Transcorneal Permeability Pilot Studies




Nguyen, Vien
Johnston, Joseph
Prokai-Tatrai, Katalin


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Purpose: Permeability of potential ocular agents across the cornea is important in evaluating their ability to enter the eye by the transcorneal route. Accordingly, the purpose of this study was to set up a transcorneal permeability protocol and develop the necessary analytical methods to evaluate flux differences among test agents across cornea from different species. Methods: Corneas from rat, pig and rabbit were used. Jacketed vertical diffusion cells were used to test transcorneal permeability. Two test compounds of comparable molecular volume but differing in lipophilicity (measured by the logarithm of the n-octanol/water partition coefficient, logP) by approximately two log units were chosen for this pilot study. Once cornea and cell chambers were equilibrated to 35°C, cornea was mounted and test compounds at a given concentration either in saline or in saline containing a permeability enhancer excipient were placed in the donor chamber. The amount of test agents in the receiver chamber versus time was measured based on methods developed in our laboratory and using LC-MS/MS selected reaction monitoring on a TSQ Quantum Ultra (Thermo) connected to a Surveyor HPLC system (Thermo). Quantification of each test compound was performed based on the principles of stable isotope dilution. Flux was calculated, based on the principles of diffusion testing. Results: We were able to establish the transcorneal permeability procedure for testing the diffusion of compounds across the cornea. In addition, selected reaction monitoring LC-MS/MS quantification methods were developed for the test compounds. Of our two test compounds in this pilot study, we were able to show that the flux across the cornea for test compound with intermediate lipophilicity was approximately one log unit higher for all species when saline vehicle was used and about 0.5 log unit higher when a permeability enhancer excipient was used, compared to those of test agent with high lipophilicity (logP about 4). Conclusions: This pilot study showed the establishment of a protocol for a convenient evaluation of the transcorneal permeability of test compounds quantified by LC-MS/MS analyses. This study was supported by NIH grant R01EY027005 (KPT)