New York, NY – OS Therapies (NYSE American: OSTX) (“OS Therapies” or “the Company”), a clinical-stage immunotherapy and Antibody Drug Conjugate (ADC) biopharmaceutical company, today announced statistically significant positive updated interim 2-year overall survival data from the Company’s Phase 2b trial of off-the-shelf immunotherapy candidate OST-HER2 in the prevention of delay of recurrent, fully resected, pulmonary metastatic osteosarcoma. 66.6% (18 out of 27) of OST-HER2 treated patients achieved 2-year overall survival compared with 40% of historical control1 (p = 0.0046).
Additionally, the U.S. Food & Drug Administration (FDA) issued a Biologics Licensing Application (BLA) number for OST-HER2 to receive a BLA submission following the Company’s pending August 27, 2025 End of Phase 2 Meeting. The Company has responded to FDA correspondences seeking to align approval metrics for Regenerative Medicine Advanced Therapy (RMAT) designation, Breakthrough Therapy designation (BTD) and BLA via the Accelerated Approval Program.
“We are seeking to bring this novel immunotherapy to market to improve the survival rates in pulmonary metastatic osteosarcoma, and today’s updated interim overall survival data continues to show a statistically significant benefit for OST-HER2 treated patients compared with control,” said Paul Romness, MPH, Chairman & CEO of OS Therapies. “We believe that continued statistically significant outperformance in overall survival of OST-HER2 treated patients compared with historical control, together with the statistically significant positive 12-month Event Free Survival data presented at MIB Factor in June 2025, will provide the necessary scientific and medical basis to support a BLA under the FDA’s Accelerated Approval Program.”
Concurrent with this announcement, the Company today announced that its NYSE American listing is included in the Russell Microcap, Russell Microcap Value and Russell Microcap Growth indexes. FTSE Russell determines membership for its Russell indexes primarily by objective, market-capitalization rankings and style attributes. Russell indexes are widely used by investment managers and institutional investors for index funds and as benchmarks for active investment strategies. Approximately $12 trillion in assets are benchmarked against Russell’s US indexes. Russell indexes are part of FTSE Russell, a leading global index provider. For more information on the US Russell Microcap Index and the Russell indexes reconstitution, including Russell 2000 and Russell 3000 reconstitution, please visit the FTSE Russell website.
About OS Therapies
OS Therapies is a clinical stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. OST-HER2, the Company’s lead asset, is an immunotherapy leveraging the immune-stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein. OST-HER2 has received Rare Pediatric Disease Designation (RPDD) from the U.S. Food & Drug Administration and Fast-Track and Orphan Drug designations from the U.S. FDA and European Medicines Agency. The Company reported positive data in its Phase 2b clinical trial of OST-HER2 in recurrent, fully resected, lung metastatic osteosarcoma, demonstrating statistically significant benefit in the 12-month event free survival (EFS) primary endpoint of the study. The Company anticipates submitting a Biologics Licensing Application (BLA) to the U.S. FDA for OST-HER2 in osteosarcoma in 2025 and, if approved, would become eligible to receive a Priority Review Voucher that it could then sell. OST-HER2 has completed a Phase 1 clinical study primarily in breast cancer patients, in addition to showing preclinical efficacy data in various models of breast cancer. OST-HER2 has been conditionally approved by the U.S. Department of Agriculture for the treatment of canines with osteosarcoma.
In addition, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC), known as tunable ADC (tADC), which features tunable, tailored antibody-linker-payload candidates. This platform leverages the Company’s proprietary silicone Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker. For more information, please visit www.ostherapies.com.
OS Therapies Contact Information
Investor Relations
Harrison Seidner, PhD
WaterSeid Partners
[email protected]
Public Relations
Stephanie Chen
Elev8 New Media
[email protected]