Gilead Announces Phase I Data for GS 9190, An Investigational Compound for the Treatment of Chronic Hepatitis C

-- Antiviral, Pharmacokinetic and Safety Data for Novel HCV

Polymerase Inhibitor Presented Today at The Liver Meeting 2007 --

BOSTON--(BUSINESS WIRE)--Nov. 4, 2007--Gilead Sciences, Inc. (Nasdaq:GILD) today announced preliminary clinical data from an ongoing Phase I study of GS 9190, an investigational compound for the potential treatment of infection with the chronic hepatitis C virus (HCV). These data were presented (Abstract # 49) by Ira Jacobson, MD, Chief of the Division of Gastroenterology and Hepatology, Vincent Astor Distinguished Professor of Clinical Medicine, Weill Medical College of Cornell University, at the annual meeting of the American Association for the Study of Liver Diseases (The Liver Meeting 2007), currently taking place in Boston, Massachusetts (November 2-6).

GS 9190 is a novel non-nucleoside polymerase inhibitor that is being evaluated in a two-part Phase I study of treatment-naive patients infected with HCV genotype 1. In the first part of the study (Part A), a single dose of GS 9190 demonstrated encouraging pharmacokinetics and antiviral activity. The second, multiple dose part of the study (Part B) is designed to enroll 60 HCV infected patients in total, and assess the safety, tolerability, pharmacokinetics and antiviral activity of ascending doses of GS 9190, once or twice daily, for eight days. Results from Part A and initial results from the first two twice daily doses evaluated in Part B of the study were presented today.

"These Phase I data support continued evaluation of GS 9190 as a potential therapeutic option for HCV," said Dr. Jacobson. "New, more convenient and better tolerated medicines for HCV are urgently needed, and we look forward to continuing our assessment of GS 9190 in this clinical program."

Phase I Study Results

This study is an ongoing dose-escalation, randomized, double-blind, placebo-controlled Phase I clinical trial among treatment-naive patients infected with HCV genotype 1. Key outcome measures of the study include antiviral activity, pharmacokinetics and safety and tolerability.

Part A of the study (n=31) evaluated escalating single doses of GS 9190 compared to placebo in five successive cohorts: 40 mg, 120 mg, 240 mg, 240 mg (dosed with food) and 480 mg. At baseline, participants in Part A had a mean age of 44 years, were predominantly white males, and had a median HCV RNA of 6.56 log(10) IU/mL.

All single doses of GS 9190 demonstrated antiviral activity. The compound showed greatest effect 24 hours after administration, at which time the change in HCV RNA log(10) copies/mL compared to baseline ranged from approximately -0.7 to -1.2 versus essentially no change for the placebo arm. Across cohorts, the median half-life of GS 9190 was 10-15 hours, supporting potential once or twice daily administration of the compound in future studies. GS 9190 pharmacokinetics were dose proportional following single-dose administration over the range of 40 mg to 240 mg.

Single doses of GS 9190 were well tolerated. There were no serious or treatment-limiting adverse events. All adverse events recorded were mild, with the exception of one moderate headache. There were no grade 3 or 4 treatment-emergent laboratory abnormalities.

On the basis of findings observed in Part A, Part B of the study (n=23) was initiated to evaluate multiple doses of the compound, administered over a period of eight days, in four successive cohorts: 40 mg BID, 120 mg BID, 240 mg QD and 240 mg BID.

Data from the 40 mg BID and 120 mg BID cohorts were presented today at The Liver Meeting 2007. At baseline, participants in Part B had a mean age of 44 years, were predominantly white males, and had a median HCV RNA of 6.65 log(10) IU/mL. Twice-daily 40 mg and 120 mg doses of GS 9190 achieved a sustained antiviral effect during eight days of treatment.

The mean change in HCV RNA log(10) copies/mL compared to baseline following administration for eight days was approximately -1.4 for the 40 mg dose and -1.7 for the 120 mg dose, compared to a negligible change in the placebo arm. Systemic clearance of drug at both doses was low, and pharmacokinetics were dose proportional. The median half-life of GS 9190 following multiple-dose administration was 10-13 hours. Twice daily administration of GS 9190 over eight days at these doses was generally well tolerated.

Included in the study design was an electrocardiographic assessment of QT duration while on drug - a standard test for cardiovascular safety. In the second multiple dose cohort, a possible but not confirmed QT elongation was observed. Gilead has therefore initiated a specific QT study, now underway, in healthy volunteers to further evaluate this finding. The study is expected to be concluded before year-end 2007.

Pending resolution of this safety concern, these encouraging preliminary Phase I trial data support further evaluation of GS 9190 in HCV-infected patients.

GS 9190 is an investigational treatment and has not yet been determined safe or efficacious in humans.

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 risks with meeting the anticipated timelines for completion of our clinical studies of GS 9190 and the risk that further data from additional clinical studies may not support the evaluation of GS 9190 for the treatment of chronic hepatitis C. For example, if results from QT study confirm a drug-related QT signal, our program for GS 9190 may be further delayed or we may decide to cease our efforts to commercialize this compound. 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, 2006 and Quarterly Reports on Form 10-Q for the first and second quarters of 2007, 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.

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. Patrick O'Brien, 650-522-1936 (Investors) Amy Flood, 650-522-5643 (Media) SOURCE: Gilead Sciences, Inc.