Hepatitis C - New drugs and treatment prospects

Molecular characterization of the nonstructural 5A (NS5A) region of hepatitis C virus in Thai blood donors

Direct acting antivirals (DAAs) have been developed for hepatitis C virus (HCV) therapy, and they are usually effective, however resistance to DAA regimens has also been reported to have a significant impact. Resistance associated substitutions (RASs) in the NS5A region are known to be correlated with failure of DAA therapy. HCV genotypes 3a and 1 are the most prevalent genotypes in Thailand. This study analyzed the type and frequency of RASs associated with DAA failure, focusing on the NS5A region. Serum samples of HCV genotype 3a, 1a, and 1b infection from Thai blood donors were selected. The NS5A region was amplified using reverse transcription-polymerase chain reaction (RT-PCR). A phylogenetic tree was constructed to identify the genotypes of HCV. Nucleotide sequencing and amino acid sequencing were conducted to determine the prevalence of RASs. Construction of the phylogenetic tree indicated that 29 samples were genotype 3a, 11 samples were genotype 1a, and 9 were genotype 1b. Both HCV genotypes 1a and 3a can be categorized into two subclades. Results showed that the NS5A substitutions A30V/K, A62T/V/I/M/P/S/L, and S98G were present in HCV genotype 3a. In HCV genotype 1a, only NS5A RASs H54Y was detected. NS5A amino acid substitutions Q54H and P58L were found in HCV genotype 1b. In conclusion, NS5A RASs at amino acid positions 30, 62, 54, 58, and 98 are present within HCV genotypes 3a and 1. While keeping in mind that additional information was not available on the anonymous blood donors tested in this study, these findings can contribute to understand the NS5A mutation. Further study with known patients under drug treatment is recommended.

A Novel Trypsin Kunitz-Type Inhibitor from Cajanus cajan Leaves and Its Inhibitory Activity on New Cancer Serine Proteases and Its Effect on Tumor Cell Growth

A novel trypsin inhibitor from Cajanus cajan (TIC) fresh leaves was partially purified by affinity chromatography. SDS-PAGE revealed one band with about 15 kDa with expressive trypsin inhibitor activity by zymography. TIC showed high affinity for trypsin (Ki = 1.617 μM) and was a competitive inhibitor for this serine protease. TIC activity was maintained after 24 h of treatment at 70 °C, after 1 h treatments with different pH values, and β-mercaptoethanol increasing concentrations, and demonstrated expressive structural stability. However, the activity of TIC was affected in the presence of oxidizing agents. In order to study the effect of TIC on secreted serine proteases, as well as on the cell culture growth curve, SK-MEL-28 metastatic human melanoma cell line and CaCo-2 colon adenocarcinoma was grown in supplemented DMEM, and the extracellular fractions were submitted salting out and affinity chromatography to obtain new secreted serine proteases. TIC inhibited almost completely, 96 to 89%, the activity of these serine proteases and reduced the melanoma and colon adenocarcinoma cells growth of 48 and 77% respectively. Besides, it is the first time that a trypsin inhibitor was isolated and characterized from C. cajan leaves and cancer serine proteases were isolated and partial characterized from SK-MEL-28 and CaCo-2 cancer cell lines. Furthermore, TIC shown to be potent inhibitor of tumor protease affecting cell growth, and can be one potential drug candidate to be employed in chemotherapy of melanoma and colon adenocarcinoma.

An Exploration of the Inhibitory Mechanism of Rationally Screened Benzofuran-1,3,4-Oxadiazoles and-1,2,4-Triazoles as Inhibitors of NS5B RdRp Hepatitis C Virus through Pharmacoinformatic Approaches

Benzofuran, 1,3,4-oxadiazole, and 1,2,4-triazole are privileged heterocyclic moieties that display the most promising and wide spectrum of biological activities against a wide variety of diseases. In the current study, benzofuran-1,3,4-oxadiazole BF1-BF7 and benzofuran-1,2,4-triazole compounds BF8-BF15 were tested against HCV NS5B RNA-dependent RNA polymerase (RdRp) utilizing structure-based screening via a computer-aided drug design (CADD) approach. A molecular docking approach was applied to evaluate the binding potential of benzofuran-appended 1,3,4-oxadiazole and 1,2,4-triazole BF1-BF15 molecules. Benzofuran-1,3,4-oxadiazole scaffolds BF1-BF7 showed lesser binding affinities (-12.63 to -14.04 Kcal/mol) than benzofuran-1,2,4-triazole scaffolds BF8-BF15 (-14.11 to -16.09 Kcal/mol) against the HCV NS5B enzyme. Molecular docking studies revealed the excellent binding affinity scores exhibited by benzofuran-1,2,4-triazole structural motifs BF-9 (-16.09 Kcal/mol), BF-12 (-15.75 Kcal/mol), and BF-13 (-15.82 Kcal/mol), respectively, which were comparatively better than benzofuran-based HCV NS5B inhibitors' standard reference drug Nesbuvir (-15.42 Kcal/mol). A molecular dynamics simulation assay was also conducted to obtain valuable insights about the enzyme-compounds interaction profile and structural stability, which indicated the strong intermolecular energies of the BF-9+NS5B complex and the BF-12+NS5B complex as per the MM-PBSA method, while the BF-12+NS5B complex was the most stable system as per the MM-GBSA calculation. The drug-likeness and ADMET studies of all the benzofuran-1,2,4-triazole derivatives BF8-BF15 revealed that these compounds possessed good medicinal chemistry profiles in agreement with all the evaluated parameters for being drugs. The molecular docking affinity scores, MM-PBSA/MM-GBSA and MD-simulation stability analysis, drug-likeness profiling, and ADMET study assessment indicated that N-4-fluorophenyl-S-linked benzofuran-1,2,4-triazole BF-12 could be a future promising anti-HCV NS5B RdRp inhibitor therapeutic drug candidate that has a structural agreement with the Nesbuvir standard reference drug.

Lipid composition modulates interactions of p7 viroporin during membrane insertion

Viral proteins interact with lipid membranes during various stages in the viral life cycle to propagate infection. p7 is an ion channel forming protein of Hepatitis C virus (HCV) that participates in viral assembly. Studies show that it has close ties to lipid metabolism in the cell and anionic phosphatidylserine (PS) lipids are suggested to be key for its permeabilizing function, but the mechanism of its interaction with the lipid environment is largely unknown. To begin unraveling the molecular processes of the protein, we evaluated the impact of lipid environment on the binding and insertion mechanism of p7 prior to channel formation and viral assembly using molecular dynamics simulations. It is seen that p7 is sensitive to its lipid environment and results in different remodeling patterns in membranes. Helix 1 (H1) is especially important for peptide insertion, with deeper entry taking place when the membrane contains phosphatidylserine (PS). Helix 2 (H2) and the adjacent loop connecting to Helix 3 (H3) prompts recruitment of phosphatidylethanolamine (PE) lipids to the protein binding site in membrane models with lower surface charge. This work provides perspectives on the interplay between protein-lipid dynamics and membrane composition, and insights on membrane reorganization in mechanisms of disease.

