OS Therapies Provides OST-HER2 UK MHRA and US FDA Osteosarcoma Regulatory Update
OS Therapies (NYSE American: OSTX) has announced updates to its regulatory submission strategy for OST-HER2, targeting osteosarcoma treatment. The company plans to prioritize its UK MHRA conditional Marketing Authorisation Application (MAA) submission in December 2025, followed by the US FDA Biologics Licensing Application (BLA) in January 2026.
Following positive feedback from the UK MHRA's August 2025 Scientific Advice Meeting, the agency has accepted the use of historical control arm data. For the FDA submission, the company will propose using immune activation biomarker coupled with overall survival data as surrogate efficacy endpoints for Accelerated Approval, following positive End of Phase 2 Meeting outcomes.
The submissions are based on data from the completed Phase 2b clinical trial, currently in long-term follow-up phase, for OST-HER2 in preventing recurrent, fully resected, pulmonary metastatic osteosarcoma.
OST Therapies (NYSE American: OSTX) ha annunciato aggiornamenti alla strategia di presentazione regolatoria per OST-HER2, mirata al trattamento dell’osteosarcoma. L’azienda intende dare la priorità alla presentazione della Conditional Marketing Authorisation Application (MAA) al UK MHRA entro dicembre 2025, seguita dalla Biologics Licensing Application (BLA) della US FDA entro gennaio 2026.
In seguito al riscontro positivo dell’incontro di consulenza scientifica di agosto 2025 con il UK MHRA, l’agenzia ha accettato l’uso di dati provenienti da bracci di controllo storici. Per la presentazione alla FDA, l’azienda proporrà l’uso di un biomarcatore di attivazione immunitaria insieme ai dati sulla sopravvivenza globale come endpoint di efficacia surrogate per l’Accelerated Approval, a seguito di esiti positivi dell’End of Phase 2 Meeting.
Le presentazioni si basano sui dati del trial di fase 2b completato, attualmente in follow-up a lungo termine, per OST-HER2 nella prevenzione della recidiva di osteosarcoma polmonare metastatico completamente asportato.
OS Therapies (NYSE American: OSTX) ha anunciado actualizaciones en su estrategia de presentación regulatoria para OST-HER2, centrada en el tratamiento del osteosarcoma. La compañía planea dar prioridad a la presentación de la Solicitud de Autorización de Comercialización Condicional (MAA) ante la MHRA del Reino Unido en diciembre de 2025, seguida de la Solicitud de Licencia de Biológicos (BLA) ante la FDA de EE. UU. en enero de 2026.
Tras recibir comentarios positivos de la Reunión de Asesoría Científica de agosto de 2025 de la MHRA, la agencia ha aceptado el uso de datos del brazo de control histórico. Para la presentación ante la FDA, la compañía propondrá usar un biomarcador de activación inmunitaria junto con datos de supervivencia global como endpoints de eficacia sustitutos para la Aprobación Acelerada, tras resultados positivos de la End of Phase 2 Meeting.
Las presentaciones se basan en datos del ensayo clínico de fase 2b completado, actualmente en seguimiento a largo plazo, para OST-HER2 en la prevención de recurrencia de osteosarcoma pulmonar metastásico completamente resecado.
OST Therapies (NYSE American: OSTX)는 OST-HER2의 규제 제출 전략 업데이트를 발표했으며, 골육종 치료를 목표로 합니다. 이 회사는 2025년 12월까지 영국 MHRA의 조건부 마케팅 승인 신청(MAA)을 우선 추진하고, 2026년 1월까지 미국 FDA의 생물학적 제제 허가 신청(BLA)을 순차적으로 제출할 계획입니다.
2025년 8월 MHRA의 과학자문회의에서 긍정적인 피드백을 받은 후, 기관은 과거 대조군 데이터의 사용을 수용했습니다. FDA 제출에 대해서는 Accelerated Approval를 위한 대체 효능 엔드포인트로 면역 활성화 바이오마커와 전체 생존 데이터를 결합하여 제시할 예정이며, Phase 2 종료 회의의 긍정적 결과에 따릅니다.
제출은 완료된 2b상 임상시험의 데이터를 기반으로 하며, 현재 장기 추적 중인 전이성 폐 전절제된 골육종의 재발 예방을 위한 OST-HER2에 관한 것입니다.
OST Therapies (NYSE American: OSTX) a annoncé des mises à jour de sa stratégie de dépôt réglementaire pour OST-HER2, visant le traitement de l’ostéosarcome. L’entreprise prévoit de privilégier la soumission de l’Application d’Autorisation de Mise sur le Marché Conditionnelle (MAA) au MHRA du Royaume-Uni en décembre 2025, suivie de la Demande de Licence Biologique (BLA) auprès de la FDA américaine en janvier 2026.
Suite aux retours positifs de la réunion scientifique d’août 2025 avec le MHRA, l’agence a accepté l’utilisation des données du bras de contrôle historique. Pour la soumission à la FDA, l’entreprise proposera d’utiliser un biomarqueur d’activation immunitaire associé aux données de survie globale comme endpoints d’efficacité substituts pour une Approbation Accélérée, à la suite des résultats positifs de la End of Phase 2 Meeting.
