NS5B Inhibitors Research Articles

1H, 15N and 13C backbone resonance assignment of the N-terminal region of Zika virus NS4B protein in detergent micelles.

Zika virus has raised global concerns due to its link to microcephaly and Guillain-Barré syndrome in adults. One of viral nonstructural proteins-NS4B, an integral membrane protein, plays crucial roles in viral replication by interacting with both viral and host proteins, rendering it an attractive drug target for antiviral development. We purified the N-terminal region of ZIKV NS4B (NS4B NTD) and reconstituted it into detergent micelles. Here, we report the assignments of the backbone resonances of NS4B NTD in detergent micelles. The available assignment is useful for understanding its structure and ligand binding to provide useful information for developing NS4B inhibitors.

An Increase in the Prevalence of Clinically Relevant Resistance-Associated Substitutions in Four Direct-Acting Antiviral Regimens: A Study Using GenBank HCV Sequences.

Direct-acting antivirals (DAAs) revolutionized the therapeutics of chronic hepatitis C. The emergence and transmission of HCV variants with resistance-associated substitutions (RASs) can undermine HCV treatment. This study aimed to assess the prevalence and temporal trends of RASs in HCV, with a particular focus on clinically relevant RASs (cr-RASs). Near-complete HCV GenBank sequences archived in the Los Alamos HCV Database were analyzed. The study period was divided into two phases: before 2011 and from 2011 onward. Identification of RASs across three DAA classes (NS3, NS5A, and NS5B inhibitors) was based on the 2020 EASL guidelines. The AASLD-IDSA recommendations were used to identify cr-RASs for three HCV genotypes/subtypes (1a, 1b, and 3) and four DAA regimens: ledipasvir/sofosbuvir; elbasvir/grazoprevir; sofosbuvir/velpatasvir; and glecaprevir/pibrentasvir. The final HCV dataset comprised 3443 sequences, and the prevalence of RASs was 50.4%, 60.2%, and 25.3% in NS3, NS5A, and NS5B, respectively. In subtype 1a, resistance to ledipasvir/sofosbuvir was 32.8%, while resistance to elbasvir/grazoprevir was 33.0%. For genotype 3, resistance to sofosbuvir/velpatasvir and glecaprevir/pibrentasvir was 4.2% and 24.9%, respectively. A significant increase in cr-RASs was observed across the two study phases as follows: for ledipasvir/sofosbuvir in subtype 1a, cr-RASs increased from 30.2% to 35.8% (p = 0.019); for elbasvir/grazoprevir in subtype 1a, cr-RASs increased from 30.4% to 36.1% (p = 0.018); In subtype 1b, neither ledipasvir/sofosbuvir nor elbasvir/grazoprevir showed any cr-RASs in the first phase, but both were present at a prevalence of 6.5% in the second phase (p < 0.001); for sofosbuvir/velpatasvir in genotype 3, cr-RASs increased from 0.9% to 5.2% (p = 0.006); and for glecaprevir/pibrentasvir, cr-RASs increased from 12.0% to 29.1% (p < 0.001). The rising prevalence of HCV RASs and cr-RASs was discernible. This highlights the necessity for ongoing surveillance and adaptation of novel therapeutics to manage HCV resistance effectively. Updating the clinical guidelines and treatment regimens is recommended to counteract the evolving HCV resistance to DAAs.

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.

