Early Clinical Assessment of the Antimicrobial Activity of Finafloxacin Compared to Ciprofloxacin in Subsets of Microbiologically Characterized Isolates

Two phase II studies were performed with patients with uncomplicated urinary tract infections (uUTIs) and complicated urinary tract infections (cUTIs) or acute pyelonephritis (PN) to compare finafloxacin (300 mg twice a day [b.i.d.] orally for uUTI and 800 mg once a day [q.d.] intravenously [i.v.] for cUTI/PN) and ciprofloxacin (250 mg b.i.d. orally for uUTI and 400 mg b.i.d. i.v. for cUTI/PN). The early response to the study medications was evaluated in the microbiological intent-to-treat population (mITT) at day 3. A total of 21% of the isolates were ciprofloxacin resistant, 13.7% were primed pathogens carrying a mutation(s) potentially fostering fluoroquinolone resistance development, and 7.1% produced extended-spectrum β-lactamases (ESBLs). Finafloxacin demonstrated very good early clinical activity, with microbiological eradication rates of 88.6% (n = 132), compared to 78.7% (n = 61) for ciprofloxacin, and 69.6% (n = 23), compared to 35.7% (n = 14) for ciprofloxacin, in patients with ciprofloxacin-resistant uropathogens; 94.1% (n = 17), compared to 80.0% (n = 10) for ciprofloxacin, in patients infected with uropathogens primed for fluoroquinolone resistance uropathogens; and 91.7% (n = 11), compared to 0% for ciprofloxacin, in patients infected with ESBL producers. Finafloxacin demonstrated early and rapid activity against uropathogens, including fluoroquinolone-resistant and/or multiresistant pathogens or ESBL producers, while ciprofloxacin was less active against this subset of resistant pathogens. Susceptibilities of pathogens were quantitated by broth microdilution. Isolates were subgrouped according to their susceptibility patterns, in particular first-step quinolone resistance, quinolone resistance, and ESBL production. Eradication was defined as the elimination or reduction of study entry pathogens to <10³ CFU/ml in urine culture. (The studies described in this paper have been registered at ClinicalTrials.gov under identifiers NCT00722735 and NCT01928433.).