The rise of degrader drugs

The cancer genomics revolution has served up a plethora of promising and challenging targets for the drug discovery community. The field of targeted protein degradation (TPD) uses small molecules to reprogram the protein homeostasis system to destroy desired target proteins. In the last decade, remarkable progress has enabled the rational development of degraders for a large number of target proteins, with over 20 molecules targeting more than 12 proteins entering clinical development. While TPD has been fully credentialed by the prior development of immunomodulatory drug (IMiD) class for the treatment of multiple myeloma, the field is poised for a "Gleevec moment" in which robust clinical efficacy of a rationally developed novel degrader against a preselected target is firmly established. Here, we endeavor to provide a high-level evaluation of exciting developments in the field and comment on steps that may realize the full potential of this new therapeutic modality.

Identification of Potential Bioactive Compounds from Aspergillus terreus against HCV NS3 Serine Protease

This study was aimed to isolate bioactive compounds from the fermentation products of Aspergillus terreus, which could inhibit NS3 protease of hepatitis C virus (HCV). The bioactive compounds were isolated by reverse-phase silica-gel column chromatography, semi-preparative reversed-phase, and Sephadex LH-20, and then their structures were elucidated through spectroscopic analysis. As a result, two small molecule compounds were isolated. Compound 1 was identified as a new benzaldehyde, (E)-2,4-dihydroxy-6-propenylbenzaldehyde. Compound 2 was identified as pleurone, which was obtained from microorganisms for the first time. Their inhibitory activities against HCV NS3 protease (IC50 ) were 32.6 μM and 78.9 μM, respectively. This study provided a new option for the development of anti-HCV drugs.

Macrocyclization of linear molecules by deep learning to facilitate macrocyclic drug candidates discovery

Interest in macrocycles as potential therapeutic agents has increased rapidly. Macrocyclization of bioactive acyclic molecules provides a potential avenue to yield novel chemical scaffolds, which can contribute to the improvement of the biological activity and physicochemical properties of these molecules. In this study, we propose a computational macrocyclization method based on Transformer architecture (which we name Macformer). Leveraging deep learning, Macformer explores the vast chemical space of macrocyclic analogues of a given acyclic molecule by adding diverse linkers compatible with the acyclic molecule. Macformer can efficiently learn the implicit relationships between acyclic and macrocyclic structures represented as SMILES strings and generate plenty of macrocycles with chemical diversity and structural novelty. In data augmentation scenarios using both internal ChEMBL and external ZINC test datasets, Macformer display excellent performance and generalisability. We showcase the utility of Macformer when combined with molecular docking simulations and wet lab based experimental validation, by applying it to the prospective design of macrocyclic JAK2 inhibitors.

Targeting Metalloenzymes: The "Achilles' Heel" of Viruses and Parasites

Metalloenzymes are central to the regulation of a wide range of essential viral and parasitic functions, including protein degradation, nucleic acid modification, and many others. Given the impact of infectious diseases on human health, inhibiting metalloenzymes offers an attractive approach to disease therapy. Metal-chelating agents have been expansively studied as antivirals and antiparasitics, resulting in important classes of metal-dependent enzyme inhibitors. This review provides the recent advances in targeting the metalloenzymes of viruses and parasites that impose a significant burden on global public health, including influenza A and B, hepatitis B and C, and human immunodeficiency viruses as well as Trypanosoma brucei and Trypanosoma cruzi.

Discovery of Terpenes as Novel HCV NS5B Polymerase Inhibitors via Molecular Docking

Hepatitis C virus (HCV) is a dangerous virus that is responsible for a large number of infections and deaths worldwide. In the treatment of HCV, it is important that the drugs are effective and do not have additional hepatotoxic effects. The aim of this study was to test the in silico activity of 1893 terpenes against the HCV NS5B polymerase (PDB-ID: 3FQK). Two drugs, sofosbuvir and dasabuvir, were used as controls. The GOLD software (CCDC) and InstaDock were used for docking. By using the results obtained from PLP.Fitness (GOLD), pKi, and binding free energy (InstaDock), nine terpenes were finally selected based on their scores. The drug-likeness properties were calculated using Lipinski's rule of five. The ADMET values were studied using SwissADME and pkCSM servers. Ultimately, it was shown that nine terpenes have better docking results than sofosbuvir and dasabuvir. These were gniditrin, mulberrofuran G, cochlearine A, ingenol dibenzoate, mulberrofuran G, isogemichalcone C, pawhuskin B, 3-cinnamyl-4-oxoretinoic acid, DTXSID501019279, and mezerein. Each docked complex was submitted to 150 ns-long molecular dynamics simulations to ascertain the binding stability. The results show that mulberrofuran G, cochlearine A, and both stereoisomers of pawhuskin B form very stable interactions with the active site region where the reaction product should form and are, therefore, good candidates for use as effective competitive inhibitors. The other compounds identified in the docking screen either afford extremely weak (or even hardly any) binding (such as ingenol dibenzoate, gniditrin, and mezerein) or must first undergo preliminary movements in the active site before attaining their stable binding conformations, in a process which may take from 60 to 80 ns (for DTXSID501019279, 3-cinnamyl-4-oxoretinoic acid or isogemichalcone C).

Protein-driven membrane remodeling: Molecular perspectives from Flaviviridae infections

The mammalian cell membrane consists of thousands of different lipid species, and this variety is critical for biological function. Alterations to this balance can be dangerous as they can lead to permanent disruption of lipid metabolism, a hallmark in several viral diseases. The Flaviviridae family is made up of positive single-stranded RNA viruses that assemble at or near the location of lipid droplet formation in the endoplasmic reticulum. These viruses are known to interfere with lipid metabolism during the onset of liver disease, albeit to different extents. Pathogenesis of these infections involves specific protein-lipid interactions that alter lipid sorting and metabolism to sustain propagation of the viral infection. Recent experimental studies identify a correlation between viral proteins and lipid content or location in the cell, but these do not assess membrane-embedded interactions. Molecular modeling, specifically molecular dynamics simulations, can provide molecular-level spatial and temporal resolution for characterization of biomolecular interactions. This review focuses on recent advancements and current knowledge gaps in the molecular mechanisms of lipid-mediated liver disease preceded by viral infection. We discuss three viruses from the Flaviviridae family: dengue, zika, and hepatitis C, with a particular focus on lipid interactions with their respective ion channels, known as viroporins.

