Phase 2, randomized, open-label clinical trials of the efficacy and safety of grazoprevir and MK-3682 (ns5b polymerase inhibitor) with either elbasvir or MK-8408 (NS5A inhibitor) in patients with chronic HCV GT1, 2 or 3 infection (part a of c-crest-1 & 2).

PURPOSE/BACKGROUND: To evaluate the safety and efficacy of all-oral therapy for HCV using combinations of 3 direct-acting antiviral drugs: grazoprevir, an NS3/4A protease inhibitor; MK-3682, an NS5B polymerase inhibitor, and either elbasvir or MK-8408, which are NS5A inhibitors. METHOD(S): In Part A of 2 ongoing randomized, dose-ranging, parallel-group, multicenter, open-label Phase 2 trials, 93 GT1 (46 GT1a, 47 GT1b), 61 GT2, and 86 GT3-infected treatment-naive, non-cirrhotic patients with chronic HCV infection were dosed once-daily for 8 weeks duration with one of 4 regimens including grazoprevir (100 mg), MK-3682 (300 mg or 450 mg), and either elbasvir (50 mg) or MK-8408 (60 mg). RESULT(S): GT1: Across treatment arms, 45/46 (98%) GT1a and 46/47 (98%) GT1b patients achieved sustained virologic response 12 weeks after end of study therapy (SVR12). In the 2 relapsers, population sequencing did not detect NS3, NS5B, or NS5A resistance associated variants (RAVs) conferring >=5-fold potency shifts at baseline or following relapse. GT2: The grazoprevir/ MK-3682 (450 mg)/MK-8408 regimen was highly effective, with SVR12 among 15/16 (94%) of GT2-infected patients, but regimens containing the 300 mg dose of MK-3682 and/or elbasvir resulted in lower efficacy (SVR12 in 29/45 (64%) GT2 patients; 60-71% across the 3 arms). Relapses were more common among patients who harbored an L31M/I NS5A variant at baseline. No treatment-emergent RAVs were observed. GT3: Across arms, SVR12 was achieved among 78/86 (91%) of GT3-infected patients; response was comparable across arms (86-95%). Eight GT3 patients relapsed. SVR12 was lower among GT3-infected patients who harbored an NS5A A30K, L31M, or Y93H RAV at baseline compared with patients without these RAVs at baseline (5/11 [45%] vs 72/74 [97%], respectively). Two of 8 GT3 relapsers acquired NS5A Y93H. All 240 patients completed the full 8 weeks of dosing. All regimens were generally well tolerated, and no cardiac or renal safety signals