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                                                                   Exhibit 10.25

                   AMENDMENT OF RESEARCH AND LICENSE AGREEMENT

This Amendment is made effective as of the 23rd day of October, 1998 (the
"Amendment Date") by and between Microcide Pharmaceuticals, Inc., a corporation
organized under Delaware law having its principal office at 850 Maude Avenue,
Mountain View, California 94043 (hereinafter called "Microcide") on the one
hand, and Ortho Pharmaceutical Corporation, a company organized under Delaware
law having its principal office at U.S. Route 202, Raritan, New Jersey 08869
(hereinafter called "Ortho") and the R.W. Johnson Pharmaceutical Research
Institute, a division of Ortho Pharmaceutical Corporation, having its principal
office at U.S. Route 202, Raritan, New Jersey 08869 (hereinafter called
"RWJPRI") (Ortho and RWJPRI are collectively referred to herein as "Licensee")
on the other hand, and amends the Research and License Agreement dated as of
October 24, 1995 between Microcide and Licensee (the "Research and License
Agreement"). Terms not otherwise defined herein shall have the meaning set forth
in the Research and License Agreement.

       WHEREAS, Microcide and Licensee wish to amend the Research and License
Agreement as set forth herein.

       NOW, THEREFORE, in consideration of the premises and the performance of
the covenants herein contained, it is agreed that the Research and License
Agreement shall be amended as follows effective as of the Amendment Date:

       1. Section (h) of Article I of the Research and License Agreement shall
be amended to delete clauses [*] from the definition of "Field", with
the result that Licensee shall not have the right to select a Collaboration
Compound for Development and subsequent commercialization as a Licensed Product
with regard to the [*] Subfield and the [*] Subfield, as
defined in clauses [*], respectively. Licensee shall not have any
rights to any new compounds in such Subfields discovered by Microcide, and
Microcide shall be free to enter into discussions and agreements with third
parties in such Subfields without obligation to Licensee.

       2. With regard to Section 2.3.1 of the Research and License Agreement,
[*]

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* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.
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[*]

       3. Further with regard to Section 2.3.1 of the Research and License
Agreement, [*]

       4. Section 4.1.1.1 of the Research and License Agreement shall be
amended to add the following to the end of such section:

          [*]

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* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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     [*]

     5. Except as set forth above, all terms of the Research and License
Agreement shall continue in full force and effect without change and the
provisions of Article 20 and Article 1 of the Research and License Agreement
shall also apply to this Amendment.

     IN WITNESS WHEREOF, the Parties hereto have hereunto set their hands and
duly executed this Amendment Agreement on the dates indicated below to be
effective as of the Amendment Date set forth above.

For and on behalf of Microcide Pharmaceuticals, Inc.

By:    /s/ James Rurka
       --------------------------
Title: President and CEO
Date:  10/23/98

For and on behalf of Ortho Pharmaceutical Corporation and Licensee

By:    /s/ Robert Savage
       --------------------------
Title: President
Date:  10-16-98

For and on behalf of the R.W. Johnson Pharmaceutical Research Institute

By:    /s/ William A. M. Duncan
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Title: Chairman
Date:  10-14-98

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* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.