Hybrid Antibiotics Targeting the Bacterial Ribosome.

Antimicrobial resistance remains a formidable challenge to modern medicine, with bacterial resistance mechanisms increasingly eroding the utility of clinically important antibiotics. While recent efforts have expanded the antibacterial pipeline, the development of resistance in priority pathogens continues to exceed the pace of new drug development. One emerging strategy to overcome resistance is the rational design of hybrid antibiotics that engage multiple binding sites. Here we describe the design, synthesis, and microbiological and structural characterization of hybrid antibiotics of azithromycin, tedizolid, and chloramphenicol that span the peptidyltransferase center (PTC) and nascent peptide exit tunnel (NPET) in the bacterial ribosome. We characterize the binding of four such hybrids by cryo-electron microscopy, granting insight into their molecular mechanisms of action. We identify a hybrid of azithromycin and tedizolid that is active against a diverse panel of multidrug-resistant Gram-positive bacteria and is minimally affected by ribosomal protection (ABC-F) resistance mechanisms. These results extend our understanding of ribosome inhibition and provide a pipeline for the rational design of dual-action antibiotics that target the ribosome. In a broader context, this work offers a framework for developing bifunctional inhibitors that engage adjacent binding sites by means of a rational cycle of synthetic optimization, biological evaluation, and structural characterization.