OS Therapies Provides OST-HER2 Recurrent, Fully Resected, Pulmonary Metastatic Osteosarcoma Program Update Following FDA End of Phase 2 Meeting
OS Therapies (NYSE:OSTX) has provided a significant update following its End of Phase 2 Meeting with the FDA regarding OST-HER2 for recurrent, fully resected, pulmonary metastatic osteosarcoma. The company plans to begin a rolling Biologics Licensing Application (BLA) submission in September 2025.
Key achievements include positive clinical data with statistically significant 12-month Event Free Survival (p=0.0197) and interim 2-year overall survival data (p=0.0046) from its 40-patient Phase 2b trial. The FDA identified no significant safety concerns and agreed on non-clinical and CMC-related matters. The company is awaiting FDA guidance on efficacy endpoints and statistical analysis plans that would support either Accelerated Approval or full marketing authorization.
A crucial FDA/OSI public meeting is scheduled for October 10, 2025, focusing on advancing osteosarcoma drug development pathways. The company is also developing the OST-400 database to potentially support a synthetic control arm for the trial.
OS Therapies (NYSE:OSTX) ha comunicato un aggiornamento significativo dopo l'End of Phase 2 Meeting con la FDA riguardo a OST-HER2 per l'osteosarcoma polmonare metastatico ricorrente completamente asportato. L'azienda prevede di avviare una presentazione BLA (Biologics Licensing Application) a scorrimento a partire da settembre 2025.
Tra i risultati principali figurano dati clinici positivi con una sopravvivenza libera da eventi a 12 mesi statisticamente significativa (p=0.0197) e dati provvisori di sopravvivenza globale a 2 anni (p=0.0046) dallo studio di Fase 2b su 40 pazienti. La FDA non ha rilevato preoccupazioni significative sulla sicurezza e ha concordato sugli aspetti non clinici e CMC. L'azienda è in attesa di indicazioni dalla FDA sugli endpoint di efficacia e sui piani di analisi statistica che possano supportare sia l'Accelerated Approval che l'autorizzazione di mercato completa.
È prevista una riunione pubblica FDA/OSI il 10 ottobre 2025 incentrata sul progresso dei percorsi di sviluppo dei farmaci per l'osteosarcoma. L'azienda sta inoltre sviluppando il database OST-400 per supportare eventualmente un braccio di controllo sintetico per lo studio.
OS Therapies (NYSE:OSTX) ha ofrecido una actualización importante tras la reunión End of Phase 2 con la FDA sobre OST-HER2 para osteosarcoma pulmonar metastásico recurrente completamente resecado. La compañía planea iniciar la presentación BLA (Biologics Licensing Application) de forma rolling en septiembre de 2025.
Logros clave incluyen datos clínicos positivos con supervivencia libre de eventos a 12 meses estadísticamente significativa (p=0.0197) y datos provisionales de supervivencia global a 2 años (p=0.0046) del ensayo de Fase 2b con 40 pacientes. La FDA no identificó preocupaciones significativas de seguridad y estuvo de acuerdo en los aspectos no clínicos y relacionados con CMC. La compañía espera orientación de la FDA sobre los endpoints de eficacia y los planes de análisis estadístico que podrían respaldar la Aprobación Acelerada o la autorización completa de comercialización.
Hay una reunión pública FDA/OSI programada para el 10 de octubre de 2025, centrada en avanzar las vías de desarrollo de fármacos para osteosarcoma. La compañía también está desarrollando la base de datos OST-400 para apoyar potencialmente un brazo de control sintético del ensayo.
OS Therapies (NYSE:OSTX)는 재발성 완전 절제된 폐 전이성 골육종을 대상으로 한 OST-HER2의 End of Phase 2 미팅 후 중요한 업데이트를 발표했습니다. 회사는 2025년 9월부터 순차적(rolling) 생물학적제제 허가신청(BLA)을 제출할 계획입니다.
