**EXHIBIT 15.1**

 

The Board of Directors

Rigel Pharmaceuticals, Inc.

 

We areaware of the incorporation by reference in the following RegistrationStatements:

 
| (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, of  our report dated May 4, 2010 relating to the unaudited condensed interim  financial statements of Rigel Pharmaceuticals, Inc. that are included in  its Form 10-Q for the quarter ended March 31, 2010. |

 

 
|                                   | /s/ Ernst & Young LLP |
|----------------------------------------|--------------------------------|
|                                   |                           |
|                                   |                           |
| Palo Alto, California May 4, 2010 |                           |

 

----