Definition

An orally bioavailable inhibitor of cyclin-dependent kinase 4 (CDK4), with potential antineoplastic activity. Upon oral administration, CDK4 inhibitor BGB-43395 selectively inhibits CDK4, which inhibits the phosphorylation of retinoblastoma protein (Rb) early in the G1 phase, prevents CDK-mediated G1-S-phase transition and leads to cell cycle arrest. This suppresses DNA replication and inhibits tumor cell proliferation. CDK4, a serine/threonine kinase, is upregulated in many tumor cell types and plays a key role in the regulation of both cell cycle progression from the G1-phase into the S-phase and tumor cell proliferation.