CD33 is frequently expressed on CD34⁺/CD38⁻LSCs from AML patients with significantly higher expression levels compared with HSCs from HDs. (A) CD33 expression on CD34⁺/CD38⁻ LSCs compared with leukemic bulk cells (n = 24). (B) Expression of CD33 on CD34⁺/CD38⁻ HSC compared with CD33⁺ bulk cells on BM samples from HDs (n = 7). (C) Colony-forming unit assay evaluating the unwanted on-target toxicity of AMG 330 on healthy human CD34⁺/Lin⁻ BM cells.