Development and validation of consensus machine learning-based models for the prediction of novel small molecules as potential anti-tubercular agents.

Tuberculosis (TB) is an infectious disease and the leading cause of death globally. The rapidly emerging cases of drug resistance among pathogenic mycobacteria have been a global threat urging the need of new drug discovery and development. However, considering the fact that the new drug discovery and development is commonly lengthy and costly processes, strategic use of the cutting-edge machine learning (ML) algorithms may be very supportive in reducing both the cost and time involved. Considering the urgency of new drugs for TB, herein, we have attempted to develop predictive ML algorithms-based models useful in the selection of novel potential small molecules for subsequent in vitro validation. For this purpose, we used the GlaxoSmithKline (GSK) TCAMS TB dataset comprising a total of 776 hits that were made publicly available to the wider scientific community through the ChEMBL Neglected Tropical Diseases (ChEMBL-NTD) database. After exploring the different ML classifiers, viz. decision trees (DT), support vector machine (SVM), random forest (RF), Bernoulli Naive Bayes (BNB), K-nearest neighbors (k-NN), and linear logistic regression (LLR), and ensemble learning models (bagging and Adaboost) for training the model using the GSK dataset, we concluded with three best models, viz. Adaboost decision tree (ABDT), RF classifier, and k-NN models that gave the top prediction results for both the training and test sets. However, during the prediction of the external set of known anti-tubercular compounds/drugs, it was realized that each of these models had some limitations. The ABDT model correctly predicted 22 molecules as actives, while both the RF and k-NN models predicted 18 molecules correctly as actives; a number of molecules were predicted as actives by two of these models, while the third model predicted these compounds as inactives. Therefore, we concluded that while deciding the anti-tubercular potential of a new molecule, one should rely on the use of consensus predictions using these three models; it may lessen the attrition rate during the in vitro validation. We believe that this study may assist the wider anti-tuberculosis research community by providing a platform for predicting small molecules with subsequent validation for drug discovery and development.

Selective Cannabinoid 2 Receptor Stimulation Reduces Tubular Epithelial Cell Damage after Renal Ischemia-Reperfusion Injury.

Ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI), which is an increasing problem in the clinic and has been associated with elevated rates of mortality. Therapies to treat AKI are currently not available, so identification of new targets that can be modulated to ameliorate renal damage upon diagnosis of AKI is essential. In this study, a novel cannabinoid receptor 2 (CB2) agonist, SMM-295 [3'-methyl-4-(2-(thiophen-2-yl)propan-2-yl)biphenyl-2,6-diol], was designed, synthesized, and tested in vitro and in silico. Molecular docking of SMM-295 into a CB2 active-state homology model showed that SMM-295 interacts well with key amino acids to stabilize the active state. In human embryonic kidney 293 cells, SMM-295 was capable of reducing cAMP production with 66-fold selectivity for CB2 versus cannabinoid receptor 1 and dose-dependently increased mitogen-activated protein kinase and Akt phosphorylation. In vivo testing of the CB2 agonist was performed using a mouse model of bilateral IRI, which is a common model to mimic human AKI, where SMM-295 was immediately administered upon reperfusion of the kidneys after the ischemia episode. Histologic damage assessment 48 hours after reperfusion demonstrated reduced tubular damage in the presence of SMM-295. This was consistent with reduced plasma markers of renal dysfunction (i.e., creatinine and neutrophil gelatinase-associated lipocalin) in SMM-295-treated mice. Mechanistically, kidneys treated with SMM-295 were shown to have elevated activation of Akt with reduced terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine nick-end labeling (TUNEL)-positive cells compared with vehicle-treated kidneys after IRI. These data suggest that selective CB2 receptor activation could be a potential therapeutic target in the treatment of AKI.

Agonists of the γ-aminobutyric acid type B (GABAB) receptor derived from ß-hydroxy and ß-amino difluoromethyl ketones.

