U.S. FDA or the EMEA, for that calendar year and each subsequent year, Solvay
shall have and maintain at all times an inventory of Bulk Product [*] at a level
that is at least [*] greater than that required to satisfy the Purchase Orders
in effect for that calendar year. If COR requests that Solvay maintain an
inventory of Bulk Product Intermediates at a higher level, then Solvay shall
produce the higher quantities of inventories, [*](i)[*] a Purchase Order that
would utilize these higher quantities of 


                                       7.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   8


inventories, (ii) they may be purchased by COR for use by another authorized
manufacturer, and will be purchased for this purpose [*] according to Article
5.2b below, or (iii) COR may purchase them from Solvay [*].

19.      Article 5.2b shall be inserted following Article 5.2a as follows:

         5.2b     SUPPLY OF [*] TO OTHER MANUFACTURERS. Solvay agrees to supply
the Secondary Source [*] with the [*] according to the terms described in
Appendix G provided reasonable delivery schedules can be agreed. If COR wants to
deliver to the Secondary Source [*] higher quantities of inventories ordered
under Article 5.2a above, they will be provided by Solvay [*] in amounts of each
intermediate sufficient to produce designated quantities of Bulk Product.

20.      Article 5.2c shall be inserted following Article 5.2b as follows:

         5.2c     ADDITIONAL BULK PRODUCT INTERMEDIATE SUPPLIERS. In the event
COR orders [*] of Bulk Product in a particular year, then Solvay shall promptly
qualify an additional supplier [*] for each subcontracted Bulk Product
Intermediate. This additional supplier may be either a third party or a Solvay
facility (including the 1997 Facility Expansion).

21.      Article 5.3 shall be deleted in its entirety and shall be replaced with
the following:

         5.3      BULK PRODUCT INVENTORY. During the term of this Agreement,
Solvay shall notify COR of the completion of the manufacture of each lot of
final, [*] Bulk Product and shall ship such lot promptly to COR or COR's
designee according to the Shipping Procedures described in Article 7.2. COR may
however request that such shipment be postponed for a period not to exceed [*].
In such event, Solvay shall put such lot into inventory at a facility [*] until
it is shipped.

22.      Article 5.5 shall be deleted in its entirety and shall be replaced with
the following:

         5.5      OWNERSHIP OF [*] Upon payment by COR for completion of the
Manufacture of [*] pursuant to Article 8.3, COR shall own such [*] and shall be
entitled to take possession of such paid-for [*] in the event of material breach
of this Agreement by Solvay, or in the event that Solvay indicates that it will
not be able to deliver Bulk Product within [*] after an agreed shipping date,
and such possession shall be COR's only remedy with respect to these materials
in such events.



                                       8.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   9

23.      Article 7.2 shall be deleted in its entirety and shall be replaced with
the following:

         7.2      PRODUCT SHIPPING PROCEDURES. Solvay shall ship to a
destination specified by COR all Bulk Product requested to be delivered, by the
delivery dates provided in an accepted shipping request. Bulk Product will be
labeled and packaged according to the Specification. Notwithstanding contrary
provisions in the Specification, however, Bulk Product shall be packaged in a
shipping container approved by COR and supplied by Solvay. Solvay shall invoice
such shipping containers to COR at Solvay's direct cost. In the event that COR
specifies that the Bulk Product be shipped to a location other than COR's
principal offices (e.g., to a different location [*], or in the event that COR's
shipping request requires that the Bulk Product be placed into inventory for a
period longer than [*] and upon COR's request, Solvay shall ship a quality
control sample to COR's principal offices (or such other place as COR may
designate) in advance of or not later than concurrently with the shipment of the
Bulk Product. Except as provided herein with respect to non-conforming product,
title and risk of loss as to all Bulk Product shipped shall pass to [*]. In the
event that, upon COR's request pursuant to Article 5.3, shipment of a lot of
Bulk Product is not made promptly after the completion of manufacture of such
lot and therefore such lot is placed into inventory, title shall pass to [*].
Solvay shall provide a packing list and a certificate of analysis to COR for
every shipment.

