2025/08/22 by Janine L. Gray, Elizabeth V. K. Ledger, Tiffany Suwatthee +16 · 1 voice
Biochemistry, Genetics and Molecular Biology · Chemistry · Pharmacology, Toxicology and Pharmaceutics · #Antibiotic Resistance in Bacteria #Chemical Reactions and Isotopes #Synthesis and Biological Evaluation
paper · pdf · doi:10.1101/2025.08.19.671038
openalex publication_date 2025/08/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract Antibiotic resistance is among the greatest threats of the modern era. Multidrug efflux pumps expel antibiotics from bacterial cells and present a particular challenge by conferring resistance to a broad range of antibiotic classes; however, there is currently a lack of potent and selective inhibitors. Here, we report the discovery of IMP-2380 , a drug-like chemical probe for the multidrug efflux pump NorA that delivers low-nanomolar potentiation of ciprofloxacin activity in vitro and activity in an in vivo S. aureus infection model. A phenotypic high-throughput screen for inhibitors of the ciprofloxacin-activated SOS DNA repair pathway in methicillin-resistant Staphylococcus aureus (MRSA) identified hit compounds targeting NorA, and subsequent optimization established IMP-2380 as the most potent NorA inhibitor discovered to date. The structure of NorA bound to IMP-2380 was solved by cryo-electron microscopy at 2.52 Å resolution, revealing that the small molecule locks the pump in the ‘outward-open’ conformation. This closes the inner face and prevents antibiotics binding from the cytosol, providing an explanation for the exceptional potency of IMP-2380 and structure-activity relationship across the series. IMP-2380 represents an in vivo active NorA inhibitor, functioning via a structurally defined outward-open binding mode, and will enable future exploration of NorA as a druggable target to combat antibiotic resistance.