Onyx Pharmaceuticals Receives $15 Million Milestone Payment From Bayer

Onyx Pharmaceuticals Receives $15 Million Milestone Payment From Bayer
Milestone Achieved with Initiation of Phase III Clinical Trial 


RICHMOND, Calif., Dec. 18  /PRNewswire-FirstCall/ -- Onyx Pharmaceuticals, Inc. 
today announced that it has received a $15 million creditable milestone-based
payment from Bayer Pharmaceuticals Corporation related to the development of BAY
43-9006, a novel anti-cancer compound, which the two companies are
co-developing.  The milestone was achieved upon the previously announced
initiation of the first Phase III clinical trial for BAY 43-9006.

This is the second milestone payment Onyx has received from Bayer.  The first
payment of $5 million was paid when the two companies began the first Phase II
trial of BAY 43-9006 in 2002.  In addition, Onyx can achieve two more
milestones, each triggering a creditable milestone-based payment from Bayer of
$10 million.  The first of these milestones is the filing of a New Drug
Application (NDA), and the second is the approval of BAY 43-9006 in any one of
the United States, Germany, Italy, Spain or the United Kingdom.  All milestone
payments are repayable to Bayer from a portion of Onyx's future profits and
royalties.

BAY 43-9006 is an orally active small molecule in Phase III clinical testing for
patients with advanced renal cancer.  The compound is also being studied in two
ongoing Phase II trials, as well as eight Phase Ib studies evaluating its use in
combination with standard chemotherapeutics.  This novel signal transduction
inhibitor has a dual mechanism of action, targeting both cell proliferation and
angiogenesis (formation of blood vessels).  By inhibiting RAF kinase, BAY
43-9006 blocks the RAS/MEK/ERK signaling pathway in cells, an important mediator
of tumor cell proliferation.  BAY 43-9006 also exerts an anti-angiogenic effect,
which could come from both direct effects on the VEGFR-2 and PDGFR-beta
receptors, as well as from downstream effects on RAF kinase.

Under the co-development agreement between Bayer and Onyx, Onyx funds 50 percent
of the development costs for BAY 43-9006.  In return, Onyx will have a 50/50
profit share in the United States, if it elects to co-promote the product and
continues to fund development costs.  Everywhere else in the world, except
Japan, Bayer has exclusive marketing rights, and Onyx's share of any profits
will be less than 50 percent. In Japan, Bayer will fund all product development,
and Onyx will receive a royalty on any product sales.

Onyx Pharmaceuticals is engaged in the development of novel cancer therapies
that target the molecular basis of cancer.  With its partners, the company is
developing small molecule drugs, including BAY 43-9006 with Bayer
Pharmaceuticals Corporation.  For more information about Onyx's pipeline and
activities, visit the company's web site at http://www.onyx-pharm.com/.

This news release contains forward-looking statements regarding expectations as
to the company's plans as to the development of BAY 43-9006, including further
clinical testing and the timing of clinical trials; the receipt of creditable
milestone-based payments; the company's expectations or beliefs of the
commercial potential of BAY 43-9006; and the mechanisms of action for BAY
43-9006. These forward-looking statements involve a number of risks and
uncertainties that could cause actual events to differ from the company's
expectations. These risks are addressed in the company's periodic reports filed
with the Securities and Exchange Commission, including but not limited to its
Annual Report on Form 10-K filed on March 25, 2003 and its Quarterly Reports on
Form 10-Q. 

DATASOURCE: Onyx Pharmaceuticals, Inc.



CONTACT:  Julianna Wood, [phone], for Onyx Pharmaceuticals, Inc.



Web site:  http://www.onyx-pharm.com/ 

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