OS Therapies Announces FDA PDUFA Waiver & EMA Grants Union Marketing Authorisation Eligibility

Rhea-AI Summary

OS Therapies (NYSE American: OSTX) announced regulatory progress for OST-HER2 and its Metastatic Osteosarcoma Program on December 5, 2025.

The U.S. FDA granted a waiver of the BLA application fee for BLA 125867 (OST-HER2). The EMA CHMP granted Union Marketing Authorisation eligibility for OST-HER2 in prevention or delay of recurrent, fully‑resected pulmonary metastatic osteosarcoma and requested an accelerated MAA submission by February 28, 2026. The company completed pre-meeting submissions to the UK MHRA for a pre‑MAA meeting on Dec 8, 2025 and scheduled a Type C meeting with the FDA on Dec 11, 2025. OS Therapies intends to review commercial CMC, non‑clinical considerations, and propose a global confirmatory study to support conditional/accelerated approvals.

Positive

• FDA granted a waiver of the BLA application fee for BLA 125867
• EMA CHMP granted Union Marketing Authorisation eligibility for OST-HER2
• EMA requested an accelerated MAA submission by Feb 28, 2026
• Completed pre‑meeting submissions to MHRA for Dec 8, 2025 meeting

Negative

• Accelerated MAA deadline (Feb 28, 2026) may compress submission timeline
• Regulatory approvals conditioned on confirmatory/global study design and CMC

Key Figures

BLA number 125867 FDA waiver of application fee for BLA 125867 for OST-HER2

MHRA pre-MAA meeting December 8, 2025 Scheduled pre-MAA meeting with UK MHRA

FDA Type C meeting December 11, 2025 Scheduled Type C meeting with FDA

EMA MAA request deadline February 28, 2026 EMA CHMP requested accelerated MAA submission by this date

Market Reality Check

$1.82 Last Close

Volume Volume 188,021 is below 20-day average 244,810 (relative volume 0.77x). normal

Technical Price $1.82 is trading slightly above 200-day MA at $1.81.

Peers on Argus

OSTX is up 4% while close peers show mixed moves (e.g., IMMX +17.87%, ANL -12.59%), and no peers appear in the momentum scanner, pointing to a stock-specific reaction.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Nov 25	Naming / regulatory	Positive	+4.7%	WHO assigned INN ‘daznelimgene lisbac’ and timelines for regulatory filings.
Nov 21	Coverage update	Positive	+5.6%	Analyst update highlighting strong Phase 2b survival and financing runway extension.
Nov 20	Spinoff announcement	Positive	-1.8%	Plan to spin off OS Animal Health and outline veterinary OST-HER2 market potential.
Nov 17	Earnings / update	Positive	-5.0%	Q3 2025 results with positive OST-HER2 data, regulatory timelines, and new financing.
Oct 22	Clinical data	Positive	+1.7%	Phase 2b subgroup OS/EFS data showing strong survival versus natural history.

Pattern Detected

Recent OSTX news has often been positive clinically/regulatorily, but price reactions have been mixed with both rallies and sell-the-news responses.

Recent Company History

Over the past six weeks, OS Therapies has steadily advanced OST-HER2 toward commercialization. On Oct 22, 2025, it reported favorable Phase 2b subgroup survival data. Subsequent Q3 2025 results highlighted strong efficacy and outlined BLA/MAA timelines. In late November, coverage updates and the WHO nonproprietary name “daznelimgene lisbac” reinforced regulatory momentum, with multiple items noting planned filings in January 2026. Today’s announcement of an FDA BLA fee waiver and EMA Union Marketing Authorisation eligibility fits this ongoing regulatory progression.

Regulatory & Risk Context

Active S-3 Shelf Registration 2025-08-08

$100,000,000 registered capacity

The company has an effective S-3 shelf filed on 2025-08-08 to offer up to $100,000,000 of securities, plus an at-the-market program for up to $18,000,000 in common stock; prospectus supplements on 2025-08-25 and 2025-09-30 indicate the shelf has already been utilized.

Market Pulse Summary

This announcement advances OST-HER2’s regulatory path, with an FDA BLA fee waiver, EMA Union Marketing Authorisation eligibility, and specific meeting dates with FDA and MHRA leading into an accelerated MAA submission by February 28, 2026. These updates build on prior Phase 2b survival data and detailed timelines disclosed in recent filings and press releases. Investors may watch execution of upcoming regulatory meetings, financing via the existing $100,000,000 shelf, and progress toward planned BLA and MAA submissions.

