Triple Combination with Direct Acting Antivirals in the Treatment of Hepatitis C Does not Prolong the QT Interval

AIMS

Antiviral drugs are considered as potentially cardiotoxic, due to prolongation of QT interval which may affect incidence of severe ventricular arrhythmias. The main aim of this retrospective study was to assess the influence of treatment by three antiviral drugs on QT interval and to find patients who are at an increased risk of developing malignant ventricular arrhythmias.

METHODS

The study included 23 patients (14 men, 9 women) who were treated with a combination of interferon alpha, ribavirin, and an NS3/4A protease inhibitor. The parameters from the 12 leads electrocardiograms were evaluated before treatment, and then 3 ± 1 and 6 ± 1 months after treatment.

RESULTS

Heart rate (HR) 69 ± 12 / min and corrected QT interval (QTc) 412 ± 35 ms were obtained before the treatment and there was not observed a significant prolongation of intervals after 3 months (HR 72 ± 11 / min, QTc 412 ± 33 ms) and after 6 months (HR 64 ± 12 / min, QTc 405 ± 28 ms) respectively. In total QTc interval was prolonged from the baseline in 53% and in 43% of the patients 3 months respectively 6 months after treatment. A QTc prolongation over of 450 ms and new treatment-related repolarization change was noted in 1 (4%) patient.

CONCLUSION

The study demonstrates that a combination therapy of 3 antiviral drugs does not significantly prolong the QTc interval and does not cause severe pathological changes on the ECG. Patients undergoing this treatment are not at risk of developing heart disease as an undesirable side effect.

Elbasvir/grazoprevir in women with hepatitis C virus infection taking oral contraceptives or hormone replacement therapy

Introduction

Some direct-acting antiviral regimens for hepatitis C virus (HCV) infection pose safety or efficacy concerns if coadministered with drugs containing ethinyl estradiol. The present analysis was conducted to examine the impact of concomitant oral contraceptive pills (OCP) or hormone replacement therapy (HRT) during treatment with elbasvir (EBR)/grazoprevir (GZR) in women with HCV genotype (GT)1 or GT4 infection.

Methods

This is a post hoc, integrated retrospective analysis of female participants with HCV GT1 or GT4 infection who received EBR 50 mg/GZR 100 mg once daily for 12 weeks in phase 2/3 clinical trials. The primary end point was sustained virologic response at 12 weeks after therapy completion (SVR12). For this analysis, participants were stratified according to whether they received OCP or HRT during the original treatment study.

Results

A total of 1,022 women with HCV GT1 or GT4 infection were included (receiving OCP/HRT, n=81; not receiving OCP/HRT, n=941). Most participants receiving OCP/HRT were treatment-naive (79%), noncirrhotic (91.4%), and aged >35 years (71.6%). SVR12 rates were similar in women receiving OCP/HRT and those not receiving OCP/HRT (95.1% vs 96.3%). SVR12 rates remained high across all subgroups within the population receiving OCP/HRT: SVR12 rates were 94.6%, 100%, and 100% in participants with GT1a, GT1b, and GT4 infection, and all women aged 18-35 years achieved SVR (21/21). Treatment-related adverse events occurred in 40.7% (33/81) and 30.1% (283/941) of women receiving and those not receiving OCP/HRT, respectively.

Conclusion

The efficacy and safety of EBR/GZR administered for 12 weeks was similar in women receiving OCP/HRT and those not on OCP/HRT. These data indicate that EBR/GZR can be safely used for the treatment of HCV GT1 or GT4 infection in women receiving concomitant OCP/HRT.

Elbasvir-grazoprevir: A new direct-acting antiviral combination for hepatitis C

PURPOSE

The chemistry, pharmacology, pharmacodynamics, pharmacokinetics, efficacy, safety, dosage, administration, and role of elbasvir-grazoprevir in the treatment of hepatitis C virus (HCV) infection are reviewed.

