Preclinical and clinical development of palbociclib and future perspectives.

Cyclin-dependent kinases (CDKs) play a key role in cell cycle regulation, which makes them a clear therapeutic target to interfere with cell division and proliferation in cancer patients. Palbociclib, a specific inhibitor of CDK4/6 with outstanding clinical efficacy data and limited toxicity, has been recently approved for the treatment of hormone receptor (HR)-positive human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer, either in combination with an aromatase inhibitor or in combination with fulvestrant in women who have received prior endocrine therapy. This review describes the mechanism of action, preclinical experiences and clinical data of palbociclib, with a special focus on integrating this data with the positioning of palbociclib in the current clinical guidelines for advanced HR-positive/HER2-negative breast cancer. Aspects of the ongoing major studies are also presented, as well as future prospects in the development of palbociclib.