EXHIBIT A
Agreement of Joint Filing
Pursuant to Rule 13d-1(k)(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 Rigel Pharmaceuticals, Inc.
Dated: May 8, 2003
MPM BIOVENTURES III, L.P. MPM BIOVENTURES III-QP, L.P.
By: MPM BioVentures III GP, L.P., By: MPM BioVentures III GP, L.P.,
its General Partner its General Partner
By: MPM BioVentures III LLC, By: MPM BioVentures III LLC,
its General Partner its General Partner
By: /s/ Luke Evnin By: /s/ Luke Evnin
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Name: Luke Evnin Name: Luke Evnin
Title: Series A Member Title Series A Member
MPM BIOVENTURES III GMBH & CO. MPM BIOVENTURES III PARALLEL
BETEILIGUNGS KG FUND, L.P.
By: MPM BioVentures III GP, L.P., in its By: MPM BioVentures III GP, L.P.,
capacity as the Managing Limited its General Partner
Partner By: MPM BioVentures III LLC,
By: MPM BioVentures III LLC, its General Partner
its General Partner
By: /s/ Luke Evnin By: /s/ Luke Evnin
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Name: Luke Evnin Name: Luke Evnin
Title: Series A Member Title: Series A Member
MPM ASSET MANAGEMENT MPM BIOVENTURES III GP, L.P.
INVESTORS 2003 BVIII LLC
By: MPM BioVentures III LLC,
its General Partner
By: /s/ Luke Evnin By: /s/ Luke Evnin
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Name: Luke Evnin Name: Luke Evnin
Title: Series A Member Title Series A Member
MPM BIOVENTURES III LLC MPM BIOEQUITIES MASTER FUND, L.P.
By: /s/ Luke Evnin By: MPM BioEquities GP, L.P.,
---------------------------------- its General Partner
Name: Luke Evnin By: MPM BioEquities GP LLC,
Title: Manager its General Partner
By: /s/ Luke Evnin
---------------------------------
Name: Luke Evnin
Title: Series A Member
MPM BIOEQUITIES GP, L.P. MPM BIOEQUITIES GP, LLC
By: MPM BioEquities GP, LLC By: /s/ Luke Evnin
its General Partner ---------------------------------
Name: Luke Evnin
Title: Manager
By: /s/ Luke Evnin
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Name: Luke Evnin
Title: Manager
By: /s/ Luke Evnin By: /s/ Ansbert Gadicke
---------------------------------- ---------------------------------
Name: Luke Evnin Name: Ansbert Gadicke
By: /s/ Nicholas Galakatos By: /s/ Dennis Henner
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Name: Nicholas Galakatos Name: Dennis Henner
By: /s/ Robert Liptak By: /s/ Nick Simon, III
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Name: Robert Liptak Name: Nick Simon, III
By: /s/ Michael Steinmetz By: /s/ Kurt von Emster
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Name: Michael Steinmetz Name: Kurt von Emster
By: /s/ Kurt Wheeler
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Name: Kurt Wheeler