Understanding HER2-low and HR+, HER2-ultralow mBC

Woman looking straight ahead 1

If you were previously diagnosed with HER2-negative metastatic breast cancer, you may actually have low HER2 levels

HER2 is a protein that tells cells to grow. When cells produce too much HER2, they can become cancerous.

Woman looking straight ahead 1

In people with breast cancer, HER2 status used to be thought of like an on/off switch: HER2-positive or HER2-negative. Now it is thought to be more like a dimmer.

Spectrum from negative to positive graphic

Spectrum from negative to positive graphic

Some doctors now recognize HER2-low and HER2-ultralow as subsets of HER2-negative.

Having HER2-low or HER2-ultralow means that there is a low level of HER2 on cancer cells but not enough HER2 to be considered HER2-positive.

If your HER2-negative mBC stops responding to endocrine (hormone) treatment, ask your doctor if you have low levels of HER2.

Woman looking straight ahead 2

Your doctor can evaluate your HER2 levels to determine if a therapy designed to target HER2 on cancer cells, like ENHERTU, is right for you.

If your doctor told you that you have HER2-negative mBC, ask if your HER2 immunohistochemistry (IHC) score could indicate a diagnosis of HER2-low or HER2-ultralow mBC.

HER2 status is different than hormone receptor (HR) status. People with low levels of HER2 can be either HR positive or HR negative.

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Learn more about HER2-low or HER2-ultralow mBC

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HER2, human epidermal growth factor receptor 2.

Important Safety Information

What is ENHERTU?
ENHERTU is a prescription medicine used to treat adults who have:

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 a prior chemotherapy
- for metastatic disease, or
- whose disease has returned during or within 6 months of completing adjuvant chemotherapy (after surgery).
Hormone receptor (HR)-positive, HER2-low or HR-positive, 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 one or more endocrine treatments for metastatic disease.

Your healthcare provider will perform a test to make sure ENHERTU is right for you.

It is not known if ENHERTU is safe and effective in children.

What is the most important information I should know about ENHERTU?
ENHERTU can cause serious side effects, including:

Lung problems that may be severe, life-threatening or that may lead to death. If you develop lung problems your healthcare provider may treat you with corticosteroid medicines. Tell your healthcare provider right away if you get any of the following signs and symptoms:
- Cough
- Trouble breathing or shortness of breath
- Fever
- Other new or worsening breathing symptoms (such as chest tightness, wheezing)
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.
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 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.

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.

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

Have lung or breathing problems.
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.

How will I receive ENHERTU?

You will receive ENHERTU into your vein through an intravenous (IV) line by your healthcare provider.
ENHERTU is given 1 time every three weeks (21-day treatment cycle).
Your healthcare provider will decide how many treatments you need.
Your healthcare provider will give you medicines before your infusion to help prevent nausea and vomiting.
Your healthcare provider may slow down or temporarily stop your infusion of ENHERTU if you have an infusion-related reaction, or permanently stop ENHERTU if you have severe infusion reactions.
If you miss a planned dose of ENHERTU, call your healthcare provider right away to schedule an appointment. Do not wait until the next planned treatment cycle.

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:

Low white blood cell counts
Nausea
Low red blood cell counts
Feeling tired
Low platelet counts
Increased liver function tests
Vomiting

Hair loss
Constipation
Low levels of blood potassium
Decreased appetite
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.

Please see full Prescribing Information, including Boxed WARNINGS, and Medication Guide.

What is ENHERTU?
ENHERTU is a prescription medicine used to treat adults who have:

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 a prior chemotherapy
- for metastatic disease, or
- whose disease has returned during or within 6 months of completing adjuvant chemotherapy (after surgery).
Hormone receptor (HR)-positive, HER2-low or HR-positive, 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 one or more endocrine treatments for metastatic disease.

Your healthcare provider will perform a test to make sure ENHERTU is right for you.

It is not known if ENHERTU is safe and effective in children.