NAB739

NAB739 is a novel polymyxin derivative antibiotic being developed by Northern Antibiotics for the treatment of multidrug-resistant Gram-negative bacterial infections, particularly complicated urinary tract infections (cUTIs) caused by *Escherichia coli* and *Klebsiella pneumoniae*. Structurally, it is a modified polymyxin B molecule that retains the cyclic portion of the parent compound but features a modified linear peptide portion consisting of a threonyl-d-serinyl sequence instead of the diaminobutyryl-threonyl-diaminobutyryl sequence. This modification reduces the net positive charge from five to three, which is associated with a three-fold reduction in nephrotoxicity compared to polymyxin B in preclinical models. NAB739 targets the bacterial outer membrane and is excreted into the urine at significantly higher concentrations than polymyxin B, potentially allowing for effective treatment of urinary infections at lower systemic doses.