Precision therapy for neuromyelitis optica spectrum disorder: A retrospective analysis of the use of class-switched memory B-cells for individualised rituximab dosing schedules

Abstract Background B-cell depleting treatments are widely used to modify the course of neuromyelitis optica spectrum disorder (NMOSD). Despite recent successful Phase 3 trials of several novel NMOSD therapies, limited availability and high cost constrains their clinical use, and rituximab (RTX) remains a core treatment in many centres. Since 2013, the Royal Prince Alfred Hospital Neuroimmunology Clinic (NIC) has regularly measured class-switched memory B-cells (SMB-cells) in the peripheral blood of patients with NMOSD, who have been treated with RTX, in order to guide retreatment intervals. Objective To assess the management and outcomes of the treated patients, and to determine the effect of SMB-cell monitoring in guiding retreatment intervals. Methods A retrospective analysis of hospital records, clinic letters and laboratory data was performed. Results Sixteen patients with NMOSD received individualised rituximab dosing at NIC between 2013 and 2018. Fourteen (87.5%) were aquaporin-4 antibody (AQP4-Ab) positive; 1 (6.25%) was myelin oligodendrocyte glycoprotein antibody (MOG-Ab) positive and 1 (6.25%) was seronegative. After commencement of RTX, individually dosed according to regular measurements of serum SMB-cells, there was a 77.5% reduction in annualised relapse rate over a mean follow-up time of 46.1 months in our recently active NMOSD patients. Their mean retreatment interval was 50.9 weeks. Conclusions This study provides real-world evidence supporting individualised rituximab dosing in the treatment of NMOSD.