Deep sequencing analysis of variants resistant to the non-structural 5A inhibitor daclatasvir in patients with genotype 1b hepatitis C virus infection

Real-world efficacy and safety of glecaprevir/pibrentasvir in Japanese adolescents with chronic hepatitis C: a prospective multicenter study

BACKGROUND

Part 1 of the DORA study, a 2019 international clinical trial of glecaprevir and pibrentasvir (G/P) treatment in adolescents with chronic hepatitis C virus (HCV) infection, demonstrated high efficacy and safety. However, few reports have considered real-world experience with G/P treatment in adolescents with chronic HCV. The present prospective multicenter study assessed real-world efficacy and safety of G/P treatment in Japanese adolescents with chronic HCV.

METHODS

Subjects between 12 and 17 years old who were treatment-naïve or previously managed with interferon-based regimens were prospectively enrolled and treated with G/P (300 mg/120 mg) once daily for 8 or 12 weeks. The primary efficacy endpoint was sustained virologic response at 12 weeks after treatment completion (SVR12). Adverse effects and laboratory abnormalities were assessed.

RESULTS

Twenty-five Japanese patients (15 female) were enrolled from 13 pediatric centers in Japan. Median age was 13 years (range 12-17). Numbers of patients with genotypes 1b, 2a, 2b, and 2b/1b were 6, 12, 6, and 1, respectively. Twenty-two were treatment-naïve, while three had experienced interferon-based treatments. All patients completed G/P treatment (24 for 8 weeks and 1 for 12). Twenty-four achieved SVR12 (96%). Most adverse events were mild. None were serious. G/P significantly decreased serum alanine aminotransferase, γ-glutamyltransferase, and Wisteria floribunda agglutinin-positive Mac-2-binding protein concentrations. No negative effects on growth or maturation were apparent at 12 weeks.

CONCLUSIONS

Under real-world conditions, G/P treatment of Japanese adolescents with chronic HCV was highly efficacious and well tolerated.

Analysis of direct-acting antiviral-resistant hepatitis C virus haplotype diversity by single-molecule and long-read sequencing

The method of analyzing individual resistant hepatitis C virus (HCV) by a combination of haplotyping and resistance-associated substitution (RAS) has not been fully elucidated because conventional sequencing has only yielded short and fragmented viral genomes. We performed haplotype analysis of HCV mutations in 12 asunaprevir/daclatasvir treatment-failure cases using the Oxford Nanopore sequencer. This enabled single-molecule long-read sequencing using rolling circle amplification (RCA) for correction of the sequencing error. RCA of the circularized reverse-transcription polymerase chain reaction products successfully produced DNA longer than 30 kilobase pairs (kb) containing multiple tandem repeats of a target 3 kb HCV genome. The long-read sequencing of these RCA products could determine the original sequence of the target single molecule as the consensus nucleotide sequence of the tandem repeats and revealed the presence of multiple viral haplotypes with the combination of various mutations in each host. In addition to already known signature RASs, such as NS3-D168 and NS5A-L31/Y93, there were various RASs specific to a different haplotype after treatment failure. The distribution of viral haplotype changed over time; some haplotypes disappeared without acquiring resistant mutations, and other haplotypes, which were not observed before treatment, appeared after treatment. Conclusion: The combination of various mutations other than the known signature RAS was suggested to influence the kinetics of individual HCV quasispecies in the direct-acting antiviral treatment. HCV haplotype dynamic analysis will provide novel information on the role of HCV diversity within the host, which will be useful for elucidating the pathological mechanism of HCV-related diseases.

Effectiveness of Glecaprevir/Pibrentasvir for Hepatitis C: Real-World Experience and Clinical Features of Retreatment Cases

Glecaprevir/pibrentasvir (G/P) are direct-acting antivirals (DAAs) that achieve a high sustained virological response (SVR) rate for hepatitis C virus (HCV) infection. We investigated G/P effectiveness for HCV patients based on real-world experience and the clinical features of retreatment cases. HCV patients (n = 182) were compared for clinical features and outcomes between first treatment (n = 159) and retreatment (n = 23) G/P groups. Overall, 77 patients (42.3%) were male, the median age was 68 years, and 86/66/1/4 cases had genotype 1/2/1 + 2/3, respectively. An SVR was achieved in 97.8% (178/182) of cases by intention-to-treat analysis and 99.4% (178/179) of cases by per-protocol analysis. There were no remarkable differences between the first treatment and retreatment groups for male (42.8% vs. 39.1%, p = 0.70), median age (68 vs. 68 years, p = 0.36), prior hepatocellular carcinoma (5.8% vs. 8.7%, p = 0.59), or the fibrosis markers AST-to-platelet ratio index (APRI) (0.5 vs. 0.5, p = 0.80) and fibrosis-4 (FIB-4) index (2.2 vs. 2.6, p = 0.59). The retreatment group had a significantly more frequent history of interferon treatment (12.3% vs. 52.2%, p < 0.01) and the Y93H mutation (25.0% vs. 64.7%, p = 0.02). The number of retreatment patients who had experienced 3, 2, and 1 DAA treatment failures was 1, 3, and 19, respectively, all of whom ultimately achieved an SVR by G/P treatment. In conclusion, G/P was effective and safe for both HCV first treatment and retreatment cases despite the retreatment group having specific resistance mutations for other prior DAAs. As G/P treatment failure has been reported for P32 deletions, clinicians should consider resistance mutations during DAA selection.

Real-world efficacy and safety of ledipasvir and sofosbuvir in patients with hepatitis C virus genotype 1 infection: a nationwide multicenter study by the Japanese Red Cross Liver Study Group

BACKGROUND

We aimed to describe the real-world efficacy and safety of combination therapy with ledipasvir and sofosbuvir (LDV/SOF) for chronic hepatitis C virus (HCV) genotype 1 (GT1) infection.

