SANGSTAT MEDICAL CORP
8-K, 1998-10-15
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION


                             WASHINGTON, D.C. 20549


                                ----------------

                                    FORM 8-K

                                 CURRENT REPORT

                     PURSUANT TO SECTION 13 OR 15(d) OF THE

                         SECURITIES EXCHANGE ACT OF 1934




      Date of Report (Date of Earliest Event Reported): SEPTEMBER 30, 1998


                          SANGSTAT MEDICAL CORPORATION
               --------------------------------------------------
               (Exact Name of Registrant as Specified in Charter)


        Delaware                        0-22890                  94-3076-069
- ----------------------------          ------------           -------------------
(State or other jurisdiction          (Commission               (IRS Employer
   of incorporation)                  File Number)           Identification No.)


     1505 Adams Drive, Menlo Park, California                     94025
     ----------------------------------------                   ----------
     (Address of Principal Executive Offices)                   (Zip Code)


       Registrant's telephone number, including area code (650) 328-0300



- --------------------------------------------------------------------------------
         (Former name or Former Address, if Changed Since Last Report.)

<PAGE>   2

ITEM 2. ACQUISITION OR DISPOSITION OF ASSETS

        (a) On September 30, 1998, SangStat Medical Corporation, a Delaware
corporation ("SangStat" or the "Registrant"), and Pasteur Merieux Connaught
announced the completion of the acquisition of PMC's organ transplant business
known as IMTIX (the "Acquisition"). The Merger was accomplished pursuant to the
Master Agreement dated June 10, 1998, between SangStat and Pasteur Merieux
Serums & Vaccins, S.A., a Pasteur Merieux Connaught company and a French Societe
Anonyme ("PMC").

        The transaction is an acquisition of the business of IMTIX Pasteur
Merieux Connaught Transplantation, a division of PMC ("IMTIX") by SangStat for
$31 million, and involves an up-front payment of $10 million and deferred cash
payments over five years of $21 million. In addition, SangStat will pay PMC
royalties on IMTIX-SangStat product sales that are variable and contingent upon
the sales of certain IMTIX-SangStat products. The transaction was structured by
having the business of IMTIX transferred to IMTIX-SangStat SAS, a French company
set up by PMC and then having 100% of the shares of IMTIX-SangStat SAS purchased
by SangStat. The transaction will be accounted for using the purchase method.
The source of funds used to acquire these assets was cash on hand at the
Company.

        (b) PMC carries on the business of researching developing,
manufacturing, marketing and distributing bio-pharmaceutical products used in
organ transplantation in humans. The Registrant intends to continue such
business.

        Acquisitions involve numerous risks including, but not limited to,
difficulties in the assimilation of the operations and products of the acquired
companies, the diversion of management's attention from other business concerns,
and the potential loss of key employees of the acquired company. Achieving the
anticipated benefits of the Acquisition will depend in part upon whether the
integration of the two companies' businesses and operations are accomplished in
an efficient and effective manner, and there can be no assurance that this will
occur. The successful combination of companies in the transplantation industry
may be more difficult to accomplish than in other industries. The combination of
the two companies will require, among other things, receipt of approvals by
regulatory agencies to transfer product manufacturing and marketing licenses and
the successful integration of IMTIX into SangStat. There can be no assurance
that such integration will be accomplished smoothly or successfully. The
difficulties of such integration may be increased by the necessity of
coordinating geographically separated organizations. The integration of certain
operations following a merger, including the Acquisition, will require the
dedication of management resources that may distract attention from the
day-to-day business of SangStat. The inability of management to successfully
integrate the operations of the two companies or any other company which
SangStat may acquire, could have a material adverse effect on the business and
results of operations of SangStat.

        The foregoing description is qualified in its entirety by reference to
the Master Agreement, a copy of which is attached hereto as Exhibit 2.1 and
incorporated herein by reference.

<PAGE>   3

        (a) Financial Statements of Business Acquired.*

        (b) Pro Forma Financial Information.*

<TABLE>
<CAPTION>
            Exhibit     Description
            -------     -----------
            <S>         <C>
              2.1       Master  Agreement  between Pasteur Merieux Serums
                        & Vaccins, S.A. dated June 10, 1998, including
                        Exhibit 8 thereto.**

             99.1       Text of Press Release dated September 30, 1998.
</TABLE>



- --------
*   Pursuant to Items 7(a)(4) and 7(b)(2) of the General Instructions to Form
    8-K, the Financial Statements of Business Acquired and the Pro Forma
    Financial Information will be filed by amendment not later than December 14,
    1998.

**  Pursuant to Item 601(b)(2) of Regulation S-K, the remaining exhibits and
    schedules to this Master Agreement have been omitted. Such exhibits and
    schedules will be submitted to the Securities and Exchange Commission upon
    request.

<PAGE>   4

                                          SIGNATURES


        Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                       SANGSTAT MEDICAL CORPORATION



Date:  October 14, 1998                By: /s/ JAMES F. HINRICHS
                                           -------------------------------------
                                           James F. Hinrichs, CFA
                                           Chief Financial Officer
                                           (Duly Authorized Officer and
                                           Principal Financial Officer)

<PAGE>   5

                                  EXHIBIT INDEX


<TABLE>
<CAPTION>
Exhibit
Number      Description
- -------     -----------
<S>         <C>
  2.1       Master Agreement between SangStat Medical Corporation and Pasteur
            Merieux Serums & Vaccins, S.A. dated June 10, 1998, including
            Exhibit 8 thereto.*

 99.1       Text of Press Release dated September 30, 1998.
</TABLE>



- --------
*   Pursuant to Item 601(b)(2) of Regulation S-K, the remaining exhibits and
    schedules to this Master Agreement have been omitted. Such exhibits and
    schedules will be submitted to the Securities and Exchange Commission upon
    request.

<PAGE>   1
                                   EXHIBIT 2.1

                                MASTER AGREEMENT
                         (Including Exhibit 8 Thereto)*



- --------
*   Pursuant to Item 601(b)(2) of Regulation S-K, the remaining exhibits and
    schedules to this Master Agreement have been omitted. Such exhibits and
    schedules will be submitted to the Securities and Exchange Commission upon
    request.
<PAGE>   2
                                                                     EXHIBIT 2.1


                              MADE ON JUNE 10, 1998


- --------------------------------------------------------------------------------

                                MASTER AGREEMENT

- --------------------------------------------------------------------------------

                                     BETWEEN


                          SANGSTAT MEDICAL CORPORATION

                                    AS BUYER


                                       AND


                      PASTEUR MERIEUX SERUMS & VACCINS S.A.

                                    AS SELLER


- --------------------------------------------------------------------------------


                                       1
<PAGE>   3
                                    CONTENTS

<TABLE>
<CAPTION>
                                                                          PAGE
                                                                          ----
<S>                                                                       <C>
THE UNDERSIGNED.......................................................      3
WHEREAS...............................................................      3
1.      INTERPRETATION................................................      4
2.      DESCRIPTION OF THE TRANSACTION................................      8
3.      PURCHASE AND SALE OF THE SHARES...............................     14
4.      CONDITIONS PRECEDENT..........................................     20
5.      COVENANTS.....................................................     22
6.      CLOSING DEADLINE..............................................     27
7.      REPRESENTATIONS AND WARRANTIES................................     28
8.      SHARE PURCHASE AGREEMENT......................................     31
9.      WARRANTY AGREEMENT............................................     34
10.     KNOW-HOW LICENSE AGREEMENT....................................     34
11.     LEASE AGREEMENT...............................................     35
12.     SERVICE AGREEMENT FOR MANUFACTURING/EQUINE
        PLASMA SUPPLY AGREEMENT.......................................     35
13.     CONFIDENTIALITY...............................................     35
14.     MISCELLANEOUS PROVISIONS......................................     38
15.     TERM AND TERMINATION..........................................     42
16.     GOVERNING LAW AND JURISDICTION................................     43
</TABLE>

<TABLE>
<S>                             <C>
Exhibit 2.1.1 a)                List of Employees
Exhibit 2.1.1 c)                List of Employees (Manufacturing)
Exhibit 2.1.2 b) (i)            Form of Know-How License Agreement
Exhibit 2.1.2 b) (ii)           Form of Commercial Lease Agreements and of Side-Letter
Exhibit 2.1.2 b) (ii-2)         Seller's Investment on V3bis Building (Avant-Projet)
Exhibit 2.1.2 b) (iii-1)        Form of Service Agreement for Manufacturing
Exhibit 2.1.2 b) (iii-2)        Form of Equine Plasma Supply Agreement
Exhibit 2.1.2 b) (iii-3)        Form of Site Service Agreement
Exhibit 2.1.3                   Distribution Agreement for Multitest
Exhibit 2.1.3-2                 Form of Letter of Assignment (Celiptium)
Exhibit 2.1.4                   List of General Services
Exhibit 2.2                     Form of Partial Business Contribution Agreement
Exhibit 2.2.1 b)                Form of Letter of Rhone-Poulenc Pharma S.A.
Exhibit 2.2.3 d)                Form of Completion Acknowledgment
Exhibit 3.2.1 a)                Form of Escrow Agreement
Exhibit 3.2.1 b)                Calculation Formula of Direct Cost
Exhibit 4.1.3                   Due Diligence List
Exhibit 4.1.3 (i)               Form of Affidavit
Exhibit 4.2.2                   Form of Amendment to the Manufacturing and Supply
                                Agreement of October 13, 1993
Exhibit 5.2.2                   Steps with French Medicine Agency (Agence du
                                Medicament)
Exhibit 8                       Form of Share Purchase Agreement
Exhibit 8 (i)                   Form of Letter of Credit
Exhibit 8 (i-2)                 Form of Certificate
Exhibit 14.2                    Form of Press Release
</TABLE>


                                       2
<PAGE>   4

BETWEEN THE UNDERSIGNED :

1.     SANGSTAT MEDICAL CORPORATION, a corporation existing and organized under
       the laws of the State of Delaware and having its principal place of
       business at 1505 Adams Drive, Menlo Park, CA 94025, USA, duly represented
       by Doctor Philippe Pouletty, its Chief Executive Officer,

       hereinafter referred to as "BUYER" or "SMC"

                                                               ON THE FIRST PART

AND

2.     PASTEUR MERIEUX SERUMS & VACCINS S.A., a Pasteur Merieux Connaught
       company and a French Societe Anonyme having its registered office at 58
       avenue Leclerc, 69007 Lyon, France, duly represented by Mr.
       Jean-Jacques Bertrand, its Chairman and Chief Executive Officer,

       hereinafter referred to as "SELLER" or "PMC"

                                                              ON THE SECOND PART

(Buyer and Seller are hereinafter collectively referred to as the "Parties" or
individually a "Party")

WHEREAS:

WHEREAS SMC is a specialty pharmaceutical company applying a disease management
approach to improve the outcome of organ transplantation;

WHEREAS the mission of PMC is to contribute to the protection and maintenance of
human health by creating superior immunological products for the prevention and
treatment of infectious diseases and cancers;

WHEREAS PMC, among its other activities, carries on the business of researching,
developing, manufacturing, marketing and distributing bio-pharmaceutical
products used in organ transplantation in humans through its division known as
IMTIX Pasteur Merieux Connaught Transplantation;


                                       3
<PAGE>   5
WHEREAS PMC's strategic intent is to focus on its core business, mainly
bio-pharmaceutical products for active immunization against infectious diseases
and immunotherapy of cancers;

WHEREAS SMC's strategic intent is to develop its business throughout the whole
spectrum of transplantation indications, products and services;

WHEREAS SMC and PMC are currently parties to a development and distribution
agreement relating to transplantation products pursuant to which SMC is actively
involved in the clinical development and registration of certain transplantation
products;

WHEREAS PMC desires to sell or otherwise transfer and SMC desires to purchase or
otherwise acquire all or substantially all tangible and intangible assets of PMC
pertaining to the transplantation business upon and subject to the terms and
conditions hereinafter set forth;

NOW, THEREFORE, in consideration of the mutual covenants, agreements,
representations and warranties and subject to the conditions precedent contained
herein, the Parties hereto agree as follows:

ARTICLE I - INTERPRETATION

1.1      DEFINITIONS

         The following terms used herein shall have, for purposes of this
         Agreement, the meanings set forth below:

         -  "ACTUAL SALES" shall have the meaning ascribed to it in Article
            3.2.1 c) hereafter.

         -  "AFFIDAVIT" shall mean a letter from the Buyer in the form of
            Exhibit 4.1.3 (i) hereto to the Seller indicating that the Initial
            Due Diligence is satisfactory to the Buyer (Affidavit 1) and that
            the Second Due Diligence is satisfactory to the Buyer (Affidavit 2).

         -  "AFFILIATE" shall mean, in relation to any entity, any other entity
            which directly or indirectly, through one or more intermediaries,
            controls, or is controlled by, or is under common control with such
            entity. For the purposes of this definition, "control" shall be
            defined by reference to Article 355-1 of the French Company Act
            dated July 24, 1966.

         -  "AGREEMENT" shall mean this Master Agreement, together with all its
            Exhibits.

         -  "AGREEMENTS" shall mean collectively this Master Agreement, the
            Share Purchase Agreement, the Ancillary Agreements and the Partial
            Business Contribution Agreement.


                                       4
<PAGE>   6

         -  "ANCILLARY AGREEMENTS" shall mean collectively the following
            agreements which the Parties agree are an integral part of the
            overall Transaction:

            -  Know-How License Agreement referred to in Article 2.1.2 b) (i)
               hereafter;

            -  Service Agreement for the Manufacturing of Thymoglobuline and
               Lymphoglobuline referred to in Article 2.1.2 b) (iii) hereafter;

            -  Commercial Lease Agreements referred to in Article 2.1.2 b) (ii)
               hereafter; 

            -  Site Service Agreement referred to in Article 2.1.2 b) (iii)
               hereafter;

            -  Equine Plasma Supply Agreement referred to in Article 2.1.2 b)
               (iii) hereafter;

            -  Distribution Agreement for Multitest referred to in Article 2.1.3
               hereafter.

         -  "ANNIVERSARY DATE(S)" shall mean the date(s) set forth in the
            schedule mentioned in Article 3.2.1 c) (ii) hereof.

         -  "ASSETS" shall have the meaning ascribed to it in Article 2.1.2 a)
            hereafter.

         -  "BUSINESS" shall mean the IMTIX business as described in Article
            2.1.1 hereafter.

         -  "BUSINESS DAY" shall mean any day which is not a Saturday, a Sunday
            or a holiday in France or in the U.S.

         -  "CHANGE OF CONTROL" shall have the meaning ascribed to it in Article
            8 (iii) hereafter.

         -  "CLOSING DATE" shall mean the date on which the Shares are
            transferred by Seller to Buyer in compliance with Article 2.2.3
            hereof, by remittance to Buyer of a transfer form ("ordre de
            mouvement") duly executed by Seller and its transcription in the
            Company's share transfer registrar, which shall be no later than the
            Closing Deadline as defined hereafter.

         -  "CLOSING DEADLINE" shall mean December 31, 1998.

         -  "COMPANY" shall mean IMTIX-SangStat SAS, a French company to be set
            up by Seller in the form of a societe par actions simplifiee.

         -  "CONFIDENTIAL INFORMATION" shall have the meaning ascribed to it in
            Article 13 a) hereafter.

         -  "DELIVERY DATE" shall have the meaning ascribed to it in Article
            3.2.2 b) hereafter.

         -  "DIRECT COSTS" shall have the meaning ascribed to it in Article
            3.2.1 b) hereafter.

         -  "DISCLOSING PERSON" shall have the meaning ascribed to it in Article
            13 a) hereafter.


                                       5
<PAGE>   7
         -  "ESCROW AGREEMENT" shall mean the escrow agreement to be executed
            between Buyer, Seller and BNP 39, rue de Grenette, 69002 Lyon,
            acting as escrow agent, on the Filing Date, substantially in the
            form of Exhibit 3.2.1 a) hereto.

         -  "EXCLUDED ASSETS" shall have the meaning ascribed to it in Article
            2.1.2 b) hereafter.

         -  "FILING DATE" shall have the meaning ascribed to it in Article
            2.2.2.

         -  "FIXED PRICE" shall have the meaning ascribed to it in Article 3.2.1
            hereafter.

         -  "GENERAL SERVICES" shall mean those services listed in Exhibit
            2.1.4.

         -  "IMTIX" or "IMTIX BUSINESS" shall have the meaning ascribed to those
            terms in Article 2.1.1 hereafter.

         -  "IMTIX PRODUCTS" shall have the meaning ascribed to it in Article
            2.1.1 (b) hereafter.

         -  "INITIAL DUE DILIGENCE PERIOD" shall have the meaning ascribed to it
            in Article 4.1.3 (i) hereafter.

         -  "INTERIM AGREEMENTS" shall have the meaning ascribed to it in
            Article 5.3 hereafter.

         -  "KNOW-HOW LICENSE AGREEMENT" shall have the meaning ascribed to it
            in Article 2.1.2 b) (i) hereafter.

         -  "MANAGEMENT COMMITTEE" shall have the meaning ascribed to it in
            Article 5.2.4 hereafter.

         -  "MASTER AGREEMENT DATE" shall mean the date of execution of this
            Agreement.

         -  "MINIMUM REFERENCE SALES" shall have the meaning ascribed to it in
            Article 3.2.1 c) (ii).

         -  "NET SALES" shall have the meaning ascribed to it in Article 3.2.2
            hereafter.

         -  "OTHER PARTY" shall have the meaning ascribed to it in Article 13 a)
            hereafter.

         -  "PARTIAL BUSINESS CONTRIBUTION" shall have the meaning ascribed to
            it in Article 2.2.3 a) hereafter.

         -  "PARTIAL BUSINESS CONTRIBUTION AGREEMENT" shall have the meaning
            ascribed to it in Article 2.2 hereafter.

         -  "PAYMENT DATE(S)" shall have the meaning ascribed to it in Article
            3.2.1 a) hereafter.


                                       6
<PAGE>   8

         -  "PAYMENTS" shall have the meaning ascribed to it in Article 3.2.1 a)
            hereafter.

         -  "PURCHASE" shall have the meaning ascribed to it in Article 2.2.3 b)
            hereafter.

         -  "PURCHASE PRICE" shall have the meaning ascribed to it in Article
            3.2 hereafter.

         -  "RECEIVING PERSON" shall have the meaning ascribed to it in 
            Article 13 a) hereafter.

         -  "REPRESENTATIVES" shall have the meaning ascribed to it in
            Article 13 a) hereafter.

         -  "RETROACTIVE DATE" shall mean the first day of the month of the
            Filing Date.

         -  "SECOND DUE DILIGENCE PERIOD" shall have the meaning ascribed to it
            in Article 4.1.3 (ii) hereafter.

         -  "SHARE PURCHASE AGREEMENT" shall mean the share purchase agreement
            to be executed between Buyer and Seller on the date hereof setting
            forth the terms and conditions of the sale by Seller to Buyer of the
            Shares, substantially in the form of Exhibit 8 hereto.

         -  "SHARES" shall mean 100% of the share capital and voting rights of
            the Company.

         -  "SUBSIDIARIES" shall mean the 4 subsidiaries fully dedicated to the
            distribution of IMTIX Products, which are IMTIX GmbH (Germany),
            IMTIX B.V. (Netherlands), IMTIX Ltd (UK) and IMTIX Srl (Italy).

         -  "TRANSACTION" shall mean collectively the transactions contemplated
            under the Master Agreement, the Partial Business Contribution
            Agreement, the Share Purchase Agreement and the Ancillary
            Agreements.

         -  "TRANSITION COMMITTEE" shall have the meaning ascribed to it in
            Article 5.2.3 hereafter.

         -  "VARIABLE PRICE" shall have the meaning ascribed to it in Article
            3.2.2 hereafter.

1.2    HEADINGS

       The division of the Agreement into Articles and Sections and the
       insertion of headings are for convenience of reference only and shall not
       affect the construction or interpretation of this Agreement. The terms
       "Agreement", "hereof", "hereunder" and similar expressions refer to this
       Agreement and not to any particular Article, Section or other portion
       hereof and include any agreement supplemental hereto. Unless something in
       the subject matter or 


                                       7
<PAGE>   9

       context is inconsistent therewith, references herein to Articles and
       Sections are to Articles and Sections of this Agreement.

1.3    EXTENDED MEANINGS

       In this Agreement words importing the singular number only shall include
       the plural and vice versa, words importing the masculine gender shall
       include the feminine and neuter genders and vice versa and words
       importing persons shall include individuals, partnerships, associations,
       trusts, unincorporated organizations and corporations.

1.4    ACCOUNTING PRINCIPLES

       Wherever in this Agreement reference is made to a calculation to be made
       in accordance with generally accepted accounting principles, such
       reference shall be deemed to be (i) accounting principles usually
       accepted such as defined in the French "Nouveau Plan Comptable" and set
       up according to the "recommandations de l'Ordre des Experts-Comptables
       francais," of the "Conseil National de la Comptabilite" and of the
       "Compagnie Nationale des Commissaires aux Comptes" or (ii) as far as the
       Subsidiaries are concerned, local generally accepted accounting
       principles.

ARTICLE II - DESCRIPTION OF THE TRANSACTION

2.1    DESCRIPTION OF THE BUSINESS

       2.1.1  The IMTIX Business:

              IMTIX Business (referred to herein as "IMTIX Business", the
              "Business" or "IMTIX") is an ongoing business carried on
              internationally as a division of Seller ("Division") and comprised
              of the research, development, manufacturing, marketing and
              distribution of, and pharmacovigilance relating to pharmaceutical
              products for transplantion in humans which includes, without such
              list being limitative:

              a)   A dedicated staff of (i) 25 full-time employees for IMTIX
                   commercial, sales, regulatory, and medical affairs located in
                   an annex of Seller headquarters at 58, avenue Debourg, 69007
                   Lyon, France, and (ii) 15 employees employed in the
                   Subsidiaries; the precise list of such employees is set forth
                   in Exhibit 2.1.1 a) hereto, specifying their respective
                   names, titles, salary and other compensation; none of these
                   employees (except one) is "protected" as this term is
                   understood under French labor law (employee delegates,
                   members of the workers council, union representatives);


                                       8
<PAGE>   10

              b)   A portfolio of products (either registered and/or marketed or
                   under development) which are:

                   -  Thymoglobuline(R),
                   -  Lymphoglobuline(R),
                   -  Antilfa(R), under development,
                   -  Celsior(R),

                   hereafter, the "IMTIX Products".

              c)   Manufacturing:

                   -  28 full-time employees dedicated to the manufacturing of
                      Thymoglobuline(R) and/or Lymphoglobuline(R); the precise
                      list of employees is set forth in Exhibit 2.1.1 c) hereto,
                      specifying their respective names, titles, salary and
                      other compensation; none of these employees is "protected"
                      as this term is understood under French labor law
                      (employee delegates, members of the workers council, union
                      representatives);

                   -  all the equipment dedicated to the manufacturing of the
                      IMTIX Products, all of which is located in (i) the C4
                      Building located at Marcy l'Etoile dedicated to the
                      manufacturing of Thymoglobuline(R) and (ii) the V3 bis
                      Building located at Marcy l'Etoile dedicated to the
                      manufacturing of Lymphoglobuline(R),

                   -  the contract manufacturing agreement with Pharmacia &
                      Upjohn for Celsior(R).

              d)   The distribution network which comprises:

                   -  The Subsidiaries fully dedicated to the distribution of
                      IMTIX Products, together with all their assets and
                      agreements with all sellers, agents, clinical
                      investigators, other distributors and/or consultants for
                      the distribution of the IMTIX Products, and

                   -  liaison offices in Austria, Canada and Hong Kong dedicated
                      to the Business;

                   -  distribution agreements in full or in part dedicated to
                      the IMTIX Products, including the existing license and
                      supply agreements between the Parties.


                                       9
<PAGE>   11

              e)   The network for the collection of thymus fragments in France,
                   Italy, Poland, Spain, Turkey, Scandinavia, Holland, the
                   United States of America and Canada which comprises in
                   particular, without limitation:

                   -  licenses and authorizations by and/or information to
                      relevant Ministries of Health or other regulatory
                      authorities;

                   -  agreements with hospitals under which Seller collects
                      thymus;

                   -  agreements with collectors for thymus.

              f)   The network for the supply of rabbit products for
                   Thymoglobuline(R):

                   -  all sub-contracting agreements with rabbit farms.

       2.1.2  The IMTIX Assets:

              a)   Subject to paragraph b) hereunder, it is expressly stated
                   that the Parties agree to transfer all of the assets related
                   to the Business including, without limitation, the following
                   assets (the "Assets"):

                   (i)    all interest in IMTIX products, immunogens, clones,
                          formulations, toxicology, pharmacology, clinical and
                          regulatory data, post-marketing surveillance data,
                          regulatory files and licenses, manufacturing and
                          quality control equipment located in the C4 Building
                          and V3 bis Building at Marcy l'Etoile, materials,
                          disposables, specific know-how, methods and procedures
                          (other than those licensed under the Know-How License
                          Agreement), protocols, assays, standard operating
                          procedures and specifications, customer information
                          and market research;

                   (ii)   all materials product inventory owned by Seller,
                          including, without limitation, raw materials,
                          work-in-progress, and finished goods and supplies, it
                          being understood that the Company will be entitled to
                          sell such inventory of work-in-progress and finished
                          goods with their existing packaging as of the Closing
                          Date, until the expiration date of the shelf life of
                          all items of said inventory, provided such inventory
                          will be sold prior to any comparable products under
                          Buyer's packaging;

                   (iii)  all claims and rights under all agreements, contracts,
                          contract rights, sales, invoices, licenses, purchase
                          and sale orders, and other executory commitments,
                          including all rights to receive payments in respect of
                          Thymoglobuline(R), Lymphoglobuline(R) and Celsior(R) 
                          sales in the United States of America and Canada;

                   (iv)   all accounts receivable;


                                       10
<PAGE>   12

                   (v)    all goodwill;

                   (vi)   all rights, title and interest to trademarks,
                          trademark rights, trade secrets exclusively dedicated
                          to IMTIX Products, information, proprietary rights,
                          license rights, service marks, trade names,
                          copyrights, design, logos and customers and suppliers
                          lists, it being understood that no right shall be
                          granted to Buyer to the name, logo, or design of
                          either "Pasteur", "Merieux", or "Connaught", or any
                          combination thereof, anywhere in the world, subject
                          however to the provisions of paragraph (ii) hereabove;

                   (vii)  all franchises, licenses, permits, consents,
                          authorizations, certificates and approvals of any
                          regulatory, administrative or other governmental
                          agency issued to or held by Seller or its subsidiaries
                          including all authorizations to export products not
                          licensed in France;

                   (viii) all rights under express or implied warranties from
                          suppliers and vendors of Seller and from clinical
                          investigators, clinical research organizations (CRO);

                   (ix)   all of Seller's causes of action, judgments and claims
                          or demands;

                   (x)    any other personal property used in the ordinary
                          course of the Business;

                   (xi)   all rights under the agreements relating to the
                          collection of thymus fragments;

                   (xii)  any and all patents, patent applications, such term
                          including continuations in part, divisions, reissues,
                          etc., and patent licenses relating exclusively to
                          IMTIX Products, and licensing agreements with
                          Immunotech and Assistance Publique des Hopitaux de
                          Paris.

              b)   The following assets shall be excluded from the definition of
                   Assets (the "Excluded Assets"), and shall be dealt with apart
                   in specific agreements (the "Ancillary Agreements"):

                   (i)    any and all know-how non-specific to the Business but
                          necessary to operate the Business shall be licensed to
                          the Company under a long term worldwide, know-how
                          license agreement (the "Know-How License Agreement"),
                          substantially in the form of Exhibit 2.1.2 b) (i)
                          attached hereto;

                   (ii)   the real estate relating to the C4 Building and V3 bis
                          Building shall be leased to the Company under
                          commercial lease agreements as completed by
                          side-letters substantially in the form of Exhibit
                          2.1.2 b) (ii) attached hereto; with respect to the V3
                          bis Building, Buyer acknowledges that it 


                                       11
<PAGE>   13

                          has been informed of the necessity to upgrade the
                          premises so as to comply with requirements of the
                          French Medicine Agency (Agence du Medicament), and of
                          Seller's undertaking to invest approximately (without
                          exceeding) 8 (eight) million French Francs for this
                          purpose as set forth in the draft (avant-projet)
                          attached as an Exhibit 2.1.2 (b) (ii-2) hereto.

                   (iii)  all equipment other than the equipment described in
                          Article 2.1.1 (c) required for the manufacturing of
                          IMTIX Products, and in particular the filling,
                          packaging and the manufacturing of IMTIX Products, all
                          quality control and quality assurance of IMTIX
                          Products not performed in the C4 Building and V3 bis
                          Building and site services the use of which shall be
                          subject to the execution of the following service
                          agreements:

                          -  a service agreement linked to the manufacturing of
                             Thymoglobuline(R) and Lymphoglobuline(R)
                             substantially in the form of Exhibit 2.1.2 b)
                             (iii-1) attached hereto including provisions
                             regarding quality control service;

                          -  an equine plasma supply agreement substantially in
                             the form of Exhibit 2.1.2 b) (iii-2) attached
                             hereto;

                          -  a site service agreement substantially in the form
                             of Exhibit 2.1.2 b) (iii-3) attached hereto;

                   (iv)   the lease of the building "Le Challenge" located at 58
                          avenue Debourg, 69007 Lyon, France.

       2.1.3  Other Products

              Celiptium and Multitest are Products which are not directly linked
              to the transplantation Business, but for which promotion,
              distribution and sale depend on the IMTIX Division of Seller.
              Multitest will be distributed by the Company according to the
              Distribution Agreement for Multitest in the form attached hereto
              as Exhibit 2.1.3. The Celiptium license agreement will be assigned
              to the Company pursuant to an assignment letter in the form
              attached hereto as Exhibit 2.1.3-2.

       2.1.4  The Business, with the Ancillary Agreements and excluding the
              General Services, constitutes a stand-alone Business that will
              allow the Company to conduct in a normal way the Business as it
              has been operated until the date hereof and as it will be operated
              until the Closing Date.


                                       12
<PAGE>   14

2.2    STRUCTURE OF THE ACQUISITION

       The transaction is structured as follows:

       The Business being located in Seller's legal structure, the Parties have
       agreed to have the Business contributed to the Company before its sale to
       Buyer. In this context, the contribution will be made to the benefit of a
       "Societe par Actions Simplifiee" (hereinafter referred to as "SAS") to be
       incorporated by Seller. The "regime juridique des scissions" will be
       elected for this contribution, it being understood that the contribution
       will be subject to the previous authorization by the General Manager of
       the French Medicine Agency of the Company as a manufacturing
       pharmaceutical establishment ("fabricant").

       The Partial Business Contribution Agreement (Traite d'Apport Partiel
       d'Actif) to be entered into between Seller and the Company shall be
       substantially in the form of Exhibit 2.2 hereto. It shall provide for a
       retroactive entering into effect of the contribution as of the
       Retroactive Date.

       Following this contribution, the Shares of the Company shall be purchased
       by Buyer. At the same date, and in order to allow the Company to conduct
       its Business in an autonomous manner (except for the Excluded Assets and
       General Services), the Ancillary Agreements shall be executed.

       2.2.1  On the Master Agreement Date:

              a)   In addition to this Agreement, the Parties shall have
                   executed the Share Purchase Agreement under conditions
                   precedent.

              b)   Seller shall have remitted to Buyer a certified copy of an
                   extract of the minutes of its Board of Directors meeting
                   having authorized the Transaction and empowered Mr.
                   Jean-Jacques Bertrand to execute this Agreement together with
                   a letter of its shareholder, Rhone-Poulenc Pharma S.A. in the
                   form of Exhibit 2.2.1 b).

              c)   Buyer shall have remitted to Seller a certified copy of the
                   minutes of its Board of Directors meeting having authorized
                   the Transaction and empowered Doctor Philippe Pouletty to
                   execute this Agreement.

       2.2.2  Following the Master Agreement Date:

              As soon as practicable after Seller has received the Affidavit 1
              issued at the end of the Initial Due Diligence Period, as provided
              under Article 4.1.3 (i) hereafter, but in no event later than 20
              days following the last day of the month in which the Affidavit 1
              is delivered, Seller and the Company shall file the draft Partial
              Business Contribution Agreement with the competent Commercial
              Court (Greffe du Tribunal de Commerce), in compliance with
              applicable laws and regulations.


