Using immune‐compromised mice grafted with human B‐ALL generated from human CD34+ cells with forced MLL‐AF9 overexpression, we found that injection of AMD3100 after allogeneic lymphocyte infusion could enhance GVL effects, leading to more efficient eradication of leukaemia cells within the immune‐privileged site BM.152. The gene discussed is KMT2A; the disease is leukemia.