METHODS

This retrospective analysis of a prospective, nationwide, multicenter registry included GT1-infected patients treated with LDV/SOF for 12 weeks. We assessed the rate of sustained virological response at 12 weeks post-treatment (SVR12), incidence of adverse events, and serum markers of hepatocellular carcinoma (HCC).

RESULTS

Among the 1461 patients included (mean age, 69 years; 29.5% aged > 75 years; cirrhosis, 23.8%; history of treatment for HCC, 10.9%), the overall SVR12 rate was 98.4% (1438/1461). Factors associated with treatment failure were cirrhosis (odds ratio, 4.19; p = 0.014) and resistance-associated substitutions (RASs) in NS5A at baseline (odds ratio, 7.78; p = 0.0004). The SVR12 rate in patients with cirrhosis and NS5A RASs was 93.0% compared to 100% in patients without cirrhosis or NS5A RASs. In patients with SVR, the levels of alpha-fetoprotein (AFP), AFP-L3, and Mac-2 binding protein glycosylation isomer (M2BPGi) decreased from baseline to end of treatment (from 13.4 ± 37.6 to 6.0 ± 10.6 ng/mL, p < 0.0001; from 2.2 ± 4.9 to 1.5 ± 6.3%, p < 0.005; and from 3.6 ± 3.7 to 2.0 ± 3.5 cut-off index, p < 0.0001; respectively). Adverse events were rare and not associated with age. No decrease in estimated glomerular filtration rate was observed in patients with baseline chronic kidney disease stage 3.

CONCLUSIONS

LDV/SOF therapy is highly effective and safe in elderly Japanese patients with HCV GT1, even in the presence of cirrhosis or NS5A RASs. Patients with SVR may have a lower risk of HCC.

Real-world efficacy of daclatasvir and asunaprevir with respect to resistance-associated substitutions

AIM

To investigate daclatasvir (DCV) and asunaprevir (ASV) efficacy in hepatitis C (HCV) patients, with respect to resistance-associated substitutions (RASs).

METHODS

A total of 392 HCV-infected patients from multiple centers were included in this study. We evaluated their clinical courses and sustained virologic responses (SVR) according to pretreatment factors (gender, age, history of interferon-based regimens, platelet counts, level of viremia, pretreatment NA5A:L31, and Y93 substitutions). We also analyzed the pretreatment and post-treatment major RASs of NS3:D168, NS5A:L31 and Y93 substitutions using a direct-sequencing method in 17 patients who were unable to achieve SVR at 12 wk after treatment completion (SVR12).

RESULTS

The overall SVR12 rate was 88.3%. Thirty-one patients discontinued treatment before 24 wk because of adverse events, 23 of whom achieved SVR12. There were no significant differences in SVR12 rates with respect to gender, age, history of interferon-based regimens, and platelet counts. The SVR12 rate in patients with viral loads of ≥ 6.0 log IU/mL was significantly lower than those with viral loads of < 6.0 log IU/mL (P < 0.001). The SVR12 rate in patients with Y93 substitution-positive was significantly lower than those with Y93 substitution-negative (P < 0.001). The L31 substitution-positive group showed a lower SVR12 rate than the L31 substitution-negative group, but the difference was not statistically significant. Seventeen patients who did not achieve SVR12 and had available pretreatment and post-treatment sera had additional RASs in NS3:D168, NS5:L31, and Y93 substitution at treatment failure.

CONCLUSION

Combination of DCV and ASV is associated with a high SVR rate. Baseline RASs should be thoroughly assessed to avoid additional RASs after treatment failure.

New resistance-associated substitutions and failure of dual oral therapy with daclatasvir and asunaprevir

BACKGROUND

Daclatasvir (DCV) and asunaprevir (ASV) combination therapy has been primarily used in patients without NS5A L31 or Y93 resistance-associated substitutions (RASs) before treatment. We examined the characteristics of patients without these baseline RASs who did not achieve hepatitis C virus eradication with DCV and ASV combination therapy and identified new baseline NS5A RASs that are closely associated with failure of combination therapy.

METHODS

Three hundred thirty-five patients with hepatitis C virus genotype 1 infection with no NS5A L31, NS5A Y93, and NS3 D168 RASs before DCV and ASV combination therapy and no history of protease inhibitor therapy were enrolled. All RASs were evaluated by direct sequencing.

RESULTS

Sustained virologic response at 12 weeks (SVR12) was achieved in 297 patients (89%). Patients with NS5A Q24, L28, and/or R30 RASs or concomitant NS5A F37 and Q54 RASs had a significantly lower SVR12 rate than patients without these RASs (70% vs 92%, p < 0.001 and 79% vs 92%, p = 0.002 respectively). Multivariate analysis showed that NS5A Q24, L28, and/or R30 RASs and concomitant NS5A F37 and Q54 RASs were significantly associated with virologic failure. The SVR12 rate in patients without NS5A Q24, L28, and/or R30 RASs and concomitant NS5A F37 and Q54 RASs was 96.2% (202/210).

CONCLUSIONS

In patients without NS5A L31 or Y93 RASs, the presence of NS5A Q24, L28, and/or R30 RASs and concomitant NS5A F37 and Q54 RASs at the baseline was associated with failure of DCV and ASV combination therapy. The coexistence of baseline RASs other than NS5A L31 and Y93 may affect the therapeutic effectiveness of DCV and ASV combination therapy.

Association between vitamin D deficiency and pre-existing resistance-associated hepatitis C virus NS5A variants

AIM

Although interferon-free therapy with direct-acting antivirals has developed as a standard of care for chronic hepatitis C, the existence of resistance-associated variants (RAVs) has a negative impact on treatment results. Recently, several studies indicated a relationship between chronic hepatitis C and serum vitamin D levels. However, the relationship between RAVs at the hepatitis C virus non-structure 5A (NS5A) region and serum vitamin D level has not yet been examined.

METHODS

Among patients with genotype 1 chronic hepatitis C who were enrolled in a multicenter cooperative study, our subjects comprised 247 patients in whom it was possible to measure RAVs at the NS5A region. These RAVs were measured using a direct sequencing method.