24.      Article 7.3 shall be deleted in its entirety and shall be replaced with
the following:

         7.3      NON-CONFORMING PRODUCT. Bulk Product supplied hereunder shall
be produced by Solvay in accordance with applicable laws and regulations,
including current Good Manufacturing Practices as set forth in the United States
Code of Federal Regulations, in conformance with the Specification. COR may
reject any shipment of Bulk Product which (a) does not conform with the
Specification or (b) is adulterated or misbranded within the meaning of the
United States Federal Food, Drug and Cosmetic Act, equivalent European Union
regulatory agency requirements, or other applicable laws or governmental
regulations. Any notice of rejection of non-conforming product or notice that
the product is adulterated or misbranded must be submitted to Solvay within [*]
after shipment, accompanied by a report of analysis (including a product sample
from the lot analyzed) prepared according to the Specification. If no such
notice of rejection of non-conforming product is submitted, COR shall be deemed
to have accepted such delivery of the product. Product may be rejected as



                                       9.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   10

nonconforming based on analysis of a product sample shipped in advance of or
concurrently with the full lot.

25.      Article 8.3 shall be deleted in its entirety and shall be replaced with
the following:

         8.3      INVOICING AND PAYMENT. Payment for Bulk Product shall be made
in the following increments:

         (a)      Before the [*] for Purchase Orders placed during that year,
[*] of the Bulk Product price specified in Appendix C [*] in the applicable
Purchase Order;

         (b)      Within [*] of receipt of Solvay's written certification of the
completion of the manufacture of Bulk Product through [*] as described in
Appendix A, [*] of the Bulk Product price specified in Appendix C [*] stated in
the applicable Purchase Order; and

         (c)      Within [*] of receipt of Solvay's written certification of the
completion of the manufacture and delivery to Solvay's inventory of a lot of
Bulk Product (if upon COR's request pursuant to Article 5.3 shipment is not made
promptly after completion of the manufacture), or within [*] of receipt of
Solvay's written certification of the completion of the manufacture and shipment
of a lot of Bulk Product to COR or COR's designee, [*] of the Bulk Product price
specified in Appendix C [*] in that lot.

26.      Except as otherwise amended herein, the Long Term Supply Agreement
shall remain in full force and effect.



                                      10.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   11

         IN WITNESS WHEREOF, the Parties hereto have executed this Amendment.

COR THERAPEUTICS, INC.                      SOLVAY, S.A.



By:                                         By:
   --------------------------------            --------------------------------
                                               General Manager Research
                                               and Development
Title:                                      
      -----------------------------         

Appendix E:       List of Major Equipment
Appendix F:       Personne de Confiance Confidentiality Agreement
Appendix G:       Sample Purchase Order [*]
Appendix H:       Amendment to Facility Expansion Summary Document
Appendix I        [*] Report






                                      11.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   12

                                    CERTAIN CONFIDENTIAL INFORMATION CONTAINED
                                    IN THIS DOCUMENT, MARKED BY BRACKETS, IS
                                    FILED WITH THE SECURITIES AND EXCHANGE
                                    COMMISSION PURSUANT TO RULE 24b-2 OF THE
                                    SECURITIES EXCHANGE ACT OF 1934, AS AMENDED.



                             LIST OF MAJOR EQUIPMENT

                                   APPENDIX E


NO.                                           ITEM

                                               [*]





                                       1.

                                          CONFIDENTIAL TREATMENT REQUESTED = [*]


<PAGE>   13

                                CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN
                                THIS DOCUMENT, MARKED BY BRACKETS, IS FILED WITH
                                THE SECURITIES AND EXCHANGE COMMISSION PURSUANT
                                TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
                                1934, AS AMENDED.


