InhA Inhibitors Research Articles

Synthesis, Biological Evaluation, Molecular Docking Studies and ADMET Prediction of Oxindole-Based Hybrids for the Treatment of Tuberculosis.

With a projected mortality toll of 1.4 million in 2019, tuberculosis (TB) continues to be a significant public health concern around the world. Studies of novel treatments are required due to decreased bioavailability, increased toxicity, increased side effects, and resistance of several first- and second-line TB therapies, including isoniazid and ethionamide. This study reports the synthesis of oxindole-based hybrids as potent InhA inhibitors targeting Mycobacterium tuberculosis. The synthesized compounds (5a-5e and 8a-8c) were evaluated for their anti-mycobacterial activity against Mycobacterium tuberculosis and nontuberculous mycobacteria (NTMs), viz. M. abscessus (ATCC 19977), M. fortuitum (ATCC 6841), and M. chelonae (ATCC 35752) using the Microplate Alamar Blue Assay (MABA). Molecular docking studies were performed using AutoDock Vina to explore the binding interactions of these compounds with the InhA enzyme (PDB: 2NSD). Additionally, biochemical and histopathological studies were conducted to assess the hepatotoxicity of the lead compounds. Insilico molecular properties and ADMET properties of the synthesized compounds were predicted using SwissADME and Deep-PK online tools to assess their drug-likeness. Among the tested compounds, 8b exhibited significant anti-mycobacterial activity with a minimum inhibitory concentration (MIC = 1 μg/mL) comparable to the reference drug ethambutol. Further, the compound demonstrated a binding affinity and orientation similar to the reference inhibitor 4PI, indicating its potential as a potent InhA inhibitor, and was found to be stabilized within the binding pocket of InhA through H-bonding, hydrophobic and van der Waal's interactions. Besides, the compounds hepatotoxicity assessment studies depicted that 8b showed no significant liver dysfunction or damage to liver tissues. Additionally, 8b adhered to Lipinski's rule of five and Veber's rule, displaying favourable pharmacokinetic and drug-like properties, including high human intestinal absorption, distribution, and acceptable metabolic stability and excretion. Compound 8b emerged as a promising candidate for further optimization and development as a therapeutic agent for tuberculosis, offering a new avenue for tackling tuberculosis.

Contribution of direct InhA inhibitors to novel drug regimens in a mouse model of tuberculosis.

Isoniazid is an important first-line medicine to treat tuberculosis (TB). Isoniazid resistance increases the risk of poor treatment outcomes and development of multidrug resistance, and is driven primarily by mutations involving katG, encoding the prodrug-activating enzyme, rather than its validated target, InhA. The chemical tractability of InhA has fostered efforts to discover direct inhibitors of InhA (DIIs). In this study, we bridge the gap in understanding the potential contribution of DIIs to novel combination regimens and demonstrate a clear distinction of DIIs, like GSK693 and the newly described GSK138, from isoniazid, based on activity against clinical isolates and contribution to novel drug regimens. The results suggest that DIIs, specifically GSK138 and GSK693, could be promising partners in novel drug regimens, including those used against isoniazid-resistant TB, potentially enhancing their efficacy and/or preventing the selection of resistant mutants and supporting the continued exploration of InhA as a promising target for TB drug development.

Synthesis and InhA Inhibition of Imidazo[1,2-a]pyridine Derivatives as Anti-Tuberculosis Agents

Abstract: Imidazopyridine holds significance as a crucial fused bicyclic heterocycle within the realm of medicinal chemistry, being acknowledged as a "privileged scaffold" owing to its extensive utility. Numerous methodologies for the synthesis of imidazo[1,2-a]pyridines have been documented, with a considerable focus on strategies aimed at functionalizing these compounds. This study aimed to explore the potential of novel imidazo[1,2- a] pyridine derivatives as agents against drug-resistant Mycobacterium tuberculosis, which poses significant challenges in tuberculosis (TB) treatment. The research involved the synthesis of substituted imidazo[1,2- a]pyridine derivatives using site identification and molecular docking techniques. Characterization of the synthesized compounds was carried out using FT-IR, LC-MS, 1H NMR, and 13C NMR analysis. Compounds 6a and 6k showed good anti-TB activity against the H37Rv strain of Mycobacterium tuberculosis, with MIC values of 0.6 μM and 0.9 μM, respectively, which were comparable with the standard drug isoniazid. These findings suggest that imidazo[1,2-a]pyridine derivatives, especially compounds 6a and 6k, have potential as agents against drug-resistant TB, providing valuable insights for ongoing efforts in developing effective TB treatments.