A preparative small-molecule mimic of liver CYP450 enzymes in the aliphatic C–H oxidation of carbocyclic N-heterocycles

An emerging trend in small-molecule pharmaceuticals, generally composed of nitrogen heterocycles (N-heterocycles), is the incorporation of aliphatic fragments. Derivatization of the aliphatic fragments to improve drug properties or identify metabolites often requires lengthy de novo syntheses. Cytochrome P450 (CYP450) enzymes are capable of direct site- and chemo-selective oxidation of a broad range of substrates but are not preparative. A chemoinformatic analysis underscored limited structural diversity of N-heterocyclic substrates oxidized using chemical methods relative to pharmaceutical chemical space. Here, we describe a preparative chemical method for direct aliphatic oxidation that tolerates a wide range of nitrogen functionality (chemoselective) and matches the site of oxidation (site-selective) of liver CYP450 enzymes. Commercial small-molecule catalyst Mn(CF3-PDP) selectively effects direct methylene oxidation in compounds bearing 25 distinct heterocycles including 14 out of 27 of the most frequent N-heterocycles found in U.S. Food and Drug Administration (FDA)-approved drugs. Mn(CF3-PDP) oxidations of carbocyclic bioisostere drug candidates (for example, HCV NS5B and COX-2 inhibitors including valdecoxib and celecoxib derivatives) and precursors of antipsychotic drugs blonanserin, buspirone, and tiospirone and the fungicide penconazole are demonstrated to match the major site of aliphatic metabolism obtained with liver microsomes. Oxidations are demonstrated at low Mn(CF3-PDP) loadings (2.5 to 5 mol%) on gram scales of substrate to furnish preparative amounts of oxidized products. A chemoinformatic analysis supports that Mn(CF3-PDP) significantly expands the pharmaceutical chemical space accessible to small-molecule C-H oxidation catalysis.

Discovery of Acyl-Indole Derivatives as Pan-Serotype Dengue Virus NS4B Inhibitors.

In the absence of any approved dengue-specific treatment, the discovery and development of a novel small-molecule antiviral for the prevention or treatment of dengue are critical. We previously reported the identification of a novel series of 3-acyl-indole derivatives as potent and pan-serotype dengue virus inhibitors. We herein describe our optimization efforts toward preclinical candidates 24a and 28a with improved pan-serotype coverage (EC50's against the four DENV serotypes ranging from 0.0011 to 0.24 μM for 24a and from 0.00060 to 0.084 μM for 28a), chiral stability, and oral bioavailability in preclinical species, as well as showing a dose-proportional increase in efficacy against DENV-2 infection in vivo in mice.

Structure-based virtual screening of ROCK1 inhibitors for the discovery of Enterovirus-A71 antivirals

Human enterovirus A71 (EV-A71) is the major causative agent of hand, foot, and mouth disease (HFMD), which may lead to neurological sequelae and even death. Although EV-A71 seriously threatens public health, there remains no efficient drug for the treatment of EV-A71 infection. We previously demonstrated that ROCK1 is a novel host dependency factor for EV-A71 replication and can serve as a target for the development of anti-EV-A71 therapeutics. In this study, we identified a subset of inhibitors with potential anti-EV-A71 activity by virtual screening using ROCK1 as a target. Among the hits, Dasabuvir, an HCV polymerase inhibitor, was found to have the best antiviral activity which is consistent with the ranking scores in Autodock Vina and iGEMDOCK. We found that Dasabuvir efficiently suppressed EV-A71 replication in a dose-dependent manner. Moreover, Dasabuvir not only efficiently suppressed the replication of EV-A71 in RD cells, but also in multiple cell lines, including HEK-293T, Caco-2, HT-29, HepG2, and Huh7. Besides, Dasabuvir alleviated the release of proinflammatory cytokines caused by EV-A71 infection. Notably, Dasabuvir also exhibited antiviral activity of CVA10, indicating it may have broad-spectrum antiviral activity against species Enteroviruses A. Hence, our results further confirm that ROCK1 can be a potential drug target and suggest Dasabuvir could be a clinical candidate for the treatment of EV-A71 infection.

