Sofosbuvir/Velpatasvir Fixed-Dose Combination in Adults With Chronic HCV Infection

Key Inclusion Criteria: * Willing and able to provide written informed consent * Chronic HCV infection (≥ 6 months) documented by prior medical history or liver biopsy * Was administered placebo to match SOF/VEL in Gilead study GS-US-342-1138 * HCV RNA ≥ 10\^4 IU/mL at screening * Classification as treatment naive or treatment experienced * Males and females of childbearing potential who engage in heterosexual intercourse must agree to use protocol specified method(s) of contraception Key Exclusion Criteria: * Current or prior history of clinically-significant illness (other than HCV) or any other major medical disorder that may interfere with treatment, assessment, or compliance with the protocol; individuals currently under evaluation for a potentially clinically-significant illness (other than HCV) are also excluded. * Screening electrocardiogram (ECG) with clinically significant abnormalities * Laboratory results outside of acceptable ranges at screening * Prior exposure to SOF or other nucleotide analogue HCV NS5B inhibitor or any HCV NS5A inhibitor * Infection with hepatitis B virus (HBV) or human immunodeficiency virus (HIV) Note: Other protocol defined Inclusion/Exclusion criteria may apply.