Cefepime Combined with Late-Generation β-Lactamase Inhibitors: Mechanisms of Action, In Vitro Activity, PK/PD Characteristics, Clinical Evidence and Resistance Mechanisms

: Cefepime combined with late-generation β-lactamase inhibitors-enmetazobactam, zidebactam, and taniborbactam-represents a promising strategy to treat multidrug-resistant Gram-negative infections. These combinations expand the therapeutic armamentarium beyond established β-lactam/β-lactamase inhibitor regimens, offering targeted activity against ESBL-, AmpC-, and carbapenemase-producing Enterobacterales, as well as multidrug-resistant Pseudomonas aeruginosa. In vitro studies highlight potent and broad activity, with mechanisms including β-lactamase inhibition and, in the case of zidebactam, dual β-lactam enhancement through PBP2 binding. Clinical evidence demonstrates efficacy in complicated urinary tract infections and suggests potential for treating extensively drug-resistant infections, including those unresponsive to conventional β-lactam/β-lactamase inhibitors. Emerging resistance mechanisms-such as PBP alterations, porin loss, efflux pump overexpression, and evolving KPC or NDM variants-underscore the need for ongoing surveillance and robust susceptibility testing. This review provides a comprehensive overview of the mechanisms of action, in vitro activity, pharmacokinetic/pharmacodynamic properties, clinical outcomes, and resistance patterns of these cefepime-based combinations. It also highlights future directions, including the establishment of clinical breakpoints, evaluation in severe infections, and exploration of combination strategies to counteract complex resistance. Overall, these agents exemplify a strategic evolution in β-lactam therapy, offering versatile options to reduce carbapenem reliance while maintaining high efficacy against multidrug-resistant Gram-negative pathogens.