MEDAREX INC
8-K, 1998-03-31
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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<PAGE>
 
          As filed with the Securities and Exchange Commission on March 31, 1998

                      SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, DC 20549

                                   FORM 8-K

                                CURRENT REPORT



                    Pursuant to Section 13 or 15(d) of the
                        Securities Exchange Act of 1934

               Date of Report (Date of earliest event reported)
                        March 30, 1998 (March 30, 1998)



                                 MEDAREX, INC.
            (Exact name of registrant as specified in its charter)

         NEW JERSEY                 0-19312                      22-2822175
(State of other jurisdiction     (Commission                    (IRS Employer
    of incorporation)              File Number)              Identification No.)


             1545 Route 22 East, Annandale, New Jersey 08801-0953
                   (Address of Principal Executive Offices)

      Registrant's telephone number, including area code: (908) 713-6001

                                NOT APPLICABLE 
         (Former name or former address, if changed since last report)
<PAGE>
 
                                 MEDAREX, INC.
                               TABLE OF CONTENTS
                                      FOR
                          CURRENT REPORT ON FORM 8-K


ITEM 5.         Other Events.........................................   3

ITEM 7.         Financial Statements and Exhibits....................   4

Signature       .....................................................   5



                                       2
<PAGE>
 
        Item 5.         Other Events.

     This Current Report Form on 8-K is being submitted in order to file certain
material contracts entered into or assumed by Medarex, Inc., including certain
material contracts assumed by Medarex, Inc. in connection with its acquisition
of GenPharm International, Inc.


                                       3
<PAGE>
 
        Item 7.         Financial Statements and Exhibits.

                (c)     Exhibits.  The following materials are filed as exhibits
to this Current Report on Form 8-K:

Exhibit                
Number                           Description of Exhibit
- -------                          ----------------------

10.70                   Cooperative Research and Development Agreement between
                        Eisai Co., Ltd. and GenPharm International, Inc. dated 
                        May 31, 1993

10.71                   Cooperative Research Agreement between LeukoSite, Inc. 
                        and GenPharm International, Inc. dated January 1, 1995

10.72                   Research and Commercialization Agreement between 
                        Centocor, Inc. and GenPharm International, Inc. dated 
                        February 24, 1997

10.73                   Research and License Agreement between Medarex, Inc. and
                        E. Merck, KGaA dated June 26, 1996

10.74                   Development and License Agreement between Medarex, Inc.
                        and Centeon L.L.C. dated April 24, 1996

                                       4
<PAGE>
 
                                   SIGNATURE


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


                                  MEDAREX, INC.
                                   Registrant
                               
                               
Date: March 30, 1998              By: /s/ Donald L. Drakeman
                                      ----------------------
                                          Donald L. Drakeman
                                          President, Chief Executive Officer
                                          and Director


                                       5
<PAGE>

                                 EXHIBIT INDEX
                                 -------------

 
EXHIBIT                                                                 PAGE
NUMBER                           DESCRIPTION                           NUMBER
- -------                          ------------                          ------

10.70                   Cooperative Research and Development 
                        Agreement between Eisai Co., Ltd. and 
                        GenPharm International, Inc. dated 
                        May 31, 1993

10.71                   Cooperative Research Agreement between 
                        LeukoSite, Inc. and GenPharm International, 
                        Inc. dated January 1, 1995

10.72                   Research and Commercialization Agreement 
                        between Centocor, Inc. and GenPharm 
                        International, Inc. dated February 24, 1997

10.73                   Research and License Agreement between 
                        Medarex, Inc. and E. Merck, KGaA dated 
                        June 26, 1996

10.74                   Development and License Agreement between 
                        Medarex, Inc. and Centeon L.L.C. dated 
                        April 24, 1996

                                       6

<PAGE>
 
                                                                   EXHIBIT 10.70

 
                COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENT

        THIS AGREEMENT is made this 31st day of May, 1993 (the "Effective
Date") by and between EISAI CO., LTD. ("Eisai"), a Japanese corporation with its
principal executive offices at 6-10, Koishikawa 4-chome, Bunkyo-ku, Tokyo
112-88, Japan, and GENPHARM INTERNATIONAL, INC. ("GenPharm"), a
California corporation with its principal executive offices at 297 North
Bernardo Avenue, Mountain View, California 94043, United States of America.

                                   RECITALS

        A. Eisai and GenPharm previously executed a letter of intent dated March
30, 1993, contemplating the conduct by GenPharm, with the close cooperation of
Eisai, of a program of research and development with the goal of generation of
anti-CD4 human monoclonal antibodies in transgenic mice suitable for use in
human therapy and diagnostics, and supply by GenPharm to Eisai of preclinical
and clinical grade antibody material for Japanese preclinical and clinical
studies in accordance with the requirements of Japanese regulatory authorities.

        B. The parties wish to set forth their agreement regarding such program
of research and development.

                                   AGREEMENT

        In consideration of their mutual promises and covenants, Eisai and
GenPharm agree as follows:

                            ARTICLE I - DEFINITIONS

        The following terms when used in this Agreement shall have the
respective meanings assigned to them below.


- -----------
Confidential treatment has been requested for portions of this exhibit. The copy
filed herewith omits the information subject to the confidentiality request.  
Omissions are designated as "[*****]".
<PAGE>
 
        1.01 Affiliate of either party or other entity shall mean any 
             ---------
corporation, firm, association or other legal entity that directly or indirectly
controls, is controlled by, or is under common control with, such entity, but
only for so long as said control continues. For purposes of this definition,
"control" means possession of the power, whether or not normally exercised, to
direct the management and affairs of an entity, directly or indirectly, whether
through the ownership of voting securities, by contract or otherwise. In the
case of a corporation, the direct or indirect ownership of 50% or more of its
outstanding voting shares shall in any case be deemed to confer control, while
the ownership of a lower percentage of such securities shall not necessarily
preclude the existence of control.

        1.02 Affiliate and Sublicensee Revenues shall mean all consideration
             ----------------------------------
except for purchase price of Anti-CD4 Antibodies received by Eisai from
Affiliates or sublicensees that is fairly attributable to Eisai's sales of Anti-
CD4 Antibodies or sublicensing of rights under GenPharm Patent Rights or
GenPharm Know-How in Other Asian Countries, including such consideration
received in the form of license fees, initial payments, technical assistance
fees and royalties.

        1.03 Anti-CD4 Antibodies shall mean human anti-CD4 monoclonal antibodies
             -------------------
produced from Transgenic Mice (as hereinafter defined) and developed in the
course of the Research Program (as hereinafter defined).

        1.04 Date of First Commercial Sale shall mean the date on which Anti-CD4
             -----------------------------
Antibodies are first sold by Eisai in Japan in accordance with this Agreement
in a commercial transaction to an unrelated third party.

        1.05 Field of Use shall mean the use of Anti-CD4 Antibodies in human
             ------------
therapy. If expanded in accordance with Section 4.04, Field of Use shall also
include the use of Anti-CD4 Antibodies in human diagnostics.

        1.06 GenPharm Know-How shall mean any information, data and/or materials
             -----------------
possessed, acquired and/or developed by GenPharm on or prior to the Effective
Date or during the term of this Agreement relating to Anti-CD4 Antibodies that
are not generally known or available, which information, data

                                       2
<PAGE>
 
and materials are necessary or useful in order to manufacture, use, conduct
research and/or development relating to, sell or seek approval to market Anti-
CD4 Antibodies and, in particular, any such information, data or materials
relating to processes for preparing, using or formulating or to the
pharmacological, biological or clinical properties of Anti-CD4 Antibodies.

        1.07 GenPharm Patent Rights shall mean:
             -----------------------
            (a) Patents and/or patent applications in the Territory that
                GenPharm now owns or controls or that GenPharm may come to own
                or control at any time during the term of this Agreement as
                listed in Appendix A attached hereto, which Appendix shall be
                promptly revised by the parties to account for any and all
                patents or patent applications that GenPharm may come to own or
                control in the Territory following the Effective Date;

            (b) Patents in the Territory issued from applications described in
                (a) above or from divisionals or continuations of such
                applications;

            (c) Claims of continuation-in-part applications in the Territory,
                and of the resulting patents, which are directed to subject
                matter specifically described in the patents and/or patent
                applications described in (a) or (b) above;

            (d) Claims of all later filed patent applications in the Territory,
                and of the resulting patents, which are directed to subject
                matter specifically described in the patents and/or patent
                applications described in (a), (b), or (c) above; and

            (e) Any reissues of patents described in (a), (b), (c) or (d) above.

        For purposes of this definition, "control" by GenPharm of a patent or
patent application shall mean GenPharm's having the right to grant to Eisai
licenses or sublicenses thereunder within the Field of Use and in the Territory,
without violating any rights of or obligations to third parties. Control may
arise through ownership or license or other contractual rights.

                                       3
<PAGE>
 
        1.08 Net Third Party Sales [*****]
             ---------------------

        1.09 Other Asian Countries shall mean all countries within the Territory
             ---------------------
other than Japan.

        1.10 Product Liability shall mean liability to a third party resulting 
             -----------------
from the consumption, handling or use of Anti-CD4 Antibodies which occurs away
from the premises of GenPharm or Eisai after GenPharm or Eisai have relinquished
possession.

        1.11 Program Committee shall mean [*****]
             -----------------

        1.12 Research Field shall mean the conduct of research and development
             --------------
activities related to the generation of Anti-CD4 Antibodies in Transgenic Mice. 

        1.13 Research Goal shall-mean generation of Anti-CD4 Antibodies in
             -------------
Transgenic Mice, and supply by GenPharm to Eisai of the quantities specified
in Sections 2.03 and 3.04 of preclinical and clinical grade biological material
containing Anti-CD4 Antibodies suitable for Japanese preclinical and clinical


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       4
<PAGE>
 
studies in accordance with the requirements of Japanese regulatory authorities.

        1.14 Research Program shall have the meaning assigned to it in Section
             ----------------
2.01 below.

        1.15 Territory shall mean Japan and the other Asian countries that are
             ---------
listed on Appendix B attached hereto.

        1.16 Transgenic Mice shall mean GenPharm proprietary mice that are
             ---------------
transgenic for unrearranged human immunoglobulin genes.

                         ARTICLE II - RESEARCH PROGRAM

        2.01 Program of Research. In a program of research and development
             -------------------
(the "Research Program"), GenPharm, with the close cooperation of Eisai, shall
use its best efforts, including the provision of qualified personnel, equipment,
materials and facilities, to achieve the Research Goal. An outline of activities
that GenPharm shall perform in the course of the Research Program is
attached hereto as Appendix C. Appendix C may be revised at any time with the
written consent of both parties, which consent shall not unreasonably be
withheld. Eisai may have access to all data and information relating to the
Research Program during the term of the Agreement. The Research Program
shall continue until December 31, 1995, and shall then terminate unless
extended by agreement of the parties.

        2.02 Oversight. The conduct of the Research Program shall be overseen
             ---------
and supervised by the Program Committee. Within 30 days after the end of each
calendar quarter, GenPharm shall provide the Program Committee with research
progress reports containing a reasonably detailed description of the work
conducted by it in the course of the Research Program during the preceding
quarter and of the results thereof. Research progress and results shall be
discussed by the parties at meetings of the Program Committee, which shall bc
held no less frequently than quarterly and more often as need arises.

                                       5
<PAGE>
 
        2.03 Information and Materials for Regulatory Studies. GenPharm shall,
             ------------------------------------------------
without any additional charge, provide Eisai with any and all GenPharm Know-How
in connection with the manufacture, use and sale of Anti-CD4 Antibodies in the
Territory during the term of this Agreement. Eisai may dispatch its scientist(s)
to GenPharm for acquiring GenPharm Know-How during the term of this Agreement
subject to agreement by the parties hereto. 

        Also, GenPharm shall without additional charge provide to Eisai five (5)
grams of preclinical grade and twenty-five (25) grams of clinical grade Anti CD4
Antibody material for use as Eisai may determine in regulatory studies in Japan.
The specifications of said preclinical and clinical grade anti-CD4 Antibody
material shall be determined by agreement of the parties. Moreover, GenPharm
shall provide to Eisai all protocols and results from GenPharm's own preclinical
and clinical study activities so that Eisai may decide upon additional work that
may be necessary to satisfy Japanese regulatory requirements.

        In addition, ten (10) days following its receipt of the first benchmark
payment scheduled in Section 3.02(a), GenPharm shall transfer a working cell
bank to Eisai to enable Eisai to perform feasibility studies or generate
additional antibody material.

        Eisai shall provide to GenPharm the results of all preclinical and
clinical studies conducted by Eisai in Japan for the purpose of Japanese
regulatory requirements. Eisai shall have and retain sole ownership of the
results of all preclinical and clinical studies conducted by Eisai. Eisai hereby
grants to GenPharm a non-exclusive and royalty-free license in the Field of Use
and outside the Territory to use the results of all preclinical and clinical
studies conducted by Eisai (without any right of sublicense except on a basis
where the sublicensee agrees to grant a non-exclusive and royalty-free license
in the Field of Use and in the Territory to Eisai to use the results of
all corresponding preclinical and clinical studies conducted by GenPharm's
sublicensee). 

        2.04 Exclusivity. During the term of this Agreement, GenPharm shall
             -----------
not act within the Research Field and the Territory for anyone other than Eisai.

                                       6
<PAGE>
 
            ARTICLE III - PAYMENTS TO GENPHARM RELATED TO RESEARCH
                                    PROGRAM

        3.01 Research Payments. [*****]
             -----------------

        3.02 Benchmark Payments. [*****]
             ------------------


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       7
<PAGE>
 
[*****]

 
        3.03 Withholding Tax. Payments due to  GenPharm under Sections 3.01 or
             ---------------
3.02(a) and 3.02(b) will be made without any withholding for or on account of
taxes or other charges. If Japanese taxing authorities subsequently determine
that taxes should have been withheld on any such payments and assess Eisai for
such taxes, GenPharm will pay or reimburse Eisai for the taxes so assessed,
together with any interest or penalties required to be paid thereon. GenPharm
agrees to provide any cost information requested by the Japanese taxing
authorities, and otherwise to cooperate with Eisai in seeking to establish that
the payments are not subject to withholding. Any tax which may be required 
by Japanese taxing authorities to be withheld on the payments provided for in
Section 3.02(c) shall be deductible from the payments, provided that Eisai shall


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       8
<PAGE>
 
furnish GenPharm with a copy of the official tax receipt for the payment of such
withholding tax.

        3.04 Supply of Additional Material for Regulatory Studies. For
GenPharm's supply to Eisai of any antibody material for regulatory studies in
Japan in excess of the five (5) grams of preclinical grade material and twenty-
five (25) grams of clinical grade material to be furnished to Eisai in
accordance with Section 2.03, Eisai shall pay GenPharm an amount equal to 
[*****] along with any invoice sent to Eisai.

          ARTICLE IV - OWNERSHIP OF INVENTIONS, GRANT OF LICENSE, AND
                                    PATENTS

        4.01 Ownership of Intellectual Property. Each party shall have and
             ----------------------------------
retain sole ownership of technical information and data, know-how, trade
secrets and inventions, whether or not patented or patentable, developed or
made by its own employees, consultants or agents. The parties shall have joint
ownership of technical information and data, know-how, trade secrets and
inventions (the "Jointly-Owned Technology"), whether or not patented or
patentable, developed or made jointly by employees, consultants or agents of
each party during the term of this Agreement. Each party shall have the right
(with the right to sublicense) to use the Jointly-Owned Technology in
perpetuity for any purpose without accounting to the other party.

        4.02 Filing and Prosecution of Patent Applications. GenPharm shall, at  
             ---------------------------------------------
its own expense, prosecute and maintain the Japanese patent applications
included in the GenPharm Patent Rights. Unless otherwise agreed in writing
by the parties, GenPharm shall, in its own name and at its sole expense, file,
prosecute and maintain in Japan any patent applications relating to Anti-CD4


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       9
<PAGE>
 
Antibodies that GenPharm has filed in any country outside the Territory, and
shall use reasonable efforts to obtain and maintain patent registrations based
on such applications.

        GenPharm may, in its own name and at its sole expense, file, prosecute
and maintain patent applications covering GenPharm Patent Rights in Other Asian
Countries. In the event that GenPharm fails to file, prosecute and maintain a
patent application covering such GenPharm Patent Rights in any Other Asian
Country within sixty (60) days after Eisai has requested that it do so, Eisai
may, in GenPharm's name but at Eisai's sole expense, file, prosecute and
maintain such application in such country. Eisai may recover the costs of any
such patent application filing, etc., by it through deduction from payments due
to GenPharm under Section 5.02 or 5.03 in respect of activities in such country,
but not so as to reduce any such payment, after allowance of any deductions
permitted under Section 5.04, by more than [*****] (if the payment is a royalty
at the rate of [*****] Net Third Party Sales or a [*****] share of Affiliate and
Sublicensee Revenues) or [*****] (if the payment is a royalty at the rate of
***** of Net Third Party Sales or a [*****] share of Affiliate and Sublicensee
Revenues).

        4.03 License. GenPharm hereby grants to Eisai and its Affiliates the
             -------
exclusive (even as to GenPharm) right and license (with the right to sublicense
upon prior written notice to GenPharm, except that sublicensing of manufacturing
rights shall require GenPharm's prior written approval, which approval shall not
unreasonably be withheld) within the Field of Use and in the Territory under the
GenPharm Patent Rights and GenPharm Know How to manufacture, use and sell Anti-
CD4 Antibodies under Eisai's trademarks or trade names, subject to the
obligation to pay royalties to GenPharm in accordance with Article V.

        In case Eisai exercises the right to manufacture Anti-CD4 Antibodies,
Eisai shall give GenPharm at least eighteen (18) months' prior written notice
of its intention to exercise such right.

        The term of this license shall continue until the later of (a) the date
of expiration or other termination of the last to expire or terminate of the
GenPharm Patent Rights in Japan, or (b) fifteen (15) years from the Date of
First Commercial Sale. Following such term, the license under this Section 4.03
shall become non-exclusive, perpetual and royalty-free.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       10
<PAGE>
 
        4.04 Expansion of Field of Use. [*****]
             -------------------------

        4.05 Patents on Jointly-Owned Technology. Eisai shall have the right to
             -----------------------------------
file, in the joint names of GenPharm and Eisai and at Eisai's sole expense,
patent applications in any country in the Territory with respect to Jointly-
Owned Technology. GenPharm shall have the right to file, in the joint names
of GenPharm and Eisai and at GenPharm's sole expense, patent applications in
any country outside the Territory with respect to Jointly-Owned Technology.
In the event that either party elects not to exercise its right to file a patent
application with respect to the Jointly-Owned Technology in any country in
which it had the right to file such application within six (6) months after it
has been requested to do so by the other party, the other party shall have the
right to file an application in such country in its own name and at its sole
expense.

        4.06 Enforcement of Patents Covering Jointly-Owned Technology. Eisai
             --------------------------------------------------------
may, at Eisai's sole expense, enforce patent protection for any patent or
application related to the Jointly-Owned Technology that was filed by Eisai in
any country in the Territory. GenPharm may, at GenPharm's sole expense,
enforce patent protection for any patent or application related to the Jointly-
Owned Technology that was filed by GenPharm in any country outside the
Territory. In the event either party elects not to enforce patent protection 
for any patent covering Jointly-Owned Technology filed by it, the other party 
may do so in its own name and at its sole expense. The party enforcing patent
protection in accordance with this Section may retain any damages awarded in
enforcement proceedings.

        4.07 Cooperation. The parties agree to cooperate with and inform each
             -----------
other with respect to patent filing and enforcement for the Jointly-Owned
Technology and GenPharm Patent Rights.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       11
<PAGE>
 
                 ARTICLE V - ROYALTIES AND BULK PURCHASE PRICE

        5.01 Supply Agreement. Upon request of Eisai, GenPharm agrees to
             ----------------
supply Eisai with bulk Anti-CD4 Antibodies under separate agreement to be
entered into between the parties.

        5.02 Earned Royalties. [*****]
             ----------------


        5.03 Affiliate and Sublicensee Revenues. [*****]
             ----------------------------------


        5.04 Third Party Royalties. [*****]
             ---------------------


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       12
<PAGE>
 
[*****]

        5.05 Bulk Purchase Price. [*****]
             -------------------


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       13
<PAGE>
 
[*****]
        5.06 Warranty. GenPharm will warrant that any bulk Anti-CD4 Antibodies
             --------
supplied by it to Eisai, under a bulk supply agreement as set forth in Section
5.01 shall conform in all respects to the specifications to be agreed upon in
writing by the parties in due course.

        5.07 Regulatory Compliance. GenPharm shall comply with all applicable
             ---------------------
cGMP's and cGLP's relating to Anti-CD4 Antibodies. The term "cGMP's" means the
current Good Manufacturing Practices as described in Title 21 of the United
States Code of Federal Regulations, Parts 210 and 211, as in effect from time to
time. The term "cGLP's" means the current Good Laboratories Practices as
described in Title 21 of the United States Code of Federal Regulations, Part 58,
as in effect from time to time.

