Hepatitis C Virus NS5A Inhibitor Research Articles

Sofosbuvir-velpatasvir in adults with hepatitis C virus infection and compensated cirrhosis in Japan.

Protease-free regimens for chronic hepatitis C virus (HCV) infection are safe and effective for persons with either compensated or decompensated cirrhosis. We examined the efficacy and safety of sofosbuvir-velpatasvir in participants with HCV and compensated cirrhosis in Japan. This was a Phase 3, multi-center, open-label study. At 20 sites, 37 individuals with chronic HCV infection of any genotype and compensated cirrhosis received sofosbuvir-velpatasvir (400mg/100mg) daily for 12weeks. Participants were treatment-naïve or treatment-experienced with interferon-based treatments with or without HCV NS3/4A protease inhibitors. Prior exposure with HCV NS5A or NS5B inhibitors was prohibited. The primary study endpoint was sustained virologic response 12weeks after treatment (SVR12). Among participants, 62% had HCV genotype 1 infection, and 38% had HCV genotype 2. More than three quarters (29/37, 78%) were HCV treatment naïve. All participants (37/37, 100%) achieved SVR12. Seventeen participants (46%) and three participants (8%) had pretreatment resistance-associated substitutions to HCV NS5A and NS5B nucleoside inhibitors respectively, yet no on-treatment breakthrough or relapse occurred. Sofosbuvir-velpatasvir for 12weeks treatment was safe and well tolerated. The most commonly reported adverse events were headache (8%, 3/37) and diarrhea (5%, 2/37). One serious adverse event, patella fracture, occurred and was considered not treatment related. No participants discontinued study treatment due to an adverse event. Three participants (8%) had a Grade 3 laboratory abnormality; all were hyperglycemia. Sofosbuvir-velpatasvir resulted in high SVR rates and was well tolerated among Japanese patients with HCV and compensated cirrhosis. This single-tablet regimen offers a highly effective, protease-inhibitor free regimen for treating HCV. gov Identifier: NCT04112303.

Cyclopeptide Kalata B12 as HCV-NS5A potent Inhibitor

Hepatitis C Virus (HCV) is the leading cause of liver diseases globally, causing severe complications such as liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Despite the advent of successful regimens, still, 71 million individuals are chronically infected every year. Therefore, more accessible novel therapies are needed to fight the challenges such as adverse effects, genotype selectivity, and resistance to these regimens due to viral mutations. HCV NS5A is a non-structural phosphoprotein, with its pivotal role in viral replication assembly, and has been the target of continuous research. Cyclopeptides are an emerging class of peptides reported to have antiviral, anticancer, and antimicrobial properties. These cyclopeptides have exceptional resistance to thermal, chemical, or enzymatic degradation. Herein, we present the inhibitory potential of cyclopeptide Kalata B12 against the HCV NS5A gene. Objective: To investigate the antiviral potential of Kalata B2, Kalata B12, and cycloviolacin O14 against HCV NS5A Methods: We investigated thirty cyclopeptides through molecular docking analysis for their anti-HCV-NS5A inhibition potential. Three cyclopeptides, Kalata B2, Kalata B12, and cycloviolacin O14 showed minimum binding energies, for their antiviral potential. The defense-related, circular mini-protein Kalata B12 showed an impressive docking score of -9.80 Kcal/mol. Further, it was synthesized and went through cytotoxicity analysis via MTT assay on HepG2 cell line, which showed more than 85% cell viability at submicromolar concentrations. Results: The peptide Kalata B12 showed significant (***P<0.0001) inhibition of NS5A gene (approx. 75%) at 100nM in In vitro trials, confirmed by real-Time PCR analysis. Conclusions: Kalata B12 cyclopeptide was found to be a potential HCV NS5A inhibitor

Synergistic inhibition of hepatitis C virus infection by a novel microtubule inhibitor in combination with daclatasvir

Even though substantial progress has been made in the treatment of hepatitis C virus (HCV) infection, viral resistance and relapse still occur in some patients and additional therapeutic approaches may ultimately be needed should viral resistance become more prevalent. Microtubules play important roles in several HCV life cycle events, including cell attachment, entry, cellular transportation, morphogenesis and progeny secretion steps. Therefore, it was hypothesized that microtubular inhibition might be a novel approach for the treatment of HCV infection. Here, the inhibitory effects of our recently developed microtubule inhibitors were studied in the HCV replicon luciferase reporter system and the infectious system. In addition, the combination responses of microtubule inhibitors with daclatasvir, which is a clinically used HCV NS5A inhibitor, were also evaluated. Our results indicated that microtubule targeting had activity against HCV replication and showed synergistic effect with a current clinical drug.

