To audit the management and outcomes of patients with NMOSD with a specific focus on rituximab and the utility of Class-Switched Memory B-cell (SMB-cells) monitoring.

To establish the safest and most effective dosing regimen of rituximab in NMOSD.

To determine whether the costs associated with rituximab dosing can be reduced without compromising efficacy.

NMOSD is a relapsing autoimmune disorder of the CNS that can cause severe disability accrual with each relapse.  Treatments have been tailored towards B-cells, since the discovery of the aquaporin-4 antibody (AQP4-Ab) in 2005.  In the largest cohort study to date, 100 cases treated with rituximab achieved a relapse risk reduction of 96% after a median of 67 months; other trials have furthered support for rituximab, but with different dosing approaches. 

Since 2012, the RPAH Neuroimmunology Clinic (NIC) has regularly measured SMB-cells in the peripheral blood of rituximab-treated patients as a biomarker for re-dosing with 500mg of rituximab.

We included patients with NMOSD, idiopathic transverse myelitis and idiopathic optic neuritis who attended NIC between 2012 and 2018.  Retrospective analysis of hospital records, clinic letters, laboratory and imaging data was performed.  Relapses pre- and post-rituximab, dosing intervals, SMB-cells and memory B-cells were analysed.  The frequency and type of poly-immunotherapy and adverse events were also investigated.

19 of 24 patients fulfilled current criteria for NMOSD; 15 have been treated consistently with rituximab; 14 are concurrently treated with mycophenolate or azathioprine. 

84% of our NMOSD patients are AQP4-Ab positive (11% MOG-Ab positive).

The mean re-dosing interval of 500mg rituximab was 47.3 weeks

Our patients exhibited an 89% reduction in annualised relapse rate (ARR) over a mean follow-up time of 41 months (mean pre-treatment vs post-treatment ARR, 0.9 vs 0.1).