The present invention provides methods and compositions for the prevention and treatment of conditions characterized by neovascularization. Preferably, the present invention is directed to a potent inhibitor of angiogenesis. This inhibitor may be useful for the treatment of ocular diseases by preventing neovascularization. The invention is based, at least in part, on the isolation of the inhibitor of angiogenesis from, inter alia, non-processed intracellular extracts from the bacteria Escherichia coli. The present invention also includes a method of treating a condition characterized by neovascularization in a mammal by administration of the inhibitor of angiogenesis, wherein the treatment shows prevention and/or regression of the condition. Such regression of the condition may be, for example, to inhibit aberrant angiogenesis in the eye or to inhibit the growth of carcinogenic tumors. Examples of diseases may include, but are not limited to, ocular diseases and cancer.