U.S. Food and Drug Administration Approves Viread(R) for Chronic Hepatitis B in Adults

- Important New Treatment Option for Millions in United States Affected by Life-Threatening Liver Disease -

FOSTER CITY, Calif.--(BUSINESS WIRE)--Aug. 11, 2008--Gilead Sciences, Inc. (NASDAQ:GILD) today announced that the U.S. Food and Drug Administration (FDA) has granted marketing approval for Viread(R) (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(R) (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.

Important Information About Viread for Chronic Hepatitis B

Viread (tenofovir disoproxil fumarate) is indicated for the treatment of chronic hepatitis B in adults.

The following points should be considered when initiating therapy with Viread for the treatment of HBV infection:

-- This indication is based on data from one year of treatment in primarily nucleoside-treatment-naive adult patients with HBeAg-positive and HBeAg-negative chronic hepatitis B with compensated liver disease. -- The numbers of patients in clinical trials who were nucleoside-experienced or who had lamivudine-associated mutations at baseline was too small to reach conclusions of efficacy. -- Viread has not been evaluated in patients with decompensated liver disease.

The recommended dose for the treatment of chronic hepatitis B is 300 mg once daily taken orally without regard to food. Dose interval adjustment is recommended in renal impairment.

LACTIC ACIDOSIS/SEVERE HEPATOMEGALY WITH STEATOSIS AND POST TREATMENT EXACERBATION OF HEPATITIS

Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with other antiretrovirals.

Severe acute exacerbations of hepatitis have been reported in HBV-infected patients who have discontinued anti-hepatitis B therapy, including Viread. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue anti-hepatitis B therapy, including Viread. If appropriate, resumption of anti-hepatitis B therapy may be warranted.

New onset or worsening of renal impairment including cases of acute renal failure and Fanconi syndrome have been reported with the use of Viread. It is recommended to assess creatinine clearance (CrCl) before initiating treatment with Viread and monitor CrCl and serum phosphorus in patients at risk. Administering Viread with concurrent or recent use of nephrotoxic drugs, including Hepsera should be avoided.

HIV antibody testing should be offered to all HBV-infected patients before initiating therapy with Viread. Viread should only be used as part of an appropriate antiretroviral combination regimen in HIV-infected patients with or without HBV coinfection.

Decreases in bone mineral density (BMD) have been observed in HIV-infected patients. It is recommended that BMD monitoring be considered for patients with a history of pathologic fracture or who are at risk for osteopenia. The bone effects of Viread have not been studies in patients with chronic HBV infection.

In controlled clinical trials in patients with chronic hepatitis B, the most common adverse reaction (all grades) is nausea. Other treatment-emergent adverse reactions reported in greater than 5 percent of patients treated with Viread included: abdominal pain, diarrhea, headache, dizziness, fatigue, nasopharyngitis, back pain and skin rash.

About Chronic Hepatitis B

The hepatitis B virus (HBV) is up to 100 times more easily transmitted than HIV. While most new cases of HBV infection in previously healthy adults are cleared by the immune system within a few months, many people - especially those infected as newborns and young children - will develop chronic, lifelong infections. In these cases, chronic hepatitis B can slowly destroy the liver, causing scarring (cirrhosis), liver disease, or liver cancer over many years or decades. Because it is believed to be the cause of 80 percent of all liver cancer cases worldwide, HBV is second only to tobacco among known human carcinogens.

The hepatitis B virus can be transmitted by any activity that involves exposure to blood and other body fluids, including sexual contact and use of contaminated needles during injection drug use. It can also be transmitted from mother to child at birth, which is the primary transmission route among Asian Americans. Asian Americans are one of the fastest-growing minority groups in the United States, numbering approximately 15 million people in 2007. A recent study showed that up to two-thirds of Asian Americans with chronic hepatitis B did not know they were infected.

Although there is no simple cure for chronic hepatitis B, antiviral treatment can slow viral replication and therefore reduce liver inflammation and liver injury.

About Gilead Sciences

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, including the risks that physicians may not prescribe the product over existing HBV medications and regulatory agencies and payers may be reluctant to approve or provide reimbursement for the product. 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, 2007 and its Quarterly Report on Form 10-Q for the second quarter of 2008, as 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.

Full U.S. prescribing information for Viread is available at www.Viread.com

Full U.S. prescribing information for Hepsera is available at www.Hepsera.com

Viread and Hepsera are registered trademarks of Gilead Sciences, Inc.

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

CONTACT: Gilead Sciences, Inc. Susan Hubbard, 650-522-5715 (Investors) Cara Miller, 650-522-1616 (Media) SOURCE: Gilead Sciences, Inc.