Tucatinib for the Treatment of Patients with Advanced or Metastatic HER2-Positive Breast Cancer

FDA Approval Summary: Tucatinib for the Treatment of Patients with Advanced or Metastatic HER2-Positive Breast Cancer:

On April 17, 2020, the FDA approved tucatinib in combination with trastuzumab and capecitabine for the treatment of patients with advanced unresectable or metastatic HER2-positive breast cancer, including patients with brain metastases, who have received one or more prior anti-HER2-based regimens in the metastatic setting. This was the first new molecular entity evaluated under Project Orbis, an FDA Oncology Center of Excellence initiative which supports concurrent review of oncology drugs by multiple global health authorities. Approval was based on the HER2CLIMB trial, which randomized patients to receive tucatinib or placebo with trastuzumab and capecitabine. Tucatinib demonstrated efficacy compared to placebo in progression-free survival (PFS) (HR: 0.54, 95% CI: 0.42-0.71, p<0.00001) and overall survival (OS) (HR: 0.66, 95% CI: 0.50-0.87, p=0.00480). Patients with either treated and stable or active brain metastases made up 48% of the study population. PFS in patients with brain metastases confirmed benefit (HR: 0.48, 95% CI: 0.34-0.69, p<0.00001). The benefit in patients with brain metastases allowed for inclusion of this specific population in the indication. Important safety signals included diarrhea and hepatotoxicity which are listed under Warnings and Precautions. This article summarizes the FDA thought process and data supporting the favorable benefit-risk profile and approval of tucatinib.