OS Therapies Announces Issuance of U.S. Patent #12,239,738 Protecting Commercial Manufacturing Market Exclusivity for OST-HER2 in Rare Pediatric Cancer Osteosarcoma and Full Listeria Cancer Immunotherapy Platform into 2040

OS Therapies (NYSE-A: OSTX) (“OS Therapies” or “the Company”), a clinical-stage immunotherapy and Antibody Drug Conjugate (ADC) biopharmaceutical company, today announced the issuance of United States Patent #12,230,738 protecting proprietary commercial manufacturing methods for the Company’s listeria monocytogenes (Lm) cancer immunotherapy platform technology into 2040. The Company is seeking to gain FDA approval for lead asset OST-HER2 in the treatment of pediatric recurrent, fully-resected, lung metastatic osteosarcoma by the end of 2025. Phase 3-stage OST-AXIL for HPV, Phase 2-stage OST-503 for NSCLC & GBM, Phase 1-stage OST-504 for Prostate cancer, 8 pre-clinical stage immunotherapy candidates are also protected under this patent. The patent also covers OST-HER2’s use in canine osteosarcoma.

“The issuance of this patent covering commercial manufacturing for the entire listeria monocytogenes platform breathes new life into our pipeline, giving us the exclusive ability to develop this exciting field of cancer immunotherapy,” said Paul Romness, CEO of OS Therapies. “Potential FDA approval of OST-HER2 in Osteosarcoma would bring a Priority Review Voucher valued at least $150 million. This non-dilutive capital will allow us to expand OST-HER2 use into metastatic & frontline osteosarcoma, and other HER2 positive cancers. The issuance of this patent resets the clock in terms of creating value from the over $250 million previously invested in the platform. Additionally, this positions OS Therapies to develop three (3) clinical and eight (8) pre-clinical assets that could improve the standard of care in a variety of cancers.”

OST-HER2 has received Rare Pediatric Disease Designation (RPDD) for osteosarcoma from the US FDA, and if it receives a conditional BLA via Accelerated Review prior to September 30, 2026, it will become eligible to receive a Priority Review Voucher (PRV) that it intends to sell immediately. The most recent PRV sale valued at $150 million occurred in February 2025.

The osteosarcoma treatment market was estimated at $1.2 billion in 2022 according to Data Bridge Market Research. Approximately 50% of patients are diagnosed with a lung metastasis at some point following chemotherapy. The Company believes the market opportunity for OST-HER2 in the prevention of lung metastases is over $500 million.

Human and Canine OST-HER2 patients are featured in the upcoming movie Shelter Me: The Cancer Pioneers. The movie focuses on canine/human 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 movie airs live and via streaming on PBS May 15, 2025.

About OS Therapies

OS Therapies is a clinical stage oncology company focused on the identification, development, and commercialization of treatments for osteosarcoma 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 has demonstrated 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 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.

Forward-Looking Statements

Statements in this press release about future expectations, plans and prospects, as well as any other statements regarding matters that are not historical facts, may constitute forward-looking statements within the meaning of the federal securities laws. These forward-looking statements and terms such as "anticipate," "expect," "intend," "may," "will," "should" or other comparable terms involve risks and uncertainties because they relate to events and depend on circumstances that will occur in the future. Those statements include statements regarding the intent, belief or current expectations of OS Therapies and members of its management, as well as the assumptions on which such statements are based. OS Therapies cautions readers that forward-looking statements are based on management’s expectations and assumptions as of the date of this news release and are subject to certain risks and uncertainties that could cause actual results to differ materially, including, but not limited to the approval of OST-HER2 by the US FDA and grant of a priority review voucher and other risks and uncertainties described in “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in the Company’s registration statement on Form S-1 filed with the Securities and Exchange Commission (the “SEC”) on November 12, 2024, as amended on November 27, 2024, and other subsequent documents we file with the SEC, including but not limited to our Quarterly Reports on Form 10-Q. Any forward-looking statements contained in this press release speak only as of the date hereof, and, except as required by the federal securities laws, OS Therapies specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.

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