In silico drug repurposing for the identification of potential candidate molecules against arboviruses infection

Repurposing of FDA-approved drugs against oligomerization domain of dengue virus NS1 protein: a computational approach

Dengue fever is a serious health hazard on a global scale and its primary causative agent is the dengue virus (DENV). The non-structural protein 1 (NS1) of DENV plays a pivotal role in pathogenesis. It is associated with several autoimmune events, endothelial cell apoptosis, and vascular leakage, which increase mainly during the critical phase of infection. In this study, important residues of the oligomerization domain of NS1 protein were identified by literature searches. Virtual screening has been conducted using the entire dataset of the DrugBank database and the potential small-molecule inhibitors against the NS1 protein have been chosen on the basis of binding energy values. This is succeeded by molecular dynamics (MD) simulations of the shortlisted compounds, ultimately giving rise to five compounds. These five compounds were further subjected to RAMD simulations by applying a random direction force of specific magnitude on the ligand center of mass in order to push the ligand out of the protein-binding pocket, for the quantitative estimation of their binding energy values to determine the interaction strength between protein and ligand which prevents ligand unbinding from its binding site, ultimately leading to the selection of three major compounds, DB00826 (Natamycin), DB11274 (Dihydro-alphaergocryptine), and DB11275 (Epicriptine), with the DB11274 having a role against idiopathic Parkinson's disease, and thus may have possible important roles in the prevention of dengue-associated Parkinsonism. These compounds may act as prospective drugs against dengue, by preventing the oligomerization of the NS1 protein, thereby preventing disease progression and pathogenesis.

Coordination Compounds as Antivirals against Neglected Tropical Diseases

Neglected tropical viral diseases are a burden to social and economic welfare being responsible for higher pathogen-related mortality rates and chronic debilitating patient conditions. Climatic changes have widened up the infectibility ratio of such diseases, with autochthonous transmission in formerly temperate-to-cold environments. The slow-paced development of potential vaccines followed by the inexistence of antiviral drugs for such diseases considerably worsens the situation. Coordination compounds are a class of molecules that have been extensively explored as antiviral drugs for viruses such as poliovirus, HIV and, more recently, SARS-CoV-2, figuring as potential molecules to be explored and capitalized as antivirals against neglected viral strains. In this review the current efforts from the inorganic medicinal chemistry to address viral neglected tropical diseases, with emphasis to coordination compounds, is presented. Since many of neglected viruses are also arthropod-borne viruses, relying on a vector for transmission, coordination entities able to mitigate vectors are also presented as a parallel strategy to prevent and control such diseases.

Alphavirus nsP2: A Multifunctional Regulator of Viral Replication and Promising Target for Anti-Alphavirus Therapies

Alphaviruses are re-emerging vector-born pathogens that cause arthralgia or encephalitic diseases on a global scale. While a vaccine against chikungunya virus was recently approved, no vaccines currently exist for other alphaviruses, nor are there antiviral drugs for the treatment of alphavirus infections. Alphaviruses have positive-strand RNA genomes, and their RNA replication is coordinated by activities of the multifunctional nonstructural protein 2 (nsP2), a helicase-protease and a subunit of viral RNA replicase. We provide a comprehensive overview of nsP2 functions and inhibitors of its activities for their potential as effective antivirals. Furthermore, analysis of nsP2 activities suggests that it could be targeted to develop advanced live attenuated vaccines and strategies for controlling alphavirus transmission by mosquito vectors.

