Although in vivo studies are limited by the poor drug-like characteristics of extant WIN site inhibitors, in vitro profiling demonstrates that small molecule WIN site blockers can inhibit cancer cells carrying oncogenic mutations in MLL1, C/EBPα, p53, and MYC2,6–10,12, forecasting that WIN site inhibitors could have widespread utility as anti-cancer agents. This evidence concerns the gene KMT2A and cancer.