RESULTS

The median age of patients was 70 years (range, 24-87 years), and the number of female patients was 135 (54.7%). The median serum 25(OH) D3 level was 22 ng/mL (range, 6-64 ng/mL). L31 and Y93 RAVs at the NS5A region were detected in 3.7% (9/247) and 13.4% (33/247) of patients, respectively. Multivariate analysis identified vitamin D deficiency (serum 25(OH) D3 ≤ 20 ng/mL) (P = 5.91 × 10⁻⁵ , odds ratio = 5.015) and elderly age (>70 years) (P = 1.85 × 10^-3 , odds ratio = 3.364) as contributing independent factors associated with the presence of the L31 and/or Y93 RAVs. The Y93H RAV was detected in 25.9% (29/112) of patients with a vitamin D deficiency, and in 8.9% (12/135) of those with a serum 25(OH) D3 level >20 ng/mL (P = 4.90 × 10^-3 ).

CONCLUSION

We showed that RAVs at the NS5A region are associated with vitamin D deficiency and elderly age, which may have a negative influence on innate/adaptive immune responses to hepatitis C virus infection.

Efficacy and safety of daclatasvir plus asunaprevir for Korean patients with HCV genotype Ib infection: a retrospective multi-institutional study

BACKGROUND/AIMS

The combination of daclatasvir (DCV) and asunaprevir (ASV) has demonstrated a high sustained virologic response at 12 weeks (SVR12) and a low rate of adverse events in previous clinical studies. The purpose of this study was to clarify the results of treatment and side effects in Korean patients with chronic hepatitis C virus (HCV) genotype Ib infection.

METHODS

We retrospectively analyzed clinical data from chronic HCV genotype Ib patients treated with DCV+ASV from August 2015 to September 2016 at five hospitals in the Daejeon-Chungcheong area.

RESULTS

A total of 152 patients were examined for resistance associated variants (RAVs). Among them, 15 (9.9%) were positive for Y93 and one (0.7%) was positive for L31. Of 126 patients treated with DCV+ASV, 83 patients completed treatment and 76 patients were included in safety and efficacy analysis. Five (6.6%) were positive for Y93 and 12 (15.8%) exhibited cirrhotic change. DCV+ASV was the first-line treatment for 58 (76.3%) patients. Eleven (14.5%) patients relapsed after previous treatment that included interferon and seven (9.2%) of these patients were found to be intolerant of interferon. Adverse events occurred in 10 (13.2%) patients and two patients stopped the medication because of severe itching and skin rash. SVR12 was 89.5% (68/76) in all patients and 91.5% (65/71) in RAV-negative patients.

CONCLUSIONS

DCV+ASV showed good efficacy in patients with HCV Ib infection in Korea. Close monitoring is needed for severe adverse events and treatment failure, which were uncommon.

Hepatic IFNL4 expression is associated with non-response to interferon-based therapy through the regulation of basal interferon-stimulated gene expression in chronic hepatitis C patients

Single nucleotide polymorphisms (SNPs) within or near interferon lambda 4 (IFNL4) gene located upstream of IFNL3 are associated with response to anti-HCV therapy both in interferon (IFN)-based and IFN-free regimens. IFNL4 encodes IFNλ4, a newly discovered type III IFN, and its expression is controlled by rs368234815-TT/ΔG, which is in strong linkage disequilibrium (LD) with other tag SNPs within or near IFNL4 such as rs12979860 and rs8099917. Intrahepatic expression levels of IFN-stimulated genes (ISGs) affect the responsiveness to IFNα and are also associated with IFNL4 genotype. However, IFNL4 expressions and its role in intrinsic antiviral innate immunity remain unclear. This study evaluated the effect of IFNL4 on intrahepatic ISG expression and investigated its relationship with treatment outcomes in liver samples obtained from 49 chronic hepatitis C patients treated with pegylated (PEG)-IFN/ribavirin therapy. IFNL4 mRNA was detected in 11 of 22 patients with IFNL4-unfavorable SNPs but not in patients with favorable genotypes. IFNL4 expression was associated with non-response to PEG-IFN/ribavirin therapy. Intrahepatic expression of antiviral ISGs (ISG15 and MX1) was significantly higher in IFNL4-unfavorable patients with detectable IFNL4 mRNA than in patients with undetectable IFNL4 mRNA, whereas the expression of suppressive ISGs (RNF125, SOCS1, SOCS3, and RNF11) was lower in patients with detectable IFNL4 mRNA. In summary, intrahepatic expression of IFNL4 was associated with increased antiviral ISG expression and decreased suppressive ISG expression at baseline, resulting in poor responsiveness to IFNα-based therapy in HCV infection.

Prevalence and characteristics of naturally occurring sofosbuvir resistance-associated variants in patients with hepatitis C virus genotype 1b infection

AIM

Sofosbuvir (SOF), a nucleotide analog pro-drug, targets hepatitis C virus (HCV) NS5B polymerase and shows potential for treating HCV infection, given its high efficacy and good barrier to resistance. However, in addition to the rare resistant-associated variant (RAV) of non-structural protein NS5B S282T, several new potential RAVs of SOF have been reported, especially related to HCV genotype 1b. However, the prevalence and characteristics of these RAVs have not been clarified.

METHODS

We analyzed the prevalence of variants in the NS3/NS5A/NS5B regions in 96 patients treated with simeprevir (SMV) combination therapy, and the prevalence of RAVs in patients showing treatment failure was determined by direct- or deep-sequencing methods. Associations between these potential RAVs and clinical factors were also analyzed.

RESULTS

Prevalence of NS5B RAV C316N was high (46.9%, 45/96), whereas that of NS5B L159F was relatively low (1.04%, 1/96); however, deep sequencing showed that 30.0% of patients with C316N also had NS5B RAV L159F. Additionally, there was no significant relationship between the existence of potential NS5B and NS5A or NS3 RAVs. However, the presence of NS5B C316N was significantly associated with an HCV core amino acid 91 substitution. No significant difference was detected between each RAV and sustained virological response in simeprevir combination therapy.

