Trastuzumab pamirtecan (BNT323/DB-1303)
Overview
A HER2-targeted antibody-drug conjugate (third-generation topoisomerase-1 inhibitor payload) co-developed with China's DualityBio - BioNTech's lead candidate for its first-ever cancer-drug regulatory submission, being tested in HER2-expressing endometrial cancer and HER2-positive breast cancer.
Phase 2 data (cutoff October 17, 2025) showed a 47.9% objective response rate in HER2-expressing advanced/recurrent endometrial cancer (exceeding 70% in IHC 3+ patients), with 8.0-month median progression-free survival and 15.0-month median overall survival; additional ESMO Gynaecological Cancers Congress 2026 data (June 2026) confirmed durable activity and a manageable safety profile, and the registrational endometrial-cancer cohort is now fully recruited. A separate pivotal Phase 3 trial (DB-1303-O-3001) in HER2-positive metastatic/unresectable breast cancer met its primary endpoint of progression-free survival versus trastuzumab emtansine (T-DM1); on that data, partner DualityBio's China BLA for the breast-cancer indication was accepted for review by the NMPA on April 9, 2026 - the first regulatory filing acceptance anywhere for the asset. The endometrial-cancer indication has not yet been filed anywhere; BioNTech and DualityBio are still determining the optimal US regulatory path across both indications, with a US BLA filing still planned for 2026.