SELECTIVE PI3Kdelta INHIBITOR AND USE THEREOF

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

• wherein,
• X is selected from the group consisting of CH and N;
• R1 and R2 are each independently selected from the group consisting of hydrogen, halogen, and C1-6 haloalkyl;
• R3 is C3-g cycloalkyl;
• R4 is selected from the group consisting of hydrogen and C1-6 alkyl;
• R5 is selected from the group consisting of hydrogen, C1-6 alkyl, C1-6 alkoxy, C2-6 alkylamido, and C1-6 alkylaminoacyl;
• R6 is selected from the group consisting of hydrogen, hydroxy, halogen, C1-6 alkyl, and C1-6 alkoxy;
• or R5 and R6 together form a phenyl group or a dioxolane group.