Antimicrobial Activity of Gepotidacin Tested against Escherichia coli and Staphylococcus saprophyticus Isolates Causing Urinary Tract Infections in Medical Centers Worldwide (2019 to 2020)

ABSTRACT The in vitro activities of gepotidacin and comparator agents against 3,560 Escherichia coli and 344 Staphylococcus saprophyticus collected from female (81.1%) and male (18.9%) patients with urinary tract infections (UTIs) in a global prospective surveillance program in 2019 to 2020 were determined. Isolates collected from 92 medical centers in 25 countries, including the United States, Europe, Latin America, and Japan, were tested for susceptibility by reference methods in a central monitoring laboratory. Gepotidacin inhibited 98.0% (3,488/3,560 isolates) of E. coli and 100% (344/344 isolates) of S. saprophyticus at gepotidacin concentrations of ≤4 μg/mL and ≤0.25 μg/mL, respectively. This activity was largely unaffected with isolates that demonstrated resistance phenotypes to other oral standard-of-care antibiotics, including amoxicillin-clavulanic acid, cephalosporins, fluoroquinolones, fosfomycin, nitrofurantoin, and trimethoprim-sulfamethoxazole. Gepotidacin also inhibited 94.3% (581/616 isolates) of E. coli isolates with an extended-spectrum β-lactamase-producing phenotype, 97.2% (1,085/1,129 isolates) of E. coli isolates resistant to ciprofloxacin, 96.1% (874/899) of E. coli isolates resistant to trimethoprim-sulfamethoxazole, and 96.3% (235/244 isolates) of multidrug-resistant E. coli isolates at gepotidacin concentrations of ≤4 μg/mL. In summary, gepotidacin demonstrated potent activity against a large collection of contemporary UTI E. coli and S. saprophyticus strains collected from patients worldwide. These data support the further clinical development of gepotidacin as a potential treatment option for patients with uncomplicated UTIs.

Prior studies of gepotidacin established in vitro activity for the most common UTI target pathogens (18)(19)(20)(21); however, this study prospectively monitored the in vitro activity of gepotidacin and comparator agents against a contemporary collection of E. coli and S. saprophyticus strains recovered from UTIs. The in vitro activity of gepotidacin against these isolates, as well as against subsets displaying resistance to other agents, is discussed.

DISCUSSION
UTIs remain a common global health problem. Increasing resistance to oral agents, including cephalosporins, fluoroquinolones, and trimethoprim-sulfamethoxazole, have limited their use as empirical treatment (4). Current oral first-line empirical options for treating uUTIs include fosfomycin, nitrofurantoin, and amdinocillim (6). The data from this large collection of recent E. coli isolates from UTIs support these treatment options, as the proportions of all E. coli isolates that were susceptible to ciprofloxacin, cefadroxil, and trimethoprim-sulfamethoxazole were smaller (68.2% to 82.5%) than those for fosfomycin, amdinocillin, nitrofurantoin, and nitroxoline (94.1% to 99.9%). The contrast between these two drug sets was even more evident when the susceptibility rates against ESBL-producing and MDR isolates were compared. Against both ESBL-producing and MDR isolates, limited activity and low susceptibility rates (,50% susceptible) were seen for amoxicillin-clavulanate, cefadroxil, ciprofloxacin, and trimethoprim-sulfamethoxazole, while susceptibility rates of .90% were observed for fosfomycin, amdinocillin, nitrofurantoin, and nitroxoline. The in vitro activities of fosfomycin, amdinocillin, nitrofurantoin, and nitroxoline against UTI E. coli strains, regardless of phenotype, have renewed interest in these old agents as oral options for treating UTIs. Nitrofurantoin is widely available and was approved by the U.S. FDA in 1954, and nitroxoline has been in clinical use in western European countries since 1962. Both agents have limitations, such as lack of PK and PD data, mainly bacteriostatic activity, and limited commercial availability (for nitroxoline) (22). Fosfomycin was introduced in Europe in the 1970s and was approved by the U.S. FDA in 1996 for single-dose treatment of uUTIs caused by E. coli or Enterococcus faecalis (23). Although fosfomycin is active in vitro, it has been reported that older clinical trial studies might have overestimated the clinical efficacy of fosfomycin (24); furthermore, a higher clinical cure rate with nitrofurantoin, compared with fosfomycin, has been reported (25). Finally, amdinocillin has been used for many decades for uUTIs in Nordic European countries and has shown in vitro stability against CTX-M-producing E. coli strains. However, clinical efficacy studies with these MDR isolates are lacking (26). Despite the potent in vitro activity shown by these older agents, these various limitations demonstrate the need for the clinical development of new agents (27).
Gepotidacin is currently under clinical development for the treatment of uUTIs and urogenital gonorrhea. In summary, gepotidacin demonstrated potent in vitro activity against a large global collection of contemporary E. coli isolates causing UTIs, inhibiting 98.0% of all E. coli isolates at MIC values of #4 mg/mL. Gepotidacin retained this activity against both ESBL-producing and MDR subsets, with 94.3% and 96.3%, respectively, of gepotidacin MIC values being #4 mg/mL. When tested against many subsets of drug-resistant E. coli phenotypes, gepotidacin maintained similar MIC 50 and MIC 90 values (2 and 4 mg/mL, respectively), with the single exception of fosfomycin-resistant E. coli strains, for which the gepotidacin MIC 90 value was one doubling dilution higher at 8 mg/mL. However, this difference may be a result of the small sample size (n = 25). Of note, gepotidacin retained activity against isolates that were resistant to current first-line agents for uUTIs, with MIC values of #4 mg/mL for 84.0%, 96.7%, 95.7%, and 96.1% of isolates that were resistant to fosfomycin, amdinocillin, nitrofurantoin, and trimethoprim-sulfamethoxazole, respectively. Previous studies demonstrated that the gepotidacin concentration in urine after administration of 1,500 mg twice a day had a maximum value of 580 mg/mL between doses on day 1 and 920 mg/mL on day 4. Also, the steady-state total trough levels remained above 4 mg/mL within 12 h (15). These PK parameters indicate that the gepotidacin concentration in urine during the dosing Finally, gepotidacin (MIC 100 , 0.25 mg/mL) also demonstrated potent in vitro activity against contemporary S. saprophyticus isolates, against which older agents, such as fosfomycin, amdinocillin, and nitroxoline, lack activity. These in vitro data provide recent information and benchmark for gepotidacin activity prior to its clinical approval and use for treating uUTIs. As resistance to current therapy options continues to increase, these data support further clinical development of gepotidacin as a potential new agent for the treatment of uUTIs.  [5.8% overall]). All isolates were cultured from urine or urethral catheter samples and deemed responsible for UTI based on local criteria. Only 1 isolate per patient per infection episode was included in this study. Isolates were collected from both female (81.1%) and male (18.9%) patients. Most isolates (68.4%) were recovered from samples that had been collected from patients associated with medical service lines representing outpatient treatment, including ambulatory/ outpatient, family practice, or emergency room services. Other isolates (31.6%) were cultured from patients in medical service lines suggestive of hospitalized individuals. Species identification was confirmed by standard biochemical tests and, where necessary, the matrix-assisted laser desorption ionization (MALDI) Biotyper (Bruker Daltonics, Billerica, MA, USA) according to the manufacturer's instructions.

