NEW YORK, NY — December 5, 2025 — OS Therapies Inc. announced two major regulatory milestones advancing its lead immunotherapy OST-HER2, including an FDA waiver of the application fee for its upcoming Biologics License Application (BLA) and an EMA Committee for Medicinal Products for Human Use (CHMP) decision granting Union Marketing Authorisation eligibility for the company’s metastatic osteosarcoma program. These developments coincide with scheduled regulatory meetings in the United Kingdom and the United States as the company prepares final CMC, non-clinical, and global confirmatory study plans ahead of accelerated approval filings.
Science Significance
OST-HER2 represents a first-in-class, listeria-based cancer immunotherapy designed to stimulate a strong immune response against the HER2 protein, a clinically validated target across multiple solid tumors. The candidate has demonstrated statistically significant 12-month event-free survival outcomes in a Phase 2b study for recurrent, fully resected, pulmonary metastatic osteosarcoma, providing essential validation for its underlying platform. With supporting preclinical data across various breast cancer models and a completed Phase 1 breast cancer trial, OST-HER2 illustrates the scientific potential of microbial vector-based immunotherapy to reshape treatment landscapes for rare and hard-to-treat malignancies.
Regulatory Significance
The regulatory progress reported today carries substantial implications. The FDA’s PDUFA application-fee waiver for BLA 125867 underscores the program’s alignment with public-health priorities, particularly within rare pediatric oncology. Concurrently, the EMA CHMP’s Union Marketing Authorisation eligibility and request for an accelerated MAA submission by February 28, 2026 signals strong European regulatory momentum for OST-HER2 in recurrent pulmonary metastatic osteosarcoma. Scheduled interactions with the MHRA on December 8 and the FDA Type C meeting on December 11 will shape the final CMC package, non-clinical datasets, and confirmatory global study design supporting conditional MHRA approval and FDA accelerated approval. These movements directly intersect with cGMP readiness, regulatory documentation, clinical-quality assurance, and global harmonization requirements, making the update highly significant for GxP-focused stakeholders.
Business Significance
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The dual regulatory advancements strengthen OS Therapies’ trajectory toward commercialization, positioning OST-HER2 as a potential first-to-market immunotherapy for metastatic osteosarcoma, an area of severe unmet medical need. Achieving BLA and MAA milestones may unlock major economic advantages, including eligibility for a Priority Review Voucher upon U.S. approval—an asset that can be monetized for substantial value. The company’s pipeline beyond OST-HER2 also includes a next-generation tunable antibody-drug conjugate (tADC) platform leveraging proprietary Si-Linker and Conditionally Active Payload (CAP) technologies. These innovations enhance OS Therapies’ long-term commercial footprint and strengthen investor confidence as the company advances toward multiple regulatory filings.
Patients’ Significance
For patients with recurrent metastatic osteosarcoma—particularly children and young adults—treatment options remain extremely limited. The strong survival signal seen with OST-HER2 and the rapid regulatory engagement across the FDA, EMA, and MHRA offer renewed hope for a population with historically poor outcomes. If approved, OST-HER2 may become the first new immunotherapy for this indication in decades, providing a targeted approach capable of eliciting durable immune activity with the potential to prevent or delay recurrence. This progress also supports broader patient communities facing HER2-positive cancers by advancing the science behind bacterial-vector immunotherapies.
Policy Significance
These regulatory events highlight a growing policy emphasis on accelerated pathways for rare pediatric cancers and innovative therapies that address critical unmet needs. The alignment across U.S. and European agencies reflects a shared commitment to expediting access to promising oncology treatments while maintaining rigorous standards for safety, manufacturing quality, and confirmatory evidence. OST-HER2’s designations—including Rare Pediatric Disease, Fast-Track, and Orphan Drug statuses—demonstrate how evolving health-policy mechanisms incentivize innovation in underserved therapeutic areas. The program may also influence future policy discussions around microbial-based therapeutic platforms and international harmonization for accelerated oncology approvals.
With the FDA’s PDUFA waiver, EMA’s Union Marketing Authorisation eligibility, and upcoming regulatory meetings, OS Therapies has entered a defining phase of its development strategy for OST-HER2. These milestones reinforce strong scientific, regulatory, and commercial momentum behind the company’s mission to transform outcomes in metastatic osteosarcoma and other HER2-driven cancers. As regulatory filings advance in early 2026, OST-HER2 stands as a leading candidate to reshape the future of immuno-oncology for rare and life-threatening tumors.
Source: OS Therapies Inc. press release
