Open-Labeled Study of PSI-7977 and RBV With and Without PEG-IFN in Treatment-Naïve Patients With HCV GT2 or GT3

This study is to assess the safety and tolerability of sofosbuvir (SOF) 400 mg with and without ribavirin (RBV) and/or with and without pegylated interferon alfa-2a (PEG) in subjects with genotype 1, 2 or 3 hepatitis C (HCV) infection.

Part 1: HCV genotype 2 or 3: participants will receive SOF 400 mg once daily with weight-based RBV for 12 weeks. Participants will be randomized in equal proportions to: no PEG (Arm 1), PEG for 4 weeks (Arm 2), PEG for 8 weeks (Arm 3), or PEG for 12 weeks (Arm 4).

Part 2: HCV genotype 2 or 3: participants will receive SOF 400 mg once daily (monotherapy) for 12 weeks (Arm 5), or SOF 400 mg once daily with PEG and weight-based RBV for 8 weeks (Arm 6); HCV genotype 1: null responders (did not respond to their prior treatment) will receive SOF 400 mg once daily with weight-based RBV for 12 weeks (Arm 7).

Part 3: HCV genotype 1 treatment-naive (Arm 8) or HCV genotype 2 or 3 treatment-experienced participants (Arm 9) will receive SOF 400 mg once daily in combination with weight-based RBV for 12 weeks.

Part 4: HCV genotype 2 or 3 treatment naive participants will receive SOF 400 mg once daily with weight-based RBV for 8 weeks (Arm 10) or SOF 400 mg once daily and 800 mg RBV for 12 weeks (Arm 11). HCV genotype 1 null responders will receive SOF 400 mg once daily, ledipasvir (LDV), and weight based RBV for 12 weeks (Arm 12). HCV genotype-1 treatment naive participants will receive SOF 400 mg once daily with weight-based RBV and LDV for 12 weeks (Arm 13).

Part 5: HCV genotype 1 null responders will receive SOF 400 mg once daily with GS-9669 500 mg once daily and weight-based RBV for 12 weeks (Arm 14). HCV genotype-1 treatment naive participants receive SOF 400 mg once daily with GS-9669 500 mg once daily and weight-based RBV for 12 weeks (Arm 15).

Part 6: HCV genotype 1 null responders with Stage F4 fibrosis will receive LDV/SOF FDC for 12 weeks (Arm 16) or LDV/SOF FDC with weight-based RBV for 12 weeks (Arm 17). HCV genotype 2 or 3 treatment-naive participants will receive LDV/SOF FDC for 12 weeks (Arm 18). HCV genotype 2 or 3 treatment-experienced participants will receive LDV/SOF FDC for 12 weeks (Arm 19). HCV genotype 1 hemophiliacs will receive LDV/SOF FDC with weight-based RBV for 12 weeks (Arm 20). HCV genotype 1 treatment-naive participants will receive LDV/SOF FDC with weight-based RBV for 6 weeks (Arm 21). HCV genotype 1 treatment-naive participants will receive LDV/SOF FDC for 6 weeks (Arm 22).

Eligibility Criteria:
Inclusion Criteria:

* Chronic Genotype 2 or 3 HCV-infection or Genotype 1, serum HCV RNA ≥ 50,000 IU/mL
* Not co-infected with HIV
* Use of highly effective contraception methods if female of childbearing potential or sexually active male

Exclusion Criteria:

* History of any other clinically significant chronic liver disease
* Pregnant or nursing female or male with pregnant female partner
* History of significant drug allergy to nucleoside/nucleotide analogs.
* Participation in a clinical study within 3 months prior to first dose
* Positive result for significant drug use at Screening