PRINCETON, N.J., March 30, 2011 /PRNewswire/ -- Pharmasset, Inc. (Nasdaq: VRUS) announced today that screening has begun in a Phase 2b study of PSI-7977, a nucleotide analog polymerase inhibitor for the treatment of chronic hepatitis C (HCV). The trial will evaluate PSI-7977 400mg QD with pegylated interferon and ribavirin in patients with HCV genotype 1, 4, 5 or 6 who have not been treated previously.
"We are encouraged by the early efficacy and safety data being generated with our nucleotide analogs, PSI-7977 and PSI-938," stated Michelle Berrey, MD, MPH, Pharmasset's Chief Medical Officer. "The ATOMIC trial is designed to explore 12 and 24 week durations of PSI-7977. The potency, high barrier to resistance, and consistent antiviral activity across genotypes provided the data to support an interferon free dosing period in this trial, as well as enabling us to enroll multiple genotypes in this trial."
About the Phase 2b ATOMIC Trial
This Phase 2b trial is planned to enroll approximately 300 patients with chronic HCV genotype 1 who have not been treated previously. The primary endpoint of the trial will be the safety and tolerability of PSI-7977 in combination with peginterferon and ribavirin over 12 or 24 weeks. The trial will be conducted in the U.S. Patients will be randomized (1:2:3) into the following arms:
- PSI-7977 400mg QD with peginterferon and ribavirin for 12 weeks;
- PSI-7977 400mg QD with peginterferon and ribavirin for 24 weeks;
- PSI-7977 400mg QD with peginterferon and ribavirin for 12 weeks, followed by either PSI-7977 400mg QD monotherapy for 12 weeks or PSI-7977 400mg QD plus ribavirin for 12 weeks.
HCV GT1 patients will be stratified by IL28B status and baseline HCV RNA to ensure balance across cohorts. An additional 25 treatment-naïve patients w