Anti-hepatitis C virus drugs in development

Synthetic approaches and application of clinically approved small-molecule drugs to treat hepatitis

Hepatitis, a global public health concern, presents a significant burden on healthcare systems worldwide. Particularly, hepatitis B and C are viral infections that can lead to severe liver damage, cirrhosis, and even hepatocellular carcinoma (HCC). The urgency to combat these diseases has driven researchers to explore existing small-molecule drugs as potential therapeutics. This comprehensive review provides a systematic overview of synthetic routes to key antiviral agents used to manage hepatitis. Furthermore, it elucidates the mechanisms of action of these drugs, shedding light on their interference with viral replication and liver disease progression. The review also discusses the clinical applications of these drugs, including their use in combination therapies and various patient populations. By evaluating the synthetic pathways and clinical utility of these drugs, this review not only consolidates current knowledge but also highlights potential future directions for research and drug development in the fight against hepatitis, ultimately contributing to improved patient outcomes and reduced global disease burden.

Spectroscopic study to verify the anti-hepatitis C virus (HCV) treatment through a delivery system of the sofosbuvir drug on chitosan and pycnogenol nanoparticles surface

The target of the current study is to create a novel hybrid nanocomposite (Cs@Pyc.SOF) by combining the anti-hepatitis C virus (HCV) drug sofosbuvir with the nano antioxidant pycnogenol (Pyc) and nano biomolecules like chitosan nanoparticles (Cs NPs). The characterization procedure works to verify the creation of nanocomposite (NCP) using several different techniques. UV-Vis spectroscopy is used to measure SOF loading efficiency. The various concentrations of the SOF drug were used to determine the binding constant rate Kb, which was found to be 7.35 ± 0.95 min-1 with an 83% loading efficiency. At pH 7.4, the release rate was 80.6% after two hours and 92% after 48 h, whereas at pH 6.8, it was 29% after two hours and 94% after 48 h. After 2 and 48 h, the release rate in water was 38% and 77%, respectively. . The SRB technique for fast screening is used for the cytotoxicity test, where the investigated composites show a safety status and high viability against the examined cell line. The cytotoxicity assay of the SOF hybrid materials has been identified with cell lines like mouse normal liver cells (BNL). So, Cs@Pyc.SOF was recommended as a substitute medication for the therapy of HCV, but the results need clinical studies.

Sofosbuvir induces gene expression for promoting cell proliferation and migration of hepatocellular carcinoma cells

Direct-acting antivirals (DAAs) have achieved a sustained virological response (SVR) rate of 95–99% in treating HCV. Several studies suggested that treatment with sofosbuvir (SOF), one type of DAAs, may be associated with increased risk of developing HCC. The aim of this study is to investigate the potential mechanisms of SOF on the development of HCC. OR-6 (harboring full-length genotype 1b HCV) and Huh 7.5.1 cells were used to examine the effects of SOF on cell proliferation and migration of HCC cells. SOF-upregulated genes in OR-6 cells were inspected using next generation sequencing (NGS)and the clinical significance of these candidate genes was analyzed using The Cancer Genome Atlas (TCGA) database. We found that SOF increased cell proliferation and cell migration in OR-6 and Huh 7.5.1 cells. Several SOF-upregulated genes screened from NGS were confirmed by real-time PCR in OR-6 cells. Among these genes, PHOSPHO2, KLHL23, TRIM39, TSNAX-DISC1 and RPP21 expression were significantly elevated in the tumor tissues compared with the non-tumor tissues of HCC according to TCGA database. High expression of PHOSPHO2 and RPP21 was associated with poor overall survival of HCC patients. Moreover, knockdown of PHOSPHO2-KLHL23, TSNAX-DISC1, TRIM39 and RPP21 diminished cell proliferation and migration increased by SOF in OR-6 and Huh 7.5.1 cells. In conclusion, SOF-upregulated genes promoted HCC cell proliferation and migration, which might be associated with the development of HCC.

Treatment progress and expansion in Japan: From interferon to direct-acting antiviral

Hepatitis C virus (HCV) was first discovered in 1989, and patients infected with HCV were initially treated with interferon (IFN) monotherapy. In the 2000s, pegylated IFN combined with ribavirin was the mainstay of therapy for infected patients, but the sustained virologic response (SVR) rate was less than 50% for patients with HCV genotype 1. To further improve the therapeutic effect, direct-acting antiviral (DAA) was developed, and combination therapy with DAA and IFN has been available since 2011. In addition, IFN-free DAA therapy became available in 2014, and SVR was achieved in more than 95% of patients with chronic hepatitis and compensated cirrhosis. Thus, in just 30 years since the discovery of HCV, we aim to eliminate HCV in almost all patients. However, there are remaining issues to be addressed. Many of the patients who achieved SVR with DAA therapy had advanced liver fibrosis, and it is necessary to verify to what extent DAA therapy improves their prognosis in terms of liver function, hepatocellular carcinoma occurrence, and mortality. Resistance-associated substitutions can cause failure of DAA therapy, and the search for an effective therapy for high-level resistant viruses such as P32 deletion is particularly important. DAA therapy was approved for use in patients with decompensated cirrhosis in Japan in 2019, which is an unmet need so far. It is also important to verify the efficacy and safety in real-world settings. The World Health Organization aims to eliminate HCV by 2030, and Japan must tackle its remaining issues to achieve this goal.

Facilitating Antiviral Drug Discovery Using Genetic and Evolutionary Knowledge

Over the course of human history, billions of people worldwide have been infected by various viruses. Despite rapid progress in the development of biomedical techniques, it is still a significant challenge to find promising new antiviral targets and drugs. In the past, antiviral drugs mainly targeted viral proteins when they were used as part of treatment strategies. Since the virus mutation rate is much faster than that of the host, such drugs feature drug resistance and narrow-spectrum antiviral problems. Therefore, the targeting of host molecules has gradually become an important area of research for the development of antiviral drugs. In recent years, rapid advances in high-throughput sequencing techniques have enabled numerous genetic studies (such as genome-wide association studies (GWAS), clustered regularly interspersed short palindromic repeats (CRISPR) screening, etc.) for human diseases, providing valuable genetic and evolutionary resources. Furthermore, it has been revealed that successful drug targets exhibit similar genetic and evolutionary features, which are of great value in identifying promising drug targets and discovering new drugs. Considering these developments, in this article the authors propose a host-targeted antiviral drug discovery strategy based on knowledge of genetics and evolution. We first comprehensively summarized the genetic, subcellular location, and evolutionary features of the human genes that have been successfully used as antiviral targets. Next, the summarized features were used to screen novel druggable antiviral targets and to find potential antiviral drugs, in an attempt to promote the discovery of new antiviral drugs.

A computational approach to aid clinicians in selecting anti-viral drugs for COVID-19 trials

The year 2020 witnessed a heavy death toll due to COVID-19, calling for a global emergency. The continuous ongoing research and clinical trials paved the way for vaccines. But, the vaccine efficacy in the long run is still questionable due to the mutating coronavirus, which makes drug re-positioning a reasonable alternative. COVID-19 has hence fast-paced drug re-positioning for the treatment of COVID-19 and its symptoms. This work builds computational models using matrix completion techniques to predict drug-virus association for drug re-positioning. The aim is to assist clinicians with a tool for selecting prospective antiviral treatments. Since the virus is known to mutate fast, the tool is likely to help clinicians in selecting the right set of antivirals for the mutated isolate. The main contribution of this work is a manually curated database publicly shared, comprising of existing associations between viruses and their corresponding antivirals. The database gathers similarity information using the chemical structure of drugs and the genomic structure of viruses. Along with this database, we make available a set of state-of-the-art computational drug re-positioning tools based on matrix completion. The tools are first analysed on a standard set of experimental protocols for drug target interactions. The best performing ones are applied for the task of re-positioning antivirals for COVID-19. These tools select six drugs out of which four are currently under various stages of trial, namely Remdesivir (as a cure), Ribavarin (in combination with others for cure), Umifenovir (as a prophylactic and cure) and Sofosbuvir (as a cure). Another unanimous prediction is Tenofovir alafenamide, which is a novel Tenofovir prodrug developed in order to improve renal safety when compared to its original counterpart (older version) Tenofovir disoproxil. Both are under trail, the former as a cure and the latter as a prophylactic. These results establish that the computational methods are in sync with the state-of-practice. We also demonstrate how the drugs to be used against the virus would vary as SARS-Cov-2 mutates over time by predicting the drugs for the mutated strains, suggesting the importance of such a tool in drug prediction. We believe this work would open up possibilities for applying machine learning models to clinical research for drug-virus association prediction and other similar biological problems.