A Novel Approach to Develop New and Potent Inhibitors for the Simultaneous Inhibition of Protease and Helicase Activities of HCV NS3/4A Protease: A Computational Approach

Infection of hepatitis C (HCV) is a major threat to human health throughout the world. The current therapy program suffers from restricted efficiency and low tolerance, and there is serious demand frr novel medication. NS3/4A protease is observed to be very effective target for the treatment of HCV. A data set of the already reported HCV NS3/4A protease inhibitors was first docked into the NS3/4A protease (PDB ID: 4A92A) active sites of both protease and helicase sites for calculating the docking score, binding affinity, binding mode, and solvation energy. Then the data set of these reported inhibitors was used in a computer-based program "RECAP Analyses" implemented in MOE to fragment every molecule in the subset according to simple retrosynthetic analysis rules. The RECAP analysis fragments were then used in another computer-based program "RECAP Synthesis" to randomly recombine and generate synthetically reasonable novel chemical structures. The novel chemical structures thus produced were then docked against HCV NS3/4A. After a thorough validation of all undertaken steps, based on Lipinski's rule of five, docking score, binding affinity, solvation energy, and Van der Waal's interactions with HCV NS3/4A, 12 novel chemical structures were identified as inhibitors of HCV NS3/4A. The novel structures thus designed are hoped to play a key role in the development of new effective inhibitors of HCV.

Assessment of alteration in antiviral plasma concentration across dialysis days: computational and analytical study

Aim: Protein-bound uremic toxins (PBUTs) may displace drugs from the plasma proteins and render them more liable to clearance. This study aims to investigate the possible interplay between PBUTs and directly acting antivirals (DAAs). Methods: PBUT plasma protein binding was compared to those of paritaprevir (PRT), ombitasivir (OMB) and ritonavir (RTV) in silico to assess the possible competitive displacement. The three drugs were LC-MS/MS determined in seven patients across dialysis and non-dialysis days and results were compared. Results & conclusion: Results showed that the PBUT exhibited a lower binding than DAA reducing the liability of their competitive displacement. This was echoed by an unaltered plasma concentration across dialysis days. Results may indicate that PBUT accumulation may have limited effect on disposition of DAA.

Comparative Effectiveness of Direct-Acting Antivirals for Posttraumatic Stress Disorder in Veterans Affairs Patients With Hepatitis C Virus Infection

We recently conducted an exploratory study that indicated that several direct-acting antivirals (DAAs), highly effective medications for hepatitis C virus (HCV) infection, were also associated with improvement in posttraumatic stress disorder (PTSD) among a national cohort of US Department of Veterans Affairs (VA) patients treated between October 1, 1999, and September 30, 2019. Limiting the same cohort to patients with PTSD and HCV, we compared the associations of individual DAAs with PTSD symptom improvement using propensity score weighting. After identifying patients who had available baseline and endpoint PTSD symptom data as measured with the PTSD Checklist (PCL), we compared changes over the 8-12 weeks of DAA treatment. The DAAs most prescribed in conjunction with PCL measurement were glecaprevir/pibrentasvir (GLE/PIB; n = 54), sofosbuvir/velpatasvir (SOF/VEL; n = 54), and ledipasvir/sofosbuvir (LDV/SOF; n = 145). GLE/PIB was superior to LDV/SOF, with a mean difference in improvement of 7.3 points on the PCL (95% confidence interval (CI): 1.1, 13.6). The mean differences in improvement on the PCL were smaller between GLE/PIB and SOF/VEL (3.0, 95% CI: -6.3, 12.2) and between SOF/VEL and LDV/SOF (4.4, 95% CI: -2.4, 11.2). While almost all patients were cured of HCV (92.5%) regardless of the agent received, PTSD outcomes were superior for those receiving GLE/PIB compared with those receiving LDV/SOF, indicating that GLE/PIB may merit further investigation as a potential PTSD treatment.

Mining Clinical Data for Novel Posttraumatic Stress Disorder Medications

BACKGROUND

Despite the prevalence and negative impact of posttraumatic stress disorder (PTSD), there are few medications approved by the U.S. Food and Drug Administration for treatment, and approved medications do not work well enough. We leveraged large-scale electronic health record data to identify existing medications that may be repurposed as PTSD treatments.

METHODS

We constructed a mechanistic tree of all Food and Drug Administration-approved medications and used the tree-based scan statistic to identify medications associated with greater than expected levels of clinically meaningful improvement in PTSD symptoms using electronic health record data from the U.S. Department of Veterans Affairs. Our cohort included patients with a diagnosis of PTSD who had repeated symptom measurements using the PTSD Checklist over a 20-year period (N = 168,941). We calculated observed numbers based on patients taking each drug or mechanistically related class of drugs and the expected numbers based on the tree as a whole.

RESULTS

Medications typically used to treat PTSD, such as the Food and Drug Administration-approved agent sertraline, were associated with improvement in PTSD symptoms, but the effects were small. Several, but not all, direct-acting antivirals used in the treatment of hepatitis C virus demonstrated a strong association with PTSD improvement. The finding was robust to a sensitivity analysis excluding patients who received established PTSD treatments, including trauma-focused psychotherapy, concurrent with hepatitis treatment.

CONCLUSIONS

Our exploratory approach both demonstrated findings that are consistent with what is known about pharmacotherapy for PTSD and uncovered a novel class of medications that may improve PTSD symptoms.

Viral hepatitis: Innovations and expectations

Viral hepatitis is a significant health problem worldwide, associated with morbidity and mortality. Hepatitis B, C, D, and occasionally E viruses (HBV, HCV, HDV, and HEV) can evolve in chronic infections, whereas hepatitis A virus (HAV) frequently produces acute self-limiting hepatitis. In the last years, different studies have been performed to introduce new antiviral therapies. The most important goal in the treatment of viral hepatitis is to avoid chronic liver disease and complications. This review analyzes currently available therapies, in particular for viruses associated with chronic liver disease. The focus is especially on HBV and HCV therapies, investigating new drugs already introduced in clinical practice and clinical trials. We also describe new entry inhibitors, developed for the treatment of chronic HDV and HBV and currently available treatments for HEV. The last drugs introduced have shown important efficacy in HCV, with achievable target HCV elimination by 2030. Concurrently, renewed interest in curative HBV therapies has been registered; current nucleotide/ nucleoside analogs positively impact liver-related complications, ensuring high safety and tolerability. Novel approaches to HBV cure are based on new antivirals, targeting different steps of the HBV life cycle and immune modulators. The improved knowledge of the HDV life cycle has facilitated the development of some direct-acting agents, as bulevirtide, the first drug conditionally approved in Europe for HDV associated compensated liver disease. Further studies are required to identify a new therapeutic approach in hepatitis E, especially in immunosuppressed patients.

Risk of hepatocellular carcinoma after hepatitis C virus cure

Hepatitis C virus (HCV) is a significant cause of hepatocellular carcinoma (HCC). The direct-acting antivirals marked a new era of HCV therapy and are associated with greater than 95% cure rate. Successful treatment of chronic hepatitis C greatly reduces the risk of HCC. A proportion of patients, especially those with pre-existing cirrhosis, remain at risk for HCC despite sustained virologic response (SVR). Diabetes mellitus, hepatic steatosis, alcohol consumption and lack of fibrosis regression are associated with risks of HCC after HCV cure. Noninvasive modalities such as aspartate aminotransferase to platelet ratio index and fibrosis-4 index and transient elastography have been used to monitor hepatic fibrosis. More recently, various fibrosis scores have been combined with clinical parameters and other novel biomarkers to predict risks of HCC for patients who achieved SVR. These models still need to be validated and standardized prior to applying to routine clinical care.

