CDK4 and breast carcinoma: Recently, novel types of drugs have provided effective treatment strategies in the prevention and control of breast cancer, including immune checkpoint inhibitors for PD-1/PD-L1/TMB/CTLA4, PARP inhibitors for BRCA mutation and HRD, CDK4/6 inhibitors against CDK4/6, PI3Kα inhibitors and AKT inhibitors targeting the PI3K/AKT/PTEN pathway, and antibody-drug conjugates targeting HER2 [2–6].