Gilead Discontinues Development of GS 9005 and GS 7340; Company Continues Commitment to Research Efforts in HIV

FOSTER CITY, Calif.--(BUSINESS WIRE)--Oct. 21, 2004--Gilead Sciences, Inc. (Nasdaq:GILD) today announced that the company is discontinuing its development programs for GS 9005 and GS 7340, two investigational products for the treatment of HIV. The company will continue to focus its research efforts on multiple targets for HIV, including protease inhibitors, non-nucleoside reverse transcriptase inhibitors, integrase inhibitors and fusion inhibitors, as well as hepatitis C virus (HCV) and diseases of the lymphatic system.

Gilead completed its investigational new drug (IND) application for GS 9005, a protease inhibitor, in December 2003, and shortly thereafter initiated studies to assess the oral bioavailability, pharmacokinetics, safety and efficacy of the compound. Gilead recently completed a Phase I/II viral dynamics study that did not demonstrate a sufficient antiviral response after administration of GS 9005. These results were consistent with the observed low oral bioavailability in an earlier Phase I study.

GS 7340, Gilead's investigational anti-HIV agent in Phase I/II studies, is a prodrug of tenofovir, the active agent in the company's HIV drug Viread(R) (tenofovir disoproxil fumarate). Based on the safety, tolerability and efficacy of Gilead's HIV products established in clinical studies and commercial use, Gilead does not believe that GS 7340 has a profile that differentiates it to an extent that supports its continued development.

"We continue to be dedicated to the development of therapeutic advances for the treatment of HIV, with ongoing research programs focused on existing and novel targets, hepatitis C and diseases of the lymphatic system," said John C. Martin, PhD, President and Chief Executive Officer of Gilead Sciences, Inc. "We also continue to carefully evaluate potential partnership opportunities to complement the internal research programs that will grow our pipeline."

About Gilead

Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes therapeutics to advance the care of patients suffering from life-threatening diseases worldwide. The company has seven marketed products and focuses its research and clinical programs on anti-infectives. Headquartered in Foster City, CA, 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. 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, 2003 and in Gilead's Quarterly Reports on Form 10-Q, all of which are on file 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.

Viread is a registered trademark of Gilead Sciences, Inc.

For more information on Gilead Sciences, please visit www.gilead.com or call the Gilead Public Affairs Department at 1-800-GILEAD-5 (1-800-445-3235).

CONTACT: Gilead Sciences, Inc. Susan Hubbard, 650-522-5715 (Investors) Amy Flood, 650-522-5643 (Media) SOURCE: Gilead Sciences, Inc.