For instance, PE toxin has been fused with Fv fragment of Anti-CD22 monoclonal antibody that binds to CD22 cell surface receptor expressed on malignant B cells and has been currently approved for treatment of relapsed or refractory hairy cell leukaemia under the trade name Moxetumomab pasudotox-tdfk (LUMOXITITM) (Dhillon 2018). Here, CD22 is linked to hairy cell leukemia.