Development of Mycobacterium tuberculosis Enoyl Acyl Reductase (InhA) Inhibitors: A Mini-Review

This review article delves into the critical role of Enoyl acyl carrier protein Reductase (InhA; ENR), a vital enzyme in the NADH-dependent acyl carrier protein reductase family, emphasizing its significance in fatty acid synthesis and, more specifically, the biosynthesis of mycolic acid. The primary objective of this literature review is to elucidate diverse scaffolds and their developmental progression targeting InhA inhibition, thereby disrupting mycolic acid biosynthesis. Various scaffolds, including thiourea, piperazine, thiadiazole, triazole, quinazoline, benzamide, rhodanine, benzoxazole, and pyridine, have been systematically explored for their potential as InhA inhibitors. Noteworthy findings highlight thiadiazole and triazole derivatives, demonstrating promising IC50 values within the nanomolar concentration range. The review offers comprehensive insights into InhA's structure, structure-activity relationships, and a detailed overview of distinct scaffolds as effective inhibitors of InhA.

Halogenated chalcones against Mycobacterium tuberculosis targeting InhA: Rational design, in silico and in vitro evaluation

A library of 25-series compounds was designed against Mycobacterium Tuberculosis (M.tb) to identify novel antitubercular drugs. In silico inhibition of InhA, an essential component of FAS-II, was successfully achieved. The drug ability, lead-likeness, and toxicity of the compounds were assessed using Swiss ADME, pkCSM, and Osiris Property Explorer, which revealed the potential for drug development of chalcone compounds. Through in silico research, it was confirmed that toxic-free compounds could bind to InhA. It was found that all of the compounds bind to InhA with binding affinities ranging from −7.78 to −10.29 kcal/mol−1 which is higher than the reference standard Isoniazid and Pyrazinamide. The top five compounds were synthesized from 15 toxic-free compounds. The structural characteristics of the compounds were determined using IR, NMR, and mass spectrometry techniques. These findings indicate that these substances are competitive, reversible, and specific InhA inhibitors of InhA. using the Alamar Blue assay method (H37RV, ATCC No. 27294), the in vitro anti-mycobacterial activity of each of the synthesized compounds against M.tb was evaluated. The two most powerful compounds were (2E)-3-[4-(benzyloxy)-3,5-dimethylphenyl] and (2E)-1-(3,5-dibromophenyl)-3-(3-phenoxyphenyl) prop-2-en-1-one. In the MABA Assay, the MIC for 1-(3,5-dibromophenyl) prop-2-en-1-one was 6.25 μg/ml.

Computational Exploration of Isatin Derivatives for InhA Inhibition in Tuberculosis: Molecular Docking, MD Simulations and ADMET Insights.