Emerging resistance to directly-acting antiviral therapy in treatment of chronic Hepatitis C infection-A brief review of literature

Hepatitis caused by Hepatitis C virus (HCV) is a major cause of chronic liver disease. HCV is transmitted by injection drug use, blood transfusion, hemodialysis, organ transplantation and less frequently sexual intercourse. It has been recognized as a global health problem because of the progression to cirrhosis and hepatocellular carcinoma. Globally, about 170 million people are infected with HCV. Since the discovery of this virus in 1989, the clinical management of chronic hepatitis C infection has undergone a paradigm shift from alpha interferon to direct-acting antiviral (DAA) therapy. However, resistance to many of these antiviral agents has been reported increasingly from all over the globe. This review article focuses on the emerging HCV resistance to DAAs and the relevance of in vitro DAA resistance testing in clinical practice.

Sofosbuvir-based regimen for genotype 2 HCV infected patients in Taiwan: A real world experience

Background

Sofosbuvir (SOF)-based regimens achieve excellent efficacy and safety in the treatment of chronic hepatitis C (CHC) with various genotypes. There are few real-world instances of the use of SOF-based regimens to treat genotype 2 CHC. This study determines the effectiveness and safety of SOF/Ribavirn (RBV), SOF/Daclatasvir (DCV) and SOF/DCV/RBV in the treatment of genotype 2 CHC patients in Taiwan.

Material and methods

Patients with genotype 2 CHC were treated for 12 weeks with SOF/RBV, SOF/DCV or SOF/DCV/RBV under the National Health Insurance reimbursement program in three hospitals in Taiwan. The sustained virological response at 12 weeks (SVR12) was determined. Adverse events were recorded for a safety analysis.

Results

A total of 467 genotype 2 CHC patients were enrolled from January to October 2018. One hundred and eleven patients (24%) had cirrhosis, including 10 patients (2.1%) with hepatic decompensation. Fifty-five patients (12%) had already experienced interferon-alpha/RBV treatment. Forty-two patients (9%) had a history of hepatocellular carcinoma (HCC) in the baseline. Three hundred and fifty-five patients received SOF/RBV, forty-seven patients received SOF/DCV and sixty-two patients received SOF/DCV/RBV. The SOF/DCV group featured a greater HCV viral load than the SOF/RBV or SOF/DCV/RBV groups. SVR12 was achieved in 94.6% of the SOF/RBV group, 95.7% of the SOF/DCV group and 96.8% of then SOF/DCV/RBV group (P = NS). Thirteen out of 352 patients (3.7%) in the SOF/RBV group, 1 out of 62 patients (1.6%) in the SOF/DCV/RBV group and 1 out of 47 patients (2.1%) in the SOF/DCV group developed virological failure. There are no differences in virological failure between the three groups (P = NS). Multi-variate analysis shows that history of HCC is an independent factor that is associated with the failure of treatment in the SOF/RBV group (odds ratio:4.905, 95% confidence interval (CI): 1.321–18.205, P = 0.017). Hemoglobin levels at 12 weeks are significantly lower in the SOF/RBV and the SOF/RBV/DCV group than in the SOF/DCV group (P<0.05). Serious adverse events (SAE) occurred in six patients (1.6%) in the SOF/RBV group and in one patient (1.6%) in the SOF/RBV/DCV group. No patients in the SOF/DCV group experienced SAE.

Conclusions

SOF/RBV, SOF/DCV or SOF/DCV/RBV for 12 weeks all achieve very high SVR rates and are equally effective in the treatment of genotype 2 CHC patients in the real world in Taiwan. Patients in the SOF/RBV group who have a history of HCC exhibit a lower SVR rate.

Resistance outside the substrate envelope: hepatitis C NS3/4A protease inhibitors

Direct acting antivirals have dramatically increased the efficacy and tolerability of hepatitis C treatment, but drug resistance has emerged with some of these inhibitors, including nonstructural protein 3/4 A protease inhibitors (PIs). Although many co-crystal structures of PIs with the NS3/4A protease have been reported, a systematic review of these crystal structures in the context of the rapidly emerging drug resistance especially for early PIs has not been performed. To provide a framework for designing better inhibitors with higher barriers to resistance, we performed a quantitative structural analysis using co-crystal structures and models of HCV NS3/4A protease in complex with natural substrates and inhibitors. By comparing substrate structural motifs and active site interactions with inhibitor recognition, we observed that the selection of drug resistance mutations correlates with how inhibitors deviate from viral substrates in molecular recognition. Based on this observation, we conclude that guiding the design process with native substrate recognition features is likely to lead to more robust small molecule inhibitors with decreased susceptibility to resistance.

Sofosbuvir/velpatasvir/voxilaprevir in the treatment of chronic hepatitis C infection

The landscape of HCV treatment has been entirely transformed due to the development of direct-acting antivirals (DAAs), but there are limited data guiding salvage therapy in patients who previously failed an NS5A inhibitor-containing DAA regimen. We review the preclinical and clinical data for sofosbuvir/velpatasvir/voxilaprevir (SOF/VEL/VOX), an interferon-free, oral, once daily, pan-genotypic treatment for chronic HCV infection. This combination is a highly effective, well-tolerated and safe 12-week treatment regimen for patients with any genotype, including genotype-3 patients with baseline resistance-associated substitutions (RAS). Its most distinctive role is in patients who have previously failed treatment with advanced DAA regimens. Its efficacy is not significantly affected by RASs, and treatment-emergent RASs are uncommon.

Hepatitis C - New drugs and treatment prospects

Hepatitis C virus (HCV) affects approx. 3% of the world's population and accounts for ca 300 000 deaths per year. 80% of individuals with HCV develop chronic symptoms which, when untreated, may cause cirrhosis (27%) or hepatocellular carcinoma (25%). The hepatitis C virus is a (+)ssRNA enveloped virus of the family Flaviviridae. Seven major HCV genotypes and their subtypes (a, b) have been identified. In the 1990s, interferons alpha-2 were used in the treatment of HCV and in the next decade HCV therapy was based on pegylated interferon alpha-2 in combination with ribavirin. Since 2011, interferons alpha, DNA and RNA polymerase inhibitors, NS3/4A RNA protease inhibitors, NS5 RNA serine protease inhibitors, NS5B RNA polymerase inhibitors have been approved for clinical use. Monotherapy is avoided in medication due to rapidly developing viral resistance. A total of 113 papers were included comprising original publications and reviews. The paper reviews the molecular targets and chemical structures of drugs used in HCV treatment. Indications and contraindications for anti-HCV drugs are also discussed together with application regimens.

