One class includes specific CDK4/6 inhibitors (such as palbociclib, ribociclib, and abemaciclib), which are being used in cancers that retain Rb-pathway functionality and/or amplification of CDK4 or CDK6, such as ER-positive breast cancers, melanomas, and sarcomas [17, 18]. The gene discussed is CDK4; the disease is melanoma.