First report on molecular docking analysis and drug resistance substitutions to approved HCV NS5A and NS5B inhibitors amongst Iranian patients

BackgroundNS5A and NS5B proteins of hepatitis C virus (HCV) are the main targets of compounds that directly inhibit HCV infections. However, the emergence of resistance-associated substitutions (RASs) may cause substantial reductions in susceptibility to inhibitors.MethodsViral load and genotyping were determined in eighty-seven naïve HCV-infected patients, and the amplified NS5A and NS5B regions were sequenced by Sanger sequencing. In addition, physicochemical properties, structural features, immune epitopes, and inhibitors-protein interactions of sequences were analyzed using several bioinformatics tools.ResultsSeveral amino acid residue changes were found in NS5A and NS5B proteins; however, we did not find any mutations related to resistance to the treatment in NS5B. Different phosphorylation and few glycosylation sites were assessed. Disulfide bonds were identified in both proteins that had a significant effect on the function and structure of HCV proteins. Applying reliable software to predict B-cell epitopes, 3 and 5 regions were found for NS5A and NS5B, respectively, representing a considerable potential to induce the humoral immune system. Docking analysis determined amino acids involved in the interaction of inhibitors and mentioned proteins may not decrease the drug efficiency.ConclusionsStrong interactions between inhibitors, NS5A and NS5B proteins and the lack of efficient drug resistance mutations in the analyzed sequences may confirm the remarkable ability of NS5A and NS5B inhibitors to control HCV infection amongst Iranian patients. The results of bioinformatics analysis could unveil all features of both proteins, which can be beneficial for further investigations on HCV drug resistance and designing novel vaccines.

The Discovery of Conformationally Constrained Bicyclic Peptidomimetics as Potent Hepatitis C NS5A Inhibitors.

HCV NS5A inhibitors are the backbone of directly acting antiviral treatments against the hepatitis C virus (HCV). While these therapies are generally highly curative, they are less effective in some specific HCV patient populations. In the search for broader-acting HCV NS5A inhibitors that address these needs, we explored conformational restrictions imposed by the [7,5]-azabicyclic lactam moiety incorporated into daclatasvir (1) and related HCV NS5A inhibitors. Unexpectedly, compound 5 was identified as a potent HCV genotype 1a and 1b inhibitor. Molecular modeling of 5 bound to HCV genotype 1a suggested that the use of the conformationally restricted lactam moiety might have resulted in reorientation of its N-terminal carbamate to expose a new interaction with the NS5A pocket located between amino acids P97 and Y93, which was not easily accessible to 1. The results also suggest new chemistry directions that exploit the interactions with the P97–Y93 site toward new and potentially improved HCV NS5A inhibitors.

Berberis lyceum and Fumaria indica: in vitro cytotoxicity, antioxidant activity, and in silico screening of their selected phytochemicals as novel hepatitis C virus nonstructural protein 5A inhibitors

Berberis lyceum and Fumaria indica are two Pakistani indigenous herbal medicines used to treat liver infections, including hepatitis C virus (HCV). This study aimed to evaluate the cytotoxicity, and antioxidant activity of these plant extracts and computationally screen their selected phytoconstituents as HCV NS5A inhibitors. The viability of HepG2 cells was assessed 24 h and 48 h post-treatment using colorimetric and dye exclusion methods. Antioxidant properties were examined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), reducing power, and total antioxidant capacity assays. Seventeen known phytochemicals identified from each plant were docked into the active binding site of HCV NS5A protein. The top hit ligands were analyzed for their druglikeness properties and the indices of absorption, distribution, metabolism, elimination, and toxicity (ADMET). The results showed that both plant extracts were non-toxic (CC50 > 200 µg/ml). The IC50 values of DPPH-radical scavenging activity were 51.02 ± 0.94 and 62.91 ± 1.85 µg/ml for B. lyceum and F. indica, respectively. They also exhibited reducing power and total antioxidant capacity.The phytochemicals were identified as potent HCV NS5A inhibitors with good druglikeness and ADMET properties. Six of the docked phytochemicals exhibited higher binding scores (-17.9 to −19.2 kcal/mol) with HCV NS5A protein than the standard drug, daclatasvir (-17.2 kcal/mol). Molecular dynamics (MD) simulation confirmed the stability of two compounds, berbamine and paprafumine at 100 ns with active site of HCV NS5A protein. The identified compounds through molecular docking and MD simulation could have potential as HCV NS5A inhibitor after further validation. Communicated by Ramaswamy H. Sarma

Glecaprevir/pibrentasvir for the treatment of chronic hepatitis C: design, development, and place in therapy.

