Seagen Announces Long-Term Results from TUKYSA (tucatinib) Pivotal Trial in Patients with HER2-Positive Breast Cancer During the Virtual Scientific Program of the 2021 ASCO Annual Meeting

Seagen Inc. (Nasdaq:SGEN) today announced that improvements in overall survival (OS) and progression-free survival (PFS) were maintained with long-term follow up from the pivotal HER2CLIMB trial evaluating the addition of TUKYSA (tucatinib) to trastuzumab and capecitabine in patients with HER2-positive metastatic breast cancer (MBC) with and without brain metastases. Data from the pre-specified exploratory analysis will be presented (Abstract #1043) as part of the virtual scientific program of the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting.

The overall survival benefit seen with TUKYSA at the time of the primary analysis was maintained after an additional 15.6 months of follow-up (total of 29.6 months), demonstrating a 5.5-month improvement in median OS (24.7 months (95% CI: 21.6, 28.9) for the TUKYSA regimen vs. 19.2 months (95% CI: 16.4, 21.4) for capecitabine and trastuzumab alone). This benefit continued to be generally consistent across pre-specified patient subgroups.

“Late-stage, HER2-positive metastatic cancer has proven difficult to treat,” said Giuseppe Curigliano, M.D., Ph.D., Head of the Division of Early Drug Development at the European Institute of Oncology, IRCCS, and Associate Professor of Medical Oncology, University of Milano, Italy. “These data further support that treatment with the tucatinib regimen helps patients live longer compared to trastuzumab and capecitabine alone. These benefits were observed across all prespecified subgroups of patients in the trial, including those with or without brain metastases.”

“These results support the significant impact that a TUKYSA regimen can have for patients with HER2-positive metastatic breast cancer,” said Roger D. Dansey, M.D., Chief Medical Officer of Seagen. “The long-term data from the HER2CLIMB trial showed that the survival benefit was sustained with median overall survival longer than that observed at the primary analysis.”

Overall Survival (OS):

• Median OS in the TUKYSA arm was 24.7 months (95% CI: 21.6, 28.9) compared to median OS of 19.2 months (95% CI: 16.4, 21.4) in the control arm (HR=0.73 [95% CI: 0.59-0.90]; p=0.004).

Progression Free Survival (PFS):

• The median PFS in the TUKYSA arm was 7.6 months (95% CI: 6.9, 8.3), compared to median PFS of 4.9 months (95% CI: 4.1, 5.6) in the control arm (HR=00.57 [95% CI: 0.47-0.70]; p<0.00001).

Safety

• The safety profile was generally consistent with the primary analysis. The most common adverse events occurring in more than 20 percent of patients who received TUKYSA included diarrhea, palmar-plantar erythrodysaesthesia syndrome, nausea, fatigue, vomiting, decreased appetite, stomatitis, headache, increased aspartate aminotransferase, anemia, increased alanine aminotransferase, and increased blood bilirubin.
• Grade 3 or greater adverse events occurring in more than five percent of patients in either arm were diarrhea (13.1% TUKYSA vs. 8.6% for the control arm), palmar-plantar erythrodysaethesia syndrome (14.1% vs. 9.1%), fatigue (5.4% vs. 4.1%), and increased alanine aminotransferase (5.7% vs. 0.5%).
• Discontinuations due to adverse events were infrequent in both arms of the trial, with 5.9 percent in the TUKYSA arm and 4.1 percent in the control arm.

TUKYSA in combination with trastuzumab and capecitabine was approved by the U.S. Food and Drug Administration (FDA) in April 2020 for 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. In February 2021, the European Medicines Agency (EMA) and U.K. Medicines and Healthcare products Regulatory Agency (MHRA) each approved TUKYSA in combination with trastuzumab and capecitabine for the treatment of adult patients with HER2-positive locally advanced or metastatic breast cancer who have received at least two prior anti-HER2 treatment regimens. TUKYSA is also approved in Canada, Switzerland, Singapore and Australia.