OS Therapies Advances OST-HER2 Regulatory Submissions for Osteosarcoma Treatment

OS Therapies Inc. announced that the FDA elevated the company's Type D Biomarker Meeting to a Type B pre-BLA Meeting for OST-HER2 in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma. The meeting is expected to occur shortly after the company completes submission of its clinical data package to the agency, targeted for the end of the first quarter of 2026.

The company is on track to complete clinical data submission by the end of Q1 2026. Following the submission of the Non-Clinical and Chemistry, Manufacturing & Controls (CMC) modules of its Biologics License Application (BLA) to the FDA at the end of January 2026, the company anticipates releasing additional biomarker data from its Human Metastatic Osteosarcoma Program in the first quarter of 2026. These analyses are intended to further characterize immune pathway activation and evaluate the relationship between biomarker expression and observed clinical outcomes.

The company expects to complete conditional Marketing Authorisation Application (MAA) submissions to both the U.K.'s Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency (EMA) by the end of the first quarter of 2026. The company remains on track to submit the Clinical BLA module to the FDA following an anticipated Type D meeting expected to occur in March 2026.

The company is assembling a meeting of U.S., U.K. and European osteosarcoma key opinion leaders to review the clinical and biomarker data from the Human Metastatic Osteosarcoma Program and provide input on proposed confirmatory trial designs for the company's confirmatory clinical development program. The company is seeking a BLA under the Accelerated Approval Program in the U.S. and conditional MAAs in the U.K. and Europe, which all require confirmatory studies to be initiated prior to approval. The company anticipates initiating the confirmatory trial in the third quarter of 2026 with the opening of a single site that allows it to meet the Accelerated Approval statutory requirement, with broader site activation expected following regulatory approval.

The company is seeking to get Accelerated Approval for OST-HER2 in osteosarcoma in the second half of 2026.

OST-HER2 has received FDA Orphan Drug Designation (ODD) and Fast Track Designation from the FDA & EMA and has also received Rare Pediatric Disease Designation (RPDD) from the FDA. Under the RPDD program, if the company receives Accelerated Approval in the United States, it will become eligible to receive a Priority Review Voucher (PRV) that it intends to sell. The most recent publicly disclosed PRV transaction occurred in February 2026 at a reported value of $205 million.

OS Therapies is a clinical stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. The company is the world leader in listeria-based cancer immunotherapies. 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. 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 announced that it has been informed that Ayala Pharmaceuticals, Inc. has informed its shareholders that Ayala is dissolving. The company acquired all listeria-based clinical, pre-clinical and intellectual property assets from Ayala in April 2025, issuing to Ayala the equivalent of 4.8 million shares of OS Therapies common stock that became eligible for trading on October 9, 2025. The company was informed by Ayala representatives that Ayala completed the liquidation of its OS Therapies common stock on February 9, 2026, and no longer holds any securities in the company.