Treatment of a diffuse large B-cell lymphoma (DLBCL) cell line which contains the Y641N mutant EZH2 with UNC1999 (Figure 10) for 8 days resulted in a potent antiproliferative effect, which is not observed following treatment with UNC2400, a related molecule which is much less active as an EZH2 inhibitor. The gene discussed is EZH2; the disease is diffuse large B-cell lymphoma.