ocular biodistribution of ^89zr-bevacizumab in new zealand rabbits determined using pet/mri: a feasibility study

Background: despite studies on positron emission tomography/magnetic resonance imaging (pet/mri) in oncological imaging with high soft-tissue contrast resolution, pet/mri has not been studied in ophthalmology. ^89zr-bevacizumab, designed as a probe for pet, targets vascular endothelial growth factor, which is highly expressed in ocular angiogenesis. intravitreal injections of bevacizumab agents have curative effects on ocular disease. objectives: to study the ocular biodistribution of ^89zr-bevacizumab in new zealand rabbits using pet/mri. materials and methods: ^89zr-bevacizumab, synthesized from conjugated bevacizumab and ^89zr-oxalate, and the purity of radiolabeled antibodies were determined using radio high-performance liquid chromatography (radio-hplc). instant thin-layer chromatography (itlc) was utilized to differentiate the labeled product from aggregates and unlabeled ^89zr. ^89zr-bevacizumab was injected 2 mm from the left limbus into the vitreous humor of six normal new zealand white rabbits. micro-pet was utilized for dynamic imaging from 5 minutes to 60 minutes postinjection and for static imaging at 4 hours, 24 hours, 48 hours, 120 hours, and 144 hours (10-minutes scans) postinjection. pet/mri scans were fused using pmod software. results: ^89zr-bevacizumab with a radiochemical purity of 93.21% was monitored via pet imaging. radioactivity levels in the eyes plateaued approximately 5 minutes after administration of ^89zr-bevacizumab, and the measured vitreous values decreased from 340.52 ± 41.6% injected dose (id)/g to 21.53 ± 3.39%id/g by 144 hours. the half-life of the drug in the eye was calculated for 84.25 hours. conclusion: ^89zr-bevacizumab could be monitored in animals by pet imaging, and the radiolabel exhibited high sensitivity in the vitreous body. radioactivity levels in the eyes plateaued approximately 5 minutes after administration. this study clearly demonstrates the biodistribution of ^89zr-bevacizumab.