131I-Naxitamab (131I-3F8) is a murine antibody targeting GD2 (disialoganglioside), labeled with 131I explored as therapeutic for the treatment of neuroblastomas. 3F8 is a murine IgG3 monoclonal antibody which binds to the cell-surface GD2, a disialoganglioside antigen expressed on tumors of neuroectodermal origin, including human neuroblastoma, melanoma and small cell carcinoma of the lung. Radiolabeled 3F8 can therefore, be explored for the diagnosis and therapy of neuroblastomas, eventually melanomas and SCLC. The concept has been known since the 1980s, and cold 3F8 has been in clinical trials for therapeutic applications. The first human trials were performed with 131I-3F8 in the 1990s. The labeling with 124I rather than 131I improved image quality and reduced dosimetry to the patient.

Presently a new humanized form of 3F8, hu3F8, is under Phase I and II clinical trials. At least nine trials are running in parallel with this cold antibody or the murine form. A phase II pivotal trial with the cold antibody hu3F8 (Naxitamab) is supposed to be completed by 2027. Since 2006, a Phase II trial with 131I-3F8 has been running to evaluate the potential of the radiolabeled drug in the treatment of patients with CNS cancer or leptomeningeal cancer. Another study was completed in patients with relapsed or refractory neuroblastoma.