Document:

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                                                                    EXHIBIT 10.1

                          STOCK CONTRIBUTION AGREEMENT

                            dated as of July 17, 2000

                                      among

                             AVAX TECHNOLOGIES, INC.

                                       and

                          PROFESSOR DAVID R. KLATZMANN

                                       and

                          PROFESSOR JEAN-LOUP SALZMANN

                                       and

                                    GPH, S.A.

                                       and

                                GENOPOIETIC, S.A.

                          relating to the contribution

                                       of

              7,792 Shares of the Common Stock of Genopoietic, S.A.

                                       and

                   93 Shares of the Common Stock of GPH, S.A.

                       in exchange for cash and shares of

                     Common Stock of AVAX Technologies, Inc.

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<S>                                                                                                              <C>
ARTICLE I - CONTRIBUTION OF SHARES................................................................................11

   SECTION 1.1    CONTRIBUTION OF SHARES..........................................................................11
   SECTION 1.2    CONTRIBUTION CONSIDERATION......................................................................11

ARTICLE II - THE CLOSING..........................................................................................12

ARTICLE III - RELATED TRANSACTIONS................................................................................12

   SECTION 3.1    RECEIPT OF OTHER HOLDINGS SHAREHOLDERS'SHARES...................................................12
   SECTION 3.2    RECEIPT OF OTHER SUBSIDIARY SHAREHOLDERS'SHARES.................................................13
   SECTION 3.3    RECEIPT OF AVENTIS SHARES BY RECIPIENT..........................................................13
   SECTION 3.4    RELEASE OF AVENTIS'RIGHTS.......................................................................13
   SECTION 3.5    RESOLUTION OF INTELLECTUAL PROPERTY ISSUE.......................................................13
   SECTION 3.6    CONTRIBUTORS'CONSULTING AND ASSIGNMENT AGREEMENTS...............................................13
   SECTION 3.7    RESIGNATION OF PROF. KLATZMANN FROM THE BOARD OF PROGENICS......................................13
   SECTION 3.8    RESIGNATION OF ALL MEMBERS OF THE BOARDS OF DIRECTORS OF HOLDINGS AND SUBSIDIARY................13
   SECTION 3.9    FINANCIAL SUPPORT PROVIDED TO SUBSIDIARY........................................................14
   SECTION 3.10   PROGENICS TERMINATION...........................................................................14

ARTICLE IV - REPRESENTATIONS AND WARRANTIES OF THE CONTRIBUTOR GROUP..............................................14

   SECTION 4.1    ORGANIZATION....................................................................................14
   SECTION 4.2    AUTHORIZATION...................................................................................15
   SECTION 4.3    VALID AND BINDING AGREEMENT.....................................................................16
   SECTION 4.4    ORGANIZATIONAL DOCUMENTS........................................................................16
   SECTION 4.5    QUALIFICATION...................................................................................17
   SECTION 4.6    CAPITALIZATION..................................................................................17
   SECTION 4.7    SHARE OWNERSHIP.................................................................................18
   SECTION 4.8    SUBSIDIARIES, AFFILIATED ENTITIES AND OTHER RELATIONSHIPS.......................................19
   SECTION 4.9    CONSENTS; NO VIOLATION..........................................................................19
   SECTION 4.10   FINANCIAL STATEMENTS............................................................................20
   SECTION 4.11   NO UNDISCLOSED LIABILITIES......................................................................20
   SECTION 4.12   ABSENCE OF CERTAIN CHANGES......................................................................20
   SECTION 4.13   CERTAIN TAX MATTERS AND SOCIAL SECURITY MATTERS.................................................21
   SECTION 4.14   TITLE TO PROPERTIES; ENCUMBRANCES...............................................................23
   SECTION 4.15   FIXED AND OTHER TANGIBLE ASSETS.................................................................23
   SECTION 4.16   LEASES..........................................................................................24
   SECTION 4.17   HOLDINGS COMPUTER PROGRAMS, DATABASES AND SOFTWARE..............................................24
   SECTION 4.18   SUBSIDIARY COMPUTER PROGRAMS, DATABASES AND SOFTWARE............................................24
   SECTION 4.19   INTELLECTUAL PROPERTY...........................................................................25
   SECTION 4.20   LITIGATION......................................................................................31
   SECTION 4.21   INSURANCE.......................................................................................31
   SECTION 4.22   CONTRACTS.......................................................................................32
   SECTION 4.23   PERSONNEL AND LABOR MATTERS.....................................................................33
   SECTION 4.24   ENVIRONMENTAL MATTERS...........................................................................34
   SECTION 4.25   REGULATORY MATTERS..............................................................................35
   SECTION 4.26   INTERESTED TRANSACTIONS.........................................................................35
   SECTION 4.27   ASSETS AND RIGHTS NECESSARY TO HOLDINGS'BUSINESS................................................35
   SECTION 4.28   ASSETS AND RIGHTS NECESSARY TO SUBSIDIARY'S BUSINESS............................................36
   SECTION 4.29   BROKERS OR FINDERS..............................................................................36
   SECTION 4.30   COMPLIANCE WITH LAWS AND COURT ORDERS...........................................................36
   SECTION 4.31   ABSENCE OF COMPETING INTERESTS..................................................................36
   SECTION 4.32   ABSENCE OF ANY INTERESTS OF AVENTIS.............................................................37
   SECTION 4.33   PROFESSOR STATUS................................................................................37
   SECTION 4.34   DISCLOSURE......................................................................................37

ARTICLE V - REPRESENTATIONS AND WARRANTIES OF THE CONTRIBUTORS....................................................38

   SECTION 5.1    RECEIPT OF AVAX STOCK...........................................................................38

ARTICLE VI - REPRESENTATIONS AND WARRANTIES OF RECIPIENT..........................................................39

   SECTION 6.1    CORPORATE EXISTENCE AND POWER...................................................................39
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<S>                                                                                                               <C>
   SECTION 6.2    CORPORATE AUTHORIZATION.........................................................................39
   SECTION 6.3    NON-CONTRAVENTION...............................................................................39
   SECTION 6.4    ACQUISITION FOR INVESTMENT......................................................................39
   SECTION 6.5    AVAX STOCK......................................................................................40
   SECTION 6.6    LITIGATION......................................................................................40
   SECTION 6.7    AVAX REPORTS AND FINANCIAL STATEMENTS...........................................................40

ARTICLE VII - COVENANTS AND AGREEMENTS............................................................................41

   SECTION 7.1    CONDUCT OF BUSINESS.............................................................................41
   SECTION 7.2    LOCK-UP ON AVAX STOCK...........................................................................43
   SECTION 7.3    NON-COMPETITION AND NON-SOLICITATION............................................................44
   SECTION 7.4    FURTHER ASSURANCES..............................................................................45
   SECTION 7.5    OTHER TRANSACTIONS..............................................................................45
   SECTION 7.6    REGULATORY MATTERS..............................................................................46
   SECTION 7.7    BEST EFFORTS....................................................................................46
   SECTION 7.8    NOTICES OF CERTAIN EVENTS.......................................................................46
   SECTION 7.9    ACCESS..........................................................................................47
   SECTION 7.10   PUBLIC ANNOUNCEMENTS............................................................................47
   SECTION 7.11   BOARD REPRESENTATION............................................................................47
   SECTION 7.12   EXPENSES........................................................................................47
   SECTION 7.13   OPTION TO EXTEND AND EXPAND BEYNOST, FRANCE FACILITY............................................48
   SECTION 7.14   RELATIONSHIP WITH PROGENICS.....................................................................48
   SECTION 7.15   OTHER TRANSACTIONS..............................................................................48
   SECTION 7.16   WORK TO BE PERFORMED............................................................................48
   SECTION 7.17   MILESTONES......................................................................................49

ARTICLE VIII - CONDITIONS TO OBLIGATIONS OF RECIPIENT.............................................................49

   SECTION 8.1    PERFORMANCE; REPRESENTATIONS AND WARRANTIES TRUE AT THE CLOSING.................................49
   SECTION 8.2    RESERVED........................................................................................49
   SECTION 8.3    AVENTIS RIGHTS..................................................................................49
   SECTION 8.4    CONTRIBUTION OF OTHER HOLDINGS SHAREHOLDERS'SHARES..............................................49
   SECTION 8.5    CONTRIBUTION OF OTHER SUBSIDIARY SHAREHOLDERS'SHARES............................................50
   SECTION 8.6    CONTRIBUTION OF AVENTIS SHARES..................................................................50
   SECTION 8.7    RECEIPT OF LYON LEASE AND OPTION BY RECIPIENT...................................................50
   SECTION 8.8    ABSENCE OF LITIGATION...........................................................................50
   SECTION 8.9    CONSULTING AND ASSIGNMENT AGREEMENTS............................................................50
   SECTION 8.10   TERMINATION OF PROGENICS CONSULTANT'S AGREEMENT.................................................50
   SECTION 8.11   RESIGNATION OF PROF. KLATZMANN FROM THE BOARD OF PROGENICS......................................50
   SECTION 8.12   RESIGNATIONS OF THE MEMBERS OF THE BOARDS OF DIRECTORS OF HOLDINGS AND SUBSIDIARY...............50
   SECTION 8.13   REQUIRED CONSENTS...............................................................................50
   SECTION 8.14   CONTRIBUTOR GROUP CORPORATE LEGAL OPINION.......................................................51
   SECTION 8.15   CONTRIBUTOR GROUP INTELLECTUAL PROPERTY LEGAL OPINION...........................................51
   SECTION 8.16   CORPORATE DOCUMENTS.............................................................................51
   SECTION 8.17   RECEIPT BY RECIPIENT OF UPMC AGREEMENT..........................................................51
   SECTION 8.18   DELIVERIES BY THE CONTRIBUTOR GROUP AT THE CLOSING..............................................51

ARTICLE IX - CONDITIONS TO OBLIGATIONS OF THE CONTRIBUTORS........................................................52

   SECTION 9.1    PERFORMANCE; REPRESENTATIONS AND WARRANTIES TRUE AT THE CLOSING.................................52
   SECTION 9.2    RECIPIENT LEGAL OPINION.........................................................................52
   SECTION 9.3    CORPORATE DOCUMENTS.............................................................................52
   SECTION 9.4    DELIVERY OF ESCROW STOCK CONSIDERATION, ESCROW INTELLECTUAL PROPERTY STOCK CONSIDERATION AND
                  NON-ESCROW STOCK CONSIDERATION..................................................................53
   SECTION 9.5    DELIVERY OF CASH CONSIDERATION..................................................................53
   SECTION 9.6    DELIVERIES BY THE RECIPIENT AT THE CLOSING......................................................53

ARTICLE X - TERMINATION...........................................................................................53

   SECTION 10.1   TERMINATION.....................................................................................53
   SECTION 10.2   EFFECT OF TERMINATION...........................................................................54
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<S>                                                                                                              <C>
ARTICLE XI - INDEMNIFICATION......................................................................................55

   SECTION 11.1   INDEMNIFICATION OF RECIPIENT....................................................................55
   SECTION 11.2   INDEMNIFICATION OF CONTRIBUTORS.................................................................55
   SECTION 11.3   PROCEDURE.......................................................................................56

ARTICLE XII - DEFINITIONS.........................................................................................58

   SECTION 12.1   AFFILIATE OR AFFILIATES.........................................................................58
   SECTION 12.2   BUSINESS DAY....................................................................................58
   SECTION 12.3   ENVIRONMENTAL LAWS..............................................................................58
   SECTION 12.4   ENVIRONMENTAL PERMITS...........................................................................58
   SECTION 12.5   EUROPEAN UNION LAW..............................................................................58
   SECTION 12.6   EXCHANGE ACT....................................................................................58
   SECTION 12.7   FRENCH LAW......................................................................................58
   SECTION 12.8   HAZARDOUS SUBSTANCES............................................................................58
   SECTION 12.9   INTELLECTUAL PROPERTY...........................................................................58
   SECTION 12.10  LIEN............................................................................................59
   SECTION 12.11  MATERIAL ADVERSE EFFECT.........................................................................59
   SECTION 12.12  PERSON..........................................................................................59
   SECTION 12.13  RESOLUTION OF THE INTELLECTUAL PROPERTY ISSUE...................................................59
   SECTION 12.14  RIGHTS..........................................................................................60
   SECTION 12.15  SEC.............................................................................................60
   SECTION 12.16  TAXES...........................................................................................60
   SECTION 12.17  TAX RETURNS.....................................................................................60

ARTICLE XIII - MISCELLANEOUS......................................................................................60

   SECTION 13.1   SURVIVAL........................................................................................60
   SECTION 13.2   NOTICES.........................................................................................61
   SECTION 13.3   SUCCESSORS AND ASSIGNS..........................................................................62
   SECTION 13.4   GOVERNING LAW...................................................................................62
   SECTION 13.5   COUNTERPARTS....................................................................................62
   SECTION 13.6   PUBLICITY.......................................................................................62
   SECTION 13.7   ENTIRE AGREEMENT................................................................................63
   SECTION 13.8   MODIFICATIONS, AMENDMENTS AND WAIVERS...........................................................63
   SECTION 13.9   HEADINGS........................................................................................63
   SECTION 13.10  CERTAIN TAXES...................................................................................63
   SECTION 13.11  JURISDICTION....................................................................................63
   SECTION 13.12  WAIVER OF JURY TRIAL............................................................................64
   SECTION 13.13  INTERPRETATION..................................................................................64
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                          STOCK CONTRIBUTION AGREEMENT

               THIS STOCK CONTRIBUTION AGREEMENT (the "AGREEMENT") is entered
into as of this 17th day of July, 2000, among AVAX TECHNOLOGIES, INC., a
Delaware corporation having its principal place of business at 4520 Main Street,
Suite 930, Kansas City, Missouri 64111 (together with its Affiliates (as defined
in Article XII), "RECIPIENT" or "AVAX"), and PROFESSOR DAVID R. KLATZMANN, an
individual residing at 11 rue de Tage, 75013 Paris, France ("PROF. KLATZMANN"),
PROFESSOR JEAN-LOUP SALZMANN, an individual residing at 70, rue Claude Bernard,
75005 Paris, France ("PROF. SALZMANN") (collectively, Prof. Klatzmann and Prof.
Salzmann are sometimes referred to herein, in both their joint and individual
capacities, as the "CONTRIBUTORS"), GPH, S.A., a French SOCIETE anonyme having
its principal place of business at 22 rue Esquirol, 75013 Paris, France
("HOLDINGS"), and GENOPOIETIC, S.A., a French SOCIETE ANONYME having its
principal place of business at 22 rue Esquirol, 75013 Paris, France
("SUBSIDIARY") (the Contributors, Holdings and Subsidiary are sometimes
collectively referred to herein as the "CONTRIBUTOR GROUP").

               WHEREAS, the Contributors are, as of the date of this Agreement
and will be as of the Closing Date (as defined in Article II), the record and
beneficial owners of ninety-three (93) shares (the "CONTRIBUTORS' HOLDINGS
SHARES") of the one hundred (100) issued and outstanding shares of the capital
stock of Holdings, forty-seven (47) of which Contributors' Holdings Shares are,
as of the date hereof, and will be, as of the Closing Date, owned by Prof.
Salzmann, and forty-six (46) of which Contributors' Holdings Shares are, as of
the date hereof, and will be, as of the Closing Date, owned by Prof. Klatzmann;
and

               WHEREAS, the Contributors are, as of the date of this Agreement,
and will be as of the Closing Date, the record and beneficial owners of seven
thousand seven hundred ninety-two (7,792) shares (the "CONTRIBUTORS' SUBSIDIARY
SHARES") of the ten million eight hundred twenty-three thousand eighty-eight
(10,823,088) issued and outstanding shares of the capital stock of Subsidiary,
three thousand eight hundred ninety-six (3,896) of which Contributors'
Subsidiary Shares are, as of the date of this Agreement, and will be as of the
Closing Date, owned by Prof. Salzmann and three thousand eight hundred
ninety-six (3,896) of which Contributors' Subsidiary Shares are, as of the date
of this Agreement, and will be as of the Closing Date, owned by Prof. Klatzmann;
and

               WHEREAS, at the Closing (as defined in Article II), Contributors
will contribute the Contributors' Holdings Shares and the Contributors'
Subsidiary Shares (collectively, the "SHARES") to Recipient in exchange for
common stock of AVAX ("AVAX STOCK"); and

                  WHEREAS, the seven (7) individuals listed on EXHIBIT A hereto
(the "OTHER HOLDINGS SHAREHOLDERS") are, as of the date of this Agreement, and
will be immediately prior to the Closing, the record and beneficial owners of
the remaining seven (7) shares (collectively, the "OTHER HOLDINGS SHAREHOLDERS'
SHARES") of the one hundred (100) issued and outstanding shares of the capital
stock of Holdings, in the individual amounts as set forth on EXHIBIT A hereto;
and

               WHEREAS, contemporaneous with the execution of this Agreement,
the Other Holdings Shareholders are executing the Other Holdings Shareholder
Stock Contribution Agreements in the form attached hereto as EXHIBIT B (the
"OTHER HOLDINGS SHAREHOLDER STOCK CONTRIBUTION AGREEMENTS"), pursuant to which
the Other Holdings Shareholders agree to contribute the Other Holdings
Shareholders' Shares to Recipient at the closing of the Other Holdings
Shareholder Stock Contribution Agreements, which will occur immediately prior to
the Closing, such that, upon the Closing, the Recipient will be the record and
beneficial owner, as a result of the contribution to Recipient of (i) the
Contributors' Holdings

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Shares pursuant to this Agreement, and (ii) the Other Holdings Shareholder's
Shares pursuant to the Other Holdings Shareholder Stock Contribution Agreements,
as contemplated hereunder, of all of the issued and outstanding shares of the
capital stock of Holdings (the "HOLDINGS SHARES"); and

               WHEREAS, Holdings is, as of the date of this Agreement, and will
be as of the Closing Date, the record and beneficial owner of nine million five
hundred eighty-nine thousand one hundred eighty-nine (9,589,189) shares (the
"HOLDINGS SUBSIDIARY SHARES") of the ten million eight hundred twenty-three
thousand eighty-eight (10,823,088) issued and outstanding shares of the capital
stock of Subsidiary; and

               WHEREAS, the nine (9) individuals listed on EXHIBIT C hereto (the
"OTHER SUBSIDIARY SHAREHOLDERS") are, as of the date of this Agreement, and will
be immediately prior to the Closing, the record and beneficial owners of one
hundred forty-three thousand nineteen (143,019) shares (the "OTHER SUBSIDIARY
SHAREHOLDERS' SHARES") of the ten million eight hundred twenty-three thousand
eighty-eight (10,823,088) issued and outstanding shares of the capital stock of
Subsidiary, in the individual amounts as set forth on EXHIBIT C hereto; and

               WHEREAS, contemporaneous with the execution of this Agreement,
the Other Subsidiary Shareholders are executing the Other Subsidiary Shareholder
Stock Contribution Agreements in the form attached hereto as EXHIBIT D (the
"OTHER SUBSIDIARY SHAREHOLDER STOCK CONTRIBUTION AGREEMENTS"), pursuant to which
the Other Subsidiary Shareholders agree to contribute the Other Subsidiary
Shareholders' Shares to Recipient at the closing of the Other Subsidiary
Shareholder Stock Contribution Agreements, which will occur immediately prior to
the Closing; and

               WHEREAS, Aventis Pharma, S.A., a French SOCIETE ANONYME, formerly
known as Rhone Poulenc Rorer, S.A. ("RPR"), ("AVENTIS"), is as of the date of
this Agreement, and will be immediately prior to the Closing, the record and
beneficial owner of one million eighty-three thousand eighty-eight (1,083,088)
shares (the "AVENTIS SHARES") of the ten million eight hundred twenty-three
thousand eighty-eight (10,823,088) issued and outstanding shares of the capital
stock of Subsidiary; and

               WHEREAS, prior to or contemporaneous with the Closing, Aventis is
executing the Aventis Stock Contribution Agreement substantially in the form
attached hereto as EXHIBIT E (the "AVENTIS STOCK CONTRIBUTION AGREEMENT"),
pursuant to which Aventis agrees to contribute the Aventis Shares to Recipient
at the closing of the Aventis Stock Contribution Agreement, which will occur
immediately prior to the Closing; and

               WHEREAS, upon the Closing, the Recipient will (i) be the record
and beneficial owner, as a result of the contribution to Recipient of the
Contributors' Subsidiary Shares pursuant to this Agreement, the Other Subsidiary
Shareholders' Shares pursuant to the Other Subsidiary Shareholder Stock
Contribution Agreements, and the Aventis Shares pursuant to the Aventis Stock
Contribution Agreement, of one million two hundred thirty-three thousand eight
hundred ninety-nine (1,233,899) of the ten million eight hundred twenty-three
thousand eighty-eight (10,823,088) issued and outstanding shares of the capital
stock of Subsidiary; and (ii) be the indirect owner, as a result of its
ownership of the Shares and of Holdings' ownership of the Holdings Subsidiary
Shares, of the remaining nine million five hundred eighty-nine thousand one
hundred eighty-nine (9,589,189) shares of the ten million eight hundred
twenty-three thousand eighty-eight (10,823,088) issued and outstanding shares of
the capital stock of Subsidiary; and

               WHEREAS, subject to the terms and conditions set forth below, the
Contributors desire to contribute the Shares to Recipient, and Recipient desires
to receive the Shares from the Contributors; and

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               WHEREAS, the parties hereto intend that the Contributors treat
the exchange of the Shares for shares of AVAX Stock as a "contribution-in-kind"
for purposes of French Law (as defined in Article XII).

               NOW, THEREFORE, in consideration of the mutual covenants and
agreements set forth herein and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the undersigned hereby
agree as follows:

                                    ARTICLE I
                             CONTRIBUTION OF SHARES

         SECTION 1.1 CONTRIBUTION OF SHARES. Upon the terms and subject to the
conditions of this Agreement, at the Closing, the Contributors hereby agree to
assign, grant, transfer and contribute the Shares to Recipient and Recipient
hereby agrees to receive the Shares from Contributors.

         SECTION 1.2 CONTRIBUTION CONSIDERATION. Subject to the terms and
conditions of this Agreement, the consideration to be delivered to the
Contributors by the Recipient in exchange for the Shares (the "CONTRIBUTION
CONSIDERATION") shall be deliverable as follows:

         (a)   ESCROW STOCK CONSIDERATION. At the Closing, Recipient shall
deliver to the Escrow Agent (as defined in the Escrow Agreement) to be held in
escrow: (i) as partial consideration for twenty-three (23) of the Holdings
Shares and one thousand nine hundred forty-eight (1,948) of the Contributors'
Subsidiary Shares to be delivered to Recipient by Prof. Salzmann at the Closing,
stock certificates payable to Prof. Salzmann representing two hundred thousand
(200,000) restricted shares of AVAX Stock with an aggregate market value of One
Million Seven Hundred Seventy-Five Thousand and 00/100 United States Dollars (US
$1,755,000.00) as of the close of trading on July 11, 2000; and (ii) as partial
consideration for twenty-three (23) of the Holdings Shares and one thousand nine
hundred forty-eight (1,948) of the Contributors' Subsidiary Shares to be
delivered to Recipient by Prof. Klatzmann at the Closing, stock certificates
payable to Prof. Klatzmann representing two hundred thousand (200,000)
restricted shares of AVAX Stock with an aggregate market value of One Million
Seven Hundred Seventy-Five Thousand and 00/100 United States Dollars (US
$1,755,000.00) as of the close of trading on July 11, 2000 (collectively and
together with sufficient stock transfer forms duly executed in blank, the
"ESCROW STOCK CONSIDERATION"). The Escrow Stock Consideration shall be held in
escrow in accordance with the Escrow Agreement substantially in the form
attached hereto as EXHIBIT F (the "ESCROW AGREEMENT") for the benefit of AVAX
and the Contributors for a period of thirty-six (36) months commencing on the
Closing Date (the "ESCROW PERIOD") and shall be distributed to the Contributors
by the Escrow Agent upon the expiration of the Escrow Period, subject to the
provisions of the Escrow Agreement and Section 11.3(d) hereof.

         (b)   NON-ESCROW STOCK CONSIDERATION. At the Closing, Recipient shall
deliver: (i) to Prof. Salzmann, as partial consideration for the remaining
twenty-four (24) Holdings Shares and one thousand nine hundred forty-eight
(1,948) Contributors' Subsidiary Shares to be delivered to Recipient by Prof.
Salzmann at the Closing, stock certificates representing thirty-three thousand
four hundred twenty-two (33,422) restricted shares of AVAX Stock with an
aggregate market value of Two Hundred Ninety-Six Thousand Six Hundred Twenty and
25/100 United States Dollars (US $296,620.25) as of the close of trading on July
11, 2000; and (ii) to Prof. Klatzmann, in consideration for remaining
twenty-three (23) Holdings Shares and one thousand nine hundred forty-eight
(1,948) Contributors' Subsidiary Shares to be delivered to Recipient by Prof.
Klatzmann at the Closing, stock certificates representing twenty-six thousand
three hundred thirty-four (26,334) restricted shares of AVAX Stock with an
aggregate market

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value of Two Hundred Thirty-Three Thousand Seven Hundred Fourteen and 25/100
United States Dollars (US $233,714.25) as of the close of trading on July 11,
2000 (collectively, the "NON-ESCROW STOCK CONSIDERATION").

         (c)   CASH CONSIDERATION. At the Closing, Recipient shall also deliver:
(i) to Prof. Klatzmann, a check in the amount of Two Thousand Five Hundred and
00/100 United States Dollars (US $2,500); and (ii) to Prof. Salzmann, a check in
the amount of Two Thousand Five Hundred and 00/100 United States Dollars (US
$2,500) (collectively, the "CASH CONSIDERATION").

         (d)   ESCROW INTELLECTUAL PROPERTY STOCK CONSIDERATION. At the Closing,
Recipient shall deliver to the Escrow Agent to be held in escrow: (i) stock
certificates payable to Prof. Salzmann representing one hundred thousand
(100,000) restricted shares of AVAX Stock with an aggregate market value of
Eight Hundred Eighty-Seven Thousand Five Hundred and 00/100 United States
Dollars (US $887,500.00) as of the close of trading on July 11, 2000; and (ii)
stock certificates payable to Prof. Klatzmann representing one hundred thousand
(100,000) restricted shares of AVAX Stock with an aggregate market value of
Eight Hundred Eighty-Seven Thousand Five Hundred and 00/100 United States
Dollars (US $887,500.00) as of the close of trading on July 11, 2000
(collectively and together with sufficient stock transfer forms duly executed in
blank, the "ESCROW INTELLECTUAL PROPERTY STOCK CONSIDERATION"). The Escrow
Intellectual Property Stock Consideration shall be held in escrow by the Escrow
Agent in accordance with the Escrow Agreement for the benefit of AVAX and the
Contributors and shall be distributed to the Contributors when and if the
Contributors are able to obtain the Resolution of the Intellectual Property
Issue (as defined in Article XII hereof) on or before the date that is
twenty-four (24) months after the Closing Date.

