We previously demonstrated that Ewing sarcoma cell lines are exquisitely sensitive to SP-2509, a reversible, non-competitive small molecule inhibitor of KDM1A. As innate resistance to SP-2509 was not observed in our Ewing sarcoma cell line cohort (n = 17) [10], we attempted to generate four drug resistant (DR) cell lines (A673, TC252, TC32, TTC-466) through chronic exposure to increasing concentrations of SP-2509. Here, KDM1A is linked to Ewing sarcoma.