Pharmasset Commences Dosing R7128 Cohorts 3 and 4 for the Treatment of Chronic H...( - Two 4-week cohorts will evaluate...),Health

- Two 4-week cohorts will evaluate R7128 1000mg BID in HCV genotype 1 treatment-naive patients and R7128 1500mg BID in HCV genotypes 2 or 3

treatment-experienced patients -

PRINCETON, N.J., May 14 /PRNewswire-FirstCall/ -- Pharmasset, Inc. (Nasdaq: VRUS) has commenced dosing two additional cohorts of a 4-week Phase 1 study of R7128 in combination with Pegasys(R) (peginterferon alfa-2a) plus Copegus(R) (ribavirin) in both treatment-naive and treatment-experienced patients chronically-infected with hepatitis C virus (HCV) genotypes 1, 2 and 3. 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 purpose of this 4-week study is to evaluate the safety, tolerability, pharmacokinetics and antiviral activity of R7128 in the clinically-relevant setting of combination therapy for chronic HCV infection. The previously planned Cohort 3 will continue dose-exploration with administration of R7128 1000mg twice-daily (BID) in treatment-naive patients with HCV genotype 1. Cohort 4 will evaluate R7128 1500mg BID administered in combination with Pegasys plus Copegus in treatment-experienced patients with genotypes 2 or 3 who did not achieve a sustained virologic response (SVR) with previous interferon-based therapy.

There will be 25 patients in each dose cohort with 20 patients randomized to receive R7128 and 5 patients randomized to receive placebo. After completing 4 weeks of the triple combination regimen and a follow-up period of 4 weeks of Pegasys plus Copegus, patients will receive an additional 16 to 40 weeks of open-label dosing of Pegasys plus Copegus under a separate protocol to complete the stand
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