DualityBio submitted a Biologics License Application (BLA) to China's National Medical Products Administration (NMPA) for trastuzumab pamirtecan (T-Pam; DB-1303/BNT323), an antibody-drug conjugate (ADC) co-developed with BioNTech, seeking approval as a second-line treatment for adults with unresectable or metastatic HER2-positive breast cancer. The NMPA has accepted the application for review, marking the first regulatory filing for this asset in any jurisdiction for a breast cancer indication.
The filing seeks approval for trastuzumab pamirtecan in patients with HER2-positive unresectable or metastatic breast cancer who have previously received trastuzumab and taxane chemotherapy, the company said. DualityBio has entered a separate commercialization collaboration with 3SBio covering Chinese mainland, Hong Kong, and Macao for multiple indications of the asset.
The BLA is supported by interim data from Study DB-1303-O-3001, a randomized, controlled, open-label, multicenter Phase III trial conducted in China. The study compared trastuzumab pamirtecan against trastuzumab emtansine (T-DM1) in patients previously treated with trastuzumab and taxane chemotherapy. The Independent Data Monitoring Committee determined that the trial met its primary endpoint of statistically significant improvement in progression-free survival, assessed by blinded independent central review, at a pre-specified interim analysis. Full PFS data and overall survival results were not disclosed in the announcement.
The choice of T-DM1 as the comparator reflects the treatment landscape in China, where access and reimbursement dynamics differ from those in Western markets. Globally, trastuzumab deruxtecan (T-DXd) has displaced T-DM1 as the preferred second-line standard following the DESTINY-Breast03 trial, which demonstrated a median PFS of approximately 28.8 months with T-DXd versus 6.8 months with T-DM1. T-DXd received US FDA approval for this setting in 2022 and, in December 2025, received further FDA approval in combination with pertuzumab for first-line HER2-positive metastatic breast cancer. The DB-1303-O-3001 trial's design therefore positions trastuzumab pamirtecan against a comparator that, while still used in China, has been substantially superseded elsewhere. The molecule has been awarded US FDA Fast Track and Breakthrough Therapy designations, though those were granted for endometrial cancer rather than breast cancer.
Trastuzumab pamirtecan is built on DualityBio's DITAC (Duality Immune Toxin Antibody Conjugates) platform and uses a topoisomerase-I inhibitor payload, placing it in the same mechanistic class as T-DXd. The HER2-positive metastatic breast cancer space is now populated by multiple topoisomerase-I inhibitor-based ADCs, and any differentiation for trastuzumab pamirtecan will depend on comparative efficacy, safety profile, and access dynamics in China. BioNTech licensed global rights outside Greater China to two DualityBio ADCs including trastuzumab pamirtecan in a 2023 deal worth over USD 1.5 billion. BioNTech is currently sponsoring global Phase I/II and III trials, respectively, for the molecule in breast cancer and uterine cancer.
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