A Comprehensive Review of the Development and Therapeutic Use of Antivirals in Flavivirus Infection

Flaviviruses are a diverse group of viruses primarily transmitted through hematophagous insects like mosquitoes and ticks. Significant expansion in the geographic range, prevalence, and vectors of flavivirus over the last 50 years has led to a dramatic increase in infections that can manifest as hemorrhagic fever or encephalitis, leading to prolonged morbidity and mortality. Millions of infections every year pose a serious threat to worldwide public health, encouraging scientists to develop a better understanding of the pathophysiology and immune evasion mechanisms of these viruses for vaccine development and antiviral therapy. Extensive research has been conducted in developing effective antivirals for flavivirus. Various approaches have been extensively utilized in clinical trials for antiviral development, targeting virus entry, replication, polyprotein synthesis and processing, and egress pathways exploiting virus as well as host proteins. However, to date, no licensed antiviral drug exists to treat the diseases caused by these viruses. Understanding the mechanisms of host-pathogen interaction, host immunity, viral immune evasion, and disease pathogenesis is highly warranted to foster the development of antivirals. This review provides an extensively detailed summary of the most recent advances in the development of antiviral drugs to combat diseases.

In silico-driven identification of Pranlukast as a Stabilizer of PD-L1 Homodimers

INTRODUCTION

Programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1) are critical immune checkpoints in cancer biology. Multiple small-molecule drugs have been developed as inhibitors of the PD-1/PD-L1 axis. Those drugs promote the formation of PD-L1 homodimers, causing their stabilization, internalization, and subsequent degradation. Drug repurposing is a strategy that expedites the clinical translation by identifying new effects of drugs with clinical use. Herein, we aimed to repurpose drugs as inductors of PD-L1 homodimerization and, therefore, as potential inhibitors of PD-L1.

METHODS

We generated a hybrid pharmacophore model by analyzing the structures of reported ligands that induce PD-L1 homodimerization and their target-binding mode. Pharmacophore-matching compounds were selected from a chemical library of Food and Drug Administration (FDA)-approved drugs. Their binding modes to PDL1 homodimers were assessed by molecular docking and the stability of the complexes and the corresponding binding energies were evaluated by molecular dynamics (MD) simulations. Finally, the activity of one drug as promoter of PD-L1 homodimerization was assessed in protein crosslinking assays.

RESULTS

We identified 12 pharmacophore-matching compounds, but only 4 reproduced the binding mode of the reference inhibitors. Further characterization by MD showed that pranlukast, an antagonist of leukotriene receptors that is used to treat asthma, generated stable and energy-favorable interactions with PD-L1 homodimers and induced homodimerization of recombinant PD-L1.

CONCLUSION

Our results suggest that pranlukast inhibits the PD-1/PD-L1 axis, meriting its repurposing as an antitumor drug.

Orthoflaviviral Inhibitors in Clinical Trials, Preclinical In Vivo Efficacy Targeting NS2B-NS3 and Cellular Antiviral Activity via Competitive Protease Inhibition

Orthoflaviviruses, including zika (ZIKV), West Nile (WNV), and dengue (DENV) virus, induce severely debilitating infections and contribute significantly to the global disease burden, yet no clinically approved antiviral treatments exist. This review offers a comprehensive analysis of small-molecule drug development targeting orthoflaviviral infections, with a focus on NS2B-NS3 inhibition. We systematically examined clinical trials, preclinical efficacy studies, and modes of action for various viral replication inhibitors, emphasizing allosteric and orthosteric drugs inhibiting NS2B-NS3 protease with in vivo efficacy and in vitro-tested competitive NS2B-NS3 inhibitors with cellular efficacy. Our findings revealed that several compounds with in vivo preclinical efficacy failed to show clinical antiviral efficacy. NS3-NS4B inhibitors, such as JNJ-64281802 and EYU688, show promise, recently entering clinical trials, underscoring the importance of developing novel viral replication inhibitors targeting viral machinery. To date, the only NS2B-NS3 inhibitor that has undergone clinical trials is doxycycline, however, its mechanism of action and clinical efficacy as viral growth inhibitor require additional investigation. SYC-1307, an allosteric inhibitor, exhibits high in vivo efficacy, while temoporfin and methylene blue represent promising orthosteric non-competitive inhibitors. Compound 71, a competitive NS2B-NS3 inhibitor, emerges as a leading preclinical candidate due to its high cellular antiviral efficacy, minimal cytotoxicity, and favorable in vitro pharmacokinetic parameters. Challenges remain in developing competitive NS2B-NS3 inhibitors, including appropriate biochemical inhibition assays as well as the selectivity and conformational flexibility of the protease, complicating effective antiviral treatment design.

