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What's the mechanism of action for tucatinib?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on April 22, 2021.

Official answer


Tucatinib (Tukysa) is a human epidermal growth factor receptor-2 (HER2) inhibitor that works by blocking the HER2 protein to help slow or stop cancer cell growth in patients with breast cancer. Some breast cancers have an over-expression of the HER2 protein causing increased growth and spread of cancer cells.

Tucatinib, an oral targeted drug therapy, is very selective for the HER2 protein and works inside the cell. Tucatinib binds to tyrosine kinase (an enzyme) of HER2, reducing PI3-kinase and MAP-kinase signaling. Reduced signaling helps to block cell growth and leads to cell death. Tucatinib is classified as a HER2 tyrosine kinase inhibitor.

Related: List of HER2 Inhibitors

How is tucatinib used?

  • Tucatinib (Tukysa) is used with the medicines trastuzumab (Herceptin) and capecitabine (Xeloda) in adult patients with HER2-positive breast cancer.
  • It is given to patients who have already received one or more anti-HER2 breast cancer treatments, but are no longer effective.
  • It is used when the cancer has spread in the body or cannot be removed with surgery, including cancer that has spread to the brain.

This is not all the information you need to know about tucatinib (Tukysa) for safe and effective use and does not take the place of talking to your doctor about your treatment. Review the full product information here, and discuss this information and any questions you have with your doctor or other health care provider.

  • Tukysa (tucatinib) product information. Seagen. Bothell, WA. Revised 4/2020. Accessed April 22, 2021 at
  • Mechanism of Action. Seagen Inc. Accessed April 22, 2021 at

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