An orally bioavailable inhibitor of cyclin-dependent kinase (CDK) types 4 (CDK4) and 6 (CDK6), with potential antineoplastic activity. Upon administration, CDK4/6 inhibitor FCN-437 selectively inhibits CDK4 and CDK6, which inhibits the phosphorylation of retinoblastoma protein (Rb) early in the G1 phase, prevents CDK-mediated G1/S transition and leads to cell cycle arrest. This suppresses DNA replication and decreases tumor cell proliferation. CDK4 and 6 are serine/threonine kinases that are upregulated in many tumor cell types and play key roles in the regulation of both cell cycle progression from the G1-phase into the S-phase and cell proliferation.