Angiogenesis, the formation of new blood vessels, plays an essential role in the pathogenesis of several important human diseases including cancer. Inhibition of angiogenesis is a promising strategy to control tumor growth and metastasis. The main objective of this application is to discover and develop new angiogenesis inhibitors from existing clinical drugs and to elucidate the molecular mechanisms of angiogenesis inhibition by two angiogenesis inhibitors previously discovered to facilitate the development of the next generation of angiogenesis inhibitors for the treatment of cancer. In preliminary studies, we have assembled a library of mostly FDA-approved clinical drugs and screened it in an endothelial cell proliferation assay. We have identified several potent hits including an immunosuppressant drug and an antifungal drug. We have further demonstrated the efficacy of both drugs in blocking VEGF- and bFGF- mediated angiogenesis in vivo. In this study, we propose to further expand the clinical drug library to include more FDA-approved drugs as well as those that have reached phase II clinical trials to identify additional inhibitors of angiogenesis and make the library available to the wider scientific community to screen in other cellular models. We will further characterize the function of the immunosuppressant target in both T cell activation and angiogenesis in mice and humans. We will attempt to identify new inhibitors for the immunosuppressant target to reduce the toxicity of the existing drug by a combination of combinatorial click chemistry and high-throughput screening. We will perform experiments to verify a potential target for the antifungal drug in endothelial cells and perform SAR studies on the antifungal drug in attempts to prepare affinity reagents to identify and validate its target in endothelial cells and to improve the efficacy of the drug for inhibition of angiogenesis and tumor growth. Angiogenesis, the formation of new blood vessels, plays an essential role in several important human diseases including cancer. The main objective of this application is to discover and develop new angiogenesis inhibitors from existing drugs to accelerate the translation of basic research findings into new cancer treatments and to facilitate the development of future generations of anti-angiogenic drugs with improved specificity and lower toxicity.