A method for treating against, or at least inhibiting or suppressing, the proliferation of an internal ribosome entry site-utilizing virus (IRES-utilizing virus) involves administering a compound, a tautomer, or a pharmaceutically acceptable salt thereof, in an amount effective for inhibiting replication of the IRES-utilizing virus in cells, wherein the compound is represented by the formula: wherein each R1 is independent of the other and represents a halogen atom selected from the group consisting of bromo, chloro, fluoro and iodo.