                                       13
<PAGE>   15

                The date on which the draft Partial Business Contribution
                Agreement is filed with the Commercial Court shall be referred
                to as the "Filing Date".

       2.2.3  Closing:

              As soon as the conditions precedent referred to in Articles 4.1.2
              and 4.1.3 hereafter are fulfilled and within 20 days thereafter,
              the following steps shall take place:

              a)   The shareholders of Seller and of the Company shall be
                   convened at general meetings to approve the Partial Business
                   Contribution and complete the Partial Business Contribution
                   in exchange for shares of the Company (the "Partial Business
                   Contribution") pursuant to the Partial Business Contribution
                   Agreement referred to in Article 4.1.1;

              b)   Sale by Seller and an Affiliate of Seller to Buyer of 100% of
                   the Shares in the Company (the "Purchase") pursuant to the
                   Share Purchase Agreement attached hereto;

              c)   Execution of the Ancillary Agreements;

              d)   Execution between the Parties of a document acknowledging (i)
                   the fulfillment of all conditions precedent and (ii) the
                   completion of the sale of the Shares in the form attached in
                   Exhibit 2.2.3 d);

              e)   Completion of all the Closing Steps defined in Article 1.3 of
                   the Share Purchase Agreement.

       The date on which the above (a), (b), (c), (d) and (e) steps take place
       shall be referred to as the "Closing Date" and shall be no later than the
       Closing Deadline (subject to Article VI hereof).

ARTICLE III - PURCHASE AND SALE OF THE SHARES

3.1    PURCHASE AND SALE OF THE SHARES

       On the Master Agreement Date, the Parties shall execute a Share Purchase
       Agreement under conditions precedent, providing for the Purchase Price
       defined hereafter.


                                       14
<PAGE>   16

3.2    PRICE

       The sale of the Shares shall be made for a total price (the "Purchase
       Price") payable by Buyer to Seller and consisting of the sum of a fixed
       price (the "Fixed Price") and a variable price (the "Variable Price")
       defined respectively in Articles 3.2.1 and 3.2.2 hereafter.

       3.2.1  Fixed Price:

              a)   Payment Schedule

                   Subject to adjustments effected pursuant to Articles 3.2.1
                   b), c) and d) hereafter, the Fixed Price shall be of a total
                   amount of $33 (thirty three) million US Dollars payable in
                   several successive payments (the "Payment(s)") in accordance
                   with the following schedule, it being specified that $12
                   (twelve) million US Dollars shall, on the Filing Date, be
                   placed in escrow pursuant to the Escrow Agreement to be
                   executed upon the Filing Date in the form of Exhibit 3.2.1 a)
                   attached hereto. Dates set forth in this schedule shall
                   hereafter be referred to as the "Payment Date(s)".

<TABLE>
<CAPTION>
                                                                PAYMENT
                         PAYMENT DATE                        (IN US DOLLARS)
                      -------------------                    ---------------
                      <S>                                    <C>
                      Closing Date ("CD")                    $12.0 million
                       6 months after CD                     $ 1.5 million
                      12 months after CD                     $ 1.5 million
                      18 months after CD                     $ 1.5 million
                      24 months after CD                     $ 1.5 million
                      30 months after CD                     $ 3.0 million
                      36 months after CD                     $ 3.0 million
                      42 months after CD                     $ 2.5 million
                      48 months after CD                     $ 2.5 million
                      54 months after CD                     $ 2.0 million
                      60 months after CD                     $ 2.0 million
</TABLE>

                   Sums placed in escrow as provided hereabove shall be released
                   to the benefit of Seller upon Closing Date, or, should the
                   Purchase not take place because of the non-fulfillment prior
                   to the Closing Deadline of any of the conditions precedent
                   referred to in Article 4.1 hereof, shall be refunded to
                   Buyer.

              b)   Adjustment of the Payments by reference to Thymoglobuline(R)
                   direct costs

                   The Payments due 12 months after Closing Date (for an amount
                   of $1,500,000 (one million five hundred thousand) US Dollars)
                   and 24 months after Closing Date (for an amount of $1,500,000
                   (one million five hundred thousand) US Dollars) shall however
                   be readjusted by reference to the average 


                                       15
<PAGE>   17

                   Thymoglobuline Direct Costs (as defined hereafter) during the
                   12 month-period preceding each of these 2 dates in accordance
                   with the following table. For the purposes of this Agreement,
                   "Direct Costs" shall mean a list of items of French Francs
                   amount computed on the basis of the calculation formula set
                   forth in Exhibit 3.2.1 b) attached hereto with figures as of
                   the Closing Date as an example. In case of any dispute
                   between the Parties on this calculation of such amount, the
                   dispute shall be referred to an expert in accordance with
                   provisions of Article 3.2.1 c) (ii) hereafter.

<TABLE>
<CAPTION>
                                                                            IMPACT ON PAYMENTS
                                     CONDITION                                (IN US DOLLARS)
                      ----------------------------------------        -----------------------------
                      <S>                                             <C>
                      if Direct Costs above   [_____*] FF/vial        Decrease by [$_____*] million
                      if Direct Costs between [_____*] FF/vial        Decrease by [$_____*] million
                      if Direct Costs between [_____*] FF/vial        Increase by [$_____*] million
                      if Direct Costs below   [_____*] FF/vial        Increase by [$_____*] million
</TABLE>

                   The Payments other than the two Payments referred to
                   hereabove shall not be affected by the Thymoglobuline(R)
                   Direct Costs.

              c)   Other adjustment of the Payments

                   (i)    The Payment normally due as of any Payment Date shall
                          be canceled and Buyer shall definitively be released
                          from making any such Payment, unless on any such
                          Payment Date:

                          (a)  Seller is performing at least one (1) of the
                               services identified in the Service Agreement for
                               the Manufacturing with respect to Thymoglobuline,
                               or if Seller is not performing at least one (1)
                               of the services, such failure to perform is due
                               to (i) an event of force majeure, (ii) a request
                               from Buyer, (iii) or a termination of the Service
                               Agreement for the Manufacturing due to Buyer's
                               fault; or

                          (b)  At least one (1) product license with respect to
                               Thymoglobuline is then issued and valid in any
                               E.U. country or in the U.S.A., provided that if
                               no licenses are then issued and valid, the reason
                               for the failure to maintain such license is
                               caused, at least in part, by the inability of
                               Seller to perform under the Service Agreement for
                               the Manufacturing of Thymoglobuline and is not
                               due to an event of force majeure.

- ----------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
  SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.


                                       16

<PAGE>   18

                   (ii)   Additionally, the Payment normally due as of any
                          Payment Date shall be canceled and Buyer shall
                          definitively be released from making such Payment, if
                          on any such Payment Date (or, if such Payment Date is
                          not an Anniversary Date as this term is defined in the
                          schedule hereafter, on the preceding Anniversary
                          Date), the Actual Sales (as defined hereafter) are,
                          despite reasonable commercial efforts of Buyer, lower
                          than the minimum reference sales set forth for that
                          date in the schedule hereafter, and, provided that
                          Buyer has not arbitrarily changed its allocation of
                          products to markets other than the E.U. and the U.S.A.
                          solely in order to avoid making Payments hereunder.

<TABLE>
<CAPTION>
                                                                            MINIMUM
                                ANNIVERSARY DATE              REFERENCE SALES OF THYMOGLOBULINE
                          ----------------------------        ---------------------------------
                          <S>                                 <C>
                          12 months after Closing Date                    [_____*] vials
                          24 months after Closing Date                    [_____*] vials
                          36 months after Closing Date                    [_____*] vials
                          48 months after Closing Date                    [_____*] vials
                          60 months after Closing Date                    [_____*] vials
</TABLE>

                   It is understood between the Parties that:

                   -  for the second Payment Date (6 months after Closing Date),
                      the minimum sales test shall be applied to the 6-month
                      period preceding such date; as a result, no payment shall
                      be due on such date if Actual Sales on this 6-month period
                      are lower than [_____*] vials;

                   -  for all Payment Dates which are not Anniversary Dates of
                      the Closing Date, the minimum sales test to be referred to
                      shall be as of the preceding Anniversary Date.

                   For the purposes hereof, on each Anniversary Date of the
                   Closing Date, the Company will measure the total number of
                   Thymoglobuline(R) vials sold on the USA and European Union
                   market during the 12-month period preceding such date ( the
                   "Actual Sales").

                   Buyer shall maintain complete records of Actual Sales and
                   shall permit an independent certified public accountant from
                   a major international accounting firm ("CPA"), appointed by
                   Seller, to inspect and audit the Company's books 

- ----------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
  SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.


                                       17
<PAGE>   19

                   and records relating to Actual Sales upon 10 Business Days
                   prior written notice. The CPA shall report to Seller, with a
                   copy to Buyer, only the extent of any discrepancy between the
                   Actual Sales reported by Buyer and the amount of Actual Sales
                   calculated by CPA. Seller may exercise the rights hereunder
                   only once each calendar year and this right shall terminate
                   72 months after the Closing Date. Seller will then have the
                   right to notify to Buyer, within 15 days from the remittance
                   by CPA to Seller of its report with a copy to Buyer, its
                   decision to refer the matter to Ernst & Young, for
                   determining the Actual Sales amount, acting as an expert
                   pursuant to the provisions of Article 1592 of the French
                   Civil Code, jointly appointed between the Parties or, in case
                   of default by such expert, to any other expert which shall be
                   appointed by the President du Tribunal de Grande Instance de
                   Paris at the request of the most diligent party (the
                   "Expert"). The Expert shall be fluent in both English and
                   French. The Parties undertake to fully cooperate with the
                   Expert. The Expert shall be instructed to render the report
                   within one (1) month of referral to him. The Expert's report
                   shall be binding on the Parties. The Expert's fees shall be
                   borne by Seller unless the valuation effected by the Expert
                   differs by more than 3% (three percent) from the initial
                   valuation of Buyer, in which case Buyer shall bear the costs.
                   Seller and Buyer shall obtain no later than the Closing Date
                   a letter by Ernst & Young stating its approval to this
                   assignment.

              d)   Additional Readjustment of the Payments

                   In the event that the Company is not allowed by the German
                   regulatory authorities to distribute on a usual commercial
                   basis Thymoglobuline for the German market by September 30,
                   1998, subsequent Payments shall be reduced by [$__________
                   (_____)]* US Dollars per month. Payment reduction will not be
                   made in any month in which batches of Thymoglobuline, in
                   adequate amounts to reasonably address the German market
                   opportunity, are released for sale prior to the license being
                   renewed by the German regulatory authorities. In no event
                   shall the cumulative amount of the reduction exceed
                   [$__________ (_____)]* US Dollars, nor shall there be any
                   Payment reductions after September 30, 2000.

                   Additionally, in the event that the U.S. approval for
                   Thymoglobuline has not been granted by December 31, 1998 and
                   the only remaining blocking issue for non-approval is due to
                   manufacturing, chemistry, control or site inspection issues
                   ("ELA related") identified in the previous FDA deficiency
                   letter dated January 16, 1998 or Form 483 dated January 16,
                   1998, FDA letter dated March 26, 1998 and subsequent letters
                   relating to such issues, subsequent Payments shall be reduced
                   by [$__________ (_____)]* US Dollars per month 

- ----------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
  SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.


                                       18
<PAGE>   20

                   until such time as the U.S. approval is granted. In no event
                   shall the cumulative amount of the reduction exceed
                   [$__________ (_____)]* US Dollars.

                   If the Parties disagree on whether the failure to receive
                   U.S. approval is due to an ELA related matter as set forth
                   above, or if Seller considers that the inability to resolve
                   the issue is attributable to Buyer, the Parties shall submit
                   the question to an expert in U.S. regulatory matters whose
                   decision shall be binding on the Parties and which shall be
                   jointly appointed by the Parties or, failing such joint
                   appointment within 15 days from the occurrence of such
                   disagreement, by the President du Tribunal de Grande Instance
                   de Paris ruling under the refere proceedings upon the request
                   of the most diligent party.

       3.2.2  Variable Price:

              The Variable Price, which shall be payable by wire transfer within
              60 days of each Payment Date, shall consist of a first part based
              on the amount of Lymphoglobuline Net Sales (a) and a second part
              based on Antilfa Net Sales (b), and payable as set forth
              hereafter. For the purposes of this Agreement, "Net Sales" shall
              mean the amount actually received on sales of Lymphoglobuline or
              Antilfa by the Company or by its Affiliates, or by its authorized
              sublicensees (it being specified that IMTIX Products manufactured
              for clinical trial shall not be taken into account for the
              calculation of Net Sales) to third parties during the preceding
              six-month period less deductions for (i) normal and customary
              trade, quantity and cash discounts and emergency drug releases
              where such releases are provided by the Company or its Affiliates
              without charge, (ii) amounts repaid or credited by reason of
              rejection or return; (iii) V.A.T. on sales, withholding and excise
              taxes and duties levied on and/or other governmental charges made
              as to production, sale, importation, transportation, delivery or
              use paid by or on behalf of the Company, and (iv) transportation
              costs including insurance.

              a)   Payments on Lymphoglobuline Net Sales shall be equal to
                   [_____*] of the amount of such Net Sales every six months for
                   a period of 10 years as from the Closing Date.

              b)   Payments on Antilfa for a period of 10 years starting on the
                   date referred to hereafter as the "Delivery Date" which shall
                   be the earlier of (i) the date of delivery by FDA of the BLA
                   marketing approval in the USA for solid organ transplants for
                   Antilfa and (ii) the date of delivery of the equivalent
                   marketing approval in European Union according to the
                   centralized market approval procedure or in any E.U. country
                   if a marketing approval is delivered for such country only,
                   shall be calculated as follows:

- ----------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
  SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.


                                       19
<PAGE>   21

                   (i)    One-time payment of [$__________ (_____)]* million US
                          Dollars upon Delivery Date;

                   (ii)   a payment based on Antilfa Net Sales equal to (i)
                          [    *] of the amount of such Net Sales by the Company
                          and its Affiliates, or (ii) if Net Sales are made by
                          Company's authorized sublicensees [    *] of such
                          Company's authorized sublicensees Net Sales every six
                          months for a period of 10 years as from the Delivery
                          Date.

       3.2.3  If, at the time the payment of a part of the Purchase Price
              becomes due, an arbitration award rendered pursuant to Article XVI
              hereafter shall have upheld (i) a claim by Buyer under the Share
              Purchase Agreement referred to in Article IX hereafter, or (ii) a
              claim by Buyer based on any other breach of representations,
              warranties or covenants by Seller to Buyer under any agreement
              referenced herein, Buyer shall be entitled to setoff the payment
              of such part of the price against the amount of such claim.

ARTICLE IV - CONDITIONS PRECEDENT

4.1    CONDITIONS PRECEDENT

       The completion of the Purchase shall be subject to the fulfillment, no
       later than the Closing Deadline, of the following conditions precedent,
       which are cumulatively stipulated for the benefit of Buyer and which only
       Buyer may therefore waive, except conditions stipulated under Articles
       4.1.1 and 4.1.2 which neither Party can waive.

       4.1.1  Completion of the Partial Business Contribution by Seller to the
              Company

              The Business shall have been contributed to the Company under a
              Partial Business Contribution (Apport Partiel d'Actif) meeting the
              following conditions. The Partial Business Contribution shall have
              been duly authorized by the shareholders of Seller and the Company
              and effected in application of the Partial Business Contribution
              Agreement (Traite d'Apport Partiel d'Actif) substantially in the
              form of Exhibit 2.2 hereto and with valuations of assets and
              liabilities which will have been submitted to Buyer during the
              Second Due Diligence Period hereafter. It is understood that such
              condition precedent shall not be fulfilled before the completion
              of conditions precedent set forth in Articles 4.1.2 and 4.1.3
              hereafter.

       4.1.2  Delivery by the General Manager of the French Medicine Agency
              ("Agence du Medicament") of (i) the authorization to operate as a
              manufacturing pharmaceutical 

- ----------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
  SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.


                                       20
<PAGE>   22

              establishment ("Autorisation d'Etablissement Pharmaceutique
              Fabricant") to the Company and (ii) the corresponding amendment to
              the existing Seller's Autorisation d'Etablissement Pharmaceutique.

       4.1.3  Completion of legal, technical and financial due diligence by
              Buyer and its counsels satisfactory to Buyer on the items listed
              in Exhibit 4.1.3 and on the latest available draft of the Partial
              Business Contribution Agreement which will have been sent to the
              prospective contribution auditor ("Commissaire a la Scission") and
              delivered to Buyer at the latest 15 days prior to the expiration
              of the Initial Due Diligence Period as defined below, which due
              diligence shall not have revealed an event which may materially
              adversely affect the Business. This due diligence will be carried
              out in two phases:

              (i)  Seller shall, within 15 days from the Master Agreement Date,
                   set up a data room for a period of five Business Days, unless
                   Seller consents to an extension up to three additional
                   Business Days, which consent shall not be unreasonably
                   withheld, which data-room can be located outside the premises
                   of Seller, and containing all documents required by Buyer as
                   per the list attached hereto as Exhibit 4.1.3 and due
                   diligence will be conducted by Buyer and its counsels within
                   30 days following the day when all information is available
                   to Buyer (the "Initial Due Diligence Period"). No copies
                   shall be made of documents in the data room without Seller's
                   consent which shall not be unreasonably withheld. All
                   documents delivered by Seller pursuant to a due diligence
                   request shall be considered Confidential Information under
                   Article XIII hereof.

                   Upon expiration of the Initial Due Diligence Period, Buyer
                   shall remit to Seller a certificate acknowledging the
                   completion to its satisfaction of the Initial Due Diligence
                   in the form of the Affidavit 1, provided that if Buyer does
                   not deliver the Affidavit 1, Buyer shall inform Seller in
                   writing at the same date of its reasons for not delivering
                   the Affidavit 1.

              (ii) Buyer shall, in addition, have the right, for 5 Business Days
                   following the Filing Date to make review of the final
                   valuation of assets and liabilities in the Partial Business
                   Contribution Agreement it would estimate appropriate (the
                   "Second Due Diligence Period").

                   Upon expiration of the Second Due Diligence Period, Buyer
                   shall remit to Seller a certificate acknowledging the
                   completion to its satisfaction of such due diligence in the
                   form of the Affidavit 2, provided that if Buyer does not
                   deliver the Affidavit 2, Buyer shall inform Seller in writing
                   at the same date of its reasons for not delivering the
                   Affidavit 2.


                                       21
<PAGE>   23

4.2    FULFILLMENT

       4.2.1  Provided the above conditions precedent set forth in Articles
              4.1.2 and 4.1.3 are fulfilled, the Parties undertake to close the
              Transaction and therefore to complete the steps set forth in
              Article 2.2.3 hereabove at the date of satisfaction of the last
              condition precedent to be satisfied and in no event later than the
              Closing Deadline, subject to the provisions of Articles 4.2.2 and
              4.2.3 hereafter.

       4.2.2  Buyer shall have no obligation to close and consummate the
              Transaction if Buyer determines that a material adverse change,
              whether legal, financial or of any kind, has occurred in the
              Business, the Company or the Seller in connection with the
              Business prior to the Closing Date. Buyer shall specify such a
              material adverse change in writing to Seller. If Buyer exercises
              its rights under this clause, Buyer will only be allowed not to
              close the Transaction and shall not be allowed to attempt to
              renegotiate the terms of the Transaction. Additionally, an
              amendment to the existing Manufacturing and Supply Agreement dated
              October 13, 1993 between the Parties in the form attached hereto
              as Exhibit 4.2.2 shall automatically become enforceable.

       4.2.3  Seller shall have no obligation to close and consummate the
              Transaction if prior to the Closing Date:

              (i)     there is a Change of Control of Buyer;

              (ii)    Buyer becomes subject to voluntary or involuntary
                      bankruptcy under applicable law;

              (iii)   Buyer is enjoined from conducting all clinical trials in
                      the United States of America;

              (iv)    an event has occurred which makes the occurrence of either
                      (i), (ii) or (iii) above unavoidable.

ARTICLE V - COVENANTS

5.1    COVENANT ON CONDITIONS PRECEDENT/CONTRIBUTION AGREEMENT

       Each Party undertakes to take in a timely manner all necessary actions
       and to make its best efforts in order that the conditions precedent set
       forth in Article IV hereabove be met as soon as possible and to inform
       from time to time the other Party on the implementation of those actions.


                                       22
<PAGE>   24

       In particular, the Parties will use their best efforts to obtain the
       authorization of the General Manager of the French Medicine Agency
       referred to in Article 4.1.2 hereabove.

       Seller also undertakes to take in a timely manner all necessary actions
       and to make its best efforts in order that steps described in Articles
       2.2.2 and 2.2.3 hereabove shall be completed as soon as possible. Seller,
       acting as shareholder of the Company, hereby covenants to vote in favor
       of the contribution at the shareholders' meeting of the Company to be
       convened as provided under Article 2.2.3 hereabove. In addition, pursuant
       to a letter in the form attached as Exhibit 2.2.1 b, Rhone-Poulenc Pharma
       S.A., acting as shareholder of Seller, has confirmed its approval of the
       Transaction provided all other conditions precedent have been fulfilled.

5.2    OBLIGATION TO COOPERATE

       5.2.1  During the Initial Due Diligence Period and the Second Due
              Diligence Period set forth in Article 4.1.3 hereabove, Seller will
              provide Buyer and its representatives with complete information
              requested in compliance with, respectively, Articles 4.1.3 (i) and
              (ii) hereabove.

              Seller will organize reasonable appointments with those senior
              employees and, to the extent possible, external advisors
              considered as involved in the Business in order to perform the
              Initial Due Diligence provided that Buyer has requested previously
              to Seller its need for such appointments, it being understood that
              all costs of external advisors (except reasonable attorney's fees)
              requested by Buyer and invoiced to Seller by such advisors in this
              respect shall be borne by Buyer.

       5.2.2  -  Seller, which has a good knowledge of the organization of the
                 French Medicine Agency and of other French and foreign public
                 authorities having competence over the pharmaceutical sector,
                 undertakes to use all its efforts and expertise to facilitate
                 in a timely manner the discussions with French and foreign
                 public authorities for the purposes of completion of this
                 Transaction.

              -  The Parties will use their best efforts to promptly obtain (i)
                 the prior authorization of the General Manager of the French
                 Medicine Agency ("Directeur General de l'Agence du Medicament")
                 to transfer to the Company all the French "Autorisations de
                 Mise sur le Marche" held by Seller and Affiliates related to
                 the IMTIX Products, (ii) from any other foreign public
                 authorities the approval to transfer foreign licenses on IMTIX
                 Products held by Seller or its Affiliates (other than those
                 held by the Subsidiaries) to the Company (to the extent
                 permitted by local regulations and laws), and (iii) the U.S.
                 PLA/ELA approval for Thymoglobuline (R). For information
                 purposes, a list of key steps to be taken with the French
                 Medicine Agency, together with an estimated timetable is
                 attached hereto in Exhibit 5.2.2.


                                       23
<PAGE>   25

              -  Seller will use its best efforts to have its Affiliates (other
                 than Subsidiaries) transfer all franchises, licenses, permits,
                 consents, authorizations, certificates, trademarks as listed in
                 the Partial Business Contribution Agreement and approvals of
                 any regulatory, administrative or other governmental agency
                 issued to or held by them, including all authorizations to
                 export products not licensed in France, to the extent relating
                 to the IMTIX Products, to the Company, except where this
                 transfer would violate local regulatory laws.

              -  Seller will use its best efforts to have third parties, which
                 are party to agreements attached in part only to the Business,
                 enter into new agreements with the Company covering the part of
                 those agreements attached to the Business, to the extent such
                 agreements are material to the Business.

       5.2.3  As of the date of this Agreement and until the expiration of a
              12-month period after the Closing Date:

              -  The Parties undertake to set up a transition committee (the
                 "Transition Committee") which will review and advise on
                 transition activities and include:

                 (i)  until the Closing Date for Seller: Gilles Alberici, Rene
                      Labatut, a Regulatory Affairs representative, a QA/QC
                      representative, a Finance representative and any other
                      necessary people; and for Buyer: the head of Regulatory
                      Affairs, the CEO, the VP of Operations, the VP of
                      Pharmaceutical Development, and

                 (ii) after the Closing Date, for Seller, the same persons
                      (except Gilles Alberici and Rene Labatut), for the
                      Company, Gilles Alberici, for Buyer, the same persons, it
                      being specified that Rene Labatut will also be a member of
                      the Transition Committee whether as a representative of
                      Seller or of the Company, subject to Article 5.5
                      hereafter.

                      The Transition Committee will meet in France, no less than
                      once every quarter and more often if appropriate. Until
                      the Closing Date, the Transition Committee will be chaired
                      by Seller's Senior Vice President and Chief Financial
                      Officer and, as from the Closing Date, by Buyer's CEO or a
                      designated representative.

       5.2.4  As of the Filing Date and until the Closing Date:

              -  The parties will establish a management committee (the
                 "Management Committee") which will consist of the members of
                 the Transition Committee referenced above in Article 5.2.3. The
                 Management Committee will oversee the operations of the Company
                 and the Business and specifically will have on an internal
                 basis management control and decision-making power regarding
                 but not limited to, the following:


                                       24
<PAGE>   26

                 a)  defining clinical development and Phase IV programs;

                 b)  all regulatory matters;

                 c)  manufacturing planning and operations;

                 d)  marketing, sales and product distribution plans for all 
                     territories;

                 e)  recruiting, legal and financial matters.

                 Subject to any legal obligations and restrictions applicable to
                 Seller, Seller will use its best efforts to implement the
                 Management Committee's decisions without materially adversely
                 affecting Seller's non-IMTIX business. Only the representatives
                 of Buyer will have voting power on the Management Committee;
                 all other members will have advisory powers only. The
                 Management Committee will meet on a monthly basis either in
                 person in France, or telephonically and more often as
                 reasonably requested by Buyer. Subject to decisions of the
                 Management Committee, Seller agrees to manage and operate the
                 Business and the Company according to normal business practices
                 and in the ordinary course of business.

                 The Management Committee shall act only according to normal
                 business practices and in the ordinary course of business.

                 The Management Committee shall not be entitled to recommend or
                 decide any dismissal of employee (other than in case of "faute
                 lourde" or "faute grave"), any divestment of or investment in
                 intangible or tangible assets nor any change in the strategy
                 followed by the Seller for the Business until the Filing Date.

       5.2.5  Cooperation for SEC audits

              Seller has been informed of the obligations of Buyer to perform
              audits of the Company and the Business for the purpose of
              information of the U.S. SEC as requested under applicable laws and
              regulations. Seller agrees to provide information to Buyer and
              cooperate with Buyer for this purpose, to the extent requests of
              Buyer in this respect are reasonable.

       5.2.6  Immunotech Agreement

              The parties shall exercise best efforts to transfer and assign the
              contract between PMC and Immunotech dated June 15, 1989, but if,
              in spite of all best efforts, they are unable to do so, PMC shall,
              subject to legal or contractual limitations in such contract,
              grant to Buyer or its Affiliate a sublicense that achieves as
              closely as possible, the same effect in all respects as a transfer
              and assignment of such contract would achieve.


                                       25
<PAGE>   27

5.3    INTERIM AGREEMENTS

       In the event that the transfer to the Company of all the French
       "Autorisations de Mise sur le Marche" or equivalent authorizations in
       foreign countries held by Seller or its Affiliates related to the IMTIX
       Products has not been authorized as of the Closing Date, the Parties
       agree to use their best efforts to negotiate and consummate a transaction
       having business, financial, tax and legal effects as similar to the
       Transaction as reasonably possible so as to take into account the delay
       in transfer of such authorizations.


5.4    MANAGEMENT OF THE BUSINESS AND THE COMPANY

       Between the date of this Agreement and the Closing Date and subject to
       the prerogatives granted to the Management Committee pursuant to Article
       5.2.4 hereabove, Seller hereby undertakes to manage and operate the
       Business and the Company according to normal business practices and in
       the ordinary course of business, and undertakes to, with respect to the
       Business, and shall procure that, with respect to the Business, the
       Company and the Subsidiaries do not take any of the following actions
       without having received the prior written consent of Buyer, which shall
       not be unreasonably or untimely withheld and which consent shall be
       deemed granted if Buyer has not responded otherwise prior to the
       expiration of a 15-day period following a written request for consent:

       (1)    enter into or vary any material contract or undertaking other than
              in the ordinary course of business;

       (2)    give or discharge any guarantee, or any loan or financing or any
              security in relation to such guarantees, loans or financing;

       (3)    subscribe or extend any borrowing;

       (4)    enter into any agreement or agreements requiring capital
              expenditure in aggregate of more than 500,000 French Francs (VAT
              not included);

       (5)    pass any board or shareholders resolution other than for the
              purposes of this Agreement or the Transaction;

       (6)    dispose of any assets other than in the ordinary course of
              business;

       (7)    vary or terminate any insurance policies dedicated to the Business
              and the Company notably decrease product liability insurance, and
              subject to reasonable changes of Rhone-Poulenc Group policies it
              being understood that Seller's insurance policies linked to the
              Business will terminate at the Closing Date;


                                       26
<PAGE>   28
       (8)    settle any existing litigation in excess of 150,000 French Francs;

       (9)    enter into or vary any material transaction with a related party
              (including the shareholders or the managers);

       (10)   hire or terminate (for reasons other than "faute lourde" or "faute
              grave") the employment of any employee with an annual gross salary
              in excess of 250,000 French Francs or of several employees the
              gross salary of which, in aggregate, exceeds 500,000 French
              Francs;

       (11)   reallocate any employee of the Business to any other division,
              business or entity of the Seller;

       (12)   disclose any proprietary or confidential information to third
              parties;

       (13)   modify the C4 building or the V3bis building, or their equipment,
              in any way, unless in response to a specific request from the FDA
              or to a request of Buyer or as provided under Article 2.1.2 b)
              (ii) hereof.

5.5    STATUS OF MR. R. LABATUT ("R.L.")

       Seller hereby expressly agrees to the following:

       -      Buyer will be entitled to make an offer to R.L. to join the
              Company, which offer Buyer will not have to disclose to Seller.

       -      If R.L. decides to remain with Seller rather than accepting
              Buyer's proposal, and for so long as R.L. so remains, Seller
              undertakes to dedicate continuously R.L. to Buyer at cost (based
              on time actually spent at Buyer's request), for a period of 3
              years, for up to (i) 45% of his time for the first year, (ii) 35%
              for the second year and (iii) 25% for the third year. Every six
              months as from the Closing Date, Buyer shall provide estimates of
              its needs for the following 12 months, of which the first 6 months
              estimates only shall be binding.

       The above shall not prohibit Seller from dismissing R.L. in case of
       "faute lourde" or "faute grave", in which case Seller shall be released
       from the foregoing obligation.

5.6    NON-SOLICITATION

       Seller undertakes, unless otherwise mutually agreed between the Parties,
       in the event that any of the employees dedicated to the Business listed
       in Exhibits 2.1.1 a) and 2.1.1 c) hereto would refuse to become an
       employee of the Company or resign from Seller or the 


                                       27
<PAGE>   29

       Company after the transfer of the Business, not to hire such employee or
       to make any offer to the same for any position in Seller or any of its
       Affiliates.

       As a general principle, each Party undertakes not to solicit, directly or
       indirectly, or entice away from employment with the other Party (or with
       the Company) any person employed thereby in the capacity of employee,
       director, representative or consultant, except with the prior written
       approval of the other Party.

       The above provisions shall remain in effect as from the Closing Date and
       until expiration of a 5-year period from the same.

       It is understood between the Parties that provisions of this Article 5.6
       are stipulated without prejudice to Article 5.5 hereof.

