Current and emerging biologics for the treatment of neuromyelitis optica spectrum disorders

MOGAD and NMOSD: insights on patients' radiological and laboratory findings from a single UAE center

Introduction

Although neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody disease (MOGAD) are rare diseases, they pose a significant burden on both society and the healthcare system. This study aims to discuss the demographics and patient characteristics of these diseases in a single center in the United Arab Emirates (UAE).

Methods

This is a retrospective, descriptive study that included patients with either NMOSD or MOGAD treated at Rashid Hospital, UAE during the period between January 2019 and January 2024. Patients were selected and categorized according to NMOSD criteria, aquaporin-4 antibodies, and MOG antibodies. Patient demographics, clinical characteristics, and medical history were retrieved from their medical records and descriptively analyzed in the light of patients' serological data.

Results

We identified 34 patients with non-multiple sclerosis atypical CNS inflammatory/demyelinating syndromes. Twenty-seven patients (79.4%) fulfilled the criteria for NMOSD, while seven (20.6%) tested positive for MOG antibodies, fulfilling the criteria for MOGAD. In the NMOSD cohort, 19% (n = 5) were AQP4-antibody negative. Seventy-four percent of the NMOSD cohort and 43% of the MOGAD cohort were female. For MOGAD patients, disease onset was at a younger age (median onset age of 25 years) compared to the overall study population (mean onset age of 28.94 years). Long segment transverse myelitis was only detected in NMOSD patients (33.3%), and brainstem syndrome with area postrema syndrome was more common in the MOGAD cohort (29% vs. 4%). The rate of positive response to intravenous methylprednisolone as initial therapy was comparable across both cohorts (74% in case of NMOSD and 71% in case of MOGAD).

Conclusion

This study provides valuable insights into the status of NMOSD and MOGAD in the UAE, highlighting the need for larger, prospective studies to further characterize these diseases in the local population, as well as the need for improved understanding of the epidemiology and management of these rare but debilitating conditions.

NMOSD and MOGAD: an evolving disease spectrum

Neuromyelitis optica (NMO) spectrum disorder (NMOSD) is a relapsing inflammatory disease of the CNS, characterized by the presence of serum aquaporin 4 (AQP4) autoantibodies (AQP4-IgGs) and core clinical manifestations such as optic neuritis, myelitis, and brain or brainstem syndromes. Some people exhibit clinical characteristics of NMOSD but test negative for AQP4-IgG, and a subset of these individuals are now recognized to have serum autoantibodies against myelin oligodendrocyte glycoprotein (MOG) - a condition termed MOG antibody-associated disease (MOGAD). Therefore, the concept of NMOSD is changing, with a disease spectrum emerging that includes AQP4-IgG-seropositive NMOSD, MOGAD and double-seronegative NMOSD. MOGAD shares features with NMOSD, including optic neuritis and myelitis, but has distinct pathophysiology, clinical profiles, neuroimaging findings (including acute disseminated encephalomyelitis and/or cortical encephalitis) and biomarkers. AQP4-IgG-seronegative NMOSD seems to be a heterogeneous condition and requires further study. MOGAD can manifest as either a monophasic or a relapsing disease, whereas NMOSD is usually relapsing. This Review summarizes the history and current concepts of NMOSD and MOGAD, comparing epidemiology, clinical features, neuroimaging, pathology and immunology. In addition, we discuss new monoclonal antibody therapies for AQP4-IgG-seropositive NMOSD that target complement, B cells or IL-6 receptors, which might be applied to MOGAD in the near future.

NMOSD IgG Impact Retinal Cells in Murine Retinal Explants

Neuromyelitis optica spectrum disorders (NMOSD) are chronic inflammatory diseases of the central nervous system, characterized by autoantibodies against aquaporin-4. The symptoms primarily involve severe optic neuritis and longitudinally extensive transverse myelitis. Although the disease progression is typically relapse-dependent, recent studies revealed retinal neuroaxonal degeneration unrelated to relapse activity, potentially due to anti-aquaporin-4-positive antibodies interacting with retinal glial cells such as Müller cells. In this exploratory study, we analysed the response of mouse retinal explants to NMOSD immunoglobulins (IgG). Mouse retinal explants were treated with purified IgG from patient or control sera for one and three days. We characterized tissue response patterns through morphological changes, chemokine secretion, and complement expression. Mouse retinal explants exhibited a basic proinflammatory response ex vivo, modified by IgG addition. NMOSD IgG, unlike control IgG, increased gliosis and decreased chemokine release (CCL2, CCL3, CCL4, and CXCL-10). Complement component expression by retinal cells remained unaltered by either IgG fraction. We conclude that human NMOSD IgG can possibly bind in the mouse retina, altering the local cellular environment. This intraretinal stress may contribute to retinal degeneration independent of relapse activity in NMOSD, suggesting a primary retinopathy.

