**EXHIBIT 15.1**

 

August 4,2009

 

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. 333-129650, of Rigel  Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| (3)  |   | 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.                                                                                                                                                                                                                                                                                                                                                                                                                             |
| (4)  |   | Form S-8 No. 333-139516, pertaining to the 2000  Employee Stock Purchase Plan of Rigel Pharmaceuticals Inc.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| (5)  |   | 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.                                                                                                                                                                                                                                                                                                                                                                                                                             |
| (6)  |   | 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.                                                                                                                                                                                                                                                                                                                                                                                                                             |
| (7)  |   | Form S-8 No. 333-111782, pertaining to the 2000  Equity Incentive Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| (8)  |   | Form S-8 No. 333-107062, pertaining to the 2000  Employee Stock Purchase Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| (9)  |   | 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.                                                                                                                                                                                                                                                                                                                                                                                                                             |
| (10) |   | Form S-8 No. 333-72492, pertaining to the 2001  Non-Officer Equity Incentive Plan of Rigel Pharmaceuticals, Inc.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| (11) |   | 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  Pharmceuticals, Inc’s common stock, and in the related prospectuses, as  applicable, contained in such Registration Statements of our report dated  August 4, 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 June 30,  2009. |

 

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

 

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