        5.08 Diligent Effort. Eisai shall diligently endeavor to commercialize
             ---------------
Anti-CD4 Antibodies within the Field of Use in [*****]

        5.09 Payments. Computations and Records
             -----------------------------------

        (a) Earned royalty payments and payments of Affiliate and Sublicensee
Revenues shall be due within forty-five (45) days after the close of the
calendar quarter in which they accrue. Each payment shall be accompanied by a
report setting forth the following:

            (i)   the amount of Net Third Party Sales, by product and country 
                  of sale;

            (ii)  the amount of Affiliate and Sublicensee Revenues, by product
                  and country of sale or sublicensing; and        

            (iii) the amount of royalty or share of Affiliate and Sublicensee
                  Revenues due for the quarter.

        (b) Payments hereunder shall be made in United States dollars or in


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       14
<PAGE>
 
such other currency or currencies as the parties may agree, subject to
deduction of any taxes or other charges required to be paid or withheld under
applicable laws, regulations or threaty, provided a copy of the official tax
receipt or other official receipt for any such deduction is furnished to the
payee. Net Third Party Sales or Affiliate and Sublicensee Revenues not
denominated in United States dollars and the amounts payable thereon shall
first be determined in the currency in which such Net Third Party Sales or
Affiliate and Sublicensee Revenues were realized, and shall then be convened
into the equivalent number of United States dollars at the average of the
closing buying and selling exchange rates, two days prior to the date of
payment, established by the Tokyo foreign exchange market.

        (c) Interest shall accrue and be payable on overdue payments at the
rate of 10% per annum.

        (d) Eisai shall keep full and accurate books and records setting forth
its and its Affiliates' and sublicensees' gross sales or other transfers for
value of Anti-CD4 Antibodies and sublicensing activities hereunder, the Net
Third Party Sales and Affiliate and Sublicensee Revenues, and the amounts
payable to GenPharm as provided above.

        Eisai shall permit independent certified public accountants selected by
GenPharm and reasonably acceptable to Eisai to examine such books and
records upon reasonable notice during normal working hours, but not later
than two years following the payment in question, for the purpose of
verifying the reports, accountings and payments hereunder. Such
independent accountants shall not disclose to GenPharm any cost data or other
confidential information of Eisai or its Affiliates or sublicensees. The opinion
of such independent accountants regarding such report, accountings and payments
shall be binding on the parties hereto. The fees and expenses of the independent
accountants shall be paid by GenPharm, except that if the opinion of the
independent accountants shows that less than 95% of the amounts due to GenPharm
has been reported and paid, such fees and expenses shall be paid by Eisai.

                                       15
<PAGE>
 
                       ARTICLE VI - TERM AND TERMINATION

        6.01 Term and Termination. This Agreement shall be deemed to have
             --------------------
become effective on the Effective Date, and shall expire upon expiration of the
term of the exclusive license granted under Section 4.03. This Agreement may
be terminated:

             (a) at any time, upon agreement of the parties;

             (b) by Eisai, upon 180 days' notice to GenPharm;

             (c) by either party immediately, if the other party materially
                 defaults in the performance of any of its obligations hereunder
                 and such default continues uncured for a period of ninety (90)
                 days after the date of written notice of such default; or

             (d) by either party immediately, if the other party shall have
                 become insolvent or bankrupt, or any case or proceeding shall
                 have been commenced by or against the other party in bankruptcy
                 or seeking liquidation, dissolution or winding-up, and any such
                 event shall have continued for sixty (60) days without being
                 dismissed, bonded or discharged (during which period Eisai's
                 payment obligations to GenPharm hereunder shall be suspended).

        6.02 Effect of Expiration or Termination. The expiration or termination
             ------------------------------------
of this Agreement shall not affect the rights or obligations of the parties that
have accrued prior to such expiration or termination. Article VII shall survive
the expiration or termination of this Agreement.

        6.03 Termination Due to Delay or Failure to Generate Antibodies. If the
             ----------------------------------------------------------
Research Program is delayed substantially from the schedule set forth in 
Appendix C attached hereto for any reason whatsoever, including resignation or
departure of key GenPharm employees, or GenPharm fails to generate, as confirmed
by Eisai, Anti-CD4 Antibodies in Transgenic Mice, with specificity and affinity
as defined in Appendix D, by March 31, 1994, Eisai may give notice to GenPharm
of its intention to terminate this Agreement if the delay in the Research
Program or failure to generate antibodies is not cured within the

                                       16
<PAGE>
 
next 240 days (during which period Eisai's payment obligations to GenPharm
shall be suspended).

        At the end of such 240 day period if no such cure has been effected, and
for the ensuing thirty (30) days (or such further period as the parties may
agree), Eisai shall have the right to terminate this Agreement by notice to
GenPharm. In such event, the license granted to Eisai in Section 4.03 shall
terminate, but GenPharm shall provide to Eisai all GenPharm Know-How and
biological materials relating to Anti-CD4 Antibodies developed during the term
of this Agreement for Eisai's use on such terms and conditions, including
reasonable compensation to GenPharm, as the parties may agree. The parties
shall endeavor in good faith to agree upon terms and conditions for the use of
such know-how and materials that would be fair to each. If they are unable to
agree, the matter shall be resolved in accordance with Section 8.13.

        6.04 Rights After Termination Due to Breach by GenPharm. In the event
             ---------------------------------------------------
that Eisai terminates this Agreement in accordance with the provisions of
Section 6.01(c) or (d), the license granted to Eisai in Section 4.03 shall
survive and become royalty-free. In such event, GenPharm shall provide to Eisai,
without charge, all GenPharm Know-How and biological materials relating to Anti-
CD4 Antibodies developed during the term of this Agreement, for Eisai's use as
permitted by the terms of such license.

        6.05 Rights After Termination Due to Breach by Eisai. In the event that
             -----------------------------------------------
GenPharm terminates this Agreement in accordance with the provisions of
Section 6.01(c) or (d), the license granted to GenPharm in Section 2.03 shall
survive. In such event, Eisai shall provide to GenPharm, without charge, all
results of preclinical and clinical studies conducted by Eisai under this
Agreement, for GenPharm's use as permitted by the terms of such license.

                       ARTICLE VII - CONFIDENTIALITY

        During the term of this Agreement and thereafter until the expiration
of five (5) years from the date of receipt thereof, each party shall keep
strictly confidential, and shall not use for any purpose other than the matter
hereof, any and all information and materials received from the other party
which

                                       17
<PAGE>
 
the disclosing party designates as confidential ("Confidential Information and
Materials"). Information and materials developed by GenPharm in the course
of the Research Program shall be deemed to be Confidential Information and
Materials disclosed to Eisai by GenPharm. There shall not be considered as
Confidential Information and Materials any information or materials which:

             (a)   is or are already part of the public domain at the time of
                   disclosure or generation under this Agreement or thereafter
                   becomes or become part of the public domain otherwise than by
                   breach of this confidentiality obligation; 

             (b)   the receiving party can show by competent proof had already
                   come into its possession without violation of this Agreement
                   at the time of disclosure or generation under this Agreement;
                   or
             (c)   is communicated by a third party which did not receive the
                   same directly or indirectly from either party or from any
                   other party under a binder of confidentiality.

        Each party may disclose Confidential Information or Materials with the
prior written approval of the disclosing pany, to third parties having a valid
need to know and who enter into confidentiality agreements with the
disclosing party containing restrictions on further disclosure and use no less
stringent than the provisions of this Article VII, or as it deems necessary

             (a)   in obtaining, maintaining, prosecuting or defending patents
                   in accordance with Sections 4.02, 4.05 and 4.06 above;
             (b)   in prosecuting or defending litigation;
             (c)   in connection with clinical trials or as otherwise required
                   for obtaining regulatory approvals; or
             (d)   in complying with applicable laws or regulations or
                   fulfilling the disclosure requirements of any securities 
                   regulatory agency or securities exchange in the event of a 
                   securities offering by it;

provided that it gives the disclosing party prior notice of such disclosure and
takes reasonable actions to limit the disclosure.

        Upon expiration or termination of this Agreement, each party shall
promptly deliver to the other party all records in its possession or control

                                       18
<PAGE>
 
containing Confidential Information furnished to it by, and all Confidential
Materials belonging to, the other party, other than an archival set to be
retained by its legal department for compliance purposes.

        Notwithstanding the foregoing, either party may retain all records in
its possession or control containing Confidential Information and all
Confidential Materials furnished to it by the other that directly relates to any
of its license rights that survive such expiration or termination.

                         ARTICLE VIII - MISCELLANEOUS

        8.01 Regulatory Matters. Eisai shall endeavor, with the close
             ------------------
cooperation of GenPharm, to obtain regulatory approvals and authorizations
required for the commercialization of Anti-CD4 Antibodies within the Field of
Use [*****]

        8.02 Adverse Drug Experiences. Each party shall promptly provide the
             ------------------------
other party with any information that it possesses with respect to adverse drug
experiences associated with Anti-CD4 Antibodies.

        8.03 Independent Contractor. Nothing in this Agreement is intended or
             ----------------------
shall be deemed to constitute a partnership, agency, employer-employee or joint
venture relationship between the parties. All activities by the parties
hereunder shall be performed by them as independent contractors. Neither party
shall incur any debts or make any commitments for or on behalf of the other
party, unless specifically authorized in writing by an officer of the other
party. 

        8.04 DISCLAIMER OF WARRANTIES: LIMITATION OF LIABILITY. UNLESS
             ---------------------------------------------------
OTHERWISE EXPRESSLY PROVIDED IN THIS AGREEMENT, GENPHARM DISCLAIMS ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT. IN NO
EVENT SHALL EITHER PARTY BE LIABLE FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES
ARISING OUT OF ANY BREACH OF THIS AGREEMENT.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       19
<PAGE>
 
        8.05 Risk. Unless otherwise provided for in this Agreement, each party
             ----
assumes any and all risks of personal injury or property damage attributable
to the negligent acts or omissions of that party or the officers, employees or
agents thereof. Unless otherwise provided for in this Agreement, each party
shall indemnify the other party and its officers, directors, employees and
agents against and hold them harmless from any loss, damage, liability or
expense (including legal costs) resulting from the indemnifying party's
conduct.

        8.06 Representation Regarding GenPharm Patent Rights. [*****]
             -----------------------------------------------


        In the event that Eisai has reason to believe that a third party is
infringing upon the rights granted hereunder in the Territory, Eisai shall
notify GenPharm, and GenPharm may, at GenPharm's sole expense, promptly
take legal action against such third party. Eisai shall cooperate with
GenPharm with respect to such legal action. If GenPharm does not take legal
action or proceed diligently with such legal action within a reasonable time
after receipt of such notice from Eisai, Eisai shall have the right, at Eisai's
sole expense, to take legal action, and GenPharm shall reimburse Eisai for its
entire expenses related to such legal action. If GenPharm takes such legal
action, any damages that may be recovered, after reimbursement to GenPharm
of its costs of litigation, including attorneys' fees, shall be divided equally
between the parties. If Eisai takes such legal action, any damages that may be
recovered may be retained by Eisai.

        8.07 General Indemnification.
             -----------------------

        [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



                                       20
<PAGE>
 
[*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



                                       21
<PAGE>
 
[*****]


        8.08 Limitations on Assignment. Neither this Agreement nor any
             -------------------------
interest hereunder shall be assignable by either party by operation of law or
otherwise without the prior written consent or agreement of the other, except
in connection with the sale by GenPharm of all or substantially all of its
assets to any person or entity other than a major Japanese pharmaceutical
company or its Affiliate. This Agreement shall inure to the benefit of and shall
be binding upon the parties and their successors and permitted assigns, and the
name of a party appearing herein shall be deemed to include the names of such
party's successors and permitted assigns to the extent necessary to carry out
the intent of this Agreement.

        8.09 Further Acts and Instruments. Each party agrees to execute,
             ----------------------------
acknowledge and deliver such further instruments and to do all such other
acts as may be necessary or appropriate to carry out the purpose and intent of
this Agreement.

        8.10 Entire Agreement; Amendment. This Agreement constitutes and
             ---------------------------
contains the entire agreement of the parties with respect to its subject matter,
and supersedes all prior negotiations, correspondence, understandings and
agreements between the parties respecting the subject matter hereof. This
Agreement may be amended or modified or one or more provisions hereof may be
waived only by a written instrument signed by authorized officers of both
parties.

        8.11 Severability. Whenever possible, each provision of this Agreement
             ------------
shall be interpreted in such a manner as to be effective and valid under
applicable law, but if any provision of this Agreement is held to be prohibited
by or invalid under applicable law, said provision shall be ineffective only to


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       22
<PAGE>
 
the extent of such prohibition or invalidity, without invalidating the remainder
of such provision or the remaining provisions of this Agreement.

        8.12 Headings and Captions. The headings and captions contained in this
             ---------------------
Agreement are for convenience only, and are to be of no force or effect in
construing and interpreting the provisions of this Agreement.

        8.13 Disputes. Any controversy or claim arising out of or relating to
             --------
this Agreement or the breach or alleged breach thereof which the parties fail to
settle amicably shall be finally settled by arbitration in accordance with the
Japan-American Trade Arbitration Agreement of September 16, 1952, by which each
party shall be bound.

        If the arbitration is demanded by GenPharm, it shall be held in Tokyo,
Japan, and if the arbitration is demanded by Eisai, it shall be held in San
Francisco, California, U.S.A.

        8.14 No Waiver for Failure to Enforce Compliance. Failure of either
             -------------------------------------------
party to insist upon strict observance of or compliance with any of the terms of
this Agreement in one or more instances shall not be deemed to be a waiver of
its rights to insist upon observance of or compliance with such term thereafter,
or with any of the other terms of this Agreement.

        8.15 No Trademark or Trade Name License. Neither party shall have any
             ----------------------------------   
right to use, for advertising, publicity .or other commercial purposes, the name
or any trade name or trademarks, or contraction, abbreviation or simulation
thereof, of the other party without the latter's prior written consent. 

        8.16 No Announcements. Neither party shall make any announcements or
             ----------------   
otherwise make public any information concerning this Agreement or GenPharm's
business dealings with Eisai except as approved by the other, which approval
shall not unreasonably be withheld; provided, however, that either party may
disclose such information in complying with applicable laws or regulations or
fulfilling the disclosure requirements of any securities regulatory agency or
securities exchange in the event of a securities offering by it.

                                       23
<PAGE>
 
        8.17 Notices. Any notice, report, request, approval, payment, consent or
             -------
other communication required or permitted to be given under this Agreement shall
be in writing and shall, for all purposes, be deemed to be fully given and
received if delivered in person or sent by registered mail, postage prepaid, to
the respective parties at their respective addresses set forth at the head of
this Agreement or by facsimile transmission to the following facsimile
telephone number of the party:

        Eisai: (03) 3811-1459 
        GenPharm: (415) 964-3537

Either party may change its address or facsimile telephone number for facsimile
transmission for the purpose of this Agreement by giving the other party written
notice of its new address or facsimile telephone number.

        IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed in duplicate by their respective authorized officers.

                                EISAI CO., LTD.

                                    /s/ Haruo Naito
                                By: Haruo Naito
                                Title: President, CEO

Attested by
/s/ Tatsuo Kowsoki
Director Logistic Licensing
and International Relations

                                GENPHARM INTERNATIONAL, INC.

                                     /s/ Jonathan MacQuitty 
                                By: Jonathan MacQuitty 
                                Title: Chief Executive Officer

Attested by
/s/ Thomas Edwin Woodhouse
Law Office
Thomas Edwin Woodhouse

                                       24
<PAGE>
 
                                 CONFIDENTIAL
                                 ------------

                                  APPENDIX A
                                  ----------

<TABLE> 
<CAPTION> 

                                                                              International   National
DOCKET NO.       Country      Title/Subiect                 Inventor(s)       Serial No.      Serial No.          Status/Action
- ----------       -------      -------------                 -----------       -------------   ----------          -------------
<S>              <C>          <C>                           <C>               <C>             <C>                 <C>           
106-2JP          Japan        TRANSGENIC NON-HUMAN          LONBERG, KAY      PCT/US91/06185  NOT YET AVAILABLE   ENTERED NATIONAL
(14643-5JP)                   ANIMALS CAPABLE OF                                                                  PHASE 02/28/93;
                              PRODUCING HETEROLOGOUS                                                              08/28/98 REQUEST
                              ANTIBODIES                                                                          EXAMINATION

106-2KR          Korea        TRANSGENIC NON-HUMAN          LONBERG, KAY      PCT/US91/06185  93-700594           ENTERED NATIONAL
(l4643-5KR)                   ANIMALS CAPABLE OF                                                                  PHASE 02/28/93
                              PRODUCING HETEROLOGOUS
                              ANTIBODIES

107-lJP          Japan        HOMOLOGOUS RECOMBINATION IN   KAY, BERNS        PCT/US91/05917  NOT YET AVAILABLE   ENTERED NATL.
(14643-32JP)                  MAMMALIAN CELLS               KRIMPENFORT                                           PHASE 02/28/93;
                                                            PIEPER, STRIJKER                                      08/28/98 REQUEST
                                                                                                                  EXAMINATION

109-2PC          PCT          TRANSGENIC IMMUNODEFICIENT    TERHORST, HUANG   PCT/US92/04823        --            ENTER NATIONAL
(14643-33-lPC)                NON-HUMAN ANIMALS                                                                   PHASE 12/14/93

110-lPC          PCT          GENE TARGETING IN ANIMAL      BERNS, ROBANUS    PCT/US92/07184        --            ENTER NATIONAL
(14643-3-lPC)                 CELLS USING ISOGENIC DNA      MAANDAG, TE RIELE                                     PHASE 02/20/94
                              CONSTRUCTS

112-2PC          PCT          TRANSGENIC NON-HUMAN          LONBERG, KAY      PCT/US92/10983        --            07/17/93 ELECT
(14643-9-2PC)                 ANIMALS FOR PRODUCING                                                               CHAPTER II
                              HETEROLOGOUS ANTIB0DIES
</TABLE> 
<PAGE>
 
                                  APPENDIX B

                    List of the Countries in the Territory
                    --------------------------------------

                                    [*****]




***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                  APPENDIX C

                                    [*****]





***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                    [*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 

        [*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                ATTACHMENT C-1



                                    [*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                  APPENDIX D


[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                ATTACHMENT D-1

[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                ATTACHMENT D-1

[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                ATTACHMENT D-2

[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                              AMENDMENT NO. 1 TO
                COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENT

        THIS AMENDMENT is effective as of the 10th day of October, 1995,
and amends the Cooperative Research and Development Agreement effective May
31,1993 (the "Agreement") between EISAI Co., LTD. and GENPHARM INTERNATIONAL,
INC. ("GenPharm").

        The parties to the Agreement hereby amend the Agreement as follows:

        [*****]

        IN WITNESS WHEREOF, this Amendment has been signed by or on behalf
of the parties to the Agreement as of the date first set forth above.

EISAICO., LTD.

BY: /s/ Haruo Naito
Name: Haruo Naito
Title: CEO

GENPHARM INTERNATIONAL, INC.    

By: /s/ Jonathan MacQuitty
Name: J. J. MacQuitty
Title:  CEO



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

<PAGE>
 
                                   GENPHARM
                                INTERNATIONAL 

                              AMENDMENT NO. 2 TO
                COOPERATIVE RESEARCH AND DEVELOPMENT AGREEMENT

        THIS AMENDMENT is effective as of the a 26th day of April, 1996, and
amends the Cooperative Research and Development Agreement effective May 31, 1993
(the "Agreement") between EISAI CO., LTD. and GENPHARM INTERNATIONAL, INC.
("GenPharm"), as previously amended by Amendment No. 1 thereto effective as of
October 10, 1995.

        The parties to the Agreement hereby agree as follows:

        [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
        IN WITNESS WHEREOF, this amendment has been signed by or on behalf of
the parties to the Agreement as of the date first set forth above.

EISAI CO., LTD. 

By: /s/ Hanuo Naito
Name: Hanuo Naito
Title: CEO

GENPHARM INTERNATIONAL, INC.    

By: /s/ Jonathan MacQuitty
Name:   J.J. MacQuitty
Title:  CEO
<PAGE>
 
                                  SCHEDULE 1

[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



<PAGE>
 
                                                                   EXHIBIT 10.71

                        COOPERATIVE RESEARCH AGREEMENT

THIS AGREEMENT is made effective as of January 1, 1995 (the "Effective Date"),
by and between LEUKOSITE, INC. (the "Company"), a Delaware corporation with
offices at 215 First St., Cambridge, Massachusetts 02142, and GENPHARM
INTERNATIONAL, INC. ("GenPharm"), a California corporation with offices at 297
North Bernardo Avenue, Mountain View, California 94043.


                                   RECITALS

A.   LeukoSite is a biopharmaceutical company with expertise in the area of
     leukocyte recruitment and adhesion processes and related technologies to 
     diagnose and treat diseases.

     GenPharm is a biotechnology company with expertise in the area of genetic
     modification of animals. The parties believe that it will be in their
     mutual benefit to collaborate in a program of research and development in
     which the Company will supply its proprietary antigens and GenPharm will
     inject such antigens into its proprietary transgenic mice in order to
     produce human antibodies against such antigens.

B.   The parties wish to set forth their agreement regarding such collaborative
     program of research and development.


                                   AGREEMENT

in consideration of their mutual promises and covenants, the Company and
GenPharm agree as follows:


                         ARTICLE 1 - RESEARCH PROGRAM

1.01 Program of Research. In a collaborative program of research and development
     -------------------
     (the "Research Program"), GenPharm and the Company shall use their
     reasonable best efforts, including the provision of qualified personnel,
     equipment, materials and facilities, to perform the respective activities
     set forth in the project outline attached hereto as Appendix A. Appendix A
     may be revised at any time with the written consent of GenPharm and the
     Company. The parties shall keep each other fully informed on a regular and
     frequent basis of their respective research activities and of the results
     thereof.

