Structure-based design of antiviral drug candidates targeting the SARS-CoV-2 main protease.

To semisynthesise piperazine derivatives of betulinic acid to evaluate antimalarial activity, cytotoxicity and action mechanism. The new derivatives were evaluated against the CQ-sensitive Plasmodium falciparum 3D7 strain by flow cytometry (FC) using YOYO-1 as stain. Cytotoxicity of 4a and 4b was performed with HEK293T cells for 24 and 48 h by MTT assay. The capability of compound 4a to modulate Ca(2+) in the trophozoite stage was investigated. The trophozoites were stained with Fluo4-AM and analysed by spectrofluorimetry. Effect on mitochondrial membrane potential (ΔΨm) was tested for 4a by FC with DiOC6 (3) as stain. For β-haematin assay, 4a was incubated for 24 h with reagents such as haemin, and the fluorescence was measured by FlexStation at an absorbance of 405 nm. Antimalarial activity of 4a and 4b was IC50 = 1 and 4 μm, respectively. Compound 4a displayed cytotoxicity with IC50 = 69 and 29 μm for 24 and 48 h, respectively, and 4b was not cytotoxic at the tested concentrations. Addition of 4a leads to an increase in cytosolic Ca(2+) . We have measured ΔΨm after treating parasites with the compound. Data on Figure 4a show that mitochondria were not affected. The action mechanism for 4a, inhibition of β-haematin formation (17%), was lower than CQ treatment (83%; IC50 = 3 mm). Compound 4a showed excellent antimalarial activity, and its action mechanism is involved in Ca(2+) pathway(s).

Endemic and pandemic viruses represent significant public health challenges, leading to substantial morbidity and mortality over time. The COVID-19 pandemic has underscored the urgent need for the development and discovery of new, potent antiviral agents. In this study, we present the synthesis and anti-SARS-CoV-2 activity of a series of benzocarbazoledinones, assessed using cell-based screening assays. Our results indicate that four compounds (4a, 4b, 4d, and 4i) exhibit EC50 values below 4 μM without cytotoxic effects in Calu-3 cells. Mechanistic investigations focused on the inhibition of the SARS-CoV-2 main protease (Mpro) and papain-like protease (PLpro) have used enzymatic assays. Notably, compounds 4a and 4b showed Mpro inhibition activity with IC50 values of 0.11 ± 0.05 and 0.37 ± 0.05 µM, respectively. Furthermore, in silico molecular docking, physicochemical, and pharmacokinetic studies were conducted to validate the mechanism and assess bioavailability. Compound 4a was selected for preliminary drug-likeness analysis and in vivo pharmacokinetics investigations, which yielded promising results and corroborated the in vitro and in silico findings, reinforcing its potential as an anti-SARS-CoV-2 lead compound.

The present study aimed to assess the repurposing potential of existing antiviral drug candidates (FDA-approved and investigational) against SARS-CoV-2 target proteins that facilitates viral entry and replication into the host body. To evaluate molecular affinities between antiviral drug candidates and SARS-CoV-2 associated target proteins such as spike protein (S) and main protease (Mpro ), a molecular interaction simulation was performed by docking software (MVD) and subsequently the applicability score was calculated by machine learning algorithm. Furthermore, the STITCH algorithm was used to predict the pharmacology network involving multiple pathways of active drug candidate(s). Pharmacophore features of active drug(s) molecule was also determined to predict structure-activity relationship (SAR). The molecular interaction analysis showed that cordycepin has strong binding affinities with S protein (-180) and Mpro proteins (-205) which were relatively highest among other drug candidates used. Interestingly, compounds with low IC50 showed high binding energy. Furthermore, machine learning algorithm also revealed high applicability scores (0.42-0.47) of cordycepin. It is worth mentioning that the pharmacology network depicted the involvement of cordycepin in different pathways associated with bacterial and viral diseases including tuberculosis, hepatitis B, influenza A, viral myocarditis, and herpes simplex infection. The embedded pharmacophore features with cordycepin also suggested strong SAR. Cordycepin's anti-SARS-CoV-2 activity indicated 65% (E-gene) and 42% (N-gene) viral replication inhibition after 48h of treatment. Since, cordycepin has both preclinical and clinical evidences on antiviral activity, in addition the present findings further validate and suggest repurposing potential of cordycepin against COVID-19.