SUMMARY

Elbasvir-grazoprevir was recently approved by the Food and Drug Administration for the treatment of chronic HCV genotype 1 or 4 infections with or without ribavirin in patients with or without compensated cirrhosis. Elbasvir exhibits antiviral activity against HCV genotypes 1a, 1b, 2a, 3a, and 4a. Elbasvir-grazoprevir undergoes fecal excretion, does not require dosage adjustment in patients with renal impairment, and is contraindicated in moderate and severe hepatic impairment. In Phase II and III clinical trials, elbasvir-grazoprevir administered orally for 12 weeks was shown to achieve a high sustained virological response 12 weeks after the end of treatment. Elbasvir-grazoprevir is a once-daily, fixed-dose combination tablet that can be taken without regard to food. The adverse drug reactions most commonly reported include fatigue, headache, and nausea. Elbasvir-grazoprevir is indicated with ribavirin for treatment-naive and treatment-experienced patients with genotype 1a with baseline NS5A polymorphisms, for treatment-experienced patients with genotype 1b, and for treatment-experienced patients with genotype 4.

CONCLUSION

Elbasvir-grazoprevir achieves a high cure rate in the treatment of patients with chronic HCV with a once-daily oral regimen and without serious adverse effects; however, it requires close monitoring of liver function values. It is an effective option for patients with HCV genotype 1a, 1b, or 4 with or without compensated cirrhosis and is a particularly attractive option in patients with chronic kidney disease receiving hemodialysis and in patients with HIV coinfection.

Glecaprevir/pibrentasvir for the treatment of chronic hepatitis C virus infection

In recent years, management of chronic hepatitis C virus (HCV) infection has been revolutionized by the availability of oral direct-acting antivirals (DAAs), which have significantly better efficacy and safety profiles than interferon-containing regimens. Simple, short-duration DAA therapies will facilitate expansion of HCV treatment to nonspecialist providers, which will be vital to achieve the WHO target of eliminating chronic HCV as a major public health threat by 2030. Coformulated glecaprevir/pibrentasvir is the only 8-week, pan-genotypic, 2-DAA regimen recommended by international guidelines as a first-line regimen in treatment-naive, noncirrhotic HCV genotype 1-6 patients. This review provides a comprehensive summary of the pharmacodynamic and pharmacokinetic parameters, efficacy, safety and place in the HCV treatment paradigm for glecaprevir/pibrentasvir.

Efficacy and Safety of Ombitasvir/Paritaprevir/Ritonavir in Patients With Hepatitis C Virus Genotype 1 or 4 Infection and Advanced Kidney Disease

Introduction

Hepatitis C virus (HCV) infection is common in patients with end-stage renal disease. We investigated the safety and efficacy of ombitasvir (OBV)/paritaprevir (PTV)/ritonavir (r) ± dasabuvir (DSV) ± ribavirin (RBV) in 2 phase 3, open-label, multicenter studies in patients with stage 4 or 5 chronic kidney disease (CKD).

Methods

RUBY-I, Cohort 2 enrolled treatment-naïve or -experienced patients with HCV genotype (GT) 1a or 1b infection, with or without cirrhosis. Patients received 12 weeks (24 weeks for GT1a patients with cirrhosis) of OBV/PTV/r + DSV; all GT1a patients received RBV. RUBY-II enrolled treatment-naïve patients with GT1a or GT4 infection without cirrhosis. All patients received 12 weeks of RBV-free treatment: OBV/PTV/r + DSV for GT1a-infected patients; OBV/PTV/r for GT4-infected patients. The primary endpoint was sustained virologic response at posttreatment week 12 (SVR12).

Results

RUBY-I, Cohort 2 and RUBY-II enrolled 66 patients, including 50 (76%) on dialysis; 15 (23%) had compensated cirrhosis. Overall, the SVR12 rate was 95% (63/66); 1 patient had virologic failure. There were 3 discontinuations due to adverse events. Seventy-three percent (27/37) of patients receiving RBV had adverse events leading to RBV dose modification. The RBV-free RUBY-II study had no hemoglobin-associated adverse events.

