CDK4 and breast cancer: Abemaciclib (Verzenio, Lilly, Indianapolis, IN, USA) is the third CDK4/6i granted quick FDA approval in September 2017, based on the results from phase III MONARCH-2 trial, aimed to investigate abemaciclib in combination with fulvestrant in women with HR-positive/HER2-negative advanced BC in which disease had progressed after ET.