Ocular Safety of Intravitreal Anti Connective Tissue Growth Factor Neutralizing Antibody

Abstract

Purpose : Connective tissue growth factor (CTGF) is the major pro fibrotic growth factor associated with the wide variety of fibrotic disorders such as proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). We have previously shown that application of 10 μg of anti-CTGF neutralizing antibody in combination with 0.8 mg of bevacizumab in 1 ml of retinal pigment epithelium cell culture decreased CTGF gene and protein expression. In the present study we determine the maximum safe dose of intravitreal injection of anti-CTGF (IVAC) in rat eyes.

Methods : 45 Lister Hooded pigmented rats were divided into five groups; 4 of these groups received IVAC (1 μl) corresponding to doses of 10 μg (B), 20 μg (C), 50 μg (D), and 100 μg (E), respectively. The sham group (A) received 1 µl of normal saline. Full field electroretinography (ERG) was performed at baseline and at days 7 and 28 after IVAC. The animals were euthanized and the corresponding eyes were subjected to routine histopathology, immunohistochemistry for Glial Fibrillary Acidic Protein (GFAP), and TUNNEL assay.

Results : Scotopic rod b wave amplitude and maximal combined b wave amplitude were 111.89±71.2µv and 178.57 ± 55.58 µv respectively at baseline which reduced significantly after 28 days (79.31 ± 52.59 µv and 128.73 ± 41.61 µv, respectively) in the group E with 100 µg/µl of IVAC (P<0.05) . There was no significant reduction of amplitudes in other groups with lower doses of anit-CTGF antibody and in the sham group. Reduction in oscillatory potentials was also noticed after 7 and 28 days in the group E (46.24±18.05 µv at baseline, 30.03±15.95 µv at 7 days, P<0.05 and 29.79±12.20 µv at 28 days, P<0.001) but not in other groups. Photopic ERG responses did not show any significant change in any groups. Excepting 4 out of 9 eyes in group E that revealed retinal inner nuclear and ganglion cell layer atrophic changes, histologic findings were unremarkable in other groups. GFAP immune reactivity was not significant in any of the groups. TUNNEL test showed inner retinal neural cell apoptosis in group E, but not in other groups.

Conclusions : ERG, histopathologic, and apoptotic assays revealed no toxic effects of 10 to 50 µg/µl IVAC in the rat eyes. A significant toxic effect was observed after100 µg/µl IVAC in terms of both functional and histopathologic findings.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.