[These data are essentially the same as what VRUS reported at EASL three weeks ago (#msg-49048250). In the dataset reported at EASL, the RVR rate was 80%, 100%, 91%, and 25% for the 100mg, 200mg, 400mg, and control arms, respectively; in the updated dataset, which includes a few more patients, the RVR rate was 88%, 94%, 93%, and 21% in the 100mg, 200mg, 400mg, and control arms, respectively. In other words, PSI-7977 appears to have adequate antiviral efficacy in combination with interferon and ribavirin; the safety profile to date is fine, so now it’s on to phase-2b, where the first SVR data will be generated. (The detailed dataset from the phase-2a study will be reported at a medical conference, presumably AASLD in November.)]
• 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:
Study Arm N Mean decrease in HCV RNA (log10 IU/mL) at Day 28 Percentage of Patients with HCV RNA below LOD (<15 IU/mL) at Day 28 100mg PSI-7977 QD + SOC 16 -5.3 88% (14/16) 200mg PSI-7977 QD + SOC 18 -5.1 94% (17/18) 400mg PSI-7977 QD + SOC 15 -5.3 93% (14/15) Placebo + SOC 14 -2.8 21% (3/14)
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/mL), or a Rapid Virologic Response (RVR). Following 28 days with PSI-7977 200mg QD with SOC, patients achieved a mean 5.1 log10 IU/mL decrease in HCV RNA and 94% (17 of 18) achieved an RVR. Following 28 days with PSI-7977 400mg QD with SOC, patients achieved a mean 5.3 log10 IU/mL decrease in HCV RNA and 93% (14 of 15) achieved an RVR. In the control group, following 28 days of treatment with placebo and SOC, patients achieved a mean 2.8 log10 IU/mL decrease in HCV RNA and 21% (3 of 14) achieved an RVR. The baseline HCV RNA for all patients enrolled in the study was approximately 6.5 log10 IU/mL, and was similar across all treatment arms. Patients were stratified by IL28B status to ensure balance across cohorts and no patient was excluded based on their status.
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[presumably at AASLD in November].
…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 .
…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/ml) as measured by Roche HCV TaqMan assay 28 days after the initiation of treatment. Patients were randomized to receive one of four treatments:
•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‹
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