OS Therapies’ OST-HER2 Vaccine Extends Survival in Metastatic Osteosarcoma Phase II Trial

OS Therapies’ cancer vaccine, OST-HER2, has demonstrated a significant improvement in overall survival (OS) in patients with recurrent, fully resected pulmonary metastatic osteosarcoma, according to results from a Phase IIb trial (NCT04974008). After two years, 75% of patients receiving OST-HER2 were alive compared to 40% in historical controls, marking a statistically significant survival benefit.

The study also revealed that all patients achieving 12-month event-free survival (EFS) remained alive at two years, while 59% of those without EFS at 12 months also survived. Following positive topline results announced in January 2025, OS Therapies plans to seek regulatory approval in the US, UK, and EU.

If approved, OST-HER2 would become the first targeted therapy for metastatic osteosarcoma, addressing a critical unmet need where current treatments rely on chemotherapy and radiotherapy with limited efficacy and substantial side effects.

14-10-2025