A Study of the Combination Regimen Grazoprevir (MK-5172) and Elbasvir (MK-8742) ± Ribavirin in Participants With Chronic Hepatitis C (MK-5172-035)

This is a study of the safety and efficacy of grazoprevir (MK-5172) in combination with elbasvir (MK-8742) ± ribavirin (RBV). The primary efficacy endpoint will be Sustained Virologic Response 12 weeks after the end of all study therapy (SVR12) in each of the treatment arms.

Part A is being done in treatment-naïve (TN), genotype 1 (GT1), interferon eligible, non-cirrhotic (N-C) participants with chronic hepatitis C (CHC). Participants will be assigned randomly to 1 of 2 treatment arms in which they will receive grazoprevir 100 mg once daily (QD) + elbasvir 20 mg or 50 mg QD and twice daily (BID) RBV, or to a treatment arm in which they will receive grazoprevir 100 mg QD + elbasvir 50 mg QD without RBV. Treatment will last 12 weeks. In Part B, participants with hepatitis C virus (HCV) GT1 and HCV ribonucleic acid (RNA) levels of ≥10,000 IU/mL will be randomly assigned to a study arm, based on absence or presence of cirrhosis (C), whether they are TN or had poor response to previous antiviral therapy (null responders \[NR\]), or whether co-infected with human immunodeficiency virus (HIV); these participants will receive open-label grazoprevir (100 mg) in combination with elbasvir (50 mg) ± RBV. Treatment will last 8 to 18 weeks dependent on arm assignment. In Part C, TN, N-C participants with HCV GT1b and HCV RNA levels of ≥10,000 IU/mL will be randomly assigned to receive open-label grazoprevir (100 mg) in combination with elbasvir (50 mg) ± RBV. Treatment will last 8 weeks. In Part D, TN N-C participants with HCV GT3 and HCV RNA levels of ≥10,000 IU/mL will be randomly assigned to receive open-label grazoprevir (100 mg) in combination with elbasvir (50 mg) + RBV for 12 or 18 weeks.