Current and Future Hepatitis C Therapies

Molecular modeling and docking revealed superiority of IDX-184 as HCV polymerase inhibitor

Aim: IDX-184 is a nonstructural 5b nucleoside inhibitor (NI) that was under clinical trials against HCV. This work adopts a molecular modeling approach in order to study the interaction between IDX-184 and HCV polymerase from four different genotypes. Methods: Comparisons to the native nucleotide (Guanosine triphosphate) and other NIs were performed using interaction descriptors, calculated using semiempirical quantum mechanics and molecular docking. Results: IDX-184 shows potent binding to the active site of the polymerases. In addition, IDX-184 was better than Sofosbuvir and Ribavirin when docked into polymerase active site (even with experimentally solved structure). Conclusion: Analysis of the interaction descriptors and docking complexes suggests IDX-184 as a superior NI against the studied HCV subtypes.

IDX-184 is a superior HCV direct-acting antiviral drug: a QSAR study

Abstract

Quantitative structure-activity relationship (QSAR) parameters are good indicators for the reactivity of direct-acting antiviral drugs. Since molecular structure is related to molecular function, careful selection of molecular substitutions will result in more drugs that are potent. In this work, QSAR parameters are selected in order to compare the four drugs used as nucleotide inhibitors (NIs) for non-structural 5B (NS5B) RNA-dependent RNA polymerase (RdRp) of hepatitis C virus (HCV). These drugs are: ribavirin (widely used over the last 20 years), sofosbuvir (approved on December 2013 by FDA), and finally IDX-184 and R7128 (phase IIb of clinical trial drugs). The nucleotide analogues uracil (U), guanine (G), and cytosine (C) from which these drugs are fabricated are also compared to that group of drugs. QSAR parameters suggested that the drug IDX-184 is the best among all of the studied NIs. It also shows that NIs are always more reactive than their parent nucleotide.

Graphical Abstract

The active site environment of 12 amino acids coordinated with IDX-184 through two Mg²⁺. The interaction with HCV subtypes 1a, 2b, and 3b is better than 4a subtype.

Assessment of health-related quality of life and how it predicts the outcome of pegylated interferon and ribavirin therapy for chronic hepatitis C

BACKGROUND AND AIM

Chronic infection with hepatitis C virus (HCV) decreases health-related quality of life (HRQOL). The present study was planned to investigate the impact of HRQOL of patients with chronic hepatitis C (CHC) on the outcomes of therapy with pegylated interferon and ribavirin (RBV), in addition to IL28B polymorphisms.

METHODS

The present study enrolled 228 CHC patients and assessed their HRQOLs prospectively with the 36-item short-form health survey.

RESULTS

The patients with CHC have lower physical HRQOL status than the general population (P = 0.037, the Z-test). The patients with advanced liver diseases exhibited further decreases in HRQOL (P = 0.036, Spearman's rank correlation coefficient). The score of total HRQOL was significantly lower in the group with sustained virological response (SVR) to the therapy with pegylated interferon and RBV than the non-SVR group (P = 0.031, the Mann-Whitney U-test), with significantly lower scores of mental component and its comprising subscales in the SVR group. Stepwise multivariate logistic regression analysis showed that low HRQOL score ≤ 400 points was significantly associated with SVR (odds ratio = 2.4, P = 0.013), independently from high platelet counts, low HCV RNA, favorable single-nucleotide polymorphism type of IL28B, and HCV serotype 2. The patients with low HRQOL score will have significantly less decrease in HRQOL score by 4 weeks of the treatment than those with high HRQOL score at baseline (P = 0.0045).

CONCLUSION

HRQOL is one of the significant predictor of the outcomes of therapy with pegylated interferon and RBV independently from IL28B polymorphism.

Restoration of type I interferon expression by heme and related tetrapyrroles through inhibition of NS3/4A protease

BACKGROUND

Tetrapyrrole substrates and products of heme oxygenase are potent inhibitors of hepatitis C virus (HCV) replication. It is not clear whether this occurs through primary induction of type I interferon (IFN), inhibition of viral NS3/4A protease, or a combination of these mechanisms. We studied the antiviral actions of tetrapyrroles and their potential influence on type I IFN induction.

METHODS

The effects of tetrapyrrole on NS3/4A protease activity and type I IFN induction were assessed in HCV-permissive cells, replicons, or human embryonic kidney (HEK) 293 cells transfected with NS3/4A protease. Activation of innate immune signaling was determined after transfection of double-strand surrogate nucleic acid antigens or infection with defined sequence HCV cell culture (HCVcc) RNA.