Essential oil components interacting with insect odorant-binding proteins: a molecular modelling approach

Essential oils (EOs) are natural products currently used to control arthropods, and their interaction with insect odorant-binding proteins (OBPs) is fundamental for the discovery of new repellents. This in silico study aimed to predict the potential of EO components to interact with odorant proteins. A total of 684 EO components from PubChem were docked against 23 odorant binding proteins from Protein Data Bank using AutoDock Vina. The ligands and proteins were optimized using Gaussian 09 and Sybyl-X 2.0, respectively. The nature of the protein-ligand interactions was characterized using LigandScout 4.0, and visualization of the binding mode in selected complexes was carried out by Pymol. Additionally, complexes with the best binding energy in molecular docking were subjected to 500 ns molecular dynamics simulations using Gromacs. The best binding affinity values were obtained for the 1DQE-ferutidine (-11 kcal/mol) and 2WCH-kaurene (-11.2 kcal/mol) complexes. Both are natural ligands that dock onto those proteins at the same binding site as DEET, a well-known insect repellent. This study identifies kaurene and ferutidine as possible candidates for natural insect repellents, offering a potential alternative to synthetic chemicals like DEET.

Chitosan decorated oleosomes loaded propranolol hydrochloride hydrogel repurposed for Candida albicans-vaginal infection

Aim: Our investigation aims to estimate the antifungal effect of propranolol hydrochloride (PNL). Methods: Oleosomes (OLs) were fabricated by thin-film hydration and evaluated for entrapment efficiency (EE%), particle size (PS), polydispersity index (PDI), zeta potential (ZP), and amount of drug released after 6 h Q6h (%). Results: The optimal OL showed a rounded shape with optimum characteristics. The ex-vivo permeation and confocal laser scanning microscopy verified the prolonged release and well deposition of PNL-loaded OLs-gel. The in-silico assessment demonstrated the good stability of PNL with OLs' ingredients. In vivo evaluations for PNL-loaded OLs-gel showed a good antifungal impact against Candida albicans with good safety. Conclusion: This work highlights the potential of PNL-loaded OLs-gel as a potential treatment for candida vaginal infection.

Anti-influenza virus activities and mechanism of antrafenine analogs

Antrafenine is a drug initially designed for anti-inflammation uses. In this work we have synthesized a library of its structural analogs and tested the anti-influenza activities. These analogs belong to a group of 2-(quinolin-4-yl)amino benzamides or 2-(quinolin-4-yl)amino benzoate derivatives. Best performers were identified, namely 12, 34, 41, with IC50 against A/WSN/33 (H1N1) of 5.53, 3.21 and 6.73 μM respectively. These chemicals were also effective against A/PR/8/34 (H1N1), A/HK/1/68 (H3N2) and B/Florida/04/2006 viruses. Time-of-addition study and minigenome luciferase reporter assay both supported that the compounds act on the ribonucleoprotein (RNP) components. Using 34 and 41 as representative compounds, we determined by microscale thermophoresis that this group of compounds bind to both PA C-terminal domain and the nucleoprotein (NP) which is the most abundant subunit of the RNP. Taken together, we have identified a new class of anti-influenza compounds with dual molecular targets and good potential to be further developed. IMPORTANCE: The influenza viruses, especially influenza A and B subtypes, cause many deaths each year. The high mutation rate of the virus renders available therapeutics less effective with time. In this work we identify a new class of compounds, structurally similar to the anti-inflammation drug antrafenine, with good potency against influenza A strains. The IC50 of the best performers are within low micromolar range and thus have good potential for further development.

