Sovaprevir (formerly ACH-1625) is an oral, once-daily, small molecule inhibitor of HCV protease being developed by Achillion Pharmaceuticals for the treatment of Hepatitis C. ACH-1625 is a linear peptidomimetic inhibitor that non-covalently binds to HCV NS3 protease with high potency and specificity. Short-term monotherapy of HCV genotype-1 infection with ACH-1625 was found to be safe and resulted in ≥3.3 log(10) IU/ml mean viral load reduction. Sovaprevir was developed as a therapy for patients with chronic HCV. Approximately 550 patients already have been treated with the drug in two phase 2 studies with 12-week treatment programs. One study included treatment with sovaprevir combined with pegylated interferon and ribavirin, and the other monitored the use of sovaprevir in combination with ACH-3102, Achillions second-generation NS5A inhibitor. In the second study, all of the patients with HCV genotype 1b achieved sustained virologic response.