OSTX · OS Therapies Incorporated

OS Therapies' announcement marks a critical advancement for its lead candidate OST-HER2, an immunotherapy targeting HER2 in recurrent, fully resected pulmonary metastatic osteosarcoma, a rare pediatric cancer with no FDA-approved treatments and stagnant survival rates over 30 years. The EMA's initiation of a rolling review, including selection into the Raw Data Pilot Program, alongside alignments with ATGA on efficacy endpoints, non-clinical, CMC, and safety data, positions the company for potential Conditional Marketing Authorizations in Europe, U.K., and Australia by Q4 2026. Key to this is the acceptance of seroconversion as a surrogate biomarker linked to overall survival improvements shown in Phase 2b data versus historical controls, with updated 2.5-year and 3-year survival data forthcoming. The U.K. MHRA's ATMP designation enhances market access prospects, supporting the company's sales forecast of over $300 million peak in Europe and $50 million in 2027. A confirmatory Phase 3 trial, aligned across regulators and initiating in Australia Q3 2026 using existing drug product, fulfills post-approval requirements. U.S. milestones include Q2 FDA pre-BLA meeting, potential RMAT designation, and BLA submission under Accelerated Approval, enabling Priority Review Voucher monetization via Rare Pediatric Disease Designation. Updates on pipeline candidates OST-504 in prostate cancer and OST-503 expanded to pancreatic cancer underscore platform validation. This progress de-risks OST-HER2's global pathway, potentially accelerating revenue and validating listeria-based immunotherapy approach.