The antimalarial ferroquine is an inhibitor of hepatitis C virus

Biologic Functions of Hydroxychloroquine in Disease: From COVID-19 to Cancer

Chloroquine (CQ) and Hydroxychloroquine (HCQ), initially utilized in the treatment of malaria, have now developed a long list of applications. Despite their clinical relevance, their mechanisms of action are not clearly defined. Major pathways by which these agents are proposed to function include alkalinization of lysosomes and endosomes, downregulation of C-X-C chemokine receptor type 4 (CXCR4) expression, high-mobility group box 1 protein (HMGB1) inhibition, alteration of intracellular calcium, and prevention of thrombus formation. However, there is conflicting data present in the literature. This is likely the result of the complex overlapping pathways between these mechanisms of action that have not previously been highlighted. In fact, prior research has focused on very specific portions of particular pathways without describing these in the context of the extensive CQ/HCQ literature. This review summarizes the detailed data regarding CQ/HCQ's mechanisms of action while also providing insight into the overarching themes. Furthermore, this review provides clinical context to the application of these diverse drugs including their role in malaria, autoimmune disorders, cardiovascular disease, thrombus formation, malignancies, and viral infections.

4-Aminoquinoline compounds from the Spanish flu to COVID-19

In 1918, quinine was used as one of the unscientifically based treatments against the H1N1 virus during the Spanish flu pandemic. Originally, quinine was extracted from the bark of Chinchona trees by South American natives of the Amazon forest, and it has been used to treat fever since the seventeenth century. The recent COVID-19 pandemic caused by Sars-Cov-2 infection has forced researchers to search for ways to prevent and treat this disease. Based on the antiviral potential of two 4-aminoquinoline compounds derived from quinine, known as chloroquine (CQ) and hydroxychloroquine (HCQ), clinical investigations for treating COVID-19 are being conducted worldwide. However, there are some discrepancies among the clinical trial outcomes.Thus, even after one hundred years of quinine use during the Spanish flu pandemic, the antiviral properties promoted by 4-aminoquinoline compounds remain unclear. The underlying molecular mechanisms by which CQ and HCQ inhibit viral replication open up the possibility of developing novel analogs of these drugs to combat COVID-19 and other viruses.

Autophagy and Liver Diseases

Autophagy plays an important role in the physiology and pathology of the liver. It is involved in the development of many liver diseases such as α-1-antitrypsin deficiency, chronic hepatitis virus infection, alcoholic liver disease, nonalcoholic fatty liver disease, and liver cancer. Autophagy has thus become a new target for the treatment of liver diseases. How to treat liver diseases by regulating autophagy has been a hot topic.

COVID-19 Diagnostics, Tools, and Prevention

The Coronavirus Disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), outbreak from Wuhan City, Hubei province, China in 2019 has become an ongoing global health emergency. The emerging virus, SARS-CoV-2, causes coughing, fever, muscle ache, and shortness of breath or dyspnea in symptomatic patients. The pathogenic particles that are generated by coughing and sneezing remain suspended in the air or attach to a surface to facilitate transmission in an aerosol form. This review focuses on the recent trends in pandemic biology, diagnostics methods, prevention tools, and policies for COVID-19 management. To meet the growing demand for medical supplies during the COVID-19 era, a variety of personal protective equipment (PPE) and ventilators have been developed using do-it-yourself (DIY) manufacturing. COVID-19 diagnosis and the prediction of virus transmission are analyzed by machine learning algorithms, simulations, and digital monitoring. Until the discovery of a clinically approved vaccine for COVID-19, pandemics remain a public concern. Therefore, technological developments, biomedical research, and policy development are needed to decipher the coronavirus mechanism and epidemiological characteristics, prevent transmission, and develop therapeutic drugs.

Function of the HCV E1 envelope glycoprotein in viral entry and assembly

HCV envelope glycoproteins, E1 and E2, are multifunctional proteins. Until recently, E2 glycoprotein was thought to be the fusion protein and was the focus of investigations. However, the recently obtained partial structures of E2 and E1 rather support a role for E1 alone or in association with E2 in HCV fusion. Moreover, they suggest that HCV harbors a new fusion mechanism, distinct from that of other members of the Flaviviridae family. In this context, E1 aroused a renewed interest. Recent functional characterizations of E1 revealed a more important role than previously thought in entry and assembly. Thus, E1 is involved in the viral genome encapsidation step and influences the association of the virus with lipoprotein components. Moreover, E1 modulates HCV–receptor interaction and participates in a late entry step potentially fusion. In this review, we outline our current knowledge on E1 functions in HCV assembly and entry.

