A Study of Tucatinib Plus Trastuzumab Deruxtecan in HER2+ Breast Cancer


About this study

This trial studies how well the drug tucatinib works when given with trastuzumab deruxtecan. It will also look at what side effects happen when these drugs are given together. A side effect is anything a drug does besides treating cancer. Participants in this trial have HER2-positive (HER2+) breast cancer that has either spread to other parts of the body (metastatic) or cannot be removed completely with surgery (unresectable). All participants will get both tucatinib and trastuzumab deruxtecan.

Participation eligibility

Participant eligibility includes age, gender, type and stage of disease, and previous treatments or health concerns. Guidelines differ from study to study, and identify who can or cannot participate. There is no guarantee that every individual who qualifies and wants to participate in a trial will be enrolled. Contact the study team to discuss study eligibility and potential participation.

Inclusion Criteria:

  • Have confirmed HER2+ breast cancer, as defined by the current American Society of Clinical Oncology - College of American Pathologists (ASCO/CAP) guidelines, previously determined at a Clinical Laboratory Improvements Amendments (CLIA)-certified or International Organization for Standardization (ISO)-accredited laboratory.
  • Have received 2 or more prior anti-HER2-based regimens in the metastatic setting.
  • Have progression of unresectable LA/M breast cancer after last systemic therapy (as confirmed by investigator), or be intolerant of last systemic therapy.
  • Have measurable disease assessable by RECIST v1.1.
  • Be at least 18 years of age at time of consent.
  • Have Eastern Cooperative Oncology Group Performance Status (ECOG PS) 0 or 1.
  • Have a life expectancy of at least 6 months, in the opinion of the investigator.
  • Based on medical history and screening contrast brain magnetic resonance imaging (MRI), participants with a history of brain metastases must have one of the following:
    • Untreated brain metastases not needing immediate local therapy. For participants with untreated central nervous system (CNS) lesions > 2.0 cm on screening contrast brain MRI, discussion with and approval from the medical monitor is required prior to enrollment;
    • Previously treated brain metastases;
    • Brain metastases previously treated with local therapy may either be stable since treatment or may have progressed since prior local CNS therapy, provided that there is no clinical indication for immediate re-treatment with local therapy in the opinion of the investigator;
    • Participants treated with CNS local therapy for newly identified or previously treated progressing lesions found on contrast brain MRI performed during screening for this study may be eligible to enroll if all of the following criteria are met:
      • Time since whole brain radiation therapy (WBRT) is ≥ 14 days prior to first dose of study treatment, time since stereotactic radiosurgery (SRS) is ≥ 7 days prior to first dose of study treatment, or time since surgical resection is ≥ 28 days. Other sites of measurable disease by RECIST v1.1 are present.
      • Relevant records of any CNS treatment must be available.
  • Relevant records of any CNS treatment must be available to allow for classification of target and nontarget lesions.

Exclusion Criteria:

  • Have previously been treated with:
    • Lapatinib or neratinib within 12 months of starting study treatment (except in cases where lapatinib or neratinib was given for ≤ 21 days and was discontinued for reasons other than disease progression or severe toxicity); 
    • Tucatinib or enrolled on a tucatinib clinical trial;
    • Any investigational HER2/epidermal growth factor receptor (EGFR) or HER2 tyrosine kinase inhibitor (TKI) (e.g., afatinib) at any time previously;
    • Trastuzumab deruxtecan or another antibody-drug conjugate (ADC) consisting of an exatecan derivative.
  • Have received treatment with:
    • Any systemic anti-cancer therapy (including hormonal therapy) or experimental agent  ≤ 21 days of first dose of study treatment or are currently participating in another interventional clinical trial. An exception for the washout of hormonal therapies is gonadotropin releasing hormone (GnRH) agonists used for ovarian suppression in premenopausal women, which are permitted concomitant medications;
    • Treatment with non-CNS radiation ≤ 7 days prior to first dose of study treatment;
    • Major surgery < 28 days of first dose of study treatment.
  • Have clinically significant cardiopulmonary disease (such as history of iterstitial lung disease (ILD)/pneumonitis that required systemic corticosteroids, or have current ILD/pneumonitis, or where suspected ILD /pneumonitis cannot be ruled out be imaging at screening).
  • Have known myocardial infarction or unstable angina within 6 months prior to first dose of study treatment.
  • Known to be positive for hepatitis B by surface antigen expression. Known to be positive for hepatitis C infection. Participants who have been treated for hepatitis C infection are permitted if they have documented sustained virologic response of 12 weeks.
  • Presence of known chronic liver disease.
  • Known to be positive for human immunodeficiency virus (HIV).
  • Active or uncontrolled clinically serious infection.
  • Are pregnant, breastfeeding, or planning a pregnancy.
  • Have inability to swallow pills or significant gastrointestinal disease which would preclude the adequate oral absorption of medications.

Participating Mayo Clinic locations

Study statuses change often. Please contact the study team for the most up-to-date information regarding possible participation.

Mayo Clinic Location Status Contact

Rochester, Minn.

Mayo Clinic principal investigator

Ciara O'Sullivan, M.B., B.Ch.

Contact us for the latest status

Contact information:

Cancer Center Clinical Trials Referral Office

(855) 776-0015

More information


Publications are currently not available

Study Results Summary

Not yet available

Supplemental Study Information

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