Discovery of 3-phenyl-1,2,4-oxadiazole derivatives as a new class of SARS-CoV-2 main protease inhibitors.

The ongoing COVID-19 pandemic has led to massive infections and deaths and caused tremendous grief among the people. Although vaccines have played an important role in fighting COVID-19, the situation that the protective effect of current vaccines significantly decreases against mutated strains reminds us of the pressing need for developing effective antiviral therapeutics. The main protease (Mpro) is a key enzyme for SARS-CoV-2 viral replication and transcription and an attractive target for drug development. In this research, we report a new series of Mpro inhibitors containing 3-phenyl-1,2,4-oxadiazole. Structure-activity relationship (SAR) studies led to the discovery of the most active compound, 16d, which showed an IC50 value of 5.27 ± 0.26 µM. Collectively, we obtained a new small molecular inhibitor targeting SARS-CoV-2 Mpro, which contains a new scaffold. This compound could be taken as a lead compound for subsequent drug discovery against SARS-CoV-2.

A Review of Computational Approaches Targeting SARS-CoV-2 Main Protease to the Discovery of New Potential Antiviral Compounds.

The new pandemic produced by coronavirus (SARS-CoV-2) has becomes the biggest challenge that the world is facing today. It has been creating a devastating global crisis, causing countless deaths and great panic. The search for an effective treatment remains a global challenge owing to controversies on available vaccines. A huge research effort (clinical, experimental, and computational) has emerged in response to this pandemic, and more than 125000 research reports have been published in relation with COVID-19. The majority of them focused on the discovery of novel drug candidates or repurposing of existing drugs through computational approaches that significantly speed up drug discovery. Among the different used targets, the SARS-CoV-2 main protease (Mpro), which plays an essential role in coronavirus replication, has become the preferred target for computational studies. In this review, we examine a representative set of computational studies that uses the Mpro as target for the discovery of COVID-19 small molecules. They will be divided into two main groups, structure-based, and ligand-based methods, and each one will be subdivided according to the strategies used in the research. From our point of view, the use of combined strategies could enhance the possibilities of success in the future, permitting to develop more rigorous computational studies in future efforts to combat current and future pandemics.

N-Containing α-Mangostin Analogs via Smiles Rearrangement as the Promising Cytotoxic, Antitrypanosomal, and SARS-CoV-2 Main Protease Inhibitory Agents.

New N-containing xanthone analogs of α-mangostin were synthesized via one-pot Smiles rearrangement. Using cesium carbonate in the presence of 2-chloroacetamide and catalytic potassium iodide, α-mangostin (1) was subsequently transformed in three steps to provide ether 2, amide 3, and amine 4 in good yields at an optimum ratio of 1:3:3, respectively. The evaluation of the biological activities of α-mangostin and analogs 2-4 was described. Amine 4 showed promising cytotoxicity against the non-small-cell lung cancer H460 cell line fourfold more potent than that of cisplatin. Both compounds 3 and 4 possessed antitrypanosomal properties against Trypanosoma brucei rhodesiense at a potency threefold stronger than that of α-mangostin. Furthermore, ether 2 gave potent SARS-CoV-2 main protease inhibition by suppressing 3-chymotrypsinlike protease (3CLpro) activity approximately threefold better than that of 1. Fragment molecular orbital method (FMO-RIMP2/PCM) indicated the improved binding interaction of 2 in the 3CLpro active site regarding an additional ether moiety. Thus, the series of N-containing α-mangostin analogs prospectively enhance druglike properties based on isosteric replacement and would be further studied as potential biotically active chemical entries, particularly for anti-lung-cancer, antitrypanosomal, and anti-SARS-CoV-2 main protease applications.

[Identifying SARS-CoV-2 main protease inhibitors by a novel sandwich-like fluorescence polarization screening assay].

