Gilead Submits New Drug Application To U.S. FDA for Ambrisentan for the Treatment of Pulmonary Arterial Hypertension

Gilead Sciences, Inc. (Nasdaq:GILD) today announced the submission
of a New Drug Application (NDA) to the U.S. Food and Drug
Administration (FDA) for marketing approval of ambrisentan (5 mg and
10 mg) for the once-daily treatment of pulmonary arterial hypertension
(PAH). The application is supported by data from two Phase III
clinical studies (ARIES-1 and ARIES-2) and three Phase II studies in
patients with PAH.

"Current therapeutic options are limited, and there remains an
urgent need for safe and effective treatments for patients with PAH,"
said John C. Martin, PhD, President and CEO, Gilead Sciences. "The
achievement of today's milestone reflects the tremendous dedication of
numerous clinical investigators and other research collaborators, all
of whom share our goal of advancing new treatment options for patients
suffering from PAH. This is also a testament to our Colorado-based
team, who designed and managed the clinical development program for
ambrisentan and whose efforts led to the completion of this new drug
application."

About ARIES Pivotal Trials

In the two ARIES clinical trials, patients were randomized in a
blinded fashion to receive placebo or one of two doses of ambrisentan.
The trials were of identical design except for the doses of
ambrisentan studied and the geographic locations of the investigative
sites. Both trials were designed to enroll 186 patients (62 patients
per dose group). ARIES-1 evaluated once-daily doses of 5 mg and 10 mg
of ambrisentan. ARIES-2 evaluated once-daily doses of 2.5 mg and 5 mg
of ambrisentan. ARIES-1 enrolled 202 patients primarily in the United
States while ARIES-2 enrolled 192 patients primarily in Europe.

Approximately 400 patients from these and other studies are
continuing ambrisentan treatment in long-term clinical trials.

About Ambrisentan

Ambrisentan is a non-sulfonamide, propanoic acid-class, endothelin
receptor antagonist that is selective for the endothelin type-A (ETa)
receptor. Endothelin is a small peptide hormone that plays a critical
role in the control of blood flow and cell growth. Elevated endothelin
blood levels are associated with PAH. Ambrisentan has been granted
orphan drug designation for the treatment of PAH in both the United
States and European Union.

Ambrisentan is an investigational compound and has not yet been
determined safe or efficacious in humans.

Gilead acquired the U.S. rights to ambrisentan when it completed
its acquisition of Myogen, Inc. on November 17, 2006. GlaxoSmithKline
holds rights to commercialize ambrisentan outside of the United
States.

About Pulmonary Arterial Hypertension

PAH is a debilitating disease characterized by constriction of the
blood vessels in the lungs leading to high pulmonary arterial
pressures. These high pressures make it difficult for the heart to
pump blood through the lungs to be oxygenated. Patients with PAH
suffer from shortness of breath as the heart struggles to pump against
these high pressures causing such patients to ultimately die of heart
failure. PAH can occur with no known underlying cause, or it can occur
secondary to diseases such as connective tissue disease, congenital
heart defects, cirrhosis of the liver and HIV infection. PAH afflicts
approximately 200,000 patients worldwide.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers,
develops and commercializes innovative therapeutics in areas of unmet
medical need. The company's mission is to advance the care of patients
suffering from life-threatening diseases worldwide. Headquartered in
Foster City, California, Gilead has operations in North America,
Europe and Australia. For more information on Gilead Sciences, please
visit the company's website at www.gilead.com or call Gilead Public
Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

This press release includes forward-looking statements, within the
meaning of the Private Securities Litigation Reform Act of 1995, that
are subject to risks, uncertainties and other factors, including risks
related to Gilead's ability to develop and commercialize this product.
For example, ambrisentan may not be approved for the doses Gilead is
seeking, the safety and efficacy data from additional clinical studies
may not warrant further development of this compound and initiating
and completing clinical trials may take longer or cost more than
expected. These risks, uncertainties and other factors could cause
actual results to differ materially from those referred to in the
forward-looking statements. The reader is cautioned not to rely on
these forward-looking statements. These and other risks are described
in detail in the Gilead Annual Report on Form 10-K for the year ended
December 31, 2005, filed with the U.S. Securities and Exchange
Commission. All forward-looking statements are based on information
currently available to Gilead and Gilead assumes no obligation to
update any such forward-looking statements.