MLEB-22043 is a synthetic siderophore-monobactam conjugate that is taken up into bacteria via its synthetic siderophore component by TonB -dependent transporters. Once inside the bacteria, it exerts antibacterial activity through its β-lactam component. MLEB-22043 is a broad-spectrum antibiotic with significant inhibitory activity against Klebsiella pneumoniae , Escherichia coli , Acinetobacter baumannii , and Pseudomonas aeruginosa.