Gilead Submits New Drug Application to U.S. FDA for Adefovir Dipivoxil 10 mg for the Treatment of Chronic Hepatitis B

Foster City, CA -- March 21, 2002

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 adefovir dipivoxil 10 mg. Gilead is seeking an indication for the treatment of patients with chronic hepatitis B, including treatment-naïve and treatment-experienced patients. The application is supported by data from Phase III studies in hepatitis B "e" antigen-positive patients, hepatitis B "e" antigen-negative patients and chronic hepatitis B patients with lamivudine-resistant HBV. Based on the unmet medical needs of patients with chronic hepatitis B, Gilead has submitted a request for a priority, or six-month, review of the adefovir dipivoxil NDA. The company will submit an application for marketing approval of adefovir dipivoxil 10 mg in Europe shortly.

"Current therapeutic options are limited, and the need for safe, effective and durable treatments for patients with chronic hepatitis B is an urgent one," said John C. Martin, PhD, President and CEO, Gilead Sciences. "The achievement of this milestone marks an important advancement toward our goal of providing a potential new treatment to the many patients suffering from chronic hepatitis B. It also marks the second NDA submission for a novel Gilead antiviral in less than one year, underscoring our expertise and our leadership role in anti-infective therapies."

About Adefovir Dipivoxil
Adefovir dipivoxil belongs to a class of drugs called nucleotide analogues which are designed to work by blocking hepatitis B virus (HBV) DNA polymerase, an enzyme involved in the replication of the virus in the body.

Data from two pivotal studies and a number of supportive studies of adefovir dipivoxil in a variety of chronic hepatitis B patient populations will be presented in April at the 37th Annual Meeting of the European Association for the Study of the Liver (EASL). Presentations include data from studies of hepatitis B "e" antigen-positive patients, precore mutant (hepatitis B "e" antigen-negative) patients, those with lamivudine-resistant HBV, patients post-liver transplantation and patients co-infected with HIV. Since 1999, Gilead has provided access to adefovir dipivoxil through Study 435 to approximately 400 chronic hepatitis B patients with lamivudine-resistant HBV who are wait listed for or have received a liver transplant. Adefovir dipivoxil is an investigational compound and has not yet been determined safe or efficacious in humans.

Chronic Hepatitis B
Worldwide, there are approximately 350 million chronic carriers of hepatitis B, of which approximately one million die each year from complications of the disease, making chronic hepatitis B one of the 10 most common causes of death. Complications of chronic hepatitis B include cirrhosis (scarring of the liver), liver failure and primary liver cancer (hepatocellular carcinoma). Between one quarter and one third of people with chronic hepatitis B are expected to develop progressive liver disease. Patients infected with the precore mutant strain of hepatitis B may be predisposed to more severe and progressive liver injury. Precore mutant hepatitis B infects up to approximately 50 percent of the 350 million chronic hepatitis B carriers worldwide and is most prevalent in countries of the Mediterranean and Southeast Asia, where between 30-80 percent of chronic hepatitis B patients are estimated to be infected with this strain.

Early Access Program Initiated
In March 2002, Gilead announced the initiation of an early access program in the United States to provide adefovir dipivoxil to chronic hepatitis B patients with lamivudine-resistant HBV. A similar program opened in France in July 2001 and has enrolled 289 patients to date. Additional programs in Canada, Australia and in other countries in Europe will open in the coming months as appropriate regulatory approvals are obtained.

For more information regarding the adefovir dipivoxil early access program, or to request program registration materials, physicians may call 1-800-GILEAD-5 or 1-650-574-3000.

Gilead Sciences
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 five marketed products and focuses its research and clinical programs on anti-infectives, including antivirals, antifungals and antibacterials. Headquartered in Foster City, CA, Gilead has operations 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 FDA may not agree that the safety and efficacy data from pivotal studies are sufficient for marketing approval, the risk that the FDA may require additional studies and data prior to approval, the risk that the FDA may not review the application in 2002 and the risk that further data from ongoing and future clinical trials may not be as favorable as current data. 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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