ESR1 and breast cancer: The other clinical trial, coopERA BC (NCT04436744) (Study Details A Study to Evaluate the Efficacy, Safety, and Pharmacokinetics of Giredestrant Plus Palbociclib Compared With Anastrozole Plus Palbociclib for Postmenopausal Women With Estrogen Receptor-Positive and HER2-Negative Untreated Early Breast Cancer coopERA Breast Cancer ClinicalTrials.gov, 2023)evaluated the efficacy, safety, and pharmacokinetics of giredestrant plus palbociclib in postmenopausal women patients with untreated early-stage ER+/HER2-breast cancer (which is also called coopERA breast cancer).