         (e)   EARN OUT CONSIDERATION; RIGHTS AGREEMENT. At the Closing,
Recipient shall deliver to each of Prof. Salzmann and Prof. Klatzmann, as an
earn-out payment, a Rights Agreement substantially in the form attached hereto
as EXHIBIT G ("RIGHTS AGREEMENT").

                                   ARTICLE II
                                   THE CLOSING

               The closing (the "CLOSING") of the contribution of the Shares
hereunder shall take place at the offices of Recipient, at 10:00 a.m. on the
third (3rd) Business Day after all conditions to Closing have been met, or at
such other time or place as the Recipient and the Contributors may agree. (The
time and date of the Closing shall be the "CLOSING DATE.")

                                   ARTICLE III
                              RELATED TRANSACTIONS

         SECTION 3.1 RECEIPT OF OTHER HOLDINGS SHAREHOLDERS' SHARES.
Contemporaneous with the execution of this Agreement, the Other Holdings
Shareholders are executing the Other Holdings Shareholder Stock Contribution
Agreements, pursuant to which the Other Holdings Shareholders will contribute
the Other Holdings Shareholders' Shares to Recipient immediately prior to the
Closing in exchange for an aggregate amount of forty-nine thousand six hundred
sixteen (49,616) restricted shares of AVAX Stock in accordance with the terms
and conditions of the Other Holdings Shareholder Stock Contribution Agreements
(the "OTHER HOLDINGS SHAREHOLDERS' SHARES ACQUISITION").

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         SECTION 3.2 RECEIPT OF OTHER SUBSIDIARY SHAREHOLDERS' SHARES.
Contemporaneous with the execution of this Agreement, the Other Subsidiary
Shareholders are executing the Other Subsidiary Shareholder Stock Contribution
Agreements, pursuant to which the Other Subsidiary Shareholders will contribute
the Other Subsidiary Shareholders' Shares to Recipient immediately prior to the
Closing in exchange for ten thousand five hundred seventy-one (10,571)
restricted shares of AVAX Stock in accordance with the terms and conditions of
the Other Subsidiary Shareholder Stock Contribution Agreements (the "OTHER
SUBSIDIARY SHAREHOLDERS' SHARES ACQUISITION").

         SECTION 3.3 RECEIPT OF AVENTIS SHARES BY RECIPIENT. Prior to or
contemporaneous with the Closing, Aventis is executing the Aventis Stock
Contribution Agreement ("AVENTIS STOCK CONTRIBUTION AGREEMENT") pursuant to
which Aventis will contribute the Aventis Shares to Recipient immediately prior
to the Closing in exchange for eighty thousand fifty-seven (80,057) restricted
shares of AVAX Stock in accordance with the terms and conditions of the Aventis
Agreement (the "AVENTIS ACQUISITION").

         SECTION 3.4 RELEASE OF AVENTIS' RIGHTS. Prior to or contemporaneous
with the Closing, Contributors shall cause Aventis to: (i) relinquish and
assign, grant and transfer to AVAX all right, title and interest Aventis has or
may have to any and all Intellectual Property (as defined in Article XII) (other
than those rights specified in Section 3.4 of the Contributor Group Disclosure
Schedule relating directly to the plasmovirus and chondrocyte freezing
technology) owned or developed, in whole or in part, by any or all members of
the Contributor Group; and (ii) terminate and assign, grant and transfer to AVAX
any and all other rights that Aventis may otherwise have, have had or granted,
with regard to, in conjunction with, or in connection with, any member of the
Contributor Group, as it appears in Article V of the Aventis Stock Contribution
Agreement (collectively, the "AVENTIS RELEASE").

         SECTION 3.5 RESOLUTION OF INTELLECTUAL PROPERTY ISSUE. On or before the
date that is twenty-four (24) months following the date hereof, the Contributors
shall have obtained a Resolution of the Intellectual Property Issue to the
reasonable satisfaction of the Chief Executive Officer of AVAX, at which time,
in accordance with the terms of the Escrow Agreement, the Contributors shall be
entitled to receive the Escrow Intellectual Property Stock Consideration.

         SECTION 3.6 CONTRIBUTORS' CONSULTING AND ASSIGNMENT AGREEMENTS. At or
prior to the Closing, AVAX International Services, Inc., a Delaware corporation,
will enter into Consulting and Assignment Agreements with each of Prof.
Klatzmann and Prof. Salzmann, substantially in the form of EXHIBIT H attached
hereto (the "CONSULTING AND ASSIGNMENT AGREEMENTS").

         SECTION 3.7 RESIGNATION OF PROF. KLATZMANN FROM THE BOARD OF PROGENICS.
Prior to Closing, Prof. Klatzmann will resign his position on the Scientific
Advisory Board of Progenics Pharmaceuticals, Inc., a Delaware corporation
("PROGENICS") (the "PROGENICS RESIGNATION") and deliver the duly executed
Progenics Resignation to Recipient at the Closing.

         SECTION 3.8 RESIGNATION OF ALL MEMBERS OF THE BOARDS OF DIRECTORS OF
HOLDINGS AND SUBSIDIARY. At or prior to the Closing, all members of the Boards
of Directors of both Holdings and Subsidiary will resign their positions on such
Boards of Directors (the "HOLDINGS AND SUBSIDIARY BOARD RESIGNATIONS"), and
Contributors will deliver the duly and validly executed Holdings and Subsidiary
Board Resignations to Recipient at the Closing.

         SECTION 3.9 FINANCIAL SUPPORT PROVIDED TO SUBSIDIARY. At the Closing,
Recipient shall execute and deliver to Contributors a Research Funding
Agreement, substantially in the form of EXHIBIT I attached hereto (the "RESEARCH
FUNDING AGREEMENT").

                                        5

<PAGE>

         SECTION 3.10 PROGENICS TERMINATION. Prior to Closing, Prof. Klatzmann
shall cause Progenics to execute and deliver to Recipient a validly executed
termination of that certain Consultant's Agreement between Progenics and Prof.
Klatzmann dated January 1, 1990 (the "PROGENICS CONSULTING AGREEMENT"), in form
and substance satisfactory to Recipient in Recipient's sole discretion (the
"PROGENICS TERMINATION"), and such Progenics Termination shall be valid and
binding on Progenics from and after the Closing Date.

                                   ARTICLE IV
             REPRESENTATIONS AND WARRANTIES OF THE CONTRIBUTOR GROUP

               Except as set forth on the Contributor Group Disclosure Schedule
attached hereto as EXHIBIT J (the "CONTRIBUTOR GROUP DISCLOSURE SCHEDULE"),
which has been delivered to Recipient prior to the execution of this Agreement,
each member of the Contributor Group, jointly and severally, makes the following
representations and warranties to Recipient as of the date hereof, such
representations and warranties to be continuing representations and warranties
through and as of the Closing Date; provided, however, that notwithstanding the
foregoing, in no event shall either of the Contributors be entitled to seek
contribution or similar remedy from Holdings and/or Subsidiary after the Closing
Date. The Contributor Group acknowledges that Recipient is relying on such
representations and warranties and that Recipient is not required to proceed
with any additional investigation regarding the factual matters that are the
subject of such representations and warranties, it being understood that, except
for information expressly set forth in this Agreement, the Contributor Group
Disclosure Schedule, the Contributors' Disclosure Schedule, Exhibit B, Exhibit
D, Exhibit E, Exhibit G, Exhibit H, Exhibit I, Exhibit K, Exhibit N, Exhibit P,
Exhibit R and Exhibit S (to the extent such Exhibits contain factual statements
relating to the Contributor Group; provided that the opinions given in Exhibit R
and Exhibit S shall not otherwise create exceptions to the following
representations and warranties) and all other schedules attached hereto or
thereto as of the date hereof, any information that Recipient may know or learn
shall in no way alter the scope of the representations and warranties made by
the Contributor Group. The Contributor Group further acknowledges that in its
calculation of the Contribution Consideration, Recipient has relied on the
representations and warranties made by the Contributor Group in this Agreement.
With the foregoing in mind, each member of the Contributor Group, jointly and
severally, represents and warrants to Recipient the following:

         SECTION 4.1 ORGANIZATION.

         (a)   Holdings is a French SOCIETE ANONYME having its registered office
at 22 rue Esquirol, 75013 Paris, France and is registered at the REGISTRE DU
COMMERCE ET DES SOCIETES of Paris, number 391 043 858. Holdings is duly
organized, validly existing and in good standing under the laws of the country
of France and has the requisite corporate power and authority to own and lease
the properties and other assets it presently owns or leases and to carry on its
business as presently conducted.

         (b)   Subsidiary is a French SOCIETE ANONYME having its registered
office at 22 rue Esquirol, 75013 Paris, France and is registered at the REGISTRE
DU COMMERCE ET DES SOCIETES of Paris, number 393 796 305. Subsidiary is duly
organized, validly existing and in good standing under the laws of the country
of France and has the requisite corporate power and authority to own and lease
the properties and other assets it presently owns or leases and to carry on its
business as presently conducted.

         SECTION 4.2 AUTHORIZATION.

         (a)   The execution and delivery of this Agreement and the consummation
of the transactions contemplated hereby have been duly authorized by the Board
of Directors of Holdings and the resolutions

                                        6

<PAGE>

adopted by the Board of Directors of Holdings evidencing such authorization were
duly and validly adopted, have not been modified, revoked or rescinded in any
respect and are in full force and effect. No other corporate proceeding on the
part of Holdings is necessary to authorize this Agreement or to consummate the
transactions contemplated hereby.

         (b)   The execution and delivery of this Agreement and the consummation
of the transactions contemplated hereby have been duly authorized by the Board
of Directors of Subsidiary and the resolutions adopted by the Board of Directors
of Subsidiary evidencing such authorization were duly and validly adopted, have
not been modified, revoked or rescinded in any respect and are in full force and
effect. No other corporate proceeding on the part of Subsidiary is necessary to
authorize this Agreement or to consummate the transactions contemplated hereby.

         (c)   The Contributors are individuals and residents of the city of
Paris, France. Prof. Salzmann is a consultant to both Holdings and Subsidiary.
Prof. Klatzmann is a consultant to both Holdings and Subsidiary. The
Contributors have the requisite capacity and authority to contribute the Shares
to Recipient and to consummate the transactions contemplated hereby and by the
Consulting and Assignment Agreements.

         (d)   Each of the Other Holdings Shareholders is an individual and
resident of the city of Paris, France. Except for Ulysse Jacob Klatzmann, Gaia
Riva Klatzmann and Maia Dina Klatzmann, each of the Other Holdings Shareholders
has the requisite capacity and authority to execute his or her respective Other
Holdings Shareholder Stock Contribution Agreement and to consummate the
transactions contemplated hereby and thereby. Each of Ulysse Jacob Klatzmann,
Gaia Riva Klatzmann and Maia Dina Klatzmann (the "KLATZMANN CHILDREN") are under
sixteen (16) years of age. Prof. Klatzmann is the father of each of the
Klatzmann Children. Prof. Klatzmann has secured all requisite capacity and
authority to execute the respective Other Holdings Shareholder Stock
Contribution Agreements on behalf of and in the name of each of the Klatzmann
Children and is duly empowered and authorized to act on behalf of the Klatzmann
Children in all respects with regard to the transactions contemplated hereby and
thereby. Jacqueline Klatzmann is the mother of Prof. Klatzmann. Prof. Klatzmann
has secured all requisite capacity and authority to execute the relevant Other
Holdings Shareholder Stock Contribution Agreement and the Other Subsidiary
Shareholder Stock Contribution Agreement on behalf of and in the name of
Jacqueline Klatzmann and is duly empowered and authorized to act on behalf of
Jacqueline Klatzmann in all respects with regard to the transactions
contemplated hereby and thereby.

         (e)   Each of the Other Subsidiary Shareholders is an individual and
resident of the city of Paris, France. Each of the Other Subsidiary Shareholders
has the requisite capacity and authority to execute his or her respective Other
Subsidiary Shareholder Stock Contribution Agreement and to consummate the
transactions contemplated hereby and thereby.

         (f)   Aventis is a French SOCIETE ANONYME and is formerly known as RPR.
Aventis has the requisite capacity and authority to execute the Aventis Stock
Contribution Agreement and to consummate the transactions contemplated hereby
and thereby.

         SECTION 4.3 VALID AND BINDING AGREEMENT.

         (a)   This Agreement constitutes a valid and binding agreement of
Holdings, enforceable against Holdings in accordance with its terms.

         (b)   This Agreement constitutes a valid and binding agreement of
Subsidiary, enforceable against Subsidiary in accordance with its terms.

                                        7

<PAGE>

         (c)   This Agreement constitutes a valid and binding agreement of each
of the Contributors, enforceable against each Contributor in accordance with its
terms.

         (d)   Each of the Other Holdings Shareholder Stock Contribution
Agreements will, when executed, constitute a valid and binding agreement of each
of the respective Other Holdings Shareholders, enforceable against each such
Other Holdings Shareholder in accordance with the terms of the respective Other
Holdings Shareholder Stock Contribution Agreements.

         (e)   Each of the Other Subsidiary Shareholder Stock Contribution
Agreements will, when executed, constitute a valid and binding agreement of each
of the respective Other Subsidiary Shareholders, enforceable against each such
Other Subsidiary Shareholder in accordance with the terms of the respective
Other Subsidiary Shareholder Stock Contribution Agreements.

         (f)   The Aventis Stock Contribution Agreement will, when executed,
constitute a valid and binding agreement against Aventis, enforceable against
Aventis in accordance with the terms thereof.

         SECTION 4.4 ORGANIZATIONAL DOCUMENTS.

         (a)   The copy of the STATUTS of Holdings, and all amendments thereto,
as certified by the Chairman of the Board of Holdings and previously furnished
to Recipient, is a true, complete and correct copy of the STATUTS of Holdings,
as presently in effect. The filings made by Holdings with the Clerk of the
Commercial Court of Paris are complete and up to date and Holdings' "K BIS
EXCERPT" delivered by the REGISTRE DU COMMERCE ET DES SOCIETES of Paris and
furnished to Recipient is up to date and reflects Holdings' current legal
situation. All minutes of Holdings are contained in the minute books of
Holdings, copies of which have been previously furnished to Recipient for
examination, and such minute books contain a complete and accurate record of the
substance of all actions taken at all meetings of (i) the Board of Directors of
Holdings and all committees thereof and (ii) the shareholders of Holdings.

         (b)   The copy of the STATUTS of Subsidiary, and all amendments
thereto, as certified by the Chairman of the Board of Subsidiary and previously
furnished to Recipient, is a true, complete and correct copy of the STATUTS of
Subsidiary, as presently in effect. The filings made by Subsidiary with the
Clerk of the Commercial Court of Paris are complete and up to date and
Subsidiary's "K BIS EXCERPT" delivered by the REGISTRE DU COMMERCE ET DES
SOCIETES of Paris and furnished to Recipient is up to date and reflects
Subsidiary's current legal situation. All minutes of Subsidiary are contained in
the minute books of Subsidiary, copies of which have been previously furnished
to Recipient for examination, and such minute books contain a complete and
accurate record of the substance of all actions taken at all meetings of (i) the
Board of Directors of Subsidiary and all committees thereof and (ii) the
shareholders of Subsidiary.

         SECTION 4.5 QUALIFICATION.

         (a)   Holdings is duly organized as a corporation under French Law (as
defined in Article XII hereof). Section 4.5(a) of the Contributor Group
Disclosure Schedule provides an accurate and complete list of every French and
foreign jurisdiction where Holdings is registered with the Registry of Companies
(or other similar French Law concept) or is licensed or qualified to lawfully
engage in business, which is every French and foreign jurisdiction where
Holdings is required to be so registered, licensed or qualified. Holdings is in
possession of all authorizations and permits necessary or desirable to conduct
its business in its present form and is in compliance with all applicable laws
and regulations.

                                        8

<PAGE>

         (b)   Subsidiary is duly organized as a corporation under French Law.
Section 4.5(b) of the Contributor Group Disclosure Schedule provides an accurate
and complete list of every French and foreign jurisdiction where Subsidiary is
registered with the Registry of Companies (or other similar French Law concept)
or is licensed or qualified to lawfully engage in business, which is every
French and foreign jurisdiction where Subsidiary is required to be so
registered, licensed or qualified. Subsidiary is in possession of all
authorizations and permits necessary or desirable to conduct its business in its
present form and is in compliance with all applicable laws and regulations.

         SECTION 4.6 CAPITALIZATION.

         (a)   The authorized capital stock of Holdings (the "HOLDINGS CAPITAL
STOCK") amounts to two hundred fifty thousand French Francs (FF 250,000) divided
up into one hundred (100) shares fully-paid with par value of two thousand five
hundred French Francs (FF 2,500) per share (the "HOLDINGS COMMON STOCK"). As of
the date of this Agreement, one hundred (100) shares of Holdings Common Stock
were issued and outstanding, and no shares of Holdings Common Stock were held by
Holdings in its treasury.

         (b)   The authorized capital stock of Subsidiary (the "SUBSIDIARY
CAPITAL STOCK") amounts to ten million eight hundred twenty-three thousand
eighty-eight French Francs (FF 10,823,088) divided up into ten million eight
hundred twenty-three thousand eighty-eight (10,823,088) shares fully-paid with
par value of one French Franc (FF 1) per share (the "SUBSIDIARY COMMON STOCK").
As of the date of this Agreement, ten million eight hundred twenty-three
thousand eighty-eight (10,823,088) shares of Subsidiary Common Stock were issued
and outstanding, and no shares of Subsidiary Common Stock were held by
Subsidiary in its treasury.

         (c)   No shares of Holdings Capital Stock have been reserved for
issuance. All of the outstanding shares of Holdings Capital Stock have been duly
authorized, fully paid and are nonassessable. There are no outstanding bonds,
debentures, notes or other obligations of Holdings. There are not any preemptive
rights or any outstanding subscriptions, options, puts, calls, warrants, rights,
convertible or exchangeable securities or other agreements or commitments of
Holdings by which it is bound, obligating Holdings to issue, deliver or sell, or
cause to be issued, delivered or sold, additional shares of Holdings Capital
Stock or other securities of Holdings or obligating Holdings to issue, grant,
extend or enter into any such security, option, warrant, call, right,
commitment, agreement, arrangement or undertaking. Other than this Agreement,
there are no outstanding contractual obligations of any Other Holdings
Shareholder, Other Subsidiary Shareholder or any member of the Contributor Group
to issue, sell, purchase, redeem, convert, exchange, register, vote or transfer
any of its or their shares or other securities of Holdings.

         (d)   No shares of Subsidiary Capital Stock have been reserved for
issuance. All of the outstanding shares of Subsidiary Capital Stock have been
duly authorized, fully paid and are nonassessable. There are no outstanding
bonds, debentures, notes or other obligations of Subsidiary. There are not any
preemptive rights or any outstanding subscriptions, options, puts, calls,
warrants, rights, convertible or exchangeable securities or other agreements or
commitments of Subsidiary by which it is bound, obligating Subsidiary to issue,
deliver or sell, or cause to be issued, delivered or sold, additional shares of
Subsidiary Capital Stock or other securities of Subsidiary or obligating
Subsidiary to issue, grant, extend or enter into any such security, option,
warrant, call, right, commitment, agreement, arrangement or undertaking. Other
than this Agreement, there are no outstanding contractual obligations of any
Other Subsidiary Shareholder, Aventis or any member of the Contributor Group to
issue, sell, purchase, redeem, convert, exchange, register, vote or transfer any
of its or their shares or other securities of Subsidiary.

                                        9

<PAGE>

         SECTION 4.7 SHARE OWNERSHIP.

         (a)   The Contributors are the record and beneficial owners of
ninety-three (93) shares of the one hundred (100) issued and outstanding shares
of the Holdings Capital Stock, free and clear of any Lien (as defined in Article
XII) and any other limitation or restriction (including any restriction on or
covenant relating to the right to vote, sell or otherwise dispose of any of such
shares of Holdings Capital Stock), forty-seven (47) of which shares are owned by
Prof. Salzmann and forty-six (46) of which shares are owned by Prof. Klatzmann.
The Other Holdings Shareholders are the record and beneficial owners of the
remaining seven (7) shares of the one hundred (100) issued and outstanding
shares of the Holdings Capital Stock, free and clear of any Lien and any other
limitation or restriction (including any restriction on or covenant relating to
the right to vote, sell or otherwise dispose of any such Holdings Capital
Stock). EXHIBIT A hereto accurately reflects the individual ownership interests
of such Other Holdings Shareholders.

         (b)   Holdings is the record and beneficial owner of nine million five
hundred eighty-nine thousand one hundred eighty-nine (9,589,189) shares of the
ten million eight hundred twenty-three thousand eighty-eight (10,823,088) issued
and outstanding shares of the Subsidiary Capital Stock, free and clear of any
Lien and any other limitation or restriction (including any restriction on or
covenant relating to the right to vote, sell or otherwise dispose of any such
Subsidiary Capital Stock). The Contributors are the record and beneficial owners
of seven thousand seven hundred ninety-two (7,792) shares of the ten million
eight hundred twenty-three thousand eighty-eight (10,823,088) issued and
outstanding shares of Subsidiary Capital Stock, free and clear of any Lien and
any other limitation or restriction (including any restriction on or covenant
relating to the right to vote, sell or otherwise dispose of any such Subsidiary
Capital Stock). Aventis is the record and beneficial owner of one million
eighty-three thousand eighty-eight (1,083,088) shares of the ten million eight
hundred twenty-three thousand eighty-eight (10,823,088) issued and outstanding
shares of Subsidiary Capital Stock, free and clear of any Lien and any other
limitation or restriction (including any restriction on or covenant relating to
the right to vote, sell or otherwise dispose of any such Subsidiary Capital
Stock). The Other Subsidiary Shareholders are the record and beneficial owners
of one hundred forty-three thousand nineteen (143,019) shares of the ten million
eight hundred twenty-three thousand eighty-eight (10,823,088) issued and
outstanding shares of Subsidiary Capital Stock, free and clear of any Lien and
any other limitation or restriction (including any restriction on or covenant
relating to the right to vote, sell or otherwise dispose of any such Subsidiary
Capital Stock). EXHIBIT C hereto accurately reflects the individual ownership
interests of such Other Subsidiary Shareholders.

         (c)   The consummation of the transactions contemplated by this
Agreement will result in the transfer and delivery to Recipient at the Closing,
directly, through Recipient's receipt of one hundred percent (100%) of the
Shares, the Other Holdings Shareholders' Shares, the Other Subsidiary
Shareholders' Shares and the Aventis Shares, and, indirectly, through Holdings
ownership of the Holdings Subsidiary Shares, of valid title to and record and
beneficial ownership of: (i) all one hundred (100) of the issued and outstanding
shares of Holdings Capital Stock, free and clear of any Lien and any other
limitation or restriction (including any restriction on or covenant relating to
the right to vote, sell or otherwise dispose of any such shares of Holdings
Capital Stock); and (ii) all ten million eight hundred twenty-three thousand
eighty-eight (10,823,088) of the issued and outstanding shares of Subsidiary
Capital Stock, free and clear of any Lien and any other limitation or
restriction (including any restriction on or covenant relating to the right to
vote, sell or otherwise dispose of any such shares of Subsidiary Capital Stock).
Commencing immediately upon the Closing, Recipient shall enjoy all rights
whatsoever which attach to all shares of both Holdings Capital Stock and
Subsidiary Capital Stock, including, but not limited to, the right to collect
all dividends that are distributed after the Closing Date.

                                       10

<PAGE>

         SECTION 4.8 SUBSIDIARIES, AFFILIATED ENTITIES AND OTHER RELATIONSHIPS.

         (a)   Holdings does not own, directly or indirectly, any capital stock
or other equity securities of any corporation other than Subsidiary, or have any
direct or indirect equity or ownership interest in any partnership, joint
venture or other business association or entity other than Subsidiary.

         (b)   Subsidiary does not own, directly or indirectly, any capital
stock or other equity securities of any corporation or have any direct or
indirect equity or ownership interest in any partnership, joint venture or other
business association or entity.

         (c)   For purposes of U.S. antitrust law, Professor Klatzmann does not
meet the "size of the person" test pursuant to 15 USC Section 18a under the
United States Code and 16 CFR Section 801.1, ET SEQ. under the United States
Code of Federal Regulations.

         SECTION 4.9 CONSENTS; NO VIOLATION.

         (a)   Neither the execution or delivery of this Agreement or the
execution or delivery of any other agreement contemplated hereby by the Other
Holding Shareholders, the Other Subsidiary Shareholders, Aventis or any member
of the Contributor Group, the consummation by the Other Holding Shareholders,
the Other Subsidiary Shareholders, Aventis or the Contributor Group of the
transactions contemplated hereby, nor compliance by the Other Holding
Shareholders, the Other Subsidiary Shareholders, Aventis or the Contributor
Group with any of the provisions hereof or of any agreement contemplated hereby
(i) violates any statute or law or any rule, regulation, order, award, judgment
or decree of any court or governmental authority affecting the Contributor Group
or any member thereof, (ii) violates or conflicts with or constitutes a default
under any contract, commitment, agreement, understanding, arrangement, trust or
restriction of any kind to which any member of the Contributor Group is a party,
or by which any of them or any of the assets of Holdings or Subsidiary is bound,
(iii) will cause, or give any Persons (as defined in Article XII) valid grounds
to cause (with or without notice, the passage of time or both), the maturity of
any debt, liability or obligation of Holdings or Subsidiary, (iv) requires any
filing with, any notification of, or the obtaining of any permit, authorization,
consent or approval of, any third party or governmental or regulatory authority,
foreign or French, other than the Required Consents (as defined below), (v)
violates or conflicts with or constitutes a default under the STATUTS or other
corporate documents of either Holdings or Subsidiary, (vi) will result in the
cancellation, termination or waiver of any contract or right of either Holdings
or Subsidiary, or (vii) will result in the creation or imposition of any Lien on
any asset of either Holdings or Subsidiary.

         (b)   Section 4.9(b) of the Contributor Group Disclosure Schedule sets
forth an accurate and complete list of the consents, approvals and
authorizations required in order to effectuate the consummation of the
transactions contemplated by this Agreement (the "REQUIRED CONSENTS").

