Pharmasset, Inc announced the complete enrolment by Roche of the 12 week RG7128 phase-2b study (PROPEL) of approximately 400 treatment-naive patients with hepatitis C virus (HCV) genotypes 1 and 4. The study remains blinded to Roche and Pharmasset.

Roche has initiated a 24 week phase-2b study with RG7128 in combination with pegylated interferon and ribavirin in treatment-naïve patients with HCV genotypes 1 and 4 in order to evaluate the safety and efficacy of RG7128 in combination with standard of care for longer durations. The data from this study could provide the flexibility for combining RG7128 with direct acting antivirals currently in development with varying durations of therapy. This study is currently enrolling at sites in the US and Canada and is expected to complete enrolment in the second quarter.

In addition, Roche is planning to initiate a phase-2b study of RG7128 in combination with pegylated interferon and ribavirin in patients with HCV genotypes 2 and 3 later in 2010. RG7128 has previously demonstrated antiviral activity with a 90 per cent RVR in HCV genotypes 2 and 3 prior non-responders in a 28 day clinical study.

Roche has also announced that it will not conduct the previously planned 28 day INFORM-2 study, designed to evaluate the combination of RG7128 with RG7227, InterMune's HCV protease inhibitor, with and without pegylated interferon and ribavirin. Roche has decided instead to conduct longer duration studies, including the INFORM-3 clinical study of RG7128 and RG7227 with and without pegylated interferon and ribavirin. INFORM-3 will commence after Roche and InterMune identify the optimal dose of ritonavir-boosted RG7227 from ongoing studies. Roche is continuing to conduct dose ranging safety and efficacy studies of RG7227, and has announced a consequent delay of the INFORM-3 clinical study.

Modifications to the INFORM programme will have no impact on the primary registration pathway for RG7128. In addition, Roche has indicated that it is evaluating the potential of combining RG7128 with non-protease complementary compounds.

"We are pleased that our partner Roche has completed the enrollment of the initial phase-2b study of RG7128, and we look forward to the announcement of data from the PROPEL study," said M. Michelle Berrey, chief medical officer of Pharmasset. "We believe that the initiation of additional phase-2b studies indicates Roche's continued commitment to RG7128. We are also encouraged by Roche's willingness to consider alternatives for potential combination with RG7128 in interferon-sparing combination studies."

Pharmasset is a clinical-stage pharmaceutical company committed to discovering, developing, and commercializing novel drugs to treat viral infections.