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Treatment Name: fam-trastuzumab deruxtecan-nxki (Enhertu®)

fam-trastuzumab deruxtecan-nxki (Enhertu®) is a Treatment Regimen for Breast Cancer - metastatic

How does fam-trastuzumab deruxtecan-nxki (Enhertu®) work?
Enhertu® targets a protein on the surface of breast cancer cells known as Human Epidermal growth factor Receptor 2 (HER-2). Once Enhertu® binds to the breast cancer cell, it enter the cell and releases a molecule called deruxtecan (DXd), a type of topoisomerase-I inhibitor designed to stop breast cancer cells from growing and dividing.

Enhertu® indications:
Enhertu® is indicated for the treatment of adults who have HER2-positive breast cancer that cannot be removed by surgery (unresectable), or that has spread throughout the body (metastatic) who have received two or more prior therapies targeting the HER2-protein, such as trastuzumab (Herceptin®) in the THP regimen, or ado-trastuzumab emtansine (T-DM1, Kadcyla®).

Goals of Enhertu® therapy:
Enhertu® is given to shrink breast cancer tumors, decrease symptoms of breast cancer, and to keep breast cancer cells from spreading further. Because it is indicated for breast cancer cells which have spread throughout the body (metastasized), it is not commonly given with the goal of cure.

Important Note: Enhertu® is not a biosimilar agent to trastuzumab. It is a unique medication with a different mechanism of action than trastuzumab and ado-trastuzumab


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  • Enhertu® (fam-trastuzumab deruxtecan-nxki) intravenous (I.V.) infusion over 90 minutes on Day 1
    • If the 90-minute infusion is well tolerated, subsequent infusions may be given over 30 minutes

Estimated total infusion time for Enhertu® treatment:

  • Up to 2 hours for Cycle 1, Day 1; as short as one hour for the first day of subsequent cycles, if well tolerated
  • Infusion times are based on clinical studies, but may vary depending on doctor preference or patient tolerability. Pre-medications and intravenous (I.V.) fluids, such as hydration, may add more time

Enhertu® is usually given in an outpatient infusion center, allowing the person to go home afterwards. On occasion, it may be given in the hospital if someone is too sick.

Enhertu® is repeated every 21 days. This is known as one Cycle. Each cycle may be repeated until the drug no longer works or unacceptable side effects occur. Duration of therapy depends upon response, tolerability, and number of cycles prescribed.

Click here for common Enhertu® starting doses.

Side Effects

In clinical studies, the most commonly reported side effects of Enhertu® are shown here:

Note: Blue words appearing in the list below link to our short, but informative side effect videos.

  • Nausea (78%)
  • Fatigue (50%)
  • Hair loss (48%)
  • Vomiting (46%)
  • Constipation (36%)
  • Decreased white blood cells [neutropenia] (35%)
  • Decreased appetite (31%)
  • Low red blood cells [Anemia] (30%)
  • Diarrhea (29%)
  • Decreased platelet count (Increased bleeding risk) (21%)
  • Headache (20%)
  • Cough (19%)
  • Lung injury, known as interstitial lung disease (ILD, 14%)
  • Abdominal pain (17%)
  • Low potassium in blood (hypokalemia, 12%)
  • Dry eye (11%)
  • Rash (10%)
  • Infusion reaction (2%)
  • Decreased heart function (2%)

On average, roughly 15% of patients discontinue Enhertu® treatment due to unacceptable side effects.

Importantly, not all people who experience a side effect from Enhertu® will experience it in the same way. It may be mild in some or severe in others, depending upon the individual. Everybody is different. Additionally, side effects may vary over time. For some, side effects may be a reason to delay or switch treatment, reduce the dose, or avoid future treatment with a certain medication altogether.

Side effects may be treatable when they occur or preventable by taking certain medications before they happen. When medications are taken to prevent a problem, this is known as prophylaxis, or "prophy" for short.

After starting treatment with Enhertu®, be sure to come back and watch all of the side effect videos shown below. Each of these videos contain valuable information about side effect management that will hopefully help you to both feel better and stay out of the hospital.

Side effect videos Side Effect Videos
Nausea and VomitingNausea and VomitingFatigue Fatigue Hair LossHair LossConstipationConstipationAnemiaAnemiaDiarrheaDiarrheaPainPain


How often is monitoring needed after receiving therapy with Enhertu®?
Labs (blood tests) may be checked before each treatment or more often at the discretion of your doctor. Labs often include: Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), plus any others your doctor may order.

Your heart function will be checked before starting treatment and repeated approximately every 3 to 6 months while receiving treatment with Enhurtu®. This is done by either an echocardiogram or a MUGA scan.