Vector-Transmitted Flaviviruses: An Antiviral Molecules Overview

Flaviviruses cause numerous pathologies in humans across a broad clinical spectrum with potentially severe clinical manifestations, including hemorrhagic and neurological disorders. Among human flaviviruses, some viral proteins show high conservation and are good candidates as targets for drug design. From an epidemiological point of view, flaviviruses cause more than 400 million cases of infection worldwide each year. In particular, the Yellow Fever, dengue, West Nile, and Zika viruses have high morbidity and mortality-about an estimated 20,000 deaths per year. As they depend on human vectors, they have expanded their geographical range in recent years due to altered climatic and social conditions. Despite these epidemiological and clinical premises, there are limited antiviral treatments for these infections. In this review, we describe the major compounds that are currently under evaluation for the treatment of flavivirus infections and the challenges faced during clinical trials, outlining their mechanisms of action in order to present an overview of ongoing studies. According to our review, the absence of approved antivirals for flaviviruses led to in vitro and in vivo experiments aimed at identifying compounds that can interfere with one or more viral cycle steps. Still, the currently unavailability of approved antivirals poses a significant public health issue.

Pharmacophore-Model-Based Drug Repurposing for the Identification of the Potential Inhibitors Targeting the Allosteric Site in Dengue Virus NS5 RNA-Dependent RNA Polymerase

Dengue virus (DENV) is the causative agent of DENV infection. To tackle DENV infection, the development of therapeutic molecules as direct-acting antivirals (DAAs) has been demonstrated as a truly effective approach. Among various DENV drug targets, non-structural protein 5 (NS5)-a highly conserved protein among the family Flaviviridae-carries the RNA-dependent RNA polymerase (DENV^RdRp) domain at the C-terminal, and its "N-pocket" allosteric site is widely considered for anti-DENV drug development. Therefore, in this study, we developed a pharmacophore model by utilising 41 known inhibitors of the DENV^RdRp domain, and performed model screening against the FDA's approved drug database for drug repurposing against DENV^RdRp. Herein, drugs complying with the pharmacophore hypothesis were further processed through standard-precision (SP) and extra-precision (XP) docking scores (DSs) and binding pose refinement based on MM/GBSA binding energy (BE) calculations. This resulted in the identification of four potential potent drugs: (i) desmopressin (DS: -10.52, BE: -69.77 kcal/mol), (ii) rutin (DS: -13.43, BE: -67.06 kcal/mol), (iii) lypressin (DS: -9.84, BE: -67.65 kcal/mol), and (iv) lanreotide (DS: -8.72, BE: -64.7 kcal/mol). The selected drugs exhibited relevant interactions with the allosteric N-pocket of DENV^RdRp, including priming-loop and entry-point residues (i.e., R729, R737, K800, and E802). Furthermore, 100 ns explicit-solvent molecular dynamics simulations and end-point binding free energy assessments support the considerable stability and free energy of the selected drugs in the targeted allosteric pocket of DENV^RdRp. Hence, these four drugs, repurposed as potent inhibitors of the allosteric site of DENV^RdRp, are recommended for further validation using experimental assays.

High-Throughput Screening of FDA-Approved Drug Library Reveals Ixazomib Is a Broad-Spectrum Antiviral Agent against Arboviruses

The emergence of significant arboviruses and their spillover transmission to humans represent a major threat to global public health. No approved drugs are available for the treatment of significant arboviruses in circulation today. The repurposing of clinically approved drugs is one of the most rapid and promising strategies in the identification of effective treatments for diseases caused by arboviruses. Here, we screened small-molecule compounds with anti-tick-borne encephalitis virus, West Nile virus, yellow fever virus and chikungunya virus activity from 2580 FDA-approved drugs. In total, 60 compounds showed antiviral efficacy against all four of the arboviruses in Huh7 cells. Among these compounds, ixazomib and ixazomib citrate (inhibitors of 20S proteasome β5) exerted antiviral effects at a low-micromolar concentration. The time-of-drug-addition assay suggested that ixazomib and ixazomib citrate disturbed multiple processes in viruses’ life cycles. Furthermore, ixazomib and ixazomib citrate potently inhibited chikungunya virus replication and relieved virus-induced footpad swelling in a mouse model. These results offer critical information which supports the role of ixazomib as a broad-spectrum agent against arboviruses.

