ESR1 and breast cancer: In 2022, the development program for amcenestrant was discontinued after the AMEERA-5 trial (amcenestrant + palbociclib vs. letrozole + palbociclib [53]) and the AMEERA-3 trial (amcenestrant vs. standard endocrine monotherapy [54]) did not show a benefit for amcenestrant in HER2−/ER+ breast cancers.