21 research outputs found
Two-Way Regulation of MmpL3 Expression Identifies and Validates Inhibitors of MmpL3 Function in Mycobacterium tuberculosis
MmpL3, an essential mycolate transporter in the inner membrane of Mycobacterium tuberculosis (Mtb), has been identified as a target of multiple, chemically diverse antitubercular drugs. However, several of these molecules seem to have secondary targets and inhibit bacterial growth by more than one mechanism. Here, we describe a cell-based assay that utilizes two-way regulation of MmpL3 expression to readily identify MmpL3-specific inhibitors. We successfully used this assay to identify a novel guanidine-based MmpL3 inhibitor from a library of 220 compounds that inhibit growth of Mtb by largely unknown mechanisms. We furthermore identified inhibitors of cytochrome bc1-aa3 oxidase as one class of off-target hits in whole-cell screens for MmpL3 inhibitors and report a novel sulfanylacetamide as a potential QcrB inhibitor
Antitubercular 2-Pyrazolylpyrimidinones:Structure-Activity Relationship and Mode-of-Action Studies
Spirocycle MmpL3 Inhibitors with Improved hERG and Cytotoxicity Profiles as Inhibitors of Mycobacterium tuberculosis Growth
Optimization of TAM16, a Benzofuran That Inhibits the Thioesterase Activity of Pks13; Evaluation toward a Preclinical Candidate for a Novel Antituberculosis Clinical Target
[Image: see text] With increasing drug resistance in tuberculosis (TB) patient populations, there is an urgent need for new drugs. Ideally, new agents should work through novel targets so that they are unencumbered by preexisting clinical resistance to current treatments. Benzofuran 1 was identified as a potential lead for TB inhibiting a novel target, the thioesterase domain of Pks13. Although, having promising activity against Mycobacterium tuberculosis, its main liability was inhibition of the hERG cardiac ion channel. This article describes the optimization of the series toward a preclinical candidate. Despite improvements in the hERG liability in vitro, when new compounds were assessed in ex vivo cardiotoxicity models, they still induced cardiac irregularities. Further series development was stopped because of concerns around an insufficient safety window. However, the demonstration of in vivo activity for multiple series members further validates Pks13 as an attractive novel target for antitubercular drugs and supports development of alternative chemotypes
Lysyl-tRNA synthetase, a target for urgently needed M. tuberculosis drugs
Tuberculosis is a major global cause of both mortality and financial burden mainly in low and middle-income countries. Given the significant and ongoing rise of drug-resistant strains of Mycobacterium tuberculosis within the clinical setting, there is an urgent need for the development of new, safe and effective treatments. Here the development of a drug-like series based on a fused dihydropyrrolidino-pyrimidine scaffold is described. The series has been developed against M. tuberculosis lysyl-tRNA synthetase (LysRS) and cellular studies support this mechanism of action. DDD02049209, the lead compound, is efficacious in mouse models of acute and chronic tuberculosis and has suitable physicochemical, pharmacokinetic properties and an in vitro safety profile that supports further development. Importantly, preliminary analysis using clinical resistant strains shows no pre-existing clinical resistance towards this scaffold
Synthesis of Chromone, Quinolone, and Benzoxazinone Sulfonamide Nucleosides as Conformationally Constrained Inhibitors of Adenylating Enzymes Required for Siderophore Biosynthesis
MbtA
catalyzes the first committed step of mycobactin biosynthesis
in <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>) and is responsible for the incorporation
of salicylic acid into the mycobactin siderophores. 5′-<i>O</i>-[<i>N</i>-(Salicyl)sulfamoyl]adenosine (Sal-AMS)
is an extremely potent nucleoside inhibitor of MbtA that possesses
excellent activity against whole-cell <i>Mtb</i> but suffers
from poor bioavailability. In an effort to improve the bioavailability,
we have designed four conformationally constrained analogues of Sal-AMS
that remove two rotatable bonds and the ionized sulfamate group on
the basis of computational and structural studies. Herein we describe
the synthesis, biochemical, and microbiological evaluation of chromone-,
quinolone-, and benzoxazinone-3-sulfonamide derivatives of Sal-AMS.
We developed new chemistry to assemble these three heterocycles from
common β-ketosulfonamide intermediates. The synthesis of the
chromone- and quinolone-3-sulfonamide intermediates features formylation
of a β-ketosulfonamide employing dimethylformamide dimethyl
acetal to afford an enaminone that can react intramolecularly with
a phenol or intermolecularly with a primary amine via addition–elimination
reaction(s). The benzoxazinone-3-sulfonamide was prepared by nitrosation
of a β-ketosulfonamide followed by intramolecular nucleophilic
aromatic substitution. Mitsunobu coupling of these bicyclic sulfonamides
with a protected adenosine derivative followed by global deprotection
provides a concise synthesis of the respective inhibitors
Two-Way Regulation of MmpL3 Expression Identifies and Validates Inhibitors of MmpL3 Function in Mycobacterium tuberculosis
Non-Nucleoside Inhibitors of BasE, an Adenylating Enzyme in the Siderophore Biosynthetic Pathway of the Opportunistic Pathogen <i>Acinetobacter baumannii</i>
Siderophores
are small-molecule iron chelators produced by bacteria
and other microorganisms for survival under iron limiting conditions
such as found in a mammalian host. Siderophore biosynthesis is essential
for the virulence of many important Gram-negative pathogens including <i>Acinetobacter baumannii</i>, <i>Klebsiella pneumoniae</i>, <i>Pseudomonas aeruginosa</i>, and <i>Escherichia
coli.</i> We performed high-throughput screening against BasE,
which is involved in siderophore biosynthesis in <i>A. baumannii</i>, and identified 6-phenyl-1-(pyridin-4-ylmethyl)-1<i>H</i>-pyrazolo[3,4-<i>b</i>]pyridine-4-carboxylic acid <b>15</b>. Herein we report the synthesis, biochemical, and microbiological
evaluation of a systematic series of analogues of the HTS hit <b>15</b>. Analogue <b>67</b> is the most potent analogue with
a <i>K</i><sub>D</sub> of 2 nM against BasE. Structural
characterization of the inhibitors with BasE reveals that they bind
in a unique orientation in the active site, occupying all three substrate
binding sites, and thus can be considered as multisubstrate inhibitors.
These results provide a foundation for future studies aimed at increasing
both enzyme potency and antibacterial activity
Dual inhibition of the terminal oxidases eradicates antibiotic‐tolerant Mycobacterium tuberculosis
Abstract The approval of bedaquiline has placed energy metabolism in the limelight as an attractive target space for tuberculosis antibiotic development. While bedaquiline inhibits the mycobacterial F1F0 ATP synthase, small molecules targeting other components of the oxidative phosphorylation pathway have been identified. Of particular interest is Telacebec (Q203), a phase 2 drug candidate inhibitor of the cytochrome bcc:aa3 terminal oxidase. A functional redundancy between the cytochrome bcc:aa3 and the cytochrome bd oxidase protects M. tuberculosis from Q203‐induced death, highlighting the attractiveness of the bd‐type terminal oxidase for drug development. Here, we employed a facile whole‐cell screen approach to identify the cytochrome bd inhibitor ND‐011992. Although ND‐011992 is ineffective on its own, it inhibits respiration and ATP homeostasis in combination with Q203. The drug combination was bactericidal against replicating and antibiotic‐tolerant, non‐replicating mycobacteria, and increased efficacy relative to that of a single drug in a mouse model. These findings suggest that a cytochrome bd oxidase inhibitor will add value to a drug combination targeting oxidative phosphorylation for tuberculosis treatment