         SECTION 4.10 FINANCIAL STATEMENTS. Section 4.10 of the Contributor
Group Disclosure Schedule contains copies of the balance sheets of Holdings and
Subsidiary for each of the three (3) fiscal years ending December 31, 1997,
December 31, 1998 and December 31, 1999, respectively, and the related
statements of income and stockholders' equity and cash flows for each company
for each of the years in the three-year period ended December 31, 1999,
certified by Holdings' and Subsidiary's independent public accountants,
respectively. Except as noted thereon, such financial statements have been
prepared from the corporate books and records of Holdings and Subsidiary,
respectively, in accordance with generally accepted accounting principles in
France ("FRENCH GAAP") and on a basis consistent with prior periods, and fairly
present the financial position of Holdings and Subsidiary as of their dates and
the results of their operations for the years then ended. Section 4.10 of the
Contributor Group Disclosure

                                       11

<PAGE>

Schedule also contains copies of the unaudited balance sheets of Holdings and
Subsidiary as of March 31, 2000, and the related statements of income for the
three (3) month period then ended (together with the audited financial
statements as set forth in this Section 4.10, collectively referred to as the
"FINANCIAL STATEMENTS"). Except as noted thereon, such unaudited financial
statements have been prepared from the corporate books and records of Holdings
and Subsidiary, respectively, in accordance with French GAAP and on a basis
consistent with prior periods and fairly present the financial position of each
company and the results of their operations as of March 31, 2000, and for the
respective three (3) month period then ended. The financial statements as of
March 31, 2000, and for the three (3) month period then ended, are hereinafter
sometimes referred to as the "INTERIM FINANCIAL STATEMENTS" and the balance
sheets as of March 31, 2000 are hereinafter sometimes referred to as the
"INTERIM BALANCE SHEETS."

         SECTION 4.11 NO UNDISCLOSED LIABILITIES. Except as and to the extent of
the amounts specifically disclosed or accrued for or reserved against in the
Interim Balance Sheets, neither Holdings nor Subsidiary has any liabilities or
obligations of any nature, including any guarantees granted to any Persons,
whether absolute, accrued, contingent or otherwise and whether due or to become
due.

         SECTION 4.12 ABSENCE OF CERTAIN CHANGES. Since December 31, 1999,
neither Holdings nor Subsidiary has:

         (a)   suffered any adverse change in its condition (financial or
otherwise), assets, liabilities or business, or experienced any work stoppages,
work slowdowns or attempts to unionize its employees or suffered any material
casualty loss (not fully insured);

         (b)   made any change in its business or operations or in the manner of
conducting its business;

         (c)   incurred any obligations or liabilities (whether absolute,
accrued, contingent or otherwise and whether due or to become due) or made any
change in any assumptions underlying or methods of calculating any bad debt,
contingency or other reserves;

         (d)   paid, discharged or satisfied any Lien or liability (whether
absolute, accrued, contingent or otherwise and whether due or to become due);

         (e)   permitted or allowed any of its properties or assets (whether
real, personal or mixed, tangible or intangible) to be subjected to any Lien;

         (f)   written down or determined to write down or written up or
determined to write up the value of any inventory, except for write downs in the
ordinary course of business, consistent with past practice and at a rate no
greater than during the prior twelve (12) months;

         (g)   canceled, waived or written off any debts, claims or rights worth
Three Thousand United States Dollars (US $3,000) or more individually or Seven
Thousand Five Hundred United States Dollars (US $7,500) or more in the
aggregate;

         (h)   acquired any additional, or sold, transferred or conveyed any
existing, properties or assets (whether real, personal or mixed, tangible or
intangible);

         (i)   granted any increase in the compensation of any legal
representative, director or employee (including, without limitation, any
increase pursuant to any bonus, pension, profit sharing or other plan or
commitment) or instituted or adopted any new benefit program, plan or other
arrangement for its legal representatives, directors or employees;

                                       12

<PAGE>

         (j)   made any pension, retirement, profit sharing, bonus or other
employee welfare or benefit payment;

         (k)   declared, paid or made or set aside for payment or making, any
dividends or other distribution in respect of the Shares, any Holdings Capital
Stock, any Subsidiary Capital Stock or any other security or securities of
either Holdings or Subsidiary, or directly or indirectly redeemed, purchased or
otherwise acquired any of the Holdings Capital Stock, Subsidiary Capital Stock
or other securities;

         (l)   made any change in any method of accounting or accounting
practice;

         (m)   entered into any agreement, arrangement or transaction with any
stockholder, legal representative, director or employee of either Holdings or
Subsidiary, or with any Affiliate of either company other than the Aventis
Release; or

         (n)   agreed, whether in writing or otherwise, to take any action
described in this Section 4.12.

         SECTION 4.13 CERTAIN TAX MATTERS AND SOCIAL SECURITY MATTERS.

         (a)   Holdings has timely filed all Tax Returns (as defined in Article
XII hereof) that it was required to file. All such Tax Returns were correct and
complete in all respects. All Taxes (as defined in Article XII) owed by Holdings
(whether or not shown on any Tax Return) have been paid. Holdings is not
currently the beneficiary of any extension of time within which to file any Tax
Return. No claim has ever been made by an authority in a jurisdiction where
Holdings does not file Tax Returns that it is or may be subject to taxation by
that jurisdiction. There are no Liens on any of the assets of Holdings that
arose in connection with any failure (or alleged failure) to pay any Tax.

         (b)   Subsidiary has timely filed all Tax Returns that it was required
to file. All such Tax Returns were correct and complete in all respects. All
Taxes owed by Subsidiary (whether or not shown on any Tax Return) have been
paid. Subsidiary is not currently the beneficiary of any extension of time
within which to file any Tax Return. No claim has ever been made by an authority
in a jurisdiction where Subsidiary does not file Tax Returns that it is or may
be subject to taxation by that jurisdiction. There are no Liens on any of the
assets of Subsidiary that arose in connection with any failure (or alleged
failure) to pay any Tax.

         (c)   Holdings has withheld and paid all Taxes required to have been
withheld or paid in connection with the amounts paid or owing to any employee,
independent contractor, creditor, stockholder or other third party.

         (d)   Subsidiary has withheld and paid all Taxes and other amounts
required to have been withheld or paid in connection with the amounts paid or
owing to any employee, independent contractor, creditor, stockholder or other
third party.

         (e)   No legal representative, director or employee (including any
employee responsible for Tax matters) of Holdings expects any authority to
assess any additional Taxes for any period for which Tax Returns have been
filed. There is no dispute or claim concerning any Tax liability of Holdings
either (i) claimed or raised by any authority in writing or (ii) as to which any
of the legal representatives, directors or employees (including employees
responsible for Tax matters) of Holdings has knowledge based upon contact with
any agent of such authority. Section 4.13(e) of the Contributor Group Disclosure
Schedule contains an accurate and complete list of all Tax Returns filed with
respect to Holdings for taxable periods

                                       13

<PAGE>

ended on or after December 31, 1998. In addition, Section 4.13(e) of the
Contributor Group Disclosure Schedule indicates those Tax Returns that have been
audited and those Tax Returns that currently are the subject of audit. Holdings
has delivered to Recipient correct and complete copies of all Tax Returns,
examination reports, and statements of deficiencies assessed against or agreed
to by Holdings relating to taxable periods ending on or after December 31, 1998.

         (f)   No legal representative, director or employee (including any
employee responsible for Tax matters) of Subsidiary expects any authority to
assess any additional Taxes for any period for which Tax Returns have been
filed. There is no dispute or claim concerning any Tax liability of Subsidiary
either (i) claimed or raised by any authority in writing or (ii) as to which any
of the legal representatives, directors or employees (including employees
responsible for Tax matters) of Subsidiary has knowledge based upon personal
contact with any agent of such authority. Section 4.13(f) of the Contributor
Group Disclosure Schedule contains an accurate and complete list of all Tax
Returns filed with respect to Subsidiary for taxable periods ended on or after
December 31, 1998. In addition, Section 4.13(f) of the Contributor Group
Disclosure Schedule indicates those Tax Returns that have been audited and
indicates those Tax Returns that currently are the subject of audit. Subsidiary
has delivered to Recipient correct and complete copies of all Tax Returns,
examination reports, and statements of deficiencies assessed against or agreed
to by Subsidiary relating to taxable periods ending on or after December 31,
1998.

         (g)   Neither Holdings nor Subsidiary has waived any statute of
limitations with respect to Taxes or agreed to any extension of time with
respect to a Tax assessment or deficiency.

         (h)   Section 4.13(h) of the Contributor Group Disclosure Schedule
contains an accurate and complete list of the following information with respect
to Holdings as of the most recent practicable date: (i) the amount of any net
operating loss, net capital loss, investment, foreign or other tax credit or
charitable contribution carryover of Holdings and (ii) the amount of any
deferred gain or loss allocable to Holdings arising out of any deferred
intracompany transaction. Consummation of the transactions contemplated hereby
will not place any limitation(s) on the use of the tax attributes referred to in
the preceding sentence.

         (i)   Section 4.13(i) of the Contributor Group Disclosure Schedule
contains an accurate and complete list of the following information with respect
to Subsidiary as of the most recent practicable date: (i) the amount of any net
operating loss, net capital loss, investment, foreign or other tax credit or
charitable contribution carryover of Subsidiary and (ii) the amount of any
deferred gain or loss allocable to Subsidiary arising out of any deferred
intracompany transaction. Consummation of the transactions contemplated hereby
will not place any limitation(s) on the use of the tax attributes referred to in
the preceding sentence.

         (j)   The unpaid Taxes of Holdings (i) did not, as of the date of its
Interim Balance Sheet, exceed the reserve for Tax liability (rather than any
reserve for deferred Taxes established to reflect timing differences between
book and Tax income) set forth on the face of such Interim Balance Sheet (rather
than in any notes thereto) and (ii) will not exceed that reserve as adjusted for
the passage of time through the Closing Date.

         (k)   The unpaid Taxes of Subsidiary (i) did not, as of the date of its
Interim Balance Sheet, exceed the reserve for Tax liability (rather than any
reserve for deferred Taxes established to reflect timing differences between
book and Tax income) set forth on the face of such Interim Balance Sheet (rather
than in any notes thereto) and (ii) will not exceed that reserve as adjusted for
the passage of time through the Closing Date.

                                       14

<PAGE>

         (l)   Holdings and Subsidiary have each duly filed, in a timely
fashion, all reports and returns required to be filed by them and have duly paid
or provided for all contributions and other charges due or claimed to be due
from them, to or by all social security and related authorities. No social
security or related filings of either Holdings or Subsidiary have been audited
by any social security or related authority. The allocations for social security
and related contributions contained in the Financial Statements and carried on
the books of Holdings and Subsidiary on the Closing Date are adequate to cover
the social security and related liabilities as of the Closing Date. Since
December 31, 1999, Holdings and Subsidiary have had no social security or
related liabilities other than in the ordinary course of business. There is no
pending inquiry by any social security or related authority concerning Holdings
or Subsidiary. Neither Holdings nor Subsidiary has received any notice of an
audit by any social security or related authority relating to, or for claims
asserted for, contributions by or assessments against either Holdings or
Subsidiary, and there is no basis for any such inquiry or claim.

         (m)   Since the date of the Interim Balance Sheet, neither Holdings nor
Subsidiary has incurred any liabilities for Taxes except in the ordinary course
of business.

         SECTION 4.14 TITLE TO PROPERTIES; ENCUMBRANCES. Each of Holdings and
Subsidiary has good, valid and marketable title to all of its owned properties
and assets, real, personal and mixed, tangible and intangible. None of such
properties or assets is owned (in whole or in part) by, or licensed to, any
other Person or is subject to any Lien.

         SECTION 4.15 FIXED AND OTHER TANGIBLE ASSETS.

         (a)   Section 4.15(a) of the Contributor Group Disclosure Schedule
contains an accurate and complete description of all fixed and other tangible
assets owned or used by Holdings and an accurate and complete list of which
assets are owned by Holdings and which assets are not.

         (b)   Section 4.15(b) of the Contributor Group Disclosure Schedule
contains an accurate and complete description of all fixed and other tangible
assets owned or used by Subsidiary and an accurate and complete list of which
assets are owned by Subsidiary and which assets are not.

         (c)   All assets listed in Sections 4.15(a) and 4.15(b) of the
Contributor Group Disclosure Schedule are structurally sound with no material
defects, in good operating condition and repair (ordinary wear and tear
excepted) and usable in the ordinary course of business, and all leasehold
improvements located on the leased real properties are structurally sound and
useable for their current purpose. Neither Holdings nor Subsidiary has received
notification that it is in violation of any applicable building or zoning law,
ordinance or regulation in respect of the assets referred to in either (a) or
(b) above or their operation.

         SECTION 4.16 LEASES.

         (a)   Section 4.16(a) of the Contributor Group Disclosure Schedule
contains an accurate and complete list of each lease pursuant to which Holdings
leases real or personal property and an accurate and complete list of the real
and personal property covered by each such lease. Holdings has previously
delivered to Recipient complete and accurate copies of all such leases. Any
permits and licenses necessary for the use of any of the leased properties have
been obtained and are in effect. Holdings does not sublease and has not
subleased any premises in any of the leased real properties to any tenants.
Holding does not sublease any of its leased personal property to any third
party. Section 4.16(a) of the Contributor Group Disclosure Schedule also sets
forth an accurate and complete list of all service,

                                       15

<PAGE>

maintenance and utility contracts affecting Holdings' leased properties. All
such contracts are currently in full force and effect and copies of all such
contracts have been delivered to Recipient.

         (b)   Section 4.16(b) of the Contributor Group Disclosure Schedule
contains an accurate and complete list of each lease pursuant to which
Subsidiary leases real or personal property and an accurate and complete list of
the real and personal property covered by each such lease. Subsidiary has
previously delivered to Recipient complete and accurate copies of all such
leases. Any permits and licenses necessary for the use of any of the leased
properties have been obtained and are in effect. Subsidiary does not sublease
and has not subleased any premises in any of the leased real properties to any
tenants. Subsidiary does not sublease any of its leased personal property to any
third party. Section 4.16(b) of the Contributor Group Disclosure Schedule also
sets forth an accurate and complete list of all service, maintenance and utility
contracts affecting Subsidiary's leased properties. All such contracts are
currently in full force and effect and copies of all such contracts have been
delivered to Recipient.

         (c)   All leases listed in Sections 4.16(a) and 4.16(b) of the
Contributor Group Disclosure Schedule are valid, binding and enforceable in
accordance with their terms and are in full force and effect. There are no
existing defaults by either Holdings or Subsidiary or by any other party
thereunder. No event has occurred which (whether with or without notice, lapse
of time or the happening or occurrence of any other event) would constitute a
default of either Holdings or Subsidiary or by any other party thereunder. All
such leases will continue in effect after the Closing Date and the consummation
of the transactions contemplated by this Agreement without the consent, approval
or act of any other party.

         SECTION 4.17 HOLDINGS COMPUTER PROGRAMS, DATABASES AND SOFTWARE.
Section 4.17 of the Contributor Group Disclosure Schedule contains an accurate
and complete list of all computer software used by Holdings. Holdings owns or
has valid licenses to all computer software used in its business. Such software,
and the documentation thereof, is sufficient to operate Holdings' management
information systems. All right, title and interest in and to any computer
software developed by or for Holdings (the "HOLDINGS SOFTWARE") is owned by
Holdings free and clear of all Liens, and no party other than Holdings has any
ownership or other proprietary interest in such Holdings Software. The
development, use or sale of the Holdings Software by Holdings did not, and does
not, violate any rights of any Person, and Holdings has not received any
communication alleging any such violation. Holdings does not have any obligation
to compensate any Person for the development, use, sale or exploitation of the
Holdings Software, and Holdings has not granted to any Person any license,
option or other right to use, develop or sell the Holdings Software.

         SECTION 4.18 SUBSIDIARY COMPUTER PROGRAMS, DATABASES AND SOFTWARE.
Section 4.18 of the Contributor Group Disclosure Schedule contains an accurate
and complete list of all computer software used by Subsidiary. Subsidiary owns
or has valid licenses to all computer software used in its business. Such
software, and the documentation thereof, is sufficient to operate Subsidiary's
management information systems. All right, title and interest in and to any
computer software developed by or for Subsidiary (the "SUBSIDIARY SOFTWARE") is
owned by Subsidiary free and clear of all Liens, and no party other than
Subsidiary has any ownership or other proprietary interest in such Subsidiary
Software. The development, use or sale of the Subsidiary Software by Subsidiary
did not, and does not, violate any rights of any Person, and Subsidiary has not
received any communication alleging any such violation. Subsidiary does not have
any obligation to compensate any Person for the development, use, sale or
exploitation of the Subsidiary Software, and Subsidiary has not granted to any
Person any license, option or other right to use, develop or sell the Subsidiary
Software.

                                       16

<PAGE>

         SECTION 4.19 INTELLECTUAL PROPERTY.

         (a)   Section 4.19(a) of the Contributor Group Disclosure Schedule
contains an accurate and complete description of all French and foreign
(non-French) patents, patent applications, patent licenses, trademarks,
trademark registrations and applications therefor, service marks, service mark
registrations and applications therefor, copyright registrations and
applications therefor and company and commercial names, all Intellectual
Property which are used by Holdings and/or which are owned or held by Holdings
and/or under which Holdings owns or holds any license, or in which Holdings owns
or holds any interest, and all other Intellectual Property as is reasonably
necessary for the operation of all business or activities now conducted by
Holdings, or proposed to be conducted by Recipient after Closing as contemplated
by the activities described on EXHIBIT K hereto ("Milestones"), except for MVAX
and AC Vaccine Technology Milestones (collectively, the "HOLDINGS INTELLECTUAL
PROPERTY"). Section 4.19(a) of the Contributor Group Disclosure Schedule further
sets forth: (i) the nature of each such Holdings Intellectual Property; (ii) the
owner of each such Holdings Intellectual Property; (iii) the jurisdictions by or
in which each such Holdings Intellectual Property has been issued or registered
or in which an application for such issuance or registration has been filed,
including the respective registration or application numbers; and (iv) licenses,
sublicenses and other agreements to which Holdings is a party and pursuant to
which Holdings or any other Person is authorized to use any Holdings
Intellectual Property. All Holdings Intellectual Property is either owned by
Holdings free and clear of any adverse claim of any nature of any third party or
the subject of an appropriate license agreement pursuant to which Holdings has
the right to make, use, sell, import, export and disclose such Intellectual
Property, including without limitation commercial exploitation of such
Intellectual Property. Copies of all such agreements have been previously
delivered to Recipient.

         (b)   Section 4.19(b) of the Contributor Group Disclosure Schedule
contains an accurate and complete description of all French and foreign
(non-French) patents, patent applications, patent licenses, trademarks,
trademark registrations and applications therefor, service marks, service mark
registrations and applications therefor, copyright registrations and
applications therefor and company and commercial names, all Intellectual
Property which are used by Subsidiary and/or which are owned or held by
Subsidiary and/or under which Subsidiary owns or holds any license, or in which
Subsidiary owns or holds any interest, and all other Intellectual Property as is
reasonably necessary for the operation of all business or activities now
conducted by Subsidiary, or proposed to be conducted by Recipient after Closing
as contemplated by the activities described on EXHIBIT K hereto, except for MVAX
and AC Vaccine Technology Milestones (collectively, the "SUBSIDIARY INTELLECTUAL
PROPERTY"). Section 4.19(b) of the Contributor Group Disclosure Schedule further
sets forth: (i) the nature of each such Subsidiary Intellectual Property; (ii)
the owner of each such Subsidiary Intellectual Property; (iii) the jurisdictions
by or in which each such Subsidiary Intellectual Property has been issued or
registered or in which an application for such issuance or registration has been
filed, including the respective registration or application numbers; and (iv)
licenses, sublicenses and other agreements to which Subsidiary is a party and
pursuant to which Subsidiary or any other Person is authorized to use any
Subsidiary Intellectual Property. All Subsidiary Intellectual Property is either
owned by Subsidiary free and clear of any adverse claim of any nature of any
third party or the subject of an appropriate license agreement pursuant to which
Subsidiary has the right to make, use, sell, import, export and disclose such
Intellectual Property, including without limitation commercial exploitation of
such Intellectual Property. Copies of all such agreements have been previously
delivered to Recipient.

         (c)   Section 4.19(c) of the Contributor Group Disclosure Schedule sets
forth an accurate and complete list of all preclinical, in vitro and clinical
studies and data owned, used, developed, learned or compiled by Holdings and/or
Subsidiary with regard to chondrocytes, "suicide" genes (e.g., the thymidine
kinase or "TK" gene) and uses of either chondrocytes (e.g., in autologous
chondrocyte implantation procedures) or suicide genes (e.g., in gene therapy
procedures for treating graft-versus-host disease or cancerous conditions),
including, but not limited to, all data prepared in anticipation of any
marketing

                                       17

<PAGE>

application of, or as support for, a product to be marketed that is to be used
in a clinical or medical study in patients. All such data are true, accurate,
and representative of the work. No material data in the possession or knowledge
of the Contributor Group exists that would undermine or void these
representations or warranties. All products, studies and data manufactured,
prepared, developed, conducted, gathered and generated by Holdings and/or
Subsidiary have been manufactured, prepared, developed, conducted, gathered, and
generated by Holdings and/or Subsidiary in accordance with Good Laboratory
Practices, Good Clinical Practices and Good Manufacturing Practices, as those
terms are commonly used by the appropriate regulatory authorities and by the
pharmaceutical industry generally, to the extent of their applicability. The
regulations and processes applicable to the chondrocytes, the "TK" gene and gene
therapy have the normal uncertainties with regard to the regulatory policies,
procedures and agencies. The Contributors cannot guarantee approval or favorable
action by the applicable government regulatory agencies. The Contributors will
use their best efforts to cooperate with Recipient and relevant regulatory
agencies to obtain all necessary or desirable regulatory approvals and
authorizations. None of the individuals who have been involved with or assisted
in manufacturing, preparing, developing, conducting, gathering or generating any
or all such products, studies or data, or who have been involved in the
preparation of any regulatory dossiers, have ever been involved in any criminal
conduct of any nature, relating to the development or approval of any drug or
medical device, or a crime that involves bribery, payment of illegal gratuities,
fraud, perjury, false statement, racketeering, blackmail, extortion,
falsification or destruction of records, or interference with, obstruction of an
investigation into, or prosecution of any criminal offense, or any conspiracy to
commit, or aiding, or abetting such a crime.

         (d)   Neither Holdings nor Subsidiary unlawfully infringes or
unlawfully or wrongly uses any Intellectual Property owned by any Person. No
process, method, machine, article of manufacture or composition of matter made,
used, sold, offered for sale or imported (or previously made, used, sold,
offered for sale or imported) by Holdings or Subsidiary infringes any
Intellectual Property of any Person. No process, method, machine, article of
manufacture or composition of matter made, used, sold, offered for sale or
imported (or previously made, used, sold, offered for sale or imported) in a
chondrocyte production, culture or implantation program of Holdings or
Subsidiary, including, without limitation, as described in patent application FR
9911564 entitled "COMPOSITIONS DE CHONDROCYTES, PREPARATION ET UTILISATIONS," or
in Brittberg, Mats, Anders Lindahl, Anders Nilsson, et al., "Treatment of Deep
Cartilage Defects in the Knee with Autologous Chondrocyte Transplantation," THE
NEW ENGLAND JOURNAL OF MEDICINE, Vol. 331, No. 14, pp. 889-895 (October 6,
1994), has unlawfully infringed or otherwise violated, or does unlawfully
infringe or otherwise violate, any Intellectual Property of any Person. No
process, method, machine, article of manufacture or composition of matter made,
used, sold, offered for sale or imported (or previously made, used, sold,
offered for sale or imported) in the area of media for preservation of
biological material of Holdings or Subsidiary, including, without limitation, as
described in patent application PCT/FR97/00385, has infringed or violated, or
does infringe or violate, any Intellectual Property of any Person. Furthermore,
no process, method, machine, article of manufacture or composition of matter
made, used, sold, offered for sale or imported (or previously made, used, sold,
offered for sale or imported) in a gene therapy program or development of
Holdings or Subsidiary, including without limitation as described in patent
application FR 91 13430 or PCT/FR92/01016, or in U.S. Pat. No. 5,843,432 or EP
674 716, or in patent application PCT/FR93/01259, has unlawfully infringed or
violated, or does unlawfully infringe or violate, any Intellectual Property of
any Person. The representations and warranties set forth in this subparagraph
4.19(d) are made with respect to all business and activities now conducted by
Contributors, Holdings and Subsidiary and all business activities to be
conducted after the Closing Date as contemplated by the activities described on
EXHIBIT K hereto.

         (e)   The Holdings Intellectual Property is sufficient to enable
Holdings to conduct its business as currently conducted. The Subsidiary
Intellectual Property is sufficient to enable Subsidiary to conduct

                                       18

<PAGE>

its business as currently conducted. To the best knowledge of Contributors,
Holdings and Subsidiary, after a reasonable evaluation of information which any
member of the Contributor Group has become aware, the Holdings Intellectual
Property and Subsidiary Intellectual Property will enable Recipient to achieve,
and will not impede, the activities to be conducted after the Closing Date as
contemplated by the activities described on EXHIBIT K hereto, except that the
Holdings Intellectual Property and the Subsidiary Intellectual Property are not
represented to enable Recipient to achieve the MVAX and AC Vaccine Technology
Milestones.

         (f)   RESERVED

         (g)   None of Holdings, its legal representatives, legal counsel,
directors or employees has received any claim in writing by any Person with
respect to the use or validity of any of Holdings Intellectual Property or
challenging or questioning the validity or effectiveness of any license or
agreement related thereto, and no such claim has been threatened. No Holdings
Intellectual Property is subject to any outstanding order, judgment, decree,
stipulation or agreement restricting the use thereof by Holdings or restricting
the licensing thereof by Holdings to any other Person. Holdings has not entered
into any agreement to indemnify any other Person against any charge of
infringement of any Holdings Intellectual Property.

         (h)   None of Subsidiary, its legal representatives, legal counsel,
directors or employees has received any claim in writing by any Person with
respect to the use or validity of any of the Subsidiary Intellectual Property or
challenging or questioning the validity or effectiveness of any license or
agreement related thereto, and no such claim has been threatened. No Subsidiary
Intellectual Property is subject to any outstanding order, judgment, decree,
stipulation or agreement restricting the use thereof by Subsidiary or
restricting the licensing thereof by Subsidiary to any other Person. Subsidiary
has not entered into any agreement to indemnify any other Person against any
charge of infringement of any Subsidiary Intellectual Property.

         (i)   Each of Holdings, its legal representatives, directors and
employees to whom any of the processes, formulae, research, development results
or other know-how of Holdings has been disclosed is subject to a confidentiality
agreement with Holdings, sufficient to adequately protect from disclosure the
Holdings Intellectual Property and all other confidential information of
Holdings.

         (j) Each of Subsidiary, its legal representatives, directors and
employees to whom any of the processes, formulae, research, development results
or other know-how of Subsidiary has been disclosed is subject to a
confidentiality agreement with Subsidiary, sufficient to adequately protect from
disclosure the Subsidiary Intellectual Property and all other confidential
information of Subsidiary.

         (k)   Holdings and Subsidiary own, are validly licensed or otherwise
have rights to such Intellectual Property as is reasonably necessary for the
operation of all business or activities now conducted by each of them. To the
best knowledge of Contributors, Holdings and Subsidiary, after a reasonable
evaluation of information which any member of the Contributor Group has become
aware, Holdings and Subsidiary own, are validly licensed or otherwise have
rights to such Intellectual Property as is reasonably necessary for the
operation of all business or activities proposed to be conducted by Recipient
after the Closing, as contemplated by the activities described on EXHIBIT K
hereto.

