Prevalence of baseline NS3 resistance-associated substitutions (RASs) on treatment with protease inhibitors in patients infected with HCV genotype 1.

•Overall RAS prevalence in this study was 13.7% (10/73). RAS prevalence for HCV subtype 1b was 17.4% (4/23) while for HCV subtype 1a was 12% (6/50).•Primary mutations V36M/L and R155K were observed only in HCV subtype 1a, whereas T54S and Q80K were identified only in HCV subtype 1b. RAS V36M, which is related to reduction of susceptibility to second-generation PIs, was the most frequent in the study (6.9%; 5/73).•Our results indicated that Brazilian isolates of HCV present a distinct pattern of RAS depending on the infecting viral subtype. In contrast to data from other countries, RAS Q80K prevalence in Brazil is low in HCV subtype 1a.•Our observations suggested that naturally occurring NS3 substitutions did not seem to negatively impact treatment outcome and the use of simeprevir, paritaprevir and grazopevir has a high probability of being effective for treating HCV chronic carriers infected with subtypes 1a and 1b.