OS Therapies files $75 million at-the-market equity offering with Jefferies

OS Therapies Incorporated filed a prospectus supplement dated August 21, 2026 for an at-the-market stock offering. Under the agreement, the company entered an Open Market Sale Agreement with Jefferies LLC, under which it may sell shares of common stock with a total offering price up to $75,000,000 over time, with Jefferies acting as sales agent or as principal.¹ Jefferies will be paid 3.0% of gross proceeds from any shares sold under the deal.¹ As of August 20, 2026, the closing price of the company's stock on the NYSE American was $1.58 per share.¹

The filing also updated investors on the company's lead program, OST-HER2, being developed for recurrent osteosarcoma. In 2021 the company opened a clinical study to generate FDA-facing safety and efficacy data on OST-HER2 in patients after resection of recurrent osteosarcoma, and enrollment reached 41 patients in October 2023.¹ In the first quarter of 2025, the company said its Phase IIb trial met its primary endpoint with statistical significance.¹ By October 2025, final two-year data showed 27 of 36 evaluable OST-HER2 patients, or 75%, reached two-year overall survival after their most recent pulmonary resection, versus 60% among historical controls (p = 0.034).¹

More recently, in May 2026 the company reported a statistically significant overall survival benefit at the 2.5-year mark, with 75% survival in treated patients compared with 47% in pooled historical controls (p = 0.003).¹ The company said it expects to submit the clinical BLA module following an anticipated Type C meeting with the FDA in September 2026, and to complete conditional marketing authorization filings with UK and EU regulators in the first quarter of 2027.¹