Therapeutic Effect of IBI302, a bispecific Fc-fusion protein, on Age-related Macular Degeneration

Abstract

 

Purpose

 

To evaluate the therapeutic activity and its mechanism of action of IBI-302, a bispecific Fc-fusion protein that effectively inhibits VEGF and complement, on the laser-induced choroidal neovascularization (CNV) in mice and oxidative stress in vitro cultured human RPE cells.

 

Methods

 

C57BL/6J mice were induced CNV by laser photocoagulation and received an intravitreal injection of phosphate-buffered saline (PBS) and IBI-302 solution respectively. Seven days after intravitreal injection, areas of CNV and leakage were measured by FFA, ICGA and fluorescein-labeled dextran perfusion. Numbers of infiltrating macrophages and neutrophils and expression of MAC in the RPE-choroid-sclera complex were detected by immunohistochemistry. The integrity of human primary RPE monolayer barrier was established by measurement of trans-epithelial resistance (TER). Oxidative stress was induced with t-butyl hydroperoxide (t-BHP). Normal human serum(NHS) was added for complement activation. Cells in each group were then treated with 1μg/ml IBI302 and PBS for 4hrs, respectively. Both in vivo and vitro study, the protein levels of VEGF, TNF-α, CCL-2 , C3a, C5a and sC5b-9 were assayed by ELISA. VEGF-Trap and CID, a soluble complement receptor, were used as controls.

 

Results

 

Both area of CNV and leakage were significantly suppressed by IBI302 treatment compared with PBS, has much better efficacy than VEGF-Trap and CID. IBI302 treatment significantly inhibited the infiltration of macrophages and neutrophils in the CNV area and the deposition of MAC in the CNV lesion. IBI302 treatment downregulated the protein expressions of VEGF, CCL-2, TNF-α and C3a, C5a, MAC both in mice with CNV and cultured RPE under oxidative stress. IBI302 also inhibited the decrease of TER.

 

Conclusions

 

IBI302 could reduce the CNV area and protect RPE cells from oxidative stress and complement activation by inhibiting the expression of VEGF, inflammation-related molecules including TNF-α, CCL-2 and complement activation-related molecules including C3a, C5a and MAC, then further inhibit the infiltration of macrophages and neutrophils and the deposition of MAC.

 

 

ICGA, FFA and IR images of mice seven days after intravitreal injection. IBI302 significantly suppress the leakage and CNV area comparing with VID and CID, however no statistic difference exist in the IR images showing the primary laser damage is comparable among the groups.

 

Keywords: 412 age-related macular degeneration • 557 inflammation • 748 vascular endothelial growth factor