OS Therapies Inc. (NYSE: OSTX) has advanced key clinical, regulatory, and commercial milestones in the third quarter of 2025, moving closer to bringing its lead candidate OST-HER2 to patients with recurrent, fully resected, pulmonary metastatic osteosarcoma. The company reported final two-year overall survival (OS) data from its 41-patient Phase 2b trial, showing a 2-year OS rate of 75% for OST-HER2 versus 40% in historical controls, with 100% 2-year survival among patients who remained event-free at 12 months, reinforcing durable benefit.
Building on a successful End-of-Phase 2 interaction with the FDA, management is preparing harmonized U.S. and ex-U.S. filings. The company expects to submit a Marketing Authorization Application (MAA) to the UK Medicines and Healthcare products Regulatory Agency (MHRA) around year-end, followed by a Biologics License Application (BLA) to the U.S. FDA in January 2026 under Project Orbis. These submissions are supported by its partnership with Eversana and a launch plan that anticipates initial Priority Review Voucher (PRV) monetization in 2026 and commercial OST-HER2 revenues beginning in early 2027.
Subsequent to quarter-end, the company announced its intent to spin off OS Animal Health (OSAH) into a separately financed, standalone public company in the first half of 2026. OSTX shareholders are expected to receive direct equity participation in the new listing, which targets a substantial U.S. canine osteosarcoma opportunity.
In the third quarter, OS Therapies further clarified the global registration path for OST-HER2. The FDA aligned on safety, non-clinical, and chemistry, manufacturing, and controls (CMC) requirements, with ongoing discussions around applying updated OS-focused oncology guidance to the existing efficacy package. The UK MHRA has accepted the use of historical controls and real-world comparators for a conditional MAA, while the European Medicines Agency (EMA) feedback supports the use of 2-year OS from the Phase 2b trial as the primary efficacy endpoint for conditional approval. The company has secured a UK MHRA pre-MAA meeting and an FDA Type C meeting, both in the fourth quarter of 2025.
For the third quarter of 2025, OS Therapies reported a net loss of $6.9 million compared to $2.9 million in the same period in 2024, driven primarily by higher regulatory and pre-commercial spending ahead of OST-HER2 filings. Cash and equivalents were approximately $1.9 million at quarter end, supplemented by post-quarter proceeds tied to a previously announced approximately $7.8 million warrant exercise and inducement exchange, extending the company's runway into late 2026. During the quarter, OSTX terminated an equity line of credit (ELOC) and established an at-the-market program, adding flexibility as it positions the balance sheet for potential OST-HER2 approval and PRV monetization ahead of the September 30, 2026 sunset date.
Stonegate Capital Partners uses a probability-adjusted discounted cash flow model to value OSTX, returning a valuation range of $5.59 to $7.58 with a midpoint of $6.44. The firm notes that this model is highly levered to the out years due to the long-term nature of OSTX's industry, leading to the potential for dramatic re-ratings as new information becomes available.
