CDK-inhibiting drugs are a novel class of cancer therapeutics and three CDK4/6 inhibitors, palbociclib, ribociclib (LEE011), and abemaciclib, are Food and Drug Administration and European Medicines Agency approved for the treatment of advanced ﻿hormone receptor-positive breast cancer and in clinical trials for other non-breast malignancies51. This evidence concerns the gene CDK4 and cancer.