Substrate‐Inspired Fragment Merging and Growing Affords Efficacious LasB Inhibitors

Extracellular virulence factors have emerged as attractive targets in the current antimicrobial resistance crisis. The Gram‐negative pathogen Pseudomonas aeruginosa secretes the virulence factor elastase B (LasB), which plays an important role in the infection process. Here, we report a sub‐micromolar, non‐peptidic, fragment‐like inhibitor of LasB discovered by careful visual inspection of structural data. Inspired by the natural LasB substrate, the original fragment was successfully merged and grown. The optimized inhibitor is accessible via simple chemistry and retained selectivity with a substantial improvement in activity, which can be rationalized by the crystal structure of LasB in complex with the inhibitor. We also demonstrate an improved in vivo efficacy of the optimized hit in Galleria mellonella larvae, highlighting the significance of this class of compounds as promising drug candidates. An efficient fragment merging and growing strategy with simple chemistry yielded a fragment‐like inhibitor of the virulence factor LasB from Pseudomonas aeruginosa with a twelve‐fold boost in activity. Our optimized structure shows an improved in vivo efficacy demonstrating the significance of exploiting alternative binding modes to succeed in simple fragment merging. The graphic was created with the software tool BioRender (www.biorender.com).