Ferrocene-based inhibitors of hepatitis C virus replication that target NS5A with low picomolar in vitro antiviral activity

An unprecedented series of organometallic HCV (hepatitis C virus) NS5A (nonstructural 5A protein) replication complex inhibitors that incorporates a 1,1'-ferrocenediyl scaffold was explored. This scaffold introduces the elements of linear flexibility and non-planar topology that are unconventional for this class of inhibitors. Data from 2-D NMR spectroscopic analyses of these complexes in solution support an anti (unstacked) arrangement of the pharmacophoric groups. Several complexes demonstrate single-digit picomolar in vitro activity in an HCV genotype-1b replicon system. One complex to arise from this investigation (10a) exhibits exceptional picomolar activity against HCV genotype 1a and 1b replicons, low hepatocellular cytotoxicity, and good pharmacokinetic properties in rat.

Identification of Novel Functions for Hepatitis C Virus Envelope Glycoprotein E1 in Virus Entry and Assembly

Hepatitis C virus (HCV) envelope glycoprotein complex is composed of E1 and E2 subunits. E2 is the receptor-binding protein as well as the major target of neutralizing antibodies, whereas the functions of E1 remain poorly defined. Here, we took advantage of the recently published structure of the N-terminal region of the E1 ectodomain to interrogate the functions of this glycoprotein by mutating residues within this 79-amino-acid region in the context of an infectious clone. The phenotypes of the mutants were characterized to determine the effects of the mutations on virus entry, replication, and assembly. Furthermore, biochemical approaches were also used to characterize the folding and assembly of E1E2 heterodimers. Thirteen out of 19 mutations led to viral attenuation or inactivation. Interestingly, two attenuated mutants, T213A and I262A, were less dependent on claudin-1 for cellular entry in Huh-7 cells. Instead, these viruses relied on claudin-6, indicating a shift in receptor dependence for these two mutants in the target cell line. An unexpected phenotype was also observed for mutant D263A which was no longer infectious but still showed a good level of core protein secretion. Furthermore, genomic RNA was absent from these noninfectious viral particles, indicating that the D263A mutation leads to the assembly and release of viral particles devoid of genomic RNA. Finally, a change in subcellular colocalization between HCV RNA and E1 was observed for the D263A mutant. This unique observation highlights for the first time cross talk between HCV glycoprotein E1 and the genomic RNA during HCV morphogenesis.IMPORTANCE Hepatitis C virus (HCV) infection is a major public health problem worldwide. It encodes two envelope proteins, E1 and E2, which play a major role in the life cycle of this virus. E2 has been extensively characterized, whereas E1 remains poorly understood. Here, we investigated E1 functions by using site-directed mutagenesis in the context of the viral life cycle. Our results identify unique phenotypes. Unexpectedly, two mutants clearly showed a shift in receptor dependence for cell entry, highlighting a role for E1 in modulating HCV particle interaction with a cellular receptor(s). More importantly, another mutant led to the assembly and release of viral particles devoid of genomic RNA. This unique phenotype was further characterized, and we observed a change in subcellular colocalization between HCV RNA and E1. This unique observation highlights for the first time cross talk between a viral envelope protein and genomic RNA during morphogenesis.

A Novel Inhibitor IDPP Interferes with Entry and Egress of HCV by Targeting Glycoprotein E1 in a Genotype-Specific Manner