Direct-acting antiviral (DAA) therapy has changed the landscape of hepatitis C virus (HCV) management and has changed the focus to the possibility of HCV elimination in the near future. Glecaprevir, an NS3/4A protease inhibitor, and pibrentasvir, an HCV NS5A inhibitor, have addressed many of the existing shortcomings in the DAA therapy spectrum. This combination has proven to be a highly efficacious pan-genotypic DAA with a high barrier to resistance as a once-daily, all-oral medication. This review explores the design and development of glecaprevir and pibrentasvir, its place in current HCV management in the midst of a myriad of DAA therapy options, and also remaining challenges.

Sofosbuvir/velpatasvir for 12 weeks in hepatitis C virus-infected patients with end-stage renal disease undergoing dialysis

Although off-label use of sofosbuvir-containing regimens occurs regularly in patients with hepatitis C virus (HCV) infection undergoing dialysis for severe renal impairment or end-stage renal disease (ESRD), these regimens are not licensed for this indication, and there is an absence of dosing recommendations in this population. This study evaluated the safety and efficacy of sofosbuvir/velpatasvir in patients with HCV infection with ESRD undergoing dialysis. In this phase II, single-arm study, 59 patients with genotype 1-6 HCV infection with ESRD undergoing hemodialysis or peritoneal dialysis received open-label sofosbuvir/velpatasvir (400 mg/100 mg) once daily for 12 weeks. Patients were HCV treatment naive or treatment experienced without cirrhosis or with compensated cirrhosis. Patients previously treated with any HCV NS5A inhibitor were not eligible. The primary efficacy endpoint was the proportion of patients achieving sustained virologic response (SVR) 12 weeks after discontinuation of treatment (SVR12). The primary safety endpoint was the proportion of patients who discontinued study drug due to adverse events. Overall, 56 of 59 patients achieved SVR12 (95%; 95% CI 86-99%). Of the 3 patients who did not achieve SVR12, 2 patients had virologic relapse determined at post-treatment Week 4 (including 1 who prematurely discontinued study treatment), and 1 patient died from suicide after achieving SVR through post-treatment Week 4. The most common adverse events were headache (17%), fatigue (14%), nausea (14%), and vomiting (14%). Serious adverse events were reported for 11 patients (19%), and all were deemed to be unrelated to sofosbuvir/velpatasvir. Treatment with sofosbuvir/velpatasvir for 12 weeks was safe and effective in patients with ESRD undergoing dialysis. Sofosbuvir/velpatasvir is a combination direct-acting antiviral that is approved for treatment of patients with hepatitis C virus (HCV) infection. Despite the lack of dosing recommendations, sofosbuvir-containing regimens (including sofosbuvir/velpatasvir) are frequently used for HCV-infected patients undergoing dialysis. This study evaluated the safety and efficacy of sofosbuvir/velpatasvir for 12 weeks in patients with HCV infection who were undergoing dialysis. Treatment with sofosbuvir/velpatasvir was safe and well tolerated, resulting in a cure rate of 95% in patients with HCV infection and end-stage renal disease. Clinical Trial Number: NCT03036852.

Discovery of velpatasvir (GS-5816): A potent pan-genotypic HCV NS5A inhibitor in the single-tablet regimens Vosevi® and Epclusa®.

Direct-acting antiviral inhibitors have revolutionized the treatment of hepatitis C virus (HCV) infected patients. Herein is described the discovery of velpatasvir (VEL, GS-5816), a potent pan-genotypic HCV NS5A inhibitor that is a component of the only approved pan-genotypic single-tablet regimens (STRs) for the cure of HCV infection. VEL combined with sofosbuvir (SOF) is Epclusa®, an STR with 98% cure-rates for genotype 1-6 HCV infected patients. Addition of the pan-genotypic HCV NS3/4A protease inhibitor voxilaprevir to SOF/VEL is the STR Vosevi®, which affords 97% cure-rates for genotype 1-6 HCV patients who have previously failed another treatment regimen.

