**EXHIBIT 15.1**

 

November 3,2009

 

The Boardof Directors

RigelPharmaceuticals, Inc.

 

We are aware of the incorporation by reference in thefollowing Registration Statements:

 
| (1)    |   | Form S-3  No. 333-148838, of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                             |
|--------|--------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (2)    |   | Form S-3 No. 333-161960,  of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                             |
| (3)    |   | Form S-3  No. 333-129650, of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                             |
| (4)    |   | Form S-8 No. 333-148132, pertaining to the 2000  Equity Incentive Plan, 2000 Employee Stock Purchase Plan and 2000  Non-Employee Directors’ Stock Option Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                    |
| (5)    |   | Form S-8  No. 333-139516, pertaining to the 2000 Employee Stock Purchase Plan of  Rigel Pharmaceuticals Inc.                                                                                                                                                                                                                                                                                                              |
| (6)    |   | Form S-8  No. 333-134622, pertaining to the 2000 Equity Incentive Plan, 2000  Employee Stock Purchase Plan and 2000 Non-Employee Directors’ Stock Option  Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                   |
| (7)    |   | Form S-8  No. 333-125895, pertaining to the 2000 Equity Incentive Plan, 2000  Employee Stock Purchase Plan and 2000 Non-Employee Directors’ Stock Option  Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                   |
| (8)    |   | Form S-8  No. 333-111782, pertaining to the 2000 Equity Incentive Plan of Rigel  Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                               |
| (9)    |   | Form S-8  No. 333-107062, pertaining to the 2000 Employee Stock Purchase Plan of  Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                        |
| (10)   |   | Form S-8  No. 333-106532, pertaining to the 2000 Equity Incentive Plan, 2000  Employee Stock Purchase Plan and 2000 Non-Employee Directors’ Stock Option  Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                   |
| (11)   |   | Form S-8 No. 333-72492,  pertaining to the 2001 Non-Officer Equity Incentive Plan of Rigel  Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                    |
| (12)   |   | Form S-8 No. 333-51184,  pertaining to the 2000 Equity Incentive Plan, 2000 Employee Stock Purchase  Plan and 2000 Non-Employee Directors’ Stock Option Plan of Rigel  Pharmaceuticals, Inc.                                                                                                                                                                                                                    |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                |
|   |   | in each case for the registration  of shares of Rigel Pharmaceuticals, Inc’s common stock, and in the related  prospectuses, as applicable, contained in such Registration Statements of our  report dated November 3, 2009 relating to the unaudited condensed interim financial statements of Rigel Pharmaceuticals, Inc.  that are included in its Form 10-Q for the quarter ended  September 30, 2009. |

 

 
|                  | /s/ Ernst & Young LLP |
|-----------------------|--------------------------------|
|                  |                           |
|                  |                           |
| Palo Alto, California |                           |

 

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