Anti-tubercular drug discovery is a critical research area aimed at addressing the global health burden imposed by Mycobacterium tuberculosis. Nowadays, computational techniques have increased the likelihood of drug development compared to traditional, labor-intensive, and time-consuming drug design approaches. The pivotal goal of drug design is to identify compounds capable of selectively targeting protein, thereby disrupting its enzymatic activity. InhA, or NADH-dependent enoyl-acyl carrier protein reductase, stands at the forefront of targeted approaches in the battle against TB. Isatin derivatives have garnered interest for their diverse pharmacological activities. To identify novel isatin derivatives that could serve as potential chemical templates for anti-TB drug discovery by targeting InhA. The present work utilized various computational approaches, including molecular docking, binding free energy calculations, and conformational alignment studies to investigate the binding mode and interactions of carefully selected dataset of 88 isatin derivatives within InhA active site. Study also employed MD simulations of the most promising molecule to check the stability of the protein-ligand complex and in-silico ADMET profiling of the top compounds to predict their pharmacokinetic and toxicity properties. Results provided insights into the structural features contributing to InhA inhibition, assessing overall drug-like characteristics of isatin derivatives and identified compound 48 (BA= -10.4 kcal mol-1 ) with potential for further optimization. MD simulation analysis revealed that compound 48 binds firmly within the InhA protein, exhibiting minimal conformational fluctuations and enhanced stability. Considering the aforementioned, isatin derivatives represents a novel framework for creating targeted InhA inhibitors during anti-TB therapy. However, experimental validations and in-depth analyses are crucial to confirm efficacy and safety of these derivatives as potential InhA inhibitors for TB treatment.

Synthesis and in silico studies of some new pyrrolylbenzamide derivatives as antitubercular and antimicrobial agents

Eighteen new pyrrolylbenzamide derivatives (6a-6r) were synthesized by reacting N-(2,5-dimethyl- 1H-pyrrol-1-yl)-4-(2-hydrazineyl-2-oxoethoxy)benzamide (4) with substituted benzoic acids (5a-5r) in the presence of 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate, diisopropyl ethylamine and dimethyl formamide. The produced compounds were subjected to molecular docking studies against the dihydrofolate reductase (DHFR) and InhA mycobacterial enzymes. The compounds were biologically screened for antimycobacterial, and antibacterial activities along with InhA and DHFR enzyme inhibition studies. The compounds were also analyzed for ADMET parameters. The compounds 6j, 6l, 6q, and 6r exhibited good antitubercular activity, and compounds 6j, 6l, 6q, and 6r were effective against the Gram-negative Escherichia coli strain. The compounds 6b, 6f, 6j, 6l, and 6q showed good InhA inhibition and compounds 6b, 6c, 6j, 6l, and 6q were effective against DHFR enzyme. Among the synthesized compounds 6j and 6l exhibited promising antitubercular, antibacterial, and effective InhA and DHFR enzyme inhibition values.. KEYWORDS :Benzamide, Dimethylpyrrole, Antimycobacterial activity, Antibacterial activity.

Design and synthesis of Thieno[3, 2-b]pyridinone derivatives exhibiting potent activities against Mycobacterium tuberculosis in vivo by targeting Enoyl-ACP reductase

In this study, a series of novel thieno [3, 2-b]pyridinone derivatives were designed and synthesized using a scaffold hopping strategy. Six compounds showed potent anti-mycobacterial activity (minimum inhibitory concentration (MIC) ≤ 1 μg/mL) against Mycobacterium tuberculosis (Mtb) UAlRa. Compound 6c displayed good activity against Mtb UAlRv (MIC = 0.5–1 μg/mL). Compounds 6c and 6i also showed activity against Mtb UAlRa in macrophages and exhibited low cytotoxicity against LO-2 cells. The selected compounds displayed a narrow antibacterial spectrum, with no activity against representative Gram-positive, Gram-negative bacteria, as well as fungi. Furthermore, compound 6c demonstrated favorable oral pharmacokinetic properties with a T1/2 value of 47.99 h and exhibited good in vivo activity in an acute mouse model of tuberculosis (TB). The target of compound 6c was identified as a NADH-dependent enoyl-acyl carrier protein reductase (InhA) by genome sequencing of spontaneously compound 6c-resistant Mtb mutants, indicating that compound 6c may not require activation and can directly target InhA. In vitro antimicrobial assays against a recombinant M. smegmatis overexpressing the Mtb-InhA, along with InhA inhibition assays, confirmed that InhA is the target of thieno [3, 2-b]pyridinone derivatives. Overall, this study identified thieno [3, 2-b]pyridinone scaffold as a novel chemotype that is promising for the development of anti-TB agents.

