Pharmasset Inc. (Nasdaq: VRUS) shares rose 5.2% to $67.55 after the drug developer released preliminary findings from a study of its Hepatitis C treatment. Volume for the stock was 658,000 shares, or about half its daily average.

A news release out September 6 noted that the Princeton, New Jersey-based company announced today sustained virologic response (SVR) results from its phase 2b PROTON study with PSI-7977 400 mg dosed once daily in combination with peginterferon alfa 2a and ribavirin (Peg-IFN/RBV) in subjects with hepatitis C virus (HCV) genotype 1 who have not been treated previously.

In all, 95 treatment-naive patients with HCV genotype 1 were enrolled into two open-label arms of the PROTON trial, receiving either PSI-7977 200 mg QD (N=48) or 400 mg QD (N=47) for 12 weeks. Individuals in both arms received Peg-IFN/RBV for 24 weeks and were followed post-treatment to assess SVR12.

What’s more, 26 subjects were enrolled in a placebo control arm and are receiving 48 weeks of Peg-IFN/RBV. Results from this study through the SVR12 endpoint are scheduled to be presented as part of a Presidential Plenary Session at the American Association for the Study of Liver Diseases (AASLD) meeting on Tuesday, November 8, 2011.

“I am very pleased with the results of this study which clearly demonstrate the benefit of the 400 mg dose of PSI-7977 with only 24 weeks of interferon for all subjects,” Dr. Eric Lawitz, the study’s principal investigator, was quoted in the release as saying. “HCV therapy is becoming overly complex, and the elimination of 24 weeks of interferon and ribavirin as well as all response guided criteria for patients with HCV genotype 1 would be a welcomed simplification.”

Pharmasset is a clinical-stage pharmaceutical company committed to discovering, developing, and commercializing novel drugs to treat viral infections.