ABT-450/r-ombitasvir and dasabuvir with or without ribavirin for HCV

Chronic Hepatitis C Infection in Children: Current Treatment and New Therapies

Viral hepatitis C is responsible for a large burden of disease worldwide. Treatment of hepatitis C infection is currently undergoing a revolution with the development of new direct acting antivirals that offer higher cure rates and fewer side effects than other medications currently available. Treatment options for children, although well-defined and evidence-based, are limited relative to adults as there are few trials regarding the use of these newly developed agents in children. With so much optimism in the development of novel therapeutic options for hepatitis C, it is timely to review and summarize the current standard of care treatment and indications for treatment of chronic hepatitis C in children. We provide here an overview of recent drug developments and their potential for use in children.

Enhancing our understanding of current therapies for hepatitis C virus (HCV)

Great progress has been made in understanding the HCV genome and its molecular virology. This understanding has culminated in the development of direct-acting antiviral (DAA) agents targeting HCV viral proteins. Telaprevir (TVR) and boceprevir (BOC) were the first DAAs introduced for treatment of genotype 1 HCV in 2011; when used in combination with pegylated interferon (pegIFN) and ribavirin (RBV), these protease inhibitors improved efficacy in patients with chronic HCV infection compared to the traditional dual therapy. However, this combination was associated with adverse events that often led to early termination of therapy. In late 2013, the FDA approved a second wave of DAAs, sofosbuvir (SOF) and simeprevir (SMV). The use of SOF with SMV opened the door for IFN-free combination regimens. This combination was highly efficacious and well tolerated in patients with HCV genotype 1. Sofosbuvir and ledipasvir (LDV) fixed-dose oral combination (FDC) therapy, and paritaprevir/ritonavir, ombitasvir and dasabuvir ± RBV were recently approved, elevating sustained virologic response (SVR) rates to over 95 %. We are anticipating the approval of additional IFN-free regimens with comparable efficacy and tolerability but with the addition of pangenotypic coverage, fewer drug-drug interactions, and a high barrier to resistance. This review will summarize current management for chronic HCV infection.

Dasabuvir : a new direct antiviral agent for the treatment of hepatitis C

INTRODUCTION

Treatment of hepatitis C virus (HCV) infection with direct-acting antivirals (DAAs) has revolutionized the care of infected patients. Among these novel compounds are non-nucleoside analogs, which bind viral RNA-dependent RNA polymerase resulting in a conformational change inhibiting RNA synthesis.

AREAS COVERED

Efficacy and tolerability of treatment regimens containing the non-nucleoside analog polymerase inhibitor dasabuvir (ABT-333).

EXPERT OPINION

Dasabuvir-containing regimens achieve high rates of sustained virologic response in HCV genotype 1a and 1b-infected patients when combined with other DAAs, namely paritaprevir (ABT-450), ritonavir and ombitasvir (ABT-267). In the populations studied, dasabuvir seems to be well tolerated and safe. The major limitations of this novel drug are its genotype-restricted activity, the necessity to include ribavirin for HCV genotype 1a and the emergence of resistance if not combined with other DDAs.

Evolution of hepatitis C virus quasispecies during repeated treatment with the NS3/4A protease inhibitor telaprevir

In treating hepatitis B virus (HBV) and human immunodeficiency virus (HIV) infections, the rapid reselection of resistance-associated variants (RAVs) is well known in patients with repeated exposure to the same class of antiviral agents. For chronic hepatitis C patients who have experienced virologic failure with direct-acting antiviral drugs, the potential for the reselection of persistent RAVs is unknown. Nine patients who received 14 days of telaprevir monotherapy were retreated with telaprevir-based triple therapy 4.3 to 5.7 years later. In four patients with virologic failure with both telaprevir-containing regimens, population-based and deep sequencing (454 GS-FLX) of the NS3 protease gene were performed before and at treatment failure (median coverage, 4,651 reads). Using deep sequencing, with a threshold of 1.0% for variant calling, no isolates were found harboring RAVs at the baseline time points. While population-based sequencing uncovered similar resistance patterns (V36M plus R155K for subtype 1a and V36A for subtype 1b) in all four patients after the first and second telaprevir treatments, deep sequencing analysis revealed a median of 7 (range, 4 to 23) nucleotide substitutions on the NS3 backbone of the resistant strains, together with large phylogenetic differences between viral quasispecies, making the survival of resistant isolates highly unlikely. In contrast, in a comparison of the two baseline time points, the median number of nucleotide exchanges in the wild-type isolates was only 3 (range, 2 to 8), reflecting the natural evolution of the NS3 gene. In patients with repeated direct antiviral treatment, a continuous evolution of HCV quasispecies was observed, with no clear evidence of persistence and reselection but strong signs of independent de novo generation of resistance. Antiviral therapy for chronic viral infections, like HIV, hepatitis B virus (HBV), or hepatitis C virus (HCV), faces several challenges. These viruses have evolved survival strategies and proliferate by escaping the host's immune system. The development of direct-acting antiviral agents is an important achievement in fighting these infections. Viral variants conferring resistance to direct antiviral drugs lead to treatment failure. For HIV/HBV, it is well known that viral variants associated with treatment failure will be archived and reselected rapidly during retreatment with the same drug/class of drugs. We explored the mechanisms and rules of how resistant variants are selected and potentially reselected during repeated direct antiviral therapies in chronically HCV-infected patients. Interestingly, in contrast to HIV and HBV, we could not prove long-term persistence and reselection of resistant variants in HCV patients who failed protease inhibitor-based therapy. This may have important implications for the potential to reuse direct-acting antivirals in patients who failed the initial direct antiviral treatment. (The phase IIIb study described in this paper is registered at ClinicalTrials.gov under registration number NCT01054573.).

Ombitasvir/paritaprevir/ritonavir and dasabuvir tablets for hepatitis C virus genotype 1 infection

OBJECTIVE

To review the data with ombitasvir/paritaprevir/ritonavir and dasabuvir for the treatment of chronic hepatitis C virus (HCV) genotype 1 infection.

DATA SOURCES

Phase I, II, and III trials and review articles were identified through MEDLINE (1996-January 2015) and PubMed (1996-January 2015), conference abstracts, and US national clinical trials registry, using the keywords NS3/4A protease inhibitor, NS5A inhibitor, NS5B polymerase inhibitor, ABT-450, ABT-267, ABT-333, paritaprevir, ombitasvir, and dasabuvir.

STUDY SELECTION AND DATA EXTRACTION

Preclinical, phase I, II, and III studies describing pharmacology, pharmacokinetics, efficacy, safety, and tolerability were identified.

