Margetuximab is used in combination with other cancer drugs to treat HER2-positive breast cancer that has spread to other parts of the body (metastatic).

Margetuximab is for use in people who have received at least two prior chemotherapy treatments for HER2-positive breast cancer.

Your doctor will test to make sure your cancer has an abnormal "HER2/neu" gene (a specific genetic marker).

Margetuximab may also be used for purposes not listed in this medication guide.

Margetuximab may cause heart problems. Call your doctor at once if you have symptoms such as: fast or pounding heartbeats, cough, shortness of breath, swelling, or rapid weight gain.

Margetuximab is given as an infusion into a vein. A healthcare provider will give you this injection.

Margetuximab is usually given once every 3 weeks. Follow your doctor's dosing instructions very carefully.

Margetuximab must be given slowly, and the infusion can take 30 minutes to 2 hours to complete. This medicine is sometimes given right after you've received other chemotherapy medication.

Your heart function may need to be checked using an electrocardiograph (sometimes called an EKG) or ultrasound. Your cancer treatments may be delayed or permanently discontinued based on the results.

Usual Adult Dose for Breast Cancer:

15 mg/kg IV every 3 weeks

Comment:
-Infuse initial dose over 120 minutes and subsequent doses over 30 minutes.
-This drug may be administered immediately after the completion of chemotherapy.
-Continue treatment until disease progression or unacceptable toxicity.
-All therapeutic proteins, including this drug, have the potential to produce an immune response.

Use: In combination with chemotherapy, for the treatment of adult patients with metastatic HER2-positive breast cancer who have received two or more prior anti-HER2 regimens, at least one of which was for metastatic disease

Tell your doctor if you have ever had heart problems.

You may need to have a negative pregnancy test before starting this treatment.

Margetuximab may harm an unborn baby. Use effective birth control to prevent pregnancy, and tell your doctor if you become pregnant. Keep using birth control for at least 4 months after your last dose.

It may not be safe to breastfeed while using margetuximab, and for at least 4 months after your last dose. Ask your doctor about any risk.

Call your doctor for instructions if you miss an appointment for your margetuximab injection.

Since margetuximab is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some side effects may occur during the injection. Tell your caregiver if you feel dizzy, tired, nauseated, light-headed, itchy, sweaty, feverish, chilled, or have a headache, rash, joint pain, cough, fast heartbeats, trouble breathing, or swelling in your face.

Margetuximab may cause serious side effects. Call your doctor at once if you have:

• new or worsening cough;

• blisters or ulcers in your mouth, red or swollen gums, trouble swallowing;

• heart problems--pounding heartbeats, dizziness, swelling in your face or lower legs, rapid weight gain (more than 5 pounds in 1 day), feeling short of breath;

• hand-foot syndrome--pain, blisters, bleeding, or severe rash on the palms of your hands or the soles of your feet; or

• low white blood cell counts--fever, mouth sores, skin sores, sore throat, cough, trouble breathing.

Common side effects of margetuximab may include:

• feeling weak or tired;

• stomach pain, nausea, vomiting, loss of appetite;

• diarrhea, constipation;

• fever;

• hair loss;

• headache;

• cough, trouble breathing;

• pain, numbness, or tingling in your arms or legs;

• muscle or joint pain;

• hand-foot syndrome; or

• side effects during the injection.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

margetuximab can have long-lasting effects on your body. For at least 4 months after your last dose of margetuximab, you should not be treated with certain other cancer drugs. Tell each of your doctors about your treatment with margetuximab.

Other drugs may affect margetuximab, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.