A high-throughput target-based screening approach for the identification and assessment of Mycobacterium tuberculosis mycothione reductase inhibitors.

The World Health Organization's goal to combat tuberculosis (TB) is hindered by the emergence of anti-microbial resistance, therefore necessitating the exploration of new drug targets. Multidrug regimens are indispensable in TB therapy as they provide synergetic bactericidal effects, shorten treatment duration, and reduce the risk of resistance development. The research within our European RespiriTB consortium explores Mycobacterium tuberculosis energy metabolism to identify new drug candidates that synergize with bedaquiline, with the aim of discovering more efficient combination drug regimens. In this study, we describe the development and validation of a luminescence-coupled, target-based assay for the identification of novel compounds inhibiting Mycobacterium tuberculosis mycothione reductase (MtrMtb), an enzyme with a role in the protection against oxidative stress. Recombinant MtrMtb was employed for the development of a highly sensitive, robust high-throughput screening (HTS) assay by coupling enzyme activity to a bioluminescent readout. Its application in a semi-automated setting resulted in the screening of a diverse library of ~130,000 compounds, from which 19 hits were retained after an assessment of their potency, selectivity, and specificity. The selected hits formed two clusters and four fragment molecules, which were further evaluated in whole-cell and intracellular infection assays. The established HTS discovery pipeline offers an opportunity to deliver novel MtrMtb inhibitors and lays the foundation for future efforts in developing robust biochemical assays for the identification and triaging of inhibitors from high-throughput library screens. IMPORTANCE: The growing anti-microbial resistance poses a global public health threat, impeding progress toward eradicating tuberculosis. Despite decades of active research, there is still a dire need for the discovery of drugs with novel modes of action and exploration of combination drug regimens. Within the European RespiriTB consortium, we explore Mycobacterium tuberculosis energy metabolism to identify new drug candidates that synergize with bedaquiline, with the aim of discovering more efficient combination drug regimens. In this study, we present the development of a high-throughput screening pipeline that led to the identification of M. tuberculosis mycothione reductase inhibitors.

Synthesis of novel furan-based chalcone derivatives as anti-tuberculosis agents: in vitro, cytotoxicity assessment and in silico.

Background: The aim of the study is to identify a novel furan-based chalcone derivative as potent inhibitor against the H37Rv strain. Materials & methods: The in silico pharmacokinetic characteristics, toxicity tests, molecular modeling, chemical synthesis and minimum inhibitory concentration (MIC; IC50) were carried out to evaluate the antitubercular potential of the synthesized furan-based chalcone analogues against H37Rv. Results & conclusion: Among the ten target compounds synthesized, DF02, DF05 and DF07 had MIC values of 1.6 µg/ml equivalent to isoniazid and DF10 showed MIC values of 3.25 µg/ml which is equipotent to pyrazinamide. All the other compounds had optimal concentrations 6.25-100 µg/ml against the H37Rv strain. Compounds DF02 and DF10 were further evaluated for cytotoxicity assay performed using HeLa cell lines.

Combined Bioinformatics and Combinatorial Chemistry Tools to Locate Drug-Able Anti-TB Phytochemicals: A Cost-Effective Platform for Natural Product-Based Drug Discovery.

