8-Cyclopentyl-5-methyl-2,6-bis((5-(piperazin-1-yl)pyridin-2-yl)amino)pyrido[2,3-d]pyrimidin-7(8H)-one is an impurity of Palbociclib (P139900),(also known as compound number PD-0332991) is an experimental drug for the treatment of breast cancer being developed by Pfizer. It is a selective inhibitor of the cyclin-dependent kinases CDK4 and CDK6.
