What Is Ontruzant® (trastuzumab-dttb)?

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

Ontruzant® (trastuzumab-dttb) is used to treat certain people with metastatic breast cancer that is positive for the human epidermal growth factor receptor 2 (HER2+). It is used for HER2+ metastatic breast cancer:1-4

  • In combination with paclitaxel as a first-line treatment
  • Alone in people who have previously been treated with at least one chemotherapy course for metastatic breast cancer

Metastatic breast cancer is cancer that has spread to other parts of the body, such as the bones or liver. Breast cancer tumors are defined as HER2+ or HER2- cancers. HER2 refers to a specific protein that appears on the surface of cancer cells and can lead to faster growth and spread of the cancer. When cancer cells produce too many HER2 molecules, they are called HER2+ tumors.2-4

Ontruzant is also used as adjuvant therapy for certain forms of HER2+ early breast cancer. Adjuvant therapy attempts to keep cancer from coming back after initial treatment, like surgery.1,2

Ontruzant is a biosimilar to Herceptin®(trastuzumab). Approved biosimilar drugs have no clinically meaningful differences from their approved reference product.2-4

What are the ingredients in Ontruzant?

The active ingredient in Ontruzant is trastuzumab-dttb.1

How does Ontruzant work?

Ontruzant is a monoclonal antibody. Antibodies are a normal part of our immune system that act against antigens. These include bacteria, viruses, and other foreign organisms that threaten our health. Monoclonal antibodies used in cancer treatment are created in a lab to attach to specific antigens on the surface of cancer cells.1-4

Ontruzant is designed to bind to HER2 receptors that appear on the surface of HER2+ breast cancers. HER2+ breast cancers can grow and spread quickly. By blocking HER2, Ontruzant helps slow or block the growth and spread of HER2+ breast cancers.1-4

Since Ontruzant works only with tumors that are HER2+, your doctor will test your tumor for HER2 before prescribing this drug.1-4

What are the possible side effects?

The most common side effects of Ontruzant, depending on the specific form of breast cancer being treated, include::1

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

Ontruzant also has a boxed warning, the strictest warning from the U.S. Food and Drug Administration. This is because it may cause severe side effects including:1

  • Heart problems, including congestive heart failure
  • Lung damage
  • Infusion-related reactions
  • Birth defects and death in unborn babies

If you notice any new or worsening side effects, contact your doctor right away.

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

Other things to know

Your doctor will monitor your heart function before and during your treatment with Ontruzant.1

Ontruzant can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of Ontruzant. Talk to your doctor about your options for birth control while taking Ontruzant. Additionally, if you are breastfeeding or plan to breastfeed, talk with your doctor about this consideration to make sure you have a plan that is safe before starting treatment.1

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 Ontruzant.

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