Based on extensive experimental studies, a huge number of phytochemicals showed potential activity against tuberculosis (TB) at a lower minimum inhibitory concentration (MIC) and fewer toxicity profiles. However, these promising drugs have not been able to convert from 'lead' to 'mainstream' due to inadequate drug-ability profiles. Thus, early drug-prospective analyses are required at the primary stage to accelerate natural-product-based drug discovery with limited resources and time. In the present study, we have selected seventy-three potential anti-TB phytochemicals (MIC value ≤10 µg/mL) and assessed the drug-ability profiles using bioinformatics and combinatorial chemistry tools, systematically. Primarily, the molecular docking study was done against two putative drug targets, catalase-peroxidase enzyme (katG) and RNA polymerase subunit-ß (rpoB) of Mycobacterium tuberculosis (Mtb) using AutoDock 4.2 software. Further, assessed the drug-ability score from Molsoft, toxicity profiles from ProTox, pharmacokinetics from SwisADME, hierarchical cluster analysis (HCA) by ChemMine tools and frontier molecular orbitals (FMOs) with Avogadro and structural activity relationships (SAR) analysis with ChemDraw 18.0 software. Above analyses indicated that, lower MIC exhibited anti-TB phytochemicals, abietane, 12-demethylmulticaulin exhibited poor docking and drug-ability scores, while tiliacorinine, 2-nortiliacorinine showed higher binding energy and drug-ability profiles. Overall, tiliacorinine, 2-nortiliacorinine, 7α-acetoxy-6ß-hydroxyroyleanone (AHR), (2S)-naringenin and isovachhalcone were found as the most active and drug-able anti-TB candidates from 73 candidates. Phytochemicals are always a vital source of mainstream drugs, but the MIC value of a phytochemical is not sufficient for it to be promoted. An ideal drug-ability profile is therefore essential for achieving clinical success, where advanced bioinformatics tools help to assess and analyse that profile. Additionally, several natural pharmacophores found in existing anti-TB drugs in SAR analyses also provide crucial information for developing potential anti-TB drug. As a conclusion, combined bioinformatics and combinatorial chemistry are the most effective strategies to locate potent-cum-drug-able candidates in the current drug-development module.

Low-cost anti-mycobacterial drug discovery using engineered E. coli.

Whole-cell screening for Mycobacterium tuberculosis (Mtb) inhibitors is complicated by the pathogen's slow growth and biocontainment requirements. Here we present a synthetic biology framework for assaying Mtb drug targets in engineered E. coli. We construct Target Essential Surrogate E. coli (TESEC) in which an essential metabolic enzyme is deleted and replaced with an Mtb-derived functional analog, linking bacterial growth to the activity of the target enzyme. High throughput screening of a TESEC model for Mtb alanine racemase (Alr) revealed benazepril as a targeted inhibitor, a result validated in whole-cell Mtb. In vitro biochemical assays indicated a noncompetitive mechanism unlike that of clinical Alr inhibitors. We establish the scalability of TESEC for drug discovery by characterizing TESEC strains for four additional targets.

Antitubercular activity assessment of fluorinated chalcones, 2-aminopyridine-3-carbonitrile and 2-amino-4H-pyran-3-carbonitrile derivatives: In vitro, molecular docking and in-silico drug likeliness studies.

A series of newer previously synthesized fluorinated chalcones and their 2-amino-pyridine-3-carbonitrile and 2-amino-4H-pyran-3-carbonitrile derivatives were screened for their in vitro antitubercular activity and in silico methods. Compound 40 (MIC~ 8 µM) was the most potent among all 60 compounds, whose potency is comparable with broad spectrum antibiotics like ciprofloxacin and streptomycin and three times more potent than pyrazinamide. Additionally, compound 40 was also less selective and hence non-toxic towards the human live cell lines-LO2 in its MTT assay. Compounds 30, 27, 50, 41, 51, and 60 have exhibited streptomycin like activity (MIC~16-18 µM). Fluorinated chalcones, pyridine and pyran derivatives were found to occupy prime position in thymidylate kinase enzymatic pockets in molecular docking studies. The molecule 40 being most potent had shown a binding energy of -9.67 Kcal/mol, while docking against thymidylate kinase, which was compared with its in vitro MIC value (~8 µM). These findings suggest that 2-aminopyridine-3-carbonitrile and 2-amino-4H-pyran-3-carbonitrile derivatives are prospective lead molecules for the development of novel antitubercular drugs.

Quality assurance in anti-tuberculosis drug procurement by the Stop TB Partnership-Global Drug Facility: Procedures, costs, time requirements, and comparison of assay and dissolution results by manufacturers and by external analysis.

