OS Therapies Announces Full Alignment with UK MHRA and EU EMA for Conditional Marketing Authorisation Application Filing
Regulatory alignment in the UK and EU supports OS Therapies’ planned OST-HER2 filings and sets the stage for a confirmatory Phase 3 trial.
Rhea-AI Summary
OS Therapies (OSTX) has obtained full alignment with the U.K. MHRA and the EU EMA on its planned Conditional Marketing Authorisation Applications (CMAAs) for OST-HER2 as of September 15, 2026.
MHRA agreed that the company’s overall survival historical-control data, derived from a systematic review of peer‑reviewed literature by independent biostatistics advisors, are appropriate for use in the orphan indication of preventing or delaying recurrence in fully resected, pulmonary metastatic osteosarcoma. Regulators also aligned on the design of the required confirmatory Phase 3 trial, including the proportion of patients to receive remaining Phase 2 drug product versus new Phase 3 material. OS Therapies expects to complete its CMAA submissions in the coming weeks, intends to start the confirmatory Phase 3 trial in the fourth quarter of 2026, and is pursuing a U.S. BLA under the Accelerated Approval Program with potential rolling review.
Positive
- MHRA and EMA alignment on CMAA approach and Phase 3 design for OST-HER2
- MHRA acceptance of historical-control overall survival data in an orphan osteosarcoma indication
- Planned completion of CMAA submissions for OST-HER2 in the coming weeks
- Confirmatory Phase 3 trial for OST-HER2 expected to start in Q4 2026
- Ongoing BLA submission in the U.S. under the Accelerated Approval Program
- Potential Priority Review Voucher upon U.S. BLA approval, with a recent PRV sale cited at $220 million as a market reference
- OST-HER2 holds multiple expedited designations (ODD, FTD, RPDD, ATMP) across FDA, EMA and MHRA
Negative
- None.
Details
Market reaction after CMAA regulatory alignment: OSTX +7.06%
Following this news, OSTX has gained 7.06%, reflecting a notable positive market reaction. Our momentum scanner has triggered 3 alerts so far, indicating moderate trading interest and price volatility. The stock is currently trading at $1.82. Trading volume is very high at 4.8x the average, suggesting strong buying interest.
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Key Figures
- Confirmatory Phase 3 trial timing
- Q4 2026
- Planned initiation of the confirmatory trial
- CMAA submission timing
- Coming weeks
- Expected completion of the Conditional Marketing Authorisation Application submission
- BLA submission start
- January 2026
- Ongoing U.S. Biologics License Application submission
- Recent PRV sale
- $220 million
- Priority Review Voucher sale cited as a recent comparable
Historical Context
-
Three-year survival favored OST-HER2 versus historical controls with statistical significance
-
Regulators aligned on survival endpoints and confirmatory Phase 3 design
-
FDA and MHRA meetings were scheduled to review survival and statistical methods
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
biologics license application regulatory
priority review voucher regulatory
accelerated approval program regulatory
rolling review regulatory
AI-generated analysis. How Rhea-AI works. Not financial advice.
- Overall Survival (OS) historical-control data gains HMRA and EMA support for pending CMAA submissions
- Full alignment achieved on confirmatory Phase 3 trial design
- Complete CMAA submission expected in coming weeks
New York, New York and Rockville, Maryland--(Newsfile Corp. - September 15, 2026) - OS Therapies, Inc. (NYSE American: OSTX) ("OS Therapies" or the "Company"), the world leader in gene-edited, Listeria-based cancer immunotherapies, today announced that it has achieved full alignment with the U.K. Medicines and Healthcare products Regulatory Agency (MHRA) on its pending Conditional Marketing Authorisation Application (CMAA). MHRA agreed that the use of comparable historical control data – derived from a systematic evaluation of all suitable available peer-reviewed literature by independent biostatistics advisors presented in its most recent Scientific Advice Meeting (SAM) - was appropriate in the orphan indication Prevention or Delay of Recurrence in Fully Resected, Pulmonary Metastatic Osteosarcoma. Further, the Company achieved full alignment on the proposed design of its upcoming confirmatory Phase 3 trial design – including the proportion of patients to be dosed with remaining Phase 2 drug product versus forthcoming Phase 3 material. The Phase 3 trial is required to have commenced prior to being granted a CMAA. OS Therapies expects to complete the CMAA submission in the coming weeks. The Company also intends to commence the confirmatory Phase 3 as soon as possible in the fourth quarter of 2026 and site outreach has commenced accordingly.
