131I-Omburtamab (131I-Burtomab, 131I-8H9) is a monoclonal murine antibody, labeled with 131I for the therapy of neuroblastomas. In March 2017, 131I-8H9 has been designated an orphan drug for the treatment of Refractory Leptomeningeal Metastasis from Neuroblastoma by the European Medicines Agency (EMA). In June 2017, 131I-Omburtamab was granted the Breakthrough Therapy status for Neuroblastoma (second-line therapy or greater, metastatic disease in neonates and children) in USA.

131I-Omburtamab is under clinical development for CNS/Leptomeningeal Metastasis from Neuroblastoma (BTD, ODD and RPDD) (Phase II) and for treatment of Desmoplastic Small Round Cell Tumor (DSRCT – Phase I). It is associated with the imaging agent 124I-Omburtamab that helps selecting the potential positive responder patients.

Results from a pivotal study of 131I-Omburtamab in Refractory Leptomeningeal Metastasis from Neuroblastoma showed a 58 months average survival for the patients treated with this drug, compared to an average of 4.7 month and no long-term survival or cure, for a contemporary cohort. After more than a decade of follow-up, data show more than 40% overall long-term survival (15 years) indicating that the treated children have been cured.

A new formulation labeled with 177Lu and based on Omburtamab-DOTA is under preclinical development and is expected to show efficacy in adult patients with B7-H3 positive LM tumors. A humanized form of 8H9 is also under development.