# MOUNTAINEER-03

Source: https://onco.cc/trials/mountaineer-03/  
OnCo record `mountaineer-03` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The trial that will decide whether HER2 drugs belong in the first treatment for HER2-positive bowel cancer rather than after chemotherapy has failed.

## Summary

MOUNTAINEER-03 is the randomised phase 3 successor to the single-arm MOUNTAINEER cohorts that won tucatinib plus trastuzumab its accelerated approval on 19 January 2023. It randomises about 400 patients with previously untreated HER2-positive, RAS wild-type metastatic colorectal cancer to tucatinib and trastuzumab with mFOLFOX6, or to mFOLFOX6 with bevacizumab or cetuximab at the investigator's choice. The registry records a start date of 24 October 2022, recruitment continuing and primary completion due 31 December 2027, so the confirmatory evidence for the accelerated approval is several years away. Until then HER2-directed treatment in colorectal cancer is a later-line option and HER2 testing is not yet required at diagnosis everywhere.

## Fields

- Kind: Trial
- Status: recruiting
- Last checked: 2026-09-24
- Registry id: NCT05253651
- Phase: 3
- Setting: First-line HER2-positive, RAS wild-type metastatic colorectal cancer: tucatinib with trastuzumab and mFOLFOX6 against mFOLFOX6 with bevacizumab or cetuximab
- Sponsor: Seagen, a wholly owned subsidiary of Pfizer
- Enrolled: 400

## Sources

- ClinicalTrials.gov NCT05253651: https://clinicaltrials.gov/study/NCT05253651
- MOUNTAINEER: tucatinib plus trastuzumab for chemotherapy-refractory HER2-positive RAS wild-type metastatic colorectal cancer (Lancet Oncology 2023): https://doi.org/10.1016/S1470-2045(23)00150-X

## Connected records

- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/), [HER2-amplified colorectal cancer](https://onco.cc/cancers/her2-amplified-colorectal/)
- technologies: [HER2 tyrosine kinase inhibitors](https://onco.cc/technologies/her2-tyrosine-kinase-inhibitors/), [Monoclonal antibodies](https://onco.cc/technologies/monoclonal-antibody/), [Small-molecule kinase inhibitors](https://onco.cc/technologies/kinase-inhibitors/)
- targets: [HER2](https://onco.cc/targets/her2/)
- drugs: [Bevacizumab](https://onco.cc/drugs/bevacizumab/), [Cetuximab](https://onco.cc/drugs/cetuximab/), [FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/), [Oxaliplatin](https://onco.cc/drugs/oxaliplatin/), [Trastuzumab](https://onco.cc/drugs/trastuzumab/), [Tucatinib](https://onco.cc/drugs/tucatinib/)
- companies: [Pfizer (incl. Seagen)](https://onco.cc/companies/pfizer/)
- trials: [DESTINY-CRC02](https://onco.cc/trials/destiny-crc02/), [MOUNTAINEER](https://onco.cc/trials/mountaineer/)

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