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

## TL;DR

This paper reviews new antibiotic combinations that effectively treat drug-resistant bacterial infections.

## Contribution

It provides a comprehensive analysis of cefepime combined with new β-lactamase inhibitors and their clinical potential.

## Key findings

- The combinations show potent activity against multidrug-resistant Gram-negative bacteria.
- Zidebactam enhances β-lactam activity by binding to PBP2.
- Emerging resistance mechanisms include PBP alterations and efflux pump overexpression.

## Abstract

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.