OS Therapies is expected to announce that OST-HER2, its lead immunotherapy candidate, has demonstrated a statistically significant overall survival benefit at 2.5 years in patients who underwent complete resection of pulmonary metastatic osteosarcoma.
According to data disclosed to the company, patients who received OST-HER2 achieved a 75% overall survival rate at the 2.5-year mark. The treated cohort experienced no additional deaths between the previously reported two-year analysis and the updated 2.5-year data cut.
These updated figures extend earlier results that showed a 75% overall survival at two years, compared with a 60% rate observed in historical control data. OS Therapies has cited a patent-pending biomarker signature intended to quantify immune activation as supporting evidence for the therapy's clinical performance.
Regulatory strategy and next steps
OS Therapies is revising regulatory submissions in the United States, Europe, the United Kingdom and Australia to incorporate the new 2.5-year survival data as it seeks potential early market access during the second half of 2026. The company reports that both the European Medicines Agency and Australia's Therapeutic Goods Administration have indicated alignment on using forthcoming three-year overall survival data together with biomarker evidence as key efficacy measures for conditional approval applications.
The three-year overall survival data are expected in early fourth quarter 2026 and will be considered alongside the biomarker findings as part of conditional approval discussions in those jurisdictions. The company also plans to meet with the U.S. Food and Drug Administration and the U.K.'s Medicines and Healthcare products Regulatory Agency this month to seek similar alignment on evidentiary requirements.
Confirmatory study and scientific communication
OS Therapies has said that a confirmatory Phase 3 study is required before any early market authorization would be granted. That study is slated to begin in Australia in late third quarter 2026.
Detailed trial results are scheduled to be presented at the MIB Agents Factor 2026 Osteosarcoma Conference later this month.
What the data show
- Patients treated with OST-HER2 recorded a 75% overall survival rate at 2.5 years.
- No new patient deaths occurred in the treated group between the two-year and 2.5-year analyses.
- Earlier reported two-year survival was 75% versus 60% in historical controls.
- The company cites a patent-pending biomarker signature designed to measure immune activation as supportive clinical evidence.
These datapoints form the basis for OS Therapies' push for conditional or early market authorizations across multiple regulatory agencies, subject to further confirmatory evidence and regulatory agreement.