CDK4 and breast cancer: Notably, gedatolisib has recently received breakthrough therapy designation by the FDA to accelerate the development and regulatory review of this agent based on data from a Phase 1b trial that assessed the safety, tolerability and clinical activity of gedatolisib in combination with endocrine therapy and CDK4/6 inhibitor in ER+ advanced breast cancer that progressed on CDK4/6 therapy and an AI [56].