A substance being studied in the treatment of some types of cancer and other conditions. Abegrin binds to a protein on the surface of blood vessels and may prevent the growth of new blood vessels that tumors need to grow. It may also prevent the spread of cancer. It is a type of antiangiogenesis agent, a type of metastasis inhibitor, and a type of monoclonal antibody. Also called etaracizumab, humanized monoclonal antibody MEDI-522, and MEDI-522.