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Phase: Phase III ID number: NCT04494425

Sponsors of the trial: Daiichi Sankyo, Inc., and AstraZeneca

Who is the trial for?

The DESTINY-Breast06 trial is a phase III trial for people diagnosed with metastatic hormone-receptor-positive breast cancer with low HER2 levels that has been previously treated with at least two hormonal therapy medicines.

In this study, HER2-low breast cancer means the cancer has a score of 1+ or 2+ on an immunohistochemistry (IHC) HER test and/or a negative result on a in situ hybridization (ISH) HER2 test.

Why the trial is being done

Breast cancer with low HER2 levels would usually be considered HER2-negative breast cancer. Still, earlier studies have shown that the medicine being studied may help treat breast cancers with very low HER2 levels, which is part of the reason why this larger study is being done.

The trial wants to see if fam-trastuzumab-deruxtecan-nxki allows people to live longer without the metastatic cancer growing or simply live longer overall, compared to people being treated with standard-of-care chemotherapy. The trial also will collect information on how the treatment affects people’s quality of life.

Under the brand name Enhertu, fam-trastuzumab-deruxtecan-nxki is approved in the United States to treat metastatic HER2-positive breast cancer, or HER2-positive breast cancer that can’t be removed with surgery, that has been treated with two or more anti-HER2 medicines.

The DESTINY-Breast06 trial is using the medicine to treat a different type of breast cancer than Enhertu is approved for, so when talking about the trial, the medicine is called by its chemical name: fam-trastuzumab-deruxtecan-nxki.

Fam-trastuzumab-deruxtecan-nxki is an antibody-drug conjugate made up of three parts:

  • fam-trastuzumab: an anti-HER2 antibody medicine that has the same basic structure as Herceptin (chemical name: trastuzumab)
  • a topoisomerase I inhibitor chemotherapy medicine called DXd; topoisomerase I inhibitors work by interfering with the cancer cells’ ability to replicate
  • a compound that links the fam-trastuzumab to the topoisomerase I inhibitor

Fam-trastuzumab-deruxtecan-nxki was designed to deliver the chemotherapy medicine to cancer cells in a targeted way by targeting the HER2 receptors on cancer cells.

Fam-trastuzumab-deruxtecan-nxki is given intravenously, which means the medicine is delivered directly into your bloodstream through an IV or a port. The medicine usually is given every 3 weeks unless the cancer grows or unacceptable side effects develop.

Specific eligibility requirements

People are eligible for the DESTINY-Breast06 trial if:

  • they are a legal adult in their country and have been diagnosed with metastatic hormone-receptor-positive breast cancer with low HER2 levels that was never considered HER2-positive
  • the metastatic cancer has been previously treated with at least two hormonal therapy medicines and has grown while being treated with hormonal therapy
  • the metastatic cancer has not been treated with chemotherapy

People are not eligible for the DESTINY-Breast06 trial if they:

  • are not eligible to be treated with any of the chemotherapy options
  • have serious lung disease
  • have serious or uncontrolled heart disease
  • have a history of interstitial lung disease, disorders that cause inflammation and scarring in the lungs
  • have spinal cord compression or brain metastases
  • are pregnant or plan to become pregnant: women in the trial who are able to become pregnant should use effective birth control during the trial and for at least 7 months after the trial ends; men in the trial with partners who are able to become pregnant should use effective birth control during the trial and for at least 4 months after the trial ends
  • have been previously treated with fam-trastuzumab-deruxtecan-nxki or have been in a trial that was studying the medicine

Potential side effects of the treatment being studied

In earlier studies, the most common side effects of fam-trastuzumab-deruxtecan-nxki were:

  • nausea
  • anemia
  • fatigue
  • low white blood cell counts
  • vomiting
  • diarrhea
  • hair loss
  • cough
  • constipation
  • low platelet counts
  • decreased appetite
  • liver problems
  • low levels of blood potassium

Fam-trastuzumab-deruxtecan-nxki also may cause serious side effects, including:

  • Interstitial lung disease: Interstitial lung disease is a general term for disorders that cause inflammation and scarring in the lungs. The scarring makes lung tissue stiff, which makes it difficult to breathe. You will be closely monitored for signs of interstitial lung disease while being treated with fam-trastuzumab-deruxtecan-nxki. You must tell your doctor right away if you experience shortness of breath or have a dry cough.
  • Heart problems: Fam-trastuzumab-deruxtecan-nxki may cause serious heart problems, including some that don’t have symptoms, such as reduced heart function, and some that do have symptoms, such as congestive heart failure. Symptoms to watch for include swelling of the ankles or legs, shortness of breath, cough, or weight gain of more than 5 pounds in less than 24 hours.
  • Neutropenia: Neutrophils are a type of white blood cell. Neutropenia means you have low levels of neutrophils in your blood. When neutropenia is severe, even the normal bacteria in your mouth and digestive tract can cause serious illness.

Your doctor will monitor you for any serious side effects while you’re being treated with fam-trastuzumab-deruxtecan-nxki and may reduce your dose, delay your treatment, or completely stop treatment if you do have serious side effects.

Study locations

The DESTINY-Breast06 trial is being conducted at multiple sites in the United States and around the world. For a complete list of sites, visit

For more information or to enroll

Email or call 877-240-9479.

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