Despite recent advances in curing chronic hepatitis C (CHC), the high economic burden to therapy, viral drug resistance, difficult to treat hepatitis C virus (HCV) genotypes and patient groups are still of concern. To address this unmet medical needs, we devised strategies to identify novel viral interventions through target-free high-throughput screening of small molecules utilizing a phenotypic-based HCV infection assay. Thereby, a very potent (EC₅₀ 46 ± 26 pM) iminodipyridinopyrimidine (IDPP) drug candidate was selected, and confirmed in primary human hepatocytes (EC₅₀ 0.5 nM). IDPP mainly targets a post-attachment step of HCV without affecting endosomal acidification, prevents the secretion of infectious particles and viral cell-to-cell spread. The putative molecular target of IDPP is glycoprotein E1, as revealed by selection for viral drug resistance (Gly-257-Arg). IDPP was synergistic in combination with FDA-approved HCV drugs and inhibited pre-existing resistant HCV strains induced by today's therapies. Interestingly, IDPP exclusively inhibited HCV genotype 2. However, we identified the genotype-specificity determining region in E1 and generated HCV genotype 1 susceptible to IDPP by changing one amino acid in E1 (Gln-257-Gly). Together, our results indicate an opportunity to provide an alternative treatment option for CHC and will shed light on the poorly understood function of HCV glycoprotein E1.

Targeting endosomal acidification by chloroquine analogs as a promising strategy for the treatment of emerging viral diseases

Emerging viruses such as HIV, dengue, influenza A, SARS coronavirus, Ebola, and other viruses pose a significant threat to human health. Majority of these viruses are responsible for the outbreaks of pathogenic lethal infections. To date, there are no effective therapeutic strategies available for the prophylaxis and treatment of these infections. Chloroquine analogs have been used for decades as the primary and most successful drugs against malaria. Concomitant with the emergence of chloroquine-resistant Plasmodium strains and a subsequent decrease in the use as antimalarial drugs, other applications of the analogs have been investigated. Since the analogs have interesting biochemical properties, these drugs are found to be effective against a wide variety of viral infections. As antiviral action, the analogs have been shown to inhibit acidification of endosome during the events of replication and infection. Moreover, immunomodulatory effects of analogs have been beneficial to patients with severe inflammatory complications of several viral diseases. Interestingly, one of the successful targeting strategies is the inhibition of HIV replication by the analogs in vitro which are being tested in several clinical trials. This review focuses on the potentialities of chloroquine analogs for the treatment of endosomal low pH dependent emerging viral diseases.

Identification of a New Benzimidazole Derivative as an Antiviral against Hepatitis C Virus

Aminoquinolines and piperazines, linked or not, have been used successfully to treat malaria, and some molecules of this family also exhibit antiviral properties. Here we tested several derivatives of 4-aminoquinolines and piperazines for their activity against hepatitis C virus (HCV). We screened 11 molecules from three different families of compounds, and we identified anti-HCV activity in cell culture for six of them. Of these, we selected a compound (B5) that is currently ending clinical phase I evaluation for neurodegenerative diseases. In hepatoma cells, B5 inhibited HCV infection in a pangenotypic and dose-dependent manner, and its antiviral activity was confirmed in primary hepatocytes. B5 also inhibited infection by pseudoparticles expressing HCV envelope glycoproteins E1 and E2, and we demonstrated that it affects a postattachment stage of the entry step. Virus with resistance to B5 was selected by sequential passage in the presence of the drug, and reverse genetics experiments indicated that resistance was conferred mainly by a single mutation in the putative fusion peptide of E1 envelope glycoprotein (F291I). Furthermore, analyses of the effects of other closely related compounds on the B5-resistant mutant suggest that B5 shares a mode of action with other 4-aminoquinoline-based molecules. Finally, mice with humanized liver that were treated with B5 showed a delay in the kinetics of the viral infection. In conclusion, B5 is a novel interesting anti-HCV molecule that could be used to decipher the early steps of the HCV life cycle.

IMPORTANCE

In the last 4 years, HCV therapy has been profoundly improved with the approval of direct-acting antivirals in clinical practice. Nevertheless, the high costs of these drugs limit access to therapy in most countries. The present study reports the identification and characterization of a compound (B5) that inhibits HCV propagation in cell culture and is currently ending clinical phase I evaluation for neurodegenerative diseases. This molecule inhibits the HCV life cycle by blocking virus entry. Interestingly, after selection of drug-resistant virus, a resistance mutation in the putative fusion peptide of E1 envelope glycoprotein was identified, indicating that B5 could be used to further investigate the fusion mechanism. Furthermore, mice with humanized liver treated with B5 showed a delay in the kinetics of the viral infection. In conclusion, B5 is a novel interesting anti-HCV molecule that could be used to decipher the early steps of the HCV life cycle.

