Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA) today announced results from the SAPPHIRE-I study, one of six phase 3 registrational studies being conducted by AbbVie for the treatment of hepatitis C virus (HCV) genotype 1 (GT1) infection, using a regimen containing Enanta’s lead protease inhibitor ABT-450. ABT-450 is part AbbVie’s investigational three direct-acting antiviral (3D) regimen, consisting of boosted protease inhibitor ABT-450/ritonavir, NS5A inhibitor ABT-267, and non-nucleoside polymerase inhibitor ABT-333. The SAPPHIRE-I study used this 3D regimen plus ribavirin. Results from the 631 patient SAPPHIRE-I trial demonstrated a sustained virologic response at 12 weeks post-treatment (SVR 12) of 96 percent in treatment-naïve adult patients chronically infected with GT1 HCV. The majority of patients were GT1a, considered the more difficult-to-treat subtype, and the SVR 12 rates of GT1a and GT1b were 95 percent and 98 percent, respectively. These results were based on an intent-to-treat analysis and were achieved after 12 weeks of treatment. The rate of virologic relapse or breakthrough was low, occurring in 1.7 percent of patients receiving the 3D regimen. The treatment regimen was well tolerated, with an equal percentage of patients in the active and placebo arms (0.6 percent) discontinuing treatment due to adverse events. “Achieving high SVR rates in this trial is an important step toward our goal of providing a well-tolerated and highly effective all-oral treatment option that doesn’t currently exist for this important patient population,” stated Jay R. Luly, Ph.D., President and Chief Executive Officer. About Study M11-646 (SAPPHIRE-I) SAPPHIRE-I is a global, multi-center, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of 12 weeks of treatment with ABT-333 (250mg), ribavirin (weight-based), both dosed twice daily, and the fixed-dose combination of ABT-450/ritonavir (150/100mg) co-formulated with ABT-267 (25mg) and dosed once daily in non-cirrhotic, GT1a and GT1b HCV-infected, treatment-naïve adult patients. The study population consisted of 631 GT1 treatment-naïve patients with no evidence of liver cirrhosis. 473 patients were randomized to the 3D regimen plus ribavirin for 12 weeks, and 158 patients were randomized to placebo for the initial 12 weeks. Patients initially randomized to placebo for the first 12 weeks then received open-label treatment with the 3D regimen plus ribavirin for 12 weeks.