Therapeutic Effects of a Novel Compound, CLT003, in Diabetic Retinopathy and Age-Related Macular Degeneration

Abstract

Purpose: : Abnormal retinal vascular leakage is on of the major pathological changes in diabetic retinopathy (DR) and age-related macular degeneration (AMD). With a goal of developing drugs to treat retinal vascular leakage, we have synthesized a series of novel thalidomide analogs and evaluated their inhibitory effects on NV and retinal vascular leakage. The purpose of this study is to evaluate the efficacy of CLT-003 which has exhibited a potent anti-angiogenic activity.

Methods: : Human Umbilical Vein Endothelial Cells (HUVEC) were grown in the EBM-MV2 medium. Bovine Retinal Endothelial Cells (BREC) and pericytes were isolated from fresh cow eyes. MTT was used to quantify the cell viability. This fluorescence-based endothelial cell invasion assay used on BD Matrigel^TM and BD Falcon^TM HTS FluoroBlok^TM 24-Multiwell Insert System. Newborn Brown Norway (BN) rats at postnatal day 7 were exposed to hyperoxia (75% O₂) for 5 days and then returned to normoxia to induce oxygen-induced retinopathy. Adult BN rats were given a single intraperitoneal injection of streptozotocin (STZ) to induce diabetes. Vascular permeability was quantified by measuring leakage of FITC-albumin or Evans blue dye-albumin complex from the blood vessels into the retina. Full-field electroretinogram (ERG) was recorded using the Espion E² ERG system.

Results: : CLT003 and thalidomide reduced retinal vascular leakage in a dose-dependent manner from 0.5 to 1.0 µg/eye in both the OIR and STZ-diabetes models. CLT003 has significantly more potent effects on retinal vascular leakage, when compared with thalidomide and other know thalidomide analogs after a single intravitreal injection. Additionally, CLT003 blocks retinal vascular leakage in an AMD mouse model. Further, CLT003 down-regulated the expression of VEGF and ICAM-1 in the retina, suggesting that the anti-vascular leakage activity of CLT003 is, at least in part, through blocking VEGF production and down-regulating inflammatory factors. ERG and histological analysis at various intervals after the drug administration showed that a single intravitreal injection of CLT003 did not cause detectable functional and morphological abnormalities in ocular tissues.

Conclusions: : CLT003 is a novel analog of thalidomide with potent vascular activities. It has therapeutic potential in retinal vascular leakage in DR and AMD.

Keywords: diabetic retinopathy • drug toxicity/drug effects • ischemia