Enhertu: What to Expect, Side Effects, and More
Enhertu (chemical name: fam-trastuzumab-deruxtecan-nxki) is a targeted therapy called an antibody-drug conjugate (ADC). ADCs target specific proteins found on the surface of cancer cells. Once the medicine attaches to these proteins and enters the cell, it releases chemotherapy, which can destroy the cell.
You may be prescribed Enhertu if:
You were diagnosed with unresectable or metastatic HER2-positive breast cancer and have previously received an anti-HER2 medicine
You were diagnosed with unresectable or metastatic hormone receptor-positive, HER2-low or -ultralow breast cancer and have previously received hormonal therapy.
You were diagnosed with unresectable or metastatic HER2-low breast cancer and have previously received chemotherapy
See Enhertu prescribing information.
Is Enhertu chemotherapy or immunotherapy?
Enhertu is targeted therapy — it’s a biosimilar of Herceptin that is attached to a chemotherapy medication. Herceptin is technically considered an immune targeted therapy, but Enhertu is not.
How Enhertu works
Some breast cancer cells make (overexpress) too many copies of the HER2 gene. The HER2 gene makes a protein known as a HER2 receptor. HER2 receptors are like ears, or antennae, on the surface of cells. These HER2 receptors receive signals that stimulate the cell to grow and multiply. But breast cancer cells with too many HER2 receptors can pick up too many growth signals and so start growing and multiplying too much and too fast. Breast cancer cells that overexpress the HER2 gene are said to be HER2-positive.
A large number of breast cancers considered HER2-negative have some HER2 proteins on the surface of their cells. There just aren’t enough HER2 proteins for the cancer to be considered HER2-positive. Doctors call these cancers HER2-low or -ultralow.
Enhertu is made up of two main parts linked together: a monoclonal antibody called fam-trastuzumab and a chemotherapy called DXd.
The antibody part of Enhertu attaches to the HER2 protein, stopping it from receiving growth signals. Once inside the cell, DXd, a topoisomerase I inhibitor is released. This chemotherapy makes it hard for the cell to divide and grow.
DXd isn’t a targeted medicine, which means it can affect healthy cells as well as cancer cells. However, because DXd is linked to the fam-trastuzumab antibody in Enhertu, the medicine is able to target cancer cells with HER2 receptors on them. This makes Enhertu less toxic to healthy cells and more effective in treating cancer cells.
What to expect during Enhertu treatment
Enhertu is given intravenously, which means the medicine is delivered directly into your bloodstream through an IV or port. Enhertu is usually given in doses of 5.4 mg/kg every three weeks unless (or until) the cancer grows.
Enhertu side effects
Like almost all breast cancer medicines, Enhertu can cause side effects, some of them severe.
The most common side effects of Enhertu are:
More rarely, Enhertu also may cause serious side effects, including:
Interstitial lung disease: Interstitial lung disease is a general term for disorders that cause inflammation and scarring in the lungs. The scarring makes lung tissue stiff, which makes it difficult to breathe. You should be closely monitored for signs of interstitial lung disease while being treated with Enhertu. Tell your doctor right away if you experience shortness of breath or have a dry cough.
Neutropenia: Neutropenia means you have abnormally low levels of neutrophils, a type of white blood cell. People with neutropenia have a much higher risk of getting serious infections. Symptoms include fever, fatigue, and swollen lymph nodes. Your doctor will monitor your neutrophil counts while you are being treated with Enhertu.
Left ventricular dysfunction (LVD): LVD occurs when the heart loses its ability to pump blood. Symptoms include shortness of breath, swelling of the ankles, feet, legs, or abdomen, and sudden weight gain.
You should not take Enhertu if you’re pregnant or planning to get pregnant should not be given Enhertu. Enhertu can cause embryo death and birth defects. You must use effective birth control for the duration of your treatment.
Real patient reviews
Members of our community discuss their experiences with Enhertu in the community forum. Here are some of their comments. Remember, it's essential to talk to your doctor about any side effects you're having and ask about ways to manage them.
“I had annoying nausea the whole time on Enhertu. I used ondansetron and compazine for it. I kept my bowels regular with Calm Magnesium gummies, which I got from Amazon. (it also comes in a powder that you mix with liquids if you don't like the gummies.)” —ninetwelve
“I've had 8 infusions of Enhertu at the full dose level and have experienced side effects of fatigue and general crappiness.” —aswans
“On treatment day for Enhertu, I was given a scopolamine patch, Zofran through IV, and some milky anti-nausea medication to prevent nausea. The first day was okay. The next day, Although I still was using a scopolamine patch to prevent nausea, the feeling of dizziness, nausea were horrendous.” —starlove
Read more in our Enhertu discussion forum.
Paying for Enhertu
The cost of Enhertu may vary. The price you’ll pay depends on the drug manufacturer, your health insurance provider and plan, where you live, and the pharmacy you use.
Note: Your insurance company may require you to get prior authorization before covering Enhertu.
If your doctor prescribes Enhertu and you have problems getting it covered by insurance or don’t have insurance, you can visit ENHERTU4U or call 1-833-ENHERTU.
Learn more about financial assistance and medicine cost-lowering tips.
— Last updated on June 1, 2025 at 2:19 PM
