Several recent studies showed the robust antitumor effects of IL-2 variant (IL-2v), an engineered variant of IL-2 not interacting with IL-2Rα, which is fused to monovalent or bivalent anti-PD-1 antibody (PD1-IL2v) in various preclinical tumor models (orthotopic pancreatic adenocarcinoma Panc02-H7-Fluc [8] or PK5L1940 [10] in C57/BL6 mice; spontaneous pancreatic tumors in RIP1-Tag5 transgenic C57BL/6 mice [9,10]; subcutaneous A20 lymphoma and Renca adenocarcinoma in BALB/C mice; and MC38 carcinoma in C57BL/6 mice [7], as well as orthotopic GL261 glioma in C57BL/6 mice [9]) (Figure 1C,D). Here, IL2 is linked to central nervous system cancer.