Seagen Inc. announced positive topline results from the pivotal phase 2 MOUNTAINEER clinical trial investigating TUKYSA® (tucatinib) in combination with trastuzumab in patients with previously treated HER2-positive metastatic colorectal cancer (mCRC). Data from this trial will form the basis of a planned supplemental New Drug Application to the U.S. Food and Drug Administration (FDA) under the FDA's Accelerated Approval Program. Merck, known as MSD outside the U.S. and Canada, is commercializing TUKYSA in regions outside of the U.S., Canada and Europe and plans to discuss these results with health authorities as it continues to accelerate the filing of TUKYSA in its territory.

Results showed a 38.1% confirmed objective response rate (cORR) [95% Confidence Interval (CI): 27.7, 49.3] per blinded independent central review (BICR). The median duration of response (DoR) per BICR was 12.4 months [95% CI: 8.5, 20.5]. The combination of tucatinib and trastuzumab was generally well-tolerated, and the most common (greater than or equal to 20%) treatment-emergent adverse events were diarrhea, fatigue, nausea and infusion-related reaction, which were primarily low-grade.

Full data from the MOUNTAINEER trial will be presented by John H. Strickler, M.D., Duke University Medical Center, at the European Society for Medical Oncology (ESMO) World Congress on Gastrointestinal Cancer in Barcelona, Spain from June 29 through July 2, 2022.