OPERA-01 - A Phase 3 Randomized, Open-Label Study of OP-1250 Monotherapy vs Standard of Care for the Treatment of ER+. HER2- Advanced or Metastatic Breast Cancer Following Endocrine and CDK4/6 Inhibitor Therapy

A new drug called OP-1250 (palazestrant) is being tested against the current standard treatment in 510 people with advanced or metastatic ER+, HER2- breast cancer whose disease has progressed after hormone therapy and CDK4/6 inhibitor treatment. This matters because ER+, HER2- breast cancer is the most common subtype, and once it becomes resistant to first-line endocrine therapy and CDK4/6 inhibitors, treatment options are limited. The current standard of care—typically fulvestrant or an aromatase inhibitor—often provides only modest benefit. OP-1250 is designed as a complete estrogen receptor antagonist, meaning it blocks the receptor more thoroughly than existing drugs, potentially overcoming resistance. If OP-1250 proves superior to standard care, it could become a new second-line treatment option for tens of thousands of patients worldwide. The trial is being conducted at roughly 210 global sites over 40 to 45 months. Success would mean a longer period of disease control before patients need chemotherapy, directly improving quality of life and survival for a large patient population that currently has few effective alternatives after initial treatment failure.