Promising Anti-Hepatitis C Virus Compounds from Natural Resources

Hepatitis C virus (HCV) infection is a major worldwide problem, which involves approximately 170 million people. High morbidity of patients is caused by chronic infection, which leads to liver cirrhosis, hepatocellular carcinoma and other HCV-related diseases. The sustained virological response (SVR) has been markedly improved to be >90% by the current standard interferon (IFN)-free treatment regimens with a combination of direct-acting antiviral agents (DAAs) targeting the viral NS3 protease, NS5A multi-function protein and NS5B RNA-dependent RNA polymerase, compared with 50–70% of SVR rates achieved by the previous standard IFN-based treatment regimens with or without an NS3 protease inhibitor. However, the emergence of DAA-resistant HCV strains and the limited access to the DAAs due to their high cost could be major concerns. Also, the long-term prognosis of patients treated with DAAs, such as the possible development of hepatocellular carcinoma, still needs to be further evaluated. Natural resources are considered to be good candidates to develop anti-HCV agents. Here, we summarize anti-HCV compounds obtained from natural resources, including medicinal plant extracts, their isolated compounds and some of their derivatives that possess high antiviral potency against HCV.

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.

Entry inhibitors: New advances in HCV treatment

Hepatitis C virus (HCV) infection affects approximately 3% of the world's population and causes chronic liver diseases, including liver fibrosis, cirrhosis, and hepatocellular carcinoma. Although current antiviral therapy comprising direct-acting antivirals (DAAs) can achieve a quite satisfying sustained virological response (SVR) rate, it is still limited by viral resistance, long treatment duration, combined adverse reactions, and high costs. Moreover, the currently marketed antivirals fail to prevent graft reinfections in HCV patients who receive liver transplantations, probably due to the cell-to-cell transmission of the virus, which is also one of the main reasons behind treatment failure. HCV entry is a highly orchestrated process involving initial attachment and binding, post-binding interactions with host cell factors, internalization, and fusion between the virion and the host cell membrane. Together, these processes provide multiple novel and promising targets for antiviral therapy. Most entry inhibitors target host cell components with high genetic barriers and eliminate viral infection from the very beginning of the viral life cycle. In future, the addition of entry inhibitors to a combination of treatment regimens might optimize and widen the prevention and treatment of HCV infection. This review summarizes the molecular mechanisms and prospects of the current preclinical and clinical development of antiviral agents targeting HCV entry.

Repurposing of the antihistamine chlorcyclizine and related compounds for treatment of hepatitis C virus infection

Hepatitis C virus (HCV) infection affects an estimated 185 million people worldwide, with chronic infection often leading to liver cirrhosis and hepatocellular carcinoma. Although HCV is curable, there is an unmet need for the development of effective and affordable treatment options. Through a cell-based high-throughput screen, we identified chlorcyclizine HCl (CCZ), an over-the-counter drug for allergy symptoms, as a potent inhibitor of HCV infection. CCZ inhibited HCV infection in human hepatoma cells and primary human hepatocytes. The mode of action of CCZ is mediated by inhibiting an early stage of HCV infection, probably targeting viral entry into host cells. The in vitro antiviral effect of CCZ was synergistic with other anti-HCV drugs, including ribavirin, interferon-α, telaprevir, boceprevir, sofosbuvir, daclatasvir, and cyclosporin A, without significant cytotoxicity, suggesting its potential in combination therapy of hepatitis C. In the mouse pharmacokinetic model, CCZ showed preferential liver distribution. In chimeric mice engrafted with primary human hepatocytes, CCZ significantly inhibited infection of HCV genotypes 1b and 2a, without evidence of emergence of drug resistance, during 4 and 6 weeks of treatment, respectively. With its established clinical safety profile as an allergy medication, affordability, and a simple chemical structure for optimization, CCZ represents a promising candidate for drug repurposing and further development as an effective and accessible agent for treatment of HCV infection.