Molecular Docking: Bioactive Compounds in Indramayu Mango (Mangifera indica L.) Peel Waste as NS5B Hepatitis C Virus (HCV) Inhibitor

Background: Hepatitis C is caused by hepatitis C virus (HCV) infection. HCV infection is one of the biggest causes of chronic liver disease. About 60-80% of patients with acute hepatitis C will develop chronic hepatitis C. Objective: This study aimed to analyze the potential of mango peel compounds as HCV NS5B inhibitors. Methods: The methods in this study are ligand preparation, physicochemical and pharmacokinetic predictions, protein structure preparation, molecular docking, data analysis, and visualization. Results: The results showed that the test ligands had binding free energies close to the reference ligands, namely Mangiferin -7.862 kcal/mol and respectively D-(+)-Maltose -6.453 kcal/mol, Dibutyl – phthalate -6.326 kcal/mol, bis-β-D-fructofuranose 1,2':2,3'-dianhydride -6.249 kcal/mol, 16-Heptadecyne-1,2,4-triol -5.476 kcal/mol, 3,4,5-trihydroxycyclohex-1-ene-1-carboxylic acid -5,360 kcal/mol, Trigonelline -4.905 kcal/mol, Hexitol -4.552 kcal/mol, α-Glucoheptitol -4.403 kcal/mol. All the test ligands bind the NS5B active site with hydrogen bonds. Furthermore, the ligand-receptor complex has a dissociation constant value and hydrogen bond length. Conclusion: The results showed that Mangiferin was the most potential ligand in inhibiting NS5B HCV of all the test ligands used.

Mechanisms of Action of the Host-Targeting Agent Cyclosporin A and Direct-Acting Antiviral Agents against Hepatitis C Virus.

Several direct-acting antivirals (DAAs) are available, providing interferon-free strategies for a hepatitis C cure. In contrast to DAAs, host-targeting agents (HTAs) interfere with host cellular factors that are essential in the viral replication cycle; as host genes, they are less likely to rapidly mutate under drug pressure, thus potentially exhibiting a high barrier to resistance, in addition to distinct mechanisms of action. We compared the effects of cyclosporin A (CsA), a HTA that targets cyclophilin A (CypA), to DAAs, including inhibitors of nonstructural protein 5A (NS5A), NS3/4A, and NS5B, in Huh7.5.1 cells. Our data show that CsA suppressed HCV infection as rapidly as the fastest-acting DAAs. CsA and inhibitors of NS5A and NS3/4A, but not of NS5B, suppressed the production and release of infectious HCV particles. Intriguingly, while CsA rapidly suppressed infectious extracellular virus levels, it had no significant effect on the intracellular infectious virus, suggesting that, unlike the DAAs tested here, it may block a post-assembly step in the viral replication cycle. Hence, our findings shed light on the biological processes involved in HCV replication and the role of CypA.

Pharmacoinformatics-based strategy in designing and profiling of some Pyrazole analogues as novel hepatitis C virus inhibitors with pharmacokinetic analysis

ABSTRACT Hepatitis C virus (HCV) infection promotes death rates all over the world. Sofosbuvir is a standard drug for the cure of HCV but unfortunately, it receives a lot of attention for its pricing problems. As a result, it is crucial to consider alternative HCV treatments that are both cost-effective and free of side effects. We report how a pharmacoinformatics-based technique was used to generate and profile certain Pyrazole analogues as novel hepatitis C virus inhibitors by exploring the PubChem drug repository for the lead molecule with further optimization. The proposed molecules all interact by filling the protein target’s binding domain to inhibit the receptor. With binding energy of −35.72 kcal/mol, compound 17e was found as a highly potent NS5B inhibitor, exceeding Sofosbuvir, the FDA-approved NS5B inhibitor with a binding energy of −30.34 kcal/mol. Additionally, the ADMET assessment of the selected molecules (17e) shows outstanding quality with a drug score of 0.74 when especially in comparison to Sofosbuvir, which has a drug score of 0.31. Future studies should therefore focus on the molecular dynamics, synthesis, in vivo testing, and in vitro evaluation of these substances to validate our hypothesis.

Single-Ascending-Dose, Food-Effect, and Multiple-Dose Study of the Safety, Tolerability, and Pharmacokinetics of the Pangenotypic Anti-Hepatitis C Virus Drug Holybuvir in Healthy Chinese Subjects.

