OS Therapies Initiates U.K. MHRA Conditional Marketing Authorisation Application for Herlystic (OST-HER2) in the Prevention or Delay of Recurrence in Fully Resected, Pulmonary Metastatic Osteosarcoma

The U.K. process carries an expected potential early market access decision in the first quarter of 2027.

Rhea-AI Summary

OS Therapies (OSTX) has initiated the U.K. conditional marketing authorisation application process for Herlystic to prevent or delay osteosarcoma recurrence.

The application covers patients with fully resected, pulmonary metastatic osteosarcoma. The company expects submission acceptance in the fourth quarter of 2026 and a potential MHRA early market access decision in the first quarter of 2027. It plans to complete U.K. and European submissions in the fourth quarter of 2026.

OS Therapies has resubmitted its Regenerative Medicine Advanced Therapy request. Completion of its ongoing U.S. biologics licence application depends on FDA alignment over using the OST-400 natural history study as a comparator to interpret Phase 2b results. MHRA has granted access to U.K. patient records to expand that study. U.S. approval would make the company eligible for a Priority Review Voucher it intends to sell.

9 points · 0 major

PositiveiHow this balance works

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Rhea-AI gives every point it takes from this document a weight. Minor counts 1, Moderate 3 and Major 9, so one Major point outweighs several Minor ones. The bar adds up the weights on each side, and when neither side holds more than 65% of the total the balance reads Mixed.

It reads the document as published, with the same rules for every company, and it does not look at what the market expected or at how the stock traded, so a point can be objectively good on a day the stock falls.

Rhea-AI Sentiment measures something else, the tone of the wording.

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0 major · 1 point

Hollow bars mark forward-looking points. How the balance works

Positive

• Moderate pointHerlystic’s U.K. conditional marketing authorisation application process has begun for fully resected, pulmonary metastatic osteosarcoma.
• Minor point. Forward-looking: it has not happened yet and may not happen.U.K. submission acceptance is expected in the fourth quarter of 2026; a potential access decision is expected in first-quarter 2027.
• Minor point. Forward-looking: it has not happened yet and may not happen.U.K. and European application submissions are planned for completion in the fourth quarter of 2026.
• Minor pointEuropean Centralised Procedure access permits a unified regulatory review rather than separate EU member-state applications.
• Minor pointFDA orphan, Fast Track and Rare Pediatric Disease designations and EMA orphan and advanced-therapy designations have been received.

4 minor points

• Minor pointRegenerative Medicine Advanced Therapy request resubmission has been completed.
• Minor pointFDA acceptance of the National Priority Voucher letter of intent occurred in the first quarter of 2026.
• Minor pointMHRA patient-data access has been granted to increase the patients included in OST-400.
• Minor point. Forward-looking: it has not happened yet and may not happen.Priority Review Voucher eligibility would follow U.S. biologics licence approval; the company intends to sell the voucher.

Negative

• Moderate pointFDA comparator alignment remains pending before the company can complete its ongoing U.S. biologics licence submission.

News Explained

The release cites two October 2026 Priority Review Voucher sales totaling $413 million, or an average of $206.5 million, as context; OS Therapies would become eligible for a voucher only if granted a U.S. BLA, and says no comparable future sale value is assured.

Key Figures

CMAA process completion: Fourth quarter of 2026 Potential MHRA decision: First quarter of 2027

CMAA process completion

Fourth quarter of 2026

Company expects to complete the U.K. application process

Potential MHRA decision

First quarter of 2027

Potential early market access decision

Historical Context

1 past event · Latest: Nov 05

1 event

1. Nov 05

   Regulatory milestone

   24h Move

   -14.8%

   Herlystic drug-substance requalification enabled U.K. conditional marketing filings and supported planned European and U.S. submissions.

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, orphan drug designation, fast track designation, priority review voucher, +1 more

5 terms

conditional marketing authorisation application regulatory

"initiated a Conditional Marketing Authorisation Application (CMAA) process"

An application submitted to a medicines regulator asking for a conditional marketing authorisation, which is a temporary approval to sell a new drug or vaccine based on early positive evidence when there is an unmet medical need. It matters to investors because conditional approval can allow a product to reach market and generate revenue sooner while the company still must provide further data and follow regulatory conditions; think of it like a provisional license that speeds market access but carries ongoing obligations and uncertainty.

orphan drug designation regulatory

"received Orphan Drug Designation (ODD)"

Orphan drug designation is a special status given to medicines developed to treat rare diseases affecting only a small number of people. This status often provides benefits like faster approval processes and financial incentives, making it more attractive for companies to develop these drugs. For investors, it signals potential for exclusive market rights and reduced competition, which can impact the drug’s profitability.

fast track designation regulatory

"Fast Track Designation (FTD)"

