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Pharmasset Adds Two Cohorts to R7128 Hepatitis C Study
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-- Two 4-week cohorts will be enrolled to evaluate R7128 1500mg BID in HCV genotypes 2 and 3 prior non-responders and R7128 1000mg BID in HCV genotype 1 treatment-naive patients --
PRINCETON, N.J. and MILAN, Italy, April 24, 2008 /PRNewswire-FirstCall via COMTEX News Network/ -- Pharmasset, Inc. (Nasdaq: VRUS) will enroll two additional cohorts in the on- going Phase 1 study protocol to evaluate 4 weeks of combination therapy with R7128. R7128, a prodrug of PSI-6130, is a nucleoside analogue polymerase inhibitor of hepatitis c virus (HCV) that is being developed through Pharmasset's collaboration with Roche.
Cohort 3 will study R7128 1000mg BID in treatment-naive patients with HCV genotype 1. This cohort is intended to provide clinical antiviral activity data in support of pharmacokinetic models from earlier studies. Cohort 4 will study R7128 1500mg BID in patients with HCV genotypes 2 and 3 who did not achieve a sustained virologic response (SVR) with previous interferon-based therapy. Cohorts 3 and 4 will both be dosed in combination with Pegasys (peginterferon alfa-2a) plus Copegus (ribavirin).
Patients in Cohorts 3 and 4 are scheduled to begin dosing by the end of May 2008. Preliminary safety and antiviral activity data from the 4-week combination studies are anticipated during the 3rd quarter of 2008. Cohorts 3 and 4 will be conducted in parallel with the global Phase 2b study preparation activities for R7128. The timing of the Phase 2b study is not dependent upon data from Cohorts 3 and 4.
"Our pharmacokinetic modeling of the 500mg and 1500mg cohorts of R7128 in combination with Pegasys plus Copegus suggests that the 1000mg dose could deliver a rapid virologic response (RVR) rate similar to the 1500mg dose," stated Dr. Michelle Berrey, Pharmasset's Chief Medical Officer. "The confirmatory results from this additional cohort will aid us in selecting the appropriate doses to evaluate in the global Phase 2b study that is being planned to evaluate R7128 in triple combination for up to 12 weeks."
"R7128 is equally potent in vitro against HCV genotypes 1, 2, 3 and 4, and we believe it is clinically and commercially important to test R7128 in patients with these HCV genotypes," stated Schaefer Price, Pharmasset's Chief Executive Officer. "Twenty percent of U.S. HCV-infected patients and approximately 30% of European and Latin American HCV-infected patients have genotypes 2 and 3. These patients are currently treated with 24 weeks of pegylated-interferon plus ribavirin, but 20% of this population fails to achieve an SVR. By potentially addressing this unmet medical need in a patient population for whom the standard of care is only 24 weeks, we could possibly design shorter clinical trials that may provide a quicker path to the market for R7128."
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