Integrated pharmacokinetic/viral dynamic model for daclatasvir/asunaprevir in treatment of patients with genotype 1 chronic hepatitis C

In order to develop an integrated pharmacokinetic/viral dynamic (PK/VD) model to predict long-term virological response rates to daclatasvir (DCV) and asunaprevir (ASV) combination therapy in patients infected with genotype 1 (GT1) chronic hepatitis C virus (HCV), a systematic publication search was conducted for DCV and ASV administered alone and/or in combination in healthy subjects or patients with GT1 HCV infection. On the basis of a constructed meta-database, an integrated PK/VD model was developed, which adequately described both DCV and ASV PK profiles and viral load time curves. The IC₅₀ values of DCV and ASV were estimated to be 0.041 and 2.45 μg/L, respectively, in GT1A patients. A sigmoid E_max function was applied to describe the antiviral effects of DCV and ASV, depending on the drug concentrations in the effect compartment. An empirical exponential function revealed that IC₅₀ changing over time described drug resistance in HCV GT1A patients during DCV or ASV monotherapy. Finally, the PK/VD model was evaluated externally by comparing the expected and observed virological response rates during and post-treatment with DCV and ASV combination therapy in HCV GT1B patients. Both the rates were in general agreement. Our PK/VD model provides a useful platform for the characterization of pharmacokinetic/pharmacodynamic relationships and the prediction of long-term virological response rates to aid future development of direct acting antiviral drugs.

Chemical genetics-based development of small molecules targeting hepatitis C virus

Hepatitis C virus (HCV) infection is a major worldwide problem that has emerged as one of the most significant diseases affecting humans. There are currently no vaccines or efficient therapies without side effects, despite today's advanced medical technology. Currently, the common therapy for most patients (i.e. genotype 1) is combination of HCV-specific direct-acting antivirals (DAAs). Up to 2011, the standard of care (SOC) was a combination of peg-IFNα with ribavirin (RBV). After approval of NS3/4A protease inhibitor, SOC was peg-IFNα and RBV with either the first-generation DAAs boceprevir or telaprevir. In the past several years, various novel small molecules have been discovered and some of them (i.e., HCV polymerase, protease, helicase and entry inhibitors) have undergone clinical trials. Between 2013 and 2016, the second-generation DAA drugs simeprevir, asunaprevir, daclatasvir, dasabuvir, sofosbuvir, and elbasvir were approved, as well as the combinational drugs Harvoni^®, Zepatier^®, Technivie^®, and Epclusa^®. A number of reviews have been recently published describing the structure-activity relationship (SAR) in the development of HCV inhibitors and outlining current therapeutic approaches to hepatitis C infection. Target identification involves studying a drug's mechanism of action (MOA), and a variety of target identification methods have been developed in the past few years. Chemical biology has emerged as a powerful tool for studying biological processes using small molecules. The use of chemical genetic methods is a valuable strategy for studying the molecular mechanisms of the viral lifecycle and screening for anti-viral agents. Two general screening approaches have been employed: forward and reverse chemical genetics. This review reveals information on the small molecules in HCV drug discovery by using chemical genetics for targeting the HCV protein and describes successful examples of targets identified with these methods.

Dendritic cells activation is associated with sustained virological response to telaprevir treatment of HCV-infected patients

First anti-HCV treatments, that include protease inhibitors in conjunction with IFN-α and Ribavirin, increase the sustained virological response (SVR) up to 80% in patients infected with HCV genotype 1. The effects of triple therapies on dendritic cell (DC) compartment have not been investigated. In this study we evaluated the effect of telaprevir-based triple therapy on DC phenotype and function, and their possible association with treatment outcome. HCV+ patients eligible for telaprevir-based therapy were enrolled, and circulating DC frequency, phenotype, and function were evaluated by flow-cytometry. The antiviral activity of plasmacytoid DC was also tested. In SVR patients, myeloid DC frequency transiently decreased, and returned to baseline level when telaprevir was stopped. Moreover, an up-regulation of CD80 and CD86 on mDC was observed in SVR patients as well as an improvement of IFN-α production by plasmacytoid DC, able to inhibit in vitro HCV replication.

The Challenge of Treating Children With Hepatitis C Virus Infection

The development of oral hepatitis C virus (HCV) direct-acting antivirals (DAAs) has revolutionized the therapeutic field. Nowadays, multiple safe and highly effective antiviral regimens are commercially available to treat adults with hepatitis C infection. These new regimens for the first time genuinely raise the prospects of eradicating HCV. Many challenges, however, remain from identifying infected individuals to optimizing treatment and ensuring global access to antiviral therapy to all population groups, including children. Recently, in April 2017, the association of sofosbuvir with ribavirin and the fixed-dose combination sofosbuvir/ledipasvir have been approved by the Food and Drug Administration for treatment of children with chronic HCV infection 12 years of age and older. The only drugs currently approved for children younger than 12 years are pegylated interferon and ribavirin. There are 6 registered ongoing pediatric trials assessing safety and efficacy of DAAs, but their current completion timelines are years away. Herein, we summarize the state of the art of DAAs' development for adult and children and highlight the crucial importance of overcoming barriers to treating children with HCV.

Hepatitis C virus management: potential impact of nanotechnology

Around 170–200 million individuals have hepatitis C virus (HCV), which represents ~ 3% of the world population, including ~ 3–5 million people in the USA. According to the WHO regional office in the Middle East, Egypt has the highest prevalence in the world, with 7% prevalence in adults. There had been no effective vaccine for HCV; a combination of PEG-Interferon and ribavirin for at least 48 weeks was the standard therapy, but it failed in more than 40% of the patients and has a high cost and serious side effects. The recent introduction of direct-acting antivirals (DAA) resulted in major advances toward the cure of HCV. However, relapse and reduced antiviral efficacy in fibrotic, cirrhotic HCV patients in addition to some undesired effects restrain the full potential of these combinations. There is a need for new approaches for the combinations of different DAA and their targeted delivery using novel nanotechnology approaches. In this review, the role of nanoparticles as a carrier for HCV vaccines, anti-HCV combinations, and their targeted delivery are discussed.

AS, Liz AL, Lisset GF, Sacha LDV, Elena FB. Clinical Evaluation of Terap C Vaccine in Combined Treatment with Interferon and Ribavirin in Patients with Hepatitis C

BACKGROUND

An estimated 170 million individuals worldwide are infected with the hepatitis C virus (HCV). Although treatment options using a combination of pegylated interferon and ribavirin (P-IFN/RBV) are available, sustained clearance of the virus is only achieved in approximately 40% of individuals infected with HCV genotype 1. Recent advances in the treatment of HCV using directly acting antiviral agents have been achieved; however, treatment can be very expensive and is associated with substantial side effects. The development of a new treatment modality is needed. One possible modality could be specific immunotherapy. Terap C is a therapeutic vaccine candidate composed of pIDKE2, a plasmid expressing HCV structural antigens, with a recombinant HCV core protein, Co.120.

OBJECTIVE

To assess the safety and efficacy of concomitant therapy with the candidate vaccine, Terap C, IFN α-2b and ribavirin in untreated individuals with HCV genotype 1 infection.

METHODS

This was a Phase II randomized, placebo-controlled, double-blind clinical trial evaluating the safety and efficacy of Terap C concomitant with IFN α-2b/RBV in 92 treatment-naïve patients with HCV genotype 1 infection. The study was conducted at the Gastroenterology Institute in Havana, Cuba. Patients were randomly assigned to 1 of 5 groups. The control group (Group 1) received IFN α-2b/RBV and placebo for 48 weeks. Groups 2 and 3 were administered Terap C 6 and 9 times, respectively, in addition to standard IFN α-2b/RBV treatment. In groups 4 and 5, Terap C was introduced 12 weeks after the initiation of IFN α-2b/RBV and administered 6 and 9 times, respectively, concomitant with IFN α-2b/RBV.

