A HER2-targeting antibody treatment for some breast cancers
Margetuximab
A HER2-targeting antibody treatment used, with chemotherapy, for some HER2-positive breast cancers, given into a vein.
What is Margetuximab?
Margetuximab is a specialist cancer treatment used for some adults with HER2-positive breast cancer (breast cancer driven by a protein called HER2) that has come back or spread after earlier treatments. It is an antibody that targets HER2 on the cancer cells and helps the immune system attack them, and it is given together with chemotherapy. It is given as a drip into a vein. The main risks are reactions during or after the infusion and effects on the heart, where it can weaken the heart's pumping (a fall in what is called the LVEF), so the heart is checked before and during treatment. It can also harm an unborn baby, so reliable contraception is essential.
Education and reference only. This is a plain-language guide to Margetuximab — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Margetuximab is an antibody-based cancer medicine that targets HER2, a protein found in larger amounts on some breast cancer cells. It is used for some adults with HER2-positive breast cancer that has come back or spread despite earlier HER2-directed treatments, and it is given together with chemotherapy. It is given as an infusion into a vein in a specialist cancer unit and is prescribed and supervised by an oncology team, with regular heart checks throughout treatment.
How it works
HER2-positive breast cancers have extra HER2 protein on their surface, which drives the cancer to grow. Margetuximab attaches to HER2, which both interferes with the signals that tell the cancer to grow and flags the cancer cells so the body's immune system can attack them — it is engineered to make that immune attack stronger. It is used alongside chemotherapy so the two work together. Because HER2 is also important for the heart muscle, interfering with it can affect how well the heart pumps, which is why the heart is monitored before and during treatment.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist treatment used in cancer centres for some adults with HER2-positive breast cancer that has come back or spread after earlier treatments.
Practical use
How to take Margetuximab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as a drip into a vein in a specialist cancer unit, together with chemotherapy on a schedule your team plans.
- You will be watched during and after the infusion for reactions such as fever, chills or breathlessness.
- Report breathlessness, swelling of the ankles, or a fast or irregular heartbeat, as these can be signs of heart strain.
- Attend your heart scans before and during treatment, as these check how well your heart is pumping.
- Use reliable contraception during treatment and for as long as your team advises, as it can harm an unborn baby.
Weighing it up
Advantages & disadvantages of Margetuximab
Advantages
- Targets HER2 and helps the immune system attack HER2-positive breast cancer cells.
- An option, with chemotherapy, for some cancers that have come back or spread after earlier HER2 treatments.
- Given as a planned hospital infusion under close specialist care.
Disadvantages
- Can cause reactions during or after the infusion.
- Can weaken the heart's pumping action (a fall in the LVEF), needing heart monitoring.
- Given with chemotherapy, which adds its own side effects, and can harm an unborn baby.
Practical use
Good to know
Two main safety points matter with margetuximab. First, reactions during or shortly after the infusion are common, such as fever, chills, flushing or breathlessness, so it is given with close watching, especially with the first doses. Second, it can affect the heart by weakening its pumping action, measured as a fall in the heart's ejection fraction (LVEF); for this reason the heart is checked with a scan before treatment and at intervals during it, and any breathlessness, swelling of the ankles, or a fast or irregular heartbeat should be reported. Like other HER2-directed treatments, it can seriously harm an unborn baby, so reliable contraception is essential during treatment and for a time afterwards, and it is not used in pregnancy. It is given with chemotherapy, which adds its own side effects, so your team will explain the combined plan and what to watch for.
Who should not take it / use with caution
- People who have had a serious allergic reaction to margetuximab should not have it.
- It is avoided in pregnancy because it can seriously harm the baby, and it is avoided while breastfeeding.
- It is used with great caution in people with existing heart problems, under specialist judgement and monitoring.
Monitoring
- Heart scans to check the heart's pumping (LVEF) before and during treatment.
- Watching for infusion reactions, especially with the first doses.
- Regular blood tests and reviewing how the cancer is responding to treatment.
Side effects
- Reactions during or after the infusion, such as fever, chills, flushing or breathlessness.
- A weakening of the heart's pumping (a fall in the LVEF), which heart scans are designed to catch.
- Tiredness, nausea and effects from the chemotherapy given alongside it.
- A fall in blood counts and an increased risk of infection.
Key interactions
- Other treatments that can affect the heart may add to the risk, so your team reviews everything you take.
- The chemotherapy given alongside it brings its own interactions and side effects.
- Tell your team about all your medicines, including anything from a pharmacy or herbal products.
Available as: A solution given as an infusion into a vein, together with chemotherapy.
Answers
Margetuximab: frequently asked questions
What is margetuximab used for?
It is used, with chemotherapy, for some adults with HER2-positive breast cancer that has come back or spread after earlier HER2-directed treatments, by targeting the HER2 protein and engaging the immune system.
Why does it affect the heart?
HER2 is also important for the heart muscle, so affecting it can weaken the heart's pumping (a fall in the LVEF); the heart is checked with a scan before and during treatment.
What should I report about my heart?
Tell your team about breathlessness, swelling of the ankles, or a fast or irregular heartbeat, as these can be signs of heart strain.
Why might I react during the infusion?
Infusion reactions such as fever, chills, flushing or breathlessness are common, especially with the first doses, so you are watched closely during and after the drip.
Can I have it during pregnancy?
No. It can seriously harm an unborn baby, so it is avoided in pregnancy and reliable contraception is essential during treatment and for a time afterwards.
Authoritative sources
- BNF
- NICE CKS
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