1.02 Costs and Expenses. Each party shall be responsible for all direct and
     ------------------
     indirect costs and expenses of work to be performed and biological
     materials to be supplied by it under the Research Program.

1.03 Exclusivity. During the term of this Agreement, neither party shall conduct
     -----------
     research activities in the field of the Research Program for or in
     collaboration with any third person or entity other than the other party.


- ------------
Confidential treatment has been requested for portions of this exhibit. The copy
filed herewith omits the information subject to the confidentiality request. 
Omissions are designated as "[*****]".
<PAGE>
 
      ARTICLE II - OWNERSHIP, PRACTICE AND PATENTS OF RESEARCH INVENTIONS

2.01 Ownership of Intellectual Property. "Research Inventions" are know-how,
     ----------------------------------
     trade secrets and inventions, whether or not patented or patentable,
     including but not limited to patents and patent applications as well as
     intellectual property rights based thereon, that are developed, made,
     conceived or first actually reduced to practice by GenPharm or the Company
     (or their respective employees, consultants or agents), or by the parties
     jointly, in the course of the Research Program. Each party shall have and
     retain sole ownership of Research inventions that are attributable
     exclusively or principally to itS own (or its employees', consultants' or
     agents') research activities, and the parties shall jointly own Research
     Inventions that are attributable to the joint research activities of the
     parties.

2.02 Practice of Research Inventions. Each party hereby grants to the other a
     -------------------------------
     world-wide co-exclusive (exclusive as to all the world except itself),
     royalty-free, transferable and/or sublicensable (to a single person or
     entity only) license under the granting party's rights in Research
            ----
     Inventions to make, have made, use and sell antibodies or derivatives of
     antibodies which are the subject of the Research Program or antigens or
     derivatives of antigens which are the subject of the Research Program for
     any purpose, without right to grant sub-licenses, except to a single person
     or entity as provided above. Each party hereby also grants to the other a
     non-exclusive, royalty-free, non-transferable license under all Research
     Inventions owned by the granting party for research purposes only,
     without right to grant sublicenses. Each party grants to the other party a
     world-wide, non-exclusive, royalty-free license under any and all other
     intellectual property rights owned or controlled by the granting party
     including but not limited to patent applications, patents, know-how,
     materials, data and information to the extent required to enable the other
     party to make, have made, use and sell antibodies and antigens and/or
     derivatives of such antibodies or antigens which are the subject of the
     Research Program in accordance with the foregoing coexclusive license.
     Where the licensed intellectual property rights are controlled by the
     granting party by virtue of a royalty-bearing license from a third party
     the grantee party shall be sublicensed to the extent that such sublicense
     can be granted and provided that the grantee agrees to the applicable terms
     and conditions of the license from the third party and that any royalties
     that may be required to be paid to the third party owing to activities of
     the grantee party within the scope of its license hereunder shall be paid
     by the grantee party to the third party or reimbursed by the grantee party
     to the granting party. However, it is the intention of the parties to seek
     to exploit Research Inventions commercially for the parties' mutual
     benefit, whether through cross-licensing, formation of a joint venture or
     other means. Accordingly, the parties agree to engage in good faith
     negotiations regarding terms and conditions for commercial exploitation of
     Research Inventions for their mutual benefit.

2.03 Patents. The parties agree to cooperate in patent related activities in
     -------
     respect of Research Inventions, and to share equally the costs of jointly
     owned Research Inventions related to patent protection. If the parties are
     unable to agree on whether
<PAGE>
 
     or how to seek or enforce patent protection for any jointly owned Research
     Invention, then either party may at its expense but in the name and on
     behalf of the parties jointly, seek or enforce patent protection therefor.


                       ARTICLE III - TERM AND TERMINATION

This Agreement shall be deemed to have become effective on the Effective Date,
and shall continue in effect for one year thereafter. Upon agreement of the
parties, this Agreement may be extended to allow completion of the Research
Program, or modified to encompass other collaborative efforts of the parties.
This Agreement may be terminated:

(a)  at any time, upon agreement of the parties;

(b)  by GenPharm or the Company immediately, if the other defaults in the
     performance of any of its obligations hereunder and such default continues
     uncured for a period of 30 days after the date of written notice of such
     default; or

(c)  by GenPharm or the Company immediately, if the other shall have become
     insolvent or bankrupt or any case or proceeding shall have been commenced
     by or against the other party in bankruptcy or seeking liquidation,
     dissolution or winding-up, and any such event shall have continued for 60
     days without being dismissed, bonded or discharged.

The expiration or termination of this Agreement shall not affect the rights or
obligations of the parties that have accrued prior to such expiration or
termination, including their respective rights and obligations under Article II.
Article IV shall survive the expiration or termination of this Agreement.


      ARTICLE IV - CONFIDENTIAL AND PROPRIETARY INFORMATION AND MATERIALS

Biological materials supplied by either party to the other or used in the
Research Program shall remain the confidential and proprietary property of the
supplying party. At the conclusion of the Research Program or upon termination
of this Agreement, all biological materials shall, at the supplying party's
direction, be returned to the supplying party or destroyed, except to the extent
required to exercise the rights and licenses granted under Article II.

During the term of this Agreement and thereafter, each party shall keep strictly
confidential, and shall not use for any purpose other than the Research Program,
and with respect to the rights and licenses granted under Article II, any and
all information and materials received from the other party which the disclosing
party designates as confidential ("Confidential Information and Materials").
There shall not be considered as Confidential Information and Materials any
information or materials which:
<PAGE>
 
(a)  is or are already part of the public domain at the time of disclosure or
     generation under this Agreement or thereafter becomes or become part of the
     public domain otherwise than by breach of this confidentiality obligation;

(b)  the receiving party can show by competent proof had already come into its
     possession without violation of this Agreement at the time of disclosure or
     generation under this Agreement;

(c)  is communicated by a third party which did not receive the same directly or
     indirectly from either party or from any other party under a binder of
     confidentiality; or

(d)  the receiving party can show by competent proof was independently developed
     by such party.

Each party may disclose Confidential Information or Materials with the prior
written approval of the disclosing party, or to third parties having a valid
need to know and who enter into confidentiality agreements with the disclosing
party containing restrictions on further disclosure and use no less stringent
than the provisions of this Article, or as it deems necessary in obtaining,
maintaining, prosecuting or defending patents in accordance with Section 2.03,
prosecuting or defending litigation, or complying with applicable laws or
regulations, provided that it gives the disclosing party prior notice of such
disclosure and takes reasonable actions to limit the disclosure.

Each party's scientists shall have the right to publish results of their
respective research activities under the Research Program, provided that
GenPharm and the Company are acknowledged in the publication as research
collaborators and GenPharm is acknowledged as the source of the transgenic mice
and rats used in the Research Program, and provided further that initial such
publication shall feature both parties' scientists as co-authors. A copy of each
proposed publication shall be provided to both parties for review and comment at
least 45 days prior to publication and, if either party wishes to obtain patent
protection, the proposed publication shall either be withheld from publication
until a mutually satisfactory patent application has been prepared and filed, or
modified to delete reference to such research results.

Upon expiration or termination of the Agreement, each party shall promptly
deliver to the disclosing party all records in its possession or control
containing Confidential Information furnished to it by the disclosing party,
other than an archival set which may be retained by its legal department or
representative for compliance purposes and other than that which is useful in
exercising the rights and licenses granted under Article II.
<PAGE>
 
                            ARTICLE V - ARBITRATION

Any and all claims, disputes or controversies arising under, out of or in
connection with this Agreement which have not been resolved by good faith
negotiations between the parties, shall be resolved by final and binding
arbitration in San Francisco, California, under rules of the American
Arbitration Association then obtaining. The arbitrators shall have no power to
add to, subtract from or modify any of the terms or conditions of this Agreement
or to decide any matter or issue or dispute other than those submitted to
arbitration. Any award rendered in such arbitration may be enforced by either
party in any court of competent jurisdiction. Nothing in this Article V shall
prevent a party from instituting a court action for injunctive relief.


                          ARTICLE VI - MISCELLANEOUS

6.01 Independent Contractor. Nothing in this agreement is intended or shall be
     ----------------------
     deemed to constitute a partnership, agency or employer-employee
     relationship between the parties. All activities by the parties hereunder
     shall be performed by them as independent contractors. Neither party shall
     incur any debts or make any commitments for or on behalf of the other
     party, unless specifically authorized in writing by an officer of the other
     party.

6.02 Risk. Each party assumes any and all risks of personal injury or property
     ----
     damage attributable to the negligent acts of omissions of that party or the
     officers, employees or agents thereof. Each party shall indemnify the other
     party and its officers, directors, employees and agents against and hold
     them harmless from any loss, damage, liability or expense (including legal
     costs) resulting from the indemnifying party's conduct of the Research
     Program.

6.03 Limitations on Assignment. Except as provided in Article 11, neither this
     -------------------------
     Agreement nor any interest hereunder shall be assignable by any party by
     operation of law or otherwise without the prior written consent or
     agreement of the others, except in connection with the sale of all its
     assets. This Agreement shall inure to the benefit of and shall be binding
     upon the parties and their successors and permitted assigns, and the name
     of a party appearing herein shall be deemed to include the names of such
     party's successors and permitted assigns to the extent necessary to carry
     out the intent of this Agreement.

6.04 Further Acts and Instruments. Each party agrees to execute, acknowledge and
     ----------------------------
     deliver such further instruments and to do all such other acts as may be
     necessary or appropriate to carryout the purpose and intent of this
     Agreement.
<PAGE>
 
6.05 Entire Agreement: Amendment. This Agreement constitutes and contains the
     ---------------------------
     entire agreement of the parties with respect to its subject matter, and
     supersedes all prior negotiations, correspondence, understandings and
     agreements between the parties respecting the subject matter hereof. This
     Agreement may be amended or modified or one or more provisions hereof may
     be waived only by a written instrument signed by authorized officers of
     both parties.

6.06 Severability. Whenever possible, each provision of this Agreement shall be
     ------------
     interpreted in such a manner as to be effective and valid under applicable
     law, but if any provision of this Agreement is held to be prohibited by or
     invalid under applicable law, said provision shall be ineffective only to
     the extent of such prohibition or invalidity, without invalidating the
     remainder of such provision or the remaining provisions of this Agreement.

6.07 Headings and Captions. The headings and captions contained in this
     ---------------------
     Agreement are for convenience only, and are to be of no force or effect in
     construing and interpreting the provisions of this Agreement.

6.98 Applicable Law. This Agreement shall be construed in accordance with the
     --------------
     laws of the State of California as applied to agreements executed and to be
     performed entirely within such State.

6.09 Notices. Any notice, report, request, approval, payment, consent or other
     -------
     communication required or permitted to be given under this Agreement shall
     be in writing and shall, for all purposes, be deemed to be fully given and
     received if delivered in person or sent by registered mail, postage
     prepaid, to the respective parties at their respective addresses set forth
     at the head of this Agreement or by confirmed facsimile transmission to the
     following facsimile telephone number or the party.

        LeukoSite, Inc.                       (617) 621-9349 
        GenPharm:                             (415) 964-3537

Either party may change its address or telephone number for facsimile
transmission for the purpose of this Agreement by giving the other party written
notice of its new address or facsimile telephone number.
<PAGE>
 
IN WITNESS WHEREOF, the parties have caused this Agreement to be executed in
duplicate by their respective authorized officers.

GENPHARM INTERNATIONAL, INC.                   LEUKOSITE, INC.

By:  /s/ Jonathan MacQuitty                    By: /s/ C.K. Mirabelli
    ----------------------------                   ----------------------------
Title:  CEO                                    Title:  CEO & Chairman
       -------------------------                      -------------------------
Date:   1/4/95                                 Date:   12/22/94
      --------------------------                     --------------------------
<PAGE>
 
       LeukoSite:GenPharm Collaborative Research Program (January, 1995)


        [*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                                                      APPENDIX A

[*****]




***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                              AMENDMENT NO. 1 TO
                        COOPERATIVE RESEARCH AGREEMENT

     THIS AMENDMENT is made effective as of January 1, 1996, by and between
GenPharm International, Inc., a California corporation ("GenPharm"), and
LeukoSite, Inc., a Delaware corporation ("LeukoSite"), and amends the
Cooperative Research Agreement effective as of January 1, 1995 (the "Effective
Date") between the same parties (the "Agreement").

     WHEREAS, Article III of the Agreement provides that it shall continue in
effect for one year after the Effective Date, unless extended by agreement of
the parties; and

     WHEREAS, the parties wish to confirm their agreement to extend the term 
of the Agreement;

     NOW, THEREFORE, GenPharm and LeukoSite agree that the Agreement shall
continue in effect until December 31, 1997, unless further extended by agreement
of the parties.

     IN WITNESS WHEREOF, the parties have caused this Amendment to be executed
in duplicate by their respective authorized officers.


GENPHARM INTERNATIONAL, INC.                   LEUKOSITE, INC.

By:  /s/ Jonathan MacQuitty                    By: /s/ C.K. Mirabelli
    ----------------------------                   ----------------------------
Title:  CEO                                    Title:  CEO & Chairman
       -------------------------                      -------------------------
Date:   9/10/96                                Date:   9/19/96
      --------------------------                     --------------------------
<PAGE>
 
                              AMENDMENT NO. 2 TO
                        COOPERATIVE RESEARCH AGREEMENT

THIS AMENDMENT is made effective as of December 1, 1996, by and between GenPharm
International, Inc., a California corporation ("GenPharm"), and LeukoSite, Inc.,
a Delaware Corporation ("LeukoSite"), and amends the Cooperative Research
Agreement effective as of January 1, 1995 between the same parties, as amended
by Amendment No. 1 effective as of January 1, 1996 (the "Agreement").

WHEREAS, Article 1.01 of the Agreement provides that the Research Program of the
Agreement may be revised by the written consent of GenPharm and LeukoSite; and

[*****]

IN WITNESS WHEREOF, the parties have caused this Amendment to be executed in
duplicate by their respective authorized officers.


GENPHARM INTERNATIONAL, INC.                   LEUKOSITE, INC.

By:  /s/ Jonathan MacQuitty                    By: /s/ C.K. Mirabelli
    ----------------------------                   ----------------------------
Title:  CEO                                    Title:  CEO & Chairman
       -------------------------                      -------------------------
Date:   11/27/96                               Date:   12/5/96
      --------------------------                     --------------------------



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SEPARATELY WITH THE SEC.
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<PAGE>
 
[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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<PAGE>
 
[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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<PAGE>
 
                                ACKNOWLEDGMENT

[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



<PAGE>
 
                                                                   EXHIBIT 10.72

                   RESEARCH AND COMMERCIALIZATION AGREEMENT

        THIS AGREEMENT is made this 24th day of February, 1997 (the "Effective 
Date") by and between CENTOCOR, INC. ("Centocor"), a Pennsylvania corporation 
with its principal executive offices at 200 Great Valley Parkway, Malvern, 
Pennsylvania 19355-1307, and GENPHARM INTERNATIONAL, INC. ("GenPharm"), a 
California corporation with its principal executive offices at 855 California 
Avenue, Suite C, Palo Alto, California 94304.

                                   RECITALS

        A. Centocor wishes to have access to GenPharm's HuMAb-Mouse(TM) system 
to enable it to recover and characterize human monoclonal antibodies resulting 
from immunization of GenPharm's transgenic mice with specified antigens, and to 
have an option to obtain an exclusive license to commercialize some or all of 
such resulting antibodies.

        B. The parties wish to set forth their agreement regarding the terms 
and conditions upon which such access and option for a commercial license will
be provided to Centocor.

                                   AGREEMENT

        In consideration of their mutual promises and covenants, Centocor and 
GenPharm, each intending to be legally bound, agree as follows:

                            ARTICLE I - DEFINITIONS

        The following terms when used in this Agreement shall have the 
respective meanings assigned to them below.


- -----------
Confidential treatment has been requested for portions of this exhibit. The copy
filed herewith omits the information subject to the confidentiality request.  
Omissions are designated as "[*****]".
<PAGE>
 
        1.01 Affiliate of either party or other entity shall mean any
             ---------
corporation, firm, association or other legal entity that directly or
indirectly controls, is controlled by, or is under common control with,
such entity, but only for so long as said control continues. For purposes of
this definition, "control" means possession of the power, whether or not
normally exercised, to direct the management and affairs of an entity,
directly or indirectly, whether through the ownership of voting securities,
by contract or otherwise. In the case of a corporation, the direct or indirect
ownership of 50% or more of its outstanding voting shares shall in any
case be deemed to confer control, while the ownership of a lower
percentage of such securities shall not necessarily preclude the existence of
control.

        1.02 Commercial Field shall mean the making, having made, use
             ----------------
and sale of Licensed Antibodies.

        1.03 Commercial License shall have the meaning assigned to it in
             ------------------
Section 3.01.

        1.04 GenPharm Know-How shall mean any information, data
             -----------------
and/or materials possessed, acquired and/or developed by GenPharm on or
prior to the Effective Date or during the term of this Agreement relating
to the subject matter of the Research License (including immunization of
Transgenic Mice and generation of Resulting Antibodies) or the subject
matter of the Commercial License that are not generally known or
available.

        1.05 GenPharrn Patent Rights shall mean any patents and/or patent
             -----------------------
applications relating to the subject matter of the Research License
(including immunization of Transgenic Mice and generation of Resulting
Antibodies) or the subject matter of the Commercial License that GenPharm
now owns or controls or that GenPharm may come to own or control at
any time during the term of this Agreement, and any divisionals,
continuations, continuations-in-part or reissues of such patents or patent
applications. The GenPharm Patent Rights include the issued patents listed

                                       2
<PAGE>
 
on Attachment 1, and shall include all patent rights of GenPharm that are
necessary for commercialization of Licensed Antibodies.

        For purposes of this definition, "control" by GenPharm of a patent
or patent application shall mean GenPharm's having the right to grant to
Centocor licenses or sublicenses thereunder within the Research Field or
the Commercial Field, without violating any rights of or obligations to
third parties. Control may arise through ownership or license or other
contractual rights.

        1.06 Licensed Antibodies shall mean Resulting Antibodies covered
             -------------------
by the Commercial License.

        1.07 [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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                                       3
<PAGE>
 
occurs away from the premises of Centocor after Centocor has relinquished
possession.

        1.09 Research Field shall mean immunization of Transgenic Mice with 
             --------------
Specified Antigens, and recovery and characterization of Resulting Antibodies,
for research purposes only, including preclinical and animal testing of
Resulting Antibodies.

        1.10 Research License shall have the meaning assigned to it in 
             ----------------
Section 2.01.

        1.11 Resulting Antibodies shall mean human monoclonal antibodies 
             --------------------
resulting directly or indirectly from immunization of Transgenic Mice with 
Specified Antigens in accordance with the Research License.

        1.12 Specified Antigens shall mean the following antigens:[*****]
             ------------------

        1.13 Transgenic Mice shall mean GenPharm proprietary transgenic mice 
             ---------------
containing unrearranged human immunoglobulin genes.

                         ARTICLE II - RESEARCH LICENSE

        2.01 License Grant. GenPharm hereby grants to Centocor a nonexclusive 
             -------------
research license, without sublicense rights, under the GenPharm Patent Rights
and the GenPharm Know-How within the Research Field (the "Research License").
The term of the Research License shall be one year, but shall be renewable for
an additional year by Centocor by notice given to GenPharm no later than 90 days
prior to the expiration of the initial term. GenPharm shall give to Centocor (at
Centocor's expense) such reasonable assistance as Centocor may request relative
to Centocor's activities under the Research License, and Centocor shall disclose
to GenPharm all data and information developed by Centocor in the course of such
activities.

***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       4
<PAGE>
 
        2.02 Provision of Transgenic Mice. GenPharm shall provide Centocor 
             ----------------------------
with up to ***** immunizable sterile Transgenic Mice per year of the then
current strain during the term of the Research License, with the first [*****]
such mice being shipped within 30 days after the Effective Date. If any such
mice die of natural causes before commencement of the immunization protocol or
for any reason during the immunization protocol, provided that their death was
not due to Centocor's misfeasance or negligence, they shall be replaced without
cost by GenPharm. Subsequent shipments of Transgenic Mice shall be in quantities
and at times to be agreed. Centocor shall not breed Transgenic Mice, use them
for any purpose other than activities under the Research License, or transfer
them to any other person or entity or to any place other than Centocor's
facilities in Malvern, Pennsylvania. Title to the Transgenic Mice shall at all
times remain with GenPharm. Upon expiration or termination of the Research
License Centocor shall return all Transgenic Mice to GenPharm, and, except as
otherwise provided in Section 3.02, shall destroy all Resulting Antibodies and
other biological materials derived from Transgenic Mice, and all cells capable
of producing Resulting Antibodies.

