Disclosed are methods of preventing or treating a viral infection of a host, the method comprising administering to the host an effective amount of an inhibitor of the histone methyltransferase activity of EZH1 or EZH2. In one embodiment, the method comprises administering to the host an effective amount of a compound of Formula (I):wherein X1, X2, R1, R2, and R3 are defined herein or pharmaceutically acceptable salts, solvates, or stereoisomers thereof. In another embodiment, the present invention provides a method of inhibiting an EZH1 or EZH2 methyltransferase in a virus-infected host, the method comprising administering to the host an effective amount of a compound of Formula (I) as defined above. In another embodiment, the present invention provides a method of improving the therapeutic effect of a pharmaceutical composition, the method comprising adding to the pharmaceutical composition a compound of Formula (I) as defined above.
