Optimization of Hydantoins as Potent Antimycobacterial Decaprenylphosphoryl-ß-d-Ribose Oxidase (DprE1) Inhibitors.

In search of novel drugs against tuberculosis, we previously discovered and profiled a novel hydantoin-based family that demonstrated highly promising in vitro potency against Mycobacterium. tuberculosis. The compounds were found to be noncovalent inhibitors of DprE1, a subunit of decaprenylphosphoryl-ß-d-ribose-2'-epimerase. This protein, localized in the periplasmic space of the mycobacterial cell wall, was shown to be an essential and vulnerable antimycobacterial drug target. Here, we report the further SAR exploration of this chemical family through more than 80 new analogues. Among these, the most active representatives combined submicromolar cellular potency and nanomolar target affinity with balanced physicochemical properties and low human cytotoxicity. Moreover, we demonstrate in vivo activity in an acute Mtb infection model and provide further proof of DprE1 being the target of the hydantoins. Overall, the hydantoin family of DprE1 inhibitors represents a promising noncovalent lead series for the discovery of novel antituberculosis agents.

Identification and Profiling of Hydantoins-A Novel Class of Potent Antimycobacterial DprE1 Inhibitors.

Tuberculosis is the leading cause of death worldwide from infectious diseases. With the development of drug-resistant strains of Mycobacterium tuberculosis, there is an acute need for new medicines with novel modes of action. Herein, we report the discovery and profiling of a novel hydantoin-based family of antimycobacterial inhibitors of the decaprenylphospho-ß-d-ribofuranose 2-oxidase (DprE1). In this study, we have prepared a library of more than a 100 compounds and evaluated them for their biological and physicochemical properties. The series is characterized by high enzymatic and whole-cell activity, low cytotoxicity, and a good overall physicochemical profile. In addition, we show that the series acts via reversible inhibition of the DprE1 enzyme. Overall, the novel compound family forms an attractive base for progression to further stages of optimization and may provide a promising drug candidate in the future.

Dynamic lateral organization of opioid receptors (kappa, muwt and muN40D ) in the plasma membrane at the nanoscale level.

Opioid receptors are important pharmacological targets for the management of numerous medical conditions (eg, severe pain), but they are also the gateway to the development of deleterious side effects (eg, opiate addiction). Opioid receptor signaling cascades are well characterized. However, quantitative information regarding their lateral dynamics and nanoscale organization in the plasma membrane remains limited. Since these dynamic properties are important determinants of receptor function, it is crucial to define them. Herein, the nanoscale lateral dynamics and spatial organization of kappa opioid receptor (KOP), wild type mu opioid receptor (MOPwt ), and its naturally occurring isoform (MOPN40D ) were quantitatively characterized using fluorescence correlation spectroscopy and photoactivated localization microscopy. Obtained results, supported by ensemble-averaged Monte Carlo simulations, indicate that these opioid receptors dynamically partition into different domains. In particular, significant exclusion from GM1 ganglioside-enriched domains and partial association with cholesterol-enriched domains was observed. Nanodomain size, receptor population density and the fraction of receptors residing outside of nanodomains were receptor-specific. KOP-containing domains were the largest and most densely populated, with the smallest fraction of molecules residing outside of nanodomains. The opposite was true for MOPN40D . Moreover, cholesterol depletion dynamically regulated the partitioning of KOP and MOPwt , whereas this effect was not observed for MOPN40D .

Differential characterization using readily accessible NMR experiments of novel N- and O-alkylated quinolin-4-ol, 1,5-naphthyridin-4-ol and quinazolin-4-ol derivatives with antimycobacterial activity.