BACKGROUND: Quality-assured medicines are a principal means of achieving health-related Sustainable Development Goals. An example of quality assurance/quality control (QA/QC) procedures in drug procurement is provided by the operation of the Global Drug Facility (GDF) of the Stop TB Partnership, the largest provider of tuberculosis (TB) medicines to the public sector worldwide. METHODS: Procedures and results of GDF's quality assurance/quality control (QA/QC) over the five-year period 2013-2017 were analysed retrospectively. 13,999 batches of 51 different medicines had been procured and reviewed within this period. 1,388 of these batches had been analysed in the laboratories of GDF's external quality control agent (QCA). Assay and dissolution results determined by the manufacturers and by the external QCA were compared using Bland-Altman analysis. RESULTS: All investigated batches of medicines were in specifications at the time of shipment. The costs for QA/QC were 0.8% of purchase costs. The median time required for chemical analysis was 10 working days. Comparison of the medicine quality analysis results showed for the poorly water-soluble compound rifampicin a bias of 4.4%, with the manufacturers reporting higher values than the external QCA, most likely due to different methods employed for the analysis. Overall 95% limits of agreement (LOAs) were -6.7 to +8.0% for assay, and -10.1 to +11.8% for dissolution. In case of kanamycin injections, 95% LOAs for assay reached -14.5 to +13.2%, largely attributable to samples from one manufacturer who had used a microbiological assay while the external QCA had used an HPLC assay. CONCLUSIONS: GDF's procedures represent a useful benchmark when evaluating QA/QC procedures of other medicine procurement operations. Inter-laboratory comparison using Bland-Altman plots allows to investigate bias and variability in medicine quality control and should be considered as a routine procedure by drug procurement agencies, to identify priorities for further improvements.

Assessment of preclinical drug interactions of bedaquiline by a highly sensitive LC-ESI-MS/MS based bioanalytical method.

A continuous effort has been given to find out a new drug that is effective against tuberculosis (TB) from both susceptible and resistant strains of Mycobacterium tuberculosis. Bedaquiline represents a recently approved anti-TB drug, which has a unique mechanism of action to fight against multi drug resistance (MDR). Some severe side effects and drug-drug interactions are associated with the treatment of bedaquiline. Moreover, World Health Organisation (WHO) has also been provided guidelines in the year of 2013 for the use of bedaquiline and encourages additional investigation into it. Hence, the pharmacokinetics of bedaquiline upon coadministration with the drug has to be explored in the preclinical model and for which a liquid chromatography tandem mass spectrometry (LC-MS/MS) based bioanalytical method for quantitation of bedaquiline will be useful. A simple, sensitive and rapid LC-MS/MS method was developed, validated and successfully applied to drug interactions of bedaquiline upon coadministration with cytochrome P450 3A4 (CYP3A4) inducers/inhibitors orally in Wistar rats. Results reveal that ciprofloxacin and fluconazole have marked effect to hinder the pharmacokinetics of bedaquiline but isoniazid, verapamil and carbamazepine have no significant effect on bedaquiline pharmacokinetics. Overall, this new bioanalytical method for estimation of bedaquiline in rat plasma was found to be helpful to assess the pharmacokinetics of bedaquiline and very much useful for evaluation of preclinical drug-drug interaction before considering costly and perilous clinical exploration.

Imidazole and 1,2,4-Triazole-based Derivatives Gifted with Antitubercular Activity: Cytotoxicity and Computational Assessment.

BACKGROUND: Mycobacterium Tuberculosis (Mtb) is the causative pathogen of Tuberculosis (TB) and outbreaks are more common among immunosuppressed persons infected with HIV. The current treatment regimens are lengthy and toxic, yet the therapy has remained unchanged for many decades, so there is a need to find new structures with selective mechanism of action. Moreover, the increased incidence of severe disseminated infections produced by undiagnosed Multidrug-resistant (MDR), worsen clinical treatment and contribute the spread of the disease. OBJECTIVE: The aim of our study was to evaluate the potential of imidazole and triazole moieties for antimycobacterial activity, by synthesizing some 1-(1-(aryl)-2-(2,6-dichlorophenyl)hydrazono)ethyl- 1H-imidazole and 1H-1,2,4-triazole derivatives 2a-l. METHODS: The title compounds were obtained via classical organic synthesis. The antimicrobial activity was evaluated using the method of microdilution and the cytotoxicity assay was performed by MTT method. RESULTS: The results indicated that the presence of both the imidazole ring and that of the 2,6- dichlorosubstituted phenyl moiety, is more relevant for inhibitory activity against Mtb than the triazole nucleus and the unsubstituted phenyl ring. Among the series, (E)-1-(2-(5-chlorothiophen-2-yl)-2-(2- (2,6-dichlorophenyl)hydrazono)ethyl)-1H-imidazole derivative 2f and (Z)-1-(2-([1,1'-biphenyl]-4-yl)- 2-(2-(2,6-dichlorophenyl)hydrazono)ethyl]-1H-imidazole derivatives 2e exhibited a promising antimycobacterial property and the latter also displayed a safe cytotoxic profile. CONCLUSION: The synthesized compounds were studied for their antitubercular activity. Among the series, the compounds 2e and 2f appeared to be the most promising agents and, according to the docking assessment, the compounds could be CYP51 inhibitors. These evidences could be useful for the future development of new antimycobacterial derivatives targeting CYP51 with more specificity for the mycobacterial cell enzyme.