CONCLUSION

We provide clear evidence of the high prevalence of two potential naturally occurring NS5B RAVs (C316N and L159F) in Japan. It may be important to pay particular attention to these new potential RAVs, especially when using SOF-based therapy in patients with RAVs due to previous direct-acting antiviral therapy failure.

Complex Pattern of Resistance-Associated Substitutions of Hepatitis C Virus after Daclatasvir/Asunaprevir Treatment Failure

Backgrounds & Aims

We aimed to clarify the characteristics of resistance-associated substitutions (RASs) after treatment failure with NS5A inhibitor, daclatasvir (DCV) in combination with NS3/4A inhibitor, asunaprevir (ASV), in patients with chronic hepatitis C virus genotype 1b infection.

Methods

This is a nationwide multicenter study conducted by the Japanese Red Cross Liver Study Group. The sera were obtained from 68 patients with virological failure after 24 weeks of DCV/ASV treatment. RASs in NS5A and NS3 were determined by population sequencing.

Results

The frequency of signature RASs at position D168 of NS3 was 68%, and at positions L31 and Y93 of NS5A was 79 and 76%, respectively. The frequency of dual signature RASs in NS5A (L31-RAS and Y93-RAS) was 63%. RASs at L28, R30, P32, Q54, P58, and A92 in addition to dual signature RAS were detected in 5, 5, 1, 22, 2, and 0 patients, respectively. In total, triple, quadruple, and quintuple RASs in combination with dual signature RAS were detected in 35, 10, and 1.5% patients, respectively. These RASs were detected in patients without baseline RASs or who prematurely discontinued therapy. Co-existence of D168 RAS in NS3 and L31 and/or Y93 RAS in NS5A was observed in 62% of patients.

Conclusion

Treatment-emergent RASs after failure with DCV/ASV combination therapy are highly complex in more than 50% of the patients. The identification of complex RAS patterns, which may indicate high levels of resistance to NS5A inhibitors, highlights the need for RAS sequencing when considering re-treatment with regimens including NS5A inhibitors.

Effects of Resistance-Associated NS5A Mutations in Hepatitis C Virus on Viral Production and Susceptibility to Antiviral Reagents

Direct-acting antivirals (DAAs) for hepatitis C virus (HCV) have potent anti-HCV effects but may provoke resistance-associated variants (RAVs). In this study, we assessed the characteristics of these RAVs and explored efficacious anti-HCV reagents using recombinant HCV with NS5A from a genotype 1b strain. We replaced the NS5A of JFH1 with that of Con1 (JFH1/5ACon1) and introduced known NS5A inhibitor resistance mutations (L31M, L31V, L31I and Y93H) individually or in combination. Susceptibilities against anti-HCV reagents were also investigated. RAVs with Y93H exhibited high extracellular core antigen levels and infectivity titers. Variants with any single mutation showed mild to moderate resistance against NS5A inhibitors, whereas variants with double mutations at both L31 and Y93 showed severe resistance. The variants with mutations exhibited similar levels of susceptibility to interferon (IFN)-α, IFN-λ1, IFN-λ3 and Ribavirin. Variants with the Y93H mutation were more sensitive to protease inhibitors compared with JFH1/5ACon1. In conclusion, the in vitro analysis indicated that the Y93H mutation enhanced infectious virus production, suggesting advantages in the propagation of RAVs with this mutation. However, these RAVs were susceptible to protease inhibitors. Thus, a therapeutic regimen that includes these reagents is a promising means to eradicate these RAVs.

Successful achievement of sustained virological response to triple combination therapy containing simeprevir in two patients with chronic hepatitis C who had failed asunaprevir:Daclatasvir combination therapy

Patients 1 and 2 were treatment-naive women who had genotype 1b chronic hepatitis C. Both had IL-28B genotype TT, and amino acid substitutions of core 70 and 91 were both wild type. Search for the presence of resistance-associated variants (RAV) in non-structural (NS)3 and NS5A regions confirmed wild-type D168 and L31, along with Y93H, in both patients. These patients participated in a Japanese phase III clinical study of asunaprevir and daclatasvir at the age of 52 and 67 years, respectively, and were treated with the combination regimen for 24 weeks. However, both experienced post-treatment relapse, and then treated with triple combination therapy with simeprevir, pegylated interferon (IFN) and ribavirin at the age of 53 and 68 years, respectively, and achieved sustained virological response. A search for RAV prior to simeprevir treatment identified multiple resistance including D168E, Y93H and L31V in both patients. It has been demonstrated that, in many cases, a treatment failure with a combination of asunaprevir and daclatasvir results in acquisition of RAV in NS3 and NS5A regions and that drug-resistant mutants, particularly those in the NS5A region, survive for a long time. In these cases, direct-acting antivirals targeted towards the NS5A region may have a limited efficacy. The present case report is based on an idea that a regimen containing IFN with simeprevir could be a therapeutic option particularly for those who are likely to be highly sensitive and tolerable to IFN.

Impact of resistance-associated variant dominancy on treatment in patients with HCV genotype 1b receiving daclatasvir/asunaprevir

Sustained virological responses (SVR) by daclatasvir (DCV) and asunaprevir (ASV) therapy for genotype 1b hepatitis C virus (HCV) infected patients has been significantly affected by pre-existence of Y93 H resistance-associated variants (RAVs) in the non-structural protein 5A (NS5A) region. The aim of this study was to elucidate the dominancy of naturally occurring RAVs in viral quasispecies on treatment outcomes in patients with HCV. In total, 138 patients were prospectively selected from 152 patients treated with DCV and ASV, where evaluation of treatment outcomes at 12 weeks post-treatment was possible. Pre-treatment RAVs in the non-structural protein 3 and NS5A regions were detected by polymerase chain reaction (PCR)-Invader assays, and the ratio of Y93H RAVs in viral quasispecies was measured by quantitative PCR-Invader assay. Among 25 patients detected the Y93H RAV, the Y93H ratio was 1-25% in 5 patients, 26-75% in 7 patients, and ≥76% in 13 patients. Overall, SVR at 12 weeks after the completion of treatment (SVR12) was 91% (125/138), and those with Y93H ratios of <1%, 1-25%, 26-75%, and ≥76% were 99%, 100%, 71%, and 23%, respectively. Thus, the SVR12 decreased as the HCV Y93H ratio increased (P < 0.0001). The dominancy of pre-treatment RAVs of DCV and ASV affected its treatment outcomes, suggesting that evaluating the dominancy of HCV RAVs could be required for every other direct-acting antiviral agent treatments. J. Med. Virol. 89:99-105, 2017. © 2016 Wiley Periodicals, Inc.