Host-Targeting Agents to Prevent and Cure Hepatitis C Virus Infection

Chronic hepatitis C virus (HCV) infection is a major cause of liver cirrhosis and hepatocellular carcinoma (HCC) which are leading indications of liver transplantation (LT). To date, there is no vaccine to prevent HCV infection and LT is invariably followed by infection of the liver graft. Within the past years, direct-acting antivirals (DAAs) have had a major impact on the management of chronic hepatitis C, which has become a curable disease in the majority of DAA-treated patients. In contrast to DAAs that target viral proteins, host-targeting agents (HTAs) interfere with cellular factors involved in the viral life cycle. By acting through a complementary mechanism of action and by exhibiting a generally higher barrier to resistance, HTAs offer a prospective option to prevent and treat viral resistance. Indeed, given their complementary mechanism of action, HTAs and DAAs can act in a synergistic manner to reduce viral loads. This review summarizes the different classes of HTAs against HCV infection that are in preclinical or clinical development and highlights their potential to prevent HCV infection, e.g., following LT, and to tailor combination treatments to cure chronic HCV infection.

Targeting Viral Entry for Treatment of Hepatitis B and C Virus Infections

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections remain major health problems worldwide, with 400-500 million chronically infected people worldwide. Chronic infection results in liver cirrhosis and hepatocellular carcinoma, the second leading cause of cancer death. Current treatments for HBV limit viral replication without efficiently curing infection. HCV treatment has markedly progressed with the licensing of direct-acting antivirals (DAAs) for HCV cure, yet limited access for the majority of patients is a major challenge. Preventative and curative treatment strategies, aimed at novel targets, are needed for both viruses. Viral entry represents one such target, although detailed knowledge of the entry mechanisms is a prerequisite. For HBV, the recent discovery of the NTCP cell entry factor enabled the establishment of an HBV cell culture model and showed that cyclosporin A and Myrcludex B are NTCP-targeting entry inhibitors. Advances in the understanding of HCV entry revealed it to be a complex process involving many factors, offering several antiviral targets. These include viral envelope proteins E1 and E2, virion-associated lipoprotein ApoE, and cellular factors CD81, SRBI, EGFR, claudin-1, occludin, and the cholesterol transporter NPC1L1. Small molecules targeting SR-BI, EGFR, and NPC1L1 have entered clinical trials, whereas other viral- and host-targeted small molecules, peptides, and antibodies show promise in preclinical models. This review summarizes the current understanding of HBV and HCV entry and describes novel antiviral targets and compounds in different stages of clinical development. Overall, proof-of-concept studies indicate that entry inhibitors are a promising class of antivirals to prevent and treat HBV and HCV infections.

"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?

Antiviral activity of cuprous oxide nanoparticles against Hepatitis C Virus in vitro

Small molecular inhibitors in combination with or without interferon have improved sustained antiviral responses against Hepatitis C Virus (HCV) infection. Nonetheless, resistance to these inhibitors is expected to emerge rapidly due to the high mutation rate of the virus. Thus, new antiviral drugs, in combination with currently available therapies, are urgently needed to treat HCV infection. In the present study, we evaluated the antiviral efficacy of cuprous oxide nanoparticles (CO-NPs) against HCV in the HCVcc/Huh7.5.1 cell culture system. CO-NPs were able to significantly inhibit the infectivity of HCVcc at a non-cytotoxic concentration. In addition, CO-NPs inhibited the entry of HCV pseudoparticle (HCVpp), including genotypes 1a, 1b, and 2a, while no effect on HCV replication was observed. Further time-of-addition experiment indicated that CO-NPs blocked HCV infection both at the attachment and entry stages. In conclusion, we report that CO-NPs can act as an anti-HCV agent by targeting the binding of infectious HCV particles to hepatic cells and the virus entry into the cells. These findings suggest that CO-NPs may have novel roles in the treatment of patients with chronic hepatitis C.

New Insights into the Understanding of Hepatitis C Virus Entry and Cell-to-Cell Transmission by Using the Ionophore Monensin A