Molecular dynamics simulation and binding free energy studies of novel leads belonging to the benzofuran class inhibitors of Mycobacterium tuberculosis Polyketide Synthase 13.

In this work, the binding mechanism of new Polyketide Synthase 13 (Pks13) inhibitors has been studied through molecular dynamics simulation and free energy calculations. The drug Tam1 and its analogs, belonging to the benzofuran class, were submitted to 100 ns simulations, and according to the results obtained for root mean square deviation, all the simulations converged from approximately 30 ns. For the analysis of backbone flotation, the root mean square fluctuations were plotted for the Cα atoms; analysis revealed that the greatest fluctuation occurred in the residues that are part of the protein lid domain. The binding free energy value (ΔGbind) obtained for the Tam16 lead molecule was of -51.43 kcal/mol. When comparing this result with the ΔGbind values for the remaining analogs, the drug Tam16 was found to be the highest ranked: this result is in agreement with the experimental results obtained by Aggarwal and collaborators, where it was verified that the IC50 for Tam16 is the smallest necessary to inhibit the Pks13 (IC50 = 0.19 µM). The energy decomposition analysis suggested that the residues which most interact with inhibitors are: Ser1636, Tyr1637, Asn1640, Ala1667, Phe1670, and Tyr1674, from which the greatest energy contribution to Phe1670 was particularly notable. For the lead molecule Tam16, a hydrogen bond with the hydroxyl of the phenol not observed in the other analogs induced a more stable molecular structure. Aggarwal and colleagues reported this hydrogen bonding as being responsible for the stability of the molecule, optimizing its physic-chemical, toxicological, and pharmacokinetic properties.

CORAL: Monte Carlo Method to Predict Endpoints for Medical Chemistry.

The applications of optimal molecular descriptors as a tool to predict endpoints related to medicinal chemistry are listed. The general scheme of building up of the optimal descriptors is represented in detail. Simplified molecular input-line entry system (SMILES) is being used to represent the molecular architecture. The optimal descriptor is the sum of correlation weights of molecular fragments extracted from SMILES. The numerical data on the correlation weights are calculated by the Monte Carlo method. The data should provide maximal correlation coefficient between experimental values of endpoint and corresponding values of the optimal descriptor. The scheme contains two phases: (i) selection of reliable parameters of the Monte Carlo optimization; and (ii) building up a model. The mechanistic interpretation for models based on the optimal descriptors is suggested. The interpretation is calculated on results of several runs of the Monte Carlo optimization. The domain of applicability for these models is defined according to the prevalence of molecular fragments in the training and calibration sets.

Use of chemometrics to compare NIR and HPLC for the simultaneous determination of drug levels in fixed-dose combination tablets employed in tuberculosis treatment.