A new coronavirus has been identified as the contributing agent of the severe acute respiratory syndrome (SARS). The main viral protease (Mpro), which controls the activities of the coronavirus replication complex, which is an essential target for the treatment of coronavirus disease. With the primary objective of targeting this receptor, we designed a new series of pyrrolo [3,2-c] pyrroles, synthesized and characterized using various analytical techniques including FT-IR, UV-Vis and NMR spectroscopic studies. The biological descriptors of the synthesized compounds were investigated using DFT calculation. The mode of binding and reactivity of the target compounds with SARS-CoV-2 main protease (Mpro) were studied using molecular docking and molecular dynamics (MD) simulation. Molecular docking of the compounds (4a and 5a) showed a promising binding affinity towards Mpro protein with the binding energy of −7.8 kcal/mol and −7.0 kcal/mol, respectively. The results of MD simulation and prime MM-GBSA calculation were consistent with molecular docking. The absorption, distribution, metabolism and excretion (ADME) properties of the compounds are in the acceptable range, as they are orally active and obey Lipinski’s rule of five without violation. In addition, in silico toxicity prediction using the Pro-Tox II revealed the non-toxic nature of the compounds. Hence the obtained results suggest that these compounds could be a possible anti-viral candidate and highlight this series of compounds for further drug design and development against SARS-CoV-2. Communicated by Ramaswamy H. Sarma

The main protease (Mpro, also known as 3CLpro), a pivotal enzyme of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been considered a prime target for drug development due to its crucial role in viral replication and transcription. Importantly, a high degree of conservation in more than 13 million SARS-CoV-2 sequences affords Mpro as a promising target for antiviral therapy to impede the genetic evolution of SARS-CoV-2. In this work, ∼16 million compounds from various small molecule databases were screened using ligand-based virtual screening (LBVS) with boceprevir as the reference compound to identify new small molecule inhibitors of Mpro. Boceprevir [hepatitis C virus (HCV) drug] has been repurposed as a drug candidate against Mpro activity (IC50 = 4.13 ± 0.61 μM). The lead compounds exhibiting higher binding affinities (-9.9 to -8.0 kcal mol-1) than boceprevir (-7.5 kcal mol-1) were identified from a library of 850 compounds using molecular docking. Furthermore, molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analysis depicted ChEMBL144205 (C3), ZINC000091755358 (C5), and ZINC000092066113 (C9) with binding affinities of -65.2 ± 6.5, -66.1 ± 7.1, and -67.3 ± 5.8 kcal mol-1, respectively, as high-affinity binders to Mpro. The identified compounds displayed a favourable drug-likeness profile without violating Lipinski's rule of five. Molecular dynamics (MD) simulations revealed the higher structural stability and reduced residue-level fluctuations in Mpro upon binding of C3, C5, and C9 as compared to apo-Mpro and Mpro-boceprevir. Notably, conformational clustering and FEL analyses depicted hydrogen bond interactions of C3 with Thr26, oxyanion hole residues (Asn142 and Gly143), the catalytic residue (Cys145), and Glu166 of Mpro, suggesting its strong binding affinity and potential inhibitory effect. The integrated computational methodology employed in this work identified promising lead compounds against Mpro activity, which warrants further experimental validation to develop them as antiviral agents against SARS-CoV-2.

Analysis of SARS-CoV-2 mutations in the main viral protease (NSP5) and its implications on the vaccine designing strategies

Analysis of SARS-CoV-2 mutations in the main viral protease (NSP5) and its implications on the vaccine designing strategies

A new pathogen severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide and become pandemic with thousands new deaths and infected cases globally. To treat the patients with coronavirus disease (COVID-19), currently no effective drug or vaccine is available. This necessity motivated us to explore potential lead compounds based natural products targeting main protease (Mpro) enzyme of SARS-CoV-2. The Mpro enzyme plays a key role in mediating viral replication and transcription and thus being considered as an attractive drug target. Herein, comprehensive computational investigations were performed to identify new lead compounds against main protease enzyme. In this study, the candidate anthocyanin-derived compounds from PubChem database were filtered considering antiviral characteristics of anthocyanins. The structure-based pharmacophore modeling was developed based on the co-crystallized structure of the enzyme with its biological active inhibitor. The generated hypotheses were applied for virtual screening-based PHASE Screen Score. Docking based virtual screening work flow was used to generate hit compounds using HTVS, SP and XP based Glide Gscore. The obtained hit compounds were filtered using ADMET pharmacological and physicochemical properties screening. Molecular dynamics simulations were performed to explore the binding affinities of the considered compounds. Our study identified six best anthocyanin-derived natural compounds which could be used as promising lead compounds against main protease SARS-CoV-2 virus.