Conclusion

Treatment with OBV/PTV/r ± DSV ± RBV was well tolerated and patients with HCV GT1 or 4 infection and stage 4 or 5 CKD had high SVR12 rates, including patients with compensated cirrhosis and/or prior treatment experience.

Characterization of hepatitis C virus resistance to grazoprevir reveals complex patterns of mutations following on-treatment breakthrough that are not observed at relapse

PURPOSE

A detailed analysis of hepatitis C virus (HCV) resistance-associated substitutions (RASs) is required to understand why people fail direct-acting antiviral therapies. This study was conducted to assess RASs in an analysis of 2 trials evaluating the second-generation NS3/4A protease inhibitor grazoprevir (GZR) in combination with peginterferon/ribavirin.

PATIENTS AND METHODS

From a total of 113 participants with HCV genotype 1 infection, RASs were evaluated in 25 patients who relapsed and 6 patients with on-treatment virologic breakthrough using consensus Sanger and clonal sequence analysis of NS3/NS4a genes, with in vitro testing of replicon mutants. Next-generation sequencing (NGS) was used in a subset of participants to assess minority variants and the evolution of the whole viral genome.

RESULTS

Baseline RASs did not predict treatment failure. Relapse was most commonly associated with RASs at D168, although additional RASs (Y56, R155 and A156) were also detected, particularly in participants with on-treatment breakthrough. Treatment-emergent RASs usually reverted to wild-type (WT), suggesting these mutations were associated with a negative fitness cost (confirmed using in vitro assays). NGS was the most sensitive assay for the detection of minor variants. Significant viral sequence divergence (up to 5.9% codons) was observed across whole genomes in association with the acquisition and reversion of RASs.

CONCLUSION

Relapse with GZR and peginterferon/ribavirin is commonly associated with single RASs in NS3 that generally revert to WT, while breakthrough follows more complex patterns of viral resistance. NGS suggests that large diverse pools of viral quasispecies that emerge with RASs facilitate rapid viral evolution.

Protease inhibitor therapy for hepatitis C virus-infection

INTRODUCTION

The hepatitis C virus (HCV) has affected an estimated of 80 million individuals worldwide and is a strain on public health. Around 25-30% of patients in Europe and the US who are infected with HIV are coinfected with HCV. Prior to 2013, treatment modalities containing an NS3/4A protease inhibitor in combination with pegylated interferon and ribavirin improved sustained virological response (SVR) rates. However, rates of severe side effects were high. Nowadays, oral direct-acting antiviral (DAA) combination therapy offers excellent treatment efficacy, safety and tolerability.

AREAS COVERED

This review focuses on the current literature and clinical evidence and their impact regarding NS3/4A protease inhibitors. The pitfalls encountered in treating HIV- and HBV-coinfected patients are also discussed.

EXPERT OPINION

In the era of DAA treatment, third-generation pan-genotypic NS3/4A protease inhibitors (mainly glecaprevir and voxilaprevir) show high antiviral activity and a genetic resistance barrier with cure rates of over 95% when combined with an NS5A inhibitor, irrespective of baseline resistance associated variants (RASs) being present. These new key components of DAA combination therapy are impressive options to eradicate HCV in the so-called difficult-to-treat population (e.g. compensated cirrhosis, end-stage renal disease and patients who failed previous DAA treatment).