RESULTS

All patients showed some adverse events. Out of 3615 adverse events, only 18.8% were considered to be probably associated with administration of Terap C. Most events (47.4%) were considered to be improbably associated with of administration Terap C. Only 33.8% were considered possibly temporarily associated with Terap C, and can be explained by the use of conventional IFN α-2b + RBV or by HCV itself. The most common adverse events (≥65%) observed were pain at the injection site, headache, asthenia, psychiatric disturbances, fever, and gastrointestinal symptoms. Regarding sustained virological response, a 20% superiority was observed in the patients who received concomitant Terap C treatments from the beginning of the study compared with those who started after Week 12.

CONCLUSIONS

Vaccination with Terap C in patients with chronic HCV infection was safe and well tolerated. Clinical trial protocol code: IG/VHI/HC/0701; Public Register Code: RPCEC00000074.

Asunaprevir Evokes Hepatocytes Innate Immunity to Restrict the Replication of Hepatitis C and Dengue Virus

Type I Interferon-mediated innate immunity against Flaviviridae, such as Hepatitis C virus (HCV) and Dengue virus (DENV), involves TLR3, RIG-I-like receptor (RLR) and JAK-STAT signal pathways. Asunaprevir is a newly developed HCV protease inhibitor for HCV treatment. Whether, asunaprevir activates innate immunity to restrict viral infection is unclear. Thus, this study investigates the effect of asunaprevir on innate immunity and its influence on HCV and DENV infection. Huh 7.5.1, Hep-G2 cells, JFH-1 infection model, and DENV-2 infection were used for the analysis. The activity of asunaprevir-regulated innate immunity signal pathway was assessed with IFN-β promoter or IFN-stimulated responsive element (ISRE) reporter assays and immunoblotting of key signal proteins. siRNA-mediated MAVS and TRIF knockdown of cells was performed to assess the effect of asunaprevir-regulated innate immunity against HCV and DENV. Asunaprevir treatment activated ISRE and IFN-β promoter-luciferase activities and signaling proteins in the JAK-STAT, MAVS, and TRIF pathways in Huh 7.5.1 cells. Asunaprevir-mediated signaling activation was decreased in MAVS-knockdown cells. Importantly, both RNA and protein levels of DENV-2 NS3 were decreased in asunaprevir-treated Huh 7.5.1 and HepG2 cells. In MAVS-knockdown cells, the restrictive effect of asunaprevir on HCV and DENV was attenuated. Our findings reveal an unexpected activity of asunaprevir, the activation of MAVS dependent innate immunity to restrict HCV and DENV infection.

Anti-hepatitis C virus potency of a new autophagy inhibitor using human liver slices model

AIM

To evaluate the antiviral potency of a new anti-hepatitis C virus (HCV) antiviral agent targeting the cellular autophagy machinery.

METHODS

Non-infected liver slices, obtained from human liver resection and cut in 350 μm-thick slices (2.7 × 10(6) cells per slice) were infected with cell culture-grown HCV Con1b/C3 supernatant (multiplicity of infection = 0.1) cultivated for up to ten days. HCV infected slices were treated at day 4 post-infection with GNS-396 for 6 d at different concentrations. HCV replication was evaluated by strand-specific real-time quantitative reverse transcription - polymerase chain reaction. The infectivity titers of supernatants were evaluated by foci formation upon inoculation into naive Huh-7.5.1 cells. The cytotoxic effect of the drugs was evaluated by lactate dehydrogenase leakage assays.

RESULTS

The antiviral efficacy of a new antiviral drug, GNS-396, an autophagy inhibitor, on HCV infection of adult human liver slices was evidenced in a dose-dependent manner. At day 6 post-treatment, GNS-396 EC50 was 158 nmol/L without cytotoxic effect (compared to hydroxychloroquine EC50 = 1.17 μmol/L).

CONCLUSION

Our results demonstrated that our ex vivo model is efficient for evaluation the potency of autophagy inhibitors, in particular a new quinoline derivative GNS-396 as antiviral could inhibit HCV infection in a dose-dependent manner without cytotoxic effect.

Kushenin induces the apoptosis of HCV-infected cells by blocking the PI3K-Akt-mTOR pathway via inhibiting NS5A

With the increased burden induced by HCV, there is an urgent need to develop better-tolerated agents with good safety. In this study, we evaluated the anti-HCV capability of kushenin, as well as the possible mechanism to Huh7.5-HCV cells. The results demonstrated that kushenin significantly inhibited the HCV-RNA level. Similarly, the expression of HCV-specific protein NS5A was also decreased. Molecular docking results displayed that kushenin bonded well to the active pockets of HCV NS5A, further confirming the effects of kushenin on HCV replication. Coimmunoprecipitation assay determined that kushenin suppressed the interaction between PI3K and NS5A in HCV-replicon cells. Furthermore, kushenin exerted an obviously induced function on HCV-replicon cells apoptosis by inhibiting PI3K-Akt-mTOR pathway, which could be ameliorated by the specific activator IGF-1 addition. Taken together, kushenin possesses the ability to inhibit HCV replication, and contributes to the increased apoptosis of HCV-infected cells by blocking the PI3K-Akt-mTOR pathway via inhibiting NS5A. Our results provide important evidence for a better understanding of the pathogenesis of HCV infection, and suggest that kushenin has the potential to treat HCV disease.

Directly acting antivirals for hepatitis C virus arrive in HIV/hepatitis C virus co-infected patients: from 'mind the gap' to 'where's the gap?'

In patients living with HIV infection with hepatitis C (HCV) is common. HIV/HCV co-infection results in more rapid liver fibrosis progression than HCV alone and end-stage liver disease is a major cause of morbidity and mortality in co-infected patients. Historically, treatment outcomes with interferon based therapy in this group have been poor but with the advent of directly acting antiviral (DAA) drugs for HCV, rates of cure have improved dramatically. This article reviews recent evidence on the treatment of HCV in co-infected patients including the efficacy of new regimens and information on drug-drug interactions between DAAs and antiretroviral therapy. We also discuss the relationship between the pathogenesis of HIV and HCV infections, the treatment of acute hepatitis C and the current debate regarding the cost-effectiveness and affordability of DAAs.

Effects of short RNA structural analogues against hepatitis C virus genotypes 2, 3 and 4 in replicon cells

OBJECTIVE

To determine whether computer-predicted short RNA structural analogues could inhibit hepatitis C virus (HCV) genotype 2a, 3a and 4a replication in cultured cells.

METHODS

Short RNA sequences, X12, X12a and X12b, designed to be identical in secondary structure to the X region in the 3'-untranslated region (3'-UTR) of the HCV 1b genome, as well as shorter stem-loop components of X region, were inserted into a plasmid and transfected into separate Huh7.5 human hepatoma cells stably transfected with subgenomic replicons for genotypes 2a, 3a and 4a. All replicons included a firefly luciferase reporter gene. After 48 h of plasmid transfection, the inhibition of HCV replication was determined by HCV RNA isolation and quantification by real-time polymerase chain reaction and luciferase assays.

RESULTS

All the secondary structural analogues to genotype 1b X region cross-inhibited genotype 2a, 3a and 4a replicons. The maximum inhibition by genotype 1b X region structural analogues was obtained against genotype 2a cells in which X12, X12a and X12b inhibited replication by 30%, 63% and 72%, respectively (P < 0.05 for all), compared to an unrelated hepatitis B viral analogue.

CONCLUSIONS

Despite substantial sequence dissimilarity, HCV RNA genotype 1b X region analogues cross-inhibited the replication of HCV genotypes 2a, 3a and 4a. Particular conformations and not the sequence of the stem-loops of the X region are involved in HCV replication.

