EZH2 inhibitor and use thereof

A compound of formula (I), or a pharmaceutically acceptable salt, solvate, ester, acid, metabolite or prodrug thereof:

• wherein,
• Y is selected from a group consisting of cyano, aminoacyl, alkylamino optionally substituted with one R4, aryl optionally substituted with 1-3 independent R4, heteroaryl optionally substituted with 1-3 independent R4, and heterocycloalkylalkylamino optionally substituted with 1-3 independent R4;
• R1 is alkyl;
• R2 is selected from a group consisting of hydrogen, alkyl and cycloalkylalkyl;
• R3 is selected from a group consisting of alkyl (excluding alkenyl), cycloalkyl, heterocycloalkyl, heteroaryl, alkylaryl, and bicyclo[2.2.1]hept-2-enyl;
• R4 is independently selected from a group consisting of hydrogen, halo, amino, cyano, alkyl, alkoxy, alkanoyl, alkylamino optionally substituted with one R5, alkylsulfonamide optionally substituted with one R5, cycloalkylsulfonamide optionally substituted with one R5, heterocycloalkyl optionally substituted with 1-3 independent R5, heterocycloalkylcarbonyl optionally substituted with 1-3 independent R5, heterocycloalkylalkyl optionally substituted with 1-3 independent R5, heterocycloalkylalkoxy optionally substituted with 1-3 independent R5, heterocycloalkylcarbonylalkyl optionally substituted with 1-3 independent R5, and aryloxy optionally substituted with 1-3 independent R5;
• and
• R5 is independently selected from a group consisting of amino, alkyl, alkanoyl, alkylamino, hydroxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, and amino protecting group.