In Vitro Antiviral Activity and Resistance Profile of the Next-Generation Hepatitis C Virus NS3/4A Protease Inhibitor Glecaprevir

Glecaprevir (formerly ABT-493) is a novel hepatitis C virus (HCV) NS3/4A protease inhibitor (PI) with pangenotypic activity. It inhibited the enzymatic activity of purified NS3/4A proteases from HCV genotypes 1 to 6 in vitro (half-maximal [50%] inhibitory concentration = 3.5 to 11.3 nM) and the replication of stable HCV subgenomic replicons containing proteases from genotypes 1 to 6 (50% effective concentration [EC50] = 0.21 to 4.6 nM). Glecaprevir had a median EC50 of 0.30 nM (range, 0.05 to 3.8 nM) for HCV replicons containing proteases from 40 samples from patients infected with HCV genotypes 1 to 5. Importantly, glecaprevir was active against the protease from genotype 3, the most-difficult-to-treat HCV genotype, in both enzymatic and replicon assays demonstrating comparable activity against the other HCV genotypes. In drug-resistant colony selection studies, glecaprevir generally selected substitutions at NS3 amino acid position A156 in replicons containing proteases from genotypes 1a, 1b, 2a, 2b, 3a, and 4a and substitutions at position D/Q168 in replicons containing proteases from genotypes 3a, 5a, and 6a. Although the substitutions A156T and A156V in NS3 of genotype 1 reduced susceptibility to glecaprevir, replicons with these substitutions demonstrated a low replication efficiency in vitro Glecaprevir is active against HCV with most of the common NS3 amino acid substitutions that are associated with reduced susceptibility to other currently approved HCV PIs, including those at positions 155 and 168. Combination of glecaprevir with HCV inhibitors with other mechanisms of action resulted in additive or synergistic antiviral activity. In summary, glecaprevir is a next-generation HCV PI with potent pangenotypic activity and a high barrier to the development of resistance.

The Second-generation of Highly Potent Hepatitis C Virus (HCV) NS3/4A Protease Inhibitors: Evolutionary Design Based on Tailor-made Amino Acids, Synthesis and Major Features of Bio-activity

Hepatitis C is a current pandemic liver disease caused by the hepatitis C virus (HCV) with high morbidity and mortality. Recently, the direct-acting antiviral agents (DAAs) targeting HCV NS3/4A, NS5A and NS5B have become the most effective therapies against HCV infection in the clinical treatment. Among them, the second-generation of NS3/4A inhibitors have emerged as the mainstay of the DAA therapies, which are derived from the peptide substrate of NS3/4A protease and modified with various tailor-made amino acids in order to achieve high sustained virologic response (SVR) against HCV. This review summarizes sixteen examples of the second-generation of HCV NS3/4A inhibitors, mainly focusing on the clinical application, structure development, structure-activity relationship (SAR) and their synthesis.

Protease inhibitors for the treatment of hepatitis C virus infection

The hepatitis C virus (HCV) has affected an estimate of 80 million individuals worldwide and is a strain of public health. Around 25-30% of patients in Europe and the US infected with HIV are coinfected with HCV. Despite treatment modalities containing a NS3/4A protease inhibitor in combination with pegylated interferon and ribavirin prior to 2013 improved SVR rates, the amount of severe side effects was high. Nowadays, oral direct-acting antivirals (DAAs) combination therapy offers excellent treatment efficacy, safety and tolerability. This review focuses on current literature and clinical evidence and their impact regarding NS3/4A protease inhibitors. In addition, pitfalls in treatment from HIV- and HBV-coinfected patients will also be discussed. In the era of DAA treatment, the third-generation pan-genotypic NS3/4A protease inhibitors (mainly grazoprevir, glecaprevir and voxilaprevir) show a high antiviral activity and genetic resistance barrier with cure rates of over 95% when combined with an NS5A inhibitor, irrespectively of baseline resistance associated variants (RASs) being present. These new key components of DAA combination therapy are impressive options to eradicate HCV in the so called difficult-to-treat population (e.g. compensated cirrhosis, end-stage renal disease and patients who failed previous DAA treatment).

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

AIM

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.

