Abnormal angiogenesis underlies vision loss in a number of ocular diseases. Growth factors (GFs) such as vascular endothelial (VEGF), fibroblast (FGF), hepatocyte (HGF) and insulin (IGF) drive ocular angiogenesis (1). Current anti-VEGF therapy or laser photocoagulation are either not effective in all patients or destructive to the retina. We have previously shown that targeting endothelial CaMKII may represent a more effective therapeutic strategy (2), and in the present study we examine the effects of two CaMKII inhibitors on retinal angiogenic signalling invitro and invivo. GF-induced changes in total and phospho-CaMKII levels in human retinal microvascular endothelial cells (hRMECs) were assessed by Western blotting. The effects of the CaMKII inhibitors, KN93 and CK59 (10μM), on GF-induced EC proliferation, migration, tube formation and sprouting angiogenesis were also evaluated (2). Downstream signalling pathways stimulated by GF activation of CaMKII in ECs were determined using phospho-kinase arrays. Invivo effects of KN93/CK59 were tested using the mouse model of oxygen-induced retinopathy (OIR). OIR was induced in C57BL6 mice as previously described (3). Mice were anesthetised at P15 with ketamine (60mg/kg,IP) and xylazine (6mg/kg,IP) and given 1µl intravitreal injection of CaMKII inhibitor/control agents. At P17 mice were killed by schedule 1 methods, eyes were enucleated and retinas stained with isolectin for quantification of avascular (AVA) and neovascular areas. Data were analysed by ANOVA. Values are mean±SEM. GFs (VEGF, HGF, FGF and IGF1; 50 ng/ml for 24 hr) increased total and phosphorylated CaMKII protein levels in ECs (n=3). Treatment of ECs with the GFs increased retinal EC proliferation, migration, tube formation and sprouting angiogenesis and these effects were largely abrogated by pre-incubation with KN93/CK59. For VEGF, for example, treating ECs with KN93/CK59 reduced the number of angiogenic sprouts formed in in vitro assays from 48.0±6.9 to 14.6±2.7 and 29.1±0.7 respectively (p<0.001 in both cases). The inactive analogue of KN93, KN92 (10μM), and vehicle controls (0.01% DMSO) were without effect. A number of kinases were phosphorylated following GF stimulation in a CaMKII-dependent manner including Erk 1/2 and MSK 1/2 and the Src family kinases, Yes and Fgr. In the OIR model, revascularisation of the retina was inhibited by 10µM KN93 (AVA 47.8±2.0%) and CK59 (AVA 50.7±4.7%) treated mice compared to untreated P17 controls (AVA 31.1±1.8%, p<0.001 in both cases). These inhibitors also reduced retinal neovascular tufts (KN93, 11.8±1.3%; CK59, 11.5±1.8%,) compared to untreated P17 controls(19.6±2.6%; p<0.05 in both cases). These data strongly suggest that targeting CaMKII may provide a novel therapeutic approach for treating neovascular diseases of the eye.