Abstact

Ethionamide (Eto) and prothionamide (Pto) are second-line antibiotics used for tuberculosis (TB) treatment. Both are prodrugs whose antibacterial activity depends on bioactivation by oxidases in Mycobacterium tuberculosis, including the Baeyer-Villiger monooxygenase MymA. Through biophysical, genetic, and cellular assays, we show that the clinical candidate alpibectir (Alp, BVL-GSK098) binds the transcriptional regulator VirS, increasing MymA expression and potentiating Eto and Pto activity. Alpibectir also boosts the activity of the corresponding host-derived sulfoxide metabolites. We additionally show that alpibectir exhibits intrinsic antibacterial activity via overexpression of the mymA operon. The alpibectir/Eto (AlpE) combination is rapidly bactericidal in vitro and in mice, lowers the frequency of spontaneous resistance of Eto, and remains active on Eto- and isoniazid-resistant strains, including isolates with inhA promoter mutations. Alpibectir was safe in a Phase 1 human clinical trial. Together with the potentiation data presented here, these findings highlight its potential to optimize TB chemotherapy by reducing Eto/Pto doses, which can minimize dose-related side effects, enhancing adherence.