                            CONFIDENTIALITY AGREEMENT

         THIS AGREEMENT is entered into effective as of October 10, 1996 among:

         SOLVAY, Societe Anonyme ("SOLVAY"), a Belgian corporation, with its
principal offices at 33, rue du Prince Albert, 1050 Brussels, Belgium, on behalf
of itself and its Affiliates; and

         COR THERAPEUTICS, INC. ("COR"), a Delaware corporation, with its
principal offices at 256 East Grand Avenue, South San Francisco, California
94080, USA, on behalf of itself and its Affiliates; and

         [*] a designee of COR with an address at [*].

         WITNESSETH:

         WHEREAS, COR owns certain patent rights, trademarks and know-how
relating to a product called INTEGRILIN(TM).

         WHEREAS, SOLVAY has developed a unique and valuable patented and
proprietary process useful for the manufacture of peptides, and is practising
the said process for the manufacture of bulk peptide products containing
INTEGRILIN sold to COR, pursuant to several Agreements entered into between
SOLVAY and COR.

         WHEREAS, SOLVAY has agreed to disclose confidential information to the
RECIPIENT who has been duly appointed as "Homme de Confiance" by COR with
responsibility for coordination of certain communications between COR and
PEPTISYNTHA, an Affiliate of SOLVAY, such mission being described in the
APPENDIX hereof and being subject to updating from time to time by SOLVAY and
COR.



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<PAGE>   14


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

1.0.     CERTAIN DEFINITIONS

         For the purposes of this Agreement, the following terms shall have the
         following meanings:

1.1      "AFFILIATES" shall mean any entity or person which controls, is
         controlled by or is under common control with either Party. For
         purposes of this section 1.1., "control" shall mean:

         (a)      in the case of corporate entities, the direct or indirect
                  ownership of at least one-half of the stock or participating
                  shares entitled to vote for the election of directors, and

         (b)      in the case of a partnership, the power to direct the
                  management and policies of such partnership.

         Without limitation on the foregoing and for purposed of this Agreement,
         PEPTISYNTHA & Cie, Societe en Nom Collectif ("PEPTISYNTHA"), which is a
         fully owned subsidiary of SOLVAY and an entity existing under the laws
         of Belgium and having its principal offices at 310, rue de Ransbeek,
         1120 Brussels, Belgium, is deemed an Affiliate of SOLVAY.

1.2      "AGREEMENT PURPOSE" shall mean the fulfilment by RECIPIENT of the
         mission of "Homme de Confiance" he has been entrusted with and which is
         described in the APPENDIX hereof.

1.3      "SOLVAY CONFIDENTIAL INFORMATION" shall mean any or all information
         disclosed by SOLVAY to RECIPIENT in order to enable him to fulfil the
         Agreement Purpose as well as any and all information that RECIPIENT may
         learn or have access to, due to his presence in SOLVAY's or
         PEPTISYNTHA's facilities, relating to SOLVAY's or PEPTISYNTHA's
         business or technology.

1.4      "EFFECTIVE DATE" shall mean October 10, 1996.

1.5      "INTEGRILIN" shall mean a specific peptide designated by COR and known
         as INTEGRILIN(TM), the chemical structure of which is known to
         RECIPIENT pursuant to the terms of separate agreements entered into
         with COR.

1.6      "PARTY" shall mean SOLVAY, COR or RECIPIENT.

2.0.     DISCLOSURE OF SOLVAY CONFIDENTIAL INFORMATION

2.1      SOLVAY shall disclose to RECIPIENT SOLVAY Confidential Information
         sufficient to enable RECIPIENT to fulfil the Agreement Purpose.



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<PAGE>   15


2.2      SOLVAY Confidential Information disclosed under paragraph 2.1 hereabove
         may be disclosed in tangible form, such as in writing and marked
         "Confidential", or provided orally.

3.0.     CONFIDENTIALITY AND EXCEPTIONS

3.1      RECIPIENT hereby agrees, regarding SOLVAY Confidential Information
         disclosed to him by SOLVAY under the terms of Article 2 hereof, that he
         shall

         (a)      make no use of said information, except for the Agreement
                  Purpose;

         (b)      not disclose said information to any party or person, except
                  to COR's employees duly appointed to receive it;

         (c)      not disclose to any party or person either the existence of
                  this Agreement or its underlying discussions except for the
                  Agreement Purpose;

         (d)      take the same steps to protect said information as he takes to
                  protect the proprietary and confidential information of COR.

