This study is being done to see if tucatinib with ado-trastuzumab emtansine (T-DM1) works better than T-DM1 alone to help patients who have a specific type of breast cancer called HER2 positive breast carcinoma. The breast cancer in this study is either metastatic (spread into other parts of the body) or cannot be removed completely with surgery.
Patients in this study will be randomly assigned to get either tucatinib or placebo (a pill with no medicine). This is a blinded study, so neither patients nor their doctors will know whether a patient gets tucatinib or placebo. All patients in the study will get T-DM1, a drug that is often used to treat this cancer.
Each treatment cycle lasts 21 days. Patients will swallow tucatinib pills or placebo pills two times every day. Patients will get T-DM1 injections from the study site staff on the first day of every cycle.
Randomized, Double-blind, Phase 3 Study of Tucatinib or Placebo in Combination With Ado-trastuzumab Emtansine (T-DM1) for Subjects With Unresectable Locally-advanced or Metastatic HER2+ Breast Cancer (HER2CLIMB-02)
This study is designed to evaluate the efficacy and safety of tucatinib in combination with T-DM1 in subjects with unresectable locally-advanced or metastatic HER2+ breast cancer who have had prior treatment with a taxane and trastuzumab in any setting. Prior pertuzumab treatment is permitted, but not required. Subjects will be randomized in a 1:1 manner to receive 21-day cycles of either tucatinib or placebo in combination with T-DM1.
While on study treatment, subjects will be assessed for progression every 6 weeks for the first 24 weeks, and every 9 weeks thereafter, irrespective of dose holds or interruptions. Study treatment will continue until unacceptable toxicity, disease progression, withdrawal of consent, or study closure. After completion of study treatment and after occurrence of disease progression, subjects in both arms of the study will continue to be followed for survival until study closure or withdrawal of consent.