Abstract: Infections caused by multidrug-resistant (MDR) bacteria, particularly Gram-negative bacteria, are an escalating global t health threat. Often clinicians are forced to administer the last resort antibiotic colistin, however colistin resistance is becoming increasingly prevalent, giving rise to the potential for a situation in which there are no treatment options for MDR Gram-negative infections. The development of adjuvants that circumvent bacterial resistance mechanisms is a promising orthogonal approach to the development of new antibiotics. We recently disclosed that the known IKK-13 inhibitor IMD-0354 potently suppresses colistin resistance in several Gram-negative strains. In this disclosure, we explore the structure activity relationship (SAR) between the IMD-0354 scaffold and colistin resistance suppression, and identify several compounds with more potent activity than the parent against highly colistin resistant strains of Acinetobacter baumannii and Klebsiella pneumoniae.