ß-Hydroxy difluoromethyl ketones represent the newest class of agonists of the GABA-B receptor, and they are structurally distinct from all other known agonists at this receptor because they do not display the carboxylic acid or amino group of γ-aminobutyric acid (GABA). In this report, the design, synthesis, and biological evaluation of additional analogues of ß-hydroxy difluoromethyl ketones characterized the critical nature of the substituted aromatic group on the lead compound. The importance of these new data is interpreted by docking studies using the X-ray structure of the GABA-B receptor. Moreover, we also report that the synthesis and biological evaluation of ß-amino difluoromethyl ketones provided the most potent compound across these two series.

Structure-Based Identification of Potent Natural Product Chemotypes as Cannabinoid Receptor 1 Inverse Agonists.

Natural products are an abundant source of potential drugs, and their diversity makes them a rich and viable prospective source of bioactive cannabinoid ligands. Cannabinoid receptor 1 (CB1) antagonists are clinically established and well documented as potential therapeutics for treating obesity, obesity-related cardiometabolic disorders, pain, and drug/substance abuse, but their associated CNS-mediated adverse effects hinder the development of potential new drugs and no such drug is currently on the market. This limitation amplifies the need for new agents with reduced or no CNS-mediated side effects. We are interested in the discovery of new natural product chemotypes as CB1 antagonists, which may serve as good starting points for further optimization towards the development of CB1 therapeutics. In search of new chemotypes as CB1 antagonists, we screened the in silico purchasable natural products subset of the ZINC12 database against our reported CB1 receptor model using the structure-based virtual screening (SBVS) approach. A total of 18 out of 192 top-scoring virtual hits, selected based on structural diversity and key protein⁻ligand interactions, were purchased and subjected to in vitro screening in competitive radioligand binding assays. The in vitro screening yielded seven compounds exhibiting >50% displacement at 10 µM concentration, and further binding affinity (Ki and IC50) and functional data revealed compound 16 as a potent and selective CB1 inverse agonist (Ki = 121 nM and EC50 = 128 nM) while three other compounds-2, 12, and 18-were potent but nonselective CB1 ligands with low micromolar binding affinity (Ki). In order to explore the structure⁻activity relationship for compound 16, we further purchased compounds with >80% similarity to compound 16, screened them for CB1 and CB2 activities, and found two potent compounds with sub-micromolar activities. Most importantly, these bioactive compounds represent structurally new natural product chemotypes in the area of cannabinoid research and could be considered for further structural optimization as CB1 ligands.

Novel, potent, orally bioavailable and selective mycobacterial ATP synthase inhibitors that demonstrated activity against both replicating and non-replicating M. tuberculosis.

The mycobacterial F0F1-ATP synthase (ATPase) is a validated target for the development of tuberculosis (TB) therapeutics. Therefore, a series of eighteen novel compounds has been designed, synthesized and evaluated against Mycobacterium smegmatis ATPase. The observed ATPase inhibitory activities (IC50) of these compounds range between 0.36 and 5.45µM. The lead compound 9d [N-(7-chloro-2-methylquinolin-4-yl)-N-(3-((diethylamino)methyl)-4-hydroxyphenyl)-2,3-dichlorobenzenesulfonamide] with null cytotoxicity (CC50>300µg/mL) and excellent anti-mycobacterial activity and selectivity (mycobacterium ATPase IC50=0.51µM, mammalian ATPase IC50>100µM, and selectivity >200) exhibited a complete growth inhibition of replicating Mycobacterium tuberculosis H37Rv at 3.12µg/mL. In addition, it also exhibited bactericidal effect (approximately 2.4log10 reductions in CFU) in the hypoxic culture of non-replicating M. tuberculosis at 100µg/mL (32-fold of its MIC) as compared to positive control isoniazid [approximately 0.2log10 reduction in CFU at 5µg/mL (50-fold of its MIC)]. The pharmacokinetics of 9d after p.o. and IV administration in male Sprague-Dawley rats indicated its quick absorption, distribution and slow elimination. It exhibited a high volume of distribution (Vss, 0.41L/kg), moderate clearance (0.06L/h/kg), long half-life (4.2h) and low absolute bioavailability (1.72%). In the murine model system of chronic TB, 9d showed 2.12log10 reductions in CFU in both lung and spleen at 173µmol/kg dose as compared to the growth of untreated control group of Balb/C male mice infected with replicating M. tuberculosis H37Rv. The in vivo efficacy of 9d is at least double of the control drug ethambutol. These results suggest 9d as a promising candidate molecule for further preclinical evaluation against resistant TB strains.