DATA SYNTHESIS

Noncirrhotic patients with HCV genotype 1b experienced sustained virological response 12 weeks after completion of therapy (SVR12) rates of 96% to 100% when ombitasvir/paritaprevir/ritonavir and dasabuvir were administered for 12 weeks, regardless of inclusion of ribavirin. SVR12 rates of 95% to 97% were seen in noncirrhotic patients with HCV genotype 1a infection who received ombitasvir/paritaprevir/ritonavir and dasabuvir with ribavirin for 12 weeks. Patients with Child-Pugh Class A cirrhosis also experienced high SVR12 rates (91.8%) when ombitasvir/paritaprevir/ritonavir and dasabuvir were administered with ribavirin for 12 weeks. Cirrhotic patients with HCV genotype 1a and a history of prior null response to peginterferon/ribavirin have higher SVR12 rates when ombitasvir/paritaprevir/ritonavir and dasabuvir and ribavirin are administered for 24 instead of 12 weeks (94.2% vs 88.6%). Adverse events are typically mild, most commonly consisting of fatigue, headache, nausea, and diarrhea.

CONCLUSION

The regimen consisting of ombitasvir/paritaprevir/ritonavir and dasabuvir is highly efficacious in the treatment of HCV genotype 1 infection, with minimal adverse events. It is expected to play an important role in the armamentarium of novel agents that have a high chance of curing HCV infection.

Population pharmacokinetic modeling of plasma and intracellular ribavirin concentrations in patients with chronic hepatitis C virus infection

Ribavirin, a guanosine analog, is a broad-spectrum antiviral agent. Ribavirin has been a fundamental component of the treatment of hepatitis C virus (HCV) infection for decades, but there is a very limited understanding of the clinical pharmacology of this drug. Furthermore, it is associated with a major dose-limiting toxicity, hemolytic anemia. Ribavirin undergoes intracellular phosphorylation by host enzymes to ribavirin monophosphate (RMP), ribavirin diphosphate (RDP), and ribavirin triphosphate (RTP). The intracellular forms have been associated with antiviral and toxic effects in vitro, but the kinetics of these phosphorylated moieties have not been fully elucidated in vivo. We developed a model to characterize the plasma pharmacokinetics of ribavirin and the difference between intracellular phosphorylation kinetics in red cells (nonnucleated) and in peripheral blood mononuclear cells (nucleated). A time-independent two-compartment model with first-order absorption described the plasma data well. The cellular phosphorylation kinetics was described by a one-compartment model for RMP, with the formation rate driven by plasma concentrations and the first-order degradation rate. RDP and RTP rapidly reached equilibrium with RMP. Concomitant telaprevir use, inosine triphosphatase genetics, creatinine clearance, weight, and sex were significant covariates. The terminal ribavirin half-life in plasma and phosphorylated anabolites in cells was approximately 224 h. We found no evidence of time-dependent kinetics. These data provide a foundation for uncovering concentration-effect associations for ribavirin and determining the optimal dose and duration of this drug for use in combination with newer direct-acting HCV agents. (This study has been registered at ClinicalTrials.gov under registration no. NCT01097395.).

The ongoing debate of who to treat for chronic hepatitis C virus

Chronic hepatitis C virus (HCV) infection is a major cause of cirrhosis and hepatocellular carcinoma worldwide and the leading indication for liver transplantation in the adult United States population. Although the incidence of chronic HCV infection is declining, the number of deaths is projected to rise over the next decade. Hence, the major reason for treating chronic HCV infection is to mitigate the morbidity and mortality associated with the infection but also to alleviate patient symptoms and to prevent person-to-person transmission. Successful eradication or virological cure is possible and a reduction in liver-related outcomes has been demonstrated in patients with advanced liver disease who achieve this desirable endpoint.^–

Simeprevir and sofosbuvir for treatment of chronic hepatitis C infection

PURPOSE

Chronic hepatitis C infection affects a large proportion of the world's population and can lead to significant morbidity and mortality. The standard of care for treatment of hepatitis C infection has been peginterferon and ribavirin, with or without a first-generation protease inhibitor. In late 2013 and early 2014, sofosbuvir and simeprevir obtained regulatory approval, offering the first possibility for all-oral treatment regimens. We provide a review of the clinical efficacy and safety of sofosbuvir- and simeprevir-containing regimens.

METHODS

Studies were identified in PubMed using the terms sofosbuvir and simeprevir in combination with hepatitis C. Abstracts of additional studies presented at professional meetings but not yet published were also reviewed. All Phase 3 trials published by August 1, 2014, as well as Phase 2 studies for which there was not a corresponding Phase 3 trial, were included in the review.

FINDINGS

Simeprevir was studied with peginterferon and ribavirin in 7 published Phase 3 trials, with overall efficacy rates of 59% to 100%. Sofosbuvir was studied with ribavirin and with or without peginterferon in 6 Phase 3 trials with overall efficacy rates of 50% to 93%. Patient groups with lower response rates tended to have cirrhosis and be older, men, and previous null responders. Simeprevir and sofosbuvir were studied in combination in 1 Phase 2a study with overall efficacy of 92%. Additional studies demonstrated the efficacy and safety of sofosbuvir regimens in patients before and after liver transplantation. Overall, the simeprevir- and sofosbuvir-containing regimens were tolerated better or as well as peginterferon and ribavirin regimens, with fatigue, headache, and nausea the most common adverse events.

IMPLICATIONS

Results from numerous Phase 3 clinical trials indicate that sofosbuvir- and simeprevir-containing regimens are highly effective and safe for the treatment of chronic hepatitis C infection. The approval of these 2 agents has led to a complete overhaul of published guidelines, with sofosbuvir- and simeprevir-containing regimens included in preferred regimens.

CIHR Canadian HIV Trials Network Co-Infection and Concurrent Diseases Core: Updated Canadian guidelines for the treatment of hepatitis C infection in HIV-hepatitis C coinfected adults

Treatment of HIV-hepatitis C virus (HCV)-coinfected individuals is considerably more complex than the treatment of monoinfected individuals, due to several factors including interactions among medications and accelerated progression of liver disease. Since the first Canadian guidelines for the treatment of HIV-HCV coinfected patients were published in the Winter 2013 issue of the Journal, several new medications that show considerable promise for the treatment of HCV have become available in Canada. Thus, the authors provide an update to the 2013 guidelines and include updated recommendations for treatment that incorporate these new medications.

BACKGROUND:

Hepatitis C virus (HCV) coinfection occurs in 20% to 30% of Canadians living with HIV and is responsible for a heavy burden of morbidity and mortality. Management of HIV-HCV coinfection is more complex due to the accelerated progression of liver disease, the timing and nature of antiretroviral and HCV therapy, mental health and addictions management, socioeconomic obstacles and drug-drug interactions between new HCV direct-acting antiviral therapies and antiretroviral regimens.

OBJECTIVE:

To update national standards for the management of HCV-HIV coinfected adults in the Canadian context.

METHODS:

A standing working group with specific clinical expertise in HIV-HCV coinfection was convened by The Canadian Institute of Health Research HIV Trials Network to review recently published data regarding HCV antiviral treatments and to update the Canadian HIV-HCV coinfection guidelines.

