NEW YORK, NY — OS Therapies (NYSE-A: OSTX) (“OS Therapies” or “the Company”), a clinical-stage immunotherapy and Antibody Drug Conjugate (ADC) biopharmaceutical company, today announced it was granted an End of Phase 2 Meeting by the United States Food & Drug Administration (“FDA”) to review the OST-HER2 program in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma. The Company expects the meeting to occur in the third quarter of 2025. The End of Phase 2 Meeting marks a pivotal point in the drug development process, and a significant milestone towards market access.
The Company intends to seek alignment with FDA to begin a Rolling Review process for the forthcoming Biologics Licensing Application (“BLA”) submission for OST-HER2. The Rolling Review process means that a company can submit completed sections of its Biologic License Application (BLA) for review by FDA, rather than waiting until every section of the BLA is completed before the entire application can be reviewed. This can contribute to augmented interactions with FDA and potentially an expedited BLA approval timeline.
OST-HER2 has received FDA Orphan Disease Designation (ODD), Fast Track and Rare Pediatric Disease Designation (RPDD) from FDA. Under the RPDD program, if the Company receives Accelerated Approval prior to September 30, 2026, it will become eligible to receive a Priority Review Voucher (PRV) that it intends to sell. The most recent PRV sale, valued at $160 million, occurred in June 2025.
OST-HER2, an immunotherapy for osteosarcoma that uses a HER2-bioengineered form of the bacterium Listeria monocytogenes to trigger a strong immune response against HER2-expressing cancer cells, is featured in the movie Shelter Me: The Cancer Pioneers. The movie offers a look into canine comparative oncology, a field that compares treatment of cancers in dogs to those in people and covers developing treatments for rare forms of cancer. The trailer is available here and the movie is available via streaming on PBS’ website.
The most recent data regarding the OST-HER2 canine osteosarcoma program is available at this link. The Company has formed subsidiary OS Animal Health to advance the canine osteosarcoma program.
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 US Food & Drug Administration and Fast-Track and Orphan Drug designations from the US FDA and European Medicines Agency. The Company 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 US 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 or X.
OS Therapies Contact Information:
Jack Doll
410.297.7793
[email protected]