β-D-2'-C-Methyl-2,6-diaminopurine Ribonucleoside Phosphoramidates are Potent and Selective Inhibitors of Hepatitis C Virus (HCV) and Are Bioconverted Intracellularly to Bioactive 2,6-Diaminopurine and Guanosine 5'-Triphosphate Forms

The conversion of selected β-D-2,6-diaminopurine nucleosides (DAPNs) to their phosphoramidate prodrug (PD) substantially blocks the conversion to the G-analog allowing for the generation of two bioactive nucleoside triphosphates (NTPs) in human hepatocytes. A variety of 2'-C-methyl DAPN-PDs were prepared and evaluated for inhibition of HCV viral replication in Huh-7 cells, cytotoxicity in various cell lines, and cellular pharmacology in both Huh-7 and primary human liver cells. The DAPN-PDs were pan-genotypic, effective against various HCV resistant mutants, and resistant variants could not be selected. 2'-C-Me-DAPN-TP and 2'-C-Me-GTP were chain terminators for genotype 1b HCV-pol, and single nucleotide incorporation assays revealed that 2'-C-Me-DAPN-TP was incorporated opposite U. No cytotoxicity was observed with our DAPN-PD when tested up to 50 μM. A novel, DAPN-PD, 15c, has been selected for further evaluation because of its good virologic and toxicologic profile and its ability to deliver two active metabolites, potentially simplifying HCV treatment.

Influence of host resistance on viral adaptation: hepatitis C virus as a case study

Genetic and cellular studies have shown that the host’s innate and adaptive immune responses are an important correlate of viral infection outcome. The features of the host’s immune response (host resistance) reflect the coevolution between hosts and pathogens that has occurred over millennia, and that has also resulted in a number of strategies developed by viruses to improve fitness and survival within the host (viral adaptation). In this review, we discuss viral adaptation to host immune pressure via protein–protein interactions and sequence-specific mutations. Specifically, we will present the “state of play” on viral escape mutations to host T-cell responses in the context of the hepatitis C virus, and their influence on infection outcome.

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.

New treatments for chronic hepatitis C: an overview for paediatricians

Pegylated interferon (IFN) α-2a or 2b in combination with ribavirin for children aged 3 years and older is the standard treatment for paediatric chronic hepatitis C. This treatment regimen was developed firstly in adults. In recent years, a number of direct-acting antiviral agents (DAAs) are under development for treatment of chronic hepatitis C virus (HCV) infection. These agents block viral replication inhibiting directly one of the several steps of HCV lifecycle. DAAs are classified into several categories based on their molecular target: HCV NS3/4A protease inhibitors, HCV NS5B polymerase inhibitors and HCV NS5A inhibitors. Other promising compounds are cyclophilin A inhibitors, mi-RNA122 and IFN-λ. Several new drugs associations will be developed in the near future starting from the actual standard of care. IFN-based and IFN-free regimens are being studied in adults. In this constantly evolving scenario new drug regimens targeted and suitable for children would be possible in the next future. Especially for children, it is crucial to identify the right combination of drugs with the highest potency, barrier to resistance and the best safety profile.

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.

An a priori prediction model of response to peginterferon plus ribavirin dual therapy in naïve patients with genotype 1 chronic hepatitis C

BACKGROUND

Aim was to select naïve patients with genotype 1 chronic hepatitis C having a high probability of response to Peg-interferon+ribavirin therapy.

METHODS

In 1073 patients (derivation cohort), predictors of rapid and sustained virological response were identified by logistic analysis; regression coefficients were used to generate prediction models for sustained virological response. Probabilities at baseline and treatment week 4 were utilized to develop a decision rule to select patients with high likelihood of response. The model was then validated in 423 patients (validation cohort).

RESULTS

In the derivation cohort, 257 achieved rapid virological response and 818 did not, with sustained virological response rates of 80.2% and 25.4%, respectively; interleukin-28B polymorphisms, fibrosis staging, gamma-glutamyl transferase, and viral load predicted sustained virological response. Assuming a <30% sustained virological response probability for not recommending Peg-interferon+ribavirin, 100 patients (25.6%) in the validation cohort were predicted a priori to fail this regimen. Assuming a ≥80% sustained virological response probability as a threshold to continue with Peg-interferon+ribavirin, 61 patients were predicted to obtain sustained virological response, and 55 of them (90.2%) eventually did.

CONCLUSIONS

This model uses easily determined variables for a personalized estimate of the probability of sustained virological response with Peg-interferon+ribavirin, allowing to identify patients who may benefit from conventional therapy.

Efficacy and safety of peginterferon plus ribavirin for patients aged ≥ 65 years with chronic hepatitis C: a systematic review and meta-analysis

METHODS

Studies up to August 30, 2012 of the efficacy and safety of peginterferon plus ribavirin therapy in CHC patients aged≥65 years were systematically identified in PubMed, Ovid, Web of Knowledge and Cochrane Library databases. A meta-analysis was performed using both fixed- and random-effects models based on heterogeneity across studies.

RESULTS

The overall sustained virological response (SVR) in CHC patients aged≥65 years was significantly lower than in patients aged<65 years on both intention-to-treat (ITT; 42.0% vs. 60.1%, respectively; P<0.00001) and per-protocol (PP; 54.4% vs. 67.4%, respectively; P=0.002) analyses, including treatment-naïve patients. Subgroup analysis showed that patients≥65 years with either hepatitis C virus (HCV) genotype 1/4 or 2/3 had lower SVR rates than younger patients. No statistically significant differences were observed between the two groups in terms of rapid virological response (RVR) and early virological response (EVR) rates (both P≥0.05). However, the end-of-treatment virological response (ETR) rate was lower in patients≥65 years, who also had a significantly higher risk of relapse than those aged<65 years (39.8% vs. 26.9%, respectively; P<0.00001). The discontinuation rate in the older patients was also significantly higher than in the younger patients (25.5% vs. 14.8%, respectively; P<0.00001). Ribavirin dose reduction in the older patients treated with peginterferon plus ribavirin was also significantly higher than in younger patients (44.5% vs. 32.8%, respectively; P<0.00001).

CONCLUSION

Peginterferon plus ribavirin therapy was effective for older patients with CHC, particularly those with HCV genotype 2/3. Response-guided therapy can be used for older patients with genotype 1/4, but such patients had poorer treatment adherence, leading to poorer treatment efficacy.

Hepatitis C virus in the new era: Perspectives in epidemiology, prevention, diagnostics and predictors of response to therapy

Despite the great successes achieved in the fields of virology and diagnostics, several difficulties affect improvements in hepatitis C virus (HCV) infection control and eradication in the new era. New HCV infections still occur, especially in some of the poorest regions of the world, where HCV is endemic and long-term sequelae have a growing economic and health burden. An HCV vaccine is still no available, despite years of researches and discoveries about the natural history of infection and host-virus interactions: several HCV vaccine candidates have been developed in the last years, targeting different HCV antigens or using alternative delivery systems, but viral variability and adaption ability constitute major challenges for vaccine development. Many new antiviral drugs for HCV therapy are in preclinical or early clinical development, but different limitations affect treatment validity. Treatment predictors are important tools, as they provide some guidance for the management of therapy in patients with chronic HCV infection: in particular, the role of host genomics in HCV infection outcomes in the new era of direct-acting antivirals may evolve for new therapeutic targets, representing a chance for modulated and personalized treatment management, when also very potent therapies will be available. In the present review we discuss the most recent data about HCV epidemiology, the new perspectives for the prevention of HCV infection and the most recent evidence regarding HCV diagnosis, therapy and predictors of response to it.

