What Is Herceptin® (trastuzumab)?

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

Herceptin® (trastuzumab) is a targeted treatment used to treat breast cancer that is positive for the human epidermal growth factor receptor 2 (HER2+). It may be used in combination with chemotherapy drugs, or it may be used alone in people who have already received chemotherapy.

What are the active ingredients in Herceptin?

The active ingredient in Herceptin is trastuzumab.1

How does trastuzumab work?

Trastuzumab is a monoclonal antibody. Antibodies are a normal part of the immune system. They attach to antigens (such as germs) to mark them for destruction by the immune system. Monoclonal antibodies used in cancer treatment are created in a lab to attach to specific antigens on the surface of cancer cells. Trastuzumab attaches to the HER2 receptor.1,2

Breast cancers that are classified as HER2+ have too many HER2 receptors, which can cause the cancer to grow and spread quickly. Trastuzumab targets these receptors and has been shown to block the growth and spread of HER2+ breast cancers.1,2

What are the possible side effects?

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

  • Fever
  • Chills
  • Headache
  • Insomnia
  • Cough
  • Rash
  • Infection
  • Nausea
  • Diarrhea

Trastuzumab has a boxed warning, the strictest warning from the US Food and Drug Administration (FDA). This is because it may also cause serious side effects, including:1,2

  • Heart problems, such as congestive heart failure or reduced heart function
  • Infusion reactions, which may cause fever, chills, nausea, vomiting, pain, headache, dizziness, and/or shortness of breath
  • Serious harm to an unborn baby, which may cause serious birth defects or death

These are not all the possible side effects of trastuzumab. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with trastuzumab.

Other things to know

Trastuzumab 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 trastuzumab. You should also not breastfeed during treatment with trastuzumab and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking trastuzumab.1

Trastuzumab may cause heart damage. Your doctor should check your heart function before and during treatment with trastuzumab.1,2

Herceptin Hylecta™ (trastuzumab and hyaluronidase-oysk) is a newer formulation of trastuzumab that is also approved by the FDA. It can be given subcutaneously (injected under the skin) in a shorter amount of time. It includes the same monoclonal antibody as intravenous trastuzumab in combination with recombinant human hyaluronidase PH20.3,4

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 trastuzumab.

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