The SAPPHO Study: Sequential Therapy With Curative Intent in de Novo HER2+ Metastatic Breast Cancer

This is an open-label phase II single-arm study to test the efficacy of a regimen of human epidermal growth factor receptor 2 (HER2)-targeted study drugs in participants with HER2-Positive metastatic Breast Cancer (HER2+ MBC). The U.S. Food and Drug Administration (FDA) has approved all the study drugs as a treatment option for metastatic, HER2+ breast cancer. In this study, investigators are planning to give a series of treatments in a row without waiting for disease worsening and then stopping HER2 treatment. The research study procedures include screening for eligibility, study treatment visits, blood tests, tumor biopsies, questionnaires, Computed Tomography (CT) scans, Magnetic Resonance Imaging (MRI) scans, echocardiograms, and electrocardiograms. Participation in this research study is expected to last about 93 weeks (12 weeks for Part A, 18 weeks for Part B, 12 weeks for Part C, and 51 weeks for Part D) for study treatment and approximately three months to ten years for follow up. It is expected that about 72 people will take part in this research study. Seagen Inc. is supporting this study by providing the study drug, tucatinib, and funding.