Description: Zidebactam sodium (WCK5107 sodium; WCK-5107 Na) is a novel and potent dual β-lactamase and penicillin-binding protein2 (PBP2) inhibitor with an IC50 of 0.26 μg/mL. It is one of the components ot WCK 5222 (Cefepime-Zidebactam) which is a bicyclo-acyl hydrazide β-lactam enhancer antibiotic with a dual action involving binding to Gram-negative bacterial PBP2 and β-lactamase inhibition. Cefepime/zidebactam demonstrated excellent activity against Enterobacteriaceae and P. aeruginosa, although activity was reduced in carbapenem-non-susceptible isolates. The activity against A. baumannii was reduced and studies examining the therapeutic efficacy in strains with high cefepime/zidebactam MICs are warranted.