The BEGONIA platform trial reported unusually deep and durable tumor responses from combining the HER2-directed antibody-drug conjugate trastuzumab deruxtecan with durvalumab and trastuzumab in a phase 1b/2 setting for HER2-low metastatic breast cancer. The coverage frames BEGONIA as one of the most closely watched experiments in oncology, because HER2-low expands the addressable population for antibody-drug conjugates while immunotherapy add-ons aim to sustain response durability. As a platform design, BEGONIA is intended to explore dosing and activity across combinations, and the provided excerpt highlights the clinical quality of responses rather than a safety-only interpretation. For biotech teams working in ADC and ICI combinations, the key takeaway is that the next-generation standard may be tested in HER2-low populations with combination regimens designed to deepen responses from first-line treatment.