An inhibitor of Cdk4/6 (IC50s = 0.53 and 2.3 nM, respectively); selective for Cdk4/6 over Cdk1, Cdk2, Cdk5, Cdk7, and Cdk9 (IC50s = >1,400, >2,500, >2,000, >2,000, and 190 nM, respectively); reduces MCF-7 and T47D cell proliferation (IC50s = 200 and 260 nM, respectively); induces cell death in C666-1 and NPC/HK1 cells (IC50s = 12.25 and 5.07 µM, respectively) and cell cycle arrest in the G0/G1 phase in the same cells at 10 µM; reduces tumor growth in combination with alpelisib in two PDX mouse models of nasopharyngeal carcinoma at 200 mg/kg every two weeks