CD33 and acute myeloid leukemia: It was initially approved in 2000 for the treatment of adults with CD33-positive acute myeloid leukemia (AML), marking the beginning of the ADC era in targeted therapies; it was, however, withdrawn from the market in 2010 because of failure of a confirmatory trial and safety concerns; it was then re-approved in 2017, using a lower dose fractionated regimen, for treatment of relapsed or refractory (R/R) CD33-positive acute myeloid leukemia (AML) in patients two years of age and older [3].