show Abstracthide AbstractINCB059872 is a selective irreversible inhibitor of Lysine-Specific Demethylase 1 (LSD1) that is in phase 1 clinical trials in hematopoietic malignancies. Mice treated with INCB059872 had reduced platelet counts within 4 days of treatment. Here, we used single-cell RNA-seq to study the effects of INCB059872 on hematopoietic progenitor populations within wild-type murine bone marrow. Our results showed that INCB059872 triggered accumulation of megakaryocyte early progenitor cells with gene expression hallmarks of stem cells, which may begin to explain the thrombocytopenia observed in patients treated with LSD1 inhibitors. Overall design: Single-cell RNA-seq of lineage-negative bone marrow from mice treated with LSD1i for 0, 4, or 6 days (3 mice per group)