Observation of total VEGF level in hyperglycemic mouse eyes after intravitreal injection of the novel anti-VEGF drug conbercept

PURPOSE Conbercept (KH902), a novel recombinant, soluble vascular endothelial growth factor (VEGF) receptor-IgG fusion protein, has been developed as a new drug for ocular neovascularization and macular edema. The present study aims to clarify the changes in conbercept levels, VEGF, and intraocular pressure (IOP) after the intravitreal injection of conbercept into diabetic mouse eyes. METHODS Five-week-old C57BL/6 mice were injected with streptozotocin to induce diabetes. Total VEGF and conbercept levels in the eyes were detected using an ELISA kit at -2 h, 1 h, 1 d, 4 d, 8 d, 16 d, 28 d, and 34 d after intravitreal injection of conbercept into diabetic and control mice. IOP was measured with a noninvasive TonoLab tonometer 7 d after intravitreal conbercept injection. RESULTS The concentration of conbercept in the treated eyes increased immediately after injection and remained at high levels for 4 d (29.77±27.19 ng/ml, 20.28±28.85 ng/ml, and 42.43±36.51 ng/ml for days 1, 2, and 4, respectively). The concentration of conbercept in the untreated fellow eyes increased from day 2 to day 4 after injection with a level of about 1% of that in the injected eyes. Conbercept concentrations in both the treated and fellow eyes decreased from day 7 after intravitreal injection. The concentration of VEGF in the treated eyes increased significantly 1 h after injection when compared with the baseline measured 2 h before injection in both the diabetic and control mice (645.91±86.47 pg/ml versus 296.10±76.11 pg/ml and 860.50±201.47 pg/ml versus 377.69±70.72 pg/ml, respectively). VEGF concentration reached its peak 24 h after injection and then decreased thereafter. At day 7 after intravitreal injection, the difference in IOP between mice that received conbercept and mice that received PBS injections was not significant (p>0.05). CONCLUSIONS Conbercept and total VEGF levels in the mouse eyes were elevated after intravitreal injection of conbercept. Increased VEGF levels likely reflect VEGF sequestered by conbercept. These data could be helpful in understanding the metabolism of anti-VEGF drugs in the eye and for determining the protocol of multiple intravitreal injections of conbercept in patients.