What Is Enhertu® (fam-trastuzumab deruxtecan-nxki)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Enhertu® (fam-trastuzumab deruxtecan-nxki) is used to treat adults with some forms of human epidermal growth factor receptor-2 (HER2)-positive breast cancer. Enhertu may be used to treat certain forms of HER2-positive breast cancer that:1

  • Cannot be removed by surgery (unresectable) or have spread to other parts of the body (metastasized)
  • Have been previously treated with at least 1 other therapy that targets HER2

Enhertu also has been approved by the US Food and Drug Administration (FDA) to treat certain forms of HER2-low breast cancer that are unresectable or have metastasized.1,2

HER2-low breast cancer is a new classification of the HER2 subtype in which there are some HER2 proteins on the cell surface but not enough to be designated HER2-positive. The HER2-low subtype accounts for about half of all breast cancers.2,3

What are the ingredients in Enhertu?

The active ingredient in Enhertu is fam-trastuzumab deruxtecan-nxki.1

How does Enhertu work?

The fam-trastuzumab portion of Enhertu is a monoclonal antibody. This means it is designed to seek out and attach to a very specific cell in the body. In this case, the target is HER2-positive breast cancer cells.1,2

The other part of Enhertu is the deruxtecan-nxki. This drug is a type of chemotherapy called a topoisomerase inhibitor. The antibody and chemotherapy drugs work together. The antibody portion helps find and attach to HER2-positive breast cancer cells. Once attached, the chemotherapy portion is released to attack the cancer cell.1,2

What are the possible side effects?

The most common side effects of Enhertu in breast cancer treatment include:1

  • Nausea
  • Fatigue
  • Vomiting
  • Hair loss
  • Constipation
  • Decreased appetite
  • Musculoskeletal pain
  • Low red blood cell, white blood cell, and platelet levels
  • Diarrhea
  • Cough
  • Changes in tests measuring liver function
  • Low potassium levels

Enhertu has a boxed warning, the strictest warning from the FDA. This is because it may cause severe, life-threatening lung problems. Tell your doctor right away if you have any of the following symptoms:1

  • Cough
  • Trouble breathing
  • Fever
  • Other new or worsening breathing symptoms, like chest tightness or wheezing

Enhertu also has a boxed warning because it can harm an unborn baby. If you or your partner can become pregnant, you should use birth control during treatment and for some time after the last dose of Enhertu. You should also not breastfeed during treatment with Enhertu and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking Enhertu.1

These are not all the possible side effects of Enhertu. Talk to your doctor about what to expect when taking Enhertu. You also should call your doctor if you have any changes that concern you when taking Enhertu.

Other things to know

Your doctor will check your heart function before and during treatment with Enhertu.1

Before taking Enhertu, tell your doctor if you have:1

  • Lung or breathing problems
  • Signs or symptoms of an infection
  • Heart problems

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Enhertu.

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