Palbociclib Hydrochloride

Palbociclib, also known as PD0332991, is an orally available pyridopyrimidine-derived cyclin-dependent kinase (CDK) inhibitor with potential antineoplastic activity. PD-0332991 selectively inhibits cyclin-dependent kinases (particularly Cdk4/cyclin D1 kinase), which may inhibit retinoblastoma (Rb) protein phosphorylation. Inhibition of Rb phosphorylation prevents Rb-positive tumor cells from entering the S phase of the cell cycle (arrest in the G1 phase), resulting in suppression of DNA replication and decreased tumor cell proliferation. PD 0332991 is a highly specific inhibitor of cyclin-dependent kinase 4 (Cdk4) (IC50 = 0.011 ?mol/L) and Cdk6 (IC50 = 0.016 ?mol/L), having no activity against a panel of 36 additional protein kinases.