Carfilzomib Demonstrates Encouraging Response Rates in Patients with Relapsed and/or Refractory Multiple Myeloma in an Ongoing Phase 2 Study

New Orleans, LA. — Dec. 07, 2009

Onyx Pharmaceuticals, Inc. (Nasdaq: ONXX) today announced results from an ongoing Phase 2 study, known as the 004 study, of the company’s lead proteasome inhibitor, carfilzomib. Results demonstrated promising overall response rates when carfilzomib was administered as a single agent in patients with relapsed and/or refractory multiple myeloma. These data were presented at the 51st annual meeting of the American Society of Hematology (ASH) in New Orleans.

Patients were divided into two populations: 73 evaluable patients with relapsed and/or refractory multiple myeloma who had not received prior bortezomib (Velcade®) treatment, classified as bortezomib-naïve patients, and 33 evaluable patients with relapsed and/or refractory disease following bortezomib treatment, classified as bortezomib-treated patients.

Michael Wang, M.D., assistant professor, department of lymphoma and myeloma at the University of Texas M. D. Anderson Cancer Center and co-investigator of the study, reported that the bortezomib-naïve patients when treated with carfilzomib achieved an overall response rate (ORR) of 46 percent in 54 evaluable patients at 20 mg/m2 and 53 percent in 19 evaluable patients with dose escalation to 27 mg/m2. Additionally, Dr. Wang reported interim results for secondary endpoints at the 20 mg/m2 dose, including time-to-progression (TTP) of 7.6 months and duration of response (DoR) of 8.4 months.

David Siegel, M.D., Ph.D., division chief of myeloma at the John Theurer Cancer Center and co-investigator of the study, reported that 33 evaluable patients who were previously treated with bortezomib achieved an ORR of 18 percent when administered carfilzomib. Dr. Siegel reported interim results for a secondary endpoint of TTP at 5.3 months and DoR of more than 9 months. More than 20 percent of patients were able to complete the full 12 cycles (48 weeks) of therapy in both studies without cumulative side effects.

“These interim results suggest that carfilzomib could benefit patients with multiple myeloma who are no longer responding to current therapies,” said Dr. Siegel. “Additionally, given the low incidence of neuropathy and generally mild and manageable adverse events in this trial, these results suggest that increasing the dosage of carfilzomib up to 27 mg/m2 is well tolerated despite a high degree of coexisting medical conditions, such as renal insufficiency and diabetes.”

Overall, treatment with carfilzomib was well tolerated and no unexpected side effects occurred. The most common grade 3 treatment-related adverse events occurred in less than 5 percent of the patients and included fatigue, pneumonia, neutropenia, lymphopenia and anemia. Peripheral neuropathy of any grade was rare and there were no grade 4 adverse events observed.

Other findings from the two populations include:

• Carfilzomib has substantial single-agent activity despite several prior treatments with different combination regimens.
• Carfilzomib was well-tolerated with chronic administration, even in patients with renal insufficiency.
• Patients were able to remain on full-dose therapy for more than 12 cycles.

“These data support our ongoing carfilzomib program in multiple myeloma, a disease that has poor long-term survival, and for which there are no alternative courses of therapy for patients who relapse following treatment or become resistant to currently approved therapies,” said Michael Kauffman, M.D., Ph.D., interim chief medical officer at Onyx. “There is a clear need to provide new treatment options to patients with multiple myeloma, and we are working to potentially file a New Drug Application for carfilzomib by the end of 2010.”

Trial Design
This open-label, single agent ongoing Phase 2 study is being conducted in collaboration with the Multiple Myeloma Research Consortium, and is designed to enroll approximately 150 patients with relapsed and/or refractory multiple myeloma who have received 1-3 prior treatments. Patients included two populations: bortezomib-naïve patients with relapsed and/or refractory multiple myeloma and bortezomib-treated patients with relapsed and/or refractory multiple myeloma. Prior therapies include alkylating agents, stem cell transplant, thalidomide, lenalidomide and anthracyclines, and bortezomib in the bortezomib-treated patients. To date, 73 evaluable bortezomib-naïve patients (54 who received 20mg/m2 and 19 who received up to 27mg/m2), and 33 evaluable patients receiving previous treatment with bortezomib have been enrolled. The primary endpoint is overall response rate and secondary endpoints include TTP, DoR, overall survival and safety.

Investor Teleconference
Principal investigators will discuss data presentations surrounding carfilzomib in relapsed or refractory multiple myeloma, as featured at ASH. The webcast event will begin at 9:00 a.m. CT/10:00 a.m. ET on December 7, 2009. The live webcast will be available at:

or by dialing 847-413-3362 and using the passcode 25914947. A replay of the presentation will be available on the Onyx website or by dialing 630-652-3044 and using the passcode 25914947 later in the day. The replay will be available on the Onyx website through January 7, 2010.

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 the 003 study, in patients with relapsed, refractory multiple myeloma, the pivotal trial that 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

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

Velcade® is a trademark of Millennium Pharmaceuticals, Inc.

Revlimid® and Thalomid® are registered trademarks of Celgene Corporation.

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 anticipated benefits of the acquisition of Proteolix and the timing, progress and results of the clinical development, safety, regulatory processes, 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 the risk that Proteolix’s operations will not be integrated successfully into Onyx’s, the risk that Onyx may not realize the anticipated benefits of the acquisition and 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.


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

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