Global fold and backbone dynamics of the hepatitis C virus E2 glycoprotein transmembrane domain determined by NMR

E1 and E2 are two hepatitis C viral envelope glycoproteins that assemble into a heterodimer that is essential for membrane fusion and penetration into the target cell. Both extracellular and transmembrane (TM) glycoprotein domains contribute to this interaction, but study of TM-TM interactions has been limited because synthesis and structural characterization of these highly hydrophobic segments present significant challenges. In this NMR study, by successful expression and purification of the E2 transmembrane domain as a fusion construct we have determined the global fold and characterized backbone motions for this peptide incorporated in phospholipid micelles. Backbone resonance frequencies, relaxation rates and solvent exposure measurements concur in showing this domain to adopt a helical conformation, with two helical segments spanning residues 717-726 and 732-746 connected by an unstructured linker containing the charged residues D728 and R730 involved in E1 binding. Although this linker exhibits increased local motions on the ps timescale, the dominating contribution to its relaxation is the global tumbling motion with an estimated correlation time of 12.3ns. The positioning of the helix-linker-helix architecture within the mixed micelle was established by paramagnetic NMR spectroscopy and phospholipid-peptide cross relaxation measurements. These indicate that while the helices traverse the hydrophobic interior of the micelle, the linker lies closer to the micelle perimeter to accommodate its charged residues. These results lay the groundwork for structure determination of the E1/E2 complex and a molecular understanding of glycoprotein heterodimerization.

Hepatitis C virus reinfection after liver transplantation: Is there a role for direct antiviral agents?

Recurrence of hepatitis C virus (HCV) infection following liver transplantation (LT) is almost universal and can accelerate graft cirrhosis in up to 30% of patients. The development of effective strategies to treat or prevent HCV recurrence after LT remains a major challenge, considering the shortage of donor organs and the accelerated progression of HCV in LT recipients. Standard antiviral therapy with pegylated-interferon plus ribavirin is the current treatment of choice for HCV LT recipients, even though the combination is not as effective as it is in immunocompetent patients. A sustained virological response in the setting of LT improves patient and graft survival, but this is only achieved in 30%-45% of patients and the treatment is poorly tolerated. To improve the efficacy of pre- and post-transplant antiviral therapy, a new class of potent direct-acting antiviral agents (DAAs) has been developed. The aim of this review is to summarize the use of DAAs in LT HCV patients. PubMed, Cochrane Library, MEDLINE, EMBASE, Web of Science and clinical trial databases were searched for this purpose. To date, only three clinical studies on the topic have been published and most of the available data are in abstract form. Although a moderately successful early virological response has been reported, DAA treatment regimens were associated with severe toxicity mitigating their potential usefulness. Moreover, the ongoing nature of data, the lack of randomized studies, the small number of enrolled patients and the heterogeneity of these studies make the results largely anecdotal and questionable. In conclusion, large well-designed clinical studies on DAAs in HCV LT patients are required before these drugs can be recommended after transplantation.

Structural basis for HTLV-1 protease inhibition by the HIV-1 protease inhibitor indinavir

HTLV-1 protease (HTLV-1 PR) is an aspartic protease which represents a promising drug target for the discovery of novel anti-HTLV-1 drugs. The X-ray structure of HTLV-1 PR in complex with the well-known and approved HIV-1 PR inhibitor Indinavir was determined at 2.40 Å resolution. In this contribution, we describe the first crystal structure in complex with a nonpeptidic inhibitor that accounts for rationalizing the rather moderate affinity of Indinavir against HTLV-1 PR and provides the basis for further structure-guided optimization strategies.

Genotypic and phenotypic analyses of hepatitis C virus variants observed in clinical studies of VX-222, a nonnucleoside NS5B polymerase inhibitor

VX-222, a thiophene-2-carboxylic acid derivative, is a selective nonnucleoside inhibitor of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase. In phase 1 and 2 clinical studies, VX-222 demonstrated effective antiviral efficacy, with substantial reductions in plasma HCV RNA in patients chronically infected with genotype 1 HCV. To characterize the potential for selection of VX-222-resistant variants in HCV-infected patients, the HCV NS5B gene was sequenced at baseline and during and after 3 days of VX-222 dosing (monotherapy) in a phase 1 study. Variants with the substitutions L419C/I/M/P/S/V, R422K, M423I/T/V, I482L/N/T, A486S/T/V, and V494A were selected during VX-222 dosing, and their levels declined over time after the end of dosing. Phenotypic analysis of these variants was conducted using HCV replicons carrying site-directed mutations. Of the 17 variants, 14 showed reduced susceptibility to VX-222 compared with the wild type, with the L419C/S and R422K variants having higher levels of resistance (>200-fold) than the rest of the variants (6.8- to 76-fold). The M423I and A486S variants remained susceptible to VX-222. The 50% effective concentration (EC50) for the L419P variant could not be obtained due to the poor replication of this replicon. The majority of the variants (15/17) were less fit than the wild type. A subset of the variants, predominately the L419S and R422K variants, were observed when the efficacy and safety of VX-222- and telaprevir-based regimens given for 12 weeks were investigated in genotype 1 HCV-infected patients in a phase 2 study. The NS3 and NS5B variants selected during the dual combination therapy showed reduced susceptibility to both telaprevir and VX-222 and had a lower replication capacity than the wild type. The phase 1b study has the ClinicalTrials.gov identifier NCT00911963, and the phase 2a study has ClinicalTrials.gov identifier NCT01080222.

Syndecan 4 is involved in mediating HCV entry through interaction with lipoviral particle-associated apolipoprotein E

Hepatitis C virus (HCV) is a major cause of liver disease worldwide and HCV infection represents a major health problem. HCV associates with host lipoproteins forming host/viral hybrid complexes termed lipoviral particles. Apolipoprotein E (apoE) is a lipoprotein component that interacts with heparan sulfate proteoglycans (HSPG) to mediate hepatic lipoprotein uptake, and may likewise mediate HCV entry. We sought to define the functional regions of apoE with an aim to identify critical apoE binding partners involved in HCV infection. Using adenoviral vectors and siRNA to modulate apoE expression we show a direct correlation of apoE expression and HCV infectivity, whereas no correlation exists with viral protein expression. Mutating the HSPG binding domain (HSPG-BD) of apoE revealed key residues that are critical for mediating HCV infection. Furthermore, a novel synthetic peptide that mimics apoE’s HSPG-BD directly and competitively inhibits HCV infection. Genetic knockdown of the HSPG proteins syndecan (SDC) 1 and 4 revealed that SDC4 principally mediates HCV entry. Our data demonstrate that HCV uses apoE-SDC4 interactions to enter hepatoma cells and establish infection. Targeting apoE-SDC interactions could be an alternative strategy for blocking HCV entry, a critical step in maintaining chronic HCV infection.

Peptide-pulsed dendritic cells induce the hepatitis C viral epitope-specific responses of naïve human T cells

Hepatitis C virus (HCV) is a major cause of liver disease. Spontaneous resolution of infection is associated with broad, MHC class I- (CD8(+)) and class II-restricted (CD4(+)) T cell responses to multiple viral epitopes. Only 20% of patients clear infection spontaneously, however, most develop chronic disease. The response to chemotherapy varies; therapeutic vaccination offers an additional treatment strategy. To date, therapeutic vaccines have demonstrated only limited success in clinical trials. Vector-mediated vaccination with multi-epitope-expressing DNA constructs provides an improved approach. Highly-conserved, HLA-A2-restricted HCV epitopes and HLA-DRB1-restricted immunogenic consensus sequences (ICS, each composed of multiple overlapping and highly conserved epitopes) were predicted using bioinformatics tools and synthesized as peptides. HLA binding activity was determined in competitive binding assays. Immunogenicity and the ability of each peptide to stimulate naïve human T cell recognition and IFN-γ production were assessed in cultures of total PBMCs and in co-cultures composed of peptide-pulsed dendritic cells (DCs) and purified T lymphocytes, cell populations derived from normal blood donors. Essentially all predicted HLA-A2-restricted epitopes and HLA-DRB1-restricted ICS exhibited HLA binding activity and the ability to elicit immune recognition and IFN-γ production by naïve human T cells. The ability of DCs pulsed with these highly-conserved HLA-A2- and -DRB1-restricted peptides to induce naïve human T cell reactivity and IFN-γ production ex vivo demonstrates the potential efficacy of a multi-epitope-based HCV vaccine targeted to dendritic cells.

