Dual-targeting ketolide-quinolone hybrids overcome erm-mediated resistant pathogens via ribosomal and DNA gyrase...

Macrolide antibiotics are classical protein synthesis inhibitors. However, the frequent development of clinical resistance significantly limits their utility. We report a novel series of ketolide-quinolone hybrids (26-31) that uniquely disrupt both protein synthesis and DNA replication. The new lead 26l exhibited balanced dual inhibition with IC₅₀ values of 1.11 μM against ribosomes and 3.31 μM against DNA gyrases. In vivo mechanistic studies, including resistance mutation mapping in E. coli SQ110DTC strains and MIC profiling against ribosome- or/and gyrase-mutated E. coli SQ110DTC, confirmed concurrent target engagement of 26l. This bifunctional activity not only restored in vitro efficacy against macrolide-resistant erm-mediated resistant Gram-positive pathogens (S. pneumoniae and S. pyogenes), but also significantly enhanced activity against Gram-negative H. influenzae and M. catarrhalis. Notably, compound 26l demonstrated reduced CYP3A4 inhibition-a common side effect associated with macrolide antibiotics-compared to telithromycin. Compound 26l exhibited good stability in both mouse plasma and liver microsomes. Molecular docking studies elucidated how the hybrid simultaneously occupies two key bacterial targets-the ribosome and DNA gyrase-through specific interactions mediated by its macrolide core and quinolone moiety. With its dual-targeting mechanism, expanded spectrum coverage, and optimized safety properties, the new lead 26l emerges as a strategic solution to the escalating crisis of macrolide resistance in community-acquired bacterial pneumonia.