Mycobacterium tuberculosis is a major human pathogen and the causative agent for the pulmonary disease, tuberculosis (TB). Current treatment programs to combat TB are under threat due to the ...emergence of multi-drug and extensively-drug resistant TB. Through the use of high throughput whole cell screening of an extensive compound library a number of imidazo1,2-apyridine (IP) compounds were obtained as potent lead molecules active against M. tuberculosis and Mycobacterium bovis BCG. The IP inhibitors (1-4) demonstrated minimum inhibitory concentrations (MICs) in the range of 0.03 to 5 µM against a panel of M. tuberculosis strains. M. bovis BCG spontaneous resistant mutants were generated against IP 1, 3, and 4 at 5× MIC and subsequent whole genome sequencing identified a single nucleotide polymorphism (937)ACC>(937)GCC (T313A) in qcrB, which encodes the b subunit of the electron transport ubiquinol cytochrome C reductase. This mutation also conferred cross-resistance against IP 1, 3 and 4 demonstrating a common target. Gene dosage experiments confirmed M. bovis BCG QcrB as the target where over-expression in M. bovis BCG led to an increase in MIC from 0.5 to >8 µM for IP 3. An acute murine model of TB infection established bacteriostatic activity of the IP series, which await further detailed characterization.
Mycobacterium tuberculosis is a major human pathogen and the causative agent for the pulmonary disease, tuberculosis (TB). Current treatment programs to combat TB are under threat due to the ...emergence of multi-drug and extensively-drug resistant TB. As part of our efforts towards the discovery of new anti-tubercular leads, a number of potent tetrahydropyrazolo1,5-apyrimidine-3-carboxamide (THPP) and N-benzyl-6',7'-dihydrospiropiperidine-4,4'-thieno3,2-cpyran (Spiro) analogues were recently identified against Mycobacterium tuberculosis and Mycobacterium bovis BCG through a high-throughput whole-cell screening campaign. Herein, we describe the attractive in vitro and in vivo anti-tubercular profiles of both lead series. The generation of M. tuberculosis spontaneous mutants and subsequent whole genome sequencing of several resistant mutants identified single mutations in the essential mmpL3 gene. This 'genetic phenotype' was further confirmed by a 'chemical phenotype', whereby M. bovis BCG treated with both the THPP and Spiro series resulted in the accumulation of trehalose monomycolate. In vivo efficacy evaluation of two optimized THPP and Spiro leads showed how the compounds were able to reduce >2 logs bacterial cfu counts in the lungs of infected mice.
Drug discovery efforts against the pathogen Mycobacterium tuberculosis (Mtb) have been advanced through phenotypic screens of extensive compound libraries. Such a screen revealed sulfolane 1 and ...indoline-5-sulfonamides 2 and 3 as potent inhibitors of mycobacterial growth. Optimization in the sulfolane series led to compound 4, which has proven activity in an in vivo murine model of Mtb infection. Here we identify the target and mode of inhibition of these compounds based on whole genome sequencing of spontaneous resistant mutants, which identified mutations locating to the essential α- and β-subunits of tryptophan synthase. Over-expression studies confirmed tryptophan synthase as the biological target. Biochemical techniques probed the mechanism of inhibition, revealing the mutant enzyme complex incurs a fitness cost but does not prevent inhibitor binding. Mapping of the resistance conferring mutations onto a low-resolution crystal structure of Mtb tryptophan synthase showed they locate to the interface between the α- and β-subunits. The discovery of anti-tubercular agents inhibiting tryptophan synthase highlights the therapeutic potential of this enzyme and draws attention to the prospect of other amino acid biosynthetic pathways as future Mtb drug targets.
Society urgently needs new, effective medicines for the treatment of tuberculosis. To kick-start the required hit-to-lead campaigns, the libraries of pharmaceutical companies have recently been ...evaluated for starting points. The GlaxoSmithKline (GSK) library yielded many high-quality hits, and the associated data were placed in the public domain to stimulate engagement by the wider community. One such series, the spiro compounds, are described here. The compounds were explored by a combination of traditional in-house research and open source methods. The series benefits from a particularly simple structure and a short associated synthetic chemistry route. Many members of the series displayed striking potency and low toxicity, and highly promising in vivo activity in a mouse model was confirmed with one of the analogues. Ultimately the series was discontinued due to concerns over safety, but the associated data remain public domain, empowering others to resume the series if the perceived deficiencies can be overcome.
