Prodrug florfenicol amine is activated by intrinsic resistance to target Mycobacterium abscessus

Non-tuberculous mycobacteria are emerging pathogens with high intrinsic drug resistance. Among these, Mycobacterium abscessus is particularly refractory owing to its extensive array of resistance mechanisms. Here we introduce florfenicol amine (FF-NH₂), a major metabolite of the antibiotic florfenicol, which acts as a prodrug with narrow-spectrum activity against M. abscessus-chelonae complex species. FF-NH₂ leverages intrinsic M. abscessus resistance conferred by the transcription factor WhiB7. It avoids WhiB7-dependent resistance mediated by the O-acetyltransferase Cat and is activated by the WhiB7-dependent N-acetyltransferase Eis2 in a prodrug fashion to generate the active translational inhibitor FF acetyl (FF-ac). FF-NH₂ induces Eis2 expression through WhiB7, creating a feed-forward bioactivation loop, which increases FF-ac accumulation and antimicrobial action. FF-NH₂ displays antiresistance properties, can synergize with other antibiotics and mitigates toxicity linked to mammalian mitochondrial ribosome inhibition. Importantly, FF-NH₂ demonstrated efficacy in a murine model of M. abscessus infection. These findings suggest intrinsic resistance can be exploited to develop safer and more effective treatments for this pathogen.