ClpP Peptidase as a Plausible Target for the Discovery of Novel Antibiotics.

Antimicrobial resistance (AMR) to currently available antibiotics/drugs is a global threat. It is desirable to develop new drugs that work through a novel target(s) to avoid drug resistance. This review discusses the potential of the caseinolytic protease P (ClpP) peptidase complex as a novel target for finding novel antibiotics, emphasising the ClpP's structure and function. ClpP contributes to the survival of bacteria via its ability to destroy misfolded or aggregated proteins. In consequence, its inhibition may lead to microbial death. Drugs inhibiting ClpP activity are currently being tested, but no drug against this target has been approved yet. It was demonstrated that Nblocked dipeptides are essential for activating ClpP's proteolytic activity. Hence, compounds mimicking these dipeptides could act as inhibitors of the formation of an active ClpP complex. Drugs, including Bortezomib, Cisplatin, Cefmetazole, and Ixazomib, inhibit ClpP activation. However, they were not approved as drugs against the target because of their high toxicity, likely due to the presence of strong electrophiles in their warheads. The modifications of these warheads could be a good strategy to reduce the toxicity of these molecules. For instance, a boronate warhead was replaced by a chloromethyl ketone, and this new molecule was shown to exhibit selectivity for prokaryotic ClpP. A better understanding of the structure and function of the ClpP complex would benefit the search for compounds mimicking N-blocked dipeptides that would inhibit ClpP complex activity and cause bacterial death.

Structural insights into small-molecule KRAS inhibitors for targeting KRAS mutant cancers.

The Kirsten rat sarcoma viral (KRAS) oncogene is the most frequently mutated isoform of RAS, associated with 85 % of RAS-driven cancers. KRAS functions as a signaling hub, participating in various cellular signaling pathways and regulating a wide range of important activities, including cell proliferation, differentiation, growth, metabolism, and migration. Despite being the most frequently altered oncogenic protein in solid tumors, over the past four decades, KRAS has historically been considered "undruggable" owing to a lack of pharmacologically targetable pockets within the mutant isoforms. However, improvements in drug design and development have culminated in the development of selective inhibitors for KRAS mutants. Recent developments have led to the successful targeting of the KRASG12C mutant through covalent inhibitors that exploit the unique cysteine residue introduced by the mutation at 12th position. These inhibitors bind covalently to C12, locking KRAS in its inactive GDP-bound state and preventing downstream signaling. Some of these inhibitors have shown encouraging results in KRASG12C mutant cancer patients but suffer from drug resistance, toxicity, and low therapeutic efficacy. Recently, there have been great advancements in the discovery of drugs that directly target the switch I (S-I), switch-II (S-II) and S-I/II interface sites of KRAS mutant proteins. These include KRASG12C inhibitors like AMG510 (Sotorasib) and MRTX849 (Adagrasib), which have got FDA approval for non-small cell lung cancer harboring the KRASG12C mutation. There is no approved drug for cancers harboring other KRAS mutations, although efforts have expanded to target other KRAS mutations and the Switch I/II interface, aiming to disrupt KRAS-driven oncogenic signaling. Structure-activity relationship (SAR) studies have been instrumental in optimizing the binding affinity, selectivity, and pharmacokinetic properties of these inhibitors, leading to the development of promising therapeutic agents like Sotorasib and Adagrasib. This review provides an overview of the KRAS pathway, KRAS binding sites, strategies for direct and indirect inhibition using small molecules, and SAR based on the co-crystal structures of inhibitors with KRAS mutants which is expected to offer new hope for patients with KRAS-driven cancers through the development of new KRAS-targeted drugs.