Flavivirus NS1 Triggers Tissue-Specific Disassembly of Intercellular Junctions Leading to Barrier Dysfunction and Vascular Leak in a GSK-3β-Dependent Manner

The flavivirus nonstructural protein 1 (NS1) is secreted from infected cells and contributes to endothelial barrier dysfunction and vascular leak in a tissue-dependent manner. This phenomenon occurs in part via disruption of the endothelial glycocalyx layer (EGL) lining the endothelium. Additionally, we and others have shown that soluble DENV NS1 induces disassembly of intercellular junctions (IJCs), a group of cellular proteins critical for maintaining endothelial homeostasis and regulating vascular permeability; however, the specific mechanisms by which NS1 mediates IJC disruption remain unclear. Here, we investigated the relative contribution of five flavivirus NS1 proteins, from dengue (DENV), Zika (ZIKV), West Nile (WNV), Japanese encephalitis (JEV), and yellow fever (YFV) viruses, to the expression and localization of the intercellular junction proteins β-catenin and VE-cadherin in endothelial cells from human umbilical vein and brain tissues. We found that flavivirus NS1 induced the mislocalization of β-catenin and VE-cadherin in a tissue-dependent manner, reflecting flavivirus disease tropism. Mechanistically, we observed that NS1 treatment of cells triggered internalization of VE-cadherin, likely via clathrin-mediated endocytosis, and phosphorylation of β-catenin, part of a canonical IJC remodeling pathway during breakdown of endothelial barriers that activates glycogen synthase kinase-3β (GSK-3β). Supporting this model, we found that a chemical inhibitor of GSK-3β reduced both NS1-induced permeability of human umbilical vein and brain microvascular endothelial cell monolayers in vitro and vascular leakage in a mouse dorsal intradermal model. These findings provide insight into the molecular mechanisms regulating NS1-mediated endothelial dysfunction and identify GSK-3β as a potential therapeutic target for treatment of vascular leakage during severe dengue disease.

Finding a chink in the armor: Update, limitations, and challenges toward successful antivirals against flaviviruses

Flaviviruses have caused large epidemics and ongoing outbreaks for centuries. They are now distributed in every continent infecting up to millions of people annually and may emerge to cause future epidemics. Some of the viruses from this group cause severe illnesses ranging from hemorrhagic to neurological manifestations. Despite decades of research, there are currently no approved antiviral drugs against flaviviruses, urging for new strategies and antiviral targets. In recent years, integrated omics data-based drug repurposing paired with novel drug validation methodologies and appropriate animal models has substantially aided in the discovery of new antiviral medicines. Here, we aim to review the latest progress in the development of both new and repurposed (i) direct-acting antivirals; (ii) host-targeting antivirals; and (iii) multitarget antivirals against flaviviruses, which have been evaluated both in vitro and in vivo, with an emphasis on their targets and mechanisms. The search yielded 37 compounds that have been evaluated for their efficacy against flaviviruses in animal models; 20 of them are repurposed drugs, and the majority of them exhibit broad-spectrum antiviral activity. The review also highlighted the major limitations and challenges faced in the current in vitro and in vivo evaluations that hamper the development of successful antiviral drugs for flaviviruses. We provided an analysis of what can be learned from some of the approved antiviral drugs as well as drugs that failed clinical trials. Potent in vitro and in vivo antiviral efficacy alone does not warrant successful antiviral drugs; current gaps in studies need to be addressed to improve efficacy and safety in clinical trials.

