In patients who progressed on an AI with palbociclib or ribociclib as their initial hormonal treatment, the phase III ELAINE 3 trial (NCT05696626) will now evaluate the effectiveness of lasofoxifene plus abemaciclib for treating locally advanced or metastatic ER+/HER2-BC with an ESR1 mutation [123]. The gene discussed is ESR1; the disease is breast cancer.