Deciphering insights into the binding mechanism and plasticity of Telacebec with M. tuberculosis cytochrome bcc-aa3 supercomplex through an unbiased molecular dynamics simulation, free-energy analysis, and DFT study.

The cytochrome bcc-aa3 supercomplex, a key component in the electron transport chain pathway involved in bacterial energy production and homeostasis, is a clinically validated target for tuberculosis (TB), leading to Telacebec (Q203). Telacebec is a potent candidate drug under Phase II clinical development for the treatment of drug-sensitive and drug-resistant TB. Recently, the cryo-electron microscopy structure of this supercomplex from Mycobacterium tuberculosis (Mtb) complexed with Q203 was resolved at 6.9 Å resolution (PDB ID: 7E1W). To understand the binding site (QP site) flexibility and Q203's stability at the QP site of the Mtb cytochrome bcc complex, we conducted molecular dynamics (MD) simulation and free energy analysis on this complex in an explicit hydrated lipid bilayer environment for 500 ns. Through this study, the persistence of a range of direct and indirect interactions was observed over the course of the simulation. The significance of the interactions with His375, Tyr161, Ala178, Ala179, Ile183, His355, Leu356, and Thr313 is underlined. Electrostatic energy was the primary source of the net binding free energy, regardless of the important interacting residues. The overall binding free energy for Q203 was -112.84 ± 7.73 kcal/mol, of which the electrostatic and lipophilic energy contributions were -116.31 ± 1.14 and -21.32 ± 2.35 kcal/mol, respectively. Meanwhile, DFT calculations were utilized to elucidate Q203's molecular properties. Overall, this study deciphers key insights into the cytochrome bcc-aa3 supercomplex with Q203 on the ground of molecular mechanics and quantum mechanics that may facilitate structure-based drug design and optimization for the discovery of the next-generation antitubercular drug(s).Communicated by Ramaswamy H. Sarma.

Identification and validation of novel non-nucleoside class of molecules inhibiting the dengue virus replication.

There is currently no drug available to treat mosquito-borne dengue. The C-terminal RNA-dependent RNA polymerase (RdRp) domain in the non-structural type 5 (NS5) protein of the dengue virus (DENV) is essential for viral RNA synthesis and replication, and therefore, it is an attractive target for the anti-dengue drug development. We report herein the discovery and validation of two novel non-nucleoside classes of small molecules as DENV RdRp inhibitors. Firstly, using the refined X-ray structure of the DENV NS5 RdRp domain (PDB-ID: 4V0R), we conducted docking, binding free-energy studies, and short-scale molecular dynamics simulation to investigate the binding sites of known small molecules that led to the optimized protein-ligand complex. Subsequently, protein structure-based screening of a commercial database (∼500,000 synthetic compounds), pre-filtered for the drug-likeness, led to the top-ranked 171 molecules, which was then subjected to structural diversity analysis and clustering. This process led to six structurally distinct and best-scored compounds that were procured from the commercial vendor, and then subjected to the in vitro testing in the MTT and dengue infection assays. It revealed two unique and structurally unique compounds, KKR-D-02 and KKR-D-03, exhibiting 84 and 81% reductions, respectively, in DENV copy number in repeated assays in comparison to the virus-infected cell controls. These active compounds represent novel scaffolds for further structure-based discovery of novel candidate molecules for the intervention of dengue.Communicated by Ramaswamy H. Sarma.

Rosmarinic acid and its derivative's duel as antitubercular agents: insights from computational prediction to functional response in vitro.

