New therapies for neuromyelitis optica spectrum disorder

Background Neuromyelitis optica spectrum disorder is an autoimmune disease of the CNS that primarily affects the optic nerves and spinal cord. Most patients have serum antibodies targeting the aquaporin-4 water channel expressed on the end-feet of astrocytes. Although the prevalence of neuromyelitis optica spectrum disorder is limited to around 1-2 people per 100 000, severe immune-mediated attacks can quickly lead to blindness and paralysis if undiagnosed and untreated. However, diagnosis is straightforward when the highly specific serum aquaporin-4 antibodies are detected with cell-based assays. Recent developments Four randomised controlled trials have tested the efficacy of three new therapies (eculizumab, satralizumab, and inebilizumab) for patients with neuromyelitis optica spectrum disorder that all showed a benefit in preventing future attacks. These therapies have different targets within the immune pathogenic process, and the four trials have similarities and differences that mean they might change the therapeutic landscape for people with neuromyelitis optica spectrum disorder in different ways. Efficacy, safety, tolerability, and practical considerations, including potential cost, differ for each drug and might affect the rate of use in real-world populations of patients with neuromyelitis optica spectrum disorder. Where next? Despite the rarity of neuromyelitis optica spectrum disorder, a relative abundance of preventive treatment options now exists. In the future, trials should focus on areas of unmet need, including aquaporin-4 seronegative disease, and on development of treatments for acute relapses and for recovery from autoimmune attacks in the CNS.