CDK4/6 inhibitors in HER2-positive breast cancer

Notwithstanding the continuous progress made in cancer treatment in the last 20 years, and the availability of new targeted therapies, metastatic Breast Cancer (BC) is still incurable. Targeting the cell cycle machinery has emerged as an attractive strategy to tackle cancer progression, showing very promising results in the preclinical and clinical settings. The first selective inhibitors of CDK4/6 received breakthrough status and FDA approval in combination with letrozole (February 2015) and fulvestrant (February 2016) as first-line therapy in ER-positive advanced and metastatic BC. Considering the success of this family of compounds in hormone-positive BC, new possible applications are being investigated in other molecular subtypes. This review summarizes the latest findings on the use of CDK4/6 inhibitors in HER2 positive B