Selective cyclin-dependent kinase inhibitors and methods of therapeutic use thereof

A compound of formula (I):

• wherein:
• X1 is CH or N;
• R1 is selected from unsubstituted or substituted branched or linear C1-C12 alkyl, C3-C12 cycloalkyl, C3-C12 heterocycloalkyl, aryl, heteroaryl, and —C(O)—R6, wherein R6 is selected from unsubstituted or substituted C1-C12 alkyl, C3-C12 cycloalkyl, C3-C12 heterocycloalkyl, aryl, and heteroaryl;
• R2, R3, R4, and R5 are each independently selected from hydrogen, halogen, amine, unsubstituted or substituted branched or linear C1-C12 alkyl, C3-C12 cycloalkyl, C3-C12 heterocycloalkyl, aryl, heteroaryl, and —C(O)—R6, wherein R6 is selected from unsubstituted or substituted C1-C12 alkyl, C3-C12 cycloalkyl, C3-C12 heterocycloalkyl, aryl, and heteroaryl;
• or a pharmaceutically acceptable salt, hydrate, solvate, stereoisomer, ester, tautomer, or prodrug thereof.