Pharmasset, Inc. has received fast track designation from the US Food and Drug Administration (FDA) for PSI-7977 for the treatment of chronic hepatitis C virus (HCV) infection. PSI-7977 is an oral uridine nucleotide analog polymerase inhibitor of HCV. Pharmasset recently completed dosing in a 28 day phase 2a trial to evaluate PSI-7977 in combination with Pegasys (pegylated interferon) plus Copegus (ribavirin) in treatment-naive patients chronically infected with HCV genotype. Pharmasset expects to initiate a 12-week phase 2b study of PSI-7977 in the fourth quarter of 2010.

Under the FDA Modernization Act of 1997, fast track designation may facilitate the development and expedite the review of a drug candidate that is intended for the treatment of a serious and life-threatening condition and demonstrates the potential to address an unmet medical need for such a condition. PSI-7977 was granted the fast track designation primarily due to the need for HCV treatments with novel mechanisms of action, oral administration, different resistance profiles and improved safety and efficacy over the existing standard of care for both treatment-naive and treatment-experienced patients.

"The FDA's fast track designation for PSI-7977 acknowledges the urgent need for new HCV drugs," stated Dr. Michael Rogers, Pharmasset's chief development officer. "Currently, there are no HCV nucleoside/tide inhibitors approved for the treatment of chronic HCV infection. We continue to work closely with the FDA on the development and regulatory review of PSI-7977, which has demonstrated compelling antiviral activity, a high barrier to resistance and has been generally well-tolerated in clinical trials to date."

Pharmasset is a clinical-stage pharmaceutical company committed to discovering, developing, and commercializing novel drugs to treat viral infections. Pharmasset's primary focus is on the development of oral therapeutics for the treatment of hepatitis C virus (HCV) and, secondarily, on the development of Racivir for the treatment of human immunodeficiency virus (HIV).