Summary
Eligible participants will be randomly assigned to one of two treatment arms. Treatment cycles are 28-days.
In the Experimental Arm, participants will receive Giredestrant hormone therapy + the Investigator's Choice of CDK4/6 inhibitor targeted therapy (either Palbociclib, Ribociclib or Abemaciclib).
Giredestrant (30mg) will be given orally once a day on Days 1-28 of each cycle. If chosen, Abemaciclib (150mg) will be given orally twice daily on Days 1-28, Palbociclib (125mg) will be given orally once daily on Days 1-21, and Ribociclib (600mg) will be given orally once daily on Days 1-21.
In the Active Comparator Arm, participants will receive Fulvestrant hormone therapy + Investigator's Choice of CDK4/6 inhibitor targeted therapy (either Palbociclib, Ribociclib, or Abemaciclib).
Fulvestrant (500mg) will be given intramuscularly on Days 1 and 15 of Cycle 1, and on Day 1 of each subsequent treatment cycle. If chosen, Abemaciclib (150mg) will be given orally twice daily on Days 1-28, Palbociclib (125mg) will be given orally once daily on Days 1-21, and Ribociclib (600mg) will be given orally once daily on Days 1-21.
In both arms, pre/perimenopausal female participants and male participants will receive a luteinizing hormone-releasing hormone (LHRH) agonist locally approved for use in breast cancer on Day 1 of each cycle.