IL2 and hairy cell leukemia: Three immunotoxins have been clinically approved for the treatment of hematologic malignancies, including Denileukin diftitox (Ontak®, interleukin-2 (IL-2)- diphtheria toxin) for cutaneous T-cell lymphoma, Tagraxofusp (Elzonris®, IL3-DT) for blastic plasmacytoid-cell neoplasms, and Moxetumomab pasudotox (Lumoxiti®, anti-CD22 disulfide-stabilized variable fragment (dsFv)-38-kDa fragment of Pseudomonas aeruginosa exotoxin A (PE38) toxin) for hairy cell leukemia [1,3].