Les dépôts reposent sur les données de l’essai de phase 2b terminé, actuellement en suivi à long terme, pour OST-HER2 dans la prévention d’une rechute de l’ostéosarcome pulmonaire métastatique entièrement réséqué.
OST Therapies (NYSE American: OSTX) hat Aktualisierungen seiner regulatorischen Einreichungsstrategie für OST-HER2 bekannt gegeben, die auf die Behandlung von Osteosarkom abzielen. Das Unternehmen plant, seine Priorität auf die britische MHRA Conditional Marketing Authorisation Application (MAA) Einreichung im Dezember 2025 zu legen, gefolgt von der US FDA Biologics Licensing Application (BLA) im Januar 2026.
Nach positivem Feedback vom Scientific Advice Meeting der MHRA im August 2025 hat die Behörde die Nutzung historischer Kontrollarm-Daten akzeptiert. Für die FDA-Einreichung wird das Unternehmen vorschlagen, einen Immunaktivierungs-Biomarker zusammen mit Daten zur Gesamtüberleben als surrogate Endpunkte für Accelerated Approval zu verwenden, nach positiven Ergebnissen des End of Phase 2 Meetings.
Die Einreichungen basieren auf Daten der abgeschlossenen Phase-2b-Studie, derzeit in Langzeit-Nachbeobachtung, für OST-HER2 zur Verhinderung von rezidivierendem, vollständig reseziertem pulmonalem metastasierendem Osteosarkom.
OST Therapies (NYSE American: OSTX) أعلنت عن تحديثات في استراتيجيتها لتقديم الطلبات التنظيمية لـ OST-HER2، والتي تستهدف علاج الأورام العظمية. تخطط الشركة لإعطاء الأولوية لتقديم طلب ترخيص التسويق المشروط (MAA) لدى MHRA المملكة المتحدة في ديسمبر 2025، يليها طلب ترخيص المستحضرات الحيوية (BLA) لدى FDA الأمريكية في يناير 2026.
بعد تلقي تعليقات إيجابية من اجتماع المشورة العلمية في أغسطس 2025 مع MHRA، قبلت الوكالة استخدام بيانات الذراع الضابط التاريخي. بالنسبة لتقديم FDA، ستقترح الشركة استخدام علامة بيولوجيةierte تحفيز المناعة بجانب بيانات البقاء على قيد الحياة الكلية كطرف نقاط للفعالية البديلة من أجل الموافقة السريعة، عقب نتائج إيجابية من End of Phase 2 Meeting.
تعتمد الطلبات على بيانات تجربة المرحلة 2b المكتملة، التي هي حالياً في متابعة طويلة الأجل، لـ OST-HER2 في الوقاية من عودة الورم العظمي النخاعي الرئوي المتناثر بشكل كامل.
OST Therapies (NYSE American: OSTX) 已宣布更新其 OST-HER2 的监管提交策略，目标是治疗骨肉瘤。公司计划在 2025年12月优先提交英国 MHRA 的有条件上市许可申请（MAA），随后在 2026年1月提交美国 FDA 的生物制品许可申请（BLA）。
在英国 MHRA 于 2025 年 8 月科学咨询会议获得积极反馈后，该机构已接受使用历史对照组数据。对于向 FDA 提交，公司将提出将免疫激活生物标志物与总体生存数据结合，作为替代性疗效终点以获得加速批准，前提是阶段末 2 会议结果积极。
这些提交基于已完成的 Phase 2b 临床试验的数据，目前处于长期随访阶段，针对 OST-HER2 用于预防完全切除的肺部转移性骨肉瘤的复发。
- None.
- FDA alignment issues regarding suitable comparators for efficacy data
- Additional Type C meeting required with FDA for biomarker data review
- Regulatory approval timeline extended due to sequential submissions
Insights
OS Therapies reports positive regulatory momentum for OST-HER2 with UK submission prioritized before FDA, both expected by January 2026.
OS Therapies is demonstrating smart regulatory strategy by sequencing its OST-HER2 submissions to prioritize the UK MHRA conditional approval pathway ahead of the US FDA. This dual-track approach maximizes chances of success, as the UK MHRA has already shown flexibility by accepting historical control arm data—a critical development that addresses one of the most challenging aspects of rare disease drug development where randomized controlled trials face ethical and practical limitations.
The company's regulatory strategy centers on a key distinction between the agencies: while both have seemingly aligned on safety considerations, the UK MHRA has explicitly accepted historical controls as a comparator arm, while the FDA still requires additional discussion about appropriate efficacy endpoints. The upcoming Type C meeting with FDA will focus on whether immune activation biomarkers coupled with overall survival data can serve as surrogate efficacy endpoints under Accelerated Approval.
