Onyx Pharmaceuticals, Inc. Initiates Phase 1 Study of Oral Proteasome Inhibitor in Advanced Solid Tumors

EMERYVILLE, Calif., June 1 /PRNewswire-FirstCall/ -- Onyx Pharmaceuticals, Inc. (Nasdaq: ONXX) today announced the initiation of a Phase 1 study of ONX 0912, an oral proteasome inhibitor, in patients with advanced refractory or recurrent solid tumors.

“Based on insights gained from our ongoing carfilzomib development program and ONX 0912’s favorable preclinical profile anti-tumor activity, safety and biodistribution we believe ONX 0912 may have the potential to expand the use of proteasome inhibitors in the treatment of cancer,” said Ted W. Love, M.D., Executive Vice President and Head of Research and Development at Onyx Pharmaceuticals. “As an orally-dosed agent, ONX 0912 is designed to provide prolonged proteasome inhibition and easy combinability with other orally available therapies.”

Trial Design

This multicenter, open-label, dose-escalation study is evaluating the safety and tolerability of ONX 0912 in up to 50 patients with advanced refractory or recurrent solid tumor malignancies for which standard curative measures do not exist or are no longer effective. The trial will determine the maximum tolerated dose (MTD), dose limiting toxicities, and pharmacokinetics/pharmacodynamics of ONX 0912 when administered orally on days 1 through 5 of a 14-day cycle. Cohorts of 3 to 6 patients will receive ONX 0912 at escalating doses, starting at 30 mg, until MTD is determined. Treatment will be repeated in 14-day cycles. The trial will be conducted in the United States.

About Onyx’s Proteasome Inhibitor Development Program

ONX 0912 inhibits the 20S proteasome that primarily targets chymotrypsin-like activity. ONX 0912 is distinct from carfilzomib, although the compound is based on the same chemistry that is employed to selectively target the proteasome. Upon completion of the Phase 1 study in advanced refractory or recurrent solid tumors, ONX 0912 is expected to be explored in hematologic malignancies.

In addition to ONX 0912, Onyx has two other proteasome inhibitors in development. The proteasome has been validated as an important clinical target in cancer, and Onyx is developing next-generation proteasome inhibitors with a high degree of selectivity, with the goal of increasing therapeutic efficacy and reducing side effects.

The lead product candidate in this program is carfilzomib, a selective, next-generation compound that is currently in multiple clinical trials to evaluate its safety and efficacy for the treatment of patients with multiple myeloma and solid tumors. Among these studies is the pivotal Phase 2b monotherapy trial, also known as 003-A1, which enrolled patients with relapsed/refractory multiple myeloma. Top-line results, expected in mid-2010, may support the filing of a U.S. New Drug Application (NDA) by year-end 2010.

The development program also includes ONX 0914, an immunoproteasome inhibitor with activity in preclinical models of autoimmune disorders.

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, and ONX 0912, an oral proteasome inhibitor, are 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 progress and results of the clinical development, safety, regulatory processes, commercialization efforts or commercial potential of carfilzomib, ONX 0912 and ONX 0914. 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, 2009, 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.

SOURCE Onyx Pharmaceuticals, Inc.

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