Daily administration of gilteritinib for 10 days significantly improved survival in all ETP-ALL PDX models except ETP2 (Figs. 6A and S10A), which expressed the lowest levels of FLT3 (Fig. 5A) and did not contain a KF population (Figs. 3G, H and S7B). The gene discussed is FLT3; the disease is acute lymphoblastic leukemia.