Treatment of chronic HCV infection with DAAs in Rio de Janeiro/Brazil: SVR rates and baseline resistance analyses in NS5A and NS5B genes.

The selection of viral strains with resistance-associated substitutions at hepatitis C virus (HCV) NS5A and NS5B genes is considered one of the limiting factors for achieving sustained virologic response (SVR) to combination of direct-acting antivirals daclatasvir (DCV) and sofosbuvir (SOF). Since 2015, this interferon-free regimen has been available in Brazilian clinical routine for treating mono- and HCV/HIV-coinfected patients chronically infected with genotypes 1 and 3. Our aim was to assess SVR rate for Brazilian patients chronically infected with genotypes 1 and 3 after DCV/SOF therapy and the frequency of baseline RASs in HCV NS5A and NS5B genes. Serum samples were collected from 107 monoinfected patients and 25 HCV/HIV co-infected patients before antiviral therapy with DCV/SOF. Genetic diversity of NS5A and NS5B genes was assessed by direct nucleotide sequencing. Overall, SVR rate was 95.4% (126/132), and treatment failure occurred in five monoinfected and one HCV/HIV co-infected patient. NS5A RASs frequency was higher for HCV/HIV patients (28%) than monoinfected patients (16.8%). No difference was evidenced between mono- and HCV/HIV-coinfected groups (15% vs. 16%) regarding NS5B gene. Genotype (GT) 1b strains had significantly more baseline substitutions in NS5A (31.6%) than GT 1a and 3a. At least one primary NS5A RAS described in literature at loci 28, 30, 31 or 93 was identified in HCV GTs 1 strains for both groups. As for NS5B, RASs at positions 159 and 316 was observed only in GT 1b strains. This study highlighted that SVR rate in clinical routine in Brazil was similar to randomized clinical trials (89-98%). Our research provided genetic data about the circulation of resistant variants in Brazil. Despite its presence, most of identified baseline mutations did not negatively impact treatment outcome. Genetic diversity of circulating strains suggested that most of the Brazilian HCV chronic carriers are susceptible to new therapeutic regimens including recently approved DAAs.

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

BACKGROUND AND AIMS: Treatment for hepatitis C has evolved significantly with the licensing of direct-acting antiviral drugs (DAAs). However, one of the limiting factors of the effectiveness of antiviral therapy with protease inhibitors (PIs) is the emergence of resistance caused by point mutations. The aim of this study was to determine the prevalence of resistance-associated substitutions (RASs) in HCV NS3 gene in patients infected with genotype 1 before therapy with simeprevir. METHODS: A total of 73 serum samples from 15 treatment-experienced patients with boceprevir/telaprevir and 58 DAA-naïve patients were collected before therapy with DAAs simeprevir, daclatasvir and/or sofosbuvir. Presence of baseline resistance-associated substitutions (RAS) in the serine protease domain of HCV NS3 was analyzed by nucleotide sequencing followed by amino acid deduction. RESULTS: 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). CONCLUSIONS: 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. This study improves the knowledge of genetic barrier for resistance to PIs involving RASs in chronically infected patients and its possible impact on an unsuccessful treatment outcome, information that might be crucial to upcoming decisions of incorporation of new DAAs in Brazilian guidelines of antiviral therapy against HCV infection.