NS5A-R30Q/H/L and NS5A-Y93H mutations at baseline determined the therapeutic efficacy of dual oral therapy with daclatasvir/asunaprevir, but rare NS5A-RAVs developed frequently in patients with previous simeprevir treatment. Such RAVs may develop in a two-hit manner, with simeprevir altering the quasispecies of HCV strains in the NS5A regions, leading to the emergence of HCV strains with NS5A-P29del and NS5A-P32del during exposure to daclatasvir/asunaprevir.

AimOral treatment with asunaprevir and daclatasvir has been reported to yield a SVR ratio of 80% in patients with genotype 1b HCV infection, however, treatment failure has been reported, especially in patients with HCV strains showing the NS5A-Y93H mutation at baseline. An assay system to detect such strains was established to facilitate selection of appropriate candidates for this antiviral therapy.MethodsPrimer sets and 2 types of cycling probe mixtures were designed, and real-time PCR was performed with HCV-RNA purified from 332 patients with genotype 1b HCV infection, and the results were compared with those obtained by direct sequencing.ResultsBoth the wild-type and mutant strains were quantified, with a threshold of 4.0 Log copies/mL, in 295 of the 332 patients (88.9%), and the percentage of the mutant strains relative to the total HCV-RNA level in the serum was calculated. The percentage was 0% in 237 patients (80.3%) and 100% in 23 patients (7.8%), identical to the results of direct sequencing. Both wild-type and mutant strains were detected in the remaining 35 patients (11.9%), at levels between 1% and 99%, despite the mutant strains having been undetectable by direct sequencing in 11 patients with percentages of these strains of less than 25%.ConclusionA novel assay system to quantify the percent RNA of Y93H mutant strains relative to the total HCV-RNA level was established. This system may be useful to determine the indication for treatment with NA5A inhibitors in patients with HCV.

NS5A-Y93H mutation was associated with sex, serum AFP levels, and IL28B-related gene polymorphisms in patients infected with genotype 1b HCV. The indications for NS5A inhibitor use should be determined based on these factors, since mutant strains seem to be sensitive to interferon.

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Aim: Factors responsible for impaired improvement of liver function despite sustained viral response after direct-acting antiviral agents therapies in cirrhotic patients with hepatitis C virus need to be elucidated.Methods: Liver function and the extent of portosystemic shunting were evaluated for 79 patients with compensated cirrhosis, in whom sustained viral response had been achieved after direct-acting antiviral agents therapies for hepatitis C virus at least 3 years earlier. Conclusions:A large size of portosystemic shunts was found to be a crucial determinant of impaired improvement of liver function, as well as of the development of portal hypertensionrelated events, even after sustained viral response in patients with compensated cirrhosis.

The significance of switching of the nucleos(t)ide analog used to treat patients with hepatitis B virus (HBV) from entecavir (ETV) to tenofovir alafenamide fumarate (TAF) is uncertain. The subjects of this study were 159 patients with HBV who received treatment with ETV followed by TAF. Among these patients, serial changes in the HBV marker levels were monitored in 92 patients in whom the serum HBsAg levels were ≥100 IU/mL during the 48-week period immediately before and after the switching. A questionnaire survey for medication compliance was performed in 127 patients. The serum HBsAg levels (log IU/ mL) decreased by 0.041 during the ETV treatment period and by 0.068 during the TAF administration period. The degree of reduction was higher during the TAF administration period than during the ETV administration period in patients without cirrhosis (P = .030), patients with genotype B HBV (P = .014), and patients with undetectable serum HBcrAg (P = .038). Multivariate analysis revealed the HBV genotype (B vs C; odds ratio, 3.400; P = .025) and serum aspartate aminotransferase level (every 1+; 1.111; P = .015) at the time of switching as factors influencing the treatment efficacy. Thirty-six patients (28%) responded that the number of days that they forgot to take the drug decreased after the drug switching, and 77 patients (61%) reported feeling satisfied with the drug switching.Switching of the nucleos(t)ide analog used from ETV to TAF may be useful in the treatment of patients with HBV infection, as it is associated with both a decrease in the serum HBsAg level and improvement of the medication compliance.

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To evaluate the effects of HCV NS5B amino acid substitutions on treatment outcome in Ledipasvir (LDV)/Sofosbuvir (SOF) for Japanese patients with genotype 1b HCV infection, NS5B sequences were examined in i) seven patients experiencing virologic failure after LDV/SOF in real-world practice, ii) 109 SOF-naïve patients, iii) 165 patients enrolled in Phase-3 LDV/SOF trial. A218S and C316N were detected in all patients with viral relapse; the percentages of these substitutions in SOF-naïve patients were 64.2% and 55.0%, respectively. Genotype 1b HCV strains with NS5B-C316N mutation were located in the leaves different from those in which HCV strains without such substitutions were present on the phylogenetic tree. Structural modeling revealed that amino acid 218 was located on the surface of the NTP tunnel. Free energy analysis based on molecular dynamics simulations demonstrated that the free energy required to pass through the tunnel was larger for triphosphate SOF than for UTP in NS5B polymerase carrying A218S, but not in wild-type. However, no susceptibility change was observed for these substitutions to SOF in replicon assay. Furthermore, the SVR rate was 100% in patients enrolled the Phase-3 trial. In conclusion, NS5B A218S and C316N were detected in all patients who relapsed following LDV/SOF in real-world practice. These substitutions did not impact the overall SVR rate after LDV/SOF, however, further studies are needed to elucidate the impact of these substitutions.