Pharmasset’s combination therapy found effective against HCV

In this study, R7128 demonstrated potent short-term antiviral activity and was generally safe and well-tolerated. Potent antiviral activity was demonstrated following four weeks of treatment with R7128 1500mg BID with Pegasys plus Copegus, in which patients achieved a mean 5.12 log10 IU/mL decrease in HCV RNA and 85% achieved undetectable levels of HCV RNA (<15 IU/mL), or Rapid Virologic Response (RVR). Following four weeks of treatment with R7128 500mg BID with Pegasys plus Copegus, patients achieved a mean 3.82 log10 IU/mL decrease in HCV RNA and 30% achieved RVR. Following four weeks of treatment with placebo with Pegasys plus Copegus, patients achieved a mean 2.95 log10 IU/mL decrease in HCV RNA and 10% achieved RVR. Baseline HCV RNA was similar across the three treatment groups. The primary objective of the Phase I combination clinical trial was to assess the safety, tolerability and pharmacokinetics of R7128 in combination with Pegasys plus Copegus. The secondary objective was to evaluate the change in HCV RNA after four weeks of treatment. The study investigated two oral dose levels of R7128, 500mg and 1500mg, each administered twice-daily (BID) with once-weekly injections of Pegasys plus Copegus. Each cohort of 25 patients was comprised of 20 patients receiving active R7128 and five patients receiving placebo with Pegasys plus Copegus (standard of care). The initial evaluation period reported is four weeks. R7128 is a prodrug of PSI-6130, a cytidine nucleoside analogue polymerase inhibitor of HCV that is being developed through Pharmasset's collaboration with Roche.