RESULTS:

Recent data suggest that the gap in sustained virological response rates between HCV monoinfection and HIV-HCV coinfection has been eliminated with newer HCV antiviral regimens. All HIV-HCV coinfected individuals should be assessed for HCV therapy. First-line treatment for genotypes 1 through 6 includes pegylated interferon and weight-based ribavirin dosing plus the nucleotide sofosbuvir for 12 weeks. Sofosbuvir in combination with the protease inhibitor simeprevir is another first-line consideration for genotype 1 infection. Sofosbuvir with ribavirin for 12 weeks (genotype 2) and 24 weeks (genotype 3) is also recommended as first-line treatment.

DISCUSSION:

Recommendations may not supersede individual clinical judgement.

Optimal IFN-free therapy in treatment-naïve patients with HCV genotype 1 infection

There has been a revolution in the treatment of chronic hepatitis C. Several oral regimens combining direct-acting antivirals (DAAs) from different families [NS5B nucleotide inhibitors, NS5B non-nucleoside inhibitors, NS5A replication complex inhibitors and NS3/4A protease inhibitors (PI)] are under development. These regimens result in an increase in sustained virological response (SVR) rates to above 90% and reduce the duration of treatment to twelve weeks or less. As of 2015 several regimens will be approved with additive potencies, without cross-resistance and with a good safety profile. Remaining issues will include increasing screening and access to care so that HCV may become the first chronic viral infection eradicated worldwide. This review summarizes results obtained with oral DAAs combinations, that have been approved and/or have completed phase III clinical trials for HCV genotype 1 (HCV-1) treatment-naïve patients.

Cure of HCV related liver disease

Chronic hepatitis C virus (HCV) causes chronic liver injury and can lead to cirrhosis and hepatocellular carcinoma (HCC). HCV can also interact with the immune system to cause several HCV related disorders including essential mixed cryoglobulinemia, vasculitis, dermatitis, glomerulonephritis and lymphoma. A strong association between HCV and diabetes mellitus also exists. These extrahepatic features may lead to increased fatigue and a reduced quality of life. It is now possible to cure most patients with chronic HCV using oral antiviral therapy. Many of these HCV-related disorders and symptoms can be cured when HCV is eradicated. However, some patients may have irreversible injury to extrahepatic sites, cirrhosis that cannot resolve, an increased risk for HCC, persistent fatigue and a reduced quality of life, despite achieving sustained virological response.

Current and future HCV therapy: do we still need other anti-HCV drugs?

Eradication of hepatitis C virus (HCV) infection, at least in compensated patients, can help improve the outcomes of liver disease such as cirrhosis, hepatocellular carcinoma (HCC) and liver transplantation, as well as perhaps extra-hepatic complications such as diabetes and cardiovascular risk. In the past few years, the landscape of antiviral therapy has evolved at a breathtaking pace from pegylated interferon (PEG-IFN) plus ribavirin (RBV) (PEG-IFN/RBV) to IFN-based strategies combining direct acting antivirals (DDAs) with PEG-IFN/RBV and finally IFN-free combinations of DAAs. In particular with these most recent developments, treatment regimens have become shorter, safer and even more effective, with a wide range of indications. Nevertheless, research continues and newer antiviral drugs are still under development. At a point when a >90% sustained virological response (SVR) is being claimed with all new available regimens, pharmacological and clinical research should be addressing unresolved areas, such as cases of suboptimal SVR or to increase effectiveness rather than pursuing the development of new 'me-too' drugs. The issues which should be given priority for further development include the following: Improving the results of IFN-free regimens in patients with genotype 3 (HCV-3) infection. Identifying the indications for the treatment in patients with compensated and decompensated cirrhosis. Identifying standardized or personalized backup strategies in patients who do not respond to IFN-free regimens. Finally, because of financial constraints, the high cost of IFN-free strategies prevents their universal use in CHC patients and coverage by national healthcare systems. Thus, efforts must be made to document cost-effectiveness in all clinical scenarios and to develop more affordable IFN-free regimens.

An update on the management of chronic hepatitis C: 2015 Consensus guidelines from the Canadian Association for the Study of the Liver

Chronic hepatitis C remains a significant medical and economic burden in Canada, affecting nearly 1% of the population. Since the last Canadian consensus conference on the management of chronic hepatitis C, major advances have occurred that warrant a review of recommended management approaches for these patients. Specifically, direct-acting antiviral agents with dramatically improved rates of virological clearance compared with standard therapy have been developed and interferon-free, all-oral antiviral regimens have been approved. In light of this new evidence, an update to the 2012 Canadian Association for the Study of the Liver consensus guidelines on the management of hepatitis C was produced. The present document reviews the epidemiology of hepatitis C in Canada, preferred diagnostic testing approaches and recommendations for the treatment of chronically infected patients with the newly approved antiviral agents, including those who have previously failed peginterferon and ribavirin-based therapy. In addition, recommendations are made regarding approaches to reducing the burden of hepatitis C in Canada.

Optimal management of patients with chronic hepatitis C and comorbidities

Although HCV infection mainly induces liver injury, chronic disease is systemic. Moreover, host and viral factors, as well as comorbidities, may influence the chance of achieving a sustained virological response or disease outcome. Although there are sufficient data on the use of peg-interferon and ribavirin in patients with comorbidities, there is very little data on first generation protease inhibitors, which include significant drug-drug interactions and have therefore been administered with caution in these patients. The availability of new, more effective direct acting antivirals should significantly change this scenario. All these issues are discussed in this review.

Optimizing triple therapy and IFN/RBV-free regimens for hepatitis C virus infection

Treatment of chronic hepatitis C virus infection has substantially improved following the advent of direct acting antiviral (DAA) agents. Although the first generation protease inhibitors telaprevir and boceprevir improved sustained viral response (SVR) rates, adverse events remain severe and immature termination of the therapy is frequent; however, intensive dose modification has improved completion and SVR rates. Interferon-free DAA combination therapies, such as asunaprevir and daclatasvir dual therapy are under development and promise higher SVR rates with fewer adverse events. Resistance monitoring and modification of DAA therapy based on pre-existing or de novo resistance variants should be considered. Future therapies are expected to have pan-genotypic activity with shorter duration and improved tolerability, even among cirrhotic and liver transplant patients.

In vitro activity and resistance profile of dasabuvir, a nonnucleoside hepatitis C virus polymerase inhibitor

Dasabuvir (ABT-333) is a nonnucleoside inhibitor of the RNA-dependent RNA polymerase encoded by the hepatitis C virus (HCV) NS5B gene. Dasabuvir inhibited recombinant NS5B polymerases derived from HCV genotype 1a and 1b clinical isolates, with 50% inhibitory concentration (IC50) values between 2.2 and 10.7 nM, and was at least 7,000-fold selective for the inhibition of HCV genotype 1 polymerases over human/mammalian polymerases. In the HCV subgenomic replicon system, dasabuvir inhibited genotype 1a (strain H77) and 1b (strain Con1) replicons with 50% effective concentration (EC50) values of 7.7 and 1.8 nM, respectively, with a 13-fold decrease in inhibitory activity in the presence of 40% human plasma. This level of activity was retained against a panel of chimeric subgenomic replicons that contained HCV NS5B genes from 22 genotype 1 clinical isolates from treatment-naive patients, with EC50s ranging between 0.15 and 8.57 nM. Maintenance of replicon-containing cells in medium containing dasabuvir at concentrations 10-fold or 100-fold greater than the EC50 resulted in selection of resistant replicon clones. Sequencing of the NS5B coding regions from these clones revealed the presence of variants, including C316Y, M414T, Y448C, Y448H, and S556G, that are consistent with binding to the palm I site of HCV polymerase. Consequently, dasabuvir retained full activity against replicons known to confer resistance to other polymerase inhibitors, including the S282T variant in the nucleoside binding site and the M423T, P495A, P495S, and V499A single variants in the thumb domain. The use of dasabuvir in combination with inhibitors targeting HCV NS3/NS4A protease (ABT-450 with ritonavir) and NS5A (ombitasvir) is in development for the treatment of HCV genotype 1 infections.

