FDA Grants Priority Review to Tucatinib With Trastuzumab to Treat HER2 Colorectal Cancer


The FDA accepted a supplemental New Drug Application for tucatinib to treat HER2 colorectal cancer, which could significantly improve outcomes for these patients.

The FDA has accepted a supplemental New Drug Application (sNDA) for the combination of tucatinib (Tukya; Seagen Inc) with trastuzumab for Priority Review. The treatment is indicated to treat adults with metastatic or unresectable human epidermal growth factor receptor 2 (HER2)-positive colorectal cancer who have already received 1 treatment regimen.

The FDA accepted the sNDA based on the results of the open-label, multicenter MOUNTAINEER phase 2 trial. In the MOUNTAINEER trial, researchers observed that the combination of tucatinib with trastuzumab was more effective against HER2-positive colorectal cancer than either medicine as a monotherapy.

“There are currently no FDA-approved therapies for metastatic colorectal cancer that specifically target HER2. 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,” said Marjorie Green, MD, senior vice president and head of Late-Stage Development, Seagen, in a press release.

The primary endpoint of MOUNTAINEER is a confirmed objective response rate (ORR) according to RECIST (Response Evaluation Criteria in Solid Tumors) version 1.1 criteria. Key secondary endpoints included response duration, progression-free survival (PFS), overall survival (OS), and safety and tolerability from the combined treatment.

The MOUNTAINEER trial evaluated the combination of tucatinib with trastuzumab for patients with HER2-positive unresectable or metastatic colorectal cancer who already received standard-of-care therapies. It was also evaluated as a single-agent treatment.

Among 117 participants, researchers assessed tucatinib as an oral, twice-daily 300 mg dose. It was taken with the intravenous injection of trastuzumab—8 mg/kg at the onset, followed by 6 mg/kg dose every 3 weeks.

Currently, the MOUNTINEER-03 clinical trial is underway. It is evaluating a treatment regimen of tucatinib, trastuzumab, and standard chemotherapy against first-line treatment of chemotherapy with/without cetuximab or bevacizumab. It will confirm the efficacy and safety of tucatinib with trastuzumab as a HER2-positive metastatic colorectal cancer treatment.

The most common serious adverse reactions among patients on tucatinib included diarrhea, which impacted 4% of participants, while 2.5% experienced vomiting, 2% nausea, 2% abdominal pain, and 2% experienced seizure.

Tucatinib is a tyrosine kinase inhibitor that shows anti-tumor activity in tumor cells expressed by the HER2 protein. In living organisms, it was found to stop the growth of these tumors.

Colorectal cancer affects more than 150,000 Americans each year, and the rate of diagnosis is growing among younger adults. Experts estimate that 52,000 people could die from the disease this year, marking it as number 3 for cancer-related deaths. The HER2 protein is overexpressed in up to 5% of patients with metastatic colorectal cancer.

The FDA granted the combination treatment of tucatinib with trastuzumab a Breakthrough Therapy Designation in July 2022, pushing tucatinib closer to being the first FDA-approved therapy for adults previously treated for HER2 colorectal cancer.


Seagen Inc. Seagen Announces TUKYSA® (tucatinib) in Combination with Trastuzumab Granted Priority Review by FDA for Previously Treated HER2-Positive Metastatic Colorectal Cancer. Seagen website. September 19, 2022. Accessed on September 19, 2022. https://investor.seagen.com/press-releases/news-details/2022/Seagen-Announces-TUKYSA-tucatinib-in-Combination-with-Trastuzumab-Granted-Priority-Review-by-FDA-for-Previously-Treated-HER2-Positive-Metastatic-Colorectal-Cancer/default.aspx

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