Study on Tucatinib vs. Placebo with T-DM1 for Advanced or Metastatic HER2+ Breast Cancer

Inclusion Criteria

• Have HER2 positive breast cancer confirmed by a central laboratory.
• Previously treated with a taxane and trastuzumab, either separately or together.
• Cancer has progressed after the last treatment or the patient cannot tolerate the last treatment.
• Have measurable or non-measurable disease that can be assessed by standard criteria.
• Have a performance status score of 0 or 1, indicating full activity or some restriction in strenuous activities.
• Based on a brain MRI, must have one of the following:
  • No evidence of brain metastases.
  • Untreated brain metastases that do not need immediate treatment.
  • Previously treated brain metastases that are stable or have progressed but do not need immediate treatment.
  • If treated for brain metastases, must meet specific timing criteria before starting the study treatment.
• Must provide records of any brain treatment to classify lesions.

Exclusion Criteria

• Have previously been treated with tucatinib, afatinib, trastuzumab deruxtecan, or other investigational anti-HER2 or anti-EGFR drugs.
• Have used lapatinib or neratinib within 12 months of starting the study treatment, unless used for 21 days or less and stopped for reasons other than cancer progression or severe side effects.
• Have used pyrotinib for recurrent breast cancer, unless used for 21 days or less and stopped for reasons other than cancer progression or severe side effects.
• Based on a brain MRI, must not have:
  • Untreated brain lesions larger than 2 cm.
  • Need for ongoing corticosteroids for brain metastases symptoms at a dose higher than 2 mg of dexamethasone daily.
  • Brain lesions that require immediate treatment.
  • Known or concurrent leptomeningeal disease.
  • Poorly controlled seizures.