ERBB2 and breast cancer: Consequently, 3 CDK4/6 inhibitors (palbociclib [Palbo], ribociclib, and abemaciclib [Abema]) have been approved by the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for treatment of patients with advanced or metastatic HR+/HER2– BC (3, 10, 11).