Gemtuzumab ozogamicin (GO), a humanized anti-CD33 monoclonal antibody linked to calicheamicin, is indicated for the treatment of adult and pediatric (aged ≥ 1 month) patients with newly diagnosed CD33-positive (CD33+) acute myeloid leukemia (AML) and adult and pediatric (aged ≥ 2 years) patients with relapsed/refractory CD33+AML [1]. The gene discussed is CD33; the disease is acute myeloid leukemia.