IL-2, IL-21, and IL-15: The FDA granted approval for the use of recombinant human IL-2 in 1992 for the treatment of metastatic renal cancer, and in 1998 for the management of metastatic melanoma.246 However, intravenous administration of IL-2 exhibits limited tumor accumulation247 and possesses a short half-life (only 5 to 7 min). Here, IL2 is linked to neoplasm.