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                                                                   EXHIBIT 10.20


                          PFIZER ROYALTY FREE LICENSE


      This AGREEMENT is entered into as of April 1, 1986 by and between PFIZER
INC.  ("PFIZER"), a Delaware corporation having an office at 235 East 42nd
Street, New York, New York 10017, and ONCOGENE SCIENCE, INC. ("OSI"), a
Delaware corporation having an office at 222 Station Plaza North, Suite 330,
Mineola, New York, 11501.

      The parties agree as follows:

      1.    DEFINITIONS

            The capitalized terms used herein have the meanings specified in
Exhibits I, II, III and IV of the Collaborative Research Agreement dated as of
April 1, 1986 between PFIZER and OSI.

      2.    GRANT

            2.1.  OSI grants to PFIZER a nonexclusive, irrevocable, worldwide,
royalty-free, perpetual right and license, including the right to grant
sublicenses, under Joint Patent Rights and Joint Technology to make, have made,
use and sell products in all fields of use except the following:

            (a)   in vitro and in vivo diagnostics, including in vivo imaging;
and

            (b)   Monoclonal Antibody Technology; and

            (c)   products sold exclusively for research use.





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      3.    INFRINGEMENT

            3.1.  PFIZER shall have the right, at its expense, to institute
actions under Joint Patent Rights and Joint Technology for infringement or
misappropriation in the fields of use in which OSI has granted rights to
PFIZER.

      4.    MISCELLANEOUS

            4.1.  This Agreement is made and delivered in New York and shall be
governed by, and construed in accordance with, the laws of the State of New
York applicable to agreements made and to be performed entirely within the
State of New York.

            4.2.  This Agreement shall be binding upon and inure to the benefit
of the parties hereto and their respective legal representatives, successors
and assigns.

                                          ONCOGENE SCIENCE, INC.


                                          By: /s/ John R. Stephens
                                             ---------------------------------

                                          Title:  Scientific Director


                                          PFIZER INC.


                                          By: /s/ Barry M. Bloom
                                             ---------------------------------

                                          Title:  Vice President





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