Pharmasset, Inc.
(Nasdaq: VRUS) announces the start of long-term chronic toxicology studies
in two animal species as part of their collaboration with Roche for the
development of R7128 for the treatment of hepatitis C virus (HCV). R7128 is
currently being evaluated in a Phase 1 clinical trial. The primary
objective of the chronic toxicology studies is to assess the safety of
R7128 when given for six months. Roche triggered a $7.5 million milestone
payment to Pharmasset by initiating these studies.
"As we progress the ongoing 14-day multiple ascending dose study of
R7128, we are encouraged that Roche has initiated the long-term chronic
toxicology studies in support of the potential advancement of R7128 into
Phase 2 clinical trials," stated Schaefer Price, Pharmasset's President &
CEO. "This achievement is a clear indication that our cooperative
partnership with Roche is focused on the common goal of accelerating the
development of R7128 in order to bring new treatment options to patients
with hepatitis C."
About R7128
R7128 is a polymerase inhibitor being developed for the treatment of
chronic hepatitis C. R7128 is a prodrug of PSI-6130, which demonstrated
potency in preclinical studies. PSI-6130 is a pyrimidine nucleoside analog
inhibitor of HCV RNA polymerase, an enzyme that is necessary for hepatitis
C viral replication. Results from an oral single ascending dose study in 24
healthy male volunteers showed that PSI-6130 was generally well tolerated
with no serious adverse events in doses up to 3000 mg.
R7128 Phase 1 Study Overview
The Phase I clinical trial is a multiple center, observer-blinded,
randomized and placebo-controlled study to investigate the
pharmacokinetics, pharmacodynamics, safety, tolerability and food effect of
R7128 in healthy volunteers and in patients chronically infected with HCV
genotype 1. This Phase 1 study is comprised of two parts:
Part 1 is a single ascending dose study conducted in 38 healthy
volunteers. The primary objective of Part 1 is to assess the safety,
tolerability and pharmacokinetics of R7128 following single ascending doses
under fasting conditions. The secondary objective of Part 1 is to explore
the effect of food on the pharmacokinetics of R7128.
Preliminary data from the single ascending dose portion of the study
indicate:
-- All doses of R7128 studied were generally well-tolerated.
-- All patients completed the study with no gastrointestinal adverse
events or serious adverse events reported during the study.
-- No hematological or laboratory abnormalities of clinical significance
were noted.
Part 2 is a multiple ascending dose study being conducted in up to 40
patients chronically infected with HCV genotype 1 who have previously
failed interferon therapy. The primary objective of Part 2 is to assess the
safety, tolerability and pharmacokinetics of R7128 after once-daily or
twice-daily dosing for 14 days. The secondary objective is to assess
antiviral efficacy by measuring the decrease in HCV RNA.
About Pharmasset
Pharmasset is a clinical-stage pharmaceutical company committed to
discovering, developing and commercializing novel drugs to treat viral
infections. Pharmasset's primary focus is on the development of oral
therapeutics for the treatment of hepatitis B virus (HBV), hepatitis C
virus (HCV) and human immunodeficiency virus (HIV).
Pharmasset is currently developing three product candidates: Clevudine
for the treatment of chronic HBV infection, which is expected to enter US,
European and South American Phase 3 registration clinical trials and is
already approved for HBV in Korea and marketed by Bukwang Pharmaceuticals
under the brand name Levovir; R7128, an oral treatment for HCV, in a Phase
1 clinical trial through a strategic collaboration with Roche; and Racivir
for the treatment of HIV in combination with other approved HIV drugs,
which has completed a Phase 2 clinical trial.
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