Three targeted toxins were approved by the FDA for cancer treatment until today: Denileukin diftitox (Ontak®), consisting of IL2 as binding and DT as toxin domain, for the treatment of cutaneous T cell lymphoma (CTCL) in 1999 [21], Moxetumomab pasudotox (Lumoxiti®), consisting of an anti-CD22 antibody fragment and PE38 from Pseudomonas Exotoxin A, for the treatment of hairy cell leukemia (HCL) [22], and Tagraxofusp-erzs (Elzonris®), consisting of IL3 and DT, for the treatment of blastic plasmacytoid dentritic cell neoplasm (BPDCN) [23], both in 2018. Here, IL2 is linked to hairy cell leukemia.