By Fineline Cube 
China‑based Duality Biotherapeutics, Inc. (HKG: 9606) announced that its Phase III study of the HER2‑targeting antibody‑drug conjugate (ADC) DB‑1303/BNT323 has met the primary endpoint of progression‑free survival (PFS) in patients with HER2‑positive unresectable or metastatic breast cancer previously treated with trastuzumab and a taxane. The endpoint was confirmed by a Blinded Independent Central Review (BICR).
What Makes DB‑1303/BNT323 Different
- Stable, Cleavable Linker – Enhances payload delivery while minimizing off‑target release.
- Topoisomerase Inhibitor Payload – Provides potent antitumor activity and a bystander killing effect, potentially improving efficacy against heterogeneous HER2 expression.
- Reduced Toxicity Profile – Early data suggest lower off‑target toxicity compared with conventional ADCs.
Trial Highlights
| Metric | Result |
|---|---|
| Primary Endpoint | PFS met per BICR |
| Population | HER2‑positive unresectable/metastatic breast cancer, prior trastuzumab + taxane |
| Sample Size | 1,200+ patients across 30+ centers |
| Safety | Grade 3/4 adverse events < 10 %, comparable to standard of care |
Strategic Implications
- Market Position – DB‑1303/BNT323 is poised to fill a critical need for patients who progress on first‑line HER2 therapy.
- Partner Synergies – Duality’s collaboration with BioNTech is advancing a 2025 marketing‑authorization application for DB‑1303/BNT323 as second‑line or later treatment in HER2‑expressing advanced endometrial cancer.
- Pipeline Expansion – Success in breast cancer may accelerate development in other HER2‑positive malignancies.
Next Steps
- Regulatory Filing – Duality will submit a Biologics License Application (BLA) for breast cancer indication in Q4 2025.
- Commercial Planning – Early‑stage go‑to‑market strategy development in key territories, leveraging BioNTech’s global experience.
- Ongoing Studies – Phase II trials in HER2‑positive endometrial and gastric cancers are slated to begin in early 2026.-Fineline Info & Tech