UNDERSTANDING POTENTIAL
SIDE EFFECTS

During treatment with ENHERTU, side effects may occur and you should notify your healthcare provider as early as possible

The most common side effects of ENHERTU when used at the 5.4 mg/kg dose include:

  • Nausea, low white blood cell counts, low red blood cell counts, feeling tired, low platelet counts, increased liver function tests, vomiting, hair loss, constipation, decreased appetite, low levels of blood potassium, diarrhea, and muscle or bone pain
  • In the clinical trial, the majority of side effects in people receiving ENHERTU were mild or moderate*; however, some people may have serious side effects that could lead to death. It is important to call your doctor for medical advice about side effects

*Mild refers to Grade 1 side effects that are asymptomatic and where intervention is not needed; moderate refers to Grade 2 side effects where local or non-invasive intervention may be needed.

What is the most important information I should know about ENHERTU?

ENHERTU can cause serious side effects

Some serious or life-threatening side effects may affect your lungs, heart, or white blood cell count, affecting your ability to fight infection.

Pay special attention to new or worsening symptoms as they may be related to:

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Lung problems, like interstitial lung disease/pneumonitis, that may be severe, life-threatening, or that may lead to death

Lung problems, like interstitial lung disease/pneumonitis, that may be severe, life-threatening, or that may lead to death

Call or see your healthcare provider right away if you develop any of the following signs and symptoms or if these symptoms get worse:

  • Cough
  • Trouble breathing or shortness of breath
  • Fever
  • Other new or worsening breathing symptoms (e.g., chest tightness, wheezing)

If lung problems develop, your healthcare provider may treat you with corticosteroid§ medicines.

Interstitial lung disease is a side effect caused by the abnormal accumulation of cells between the air sacs of the lungs.

Pneumonitis is inflammation of the lungs.

§Corticosteroids are medicines used to help reduce inflammation.

Call or see your healthcare provider right away if you develop any of the following signs and symptoms or if these symptoms get worse:

  • Cough
  • Trouble breathing or shortness of breath
  • Fever
  • Other new or worsening breathing symptoms (e.g., chest tightness, wheezing)

If lung problems develop, your healthcare provider may treat you with corticosteroid§ medicines.

Interstitial lung disease is a side effect caused by the abnormal accumulation of cells between the air sacs of the lungs.

Pneumonitis is inflammation of the lungs.

§Corticosteroids are medicines used to help reduce inflammation.

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Low white blood cell count (neutropenia)

Low white blood cell count (neutropenia)

  • Low white blood cell counts are common with ENHERTU and can sometimes be severe
  • Your healthcare provider will check your white blood cell counts before starting ENHERTU and before starting each dose
  • Tell your healthcare provider right away if you develop any signs or symptoms of an infection or have fever or chills during treatment with ENHERTU

Neutropenia occurs when you have too few neutrophils, a type of white blood cell that is important for fighting certain infections, especially those caused by bacteria.

  • Low white blood cell counts are common with ENHERTU and can sometimes be severe
  • Your healthcare provider will check your white blood cell counts before starting ENHERTU and before starting each dose
  • Tell your healthcare provider right away if you develop any signs or symptoms of an infection or have fever or chills during treatment with ENHERTU

Neutropenia occurs when you have too few neutrophils, a type of white blood cell that is important for fighting certain infections, especially those caused by bacteria.

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Heart problems that may affect your heart’s ability to pump blood

Heart problems that may affect your heart’s ability to pump blood

Your healthcare provider will check your heart function before starting treatment with ENHERTU. Tell your healthcare provider right away if you get any of the following signs and symptoms:

  • New or worsening shortness of breath
  • Coughing
  • Feeling tired
  • Swelling of your ankles or legs
  • Irregular heartbeat
  • Sudden weight gain
  • Dizziness or feeling light-headed
  • Loss of consciousness

Your healthcare provider will check your heart function before starting treatment with ENHERTU. Tell your healthcare provider right away if you get any of the following signs and symptoms:

  • New or worsening shortness of breath
  • Coughing
  • Feeling tired
  • Swelling of your ankles or legs
  • Irregular heartbeat
  • Sudden weight gain
  • Dizziness or feeling light-headed
  • Loss of consciousness
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Harm to your unborn baby

Harm to your unborn
baby

Tell your healthcare provider right away if you become pregnant or think you might be pregnant during treatment with ENHERTU.

