OS Therapies Seeks Patent for Biomarker Surrogate Endpoint Linked to 1-Year EFS, 2-Year OS
OS Therapies filed a patent application for a biomarker signature in its OST-HER2 Phase 2b trial that met FDA BEST criteria as a surrogate endpoint for 1-year event-free survival and 2-year overall survival in metastatic osteosarcoma. The company plans an EMA market access filing April 30, 2026 and Q2 meetings with FDA, EMA, MHRA and TGA.
1. Patent Application for Immune Signature
OS Therapies filed a new patent covering a treatment-emergent immune signature from its Listeria-based OST-HER2 platform in Phase 2b osteosarcoma patients. Claims focus on downregulation of tumor immune evasion genes and upregulation of cytotoxic immune activation genes, which correlated with improved anti-tumor cellular immunity.
2. Biomarker Meets FDA Surrogate Endpoint Criteria
The identified signature satisfies FDA’s BEST program pharmacodynamic/response criteria as a surrogate endpoint for 1-year event-free survival and 2-year overall survival in fully resected, pulmonary metastatic osteosarcoma. In the trial, 100% of patients achieving 1-year EFS exhibited this signature and subsequently reached 2-year OS.
3. Regulatory Path and Next Steps
A conference call is scheduled for late April 2026 to review biomarker data and discuss implications for upcoming Q2 meetings with FDA, EMA, MHRA and TGA. The company will submit its first complete OST-HER2 market access filing to the EMA on April 30, 2026 and aims for a BLA under Accelerated Approval in H2 2026, with potential Priority Review Voucher value around $205 million.