RESULTS

Tetrapyrroles failed to directly induce IFN expression at concentrations that inhibited HCV replication and NS3/4A protease activity. However, they potently restored IFN induction after attenuation with NS3/4A protease, a process accompanied by preservation of the adapter protein, mitochondrial antiviral signaling protein, nuclear localization of IFN regulatory factor 3, and augmentation of IFN-stimulated gene products.

CONCLUSIONS

Tetrapyrroles do not directly induce IFN, but they dramatically restore type I IFN signaling pathway after attenuation with NS3/4A protease. They show immunomodulatory as well as antiprotease activity and may be useful for treatment of HCV infection.

Molecular modeling comparison of the performance of NS5b polymerase inhibitor (PSI-7977) on prevalent HCV genotypes

The current available treatment for hepatitis C virus (HCV)-the causative of liver cirrhosis and development of liver cancer-is a dual therapy using modified interferon and ribavirin. While this regimen increases the sustained viral response rate up to 40-80 % in different genotypes, unfortunately, it is poorly tolerated by patients. PSI-7977, a prodrug for PSI-7409, is a Non-Structural 5b (NS5b) polymerase nucleoside inhibitor that is currently in phase III clinical trials. The activated PSI-7977 is a direct acting antiviral (DAA) drug that acts on NS5b polymerase of HCV through a coordination bond with the two Mg(+2) present at the GDD active site motif. The present work utilizes a molecular modeling approach for studying the interaction between the activated PSI-7977 and the 12 amino acids constituting a 5 Å region surrounding the GDD active triad motif for HCV genotypes 1a, 2b, 3b and 4a. The analysis of the interaction parameters suggests that PSI-7977 is probably a better DAA drug for HCV genotypes 1a and 3b rather than genotypes 2b and 4a.

Predictive impact of polymorphism of PNPLA3 on HCC development after interferon therapy in Japanese patients with chronic hepatitis C

The impact of single-nucleotide polymorphisms (SNP) of patatin-like phospholipase domain-containing protein 3 (PNPLA3) on development of hepatocellular carcinoma (HCC) is not clarified for Japanese patients with chronic hepatitis C. The present study investigated the associations of rs738409 PNPLA3 with HCC development after the antiviral therapy with peg-interferon and ribavirin for Japanese patients with hepatitis C virus serotype 1 and high viral load. Of the 271 patients enrolled in the study, 20 patients developed HCC, during a median follow-up period of 4.6 years. Multivariate analysis in the proportional hazards models revealed that sex, body mass index, platelet counts, and alpha feroprotein (AFP) had significant associations with HCC development (p = 0.011, 0.029, 0.0002, and 0.046, respectively). Multivariate regression analysis revealed that PNPLA3 148 M was significantly associated with serum AFP level (p = 0.032), other than body mass index, platelet count, and alanine aminotransferase (p = 0.0006, 0.0002, and 0.037, respectively), and that serum AFP level was significantly associated with PNPLA3 148 M (p = 0.017). Serum AFP level is an important factor in predicting HCC development after the antiviral therapy for Japanese patients with chronic hepatitis C, the mechanism of which might involve its significant associations with the SNP genotype of PNPLA3.

Risk factor profiles among intravenous drug using young adults: a latent class analysis (LCA) approach

Using data from a cross-sectional study that examined health risk behaviors among urban intravenous drug-using (IDU) adolescents and young adults, this study investigated risk profiles among a high-risk sample (n=274). Risk profiles were empirically derived through latent class analysis based on indicators of engagement in health-risking behaviors, experience of abuse and violence as well as individual and family risk factors. The best fitting model was a 3-class model. Class 1 (n=95) captured participants with the lowest risk across all indicators. Compared to Class 1, Class 2 (n=128) and Class 3 (n=51) had elevated rates of engagement in health-risking behaviors as well as individual and family risk factors; however, Class 3 had the highest rate of engagement in sexual risk behavior, and backgrounds of substantial abuse and violence as well as familial psychopathology. Class 2 was the group most socioeconomically disadvantaged, with the highest percentage of participants coming from poor backgrounds, spending the longest time homeless and working the fewest months. Identifying subgroups of IDU has the potential to guide the development of more targeted and effective strategies for prevention and treatment of this high-risk population.

