BioNTech and DualityBio have reported topline results from DYNASTY-Breast02, a global phase 3 clinical trial evaluating trastuzumab pamirtecan (t-pam) in patients with hormone receptor-positive (HR-positive), HER2-low metastatic breast cancer. The study demonstrated a statistically significant but modest improvement in progression-free survival (PFS) compared with chemotherapy, alongside a higher rate of interstitial lung disease (ILD) than observed in earlier trials of the drug.
BioNTech said the available efficacy and safety findings suggest that the candidate’s potential benefits would be limited within the current treatment landscape for this patient population. The companies will discuss the results and determine the next steps for its development.
Differences Between HER2-Directed ADCs
T-pam is an antibody-drug conjugate (ADC) that uses the same anti-HER2 antibody as Enhertu, developed by AstraZeneca and Daiichi Sankyo. The treatments differ in their linker technology and cytotoxic payload. Enhertu was used to define the HER2-low category.
The trial results have raised questions about whether these differences translate into improved clinical outcomes for patients receiving t-pam.
BMO Capital Markets analysts said a statistically significant PFS improvement compared with chemotherapy had been anticipated. However, BioNTech’s announcement did not specify the magnitude of the benefit, prompting the analysts to characterize the findings as a negative development for the candidate.
Lung Disease Findings Raise Concerns
The study identified more cases of ILD than BioNTech had observed in previous trials of t-pam. Most cases were grade 1 or 2, while a small proportion of patients experienced severe or fatal events.
The company declined to provide further details about the safety findings or their potential implications for its other ADC candidates.
BMO analysts said increasing physician sensitivity to pulmonary toxicity associated with HER2-directed ADCs could affect t-pam’s competitive position. They also expressed reduced confidence in the drug’s prospects for HR-positive, HER2-low metastatic breast cancer.
Overall survival data were immature at the interim analysis.
Regulatory Prospects and Development Decisions
Questions about t-pam’s future had emerged before the latest results. During BioNTech’s August earnings call, executives indicated that the candidate’s development path had become less certain amid changes in the treatment landscape, according to BMO analysts.
BioNTech also has data from a registrational cohort of patients with endometrial carcinoma. TD Cowen analysts said a regulatory filing for this indication technically remained on track for 2026. However, they questioned whether the company would seek approval for endometrial cancer alone, given the market’s size, and suggested it might wait to incorporate breast cancer data into the filing package.
Other Pipeline Programs
The findings follow a setback for BioNTech’s mRNA cancer vaccine BNT113, which missed one of its dual primary endpoints in a phase 2/3 clinical trial two weeks earlier.
The company is also awaiting results for gotistobart, an anti-CTLA-4 antibody, while pumitamig, a PD-L1xVEGF-A bispecific, remains central to its longer-term prospects.
At the European Society for Medical Oncology conference, BioNTech presented early data on pumitamig combined with its B7-H3-directed ADC. The company reported “deep tumor shrinkage and responses that deepened beyond initial disease stabilization” in its presentation, describing the findings as encouraging early activity. The results added to the company’s evidence supporting the potential use of pumitamig in combination with ADCs.
BioNTech Reports Modest Benefits in Breast Cancer Trial
BioNTech and its partner DualityBio have reported mixed results from the Phase 3 DYNASTY-Breast02 clinical trial, which evaluated trastuzumab pamirtecan, an experimental antibody-drug conjugate for patients with hormone receptor-positive, HER2-low metastatic breast cancer. Announced on October 26, 2026, the results showed a statistically significant but modest improvement in progression-free survival compared with chemotherapy. Although BioNTech achieved the study’s primary endpoint, the findings raised questions about the treatment’s potential value in an increasingly competitive oncology market.
