In part A of the study we randomly assigned HCV-mono-infected patients to receive 12 weeks of grazoprevir ( 100 mg ) plus elbasvir ( 20 mg or 50 mg ) with or without ribavirin ( arms A1-3 ) ; in part B we assigned HCV-mono-infected patients to 8 or 12 weeks of grazoprevir ( 100 mg ) plus elbasvir ( 50 mg ) with or without ribavirin ( arms B1-3 ) and HIV/HCV co-infected patients to 12 weeks of therapy with or without ribavirin .