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OPERA-01 is a study to test how safe and effective the investigational drug palazestrant (OP-1250) is compared to one of the available standard-of-care medications. This phase 3 study is for people with advanced and/or metastatic estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer that has progressed after receiving CDK4/6 inhibitor medicines in combination with an endocrine (hormone) therapy.

About 80% of all breast cancers are hormone receptor-positive (HR+). Most HR+ breast cancers are estrogen-receptor positive (ER+). Therefore, sometimes ER+ breast cancer is referred to as HR+ breast cancer.

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About the study

What is the OPERA-01 study?

The OPERA-01 phase 3 study will evaluate how safe and effective the investigational drug palazestrant is compared to one of the available standard-of-care medications in adults with ER+/HER2- advanced and/or metastatic breast cancer that has progressed after receiving CDK4/6 inhibitor medicines in combination with an endocrine therapy.

What will happen in this study?

If you are eligible to enroll in this study, you will be randomly assigned (by chance) to receive the study drug (palazestrant) or a standard-of-care endocrine therapy for advanced breast cancer. You and your study doctor will be aware of your study group assignment.

Palazestrant oral tablets will be taken once daily in 28-day cycles. Standard-of-care endocrine therapy will be administered either as oral tablets taken once daily in 28-day cycles or as injections (once per cycle except for the first cycle).

Other tests including medical examinations and laboratory assessments will be performed at the regular visits.

How long will the OPERA-01 study last?

Your time in the study will vary. You should expect to receive palazestrant or standard-of-care endocrine therapy until you complete the study treatment and the follow-up after the study treatment.

Is the study right for you?

If you meet the following criteria, you may be eligible to participate in the OPERA-01 study:

  • Adult female or male
  • Diagnosis of ER+/HER2- advanced and/or metastatic breast cancer that has progressed after prior endocrine therapy
  • Previously received a CDK4/6 inhibitor medicine in combination with an endocrine therapy
  • Have not previously received chemotherapy for advanced and/or metastatic breast cancer
  • Female participants can be pre-, peri-, or postmenopausal

Please note, this is not a complete list of study requirements. The study coordinator will review the full requirements with you or you can review key inclusion criteria at clinicaltrials.gov (NCT06016738).

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Your questions answered

Why is the OPERA-01 study important?

Breast cancer is one of the most prevalent cancers worldwide, with more than two million new diagnoses globally each year. Studies like OPERA-01 help researchers better understand breast cancer and look for drugs that could help more people with this cancer.

What are the goals of the OPERA-01 study?

The main goals are to evaluate how safe and effective an oral study drug palazestrant is compared to one of the available standard-of-care medications in adults with ER+/HER2- advanced and/or metastatic breast cancer that has progressed after receiving CDK4/6 inhibitor medicines in combination with an endocrine therapy.

What is a clinical study?

A clinical study is a research study involving volunteers (also called participants) that is intended to add to medical knowledge. Clinical studies are important to help improve how advanced breast cancer is treated today and discover new solutions for the future. These advances are only possible thanks to volunteer participation.

What is a study drug?

A study drug (also called an investigational drug) is a substance that is being tested in a clinical study and has not been approved by regulatory agencies, such as the United States (US) Food and Drug Administration (FDA), European Medicines Agency (EMA), or others. Every study drug is reviewed by an ethics committee (or institutional review board) for testing in people, and the study doctors and healthcare professionals must follow strict rules set by the FDA and other regulatory agencies.

What are the costs to take part in the OPERA-01 study?

You do not have to pay for the study drugs or any tests that are part of this study. You may be reimbursed for the reasonable costs associated with travel (if needed) to participate in this study.

What risks are involved in study participation?

There are risks involved with any clinical study. The study doctor will review the risks with you, and you will be closely monitored throughout the study.

What if I change my mind or decide to stop participating?

Taking part in a study is voluntary. Participants are free to leave the study at any time.

What happens when the study ends?

After a clinical study is completed, the researchers carefully examine information collected during the study before making decisions about the meaning of the findings and about the need for further testing.

How can I learn more?

For more information about the OPERA-01 study, please contact us at [email protected] or visit clinicaltrials.gov.

Study site locations

Visit clinicaltrials.gov to see OPERA-01 study site locations near you.

Thank you for your interest in the OPERA-01 study.

If you would like to learn more about this study, please contact us at [email protected] or visit clinicaltrials.gov.