IL2 and B-cell chronic lymphocytic leukemia: Immunotoxins that contain bacterial toxins which achieve potent cytotoxicity by blocking protein translation have been proved to be effective in treating some hematological malignancies.[100] In a previous study, Ontak, a fusion protein composed of DT and anti‐IL‐2, was studied for treating chronic lymphocytic leukaemia (CLL) based on the overexpression of high‐affinity IL‐2 receptors on CLL cells, and satisfactory results were achieved.[101] Similar to chemotherapy, repeated administration is necessary for immunotoxins treatment to maintain the optimal cell lethal concentration.