Pharmacological perspectives and molecular mechanisms of coumarin derivatives against virus disease

Infections caused by viruses are one of the foremost causes of morbidity and mortality in the world. Although a number of antiviral drugs are currently used for treatment of various kinds of viral infection diseases, there is still no available therapeutic agent for most of the viruses in clinical practice. Coumarin is a chemical compound which is found naturally in a variety of plants, it can also be synthetically produced possessing diverse biological effects. More recently, reports have highlighted the potential role of coumarin derivatives as antiviral agents. This review outlines the advances in coumarin-based compounds against various viruses including human immunodeficiency virus, hepatitis virus, herpes simplex virus, Chikungunya virus and Enterovirus 71, as well as the structure activity relationship and the possible mechanism of action of the most potent coumarin derivatives.

Computational insight to design new potential hepatitis C virus NS5B polymerase inhibitors with drug-likeness and pharmacokinetic ADMET parameters predictions

Background

Hepatitis C virus (HCV) is considered a worldwide health problem since it affects over 3% of the population and causes 300,000 fatalities per year. Chronic infection causes high morbidity and mortality in patients, leading to liver cirrhosis, hepatocellular carcinoma, fibrosis, liver cancer, and other HCV-related illnesses. Finding novel and better HCV treatments is a top international health goal right now. As a result, the pressing need for new HCV antiviral drugs has fueled research into the structural requirements of NS5B polymerase inhibitors at a molecular basis.

Results

In this study, an in silico technique was applied to study 79 compounds with HCV inhibitory bioactivity, with the best statistical results ($$R^{2}$$ R 2 = 0.7051, $$Q^{2}$$ Q 2 = 0.6455, $$R_{{{\text{pred}}}}^{2}$$ R pred 2 = 0.6992, $$^{{\text{c}}} R_{{\text{r}}}^{2}$$ c R r 2 = 0.6570, SEE = 0.2694).

Conclusions

This QSAR investigation allowed the research team to evaluate the influence of straightforward descriptors, shedding insight into the critical elements that guide the design of innovative effective molecules. Most of the innovative effective molecules exhibited better binding affinity (− 195.6 kcal/mol) than dasabuvir the reference drug (− 171.0 kcal/mol) with the target receptor (hepatitis C virus NS5B RNA polymerase). ADMET prediction disclosed enhanced pharmacokinetic properties with lower MRTD (maximum tolerated dose) of some new derivatives.

Antiprotozoal agents: How have they changed over a decade?

Neglected tropical diseases are a diverse group of communicable diseases that are endemic in low- or low-to-middle-income countries located in tropical and subtropical zones. The number and availability of drugs for treating these diseases are low, the administration route is inconvenient in some cases, and most of them have safety, efficacy, or adverse/toxic reaction issues. The need for developing new drugs to deal with these issues is clear, but one of the most drastic consequences of this negligence is the lack of interest in the research and development of new therapeutic options among major pharmaceutical companies. Positive changes have been achieved over the last few years, although the overall situation remains alarming. After more than one decade since the original work reviewing antiprotozoal agents came to light, now it is time to question ourselves: How has the scenario for the treatment of protozoal diseases such as malaria, leishmaniasis, human African trypanosomiasis, and American trypanosomiasis changed? This review covers the last decade in terms of the drugs currently available for the treatment of these diseases as well as the clinical candidates being currently investigated.

Precursors of Viral Proteases as Distinct Drug Targets

Viral proteases are indispensable for successful virion maturation, thus making them a prominent drug target. Their enzyme activity is tightly spatiotemporally regulated by expression in the precursor form with little or no activity, followed by activation via autoprocessing. These cleavage events are frequently triggered upon transportation to a specific compartment inside the host cell. Typically, precursor oligomerization or the presence of a co-factor is needed for activation. A detailed understanding of these mechanisms will allow ligands with non-canonical mechanisms of action to be designed, which would specifically modulate the initial irreversible steps of viral protease autoactivation. Binding sites exclusive to the precursor, including binding sites beyond the protease domain, can be exploited. Both inhibition and up-regulation of the proteolytic activity of viral proteases can be detrimental for the virus. All these possibilities are discussed using examples of medically relevant viruses including herpesviruses, adenoviruses, retroviruses, picornaviruses, caliciviruses, togaviruses, flaviviruses, and coronaviruses.

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.

Role of Virus-Related Chronic Inflammation and Mechanisms of Cancer Immune-Suppression in Pathogenesis and Progression of Hepatocellular Carcinoma

Simple Summary

Hepatocellular carcinoma pathogenesis is dependent on a chronic inflammation caused by several factors, including hepatotropic viruses, such as HCV and HBV. This chronic inflammation is established in the context of the immunotolerogenic environment peculiar of the liver, in which the immune system can be stimulated by HCV and HBV viral antigens. This complex interaction can be influenced by direct-acting antiviral drug treatments, capable of (almost totally) rapidly eradicating HCV infection. The influence of anti-viral treatments on HCC pathogenesis and progression remains to be fully clarified.

Abstract

Hepatocellular carcinoma (HCC) can be classified as a prototypical inflammation-driven cancer that generally arises from a background of liver cirrhosis, but that in the presence of nonalcoholic steatohepatitis (NASH), could develop in the absence of fibrosis or cirrhosis. Tumor-promoting inflammation characterizes HCC pathogenesis, with an epidemiology of the chronic liver disease frequently encompassing hepatitis virus B (HBV) or C (HCV). HCC tumor onset and progression is a serial and heterogeneous process in which intrinsic factors, such as genetic mutations and chromosomal instability, are closely associated with an immunosuppressive tumor microenvironment (TME), which may have features associated with the etiopathogenesis and expression of the viral antigens, which favor the evasion of tumor neoantigens to immune surveillance. With the introduction of direct-acting antiviral (DAA) therapies for HCV infection, sustained virological response (SVR) has become very high, although occurrence of HCC and reactivation of HBV in patients with co-infection, who achieved SVR in short term, have been observed in a significant proportion of treated cases. In this review, we discuss the main molecular and TME features that are responsible for HCC pathogenesis and progression. Peculiar functional aspects that could be related to the presence and treatment of HCV/HBV viral infections are also dealt with.

Thiophen urea derivatives as a new class of hepatitis C virus entry inhibitors

To develop unique small-molecule inhibitors of hepatitis C virus (HCV), thiophen urea (TU) derivatives were synthesised and screened for HCV entry inhibitory activities. Among them, seven TU compounds exhibited portent anti-viral activities against genotypes 1/2 (EC₅₀ < 30 nM) and subsequently, they were further investigated; based on the pharmacological, metabolic, pharmacokinetic, and safety profiles, J2H-1701 was selected as the optimised lead compound as an HCV entry inhibitor. J2H-1701 possesses effective multi-genotypic antiviral activity. The docking results suggested the potential interaction of J2H-1701 with the HCV E2 glycoprotein. These results suggest that J2H-1701 can be a potential candidate drug for the development of HCV entry inhibitors.