Tuberculosis is one of the most dreadful infectious diseases, afflicting global populations with anguish. With the emergence of multi-drug resistant strains of mycobacteria, the imperative for new anti-tuberculosis drugs has grown exponentially. Thus, the current study delves into evaluating the impact of Perovskia abrotanoides and its active metabolites-namely, rosmarinic acid and its derivatives-against strains of Mycobacterium tuberculosis (Mtb). Through the use of the CRI assay, the antimycobacterial potential of the high-altitude medicinal plant P. abrotanoides was gauged, while docking and molecular dynamics simulations unveiled plausible targets. Of these, the peak antimycobacterial effectiveness was observed in the P. abrotanoides ethyl acetate extract with 125 µg/mL as minimum inhibitory concentration against various strains of M. tuberculosis, encompassing H37Rv and strains resistant to multiple drugs. Following bioassay-guided fractionation and isolation, rosmarinic acid and rosmarinic acid methyl ester emerged as potent molecules against H37Rv and multidrug-resistant M. tuberculosis strains; minimum inhibitory concentration ranging from 15 to 32 µg/mL. Additionally, out of 22 targets explored, Mtb lipoamide dehydrogenase (PDB: 3II4) and Rv2623 (PDB: 3CIS) were forecasted as potential Mtb targets for rosmarinic acid and rosmarinic acid methyl ester, respectively, a supposition further affirmed by molecular simulations (100 ns). The stability of both complexes throughout the simulation was measured by protein backbone root-mean-square deviation, substantiating their roles as respective targets for antimycobacterial activities.Communicated by Ramaswamy H. Sarma.

The Abundant Phytocannabinoids in Rheumatoid Arthritis: Therapeutic Targets and Molecular Processes Identified Using Integrated Bioinformatics and Network Pharmacology.

The endocannabinoid system consists of several phytocannabinoids, cannabinoid receptors, and enzymes that aid in numerous steps necessary to manifest any pharmacological activity. It is well known that the endocannabinoid system inhibits the pathogenesis of the inflammatory and autoimmune disease rheumatoid arthritis (RA). To the best of our knowledge, no research has been done that explains the network-pharmacology-based anti-rheumatic processes by focusing on the endocannabinoid system. Therefore, the purpose of this study is to further our understanding of the signaling pathways, associated proteins, and genes underlying RA based on the abundant natural endocannabinoids. The knowledge on how the phytocannabinoids in Cannabis sativa affect the endocannabinoid system was gathered from the literature. SwissTarget prediction and BindingDB databases were used to anticipate the targets for the phytocannabinoids. The genes related to RA were retrieved from the DisGeNET and GeneCards databases. Protein-protein interactions (high confidence > 0.7) were carried out with the aid of the string web server and displayed using Cytoscape. The Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis was used to perform enrichment analyses on the endocannabinoid-RA common targets. ShinyGO 0.76 was used to predict the biological processes listed in the Gene Ontology (GO) classification system. The binding affinity between the ligand and the receptors was precisely understood using molecular docking, induced-fit docking, and a molecular dynamics simulation. The network pharmacology analyses predicted that processes like response to oxygen-containing compounds and peptodyl-amino acid modification are related to the potential mechanisms of treatment for RA. These biological actions are coordinated by cancer, neuroactive ligand-receptor interaction, lipids and atherosclerosis, the calcium signaling pathway, and the Rap1 signaling pathway. According to the results of molecular docking, in the context of RA, phytocannabinoids may bind to important target proteins such PIK3CA, AKT1, MAPK9, PRKCD, BRAF, IGF1R, and NOS3. This entire study predicted the phytocannabinoids' systemic biological characteristics. Future experimental research is needed, however, to confirm the results so far.

The Potential of Mur Enzymes as Targets for Antimicrobial Drug Discovery.

The extensive development in the strains of resistant bacteria is a potential hazard to public health worldwide. This necessitates the development of newer agents with the antibacterial property having new mechanisms of action. Mur enzymes catalyze the steps related to the biosynthesis of peptidoglycan, which constitutes a major part of the cell wall in bacteria. Peptidoglycan increases the stiffness of the cell wall, helping it to survive in unfavorable conditions. Therefore, the inhibition of Mur enzymes may lead to novel antibacterial agents that may help in controlling or overcoming bacterial resistance. Mur enzymes are classified into MurA, MurB, MurC, MurD, MurE, and MurF. Until-date, multiple inhibitors are reported for each class of the Mur enzymes. In this review, we have summarized the development of Mur enzyme inhibitors as antibacterial agents in the last few decades.