How often is imaging needed?
Imaging may be checked before treatment and then during therapy if there is concern for disease progression or certain side effects. Imaging may include: X-rays, magnetic resonance imaging (MRI), computerized tomography (CT) scans, or positron emission tomography (PET) scans. A CT scan may be performed if there any sugns or symptoms of intersitital lung disease (ILD).

How might blood test results/imaging affect treatment?
Depending upon the results, your doctor may advise to continue Enhertu® as planned, reduce the dose of future treatments, delay the next dose until the side effect goes away, or switch to an alternative therapy.

ChemoExperts Tips

  • Serious lung injury (known as interstitial lung disease, ILD) can occur in up to 9% of patients receiving Enhertu®, which has lead to death to in a small number of patients. If lung injury occurs, it may be treated with a corticosteroid such as prednisone or methylprednisolone (Solumedol®). Contact your doctor if you experience a new cough, worsening shortness of breath, or chest pain
  • Although rare, Enhertu® increases your risk of experiencing a decrease in your heart's ability to effectively pump blood. Your heart function should be checked before starting treatment. If your heart's ability to pump is decreased, you may be started on medication to help improve your heart function before starting treatment
  • A pharmacist should ALWAYS review your medication list to ensure that drug interactions are prevented or managed appropriately
  • Clinical trials may exist for metastatic breast cancer. Ask your doctor if any studies are currently enrolling in your area. If not, go to to search for other centers offering study medications

Patient Assistance & Co-payment Coverage

Patients under the age of 65 years, or those with private insurance plans:
If you have insurance and are looking for patient assistance or copay assistance for fam-trastuzumab deruxtecan-nxki (Enhertu®), we have provided links that may help.

Visit our Patient Assistance page and click the links to various patient assistance programs for help paying for fam-trastuzumab deruxtecan-nxki (Enhertu®). Depending upon your income, they may be able to help cover the cost of:

  • fam-trastuzumab deruxtecan-nxki

For Branded medications (may be available for generic medications too), check with the manufacturer to determine if a co-pay card is offered and if it could reduce your monthly copay.

  • If you are uninsured, check with the manufacturer to determine if you are eligible to receive medication at no cost.

Medicare and Medicaid patients (Patients 65 years or older):
The clinic providing treatment will likely pre-authorize medications and immune therapies such as fam-trastuzumab deruxtecan-nxki (Enhertu®) and are the best source to help you understand drug cost.

  • Ask to speak with a patient assistance technician or financial counselor at the clinic or hospital administering this therapy.

Emotional Wellness

What is Emotional Wellness?
Emotional wellness is having a positive outlook balanced with a realistic understanding of current life events. This requires both an awareness and acceptance of your emotions. It is with this knowledge that you can develop a plan to take the necessary actions to positively impact your life.

Emotional wellness uses an ongoing process to continually reflect on the stressors of life in a constructive manner to move forward and create happiness.

Because emotional wellness is deeply connected with physical, social, and spiritual wellness, pursuing it often becomes particularly difficult in times of major illness. Despite this difficulty, working toward emotional wellness has been connected to improved treatment outcomes and a higher likelihood of achieving goals of therapy.

Learn more about pursuing emotional wellness while receiving treatment with fam-trastuzumab deruxtecan-nxki (Enhertu®)

Individual Drug Label Information

fam-trastuzumab deruxtecan-nxki (Enhertu®)

  • ​Is an intravenous infusion
  • FDA Black Box Warning for lung injury. Contact your doctor if you experience a new cough, worsening shortness of breath, fever, or chest pain.
  • Dosage adjustments may be required for low blood counts, infections, or lung toxicity
  • May cause fetal harm if given to pregnant women. Females should use effective contraception during treatment and for at least 7 months following the last dose. Males should use effective contraception during treatment and for at least 4 months following the last dose
  • Do not breastfeed during treatment or for 7 months after the last dose
General side effects from fam-trastuzumab deruxtecan-nxki (Enhurtu®)
  • Nausea and vomiting
  • Fatigue
  • Hair loss
  • Rash
  • Constipation or diarrhea
  • Decreased white blood cells, red blood cells, or platelets
  • Decreased appetite
  • Headache
  • Cough
  • Stomach pain
  • Infusion reaction
  • Decreased heart function 
  • Click on the fam-trastuzumab deruxtecan-nxki (Enhertu®) package insert below for reported side effects, possible drug interactions, and other Enhertu® prescribing information

Side Effect Videos
Nausea and VomitingNausea and VomitingDiarrheaDiarrheaHair LossHair LossFatigue Fatigue ConstipationConstipationPainPainAnemiaAnemia

See DailyMed package insert.