3.2      RECIPIENT hereby agrees, regarding SOLVAY Confidential Information he
         may learn or have access to due to his presence in SOLVAY's
         PEPTISYNTHA's facilities and which is not comprised in the Confidential
         Information referred to in Article 2 hereof, that he shall:

         (a)      make no use of said information, except for the Agreement
                  Purpose;

         (b)      not disclose said information to any party or person;

         (c)      not disclose to any party or person either the existence of
                  this Agreement or its underlying discussions except for the
                  Agreement Purpose;

         (d)      take the same steps to protect said information as he takes to
                  protect the proprietary and confidential information of COR.

3.3      The obligations under paragraph 3.1 and 3.2 hereabove shall not,
         however, apply to any SOLVAY Confidential Information which:

         (a)      RECIPIENT can prove is at the time of disclosure or thereafter
                  becomes public knowledge through no fault or negligence of
                  RECIPIENT, OR

         (b)      RECIPIENT can prove was known to him, prior to the receipt of
                  such Confidential Information from SOLVAY, or

         (c)      is lawfully obtained by RECIPIENT from any party not bound by
                  a secrecy obligation towards SOLVAY relating to the
                  Confidential Information.



                                       3.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
<PAGE>   16


For the purposes of this paragraph 3.3, information shall not be deemed to be
public knowledge or known on the ground only that:

(i)      the general principle is public knowledge or known to RECIPIENT if the
         particular practice is not itself public knowledge or so known, or

(ii)     it constitutes a combination of or is drawn from information which is
         public knowledge or known to RECIPIENT unless the combination itself
         and its principle and mode of operation is also public knowledge or
         known to the RECIPEINT.

4.0.     DOCUMENTS DELIVERY OR DESTRUCTION

Upon the written request of SOLVAY, RECIPIENT undertakes to promptly deliver it,
or destroy if so instructed by it, all documents furnished by SOLVAY to
RECIPIENT and constituting Confidential Information, as well as all copies
thereof which might be in his possession.

5.0.     NO IMPLIED LICENSE

Nothing in this Agreement shall be construed as to grant RECIPIENT any title or
right or license to own or use at any time the SOLVAY Confidential Information,
except as expressly set forth herein.

6.0.     COR'S RESPONSIBILITY

COR shall guarantee the performance of this Agreement by RECIPIENT.

7.0.     TERM

This Agreement shall become effective on the Effective Date and shall remain in
effect until terminated by any Party. The provisions of Article 3 shall however
survive until the [*].

8.0.     GENERAL PROVISIONS

8.1      Notices

         All notices and demands required or permitted to be given or made
         pursuant to this Agreement shall be in writing and shall be deemed
         given if delivered personally or by given facsimile transmission
         (receipt verified), telexed, mailed by registered or certified mail
         (return receipt requested), postage prepaid, or sent by express courier
         service, properly addressed to the address of the Party to be notified
         as shown below:

         If to SOLVAY:

                  SOLVAY S.A.
                  DCR-LC
                  310, rue de Ransbeek
                  B - 1120 Brussels, Belgium
                  Attention : General Manager Research and Development




                                       4.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
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         If to COR:

                  President, COR Therapeutics, Inc.
                  256 East Grant Avenue
                  South San Francisco, California  94080, USA
     
         If to RECIPIENT:

                           [*]

         or to such other address as to which any Party may notify the others.
         Any notice sent by facsimile transmission or telex shall be followed
         within twenty-four (24) hours by a signed notice sent by first class
         mail, postage prepaid.

8.2      Assignment and Delegation

         RECIPIENT may not assign his rights and/or delegate his obligations
         under this Agreement to any third party without the prior consent of
         SOLVAY and COR.

