Antibody drug conjugates (ADCs) are showing a growing clinical utility 1,2 and in recent years the United States Food and Drug Administration (FDA) approved brentuximab vedotin in 2011 (Adcetris®, CD30-positive Hodgkin lymphoma and anaplastic large-cell lymphoma), trastuzumab emtansine in 2013 (Kadcyla®, HER2NEU 3-positive breast cancer), inotuzumab ozogamicin in 2017 (Besponsa®, adults with CD20-positive relapsed or refractory B cell precursor acute lymphoblastic leukemia [ALL]) and gemtuzumab ozogamicin in 2017 (Mylotarg®,, newly diagnosed CD33-positive acute myeloid leukemia [AML]). The gene discussed is CD33; the disease is acute myeloid leukemia.