  • If you are able to become pregnant, your healthcare provider should do a pregnancy test before you start treatment with ENHERTU
  • Females who are able to become pregnant should use effective birth control (contraception) during treatment with ENHERTU and for 7 months after the last dose
  • Males who have female partners that are able to become pregnant should use effective birth control (contraception) during treatment with ENHERTU and for 4 months after the last dose

Tell your healthcare provider right away if you become pregnant or think you might be pregnant during treatment with ENHERTU.

  • If you are able to become pregnant, your healthcare provider should do a pregnancy test before you start treatment with ENHERTU
  • Females who are able to become pregnant should use effective birth control (contraception) during treatment with ENHERTU and for 7 months after the last dose
  • Males who have female partners that are able to become pregnant should use effective birth control (contraception) during treatment with ENHERTU and for 4 months after the last dose

Your healthcare provider will check you for these side effects during your treatment with ENHERTU. Your healthcare provider may reduce your dose, delay treatment, or completely stop treatment with ENHERTU if you have severe side effects.

Call your healthcare provider right away for medical advice if you develop any of these side effects, experience new symptoms, or if your current symptoms get worse.

Tips for managing common side effects that may happen during treatment

The tips below are not intended to take the place of your healthcare team’s advice. Always talk to your healthcare provider first.

For nausea and vomiting

For nausea and
vomiting

Your healthcare provider should give you medicine to help with nausea and vomiting before your infusion. Talk to your doctor immediately if you did not receive these medications or if you continue to experience nausea and vomiting with your current medicine. These tips may help:

  • Try to eat 5 or 6 small meals and snacks each day instead of 3 large meals
  • Eat bland, easy-to-digest food and drinks
  • Avoid food and drinks that are too hot or too cold
  • Avoid strong smells, if possible
  • If you feel like vomiting, take deep, slow breaths and, if possible, get fresh air

Your healthcare provider should give you medicine to help with nausea and vomiting before your infusion. Talk to your doctor immediately if you did not receive these medications or if you continue to experience nausea and vomiting with your current medicine. These tips may help:

  • Try to eat 5 or 6 small meals and snacks each day instead of 3 large meals
  • Eat bland, easy-to-digest food and drinks
  • Avoid food and drinks that are too hot or too cold
  • Avoid strong smells, if possible
  • If you feel like vomiting, take deep, slow breaths and, if possible, get fresh air

For diarrhea

For diarrhea

  • Try to eat 5 or 6 small meals and snacks each day instead of 3 large meals
  • Eat foods low in fiber
  • Drink clear liquids to replace lost fluids. Check with your healthcare provider to figure out how much and what types of fluid might be best
  • Try to eat 5 or 6 small meals and snacks each day instead of 3 large meals
  • Eat foods low in fiber
  • Drink clear liquids to replace lost fluids. Check with your healthcare provider to figure out how much and what types of fluid might be best

For tiredness or fatigue

For tiredness or fatigue

  • Drink plenty of fluids each day. Ask your doctor what types of liquids are appropriate for you
  • Try activities such as meditation, which helps with relaxation and decreases stress
  • Plan rest time and try not to do too much
  • Try regular exercise during times when your energy level is high (according to your healthcare provider’s approval)
  • If possible, let other people help you with everyday tasks, such as household chores, shopping, cooking, or driving to and from doctor’s visits
  • Drink plenty of fluids each day. Ask your doctor what types of liquids are appropriate for you
  • Try activities such as meditation, which helps with relaxation and decreases stress
  • Plan rest time and try not to do too much
  • Try regular exercise during times when your energy level is high (according to your healthcare provider’s approval)
  • If possible, let other people help you with everyday tasks, such as household chores, shopping, cooking, or driving to and from doctor’s visits

For dealing with hair thinning or hair loss (alopecia)