Clinical and epidemiological correlates of treatment change in patients with NMOSD: insights from the CIRCLES cohort

OBJECTIVE

Neuromyelitis optica spectrum disorders (NMOSD) represent rare autoimmune diseases of the central nervous system largely targeting optic nerve(s) and spinal cord. The present analysis used real-world data to identify clinical and epidemiological correlates of treatment change in patients with NMOSD.

METHODS

CIRCLES is a longitudinal, observational study of NMOSD conducted at 15 centers across North America. Patients with ≥ 60 days of follow-up and receiving on-study maintenance treatment were evaluated. The mean annual relapse rate (ARR) was estimated using negative binomial models; the likelihood of treatment change was estimated using Cox proportional hazards models. Relapses were included as time-varying covariates to estimate the relationship to treatment change.

RESULTS

Of 542 patients included, 171 (31.5%) experienced ≥ 1 relapse on the study and 133 patients (24.5%) had ≥ 1 change in the treatment regimen. Two categories of variables significantly correlated with the likelihood of treatment change: (1) relapse: any on-study relapse (hazard ratio [HR] = 2.91; p < 0.001), relapse phenotypes (HR range = 2.15-5.49; p < 0.001), and pre-study ARR > 0.75 (HR 2.28; p < 0.001); 2) disease phenotype: brain syndrome only vs transverse myelitis involvement at onset (HR 2.44; p = 0.008), disease duration < 1 vs > 5 years (HR 1.66; p = 0.028), or autoimmune comorbidity (HR 1.55; p = 0.015). A subset of these factors significantly correlated with shorter time to first rituximab discontinuation.

CONCLUSIONS

In CIRCLES, relapse patterns and disease phenotype significantly correlated with changes in the maintenance treatment regimen. Such findings may facilitate the identification of patients with NMOSD who are likely to benefit from treatment change to reduce relapse risk or disease burden and enhance the quality of life.

Glial fibrillary acidic protein as a biomarker in neuromyelitis optica spectrum disorder: a current review

INTRODUCTION

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing, often debilitating neuroinflammatory disease, whose predominant clinical manifestations are longitudinally extensive transverse myelitis and optic neuritis. About 80% of the patients with an NMOSD phenotype have pathogenic autoantibodies against the astrocyte water channel aquaporin-4 (AQP4-IgG). While therapeutic options for NMOSD have greatly expanded in recent years, well-established biomarkers for prognosis or treatment response are still lacking. Glial fibrillary acidic protein (GFAP) is mainly expressed in astrocytes and can be detected in cerebrospinal fluid (CSF) and blood of patients with NMOSD.

AREAS COVERED

Here, we comprehensively review the current knowledge on GFAP as a biomarker in NMOSD.

EXPERT OPINION

In patients with AQP4-IgG⁺ NMOSD, GFAP levels are elevated in CSF and serum during acute attacks and correlate with disability, consistent with the pathophysiology of this antibody-mediated astrocytopathy. Serum GFAP levels tend to be higher in AQP4-IgG⁺ NMOSD than in its differential diagnoses, multiple sclerosis, and myelin oligodendrocyte antibody-associated disease. Importantly, serum GFAP levels in AQP4-IgG⁺ NMOSD during remission may be predictive of future disease activity. Serial serum GFAP measurements are emerging as a biomarker to monitor disease activity in AQP4-IgG⁺ NMOSD and could have the potential for application in clinical practice.

