Pharmasset Presents R7128 Phase 1 Single Ascending Dose Study in Healthy ...( -R7128 Demonstrates Safety and Toler...),Health

-R7128 Demonstrates Safety and Tolerability with No Clinically Significant

Adverse Events-

-Conference Call Scheduled for 8:30AM (ET) Today-

PRINCETON, N.J., Sept. 10 /PRNewswire-FirstCall/ -- Pharmasset, Inc. (Nasdaq: VRUS) is presenting safety, tolerability, pharmacokinetic and food effect data following single ascending doses of R7128 at the 14th International Symposium on Hepatitis C Virus and Related Viruses being held from September 9-13, 2007 in Glasgow, Scotland. R7128 is a prodrug of PSI- 6130, an oral cytidine nucleoside analog polymerase inhibitor of hepatitis C virus (HCV) that is being developed through Pharmasset's collaboration with Roche. The poster presentation from the conference is available in the "Events and Presentations" section of the Investor Center on Pharmasset's website at http://www.pharmasset.com.

The Phase 1 single ascending dose study of R7128 was designed to assess the safety, tolerability and pharmacokinetics of R7128 following single ascending doses under fasting conditions. The secondary objective of this study was to explore the effect of food on the pharmacokinetics of R7128. Single oral doses of R7128 were administered to 46 healthy volunteers in five sequential dose groups (500 mg, 1500 mg, 4500 mg, 6000 mg, and 9000 mg) and one food effect group (1500 mg). There were 8 subjects per sequential dose group (6 active, 2 placebo) and 6 subjects in the food effect group (all active).

Nineteen adverse events (AEs) were reported during the study, including headache, sunburn, sore throat and nasal congestion. All AEs were mild to moderate, none were related to dose and no
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