JOINT FILING AGREEMENT

     The  undersigned  hereby  agree that the  statement  on  Schedule  13G with
respect to the shares of common stock of Threshold Pharmaceuticals, Inc. is, and
any amendment thereto  (collectively,  the "Schedule 13G") signed by each of the
undersigned shall be, filed on behalf of each of the undersigned pursuant to and
in  accordance  with the  provisions  of Rule  13d-1(k)  promulgated  under  the
Securities  Exchange Act of 1934, as amended.  The  undersigned  hereby  further
agree  that this  Joint  Filing  Agreement  be  included  as an  exhibit to such
statement and any such amendment. This Joint Filing Agreement may be executed in
any number of counterparts, all of which taken together shall constitute one and
the same instrument.


Dated:  February 10, 2006

                                  /S/ PASQUALE DEANGELIS
                                  ---------------------------------------------
                                  Pasquale DeAngelis, as a member of ProQuest
                                  Associates II LLC and on  behalf  of  ProQuest
                                  Investments   II,  L.P.  and  ProQuest
                                  Investments II Advisors Fund, L.P.


                                                        *
                                  ----------------------------------------------
                                  Jay Moorin, individually


                                                        *
                                  ----------------------------------------------
                                  Alain Schreiber, individually


*By: /S/ PASQUALE DEANGELIS
     ------------------------------------
     Pasquale DeAngelis, Attorney-in-Fact
     Power of Attorney filed as an exhibit to the Schedule 13G