METHODS

A total of 206 patients with genotype-1b HCV infection, including 5 patients with previous simeprevir therapy, were treated with daclatasvir/asunaprevir for 24 weeks. Resistance-associated variants in the NS5A regions at baseline and during/after therapy were evaluated using cycling-probe real-time polymerase chain reaction combined with direct sequencing. The dynamics of rare RAVs were also assessed using ultra-deep sequencing.

RESULTS

A sustained virologic response (SVR12) was achieved in 180 patients (87%); the rates were 95% in patients without baseline NS5A-RAVs and 83%, 59%, and 77% in those with hepatitis C virus (HCV) strains carrying NS5A-L31M, NS5A-Y93H/C, and NS5A-R30Q/H/L mutations, respectively. A multivariate analysis revealed baseline NS5A-R30Q/H/L mutation and NS5A-Y93H mutations as significant factors associated with SVR12. Virologic failure developed in all 5 patients with previous simeprevir treatment, and rare RAVs (HCV strains with NS5A-R30H, NS5A-A92K, NS5A-P29del, and NS5A-P32del) developed at virologic failure. Ultra-deep sequencing revealed that HCV strains with NS5A-P29del or NS5A-P32del were absent at baseline and emerged within 4 weeks of dual oral therapy among the strains appearing after simeprevir administration.

CONCLUSION

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

GS-9857 in patients with chronic hepatitis C virus genotype 1-4 infection: a randomized, double-blind, dose-ranging phase 1 study

GS-9857, an inhibitor of the hepatitis C virus (HCV) nonstructural protein (NS) 3/4A, demonstrates potent activity against HCV genotypes 1-6 and improved coverage against commonly encountered NS3 resistance-associated variants (RAVs). In this study, the safety, tolerability, antiviral activity and pharmacokinetics (PK) of GS-9857 were evaluated in patients with chronic HCV genotype 1-4 infection. Patients with genotype 1-4 infection received placebo or once-daily GS-9857 at doses ranging from 50 to 300 mg for 3 days under fasting conditions. GS-9857 was well tolerated; all reported adverse events (AEs) were mild or moderate in severity. Diarrhoea and headache were the most commonly reported AEs. Grade 3 or 4 laboratory abnormalities were observed in 17% of patients receiving GS-9857; there were no Grade 3 or 4 abnormalities in alanine aminotransferase, aspartate aminotransferase or alkaline phosphatase levels. GS-9857 demonstrated potent antiviral activity in patients with chronic HCV infection, achieving mean and median maximum reductions in HCV RNA of ≥3 log10 IU/mL following administration of a 100-mg dose in patients with HCV genotype 1a, 1b, 2, 3 or 4 infection. The antiviral activity of GS-9857 was unaffected by the presence of pretreatment NS3 RAVs. In patients with genotype 1-4 infection, GS-9857 exhibited linear PK and was associated with a median half-life of 29-42 h, supporting once-daily dosing. Thus, the tolerability, efficacy and pharmacokinetic profile of GS-9857 support its further evaluation for treatment of patients with chronic HCV infection.

Open-label study of faldaprevir plus peginterferon and ribavirin in hepatitis C virus genotype 1-infected patients who failed placebo plus peginterferon and ribavirin

