Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA) today announced results from the SAPPHIRE-II study, the second 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 of 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-II study used this 3D regimen plus ribavirin. Results from the 394-patient SAPPHIRE-II trial demonstrated a sustained virologic response at 12 weeks post-treatment (SVR 12) of 96 percent in chronically infected GT1 HCV treatment experienced adult patients who had previously failed pegylated interferon and ribavirin treatment. Approximately 49 percent of these patients were prior null responders, namely patients defined as not achieving a significant reduction in the HCV virus during their prior treatment. The majority of patients were GT1a, considered the more difficult-to-treat subtype, and the SVR 12 rates of GT1a and GT1b were 96 percent and 97 percent, respectively. These results were based on an intent-to-treat analysis and were achieved after 12 weeks of treatment. Virologic relapse or breakthrough was noted in 2 percent of patients receiving the 3D regimen plus ribavirin. The treatment regimen was well tolerated, with 1 percent of patients discontinuing treatment due to adverse events. “The high SVR rates in this SAPPHIRE-II trial and the previously reported SAPPHIRE-I trial further validate this 3D regimen plus ribavirin for both treatment-naive and treatment-experienced patients,” stated Jay R. Luly, Ph.D., President and Chief Executive Officer. “We look forward to the remaining phase 3 studies reading out using the same 3D regimen with and without ribavirin, as well as in the treatment of HCV patients with cirrhosis.” About Study M13-098 (SAPPHIRE-II) Following SAPPHIRE-I, SAPPHIRE-II is the second placebo-controlled trial and the second of six phase 3 trials supporting AbbVie’s investigational 3D regimen for the treatment of GT1 hepatitis C patients. AbbVie will disclose detailed SAPPHIRE-II results at future scientific congresses and in publications.