Anti-IL-6 therapies in central nervous system inflammatory demyelinating diseases

Current treatments for central nervous system (CNS) inflammatory demyelinating diseases (IDDs) include corticosteroids, plasma exchange, intravenous immunoglobulin, and immunosuppressant drugs. However, some patients do not respond well to traditional therapies. In recent years, novel drugs, such as monoclonal antibodies, targeting the complement component C5, CD19 on B cells, and the interleukin-6 (IL-6) receptor, have been used for the treatment of patients with refractory CNS IDDs. Among these, tocilizumab and satralizumab, humanized monoclonal antibodies against the IL-6 receptor, have shown beneficial effects in the treatment of this group of diseases. In this review, we summarize current research progress and prospects relating to anti-IL-6 therapies in CNS IDDs.

Costs and Health-Related Quality of Life in Patients With NMO Spectrum Disorders and MOG-Antibody-Associated Disease: CHANCENMO Study

Background and Objectives

To evaluate costs and health-related quality of life (HRQoL) of neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody–associated disease (MOGAD).

Methods

In this multicenter cross-sectional study, data on consumption of medical and nonmedical resources and work ability were assessed via patient questionnaires. Costs were analyzed in Euros for 2018 from the societal perspective. HRQoL was captured by the EuroQoL Group 5 Dimension 5 Level Scale (EQ-5D-5L) questionnaire. Clinical data were retrieved from the Neuromyelitis Optica Study Group (NEMOS) database.

Results

Two hundred twelve patients (80% women, median age 50 [19–83] years, median disease duration 7 [0–43] years, median Expanded Disability Status Scale [EDSS] score 3.5 [0–8.5], 66% aquaporin-4 immunoglobulin G [IgG] positive, 22% MOG IgG positive, 12% double seronegative) were analyzed. The mean total annual per capita cost of illness accounted for €59,574 (95% CI 51,225–68,293 or US dollars [USD] 70,297, 95% CI 60,445–80,586), and the mean index value of the EQ-5D-5L was 0.693 (95% CI 0.65–0.73). The most important cost drivers were informal care costs (28% of total costs), indirect costs (23%), and drugs (16%), especially immunotherapeutics. Costs showed a positive correlation with disease severity (ρ = 0.56, 95% CI 0.45–0.65); in the EDSS score 6.5 to 8.5 subgroup, the mean annual costs were €129,687 (95% CI 101,946–160,336 or USD 153,031, 95% CI 120,296–189,196). The HRQoL revealed a negative correlation to disease severity (ρ = −0.69, 95% CI −0.76 to −0.61); in the EDSS score 6.5 to 8.5 subgroup, the EQ-5D-5L mean index value was 0.195 (95% CI 0.13–0.28). Neither antibody status nor disease duration influenced the total annual costs or HRQoL.

Discussion

These German data from the era without approved preventive immunotherapies show enormous effects of the diseases on costs and quality of life. An early and cost-effective therapy should be provided to prevent long-term disability and to preserve quality of life.

Imaging features to distinguish AQP4-positive NMOSD and MS at disease onset: A retrospective analysis in a single-center cohort

PURPOSE

To compare the diagnostic performance of imaging criteria that differentiate AQP4⁺ Neuromyelitis Optica Spectrum Disorders (NMOSD) and Multiple Sclerosis (MS) at disease onset (DO) and follow-up (FU).

METHODS

We retrospectively analyzed MRI scans at DO (defined as the first 60 days of patient-reported symptom onset) in 10 AQP4⁺NMOSD and 25 (time to MRI matched) relapsing-remitting MS patients from a monocentric cohort.

RESULTS

The Matthews criteria were met in 20% of AQP4⁺NMOSD patients at DO vs. 33% at FU, and in 96% of RRMS patients vs.100% at FU. Specificity (SP) and sensitivity (SE) were thus high at both time-points: SP-DO: 96%; SP-FU:100%; and SE-DO: 80%; SE-FU: 67%, with similar area under the curve (AUC) values at DO: 88% [95% CI 74%-100%] and FU: 83% [95% CI 67%-100%]. The Cacciaguerra criteria were met in 90% of AQP4⁺NMOSD patients at DO vs. 88.9% at FU and in 24% of RRMS patients vs. 14% at FU; SP-DO: 87%; SP-FU: 86%; and SE-DO: 90%; SE-FU: 89%, with similar AUC values at DO: 88% [95% CI 76%-98%] and FU: 87% [95% CI 74%-98%].

