Exhibit 5.1

 

[COOLEY LLP LETTERHEAD]

 

August 7, 2012

 

Rigel Pharmaceuticals, Inc.

1180 Veterans Boulevard

South San Francisco, CA 94080

 

Ladies and Gentlemen:

 

You have requested our opinion with respect to certain matters in connection with the filing by Rigel Pharmaceuticals, Inc., a Delaware corporation (the “Company”), of a Registration Statement on Form S-8 (the “Registration Statement”) with the U.S. Securities and Exchange Commission covering the offering of up to six hundred thousand (600,000) shares (the “Shares”) of the Company’s Common Stock, $0.001 par value (the “Common Stock”), issuable pursuant to the Company’s 2011 Equity Incentive Plan (the “Plan”).

 

In connection with this opinion, we have examined the Registration Statement and related Prospectus, your Certificate of Incorporation and Bylaws, each as currently in effect, the Plan and such other documents, records, certificates, memoranda and other instruments as we deem necessary as a basis for this opinion.  We have assumed the genuineness and authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies thereof, and the due execution and delivery of all documents where due execution and delivery are a prerequisite to the effectiveness thereof.

 

Our opinion is expressed only with respect to the federal laws of the United States of America and the General Corporation Law of the State of Delaware. We express no opinion as to whether the laws of any particular jurisdiction other than those identified above are applicable to the subject matter hereof.