Novel Side Effect of a Novel Medication

Introduction Glecaprevir/pibrentasvir (Mavyret) is a combination drug containing glecaprevir (100 mg) and pibrentasvir (40 mg). In the United States, it was approved by the Food and Drug Administration in August 2017 for treatment of hepatitis C. In Europe, it was also approved in August 2017 for the same indication. Here we report a new side effect of reversible hand tremors associated with the use of this drug. Case presentation This case involves a 45-year-old female with 1-year history of treatment naive chronic hepatitis C secondary to intravenous drug abuse. She had HCV viral load of 6.98 IU/ml, indeterminate genotype and ultrasound liver elastography showed mild to moderate fibrosis. She was started on 3 daily tablets glecaprevir/pibrentasvir for 8 weeks. 2 weeks into the treatment, she developed hand tremors, epigastric pain and gastroesophageal reflux. ON examination, she had fine resting tremors involving the fingers. She denied taking any other prescription or over the counter medication. Medication was stopped, and all symptoms improved in 3-4 days. Discussion Glecaprevir/pibrentasvir (MAVYRET) is a fixed-dose combination of glecaprevir, a hepatitis C virus (HCV) NS3/4A protease inhibitor, and pibrentasvir, an HCV NS5A inhibitor, and is indicated for the treatment of patients with chronic HCV genotype (GT) 1, 2, 3, 4, 5 or 6 infections without cirrhosis and with compensated cirrhosis (Child-Pugh A). Known side effects include hepatitis B reactivation, and more commonly increased serum bilirubin, headache, nausea, tiredness, and diarrhea. Our patient with Hepatitis C was started on glecaprevir/pibrentasvir and developed fine hand tremors after 2 weeks of treatment. This side effect was reversible and completely went away after stopping the medication.

Highlights of the Structure-Activity Relationships of Benzimidazole Linked Pyrrolidines Leading to the Discovery of the Hepatitis C Virus NS5A Inhibitor Pibrentasvir (ABT-530).

Curative interferon and ribavirin sparing treatments for hepatitis C virus (HCV)-infected patients require a combination of mechanistically orthogonal direct acting antivirals. A shared component of these treatments is usually an HCV NS5A inhibitor. First generation FDA approved treatments, including the component NS5A inhibitors, do not exhibit equivalent efficacy against HCV virus genotypes 1-6. In particular, these first generation NS5A inhibitors tend to select for viral drug resistance. Ombitasvir is a first generation HCV NS5A inhibitor included as a key component of Viekira Pak for the treatment of patients with HCV genotype 1 infection. Since the launch of next generation HCV treatments, functional cure for genotype 1-6 HCV infections has been achieved, as well as shortened treatment duration across a wider spectrum of genotypes. In this paper, we show how we have modified the anchor, linker, and end-cap architecture of our NS5A inhibitor design template to discover a next generation NS5A inhibitor pibrentasvir (ABT-530), which exhibits potent inhibition of the replication of wild-type genotype 1-6 HCV replicons, as well as improved activity against replicon variants demonstrating resistance against first generation NS5A inhibitors.

Sofosbuvir/Velpatasvir/Voxilaprevir: A Review in Chronic Hepatitis C.

A fixed-dose combination of the hepatitis C virus (HCV) NS5B polymerase inhibitor sofosbuvir, the HCV NS5A inhibitor velpatasvir and the HCV NS3/4A protease inhibitor voxilaprevir (sofosbuvir/velpatasvir/voxilaprevir; Vosevi®) is approved in the EU for the treatment of chronic HCV genotype 1, 2, 3, 4, 5 or 6 infection in adults. In the phase III POLARIS trials, in patients who had HCV genotype 1-6 infection with or without compensated cirrhosis, overall rates of sustained virological response at 12weeks post-treatment (SVR12) with sofosbuvir/velpatasvir/voxilaprevir were high after 8weeks of treatment in direct-acting antiviral (DAA)-naïve patients and 12weeks of treatment in DAA-experienced patients. However, 8weeks of sofosbuvir/velpatasvir/voxilaprevir was inferior to 12weeks of sofosbuvir/velpatasvir in cirrhotic or non-cirrhotic DAA-naïve patients with HCV genotype 1, 2, 4, 5 or 6 infection and non-cirrhotic DAA-naïve patients with HCV genotype 3 infection, mostly due to an insufficient treatment period. Sofosbuvir/velpatasvir/voxilaprevir was generally well tolerated, with most adverse events being of mild or moderate intensity. The most common adverse events included headache, fatigue, nausea and diarrhoea. In conclusion, sofosbuvir/velpatasvir/voxilaprevir is an important and effective option for the treatment of HCV genotype 1-6 infection in adults, especially those who have previously failed a DAA therapy with or without an HCV NS5A inhibitor.

