The CDK4/6 specific inhibitors palbociclib (breast cancer phase III trial NCT01942135), ribociclib (melanoma phase II trial NCT01719380), and abemaciclib (breast cancer phase Ib trial NCT02057133) all potently inhibit CDK4/6 [57] and are potentially useful in acute leukemias with CDKN2A/B alterations [58]. Here, CDK4 is linked to breast cancer.