- Study Drug(s): The participant will be given a study drug-dosing calendar for each treatment cycle. Each treatment cycle lasts 4 weeks during which time you will be taking the study drug for 3 weeks at a time. The participant will take Palbociclib by mouth once a day, every day for 3 weeks. The participant will take PD-0325901 by mouth twice a day, every day for 3 weeks.