[Letterhead of Cooley LLP]

Michael E. Tenta

(650) 843-5636

mtenta@cooley.com

June 16, 2010

Securities and Exchange Commission
Attention:	Jim B. Rosenberg
	Joel Parker
	Vanessa Robertson
	Suzanne Hayes
	Karen Ubell
100 F Street, N.E.
Washington, D.C. 20549

Re:	Onyx Pharmaceuticals, Inc.
	Form 10-K for Fiscal Year Ended December 31, 2009
	Filed February 23, 2010
	Definitive Proxy Statement filed April 9, 2010
	File No. 000-28928

Ladies and Gentlemen:

          On behalf of Onyx Pharmaceuticals, Inc. (the “Company”), this letter is being submitted in response to comments received from the staff of the Commission (the “Staff”) by letter dated June 9, 2010, with respect to the Company’s Form 10-K for Fiscal Year Ended December 31, 2009 and Definitive Proxy Statement filed April 9, 2010.

          As a follow-up to my telephone conversation on June 10, 2008 with Ms. Ubell, this letter confirms the Company’s request that it be granted an additional 10 business days to provide a response to the Staff’s comment letter. Accordingly, the Company expects that it will provide its response to the Staff on or before July 8, 2010 and will further advise the Staff if it becomes unable to do so.

          Please do not hesitate to contact me at (650) 843-5636 if you have any questions or would like any additional information regarding this matter.

Sincerely,
 

/s/ Michael E. Tenta  

Michael E. Tenta 

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