MATERIALS AND METHODS
Susceptibility testing. The broth microdilution method was performed according to CLSI methods to determine susceptibility to gepotidacin and its comparator agents (28). Susceptibility to amoxicillin-clavulanate was tested at the CLSI-recommended 2:1 ratio. Susceptibility to amdinocillin and fosfomycin was determined by reference agar dilution following recommendations made by the CLSI in the M07 (28) and M100 (29) documents. The testing medium utilized was Mueller-Hinton agar, and fosfomycin testing included supplementation with glucose-6-phosphate at a final concentration of 25 mg/mL. Susceptibility to the comparators nitroxoline (30 mg) and cefadroxil (30 mg) was determined by disk diffusion following the CLSI M02 and M100 guidelines (29,30). Disk inhibition zones and MIC values were validated by concurrently testing CLSI-and/or EUCAST-recommended quality control (QC) reference strains ATCC 25922, ATCC 27853, ATCC 29213, and ATCC 35218. All QC results were within published ranges (29). CLSI (29) and EUCAST (31) susceptibility interpretive criteria were used to determine susceptibility/resistance percentages for comparator agents. A single value was reported when susceptibility breakpoints agreed between CLSI and EUCAST guidelines (ciprofloxacin, ceftriaxone, amdinocillin, and trimethoprim-sulfamethoxazole) or when breakpoints exist for only one agency (cefadroxil and nitroxoline [EUCAST]). A single value (CLSI) was also reported for amoxicillin-clavulanate tested at a 2:1 ratio. When breakpoints differ between CLSI and EUCAST guidelines (fosfomycin and nitrofurantoin), the percentages of isolates considered susceptible with each breakpoint are labeled accordingly.
Resistant subsets. CLSI breakpoints were applied to define isolates with a phenotype of resistance to the following standard-of-care agents: amoxicillin-clavulanate, ciprofloxacin, fosfomycin, mecillinam, nitrofurantoin, and trimethoprim-sulfamethoxazole. The ESBL-producing phenotype was defined for E. coli as MIC values of $2 mg/mL for aztreonam, ceftazidime, or ceftriaxone (29). Isolates meeting these criteria can produce ESBL, have plasmid AmpC, and/or overexpress the intrinsic AmpC gene but are described here as presumptive ESBL producers. All E. coli strains were susceptible to meropenem. The MDR designation for isolates was similar to the criteria published by Magiorakos et al. (32), who define MDR as not susceptible to $1 agent in $3 antimicrobial classes. The antimicrobial classes and representative drugs used in the E. coli MDR analysis included broad-spectrum cephalosporins (ceftriaxone and ceftazidime), carbapenems (meropenem), a broad-spectrum penicillin combined with a b-lactamase inhibitor (piperacillin-tazobactam), fluoroquinolones (ciprofloxacin and levofloxacin), and aminoglycosides (gentamicin and amikacin).

ACKNOWLEDGMENTS
We thank all participants in the SENTRY surveillance program for providing bacterial isolates.
JMI Laboratories received compensation fees to run the study. This project has been funded in whole or in part with federal funds from the Office of the Assistant Secretary for Preparedness and Response, Biomedical Advanced Research and Development Authority (OTA agreement HHSO100201300011C).