A Safety Study Of High Concentration And High Frequency Intravitreal Injection Of Conbercept In Rabbits

Purpose: To study the short-term safety of high concentration and high frequency intravitreal injection of conbercept in rabbits.Methods: Ninety-three Chinchila rabbits were randomized into nine groups and only the right eyes were injected intravitreally. Group A(n=6) was untreated; Group B(n=18) received injection of 50 μL PBS; Groups C, D and E(n=18 each) received a single injection of 0.2, 0.5 and 2.0 mg conbercept respectively; Groups F and G(n=6 each) were injected respectively with 50 μL PBS and 0.2 mg conbercept weekly for continuous six week. Groups H and I(n=3 each) were injected with 100μg LPS and 400 nmole NMDA as positive control. Intraocular pressure, fundus-photography, dark- and light-adapted ERG were applied at the 4th, 7th, 14 th day after the single injection and at the 7th day after the sixth weekly injections. Retinal morphology was examined with hematoxylin and eosin staining, and the amount of apoptotic cells was determined using a TUNEL assay. Protein levels of IL-6, IL-8 and TNF-α in the aqueous humor were detected using ELISA kits. Relative quantification of proteins in the retina was detected using the tandem mass tags(TMT) quantitative mass spectrometry.Results: At day 4, 7 and 14 after single intravitreal injection and at day 7 after the 6th weekly intravitreal injection, the difference in IOP among rabbits received various concentrations of conbercept and rabbits received PBS was not significant(p>0.05). Fundus photographs of animals in the conbercept and the PBS-injected groups mimic those observed in the untreated eyes. There was no much difference in the a- and b-wave amplitudes of the dark- and light-adapted ERGs among these groups(p>0.05). No sign of retinal toxicity was seen in the conbercept-injected groups under light microscope. The number of cells in the GCL and the thickness of INL did not show significant changes(p>0.05). No TUNEL-positive cell was seen in the GCL in the retina of the conbercept-injected groups. The protein levels of IL-6, IL-8 and TNF-α in the aqueous humor from different groups were similar(p>0.05). Compared to the untreated group, the variation of proteins related to inflammation, hypoxia, apoptosis and other pathological processes was not significant in TMT spectrometry.Conclusions: Our study indicates that intravitreal injection of high concentration and high frequency application of conbercept is well tolerated at least in a short-term in rabbits.