ARTICLE VI - CLOSING DEADLINE

If, as of thirty days prior to the Closing Deadline, the condition in Article
4.1.2 has not been met, the Parties agree as follows:

       (i)    The Parties shall jointly appoint a regulatory expert, who shall
              be fluent in French and in English and who shall be a recognized
              professional in the pharmaceutical business community. If the
              Parties fail to agree on such expert, such expert shall be
              appointed by the President du Tribunal de Grande Instance de Paris
              at the request of the most diligent party. Such expert shall
              review the status of the pharmaceutical establishment license
              application. If the expert, who shall deliver his or her report
              within 15 days of appointment, determines that it is probable that
              a pharmaceutical establishment license at least with respect to
              Thymoglobuline will be granted to the Company prior to August 31,
              1999, then the Parties agree to enter into a restated Master
              Agreement reiterating substantially all the provisions of this
              Agreement, as adjusted to conform with any legal, tax and
              accounting requirements, and with a new Closing Deadline as of
              August 31, 1999;

       (ii)   If the Closing Deadline is redefined as set forth above, the
              Parties agree to use their best efforts to negotiate and
              consummate agreements having business, financial, tax and legal
              effects as similar to the Transaction as reasonably possible for
              the period ending on August 31, 1999;

       (iii)  The Parties also agree that the valuations in the Partial Business
              Contribution Agreement shall be reset to January 1, 1999;

       (iv)   Additionally, if the Transaction contemplated hereby is not
              consummated prior to the Closing Deadline, as redefined, Buyer
              shall have a right of first offer with respect to a sale of the
              Business in any form by Seller until February 29, 2000. In the
              event 


                                       28
<PAGE>   30

              Seller receives a bona fide offer from a third party to buy the
              Business at any time prior to February 29, 2000, Seller shall
              provide written notice to Buyer of such bona fide third party
              offer, which notice shall include all material terms, including
              price. Buyer shall have fifteen (15) days to review the proposed
              sale and shall have the right, upon written notice to Seller
              within such 15-day period to exercise its right to purchase the
              Business on the same financial terms as provided in the notice.
              Upon notice of Buyer's intention to exercise its purchase rights
              hereunder, the Parties shall be bound by the terms and conditions
              as provided for in the notice and they agree to negotiate in good
              faith and to promptly execute and deliver all agreements and
              documents which are necessary to consummate such a transaction. If
              Buyer does not exercise its purchase rights hereunder, Seller
              shall have the right to enter into definitive acquisition
              documents with such third party provided it is on substantially
              the same financial terms as set forth in the notice to Buyer, and
              provided further that the financial terms may be changed if there
              has been a major change in the Business after delivery of the
              notice.

It is agreed between the Parties that, should the Closing not take place prior
to the Closing Deadline due to a delay attributable to the French Medicine
Agency in granting the Pharmaceutical Establishment authorization referred to in
Article 4.1.2 hereof, the provisions hereabove shall apply. Should the Closing
not take place prior to the Closing Deadline because of a delay in receiving the
Pharmaceutical Establishment authorization referred to in Article 4.1.2 hereof,
due to issues relating to Lymphoglobuline manufacturing, the Parties agree to
negotiate in good faith a contract manufacturing and distribution agreement with
respect to Lymphoglobuline and more generally to use their best efforts to
negotiate and consummate a transaction having business, financial, tax and legal
effects as similar to the Transaction as reasonably possible.

ARTICLE VII - REPRESENTATIONS AND WARRANTIES

7.1    REPRESENTATIONS AND WARRANTIES OF THE SELLER

       Seller represents and warrants for itself, the Subsidiaries and the
       Company to Buyer the following as of the Master Agreement Date and as of
       the Closing Date

       7.1.1  Organization

              Seller, the Company and the Subsidiaries are corporations duly
              organized, validly existing and in good standing under the laws of
              France (or under the laws of their country of incorporation for
              the Subsidiaries) and have all requisite corporate power and
              authority to own or lease and operate their properties and to
              carry on their business.


                                       29
<PAGE>   31

       7.1.2  Capacity and Power of Seller; Binding effect

              Seller has duly executed this Agreement and no further proceeding,
              action or consent is necessary to authorize the execution of this
              Agreement and the consummation of the Transaction, except for
              Board of Directors' and shareholders' authorization relating to
              the Partial Business Contribution Agreement as set forth herein.
              This Transaction has been duly authorized by Seller's Board of
              Directors, and Seller's Work Council (Comite Central d'Entreprise)
              has been duly consulted in compliance with provisions of the
              French Labor Code. This Agreement represents a validly binding
              obligation of Seller in accordance with its terms.

       7.1.3  Non-Violation

              The performance of this Agreement and the consummation of the
              Transaction by Seller, the Company and the Subsidiaries will not
              constitute a violation of, or a default under, or conflict with
              (i) any provision of the Articles of Incorporation of Seller, the
              Company or the Subsidiaries or (ii) any legal requirement,
              judgment or administrative decision which may apply to Seller, the
              Company or the Subsidiaries or by which Seller, the Company or the
              Subsidiaries are bound or (iii) any agreement or undertaking to
              which Seller, the Company or the Subsidiaries are a party or by
              which any of the same are bound, the consequence of which could
              materially affect the validity and the enforceability of this
              Agreement or of the Transaction.

7.2    REPRESENTATIONS AND WARRANTIES OF THE BUYER

       Buyer represents and warrants to Seller the following as of the Master
       Agreement Date and as of the Closing Date:

       7.2.1  Organization

              Buyer is a company duly organized, validly existing and in good
              standing under the laws of the State of Delaware and has all
              requisite corporate power and authority to own or lease and
              operate its properties and to carry on its business.

       7.2.2  Capacity and Power of Buyer; Binding effect

              Buyer has duly executed this Agreement and no further proceeding,
              action or consent is necessary to authorize the execution of this
              Agreement and this Agreement has been duly authorized by Buyer's
              Board of Directors. This Agreement represents a validly binding
              obligation of Buyer in accordance with its terms.


                                       30
<PAGE>   32

       7.2.3  Non-Violation

              The performance of this Agreement and consummation of the
              transactions contemplated hereby by Buyer will not constitute a
              violation of, or a default under, or conflict with (i) any
              provision of the Articles of Incorporation of Buyer or (ii) any
              legal requirement, judgment or administrative decision which may
              apply to Buyer or by which Buyer is bound or (iii) any agreement
              or undertaking to which Buyer is a party or by which it is bound,
              the consequence of which could materially affect the validity and
              the enforceability of this Agreement or of the Transaction.

       7.2.4  Structure of the Transaction

              Buyer acknowledges that at its request the Company to which Seller
              will contribute the Business will have the form of a societe par
              actions simplifiee ("SAS") and hereby undertakes to indemnify and
              hold Seller harmless from and against any liability that it may
              incur only as a direct consequence of the choice of an SAS as
              opposed to an Societe Anonyme ("SA") as the legal form of the
              Company.

       7.2.5  Environmental Provisions

              Buyer acknowledges that it is jointly bound by and guarantees the
              due performance of those environmental provisions set forth under
              each of the Commercial Lease Agreements to be executed in the form
              attached as Exhibit 2.1.2 b) (ii) hereto and this guarantee shall
              survive 18 (eighteen) months after expiration date of the
              Commercial Lease Agreements.

ARTICLE VIII - SHARE PURCHASE AGREEMENT

As mentioned hereabove, the Parties shall execute on the Master Agreement Date a
Share Purchase Agreement under conditions precedent substantially in the form of
Exhibit 8 hereto which the Parties agree is an integral part of the overall
Transaction. The Share Purchase Agreement will contain the following provisions
with respect to security interest to be granted by Buyer:

       (i)    In order to secure Payments hereunder, Buyer shall provide that a
              letter of credit from Nationsbank, or a financial institution of
              equivalent standing, in the amount of $6 (six) million US Dollars
              be issued in favor of Seller for a period of 2 1/2years beginning
              on the Closing Date substantially in the form attached hereto as
              Exhibit 8 (i). Such letter of credit shall provide that Seller
              shall be entitled to payment after delivering a certificate also
              in the form attached in Exhibit 8 (i-2), executed solely by Seller
              to Nationsbank. At the expiration of such 2 1/2year period, Buyer
              shall provide that a new letter of credit in the amount of $4
              (four) million US Dollars be issued in favor of Seller for an
              additional 2 1/2year period in the form attached hereto as Exhibit
              8 (i). The transaction costs of issuing such letters of credit
              shall be shared 


                                       31
<PAGE>   33

              equally between Buyer and Seller, and Seller agrees to immediately
              reimburse Buyer for 50% of such costs with Seller's portion not to
              exceed 0.5% of the secured amount per year upon invoice, provided
              that Buyer shall remain solely responsible for any pledge of
              assets associated therewith.

       (ii)   In the event that Buyer is unable or fails to make Payments, and
              such failure is not cured within 30 days of written notice from
              Seller to Buyer of such failure, then at such time SMC shall
              immediately issue to Seller up to 100,000 (one hundred thousand)
              shares of the common stock of SMC at no cost to Seller, such
              number of shares to be proportionally adjusted in case of stock
              splits, dividends and recapitalization. SMC shall at all times
              keep such 100,000 (one hundred thousand) shares reserved and
              available for immediate issuance to Seller. In order to determine
              the amount paid through the issuance of 100,000 (one hundred
              thousand) shares, the shares shall be valued at their fair market
              value at the time of issuance. However, the valuation shall only
              be definitive at the time Seller has been able to sell the shares
              and to recover the corresponding price. Such recovered price shall
              be the sole amount to be offset against failed Payments. Any
              recovered amount in excess of the failed Payments shall not be
              reimbursed to Buyer, and shall be considered as an indemnification
              for late payment. The recovery of any failed Payment not
              recovered, in full or in part, through the sale of shares will be
              pursued by any other means. At the Closing Date, SMC shall deliver
              to Seller a certificate stating the fair market value of the
              100,000 (one hundred thousand) shares as of the Closing Date, and
              the corresponding percentage in SMC's capital stock on a fully
              diluted basis.

       (iii)  In the event that there is a "Change of Control" (as defined
              below) of either the Company or Buyer involving an unrelated third
              party after the Closing Date, Buyer will provide that a letter of
              credit be issued by Nationsbank, or a financial institution of
              equivalent standing, in favor of Seller with respect to all unpaid
              Payments as of the date of the Change of Control. For purposes of
              this Article, a "Change of Control" shall mean a sale of
              substantially all of the assets of either the Company or Buyer to
              a non-Affiliate of Buyer or any transfer by way of contribution,
              merger or reorganization of more than 50% of the voting power of
              the capital stock of either the Company or Buyer to a
              non-Affiliate of Buyer. In the event that such letter of credit
              has been issued, clauses (i) and (ii) hereof automatically
              terminate.

       (iv)   In no event shall Seller be entitled to cumulative remedies and
              guarantees pursuant to this Article VIII in an amount which
              exceeds the amount of unpaid Payments, plus any interest accrued
              at the French legal rate (taux d'interet legal) between the
              Payment Date and the effective date of Payment.

The Share Purchase Agreement will, in addition, contain the following
non-competition provisions.


                                       32
<PAGE>   34

              a)     As of the Closing and continuing for a period of 5 (five)
                     years after the Closing, Seller undertakes, unless
                     otherwise mutually agreed between the Parties, in the event
                     that any of the employees dedicated to the Business listed
                     in Exhibits 2.1.1 (a) and 2.1.1 (c) hereto would refuse to
                     become an employee of the Company or resign from Seller,
                     the Company or any of the Subsidiaries after the transfer
                     of the Business, not to hire such employee or to make any
                     offer to the same for any position in Seller or any of its
                     Affiliates.

              b)     As of the Closing and continuing for a period ending five
                     (5) years after the Closing, PMC agrees that it shall not
                     (and cause its Affiliates other than its shareholders not
                     to) engage, associate itself with, or collaborate in,
                     directly or indirectly, in any country, whether for its own
                     account or as a shareholder (other than as a less than 3%
                     shareholder of a publicly-held company), partner, joint
                     venturer, firm, corporation, or other entity, in any
                     activity in the fields of R&D, production, marketing,
                     distribution or management relating to the field of (i)
                     transplantation or (ii) immunosuppression (within or
                     outside of the field of transplantation) using anti Tcell
                     agents.

                     This provision shall not preclude Seller from acquiring
                     companies or businesses which involve organ transplantation
                     activity provided (i) that such activity represents only a
                     minor portion of such company or business and (ii) that
                     Seller shall in such case notify Buyer of such event and
                     offer for sale to Buyer such branch of activity at a
                     reasonable price based on the price paid by Seller.

                     Seller further undertakes not to grant or transfer any
                     license or right whatsoever, relating to the field of (i)
                     transplantation or (ii) immunosuppression (within or
                     outside of the field of transplantation) using anti Tcell
                     agents, which is the subject of a license or grant to the
                     Company or Buyer pursuant to this Agreement and the
                     Ancillary Agreements in relation to the Business to any
                     Affiliate (including its shareholders) or third party.

              (c)    As of the Closing and continuing for a period of 5 (five)
                     years after the Closing, PMC agrees that it shall not (and
                     cause its Affiliates not to):

                     (i)    solicit, directly or indirectly, or entice or
                            endeavor to solicit or entice away from employment
                            with Buyer, the Company or any of the Subsidiaries
                            any person employed thereby in the capacity of
                            employee, director, representative, consultant,
                            except with the prior written approval of Buyer, the
                            Company or any of the Subsidiaries, and Buyer agrees
                            to take the same commitment in favor of PMC;

                     (ii)   use any trademark, tradename or any other
                            identifying symbol presently used by the Company in
                            the Business.


                                       33
<PAGE>   35

              (d)    Except as required by law or expressly permitted under this
                     Agreement or any of the other Agreements, PMC shall cause
                     its respective Affiliates, officers, directors, employees,
                     agents and subcontractors (collectively, "Representatives")
                     and Representatives of its Affiliates to keep confidential
                     any and all technical, commercial, scientific, financial
                     and other data, processes, documents or other information
                     (whether in oral or written form) or physical object
                     (including, without limitation, intellectual property,
                     marketing data, agreements with any third party, license
                     applications, business plans and projections) it may have
                     with respect to the IMTIX Products, the Assets, the
                     Business, the Company or any of the Subsidiaries and cease
                     use of proprietary and other confidential business and
                     technical information related to the same, for a period
                     expiring 15 (fifteen) years as from the Closing.

              (e)    The Parties agree that due to the unique nature of the
                     experience, knowledge and capabilities of PMC, there can be
                     no adequate remedy at law for any breach of its obligations
                     hereunder, that any such breach may allow PMC, and/or third
                     parties to unfairly compete with Buyer, the Company or the
                     Subsidiaries resulting in irreparable harm to Buyer, the
                     Company or the Subsidiaries, and therefore, that upon any
                     such breach or any threat thereof, Buyer, or the Company,
                     or the Subsidiaries, shall be entitled to appropriate
                     equitable remedy it might have at law.

ARTICLE IX - WARRANTY AGREEMENT

The Share Purchase Agreement that the Parties shall enter into on the Master
Agreement Date substantially in the form of Exhibit 8 hereto will necessarily
include a warranty agreement as to the assets and liabilities of the Company,
among other things, as is common practice.

Concerning tax liabilities, the following provisions are here specified:

       --     Buyer shall be liable for any transfer tax stemming from the
              Transaction after the Closing Date, directly caused by an act or
              omission to act by the Buyer,

       --     Other than the 1% registration tax (not to exceed 20,000 French
              Francs) which shall be borne by Buyer in connection with the
              purchase of the Shares, Buyer and Seller shall share equally any
              other additional registration tax stemming from the Transaction
              and assessed after the Closing Date and resulting from Case Law or
              a retroactive change of Law.

ARTICLE X - KNOW-HOW LICENSE AGREEMENT


                                       34
<PAGE>   36

The Parties undertake to execute the worldwide Know-How License Agreement
between Seller and the Company substantially in the form of Exhibit 2.1.2 b) (i)
hereto, which the Parties agree is an integral part of the overall Transaction.

It is specified that as from year 11, the Know-How License Agreement will remain
in effect if renewed by Buyer regardless of the fact that no royalties may be
due by the Company.

With respect to patents, to Seller's best knowledge, Seller has no rights under
any patents that cover or otherwise affect the development, manufacture,
distribution or use of the IMTIX Products. In the event that at any future time,
it is determined that such patent(s) has such effect, then they will each
automatically be deemed licensed pursuant to and as part of the Know-How
license, without further action by the parties, effective as of the Closing
Date.

ARTICLE XI - LEASE AGREEMENT

The Parties undertake to execute the Commercial Lease Agreements between Seller
and the Company and the side letter substantially in the form of Exhibit 2.1.2
b) (ii) hereto, which agreements and letter the Parties agree are an integral
part of the overall Transaction.

ARTICLE XII - SERVICE AGREEMENT FOR MANUFACTURING/EQUINE PLASMA SUPPLY AGREEMENT

The Parties undertake to execute the Service Agreement for Manufacturing and the
Equine Plasma Supply Agreement between Seller and the Company respectively in
the form of Exhibit 2.1.2 b) (iii-1) and Exhibit 2.1.2 b) (iii-2) hereto, which
the Parties agree are both an integral part of the overall Transaction.

ARTICLE XIII - CONFIDENTIALITY

a)     General:

       Except as expressly set forth in this Article, each Party shall cause its
       respective Affiliates, officers, directors, employees, agents and
       subcontractors (collectively, "Representatives") and Representatives of
       its Affiliates to keep confidential any and all technical, commercial,
       scientific and other data, processes, documents or other information
       (whether in oral or written form) or physical object (including, without
       limitation, intellectual property, marketing data, agreements between any
       Party and a third party, license applications, and business plans and
       projections of any Party) acquired from the other Party (the "Other
       Party"), its Affiliates or its Representatives prior to or after the date
       of this Agreement and which relates to the Transaction, including all
       information exchanged as of the date of this Agreement; provided in each
       case that such information is marked "confidential" or, if 


                                       35
<PAGE>   37

       verbal, such information is reduced to writing and marked "confidential"
       within 30 days of the date of disclosure ("Confidential Information"),
       and each Party shall not disclose, directly or indirectly, and shall
       cause its Representatives not to disclose, directly or indirectly, any
       Confidential Information to anyone outside such person, such Affiliates
       and their respective Representatives, except that the following
       information disclosed hereunder to any Party will not be deemed
       Confidential Information for purposes of this Agreement, if such person
       (the "Receiving Person") can demonstrate that such Confidential
       Information:

       (i)    is or hereafter becomes generally available to the trade or public
              other than by reason of any breach or default by the Receiving
              Person, any of its Affiliates or any Representative of the
              foregoing with respect to a confidentiality obligation under this
              Agreement;

       (ii)   was already known to the Receiving Person or such Affiliate or
              Representative prior to disclosure; provided, however, that this
              exception shall not apply to any Confidential Information
              transferred by Seller to Buyer by virtue of the Transaction;

       (iii)  is disclosed to the Receiving Person or such Affiliate or
              Representative by a third party who has the right to disclose such
              information;

       (iv)   based on such Receiving Person's good faith judgment with the
              advice of counsel, is otherwise required to be disclosed in
              compliance with applicable legal requirements to a public
              authority.

       Whenever the Receiving Person becomes aware of any state of facts which
       would or might result in disclosure of Confidential Information pursuant
       to subparagraph (iv) above, it shall, if possible, promptly notify the
       person making disclosure (the "Disclosing Person") prior to any such
       disclosures so that the Disclosing Person may seek a protective order or
       other appropriate remedy and/or waive compliance with the provisions of
       this Agreement. In any event, if the Receiving Person is unable to
       promptly notify the Disclosing Person or if such protective order or
       other remedy is not obtained, or if the Disclosing Person waives
       compliance with the provisions of this Agreement, the Receiving Person
       will furnish only that portion of the information which it is advised by
       counsel is legally required and will exercise reasonable efforts to
       obtain assurance that confidential treatment will be accorded to the
       Confidential Information.

b)     Use of Confidential Information:

       Each Party agrees that no Confidential Information shall:

       (i)    be used in its own business except as necessary to the fulfillment
              of the rights and obligations of such Party under this Agreement;

       (ii)   be assigned, licensed, sublicensed, marketed, transferred or
              loaned, directly or indirectly to any third party other than a
              Representative or an Affiliate Representative


                                       36
<PAGE>   38

              of such Party, except as necessary to the fulfillment of the
              rights and obligations of the Parties under this Agreement;

       (iii)  be used or exploited by such Party or any of its Affiliates or
              their Representatives for its or their respective benefit or the
              benefit of any other relationships with customers of such Party
              and its Affiliates.

       Without limiting the generality of the foregoing, each Party agrees that
       it shall not (and shall not permit any of its Affiliates) at any time use
       any Confidential Information in the conduct of its business without the
       prior written consent of the other Party. The obligations set forth in
       this Article shall extend to copies, if any, of Confidential Information
       made by any Representatives referred to in paragraph (a) and to documents
       prepared by such Persons which embody or contain Confidential
       Information.

       The present confidentiality provisions shall not prevent the Parties from
       providing information requested by the French Medicine Agency (Agence du
       Medicament) in order to obtain the approval of the Company as a
       pharmaceutical establishment and the transfer of all licenses.

c)     Protection of Confidential Information:

       Each Party shall deal with Confidential Information so as to protect it
       from disclosure with a degree of care not less than that used by it in
       dealing with its own confidential information and shall take reasonable
       steps to minimize the risk of disclosure of Confidential Information
       which shall include, without limitation, ensuring that only its
       Affiliates and its and their Representatives who have a bona fide "need
       to know" such Confidential Information for purposes permitted or
       contemplated by this Agreement shall have access thereto. Each Party
       shall notify all of its Representatives who have access to Confidential
       Information of its confidentiality and the care therefor required, and
       shall obtain from any Affiliate or any agent or subcontractor who is a
       Representative that is permitted access to such Confidential Information
       in accordance with this Article, an agreement of confidentiality
       incorporating provisions at least as restrictive as those set forth
       herein, unless such Representative is a legal counsel legally bound by
       such confidentiality.

d)     Term of Confidentiality Obligations / Survival:

       Notwithstanding any contrary provisions provided elsewhere in this
       Article, the obligations set forth in this Article shall (i) terminate 15
       (fifteen) years after the Closing in case the Transaction is completed,
       or (ii) survive for a period of five (5) years as from the Closing
       Deadline if this Transaction is not completed.

e)     Return of Confidential Information:


                                       37
<PAGE>   39

       In the event the contemplated Transaction were not completed for whatever
       reason, within thirty (30) days after such decision not to carry out the
       Transaction, the Receiving Person shall (and shall cause its Affiliates'
       Representatives and its Affiliates to) return to the Disclosing Person or
       destroy all related documents and tangible items then in its possession
       which it has received from the Disclosing Person or any Affiliate or
       Representative thereof pertaining, referring or relating to the
       Disclosing Person's Confidential Information, as well as all copies,
       summaries, records, descriptions, modifications and duplications that it,
       or any of its Affiliates or Representatives, has made from the documents
       or tangible items received from the Disclosing Person or any Affiliate or
       Representative thereof; provided, however, that the Receiving Person may
       retain one copy of each document in its legal files solely to permit the
       Receiving Person to continue to comply with its obligations hereunder
       and, in addition, may upon notice to the Disclosing Person, retain in its
       legal files or in the offices of outside legal counsel one copy of any
       document solely for use in any pending legal proceeding to which such
       document relates.

f)     Confidential Disclosure Agreement of October 16, 1997:

       The obligations set forth in this Article supersede the Confidential
       Disclosure Agreement executed between Seller and Buyer on October 16,
       1997.

ARTICLE XIV - MISCELLANEOUS PROVISIONS

14.1   SCOPE OF OBLIGATIONS

       This Agreement shall be binding on and inure to the benefit of Buyer,
       Seller, their heirs, successors and successors in law, subject to Article
       14.5 hereof.

14.2   PRESS RELEASES

       An initial press release announcing the Parties' intent to consummate the
       Transaction shall be in the form attached hereto as Exhibit 14.2.

       All other major public communication of any kind relating to the
       Transaction or any transactions contemplated thereby (hereinafter "Press
       Release") shall be jointly drafted and reviewed by a press release review
       committee which shall be composed by:

       For PMC: the General Counsel

       For SangStat: CEO

       In the event that a Press Release is not jointly drafted or that one
       Party desires to draft the Press Release first, the drafting Party shall
       communicate to the other Party the draft of the Press Release at least
       three Business Days before the date of external communication for 


                                       38
<PAGE>   40

       review. Written approval or comments by the non drafting Party's persons
       sitting on the press release review committee shall be given as soon as
       practicable and in any event no later than 3 Business Days after receipt.

       The above mentioned procedure may be waived in writing by the non
       drafting Party's CEO or the non drafting CFO and General Counsel jointly.

       In no event shall either Party be prohibited from making any disclosures
       it determines are required by applicable law; nevertheless, to the extent
       practicable, the procedure described hereabove shall be respected.

       Additionally, in no event shall either Party be prohibited from making
       any public communications relating to and substantially in the form of
       prior approved communications.

       In addition, occasional brief comments by the respective officers of SMC
       and PMC regarding this Agreement shall be allowed only to the extent such
       statements are consistent with guidelines for public statements as may be
       mutually agreed upon by SMC and PMC and if made in connection with
       routine interviews with analysts or members of the financial press.

14.3   EXPENSES

       Each of the Parties shall pay its own fees and expenses in relation to
       the negotiation, preparation and execution of this Agreement and more
       generally in relation to the Transaction contemplated hereby, including
       lawyers', brokers' and accountants' fees. Except as otherwise provided
       herein, in the Share Purchase Agreement or in the Ancillary Agreements,
       each Party shall be responsible for their own tax obligations as a result
       of this Agreement and the Transaction.

14.4   AMENDMENTS; WAIVER

       No provision of this Agreement may be amended, waived or otherwise
       modified without the prior written consent of the Parties duly
       represented.

14.5   ASSIGNMENT

       Without prejudice of the right of substitution of Buyer as set forth in
       Article 14.10 hereof, neither Party shall transfer or assign this
       Agreement, in whole or in part without the other Party's prior written
       consent, except that either Party may transfer, assign and delegate this
       Agreement to an Affiliate or in connection with a merger, reorganization
       or sale of substantially all of its assets, without the other Party's
       consent.


                                       39
<PAGE>   41
14.6   ENTIRE AGREEMENT

       The terms and provisions of this Agreement and the Exhibits hereto
       constitute the entire agreement between the Parties with respect to the
       subject matter hereof and shall prevail over any prior written or oral
       communications, declarations or agreements between the parties hereto
       concerning the subject matter hereof. The Parties agree that this
       Agreement may only be amended by a written document signed by the Parties
       hereto in which this Agreement is specifically identified.

14.7   SEVERABILITY

       Any provision of this Agreement which is prohibited, unenforceable or not
       authorized in any jurisdiction shall, as to such jurisdiction, be
       ineffective to the extent of such prohibition, unenforceability or
       non-authorization without invalidating the remaining provisions hereof or
       affecting the validity, enforceability or legality of such provision in
       any other jurisdiction, as long as this does not materially affect the
       economics of the Transaction.

14.8   NON-DISCLOSURE

       a)     Notwithstanding anything to the contrary in this Agreement and
              except as required by law, the Parties expressly agree that this
              Agreement shall remain strictly confidential and each Party
              therefore undertakes not to provide any copy of the same to any
              third party and to ensure that its officers, directors, employees
              and agents similarly respect the present confidentiality
              obligation.

       b)     The non-complying party will be responsible for all adverse
              effects resulting from such breach.

14.9   CONFLICT

       In the case of any conflict or contradiction whatsoever between (i) the
       provisions of this Agreement and (ii) those of the Partial Business
       Contribution Agreement or the Share Purchase Agreement or any of the
       Ancillary Agreements, the provisions of the agreements listed in (ii)
       shall prevail.

14.10  BUYER'S RIGHT OF SUBSTITUTION

       SMC may substitute any of its Affiliates for the purposes hereof provided
       that, in this case, SMC will remain jointly liable for the obligations of
       such Affiliate including but not limited to payments under the terms
       hereof. In such a case, the term "Buyer" as used herein shall mean SMC
       and its substituted Affiliate.


                                       40
<PAGE>   42

14.11  NOTICES

       Notices and other communications required or called for under this
       Agreement shall be in writing, shall be transmitted by fax and by
       certified mail postage prepaid, and shall be deemed delivered upon
       receipt by the Party to whom it is addressed.

       In the case of SMC such communications shall be addressed to:

             SangStat Medical Corporation
             1505 Adams Drive
             Menlo Park, CA  94025
             Attention: _____________, Chief Executive Officer

       In the case of PMC, such communications shall be addressed to:

             Pasteur Merieux Serums et Vaccins S.A.
             58, avenue Leclerc
             69007 Lyon
             FRANCE
             Attention:  ____________,  Chairman,  and Chief Executive Officer,
             with copy to the "Directeur Juridique"

       or to the attention of such other individual or to such other address as
       either Party may give to other in writing.

14.12  FORCE MAJEURE

       No Party hereto (or any of its Affiliates) shall be responsible or liable
       to the other Party hereto (or any of its Affiliates) for any failure to
       perform any of its agreements, covenants or obligations under this
       Agreement if such failure results from events or circumstances reasonably
       beyond the control of such Party (or of its Affiliates), including,
       without limitation, war or other national emergency, riot, fire,
       explosion, flood or other Act of God, general and long-lasting strike
       affecting the entire activity of Seller on the site of Marcy l'Etoile,
       any injunction, decree, order, law or regulation of any public authority,
       or inability to obtain electricity or fuel or raw material (collectively,
       "Events of Force Majeure").

       The affected Party shall (i) forthwith inform the other Party in writing
       of the occurrence of the Event of Force Majeure, and (ii) exert best
       efforts to eliminate, cure or overcome any such Event of Force Majeure
       and to resume performance hereunder with all possible speed; provided,
       however, that nothing contained herein shall require any Party to settle
       on terms unsatisfactory to such Party any strike. To the extent that an
       Event of Force 


                                       41
<PAGE>   43

       Majeure continues for a period in excess of six (6) months, the Parties
       agree to negotiate in good faith either (i) to resolve the Event of Force
       majeure, if possible, (ii) to extend by mutual agreement the time period
       to resolve, eliminate or overcome such Event, or (iii) to terminate this
       Agreement.

ARTICLE XV - TERM AND TERMINATION

15.1   TERM

       Without prejudice of the survival of the confidentiality provisions set
       forth in Article XIII and 14.8 of this Agreement, this Agreement shall
       expire 25 (twenty-five) years after the Closing Date.

15.2   TERMINATION

       This Agreement may be terminated and shall be of no further force and
       effect:

       a)     upon mutual written agreement by the Parties; or

       b)     subject to Article VI, if the Closing has not occurred by December
              31, 1998.

       Additionally, (i) in the event any of the conditions precedent of Article
       4 hereof is not fulfilled on or before the Closing Deadline and subject
       to waiver by Buyer of Condition 4.1.3, or (ii) in the event Buyer has
       exercised its right under Article 4.2.2 hereabove or Seller has exercised
       its right under Article 4.2.3 hereabove, this Agreement shall be
       considered as null and void and with no further force or effect. In such
       a case, it is expressly agreed however that the confidentiality
       commitment from the Parties set forth in Article XIII and 14.8 hereof,
       will remain in force according to its terms.

ARTICLE XVI - GOVERNING LAW AND JURISDICTION

16.1   GOVERNING LAW

       The Agreement is governed by, and shall be construed in accordance with,
       French law.

       16.2   DISPUTE RESOLUTION

       Any and all disputes arising in connection with this Agreement which will
       not be solved on an amicable basis between the Parties shall be finally
       settled by arbitration under the 


                                       42
<PAGE>   44

       Rules of Conciliation and Arbitration of the International Chamber of
       Commerce, rules that the Parties recognize that they know. The
       arbitration shall be conducted in Paris, France, in English by one
       arbitrator if the dispute involves a claim of damage of and below five
       hundred thousand (500.000) US Dollars or by three arbitrators if the
       dispute involves a claim of damage above five hundred thousand (500.000)
       US Dollars appointed in accordance with the said rules. The arbitrator(s)
       shall apply French law to the merits of the case. The arbitration shall
       be final and binding upon the parties.


Executed in Menlo Park, California (U.S.A.)
in two (2) originals on June 10, 1998.


            Buyer                                            Seller

represented by Philippe Pouletty            represented by Jean-Jacques Bertrand

/s/ PHILIPPE POULETTY                       /s/ JEAN-JACQUES BERTRAND
- --------------------------------            ------------------------------------
Philippe Pouletty                           Jean-Jacques Bertrand


                                       43
<PAGE>   45
                        AMENDMENT TO THE MASTER AGREEMENT

                               DATED JUNE 10,1998

Between the undersigned:

1.       Sangstat Medical Corporation, a corporation existing and organized
         under the laws of the State of Delaware and having its principal place
         of business at 1505 Adam Drive, Menlo Park, CA 94025, USA, duly
         represented by Doctor Philippe Pouletty, its Chief Executive Officer,

hereinafter referred to as "Buyer" or "SMC"

                                                               ON THE FIRST PART

AND

2.       Pasteur Merieux Serums Section Vaccins S.A., a Pasteur Merieux
         Connaught company and a French "Societe Anonyme" having its registered
         office at 58 avenue Leclerc, 69 007 Lyon, France, duly represented by
         Mr. Jean-Jacques Bertrand, its Chairman and Chief Executive Officer,

hereinafter referred to as "Seller" or "PMC"

                                                             ON THE SECOND PART.

