Moxetumomab pasudotox (Lumoxiti, Innate Pharma Inc., Rockville, MD, USA), which targets CD22 on B cell malignancies, has a very high response rate in hairy cell leukemia, has produced complete and durable responses in many patients and was approved by the FDA for treatment of relapsed or refractory hairy cell leukemia patients [34]. The gene discussed is CD22; the disease is hairy cell leukemia.