         (l)   Neither Holdings nor Subsidiary has been notified or advised, has
been the recipient of a claim, or has any knowledge, after a reasonable
evaluation of information which any member of the Contributor Group has become
aware, that any activity of Holdings or Subsidiary, now conducted or

                                       19

<PAGE>

proposed to be conducted after the Closing Date, as contemplated by the
activities described on EXHIBIT K hereto, infringes, violates or adversely
affects the Intellectual Property of any Person.

         (m)   With respect to each item of Intellectual Property identified in
Section 4.19(a) of the Contributor Group Disclosure Schedule:

               (i)   Holdings owns and possesses all right, title and interest
         in and to the item, free and clear of any Lien;

               (ii)  The item is not subject to any outstanding order,
         judgment or decree;

               (iii) No action is pending in any administrative or judicial
         proceeding or is threatened, which challenges the validity,
         enforceability, protectability, use or ownership of the item;

               (iv)  The item is valid, subsisting, enforceable and patentable
         or otherwise protectable or defendable, and Holdings is unaware of any
         fact which, individually or in the aggregate, could reasonably be
         argued to detrimentally affect the validity, ownership, patentability,
         protectability, defendability or enforceability of such item;

               (v)   Holdings has never agreed to indemnify and has never
         indemnified any Person for or against any interference, infringement,
         misappropriation or other conflict with respect to the item;

               (vi)  The consummation of the transactions contemplated by this
         Agreement will not have a Material Adverse Effect (as defined in
         Article XII) on any right to or the use of the item;

               (vii) Holdings has not received notice and does not have any
         knowledge, after a reasonable evaluation of information which any
         member of the Contributor Group has become aware, that the manufacture,
         use, sale, importation or exportation of any information, product,
         process or other technology described or disclosed in any such item
         infringes or violates, or would infringe or violate, the Intellectual
         Property of any Person;

               (viii) Holdings is not aware of any license agreement listed,
         or required to be listed, on the Contributor Group Disclosure Schedule
         which has been revoked, terminated or canceled;

               (ix)  Holdings has not received notice that any Person is
         infringing, violating or interfering with, or has misappropriated the
         rights of Holdings to such item and Holdings does not have any
         knowledge, after a reasonable evaluation of information which any
         member of the Contributor Group has become aware, that any Person is
         infringing, violating or interfering with, or has misappropriated the
         rights of Holdings to such item;

               (x)   There is no restriction affecting the use by Holdings of
         such item and no license has been granted with respect thereto, except
         as specifically identified on the Contributor Group Disclosure
         Schedule; and

               (xi)  The execution of this Agreement and the consummation of
         the transactions contemplated hereby will not affect the nature, scope,
         existence, validity or enforceability of any Holdings Intellectual
         Property or any license, sublicense, or other agreement relating to, or
         other rights under, any Holdings Intellectual Property; and

               (xii) Any control transferred to Recipient of any Holdings
         Intellectual Property--or any or all rights under any licenses,
         sublicenses, or agreements relating to Holdings Intellectual
         Property--on execution of the Agreement will not affect the nature,
         scope, existence, validity or

                                       20

<PAGE>

         enforceability of any such Holdings Intellectual Property or any such
         license, sublicense, or other agreement relating to, or other rights
         under, any such Holdings Intellectual Property.

         (n)   With respect to each item of Intellectual Property identified in
Section 4.19(b) of the Contributor Group Disclosure Schedule:

               (i)   Subsidiary owns and possesses all right, title and
         interest in and to the item, free and clear of any Lien;

               (ii)  The item is not subject to any outstanding order,
         judgment or decree;

               (iii) No action is pending in any administrative or judicial
         proceeding or is threatened, which challenges the validity,
         enforceability, protectability, use or ownership of the item;

               (iv)  The item is valid, subsisting, enforceable and patentable
         or otherwise protectable or defendable and Subsidiary is unaware of any
         fact which, individually or in the aggregate, could reasonably be
         argued to detrimentally affect the validity, ownership, patentability,
         protectability, defendability or enforceability of such item;

               (v)   Subsidiary has never agreed to indemnify and has never
         indemnified any Person for or against any interference, infringement,
         misappropriation or other conflict with respect to the item;

               (vi)  The consummation of the transactions contemplated by this
         Agreement will not have a Material Adverse Effect on any right to or
         the use of the item;

               (vii) Subsidiary has not received notice and does not have any
         knowledge, after a reasonable evaluation of information which any
         member of the Contributor Group has become aware, that the manufacture,
         use, sale, importation or exportation of any information, product,
         process or other technology described or disclosed in any such item
         infringes or violates, or would infringe or violate, the Intellectual
         Property of any Person;

               (viii) Subsidiary is not aware of any license agreement
         listed, or required to be listed, on the Contributor Group Disclosure
         Schedule which has been revoked, terminated or canceled;

               (ix)  Subsidiary has not received notice that any Person is
         infringing, violating or interfering with, or has misappropriated the
         rights of Subsidiary to such item and Subsidiary does not have any
         knowledge, after a reasonable evaluation of information which any
         member of the Contributor Group has become aware, that any Person is
         infringing, violating or interfering with, or has misappropriated the
         rights of Subsidiary to such item; and

               (x)   There is no restriction affecting the use by Subsidiary of
         such item and no license has been granted with respect thereto, except
         as specifically identified on the Contributor Group Disclosure
         Schedule; and

               (xi)  The execution of this Agreement and the consummation of
         the transactions contemplated hereby will not affect the nature, scope,
         existence, validity or enforceability of any Subsidiary Intellectual
         Property or any license, sublicense, or other agreement relating to, or
         other rights under, any Subsidiary Intellectual Property; and

               (xii) Any control transferred to Recipient of any Subsidiary
         Intellectual Property--or any or all rights under any licenses,
         sublicenses, or agreements relating to Subsidiary Intellectual
         Property--on execution of the Agreement will not affect the nature,
         scope, existence, validity or

                                       21

<PAGE>

         enforceability of any such Subsidiary Intellectual Property or any such
         license, sublicense, or other agreement relating to, or other rights
         under, any such Subsidiary Intellectual Property.

         (o)   The Contributor Group has no knowledge, after a reasonable
evaluation of information which any member of the Contributor Group has become
aware, of any products, inventions, procedures, compositions or methods that any
competitor or other Person has developed which reasonably, either as of the date
hereof or as of the Closing Date, could be expected to supercede or make
obsolete any product, process or development of Holdings or Subsidiary.

         (p)   To the best knowledge of the Contributor Group, after acting
reasonably and with diligence to ascertain the verity of contrary information if
and when such information has been received by any member of the Contributor
Group, neither the contract between RPR and Subsidiary of January 13, 1998
(CONTRAT DE RECHERCHE ENTRE RHONE POULENC RORER ET GENOPOIETIC EN DATE DU 13
JANVIER 1998) nor any other contract or agreement between individuals and/or
associations of the Contributor Group provides Aventis or RPR with access to or
rights with respect to any or all vaccines derived from plasmorviruses, such
vaccine technology being disclosed in international patent application
PCT/FR97/00619 (i.e.- WO 97/38118) entitled "NOUVEAUX VACCINS ISSUS DE
PLASMOVIRUS."

         (q)   The UNIVERSITE DE NANTES ("UN") will promptly assign to the
L'UNIVERSITE PIERRE ET MARIE CURIE ("UPMC") all rights that UN may have, or will
have, in patent application FR 99 11564 entitled "COMPOSITIONS DE CHONDROCYTES,
PREPARATION ET UTILISATIONS," additions in France (i.e., divisionals,
continuations, continuations-in-part, etc.), foreign extensions (i.e.,
counterpart applications filed for patent protection outside of France), and any
foreign additions of these foreign extensions, as well as all intellectual
property rights that UN may have, or will have, concerning chondrocyte-related
technologies that result from research pursued under the CONTRAT DE COOPERATION
ENTRE GENOPOIETIC ET L'UNIVERSITE DE NANTES EN DATE DU 21 OCTOBRE 1999.
Recipient will be presented with a timely opportunity to purchase these rights
on the same terms that are available to AVAX (via Subsidiary) for the purchase
from UPMC of eighteen families of patents and patent applications through
Agreement No. W 20007 (between UPMC and Subsidiary, and as completed by
Subsidiary on April 20, 2000).

         (r)   Subsidiary has developed and is developing media for storing
(under cool, but nonfreezing conditions, as well as under cryopreservation
conditions) chondrocytes. Such Subsidiary developed media includes media that is
disclosed and claimed in patent application FR 99 11564 entitled "COMPOSITIONS
DE CHONDROCYTES, PREPARATION ET UTILISATIONS." Such Subsidiary developed media,
as well as other media that Subsidiary is developing for storing chondrocytes,
is more effective in storing chondrocytes than the media disclosed and claimed
in international patent application WO 97/33975 (i.e., PCT/FR97/00385) entitled
"MILIEU POUR LA CONSERVATION DE MATERIEL BIOLOGIQUE." The manufacture, use,
sale, offer for sale, or importation in the United States, Europe and Australia
of such media that Subsidiary has developed and is developing would not infringe
or otherwise violate any current or future rights that Aventis or any other
Person has or may have.

         (s)   Recipient will have the opportunity to license exclusively all
rights in the patent application entitled "AAV Production" (filed in the U.S. on
March 5, 1999), additions in the U.S. (i.e., divisionals, continuations,
continuations-in-part, etc.), non-U.S. extensions (i.e., counterpart
applications filed for patent protection outside of the U.S.), and any non-U.S.
additions of these non-U.S. extensions, as well as all intellectual property
rights concerning AAV-related technologies that result from research pursued
under the CONTRAT DE COLLABORATION ET DE RECHERCHE ENTRE GENOPOIETIC ET
L'UNIVERSITE DE NANTES EN DATE DU 27 AVRIL 1999. The opportunity for Recipient
to license exclusively these rights will

                                       22

<PAGE>

be made in a timely manner and in substance on the same terms that are available
to AVAX (via Subsidiary) for the purchase of eighteen families of patents and
patent applications of UPMC through Agreement No. W 20007 (between UPMC and
Subsidiary, and as completed by GP on April 20, 2000).

         SECTION 4.20 LITIGATION.

         (a)   There is no claim, action, suit, proceeding or investigation
pending or threatened against or affecting (I) either Holdings or Subsidiary,
any of either company's legal representatives, directors or employees or any of
either company's assets or (II) any transaction contemplated hereby.

         (b)   Neither Holdings nor Subsidiary has received any notice, demand
or claim, nor is there any action, suit, inquiry, hearing, proceeding or
investigation of a civil, criminal or administrative nature or before any court
or governmental or other regulatory or administrative agency, commission or
authority which is pending or threatened, directly or indirectly concerning,
relating to or resulting from any accident, happening, condition or event caused
by or allegedly caused by an alleged hazard or alleged defect in manufacture,
design, materials or workmanship (including, without limitation, any alleged
failure to warn or any breach of any express or implied warranty or
representation) with respect to any product manufactured, produced, distributed,
marketed, delivered or sold by either Holdings or Subsidiary nor is there any
valid basis therefor.

         SECTION 4.21 INSURANCE.

         (a)   Section 4.21(a) of the Contributor Group Disclosure Schedule sets
forth an accurate and complete list of all policies of fire, liability, legal
representatives, directors or employees coverage, product liability, workmen's
compensation, health, title and other forms of insurance in effect with respect
to Holdings and the current annual cost of each such policy, true copies of
which policies have previously been delivered to Recipient. Section 4.21(a) of
the Contributor Group Disclosure Schedule also sets forth an accurate and
complete list of all policies of fire, liability, legal representatives,
directors or employees coverage, product liability, workmen's compensation,
health, title and other forms of insurance in effect with respect to Subsidiary
and the current annual cost of each such policy, true copies of which policies
have previously been delivered to Recipient. All such policies (I) are valid,
outstanding and enforceable, (II) will not in any way be adversely affected by,
or terminate or lapse by reason of, the transactions contemplated by this
Agreement, and (iii) will remain in full force and effect through the Closing
Date without the payment of additional premiums (other than premiums which are
due and payable in the ordinary course of business).

         (b)   Each of Holdings and Subsidiary has been and is insured with
respect to its properties and the conduct of its business in such amounts and
against such risks as are reasonable in relation to its business. Neither
Holdings nor Subsidiary has been refused any insurance nor has either company's
coverage been limited by any insurance carrier to which it has applied for
insurance or with which it has carried insurance.

         SECTION 4.22 CONTRACTS.

         (a)   Section 4.22(a) of the Contributor Group Disclosure Schedule sets
forth an accurate and complete list of:

               (i)   all contracts, commitments, arrangements and agreements
         related to the development, licensing, marketing or distribution of any
         right, product, development, good or

                                       23

<PAGE>

         therapy to which Holdings is a party or under which Holdings is
         obligated or bound or to which any of its properties or assets may be
         subject;

               (ii)  all contracts, commitments, arrangements and agreements
         related to the development, licensing, marketing or distribution of any
         right, product, development, good or therapy to which Subsidiary is a
         party or under which Subsidiary is obligated or bound or to which any
         of its properties or assets may be subject;

               (iii) all contracts, proposals, commitments, arrangements and
         agreements related to the manufacturing or proposed manufacturing of
         any development, product, good or therapy to which Holdings is a party
         or under which Holdings is obligated or bound or to which any of its
         properties or assets may be subject;

               (iv)  all contracts, proposals, commitments, arrangements and
         agreements related to the manufacturing or proposed manufacturing of
         any development, product, good or therapy to which Subsidiary is a
         party or under which Subsidiary is obligated or bound or to which any
         of its properties or assets may be subject;

               (v)   all contracts, proposals, commitments, arrangements and
         agreements with contract research organizations, laboratories,
         consultants, research manufacturers, and similar third parties related
         to the study or investigation of any right, development, product, good
         or therapy, or the manufacturing processes and/or materials related
         thereto to which Holdings is a party or under which Holdings is
         obligated or bound or to which any of its properties or assets may be
         subject;

               (vi)  all contracts, proposals, commitments, arrangements and
         agreements with contract research organizations, laboratories,
         consultants, research manufacturers, and similar third parties related
         to the study or investigation of any right, development, product, good
         or therapy, or the manufacturing processes and/or materials related
         thereto to which Subsidiary is a party or under which Subsidiary is
         obligated or bound or to which any of its properties or assets may be
         subject;

               (vii) all contracts, commitments, arrangements and agreements
         related to the employment, indemnification, retention, severance or
         termination of any current or former employee, consultant, executive,
         legal representative or director of Holdings to which Holdings is a
         party or under which Holdings is obligated or bound or to which any of
         its properties or assets may be subject;

               (viii) all contracts, commitments, arrangements and agreements
         related to the employment, indemnification, retention, severance or
         termination of any current or former employee, consultant, executive,
         legal representative or director of Subsidiary to which Subsidiary is a
         party or under which Subsidiary is obligated or bound or to which any
         of its properties or assets may be subject;

               (ix)  all bonds, debentures, evidences of indebtedness,
         contracts, proposals, commitments, arrangements, grants, instruments
         and agreements under which Holdings has borrowed from, or is liable to,
         any third party, with respect to borrowed funds, to which Holdings is a
         party or under which Holdings is obligated or bound, or to which any of
         its properties or assets may be subject;

               (x)   all bonds, debentures, evidences of indebtedness,
         contracts, proposals, commitments, arrangements, grants, instruments
         and agreements under which Subsidiary has borrowed from, or is liable
         to, any third party, with respect to borrowed funds, to which

                                       24

<PAGE>

         Subsidiary is a party or under which Subsidiary is obligated or bound,
         or to which any of its properties or assets may be subject;

               (xi)  all other contracts, commitments, grants and agreements,
         licenses, sublicenses, license agreements, joint ventures,
         collaborative arrangements, partnership or similar relationships or
         investment relationships concerning Holdings or to which Holdings is a
         party or under which Holdings is obligated or bound or to which any of
         its properties or assets may be subject; and

               (xii) all other contracts, commitments, grants and agreements,
         licenses, sublicenses, license agreements, joint ventures,
         collaborative arrangements, partnerships, similar relationships or
         investment relationships concerning Subsidiary or to which Subsidiary
         is a party or under which Subsidiary is obligated or bound or to which
         any of its properties or assets may be subject.

         (b)   All terms of each of the items listed in Section 4.22(a) of the
Contributor Group Disclosure Schedule are in full force and effect and are
enforceable against all parties thereto in accordance with their terms. Neither
Holdings nor Subsidiary is now in default or is likely to become in default
under any such contract, commitment or agreement and no party having any
commitment to, or contract or agreement with, either Holdings or Subsidiary is
in default thereunder or is likely to become in default thereunder.

         (c)   Set forth in Section 4.22(c) of the Contributor Group Disclosure
Schedule is an accurate and complete description and identification of:

               (i)   any agreements that limit the ability of Holdings or
         Subsidiary (or any Affiliate of either company) to participate or
         compete in any line of business;

               (ii)  any agreements that provide for an indemnification or
         guaranty of a third-party by Holdings or Subsidiary (or any Affiliate
         of either company);

               (iii) any agreements that involve annual payments of more than
         Five Thousand United States Dollars ($5,000) by either Holdings or
         Subsidiary (or any Affiliate of either company) and that may not be
         terminated by Holdings or Subsidiary within six (6) months after the
         date of this Agreement; and

               (iv)  any other agreement not made in the ordinary course of
         business that is material to either Holdings or Subsidiary, taken as a
         whole.

         SECTION 4.23 PERSONNEL AND LABOR MATTERS.

         (a)   Section 4.23(a) of the Contributor Group Disclosure Schedule
contains an accurate and complete list of the names, dates of birth, titles,
duties, annual salaries, wages and other compensation or benefits (including
incentive compensation) of all legal representatives, directors and employees of
Holdings and of Subsidiary, as well as the dates on which each such
representative, director, and employee commenced working for Holdings or
Subsidiary (as appropriate) and all the material provisions of the agreements or
arrangements between Holdings and/or Subsidiary and such representative,
director and employee.

         (b)   (i)   Both Holdings and Subsidiary are in compliance with all
French Laws respecting employment and employment practices, terms and conditions
of employment and wages and hours and are not engaged in any unfair labor
practice; (ii) there is no unfair labor practice complaint against either
Holdings or Subsidiary pending or threatened before any governmental or
administrative body or entity; (iii) there is no labor strike, dispute, slowdown
or stoppage pending or threatened against or involving

                                       25

<PAGE>

either Holdings or Subsidiary; (iv) no charge with respect to or relating to
either Holdings or Subsidiary is pending before any agency responsible for the
prevention of unlawful practices; (v) neither Holdings nor Subsidiary has
received notice of the intent of any agency responsible for the enforcement of
labor or employment laws to conduct an investigation of, or relating to, either
company and no such investigation is in progress; (vi) no labor agreement
restricts either Holdings or Subsidiary from relocating, closing or terminating
any of its operations or facilities; and (vii) neither Holdings nor Subsidiary
has in the past experienced any work stoppage or other labor difficulty or
committed any unfair labor practice.

         (c)   The agreements or arrangements with all of the legal
representatives, directors and employees of Holdings and Subsidiary contain only
those terms imposed by law or the applicable collective bargaining agreement
(CONVENTION COLLECTIVE NATIONALE DE L'INDUSTRIE PHARMACEUTIQUE), except with
respect to salary.

         (d)   Section 4.23(d) of the Contributor Group Disclosure Schedule
contains an accurate and complete list of accrued amounts for any and all
"INDEMNITES DE CONGES PAYES" payments to employees and legal representatives of
Holdings and of Subsidiary.

         (e)   Neither the Contributors, Holdings nor Subsidiary have granted or
promised to grant any increase whatsoever in salary or other benefit to any of
the legal representatives, directors or employees of Holdings or Subsidiary, and
neither Holdings nor Subsidiary has any obligation to contribute to any
compensation, bonus, profit sharing or purchase plan of any nature whatsoever,
other than as provided by law and the collective bargaining agreement applicable
to its legal representatives, directors and employees. Insofar as such benefit
or plan exists, all payments due by Holdings or Subsidiary have been made when
due and all accrued amounts have been properly recorded in the Financial
Statements.

         SECTION 4.24 ENVIRONMENTAL MATTERS.

         (a)   Neither Holdings nor Subsidiary has violated or is in violation
of any applicable Environmental Laws (as defined in Article XII);

         (b)   Both Holdings and Subsidiary have obtained all Environmental
Permits (as defined in Article XII) necessary to enable them to conduct their
businesses and are in compliance with such Environmental Permits' requirements,
and both Holdings and Subsidiary will have all Environmental Permits necessary
to conduct such businesses immediately following the Closing;

         (c)   Neither Holdings nor Subsidiary has unlawfully discharged,
disposed of or released any Hazardous Substances (as defined in Article XII) on
any property now or previously owned, leased or used by Holdings or Subsidiary
(including, without limitation, soils, surface and ground waters, sewer systems
and buildings thereof);

         (d)   Neither Holdings nor Subsidiary has disposed of or contracted for
the disposal of any Hazardous Substances for any property now or previously
owned, leased or used without using a licensed, certified disposal company;

         (e)   There are no underground storage tanks for Hazardous Substances,
active or abandoned, present at any property now owned, leased or used by either
Holdings or Subsidiary, and neither Holdings nor Subsidiary has received any
notice of the presence of, nor are there present, any such tanks on any property
previously owned, leased or used by either Holdings or Subsidiary; and

                                       26

<PAGE>

         (f)   Both Holdings and Subsidiary have filed all reports and other
documents required by any applicable Environmental Laws.

         SECTION 4.25 REGULATORY MATTERS. Neither Holdings, Subsidiary nor any
of their legal representatives, directors, employees or consultants, have been
disciplined by any governmental, regulatory, administrative or supervisory
official or agency or are now or have been made the subject of any disciplinary
proceedings by any governmental or administrative entity or have been convicted
of a crime for which a Person can be so disciplined.

         SECTION 4.26 INTERESTED TRANSACTIONS.

         (a)   No legal representative, director or employee of Holdings and no
stockholder of the Holdings Capital Stock, owns, directly or indirectly, in
whole or in part, any property, asset or right, tangible or intangible, owned in
whole or in part by Holdings or which Holdings has licensed, is using or the use
of which is contemplated in its business, or which is useful for the
development, manufacture, marketing or distribution of any product, good,
service or therapy of Holdings.

         (b)   No legal representative, director or employee of Subsidiary and
no stockholder of the Subsidiary Capital Stock, owns, directly or indirectly, in
whole or in part, any property, asset or right, tangible or intangible, owned in
whole or in part by Subsidiary or which Subsidiary has licensed, is using or the
use of which is contemplated in its business or which is useful for the
development, manufacture, marketing or distribution of any product, good,
service or therapy of Subsidiary.

         (c)   No legal representative, director or employee of Holdings or any
Affiliate or associate of any such individual, and no stockholder of the issued
and outstanding Holdings Capital Stock, is a party to any contract or
arrangement (whether written or oral) with Holdings, which is not on terms at
least as favorable to Holdings as could be obtained in a comparable arm's length
transaction with a Person not so affiliated or associated with such legal
representative, director, employee or stockholder.

         (d)   No legal representative, director or employee of Subsidiary or
any Affiliate or associate of any such individual, and no stockholder of the
issued and outstanding Subsidiary Capital Stock, is a party to any contract or
arrangement (whether written or oral) with Subsidiary, which is not on terms at
least as favorable to Subsidiary as could be obtained in a comparable arm's
length transaction with a Person not so affiliated or associated with such legal
representative, director, employee or stockholder.

         SECTION 4.27 ASSETS AND RIGHTS NECESSARY TO HOLDINGS' BUSINESS.
Holdings has good, valid and marketable title to all properties and assets,
real, personal and mixed, tangible and intangible, including, but not limited
to, inventories, clinical data, regulatory filings and approvals, contractual
rights and Holdings Intellectual Property and will continue to be a party, after
the Closing, to all leases, licenses and other agreements reasonably necessary
to permit it to carry on its business as it has been conducted. In particular,
Holdings has all rights reasonably necessary to practice and enforce Holdings
Intellectual Property.

         SECTION 4.28 ASSETS AND RIGHTS NECESSARY TO SUBSIDIARY'S BUSINESS.
Subsidiary has good, valid and marketable title to all properties and assets,
real, personal and mixed, tangible and intangible, including, but not limited
to, inventories, clinical data, regulatory filings and approvals, contractual
rights and Subsidiary Intellectual Property and will continue to be a party,
after the Closing, to all leases, licenses and other agreements reasonably
necessary to permit it to carry on its business as it has been conducted. In
particular, Subsidiary has all rights reasonably necessary to practice and
enforce Subsidiary Intellectual Property.

                                       27

<PAGE>

         SECTION 4.29 BROKERS OR FINDERS. No Person is entitled to any brokerage
commission, finder's fee, advisory (other than legal) fee or like payment from
either Holdings or Subsidiary in connection with the transactions contemplated
by this Agreement.

         SECTION 4.30 COMPLIANCE WITH LAWS AND COURT ORDERS. Since their
inception, each of Holdings and Subsidiary has complied in all material respects
with its obligations to make all required or desirable filings and reports with
all governmental and regulatory bodies and has complied in all material respects
with all laws, rules, regulations, licensing requirements and orders applicable
to Holdings and Subsidiary and to the operation of each company's business, and
there has been no written assertion received, and no legal representative,
director or employee of either company has received any oral notice, from any
party responsible for the administration or enforcement thereof that either
Holdings or Subsidiary has violated any such laws, rules, regulations,
requirements or orders.

         SECTION 4.31 ABSENCE OF COMPETING INTERESTS.

         (a)   Neither of the Contributors nor any of the Other Subsidiary
Shareholders or Other Holdings Shareholders, has any interest whatsoever,
ownership or otherwise, direct or indirect, in any enterprise or undertaking
that is (i) a direct or indirect competitor, supplier, principal or customer of
either Holdings or Subsidiary, (ii) a direct or indirect owner, lessor, lessee,
licensor or licensee of any one or more of the assets, tangible or intangible,
owned or used by either Holdings or Subsidiary in the operation of its business,
or (iii) a direct or indirect party to any agreement or undertaking with either
Holdings or Subsidiary.

         (b)   Neither of the Contributors, nor any of the Other Subsidiary
Shareholders or Other Holdings Shareholders is a legal representative,
consultant, agent, director or employee of any direct or indirect competitor of
either Holdings or Subsidiary, other than Prof. Klatzmann's participation prior
to the Closing Date on the Scientific Advisory Board of Progenics.

         (c)   Prof. Klatzmann hereby represents and warrants that, as a result
of his relationship with Progenics, he gained no specific knowledge of and was
not involved, either directly or indirectly, in any research or clinical
development related in any way, directly or indirectly, to any form of cancer or
any cure, vaccine and/or treatment therefor or related to any area or scientific
field that is competitive in any way with the business of Recipient and/or
Holdings or Subsidiary.

