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Palazestrant for ER+/HER2- Advanced Breast Cancer

This study is testing a new drug called palazestrant (OP-1250) for people with advanced breast cancer that is estrogen receptor-positive (ER+) and HER2-negative (HER2-). This type of cancer uses hormones to grow. The study will compare palazestrant to standard treatments like fulvestrant, anastrozole, letrozole, or exemestane. You may be able to join if you are an adult with this type of breast cancer that has spread or gotten worse after previous treatments, including a CDK4/6 inhibitor. The main goals are to see how safe palazestrant is and how well it works. The study plans to enroll 510 participants.

Study design
This is an international, multi-center, randomized, open-label, active-controlled Phase 3 clinical trial. Approximately 510 participants will be randomly assigned to receive either palazestrant or a standard-of-care endocrine therapy.
What's involved
Not specified in the trial record.
Compensation
Not stated in the trial record.
Follow-up
For the dose-selection part, adverse events, dose reductions, and drug discontinuations will be measured for up to 16 weeks from the date of randomization.

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT06016738

OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast Cancer

Active, Not Recruiting
PHASE3Ages 18+InterventionalTreatment
Olema Pharmaceuticals, Inc.
~510 participants
Updated 2026-08-13 on ClinicalTrials.gov
What's tested:PalazestrantFulvestrantAnastrozoleLetrozoleExemestane

At a glance

Recruiting sites
0 of 233 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Dose-Selection Part: Incidence of adverse events
Measured over From Date of Randomization up to 16 weeks
+3 more outcomes measured

Conditions

Breast Cancer
Advanced Breast Cancer
Metastatic Breast Cancer
ER Positive Breast Cancer
HER2 Negative Breast Carcinoma

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Breast Carcinoma

Where it's being run

233 sites across 137 states
South Korea9
Taiwan9
Spain7
California6
Thailand6
Florida5
Hong Kong5
Italy5

Study leadership

  • Medical Director, MD · STUDY_DIRECTOR · Olema Pharmaceuticals, Inc.

Who to contact

This trial hasn't published a contact. View it on ClinicalTrials.gov

Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

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 is allowed. Duration of the most recent prior ET must be at least 6 months.
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 (or LHRH) agonist.

Exclusion

Symptomatic visceral disease, imminent organ failure, or any other reason that makes the participant ineligible for endocrine monotherapy.
Previously received chemotherapy in the advanced/metastatic setting.
Previously received 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.

What this trial measures

  • Dose-Selection Part: Incidence of adverse eventsFrom Date of Randomization up to 16 weeks

    To evaluate the number of participants with adverse events

  • Dose-Selection Part: Incidence of dose reductionFrom Date of Randomization up to 16 weeks

    To evaluate the number of participants reducing the dose of palazestrant

  • Dose-Selection Part: Incidence of drug discontinuationFrom Date of Randomization up to 16 weeks

    To evaluate the number of participants discontinuing palazestrant

  • Trial: Progression-Free Survival (PFS)From Date of Randomization until Disease Progression or Death Due to Any Cause (estimated as up to 2 years)

    To compare PFS, based on a Blinded Independent Review Committee (BIRC) assessment, between arms of OP-1250 and standard-of-care treatment. This will be assessed separately in populations of ESR1-mutation detected and ESR1-mutation not detected participants.