Holybuvir is a novel pangenotypic hepatitis C virus NS5B inhibitor. This first in-human study aimed to evaluate the pharmacokinetics (PK), safety, and tolerability of holybuvir and its metabolites and the effect of food on the PK of holybuvir and its metabolites in healthy Chinese subjects. A total of 96 subjects were enrolled in this study which included (i) a single-ascending-dose (SAD) study (100 to 1,200 mg), (ii) a food-effect (FE) study (600 mg), and (iii) a multiple-dose (MD) study (400 and 600 mg once daily for 14 days). The results showed that single oral administration of holybuvir at doses up to 1,200 mg was well tolerated. Holybuvir was rapidly absorbed and metabolized in the human body, which was consistent with the characteristics of holybuvir as a prodrug. PK analysis showed that Cmax and area under the curve (AUC) increased with dose in no dose-proportional manner after a single-dose administration (100 to 1,200 mg). Although high-fat meals did change the PK of holybuvir and its metabolites, clinical significance of changes in PK parameters induced by eating a high-fat diet would be further confirmed. Following multiple-dose administration, accumulation of metabolites SH229M4 and SH229M5-sul was observed. The favorable PK and safety results support the further development of holybuvir for patients with HCV. (This study was registered at Chinadrugtrials.org under identifier CTR20170859.).

Piperazine-derived small molecules as potential Flaviviridae NS3 protease inhibitors. In vitro antiviral activity evaluation against Zika and Dengue viruses

Since 2011 Direct Acting antivirals (DAAs) drugs targeting different non-structural (NS) viral proteins (NS3, NS5A or NS5B inhibitors) have been approved for clinical use in HCV therapies. However, currently there are not licensed therapeutics to treat Flavivirus infections and the only licensed DENV vaccine, Dengvaxia, is restricted to patients with preexisting DENV immunity.Similarly to NS5 polymerase, the NS3 catalytic region is evolutionarily conserved among the Flaviviridae family sharing strong structural similarity with other proteases belonging to this family and therefore is an attractive target for the development of pan-flavivirus therapeutics.In this work we present a library of 34 piperazine-derived small molecules as potential Flaviviridae NS3 protease inhibitors. The library was developed through a privileged structures-based design and then biologically screened using a live virus phenotypic assay to determine the half-maximal inhibitor concentration (IC50) of each compound against ZIKV and DENV. Two lead compounds, 42 and 44, with promising broad-spectrum activity against ZIKV (IC50 6.6 µM and 1.9 µM respectively) and DENV (IC50 6.7 µM and 1.4 µM respectively) and a good security profile were identified. Besides, molecular docking calculations were performed to provide insights about key interactions with residues in NS3 proteases’ active sites.

Novel 6-Aminoquinazolinone Derivatives as Potential Cross GT1-4 HCV NS5B Inhibitors.

Chronic hepatitis C virus (HCV) infections are a worldwide medical problem responsible for diverse types of liver diseases. The NS5B polymerase enzyme has become a very interesting target for the development of anti-HCV drugs owing to its fundamental role in viral replication. Here we report the synthesis of a novel series of 1-substituted phenyl-4(1H)-quinazolinone and 2-methyl-1-substituted phenyl-4(1H)-quinazolinone derivatives and evaluate their activity against HCV in HCV subgenomic replicon assays. The biological data revealed that compound 11a showed the highest activity against HCV GT1b at a micromolar concentration (EC50 = 0.984 µM) followed by compound 11b (EC50 = 1.38 µM). Both compounds 11a and 11b had high selectivity indices (SI = CC50/EC50), 160.71 and 71.75, respectively, which make them very interesting candidates for further development of more potent and selective anti-HCV agents.