CONCLUSIONS

While diagnostic MRI criteria were developed on data acquired years after disease onset, our study demonstrates their high applicability at the earliest disease stages, thus emphasising their valuable use in clinical practice.

Randomized Controlled Trials for Neuromyelitis Optica Spectrum Disorder: A Review of Trial Architecture

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing inflammatory disease that primarily affects the optic nerves and the spinal cord. Randomized controlled trials (RCTs) assessing treatments for NMOSD have only been performed in the past decade, and to date, there are 3 drugs approved by the US Food and Drug Administration (FDA) for antiaquaporin-4 immunoglobulin G seropositive NMOSD. This review assesses the characteristics and challenges of RCTs when evaluating treatments for NMOSD.

REVIEW SUMMARY

We conducted a review using the terms ("neuromyelitis optica" OR "NMO" OR "NMOSD") AND "clinical trial" in any language on March 28, 2021. Seven RCTs were included, and the trials' architecture was analyzed and synthesized. Overall, 794 subjects were randomized [monoclonal antibody intervention group, n= 493 (62.1%), placebo, n=196 (24.7%), and active control, n=105 (13.2%)]; 709 (89.3%) were females; and 658 (82.9%) were aquaporin-4 (AQP4) antibody seropositive. The primary outcome was time to relapse in 6/7 of the trials, and annualized relapse rate in the remaining one. Four RCTs used placebo in their design. Among the seven published RCTs, the trial design differed by the criteria used to define NMOSD relapse, selection of subjects, proportion of AQP4 immunoglobulin G seronegative patients, and baseline characteristics indicating NMO disease severity.

CONCLUSIONS

Ethical considerations for the use of placebo should change in light of the approval of 3 therapies for seropositive NMOSD. Remaining challenges for clinical trials in NMOSD include the assessment of long-term safety and efficacy, standardization of trial design and endpoints, and head-to-head study designs.

Rescue immunoadsorption treatment for neuromyelitis optica spectrum disorder attacks unresponsive to intravenous methylprednisolone

We aimed to evaluate the value of immunoadsorption (IA) treatment after the failure of intravenous methylprednisolone (IVMP) therapy for neuromyelitis optica spectrum disorder (NMOSD). Sixty-one NMOSD attacks unresponsive to IVMP were included: 22 patients received rescue IA (IVMP+IA), 24 underwent rescue plasma exchange (PE) (IVMP+PE), and 21 received no further rescue therapy (IVMP alone). The improvement frequencies were higher in the IVMP+IA and IVMP+PE groups than in the IVMP-alone group (P = 0.024). The effective period for IA treatment may be longer than previously thought. IA treatment for IVMP-resistant NMOSD attacks was effective and comparable to PE treatment.

Satralizumab in the treatment of neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is a rare and debilitating autoimmune astrocytopathy with a predominantly relapsing disease course. Satralizumab, a humanized monoclonal antibody, was designed to treat NMOSD by targeting the IL-6 receptor. Satralizumab builds on positive experiences of off-label use tocilizumab in recent years. Before 2019, no medications were approved for the treatment of NMOSD. In 2020, satralizumab became the third compound to enter the US market, adding to the complement inhibitor eculizumab and the CD19 inhibitor inebilizumab. Here, we review the two randomized, double-blind, Phase III trials that investigated the subcutaneous administration of satralizumab as add-on treatment and monotherapy. Both studies revealed positive effects concerning the reduction of relapse risk for AQP4 seropositive NMOSD patients and generally good tolerability.

Neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein IgG associated disorder: A comprehensive neuro-ophthalmic review

Neuromyelitis optica spectrum disorder (NMOSD) is an antibody-mediated inflammatory disease of the central nervous system that involves the optic nerves, spinal cord, and often other specific brain regions such as area postrema of the medulla. NMOSD was formerly classified as a variant of multiple sclerosis (MS), given the similar symptomatology and relapsing course but is now considered to have distinct clinical, paraclinical, immunological and prognostic features. The discovery of aquaporin 4 (AQP4) immunoglobulin G (IgG) has improved the ability to diagnose NMOSD. AQP4-IgG targets the astrocytic AQP4 water channel leading to complement activation and increased blood-brain barrier permeability. Accurate and early diagnosis is crucial as timely treatment may result in mitigation of long-term disability. Myelin oligodendrocyte glycoprotein (MOG)-IgG associated disorder (MOGAD) is a distinct nosologic entity, which has been more recently described. Its clinical spectrum partly overlaps that of seronegative NMOSD and MS. Although it is considered to have fewer relapses and better prognosis than NMOSD, the clinical course and outcome of MOGAD has not been fully characterized.

