Palbociclib is a pyridopyrimidine compound with the structure 2-{[5-(piperazin-1-yl)pyridin-2-yl]amino}pyrido[2,3-d]pyrimidin-7-one, bearing methyl, acetyl, and cyclopentyl substituents at positions 5, 6, and 8, respectively. It is used in combination with letrozole to treat metastatic breast cancer. It functions as a cyclin-dependent kinase inhibitor (EC 2.7.11.22) and an antineoplastic agent. It is also classified as an aminopyridine, secondary amino compound, piperidine, aromatic ketone, cyclopentane, and tertiary amino compound.