Fast track designation is a status the U.S. Food and Drug Administration grants to drugs intended to treat serious conditions and address an unmet medical need. It gives the developer more frequent communication with the FDA and can allow parts of the application to be reviewed on a rolling basis, and it may pave the way to priority review or accelerated approval. It can shorten development timelines, though it does not guarantee approval.

priority review voucher regulatory

"eligible to receive a Priority Review Voucher (PRV)"

A priority review voucher is a transferable regulatory incentive that lets a company move a future drug or device application to the front of the review line, shortening the review period by several months. For investors it matters because the voucher can speed up market access for a high-value product or be sold to other companies for significant cash, acting like a tradable fast-pass that can accelerate revenue or create immediate financial upside.

biologics license application regulatory

"complete a Biologics License Application (BLA)"

A biologics license application is a formal request submitted to regulatory authorities seeking approval to market a new biological medicine, such as vaccines or treatments made from living organisms. It is a comprehensive review process that evaluates the safety, effectiveness, and manufacturing quality of the product. For investors, receiving approval signals that a biological therapy can be sold to the public, potentially leading to revenue growth and market success.

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US Based Clinical Stage Oncology Company Begins Critical Step Following Successful September 2026 Scientific Advice Meeting

• Submission expected to be accepted in the fourth quarter of 2026
• Potential early market access decision expected from MHRA in the first quarter of 2027

Grasonville, Maryland--(Newsfile Corp. - November 10, 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 initiated a Conditional Marketing Authorisation Application (CMAA) process with the U.K. Medicines and Healthcare products Regulatory Agency (MHRA) for Herlystic™ (OST-HER2) in the prevention or delay of recurrence in fully resected, pulmonary metastatic osteosarcoma. The Company expects to complete the CMAA process later in the fourth quarter of 2026.

"The initiation of regulatory submissions to bring Herlystic to patients in 2027 has now begun," said Paul Romness, Chairman and CEO of OS Therapies. "With the very productive interactions we have had with MHRA, this filing sets the stage for our international regulatory early market access strategy. We expect that progress with MHRA will help facilitate international regulatory coordination under Project Orbis."

Herlystic has received Orphan Drug Designation (ODD), Fast Track Designation (FTD) and Rare Pediatric Disease Designation (RPDD) from the U.S. Food Drug Administration (FDA), as well as ODD and Advanced Therapeutic Medicinal Product (ATMP) designation from the European Medicines Agency (EMA). Herlystic was permitted access to the Centralised Procedure in Europe, allowing a unified, expedited regulatory review process rather than review of individual applications by each European Union (EU) Member State. 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. Two recent PRV sales occurred in October 2026, totaling $413 million (average $206.5 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 is engaging with FDA towards alignment on a suitable comparator (OST-400 osteosarcoma natural history study) to achieve interpretability of Herystic's Phase 2b clinical trial results such that biomarker data generated from that trial can be accepted as a surrogate clinical endpoint of treatment efficacy. The Company's Commissioner's National Priority Voucher (CNPV) letter of intent was accepted by FDA in the first quarter of 2026. OS Therapies intends to complete its CMAA submissions in the U.K. and Europe for Herlystic in metastatic osteosarcoma in the fourth quarter of 2026, and align with FDA in the near future on the suitability of OST-400 as comparator such that the Company can complete its ongoing BLA submission. MHRA has granted OS Therapies access to the U.K.'s Clinical Practice Research Datalink (CPRD) to increase patient data included in OST-400.

About OS Therapies
OS Therapies is a clinical stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma 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, 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 intends to complete a Biologics License Application (BLA) submission to the U.S. FDA for OST-HER2 in osteosarcoma, if approved, would become eligible to receive a Priority Review Voucher that it could then sell. The Company also anticipates requesting Conditional Marketing Authorisation Applications (CMAAs) from the U.K.'s Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency (EMA) . 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 chemistry, manufacturing and controls (CMC) of OST-HER; OST-HER2 product stability; Company funding runway and need for additional capital; Commissioner's National Priority Voucher(CNPV) status, priority review voucher value, 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/

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To view the source version of this press release, please visit https://www.newsfilecorp.com/release/323275

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

When does OS Therapies expect a U.K. decision on Herlystic?

OS Therapies expects a potential MHRA early market access decision in the first quarter of 2027. Submission acceptance is expected in the fourth quarter of 2026. The application concerns prevention or delay of recurrence in fully resected, pulmonary metastatic osteosarcoma.

Why is OS Therapies seeking FDA alignment on OST-400 for Herlystic?

OS Therapies is seeking agreement on OST-400 as a suitable comparator to interpret Herlystic’s Phase 2b results so that trial biomarker data can be accepted as a surrogate clinical endpoint of treatment efficacy. A surrogate endpoint is a substitute measure for treatment benefit.