In the Phase 2 MOUNTAINEER-01 study of patients with HER2-positive metastatic colorectal cancer who were chemo-refractory, the combination of tucatinib and trastuzumab showed an impressive response rate and disease control rate, and median duration of response up to 12 months; Dr. Ahn notes these results compare favorably to prior studies of dual HER2 inhibition, with MOUNTAINEER-01 showing higher response rates.