The tight submission timeline (both applications expected within 30 days of each other between December 2025-January 2026) suggests the company has confidence in its data package. The UK submission could potentially create regulatory momentum that influences the FDA review, particularly given the cross-reference to canine overall survival data published in the Journal of Molecular Therapy that correlates immune activation with clinical benefit. For a rare and aggressive cancer like osteosarcoma with pulmonary metastases, this biomarker-based approach represents a pragmatic pathway to bring a potentially beneficial treatment to patients while continuing to gather definitive survival data.
Positive MHRA feedback and FDA engagement suggest promising regulatory pathway for OST-HER2 in treating recurrent metastatic osteosarcoma.
The regulatory update for OST-HER2 in metastatic osteosarcoma represents meaningful progress in addressing a serious unmet medical need. Osteosarcoma with pulmonary metastases has historically poor outcomes, and the prevention or delay of recurrent, fully resected disease represents an important clinical goal. The company's Phase 2b trial, now in long-term follow-up, appears to have generated sufficient data to pursue approval pathways in both the UK and US.
What's particularly notable is the company's scientific approach of correlating immune activation biomarkers with survival outcomes. This translational approach leverages their previously published animal data showing this correlation in the Journal of Molecular Therapy. Such biomarker-driven strategies are increasingly important in modern oncology drug development, especially for rare cancers where traditional endpoints may take prohibitively long to reach statistical significance.
The UK MHRA's willingness to accept historical control data is significant and reflects the growing recognition among regulators that traditional randomized controlled trials may not always be feasible for rare diseases. The additional support from MHRA to access the UK's Clinical Practice Research Datalink for case-matched external control arm data further strengthens the company's approach. If successful, this regulatory strategy could establish an important precedent for other rare cancer therapies, particularly immunotherapeutic approaches where biomarker-driven development may accelerate patient access while maintaining scientific rigor.
- Company updates sequence of OST-HER2 regulatory submissions, prioritizing UK MHRA conditional Marketing Authorisation Application (MAA) submission following positive August 2025 Scientific Advice Meeting feedback from UK MHRA
- In principle, UK MHRA accepts use of historical control arm to support conditional MAA
- UK MHRA conditional MAA and US FDA Biologics Licensing Application (BLA) submissions expected to be completed within 30 days of each other, between December 2025 and January 2026
- Company to propose use of immune activation biomarker coupled with overall survival data as surrogate efficacy endpoint to support Accelerated Approval in Type C Meeting invited by FDA, following positive End of Phase 2 Meeting and follow-up interactions
New York, New York--(Newsfile Corp. - September 30, 2025) - OS Therapies Inc. (NYSE American: OSTX) ("OS Therapies" or "the Company"), a clinical-stage cancer immunotherapy and antibody drug conjugate biotechnology company, today provided a regulatory update on its plans for filing marketing authorizations in the United States (US) and United Kingdom (UK) for OST-HER2 in the prevention or delay of recurrent, fully resected, pulmonary metastatic osteosarcoma based on a data generated from its completed Phase 2b clinical trial currently in the long term follow-up phase. The Company has updated its regulatory filing sequence to prioritize the UK Medicines and Healthcare products Regulatory Agency (MHRA) conditional Marketing Authorisation Application (MAA) final module submission to immediately precede its US FDA Biologics Licensing Application (BLA) final module submission under the Accelerated Approval Program (Accelerated Approval). The Company expects to complete the MHRA conditional MAA submission in December 2025, with the FDA BLA Accelerated Approval submission expected in January 2025.
The Company has submitted a conditional MAA Pre-Submission Request following MHRA feedback arising from its August 2025 Scientific Advice Meeting (SAM). The Company expects to receive formal acceptance of a rolling review request to MHRA in the near future. MHRA has aligned around the use of peer-reviewed historical control data as a suitable comparator arm to support the Company's conditional MAA request. MHRA further agreed to support OS Therapies efforts to obtain case-matched external control arm data by providing access to the UK's Clinical Practice Research Datalink (CPRD).
The information in the MHRA conditional MAA submission is closely aligned with the information in the planned US FDA BLA Accelerated Approval request, apart from alignment around an acceptable comparator arm against which to compare the efficacy data from the Company's Phase 2b trial of OST-HER2. After the End of Phase 2 and follow-up conversations with FDA, general alignment was reached on all matters, except for suitable comparators. At the direction of FDA, the Company has requested an additional Type C meeting to review updated overall survival and new biomarker data. The Company intends to confirm whether immune activation biomarker data as the surrogate marker correlated with 2-year interim overall survival as a secondary endpoint would be a suitable surrogate marker of efficacy to support Accelerated Approval.
"We've gained a deeper understanding of what FDA is now looking for to support an efficacy claim as a result of our interactions over the last 45 days," said Paul Romness, MHP, Chairman & CEO of OS Therapies. "The FDA agreed with the Company that OST-HER2 had a strong safety profile and the canine overall survival data correlating with immune activation biomarker data recently published in Journal of Molecular Therapy, attributing clinical benefit to OST-HER2 treatment. We intend to present a similar data package generated from our Phase 2b human clinical trial of OST-HER2 and believe the FDA will support this approach to Accelerated Approval."
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. 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 2025 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
Jessica Starman, MBA
Elev8 New Media
media@ostherapies.com
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