A compound represented by formula, a salt thereof, or a prodrug thereof for use in a treatment of leukemia in the human or animal body by killing leukemic stem cells: wherein Ar 1 represents a substituted or unsubstituted arylene group; Ar 2 represents a substituted or unsubstituted aryl or heteroaryl group; L represents an oxygen atom or -NHCO-; X 1 represents CH or nitrogen atom; X 2 and X 3 each independently represent CH or nitrogen atom, provided that X 2 and X 3 are not the same; Y represents C 1-3 -alkylene group; W 1, which is a substituent on the ring including Y and X 2, each independently represent C 1-6 -alkyl group; m is an integer from 0 to 3; and Z 1 and Z 2 each independently represent hydrogen atom, C 1-6 -alkyl group, amino-C 1-6 -alkyl group, C 1-6 -alkylamino-C 1-6 -alkyl group, di(C 1-6 -alkyl)amino-C 1-6 -alkyl group, hydroxy-C 1-6 -alkyl group, C 1-6 -alkoxy-C 1-6 -alkyl group, C 2-7 -aliphatic acyl group, carboxy-C 1-6 -alkyl group, carbamoyl-C 1-6 -alkyl group, substituted or unsubstituted saturated heterocyclic group, substituted or unsubstituted aryl-C 1-6 -alkyl group, substituted or unsubstituted heteroaryl-C 1-6 -alkyl group, substituted or unsubstituted arylcarbonyl group, or substituted or unsubstituted heteroarylcarbonyl group, excluding the case in which both Z 1 and Z 2 represent hydrogen atoms; when X 2 represents CH and X 3 represents nitrogen atom, Z 1 and Z 2 may form a substituted or unsubstituted, monocyclic or polycyclic heterocyclic group including X 3 and containing as a ring member two or more hetero atoms selected from the group consisting of oxygen, sulfur, and nitrogen atoms, or when X 2 represents nitrogen atom and X 3 represents CH, Z 1 and Z 2 may form a substituted or unsubstituted, monocyclic or polycyclic heterocyclic group including X 3 and containing a hetero atom selected from among oxygen, sulfur, and nitrogen atoms and wherein the prodrug is a compound having a hydroxyl or amino group substituted with C 2-7 -acyl, C 1-6 -alkoxy(C 2-7 acyl), C 1-6 -alkoxycarbonyl(C 2-7 -acyl), C 1-6 -alkoxycarbonyl, C 1-6 -alkoxy(C 2-7 -alkoxycarbonyl), (C 2-7 -acyloxy)methyl, 1-(C 2-7 -acyloxy)ethyl, (C 2-7 -alkoxycarbonyl)oxymethyl, or 1-[(C 2-7 -alkoxycarbonyl)oxy]ethyl, or a compound having a carboxyl group substituted with C 1-6 -alkyl, C-alkoxy-C 1-6 -alkyl, (C 2-7 -acyloxy)methyl, 1-(C 2-7 -acyloxy)ethyl, (C 2-7 -alkoxycarbonyl)oxymethyl, or 1-[(C 2-7 -alkoxycarbonyl)oxy]ethyl. Ar 1 represents a substituted or unsubstituted arylene group; Ar 2 represents a substituted or unsubstituted aryl or heteroaryl group; L represents an oxygen atom or -NHCO-; X 1 represents CH or nitrogen atom; X 2 and X 3 each independently represent CH or nitrogen atom, provided that X 2 and X 3 are not the same; Y represents C 1-3 -alkylene group; W 1, which is a substituent on the ring including Y and X 2, each independently represent C 1-6 -alkyl group; m is an integer from 0 to 3; and Z 1 and Z 2 each independently represent hydrogen atom, C 1-6 -alkyl group, amino-C 1-6 -alkyl group, C 1-6 -alkylamino-C 1-6 -alkyl group, di(C 1-6 -alkyl)amino-C 1-6 -alkyl group, hydroxy-C 1-6 -alkyl group, C 1-6 -alkoxy-C 1-6 -alkyl group, C 2-7 -aliphatic acyl group, carboxy-C 1-6 -alkyl group, carbamoyl-C 1-6 -alkyl group, substituted or unsubstituted saturated heterocyclic group, substituted or unsubstituted aryl-C 1-6 -alkyl group, substituted or unsubstituted heteroaryl-C 1-6 -alkyl group, substituted or unsubstituted arylcarbonyl group, or substituted or unsubstituted heteroarylcarbonyl group, excluding the case in which both Z 1 and Z 2 represent hydrogen atoms; when X 2 represents CH and X 3 represents nitrogen atom, Z 1 and Z 2 may form a substituted or unsubstituted, monocyclic or polycyclic heterocyclic group including X 3 and containing as a ring member two or more hetero atoms selected from the group consisting of oxygen, sulfur, and nitrogen atoms, or when X 2 represents nitrogen atom and X 3 represents CH, Z 1 and Z 2 may form a substituted or unsubstituted, monocyclic or polycyclic heterocyclic group including X 3 and containing a hetero atom selected from among oxygen, sulfur, and nitrogen atoms and wherein the prodrug is a compound having a hydroxyl or amino group substituted with C 2-7 -acyl, C 1-6 -alkoxy(C 2-7 acyl), C 1-6 -alkoxycarbonyl(C 2-7 -acyl), C 1-6 -alkoxycarbonyl, C 1-6 -alkoxy(C 2-7 -alkoxycarbonyl), (C 2-7 -acyloxy)methyl, 1-(C 2-7 -acyloxy)ethyl, (C 2-7 -alkoxycarbonyl)oxymethyl, or 1-[(C 2-7 -alkoxycarbonyl)oxy]ethyl, or a compound having a carboxyl group substituted with C 1-6 -alkyl, C-alkoxy-C 1-6 -alkyl, (C 2-7 -acyloxy)methyl, 1-(C 2-7 -acyloxy)ethyl, (C 2-7 -alkoxycarbonyl)oxymethyl, or 1-[(C 2-7 -alkoxycarbonyl)oxy]ethyl.