Faldaprevir, a hepatitis C virus (HCV) NS3/4A protease inhibitor, was evaluated in HCV genotype 1-infected patients who failed peginterferon and ribavirin (PegIFN/RBV) treatment during one of three prior faldaprevir trials. Patients who received placebo plus PegIFN/RBV and had virological failure during a prior trial were enrolled and treated in two cohorts: prior relapsers (n = 43) and prior nonresponders (null responders, partial responders and patients with breakthrough; n = 75). Both cohorts received faldaprevir 240 mg once daily plus PegIFN/RBV for 24 weeks. Prior relapsers with early treatment success (ETS; HCV RNA <25 IU/mL detectable or undetectable at week 4 and <25 IU/mL undetectable at week 8) stopped treatment at week 24. Others received PegIFN/RBV through week 48. The primary efficacy endpoint was sustained virological response (HCV RNA <25 IU/mL undetectable) 12 weeks post treatment (SVR12). More prior nonresponders than prior relapsers had baseline HCV RNA ≥ 800,000 IU/mL (80% vs 58%) and a non-CC IL28B genotype (91% vs 70%). Rates of SVR12 (95% CI) were 95.3% (89.1, 100.0) among prior relapsers and 54.7% (43.4, 65.9) among prior nonresponders; corresponding ETS rates were 97.7% and 65.3%. Adverse events led to faldaprevir discontinuations in 3% of patients. The most common Division of AIDS Grade ≥ 2 adverse events were anaemia (13%), nausea (10%) and hyperbilirubinaemia (9%). In conclusion, faldaprevir plus PegIFN/RBV achieved clinically meaningful SVR12 rates in patients who failed PegIFN/RBV in a prior trial, with response rates higher among prior relapsers than among prior nonresponders. The adverse event profile was consistent with the known safety profile of faldaprevir.

Direct anti-HCV agents

Unlike human immunodeficiency virus (HIV) and hepatitis B virus (HBV), hepatitis C virus (HCV) infection is a curable disease. Current direct antiviral agent (DAA) targets are focused on HCV NS3/4A protein (protease), NS5B protein (polymerase) and NS5A protein. The first generation of DAAs includes boceprevir and telaprevir, which are protease inhibitors and were approved for clinical use in 2011. The cure rate for genotype 1 patients increased from 45% to 70% when boceprevir or telaprevir was added to standard PEG-IFN/ribavirin. More effective and less toxic second generation DAAs supplanted these drugs by 2013. The second generation of DAAs includes sofosbuvir (Sovaldi), simeprevir (Olysio), and fixed combination medicines Harvoni and Viekira Pak. These drugs increase cure rates to over 90% without the need for interferon and effectively treat all HCV genotypes. With these drugs the “cure HCV” goal has become a reality. Concerns remain about drug resistance mutations and the high cost of these drugs. The investigation of new HCV drugs is progressing rapidly; fixed dose combination medicines in phase III clinical trials include Viekirax, asunaprevir+daclatasvir+beclabuvir, grazoprevir+elbasvir and others.

STARTVerso1: A randomized trial of faldaprevir plus pegylated interferon/ribavirin for chronic HCV genotype-1 infection

BACKGROUND & AIMS

The efficacy and tolerability of faldaprevir, a potent hepatitis C virus (HCV) NS3/4A protease inhibitor, plus peginterferon (PegIFN) and ribavirin (RBV) was assessed in a double-blind, placebo-controlled phase 3 study of treatment-naïve patients with HCV genotype-1 infection.

METHODS

Patients were randomly assigned (1:2:2) to PegIFN/RBV plus: placebo (arm 1, n = 132) for 24 weeks; faldaprevir (120 mg, once daily) for 12 or 24 weeks (arm 2, n = 259); or faldaprevir (240 mg, once daily) for 12 weeks (arm 3, n = 261). In arms 2 and 3, patients with early treatment success (HCV-RNA <25 IU/ml at week 4 and undetectable at week 8) stopped all treatment at week 24. Other patients received PegIFN/RBV until week 48 unless they met futility criteria. The primary endpoint was sustained virologic response 12 weeks post-treatment (SVR12).

RESULTS

SVR12 was achieved by 52%, 79%, and 80% of patients in arms 1, 2, and 3, respectively (estimated difference for arms 2 and 3 vs. arm 1: 27%, 95% confidence interval 17%-36%; and 29%, 95% confidence interval, 19%-38%, respectively; p < 0.0001 for both). Early treatment success was achieved by 87% (arm 2) and 89% (arm 3) of patients, of whom 86% and 89% achieved SVR12. Adverse event rates were similar among groups; few adverse events led to discontinuation of all regimen components.

