Resistance associated mutations in HCV patients failing DAA treatment

Currently, treatment of chronic hepatitis C is based on a combination of direct-acting antiviral agents (DAAs) which achieve HCV clearance in more than 95% of patients. Despite this high rate of cure, treatment failures can occur in about 3-5% of treated patients. Resistance associated substitutions (RAS) are commonly detected after virological failure, although their role in real-life DAA failures is still debated. This study aimed to evaluate in real-life DAA-failing patients the prevalence of clinically relevant RASs for the different DAA classes and to identify possible predictors. Fifty consecutive HCV-infected patients who experienced a virological failure to a DAA-containing regimen were included in the study. Direct sequencing of HCV regions involved in DAA resistance (NS3, NS5A and NS5B) was performed with Sanger-based homemade protocols. The presence of mutations in the NS3 and NS5A regions was statistically associated with regimens containing protease inhibitors (p<0.0032) and NS5A inhibitors (p<0.0006), respectively. On the contrary, for the NS5B region, the known mutations associated with the NS5B RNA polymerase inhibitors were detected in treated HCV patients, although there was no statistical significance (p>0.5). A significant correlation was found between the presence of RASs and advanced fibrosis/cirrhosis, but not with age, sex and viral load. Our study demonstrates a high frequency of RASs in patients with DAA failure, thus highlighting the usefulness of genotypic tests in this setting. The identification of RASs may guide the choice of the most appropriate drugs for HCV re-treatment.