Computational Studies to Explore Plant-based Inhibitors for Enoyl- (Acyl Carrier Protein)- Reductase (InhA) of Mycobacterium tuberculosis

Aims: A computational approach has been adopted to find therapeutically potent herbal compounds with anti-TB properties Background: The second largest cause of death globally is Mycobacterium tuberculosis. Considering that the BCG vaccine is only marginally effective. This study has focused on enoyl- (acyl carrier protein)- reductase (InhA), one of the important enzymes in M. tuberculosis's type II fatty acid (mycolic acid synthesis) biosynthesis pathway. Bioinformatics-based tools have been used to explore therapeutically sound phytocompounds against InhA. Objective: To conduct an insightful study using bioinformatics-based tools to explore phytocompounds originating from different medicinal plants which would act as potent inhibitors of enoyl - (acyl carrier protein)- reductase (InhA) to obstruct the growth of M. tuberculosis. Methods: Molecular docking (using EasyDockVina) has been used for screening the 150 phytocompounds against Enoyl - (acyl carrier protein)- reductase (InhA). AMDET analysis was performed using DruLito and protox II to test the drug-likeness properties of phytocompounds. Results: From the results of molecular docking and two-dimensional interaction, it is concluded that Licoflavone B, Tembaterine, Colubrine and Shinpterocarpin are the potent inhibitors of InhA. Conclusion: According to this study, Licoflavone B, Tembaterine, Columbin, and Shinpterocarpin have positively passed AMDET screening and have high docking scores. These phytocompounds can be considered safe drug candidates against InhA of Mycobacterium tuberculosis.

Evaluation of Phytochemicals for Anti‐Tubercular Potential Targeting Enoyl‐Acyl Carrier Protein Reductase (InhA): An In Silico Approach

AbstractTuberculosis (TB) caused by the Mycobacterium tuberculosis (MTB) pathogen is a serious contagious illness that endangers the public's health. However, TB is treatable but due to the result of ineffective and protracted medication, MDR‐MTB and XDR‐MTB were able to develop, making their eradication highly challenging and necessitating potential treatments to be cured. This study aimed to identify the novel inhibitor for the InhA enzyme, a potential target of MTB. Initially, 2721 phytochemicals libraries were screened for ADME/Tox profiling and 49 phytochemicals were filtered out. Moreover, these phytochemicals with reference inhibitor triclosan were docked against InhA (PDB ID: 1BVR)., were showing binding energies ranging from −9.16–−6.3 kcal/mol, whereas triclosan showed −6.90 kcal/mol of binding energy. The docking results reveal that irilone (−9.16 kcal/mol) and aurantio‐obtusin (−8.84 kcal/mol) exhibit promising binding energy and perfectly occupy the binding site of InhA. Furthermore, molecular dynamics simulation (MDS) and MMGBSA studies showed better affinities of selected compounds in terms of stability, compactness, flexibility, and total BFE in complexes with InhA. This study concluded that irilone and aurantio‐obtusin could be promising InhA inhibitors based on their impressive pharmacokinetic profiling, toxicity, binding affinity, and stability. However experimental validation is a subject of further research.

A SIMULATION APPROACH FOR NOVEL 1,3,4 THIADIAZOLE ACETAMIDE MOIETIES AS POTENT ANTIMYCOBACTERIAL AGENTS

Objective: To design novel series of 1,3,4 thiadiazoles and to evaluate their anti-mycobacterial potency via In silico modeling. Methods: In silico modeling comprising of Lipinski rule evaluation, ADMET prediction, Molecular docking and Simulation studies aimed to identify potent 1,3,4 thiadiazoles. Results: The various physiochemical parameters and molecular descriptors of the proposed 1,3,4 thiadiazoles were predicted. And they exhibited good binding score compared with standard drug INH. The simulation studies showed minimal fluctuation of the ligand receptor complexes. Conclusion: The MD simulation and binding affinity of designed 1,3,4 thiadiazoles proved their efficiency as InhA inhibitors. The potency of the selected derivatives can be confirmed by further in vitro and in vivo experiments.

