This includes Palbociclib, Abemaciclib, and Ribociclib, clinically approved CDK4/6 inhibitors commonly used in treating breast cancers, as well as Atirmociclib, a novel CDK4-selective inhibitor, and two CDK2 inhibitors in clinical trials, Tagtociclib and INX-315. This evidence concerns the gene CDK2 and breast cancer.