Seagen announces long-term results from Tukysa pivotal trial for HER2-positive breast cancer during the 2021 ASCO Annual Meeting

Seagen Inc. 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.

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.