High-dose interleukin 2 (Proleukin, Novartis) (IL-2) is approved by the U.S Food and Drug Administration (FDA) for the treatment of metastatic kidney cancer and is a standard treatment of this disease. At the present time, IL-2 is the only therapy for kidney cancer that can produce a remission of disease that lasts after treatment is completed. However, most patients who receive IL-2 do not benefit and all patients experience potentially dangerous side effects.