SARS-CoV-2 main protease (Mpro) is responsible for polyprotein cleavage to release non-structural proteins (nsps) for viral genomic RNA replication, and its homologues are absent in human cells. Therefore, Mpro has been regarded as one of the ideal drug targets for the treatment of coronavirus disease 2019 (COVID-19). In this study, we first combined the fluorescence polarization (FP) technique with biotin-avidin system (BAS) to develop a novel sandwich-like FP screening assay for quick discovery of SARS-CoV-2 Mpro inhibitors from a natural product library. With this screening assay, anacardic acid (AA) and 1, 2, 3, 4, 6-O-pentagalloylglucose (PGG) were found to be the competitive inhibitor and mixed-type inhibitor targeting Mpro, respectively. Importantly, our results showed that the majority of the reported Mpro inhibitors are promiscuous cysteine inhibitors that are not specific to Mpro. In summary, this novel sandwich-like FP screening assay is simple, sensitive, and robust, which is ideal for large-scale screening. Natural products AA and PGG will be the promising lead compounds for generating more potent antiviral agents targeting Mpro, and the stringent hit validation at the early stage of drug discovery is urgently needed.

[Discovery of SARS-CoV-2 main protease inhibitors using an optimized FRET-based high-throughput screening assay].

For rapid discovery of novel SARS-CoV-2 main protease (Mpro) inhibitors, an optimized fluorescence resonance energy transfer (FRET)-based high-throughput screening (HTS) assay was developed. The recombinant Mpro was expressed in Escherichia coli Rosetta (DE3) cells and the specific activity of purified Mpro was assessed by a FERT assay using a fluorescently labeled substrate. Subsequently, the reaction buffer, working concentration of Mpro, incubation temperature and length, and DMSO tolerance were systematically optimized. The Mpro was solubly expressed in E. coli cells and exhibited an expected enzymatic activity (40 000 U/mg) in a FRET assay. Through these systematic optimizations, we selected 0.4 µmol/L Mpro and 5 µmol/L FRET substrate as the optimal working concentrations in this FRET screening assay, and a high Z' factor of 0.79 was achieved. More importantly, the addition of reducing reagent 1, 4-dithiothreitol in reaction buffer is necessary to faithfully assess the reliability of the screening assay. Using this assay, plumbagin (PLB) and ginkgolic acid (GA) were identified as potential Mpro inhibitors in vitro from a natural product library. In summary, we developed an optimized FRET-based HTS assay for the discovery of Mpro inhibitors, and PLB and GA could serve as the promissing lead compounds to generate more potent antiviral agents targeting SARS-CoV-2 Mpro.

Indole alkaloids as potential candidates against COVID-19: an in silico study.

COVID-19 has recently grown to be pandemic all around the world. Therefore, efforts to find effective drugs for the treatment of COVID-19 are needed to improve humans' life quality and survival. Since the main protease (Mpro) of SARS-CoV-2 plays a crucial role in viral replication and transcription, the inhibition of this enzyme could be a promising and challenging therapeutic target to fight COVID-19. The present study aims to identify alkaloid compounds as new potential inhibitors for SARS-CoV-2 Mpro by the hybrid modeling analyses. The docking-based virtual screening method assessed a collection of alkaloids extracted from over 500 medicinal plants and sponges. In order to validate the docking process, classical molecular dynamic simulations were applied on selected ligands, and the calculation of binding free energy was performed. Based on the proper interactions with the active site of the SARS-CoV-2 Mpro, low binding energy, few side effects, and the availability in the medicinal market, two indole alkaloids were found to be potential lead compounds that may serve as therapeutic options to treat COVID-19. This study paves the way for developing natural alkaloids as stronger potent antiviral agents against the SARS-CoV-2.

Blockage of the Monoamine Oxidase by a Natural Compound to Overcome Parkinson's Disease via Computational Biology