For dealing with hair thinning or hair loss (alopecia)

  • Talk to your healthcare provider about the possibility of hair thinning or hair loss
  • Consider cutting your hair short to feel more in control of hair loss and be gentle when washing your hair. Use a mild shampoo
  • Avoid electric hair dryers, products to perm or relax hair, hair bands, and/or clips that can hurt your scalp
  • Consider asking your healthcare provider about cold caps or scalp cooling systems, which may help reduce hair loss by narrowing the blood vessels beneath your scalp
  • Protect your scalp by wearing a hat or head covering, applying sunscreen, and avoiding very hot or cold places
  • Sleep on a satin pillowcase. Satin creates less friction and may be more comfortable
  • Talk to your healthcare provider about the possibility of hair thinning or hair loss
  • Consider cutting your hair short to feel more in control of hair loss and be gentle when washing your hair. Use a mild shampoo
  • Avoid electric hair dryers, products to perm or relax hair, hair bands, and/or clips that can hurt your scalp
  • Consider asking your healthcare provider about cold caps or scalp cooling systems, which may help reduce hair loss by narrowing the blood vessels beneath your scalp
  • Protect your scalp by wearing a hat or head covering, applying sunscreen, and avoiding very hot or cold places
  • Sleep on a satin pillowcase. Satin creates less friction and may be more comfortable

Will my healthcare provider adjust my dose if I have side effects?

Your healthcare provider may modify your dose to help you manage side effects and potentially continue
treatment. It is important to call your healthcare provider right away for medical advice. To help manage side
effects, your healthcare provider may:

Delay
your dose

Reduce
your dose

Stop
ENHERTU

What are the possible side effects of ENHERTU?

ENHERTU can cause serious side effects. See “What is the most important information I should know about ENHERTU?”

The most common side effects of ENHERTU when used at the 5.4 mg/kg dose include:

  • Nausea
  • Low white blood cell counts
  • Low red blood cell counts
  • Feeling tired
  • Low platelet counts
  • Increased liver function tests
  • Vomiting
  • Hair loss
  • Constipation
  • Decreased appetite
  • Low levels of blood potassium
  • Diarrhea
  • Muscle or bone pain
  • Nausea
  • Low white blood cell counts
  • Low red blood cell counts
  • Feeling tired
  • Low platelet counts
  • Increased liver function tests
  • Vomiting
  • Hair loss
  • Constipation
  • Decreased appetite
  • Low levels of blood potassium
  • Diarrhea
  • Muscle or bone pain

ENHERTU may cause fertility problems in males, which may affect the ability to father children. Talk to your healthcare provider if you have concerns about fertility.

These are not all of the possible side effects of ENHERTU. Call your doctor for medical advice about side effects. You may report side effects to Daiichi Sankyo at 1-877-437-7763 or to FDA at 1-800-FDA-1088.

Before you receive ENHERTU, tell your healthcare provider about all of your medical conditions, including if you:

  • Have lung or breathing problems.
  • Have kidney problems. Your healthcare provider may follow you more closely. In clinical trials, more serious lung problems were seen in patients with certain kidney problems.
  • Have liver problems. Your healthcare provider may follow you more closely.
  • Have signs or symptoms of an infection.
  • Have or have had any heart problems.
  • Are breastfeeding or plan to breastfeed. It is not known if ENHERTU passes into your breast milk. Do not breastfeed during treatment with ENHERTU and for 7 months after the last dose.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Harm to your unborn baby. Tell your healthcare provider right away if you become pregnant or think you might be pregnant during treatment with ENHERTU.

  • If you are able to become pregnant, your healthcare provider should do a pregnancy test before you start treatment with ENHERTU.
  • Females who are able to become pregnant should use effective birth control (contraception) during treatment with ENHERTU and for 7 months after the last dose.
  • Males who have female partners that are able to become pregnant should use effective birth control (contraception) during treatment with ENHERTU and for 4 months after the last dose.

Download the Medication Guide.

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for patients and caregivers

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HER2, human epidermal growth factor receptor 2; mBC, metastatic breast cancer.

Not actual patients.