8.3      Amendment

         No amendment or modification of the terms of this Agreement shall be
         binding on any Party unless reduced to writing and signed by the
         respective authorised officers of SOLVAY and COR and by RECIPIENT.

8.4      Publicity

         The Parties agree that, except as may otherwise be required by
         applicable laws, regulations, rules or orders, no information
         concerning this Agreement and the transactions contemplated herein
         shall be made public by any Party without the prior written consent of
         the others.

8.5      Waiver

         Failure of any Party to insist upon strict observance of or compliance
         with any of the terms of this Agreement in one or more instances shall
         not be deemed to be a waiver of its rights to insist upon such
         observance or compliance with the other terms hereof, at that point in
         time or in the future.

8.6      Counterparts

         This Agreement may be executed in multiple counterparts, each of which
         shall be an original, but all of which shall constitute but one
         agreement.

8.7      Governing Law

         This Agreement shall be governed by the laws of England. SOLVAY, COR
         and RECIPIENT consent to the exclusive jurisdiction and venue of the
         Courts of England.



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                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
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         IN WITNESS THEREOF, the parties hereto have executed this Agreement, in
three original copies.

SOLVAY S.A.                                 COR THERAPEUTICS, INC.


By:                                         By:
   --------------------------------            --------------------------------


Title:                                      Title:
      -----------------------------               -----------------------------


                                    RECIPIENT

                                       [*]

APPENDIX: Mission of the "Homme de Confiance"

                                APPENDIX F (PG 7)





                                       6.


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                                APPENDIX F (PG 8)

                       MISSION OF THE "HOMME DE CONFIANCE"

The mission of the "Homme de Confiance" aims at improving communications between
SOLVAY and COR and at facilitating prompt resolution of issues between them.

The mission will include the following activities:

[*]

Any additional activity, within the scope of COR's letter dated October 6, 1996
attached, is subject to SOLVAY's approval.





                                       7.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]
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                                CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN
                                THIS DOCUMENT, MARKED BY BRACKETS, IS FILED WITH
                                THE SECURITIES AND EXCHANGE COMMISSION PURSUANT
                                TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
                                1934, AS AMENDED.


October 6, 1996

Mr. Alfred Hoffait
General Manager, Research & Development
Solvay, S.A.
Rue de Ransbeek 310
B-1120 Brussels, Belgium

Dear Alfred:

This letter serves to clarify any issues regarding [*] level of confidentiality
and access to information from COR's perspective. As "homme de confiance", COR
views [*] as a COR representative in frequent attendance at Solvay, and as such,
we would like him to have access to the same information that could be
communicated to any other COR personnel.

[*] has entered into a confidentiality arrangement with COR, and therefore this
letter specifically authorizes you to show [*] confidential COR information that
may be in your files, and to discuss with him any issues regarding the
relationship between COR and Solvay.

It is our hope that involving [*] in COR/Solvay issues on a regular basis will
improve communications between our companies and facilitate prompt resolution of
issues. However, you understand that [*] is not COR's general agent and he does
not have the power to commit COR or enter into agreements on behalf of COR
without specific instructions from COR.

We appreciate your willingness to include [*] as a representative of COR.

Regards,



Mark D. Perrin
Executive Vice President, Commercial Operations



                                       1.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]

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                                CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN
                                THIS DOCUMENT, MARKED BY BRACKETS, IS FILED WITH
                                THE SECURITIES AND EXCHANGE COMMISSION PURSUANT
                                TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
                                1934, AS AMENDED.



                                APPENDIX G (P 1)

[*]

* The unit price for such a complete set of all [*] shall be computed by [*].





                                       1.


                                          CONFIDENTIAL TREATMENT REQUESTED = [*]

<PAGE>   22

                                CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN
                                THIS DOCUMENT, MARKED BY BRACKETS, IS FILED WITH
                                THE SECURITIES AND EXCHANGE COMMISSION PURSUANT
                                TO RULE 24b-2 OF THE SECURITIES EXCHANGE ACT OF
                                1934, AS AMENDED.