An interferon-free antiviral regimen for HCV after liver transplantation

BACKGROUND

Hepatitis C virus (HCV) infection is the leading indication for liver transplantation worldwide, and interferon-containing regimens are associated with low response rates owing to treatment-limiting toxic effects in immunosuppressed liver-transplant recipients. We evaluated the interferon-free regimen of the NS5A inhibitor ombitasvir coformulated with the ritonavir-boosted protease inhibitor ABT-450 (ABT-450/r), the nonnucleoside NS5B polymerase inhibitor dasabuvir, and ribavirin in liver-transplant recipients with recurrent HCV genotype 1 infection.

METHODS

We enrolled 34 liver-transplant recipients with no fibrosis or mild fibrosis, who received ombitasvir-ABT-450/r (at a once-daily dose of 25 mg of ombitasvir, 150 mg of ABT-450, and 100 mg of ritonavir), dasabuvir (250 mg twice daily), and ribavirin for 24 weeks. Selection of the initial ribavirin dose and subsequent dose modifications for anemia were at the investigator's discretion. The primary efficacy end point was a sustained virologic response 12 weeks after the end of treatment.

RESULTS

Of the 34 study participants, 33 had a sustained virologic response at post-treatment weeks 12 and 24, for a rate of 97% (95% confidence interval, 85 to 100). The most common adverse events were fatigue, headache, and cough. Five patients (15%) required erythropoietin; no patient required blood transfusion. One patient discontinued the study drugs owing to adverse events after week 18 but had a sustained virologic response. Blood levels of calcineurin inhibitors were monitored, and dosages were modified to maintain therapeutic levels; no episode of graft rejection was observed during the study.

CONCLUSIONS

Treatment with the multitargeted regimen of ombitasvir-ABT-450/r and dasabuvir with ribavirin was associated with a low rate of serious adverse events and a high rate of sustained virologic response among liver-transplant recipients with recurrent HCV genotype 1 infection, a historically difficult-to-treat population. (Funded by AbbVie; CORAL-I ClinicalTrials.gov number, NCT01782495.).

Sofosbuvir as backbone of interferon free treatments

Sofosbuvir is the first-in-class NS5B nucleotide analogues to be launched for hepatitis C virus (HCV) treatment. Its viral potency, pangenotypic activity and high barrier to resistance make it the ideal candidate to become a backbone for several IFN-free regimens. Recent data demonstrated that sofosbuvir either with ribavirin alone or in combination with other direct-acting antivirals (DAAs) as daclatasvir, ledipasvir or simeprevir are able to cure HCV in at least 90% or over of patients. Treatment experienced genotype 3 population may remain the most difficult to treat population, but ongoing DAA combination studies will help to fill this gap. Safety profile of sofosbuvir or combination with other DAAs is good. Resistance to sofosbuvir did not appear as a significant issue. The rationale for using this class of drug and the available clinical data are reviewed.

The impact of the new antiviral regimens on patient reported outcomes and health economics of patients with chronic hepatitis C

Hepatitis C is an important cause of chronic liver disease worldwide with an estimated 170 million people infected. Hepatitis C virus (HCV)-infected patients are physically and mentally impacted by fatigue, depression and anxiety causing an impairment of health related quality of life (HRQOL), lower worker productivity and other patient reported outcomes (PROs). Although anti-HCV regimens containing first generation direct acting antiviral agents (DAAs) were associated with significant side effects, the second generation DAAs, sofosbuvir (SOF) and simeprevir (SMV), are associated with fewer side effects, better tolerability and high cure rates. Despite these advantages, key stakeholders are currently trying to find ways to best integrate these new therapeutic regimens into the management of patients with chronic hepatitis C for the benefit of all. The purpose of this article is to offer insight into the other key and equally important outcomes (PRO's, HRQOL and cost) which should be considered when assessing the applicability of these new regimens for the care of patients infected with HCV. Our review provides evidence that the new treatment regimens for HCV not only have high efficacy rates but are also associated with better patient reported outcomes and cost per case of HCV cured. Additionally, compared to other medical interventions, these new regimens are cost-effective from a societal perspective.

In vitro and in vivo antiviral activity and resistance profile of the hepatitis C virus NS3/4A protease inhibitor ABT-450

The development of direct-acting antiviral agents is a promising therapeutic advance in the treatment of hepatitis C virus (HCV) infection. However, rapid emergence of drug resistance can limit efficacy and lead to cross-resistance among members of the same drug class. ABT-450 is an efficacious inhibitor of HCV NS3/4A protease, with 50% effective concentration values of 1.0, 0.21, 5.3, 19, 0.09, and 0.69 nM against stable HCV replicons with NS3 protease from genotypes 1a, 1b, 2a, 3a, 4a, and 6a, respectively. In vitro, the most common amino acid variants selected by ABT-450 in genotype 1 were located in NS3 at positions 155, 156, and 168, with the D168Y variant conferring the highest level of resistance to ABT-450 in both genotype 1a and 1b replicons (219- and 337-fold, respectively). In a 3-day monotherapy study with HCV genotype 1-infected patients, ABT-450 was coadministered with ritonavir, a cytochrome P450 3A4 inhibitor shown previously to markedly increase peak, trough, and overall drug exposures of ABT-450. A mean maximum HCV RNA decline of 4.02 log10 was observed at the end of the 3-day dosing period across all doses. The most common variants selected in these patients were R155K and D168V in genotype 1a and D168V in genotype 1b. However, selection of resistant variants was significantly reduced at the highest ABT-450 dose compared to lower doses. These findings were informative for the subsequent evaluation of ABT-450 in combination with additional drug classes in clinical trials in HCV-infected patients. (Study M11-602 is registered at ClinicalTrials.gov under registration no. NCT01074008.).

