Given the activity of IL-2 on a broad range of effector lymphocytes, its preferential activity for Tregs and its lack of specificity for targeting tumor-resident NK cells or neoantigen-specific T cells, most IL-2 drug development activity is focused on engineering cytokines to preferentially bind and act on activated conventional T cells, which in cancer patients are likely enriched in neoantigen-reactive T cells [67, 68]. Here, IL2 is linked to cancer.