Pharmasset Presents Results of 4-Week Combination Study of R7128 for the Treatment of Chronic H...( - 85% of patients achieve undetectab...),Health

- 85% of patients achieve undetectable HCV RNA levels following 4 weeks of

treatment with R7128 1500mg BID with Pegasys(R) plus Copegus(R) - - Safety and tolerability comparable to placebo administered with Pegasys

plus Copegus -

- EASL presentation available on Pharmasset website - - Conference call scheduled for Friday, April 25, 2008 at 1:00 PM ET (US)

and 7:00 PM CEST (Milan) -

PRINCETON, N.J. and MILAN, Italy, April 25 /PRNewswire-FirstCall/ -- Pharmasset, Inc. (Nasdaq: VRUS) announces the results of a 4-week Phase 1 clinical trial evaluating two oral dose levels of R7128 in combination with Pegasys (pegylated interferon) plus Copegus (ribavirin) in 50 treatment-naive patients chronically infected with hepatitis C virus (HCV) genotype 1. R7128, a prodrug of PSI-6130, is a nucleoside analogue polymerase inhibitor of HCV that is being developed through Pharmasset's collaboration with Roche. The results of this study were presented today at the 43rd Annual Meeting of the European Association for the Study of the Liver (EASL) being held from April 23-27, 2008 in Milan, Italy.

In this study, R7128 demonstrated potent short-term antiviral activity and was generally safe and well tolerated. Eighty-five percent (85%) of patients receiving R7128 1500mg twice-daily (BID) with Pegasys plus Copegus for 4 weeks achieved undetectable HCV RNA levels with safety and tolerability comparable to placebo with Pegasys plus Copegus.

Dr. John McHutchison, professor of medicine at Duke University Medical Center and a clinical investigator for this study, stated, "R7128, in combination with Pegasys plus Copegus, has demonstrated Rapid Virologic Response (RVR)
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