Chikungunya virus time course infection of human macrophages reveals intracellular signaling pathways relevant to repurposed therapeutics

Background

Chikungunya virus (CHIKV) is a mosquito-borne pathogen, within the Alphavirus genus of the Togaviridae family, that causes ~1.1 million human infections annually. CHIKV uses Aedes albopictus and Aedes aegypti mosquitoes as insect vectors. Human infections can develop arthralgia and myalgia, which results in debilitating pain for weeks, months, and even years after acute infection. No therapeutic treatments or vaccines currently exist for many alphaviruses, including CHIKV. Targeting the phagocytosis of CHIKV by macrophages after mosquito transmission plays an important role in early productive viral infection in humans, and could reduce viral replication and/or symptoms.

Methods

To better characterize the transcriptional response of macrophages during early infection, we generated RNA-sequencing data from a CHIKV-infected human macrophage cell line at eight or 24 hours post-infection (hpi), together with mock-infected controls. We then calculated differential gene expression, enriched functional annotations, modulated intracellular signaling pathways, and predicted therapeutic drugs from these sequencing data.

Results

We observed 234 pathways were significantly affected 24 hpi, resulting in six potential pharmaceutical treatments to modulate the affected pathways. A subset of significant pathways at 24 hpi includes AGE-RAGE, Fc epsilon RI, Chronic myeloid leukemia, Fc gamma R-mediated phagocytosis, and Ras signaling. We found that the MAPK1 and MAPK3 proteins are shared among this subset of pathways and that Telmisartan and Dasatinib are strong candidates for repurposed small molecule therapeutics that target human processes. The results of our analysis can be further characterized in the wet lab to contribute to the development of host-based prophylactics and therapeutics.

Identification of Hypericin as a Candidate Repurposed Therapeutic Agent for COVID-19 and Its Potential Anti-SARS-CoV-2 Activity

The COVID-19 pandemic has had an unprecedented impact on the global economy and public health. Its etiologic agent, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly transmissible, pathogenic and has a rapid global spread. Currently, the increase in the number of new confirmed cases has been slowed down due to the increase of vaccination in some regions of the world. Still, the rise of new variants has influenced the detection of additional waves of rising cases that some countries have experienced. Since the virus replication cycle is composed of many distinct stages, some viral proteins related to them, as the main-protease (Mpro) and RNA dependent RNA polymerase (RdRp), constitute individual potential antiviral targets. In this study, we challenged the mentioned enzymes against compounds pre-approved by health regulatory agencies in a virtual screening and later in Molecular Mechanics/Poisson–Bolzmann Surface Area (MM/PBSA) analysis. Our results showed that, among the identified potential drugs with anti-SARS-CoV-2 properties, Hypericin, an important component of the Hypericum perforatum that presents antiviral and antitumoral properties, binds with high affinity to viral Mpro and RdRp. Furthermore, we evaluated the activity of Hypericin anti-SARS-CoV-2 replication in an in vitro model of Vero-E6 infected cells. Therefore, we show that Hypericin inhibited viral replication in a dose dependent manner. Moreover, the cytotoxicity of the compound, in cultured cells, was evaluated, but no significant activity was found. Thus, the results observed in this study indicate that Hypericin is an excellent candidate for repurposing for the treatment of COVID-19, with possible inhibition of two important phases of virus maturation.

In silico identification of widely used and well-tolerated drugs as potential SARS-CoV-2 3C-like protease and viral RNA-dependent RNA polymerase inhibitors for direct use in clinical trials