Identification of 5-(3-(methylsulfonyl)phenyl)-3-(4-(methylsulfonyl)phenyl)-3H-imidazo[4,5-b]pyridine as novel orally bioavailable and metabolically stable antimalarial compound for further exploration.

Malaria continues to be a significant public health problem threatened by the emergence and spread of resistance to artemisinin-based combination therapies and marked half a million deaths in 2016. A new imidazopyridine chemotype has been envisaged through scaffold-hopping approach combined with docking studies for putative-binding interactions with Plasmodium falciparum phosphatidylinositol-4-kinase (PfPI4K) target. The docking results steered to the synthesis of compound 1 [5-(3-(methylsulfonyl)phenyl)-3-(4-(methylsulfonyl)phenyl)-3H-imidazo[4,5-b]pyridine] followed by the in vitro screening for antiplasmodial activity and ADME-PK studies. Combined with potent antimalarial activity of compound 1 (Pf3D7 IC50  = 29 nM) with meager in vitro intrinsic clearance, moderate plasma-protein binding, and acceptable permeability, compound 1 displayed sustained exposure and high oral bioavailability in mice and can thus have the potential as next generation PI4K inhibitor for in vivo studies.

Lead optimization studies towards the discovery of novel carbamates as potent AChE inhibitors for the potential treatment of Alzheimer's disease.

The optimization of our previous lead compound 1 (AChE IC(50)=3.31 µM) through synthesis and pharmacology of a series of novel carbamates is reported. The synthesized compounds were evaluated against mouse brain AChE enzyme using the colorimetric method described by Ellman et al. The three compounds 6a (IC(50)=2.57µM), 6b (IC(50)=0.70 µM) and 6i (IC(50)=2.56 µM) exhibited potent in vitro AChE inhibitory activities comparable to the drug rivastigmine (IC(50)=1.11 µM). Among them, the compound 6b has been selected as possible optimized lead for further neuropharmacological studies. In addition, the AChE-carbamate Michaelis complexes of these potent compounds including rivastigmine and ganstigmine have been modeled using covalent docking protocol of GOLD and important direct/indirect interactions contributing to stabilization of the AChE-carbamate Michaelis complexes have been investigated.

Structural basis for the binding of a selective inverse agonist AF64394 with the human G-protein coupled receptor 3 (GPR3).

The orphan class A G-protein coupled receptor 3 (GPR3) is highly expressed in brain and linked with various neuronal functions, and therefore, expected to play a vital role in the progression of Alzheimer's disease. In view of the lack of its experimental structure, we describe herein the three-dimensional structure and conformational dynamics of GPR3 complexed with the inverse agonist AF64394. The GPR3 model was predicted using the Iterative Threading ASSEmbly Refinement (I-TASSER) method. The Induced Fit Docking predicted two unique poses, Pose 1 and Pose 2, for AF64394, and then, molecular dynamics (MD) simulations followed by binding free-energy calculation revealed the Pose 1 as a very stable pose with the least fluctuation during the MD simulation while the Pose 2 underwent a significant fluctuation. The [1,2,4]triazolo[1,5-a]pyrimidine core was engaged in multiple hydrogen bonds (H-bonds), such as a water-mediated H-bond between the triazole nitrogen and T31, two direct H-bonds between the protonated triazole-ring nitrogen and V186 and T279, a direct H-bond between the secondary amine and V187. The phenyl substituent of AF64394 exhibited aromatic π-π stacking interactions with F97, F101, W43 and Y280. AF64394 showed a direct interaction with E28 and polar interactions with H96, T31 and T279. Throughout the MD simulation, the toggle switch residues, F120 and W260, remained in close contact, indicating that the GPR3 conformation represented an inactive state. The 4-(3-chloro-5-isopropoxyphenethyl) group resided near to the toggle switch residues. The insights gained here are expected to be useful in the structure-based design of new ligands targeting GPR3 modulation. Communicated by Ramaswamy H. Sarma.

Emerging Roles and Potential Applications of Non-Coding RNAs in Cervical Cancer.