        2.03 Injunctive Relief. Centocor acknowledges that limitations and 
             -----------------
restrictions on its possession and use of Transgenic Mice and other biological 
materials hereunder are necessary and reasonable to protect GenPharm, and 
expressly agrees that monetary damages would be inadequate to compensate 
GenPharm for any violation by Centocor of any such limitations or restrictions. 
Centocor acknowledges that any such violation would cause irreparable injury to
GenPharm and agrees that, in addition to any other remedies that may be
available in law, in equity or otherwise, GenPharm shall be entitled to obtain
temporary and permanent injunctive relief against any threatened violation of
such limitations or restrictions or the continuation of any such violation in
any court of competent jurisdiction, without the necessity of proving actual
damages.

        2.04 Ownership of Inventions. Any inventions made by Centocor or its 
             -----------------------
employees, consultants or agents in the course of activities under the Research 
License that are or relate to cells, antibodies, genes, DNA sequences or other 
biological materials derived directly or indirectly from

***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       5
<PAGE>
 
Transgenic Mice shall be owned by GenPharm, subject to the provisions of Article
III should Centocor obtain a commercial license. All other such inventions shall
be owned by Centocor.

        2.05 License Fee. In consideration of the Research License, Centocor 
             -----------
shall pay GenPharm an annual license fee of [*****] during the term of the 
Research License. The license fee for the initial one year term of the Research
License shall be due and payable on the Effective Date, and the license fee for
the renewed term of the Research License, if Centocor exercises its right for a
renewed term, shall be due and payable on the first day of the renewed term.

                  ARTICLE III - OPTION FOR COMMERCIAL LICENSE

        3.01 License. GenPharm hereby grants to Centocor and its Affiliates the 
             -------
option to obtain an exclusive (even as to GenPharm), worldwide license, without
sublicense rights, under the GenPharm Patent Rights and the GenPharm Know-How
within the Commercial Field as to one or more Resulting Antibodies derived from
immunization with Specified Antigens (the "Commercial License"), provided that
GenPharm has not granted any licenses to antibodies to that Specified Antigen
within the Commercial Field to third parties prior to Centocor's exercise of its
option, subject to the obligation of Centocor to make benchmark payments to
GenPharm in accordance with Section 3.04 and to pay royalties to GenPharm in
accordance with Section 3.05. The term of the Commercial License for each
Licensed Antibody shall commence on the date of Centocor's exercise of its
option for that Licensed Antibody, and continue until the earlier of [*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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                                       6
<PAGE>
 
[*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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                                       7
<PAGE>
 
[*****]

        (b) Each payment of royalties shall be accompanied by a written
statement setting forth the calculation of Net Sales for the quarter by Licensed
Antibody, and the number or quantity of each Licensed Antibody sold during the
quarter.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       8
<PAGE>
 
        (c) GenPharm shall have the right to cause an examination of all
relevant books and records of Centocor and its Affiliates to be made by an
independent accounting firm upon reasonable notice during regular business
hours and no more frequently than once for any year solely to verify information
necessary to assure the accuracy of Centocor's calculation and reporting of Net
Sales. The cost of such examinations shall be borne by GenPharm, except that if
the results of any such examination show an underpayment of royalties of 5% or
more in any calendar quarter, all costs of such examination shall be borne by
Centocor.

        (d) Only one royalty shall be due and payable for the sale of a Licensed
Antibody, irrespective of the number of claims within the GenPharm Patent
Rights which cover the making, use or sale of such Licensed Antibody.

        (e) Any tax required to be withheld by Centocor under the laws of any
foreign country for the account of GenPharm shall be promptly paid by Centocor
for and on behalf of GenPharm to the appropriate governmental authority, and
Centocor shall use its best efforts to furnish GenPharm with proof of payment of
such tax. Any such tax actually paid on GenPharm's behalf shall be deducted from
royalty payments due GenPharm.

        [*****]

                 ARTICLE IV - REPRESENTATIONS, WARRANTIES AND 
                                   INDEMNITY

        4.01 [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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                                       9
<PAGE>
 
[*****]


        (b) Centocor represents and warrants to GenPharm that it has full power,
right and authority to enter into and carry out its obligations under this
Agreement.

        4.02 Warranties Limitation. EXCEPT FOR THE EXPRESS WARRANTIES IN 
             ---------------------
SECTION 4.01, GENPHARM MAKES NO WARRANTIES TO CENTOCOR, AND CENTOCOR MAKES NO
WARRANTIES TO GENPHARM, EXPRESS OR IMPLIED, EITHER IN FACT OR BY OPERATION OF
LAW, STATUTORY OR OTHERWISE. GENPHARM SPECIFICALLY DISCLAIMS ANY IMPLIED
WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
NONINFRINGEMENT. IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR ANY INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF ANY BREACH OF THIS AGREEMENT.

        4.03 Disclaimer of Other Commitments. Nothing in this Agreement or 
             -------------------------------
other dealings between the parties shall be construed as, and GenPharm
disclaims, any: (i) warranty or representation by GenPharm as to the validity or
scope of any of the GenPharm Patent Rights; (ii) warranty or representation by
GenPharm that the practice by Centocor of the rights and licenses granted to
Centocor herein will not infringe the patent or other intellectual property
rights of any third party; (iii) obligation of GenPharm to bring or prosecute
any action or suit against third parties for patent infringement; or (iv) grant
by implication, estoppel or otherwise of a right or license under any patent or
other intellectual property rights of GenPharm other than the GenPharm Patent
Rights and the GenPharm Know-How.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                       10
<PAGE>
 
                  ARTICLE V - PATENT PROSECUTION, ENFORCEMENT
                               AND INFRINGEMENT

        5.01 Patent Prosecution.
             ------------------
             (a) GenPharm shall take all action reasonably necessary and
appropriate to prosecute the patent applications within the GenPharm Patent
Rights, and all divisions, continuations or continuations-in-part thereof,
worldwide, to seek prompt issuance of all patents from such patent applications,
and to maintain all patents within the GenPharm Patent Rights (including
without limitation inventor's certificates) and all substitutions, extensions,
reissues and renewals thereof or therefor.

             (b) GenPharm shall, to the extent practicable, keep Centocor
informed as to the status of each patent application and each patent within the
GenPharm Patent Rights, including without limitation providing copies of all
relevant written communications from and with all patent offices, and shall
consult with Centocor on all relevant responses to such patent offices
sufficiently in advance of submission of any such response to permit Centocor to
review such response and to provide comments to GenPharm for consideration for
inclusion by GenPharm into such response.

        5.02 Patent Enforcement. During the term of any Commercial License,
             ------------------
GenPharm shall institute and conduct legal action as it deems appropriate in its
reasonable judgment against third party infringers of any of the GenPharm Patent
Rights within the Commercial Field relating to such Commercial License. GenPharm
shall not enter into any settlement agreement respecting alleged infringement
within the Commercial Field without the consent of Centocor, which consent shall
not be unreasonably withheld or delayed. GenPharm shall receive the full benefit
of any action it takes pursuant to this Section 5.02.

[*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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                                       11
<PAGE>
 
[*****]


                       ARTICLE VI - TERM AND TERMINATION

        6.01 Term and Termination. This Agreement shall be deemed to have become
             --------------------
effective on the Effective Date, and shall expire upon expiration or termination
of the Research License or, if Centocor has exercised its option for a
Commercial License under Section 3.01, upon expiration or termination of the
Commercial License. This Agreement and the Research License and Commercial
License may be terminated:
             (a) at any time, upon agreement of the parties;
             (b) by Centocor, upon 90 days' prior written notice to GenPharm;
             (c) by either party immediately, if the other party materially
        defaults in the performance of any of its obligations hereunder and
        such default continues uncured for a period of 30 days after the date
        of written notice of such default.

        6.02 Effect of Expiration or Termination. The expiration or
             -----------------------------------
termination of this Agreement shall not affect the rights or obligations of
the parties that have accrued prior to such expiration or termination.
Article VII shall survive the expiration or termination of this Agreement.

                         ARTICLE VII - CONFIDENTIALITY

        During the term of this Agreement and thereafter until the
expiration of five years from the end of the term of the Research License,
each party shall keep strictly confidential, and shall not use for any purpose
other than the matter hereof, any and all information and materials
received from the other party which the disclosing party designates as
confidential ("Confidential Information and Materials"). There shall not be


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
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                                       12
<PAGE>
 
considered as Confidential Information and Materials any information or
materials which:

             (a) is or are already part of the public domain at the time of
        disclosure or generation under this Agreement or thereafter becomes
        or become part of the public domain otherwise than by breach of this
        confidentiality obligation;
             (b) the receiving party can show by competent proof had already
        come into its possession without violation of this Agreement at the time
        of disclosure or generation under this Agreement; or
             (c) is communicated by a third party which did not receive the same
        directly or indirectly from either party or from any other party under a
        binder of confidentiality.
        Each party may disclose Confidential Information or Materials, with the
prior written approval of the original disclosing party, to third parties having
a valid need to know and who enter into confidentiality agreements with the
original disclosing party containing restrictions on further disclosure and use
no less stringent than the provisions of this Article VII, or as it deems
necessary

             (i) in obtaining, maintaining, prosecuting or defending patents
        in accordance with this Agreement and in prosecuting or defending
        litigation;

             (ii) in connection with clinical trials or as otherwise required
        for obtaining regulatory approvals; or

             (iii) in complying with applicable laws or regulations or
        fulfilling the disclosure requirements of any securities regulatory
        agency or securities exchange in the event of a securities offering by
        it;
provided that it gives the original disclosing party prior notice of such
disclosure and takes reasonable actions to limit the disclosure.
        Upon expiration or termination of this Agreement, each party shall
promptly deliver to the other party all records in its possession or control
containing Confidential Information furnished to it by, and all Confidential
Materials belonging to, the other party, other than an archival set to be
retained by its legal department for compliance purposes.

                                       13
<PAGE>
 
                         ARTICLE VIII - MISCELLANEOUS

        8.01 Independent Contractor. Nothing in this Agreement is intended or
             ----------------------
shall be deemed to constitute a partnership, agency, employer-employee or joint
venture relationship between the parties. All activities by the parties
hereunder shall be performed by them as independent contractors. Neither party
shall incur any debts or make any commitments for or on behalf of the other
party, unless specifically authorized in writing by an officer of the other
party.

        8.02 Risk. Centocor assumes any and all risks of personal injury or
             ----
property damage attributable to its negligent acts or omissions or those of
its officers, employees or agents. Centocor shall indemnify GenPharm and
its officers, directors, employees and agents against and hold it and them
harmless from any loss, damage, liability or expense (including legal costs)
resulting from Centocor's activities under the Research License or the
Commercial License.

        8.03 Indemnification. Each party shall indemnify the other and its
             ---------------
Affiliates and their officers, directors, employees and agents against and hold
it and them harmless from any loss or damage incurred by the indemnified party
on account of any material misstatement or omission in the representations and
warranties of the indemnifying party set forth in Section 4.01, or arising out
of any breach of this Agreement by the indemnifying party. Centocor shall
indemnify GenPharm, its Affiliates and its sublicensees and their officers,
directors, employees and agents against and hold them harmless from any and all
claims to the extent that such claims arise out of Centocor's intentional
misconduct or negligence in the manufacture, use, distribution and/or sale of
Licensed Antibodies. Centocor shall assume any and all Product Liability with
respect to Licensed Antibodies that are distributed and/or sold by it.

        8.04 Limitations on Assignment. Neither this Agreement nor any interest
             -------------------------
hereunder shall be assignable by either party by operation of law or otherwise
without the prior written consent or agreement of the other, except to an
Affiliate or in connection with a merger with or the sale of all

                                       14
<PAGE>
 
or substantially all of its assets to any person or entity. This Agreement shall
inure to the benefit of and shall be binding upon the parties and their
successors and permitted assigns, and the name of a party appearing herein shall
be deemed to include the names of such party's successors and permitted assigns
to the extent necessary to carry out the intent of this Agreement. In the event
of a merger or sale of assets of GenPharm, the obligation of Centocor to
purchase GenPharm stock pursuant to Section 3.03 shall be converted to an
obligation to purchase corresponding stock of the surviving or acquiring
company.

        8.05 Further Acts and Instruments. Each party agrees to execute,
             ----------------------------
acknowledge and deliver such further instruments and to do all such other acts
as may be necessary or appropriate to carry out the purpose and intent of this
Agreement.

        8.06 Entire Agreement: Amendment. This Agreement constitutes and
             ---------------------------
contains the entire agreement of the parties with respect to its subject matter,
and supersedes all prior negotiations, correspondence, understandings and
agreements between the parties respecting the subject matter hereof. This
Agreement may be amended or modified or one or more provisions hereof may be
waived only by a written instrument signed by authorized officers of both
parties.

        8.07 Severability. Whenever possible, each provision of this Agreement
             ------------
shall be interpreted in such a manner as to be effective and valid under
applicable law, but if any provision of this Agreement is held to be prohibited
by or invalid under applicable law, said provision shall be ineffective only to
the extent of such prohibition or invalidity, without invalidating the remainder
of such provision or the remaining provisions of this Agreement.

        8.08 Headings and Captions. The headings and captions contained in this
             ---------------------
Agreement are for convenience only, and are to be of no force or effect in
construing and interpreting the provisions of this Agreement.

                                       15
<PAGE>
 
        8.09 Disputes. Any and all claims, disputes or controversies arising
             --------
under, out of, or in connection with this Agreement which have not been resolved
by good faith negotiations between the parties, shall be resolved by final and
binding arbitration under the Licensing Agreement Arbitration Rules of the
American Arbitration Association then obtaining. The arbitration shall take
place in San Francisco, California if invoked by Centocor or in Philadelphia,
Pennsylvania if invoked by GenPharm. The arbitrators shall have no power to add
to, subtract from or modify any of the terms or conditions of this Agreement.
Any award rendered in such arbitration may be enforced by either party in a
federal district court sitting in the Northern District of the State of
California or in the Eastern District of Pennsylvania, to whose jurisdiction for
such purposes the parties each hereby irrevocably consent and submit.

        The parties agree that the arbitrators shall have no authority to award
injunctive or other equitable relief, including punitive or exemplary damages
against either party. Notwithstanding their agreement to submit, or any
submission of, their disputes to binding arbitration, the parties shall be free
to seek injunctive or other equitable relief in a federal district court sitting
in the Northern District of the State of California or in the Eastern District
of Pennsylvania, to whose jurisdiction for such purposes the parties each hereby
irrevocably consent and submit.

        8.10 No Waiver for Failure to Enforce Compliance. Failure of either
             -------------------------------------------
party to insist upon strict observance of or compliance with any of the terms of
this Agreement in one or more instances shall not be deemed to be a waiver of
its rights to insist upon observance of or compliance with such term thereafter,
or with any of the other terms of this Agreement. If either party wishes to
waive any of its rights hereunder, it shall do so in writing delivered to the
other party.

        8.11 No Trademark or Trade Name License. Neither party shall have any
             ----------------------------------
right to use, for advertising, publicity or other commercial purposes, the name
or any trade name or trademarks, or contraction, abbreviation or simulation
thereof, of the other party without the latter's prior written consent.

                                       16
<PAGE>
 
        8.12 No Announcements. Neither party shall make any announcements or
             ----------------
otherwise make public any information concerning this Agreement or either
party's business dealings with the other except as approved by the other, which
approval shall not unreasonably be withheld; provided, however, that either
party may disclose such information in complying with applicable laws or
regulations or fulfilling the disclosure requirements of any securities
regulatory agency or securities exchange in the event of a securities offering
by it. It is intended by the parties that a mutually agreed announcement
regarding the execution of this Agreement shall be made shortly after the date
of such execution.

        8.13 Notices. Any notice, report, request, approval, payment, consent or
             -------
other communication required or permitted to be given under this Agreement
shall be in writing and shall, for all purposes, be deemed to be fully given and
received if delivered in person or by overnight courier to the respective
parties at their respective addresses set forth at the head of this Agreement.

        Either party may change its address for the purpose of this Agreement by
giving the other party written notice of its new address.

        IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed in duplicate by their respective authorized officers.

                                CENTOCOR, INC.
                                By: /s/ David P. Holveck
                                   ------------------------------
                                Name:  David P. Holveck
                                     ----------------------------
                                Title: President and 
                                       Chief Executive Officer
                                      ---------------------------
                                Date: 2-25-97
                                      ---------------------------

                                GENPHARM INTERNATIONAL,
                                INC.
                                By:  /s/ Jonathan MacQuitty
                                     ----------------------------
                                Name:    Jonathan MacQuitty
                                     ----------------------------
                                Title:       CEO
                                      ---------------------------
                                Date:        2/25/97
                                      ---------------------------

                                       17
<PAGE>
 
                                 ATTACHMENT I
                            GENPHARM INTERNATIONAL

<TABLE> 
<CAPTION>                                                                         U.S. SERIAL 
  PATENT APPLICATION            INVENTORS               ASSIGNEE                 NO/PATENT NO. 
<S>                             <C>                     <C>                      <C> 
1. Transgenic Non-Human         Lonberg, Kay            GenPharm International   5,545,806
   Animals for Producing                                                         August 13, 1996
   Heterologous
   Antibodies

2. Transgenic Non-Human         Lonberg, Kay            GenPharm International   5,569,825
   Animals Capable of                                                            October 29, 1996
   Producing Heterologous
   Antibodies of Various
   Isotypes

3. Transgenic Mice              Krimpenfort, Berns      GenPharm International   5,591,669
   Depleted in a Mature                                                          January 7, 1997
   Lymphocytic Cell-Type
</TABLE> 

                                       18

<PAGE>
 
                                                                   EXHIBIT 10.73

                        RESEARCH AND LICENSE AGREEMENT
                        ------------------------------

between

MEDAREX KGaA
1545 Route 22 East
Annandale, NJ 08801-0953
USA

(hereinafter called MEDAREX)

and

Merck KGaA
Frankfurter Strasse 250
64293 Darmstadt
Germany

(hereinafter called MERCK)



PREAMBLE
- --------

WHEREAS, MEDAREX is a research based biotechnology corporation and is developing
therapeutics on its patented Bispecific antibody technology such as for the
treatment of cancer;

WHEREAS, MERCK is also engaged in the development of therapeutics based on
Bispecific antibodies and in the possession of related patents and know-how;

WHEREAS, the parties like to cooperate in the development of a Bispecific
composed of MERCK's humanized anti-EGF receptor antibody MAB 425 linked to
MEDAREXs humanized anti-Fc RI antibody Mab 22 (PROJECT 1) and in additional
projects and have signed a Letter of Intent as of 30 March 1994;

WHEREAS, the parties are willing to grant each other certain licenses under its
patent rights to be defined herein below under the terms and conditions
hereinafter set forth;

WHEREAS, the parties in their territories defined herein below like to
commercialize products resulting from their cooperation in the field of oncology
(EGF-receptor positive tumors);

NOW, THEREFORE it is agreed between the parties as follows:

ARTICLE I - DEFINITIONS
- -----------------------

1.1      The term "FIELD" shall mean the project as laid down in APPENDIX 1 to
    this Agreement.


- -------------
Confidential treatment has been requested for portions of this exhibit. The copy
filed herewith omits the information subject to the confidentiality request. 
Omissions are designated as "[*****]".
<PAGE>
 
                                      -2-



1.2      The term "RESULTS" shall mean all result generated by either party in
    the commencement of the work on the FIELD.

1.3      The term "PATENT RIGHTS" shall mean all patents and patent applications
    and patents issuing thereon claiming any RESULTS.

1.4      The term "MERCK COMPOUNDS" shall mean the monoclonal antibodies
    described (including existing patent rights on such MERCK COMPOUNDS) in
    APPENDIX 2 which may be amended by the parties from time to time.

1.5      The term "MEDAREX COMPOUNDS" shall mean the himanized anti-FcRI
    antibody MAB 22 described (including existing patent rights on such MEDAREX
    COMPOUNDS) in APPENDIX 3.

1.6      The term "PRODUCTS" shall mean all products resulting from the
    cooperation in the FIELD incorporating both the MEDAREX COMPOUNDS and MERCK
    COMPOUNDS.

1.7      "RESTRICTED INFORMATION" shall mean any information which is
    disclosed by either party to the other pursuant to or in connection with
    this Agreement (whether orally or in writing and whether or not such
    information is expressly stated to be confidential or is marked as such).

1.8      The term "MERCK TERRITORY" shall mean all European countries including
    Russia and Turkey.

1.9      The term "MEDAREX TERRITORY" shall mean the United States of
    America.

1.10     The term "DEVELOPMENT PLAN" or "WBS" shall mean the plan for the
    conduct of the research and development of the PRODUCTS as agreed by the
    parties and as may be amended by the parties from time to time.

1.11     The term "AFFILIATE" shall mean any entity which is directly or
    indirectly controlled by or is under common control with a party or the
    partners of either party, control being the ownership directly or indirectly
    of more than 50 (fifty) percent of the outstanding voting stock of the
    corporation or other business entity.

1.12     The term "NET SALES" shall mean [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                      -3-

1.13      The term "NET ROYALTIES" shall mean royalties paid by independent, non
     affiliated sublicensees of a party less value added tax (V.A.T.).

ARTICLE II - JOINT DEVELOPMENT
- ------------------------------

2.1      The parties shall exchange immediately after signing the Agreement
    their know-how in the FIELD. The parties agree to exert their best efforts
    to conduct the development of PRODUCTS in accordance with the DEVELOPMENT
    PLAN.

