Dataset from Phase IB/II Open-label Single Arm Study to Evaluate Safety and Efficacy of Tucatinib in Combination With Palbociclib and Letrozole in Subjects With Hormone Receptor Positive and HER2-positive Metastatic Breast Cancer

This is a multicenter run-in phase Ib / roll-over phase II study of triple targeted drug combination (HER2-targeted small molecule inhibitor tucatinib, CDK4/6 inhibitor palbociclib and aromatase inhibitor letrozole) as a first or second line of therapy in patients with metastatic hormone receptor positive and HER2-positive breast cancer.