CDK4 and breast cancer: In the eBC setting, the lidERA BC study is evaluating adjuvant giredestrant versus endocrine monotherapy; in the mBC setting, persevERA BC is a study of 1L giredestrant plus palbociclib versus letrozole plus palbociclib; and evERA BC will assess giredestrant versus physician’s choice of ET, both in combination with everolimus, in patients previously treated with a CDK4/6 inhibitor plus ET [44–46].