The World Health Organization recommends that TB treatment be administered using combination therapy. The methodologies for quantifying simultaneously associated drugs are highly complex, being costly, extremely time consuming and producing chemical residues harmful to the environment. The need to seek alternative techniques that minimize these drawbacks is widely discussed in the pharmaceutical industry. Therefore, the objective of this study was to develop and validate a multivariate calibration model in association with the near infrared spectroscopy technique (NIR) for the simultaneous determination of rifampicin, isoniazid, pyrazinamide and ethambutol. These models allow the quality control of these medicines to be optimized using simple, fast, low-cost techniques that produce no chemical waste. In the NIR - PLS method, spectra readings were acquired in the 10,000-4000cm-1 range using an infrared spectrophotometer (IRPrestige - 21 - Shimadzu) with a resolution of 4cm-1, 20 sweeps, under controlled temperature and humidity. For construction of the model, the central composite experimental design was employed on the program Statistica 13 (StatSoft Inc.). All spectra were treated by computational tools for multivariate analysis using partial least squares regression (PLS) on the software program Pirouette 3.11 (Infometrix, Inc.). Variable selections were performed by the QSAR modeling program. The models developed by NIR in association with multivariate analysis provided good prediction of the APIs for the external samples and were therefore validated. For the tablets, however, the slightly different quantitative compositions of excipients compared to the mixtures prepared for building the models led to results that were not statistically similar, despite having prediction errors considered acceptable in the literature.

Assessment of halloysite nanotubes as vehicles of isoniazid.

Equilibrium and thermodynamic aspects of the adsorption of isoniazid (INH) onto halloysite nanotubes (HLNTs) and characteristics of the resultant drug/nanocarrier systems are investigated. Equilibrium studies were performed in aqueous medium at different times, temperatures and drug concentrations. The overall adsorption process was explained as the result of two simple processes: adsorption on the activated sites of HLNTs and precipitation of INH on HLNTs surface. Formation of the INH-loaded HLNTs was spontaneous, endothermic and endoentropic, increasing the thermodynamic stability of the system (ΔH=70.40kJ/mol; ΔS=0.2519kJ/molK). Solid state characterization corroborated the effective interaction between the components that was also described by modeling at molecular level by quantum mechanics calculations along with empirical interatomic potentials. Transmission electron microphotographs confirmed the double allocation and homogeneous distribution of INH in the nanohybrids. FTIR spectra revealed the interaction via hydrogen bonds between the inner hydroxyl groups of HLNTs and N in INH molecules. Loading of INH in the nanohybrids was approximately 20% w/w. Effective loading of INH and activation energies of the interactions enable to propose the designed nanohybrids in the development of modified drug delivery systems.

QSAR Studies, Synthesis and Antibacterial Assessment of New Inhibitors Against Multidrug-Resistant Mycobacterium tuberculosis.

BACKGROUND: The increasing rate of appearance of multidrug-resistant strains of Mycobacterium tuberculosis (MDR-TB) is a serious problem at the present time. MDR-TB forms do not respond to the standard treatment with the commonly used drugs and can take some years or more to treat with drugs that are less potent, more toxic and much more expensive. OBJECTIVE: The goal of this work is to identify the novel effective drug candidates active against MDR-TB strains through the use of methods of cheminformatics and computeraided drug design. METHODS: This paper describes Quantitative Structure-Activity Relationships (QSAR) studies using Artificial Neural Networks, synthesis and in vitro antitubercular activity of several potent compounds against H37Rv and resistant Mycobacterium tuberculosis (Mtb) strains. RESULTS: Eight QSAR models were built using various types of descriptors with four publicly available structurally diverse datasets, including recent data from PubChem and ChEMBL. The predictive power of the obtained QSAR models was evaluated with a cross-validation procedure, giving a q2=0.74-0.78 for regression models and overall accuracy 78.9-94.4% for classification models. The external test sets were predicted with accuracies in the range of 84.1-95.0% (for the active/inactive classifications) and q2=0.80- 0.83 for regressions. The 15 synthesized compounds showed inhibitory activity against H37Rv strain whereas the compounds 1-7 were also active against resistant Mtb strain (resistant to isoniazid and rifampicin). CONCLUSION: The results indicated that compounds 1-7 could serve as promising leads for further optimization as novel antibacterial inhibitors, in particular, for the treatment of drug resistance of Mtb forms.

Bioluminescent Reporters for Rapid Mechanism of Action Assessment in Tuberculosis Drug Discovery.