                                APPENDIX H (PG 1)

                         PEPTISYNTHA FACILITY EXPANSION

              SUMMARY DESCRIPTION PREPARED FOR THE 10 OCTOBER 1996
                                   PCT MEETING

The purpose of this document is to provide an overview of the proposed
PEPTISYNTHA expansion project as it is currently defined and to highlight any
proposed process changes which may be introduced concurrent with the expansion.
The tentative timeline for execution of the project is also provided. As we are
still in the early stages of the project, certain aspects are not yet fully
defined and are still under evaluation. It is envisioned that as the project
progresses, updates will be provided to COR Therapeutics at each PCT meeting.

1.       PROJECT ORGANIZATION

         [*]

2.       PROJECT OBJECTIVE

         [*]



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                                APPENDIX H (PG 2)


         [*] The building design and equipment will be thoroughly reviewed to
facilitate possible future expansions in a later stage to accommodate [*].

         [*]

         [*]





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                                APPENDIX H (PG 3)

[*]





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                                APPENDIX H (PG 4)

[*]

3.       PROJECT DESCRIPTION

[*]






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                                APPENDIX H (PG 5)

[*]

4.       EQUIPMENT

[*]





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                                APPENDIX H (PG 6)

[*]

6.       GMP ISSUES

[*]





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                                APPENDIX H (PG 7)

[*]

7.       PROJECT TIMELINES

The project timeline is provided in annex to this summary document.

8.       ATTACHMENTS

8.1.     PROCESS FLOW DIAGRAMS

8.2.     [*] CHART SHOWING ORGANIZATION OF PRODUCTION CAMPAIGNS

8.3.     EQUIPMENT LIST

8.4.     PROPOSED LAYOUT

8.5.     TIMELINE





                                       7.


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                                APPENDIX H (PG 8)

8.1      PROCESS FLOW DIAGRAMS





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                                APPENDIX H (PG 9)

[*]





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                               APPENDIX H (PG 10)

[*]





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                               APPENDIX H (PG 11)



[*]




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                               APPENDIX H (PG 12)

[*]






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                               APPENDIX H (PG 13)

[*]






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                               APPENDIX H (PG 14)

[*]





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                               APPENDIX H (PG 15)

8.2               [*] CHART - PRODUCTION CAMPAIGNS





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                               APPENDIX H (PG 16)

[*]




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                               APPENDIX H (PG 17)



8.3      EQUIPMENT LIST



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                               APPENDIX H (PG 18)

                           EQUIPMENT NUMBERING SYSTEM

[*]




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                               APPENDIX H (PG 19)

                                 EQUIPMENT LIST

[*]



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                               APPENDIX H (PG 20)

                           EQUIPMENT LIST (CONTINUED)

[*]





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                               APPENDIX H (PG 21)

                           EQUIPMENT LIST (CONTINUED)


[*]



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                               APPENDIX H (PG 22)

8.4      PROPOSED LAYOUT




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                               APPENDIX H (PG 23)

[*]



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                               APPENDIX H (PG 24)

8.5      TIMELINE





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                               APPENDIX H (PG 25)

[*]



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                               APPENDIX H (PG 26)

Amendment to the PEPTISYNTHA FACILITY EXPANSION document

[*]




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                               APPENDIX H (PG 27)

[*]




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                               APPENDIX H (PG 28)

[*]





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                               APPENDIX H (PG 29)

                     COMMISSIONING AND VALIDATION TIMETABLE

[*]





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                                APPENDIX I (PG 1)

[*]





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                                APPENDIX I (PG 2)

[*]



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                                APPENDIX I (PG 3)

[*]





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                                APPENDIX I (PG 4)

[*]





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                                APPENDIX I (PG 5)

[*]





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                                APPENDIX I (PG 6)

[*]





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                                APPENDIX I (PG 7)

[*]





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                                APPENDIX I (PG 8)

[*]





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                                APPENDIX I (PG 9)

[*]








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