Gilead Announces Initiation of Phase I/II Clinical Trial Evaluating HIV Integrase Inhibitor GS 9137

FOSTER CITY, Calif.--(BUSINESS WIRE)--June 21, 2005--Gilead Sciences, Inc. (Nasdaq:GILD) today announced that it has begun enrolling patients in a Phase I/II study of the company's oral HIV integrase inhibitor, GS 9137 (also known as JTK-303) for the treatment of HIV. This double-blind, randomized, placebo-controlled Phase I/II dose-escalation study will evaluate the tolerability, safety and antiviral activity of GS 9137 in HIV-positive patients.

GS 9137 is a novel HIV integrase inhibitor discovered by Japan Tobacco, Inc (JT) and licensed to Gilead in March 2005. The license granted Gilead exclusive rights to develop and commercialize GS 9137 in all countries of the world, excluding Japan where JT will retain rights. GS 9137 has been previously evaluated in a Phase I study in Japan to assess pharmacokinetics and safety in healthy volunteers.

"The initiation of this trial underscores Gilead's ongoing commitment to HIV and efforts to advance novel compounds with the potential to address unmet medical needs of people living with HIV," said Norbert Bischofberger, PhD, Executive Vice President, Research and Development, Gilead Sciences. "HIV continues to be a major focus for Gilead, and integrase inhibitors represent a promising novel class of agents with the potential to inhibit HIV replication, particularly for patients whose HIV has developed resistance to other agents."

As an investigational compound, GS 9137 has not yet been determined safe or efficacious in humans for its ultimate intended use.

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.

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, the safety and efficacy data from this trial 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, 2004, 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.

For more information on Gilead Sciences, please visit the company's web site at www.gilead.com or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

CONTACT: Gilead Sciences, Inc.
Susan Hubbard, 650-522-5715 (Investors)
James Loduca, 650-522-5908 (Media)

SOURCE: Gilead Sciences, Inc.