Pharmasset Initiates Phase 1b Multiple Ascending Dose Clinical Trial of PSI-7851 in Chronic Hepatitis ...( - PSI-7851 was generally safe and wel...),Health

- PSI-7851 was generally safe and well tolerated in Phase 1a single ascending dose trial

- Further results from single ascending and multiple ascending dose trials are expected in second half 2009

PRINCETON, N.J., June 9 /PRNewswire-FirstCall/ -- Pharmasset, Inc. (Nasdaq: VRUS) announced today that it had completed the single ascending dose study and begun dosing in a multiple ascending dose trial with PSI-7851, a nucleotide analog polymerase inhibitor for the treatment of chronic hepatitis C virus (HCV) infection. This study is designed to assess the safety, tolerability and antiviral activity of PSI-7851 over 3 days in HCV-infected individuals.

"We are encouraged by the safety and pharmacokinetics of PSI-7851 thus far," stated Michelle Berrey, MD, MPH, Pharmasset's Chief Medical Officer. "We believe PSI-7851, Pharmasset's lead second generation nucleotide, has the potential to be administered once a day at low milligram doses, while also continuing to demonstrate the many benefits nucleos(t)ides have over other classes of HCV direct acting antivirals, including a high barrier to resistance, pan-genotype potency, and ability to combine with other classes of compounds."

PSI-7851 Phase 1 Program Overview

The Phase 1 program is investigating the safety, tolerability and pharmacokinetics of PSI-7851 in healthy subjects following single doses (Phase 1a) and in patients chronically infected with HCV genotype 1 following repeat dosing for 3 days (Phase 1b). The Phase 1b study will additionally investigate hepatitis C viral dynamics and monitor for the development of drug resistance.

Subjects in the phase 1a single ascending dose study received single doses of PSI-7851 ranging from 25mg to 800mg or a matching placebo. Preliminary data from the phase 1a single ascending
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