OST-HER2 pursues accelerated approval in pediatric osteosarcoma; BLA acceptance and regulatory conversion will determine whether Phase 2b data translates to a first approval

OS Therapies is a clinical-stage company developing a targeted cancer immunotherapy for pediatric osteosarcoma that has spread to the lungs and been surgically removed, which is not yet approved.

OST-HER2 is a HER2-targeted immunotherapy seeking accelerated approval for recurrent, fully resected, lung-metastatic osteosarcoma in pediatric patients. The thesis turns on whether FDA accepts the BLA and grants accelerated approval on the basis of Phase 2b EFS and seroconversion surrogate data. The primary risk is that FDA demands a higher evidentiary standard than EMA and TGA have accepted, or that the confirmatory Phase 3 design is not agreed before approval, leaving the program in regulatory limbo.