Exhibit 10.11

                      FIRST AMENDMENT TO SUBLEASE AGREEMENT

         This First Amendment to Sublease Agreement ("First Amendment") dated
July 20,1999, for reference purposes only, is entered into by and between
METAXEN LLC, a Delaware limited liability company ("Sublessor") and
CYTOKINETICS, INC. a Delaware corporation ("Sublessee"), and is subject to the
terms and conditions of that certain Build-To-Suit Lease ("Master Lease") dated
May 27,1997 (as amended) entered into by BRITANNIA POINTE GRAND LIMITED
PARTNERSHIP, a California limited partnership ("Master Lessor"), as Landlord,
and Sublessor as Tenant, with reference to the following facts:

         A.       Sublessor and Sublessee are parties to a sublease, dated
May 1, 1998 ("Sublease"), covering certain premises of approximately 13,750
leasable square feet located within Building H in the Britannia Pointe Grand
Business Park, South San Francisco, California;

         B.       By an Assignment and Assumption Agreement and Consent dated as
of June 11,1999 among Sublessor, Master Lessor, Xenova Group plo and Exelixis
Pharmaceuticals, Inc, ("Exelixis"), Sublessor assigned its entire leasehold
interest under the Master Lease to Exelixis, with Master Lessor's consent, upon
terms and conditions set forth in such Assignment Agreement; .

         C.       By an Agreement and Consent dated as of even date herewith,
among Sublessee, Exelixis, and Master Lessor, Exelixis agreed that, in exchange
for certain payments and other consideration and upon and subject to the terms
and conditions set forth in such Agreement and Consent, it will assign to
Sublessee its interests and rights under the Master Lease;

         D.       Sublessee wishes to extend the Expiration Date of the
Sublease;

         E.       Capitalized tarms used in this Amendment which are not
otherwise specifically defined herein shall have the meanings assigned to such
terms in the Sublease.

         NOW THEREFORE, in consideration of the mutual agreements and promises
set forth herein, the parties agree as follows:

         1.       Sublease Term. The parties agree that the Expiration Date is
amended to February 28, 2001.

         2.       Full Force and Effect. Except as expressly set forth herein,
the Sublease has not been modified or amended and remains in full force and
effect.

                                       1



         IN WITNESS WHEREOF, the undersigned have executed this Amendment as of
the date first set forth above.

             "Sublesseor"                                     "Sublessee"

         METAXEN, LLC a Delaware                         CYTOKINETICS, INC.,
         limited liability company                       a Delaware corporation

By: /s/ [ILLEGIBLE]                                  By: /s/ James Sabry
    ------------------------                             --------------------
       ------------------                                  James Sabry
       ------------------                                  President & CEO

By: /s/ [ILLEGIBLE]                                  By: /s/ Robert Blum
    ------------------------                             --------------------
       ------------------                                  Robert Blum
       ------------------                                  Vice President

         The undersigned hereby consent to the foregoing, effective of the date
first above written.

         BRITANNIA POINTE GRAND LIMITED PARTNERSHIP,
         a Delaware limited partnership

         By: Britannia Pointe Grand LLC, a California limited liability company
             General Partner

         By: /s/ T.J. Bristow
            -------------------------------------
               T.J. Bristow
               Manager, President and Chief Financial Officer

         EXELIXIS PHARMACEUTICALS, INC.
         a Delaware corporation

         By:  /s/ [ILLEGIBLE]
              -----------------------------------
                  Its: PRES & CEO
                      ----------------------------------

         By:  /s/ [ILLEGIBLE]
              -----------------------------------
                  Its: SECRETARY

                                       2