Mechanism of Action
ZAYNICH is a combination of cefepime, a cephalosporin antibacterial drug and zidebactam, a beta-lactamase inhibitor and non-beta-lactam antibacterial. Cefepime primarily targets PBP3 in Gram-negative bacterial pathogens, while zidebactam selectively inhibits penicillin-binding protein-2 (PBP2). Cefepime and zidebactam work together by binding multiple PBPs, leading to bacterial killing. This synergy occurs even in the presence of beta-lactamases, including metallo-beta-lactamases (MBLs), which are not inhibited by zidebactam, and other non-enzymatic cefepime resistance mechanisms, such as hyper-efflux and downregulation of outer membrane porin channels.
This is hypothesized to be due to cefepime's ability to bind to its PBP targets at a faster rate than it is hydrolyzed by beta-lactamases. Zidebactam, as a non-beta-lactam, is less susceptible to degradation by beta-lactamases. Zidebactam demonstrates
in vitroactivity against certain Enterobacterales and
P. aeruginosa. The zidebactam component of ZAYNICH exhibits
in vitroactivity against Ambler Class A (SHV, TEM, CTX-M, and KPC) and Class C (CMY) beta-lactamases.
ZAYNICH demonstrated
in vitroactivity against Enterobacterales isolates genetically confirmed to contain Ambler Class A (such as KPCs), Class B (such as NDM, VIM and IMP), Class C (such as CMY), and Class D beta-lactamases (such as OXA-48-like). In
P. aeruginosa, ZAYNICH demonstrates in vitro activity against isolates with elevated expression of AmpC as well as isolates genetically confirmed to contain MBLs, OXAs, VEB, GES, KPC, as well as those with
oprDdownregulation, increased efflux, or PBP mutations.
Resistance
The antibacterial activity of ZAYNICH may be affected by resistance mechanisms such as mutations in PBPs, decreased outer membrane permeability, overexpression of efflux pumps, or hyperproduction of beta-lactamases. Culture and susceptibility information and local epidemiology should be considered in selecting or modifying antibacterial therapy.
The frequency of resistance development in Gram-negative bacteria exposed to ZAYNICH at 5x minimum inhibitory concentration (MIC) was less than 10
-7. In a 10-day in vitro hollow-fiber infection model using a high starting inoculum (~1 x 10
8CFU/mL), resistance to ZAYNICH was not observed in two clinical isolates of
Klebsiella pneumoniaeharboring either KPC-2 or KPC-3. The model simulated human exposures associated with cefepime 2 grams and zidebactam 1 gram administered every 8 hours.
Interactions with Other Antimicrobials
No antagonism was demonstrated
in vitrostudies between ZAYNICH and beta-lactams, aminoglycosides, tetracyclines, fluoroquinolones, and polymyxins.
The combination of cefepime and zidebactam shows a synergistic antibacterial activity with aztreonam.
Activity Against Cefepime Non-Susceptible Bacteria in Animal Infection Models
The addition of zidebactam restored
in vivoactivity of cefepime against cefepime-resistant Enterobacterales, including isolates genetically confirmed to harbor metallo-β-lactamases (MBLs; e.g., NDM, VIM, and IMP), KPC, and OXA-48-like carbapenemases. Activity was also observed against
Pseudomonas aeruginosa, including isolates with
OprDloss, efflux pump overexpression, and those harboring carbapenemase genes (e.g., NDM).
Antimicrobial Activity
ZAYNICH has been shown to be active against most isolates of the following bacteria, both
in vitroand in clinical infections
[see Indications and Usage (
1)]
.
Complicated urinary tract infections, including pyelonephritis
Gram-negative bacteria:
- Escherichia coli
- Klebsiella pneumoniae
- Proteus mirabilis
- Enterobacter cloacae complex
- Pseudomonas aeruginosa
The following
in vitrodata are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an
in vitrominimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint of ZAYNICH against isolates of similar genus or organism group.
However, the efficacy of ZAYNICH in treating clinical infections caused by these bacteria has not been established in adequate and well-controlled clinical trials.
Gram-negative bacteria:
- Klebsiella oxytoca
- Morganella morganii
- Klebsiella variicola
- Citrobacter braakii
- Serratia marcescens
- Providencia rettgeri
- Citrobacter freundii
- Citrobacter koseri
- Klebsiella aerogenes
- Proteus vulgaris
- Providencia stuartii
Susceptibility Test Methods
For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.