Despite strict measures taken by many countries, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to be an issue of global concern. Currently, there are no clinically proven pharmacotherapies for coronavirus disease 2019, despite promising initial results obtained from drugs such as azithromycin and hydroxychloroquine. Therefore, the repurposing of clinically approved drugs for use against SARS-CoV-2 has become a viable strategy. Here, we searched for drugs that target SARS-CoV-2 3C-like protease (3CLpro) and viral RNA-dependent RNA polymerase (RdRp) by in silico screening of the U.S. Food and Drug Administration approved drug library. Well-tolerated and widely used drugs were selected for molecular dynamics (MD) simulations to evaluate drug-protein interactions and their persistence under physiological conditions. Tetracycline, dihydroergotamine, ergotamine, dutasteride, nelfinavir, and paliperidone formed stable interactions with 3CLpro based on MD simulation results. Similar analysis with RdRp showed that eltrombopag, tipranavir, ergotamine, and conivaptan bound to the enzyme with high binding free energies. Docking results suggest that ergotamine, dihydroergotamine, bromocriptine, dutasteride, conivaptan, paliperidone, and tipranavir can bind to both enzymes with high affinity. As these drugs are well tolerated, cost-effective, and widely used, our study suggests that they could potentially to be used in clinical trials for the treatment of SARS-CoV-2-infected patients.Communicated by Ramaswamy H. Sarma.

Antivirals against the Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has re-emerged in recent decades, causing large-scale epidemics in many parts of the world. CHIKV infection leads to a febrile disease known as chikungunya fever (CHIKF), which is characterised by severe joint pain and myalgia. As many patients develop a painful chronic stage and neither antiviral drugs nor vaccines are available, the development of a potent CHIKV inhibiting drug is crucial for CHIKF treatment. A comprehensive summary of current antiviral research and development of small-molecule inhibitor against CHIKV is presented in this review. We highlight different approaches used for the identification of such compounds and further discuss the identification and application of promising viral and host targets.

Targeting Chikungunya Virus Entry: alternatives for new inhibitors in drug discovery

Chikungunya virus (CHIKV) is an Alphavirus (Togaviridae) responsible for Chikungunya fever (CHIKF) that is mainly characterized by a severe polyarthralgia, in which it is transmitted by the bite of infected Aedes aegypti and Ae. albopictus mosquitoes. Nowadays, there no licensed vaccines or approved drugs to specifically treat this viral disease. Structural viral proteins participate in key steps of its replication cycle, such as viral entry, membrane fusion, nucleocapsid assembly, and virus budding. In this context, envelope E3-E2-E1 glycoproteins complex could be targeted for designing new drug candidates. In this review, aspects of the CHIKV entry process are discussed to provide insights to assist the drug discovery process. Moreover, several natural, nature-based and synthetic compounds, as well as repurposed drugs and virtual screening, are also explored as alternatives for developing CHIKV entry inhibitors. Finally, we provided a complimentary analysis of studies involving inhibitors that were not explored by in silico methods. Based on this, Phe118, Val179, and Lys181 were found to be the most frequent residues, being present in 89.6, 82.7, and 93.1% of complexes, respectively. Lastly, some chemical aspects associated with interactions of these inhibitors and mature envelope E3-E2-E1 glycoproteins' complex were discussed to provide data for scientists worldwide, supporting their search for new inhibitors against this emerging arbovirus.

Drug Repurposing: A Strategy for Discovering Inhibitors against Emerging Viral Infections

BACKGROUND

Viral diseases are responsible for several deaths around the world. Over the past few years, the world has seen several outbreaks caused by viral diseases that, for a long time, seemed to possess no risk. These are diseases that have been forgotten for a long time and, until nowadays, there are no approved drugs or vaccines, leading the pharmaceutical industry and several research groups to run out of time in the search for new pharmacological treatments or prevention methods. In this context, drug repurposing proves to be a fast and economically viable technique, considering the fact that it uses drugs that have a well-established safety profile. Thus, in this review, we present the main advances in drug repurposing and their benefit for searching new treatments against emerging viral diseases.

METHODS

We conducted a search in the bibliographic databases (Science Direct, Bentham Science, PubMed, Springer, ACS Publisher, Wiley, and NIH's COVID-19 Portfolio) using the keywords "drug repurposing", "emerging viral infections" and each of the diseases reported here (CoV; ZIKV; DENV; CHIKV; EBOV and MARV) as an inclusion/exclusion criterion. A subjective analysis was performed regarding the quality of the works for inclusion in this manuscript. Thus, the selected works were those that presented drugs repositioned against the emerging viral diseases presented here by means of computational, high-throughput screening or phenotype-based strategies, with no time limit and of relevant scientific value.

