<i>trans</i>-Translation inhibitors that kill <i>Mycobacterium tuberculosis</i> and pathogenic non-tuberculous mycobacteria also disrupt metal homeostasis

Mycobacterium tuberculosis and pathogenic nontuberculous mycobacteria pose a growing challenge to human health, and new antibiotics that target new pathways with novel mechanisms of action are urgently needed. Acylaminooxadiazole derivatives have previously been shown to inhibit the trans- translation ribosome rescue pathway and kill M. tuberculosis . Here, we show that modifications to the acylaminooxadiazole scaffold can improve potency and tune mycobacterial species specificity, resulting in molecules that kill Mycobacterium avium , Mycobacterium abscessus and M. tuberculosis clinical isolates. Free iron was previously shown to antagonize antibacterial activity and decrease the inhibition of trans -translation by acylaminooxadiazoles, but we found that biologically relevant iron sources such as haemin and transferrin do not affect activity. Depletion of transfer-messenger RNA resulted in potentiation of acylaminooxadiazole-based trans -translation inhibitors, confirming inhibition of trans -translation as a mechanism of action. Acylaminooxadiazoles disrupted metal homeostasis in M. tuberculosis , and mutants defective in siderophore-mediated iron utilization were hypersusceptible to some acylaminooxadiazole derivatives, suggesting that these compounds may have a dual mechanism for killing mycobacteria.