In vitro and in vivo antiviral activity and resistance profile of ombitasvir, an inhibitor of hepatitis C virus NS5A

Ombitasvir (ABT-267) is a hepatitis C virus (HCV) NS5A inhibitor with picomolar potency, pan-genotypic activity, and 50% effective concentrations (EC50s) of 0.82 to 19.3 pM against HCV genotypes 1 to 5 and 366 pM against genotype 6a. Ombitasvir retained these levels of potency against a panel of 69 genotype 1 to 6 chimeric replicons containing the NS5A gene derived from HCV-infected patients, despite the existence of natural sequence diversity within NS5A. In vitro resistance selection identified variants that conferred resistance to ombitasvir in the HCV NS5A gene at amino acid positions 28, 30, 31, 58, and 93 in genotypes 1 to 6. Ombitasvir was evaluated in vivo in a 3-day monotherapy study in 12 HCV genotype 1-infected patients at 5, 25, 50, or 200 mg dosed once daily. All patients in the study were HCV genotype 1a infected and were without preexisting resistant variants at baseline as determined by clonal sequencing. Decreases in HCV RNA up to 3.1 log10 IU/ml were observed. Resistance-associated variants at position 28, 30, or 93 in NS5A were detected in patient samples 48 hours after the first dose. Clonal sequencing analysis indicated that wild-type virus was largely suppressed by ombitasvir during 3-day monotherapy, and at doses higher than 5 mg, resistant variant M28V was also suppressed. Ombitasvir was well tolerated at all doses, and there were no serious or severe adverse events. These data support clinical development of ombitasvir in combination with inhibitors targeting HCV NS3/4A protease (ABT-450 with ritonavir) and HCV NS5B polymerase (ABT-333, dasabuvir) for the treatment of chronic HCV genotype 1 infection. (Study M12-116 is registered at ClinicalTrials.gov under registration no. NCT01181427.).

Performance of two HCV RNA assays during protease inhibitor-based triple therapy in patients with advanced liver fibrosis and cirrhosis

Introduction

On-treatment HCV RNA measurements are crucial for the prediction of a sustained virological response (SVR) and to determine treatment futility during protease inhibitor-based triple therapies. In patients with advanced liver disease an accurate risk/benefit calculation based on reliable HCV RNA results can reduce the number of adverse events. However, the different available HCV RNA assays vary in their diagnostic performance.

Aim

To investigate the clinical relevance of concordant and discordant results of two HCV RNA assays during triple therapy with boceprevir and telaprevir in patients with advanced liver fibrosis/cirrhosis.

Methods

We collected on-treatment samples of 191 patients with advanced liver fibrosis/cirrhosis treated at four European centers for testing with the Abbott RealTime (ART) and COBAS AmpliPrep/COBAS TaqMan HCV v2.0 (CTM) assays.

Results

Discordant test results for HCV RNA detectability were observed in 23% at week 4, 17% at week 8/12 and 9% at week 24 on-treatment. The ART detected HCV RNA in 41% of week 4 samples tested negative by the CTM. However, the positive predictive value of an undetectable week 4 result for SVR was similar for both assays (80% and 82%). Discordance was also found for application of stopping rules. In 27% of patients who met stopping rules by CTM the ART measured levels below the respective cut-offs of 100 and 1000 IU/ml, respectively, which would have resulted in treatment continuation. In contrast, in nine patients with negative HCV RNA by CTM at week 24 treatment would have been discontinued due to detectable residual HCV RNA by the ART assay. Importantly, only 4 of these patients failed to achieve SVR.

Conclusion

Application of stopping rules determined in approval studies by one assay to other HCV RNA assays in clinical practice may lead to over and undertreatment in a significant number of patients undergoing protease inhibitor-based triple therapy.

Hepatitis C virus-associated cancer

Hepatitis C virus (HCV) is one of the major etiologic agents of liver cancer. HCV is an RNA virus that, unlike hepatitis B virus, is unable to integrate into the host genome. Through complex interactions between viral and host proteins that induce host responses and promote inflammation, fibrosis, and ultimately cirrhosis, HCV infection can result in the development of hepatocellular carcinoma (HCC). The HCV oncogenic process involves genetic and epigenetic alterations and oncogenic effects mediated by viral proteins in the activation of cellular oncogenes, inactivation of tumor-suppressor genes, and dysregulation of multiple signal-transduction pathways. Advances in genetics and gene expression profiling have enhanced our current understanding of the pathways involved in HCV-associated liver cancer development. In this review, we summarize the current understanding of mechanisms of hepatocarcinogenesis induced by HCV infection.

Pharmacokinetics and pharmacodynamics of setrobuvir, an orally administered hepatitis C virus non-nucleoside analogue inhibitor

PURPOSE

New antiviral agents with activity against hepatitis C virus (HCV) are needed to optimize treatment for chronic hepatitis C (CHC). We evaluated the pharmacokinetics of setrobuvir (a non-nucleoside HCV polymerase inhibitor) in healthy volunteers (study 1 & 2) and its antiviral efficacy in patients with genotype 1, noncirrhotic treatment-naive CHC (study 3).

METHODS

Three studies investigated the pharmacokinetics and pharmacodynamics of setrobuvir. First, sequential cohorts of volunteers were randomly assigned to receive single oral doses of setrobuvir 400 to 3000 mg or placebo in a double-blind, ascending dose study. In the second study, volunteers were randomly assigned to receive multiple doses of setrobuvir (400 or 800 mg once daily [QD] or 600 mg twice a day [BID]). In the third study, patients with genotype 1 CHC received setrobuvir (200, 400, or 800 mg) or placebo BID for 3 days.

FINDINGS

After single doses of setrobuvir (400-3000 mg) to volunteers in a fasted state, peak Cmax and AUC0-∞ increased in a less than dose-proportional manner. The mean apparent t½z ranged from 22.0 to 31.3 hours and was not dose related. Cmax and AUC increased significantly (4.3- and 6.3-fold, respectively) in volunteers who received 2000 mg with a high-fat meal versus fasting. After multiple oral doses, steady state was achieved after 7 days of dosing (400 or 800 mg QD and 600 mg BID) and accumulation was dose-independent. Mean day 14 plasma exposure increased in a less than dose-proportional manner in volunteers who received 400 and 800 mg QD, but it was more than dose-proportional in volunteers receiving 600 mg BID. Dose did not affect the mean t½z (range, 24.1-26.6 hours), apparent oral clearance (0.254-0.516 L/h), or apparent volume of distribution (9.60-18.1 L). In patients with CHC, dose-related reductions in HCV RNA concentration were apparent within 24 hours of the start of treatment. Reductions from baseline to the end of treatment (day 3) in patients treated with setrobuvir 200, 400, and 800 mg BID were -2.1, -2.2, and -2.9 log10 IU/mL, respectively (vs ≤0.1 log10 IU/mL with placebo). Reductions in HCV RNA were greater in patients with genotype 1b (range, -2.7 to -3.1 log10 IU/mL) than in patients with genotype 1a (range, -1.3 to -2.7 log10 IU/mL). Setrobuvir was well tolerated, with no serious adverse events.

IMPLICATIONS

The steady state pharmacokinetics of setrobuvir appear to be dose proportional, and setrobuvir produces a mean reduction of 2.9 log10 IU/mL in HCV RNA over 3 days in patients with genotype 1 (a and b) treated with 800 mg BID. ClinicalTrials.gov identifier: NCT00782353.

