Pharmasset Inc. (fka VRUS)

[surf1944]

Pharmasset Announces Interim Data from an Ongoing 28-day Phase 2a Study with PSI-7977 for the Treatment of Chronic Hepatitis C Infection

Press Release Source: Pharmasset, Inc. On Thursday April 15, 2010, 4:41 am EDT
PRINCETON, N.J., April 15 /PRNewswire-FirstCall/ -- Pharmasset, Inc. (Nasdaq:VRUS - News) announced today interim efficacy and safety results from its ongoing 28-day phase 2a study with PSI-7977 dosed once daily in combination with Pegasys® (peginterferon alfa 2a) and Copegus® (ribavirin) in patients with hepatitis C virus (HCV) genotype 1 who have not been treated previously. PSI-7977 is Pharmasset's nucleotide analog for the treatment of HCV. The Company announced the interim results in conjunction with the European Association for the Study of Liver Congress that commenced in Vienna, Austria on April 14, 2010.

Interim Safety and Efficacy Data

The study is fully enrolled with 63 patients. Thirty-eight patients have completed 28 days of therapy, out of which, eight of ten patients receiving 100mg QD, nine of nine patients at 200mg QD doses, and ten of eleven patients receiving the 400 mg QD dose, have achieved a Rapid Virologic Response (RVR), defined as an undetectable HCV viral load (<15 IU/ml) as measured by Roche HCV TaqMan assay 28 days after the initiation of treatment.


Interim 28-day RVR efficacy data from the trial are summarized as follows:


Study Arm
Patients with Undetectable Viral Load (<15 IU/ml) at Day 28

100mg PSI-7977 QD + Pegasys + Copegus
8 of 10

200mg PSI-7977 QD + Pegasys + Copegus
9 of 9

400mg PSI-7977 QD + Pegasys + Copegus
10 of 11

Pegasys + Copegus
2 of 8


"To date, this drug candidate appears safe and well tolerated" stated M. Michelle Berrey, M.D., MPH, Chief Medical Officer of Pharmasset. This study is ongoing and Pharmasset anticipates reporting the complete data set for all dosing cohorts through day 28 later this quarter.

About the Phase 2a trial

The Phase 2a trial is completely enrolled with 63 chronic hepatitis C infected patients who have not been treated previously. The primary goal of the study is to determine the safety and tolerability of PSI-7977 in combination with pegylated interferon and ribavirin. The primary efficacy endpoint of the trial will be the proportion of patients who achieve an RVR. Patients will continue to be followed through a Sustained Virologic Response (SVR) endpoint. Patients were randomized to receive one of four treatments:


•16 subjects taking PSI-7977 100mg QD in combination with Pegasys® and Copegus® for four weeks, followed by 44 weeks of Pegasys® and Copegus®
•18 subjects taking PSI-7977 200mg QD in combination with Pegasys® and Copegus® for four weeks, followed by 44 weeks of Pegasys® and Copegus®
•15 subjects taking PSI-7977 400mg QD in combination with Pegasys® and Copegus® for four weeks, followed by 44 weeks of Pegasys® and Copegus®
•A control arm of 14 subjects taking only Pegasys® and Copegus®

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