The VERITAC-3 study (NCT05909397) will evaluate first-line vepdegestrant with palbociclib versus letrozole with palbociclib in patients with ER+/HER2- advanced breast cancer; a study lead-in assessing two doses of palbociclib (100 mg or 75 mg) with vepdegestrant is ongoing. Here, ESR1 is linked to breast carcinoma.