Interferon-free antiviral combination therapies without nucleosidic polymerase inhibitors

The establishment of robust HCV cell culture systems and characterization of the viral life cycle provided the molecular basis for highly innovative, successful years in HCV drug development. With the identification of direct-acting antiviral agents (DAAs), such as NS3/4A protease inhibitors, NS5A replication complex inhibitors, nucleotide and non-nucleoside polymerase inhibitors, as well as host cell targeting agents, novel therapeutic strategies were established and competitively entered clinical testing. The first-in-class NS3/4A protease inhibitors telaprevir and boceprevir, approved in 2011, were recently outpaced by the pan-genotypic nucleotide polymerase inhibitor sofosbuvir that in combination with pegylated interferon and ribavirin, further shortens therapy durations and also offers the first interferon-free HCV treatment option. In the challenging race towards the goal of interferon-free HCV therapies, however, several oral DAA regimens without nucleotide polymerase inhibitors that combine a NS3/4A protease inhibitor, a NS5A inhibitor and/or a non-nucleoside polymerase inhibitor yielded competitive results. Second generation NS3/4A protease and NS5A inhibitors promise an improved genotypic coverage and a high resistance barrier. Results of novel DAA combination therapies without the backbone of a nucleotide polymerase inhibitor, as well as treatment strategies involving host targeting agents are reviewed herein.

Management of acute and chronic HCV infection in persons with HIV coinfection

Due to shared routes of transmission, acute and chronic infection with hepatitis C virus is common among persons living with HIV infection in many regions of the world. In the era of effective antiretroviral therapy, acute HCV infection has been increasingly recognized in HIV-infected persons, particularly men who have sex with men, and liver disease, including hepatocellular carcinoma, has emerged as a leading cause of morbidity and mortality in those with chronic HCV infection, particularly older adults with long-standing coinfection. Over the past decade, the foundation for the management of acute and chronic HCV infection has been interferon alfa. However, due the high burden of treatment-related side effects and low likelihood of sustained virologic response, the impact of treatment with peginterferon/ribavirin on the burden of HCV disease in has been limited. However, the anticipated availability of safe, tolerable and highly efficacious interferon-free, oral HCV direct-acting antiviral combination therapies promise to dramatically change the management of acute and chronic HCV infection in HIV-infected persons. Preliminary data from studies of such oral DAA regimens in HIV/HCV coinfected patients suggest that coinfection with HIV will not impair HCV cure with these regimens. Indeed, in the coming era of high effective oral HCV DAA treatments, the only special feature concerning treatment of acute and chronic HCV infection in HIV-infected patients may be drug interactions between the antiretroviral drugs for HIV infection and direct-acting antiviral drugs for HCV infection.

The clinical management of HCV in the HIV-infected patient

Chronic hepatitis C affects an estimated 170 million persons worldwide and due to shared transmission routes many persons are coinfected with HIV. Since the advent of HAART, HIV patients have longer life expectancy and suffer fewer AIDS-related complications. The result has been an increase in morbidity and mortality from HIV-associated non-AIDS conditions, with high rates of liver-related deaths resulting from HCV in the coinfected population. Coinfection with HIV is an independent predictor of liver disease progression, and proper staging of fibrosis is of critical importance in the coinfected patient. In contrast to HIV, it is possible to eradicate HCV infection; and undetectable viral load 12 weeks after cessation of therapy, or sustained viral response (SVR), is considered a clinical cure. As achievement of SVR has been associated with significantly reduced mortality from liver disease and liver disease complications, it is imperative that patients coinfected with HIV-HCV receive therapy for their HCV infection. The length of therapy with previously available interferon-based regimens added a significant burden to HIV-HCV-coinfected patients. Newer, all-oral, interferon-free regimens promise to simplify treatment regimens, reduce side-effect profiles, and demonstrate reduced drug interactions with numerous HAART regimens.

Sofosbuvir-based treatment regimens for chronic, genotype 1 hepatitis C virus infection in U.S. incarcerated populations: a cost-effectiveness analysis

BACKGROUND

Prevalence of chronic hepatitis C virus (HCV) infection is high among incarcerated persons in the United States. New, short-duration, high-efficacy therapies may expand treatment eligibility in this population.

OBJECTIVE

To assess the cost-effectiveness of sofosbuvir for HCV treatment in incarcerated populations.

DESIGN

Markov model.

DATA SOURCES

Published literature and expert opinion.

TARGET POPULATION

Treatment-naive men with chronic, genotype 1 HCV monoinfection.

TIME HORIZON

Lifetime.

PERSPECTIVE

Societal.

INTERVENTION

No treatment, 2-drug therapy (pegylated interferon and ribavirin), or 3-drug therapy with either boceprevir or sofosbuvir. For inmates with short remaining sentences (<1.5 years), only no treatment or sofosbuvir 3-drug therapy was feasible; for those with long sentences (≥1.5 years; mean, 10 years), all strategies were considered. After release, eligible persons could receive sofosbuvir 3-drug therapy.

OUTCOME MEASURES

Discounted costs (in 2013 U.S. dollars), discounted quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios.

RESULTS OF BASE-CASE ANALYSIS

The strategies yielded 13.12, 13.57, 14.43, and 15.18 QALYs, respectively, for persons with long sentences. Sofosbuvir produced the largest absolute reductions in decompensated cirrhosis (16%) and hepatocellular carcinoma (9%), resulting in 2.1 additional QALYs at an added cost exceeding $54,000 compared with no treatment. For persons with short sentences, sofosbuvir cost $25,700 per QALY gained compared with no treatment; for those with long sentences, it dominated other treatments, costing $28,800 per QALY gained compared with no treatment.

RESULTS OF SENSITIVITY ANALYSIS

High reinfection rates in prison attenuated cost-effectiveness for persons with long sentences.

LIMITATIONS

Data on sofosbuvir's long-term effectiveness and price are limited. The analysis did not consider women, Hispanic persons, or patients co-infected with HIV or hepatitis B virus.

CONCLUSION

Sofosbuvir-based treatment is cost-effective for incarcerated persons, but affordability is an important consideration.

PRIMARY FUNDING SOURCE

National Institutes of Health.

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.

Interferon-based treatment for patients with mycosis fungoides and hepatitis C virus infection: a case series

BACKGROUND

Interferon (IFN) is a treatment option for both mycosis fungoides (MF) and hepatitis C virus (HCV) infection. Chemotherapy and anti-HCV treatment are generally not administered concurrently for fear of overlapping side effects.

OBJECTIVE

Herein, we report on a subset of patients who received IFN-containing therapy for MF and HCV infection simultaneously. We aimed to evaluate whether concomitant treatment for MF and HCV is effective and well tolerated.

METHODS

We reviewed the records of patients who were seen at MD Anderson Cancer Center from 2008 to 2013 with histologically confirmed MF and chronic HCV infection, and were treated with simultaneous focus on both diseases.

