Less frequent rituximab retreatment maintains remission of neuromyelitis optica spectrum disorder, following long-term rituximab treatment

Rituximab, a chimeric monoclonal antibody that selectively targets CD20+ B cells, has exhibited robust efficacy and an acceptable safety profile in neuromyelitis optica spectrum disorder (NMOSD).1–3 Previously, we reported that the therapeutic response of B cell depletion varied among 100 patients with NMOSD, which resulted from multiple factors including Fc gamma polymorphism, and that monitoring CD27+ memory B cell appears to improve treatment outcomes via individualised treatment.2 Our treatment strategy has also proven to effectively prevent relapse at a lower cumulative dose, compared with the fixed maintenance therapy every 6 months, in a French cohort.4 Currently, we have a group of patients with NMOSD who have undergone long-term rituximab treatment for more than 7 years. We found that retreatment interval became significantly prolonged over time when we targeted depletion of memory B cells. Here, we analysed clinical outcomes and changes in B cell reconstitution over time, following long-term repeated rituximab treatment. Through December 2017, sixty-eight patients with NMOSD had been treated with rituximab for at least 7 years. Twenty-one patients who had been treated with mitoxantrone, prior to rituximab, were excluded; the remaining 47 patients were included. Written informed consent was obtained from all patients. After induction therapy, patients received a single infusion of rituximab, at a dose of 375 mg/m2, as maintenance therapy; this was performed whenever the frequency of re-emerging CD27+ memory B cells in peripheral blood mononuclear cells (PBMC) exceeded 0.05% as revealed by flow cytometry for the initial 2 years, and, subsequently, when the frequency exceeded …