Impact of Pre-existing NS5A-L31 or -Y93H Minor Variants on Response Rates in Patients Infected with HCV Genotype-1b Treated with Daclatasvir/Asunaprevir

INTRODUCTION

The combination of daclatasvir (DCV, pan-genotypic NS5A inhibitor) plus asunaprevir (ASV; NS3 protease inhibitor) is approved in Japan, Korea and other countries for the treatment of chronic hepatitis C virus (HCV) genotype (GT)-1. A high (~90 to 100%) sustained virologic response (SVR) with DCV/ASV therapy has been achieved by excluding patients infected with HCV GT-1b with baseline NS5A resistance-associated variants (RAVs) at L31 or Y93H detected by direct sequencing (DS). We set out to determine whether patients with minor variants at NS5A-L31 or -Y93H, detected by next-generation sequencing (NGS), impacted SVR rates with DCV/ASV therapy.

METHODS

Baseline samples from 222 interferon (IFN)-ineligible/intolerant (N = 135) and prior non-responder (N = 87) patients infected with GT-1b who were treated with DCV/ASV for 24 weeks in the Phase 3 clinical study AI447026 were prepared for NGS (Ion-Torrent platform). The prevalence of baseline NS5A RAVs and their impact on SVR when observed at ≥1% by NGS in a patient's virus population were examined. NGS and DS (sensitivity ≥20%) data were compared.

RESULTS

The prevalence of baseline NS5A RAVs at L31 or Y93H was 29% (63/219) and 18% (39/214) by NGS and DS, respectively. SVR24 rates were comparable in patients without observed baseline L31 or Y93H polymorphisms whether assessed by NGS (96%; 148/154) or by the less sensitive DS platform (95%; 164/173).

CONCLUSION

Optimal SVR rates (≥95%) to DCV/ASV treatment were achieved using DS to exclude patients infected with GT-1b with NS5A RAVs at L31 or Y93H representing ≥20% of their virus population. Exclusion by NGS of patients with minor variants in NS5A (<20%) did not enhance SVR rates. These results suggest that the presence of minor variants in NS5A does not appear to impact the overall SVR rate in patients with GT-1b treated with DCV/ASV.

FUNDING

This study was sponsored by Bristol-Myers Squibb.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01497834.

Naturally occurring hepatitis C virus protease inhibitors resistance-associated mutations among chronic hepatitis C genotype 1b patients with or without HIV co-infection

The aim of this study was to measure the frequency of natural mutations in hepatitis C virus (HCV) mono-infected and HIV/HCV co-infected protease inhibitor (PI)-naive patients.

METHODS

Population sequence of the non-structural (NS)3 protease gene was evaluated in 90 HCV mono-infected and 96 HIV/HCV co-infected PI treatment-naive patients. The natural prevalence of PI resistance mutations in both groups was compared.

RESULTS

Complete HCV genotype 1b NS3 sequence information was obtained for 152 (81.72%) samples. Seven sequences (8.33%) of the 84 HCV mono-infected patients and 21 sequences (30.88%) of the 68 HIV/HCV co-infected patients showed amino acid substitutions associated with HCV PI resistance. There was a significant difference in the natural prevalence of PI resistance mutations between these two groups (P = 0.000). The mutations T54S, R117H and N174F were observed in 1.19%, 5.95% and 1.19% of HCV mono-infected patients. The mutations F43S, T54S, Q80K/R, R155K, A156G/V, D168A/E/G and V170A were found in 1.47%, 4.41%, 1.47%/1.47%, 2.94%, 23.53%/1.47%, 1.47%/1.47%/1.47% and 1.47% of HIV/HCV co-infected patients, respectively. In addition, the combination mutations in the NS3 region were detected only in HIV/HCV genotype 1b co-infected patients.

CONCLUSION

Naturally occurring HCV PI resistance mutations existed in HCV mono-infected and HIV/HCV co-infected genotype 1b PI-naive patients. HIV co-infection was associated with a greater frequency of PI resistance mutations. The impact of HIV infection on baseline HCV PI resistance mutations and treatment outcome in chronic hepatitis C (CHC) patients should be further analyzed.

Combination therapy with daclatasvir and asunaprevir for dialysis patients infected with hepatitis C virus

The standard antiviral therapy for dialysis patients infected with hepatitis C virus (HCV) is (pegylated) interferon monotherapy, but its efficacy is insufficient. Oral direct-acting antiviral agents (DAAs) have recently been developed for chronic hepatitis C patients. However, some DAAs have contraindications for chronic renal failure (CRF). Daclatasvir and asunaprevir are metabolized largely in the liver and are not contraindicated in CRF. Combination therapy with daclatasvir and asunaprevir was used for 4 dialysis patients infected with genotype 1b HCV. One patient had viral breakthrough, and the 3 others had sustained virological response 12. One patient was admitted for heart failure and percutaneous coronary intervention due to concomitant ischemic disease. Heart failure was unlikely to be caused by the combination therapy, as it was probably due to water overload. The patient continued to receive the combination therapy after the remission of the heart failure. The combination therapy was well tolerated in the other patients.

