OST-HER2 (AOST-2121)

July 6, 2026: OS Therapies, Inc. (NYSE: OSTX) outlined Q3 2026 catalysts for OST-HER2 in prevention/delay of recurrence in fully resected pulmonary metastatic osteosarcoma. The company said it has “full alignment” with EMA, MHRA and Australia’s TGA on requirements for Conditional Marketing Authorisation Applications (CMAAs); remaining key items are 3-year overall survival data and Pediatric Investigation Plans (PIPs). EMA provided a CMAA submission window of September 30, 2026; the company is working with MHRA/TGA on earliest submission timing. A confirmatory Phase 3 trial must be started before CMAAs and is expected to initiate toward end of Q3 2026 (initially Australia). MHRA and TGA will allow Phase 3 initiation using the same drug product batch used in the Phase 2b trial and current U.S. expanded access.

U.S./FDA: OS Therapies said it submitted non-clinical and clinical BLA modules in January 2026 and held a Type C meeting aligning Phase 3 design and other requirements. It is awaiting scheduling of a requested Type B Statistical Methods meeting (to align on efficacy evaluation at 2.5 years, historical control and/or OST-400 comparator, rolling review, and RMAT), followed by an invited Type B pre-BLA meeting in early Fall 2026; it expects 3-year OS data (Fall 2026) to support a complete BLA and is targeting accelerated approval/complete BLA by year-end 2026. FDA accepted its letter of intent for the Commissioner’s National Priority Review Voucher program (Jan 2026).

OS Animal Health: peer-reviewed canine osteosarcoma data (OST-HER2 + radiation) showed significantly improved survival vs radiation alone; a USDA strategy meeting is expected in summer 2026 to pursue return-to-market for canine osteosarcoma.