Buyer and Seller are hereinafter referred to as the "Parties" or individually a
"Party".

WHEREAS:

Whereas the Parties have signed on the date hereof an agreement entitled Master
Agreement,

Whereas the Parties agreed to amend some Articles of the Master Agreement
through the present amendment,

THE PARTIES AGREED TO AMEND THE MASTER AGREEMENT AS FOLLOWS:

1.       Article 1.1 Definitions:

         The definition of "Retroactive Date" is replaced by:

         ""Retroactive Date" shall mean the first day of the month of the
         Filing Date, or the 1st of July if the Filing Date is in August."

2. The first paragraph of article 2.2.3 is replaced by:

                                       44
<PAGE>   46

         "As soon as the conditions precedent referred to in Articles 4.1.2 and
         4.1.3 hereafter are fulfilled and within 20 days thereafter, it being
         specified that, due to legal requirements, the minimum period of time
         between the Filing Date and the Closing Date must be at least 30 days,
         the following steps shall take place:"

3. Article 4.1.3 is amended as follows:

         The first paragraph is replaced by:

         "Completion of legal, technical and financial due diligence by Buyer
         and its counsels satisfactory to Buyer on the items listed in Exhibit
         4.1.3, which due diligence shall not have revealed an event which may
         materially adversely affect the Business. This due diligence will be
         carried out in two phases:"

         Paragraph (ii) is replaced by:

         "(ii)   Buyer shall, in addition, have the right, for 10 Business Days
                 following the Filing Date to make review of the valuation of
                 the assets and liabilities in the Partial Business Contribution
                 Agreement it would estimate appropriate (the "Second Due
                 Diligence Period")"

4.       Article 14.10: The following sentence is added at the end of the
         Article:

         "Should the substitution apply, SMC shall provide Seller with an
         assignment contract signed by duly authorized representatives of
         signatories, including in exhibit the Master Agreement dated June 10,
         1998, in a form preserving the rights of Seller under the Master
         Agreement."

The Parties agreed that this amendment is a part of the Master Agreement dated
June 10, 1998.

Executed in San Francisco
In two originals
On June 10, 1998

Pasteur Merieux Serums & Vaccins                    Sangstat Medical Corporation


/s/  JEAN-JACQUES BERTLAND                      /s/ PHILIPPE POULETTY
- -------------------------------------           --------------------------------
Represented by Jean-Jacques Bertrand            Represented by Philippe Pouletty

                                       45
<PAGE>   47

                     AMENDMENT NO. 2 TO THE MASTER AGREEMENT

                               DATED JUNE 10, 1998


Between the undersigned:

1.       Sangstat Medical Corporation, a corporation existing and organized
         under the laws of the State of Delaware and having its principal place
         of business at 1505 Adams Drive, Menlo Park, CA 94025, USA, duly
         represented by Doctor Philippe Pouletty, its Chief Executive Officer,

hereinafter referred to as "Buyer" or "SMC"

                                                               ON THE FIRST PART
AND

2.       Pasteur Merieux Serums & Vaccins S.A., a Pasteur Merieux Connaught
         company and a French "Societe Anonyme" having its registered office at
         58 Avenue Leclerc, 69007 Lyon, France, duly represented by Mr.
         Jean-Jacques Bertrand, its Chairman and Chief Executive Officer,

hereinafter referred to as "Seller" or "PMC"

                                                             ON THE SECOND PART,

Buyer and Seller are hereinafter referred to as the "Parties" or individually a
"Party".

WHEREAS:

Whereas the Parties have signed on the date hereof an agreement entitled Master
Agreement,

Whereas the Parties agreed to amend some Articles of the Master Agreement
through the present amendment,

THE PARTIES AGREED TO AMEND THE MASTER AGREEMENT AS FOLLOWS:

1.       Article 2.2.1(a) is hereby amended to include the following:

         "To the extent PMC cannot, pursuant to the Partial Business
         Contribution Agreement, transfer to Buyer all of the persons identified
         in Exhibit A to this Amendment No. 2 to the Master Agreement, PMC
         agrees to use its best efforts to have such non-transferred employees
         accept employment voluntarily with Buyer at the Closing. PMC's best
         efforts will include, but not be limited to, informing such
         non-transferred employees in writing as soon as practicable of Buyer's
         offer of employment under similar terms and

                                       46
<PAGE>   48

         conditions, and taking any other actions reasonably requested by Buyer.
         PMC further agrees that the provisions of Article 5.6 of the Master
         Agreement regarding non-solicitation will apply to all of such
         non-transferred employees" of PMC and subsidiaries and PMC will use
         best efforts to cause Rhone Poulens and its subsidiaries to apply such
         provision.

The parties agreed that this amendment is a part of the Master Agreement dated
June 10, 1998.


Executed in San Francisco
In two originals
One June 10, 1998

Pasteur Merieux Serums & Vaccins                    Sangstat Medical Corporation


/s/  JEAN-JACQUES BERTLAND                      /s/ PHILIPPE POULETTY
- -------------------------------------           --------------------------------
Represented by Jean-Jacques Bertrand            Represented by Philippe Pouletty



                                       47
<PAGE>   49

                     AMENDMENT NO. 3 TO THE MASTER AGREEMENT

                               DATED JUNE 10, 1998

Between the undersigned:

1.       Sangstat Medical Corporation, a corporation existing and organized
         under the laws of the State of Delaware and having its principal place
         of business at 1505 Adams Drive, Menlo Park, CA 94025, USA, represented
         by Doctor Philippe Pouletty, its Chief Executive Officer, duly
         empowered for the purpose hereof,

hereinafter referred to as "Buyer" or "SMC"

                                                               ON THE FIRST PART

AND

2.       Pasteur Merieux Serums & Vaccins S.A., a Pasteur Merieux Connaught
         company and a French "Societe Anonyme" having its registered office at
         58 avenue Leclerc, 69 007 Lyon, France, represented by Mr. Herve
         Tainturier, duly empowered for the purpose hereof,

hereinafter referred to as "Seller" or "PMC"

                                                             ON THE SECOND PART.

Buyer and Seller are hereinafter referred to as the "Parties" or individually a
"Party".

WHEREAS:

Whereas the Parties have signed on June 10, 1998 an agreement entitled Master
Agreement, as well as an amendment to this Master Agreement,

Whereas the Parties agreed to amend some Articles of the Master Agreement as
amended on June 10, 1998 through the present amendment,

THE PARTIES AGREED TO AMEND THE MASTER AGREEMENT AS OF THE 31st OF JULY 1998 AS
FOLLOWS:


                                       48
<PAGE>   50

1.       Article 1.1 Definitions:

         The definition of "Retroactive Date" is replaced by:

         ""Retroactive Date" shall mean the first day of the month of the Filing
         Date, or the 1st of July if the Filing Date is in August or in
         September."

2.       Article 2.2.2: the following sentence is added at the end of the first
         paragraph:

         "Shall the Affidavit 1 be remitted in July, the computation of the 20
         days for the filing of the draft Partial Business Contribution
         Agreement shall start as from August 31."

3.       Article 2.2.3: the following sentence is added at the end of paragraph
         a):

         "Should the 20 day period hereabove not allow Seller and the Company to
         hold these general meetings the last day of a month, this 20 day period
         shall be extended to the last day of the month during which the 20 day
         period ended;".

4.       Article 3.2.1 a) of the Master Agreement is hereby amended to provide
         that the Fixed Price as defined therein shall be reduced to a total
         amount of thirty-one million ($31,000,000) US Dollars payable in
         several successive payments (the "Payment(s)"), it being specified that
         ten million ($10,000,000) US Dollars shall, on the Filing Date, be
         placed in escrow pursuant to the Escrow Agreement to be executed upon
         the Filing Date in the form of Exhibit 3.2.1 a). The above mentioned
         reduction in the Fixed Price has been agreed upon by the Parties [*] of
         the Share Purchase Agreement signed between the Parties on June 10,
         1998, as amended on June 10, 1998 and as of July 31, 1998). Such
         reduction in Fixed Price [*].

         Additionally,  the table of payments  set forth in  Article 3.2.1
         a) is hereby  replaced in its  entirety with the following:

<TABLE>
<CAPTION>
                  PAYMENT DATE                         PAYMENT (IN U.S. DOLLARS)
                  ------------                         -------------------------
               <S>                                           <C>
               Closing Date ("CD")                           $10.0 million
                6 months after CD                             $1.5 million
               12 months after CD                             $1.5 million
               18 months after CD                             $1.5 million
               24 months after CD                             $1.5 million
               30 months after CD                             $3.0 million
               36 months after CD                             $3.0 million
               42 months after CD                             $2.5 million
</TABLE>

- --------------------------
* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.

                                       49
<PAGE>   51

<TABLE>
<CAPTION>
                  PAYMENT DATE                         PAYMENT (IN U.S. DOLLARS)
                  ------------                         -------------------------
               <S>                                           <C>
               48 months after CD                             $2.5 million
               54 months after CD                             $2.0 million
               60 months after CD                             $2.0 million
</TABLE>

5.       Article 3.2.1c) (I)(a) of the Master Agreement is hereby amended to
         read in its entirety as follows:

         "(a)   Seller is performing at least one (1) of the services identified
                in the Service Agreement for the Manufacturing with respect to
                Thymoglobuline, or if Seller is not performing at least one (1)
                of the services, such failure to perform is due to (i) an event
                of force majeure, (ii) a request from Buyer, (iii) or a
                termination of the Service Agreement for the Manufacturing due
                to Buyer's fault; and"

6.       The table set forth in Article 3.2.1 c) (ii) of the Master Agreement is
         hereby replaced in its entirety with the following:

<TABLE>
<CAPTION>
                                                   MINIMUM
                                              REFERENCE SALES OF
ANNIVERSARY DATE                                THYMOGLOBULINE                          MARKET
- ----------------                                --------------                          ------
<S>                                              <C>                            <C>
12 months after Closing Date                      [*] vials                            Worldwide
24 months after Closing Date                      [*] vials                     European Union and USA
36 months after Closing Date                      [*] vials                     European Union and USA
48 months after Closing Date                      [*] vials                     European Union and USA
60 months after Closing Date                      [*] vials                     European Union and USA
</TABLE>

Additionally, the two paragraphs immediately following the table in Article
3.2.1 c) (ii) are hereby replaced in their entirety with the following:

"It is understood between the Parties that:

         *  for the second Payment Date (6 months after Closing Date), the
            minimum sales test shall be applied to the 6-month period preceding
            such date; as a result, no payment shall be due on such date if
            Actual Sales in this 6-month period are lower than [*] vials;

         *  for all Payment Dates which are not Anniversary Dates of the Closing
            Date, the minimum sales test to be referred to shall be as of the
            preceding Anniversary Date.

         For the purposes hereof, on each Anniversary Date of the Closing Date,
         the Company will measure the total number of Thymoglobuline(R) vials
         sold on the market referred to 


- --------------------------
* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.

                                       50
<PAGE>   52

         in the schedule hereabove mentioned during the l2-month period
         preceding such date (the "Actual Sales")."

7.       Paragraph (i) of Article 4.1.3 and correlatively the first paragraph of
         Article 2.2.2 are hereby amended to provide that due to the extension
         of the Initial Due Diligence Period, the Affidavit acknowledging the
         completion to Buyer's satisfaction of the Initial Due Diligence, shall
         be remitted on the date hereof.

8.       Amendment dated June 10, 1998, paragraph 3., Article 4.1.3: the title
         of the second paragraph is to be read as follows:

         "The first paragraph of paragraph (ii) is replaced by:"

         instead of

         "Paragraph (ii) is replaced by:"

9.       Article 5.2 of the Master Agreement is hereby amended to include a new
         Article 5.2.7 which shall read in its entirety as follows:

         "5.2.7 [*]

         Seller shall use its best efforts to contribute to the development of
         an [*] test for Thymoglobuline by August 31, 1998, and such best
         efforts shall include, but not be limited to, (i) having one (1)
         trained biochemist from Seller dedicated to this development effort for
         the four (4) weeks preceding August 31, 1998, (ii) retaining at
         Seller's expense the services of one external immunochemistry
         laboratory and (iii) interacting with Buyer with respect to Buyer's own
         laboratory work regarding the above mentioned test."

The Parties agreed that this amendment no. 3 is a part of the Master Agreement
dated June 10, 1998. Any provision of the Master Agreement not expressly
modified by this amendment no. 3 shall remain unchanged. All Exhibits shall be
deemed to be modified to the extent necessary to make each of them consistent
with this Amendment no. 3. Capitalized terms in this amendment no. 3 shall have
the meaning set-forth in the Master Agreement.


Executed in two originals


                In Lyon                                   In Menlo Park
For Pasteur Merieux Serums & Vaccins S.A.       For SangStat Medical Corporation

- --------------------------
* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.

                                       51
<PAGE>   53

/s/ HERVE TAINTURIER                            /s/ PHILIPPE POULETTY
- -------------------------------                 --------------------------------
Represented by Herve Tainturier                 Represented by Philippe Pouletty





                                       52
<PAGE>   54




                     AMENDMENT NO. 4 TO THE MASTER AGREEMENT

                               DATED JUNE 10, 1998

Between the undersigned:

1.       SangStat Medical Corporation, a corporation existing and organized
         under the laws of the State of Delaware and having its principal place
         of business at 1505 Adams Drive, Menlo Park, CA 94025, USA, duly
         represented by Doctor Philippe Pouletty, its Chief Executive Officer,

hereinafter referred to as "BUYER" or "SMC"

                                                               ON THE FIRST PART

And:

2.       Pasteur Merieux Serums & Vaccins S.A., a Pasteur Merieux Connaught
         company and a French "Societe Anonyme" having its registered office at
         58 Avenue Leclerc, 69007 Lyon, France, duly represented by Mr. Herve
         Tainturier, duly empowered for the purpose hereof,

hereinafter referred to as "SELLER" or "PCM"

                                                             ON THE SECOND PART,

Buyer and Seller are hereinafter referred to as the "PARTIES" or individually a
"PARTY".

WHEREAS:

Whereas the Parties have signed on the 10th of June 1998 an agreement entitled
Master Agreement,

Whereas the Parties have amended the Master Agreement through three amendments
dated June 10, 1998 and July 31, 1998,

Whereas the Parties agreed to amend this Master Agreement through the present
amendment,

THE PARTIES AGREED TO AMEND THE MASTER AGREEMENT AND THE AMENDMENTS TO THE
MASTER AGREEMENT DATED JUNE 10, 1998 AND JULY 31, 1998 AS FOLLOWS:


                                       53
<PAGE>   55

The paragraph (ii) of Article 4.l.3 of the Master Agreement and the last
paragraph of section 3 of the amendment to the Master Agreement dated June 10,
1998 are replaced by:

         "(i)   Buyer shall, in addition, have the right, for 12 Business Days
                following the Filing Date to make review of the valuation of the
                assets and liabilities in the Partial Business Contribution
                Agreement it would estimate appropriate (the "SECOND DUE
                DILIGENCE PERIOD").

                Upon expiration of the Second Due Diligent period, that is to
                say at the latest on the 10th September 1998 at 11:59 p.m.
                California time, Buyer shall remit to Seller a certificate
                acknowledging the completion to its satisfaction of such due
                diligence in the form of the Affidavit 2, provided that if Buyer
                does not deliver the Affidavit 2, buyer shall inform Seller in
                writing at the same date of its reasons for not delivering the
                Affidavit 2."

Section 8 of the amendment to the Master Agreement dated July 31, 1998 shall be
deemed to be modified to the extent necessary to make it consistent with this
amendment no. 4.

The Parties agreed that this amendment no. 4 is a part of the Master Agreement
dated June 10, 1998. Any provision of the Master Agreement and of the amendments
to the Master Agreement not expressly modified by this amendment no. 4 shall
remain unchanged. All Exhibits shall be deemed to be modified to the extent
necessary to make each of them consistent with this amendment no. 4. Capitalized
terms of this amendment no. 4 shall have the meaning set forth in the Master
Agreement.


Executed in Lyon
In two originals
On September 9, l998


   Pasteur Merieux Serums & Vaccins                 SangStat Medical Corporation

/s/ HERVE TAINTURIER                            /s/ PHILIPPE POULETTY
- -------------------------------                 --------------------------------
Represented by Herve Tainturier                 Represented by Philippe Pouletty



                                       54
<PAGE>   56


                               [Exhibit 2.1.1 a)]

                                LIST OF EMPLOYEES



                                       55
<PAGE>   57




                               [Exhibit 2.1.1 c)]

                        LIST OF EMPLOYEES (MANUFACTURING)



                                       56
<PAGE>   58



                             [Exhibit 2.1.2 b) (i)]

                       FORM OF KNOW-HOW LICENSE AGREEMENT



                                       57
<PAGE>   59



                             [Exhibit 2.1.1 b) (ii)]

             FORM OF COMMERCIAL LEASE AGREEMENTS AND OF SIDE-LETTER



                                       58

<PAGE>   60



                            [Exhibit 2.1.2 b) (ii-2)]

              SELLER'S INVESTMENT ON V3BIS BUILDING (AVANT-PROJET)



                                       59
<PAGE>   61



                           [Exhibit 2.1.2 b) (iii-1)]

                   FORM OF SERVICE AGREEMENT FOR MANUFACTURING



                                       60
<PAGE>   62



                           [Exhibit 2.1.2 b) (iii-2)]

                     FORM OF EQUINE PLASMA SUPPLY AGREEMENT



                                       61
<PAGE>   63



                           [Exhibit 2.1.2. b) (iii-3)]

                         FORM OF SITE SERVICE AGREEMENT



                                       62
<PAGE>   64



                                 [Exhibit 2.1.3]

                      DISTRIBUTION AGREEMENT FOR MULTITEST



                                       63
<PAGE>   65



                                [Exhibit 2.1.3-2]

                    FORM OF LETTER OF ASSIGNMENT (CELIPTIUM)



                                       64
<PAGE>   66



                                 [Exhibit 2.1.4]

                            LIST OF GENERAL SERVICES



                                       65
<PAGE>   67



                                  [Exhibit 2.2]

                 FORM OF PARTIAL BUSINESS CONTRIBUTION AGREEMENT



                                       66
<PAGE>   68



                               [Exhibit 2.2.1 b)]

                   FORM OF LETTER OF RHONE-POULENC PHARMA S.A.




                                       67
<PAGE>   69



                               [Exhibit 2.2.3 d)]

                        FORM OF COMPLETION ACKNOWLEDGMENT



                                       68
<PAGE>   70



                               [Exhibit 3.2.1 a)]

                            FORM OF ESCROW AGREEMENT



                                       69
<PAGE>   71



                               [Exhibit 3.2.1 b)]

                       CALCULATION FORMULA OF DIRECT COST



                                       70
<PAGE>   72



                                 [Exhibit 4.1.3]

                               DUE DILIGENCE LIST



                                       71
<PAGE>   73



                               [Exhibit 4.1.3 (i)]

                                FORM OF AFFIDAVIT



                                       72
<PAGE>   74



                                 [Exhibit 4.2.2]

FORM OF AMENDMENT TO THE MANUFACTURING AND SUPPLY AGREEMENT OF OCTOBER 13, 1993



                                       73
<PAGE>   75



                                 [Exhibit 5.2.2]

            STEPS WITH FRENCH MEDECINE AGENCY (AGENCE DU MEDICAMENT)



                                       74
<PAGE>   76



                                   [Exhibit 8]

                        FORM OF SHARE PURCHASE AGREEMENT




                                       75
<PAGE>   77



                            SHARE PURCHASE AGREEMENT

                                  BY AND AMONG




                     PASTEUR MERIEUX SERUMS & VACCINS, S.A.

                                       AND

                          SANGSTAT MEDICAL CORPORATION





                                       1

<PAGE>   78

                                TABLE OF CONTENTS


<TABLE>
<S>                                                                                                    <C>
Whereas..................................................................................................5
A.   Definitions.........................................................................................6
B.   Headings...........................................................................................10
C.   Extended Meanings..................................................................................10
D.   Accounting Principles..............................................................................10

1.   Purchase and Sale of Shares........................................................................11
     1.1      Purchase and Sale of Shares...............................................................11
     1.2      Conditions Precedent......................................................................17
     1.3      Closing...................................................................................20

2.   Representations and Warranties of PMC..............................................................23
     2.1      Organization, Good Standing and Qualification.............................................23
     2.2      Shares....................................................................................23
     2.3      Subsidiaries..............................................................................24
     2.4      Authorization.............................................................................24
     2.5      Governmental Consents and Authorizations..................................................24
     2.6      Financial Information.....................................................................24
     2.7      Receivables...............................................................................25
     2.8      Compliance With Law.......................................................................25
     2.9      Necessary Assets; Entire Business.........................................................25
     2.10     Operating Condition.......................................................................26
     2.11     Litigation................................................................................26
     2.12     Patents and Trademarks....................................................................26
     2.13     No Conflict or Default....................................................................27
     2.14     Third Party Consents......................................................................27
     2.15     Finders' Fees.............................................................................27
     2.16     Certain Payments..........................................................................27
     2.17     Permits...................................................................................27
     2.18     Complete Disclosure.......................................................................28
     2.19     Title to Property and Assets..............................................................28
     2.20     Changes...................................................................................28
     2.21     Tax Returns, Payments and Elections.......................................................29
     2.22     Inventory.................................................................................29
     2.23     Product Liability.........................................................................30
     2.24     Employees.................................................................................30
     2.25     Contracts in General......................................................................31
     2.26     Contracts Outside the Ordinary Course of Business,
              Contracts with Shareholders...............................................................32
     2.27     Insurance.................................................................................32
     2.28     Scope and Accuracy of the Representations.................................................32
</TABLE>



                                       2
<PAGE>   79


<TABLE>
<S>                                                                                                    <C>
3.   Representations and Warranties of Buyer............................................................33
     3.1      Authorization.............................................................................33
     3.2      Organization..............................................................................33
     3.3      Non-Violation.............................................................................33

4.   Covenants..........................................................................................33
     4.1      Covenant on Conditions Precedent / Contribution Agreement.................................33
     4.2      Obligation to Cooperate...................................................................34
     4.3      Interim Agreements........................................................................37
     4.4      Management of the Business and the Company................................................37
     4.5      Status of Mr. R. Labatut (R.L.)...........................................................38
     4.6      Non-Competition/Non-Solicitation..........................................................38

5.   Indemnification....................................................................................40

6.   Miscellaneous......................................................................................44
     6.1      Successors and Assigns....................................................................44
     6.2      Governing Law and Jurisdiction............................................................44
     6.3      Expenses..................................................................................44
     6.4      Amendments and Waivers....................................................................45
     6.5      Severability..............................................................................45
     6.6      Press Release.............................................................................45
     6.7      Buyer's Right of Substitution.............................................................46
     6.8      Termination...............................................................................46
     6.9      Notices...................................................................................46
     6.10     Force Majeure.............................................................................47

7.   Closing Deadline...................................................................................47

8.   Confidentiality....................................................................................48

Exhibits
     Exhibit 1.1.1(a)               Form of Escrow Agreement
     Exhibit 1.1.1(b)               Calculation Formula of Direct Costs
     Exhibit 1.1.1 (c)(i)(a)        Form of Service Agreement for the Manufacturing
     Exhibit 1.1.4 (i)              Form of Letter of Credit
     Exhibit 1.1.4 (i-2)            Form of Certificate
     Exhibit 1.2.1(a)               Form of Partial Business Contribution Agreement
     Exhibit 1.2.1(c)               Due Diligence List
     Exhibit 1.2.1(c)(i)            Form of Affidavit 1/Form of Affidavit 2
     Exhibit 1.2.2(b)               Form of Amendment to the Manufacturing and Supply Agreement of October 13, 1993
     Exhibit 1.3.1 (a)(i)           Form of Reiteration
     Exhibit 2                      Schedule of Exceptions
</TABLE>







                                       3
<PAGE>   80


<TABLE>
<S>                                 <C>
     Exhibit 2.5(a)                 Exceptions to Article 2.5 (licenses)
     Exhibit 2.5(b)                 Permits and Authorizations
     Exhibit 2.6                    Management Accounts
     Exhibit 2.9                    List of General Services
     Exhibit 2.11                   Disputes with Employee Committee and Work Council
     Exhibit 2.12                   Exceptions to Article 2.12 (outstanding options, licenses or agreements)
     Exhibit 2.14                   Third Party Consents
     Exhibit 2.17                   List of Licenses Held by Third Party Distributors
     Exhibit 2.24(a)                List of Employees
     Exhibit 2.24(h)                Pension and Employee Insurance Plans
     Exhibit 2.24(i)                Loans to Employees, agents or representatives
     Exhibit 2.26                   Contracts Outside the Ordinary Course of Business
     Exhibit 4.2.2                  Steps with French Medicine Agency (Agence du Medicament)
     Exhibit 6.6                    Press Release
</TABLE>





                                       4
<PAGE>   81

                            SHARE PURCHASE AGREEMENT


         THIS SHARE PURCHASE AGREEMENT is made as of the 10th day of June, 1998,
by and among Pasteur Merieux Serums & Vaccins S.A., a Pasteur Merieux Connaught
company and a French Societe Anonyme having its registered office at 58 Avenue
Leclerc, 69007 Lyon, France, duly represented by Mrs. Oleanda Izquierdo pursuant
to a power of attorney granted by Mr. Jean-Jacques Bertrand, its Chairman and
Chief Executive Officer ("PMC" or "Seller") and SangStat Medical Corporation, a
corporation existing and organized under the laws of the State of Delaware and
having its principal place of business at 1505 Adams Drive, Menlo Park,
California, 94025 USA, duly represented by Mr. Robert Floc'h pursuant to a
resolution of the board of directors ("SMC" or "Buyer"), in relation to the sale
of the shares of IMTIX-SangStat, S.A.S., a French corporation to be registered
in the form of a societe par actions simplifiee (the "Company").

         Buyer and Seller are hereinafter collectively referred to as the
"Parties" or individually as a "Party".

WHEREAS:

WHEREAS SMC is a specialty pharmaceutical company applying a disease management
approach to improve the outcome of organ transplantation;

WHEREAS the mission of PMC is to contribute to the protection and maintenance of
human health by creating superior immunological products for the prevention and
treatment of infectious diseases and cancers;

WHEREAS PMC, among its other activities, carries on the business of researching,
developing, manufacturing, marketing and distributing bio-pharmaceutical
products used in organ transplantation in humans through its division known as
IMTIX Pasteur Merieux Connaught Transplantation;

WHEREAS PMC's strategic intent is to focus on its core business, mainly
bio-pharmaceutical products for active immunization against infectious diseases
and immunotherapy of cancers;

WHEREAS SMC's strategic intent is to develop its business throughout the whole
spectrum of transplantation indications, products and services;

WHEREAS SMC and PMC are currently parties to a development and distribution
agreement relating to transplantation products pursuant to which SMC is actively
involved in the clinical development and registration of certain transplantation
products;

NOW, THEREFORE, in consideration of the mutual covenants, agreements,
representations and warranties and subject to the conditions precedent contained
herein,





                                       5
<PAGE>   82

THE PARTIES HEREBY AGREE AS FOLLOWS:

A- Definitions

         -    "Actual Sales" shall have the meaning ascribed to it in Article
              1.1.1 c)(ii) hereafter;

         -    "Affidavit" shall mean a letter from the Buyer in the form of
              Exhibit 1.2.1(c)(i) hereto to the Seller indicating that the
              Initial Due Diligence is satisfactory to the Buyer (Affidavit 1)
              and that the Second Due Diligence is satisfactory to the Buyer
              (Affidavit 2);

         -    "Affiliate" shall mean, in relation to any entity, any other
              entity which directly or indirectly, through one or more
              intermediaries, controls, or is controlled by, or is under common
              control with such entity. For the purposes of this definition,
              "control" shall be defined by reference to Article 355-1 of the
              French Company Act dated July 24, 1966;

         -    "Agreement" shall mean this Share Purchase Agreement, together
              with all its Exhibits;

         -    "Agreements" shall mean collectively this Agreement, the Ancillary
              Agreements and the Partial Business Contribution Agreement;

         -    "Ancillary Agreements" shall mean collectively the following
              agreements, which the Parties agree shall be part of the overall
              Transaction:

              -    Know-How License Agreement
              -    Service Agreement for the Manufacturing of Thymoglobuline and
                   Lymphoglobuline
              -    Commercial Lease Agreements
              -    Site Service Agreement
              -    Equine Plasma Supply Agreement
              -    Distribution Agreement for Multitest;

         -    "Anniversary Date(s)" shall mean the date(s) set forth in the
              schedule mentioned in Article 1.1.1(c)(ii) hereafter;

         -    "Assets" shall mean those assets listed in the Partial Business
              Contribution Agreement;

         -    "Business" shall mean the IMTIX Business as described in the
              Partial Business Contribution Agreement;




                                       6
<PAGE>   83

         -    "Business Day" shall mean any day which is not a Saturday, a
              Sunday or a holiday in France or in the U.S.;

         -    "Change of Control" shall have the meaning ascribed to it in
              Article 1.1.4 (iii) hereafter;

         -    "Claim" shall have the meaning ascribed to it in Article 5 b)
              hereafter;

         -    "Closing" shall mean the sale of the Shares by PMC to Buyer and
              the settlement of the Closing Payment of $12 (twelve) million US
              Dollars by Buyer to PMC which shall take place on the Closing Date
              as set forth in Article 1.3 hereafter;

         -    "Closing Date" shall have the meaning ascribed to it in Article
              1.2.2 a) hereafter;

         -    "Closing Deadline" shall mean December 31, 1998;

         -    "Commercial Lease Agreement" shall mean the commercial lease
              agreement to be executed on the Closing Date between PMC and the
              Company setting forth the terms and conditions of the lease by PMC
              to the Company of the real estate relating to the C4 Building and
              V3 bis Building;

         -    "Contribution Valuations" shall have the meaning ascribed to it in
              Article 2.6 hereafter;

         -    "Damages" shall have the meaning ascribed to it in Article 5 a)
              hereafter;

         -    "Delivery Date" shall have the meaning ascribed to it in Article
              1.1.2 b) hereafter;

         -    "Direct Costs" shall have the meaning ascribed to it in Article
              1.1.1 b) hereafter;

         -    "Distribution Agreement for Multitest" shall mean the distribution
              agreement to be executed between PMC and the Company on the
              Closing Date setting forth the terms and conditions of the
              distribution by the Company of Multitest which is and will be
              manufactured by PMC;

         -    "Employees" shall have the meaning ascribed to it in Article 2.24
              hereafter;

         -    "Environmental and Safety Law" shall have the meaning ascribed to
              it in Article 2.8 hereafter;

         -    "Equine Plasma Supply Agreement" shall mean the equine plasma
              supply agreement to be executed on the Closing Date between PMC
              and the Company setting forth the terms and conditions of the
              supply by PMC to the Company of equine plasma for Lymphoglobuline
              (R) manufacturing;



                                       7
<PAGE>   84


         -    "Escrow Agreement" shall mean the escrow agreement to be executed
              between Buyer, Seller and BNP 39, rue Grenette, 69002 Lyon, acting
              as escrow agent, on the Filing Date, substantially in the form of
              Exhibit 1.1.1 a) hereto;

         -    "Filing Date" shall have the meaning ascribed to it in Article
              1.1.1 a) hereafter;

         -    "First Notice of Claim" shall have the meaning ascribed to it in
              Article 5 b) hereafter;

         -    "Fixed Price" shall have the meaning ascribed to it in Article
              1.1.1 hereafter;

         -    "General Services" shall mean the general services set forth in
              Exhibit 2.9 hereto;

         -    "IMTIX Products" shall mean those products listed in the Form of
              the Partial Business Contribution Agreement set forth in Exhibit
              1.2.1 (a) hereto;

         -    "Initial Due Diligence Period" shall have the meaning ascribed to
              it in Article 1.2.1 c) (i) hereafter;

         -    "Interim Agreements" shall have the meaning ascribed to it in
              Article 4.3 hereafter;

         -    "Know-How License Agreement" shall mean the know-how license
              agreement to be executed on the Closing Date between PMC and the
              Company setting forth the terms and conditions of the license by
              PMC to the Company of any and all know-how non-specific to the
              Business but necessary to operate the Business;

         -    "Laws" shall have the meaning ascribed to it in Article 2.8
              hereafter;

         -    "Management Accounts" shall have the meaning ascribed to it in
              Article 2.6 hereafter;

         -    "Management Committee" shall have the meaning ascribed to it in
              Article 4.2.4 hereafter;

         -    "Minimum Reference Sales" shall have the meaning ascribed to it in
              Article 1.1.1(c)(ii) hereafter;

         -    "Net Sales" shall have the meaning ascribed to it in Article 1.1.2
              hereafter;

         -    "Partial Business Contribution" shall mean the contribution to be
              made by PMC to the Company in accordance with the Partial Business
              Contribution Agreement (as defined hereafter);

         -    "Partial Business Contribution Agreement" shall mean the partial
              business contribution agreement (traite d'apport partiel d'actif)
              to be executed substantially in



                                       8
<PAGE>   85


               the form of Exhibit 1.2.1(a) hereto between PMC and the Company
               setting forth the terms and conditions of the contribution by PMC
               to the Company of the IMTIX Business;

         -    "Payments" shall have the meaning ascribed to it in Article 1.1.1
              a) hereafter;

         -    "Payment Date(s)" shall have the meaning ascribed to it in Article
              1.1.1 a) hereafter;

         -    "Press Release" shall have the meaning ascribed to it in Article
              6.6 hereafter;

         -    "Purchase" shall have the meaning ascribed to it in Article 1.1
              hereafter;

         -    "Purchase Price" shall have the meaning ascribed to it in Article
              1.1 hereafter;

         -    "Representatives" shall have the meaning ascribed to it in
              Articles 4.6 d) and 8a) hereafter;

         -    "Retroactive Date" shall mean the first day of the month of the
              Filing Date;

         -    "Schedule of Exceptions" shall have the meaning ascribed to it in
              Article 2 hereafter;

         -    "Second Due Diligence Period" shall have the meaning ascribed to
              it in Article 1.2.1 c) (ii) hereafter;

         -    "Second Notice of Claim" shall have the meaning ascribed to it in
              Article 5(d)(i) hereafter;

         -    "Second Shareholder" shall mean Rhone-Poulenc Pharma S.A., an
              Affiliate of Seller and French societe anonyme having its
              registered office at 25 quai Paul Doumer, 92400 Courbevoie;

         -    "Service Agreement for Manufacturing" shall mean the service
              agreement to be executed on the Closing Date between PMC and the
              Company setting forth the terms and conditions of the rendering by
              PMC for the Company of certain services required for the
              manufacturing of Thymoglobuline and Lymphoglobuline;

         -    "Shares" shall mean all of the shares of the Company held by PMC
              and the Second Shareholder at Closing and representing 100% of the
              share capital (capital social) and voting rights of the Company;

         -    "Site Service Agreement" shall mean the site service agreement to
              be executed on the Closing Date between PMC and the Company
              setting forth the terms and conditions of the use by the Company
              of PMC's site services;



                                       9
<PAGE>   86

         -    "Subsidiaries" shall mean the 4 subsidiaries fully dedicated to
              the distribution of IMTIX Products, which are IMTIX GmbH
              (Germany), IMTIX B.V. (Netherlands), IMTIX Ltd (UK) and IMTIX Srl
              (Italy);

         -    "Transaction" shall mean collectively the transactions
              contemplated in the Agreements;

         -    "Transition Committee" shall have the meaning ascribed to it in
              Article 4.2.3 hereafter;

         -    "Variable Price" shall have the meaning ascribed to it in Article
              1.1.2 hereafter.


