Antibiotic hybrids: A promising strategy to replenish the pipeline and combat antimicrobial resistance.

Antimicrobial resistance (AMR) poses an ongoing threat to global health, with the number of deaths directly attributable to AMR projected to rise to 8 million. One of the main reasons for the current crisis is the depletion of antibiotic candidates in clinical pipelines. To address this, more preclinical candidates must be advanced into development. However, the scientific challenges and limited economic incentives associated with antibiotic research have further aggravated the situation. Antibiotic hybrids, which combine two antibiotics with different modes of action, have emerged as a promising strategy to overcome AMR and are already being developed for clinical use. This approach takes advantage of the strong selective pressure exerted when two bactericidal agents act simultaneously. Importantly, because hybrids are administered as a single chemical entity, they may offer advantages over conventional combination therapies, such as simplified pharmacokinetics and dosing. Furthermore, since clinically validated antibiotics are used as the building blocks of hybrids, this strategy provides an efficient platform for generating new lead compounds. Recently, the concept of antibiotic hybrids has expanded beyond antibiotic-antibiotic conjugates to include the attachment of functional molecules designed to mitigate the disadvantages of the parent antibiotics. In this review, we summarize the definition of antibiotic hybrids, highlight representative compounds that have entered clinical evaluation, and discuss recent advances in their development.