2011 Press Releases

Phase 3 Trial of Investigational Compound Regorafenib in Metastatic Colorectal Cancer Meets Primary Endpoint of Improving Overall Survival

Bayer trial stopped based on data from a pre-planned interim analysis

South San Francisco, CA. — Oct. 25, 2011

Onyx Pharmaceuticals, Inc. (Nasdaq: ONXX) today announced results from a Bayer HealthCare Pharmaceuticals Phase 3 trial evaluating the investigational compound regorafenib (BAY 73-4506) for the treatment of patients with metastatic colorectal cancer (mCRC) whose disease has progressed after approved standard therapies. The trial met its primary endpoint of statistically significant improvement in overall survival. This is the result of a pre-planned interim analysis conducted by an independent Data Monitoring Committee (DMC) of the CORRECT (Patients with metastatic colorectal cancer treated with regorafenib or placebo after failure of standard therapy) trial. Per the recommendation of the DMC, the study has been unblinded and patients in the placebo arm will be offered treatment with regorafenib. In this trial, the safety and tolerability of regorafenib were generally as expected. Data from the study are expected to be presented at a forthcoming scientific meeting.

Onyx recently entered into an agreement with Bayer under which Bayer will pay Onyx a royalty on any future global net sales of regorafenib in oncology.

“Patients with metastatic colorectal cancer are in need of new treatment options, and these data demonstrate that regorafenib increased overall survival,” said Ted W. Love, M.D., Executive Vice President, Research and Development and Technical Operations at Onyx Pharmaceuticals. “We look forward to seeing this promising therapy become available to patients as quickly as possible.”

Bayer will continue discussions with health authorities worldwide, including the European Medicines Agency (EMA) and the United States Food and Drug Administration (FDA), regarding next steps in filing for approval of regorafenib in the treatment of mCRC.

About the CORRECT Study
The CORRECT trial is an international, multicenter, randomized, double-blind, placebo-controlled study that enrolled 760 patients with metastatic CRC whose disease has progressed after approved standard therapies. The study was conducted in North America, Europe, China, Japan and Australia.

Patients were randomized to receive either regorafenib plus best supportive care (BSC) or placebo plus BSC. Treatment cycles consisted of 160 mg of regorafenib (or matching placebo) once daily for three weeks on/one week off plus BSC. The primary endpoint of this trial was overall survival. Secondary endpoints included progression-free survival, objective tumor response rate and disease control rate. The safety and tolerability of the two treatment groups were also compared.

About Colorectal Cancer
Colorectal cancer (CRC) is a disease in which malignant (cancer) cells form in the tissues of the colon or rectum. The majority of cancers occurring in the colon and rectum are adenocarcinomas, which account for more than 90 percent of all large bowel tumors.1

Colorectal cancer is the third most commonly diagnosed cancer and the third leading cause of cancer death in the United States, in both men and women. It is estimated that more than 140,000 people will be diagnosed with CRC in 2011, and nearly 50,000 people will die from the disease.2 Approximately 50 percent of colon cancer patients will be diagnosed with metastases (most commonly in the liver) either at the time of diagnosis or due to recurrent disease.3

About Regorafenib
Regorafenib is an investigational oral multi-kinase inhibitor of angiogenic, stromal and oncogenic receptor tyrosine kinases (TK)4 currently being investigated in clinical trials for its potential to treat patients with various tumor types.

Regorafenib is an investigational agent and is not approved by the FDA, EMA or other Health Authorities.

Regorafenib was granted orphan drug designation by the FDA for the treatment of patients with gastrointestinal stromal tumors (GIST). Orphan drug designation aims to encourage the development of drugs involved in the diagnosis, prevention or treatment of a medical condition affecting fewer than 200,000 people in the country.

Regorafenib was granted Fast Track designation by the FDA for the treatment of patients with metastatic and/or unresectable GIST whose disease has progressed despite at least imatinib and sunitinib as prior treatments, as well as for the treatment of patients with mCRC who have progressed after approved standard therapies. Fast Track is a process designed to facilitate the development, and expedite the review of drugs to treat serious diseases and fill an unmet medical need.

About Onyx Pharmaceuticals, Inc.
Based in South San Francisco, California, Onyx Pharmaceuticals, Inc. is a global biopharmaceutical company engaged in the development and commercialization of innovative therapies for improving the lives of people with cancer and other serious diseases. The company is focused on developing novel medicines that target key molecular pathways. For more information about Onyx, visit the company’s website at www.onyx-pharm.com.

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 clinical development, safety, and regulatory processes of regorafenib and its commercial potential. 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 fact that Nexavar is Onyx’s only approved product; regorafenib is not approved, may never receive marketing approval and may never generate royalties for Onyx; competition; failures or delays in clinical trials or the regulatory process; dependence on Onyx’s collaborative relationship with Bayer; market acceptance and the rate of adoption of products; pharmaceutical pricing and reimbursement pressures; and serious adverse side effects, if they are associated with Nexavar, regorafenib or carfilzomib. 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, 2010, filed with the Securities and Exchange Commission under the heading “Risk Factors” and Onyx’s subsequent 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.

American Cancer Society. What is colorectal cancer? Available at: http://www.cancer.org/acs/idcplg?IdcService=GET_DOC_PAGE&Action=GetTemplatePage&Page=HOME_PAGE003170-1. Accessed on October 25, 2011.
2 American Cancer Society. Colorectal Cancer. Available at: http://www.cancer.org/Cancer/ColonandRectumCancer/DetailedGuide/colorectal-cancer-key-statistics. Accessed on October 25, 2011.
3 National Cancer Institute. Stage IV and Recurrent Colon Cancer. Available at: http://www.cancer.gov/cancertopics/pdq/treatment/colon/HealthProfessional/page9. Accessed on October 24, 2011.
4 S. Wilhelm, et al. Regorafenib (Bay 73-4506): A New Oral Multikinase Inhibitor of Angiogenic, Stromal, and Oncogenic Receptor Tyrosine Kinases with Potent Preclinical Antitumor Activity. Online International Journal of Cancer. December 17, 2010.