The hepatitis C virus life cycle as a target for new antiviral therapies

Pharmacophore-Assisted Covalent Docking Identifies a Potential Covalent Inhibitor for Drug-Resistant Genotype 3 Variants of Hepatitis C Viral NS3/4A Serine Protease

The emergence of drug-resistance-inducing mutations in Hepatitis C virus (HCV) coupled with genotypic heterogeneity has made targeting NS3/4A serine protease difficult. In this work, we investigated the mutagenic variations in the binding pocket of Genotype 3 (G3) HCV NS3/4A and evaluated ligands for efficacious inhibition. We report mutations at 14 positions within the ligand-binding residues of HCV NS3/4A, including H57R and S139P within the catalytic triad. We then modelled each mutational variant for pharmacophore-based virtual screening (PBVS) followed by covalent docking towards identifying a potential covalent inhibitor, i.e., cpd-217. The binding stability of cpd-217 was then supported by molecular dynamic simulation followed by MM/GBSA binding free energy calculation. The free energy decomposition analysis indicated that the resistant mutants alter the HCV NS3/4A-ligand interaction, resulting in unbalanced energy distribution within the binding site, leading to drug resistance. Cpd-217 was identified as interacting with all NS3/4A G3 variants with significant covalent docking scores. In conclusion, cpd-217 emerges as a potential inhibitor of HCV NS3/4A G3 variants that warrants further in vitro and in vivo studies. This study provides a theoretical foundation for drug design and development targeting HCV G3 NS3/4A.

Promising Potential of Curcumin and Related Compounds for Antiviral Drug Discovery

Viruses are acellular, microscopic, and mobile particles containing genetic particles, either DNA/RNA strands as nucleoproteins, responsible for 69,53,743 deaths till the year 2023. Curcumin and related compounds are among the areas of pivotal interest for researchers because of their versatile pharmacological profile. Chemically known as diferuloylmethane, which is a main constituent of turmeric along with demethoxycurcumin and bisdemethoxycurcumin, they have a broad spectrum of antiviral activity against viruses such as human immunodeficiency virus, herpes simplex virus, influenza virus (Avian influenza) and Hepatitis C virus HIV. The possible role of curcumin as an antiviral agent may be attributed to the activation of the 20S proteasome, a cellular machinery responsible for degrading unfolded or misfolded proteins in a ubiquitin-independent manner. It shows suppression of HBV entry at various infection stages by inhibiting cccDNA replication by inhibiting the Wnt/β-catenin signaling pathway to attenuate IAV-induced myocarditis.

Insights into the secondary and tertiary structure of the Bovine Viral Diarrhea Virus Internal Ribosome Entry Site

The internal ribosome entry site (IRES) RNA of bovine viral diarrhoea virus (BVDV), an economically significant Pestivirus, is required for the cap-independent translation of viral genomic RNA. Thus, it is essential for viral replication and pathogenesis. We applied a combination of high-throughput biochemical RNA structure probing (SHAPE-MaP) and in silico modelling approaches to gain insight into the secondary and tertiary structures of BVDV IRES RNA. Our study demonstrated that BVDV IRES RNA in solution forms a modular architecture composed of three distinct structural domains (I-III). Two regions within domain III are represented in tertiary interactions to form an H-type pseudoknot. Computational modelling of the pseudoknot motif provided a fine-grained picture of the tertiary structure and local arrangement of helices in the BVDV IRES. Furthermore, comparative genomics and consensus structure predictions revealed that the pseudoknot is evolutionarily conserved among many Pestivirus species. These studies provide detailed insight into the structural arrangement of BVDV IRES RNA H-type pseudoknot and encompassing motifs that likely contribute to the optimal functionality of viral cap-independent translation element.

StackHCV: a web-based integrative machine-learning framework for large-scale identification of hepatitis C virus NS5B inhibitors

Fast and accurate identification of inhibitors with potency against HCV NS5B polymerase is currently a challenging task. As conventional experimental methods is the gold standard method for the design and development of new HCV inhibitors, they often require costly investment of time and resources. In this study, we develop a novel machine learning-based meta-predictor (termed StackHCV) for accurate and large-scale identification of HCV inhibitors. Unlike the existing method, which is based on single-feature-based approach, we first constructed a pool of various baseline models by employing a wide range of heterogeneous molecular fingerprints with five popular machine learning algorithms (k-nearest neighbor, multi-layer perceptron, partial least squares, random forest and support vectors machine). Secondly, we integrated these baseline models in order to develop the final meta-based model by means of the stacking strategy. Extensive benchmarking experiments showed that StackHCV achieved a more accurate and stable performance as compared to its constituent baseline models on the training dataset and also outperformed the existing predictor on the independent test dataset. To facilitate the high-throughput identification of HCV inhibitors, we built a web server that can be freely accessed at http://camt.pythonanywhere.com/StackHCV . It is expected that StackHCV could be a useful tool for fast and precise identification of potential drugs against HCV NS5B particularly for liver cancer therapy and other clinical applications.

Multiscale model of hepatitis C virus dynamics in plasma and liver following combination therapy

This work explores the application of a physiologically structured population (PSP) framework in modeling hepatitis C virus (HCV) kinetics. To do so, a model was developed for the viral RNA load in plasma and liver as observed in 15 patients treated with a combination therapy of pegylated interferon, ribavirin, and telaprevir. By including both intracellular and extracellular processes of the HCV lifecycle, the model provided a description of the treatment effect on the intracellular HCV lifecycle. Combining PSP models with a nonlinear mixed effects approach in a single model permits a natural inclusion of the direct‐acting antiviral effect on intracellular processes, which can then be integrated with the viral kinetics within the host while accounting for the interindividual variability between patients. This should allow an exploration of the treatment effect within the entire chronic HCV‐infected population.

