Systemic radioimmunotherapy using a monoclonal antibody, anti-Tac directed toward the alpha subunit of the IL-2 receptor armed with the α-emitting radionuclides 212Bi or 211At

To exploit the fact that IL-2 receptors are expressed by T-cells responding to foreign antigens but not by resting T-cells, humanized anti-Tac (HAT) armed with alpha-emitting radionuclides 212Bi and 211At was evaluated in a cynomolgus cardiac allograft model. Control graft survival was 8.2± 0.5 days compared with 14.0±1.3 days (p<0.01) survival for monkeys treated with 212Bi labeled HAT and 26.7±2.4 days survival (p<0.001 versus controls) with 211At labeled HAT. Thus, 211At labeled HAT may have application in organ transplantation and in treatment of IL-2 receptor expressing T-cell leukemia.