Discovery of dual-active ethionamide boosters inhibiting the Mycobacterium tuberculosis ESX-1 secretion system

Drug-resistant Mycobacterium tuberculosis (Mtb) remains a major public health concern requiring complementary approaches to standard anti-tuberculous regimens. Anti-virulence molecules or compounds that enhance the activity of antimicrobial prodrugs are promising alternatives to conventional antibiotics. Exploiting host cell-based drug discovery, we identified an oxadiazole compound (S3) that blocks the ESX-1 secretion system, a major virulence factor of Mtb. S3-treated mycobacteria showed impaired intracellular growth and a reduced ability to lyse macrophages. RNA sequencing experiments of drug-exposed bacteria revealed strong upregulation of a distinct set of genes including ethA, encoding a monooxygenase activating the anti-tuberculous prodrug ethionamide. Accordingly, we found a strong ethionamide boosting effect in S3-treated Mtb. Extensive structure-activity relationship experiments revealed that anti-virulence and ethionamide-boosting activity can be uncoupled by chemical modification of the primary hit molecule. To conclude, this series of dual-active oxadiazole compounds targets Mtb via two distinct mechanisms of action. [Display omitted] •1,3,4-oxadiazoles limit intracellular growth of Mycobacterium tuberculosis•These compounds inhibit the mycobacterial ESX-1 secretion system•Some analogs have a dual mechanism and strongly improve ethionamide activity Gries et al. identified oxadiazole derivatives that block pathogenicity of Mycobacterium tuberculosis by inhibiting the ESX-1 secretion system. Mode of action studies revealed two analogs which potently upregulate monooxygenases leading to increased efficacy of the prodrug ethionamide. These dual-active compounds allow for the development of new treatment options against tuberculosis.