RESULTS

291 papers were selected, 24 of which were CHIKV; 52 for ZIKV; 43 for DENV; 35 for EBOV; 10 for MARV; and 56 for CoV and the rest (72 papers) related to the drugs repurposing and emerging viral diseases. Among CoV-related articles, most were published in 2020 (31 papers), updating the current topic. Besides, between the years 2003 - 2005, 10 articles were created, and from 2011 - 2015, there were 7 articles, portraying the outbreaks that occurred at that time. For ZIKV, similar to CoV, most publications were during the period of outbreaks between the years 2016 - 2017 (23 articles). Similarly, most CHIKV (13 papers) and DENV (14 papers) publications occur at the same time interval. For EBOV (13 papers) and MARV (4 papers), they were between the years 2015 - 2016. Through this review, several drugs were highlighted that can be evolved in vivo and clinical trials as possible used against these pathogens showed that remdesivir represent potential treatments against CoV. Furthermore, ribavirin may also be a potential treatment against CHIKV; sofosbuvir against ZIKV; celgosivir against DENV, and favipiravir against EBOV and MARV, representing new hopes against these pathogens.

CONCLUSION

The conclusions of this review manuscript show the potential of the drug repurposing strategy in the discovery of new pharmaceutical products, as from this approach, drugs could be used against emerging viral diseases. Thus, this strategy deserves more attention among research groups and is a promising approach to the discovery of new drugs against emerging viral diseases and also other diseases.

Drug targets for COVID-19 therapeutics: Ongoing global efforts

The current global pandemic COVID-19 caused by the SARS-CoV-2 virus has already inflicted insurmountable damage both to the human lives and global economy. There is an immediate need for identification of effective drugs to contain the disastrous virus outbreak. Global efforts are already underway at a war footing to identify the best drug combination to address the disease. In this review, an attempt has been made to understand the SARS-CoV-2 life cycle, and based on this information potential druggable targets against SARS-CoV-2 are summarized. Also, the strategies for ongoing and future drug discovery against the SARS-CoV-2 virus are outlined. Given the urgency to find a definitive cure, ongoing drug repurposing efforts being carried out by various organizations are also described. The unprecedented crisis requires extraordinary efforts from the scientific community to effectively address the issue and prevent further loss of human lives and health.

Alphavirus capsid protease inhibitors as potential antiviral agents for Chikungunya infection

Chikungunya virus (CHIKV) is an arthritogenic alphavirus and currently, no antiviral drug is available to combat it. Capsid protein (CP) of alphaviruses present at the N-terminus of the structural polyprotein possesses auto-proteolytic activity which is essential for initiating the structural polyprotein processing. We are reporting for the first time antiviral molecules targeting capsid proteolytic activity. Structure-assisted drug-repositioning identified three molecules: P1,P4-Di(adenosine-5') tetraphosphate (AP4), Eptifibatide acetate (EAC) and Paromomycin sulphate (PSU) as potential capsid protease inhibitors. A FRET-based proteolytic assay confirmed anti-proteolytic activity of these molecules. Additionally, in vitro cell-based antiviral studies showed that EAC, AP4, and PSU drastically stifled CHIKV at the post-entry step with a half-maximal effective concentration (EC₅₀) of 4.01 μM, 10.66 μM and 22.91 μM; respectively. Interestingly, the inhibitors had no adverse effect on viral RNA synthesis and treatment of cells with inhibitors diminished levels of CP in virus-infected cells, which confirmed inhibition of capsid auto-proteolytic activity. In conclusion, the discovery of antiviral molecules targeting capsid protease demystifies the alphavirus capsid protease as a potential target for antiviral drug discovery.