Title:  An open-label randomized phase 3 study of tucatinib in combination with trastuzumab and mFOLFOX6 versus mFOLFOX6 given with or without either cetuximab or bevacizumab as first-line treatment for subjects with HER2+ metastatic colorectal cancer

Study Director: Jorge Ramos, DO, of Seagen Inc.

Description: Researchers are conducting a phase 3 trial to compare standard care with combination tucatinib, trastuzumab, and chemotherapy as first-line treatment in HER2-positive, unresectable or metastatic colorectal cancer (CRC).

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Patients in the standard care arm will receive fluorouracil, oxaliplatin, and leucovorin/levoleucorvorin (mFOLFOX6) alone, mFOLFOX6 in combination with bevacizumab, or mFOLFOX6 in combination with cetuximab. Bevacizumab will be given intravenously at a dose of 5 mg/kg every 2 weeks. Cetuximab will be given intravenously at a loading dose of 400 mg/m2 on day 1 of cycle 1, followed by a weekly dose of 250 mg/m2.

Patients in the experimental arm will receive tucatinib, trastuzumab, and mFOLFOX6. Tucatinib will be administered at a dose of 300 mg by mouth twice daily. On day 1 of cycle 1, trastuzumab will be given intravenously at a loading dose of 8 mg/kg, followed by a dose of 6 mg/kg given every 3 weeks.

The primary endpoint is progression-free survival by blinded independent central review. Secondary endpoints include overall survival, objective response rate, duration of response, adverse events, and more.

To be eligible for this trial, patients must be 18 years of age or older. They must have histologically and/or cytologically confirmed unresectable and/or metastatic CRC. They must have HER2-positive and RAS wild-type disease. For a complete list of eligibility criteria, please see the reference.

Status: Recruiting

This trial is sponsored by Seagen Inc. and Merck Sharp & Dohme LLC.


ClinicalTrials.gov. A study of tucatinib with trastuzumab and mFOLFOX6 versus standard of care treatment in first-line HER2+ metastatic colorectal cancer (MOUNTAINEER-03). NCT05253651. Accessed March 23, 2023.