2.2      The parties agree to extablish within one month from the date of this
    Agreement a research committee [*****] as laid down in APPENDIX 4 which 
    shall review the development of PRODUCTS on a regular basis, at least
    quarterly. The research committee shall also be responsible for any
    alterations of the WBS. In case the research committee cannot agree on the
    activities of the parties the decision shall be taken by [*****]

2.3      [*****]

2.4      [*****]

2.5      [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                      -4-


    [*****]

2.6      [*****]

2.7      [*****]

2.8      The parties upon wish of one party agree to enter into good faith
    negotiations regarding additional projects in the FIELD.

ARTICLE III - PATENTS, PATENT INFRINGEMENT
- ------------------------------------------

3.1      Any invention independently made by either party without the use of the
    COMPOUNDS of the other party shall belong to such party.

3.2      Patentable inventions jointly made under this Agreement shall be
    jointly owned by the parties and jointly be applied for patent or like
    protection. A joint application for patent or like protection shall be
    considered to be based on equal contributions of MEDAREX and MERCK unless
    the parties agree on differing quotas for their respective contributions.

3.3      In the event of joint inventions the parties shall mutually agree upon
    the countries in which patent or like protection is to be sought and on
    their quotas of the patenting costs. MERCK shall be responsible for filing
    patent applications of joint inventions. Latest 2 (two) months before filing
    MERCK shall send to MEDAREX copy of the suggested application for MEDAREX to
    comment on which shall be taken into due consideration. MERCK agrees to
    supply MEDAREX of all office actions and other communications concerning
    such applications received without undue delay. Any statements from MERCK
    shall be forwarded to MEDAREX at least 2 (two) months before contemplated
    submission to a patent office in order to provide MEDAREX the opportunity
    to comment on such statements which shall be taken into due consideration.

3.4      The parties agree to inform each other without undue delay about any
    inventions made in the FIELD. Provided one party is not interested in filing
    a patent application such party shall lose any rights regarding such
    invention to the other party applying for patent protection.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

<PAGE>
 
                                      -5-


         If a party is no more interested in its patent right covering any
     invention made in the FIELD such party shall offer in writing to assign its
     patent rights relating to this invention to the other party. The costs of
     such assignment shall be borne by the party taking over such patent rights.
     If the other party does not within ninety (90) days from receipt of such
     offer express in writing its interest in the assignment, the offering party
     shall be free to abandon its patent rights.

3.5      Either party shall without undue delay inform the other party of any
    infringement of a PATENT RIGHT coming to its knowledge. Either party, if
    permitted by the applicable law, shall have the right to bring an
    infringement action against any such infringer at its expense in the
    TERRITORY in which it has the right to sell PRODUCTS and the other party
    hereto may join such action, at its own expense. Any settlement or recovery,
    after reimbursing the parties for their expenses, shall be treated as NET
    SALES.

3.6      In the event of 3.5 the party enforcing a PATENT RIGHT against an
    alleged infringer shall have the right to ask the other party to fully
    cooperate with and supply all assistance reasonably requested by the party
    enforcing a PATENT RIGHT. No settlement whatsoever which concerns the
    validity of any PATENT RIGHT shall be entered into without the prior written
    consent of both parties, which consent shall not be unreasonably withheld.

3.7      In the event any claim is made against either party, its AFFILIATES or
    other sublicensees alleging that the manufacture, use, sale or other
    distribution of a PRODUCT infringes any patent right of a third party, the
    party subject to such claim shall have the exclusive right and obligation to
    defend and control the defense of any such claim, at its own expense, using
    counsel of its own choice; provided, however, it shall not enter into any
    settlement which admits or concedes that any aspect of the PATENT RIGHTS is
    invalid or unenforceable, without the prior written consent of such other
    party, which shall not be withheld unreasonably. The party subject to the
    claim shall keep the other party informed of all material developments in
    connection with any such claim, suit or proceeding.

3.8.1    In the event any claim is made against the validity of a solely-owned
    PATENT RIGHT by a third party, the party subject to such claim shall
    promptly notify the other party hereto in writing setting forth the facts of
    such claim in reasonable detail. The party subject to such claim shall have
    the exclusive right and obligation to defend and control the defense of any
    such claim, at its own expense, using counsel of its own choice; provided,
    either party shall have the right at its own expense to intervene in such
    proceeding, if permitted by the applicable law. However, neither party shall
    enter into any settlement which admits or concedes that any aspect of the
    PATENT RIGHTS is invalid, without the prior written consent of such other
    party, which shall not be withheld unreasonably.

3.8.2    In case of a joint invention, the parties will agree on appropriate
    measures to defend such PATENT RIGHTS, provided, if the parties are unable
    to agree within 90 (ninety) days of both becoming aware of such a claim,
    either party may initiate such a defense, at its expense.

3.9      Each party shall keep the other party informed as to the status of
    PATENT RIGHTS, including, without limitation, by promptly notifying the
    other party of its knowledge of any potential infringement of the PATENT
    RIGHTS by a third party.
<PAGE>
 
                                      -6-

ARTICLE IV - GRANT OF LICENSES
- ------------------------------

4.1      MEDAREX hereby grants to MERCK an exclusive licence in the FIELD under
    the respective PATENT RIGHTS, patent rights related to its COMPOUNDS and its
    know-how to make, use, sell or have sold the PRODUCTS in the MERCK
    TERRITORY.

4.2      MERCK hereby grants to MEDAREX an exclusive licence in the FIELD under
    the respective PATENT RIGHTS, patent rights related to its COMPOUNDS and its
    know-how to make, use, sell or have sold the PRODUCTS in the MEDAREX
    TERRITORY.

4.3      As to countries outside the MEDAREX/MERCK TERRITORY the parties
    shall jointly hold one exclusive right in the FIELD and shall use their best
    efforts to mutually agree on a commercialization of the PRODUCTS in each
    country. If the parties are unable to reach a mutual agreement on such
    commercialization within a reasonable time not to exceed 6 (six) months both
    parties shall have a semi-exclusive license in the FIELD under the
    respective PATENT RIGHTS, patent rights related to its COMPOUNDS and their
    know-how to use, sell or have sold the PRODUCTS. [*****]

4.4      Each party shall have the right to sublicense the PRODUCTS in their
    respective MEDAREX/MERCK TERRITORY and, if they have semi-exclusive rights
    in such territories, in the territory defined in 4.3. However, before
    offering the opportunity of sublicensing to any third party which is no
    AFFILIATE of a party, the sublicensing party will offer such opportunity to
    the other party in which case the parties shall negotiate in good faith on a
    sublicense agreement to be concluded within 6 (six) months.

ARTICLE V - ROYALTIES, OPTION ON MEDAREX SHARES
- -----------------------------------------------

5.1      [*****]  Fifty percent of these royalties shall be paid as a
    compensation for licenses granted to the other party under PATENT RIGHTS
    existing at the beginning of the reserach cooperation. However, in the light
    of the growing value of the know how generated under this Agreement, the
    royalty rates fixed hereinabove shall not be reduced in case such PATENT
    RIGHTS expire or otherwise lapse.

5.2      [*****]  The second and third sentence of 5.1 shall apply
    correspondingly.

5.3      Royalties are due to be paid on a country-by-country basis until the
    expiry of the last-to-expire PATENT RIGHT but at least as long as any patent
    right covering a COMPOUND is in force or, if longer, for a period of [*****]
    years following the first


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                      -7-


    commercialization of PRODUCTS. Thereafter the license shall survive without
    further royalty payments. No royalties for the sale of PRODUCTS in a
    particular country may be paid for a period longer than the applicable law
    of such country allows.

5.4      Within 30 (thirty) days following the end of a calendar half year the
    parties shall supply to each other a written report on a country-by-country
    and PRODUCT-by-PRODUCT-basis stating their NET SALES and NET ROYALTIES in
    their respective TERRITORIES in the preceeding calendar half year and the
    royalty due to be paid. The party who according to the reports has to pay
    more royalties to the other party shall pay such balance to the other party
    within 15 (fifteen) days following receipt of the written report.

5.5      All royalties required to be paid shall be paid in Deutsche Mark and
    shall be converted to Deutsche Mark at the rate of exchange at which
    Deutsche Mark may be obtainable for such purpose at the stock exchange of
    Frankfurt am Main, Federal Republic of Germany, at the close of business on
    the last day of the respective accounting period. 

        In case Deutsche Mark are no longer available, all such payments shall
    be paid in USD.

5.6      The parties shall keep proper accounting records showing all NET SALES
    and NET ROYALTIES and if so required will allow an independent auditor -
    except one to whom the other party has some reasonable objections - access
    to its accounting records for the purpose of verifying the reports. Such
    auditor shall disclose to the auditing party only information relating to
    the accuracy of the accounting reports and payments under this Agreement.
    The auditing shall not go back more than 2 years. The costs for such
    auditing shall be borne by the auditing party. However, if the auditing
    discloses an uncorrect accounting of more than 5 (five) percent to the
    disadvantage of the auditing party, the costs shall be borne by the other
    party. If the auditing shows an underpayment of royalties, the repayment
    shall be made with 10 (ten) percent interest.

5.7.1    [*****]

5.7.2    [*****]

5.7.3    [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


<PAGE>
 
                                      -8-


                   [******]

5.8      All payments mentioned in this Article shall be paid with value added
    tax if such value added tax is required by the tax authorities on such
    payments.

ARTICLE VI - EXCHANGE OF INFORMATION, CONFIDENTIALITY
- -----------------------------------------------------

6.1      The parties agree to exchange all RESULTS and additional information
    related to their projects according to the scheme as is laid down in the
    DEVELOPMENT PLAN.

6.2      The parties understand the importance of the patent situation in the
    FIELD and the need to revise at least each calendar half year the patent
    status (APPENDIX 6) as well as the licensing status (APPENDIX 7) of the
    projects. The parties agree to inform each other at least each calendar half
    year about planned or existing activities coming to their knowledge which
    may compete with their common activities in the FIELD.

6.3      Except as provided for in 6.4 and 6.5, the parties shall at all times
    during the term of this Agreement and for a period of 5 (five) years after
    its termination:

    6.3.1  use their best endavours to keep all RESTRICTED INFORMATION
           confidential and not to disclose it to any other person except;

         a)  such of its employees or agents who require access to it for the
           purposes of this Agreement; and

         b)  governmental or other regulatory bodies;

         c)  as required by law.

    6.3.2  not to use any RESTRICTED INFORMATION for any purpose other than the
           performance of their respective obligations under this Agreement.

6.4      The provisions of 6.3 shall not apply to any items of RESTRICTED
    INFORMATION which:

    6.4.1  is at the date of its disclosure by either party to the other in the
           public domain; or

    6.4.2  after the date of its disclosure by either party to the other becomes
           part of the public domain otherwise than by reason of a culpable act
           or omission on the part of the receiving party or any person to whom
           that party has disclosed it; or

    6.4.3  the receiving party can prove was in its possession at the date of
           its disclosure by the other party and was not acquired directly or
           indirectly from that other party.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

<PAGE>
 
                                      -9-

6.5      The parties shall agree on press releases and any other informations
    and publications regarding their common activities under this Agreement
    beforehand.

ARTICLE VII - SAFETY MEASURES
- -----------------------------

7.1      The parties shall promptly inform to each other all adverse drug events
    (ADEs) reported to them with respect to the COMPOUNDS and PRODUCTS.

7.2      The parties will agree on detailed routines for ADE reporting relating
    to the clinical trials and the commercialization with the PRODUCT.

ARTICLE VIII - REPRESENTATIONS AND INDEMNIFICATIONS
- ---------------------------------------------------

8.1      [*****]

8.2      [*****]


ARTICLE IX - PRODUCTION
- -----------------------

         The parties shall agree separately on the production of PRODUCTS, e.g.
    through third parties. It is understood that it is preferred to have one
    party producing PRODUCTS for pivotal clinical test medication and the final
    PRODUCTS to be sold.

ARTICLE X - TERMINATION
- ------------------------

10.1     This Agreement, unless terminated as herein provided, shall remain in
    full force and effect until the end of the commercialization of the last to
    commercialize PRODUCT.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

<PAGE>
 
                                      -10-

10.2     [*****]

10.3     Either party shall be entitled forthwith to terminate this Agreement by
     written notice to the other if:

         10.3.1 the other party commits any material breach of any of the
    provisions of this Agreement and, in the case where the breach is capable of
    remedy, fails to commence to remedy the same within 90 (ninety) days, but
    within 30 (thirty) days regarding payments, after receipt of a written
    notice giving full particulars of the breach and to diligently thereafter
    remedy the same; or

         10.3.2 if the other party compounds or makes arrangements with its
    creditors or is adjudged insolvent or goes into liquidation other than for
    the purposes of a bona fide reconstruction in which its ultimate parent
    remains unchanged or has a receiver appointed of any of its property or
    assest or if one party has been acquired by an independent third party.

         10.3.3 The rights to terminate the Agreement according to this clause
    shall not prejudice any other right or remedy of either party in respect of
    the breach concerned or any other breach.

10.4.1   [*****]

10.4.2   [*****]

10.5     Should a notice of termination be given either party shall have the
    right to sell off the PRODUCTS located in its inventory unless the
    terminating party accepts the unsold quantities of PRODUCTS against
    reimbursement of any price paid by the other party. In the latter case the
    terminating party shall have the exclusive right to sell off the PRODUCTS
    located in the inventories.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

<PAGE>
 
                                      -11-

Article XI - FORCE MAJEURE
- --------------------------

11.1     If and to the extent that any failure on the part of either party to
    perform an obligation hereunder shall have been caused by or shall have been
    due to FORCE MAJEURE, such failure shall not be deemed to constitute a
    breach of this Agreement.

11.2     For the purpose of this Article, FORCE MAJEURE shall mean any cause
    affecting the performance of this Agreement and arising from events beyond
    the reasonable control of either party including, without limitation, any
    strikes, lockouts and other industrial action, civil commotion, riot,
    invasion, war, threat of war or preparation for war, explosion, storm,
    flood, earthquake, subsidence, epidemic, other natural physical disorder,
    delay at sea, breakdown of transport, political interference with the
    operations of any party and actions of any governmental authority.

ARTICLE XII - MISCELLANEOUS
- ---------------------------

12.1     Neither party shall assign or delegate any of its rights or obligations
    hereunder without the prior written approval of the other party, which
    approval shall not be withheld unreasonably.

12.2     If any provision of this Agreement were to be or become fully or partly
    invalid or unenforceable for any reason whatever, or to violate any
    applicable law, the same shall be considered divisible as to such provision
    and such provision shall be deemed deleted herefrom, and the remainder
    hereof shall be valid and binding as if such provision were not included
    herein. The parties hereto shall then, if necessary, negotiate for an
    appropriate amendment of this Agreement.

12.3     All notices pursuant to this Agreement shall be mailed to the above
    given addresses,

         if to MERCK:

         Merck KGaA 
         Attn.: Licensing Department 
         Frankfurter Strasse 250 
         64293 Darmstadt 
         Germany 

         if to MEDAREX

         Medarex Inc.
         Attn.: Mr. Donald L. Drakeman
         President and Chief Executive Officer
         1545 Route 22 East
         Annandale, NJ 08801-0953

         or such other addresses as may be designated by the parties in writing.

12.4     The parties agree to keep each other informed about their other
    activities in the FIELD.
<PAGE>
 
                                      -12-

12.5     All amendments or alterations of this Agreement shall be in writing
    including an alteration of this clause. No variation of this Agreement shall
    be deemed valid unless in writing and signed by both parties. MEDAREX
    understands that MERCK as a rule will only be bound to Agreements if signed
    by two persons having the power to sign.

12.6    This Agreement together with its Appendices, constitutes the entire
    understanding between the parties with respect to the subject matter hereof
    and supersedes any previous understandings or agreement between the parties.
    No modification or amendment of this Agreement shall be valid or binding
    upon the parties unless made in writing and duly executed on behalf of both
    of the parties.

ARTICLE XIII - GOVERNING LAW, ARBITRATION
- -----------------------------------------

13.1    This Agreement and the obligations of the parties hereto shall be
    governed by and construed and enforced in accordance with the laws of
    Germany (with the exemption of the rules of conflict of law) if MERCK is the
    defendant or the laws of New Jersey if MEDAREX is the defendant. Each of the
    parties irrevocably submits itself to the exclusive and final jurisdiction
    of three (3) arbitrators to be selected by the President of the
    International Chamber of Commerce, Paris who shall rule according to the
    rules of the International Chamber of Commerce, Paris. The arbitration shall
    take place in Basle, Switzerland.



Annandale,                        Darmstadt, 26. Juni 1996

MEDAREX, Inc.                     MERCK KGaA

                                  ppa.   i.V.

By /s/ Donald Drakeman            /s/ Dr. Orth  /s/ Dr. Hintze
   Donald Drakeman
                                  Dr. Orth      Dr. Hintze

Appendices:
- -----------

Appendix 1 - Field
Appendix 2 - Merck Compounds
Appendix 3 - Medarex Compounds
Appendix 4 - Research Committee
Appendix 5 - Cost Plan
Appendix 6 - Patent Status
Appendix 7 - Licensing Status
<PAGE>
 
Appendix 1

Field

For the purposes of this Agreement, the term "Field" wall mean the development
of bispecific antibodies for the treatment of tumors expressing the human
EGF-Receptor. Merck and Medarex have decided to make a combined effort in order
to develop bispecific antibodies for the treatment of human cancer. The idea
behind this concept is to activate the bodies own immune cells via bispecific
antibodies and to redirected them to the tumor cells. The approach relies on the
antibodies' tumor selective binding properties on one hand and on the other hand
on the specificity of defined antibodies to bind and then activate selected
effector cell populations of the human immune system. Both the tumor targeting
as well as the effector cell triggering properties can be brought together in
a single bispecific antibody molecule by means of advanced biochemical coupling
technology. The trigger element used in our approaches is the human CD64
molecule. The potential effector cells addressed are consequently PMN's and
monocytes.
<PAGE>
 
Appendix 2

Merck Compounds

Tumor selective antibodies (Table 1)

Mab 425 was originally a murine IgG2a monoclonal antibody specific for human
EGF-Receptor. The antibody was raised by immunization with A431 cells at the
Wistar Institute (1) The antibody recognizes a peptide epitope located at the
external domain of the EGF-R. The anti-tumor responses induced by the antibody
are immunological as well non immunological. The antibody has been chimerized as
well as reshaped by the Winter method. The reshaped version has been developed
for therapy of EGF-R positive tumors.

Table 1:
 
Name        Isotype           Specificity (antigen)    EMD No.
- ----        -------           -----------------------  -------

Mab 425     murine IgG2a      MAb(EGF-R)IgG2a           55900
Mab 425     reshaped hu IgG1  MAb(EGF-R)IgGI            72000

(1) Murthy, U. et al., Arch. Biochem. Biophys. 252: 549-560, 1987
<PAGE>
 
Appendix 3

Medarex Compounds

MAb22 was originally a murine IgG1 monoclonal antibody specific for the human
FcyR1 receptor. The antibody recognizes an epitope distinct from the ligand
binding site. The antibody has been humanized.

    MAb22     murine IgG1        anti-CD64
    MAb H22   humanized IgG1     anti-CD64.

MAb22 and MAb H22 constitute the Medarex Compounds.
<PAGE>
 
Appendix 4

[*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

<PAGE>
 
                                                                   EXHIBIT 10.74

                       DEVELOPMENT AND LICENSE AGREEMENT

     This DEVELOPMENT AND LICENSE AGREEMENT (the "Agreement"), effective as of
April 24, 1996 (the "Effective Date"), is made by and between Centeon L.L.C., a
Delaware limited liability company, with a principal place of business at 1020
First Avenue, King of Prussia, Pennsylvania 19406-13 10 ("Centeon"), and
Medarex, Inc., a New Jersey corporation, with a principal place of business 1545
Route 22 East, P.O. Box 953, Annandale, New Jersey 08801 ("Medarex").

                              RECITALS

     WHEREAS, Medarex is the owner of certain monoclonal antibodies within the
scope of the Patent Rights (as defined below), including but not limited to H-
22, and has conducted pre-clinical studies on the H-22 antibody, and intends to
conduct further clinical trials with the H-22 antibody, and may, subject to the
terms and conditions hereof, conduct pre-clinical and clinical studies on one or
more other monoclonal antibodies within the scope of the Patent Rights in
conjunction with the Development Program (as defined below);

     Whereas, Centeon wishes to commercialize a Product (as defined below)
within the Field and support further developmental efforts by Medarex with
respect thereto, and has at its disposal broad capabilities for clinical
testing, obtaining necessary regulatory approvals and registration with
governmental agencies and marketing therapeutic products throughout the world;

     WHEREAS, Medarex is willing to allow Centeon to commercialize a Product
and has facilities and experienced personnel that enable it to conduct further
development of the H-22 antibody or another antibody Medarex owns within the
scope of the Patent Rights that subsequently is developed as a Product in the
Development Program; and

     WHEREAS, Centeon and Medarex have entered into a Stock Purchase Agreement
of even date herewith

     NOW THEREFORE, it is agreed by and between the parties as follows:

1.   DEFINITIONS

     1.1  "Affiliate(s)" shall mean all corporations or business entities which,
          ---------------                                                       
directly or indirectly, are controlled by, control, or are under common control
with a Party. For this purpose, the meaning of the word "control" ("Control")
shall mean the ownership of fifty percent (50%) or more of the voting shares of
interest of such corporation or business entity or any corporation or business
entity in which a Party can demonstrate, even though the extent of ownership of
a Party in such corporation or business entity is less than fifty percent (50%),
that the operation and management of such corporation or business entity is
carried out in conformity with a Party's standing policy, such corporation or
business entity to be deemed an Affiliate only so long as such ownership of
voting shares or interest or adherence to such standing policy continues.


