Abstract
Purpose :
Current methods of drug release testing fail to correlate with the in vivo behavior of drug formulations in the eye, resulting in inaccurate predictions of intravitreal kinetics. This study aims to develop a cost-efficient drug release assay that closely mimics the dimensions of a rabbit eye. The goal is to establish a reliable model that could potentially replace some of the initial pharmacokinetic experiments for novel drug formulations, thereby expediting drug development.
Methods :
Dulbecco’s phosphate buffered saline (DPBS), homogenized (HBV) and non-homogenized bovine vitreous (NHBV) were placed in dialysis tubing (molecular weight cut-off 12-14 kDa) with the same dimensions of a rabbit eye (Ø 1.4 cm), and dosed with a cassette containing four compounds of differing chemical properties (ciprofloxacin, fluconazole, ketorolac, and methotrexate). The release of the compounds in DPBS, at 37°C and with constant shaking was monitored by high-performance liquid chromatography coupled with tandem mass spectrometry over time. The elimination rate constants were obtained by fitting the cumulative release data using R, and converted to clearance using a surface area ratio that reflects the compound’s elimination from the vitreous.
Results :
Initial experiments suggested that the used release medium affects the elimination rate constant of each compound. Elimination rate constants in differing media were between 0.50-0.88, 0.39-0.63, and 0.34-0.60 for DPBS, HBV and NHBV, respectively. NHBV was chosen for further studies. The clearances of the four compounds (N=3) were 0.333 ± 0.111 (ciprofloxacin), 0.817 ± 0.288 (fluconazole), 0.443 ± 0.164 (ketorolac), and 0.119 ± 0.041 (methotrexate) mL/h. These values were on average 106 ± 39 % of the intravitreal clearances reported in rabbits for the same compounds.
Conclusions :
The model provides a simple and reliable method to estimate the intravitreal kinetics of drug formulations in rabbits. Given the simplicity of our method setup, it could potentially replace traditional release studies with a model that more closely resembles an eye. Further studies involving more compounds, drug delivery systems, and artificial vitreous substitutes are needed to replace animal studies in this step of preclinical development. However, improvements in preclinical development are necessary for increased cost-effectiveness and adherence to the three R principles used in animal studies.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.