Study Comparing Lasofoxifene and Abemaciclib against Fulvestrant and Abemaciclib for Breast Cancer (H-54023)

An Open Label, Randomized, Multicenter Study Comparing the Efficacy and Safety of the Combination of Lasofoxifene and Abemaciclib to the Combination of Fulvestrant and Abemaciclib for the Treatment of Pre- and Postmenopausal Women and Men with Locally Advanced or Metastatic ER+/HER2- Breast Cancer with an ESR1 Mutation (ELAINE-3)

Women of any menopausal status, and men, with ER+/HER2- metastatic or locally advanced breast cancer with ESR1 mutation, with evidence of progression (greater than or equal to six months ago) on AI in combination with either palbociclib or ribociclib as first ET for metastatic disease are randomized to either lasofoxifene and abemaciclib or fulvestrant and abemaciclib. The purpose of this study is to compare the effects of the 2 treatment regimens and determine which is better for the treatment of metastatic breast cancer.