Serinol-Based Benzoic Acid Esters as New Scaffolds for the Development of Adenovirus Infection Inhibitors: Design, Synthesis, and In Vitro Biological Evaluation

Over the years, human adenovirus (HAdV) has progressively been recognized as a significant viral pathogen. Traditionally associated with self-limited respiratory, gastrointestinal, and conjunctival infections, mainly in immunocompromised patients, HAdV is currently considered to be a pathogen presenting significant morbidity and mortality in both immunosuppressed and otherwise healthy individuals. Currently available therapeutic options are limited because of their lack of effectivity and related side effects. In this context, there is an urgent need to develop effective anti-HAdV drugs with suitable therapeutic indexes. In this work, we identified new serinol-derived benzoic acid esters as novel scaffolds for the inhibition of HAdV infections. A set of 38 compounds were designed and synthesized, and their antiviral activity and cytotoxicity were evaluated. Four compounds (13, 14, 27, and 32) inhibited HAdV infection at low micromolar concentrations (2.82-5.35 μM). Their half maximal inhibitory concentration (IC₅₀) values were lower compared to that of cidofovir, the current drug of choice. All compounds significantly reduced the HAdV DNA replication process, while they did not block any step of the viral entry. Our results showed that compounds 13, 14, and 32 seem to be targeting the expression of the E1A early gene. Moreover, all four derivatives demonstrated a significant inhibition of human cytomegalovirus (HCMV) DNA replication. This new scaffold may represent a potential tool useful for the development of effective anti-HAdV drugs.

Hepatitis C Virus Glycan-Dependent Interactions and the Potential for Novel Preventative Strategies

Chronic hepatitis C virus (HCV) infections continue to be a major contributor to liver disease worldwide. HCV treatment has become highly effective, yet there are still no vaccines or prophylactic strategies available to prevent infection and allow effective management of the global HCV burden. Glycan-dependent interactions are crucial to many aspects of the highly complex HCV entry process, and also modulate immune evasion. This review provides an overview of the roles of viral and cellular glycans in HCV infection and highlights glycan-focused advances in the development of entry inhibitors and vaccines to effectively prevent HCV infection.

Fludarabine Inhibits Infection of Zika Virus, SFTS Phlebovirus, and Enterovirus A71

Viral infections are one of the leading causes in human mortality and disease. Broad-spectrum antiviral drugs are a powerful weapon against new and re-emerging viruses. However, viral resistance to existing broad-spectrum antivirals remains a challenge, which demands development of new broad-spectrum therapeutics. In this report, we showed that fludarabine, a fluorinated purine analogue, effectively inhibited infection of RNA viruses, including Zika virus, Severe fever with thrombocytopenia syndrome virus, and Enterovirus A71, with all IC₅₀ values below 1 μM in Vero, BHK21, U251 MG, and HMC3 cells. We observed that fludarabine has shown cytotoxicity to these cells only at high doses indicating it could be safe for future clinical use if approved. In conclusion, this study suggests that fludarabine could be developed as a potential broad-spectrum anti-RNA virus therapeutic agent.

Hepatitis C Viral Replication Complex

The life cycle of the hepatitis C virus (HCV) can be divided into several stages, including viral entry, protein translation, RNA replication, viral assembly, and release. HCV genomic RNA replication occurs in the replication organelles (RO) and is tightly linked to ER membrane alterations containing replication complexes (proteins NS3 to NS5B). The amplification of HCV genomic RNA could be regulated by the RO biogenesis, the viral RNA structure (i.e., cis-acting replication elements), and both viral and cellular proteins. Studies on HCV replication have led to the development of direct-acting antivirals (DAAs) targeting the replication complex. This review article summarizes the viral and cellular factors involved in regulating HCV genomic RNA replication and the DAAs that inhibit HCV replication.

Virological Factors Associated with Failure to the Latest Generation of Direct Acting Agents (DAA) and Re-Treatment Strategy: A Narrative Review

The availability of all oral direct acting antiviral agents (DAAs) has revolutionized the management of HCV infections in recent years, allowing to achieve a sustained virological response (SVR) in more than 95% of cases, irrespective of hepatitis C Virus (HCV) genotype or staging of liver disease. Although rare, the failure to the latest-generation regimens (grazoprevir/elbasvir, sofosbuvir/velpatasvir, pibrentasvir/glecaprevir) represents a serious clinical problem, since the data available in the literature on the virological characteristics and management of these patients are few. The aim of the present narrative review was to provide an overview of the impact of baseline RASs in patients treated with the latest-generation DAAs and to analyze the efficacy of the available retreatment strategies in those who have failed these regimens.

Antiviral Bioactive Compounds of Mushrooms and Their Antiviral Mechanisms: A Review

Mushrooms are used in their natural form as a food supplement and food additive. In addition, several bioactive compounds beneficial for human health have been derived from mushrooms. Among them, polysaccharides, carbohydrate-binding protein, peptides, proteins, enzymes, polyphenols, triterpenes, triterpenoids, and several other compounds exert antiviral activity against DNA and RNA viruses. Their antiviral targets were mostly virus entry, viral genome replication, viral proteins, and cellular proteins and influenced immune modulation, which was evaluated through pre-, simultaneous-, co-, and post-treatment in vitro and in vivo studies. In particular, they treated and relieved the viral diseases caused by herpes simplex virus, influenza virus, and human immunodeficiency virus (HIV). Some mushroom compounds that act against HIV, influenza A virus, and hepatitis C virus showed antiviral effects comparable to those of antiviral drugs. Therefore, bioactive compounds from mushrooms could be candidates for treating viral infections.

Medicinal chemistry strategies for discovering antivirals effective against drug-resistant viruses

During the last forty years we have witnessed impressive advances in the field of antiviral drug discovery culminating with the introduction of therapies able to stop human immunodeficiency virus (HIV) replication, or cure hepatitis C virus infections in people suffering from liver disease. However, there are important viral diseases without effective treatments, and the emergence of drug resistance threatens the efficacy of successful therapies used today. In this review, we discuss strategies to discover antiviral compounds specifically designed to combat drug resistance. Currently, efforts in this field are focused on targeted proteins (e.g. multi-target drug design strategies), but also on drug conformation (either improving drug positioning in the binding pocket or introducing conformational constraints), in the introduction or exploitation of new binding sites, or in strengthening interaction forces through the introduction of multiple hydrogen bonds, covalent binding, halogen bonds, additional van der Waals forces or multivalent binding. Among the new developments, proteolysis targeting chimeras (PROTACs) have emerged as a valid approach taking advantage of intracellular mechanisms involving protein degradation by the ubiquitin-proteasome system. Finally, several molecules targeting host factors (e.g. human dihydroorotate dehydrogenase and DEAD-box polypeptide 3) have been identified as broad-spectrum antiviral compounds. Implementation of herein described medicinal chemistry strategies are expected to contribute to the discovery of new drugs effective against current and future threats due to emerging and re-emerging viral pandemics.

