• Request for FDA Rolling Review submitted to FDA on January 30, 2026
• Non-Clinical and CMC BLA modules submitted to FDA
• At FDA's request, Type D Meeting expected in March 2026 to review Comparative Oncology biomarker data from patients treated in OST-HER2 Phase 2b human clinical trial and OST-HER2 trial in spontaneous osteosarcoma in canines
• Final BLA clinical module expected to be submitted to FDA by end of March 2026 after Type D Meeting
• Regenerative Medicine Advanced Therapy (RMAT) designation requests update submitted to FDA with recent biomarker data
• Company remains on track to be eligible to receive Priority Review Voucher under Rare Pediatric Disease Designation (RPDD) with approval anticipated by September 30, 2026

New York, New York--(Newsfile Corp. - February 2, 2026) - OS Therapies Inc. (NYSE American: OSTX) ("OS Therapies" or "the Company"), the world leader in listeria-based cancer immunotherapies, today announced that it has formally initiated a Biologics License Application (BLA) submission to the U.S. Food & Drug Administration (FDA) for OST-HER2 in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma ("Human Metastatic Osteosarcoma"). The Company has submitted the Non-Clinical and the Chemistry, Manufacturing, and Controls (CMC) modules of the BLA to FDA, along with a request for Rolling Review. At FDA's invitation following a December 2025 Type C Meeting, the Company has requested a Type D Meeting to review new Comparative Oncology OST-HER2 biomarker data generated from the Company's Phase 2b human clinical trial in Human Metastatic Osteosarcoma and a similar trial of OST-HER2 in spontaneous osteosarcoma in canines (the "OST-HER2 Comparative Oncology Data"). The Company expects to submit the clinical BLA module that will rely upon the OST-HER2 Comparative Oncology Data by the end of March 2026, keeping it on schedule to be eligible to receive approval by September 30, 2026.

"We are delighted in the FDA's interest in reviewing OST-HER2 Comparative Oncology Data," said Paul Romness, MPH, Chairman & CEO of OS Therapies. "There is strong demand for compassionate use of OST-HER2 from the patient community, underscoring the urgent need for new therapies in Human Metastatic Osteosarcoma. We remain committed to bringing OST-HER2 to market as expeditiously as possible and are grateful for FDA's engagement as we finalize the biomarker data package that will be submitted as part of Type D meeting preparations to support our request for a BLA under the Accelerated Approval Program."

Concurrent with this announcement, the Company announced it has updated its Regenerative Medicine Advanced Therapy (RMAT) designation requests to FDA with recent biomarker data. RMAT designation typically shortens the timeframe granted for review of a BLA submission significantly from the standard timelines, expediting the time to patient access.

OST-HER2 has received FDA Orphan Disease Designation (ODD) and Fast Track Designation from FDA & EMA and has received 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 $200 million, occurred in January 2026.

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. 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. 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 completing submission of a BLA to the U.S. FDA for OST-HER2 in osteosarcoma in March 2026 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 press 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 U.S. FDA and other risks and uncertainties described in "Risk Factors" in the Company's most recent Annual Report on Form 10-K, most recent Quarterly Report on Form 10-Q and other subsequent documents the Company files with the Securities and Exchange Commission. 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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