ESR1 and breast cancer: The ongoing persevERA trial, a phase III, randomized, double-blind, multicenter trial, aims to evaluate the efficacy of first-line giredestrant plus palbociclib versus letrozole plus palbociclib among patients with ER + /HER2-negative locally advanced or metastatic breast cancer, whereas the lidERA trial randomized patients with ER + /HER2 − early breast cancer to giredestrant versus endocrine therapy in the adjuvant setting.