The dopamine (DA) metabolism changes are significant in Parkinson's disease (PD). Levels of monoamine oxidases (MAOs) play a critical role in DA metabolism and oxidative damage. Increased levels of the MAO-B enzyme in the elderly raise oxidative damage and enhance neurodegenerative processes. Inhibiting MAO-B as an attractive target would be the best method for treating and understanding Parkinson's disease. This study aimed to recognize a suitable inhibitor for the MAO-B enzyme using computational biology and compared it with Safinamide as a positive control. We used various computational biology techniques such as binding free energy, virtual screening, molecular dynamics (MD), and docking considerations to achieve the goal. To obtain a potent inhibitor, 41,852 compounds were taken from the Zinc database. After preparing compounds and the MAO-B enzyme, screening was performed using AutoDock Vina software. After screening, a potent natural inhibitor (ZINC00261335) was picked, and then, subsequent MD simulations for both ZINC00261335 and Safinamide were conducted via GROMACS software. The stability of the MAO-B_ZINC00261335 complex was excellent during the simulation, and the results of MM-PBSA analysis explicated that ZINC00261335 with (-118.353kJmol-1) is more potent than Safinamide (-89.305kJmol-1). Ultimately, the ADME study (lipophilicity, drug similarity and pharmacokinetic parameters) for ZINC00261335 was revealed, which is acceptable for human use. This study indicates that ZINC00261335 is a suitable MAO-B inhibitor and a great candidate for more laboratory studies.

Development of a simple and miniaturized sandwich-like fluorescence polarization assay for rapid screening of SARS-CoV-2 main protease inhibitors.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly transmissible and has caused a pandemic named coronavirus disease 2019 (COVID-19), which has quickly spread worldwide. Although several therapeutic agents have been evaluated or approved for the treatment of COVID-19 patients, efficacious antiviral agents are still lacking. An attractive therapeutic target for SARS-CoV-2 is the main protease (Mpro), as this highly conserved enzyme plays a key role in viral polyprotein processing and genomic RNA replication. Therefore, the identification of efficacious antiviral agents against SARS-CoV-2 Mpro using a rapid, miniaturized and economical high-throughput screening (HTS) assay is of the highest importance at the present. RESULTS: In this study, we first combined the fluorescence polarization (FP) technique with biotin-avidin system (BAS) to develop a novel and step-by-step sandwich-like FP screening assay to quickly identify SARS-CoV-2 Mpro inhibitors from a natural product library. Using this screening assay, dieckol, a natural phlorotannin component extracted from a Chinese traditional medicine Ecklonia cava, was identified as a novel competitive inhibitor against SARS-CoV-2 Mpro in vitro with an IC50 value of 4.5 ± 0.4 µM. Additionally, dieckol exhibited a high affinity with SARS-CoV-2 Mpro using surface plasmon resonance (SPR) analysis and could bind to the catalytic sites of Mpro through hydrogen-bond interactions in the predicted docking model. CONCLUSIONS: This innovative sandwich-like FP screening assay enables the rapid discovery of antiviral agents targeting viral proteases, and dieckol will be an excellent lead compound for generating more potent and selective antiviral agents targeting SARS-CoV-2 Mpro.

Structure-based virtual screening and molecular dynamics simulation studies to discover new SARS-CoV-2 main protease inhibitors.

Computational methods were used to filter two datasets (> 8,000 compounds) based on two criteria: higher binding affinity for MPRO than cocrystallized inhibitor and binding interactions with MPRO catalytic dyad (Cys145 and His41). After virtual screening involving ranking and reranking, eleven compounds were identified to satisfy these criteria and analysis of their structures revealed an unparallel common features among them which could be critical for their interactions with MPRO. However, only the topmost scoring compound (AV-203: K i = 0.31 µM) exhibited relatively stable binding interaction during the period of 50 ns MD simulation and thus is a suitable template for drug development.

Protease inhibitor GC376 for COVID-19: Lessons learned from feline infectious peritonitis.

The main protease (Mpro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important therapeutic target as it plays a major role in the processing and maturation of the viral polyprotein. GC376 is a pre-clinical dipeptide-based protease inhibitor that has been previously used for managing feline infectious peritonitis virus (FIPV). Since both GC373 and GC376 have already been successfully used in treating animal coronavirus infection, they can be considered as strong drug candidates for COVID-19 in humans. GC376 is a broad-spectrum antiviral drug that inhibits Mpro of several viruses, including the coronaviruses like feline coronavirus, porcine epidemic diarrhoea virus, severe acute respiratory syndrome coronavirus, Middle East respiratory syndrome coronavirus, ferret, and mink coronavirus. However, further studies should be conducted to evaluate the potency, efficacy, and safety of these broad-spectrum Mpro inhibitors in patients with COVID-19. The lessons learned from the successful use of drug candidates for treating animal coronavirus infections will help us to develop framework for their use in human trials.