Ligand and Structure-Based Pharmacophore Modelling, Computer-aided Screening and Molecular Docking to Detect Novel NS5B Polymerase Inhibitors as Anti-HCV Compounds

The ongoing interest of researchers in the direct-acting NS5B inhibitors in the development of viral disease hepatitis has attracted our attention in the direction of the development of a quantitative four-featured pharmacophore model containing HBA (2), HY (1), and PI (1) features. The model showed correlation coefficient, RMSD, and cost difference values as 0.895, 0.911, and 30.896, respectively. The model validation is done by using Fisher's randomization test (99%), internal and external tests set the expectation with r2 values of 0.80 and 0.65. Simultaneously, the 3D crystal structure of NS5B was utilized for generating a pharmacophore model design based on a structure with features generation 2 Hydrogen Bond Acceptors, 2 Hydrogen Bond Donors, and 2 Hydrophilic features. Further on these two models, HITS searches using NCI and Maybridge databases were done. Three hundred forty-five compounds were screened, and the three greatest potent hits were docked to the active site of NS5B. It was found that these docked conformations showed interactions with GLN446 and TYR448 amino acids, which are located at NS5B active site. In an instant, with the use of various computational methods in a sequence, we have identified novel structurally diverse NS5B inhibitors.

Dengue virus NS4B protein as a target for developing antivirals.

Dengue virus is an important pathogen affecting global population while no specific treatment is available against this virus. Effort has been made to develop inhibitors through targeting viral nonstructural proteins such as NS3 and NS5 with enzymatic activities. No potent inhibitors entering clinical studies have been developed so far due to many challenges. The genome of dengue virus encodes four membrane-bound nonstructural proteins which do not possess any enzymatic activities. Studies have shown that the membrane protein-NS4B is a validated target for drug discovery and several NS4B inhibitors exhibited antiviral activities in various assays and entered preclinical studies.. Here, we summarize the recent studies on dengue NS4B protein. The structure and membrane topology of dengue NS4B derived from biochemical and biophysical studies are described. Function of NS4B through protein-protein interactions and some available NS4B inhibitors are summarized. Accumulated studies demonstrated that cell-based assays play important roles in developing NS4B inhibitors. Although the atomic structure of NS4B is not obtained, target-based drug discovery approach become feasible to develop NS4B inhibitors as recombinant NS4B protein is available.

Sofosbuvir-velpatasvir in adults with hepatitis C virus infection and compensated cirrhosis in Japan.

Protease-free regimens for chronic hepatitis C virus (HCV) infection are safe and effective for persons with either compensated or decompensated cirrhosis. We examined the efficacy and safety of sofosbuvir-velpatasvir in participants with HCV and compensated cirrhosis in Japan. This was a Phase 3, multi-center, open-label study. At 20 sites, 37 individuals with chronic HCV infection of any genotype and compensated cirrhosis received sofosbuvir-velpatasvir (400mg/100mg) daily for 12weeks. Participants were treatment-naïve or treatment-experienced with interferon-based treatments with or without HCV NS3/4A protease inhibitors. Prior exposure with HCV NS5A or NS5B inhibitors was prohibited. The primary study endpoint was sustained virologic response 12weeks after treatment (SVR12). Among participants, 62% had HCV genotype 1 infection, and 38% had HCV genotype 2. More than three quarters (29/37, 78%) were HCV treatment naïve. All participants (37/37, 100%) achieved SVR12. Seventeen participants (46%) and three participants (8%) had pretreatment resistance-associated substitutions to HCV NS5A and NS5B nucleoside inhibitors respectively, yet no on-treatment breakthrough or relapse occurred. Sofosbuvir-velpatasvir for 12weeks treatment was safe and well tolerated. The most commonly reported adverse events were headache (8%, 3/37) and diarrhea (5%, 2/37). One serious adverse event, patella fracture, occurred and was considered not treatment related. No participants discontinued study treatment due to an adverse event. Three participants (8%) had a Grade 3 laboratory abnormality; all were hyperglycemia. Sofosbuvir-velpatasvir resulted in high SVR rates and was well tolerated among Japanese patients with HCV and compensated cirrhosis. This single-tablet regimen offers a highly effective, protease-inhibitor free regimen for treating HCV. gov Identifier: NCT04112303.