Efficacy of interferon-beta plus ribavirin combination treatment on the development of hepatocellular carcinoma in Japanese patients with chronic hepatitis C

AIM

Although there is much evidence of an antitumor effect of pegylated interferon (IFN)-α-based treatment, limited data is available about that of IFN-β-based treatment. Our goal was to evaluate the impact of IFN-β plus ribavirin (RBV) treatment on the suppression of hepatocellular carcinoma (HCC).

METHODS

This retrospective, multicenter study consisted of 124 chronic hepatitis C patients who were treated with IFN-β plus RBV treatment, including 61 with advanced fibrosis and five with pretreatment HCC. All participants were followed for a median of 2.8 years (range, 2.2-3.2) after the end of their antiviral treatment. The data of 112 patients who finished the treatment were available for analysis. Cox proportional hazard analyses were performed to determine factors significantly associated with HCC development. Cumulative incidence curves for HCC were plotted using the Kaplan-Meier method and differences between groups were assessed using the log-rank test.

RESULTS

The 2.9% rate of HCC development of patients with sustained virological response (SVR) was significantly lower (P = 0.027) than the 15.9% of non-SVR patients. Interestingly, no significant difference was observed between the rates of HCC development of patients with and without advanced fibrosis (P = 0.733), even though the SVR rate of patients with advanced fibrosis was significantly lower than that of those without advanced fibrosis (P < 0.001). Stepwise multivariable Cox analysis extracted that only SVR was significantly associated with HCC development (hazard ratio, 0.20; 95% confidence interval, 0.03-0.84, P = 0.027).

CONCLUSION

SVR was significantly associated with a lower risk of HCC development after IFN-β plus RBV treatment.

Significance of variants associated with resistance to NS5A inhibitors in Japanese patients with genotype 1b hepatitis C virus infection as evaluated using cycling-probe real-time PCR combined with direct sequencing

BACKGROUND

Dual oral therapy with daclatasvir plus asunaprevir yielded an SVR rate of 85% among patients with genotype 1b HCV. Treatment failure mainly occurred in patients with pre-existing HCV with NS5A-Y93H mutation. The significance of the mutation was evaluated.

METHODS

The percent of serum NS5A-Y93H strains relative to the total strains was quantified using cycling-probe real-time PCR combined with direct sequencing in 444 patients with genotype 1b HCV, and the factors associated with mutation were analyzed. The mutation rates during interferon therapy were measured sequentially.

RESULTS

NS5A-Y93H strains (1-100% of the total strains) were detected in 87 patients (19.6%). Mutant strains were detected more frequently among women than among men, in patients with a favorable allele in the IL28B-related gene SNP than among those with unfavorable alleles, and among patients without HCC and/or with serum AFP levels less than 6.0 ng/ml than among those with HCC and/or levels of 6.0 ng/ml or more. A multivariate analysis revealed that IL28B-related gene polymorphisms were significant factors associated with mutant strains. Although the frequency of patients with mutant strains was equivalent among patients depending on their previous interferon therapies, a sequential analysis during the interferon administrations revealed that the mutant strains disappeared earlier than the wild-type strains.

CONCLUSIONS

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.

The importance of resistance to direct antiviral drugs in HCV infection in clinical practice

Treatment of chronic hepatitis C virus (HCV) infection with direct-acting antiviral agents (DAA) is associated with high rates of sustained virologic response. Remaining factors associated with treatment failure include advanced stages of liver fibrosis, response to previous antiviral therapy and viral factors such as baseline viral load and suboptimal interaction of the DAA with the target based on viral variants. Heterogeneity within NS3, NS5A, and NS5B areas interacting with DAAs exist between HCV geno- and subtypes as well as HCV isolates of the same geno- and subtype and amino acid polymorphisms associated with suboptimal efficacy of DAAs are termed resistance-associated variants (RAVs). RAVs may be associated with virologic treatment failure. However, virologic treatment failure typically occurs only if other negative predictive host or viral factors are present at the same time, susceptibility to additional antiviral agents is reduced or duration of treatment is suboptimal. In this review geno- and phenotypic resistance testing as well as clinical data on the importance of RAVs for conventional triple therapies with sofosbuvir, simeprevir, and daclatasvir and available interferon-free DAA combinations are discussed.

The clinical features of patients with a Y93H variant of hepatitis C virus detected by a PCR invader assay

BACKGROUND

Resistance-associated variants (RAVs) reduce the efficacy of interferon (IFN)-free therapy with asunaprevir and daclatasvir for patients infected with hepatitis C virus (HCV) genotype 1b. The characteristics of patients with an L31 or a Y93 variant in the nonstructural 5A region detected by a polymerase chain reaction invader assay were investigated.

METHODS

In total, 201 patients with HCV genotype 1b were examined for L31F/M/V variants or a Y93H variant by the polymerase chain reaction invader assay.

RESULTS

L31M and Y93H variants were detected in 4.6 and 21.4 % of patients, respectively. Patients with an L31M variant had no significant characteristics. Patients with a Y93H variant had significantly higher HCV RNA levels (6.5 ± 0.5 log copies per milliliter vs 6.1 ± 0.7 log copies per milliliter, p = 0.0002), higher frequency of mutant type of the IFN-sensitivity-determining region (88.4 % vs 71.7 %, p = 0.0251), and higher frequency of TT genotype at rs8099917 of IL28B (91.7 % vs 54.3 %, p < 0.0001) than those with Y93 wild-type strains. Multivariate analysis identified HCV RNA levels [odds ratio (OR) 3.72, 95 % confidence interval (CI) 1.71-8.06, p = 0.0009] and TT genotype at rs8099917 (OR 7.45, 95 % CI 2.11-26.4, p = 0.0018) as factors associated with the presence of a Y93H variant.

CONCLUSION

The presence of a Y93H variant was associated with higher HCV RNA levels and TT genotype at rs8099917 of IL28B. Thus, patients with a Y93H variant may be ideal candidates for IFN-based therapy rather than IFN-free therapy, although the high viral load of these patients may reduce the response rate of IFN-based therapy.