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) poses an enormous challenge to human health and economy at a global level. According to WHO's latest data, till now, there have been a total of 641,435,884 confirmed cases of COVID-19, and the associated deaths are 6,621,060. Though few vaccinations have been approved for emergency usage, antiviral medications for long-term therapeutics are still being sought. The current research seeks to identify the inhibitory effect of iminosugars, particularly 1-deoxynojirmycin (IDNJ) series, against SARS-CoV-2 main protease (SARS-CoV2-Mpro) using an inhibitor optimization approach for 1DNJ series. The aim of this study was to investigate the inhibitory effect of iminosugars, specifically 1-deoxynojirmycin (1-DNJ) derivatives, on SARS-CoV-2 main protease (Mpro) as it plays a vital role in viral propagation and transcription and is shaped like a heart. The main objective of this study was to find the possibility of 1-DNJ derivatives being potent inhibitors against SARS CoV2 Mpro. This study was focused on finding the most probable conformation in which DNJ derivatives could bind to Mpro. Another objective was to obtain molecular-level details by getting insights into stable interactions formed between the ligand and receptor. In silico molecular mechanics (MM) based techniques were employed to identify the best-docked inhibitors using molecular docking, and complexes that showed stable interactions were further subjected to 200 ns of molecular dynamics (MD) simulations to check the stability of ligand into the binding pocket of SARS-CoV2-Mpro. The inhibitors that formed stable complexes were further tested for their ADME properties in order to check the pharmacokinetic parameters as well as their therapeutic importance. Docking was performed on 29 compounds from two different series against SARS-CoV-2 main protease, Mpro (PDB ID: 6LZE). Twelve compounds were found to have high docking scores and better interactions with the active site of Mpro, as compared to the co-crystallized ligand. Furthermore, the three highest-scoring docked compounds (17a, 7, and 8) depicted strong and stable complex formation, throughout the 200 ns molecular dynamics simulation, by analyzing the binding energy (MM/GBSA). The molecules were discovered to form stable interactions with conserved active-site residues, which play an important role in demonstrating activity in structure-based drug design. The ADMET analysis was performed using Qikprop, and the proposed stable derivatives passed all of the needed drug discovery standards, potentially inhibiting the Mpro of SARS-CoV-2. The present findings confer opportunities for compounds 17a, 7, and 8 that could be developed as new therapeutic agents against COVID-19. These compounds are suggested on the basis of pharmacokinetic parameters as well as therapeutic importance and hence could be tested in-vitro.

Aim: The identification of drugs for the coronavirus disease-19 pandemic remains urgent. In this manner, drug repurposing is a suitable strategy, saving resources and time normally spent during regular drug discovery frameworks. Essential for viral replication, the main protease has been explored as a promising target for the drug discovery process. Materials & methods: Our virtual screening pipeline relies on the known 3D properties of noncovalent ligands and features of crystalized complexes, applying consensus analyses in each step. Results: Two oral (bedaquiline and glibenclamide) and one buccal drug (miconazole) presented 3D similarity to known ligands, reasonable predicted binding modes and micromolar predicted binding affinity values. Conclusion: We identified three approved drugs as promising inhibitors of the main viral protease and suggested design insights for future studies for development of novel selective inhibitors.

The COVID-19 pandemic is spreading rapidly due to the outbreak of novel coronavirus SARS-CoV-2 across the globe. Anti-COVID-19 drugs are urgently required in this situation. In this regard, the discovery of promising new anti-COVID-19 moieties is expected from traditional medicine. The study is aimed to discover phytochemicals of Cocculus hirsutus having anti-COVID-19 activity via inhibiting main proteases of SARS-CoV-2. Main proteases (Mpro) of SARS-CoV-2 serve as a protuberant target for anti-COVID-19 drug discovery because it is a key enzyme of coronaviruses and has a pivotal role in mediating viral replication and transcription that makes it an attractive drug target. Recent studies indicated the utility of C. hirsutus in the treatment of viral disorders like Dengue. Phytochemicals from C. hirsutus were docked against SARS-CoV-2 main proteases (6LU7, 5R7Y, 5R7Z, 5R80, 5R81, 5R82) using the PyRx virtual screen tool and discovery studio visualizer. Further, molecular dynamics simulations were performed (for 100 ns) to see conformational stability for all complexes. Pharmacokinetic properties and drug-likeness prediction of selected C. hirsutus phytoconstituents were also performed. Betulin, coclaurine, and quinic acid of C. hirsutus were found promising with significant binding affinity to SARS-CoV-2 Mpro in comparison to control. They have shown stable interactions with the amino acid residues present on the active site of most of the SARS-CoV-2 Mpro and were found as promising anti-COVID-19 candidates. These compounds could be potential leads for the development of target-specific anti-COVID-19 therapeutics while ethnomedicinal uses of this herb could further needed for its detailed antiviral therapeutic exploration. Communicated by Ramaswamy H. Sarma

