Fam-trastuzumab deruxtecan is used in adults to treat HER2-positive breast cancer that has spread to other parts of the body (metastatic) or cannot be removed with surgery.

Fam-trastuzumab deruxtecan is also used in adults who have received an anti-HER2 breast cancer treatment before for metastatic diseases, or have breast cancer that has come back within 6 months of completing treatment for early stages breast cancer.

Fam-trastuzumab deruxtecan can also used in adults to treat a certain type of HER2-positive esophageal cancer.

Fam-trastuzumab deruxtecan is usually given after other cancer treatments did not work or have stopped working.

Fam-trastuzumab deruxtecan may also be used for purposes not listed in this medication guide.

Fam-trastuzumab deruxtecan can cause serious or life-threatening side effects on your heart or lungs. Call your doctor right away if you have a cough, tiredness, dizziness, chest tightness, wheezing, irregular heartbeats, new or worsening shortness of breath.

Fam-trastuzumab deruxtecan can weaken (suppress) your immune system, and you may get an infection or bleed more easily. Tell your doctor if you have unusual bruising or bleeding, or signs of infection (fever, chills, weakness, cold or flu symptoms, frequent or recurring illness).

Both men and women using fam-trastuzumab deruxtecan should use effective birth control to prevent pregnancy. Birth control should be continued for 7 months after the last dose of fam-trastuzumab deruxtecan in women and 4 months after in men.

Your doctor will perform blood tests to make sure you do not have conditions that would prevent you from safely using fam-trastuzumab deruxtecan.

Fam-trastuzumab deruxtecan is given as an infusion into a vein. A healthcare provider will give you this injection.

Fam-trastuzumab deruxtecan is usually given once every 3 weeks in a 21-day treatment cycle. Your doctor will determine how long to treat you with fam-trastuzumab deruxtecan.

You may be given medication to prevent nausea or vomiting while you are receiving fam-trastuzumab deruxtecan.

You will need frequent medical tests.

Usual Adult Dose for Breast Cancer:

5.4 mg/kg IV every 3 weeks (21-day cycle) until disease progression or unacceptable toxicity

Comments:
-Administer the first infusion over 90 minutes; administer subsequent infusions over 30 minutes if prior infusions were well tolerated.
-Slow or interrupt the infusion rate if the patient develops infusion-related symptoms.
-Permanently discontinue therapy for severe infusion reactions.

Use: For the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer who have received 2 or more prior anti-HER2-based regimens in the metastatic setting

Tell your doctor if you have ever had:

• heart problems;

• breathing problems; or

• an infection.

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

Fam-trastuzumab deruxtecan can harm an unborn baby if the mother or the father is using this medicine.

• If you are a woman, do not use fam-trastuzumab deruxtecan if you are pregnant. Use effective birth control to prevent pregnancy while you are using this medicine and for at least 7 months after your last dose.

• If you are a man, use effective birth control if your sex partner is able to get pregnant. Keep using birth control for at least 4 months after your last dose.

• Tell your doctor right away if a pregnancy occurs while either the mother or the father is using fam-trastuzumab deruxtecan.

This medicine may affect fertility (ability to have children), in men.

Do not breastfeed while using this medicine, and for at least 7 months after your last dose.

Call your doctor for instructions if you miss an appointment for your fam-trastuzumab deruxtecan injection.

Since fam-trastuzumab deruxtecan 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.

Fam-trastuzumab deruxtecan may cause serious side effects. Call your doctor at once if you have:

• chest tightness, wheezing, cough, new or worsening shortness of breath;

• pounding heartbeats or fluttering in your chest;

• fever, tiredness, dizziness;

• swelling in your lower legs, sudden weight gain;

• a light-headed feeling, like you might pass out;

• low blood cell counts--fever, chills, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet; or

• low potassium level--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling.

Your cancer treatments may be delayed or permanently discontinued if you have certain side effects.

Common side effects of fam-trastuzumab deruxtecan may include:

• nausea, vomiting, loss of appetite;

• diarrhea, constipation;

• cough;

• fever, feeling tired;

• low blood cell counts;

• low potassium;

• abnormal liver function tests; or

• hair loss.

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.

Other drugs may affect fam-trastuzumab deruxtecan, 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.