PRINCETON, N.J., June 8, 2011 /PRNewswire/ — Pharmasset, Inc.
(Nasdaq:
VRUS) announced today the addition of three treatment cohorts
to the ELECTRON trial of PSI-7977, a nucleotide analog polymerase
inhibitor, for the treatment of chronic hepatitis C (HCV). The
rapid and consistent antiviral effects and high barrier to
resistance demonstrated with PSI-7977 to date provide the rationale
for additional exploratory regimens in this setting.  This
amendment will add one arm exploring 12 weeks of PSI-7977
monotherapy (without peginterferon and ribavirin) and two arms of
interferon-sparing therapy: one for 8 weeks of PSI-7977 plus
peginterferon and ribavirin (Peg-IFN/RBV) in patients with HCV
genotype 2 (GT2) or 3 (GT3) and one for 12 weeks of PSI-7977 plus
Peg-IFN/RBV in patients with HCV genotype 1 (GT1) prior null
responses.  

“The combination data reported at EASL demonstrated that SVRs
were achievable with two oral DAAs in the absence of peginterferon
and ribavirin,” stated Bill Symonds, PharmD, Pharmasset’s Senior
Vice President of Clinical Pharmacology and Translational Medicine,
“We continue to explore the potential for removing peginterferon
and ribavirin from the HCV treatment regimen. Given the encouraging
data we are seeing in ELECTRON, we have decided to expand the study
to investigate PSI-7977 monotherapy, as well as shorter treatment
regimens based on the promising data we reported at EASL from
PROTON.”

Pharmasset anticipates reporting results from the first four
arms of the trial (n=40) during the second half of 2011. We have
submitted a number of abstracts to the 2011 American Association
for the Study of Liver Diseases (AASLD) meeting, including data
from the ELECTRON and PROTON trials.

About the Trial

The ELECTRON trial is an exploratory study of PSI-7977 for the
treatment of chronic HCV infection. Part 1 of the trial is ev

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