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

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.