Neuromyelitis optica (NMO) and its spectrum disorder (NMOSD) is a severe autoimmune inflammatory disorder of the central nervous system, with recurrent attacks mainly focused on the optic nerves and spinal cord. Untreated, it has a high morbidity and mortality. Serum aquaporin-4 (AQP4) antibodies are present in the majority of patients, are recognised as pathogenic and are a predictor of further relapses.1

Most specialists treat AQP4 antibody-positive patients early and aggressively with immunosuppression to prevent further attacks. There have been no randomised trials in NMO, but prednisolone, azathioprine, mycophenolate mofetil, methotrexate and rituximab are among the therapies currently used and appear to have comparable efficacy.2 ,3 Because of the potentially devastating nature of NMO relapses, many clinicians would consider a single relapse on treatment to represent treatment failure and an indication to alter therapy, particularly if the relapse is severe and the therapy has had adequate time to work. This alteration can take the form of an increase in dosage of current treatment or a switch to an alternative agent.

There is an urgent need to identify the most effective treatment regimens, particularly because there are many novel therapeutic candidates being developed, including those which act on the antibody-producing or complement pathways, and an AQP4 monoclonal antibody blocker.4 Current NMO study designs under discussion vary, with some regulatory authorities requesting placebo comparator arms but others accepting standard treatments (azathioprine or alternative plus low dose oral steroids)3 as comparators either as add-on or …