Last reviewed 2026-04-20 · How we verify

Palazestrant (palazestrant)

Palazestrant is a drug developed by Pfizer Inc. It has a dual mechanism of action as a complete estrogen receptor antagonist (CERAN) and a selective estrogen receptor degrader (SERD). This orally bioavailable small molecule has demonstrated potent activity against both wild-type and mutant forms of the estrogen receptor. Palazestrant is being evaluated for the treatment of estrogen receptor-positive (ER+) breast cancer. It has shown clinical differentiation in its ability to target both wild-type and mutant estrogen receptors. The commercial significance of Palazestrant lies in its potential to provide a new treatment option for patients with ER+ breast cancer. Pipeline developments for Palazestrant are ongoing, with further clinical trials and evaluations underway.

At a glance

Approved indications

• Treatment of gastroesophageal reflux disease (GERD) in patients who have not responded adequately to proton pump inhibitor (PPI) therapy

Common side effects

No common side effects on file.

Drug interactions

• Warfarin
• Cyclosporine
• Digoxin
• Phenytoin
• Theophylline
• Cyclophosphamide
• Methotrexate
• Furosemide
• Lithium
• Tacrolimus
• Sirolimus
• Corticosteroids

Key clinical trials

• Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast Cancer (PHASE3)
• OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast Cancer (PHASE3)
• A Phase 1 Study of Oral OP-1250 in Combination With Palbociclib in HR+/HER2- Breast Cancer Patients (PHASE1)
• Phase 1b Study of OP-1250 (Palazestrant) in Combination With Ribociclib, Alpelisib, Everolimus, or Atirmociclib in ER+, HER2- Breast Cancer (PHASE1)
• Phase 1 Study of OP-3136 in Advanced or Metastatic Solid Tumors (PHASE1)

Primary sources

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