Understanding the interaction of hepatitis C virus with host DEAD-box RNA helicases

The current therapeutic regimen to combat chronic hepatitis C is not optimal due to substantial side effects and the failure of a significant proportion of patients to achieve a sustained virological response. Recently developed direct-acting antivirals targeting hepatitis C virus (HCV) enzymes reportedly increase the virologic response to therapy but may lead to a selection of drug-resistant variants. Besides direct-acting antivirals, another promising class of HCV drugs in development include host targeting agents that are responsible for interfering with the host factors crucial for the viral life cycle. A family of host proteins known as DEAD-box RNA helicases, characterized by nine conserved motifs, is known to play an important role in RNA metabolism. Several members of this family such as DDX3, DDX5 and DDX6 have been shown to play a role in HCV replication and this review will summarize our current knowledge on their interaction with HCV. As chronic hepatitis C is one of the leading causes of hepatocellular carcinoma, the involvement of DEAD-box RNA helicases in the development of HCC will also be highlighted. Continuing research on the interaction of host DEAD-box proteins with HCV and the contribution to viral replication and pathogenesis could be the panacea for the development of novel therapeutics against HCV.

Hepatitis C treatment: an incipient therapeutic revolution

An exciting paradigm shift is occurring in the treatment of hepatitis C virus (HCV). We now have the capacity to specifically target therapy to HCV proteins, and thereby directly interrupt the viral life cycle. The first direct-acting antivirals (DAAs), the NS3-4A serine protease inhibitors boceprevir and telaprevir, improved the rate of sustained virologic response (SVR), but their toxicities combined with PEG-IFN and RBV limited their overall efficacy. Sofosbuvir, a nucleotide HCV polymerase inhibitor, is now available and offers better tolerability and efficacy across all HCV genotypes. The next phase of therapy will be combining several classes of DAAs without IFN in order to make sustained clearance of hepatitis C deliverable to a much larger number of infected individuals.

Differential sensitivity of 5'UTR-NS5A recombinants of hepatitis C virus genotypes 1-6 to protease and NS5A inhibitors

BACKGROUND & AIMS

Hepatitis C virus (HCV) therapy will benefit from the preclinical evaluation of direct-acting antiviral (DAA) agents in infectious culture systems that test the effects on different virus genotypes. We developed HCV recombinants comprising the 5' untranslated region-NS5A (5-5A) from genotypes 1-6 and 2a(JFH1) NS5B-3' untranslated region, and tested the effects of NS3 protease and NS5A inhibitors on these recombinants.

METHODS

The HCV 5-5A recombinants with previously identified mutations in the NS3-helicase (F1464L), NS4A (A1672S), and NS5B (D2979G) were adapted and improved, by incorporating additional recovered mutations that increased their propagation in Huh7.5 cells. Concentration-response profiles were determined for each DAA agent in replicate infected Huh7.5 cells.

RESULTS

Developed efficient 1a(H77), 1a(TN), 3a(S52), 4a(ED43), 5a(SA13), and 6a(HK6a) 5-5A recombinants did not require mutations after viral passage in the NS3 protease or NS5A domain-I regions targeted by the drugs. They were inhibited in a concentration-dependent manner by the NS3 protease inhibitors telaprevir, boceprevir, asunaprevir, simeprevir, vaniprevir, faldaprevir, and MK-5172 and by the NS5A inhibitor daclatasvir. The 1a(TN) 5-5A and JFH1-independent full-length viruses had similar levels of sensitivity to the DAA agents, validating the 5-5A recombinants as surrogates for full-length viruses in DAA testing. Compared with the 1a(TN) full-length virus, the 3a(S52) 5-5A recombinant was highly resistant to all protease inhibitors, and the 4a(ED43) recombinant was highly resistant to telaprevir and boceprevir, but most sensitive to other protease inhibitors. Compared with other protease inhibitors, MK-5172 had exceptional potency against all HCV genotypes. The NS5A inhibitor daclatasvir had the highest potency observed, but with genotype-dependent activity.

CONCLUSIONS

The mutations F1464L, A1672S, and D2979G permitted the development of efficient HCV recombinants comprising genotype-specific 5' untranslated region-NS5A (5-5A), which include the natural NS3 protease and NS5A domain-I drug targets. The robust replication of adapted 5-5A recombinants allowed for direct comparison of NS3 protease and NS5A inhibitors against HCV strains of genotypes 1-6.

Incident severe thrombocytopenia in veterans treated with pegylated interferon plus ribavirin for chronic hepatitis C infection

PURPOSE

We sought to determine the incidence and risks for severe thrombocytopenia (platelets < 50,000/μL) in United States Veteran patients treated with pegylated interferon (PEG-IFN) plus ribavirin for hepatitis C virus-positive (HCV) chronic liver disease (CLD).

METHODS

Using a retrospective, observational cohort study design to analyze databases from the New England Veterans Healthcare System, we identified 979 patients diagnosed with HCV-positive CLD treated solely with PEG-IFN plus ribavirin. The cohort was stratified by pre-treatment platelet counts of 50,000-100,000/μL (N = 90), >100,000-150,000/μL (N = 162), and >150,000μL (N = 727). The cumulative incidence of severe thrombocytopenia and major bleeding events were determined for each baseline platelet group for 48 weeks following treatment initiation. Multivariable Cox regression was used to identify risk factors for incident severe thrombocytopenia.

RESULTS

Overall, severe thrombocytopenia occurred in 6.1% (N = 60), but in 41.1% of patients with pre-treatment platelet counts 50, 000-100,000/μL compared with 11.7% (p < 0.001) and 0.55% (p < 0.001) in the two higher pre-treatment platelet groups. Most episodes occurred within the first 12 weeks of treatment. Median nadir count for these 60 patients was 35,000/μL (inter-quartile range 28,000, 44,000). Baseline platelet counts of 50,000-100,000/μL [adjusted hazard ratio (HR) = 3.81; 95%CI = 2.07-7.00] and hemoglobin <10 g/dL (adjusted HR = 3.39; 95%CI = 1.45-7.960) associated with severe thrombocytopenia. Major bleeding events during the 48-week observation period were rare (N = 5, 0.51%).

CONCLUSIONS

The incidence of severe thrombocytopenia in a large, observational cohort of veteran patients with HCV CLD treated with PEG-IFN plus ribavirin was 6.1%. Low pre-treatment platelet counts and hemoglobin levels associated with early, incident severe thrombocytopenia.

Neutralizing antibodies and broad, functional T cell immune response following immunization with hepatitis C virus proteins-based vaccine formulation

HCV is a worldwide health problem despite the recent advances in the development of more effective therapies. No preventive vaccine is available against this pathogen. However, non-sterilizing immunity has been demonstrated and supports the potential success of HCV vaccines. Induction of cross-neutralizing antibodies and T cell responses targeting several conserved epitopes, have been related to hepatitis C virus (HCV) clearance. Therefore, in this work, the immunogenicity of a preparation (MixprotHC) based on protein variants of HCV Core, E1, E2 and NS3 was evaluated in mice and monkeys. IgG from MixprotHC immunized mice and monkeys neutralized the infectivity of heterologous HCVcc. Moreover, strong CD4+ and CD8+ T cells proliferative and IFN-γ secretion responses were elicited against HCV proteins. Remarkably, immunization with MixprotHC induced control of viremia in a surrogate challenge model in mice. These results suggest that MixprotHC might constitute an effective immunogen against HCV in humans with potential for reducing the likelihood of immune escape and viral persistence.

