Characterization of gepotidacin activity, including in vitro kill kinetics, checkerboard, and PAE/SME testing against gram-positive and gram-negative bacteria

Gepotidacin is a novel, first-in-class triazaacenaphthylene antibiotic that inhibits bacterial DNA replication through a distinct binding site and unique mechanism of action that provides well-balanced inhibition of two different type II topoisomerase enzymes (DNA gyrase and topoisomerase IV) for most pathogens. Gepotidacin was recently approved by the US Food and Drug Administration (FDA) and the Medicines and Healthcare Products Regulatory Agency (MHRA) for the treatment of uncomplicated urinary tract infections (uUTI) and by the FDA for uncomplicated urogenital gonorrhea. This study investigated the in vitro time-kill kinetics, post-antibiotic effect (PAE), and sub-inhibitory MIC effect (PAE-SME) of gepotidacin, as well as interactions between gepotidacin and select marketed antibacterial agents for species where the published activity of gepotidacin was limited. Species included are those known to be associated with uUTI: Citrobacter freundii species complex, Enterobacter cloacae species complex, Klebsiella aerogenes , Klebsiella pneumoniae , Proteus mirabilis , Providencia rettgeri , Enterococcus faecalis , and Staphylococcus saprophyticus . Isolates were selected to represent various phenotypes, including wild type, extended-spectrum beta-lactamase positive (ESBL), and fluoroquinolone-resistant. Gepotidacin displayed concentration-dependent activity in time-kill, PAE, and PAE-SME experiments. Gepotidacin displayed bactericidal activity, often by 8 h, against 83% of isolates when tested at 4× and 10× MIC. In general, modest PAEs (>1–4 h) and extended PAE-SMEs (>4 h) were observed for gepotidacin. No antagonism was observed in broth microdilution checkerboard studies with marketed antibiotics, and the only consistent synergy observed was with gepotidacin and vancomycin against S. saprophyticus . These data add to the understanding of pharmacodynamics at play when treating with gepotidacin relevant uUTI species other than Escherichia coli .

IMPORTANCE

Antibiotic resistance continues to limit treatment options for common infections such as urinary tract infections (UTIs). Gepotidacin is a recently approved antibiotic that works in a new way compared with existing drugs, allowing it to remain active against bacteria that are resistant to many commonly used treatments. In this study, we examined how effectively gepotidacin kills several bacterial species that cause UTIs, including organisms that are resistant to fluoroquinolones or produce extended-spectrum β-lactamases. Gepotidacin was shown to rapidly reduce bacterial populations at clinically relevant concentrations and continued to suppress bacterial growth even after short exposures. Importantly, gepotidacin did not interfere with the activity of other commonly used antibiotics, suggesting it can potentially be used alongside existing therapies if needed. These findings provide additional evidence supporting the effectiveness of gepotidacin against a broad range of UTI pathogens and help improve our understanding of how this new antibiotic may perform in clinical treatment.