Sustained Delivery and Pharmacodynamics of an Integrin Antagonist for Ocular Angiogenesis
Wang, Nam Sun
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Ocular angiogenesis, or the formation of new blood vessels in the eye, is the leading cause of blindness in a variety of clinical conditions. Success in elucidation of several key steps in angiogenesis cascade has opened a door for anti-angiogenesis therapies. Development of novel therapeutic agents provides effective treatment for ocular disorders. However, treatment of many posterior segment diseases like age-related macular degeneration (AMD) and diabetic retinopathy (DRP) is far from satisfactory due to the limited availability of novel therapeutic drugs and the low efficiency of traditional drug delivery methods. In the present study, we investigated the anti-angiogenic properties of a novel small integrin antagonist, EMD478761, and developed sustained release systems to locally and continuously deliver this compound. In part I, sustained delivery implants were designed and investigation of their anti-angiogenic efficacy, including inhibition and regression, was performed using <em>in vivo</em> chick chorioallantoic membrane (CAM) assay. In part II, laser-induced choroidal neovascularization (CNV) rat model was employed to further examine the angiogenic inhibitory effect of EMD478761 from a sustained release microimplant. And in part III, the pharmacodynamics of EMD478761 was studied to reveal the mechanisms by which EMD478761 inhibited angiogenesis. Results from <em>in vivo</em> CAM assay and CNV rat model demonstrated that EMD478761 inhibited and regressed basic fibroblast growth factor (bFGF)-induced angiogenesis, and suppressed laser-induced CNV via sustained release implants. The pharmacodynamics of this drug was studied to better understand the mechanisms of the drug's action mode in preventing neovascularization. <em>In vitro</em>, EMD478761 inhibited human umbilical vein endothelial cell (HUVEC) proliferation, caused HUVEC detachment in vitronectin-coated surfaces in a time- and dose-dependent manner, and disrupted endothelial cell tube formation on Matrigel. In addition, EMD478761 induced HUVEC apoptosis on vitronectin via caspase-3 activation pathway. <em>In vivo</em>, EMD478761 induced endothelial cell apoptosis within CNV lesions as demonstrated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. In addition, EMD478761 increased the integrin α<sub>v</sub>β<sub>3</sub> internalization in HUVECs, while it did not affect integrin α<sub>v</sub>β<sub>3</sub> expression levels after 12 hours treatment. Taken together, these findings demonstrate that sustained delivery of EMD478761 may provide an effective antiangiogenic approach for the treatment of ocular angiogenesis.