RESULTS

Six HCV-infected patients with MF received simultaneous anti-HCV and anti-MF treatment with IFN-containing therapy. Two patients achieved sustained virological response (regarded as virological cure). They both received antiviral combination therapy with ribavirin. All patients experienced some improvement of their cutaneous lesions, with two of them achieving complete MF remission. All six patients developed side effects while receiving treatment; two of them had grade 4 toxic effects requiring treatment discontinuation.

CONCLUSION

IFN-based therapy can be administered for MF and HCV infection concurrently to provide not only virological but also oncological benefits to chronically HCV-infected MF patients. However, this regimen is poorly tolerated. Further studies are warranted in this patient population, using different treatment combinations with improved efficacy, safety, and tolerability.

Exploratory trial of ombitasvir and ABT-450/r with or without ribavirin for HCV genotype 1, 2, and 3 infection

OBJECTIVES

To examine the safety and efficacy of ombitasvir and ABT-450 with ritonavir (ABT-450/r) ± ribavirin (RBV) in treatment-naïve, non-cirrhotic adults with chronic HCV genotype 1-3 infection.

METHODS

Patients in this open-label, exploratory, phase 2, multicenter study received ombitasvir (25 mg QD) and ABT-450/r (200/100 mg QD) ± RBV for 12 weeks. Primary efficacy endpoint was HCV RNA < lower limit of quantitation (LLOQ) from week 4 through 12. Sustained virologic response 12 weeks post-treatment (SVR12) was a secondary endpoint.

RESULTS

Sixty-one patients were enrolled. Among genotype 1-, 2-, and 3-infected patients, respectively, HCV RNA was<LLOQ from week 4 through 12 in 10 (100%; 95% CI 69-100), 9 (90%; 56-100), and 7 (70%; 35-93) receiving the RBV-containing regimen and 9 (90%; 56-100), 8 (80%; 44-97), and 2 (18%; 2-52) receiving the RBV-free regimen. Among genotype 1-, 2-, and 3-infected patients, respectively, SVR12 was achieved by 10 (100%), 8 (80%), and 5 (50%) receiving the RBV-containing regimen, and 6 (60%), 6 (60%), and 1 (9%) receiving the RBV-free regimen. The most common adverse events were fatigue, nausea, and headache. One patient discontinued due to an adverse event.

CONCLUSIONS

In this study, ombitasvir and ABT-450/r ± RBV regimens were generally well-tolerated. Sustained virologic response was achieved in most patients with HCV genotype 1 or 2 infection, but low SVR rates were observed in HCV genotype 3-infected patients.

Hepatitis C drugs: the end of the pegylated interferon era and the emergence of all-oral interferon-free antiviral regimens: a concise review

Between 2001 and 2011, the standard of care for chronic hepatitis C virus (HCV) infection was a combination of pegylated interferon (PEG-IFN) and ribavirin (RBV). In May 2011, boceprevir and telaprevir, two first-generation NS3/4A protease inhibitors, were approved in combination with PEG-IFN and RBV for 24 to 48 weeks in hepatitis C virus genotype 1 infections. In December 2013, simeprevir, a second-generation NS3/4A protease inhibitor, was approved for use with PEG-IFN and RBV for 12 weeks in genotype 1, while sofosbuvir, a NS5B nucleotide polymerase inhibitor, was approved for use with PEG-IFN and RBV for 12 weeks in genotypes 1 and 4, as well as with RBV alone for 12 weeks in genotype 2 and for 24 weeks in genotype 3. Sofosbuvir combined with simeprevir or an NS5A replication complex inhibitor (ledipasvir or daclatasvir) with or without RBV for 12 weeks in genotype 1 resulted in a sustained virological response >90%, irrespective of previous treatment history or presence of cirrhosis. Similarly impressive sustained virological response rates have been shown with ABT-450/r (ritonavir-boosted NS3/4A protease inhibitor)-based regimens in combination with other direct-acting antiviral agent(s) with or without RBV for 12 weeks in genotype 1. The optimal all-oral interferon-free antiviral regimen likely entails a combination of an NS5B nucleotide polymerase inhibitor with either a second-generation NS3/4A protease inhibitor or an NS5A replication complex inhibitor with or without RBV. Further research is needed to determine the role of resistance testing, clarify the optimal follow-up duration post-treatment, and evaluate the antiviral efficacy and safety in difficult-to-cure patient populations.

Treatment of hepatitis C: perspectives

The treatment of hepatitis C virus (HCV) infection has significantly improved in the last 2 decades. The association of pegylated interferon alfa and ribavirin (PR) has allowed a sustained virologic response (SVR) for nearly 15 years i.e. a viral cure of the infection for 45% of genotype 1-, 65% of genotype 4-, 70% of genotype 3- and around 85% of genotype 2-infected patients. A better understanding of the HCV life cycle has led to the development of direct-acting antiviral drugs (DAAs) targeted against viral proteins (NS3/4A protease, NS5B polymerase with nucleotide and non-nucleotide inhibitors, NS5A viral replication complex). The combination of first-generation protease inhibitors with PR demonstrated a high antiviral effectiveness (75% of SVR but restricted to genotypes 1) with substantial adverse effects for the first-generation protease inhibitors, which obtained market approval in 2011 (telaprevir and boceprevir), recommendations for use in HCV monoinfected patients in 2012, and in HCV/HIV coinfected in 2013. Then, the combination of second-generation protease inhibitors with PR increased SVR rates from 75 to 90%, while reducing treatment duration, adverse effects, and the number of pills. The next step will be using an interferon and ribavirin-free combination of DAAs; it should become the standard of care in 2015. These excellent results in "easy-to-treat" patients and in small populations in the first studies were confirmed in phase III studies and in "difficult-to-treat" patients (treatment-- especially protease inhibitors--previously treated patients, cirrhotic patients, liver and renal transplant patients, HIV coinfected patients, and multi-drug treated patients, at increased risk of drug interaction). The high antiviral potency of these new combinations has changed the definition of "difficult-to-treat patients". These unique achievements in drug history make any previous publication on hepatitis C treatment obsolete.

Treatment of HCV infection with the novel NS3/4A protease inhibitors

HCV NS3/4A serine protease inhibitors are the first class of direct acting antivirals (DAA) introduced in clinical practice. The first generation agents, selective against HCV genotype 1, are used in association with pegylated interferons and ribavirin allowing increased cure rates at the price of increased toxicity, significant drug interactions and high risk of selecting mutants conferring cross-resistance to the entire class. A large number of second-wave HCV protease inhibitors are currently in clinical development. Advancements include higher potency, activity against a wider number of genotypes, improved tolerability, easier dosing schedules, although their genetic barrier to resistance remains low, especially for subtype 1a, except for the most recent grazoprevir and ACH-2684. The most relevant progress regards the combination with other classes of DAA allowing construction of interferon-free regimens of short duration, good tolerability with exceptionally high cure rates.

