Enroll in Research > Research Search & Enroll Tool > Tucatinib Plus Trastuzumab in Patients With HER2+ Colorectal Cancer (MOUNTAINEER)
Tucatinib Plus Trastuzumab in Patients With HER2+ Colorectal Cancer (MOUNTAINEER)

Tucatinib Plus Trastuzumab in Patients With HER2+ Colorectal Cancer (MOUNTAINEER)

Clinicaltrials.gov identifier:


Study Contact Information:

For more information, contact Seagen Trial Information Support at 866-333-7436 or by email

Tucatinib Plus Trastuzumab in Patients With HER2+ Colorectal Cancer (MOUNTAINEER)

About the Study

This is a study for people who have been diagnosed with HER2-positive (HER2+) metastatic colorectal cancer (mCRC).  The goal of this study is to look at how well the drug tucatinib (Tukysa) works to improve outcomes when given with trastuzumab (Herceptin), versus how well tucatinib works when administered by itself.

Type of Study

The study participants will be placed into one of two groups

  • Participants will be assigned to either Group B or Group C (Group A, a non-randomized group has completed enrollment). 
    • Group B: Participants in this group receivea combination of the study drugs tucatinib and trastuzumab.
    • Group C: Participants in this group receive study drug tucatinib alone.
  • The study is open-label, all patients will know which group they have been placed into. 

What the Study Entails

Group B treatment

Participants in Group B will take tucatinib twice per day orally on Days 1-21, and trastuzumab intravenously on Day 1. Cycles repeat every 21 days.

Group C treatment

Participants in Group C will take tucatinib twice per day orally every day. Participants who do not respond to tucatinib monotherapy may have the option to receive combination tucatinib and trastuzumab therapy.


Participants will be followed for up to approximately 4 years.

Study Sites

Arizona California Colorado District of Columbia Florida
Georgia Illinois Iowa Kansas Massachussets
Minnesota Nevada New York North Carolina Ohio
Tennessee Texas Utah Washington  Wisconsin



  • Phoenix: Mayo Clinic Arizona  
    Contact: Theresa Araque by phone at 480-301-2048 or by email          


  • Los Angeles: Keck Medical Center / University of Southern California     
    Contact: Rabia Rehman by phone at 323-865-0460 or by email
  • Los Angeles: Cedars Sinai Medical Center / Samuel Oschin Comprehensive Cancer Institute     
    Contact: Brian Minton by email
  • Santa Rosa: Saint Joseph Heritage Medical Group
    Contact: Kayla Cordes by phone at 707-521-3830 or by email     
    Contact: Kimberly Young by phone at 707-521-3830 or by email     


  • Aurora: Rocky Mountain Cancer Centers - Aurora    
    Principal Investigator: Sujatha Nallapareddy      

District of Columbia

  • Washington DC: Lombardi Cancer Center / Georgetown University Medical Center 
    Principal Investigator: Benjamin Weinberg


  • Fort Myers: Florida Cancer Specialists - South Region     
    Contact: Lynn Bentz by phone 941-363-5713 or by email 
  • St. Petersburg: Florida Cancer Specialists - North Region     
    Contact: Margie Simonetta by phone 727-821-0017 or by email      


  • Atlanta: Winship Cancer Institute/Emory University School of Medicine     
    Contact: Sunisha Thomas by phone 404-778-1900 or by email     


  • Chicago: University of Chicago Medical Center
    Contact: Alex (Ryan) El-Naggar by phone: 773-702-7763 or by email      


  • Iowa City: University of Iowa Hospitals and Clinics       
    Principal Investigator: Pashtoon Kasi    


  • Westwood: University of Kansas Cancer Center  
    Contact: Kayra Thompson by phone 913-588-6029 or by email        


  • Boston: Massachusetts General Hospital     
    Contact: Amy Gisondi by phone 617-724-4000 or by email     
    Contact: Ashley O'Meara by phone 617-724-4000 or by email 
  • Boston: Dana Farber Cancer Institute
    Contact: GI Clinical Research Line by phone 617-632-5960 


  • Detroit: Karmanos Cancer Institute / Wayne State University          
    Principal Investigator: Anthony Shields


  • Rochester: Mayo Clinic Rochester           
    Contact: Lucas Hamann by phone 507-284-0923 or by email       


  • Las Vegas: Comprehensive Cancer Centers of Nevada  
    Principal Investigator: Fadi Braiteh      

New York

  • Buffalo: Roswell Park Cancer Institute
    Contact: Karen Hicks by phone 716-845-8947 or by email     
  • New York City: Memorial Sloan Kettering Cancer Center     
    Contact: Jill Weiss by phone 646-227-3010 or by email             

North Carolina

  • Durham: Duke University Medical Center       
    Contact: Ireka Burrus by phone 919-668-1861 or by email          


  • Cleveland: Case Western Reserve University / University Hospitals Cleveland Medical Center
    Contact: Brenda Hovanec by phone 216-844-8573 or by email         


  • Portland: Oregon Health and Science University         
    Contact: Erin Taber by phone 503-494-3606 or by email      


  • Pittsburgh: Allegheny General Hospital  
    Contact: Luann Healy by phone 412-359-6147 or by email      


  • Nashville: Tennessee Oncology-Nashville/Sarah Cannon Research Institute   
    Contact: Rita Baker by email
  • Nashville: Vanderbilt University Medical Center          
    Principal Investigator: Kristen Ciombor    


  • Dallas: Texas Oncology - Baylor Sammons Cancer Center   
    Principal Investigator: Andrew Scott Paulson
  • Lubbock: Joe Arrington Cancer Research and Treatment Center        
    Contact: Sonia Salas by phone 806-725-8000 or by email
  • McAllen: Texas Oncology - McAllen     
    Principal Investigator: Suresh Ratnam
  • Tyler: Texas Oncology - Tyler          
    Principal Investigator: Donald Richards  


  • Salt Lake City: Huntsman Cancer Institute/University of Utah        
    Contact: Ashley Leary by phone 801-213-8429 or by email     


  • Everett: Providence Regional Medical Center Everett
    Principal Investigator: Ajay Kundra
  • Seattle: Seattle Cancer Care Alliance / University of Washington    
    Contact: Sean Park by phone 206-606-6439 or by email      


  • Milwaukee: Aurora Research Institute Cancer Center     
    Contact: Kevin Morrow by phone 414-646-9826 or by email         
This Study is Open To:

People, age 18 years or older, are eligible if they have:

  • HER2-positive metastatic colon or rectum cancer
  • Received and recurred or progressed after prior cancer therapy 
  • Tumor testing shows absence of KRAS or NRAS mutations
  • Able to provide most recently available tumor tissue sample obtained prior to any treatment initiation (or else able to undergo a new biopsy)
  • Have at least one site of disease that has not been previously irradiated, or evidence of disease progression after receiving radiation
  • Life expectancy greater than 3 months
This Study is Not Open To:
  • Those who have had previous treatment with anti-HER2 targeting therapies
  • Patients with toxicity related to prior cancer therapies that has not resolved sufficiently
  • Those with clinically significant cardiopulmonary disease, or have had a cardiac surgery within 6 months prior to first dose of study treatment
  • Those with Hepatitis B or Hepatitis C
  • Those who are HIV positive
  • Patients who are unable to swallow pills or have significant gastrointestinal disease which would prevent adequate oral absorption of study medications
  • Those with known Central Nervous System metastasis