A Two-part, Seamless, Multicenter, Randomized, Open-label, Adaptive Phase II/III Study of the Blood-brain Barrier Penetrant RO7771950 Versus Tucatinib, Both in Combination With Trastuzumab and Capecitabine, in Patients With Pretreated Unresectable Locally Advanced or Metastatic HER2-Positive Breast Cancer, With or Without Central Nervous System Metastases

Inclusion Criteria: * Pathologically documented locally advanced inoperable (LAI) or metastatic breast cancer (MBC) with confirmed HER2-positive status by central laboratory. * Measurable disease as per by RECIST v1.1 in stage 1. Non-measurable disease allowed in stage 2. * Previously treated (stable or progressive) or previously untreated CNS metastases, or leptomeningeal metastases. * At least one prior line of anti-HER2-based therapy for LAI or metastatic disease. * Prior anti-HER2 antibody-drug conjugate (ADC), such as trastuzumab-deruxtecan (T-DXd) or trastuzumab emtansine (T-DM1), in an…