| Active, not recruiting | 3 | 654 | Europe, Canada, Japan, US, RoW | Tucatinib, TUKYSA, ONT-380, ARRY-380, Trastuzumab, Herceptin, Herceptin Hylecta, Pertuzumab, Perjeta, Combination product: Trastuzumab + Pertuzumab, Phesgo, Placebo | Seagen Inc., Merck Sharp & Dohme LLC | HER2 Positive Breast Cancer | 05/25 | 10/27 | | |