Enhertu Approved for Metastatic HER2-Positive Breast Cancer

This past week, the United States Food and Drug Administration (US FDA) approved Enhertu for HER2-positive breast cancer. Enhertu (fam-trastuzumab deruxtecan-nxki) is for people with metastatic or unresectable HER2-positive breast cancer. However, at least 2 or more anti-Her2 treatments must have been tried before starting Enhertu.

Enhertu was granted Breakthrough Therapy designation, priority review, and fast-track designation by the FDA. These are all special considerations that can be given to drugs that could potentially fill an unmet need for serious or life-threatening conditions. Enhertu was approved 4 months ahead of its goal date because of the promise it showed in treating this group of people.

How does Enhertu work?

Enhertu is an antibody-drug conjugate directed at specific cells. The fam-trastuzumab portion of the drug 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 HER-2 positive breast cancer cells. The other portion of the drug is the deruxtecan-nxki. This drug is a type of chemotherapy called a topoisomerase inhibitor. It causes the death of cancer cells. By combining these 2 drugs together, Enhertu can specifically target breast cancer cells and deliver chemotherapy directly to these locations.

Enhertu in clinical trials

The FDA based its approval of Enhertu on the results from a clinical trial called the DESTINY-Breast01 trial. Over 180 women with HER2-positive, metastatic or unresectable breast cancer participated in the study. All participants had tried at least 2 other anti-HER2 treatments and received Enhertu every 3 weeks. A participant stopped receiving Enhertu if they had a very serious side effect or if their cancer progressed.

The researchers measured the response to treatment, called the objective response rate (ORR). Overall, 60 percent of participants had a response to treatment, with 4 percent having a complete response and 56 percent having at least a partial response. The average length of response (time until cancer progressed) was about 15 months. The DESTINY-Breast01 trial and another small trial were used to determine the safety and side effects of Enhertu.

What are the side effects of Enhertu?

The most common side effects of Enhertu include, but are not limited to:

  • Nausea
  • Fatigue
  • Hair loss
  • Vomiting
  • Low counts of red blood cells (the cells involved in delivering oxygen throughout the body)
  • Low counts of white blood cells (the cells that help protect the body from infection)
  • Low platelet counts (the cells involved in blood clotting and bleeding)
  • Diarrhea
  • Constipation
  • Decreased appetite
  • Cough

Things to know about Enhertu

Enhertu comes with a boxed warning on the risk of interstitial lung disease (ILD) and pneumonitis (inflammation of the lungs). These conditions can lead to death in rare cases. If a person taking Enhertu develops Grade 2 or higher ILD/pneumonitis, Enhertu needs to be stopped as soon as possible. Tell your doctor as soon as possible if you notice any signs of ILD or pneumonitis, including:

  • Cough
  • Shortness of breath
  • Fever
  • Other new or worsening respiratory symptoms

Enhertu may cause harm to a developing fetus. Women who are pregnant or planning to become pregnant should not take Enhertu, and should use appropriate contraception.

People taking Enhertu will need to have their blood counts monitored regularly. Some people taking Enhertu may need to have their heart monitored if they have a history of heart-related issues, including congestive heart failure.

Read the prescribing information to learn more about Enhertu.

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