CDK4 and breast cancer: Nonetheless, we observed some particularly well-performing drugs: abemaciclib, a potent CDK4/6 inhibitor with good brain penetration approved for breast cancer, and the combination of dabrafenib/trametinib, a BRAF/mitogen-activated protein kinase kinase (MEK) inhibitor approved for the adjuvant treatment of melanoma with BRAF-V600E or -V600K mutations.