Leukemic stem cell subtypes determine venetoclax resistance and therapeutic vulnerabilities in AML.

The BCL-2 inhibitor venetoclax has transformed the treatment of acute myeloid leukemia (AML), but relapse due to resistance of leukemic stem cells (LSCs) remains a major challenge. By molecular and functional profiling of LSCs from >150 patients, we identify four LSC subtypes. These mirror distinct hematopoietic lineage stages, which determine the expression ratio between the venetoclax target BCL-2 and resistance-inducing proteins MCL-1 and BCL-xL (MAC-score). Longitudinal analyses reveal that venetoclax resistance mostly arises in LSCs through plasticity toward a megakaryocytic/erythroid-progenitor (MEP)-LSC state that switches survival dependency from BCL-2 to BCL-xL. In rare cases, mature monocytic/dendritic (MoDe)-LSCs, found within LAMP5+ monocytic AMLs, drive venetoclax resistance. LSC subtyping improves genetic risk stratification and provides subtype-specific therapies: venetoclax-resistant MEP-LSCs respond to BCL-xL inhibitors, whereas MoDe-LSCs are sensitive to MEK1/2 inhibition. Our findings reveal four distinct LSC types with unique vulnerabilities and propose biomarker-guided treatment strategies that complement genetic profiling to overcome venetoclax resistance.