On Dec. 16, 2020, the U.S. Food and Drug Administration approved the targeted therapy Margenza (chemical name: margetuximab-cmkb) in combination with chemotherapy to treat people diagnosed with metastatic HER2-positive breast cancer who have been treated previously with two or more anti-HER2 regimens, at least one of which was for metastatic disease.
Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver.
HER2-positive breast cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. About one out of every four breast cancers is HER2-positive. HER2-positive breast cancers tend to be more aggressive and may be harder to treat than HER2-negative breast cancers.
The approval is based on results from the SOPHIA study showing that Margenza combined with chemotherapy offered better progression-free survival compared to Herceptin (chemical name: trastuzumab) and chemotherapy for metastatic HER2-positive breast cancer that had been previously treated with anti-HER2 medicines.
Progression-free survival is how long a person lives without the cancer growing.
Margenza is a type of targeted therapy called a HER2 inhibitor. Margenza works by blocking the ability of HER2-positive cancer cells to receive chemical signals that tell them to grow. Margenza also was designed to improve the ability of immune cells to bind to HER2-positive breast cancer cells, allowing the immune cells to destroy the cancer cells.
Margenza is given intravenously, which means it’s delivered directly into your bloodstream through an IV or a port. The first dose of Margenza takes 2 hours to get. Doses after that take at least 30 minutes. You are treated with Margenza every 3 weeks until the cancer grows or unacceptable side effects develop.
On days that you receive both Margenza and chemotherapy, you can receive Margenza immediately after the chemotherapy infusion is completed.
Margenza side effects
Like any cancer medicine, Margenza can cause side effects, some of them severe.
The most common side effects of Margenza and chemotherapy are:
- hair loss
- abdominal pain
- peripheral neuropathy
- joint and muscle pain
- decreased appetite
- trouble breathing
- hand-foot syndrome
- pain in the hands and feet
- reactions at the infusion site
Margenza also 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. Contact your doctor immediately if you have any of these symptoms.
Your risk of heart problems is higher if you are treated with an anthracycline chemotherapy medicine less than 4 months after stopping Margenza.
Your doctor will assess your heart function before you start treatment with Margenza and will monitor your heart function the entire time you are being treated with Margenza.
It’s important to know that women who are pregnant or planning to get pregnant should not be treated with Margenza. If there is any chance you can become pregnant, you must use effective birth control while you’re taking Margenza and for at least 4 months after your last dose.
If you are breastfeeding or plan to breastfeed talk to your doctor about whether you should be treated with Margenza or breastfeed.
What this means for you
If you’ve been diagnosed with metastatic HER2-positive breast cancer that has grown after several lines of anti-HER2 treatment, you and your doctor may want to talk about whether Margenza may be right for your unique situation.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser
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