OS Therapies has secured approximately $7.2 million in gross proceeds through the initial closing of a warrant exercise inducement and exchange offer, providing additional funding as the clinical-stage oncology company prepares regulatory submissions for its lead cancer immunotherapy, Herlystic (OST-HER2). The announcement comes as OS Therapies works toward potential early market access for the investigational treatment in the United States and internationally.
Financing Supports Upcoming Regulatory Milestones
According to the company’s SEC filing, seven investors participated in the initial closing, exercising or pre-funding warrants covering approximately 5.5 million shares at $1.30 per share, or $1.299 for pre-funded warrants. Participating investors received new warrants exercisable at $1.40 per share. If all eligible warrants are exercised or pre-funded, the transaction could generate approximately $12.3 million in total gross proceeds. The offer is scheduled to expire October 30, 2026, unless extended or terminated earlier.
OS Therapies also reported $7 million in accrued refundable U.K. research and development tax credits, which it expects to receive in early 2027 following a planned filing later this year. These credits have not yet been received. The company expects the financing and anticipated tax credits to support operations through upcoming regulatory milestones.
Advancing Herlystic for Osteosarcoma Patients
The proceeds will support regulatory filings and commercialization preparations for Herlystic, an investigational Listeria-based immunotherapy designed to stimulate an immune response against HER2-expressing cancer cells. The treatment is being developed to prevent or delay recurrence in patients with fully resected pulmonary metastatic osteosarcoma, a rare bone cancer that has spread to the lungs.
In an October 6 clinical update, OS Therapies reported a three-year overall survival rate of 72.7% among Herlystic-treated patients, compared with 45.8% in a combined historical control group. The Phase 2b study enrolled 41 patients, with four lost to follow-up. While the findings support continued development, the comparison relied on historical data rather than a randomized control group.
Preparing for Potential Market Access
OS Therapies plans to complete a Biologics License Application submission to the U.S. Food and Drug Administration under its Accelerated Approval Program during the fourth quarter of 2026. The company is also pursuing conditional marketing authorization applications in the United Kingdom, European Union and Australia.
Herlystic has received FDA Orphan Drug, Fast Track and Rare Pediatric Disease designations. These designations support the drug development process but do not constitute marketing approval. The company is also preparing a confirmatory Phase 3 trial as part of its regulatory strategy.
About OS Therapies
OS Therapies is a clinical-stage oncology company with principal executive offices in Grasonville, Maryland. The company develops treatments for osteosarcoma and other solid tumors, with a pipeline that includes Listeria-based immunotherapies and antibody-drug conjugate technologies.
