Study to Evaluate Safety, Tolerability, Pharmacokinetics, and Antiviral Activity of Voxilaprevir in Adults With Chronic Hepatitis C Virus Infection

Phase 1b, Randomized, Double-Blind, Multiple-Dose Ranging Study Evaluating the Safety, Tolerability, Pharmacokinetics, and Antiviral Activity of GS-9857 in Subjects With Chronic Hepatitis C Virus Infection

The primary objective of the study is to evaluate the safety and tolerability of voxilaprevir (formerly GS-9857) alone or with sofosbuvir (SOF)/velpatasvir (VEL) fixed dose combination (FDC) and antiviral activity of voxilaprevir in adults with genotype 1, 2, 3, 4 hepatitis C virus (HCV) infection. All participants will be monitored for up to 48 weeks after the last dose.

Key Inclusion Criteria:

• Chronic genotype 1-4 HCV infection
• For Cohorts 1-9, HCV RNA ≥ 100,000 IU/mL at screening (no HCV RNA restriction for Cohort 10)
• Screening laboratory values within defined thresholds
• Use of two effective contraception methods if female of childbearing potential or sexually active male

Key Exclusion Criteria:

• Pregnant or nursing female or male with pregnant female partner
• Presence of cirrhosis
• Prior exposure to approved or experimental HCV Protease Inhibitors
• Co-infection with HIV or hepatitis B virus (HBV)
• Current or prior history of clinical hepatic decompensation
• Chronic use of systemic immunosuppressive agents
• History of clinically significant illness or any other medical disorder that may interfere with participant's treatment, assessment or compliance with the protocol

Note: Other protocol defined Inclusion/Exclusion criteria may apply.