Analysis of drug-resistance-associated mutations and genetic barriers in hepatitis C virus NS5B sequences in China

The hepatitis C virus (HCV) NS5B protein is an RNA-dependent RNA polymerase that is required for viral genome replication and constitutes the most important target region for drugs being developed as direct-acting antivirals (DAAs) against HCV genotype 1. However, the extreme genetic variability leading to drug resistance mutations and genetic barriers has dramatically compromised the effectiveness of DAA therapy. The purpose of this study was to analyze the genetic variability of NS5B polymerase in HCV patients from different provinces of China to identify the impact of these resistance sites on genetic barriers. We analyzed 3489 NS5B sequences of HCV strains circulating in different regions of China, obtained from the GenBank database, 153 of which were from three cities in Sichuan Province (Yibin, Zigong and Zhangzhou). Sequence alignment was conducted using MEGA 6.0, the genetic information was translated into amino acids, and the percentage of polymorphic amino acid sites was calculated. The Vijver method was used to evaluate the occurrence of genetic barriers in HCV NS5B sequences. Blood samples were collected from 153 HCV patients from Sichuan for NS5B sequence analysis using real-time PCR and the Sanger method. Of the 17 antiviral drug resistance sites summarized from the published literature, nine were found in Chinese NS5B sequences, and C316Y was identified as the dominant mutation. Analysis of genetic barriers revealed that the probability of mutation to a drug-resistance-associated amino acid, in response to selective pressure from antiviral drugs was 100% at site 96 and 99.7% at site 282. Our study is the first to analyze the drug resistance sites and to evaluate genetic barriers in NS5B sequences that could affect the responsiveness of Chinese HCV patients to DAA therapy. The results provide a valuable basis for drug development and introduction of foreign-origin antiviral drugs in China that targeting the HCV NS5B region.

Molecular Mechanism of the Antiproliferative Activity of Short Immunostimulating dsRNA

Small double-stranded RNAs with certain sequence motifs are able to interact with pattern-recognition receptors and activate the innate immune system. Recently, we identified a set of short double-stranded 19-bp RNA molecules with 3-nucleotide 3′-overhangs that exhibited pronounced antiproliferative activity against cancer cells in vitro, and antitumor and antimetastatic activities in mouse models in vivo. The main objectives of this study were to identify the pattern recognition receptors that mediate the antiproliferative action of immunostimulating RNA (isRNA). Two cell lines, epidermoid carcinoma KB-3-1 cells and lung cancer A549 cells, were used in the study. These lines respond to the action of isRNA by a decrease in the growth rate, and in the case of A549 cells, also by a secretion of IL-6. Two sets of cell lines with selectively silenced genes encoding potential sensors and signal transducers of isRNA action were obtained on the basis of KB-3-1 and A549 cells. It was found that the selective silencing of PKR and RIG-I genes blocked the antiproliferative effect of isRNA, both in KB-3-1 and A549 cells, whereas the expression of MDA5 and IRF3 was not required for the antiproliferative action of isRNA. It was shown that, along with PKR and RIG-I genes, the expression of IRF3 also plays a role in isRNA mediated IL-6 synthesis in A549 cells. Thus, PKR and RIG-I sensors play a major role in the anti-proliferative signaling triggered by isRNA.

Identification of potential inhibitors for HCV NS5b of genotype 4a by combining dynamic simulation, protein-ligand interaction fingerprint, 3D pharmacophore, docking and 3D QSAR

HCV NS5B polymerase has been one of the most attractive targets for developing new drugs for HCV infection and many drugs were successfully developed, but all of them were designed for targeting Hepatitis C Virus genotype 1 (HCV GT1). Hepatitis C virus genotype 4a (HCV GT4a) dominant in Egypt has paid less attention. Here, we describe our protocol of virtual screening in identification of novel potential potent inhibitors for HCV NS5B polymerase of GT4a using homology modeling, protein-ligand interaction fingerprint (PLIF), docking, pharmacophore, and 3D CoMFA quantitative structure activity relationship (QSAR). Firstly, a high-quality 3D model of HCV NS5B polymerase of GT4a was constructed using crystal structure of HCV NS5B polymerase of GT1 (PDB ID: 3hkw) as a template. Then, both the model and the template were simulated to compare conformational stability. PLIF was generated using five crystal structures of HCV NS5B (PDB ID: 4mia, 4mib, 4mk9, 4mka, and 4mkb), which revealed the most important residues and their interactions with the co-crystalized ligands. After that, a 3D pharmacophore model was developed from the generated PLIF data and then used as a screening filter for 17000328 drug-like zinc database compounds. 900 compounds passed the pharmacophore filter and entered the docking-based virtual screening stage. Finally, a 3D CoMFA QSAR was developed using 42 compounds as a training and 19 compounds as a test set. The 3D CoMFA QSAR was used to design and screen some potential inhibitors, these compounds were further evaluated by the docking stage. The highest ranked five hits from docking result (compounds (p1-p4) and compound q1) were selected for further analysis.Communicated by Ramaswamy H. Sarma.

Humanized Mouse Models for the Study of Hepatitis C and Host Interactions

Hepatitis C virus (HCV) infection is commonly attributed as a major cause of chronic hepatotropic diseases, such as, steatosis, cirrhosis and hepatocellular carcinoma. As HCV infects only humans and primates, its narrow host tropism hampers in vivo studies of HCV-mammalian host interactions and the development of effective therapeutics and vaccines. In this context, we will focus our discussion on humanized mice in HCV research. Here, these humanized mice are defined as animal models that encompass either only human hepatocytes or both human liver and immune cells. Aspects related to immunopathogenesis, anti-viral interventions, drug testing and perspectives of these models for future HCV research will be discussed.

Review on chemogenomic approaches towards hepatitis C viral targets

Hepatitis C virus (HCV) is the most prevalent viral pathogen that infects more than 185 million people worldwide. HCV infection leads to chronic liver diseases such as liver cirrhosis and hepatocellular carcinoma. Direct-acting antivirals (DAAs) are the recent combination therapy for HCV infection with reduced side effects than prior therapies. Sustained virological response (SVR) acts as a gold standard marker to monitor the success of antiviral treatment. Older treatment therapies attain 50-55% of SVR compared with DAAs which attain around 90-95%. The current review emphasizes the recent chemogenomic updates that have been unfolded through structure-based drug design of HCV drug target proteins (NS3/4A, NS5A, and NS5B) and ligand-based drug design of DAAs in achieving a stable HCV viral treatment strategies.

