Pharmacodynamic characteristics, safety profile, and interactions of CDK4/6 inhibitors (CDK4/6i) in HR+/HER2– advanced/metastatic breast cancer

Targeted therapies such as cyclin-dependent kinase 4 and 6 inhibitors (CDK 4/6i) have improved the prognosis of hormone receptor-positive/human epidermal growth factor receptor-2 negative (HR+)/(HER2–) advanced/metastatic breast cancer (a/mBC) by combating the resistance observed with traditional endocrine therapy. Currently, palbociclib, ribociclib, and abemaciclib are the three medicinal products authorized by the European Medicines Agency and the Food and Drug Administration. In addition to their overall similarities, related to their primary molecular mechanism of action through CDK4/6 inhibition, they also exhibit significant pharmacodynamic differences that affect their efficacy and safety profile, which may, through further research, help in understanding predicted toxicity, safety, and interactions and assist in adjusting dosing regimens in daily clinical practice. This review article will examine the pharmacodynamic profile of CDK4/6 inhibitors, their efficacy and safety in the treatment of HR+/HER2– a/mBC.