- ------------
Confidential treatment has been requested for portions of this exhibit. The copy
filed herewith omits the information subject to the confidentiality request. 
Omissions are designated as "[*****]".
<PAGE>
 
     1.2  "Celltech/MRC Agreement" shall mean that certain agreement entered
          -------------------------                                         
between Celltech and the Medical Research Council effective as of November 27,
1987, pursuant to which the Medical Research Council has granted Medarex the MRC
Sublicense.

     1.3  "Confidential Information" shall mean (i) any proprietary or
          ---------------------------                               
confidential information or material in tangible form disclosed hereunder that
is marked as "Confidential" at the time it is delivered to the receiving party,
or (ii) proprietary or confidential information disclosed orally hereunder
which is identified as confidential or proprietary when disclosed and such
disclosure of confidential information is confirmed in writing within thirty
(30) days by the disclosing party.

     1.4 "Core Countries " shall mean [*****]
          ---------------                                                       


     1.5  "Development Plan" shall have the meaning set forth in Section 2.1.2
          -------------------                                                 
     below.

     1.6  "FDA" means the U.S. Food and Drug Administration or any corresponding
foreign registration or foreign regulatory authority.

     1.7  "Field"" shall mean [*****]

     1.8  "IND" shall mean an Investigational New Drug application, as defined
in the U.S. Food, Drug and Cosmetic Act and the regulations promulgated
thereunder for initiating clinical trials in the United States, or any
corresponding foreign application, registration or certification.

     1.9  [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -2-
<PAGE>
 
     1.10 "Know-How" shall mean any and all unpatented and/or non-patentable
          -----------                                                       
technical data, materials (including without limitation, biological materials
such as plasmids, vectors, DNA sequences, organisms, cell lines and antibodies),
samples and other information (A) which are owned or controlled by Medarex
during the term of the Agreement, (B) which Medarex has the right to license or
sublicense, including, without limitation, information and materials developed
by Medarex in connection with the performance of the Development Program, and
(C) which (i) relate to the Product, including, without limitation, its
chemical, biological, pharmacological, toxicological, nonclinical and clinical
data, formulations, specifications and/or usage, or (ii) relate to processes,
techniques and specifications for the manufacture of the Product including,
without limitation, preparation, synthesis, culture, recovery, purification,
formulation and quality control processes, techniques and specifications. Know-
How shall not include the Patent Rights.

     1.11  "Manufacturing Cost " shall mean [*****]
           --------------------                                          

     1. 12 "Medarex Technology" means the Know-How and Patent Rights.
           ---------------------                                     

     1.13 "MRC Sublicense" shall mean that certain Sublicense Agreement entered
          -----------------                                                    
by and between Medarex, Inc. and the Medical Research Council, effective as of
May 16, 1995, as may be amended from time to time.

     1-14 "MRC/Scotgen Agreement" shall mean that certain agreement entered
          ------------------------                                         
between Scotgen and the Medical Research Council effective as of January 31,
1989, pursuant to which Scotgen has granted Medarex the Scotgen Sublicense.

     1-15 "Net Sales " shall mean [*****]
          ----------                                                        


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -3-
<PAGE>
 
[*****]

     1.16 "Patent Rights" shall mean (i) the U.S, and foreign patent
           -------------
applications and patents listed on Exhibit B hereto; (ii) any U.S. or foreign
patent application or patent which is not listed on Exhibit B and that claims
priority from one or more patent applications listed on Exhibit 13 or that
corresponds thereto and relates to the Product or the manufacture thereof or to
the use thereof in the Field; (iii) any U.S. or foreign patent or patent
application which claims an invention made or conceived and reduced to practice
by one or more employees, agents or consultants of Medarex or of a Medarex
Affiliate in connection with the performance of the Development Program and
related to the Product or the manufacture thereof or to the use thereof in the
Field and which is not jointly owned by Centeon and which is added to the Patent
Rights pursuant to Section 8.2 of this Agreement; (iv) any U. S. or foreign
patent application or patent which (A) claims an invention that is made or
conceived and reduced to practice by one or more employees, agents or
consultants of Medarex or of a Medarex Affiliate after the termination of the
Development Program, but during the term of this Agreement, and that is related
to the Product or to the manufacture thereof or to the use thereof in the Field
and that falls within the scope of one or more of the claims of any of the
patent applications or patents which are referenced in subsection (i) or (ii) of
this Section 1. 16; (B) is not jointly owned by Centeon; and (C) is added to the
Patent Rights pursuant to Section 8.2 of this Agreement; and (v) any U. S. or
foreign patent application or patent which claims an invention that is related
to the Product or to the manufacture thereof or to the use thereof in the Field,
that falls within the scope of one or more of the claims of any of the patent
applications or patents which are referred to in subsection (i) or (ii) of this
Section 1. 16, and that is acquired by Medarex or by a Medarex Affiliate from a
Third Party(ies) during the term of this Agreement; and any substitution,
continuation, continuation-in-part, or divisional application of any of the
preceding, and any patent issuing thereon, including any reissue, reexamination,
renewal or extension thereof.

     1.17 "Phase I", "Phase II", and "Phase III " shall mean Phase I (or Phase
          -----------------------    ----------                              
I/II), Phase II (or Phase II/III), and Phase III clinical trials, respectively,
in each case as prescribed by applicable FDA regulations, or corresponding
regulations of any comparable foreign entity.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -4-
<PAGE>
 
     1.18 "Product" shall mean a monoclonal antibody which is within the 
          ---------                                                             
scope of U.S. Patent No. 4,954,617, and which has an antigen binding region
having a binding affinity for cd64. As used herein, cd64 shall mean the human
high affinity Fc receptor for IgG present on macrophages and monocytes. For the
avoidance of doubt, it is understood that any other monoclonal antibody,
including without limitation, a bifunctional antibody or a hetero antibody or a
single chain antibody, shall not be a Product. The humanized anti-cd64
monoclonal antibody known as H-22 shall be the Product for initial development
under the Development Program.

     1.19 "Product License Application" or "PLA" means a Product License
          -----------------------------     ---
Application, as defined in the U.S. Food, Drug and Cosmetic Act and the
regulations promulgated thereunder and any corresponding foreign application,
registration or certification.

     1-20 "Scotgen Sublicense" shall mean that certain Sublicense Agreement
          -------------------                                              
entered by and between Medarex, Inc. and Scotgen, Ltd., effective as of May 16,
1995, as amended from time to time.

     1.21  "Stock Purchase Agreement" shall mean that certain Stock Purchase
           --------------------------                                      
Agreement entered by Centeon and Medarex of even date herewith.

     1.22 "Sublicensee" shall mean a third party to whom Centeon has granted a
          --------------                                                      
license or sublicense under the Medarex Technology to make, use and/or sell the
Product. As used in this Agreement, it is understood that "Sublicensee" shall
also include a Third Party or Third Parties to whom Centeon has granted the
right to distribute the Product, provided that such Third Party or Third Par-
ties has (have) the responsibility for marketing and promotion of the Product
within the field or territory for which such distribution rights are granted.

     1.23 "Territory" shall mean worldwide.
          ------------                      

     1.24 "Third Party(ies)" shall mean any person or entity other than Centeon,
          ------------------                                                   
Medarex, their respective Affiliates, or their respective employees.

2.   DEVELOPMENT PROGRAM

     2.1  DEVELOPMENT PROGRAM
          --------------------

          2.1.1 Development Program Activities. Subject to the terms and
                ---------------------------------                        
conditions set forth herein, Medarex shall (i) conduct clinical development of
the Product pursuant to the Development Plan, and (ii) for a three (3) year
period commencing on the Effective Date, perform research with regard to Product
manufacture improvements. Such activities shall comprise the "Development
Program." Medarex shall use reasonable efforts to conduct the Development
Program in accordance with the Development Plan and within the time schedules
contemplated therein, and shall use reasonable efforts to comply with all
submission procedures to the appropriate regulatory authorities,

                                      -5-
<PAGE>
 
to respond timely to inquires of said regulatory authorities and to maintain
submissions and support new submissions. Medarex shall keep the Development
Committee reasonably informed of the progress of the Development Program and
shall provide the Development Committee a reasonable opportunity to review and
comment on trial protocols, study designs, endpoints, target patient population
and other relevant factors to such trials.

          2.1.2 Development Plan.  Medarex will conduct the Development Program
                ----------------                                              
in accordance with a plan approved by the Development Committee (the
"Development Plan"). The Development Plan shall establish: (i) the scope of the
development which will be performed; (ii) development objectives, work plan
activities and time schedules with respect to the development and (iii) the
annual research goals of Medarex with regard to Product manufacture
improvements. The initial Development Plan is attached hereto as Exhibit A. The
Development Committee shall review the Development Plan on an ongoing basis and
may make changes to the Development Plan then in effect. Each year during the
Development Program prior to the end of the tenth month of such year, the
parties shall agree on an annual Development Plan for the following calendar
year.

          2.1.3 Product Changes. During the term of the Development Program, the
                ---------------
Development Committee may agree to discontinue the activities of the Development
Program with respect to the H-22 monoclonal antibody, and redirect those
activities with respect to a different monoclonal antibody which is a Product.
In such event, subject to the provisions of Section 4.3.2, the parties shall
discuss and agree on (i) the substitute monoclonal antibody, (ii) the objectives
of the redirected Development Program, and (iii) the further payments, if any,
which will be made by Centeon in support of the Development Program, which shall
cover the fully burdened costs of all such activities.

     2.2  Development Committee.
          ---------------------

          [*****]

          [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -6-
<PAGE>
 
[*****]

          2.2.3 Responsibilities. It will be the responsibility of the 
                ----------------
Development Committee, among other things, to (i) oversee the conduct of the
Development Program, (ii) prepare and approve the Development Plan and the
detailed working program (including timetables) to be carried out, and (iii)
determine whether Medarex has materially achieved its annual research goals with
regard to Product manufacture improvements. The activities conducted in
connection with the Development Plan shall be monitored by the Development
Committee and periodically reviewed.

          2.2.4 Meetings, During the term of this Agreement, the Development
                ----------                                                  
Committee shall meet quarterly, or more often as may be necessary, to discharge
its responsibilities. Such meeting shall alternate between Annandale, New
Jersey, and King of Prussia, Pennsylvania, or such other locations as the
parties agree, or by way of video or telephone conference, if possible and
appropriate. Each party will be responsible for paying its own expenses in
connection with the meetings of the Development Committee. Medarex shall prepare
minutes of the Development Committee meetings covering all essential points
discussed, which minutes shall be approved and signed by a Development Committee
representative of each party.

     2.3  Records; Exchange of Information.
          ---------------------------------

          2.3.1 Records. The Parties shall maintain (i) financial records in
                ---------                                                   
sufficient detail to establish how Development Program funds are expended, and
(ii) scientific records as will properly reflect all work done and results
achieved in the performance of the Development Plan (including all data in the
form required under any applicable governmental regulations). During the term of
this Agreement, the Parties shall provide each other access to such records,
upon request, during ordinary business hours. During the Development Program,
Medarex shall provide Centeon with a quarterly accounting report regarding
Development Program expenditures by Medarex.

          2.3.2 Reports. The Development Committee shall periodically and not
                ---------                                                    
less often than semiannually during the term of the Development Program, request
and the Parties shall have the obligation to prepare and provide to the
Development Committee written reports summarizing the progress of the research
performed pursuant to the Development Plan during the preceding half-year.

     2.4  Development Program Funding.
          -----------------------------

          2.4.1 Product Manufacture Research. In consideration for Medarex'
                ----------------------------                             
research activities with regard to Product manufacture improvements in
connection with the Development Program, Centeon shall pay to Medarex [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -7-
<PAGE>
 
          2.4.2 Clinical Trial Expenses
                -----------------------

          [*****]


     2.5  Termination Of Support of Product Manufacture Research. In the event
          -------------------------------------------------------              
that the Development Committee determines that Medarex has materially failed to
achieve the research goals with regard to Product manufacture improvements
established by the Development Committee for a particular year, Centeon may,
with sixty (60) days notice to Medarex, terminate its support for research by
Medarex regarding Product manufacture in connection with the Development Program
as provided in Section 2.4.1; provided, however, Centeon shall continue to be
responsible for the payment of all clinical activities conducted by Medarex in
connection with the Development Program. In such an event, Medarex may continue
such research at its own expense, and such later activities shall not be
included in or be part of the Development Program but shall be subject to the
provisions of Section 3.6 below.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -8-
<PAGE>
 
3.   LICENSE GRANT

     3.1  License to Centeon. Subject to the terms and conditions of this
          --------------------                                           
Agreement, Medarex hereby grants to Centeon an exclusive (subject to Sections
3.4 and 3.6), worldwide, royalty-bearing license under the Medarex Technology to
make, have made, import, use, offer for sale and sell the Product for use in the
Field in the Territory. The preceding rights granted Centeon to make and have
made the Product shall only become effective upon receipt by Medarex of notice
from Centeon pursuant to Section 7.2 that Centeon wishes to manufacture the
Product.

     3.2  Sublicenses. Centeon may sublicense the rights granted in Section 3.1
          -------------                                                        
to its Affiliates without the prior consent of Medarex, and to Third Parties
with the prior written consent of Medarex, which consent shall not be
unreasonably withheld. Each such sublicense shall be consistent with all the
terms and conditions of this Agreement. Centeon shall remain responsible to
Medarex for all of each such Sublicensee's applicable financial and other
obligations under the sublicense.

     3.3  Affiliate Licenses. Medarex agrees, if Centeon so requests, to enter
          --------------------                                                
into a separate agreement with any Affiliate(s) of Centeon granting a license in
accordance with the provisions of this Agreement. Such agreement shall be
consistent with all of the provisions hereof and incorporate all of the terms of
this Agreement to the extent that they are applicable. Centeon shall guarantee
the performance of any and all responsibilities of the Affiliate(s) under such
separate agreement. Centeon shall reimburse Medarex for its reasonable
attorneys' fees and costs incurred in connection with the preparation, review
and execution of any such separate license agreement.

     3.4  Acknowledgments.
          ----------------

          3.4.1 Scotgen Sublicense. Notwithstanding Section 3.1 above, Centeon
                ---------------------                                          
acknowledges that it has been informed by Medarex that the patent applications
and patents subject to the Scotgen Sublicense were licensed to Medarex on a non-
exclusive basis, and that the sublicenses granted Centeon under such particular
Patent Rights are accordingly non-exclusive. Medarex agrees, however, that the
license granted Centeon with respect to such Patent Rights shall be exclusive
with respect to the Product and the Field as to Medarex' interest in such Patent
Rights. The parties further acknowledge that Centeon has been provided a copy of
the Scotgen Sublicense, and understand that pursuant to the Scotgen Sublicense
Centeon shall have the right to acquire sublicense from Scotgen if the Scotgen
Sublicense terminates, pursuant to Clause 8(xiv) of the Scotgen Sublicense which
states in its entirety:

     The duration of any sublicense which the Sublicensee shall validly grant
     pursuant to the provisions of this Agreement shall be independent of the
     term of this Agreement but that only insofar as each Medarex sublicensee
     (as hereinafter defined) may, upon termination of this Agreement, apply
     direct to Scotgen for the adoption of such sublicense direct whereupon
     Scotgen shall, if the Medarex sublicensee is not in default and there are
     no other impediments to such adoption, adopt the same, always provided that
     in no circumstances shall the provisions of this Clause operate so as to
     impose

                                      -9-
<PAGE>
 
     upon Scotgen any Obligation which is more extensive or more onerous or
     different in nature to the obligations undertaken by Scotgen to Medarex
     under this Agreement, and further provided that each Medarex sublicensee
     shall from the date of termination of this Agreement owe to Scotgen all of
     its royalty and other obligations under its sublicense. For the purposes of
     this Clause 8(xiv), a "Medarex sublicensee" means any person to which
     Medarex shall have granted a sublicense in accordance with and pursuant to
     the provisions of Clause 8(iv) of this Agreement.

          3.4.2 MRC Sublicense. Centeon further acknowledges that Medarex does
                ----------------                                               
not have the right to grant Centeon a sublicense under the MRC Sublicense, and
that the sublicense under the Scotgen Sublicense to the Winter patents granted
Centeon pursuant to Section 3.1 may only be practiced with a concurrent
sublicense from the MRC under the Boss patents; provided, however, [*****]

          3.4.3 Boss Interference.
                -----------------

          [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -10-
<PAGE>
 
[*****]

     3.5  Right of First Negotiation for Product Commercialization Outside the
          --------------------------------------------------------------------
          Field.
          -----

          3.5.1 Commercialization of the Product Outside the Field by Third 
                -----------------------------------------------------------
                Parties.
                -------
If at any time during the Development Program or two (2) years thereafter,
Medarex wishes to develop or commercialize the Product for the treatment of an
autoimmune disorder outside the Field [*****]
with a Third Party, or Centeon wishes to acquire a license from Medarex with
respect to the development or commercialization of the Product for the treatment
of an autoimmune disorder outside the Field, such party shall notify the other
party hereto, identifying the indication of interest. In such event, the parties
shall negotiate in good faith for a period of ninety (90) days with respect to
an agreement regarding co-development and commercialization of such products by
Centeon and Medarex. If Centeon and Medarex fail to agree on the terms of such
an agreement within the ninety (90) day period, or such longer period as the
parties may agree, Medarex shall be free to develop and commercialize the
Product for such indication, itself or with third parties, and Centeon shall
have no further rights with respect thereto. In the event that Medarex and
Centeon enter a further agreement regarding the development and
commercialization of such products for the treatment of any autoimmune
disorder outside the Field, Centeon shall pay Medarex such additional
consideration as is mutually agreed.

          3.5.2 Commercialization of the Product Outside the Field by Medarex.
                -------------------------------------------------------------
                If Medarex intends to itself develop or commercialize the
Product for the treatment of an autoimmune disorder outside the Field, it shall
notify Centeon. In such event, Centeon may notify Medarex it wishes to negotiate
an agreement regarding co-development and commercialization of the Products for
such indication, and the parties shall negotiate the terms of such an agreement
in good faith. If Medarex and Centeon fail to enter into a written letter of
intent for such an agreement within ninety (90) days from Medarex' notice to
Centeon, or such longer period as the parties may agree, then Medarex shall be
free to conduct any such activities, itself or with a third party, and Centeon
shall have no rights with respect thereto.

     3.6  Right of First Refusal for Other Products in the Field. During the 
          ------------------------------------------------------               
term of the Agreement, if Medarex develops a monoclonal antibody or product
(other than a Product) which it intends to commercialize, itself or with a Third
Party, in the Field (an "Improvement"), Medarex


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -11-
<PAGE>
 
hereby grants to Centeon a right of first refusal to negotiate for an exclusive,
worldwide license to Medarex' interest in any patent rights other than the
Patent Rights for the development and commercialization of such Product in
the Field, to the extent that Medarex may grant such rights. Medarex shall
promptly notify Centeon of any Improvement and provide Centeon with a detailed
written description of such Improvement. Centeon shall have thirty (30) days
from the date it receives such written description of any Improvement to
exercise its exclusive right of first refusal with respect to negotiating a
license with Medarex for such Improvement. If Centeon notifies Medarex it wishes
to negotiate for such a license, the parties shall negotiate in good faith for a
period of up to one hundred and twenty (120) days. If the parties fail to enter
into a written letter of intent for such an agreement or a written agreement
within such period, or mutually agreed extension thereof, Medarex shall have the
right to seek other licensees of said Improvement; provided however that Medarex
shall not offer a license to such Improvement to any Third Parties on financial
terms substantially more favorable in their entirety to such Third Parties than
those offered to Centeon for the Improvement without first offering such terms
to Centeon.

     3.7  Retained Rights. It is understood and agreed that Medarex shall retain
          -----------------                                                     
rights to (i) make, have made, import, use, offer for sale, sell and otherwise
commercialize the Product for all uses outside the Field; and (ii) to make, have
made, import, use, and offer for sale and sell Product to Centeon in connection
with the activities conducted by Medarex pursuant to this Agreement, unless and
until Centeon assumes manufacture of the Product pursuant to Section 7.2. It is
understood that such retained rights shall not permit Medarex to knowingly sell
the Product to a third party which intends to sell it for use in the Field or
use it in the Field.

     3.8  Product License. It is understood and agreed that the license granted
          -----------------                                                    
Centeon under the Medarex Technology herein relates only to specific monoclonal
antibodies which are within the scope of the Product definition in Section 
1.18, and does not extend to any other monoclonal antibody, heteroantibody,
bifunctional antibody or any other product.

4.   PAYMENTS

     [*****]

     4.2  Purchase of Medarex Common Stock. On the Effective Date, Centeon shall
          --------------------------------                                      
enter into the Stock Purchase Agreement with Medarex.

     4.3  Milestone Payments.
          ------------------

          4.3.1  Within thirty (30) days following each occurrence of the events
specified below, Centeon shall pay to Medarex the following amounts:


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -12-
<PAGE>

[*****]

The amounts paid upon achievement of such milestones shall be non-refundable and
not be creditable against any other amounts due Medarex.