Cervical cancer (CC) is a preventable disease using proven interventions, specifically prophylactic vaccination, pervasive disease screening, and treatment, but it is still the most frequently diagnosed cancer in women worldwide. Patients with advanced or metastatic CC have a very dismal prognosis and current therapeutic options are very limited. Therefore, understanding the mechanism of metastasis and discovering new therapeutic targets are crucial. New sequencing tools have given a full visualization of the human transcriptome's composition. Non-coding RNAs (NcRNAs) perform various functions in transcriptional, translational, and post-translational processes through their interactions with proteins, RNA, and even DNA. It has been suggested that ncRNAs act as key regulators of a variety of biological processes, with their expression being tightly controlled under physiological settings. In recent years, and notably in the past decade, significant effort has been made to examine the role of ncRNAs in a variety of human diseases, including cancer. Therefore, shedding light on the functions of ncRNA will aid in our better understanding of CC. In this review, we summarize the emerging roles of ncRNAs in progression, metastasis, therapeutics, chemo-resistance, human papillomavirus (HPV) regulation, metabolic reprogramming, diagnosis, and as a prognostic biomarker of CC. We also discussed the role of ncRNA in the tumor microenvironment and tumor immunology, including cancer stem cells (CSCs) in CC. We also address contemporary technologies such as antisense oligonucleotides, CRISPR-Cas9, and exosomes, as well as their potential applications in targeting ncRNAs to manage CC.

Structure-based discovery of (S)-2-amino-6-(4-fluorobenzyl)-5,6,11,11a-tetrahydro-1H-imidazo[1',5':1,6]pyrido[3,4-b]indole-1,3(2H)-dione as low nanomolar, orally bioavailable autotaxin inhibitor.

Inhibition of extracellular secreted enzyme autotaxin (ATX) represents an attractive strategy for the development of new therapeutics to treat various diseases and a few inhibitors entered in clinical trials. We herein describe structure-based design, synthesis, and biological investigations revealing a potent and orally bioavailable ATX inhibitor 1. During the molecular docking and scoring studies within the ATX enzyme (PDB-ID: 4ZGA), the S-enantiomer (Gscore = -13.168 kcal/mol) of the bound ligand PAT-494 scored better than its R-enantiomer (Gscore = -9.562 kcal/mol) which corroborated with the reported observation and analysis of the results suggested the scope of manipulation of the hydantoin substructure in PAT-494. Accordingly, the docking-based screening of a focused library of 10 compounds resulted in compound 1 as a better candidate for pharmacological studies. Compound 1 was synthesized from L-tryptophan and evaluated against ATX enzymatic activities with an IC50 of 7.6 and 24.6 nM in biochemical and functional assays, respectively. Further, ADME-PK studies divulged compound 1 as non-cytotoxic (19.02% cell growth inhibition at 20 µM in human embryonic kidney cells), metabolically stable against human liver microsomes (CLint  = 15.6 µl/min/mg; T1/2  = 113.2 min) with solubility of 4.82 µM and orally bioavailable, demonstrating its potential to be used for in vivo experiments.

Synthesis and biological evaluation of substituted 4-arylthiazol-2-amino derivatives as potent growth inhibitors of replicating Mycobacterium tuberculosis H37Rv.

In search of potential therapeutics for tuberculosis, we describe herein synthesis and biological evaluation of some substituted 4-arylthiazol-2-amino derivatives as modified analogues of the antiprotozoal drug Nitazoxanide (NTZ), which has recently been reported as potent inhibitor of Mtb H(37)Rv (Mtb MIC=52.12 µM) with an excellent ability to evade resistance. Among the synthesized derivatives, the two compounds 7a (MIC=15.28 µM) and 7c (MIC=17.03 µM) have exhibited about three times better Mtb growth inhibitory activity over NTZ and are free from any cytotoxicity (Vero CC(50) of 244 and 300 µM respectively). These two compounds represent promising leads for further optimization.

Structural basis for the ß-adrenergic receptor subtype selectivity of the representative agonists and antagonists.

