BACKGROUND: The humanized anti-disialoganglioside-2 monoclonal antibody naxitamab was approved in the USA in 2020 for the treatment of patients with relapsed/refractory high-risk neuroblastoma, limited to the bone or bone marrow, in combination with granulocyte-macrophage colony-stimulating factor. Treatment with naxitamab under expanded access was initiated by physicians from the Children's Hospital of Fudan University, Shanghai, China, in August 2021. OBJECTIVE: We reviewed all suspected adverse reactions (ARs) reported to the Y-mAbs Argus Global Pharmacovigilance Safety Database for patients treated with naxitamab under expanded access in China from 1 August 2021 to 31 July 2022. METHODS: We assessed patient demographics and the safety profile of naxitamab over multiple treatment cycles. RESULTS: At the data cutoff, 41 patients with relapsed/refractory high-risk neuroblastoma had received a total of 150 treatment cycles (451 infusions) of naxitamab. The median number of cycles completed was three
13 patients (32%) were receiving ongoing naxitamab treatment. The median patient age was 3 years (range 1-9 years) and 63% were female. Overall, ARs were reported in 89/150 cycles (59%)
serious ARs were reported in 23/150 cycles (15%). The cumulative reporting rate (ARs/cycle) decreased after 3 versus 12 months of expanded access: all ARs (8.7-4.6), serious ARs (0.9-0.3), hypotension (1.4-1.0), flushing (0.7-0.5), cough (0.6-0.3), pain (0.5-0.2), and hypoxia (0.3-0.2). CONCLUSIONS: During the first 12 months of expanded access treatment in China, 41 patients received naxitamab therapy with a cumulative 451 infusions administered. Over the course of this expanded access program, a reduction in the AR rate, including serious ARs, was observed as more patients were initiated and proceeded to later treatment cycles. While additional research is needed, the observed decrease in the AR rate may be attributed to clinicians' increased knowledge of AR management and hands-on experience with naxitamab-treated patients.