         (d)   The Contributor Group further represents and warrants that no
impediment, obstacle, hindrance or barrier of any nature, including, but not
limited to, any contract, duty, right, obligation or covenant exists or will
come into existence with the passage of time or upon the occurrence of any event
or action, that prevents, impedes, obstructs, hinders or bars, or that would or
might prevent, impede, obstruct, hinder or bar, in any way, directly or
indirectly, the right, ability or capacity of either of the Contributors to
render services and perform their obligations as a consultant to AVAX, Holdings,
and/or Subsidiary as contemplated herein and in the Consulting and Assignment
Agreement for a period of not less than ten (10) years following the Closing
Date; provided, however, that AVAX acknowledges that Prof. Klatzmann and Prof.
Salzmann currently work and will continue after the Closing to work in
non-commercial capacities as professors at UPMC and UNIVERSITE PARIS-NORD
("PARIS-NORD"), respectively, and as a result, must comply with their respective
duties to such universities as such duties are fixed by French Law.

         (e)   The Contributor Group represents and warrants that neither of the
Contributors nor Holdings or Subsidiary is a party to any agreement containing
any non-disclosure, non-solicitation, non-competition or similar provision that
might preclude or hinder either Contributor, Holdings or

                                       28

<PAGE>

Subsidiary from performing any action or service to be performed by either such
Contributor, Holdings or Subsidiary as contemplated by this Agreement and/or by
the Consulting and Assignment Agreements.

         (f)   The Contributor Group represents and warrants that the
transactions contemplated by this Agreement will result in the grant, assignment
and transfer from Contributors to Recipient at the Closing of all right, title
and interest the Contributors have as of the Closing Date, or will have after
the Closing Date, without any further action on the part of the Contributors
with the passage of time or upon the occurrence of any event, jointly and
severally, directly or indirectly and regardless of how or when arising, in and
to any and all Intellectual Property of any nature whatsoever, regardless of the
subject matter thereof, including, but not limited to, the right to sue and to
protect such right, title and interest for the benefit of Recipient in the name
of either or both of the Contributors, subject only to the rights of UPMC and
Paris-Nord described above in this Section 4.31.

         SECTION 4.32 ABSENCE OF ANY INTERESTS OF AVENTIS. Aventis has no rights
(contract or otherwise) in connection with either of the Contributors, Holdings
or Subsidiary, including, but not limited to, with regard to any Intellectual
Property owned, licensed, developed, created or used, in whole or in part,
directly or indirectly, to or by Holdings, Subsidiary or either or both
Contributors or with regard to any other asset of Holdings, Subsidiary or either
or both Contributors, tangible or intangible, owned, licensed or used by
Holdings or Subsidiary in the operation of its business.

         SECTION 4.33 PROFESSOR STATUS. Prof. Klatzmann is a professor of
medicine at UPMC. Prof. Salzmann is a professor of medicine at Paris-Nord.
Except as provided in this Section 4.33, neither of the Contributors owes any
employment, teaching or consulting commitment or obligation to any third party.

         SECTION 4.34 DISCLOSURE. No representation or warranty to Recipient
contained in this Agreement or in any agreement contemplated hereby, and no
statement contained in the Contributor Group Disclosure Schedule attached hereto
or any certificate furnished to Recipient pursuant to the provisions hereof
contains any untrue statement of a material fact or omits to state a material
fact necessary in order to make the statements herein or therein not misleading.

                                       29

<PAGE>

                                    ARTICLE V
               REPRESENTATIONS AND WARRANTIES OF THE CONTRIBUTORS

               Except as set forth on the Contributors' Disclosure Schedule
attached hereto as EXHIBIT L ("CONTRIBUTORS' DISCLOSURE SCHEDULE"), which has
been delivered to Recipient prior to the execution of this Agreement, each of
the Contributors, jointly and severally, hereby represents and warrants to
Recipient, as of the date of this Agreement, such representations and warranties
to be continuing representations and warranties through the Closing Date, as
follows:

         SECTION 5.1 RECEIPT OF AVAX STOCK.

         (a)   Each of the Contributors, the Other Holdings Shareholders and the
Other Subsidiary Shareholders intend to hold AVAX Stock for investment for their
own account and not with a view to, or for sale in connection with, any resale
or distribution thereof. Each of the Contributors, the Other Holdings
Shareholders and the Other Subsidiary Shareholders, either alone or together
with their advisors, has sufficient knowledge and experience in financial and
business matters so as to be capable of evaluating the merits and risks of his
investments in AVAX Stock and is capable of bearing the economic risks of such
investment. All of the Contributors, the Other Holdings Shareholders and the
Other Subsidiary Shareholders are "accredited investors" as that term is defined
in Rule 501(a) under the U.S. Securities Act of 1933, as amended (the
"SECURITIES ACT").

         (b)   Each of the Contributors, the Other Holdings Shareholders and the
Other Subsidiary Shareholders is aware of AVAX's business affairs and financial
condition and have received and reviewed copies of the AVAX SEC Reports (as
defined in Section 6.7 below) and have acquired sufficient information about
AVAX to reach an informed and knowledgeable decision to acquire shares of AVAX
Stock. All of the Contributors, the Other Holdings Shareholders and the Other
Subsidiary Shareholders are able to bear the economic risk of holding shares of
AVAX Stock for an indefinite period, including the loss of their entire
investment.

         (c)   AVAX Stock was not offered or sold to the Contributors, the Other
Holdings Shareholders and/or the Other Subsidiary Shareholders by any form of
general solicitation or advertising. All of the Contributors, the Other Holdings
Shareholders and the Other Subsidiary Shareholders understand that their
acquisition of AVAX Stock has not been registered under the Securities Act or
registered or qualified under any state securities law in reliance on specific
exemptions therefrom, which exemptions may depend upon, among other things, the
bona fide nature of the Contributors', the Other Holdings Shareholders' and the
Other Subsidiary Shareholders' investment intent as expressed herein. All of the
Contributors, the Other Holdings Shareholders and the Other Subsidiary
Shareholders have, in connection with their decision to receive AVAX Stock,
relied solely upon information publicly available to the Contributors, the Other
Holdings Shareholders and the Other Subsidiary Shareholders and filed by AVAX
with the SEC (as defined in Article XII).

         (d)   The Contributors, the Other Holdings Shareholders and the Other
Subsidiary Shareholders further acknowledge and understand that the AVAX Stock
will be required to be held by them for at least twenty-four (24) months
following their receipt of any such shares of AVAX Stock and may be required to
be held indefinitely, and it may not be resold or otherwise transferred except
in a transaction registered under the Securities Act or where an exemption from
such registration is available. The Contributors, the Other Holdings
Shareholders and the Other Subsidiary Shareholders understand that the
certificate(s) evidencing the AVAX Stock will be imprinted with a legend that
prohibits the transfer of such stock unless (i) it is registered or such
registration is not required, and (ii) if the transfer is pursuant to an
exemption from registration other than Rule 144 promulgated under the Securities
Act and, if Recipient

                                       30

<PAGE>

shall so request in writing, an opinion of counsel satisfactory to Recipient is
obtained to the effect that the transaction is so exempt and in compliance with
applicable state law.

         (e)   The Contributors, the Other Holdings Shareholders and the Other
Subsidiary Shareholders understand that nothing in this Agreement or any other
materials presented to them in connection with their acquisition of AVAX Stock
constitutes legal, tax or investment advice. Contributors, the Other Holdings
Shareholders and the Other Subsidiary Shareholders are represented by legal
counsel sophisticated in financial and corporate transactions and have each
consulted such other legal, tax and investment advisors as each of them, in
their sole discretion, has deemed necessary or appropriate in connection with
their acquisition of AVAX Stock.

                                   ARTICLE VI
                   REPRESENTATIONS AND WARRANTIES OF RECIPIENT

               Except as set forth on Recipient's Disclosure Schedule attached
hereto as EXHIBIT M ("RECIPIENT'S DISCLOSURE SCHEDULE"), Recipient hereby
represents and warrants to Contributors as of the date hereof, such
representations and warranties to be continuing representations and warranties
through the Closing Date, as follows:

         SECTION 6.1 CORPORATE EXISTENCE AND POWER. Recipient is a corporation
duly incorporated, validly existing and in good standing under the laws of
Delaware and has all corporate powers and all material governmental licenses,
authorizations, permits, consents and approvals required to carry on its
business as now conducted, except for those licenses, authorizations, permits,
consents and approvals the absence of which would not, individually or in the
aggregate, have a Material Adverse Effect on Recipient's ability to consummate
the transactions contemplated hereby.

         SECTION 6.2 CORPORATE AUTHORIZATION. The execution, delivery and
performance by Recipient of this Agreement are within the corporate powers of
Recipient and, except for any required approval by the AVAX stockholders, have
been duly authorized by all necessary corporate action on the part of Recipient.
This Agreement constitutes a valid and binding agreement of Recipient
enforceable against Recipient in accordance with its terms, except as the
enforceability hereof may be limited by bankruptcy, insolvency, moratorium or
other similar laws affecting the enforcement of creditors' rights generally and
by equitable principles of general applicability.

         SECTION 6.3 NON-CONTRAVENTION. The execution, delivery and performance
by Recipient of this Agreement do not and will not (I) violate the certificate
of incorporation or by-laws of Recipient, (II) violate any judgment, injunction,
order or decree or any license, franchise, permit or other similar authorization
held by Recipient or (III) require any consent or other action by any Person
under, constitute a default under, or give rise to any right of termination,
cancellation or acceleration of any right or obligation of Recipient under, any
agreement or other instrument binding upon Recipient or its properties or
assets, except to the extent that any such violation, failure to obtain any such
consent or other action, default, right or loss would not reasonably be expected
to have a Material Adverse Effect on Recipient's ability to consummate the
transactions contemplated hereby or a Material Adverse Effect on the Recipient
and its Affiliates, taken as a whole.

         SECTION 6.4 ACQUISITION FOR INVESTMENT. Recipient is acquiring the
Shares for investment for its own account and not with a view to, or for sale in
connection with, any distribution thereof. Recipient (either alone or together
with its advisors) has sufficient knowledge and experience in financial and
business matters so as to be capable of evaluating the merits and risks of its
investments in the Shares and is capable of bearing the economic risks of such
investment.

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         SECTION 6.5 AVAX STOCK. The Escrow Stock Consideration, the Non-Escrow
Stock Consideration and the Escrow Intellectual Property Stock Consideration to
be issued to Contributors at the Closing, will be duly authorized, validly
issued, fully paid and non-assessable. Shares of AVAX Stock issued pursuant to
Rights (as defined in Article XII) will, when issued in accordance with the
terms and conditions hereof and of the Consulting and Assignment Agreements, be
duly authorized, validly issued, fully paid and non-assessable.

         SECTION 6.6 LITIGATION. There is no action, suit, investigation or
proceeding pending against, or to the knowledge of Recipient, threatened against
or affecting Recipient before any court or arbitrator or any governmental body,
agency or official that in any manner challenges or seeks to prevent, enjoin,
alter or materially delay the transactions contemplated by this Agreement.

         SECTION 6.7 AVAX REPORTS AND FINANCIAL STATEMENTS.

         (a)   Since December 31, 1997, each of Recipient and its subsidiaries
has filed all reports, registration statements and other filings, together with
any amendments required to be made with respect thereto, that it has been
required to file with the SEC under the Exchange Act (as defined in Article
XII). All reports, registration statements and other filings (including all
exhibits, notes and schedules thereto and documents incorporated by reference
therein) filed by Recipient with the SEC on or after January 1, 1998 together
with any amendments thereto, are herein sometimes collectively referred to as
the "AVAX SEC REPORTS." Recipient has heretofore delivered to Contributors true
and complete copies of all of the AVAX SEC Reports that have been filed with the
SEC since December 31, 1997 and prior to the date hereof. As of (i) with respect
to all of the AVAX SEC Reports other than registration statements filed under
the Securities Act, the respective dates of their filings with the SEC and (ii)
with respect to all registration statements filed under the Securities Act,
their respective effective dates, the AVAX SEC Reports complied or will comply,
as the case may be, in all material respects with the rules and regulations of
the SEC and did not or will not, as the case may be, contain any untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein not misleading.

         (b)   All material contracts and agreements of Recipient have been
disclosed in the AVAX SEC Reports filed with the SEC, except for those contracts
and agreements not required to be filed pursuant to the rules and regulations of
the SEC and those contracts and agreements that have already been fully
performed and as to which there are no material contingent liabilities on the
part of Recipient.

         (c) The consolidated financial statements (including any related notes
or schedules) included in Recipient's annual reports on Form 10-K for its fiscal
years ended December 31, 1997, 1998 and 1999 (the "AVAX 10-KS") and any of
Recipient's Quarterly Reports on Form 10-Q for any fiscal quarters that are
filed prior to the Closing Date (the "AVAX 10-QS"), as filed with the SEC, were
prepared in accordance with generally accepted accounting principles in the
United States ("U.S. GAAP") applied on a consistent basis (except as may be
noted therein or in the notes or schedules thereto) and fairly present in all
material respects the consolidated financial position of Recipient as of the
dates of such financial statements and the consolidated results of their
operations and cash flows for the periods covered by such financial statements,
in the case of the unaudited interim financial statements contained in the AVAX
10-Qs, to normal year-end adjustments on a basis comparable with prior periods.
The accountants who certified any financial statements and supporting schedules
included or incorporated by reference in the AVAX SEC Reports are independent
public accountants with respect to Recipient as required by the rules and
regulations of the SEC.

                                       32

<PAGE>

                                   ARTICLE VII
                            COVENANTS AND AGREEMENTS

         SECTION 7.1 CONDUCT OF BUSINESS.

         (a)   The members of the Contributor Group, jointly and severally,
covenant and agree that, except as expressly contemplated by this Agreement,
from the date hereof and continuing through the Closing, the businesses of both
Holdings and Subsidiary shall be conducted only in the ordinary and usual course
of business consistent with past practices, that Holdings and Subsidiary shall
maintain and preserve their business relationships, business prospects, the
Holdings Intellectual Property, the Subsidiary Intellectual Property, and keep
available the services of their legal representatives, directors and employees
and not take any of the following actions or permit to occur any of the
following events without the prior written consent of Recipient:

               (i)   Issue or sell, agree to issue or sell or authorize the
         issuance or sale of any shares of either Holdings Capital Stock or
         Subsidiary Capital Stock or other securities exchangeable for or
         convertible into shares of Holdings Capital Stock or Subsidiary Capital
         Stock;

               (ii)  Grant any options, warrants or rights to acquire any
         shares of either Holdings Capital Stock or Subsidiary Capital Stock;

               (iii) Purchase or otherwise acquire, directly or indirectly,
         additional shares of Holdings Capital Stock, Subsidiary Capital Stock
         or any securities exchangeable for or convertible into shares of
         Holdings Capital Stock or Subsidiary Capital Stock;

               (iv)  Declare or pay any dividends on any of the shares of
         Holding Capital Stock or Subsidiary Capital Stock;

               (v)   Enter into any transaction relating to Holdings or
         Subsidiary, including, without limitation, any research, development
         or collaborative arrangements or relationships, or modify or effect
         changes to any existing research, development or collaborative
         relationships;

               (vi)  Fail to comply with any statutes, laws, ordinances,
         rules, regulations or other governmental restrictions applicable to
         Holdings or Subsidiary or with any contract, commitment or agreement
         to which Holdings or Subsidiary is a party;

               (vii) Merge or consolidate with (regardless of the mode of
         effecting same), (ii) sell, transfer, assign or pledge any material
         assets of Holdings or Subsidiary to, (iii) purchase substantially all
         of the assets of, or (iv) otherwise acquire, any business or any
         proprietorship, firm, association, corporation or other business
         organization or division thereof;

               (viii) Make any change in the banking or safety deposit box
         arrangements of Holdings or Subsidiary;

               (ix)  Grant any powers of attorney;

               (x)   Modify or amend any employee benefit or similar plan to
         increase the benefits thereunder, or adopt any new employee benefit
         plan, program or arrangement;

               (xi)  Increase the rates of compensation payable or to become
         payable to any or all legal representatives, directors, employees or
         consultants, or grant, make or agree to any bonus, service award or
         other like benefit for any or all legal representatives, directors,
         employees or consultants, or make or agree to any welfare, pension,
         retirement or similar payment or arrangement;

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<PAGE>

               (xii) Amend or change the STATUTS of Holdings or Subsidiary,
         or engage in any reorganization or recapitalization of either company;

               (xiii) Issue or sell any promissory notes, bonds or other
         corporate debt securities of Holdings or Subsidiary or otherwise incur
         any indebtedness for borrowed money;

               (xiv) Discharge or satisfy any Lien, or payment of any
         obligation or liability, absolute or contingent;

               (xv)  Forgive any receivable from any third party, including,
         but not limited to, any legal representative, director, employee or
         consultant of Holdings or Subsidiary;

               (xvi) Undertake indemnification, however arising, of any third
         party;

               (xvii) Subject to Lien, any asset of Holdings or Subsidiary,
         tangible or intangible;

               (xviii) Lend any money or otherwise pledge, sell, assign or
         transfer any tangible or intangible asset or cancel any debt or claim;

               (xix) Cancel, amend, license, sub-license, terminate, waive,
         sell, assign or transfer any Holdings Intellectual Property or any
         Subsidiary Intellectual Property;

               (xx)  Waive any material rights belonging to, or benefiting
         Holdings or Subsidiary, whether or not in the ordinary course of
         business;

               (xxi) Settle or otherwise compromise any litigation against
         Holdings or Subsidiary;

               (xxii) Reclassify any shares of the Holdings Capital Stock or
         the Subsidiary Capital Stock or create any classes of preferred stock;

               (xxiii) Enter into or amend any collective bargaining
         agreement;

               (xxiv) Cancel, terminate or amend any contract, agreement or
         commitment or other instrument to which Holdings or Subsidiary is a
         party;

               (xxv) Change the method of accounting or accounting practice
         of either Holdings or Subsidiary, except in response to changes in
         French GAAP;

               (xxvi) Enter into any contract, agreement, or understanding to
         cause or allow any of the foregoing listed in Section 7.1(a)(i)-(xxv)
         to occur.

         (b)   The Contributor Group further covenants and agrees that, prior to
the Closing Date, they shall promptly advise Recipient in writing of any adverse
change in either Holdings' or Subsidiary's condition (financial or otherwise),
results of operations, assets, liabilities, prospects, Holdings Intellectual
Property or Subsidiary Intellectual Property, and any material change to any
item listed on a schedule attached hereto or to the business of Holdings or
Subsidiary, or the occurrence of any event listed in Section 7.1(a)(i)-(xxv),
and shall:

               (i)   take appropriate and diligent action to obtain and
         maintain exclusive rights to Holdings Intellectual Property and to
         Subsidiary Intellectual Property within France;

               (ii)  take appropriate and diligent action to obtain and
         maintain exclusive rights to Holdings Intellectual Property and
         Subsidiary Intellectual Property outside of France; and

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<PAGE>

               (iii) take appropriate and diligent action to enable Recipient
         to effectively acquire ownership of Holdings and Subsidiary in
         accordance with the terms and conditions hereof.

         (c)   CONSENTS. The Contributor Group covenants and agrees that the
Contributors, Holdings and Subsidiary will obtain all requisite consents and
will secure all requisite actions of third parties prior to the Closing and will
deliver to the Recipient, promptly after receipt thereof, but in no event later
than immediately prior to the Closing, executed counterparts of all such
consents or other evidence of such actions. The Contributor Group further
covenants and agrees that prior to the Closing it will cause UPMC to duly and
validly execute the UPMC Agreement in substantially in the form attached hereto
as EXHIBIT N ("UPMC AGREEMENT"), which UPMC Agreement shall continue to be
effective following the Closing in accordance with its terms.

         SECTION 7.2 LOCK-UP ON AVAX STOCK. The Contributors each covenant and
agree that they will not, directly or indirectly, sell or attempt to sell,
transfer or attempt to transfer, assign or attempt to assign, hypothecate or
attempt to hypothecate, encumber or attempt to encumber, or otherwise dispose or
attempt to dispose of all or any portion of the AVAX Stock they receive pursuant
to this Agreement and/or pursuant to any transaction or agreement contemplated
hereby (including, but not limited to, pursuant to any Right), whether
voluntarily, involuntarily or by operation of law (collectively, a "TRANSFER"),
for a period of twenty-four (24) months following the Contributors' receipt of
any such shares of AVAX Stock (the "LOCK-UP PERIOD") (the "LOCK-UP"); provided,
however, that notwithstanding the foregoing, each Contributor shall be relieved
of his obligations under the Lock-Up to the extent it becomes reasonably
necessary for him to sell shares of AVAX Stock which would otherwise be subject
to the Lock-Up in order to satisfy indemnification obligations imposed on him
pursuant to Article XI hereof, pursuant to Article IX of the relevant
Contributor's Consulting and Assignment Agreement, pursuant to Section 5 of the
Escrow Agreement and/or pursuant to any other indemnification provision agreed
to in writing by the Contributors and Recipient as of the date hereof or as of
the Closing Date, to pay for litigation taking place in the United States
between AVAX and such Contributor or to pay for litigation initiated by
Recipient that takes place outside of the United States. The Contributors
further covenant and agree that, following the Lock-Up Period and during the
Consulting Period (as defined in the Consulting and Assignment Agreement) and
for as long thereafter as the Contributors are in possession of material
non-public information about AVAX, they will only attempt a Transfer in
accordance with the policies of AVAX applicable to key personnel generally
concerning insider trading and sales of shares of AVAX Stock by Officers and
Directors of AVAX, substantially in the form attached hereto as EXHIBIT O (the
"AVAX SALES POLICIES"). The Contributors also covenant and agree that from the
date hereof until the later of (i) a period of ten (10) years from the Closing
Date or (ii) a period of two (2) years from the expiration or earlier
termination of their respective Consulting and Assignment Agreements, neither of
the Contributors nor any of either of the Contributor's Affiliates will
undertake any of the prohibited activities described in this Section 7.2 below
("PROHIBITED ACTIVITIES"), directly or indirectly, unless specifically requested
in writing to do so in advance by AVAX or consented prior thereto in writing by
AVAX. Likewise, neither of the Contributors nor any of the Affiliates of either
of the Contributors will assist or encourage others to undertake such Prohibited
Activities, directly or indirectly, unless specifically requested in writing to
do so in advance by AVAX or consented prior thereto in writing by AVAX. The
Prohibited Activities include the following:

               (a)   acquire, offer to acquire, or agree to acquire, directly or
                     indirectly, by purchase or otherwise, any voting securities
                     of AVAX or any Affiliate of AVAX, or of any successor to or
                     Person in control of AVAX, or any assets of AVAX or any
                     Affiliate or division thereof or of any such successor or
                     controlling Person;

                                       35

<PAGE>

               (b)   make, or in any way participate, directly or indirectly, in
                     any "solicitation" or "proxies" to vote (as such terms are
                     defined under Regulation 14A of the Exchange Act), or seek
                     to advise or influence any Person with respect to the
                     voting of any securities of AVAX;

               (c)   make any public announcement with respect to, or submit a
                     proposal for, or offer of (with or without conditions), any
                     extraordinary transaction involving AVAX or its securities
                     or assets; or

               (d)   form, join or in any way participate in a "group" as
                     defined in Section 13(d) (3) of the Exchange Act, in
                     connection with any of the foregoing.

               The Contributors covenant and agree to promptly advise Recipient
of any inquiry or proposal made to either or both of them with respect to any of
the foregoing.

               Any attempt to Transfer any shares of AVAX Stock other than in
accordance with this Section 7.2 shall be null and void and neither AVAX nor any
transfer agent of such shares of AVAX Stock shall give any effect to such
attempted Transfer on the transfer ledger of AVAX.

         SECTION 7.3 NON-COMPETITION AND NON-SOLICITATION.

         (a)   As additional consideration for the issuance by Recipient to the
Contributors of the Escrow Stock Consideration, the Non-Escrow Stock
Consideration, the Escrow Intellectual Property Stock Consideration and the Cash
Consideration, each Contributor hereby covenants and agrees that for a period of
(x) five (5) years from the date hereof, or (y) twelve (12) months following
termination (for any reason whatsoever, whether voluntary or involuntary and
whether with or without cause) of such Contributor's consulting obligations to
Recipient and/or Holdings pursuant to such Contributor's Consulting and
Assignment Agreement, whichever date is later (the "EXCLUSIVITY PERIOD"), such
Contributor will not directly or indirectly compete with Recipient, Holdings
and/or Subsidiary (or any successor to any such company) by taking or allowing
to occur, any or all of the following actions, anywhere in the Territory (as
defined below):

               (i)   carrying on, engaging in, or acting as principal,
         director, officer, agent, employee, independent contractor,
         representative, researcher, consultant, partner, stockholder, member or
         otherwise participating in, any business, enterprise or endeavor
         (whether for-profit or not-for-profit) that, in the reasonable opinion
         of Recipient, is competitive with, directly or indirectly, or
         detrimental to, any of the businesses in which Recipient, Holdings
         and/or Subsidiary (or any successor to each such company) is engaged at
         any time during the Exclusivity Period, including, but not limited to,
         biological treatment for cancer and related diseases, autologous
         therapies for cancerous and orthopedic conditions and diseases, and
         related pre-clinical and clinical studies; or

               (ii)  lending credit or money, or seeking credit or borrowing
         money, for the purpose of establishing, operating or participating in
         any business described in Section 7.3(a)(i) above; or

               (iii) giving any advice or information to any Person engaging
         in any business described in Section 7.3(a)(i) above; or

               (iv)  lending or allowing his name or reputation to be used in
         connection with any business described in Section 7.3(a)(i) above; or

                                       36

<PAGE>

               (v)   otherwise allowing his skill, knowledge, experience and/or
         expertise to be used in any business described in Section 7.3(a)(i)
         above; or

               (vi)  providing research, scientific or consulting services to
         any account or customer, or to any Person that is or was at any time
         during the Exclusivity Period, an account or customer, of Recipient,
         Holdings and/or Subsidiary (or any successor to any such company) at
         any time during the Consulting Period.

               Notwithstanding anything contained in Section 4.31 hereof to the
contrary, the Contributors each covenants and agrees to use his best efforts to
refrain, to the extent possible consistent with their respective duties as
public university professors under French Law, from performing any functions
that give rise to, or could give rise to, commercial or competitive advantages
benefiting Persons other than AVAX, Holdings or Subsidiary.

               For purposes of this Agreement, the "TERRITORY" shall mean the
United States, Europe and Australia.

         (b)   Contributors covenant and agree that during the Exclusivity
Period, the Contributors will not solicit, disturb, hire, entice, or in any
other manner persuade or attempt to persuade any director, employee, dealer,
agent, representative, supplier, contractor, licensor, licensee or customer of
Recipient, Holdings and/or Subsidiary (or any successor of any such company) to
discontinue his, her or its relationship with such company as director,
employee, dealer, agent, representative, supplier, contractor, licensor,
licensee or customer, as the case may be.

