Pharmasset commences PSI-7977 Phase 2a trial for HCV

Pharmasset, Inc. (Nasdaq: VRUS) today announces the initiation of a 28-day Phase 2a study with PSI-7977, a chirally pure isomer form of PSI-7851, a nucleotide analog polymerase inhibitor in development for the treatment of chronic hepatitis C (HCV). The trial will evaluate various doses of PSI-7977 in combination with Pegasys (peginterferon alfa 2a) and Copegus (ribavirin) in patients with HCV genotype 1 who have not been treated previously.

"We recently reported encouraging clinical results with PSI-7851," said Michelle Berrey, MD, MPH, Pharmasset's Chief Medical Officer. "We now believe there are a number of advantages in moving forward with a chirally pure isomer of PSI-7851, PSI-7977, including improvements in manufacturing. We look forward to reporting interim data from the Phase 2a trial in the third quarter of 2010, and hope to rapidly progress PSI-7977 into longer-term studies to demonstrate the safety and efficacy of the nucleosides/tides in all HCV genotypes."