Heme and HO-1 Inhibition of HCV, HBV, and HIV

Hepatitis C virus, human immunodeficiency virus, and hepatitis B virus are chronic viral infections that cause considerable morbidity and mortality throughout the world. In the decades following the identification and sequencing of these viruses, in vitro experiments demonstrated that heme oxygenase-1, its oxidative products, and related compounds of the heme oxygenase system inhibit replication of all 3 viruses. The purpose of this review is to critically evaluate and summarize the seminal studies that described and characterized this remarkable behavior. It will also discuss more recent work that discovered the antiviral mechanisms and target sites of these unique antiviral agents. In spite of the fact that these viruses are diverse pathogens with quite profound differences in structure and life cycle, it is significant that heme and related compounds show striking similarity for viral target sites across all three species. Collectively, these findings strongly indicate that we should move forward and develop heme and related tetrapyrroles into versatile antiviral agents that could be used therapeutically in patients with single or multiple viral infections.

Biliverdin inhibits hepatitis C virus nonstructural 3/4A protease activity: mechanism for the antiviral effects of heme oxygenase?

Induction of heme oxygenase-1 (HO-1) inhibits hepatitis C virus (HCV) replication. Of the products of the reaction catalyzed by HO-1, iron has been shown to inhibit HCV ribonucleic acid (RNA) polymerase, but little is known about the antiviral activity of biliverdin (BV). Herein, we report that BV inhibits viral replication and viral protein expression in a dose-dependent manner in replicons and cells harboring the infectious J6/JFH construct. Using the SensoLyte 620 HCV Protease Assay with a wide wavelength excitation/emission (591 nm/622 nm) fluorescence energy transfer peptide, we found that both recombinant and endogenous nonstructural 3/4A (NS3/4A) protease from replicon microsomes are potently inhibited by BV. Of the tetrapyrroles tested, BV was the strongest inhibitor of NS3/4A activity, with a median inhibitory concentration (IC(50)) of 9 μM, similar to that of the commercial inhibitor, AnaSpec (Fremont, CA) #25346 (IC(50) 5 μM). Lineweaver-Burk plots indicated mixed competitive and noncompetitive inhibition of the protease by BV. In contrast, the effects of bilirubin (BR) on HCV replication and NS3/4A were much less potent. Because BV is rapidly converted to BR by biliverdin reductase (BVR) intracellularly, the effect of BVR knockdown on BV antiviral activity was assessed. After greater than 80% silencing of BVR, inhibition of viral replication by BV was enhanced. BV also increased the antiviral activity of α-interferon in replicons.

CONCLUSION

BV is a potent inhibitor of HCV NS3/4A protease, which likely contributes to the antiviral activity of HO-1. These findings suggest that BV or its derivatives may be useful in future drug therapies targeting the NS3/4A protease.

Amino acid substitutions of hepatitis C virus core protein are not associated with intracellular antiviral response to interferon-α in vitro

BACKGROUND

Studies on patients with hepatitis C virus (HCV) of genotype 1b have suggested that amino acids (aa) 70 and/or 91 of the HCV core protein affect the outcome of interferon (IFN)-α and ribavirin (RBV) therapy, although there are no clear supporting data in vitro.

AIMS

This study was designed to determine the differences among the antiviral activities of HCV core proteins with various substitutions at aa70 and/or aa91.

METHODS

The retroviral vectors expressing the HCV core proteins with substitutions of arginine/leucine, arginine/methionine, glutamine/leucine or glutamine/methionine at aa70/aa91 were transiently transfected or stably transducted into an immortalized hepatocyte line (PH5CH8), hepatoma cell lines and an HCV-RNA replicating cell line (sOR) to evaluate antiviral responses to IFN-α or IFN-α/RBV. Sequence analysis was performed using genome-length HCV-RNA replicating cells (OR6 and AH1) to evaluate HCV core mutations during IFN-α treatment.

RESULTS

The promoter activity levels of IFN-stimulated genes in the transiently transfected cells or the mRNA levels of 2'-5'-oligoadenylate synthetase in the stably transducted PH5CH8 cells were not associated with the HCV core aa70 and/or aa91 substitutions during IFN-α treatment. Antiviral responses to IFN-α or IFN-α/RBV treatment were enhanced in sOR cells stably transducted with the HCV core, although there were no differences in antiviral responses among the cells expressing different core types. Sequence analysis showed no aa mutations after IFN-α treatment.

CONCLUSIONS

Antiviral activities were enhanced by HCV core transduction, but they were not associated with the HCV core aa70 and/or aa91 substitutions by in vitro analysis.