B- Headings

         The division of this Agreement into Articles and Sections and the
insertion of headings are for convenience of reference only and shall not affect
the construction or interpretation of this Agreement. The terms "Agreement",
"hereof", "hereunder" and similar expressions refer to this Agreement and not to
any particular Article, Section or other portion hereof and include any
agreement supplemental hereto. Unless something in the subject matter or context
is inconsistent therewith, references herein to Articles and Sections are to
Articles and Sections of this Agreement.



C- Extended Meanings

         In this Agreement words importing the singular number only shall
include the plural and vice versa, words importing the masculine gender shall
include the feminine and neuter genders and vice versa and words importing
persons shall include individuals, partnerships, associations, trusts,
unincorporated organizations and corporations.



D- Accounting Principles

         Wherever in this Agreement reference is made to a calculation to be
made in accordance with generally accepted accounting principles, such reference
shall be deemed to be (i) accounting principles usually accepted such as defined
in the French "Nouveau Plan Comptable" and set up according to the
"recommandations de l'Ordre des Experts-Comptables francais," of the "Conseil
National de la Comptabilite" and of the "Compagnie Nationale des Commissaires
aux Comptes" or (ii) as far as the Subsidiaries are concerned, local generally
accepted accounting principles.




                                       10
<PAGE>   87

1.       Purchase and Sale of Shares.

         1.1 Purchase and Sale of Shares. Subject to the terms and conditions of
this Agreement, in particular to the conditions precedent provided in Article
1.2 below, Buyer agrees to purchase at the Closing and PMC agrees to sell to
Buyer at the Closing, the Shares for the purchase price defined as follows (the
purchase of the Shares by Buyer being referred to hereafter as the "Purchase").

         The sale of the Shares shall be made for a total price (the "Purchase
Price") payable by Buyer to Seller and consisting of the sum of a fixed price
(the "Fixed Price") and a variable price (the "Variable Price") defined
respectively in Articles 1.1.1 and 1.1.2 hereafter.

         1.1.1    Fixed Price:

                  a)       Payment Schedule

                           Subject to adjustments effected pursuant to Articles
                           1.1.1 b), c) and d) hereafter, the Fixed Price shall
                           be of a total amount of $33 (thirty three) million US
                           Dollars payable in several successive payments (the
                           "Payment(s)") in accordance with the following
                           schedule, it being specified that $12 (twelve)
                           million US Dollars shall, on the date on which the
                           draft Partial Business Contribution Agreement is
                           filed with the Commercial Court of Commerce (the
                           "Filing Date"), be placed in escrow pursuant to the
                           Escrow Agreement to be executed upon the Filing Date
                           in the form of Exhibit 1.1.1 a) attached hereto.
                           Dates set forth in this schedule shall hereafter be
                           referred to as the "Payment Date(s)".


<TABLE>
<CAPTION>
                                                            Payment
                      Payment Date                        (in US Dollars)
                      ------------                        ---------------
<S>                                                      <C>
                      Closing Date ("CD")                 $ 12.0 million (the "Closing Payment")
                      6 months after CD                   $  1.5 million
                      12 months after CD                  $  1.5 million
                      18 months after CD                  $  1.5 million
                      24 months after CD                  $  1.5 million
                      30 months after CD                  $  3.0 million
                      36 months after CD                  $  3.0 million
                      42 months after CD                  $  2.5 million
                      48 months after CD                  $  2.5 million
                      54 months after CD                  $  2.0 million
                      60 months after CD                  $  2.0 million
</TABLE>

                  Sums placed in escrow as provided hereabove shall be released
                  to the benefit of Seller upon Closing Date, or, should the
                  Purchase not take place because of the



                                       11
<PAGE>   88


                  non-fulfillment prior to the Closing Deadline of any of the
                  conditions precedent referred to in Article 1.2 hereof, shall
                  be refunded to Buyer.

                  b)       Adjustment of the Payments by reference to
                           Thymoglobuline (R) direct costs

                           The Payments due 12 months after Closing Date (for an
                           amount of $1,500,000 (one million five hundred
                           thousand) US Dollars) and 24 months after Closing
                           Date (for an amount of $1,500,000 (one million five
                           hundred thousand) US Dollars) shall however be
                           adjusted by reference to the average Thymoglobuline
                           Direct Costs (as defined hereafter) during the 12
                           month-period preceding each of these 2 dates in
                           accordance with the following table. For the purposes
                           hereof, "Direct Costs" shall mean a list of items of
                           French Francs amount computed on the basis of the
                           calculation formula set forth in Exhibit 1.1.1 b)
                           attached hereto with figures as of the Closing Date
                           as an example. In case of any dispute between the
                           Parties on this calculation of such amount, the
                           dispute shall be referred to an expert in accordance
                           with provisions of Article 1.1.1 c) (ii) hereafter.

<TABLE>
<CAPTION>
                                                                           Impact on Payments
                      Condition                                            (in US Dollars)
                      ---------                                            ---------------
<S>                                                                       <C>
                      if Direct Costs above [_____*] FF/vial               Decrease by [$_____*] million
                      if Direct Costs between [_____*] FF/vial             Decrease by [$_____*] million
                      if Direct Costs between [_____*] FF/vial             Increase by [$_____*] million
                      if Direct Costs below [_____*] FF/vial               Increase by [$_____*] million
</TABLE>

                  The Payments other than the two Payments referred to hereabove
                  shall not be affected by the Thymoglobuline (R) Direct Costs.

         c)       Other adjustment of the Payments

                  (i)      The Payment normally due as of any Payment Date shall
                           be canceled and Buyer shall definitively be released
                           from making any such Payment, unless on any such
                           Payment Date:

                           (a)      Seller is performing at least one (1) of the
                                    services identified in the Service Agreement
                                    for the Manufacturing attached hereto as
                                    Exhibit 1.1.1 c)(i)(a) with respect to
                                    Thymoglobuline, or if Seller is not
                                    performing at least one (1) of the services,
                                    such failure to perform is due to (i) an
                                    event of force majeure, (ii) a request from





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SECURITIES AND EXCHANGE COMMISSION.



                                       12
<PAGE>   89


                                    Buyer, (iii) or a termination of the Service
                                    Agreement for the Manufacturing due to
                                    Buyer's fault; or

                           (b)      At least one (1) product license with
                                    respect to Thymoglobuline is then issued and
                                    valid in any E.U. country or in the U.S.A.,
                                    provided that if no licenses are then issued
                                    and valid, the reason for the failure to
                                    maintain such license is caused, at least in
                                    part, by the inability of Seller to perform
                                    under the Service Agreement for the
                                    Manufacturing of Thymoglobuline and is not
                                    due to an event of force majeure.

                  (ii)     Additionally, the Payment normally due as of any
                           Payment Date shall be canceled and Buyer shall
                           definitively be released from making such Payment, if
                           on any such Payment Date (or, if such Payment Date is
                           not an Anniversary Date as this term is defined in
                           the schedule hereafter, on the preceding Anniversary
                           Date), the Actual Sales (as defined hereafter) are,
                           despite reasonable commercial efforts of Buyer, lower
                           than the minimum reference sales set forth for that
                           date in the schedule hereafter, and, provided that
                           Buyer has not arbitrarily changed its allocation of
                           products to markets other than the E.U. and the
                           U.S.A. solely in order to avoid making Payments
                           hereunder.

<TABLE>
<CAPTION>
                      Anniversary Date                                    Minimum Reference Sales of Thymoglobuline
                      ----------------                                    -----------------------------------------
<S>                                                                       <C>
                      12 months after Closing Date                                       [_____*] vials
                      24 months after Closing Date                                       [_____*] vials
                      36 months after Closing Date                                       [_____*] vials
                      48 months after Closing Date                                       [_____*] vials
                      60 months after Closing Date                                       [_____*] vials
</TABLE>

                  It is understood between the Parties that:

                  -        for the second Payment Date (6 months after Closing
                           Date), the minimum sales test shall be applied to the
                           6-month period preceding such date; as a result, no
                           payment shall be due on such date if Actual Sales on
                           this 6-month period are lower than [_____*] vials;

                  -        for all Payment Dates which are not Anniversary Dates
                           of the Closing Date, the minimum sales test to be
                           referred to shall be as of the preceding Anniversary
                           Date.




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* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.






                                       13
<PAGE>   90

                  For the purposes hereof, on each Anniversary Date of the
                  Closing Date, the Company will measure the total number of
                  Thymoglobuline (R) vials sold on the USA and European Union
                  market during the 12-month period preceding such date ( the
                  "Actual Sales").

                  Buyer shall maintain complete records of Actual Sales and
                  shall permit an independent certified public accountant from a
                  major international accounting firm ("CPA") appointed by
                  Seller to inspect and audit the Company's books and records
                  relating to Actual Sales upon 10 Business Days prior written
                  notice. The CPA shall report to Seller, with a copy to Buyer,
                  only the extent of any discrepancy between the Actual Sales
                  reported by Buyer and the amount of Actual Sales calculated by
                  CPA. Seller may exercise the rights hereunder only once each
                  calendar year and this right shall terminate 72 months after
                  the Closing Date. Seller will then have the right to notify to
                  Buyer, within 15 days from the remittance by CPA to Seller of
                  its report with a copy to Buyer, its decision to refer the
                  matter to Ernst & Young, for determining the Actual Sales
                  amount, acting as an expert pursuant to the provisions of
                  Article 1592 of the French Civil Code, jointly appointed
                  between the Parties or, in case of default by such expert, to
                  any other expert which shall be appointed by the President du
                  Tribunal de Grande Instance de Paris at the request of the
                  most diligent party (the "Expert"). The Expert shall be fluent
                  in both English and French. The Parties undertake to fully
                  cooperate with the Expert. The Expert shall be instructed to
                  render the report within one (1) month of referral to him. The
                  Expert's report shall be binding on the Parties. The Expert's
                  fees shall be borne by Seller unless the valuation effected by
                  the Expert differs by more than 3% (three percent) from the
                  initial valuation of Buyer, in which case Buyer shall bear the
                  costs. Seller and Buyer shall obtain no later than the Closing
                  Date a letter by Ernst & Young stating its approval to this
                  assignment.

         d)       Additional Readjustment of the Payments

                  In the event that the Company is not allowed by the German
                  regulatory authorities to distribute on a usual commercial
                  basis Thymoglobuline for the German market by September 30,
                  1998, subsequent Payments shall be reduced by [$__________
                  (_____)]* US Dollars per month. Payment reduction will not be
                  made in any month in which batches of Thymoglobuline in
                  adequate amounts to reasonably address the German market
                  opportunity are released for sale prior to the license being
                  renewed by the German regulatory authorities. In no event
                  shall the cumulative amount of the reduction exceed
                  [$__________ (_____)]* US Dollars, nor shall there be any
                  Payment reductions after September 30, 2000.




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* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.





                                       14
<PAGE>   91

                  Additionally, in the event that the U.S. approval for
                  Thymoglobuline has not been granted by December 31, 1998 and
                  the only remaining blocking issue for non-approval is due to
                  manufacturing, chemistry, control or site inspection issues
                  ("ELA related") identified in the previous FDA deficiency
                  letter dated January 16, 1998 or Form 483 dated January 16,
                  1998, the FDA letter dated March 26, 1998 and subsequent
                  letters relating to such issues, subsequent Payments shall be
                  reduced by [$__________ (_____)]* US Dollars per month until
                  such time as the U.S. approval is granted. In no event shall
                  the cumulative amount of the reduction exceed [$__________
                  (_____)]* US Dollars.

                  If the Parties disagree on whether the failure to receive U.S.
                  approval is due to an ELA related matter as set forth above,
                  or if Seller considers that the inability to resolve the issue
                  is attributable to Buyer, the Parties shall submit the
                  question to an expert in U.S. regulatory matters whose
                  decision shall be binding on the Parties and which shall be
                  jointly appointed by the Parties or, failing such joint
                  appointment within 15 days from the occurrence of such
                  disagreement, by the President du Tribunal de Grande Instance
                  de Paris ruling under the refere proceedings upon the request
                  of the most diligent party.

         1.1.2    Variable Price:

         The Variable Price, which shall be payable by wire transfer within 60
days of each Payment Date, shall consist of a first part based on the amount of
Lymphoglobuline Net Sales (a) and a second part based on Antilfa Net Sales (b),
and payable as set forth hereafter. For the purposes of this Agreement, "Net
Sales" shall mean the amount actually received on sales of Lymphoglobuline or
Antilfa by the Company or by its Affiliates, or by its authorized sub-licensees
(it being specified that IMTIX Products manufactured for clinical trial shall
not be taken into account for the calculation of Net Sales) to third parties
during the preceding six-month period less deductions for (i) normal and
customary trade, quantity and cash discounts and emergency drug releases where
such releases are provided by the Company or its Affiliates without charge, (ii)
amounts repaid or credited by reason of rejection or return; (iii) V.A.T. on
sales, withholding and excise taxes and duties levied on and/or other
governmental charges made as to production, sale, importation, transportation,
delivery or use paid by or on behalf of the Company, and (iv) transportation
costs including insurance.

         a)       Payments on Lymphoglobuline Net Sales shall be equal to 8% of
                  the amount of such Net Sales every six months for a period of
                  10 years as from the Closing Date.





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* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.


                                       15
<PAGE>   92




         b)       Payments on Antilfa for a period of 10 years starting on the
                  date referred to hereafter as the "Delivery Date" which shall
                  be the earlier of (i) the date of delivery by FDA of the BLA
                  marketing approval in the USA for solid organ transplants for
                  Antilfa and (ii) the date of delivery of the equivalent
                  marketing approval in European Union according to the
                  centralized market approval procedure or in any E.U. country
                  if a marketing approval is delivered for such country only,
                  shall be calculated as follows:

                  (i)      One-time payment of [$__________ (_____*)] million US
                           Dollars upon Delivery Date;

                  (ii)     a payment based on Antilfa Net Sales equal to (i)
                           [_____*] of the amount of such Net Sales by the
                           Company and its Affiliates, or (ii) if Net Sales are
                           made by the Company's authorized sublicensees,
                           [_____*] of such Company's authorized sublicensees
                           Net Sales, every six months for a period of 10 years
                           as from the Delivery Date.

                  1.1.3 If, at the time the payment of a part of the Purchase
Price becomes due, an arbitration award rendered pursuant to Article 6.2
hereafter shall have upheld (i) a claim by Buyer under this Agreement, or (ii) a
claim by Buyer based on any other breach of representations, warranties or
covenants by Seller to Buyer under any agreement referenced herein, Buyer shall
be entitled to set-off the payment of such part of the price against the amount
of such claim.

                  1.1.4    Issue of a security interest

                  (i)      In order to secure Payments hereunder, Buyer shall
                           provide that a letter of credit from Nationsbank, or
                           a financial institution of equivalent standing, in
                           the amount of $6 (six) million US Dollars be issued
                           in favor of Seller for a period of 21/2years
                           beginning on the Closing Date substantially in the
                           form attached hereto as Exhibit 1.1.4 (i). Such
                           letter of credit shall provide that Seller shall be
                           entitled to payment after delivering a certificate
                           also in the form attached in Exhibit 1.1.4 (i-2),
                           executed solely by Seller to Nationsbank. At the
                           expiration of such 21/2year period, Buyer shall
                           provide that a new letter of credit in the amount of
                           $4 (four) million US Dollars be issued in favor of
                           Seller for an additional 21/2year period in the form
                           attached hereto as Exhibit 1.1.4 (i). The transaction
                           costs of issuing such letters of credit shall be
                           shared equally between Buyer and Seller, and Seller
                           agrees to immediately reimburse Buyer for 50% of such
                           costs with Seller's portion not to exceed 0.5% of the
                           secured amount per year upon 




- ----------------------------------
* CONFIDENTIAL TREATMENT REQUESTED.  CONFIDENTIAL
PORTION HAS BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION.


                                       16
<PAGE>   93


                           invoice, provided that Buyer shall remain solely
                           responsible for any pledge of assets associated
                           therewith.

                  (ii)     In the event that Buyer is unable or fails to make
                           Payments, and such failure is not cured within 30
                           days of written notice from Seller to Buyer of such
                           failure, then at such time SMC shall immediately
                           issue to Seller up to 100,000 (one hundred thousand)
                           shares of the common stock of SMC at no cost to
                           Seller, such number of shares to be proportionally
                           adjusted in case of stock splits, dividends and
                           recapitalization. SMC shall at all times keep such
                           100,000 (one hundred thousand) shares reserved and
                           available for immediate issuance to Seller. In order
                           to determine the amount paid through the issuance of
                           100,000 (one hundred thousand) shares, the shares
                           shall be valued at their fair market value at the
                           time of issuance. However, the valuation shall only
                           be definitive at the time Seller has been able to
                           sell the shares and to recover the corresponding
                           price. Such recovered price shall be the sole amount
                           to be offset against failed Payments. Any recovered
                           amount in excess of the failed Payments shall not be
                           reimbursed to Buyer, and shall be considered as an
                           indemnification for late payment. The recovery of any
                           failed Payment not recovered, in full or in part,
                           through the sale of shares will be pursued by any
                           other means. At the Closing Date, SMC shall deliver
                           to Seller a certificate stating the fair market value
                           of the 100,000 (one hundred thousand) shares as of
                           the Closing Date, and the corresponding percentage in
                           SMC's capital stock on a fully diluted basis.

                  (iii)    In the event that there is a "Change of Control" (as
                           defined below) of either the Company or Buyer
                           involving an unrelated third party after the Closing
                           Date, Buyer will provide that a letter of credit be
                           issued by Nationsbank, or a financial institution of
                           equivalent standing, in favor of Seller with respect
                           to all unpaid Payments as of the date of the Change
                           of Control. For purposes of this article, a "Change
                           of Control" shall mean a sale of substantially all of
                           the assets of either the Company or Buyer to a
                           non-Affiliate of Buyer or any transfer by way of
                           contribution, merger or reorganization of more than
                           50% of the voting power of the capital stock of
                           either the Company or Buyer to a non-Affiliate of
                           Buyer. In the event that such letter of credit has
                           been issued, clauses (i) and (ii) hereof
                           automatically terminate.

                  (iv)     In no event shall Seller be entitled to cumulative
                           remedies and guarantees pursuant to this Article
                           1.1.4 in an amount which exceeds the amount of unpaid
                           Payments, plus any interest accrued at the French
                           legal rate (taux d'interet legal) between the Payment
                           Date and the effective date of Payment.

1.2      Conditions Precedent.






                                       17
<PAGE>   94


         1.2.1    Conditions Precedent

                  The completion of the Purchase shall be subject to the
fulfillment, no later than the Closing Deadline, of the following conditions
precedent which are cumulatively stipulated for the benefit of Buyer, and which
only Buyer may therefore waive, except conditions stipulated under a) and b)
hereafter, which neither Party can waive.

         a)       Completion of the Partial Business Contribution by Seller to
                  the Company:

                  The Business shall have been contributed to the Company under
                  a Partial Business Contribution (Apport Partiel d'Actif)
                  meeting the following conditions. The Partial Business
                  Contribution shall have been duly authorized by the
                  shareholders of Seller and the Company and effected in
                  application of the Partial Business Contribution Agreement
                  (Traite d'apport partiel d'actif) substantially in the form of
                  Exhibit 1.2.1(a) hereto and with valuations of assets and
                  liabilities which will have been submitted to Buyer at the
                  beginning of the Second Due Diligence Period hereafter. It is
                  understood that such condition precedent shall not be
                  fulfilled before the completion of conditions precedent set
                  forth in Articles 1.2.1 b) and 1.2.1 c) hereafter.

         b)       Delivery by the General Manager of the French Medicine Agency
                  ("Agence du Medicament") of (i) the authorization to operate
                  as a manufacturing pharmaceutical establishment ("Autorisation
                  d'Etablissement Pharmaceutique Fabricant") to the Company, and
                  (ii) the corresponding amendment to the existing Seller's
                  Autorisation d'Etablissement Pharmaceutique.

         c)       Completion of legal, technical and financial due diligence by
                  Buyer and its counsels satisfactory to Buyer on the items
                  listed in Exhibit 1.2.1 c) and on the latest available draft
                  of the Partial Business Contribution Agreement which will have
                  been sent to the prospective contribution auditor
                  ("Commissaire a la Scission") and delivered to Buyer at the
                  latest 15 days prior to the expiration of the Initial Due
                  diligence Period as defined below, which due diligence shall
                  not have revealed an event which may materially adversely
                  affect the Business.
                  This due diligence will be carried out in two phases:

                  (i)      Seller shall, within 15 days as from the date hereof,
                           set up a data room for a period of five Business
                           Days, unless Seller consents to an extension up to
                           three additional Business Days, which consent shall
                           not be unreasonably withheld, which data-room can be
                           located outside the premises of Seller, and
                           containing all documents required by Buyer as per the
                           list attached hereto as Exhibit 1.2.1 c) and due
                           diligence will be conducted by Buyer and its counsels
                           within 30 days following the day when all information
                           is available to Buyer (the "Initial Due Diligence
                           Period"). No copies shall be made of documents in the
                           data room without



                                       18
<PAGE>   95


                           Seller's consent which shall not be unreasonably
                           withheld. All documents delivered by Seller pursuant
                           to a due diligence request shall be considered
                           Confidential Information as provided for in Articles
                           4.6 d) and 8) hereafter.

                           Upon expiration of the Initial Due Diligence Period,
                           Buyer shall remit to Seller a certificate
                           acknowledging the completion to its satisfaction of
                           the Initial Due Diligence in the form of the
                           Affidavit 1, provided that if Buyer does not deliver
                           the Affidavit 1, Buyer shall inform Seller in writing
                           at the same date of its reasons for not delivering
                           the Affidavit 1.

                  (ii)     Buyer shall, in addition, have the right, for 5
                           Business Days following the Filing Date to make
                           review of the final valuation of assets and
                           liabilities in the Partial Business Contribution
                           Agreement it would estimate appropriate (the "Second
                           Due Diligence Period").

                           Upon expiration of the Second Due Diligence Period,
                           Buyer shall remit to Seller a certificate
                           acknowledging the completion to its satisfaction of
                           such due diligence in the form of the Affidavit 2,
                           provided that if Buyer does not deliver the Affidavit
                           2, Buyer shall inform Seller in writing at the same
                           date of its reasons for not delivering the Affidavit
                           2.

         The Parties agree that the Purchase will enter into force without any
         retroactive effect after the completion of the above conditions
         precedent and on the date of fulfillment of the last of those
         conditions.

         1.2.2    Fulfillment

         a)       At the date of satisfaction of the last condition precedent to
                  be satisfied (the "Closing Date"), the Parties undertake to
                  proceed with the sale of the Shares and therefore to complete
                  the steps set forth in Article 1.3 hereafter subject to the
                  provisions of paragraphs b) and c) hereafter, and in no event
                  later than the Closing Deadline.

         b)       Buyer shall have no obligation to close and consummate the
                  Transaction if Buyer determines that a material adverse
                  change, whether legal, financial or of any kind, has occurred
                  in the Business, the Company or the Seller in connection with
                  the Business prior to the Closing Date. Buyer shall specify
                  such a material adverse change in writing to Seller. If Buyer
                  exercises its rights under this clause, Buyer will only be
                  allowed not to close the Purchase and shall not be allowed to
                  attempt to renegotiate the terms of the Transaction.
                  Additionally, an amendment to the existing Manufacturing and
                  Supply Agreement dated October 13, 1993 between the Parties in
                  the form attached hereto as Exhibit 1.2.2 b) shall
                  automatically become enforceable.




                                       19
<PAGE>   96

         c)       Seller shall have no obligation to close and consummate the
                  Transaction if prior to the Closing Date:

                  (i)      there is a Change of Control of Buyer;

                  (ii)     Buyer becomes subject to voluntary or involuntary
                           bankruptcy under applicable law;

                  (iii)    Buyer is enjoined from conducting all clinical trials
                           in the United States of America;

                  (iv)     an event has occurred which makes the occurrence of
                           either (i), (ii) or (iii) above unavoidable.

1.3      Closing.

                  On the Closing Date, on which the transfer of title of
ownership of the Shares from Buyer to Seller shall occur, the following steps
shall be completed simultaneously:


                  1.3.1    The Parties will exchange the following documents:

         a)       PMC will provide Buyer with the following documents:

                  (i)      the share transfer forms ("ordres de mouvement") in
                           favor of Buyer, duly signed by PMC and the Second
                           Shareholder, as well as evidence that the transfer of
                           the Shares has been inscribed in the register of
                           transfers of the Company as well as a duly signed
                           reiteration in French of this Agreement (such
                           document not being a translation but a summarized
                           document referring only to the Parties, the context
                           of the sale, the price and object of the sale) for
                           purposes of registration with French tax authorities,
                           in the form attached in Exhibit 1.3.1 a) (i) hereto;

                  (ii)     the corporate books of the Company (register of
                           transfers, shareholders accounts, minutes of the
                           board of directors and of the general meetings of the
                           shareholders, attendance registers of the board of
                           directors and attendance sheets of the shareholders'
                           meetings);

                  (iii)    relevant extracts of the minutes of the meetings of
                           PMC's Employee Committee ("Comite d'Entreprise") and
                           Central Employee Committee ("Comite Central
                           d'Entreprise") consulted on the Transaction;

                  (iv)     the minutes (or relevant extracts of the minutes) of
                           (a) the board of directors meetings of PMC approving
                           the Transaction, this Agreement, and the Partial
                           Business Contribution Agreement to be filed with the



                                       20
<PAGE>   97

                           Commercial Court of Commerce, (b) the board of
                           directors (or other competent corporate body)
                           meetings of the Company approving the Partial
                           Business Contribution Agreement to be filed with the
                           Commercial Court of Commerce, (c) the shareholder's
                           meetings of each of PMC and the Company deciding the
                           Partial Business Contribution to the Company, and (d)
                           the meeting of the board of directors (or other
                           competent corporate body) of the Company and the
                           Subsidiaries, if applicable, each convening an
                           ordinary shareholders meeting for the purpose of
                           electing new directors and new statutory auditors, as
                           applicable, which election shall take place
                           immediately after completion of the sale;

                  (v)      letters of resignation of, all members of the board
                           of directors, if any, the President of the Company
                           and of the Subsidiaries (if requested by Buyer),
                           specifying in addition that the Company or the
                           Subsidiaries do not owe them any moneys or any other
                           compensation ;

                  (vi)     letters of resignation of the statutory auditors of
                           the Company and the Subsidiaries, as applicable;

                  (vii)    a copy certified true and accurate of the Partial
                           Business Contribution Agreement duly signed;

                  (viii)   all documents from the German regulatory authorities
                           evidencing the renewal of the Thymoglobuline (R)
                           market approval and from the U.S. regulatory
                           authorities evidencing the approval of Thymoglobuline
                           (R) in the U.S., it being understood that, should
                           such renewal and authorization not be granted as of
                           the Closing Date, Seller covenants to remit to Buyer
                           copy of the same documents as soon as they are
                           available to it and provisions of Article 1.1.1 d)
                           shall apply;

                  (ix)     all documents evidencing (a) the delivery by the
                           General Manager of the French Medicine Agency
                           ("Directeur General de l'Agence du Medicament") of
                           the authorization to operate the Company as a
                           manufacturing pharmaceutical establishment and the
                           corresponding amendment to the existing Seller's
                           authorization (which corresponds to condition
                           precedent of Article 1.2.1(b) hereabove), (b) the
                           delivery by the General Manager of the French
                           Medicine Agency ("Directeur General de l'Agence du
                           Medicament") of the authorization to transfer all the
                           French "Autorisations de Mise sur le Marche" related
                           to the IMTIX Products to the Company, and (c) the
                           delivery by any foreign public authorities of
                           approvals to transfer to the Company foreign licenses
                           on IMTIX Products, it being understood that, for
                           those of the approvals referred to in (b) and (c)
                           which would not be granted as of the Closing Date,
                           Seller covenants to remit to Buyer copy of the same
                           documents as soon as they are available to it and
                           provisions of Article 4.3 shall apply;



                                       21
<PAGE>   98


                  (x)      a certified copy of the declaration filed with the
                           competent council of the Pharmacists' Association
                           ("Ordre des Pharmaciens") in connection with the
                           change of control of the Company, in compliance with
                           Article R.5015-17 of the French Public Health Code
                           ("Code de la Sante Publique");

         b)       Buyer will provide PMC with the following documents:

                  (i)      a certified copy of the declaration for foreign
                           investment to be filed by Buyer or its advisers, with
                           the French Treasury Department;

                  (ii)     a Letter of Credit of an amount of $6,000,000 (six
                           million U.S. dollars) substantially in the form of
                           Exhibit 1.1.4 (i) hereto, as provided for under
                           Article 1.1.4 hereof;

                  (iii)    three insurance certificates certifying that Buyer
                           has subscribed for insurance coverage for the Company
                           against (a) general and product liabilities, (b)
                           property and business interruption, and (c)
                           environmental liability (comparable and prorated to
                           PMC's external environmental insurance coverage) ;


         1.3.2    The Parties will remit to the Escrow Agent a joint letter of
                  instruction, in the form specified under the Escrow Agreement,
                  giving instruction to the Escrow Agent to release the amount
                  of $12,000,000 (twelve million U.S dollars) held in escrow
                  since the Filing Date to Seller, in accordance with provisions
                  of Article 1.1.1 a) hereof.

