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

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.

Validation and use of 22Na turnover to measure food intake in free-ranging lizards.

As the food intake of free-ranging animals has proved to be difficult to measure by traditional means, the feasibility of using radioactive Na to measure food consumption in a small scincid lizard (Lampropholis guichenoti) was assessed. This technique has previously been used only for several species of mammal. A significant relationship between food intake and Na turnover was found in the laboratory, with Na turnover underestimating intake by 7.6%. The food intake of free-ranging members of a field population was estimated by 22Na turnover to be 9.55, 0.65, 9.39 and 13.75 mg dry weight (day)-1 during autumn, winter, spring and summer respectively. Estimates of assimilated and expended energy from these food intake values agree closely with data reported for other lizards using alternative techniques. This study also describes the technical innovations which were necessary to study lizards weighing less than 1 g; and it suggests that 22Na can provide an easy, reliable and inexpensive means of studying the energetics of many free-living animals.