주요 성과로는 40명 대상의 2b상 시험에서 12개월 무사건 생존율이 통계적으로 유의미(p=0.0197)했고, 중간 2년 전체생존 데이터도 유의미(p=0.0046)한 긍정적 임상 결과를 확보한 점이 있습니다. FDA는 심각한 안전성 문제 없음을 확인했으며 비임상 및 CMC 관련 사항에 동의했습니다. 회사는 가속 승인(Accelerated Approval) 또는 완전 시판허가를 뒷받침할 수 있는 효능 평가 변수와 통계분석 계획에 대한 FDA의 지침을 기다리고 있습니다.
골육종 약물 개발 경로 진전에 관한 FDA/OSI 공개회의가 2025년 10월 10일로 예정되어 있습니다. 또한 회사는 시험의 합성 대조군을 지원할 수 있는 OST-400 데이터베이스도 개발 중입니다.
OS Therapies (NYSE:OSTX) a fourni une mise à jour importante à la suite de son End of Phase 2 Meeting avec la FDA concernant OST-HER2 pour l'ostéosarcome pulmonaire métastatique récurrent, complètement réséqué. La société prévoit d'entamer un dépôt BLA (Biologics Licensing Application) en mode progressif en septembre 2025.
Parmi les réalisations clés figurent des données cliniques positives montrant une survie sans événement à 12 mois significative sur le plan statistique (p=0.0197) et des données provisoires de survie globale à 2 ans (p=0.0046) issues de l'essai de phase 2b impliquant 40 patients. La FDA n'a identifié aucune préoccupation de sécurité majeure et a validé les aspects non cliniques et liés au CMC. La société attend les directives de la FDA sur les critères d'efficacité et les plans d'analyse statistique susceptibles de soutenir une approbation accélérée ou une autorisation commerciale complète.
Une réunion publique FDA/OSI est prévue le 10 octobre 2025, portant sur l'avancement des voies de développement de médicaments pour l'ostéosarcome. La société développe également la base de données OST-400 pour potentiellement étayer un bras de contrôle synthétique de l'essai.
OS Therapies (NYSE:OSTX) hat nach dem End of Phase 2 Meeting mit der FDA ein wichtiges Update zu OST-HER2 bei rezidiviertem, vollständig reseziertem, pulmonalem metastasiertem Osteosarkom veröffentlicht. Das Unternehmen plant, im September 2025 eine fortlaufende (rolling) BLA-Einreichung (Biologics Licensing Application) zu starten.
Zu den wichtigsten Errungenschaften zählen positive klinische Daten mit einer statistisch signifikanten 12‑Monats-ereignisfreien Überlebensrate (p=0.0197) sowie vorläufige 2‑Jahres-Gesamtüberlebensdaten (p=0.0046) aus der 40‑Patienten-Phase‑2b‑Studie. Die FDA erkannte keine wesentlichen Sicherheitsbedenken und stimmte nicht-klinischen sowie CMC‑Fragen zu. Das Unternehmen erwartet FDA‑Leitlinien zu Wirksamkeitsendpunkten und statistischen Analyseplänen, die entweder eine beschleunigte Zulassung oder eine vollständige Marktzulassung unterstützen könnten.
Eine öffentliche FDA/OSI‑Sitzung zum Thema Weiterentwicklung der Arzneimittelzulassungswege für Osteosarkom ist für den 10. Oktober 2025 angesetzt. Zudem entwickelt das Unternehmen die OST-400‑Datenbank, um möglicherweise eine synthetische Kontrollgruppe für die Studie zu unterstützen.
- Statistically significant positive clinical results in Phase 2b trial
- No significant safety concerns identified by FDA
- Agreement reached on non-clinical and CMC-related matters
- Eligibility for PDUFA small business fee waiver
- FDA acceptance of Expression of Interest for National Priority Voucher
- Final FDA decisions on acceptable efficacy outcome measures still pending
- Uncertainty regarding which FDA guidance to rely upon for clinical efficacy
- Additional data generation required for Q4/25 submission
Insights
OS Therapies achieves FDA alignment on BLA submission for metastatic osteosarcoma treatment, with statistically significant survival data already shown.
