Effects of low incubation temperatures on the bactericidal activity of anti-tuberculosis drugs

OBJECTIVES: to explore the effect of low incubation temperatures and the consequent slowing of bacterial metabolism on the bactericidal action of anti-tuberculosis drugs against Mycobacterium tuberculosis. METHODS: counting of surviving bacteria during exposure of static cultures to 1 mg/L isoniazid, 2 mg/L rifampicin, 0.5 or 2 mg/L TMC207 and 40 or 160 mg/L pyrazinamide, usually for periods of 21 days at temperatures of 37, 25, 22, 19, 16 or 8°C. RESULTS: the bactericidal activities of isoniazid and rifampicin were progressively reduced at 25 and 22°C, and were minimal at lower temperatures. TMC207 was immediately bactericidal at 37°C, in contrast to the early static phase reported with log phase cultures, and showed less change in activity as incubation temperatures were reduced than did rifampicin or isoniazid. Pyrazinamide was more bactericidal when incubation temperatures were reduced below 37°C and when the static seed cultures were most dormant. CONCLUSIONS: these results can be explained by the surmise that at low temperatures bacterial energy is at a low level with only just sufficient ATP to maintain homeostasis, making the bacteria more susceptible to the blocking of ATP synthesis by TMC207. Insufficient ATP at low temperature would also hinder the export of pyrazinoic acid, the toxic product of the pro-drug pyrazinamide, from the mycobacterial cell by an inefficient efflux pump that requires energ

Probing the Interaction of the Diarylquinoline TMC207 with Its Target Mycobacterial ATP Synthase

Infections with Mycobacterium tuberculosis are substantially increasing on a worldwide scale and new antibiotics are urgently needed to combat concomitantly emerging drug-resistant mycobacterial strains. The diarylquinoline TMC207 is a highly promising drug candidate for treatment of tuberculosis. This compound kills M. tuberculosis by binding to a new target, mycobacterial ATP synthase. In this study we used biochemical assays and binding studies to characterize the interaction between TMC207 and ATP synthase. We show that TMC207 acts independent of the proton motive force and does not compete with protons for a common binding site. The drug is active on mycobacterial ATP synthesis at neutral and acidic pH with no significant change in affinity between pH 5.25 and pH 7.5, indicating that the protonated form of TMC207 is the active drug entity. The interaction of TMC207 with ATP synthase can be explained by a one-site binding mechanism, the drug molecule thus binds to a defined binding site on ATP synthase. TMC207 affinity for its target decreases with increasing ionic strength, suggesting that electrostatic forces play a significant role in drug binding. Our results are consistent with previous docking studies and provide experimental support for a predicted function of TMC207 in mimicking key residues in the proton transfer chain and blocking rotary movement of subunit c during catalysis. Furthermore, the high affinity of TMC207 at low proton motive force and low pH values may in part explain the exceptional ability of this compound to efficiently kill mycobacteria in different microenvironments

Sterilizing Activity of Second-Line Regimens Containing TMC207 in a Murine Model of Tuberculosis

RATIONALE: The sterilizing activity of the regimen used to treat multidrug resistant tuberculosis (MDR TB) has not been studied in a mouse model. OBJECTIVE AND METHODS: Swiss mice were intravenously inoculated with 6 log10 of Mycobacterium tuberculosis (TB) strain H37Rv, treated with second-line drug combinations with or without the diarylquinoline TMC207, and then followed without treatment for 3 more months to determine relapse rates (modified Cornell model). MEASUREMENTS: Bactericidal efficacy was assessed by quantitative lung colony-forming unit (CFU) counts. Sterilizing efficacy was assessed by measuring bacteriological relapse rates 3 months after the end of treatment. MAIN RESULTS: The relapse rate observed after 12 months treatment with the WHO recommended MDR TB regimen (amikacin, ethionamide, pyrazinamide and moxifloxacin) was equivalent to the relapse rate observed after 6 months treatment with the recommended drug susceptible TB regimen (rifampin, isoniazid and pyrazinamide). When TMC207 was added to this MDR TB regimen, the treatment duration needed to reach the same relapse rate dropped to 6 months. A similar relapse rate was also obtained with a 6-month completely oral regimen including TMC207, moxifloxacin and pyrazinamide but excluding both amikacin and ethionamide. CONCLUSIONS: In this murine model the duration of the WHO MDR TB treatment could be reduced to 12 months instead of the recommended 18-24 months. The inclusion of TMC207 in the WHO MDR TB treatment regimen has the potential to further shorten the treatment duration and at the same time to simplify treatment by eliminating the need to include an injectable aminoglycoside

Sterilizing Activity of Second-Line Regimens Containing TMC207 in a Murine Model of Tuberculosis