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Efficacy of direct-acting antiviral treatment for chronic hepatitis C: A single hospital experience.

AIMTo evaluate the efficacy of direct-acting antivirals (DAAs) in Kanto Rosai Hospital.METHODSAll patients with hepatitis C virus (HCV) who underwent DAA prescription were enrolled in this study. The present study was a single center retrospective analysis using patients infected with HCV genotype 1 or 2. Resistance analysis was performed by using direct sequencing and cycleave PCR in genotype 1 patients treated with interferon (IFN)-free DAA. The primary endpoint was sustained virologic response at 12 wk after therapy (SVR12).RESULTSA total of 117 patients participated in the study, including 135 with genotype 1 and 42 with genotype 2. Of the 135 patients with genotype 1, 16 received protease inhibitor + IFN + ribavirin and all achieved SVR. Of the 119 patients who received IFN-free DAA (in different combinations), 102 achieved SVR and 9 failed (7/9 were on daclatasvir/asunaprevir and 2/9 on ledipasvir/sofosbuvir). Efficacy analysis was done only for 43 patients who received daclatasvir/asunaprevir. From this analysis, Y93 resistance-associated substitutions were significantly correlated with SVR.CONCLUSIONThe SVR rate was 98% for genotype 1 and 100% for genotype 2. However, caution is needed for HCV NS5A resistance-associated substitutions that are selected by HCV NS5A inhibitors because cerebrovascular adverse events are induced by some DAA drugs.

Successful retreatment with sofosbuvir plus ledipasvir for cirrhotic patients with hepatitis C virus genotype 1b, who discontinued the prior treatment with asunaprevir plus daclatasvir: A case series and review of the literature.

BackgroundInterferon-free treatment results in higher sustained virologic response (SVR) rates, with no serious adverse events in hepatitis C virus (HCV)-infected patients. However, in some patients with treatment-failure in HCV NS5A inhibitor-including interferon-free regimens, the treatment-emergent HCV NS5A resistance-associated variants (RAVs), which are resistant to interferon-free retreatment including HCV NS5A inhibitors, are observed. In HCV-infected Japanese patients with daclatasvir and asunaprevir treatment failure, retreatment with sofosbuvir and ledipasvir could lead to only ∼70% SVR rates.Case summaryThree HCV genotype (GT)-1b-infected cirrhotic patients who discontinued the combination of daclatasvir and asunaprevir due to adverse drug reactions within 4 weeks; retreatment with sofosbuvir and ledipasvir combination could result in SVR in these patients without RAVs. One HCV GT-1b-infected cirrhotic patient who discontinued the combination of daclatasvir and asunaprevir due to viral breakthrough at week 10; retreatment with sofosbuvir and ledipasvir combination for this patient with the treatment-emergent HCV NS5A RAV-Y93H resulted in viral relapse at week 4 after the end of the treatment.ConclusionRetreatment with sofosbuvir and ledipasvir is effective for HCV GT-1b patients who discontinue the combination of daclatasvir and asunaprevir within 4 weeks. The treatment response should be related to the existence of treatment-emergent HCV NS5A RAVs, but may not be related to the short duration of treatment.