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has fomented a climate of fear worldwide due to its rapidly spreading nature, and high mortality rate. The World Health Organization (WHO) declared it as a global pandemic on 11th March, 2020. Many endeavors have been made to find appropriate medications to restrain the SARS CoV-2 infection from spreading but there is no specific antiviral therapy to date. However, a computer-aided drug design approach can be an alternative to identify probable drug candidates within a short time. SARS-CoV-2 main protease is a proven drug target, and it plays a pivotal role in viral replication and transcription. Methods: In this study, we identified a total of 114 essential oil compounds as a feasible anti-SARS-CoV-2 agent from several online reservoirs. These compounds were screened by incorporating ADMET profiling, molecular docking, and 50 ns of molecular dynamics simulation to identify potential drug candidates against the SARS-CoV-2 main protease. The crystallized SARS-CoV-2 main protease structure was collected from the RCSB PDB database (PDB ID 6LU7). Results: According to the results of the ADMET study, none of the compounds have any side effects that could reduce their druglikeness or pharmacokinetic properties. Out of 114 compounds, we selected bisabololoxide B, eremanthin, and leptospermone as our top drug candidates based on their higher binding affinity scores, and strong interaction with the Cys 145-His 41 catalytic dyad. Finally, the molecular dynamics simulation was implemented to evaluate the structural stability of the ligand-receptor complex. MD simulations disclosed that all the hits showed conformational stability compared to the positive control α-ketoamide. Conclusions: Our study showed that the top three hits might work as potential anti-SARS-CoV-2 agents, which can pave the way for discovering new drugs, but for experimental validation, they will require more in vivo trials.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has fomented a climate of fear worldwide due to its rapidly spreading nature, and high mortality rate. The World Health Organization (WHO) declared it as a global pandemic on 11th March, 2020. Many endeavors have been made to find appropriate medications to restrain the SARS CoV-2 infection from spreading but there is no specific antiviral therapy to date. However, a computer-aided drug design approach can be an alternative to identify probable drug candidates within a short time. SARS-CoV-2 main protease is a proven drug target, and it plays a pivotal role in viral replication and transcription. Methods: In this study, we identified a total of 114 essential oil compounds as a feasible anti-SARS-CoV-2 agent from several online reservoirs. These compounds were screened by incorporating ADMET profiling, molecular docking, and 50 ns of molecular dynamics simulation to identify potential drug candidates against the SARS-CoV-2 main protease. The crystallized SARS-CoV-2 main protease structure was collected from the RCSB PDB database (PDB ID 6LU7). Results: According to the results of the ADMET study, none of the compounds have any side effects that could reduce their druglikeness or pharmacokinetic properties. Out of 114 compounds, we selected bisabololoxide B, eremanthin, and leptospermone as our top drug candidates based on their higher binding affinity scores, and strong interaction with the Cys 145-His 41 catalytic dyad. Finally, the molecular dynamics simulation was implemented to evaluate the structural stability of the ligand-receptor complex. MD simulations disclosed that all the hits showed conformational stability compared to the positive control α-ketoamide. Conclusions: Our study showed that the top three hits might work as potential anti-SARS-CoV-2 agents, which can pave the way for discovering new drugs, but for experimental validation, they will require more in vivo trials.

Molecular docking and dynamics simulation study of medicinal fungi derived secondary metabolites as potential inhibitor for COVID-19 treatment

Tetrahydro-4H-chromene-3-carbonitrile derivatives 4a-c where prepared from the reaction of 1,4-cyclohexane dione (1), malononitrile (2) and either of benzaldehyde (3a), 2-chlorobenzaldehyde (3b) or 4-methoxybenzaldehyde (3c) in ethanol containing triethylamine. Compound 4b was used to prepare pyrazole, pyrimidine and thiazole derivatives. Moreover, tetrahydrobenzo[d]thiazole derivative 18 was prepared from the reaction of 1,4-cyclohexane dione (1) with elemental sulfur followed by phenyl isothiocyanate (12) in absolute ethanol containing triethylamine. The latter compound reacted with ethyl orthoformate and either malononitrile or ethyl cyanoacetate in 1,4-dioxane in the presence of triethylamine to produce the 9-ethoxy-2H-chromeno[6,5-d]thiazole derivatives 20a,b. In addition, fused thiophene and pyran derivatives were synthesized starting from compound 18. The screened compounds were designed as mimics of the transition state of RNA2’-O-methylation were screened against several viral RNA 2’-OMTases from SARS-CoV (nsp10/nsp16 complex), Zika, West Nile, dengue, vaccinia (VP39) viruses. At the same time, the compounds were tested against human RNA N7-MTase (hRNMT) and selected viral N7-MTases such as SARS-CoV nsp14 and vaccinia D1-D12 complex to evaluate their specificity. Compounds 4a, 4b, 6b, 6c, 6e, 9a, 9b, 15, 16, 21b, and 23b showed high % inhibitions against SARs-Cov nsp 14 with values 93.42, 87.49, 98.23, 88.15, 89.24, 96.31, 93.28, 89.25, 89.20, 87.24, and 94.49, respectively.