Solubility and stability characterization of zileuton in a ternary solvent system

Zileuton ameliorates aminoglycoside and polymyxin-associated acute kidney injury in an animal model

OBJECTIVES

Aminoglycosides and polymyxins are antibiotics with in vitro activity against MDR Gram-negative bacteria. However, their clinical use is hindered by dose-limiting nephrotoxicity. The objective of this project was to determine if zileuton can reduce nephrotoxicity associated with amikacin and polymyxin B in a rat model of acute kidney injury.

METHODS

Sprague Dawley rats (n = 10, both genders) were administered either amikacin (300 mg/kg) or polymyxin B (20 mg/kg) daily for 10 days. Zileuton (4 and 10 mg/kg) was delivered intraperitoneally 15 min before antibiotic administration. Blood samples were collected at baseline and daily to determine serum creatinine concentration. Nephrotoxicity was defined as a ≥2× elevation of baseline serum creatinine. Time-to-event analysis and log rank test were used to compare the onset of nephrotoxicity in different cohorts. Histopathological analysis was also conducted to characterize the extent of kidney injury.

RESULTS

Animals receiving amikacin or polymyxin B alone had nephrotoxicity rates of 90% and 100%, respectively. The overall rate was reduced to 30% in animals receiving adjuvant zileuton. The onset of nephrotoxicity associated with amikacin and polymyxin B was also significantly delayed by zileuton at 4 and 10 mg/kg, respectively. Histopathology confirmed reduced kidney injury in animals receiving amikacin concomitant with zileuton.

CONCLUSIONS

Our pilot data suggest that zileuton has the potential to attenuate nephrotoxicity associated with last-line antibiotics. This would allow these antibiotics to treat MDR Gram-negative bacterial infections optimally without dose-limiting constraints. Further studies are warranted to optimize drug delivery and dosing in humans.

Pharmaceutical analysis combined with in-silico therapeutic and toxicological profiling on zileuton and its impurities to assist in modern drug discovery

The obligatory testing of drug molecules and their impurities to protect users against toxic compounds seems to provide interesting opportunities for new drug discovery. Impurities, which proved to be non-toxic, may be explored for their own therapeutic potential and thus be a part of future drug discovery. The essential role of pharmaceutical analysis can thus be extended to achieve this purpose. The present study examined these objectives by characterizing the major degradation products of zileuton (ZLT), a 5-lipoxygenase (5-LOX) inhibitor being prevalently used to treat asthma. The drug sample was exposed to forced degradation and found susceptible to hydrolysis and oxidative stress. The obtained Forced Degradation Products (FDP's) were resolved using an earlier developed and validated Ultra-High-Pressure Liquid Chromatography Photo-Diode-Array (UHPLC-PDA) protocol. ZLT, along with acid-and alkali-stressed samples, were subjected to Liquid-chromatography Mass-spectrometry Quadrupole Time-of-flight (LC/MS-QTOF) studies. Major degradation products were isolated using Preparative TLC and characterized using Q-TOF and/or Proton nuclear magnetic resonance (¹HNMR) studies. The information obtained was assembled for structural conformation. Toxicity Prediction using Komputer Assisted Technology (TOPKAT) toxicity analyses indicated some FDP's as non-toxic when compared to ZLT. Hence, these non-toxic impurities may have bio-affinity and can be explored to interact with other therapeutic targets, to assist in drug discovery. The drug molecule and the characterized FDP's were subjected to 3-Dimensional Extra Precision (3D-XP)-molecular docking to explore changes in bio-affinity for the 5-LOX enzyme (PDB Id: 3V99). One FDP was found to have a higher binding affinity than the drug itself, indicating it may be a suitable antiasthmatic. The possibility of being active at other sites cannot be neglected and this is evaluated to a reasonable extent by Prediction of Activity Spectra for Substances (PASS). Besides being antiasthmatic, some FDP's were predicted antineoplastic, antiallergic and inhibitors of Complement Factor-D.

Cocrystals of zileuton with enhanced physical stability

Zileuton can form two promising pharmaceutical cocrystals with nicotinamide and isonicotinamide, which demonstrate superior phase stability against moisture.