Efficacy of Ledipasvir and Sofosbuvir Treatment of HCV Infection in Patients Coinfected With HBV

There have been reports of reactivation of hepatitis B virus (HBV) infection during treatment of hepatitis C virus (HCV) infection with direct-acting antiviral agents. We performed a prospective study of risks and outcomes of HCV infection treatment with ledipasvir and sofosbuvir in patients with HBV infection. We performed a phase 3b, multicenter, open-label study in Taiwan of 111 patients with HCV infection (61% HCV genotype 1, 39% HCV genotype 2 infection; 62% women, 16% with compensated cirrhosis) along with HBV infection. All but 1 were positive for the hepatitis B surface antigen (HBsAg); 1 patient who was HBsAg-positive at screening was found to be HBsAg-negative at baseline. Overall, 33% of participants had received prior treatment for HCV and 5% had previously been treated for HBV; no patient was on HBV therapy at the start of the study. All patients received a fixed-dose combination of 90 mg of the HCV NS5A inhibitor ledipasvir with 400 mg of the NS5B nucleotide analogue inhibitor sofosbuvir, once daily for 12 weeks. The primary endpoint was sustained virologic response 12 weeks after the end of therapy. All 111 patients (100%) achieved a sustained virologic response. Of the 37 patients with baseline HBV DNA below 20 IU/mL, 31 (84%) had at least 1 episode of quantifiable HBV DNA through posttreatment week 12. Of the 74 patients with baseline HBV DNA levels of 20 IU/mL or more, 39 (53%) had increases of HBV DNA greater than 1 log10 IU/mL through posttreatment week 12. Overall, 5 patients had increased levels of HBV DNA concomitant with a level of alanine aminotransferase >2 times the upper limit of normal through posttreatment week 12. Of these, 3 patients started HBV treatment. In addition, 1 patient with HBV reactivation since week 8 and concomitant alanine aminotransferase elevation >2 times upper limit of normal at posttreatment week 48 started treatment at posttreatment week 53. This patient had clinical signs and symptoms associated with HBV reactivation. The most common adverse events were headache, upper respiratory infection, and fatigue. In a prospective study, the combination of ledipasvir and sofosbuvir for 12 weeks produced a sustained virologic response in 100% of patients with HCV infection who were coinfected with HBV. Most patients had an increase in level of HBV DNA not associated with signs or symptoms. ClinicalTrials.gov no: NCT02613871.

Glecaprevir/Pibrentasvir: First Global Approval.

A fixed-dose combination tablet of the hepatitis C virus (HCV) NS3/4A protease inhibitor (PI) glecaprevir and the HCV NS5A inhibitor pibrentasvir [glecaprevir/pibrentasvir; MAVIRET™ (EU); MAVYRET™ (USA)] has been developed by AbbVie. Oral glecaprevir/pibrentasvir 300mg/120mg (three 100mg/40mg tablets) taken once daily has been approved by the EMA for the treatment of all major genotypes (genotypes 1-6) of chronic HCV infection in adults. It has also been approved by the US FDA for the treatment of adult patients with chronic HCV genotype 1-6 infection without cirrhosis and with compensated cirrhosis, and for the treatment of adult patients with HCV genotype 1 infection who previously have been treated with a regimen containing either an HCV NS5A inhibitor or an NS3/4A PI, but not both. This article summarizes the milestones in the development of glecaprevir/pibrentasvir leading to its first global approval in the EU and subsequent approval in the USA for chronic HCV infection.

Antiviral Activity and Resistance Analysis of NS3/4A Protease Inhibitor Grazoprevir and NS5A Inhibitor Elbasvir in Hepatitis C Virus GT4 Replicons.

Although genotype 4 (GT4)-infected patients represent a minor overall percentage of the global hepatitis C virus (HCV)-infected population, the high prevalence of the genotype in specific geographic regions coupled with substantial sequence diversity makes it an important genotype to study for antiviral drug discovery and development. We evaluated two direct-acting antiviral agents-grazoprevir, an HCV NS3/4A protease inhibitor, and elbasvir, an HCV NS5A inhibitor-in GT4 replicons prior to clinical studies in this genotype. Following a bioinformatics analysis of available GT4 sequences, a set of replicons bearing representative GT4 clinical isolates was generated. For grazoprevir, the 50% effective concentration (EC50) against the replicon bearing the reference GT4a (ED43) NS3 protease and NS4A was 0.7 nM. The median EC50 for grazoprevir against chimeric replicons encoding NS3/4A sequences from GT4 clinical isolates was 0.2 nM (range, 0.11 to 0.33 nM; n = 5). The difficulty in establishing replicons bearing NS3/4A resistance-associated substitutions was substantially overcome with the identification of a G162R adaptive substitution in NS3. Single NS3 substitutions D168A/V identified from de novo resistance selection studies reduced grazoprevir antiviral activity by 137- and 47-fold, respectively, in the background of the G162R replicon. For elbasvir, the EC50 against the replicon bearing the reference full-length GT4a (ED43) NS5A gene was 0.0002 nM. The median EC50 for elbasvir against chimeric replicons bearing clinical isolates from GT4 was 0.0007 nM (range, 0.0002 to 34 nM; n = 14). De novo resistance selection studies in GT4 demonstrated a high propensity to suppress the emergence of amino acid substitutions that confer high-potency reductions to elbasvir. Phenotypic characterization of the NS5A amino acid substitutions identified (L30F, L30S, M31V, and Y93H) indicated that they conferred 15-, 4-, 2.5-, and 7.5-fold potency losses, respectively, to elbasvir. The activity profiles of grazoprevir and elbasvir supported the testing of the direct-acting antivirals in clinical studies.

