Data from Preclinical Studies of Gilead Nucleotide Compound GS 9219 to be Presented at AACR

FOSTER CITY, Calif.--(BUSINESS WIRE)--March 15, 2007--Gilead Sciences, Inc. (Nasdaq:GILD) today announced that the company will present data on a novel nucleotide analog, GS 9219, which has shown evidence of anti-cancer activity in preclinical studies, at the 2007 Annual Meeting of the American Association for Cancer Research (AACR), which will take place in Los Angeles on April 14-18, 2007.

"While Gilead's R&D program is not currently focused on oncology, GS 9219 emerged from our efforts in antiviral nucleotide chemistry and cellular targeting and was advanced based on its promising preclinical profile," commented Norbert Bischofberger, PhD, Gilead's Executive Vice President, Research and Development and Chief Scientific Officer. "The early data that will be shared at AACR have formed the basis for our decision to initiate Phase I clinical studies later this year."

GS 9219 was cleared for Phase I human trials by the U.S. Food and Drug Administration following Gilead's submission of an investigational New Drug Application for the compound in late 2006. Gilead expects to initiate a Phase I study of patients with non-Hodgkin's lymphoma and chronic lymphocytic leukemia later this year at cancer centers in the United States.

About GS 9219

GS 9219 is a prodrug of the nucleotide analog PMEG (9-(2-phosphonylmethoxyethyl)guanine). It is selectively enriched in lymphocytes, and therefore may have potential applications in combating hematological malignancies. As an investigational compound, GS 9219 has not been determined safe or efficacious in humans.

About Gilead

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. GS 9219 is a new compound that has not yet been tested in humans. Gilead can provide no assurance that GS 9219 will be effective in humans, or that any approved drug will result or be commercialized successfully. For example, numerous risks and uncertainties exist that could prevent completion of development, including the ability to enroll patients in clinical trials, the possibility of unfavorable results of our clinical trials, and the risk of failing to obtain U.S. Food and Drug Administration and other regulatory body approvals. Feedback from regulatory authorities or results from clinical trials might require modifications or delays in later stage clinical trials or additional trials to be performed. In addition, Gilead may make a strategic decision to discontinue development of this product candidate if, for example, Gilead believes commercialization will be difficult relative to other opportunities in our pipeline. 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 Gilead's Annual Report on Form 10-K for the year ended December 31, 2006 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 website 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) Amy Flood, 650-522-5643 (Media) SOURCE: Gilead Sciences, Inc.