Baseline Intrahepatic and Peripheral Innate Immunity are Associated with Hepatitis C Virus Clearance During Direct-Acting Antiviral Therapy

Hepatitis C virus (HCV) infection induces interferon (IFN)-stimulated genes (ISGs) and downstream innate immune responses. This study investigated whether baseline and on-treatment differences in these responses predict response versus virological breakthrough during therapy with direct-acting antivirals (DAAs). Thirteen HCV genotype 1b-infected patients who had previously failed a course of pegylated IFN/ribavirin were retreated with asunaprevir/daclatasvir for 24 weeks. After pretreatment biopsy, patients were randomized to undergo a second biopsy at week 2 or 4 on therapy. Microarray and NanoString analyses were performed on paired liver biopsies and analyzed using linear mixed models. As biomarkers for peripheral IFN responses, peripheral blood natural killer cells were assessed for phosphorylated signal transducer and activator of transcription 1 (pSTAT1) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression and degranulation. Nine of 13 (69%) patients achieved sustained virological response at 12 weeks off therapy (SVR12), and 4 experienced virological breakthroughs between weeks 4 and 12. Patients who achieved SVR12 displayed higher ISG expression levels in baseline liver biopsies and a higher frequency of pSTAT1 and TRAIL-expressing, degranulating natural killer cells in baseline blood samples than those who experienced virological breakthrough. Comparing gene expression levels from baseline and on-therapy biopsies, 408 genes (±1.2-fold, P < 0.01) were differentially expressed. Genes down-regulated on treatment were predominantly ISGs. Down-regulation of ISGs was rapid and correlated with HCV RNA suppression. Conclusion: An enhanced IFN signature is observed at baseline in liver and blood of patients who achieve SVR12 compared to those who experience a virological breakthrough; the findings suggest that innate immunity may contribute to clearance of HCV during DAA therapy by preventing the emergence of resistance-associated substitutions that lead to viral breakthrough during DAA therapy.

Population Pharmacokinetics of AL-335 and Its Two Main Metabolites (ALS-022399, ALS-022227) in Monotherapy and in Combination with Odalasvir and/or Simeprevir

The aim of the current study was to characterize the time course of plasma concentrations of AL-335 and its main metabolites (ALS-022399 and ALS-022227) after oral administration in healthy and hepatitis C virus (HCV)-infected subjects, in monotherapy as well as in combination with simeprevir and/or odalasvir. AL-335, ALS-022399, and ALS-022227 plasma concentrations from subjects receiving 800 mg of AL-335 orally once daily (qd) as monotherapy or in combination were pooled and analyzed using a nonlinear mixed effect modeling approach. The typical values (between subject variability) of AL-335 and ALS-022399 apparent linear clearances were 3300 L/h (33.9%) and 1910 L/h (30.0%), respectively. ALS-022227 elimination was characterized as a nonlinear process, with typical values of V_{max,ALS-022227} and K_m,ALS-022227 estimated to be 84,799 ng/h (14.9%) and 450.2 ng/mL, respectively. AL-335 and ALS-022399 plasma concentrations were increased more than 2-fold in presence of simeprevir and/or odalasvir, while the effect on ALS-022227 plasma concentrations was limited. The effect of simeprevir and/or odalasvir might be explained by their capacity to inhibit P-glycoprotein. Internal evaluation confirmed that the population pharmacokinetic model developed was deemed appropriate to describe the time course of AL-335, ALS-022399, and ALS-022227 plasma concentrations and their associated variability in both healthy and HCV-infected subjects, as well as the interaction effect of simeprevir and/or odalasvir over AL-335 and its metabolites in healthy subjects. This model can be used as a starting point to evaluate drug-drug interaction processes in HCV-infected patients and support the development of a direct-acting antiviral (DAA) combination.

Characterizing the Pharmacokinetic Interaction Between Simeprevir and Odalasvir in Healthy Volunteers Using a Population Modeling Approach

The aim of this study was to characterize the pharmacokinetic drug-drug interaction (DDI) between simeprevir (NS3/4A protease inhibitor) and odalasvir (NS5A inhibitor) after oral administration to support the design and dose selection of clinical studies with this combination for the treatment of chronic hepatitis C infection (HCV). Simeprevir and odalasvir plasma concentrations from 30 healthy subjects receiving these drugs in monotherapy as well as in combination were pooled and analyzed using a population pharmacokinetic modeling approach. Previous pharmacokinetic models developed to characterize the pharmacokinetics for each drug were used as starting point. The dual effect of simeprevir and odalasvir on their pharmacokinetic parameters was explored. Simulations were performed to assess the impact of the DDI on exposure parameters. In presence of odalasvir, the relative bioavailability of simeprevir increased by 26% and the apparent clearance was reduced following competitive inhibition depending on odalasvir plasma concentrations, with an inhibitory constant (K_i) estimated to be 1610 ng/mL. The apparent odalasvir clearance was reduced by simeprevir plasma concentrations following an I_max model, characterized by a maximum inhibitory effect of 46.7% and an IC₅₀ of 257 ng/mL. Model-based simulations indicated that both C_max and AUC_24h increased for both drugs, when co-administered. The pharmacokinetic model adequately describes the time course of plasma concentrations and their variability when simeprevir and/or odalasvir were orally administered. This model can be used as a first step to predict the exposures of concomitant administration of simeprevir and odalasvir in HCV-infected subjects. Data from study AL355-602 (NCT02512562) were used for this analysis.

[Chronic HCV infection: An internist's opinion (Part 2)]

Hepatitis C virus (HCV) infection results in not only chronic hepatitis and subsequent complications as liver cirrhosis and hepatocellular carcinoma, but also in a significant number of other diseases, the so-called extrahepatic manifestations of chronic HCV infection. In addition to lymphoproliferative and autoimmune disorders discussed in Part 1 of this review, many other diseases turned to be associated with chronic HCV infection. Part 2 of this review is dedicated to the analysis of the relationship of chronic HCV-infection to the development of some endocrine diseases, such as thyroiditis and diabetes mellitus, and cardiovascular disorders. It also provides the characteristics of the currently available antiviral agents and considers whether they may be used in patents with extrahepatic manifestations of chronic HCV infection.

In vitro methods for testing antiviral drugs

Despite successful vaccination programs and effective treatments for some viral infections, humans are still losing the battle with viruses. Persisting human pandemics, emerging and re-emerging viruses, and evolution of drug-resistant strains impose continuous search for new antiviral drugs. A combination of detailed information about the molecular organization of viruses and progress in molecular biology and computer technologies has enabled rational antivirals design. Initial step in establishing efficacy of new antivirals is based on simple methods assessing inhibition of the intended target. We provide here an overview of biochemical and cell-based assays evaluating the activity of inhibitors of clinically important viruses.

