CD22 and hairy cell leukemia: These immunotherapeutic agents are being developed as humanized whole antibodies, while in another approach an antibody fragment have been used to develop moxetumomab pasudotox, an immunotoxin composed of a variable fragment (Fv) of the anti-CD22 antibody, RFB4, fused to the truncated pseudomonas exotoxin and is being evaluated in phase III in patients with hairy cell leukemia (Kreitman and Pastan 2011, 2015; Teo et al. 2016).