OPERA-1 Trial for Advanced-Stage, Estrogen Receptor-Positive Breast Cancer

Overview: The goal of the OPERA-1 trial (OP-1250 [Palazestrant] vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast Cancer) is to see if the experimental medicine palazestrant is better for people with advanced-stage, estrogen receptor-positive, HER2-negative breast cancer than the current hormonal therapy standard of care, which is either an aromatase inhibitor or Faslodex (chemical name: fulvestrant).

Phase: Phase III; Phase III trials compare the safety and effectiveness of a new treatment to the current standard of care. Phase III trials are usually large – some involve thousands of people – and are done at many places in the United States and around the world. 

Number of people to enroll: 510

ClinicalTrials.gov ID number: NCT06016738

Sponsor of the trial: Olema Pharmaceuticals, Inc.

The OPERA-1 trial is for adults diagnosed with locally advanced or metastatic estrogen receptor-positive, HER2-negative breast cancer that has been previously treated with a CDK4/6 inhibitor combined with hormonal therapy.

Locally advanced breast cancer is breast cancer that has spread to tissue near the breast, but not to parts of the body away from the breast. Metastatic breast cancer is cancer that has spread to parts of the body away from the breast.

Researchers are conducting the OPERA-1 trial to see if the experimental medicine palazestrant, a type of hormonal therapy called a selective estrogen degrader, is better than the standard hormonal therapy treatments for people with advanced-stage estrogen receptor-positive, HER2-negative breast cancer that has previously been treated with hormonal therapy combined with a CDK4/6 inhibitor. The standard of care includes either Faslodex or an aromatase inhibitor.

There will be two treatment groups in the study. 

The first group will receive palazestrant, a pill taken once a day for each 28-day cycle.

The second group will receive their doctors’ choice of one of the following standard-of-care hormonal therapies:

• Sponsor Message

  Faslodex, which is given as two injections, one into each butt cheek, on days 1, 15, and 29, of the first 28-day cycle and then on day one of each cycle after that

• Sponsor Message

  Arimidex (chemical name: anastrozole), a pill, once a day for each 28-day cycle

• Sponsor Message

  Aromasin (chemical name: exemestane), a pill, once a day for each 28-day cycle

• Sponsor Message

  Femara (chemical name: letrozole), a pill, once a day for each 28-day cycle

The researchers will compare the side effects caused by each medicine, as well as progression-free survival (how long a person lives without the cancer growing) among each group.

People are eligible for the OPERA-1 study if they:

• Sponsor Message

  have been diagnosed with advanced-stage estrogen receptor-positive, HER2-negative breast cancer that grew while being treated with hormonal therapy and a CDK4/6 inhibitor

• Sponsor Message

  are men or pre-, peri-, or post-menopausal women

• Sponsor Message

  take a luteinizing hormone-releasing hormone medicine, such as Zoladex or Lupron, if they are men or pre- or peri-menopausal women

People are not eligible for the OPERA-1 study if they:

• Sponsor Message

  received chemotherapy for advanced-stage breast cancer

• Sponsor Message

  received Orserdu (chemical name: elacestrant)

Read the detailed eligibility requirements.

In previous studies, the most common side effects of palazestrant included:

• Sponsor Message

  low white blood cell counts

• Sponsor Message

  nausea

• Sponsor Message

  vomiting

Read more about the side effects of Faslodex, Arimidex, Aromasin, and Femara.

The study is being conducted at multiple locations across the United States and around the world, including sites in Australia and Asia.

For a complete list of sites, visit: https://clinicaltrials.gov/study/NCT06016738#contacts-and-locations 

Call Olema Pharmaceuticals at 1-415-651-7206 or email: OPERA-01@olema.com.