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                                                                   EXHIBIT 10.43
January 22, 2002

Mr. Gary Grubbs
John Wayne Cancer Institute
2200 Santa Monica Boulevard
Santa Monica, CA 90404

         Re:      Master Services Agreement between CancerVax Corporation
                  ("CancerVax"), the John Wayne Cancer Institute ("JWCI") and
                  Synteract, Inc. ("Synteract"), dated January __, 2002 (the
                  "Master Agreement")

Dear Gary:

         This letter agreement (the "Letter Agreement"), which is made and
entered into as of the __ day of January, 2002, between JWCI and CancerVax, is
intended to allocate financial responsibility between the parties hereto for
fees and expenses charged by Synteract in connection with the provision of the
Services under the Master Agreement (the "Fees & Expenses"). Capitalized terms
which are not defined in this Letter Agreement shall have the meanings ascribed
to such terms in the Master Agreement.

         In consideration of the covenants and agreements hereinafter set forth,
the parties hereto agree as follows:

     1.  JWCI's share of each monthly invoice received from Synteract for the
         Fees & Expenses shall calculated by dividing the total amount of
         funding then available for data management under the NIH Grants by the
         number of months in which such funds are intended to be utilized in
         accordance with the terms of such NIH Grants (the "Remaining Grant
         Period"). By way of example, if, upon the date an invoice is received
         from Synteract, the total amount then available for data management
         under the NIH Grants is $120,000, and the Remaining Grant Period is
         twelve months, then the amount to be paid by JWCI shall be $10,000
         (i.e., $120,000 / 12 months). Any additional funding for data
         management related to the Studies which becomes available to JWCI
         during the term of the Master Agreement under any renewals, extensions
         or related grants from NIH, shall be added to the total amount
         available for payment of the Fees & Expenses

     2.  CancerVax agrees that JWCI's financial liability to Synteract for the
         Services shall be limited to the amounts available to JWCI under the
         NIH Grants, payable as outlined in paragraph (1), above. CancerVax
         further agrees to pay the difference, on a monthly basis, between the
         NIH Grant funding and the Fees & Expenses.

         This Letter Agreement may be executed in any number of counterparts,
each of which shall be deemed an original but which together shall constitute a
single instrument. If this letter contains principal terms and conditions which
are agreeable to you and you agree to be bound as described above, please
indicate by executing the enclosed copy of this letter and returning it to
CancerVax.

                                           Very truly yours,
                                           CancerVax Corporation

                                           By: /s/ David F. Hale
                                           David F. Hale
                                           President and Chief Executive Officer

ACCEPTED AND AGREED:
Effective as of January 22, 2002
The John Wayne Cancer Institute

By:      /s/ Gary Grubbs
         Gary Grubbs
         Executive Vice President, Finance & Administration