{"entity":{"id":"mountaineer","kind":"trial","name":"MOUNTAINEER","aka":[],"tldr":"A HER2 pill plus antibody gave durable responses in the 3-5% of bowel cancers driven by HER2, and is now being tested as first-line treatment.","summary":"MOUNTAINEER phase 2: confirmed ORR 38.1%, median duration of response 12.4 months; FDA accelerated approval January 2023 (first HER2-directed regimen in CRC). The randomised phase 3 successor is a separate record, MOUNTAINEER-03 (NCT05253651, 400 patients, primary completion December 2027).","status":"completed","asOf":"2026-09-07","links":[{"label":"ClinicalTrials.gov NCT03043313","url":"https://clinicaltrials.gov/study/NCT03043313"},{"label":"MOUNTAINEER-03 NCT05253651","url":"https://clinicaltrials.gov/study/NCT05253651"},{"label":"MOUNTAINEER: tucatinib plus trastuzumab for chemotherapy-refractory HER2-positive RAS wild-type metastatic colorectal cancer (Lancet Oncology 2023)","url":"https://doi.org/10.1016/S1470-2045(23)00150-X"}],"tags":[],"related":[],"cancers":["colorectal","her2-amplified-colorectal"],"sections":[],"technologies":["her2-tyrosine-kinase-inhibitors","kinase-inhibitors"],"targets":["her2"],"drugs":["tucatinib","trastuzumab","folfox","bevacizumab","cetuximab","oxaliplatin"],"companies":["pfizer"],"institutions":[],"pathways":[],"terms":[],"trials":["mountaineer-03","destiny-crc01"],"people":["tanios-bekaii-saab"],"bottlenecks":[],"keyPapers":["paper-valtorta-her2-scoring-colorectal-heracles-mod-pathol-2015","paper-richman-her2-amplification-quasar-focus-piccolo-j-pathol-2016","paper-strickler-mountaineer-tucatinib-trastuzumab-lancet-oncol-2023","paper-mountaineer-nat-commun-2026-update"],"journals":[],"dependsOn":[],"notes":["The randomised phase 3 successor is a separate record, `mountaineer-03` (NCT05253651), which is recruiting with primary completion due 31 December 2027."],"nct":"NCT03043313","phase":"2","setting":"Chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer: tucatinib plus trastuzumab (cohorts A and B) or tucatinib alone (cohort C)","sponsor":"Pfizer (Seagen)","result":"Phase 2 ORR 38.1%, DOR 12.4 months; phase 3 ongoing.","started":"2017-06-23","startedType":"actual","yearReported":2022,"enrolledBasis":"registry","outcomes":[{"endpoint":"Objective response rate (phase 2)","primary":true,"unit":"percent","arms":[{"name":"Tucatinib + trastuzumab","n":84,"value":38.1}],"source":"https://ascopubs.org/doi/10.1200/JCO.2024.42.16_suppl.3509"}]},"route":"/trials/mountaineer/","neighbours":{"cancer":[{"id":"colorectal","kind":"cancer","name":"Colorectal cancer","route":"/cancers/colorectal/"},{"id":"her2-amplified-colorectal","kind":"cancer","name":"HER2-amplified colorectal cancer","route":"/cancers/her2-amplified-colorectal/"}],"technology":[{"id":"her2-tyrosine-kinase-inhibitors","kind":"technology","name":"HER2 tyrosine kinase inhibitors","route":"/technologies/her2-tyrosine-kinase-inhibitors/"},{"id":"kinase-inhibitors","kind":"technology","name":"Small-molecule kinase inhibitors","route":"/technologies/kinase-inhibitors/"}],"target":[{"id":"her2","kind":"target","name":"HER2","route":"/targets/her2/"}],"drug":[{"id":"bevacizumab","kind":"drug","name":"Bevacizumab","route":"/drugs/bevacizumab/"},{"id":"cetuximab","kind":"drug","name":"Cetuximab","route":"/drugs/cetuximab/"},{"id":"folfox","kind":"drug","name":"FOLFOX (5-FU, leucovorin, oxaliplatin)","route":"/drugs/folfox/"},{"id":"oxaliplatin","kind":"drug","name":"Oxaliplatin","route":"/drugs/oxaliplatin/"},{"id":"trastuzumab","kind":"drug","name":"Trastuzumab","route":"/drugs/trastuzumab/"},{"id":"tucatinib","kind":"drug","name":"Tucatinib","route":"/drugs/tucatinib/"}],"company":[{"id":"pfizer","kind":"company","name":"Pfizer (incl. Seagen)","route":"/companies/pfizer/"}],"trial":[{"id":"destiny-crc01","kind":"trial","name":"DESTINY-CRC01","route":"/trials/destiny-crc01/"},{"id":"mountaineer-03","kind":"trial","name":"MOUNTAINEER-03","route":"/trials/mountaineer-03/"},{"id":"triumph","kind":"trial","name":"TRIUMPH","route":"/trials/triumph/"}],"person":[{"id":"tanios-bekaii-saab","kind":"person","name":"Tanios Bekaii-Saab","route":"/people/tanios-bekaii-saab/"}],"paper":[{"id":"paper-valtorta-her2-scoring-colorectal-heracles-mod-pathol-2015","kind":"paper","name":"Assessment of a HER2 scoring system for colorectal cancer: results from a validation study","route":"/key-papers/paper-valtorta-her2-scoring-colorectal-heracles-mod-pathol-2015/"},{"id":"paper-richman-her2-amplification-quasar-focus-piccolo-j-pathol-2016","kind":"paper","name":"HER2 overexpression and amplification as a potential therapeutic target in colorectal cancer: analysis of 3256 patients enrolled in the QUASAR, FOCUS and PICCOLO colorectal cancer trials","route":"/key-papers/paper-richman-her2-amplification-quasar-focus-piccolo-j-pathol-2016/"},{"id":"paper-mountaineer-nat-commun-2026-update","kind":"paper","name":"Tucatinib plus trastuzumab for chemotherapy-refractory, HER2 +, RAS wild-type metastatic colorectal cancer (MOUNTAINEER): final analysis","route":"/key-papers/paper-mountaineer-nat-commun-2026-update/"},{"id":"paper-strickler-mountaineer-tucatinib-trastuzumab-lancet-oncol-2023","kind":"paper","name":"Tucatinib plus trastuzumab for chemotherapy-refractory, HER2-positive, RAS wild-type unresectable or metastatic colorectal cancer (MOUNTAINEER)","route":"/key-papers/paper-strickler-mountaineer-tucatinib-trastuzumab-lancet-oncol-2023/"}],"roadmap":[{"id":"colorectal-roadmap","kind":"roadmap","name":"Colorectal cancer roadmap: from the adenoma-carcinoma sequence and the first screening trials to total mesorectal excision, oxaliplatin, RAS testing, immunotherapy for mismatch repair-deficient disease, ctDNA-guided treatment and organ preservation","route":"/roadmaps/colorectal-roadmap/"}],"biomarker":[{"id":"ras-wild-type","kind":"biomarker","name":"RAS wild-type (extended KRAS and NRAS testing)","route":"/biomarkers/ras-wild-type/"}]}}