In our study, we characterized the effect of monensin, an ionophore that is known to raise the intracellular pH, on the hepatitis C virus (HCV) life cycle. We showed that monensin inhibits HCV entry in a pangenotypic and dose-dependent manner. Monensin induces an alkalization of intracellular organelles, leading to an inhibition of the fusion step between viral and cellular membranes. Interestingly, we demonstrated that HCV cell-to-cell transmission is dependent on the vesicular pH. Using the selective pressure of monensin, we selected a monensin-resistant virus which has evolved to use a new entry route that is partially pH and clathrin independent. Characterization of this mutant led to the identification of two mutations in envelope proteins, the Y297H mutation in E1 and the I399T mutation in hypervariable region 1 (HVR1) of E2, which confer resistance to monensin and thus allow HCV to use a pH-independent entry route. Interestingly, the I399T mutation introduces an N-glycosylation site within HVR1 and increases the density of virions and their sensitivity to neutralization with anti-apolipoprotein E (anti-ApoE) antibodies, suggesting that this mutation likely induces conformational changes in HVR1 that in turn modulate the association with ApoE. Strikingly, the I399T mutation dramatically reduces HCV cell-to-cell spread. In summary, we identified a mutation in HVR1 that overcomes the vesicular pH dependence, modifies the biophysical properties of particles, and drastically reduces cell-to-cell transmission, indicating that the regulation by HVR1 of particle association with ApoE might control the pH dependence of cell-free and cell-to-cell transmission. Thus, HVR1 and ApoE are critical regulators of HCV propagation.

IMPORTANCE

Although several cell surface proteins have been identified as entry factors for hepatitis C virus (HCV), the precise mechanisms regulating its transmission to hepatic cells are still unclear. In our study, we used monensin A, an ionophore that is known to raise the intracellular pH, and demonstrated that cell-free and cell-to-cell transmission pathways are both pH-dependent processes. We generated monensin-resistant viruses that displayed different entry routes and biophysical properties. Thanks to these mutants, we highlighted the importance of hypervariable region 1 (HVR1) of the E2 envelope protein for the association of particles with apolipoprotein E, which in turn might control the pH dependency of cell-free and cell-to-cell transmission.

Chloroquine-containing compounds: a patent review (2010 - 2014)

INTRODUCTION

Chloroquine (CQ) has been well known for its antimalarial effects since World War II. However, it is gradually being phased out from clinical use against malaria due to emergence of CQ-resistant Plasmodium falciparum strains. Besides low cost and tolerability, ongoing research has revealed interesting biochemical properties of CQ that have inspired its repurposing/repositioning in the management of various infectious/noninfectious diseases. Consequently, several novel compounds and compositions based on its scaffold have been studied and patented.

AREAS COVERED

In this review, patents describing CQ and its derivatives/compositions over the last 5 years are analyzed. The review highlights the rationale, chemical structures, biological evaluation and potential therapeutic application of CQ, its derivatives and compositions.

EXPERT OPINION

Repurposing efforts have dominantly focused on racemic CQ with no studies exploring the effect of the (R) and (S) enantiomers, which might potentially have additional benefits in other diseases. Additionally, evaluating other similarly acting antimalarials in clinical use and structural analogs could help maximize the intrinsic value of the 4-aminoquinolines. With regard to cancer therapy, successful repurposing of CQ-containing compounds will require linking the mode of action of these antimalarials with the signaling pathways that drive cancer cell proliferation to facilitate the development of a 4-amino-7-chloroquinoline that can be used as a synergistic partner in anticancer combination chemotherapy.

Identification of a novel drug lead that inhibits HCV infection and cell-to-cell transmission by targeting the HCV E2 glycoprotein

Hepatitis C Virus (HCV) infects 200 million individuals worldwide. Although several FDA approved drugs targeting the HCV serine protease and polymerase have shown promising results, there is a need for better drugs that are effective in treating a broader range of HCV genotypes and subtypes without being used in combination with interferon and/or ribavirin. Recently, two crystal structures of the core of the HCV E2 protein (E2c) have been determined, providing structural information that can now be used to target the E2 protein and develop drugs that disrupt the early stages of HCV infection by blocking E2’s interaction with different host factors. Using the E2c structure as a template, we have created a structural model of the E2 protein core (residues 421–645) that contains the three amino acid segments that are not present in either structure. Computational docking of a diverse library of 1,715 small molecules to this model led to the identification of a set of 34 ligands predicted to bind near conserved amino acid residues involved in the HCV E2: CD81 interaction. Surface plasmon resonance detection was used to screen the ligand set for binding to recombinant E2 protein, and the best binders were subsequently tested to identify compounds that inhibit the infection of Huh-7 cells by HCV. One compound, 281816, blocked E2 binding to CD81 and inhibited HCV infection in a genotype-independent manner with IC50’s ranging from 2.2 µM to 4.6 µM. 281816 blocked the early and late steps of cell-free HCV entry and also abrogated the cell-to-cell transmission of HCV. Collectively the results obtained with this new structural model of E2c suggest the development of small molecule inhibitors such as 281816 that target E2 and disrupt its interaction with CD81 may provide a new paradigm for HCV treatment.

