A Phase II Study of Abemaciclib in Patients with Brain Metastases Secondary to Hormone Receptor–Positive Breast Cancer

Abstract

This study did not meet its primary endpoint. Abemaciclib was associated with an iCBR of 24% in patients with heavily pretreated HR⁺, HER2^- MBC. Abemaciclib achieved therapeutic concentrations in brain metastases tissue, far exceeding those necessary for CDK4 and CDK6 inhibition. Further studies are warranted, including assessing novel abemaciclib-based combinations.