Protein expression in E. coli and copurification of LSD1Δ124-CoREST1Δ305 (LSD1-COREST) were performed using previously described procedures. 13 (link) LSD1-CoREST crystals were prepared in hanging drop at 20°C in 100 mM N-(2-acetamido)iminodiacetic acid (ADA) pH 6.5, 1.2 M Na/K Tartrate. Crystals were soaked in a solution containing 1 mM bomedemstat for 2 h at 20°C, followed by washing in a reservoir solution supplemented with 20% glycerol for cryo-protection and immediate freezing in liquid nitrogen. X-ray diffraction data were collected on the X06SA beamline at the SLS synchrotron. Data processing and scaling were carried out using XDS and AIMLESS. Structure refinement was performed using REFMAC5. Topologies for the inhibitors were obtained from the PRODRG server. The PDB validation tools were used for structure validation. Final data collection and refinement statistics are shown in Supporting Information S1: Table 1.