Identification of Morpholino Thiophenes as Novel Mycobacterium tuberculosis Inhibitors, Targeting QcrB

With the emergence of multidrug-resistant strains of <i>Mycobacterium tuberculosis</i> there is a pressing need for new oral drugs with novel mechanisms of action. Herein, we describe the identification of a novel morpholino–thiophenes (MOT) series following phenotypic screening of the Eli Lilly corporate library against <i>M. tuberculosis</i> strain H37Rv. The design, synthesis, and structure–activity relationships of a range of analogues around the confirmed actives are described. Optimized leads with potent whole cell activity against H37Rv, no cytotoxicity flags, and in vivo efficacy in an acute murine model of infection are described. Mode-of-action studies suggest that the novel scaffold targets QcrB, a subunit of the menaquinol cytochrome <i>c</i> oxidoreductase, part of the bc1-aa3-type cytochrome <i>c</i> oxidase complex that is responsible for driving oxygen-dependent respiration

Antitubercular drugs for an old target: GSK693 as a promising InhA direct inhibitor

AbstractDespite being one of the first antitubercular agents identified, isoniazid (INH) is still the most prescribed drug for prophylaxis and tuberculosis (TB) treatment and, together with rifampicin, the pillars of current chemotherapy. A high percentage of isoniazid resistance is linked to mutations in the pro-drug activating enzyme KatG, so the discovery of direct inhibitors (DI) of the enoyl-ACP reductase (InhA) has been pursued by many groups leading to the identification of different enzyme inhibitors, active against Mycobacterium tuberculosis (Mtb), but with poor physicochemical properties to be considered as preclinical candidates. Here, we present a series of InhA DI active against multidrug (MDR) and extensively (XDR) drug-resistant clinical isolates as well as in TB murine models when orally dosed that can be a promising foundation for a future treatment

Determination of the Pharmacokinetics and Pharmacodynamics of Isoniazid, Rifampicin, Pyrazinamide and Ethambutol in a Cross-Over Cynomolgus Macaque Model of Mycobacterium tuberculosis Infection

Innovative cross-over study designs were explored in non-human primate (NHP) studies to determine the value of this approach for the evaluation of drug efficacy against tuberculosis (TB). Firstly, the pharmacokinetics (PK) of each of the drugs Isoniazid (H), Rifampicin (R), Pyrazinamide (Z) and Ethambutol (E), that are standardly used for the treatment of tuberculosis, was established in the blood of macaques after oral dosing as a monotherapy or in combination. Two studies were conducted to evaluate the pharmacokinetics and pharmacodynamics of different drug combinations using cross-over designs. The first employed a balanced, three-period Pigeon design with an extra period; this ensured that treatment by period interactions and carry-over could be detected comparing the treatments HR, HZ and HRZ using H37Rv as the challenge strain of Mycobacterium tuberculosis (M. tb). Although the design accounted for considerable variability between animals, the three regimens evaluated could not be distinguished using any of the alternative endpoints assessed. However, the degree of pathology achieved using H37Rv in the model during this study was less than expected. Based on these findings, a second experiment using a classical AB/BA design comparing HE with HRZ was conducted using the M. tb Erdman strain. More extensive pathology was observed, and differences in computerized tomography (CT) scores and bacteriology counts in the lungs were detected, although due to the small group sizes, clearer differences were not distinguished. Type 1 T helper (Th1) cell response profiles were characterized using the IFN-γ ELISPOT assay and revealed differences between drug treatments that corresponded to decreases in disease burden. Therefore, the studies performed support the utility of the NHP model for the determination of PK/PD of TB drugs, although further work is required to optimize the use of cross-over study designs

The multistate tuberculosis pharmacometric model : a semi-mechanistic pharmacokinetic-pharmacodynamic model for studying drug effects in an acute tuberculosis mouse model

