Margenza (chemical name: margetuximab-cmkb) is used 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.
How Margenza works
Cancer cells grow in an uncontrolled fashion. Margenza works on the surface of the cancer cell by blocking the chemical signals that can stimulate this uncontrolled growth.
Genes are like instruction manuals that tell each cell of your body how to grow, what kind of cell to become, and how to behave. Genes do this by ordering the cell to make special proteins that cause a certain activity — such as cell growth, rest, or repair.
Some cancer cells have abnormalities in genes that tell the cell how much and how fast to grow. Sometimes the cancer cells have too many copies of these genes with abnormalities. When there are too many copies of these genes, doctors refer to it as "overexpression." With some forms of gene overexpression, cancer cells will make too many of the proteins that control cell growth and division, causing the cancer to grow and spread.
Some breast cancer cells make too many copies of (overexpress) a particular gene known as HER2. The HER2 gene makes a protein known as a HER2 receptor. HER2 receptors are like ears, or antennae, on the surface of all cells. These HER2 receptors receive signals that stimulate the cell to grow and multiply. But breast cancer cells with too many HER2 receptors can pick up too many growth signals. This causes them to start growing and multiplying too much and too fast. Breast cancer cells that overexpress the HER2 gene are said to be HER2-positive.
Margenza works by attaching itself to the HER2 receptors on the surface of breast cancer cells and blocking them from receiving growth signals. By blocking the signals, Margenza can slow or stop the growth of the breast cancer. Margenza is an example of an immune targeted therapy. In addition to blocking HER2 receptors, 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.
Is Margenza right for you?
Margenza is used to treat metastatic breast cancer that is HER2-positive.
There are several tests used to find out if breast cancer is HER2-positive. Two of the most common tests are:
The IHC test uses a chemical dye to stain the HER2 proteins. The IHC gives a score of 0 to 3+ that measures the amount of HER2 proteins on the surface of cells in a breast cancer tissue sample. If the score is 0 to 1+, it’s considered HER2-negative. If the score is 2+, it's considered borderline. A score of 3+ is considered HER2-positive.
If the IHC test results are borderline, it’s likely that a FISH test will be done on a sample of the cancer tissue to determine if the cancer is HER2-positive.
The FISH test uses special labels that attach to the HER2 proteins. The special labels have chemicals added to them so they change color and glow in the dark when they attach to the HER2 proteins. This test is the most accurate, but it is more expensive and takes longer to return results. This is why an IHC test is usually the first test done to see if a cancer is HER2-positive. With the FISH test, you get a score of either positive or negative (some hospitals call a negative test result “zero”).
Learn more about HER2 status.
What to expect when being treated with Margenza
Margenza is given in combination with chemotherapy.
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.
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. Visit Treatment for Breast Cancer During Pregnancy for more information.
If you are breastfeeding or plan to breastfeed, talk to your doctor about whether you should be treated with Margenza or breastfeed.
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:
pain in the bones, joints, and muscles
Margenza also may cause serious side effects, including:
Margenza 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.
Before starting Margenza therapy, you should have an echocardiogram or a MUGA (multigated blood-pool imaging) scan to check how well your heart is functioning.
An echocardiogram uses sound waves to take detailed pictures of the heart as it pumps blood. For this quick test, you lie still for a few minutes while a device that gives off sound waves is briefly placed on your ribs, over your heart. There is no radiation exposure with this test.
A MUGA scan takes about an hour. In this test, a tiny amount of radioactive material is injected into a vein in your arm. This material temporarily hooks onto your red blood cells. You lie still while a special camera that can detect the radioactive material takes pictures of the blood flow through your heart as it beats.
Your doctor will continue to monitor your heart function while you are receiving Margenza as well as after you complete treatment.
Margenza can cause serious infusion-related allergic reactions, including:
pain at the infusion site
low blood pressure
The team at your infusion center will monitor you for any signs of an allergic reaction while you’re receiving Margenza and after the infusion is completed. Contact your doctor immediately if you develop any of the symptoms above after you leave the infusion center.
Margenza (chemical name: margetuximab-cmkb) prescribing information. MacroGenics. Rockville, MD. 2020. Available at: https://www.margenza.com/pdf/prescribing-information.pdf. (PDF)
— Last updated on April 1, 2022, 1:30 PM