ESR1 and breast cancer: Based on the encouraging preclinical data, a first-in-human phase 1/2 study (ClinicalTrials.gov identifier: NCT04072952) of vepdegestrant monotherapy and in combination with palbociclib was conducted in ER+/HER2− breast cancer patients; vepdegestrant demonstrated antitumor activity and was tolerated in daily doses from 30 to 700 mg, with no dose-limiting toxicities [122].