Benzhydrylpiperazine compounds inhibit cholesterol-dependent cellular entry of hepatitis C virus

Hepatitis C virus (HCV) remains a serious global health problem that lacks an effective cure. Although the introduction of protease inhibitors to the current standard-of-care interferon/ribavirin therapy for HCV infection has improved sustained virological response of genotype 1-infected patients, these inhibitors exacerbate already problematic side effects. Thus, new HCV antivirals are urgently needed. Using a cell-protection screen previously developed in our laboratory, we evaluated 30,426 compounds for inhibitors of potentially any stage of the HCV life cycle and identified 49 new HCV inhibitors. The two most potent hits, hydroxyzine and chlorcyclizine, belong to the family of benzhydrylpiperazines and were found to inhibit the entry of cell culture-produced HCV with IC50 values of 19 and 2.3 nM, respectively, and therapeutic indices of >500 and >6500. Both compounds block HCV entry at a late stage of entry prior to viral fusion and their inhibitory activities are highly dependent on the host's cholesterol content. Both compounds are currently used in the clinic for treating allergy-related disorders and the reported peak plasma level (160 nM) and estimated liver concentration (1.7 μM) of hydroxyzine in humans are much higher than the molecule's anti-HCV IC90 in cell culture (64 nM). Further studies are therefore justified to evaluate the use of these molecules in an anti-HCV therapeutic regimen.

Severity of liver disease affects HCV kinetics in patients treated with intravenous silibinin monotherapy

BACKGROUND

HCV kinetic analysis and modelling during antiviral therapy have not been performed in decompensated cirrhotic patients awaiting liver transplantation. Here, viral and host parameters were compared in three groups of patients treated with daily intravenous silibinin (SIL) monotherapy for 7 days according to the severity of their liver disease.

METHODS

Data were obtained from 25 patients, 12 non-cirrhotic, 8 with compensated cirrhosis and 5 with decompensated cirrhosis. The standard-biphasic model with time-varying SIL effectiveness (from 0 to final effectiveness [εmax]) was fitted to viral kinetic data.

RESULTS

Baseline viral load and age were significantly associated with the severity of liver disease (P<0.0001). A biphasic viral decline was observed in most patients with a higher first phase decline in patients with less severe liver disease. The εmax was significantly (P≤0.032) associated with increasing severity of liver disease (non-cirrhotic εmax [se]=0.86 [0.05], compensated cirrhotic εmax=0.69 [0.06] and decompensated cirrhotic εmax=0.59 [0.1]). The second phase decline slope was not significantly different among groups (mean 1.88 ±0.15 log10 IU/ml/week, P=0.75) as was the rate of change of SIL effectiveness (k=2.12/day [se=0.18/day]). HCV-infected cell loss rate (δ [se]=0.62/day [0.05/day]) was high and similar among groups.

CONCLUSIONS

The high loss rate of HCV-infected cells suggests that sufficient dose and duration of SIL might achieve viral suppression in advanced liver disease.

How hepatitis C virus invades hepatocytes: The mystery of viral entry

Hepatitis C virus (HCV) infection is a global health problem, with an estimated 170 million people being chronically infected. HCV cell entry is a complex multi-step process, involving several cellular factors that trigger virus uptake into the hepatocytes. The high- density lipoprotein receptor scavenger receptor class B type I, tetraspanin CD81, tight junction protein claudin-1, and occludin are the main receptors that mediate the initial step of HCV infection. In addition, the virus uses cell receptor tyrosine kinases as entry regulators, such as epidermal growth factor receptor and ephrin receptor A2. This review summarizes the current understanding about how cell surface molecules are involved in HCV attachment, internalization, and membrane fusion, and how host cell kinases regulate virus entry. The advances of the potential antiviral agents targeting this process are introduced.

