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.

Studies in patients with desmotic small round cell tumors and other solid tumors in the peritoneum and patients with recurrent medulloblastoma and ependymoma were initiated recently.

A humanized form of 8H9 is also under development.

Target/Mechanism: B7-H3/CD276

Carrier/Ligand: Omburtamab

Radiation Type: beta electrons (β)