The antiviral activity of all-oral, ribavirin-free, direct-acting antiviral regimens requires evaluation in patients with chronic hepatitis C virus (HCV) infection. OBJECTIVE To determine the rates of sustained virologic response (SVR) in patients receiving the 3-drug combination of daclatasvir (a pan-genotypic NS5A inhibitor), asunaprevir (an NS3 protease inhibitor), and beclabuvir (a nonnucleoside NS5B inhibitor). DESIGN, SETTING, AND PARTICIPANTS This was an open-label, single-group, uncontrolled international study (UNITY-1) conducted at 66 sites in the United States, Canada, France, and Australia between December 2013 and August 2014. Patients without cirrhosis who were either treatment-naive (n = 312) or treatment-experienced (n = 103) and had chronic HCV genotype 1 infection were included. INTERVENTIONS Patients received a twice-daily fixed-dose combination of daclatasvir, 30 mg; asunaprevir, 200 mg; and beclabuvir, 75 mg. MAIN OUTCOMES AND MEASURES The primary study outcome was SVR12 (HCV-RNA <25 IU/mL at posttreatment week 12) in patients naive to treatment. A key secondary outcome was SVR12 in the treatment-experienced cohort. RESULTS Baseline characteristics were comparable between the treatment-naive and treatment-experienced cohorts. Patients were 58% male, 26% had IL28B (rs12979860) CC genotype, 73% were infected with genotype 1a, and 27% were infected with genotype 1b. Overall, SVR12 was observed in 379 of 415 patients (91.3%; 95% CI, 88.6%-94.0%): 287 of 312 treatment-naive patients (92.0%; 95% CI, 89.0%-95.0%) and 92 of 103 treatment-experienced patients (89.3%; 95% CI, 83.4%-95.3%). Virologic failure occurred in 34 patients (8%) overall. One patient died at posttreatment week 3; this was not considered related to study medication. There were 7 serious adverse events, all considered unrelated to study treatment, and 3 adverse events (<1%) leading to treatment discontinuation, including 2 grade 4 alanine aminotransferase elevations. The most common adverse events (in Ն10% of patients) were headache, fatigue, diarrhea, and nausea. CONCLUSIONS AND RELEVANCE In this open-label, nonrandomized, uncontrolled study, a high rate of SVR12 was achieved in treatment-naive and treatment-experienced noncirrhotic patients with chronic HCV genotype 1 infection who received 12 weeks of treatment with the oral fixed-dose regimen of daclatasvir, asunaprevir, and beclabuvir.