The sterilizing activity of the regimen used to treat multidrug resistant tuberculosis (MDR TB) has not been studied in a mouse model. (TB) strain H37Rv, treated with second-line drug combinations with or without the diarylquinoline TMC207, and then followed without treatment for 3 more months to determine relapse rates (modified Cornell model).Bactericidal efficacy was assessed by quantitative lung colony-forming unit (CFU) counts. Sterilizing efficacy was assessed by measuring bacteriological relapse rates 3 months after the end of treatment.The relapse rate observed after 12 months treatment with the WHO recommended MDR TB regimen (amikacin, ethionamide, pyrazinamide and moxifloxacin) was equivalent to the relapse rate observed after 6 months treatment with the recommended drug susceptible TB regimen (rifampin, isoniazid and pyrazinamide). When TMC207 was added to this MDR TB regimen, the treatment duration needed to reach the same relapse rate dropped to 6 months. A similar relapse rate was also obtained with a 6-month completely oral regimen including TMC207, moxifloxacin and pyrazinamide but excluding both amikacin and ethionamide.In this murine model the duration of the WHO MDR TB treatment could be reduced to 12 months instead of the recommended 18–24 months. The inclusion of TMC207 in the WHO MDR TB treatment regimen has the potential to further shorten the treatment duration and at the same time to simplify treatment by eliminating the need to include an injectable aminoglycoside

Nano-Warriors against Drug-Resistant Tuberculosis: Unleashing Nanoparticles for Enhanced Treatment

Tuberculosis (TB) is a global health crisis, with millions of cases and deaths annually. Drug-resistant strains like multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB further complicate treatment. Conventional TB treatment, reliant on lengthy drug regimens, faces issues of non-compliance, drug resistance, and side effects. Nanoparticles (NPs) offer a promising solution. NPs, with their small size and unique properties, can enhance TB drug delivery. They improve drug solubility and stability, minimize side effects, and enable targeted therapy. NPs encapsulate drugs, shielding them from degradation during delivery and ensuring controlled drug release at the infection site. NPs' controlled release leads to prolonged drug efficacy, reducing dosing frequency and improving patient compliance. Moreover, NPs can encapsulate multiple drugs, a critical advantage in combating drug-resistant TB strains. In conclusion, NPs hold immense promise in TB treatment. They address the limitations of traditional therapies by improving drug delivery, bioavailability, and targeting drug-resistant TB. Ongoing research in nanoparticles-based formulations offers hope for more effective and patient-friendly TB treatments

Am J Respir Crit Care Med

CC999999/Intramural CDC HHS/United States2018-04-04T00:00:00Z25876201PMC5884099vault:2774

Tuberculosis research in South Africa over the past 30 years: From bench to bedside

The South African Medical Research Council Centre for Tuberculosis Research has a rich history of high-impact research that has influenced our understating of this hyper-epidemic which is further exacerbated by the emergence and spread of drug-resistant forms of the disease. This review aims to summarise the past 30 years of research conducted in the Centre which has influenced the way that tuberculosis (TB) is diagnosed and treated. The review includes the development of new technologies for rapid screening of people with probable TB and the repurposing of human diagnostics for wildlife conservation

Mini review on diarylquinolone compound Bedaquiline and some other quinolone derivatives and their antitubercular activity

The strategies design for new anti-tuberculosis (anti-TB) compounds is based on the development of analogs of currently used drugs and novel compounds. The strategies employed and analyze structural features which have led to the development of new anti-TB agents. It is important to determine if compounds have potential activity against these bacteria at the onset of design. The physicochemical properties that directly affect the pharmacokinetics and pharmacodynamics of drugs, influence of stereoisomers on biological activity, because individual enantiomers have significant differences in activity, although sometimes the activity of some enantiomers cannot be explained. In this article, detailed study of diarylquinoline and some other quinoline compounds have been reported

How long will treatment guidelines for TB continue to overlook variability in drug exposure?

BACKGROUND: Despite wide clinical acceptance, the use of weight-banded dosing regimens for the treatment of TB in adults has been defined on an empirical basis. The potential impact of known covariate factors on exposure to different drugs has not been taken into account. OBJECTIVES: To evaluate the effect of demographic factors on the exposure to standard of care drugs after weight-banded dosing, as currently recommended by TB treatment guidelines. In addition, we aim to identify alternative dosing regimens that ensure comparable systemic exposure across the overall patient population. METHODS: Clinical trial simulations were performed to assess the differences in systemic exposure in a cohort of virtual patients. Secondary pharmacokinetic parameters were used to evaluate the adequacy of each regimen along with the percentage of patients achieving predefined thresholds. RESULTS: Our results show that patients weighing less than 40 kg are underexposed relative to patients with higher body weight. The opposite trend was observed following a crude weight band-based dosing regimen with 50 kg as the cut-off point. Simulations indicate that a fixed-dose regimen based on three (70 kg) tablets of 150 mg rifampicin, 75 mg isoniazid, 400 mg pyrazinamide and 275 mg ethambutol reduces variability in exposure, increasing the overall probability of favourable long-term outcome across the population. CONCLUSIONS: These findings suggest the need to revisit current guidelines for the dose of standard of care drugs for TB treatment in adults. The proposed fixed-dose regimen should be considered in future clinical trials