What Is Kadcyla® (ado-trastuzumab emtansine)?

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

Kadcyla is a targeted treatment used to treat some metastatic breast cancers. It is approved to treat some people with human epidermal growth factor receptor 2 positive (HER2+), metastatic breast cancer who previously received trastuzumab and taxane chemotherapy, either separately or in combination.1,2

Kadcyla is also approved in certain people with early breast cancer for use after surgery when the breast cancer is HER2-positive and the person has received treatment prior to surgery that included a taxane and trastuzumab, and cancer was still found in the surgically removed tissue.1,2

What is the ingredient in Kadcyla?

The active ingredient in Kadcyla is ado-trastuzumab emtansine.1,2

How does Kadcyla work?

Kadcyla is known as an antibody-drug conjugate. It is a combination of a monoclonal antibody and a chemotherapy drug. Monoclonal antibodies are created in a lab to attach to specific proteins. Kadcyla targets the HER2 receptor protein. Breast cancers that have too many HER2 receptors can grow and spread quickly. Blocking the HER2 receptor can slow or stop the growth of these cancers. By attaching to the HER2 receptor, Kadcyla can also deliver its chemotherapy ingredient directly to cancer cells that have the receptor. This causes the cancer cell to die.3

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What are the possible side effects?

The most common side effects of Kadcyla, depending on the specific form of breast cancer being treated, include:1,2

  • Fatigue
  • Nausea
  • Muscle and bone pain
  • Lowered platelet counts and/or bleeding
  • Headache
  • Liver problems
  • Constipation
  • Nosebleeds
  • Joint pain
  • Pain, numbness, or weakness in the feet and hands

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

  • Liver failure
  • Heart problems, such as congestive heart failure or reduced heart function
  • Harm to an unborn baby, which may cause serious birth defects or death

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

Other things to know

During treatment with Kadcyla, your doctor will monitor you for signs of:1,2

  • Infusion-related reactions
  • Liver problems
  • Bleeding

Kadcyla 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 Kadcyla. You should also not breastfeed during treatment with Kadcyla and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking Kadcyla.1,2

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 Kadcyla.