The Mechanism of Synchronous Precise Regulation of Two Shrimp White Spot Syndrome Virus Targets by a Viral MicroRNA

MicroRNAs (miRNAs), important factors in animal innate immunity, suppress the expressions of their target genes by binding to target mRNA’s 3′ untranslated regions (3′UTRs). However, the mechanism of synchronous regulation of multiple targets by a single miRNA remains unclear. In this study, the interaction between a white spot syndrome virus (WSSV) miRNA (WSSV-miR-N32) and its two viral targets (wsv459 and wsv322) was characterized in WSSV-infected shrimp. The outcomes indicated that WSSV-encoded miRNA (WSSV-miR-N32) significantly inhibited virus infection by simultaneously targeting wsv459 and wsv322. The silencing of wsv459 or wsv322 by siRNA led to significant decrease of WSSV copies in shrimp, showing that the two viral genes were required for WSSV infection. WSSV-miR-N32 could mediate 5′–3′ exonucleolytic digestion of its target mRNAs, which stopped at the sites of target mRNA 3′UTRs close to the sequence complementary to the miRNA seed sequence. The complementary bases (to the target mRNA sequence) of a miRNA 9th–18th non-seed sequence were essential for the miRNA targeting. Therefore, our findings presented novel insights into the mechanism of miRNA-mediated suppression of target gene expressions, which would be helpful for understanding the roles of miRNAs in innate immunity of invertebrate.

Naturally Occurring Resistance-Associated Variants to Hepatitis C Virus Direct-Acting Antiviral Agents in Treatment-Naive HCV Genotype 6a-Infected Patients

BACKGROUND AND OBJECTIVE

The direct-acting antiviral agents (DAAs) antiviral therapy has drastically improved the prognosis of hepatitis C virus (HCV) patients. However, the viral drug resistance-associated variants (RAVs) can limit the efficacy of DAAs. For the HCV-6a is not the predominant prevalent genotype; the data on the prevalence of naturally occurring RAVs in it is scarce. Our study aims to assess the prevalence of RAVs in treatment-naive HCV-6a patients.

METHODS

Nested PCR assays were performed on 95 HCV-6a patients to amplify HCV viral regions of NS3, NS5A, and NS5B.

RESULTS

In NS3/4A region, we detected Q80K in 95.5% isolates (84/88) and D168E in 2.3% isolates (2/88). In NS5A region, we detected Q30R in 93.2% isolates (82/88), L31M in 4.6% isolates (4/88), and H58P in 6.8% isolates (6/88). In NS5B region, we detected A15G in 2.3% isolates (2/88), S96T in 1.1% isolates (1/88), and S282T in 20.7% isolates (17/88) and we detected I482L in 100% isolates (4/4), V494A in 50% isolates (2/4), and V499A in 100% isolates (4/4).

CONCLUSIONS

RAVs to DAAs preexist in treatment-naive HCV-6a patients. Further studies should address the issue of the impact of RAVs in response to DAA therapies for HCV-6a patients.

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.

Determinants of Infection Outcome in HCV-Genotype 4

Hepatitis C virus (HCV) infection represents a worldwide health problem and has been for long an attractive point of research due to diversity among different genotypes regarding unique geographical distribution and diverse treatment outcome. HCV is considered a major cause of chronic liver disease and cirrhosis, which leads to liver failure and hepatocellular carcinoma requiring liver transplantation. Of the HCV genotypes identified, HCV genotype 4 (HCV-4) is the least studied. HCV-4 is responsible for ∼10% of HCV infections and is common in the Middle East and Africa; recently it is increasingly prevalent in European Countries. HCV-4 is a continuing epidemic in Egypt, having the highest prevalence of HCV worldwide. "Know your epidemic, know your response" concept necessitates better understanding of HCV-4 characteristics to control disease dissemination and progression, which compromises the life quality of chronic HCV-infected patients. In this review, we discuss the epidemiology, natural history, and treatment options for patients with HCV-4 infection.

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.

Naturally occurring drug resistance associated variants to hepatitis C virus direct-acting antiviral agents in treatment-naive HCV genotype 1b-infected patients in China

The direct-acting antiviral agents (DAAs) have drastically improved the prognosis of hepatitis C virus (HCV) patients. However, the resistance-associated variants (RAVs) to DAAs may hamper treatment. There was a lack of data on the prevalence of pre-exist RAVs in Chinese HCV-infected patients. We performed nested PCR assays on 74 HCV genotype 1b-infected patients to amplify HCV viral regions of NS3, NS5A, and NS5B to investigate the prevalence of RAVs to DAAs in treatment-naive HCV genotype1b-infected patients in China. The mutations A156S, T54S, and D168Y of the NS3/4A region were found in 18.33% (11/60), 6.67% (4/60), and 1.67% (1/60) of the successfully amplified cases. Mutations Q30R, L31M, and H58P of the NS5A region were confirmed in 57.63% (34/59), 1.69%(1/59), and 86.44% (51/59) of the cases. Mutations C316N, S365A, M414L, M423I, Y448H, I482T, I482 V, V494L, P495S, and V499A of the NS5B region were detected in 100% (60/60), 3.33% (2/60), 5.88% (3/51), 1.96% (1/51), 1.96% (1/51), 5.88% (3/51), 1.96% (1/51), 3.92% (2/51), 5.88% (3/51), and 15.69% (8/51) of cases, respectively. Naturally occurring RAVs to DAAs pre-exist in treatment-naive Chinese HCV genotype 1b-infected patients and the characteristic is different from that in Europe and the United States. Clinicians should consider RAVs upon the introduction of DAA-based antiviral therapy.

Efficient programming of human mesenchymal stem cell-derived hepatocytes by epigenetic regulations

BACKGROUND AND AIM

In view of its unique properties of detoxification and involvement of metabolic and biochemical functions, in vitro hepatocyte culture serves as a valuable material for drug screening and mechanistic analysis for pathology of liver diseases. The restriction of rapid de-differentiation and inaccessibility of human hepatocytes from routine clinical procedure, however, limits its use.

