Exhibit 2 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...

                                                                       Exhibit 2

         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 Essential Therapeutics, Inc.

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

         Executed this 29th day of April, 2003.


                                    INTERNATIONAL BIOTECHNOLOGY TRUST PLC


                                    By: /s/ Xxxxxx Xxxxxx
                                       -----------------------------------------
                                    Title:  Director
                                          --------------------------------------


                                    XXXXXXXX INVESTMENT MANAGEMENT LIMITED


                                    By: /s/ Xxxx Xxxxxxxx
                                       -----------------------------------------
                                    Title:  Secretary
                                          --------------------------------------


                                    /s/ Xxx Xxxxxx
                                    --------------------------------------------
                                    Xxx Xxxxxx


                                    /s/ Xxxx Xxxxxxx
                                    --------------------------------------------
                                    Xxxx Xxxxxxx


                                    /s/ Xxx Xxxx
                                    --------------------------------------------
                                    Xxx Xxxx