OS Therapies Submits OST-HER2 Phase 2b Data for FDA Pre-BLA Meeting, Eyes H2 2026 Approvals
OS Therapies has submitted Phase 2b clinical and biomarker data for OST-HER2 to the FDA for a May 2026 Pre-BLA meeting and plans a confirmatory Phase 3 trial in Australia in Q3 2026. The company expects U.S. Accelerated Approval and EU/UK conditional authorizations in H2 2026.
1. Phase 2b Data Submission
OS Therapies completed the submission of clinical and biomarker data from its Phase 2b OST-HER2 trial in pulmonary metastatic osteosarcoma to the FDA, confirming immune biomarkers as suitable surrogate endpoints for a Biologics License Application under the Accelerated Approval pathway.
2. Regulatory Timeline and Approvals
The company anticipates a Pre-BLA meeting with the FDA in May 2026 and is preparing Marketing Authorization Applications for the EMA and MHRA in April 2026, targeting U.S. Accelerated Approval and EU/UK Conditional Marketing Authorizations in the second half of 2026.
3. Phase 3 Trial Plan
OS Therapies plans to initiate a confirmatory Phase 3 trial of OST-HER2 in Australia in the third quarter of 2026, with protocol reviews scheduled with the FDA, EMA, MHRA and the Australian Therapeutics Goods Administration.
4. Corporate and Financial Highlights
In full-year 2025, the company acquired Ayala’s listeria monocytogenes immunotherapy platform—eliminating $20 million in milestone payments and reducing net royalties to 1.5%—reported 75% two-year overall survival in its Phase 2b trial and raised $5.5 million in Q1 2026.