OS Therapies has reached a critical regulatory milestone in their development of OST-HER2, a therapy targeting recurrent, fully resected, pulmonary metastatic osteosarcoma. Following their End of Phase 2 Meeting with the FDA, the company reports significant alignment on several crucial aspects required for a successful Biologics Licensing Application (BLA). The FDA acknowledged no significant safety concerns with OST-HER2, and agreements were reached on non-clinical matters and Chemistry, Manufacturing, and Controls (CMC) requirements.
The most promising aspect of this update is the statistically significant clinical data already achieved in their 40-patient Phase 2b trial, including 12-month Event Free Survival (p = 0.0197) and interim 2-year overall survival data (p = 0.0046). These p-values indicate strong evidence against the null hypothesis, suggesting the treatment effect is unlikely due to chance.
The regulatory pathway for this therapy appears to be gaining clarity, with several potential routes to approval. The FDA is actively evaluating potential amended clinical trial endpoints and statistical analysis plans that could support either Accelerated Approval or full marketing authorization. The upcoming FDA workshop on October 10, 2025, in collaboration with the Osteosarcoma Institute, represents an important forum to establish consensus on clinically meaningful outcome measures for osteosarcoma treatments.
OS Therapies is also building a natural history database (OST-400) to potentially develop a synthetic control arm, which could serve as a comparator using FDA-accepted statistical methods for single-arm trials in rare diseases. The company has already begun preparations for a rolling BLA submission, expected to start later this quarter, and has received confirmation of eligibility for a PDUFA small business fee waiver, which would reduce regulatory filing costs.
For a rare pediatric cancer with high mortality rates and limited treatment options, this regulatory progress represents a significant step toward potentially bringing a new therapeutic option to patients with metastatic osteosarcoma.
- Company on track to begin submission of a rolling Biologics Licensing Application (BLA) request for OST-HER2 to U.S. Food & Drug Administration in September 2025
New York, New York--(Newsfile Corp. - September 2, 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 stakeholders with a detailed update regarding the Company's OST-HER2 recurrent, fully resected, pulmonary metastatic osteosarcoma program (the "Metastatic Osteosarcoma Program") following a highly productive End of Phase 2 Meeting with the US Food & Drug Administration ("FDA"). The Company remains on track to begin rolling submission of a Biologics Licensing Application ("BLA") request to FDA for the Metastatic Osteosarcoma Program in September 2025.
Key Metastatic Osteosarcoma Program updates following FDA End of Phase 2 Meeting
FDA and the Company achieved alignment in a number of areas crucial for a successful BLA:
- No significant safety concerns with OST-HER2 in the targeted indication were identified based on the excellent safety profile from clinical data to date
- Non-clinical related matters were agreed to with minimal follow-up required
- Chemistry, Manufacturing, and Controls ("CMC")-related matters were agreed to, with clear guidance on final steps needed to support a BLA approval. The Company expected the feedback it received from FDA, based on prior feedback from the OST-AXAL (previously ADXS-AXAL) program. In February 2025, the Company began generating the necessary data and expects to have it ready for submission to FDA as part of the rolling BLA submission in Q4/25, ahead of an expected pre-BLA meeting
FDA continues to evaluate the appropriateness of various potential amended clinical trial efficacy endpoints, statistical analysis plans, and other protocol amendments that would support a BLA, whether via the Accelerated Approval Program ("Accelerated Approval") or full marketing authorization. As part of the effort to understand the unique challenges presented by osteosarcoma, FDA, together with patient advocacy group the Osteosarcoma Institute ("OSI"), is holding a public meeting with key osteosarcoma stakeholders on October 10, 2025, entitled "Advancing Osteosarcoma Drug Development – Connecting Research and Regulatory Pathways for Improved Outcomes" to gain alignment on the best path(s) forward to rapidly bring new therapies to market. FDA committed to working closely with the Company by prioritizing formal and informal meetings, with the first informal meeting scheduled for mid-September 2025
