FDA Accepts sNDA for Tukysa for HER2 Positive Colorectal Cancer

There are currently no FDA-approved therapies that specifically target HER2 in colorectal cancer. The agency has set a target action date of Jan. 19, 2023.

The FDA has accepted for priority review Seagen’s supplemental new drug application (sNDA) seeking accelerated approval for Tukysa (tucatinib). The company is seeking an indication 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.

Tukysa is an oral medicine that is a tyrosine kinase inhibitor of the HER2 protein. The FDA approved Tukysa in April 2020 in combination with trastuzumab and capecitabine to treat 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.

“There are currently no FDA-approved therapies for metastatic colorectal cancer that specifically target HER2,” Marjorie Green, M.D., senior vice president and head of late-stage development at Seagen, said in a press release. “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 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.

In the study, Tukysa in combination with trastuzumab was well-tolerated with durable responses in patients with previously treated HER2-positive metastatic colorectal cancer. At a median duration of follow-up of 20.7 months, results of the MOUNTAINEER trial showed a 38.1% confirmed objective response rate per blinded independent central review in the HER2-positive patients who were assigned to receive tucatinib in combination with trastuzumab. In these patients, the median duration of response was 12.4 months, median progression-free survival was 8.2 months, and median overall survival was 24.1 months.

In a cohort of 30 patients who received tucatinib monotherapy, objective response rate per BICR by 12 weeks was 3.3% and the disease control rate was 80.0%. Participants who did not respond to tucatinib monotherapy by 12 weeks or progressed at any time had the option to receive the combination of treatment.

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 United States and to support global filings.

Globally, more than 1.9 million new colorectal cancer cases and 935,000 deaths were estimated to occur in 2020. Colorectal cancer is the third leading cause of cancer-related deaths in the United States and is anticipated to lead to about 52,580 deaths in 2022. HER2 is overexpressed in 3% to 5% of patients with metastatic colorectal cancer.

According to Seagen, the wholesale acquisition cost of Tukysa 50 mg in 60 count bottle is $5,365; 150 mg 60 count bottle is $10,788.