Antiangiogenic therapies Angiogenesis is the formation of new blood vessels that sprout from existing vessels via a complex cascade of events. The first events in that cascade are vasodilation of existing vessels and increased vascular permeability. Next comes degradation of the surrounding extracellular matrix, facilitating migration and proliferation of endothelial cells. As endothelial cells join to create lumen, new capillaries develop and then mature, remodeling into stable vascular networks. This cascade requires a balanced interplay of growth-promoting and growth-inhibiting angiogenic factors to proceed. Activators of angiogenesis include vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), transforming growth factor α (TGF-α) and TGF-β, angiopoietin-1, and angiopoietin-2. Inhibitors of angiogenesis include thrombospondin, angiostatin, endostatin, and pigment epithelium–derived factor (PEDF).