# CD33 expression (CD33-positive)

Source: https://onco.cc/biomarkers/cd33-expression/  
OnCo record `cd33-expression` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: CD33-positive; CD33+; CD33 expression; CD33 positive AML
- Tags: biomarker; surface-antigen

## Sources

- Mylotarg prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=32fd2bb2-1cfa-4250-feb8-d7956c794e05

## Connected records

- biomarkers: [FLT3-ITD (internal tandem duplication)](https://onco.cc/biomarkers/flt3-itd/), [NPM1 mutation](https://onco.cc/biomarkers/npm1-mutation/)
- cancers: [Acute myeloid leukaemia](https://onco.cc/cancers/aml/), [Acute myeloid leukaemia in children](https://onco.cc/cancers/aml-paediatric/)
- drugs: [Gemtuzumab ozogamicin](https://onco.cc/drugs/gemtuzumab-ozogamicin/)
- terms: [Cytogenetics and karyotype](https://onco.cc/terms/cytogenetics/), [Flow cytometry (immunophenotyping)](https://onco.cc/terms/flow-cytometry/)
- targets: [CD33](https://onco.cc/targets/cd33/)

---
JSON: https://onco.cc/api/v1/entities/cd33-expression.json