Interferon lambda 4 genotypes and resistance-associated variants in patients infected with hepatitis C virus genotypes 1 and 3

Single-nucleotide polymorphisms (SNPs) in the interferon lambda 4 (IFNL4) gene are predictors for treatment success in patients with hepatitis C virus (HCV) infection. For direct-acting antiviral combinations only weak association with IFNL4 SNPs was observed. Little is known about potential selections of resistance-associated variants (RAVs) by the IFNL4 genotype. This study analyzed the prevalence of RAVs to currently approved direct-acting antivirals in a large European population in correlation to SNPs in IFNL4. Samples of 633 patients chronically infected with HCV genotypes 1a (n = 259), 1b (n = 323), and 3 (n = 51) were genotyped for rs12979860 (formerly known as IL28B) and rs368234815. RAVs in NS3, NS5A, and NS5B were detected by population-based sequencing. In addition, IFNL4 SNPs and NS5A RAVs were analyzed including deep sequencing (n = 109) in an independent replication cohort of HCV genotype 1-infected patients (n = 201). No significant correlation was found between IFNL4 SNPs and rare and common RAVs within NS3 and NS5B. In contrast, the NS5A RAV Y93H was detected frequently in HCV genotype 1b (14%) and significantly associated with the beneficial IFNL4 SNPs (P < 0.001 and P = 0.002, respectively). Moreover, the presence of Y93H in HCV genotype 1b patients was significantly associated with the second site variant T83M (P < 0.001). Independent factors significantly associated with the presence of Y93H were IFNL4 genotype and high baseline viral load.

CONCLUSION

The NS5A RAV Y93H is significantly associated with the presence of beneficial IFNL4 SNPs and a high baseline viral load in HCV genotype 1-infected patients, which may explain a lack of correlation or even an inverse correlation of treatment response with IFNL4 genotype in some NS5A inhibitor containing IFN-free regimens.

Naturally occurring, resistance-associated hepatitis C virus NS5A variants are linked to interleukin-28B genotype and are sensitive to interferon-based therapy

AIM

The presence of resistance-associated variants (RAV) may attenuate the efficacy of direct-acting antivirals (DAA) in combination therapy for hepatitis C. The aim of this study was to characterize the NS3 and NS5A regions of hepatitis C virus (HCV) in naturally occurring RAV.

METHODS

The NS3 and NS5A regions of HCV were amplified by nested polymerase chain reaction and their nucleotide sequences were determined by direct sequencing in 493 genotype 1b patients naive to DAA-based therapies. The effect of baseline RAV on response to pegylated interferon and ribavirin therapy was analyzed in 65 patients after stratification by interleukin (IL)-28B genotype.

RESULTS

The incidence of RAV was 7.9% in NS3 (V36I/L, 1.2%; T54S, 2.8%; Q80K/R, 3.0%; A156S, 0.2%; and D168E/T, 2.4%) and 20.2% in NS5A (L31I/M, 2.2%; and Y93H, 19.0%). The incidence in interferon experienced and naive patients was similar. The incidence of Y93H in NS5A was significantly higher in the IL-28B TT genotype (rs8099917) than non-TT (27.1% vs 9.5%, P < 0.001). The virological response to pegylated interferon plus ribavirin therapy was not affected by the presence of RAV in IL-28B TT genotype.

CONCLUSION

RAV, especially Y93H in the NS5A region, were highly prevalent in DAA naive patients with genotype 1b HCV in Japan and were linked to IL-28B TT genotype. Interferon-based therapy could be an alternative for patients with RAV because these variants did not attenuate the response to that therapy. The analysis of RAV may impact the selection of the optimal treatment strategy.

Resistance-Associated NS5A Variants of Hepatitis C Virus Are Susceptible to Interferon-Based Therapy

BACKGROUND & AIMS

The presence of resistance-associated variants (RAVs) of hepatitis C virus (HCV) attenuates the efficacy of direct acting antivirals (DAAs). The objective of this study was to characterize the susceptibility of RAVs to interferon-based therapy.

METHODS

Direct and deep sequencing were performed to detect Y93H RAV in the NS5A region. Twenty nine genotype 1b patients with detectable RAV at baseline were treated by a combination of simeprevir, pegylated interferon and ribavirin. The longitudinal changes in the proportion of Y93H RAV during therapy and at breakthrough or relapse were determined.

RESULTS

By direct sequencing, Y93H RAV became undetectable or decreased in proportion at an early time point during therapy (within 7 days) in 57% of patients with both the Y93H variant and wild type virus at baseline when HCV RNA was still detectable. By deep sequencing, the proportion of Y93H RAV against Y93 wild type was 52.7% (5.8%- 97.4%) at baseline which significantly decreased to 29.7% (0.16%- 98.3%) within 7 days of initiation of treatment (p = 0.023). The proportion of Y93H RAV was reduced in 21 of 29 cases (72.4%) and a marked reduction of more than 10% was observed in 14 cases (48.7%). HCV RNA reduction was significantly greater for Y93H RAV (-3.65±1.3 logIU/mL/day) than the Y93 wild type (-3.35±1.0 logIU/mL/day) (p<0.001).

CONCLUSION

Y93H RAV is more susceptible to interferon-based therapy than the Y93 wild type.

Association between variants in the interferon lambda 4 locus and substitutions in the hepatitis C virus non-structural protein 5A

BACKGROUND & AIMS

Single nucleotide polymorphisms within the interferon lambda 4 (IFNL4) locus are strongly associated with spontaneous clearance of hepatitis C virus (HCV) infection and early viral response to interferon therapy. Interaction between host genotype and amino acid substitutions might also influence the risk of antiviral resistance in interferon-free direct acting antiviral (DAA) therapies.

METHODS

The relationship between IFNL4 genotype and HCV substitutions was analyzed in 929 patients with chronic HCV genotype 1b infection. Ultra-deep sequencing and quasispecies reconstruction was performed on the N-terminal region of NS5A in 57 patients.