         (c)   Contributors further covenant and agree that, during the
Exclusivity Period, they will not accept or agree to any employment or
consulting arrangement of any nature without having received the prior written
consent of AVAX; provided, however, that Prof. Klatzmann shall continue to be
able to work as a university professor at UPMC and Prof. Salzmann shall continue
to be able to work as a university professor at Paris-Nord.

         SECTION 7.4 FURTHER ASSURANCES. From time to time (whether on or after
the Closing Date), at the request of any other party to this Agreement and
without further consideration, at its own expense, each party hereto will
execute and deliver to such other party such other documents, and take such
other actions as the other party may reasonably request in order to consummate
more effectively the transactions contemplated hereby.

         SECTION 7.5 OTHER TRANSACTIONS. The Contributor Group covenants and
agrees that prior to the Closing the Contributors will not, and will cause
Holdings and Subsidiary not to, and will use their best efforts to cause the
legal representatives, directors, employees and other agents of Contributors,
Holdings and Subsidiary not to, directly or indirectly, (I) take any action to
solicit, initiate or encourage any offer or indication of interest from any
Person with respect to any Acquisition Proposal (as defined below) or (II)
engage in any discussion, negotiation, understanding or agreement with any
Person other than Recipient, or disclose any nonpublic information relating to
Holdings or Subsidiary, or afford access to the properties, books or records of
Holdings or Subsidiary, to any Person other than Recipient that may be
considered making, accepting, facilitating or encouraging an offer with respect
to an Acquisition Proposal. For purposes hereof, "ACQUISITION PROPOSAL" means
any proposal for a merger or other business combination involving Holdings or
Subsidiary or the acquisition of any equity interest in, or a substantial
portion of the assets of, Holdings or Subsidiary, other than the transactions
contemplated by this Agreement. Contributors will, and will cause Holdings and
Subsidiary to, terminate any existing discussions or negotiations with any
Person other than Recipient relating to any Acquisition Proposal.

                                       37

<PAGE>

Should Contributors, Holdings or Subsidiary receive such an Acquisition
Proposal, or obtain information that such a proposal is likely to be made, it
will provide Recipient with prompt notice thereof, including the identity of the
prospective offeror and the terms and conditions of such proposal.

         SECTION 7.6 REGULATORY MATTERS. If at any time prior to the Closing
Date, the transactions contemplated herein require or render appropriate or
desirable the filing of Notification and Report Forms under the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and the
implementing regulations promulgated thereunder (the "HSR ACT") with the Federal
Trade Commission ("FTC") and the Antitrust Division of the Department of Justice
(the "ANTITRUST DIVISION") or any similar authority or counterpart in France or
the European Union, the parties shall cooperate to prepare and file same
promptly following the occurrence of the event causing such required, desirable
or appropriate filing to arise. Similarly, if at any time prior to the Closing
Date, the transactions contemplated herein require or render appropriate or
desirable that any other antitrust report or filing, or other report or filing,
be made to, or any approval required from, any governmental or similar authority
of France, other European country or countries, the European Commission (or any
part thereof), the European Union and/or the United States, the parties shall
cooperate to prepare, file and/or request same promptly following the occurrence
of the event causing such required, appropriate or desirable obligation to
arise.

         SECTION 7.7 BEST EFFORTS. Subject to the terms and conditions of this
Agreement, Recipient, Contributors, Holdings and Subsidiary will each use their
best efforts to take, or cause to be taken, all actions and to do, cause to be
done, or cooperate with the other party in doing or causing to be done, all
things necessary or desirable under applicable laws and regulations to satisfy
the conditions to Closing stated herein and to consummate the transactions
contemplated by this Agreement as soon as is reasonably possible after the date
of this Agreement.

         SECTION 7.8 NOTICES OF CERTAIN EVENTS. Each party shall promptly notify
the other party of:

         (a)   any notice or other communication from any Person alleging that
the consent of such Person is or may be required in connection with the
transactions contemplated by this Agreement;

         (b)   any notice or other communication from any governmental or
regulatory agency or authority in connection with the transactions contemplated
by this Agreement;

         (c)   the occurrence of any event which will or may result in the
failure to satisfy any of the conditions specified in Articles VIII and IX;

         (d)   any matter hereafter arising or discovered which, if existing or
known at the date of this Agreement, would have been required to be set forth or
described in any schedule attached hereto;

         (e)   any actions, suits, claims, investigations or proceedings
commenced or, to its knowledge, threatened against, relating to or involving or
otherwise affecting Holdings, Subsidiary and/or either or both of the
Contributors that, if pending on the date of this Agreement, would have been
required to have been disclosed or that relate to the consummation of the
transactions contemplated by this Agreement; and

         (f)   notices of investigations, proceedings or regulatory actions
instituted or to be instituted against Holdings, Subsidiary and/or either or
both of the Contributors by governmental or regulatory agencies or authorities.

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<PAGE>

         SECTION 7.9 ACCESS. Between the date hereof and the Closing Date,
Contributors, Holdings and Subsidiary shall (I) give Recipient's authorized
representatives full access to any and all of its premises, properties,
contracts, books, records and affairs, (II) cause its directors, employees,
agents, representatives, counsel, appraisers or other experts and independent
certified public accountants to (A) furnish to Recipient's authorized
representatives any and all financial, patent, scientific, environmental and
other information pertaining to its business as Recipient shall from time to
time reasonably request and (B) be available upon reasonable notice to answer
questions from Recipient's representatives and (III) instruct the employees,
counsel and financial advisors of Contributors, Holdings and Subsidiary to
cooperate with Recipient in its investigation of Holdings and Subsidiary,
including, but not limited to, facilitating and assisting Recipient with any
communications between Recipient and relevant regulatory agencies Recipient
deems appropriate concerning any action taken by any such authority with regard
to the Contributors, Holdings and/or Subsidiary; provided, that if requested by
the Contributor Group, Recipient shall execute a reasonably appropriate
confidentiality agreement to protect against the disclosure of Holdings' and
Subsidiary's confidential information to third parties.

         SECTION 7.10 PUBLIC ANNOUNCEMENTS. The parties agree to consult with
each other before issuing any press release or making any public statement with
respect to this Agreement or the transactions contemplated hereby and, except as
may be required by applicable law or any listing agreement with any national
securities exchange, not to issue any such press release or make any such public
statement prior to such consultation and the approval of such press release or
public statement by the other party, which approval will not be unreasonably
withheld.

         SECTION 7.11 BOARD REPRESENTATION. In connection with each of the
elections to the Board of Directors of AVAX (the "AVAX BOARD") that occurs in
the twenty-four (24) month period immediately following the Closing, Recipient
agrees that it shall nominate one (1) person chosen by mutual agreement of the
Contributors (the "REPRESENTATIVE") for election to one (1) one-year term on the
AVAX Board and shall use its best efforts to cause such person to be elected to
the AVAX Board (subject, however, to all provisions normally applicable to all
directors of Recipient), and each year thereafter shall continue to take such
action so long as each of the following are true: (i) Contributors have combined
shareholdings of no less than three and one-half percent (3 1/2%) of all issued
and outstanding common stock of AVAX (which, for purposes of this Section 7.11
shall include all convertible preferred stock and other convertible debt as if
such convertible preferred stock and other convertible debt has been fully
converted); (ii) the Consulting and Assignment Agreement to be signed by Prof.
Klatzmann as of the Closing Date shall be in full force and effect and the
Consulting Period (as defined therein) shall not have expired or been terminated
for any reason; and (iii) the Consulting and Assignment Agreement to be signed
by Prof. Salzmann as of the Closing Date shall be in full force and effect and
the Consulting Period (as defined therein) shall not have expired or been
terminated for any reason.

         SECTION 7.12 EXPENSES. All costs and expenses (including broker's fees,
if any) incurred in connection with this Agreement and the transactions
contemplated hereby shall be paid by the party incurring such expenses.
Notwithstanding the preceding sentence, at Closing, Recipient shall pay the
legal fees of Laurent Chambaz, Esq., corporate legal counsel to the Contributor
Group ("MR. CHAMBAZ"), incurred by the Contributor Group and directly related to
this Agreement up to a maximum of Twenty-Five Thousand United States Dollars (US
$25,000) (the "LEGAL CAP"); provided, however, that Recipient shall have
previously received from Mr. Chambaz a detailed invoice for services rendered by
Mr. Chambaz acceptable to Recipient in Recipient's sole discretion, which
invoice shall provide among other things an entry for each day that Mr. Chambaz
worked on this Agreement, the number of hours Mr. Chambaz worked on this
Agreement on each such day, his fee for such time and a detailed description of
his activities in connection with this Agreement for such day. Prof. Klatzmann
and Prof. Salzmann each covenant and agree to pay any and all fees of any nature
in excess of the Legal Cap incurred prior to the

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Closing Date by either or both of them and/or by Holdings and/or Subsidiary,
including all fees of Mr. Chambaz (in excess of the Legal Cap) and Mr. Phillipe

Becker, Esq.

         SECTION 7.13 OPTION TO EXTEND AND EXPAND BEYNOST, FRANCE FACILITY. The
Contributor Group covenants and agrees that it will cause the L'ETABLISSEMENT DE
TRANSFUSION SANGUINE DE LYON to validly execute and deliver prior to the Closing
the lease and option substantially in the form attached hereto as EXHIBIT P (the
"LYON LEASE AND OPTION").

         SECTION 7.14 RELATIONSHIP WITH PROGENICS.

         (a)   The Contributor Group covenants and agrees that, except as
provided in subsection (b) below, as of the Closing Date all rights of Progenics
of any nature relating to Prof. Klatzmann, Holding and/or Subsidiary shall
terminate and be of no force or effect and Prof. Klatzmann shall have no
continuing duties or obligations with regard to Progenics.

         (b)   The Contributor Group covenants and agrees that, prior to the
Closing Date, the Progenics Termination shall have been executed by all parties
thereto, which shall cause the Progenics Consulting Agreement to be null and
void and of no force or effect (including, but not limited to, all provisions of
Section 6 thereof); provided, however, that Prof. Klatzmann's duties under (i)
Article 5, to the extent such duties pertain exclusively to AIDS or CD4 work,
research or technology, (ii) Article 7, and (iii) Article 9, to the extent such
Article 9 applies to sub-sections (i) and (ii) above, may remain in effect for a
period of no more than twelve (12) months from the date hereof.

         SECTION 7.15 OTHER TRANSACTIONS. The Contributor Group covenants and
agrees that, on or prior to the Closing Date, as appropriate, it will cause: (i)
each of the Other Holdings Shareholders to execute and fulfill the terms and
conditions of the respective Other Holdings Shareholder Stock Contribution
Agreements; (ii) each of the Other Subsidiary Shareholders to execute and
fulfill the terms and conditions of the Other Subsidiary Shareholder Stock
Contribution Agreements; and (iii) Aventis to execute and fulfill the terms and
conditions of the Aventis Stock Contribution Agreement. Each Contributor
covenants and agrees not to breach any of his duties or obligations pursuant to
any other agreement contemplated by this Agreement.

         SECTION 7.16 WORK TO BE PERFORMED. Each of the Contributors covenants
and agrees that, during the term of the Consulting Period (as that term is
defined in the Consulting and Assignment Agreements), he will use his best
efforts to ensure that all products, studies, and data manufactured, prepared,
developed, and generated by either of the Contributors, Holdings and/or
Subsidiary will be manufactured, prepared, developed, conducted, gathered, and
generated by the Contributors, Holdings and/or Subsidiary in accordance with
Good Laboratory Practices, Good Clinical Practices, and Good Manufacturing
Practices, as those terms are commonly used by the appropriate regulatory
authorities and by the pharmaceutical industry generally, to the extent of their
applicability; provided, however, that the Contributors shall not be found to
have breached this covenant and agreement if (i) the alleged breach was caused
by circumstances outside the Contributors' reasonable control, (ii) the
Contributors send written notice to Recipient of such alleged breach within
thirty (30) days after such alleged breach detailing such lack of control and
specifying appropriate remedies for the situation and (iii) AVAX, within thirty
(30) days of receipt of such notice, has not taken reasonably appropriate action
to address the situation. Nothing contained in the preceding sentence shall
impose any duty on AVAX to act or refrain from acting in any respect, nor shall
anything contained in the preceding sentence limit in any respect AVAX's rights
or abilities to supervise or direct the actions of the Contributors to the
extent AVAX deems necessary, desirable or appropriate.

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<PAGE>

         SECTION 7.17 MILESTONES. Each of the Contributors covenants and agrees
to use his best efforts to ensure that each and every Milestone is achieved on
or before its corresponding Milestone Target Date (as defined in the Rights
Agreement), or, if any Milestone cannot be achieved by its applicable Milestone
Target Date, then as soon thereafter as possible; provided, however, that
nothing contained in this Agreement shall be deemed to be a guarantee by the
Contributors that any or all of the Milestone will be achieved.

                                  ARTICLE VIII
                     CONDITIONS TO OBLIGATIONS OF RECIPIENT

               The obligation of Recipient to effect the Closing shall be
subject to the fulfillment or waiver, at or prior to the Closing, of the
following conditions, each of which may be waived by Recipient in Recipient's
sole discretion:

         SECTION 8.1 PERFORMANCE; REPRESENTATIONS AND WARRANTIES TRUE AT
THE CLOSING.

         (a)   Each of the obligations and covenants of each of the
Contributors, Holdings and Subsidiary to be performed by them on or before the
Closing Date, pursuant to the terms of this Agreement, shall have been performed
in all respects by them on or prior to the Closing Date;

         (b)   the representations and warranties of each of the Contributors,
Holdings and Subsidiary contained in this Agreement and in any certificate or
other writing delivered by Contributors, Holdings or Subsidiary pursuant hereto,
shall be true in all material respects at and as of the Closing Date, as if made
at and as of such date, except for those representations and warranties made as
of a specified date and those changes from the date of this Agreement until the
Closing such as will not reasonably be expected to have a Material Adverse
Effect; and

         (c)   Recipient shall have received a certificate signed by the
Chairmen of the Boards of Directors of both Holdings and Subsidiary to the
foregoing effect.

         SECTION 8.2 RESERVED

         SECTION 8.3 AVENTIS RIGHTS. Contributors shall have obtained the
Aventis Release in form satisfactory to Recipient and such Aventis Release shall
be valid, binding and legally enforceable against Aventis as of the Closing
Date.

         SECTION 8.4 CONTRIBUTION OF OTHER HOLDINGS SHAREHOLDERS' SHARES. The
Other Holdings Shareholders' Shares Acquisition shall have been successfully and
validly completed and closed in all respects in accordance with the terms and
conditions of the Other Holdings Shareholders Contribution Agreements.

         SECTION 8.5 CONTRIBUTION OF OTHER SUBSIDIARY SHAREHOLDERS' SHARES. The
Other Subsidiary Shareholders' Shares Acquisition shall have been successfully
and validly completed and closed in all respects in accordance with the terms
and conditions of the Other Subsidiary Shareholders Contribution Agreements.

         SECTION 8.6 CONTRIBUTION OF AVENTIS SHARES. The Aventis Acquisition
shall have been successfully and validly completed and closed in all respects in
accordance with the Aventis Stock Contribution Agreement.

                                       41

<PAGE>

         SECTION 8.7 RECEIPT OF LYON LEASE AND OPTION BY RECIPIENT. The
Recipient shall have received the duly executed Lyon Lease and Option, and such
Lyon Lease and Option shall be valid, binding and enforceable against Landlord
in accordance with its terms as of the Closing Date.

         SECTION 8.8 ABSENCE OF LITIGATION. No claim, action, suit, or other
proceeding shall be pending by any public authority before any court, agency or
governmental administrative body or other entity of competent jurisdiction nor
shall any injunction have been issued pursuant to any claim by any Person which,
in either case, in the reasonable opinion of Recipient, creates any reasonable
possibility of interference with Recipient's ability to effect the transactions
contemplated hereby or to manage following the Closing Date the business
theretofore conducted by Holdings and/or Subsidiary.

         SECTION 8.9 CONSULTING AND ASSIGNMENT AGREEMENTS. At or prior to the
Closing, the Contributors shall have each executed and delivered to Recipient
the Consulting and Assignment Agreements.

         SECTION 8.10 TERMINATION OF PROGENICS CONSULTANT'S AGREEMENT. At or
prior to the Closing, Prof. Klatzmann shall have caused Progenics to execute and
deliver to Recipient the Progenics Termination, and Prof. Klatzmann shall have
no further duties or obligations with respect to Progenics, except as expressly
provided in the Progenics Termination.

         SECTION 8.11 RESIGNATION OF PROF. KLATZMANN FROM THE BOARD OF
PROGENICS. At or prior to the Closing, Prof. Klatzmann shall have executed and
delivered to Recipient a written resignation of his position on the Scientific
Advisory Board of Progenics, and Prof. Klatzmann shall have no further duties or
obligations with respect to Progenics.

         SECTION 8.12 RESIGNATIONS OF THE MEMBERS OF THE BOARDS OF DIRECTORS OF
HOLDINGS AND SUBSIDIARY. At or prior to the Closing, each of the members of the
Boards of Directors of both Holdings and Subsidiary shall have executed and
delivered to Recipient written resignations of their positions on such Boards of
Directors.

         SECTION 8.13 REQUIRED CONSENTS. All consents, authorizations, orders
and approvals of, and filings and registrations with, any governmental authority
or third party, including, but not limited to, the UPMC Agreement, that are
required or desirable for the consummation by each party hereto of the
transactions provided for herein shall have been obtained or made and shall be
effective through the Closing Date and any applicable waiting period under the
HSR Act or any comparable French Law or European Union Law (as defined in
Article XII) shall have expired or been terminated.

         SECTION 8.14 CONTRIBUTOR GROUP CORPORATE LEGAL OPINION. Recipient shall
have received an opinion of Laurent Chambaz, Esq., Corporate Counsel to each of
the Contributors, Holdings and Subsidiary, dated as of the Closing Date,
substantially in the form attached as EXHIBIT Q hereto ("CONTRIBUTOR GROUP
CORPORATE LEGAL OPINION"). In rendering such opinion, such counsel may rely: (i)
upon certificates of public officers; (ii) as to matters governed by the laws of
jurisdictions other than French Law, upon the opinions of local counsel selected
by Contributors, Holdings or Subsidiary and reasonably satisfactory to
Recipient; and (iii) as to matters of fact, upon certificates of executive
employees of Contributors, Holdings and Subsidiary, copies of which opinions and
certificates shall be contemporaneously delivered to Recipient.

         SECTION 8.15 CONTRIBUTOR GROUP INTELLECTUAL PROPERTY LEGAL OPINION.
Recipient shall have received an opinion of Philippe Becker, Esq., Intellectual
Property Counsel to Contributors, Holdings and Subsidiary, dated as of the
Closing Date, in the form attached as EXHIBIT R hereto ("CONTRIBUTOR GROUP

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<PAGE>

INTELLECTUAL PROPERTY LEGAL OPINION"). In rendering such opinion, such counsel
may rely: (i) upon certificates of public officers; (ii) as to matters governed
by the laws of jurisdictions other than French Law, upon the opinions of local
counsel selected by Contributors, Holdings or Subsidiary and reasonably
satisfactory to Recipient; and (iii) as to matters of fact, upon certificates of
executive employees of Contributors, Holdings and Subsidiary, copies of which
opinions and certificates shall be contemporaneously delivered to Recipient.

         SECTION 8.16 CORPORATE DOCUMENTS. Recipient shall have received all
documents it may reasonably request relating to the existence of Contributors,
Holdings and Subsidiary and the authority of Contributors, Holdings and
Subsidiary for this Agreement, all in form and substance reasonably satisfactory
to Recipient.

         SECTION 8.17 RECEIPT BY RECIPIENT OF UPMC AGREEMENT. The Recipient
shall have received the duly executed UPMC Agreement, and such UPMC Agreement
shall be valid, binding and enforceable against UPMC in accordance with its
terms as of the Closing Date.

         SECTION 8.18 DELIVERIES BY THE CONTRIBUTOR GROUP AT THE CLOSING. At the
Closing, the Contributor Group shall have delivered or caused to be delivered to
Recipient the following, all of which shall be in form and content reasonably
satisfactory to the Recipient:

               (a)   Copies of the current STATUTS of both Holdings and
         Subsidiary certified by the Chairmen of the Boards of Directors of
         Holdings and Subsidiary as of the Closing Date.

               (b)   Certificates of the Chairmen of the Boards of Directors of
         both Holdings and Subsidiary stating that: (1) the resolutions of the
         Boards of Directors of Holdings and Subsidiary approving the
         transactions contemplated hereby, approving Recipient and its assignees
         as shareholders of Holdings and Subsidiary and approving the transfer
         of the Shares to Recipient as contemplated herein, have been duly and
         validly adopted, have not been modified, revoked or rescinded in any
         respect and are in full force and effect as of the Closing Date; (2) as
         of the date hereof, the Shares, the Aventis Shares, the Holdings
         Subsidiary Shares, the Other Holdings Shareholders' Shares and the
         Other Subsidiary Shareholder Shares constitute all of the issued and
         outstanding capital stock of both Holdings and Subsidiary,
         respectively.

               (c)   All consents referred to in Section 7.1(c).

               (d)   Duly executed share transfer forms (ORDRES DE MOUVEMENTS
         DE TITRES) for the transfer of the Shares, the Aventis Shares, the
         Other Holdings Shareholders' Shares and the Other Subsidiary
         Shareholders' Shares to Recipient and to the Persons which shall be
         designated by Recipient.

               (e)   The minute books, shareholder account books and share
         transfer ledgers of both Holdings and Subsidiary, the shareholder
         account books and share transfer ledgers reflecting the shareholders
         of Holdings and of Subsidiary, and all such books and ledgers shall be
         complete and accurate since the inception of each company.

               (f)   The Escrow Agreement duly executed by the Contributors and
         Escrow Agent.

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<PAGE>

                                   ARTICLE IX
                  CONDITIONS TO OBLIGATIONS OF THE CONTRIBUTORS

               The obligation of the Contributors to effect the Closing shall be
subject to the fulfillment or waiver, at or prior to the Closing, of the
following conditions, each of which may be waived by the Contributors in the
Contributors' sole discretion:

         SECTION 9.1 PERFORMANCE; REPRESENTATIONS AND WARRANTIES TRUE AT
THE CLOSING.

         (a)   Each of the obligations and covenants of Recipient to be
performed by it on or before the Closing Date, pursuant to the terms of this
Agreement, shall have been performed in all respects by it on or prior to the
Closing Date;

         (b)   the representations and warranties of Recipient contained in this
Agreement and in any certificate or other writing delivered by Recipient
pursuant hereto shall be true in all material respects at and as of the Closing
Date, as if made at and as of such date, except for those representations and
warranties made as of a specified date and those changes from the date of this
Agreement until the Closing such as will not reasonably be expected to have a
Material Adverse Effect; and

         (c)   Contributors shall have received a certificate signed by an
executive officer of Recipient to the foregoing effect.

         SECTION 9.2 RECIPIENT LEGAL OPINION. Contributors shall have received
an opinion of Shook, Hardy & Bacon L.L.P., Legal Counsel to Recipient dated as
of the Closing Date, substantially in the form attached as EXHIBIT S hereto
("RECIPIENT'S LEGAL OPINION"). In rendering such opinion, such counsel may rely
upon (i) certificates of public officers, (ii) as to matters governed by the
laws of jurisdictions other than Missouri or the General Corporate Law of the
State of Delaware or the federal laws of the Untied States of America, upon the
opinions of counsel reasonably satisfactory to Contributors and (iii) as to
matters of fact, upon certificates of officers of Recipient, copies of which
opinions and certificates shall be contemporaneously delivered to Contributors.

         SECTION 9.3 CORPORATE DOCUMENTS. Contributors shall have received all
documents it may reasonably request relating to the existence of Recipient and
the authority of Recipient to enter into this Agreement, all in form and
substance reasonably satisfactory to Contributors.

         SECTION 9.4 DELIVERY OF ESCROW STOCK CONSIDERATION, ESCROW INTELLECTUAL
PROPERTY STOCK CONSIDERATION AND NON-ESCROW STOCK CONSIDERATION. Recipient shall
have delivered: (i) into escrow, stock certificates representing the Escrow
Stock Consideration in accordance with Section 1.2(a) hereof; (ii) into escrow,
stock certificates representing the Escrow Intellectual Property Stock
Consideration in accordance with Section 1.2(d) hereof; and (iii) to Prof.
Klatzmann and Prof. Salzmann, stock certificates representing the Non-Escrow
Stock Consideration in accordance with Section 1.2 (b) hereof.

         SECTION 9.5 DELIVERY OF CASH CONSIDERATION. Recipient shall have
delivered the Cash Consideration to Prof. Klatzmann and Prof. Salzmann as
provided in Section 1.2(c) hereof.

         SECTION 9.6 DELIVERIES BY THE RECIPIENT AT THE CLOSING. At the Closing,
the Recipient shall have delivered or caused to be delivered to the Contributors
the following:

         (a)   The Research Funding Agreement.

         (b)   Consulting and Assignment Agreements for each of Prof. Klatzmann
and Prof. Salzmann.

         (c)   Rights Agreements for each of Prof. Klatzmann and Prof. Salzmann.

                                       44

<PAGE>

         (d)   A certificate of the Secretary of the Recipient stating that the
resolutions of its Board of Directors approving the transactions contemplated
hereby have been duly and validly adopted, have not been modified, revoked or
rescinded in any respect and are in full force and effect on the Closing Date.

         (e)   Escrow Agreement duly executed by Recipient and Escrow Agent.

         (f)   All other documents, instruments, payments and writings required
to be delivered by the Recipient to the Contributors at the Closing pursuant to
this Agreement.

         (g)   Written confirmation from the AVAX Board that it has appointed,
effective as of the Closing Date, the Representative to serve as a director on
the AVAX Board until the next election of any director to the AVAX Board.