Changes of Gut-Microbiota-Liver Axis in Hepatitis C Virus Infection

Simple Summary

Gut microbiota alteration is linked to many health disorders including hepatitis C virus (HCV) infection. This dysbiosis in turn impacts the coordination between the gut and the liver that is known as the gut–liver-axis. Here, we discuss the latest findings regarding the changes in gut microbiota structure and functionality post HCV infection and its treatment regimens. In addition, we underline the contribution of the microbiota alterations to HCV associated liver complications.

Abstract

The gut–liver-axis is a bidirectional coordination between the gut, including microbial residents, the gut microbiota, from one side and the liver on the other side. Any disturbance in this crosstalk may lead to a disease status that impacts the functionality of both the gut and the liver. A major cause of liver disorders is hepatitis C virus (HCV) infection that has been illustrated to be associated with gut microbiota dysbiosis at different stages of the disease progression. This dysbiosis may start a cycle of inflammation and metabolic disturbance that impacts the gut and liver health and contributes to the disease progression. This review discusses the latest literature addressing this interplay between the gut microbiota and the liver in HCV infection from both directions. Additionally, we highlight the contribution of gut microbiota to the metabolism of antivirals used in HCV treatment regimens and the impact of these medications on the microbiota composition. This review sheds light on the potential of the gut microbiota manipulation as an alternative therapeutic approach to control the liver complications post HCV infection.

Exploring of paritaprevir and glecaprevir resistance due to A156T mutation of HCV NS3/4A protease: molecular dynamics simulation study

Hepatitis C virus (HCV) NS3/4A serine protease is a promising drug target for the discovery of anti-HCV drugs. However, its amino acid mutations, particularly A156T, commonly lead to rapid emergence of drug resistance. Paritaprevir and glecaprevir, the newly FDA-approved HCV drugs, exhibit distinct resistance profiles against the A156T mutation of HCV NS3/4A serine protease. To illustrate their different molecular resistance mechanisms, molecular dynamics simulations and binding free energy calculations were carried out on the two compounds complexed with both wild-type (WT) and A156T variants of HCV NS3/4A protease. QM/MM-GBSA-based binding free energy calculations revealed that the binding affinities of paritaprevir and glecaprevir towards A156T NS3/4A were significantly reduced by ∼4 kcal/mol with respect to their WT complexes, which were in line with the experimental resistance folds. Moreover, the relatively weak intermolecular interactions with amino acids such as H57, R155, and T156 of NS3 protein, the steric effect and the destabilized protein binding surface, which is caused by the loss of salt bridge between R123 and D168, are the main contributions for the higher fold-loss in potency of glecaprevir due to A156T mutation. An insight into the difference of molecular mechanism of drug resistance against the A156T substitution among the two classes of serine protease inhibitors could be useful for further optimization of new generation HCV NS3/4A inhibitors with enhanced inhibitory potency.Communicated by Ramaswamy H. Sarma.

In silico design and analysis of NS4B inhibitors against hepatitis C virus

The hepatitis C virus is a communicable disease that gradually harms the liver leading to cirrhosis and hepatocellular carcinoma. Important therapeutic interventions have been reached since the discovery of the disease. However, its resurgence urges the need for new approaches against this malady. The NS4B receptor is one of the important proteins for Hepatitis C Virus RNA replication that acts by mediating different viral properties. In this work, we opt to explore the relationships between the molecular structures of biologically tested NS4B inhibitors and their corresponding inhibitory activities to assist the design of novel and potent NS4B inhibitors. For that, a set of 115 indol-2-ylpyridine-3-sulfonamides (IPSA) compounds with inhibitory activity against NS4B is used. A hybrid genetic algorithm combined with multiple linear regressions (GA-MLR) was implemented to construct a predictive model. This model was further used and applied to a set of compounds that were generated based on a pharmacophore modeling study combined with virtual screening to identify structurally similar lead compounds. Multiple filtrations were implemented for selecting potent hits. The selected hits exhibited advantageous molecular features, allowing for favorable inhibitory activity against HCV. The results showed that 7 out of 1285 screened compounds, were selected as potent candidate hits where Zinc14822482 exhibits the best predicted potency and pharmacophore features. The predictive pharmacokinetic analysis further justified the compounds as potential hit molecules, prompting their recommendation for a confirmatory biological evaluation. We believe that our strategy could help in the design and screening of potential inhibitors in drug discovery.Communicated by Ramaswamy H. Sarma.

Structurally distinct cyclosporin and sanglifehrin analogs CRV431 and NV556 suppress established HCV infection in humanized-liver mice

We previously reported that the non-immunosuppressive cyclophilin inhibitors (CypIs)—cyclosporin A analog CRV431 and sanglifehrin analog NV556—efficiently inhibit HCV replication in vitro. In this study, we asked whether they can also reduce HCV replication in vivo. We found that a single oral administration of CRV431 and NV556 to HCV-infected humanized-liver mice drastically reduced HCV blood levels. The antiviral effect was observed when CRV431 or NV556 were each individually administered with HCV, 3, 6 weeks or even 3 months post-infection when viral replication is robust. These results were confirmed in chimeric mice implanted with human hepatocytes isolated from three distinct donors. Remarkably, no viral rebound was observed 5 months after a single dose administration of 50 mg/kg of CRV431 or NV556 four weeks post-HCV infection, indicating the possibility of suppression of an established viral infection. Since we recently demonstrated that both CRV431 and NV556 also inhibit the development of liver fibrosis and hepatocellular carcinoma in nonviral-induced non-alcoholic steatohepatitis mouse models, our present data suggest that the two entirely structurally different CypIs—CRV431 and NV556—derived from unrelated natural products, represent attractive partners to current direct-acting agent (DAA) regimens for the treatment of hepatitis C and liver diseases.

Exploring Sodium Glucose Co-Transporter-2 (SGLT2) Inhibitors for Organ Protection in COVID-19

Hospital admissions and mortality from the Coronavirus disease 2019 (COVID-19) pandemic are spreading throughout the world, and second and third waves are thought to be likely. Risk factors for severe COVID-19 include diabetes, chronic kidney disease and cardiovascular disease. Currently, there is no vaccine and no approved therapy. Therapeutic approaches are aimed at preventing viral replication and spread, limiting the impact of the inflammatory overdrive (cytokine storm), preventing thromboembolic complications and replacing or supporting organ function. However, despite organ support, mortality is currently 65% for those receiving advanced respiratory support and 78% for those requiring renal replacement therapies. Thus, efforts should be made to provide adjuvant organ protection therapy. This may imply novel therapies in clinical development (e.g., the Fas ligand trap asunercept), but uptake of repurposed drugs already in clinical use may be faster. In this regard, sodium glucose co-transporter-2 (SGLT2) inhibitors were recently shown to protect the heart and kidney both within and outside of a diabetic milieu context. Further, preclinical data support a beneficial effect for the lung. We now discuss the potential benefits and risks of SGLT2 inhibitors in COVID-19 and an ongoing clinical trial testing the impact of dapagliflozin on outcomes in COVID-19 patients with respiratory failure.

