BioNTech Phase 3 trial meets endpoint amid safety concerns

• BioNTech and DualityBio reported that trastuzumab pamirtecan met the primary endpoint in the global Phase 3 DYNASTY-Breast02 trial, demonstrating a statistically significant but modest improvement in progression-free survival.
• Interstitial lung disease occurred more frequently than in previous trials, including a small proportion of severe and fatal cases, while overall survival data remained immature.
• The companies acknowledged limited potential patient benefit in this treatment setting and plan to review the efficacy and safety findings before determining their next steps.

BioNTech (NASDAQ:BNTX) and DualityBio announced that trastuzumab pamirtecan met the primary endpoint of the global Phase 3 DYNASTY-Breast02 trial in patients with HR-positive, HER2-low metastatic breast cancer.

The investigational antibody-drug conjugate produced a statistically significant but modest improvement in progression-free survival compared with investigator-selected chemotherapy in patients previously treated with endocrine therapy.

Overall survival data remained immature at the interim analysis, preventing firm conclusions about whether trastuzumab pamirtecan extends patients' lives.

Interstitial lung disease occurred more frequently than in earlier trastuzumab pamirtecan studies, with most cases classified as Grade 1 or 2 but some patients experiencing severe or fatal Grade 3–5 events.

BioNTech and DualityBio said the overall efficacy and safety findings suggest limited potential patient benefit in this treatment setting and intend to discuss the data before determining further development steps.

Apart from the increased incidence of interstitial lung disease, the companies reported that the safety profile was generally consistent with previous studies, without other new safety signals.

DYNASTY-Breast02 completed enrollment in February 2026 and evaluates trastuzumab pamirtecan, also known as BNT323/DB-1303, as part of the companies' broader collaboration on HER2-targeted cancer therapies.