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Tucatinib (TUKYSA®) is an oral medicine that is a tyrosine kinase inhibitor of the HER2 protein, a protein that contributes to cancer cell growth.1,2 HER2 is overexpressed in multiple cancers, including breast, colorectal, and gastric cancers.3

In preclinical in vitro studies, TUKYSA inhibited phosphorylation of HER2 and HER3, resulting in inhibition of downstream MAPK and AKT signaling and cell growth (proliferation), and showed anti-tumor activity in HER2-expressing tumor cells. In preclinical and clinical studies, TUKYSA inhibited the growth of HER2-expressing tumors. The combination of TUKYSA and the anti-HER2 antibody trastuzumab has also been shown to increase anti-tumor activity in vitro and in vivo compared to either medicine alone.1

Proposed mechanism of action

Seagen medication tucatinib
Seagen medication tucatinib


  1. TUKYSA Prescribing Information. Bothell, WA: Seagen, Inc. April 2020.
  2. Kulukian A, Lee P, Taylor J, et al. Preclinical activity of HER2-selective tyrosine kinase inhibitor tucatinib as a single agent or in combination with trastuzumab or docetaxel in solid tumor models. Mol Cancer Ther. 2020;19(4):976-987.
  3. Loibli S, Gianni L. HER2-positive breast cancer. Lancet. 2017;389(10087):2415-2429.