OS Therapies Plans Dual UK US OST-HER2 Regulatory Filings 2025

OS Therapies Inc. is advancing regulatory submissions for OST-HER2, a cancer immunotherapy targeting recurrent, fully resected, pulmonary metastatic osteosarcoma. The company has updated its filing sequence to prioritize a conditional Marketing Authorisation Application (MAA) with the UK Medicines and Healthcare products Regulatory Agency (MHRA), which follows positive feedback from an August 2025 Scientific Advice Meeting. The MHRA has accepted the use of a historical control arm for the conditional MAA, expected to be submitted by December 2025. Shortly after, OS Therapies plans to submit a Biologics Licensing Application (BLA) to the US Food and Drug Administration (FDA) under the Accelerated Approval program, anticipated in January 2026. The company intends to propose an immune activation biomarker combined with overall survival data as a surrogate efficacy endpoint to support this accelerated approval. These coordinated submissions aim to expedite access to OST-HER2 based on promising Phase 2b clinical trial data currently in long-term follow-up.