A case of neuromyelitis optica spectrum disorder requiring a change in biologic therapy due to the development of anti–drug antibodies after satralizumab initiation

Abstract

A 38–year–old woman with anti–aquaporin–4 (AQP4) antibody–positive neuromyelitis optica spectrum disorder (NMOSD) experienced a relapse of myelitis triggered by childbirth. Satralizumab was initiated, but the dosing interval was extended to 5–6 weeks owing to childcare demands. Despite treatment with satralizumab, the patient relapsed, and anti–satralizumab antibodies (antidrug antibodies) were detected. No further relapse occurred after switching to inebilizumab treatment.

The extended dosing interval of satralizumab likely led to lower serum drug concentrations, thereby increasing the risk of antidrug antibody production. In cases where relapses occur during satralizumab treatment, measuring antidrug antibodies may help assess the disease status.