        4.3.2. Back-up Products. [*****] 
               -----------------


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



                                      -13-
<PAGE>

[*****]

          4.3.3 Acknowledgment. For purposes of this Section 4.3, the parties
                -----------------                                             
acknowledge and agree that a clinical trial shall be deemed completed when all
patients enrolled in such trial have been treated with the Product, and all
patient case report forms have been submitted to the sponsor of the trial (or
its designee). As soon as practicable after the completion of a particular
clinical trial the Development Committee shall review the data from such trial
and within forty-five (45) days of such review, or such longer period as may be
agreed by the parties, shall issue or decline to issue a positive recommendation
to proceed to the next clinical trial or filing, as the case may be. As used in
this Section 4.3, the parties acknowledge and agree that "front line therapy"
means a therapeutic treatment for patients with [*****]
disorder that is administered to said patients before they become refractory to
other treatments or is administered in combination with other treatments.

          4.3.4 Further Payment. [*****]
                ---------------                                                


     4.4  Royalties. In consideration of the rights granted hereunder, Centeon
          ---------
shall pay the following royalties to Medarex:


          [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -14-
<PAGE>
 
     [*****]

     4.7 Single Royalty; Non-Royalty Sales. No royalty shall be payable under
         ----------------------------------                                 
Section 4.4 above with respect to sales of the Product among Centeon, its
Affiliates and sublicensees for resale and in no event shall more than one
royalty be due Medarex hereunder with respect to any Product unit.

     [*****]



***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



                                      -15-
<PAGE>
 
     4.9  Royalty Term. The royalties due hereunder shall be payable on a
          --------------                                                  
country-by-country basis in each country until the date which is the later of
(i) the expiration of the last to expire of the patents within the Patent Rights
covering the Product or the manufacture, use or sale of the Product in such
country (such expiration to occur only after expiration of extensions of any
nature to such patents which may be obtained under applicable statutes or
regulations in the respective countries of Territory, such as the Drug Price
Competition and Patent Term Restoration Act of 1984 in the U.S.A. and similar
patent extension laws in other countries), or (ii) if there are no Patent Rights
covering the Product or the manufacture, use or sale of the Product in a
country, until [*****] years following the first commercial sale of a Product
in such country.

     4.10 Payment Method. Amounts due Medarex hereunder shall be paid in U. S.
          ---------------                                                    
dollars by wire transfer in immediately available funds to an account designated
by Medarex.

     4.11 Currency Conversion. If any currency conversion shall be required in
          -------------------
connection with the calculation of royalties due on a quarterly basis hereunder,
such conversion shall be made using the monthly exchange rates used by Centeon
to translate its net sales to U.S. dollars. Such monthly rate is a simple
average of the daily noon bid/ask exchange rates for the month. At such time
that Centeon provides any royalty report and payment to Medarex pursuant to
Section 5.1 which relates to payments based on Net Sales in any country outside
the U.S., Centeon shall provide Medarex with a detailed calculation setting
forth how each applicable monthly exchange rate was determined and applied by
Centeon.

     4.12  Taxes.
           ------

          4.12.1  Withholding Taxes. All royalty amounts required to be paid to
                  -------------------                                          
Medarex pursuant to this Agreement may be paid with deduction for withholding
for or on account of any taxes (other than taxes imposed on or measured by net
income) or similar governmental charge imposed by a jurisdiction other than
the United States ("Withholding Taxes"). At Medarex' request, Centeon shall
provide Medarex a certificate evidencing payment of any Withholding Taxes
hereunder and shall reasonably assist Medarex to obtain the benefit of any
applicable tax treaty.

          4.12.2 Sales Taxes. Any sales taxes, use taxes, transfer taxes or
                 --------------                                             
similar governmental charges required to be paid in connection with the transfer
of any Products manufactured by Medarex and sold by Centeon hereunder shall be
the sole responsibility of Centeon. In the event that Medarex is required to pay
any such amounts, and reasonably documents payment, Centeon shall promptly remit
payment to Medarex of such amounts.

5.   BOOKS AND RECORDS

     5.1  Royalty Reports and Payments. After the first commercial sale of a
          ----------------------------
Product on which royalties are required hereunder, Centeon shall make quarterly
written reports to Medarex within ninety (90) days after the end of each
calendar quarter, stating in each such report, by country, the


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -16-
<PAGE>
 
number, description, and aggregate Net Sales of the Product sold during the
calendar quarter upon which a royalty is payable under Article 4 above. Medarex
shall treat all such reports as Confidential Information of Centeon.
Concurrently with the making of such reports, Centeon shall pay Medarex the
royalties specified in Sections 4.4 and 4.8.

     5.2 Records; Inspection. Centeon and its Affiliates and Sublicensees shall
         -------------------
keep complete, true and accurate books of account and records for the purpose of
determining the royalty amounts payable under this Agreement. Such books and
records shall be kept at the principal place of business of Centeon or its
Affiliate or Sublicensee, as the case may be, for at least four (4) years
following the end of the calendar quarter to which they pertain. Such records
will be open for inspection during such four (4) year period by a representative
of Medarex for the purpose of verifying the royalty statements. Such inspections
may be made no more than once each calendar year, at reasonable times mutually
agreed. The representative will be obliged to execute a reasonable
confidentiality agreement prior to commencing any such inspection. Inspections
conducted under this Section 5.2 shall be at the expense of Medarex, unless a
variation or error producing an increase exceeding five percent (5%) of the
amount stated for any period covered by the inspection is established in the
course of any such inspection, whereupon all costs relating to the inspection
for such period and any unpaid amounts that are discovered will be paid by
Centeon, with interest from the date such amounts were due, at the prime rate
reported by the Chase Manhattan Bank.

6.   COMMERCIALIZATION

     6.1  Reasonable Efforts. Centeon shall use commercially reasonable efforts,
          -------------------                                                
comparable to those efforts Centeon makes with respect to other products of
comparable value, developmental stage and clinical indication, to obtain and
maintain all approvals, registrations and government authorizations necessary
for commercial sale of the Product worldwide. Centeon will use commercially
reasonable efforts to actively pursue commercial sales of the Product in each
country in which regulatory approval is obtained. Centeon shall notify Medarex
as provided in Section 6.4 below should it elect to abandon its rights to pursue
commercialization of the Product in a country.

     6.2  Reports to Medarex. During the term of this Agreement, Centeon shall
          --------------------                                                
keep Medarex fully informed of its activities subject to this Agreement,
including without limitation, the achievement of the milestones set forth in
Section 4.3 and the commercialization of the Product, and following January 31
of each year shall provide Medarex with a written report detailing such events
and activities. When the registration package requesting approval for commercial
sale of the Product (including approval for reimbursement by the appropriate
health insurance authorities as well as price approvals where required) is first
filed in the U.S., the European Union and Japan, and in each case when approval
is received therefor, Centeon will notify Medarex in writing immediately by
facsimile.

     6.3  Regulatory Filings. Centeon shall submit registration packages 
          ------------------
requesting approval for commercial sale of the Product as soon as reasonably
practicable. Centeon (or its designee) shall file and hold title to all clinical
results, regulatory applications, approvals and supplements thereto.

                                      -17-
<PAGE>
 
Medarex and its Affiliates, shall have the irrevocable right, without charge, to
refer to, access, cross reference, and use all such documents, including
clinical studies and other supporting information, and any written
communications to and with the FDA and comparable foreign regulatory bodies in
connection with the Development Program and with regard to any product for use
outside the Field. Centeon shall have no obligation to provide and Medarex shall
not provide, without the written consent of Centeon, such access or rights to
any third party, including, without limitation, a Medarex Affiliate, which has
acquired the right to use a Product in monoclonal antibody form (as opposed to a
bi-specific antibody) for indications outside the Field.

     6.4  Abandoned Products. Centeon may voluntarily abandon its right 
          ------------------      
hereunder to market the Product in any individual country, upon sixty (60) days
written notice to Medarex at any time. Such notice will effectuate Centeon's
voluntary abandonment of its right hereunder to market the Product in such
country; provided, the abandonment of the Product in any particular country
hereunder shall not be construed to be a termination of this Agreement for any
other country.

     6.5  Consultation. If Medarex at any time should advise Centeon of its
          --------------                                                   
concern, and the specific reasons for same, that Centeon is not pursuing
development, commercialization and sale of the Product in the manner
contemplated by this Agreement, then the parties shall discuss the situation in
good faith to reach a satisfactory resolution addressing Medarex' concerns as
appropriate. In the event that the parties are unable to agree upon a
resolution, Medarex may submit the matter to arbitration pursuant to Section
13.2, and in the event that Centeon is found not to have used reasonable efforts
to obtain regulatory approval for the Product in any country, or actively
commercialize the Product in any country where the Product has received
regulatory approval, then Centeon's rights hereunder shall terminate in such
country, but shall not be construed as termination for any other country.

     6.6  Loss of Rights. If Centeon abandons its right to market the Product in
          --------------
a country in accordance with Section 6.4, or loses such rights in a country
pursuant to Section 6.5, or as result of the termination of this Agreement by
Medarex pursuant to Section 12.2 or Centeon pursuant to Section 12.4 or Section
12.5, such rights shall revert to Medarex, and Medarex shall thereafter have the
exclusive rights to market the Product in such country. In such event, Medarex
or a Third Party licensee or sublicensee of Medarex may freely carry on future
development and commercialization of the Product in any such country. At
Medarex' request, Centeon shall cooperate with and assist Medarex in exercising
such rights, including without limitation, by providing Medarex, without charge,
access to and the right to use all regulatory approvals relating to the Product
in such country.

     6.7  Adverse Reactions. If Medarex and Centeon market the Product at the
          -------------------                                                
same time, the parties shall have a continuing obligation to timely advise one
another of all adverse drug reactions and other similar matters relevant to
maintaining approvals and registrations of the Product in accordance with
applicable laws and regulations.

                                      -18-
<PAGE>
 
     6.8  Delivery of Know-How. During the term of this Agreement, Medarex
          ---------------------                                                 
shall deliver to Centeon such Know-How relating to the Product as is necessary 
for Centeon's performance under this Agreement.

7.   PRODUCT MANUFACTURE

     7.1  Product for Use in Clinical Trials. Medarex shall be responsible for 
          ----------------------------------                                    
the manufacture of all Product for use in Phase 1, Phase II and Phase III
clinical trials pursuant to the terms of the Development Plan. All such Products
manufactured by or on behalf of Medarex for all such clinical trials will
conform to all FDA requirements relating to Good Manufacturing Practices and all
applicable comparable foreign laws and regulations. [*****]


     7.2  Election of Product Manufacture.  Medarex shall be responsible for the
          ----------------------------------                                    
manufacture of all Product for commercial uses unless Centeon elects to
manufacture the Product as provided in this Section 7.2. All Product
manufactured by or on behalf of Medarex will conform with all FDA regulations
relating to Good Manufacturing Practices and all applicable comparable foreign
laws and regulations. During the term of this Agreement, Centeon shall have the
right to elect whether it wishes to (i) manufacture Products for sale by Centeon
and its Affiliates and Sublicensees pursuant to this Agreement, or (ii) purchase
for resale from Medarex Product manufactured by or on behalf of Medarex. To
exercise such option, Centeon shall notify Medarex that it wishes to manufacture
the Product at least six (6) months prior to the date Centeon wishes to commence
Product manufacture. In such event, Centeon shall purchase all Product
manufactured by Medarex pursuant to invoices or requests for Product manufacture
received by Medarex prior to the date Centeon provides Medarex notice that it
wishes to assume responsibility for Product manufacture.

     7.3  Transfer of Manufacturing Know-How. Within sixty (60) days of the
          ----------------------------------                               
election by Centeon to manufacture the Product, or at such other time as the
parties agree, subject to Section 7.5, Medarex will deliver to Centeon all Know-
How relating to the manufacture of the Product existing as of the Effective Date
and developed in connection with the Development Program. In such event, the
parties shall cooperate with each other in order that Centeon may initiate
manufacture of the Product as soon as practicable, and shall take such actions
as are appropriate to achieve such goal.

     7.4  Manufacture by Centeon or a Third Party.
          ---------------------------------------

          7.4.1 Centeon Responsibilities. If Centeon elects to manufacture the
                ------------------------
Product for commercialization itself or through a Third Party, Centeon shall be
responsible thereafter for the


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -19-
<PAGE>
 
development of scale-up and manufacturing procedures, and all costs associated
therewith. All Product manufactured by or on behalf of Centeon will conform with
all FDA regulations relating to Good Manufacturing Practices and all applicable
comparable foreign laws and regulations. Centeon shall keep Medarex fully
informed of the Product manufacturing procedure and developments relating
thereto and Medarex shall have the right for reasonable purposes and on
reasonable prior notice to visit the manufacturing facility during ordinary
business hours and review any relevant records relating to Product manufacture,
and to comment thereon.

          7.4.2 Third Party Manufacture.  If Medarex is unable to meet its
                -------------------------                                
obligations to supply Product as established in any Supply Agreement entered by
the parties pursuant to Section 7.6 below, or with the prior written consent of
Medarex, Centeon may have the Product manufactured on its behalf by a Third
Party; provided, Centeon shall not enter into a supply agreement for the Product
with such Third Party on terms more favorable than those offered to Medarex for
Product manufacture. If a Third Party manufactures the Product for
commercialization, Centeon shall inform Medarex of the outcome of the
negotiations with such Third Party.

          7.4.3 Site of Manufacturing. In the event that Centeon or its designee
                --------------------- 
manufactures the Product, such manufacturing may only be conducted in a country
where an issued, unexpired patent within the Patent Rights covering the Product
is in effect, unless otherwise agreed by the parties.

     7.5  Manufacturing Technology Fee. If Centeon elects to terminate its 
          ----------------------------                                          
funding of Product manufacture improvements in connection with the Development
Program pursuant to Section 2.6, and Medarex, at its own expense, conducts
further research which leads to improvements relating to the manufacture of the
Product, then even if Centeon elects to manufacture the Product, Medarex shall
have no obligation to provide Centeon with access to or rights to any such
technology developed after the date that Centeon provides notice that it will
not fund such activities in connection with the Development Program [*****]

     7.6  Manufacture by Medarex - If Centeon elects to purchase the Product 
          ----------------------                                                
from Medarex for commercial sale, Centeon and Medarex shall promptly negotiate
in good faith and enter into a Supply Agreement containing reasonable and
customary terms; provided, such agreement shall provide that Centeon will
purchase the Product from Medarex at a transfer price equal [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -20-
<PAGE>
 
8.   INTELLECTUAL PROPERTY

     8.1  Ownership of Inventions. Title to all inventions and other 
          -----------------------
intellectual property made solely by employees of Medarex during the term of the
Agreement shall be owned by Medarex; provided, any inventions and other
intellectual property made by Medarex employees in connection with the
Development Program which relate solely to improvements in Product manufacture
processes shall be jointly owned by Medarex and Centeon. Title to all inventions
and other intellectual property made solely by Centeon employees in connection
with the Development Program shall be owned by Centeon. Title to all inventions
and other intellectual property made jointly by employees of Centeon and Medarex
in connection with the Development Program shall be jointly owned by Medarex and
Centeon (each a "Centeon/Medarex Invention"). Inventorship of inventions and
other intellectual property rights conceived and/or reduced to practice in
connection with the Development Program and ownership rights with respect
thereto shall be determined in accordance with the patent and other intellectual
property laws of the United States and the State of New York, as applicable. 
[*****]

     8.2  Patent Prosecution.
          ------------------

          8.2.1 Patent Rights. Medarex shall be responsible, at its expense, for
                --------------                                                 
the preparation, filing, prosecution and maintenance of the patent applications
and patents within Patent Rights in countries selected by Medarex, and for
conducting any interferences, reexaminations, reissues, oppositions, or request
for patent term extension relating thereto.

          8.2.2 Failure to Prosecute. In the event that Medarex declines to file
                ---------------------                                          
or, having filed, declines to further prosecute and maintain any patent
applications or patents subject to Section 8.2.1 above, Medarex shall provide
Centeon notice thereof prior to the expiration of any deadline relating to such
activities, but in any event at least thirty (30) days prior notice, and Centeon
shall have the right to file, prosecute and maintain such patent applications or
patents in the name of Medarex, at Centeon's expense, using counsel of its
choice.

          8.2.3 Medarex/Centeon Inventions.
                ----------------------------

          (a) The parties will cooperate to file, prosecute and maintain patent
applications covering the Centeon/Medarex Invention(s) in the Core Countries 
[*****] and other countries agreed by the parties. The parties shall agree which
parties shall be responsible for conducting such activities with respect to a
particular Centeon/Medarex Invention. The party conducting such activities shall
keep the other party fully informed as to the status of such patent matters,
including, without limitation, by providing the other party the opportunity, at
the other party's expense, to review and comment on any documents relating to
the Centeon/Medarex Invention which will be filed in any patent office at least
thirty (30) days before such filing, and promptly providing the other party
copies of any documents relating to Centeon/Medarex Invention which the party
conducting such activities receives from such patent


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -21-
<PAGE>
 
offices, including notice of all interferences, reissues, reexaminations,
oppositions or requests for patent term extensions. The parties will share
equally all expenses and fees associated with the filing, prosecution, issuance
and maintenance of any patent application and resulting patent for a
Centeon/Medarex Invention in the Core Countries and other agreed countries.

          (b) In the event that either party wishes to seek patent protection
with respect to any Centeon/Medarex Invention outside the Core Countries, it
shall notify the other party hereto. If both parties wish to seek patent
protection with respect to such Centeon/Medarex Invention in such country or
countries, activities shall be subject to Section 8.2.3(a) above. If only one
party wishes to seek patent protection with respect to such Centeon/Medarex
Invention in such country or countries, it may file, prosecute and maintain
patent applications and patents with respect thereto, at its own expense. In any
such case, the party declining to participate in such activities shall not grant
any third party a license under its interest in the applicable Centeon/Medarex
Invention without the prior written consent of the other party.

          8.2.4 Notice. During the term of this Agreement, each party will
                --------                                                  
advise the other of the filing of any patent applications subject to Section 
8.1 promptly after such patent application is filed. With respect to inventions
solely owned by Medarex, at Centeon's option, any patent application or patent
covering such an invention may be added to the list of Patent Rights as
described in Exhibit B hereto, with a writing signed by the parties.

          8.2.5 Cooperation. Centeon shall be given an opportunity to review
                -----------                                                 
Medarex' activities pursuant to Section 8.2.1 and provide input thereto. Medarex
shall include in such patent applications such claims as Centeon may request.
Medarex shall keep Centeon fully informed as to the status of such patent
matters, including, without limitation, by providing Centeon the opportunity, at
Centeon's expense, to review and comment on any documents relating to Medarex
Technology which will be filed in any patent office at least thirty (30) days
before such filing, and promptly providing Centeon copies of any documents
relating to Medarex Technology which Medarex receives from such patent offices,
including notice of all interferences, reissues, reexaminations, oppositions or
requests for patent term extensions.

     8.3  Enforcement. In the event that any Medarex Technology necessary for
          -----------
manufacture, use and sale of a Product is infringed or misappropriated by a
third party in any country or is subject to a declaratory judgment action
arising from such infringement or misappropriation in such country, or is the
subject of an interference, re-examination, reissue or opposition proceeding,
the party becoming aware thereof shall promptly notify the other party hereto.
Medarex shall have the initial right (but not the obligation), at its expense,
to bring suit to abate any infringement or misappropriation of Medarex
Technology, using counsel of its choice. In the event that Medarex fails to
initiate a suit to enforce such Medarex Technology against a commercially
significant infringement in the Field by a third party within one hundred eighty
(180) days, Centeon may initiate such suit to abate such infringement or
misappropriation, and the parties shall equally share the expenses associated
therewith, provided, Centeon may not enter into any settlement without the prior
consent of Medarex, which shall not be unreasonably withheld, and may not make
any statement which admits

                                      -22-
<PAGE>
 
that any of the Patent Rights or other intellectual property licensed to Centeon
pursuant to this Agreement are invalid or unenforceable. The party involved in
any such claim, suit or proceeding, shall keep the other party hereto reasonably
informed of the progress of any such claim, suit or proceeding and each party
shall cooperate reasonably in connection with the pursuit of any such action, at
the request and expense of the party requesting such cooperation. Any recovery
by such party received as a result of any such claim, suit or proceeding shall
be used first to reimburse the parties hereto for all expenses (including court
costs, attorneys and professional fees and other expenses of all kinds) incurred
in connection with such claim, suit or proceeding. [*****]

     8.4  Infringement Claims. If the manufacture, sale or use of the Product
          -------------------
pursuant to this Agreement results in any claim, suit or proceeding alleging
patent infringement against Centeon or Medarex, such party shall promptly notify
the other party hereto. If Medarex is not named as a party in such a suit or
proceeding, Medarex may, at its own expense and through counsel of its own
choice, seek leave to intervene in such suit or proceeding. Centeon agrees not
to oppose such intervention. If Medarex, and not Centeon, is named as a party to
such suit or proceeding, Medarex shall have the right to control the defense and
settlement of such suit or proceeding, at its own expense, using counsel of its
own choice, however Centeon, at its own expense and through counsel of its
own choice, may seek to intervene if the suit or proceeding relates to the
commercialization of the Product in the Field. Medarex agrees not to oppose
such intervention. If both Medarex and Centeon are named as parties in such suit
or proceeding, or become parties through intervention, each shall have the
right, at its own expense and through counsel of its own choice, to present its
own defense and to determine its own terms for settlement. [*****] The parties 
shall cooperate with each other in connection with any such claim, suit or
proceeding and shall keep each other reasonably informed of all material
developments in connection with any such claim, suit or proceeding.

