Enhertu: Uses, Side Effects and Dosage

Serious warnings and precautions box

What ENHERTU is used for:

Breast Cancer

ENHERTU is used to treat adults who have:

• Human epidermal growth factor 2 (HER2)-positive early breast cancer at higher risk of recurrence who have received HER2-targeted treatment before surgery and have cancer remaining in the tissue removed during surgery. A test will be performed to make sure ENHERTU is the right treatment.
• HER2-positive breast cancer that has spread to other parts of the body (metastatic) or cannot be taken out by surgery and

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• also received a prior treatment that targeted HER2-positive breast cancer. A test will be performed to make sure ENHERTU is the right treatment.

ENHERTU is used to treat adults who have:

• Hormone receptor (HR)-positive, HER2-low or HER2-ultralow breast cancer that cannot be removed by surgery or that has spread to other parts of the body (metastatic), and who have received at least one endocrine treatment for metastatic disease and are not considered suitable for endocrine therapy as the next line of treatment. A test will be performed to make sure ENHERTU is the right treatment.
• HER2-low breast cancer that cannot be removed by surgery or that has spread to other parts of the body (metastatic) and who have received prior chemotherapy for metastatic disease, or the disease has returned during or within 6 months of completing adjuvant chemotherapy (after surgery). If the breast cancer is also hormone receptor positive (HR+), patients should have received hormonal therapy. A test will be performed to make sure ENHERTU is the right treatment.

Stomach (Gastric or Gastroesophageal Junction) Cancer

ENHERTU is used to treat adults who have:

• a HER2-positive stomach cancer called gastric or gastroesophageal junction (GEJ) adenocarcinoma that has spread to areas near the stomach (inoperable, locally advanced) or that has spread to other parts of the body (metastatic) and
• who have also received a prior trastuzumab-based treatment.

Unresectable or Metastatic Solid Tumours

ENHERTU is used to treat adults who have:

• HER2-positive (immunohistochemistry 3+) solid cancer that has spread to other parts of the body (metastatic) or cannot be taken out by surgery (unresectable) and
• who have received a prior systemic treatment and have no satisfactory alternative treatment options. A test will be performed to make sure ENHERTU is the right treatment.

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What is a Notice of Compliance with Conditions (NOC/c)?

A Notice of Compliance with Conditions (NOC/c) is a type of approval to sell a drug in Canada.

Health Canada only gives an NOC/c to a drug that treats, prevents, or helps identify a serious or life-threatening illness. The drug must show promising proof that it works well, is of high quality, and is reasonably safe. Also, the drug must either respond to a serious medical need in Canada, or be much safer than existing treatments.

Drug makers must agree in writing to clearly state on the label that the drug was given an NOC/c, to complete more testing to make sure the drug works the way it should, to actively monitor the drug’s performance after it has been sold, and to report their findings to Health Canada.

How ENHERTU works:

ENHERTU contains the active substance trastuzumab deruxtecan, which is made up of a monoclonal antibody connected to a medicine intended to kill cancer cells. The monoclonal antibody delivers the medicine to cancer cells that express human epidermal growth factor receptor 2 (HER2) proteins. Once ENHERTU enters the cell, the medicine becomes active and kills the cancer cells.

The ingredients in ENHERTU are:

Medicinal ingredient(s): trastuzumab deruxtecan

Non-medicinal ingredients: L histidine, L histidine hydrochloride monohydrate, polysorbate 80, sucrose.

ENHERTU comes in the following dosage form(s):

Vial containing 100 mg of trastuzumab deruxtecan.

Do not use ENHERTU if:

• You are allergic to trastuzumab deruxtecan or to any ingredients in ENHERTU. If you are not sure, talk to your healthcare professional before you are given ENHERTU.

To help avoid side effects and ensure proper use, talk to your healthcare professional before you take ENHERTU. Talk about any health conditions or problems you may have, including if you:

• have or have had any lung problems, any kidney problems, any heart problems or any blood problems (low blood count).