         1.3.3    The Escrow Agent shall remit to Seller the Payment of
                  $12,000,000 (twelve million U.S. dollars).

         1.3.4    Buyer and Seller shall duly execute the Ancillary Agreements.

         1.3.5    Buyer and Seller shall have obtained from Ernst & Young a
                  letter stating its approval to the assignment set forth in
                  Article 1.1.1 c) (ii) and Article 1.1.1. b) hereabove.


2.       Representations and Warranties of PMC.

                  PMC hereby represents and warrants for itself, the
Subsidiaries and the Company to Buyer that, except as set forth on a Schedule of
Exceptions (the "Schedule of Exceptions") (attached hereto as Exhibit 2), and it
being understood that any representation made hereafter with respect to the
Company shall be deemed to have been made also with respect to PMC in relation
to the Business before the contribution to the Company of the Business and with
respect




                                       22
<PAGE>   99



to the Subsidiaries, and that the following representations and warranties are
true and accurate as of the date hereof and shall be true and accurate as of the
Closing Date, on which date they will be deemed reiterated.


2.1 Organization, Good Standing and Qualification. PMC, the Company and the
Subsidiaries are corporations duly organized, validly existing and in good
standing under the laws of France (or under the laws of their country of
location for the Subsidiaries) and have all requisite corporate power and
authority to own or lease and operate their properties and to carry on their
business. There has been no formal request for the annulment or dissolution of
the Company or any of the Subsidiaries, nor has any petition been filed with any
competent authorities requesting the initiation of any restructuring or
liquidation procedures, and none of the Company or any of the Subsidiaries is
insolvent.

2.2      Shares.

         a)       The Shares represents 100% of the share capital and of the
                  voting rights of the Company, fully paid and non-assessable
                  and were duly and validly authorized and issued in accordance
                  with the French Company Act n(degree) 66-537 dated July 24,
                  1966 as amended and the Decree n(degree) 67-236 dated March
                  23, 1967 as amended. The Shares will entitle Buyer to receive
                  all dividends distributed by the Company as of its
                  incorporation.

         b)       There are not any outstanding options, warrants, rights
                  (including conversion or preemptive rights) or agreements for
                  the purchase or acquisition of any shares of the share capital
                  of the Company. The Company is not a party or subject to any
                  agreement or understanding, and there is no agreement or
                  understanding between any persons and/or entities, which
                  affects or relates to the voting rights or share capital of
                  the Company.

         c)       PMC and the Second Shareholder have good title to the Shares,
                  free and clear of any liens, encumbrances, equities and
                  claims, and full right, power and authority to effect the sale
                  and delivery of such Shares; upon the delivery of, against
                  payment for, such Shares pursuant to this Agreement, Buyer
                  will acquire good title thereto, free and clear of any liens,
                  encumbrances, equities and claims.

2.3 Subsidiaries. Other than the Subsidiaries, the Company does not presently
own or control, directly or indirectly, any interest in any other corporation,
association, grouping or partnership of whatever kind, including any "Groupement
d'Interet Economique", "Societe en Participation", "Societe Civile" or other
entity in which the liability of the members and partners is not limited to
their ownership interest, or other business entity. The Company is not a
participant in any joint venture, partnership, or similar arrangement. The
outstanding shares of the Subsidiaries are all duly and validly authorized and
issued and fully paid-up and were issued in accordance with the laws of their
country of location. These shares are free of all rights, charges, liens or
encumbrances whatsoever and there are not outstanding any options, warrants,



                                       23
<PAGE>   100

rights (including conversion or preemptive rights) or agreements for the
purchase or acquisition of such shares except as contemplated under the
Agreements.

2.4 Authorization. All action on the part of the Company, its officers,
directors and shareholders and all action on the part of PMC, its officers,
directors and shareholders, necessary for the authorization and execution of the
Agreements, the performance of all obligations of the Company and PMC hereunder
and thereunder, and the sale of the Shares has been taken and this Agreement and
the other Agreements constitute valid and legally binding obligations of the
Company and PMC subject to Article 1.2.1 a), enforceable in accordance with
their respective terms, except (i) as limited by applicable bankruptcy,
insolvency, reorganization, moratorium, and other laws of general application
affecting enforcement of creditors' rights generally and (ii) as limited by laws
relating to the availability of specific performance, injunctive relief, or
other equitable remedies. In particular, this Agreement has been duly authorized
by PMC's Board of Directors and PMC's Employee Committees ("Comites
d'Etablissement") and Work Council ("Comite Central d'Entreprise") have been
duly informed and consulted in compliance with provisions of the French Labor
Code.

2.5 Governmental Consents and Authorizations. Except as provided in Exhibit 2.5
(a) attached hereto, the Company and the Subsidiaries have been granted all
licenses, permits, authorizations and approvals from governmental or other
regulatory bodies (including in particular the ones set forth in Exhibit 2.5 (b)
which Exhibit contains a list of all permits and authorizations with respect to
their assets and the operation of the Business in relation to Thymoglobuline and
Lymphoglobuline) necessary to carry on the Business, and each of such permits is
currently valid and in full force and effect.

                  In addition, no consent, approval, order or authorization of,
or registration, qualification, designation, declaration or filing with, any
governmental or other authority on the part of the Company and the Subsidiaries
is required in connection with the consummation of the transactions contemplated
by the Agreements.

2.6 Financial Information. PMC's existing management accounts as already
provided relating to the Business as of December 31, 1997 attached hereto as
Exhibit 2.6 (the "Management Accounts") accurately describe and fairly present
the financial condition and operating results of the Business as of the date,
and for the period, indicated therein. The valuations of the assets and
liabilities of the Business attached to the Partial Business Contribution
Agreement (the "Contribution Valuations") as of the Retroactive Date accurately
describe and fairly present all the assets and liabilities attached to the
Business as of such date. The accounts of the Subsidiaries as of December 31,
1997 attached to the Partial Business Contribution Agreement shall have been or
have been duly established in accordance with all applicable legal and
administrative provisions and accounting principles and rules. They accurately
describe and fairly present the financial condition and operating results of the
Subsidiaries as of the dates, and for the periods, indicated therein. All
financial information previously provided by Seller to Buyer relating to the
Business is accurate in all material respects, provided however that no
representation or warranty is made with respect to financial and sales
projections other than that such projections represent Seller's best estimate
under the 



                                       24
<PAGE>   101


circumstances of what it reasonably believes. PMC does not make any other
representations or warranty regarding such financial and sales projections. All
expenses and financial undertakings (whether contingent or not) borne by the
Company and the Subsidiaries necessary to the operation of the Business are
properly accounted for in their accounts, and due provisions have been made by
the Company and the Subsidiaries for all charges relating to the Business, all
in accordance with the generally accepted accounting principles of the country
of location of the Company and the Subsidiaries.

2.7 Receivables. All accounts receivable arisen in the ordinary course of
business, have been collected or are collectible in the book amounts thereof and
none of such accounts receivable are subject to any material claim of offset,
recoupment, setoff, or counter-claim and neither the Company nor PMC nor the
Subsidiaries has any knowledge of any specific facts or circumstances (whether
asserted or unasserted) that would give rise to any such claim. The accounts
receivable have been accurately accounted and reserved in the Contribution
Valuations.

2.8 Compliance With Law. The use of the Assets and PMC's and the Company's and
the Subsidiaries' conduct of the Business is and has been in compliance, in all
material respects, with all applicable laws and regulations (each and all of the
foregoing being herein referred to as "Laws"), including Laws relating to the
pharmaceutical sector, employment, employment practices, labor and safety, and
Laws relating to the generation, handling, storage, release, discharge or
transportation of hazardous materials or substances or the environmental or
occupational health and safety ("Environmental and Safety Laws"), and the
Company and the Subsidiaries are not subject to any liability in connection with
any such Laws.

2.9 Necessary Assets; Entire Business. The present representation and warranty
2.9 shall be deemed only made as of the Closing Date. Except for the Excluded
Assets, as defined in the Partial Business Contribution Agreement, and for the
General Services, PMC has contributed to the Company the entire Business
(including any receivables from SangStat U.S. to PMC under the existing license
agreement which have become an asset of the Company) and the Assets constitute
all assets related to and necessary for the conduct of the Business. The said
contribution has been effected in accordance with the Partial Business
Contribution Agreement such as filed with the Court of Commerce. The Company has
not sold, leased or otherwise encumbered any of the Assets since the date of
said contribution, except under ordinary course of business. As a result, the
Company owns (or otherwise manages through the Ancillary Agreements) the entire
Business which, with the Ancillary Agreements and excluding the General Services
listed in Exhibit 2.9 hereto, constitutes a stand-alone business that will allow
the Company to conduct in a normal way the Business as it has been operated
until the date hereof and as it will be operated until the Closing Date.

2.10 Operating Condition. All of the tangible assets necessary for the operation
of the Business are suitable for the purposes for which they are used, are in
good operating condition and in reasonable repair (ordinary wear and tear
excepted).

2.11 Litigation. Neither PMC, the Company, the Subsidiaries, nor any of their
officers or directors is engaged in, or has received any threat of, any
litigation, arbitration, investigation, or



                                       25
<PAGE>   102


other proceeding, at law or in equity, before any court, regulatory agency, or
other governmental authority, involving the Company, the Subsidiaries, the
Business or the Assets, the employees of the Business in a Business-related
matter, or the transactions contemplated by any of the Agreements. During the
process of consultation of the Employee Committees ("Comites d'Etablissement")
and Work Council ("Comite Central d'Entreprise") in relation to the Transaction,
no dispute has arisen other than as summarized in Exhibit 2.11 hereto. There is
no action, suit, proceeding, or investigation pending or to the knowledge of PMC
threatened against the Company, the Subsidiaries or their officers or directors
that questions the validity of any of the Agreements, or the right of the
Company or PMC, to enter into the Agreements (to the extent each is a party to
such agreements), to consummate the transactions contemplated hereby or thereby,
or that might result in any material adverse change in the Business, the Assets
or the results of operations or financial condition of the Business, the
Subsidiaries or the Company, each taken as a whole. Neither the Company, nor the
Subsidiaries, nor their officers or directors is bound by any judgment, decree,
injunction, ruling, or order of any court, governmental, regulatory or
administrative department, commission, agency or instrumentality or arbitrator,
that has or is reasonably likely to have a material adverse effect on the
Business, the Assets, or the results of operations or financial condition of the
Business, the Subsidiaries or the Company, each taken as a whole. Without
prejudice to the foregoing, PMC shall indemnify and hold Buyer harmless against
all Claims relating to the operation of the Business until the Closing Date, in
accordance with the terms of Article 5. Neither PMC, the Company, the
Subsidiaries nor any of their officers, directors has received any
correspondence, notice, request, or threat thereof, orally or in writing, from
any regulatory agency which could affect existing or future regulatory approvals
or licenses related to the Business or the Assets.

2.12 Patents and Trademarks. The Company, except for the name "SangStat" which
is part of the corporate name of the Company, and the Subsidiaries have
sufficient title and ownership of or appropriate licenses to all know-how,
patents, trademarks, service marks, trade names, copyrights, trade secrets,
information, proprietary rights and processes necessary for their Business as
now conducted (including under the Know-How License Agreement) without any
conflict with or infringement of the rights of others, except for such items as
have yet to be conceived or developed. Except as provided in Exhibit 2.12
attached hereto, there are no outstanding options, licenses, or agreements of
any kind relating to the foregoing, nor is the Company, nor the Subsidiaries
bound by or a party to any options, licenses or agreements of any kind with
respect to the patents, trademarks, service marks, trade names, copyrights,
trade secrets, licenses, information, proprietary rights and processes of any
other person or entity. Neither the Company, nor the Subsidiaries, nor PMC has
received any communications alleging that the Company, the Subsidiaries or PMC
has violated or would violate any of the patents, trademarks, service marks,
trade names, copyrights or trade secrets or other proprietary rights of any
other person or entity.

2.13 No Conflict or Default. The execution of this Agreement or any of the other
Agreements by PMC or the Company or the Subsidiaries, nor compliance by PMC or
the Company or the Subsidiaries with the terms and provisions hereof and
thereof, including without limitation, the consummation of the transactions
contemplated hereby, will violate any statute, regulation, or ordinance of any
governmental authority, or conflict with or result in the breach of any term,



                                       26
<PAGE>   103

condition, or provision of the Articles of Incorporation ("Statuts") of PMC, the
Company or the Subsidiaries or of any order, decree, legal obligation, to which
PMC, the Company or the Subsidiaries is a party or by which it or any of the
assets are or may be bound, or constitute a default (or an event which, with the
lapse of time or the giving of notice, or both, would constitute a default)
thereunder, where such violation, conflict and/or default could have a material
adverse effect on (i) the continued operation by Buyer of the Business after the
Closing on substantially the same basis as theretofore operated by PMC or the
Company or the Subsidiaries, (ii) the consummation of the transactions
contemplated by this Agreement or any of the other Agreements, or (iii) the
results of operations or financial condition of the Business or the Assets, or
result in the creation or imposition of any material lien, charge, or
encumbrance, or restriction with respect to any of the Assets, or give to any
third party any rights of termination, acceleration, or cancellation in or with
respect to the Assets.

2.14 Third Party Consents. Without prejudice to provision of Article 2.5
hereabove, no consent, approval or authorization of or registration,
qualification, designation, declaration, or filing with any third party, on the
part of PMC or the Company or the Subsidiaries is required in connection with
the consummation of the transactions contemplated hereunder, except as provided
in Exhibit 2.14, where the failure to obtain such consent, approval, and/or
authorization could have a material adverse effect on (i) the consummation of
the transactions contemplated by the Agreements or (ii) the Assets or the
Business.

2.15 Finders' Fees. No third party shall be entitled to receive any finder's
fees, fees for financial advisory services or similar compensation in connection
with the transactions contemplated by this Agreement based on any arrangement or
agreement made by or on behalf of the Company.

2.16 Certain Payments. To the knowledge of PMC, in connection with the Business,
neither the Company, nor the Subsidiaries, nor PMC with respect to the Business,
nor any person directly or indirectly on behalf of the Company, PMC with respect
to the Business and the Subsidiaries, has made or received any payment that was
not legal to make or receive.

2.17 Permits. Subject to licences held by the distributors which are listed in
Exhibit 2.17 hereto, the Company and Subsidiaries have all franchises, permits,
licenses, and any similar authority necessary for the conduct of its business as
now being conducted by it, the lack of which could materially and adversely
affect the business, properties, or financial condition of the Company and
Subsidiaries, and the Company and Subsidiaries believe they can obtain, without
undue burden or expense, any similar authority for the conduct of its business
as planned to be conducted. The Company and the Subsidiaries are not in default
in any material respect under any of such franchises, permits, licenses, or
other similar authority.

2.18 Complete Disclosure. The Company and PMC have fully provided Buyer with all
the information that Buyer has requested and all information that the Company
and PMC, after due inquiry with all officers and directors involved in the
Business (including, but not limited to, manufacturing, QA/AC, regulatory,
marketing, sales, finance, administration, human resources in France and other
countries where the Business is operated), believe is material and related to
the



                                       27
<PAGE>   104


Business. Neither this Agreement, or any of the other Agreements, nor any other
statements or certificates made or delivered in connection herewith contains any
untrue statement of a material fact.

2.19 Title to Property and Assets. The Company as of the Closing Date and the
Subsidiaries own their property and assets (including the Assets) free and clear
of all mortgages, liens, loans and encumbrances, except such encumbrances and
liens that arise in the ordinary course of business and do not materially impair
the Company's and Subsidiaries' ownership or use of such property or assets.
With respect to the property and assets it leases, the Company and Subsidiaries
are in compliance with such leases and, to the best of its knowledge, holds a
valid leasehold interest free of any liens, claims or encumbrances.

2.20 Changes. Since December 31, 1997 for the Subsidiaries and, for the Company,
since the Retroactive Date on which the Contribution Valuations will have been
established, there has not been, subject to decisions taken by the Management
Committee:

         a)       any change in the assets, liabilities or financial condition
                  of the Business, the Company or the Subsidiaries from that
                  reflected in the financial documents referred to in Article
                  2.6 hereabove, except changes in the ordinary course of
                  business that have not been, in the aggregate, materially
                  adverse;

         b)       any change in the Business and management of the Company (or
                  Subsidiaries) which have been carried on in the ordinary
                  course, in a reasonable manner, "en bon pere de famille" as it
                  is understood under French law, and in a consistent manner in
                  order to ensure the continuity of the Business, and the
                  Company and Subsidiaries have not entered into any agreement
                  or taken any decision outside the ordinary course of business;

         c)       any damage, destruction or loss, whether or not covered by
                  insurance, materially and adversely affecting the Assets or
                  the Business or, any occurrence, circumstance, or combination
                  thereof which reasonably could be expected to result in any
                  such change;

         d)       receipt of notice that there has been a loss of, or material
                  order cancellation by, any major customer of the Business; or

         e)       any dividends, nor any distribution of any profits whatsoever;

         f)       any change in the Company's or the Subsidiaries' accounting
                  methods; any written off debts;

         g)       any granting by the Company or the Subsidiaries to any officer
                  or employee, any increase in compensation in any form, or any
                  severance or termination pay, any entering into by the Company
                  or the Subsidiaries of any employment agreement, any adoption
                  or amendment of any collective bargaining, bonus,
                  compensation,



                                       28
<PAGE>   105


                  stock option, pension, retirement, deferred compensation or
                  other plan, agreement, trust, fund or arrangement for the
                  benefit of employees;

         h)       to the best of PMC and the Company's knowledge, any other
                  event or condition of any character that might materially and
                  adversely affect the Assets, Business or the Company and
                  Subsidiaries (as such Business is presently conducted);

         i)       any communication with any regulatory agencies worldwide,
                  relating to the Business, except in the ordinary course of
                  business and that do not and will not have a material adverse
                  effect on the Business or the Assets.

2.21 Tax Returns, Payments and Elections. The Company and each of the
Subsidiaries, and PMC with respect to the Business, has filed all tax returns
and reports (including information returns and reports) as required by law,
including, but not limited to, the tax, customs and social security taxes. These
returns and reports are true and correct in all material respects. The Company,
the Subsidiaries and PMC with respect to the Business have paid all taxes and
other assessments due. There is no current dispute with any governmental
authority concerning taxes, customs or social security charges and to the best
knowledge of PMC and the Company, there is no reason to believe any such dispute
might arise.

2.22 Inventory. The inventories shown on the Management Accounts, the
Contribution Valuations and the balance sheet and accounts of the Subsidiaries
or thereafter acquired by PMC, or the Company or the Subsidiaries and relating
to the Business, consist of items of a quality usable or sellable in the
ordinary course of business. Neither PMC nor the Company nor the Subsidiaries
have received notice that it will experience in the foreseeable future any
difficulty in obtaining, in the desired quantity and quality and at a reasonable
price and upon reasonable terms and conditions, the raw materials, supplied or
component products required for the manufacture or production of products
relating to the Business. Due provision has been made on the books of the
Company and Subsidiaries in the ordinary course of business consistent with past
practices to provide for the obsolete, or unusable inventories to their
estimated useful or scrap values and such inventory reserves are adequate to
provide for such obsolete or unusable inventory. It is specified that the
Company will be entitled to sell inventory of work-in-progress and finished
goods with their existing packaging as of the Closing Date, until the expiration
date of the shelf life of all items of said inventory, provided such inventory
will be sold prior to any comparable products under Buyer's packaging.

2.23 Product Liability. Neither PMC nor the Company nor the Subsidiaries nor any
of their respective officers or directors is engaged in, or has received any
threat of any litigation, action, arbitration, investigation, or other
proceeding, at law or in equity, before any court, regulatory agency, or other
governmental authority in connection with any damages, loss, accident, disaster
caused by or related to a defect of any of the IMTIX Products and which would be
likely to incur the Company's or any of the Subsidiaries' liability. Neither PMC
nor the Company nor the Subsidiaries have received any client complaint or other
information whatsoever in relation to the same. In any event, it is agreed
between the Parties that any liabilities related to damages caused by the IMTIX
Products manufactured or sold by PMC, the Company or the Subsidiaries



                                       29
<PAGE>   106


before the Closing Date will be assumed by PMC only and PMC will indemnify and
hold harmless Buyer, or the Company, or the Subsidiaries, against any such
liabilities. It is expressly specified between the Parties that any liability
arising in connection with those representations of Article 2.23 shall be
subject to the specific limitation provided under Article 5 e) (iii) hereafter.

2.24     Employees.

         a)       No sum is due to any present or former employee, agent or
                  representative of the Company, the Subsidiaries or of the
                  Seller (dedicated to the Business) in connection with their
                  employment and/or other contracts or agreements other than
                  rights to payments accrued but not yet payable or to repayment
                  of business expenses, or debts disclosed in the Management
                  Accounts, in the Contribution Valuations and the balance
                  sheets and accounts of the Subsidiaries. The names of the
                  employees of the Business and the Subsidiaries as at the date
                  hereof, along with an indication of their age, seniority,
                  current salary, bonuses and other compensation, are listed in
                  Exhibit 2.24 (a) (the "Employees"). No promise to hire any
                  person has been granted. Only one (1) of the Employees is a
                  "protected employee" as this term is understood under French
                  labor law (employee delegate, member of the workers council,
                  union representative) or any equivalent foreign laws.

         b)       The Company and the Subsidiaries have not paid or agreed to
                  pay any sum of any kind to any of their employees, agents or
                  representatives that is not tax deductible.

         c)       The Company and the Subsidiaries have incurred no obligations
                  of any kind toward former employees, especially unfulfilled
                  obligations resulting from the breach of any labor or service
                  contract or from indemnities for dismissal or indemnities for
                  unjustified dismissal or from not having complied with the
                  obligation to reinstate an employee.

         d)       The Company and the Subsidiaries have complied with all
                  instructions and obligations imposed by the competent
                  authorities in the fields of labor law, social security law,
                  health and safety law and all other laws and regulations
                  applicable to employment.

         e)       The regulations relating to the representation of the
                  employees in the Company and the Subsidiaries have been duly
                  complied with.

         f)       No employment contract has been concluded with any current or
                  former employee, representative or agent, which breaches
                  applicable laws and regulations and the collective bargaining
                  agreement applicable to the Company or Subsidiaries.

         g)       No executive or manager has resigned from the Company or the
                  Subsidiaries nor notified in writing of an intention to resign
                  since December 31, 1997.







                                       30
<PAGE>   107

         h)       All pension and employee insurance plans in which the Company
                  and the Subsidiaries participate are mentioned in Exhibit 2.24
                  (h).

         i)       The Company and the Subsidiaries have not made any loans to
                  its employees, agents or representatives other than specified
                  under Exhibit 2.24i).

         j)       All contributions payable and due by the Company and the
                  Subsidiaries under retirement, dismissals and benefit plans
                  and all future obligations of the Company and the Subsidiaries
                  thereunder have been duly paid or reserved for in the
                  Contribution Valuations or the balance sheets and accounts of
                  the Subsidiaries in accordance with GAAP of their country of
                  location.

2.25 Contracts in General. The Company and the Subsidiaries are validly bound by
all their contracts in force and their co-contractors specifically dedicated to
the Business are validly obligated to them. The Company and the Subsidiaries
have performed and will perform all their obligations under these contracts. All
agreements to which the Company and the Subsidiaries are a party are in the form
of appropriate legal documentation allowing the Company and the Subsidiaries to
exercise and enforce all its rights thereunder. Without prejudice to the
generality of the preceding terms, there exists no commercial litigation or any
other event of whatever nature that might affect the timely performance of these
contracts.

                  As far as the following contracts are concerned, there exists
no event that might bring about the nullification or termination of these
contracts, that might entitle a third party to demand an early payment
thereunder, or that might involve in any manner the liability of the Company or
the Subsidiaries or that of their directors or employees:


         -        Various rabbit supply agreements;
         -        Agreement dated October 27, 1997 with Pharmacia & Upjohn;
         -        Agreements entered into with Immunotech and APHP respectively
                  on June 15, 1989 and March 6, 1995.

2.26 Contracts Outside the Ordinary Course of Business, Contracts with
Shareholders. Except as indicated in Exhibit 2.26 or permitted by the Management
Committee, the Company and the Subsidiaries:

         a)       have not concluded any contract which would involve their
                  joint or unlimited liability;

         b)       have not concluded any license agreement, any option to enter
                  into a license agreement nor any distribution agreement;

         c)       have not concluded any contract which would expressly or
                  implicitly provide for an early termination as a consequence
                  of the Transaction;



                                       31
<PAGE>   108

         d)       have not concluded any contract which by its terms cannot be
                  terminated without paying a penalty in excess of FF 25,000 or
                  without giving prior notice more than 3 months in advance;

         e)       have not concluded any agreement or arrangement limiting their
                  freedom to compete in any line of business with any person or
                  in any geographic area;

         f)       are not a party to any contract or agreement with any
                  Affiliate of PMC nor with any director of PMC or Affiliate of
                  PMC;

         g)       have not incurred, vis-a-vis PMC or an Affiliate of PMC, any
                  obligation or debt;

         h)       have not modified or received any request for modification of
                  any existing license, distribution or manufacturing agreement.

2.27 Insurance. The Company and the Subsidiaries shall have been insured until
the Closing Date under insurance policies for which all premiums have been paid
when due and which cover under normal conditions the risks regularly incurred by
companies operating a business similar to that of the Company. Neither the
Company nor any of the Subsidiaries have committed or omitted any act which
might render null or inoperative such insurance policies or might bring about
their cancellation.

                  There is no pending lawsuit involving the application of the
Company's or the Subsidiaries' insurance policies, and no event has occurred
which might bring about such a lawsuit.

2.28 Scope and Accuracy of the Representations. Buyer has undertaken to buy the
Shares upon the making of the above representations by PMC and on the express
condition that PMC grant the warranties referred to in Article 5 of this
Agreement. All information contained in this Agreement and the Exhibits thereto
is true and accurate. The above representations and warranties are stipulated
for the benefit of Buyer and its Affiliates.


3. Representations and Warranties of Buyer. Buyer hereby represents and warrants
that:

3.1 Authorization. Buyer has full power and authority to enter into the
Agreements, and the Agreements constitute valid and legally binding obligations,
enforceable in accordance with their terms except (i) as limited by applicable
bankruptcy, insolvency, reorganization, moratorium, and other laws of general
application affecting enforcement of creditors' rights generally and (ii) as
limited by laws relating to the availability of specific performance, injunctive
relief, or other equitable remedies.




                                       32
<PAGE>   109

3.2 Organization. Buyer is a company duly organized, validly existing and in
good standing under the laws of its country of incorporation and has all
requisite corporate power and authority to own or lease and operate its
properties and to carry on its business.

3.3 Non-Violation. The performance of the Agreements and consummation of the
transactions contemplated hereby and thereby by Buyer will not constitute a
violation of, or a default under, or conflict with (i) any provision of the
Articles of Incorporation ("Statuts") of Buyer or (ii) any legal requirements,
judgment or administrative decision which may apply to Buyer or by which Buyer
is bound or (iii) any agreement or undertaking to which Buyer is a party or by
which it is bound, the consequence of which could affect the validity and the
enforceability of the Agreements or of the transactions contemplated hereby or
thereby.


4. Covenants.

4.1 Covenant on Conditions Precedent/Contribution Agreement. Each Party
undertakes to take in a timely manner all necessary actions and to make its best
efforts in order that the conditions precedent set forth in Article 1.2
hereabove be met as soon as possible and to inform from time to time the other
Party on the implementation of those actions.

                  In particular, the Parties will use their best efforts to
obtain the authorization of the General Manager of the French Medicine Agency
referred to in Article 1.2.1 b) hereabove.

                  Seller also undertakes to take in a timely manner all
necessary actions and to make its best efforts in order that the Partial
Business Contribution shall be completed as soon as possible. In particular, as
soon as practicable after Seller has received the Affidavit 1 issued at the end
of the Initial Due Diligence Period, as provided under Article 1.2.1(c)
hereafter, but in no event later than 20 days following the last day of the
month in which the Affidavit 1 is delivered, Seller and the Company shall file
the draft Partial Business Contribution Agreement with the competent Commercial
Court (Greffe du Tribunal de Commerce), in compliance with applicable laws and
regulations.

                  As soon as the conditions precedent referred to in Articles
1.2.1 b) and 1.2.1 c) hereafter are fulfilled and within 20 days thereafter, the
shareholders of Seller and of the Company shall be convened at general meetings
to decide upon the Partial Business Contribution and complete the Partial
Business Contribution of the Business in exchange for shares of the Company,
pursuant to the Partial Business Contribution Agreement, as provided under
Article 1.2.1(a) hereabove.

4.2      Obligation to Cooperate.

4.2.1 During the Initial Due Diligence Period and the Second Due Diligence
Period set forth in Article 1.2.1 c) hereabove, Seller will provide Buyer and
its representatives with complete information requested in compliance
respectively with Articles 1.2.1 c) (i) and (ii) hereabove.



                                       33
<PAGE>   110


                  Seller will organize reasonable appointments with those senior
employees, and to the extent possible, external advisors, considered as involved
in the Business in order to perform the Initial Due Diligence provided that
Buyer has requested previously to Seller its need for such appointments, it
being understood that all costs of external advisors (except reasonable
attorney's fees) requested by Buyer and invoiced to Seller by such advisors in
this respect shall be borne by Buyer.

4.2.2    -        Seller, which has a good knowledge of the organization of the
                  French Medicine Agency and of other French and foreign public
                  authorities having competence over the pharmaceutical sector,
                  undertakes to use all its efforts and expertise to facilitate
                  in a timely manner the discussions with French and foreign
                  public authorities for the purposes of completion of the
                  Transaction.

         -        The Parties will use their best efforts to promptly obtain (i)
                  the prior authorization of the General Manager of the French
                  Medicine Agency ("Directeur General de l'Agence du
                  Medicament") to transfer to the Company all the French
                  "Autorisations de Mise sur le Marche" related to the IMTIX
                  Products, (ii) from any other foreign public authorities the
                  approval to transfer foreign licenses on IMTIX Products held
                  by Seller or its Affiliates (other than those held by the
                  Subsidiaries) to the Company (to the extent permitted by local
                  regulations and laws), and (iii) the U.S. PLA/ELA approval for
                  Thymoglobuline (R). For information purposes, a list of
                  key-steps to be taken with the French Medicine Agency,
                  together with an estimated timetable is attached hereto in
                  Exhibit 4.2.2.

         -        Seller will use its best efforts to have its Affiliates other
                  than Subsidiaries transfer all franchises, licenses, permits,
                  consents, authorizations, certificates, trademarks as listed
                  in the Partial Business Contribution Agreement and approvals
                  of any regulatory, administrative or other governmental agency
                  issued to or held by them, including all authorizations to
                  export products not licensed in France, to the extent relating
                  to the IMTIX Products, to the Company, except where this
                  transfer would violate local regulatory laws.

         -        Seller will use its best efforts to have third parties, which
                  are party to agreements attached in part only to the Business,
                  enter into new agreements with the Company covering the part
                  of those agreements attached to the Business, to the extent
                  such agreements are material to the Business.

4.2.3 As of the date of this Agreement and until the expiration of a 12-month
period after the Closing Date:

         -        The Parties undertake to set up a transition committee (the
                  "Transition Committee") which will review and advise on
                  transition activities and include:

                  (i)      until the Closing Date for Seller: Gilles Alberici,
                           Rene Labatut, a Regulatory Affairs representative, a
                           QA/QC representative, a Finance



                                       34
<PAGE>   111


                           representative and any other necessary people; and
                           for Buyer: the head of Regulatory Affairs, the Chief
                           Executive Officer, the VP of Operations, the VP of
                           Pharmaceutical Development, and

                  (ii)     after the Closing Date, for Seller, the same persons
                           (except Gilles Alberici, and Rene Labatut), for the
                           Company, Gilles Alberici, for Buyer, the same
                           persons, it being specified that Rene Labatut will
                           also be a member of the Transition Committee whether
                           as a representative of Seller or of the Company,
                           subject to Article 4.5 hereafter.