9.   REPRESENTATIONS AND WARRANTIES

     9.1  Medarex. Medarex represents and warrants that:
          -------                                       

          9.1.1 it is a corporation duly organized, validly existing and in good
standing under the laws of the State of New Jersey;

          9.1.2 when executed and delivered, this Agreement will become valid
and binding on Medarex, and enforceable against Medarex in accordance with its
terms;


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -23-
<PAGE>
 
          9.1.3 it is not a party to any agreement, indenture or other
instrument and has no by-law or charter provision and knows of no law or
regulation which would prohibit it from entering into this Agreement, performing
the agreement contemplated hereunder or granting the licenses granted hereunder;

          9.1.4 it has not previously granted and will not grant any rights in
conflict with the rights and license granted to Centeon herein, and is the owner
or licensee of the Medarex Technology, with the right to license the Medarex
Technology to Centeon, except as expressly set forth in Section 3.4;

          9.1.5 Medarex bas not been served with any lawsuit with respect to the
Medarex Technology or the right of Medarex to enter into and perform its
obligations under this Agreement and, to the best of Medarex' knowledge as of
the Effective Date, there are no existing or threatened actions, suits or claims
pending with respect to the Medarex Technology or the right of Medarex to enter
into and perform its obligations under this Agreement;

          9.1.6 the Medarex Technology owned by Medarex is free and clear of any
lien, encumbrance, security interest and restriction on transfer and license,
and to the best of Medarex' knowledge as of the Effective Date, the Medarex
Technology licensed from third parties is free and clear of any lien,
encumbrance, security interest and restriction on transfer and license;

          9.1.7 as of the Effective Date, the MRC Sublicense and the Scotgen
Sublicense, are in full force and effect and there are no existing defaults, or
events, which, with the passage of time, would become defaults under such
agreements, which, individually or taken as a whole, would materially and
adversely affect the ability of Medarex to enter into this Agreement or the
ability of the parties to perform the transactions contemplated hereunder;

          9.1.8 to the best of Medarex' knowledge as of the Effective Date,
the Celltech/MRC Agreement and the MRC/Scotgen Agreement, are in full force and
effect and there are no existing defaults, or events, which, with the passage of
time, would become defaults under such agreements, which, individually or taken
as a whole, would materially and adversely affect the ability of Medarex to
enter into this Agreement or the ability of the parties to perform the
transactions contemplated hereunder;

          9.1.9 as of the Effective Date, the execution, delivery of this
Agreement and performance hereunder by Medarex does not conflict with, or cause
a default under, the MRC Sublicense or the Scotgen Sublicense; and

          9.1.10 to the best of Medarex' knowledge as of the Effective Date,
the execution, delivery of this Agreement and performance hereunder by Medarex
does not conflict with, and will not cause a default under, the Celltech/MRC
Agreement or the MRC/Scotgen Agreement;

                                      -24-
<PAGE>
 
          [*****]

     9.2  Centeon. Centeon represents and warrants that:
          -------

          9.2.1 it is a limited liability company duly organized, validly
existing and in good standing under the laws of the State of Delaware;

          9.2.2 when executed and delivered, this Agreement will become valid
and binding on Centeon, and enforceable against Centeon in accordance with its
terms.

     9.3  Effect of Representations and Warranties. It is understood that if the
          -----------------------------------------                            
representations and warranties under this Article 9 are not true and accurate
and Medarex or Centeon incurs liabilities, costs or other expenses as a result
of such falsity, Medarex or Centeon, as the case may be, shall indemnify, defend
and hold the other party harmless from and against any such liabilities, costs
or expenses incurred, provided that the indemnifying party receives prompt
notice of any claim against Medarex or Centeon, as the case may be, resulting
from or related to such falsity, the cooperation of the indemnified party, as
requested in connection with any such claim, and the sole right to control the
defense or settlement thereof.

     9.4  Notice. Upon learning of any default under or material adverse changes
          ---------                                                             
in or to the Celltech/MRC Agreement, MRC/Scotgen Agreement, Scotgen Sublicense
and MRC Sublicense, Medarex shall promptly send notice to Centeon of such
defaults or material adverse changes.

     9.5  Disclaimer of Warranties, Medarex specifically disclaims that the
          --------------------------                                       
Development Program will be successful in whole or part. EXCEPT AS OTHERWISE
EXPRESSLY SET FORTH IN THIS AGREEMENT AND SUBJECT TO THE INDEMNITY PROVISIONS OF
ARTICLE 11, MEDAREX AND CENTEON AND THEIR RESPECTIVE AFFILIATES MAKE NO
REPRESENTATIONS AND EXTEND NO WARRANTIES OR CONDITIONS OF ANY KIND, EITHER
EXPRESS OR IMPLIED, WITH RESPECT TO THE PATENT RIGHTS AND KNOW-HOW, OR PRODUCTS
INCLUDING, BUT NOT LIMITED TO, WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE, VALIDITY OF THE PATENT RIGHTS OR KNOW-HOW LICENSED
HEREUNDER, OR NONINFRINGEMENT OF THE INTELLECTUAL PROPERTY RIGHTS OF THIRD
PARTIES.

10.  CONFIDENTIALITY

     10.1 Confidential Information.  Except as expressly provided herein, the
          ---------------------------                                        
parties agree that, for the term of this Agreement and for five (5) years
thereafter, the receiving party shall keep


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -25-
<PAGE>
 
completely confidential and shall not publish or otherwise disclose and shall
not use for any purpose except for the purposes contemplated by this Agreement
any Confidential Information furnished to it by the disclosing party hereto
pursuant to this Agreement, except that to the extent that it can be established
by the receiving party by competent proof that such Confidential Information:

          (a) was already known to the receiving party, other than under an
obligation of confidentiality, at the time of disclosure;

          (b) was generally available to the public or otherwise part of the
          public domain at the time of its disclosure to the receiving party;

          (c) became generally available to the public or otherwise part of the
public domain after its disclosure and other than through any act or omission
of the receiving party in breach of this Agreement;

          (d) was independently developed by the receiving party as demonstrated
by documented evidence prepared contemporaneously with such independent
development; or

          (e) was subsequently lawfully disclosed to the receiving party by a
person other than a party.

     10.2 Permitted Use and Disclosures. Each party hereto may use or disclose
          --------------------------------                                     
information disclosed to it by the other party, to the extent such use or
disclosure is reasonably necessary in filing or prosecuting patent applications,
prosecuting or defending litigation, complying with applicable governmental
regulations or otherwise submitting information to tax or other governmental
authorities, conducting clinical trials, or making a permitted sublicense or
otherwise exercising its rights hereunder, provided that if a party is required
to make any such disclosure of another party's confidential information, other
than pursuant to a confidentiality agreement, it will give reasonable advance
notice to the latter party, of such disclosure and, save to the extent
inappropriate in the case of patent applications, will use its best efforts to
secure confidential treatment of such information (including the significant
financial terms of this Agreement) prior to its disclosure (whether through
protective orders or otherwise) and disclose such information only to the
minimum extent necessary to comply with such requirements. 


     10.3 Public Disclosure. Except as otherwise required by law, neither party
          -----------------
shall issue a press release or make any other public disclosure of the terms of
this Agreement or regarding the results of the Development Program without the
prior approval of such press release or public disclosure. Each party shall
submit any such press release or public disclosure to the other party, and the
receiving party shall have fifteen (15) days to review and approve any such
press release or public disclosure, which approval shall not be unreasonably
withheld. If the receiving party does not respond within such fifteen (15) day
period, the press release or public disclosure shall be deemed approved. In
addition, if a public disclosure is required by law, including without 
limitation in a filing with the Securities and Exchange Commission, the
disclosing party shall provide copies of the disclo-

                                      -26-
<PAGE>
 
sure reasonably in advance of such filing or other disclosure for the
nondisclosing party's prior review and comment.

     10.4 Injunctive Relief Notwithstanding Section 13.2, Medarex and Centeon
          ------------------                                                 
hereby acknowledge that damages at law may be an inadequate remedy for the
breach of any of the covenants, promises and agreements contained in this
Section 10, and accordingly, Medarex or Centeon, as the case may be, may be
entitled to injunctive relief with respect to any such breach, including
specific performance of such covenants, promises or agreements or an order
enjoining Medarex or Centeon from any threatened, or from the continuation of
any actual, breach of covenants, promises or agreements. The rights set forth in
this Section 10.4 shall be in addition to any other rights which Medarex or
Centeon may have at law or in equity.

11.  INDEMNIFICATION

     [*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -27-
<PAGE>
 
[*****]


12.  TERM AND TERMINATION

     12.1 Term. This Agreement shall be effective as of the Effective Date and
          ----
unless otherwise terminated earlier pursuant to this Article 12, shall continue
in full force and effect on a country-by-country basis until Centeon and it's
Affiliates and Sublicensees have no remaining royalty obligations in such
country. Following the expiration of royalty obligations in any country,
Centeon shall have a non-exclusive, fully paid license under the Know-How to
commercialize the Product in the Field in such country.

     12.2 Termination for Cause. Either party may terminate this Agreement in
          ----------------------
the event the other party has materially breached or defaulted in the
performance of any of its obligations hereunder, and such default has continued
for sixty (60) days after written notice thereof was provided to the breaching
party by the nonbreaching party. Any termination shall become effective at the
end of such sixty (60) day period unless the breaching party has cured any such
breach or default prior to the expiration of the sixty (60) day period.
Notwithstanding the above, in the case of a failure to pay any amount due
hereunder the period for cure of any such default following notice thereof shall
be ten (10) days and, unless payment is made within such period, the termination
shall become effective at the end of such period. Notwithstanding the above, if
Centeon disputes the amount of a particular payment obligation, Centeon shall
timely pay to Medarex all amounts except the specific amount in dispute and may
establish an interest-bearing escrow account and tender the disputed amount
thereto, and the balance of the account shall be paid out to either party
pursuant to the outcome of arbitration conducted in accordance with the
provisions of Section 13.2 of this Agreement.

     12.3 Termination for Insolvency. If voluntary or involuntary proceedings by
          --------------------------                                            
or against a party are instituted in bankruptcy under any insolvency law, or a
receiver or custodian is appointed for such party, or proceedings are instituted
by or against such party for corporate reorganization or the dissolution of such
party which proceedings, if involuntary, shall not have been dismissed within
sixty (60) days after the date of filing, or if such party makes an assignment
for the benefit of


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.

                                      -28-
<PAGE>
 
creditors, or substantially all of the assets of such party are seized or
attached and not released within sixty (60) days thereafter, the other party may
immediately terminate this Agreement effective upon notice of such termination.

     12.4 [*****]

     12.5 [*****]

     12.6 Effect of Breach or Termination.
          -------------------------------

          12.6.1 Accrued Obligations. Termination of this Agreement for any 
                 -------------------                                            
reason shall not release any party hereto from any liability which, at the time
of such termination, has already accrued to the other party or which is
attributable to a period prior to such termination nor preclude either party
from pursuing all rights and remedies it may have hereunder or at law or in
equity with respect to any breach of this Agreement. For the avoidance of doubt,
it is agreed that following the termination of the Agreement Centeon shall have
no obligation to pay Medarex any amount for Product development after such date,
or the achievement of any milestone after such date.

           12.6.2 Return of Materials. Upon any termination of this Agreement,
                  -------------------
Centeon and Medarex shall promptly return to the other party all Confidential
Information received from the other party (except one copy of which may be
retained for archival purposes).

           12.6.3 Stock on Hand. In the event this Agreement is terminated for
                  -------------
any reason, Centeon and its Affiliates and Sublicensees shall have the right to
sell or otherwise dispose of the stock of any Product then on hand or purchased
pursuant to Section 12.6.5, subject to Articles 4 and 5 and the other applicable
terms of this Agreement.


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -29-
<PAGE>
 
          12.6.4 Licenses.  Subject to Section 12.6.3 regarding post-termination
                 ---------                                                      
Product sales, upon any termination of this Agreement pursuant to Section 12.2
or 12.3, the licenses and rights granted Centeon shall terminate concurrently.
Upon any termination of this Agreement pursuant to Section 12.4, the licenses
granted to Centeon shall terminate concurrently.

          12.6.5 Product in Manufacture. In the event of any termination by
                 ----------------------                                  
Centeon pursuant to Section 12.4, Centeon shall purchase from Medarex all
Product which Medarex. commenced the manufacture of at Centeon's request prior
to the date Medarex received notice from Centeon of such termination.

     12.7 Survival. Sections 3.6, 5.1, 5.2, 6.3, 6.6, 6.7, 8.1, 8.4 and
          ----------                                                    
Articles 9, 10, 11 and 13 shall survive the expiration or termination of this
Agreement for any reason.

13.  MISCELLANEOUS

     13.1  Governing Law. This Agreement and any dispute, including without
           -------------                                                  
limitation any arbitration, arising from the performance or breach hereof shall
be governed by and construed and enforced in accordance with the laws of the
state of New York, without reference to conflicts of laws principles.

     13.2  Arbitration. Any dispute under this Agreement which is not settled by
           -----------
mutual consent shall be finally settled by binding arbitration, conducted
in accordance with the Commercial Arbitration Rules of the American Arbitration
Association by three (3) arbitrators appointed in accordance with said rules.
The arbitration shall be held in New York, New York and at least one of the
arbitrators shall be an independent expert in pharmaceutical product development
(including clinical development and regulatory affairs). The arbitrators shall
determine what discovery will be permitted, consistent with the goal of limiting
the cost and time which the Parties must expend for discovery; provided the
arbitrators shall permit such discovery as they deem necessary to permit an
equitable resolution of the dispute. Any written evidence originally in a
language other than English shall be submitted in English translation
accompanied by the original or a true copy thereof. The costs of the
arbitration, including, administrative and arbitrators' fees, shall be shared
equally by the parties and each party shall bear its own costs and attorneys'
and witness' fees incurred in connection with the arbitration. A disputed
performance or suspended performances pending the resolution of the arbitration
must be completed within thirty (30) days following the final decision of the
arbitrators or such other reasonable period as the arbitrators determine in a
written opinion. Any arbitration subject to this Section 13.2 shall be completed
within one (1) year from the filing of notice of a request for such arbitration.
The arbitration proceedings and the decision shall not be made public without
the joint consent of the parties and each party shall maintain the
confidentiality of such proceedings and decision unless otherwise permitted by
the other party. Any decision which requires a monetary payment shall require
such payment to be payable in United States dollars, free of any tax or other
deduction. The parties agree that the decision shall be the sole, exclusive and
binding remedy between them regarding any and all disputes, controversies,
claims and counterclaims

                                      -30-
<PAGE>
 
presented to the arbitrators. Application may be made to any court having
jurisdiction over the party (or its assets) against whom the decision is
rendered for a judicial recognition of the decision and an order of enforcement.

     13.3 Waiver. Neither party may waive or release any of its rights or
          ------                                                         
interests in this Agreement except in writing. The failure of either party to
assert a right hereunder or to insist upon compliance with any term or condition
of this Agreement shall not constitute a waiver of that right or excuse a
similar subsequent failure to perform any such term or condition.

     13.4 Assignment. This Agreement shall not be assignable by either party to
          ------------                                                         
any third party hereto without the written consent of the other party hereto;
except either party may assign this Agreement, without such consent, to an
entity that acquires all or substantially all of the business or assets of such
party to which this Agreement pertains, whether by merger, reorganization,
acquisition, sale, or otherwise.

     13.5 Notices. All notices, requests and other communications hereunder
          ---------                                                        
shall be in writing and shall be personally delivered or sent by telecopy or
other electronic facsimile transmission or by registered or certified mail,
return receipt requested, postage prepaid, in each case to the respective
address specified below, or such other address as may be specified in writing
to the other parties hereto:

          CENTEON:   Centeon L.L.C.
                     1020 First Avenue
                     King of Prussia, Pennsylvania 19406-1310
                     Attn: General Counsel

          MEDAREX    Medarex, Inc.
                     1545 Route 22 East
                     P.O. Box 953
                     Annandale, New Jersey 08801
                     Attn: President

     13.6 Performance by Affiliates. Centeon shall warrant the performance of 
          --------------------------                                            
any and all rights and obligations of this Agreement by its Affiliate(s) and
Sublicensees. 

     13.7 Force Majeure. Neither party shall be liable to the other for failure
          -------------                                                        
or delay in the performance of any of its obligations under this Agreement for
the time and to the extent such failure or delay is caused by riots, civil
commotions, wars, hostilities between nations, governmental laws, orders or
regulations, embargoes, actions by the government or any agency thereof, acts
of God, storms, fires, accidents, labor disputes or strikes, sabotage,
explosions or other similar or different contingencies, in each case, beyond the
reasonable control for the respective parties. The party affected by Force
Majeure shall provide the other party with full particulars thereof as soon as
it becomes aware of the same (including its best estimate of the likely extent
and duration of the

                                      -31-
<PAGE>
 
interference with its activities), and will use its best endeavors to overcome
the difficulties created thereby and to resume performance of its obligations as
soon as practicable. If the performance of any obligation under this Agreement
is delayed owing to a force majeure for any continuous period of more than six
(6) months, the parties hereto shall consult with respect to an equitable
solution, including the possible termination of this Agreement.

     13.8 Independent Contractors. Both parties are independent contractors
          ----------------------                                           
under this Agreement. Nothing contained ih this Agreement is intended nor is to
be construed so as to constitute Medarex or Centeon as partners or joint
venturers with respect to this Agreement. Neither party shall have any express
or implied right or authority to assume or create any obligations on behalf of
or in the name of the other party or to bind the other party to any other
contract, agreement, or undertaking with any Third Party.

     13.9 Advice of Counsel. Medarex and Centeon have each consulted counsel of
          -----------------                                                   
their choice regarding this Agreement and each acknowledges and agrees that this
Agreement shall not be deemed to have been drafted by one party or another and
will be construed accordingly.

     13.10 Trademarks. Centeon and its Affiliates shall have the right to
           ------------                                                   
market the Product under their own labels and trademark(s). All Product packages
shall carry the notice "Manufactured under license from Medarex, Inc." or a
similar slogan, in a typeface and size agreed by the parties.

     13.11 Other Obligations. Except as expressly provided in this Agreement or
           -------------------                                                  
as separately agreed upon in writing between Medarex and Centeon, each party
shall bear its own costs incurred in connection with the implementation of the
obligations under this Agreement.

     13.12 Severability. In the event that any provision of this Agreement 
           -----------                                                         
becomes or is declared by a court of competent jurisdiction to be illegal,
unenforceable or void, this Agreement shall continue in full force and effect
without said provision.

     13.13 No Implied Licenses. No rights or licenses with respect to the
           -------------------
Medarex Technology are granted or deemed granted hereunder or in connection
herewith, other than those rights expressly granted in this Agreement.

     13.14 Patent Marking. Centeon agrees to mark and have its Affiliates and
           -----------------                                                  
sublicensees mark all Products they sell or distribute pursuant to this
Agreement in accordance with the applicable statute or regulations in the
country or countries of manufacture and sale thereof.

     13.15 Compliance with Laws. Each party shall furnish to the other party 
          ----------------                                                      
any information requested or required by that party during the term of this 
Agreement or any extensions hereof to enable that party to comply with the 
requirements of any U.S. or foreign federal, state and/or government agency.

                                      -32-
<PAGE>
 
     13.16 Complete Agreement. This Agreement with its Exhibits constitutes the
           --------------------                                                
entire agreement, both written and oral, between the parties with respect to the
subject matter hereof, and that all prior agreements respecting the subject
matter hereof, either written or oral, expressed or implied, are merged and
canceled, and are null and void and of no effect. No amendment or change hereof
or addition hereto shall be effective or binding on either of the parties hereto
unless reduced to writing and duly executed on behalf of both parties,

     13.17 Headings. The captions to the several Sections and Articles hereof
           ----------                                                        
are not a part of this Agreement, but are included merely for convenience of
reference only and shall not affect its meaning or interpretation.

     13.18 Counterparts. This Agreement may be executed in counterparts, each
           --------------                                                     
of which shall be deemed to be an original, and both together shall be deemed to
be one and the same agreement.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed by their authorized representatives as of the Effective Date.
 
CENTEON L.L.C.                                  MEDAREX, INC.
 
By: /s/ John A. Sedor                           By: /s/ Michael Appelbaum 
     --------------------  

Name:   John A. Sedor                           Name:   Michael Appelbaum 
     --------------------                            --------------------    

Title:  CEO                                     Title:  Sr. Vice President
     --------------------                            --------------------    

By: /s/ P. Fuhge  
     --------------------
Name:   P. Fuhge  
     -------------------- 

Title:  Senior Executive V.P.
     ------------------------
        and Chief Research &
        Development Officer

                                      -33-
<PAGE>
 
                                   EXHIBIT A

                               Development Plan

[*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.



                                      -34-
<PAGE>
 
[*****]


***** REPRESENTS CONFIDENTIAL PORTION WHICH HAS BEEN OMITTED AND FILED 
SEPARATELY WITH THE SEC.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE OMITTED PORTIONS.


                                      -35-
<PAGE>
 
                                   EXHIBIT B
                U.S. and Foreign Patent Applications and Patents

                                      -36-


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