Other warnings you should know about:

When you first receive this medicine and anytime during treatment, immediately tell your doctor

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• cough, shortness of breath, fever, or other new or worsening breathing problems. These may be symptoms of a serious and potentially fatal lung disease (interstitial lung disease [ILD]/pneumonitis). History of this lung disease or kidney problems may increase the risk of developing ILD. Your doctor may have to monitor your lungs while you are taking this medicine.
• chills, fever, sores in your mouth, stomach pain, or pain when urinating. These may be symptoms of an infection caused by low levels of a type of white blood cell called neutrophils (neutropenia).
• new or worsening shortness of breath, cough, feeling tired, swelling of your ankles or legs, irregular heartbeat, sudden weight gain, dizziness, or loss of consciousness. These may be symptoms of a problem with your heart’s ability to pump blood (left ventricular dysfunction).
• chills or shaking, shortness of breath or wheezing, itching, rash or hives, flushing, dizziness, fever, feeling like passing out (infusion-related reaction).

Children and adolescents

• ENHERTU is not recommended for anyone under the age of 18 years.

Pregnancy

• ENHERTU is not recommended if you are pregnant because this medicine may cause harm to the unborn baby.
• Tell your doctor before using ENHERTU if you are pregnant, think you may be pregnant, or are planning to have a baby.
• Use effective contraception to avoid becoming pregnant while you are being treated with ENHERTU. Talk to your doctor about the best contraception for you.
• Females should continue to take contraception for at least 7 months after your last dose of ENHERTU. Talk to your doctor before stopping your contraception.
• Male patients with a female partner who could become pregnant should use effective contraception during treatment and for at least 4 months after the last dose of ENHERTU.
• If you do become pregnant during treatment with ENHERTU, tell your doctor right away.

Breastfeeding

• You should not breastfeed during treatment with ENHERTU.
• You should not breastfeed for at least 7 months after your last treatment of ENHERTU.
• It is not known whether the ingredients in ENHERTU pass into breast milk. Talk to your doctor about this.

Fertility

• Talk to your doctor about sperm storage before treatment with ENHERTU because the medicine may reduce your fertility. Do not freeze or donate sperm throughout the treatment period, and for at least 4 months after the final dose of ENHERTU.

Driving and using machines: ENHERTU may reduce your ability to drive or use machines. Be careful if you feel tired, dizzy or have a headache.

Tell your healthcare professional about all the medicines you take, including any drugs, vitamins, minerals, natural supplements or alternative medicines.

How to take ENHERTU:

• ENHERTU will be given to you by a healthcare professional in a healthcare setting.

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Usual dose:

ENHERTU will be given to you in a hospital or clinic.

• The recommended dose of ENHERTU for the treatment of HER2-positive early breast cancer after HER2-targeted treatment and surgery is 5.4 mg for every kilogram of your body weight, every 3 weeks for 14 cycles.
• The recommended dose of ENHERTU for the treatment of metastatic HER2-positive breast cancer or other HER2-positive (immunohistochemistry 3+) solid tumours is 5.4 mg for every kilogram of your body weight, every 3 weeks.
• The recommended dose of ENHERTU for the treatment of HER2-positive stomach cancer is 6.4 mg for every kilogram of your body weight, every 3 weeks.
• Your doctor or nurse will give you ENHERTU through an infusion into your vein (IV).
• Your first infusion will be given to you over 90 minutes. If you have no problems with the first infusion, the infusion on your next visits may be given over 30 minutes.
• Your doctor will decide how many treatments you need.
• Before each ENHERTU infusion, your doctor may give you medicines to help prevent nausea and vomiting.

If you experience infusion-related symptoms, your doctor or nurse may slow, interrupt or stop your treatment.

Overdose:

Missed dose:

If you miss an appointment to get ENHERTU

• Call your doctor right away to reschedule your appointment.
• It is very important that you do not miss a dose of this medicine.

