– FDA Has Set Action Date of January 19, 2023 –

BOTHELL, WA, USA I September 19, 2022 ISeagen Inc. (Nasdaq: SGEN) today announced that the U.S. Food and Drug Administration (FDA) has accepted for Priority Review the supplemental New Drug Application (sNDA) seeking accelerated approval for TUKYSA® (tucatinib) in combination with trastuzumab for adult patients with HER2-positive colorectal cancer who have received at least one prior treatment regimen for unresectable or metastatic disease.

The sNDA submission is based on the results of the pivotal phase 2 MOUNTAINEER trial. These data were presented at the European Society for Medical Oncology (ESMO) World Congress on Gastrointestinal Cancer in July 2022.

“There are currently no FDA-approved therapies for metastatic colorectal cancer that specifically target HER2,” said Marjorie Green, M.D., Senior Vice President and Head of Late-Stage Development, Seagen. “The FDA’s prioritization of our application for tucatinib in combination with trastuzumab supports our belief in its significant potential to benefit people with previously treated HER2-positive metastatic colorectal cancer.”

The FDA grants Priority Review to applications for medicines that, if approved, would provide significant improvements in safety or effectiveness of the treatment, diagnosis or prevention of serious diseases. Under the Prescription Drug User Fee Act (PDUFA), the FDA has set a target action date of January 19, 2023. In July 2022, the FDA granted Breakthrough Therapy Designation for tucatinib in combination with trastuzumab for the treatment of adult patients with unresectable or metastatic HER2-positive colorectal cancer who have previously received fluoropyrimidine-, oxaliplatin- and irinotecan-containing chemotherapy based on results from the MOUNTAINEER trial.

In February 2022, Seagen initiated the randomized, global phase 3 MOUNTAINEER-03 clinical trial, which is evaluating tucatinib in combination with trastuzumab and standard chemotherapy versus chemotherapy given with or without cetuximab or bevacizumab in first-line HER2-positive metastatic colorectal cancer. MOUNTAINEER-03 is intended to serve as a confirmatory trial in the U.S. and to support global filings. Merck, known as MSD outside of the U.S. and Canada, is commercializing TUKYSA in regions outside of the U.S., Canada and Europe.


MOUNTAINEER is a U.S. and European open-label, multicenter phase 2 clinical trial of tucatinib in combination with trastuzumab or as a single agent that enrolled 117 patients with HER2-positive unresectable or metastatic colorectal cancer following previous standard-of-care therapies. Patients evaluated in MOUNTAINEER had not received prior anti-HER2 therapy. Patients received tucatinib (300 mg) twice per day orally in combination with trastuzumab intravenously (8 mg/kg loading dose, then 6 mg/kg every three weeks thereafter). The primary endpoint of the trial is confirmed objective response rate by RECIST (Response Evaluation Criteria in Solid Tumors) version 1.1 criteria per blinded independent central review. Duration of response, progression-free survival, overall survival and safety and tolerability of the combination regimen are secondary objectives.

About Colorectal Cancer

In the U.S., approximately 151,000 people will be diagnosed with colorectal cancer in 2022, and the rate of the disease is increasing in younger adults.[1] Approximately 22% of U.S. patients with colorectal cancer are diagnosed at the advanced stage.[2] Human epidermal growth factor receptor 2 (HER2) is overexpressed in 3-5% of patients with metastatic colorectal cancer.[3] In 2022, colorectal cancer is anticipated to lead to about 52,500 deaths in the U.S., where it is the third-leading cause of cancer-related deaths.[1]

About TUKYSA (tucatinib)

TUKYSA is an oral medicine that is a tyrosine kinase inhibitor of the HER2 protein. In vitro (in lab 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 vivo (in living organisms), TUKYSA inhibited the growth of HER2-expressing tumors. The combination of TUKYSA and the anti-HER2 antibody trastuzumab showed increased anti-tumor activity in vitro and in vivo compared to either medicine alone.

TUKYSA is approved in 38 countries. It was approved by the U.S. FDA in April 2020 and by the European Medicines Agency and the UK Medicines and Healthcare Products Regulatory Agency in February 2021.

U.S. Indication and Important Safety Information

TUKYSA is indicated in combination with trastuzumab and capecitabine for treatment of adult patients with advanced unresectable or metastatic HER2-positive breast cancer, including patients with brain metastases, who have received one or more prior anti-HER2-based regimens in the metastatic setting.

For more information, please see the full Prescribing Information for TUKYSA here.

About Seagen

Seagen is a global biotechnology company that discovers, develops and commercializes transformative cancer medicines to make a meaningful difference in people’s lives. Seagen is headquartered in the Seattle, Washington area, and has locations in California, Canada, Switzerland and the European Union. For more information on the company’s marketed products and robust pipeline, visit www.seagen.com and follow @SeagenGlobal on Twitter.

[1] American Cancer Society: Key Statistics for Colorectal Cancer-2022. https://www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html. Accessed July 2022.
[2] Wang J., et al. Metastatic patterns and survival outcomes in patients with stage IV colon cancer: A population‐based analysis. Cancer Med. 2020 Jan; 9(1): 361–373.
[3] Ahcene Djaballah S, Daniel F, Milani A, Ricagno G, Lonardi S. HER2 in Colorectal Cancer: The Long and Winding Road From Negative Predictive Factor to Positive Actionable Target. Am Soc Clin Oncol Educ Book. 2022;42:1-14. doi:10.1200/EDBK_351354.