Key Terms

pdufa regulatory

"OS Therapies Announces FDA PDUFA Waiver & EMA Grants Union"

PDUFA, short for the Prescription Drug User Fee Act, is a law that allows drug companies to pay fees to the government to speed up the review process for new medicines. This helps bring important drugs to market more quickly, which can impact their availability and pricing. For investors, PDUFA timelines can influence the timing of a drug’s approval and potential market success.

marketing authorisation application regulatory

"requested an accelerated Marketing Authorisation Application ('MAA') submission"

A marketing authorisation application is the formal package a drug or medical-device maker submits to a health regulator to get permission to sell a product. Think of it as an application for a sales license: regulators review safety, effectiveness and manufacturing quality before granting permission. Investors watch these submissions because approval unlocks revenue and reduces development risk, while rejection or delays can materially affect a company’s value and timeline.

conditional approval regulatory

"design to support an MAA Conditional Approval from MHRA"

Conditional approval is a formal confirmation that a product or plan is permitted to proceed, provided certain specified requirements are met within a designated timeframe. For investors, it signals that approval is nearly complete but depends on the fulfillment of specific conditions, which could influence the final outcome or timeline. This status helps stakeholders assess the likelihood of success while identifying any remaining hurdles.

accelerated approval regulatory

"a Biologics Licensing Application (BLA) under the Accelerated Approval Program"

Accelerated approval is a process that allows new medical treatments to be approved more quickly than usual if they address serious or life-threatening conditions and show promising early results. For investors, it signals that a treatment may reach the market sooner, potentially boosting a company's prospects, but it also involves some uncertainty since full evidence of effectiveness is still being gathered.

AI-generated analysis. Not financial advice.

• U.S. FDA grants waiver of application fee for BLA Filing of OST-HER2
• Scheduled pre-Marketing Authorisation Application meeting with United Kingdom's Medicines and Healthcare products Regulatory Agency on December 8, 2025
• Scheduled Type C Meeting with United States Food & Drug Administration on December 11, 2025

New York, New York--(Newsfile Corp. - December 5, 2025) - OS Therapies Inc. (NYSE American: OSTX) ("OS Therapies" or "the Company"), the world leader in listeria-based cancer immunotherapies, today announced the United States Food & Drug Administration (FDA) granted the Company waiver of the application fee for BLA 125867 for OST-HER2.

Additionally, the European Medicines Agency (EMA) Committee for Medicinal Products for Human Use ('CHMP') granted Union Marketing Authorisation eligibility for OST-HERs in the prevention or delay of recurrent, fully-resected, pulmonary metastatic osteosarcoma (the 'Metastatic Osteosarcoma Program'). EMA CHMP requested an accelerated Marketing Authorisation Application ('MAA') submission for the Metastatic Osteosarcoma Program by February 28, 2026. The intent of the European Union-wide Centralised Procedure is to support the marketing authorization of medicines, where there is a single application, a single evaluation and a single authorization for all EU Member States.

Concurrent with this announcement, the Company has completed pre-meeting submissions to the United Kingdom's Medicines and Healthcare products Regulatory Agency (MHRA) for its pre-MAA meeting on December 8, 2025 and its Type C Meeting with the FDA on December 11, 2025. The Company intends to review final commercial CMC and non-clinical considerations, as well as propose the global confirmatory study design to support an MAA Conditional Approval from MHRA, and a Biologics Licensing Application (BLA) under the Accelerated Approval Program ('Accelerated Approval') from FDA, respectively.

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 Rare Pediatric Disease Designation (RPDD) from the U.S. Food & Drug Administration and Fast-Track and Orphan Drug designations from the U.S. FDA and 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. The Company anticipates submitting a Biologics Licensing Application (BLA) to the U.S. FDA for OST-HER2 in osteosarcoma in early 2026 and, if approved, would become eligible to receive a Priority Review Voucher that it could then sell. 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.

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 the 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, most recent Quarterly Report on Form 10-Q 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.

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/277041

FAQ

What did OS Therapies (OSTX) announce about OST-HER2 on December 5, 2025?

OS Therapies announced the FDA waived the BLA 125867 application fee and EMA CHMP granted Union Marketing Authorisation eligibility for OST-HER2.

What deadline did EMA CHMP set for OS Therapies' MAA submission for OST-HER2 (OSTX)?

EMA CHMP requested an accelerated MAA submission by February 28, 2026 for the metastatic osteosarcoma program.

When are OS Therapies' regulatory meetings with MHRA and FDA scheduled (OSTX)?

OS Therapies completed pre‑MAA submissions to MHRA for a meeting on Dec 8, 2025 and has a Type C meeting with FDA on Dec 11, 2025.

How does the FDA fee waiver affect OSTX's BLA filing plans?

The fee waiver removes the BLA application cost for BLA 125867, reducing upfront regulatory expense for the OST-HER2 filing.

What regulatory pathway is OS Therapies pursuing for OST-HER2 in the U.S. and EU (OSTX)?

OS Therapies intends to pursue a U.S. BLA under Accelerated Approval and an EU MAA via the centralised procedure with conditional/confirmatory study plans.