The ß(3)-adrenegic receptor (ß(3)-AR) selectivity over ß(1)- and ß(2)-ARs has been the most important aspect for successful therapeutic agents for obesity and type-II diabetes, as the concomitant activation of ß(1)- and ß(2)-ARs would lead to undesirable side effects, such as increased heart rate. In order to explore the structural basis for the ß-AR subtype selectivity of agonists and anatagonists, a three-dimensional structure of until date unresolved ß(3)-AR has been modeled, compared with the resolved X-ray structures of ß(1)- and ß(2)-ARs, and used to study its stereoselective binding with until-date known diverse classes of representative agonists and antagonist. The obtained binding structures and calculated prime molecular mechanics-generalized Born surface area (MM-GBSA) binding free energies consistently reveal that while the subtype selectivity is strongly governed by the residues present in the extracellular ends of TM3, TM5, TM6, TM7 helices and of the ECL2 domain, the binding affinity is governed by the conserved residues present in the deep pocket limiting the degree of conformational and rotational freedoms to the bound ligand. The study demonstrates that the key structural requirements for the ß(3)-selectivity are: (i) a negatively ionizable group (NIG) for direct interaction with ß(3)-specific residue R315(6.58), (ii) a linker (9-10 Å length) between the protonated amine and NIG, and (iii) a substituted aryl ring directly attached to the ß-hydroxyl carbon. The new computational insights acquired in this study are expected to be valuable in structure-based rational design of high-affinity agonists and antagonists with pronounced ß(3)-selectivity for successful therapeutic agents for type-II diabetes and obesity.

Profiling the structural determinants for the selectivity of representative factor-Xa and thrombin inhibitors using combined ligand-based and structure-based approaches.

The current study deciphers the combined ligand- and structure-based computational insights to profile structural determinants for the selectivity of representative diverse classes of FXa-selective and thrombin-selective as well as dual FXa-thrombin high affinity inhibitors. The thrombin-exclusive insertion 60-loop (D-pocket) was observed to be one of the most notable recognition sites for the known thrombin-selective inhibitors. Based on the topological comparison of four common active-site pockets (S1-S4) of FXa and thrombin, the greater structural disparity was observed in the S4-pocket, which was more symmetrical (U-shaped) in FXa as compared to thrombin mainly due to the presence of L99 and I174 residues in latter in place of Y99 and F174 respectively in former protease. The S2 pocket forming partial roof at the entry of 12 Å deep S1-pocket, with two extended ß-sheets running antiparallel to each other by undergoing U-turn (∼180̊), has two conserved glycine residues forming H-bonds with the bound ligand for governing ligand binding affinity. The docking, scoring, and binding pose comparison of the representative high-affinity and selective inhibitors into the active sites of FXa and thrombin revealed critical residues (S214, Y99, W60D) mediating selectivity through direct- and long-range electrostatic interactions. Interestingly, most of the thrombin-selective inhibitors attained S-shaped conformation in thrombin, while FXa-selective inhibitors attained L-shaped conformations in FXa. The role of residue at 99th position of FXa and thrombin toward governing protease selectivity was further substantiated using molecular dynamics simulations on the wild-type and mutated Y99L FXa bound to thrombin-selective inhibitor 2. Furthermore, predictive CoMFA (FXa q² = 0.814; thrombin q² = 0.667) and CoMSIA (FXa q² = 0.807; thrombin q² = 0.624) models were developed and validated (FXa r²(test) = 0.823; thrombin r(2)(test) = 0.816) to feature molecular determinants of ligand binding affinity using the docking-based conformational alignments (DBCA) of 141 (88(train)+53(test)) and 39 (27(train)+11(test)) nonamidine class of potent FXa (0.004 ≤ K(i) (nM) ≤ 4700) and thrombin (0.001 ≤ K(i) (nM) ≤ 940) inhibitors, respectively. Interestingly, the ligand-based insights well corroborated with the structure-based insights in terms of the role of steric, electrostatic, and hydrophobic parameters for governing the selectivity for the two proteases. The new computational insights presented in this study are expected to be valuable for understanding and designing potent and selective antithrombotic agents.