METHODS

To address this issue, the effort to direct human mesenchymal stem cells (hMSCs) into hepatocytes using a modified protocol was proposed. With the additional treatment of histone deacetylase inhibitor (HDACi) and DNA methyltransferase inhibitor (DNMTi), in vitro hMSC-derived hepatocytes were cultivated and their hepatic characteristics were examined.

RESULTS

By using a modified protocol, it was shown that Trichostatin A and 5-aza-2-deoxycitidine protected differentiating cells from death and could sufficiently trigger a wide range of liver-specific markers as well as liver functions including albumin production, glycogen storage, and urea cycle in hMSC-derived hepatocytes. The increased mRNA expression for hepatitis C virus (HCV) entry including CD81, Occludin, LDL receptor, and scavenger receptor class B type I in hMSC-derived hepatocytes was also detected, implying its potential to be utilized as an in vitro model to analyze dynamic HCV infection.

CONCLUSIONS

The present study successfully established a protocol to direct hMSCs into hepatocyte-like cells suggesting the beneficial impact to apply HDACi and DNMTi as potent modulators for hMSCs to liver differentiation.

Tolerability and efficacy of pegylated consensus interferon-α in the treatment of chronic hepatitis C

This study aimed to explore and evaluate the tolerability and antiviral activity of pegylated recombinant human consensus interferon-α (PEG-CIFN) in adults with hepatitis C virus (HCV) infection. A total of 48 adult subjects chronically infected with HCV were divided into five groups, which were treated separately with PEG-CIFN 1.0 µg/kg (n=10), 1.5 µg/kg (n=10), 2.0 µg/kg (n=9) or 3.0 µg/kg (n=10), or pegylated IFN α-2a (Pegasys) 180 µg (n=9) as controls. Symptoms were observed and laboratory results collected to monitor adverse reactions, adjust drug dosage and evaluate tolerability. The thrombocytopenic effects in all PEG-CIFN dose groups were less than that of pegylated IFN α-2a (at week 14, P<0.05). The rapid virologic response of the PEG-CIFN 1.5, 2.0 and 3.0 µg/kg groups and the pegylated IFN α-2a group were significantly higher than that of the PEG-CIFN 1.0 µg/kg group (P<0.05). Patients who had HCV genotype 1b infections had relatively high responses. The early virologic response of the PEG-CIFN 1.0, 1.5 and 2.0 µg/kg groups and the pegylated IFN α-2a group were 30, 90, 88.8 and 88.8% respectively. PEG-CIFN is well tolerated, and was found to have dose-dependent effectiveness in subjects with chronic hepatitis C. Virological response rates between PEG-CIFN 1.5 or 2.0 µg/kg, and pegylated IFNα-2a were similar, and not significantly different. It is concluded that 1.5 µg/kg PEG-CIFN may be the clinically recommended dose. PEG-CIFN is superior to pegylated IFN α-2a in maintaining platelet levels.

The Presence of Autoantibodies to Cytoplasmic Rod and Ring Particles in the Serum of Patients with Chronic Hepatitis C Virus Infection

BACKGROUND

Chronic hepatitis C virus (HCV) is associated with extra hepatic autoimmune disorders, while peg-IFNa-2a/RBV combination therapy may exacerbate these conditions. Autoantibodies to cytoplasmic structures, called rod and ring particles (RR), have strong associations with these patients and are identified by HEp-2 cells.

OBJECTIVES

Our purpose was to study the correlation of autoantibodies to cytoplasmic rod and ring particles in the serum of patients with chronic HCV infection with their response to standard therapy.

METHODS

Serum samples were gathered from 120 patients with HCV infection (40 naive treatments, 40 with sustained virological response (SVR), and 40 with relapse response) during peg-IFNa-2a/RBV combination therapy and analyzed for the presence of RR antibodies by IIF on commercially available HEp-2 cell substrate slides from Euroimmun (Lu beck, Germany).

RESULTS

Anti-rod and ring (anti-RR) autoantibodies were detected in only the serum of 1 out of 120 patients (0.8%), which belonged to a patient (out of 40) with relapse response (2.5%). No correlation was found between the types of response to peg-IFNa-2a/RBV combination therapy and the presence of anti-RR autoantibodies.

CONCLUSIONS

The only HCV patient with RR autoantibodies previously had received IFN/ribavirin antiviral therapy. The presence of these autoantibodies is extremely rare in Iranian HCV patients. Further studies are warranted to determine the role of genetic background and geographical pattern in the prevalence of these novel autoantibodies worldwide.

Management of chronic hepatitis C in 2017

Hepatitis C virus (HCV) represents one of the most common aetiologies of chronic liver disease and causes a major global health burden. Globally an estimated 80 million people are chronically infected, but the majority of whom is still undiagnosed. Prior to the discovery of the virus in 1989 a significant number of patients were exposed and consecutively infected with HCV via contaminated transfusions, as it is a blood-borne disease. Chronic HCV infection pursues a progressive course that ultimately results in the development of cirrhosis, liver failure and hepatocellular carcinoma (HCC), if left untreated. The efficiency and tolerability of therapeutical approaches improved considerably with the development of direct-acting antivirals (DAA). The majority of patients treated with the recommended DAA combinations can be cured, which is reflected in achievement of sustained virological response (SVR). This review is intended to provide guidance in the management of patients with chronic hepatitis C, including recommendations for adequate screening, diagnostic procedures, clinical care, treatment and follow-up strategies.

Sofosbuvir plus simeprevir for the treatment of genotype 1 chronic hepatitis C: a review of evidence

Sofosbuvir (SOF) with simeprevir (SIM) combination was the first interferon-free regimen that reached optimal results in terms of sustained viral response (SVR). Areas covered: A systematic review of the scientific literature concerning the effects that the SOF/SIM combination had on hepatitis C genotype 1 patients yielded 771 references. After the revision process, four clinical trials and 15 observational studies met the inclusion criteria; in total, these studies involved 5,766 patients. The SVR ranged from 67% to 100% depending on the patients' viral subtype and cirrhosis status. Adverse effects were common, but treatment discontinuation related to drug toxicity occurred in less than 5% of cases. Expert commentary: The SOF/SIM combination exhibits efficacy and tolerability profiles that are similar to those of the other available interferon-free combinations used for non-cirrhotic genotype 1b patients. Meanwhile, for patients with advanced cirrhosis or genotype 1a, this approach cannot be considered a routine treatment option due to the unsatisfactory results.

