FDA Approves Tukysa for HER2 Positive Colorectal Cancer

The FDA has granted an accelerated approval for Seagen’s Tukysa (tucatinib) for adult patients with unresectable or metastatic colorectal cancer. It is indicated in combination with trastuzumab as a second-line treatment for patients who are HER2-positive. Tukysa is an oral medicine that is a tyrosine kinase inhibitor of the HER2 protein.

In the United States, about 153,000 people will be diagnosed with colorectal cancer in 2023, and the rate of the disease is increasing in younger adults. HER2 is overexpressed in 3% to 5% of patients with metastatic colorectal cancer and about 10% of patients with RASwild-type metastatic colorectal cancer. In 2023, colorectal cancer is anticipated to lead to about 52,550 deaths in the United States.

John Strickler, M.D.

“Historically, patients with HER2-positive metastatic colorectal cancer who have progressed following frontline therapy have had poor outcomes,” John Strickler, M.D., associate professor of medicine, Duke University Medical Center, and lead investigator for the MOUNTAINEER trial, said in a press release. “The FDA approval of a chemotherapy-free combination regimen that specifically targets HER2 is great news for these patients.”

Tukysa was granted accelerated approval based on tumor response rate and durability of response from the phase 2 MOUNTAINEER clinical trial. The results showed a 38% overall response rate in the patients who received the combination treatment. Complete responses were observed in 3.6% of patients, and partial responses were observed in 35% of patients. The median duration of response was 12.4 months.

The prescribing information includes warnings and precautions for diarrhea, hepatotoxicity and embryo-fetal toxicity, some of which may be severe or fatal. In MOUNTAINEER, serious adverse reactions occurred in 22% of patients; the most common were intestinal obstruction, urinary tract infection, pneumonia, abdominal pain and rectal perforation. Adverse reactions leading to permanent discontinuation occurred in 6% of patients.

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.

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.