OS Therapies Advances Osteosarcoma Treatment Toward Regulatory Submissions

Stonegate Capital Partners has updated coverage on OS Therapies Inc. (NYSE: OSTX) following the company's third quarter 2025 achievements. The biopharmaceutical company advanced key clinical, regulatory, and commercial milestones as it moves closer to bringing OST-HER2 to patients with recurrent, fully resected, pulmonary metastatic osteosarcoma. Final 2-year overall survival data from the 41-patient Phase 2b trial demonstrated a 75% survival rate for OST-HER2 compared to 40% in historical controls, with 100% 2-year survival among patients event-free at 12 months, reinforcing durable benefit.

Building on a successful End-of-Phase 2 interaction, management is preparing harmonized U.S. and international filings with UK MHRA and FDA submissions expected around year-end. This regulatory progress is supported by the company's Eversana partnership and a launch plan that anticipates initial Priority Review Voucher monetization in 2026 and commercial OST-HER2 revenues beginning in early 2027. The company has secured both a UK MHRA pre-MAA meeting and an FDA Type C meeting in the fourth quarter of 2025, providing plans for a UK Marketing Authorization Application submission and a U.S. Biologics License Application filing in January 2026 under Project Orbis.

Subsequent to quarter-end, OS Therapies announced its intent to spin off OS Animal Health into a separately financed, standalone public company in the first half of 2026, with OSTX shareholders expected to receive direct equity participation in the new listing. The animal health division targets a substantial U.S. canine osteosarcoma opportunity and will be housed within OSAH as a standalone public entity. Beyond the lead OST-HER2 asset, the company continues to leverage the acquired Ayala/Advaxis listeria platform, with the OST-504 Phase 1b trial in biochemically recurrent prostate cancer completing last patient visit and an initial data readout expected in the fourth quarter of 2025.

Financially, OS Therapies reported a third quarter 2025 net loss of $6.9 million versus $2.9 million in the same period last year, 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 financial runway into late 2026. During the quarter, OSTX terminated an equity line of credit 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 utilizes a probability-adjusted Discounted Cash Flow Model when valuing 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 leveraged to future periods due to the long-term nature of OS Therapies' industry, leading to the potential for significant re-ratings as new information becomes available throughout the regulatory and commercialization process.