Genetic Barrier to Direct Acting Antivirals in HCV Sequences Deposited in the European Databank

Background & Aims

Development of resistance results from mutations in the viral genome, and the presence of selective drug pressure leads to the emergence of a resistant virus population. The aim of this study was to analyze the impact of genetic variability on the genetic barrier to drug resistance to DAAs.

Methods

The genetic barrier was quantified based on the number and type of nucleotide mutations required to impart resistance, considering full-length HCV NS3, NS5A and NS5B regions segregated by genotype into subtypes 1a, 1b, 2a, 2b and 3a. This study analyzeds 789 NS3 sequences, 708 sequences and 536 NS5B sequences deposited in the European Hepatitis C Virus Database, in the following resistance-associated positions: NS3: F43/I/L/S/V, Q80K/R, R155K/G, A156G/S/T and D168A/C/E/G/H/N/T/V/Y; NS5A: L/M28A/T/V, Q30E/H/R, L31F/I/M/V, H58D or P58S and Y93C/F/H/N/S; NS5B: S282P/R/T, C316H/N/Y, S368T, Y448C/H, S556G/R, D559R.

Results

Variants that require only one transversion in NS3 were found in 4 positions and include F43S, R80K, R155K/G and A156T. The genetic barrier to resistance shows subtypic differences at position 155 of the NS3 gene where a single transition is necessary in subtype 1a. In the NS5A gene, 5 positions where only one nucleotide change can confer resistance were found, such as L31M which requires one transversion in all subtypes, except in 0.28% of 1b sequences; and R30H, generated by a single transition, which was found in 10.25% of the sequences of genotype 1b. Other subtypic differences were observed at position 58, where resistance is less likely in genotype 1a because a transversion is required to create the variant 58S. For the NS5B inhibitors, the genetic barrier at positions conferring resistance was nearly identical in subtypes 1a and 1b, and single transitions or transversions were necessary in 5 positions to generate a drug-resistant variant of HCV. The positions C316Y and S556D required only one transition in all genotypes, Y448H and S556 G/N/R positions required only one transition for up to 98.8% of the sequences analyzed. A single variant in position 448 in genotype 1a is less likely to become the resistance variant 448H because it requires two transversions. Also, in the position 559D a transversion and a transition were necessary to generate the resistance mutant D559H.

Conclusion

Results revealed that in 14 out of 16 positions, conversion to a drug-resistant variant of HCV required only one single nucleotide substitutions threatening direct acting antivirals from all three classes.

Review article: treatment as prevention - targeting people who inject drugs as a pathway towards hepatitis C eradication

BACKGROUND

Hepatitis C virus (HCV) is a leading cause of chronic liver disease worldwide. HCV predominates in people who inject drugs; a group in whom anti-viral therapy has previously been withheld on the basis of chaotic lifestyles and associated risks of reinfection. New research has emerged which suggests that by specifically targeting HCV-infected people who inject drugs for treatment, the pool of HCV would deplete, thus reducing overall transmission and eventually leading to HCV eradication.

AIM

To outline the requirements for HCV eradication and review the evidence that this is achievable.

METHODS

Expert review of the literature.

RESULTS

The achievement of HCV eradication using 'treatment as prevention' is supported by numerous epidemiological modelling studies employing a variety of models in several contexts including people who inject drugs, men who have sex with men and prisoners. More recent studies also incorporate the newer, more efficacious direct-acting anti-viral drugs. These drugs have been shown to be safe and effective in people who inject drugs in clinical trials. There is no empirical evidence of the impact of treatment as prevention strategies on population prevalence.

CONCLUSIONS

This review highlights the efforts to control HCV and evaluates the possibilities of achieving eradication of HCV. Currently, the technologies required to achieve HCV eradication exist, but the infrastructure to deliver them is not generally available or of insufficient scale outside of specific areas. Such areas are yet to demonstrate that elimination is possible, but results of studies in these areas are awaited. Such a demonstration would be proof of principle for eradication. Although we are aspiring towards HCV eradication, elimination is the more realistic prospect.

A robust model of natural hepatitis C infection using hepatocyte-like cells derived from human induced pluripotent stem cells as a long-term host

BACKGROUND

Hepatitis C virus (HCV) could induce chronic liver diseases and hepatocellular carcinoma in human. The use of primary human hepatocyte as a viral host is restrained with the scarcity of tissue supply. A culture model restricted to HCV genotype 2a (JFH-1) has been established using Huh7-derived hepatocyte. Other genotypes including the wild-type virus could not propagate in Huh7, Huh7.5 and Huh7.5.1 cells.

METHODS

Functional hepatocyte-like cells (HLCs) were developed from normal human iPS cells as a host for HCV infection. Mature HLCs were identified for selective hepatocyte markers, CYP450s, HCV associated receptors and HCV essential host factors. HLCs were either transfected with JFH-1 HCV RNA or infected with HCV particles derived from patient serum. The enhancing effect of α-tocopherol and the inhibitory effects of INF-α, ribavirin and sofosbuvir to HCV infection were studied. The HCV viral load and HCV RNA were assayed for the infection efficiency.

RESULTS

The fully-developed HLCs expressed phase I, II, and III drug-metabolizing enzymes, HCV associated receptors (claudin-1, occludin, CD81, ApoE, ApoB, LDL-R) and HCV essential host factors (miR-122 and SEC14L2) comparable to the primary human hepatocyte. SEC14L2, an α-tocopherol transfer protein, was expressed in HLCs, but not in Huh7 cell, had been implicated in effective HCVser infection. The HLCs permitted not only the replication of HCV RNA, but also the production of HCV particles (HCVcc) released to the culture media. HLCs drove higher propagation of HCVcc derived from JFH-1 than did the classical host Huh7 cells. HLCs infected with either JFH-1 or wild-type HCV expressed HCV core antigen, NS5A, NS5B, NS3 and HCV negative-stand RNA. HLCs allowed entire HCV life cycle derived from either JFH-1, HCVcc or wild-type HCV (genotype 1a, 1b, 3a, 3b, 6f and 6n). Further increasing the HCVser infection in HLCs was achieved by incubating cell with α-tocopherol. The supernatant from infected HLCs could infect both naïve HLC and Huh7 cell. Treating infected HLC with INF-α and ribavirin decreased HCV RNA in both the cellular fraction and the culture medium. The HLCs reacted to HCVcc or wild-type HCV infection by upregulating TNF-α, IL-28B and IL-29.

