OS Therapies Advances Key Cancer Treatment Toward Regulatory Filings and Plans Animal Health Spin-off
OS Therapies Inc. is progressing its lead cancer drug OST-HER2 toward U.S. and U.K. regulatory submissions while planning to spin off its animal health division into a separate public company, potentially creating significant value for shareholders.
Stonegate Capital Partners has updated its coverage of OS Therapies Inc. (NYSE: OSTX), highlighting the company's advancement of key clinical, regulatory, and commercial milestones in the third quarter of 2025. The company is moving closer to bringing its lead asset, OST-HER2, to patients with recurrent, fully resected, pulmonary metastatic osteosarcoma, a rare and aggressive bone cancer.
Final two-year overall survival data from the 41-patient Phase 2b trial showed a two-year OS rate of 75% for OST-HER2 compared to 40% in historical controls. Notably, 100% of patients who were event-free at 12 months survived to the two-year mark, reinforcing the treatment's durable benefit. Building on a successful End-of-Phase 2 interaction with regulators, management is preparing harmonized U.S. and ex-U.S. filings. Submissions to the UK Medicines and Healthcare products Regulatory Agency (MHRA) and the U.S. Food and Drug Administration (FDA) are expected around year-end.
The regulatory pathway has been clarified, with the FDA aligned on safety, non-clinical, and Chemistry, Manufacturing, and Controls (CMC) requirements. Discussions are ongoing regarding the application of updated oncology guidance focused on overall survival to the existing efficacy package. In parallel, the UK MHRA has accepted the use of historical controls and real-world comparators for a conditional Marketing Authorisation Application (MAA). The European Medicines Agency (EMA) has provided feedback supporting the use of the two-year overall survival data 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 scheduled for the fourth quarter of 2025, with plans for a UK MAA submission and a U.S. Biologics License Application (BLA) filing in January 2026 under Project Orbis.
Commercially, the launch plan is supported by a partnership with Eversana. It anticipates initial Priority Review Voucher (PRV) monetization in 2026 and commercial OST-HER2 revenues beginning in early 2027. Subsequent to the quarter's 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 the substantial U.S. canine osteosarcoma market.
Financially, OS Therapies reported a net loss of $6.9 million for the third quarter of 2025, compared to $2.9 million in the same period last year. This increase was driven primarily by higher regulatory and pre-commercial spending ahead of the OST-HER2 filings. Cash and equivalents were approximately $1.9 million at quarter-end, supplemented by post-quarter proceeds from a previously announced warrant exercise and inducement exchange totaling approximately $7.8 million. This extends the company's financial runway into late 2026. During the quarter, OSTX terminated an Equity Line of Credit (ELOC) and established an at-the-market (ATM) equity program, adding flexibility as it positions its balance sheet for potential OST-HER2 approval and PRV monetization ahead of the September 30, 2026 sunset date for the voucher.
Beyond OST-HER2, the company continues to leverage its acquired Ayala/Advaxis listeria platform. The OST-504 Phase 1b trial in biochemically recurrent prostate cancer has completed its last patient visit, with an initial data readout expected in the fourth quarter of 2025. Stonegate's valuation model, a probability-adjusted Discounted Cash Flow model, returns a valuation range of $5.59 to $7.58 for OSTX, with a midpoint of $6.44. The firm notes the model is highly leveraged to future years due to the long-term nature of the industry, leading to the potential for significant re-ratings as new clinical and regulatory information becomes available.