                                    ARTICLE X
                                   TERMINATION

         SECTION 10.1 TERMINATION. This Agreement may be terminated at any time
prior to the Closing Date as follows, and in no other manner:

               (a)   by mutual consent of Recipient and the Contributors;

               (b)   by either the Contributors or Recipient on or after
         September 30, 2000, if the Closing shall have not occurred and if the
         failure of the Closing to occur was not due to any action or inaction
         by the party seeking to terminate this Agreement;

               (c)   by either the Contributor Group or Recipient, if any
         representation or warranty of the other (or in the case of the
         Contributor Group, any representation or warranty of any member of the
         Contributor Group) is discovered to have been materially untrue or
         incorrect at the time it was made, or if the other party materially
         breaches a covenant contained herein;

               (d)   by either the Contributor Group or Recipient if the other
         breaches any covenant or agreement to be performed hereunder on or
         prior to the Closing Date and fails to cure such breach within five (5)
         days of receipt of written notice of such breach given by the party
         claiming the breach;

               (e)   by either the Contributors or Recipient, if any permanent
         injunction or action by any governmental authority preventing the
         consummation of the transaction contemplated hereby shall have become
         final and nonappealable;

               (f)   RESERVED

               (g)   by Recipient, if less than one hundred percent (100%) of
         the outstanding shares of Holdings Capital Stock is tendered
         collectively by the Contributors and the Other Holdings Shareholders to
         Recipient at the Closing or if less than one hundred percent (100%) of
         the outstanding shares of the Subsidiary Capital Stock is tendered,
         directly, by the Contributors, Aventis and the Other Subsidiary
         Shareholders, collectively, and, indirectly, through the tendering of
         the Holding Shares and Holdings' Ownership of the Holdings' Subsidiary
         Shares to Recipient at the Closing;

                                       45

<PAGE>

               (h)   by Contributors if events occur which render impossible
         compliance with one or more conditions set forth in Article IX hereof
         and such conditions are not waived by Contributors; provided, that such
         events did not result from any action or omission by either Holdings,
         Subsidiary or either of the Contributors that were within the control
         of such person or entity and that such person or entity was not
         expressly permitted to take or omit, as appropriate, by the terms of
         this Agreement; or

               (i)   by Recipient if events occur which render impossible
         compliance with one or more conditions set forth in Article VIII hereof
         and such conditions are not waived by Recipient; provided that such
         events did not result from any action or omission by Recipient that was
         within its control and that Recipient was not expressly permitted to
         take or omit, as appropriate, by the terms of this Agreement.

               The party desiring to terminate this Agreement shall give prompt
notice of such termination to the other parties.

         SECTION 10.2 EFFECT OF TERMINATION. Subject to Section 13.1 below, the
termination of this Agreement pursuant to this Article shall not terminate,
limit or otherwise affect the right of a party hereto to recover damages
(including, without limitation, if deemed appropriate by a court of competent
jurisdiction, lost profits from failure to consummate the transaction
contemplated by this Agreement) or exercise any other remedies against a party
hereto based upon breach by such party of any representations or warranties
contained in this Agreement or any covenant or agreement of such other party
under this Agreement.

                                       46

<PAGE>

                                   ARTICLE XI
                                 INDEMNIFICATION

         SECTION 11.1 INDEMNIFICATION OF RECIPIENT.

         (a)   BY THE CONTRIBUTORS OR CONTRIBUTOR GROUP. Upon the terms and
subject to the conditions of this Article XI, the Contributors (if after the
Closing) and the Contributor Group (if prior to the Closing), jointly and
severally, shall, to the fullest extent permitted under applicable law,
indemnify and hold harmless Recipient, its directors, officers, agents and
employees, and all of Recipient's Affiliates, and such Affiliate's directors,
officers, agents and employees (collectively, the "RECIPIENT GROUP") from and
against any and all demands, claims, actions, causes of actions, assessments,
losses, damages, liabilities, costs and expenses, including but not limited to,
interest, penalties, costs of defense and reasonable attorney's fees and
expenses (collectively "CLAIMS"), asserted against, resulting to, imposed upon
or incurred by any member of the Recipient Group, directly or indirectly, by
reason of, relating to or resulting from:

               (i)   the inaccuracy of any representation or warranty, or the
         breach of any covenant or agreement, made by Contributors, Holdings or
         Subsidiary herein, in either of the Consulting and Assignment
         Agreements, in either of the Rights Agreements, in the Research Funding
         Agreement, or in any other document or agreement contemplated in any
         such document or agreement, or as reaffirmed in any certificate
         delivered at the Closing with respect thereto or any facts or
         circumstances constituting such a breach; and

               (ii)  the ownership or operation of Holdings and/or Subsidiary
         prior to the Closing; and

               (iii) any amounts paid to any directors, employees, agents or
         representatives of Holdings or Subsidiary as indemnification payments
         pursuant to the STATUTS or any contract or contracts with any party
         hereto or with third parties; and

               (iv)  the amount or sufficiency of any consideration paid to
         any or all of the Other Holdings Shareholders pursuant to any Other
         Holdings Shareholder Stock Contribution Agreement(s) or any or all of
         the Other Subsidiary Shareholders pursuant to any Other Subsidiary
         Shareholder Stock Contribution Agreement(s); and

               (v)   the Aventis Stock Contribution Agreement; and

               (vi)  that certain CONTRAT DE LOCATION dated November 22, 1994
         between SOCIETE CIVILE IMMOBILIERE R.A.G. and Genopoietic, SARL.

         (b)   BY PROF. KLATZMANN. Upon the terms and subject to the conditions
of this Article XI, Prof. Klatzmann shall, to the fullest extent permitted under
applicable law, indemnify and hold harmless the Recipient Group from and against
any and all Claims asserted against, resulting to, imposed upon or incurred by
any member of the Recipient Group, directly or indirectly, by reason of,
relating to or resulting from Prof. Klatzmann's relationship with Progenics or
resulting from or arising under the Consulting Agreement.

         SECTION 11.2 INDEMNIFICATION OF CONTRIBUTORS. Upon the terms and
subject to the conditions of this Article XI, the Recipient hereby agrees to
indemnify, defend and hold harmless the Contributors from and against all Claims
asserted against, resulting to, imposed upon or incurred by Contributors,
directly or indirectly, by reason of, relating to or resulting from a breach of
any agreement, covenant, representation or warranty of the Recipient contained
in this Agreement or any facts or circumstances constituting such a breach or by
reason of the ownership or operation of Holdings and/or Subsidiary after the
Closing.

                                       47

<PAGE>

         SECTION 11.3  PROCEDURE.

         (a)   Whenever any Claim arises for which indemnification is sought
hereunder, the party seeking indemnification (the "INDEMNIFIED PARTY") shall
promptly notify each party from whom indemnification is due (the "INDEMNIFYING
PARTY") of the Claim and, when known, the facts constituting the basis for such
Claim. In the event any party seeks indemnification hereunder resulting from or
in connection with any Claim or legal proceedings by a third person, the notice
to the Indemnifying Party shall specify, if known, the amount or an estimate of
the amount of the liability arising therefrom.

         (b)   In connection with any Claim giving rise to indemnity hereunder,
the Indemnifying Party at its sole cost and expense may, upon written notice to
the Indemnified Party, assume the defense of any such Claim or legal proceeding
with counsel reasonably satisfactory to the Indemnified Party. The Indemnified
Party shall be entitled to participate in (but not control) the defense of any
such action, with its counsel and at its own expense, and the Indemnifying Party
shall not settle or compromise such action without the prior written consent of
the Indemnified Party. If the Indemnifying Party does not assume the defense of
any such Claim or litigation resulting therefrom within twenty (20) days after
notice of such Claim is given, (i) the Indemnified Party may defend against such
Claim or litigation in such manner as it may deem appropriate, including, but
not limited to, settling such Claim or litigation on such terms as the
Indemnified Party may deem appropriate, and (ii) the Indemnifying Party shall be
entitled to participate in (but not control) the defense of such action, with
its counsel and at its own expense.

         (c)   The parties acknowledge that, although a tax examination or audit
does not necessarily constitute a Claim, such examination or audit may give rise
to a Claim. Accordingly, it is agreed that any party hereto receiving notice of
an examination or audit of any Tax Return, which Tax Return relates in whole or
in part to the period prior to the Closing, shall give notice thereof to the
others within ten (10) Business Days after receipt of such notice.

         (d)   If any amount owed to Recipient pursuant to this Article XI is
not paid in full by the Contributors in immediately available funds within
thirty (30) days after such amount becomes due and payable under this Article XI
(the "OUTSTANDING BALANCE"), then Recipient shall have the right, to be
exercised by Recipient in Recipient's sole discretion, to take possession and
ownership of and title to and/or to cancel such number of shares (or fractions
thereof, or certificates representing such shares or fractions thereof) of AVAX
Stock that would otherwise be payable to either or both of the Contributors
pursuant to Sections 1.2(a) and 1.2(d) of this Agreement as is equal to the
Outstanding Balance divided by the fair market value of the common stock of
Recipient traded on the NASDAQ Small Cap Market (or such other national market
on which the AVAX Stock may be publicly traded) at the time of the expiration of
such thirty (30) day period (the "OFFSET SHARES") (a "RIGHT OF OFFSET");
provided, however, that Recipient complies with the procedures set forth below.
For purposes of enabling Recipient to exercise its Right of Offset, the
Contributors, jointly and severally, hereby grant to the President, Chief
Executive Officer and Chief Financial Officer of Recipient such Contributors'
irrevocable powers of attorney to endorse and/or transfer any and all stock
certificates representing the Offset Shares, to cancel any and all stock
certificates representing such Offset Shares and to take any and all such other
action as is necessary or desirable, in such officer's reasonable discretion, to
enable Recipient to exercise a Right of Offset and to vest all right, title and
interest in and to such Offset Shares in Recipient. In the event Recipient
exercises a Right of Offset, neither Contributor shall have any further right,
title or interest in or to the Offset Shares. If Recipient believes that it is
entitled to indemnity hereunder and desires to exercise its Right of Offset
pursuant to this Section 11.3(d), Recipient shall submit to the Contributors and
the Escrow Agent prior written notice of Recipient's intent to exercise its
Right of Offset (an "OFFSET NOTICE"), including a reasonably detailed statement
of the factual basis for such Claim. If the Contributors do not deliver a
written objection to such claim to Recipient and the Escrow Agent within

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<PAGE>

thirty (30) days after the delivery of such Offset Notice, stating in reasonable
detail the factual basis for such objection, then all right, title and interest
that either or both Contributors might otherwise have had in or to the Offset
Shares shall terminate and be of no force or effect, the Escrow Agent shall
immediately transfer and deliver the Offset Shares to Recipient and Recipient
shall be entitled to transfer, retain, dispose, cancel or otherwise exercise any
and all rights with respect to the Offset Shares. If the Contributors do object
in writing to such Claim within such thirty (30) day period, stating in
reasonable detail the factual basis for such objection, then either or both of
the parties may submit this dispute for judicial resolution. The Escrow Agent
shall retain the Offset Shares pending final judicial resolution of the dispute.
The exercise of the Right of Offset by Recipient in good faith, whether or not
ultimately determined to be justified, will not constitute an event of default
under this Agreement, any Consulting and Assignment Agreement, the Escrow
Agreement, any agreement for Rights, or otherwise, nor will the exercise of or
the failure to exercise such Right of Offset constitute an election of remedies
or limit Recipient in any manner in the enforcement of other remedies that may
be available to it.

         (e)   In no event shall each of the Contributors' aggregate obligation
to indemnify Recipient for Claims hereunder, under each such Contributor's
Consulting and Assignment Agreement, under the Escrow Agreement or each such
Contributor's Rights Agreement, as a result of either or both of the
Contributor's ordinary negligence, exceed the lesser of (i) Two Million Five
Hundred Thousand United States Dollars (US $2,500,000) or (ii) the fair market
value (as calculated as of the date any such indemnification obligation arises)
of all shares of AVAX Stock received by or held in escrow for such Contributor
at any time (both before and after the date any Claim arises) pursuant to (A)
this Agreement; (B) such Contributor's Rights Agreement; (C) the Escrow
Agreement; and (D) any other agreement contemplated by this Agreement, the
Escrow Agreement or such Rights Agreement, including, but not limited to, all
shares of AVAX Stock issued as a result of the achievement of any Milestone.
Nothing herein shall be deemed to limit in any way the Contributors'
indemnification obligations relating to either or both Contributor's gross
negligence or intentional misconduct.

         (f)   No indemnification shall be required to be made by any party with
respect to any Claim for indemnity, which, when aggregated with any similar
Claims is less than Two Hundred Thousand United States Dollars (US $200,000), at
which point indemnity may be validly sought for the entire amount of any and all
Claims allowed hereunder, including without limitation, the initial Two Hundred
Thousand United States Dollars (US $200,000).

         (g)   Each of the parties agrees that to the extent another party
indemnifies it from any Claim, the Indemnified Party shall assign its rights to
such Claim to the Indemnifying Party to the extent of any amounts actually
received by the Indemnified Party from the Indemnifying Party.

         (h)   In the event the Consulting Period (as defined in each Consulting
and Assignment Agreement) of either Contributor is terminated during the initial
three (3) years of such Consultant's Consulting and Assignment Agreement
pursuant to Sections 7.01(c), 7.01(e) or 7.01(f) thereof, then any and all
Escrow Stock Consideration and Escrow Intellectual Property Stock Consideration
otherwise payable or deliverable (or which would or might otherwise become
payable or deliverable at some later date) to such Contributor shall be paid and
delivered to AVAX upon such termination and shall thereupon become the sole and
exclusive property of AVAX and neither of the Contributors shall have any right,
title or interest in or to such Escrow Stock Consideration or Escrow
Intellectual Property Stock Consideration.

                                       49

<PAGE>

                                   ARTICLE XII
                                   DEFINITIONS

         SECTION 12.1 AFFILIATE OR AFFILIATES. "Affiliate" or "Affiliates"
means, with respect to any Person, any other Person directly or indirectly
controlling, controlled by, or under common control with, such Person.

         SECTION 12.2 BUSINESS DAY. "Business Day" means any day other than a
Saturday, Sunday or a day on which banking institutions in the State of Missouri
are authorized or obligated by law or executive order to close.

         SECTION 12.3 ENVIRONMENTAL LAWS. "Environmental Laws" means all laws,
statutes, ordinances, rules, regulations, principles of law, common law, orders,
decrees, judgments and injunctions relating to pollution, the environment,
natural resources, nuclear power production or Hazardous Substances.

         SECTION 12.4 ENVIRONMENTAL PERMITS. "Environmental Permits" means all
permits, approvals, identification numbers, licenses, registrations and other
authorizations required under any applicable Environmental Law.

         SECTION 12.5 EUROPEAN UNION LAW. "European Union Law" means all laws,
statutes, ordinances, rules, regulations, principles of law, common law, orders,
decrees, judgments and injunctions promulgated, issued, codified or enacted
under the authority of the European Union.

         SECTION 12.6 EXCHANGE ACT. "Exchange Act" means the Securities Exchange
Act of 1934, as amended.

         SECTION 12.7 FRENCH LAW. "French Law" means all laws, statutes,
ordinances, rules, regulations, principles of law, common law, orders, decrees,
judgments and injunctions promulgated, issued, codified or enacted by any
governmental authority in the Country of France.

         SECTION 12.8 HAZARDOUS SUBSTANCES. "Hazardous Substances" means any
waste, pollutant, hazardous substance, toxic substance, hazardous waste, special
waste, nuclear substance or waste, radioactive substance or waste, petroleum and
petroleum-derived substance or waste, with respect to any of such items to the
extent regulated under, or defined by, any Environmental Laws.

         SECTION 12.9 INTELLECTUAL PROPERTY. "Intellectual Property" means all
(i) inventions (whether patentable or unpatentable and whether or not reduced to
practice), proprietary ideas, designs, improvement and French and foreign
(non-French) patents and patent applications and design registrations and
applications, together with any and all reissuances, continuations,
continuations-in-part, revisions, extensions, and reexaminations relating
thereto, (ii) trademarks, service marks, trade dress, logos, appellations of
origin, trade names, domain names and corporate names, and all goodwill
associated therewith, and French and foreign mark registrations and applications
for registration, (iii) copyrightable works, translations, adaptations,
derivations, and combinations thereof, and all copyright registrations and
registration applications relating thereto, (iv) mask works and all
applications, registrations and renewals relating thereto, (v) trade secrets and
confidential business information (including ideas, research and development,
know-how, formulas, compositions, manufacturing and production processes and
techniques, technical data, designs, drawings, specifications, customer and
supplier lists, pricing and cost information, and business and marketing plans
and proposals), (vi) proprietary organisms, cell or virus lines, proteins
(including antibodies), genes (including sequence

                                       50

<PAGE>

information) and chemicals, (vii) in vitro and in vivo preclinical and clinical,
and analytical and laboratory trials and tests developed for regulatory filings
for, or to support manufacturing of, products; and (viii) all other creative
works and measures of protection thereof (by way of the common law, statute or
otherwise) and proprietary, personal and moral rights, including but not limited
to rights of publicity, rights of privacy, and neighboring rights.

         SECTION 12.10 LIEN. "Lien" means, with respect to any property or
asset, any mortgage, lien, pledge, charge, security interest, encumbrance or
other adverse claim or liability of any kind in respect of such property or
asset other than (i) liens arising by operation of law and in the ordinary
course of business, such as mechanics', carriers' or materialmen's liens (none
of which would materially impair or interfere with the use or operation of such
property or asset); (ii) liens for Taxes which are not delinquent and for which
adequate provision is made on the December 31, 1999 Balance Sheet; and (iii)
liens which secure indebtedness for borrowed money reflected on the December 31,
1999 Balance Sheet. For the purposes of this Agreement, a Person shall be deemed
to own subject to a Lien any property or asset which it has acquired or holds
subject to the interest of a vendor or lessor under any conditional sale
agreement, capital lease or other title retention agreement relating to such
property or asset.

         SECTION 12.11 MATERIAL ADVERSE EFFECT. "Material Adverse Effect" means
any changes or effects that either individually, or in the aggregate, (i)
materially and adversely impacts the business, operations, prospects, condition
(financial or otherwise) or results of operations of AVAX, Holdings or
Subsidiary, as appropriate, each taken as a whole, or (ii) is materially adverse
to (A) the validity or enforceability of this Agreement or (B) the ability of
AVAX or the Contributors, as appropriate, to execute and deliver this Agreement
or to perform their respective obligations under this Agreement.

         SECTION 12.12 PERSON. "Person" means any individual, corporation,
partnership, association, trust or other entity or organization, including a
government or political subdivision or an agency or instrumentality thereof.

         SECTION 12.13 RESOLUTION OF THE INTELLECTUAL PROPERTY ISSUE.
"Resolution of the Intellectual Property Issue" means obtaining for Recipient
the freedom of operation--as conducive for the achievement of Milestone projects
of Exhibit K (including Milestone projects that are identified on execution of
this Agreement and projects that may be the subject of Milestone reallocation,
which could involve, without limitation, the making, using, selling, offering
for sale, or importing of genetically transformed cells--including chondrocytes,
tenocytes, lymphocytes, or other cell types--or tissues containing such
genetically transformed cells) or as otherwise reasonably necessary for the
accomplishment of objectives related to, or contemplated by, this
Agreement--with respect to, and all rights to practice under (i.e., to make,
use, sell, offer for sale, and import), U.S. Pat. No. 5,399,346 (Anderson ET
AL.), U.S. Pat. No. 5,888,502 (Guber ET AL.), U.S. Pat. No. 5,925,345 (Blaese ET
AL.), U.S. Pat. No. 5,997,859 (Barber ET AL.), and any and all counterpart
non-U.S. patents of these four U.S. patents in the countries and territories to
which such Milestones pertain, all on terms and conditions reasonably acceptable
to Recipient, and, by December 31, 2000, obtaining for Recipient sole and
exclusive ownership of all rights to Patent Asset # 16 of Exhibit J of this
Agreement (priority application entitled "Compositions of Chondrocytes,
Preparation and Utilization") and the inventions disclosed in said application,
additions in France (i.e. divisionals), foreign extensions (i.e. counterpart
applications filed for patent protection outside of France), and any foreign
additions (i.e. divisionals, continuations, continuations-in-part, etc.) of
these foreign extensions in the countries and territories to which such
Milestones pertain, all on terms and conditions reasonably acceptable to
Recipient, and, in other countries and territories, to use best efforts to
obtain for Recipient sole and exclusive ownership of all rights to Patent Asset
#16 of Appendix J of this Agreement, all on terms and conditions reasonably
acceptable to Recipient.

                                       51

<PAGE>

         SECTION 12.14 RIGHTS. "Rights" means Rights as defined in the form of
Rights Agreement attached hereto as EXHIBIT G.

         SECTION 12.15 SEC. "SEC" means the U.S. Securities and Exchange
Commission.

         SECTION 12.16 TAXES. "Taxes" means all taxes, however denominated,
including any interest, penalties or additions to tax that may become payable in
respect thereof, imposed by any French, U.S. or foreign government or any agency
or political subdivision of any such government, which taxes shall include,
without limiting the generality of the foregoing, all income taxes (including,
but not limited to, United States and French income taxes and other income
taxes), payroll, employee and other withholding taxes, unemployment insurance,
social security, sales and use taxes, excise taxes, franchise taxes, net worth
taxes, gross receipts taxes, occupation taxes, value added taxes, real and
personal property taxes, stamp taxes, transfer taxes, workers' compensation, and
other obligations of the same or of a similar nature whether arising before, on
or after the Closing Date.

         SECTION 12.17 TAX RETURNS. "Tax Returns" means all reports, elections,
estimates, information statements and returns relating to, or required to be
filed in connection with, any Taxes pursuant to the statutes, rules and
regulations of any governmental taxing authorities.

                                  ARTICLE XIII
                                  MISCELLANEOUS

         SECTION 13.1 SURVIVAL. All representations, warranties, covenants and
agreements made by any party in this Agreement shall survive the Closing and any
investigation at any time made by or on behalf of any party hereto for a period
of thirty-six (36) months after the earlier of (i) the Closing Date or (ii) the
termination of this Agreement; provided, however, that the Contributors'
obligations with respect to Section 11.1(a)(vi) above shall survive until
expiration of the applicable statute of limitations. Nothing contained in this
Section 13.1 shall limit any covenant or agreement of the parties hereto which
by its terms requires performance after the Closing. The obligation of each of
the parties to indemnify and hold harmless the other parties shall not terminate
with respect to any item as to which the Person to be indemnified shall have,
before the expiration of the applicable statute of limitations, previously made
a claim by delivering a notice pursuant hereto to the party to be providing the
indemnity. Notwithstanding anything contained herein to the contrary, the
Contributors' representations, warranties, covenants and agreements shall remain
in effect with respect to (i) any and all Claims by the French tax or social
security authorities until the expiration of the statute of limitation periods
applicable to any such Claims, increased by thirty (30) days, (ii) any other
Claims related to the matters covered by Section 4.13 above until the expiration
of the statute of limitation periods applicable to any such Claims, increased by
thirty (30) days, and (iii) any and all Claims by Aventis against Recipient by
reason of, relating to or resulting from the Aventis Stock Contribution
Agreement until such time as Aventis no longer has such a Claim, increased by
thirty (30) days. The Contributors' representations and warranties shall survive
in case of transformation of Holdings or Subsidiary into any other form of
company or in case Holdings or Subsidiary is subject to merger, spin-off or any
other reorganization.

         SECTION 13.2 NOTICES. All notices, requests, claims, demands or other
communications required or permitted by this Agreement or any instrument
provided for herein to be given or made by the parties shall be in writing
(including, without limitation, by telecopy) and shall be deemed delivered if
delivered in person, by telecopy or by registered or certified mail (postage
prepaid, return receipt requested) to the respective parties:

                                       52

<PAGE>

                     If to Recipient:

                     AVAX Technologies, Inc.
                     Attention:  Dave Tousley
                     4520 Main Street, Suite 930
                     Kansas City, Missouri 64111  USA

                     with a copy to:

                     Shook, Hardy & Bacon L.L.P.
                     Attention:  Kevin R. Sweeney, Esq.
                     1010 Grand Boulevard, Suite 500
                     Kansas City, Missouri 64106-2220  USA

                     If to Holdings, Subsidiary or the
                     Contributors prior to the
                     Closing Date:

                     GPH, S.A.
                     22 rue Esquirol
                     75013 Paris, France

                     Genopoietic, S.A.
                     22 rue Esquirol
                     75013 Paris, France

                     Professor David Klatzmann
                     11, rue de Tage
                     75013 Paris, France

                     Professor Jean Loup Salzmann
                     70, rue Claude Bernard
                     75005 Paris, France

                     with a copy to:

                     Laurent Chambaz, Esq.
                     47, rue de Monceau
                     75008 Paris, France

                                       53

<PAGE>

                     If to the Contributors
                     after the Closing Date:

                     Professor David Klatzmann
                     11, rue de Tage
                     75013 Paris, France

                     Professor Jean Loup Salzmann
                     70, rue Claude Bernard
                     75005 Paris, France

                     with a copy to:

                     Laurent Chambaz, Esq.
                     47, rue de Monceau
                     75008 Paris, France

               Any of the respective parties may, however, designate in writing
such new or other addresses or telecopy numbers to which such notice shall
thereafter be mailed or telecopied. Any notice or demand given in accordance
with this section shall be deemed received on the date of receipt by the
recipient thereof if received prior to 5 p.m. in the place of receipt and such
day is a Business Day in the place of receipt. Otherwise, any such notice,
request or communication shall be deemed not to have been received until the
next succeeding Business Day in the place of receipt.

         SECTION 13.3 SUCCESSORS AND ASSIGNS. The provisions of this Agreement
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors, permitted assigns, heirs, personal representatives,
executors, administrators and trustees. No party shall assign, delegate or
otherwise transfer any of its rights or obligations under this Agreement without
the prior written consent of each other party hereto. Notwithstanding the
preceding sentence, however, Recipient may assign all or any part of its rights,
interests or obligations hereunder to any Affiliate of Recipient without the
prior written consent of any other party; provided that such assignment shall
not release Recipient from, or in any manner limit, Recipient's obligations
hereunder.

         SECTION 13.4 GOVERNING LAW. This Agreement shall be governed by,
construed and enforced in accordance with, the laws of the State of Missouri,
United States of America, without giving effect to the choice of law provisions
of such State.

         SECTION 13.5 COUNTERPARTS. This Agreement may be signed in any number
of counterparts, each of which shall be an original, with the same effect as if
the signature thereto and hereto were upon the same instrument. No provision of
this Agreement is intended to confer upon any Person other than the parties
hereto any rights or remedies hereunder.

         SECTION 13.6 PUBLICITY. Contributors, Holdings, Subsidiary and
Recipient each agree that press releases and other announcements or disclosure
with respect to the transactions contemplated by this Agreement shall be subject
to mutual agreement to the maximum extent feasible consistent with the parties'
respective legal obligations; provided that Recipient may issue such press
releases as it deems appropriate which accurately describe the transactions
contemplated hereby.

         SECTION 13.7 ENTIRE AGREEMENT. This Agreement, the Other Holdings
Shareholder Stock Contribution Agreements, the Other Subsidiary Shareholder
Stock Contribution Agreements, the Aventis

                                       54

<PAGE>

Stock Contribution Agreement, the Research Funding Agreement, the Consulting and
Assignment Agreements and the Rights Agreements, including the Schedules and
Exhibits attached hereto or thereto and all recitals contained herein or
therein, which are all hereby expressly incorporated herein by reference,
constitute the entire agreement between the parties with respect to the subject
matter of this Agreement and supersedes all prior agreements and understandings,
both oral and written, between the parties with respect to the subject matter of
this Agreement. No representation, inducement, promise, understanding, condition
or warranty not set forth herein has been made or relied upon by either party
hereto.