CONCLUSIONS

This robust cell culture model for serum-derived HCV using HLCs as host cells provides a remarkable system for investigating HCV life cycle, HCV-associated hepatocellular carcinoma development and the screening for new anti HCV drugs.

Clinical Trial Risk in Hepatitis C: Endpoint Selection and Drug Action

Background and Aims. This study analyzed the risk of clinical trial failure of new drugs for hepatitis C between January 1998 and January 2015. Methods. Hepatitis C drug development trials that were in phases I-III of clinical trial testing were obtained from the publicly accessible clinical trial repository and other publicly available databases. Drug compounds were excluded from the study if they began their phase I testing before 1998, if they were not industry sponsored, or if they treated secondary complications of hepatitis C. Clinical trial success rates were analyzed in comparison to industry expectations. Further analysis was conducted on the molecule classifications, the mechanisms of action, and the trial endpoints. Results. One hundred and twenty-three unique drug compounds were found to fulfill the inclusion criteria, eight of which had FDA approval. The overall cumulative pass rate for hepatitis C drugs was 20%, which is double the industry expectation rate. Viral inhibitor small molecule drugs significantly reduced the risk of drug failure during clinical trials compared to other mechanisms of action. Conclusion. On average, one in every five drugs that began clinical testing will be approved for market. Viral inhibitor small molecule drugs are the most promising and hold the least risk.

Targeting the Channel Activity of Viroporins

Since the discovery that certain small viral membrane proteins, collectively termed as viroporins, can permeabilize host cellular membranes and also behave as ion channels, attempts have been made to link this feature to specific biological roles. In parallel, most viroporins identified so far are virulence factors, and interest has focused toward the discovery of channel inhibitors that would have a therapeutic effect, or be used as research tools to understand the biological roles of viroporin ion channel activity. However, this paradigm is being shifted by the difficulties inherent to small viral membrane proteins, and by the realization that protein-protein interactions and other diverse roles in the virus life cycle may represent an equal, if not, more important target. Therefore, although targeting the channel activity of viroporins can probably be therapeutically useful in some cases, the focus may shift to their other functions in following years. Small-molecule inhibitors have been mostly developed against the influenza A M2 (IAV M2 or AM2). This is not surprising since AM2 is the best characterized viroporin to date, with a well-established biological role in viral pathogenesis combined the most extensive structural investigations conducted, and has emerged as a validated drug target. For other viroporins, these studies are still mostly in their infancy, and together with those for AM2, are the subject of the present review.

Prolactin Regulatory Element Binding Protein Is Involved in Hepatitis C Virus Replication by Interaction with NS4B

It has been proposed that the hepatitis C virus (HCV) NS4B protein triggers the membranous HCV replication compartment, but the underlying molecular mechanism is not fully understood. Here, we screened for NS4B-associated membrane proteins by tandem affinity purification and proteome analysis and identified 202 host proteins. Subsequent screening of replicon cells with small interfering RNA identified prolactin regulatory element binding (PREB) to be a novel HCV host cofactor. The interaction between PREB and NS4B was confirmed by immunoprecipitation, immunofluorescence, and proximity ligation assays. PREB colocalized with double-stranded RNA and the newly synthesized HCV RNA labeled with bromouridine triphosphate in HCV replicon cells. Furthermore, PREB shifted to detergent-resistant membranes (DRMs), where HCV replication complexes reside, in the presence of NS4B expression in Huh7 cells. However, a PREB mutant lacking the NS4B-binding region (PREBd3) could not colocalize with double-stranded RNA and did not shift to the DRM in the presence of NS4B. These results indicate that PREB locates at the HCV replication complex by interacting with NS4B. PREB silencing inhibited the formation of the membranous HCV replication compartment and increased the protease and nuclease sensitivity of HCV replicase proteins and RNA in DRMs, respectively. Collectively, these data indicate that PREB promotes HCV RNA replication by participating in the formation of the membranous replication compartment and by maintaining its proper structure by interacting with NS4B. Furthermore, PREB was induced by HCV infection in vitro and in vivo. Our findings provide new insights into HCV host cofactors.

IMPORTANCE

The hepatitis C virus (HCV) protein NS4B can induce alteration of the endoplasmic reticulum and the formation of a membranous web structure, which provides a platform for the HCV replication complex. The molecular mechanism by which NS4B induces the membranous HCV replication compartment is not understood. We screened for NS4B-associated membrane proteins by tandem affinity purification and proteome analysis, followed by screening with small interfering RNA. We identified prolactin regulatory element binding (PREB) to be a novel HCV host cofactor. PREB is induced by HCV infection and recruited into the replication complex by interaction with NS4B. Recruited PREB promotes HCV RNA replication by participating in the formation of the membranous HCV replication compartment. To our knowledge, the effect of NS4B-binding protein on the formation of the membranous HCV replication compartment is newly described in this report. Our findings are expected to provide new insights into HCV host cofactors.

Update on hepatitis C: Direct-acting antivirals

Hepatitis C virus (HCV) was discovered 26 years ago. For decades, interferon-based therapy has been the mainstay of treatment for HCV. Recently, several direct-acting antivirals (DAAs) have been approved for treatment of HCV-infected patients and to help combat the virus. These drugs have revolutionized the management of HCV as all-oral regimens with favorable side effect profiles and superior rates of sustained virological response. Emerging real-world data are demonstrating results comparable to registration trials for DAA agents. Suddenly, the potential for eradicating HCV is on the horizon.

Meet the Classes of Directly Acting Antiviral Agents: Strengths and Weaknesses

This article discusses direct-acting antiviral agents that target hepatitis C virus replication, their mechanism of action, strengths, and weaknesses. In addition, varying strategies using combinations of these agents are discussed.

Early Viral Entry Assays for the Identification and Evaluation of Antiviral Compounds

Cell-based systems are useful for discovering antiviral agents. Dissecting the viral life cycle, particularly the early entry stages, allows a mechanistic approach to identify and evaluate antiviral agents that target specific steps of the viral entry. In this report, the methods of examining viral inactivation, viral attachment, and viral entry/fusion as antiviral assays for such purposes are described, using hepatitis C virus as a model. These assays should be useful for discovering novel antagonists/inhibitors to early viral entry and help expand the scope of candidate antiviral agents for further drug development.