The Multistate Tuberculosis Pharmacometric (MTP) model, a pharmacokinetic-pharmacodynamic disease model, has been used to describe the effects of rifampicin on Mycobacterium tuberculosis (M. tuberculosis) in vitro. The aim of this work was to investigate if the MTP model could be used to describe the rifampicin treatment response in an acute tuberculosis mouse model. Sixty C57BL/6 mice were intratracheally infected with M. tuberculosis H37Rv strain on Day 0. Fifteen mice received no treatment and were sacrificed on Days 1, 9 and 18 (5 each day). Twenty-five mice received oral rifampicin (1, 3, 9, 26 or 98 mg·kg-1·day-1; Days 1–8; 5 each dose level) and were sacrificed on Day 9. Twenty mice received oral rifampicin (30 mg·kg-1·day-1; up to 8 days) and were sacrificed on Days 2, 3, 4 and 9 (5 each day). The MTP model was linked to a rifampicin population pharmacokinetic model to describe the change in colony forming units (CFU) in the lungs over time. The transfer rates between the different bacterial states were fixed to estimates from in vitro data. The MTP model described well the change in CFU over time after different exposure levels of rifampicin in an acute tuberculosis mouse model. Rifampicin significantly inhibited the growth of fast-multiplying bacteria and stimulated the death of fast- and slow-multiplying bacteria. The data did not support an effect of rifampicin on non-multiplying bacteria possibly due to the short duration of the study. The pharmacometric modelling framework using the MTP model can be used to perform investigations and predictions of the efficacy of anti-tubercular drugs against different bacterial states

Combinations of beta-Lactam Antibiotics Currently in Clinical Trials Are Efficacious in a DHP-I-Deficient Mouse Model of Tuberculosis Infection

We report here a dehydropeptidase-deficient murine model of tuberculosis (TB) infection that is able to partially uncover the efficacy of marketed broad-spectrum beta-lactam antibiotics alone and in combination. Reductions of up to 2 log CFU in the lungs of TB-infected mice after 8 days of treatment compared to untreated controls were obtained at blood drug concentrations and time above the MIC (T->MIC) below clinically achievable levels in humans. These findings provide evidence supporting the potential of beta-lactams as safe and mycobactericidal components of new combination regimens against TB with or without resistance to currently used drugs

Novel pyrazole-containing compounds active against mycobacterium tuberculosis

In this study, a series of 49 five-membered heterocyclic compounds containing either a pyridine- or a pyrrole-type nitrogen were synthesized and tested against Mycobacterium tuberculosis. Among them, only the 1,3,5-trisubstituted pyrazoles 5−49 exhibited minimum inhibitory concentration values in the low micromolar range, and some also exhibited an improved physicochemical profile without cytotoxic effects. Three pyrazoles were subjected to an animal tuberculosis efficacy model, and compound 6 induced a statistically significant difference in lung bacterial counts compared with untreated mice. Moreover, to determine the target of this series, resistors were generated, and whole genome sequencing revealed mutations in the mmpL3 gene

Improved BM212 MmpL3 Inhibitor Analogue Shows Efficacy in Acute Murine Model of Tuberculosis Infection

1,5-Diphenyl pyrroles were previously identified as a class of compounds endowed with high in vitro efficacy against M. tuberculosis. To improve the physical chemical properties and drug-like parameters of this class of compounds, a medicinal chemistry effort was undertaken. By selecting the optimal substitution patterns for the phenyl rings at N1 and C5 and by replacing the thiomorpholine moiety with a morpholine one, a new series of compounds was produced. The replacement of the sulfur with oxygen gave compounds with lower lipophilicity and improved in vitro microsomal stability. Moreover, since the parent compound of this family has been shown to target MmpL3, mycobacterial mutants resistant to two compounds have been isolated and characterized by sequencing the mmpL3 gene; all the mutants showed point mutations in this gene. The best compound identified to date was progressed to dose-response studies in an acute murine TB infection model. The resulting ED99 of 49 mg/Kg is within the range of commonly employed tuberculosis drugs, demonstrating the potential of this chemical series. The in vitro and in vivo target validation evidence presented here adds further weight to MmpL3 as a druggable target of interest for anti-tubercular drug discovery

Design, Synthesis, and Evaluation of New Thiadiazole-Based Direct Inhibitors of Enoyl Acyl Carrier Protein Reductase (InhA) for the Treatment of Tuberculosis

Mycobacterial enoyl acyl carrier protein reductase (InhA) is a clinically validated target for the treatment of tuberculosis infections, a disease that still causes the death of at least a million people annually. A known class of potent, direct, and competitive InhA inhibitors based on a tetracyclic thiadiazole structure has been shown to have in vivo activity in murine models of tuberculosis infection. On the basis of this template, we have here explored the medicinal chemistry of truncated analogues that have only three aromatic rings. In particular, compounds <b>8b</b>, <b>8d</b>, <b>8f</b>, <b>8l</b>, and <b>8n</b> show interesting features, including low nanomolar InhA IC₅₀, submicromolar antimycobacterial potency, and improved physicochemical profiles in comparison with the tetracyclic analogues. From this series, <b>8d</b> is identified as having the best balance of potency and properties, whereby the resolved <b>8d</b> <i>S</i>-enatiomer shows encouraging in vivo efficacy