A Study Evaluating the Safety, Tolerability, Pharmacokinetics and Antiviral Activity of GS-6620 in Treatment Naïve Subjects With Chronic Hepatitis C Virus Infection

Inclusion Criteria: * Adult subjects (18-60 years of age or up to 64 years of age with approval) * Documented chronic HCV infection to be of at least 6 months duration and plasma HCV RNA ≥ 5 log10 IU/mL at screening. * HCV treatment naïve * Estimated creatinine clearance ≥ 80 mL/min, * QTcF interval ≤ 450 msec, QRS duration \< 100 msec, PR interval \< 220 msec, * Body mass index (BMI) of 19.0 to 34.0 kg/m2, inclusive. * Eligible subjects must also be HCV treatment-naïve. Exclusion Criteria: * Subjects with prior documentation of cirrhosis, excessive current alcohol intake, any evidence of hepatocellular carcinoma (i.e., α-fetoprotein \> 50 ng/mL or by any other standard of care measure) * Urine drug screen positive for illicit/illegal drugs * ALT and AST levels \> 5 times the upper limit of the normal range (ULN) * Direct bilirubin \> ULN, clinical or other laboratory evidence of hepatic decompensation (i.e., platelets \< 100,000/mm3, prothrombin time ≥ 1.5 × ULN and albumin \< 3.5 g/dL) are not eligible for study participation. * Subjects with an absolute neutrophil count (ANC) \< 1,000 cells/mm3 (\< 750 cells/mm3 for black or African-American subjects), hemoglobin (Hb) \< 11 g/dL, * Coinfected with hepatitis B virus (HBV), human immunodeficiency virus (HIV), or another HCV genotype (other than type 1 for Cohorts 1-5 and type 2 or 3 for Cohort 6) are not eligible for study participation. * Evidence of hepatocellular carcinoma * Any sign of decompensated liver disease, including prothrombin time ≥ 1.5 X ULN, platelets \< 100,000/mm3 or albumin \< 3.5 g/dL at screening OR current or prior history of clinical hepatic decompensation (e.g., ascites, jaundice, encephalopathy or variceal hemorrhage) * History of clinically-significant illness or any other major medical disorder that may interfere with subject treatment, assessment or compliance with the protocol * History of a primary gastrointestinal disorder that could interfere with the absorption of the study drug or that could interfere with normal gastrointestinal anatomy or motility