The tuberculosis (TB) drug discovery pipeline is fueled by compounds identified in whole-cell screens against the causative agent, Mycobacterium tuberculosis Phenotypic screening enables the selection of molecules that inhibit essential cellular functions in live, intact bacilli grown under a chosen in vitro condition. However, deducing the mechanism of action (MOA), which is important to avoid promiscuous targets, often requires significant biological resources in a lengthy process that risks decoupling medicinal chemistry and biology efforts. Therefore, there is a need to develop methods enabling rapid MOA assessment of putative "actives" for triage decisions. Here, we describe a modified version of a bioluminescence reporter assay that allows nondestructive detection of compounds targeting either of two macromolecular processes in M. tuberculosis: cell wall biosynthesis or maintenance of DNA integrity. Coupling the luxCDABE operon from Photorhabdus luminescens to mycobacterial promoters driving expression of the iniBAC operon (PiniB-LUX) or the DNA damage-inducible genes, recA (PrecA-LUX) or radA (PradA-LUX), provided quantitative detection in real time of compounds triggering expression of any of these promoters over an extended 10- to 12-day incubation. Testing against known anti-TB agents confirmed the specificity of each reporter in registering the MOA of the applied antibiotic in M. tuberculosis, independent of bactericidal or bacteriostatic activity. Moreover, profiles obtained for experimental compounds indicated the potential to infer complex MOAs in which multiple cellular processes are disrupted. These results demonstrate the utility of the reporters for early triage of compounds based on the provisional MOA and suggest their application to investigate polypharmacology in known and experimental anti-TB agents.

Facile synthesis of 1,3-thiazolidin-4-ones as antitubercular agents.

We have developed, highly efficient, one-pot, solvent-free, [Et3NH][HSO4] catalyzed multicomponent reaction protocol for the synthesis of 1,3-thiazolidin-4-ones in excellent yields. For the first time, the 1,3-thiazolidin-4-ones were evaluated in vitro for their antimycobacterial activity against Mycobacterium tuberculosis dormant MTB H37Ra and Mycobacterium bovis BCG strains. Among the synthesized basic 1,3-thiazolidin-4-ones, particularly the compounds 4c, 4d, 4e, 4f, 4h, 4i and 4j displays promising antitubercular activity along with no significant cytotoxicity against the cell lines MCF-7, A549 and HCT-116.

Assessment of the efficacy of drug transdermal delivery by electro-phonophoresis in treating tuberculous lymphadenitis.

Electro-phonophoresis (EP) has been used in various clinical fields. The objective of present study is to evaluate the skin permeability of isoniazid (INH) and rifampicin (RIF) in patients with tuberculous lymphadenitis with the aid of EP to validate the clinical applications of this transdermal delivery system for the treatment of superficial extrapulmonary tuberculosis. INH and RIF solutions were delivered transdermally, with or without EP, in the surrounding tissue of the lesion for 0.5 h. Local pyogenic fluids or necrotic tissue samples from the infection sites in patients were collected at 1 h after dosing. Drug concentrations in samples were evaluated by high performance liquid chromatography. The median INH and RIF intra-lesional concentrations were 0.365 (interquartile range [IQR] 0.185-1.775) µg/mL and 1.231 (IQR 0.304-1.836) µg/mL in oral group; 2.964 (IQR 0.193-7.325) µg/mL and 2.646 (IQR 1.211-3.753) µg/mL in INH- and RIF-transdermal plus EP group. Drug concentrations in the local sites of patients receiving INH or RIF through EP transdermal delivery were statistically higher than those observed in patients only taking INH and RIF orally. However, this enhancement was not observed in the transdermal delivery of INH or RIF without EP in contrast to the oral administrations of drugs. EP can effectively enhance the skin permeability of INH and RIF in patients with tuberculous lymphadenitis. The increase in drug concentrations in the lesions could help eradication of the germs; shorten the treatment course and increase the cure rate of patients with tuberculous lymphadenitis.

Computational Sampling and Simulation Based Assessment of Novel Mycobacterium tuberculosis Glutamine Synthetase Inhibitors: Study Involving Structure Based Drug Design and Free Energy Perturbation.

