Pyrylium derivatives as outer membrane permeabilizers against MDR gram-negative bacteria via multi-target mode of action.

The prevalence of MDR Gram-negative bacteria has posed a great impetus for the discovery of new therapeutic approaches. Here, we synthesized a series of pyrylium derivatives as antibiotic adjuvants based on IMB-0042, and evaluated their activities against Acinetobacter baumannii (A. baumannii) and Escherichia coli (E. coli). Compound 4a significantly synergized polymyxin B in combating A. baumannii and E. coli both in vitro and on the infected Galleria mellonella models. Furthermore, we identified 4a to be an effective perturbant of the Gram-negative outer membrane (OM) through the blockage on LptA/LptC interaction via targeting Met47 in LptA. And cationic pyrylium reduced the OM densification by electrostatic interaction with anion-rich lipopolysaccharide (LPS). Thus, pyrylium derivatives constitute a new class of multi-target OM permeabilizers, which can significantly potentiate antibiotics against MDR Gram-negative bacteria.