CONCLUSIONS

Faldaprevir plus PegIFN/RBV significantly increased SVR12, compared with PegIFN/RBV, in treatment-naïve patients with HCV genotype-1 infection. No differences were seen in responses of patients given faldaprevir once daily at 120 or 240 mg.

Emerging treatments for chronic hepatitis C

Advances in understanding the hepatitis C virus (HCV) life cycle and the urgent need to find complementary direct-acting antiviral (DAA) therapies has led to substantial advancements in treating chronic hepatitis C. The introduction of telaprevir and boceprevir in 2011 increased the sustained virological response (SVR) rate from approximately 50% to > 70%, but this therapy further restricted patient eligibility and is only approved for treating HCV genotype 1 infection. Interferon has long remained the backbone of HCV therapy and helps prevent viral breakthrough. However, interferon has limited effectiveness and is associated with severe adverse effects and toxicity, especially among cirrhotic patients. Moving to interferon-free therapies should greatly improve SVR rates and offer new treatments for other HCV genotypes and for ineligible patients or patients failing to respond to prior therapies. However, without the relative safety of interferon to suppress viral escape, vigilance will be required to select appropriate therapies and monitor resistance. Several DAAs are currently undergoing clinical trials and will soon undergo the approval process. Goals of future HCV clinical research will be to identify combinations of DAAs with high genetic barriers, investigate optimal treatment doses and durations, and determine the role of ribavirin in DAA therapies.

A case of successful treatment with telaprevir-based triple therapy for hepatitis C infection after treatment failure with vaniprevir-based triple therapy

Recently direct-acting antiviral agents, such as hepatitis C virus (HCV) non-structural 3/4A (NS3/4A) protease inhibitors (PI), have been introduced, and triple therapy regimens that include PI with conventional pegylated interferon α and ribavirin have significantly improved the sustained virological response (SVR) rate, up to 80% for both treatment-naïve and treatment-experienced patients with HCV genotype 1. We here report for the first time a case of the successful treatment of HCV genotype 1 infection with a first generation PI drug (telaprevir) based triple therapy after treatment failure with a second generation PI drug (vaniprevir) based triple therapy. A 67-year-old treatment-naïve Japanese man with HCV genotype 1b infection took part in a phase III clinical trial of vaniprevir-based triple therapy. His serum HCV RNA had become undetectable at week 2 and SVR was highly expected, but HCV RNA reappeared at week 4 after vaniprevir treatment. Polymerase chain reaction direct sequence of the HCV NS3/4A gene at week 8 after vaniprevir treatment showed the emergence of a vaniprevir-resistance mutation (D168V), the probable reason for the treatment failure. Six months later, retreatment with telaprevir-based triple therapy was started. Although the dosages of telaprevir and ribavirin had to be reduced due to severe anemia, the patient achieved an SVR. This case shows the value of repeating PI-based triple therapy with a different drug, a process that would reduce the chance of drug resistant mutation.

Development of boceprevir: a first-in-class direct antiviral treatment for chronic hepatitis C infection

The identification of hepatitis C virus (HCV) as the causative agent of non-A and non-B hepatitis, over 20 years ago, fueled an intensive effort to develop direct-acting antivirals targeting the viral polymerase and protease, two key proteins critical for HCV replication. However, it took more than two decades for these efforts to be realized with boceprevir, one of the two HCV protease inhibitors approved for treatment of HCV infection in 2011. The development of boceprevir is a major advancement in the ability to treat HCV infection and a significant step toward the long-term goal of eradicating chronic HCV infection. Both as a first-in-class agent and an entirely new modality for treating HCV infection, many challenges were encountered during the discovery and development of this compound. The lessons learned in overcoming these obstacles offer insights and pave the way for the newly emerging field of HCV antiviral therapeutics. This paper will describe the discovery and development of a first-in-class direct antiviral treatment for chronic hepatitis C infection, boceprevir, marketed around the world as Victrelis™.