During the construction of bioactive molecules, regioselective alkylation of heterocyclic, N/O ambident nucleophiles is a frequently encountered synthetic transformation. In this framework, specific attention is required to unambiguously determine the structures of obtained reaction products. As part of our project on quinoloxyacetamide based antimycobacterial agents, a series of N- or O- alkylated quinolin-4-ol, 1,5-naphthyridin-4-ol and quinazolin-4-ol derivatives were prepared during the course of which we observed unexpected selectivity issues. After finding that no consistent procedure existed in the literature for assigning regioisomers of this type, we applied three readily accessible NMR experiment types (13C NMR, HSQC/HMBC and NOE) to resolve any uncertainties regarding the obtained regioisomeric structures. Furthermore, the antimycobacterial activity of all final compounds was evaluated with the best compound 23 showing potent antitubercular activity (MIC = 1.25 µM) without cytotoxic effects.

Searching for New Leads for Tuberculosis: Design, Synthesis, and Biological Evaluation of Novel 2-Quinolin-4-yloxyacetamides.

In this study, a new series of more than 60 quinoline derivatives has been synthesized and evaluated against Mycobacterium tuberculosis (H37Rv). Apart from the SAR exploration around the initial hits, the optimization process focused on the improvement of the physicochemical properties, cytotoxicity, and metabolic stability of the series. The best compounds obtained exhibited MIC values in the low micromolar range, excellent intracellular antimycobacterial activity, and an improved physicochemical profile without cytotoxic effects. Further investigation revealed that the amide bond was the source for the poor blood stability observed, while some of the compounds exhibited hERG affinity. Compound 83 which contains a benzoxazole ring instead of the amide group was found to be a good alternative, with good blood stability and no hERG affinity, providing new opportunities for the series. Overall, the obtained results suggest that further optimization of solubility and microsomal stability of the series could provide a strong lead for a new anti-TB drug development program.

Inhibition of renal gluconeogenesis contributes to hypoglycaemic action of NADPH oxidase inhibitor, apocynin.

NADPH oxidase, catalysing superoxide radical (O2(.-)) formation, is considered as a main source of reactive oxygen species in kidneys and its increased activity is supposed to be involved in the development of diabetic nephropathy. The aim of this study was to investigate the effect of NADPH oxidase inhibitor, apocynin, on renal gluconeogenesis, which is an important source of endogenous glucose under diabetic conditions. The following observations were made during the experiments performed on isolated renal proximal tubules of control and alloxan diabetic rabbits: (1) apocynin (200 µM) inhibited the rate of glucose synthesis by 45-80%, depending on the substrate applied; (2) the rate of glucose production was also significantly diminished in the presence of TEMPOL (5mM), a superoxide radical scavenger, suggesting that the decrease in O2(.-) formation might be involved in apocynin-evoked gluconeogenesis inhibition; (3) the activities of phosphoenolpyruvate carboxykinase (PEPCK) and/or aldolase were lowered in the presence of either apocynin or TEMPOL, as concluded from the intracellular levels of gluconeogenic intermediates. The data from in vivo experiments indicated that apocynin treatment (2g/l of drinking water): (1) significantly (by about 30%) attenuated serum glucose concentration in diabetic rabbits and did not affect glycaemia in control animals; (2) normalized diabetes-stimulated rate of glucose synthesis and slightly inhibited gluconeogenesis in control rabbits; (3) normalized diabetes-increased activity of mitochondrial PEPCK and lowered cytosolic PEPCK activity by about 20% below the value for untreated control animals; (4) slightly decreased the activity of mitochondrial PEPCK and did not change the activity of cytosolic one in control rabbits. Thus, it is concluded that: (1) the inhibition of NADPH oxidase might contribute to lowered rate of renal gluconeogenesis, probably due to decreasing PEPCK activity; (2) inhibition of renal gluconeogenesis is involved in apocynin hypoglycaemic action in vivo; (3) apocynin might be beneficial for diabetes treatment.

Unprecedented 1,3-dipolar cycloaddition: from 1,4,5,8-naphthalene bisimides to a new heterocyclic skeleton.

1,4,5,8-Naphthalene bisimides react as dipolarophiles with in situ formed azomethine ylides. Double 1,3-dipolar cycloaddition is followed by unique ring rearrangement and leads to the formation of two six-membered rings. The formation of hexacyclic products is rationalized based on DFT calculations.