Kayoko Naiki

A Novel Simple Assay System to Quantify the Percent HCV-RNA Levels of NS5A Y93H Mutant Strains and Y93 Wild-Type Strains Relative to the Total HCV-RNA Levels to Determine the Indication for Antiviral Therapy with NS5A Inhibitors

Aim Oral 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. Methods Primer 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. Results Both 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%. Conclusion A 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.

Development of rare resistance-associated variants that are extremely tolerant against NS5A inhibitors during daclatasvir/asunaprevir therapy by a two-hit mechanism

The virologic characteristics of resistance‐associated variants (RAVs) developing in patients receiving dual oral therapy with daclatasvir/asunaprevir, including those with previous triple therapy with simeprevir, were evaluated.

Development of rare RAVs that are extremely tolerant against NS5A inhibitors during daclatasvir/asunaprevir therapy Via a Two-Hit mechanism.

The virologic characteristics of resistance‐associated variants (RAVs) developing in patients receiving dual oral therapy with daclatasvir/asunaprevir, including those with previous triple therapy with simeprevir, were evaluated.

“Reversi‐type virologic failure” involved in the development of non‐structural protein 5A resistance‐associated variants (RAVs) in patients with genotype 1b hepatitis C carrying no signature RAVs at baseline

The therapeutic efficacy of daclatasvir/asunaprevir was inferior in patients with non‐structural protein 5A (NS5A)‐R30Q mutant hepatitis C virus strains at baseline, compared with those with wild‐type strains, even though the half maximal effective concentration of NS5A inhibitors was lower in mutant strains than in wild‐type strains. In these patients, R30Q and Y93H mutant strains, which are highly resistant to NS5A inhibitors, emerged at virologic failure. The mechanisms involved in such virologic failure were examined.

“Reversi-Type Virologic Failure” Involved in the Development of NS5A-RAVs in Patients with Genotype 1b HCV Carrying No Signature RAVs at Baseline

The therapeutic efficacy of daclatasvir/asunaprevir was inferior in patients with non‐structural protein 5A (NS5A)‐R30Q mutant hepatitis C virus strains at baseline, compared with those with wild‐type strains, even though the half maximal effective concentration of NS5A inhibitors was lower in mutant strains than in wild‐type strains. In these patients, R30Q and Y93H mutant strains, which are highly resistant to NS5A inhibitors, emerged at virologic failure. The mechanisms involved in such virologic failure were examined.

Novel hepatitis B virus strain developing due to recombination between genotypes H and B strains isolated from a Japanese patient

In Japan, genotypes B and C are the predominant genotypes isolated from patients with chronic hepatitis B, while genotype A predominates in patients with acute hepatitis B. Globalization, however, appears to have changed the distribution of the hepatitis B virus (HBV) genotypes. Thus, the viral characteristics of HBV genotypes other than genotypes A, B and C were examined.

Retreatment with sofosbuvir/ledipasvir with or without lead-in interferon-β injections in patients infected with genotype 1b hepatitis C virus after unsuccessful daclatasvir/asunaprevir therapy

To improve the therapeutic efficacy of sofosbuvir/ledipasvir (SOF/LDV) for the retreatment of patients after daclatasvir/asunaprevir (DCV/ASV), a customized therapy with or without lead‐in interferon (IFN)‐β injections was formulated according to the types of resistance‐associated substitutions (RAS) in the non‐structural protein (NS)5A region of genotype 1b hepatitis C virus (HCV).

Significance of NS5B Substitutions in Genotype 1b Hepatitis C Virus Evaluated by Bioinformatics Analysis

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.

Serum asunaprevir concentrations showing correlation with the extent of liver fibrosis as a factor inducing liver injuries in patients with genotype-1b hepatitis C virus receiving daclatasvir plus asunaprevir therapy

Aims Liver injury can occur during antiviral therapies with direct-acting antivirals (DAAs), potentially necessitating discontinuation of the therapies, with consequent worsening of the sustained viral response (SVR) rates, in patients with hepatitis C virus (HCV). To clarify the mechanisms involved in serum transaminase level elevation, we performed a retrospective evaluation of the serum concentrations of daclatasvir and asunaprevir, both classified as DAAs, in patients receiving treatment with a combination of the two drugs. Methods Subjects were 278 Japanese patients with genotype-1b HCV who received daclatasvir plus asunaprevir therapy for more than 4 weeks. Serum concentrations of both the DAAs were measured at 4 weeks after the initiation of therapy. Result Liver injuries including serum AST and/or ALT level elevation to 150 U/L or over were found in 34 patients (12.2%). Multivariate logistic regression analysis identified serum asunaprevir concentrations as being significantly associated with developing liver injury, with an odds ratio of 1.046 (95% confidence interval 1.011–1.082, p<0.05). Serum asunaprevir concentrations showed correlation with the extent of liver fibrosis, estimated by peripheral platelets counts and serum albumin levels and baseline and FIB4 index and serum Mac-2 binding protein glycosylation isomer (M2BPGi) levels at 4 weeks of the therapy; the concentrations were significantly higher among patients showing 3.0 or more of M2BPGi levels than among those with the levels less than 3.0; on the other hand, no such correlation/difference was found in serum daclatasvir concentrations. Conclusion High serum concentrations of serum asunaprevir, which were associated with the extent of liver fibrosis, appear to provoke the occurrence of liver injury in patients with genotype-1b HCV receiving combined daclatasvir plus asunaprevir therapy.

A Case of Chronic Hepatitis Caused by Hepatitis C Virus Exhibiting a Discrepancy Between Serogroup and Genotype Because of Inter-Genotypic 2b/1b Recombination - A Pitfall in Antiviral Therapy with Direct-Acting Antivirals -

A 40‐year‐old male patient with virologic relapse after daclatasvir plus asunaprevir therapy for a serogroup 1 hepatitis C virus (HCV) infection visited our hospital for retreatment. Virologic examinations revealed that a genotype 2b HCV strain carrying both NS3‐S122N / D168A and NA5A‐R30Q / L31M / Q54H / Y93H mutations had relapsed. The patient received sofosbuvir plus ribavirin therapy, but virologic relapse occurred once again. Sequencing of the HCV genome clarified an intergenotypic recombination of 2b and 1b with an estimated crossover point between nucleotides 3114 and 3115, corresponding to the N‐terminal end of the NS3 region (DDBJ/EMBL/GenBank databases accession no. LC273304). The NS5B‐S282T mutation was not detected in the HCV strain, and resistance‐association substitutions in the NS3 and NS5A regions were similar to those at baseline. Direct sequencing of the core and NS4A regions corresponding to the targeting sites of genotyping and serogrouping, respectively, is useful to determine the combination of direct‐acting antivirals when a discrepancy is observed between the serogroup and genotype of HCV strains.