Exhibit 99.1
 
Joint Filing Agreement

The undersigned hereby agree that the Statement on Schedule 13G dated June 6, 2011 with respect to the shares of Common Stock of Rigel Pharmaceuticals, Inc., and any further amendments thereto executed by each and any 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)(1) under the Securities Exchange Act of 1934, as amended.
 
Dated: June 6, 2011
 
BIOTECHNOLOGY VALUE FUND, L.P.
 
INVESTMENT 10, L.L.C.
         
By:
BVF Partners L.P., its general partner
 
By:
BVF Partners L.P., its investment manager
         
By:
BVF Inc., its general partner
 
By:
BVF Inc., its general partner
         
By:
/s/ Mark N. Lampert
 
By:
/s/ Mark N. Lampert
 
Mark N. Lampert
   
Mark N. Lampert
 
President
   
President
         
         
BIOTECHNOLOGY VALUE FUND II, L.P.
 
BVF PARTNERS L.P.
         
By:
BVF Partners L.P., its general partner
 
By:
BVF Inc., its general partner
         
By:
BVF Inc., its general partner
 
By:
/s/ Mark N. Lampert
       
Mark N. Lampert
By:
/s/ Mark N. Lampert
   
President
 
Mark N. Lampert
     
 
President
     
     
BVF INC.
         
BVF INVESTMENTS, L.L.C.
 
By:
/s/ Mark N. Lampert
       
Mark N. Lampert
By:
BVF Partners L.P., its manager
   
President
         
By:
BVF Inc., its general partner
     
         
By:
/s/ Mark N. Lampert
   
/s/ Mark N. Lampert
 
Mark N. Lampert
   
MARK N. LAMPERT
 
President