EXHIBIT 99.1

           ONYX TO FOCUS EXCLUSIVELY ON SMALL MOLECULE CANCER PROGRAM
     BAY 43-9006 TAKES PRIORITY AS THERAPEUTIC VIRUS PROGRAM IS DISCONTINUED

RICHMOND, Calif., June 11, 2003 - Onyx Pharmaceuticals, Inc. (Nasdaq:ONXX) today
announced that the company is further prioritizing the clinical development of
BAY 43-9006, a novel anticancer compound expected to enter Phase III clinical
testing later this year. Based on encouraging results to date from Phase I and
Phase Ib clinical trials, the company, together with its partner Bayer
Pharmaceuticals Corporation, intends to pursue multiple clinical paths with BAY
43-9006. As a result, Onyx will discontinue its therapeutic virus program,
resulting in a reduction in force of approximately 50 of the company's
employees, most of whom were dedicated to the virus program. Following this
reduction in force, Onyx's remaining scientific and administrative personnel
will be focused on furthering the development of BAY 43-9006. Onyx expects to
record a restructuring charge related to this activity in the third quarter of
this year. It is estimated that the company will save approximately $4 million
on a quarterly basis. However, these savings are expected to be offset by
increased clinical development expenses for BAY 43-9006 as the compound enters
Phase III testing.

"Though the decision to close our therapeutic virus program was not an easy one,
it was an appropriate business action," said Hollings Renton, Onyx's chairman
and chief executive officer. "BAY 43-9006 has continued to generate positive
data in clinical trials, resulting in some difficult but necessary portfolio
management choices."

Mr. Renton continued, "Without a corporate partner in the near term to share the
investment needed to make meaningful progress in our therapeutic virus program,
we cannot continue to fund this program as well as BAY 43-9006. At this point in
time, it is important that we apportion our resources in a way that will most
directly advance the commercialization of BAY 43-9006."

According to the codevelopment collaboration between Onyx and Bayer, Onyx funds
50 percent of the development costs for BAY 43-9006. In return, Onyx will share
equally in any profits generated in the United States, where the companies can
copromote the product. Everywhere else in the world, except Japan, Onyx's share
of any profits will be somewhat less than 50 percent since Bayer has exclusive
marketing rights. In Japan, Bayer will fund product development, and Onyx will
receive a royalty based on any sales.

To date, BAY 43-9006 has been evaluated in hundreds of patients with cancer.
Clinical trials include four completed Phase I single agent studies, eight
ongoing Phase Ib studies combining BAY 43-9006 with different standard
chemotherapies and two ongoing Phase II single agent studies. Final Phase I
monotherapy results, along with data from two of the Phase Ib combination
studies, were recently reported at the annual meeting of the American Society of
Clinical Oncology (ASCO). Onyx and Bayer intend to conduct further clinical
testing of BAY 43-9006, including a Phase III study planned for later this year.

Cancer is the second leading cause of death in the U.S. Despite its prevalence,
many forms of cancer are inadequately treated with conventional approaches. Due
to this large unmet medical

need, BAY 43-9006 may have significant commercial potential across a number of
tumor types -- either as a monotherapy or in tandem with current treatments with
chemotherapeutic agents.

"Though we are winding down our therapeutic virus program, I have great faith in
the ultimate potential of this novel approach. We are leaving open the option of
restarting this program, either directly or in combination with outside
investigators," said Mr. Renton. "Our employees have made important scientific
progress in this area, and I thank them for their numerous contributions."

ABOUT ONYX PHARMACEUTICALS

Onyx Pharmaceuticals is engaged in the development of novel cancer therapies and
has proprietary technologies that target the molecular basis of cancer. The
company is developing small molecule drugs, including BAY 43-9006 in
codevelopment with Bayer. For more information about Onyx's pipeline and
activities, visit the company's website at www.onyx-pharm.com.

This news release contains forward-looking statements regarding expectations as
to timing and amount of any restructuring charges; cost savings or clinical
development expenses; the company's plans as to the development of BAY 43-9006,
including further clinical testing and the timing of such clinical trials; the
company's expectations or beliefs of the commercial potential of BAY 43-9006;
and its plans with respect to strategic alternatives for its therapeutic virus
program. 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.