Amodiaquine, an antimalarial drug, inhibits dengue virus type 2 replication and infectivity

Dengue virus serotypes 1-4 (DENV1-4) are transmitted by mosquitoes which cause most frequent arboviral infections in the world resulting in ∼390 million cases with ∼25,000 deaths annually. There is no vaccine or antiviral drug currently available for human use. Compounds containing quinoline scaffold were shown to inhibit flavivirus NS2B-NS3 protease (NS2B-NS3pro) with good potencies. In this study, we screened quinoline derivatives, which are known antimalarial drugs for inhibition of DENV2 and West Nile virus (WNV) replication using the corresponding replicon expressing cell-based assays. Amodiaquine (AQ), one of the 4-aminoquinoline drugs, inhibited DENV2 infectivity measured by plaque assays, with EC50 and EC90 values of 1.08±0.09μM and 2.69±0.47 μM, respectively, and DENV2 RNA replication measured by Renilla luciferase reporter assay, with EC50 value of 7.41±1.09μM in the replicon expressing cells. Cytotoxic concentration (CC50) in BHK-21 cells was 52.09±4.25μM. The replication inhibition was confirmed by plaque assay of the extracellular virions as well as by qRT-PCR of the intracellular and extracellular viral RNA levels. AQ was stable for at least 96h and had minor inhibitory effect on entry, translation, and post-replication stages in the viral life cycle. DENV protease, 5'-methyltransferase, and RNA-dependent RNA polymerase do not seem to be targets of AQ. Both p-hydroxyanilino and diethylaminomethyl moieties are important for AQ to inhibit DENV2 replication and infectivity. Our results support AQ as a promising candidate for anti-flaviviral therapy.

Permissivity of primary human hepatocytes and different hepatoma cell lines to cell culture adapted hepatitis C virus

Significant progress has been made in Hepatitis C virus (HCV) culture since the JFH1 strain cloning. However, developing efficient and physiologically relevant culture systems for all viral genotypes remains an important goal. In this work, we aimed at producing a high titer JFH1 derived virus to test different hepatic cells’ permissivity. To this end, we performed successive infections and obtained a JFH1 derived virus reaching high titers. Six potential adaptive mutations were identified (I599V in E2, R1373Q and M1611T in NS3, S2364P and C2441S in NS5A and R2523K in NS5B) and the effect of these mutations on HCV replication and infectious particle production was investigated. This cell culture adapted virus enabled us to efficiently infect primary human hepatocytes, as demonstrated using the RFP-NLS-IPS reporter protein and intracellular HCV RNA quantification. However, the induction of a strong type III interferon response in these cells was responsible for HCV inhibition. The disruption of this innate immune response led to a strong infection enhancement and permitted the detection of viral protein expression by western blotting as well as progeny virus production. This cell culture adapted virus also enabled us to easily compare the permissivity of seven hepatoma cell lines. In particular, we demonstrated that HuH-7, HepG2-CD81, PLC/PRF/5 and Hep3B cells were permissive to HCV entry, replication and secretion even if the efficiency was very low in PLC/PRF/5 and Hep3B cells. In contrast, we did not observe any infection of SNU-182, SNU-398 and SNU-449 hepatoma cells. Using iodixanol density gradients, we also demonstrated that the density profiles of HCV particles produced by PLC/PRF/5 and Hep3B cells were different from that of HuH-7 and HepG2-CD81 derived virions. These results will help the development of a physiologically relevant culture system for HCV patient isolates.

New horizons in hepatitis C antiviral therapy with direct-acting antivirals

Most direct-acting antivirals (DAAs) that are being developed as therapy against hepatitis C virus target the NS3/4A protease, the NS5A protein, and the NS5B polymerase. The latter enzyme offers different target sites: the catalytic domain for nucleos(t)ide analogues as well as a number of allosteric sites for nonnucleos(t)ide inhibitors. Two NS3/4A protease inhibitors have been approved recently, and more than 40 new NS3/4A, NS5A, or NS5B inhibitors are in development. These agents can achieve very high cure rates when combined with pegylated interferon-β and ribavirin and show promising clinical results when administered in all-oral combinations. In addition to the more canonical drug targets, new alternative viral targets for small-molecule drug development are emerging, such as p7 or NS4B and viral entry. Future research will need to define well-tolerated and cost-effective DAA combinations that provide the highest rates of viral eradication in all patients (including those with advanced liver disease), the broadest spectrum of action on viral genotypes showing minimal or no clinical resistance, and the shortest treatment duration.