Synthesis of 1'-C-cyano pyrimidine nucleosides and characterization as HCV polymerase inhibitors

Ribose modified 1'-C-cyano pyrimidine nucleosides were synthesized. A silver triflate mediated Vorbrüggen reaction was used to generate the nucleoside scaffold and follow-up chemistry provided specific ribose modified analogs. Nucleosides and phosphoramidate prodrugs were tested for their anti-HCV activity.

"Too little, too late?" Will inhibitors of the hepatitis C virus p7 ion channel ever be used in the clinic?

Hepatitis C virus (HCV) p7 is a virus-coded ion channel, or 'viroporin'. p7 is an essential HCV protein, promoting infectious virion production, and this process can be blocked by prototypic p7 inhibitors. However, prototype potency is weak and effects in clinical trials are unsatisfactory. Nevertheless, recent structural studies render p7 amenable to modern drug discovery, with studies supporting that effective drug-like molecules should be achievable. However, burgeoning HCV therapies clear infection in the majority of treated patients. This perspective summarizes current understanding of p7 channel function and structure, pertaining to the development of improved p7 inhibitors. We ask, 'is this too little, too late', or could p7 inhibitors play a role in the long-term management of HCV disease?

Computational Docking Study of p7 Ion Channel from HCV Genotype 3 and Genotype 4 and Its Interaction with Natural Compounds

BACKGROUND

The current standard care therapy for hepatitis C virus (HCV) infection consists of two regimes, namely interferon-based and interferon-free treatments. The treatment through the combination of ribavirin and pegylated interferon is expensive, only mildly effective, and is associated with severe side effects. In 2011, two direct-acting antiviral (DAA) drugs, boceprevir and telaprevir, were licensed that have shown enhanced sustained virologic response (SVR) in phase III clinical trial, however, these interferon-free treatments are more sensitive to HCV genotype 1 infection. The variable nature of HCV, and the limited number of inhibitors developed thus aim in expanding the repertoire of available drug targets, resulting in targeting the virus assembly therapeutically.

AIM

We conducted this study to predict the 3D structure of the p7 protein from the HCV genotypes 3 and 4. Approximately 63 amino acid residues encoded in HCV render this channel sensitive to inhibitors, making p7 a promising target for novel therapies. HCV p7 protein forms a small membrane known as viroporin, and is essential for effective self-assembly of large channels that conduct cation assembly and discharge infectious virion particles.

METHOD

In this study, we screened drugs and flavonoids known to disrupt translation and production of HCV proteins, targeted against the active site of p7 residues of HCV genotype 3 (GT3) (isolatek3a) and HCV genotype 4a (GT4) (isolateED43). Furthermore, we conducted a quantitative structure-activity relationship and docking interaction study.

RESULTS

The drug NB-DNJ formed the highest number of hydrogen bond interactions with both modeled p7 proteins with high interaction energy, followed by BIT225. A flavonoid screen demonstrated that Epigallocatechin gallate (EGCG), nobiletin, and quercetin, have more binding modes in GT3 than in GT4. Thus, the predicted p7 protein molecule of HCV from GT3 and GT4 provides a general avenue to target structure-based antiviral compounds.

CONCLUSIONS

We hypothesize that the inhibitors of viral p7 identified in this screen may be a new class of potent agents, but further confirmation in vitro and in vivo is essential. This structure-guided drug design for both GT3 and GT4 can lead to the identification of drug-like natural compounds, confirming p7 as a new target in the rapidly increasing era of HCV.

vRNA structured population model for Hepatitis C Virus dynamics

Improvements in the understanding of the Hepatitis C Virus (HCV) life-cycle have led to the identification of targets and the development of drugs affecting the intracellular reproduction of the virus. These advancements have presented new modeling challenges as the classic models have focused on describing the macroscopic viral kinetics only. Our primary objective is to apply the existing theory of Physiologically Structured Population (PSP) modeling to describe dynamics of viral RNA (vRNA) in infected hepatocytes of patients receiving treatment with Direct-acting Antiviral Agents (DAA). Using vRNA as a physiological structure this work expands on previous structured population models allowing exploration of micro- and macroscopic implications of such treatments. The PSP model provides a description of vRNA distribution in the infected cells at steady state and its time evolution following treatment. The long term behavior of the model predicts viral load time courses in plasma and permits to quantify conditions for the virus eradication. Finally, we demonstrate that PSP models can account for additional structures, which are essential for the viral replication process with potentially far reaching implications in our understanding of HCV infections and treatment options.

Daclatasvir + asunaprevir: first global approval

The combination of daclatasvir + asunaprevir [Daklinza(®) + Sunvepra(®) (Japan)], two direct-acting antiviral agents, has been developed by Bristol-Myers Squibb for the treatment of patients with chronic hepatitis C virus (HCV) genotype 1 infections, including those with compensated cirrhosis. Daclatasvir + asunaprevir has received its first global approval in this indication in Japan. Daclatasvir + asunaprevir is the first all-oral, interferon- and ribavirin-free regimen for this indication. This article summarizes the milestones in the development of daclatasvir + asunaprevir leading to this first approval for the treatment of chronic HCV genotype 1 infections.

ABT-450: a novel agent for the treatment of CHC genotype 1: focus on treatment-experienced patients

Chronic hepatitis C (CHC) constitutes a major health concern. Hepatitis C virus eradication by antiviral treatment can markedly reduce the risk of developing cirrhosis, hepatocellular carcinoma and liver-related death. A plethora of new direct antiviral agents have been developed and are being explored in clinical trials. One of the newest members of this family is the NS3/4A protease inhibitor ABT-450. The multi-targeted approach combining ritonavir-enhanced ABT-450 with ombitasvir and dasabuvir has been evaluated for the treatment of CHC Gt1 in treatment-naïve and treatment-experienced adults. In this article, we sought to discuss the current knowledge on ABT-450-containing regimens, with special emphasis on treatment-experienced CHC Gt1 patients. This new combination was found to be potent, safe and well tolerated. Future Phase III trials with larger sample size in patients with decompensated cirrhosis, non-Gt1, end-stage renal disease and liver transplant recipients are eagerly awaited.

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.