NCIt definition : An orally available cyclin-dependent kinase (CDK) inhibitor that targets the CDK4
(cyclin D1) and CDK6 (cyclin D3) cell cycle pathway, with potential antineoplastic
activity. Abemaciclib specifically inhibits CDK4 and 6, thereby inhibiting retinoblastoma
(Rb) protein phosphorylation in early G1. Inhibition of Rb phosphorylation prevents
CDK-mediated G1-S phase transition, thereby arresting the cell cycle in the G1 phase,
suppressing DNA synthesis and inhibiting cancer cell growth. Overexpression of the
serine/threonine kinases CDK4/6, as seen in certain types of cancer, causes cell cycle
deregulation.;