                           The Transition Committee will meet in France, no less
                           than once every quarter, except otherwise agreed
                           between the Parties, and more often if appropriate.
                           Until the Closing Date, the Transition Committee will
                           be chaired by Seller's Senior Vice President and
                           Chief Financial Officer and, as from the Closing
                           Date, by Buyer's Chief Executive Officer or a
                           designated representative.

         4.2.4 As of the Filing Date and until the Closing Date:

         -        The parties will establish a management committee (the
                  "Management Committee") which will consist of the members of
                  the Transition Committee referenced above in Article 4.2.3.
                  The Management Committee will oversee the operations of the
                  Company and the Business and specifically will have on an
                  internal basis management control and decision-making power
                  regarding but not limited to, the following:

                  a)       defining clinical development and Phase IV programs;

                  b)       all regulatory matters;

                  c)       manufacturing planning and operations;

                  d)       marketing, sales and product distribution plans for
                           all territories;

                  e)       recruiting, legal and financial matters.

                  Subject to any legal obligations and restrictions applicable
to Seller, Seller will use its best efforts to implement the Management
Committee's decisions, without materially affecting Seller's non-IMTIX business.
Only the representatives of Buyer will have voting power on the Management
Committee; all other members will have advisory powers only. The Management
Committee will meet on a monthly basis, either in person in France, or
telephonically and more often as reasonably requested by Buyer. Subject to
decisions of the Management Committee, Seller agrees to manage and operate the
Business and the Company according to normal business practices and in the
ordinary course of business.




                                       35
<PAGE>   112

                  The Management Committee shall act only according to normal
business practices and in the ordinary course of business.

                  The Management Committee shall not be entitled to recommend or
decide any dismissal of employee (other than in case of "faute lourde" or "faute
grave"), any divestment of or investment in intangible or tangible assets nor
any change in the strategy followed by the Seller for the Business until the
Filing Date.

4.2.5    Obligation to cooperate for SEC audits

                  Seller has been informed of the obligations of Buyer to
perform audits of the Company and the Business for the purpose of information of
the U.S. SEC as requested under applicable laws and regulations. Seller agrees
to provide information to Buyer and cooperate with Buyer for this purpose, to
the extent requests of Buyer in this respect are reasonable.

4.2.6    Immunotech Agreement

                  The parties shall exercise best efforts to transfer and assign
the contract between PMC and Immunotech dated June 15, 1989, but if, in spite of
all best efforts, they are unable to do so, PMC shall, subject to legal or
contractual limitations in such contract, grant to Buyer or its Affiliate a
sublicense that achieves as closely as possible, the same effect in all respects
as a transfer and assignment of such contract would achieve.


4.3 Interim Agreements. In the event that the transfer to the Company of all the
French "Autorisations de Mise sur le Marche" or equivalent authorizations in
foreign countries held by Seller or its Affiliates related to the IMTIX Products
has not been authorized as of the Closing Date, the Parties agree to use their
best efforts to negotiate and consummate a transaction having business,
financial, tax and legal effects as similar to the Transaction as reasonably
possible so as to take into account the delay in the transfer of such
authorizations.

4.4 Management of the Business and the Company. Between the date of this
Agreement and the Closing Date and subject to the prerogatives granted to the
Management Committee pursuant to Article 4.2.4 hereabove, Seller hereby
undertakes to manage and operate the Business and the Company according to
normal business practices and in the ordinary course of business and undertakes
to with respect to the Business, and shall procure that, with respect to the
Business, the Company and the Subsidiaries not to take any of the following
actions without having received the prior written consent of Buyer, which shall
not be unreasonably or untimely withheld and which consent shall be deemed
granted if Buyer has not responded otherwise prior to the expiration of a 15-day
period following a written request for consent:

         (1)      enter into or vary any material contract or undertaking other
                  than in the ordinary course of business;




                                       36
<PAGE>   113

         (2)      give or discharge any guarantee, or any loan or financing or
                  any security in relation to such guarantees, loans or
                  financing;

         (3)      subscribe or extend any borrowing;

         (4)      enter into any agreement or agreements requiring capital
                  expenditure in aggregate of more than 500,000 French Francs
                  (VAT not included);

         (5)      pass any board or shareholders resolution other than for the
                  purposes of this Agreement or the Transaction;

         (6)      dispose of any assets other than in the ordinary course of
                  business;

         (7)      vary or terminate any insurance policies dedicated to the
                  Business and the Company notably decrease product liability
                  insurance, and subject to reasonable changes of Rhone-Poulenc
                  Group policies, it being understood that Seller insurance
                  policies linked to the Business will terminate at the Closing
                  Date;

         (8)      settle any existing litigation in excess of 150,000 French
                  Francs;

         (9)      enter into or vary any material transaction with a related
                  party (including the shareholders or the managers);

         (10)     hire or terminate (for reasons other than "faute lourde" or
                  "faute grave") the employment of any employee with an annual
                  gross salary in excess of 250,000 French Francs or of several
                  employees the gross salary of which, in aggregate, exceeds
                  500,000 French Francs;

         (11)     reallocate any employee of the Business to any other division,
                  business or entity of the Seller;

         (12)     disclose any proprietary or confidential information to third
                  parties;

         (13)     modify the C4 building, the V3bis building or their equipment,
                  in any way, unless in response to a specific request from the
                  FDA or to a request of Buyer or as provided under Exhibit 3 to
                  the V3bis Commercial Lease Agreement.

4.5 Status of Mr. R. Labatut (R.L). Seller hereby expressly agrees to the
following:

         -        Buyer will be entitled to make an offer to R.L. to join the
                  Company, which offer Buyer will not have to disclose to
                  Seller.

         -        If R.L. decides to remain with Seller rather than accepting
                  Buyer's proposal, and for so long as R.L. so remains, Seller
                  undertakes to dedicate continuously R.L. to



                                       37
<PAGE>   114


                  Buyer at cost (based on time actually spent at Buyer's
                  request), for a period of 3 years, for up to (i) 45% of his
                  time for the first year, (ii) 35% for the second year, and
                  (iii) 25% for the third year. Every six months as from the
                  Closing Date, Buyer shall provide estimates of its needs for
                  the following 12 months, of which the first 6 months estimates
                  only shall be binding.

                  The above shall not prohibit Seller from dismissing R.L. in
case of "faute lourde" or "faute grave", in which case Seller shall be released
from the foregoing obligation.

4.6      Non-Solicitation.

         a)       As of the Closing and continuing for a period ending five (5)
                  years after the Closing, Seller undertakes unless otherwise
                  mutually agreed between the Parties, in the event that any of
                  the employees dedicated to the Business listed in Exhibit
                  2.2.4 (a) hereto would refuse to become an employee of the
                  Company or resign from Seller, the Company or any of the
                  Subsidiaries after the transfer of the Business, not to hire
                  such employee or to make any offer to the same for any
                  position in Seller or any of its Affiliates.

         b)       As of the Closing and continuing for a period ending five (5)
                  years after the Closing, PMC agrees that it shall not (and
                  cause its Affiliates other than its shareholders not to)
                  engage, associate itself with, or collaborate in, directly or
                  indirectly, in any country, whether for its own account or as
                  a shareholder (other than as a less than 3% shareholder of a
                  publicly-held company), partner, joint venturer, firm,
                  corporation, or other entity, in any activity in the fields of
                  R&D, production, marketing, distribution or management
                  relating to the field of (i) transplantation or (ii)
                  immunosuppression (within or outside of the field of
                  transplantation) using anti Tcell agents.

                  This provision shall not preclude Seller from acquiring
                  companies or businesses which involve organ transplantation
                  activity provided (i) that such activity represents only a
                  minor portion of such company or business and (ii) that Seller
                  shall in such case notify Buyer of such event and offer for
                  sale to Buyer such branch of activity at a reasonable price
                  based on the price paid by Seller.

                  Seller further undertakes not to grant or transfer any license
                  or right whatsoever, relating to the field of (i)
                  transplantation or (ii) immunosuppression (within or outside
                  of the field of transplantation) using anti Tcell agents,
                  which is the subject of a license or grant to the Company or
                  Buyer pursuant to this Agreement and the Ancillary Agreements
                  in relation to the Business to any Affiliate (including its
                  shareholders) or third party.

         (c)      As of the Closing and continuing for a period of 5 (five)
                  years after the Closing, PMC agrees that it shall not (and
                  cause its Affiliates not to):



                                       38
<PAGE>   115


                  (i)      solicit, directly or indirectly, or entice or
                           endeavor to solicit or entice away from employment
                           with Buyer, the Company or any of the Subsidiaries
                           any person employed thereby in the capacity of
                           employee, director, representative, consultant,
                           except with the prior written approval of Buyer, the
                           Company or any of the Subsidiaries, and Buyer agrees
                           to take the same commitment in favor of PMC;

                  (ii)     use any trademark, tradename or any other identifying
                           symbol presently used by the Company in the Business.

         (d)      Except as required by law or expressly permitted under this
                  Agreement or any of the other Agreements, PMC shall cause its
                  respective Affiliates, officers, directors, employees, agents
                  and subcontractors (collectively, "Representatives") and
                  Representatives of its Affiliates to keep confidential any and
                  all technical, commercial, scientific, financial and other
                  data, processes, documents or other information (whether in
                  oral or written form) or physical object (including, without
                  limitation, intellectual property, marketing data, agreements
                  with any third party, license applications, business plans and
                  projections) it may have with respect to the IMTIX Products,
                  the Assets, the Business, the Company or any of the
                  Subsidiaries and cease use of proprietary and other
                  confidential business and technical information related to the
                  same, for a period expiring 15 (fifteen) years as from the
                  Closing.

         (e)      The Parties agree that due to the unique nature of the
                  experience, knowledge and capabilities of PMC, there can be no
                  adequate remedy at law for any breach of its obligations
                  hereunder, that any such breach may allow PMC, and/or third
                  parties to unfairly compete with Buyer, or the Company, or the
                  Subsidiaries, resulting in irreparable harm to Buyer, or the
                  Company, or the Subsidiaries, and therefore, that upon any
                  such breach or any threat thereof, Buyer, or the Company, or
                  the Subsidiaries, shall be entitled to appropriate equitable
                  remedy it might have at law.

5. Indemnification.

                  The application of this Article shall in no way be affected by
any investigation of the subject matter thereof made by or on behalf of the
Parties to this Agreement, notably the Due Diligences.

         a)       Seller shall indemnify and hold harmless Buyer (or the
                  Company, if Buyer elects to choose so) against and in respect
                  of all claims, losses, liabilities, damages, reduction of
                  value of assets, costs and expenses (including reasonable fees
                  and expenses of counsel) which Buyer, the Company or the
                  Subsidiaries may suffer in connection with (a) a breach of
                  representations and warranties such as



                                       39
<PAGE>   116


                  described in d) hereafter, or (b) an increase of liability or
                  reduction of value of assets such as described in d)
                  hereafter. All such adverse consequences shall be referred to
                  herein collectively as "Damages".

         b)       Obligations of Buyer in the event of claims, losses,
                  liabilities, damages, reduction of value of assets, costs and
                  expenses, shall be referred to herein collectively as "Claim".
                  Any initial notification by any social, tax or customs
                  authority (such as "avis de controle fiscal") shall also be
                  referred for the purpose hereof as Claim.

         Buyer and/or the Company, as the case may be, shall notify Seller in
writing of any Claim.

         Such notification shall be made within a maximum period of:

                  (i)      At the latest 15 (fifteen) calendar days after
                           reception of written notice of the Claim by social,
                           tax, or customs authorities against Buyer, the
                           Company or the Subsidiaries. However, Buyer will use
                           its best efforts to provide notice within 5 (five)
                           Business days after reception of the same;

                  (ii)     30 (thirty) calendar days after receipt of written
                           notice of other Claims by a third party against
                           Buyer, the Company or the Subsidiaries. However, if
                           an answer to such third party Claims is due sooner
                           than 30 (thirty) days, the time period for notice
                           shall be no later than 5 (five) days prior to the
                           date the answer is due;

                  (iii)    30 (thirty) calendar days after the discovery by
                           Buyer and/or the Company of any other Damage than
                           those covered by (i) and (ii).

         and shall include either a copy of the original Claim or, if not
         possible, a brief description of the nature of this Claim, the identity
         of the person for whom it is being investigated, and an estimate of the
         Damage for Buyer or the Company which could result therefrom. Seller,
         or his duly appointed counsel, shall have access to all books and other
         necessary documents of the Company, as the case may be, relating to
         such Claim, which shall be made available at the registered office of
         the Company or at any place mutually agreed upon, subject to reasonable
         notice and for reasonable periods.

         Such notice shall be labeled "First Notice of Claim", and shall serve
         to preserve Buyer's rights to seek indemnification from Seller. Should
         Buyer or the Company fail to send the First Notice of Claim within the
         applicable period of time such as described hereinabove, Seller shall
         be relieved of its obligation to indemnify Buyer or the Company with
         respect to such corresponding matters.

                  c)       Right of Defense:

                  Within a maximum period of 10 (ten) Business days following
                  the receipt of the First Notice of Claim by which Seller was
                  informed that a Claim was lodged by a third party against
                  Buyer, the Company or the Subsidiaries, and that Buyer



                                       40
<PAGE>   117



                  requires indemnification from Seller, Seller shall notify
                  Buyer in writing if it chooses to settle such Claim or to
                  defend the matter at its own expense, provided that if Seller
                  elects to control the defense of the third-party claim, Seller
                  will be deemed obligated to indemnify Buyer for Damages as set
                  forth herein as a result of such procedure under the terms and
                  conditions of this Agreement, as long as Buyer provides
                  reasonable requested information. If it opts to defend such
                  Claim, Seller shall inform Buyer of the identity of the
                  counsel it has chosen to defend the Claim and keep Buyer
                  regularly informed of the developments of the defense.

                  Buyer shall retain the right to participate, either directly
                  or indirectly, at its own expense and with the counsel of its
                  choice in the defense of the matter, it being understood that
                  Seller's position shall prevail. The Company shall in this
                  situation forward the defense as prepared by Seller without
                  modification.

                  If Seller fails to respond within the above required period of
                  time to the notice sent by Buyer or the Company, or elects not
                  to control the defense, Buyer or the Company, as the case may
                  be, shall, acting alone, have the power to settle, negotiate,
                  or otherwise resolve the matter relating to the Claim.

                  d)       Indemnification:

                  (i)      Subject to (ii) hereafter, and provided the procedure
                           set up in the present Article is respected, Seller
                           shall indemnify and hold harmless Buyer (or the
                           Company, if Buyer elects to do so), 30 (thirty) days
                           after receipt from Buyer or the Company of a Claim
                           for indemnification labeled "Second Notice of Claim".
                           Such Second Notice of Claim shall be sent only in the
                           following cases and at the following period of time:

                  -        a judgment is rendered against Buyer, the Company or
                           the Subsidiaries which is no longer appealable, or,
                           if a settlement is reached with the third party
                           claimant and such judgement or settlement is based on
                           events which occurred prior to the Retroactive Date,
                           except with respect to product liability claims which
                           are covered by Article 5e)(iii) hereof;

                  -        a liability which does not appear in the Partial
                           Business Contribution Agreement approved by the
                           Extraordinary Shareholders Meeting of Seller and the
                           Company is finally due and effectively paid, or a
                           reduction of value of assets is definitively
                           assessed, in so far as such liability or reduction of
                           value of assets is based on events which occurred
                           prior to the Retroactive Date. Concerning the
                           Subsidiaries, the balance sheets as of December 31,
                           1997, attached to the Partial Business Contribution
                           Agreement will be considered as the basis of
                           references to determine if an increase of liability
                           or decrease of assets was suffered;



                                       41
<PAGE>   118

                  -        any other Damage that is finally suffered by Buyer,
                           the Company or the Subsidiaries, to the extent that
                           it results from an inaccuracy in the representations
                           and warranties appearing in the final version of the
                           representation and warranties as of the Closing Date.

                  (ii)     In the case Seller challenges such Claim of Buyer or
                           the Company, Seller shall indemnify Buyer within 10
                           (ten) days following the final award rendered
                           pursuant to Article 6.2.

                  (iii)    The amount to be paid shall be equal and limited to
                           the actual damage suffered and the cost effectively
                           borne by Buyer. Thus:

                  -        Damages shall be reduced by an amount by which the
                           actual value as of the Retroactive Date of the assets
                           contributed to the Company by Seller pursuant to the
                           Partial Business Contribution Agreement turns out to
                           be greater than the value of such assets as it was
                           initially listed in the Partial Business Contribution
                           Agreement;

                  -        Damages shall give right to indemnification after
                           deduction of the tax economy which may be made by
                           Buyer, the Company or the Subsidiaries due to such
                           Damage. All value added tax or all advances with
                           respect to corporation tax, which may be recuperated
                           by Buyer, the Company or the Subsidiaries, shall be
                           excluded from the actual damage.

                  (iv)     Payments due according to this Article shall be made
                           within 30 (thirty) days of the Second Notice of Claim
                           as indicated by Buyer in the Second Notice of Claim,
                           either:

                  -        by means of set-off, in accordance with provisions of
                           Article 1.1.3 hereof, against what Buyer owes to
                           Seller, in particular against the deferred portion of
                           the payment of the Purchase Price; or

                  -        by means of an actual payment.

                  e)       Duration, Limitations and Threshold:

                  (i)      Duration:

                           Buyer must notify Seller's representative of all
                           demands of payments of indemnification under this
                           Article:

                  -        as far as they relate to tax, customs or social
                           security matters, no later than the expiration of
                           their respective applicable statute of limitation;
                           and



                                       42
<PAGE>   119

                  -        as far as they relate to any other matter, not later
                           than the expiration of an 18 (eighteen) month period
                           starting as from the Retroactive Date.

                  Seller shall remain liable for Damage notified before these
                  dates.

                  (ii)     Threshold:

                  No claim for payment shall be made by Buyer until the
                  aggregate of all Damages exceeds $500,000 (five hundred
                  thousand U.S. dollars), it being specified between the Parties
                  that this amount constitutes a threshold and that, if the
                  aggregate amount of Damages exceeds that amount, then Buyer
                  shall be entitled to indemnification for:

                  -        the total amount of such Damage;

                  -        less a one-time deduction of $200,000 (two hundred
                           thousand U.S. dollars).

                  Nevertheless, the procedure described in this Article remains
                  applicable regardless of the application of the present
                  section (ii).

                  (iii)    The total amount of indemnification pursuant to the
                           Agreement shall not exceed the total amount of the
                           Fixed Price (i.e., $33,000,000 (thirty-three million
                           US Dollars), or the Fixed Price such as reduced in
                           accordance with Articles 1.1.1 b), c) and d)). It is
                           expressly agreed between the Parties that, with
                           respect to Damages consisting in product liability
                           which would arise in connection with representations
                           of Article 2.23 hereof:

                  (i)      any Damages resulting from a product manufactured
                           prior to the Retroactive Date shall give right to a
                           full indemnification without any limitation of amount
                           applying,

                  (ii)     any Damages resulting from a product manufactured
                           between the Retroactive Date and the Closing Date
                           shall give right to an indemnification limited to an
                           amount of $70,000,000 (seventy million US Dollars),
                           unless such Damages are due to the distribution (and
                           not to the manufacturing) of the products, in which
                           case no indemnification shall be due.

6.       Miscellaneous.

6.1 Successors and Assigns. Without prejudice of the right of substitution of
Buyer as set forth in Article 6.7 hereof, neither Party shall transfer or assign
this Agreement, in whole or in part without the other Party's prior written
consent, except that either Party may transfer, assign 



                                       43
<PAGE>   120


and delegate this Agreement to an Affiliate or in connection with a merger,
reorganization or sale of substantially all of its assets, without the other
Party's consent.

6.2 Governing Law/Dispute Resolution. This Agreement is governed by, and shall
be construed in accordance with, French law. Any and all disputes arising in
connection with this Agreement which will not be solved on an amicable basis
between the Parties shall be finally settled by arbitration under the Rules of
Conciliation and Arbitration of the International Chamber of Commerce, rules
that the Parties recognize that they know. The arbitration shall be conducted in
Paris, France, in English by one arbitrator if the dispute involves a claim of
damage of and below five hundred thousand (500.000) US Dollars or by three
arbitrators if the dispute involves a claim of damage above five hundred
thousand (500.000) US Dollars appointed in accordance with the said rules. The
arbitrator(s) shall apply French law to the merits of the case. The arbitration
shall be final and binding upon the Parties.

6.3 Expenses. Subject to Article 5(a), each Party hereto shall pay all costs and
expenses that it incurs with respect to the negotiation, execution, delivery and
performance of this Agreement. If any action at law is necessary to enforce or
interpret the terms of this Agreement, the winning Party shall be entitled to
reasonable attorney's fees, costs and necessary disbursements in addition to any
other relief to which such Party may be entitled.

6.4 Amendments and Waivers. Any term of this Agreement may be amended and the
observance of any term of this Agreement may be waived (either generally or in a
particular instance and either retroactively or prospectively), only with the
written consent of PMC and Buyer.

6.5 Severability. Any provision of this Agreement which is prohibited,
unenforceable or not authorized in any jurisdiction shall, as to such
jurisdiction, be ineffective to the extent of such prohibition, unenforceability
or non-authorization without invalidating the remaining provisions hereof or
affecting the validity, enforceability or legality of such provision in any
other jurisdiction, as long as this does not materially affect the economics of
the Transaction.

6.6 Press Release. An initial press release announcing the Parties' intent to
consummate the Transaction shall be in the form attached hereto as Exhibit 6.6.

                  All other major public communication of any kind relating to
the Transaction or any transactions contemplated thereby (hereinafter "Press
Release") shall be jointly drafted and reviewed by a press release review
committee which shall be composed by:

                  For PMC: a General Counsel

                  For SangStat: CEO

                  In the event that a Press Release is not jointly drafted or
that one Party desires to draft the Press Release first, the drafting party
shall communicate to the other Party the draft of the Press Release at least
three Business Days before the date of external communication for



                                       44
<PAGE>   121


review. Written approval or comments by the non drafting Party's persons sitting
on the press release review committee shall be given as soon as practicable and
in any event no later than 3 Business Days after receipt.

                  The above mentioned procedure may be waived in writing by the
non drafting Party's CEO or the non drafting CFO and General Counsel jointly.

                  In no event shall either Party be prohibited from making any
disclosures it determines are required by applicable law, nevertheless, to the
extent practicable, the procedure described hereabove shall be respected.

                  Additionally, in no event shall either Party be prohibited
from making any public communications relating to and substantially in the form
of prior approved communications.

                  In addition, occasional brief comments by the respective
officers of SMC and PMC regarding this Agreement shall be allowed only to the
extent such statements are consistent with guidelines for public statements as
may be mutually agreed upon by SMC and PMC and if made in connection with
routine interviews with analysts or members of the financial press.

6.7 Buyer's Right of Substitution. Buyer may substitute any of its Affiliates
(as defined herein) for the purposes hereof provided that, in this case, Buyer
will remain jointly liable for the obligations of such Affiliate, including but
not limited to payments of the Price, under the terms hereof. In such a case,
the term "Buyer" as used herein shall mean SMC and its substituted Affiliate.

6.8 Termination. This Agreement may be terminated and of no further force and
effect:

         a)       upon mutual written agreement by the Parties; or

         b)       subject to Article 7, if the Closing has not occurred by
                  December 31, 1998.

                  Additionally, (i) in the event any of the conditions precedent
of Article 1.2.1 hereof is not fulfilled on or before the Closing Deadline and
subject to waiver by Buyer of Condition 1.2.1 c), or (ii) in the event Buyer has
exercised its right of Article 1.2.2 b) hereabove or Seller has exercised its
right of Article 1.2.2 c) hereabove, this Agreement shall be considered as null
and void and with no further force or effect. In such a case, it is expressly
agreed however that the confidentiality commitment from the Parties set forth in
Article 8 hereof will remain in force according to its terms.

6.9 Notices. Notices and other communications required or called for under this
Agreement (including notices provided under Article 5) shall be in writing, and
shall be transmitted by fax and by certified mail postage prepaid, and shall be
deemed delivered upon receipt by the Party to whom it is addressed.

                  In the case of SMC such communications shall be addressed to:



                                       45
<PAGE>   122

                    SangStat Medical Corporation
                    1505 Adams Drive
                    Menlo Park, CA  94025
                    Attention:      Chief Executive Officer

         In the case of PMC, such communications shall be addressed to:

                     Pasteur Merieux Serums et Vaccins S.A.
                     58, avenue Leclerc
                     69007 Lyon
                     FRANCE
                     Attention:     Chairman, and Chief Executive Officer 
                                    with copy to the
                                   "Directeur Juridique"

         or to the attention of such other individual or to such other address
         as either Party may give to other in writing.

6.10     Force Majeure.

                  No Party hereto (or any of its Affiliates) shall be
responsible or liable to the other Party hereto (or any of its Affiliates) for
any failure to perform any of its agreements, covenants or obligations under
this Agreement if such failure results from events or circumstances reasonably
beyond the control of such Party (or of its Affiliates), including, without
limitation, war or other national emergency, riot, fire, explosion, flood or
other Act of God, general and long-lasting strike affecting the entire activity
of Seller on the site of Marcy l'Etoile, any injunction, decree, order, law or
regulation of any public authority, or inability to obtain electricity or fuel
or raw material (collectively, "Events of Force Majeure").

                  The affected Party shall (i) forthwith inform the other Party
in writing of the occurrence of the Event of Force Majeure, and (ii) exert best
efforts to eliminate, cure or overcome any such Event of Force Majeure and to
resume performance hereunder with all possible speed; provided, however, that
nothing contained herein shall require any Party to settle on terms
unsatisfactory to such Party any strike. To the extent that an Event of Force
Majeure continues for a period in excess of six (6) months, the Parties agree to
negotiate in good faith either (i) to resolve the Event of Force majeure, if
possible, (ii) to extend by mutual agreement the time period to resolve,
eliminate or overcome such Event, or (iii) to terminate this Agreement.

7.       Closing Deadline.

                  If, as of thirty days prior to the Closing Deadline, the
condition in Article 1.2.1(b) has not been met, the Parties agree as follows:

                  (i)      The Parties shall jointly appoint a regulatory
                           expert, who shall be fluent in French and in English
                           and who shall be a recognized professional in the



                                       46
<PAGE>   123



                           pharmaceutical business community. If the Parties
                           fail to agree on such expert, such expert shall be
                           appointed by the President du tribunal de Grande
                           Instance de Paris at the request of the most diligent
                           Party. Such expert shall review the status of the
                           pharmaceutical establishment license application. If
                           the expert, who shall deliver his/her report within
                           15 days of appointment, determines that it is
                           probable that a pharmaceutical establishment license
                           at least with respect to Thymoglobuline will be
                           granted to the Company prior to August 31, 1999, then
                           the Parties agree to enter into a restated Share
                           Purchase Agreement reiterating substantially all the
                           provisions of this Agreement, as adjusted to conform
                           with any legal, tax and accounting requirements, and
                           with a new Closing Deadline as of August 31, 1999;

                  (ii)     If the Closing Deadline is redefined as set forth
                           above, the Parties agree to use their best efforts to
                           negotiate and consummate agreements having business,
                           financial, tax and legal effects as similar to the
                           Transaction as reasonably possible for the period
                           ending on August 31, 1999;

                  (iii)    The Parties also agree that the valuations in the
                           Partial Business Contribution Agreement shall be
                           reset to January 1, 1999;

                  (iv)     Additionally, if the Transaction contemplated hereby
                           is not consummated prior to the Closing Deadline, as
                           redefined, Buyer shall have a right of first offer
                           with respect to a sale of the Business or the Shares
                           (as long as the Partial Business Contribution has
                           been completed) in any form by Seller until February
                           29, 2000. In the event Seller receives a bona fide
                           offer from a third party to buy the Business or the
                           Shares (as long as the Partial Business Contribution
                           has been completed) at any time prior to February 29,
                           2000, Seller shall provide written notice to Buyer of
                           such bona fide third party offer, which notice shall
                           include all material terms, including price. Buyer
                           shall have fifteen (15) days to review the proposed
                           sale and shall have the right, upon written notice to
                           Seller within such 15 -day period to exercise its
                           right to purchase the Business or the Shares on the
                           same financial terms as provided in the notice. Upon
                           notice of Buyer's intention to exercise its purchase
                           rights hereunder, the Parties shall be bound by the
                           terms and conditions as provided for in the notice
                           and they agree to negotiate in good faith and to
                           promptly execute and deliver all agreements and
                           documents which are necessary to consummate such a
                           transaction. If Buyer does not exercise its purchase
                           rights hereunder, Seller shall have the right to
                           enter into definitive acquisition documents with such
                           third party provided it is on substantially the same
                           financial terms as set forth in the notice to Buyer,
                           and provided further that the financial terms may be
                           changed if there has been a major change in the
                           Business after delivery of the notice.



                                       47
<PAGE>   124


                  It is agreed between the Parties that, should the Closing not
take place prior to the Closing Deadline due to a delay attributable to the
French Medicine Agency in granting the Pharmaceutical Establishment
authorization referred to in Article 1.2.1 b) hereof, the provisions hereabove
shall apply. Should the Closing not take place prior to the Closing Deadline
because of a delay in receiving the Pharmaceutical Establishment authorization
referred to in Article 1.2.1 b) hereof, due to issues relating to
Lymphoglobuline manufacturing, the Parties agree to negotiate in good faith a
contract manufacturing and distribution agreement with respect to
Lymphoglobuline and more generally to use their best efforts to negotiate and
consummate a transaction having business, financial, tax and legal effects as
similar to the Transaction as reasonably possible.

8.      Confidentiality.

         a)       General:

                  Except as expressly set forth in this Article, each Party
                  shall cause its respective Affiliates, officers, directors,
                  employees, agents and subcontractors (collectively,
                  "Representatives") and Representatives of its Affiliates to
                  keep confidential any and all technical, commercial,
                  scientific and other data, processes, documents or other
                  information (whether in oral or written form) or physical
                  object (including, without limitation, intellectual property,
                  marketing data, agreements between any Party and a third
                  party, license applications, and business plans and
                  projections of any Party) acquired from the other Party (the
                  "Other Party"), its Affiliates or its Representatives prior to
                  or after the date of this Agreement and which relates to the
                  Transaction, including all information exchanged as of the
                  date of this Agreement; provided in each case that such
                  information is marked "confidential" or, if verbal, such
                  information is reduced to writing and marked "confidential"
                  within 30 days of the date of disclosure ("Confidential
                  Information"), and each Party shall not disclose, directly or
                  indirectly, and shall cause its Representatives not to
                  disclose, directly or indirectly, any Confidential Information
                  to anyone outside such person, such Affiliates and their
                  respective Representatives, except that the following
                  information disclosed hereunder to any Party will not be
                  deemed Confidential Information for purposes of this
                  Agreement, if such person (the "Receiving Person") can
                  demonstrate that such Confidential Information:

                  (i)      is or hereafter becomes generally available to the
                           trade or public other than by reason of any breach or
                           default by the Receiving Person, any of its
                           Affiliates or any Representative of the foregoing
                           with respect to a confidentiality obligation under
                           this Agreement;

                  (ii)     was already known to the Receiving Person or such
                           Affiliate or Representative prior to disclosure;
                           provided, however, that this exception shall not
                           apply to any Confidential Information transferred by
                           Seller to Buyer by virtue of the Transaction;



                                       48
<PAGE>   125

                  (iii)    is disclosed to the Receiving Person or such
                           Affiliate or Representative by a third party who has
                           the right to disclose such information;

                  (iv)     based on such Receiving Person's good faith judgment
                           with the advice of counsel, is otherwise required to
                           be disclosed in compliance with applicable legal
                           requirements to a public authority.

                  Whenever the Receiving Person becomes aware of any state of
facts which would or might result in disclosure of Confidential Information
pursuant to subparagraph (iv) above, it shall, if possible, promptly notify the
person making disclosure (the "Disclosing Person") prior to any such disclosures
so that the Disclosing Person may seek a protective order or other appropriate
remedy and/or waive compliance with the provisions of this Agreement. In any
event, if the Receiving Person is unable to promptly notify the Disclosing
Person or if such protective order or other remedy is not obtained, or if the
Disclosing Person waives compliance with the provisions of this Agreement, the
Receiving Person will furnish only that portion of the information which it is
advised by counsel is legally required and will exercise reasonable efforts to
obtain assurance that confidential treatment will be accorded to the
Confidential Information.

         b)       Use of Confidential Information:

                  Each Party agrees that no Confidential Information shall:

                  (i)      be used in its own business except as necessary to
                           the fulfillment of the rights and obligations of such
                           Party under this Agreement;

                  (ii)     be assigned, licensed, sublicensed, marketed,
                           transferred or loaned, directly or indirectly to any
                           third party other than a Representative or an
                           Affiliate Representative of such Party, except as
                           necessary to the fulfillment of the rights and
                           obligations of the Parties under this Agreement;

                  (iii)    be used or exploited by such Party or any of its
                           Affiliates or their Representatives for its or their
                           respective benefit or the benefit of any other
                           relationships with customers of such Party and its
                           Affiliates.

