Gilead Sciences Initiates Phase I Study in China of Adefovir Dipivoxil, Investigational Compound for the Treatment of Chronic Hepatitis B Infection

Gilead Sciences, Inc. (Nasdaq: GILD) today announced that it has initiated Phase I trials of adefovir dipivoxil for the treatment of chronic hepatitis B (HBV) infection in China. Gilead is currently evaluating adefovir dipivoxil in Phase III clinical studies in North America, Europe, Asia and Australia.

"Of the nearly 400 million patients who suffer from chronic HBV infection, more than 100 million live in China," said John C. Martin, Ph.D., President and Chief Executive Officer, Gilead Sciences. "We are working rapidly to advance the clinical development of adefovir dipivoxil in this important market. We believe the compound has the potential to address the unmet medical need of many patients with chronic HBV infection."

Phase I Program in ChinaGilead was granted Class 1 designation for adefovir dipivoxil in December 1999 by the People's Republic of China State Drug Administration (SDA). In December 2000, Gilead received approval from the SDA to initiate clinical trials in China. To meet the requirements stipulated by the SDA, for drug registration in China, clinical trials must be conducted in China within the Chinese population. In addition, Phase I studies are required regardless of existing data from later-stage clinical studies conducted in other parts of the world.

The adefovir dipivoxil clinical program design in China will be initiated with three separate Phase I trials (Studies 487, 488 and 489) that will be conducted in sequential order. After the completion of Phase I studies, a final report reviewing the safety and pharmacokinetic (PK) profile of the drug will be submitted to the SDA. The Class 1 designation of adefovir dipivoxil allows for an expedited review of these data. After the SDA's review and subject to its approval, a single Phase II/III study will be initiated.

Adefovir Dipivoxil Global Phase III ProgramOutside of China, two pivotal Phase III trials currently are underway to evaluate adefovir dipivoxil monotherapy as a potential treatment for chronic HBV infection. Study 437, initiated in March 1999 and conducted in Australia, Europe, North America and Southeast Asia, is a randomized, double-blind, placebo-controlled trial which is evaluating the safety and efficacy of adefovir dipivoxil at two active doses (10 mg and 30 mg) given once daily in hepatitis B "e" antigen positive patients. Enrollment in this trial was completed in March 2000 with 515 patients. Study 438, initiated in January 2000, is a randomized, double-blind, placebo-controlled trial which is evaluating adefovir dipivoxil 10 mg for the treatment of hepatitis B "e" antigen negative patients (precore mutant HBV infection). This trial is being conducted in Australia, Canada, France, Greece, Israel, Italy and Southeast Asia. Enrollment was completed in June 2000 with 185 patients.

Gilead anticipates the release or presentation of data from the 48-week analyses of these studies during the second half of 2001 and potential U.S. and European regulatory filings during the first half of 2002.

Patients and physicians who would like more information about adefovir dipivoxil may contact Gilead Sciences Medical Information at 1-800-GILEAD-5 (1-800-445-3235) or 1-650-574-3000 from outside the United States.

Gilead SciencesGilead Sciences, Inc., headquartered in Foster City, CA, is an independent biopharmaceutical company that seeks to provide accelerated solutions for patients and the people who care for them. Gilead discovers, develops, manufactures and commercializes proprietary therapeutics for challenging infectious diseases (viral, fungal and bacterial infections) and cancer. Gilead maintains research, development or manufacturing facilities in Foster City, CA; Boulder, CO; San Dimas, CA; Cambridge, UK and Dublin, Ireland and sales and marketing organizations in the United States, 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 that could cause actual results to differ materially from those referred to in the forward-looking statements. Such risks and uncertainties include: the risk that the safety, efficacy and resistance data observed in Gilead's clinical trials and preclinical testing outside of China may not be observed in Gilead's clinical trials in China within the Chinese population; risks associated with the ability of Gilead to successfully conduct clinical trials and, if successful, to commercialize adefovir dipivoxil in China, a country where Gilead has limited experience, no operations or employees and no commercial partner; uncertainty relating to Gilead's ability to obtain meaningful patent protection or regulatory exclusivity for adefovir dipivoxil in China; and the risk that adefovir dipivoxil is an investigational compound and has not yet been determined safe or efficacious in humans for its ultimate intended use. 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, 2000 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.

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For more information on Gilead Sciences, please visit the company's Web site at www.gilead.com or call the Gilead Corporate Communications Department at 1-800-GILEAD-5 (1-800-445-3235).