Cannabidiol for Viral Diseases: Hype or Hope?

Background: The possibility of cannabidiol (CBD) to be used as an antiviral or to treat viral diseases has received limited attention so far, despite the growing number of claims that CBD could be used for the treatment of viral infection-related conditions. Aim and Methods: Therefore, we systematically retrieved and critically evaluated the scientific literature available on PubMed and the claims on the Internet, to assess the current state of knowledge on the use of CBD in viral diseases, and to provide suggestions for future research directions. Results: PubMed search referenced two original articles supporting the use of CBD for the treatment of hepatitis C and Kaposi sarcoma and one article reporting the ability of CBD to reduce neuroinflammation in a virus-induced animal model of multiple sclerosis. Internet search found 25 websites claiming more indications for CBD. Remarkably, those claims were provided mostly by commercial websites and were not supported by appropriate scientific references. Conclusion: Although preclinical studies suggest the potential effectiveness of CBD in viral diseases such as hepatitis C and Kaposi sarcoma, clinical evidence is still lacking. Anecdotal experiences of CBD use retrieved on the Internet, on the other side, lack any support from sound scientific evidence, although they might in some cases provide suggestions for conditions associated with viral infections that may deserve proper assessment in well-designed clinical trials.

The Prevalence and Impact of Hepatic Steatosis on Response to Direct-Acting Antiviral Therapy in HIV-HCV Coinfection

(1) Background: Direct-acting antiviral therapy for chronic hepatitis C virus (HCV) infection is associated with high sustained virologic response (SVR) and overcomes negative predictive factors, including steatosis, in patients without human immunodeficiency virus (HIV) coinfection. The impact of steatosis on SVR in patients with HIV–HCV coinfection is unknown. (2) Methods: A retrospective analysis of patients treated with direct-acting antivirals was performed. Demographic, laboratory and direct-acting antiviral regimen data were prospectively collected. Metabolic syndrome and its components—diabetes mellitus, hypertension, dyslipidemia and obesity—were assessed. Hepatic steatosis (≥5%) was defined by liver biopsy or controlled attenuation parameter (CAP) measurement during vibration-controlled transient elastography (VCTE). (3) Results: A total of 151 HIV–HCV-coinfected patients on combined antiretroviral therapy and direct-acting antiviral therapy were included in this analysis. Prevalence of steatosis by liver biopsy (n = 34) or CAP (≥263 db/m) during VCTE (n = 92) was 27% and was independently associated with obesity (OR 3.11; 95% CI 1.43–6.82; p = 0.004) and the metabolic syndrome (OR 1.08; 95% CI 1.01–0.15; p = 0.01). The overall SVR rate (n = 148) was 95% and was not impacted by the presence of steatosis (p = 0.42). (4) Conclusions: Hepatic steatosis is common in HIV–HCV coinfection, correlates with obesity and the metabolic syndrome and does not impact SVR.

A New Look at an Old Drug: Cumulative Effects of Low Ribavirin Doses in Amphetamine-Sensitized Rats

Background

Psychotic states related to psychostimulant misuse in patients with hepatitis C virus infection may complicate acceptance and reaction to antiviral treatment. This observation equally applies to the widely used ribavirin therapy.

Objective

We examined psychomotor and body weight gain responses to low ribavirin doses after cessation of intermittent amphetamine treatment in adult rats to assess its role in neurobehavioral outcome during psychostimulant withdrawal.

Method

The model of amphetamine-induced (1.5 mg/kg/day, i.p., 7 consecutive days) motor sensitization and affected body weight gain was established in adult male Wistar rats. Then, additional cohort of amphetamine-sensitized rats was subjected to saline (0.9% NaCl; 1 mL/kg/day; i.p.) or ribavirin (10, 20 and 30 mg/kg/day, i.p.) treatment for 7 consecutive days. Animals’ motor activity in a novel environment was monitored after the 1^st and the 7^th saline/ribavirin injection. Body weight gain was calculated as appropriate. Determination and quantification of ribavirin in the brain tissue were performed also.

Results

The 1^st application of ribavirin to amphetamine-sensitized rats affected/decreased their novelty-induced motor activity only at a dose of 30 mg/kg. After the 7^th application, ribavirin 30 mg/kg/day still decreased, while 10 and 20 mg/kg/day increased novelty-induced motor activity. These behavioral effects coincided with the time required to reach maximum ribavirin concentration in the brain. Body weight gain during withdrawal was not influenced by any of the doses tested.

Conclusion

Ribavirin displays central effects that in repeated treatment, depending on the applied dose, could significantly influence psychomotor response but not body weight gain during psychostimulant/amphetamine withdrawal.

Molecular design, synthesis, and biological evaluation of bisamide derivatives as cyclophilin A inhibitors for HCV treatment

Hepatitis C virus (HCV) is a major cause of end-stage liver diseases. Direct-acting antivirals (DAAs), including inhibitors of nonstructural proteins (NS3/4A protease, NS5A, and NS5B polymerase), represent key components of anti-HCV treatment. However, some DAAs are associated with increased drug resistance and undesired side effects. Previous reports have shown that bisamides could be a novel class of cyclophilin A (CypA) inhibitors for treating HCV as a member of combinational therapies. To fully elucidate structure-activity relationships of bisamide derivatives and find a better hit compound with diverse binding modes, 16 biamides were designed with the help of docking program. They were then synthesized using one-pot four-component Ugi reaction. 7e with selectivity index of more than 18.9 (50% effective concentration of 5.3 μM, but no cytotoxicity at 100 μM) and unique binding mode that could be dived into gatekeeper pocket was selected as a new hit compound. Surface plasmon resonance experiments revealed that 7e is able to bind to CypA with a K_D of 3.66 μM. Taken together, these results suggest that 7e as a CypA inhibitor could be used as an alternative anti-HCV agent in combinational therapy in the future.

Novel triazole nucleoside analogues promote anticancer activity via both apoptosis and autophagy

Novel triazole nucleosides developed by the strategy of “terminal N,N-dimethylation” displayed anticancer activity mediated via apoptosis and autophagy.

Critical View on the Usage of Ribavirin in Already Existing Psychostimulant-Use Disorder

Substance-use disorder represents a frequently hidden non-communicable chronic disease. Patients with intravenous drug addiction are at high risk of direct exposure to a variety of viral infections and are considered to be the largest subpopulation infected with the hepatitis C virus. Ribavirin is a synthetic nucleoside analog that has been used as an integral component of hepatitis C therapy. However, ribavirin medication is quite often associated with pronounced psychiatric adverse effects. It is not well understood to what extent ribavirin per se contributes to changes in drug-related neurobehavioral disturbances, especially in the case of psychostimulant drugs, such as amphetamine. It is now well-known that repeated amphetamine usage produces psychosis in humans and behavioral sensitization in animals. On the other hand, ribavirin has an affinity for adenosine A1 receptors that antagonistically modulate the activity of dopamine D1 receptors, which play a critical role in the development of behavioral sensitization. This review will focus on the current knowledge of neurochemical/ neurobiological changes that exist in the psychostimulant drug-addicted brain itself and the antipsychotic-like efficiency of adenosine agonists. Particular attention will be paid to the potential side effects of ribavirin therapy, and the opportunities and challenges related to its application in already existing psychostimulant-use disorder.

