New York, New York and Rockville, Maryland – OS Therapies, Inc. (NYSE American: OSTX) (“OS Therapies” or the “Company”), the world leader in gene-edited, Listeria-based cancer immunotherapies, today provided an update on global early market access regulatory coordination efforts being led by the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA) following the Company’s acceptance of MHRA’s request to become the lead regulatory agency to drive early market access for OST-HER2 in the prevention or delay of recurrence in fully resected, pulmonary metastatic osteosarcoma (the “Metastatic Osteosarcoma Program”) under Project Orbis.
Project Orbis is the U.S. Food & Drug Administration (FDA) Oncology Center of Excellence (OCE) initiative started in May 2019 to provide a framework for concurrent submission and review of oncology products among international partners. Since 2021, 29 MHRA-led oncology products have been approved by the FDA under Project Orbis.
“With FDA aligning on the updated adaptive design of pending Phase 3 study in our recent Type C Statistical Methods Meeting, MHRA is now taking the lead in the international OST-HER2 regulatory review process under Project Orbis to de-risk our harmonized global regulatory early market access pathway,” said Paul Romness, MPH, Chairman and CEO of OS Therapies. “We now have confirmation that MHRA will accept our pending Conditional Marketing Authorisation Application (CMAA) submission expected in the coming weeks which we expect to trigger the increased international coordination. The U.K. has also provided the Company access to data from the U.K.’s national patient registry (the “UK Database”), with some U.K. data already included in the Company’s actively accruing OST-400 natural history study of osteosarcoma patients treated concurrently with the OST-HER2 Phase 2b study timeline. MHRA has had access to this UK Database as part of its review of the OST-HER2 regulatory dossier. With the confirmatory Phase 3 study set to initiate in the U.K. following requalification of material used as part of the Phase 2b study, access to the UK Database will further increase resolution of the magnitude of OST-HER2 treatment effect during the global early market access phase.”
FDA has aligned with the Company on the proposed adaptive design of the pending Phase 3 study, paving the way for the U.K. portion of the global study to begin with the requalified material initially used in the Phase 2b study. FDA and the European Medicines Agency (EMA) have indicated that they will allow the Phase 3 study to move forward in their respective jurisdictions upon availability of Phase 3-ready drug product that is also expected to be used to support early market access commercial launch in the U.K., U.S., Europe and Australia, in addition to other Project Orbis countries. The Company expects to have Phase 3/commercial-ready drug product in 2027 to support expansion of the Phase 3 trial into the U.S. and Europe, as well as to support commercial launch. Products targeting ultra orphan diseases typically are able to receive regulatory approval with MHRA, FDA, EMA and the Australian Therapeutic Goods Agency (TGA), with a formal review of the final drug product prior to being allowed to commercially launch the product.
OST-HER2 has received Orphan Drug Designation (ODD), Fast Track Designation (FTD) and Rare Pediatric Disease Designation (RPDD) from the FDA. OST-HER2 has received ODD, FTD and ATMP from the EMA. OST-HER2 has received ODD and ATMP from MHRA, who also recruited the Company into Project Orbis. Under the RPDD program, if the Company is granted a BLA in the United States, it will become eligible to receive a Priority Review Voucher (PRV) that it intends to sell. A recent PRV sale occurred in August 2026 for $220 million. However, there can be no assurance that the Company would realize a comparable value, if any, in connection with any future PRV sale. OS Therapies has completed resubmission of a Regenerative Medicine Advanced Therapy (RMAT) request and the Company’s Commissioner’s National Priority Review Voucher (CNPV) letter of intent has been accepted by FDA. OS Therapies is seeking a Conditional Marketing Authorization Application from MHRA in the U.K. under Project Orbis for OST-HER2 in metastatic osteosarcoma in the fourth quarter of 2026, and immediately thereafter is seeking to obtain a BLA under the Accelerated Approval Program in the U.S., followed by CMAAs in Europe, and Australia.
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 gene-edited, 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 is designed to target two mutated extracellular epitopes and one mutated intracellular epitope of the HER2 oncogene, requiring only one of these three epitopes to be present in a tumor (or micro-metastasis) to trigger the desired immune response. 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 Advanced Therapy Medicinal Products (ATMP) from the European Medicines Agency.
The Company reported positive data in its Phase 2b clinical trial of OST-HER2 in the prevention or delay of recurrence in fully resected, pulmonary metastatic osteosarcoma, demonstrating clinically significant benefit in the 12-month event free survival (EFS) primary endpoint of the study and the overall survival (OS) secondary endpoint. The Company is seeking 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 Authorisation Applications 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 was previously conditionally approved by the U.S. Department of Agriculture for the treatment of canines with osteosarcoma. The Company has also completed dosing in a Phase 1 study of OST-504 for castration-resistant prostate cancer.
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 silicon Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker. For more information, please visit www.ostherapies.com.
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