Multinational phase 2 trial of tucatinib plus trastuzumab for chemorefractory, HER2-positive, RAS wild-type mCRC: final analysis of MOUNTAINEER

MOUNTAINEER was a multinationl phase 2 trial that evaluated the HER2-directed, chemotherapy-free regimen of tucatinib plus trastuzumab for chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer (CRC). Final analysis of the trial after a median follow-up of 32.4 months has now been reported. Among the 84 patients who received the combination of tucatinib plus trastuzumab, the confirmed objective response rate was 39.3%; the median duration of response was 15.2 months. The median progression-free survival was 8.1 months, and the median overall survival was 23.9 months. No clear association of treatment response with co-occurring biomarker alterations was seen. Few patients discontinued treatment due to adverse events; no treatment-emergent deaths occurred. The authors conclude that the combination of tucatinib plus trastuzumab showeld clinically meaningful efficacy and favorable safety among patients with chemotherapy-refractory, HER2-positive, RAS wild-type metastatic CRC.