The MHRA's supportive advice aligns with the Agency's recently published Rare Disease Regulatory Framework (https://www.gov.uk/government/consultations/draft-rare-disease-therapies-regulatory-framework/draft-rare-disease-therapies-regulatory-framework); and advice from the European Medicines Agency (EMA) pertaining to a forthcoming CMAA via the pan-European Centralised Procedure.
"Achieving full alignment with MHRA and EMA, which paves the way for our upcoming CMAA submissions, and the initiation of our confirmatory Phase 3 trial is a major achievement," said Paul Romness, MPH, Chairman & CEO of OS Therapies. "With this full alignment now in hand, and with it the recognition from international regulators that the standard of care in Osteosarcoma has not meaningfully changed in the last forty years, we are bringing this to the U.S. Food & Drug Administration (FDA). The FDA is part of the Orbis Project that coordinates approvals between international regulators, including the UK. The FDA is considering the ongoing Biologics License Application (BLA) submission that began in January 2026, with potential early market access under the Accelerated Approval Program. Additionally, the EMA recently informed the Company that a previously requested SAWP meeting was no longer required prior to submission of the CMAA to EMA."
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 Advanced Therapy Medicinal Products (ATMP – RMAT equivalent in the EU and UK) from the EMA and MHRA. 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. The most 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 Relations
Harrison Seidner, PhD
WaterSeid Partners
OSTX@waterseid.com
Public Relations
Stephanie Chen
Elev8 New Media
media@ostherapies.com
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/314396
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
What indication is OS Therapies targeting with OST-HER2 in its regulatory submissions?
OST-HER2 is being developed for the prevention or delay of recurrence in fully resected, pulmonary metastatic osteosarcoma. OS Therapies is seeking a Biologics License Application in the United States and Conditional Marketing Authorisation in Europe, the U.K. and Australia for this metastatic osteosarcoma setting.
What is the status of the planned confirmatory Phase 3 trial for OST-HER2?
The company has reached full alignment with MHRA on the Phase 3 design, including how many patients will receive remaining Phase 2 drug product versus new Phase 3 material. OS Therapies intends to initiate the confirmatory Phase 3 trial in the fourth quarter of 2026, and site outreach has already begun.
Which expedited regulatory designations has OST-HER2 received?
OST-HER2 has received Orphan Drug Designation (ODD), Fast Track Designation (FTD) and Rare Pediatric Disease Designation (RPDD) from the U.S. FDA. From the EMA and MHRA, it has received ODD, FTD and Advanced Therapy Medicinal Products (ATMP) classification, which the company describes as RMAT equivalent in the EU and U.K.
How could a Priority Review Voucher affect OS Therapies financially?
Under the Rare Pediatric Disease Designation program, if OS Therapies is granted a BLA for OST-HER2 in the U.S., it would become eligible to receive a Priority Review Voucher (PRV). The company states that it intends to sell any such PRV and notes that the most recent PRV sale in August 2026 was for $220 million, while cautioning there is no assurance it would achieve a comparable value, if any.
What additional regulatory steps is OS Therapies taking with the FDA for OST-HER2?
OS Therapies has resubmitted an RMAT request and its Commissioner’s National Priority Review Voucher (CNPV) letter of intent has been accepted by the FDA. The company plans to request Rolling Review of its ongoing BLA submission after an upcoming mid‑September 2026 FDA Type C Statistical Methods Meeting.
How does OST-HER2 work as a cancer immunotherapy?
OST-HER2 is described as a gene-edited, Listeria-based cancer immunotherapy that uses the immune‑stimulatory properties of Listeria bacteria to trigger an immune response against the HER2 protein. It 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 initiate the desired immune response.