Electrophysiological toxicity testing of VEGF Trap-Eye in an isolated perfused vertebrate retina organ culture model

Abstract

Purpose: Age-related macular degeneration (AMD) is the leading cause of visual impairment in Western nations. Since the discovery of the importance of vascular endothelial growth factor (VEGF) in the pathogenesis of neovascular AMD, anti-VEGF agents including pegaptanib, ranibizumab and bevacizumab provide a treatment option to improve vision in affected persons. VEGF Trap-Eye (Aflibercept) is a new agent available for the treatment of exudative AMD. The molecule is a receptor decoy with a longer half-life and a higher affinity to VEGF compared with ranibizumab or bevacizumab. The presented study has been designed to evaluate the short-term toxic effects of VEGF Trap-Eye on retinal function during and after direct exposure to the drug.

Methods: Isolated bovine retinas were perfused with an oxygen-saturated nutrient solution, and the electroretinogram (ERG) was recorded using silver/silver chloride electrodes. A total of 0.5 mg or 2 mg VEGF Trap-Eye was added to the nutrient solution and retinas were exposed for 45 min, followed by a washout period of 100 min. The percentage of a- and b-wave reduction at the end of the washout was compared with the baseline values. Additionally, retinal whole mount cultures were exposed for 24 hr to VEGF Trap-Eye, and the amount of apoptotic cells were determined using the terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labelling (TUNEL) assay.

Results: During simulation of intraocular application, no significant reduction in the a-wave amplitude for 0.5 mg (2.70%, p = 0.37) and 2 mg (3.84%, p = 0.37) VEGF Trap-Eye and b-wave amplitude for 0.5 mg (19.68%, p = 0.17) and 2 mg (24.1%, p = 0.06) VEGF Trap-Eye was observed at the end of the washout. However, there were significant changes in a-wave and b-wave amplitudes directly after exposure to 0.5 mg VEGF Trap-Eye (18.4%, p = 0.004 and 43.1%, p = 0.006, respectively).

Conclusions: The presented data suggest that intraocular application of up to 2 mg VEGF Trap-Eye does not induce irreversible toxic retinal damage. However, short-term results showed a negative effect directly after the application for 0.5 mg and 2 mg VEGF Trap-Eye.

Keywords: aflibercept; electroretinogram; intraocular toxicity; retinal toxicity; superfused retina.