HCV resistance-associated substitutions following direct-acting antiviral therapy failure - Real-life data from Poland.

Background: This study analysed the NS3 and NS5A mutation frequencies, persistence and drug susceptibility in a cohort of real-life patients, with failed hepatitis C virus (HCV) therapy following directly acting antiviral (DAA) treatment.

Methods: NS3/NS5A Sanger sequences from 105 patients infected with HCV genotype (G) 1a (6,5.7%), G1b (94,89.5%), G3a (4,3.8%), and G4 (1,1.0%) post DAA treatment failure were analysed. NS3 and NS5A resistance-associated substitutions (RASs) were identified using the geno2pheno algorithm and associated with clinical variables. Time trends were examined using logistic regression.

Results: NS5A RAS were found in 87.9% of sequences derived from patients exposed to this class of agents, whereas NS3 RAS was found in 59.1% of HCV protease-exposed subjects. The frequency of the NS3 RAS increased with fibrosis stage, from 40.0% among F0/F1 individuals to 81.8% among patients with liver cirrhosis (F4, p = 0.094). NS5A mutation frequencies were 7.6% for 28A/V/M, 10.6% for 30 K/Q/R, 42.4% for 31I/F/M/V, and 75.8% for 93H. For NS3, the most common RASs were 56F-23.7%, 168A/E/I/Y/T/V-14.0%, and 117H-5.4%. Susceptibility to glecaprevir/pibrentasvir, velpatasvir/voxlaprevir, and elbasvir/grazoprevir was retained in 92.9%, 43.4%, and, 25.3% of patients, respectively. The frequency of NS3 RAS decreased with time elapsed from failure to sampling (p = 0.034 for trend). NS5A RAS frequency remained stable over the 24-months.

Conclusions: Following DAA treatment failure, NS5A and NS3 RASs were common with increasing frequency among patients with advanced liver disease. In most cases, despite the presence of RASs, susceptibility to DAA combinations with higher genetic barrier was retained.