Syntheses and Binding Testing of N1-Alkylamino-Substituted 2-Aminobenzimidazole Analogues Targeting the Hepatitis C Virus Internal Ribosome Entry Site

A series of 2-aminobenzimidazole analogues have been synthesised and tested for binding to a previously established RNA target for viral translation inhibitors in the internal ribosome entry site (IRES) of the hepatitis C virus (HCV). Synthesis of new inhibitor compounds followed a highly convergent strategy which allowed for incorporation of diverse tertiary amino substituents in high overall yields (eight-steps, 4–22%). Structure–activity relationship (SAR) studies focussed on the tertiary amine substituent involved in hydrogen bonding with the RNA backbone at the inhibitor binding site. The SAR study was further correlated with in silico docking experiments. Analogous compounds showed promising activities (half maximal effective concentration, EC50: 21–89µM). Structures of the synthesised analogues and a correlation to their mode of binding, provided the opportunity to explore parameters required for selective targeting of the HCV IRES at the subdomain IIa which acts as an RNA conformational switch in HCV translation.

Discovery and Characterization of Potent Pan-Genotypic HCV NS5A Inhibitors Containing Novel Tricyclic Central Core Leading to Clinical Candidate

The identification of a novel class of potent pan-genotypic NS5A inhibitors with good pharmacokinetic profile suitable for potential use in treating HCV infections is disclosed here. The present series of compounds are with less complex tricyclic central core, identified through a systematic SAR study carried out on biphenyl moiety. The SAR outcome has confirmed the requirement of near planar and linear conformation of the molecule to achieve the best pan-genotypic activity. In addition, SAR with substituted imidazoles on improvement of antiviral activity is disclosed. The newly identified compounds 12, 16, 19-21 have shown desirable pharmacokinetic profiles with a favorable uptake of compounds in liver and maintained a significant concentration for up to 8 h in the liver. In addition, compounds 20 and 21 have shown superior pan-genotypic anti-HCV activity compared to ledipasvir and daclatasvir. Additional characterization and preliminary safety assessment resulted in the identification of compound 20 as a potential clinical candidate.

2'-C-methylated nucleotides terminate virus RNA synthesis by preventing active site closure of the viral RNA-dependent RNA polymerase

The 2'-C-methyl ribonucleosides are nucleoside analogs representing an important class of antiviral agents, especially against positive-strand RNA viruses. Their value is highlighted by the highly successful anti-hepatitis C drug sofosbuvir. When appropriately phosphorylated, these nucleotides are successfully incorporated into RNA by the virally encoded RNA-dependent RNA polymerase (RdRp). This activity prevents further RNA extension, but the mechanism is poorly characterized. Previously, we had identified NMR signatures characteristic of formation of RdRp-RNA binary and RdRp-RNA-NTP ternary complexes for the poliovirus RdRp, including an open-to-closed conformational change necessary to prepare the active site for catalysis of phosphoryl transfer. Here we used these observations as a framework for interpreting the effects of 2'-C-methyl adenosine analogs on RNA chain extension in solution-state NMR spectroscopy experiments, enabling us to gain additional mechanistic insights into 2'-C-methyl ribonucleoside-mediated RNA chain termination. Contrary to what has been proposed previously, poliovirus RdRp that was bound to RNA with an incorporated 2'-C-methyl nucleotide could still bind to the next incoming NTP. Our results also indicated that incorporation of the 2'-C-methyl nucleotide does not disrupt RdRp-RNA interactions and does not prevent translocation. Instead, incorporation of the 2'-C-methyl nucleotide blocked closure of the RdRp active site upon binding of the next correct incoming NTP, which prevented further nucleotide addition. We propose that other nucleotide analogs that act as nonobligate chain terminators may operate through a similar mechanism.

Review article: direct-acting antivirals for the treatment of HCV during pregnancy and lactation - implications for maternal dosing, foetal exposure, and safety for mother and child

BACKGROUND

With the global efforts to eradicate hepatitis C virus (HCV), treatment during pregnancy is becoming a priority for research as this, and maternal cure should reduce vertical transmission. However, as information on the efficacy and safety of direct-acting antivirals (DAAs) in pregnancy is generally lacking, treatment of HCV infection during pregnancy is not currently recommended.

AIM

To provide an overview of current knowledge regarding maternal exposure, placental handling and safety of DAAs during pregnancy and lactation METHODS: A literature search was performed focusing on the effect of pregnancy on maternal exposure to DAAs, the placental handling of DAAs, the safety of DAAs for mother and child during pregnancy and the safety of DAAs during lactation.

RESULTS

Exposure to all DAAs studied is likely to be altered during pregnancy, mostly related to pregnancy-induced effects on drug absorption and metabolism. Although animal studies show that most DAAs are reported to cross the placenta and transfer into breast milk, most DAA combinations show a favourable safety profile. Because of the rapid viral decline after treatment initiation, and to avoid the critical period of organogenesis, treatment may be started at the end of the second trimester or early third trimester.

CONCLUSIONS

Treatment of HCV infection during pregnancy is realistic, as DAAs are highly effective and treatment duration is relatively short. There is an urgent need to study DAAs during pregnancy and lactation to contribute to the goal of HCV elimination.

Design, Synthesis, Antiviral Evaluation, and SAR Studies of New 1-(Phenylsulfonyl)-1H-Pyrazol-4-yl-Methylaniline Derivatives

A series of N-((3-phenyl-1-(phenylsulfonyl)-1H-pyrazol-4-yl)methyl)anilines 7a-p and 8a-l, structurally related to previously synthesized and tested (N-(1,3-diphenyl-1H-pyrazol-4-yl)methyl)anilines (1a-v), were designed and synthesized. The new derivatives were evaluated in cell-based assays for their cytotoxicity and antiviral activity against a large panel of RNA and DNA viruses of public health significance. Generally, the tested compounds did not display cytotoxicity toward the cell lines used. The majority of derivatives 7a-p were able to interfered with YFV and RSV replication in the micromolar range showing a marked improvement in potency and selectivity with respect to the reference inhibitors 6-azauridine and ribavirin, respectively. The introduction of a p-methoxy substituent on the phenylsulfonyl group (compounds 8a-l) completely abolished the anti-RSV activity and reduced or eliminated the potency against YFV. On the contrary, several p-methoxy analogs were able to interfere with BVDV replication with a comparable (8b, 8c, 8g, and 8k) or better (8a and 8f) potency than the reference inhibitor, ribavirin. Compound 7e, selected for time of addition experiments on BHK-21 cell cultures infected with YFV, achieved the highest reduction of virus titer when added 2 h post infection and maintained up to 4 h post infection.