Isolation of resistant mutants to quinazoline 11626252 in Mycobacterium tuberculosis

New anti-tuberculosis (TB) drugs are needed to handle the current TB situation worldwide caused by M. tuberculosis. We report here lead optimisation efforts of a new series of cytochrome bc1 oxidase inhibitors, the quinazoline derivatives. Four derivatives showed mild to no cytotoxicity as potent in vitro and ex vivo activity in infected THP-1 macrophages against M. tuberculosis. Isolation of resistant mutants to one of the derivatives in M. tuberculosis revealed mutations in both QcrA and QcrB of the cytochrome bc1 oxidase, one of two terminal oxidases of the mycobacterial electron transport chain. Cross-resistance studies, transcriptomic analyses and bioenergetics flux assays provide further evidence of the cytochrome bc1 as the target of the quinazolines compounds.