Safety, Tolerability, and Antiviral Activity of 24 or 48 Weeks of GS-9190 in Combination With Peginterferon Alfa 2a and Ribavirin for the Treatment of Genotype-1 Chronic HCV Infection

The safety, tolerability and antiviral efficacy GS-9190, administered orally twice daily at 40 mg, will be compared to placebo when used in combination with peginterferon alfa 2a (PEG) and ribavirin (RIBA) in treatment-naïve subjects chronically infected with HCV genotype 1 infection. Two-hundred forty-eight (248) subjects will be randomized (ratio: 1:2:1) to one of three treatment arms:

Arm 1: PEG/RIBA + placebo BID for 48 weeks + 24 weeks treatment-free follow-up (n = 62)

Arm 2: PEG/RIBA + GS 9190 40 mg BID for 48 weeks + 24 weeks treatment-free follow-up (n = 124)

Arm 3: PEG/RIBA + GS 9190 40 mg BID for 48 weeks + 24 weeks treatment-free follow-up. However, subjects who achieve RVR (HCV RNA undetectable at Week 4) and maintain that response through Week 24 will stop all study drugs at Week 24 and be followed for an additional 48 weeks (n = 62).

Randomization will be stratified by plasma HCV RNA level (< or ≥ 400,000 IU/mL) at screening and race (of African descent or other).

In order to ensure adequate representation of subjects with genotypes 1a and 1b in this trial, enrollment for either genotype will be capped at 120 subjects. Once 120 subjects of either genotype (e.g., genotype 1a) have been randomized, subsequent enrollment will only be allowed for subjects with the other genotype (e.g., genotype 1b).

The duration of double-blind treatment is 48 weeks plus 24 weeks of treatment-free follow-up; however subjects in Arm 3 will stop all medication at Week 24 if they have achieved an RVR (defined by undetectable HCV RNA following 4 weeks on therapy) and have maintained that response thereafter. Subjects will only learn that they have been randomized to Arm 3 if, at Week 24, having achieved criteria for stopping therapy, they are instructed to stop. All other subjects will remain blinded to their treatment status throughout the course of the study.

The standard of care treatment stopping criterion used in clinical practice when treating HCV with PEG/RIBA, failure to achieve EVR, will be utilized in this trial. Additionally, subjects with detectable plasma HCV RNA at Week 24 will discontinue all study medications no later than the Week 28 visit and will be followed off-treatment for 24 weeks.