Margetuximab-cmkb injection may cause serious or life-threatening heart problems. Tell your doctor if you have or have ever had heart disease. Your doctor will order tests before and during your treatment to see if your heart is working well enough for you to safely receive margetuximab-cmkb injection. Tell your doctor and pharmacist if you are being treated with anthracycline medications for cancer such as daunorubicin (Cerubidine), doxorubicin (Doxil), epirubicin (Ellence), and idarubicin (Idamycin) or within 4 months after receiving margetuximab-cmkb injection. If you experience any of the following symptoms, call your doctor immediately: cough; shortness of breath; swelling of the arms, hands, feet, ankles or lower legs; weight gain (more than 5 pounds [about 2.3 kilograms] in 24 hours); dizziness; loss of consciousness; or fast, irregular, or pounding heartbeat.

Margetuximab-cmkb injection should not be used by women who are pregnant or who may become pregnant. There is a risk that margetuximab-cmkb will cause loss of the pregnancy or will cause the baby to be born with birth defects (physical problems that are present at birth). Tell your doctor if you are pregnant or plan to become pregnant. You will need to have a pregnancy test before you receive this medication. You should use effective birth control during treatment with margetuximab-cmkb and for 4 months after your final dose. Talk to your doctor about birth control methods that will work for you. If you become pregnant during treatment with margetuximab-cmkb injection, or think you might be pregnant, call your doctor immediately.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain tests to check your body’s response to margetuximab-cmkb.

Talk to your doctor about the risk(s) of receiving margetuximab-cmkb.

Margetuximab-cmkb is used along with chemotherapy to treat a certain type of breast cancer (HER-2 positive) that has spread to other parts of the body after treatment with at least two other chemotherapy medications. Margetuximab-cmkb is in a class of medications called monoclonal antibodies. It works by stopping the growth of cancer cells.

Margetuximab-cmkb comes as a solution to be injected into a vein by a doctor or nurse in a hospital. It is usually given over 120 minutes for the first dose and then over 30 minutes once every 3 weeks (21 days) for the following doses. The length of your treatment will depend on the condition that you have and how well your body responds to treatment.

Margetuximab-cmkb may cause serious reactions during the infusion of the medication. A doctor or nurse will monitor you carefully while you are receiving the medication. Tell your doctor or nurse if you experience any of the following during your infusion: fever, chills, joint pain, cough, dizziness, fatigue, nausea, vomiting, headache, sweating, racing heartbeat, hives, rash, itching, or shortness of breath. Call your doctor immediately or get immediate emergency medical attention if you experience any of these symptoms after you leave your doctor’s office or medical facility.

Your doctor may slow down your infusion or temporarily or permanently stop your treatment. This depends on how well the medication works for you and the side effects you experience. Be sure to tell your doctor how you are feeling during your treatment with margetuximab-cmkb injection.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before receiving margetuximab-cmkb injection,

• tell your doctor and pharmacist if you are allergic to margetuximab-cmkb, any other medications, or any of the ingredients in margetuximab-cmkb injection. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had any of the conditions mentioned in the IMPORTANT WARNING section or any other medical condition.
• tell your doctor if you are breastfeeding. You should not breastfeed during your treatment with margetuximab-cmkb and for 4 months after your final dose.

Unless your doctor tells you otherwise, continue your normal diet.

Call your doctor right away if you are unable to keep an appointment to receive a dose of margetuximab-cmkb injection.

Margetuximab-cmkb may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• headache
• fatigue
• nausea
• diarrhea
• vomiting
• constipation
• loss of appetite
• stomach pain
• hair loss
• pain in hands or feet
• joint or muscle pain

Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING or HOW sections, call your doctor immediately or get emergency medical treatment:

• rash with blisters on hands and feet

Margetuximab-cmkb may cause other side effects. Call your doctor if you have any unusual problems while receiving this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Ask your pharmacist any questions you have about margetuximab-cmkb.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

• Margenza^®