The safety and efficacy of palbociclib in the treatment of metastatic breast cancer

Introduction: Palbociclib (Ibrance (R)) is the first-in-class CDK4/6 inhibitor which has been introduced into clinical practice for the treatment of estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC). It is an orally administered drug, which acts by selectively inhibiting cyclin-dependant kinases CDK4 and CDK6. Given together with anti-estrogens like letrozole and fulvestrant it enhances the antiproliferative effect of these drugs without compromising the favorable toxicity profile of endocrine therapy. Areas covered: This review gives a concise overview of the current available preclinical and clinical data about pabociclib including its chemistry, mechanism of action, pharmacokinetics and evidence of its substantial anti-tumor efficacy and safety profile when combined with endocrine therapy Expert commentary: Palbociclib doubles treatment efficacy of letrozole and fulvestrant with a restricted and well manageable toxicity profile. Efficacy as well as safety results from the three registration trials are remarkably consistent. Patients' quality of life is maintained on palbociclib treatment. The treatment landscape in ER+ HER2- MBC will be highly influenced by this compound and development of two other CDK4/6 inhibitors.