Exhibit 3 --------- Pursuant to Rule 13d-1(f)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need be filed with respect to the ownership by each of...

                                                                       Exhibit 3
                                                                       ---------

     Pursuant to Rule 13d-1(f)(1) under the Securities Exchange Act of 1934, the
undersigned hereby agree that only one statement containing the information
required by Schedule 13D need be filed with respect to the ownership by each of
the undersigned of shares of stock of Microcide Pharmaceuticals, Inc.

     This Agreement may be executed in any number of counterparts, each of which
shall be deemed an original.

     Executed this 2nd day of November, 2001.

                                         XXXXXXXX VENTURE MANAGERS LIMITED


                                         By: /s/ Xxxxxx Xxxxxx, Xxxx Xxxx
                                             ---------------------------------
                                         Title: Directors
                                                ------------------------------


                                         XXXXXXXX VENTURES INTERNATIONAL LIFE
                                         SCIENCES FUND II LP1 by Xxxxxxxx
                                         Venture Managers Inc. as General
                                         Partner


                                         By: /s/ Xxxxxx Xxxxxx, Xxxx Xxxx
                                             ---------------------------------
                                         Title: Directors and Vice Presidents
                                                ------------------------------


                                         XXXXXXXX VENTURES INTERNATIONAL LIFE
                                         SCIENCES FUND II LP2 by Xxxxxxxx
                                         Venture Managers Inc. as General
                                         Partner


                                         By: /s/ Xxxxxx Xxxxxx, Xxxx Xxxx
                                             ---------------------------------
                                         Title: Directors and Vice Presidents
                                                ------------------------------


                                         XXXXXXXX VENTURES INTERNATIONAL LIFE
                                         SCIENCES FUND II LP3 by Xxxxxxxx
                                         Venture Managers Inc. as General
                                         Partner


                                         By: /s/ Xxxxxx Xxxxxx, Xxxx Xxxx
                                             ---------------------------------
                                         Title: Directors and Vice Presidents
                                                ------------------------------


                                         XXXXXXXX VENTURES INTERNATIONAL LIFE
                                         SCIENCES FUND II STRATEGIC PARTNERS
                                         L.P. by Xxxxxxxx Venture Managers Inc.
                                         as General Partner


                                         By: /s/ Xxxxxx Xxxxxx, Xxxx Xxxx
                                             ---------------------------------
                                         Title: Directors and Vice Presidents
                                                ------------------------------


                                         XXXXXXXX VENTURES INTERNATIONAL LIFE
                                         SCIENCES FUND GROUP CO-INVESTMENT
                                         SCHEME by Sitco Nominees Ltd. VC 01903


                                         By: /s/ Xxxx Xxxx and Xxxxx Xxxxxxx
                                             ---------------------------------
                                         Title: Directors
                                                ------------------------------



                                              /s/ Xxxxx Xxxxxxx
                                         -------------------------------------
                                         Xxxxx Xxxxxxx, in his capacity as
                                         director of Xxxxxxxx Venture Managers
                                         Limited


                                                /s/ Xxxxxxx Xxxxxxx
                                         -------------------------------------
                                         Xxxxxxx Xxxxxxx, in her capacity as
                                         director of Xxxxxxxx Venture Managers
                                         Limited


                                                /s/ Xxxxxx Xxxxxx
                                         -------------------------------------
                                         Xxxxxx Xxxxxx, in her capacity as
                                         director of Xxxxxxxx Venture Managers
                                         Limited


                                                /s/ Xxxx Xxxx
                                         -------------------------------------
                                         Xxxx Xxxx, in his capacity as director
                                         of Xxxxxxxx Venture Managers Limited