EXHIBIT 3.3

                           CERTIFICATE OF AMENDMENT TO
                      RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                         MICROCIDE PHARMACEUTICALS, INC.

                             a Delaware Corporation

                Pursuant to (S)242 of the General Corporation Law
                            of the State of Delaware

     Microcide Pharmaceuticals, Inc., a corporation organized and existing under
the General Corporation Law of the State of Delaware (the "Corporation") does
hereby certify:

     1.  The name of the Corporation is Microcide Pharmaceuticals, Inc. and was
originally incorporated under the same name, and the original Certificate of
Incorporation was filed with the Secretary of State of the State of Delaware on
February 29, 1996.

     2.  The following amendment to the Restated Certificate of Incorporation
of the corporation has been duly adopted in accordance with the provisions of
Section 242 of the General Corporation Law of the State of Delaware:

          Article I of the Restated Certificate of Incorporation is hereby
     amended to read in its entirety as follows:

                                   "ARTICLE I.

               The name of this corporation is Essential Therapeutics, Inc."

     3.  The capital of the corporation will not be reduced under or by reason
of the foregoing amendment.

     IN WITNESS WHEREOF, Microcide Pharmaceuticals, Inc. has caused this
Certificate to be executed by its duly authorized officer this 24th day of
October, 2001.

                                MICROCIDE PHARMACEUTICALS, INC.


                                By:      /s/ James E. Rurka
                                   --------------------------------------------
                                Name:    James E. Rurka
                                Title:   President and Chief Executive Officer