OS Therapies, Inc. (OSTX) announced that it has secured meetings with the U.S. Food & Drug Administration, the U.K. Medicines and Healthcare products Regulatory Agency, the European Medicines Agency, and the Australian Therapeutic Goods Administration to review the design of a global confirmatory Phase 3 trial for its lead product, OST‑HER2, in metastatic osteosarcoma. The meetings are scheduled for the second quarter of 2026.
The meetings are part of the company’s accelerated‑approval strategy. OST‑HER2 is a first‑in‑class Listeria‑based immunotherapy that has received orphan drug, fast‑track, and rare pediatric disease designations in the United States, and orphan drug, fast‑track, and advanced therapy medicinal product status in the European Union. The Phase 3 trial will be required for a Biologics License Application in the U.S. and for conditional marketing authorisations in the U.K. and Europe.
Enrollment for the global confirmatory trial is slated to begin in the third quarter of 2026, initially in Australia, and will expand worldwide. Positive Phase 2b data showing significant improvements in event‑free and overall survival in patients with resected lung‑metastatic osteosarcoma underpin the design of the Phase 3 study.
Under the rare pediatric disease designation, a successful U.S. approval would make OST‑HER2 eligible for a priority review voucher worth an estimated $205 million, providing a potential upside beyond the drug’s commercial value. The meetings signal that regulators are engaged and that the company is on track to meet the milestones required for accelerated approval and conditional authorisations.
The announcement underscores the unmet need in metastatic osteosarcoma, where standard MAP chemotherapy offers limited long‑term survival. OST‑HER2’s novel mechanism could transform treatment and expand the company’s portfolio in a rare‑disease market.
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