BioNTech's trastuzumab pamirtecan shows modest PFS benefit in HER2-low breast cancer
A Phase 3 trial for BioNTech and DualityBio's antibody-drug conjugate trastuzumab pamirtecan met its primary endpoint, delaying tumor progression in HER2-low metastatic breast cancer, though safety concerns and immature survival data temper its impact.
BioNTech and DualityBio's trastuzumab pamirtecan has demonstrated a statistically significant improvement in progression-free survival for patients with HER2-low metastatic breast cancer. The global, randomized, multi-center, open-label Phase 3 trial, known as DYNASTY-Breast02, met its primary endpoint in 541 chemotherapy-naïve patients.
The trial randomized patients with HER2-low expression, defined as IHC 2+/ISH- or IHC 1+, in a one-to-one ratio to receive either the investigational antibody-drug conjugate or a standard chemotherapy chosen by the investigator. The available chemotherapy options were capecitabine, paclitaxel, or nab-paclitaxel. While the trial successfully delayed tumor progression, the observed benefit was described as modest. Overall survival data were not mature at the time of the interim analysis, meaning the trial had not run long enough to detect a clear survival benefit. The combined findings suggest the potential benefit to patients may be limited given the current treatment landscape for HER2-low metastatic breast cancer.
Safety concerns persist with new ADC therapy
The treatment was associated with a higher rate of interstitial lung disease compared to what was seen in earlier testing. Most of these cases were low-grade, but a small proportion of patients experienced severe and even fatal events. The overall safety profile was consistent with prior trials of the drug, with no new safety signals identified.
ADC innovation advances cancer care landscape
Trastuzumab pamirtecan is a third-generation antibody-drug conjugate targeting HER2, developed using DualityBio's DITAC platform. ADCs have become a mainstay of targeted cancer care and have been able to supplant traditional chemotherapy in some tumor types. This drug is also being studied in other cancer settings, including a late-stage trial for HER2-expressing recurrent endometrial cancer and an early-stage trial for advanced metastatic solid tumors.
BioNTech expands ADC pipeline through strategic deal
BioNTech obtained rights to trastuzumab pamirtecan through a 2023 licensing deal with DualityBio worth potentially more than $1.6 billion. This agreement marked BioNTech's first foray into the antibody-drug conjugate field. The companies are now evaluating the results from the DYNASTY-Breast02 trial and planning their next steps. The established treatment in this space is AstraZeneca and Daiichi Sankyo's Enhertu, which was approved for HER2-low breast cancer in 2022 and later expanded to include tumors with 'ultralow' HER2 expression in 2025.
