Title : Simultaneous inhibition of terminal oxidases eradicates heterogenous population of Mycobacterium tuberculosis
Abstract:
Background: The persistence of mycobacterium tuberculosis (Mtb) during chemotherapy is a major obstacle to shortening tuberculosis (TB) treatment. A key survival mechanism is the bacterium's metabolic redundancy, specifically the presence of two terminal oxidases for respiration. The clinical candidate Telacebec (Q203) inhibits the primary cytochrome bc1:aa3 oxidase, but its efficacy is limited because the alternative cytochrome bd oxidase (Cyt-bd) compensates, allowing bacterial survival. We hypothesized that co-targeting both oxidases would overcome this evasion and lead to a more effective sterilizing regimen.
Methods: We conducted a whole-cell phenotypic screen to identify a Cyt-bd inhibitor, resulting in the discovery of BD-2. The therapeutic potential of BD-2, both alone and in combination with Q203, was rigorously evaluated. Key assessments included bacterial respiration, ATP homeostasis, and bactericidal activity against replicating and non-replicating Mtb. The combination was further tested in a THP-1 macrophage infection model to simulate an intracellular environment.
Results: While BD-2 showed minimal efficacy as a monotherapy, its combination with Q203 produced a powerful synergistic effect. The dual-inhibition strategy severely disrupted the core energy metabolism of Mtb, simultaneously halting respiration and depleting intracellular ATP. This bioenergetic collapse resulted in potent bactericidal activity against both actively growing and non-replicating, drug-tolerant Mtb populations. Critically, the BD-2/Q203 combination demonstrated significantly enhanced efficacy in clearing Mtb infection within human macrophages compared to Q203 alone.
Conclusion: The simultaneous inhibition of both terminal oxidases with BD-2 and Q203 represents a promising new therapeutic paradigm for TB. By dismantling the bacterium's metabolic redundancy, this approach achieves potent, sterilizing activity against heterogeneous bacterial populations. This strategy has strong potential to improve patient outcomes by accelerating treatment and combating persistent infections, warranting its progression to further preclinical and clinical development.
