OS Therapies Completes FDA Type C Statistical Methods Meeting and Provides Update on Global Regulatory Coordination for OST-HER2 Under Project Orbis
MHRA will lead global OST‑HER2 review under Project Orbis, with Phase 3 launch in the U.K. in late 2026 and BLA completion targeted for Q4 2026.
Rhea-AI Summary
OS Therapies (OSTX) has aligned global regulators and updated development plans for OST‑HER2 in metastatic osteosarcoma under Project Orbis as of September 21, 2026.
Following a U.K. MHRA Scientific Advice Meeting, MHRA agreed to initiate and lead a confirmatory Phase 3 trial in the U.K. using requalified Phase 2b drug product, with trial start expected in mid‑Q4 2026 and a Conditional Marketing Authorisation Application submission in the coming weeks. MHRA is taking the global regulatory lead with FDA and EMA and has granted access to the U.K. Clinical Practice Research Datalink registry to strengthen comparator data during early market access.
FDA has aligned with the adaptive Phase 3 design in a Type C Statistical Methods Meeting. A rolling BLA filing for OST‑HER2 in osteosarcoma, initiated in Q1 2026, is targeted for completion in Q4 2026 as the company awaits FDA decisions on RMAT, Rolling Review and CNPV requests. Commercial/Phase 3‑ready OST‑HER2 product is expected in 2027 to support trial expansion and launches in Project Orbis countries. OST‑HER2 holds multiple ODD, FTD, RPDD and ATMP designations, and a future U.S. BLA could yield a Priority Review Voucher, with a recent comparable PRV sale disclosed at $220 million.
Positive
- MHRA leadership under Project Orbis for OST‑HER2 global early market access coordination
- Phase 3 UK start planned for mid‑Q4 2026 using requalified Phase 2b drug product
- FDA alignment on adaptive Phase 3 design after Type C Statistical Methods Meeting
- Rolling BLA for OST‑HER2 initiated Q1 2026, completion targeted Q4 2026
- Multiple regulatory designations (ODD, FTD, RPDD, ATMP) from FDA, EMA and MHRA
- Potential PRV monetization if U.S. BLA granted; a recent PRV sale reached $220 million
Negative
- Key approvals pending, with UK CMAA, U.S. BLA and other CMAAs still to be obtained
- Phase 3/commercial‑ready product not expected until 2027, delaying broader trial expansion
- PRV value uncertainty; company cautions no assurance of a comparable $220 million sale
Key Figures
- Project Orbis approvals
- 29 products
- MHRA-led oncology products approved by FDA since 2021
- CMAA timing
- Q4 2026
- Targeted MHRA submission for OST-HER2
- Phase 3/commercial-ready product
- 2027
- Expected timing for expansion into the U.S. and Europe and commercial launch
- Recent PRV sale
- $220 million
- Comparable Priority Review Voucher sale reported in August 2026; future value not assured
Historical Context
-
FDA aligned on adaptive Phase 3 design and MHRA joined Project Orbis
-
MHRA and EMA aligned on CMAA filing and confirmatory Phase 3 design
24h Move is the share-price change in the day after each event; other market factors may also have contributed.
Key Terms
conditional marketing authorisation application regulatory
adaptive design technical
orphan drug designation regulatory
priority review voucher regulatory
biologics license application regulatory
AI-generated analysis. How Rhea-AI works. Not financial advice.
