( FOSTER CITY Calif.--(BUSINESS WIRE)--...)Second Phase III Study Evaluating Gilead's Viread for the Treatment,of Chronic Hepatitis B Virus Meets Primary Endpoint,Health

FOSTER CITY, Calif.--(BUSINESS WIRE)--June 25, 2007--Gilead Sciences, Inc. (Nasdaq:GILD) today announced that Study 103, a Phase III clinical trial evaluating the company's once-daily anti-HIV drug Viread(R) (tenofovir disoproxil fumarate or tenofovir DF) 300 mg as a potential treatment for chronic hepatitis B virus (HBV) infection, met its primary efficacy endpoint. The data show that Viread is non-inferior to the company's once-daily antiviral drug Hepsera(R) (adefovir dipivoxil) among patients with "e" antigen (HBeAg)-positive chronic hepatitis B. The primary efficacy endpoint, the proportion of patients with a complete response at week 48, was defined by 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).

At 48 weeks, 66.5 percent of patients in the Viread arm (n=176) had a complete response compared to 12.2 percent in the Hepsera arm (n=90; p less than 0.001). The most commonly observed treatment-emergent adverse events of moderate intensity or higher were abdominal pain, back pain, headache, respiratory infections and transaminase elevations. The incidence of these events was comparable between the Viread and Hepsera arms of the study. In addition, the most frequently observed grade 3 or 4 laboratory abnormalities were elevations in transaminase and serum amylase and were comparable between the two arms. Full study results will be submitted for presentation at an upcoming scientific meeting.

Study 103 is the second of two Phase III pivotal studies evaluating the efficacy, safety and tolerability of Viread for the treatment of chronic hepatitis B to have met its primary efficacy endpoint. Earlier this month,
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