Inhibition of cytochrome bd oxidase in Mycobacterium tuberculosis by benzothiazole amides

Cytochrome bd (Cyt-bd) oxidase, a key enzyme in the Mtb respiratory chain, is particularly crucial for ATP synthesis when the primary cytochrome bc₁:aa₃ (Cyt-bc₁:aa₃) complex is compromised. There are several reported inhibitors of the Cyt-bd oxidase, predominantly featuring quinoline and quinazoline scaffolds. This study explores benzothiazole amides as potential inhibitors of Cyt-bd oxidase for their ability to deplete ATP in the presence of the Cyt-bc₁:aa₃ inhibitor Q203. These compounds demonstrated significant bactericidal activity against both replicating and non-replicating Mtb strains in this combined approach. Methylene blue assays confirmed their ability to inhibit oxygen consumption, validating their Cyt-bd inhibitory mechanism. Moreover, cytotoxicity studies indicated low toxicity and high selectivity for bacterial cells over mammalian cells. Molecular docking studies elucidated favourable binding interactions with the Cyt-bd protein, while in silico ADME profiling suggested promising pharmacokinetic properties. These results highlight the potential of benzothiazole amides as promising candidates for anti-TB drug development, specifically targeting the Cyt-bd oxidase. Future research will focus on further optimising these compounds and conducting preclinical evaluations to realize their clinical potential as adjuncts in TB therapy.