{"entity":{"id":"cd33-expression","kind":"biomarker","name":"CD33 expression (CD33-positive)","aka":["CD33-positive","CD33+","CD33 expression","CD33 positive AML"],"tldr":"CD33 is a myeloid antigen on the blasts of about 90 percent of acute myeloid leukaemias. Gemtuzumab ozogamicin's label requires CD33-positive disease.","summary":"CD33 is measured by flow cytometry on marrow or blood blasts. Gemtuzumab ozogamicin (Mylotarg) is a CD33-directed antibody-drug conjugate labelled for newly diagnosed CD33-positive AML with chemotherapy in adults and children from one month, and relapsed or refractory CD33-positive AML; the label does not set a percentage, though trials used 20 percent or more of blasts and benefit is greatest in favourable-risk cytogenetics. CD33 is also the target of bispecifics and CAR-T cells in trials.","asOf":"2026-09-23","links":[{"label":"Mylotarg prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=32fd2bb2-1cfa-4250-feb8-d7956c794e05"}],"tags":["biomarker","surface-antigen"],"related":["flt3-itd","npm1-mutation"],"cancers":["aml","aml-paediatric"],"sections":[],"technologies":[],"targets":[],"drugs":["gemtuzumab-ozogamicin"],"companies":[],"institutions":[],"pathways":[],"terms":["flow-cytometry","cytogenetics"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"cd33","measurement":"ihc-score","scoringRule":{"text":"CD33 detected on leukaemia blasts by flow cytometry; the label states CD33-positive without a percentage.","quote":"MYLOTARG is a CD33-directed antibody and cytotoxic drug conjugate indicated for: • treatment of newly-diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients 1 month and older","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=32fd2bb2-1cfa-4250-feb8-d7956c794e05","sourceLabel":"Mylotarg prescribing information"},"thresholds":[{"value":"CD33-positive","drugId":"gemtuzumab-ozogamicin","cancerId":"aml","regulator":"FDA","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=32fd2bb2-1cfa-4250-feb8-d7956c794e05","quote":"treatment of newly-diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients 1 month and older","status":"current"}],"tests":[],"assays":[],"companionDiagnostics":[],"forPatient":"A CD33-positive result, present in most acute myeloid leukaemias, means gemtuzumab ozogamicin can be added to your first chemotherapy or used if the disease returns; it helps most when the leukaemia's chromosomes are in the favourable group, so both results are read together."},"route":"/biomarkers/cd33-expression/","neighbours":{"biomarker":[{"id":"flt3-itd","kind":"biomarker","name":"FLT3-ITD (internal tandem duplication)","route":"/biomarkers/flt3-itd/"},{"id":"npm1-mutation","kind":"biomarker","name":"NPM1 mutation","route":"/biomarkers/npm1-mutation/"}],"cancer":[{"id":"aml","kind":"cancer","name":"Acute myeloid leukaemia","route":"/cancers/aml/"},{"id":"aml-paediatric","kind":"cancer","name":"Acute myeloid leukaemia in children","route":"/cancers/aml-paediatric/"}],"drug":[{"id":"gemtuzumab-ozogamicin","kind":"drug","name":"Gemtuzumab ozogamicin","route":"/drugs/gemtuzumab-ozogamicin/"}],"term":[{"id":"cytogenetics","kind":"term","name":"Cytogenetics and karyotype","route":"/terms/cytogenetics/"},{"id":"flow-cytometry","kind":"term","name":"Flow cytometry (immunophenotyping)","route":"/terms/flow-cytometry/"}],"target":[{"id":"cd33","kind":"target","name":"CD33","route":"/targets/cd33/"}]}}