Abstract
Abstract: :
Purpose: Vascular Endothelial Growth Factor (VEGF) is one of the proteins implicated in angiogenesis in several ocular diseases, including age related macular degeneration (AMD). rhuFab V2 is a recombinant humanized antibody fragment which binds VEGF with high affinity and is currently investigated in subjects with AMD following intravitreal (ITV) administration. Pharmacokinetic studies in humans and animals are hindered by difficulties in accessing the vitreous body safely for collection and measurement of vitreous drug concentrations, and usually require a large number of animals since serial sampling is limited. The goal of the present study was to evaluate the feasibility of using fluorescein-labeled rhuFab V2 to characterize drug disposition after ITV administration to rabbits, using a method that does not require collection of vitreous samples. Methods: rhuFab V2 was labeled with 5-(and -6)carboxyfluorescein succinimidyl ester, and characterization of the labeled material was done by ELISA and mass spectroscopy. Dutch belted rabbits (N=4) received a total of 500 µg of rhuFab V2 (100 µg of fluorescein-labeled rhuFab V2 and 400 µg unlabelled rhuFab V2) ITV in each eye, under general and topical anesthesia. Using a fluorophotometer, rhuFab V2 concentrations in the vitreous were measured in conscious animals following dilation of the eyes at several time points for up to 10 days. Vitreous concentrations were averaged for the entire vitreous cavity at each time point, and the pharmacokinetic parameters were then estimated by compartmental methods for each eye. Results: Fluorescein-labeled rhuFab V2 disappeared from the vitreous with a mean (s.d.) terminal half-life of 2.9 (0.75) days and a mean residence time of 4.2 (1.0) days. By gross examination, no signs of ocular inflammation were noted. These results were consistent with those obtained previously in New Zealand white rabbits which were sacrificed at different time points for vitreous collection and drug concentrations were determined by ELISA. Conclusion: Results from these experiments indicate that fluorescein-labeled rhuFab V2 with fluorophotometer detection can be used as a non-invasive technique to characterize rhuFab V2 vitreous pharmacokinetics.
Keywords: 308 age-related macular degeneration • 514 pharmacology • 316 animal model