The Global Colon Cancer Association has partnered with Seagen Inc. to raise awareness of clinical trials, specifically the MOUNTAINEER study.


MOUNTAINEER is a phase II trial for people diagnosed with metastatic or unresectable HER2-positive colorectal cancer.


This trial studies how the drug tucatinib works and how safe it is when given with trastuzumab and when given by itself.


The use of tucatinib described here is experimental. Because of that, not all risks are known before starting a clinical trial.




Phase: Phase II


ClinicalTrials.gov ID Numberhttps://clinicaltrials.gov/ct2/show/NCT03043313


Sponsor of the Clinical Trial: Seagen Inc.


Study Website: www.MOUNTAINEERSTUDY.com


Who is the trial for?


The MOUNTAINEER trial is currently enrolling people diagnosed with metastatic or unresectable HER2-positive colorectal cancer. The cancer must have previously been treated with fluoropyrimidines (e.g., 5-fluorouracil or capecitabine), oxaliplatin, irinotecan, and anti-VEGF antibodies (bevacizumab, ramucirumab, or ziv-aflibercept).


Doctors call cancer that can’t be completely removed with surgery unresectable. Metastatic cancer is cancer that has spread to parts of the body away from the colon or rectum, such as the bones or liver.


Why is the trial is being done?


Some people with metastatic colorectal cancer may have a protein on their tumor called human epidermal growth factor receptor 2 (HER2). This protein promotes the growth and spread of cancer cells. This study uses experimental treatments that target HER2 proteins to kill the cancer cells.


Tucatinib is a tyrosine kinase inhibitor, which is approved to treat HER2-positive breast cancer. Tyrosine kinases are enzymes that help control how cells grow and divide, among other functions. If there is an increase in the amount of the enzyme due to an increase in the number of HER2 proteins expressed on the cancer cell, it can make the cells grow uncontrollably.  Tucatinib blocks the enzyme that is responsible for triggering survival pathways for the cancer cell, thereby stopping the cells from growing and spreading.

The study also uses a drug called trastuzumab, which is approved to treat HER2-positive breast and stomach cancer.


The use of tucatinib and trastuzumab described here is considered experimental.


MOUNTAINEER is a trial looking to see how the drug tucatinib works and how safe it is when given with trastuzumab and when given by itself.


Tucatinib is a pill taken by mouth. Trastuzumab is given intravenously, which means the medicine is delivered directly into your bloodstream through an IV or port.


MOUNTAINEER is an open-label study. An open-label study means both the researcher and the participant will know the treatment they are receiving. Participants in this study will be randomly assigned to get either tucatinib or tucatinib with trastuzumab.  Patients that start on trial receiving tucatinib may have the opportunity to receive tucatinib with trastuzumab if their cancer is not responding to therapy.


In the MOUNTAINEER trial, everyone in the study will take tucatinib twice per day. Participants who take part in the study who also get trastuzumab will get it as an infusion once every 3 weeks. Cycles will continue until a person’s cancer worsens, a person experiences a side effect that requires treatment to stop, or they decide they no longer want to participate in the trial.


Specific Eligibility Requirements:


People are eligible for the MOUNTAINEER trial if they:

  • They are 18 years and older and have been diagnosed with HER2-positive colorectal cancer that has come back after treatment or has spread to parts of the body away.

  • Have no RAS mutations present in their tumor

  • Have already been treated with fluoropyrimidines, oxaliplatin, irinotecan, and anti-VEGF antibodies


People are not eligible for the MOUNTAINEER trial if they:


  • Been previously treated with an anti-HER2 therapy

  • have a history of significant lung or heart disease

  • are pregnant, breastfeeding, or plan to become pregnant during the study or 7 months after the last dose of medicine during the study


There are additional eligibility requirements for this study. Contact your doctor if you are unsure of your eligibility. You can also contact a study doctor who will review the criteria with you and help determine your eligibility.


Potential side effects of the treatment being studied.


The most common side effects of tucatinib are:

  • nausea

  • diarrhea

  • fatigue

  • high liver enzyme levels

  • rash

  • vomiting

  • increased creatinine levels


In earlier studies, side effects of tucatinib in combination with trastuzumab (in addition to the ones listed above) were:


  • infusion-related reactions

  • low platelet counts

  • hypertension

Study Locations

The MOUNTAINEER trial is being conducted at multiple sites around the world and the United States. For a complete list of open sites, visit www.MOUNTAINEERSTUDY.com


For more information on detailed eligibility requirements or to enroll:

Visit the www.MOUNTAINEERSTUDY.com. You also may email clinicaltrials@seagen.com or call 1-866-333-7436.

More Information on Clinical Trials :

For more information about joining a clinical trial, frequently asked questions, a glossary of clinical trial terms, and links to colorectal cancer clinical trial finders, visit the GCCA's Clinical Trial Awareness Page. 


Thank you to our sponsor.

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