Identification of potent indolizine derivatives against Mycobacterial tuberculosis: In vitro anti-TB properties, in silico target validation, molecular docking and dynamics studies

In the current study, two sets of compounds: (E)-1-(2-(4-substitutedphenyl)-2-oxoethyl)-4-((hydroxyimino)methyl)pyridinium derivatives (3a-3e); and (E)-3-(substitutedbenzoyl)-7-((hydroxyimino)methyl)-2-substitutedindolizine-1-carboxylate derivatives (5a-5j), were synthesized and biologically evaluated against two strains of Mycobacterial tuberculosis (ATCC 25177) and multi-drug resistant (MDR) strains. Further, they were also tested in vitro against the mycobacterial InhA enzyme. The in vitro results showed excellent inhibitory activities against both MTB strains and compounds 5a-5j were found to be more potent, and their MIC values ranged from 5 to 16 μg/mL and 16–64 μg/mL against the M. tuberculosis (ATCC 25177) and MDR-TB strains, respectively. Compound 5h with phenyl and 4-fluorobenzoyl groups attached to the 2- and 3-position of the indolizine core was found to be the most active against both strains with MIC values of 5 μg/mL and 16 μg/mL, respectively. On the other hand, the two sets of compounds showed weak to moderate inhibition of InhA enzyme activity that ranged from 5 to 17 % and 10–52 %, respectively, with compound 5f containing 4-fluoro benzoyl group attached to the 3-position of the indolizine core being the most active (52 % inhibition of InhA). Unfortunately, there was no clear correlation between the InhA inhibitory activity and MIC values of the tested compounds, indicating the probability that they might have different modes of action other than InhA inhibition.Therefore, a computational investigation was conducted by employing molecular docking to identify their putative drug target(s) and, consequently, understand their mechanism of action. A panel of 20 essential mycobacterial enzymes was investigated, of which β-ketoacyl acyl carrier protein synthase I (KasA) and pyridoxal-5′-phosphate (PLP)-dependent aminotransferase (BioA) enzymes were revealed as putative targets for compounds 3a-3e and 5a-5j, respectively. Moreover, in silico ADMET predictions showed adequate properties for these compounds, making them promising leads worthy of further optimization.

Preparation and InhA inhibitory properties of novel dehydroacetic acid-derived thiazoles

A series of 4-hydroxy-6-methyl-3-(1-(4-(aryl/methyl)thiazol-2-yl)-1H-pyrazol-3-yl)-2H-pyran-2-ones 3a–h have been synthesized from aryl/methyl halomethylketones and a key pyrazole intermediate 1 using a convenient one-pot synthesis method. All compounds were characterized by NMR and MS, and the structure of three of them (3a, 3b and 3f) was resolved by X-ray diffraction. These heteroatom-rich thiazole compounds were then evaluated as inhibitors of Mycobacterium tuberculosis InhA, a key enzyme involved in the type II fatty acid biosynthesis pathway of the mycobacterium. Although inhibitory activities were found to be rather weak, molecular docking studies were also been carried out to understand a possible mode of interaction with key residues in the enzyme’s active site.

The key players in the arsenal of combating TB; reviewing the lead InhA inhibitors

The key players in the arsenal of combating TB; reviewing the lead InhA inhibitors

Synthesis, biological evaluation, and docking studies of pyrazole-linked benzothiazole hybrids as promising anti-TB agents