                  Without limiting the generality of the foregoing, each Party
agrees that it shall not (and shall not permit any of its Affiliates) at any
time use any Confidential Information in the conduct of its business without the
prior written consent of the other Party. The obligations set forth in this
Article shall extend to copies, if any, of Confidential Information made by any
Representatives referred to in paragraph (a) and to documents prepared by such
Persons which embody or contain Confidential Information.

                  The present confidentiality provisions shall not prevent the
Parties from providing information requested by the French Medicine Agency
(Agence du Medicament) in order to obtain the approval of the Company as a
pharmaceutical establishment and the transfer of all licenses.





                                       49
<PAGE>   126
         c)       Protection of Confidential Information:

                  Each Party shall deal with Confidential Information so as to
                  protect it from disclosure with a degree of care not less than
                  that used by it in dealing with its own confidential
                  information and shall take reasonable steps to minimize the
                  risk of disclosure of Confidential Information which shall
                  include, without limitation, ensuring that only its Affiliates
                  and its and their Representatives who have a bona fide "need
                  to know" such Confidential Information for purposes permitted
                  or contemplated by this Agreement shall have access thereto.
                  Each Party shall notify all of its Representatives who have
                  access to Confidential Information of its confidentiality and
                  the care therefor required, and shall obtain from any
                  Affiliate or any agent or subcontractor who is a
                  Representative that is permitted access to such Confidential
                  Information in accordance with this Article, an agreement of
                  confidentiality incorporating provisions at least as
                  restrictive as those set forth herein, unless such
                  Representative is a legal counsel legally bound by such
                  confidentiality.

         d)       Term of Confidentiality Obligations / Survival:

                  Notwithstanding any contrary provisions provided elsewhere in
                  this Article, the obligations set forth in this Article shall
                  (i) terminate 15 (fifteen) years after the Closing in case the
                  Transaction is completed, or (ii) survive for a period of five
                  (5) years as from the Closing Deadline if this Transaction is
                  not completed.

         e)       Return of Confidential Information:

                  In the event the contemplated Transaction were not completed
                  for whatever reason, within thirty (30) days after such
                  decision not to carry out the Transaction, the Receiving
                  Person shall (and shall cause its Affiliates' Representatives
                  and its Affiliates to) return to the Disclosing Person or
                  destroy all related documents and tangible items then in its
                  possession which it has received from the Disclosing Person or
                  any Affiliate or Representative thereof pertaining, referring
                  or relating to the Disclosing Person's Confidential
                  Information, as well as all copies, summaries, records,
                  descriptions, modifications and duplications that it, or any
                  of its Affiliates or Representatives, has made from the
                  documents or tangible items received from the Disclosing
                  Person or any Affiliate or Representative thereof; provided,
                  however, that the Receiving Person may retain one copy of each
                  document in its legal files solely to permit the Receiving
                  Person to continue to comply with its obligations hereunder
                  and, in addition, may upon notice to the Disclosing Person,
                  retain in its legal files or in the offices of outside legal
                  counsel one copy of any document solely for use in any pending
                  legal proceeding to which such document relates.

         f)       Confidential Disclosure Agreement of October 16, 1997:





                                       50
<PAGE>   127

                  The obligations set forth in this Article supersede the
                  Confidential Disclosure Agreement executed between Seller and
                  Buyer on October 16, 1997.

                  IN WITNESS WHEREOF, the parties have executed this Agreement
in Lyon (France) as of the date first above written.


                                       SELLER:

                                       /s/ OLEANDA IZQUIERDO
                                       -------------------------------------
                                       Pasteur Merieux Serums & Vaccins S.A.
                                       By: Oleanda Izquierdo


                                       BUYER:


                                       /s/ ROBERT FLOC'H
                                       -------------------------------------
                                       SANGSTAT MEDICAL CORPORATION
                                       By: Robert Floc'h





                                       51
<PAGE>   128
                    AMENDMENT TO THE SHARE PURCHASE AGREEMENT

                               DATED JUNE 10,1998


This amendment of the Share Purchase Agreement is made as of the 10th of June
1998 by and among Pasteur Merieux Serums & Vaccins S.A., a Pasteur Merieux
Connaught company and a French Societe Anonyme having its registered office at
58 Avenue Leclerc, 69007 Lyon, France, duly represented by Mrs. Oleanda
Izquierdo, ("PMC" or "Seller") and SangStat Medical Corporation, a corporation
existing and organized under the laws of the State of Delaware and having its
principal place of business at 1505 Adams Drive, Menlo Park, California, 94025
USA, duly represented by Mr. Robert Floc'h ("SMC" or "Buyer"), in relation to
the sale of the shares of IMTIX-SangStat, S.A.S., a French corporation
registered in the form of a societe par actions simplifiee (the "Company").

Seller and Buyer are hereinafter referred to as the "Parties" or individually a
"Party".

WHEREAS:

Whereas the parties have signed on the date hereof an agreement entitled Share
Purchase Agreement,

Whereas the parties agreed to amend some Articles of the Share Purchase
Agreement through the present amendment,

The parties agreed to amend the Share Purchase Agreement as follows:

1. The retroactive date mentioned in the definitions page 9 is replaced by:

   ""Retroactive date" shall mean the first day of the month of the Filing Date,
   or the 1st of July if the filing Date is in August."

2. Article 1.2.1 c)

   - The first paragraph is replaced by:

   "Completion of legal, technical and financial due diligence by Buyer and its
   counsels satisfactory to Buyer on the items listed in Exhibit 1.2.1 c) which
   due diligence shall not have revealed an event which may materially adversely
   affect the Business. This due diligence will be carried out in two phases."

   - The paragraph (ii) is replaced by:


                                       52
<PAGE>   129

   "(ii)   Buyer shall, in addition, have the right, for 10 Business Days
           following the filing Date to make review of the valuation of assets
           and liabilities in the Partial Business Contribution Agreement it
           would estimate appropriate (the "Second Due Diligence Period")."

3. Article 1.3.1 b)

   A paragraph (iv) is added as follows:

   "(iv)   Should the effective Buyer not be SMC but one of its Affiliates
           according to Article 6.7: an assignment contract signed by duly
           authorized representatives of signatories, including in exhibit the
           Share Purchase Agreement, and in a form preserving the rights of
           Seller under the Share Purchase Agreement and in a form in compliance
           with the requests of a notary."

4. Article 1.3.4 is replaced by:

   "The Ancillary Agreements shall be duly executed".

The Parties agreed that:

   -       This amendment is a part of the Share Purchase Agreement dated June
           10, 1998,

   -       The Share Purchase Agreement will be filed with a notary on the
           Closing Date, it being expressly specified that, should the notary
           request that the Share Purchase Agreement be translated into French,
           in the case of a conflict or contradiction whatsoever between the
           Share Purchase Agreement and its translation into French, the
           provision of the Share Purchase Agreement (in English) shall prevail
           over those of the French translation.

Executed in Lyon
In two originals
on June 10,1998


Pasteur Merieux Serums & Vaccins         SangStat Medical Corporation


/s/ OLEANDRA IZQIERDO                    /s/ ROBERT FLOC'H
- -------------------------------------    ---------------------------------------
Represented by Oleanda Izquierdo         Represented by Robert Floc'h


                                       53
<PAGE>   130

                 AMENDMENT NO. 2 TO THE SHARE PURCHASE AGREEMENT

                               DATED JUNE 10,1998


This amendment of the Share Purchase Agreement is made as of the 31st of July
1998 by and among Pasteur Merieux Serums & Vaccins S.A., a Pasteur Merieux
Connaught company and a French Societe Anonyme having its registered office at
58 Avenue Leclerc, 69007 Lyon, France, represented by Mr. Herve Tainturier, duly
empowered for the purpose hereof ("PMC" or "Seller"), and SangStat Medical
Corporation, a corporation existing and organized under the laws of the State of
Delaware and having its principal place of business at 1505 Adams Drive, Menlo
Park, California, 94025 USA, represented by Doctor Philippe Pouletty its Chief
Executive Officer, duly empowered for the purpose hereof ("SMC" or "Buyer"), in
relation to the sale of the shares of IMTIX-SangStat S.A.S., a French
corporation registered in the form of a societe par actions simplifiee (the
"Company").

Seller and Buyer are hereinafter referred to as the "Parties" or individually a
"Party".

WHEREAS:

Whereas the Parties have signed on June 10, 1998 an agreement entitled Share
Purchase Agreement, as well as an amendment to this Share Purchase Agreement,

Whereas the parties agreed to amend some Articles of the Share Purchase
Agreement as amended on June 10, 1998 through the present amendment,

The parties agreed to amend the Share Purchase Agreement as follows:

1. The definition of "Closing" (page 7) is replaced by:

   ""Closing" shall mean the sale of the Shares by PMC to Buyer and the
   settlement of the Closing Payment of $10 (ten) million US Dollars by Buyer to
   PMC which shall take place on the Closing Date as set forth in Article 1.3
   hereafter;"

2. The Retroactive Date mentioned in the definitions page 9 is replaced by:

   ""Retroactive Date" shall mean the first day of the month of the Filing Date,
   or the 1st of July if the Filing Date is in August or in September;"

3. Article 1.1.1 a) of the Share Purchase Agreement is hereby amended to provide
that the Fixed Price as defined therein shall be reduced to a total amount of
thirty-one million ($31,000,000) US Dollars payable in several successive
payments (the "Payment(s)"), it being specified that ten million ($10,000,000)
US Dollars shall, on the date on which the draft partial Business Contribution
Agreement is filed with the Commercial Court of Commerce (the "Filing


                                       54
<PAGE>   131

Date"), be placed in escrow pursuant to the Escrow Agreement to be executed upon
the Filing Date in the form of Exhibit 1.1.1 a). The above mentioned reduction
in the Fixed Price has been agreed upon by the Parties [*] of the Schedule of
Exceptions as amended hereafter). Such reduction in Fixed Price shall be [*]

Additionally, the table of payments set forth in Article 1.1.1 a) is hereby
replaced in its entirety with the following:

<TABLE>
<CAPTION>
                                                      PAYMENT
           PAYMENT DATE                            (IN US DOLLARS)
           ------------                            ---------------
         <S>                               <C>
         Closing Date ("CD")               $10.0 million (the "Closing Payment")
         6  months after CD                         $1.5 million
         12 months after CD                         $1.5 million
         18 months after CD                         $1.5 million
         24 months after CD                         $1.5 million
         30 months after CD                         $3.0 million
         36 months after CD                         $3.0 million
         42 months after CD                         $2.5 million
         48 months after CD                         $2.5 million
         54 months after CD                         $2.0 million
         60 months after CD                         $2.0 million
</TABLE>

4. Article 1.1.1c) (i) (a) of the Share Purchase Agreement is hereby amended to
   read in its entirety as follows:

   "(a) Seller is performing at least one (1) of the services identified in the
        Service Agreement for the Manufacturing attached hereto as Exhibit
        1.1.1c)(i)(a) with respect to Thymoglobuline, or if Seller is not
        performing at least one (1) of the services, such failure to perform is
        due to (i) an event of force majeure, (ii) a request from Buyer, (iii)
        or a termination of the Service Agreement for the Manufacturing due to
        Buyer's fault; and"

5. The table set forth in Article 1.1.1c) (ii) of the Share Purchase Agreement
   is hereby replaced in its entirety with the following:

- --------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       55
<PAGE>   132

<TABLE>
<CAPTION>
                                      Minimum
                                 Reference Sales of
      Anniversary Date             Thymoglobuline                  Market
      ----------------           ------------------                ------
<S>                              <C>                      <C>
12 months after Closing Date          [*] vials                   Worldwide
24 months after Closing Date          [*] vials           European Union and USA
36 months after Closing Date          [*] vials           European Union and USA
48 months after Closing Date          [*] vials           European Union and USA
60 months after Closing Date          [*] vials           European Union and USA
</TABLE>


        Additionally, the two paragraphs immediately following the table in
Article 1.1.1.c) (ii) are hereby replaced in their entirety with the following:

"It is understood between the Parties that:

- -  for the second Payment Date (6 months after Closing Date), the minimum sales
   test shall be applied to the 6-month period preceding such date; as a result,
   no payment shall be due on such date if Actual Sales in this 6-month period
   are lower than [_____]* vials;

- -  for all Payment Dates which are not Anniversary Dates of the Closing Date,
   the minimum sales test to be referred to shall be as of the preceding
   Anniversary Date.

   For the purposes hereof, on each Anniversary Date of the Closing Date, the
   Company will measure the total number of Thymoglobuline R vials sold on the
   market referred to in the schedule hereabove mentioned during the 12-month
   period preceding such date (the "Actual Sales")."

6. Paragraph (i) of Article 1.2.1 c) and correlatively the third paragraph of
   Article 4.1 are hereby amended to provide that due to the extension of the
   Initial Due Diligence Period, the Affidavit 1 acknowledging the completion to
   Buyers satisfaction of the Initial Due Diligence, shall be remitted on the
   date hereof.

7. Amendment dated June 10, 1998, paragraph 2., Article 1.2.1 c): the title of
   the second dash is to be read as follows:

   "-   The first paragraph of paragraph (ii) is replaced by:"

instead of

   "-   The paragraph (ii) is replaced by:"

8. Article 1.3.2 is replaced by:

- --------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       56
<PAGE>   133
    "The Parties will remit to the Escrow Agent a joint letter of instruction,
    in the form specified under the Escrow Agreement, giving instruction to the
    Escrow Agent to release the amount of $10,000,000 (ten million U.S. dollars)
    held in escrow since the Filing Date to Seller, in accordance with
    provisions of Article 1.1.1. a) hereof."

9.  Article 1.3.3 is replaced by:

    "The Escrow Agent shall remit to Seller the Payment of $10,000,000 (ten
    million U.S. dollars)."

10. Article 4.1:

    -   the following sentence is added at the end of the third paragraph:

    "Shall the Affidavit 1 be remitted in July, the computation of the 20 days
    for the filing of the draft Partial Business Contribution Agreement shall
    start as from August 31."

    -   the fourth paragraph is replaced by:

    "As soon as the conditions precedent referred to in Articles 1.2.1 b) and
    1.2.1 c) hereafter are fulfilled and within 20 days thereafter, it being
    specified that, due to legal requirements, the minimum period of time
    between the Filing Date and the Closing Date must be at least 30 days, the
    shareholders of Seller and of the Company shall be convened at general
    meetings to decide upon the Partial Business Contribution and complete the
    Partial Business Contribution of the Business in exchange for shares of the
    Company, pursuant to the Partial Business Contribution Agreement, as
    provided under Article 1.2.1 a) hereabove. Should the 20 day period
    hereabove not allow Seller and the Company to hold these general meetings
    the last day of a month, this 20 day period shall be extended to the last
    day of the month during which the 20 day period ended."

11. Article 4.2 of the Share Purchase Agreement is hereby amended to include a
    new Article 4.2.7 which shall read in its entirety as follows:

    "4.2.7 [*]

    Seller shall use its best efforts to contribute to the development of an [*]
    test for Thymoglobuline by August 31, 1998, and such best efforts shall
    include, but not be limited to, (i) having one (1) trained biochemist from
    Seller dedicated to this development effort for the four (4) weeks preceding
    August 31, 1998, (ii) retaining at Seller's expense the services of one
    external immunochemistry

- --------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       57
<PAGE>   134

laboratory and (iii) interacting with Buyer with respect to Buyer's own
laboratory work regarding the above mentioned test."

12. Article 5.e:

    The first paragraph of paragraph (iii) is replaced by:

    "The total amount of indemnification pursuant to the Agreement shall not
    exceed the total amount of the Fixed Price (i.e., $31,000,000 (thirty-one
    million U.S. Dollars), or the Fixed Price such as reduced in accordance with
    Articles 1.1.1 b), c) and d)). It is expressly agreed between the Parties
    that, with respect to Damages consisting in product liability which would
    arise in connection with representations of Article 2.23 hereof:"

    Paragraph (ii) of paragraph (iii) is replaced by:

    "any Damages resulting from a product manufactured between the Retroactive
    Date and the Closing Date shall give right to an indemnification limited to
    an amount of $68,000,000 (sixty-eight million U.S. Dollars), unless such
    Damages are due to the distribution (and not to the manufacturing) of the
    products, in which case no indemnification shall be due."

13. The schedule of Exceptions in section 2.22 (Inventory) of Exhibit 2. to the
    Share Purchase Agreement is amended as follows:

    The first paragraph is replaced by:

    "Existing inventories of Thymoglobuline [*] which could through time [*]
    according to the current test method within the limits of specificity,
    accuracy and uncertainty of such method."

    The following paragraph is added after the first paragraph:

    [*]

<TABLE>
<CAPTION>
         BATCH NO.                         [*]
         ---------                       -----
         <S>                             <C>
           [*]                           - [*]
                                         - [*]
                                         - [*]
           [*]                             [*]
           [*]                             [*]
           [*]                             [*]
</TABLE>

- --------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       58
<PAGE>   135

The Parties agreed that this amendment no. 2 is a part of the Share Purchase
Agreement dated June 10, 1998. Any provision of the Share Purchase Agreement not
expressly modified by this amendment no. 2 shall remain unchanged. All Exhibits
shall be deemed to be modified to the extent necessary to make each of them
consistent with this amendment no. 2. Capitalized terms in this amendment no. 2
shall have the meaning set-forth in the Share Purchase Agreement.

Executed in two originals


             In Lyon                                  In Menlo Park
For Pasteur Merieux Serums & Vaccins        For SangStat Medical Corporation


/s/  HERVE TAINTURIER                       /s/  PHILIPPE POULETTY
- -----------------------------------         ------------------------------------
Represented by Mr. Herve Tainturier         Represented by Mr. Philippe Pouletty

- --------
* CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTION HAS BEEN FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION.

                                       59
<PAGE>   136

                 AMENDMENT NO. 3 TO THE SHARE PURCHASE AGREEMENT

                               DATED JUNE 10,1998


This amendment of the Share Purchase Agreement is made as of the 9th of
September 1998 by and among Pasteur Merieux Serums & Vaccins S.A., a Pasteur
Merieux Connaught company and a French Societe Anonyme having its registered
office at 58 Avenue Leclerc, 69007 Lyon, France, duly represented by Mr. Herve
Tainturier, duly empowered for the purpose hereof ("PMC" or "Seller") and
SangStat Medical Corporation, corporation existing and organized under the laws
of the State of Delaware and having its principal place of business at 1505
Adams Drive, Menlo Park, California, 94025 USA, duly represented by Mr. Philippe
Pouletty ("SMC" or "Buyer"), in relation to the sale of the shares of
IMTIX-SangStat, S.A.S., a French corporation registered in the form of a societe
par actions simplifiee (the "COMPANY").

Seller and Buyer are hereinafter referred to as the "PARTIES" or individually a
"PARTY".

WHEREAS:

Whereas the Parties have signed on the 10th of June 1998 an agreement entitled
Share Purchase Agreement,

Whereas the Parties have amended the Share Purchase Agreement through two
amendments dated June 10, 1998 and July 31, 1998,

Whereas the Parties agreed to amend this Share Purchase Agreement through the
present amendment,

The Parties agreed to amend the Share Purchase Agreement and the amendments to
the Share Purchase Agreement dated June 10, 1998 and July 31, 1998 as follows:

The paragraph (ii) of Article 1.2.1 c) of the Share Purchase Agreement and the
last paragraph of section 2 of the amendment to the Share Purchase Agreement
dated June 10, 1998 are replaced by:

   "(ii)   Buyer shall, in addition, have the right, for 12 Business Days
           following the filing Date to make review of the valuation of assets
           and liabilities in the Partial Business Contribution Agreement it
           would estimate appropriate (the "SECOND DUE DILIGENCE PERIOD").

           Upon expiration of the Second Due Diligence period, that is to say at
           the latest on the 10th September 1998 at 11:59 p.m. California time,
           Buyer shall remit to Seller


                                       60
<PAGE>   137

           a certificate acknowledging the completion to its satisfaction of
           such due diligence in the form of the Affidavit 2, provided that if
           Buyer does not deliver the Affidavit 2, Buyer shall inform Seller in
           writing at the same date of its reasons for not delivering the
           Affidavit 2."

Section 7 of the amendment to the Share Purchase Agreement dated July 31, 1998
shall be deemed to be modified, to the extent necessary to make it consistent
with this amendment no. 3.

The Parties agreed that this amendment no. 3 is a part of the Share Purchase
Agreement dated June 10, 1998. Any provision of the Share Purchase Agreement and
of the amendments to the Share Purchase Agreement not expressly modified by this
amendment no. 3 shall remain unchanged. All Exhibits shall be deemed to be
modified to the extent necessary to make each of them consistent with this
amendment no. 3. Capitalized terms of this amendment no. 3 shall have the
meaning set forth in the Share Purchase Agreement.


Executed in Lyon
In two originals
On September 9, 1998


Pasteur Merieux Serums & Vaccins            SangStat Medical Corporation


/s/  HERVE TAINTURIER                       /s/  PHILEPPE POULETTY
- -----------------------------------         ------------------------------------
Represented by Mr. Herve Tainturier         Represented by Mr. Philippe Pouletty


                                       61
<PAGE>   138

                               [Exhibit 1.1.1 (a)]

                            FORM OF ESCROW AGREEMENT


                                       62
<PAGE>   139

                               [Exhibit 1.1.1 (b)]

                       CALCULATION FORMULA OF DIRECT COST


                                       63
<PAGE>   140

                            [Exhibit 1.1.1 (c)(i)(a)]

                 FORM OF SERVICE AGREEMENT FOR THE MANUFACTURING


                                       64
<PAGE>   141

                               [Exhibit 1.1.4 (i)]

                            FORM OF LETTER OF CREDIT


                                       65
<PAGE>   142

                              [Exhibit 1.1.4 (i-2)]

                               FORM OF CERTIFICATE


                                       66
<PAGE>   143

                               [Exhibit 1.2.1 (a)]

                 FORM OF PARTIAL BUSINESS CONTRIBUTION AGREEMENT


                                       67
<PAGE>   144

                               [Exhibit 1.2.1 (c)]

                               DUE DILIGENCE LIST


                                       68
<PAGE>   145

                             [Exhibit 1.2.1 (c)(1)]

                     FORM OF AFFIDAVIT 1/FORM OF AFFIDAVIT 2


                                       69
<PAGE>   146

                               [Exhibit 1.2.2 (b)]

 FORM OF AMENDMENT TO THE MANUFACTURING AND SUPPLY AGREEMENT OF OCTOBER 13, 1993


                                       70
<PAGE>   147

                             [Exhibit 1.3.1 (a)(i)]

                               FORM OF REITERATION


                                       71
<PAGE>   148

                                   [Exhibit 2]

                             SCHEDULE OF EXCEPTIONS


                                       72
<PAGE>   149

                                [Exhibit 2.5 (a)]

                      EXCEPTIONS TO ARTICLE 2.5 (LICENSES)


                                       73
<PAGE>   150

                                [Exhibit 2.5 (b)]

                           PERMITS AND AUTHORIZATIONS


                                       74
<PAGE>   151

                                  [Exhibit 2.6]

                               MANAGEMENT ACCOUNTS


                                       75
<PAGE>   152

                                  [Exhibit 2.9]

                            LIST OF GENERAL SERVICES


                                       76
<PAGE>   153

                                 [Exhibit 2.11]

                DISPUTES WITH EMPLOYEE COMMITTEE AND WORK COUNCIL


                                       77
<PAGE>   154

                                 [Exhibit 2.12]

    EXCEPTIONS TO ARTICLE 2.12 (OUTSTANDING OPTIONS, LICENSES OR AGREEMENTS)


                                       78
<PAGE>   155

                                 [Exhibit 2.14]

                              THIRD PARTY CONSENTS


                                       79
<PAGE>   156

                                 [Exhibit 2.17]

                LIST OF LICENSES HELD BY THIRD PARTY DISTRIBUTORS


                                       80
<PAGE>   157

                               [Exhibit 2.24 (a)]

                                LIST OF EMPLOYEES


                                       81
<PAGE>   158

                               [Exhibit 2.24 (h)]

                      PENSION AND EMPLOYEE INSURANCE PLANS


                                       82
<PAGE>   159

                               [Exhibit 2.24 (i)]

                  LOANS TO EMPLOYEES, AGENTS OR REPRESENTATIVES


                                       83
<PAGE>   160

                                 [Exhibit 2.26]

                CONTRACTS OUTSIDE THE ORDINARY COURSE OF BUSINESS


                                       84
<PAGE>   161

                                 [Exhibit 4.2.2]

            STEPS WITH FRENCH MEDECINE AGENCY (AGENCE DU MEDICAMENT)

                                       85
<PAGE>   162

                                  [Exhibit 6.6]

                                  PRESS RELEASE

                                       86
<PAGE>   163

                                 [Exhibit 8 (i)]

                            FORM OF LETTER OF CREDIT


                                       87
<PAGE>   164

                                [Exhibit 8 (i-2)]

                               FORM OF CERTIFICATE


                                       88
<PAGE>   165

                                 [Exhibit 14.2]

                                  PRESS RELEASE

                                       89

<PAGE>   1
                                  EXHIBIT 99.1

                 TEXT OF PRESS RELEASE DATED SEPTEMBER 30, 1998



        MENLO PARK, Calif. and LYON, France--(BW HealthWire)--Sept. 30,
1998--SangStat, The Transplant Company(R) (Nasdaq: SANG - news) and Pasteur
Merieux Connaught (Rhone-Poulenc group) announced today the closing of the
acquisition of Pasteur Merieux Connaught's organ transplant business known as
IMTIX. The resulting wholly owned subsidiary of SangStat, named IMTIX-SangStat,
is dedicated to the development, manufacturing and sale of transplantation
products in more than 60 countries outside of North America, and is expected to
generate sales of approximately $22-28 million in 1998.

        "The successful creation of IMTIX-SangStat is a key component of our
global plan to become a competitive force in the $2 billion worldwide transplant
market," said Philippe Pouletty, M.D., SangStat's Chairman and CEO. "We look
forward to the productive integration of IMTIX into SangStat and to the many
value-added benefits that this very timely union offers given the potential
European CYCLOSPORINE approval in 1999."

        The transaction is an acquisition of IMTIX by SangStat for $31 million,
and involves an up-front payment of $10 million and deferred cash payments over
five years of $21 million. In addition, SangStat will pay Pasteur Merieux
Connaught royalties on IMTIX-SangStat product sales that are variable and
contingent upon the sales of certain IMTIX-SangStat products. The transaction
will be accounted for using the purchase method.

        "IMTIX's products and turn-key sales and manufacturing operations are a
welcome addition to our current portfolio of transplant products and services,"
said Jean-Jacques Bienaime, SangStat's President and COO. "The significant
development, marketing and sales synergies offered by this acquisition should
contribute to SangStat's growth over the coming years and help us to penetrate
the large European market."

IMTIX

        Pasteur Merieux Connaught's organ transplant business operated as a
business unit called IMTIX. Established in 1995, IMTIX is dedicated to the
research, development, manufacture and marketing of pharmaceuticals for
transplantation. Its portfolio includes i) products for prevention and treatment
of rejection, THYMOGLOBULIN(R) and LYMPHOGLOBULINE(R), polyspecific antibodies
currently distributed in Europe and other countries, ii) Odulimomab
(anti-LFA-1), a monoclonal antibody currently in Phase III for prevention of
delayed graft function in transplant patients, and iii) Celsior(R), an organ
preservation solution. Based in Lyon, France, with several European subsidiaries
and offices, IMTIX has approximately 80 employees, of whom approximately 50 are
dedicated to R&D, regulatory, medical affairs, marketing and sales, and
approximately 30 to product manufacturing. Products are manufactured in Lyon and
distributed by Pasteur Merieux Connaught's affiliates in more than 60 countries
outside of North America, including most of the EU countries, Brazil, South
Africa and Japan. "We are pleased to contribute, through the sale of IMTIX to
SangStat, to the growth of a focused transplant care company," said Jean-Jacques
Bertrand, Chairman and

<PAGE>   2

CEO of Pasteur Merieux Connaught. "Since initiating our collaboration with
SangStat in 1993, with the licensing of THYMOGLOBULIN and CELSIOR North American
rights to SangStat, our two companies have built a fruitful and cooperative
relationship."

        "This is viewed within our organization as a very positive step
forward," said Dr. Gilles Alberici, previously the Head of IMTIX, Pasteur
Merieux Connaught Transplant Division and the newly appointed President of
IMTIX-SangStat. "We are excited about the opportunity to work within a company
that is completely focused on organ transplantation."

Products Included In Acquisition

        THYMOGLOBULIN is a pasteurized, rabbit anti-human thymocyte
immunoglobulin, which induces immunosuppression as a result of T-cell depletion.
It was first registered in 1985, is currently marketed in 51 countries
worldwide, and has been used in more than 40,000 patients worldwide for the
treatment and prevention of acute graft rejection episodes in transplant
recipients. CELSIOR is an organ preservation solution currently used for heart
preservation and available in three countries so far. SangStat acquired
exclusive licenses from Pasteur Merieux Connaught in 1993 to market
THYMOGLOBULIN and CELSIOR in the United States and Canada. An application for
market clearance for THYMOGLOBULIN in the United States is in the final stages
of review at the U.S. Food and Drug Administration, and an application for
510(k) clearance of the one-bag system for CELSIOR is expected to be filed later
in the year. LYMPHOGLOBULINE is a horse anti-human thymocyte immunoglobulin
available in 55 countries for the prevention and treatment of graft rejection
and for treatment of severe hematological disorders, and Odulimomab (anti-LFA-1)
is a monoclonal antibody in Phase III in North America and Europe for the
prevention of delayed graft function in transplant patients.

SangStat, The Transplant Company(R) and Pasteur Merieux Connaught

        SangStat is a specialty pharmaceutical company applying a disease
management approach to improve the outcome of organ transplantation. The Company
has a total of 12 monitoring and therapeutic products and product candidates to
address the pre-transplant, acute care and chronic phases of transplantation.
SangStat is located in Menlo Park, California, and operates The Transplant
Pharmacy(R), a comprehensive pharmacotherapy management program, and
wholly-owned subsidiaries, SangStat Atlantique S.A.S., SangStat's European base
of operations in Nantes, France, SangStat Canada, Ltd., in Mississauga, Ontario,
Canada and Human Organ Sciences(TM), Inc. in Menlo Park, California.

        Pasteur Merieux Connaught is the world's largest vaccine company with
the broadest range of products. The company produces more than one billion doses
every year. Rhone-Poulenc SA is a leading life sciences company, growing through
innovations in human, plant and animal health and through its specialty
chemicals subsidiary, Rhodia. With sales in 1997 of FF90 billion (US$15
billion), the company employs 68,000 people in 160 countries worldwide.

        This press release contains forward-looking statements that involve
risks and uncertainties. Forward-looking statements reflect SangStat and Pasteur
Merieux Connaught's current views with respect to future events. Actual results
may vary materially and adversely

<PAGE>   3

from those anticipated, believed, estimated, or otherwise indicated. Important
factors common to the drug review and clearance process by the FDA and EU
regulatory agencies could cause actual results to differ materially with regard
to the approvability and possible market acceptance of THYMOGLOBULIN,
CYCLOSPORINE, and other product candidates. Other risks associated with this
acquisition could cause actual results to differ materially. These factors
include, without limitation, receipt of approvals by regulatory agencies to
transfer product manufacturing and marketing licenses, the successful
integration of IMTIX into SangStat and failure to successfully exploit the
potential benefits and synergies of the acquisition.

        Other factors that could cause actual results to differ materially
include, without limitation, uncertainty relating to the current or future
manufacturing of commercial quantities of products on commercially favorable
terms, market size, market acceptance, profitability and competition. For a
discussion of factors that might result in different outcomes, see SangStat's
1997 Form 10-K and most recent 10-Q filed with the Securities and Exchange
Commission.


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