Duality Biotherapeutics and BioNTech Report Global Phase III Data for Trastuzumab Pamitamab, Hitting Primary Endpoint Below Expectations

On October 26, 2026, Duality Biotherapeutics and BioNTech announced topline data from the global Phase III DYNASTY-Breast02 trial of trastuzumab pamitamab (DB-1303/BNT323), which met its primary endpoint but fell short of expectations. The global multicenter, randomized, open-label Phase III trial enrolled 541 patients with HR-positive, HER2-low metastatic breast cancer, randomized 1:1 to trastuzumab pamitamab or single-agent chemotherapy of investigator's choice. All patients had progressed on endocrine therapy and had not received prior chemotherapy.