Pharmasset Announces Results of a 28-day Phase 2a Study with PSI-7977 for the Treatment of Chronic Hepatitis C Infection
94% or 93% of patients achieved undetectable HCV RNA levels following 28 days of treatment with PSI-7977 200mg or 400mg QD, respectively, in combination with Pegasys® and Copegus® Safety and tolerability across all doses were comparable to placebo administered with Pegasys® and Copegus® Conference call scheduled for Tuesday, May 4, 2010 at 8:00 AM ET (US)
PRINCETON, N.J., May 4 /PRNewswire-FirstCall/ -- Pharmasset,
Inc. (NASDAQ: VRUS) announced today the efficacy and
preliminary safety results from its 28 day phase 2a study with
PSI-7977 dosed once daily (QD) in combination with Pegasys®
(peginterferon alfa-2a) and Copegus® (ribavirin), the current
standard of care (SOC) in patients with hepatitis C virus (HCV)
genotype 1 who were naïve to antiviral therapy. PSI-7977 is
one of Pharmasset's investigational nucleotide analogs.
In this study, PSI-7977 demonstrated potent short term antiviral
activity and was generally safe and well tolerated. All patients
receiving active PSI-7977 demonstrated continuous and substantial
declines in HCV RNA with no viral breakthrough during 28 days of
therapy at any dose.
"We are encouraged by the emerging clinical profile of PSI-7977,
which was well-tolerated by the patients in this study, and which
confirms the consistently high RVR rates of these nucleoside and
nucleotide analogs," stated M. Michelle Berrey, M.D., MPH, Chief
Medical Officer of Pharmasset. "Our platform technology continues
to generate nucleoside/tide analogs with a high degree of efficacy,
high barrier to resistance, and a safety profile that we believe
differentiates them from other classes of direct acting antivirals
(DAA). We plan to quickly progress PSI-7977 into phase 2b studies
starting in the fourth quarter 2010, to generate longer term
efficacy and safety data."
Intent-to-Treat (ITT) 28-day RVR data from the trial are
summarized as follows:
Mean decrease in HCV RNA Percentage of Patients
Study Arm N (log10 IU/mL) at Day 28 with HCV RNA below LOD
(<15 iu>
Potent and consistent antiviral activity was demonstrated in
this study following 28 days of treatment with PSI-7977 in
combination with SOC. Patients receiving PSI-7977 100mg QD with SOC
achieved a mean 5.3 log10 IU/mL decrease in HCV RNA and 88% (14 of
16) had HCV RNA levels below the limit of detection (<15 iu>
Preliminary Safety Summary
Preliminary safety and tolerability for the 28 day treatment
period were similar for PSI-7977 with SOC compared to placebo with
SOC. There were no serious adverse events reported during the 28
day treatment period, and no adverse events leading to treatment
discontinuation. All adverse events reported were of mild to
moderate intensity, of which the majority were mild. A similar
proportion of patients in each cohort reported adverse events, with
the most common adverse events reported as fatigue, nausea, and
arthralgias. The frequency and severity of these adverse events, as
well as general body system observations, were similar to clinical
experience with the standard of care. There were no dose-related
changes in safety laboratory assessments, vital signs or ECGs. A
dose-dependent decrease in serum ALT was observed coincident with
HCV RNA decline.
Overall, there were no drug-related discontinuations, no serious
adverse events, and no dose-related trends in adverse events or
laboratory abnormalities as compared to placebo with standard of
care.
Full analyses of safety, efficacy, and resistance will be
presented at a scientific meeting later in 2010.
About Hepatitis C
Hepatitis C is a blood-borne infectious disease of the liver and
is a leading cause of chronic liver disease and liver transplants.
The WHO estimates that nearly 180 million people worldwide, or
approximately 3% of the world's population, are infected with
hepatitis C virus (HCV). The CDC has reported that almost three
million people in the United States are chronically infected with
HCV.
Conference Call
Pharmasset will host a conference call at 8:00 AM ET (US) on
Tuesday, May 4, 2010 to discuss these PSI-7977 phase 2a study
results.
Dial-in Information:
US/Canada Toll-Free callers: +1 (877) 771-7028
US/Canada Toll or International Toll callers: +1 (973) 200-3092
Live audio of the conference call will be simultaneously
broadcast over the internet via a webcast. To access the live
webcast, log on to the "Events & Presentations" section of the
Investor Center on Pharmasset's corporate website at http://investor.pharmasset.com/events.cfm
.