- Current single arm, open-label Phase 2b study design, originally recommended by FDA in 2020 as a proof-of-concept study, compares OST-HER2-treated patients with historical clinical outcomes data published by the Children's Oncology Group ("COG") consortium. The Company continues to seek direction on which FDA guidance to rely upon with respect to clinical efficacy for the pending BLA submission
- New FDA Draft Guidance entitled 'Approaches to Assessment of Overall Survival in Oncology Clinical Trials' made public on August 18, 2025 (the "Draft FDA Overall Survival Guidance"), provides potential pathways to evaluate osteosarcoma clinical trial efficacy data. The Company has achieved statistically significant positive final 12-month Event Free Survival (EFS) data (p = 0.0197) and interim 2-year overall survival data (p = 0.0046) from its 40 patient Phase 2b trial
- Final FDA guidance made public in December 2023 entitled 'Rare Diseases: Considerations for the Development of Drugs and Biological Products,' provides additional potential pathways to evaluate osteosarcoma clinical trial efficacy data. From 2015 to 2022, single arm Phase 1 or Phase 2 trials supported 45 out of 84 molecular targeted marketing authorizations in oncology
The Company is continuing to support the expansion of natural history database OST-400, "Recurrent Osteosarcoma after Resection in Children and Young Adults: A Retrospective Longitudinal Study". Data is being sourced from multiple leading US and international oncology research institutions, in addition to real world data sources. OST-400 database is being assembled in order to be able to develop a synthetic control arm suitable to support a randomization process that could serve as comparator arm in the event FDA relies upon its 2023 Rare Diseases guidance. Various FDA-accepted statistical analysis methods reviewed in this Guidance allow for randomization after treatment in single-arm trials. Final decisions on acceptable efficacy outcome measures are needed to support Regenerative Medicine Advanced Therapy ("RMAT") designation, Breakthrough Therapy designation ("BTD") and Accelerated Approval or full approval, and the Company expects significant progress to be made towards that end at the October 10, 2025 FDA/OSI osteosarcoma workshop.
Additionally, the Company received confirmation from FDA that it is eligible for a Prescription Drug User Fee Act (“PDUFA”) small business fee waiver, with a final decision on the PDUFA fee waiver anticipated by the end of the third quarter of 2025. FDA has also accepted the Company’s Expression of Interest for the Commissioner’s National Priority Voucher (CNPV).
"It is clear from the End of Phase 2 Meeting that FDA is committed to finding paths forward to bring new therapies forward for osteosarcoma given the continued high mortality rates in this rare pediatric cancer," said Paul Romness, MHP, Chair & CEO of OS Therapies. "We have already begun the work of preparing responses to FDA's comments stemming from the meeting and look forward to beginning the rolling BLA submission later this quarter. We will continue the highly productive ongoing dialogue we have with FDA as it relates to OST-HER2's potential to improve both Event Free Survival and Overall Survival in the fully resected, pulmonary metastatic osteosarcoma setting. We expect that the October 10th, 2025 workshop FDA and OSI are holding will provide the opportunity for stakeholders to coalesce around the key outcome measures that are clinically meaningful for the brave patients, their families and clinicians who help manage this difficult to treat patient population."
Concurrent with today's announcement, the Company announced that Luis Rojas, PhD (CEO of InCSD, an independent biostatistics firm managing the Metastatic Osteosarcoma Program and compiling data for the OST-400 natural history database) has accepted an invitation to present at the Rare Trials Summit being held in Boston on September 9, 2025. Dr. Rojas' presentation entitled "Accelerating Rare Disease Therapies: Strategies for Efficient Clinical Development" will review the key challenges in developing new treatments for ultra-rare diseases and clinical subsets thereof, such as recurrent, fully resected, pulmonary metastatic osteosarcoma and how to efficiently overcome them. Dr. Rojas will highlight how the data generated from the OST-HER2 Phase 2b clinical trial can be used in a manner compliant with FDA guidance to support Accelerated Approval or full approval for OST-HER2.
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
Stephanie Chen
Elev8 New Media
stephanie@elev8newmedia.com
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FAQ
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