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                                                                    EXHIBIT 10.1

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Portions of this Exhibit 10.1 have been redacted and are the subject of a 
confidential treatment request filed with the Secretary of the Securities and 
Exchange Commission.
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                                                                    Exhibit 10.1


                              AMENDATORY AGREEMENT

         This AMENDATORY AGREEMENT is entered into as of December 31, 1993 by
and between AMERICAN HOME PRODUCTS CORPORATION, a corporation of the State of
Delaware, U.S.A., having its principal place of business at Five Giralda Farms,
Madison, New Jersey 07940-0874, U.S.A., as represented by its agent,
WYETH-AYERST LABORATORIES DIVISION (hereinafter collectively referred to as
"Wyeth") and ONCOGENE SCIENCE, INC. (hereinafter referred to as "OSI"), a
corporation of the State of Delaware, having its principal place of business at
106 Charles Lindbergh Boulevard, Uniondale, New York 11553, U.S.A.

         WHEREAS, Wyeth and OSI entered into a Collaborative Research Agreement
as of December 31, 1991 (the "Collaborative Research Agreement") pursuant to
which, among other things, OSI is currently screening chemical compounds
included within the Wyeth Technology against the Targets which are the subject
of the Research Program.

         WHEREAS, Wyeth and OSI wish to amend the Collaborative Research
Agreement to extend its term, to provide additional funding commitments on the
part of Wyeth and to make the additional changes hereinafter provided for.

         NOW, THEREFORE, the parties agree as follows:

         1.       Defined terms used but not defined herein shall have the
meanings specified in Section 1 of the Collaborative Research Agreement.

         2.       Effective December 31, 1993, the Collaborative Research
Agreement shall be extended and amended as more fully provided in this
Amendatory Agreement.

         3.       From and after January 1, 1994, the OSI Appointees referred to
in Section 2.2.2 of the Collaborative Research Agreement shall be as follows:

                                      ***
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and Wyeth-Ayerst appointees:          ***

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                                      ***



*** These portions deleted pursuant to a request for confidential treatment.
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         4.       The following shall be added at the end of Section 3.1 of the
Collaborative Research Agreement:

                  "The Annual Commitment from the Commitment Year beginning
                  January 1, 1994 is ***. The Annual Commitment for the
                  Commitment Year beginning January 1, 1995 is *** and
                  the Annual Commitment for the Commitment Year beginning
                  January 1, 1996 is ***."

         5.       The second sentence of Section 3.2 of the Collaborative
Research Agreement is amended to read in its entirety as follows:

                  "Each Annual Commitment is subject to modification by mutual
                  agreement if an unusually large number of lead compounds are
                  identified or if additional genetic constructs are required by
                  OSI to facilitate lead development as specified in the
                  applicable Annual Sponsored Research Plan."

         6.       Section 9.1 of the Collaborative Research Agreement is amended
to read in its entirety as follows:

                  "9.1 Term. Unless sooner terminated or extended, this
                  Agreement shall expire on December 31, 1996, subject to the
                  early termination provisions of Section 9.5 and subject
                  further to the ability of the parties to extend the term of
                  this Agreement if they so agree."

         7.       Section 9.5 of the Collaborative Research Agreement is amended
to read in its entirety as follows:

                  "9.5 Termination by Wyeth. After this Agreement has been in
                  effect for a period of thirty-two (32) months, Wyeth may
                  terminate this Agreement, with or without cause, by giving OSI
                  four (4) months notice at any time after the expiration of
                  said thirty-two (32) month period. If Wyeth terminates this
                  Agreement pursuant to this section, it will make the Funding
                  Payments which would otherwise have been due for such
                  four-month period and will retain all rights set forth in any
                  License Agreements then in effect subject to the requirements
                  of those Agreements."

         8.       The forms of License Agreements annexed as Exhibit 2 and
Exhibit 3 to the Collaborative Research Agreement are amended by adding words ",
as amended by an Amendatory Agreement dated as of December 31, 1993" at the end
of the definition of

*** These portions deleted pursuant to a request for confidential treatment.


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"Collaborative Research Agreement" set forth in Section 1.1 of each such forms
of License Agreement.

         9.       The parties hereto acknowledge that except as hereby modified
the Collaborative Research Agreement remains in full force and effect and sets
forth the entire agreement and understanding of such parties as to the subject
matter thereof.

         10.      The Amendatory Agreement shall be construed in accordance with
the laws of the State of New Jersey.

         11.      This Amendatory Agreement may be executed simultaneously in
two or more counterparts, each of which shall be deemed an original.

         IN WITNESS WHEREOF, the parties have hereunto set their hands and duly
executed this Amendment as of the day and year set forth below.

                                         AMERICAN HOME PRODUCTS CORPORATION


                                         By:      _____________________________
                                         Title:   _____________________________

                                         ONCOGENE SCIENCE, INC.


                                         By:      _____________________________
                                         Title:   _____________________________

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