The highly persistent nature of Mycobacterium tuberculosis can be attributed to its lipophilic cell wall which acts as a major barrier in the process of drug discovery against tuberculosis. Glutamine synthetase plays a major role in nitrogen metabolism and cell wall biosynthesis of pathogenic mycobacteria. The current review focuses on the structural and functional aspects of Mtb glutamine synthetase and an overview of its reported inhibitors till date. Also in the present study, we employed a computational structure based drug design protocol for identifying novel inhibitors against Mtb glutamine synthetase (MtbGS). A total of 12 hits were identified based on e-pharmacophore related search and virtual screening, which were further tested for their in vitro MtbGS inhibitory activity. Three compounds (compound 6, 1 and 12) were found with IC50 less than 5 µM, of which compound 6 being top active with IC50 of 2.124 µM. Differential scanning fluorimetry studies were employed so as to measure the thermal stability of the protein complexed with the most active compound. Also the protein complexes with top three active compounds were subjected for molecular dynamics simulations to study their binding pattern and stabilization effect. The solvation free energies were also determined for these compounds, undertaking free energy perturbation studies, which can be used further for lead optimization in the process of anti-tubercular drug discovery targeting Mtb glutamine synthetase.

Perspectives on Advances in Tuberculosis Diagnostics, Drugs, and Vaccines.

Despite concerted efforts over the past 2 decades at developing new diagnostics, drugs, and vaccines with expanding pipelines, tuberculosis remains a global emergency. Several novel diagnostic technologies show promise of better point-of-care rapid tests for tuberculosis including nucleic acid-based amplification tests, imaging, and breath analysis of volatile organic compounds. Advances in new and repurposed drugs for use in multidrug-resistant (MDR) or extensively drug-resistant (XDR) tuberculosis have focused on development of several new drug regimens and their evaluation in clinical trials and now influence World Health Organization guidelines. Since the failure of the MVA85A vaccine 2 years ago, there have been no new tuberculosis vaccine candidates entering clinical testing. The current status quo of the lengthy treatment duration and poor treatment outcomes associated with MDR/XDR tuberculosis and with comorbidity of tuberculosis with human immunodeficiency virus and noncommunicable diseases is unacceptable. New innovations and political and funder commitment for early rapid diagnosis, shortening duration of therapy, improving treatment outcomes, and prevention are urgently required.

Efficient Synthesis and Anti-Tubercular Activity of a Series of Spirocycles: An Exercise in Open Science.

Tuberculosis afflicts an estimated 2 billion people worldwide and causes 1.3 million deaths annually. Chemotherapeutic solutions rely on drugs developed many years ago, with only one new therapeutic having been approved in the last 40 years. Given the rise of drug-resistant strains, there is an urgent need for the development of a more robust drug development pipeline. GlaxoSmithKline recently placed the structures and activities of 177 novel anti-tubercular leads in the public domain, as well as the results of ongoing optimisation of some of the series. Since many of the compounds arose from screening campaigns, their provenance was unclear and synthetic routes were in many cases not reported. Here we present the efficient synthesis of several novel analogues of one family of the GSK compounds-termed "Spiros"-using an oxa-Pictet-Spengler reaction. The new compounds are attractive from a medicinal chemistry standpoint and some were potent against the virulent strain, suggesting this class is worthy of further study. The research was carried out using open source methodology, providing the community with full access to all raw experimental data in real time.

Pharmacophore assessment through 3-D QSAR: evaluation of the predictive ability on new derivatives by the application on a series of antitubercular agents.

Pharmacophoric mapping is a useful procedure to frame, especially when crystallographic receptor structures are unavailable as in ligand-based studies, the hypothetical site of interaction. In this study, 71 pyrrole derivatives active against M. tuberculosis were used to derive through a recent new 3-D QSAR protocol, 3-D QSAutogrid/R, several predictive 3-D QSAR models on compounds aligned by a previously reported pharmacophoric application. A final multiprobe (MP) 3-D QSAR model was then obtained configuring itself as a tool to derive pharmacophoric quantitative models. To stress the applicability of the described models, an external test set of unrelated and newly synthesized series of R-4-amino-3-isoxazolidinone derivatives found to be active at micromolar level against M. tuberculosis was used, and the predicted bioactivities were in good agreement with the experimental values. The 3-D QSAutogrid/R procedure proved to be able to correlate by a single multi-informative scenario the different activity molecular profiles thus confirming its usefulness in the rational drug design approach.