Acute myeloid leukaemia following direct acting antiviral drugs in HCV-infected patients: A 10 years’ retrospective single-center study

BackgroundAfter several cases of peculiar hematological malignancies following introduction of new oral anti-hepatitis C virus (HCV) treatments in our recent practice, we aimed to systematically identify all cases of hematological malignancies (HM) in patients with chronic HCV infection and to compare them according to the prescription of oral anti-HCV Direct Acting Antivirals (DAA) treatment or not. Material/methodsIn this single-center retrospective observational study, we included all patients with confirmed HM and chronic HCV infection managed between 2010 and 2019 in the Pitié-Salpêtrière hospital, Paris. Non-inclusion criteria were a benign hematological disorder, an HM preceding chronic HCV infection and HCV acute infection. We compared characteristics of patients who received DAA before HM diagnosis to those with no DAA before HM. ResultsOver the 10 years, 61 cases of HM among HCV infected patients were identified (female 29%, median age of 58.0 years [IQR 17]). Twenty-one received DAA before the onset of HM (Group DAA+) and 40 did not (Group DAA-) including 22 having received DAA after HM. In the DAA+ group, oral NS5B, NS5A and NS3A inhibitors were used in 90, 76 and 29% respectively. HM developed in the two years following DAA initiation in 76%. Eight (38%) had Non-Hodgkin Lymphoma, 5 (24%) had an Acute Myeloid Leukaemia (AML) including two with a mixed phenotype, 2 each had Hodgkin Lymphoma, Multiple Myeloma or a myeloproliferative disorder and one each had a chronic Lymphocytic Leukaemia or AL Amyloidosis. In the Group DAA–, HM were NHL in 20(50%) patients, Myeloproliferative neoplasms in 7 (17%), Multiple Myeloma in 5, Hodgkin Lymphoma in 3, Myelodysplastic syndrome and AML in 2 (5%) each and Acute Lymphoblastic Leukaemia in one. No significant difference between the groups DAA + and – was found according to age, sex, HCV genotype, viral load, co-infection or type and exposition of previous HCV treatments. AML, liver transplantation and cirrhosis were significantly more frequent in the DAA+ group (p = 0.020, 0.045 and 0.032, respectively). ConclusionAML seemed more frequent after using DAA treatments, notably in severe HCV patients including cirrhotic and/or liver transplanted patients. A multicentric observational study is ongoing to confirm and explore the results.

Impact of HCV ns5a resistance associated substitutions on treatment outcome of chronic HCV in daclatasvir-based antiviral regimens

Background: RASs have direct relation to the treatment outcome in chronic HCV patients receiving DAAs. Aim and objectives: to evaluate prevalence of NS5A HCV RASs and their impact on the treatment outcome in daclatasvir-based antiviral regimens in a cohort of Egyptian patients. Subjects and methods: This study was conducted on 40 Egyptian chronic HCV patients at the virology unit of Cairo Fatemya hospital. The study participants were recruited from cases attending the virology unit of Cairo Fatemya hospital in the period from 1/11/2019 to 1/6/2020. Those patients were divided to two equal groups: responders and non responders (20 patient each).Result:Significant difference was found between the two groups as regard RAS in NS5A region in amino acid position 332 (K substitution was detected in responders while E substitution was detected in non-responders), There was a significant difference between the two groups of studied patients as regard RAS in NS5A region in amino acid position 28 (L substitution was found in responders while M substitution was found in non-responders).Conclusion; Although our results showed that RASs against NS5A and NS5B inhibitors have impact on treatment outcome, this finding needs to be confirmed by a larger study.

The Inhibitory Potential of 2'-dihalo Ribonucleotides against HCV: Molecular Docking, Molecular Simulations, MM-BPSA, and DFT Studies.

