Cassette Dosing Pharmacokinetic Studies for Evaluation of Ophthalmic Drugs for Posterior Ocular Diseases

The purpose of this investigation was to evaluate the utility of cassette dosing as a means for increasing throughput and decreasing animal usage for intravitreal ocular pharmacokinetic studies. Pigmented rabbits received a single intravitreal injection of test article containing either a single compound or a mixture of up to five compounds. Samples of vitreous, choroid and retina were collected at predetermined intervals through 7 or 28 days after dosing. Concentrations of each compound were determined by LC/MS/MS, with subsequent pharmacokinetic data analysis. The ocular pharmacokinetic properties of four test compounds administered as a cassette were in agreement with the ocular pharmacokinetics of each compound when administered as a single entity. Cassette dosing was subsequently used to screen an additional 15 compounds, with injection of 5 compounds per study. Based on the results from these cassette-dosing studies, some compounds demonstrated favorable ocular pharmacokinetics, with sustained concentrations above 300 ng/g in retina for at least 1 week after dosing while other compounds showed either considerably less penetration into retina or a shorter residence time in the retina. These findings suggest that the cassette dosing approach can be used in evaluating the intravitreal ocular pharmacokinetic properties of compounds intended for ocular use.