Onyx Announces Proposed Public Offering of Common Stock

EMERYVILLE, CALIF. — Jun. 18, 2007

Onyx Pharmaceuticals, Inc. (Nasdaq: ONXX) today announced that it plans to offer, subject to market and other conditions, 6,000,000 shares of its common stock pursuant to an automatically effective shelf registration statement on file with the Securities and Exchange Commission. The company also expects to grant to the underwriters an overallotment option to purchase up to an additional 900,000 shares of common stock in connection with the common stock offering. All of the shares are being offered by Onyx Pharmaceuticals.

Morgan Stanley & Co. Incorporated and Merrill Lynch & Co. are acting as joint book running managers. Morgan Stanley & Co. Incorporated, Merrill Lynch & Co., J.P. Morgan Securities Inc. and Banc of America Securities LLC are acting as the underwriters.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such jurisdiction. Copies of the preliminary prospectus supplement relating to the offering may be obtained from Morgan Stanley & Co. Incorporated (180 Varick Street, New York, NY 10014 Attn: Prospectus Department or by email at [email protected]), Merrill Lynch & Co. (Attn: Prospectus Department, 4 World Financial Center, New York, New York 10080) or from Onyx Pharmaceuticals, Inc. (2100 Powell Street, Emeryville, CA 94608, fax 510-597-6600).

About Onyx Pharmaceuticals, Inc.
Onyx Pharmaceuticals, Inc. is a biopharmaceutical company developing innovative therapies that target the molecular mechanisms that cause cancer. The company is developing Nexavar®, a small molecule drug, with Bayer HealthCare Pharmaceuticals Inc. Nexavar is approved for the treatment of advanced kidney cancer in more than 50 countries.

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

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 expectations as to completion, timing and size of any public offering. These statements are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated. Reference should be made to Onyx’s Annual Report on Form 10-K for the year ended December 31, 2006, filed with the Securities and Exchange Commission under the heading “Risk Factors” for a more detailed description of such factors, as well as the Company’s subsequent quarterly report on Form 10-Q. 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.

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