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RecruitingLast updated: 6 February 2024

OPERA-01: This study is comparing the safety and effectiveness of a new drug (called OP-1250) to standard of care hormone therapy in people with ER+, HER2- locally advanced or metastatic breast cancer who have had prior treatmentA 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 CDK 4/6 Inhibitor Therapy

Clinical summary


Eligible participants will be randomly allocated to one of two treatment cohorts. Treatment cycles are 4 weeks (28 days).

In Cohort 1 (Experimental), participants will receive the experimental drug OP-1250 (also called palazestrant) once daily.

In Cohort 2 (Active Comparator), participants will receive the Investigator's choice of one of the Standard of Care hormone therapies, either fulvestrant, anastrozole, letrozole or exemestane. Fulvestrant will be administered on C1D1, C1D15, and C2D1 in the first cycle, and on Day 1 of every subsequent cycle. Anastrozole, letrozole and exemestane will be administered once daily.


This trial is treating patients with ER+, HER2- locally advanced or metastatic breast cancer whose disease has advanced after receiving at least one hormone therapy in combination with a CDK4/6 inhibitor


Breast Cancers Breast





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Trial Identifiers

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Trial sponsor

Olema Pharmaceuticals, Inc.

Scientific Title

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 CDK 4/6 Inhibitor Therapy



  • Adult female or male participants.
  • ER+, HER2- locally advanced or metastatic breast cancer that is not amenable to curative therapy.
  • Evaluable disease (measurable disease or bone-only disease).
  • Previously received a CDK4/6 inhibitor in combination with an endocrine therapy in the advanced setting. One additional line of ET as a monotherapy will be allowed.
  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
  • Adequate hematologic, hepatic, and renal functions.
  • Female participants can be pre-, peri- or postmenopausal.
  • Male and pre- or peri-menopausal female participants must be willing to take a GnRH (LHRH) agonist.


  • Symptomatic visceral disease, imminent organ failure, or any disease burden that makes the participant ineligible for endocrine therapy.
  • Have received prior chemotherapy in the advanced/metastatic setting.
  • Have received prior treatment with elacestrant or an investigational estrogen receptor-directed therapy.
  • History of allergic reactions to study treatment.
  • Any contraindications to the selected standard of care endocrine therapy in the local prescribing information.
  • Symptomatic central nervous system metastases, carcinomatous meningitis, leptomeningeal disease, or a spinal cord compression that require immediate treatment.
  • Clinically significant comorbidities such as significant cardiac or cerebrovascular disease, gastrointestinal disorders that could affect absorption of study treatment and others.


  • You have had a certain type of treatment or surgical procedure.
  • You have had treatment but your cancer has gotten worse or has not responded to the treatment you have been given.
  • You have had treatment, but your cancer has come back.
  • Your cancer has not spread to other parts of the body.
  • Your cancer has spread to other parts of the body.


  • You have certain types of non-cancer medical conditions.
  • You have had certain treatments, surgical procedures or drugs.

Clinical trials have complex eligibility criteria.

Ask your doctor if this trial could be right for you.

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