Efficacy of 12 or 18weeks of elbasvir plus grazoprevir with ribavirin in treatment-naive, noncirrhotic HCV genotype 3-infected patients

Elbasvir (EBR; HCV NS5A inhibitor) and grazoprevir (GZR; HCV NS3/4A protease inhibitor) are approved as a fixed-dose combination to treat patients chronically infected with HCV genotypes 1 and 4. During the development programme and supported by in vitro potency, the efficacy of EBR+GZR was assessed in HCV GT3-infected patients. This study's aim was to determine the efficacy and tolerability of 12 or 18weeks of EBR+GZR with ribavirin (RBV) in treatment-naive, noncirrhotic HCV GT3-infected patients. Randomized patients received open-label EBR (50mg once daily) + GZR (100mg once daily) + RBV. The primary efficacy objective was to evaluate the sustained virologic response rates 12weeks after the end of all study therapy (SVR12). SVR12 rates (95% confidence interval) were 45.0% (23.1, 68.5) and 57.1% (34.0, 78.2) after treatment with EBR+GZR+RBV for 12weeks or 18weeks, respectively. On-treatment virologic failure was observed in 41% (17 of 41) of patients. At virologic failure, resistance-associated substitutions (RASs) with a >five-fold shift in potency occurred in the NS3 region in six (35%) patients and in the NS5A region in 16 (94%) patients. The most common RAS at virologic failure was Y93H in NS5A which was identified in 13 of 17 (76%) patients. The efficacy of EBR+GZR+RBV was suboptimal in HCV GT3-infected patients due to a high rate of on-treatment virologic failure and treatment-emergent RASs which demonstrates an inadequate barrier to the development of GT3 resistance. However, rapid viral clearance demonstrated the antiviral activity of EBR+GZR+RBV in GT3-infected patients.clinicaltrials.gov: NCT01717326.