Intravitreal Half-lives of Aflibercept and Brolucizumab in Rabbit Measured Using In Vivo Fluorophotometry

Abstract

Purpose : To determine the intravitreal half lives of aflibercept and brolucizumab using in vivo fluorophotometry of fluorescently labeled molecules in rabbits.

Methods : Aflibercept and brolucizumab were tagged with Alexa Fluor 488 (AF488) through amine conjugation. The binding kinetics of conjugated and un-conjugated aflibercept and brolucizumab were tested with serially diluted molecules passing over human VEGF165 coupled to a CM5 Biacore Chip. The kinetics parameters were evaluated by fitting the real time data using 1:1 binding model with mass transport limitation. Bilateral (intravitreal) IVT injections were made to 6 male New Zealand White (NZW) rabbits (6 eyes/3 rabbits /molecule). All eyes were examined for vitreous baseline fluorescence with OcuMetrics Fluorotron fluorophotometer (Mountain View, CA) before injection, and followed up for vitreous fluorescence intensity post injection at Day 2, 6, 10 and 14. General ocular examination included intraocular pressure (IOP), inflammation signs, corneal and conjunctival edema, hemorrhages, floaters in anterior chamber, pupil size and shape, cataract, and retinal detachment before and 10 minutes after IVT injection, and at each follow-up time point. Fluorescence intensity and position information were extracted and imported in GraphPad Prism for graphical display and analysis. The data were fitted to a first order, single compartment model.

Results : AF488 conjugation did not affect the affinity of either aflibercept or brolucizumab for human VEGF165. PK study of aflibercept and brolucizumab in NZW rabbit vitreous showed the half-lives were 4.7 (±0.7) and 3.0 (±0.1) days, respectively. There was no significant IOP change before and after IVT injection of either molecule. There were no clinically notable signs observed in general ocular examination.

Conclusions : The rabbit vitreal half-life of aflibercept measured conventionally in previous studies was 4.8 days, comparable to that measured here by in vivo fluorophotometry. Our study shows the half-life of brolucizumab is shorter than that of aflibercept in NZW rabbit vitreous, aflibercept persisting about 50% longer (4.7 days vs 3 days).

This is a 2020 ARVO Annual Meeting abstract.