Phase 1b Study of OP-1250 (Palazestrant) in Combination With Ribociclib, Alpelisib, Everolimus, or Atirmociclib in ER+, HER2- Breast Cancer

This is a Phase 1b open-label, 2-part study in 4 treatment groups. The 4 treatment groups are as follows: Treatment Group 1: Palazestrant (OP-1250) in combination with ribociclib (KISQALI®, Novartis Pharmaceuticals Corporation). Treatment Group 2: Palazestrant (OP-1250) in combination with alpelisib (PIQRAY®, Novartis Pharmaceuticals Corporation). Treatment Group 3: Palazestrant (OP-1250) in combination with everolimus. Treatment Group 4: Palazestrant (OP-1250) in combination with atirmociclib.