21 Two clinical paradigms have emerged to enhance the genetic barrier of interferon-free regimens. First, treatment with Selleck BMN-673 a combination of 2 direct-acting antivirals, including a nucleotide polymerase inhibitor with a high barrier to viral resistance such as sofosbuvir, combined with a direct-acting antiviral with a different mechanism of action with high potency such as the NS5A inhibitor daclatasvir or the NS3 protease inhibitor simeprevir, can achieve sustained response without viral breakthrough.22 and 23 An alternative strategy involves combining 2 or more non-nucleotide direct-acting antivirals with or without ribavirin to improve the genetic barrier

to resistance.24, 25, 26 and 27 An interferon-free combination of 3 direct-acting antivirals (an NS5B non-nucleoside inhibitor, a ritonavir-boosted protease inhibitor, and an NS5A inhibitor) plus ribavirin showed high SVR rates, but treatment success was reduced when ribavirin or any single direct-acting antiviral

was omitted.27 In this study, combining 3 direct-acting antivirals without interferon or ribavirin showed a high SVR rate after 12 weeks of Stem Cells inhibitor treatment in HCV GT 1-infected, treatment-naive patients. This all-oral, interferon-free, ribavirin-free treatment consisting of daclatasvir, asunaprevir, and BMS-791325 75 or 150 mg twice daily achieved up to 94% SVR12 after 24 or 12 weeks of treatment. Sustained response was achieved in both HCV GT 1a-infected and HCV GT 1b-infected patients, including patients with reduced interferon responsiveness predicted by IL28B non-CC genotypes. No viral breakthrough or relapse was observed

in patients treated with the 75 mg twice-daily dose of BMS-791325. There was 100% concordance between SVR4 and subsequent SVR time points in all patients with available data. An important aspect to this study is that SVR was achieved without Phosphoprotein phosphatase inclusion of ribavirin. Ribavirin contributes to anemia and it is teratogenic; thus, effective treatments without ribavirin are desirable. This interferon- and ribavirin-free regimen did not alter hemoglobin levels in a clinically meaningfully manner as evidenced by no grade 1 or higher hemoglobin reductions and no adverse events of anemia. The mechanism of action of ribavirin is not clear, and its contribution to clinical efficacy varies by regimen. Ribavirin clearly improves SVR rates in interferon-based therapies, including telaprevir-based regimens.28 Among interferon-free regimens, the benefit of ribavirin remains unclear. The combination of the ritonavir-boosted protease inhibitor ABT-450, the NS5B non-nucleoside inhibitor ABT-333, and the NS5A inhibitor ABT-267 with or without ribavirin showed lower SVR rates without ribavirin.27 However, the combination of daclatasvir and sofosbuvir did not require ribavirin to achieve high SVR rates in patients with unfavorable characteristics, including HCV genotypes 1a and 3, and host IL28B non-CC genotypes.