CD33 and acute myeloid leukemia: Gemtuzumab ozogamicin (GO), a CD33-specific ADC to calicheamicin, was approved again in 2017 after being withdrawn from the market in 2010 due to safety concerns, for combination therapy with daunorubicin and cytarabine in newly diagnosed CD33+ AML after it doubled the event-free survival from 9.5 to 17.3 months [137].