The goal of this program is to develop novel inhibitors of human sphingosine kinase (SK) that are effective as therapeutic agents for retinal and choroidal vascular diseases. Because of its critical role in sphingolipid metabolism, we have focused on SK as an innovative molecular target for the development of new drugs for the treatment of ocular diseases associated with excessive angiogenesis. Sphingolipids are being increasingly recognized as key mediators of stress responses, cell differentiation and proliferation, and are known to mediate the effects of vascular endothelial growth factor (VEGF) and tumor necrosis factor-a (TNFa) that are of central importance in eye disease. We hypothesized that sphingosine-1-phosphate (S1P) produced by SK within retinal endothelial cells in response to VEGF is critical to the cascade of events that results in the vascular leakiness and neovascularization that are hallmark pathologies in eye disease. Therefore, SK is a key molecular target for the development of new therapeutic agents. Because of the pivotal role of SK in regulating proliferation, we are developing SK inhibitors to be used as drugs to treat eye disease. In Phase I of this program, we demonstrated that our proprietary SK inhibitors block signaling pathways induced by VEGF and TNFa in human retinal endothelial cells. Importantly, we further demonstrated that administration of our SK inhibitors reduces vascular leakiness in two animal models, including a VEGF-induced subcutaneous model in nude mice and a 3-month diabetic retinopathy model in STZ-treated rats. No toxicity to the animals was observed in either model. These studies provide the first proof-of-principle demonstration that SK inhibitors are likely to be effective in the treatment of eye disease. In this Phase II project, we will evaluate the therapeutic activity of the SK inhibitor in two additional in vivo models of ocular disease, including oxygen-induced retinopathy and laser-induced chorodial neovascularization. Additionally, we will determine the optimal schedule for treatment of the animals in the eye disease models. Finally, FDA-required studies will be completed to enable the submission of an Investigational New Drug application for the SK inhibitor ABC294640. The following Specific Aims will be addressed: 1.) To evaluate the protective effects of ABC294640 in a model of oxygen-induced retinopathy. 2.) To evaluate the protective effects of ABC294640 in a model of laser-induced choroidal neovascularization. 3.) To complete cGMP synthesis and IND-directed toxicology studies with ABC294640. Overall, the studies proposed represent a focused approach to evaluate and move the SK inhibitor ABC294640 into clinical trials for the treatment of ocular disease. This will provide rapid evaluation of the first-in-class inhibitor of this innovative molecular target. ? ? ? ? ? ?