Please connect to the company's website at least ten minutes
prior to the start of the presentation to ensure adequate time for
a reliable connection and any software download that may be
necessary to listen to the webcast. The archived replay of the
webcast will be available on the Pharmasset website for two weeks
following the conference call.
About the Phase 2a trial
The Phase 2a trial enrolled 63 chronic hepatitis C virus
infected patients who have not been treated previously. The primary
goal of the study was to determine the safety and tolerability of
PSI-7977 in combination with SOC. The primary efficacy endpoint of
the trial was the proportion of patients who achieve an RVR,
defined as HCV RNA below the limit of detection (<15 iu>
-- 16 subjects taking PSI-7977 100mg QD in combination with SOC for four
weeks, followed by 44 weeks of SOC
-- 18 subjects taking PSI-7977 200mg QD in combination with SOC for four
weeks, followed by 44 weeks of SOC
-- 15 subjects taking PSI-7977 400mg QD in combination with SOC for four
weeks, followed by 44 weeks of SOC
-- A control arm of 14 subjects taking placebo with SOC for four weeks,
followed by 44 weeks of SOC
About Pharmasset
Pharmasset is a clinical-stage pharmaceutical company committed
to discovering, developing, and commercializing novel drugs to
treat viral infections. Pharmasset's is focusing primarily on the
development of oral therapeutics for the treatment of hepatitis C
virus (HCV) and, secondarily, on the development of Racivir(TM) for
the treatment of human immunodeficiency virus (HIV). Our research
and development efforts focus on nucleoside/tide analogs, a class
of compounds which act as alternative substrates for the viral
polymerase, thus inhibiting viral replication. We currently have
four clinical-stage product candidates. RG7128, a cytosine
nucleoside analog for chronic HCV infection, is in two Phase 2b
clinical trials in combination with Pegasys® plus Copegus®
and is also in the INFORM studies, the first series of studies
designed to assess the potential of combinations of small molecules
without pegylated interferon and ribavirin to treat chronic HCV.
These clinical studies are being conducted through a strategic
collaboration with Roche. Our other, unpartnered, clinical stage
candidates for the treatment of HCV include PSI-7977, a uracil
nucleotide analog that is in a Phase 2a trial, and PSI-938, a
guanine nucleotide analog that is in a Phase 1 trial. We also have
in our pipeline an additional guanine nucleotide analog, PSI-661,
in advanced preclinical development for the treatment of HCV.
Racivir, for the treatment of HIV, has completed a Phase 2 clinical
trial.
Pegasys® and Copegus® are registered trademarks of Roche.
Contact
Richard E. T. Smith, Ph.D.
VP, Investor Relations and Corporate Communications
Office: +1 (609) 613-4181
Forward-Looking Statements
Pharmasset "Safe Harbor" Statement under the Private Securities
Litigation Reform Act of 1995: Statements in this press release
regarding our business that are not historical facts are
"forward-looking statements" that involve risks, uncertainties and
other important factors, including, without limitation, the risk
that adverse events could cause the cessation or delay of any of
the ongoing or planned clinical trials and/or our development of
our product candidates, the risk that the results of previously
conducted studies involving our product candidates will not be
repeated or observed in ongoing or future studies involving our
product candidates, the risk that our collaboration with Roche will
not continue or will not be successful, and the risk that any one
or more of our product candidates will not be successfully
developed and commercialized. For a discussion of these and other
risks, uncertainties and important factors, any of which could
cause our actual results to differ from those contained in the
forward-looking statements, see the section entitled "Rick Factors"
in our Annual Report on Form 10-K for the fiscal year ended
September 30, 2009 and our Quarterly Report on Form 10-Q for the
period ended December 31, 2009 filed with the Securities and
Exchange Commission and discussions of potential risks,
uncertainties and other important factors in our subsequent filings
with the Securities and Exchange Commission.
Source: Pharmasset, Inc.
CONTACT: Richard E. T. Smith, Ph.D., VP, Investor Relations
and
Corporate Communications, Pharmasset, Inc. Office:
+1-609-613-4181
Web Site: http://www.pharmasset.com/
Posted: May 2010