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1) Modi S, Saura C, Yamashita T, et al. Trastuzumab Deruxtecan in Previously Treated HER2-Positive Breast Cancer. N Engl J Med. 2019

Created: January 29, 2020 Updated: January 29, 2020

What is Breast Cancer - metastatic?

What is Metastatic Breast Cancer?
A disease of the milk-producing glands known as lobules, milk ducts, or other cells found in the breast. Metastatic breast cancer is one that has moved from the breast to other areas of the body, which may include the brain, liver, or bone. Breast cancer is one of the most common types of cancers in women, but may rarely affect men as well. Known causes of breast cancer include genetic causes, such as the BRCA mutation, or obesity. The effectiveness of the treatment may depend upon the stage at diagnosis.

Types of metastatic breast cancer:
1. Hormone-receptor positive or negative (60 - 65% of patients)

  • Estrogen Receptor positive (ER)+ or negative (ER)-
  • Progestin Receptor positive (PR)+ or negative (PR)-

2. Hormone Epidermal growth factor Receptor-2 (HER-2) positive or negative (20 - 25% of patients)

  • HER-2 +
  • HER-2 -

3. Triple Negative (15 - 18% of patients)

  • ER- and PR- and (HER-2)-
NOTE: Treatment Options listed below are not all-inclusive. Other treatments may be available. ChemoExperts provides drug information and does not recommend any one treatment over another. Only your Doctor can choose which therapy is appropriate for you.

What does Cure mean?

The word “cure” means there are no cancer cells left in the body and cancer will never come back. Depending on the cancer type and stage, this may be the true goal of therapy. However, it is very difficult to prove all cancer cells are gone. Even though images, like X-rays and MRI’s, and blood tests may not show any signs of cancer, there can be a small amount of cancer cells still left in the body. Because of this, the word “remission” is used more often. This means there are no signs or symptoms of cancer. Patients in remission are followed closely for any signs of cancer returning. Sometimes, more chemotherapy may be given while in remission to prevent the cancer from coming back.

Doctors usually do not consider a patient “cured” until the chance of cancer returning is extremely low. If cancer does return, it usually happens within 5 years of having a remission. Because of this, doctors do not consider a patient cured unless the cancer has not come back within 5 years of remission. The five-year cutoff does not apply to all cancers.

Common Enhertu® starting doses

  • Enhertu® (fam-trastuzumab deruxtecan-nxki) 5.4 mg/kg intravenous (I.V.) infusion over 90 minutes on Day 1
    • If the 90-minute infusion is well tolerated, subsequent infusions may be given over 30 minutes

Note: Individual doses may vary based upon your Doctor's recommendation, or drug availability.

What is a CBC?

A Complete Blood Count (CBC) is a frequently ordered blood test that tells clinicians the status of your: 1) White blood cell count, 2) Hemoglobin, and 3) Platelet count at the time the test was taken.

Common uses:
1) White blood cell count (WBC): is used to determine infection risk, or response to chemotherapy. Certain chemotherapy agents may harm our good infection-fighting cells. Sometimes chemotherapy may need to be delayed to allow these cells to recover.

2) Hemoglobin: is used to determine if someone is anemic. Anytime the hemoglobin is below 12 g/dL, the person is said to be anemic. Red blood cell transfusions, and sometimes iron can be given to restore the hemoglobin level, but anemia treatment should always aim at treating the underlying cause or condition.

3) Platelet count: is used to determine if the risk of bleeding is increased or if a platelet transfusion is required to prevent bleeding. Certain medications that increase bleeding risk, such as: aspirin, certain chemotherapy agents, and blood thinners, may need to be stopped temporarily until the platelet count is within a safe range.

What is a CMP?

A Comprehensive Metabolic Panel (CMP) is a frequently ordered blood test that tells clinicians the status of your: 1) Electrolytes & Acid/Base status2) Kidney function, 3) Liver function, 4) Blood sugar, and 5) Calcium at the time the test was taken. It is commonly used to monitor liver and kidney function when beginning new medications such as chemotherapy. A total of 14 tests are run simultaneously and are shown below.

Electrolytes & Acid/Base status:
1) Sodium, 2) Potassium, 3) Carbon dioxide, 4) Chloride

Kidney Function:
5) BUN (blood urea nitrogen), 6) Serum creatinine (Scr)

Liver Function:
7) AST, 8) ALT, 9) Total bilirubin, 10) Alk Phos, 11) Albumin, 12) Total protein

Blood sugar:
13) Serum glucose

14) Serum calcium