Introduction: Delafloxacin is a novel anionic fluoroquinolone with broad-spectrum activity against aerobic and anaerobic Gram-positive and Gram-negative pathogens, including several clinically relevant resistant organisms. Although delafloxacin has primarily been developed and approved for acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia, its antibacterial spectrum, dual intravenous and oral formulations, and renal elimination characteristics suggest potential utility in urinary tract infections (UTIs). However, the clinical positioning of delafloxacin for UTIs remains insufficiently defined. In particular, urinary drug exposure may be influenced by renal function and urinary pH, both of which are highly relevant in UTI populations. Moreover, the extent to which delafloxacin achieves urinary exposure comparable to established quinolones, such as ciprofloxacin and levofloxacin, has not been systematically assessed. A mechanistic pharmacokinetic/pharmacodynamic framework integrating urinary exposure simulation with comparative clinical evidence may therefore help clarify the potential role of delafloxacin as a candidate for UTI treatment.
Aims: This study aimed to characterize the pharmacokinetic/pharmacodynamic profile of delafloxacin across different renal function and urinary pH conditions, compare its urinary exposure with that of other quinolones commonly used or evaluated for UTIs, and assess its clinical potential as a candidate for UTI indication development.
Methods: A minimal physiologically based pharmacokinetic model incorporating systemic, kidney, and bladder compartments was developed to describe delafloxacin disposition and simulate plasma and urinary concentration–time profiles following both intravenous and oral administration. The model was constructed to account for renal excretion, urinary accumulation, and clinically relevant variation in renal function, including healthy renal function and mild, moderate, and severe chronic kidney disease. Model performance was evaluated by comparing simulated plasma and urinary pharmacokinetic profiles with observed clinical data. The validated model was then used to estimate urinary exposure metrics, including urine-to-plasma exposure ratios, under different renal function scenarios. To further characterize the pharmacodynamic activity of delafloxacin in urinary infection-related conditions, in vitro time-kill assays were conducted against Escherichia coli under neutral and acidic conditions, corresponding to pH 7.4 and pH 6.0, respectively. The resulting pharmacodynamic data were integrated with the mPBPK model to establish an mPBPK-PD framework for simulating the bacterial killing profiles of delafloxacin in the urinary tract. This model was subsequently used to explore potential dosage regimens and identify dosing strategies with favorable predicted efficacy for controlling UTIs. In parallel, model-integrated evidence was combined with a network meta-analysis of quinolone efficacy in UTIs to relate simulated urinary exposure patterns to comparative clinical performance across the quinolone class. And a comparison between the delafloxacin and other representative quinolones was carried.
Results: The mPBPK model adequately captured the observed plasma and urinary pharmacokinetics of delafloxacin after both intravenous and oral administration, supporting its use for urinary exposure prediction. In subjects with normal renal function, simulated urinary exposure was substantially higher than systemic exposure, with urinary AUC approximately 43-fold greater than plasma AUC. This urine-to-plasma exposure advantage decreased progressively with renal impairment, with ratios of 28.99-, 16.94-, and 8.74-fold predicted in mild, moderate, and severe chronic kidney disease, respectively. These findings indicate that renal dysfunction can meaningfully reduce urinary exposure of delafloxacin, although urinary exposure remains higher than plasma across renal function strata. The network meta-analysis identified ciprofloxacin and levofloxacin as the most clinically supported quinolones for UTI treatment, consistent with their established role and favorable urinary pharmacokinetic profiles. Comparative pharmacokinetic analysis showed that delafloxacin achieved urinary concentrations broadly comparable to ciprofloxacin and levofloxacin, with urinary exposure approximately 30-fold higher than plasma exposure under clinically relevant conditions. In contrast, moxifloxacin showed only limited urinary enrichment, with urine exposure approximately 2-fold higher than plasma exposure, consistent with its weaker clinical utility in UTIs. Collectively, these results suggest that delafloxacin has a urinary exposure profile closer to clinically effective UTI quinolones than to quinolones with limited UTI applicability.
Conclusion: This study integrates mechanistic mPBPK modeling, urinary exposure simulation, comparative quinolone pharmacokinetics, and network meta-analysis to evaluate the potential repositioning of delafloxacin for UTIs. The results demonstrate that delafloxacin can achieve high urinary exposure, comparable to established UTI-active quinolones, while also highlighting the importance of renal function as a determinant of urinary drug accumulation.