Immunotherapy of viral infections

Among the microorganisms that cause diseases of medical or veterinary importance, the only group that is entirely dependent on the host, and hence not easily amenable to therapy via pharmaceuticals, is the viruses. Since viruses are obligate intracellular pathogens, and therefore depend a great deal on cellular processes, direct therapy of viral infections is difficult. Thus, modifying or targeting nonspecific or specific immune responses is an important aspect of intervention of ongoing viral infections. However, as a result of the unavailability of effective vaccines and the extended duration of manifestation, chronic viral infections are the most suitable for immunotherapies. We present an overview of various immunological strategies that have been applied for treating viral infections after exposure to the infectious agent.

A model of patient choice with mid-therapy information

For many treatments, a patient's prognosis may be refined by conducting a mid-therapy assessment (MTA). When therapy lasts some time, an MTA predicts a patient's ultimate outcome based on early signs of response. The availability and timing of such assessments also serve as a mechanism by which policy makers can influence patients' treatment-initiation decisions. In this article, we examine how patients evaluate treatment options using MTAs of treatment effectiveness and discuss the policy implications of patient decision making in such contexts. To this end, we use indifference-curve analysis to characterize trade-offs between potential treatment success versus potential adverse effects in therapeutic situations where patients are encouraged to consider their own motivations for initiating treatment. Treatment initiation for chronic hepatitis C virus (HCV) infection is used for illustration, but the analysis can be easily adapted to a variety of clinical scenarios.Analysis shows that the existence of MTAs influences patients' initial treatment decisions by affecting the expectations of treatment success and adverse effects. Earlier MTAs have lower sensitivity and higher specificity, and the prior expectation of adverse effects is accordingly lower for two reasons. First, the lower chance for a false signal of treatment response and the higher chance for a false signal of no response make it more likely that the patient receives a signal leading to discontinuation. Second, if a signal to discontinue is received, fewer weeks of adverse effects have been endured before discontinuation occurs. Both factors make the expected burden of adverse effects lower when the MTA occurs earlier. Later MTAs have higher sensitivity and lower specificity, both of which serve to increase the probability of treatment completion, causing a higher prior likelihood of treatment success.These findings indicate that treatment demand may be increased by changing the timing of MTAs, depending on the information content of the alternative mid-therapy signals and the nature of patient preferences. In HCV infection and other diseases, clinical practice guidelines for conducting MTAs might be modified to better achieve public health or other policy objectives by studying the economics of patient choice.

Substituted imidazopyridines as potent inhibitors of HCV replication

BACKGROUND/AIMS

Following lead optimization, a set of substituted imidazopyridines was identified as potent and selective inhibitors of in vitro HCV replication. The particular characteristics of one of the most potent compounds in this series (5-[[3-(4-chlorophenyl)-5-isoxazolyl]methyl]-2-(2,3-difluorophenyl)-5H-imidazo[4,5-c]pyridine or GS-327073), were studied.

METHODS

Antiviral activity of GS-327073 was evaluated in HCV subgenomic replicons (genotypes 1b, 1a and 2a), in the JFH1 (genotype 2a) infectious system and against replicons resistant to various selective HCV inhibitors. Combination studies of GS-327073 with other selective HCV inhibitors were performed.

RESULTS

Fifty percent effective concentrations for inhibition of HCV subgenomic 1b replicon replication ranged between 2 and 50 nM and were 100-fold higher for HCV genotype 2a virus. The 50% cytostatic concentrations were > or = 17 microM, thus resulting in selectivity indices of > or = 340. GS-327073 retained wild-type activity against HCV replicons that were resistant to either HCV protease inhibitors or several polymerase inhibitors. GS-327073, when combined with either interferon alpha, ribavirin, a nucleoside polymerase or a protease inhibitor resulted in overall additive antiviral activity. Combinations containing GS-327073 proved highly effective in clearing hepatoma cells from HCV.

CONCLUSIONS

GS-327073 is a potent in vitro inhibitor of HCV replication either alone or in combination with other selective HCV inhibitors.

Effects of a hepatitis C virus educational intervention or a motivational intervention on alcohol use, injection drug use, and sexual risk behaviors among injection drug users

OBJECTIVES

We compared the effects of 2 interventions on alcohol use, use of a new syringe at last injection, and condom use at last sexual encounter in a community sample of injection drug users.