Tuberculosis (TB) is a global pandemic killing millions of people every year. Yet, resistant strains make curing TB quite challenging. Herein, a series of new pyrazole-linked benzothiazole hybrids was synthesized and evaluated for their anti-TB activity against three Mycobacterium tuberculosis strains (drug sensitive (DS), multidrug-resistant (MDR) and extensively drug-resistant (XDR)). The substituted 2,5-dimethylphenoxy -, 2,6-dichlorophenoxy -, 2,6-dimethoxyphenoxy -, 4-methylpiperazin-1-yl-,and pyrrolidin-1-ylpyrazole-benzothiazole conjugates (compounds 10j, 10k,10l, 11cand 12 respectively) displayed promising anti-TB activity in comparison to the reference compound isoniazid against the DS strain with (MIC: 1.74–3.68 μM/mL)To further study the mode of action of these anti-TB compounds, their inhibition of the Mycobacterium tuberculosisenoyl-acyl carrier protein reductase enzyme (InhA) was tested. The 3-acetamidophenoxy-, 2,6-dichlorophenoxy -,andpyrrolidin-1-ylpyrazole-benzothiazole conjugates(Compounds 10i, 10j and 12 respectively) showed strong inhibition of InhA in comparison to the reference compound, triclosan, with IC50 values of 6.4–7.9 μM. Moreover, a molecular docking study was carried out to investigate the predicted binding interactions of the synthesized inhA inhibitors in the binding pocket of the inhA enzyme. The calculated docking energies of the developed novel pyrazole-linked benzothiazole hybrids were consistent with their tested anti-tubercular activity.

Inducing vulnerability to InhA inhibition restores isoniazid susceptibility in drug-resistant Mycobacterium tuberculosis.

Of the approximately 10 million cases of Mycobacterium tuberculosis (Mtb) infections each year, over 10% are resistant to the frontline antibiotic isoniazid (INH). INH resistance is predominantly caused by mutations that decrease the activity of the bacterial enzyme KatG, which mediates the conversion of the pro-drug INH to its active form INH-NAD. We previously discovered an inhibitor of Mtb respiration, C10, that enhances the bactericidal activity of INH, prevents the emergence of INH-resistant mutants, and re-sensitizes a collection of INH-resistant mutants to INH through an unknown mechanism. To investigate the mechanism of action of C10, we exploited the toxicity of high concentrations of C10 to select for resistant mutants. We discovered two mutations that confer resistance to the disruption of energy metabolism and allow for the growth of Mtb in high C10 concentrations, indicating that growth inhibition by C10 is associated with inhibition of respiration. Using these mutants as well as direct inhibitors of the Mtb electron transport chain, we provide evidence that inhibition of energy metabolism by C10 is neither sufficient nor necessary to potentiate killing by INH. Instead, we find that C10 acts downstream of INH-NAD synthesis, causing Mtb to become particularly sensitive to inhibition of the INH-NAD target, InhA, without changing the concentration of INH-NAD or the activity of InhA, the two predominant mechanisms of potentiating INH. Our studies revealed that there exists a vulnerability in Mtb that can be exploited to render Mtb sensitive to otherwise subinhibitory concentrations of InhA inhibitor.IMPORTANCEIsoniazid (INH) is a critical frontline antibiotic to treat Mycobacterium tuberculosis (Mtb) infections. INH efficacy is limited by its suboptimal penetration of the Mtb-containing lesion and by the prevalence of clinical INH resistance. We previously discovered a compound, C10, that enhances the bactericidal activity of INH, prevents the emergence of INH-resistant mutants, and re-sensitizes a set of INH-resistant mutants to INH. Resistance is typically mediated by katG mutations that decrease the activation of INH, which is required for INH to inhibit the essential enzyme InhA. Our current work demonstrates that C10 re-sensitizes INH-resistant katG-hypomorphs without enhancing the activation of INH. We furthermore show that C10 causes Mtb to become particularly vulnerable to InhA inhibition without compromising InhA activity on its own. Therefore, C10 represents a novel strategy to curtail the development of INH resistance and to sensitize Mtb to sub-lethal doses of INH, such as those achieved at the infection site.

Molecular Docking Study of New Pyrrolyl Benzohydrazide Schiff Bases as M. tuberculosis InhA Enzyme Inhibitors