Structure-based identification of potential SARS-CoV-2 main protease inhibitors.

To address coronavirus disease (COVID-19), currently, no effective drug or vaccine is available. In this regard, molecular modeling approaches are highly useful to discover potential inhibitors of the main protease (Mpro) enzyme of SARS-CoV-2. Since, the Mpro enzyme plays key roles in mediating viral replication and transcription; therefore, it is considered as an attractive drug target to control SARS-CoV-2 infection. By using structure-based drug design, pharmacophore modeling, and virtual high throughput drug screening combined with docking and all-atom molecular dynamics simulation approach, we have identified five potential inhibitors of SARS-CoV-2 Mpro. MD simulation studies revealed that compound 54035018 binds to the Mpro with high affinity (ΔGbind -37.40 kcal/mol), and the complex is more stable in comparison with other protein-ligand complexes. We have identified promising leads to fight COVID-19 infection as these compounds fulfill all drug-likeness properties. However, experimental and clinical validations are required for COVID-19 therapy.Communicated by Ramaswamy H. Sarma.

The coronavirus disease 2019 main protease inhibitor from Andrographis paniculata (Burm. f) Ness.

The coronavirus disease 2019 (COVID-19) pandemic has attracted worldwide attention. Andrographis paniculata (Burm. f) Ness (AP) is naturally used to treat various diseases, including infectious diseases. Its Andrographolide has been clinically observed for anti-HIV and has also in silico tested for COVID-19 main protease inhibitors. Meanwhile, the AP phytochemicals content also provides insight into the molecular structures diversity for the bioactive discovery. This study aims to find COVID-19 main protease inhibitor from AP by the molecular docking method and determine the toxicity profile of the compounds. The results obtained two compounds consisting of flavonoid glycosides 5,4'-dihydroxy-7-O-ß -D-pyran-glycuronate butyl ester and andrographolide glycoside 3-O-ß-D-glucopyranosyl-andrographolide have lower free binding energy and highest similarity in types of interaction with amino acid residues compared to its co-crystal ligands (6LU7) and Indinavir or Remdesivir. The toxicity prediction of the compounds also reveals their safety. These results confirm the probability of using AP phytochemical compounds as COVID-19 main protease inhibitors, although further research must be carried out.

1,2,4 triazolo[1,5-a] pyrimidin-7-ones as novel SARS-CoV-2 Main protease inhibitors: In silico screening and molecular dynamics simulation of potential COVID-19 drug candidates.

Discovery of a potent SARS-CoV-2 main protease (Mpro) inhibitor is the need of the hour to combat COVID-19. A total of 1000 protease-inhibitor-like compounds available in the ZINC database were screened by molecular docking with SARS-CoV-2 Mpro and the top 2 lead compounds based on binding affinity were found to be 1,2,4 triazolo[1,5-a] pyrimidin-7-one compounds. We report these two compounds (ZINC000621278586 and ZINC000621285995) as potent SARS-CoV-2 Mpro inhibitors with high affinity (<-9 kCal/mol) and less toxicity than Lopinavir and Nelfinavir positive controls. Both the lead compounds effectively interacted with the crucial active site amino acid residues His41, Cys145 and Glu166. The lead compounds satisfied all of the druglikeness rules and devoid of toxicity or mutagenicity. Molecular dynamics simulations showed that both lead 1 and lead 2 formed stable complexes with SARS-CoV-2 Mpro as evidenced by the highly stable root mean square deviation (<0.23 nm), root mean square fluctuations (0.12 nm) and radius of gyration (2.2 nm) values. Molecular mechanics Poisson-Boltzmann surface area calculation revealed thermodynamically stable binding energies of -129.266 ± 2.428 kJ/mol and - 116.478 ± 3.502 kJ/mol for lead1 and lead2 with SARS-CoV-2 Mpro, respectively.