- Recent U.K. MHRA Scientific Advice Meeting (SAM) that resulted in full alignment to initiate confirmatory Phase 3 trial in U.K. with existing Phase 2 drug product paved the way Conditional Marketing Authorisation Application (CMAA) submission in the coming weeks and Phase 3 trial initiation in mid Q4/'26 following Phase 2b drug product requalification
- MHRA's SAM participants' recommendation to Project Orbis U.K. leadership to take the global regulatory leadership mantle with U.S. FDA and EMA, coupled with granting the Company access to U.K. national patient registry, the UK Clinical Practice Research Datalink (CPRD) to strengthen comparator data while Phase 3 is ongoing to further improve interpretability of data during early market access phase
- Since 2021, 29 MHRA-led products have been approved by U.S. FDA via Project Orbis
- Company continues to engage with U.S. FDA on the non-Orbis Accelerated Approval route after successful Type C Statistical Methods Meeting that resulted in alignment on amended Phase 3 study design as buildout of OST-400 natural history database expands to include U.K. national patient registry data and Company awaits FDA decisions on RMAT, Rolling Review and CNPV ahead of the pending Q4/'26 completion of its ongoing BLA filing initiated in Q1/'26
- BLAs granted via Project Orbis are eligible to receive Priority Review Vouchers (PRVs) and may also be granted via the Accelerated Approval Program
- Patient previously reported as lost to follow-up confirmed to be alive
New York, New York and Rockville, Maryland--(Newsfile Corp. - September 21, 2026) - 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
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.
Forward-Looking Statements
Statements in this press release regarding future expectations, plans, prospects or performance, as well as any other statements that are not historical facts, may constitute forward-looking statements within the meaning of the federal securities laws. Forward-looking statements are generally identified by words such as "anticipate," "believe," "could," "expect," "intend," "may," "plan," "potential," "should," "will" and similar expressions, although not all forward-looking statements contain these words. These statements are based on the current expectations and assumptions of OS Therapies and its management and are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such forward-looking statements. Such risks and uncertainties include, but are not limited to, the Company's expectations regarding its cash runway; the timing, amount and receipt of VAT refunds and R&D tax credits; the Company's ability to obtain additional financing on acceptable terms or at all; the timing and outcome of regulatory submissions and potential approval of OST-HER2 by the U.S. Food and Drug Administration and applicable foreign regulatory authorities; and other risks and uncertainties described under the heading "Risk Factors" in the Company's most recent Annual Report on Form 10-K and in its other filings with the Securities and Exchange Commission. The forward-looking statements contained in this press release speak only as of the date of this press release, and OS Therapies undertakes no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by applicable law.
OS Therapies Contact Information:
INVESTOR CONTACT Harrison Seidner, PhD, WaterSeid Partners
OSTX@waterseid.com
MEDIA CONTACT James Lambert, Vice President, Rubenstein Public Relations
jlambert@rubensteinpr.com 212-805-3024
https://x.com/OSTherapies
https://www.instagram.com/ostherapies/
https://www.facebook.com/OSTherapies/
https://www.linkedin.com/company/os-therapies/
###
To view the source version of this press release, please visit https://www.newsfilecorp.com/release/315136
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
What specific regulatory path is OS Therapies pursuing for OST‑HER2 in the U.S., U.K., Europe and Australia?
OS Therapies is seeking a Conditional Marketing Authorisation Application from MHRA in the U.K. under Project Orbis for metastatic osteosarcoma in Q4 2026, then aims to obtain a U.S. BLA under the Accelerated Approval Program, followed by CMAAs in Europe and Australia. FDA and EMA have indicated that the Phase 3 study may proceed in their regions once Phase 3‑ready drug product is available.
How will U.K. registry data be used in the OST‑HER2 program?
The company has access to the U.K. Clinical Practice Research Datalink national patient registry, some of which is already included in the OST‑400 natural history study that runs alongside the OST‑HER2 Phase 2b timeline. MHRA has reviewed this U.K. database as part of the OST‑HER2 dossier, and ongoing access is intended to strengthen comparator data and improve interpretation of treatment effect during the early market access phase.
What additional FDA designations or programs is OS Therapies seeking for OST‑HER2?
OS Therapies has resubmitted a Regenerative Medicine Advanced Therapy (RMAT) request and its Commissioner's National Priority Review Voucher (CNPV) letter of intent has been accepted by FDA. The company is also seeking Rolling Review for the OST‑HER2 BLA while it builds out the OST‑400 natural history database, which will include U.K. registry data.