This multi-center, fixed-sequence, open-label, multiple-dose, 2-period study will evaluate the safety, tolerability and pharmacokinetics of setrobuvir alone or in combination with ritonavir-boosted danoprevir in subjects with mild hepatic impairment compared to healthy controls. All subjects will receive multiple doses of setrobuvir orally for 10 days in Period 1 and multiple doses of setrobuvir plus ritonavir-boosted danoprevir orally for 10 days in Period 2, with a washout phase of at least 9 days between treatments.

Inclusion Criteria:

• Male and female adults, 18-65 years of age, inclusive
• Weight >/= 45.0 kg
• Body mass index (BMI) 18.0 - 35.0 kg/m2, inclusive
• Females of childbearing potential and males and their female partners of childbearing potential must agree to use two forms of non-hormonal contraception as defined by protocol
• Subjects with a history of substance abuse may be enrolled provided they have not abused drugs or alcohol for at least 6 months
• Healthy subjects only:

Medical history without major recent or ongoing pathology Laboratory values at screening and Day -1 within the normal range or showing no clinically relevant deviations

• Subjects with hepatic impairment only:

Stable mild liver disease (Child-Pugh A) of cryptogenic, post-hepatic, hepatitis B/C, or alcoholic origin Stable hepatic impairment defined as no clinically significant change in disease status within the last 30 days Must be on stable dose of medication and/or treatment regimen at least 2 weeks before dosing of study medication

Exclusion Criteria:

• Pregnant or lactating women or males with female partners who are pregnant or lactating
• Active infection or febrile illness \