This is a Phase 2, randomized, open-label exploratory study that will examine the antiviral efficacy, safety, and tolerability of Response guided treatment (RGT) with GS-5885 + GS-9451 + PEG/RBV (6 or 12 weeks), or Peginterferon Alfa 2a (PEG)/Ribavirin (RBV)alone (24 weeks) in treatment naïve subjects with chronic Hep C (HCV) infection with genotype (GT) 1 and IL28B CC genotype.

Inclusion Criteria:

• Males and females 18-70 years of age
• Chronic HCV infection
• Subjects must have liver biopsy results (≤ 3 years prior to screening) indicating the absence of cirrhosis. Alternatively a non-invasive alternative to liver biopsy (such as FibroTest, FibroScan, or Acoustic Radiation Force Impulse imaging) within 6 months of Screening in countries where allowed
• Monoinfection with HCV genotype 1a or 1b
• HCV RNA > 10^4 IU/mL at Screening
• IL28B CC genotype
• HCV treatment naïve
• Candidate for PEG/RBV therapy
• Body mass index (BMI) between 18 and 36 kg/m2
• Creatinine clearance >= 50 mL/min
• Agree to use two forms of highly effective contraception methods for the duration of the study and for 7 months after the last dose study medication. Females of childbearing potential must have negative pregnancy test at Screening and Baseline

Exclusion Criteria:

• Exceed defined thresholds for key laboratory parameters at Screening
• Diagnosis of autoimmune disease, decompensated liver disease, poorly controlled diabetes mellitus, significant psychiatric illness, severe chronic obstructive pulmonary disease (COPD), HIV, hepatitis B virus (HBV), hepatocellular carcinoma or other malignancy (with exception of certain skin cancers), hemoglobinopathy, retinal disease, or are immunosuppressed
• Subjects with current use of amphetamines, cocaine, opiates (e.g., morphine, heroin), or ongoing alcohol abuse are excluded. Subjects on stable methadone maintenance treatment for at least 6 months prior to Screening may be included into the study
• Use of prohibited concomitant medications two weeks prior to baseline through the end of treatment