A dual-targeting succinate dehydrogenase and F1Fo-ATP synthase inhibitor rapidly sterilizes replicating and non-replicating Mycobacterium tuberculosis.

Mycobacterial bioenergetics is a validated target space for antitubercular drug development. Here, we identify BB2-50F, a 6-substituted 5-(N,N-hexamethylene)amiloride derivative as a potent, multi-targeting bioenergetic inhibitor of Mycobacterium tuberculosis. We show that BB2-50F rapidly sterilizes both replicating and non-replicating cultures of M. tuberculosis and synergizes with several tuberculosis drugs. Target identification experiments, supported by docking studies, showed that BB2-50F targets the membrane-embedded c-ring of the F1Fo-ATP synthase and the catalytic subunit (substrate-binding site) of succinate dehydrogenase. Biochemical assays and metabolomic profiling showed that BB2-50F inhibits succinate oxidation, decreases the activity of the tricarboxylic acid (TCA) cycle, and results in succinate secretion from M. tuberculosis. Moreover, we show that the lethality of BB2-50F under aerobic conditions involves the accumulation of reactive oxygen species. Overall, this study identifies BB2-50F as an effective inhibitor of M. tuberculosis and highlights that targeting multiple components of the mycobacterial respiratory chain can produce fast-acting antimicrobials.

Antituberculosis Activity of the Antimalaria Cytochrome bcc Oxidase Inhibitor SCR0911.

The ability to respire and generate adenosine triphosphate (ATP) is essential for the physiology, persistence, and pathogenicity of Mycobacterium tuberculosis, which causes tuberculosis. By employing a lead repurposing strategy, the malarial cytochrome bc1 inhibitor SCR0911 was tested against mycobacteria. Docking studies were carried out to reveal potential binding and to understand the binding interactions with the target, cytochrome bcc. Whole-cell-based and in vitro assays demonstrated the potency of SCR0911 by inhibiting cell growth and ATP synthesis in both the fast- and slow-growing M. smegmatis and M. bovis bacillus Calmette-Guérin, respectively. The variety of biochemical assays and the use of a cytochrome bcc deficient mutant strain validated the cytochrome bcc oxidase as the direct target of the drug. The data demonstrate the broad-spectrum activity of SCR0911 and open the door for structure-activity relationship studies to improve the potency of new mycobacteria specific SCR0911 analogues.