Coronaviruses resistant to a 3C-like protease inhibitor are attenuated for replication and pathogenesis, revealing a low genetic barrier but high fitness cost of resistance

Viral protease inhibitors are remarkably effective at blocking the replication of viruses such as human immunodeficiency virus and hepatitis C virus, but they inevitably lead to the selection of inhibitor-resistant mutants, which may contribute to ongoing disease. Protease inhibitors blocking the replication of coronavirus (CoV), including the causative agents of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), provide a promising foundation for the development of anticoronaviral therapeutics. However, the selection and consequences of inhibitor-resistant CoVs are unknown. In this study, we exploited the model coronavirus, mouse hepatitis virus (MHV), to investigate the genotype and phenotype of MHV quasispecies selected for resistance to a broad-spectrum CoV 3C-like protease (3CLpro) inhibitor. Clonal sequencing identified single or double mutations within the 3CLpro coding sequence of inhibitor-resistant virus. Using reverse genetics to generate isogenic viruses with mutant 3CLpros, we found that viruses encoding double-mutant 3CLpros are fully resistant to the inhibitor and exhibit a significant delay in proteolytic processing of the viral replicase polyprotein. The inhibitor-resistant viruses also exhibited postponed and reduced production of infectious virus particles. Biochemical analysis verified double-mutant 3CLpro enzyme as impaired for protease activity and exhibiting reduced sensitivity to the inhibitor and revealed a delayed kinetics of inhibitor hydrolysis and activity restoration. Furthermore, the inhibitor-resistant virus was shown to be highly attenuated in mice. Our study provides the first insight into the pathogenicity and mechanism of 3CLpro inhibitor-resistant CoV mutants, revealing a low genetic barrier but high fitness cost of resistance. Importance: RNA viruses are infamous for their ability to evolve in response to selective pressure, such as the presence of antiviral drugs. For coronaviruses such as the causative agent of Middle East respiratory syndrome (MERS), protease inhibitors have been developed and shown to block virus replication, but the consequences of selection of inhibitor-resistant mutants have not been studied. Here, we report the low genetic barrier and relatively high deleterious consequences of CoV resistance to a 3CLpro protease inhibitor in a coronavirus model system, mouse hepatitis virus (MHV). We found that although mutations that confer resistance arise quickly, the resistant viruses replicate slowly and do not cause lethal disease in mice. Overall, our study provides the first analysis of the low barrier but high cost of resistance to a CoV 3CLpro inhibitor, which will facilitate the further development of protease inhibitors as anti-coronavirus therapeutics.

Enhanced antiviral treatment efficacy and uptake in preventing the rising burden of hepatitis C-related liver disease and costs in Australia

BACKGROUND AND AIM

Chronic hepatitis C virus (HCV) infection is an important cause of advanced liver disease and liver-related deaths in Australia. Our aim was to describe the burden of HCV infection and consider treatment strategies to reduce HCV-related morbidity and mortality.

METHODS

Baseline model parameters were based upon literature review and expert consensus with a focus on Australian data. Three treatment scenarios based on anticipated introduction of improved direct-acting antiviral regimens were considered to reduce HCV disease burden. Scenario 1 evaluated the impact of increased treatment efficacy alone (to 80-90% by 2016). Scenario 2 evaluated increased efficacy and increased treatment uptake (2550 to 13,500 by 2018) without treatment restriction, while Scenario 3 considered the same increases with treatment limited to ≥ F3 during 2015-2017.

RESULTS

In 2013, there were an estimated 233,490 people with chronic HCV infection: 13,850 with cirrhosis, 590 with hepatocellular carcinoma (HCC) and 530 liver-related deaths. If the current HCV treatment setting is unchanged, threefold increases in the number of people with cirrhosis, HCC, and liver disease deaths will be seen by 2030. Scenario 1 resulted in modest impacts on disease burden (4% decrease in HCC, decompensated cirrhosis, and liver deaths) and costs. Scenario 3 had the greatest impact on disease burden (approximately 50% decrease in HCC, decompensated cirrhosis, and liver deaths) and costs, while Scenario 2 had slightly lesser impact.

CONCLUSIONS

Considerable increases in the burden of HCV-related advanced liver disease and its complications will be seen in Australia under current treatment levels and outcomes. Introduction of improved direct-acting antiviral regimens with enhanced efficacy at current treatment levels will lead to limited impacts on this disease burden. A combination of increased treatment efficacy and greater uptake is required to achieve major reductions in advanced liver disease and related costs.

Antiviral treatment of hepatitis C

Hepatitis C virus (HCV) infection is a substantial health problem worldwide. Most patients infected with HCV remain chronically infected, with an increased risk of cirrhosis and hepatocellular carcinoma. Although they are associated with toxicities and low sustained viral response rates, interferon alfa and ribavirin have been the mainstay of treatment until recently. New direct acting antivirals, specifically designed to inhibit three viral proteins (the NS3/4A protease, the NS5A protein, and the NS5B RNA dependent RNA polymerase) are now becoming available. The NS3/4A inhibitor simeprevir and NS5B inhibitor sofosbuvir have recently been licensed and can reduce the length of antiviral treatment, improve response rates, and allow for interferon-free regimens for some HCV genotypes. Several other newer direct acting antivirals have shown promise in clinical studies and are likely to be licensed soon. These agents seem to facilitate the use of shortened courses of combination interferon-free therapy, which are associated with high (>95%) sustained response rates and relatively few toxicities. These regimens have also been successful in patients who were previously difficult to treat, including those with cirrhosis, HIV coinfection, and those who have undergone liver transplantation. The high cost of these agents may be the biggest challenge to their implementation worldwide.

Targeting gap junction intercellular communication as a potential therapy for HCV-related carcinogenesis

ABSTRACT: 

Worldwide, at least 170 million people are infected with hepatitis C virus (HCV), which is associated with hepatocellular carcinoma (HCC). With the recent success of Sofosbuvir (and other agents) antiviral therapy may be used as a future early-stage HCC treatment; however, in the short term, a cost-effective solution is needed to treat patients with viral-associated HCC. Here, we emphasize the potential of targeting gap junction intercellular communication (GJIC) as a therapeutic approach for HCC as HCV perturbs GJIC, which is linked to cellular transformation. We review the ROCK inhibitor Y-27632 and structurally related compounds that may inhibit the carcinogenic properties of HCV.

Community-based seroepidemiological survey of HCV infection in Catalonia, Spain

In a recent expert meeting, Swedish recommendations for the treatment of HCV infection were updated. An interferon-free combination of direct-acting antiviral agents was recommended as the first line standard-of-care treatment for chronic HCV infection. Interferon-based therapy should be considered as a second line option after an individual benefit-risk assessment. Treatment is strongly recommended for HCV infected patients with bridging fibrosis or cirrhosis (Metavir stages F3–4), before and after liver transplantation, and in the presence of extra-hepatic manifestations. Additionally, patients with moderate liver fibrosis (stage F2) as well as women in need of in vitro fertilisation should be prioritised for therapeutic intervention. Treatment indications for people who inject drugs, children, chronic kidney disease and HIV co-infection are also discussed.