         SECTION 13.8 MODIFICATIONS, AMENDMENTS AND WAIVERS. Except as expressly
provided otherwise in Article VIII and Article IX, at any time prior to the
Closing Date, the parties hereto may, by written agreement signed by the parties
(A) extend the time for the performance of any of the obligations or other acts
of the parties hereto, (B) waive any inaccuracies in the representations and
warranties contained in this Agreement or in any schedule or document delivered
pursuant hereto and/or (C) waive compliance with any of the covenants or
agreements contained in this Agreement. At any time prior to the Closing Date,
if authorized by their respective Boards of Directors, the parties hereto may,
by written agreement, amend or supplement any of the provisions of this
Agreement. Any written instrument or agreement referred to in this Section 13.8,
if executed prior to the Closing, shall be validly and sufficiently authorized
for the purposes of this Agreement if signed, on behalf of Contributors,
Holdings, Subsidiary and Recipient, by persons authorized to sign this
Agreement. No failure or delay by any party in exercising any right, power or
privilege hereunder shall operate as a waiver thereof nor shall any single or
partial exercise thereof preclude any other or further exercise thereof or the
exercise of any other right, power or privilege. The rights and remedies herein
provided shall be cumulative and not exclusive of any rights or remedies
provided by law; provided, however, that in no event shall any party hereto be
required to make the other party completely whole under two (2) different legal
theories of recovery.

         SECTION 13.9 HEADINGS. The section and paragraph headings contained in
this Agreement are for reference purposes only and shall not affect in any way
the meaning or interpretation of this Agreement.

         SECTION 13.10 CERTAIN TAXES. All transfer, documentary, sales, use,
stamp, registration and other such Taxes and fees (including any penalties and
interest) incurred in connection with this Agreement shall be treated as a
reduction to the Contribution Consideration. Holdings or Subsidiary will file
all necessary Tax Returns and other documentation with respect to all such
transfer, documentary, sales, use, stamp, registration and other Taxes and fees.

         SECTION 13.11 JURISDICTION. The parties acknowledge that this Agreement
was drafted, negotiated and executed in large part in Kansas City, Missouri,
United State of America. Except as otherwise expressly provided in this
Agreement, any suit, action or proceeding seeking to enforce any provision of,
or based on any matter arising out of or in connection with, this Agreement or
the transactions contemplated hereby shall be brought in the United States
District Court for the Western District of Missouri or in any Missouri State
Court sitting in Kansas City, Missouri, and each of the parties hereby consents
to the jurisdiction of such courts (and of the appropriate appellate courts
therefrom) in any such suit, action or proceeding and irrevocably waives, to the
fullest extent permitted by law, any objection which it may now or hereafter
have to the laying of the venue of any such suit, action or proceeding in any
such court or that any such suit, action or proceeding which is brought in any
such court has been brought in an inconvenient form. Process in any such suit,
action or proceeding may be served on any party anywhere in the world, whether
within or without the jurisdiction of any such court. Without limiting the
foregoing, each party agrees that service of process on such party as provided
in Section 13.2 shall be deemed effective service of process on such party.

                                       55

<PAGE>

         SECTION 13.12 WAIVER OF JURY TRIAL. EACH OF THE PARTIES HERETO HEREBY
IRREVOCABLY WAIVES ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING
ARISING OUT OF OR RELATED TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED
HEREBY.

         SECTION 13.13 INTERPRETATION. In the event any portion of this
Agreement shall, for any reason, be held to be invalid, illegal or unenforceable
in whole or in part, the remaining provisions shall not be affected thereby and
shall continue to be valid and enforceable. If, for any reason, a court finds
that any provision of this Agreement is invalid, illegal or unenforceable as
written, but by limiting such provision it would become valid, legal and
enforceable, then such provision shall be deemed to be written, construed and
enforced as so limited. Words and phrases herein shall be construed as in the
singular or plural number, and as masculine, feminine or neuter gender,
according to the context. Nothing contained in this Agreement and no action
taken by the parties pursuant hereto shall be deemed to constitute a
partnership, an association, a joint venture or other entity between the
parties.

                                       56

<PAGE>

               IN WITNESS WHEREOF, the Contributors, Holdings, Subsidiary and
Recipient have caused this Agreement to be executed by their respective duly
authorized legal representatives as of the date first above written.

AVAX TECHNOLOGIES, INC., a Delaware
Corporation ("AVAX")

By:
   ---------------------------------------------
Name:  Jeffrey M. Jonas, M.D.
Title: President and Chief Executive Officer
Date:
     -------------------------------------------

GPH, S.A., a French SOCIETE
ANONYME ("Holdings")

By:
   ---------------------------------------
Name:  Charles Salzmann
Title: President Directeur General
Date:
     ---------------------------------------

GENOPOIETIC, S.A., a French SOCIETE
ANONYME ("Subsidiary")

By:
   ---------------------------------------
Name:  Charles Salzmann
Title: President Directeur General
Date:
     ---------------------------------------

------------------------------------
PROF. JEAN-LOUP SALZMANN, an individual
and resident of Paris, France

------------------------------------
PROF. DAVID ROBERT KLATZMANN, an individual
and resident of Paris, France

                                       57<PAGE>

                                                                    EXHIBIT 10.2

                                    AGREEMENT

               This Agreement (the "Agreement") sets forth the terms and
conditions upon which AVAX Technologies, Inc., a Delaware corporation ("AVAX"),
and David R. Klatzmann, an individual ("Klatzmann") and Jean-Loup Salzmann, an
individual ("Salzmann") (collectively, Klatzmann and Salzmann are referred to
herein as the "Contributors"), agree to (i) resolve the Contributors' Tax Matter
(as defined below) and (ii) amend the Contribution Agreement (as defined below)
pursuant to Section 13.8 thereto. (Capitalized terms used herein but not defined
herein shall have the meaning attributed to them in the Contribution Agreement).

                                     RECITAL

               On July 17, 2000, AVAX and the Contributors, among others,
entered into that certain Stock Contribution Agreement (the "Contribution
Agreement") relating to the contribution of all of the Contributors' interest in
and to Genopoietic, S.A. and GPH, S.A. (which interests comprise roughly
eighty-three percent (83%) of all of the issued and outstanding capital stock of
such companies) to AVAX in exchange for AVAX Stock. In a side letter to the
Contribution Agreement dated July 17, 2000 (the "Side Letter"), AVAX and the
Contributors agreed to use commercially reasonable efforts to provide that, as
of September, 2001, the Contributors will have the ability to pay their capital
gains tax liability, if any, owing to the French tax authorities as a result of
the Contributors' acquisition pursuant to the Contribution Agreement of an
aggregate amount of 659,756 shares of AVAX Stock ("Contributors' AVAX Stock")
(the "Tax Matter"). The Contributors' collective tax obligation as a result of
the Tax Matter will be calculated by multiplying 659,756 times the closing price
of the shares ("Closing Price") of AVAX Technologies, Inc. traded on the NASDAQ
small cap market on the Closing Date, and then multiplying this result by zero
point two six (0.26) (the "Capital Gains Tax").

               NOW, THEREFORE, in consideration for the premises and the
covenants and agreements herein contained, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto hereby agree as follows:

         SECTION 1. AMENDMENTS TO CONTRIBUTION AGREEMENT.

         (A)   The parties hereto agree that Section 1.2 of the Contribution
Agreement is hereby deleted in its entirety and replaced with the following:

                    "SECTION 1.2 CONTRIBUTION CONSIDERATION. Subject to the
         terms and conditions of this Agreement, the consideration to be
         delivered to the Contributors by the Recipient in exchange for the
         Shares (the "CONTRIBUTION CONSIDERATION") shall be deliverable as
         follows:

                             (a) ESCROW STOCK CONSIDERATION. At the Closing,
                    Recipient shall deliver to the Escrow Agent (as defined in
                    the Escrow Agreement) to be held in escrow: (i) as partial
                    consideration for twenty-three (23) of the Holdings Shares
                    and one thousand nine hundred forty-eight (1,948) of the
                    Contributors' Subsidiary Shares to be delivered to Recipient
                    by Prof. Salzmann at the Closing, stock certificates payable
                    to Escrow Agent for the

                                        1

<PAGE>

                    benefit of Prof. Salzmann and AVAX representing two hundred
                    thousand (200,000) restricted shares of AVAX Stock with an
                    aggregate market value of One Million Seven Hundred
                    Seventy-Five Thousand and 00/100 United States Dollars (US
                    $1,755,000.00) as of the close of trading on July 11, 2000;
                    and (ii) as partial consideration for twenty-three (23) of
                    the Holdings Shares and one thousand nine hundred
                    forty-eight (1,948) of the Contributors' Subsidiary Shares
                    to be delivered to Recipient by Prof. Klatzmann at the
                    Closing, stock certificates payable to Escrow Agent for the
                    benefit of Prof. Klatzmann and AVAX representing two hundred
                    thousand (200,000) restricted shares of AVAX Stock with an
                    aggregate market value of One Million Seven Hundred
                    Seventy-Five Thousand and 00/100 United States Dollars (US
                    $1,755,000.00) as of the close of trading on July 11, 2000
                    (collectively and together with sufficient stock transfer
                    forms duly executed in blank, the "ESCROW STOCK
                    CONSIDERATION"). The Escrow Stock Consideration shall be
                    held in escrow in accordance with the Escrow Agreement
                    substantially in the form attached hereto as EXHIBIT F (the
                    "ESCROW AGREEMENT") for the benefit of AVAX and the
                    Contributors for a period of thirty-six (36) months
                    commencing on the Closing Date (the "ESCROW PERIOD") and
                    shall be distributed to the Contributors by the Escrow Agent
                    upon the expiration of the Escrow Period, subject to the
                    provisions of the Escrow Agreement and Section 11.3(d)
                    hereof.

                             (b) ESCROW TAX STOCK CONSIDERATION. At the Closing,
                    Recipient shall deliver to Escrow Agent to be held in
                    escrow: (i) as partial consideration for the remaining
                    twenty-four (24) Contributors' Holdings Shares and one
                    thousand nine hundred forty-eight (1,948) Contributors'
                    Subsidiary Shares to be delivered to Recipient by Prof.
                    Salzmann at the Closing, stock certificates payable to
                    Escrow Agent for the benefit of Prof. Salzmann and AVAX
                    representing thirty-three thousand four hundred twenty-two
                    (33,422) restricted shares of AVAX Stock with an aggregate
                    market value of Two Hundred Ninety-Six Thousand Six Hundred
                    Twenty and 25/100 United States Dollars (US $296,620.25) as
                    of the close of trading on July 11, 2000; and (ii) in
                    consideration for remaining twenty-three (23) Contributors'
                    Holdings Shares and one thousand nine hundred forty-eight
                    (1,948) Contributors' Subsidiary Shares to be delivered to
                    Recipient by Prof. Klatzmann at the Closing, stock
                    certificates payable to Escrow Agent for the benefit of
                    Prof. Klatzmann and AVAX representing twenty-six thousand
                    three hundred thirty-four (26,334) restricted shares of AVAX
                    Stock with an aggregate market value of Two Hundred
                    Thirty-Three Thousand Seven Hundred Fourteen and 25/100
                    United States Dollars (US $233,714.25) as of the close of
                    trading on July 11, 2000 (collectively and together with
                    sufficient stock transfer forms duly executed in blank, the
                    "ESCROW TAX STOCK CONSIDERATION"). The Escrow Tax Stock
                    Consideration shall be held in escrow in accordance with the
                    Escrow Agreement for the benefit of AVAX and the
                    Contributors until such time as the Escrow Agent receives
                    joint written instructions from AVAX and both of the
                    Contributors related to the proper distribution of such
                    Escrow Tax Stock Consideration.

                                        2

<PAGE>

                             (c) CASH CONSIDERATION. At the Closing, Recipient
                    shall deliver: (i) to Prof. Klatzmann, a check in the amount
                    of Two Thousand Five Hundred and 00/100 United States
                    Dollars (US $2,500); and (ii) to Prof. Salzmann, a check in
                    the amount of Two Thousand Five Hundred and 00/100 United
                    States Dollars (US $2,500) (collectively, the "CASH
                    CONSIDERATION").

                             (d) ESCROW INTELLECTUAL PROPERTY STOCK
                    CONSIDERATION. At the Closing, Recipient shall deliver to
                    the Escrow Agent to be held in escrow: (i) stock
                    certificates payable to Escrow Agent for the benefit of
                    Prof. Salzmann and AVAX representing one hundred thousand
                    (100,000) restricted shares of AVAX Stock with an aggregate
                    market value of Eight Hundred Eighty-Seven Thousand Five
                    Hundred and 00/100 United States Dollars (US $887,500.00) as
                    of the close of trading on July 11, 2000; and (ii) stock
                    certificates payable to Escrow Agent for the benefit of
                    Prof. Klatzmann and AVAX representing one hundred thousand
                    (100,000) restricted shares of AVAX Stock with an aggregate
                    market value of Eight Hundred Eighty-Seven Thousand Five
                    Hundred and 00/100 United States Dollars (US $887,500.00) as
                    of the close of trading on July 11, 2000 (collectively and
                    together with sufficient stock transfer forms duly executed
                    in blank, the "ESCROW INTELLECTUAL PROPERTY STOCK
                    CONSIDERATION"). The Escrow Intellectual Property Stock
                    Consideration shall be held in escrow by the Escrow Agent in
                    accordance with the Escrow Agreement for the benefit of AVAX
                    and the Contributors and shall be distributed to the
                    Contributors when and if the Contributors are able to obtain
                    the Resolution of the Intellectual Property Issue (as
                    defined in Article XII hereof) on or before the date that is
                    twenty-four (24) months after the Closing Date.

                             (e) EARN OUT CONSIDERATION; RIGHTS AGREEMENT. At
                    the Closing, Recipient shall deliver to each of Prof.
                    Salzmann and Prof. Klatzmann, as an earn-out payment, a
                    Rights Agreement substantially in the form attached hereto
                    as EXHIBIT G ("RIGHTS AGREEMENT")."

         (B)   The parties hereto agree that the following Section 4.35 is added
to the Contribution Agreement:

               "4.35 PROGENICS TERMINATION. As of the Closing Date, the
         Progenics Termination has been duly and validly executed by all parties
         thereto, is in full force and effect and is binding on each of the
         parties thereto. A facsimile copy of the Progenics Termination executed
         by Progenics has previously been delivered by Prof. Klatzmann to
         Recipient. The Contributors will deliver to Recipient the original
         execution copy of the Progenics Termination within thirty (30) days
         after the Closing Date."

         Except as modified herein, the Contribution Agreement shall remain in
full force and effect.

         SECTION 2. TREATMENT OF TAX MATTER. AVAX hereby agrees that it will
take the action described in one (1) of the steps described in Section A or
Section B below, at its sole option.

                                        3

<PAGE>

         A.    IF AVAX ELECTS TO DEVELOP A PLAN FOR SALE OF STOCK.

               Upon appropriate documentation of the Contributors' Capital Gains
Tax liability reasonably acceptable to AVAX, AVAX may elect to develop a plan
("Plan") whereby it is reasonably anticipated that the Contributors will be able
to sell that number of shares (the "Tax Payment Shares") of AVAX Stock that will
enable the Contributors to pay their Capital Gains Tax to the French government
in September of 2001 and to realize a net value per share of AVAX Stock of no
less than eighty percent (80%) of the Closing Price ("Minimum Price"). The Plan
may be implemented by AVAX at any time during the period beginning on the date
that the precise Capital Gains Tax can be calculated (presumably the Closing
Date) and ending fifteen (15) days prior to the date on which the Contributors
actually pay the Capital Gains Tax to the French tax authorities. The Plan will
include freeing the Tax Payment Shares from the "lock-up" restriction contained
in the Contribution Agreement and, at AVAX's option, causing the Tax Payment
Shares to be "registered" with the U.S. Securities and Exchange Commission. If
AVAX elects to develop such a Plan and it is reasonably anticipated that the
Contributors will realize net per share proceeds from the sale of their Tax
Payment Shares of no less than the Minimum Price, then the Contributors will
have the option of whether to proceed with the Plan or not, in accordance with
the following:

         1.    IF THE CONTRIBUTORS ELECT TO PROCEED WITH THE PLAN. If the
Contributors elect to proceed with the Plan, then AVAX shall arrange for the
sale of the Tax Payment Shares, beginning with the Escrow Tax Stock
Consideration, the Escrow Intellectual Property Stock Consideration and the
Escrow Stock Consideration, in that order, and the proceeds of such sale shall
be used by the Contributors to pay the Contributors' actual capital gains tax
liability as a result of their receipt of AVAX Stock pursuant to the
Contribution Agreement. In such event, AVAX shall have a lien against any and
all shares of AVAX Stock to be received by the Contributors pursuant to either
of the Rights Agreements and such shares shall be made available to and used by
the Escrow Agent to replace the Tax Payment Shares. In the event the Escrow
Period has terminated and the Escrow Agent shall have delivered to AVAX all of
the Escrow Stock Consideration then remaining in escrow, then, upon achievement
of any Milestone(s), AVAX shall be entitled to retain that number of shares of
AVAX Stock that were withdrawn from escrow as Tax Payment Shares and shall
promptly deliver to the Contributors any excess shares of AVAX Stock owing to
the Contributors. In the event the Escrow Period has terminated and the Escrow
Agent shall not have delivered to AVAX all of the Escrow Stock Consideration
then remaining in escrow, then, upon achievement of any Milestone(s), the
Contributors shall be entitled to receive all shares of AVAX Stock then owing to
the Contributors as a result of the achievement of the Milestone(s).

               Within ten (10) days of the Contributors' paying their capital
gains tax to the French authorities in 2001, the Contributors shall provide AVAX
with a copy of each of their capital gains tax returns showing the precise
amount of the capital gains tax actually paid by the Contributors. In the event
the amount of capital gains tax actually paid by the Contributors is less than
the amount of the Capital Gains Tax, then the Contributors shall immediately pay
to AVAX a fee in the amount of the difference, which amount shall immediately
become the sole and exclusive property of AVAX (a "Discrepancy Charge").

         2.    IF THE CONTRIBUTORS DO NOT ELECT TO PROCEED WITH THE PLAN.
If the Contributors do not elect to proceed with the Plan, then AVAX shall be
relieved of, and the Contributors shall be deemed to have conclusively waived
all rights with regard to, any obligation on the part of AVAX to assist the
Contributors with regard to the Tax Matter and this Letter Agreement shall
immediately terminate.

                                        4

<PAGE>

         B.    IF AVAX ELECTS NOT TO DEVELOP A PLAN FOR SALE OF STOCK.

               If AVAX elects not to develop a Plan, or is unable to develop
such a Plan, then AVAX agrees that, upon appropriate documentation of the
Contributors' Capital Gains Tax liability, AVAX will loan to the Contributors on
commercially reasonable terms, including those set forth herein, an amount of
United States Dollars equal to the Capital Gains Tax ("Loan") in exchange for
the execution by each of the Contributors of a Promissory Note ("Note") and a
Pledge Agreement ("Pledge Agreement"), each of which will be subject to the
Uniform Commercial Code then effective in the state of Missouri and in form and
substance reasonably satisfactory to AVAX. The proceeds of the Loan shall be
used by the Contributors to pay the Contributors' actual capital gains tax
liability as a result of their receipt of AVAX Stock pursuant to the
Contribution Agreement. Interest on the Note shall begin to accrue immediately
upon funding and shall be payable at a rate of five percent (5%) per annum. The
principal amount of the Note, together with all interest due thereon, shall be
due and payable on the day immediately preceding the date on which the Escrow
Period (as defined in the Escrow Agreement) expires. The security for the Loan
will be the Pledge Agreement, pursuant to which the Contributors will assign and
pledge to AVAX, and grant AVAX a lien against, all of the Contributors' right,
title and interest in and to all AVAX Stock received, or which may be received
at some later date, by the Contributors pursuant to the Contribution Agreement
and/or pursuant to either Rights Agreement. In the event shares of AVAX Stock
are earned by the Contributors pursuant to the Rights Agreement upon achievement
of any Milestone ("Milestone Shares"), such Milestone Shares shall be placed in
escrow with the Escrow Agent and shall be held in escrow in accordance with and
subject to both the Pledge Agreement and the Escrow Agreement and such shares of
AVAX Stock shall be made part of the Escrow Tax Stock Consideration. If the
Contributors sell shares of AVAX Stock to repay the Note (including interest
thereon), the provisions of Section A1 (above) shall apply to any such sale.

               Upon timely repayment of the Note in full by the Contributors
(including all interest thereon), the Pledge Agreement shall be terminated and
any shares remaining in the Escrow Tax Stock Consideration (including any
Milestone Shares) shall be promptly delivered to the Contributors and released
from the escrow. In the event the Note is not repaid by the Contributors on or
before expiration of the Escrow Period, then as its sole remedy against the
Contributors for the Contributors' failure to repay the Note, AVAX shall be
entitled to all right, title and interest in and to all shares of AVAX Stock
held pursuant to the Escrow Agreement as well as all shares of AVAX Stock that,
but for the execution of the Note and the Pledge Agreement, would otherwise have
been delivered to, or might be earned by, either or both Contributors (including
pursuant to the Rights Agreements) until AVAX has received that number of shares
of AVAX Stock the fair market value of which equals the amount due by the
Contributors pursuant to the Note.

               Within ten (10) days of the Contributors' paying their capital
gains tax to the French authorities in 2001, the Contributors shall provide AVAX
with a copy of each of their capital gains tax returns showing the precise
amount of the capital gains tax actually paid by the Contributors. In the event
the amount of capital gains tax actually paid by the Contributors is less than
the amount of the Capital Gains Tax, then the Contributors shall immediately pay
to AVAX a fee in the amount of the difference, which amount shall immediately
become the sole and exclusive property of AVAX (a "Discrepancy Charge").

               In the event AVAX elects not to develop a Plan but is unable to
fund the Loan to the Contributors, then AVAX agrees that upon the written
request of the Contributors AVAX will use commercially reasonable efforts to
allow the Contributors to sell shares of AVAX Stock held in escrow pursuant to
the Escrow Agreement in accordance with the terms and conditions of Section A
(above).

                                        5

<PAGE>

               AVAX agrees that the Chief Executive Officer will not use his
discretionary powers under the AVAX Sales Policy to prevent the Contributors
from selling those certain shares of AVAX Stock sufficient to enable the
Contributors to pay in September of 2001 their actual capital gains tax
liability as a result of their receipt of AVAX Stock pursuant to the
Contribution Agreement; provided, however, that nothing contained herein shall
be deemed to enable or permit the Contributors to violate applicable securities
laws nor shall anything herein be deemed to require the Chief Executive Officer
of AVAX to do anything that he believes, based on advice of counsel to AVAX,
might be construed as potentially in conflict with any applicable law or
regulation.

               In the event that AVAX funds the Loan, the parties agree to use
commercially reasonable efforts to ensure the sale of shares of AVAX Stock owned
by the Contributors necessary to pay back the Loan (together with all interest
thereon).

               In the event that at the time the Contributors are obligated to
repay the Loan (together with interest thereon) the shares of AVAX Stock have a
value below the Minimum Price per share, AVAX agrees to use commercially
reasonable efforts to allow the Contributors to find alternate financing sources
to repay the Loan (together with all interest thereon).

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

               In the event that the Contributors do not pay any capital gains
tax on the acquisition of AVAX Stock at any time during 2001, AVAX will have no
obligation under this Agreement. In the event that the Contributors sell shares
of AVAX Stock in accordance with Section A above and then do not pay the Capital
Gains Tax to the French authorities in 2001, the Contributors shall immediately
pay to AVAX one-half (1/2) of the amount received by them in exchange for the
shares of AVAX Stock sold by them, which amount shall immediately become the
sole and exclusive property of AVAX (a "Discrepancy Charge"). In the event that
the Contributors receive a Loan from AVAX in accordance with Section B above and
then do not pay the Capital Gains Tax to the French authorities in 2001, then
the full amount of the Loan shall immediately be due and payable on January 1,
2002, and the Contributors shall immediately repay the full amount of the Loan
(with interest) to AVAX plus all of AVAX's reasonable fees (including attorneys
fees) and expenses in making the Loan to the Contributors.

               In the event that circumstances giving rise to a Discrepancy
Charge hereunder are caused because of an action on the part of the French
government that occurs between the date hereof and September of 2001 and reduces
the capital gains tax rate generally applicable to transactions of the nature
contemplated in the Contribution Agreement, then the Contributors shall be
relieved of their obligation to pay to AVAX such Discrepancy Charge; provided,
however, that the Contributors shall immediately place into escrow, subject to
the Escrow Agreement, all proceeds of any nature whatsoever received by them
(together with any proceeds of proceeds and any interest earned thereon)
("Proceeds"), which Proceeds shall, at AVAX's option, be deemed to replace any
shares of AVAX Stock that have previously been withdrawn from escrow in
accordance with the terms hereof or shall be used to pay down any amount
then-owing to AVAX by the Contributors, including all principal and interest
outstanding pursuant to any Loan.

               In the event that the Contributors discover that their capital
gains tax liability to the French government upon their receipt of the 659,756
shares of AVAX Stock pursuant to the Contribution Agreement will be less than
the Capital Gains Tax, they will notify AVAX in writing within five (5) days of
such discovery (a "Tax Notice"). In the event that AVAX receives such a Tax
Notice prior to the time when AVAX begins the implementation a Plan or funds the
Loan, the Contributors shall be relieved of their obligation to pay to AVAX the
relevant Discrepancy Charge; provided, however, that AVAX is

                                        6

<PAGE>

given reasonable advance notice to enable AVAX to reduce the amount of the Loan
and/or to reduce the number of shares of the Contributors' AVAX Stock sold
pursuant to a Plan.

               The parties agree that this letter agreement satisfies the
condition to Closing contained in the Side Letter, and the Side Letter is hereby
terminated and of no further force or effect.

               In addition, the Contributors hereby waive the condition to
Closing contained in Section 9.6(g) of the Contribution Agreement.

               IN WITNESS WHEREOF, the Contributors and AVAX have caused this
Agreement to be executed as of this ____ day of August, 2000.

AVAX TECHNOLOGIES, INC., a Delaware
Corporation ("AVAX")

By:
   ---------------------------------------------
Name:   Jeffrey M. Jonas, M.D.
Title:  President and Chief Executive Officer

GPH, S.A., a French SOCIETE ANONYME ("Holdings")

By:
   ---------------------------------------
Name:   Charles Salzmann
Title:  President Directeur General

GENOPOIETIC, S.A., a French SOCIETE
ANONYME ("Subsidiary")

By:
   ---------------------------------------
Name:   Charles Salzmann
Title:  President Directeur General

------------------------------------
PROF. JEAN-LOUP SALZMANN, an individual
and resident of Paris, France

------------------------------------
PROF. DAVID ROBERT KLATZMANN, an individual
and resident of Paris, France

                                        7

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