Real-World Experiences with the Combination Treatment of Ledipasvir plus Sofosbuvir for 12 Weeks in HCV Genotype 1-Infected Japanese Patients: Achievement of a Sustained Virological Response in Previous Users of Peginterferon plus Ribavirin with HCV NS3/4A Inhibitors.

The aim of this study was to characterize the treatment response and serious adverse events of ledipasvir plus sofosbuvir therapies in Japanese patients infected with hepatitis C virus (HCV) genotype 1 (GT1). This retrospective study analyzed 240 Japanese HCV GT1 patients treated for 12 weeks with 90 mg of ledipasvir plus 400 mg of sofosbuvir daily. Sustained virological response at 12 weeks post-treatment (SVR12) was achieved in 236 of 240 (98.3%) patients. Among treatment-naïve patients, SVR12 was achieved in 136 of 138 (98.6%) patients, and among treatment-experienced patients, SVR12 was achieved in 100 of 102 (98.0%) patients. In patients previously treated with peginterferon plus ribavirin with various HCV NS3/4A inhibitors, 100% SVR rates (25/25) were achieved. Two relapsers had HCV NS5A resistance-associated variants (RAVs), but no HCV NS5B-S282 was observed after they relapsed. We experienced two patients with cardiac events during treatment. In conclusion, combination of ledipasvir plus sofosbuvir for 12 weeks is a potential therapy for HCV GT1 patients. Caution is needed for HCV NS5A RAVs, which were selected by HCV NS5A inhibitors and cardiac adverse events.

In Vitro Antiviral Activity and Resistance Profile of the Next-Generation Hepatitis C Virus NS5A Inhibitor Pibrentasvir.

ABSTRACTPibrentasvir (ABT-530) is a novel and pan-genotypic hepatitis C virus (HCV) NS5A inhibitor with 50% effective concentration (EC50) values ranging from 1.4 to 5.0 pM against HCV replicons containing NS5A from genotypes 1 to 6. Pibrentasvir demonstrated similar activity against a panel of chimeric replicons containing HCV NS5A of genotypes 1 to 6 from clinical samples. Resistance selection studies were conducted using HCV replicon cells with NS5A from genotype 1a, 1b, 2a, 2b, 3a, 4a, 5a, or 6a at a concentration of pibrentasvir that was 10- or 100-fold over its EC50 for the respective replicon. With pibrentasvir at 10-fold over the respective EC50, only a small number of colonies (0.00015 to 0.0065% of input cells) with resistance-associated amino acid substitutions were selected in replicons containing genotype 1a, 2a, or 3a NS5A, and no viable colonies were selected in replicons containing NS5A from other genotypes. With pibrentasvir at 100-fold over the respective EC50, very few colonies (0.0002% of input cells) were selected by pibrentasvir in genotype 1a replicon cells while no colonies were selected in other replicons. Pibrentasvir is active against common resistance-conferring substitutions in HCV genotypes 1 to 6 that were identified for other NS5A inhibitors, including those at key amino acid positions 28, 30, 31, or 93. The combination of pibrentasvir with HCV inhibitors of other classes produced synergistic inhibition of HCV replication. In summary, pibrentasvir is a next-generation HCV NS5A inhibitor with potent and pan-genotypic activity, and it maintains activity against common amino acid substitutions of HCV genotypes 1 to 6 that are known to confer resistance to currently approved NS5A inhibitors.