A Phase 1, Multicenter Trial of Subcutaneous Trastuzumab Deruxtecan in Participants With Metastatic Solid Tumors

Key Inclusion Criteria: 1. Adults ≥18 years or the minimum legal adult age (whichever is greater). 2. a) Disease State: If HER2 status is required for eligibility (for all populations), a documented HER2 test result must be available. Breast Cancer: adults with pathologically documented unresectable or metastatic breast cancer HER2-positive BC: have received a prior anti-HER2-based regimen. For HER2-positive BC participants in Part 2 only, prior anti-HER2 based therapy should have been received in either: * the metastatic setting, or * the neoadjuvant or adjuvant setting and have de…