Overview
Enhertu is approved by the U.S. Food and Drug Administration (FDA) for the treatment of several types of breast cancer. It is indicated in combination with pertuzumab as a first-line treatment for adults with HER2-positive breast cancer that is either unresectable (cannot be removed with surgery) or metastatic (has spread to other parts of the body). It is also approved as a standalone treatment for adults with HER2-positive, HER2-low, or HER2-ultralow unresectable or metastatic breast cancer who have received prior therapies. Enhertu is also known by its drug name, fam-trastuzumab deruxtecan-nxki.

Enhertu is a HER2-directed antibody-drug conjugate. It combines a targeted therapy that attaches to HER2-positive cancer cells with a chemotherapy drug that kills them. This helps deliver the chemotherapy directly to cancer cells, reducing harm to healthy cells.

How do I take it?
Prescribing information states that Enhertu is given by intravenous (IV) infusion. For HER2-positive, HER2-low, or HER2-ultralow breast cancer, it is typically administered once every three weeks. In first-line treatment for HER2-positive metastatic breast cancer, it is given in combination with pertuzumab on the same schedule, with a higher dose of pertuzumab during the first cycle and a reduced dose in subsequent cycles. Enhertu should be administered exactly as prescribed by a healthcare provider.

Side effects
Common side effects of Enhertu include decreased white blood cell count, nausea, decreased hemoglobin (red blood cell protein), decreased neutrophil and lymphocyte counts (types of white blood cells), fatigue, decreased platelet count, increased liver enzymes, vomiting, hair loss, constipation, decreased blood potassium, decreased appetite, diarrhea, and muscle or joint pain. 

In combination therapy, additional common side effects include weight loss, abdominal pain, and upper respiratory tract infections, including COVID-19.

Rare but serious side effects may include interstitial lung disease or pneumonitis (inflammation of lung tissue), which can be fatal. Other serious risks include neutropenia (low white blood cells), left ventricular dysfunction (heart problems), and embryo-fetal toxicity (harm to an unborn baby). People receiving Enhertu should be monitored closely for these risks and report any symptoms immediately.

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Highlights of Prescribing Information: Enhertu (Fam-Trastuzumab Deruxtecan-Nxki) for Injection, for Intravenous Use — Daiichi Sankyo