RESULTS

IFNL4 genotype was strongly associated with HCV NS5A Y93 and core protein substitutions, and the number and diversity of predicted quasispecies was marginally greater in IFNL4 TT/TT patients compared to TT/ΔG, ΔG/ΔG patients. RNA secondary structure prediction of the NS5A region suggests that variable sites are more likely to occupy unpaired, high entropy positions.

CONCLUSIONS

HCV infection is proposed to induce a more efficient antiviral response in individuals with the IFNL4 TT/TT genotype that results either in viral clearance or selection for viral adaptations. The association between IFNL4 TT/TT genotype and Y93 substitutions may impact the risk of antiviral resistance in NS5A inhibitors in DAA therapy.

Rapid, Sensitive, and Accurate Evaluation of Drug Resistant Mutant (NS5A-Y93H) Strain Frequency in Genotype 1b HCV by Invader Assay

Daclatasvir and asunaprevir dual oral therapy is expected to achieve high sustained virological response (SVR) rates in patients with HCV genotype 1b infection. However, presence of the NS5A-Y93H substitution at baseline has been shown to be an independent predictor of treatment failure for this regimen. By using the Invader assay, we developed a system to rapidly and accurately detect the presence of mutant strains and evaluate the proportion of patients harboring a pre-treatment Y93H mutation. This assay system, consisting of nested PCR followed by Invader reaction with well-designed primers and probes, attained a high overall assay success rate of 98.9% among a total of 702 Japanese HCV genotype 1b patients. Even in serum samples with low HCV titers, more than half of the samples could be successfully assayed. Our assay system showed a better lower detection limit of Y93H proportion than using direct sequencing, and Y93H frequencies obtained by this method correlated well with those of deep-sequencing analysis (r = 0.85, P <0.001). The proportion of the patients with the mutant strain estimated by this assay was 23.6% (164/694). Interestingly, patients with the Y93H mutant strain showed significantly lower ALT levels (p=8.8 x 10^-4), higher serum HCV RNA levels (p=4.3 x 10^-7), and lower HCC risk (p=6.9 x 10^-3) than those with the wild type strain. Because the method is both sensitive and rapid, the NS5A-Y93H mutant strain detection system established in this study may provide important pre-treatment information valuable not only for treatment decisions but also for prediction of disease progression in HCV genotype 1b patients.

HCV NS5A resistance-associated variants in a group of real-world Japanese patients chronically infected with HCV genotype 1b

BACKGROUND

Recent advances in interferon-free treatment could lead to the eradication of hepatitis C virus (HCV) from patients infected with HCV. One of the direct-acting anti-viral agents, HCV NS5A inhibitor, is available for these combination therapies. However, naturally occurring resistance-associated variants (RAVs) to HCV NS5A inhibitors in treatment-naïve patients chronically infected with HCV genotype 1b are still unknown.

METHODS

We performed ultra-deep sequencing and analysed previously reported RAVs in a total 132 HCV genotype 1b-infected Japanese patients who had never used HCV NS5A inhibitors. We also performed direct-sequencing by Sanger method in consecutively selected 50 of the total 132 samples, and the differences between the results of the two methods were compared.

RESULTS

In the comparison of the variant frequencies of ultra-deep sequencing with RAVs of direct-sequencing by Sanger method in 50 patients, we identified 32 RAVs by direct-sequencing with the Sanger method; minimum variant frequency was shown by ultra-deep sequencing to be 9%. A total of 110 RAVs were identified only by ultra-deep sequencing. In the samples from all 132 patients, L31W (2.3%), L31V (49.2%), L31F (41.7%), L31M (1.5%), L31I (5.3%), L31S (2.0%), L31P (3.0%) and L31R (0.8%), and Y93N (2.3%), Y93H (25%), Y93C (0.8%), Y93P (2.3%) and Y93D (0.8%) were identified.

CONCLUSIONS

We demonstrated naturally-occurring RAVs of HCV NS5A inhibitors by ultra-deep sequencing and that several mutations including Y93H are common in HCV NS5A inhibitor-treatment-naïve patients with chronic HCV genotype 1b. Careful attention should be paid to these RAVs, and further improvement of treatment options might be needed.

Dengue Virus Evolution under a Host-Targeted Antiviral

The host-targeted antiviral drug UV-4B reduces viral replication and promotes survival in a mouse model of experimental dengue virus (DENV) infection. UV-4B is an iminosugar that inhibits the α-glucosidase family of enzymes and subsequently the folding of glycosylated proteins, both viral and host. Here, we utilized next-generation sequencing to investigate evolution of a flavivirus under selective pressure by a host-targeted antiviral in vivo. In viral populations recovered from UV-4B-treated mice, there was a significant increase in the number of single-nucleotide polymorphisms (SNPs) and the ratio of nonsynonymous to synonymous SNPs compared to findings in viral populations from vehicle-treated mice. The strongest evidence of positive selection was in the glycosylated membrane protein, thereby providing in vivo validation of the mechanism of action of an iminosugar. In addition, mutations in glycosylated proteins were present only in drug-treated mice after a single passage. However, the bulk of the other mutations were present in both populations, indicating nonspecific selective pressure. Together with the continued control of viremia by UV-4B, these findings are consistent with the previously predicted high genetic barrier to escape mutations in host-targeted antivirals.

IMPORTANCE

Although hundreds of millions of people are infected with DENV every year, there is currently no approved vaccine or antiviral therapy. UV-4B has demonstrated antiviral activity against DENV and is expected to enter clinical trials soon. Therefore, it is important to understand the mechanisms of DENV resistance to UV-4B. Host-targeted antivirals are thought to have a higher genetic barrier to escape mutants than directly acting antivirals, yet there are very few published studies of viral evolution under host-targeted antivirals. No study to date has described flavivirus evolution in vivo under selective pressure by a host-based antiviral drug. We present the first in vivo study of the sequential progression of viral evolution under selective pressure by a host-targeted antiviral compound. This study bolsters support for the clinical development of UV-4B as an antiviral drug against DENV, and it provides a framework to compare how treatment with other host-targeted antiflaviviral drugs in humans and different animal models influence viral genetic diversity.

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.

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.