Pharmacotherapy for Neuromyelitis Optica Spectrum Disorders: Current Management and Future Options

Neuromyelitis optica (NMO) is an inflammatory and demyelinating disease of the central nervous system. Although the prevalence of NMO is low, the rapid and severe impairment observed in patients has led to extensive development of research in the fields of diagnostic criteria and therapy in the past 15 years. With improved understanding of the pathophysiology of NMO and the role of aquaporin-4 (AQP4) or myelin oligodendrocyte glycoprotein antibodies, numerous therapeutic approaches have been proposed and are currently undergoing evaluation. In this review, we describe the rationale for existing therapeutics and their benefit/risk ratio. We also discuss the pharmacological and clinical interest of future approaches targeting, among others, B or T cells, the blood-central nervous system barrier, complement, polynuclear cells, AQP4-antibody linkage and AQP4 activity. The numerous agents under development are the result of a major collaborative effort all over the world. After the considerable progress on diagnosis, we are now close to class I evidence for a therapeutic effect of several drugs in NMO spectrum disorders, most notably with the anti-interleukin-6 receptor antibody (satralizumab) and anti-complement-5 antibody (eculizumab).

Increased cerebrospinal fluid neurofilament light chain in central nervous system inflammatory demyelinating disease

BACKGROUND

Central nervous system (CNS) inflammatory demyelinating disease (IDD) is an immune-mediated disease that is pathologically characterized by demyelination and inflammatory infiltration in the CNS and includes clinically isolated syndrome (CIS), multiple sclerosis (MS), and neuromyelitis optica spectrum disorders (NMOSD). IDD is usually characterized by variable symptoms, multivariate imaging, uncertain reactions to treatment, and a variable prognosis, which makes it difficult to diagnose early. In recent years, the role of the neurofilament light chain (NFL), an axonal injury biomarker, in IDD has become increasingly important. We will detect and analyse cerebrospinal fluid (CSF) NFL levels in IDD and normal control patients to determine the significance of NFL in the diagnosis and prognostic prediction of IDD.

METHODS

A total of 41 CIS, 34 MS and 73 NMOSD patients and 40 other patients with conditions such as neurosis and migraine with lumbar puncture were enrolled as the patient groups and the normal control (NC) group from the population of in- and outpatients of the Department of Neurology of the Sixth Medical Centre of Chinese People's Liberation Army General Hospital from January 2014 to October 2016. Clinical and neuroimaging features of the patient groups as well as CSF samples from both types of groups were collected, and the NFL levels of CSF were measured by enzyme linked immunosorbent assay.

RESULTS

CSF NFL levels in the CIS, MS and NMOSD groups were significantly higher than those in the NC group (P < 0.05, analysis of variance of NFL levels was performed after logarithmic transformation based on 10). There were no statistically significant differences in the CSF NFL levels among the CIS, MS and NMOSD groups (P > 0.05). The NFL levels of CSF in the CIS, MS and NMOSD groups were correlated with the expanded disability status scale score and enhancement in gadolinium-magnetic resonance imaging (all P < 0.05). Gender, oligoclonal band in CSF, aquaporin 4 antibody and 25‑hydroxy vitamin D₃ [25(OH)D₃] in serum were not related to the NFL levels (P > 0.05).

CONCLUSION

The NFL level of CSF is conducive to assessing the severity and probable progress of IDD but is not helpful in distinguishing IDD among Chinese.

Monitoring neuromyelitis optica activity

Neuromyelitis optica (NMO) is a demyelinating and inflammatory disease essentially restricted to the spinal cord and the optic nerves. Emerging evidence indicates that serum antiaquaporin-4 (AQP4) antibodies have a critical role in its pathogenesis. NMO courses with multiple relapses, often leading to severe disability. Management of NMO focuses on the effective treatment of acute attacks and the prevention of relapses. The latter is currently attempted with immunosuppressive drugs. Although several factors have been associated with disease activity, especially serum levels of anti-AQP4 IgG, no single one of them has been proved clinically useful for guiding treatment. New drugs that target specifically AQP4 antibodies and complement activation are being developed; they may prove to be more efficient with fewer side effects.

Neuromyelitis optica and pregnancy during therapeutic B cell depletion: infant exposure to anti-AQP4 antibody and prevention of rebound relapses with low-dose rituximab postpartum

Neuromyelitis optica (NMO) predominantly affects women, some in childbearing age, and requires early therapeutic intervention to prevent disabling relapses. We report an anti-AQP4 antibody-seropositive patient who became pregnant seven months after low-dose (100 mg) rituximab application. Pregnancy showed no complications, and low-dose rituximab restarted two days after delivery resulted in neurological stability for 24 months. Remarkably, her otherwise healthy newborn presented with anti-AQP4 antibody and reduced B lymphocyte counts in umbilical cord blood, which normalized three months later. Confirming and extending previous reports, our case suggests that low-dose rituximab might be compatible with pregnancy and prevent rebound NMO disease activity postpartum.