What is Ontruzant® (trastuzumab-dttb)?

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

  • In combination with Taxol as a first treatment
  • Alone in people who have been treated with 1 or more chemotherapy drugs

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 makes the cells multiply faster. When cancer cells produce too many HER2 molecules, they are called HER2+ tumors. HER2- cancers produce few or no HER2 molecules. About 15 to 30 percent of breast cancers are HER2+.2-4

Ontruzant is also used to treat certain people with non-metatstatic HER2+ breast cancer. Ontruzant is a biosimilar to Herceptin®(trastuzumab). Drugs similar in structure to known biologic drugs are called biosimilars.2-4

What are the ingredients in Ontruzant?

The active ingredient in Ontruzant is trastuzumab.1

How does Ontruzant work?

Ontruzant is a monoclonal antibody. Antibodies are a normal part of our immune system that act against antigens. These are bacteria, viruses, and other foreign organisms that threaten our health. Monoclonal antibodies 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 antigens that appear on the surface of HER2+ breast cancers. HER2 antigens stimulate tumors to grow especially fast. By blocking HER2, Ontruzant slows the uncontrolled growth of the tumor cells.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 of Ontruzant?

The most common side effects of Ontruzant include:1

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

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

  • Serious heart problems, including congestive heart failure
  • Severe lung problems, including swelling of the lungs
  • Severe reaction to infusion, which is how the drug is given
  • Birth defects or death of an unborn baby

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.

Things to know about Ontruzant

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. You should also not breastfeed during treatment with Ontruzant and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking Ontruzant.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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Written by: Emily Downward and Heather Morse | Last reviewed: March 2021