Do not stop treatment with ENHERTU unless you have discussed this with your doctor. If you have any further questions about your treatment, ask your doctor.

Possible side effects from using ENHERTU:

These are not all the possible side effects you may have when taking ENHERTU. If you experience any side effects not listed here, tell your healthcare professional.

While you are taking ENHERTU:

• Your doctor will carry out tests before and during your treatment with ENHERTU.
• Depending on the side effects you experience, your doctor may decide to lower your dose, temporarily stop your treatment or permanently stop your treatment.

Tell your doctor right away if you notice any of the following symptoms because some of them may be signs of a serious or possibly fatal condition.

Getting medical treatment right away may help keep these problems from becoming more serious.

• cough, shortness of breath, fever, or other new or worsening breathing problems as these

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  • may be symptoms of a lung problem.
• chills, fever, sores in your mouth, stomach pain or pain when urinating as these may be symptoms of an infection.
• new onset or worsening shortness of breath, cough, feeling tired, swelling of your hands, ankles or legs, irregular heartbeat, sudden weight gain, dizziness, or loss of consciousness as these may be symptoms of a heart problem.

The frequency and severity of side effects may vary with the dose you received. You may experience the following side effects while you are being treated with ENHERTU:

Very common (may affect more than 1 in 10 people)

• Blood tests showing increased level of liver enzymes such as transaminases
• Constipation
• Coughing
• Decrease in the number of platelets (thrombocytopenia)
• Diarrhea
• Feeling less hungry (decreased appetite)
• Feeling tired (fatigue)
• Fever (pyrexia)
• Hair loss (alopecia)
• Headache
• Indigestion (dyspepsia)
• Low potassium in the blood (hypokalemia)
• Nausea
• Numbness and tingling in hands and feet
• Pain in muscles and bone
• Sores in or around your mouth (stomatitis)
• Stomach (abdominal) pain
• Swollen hands, ankles, feet (edema)
• Vomiting
• Weight loss

Common (may affect up to 1 in 10 people)

• Abnormal blood test (increase in blood alkaline phosphatase)
• Abnormal blood test (increase in blood bilirubin or blood creatinine)
• Bad taste in mouth (dysgeusia)
• Bloating (abdominal distension)
• Blurry vision
• Darkening of the skin (skin hyperpigmentation)
• Dizziness
• Dry eye
• Excessive gas in the stomach or intestine (flatulence)
• Feeling thirsty, dry mouth (dehydration)
• Infection of the lungs (pneumonia)
• Inflammation of the stomach (gastritis)
• Itching (pruritus)
• Rash

• Severe nosebleeds (epistaxis)

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The following additional side effects have been reported in patients taking ENHERTU and adjuvant radiotherapy (the frequency and severity of side effects may vary):

Very common (may affect more than 1 in 10 people)

• Lung problems (radiotherapy-related pneumonitis)

Serious side effects and what to do about them

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If you have a troublesome symptom or side effect that is not listed here or becomes bad enough to interfere with your daily activities, tell your healthcare professional.

Reporting side effects

Storage:

ENHERTU will be stored by the healthcare professionals at the hospital or clinic where you receive treatment.

If you want more information about ENHERTU:

• Talk to your healthcare professional.
• Find the full product monograph that is prepared for healthcare professionals and includes the Patient Medication Information by visiting the Health Canada Drug Product Database website (Drug Product Database: Access the database); the manufacturer’s website www.astrazeneca.ca; or by calling 1-800-668-6000.
• This Patient Medication Information is current at the time of printing. The most up-to-date version can be found at www.astrazeneca.ca.

Date of Authorization: 2026-09-17

ENHERTU^® is a registered trademark of Daiichi Sankyo Company, Limited used under license by AstraZeneca Canada Inc. The AstraZeneca logo is a registered trademark of AstraZeneca AB, used under license by AstraZeneca Canada Inc.