Palbociclib Impurity VIP(LA)d4 is the deuterated form of Palbociclib Impurity A (P139940) which is related to the parent compound, Palbocicib (P139900) (also known as compound number PD-0332991), 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.Also, it is derived from 3-Fluoro-2-nitropyridine (F597685).