Onyx Pharmaceuticals Announces Agreement with the FDA on a Special Protocol Assessment for Planned Phase 3 Carfilzomib Combination Trial in Relapsed Multiple Myeloma

Emeryville, CA. — Feb. 02, 2010

Onyx Pharmaceuticals, Inc. (Nasdaq: ONXX) today announced that the company reached agreement with the U.S. Food and Drug Administration (FDA) on a Special Protocol Assessment (SPA) for the Phase 3 international randomized trial. This pivotal trial, which is expected to begin in the first half of 2010, will enroll patients with relapsed multiple myeloma following treatment with one to three prior regimens. It is designed to evaluate the efficacy of carfilzomib in combination with lenalidomide and low dose dexamethasone, versus lenalidomide and low dose dexamethasone alone.

“The SPA enables us to initiate this carfilzomib Phase 3 combination trial in the first half of this year with increased clarity on the full approval pathway,” said Michael Kauffman, M.D., Ph.D., chief medical officer at Onyx. “In the Phase 1b data (from the “006” trial) reported at the American Society of Hematology meeting last December, carfilzomib showed promising response rates and good tolerability with this three-drug combination in patients with relapsed or refractory myeloma.”

Dr. Kauffman continued, “This planned Phase 3 study complements and builds upon the encouraging single-agent carfilzomib data reported earlier in heavily pretreated patients with relapsed and refractory multiple myeloma. Despite the established use of existing therapies, over time virtually all multiple myeloma patients relapse and succumb to their disease, meaning new innovative agents are needed. As a medical community, we have made important strides in extending the life of myeloma patients and need to continue to identify new ways we can benefit those who have this disease.”

Carfilzomib Development Strategy
Based on carfilzomib’s efficacy and tolerability profile demonstrated to-date, Onyx is pursuing a broad approach to advancing this therapy for multiple myeloma patients. In the advanced relapsed refractory setting, carfilzomib is currently being evaluated in a Phase 2b study that could support a new drug application filing by the end of 2010. In addition to this potential accelerated approval pathway and for patients earlier in the course of their disease, Onyx is evaluating the combination of carfilzomib, Revlimid® and low-dose dexamethasone in a Phase 3 study, as covered by this SPA, which is expected to begin in the first half of 2010.

About Special Protocol Assessments
A Special Protocol Assessment is a written agreement with the FDA on the design and planned analysis for a clinical trial. It is intended to form the basis for a marketing application and may only be changed through a written agreement between the sponsor and the FDA, or if the FDA becomes aware of new public health concerns.

About the Phase 3 Trial
The Phase 3 (“009”) trial is a 700 patient, randomized, open-label, global multi-center study comparing two treatment regimens for patients with relapsed multiple myeloma and will be conducted in approximately 200 centers worldwide. This study is designed to demonstrate the clinical benefit of carfilzomib in combination with lenalidomide and dexamethasone based on a primary endpoint of progression-free survival. Patients will be randomized to receive carfilzomib (20mg/m2 on days 1 and 2 of cycle 1 only, then 27mg/m2 subsequently), in addition to a standard dosing schedule of lenalidomide (25mg qd 21 days on, 7 days off) and low-dose dexamethasone (40mg q week) versus lenalidomide and low-dose dexamethasone alone.

About Carfilzomib
Carfilzomib is a selective, next-generation proteasome inhibitor that has shown encouraging results in a broad clinical trial program in multiple myeloma. Carfilzomib is currently undergoing evaluation as a single agent in multiple Phase 2 and Phase 1 clinical trials in relapsed or refractory multiple myeloma. These trials include a Phase 2b monotherapy study (known as “003-A1”) in patients with relapsed, refractory multiple myeloma, which could support a new drug application (NDA) filing by the end of 2010. Carfilzomib is also being evaluated in advanced solid tumors.

About Multiple Myeloma
Multiple myeloma (MM) is the second most common hematologic cancer and results from an abnormality of plasma cells, usually in the bone marrow. In the United States, more than 50,000 people are living with MM and approximately 20,000 new cases are diagnosed annuallyi. Worldwide, more than 180,000 people are living with MM and approximately 86,000 new cases are diagnosed annuallyii.

About Onyx Pharmaceuticals, Inc.
Onyx Pharmaceuticals, Inc. is a biopharmaceutical company committed to improving the lives of people with cancer. The company, in collaboration with Bayer HealthCare Pharmaceuticals, Inc., is developing and marketing Nexavar® (sorafenib) tablets, a small molecule drug that is currently approved for the treatment of liver cancer and advanced kidney cancer. Additionally, Nexavar is being investigated in several ongoing trials in a variety of tumor types. Beyond Nexavar, Onyx has established a development pipeline of anticancer compounds at various stages of clinical testing, including carfilzomib, a next-generation proteasome inhibitor, that is currently being evaluated in multiple clinical trials for the treatment of patients with relapsed or relapsed/refractory multiple myeloma and solid tumors. ONX 0801, a targeted alpha-folate inhibitor, is currently in Phase 1 testing. For more information about Onyx, visit the company’s website at www.onyx-pharm.com.

Nexavar® (sorafenib) tablets is a registered trademark of Bayer HealthCare Pharmaceuticals.

Forward Looking Statements
This news release contains “forward-looking statements” of Onyx within the meaning of the federal securities laws. These forward-looking statements include without limitation, statements regarding the timing, progress and results of the clinical development, safety, regulatory processes and approval, commercialization efforts or commercial potential of carfilzomib. These statements are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated, including risks related to the development and commercialization of pharmaceutical products. Any statements contained in this press release that are not statements of historical fact may be deemed to be forward-looking statements. Reference should be made to Onyx’s Annual Report on Form 10-K for the year ended December 31, 2008, filed with the Securities and Exchange Commission under the heading “Risk Factors” and Onyx’s Quarterly Reports on Form 10-Q for a more detailed description of such factors. Readers are cautioned not to place undue reliance on these forward-looking statements that speak only as of the date of this release. Onyx undertakes no obligation to update publicly any forward-looking statements to reflect new information, events, or circumstances after the date of this release except as required by law.

i National Cancer Institute, Surveillance Epidemiology and End Results, 2007 Facts and Figures
iiInternational Agency for Research on Cancer, GLOBOCAN 2002 database

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