Combining abemaciclib (Verzenio), a selective CDK4/6 inhibitor, with fulvestrant significantly improved PFS and objective response rate (ORR) compared with fulvestrant monotherapy in women with HR-positive, HER2-negative advanced breast cancer who progressed while receiving either first-line, neoadjuvant, or adjuvant endocrine therapy. Here, CDK4 is linked to breast cancer.