BEGONIA, a phase 1b/2 platform trial, reported durable responses by pairing durvalumab with trastuzumab deruxtecan in women with HER2-low metastatic breast cancer. The study framework is designed to test an immunotherapy plus an antibody-drug conjugate approach in a disease subset where treatment options have been expanding but outcomes remain variable. The combination’s early signals—described as unusually deep and durable for a first-line setting—place the regimen into the growing race for next-generation HER2-low strategies. On the development side, BEGONIA’s readouts signal continuing interest in checkpoint inhibition to enhance ADC-driven tumor control, while the platform structure allows follow-on cohorts to refine patient selection and dosing.