Sofosbuvir is the first approved direct-acting antiviral (DAA) agent that inhibits the HCV NS5B polymerase, resulting in chain termination. The molecular models of the 2′-dihalo ribonucleotides used were based on experimental biological studies of HCV polymerase inhibitors. They were modeled within HCV GT1a and GT1b to understand the structure–activity relationship (SAR) and the binding interaction of the halogen atoms at the active site of NS5B polymerase using different computational approaches. The outputs of the molecular docking studies indicated the correct binding mode of the tested compounds against the active sites in target receptors, exhibiting good binding free energies. Interestingly, the change in the substitution at the ribose sugar was found to produce a mild effect on the binding mode. In detail, increasing the hydrophobicity of the substituted moieties resulted in a better binding affinity. Furthermore, in silico ADMET investigation implied the general drug likeness of the examined derivatives. Specifically, good oral absorptions, no BBB penetration, and no CYP4502D6 inhibitions were expected. Likely, the in silico toxicity studies against several animal models showed no carcinogenicity and high predicted TD50 values. The DFT studies exhibited a bioisosteric effect between the substituents at the 2′-position and the possible steric clash between 2′-substituted nucleoside analogs and the active site in the target enzyme. Finally, compound 6 was subjected to several molecular dynamics (MD) simulations and MM-PBSA studies to examine the protein-ligand dynamic and energetic stability.

Antivirals against HCV infection: the story thus far.

Remarkable scientific breakthroughs have been made in the stride towards the development of potent and tolerable hepatitis C regimens within the last three decades. Earlier approaches involved the use of pegylated interferon alfa and ribavirin as standard-of-care treatment. Treating genotype 1a infection with this regimen which was at that time considered the gold standard for hepatitis C virus therapy was rife with challenges; safety and toxicity issues necessitated a rigorous quest for alternative regimens. Deeper understanding of the pathogenesis of hepatitis C virus ushered in the era of direct acting antiviral agents. These agents have been the subject of intensive research in the last two decades, leading to the development of drug classes such as protease inhibitors (e.g., grazoprevir), NS5A inhibitors (e.g., daclatasvir) and NS5B inhibitors (e.g., sofosbuvir). While many are still under development, several have been approved for hepatitis C therapy. A number of studies investigating the combination of direct acting antiviral agents with or without pegylated interferon and/or ribavirin for the treatment of chronic hepatitis have demonstrated sustained virologic response of > 90%. Given the array of direct acting antiviral agents currently available, the present landscape of hepatitis C therapy is now characterized by a gradual transition to all-oral interferon-free regimens. Despite these milestones, the WHO global target of eliminating hepatitis C as a public health problem by 2030 seems uncertain. In this review, we provide a concise account of the evolution and advancements in the development of anti-HCV regimens.

Structures and Dynamics of Dengue Virus Nonstructural Membrane Proteins.

Dengue virus is an important human pathogen threating people, especially in tropical and sub-tropical regions. The viral genome has one open reading frame and encodes one polyprotein which can be processed into structural and nonstructural (NS) proteins. Four of the seven nonstructural proteins, NS2A, NS2B, NS4A and NS4B, are membrane proteins. Unlike NS3 or NS5, these proteins do not harbor any enzymatic activities, but they play important roles in viral replication through interactions with viral or host proteins to regulate important pathways and enzymatic activities. The location of these proteins on the cell membrane and the functional roles in viral replication make them important targets for antiviral development. Indeed, NS4B inhibitors exhibit antiviral activities in different assays. Structural studies of these proteins are hindered due to challenges in crystallization and the dynamic nature of these proteins. In this review, the function and membrane topologies of dengue nonstructural membrane proteins are presented. The roles of solution NMR spectroscopy in elucidating the structure and dynamics of these proteins are introduced. The success in the development of NS4B inhibitors proves that this class of proteins is an attractive target for antiviral development.