PostMONARCH (NCT05169567) is a randomized, double-blind, placebo-controlled, phase III trial that compares the efficacy of abemaciclib plus fulvestrant to placebo plus fulvestrant in patients with HR+/HER2−, advanced or metastatic BC following progression on CDK4/6is and ET (recruiting);. The gene discussed is CDK4; the disease is breast cancer.