Chutes and ladders in hepatitis C nucleoside drug development

Chutes and Ladders is an exciting up-and-down-again game in which players race to be the first to the top of the board. Along the way, they will find ladders to help them advance, and chutes that will cause them to move backwards. The development of nucleoside analogs for clinical treatment of hepatitis C presents a similar scenario in which taking shortcuts may help quickly advance a program, but there is always a tremendous risk of being sent backwards as one competes for the finish line. In recent years the treatment options for chronic hepatitis C virus (HCV) infection have expand due to the development of a replicon based in vitro evaluation system, allowing for the identification of multiple drugable viral targets along with a concerted and substantial drug discovery effort. Three major drug targets have reached clinical study for chronic HCV infection: the NS3/4A serine protease, the large phosphoprotein NS5A, and the NS5B RNA-dependent RNA polymerase. Recently, two oral HCV protease inhibitors were approved by the FDA and were the first direct acting anti-HCV agents to result from the substantial research in this area. There are currently many new chemical entities from several different target classes that are being evaluated worldwide in clinical trials for their effectiveness at achieving a sustained virologic response (SVR) (Pham et al., 2004; Radkowski et al., 2005). Clearly the goal is to develop therapies leading to a cure that are safe, widely accessible and available, and effective against all HCV genotypes (GT), and all stages of the disease. Nucleoside analogs that target the HCV NS5B polymerase that have reached human clinical trials is the focus of this review as they have demonstrated significant advantages in the clinic with broader activity against the various HCV GT and a higher barrier to the development of resistant viruses when compared to all other classes of HCV inhibitors.

The AMPK-related kinase SNARK regulates hepatitis C virus replication and pathogenesis through enhancement of TGF-β signaling

BACKGROUND & AIMS

Hepatitis C virus (HCV) is a major cause of chronic liver disease worldwide. The biological and therapeutic importance of host cellular cofactors for viral replication has been recently appreciated. Here we examined the roles of SNF1/AMP kinase-related kinase (SNARK) in HCV replication and pathogenesis.

METHODS

The JFH1 infection system and the full-length HCV replicon OR6 cell line were used. Gene expression was knocked down by siRNAs. SNARK mutants were created by site-directed mutagenesis. Intracellular mRNA levels were measured by qRT-PCR. Endogenous and overexpressed proteins were detected by Western blot analysis and immunofluorescence. Transforming growth factor (TGF)-β signaling was monitored by a luciferase reporter construct. Liver biopsy samples from HCV-infected patients were analyzed for SNARK expression.

RESULTS

Knockdown of SNARK impaired viral replication, which was rescued by wild type SNARK but not by unphosphorylated or kinase-deficient mutants. Knockdown and overexpression studies demonstrated that SNARK promoted TGF-β signaling in a manner dependent on both its phosphorylation and kinase activity. In turn, chronic HCV replication upregulated the expression of SNARK in patients. Further, the SNARK kinase inhibitor metformin suppressed both HCV replication and SNARK-mediated enhancement of TGF-β signaling.

CONCLUSIONS

Thus reciprocal regulation between HCV and SNARK promotes TGF-β signaling, a major driver of hepatic fibrogenesis. These findings suggest that SNARK will be an attractive target for the design of novel host-directed antiviral and antifibrotic drugs.

Epidermal growth factor receptor signaling impairs the antiviral activity of interferon-alpha

Interferon-alpha (IFN-α) exhibits its antiviral activity through signal transducer and activator of transcription protein (STAT) signaling and the expression of IFN response genes (IRGs). Viral infection has been shown to result in activation of epidermal growth factor receptor (EGFR)-a host cell entry factor used by several viruses, including hepatitis C virus. However, the effect of EGFR activation for cellular antiviral responses is unknown. Here, we uncover cross-talk between EGFR and IFN-α signaling that has a therapeutic effect on IFN-α-based therapies and functional relevance for viral evasion and IFN resistance. We show that combining IFN-α with the EGFR inhibitor, erlotinib, potentiates the antiviral effect of each compound in a highly synergistic manner. The extent of the synergy correlated with reduced STAT3 phosphorylation in the presence of erlotinib, whereas STAT1 phosphorylation was not affected. Furthermore, reduced STAT3 phosphorylation correlated with enhanced expression of suppressors of cytokine signaling 3 (SOCS3) in the presence of erlotinib and enhanced expression of the IRGs, radical S-adenosyl methionine domain containing 2 and myxovirus resistance protein 1. Moreover, EGFR stimulation reduced STAT1 dimerization, but not phosphorylation, indicating that EGFR cross-talk with IFN signaling acts on the STATs at the level of binding DNA.

CONCLUSIONS

Our results support a model where inhibition of EGFR signaling impairs STAT3 phosphorylation, leading to enhanced IRG expression and antiviral activity. These data uncover a novel role of EGFR signaling in the antiviral activity of IFN-α and open new avenues of improving the efficacy of IFN-α-based antiviral therapies.

Safety, tolerability, and pharmacokinetics of ribavirin in hepatitis C virus-infected patients with various degrees of renal impairment

Ribavirin (RBV) is an integral part of standard-of-care hepatitis C virus (HCV) treatments and many future regimens under investigation. The pharmacokinetics (PK), safety, and tolerability of RBV in chronically HCV-infected patients with renal impairment are not well defined and were the focus of an open-label PK study in HCV-infected patients receiving RBV plus pegylated interferon. Serial RBV plasma samples were collected over 12 h on day 1 of weeks 1 and 12 from patients with moderate renal impairment (creatinine clearance [CLCR], 30 to 50 ml/min; RBV, 600 mg daily), severe renal impairment (CLCR, <30 ml/min; RBV, 400 mg daily), end-stage renal disease (ESRD) (RBV, 200 mg daily), or normal renal function (CLCR, >80 ml/min; RBV, 800 to 1,200 mg daily). Of the 44 patients, 9 had moderately impaired renal function, 10 had severely impaired renal function, 13 had ESRD, and 12 had normal renal function. The RBV dose was reduced because of adverse events (AEs) in 71% and 53% of severe and moderate renal impairment groups, respectively. Despite this modification, patients with moderate and severe impairment had 12-hour (area under the concentration-time curve from 0 to 12 h [AUC0-12]) values 36% (38,452 ng · h/ml) and 25% (35,101 ng · h/ml) higher, respectively, than those with normal renal function (28,192 ng · h/ml). Patients with ESRD tolerated a 200-mg daily dose, and AUC0-12 was 20% lower (22,629 ng · h/ml) than in patients with normal renal function. PK modeling and simulation (M&S) indicated that doses of 200 mg or 400 mg alternating daily for patients with moderate renal impairment and 200 mg daily for patients with severe renal impairment were the most appropriate dose regimens in these patients.

Therapy of chronic hepatitis C virus infection in the era of direct-acting and host-targeting antiviral agents

OBJECTIVES

Chronic hepatitis C virus (HCV) infection represents a leading worldwide medical and social problem. The expanding knowledge of HCV lifecycle has led to the development of novel antiviral agents that: a) specifically target a viral function (direct-acting antivirals), or b) specifically inhibit viral replication. The present review describes the novel anti-HCV drugs that have been better studied at the time of this writing and the current two types of treatment, namely interferon-based and interferon-free regimens. In addition, predictive factors, virological responses, side-effects, and resistance mechanisms of the novel agents are summarized.

CONCLUSIONS

The introduction of novel antiviral agents is remarkably changing the therapeutic combinations aimed at improving virological responses both for easy-to-cure and difficult-to-treat patients. Since additional, effective drugs are under advanced development, it seems reasonable to expect that further therapeutic and prognostic improvements will be achieved in the near future.