AIM We evaluated the safety and efficacy of the hepatitis C virus (HCV) NS3/4A A protease inhibitor faldaprevir plus pegylated interferon α-2b and ribavirin (PegIFNα-2b/RBV) in Japanese patients with HCV genotype-1 infection. METHODS Treatment-naive patients were randomized (1:1) to faldaprevir 120 mg q.d. for 12 or 24 weeks (response-guided therapy [RGT], n = 44), or faldaprevir 240 mg q.d. for 12 weeks (n = 43), each combined with PegIFNα-2b/RBV for 24 or 48 weeks (RGT). Response-guided therapy was based on early treatment success (HCV RNA