Mechanism of Action
The cefepime component of EXBLIFEP is a cephalosporin antibacterial drug. The bactericidal action of cefepime results from the inhibition of cell wall synthesis. Cefepime penetrates the cell wall of most gram-positive and gram-negative bacteria to bind penicillin-binding protein (PBP) targets. Cefepime is stable to hydrolysis by some beta-lactamases, including penicillinases and cephalosporinases produced by gram-negative and gram-positive bacteria, with the exception of extended spectrum beta-lactamases (ESBL), some oxacillinases, and carbapenem hydrolyzing beta-lactamases.
The enmetazobactam component of EXBLIFEP is a beta-lactamase inhibitor that protects cefepime from degradation by certain serine beta-lactamases such as ESBL.
Resistance
Mechanisms of resistance to EXBLIFEP may include the production of beta-lactamases that are not inhibited by enmetazobactam, modification of PBPs by target alteration, overexpression of efflux pumps, and outer membrane porin mutations.
Clinical isolates may produce multiple beta-lactamases, express varying levels of beta-lactamases, or have amino acid sequence variations, and other resistance mechanisms that have not been identified.
Culture and susceptibility information and local epidemiology should be considered in selecting or modifying antibacterial therapy.
Cefepime-enmetazobactam demonstrated in vitro activity against Enterobacterales in the presence of some beta-lactamases and extended-spectrum beta-lactamases (ESBL) of the following groups: CTX-M, SHV, TEM, and VEB. EXBLIFEP is not active against bacteria that produce KPC, metallo-beta-lactamases or some oxacillinases (OXA). Cefepime is inherently stable to hydrolysis by some AmpC cephalosporinases and OXA-48.
In the Phase 3 cUTI trial with EXBLIFEP, some isolates of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae species complex, Citrobacter braakii, Citrobacter freundii, and Proteus mirabilis, that produced beta-lactamases had a minimum inhibitory concentration ≤4 μg/mL for EXBLIFEP. These isolates carried genes for one or more beta-lactamases of the following enzyme groups: CTX-M, TEM, SHV, VEB, CMY, and OXA-48.
In the Phase 3 cUTI trial with EXBLIFEP, some beta-lactamases were also produced by isolates of K. pneumoniae and an isolate of E. cloacae that had a minimum inhibitory concentration ≥16 mcg/mL for EXBLIFEP. The K. pneumoniae isolates contained genes for NDM-1, OXA-48, or KPC-3 along with CTX-M, CMY, TEM, and/or SHV. The E. cloacae isolate encoded CTX-M.
No cross-resistance with other non-beta-lactam classes of antimicrobials has been identified. Some isolates resistant to carbapenems and to cephalosporins may be susceptible to EXBLIFEP.