Introduction: The dysregulation of cell cycle control can lead to cancer development. In breast cancer, cyclin D, CDK 4,6 and the retinoblastoma protein play a central role in the control of cell proliferation, in crosstalk with the estrogen receptor and Her2 pathways. Although the mechanisms by which the CDK4/6 complex is involved in the control of cell growth in triple negative breast cancer (TNBC) are still unclear, some TNBCs might be sensitive to CDK4/6 inhibitors.Areas covered: The authors provide an overview of the treatments that target cell cycle machinery in breast cancer and provide their perspectives for the future.Expert opinion: CDK 4/6 inhibitors are active drugs in HR+ MBC, but some unresolved issues remain. We need to identify biomarkers of response. Moreover, we need to determine the optimal timing for the incorporation of CDK 4/6 inhibitors in the current treatment algorithm. In the Her2 positive subtype, the triple combination of anti Her2 therapies with CDK4/6 inhibitors and endocrine therapy seems to be a promising chemotherapy free approach. Efforts must still be made for the treatment of the TNBC subtype, even though new CDK 4/6 combinations are emerging as promising approaches to selected patients.
Keywords: CDK4/6 inhibitors; HR+ breast cancer; Her2 positive breast cancer; cell cycle; targeted treatment; triple negative breast cancer.