OS Therapies Appoints Biotech Industry Luminary Robert "Bob" S. Langer, PhD as Strategic Advisor

• Co-founder of more than 40 biotechnology companies, including 16 IPOs and 19 successful acquisitions
• Scientific and medical titan focused on driving innovation for human health
• Will assist with listeria oncology pipeline prioritization, combinations with other oncology-focused biotechnologies and tADC candidate selection for further development

New York, New York--(Newsfile Corp. - April 13, 2026) - OS Therapies, Inc. (NYSE:OSTX) ("OS Therapies" or "the Company"), the world leader in gene-edited, listeria-based cancer immunotherapies, announced today that Dr. Robert "Bob" S. Langer, co-founder of Moderna, was appointed to the Company's strategic advisory board. Dr. Langer will assist management with listeria oncology pipeline prioritization, combinations of listeria product candidates with other oncology-focused biotechnologies, as well as tunable Antibody Drug Conjugate (tADC) candidate selection for further development. Dr. Langer is a luminary in the field of biotechnology, having developed core technologies used ubiquitously throughout the field for drug discovery and development, improving the health of millions worldwide.

"The use of listeria monocytogenes as a vehicle to activate the immune system to kill cancer has been studied for decades but may soon become a medical reality thanks to OS Therapies," said Dr. Langer, newly-appointed member of the Company's strategic advisory board. "Listeria's unique properties as an intracellular bacterium create major opportunities both to treat cancers which have not responded to existing immunotherapies and to enhance outcomes for patients already receiving other anti-cancer agents, given the strong safety profile exhibited in the Phase 2b study of OST-HER2 and the more than one thousand patients treated with the platform. I will be working with the OS Therapies team implement a robust pipeline development strategy for both standalone and combination product development. Moreover, the unique proprieties of silicone dioxide that underlie the tADC linker/cap technology present tremendous opportunities to design more comprehensive and efficacious candidates which can deliver combinations of cytotoxic and immune stimulatory compounds in a targeted way: this means we can more effectively treat solid tumors and ultimately aim to improve patient outcomes."

Dr. Bob Langer is one of nine Institute Professors at the Massachusetts Institute of Technology (MIT), MIT's highest faculty honor. His pioneering work includes isolating the first angiogenesis inhibitors (with Dr. Judah Folkman) leading to new treatments for cancer and blindness. He also created the first nanoparticles and microparticles for delivering large molecules, including nucleic acids, and helped establish the field of tissue engineering which enabled artificial skin for burn victims and organ-on-a-chip technology. Dr. Langer has authored more than 1,600 papers, cited more than 473,000 times. With an h-index of 336, Langer is the most cited engineer in history. His patents have been licensed or sublicensed to over 400 companies, and he has co-founded more than 40 ventures, including Moderna. Dr. Langer chaired the FDA's Science Board, the agency's highest advisory board, from 1999-2002 and has received over 220 awards, including the U.S. National Medal of Science and the National Medal of Technology and Innovation (one of only three living individuals to receive both). His accolades include the Draper Prize (considered engineering's Nobel Prize), Queen Elizabeth Prize for Engineering, Albany Medical Center Prize, Breakthrough Prize in Life Sciences, Kyoto Prize, Wolf Prize in Chemistry, Millennium Technology Prize, and the Kavli Prize in Nanoscience. He holds 44 honorary doctorates from institutions such as Harvard, Yale, Columbia, and Oxford, and has been elected to the National Academies of Medicine, Engineering, and Sciences, as well as the National Academy of Inventors.

"It is a tremendous honor to have a biotechnologist of Dr. Langer's distinction join our fight against cancer," said Paul Romness, MPH, Chair & CEO of OS Therapies. "Taken together with Dr. Craig Eagle's appointment last week, these recent additions to our strategic advisory board elevate the Company's standing in the biotechnology community, sending a powerful vote of confidence in our core technologies and the Company's future. We now have a tremendous opportunity to leverage Dr. Langer's unique expertise and vast network to help drive our mission forward as we engage with international regulators and potential industry partners regarding OST-HER2's potential in osteosarcoma and beyond. In the near-term, we are continuing to focus on regulatory execution surrounding gaining market access for OST-HER2 in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma in the U.S., U.K. and Europe, as well as countries with regulatory reciprocity with these jurisdictions. We will now begin working more closely with our strategic advisory board to fully build out our strategy for the diligent development of our pipeline as resources become available from product revenues, partnership agreements and/or the sale of a potential priority review voucher following approval in the U.S."

OST-HER2 has received Orphan Drug Designation (ODD), Fast Track Designation (FTD) and Rare Pediatric Disease Designation (RPDD) from the FDA, and ODD, FTD and ATMP from the EMA. Under the RPDD program, if the Company receives a Biologics License Application (BLA) 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. The Company is seeking to obtain a BLA under the Accelerated Approval Program for OST-HER2 in osteosarcoma in the second half of 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 Orphan Drug Designation (ODD), Fast Track Designation (FTD) and Rare Pediatric Disease Designation (RPDD) from the U.S. Food & Drug Administration and has received ODD, FTD and ATMP from the 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 and the overall survival (OS) secondary endpoint. The Company anticipates receiving a Biologics License Application (BLA) from the U.S. FDA for OST-HER2 in osteosarcoma in 2026 and, if approved, would become eligible to receive a Priority Review Voucher that it could then sell. The Company also anticipates receiving Conditional Marketing Authorisations from the U.K.'s Medicines and Healthcare products Regulatory Agency and the EMA for OST-HER2 in 2026. 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. The Company also anticipates reading out data from a Phase 1b study of OST-504 in castration resistant prostate cancer in the first half of 2026.

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 our expected to provide cash runway into 2027, the intended use of net proceeds from the offering, the potential 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 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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