Pharmasset Announces Final SVR Data from PROTON trial with PSI-7977 in Subjects Infected with Hepatitis C Infection Genotype 2 or 3
PRINCETON, N.J. , July 20, 2011 /PRNewswire/ -- Pharmasset, Inc. (Nasdaq: VRUS) announced today the final sustained virologic response (SVR) results from its phase 2b PROTON study with PSI-7977 dosed once daily in combination with peginterferon alfa 2a and ribavirin (Peg-IFN/RBV) in subjects with hepatitis C virus (HCV) genotype 2 or 3 who have not been treated previously. Twenty four out of twenty four subjects (100%) who completed treatment achieved an SVR, defined as HCV RNA below the limit of detection (<15 IU/ml) 24 weeks after the completion of treatment. No subject exhibited breakthrough on treatment or relapse after treatment.
Twenty five treatment-naive subjects with HCV genotype 2 or 3 were enrolled in an open label arm of the PROTON trial, receiving PSI-7977 400mg QD with Peg-IFN/RBV for 12 weeks, with no Peg-IFN/RBV follow-up. At the European Association for the Study of the Liver (EASL) in April 2011 , Dr J. Lalezari presented interim results from this arm showing that 24 out of 24 subjects achieved an SVR12, defined as HCV RNA below the limit of detection (<15 IU/ml) 12 weeks after the completion of treatment. The combination was generally safe and well tolerated with one subject discontinuing treatment after day 1 and was lost to follow up. Overall PSI-7977 with Peg-IFN/RBV demonstrated potent viral suppression in subjects with HCV genotype 2 or 3 over 12 weeks of treatment.
Pharmasset anticipates reporting the SVR12 results from the PROTON trial in genotype 1 HCV subjects in the second half of 2011.
About the PROTON Trial
The Phase 2b PROTON trial enrolled 121 subjects infected with HCV genotype 1 who have not been treated previously. The primary endpoint of the trial will be the assessment of safety and tolerability of PSI-7977 in combination with Peg-IFN/RBV over 12 weeks with response-guided therapy allowing discontinuation of Peg-IFN/RBV at week 24. The trial was conducted in the U.S. Subjects were randomized (2:2:1) into one of 3 arms:
•PSI-7977 200mg QD in combination with Peg-IFN/RBV for 12 weeks, followed by 12 or 36 weeks of Peg-IFN/RBV;
•PSI-7977 400mg QD in combination with Peg-IFN/RBV for 12 weeks, followed by 12 or 36 weeks of Peg-IFN/RBV;
•A control arm of matching placebo with Peg-IFN/RBV for 48 weeks.
In addition, 25 treatment-naive subjects with HCV genotype 2 or 3 were enrolled in a fourth, open label arm, receiving PSI-7977 400mg QD with Peg-IFN/RBV for 12 weeks, with no Peg-IFN/RBV follow-up. Subjects were followed for an additional 24 weeks after discontinuation of all therapy to assess SVR.
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