METHODS

Between 2003 and 2006, 851 out-of-treatment injection drug users were recruited in Raleigh, NC, and Durham, NC, through street outreach and were randomly assigned to either a 6-session educational intervention or a 6-session motivational intervention. Intervention effects were examined at 6 and 12 months after enrollment.

RESULTS

In multiple logistic regression analyses adjusted for baseline alcohol use and HCV status, participants assigned to the motivational intervention were significantly less likely than were participants in the educational intervention to be drinking at the 6-month follow-up (odds ratio = 0.67; 95% confidence interval = 0.46, 0.97). There were no significant between-group differences in use of a new syringe at last injection or condom use at last sexual encounter at either follow-up.

CONCLUSIONS

Reducing alcohol use among persons with HCV may slow disease progression and provide important health benefits. Additional strategies are needed for slowing HCV disease progression until more effective HCV treatments are available.

The influence of race and language on chronic hepatitis C virus infection management

Race, ethnicity and language influence health care delivery and satisfaction with treatment in many disease states including chronic hepatitis C virus (HCV) infection. In this review, HCV epidemiology and current standard of care is reviewed. The influence of race, ethnicity and language on screening, work-up and initiation of HCV antiviral treatment is evaluated. Acknowledging that these factors do influence health care quality and taking steps to improve communication (e.g. translated written documents; use of reliable, trained translators in the clinic setting) will facilitate the delivery of an equivalent level of care to all patients living with HCV.

Heme oxygenase-1 suppresses hepatitis C virus replication and increases resistance of hepatocytes to oxidant injury

Oxidative injury to hepatocytes occurs as a result of hepatitis C virus (HCV) infection and replication. Modulation of host cell antioxidant enzymes such as heme oxygenase-1 (HO-1) may be useful therapeutically to minimize cellular injury, reduce viral replication, and attenuate liver disease. In this report, we evaluated the effects of HO-1 overexpression on HCV replication and hepatocellular injury. Full-length (FL) (Con1) or nonstructural (NS) replicons (I 389 NS3-3') were transfected with complete human HO-1 sequences or empty vector for control. Cell lines overexpressing HO-1 (twofold to sixfold above basal values) or empty vector were isolated, and their HCV RNA synthesis, pro-oxidant levels, and resistance to oxidative injury were assessed. HO-1 overexpression decreased HCV RNA replication in both FL and NS replicons without affecting cellular growth or DNA synthesis. The attenuation of HCV replication was significantly reversed in both replicon systems with HO-1 small interfering RNA (siRNA) knockdown. Both FL and NS replicons that overexpress HO-1 showed reduced prooxidant levels at baseline and increased resistance to oxidant-induced cytotoxicity. HO-1 induction with hemin also markedly decreased HCV replication in both parental FL and NS replicon cell lines. Conversely, knockdown of HO-1 messenger RNA (mRNA) by siRNA in parental FL or NS replicons did not significantly affect HCV replication, suggesting that less than basal levels of HO-1 had minimal effect on HCV replication.

CONCLUSION

Overexpression or induction of HO-1 results in decreased HCV replication as well as protection from oxidative damage. These findings suggest a potential role for HO-1 in antiviral therapy and therapeutic protection against hepatocellular injury in HCV infection.

Liver fibrosis

Liver damage leads to an inflammatory response and to the activation and proliferation of mesenchymal cell populations within the liver which remodel the extracellular matrix as part of an orchestrated wound-healing response. Chronic damage results in a progressive accumulation of scarring proteins (fibrosis) that, with increasing severity, alters tissue structure and function, leading to cirrhosis and liver failure. Efforts to modulate the fibrogenesis process have focused on understanding the biology of the heterogeneous liver fibroblast populations. The fibroblasts are derived from sources within and out with the liver. Fibroblasts expressing alpha-smooth muscle actin (myofibroblasts) may be derived from the transdifferentiation of quiescent hepatic stellate cells. Other fibroblasts emerge from the portal tracts within the liver. At least a proportion of these cells in diseased liver originate from the bone marrow. In addition, fibrogenic fibroblasts may also be generated through liver epithelial (hepatocyte and biliary epithelial cell)-mesenchymal transition. Whatever their origin, it is clear that fibrogenic fibroblast activity is sensitive to (and may be active in) the cytokine and chemokine profiles of liver-resident leucocytes such as macrophages. They may also be a component driving the regeneration of tissue. Understanding the complex intercellular interactions regulating liver fibrogenesis is of increasing importance in view of predicted increases in chronic liver disease and the current paucity of effective therapies.