Enantioselective Organocatalytic Allylic Amination Poulsen, Thomas B; Alemparte, Carlos; Jørgensen, Karl Anker
Journal of the American Chemical Society,
08/2005, Letnik:
127, Številka:
33
Journal Article
Recenzirano
A new strategy for catalytic enantioselective allylic amination based on organocatalysis has been developed. Using a commercially available organocatalyst we demonstrate a direct highly ...enantioselective allylic electrophilic functionalization of alkylidene cyanoacetates and malononitriles with azodicarboxylates. The reaction is broad in scope and proceeds in high yields and with enantioselectivities up to 99%. Furthermore, we demonstrate the synthetic utility of the optically active products formed: highly diastereoselective Diels−Alder reaction, reduction, and formation of optically active building blocks, which are found in various important bioactive compounds such as quinacrine, chloroquine, and analogues thereof.
Silver fluoride and cinchona alkaloids catalyze the diastereo- and enantioselective 1,3-dipolar cycloaddition between azomethine ylides, generated from N-alkylideneglycine esters, and acrylates to ...give the corresponding endo-adducts. Azomethine ylides derived from aromatic and aliphatic aldehydes react in a highly diastereoselective reaction with good yields and enantioselectivities of the substituted pyrrolidines.
The human pathogen Mycobacterium tuberculosis is the causative agent of pulmonary tuberculosis (TB), a disease with high worldwide mortality rates. Current treatment programs are under significant ...threat from multi-drug and extensively-drug resistant strains of M. tuberculosis, and it is essential to identify new inhibitors and their targets. We generated spontaneous resistant mutants in Mycobacterium bovis BCG in the presence of 10× the minimum inhibitory concentration (MIC) of compound 1, a previously identified potent inhibitor of mycobacterial growth in culture. Whole genome sequencing of two resistant mutants revealed in one case a single nucleotide polymorphism in the gene aspS at (535)GAC>(535)AAC (D179N), while in the second mutant a single nucleotide polymorphism was identified upstream of the aspS promoter region. We probed whole cell target engagement by overexpressing either M. bovis BCG aspS or Mycobacterium smegmatis aspS, which resulted in a ten-fold and greater than ten-fold increase, respectively, of the MIC against compound 1. To analyse the impact of inhibitor 1 on M. tuberculosis AspS (Mt-AspS) activity we over-expressed, purified and characterised the kinetics of this enzyme using a robust tRNA-independent assay adapted to a high-throughput screening format. Finally, to aid hit-to-lead optimization, the crystal structure of apo M. smegmatis AspS was determined to a resolution of 2.4 Å.
There is an urgent need to develop new and safer antitubercular agents that possess a novel mode of action. We synthesized and evaluated a novel series of 3-aminomethyl 4-halogen benzoxaboroles as ...Mycobacterium tuberculosis (Mtb) leucyl-tRNA synthetase (LeuRS) inhibitors. A number of Mtb LeuRS inhibitors were identified that demonstrated good antitubercular activity with high selectivity over human mitochondrial and cytoplasmic LeuRS. Further evaluation of these Mtb LeuRS inhibitors by in vivo pharmacokinetics (PK) and murine tuberculosis (TB) efficacy models led to the discovery of GSK3036656 (abbreviated as GSK656). This molecule shows potent inhibition of Mtb LeuRS (IC50 = 0.20 μM) and in vitro antitubercular activity (Mtb H37Rv MIC = 0.08 μM). Additionally, it is highly selective for the Mtb LeuRS enzyme with IC50 of >300 μM and 132 μM for human mitochondrial LeuRS and human cytoplasmic LeuRS, respectively. In addition, it exhibits remarkable PK profiles and efficacy against Mtb in mouse TB infection models with superior tolerability over initial leads. This compound has been progressed to clinical development for the treatment of tuberculosis.
Tuberculosis (TB) is the biggest global killer in history. One of the main objectives for fighting TB is to find a shorter treatment and also to target multidrug-resistant (MDR) and extensively ...drug-resistant XDR strains. ...
Decaprenylphosphoryl-β-d-ribose 2′-epimerase (DprE1) is an essential enzyme in Mycobacterium tuberculosis and has recently been studied as a potential drug target, with inhibitors progressing to ...clinical studies. Here we describe the identification of a novel series of morpholino-pyrimidine DprE1 inhibitors. These were derived from a phenotypic high-throughput screening (HTS) hit with suboptimal physicochemical properties. Optimization strategies included scaffold-hopping, synthesis, and evaluation of fragments of the lead compounds and property-focused optimization. The resulting optimized compounds had much improved physicochemical properties and maintained enzyme and cellular potency. These molecules demonstrated potent efficacy in an in vivo tuberculosis murine infection model.
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