Background Tuberculosis TB is an ancient chronic infectious disease affecting primarily the lungs of humans and rapidly co-evolved with humans since several million years. It is mainly caused by a group of bacterial species termed Mycobacterium tuberculosis a principal strain of this infection. Each second millions are at risk of acquiring new infection of becoming sick prone to death and a conclusive understanding of pathogenesis is still deficient.Objective To design a series of new pyrrole benzohydrazide schiff bases as M. tuberculosis InhA inhibitors.Methods Docking software Sybyl-X version 2.0 was used for molecular modeling. To dock intended compounds Surflex-Dock procedure of sybyl was castoff. M. tuberculosis enoyl reductase InhA inhibitor target protein 4TZK complexed with ligand 1-cyclohexyl-N-3 5-dichlorophenyl-5-oxopyrrolidine3-carboxamide was taken from Protein Data Bank PDB entry code 4TZK httpwww.rcsb.orgpdb.Results Docking scores of the compounds ranged between 5.47 - 3.32 summarizing the interface force field between enzyme and the ligands.Conclusion Sixteen molecules bearing pyrrole hydrazone moiety were docked showing promising M. tuberculosis inhibition activity. In silico molecular docking analysis exhibited that peptide linkage -CO-NH- and imine -CN- of pyrrole hydrazones were important in binding with the targeted receptor.

Design, synthesis and computational studies of new azaheterocyclic coumarin derivatives as anti-Mycobacterium tuberculosis agents targeting enoyl acyl carrier protein reductase (InhA).

In this study, we designed and synthesized a series of coumarin derivatives as antitubercular agents targeting the enoyl acyl carrier protein reductase (InhA) enzyme. Among the synthesized compounds, the tetrazole derivative 4c showed the most potent antitubercular effect with a minimum inhibitory concentration value (MIC) of 15 μg mL-1 against Mtb H37Rv and could also inhibit the growth of the mutant strain (ΔkatG). Compound 4c was able to penetrate Mtb-infected human macrophages and suppress the intracellular growth of tubercle bacilli. Moreover, the target derivative 4c showed a potent inhibitory effect against InhA enzyme with an IC50 value of 0.565 μM, which was superior to the reference InhA inhibitor triclosan. Molecular docking of compound 4c within the InhA active site revealed the importance of the 4-phenylcoumarin ring system and tetrazole moiety for activity. Finally, the physicochemical properties and pharmacokinetic parameters of 4c were investigated.

Exploring the plasticity of the InhA substrate-binding site using new diaryl ether inhibitors

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a worldwide scourge with more than 10 million people affected yearly. Among the proteins essential for the survival of Mtb, InhA has been and is still clinically validated as a therapeutic target. A new family of direct diaryl ether inhibitors, not requiring prior activation by the catalase peroxidase enzyme KatG, has been designed with the ambition of fully occupying the InhA substrate-binding site. Thus, eleven compounds, featuring three pharmacophores within the same molecule, were synthesized. One of them, 5-(((4-(2-hydroxyphenoxy)benzyl)(octyl)amino)methyl)-2-phenoxyphenol (compound 21), showed good inhibitory activity against InhA with IC50 of 0.70 µM. The crystal structure of compound 21 in complex with InhA/NAD+ showed how the molecule fills the substrate-binding site as well as the minor portal of InhA. This study represents a further step towards the design of new inhibitors of InhA.

In silico development of potential InhA inhibitors through 3D-QSAR analysis, virtual screening and molecular dynamics

Tuberculosis is one of the most ancient infectious diseases known to mankind predating upper Paleolithic era. In the current scenario, treatment of drug resistance tuberculosis is the major challenge as the treatment options are limited, less efficient and more toxic. In our study we have developed an atom based 3D QSAR model, statistically validated sound with R2 > 0.90 and Q2 > 0.72 using reported direct inhibitors of InhA (2018–2022), validated by enzyme inhibition assay. The model was used to screen a library of 3958 molecules taken from Binding DB and candidates molecules with promising predicted activity value (pIC50) > 5) were selected for further analyzed screening by using molecular docking, ADME profiling and molecular dynamic simulations. The lead molecule, ZINC11536150 exhibited good docking score (glideXP = −11.634 kcal/mol) compared to standard triclosan (glideXP = −7.129 kcal/mol kcal/mol) and through molecular dynamics study it was observed that the 2nv6-complex of ZINC11536150 with Mycobacterium tuberculosis InhA (PDB entry: 2NV6) complex remained stable throughout the entire simulation time of 100 ns.Communicated by Ramaswamy H. Sarma