OS Therapies Announces Significant Survival Benefits in Osteosarcoma Trial

OS Therapies, a clinical stage oncology company, has announced significant progress in its ongoing Phase 2b trial for the treatment of pulmonary metastatic osteosarcoma. The interim analysis of the 3-year overall survival data shows a marked improvement in patient outcomes for those treated with OST-HER2, the company's lead gene-edited, Listeria-based cancer immunotherapy.

According to the press release, the 3-year overall survival rate for patients treated with OST-HER2 was 71.2%, compared to 45.8% for a comparable combined historical control group (p = 0.002). This data was derived from a trial with 41 enrolled patients, with two remaining patients scheduled to reach the 3-year mark in September and October 2026, respectively. Six patients were lost to follow-up.

Dr. Craig Eagle, Chief Medical Advisor and Director of OS Therapies, expressed optimism about the findings, stating, "The increasing survival benefit as time goes on for OST-HER2 treated patients, when compared to any and all available published literature, presents a compelling case for early market access for osteosarcoma patients who have not seen a new drug approved in the last forty years."

The company is preparing to complete the final data analysis in the coming month while continuing to engage with regulatory authorities worldwide. Dr. Eagle added, "We believe that the 3-year survival endpoint, which the European Medicines Agency (EMA) and the U.K.'s Medicines and Healthcare products Regulatory Agency (MHRA) have accepted, will also be acceptable to the U.S. Food & Drug Administration (FDA) for a Biologics License Application (BLA) under the Accelerated Approval Program."

In other financial news, OS Therapies has received $3.15 million in Value Added Tax (VAT) refunds into its wholly-owned subsidiary, OS Therapies UK, Ltd. Additionally, the company is eligible to receive an additional $7.2 million in VAT and R&D Tax Credits. These funds will support the initiation of the confirmatory Phase 3 clinical trial that is set to commence in the U.K. to further validate the drug's efficacy and safety.

"We are pleased with the positive VAT outcome and the confirmation of our eligibility for R&D tax credits," said Paul Romness, MPH, Chair and CEO of OS Therapies. "These resources will enable us to commence the confirmatory Phase 3 trial, which is crucial for regulatory approval, and support our ongoing efforts to bring OST-HER2 to market."

The company has also received Orphan Drug Designation (ODD), Fast Track Designation (FTD), and Rare Pediatric Disease Designation (RPDD) from the FDA, as well as similar designations from the EMA. OST-HER2 has completed a Phase 1 clinical study primarily in breast cancer patients and has shown preclinical efficacy data in various models of breast cancer. The drug has also received conditional approval by the U.S. Department of Agriculture for the treatment of canines with osteosarcoma.

OS Therapies is focused on the identification, development, and commercialization of treatments for osteosarcoma and other solid tumors. The company's next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC), known as tunable ADC (tADC), are also in development, leveraging the company's proprietary silicon Si-Linker and Conditionally Active Payload (CAP) technology.

The press release concludes with forward-looking statements, emphasizing the company's intention to seek a Biologics License Application (BLA) from the U.S. FDA for OST-HER2 in osteosarcoma in 2026, with the potential to receive a Priority Review Voucher if approved. The company also anticipates receiving Conditional Marketing Authorization Applications (CMAAs) from the U.K.'s MHRA, EMA, and Australia's Therapeutic Goods Administration for OST-HER2 in 2026.