Additional findings highlighted here are that disruption of LSD1-CoREST-HDAC1/2 complex derepresses GFI1/1B SE/Es to cause early induction of GFI1/1B47, which could serve as a predictive early biomarker of achieving biologically effective intracellular levels of LSD1i in AML and post-MPN sAML cells. Here, RCOR1 is linked to acute myeloid leukemia.