Tuspetinib enhances the activity of polymyxin B by inhibiting the GlcNAc6P deacetylase.

The past decade has witnessed the recognition of antibiotic resistance as an emerging threat to public health. Polymyxin B (PMB) is a last-resort antibiotic against multidrug-resistant (MDR) Gram-negative bacteria, but it has nephrotoxicity. A cocktail with molecules to sensitize microbes to PMB is an effective approach to rescue and expand its clinical application range. Tuspetinib (TUS) is a selective FMS-like tyrosine kinase 3 (FLT3) inhibitor with activity against acute myeloid leukemia (AML) and a favorable safety profile. In this study, we found that TUS can enhance the antibacterial activity of PMB against Klebsiella pneumoniae and its clinical PMB-resistant isolates. We also revealed the mechanism by which TUS inhibits the activity of GlcNAc6P deacetylase (NagA) and clarified the association between NagA and PMB resistance. Finally, we demonstrated the efficacy of TUS plus PMB therapy in a mouse model of pulmonary infection with a clinical PMB-resistant K. pneumoniae isolate. In all, this work discovers a promising drug combination strategy based on PMB and TUS and underlies the special mode of action that involves inhibiting the activity of NagA.