Foster City, CA -- August 11, 2008 -- Gilead Sciences today announced that the U.S. Food and Drug Administration (FDA) has granted marketing approval for Viread (tenofovir disoproxil fumarate) for the treatment of chronic hepatitis B, a serious liver disease caused by the hepatitis B virus (HBV). Chronic hepatitis B is the leading cause of liver cancer worldwide and affects an estimated two million individuals in the United States.

Viread is now also indicated for the treatment of chronic hepatitis B in adults. The drug is administered as a once-daily tablet, and works by blocking HBV DNA polymerase, the enzyme that is necessary for the virus to replicate in liver cells. Viread has been available in the United States as a treatment for HIV infection in adults since 2001.

"Viread will be an important new treatment option and its approval represents a significant step forward in the fight against chronic hepatitis B," said Ira Jacobson, M.D., Chief, Division of Gastroenterology and Hepatology, Weill Cornell Medical College.

Pivotal Clinical Trials

Today's approval is based on data from two ongoing, randomized and double-blind Phase III clinical trials, Studies 102 and 103, which compared Viread to Gilead's Hepsera (adefovir dipivoxil) over 48 weeks of treatment. Results from both studies show that a significantly greater percentage of patients with chronic hepatitis B who received Viread achieved a complete response to treatment compared to those who received Hepsera.

A complete response was defined as serum HBV DNA levels below 400 copies/mL and histologic improvement characterized by at least a two point reduction in the Knodell necroinflammatory score (a measure of necro-inflammation - an inflammatory process in the liver including or leading to death of liver cells) with no concurrent worsening of fibrosis (scarring of liver tissue). Trial participants included both patients new to HBV therapy (n=375) and patients (n=51) who had received prior nucleoside treatment. To date, more than 400 chronic hepatitis B patients have been treated with Viread in these studies.

"The approval of Viread for hepatitis B represents more than a decade of work in both the fields of HIV and hepatitis B to develop a medication that offers significant viral suppression, once-daily dosing and a well-established safety profile," said Kevin Young, Executive Vice President, Commercial Operations, Gilead Sciences. "We extend our thanks to the investigators and patients who participated in the clinical trials that support today's approval, and we look forward to partnering with community members to increase disease awareness and expand access to treatment for those patients in need."

Because chronic HBV infection can persist for years without causing any noticeable symptoms, many people are unaware they are infected and do not seek treatment. The disease disproportionately affects Asian Americans: One in 10 foreign-born Asian Americans is estimated to be living with chronic HBV infection, a rate 100 times greater than that of the non-Asian U.S. population, which reflects the high prevalence of HBV in many Asian countries.

"Although we've made great strides in reducing the overall incidence of chronic hepatitis B in the United States, the disease still takes a devastating toll in Asian-American communities," said Danny Chu, M.D., Community Physician, New York. "Greater public awareness and effective new treatment options are urgently needed to help reduce this significant health disparity."

The approval of Viread expands Gilead's hepatic health franchise. The company's first treatment for chronic hepatitis B, Hepsera, is currently the most widely prescribed oral agent for the disease in the United States. The company is also developing small-molecule compounds for the treatment of hepatitis C and a hepatoprotectant for multiple forms of hepatitis-related liver fibrosis, including nonalcoholic steatohepatitis (also known as NASH).

Viread was approved for the treatment of chronic hepatitis B in the European Union, Turkey, Australia and New Zealand earlier this year, and a marketing application is currently pending in Canada.

The full announcement, including safety information about tenofovir, can be found at www.gilead.com/pr_1186292.

Full U.S. prescribing information for tenofovir for hepatitis B is available at www.viread.com.

For more information about Gilead Sciences, visit www.gilead.com.