Grazoprevir (GZR) is a second-generation hepatitis C virus NS3/4A protease inhibitor. The aim of this study was to evaluate GZR plus ribavirin (RBV) in patients with HCV GT1 infection. Noncirrhotic, IL28B CC patients with HCV genotype 1 infection were randomized to GZR 100 mg once daily and RBV for 12 or 24 weeks. Patients in the 12-week arm with detectable HCV RNA at treatment week 4 (TW4) had treatment extended to 24 weeks (response-guided therapy, RGT). The primary endpoint was sustained virologic response (SVR12) at follow-up week 12 (HCV RNA <25 IU/mL) in the per-protocol (PP) population (excluding patients with important protocol deviations). Twenty-six patients were randomized and 22 were included in the PP population. SVR12 was 58.3% (7 of 12) and 90% (9 of 10) in the RGT and 24-week arms, respectively. Seven PP patients had virologic failure, including one patient in the 24-week arm who relapsed after follow-up week 12. All three breakthrough patients had wild-type (WT) virus at baseline and developed breakthrough at TW6 or TW12 with Y56H, A156T and D168A/N mutations. Of the five relapse patients, four had WT at baseline (at relapse three had WT and one had V55A and D168A), and one had S122A/T at baseline and S122T at relapse. There were no serious adverse events (AEs), discontinuations due to AEs or grade 3/4 elevations in total and/or direct bilirubin. Grazoprevir plus RBV was associated with a rapid and sustained suppression of HCV RNA. These results support further evaluation of grazoprevir-based regimens (NCT01716156; protocol P039).
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