Complement in neurological disorders and emerging complement-targeted therapeutics

The complement system consists of a network of plasma and membrane proteins that modulate tissue homeostasis and contribute to immune surveillance by interacting with the innate and adaptive immune systems. Dysregulation, impairment or inadvertent activation of complement components contribute to the pathogenesis of some autoimmune neurological disorders and could even contribute to neurodegenerative diseases. In this Review, we summarize current knowledge about the main functions of the complement pathways and the involvement of complement in neurological disorders. We describe the complex network of complement proteins that target muscle, the neuromuscular junction, peripheral nerves, the spinal cord or the brain and discuss the autoimmune mechanisms of complement-mediated myopathies, myasthenia, peripheral neuropathies, neuromyelitis and other CNS disorders. We also consider the emerging role of complement in some neurodegenerative diseases, such as Alzheimer disease, amyotrophic lateral sclerosis and even schizophrenia. Finally, we provide an overview of the latest complement-targeted immunotherapies including monoclonal antibodies, fusion proteins and peptidomimetics that have been approved, that are undergoing phase I–III clinical trials or that show promise for the treatment of neurological conditions that respond poorly to existing immunotherapies.

In this Review, Dalakas et al. discuss the complement system, the role it plays in autoimmune neurological disease and neurodegenerative disease, and provide an overview of the latest therapeutics that target complement and that can be used for or have potential in neurological disorders.

Complement has an important physiological role in host immune defences and tissue remodelling.

The physiological role of complement extends to the regulation of synaptic development.

Complement has a key pathophysiological role in autoimmune neurological diseases and mediates the actions of pathogenic autoantibodies, such as acetylcholine receptor antibodies and aquaporin 4 antibodies.

For some autoimmune neurological diseases, such as myasthenia gravis and neuromyelitis optica spectrum disorders, approved complement-targeted treatments are now available.

Complement also seems to be of pathogenic relevance in neurodegenerative diseases such as Alzheimer disease, in which innate immune-driven inflammation is receiving increasing attention.

The field of complement-targeted therapeutics is rapidly expanding, with several FDA-approved agents and others currently in phase II and phase III clinical trials.

Pain in NMOSD and MOGAD: A Systematic Literature Review of Pathophysiology, Symptoms, and Current Treatment Strategies

Neuromyelitis optica spectrum disorders (NMOSDs) and myelin oligodendrocyte glycoprotein-antibody-associated disease (MOGAD) are autoimmune inflammatory disorders of the central nervous system (CNS). Pain is highly prevalent and debilitating in NMOSD and MOGAD with a severe impact on quality of life, and there is a critical need for further studies to successfully treat and manage pain in these rare disorders. In NMOSD, pain has a prevalence of over 80%, and pain syndromes include neuropathic, nociceptive, and mixed pain, which can emerge in acute relapse or become chronic during the disease course. The impact of pain in MOGAD has only recently received increased attention, with an estimated prevalence of over 70%. These patients typically experience not only severe headache, retrobulbar pain, and/or pain on eye movement in optic neuritis but also neuropathic and nociceptive pain. Given the high relevance of pain in MOGAD and NMOSD, this article provides a systematic review of the current literature pertaining to pain in both disorders, focusing on the etiology of their respective pain syndromes and their pathophysiological background. Acknowledging the challenge and complexity of diagnosing pain, we also provide a mechanism-based classification of NMOSD- and MOGAD-related pain syndromes and summarize current treatment strategies.

Eculizumab in the treatment of neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disease of the CNS which is distinct from multiple sclerosis and typically presents with a relapsing course of optic neuritis, myelitis and midline brain inflammatory lesions. In at least two-thirds of cases, antibodies against the water channel AQP4 can be found, which lead to an antibody-mediated activation of the complement system with consecutive damage to neuronal structures. Eculizumab, a humanized monoclonal antibody against the terminal complement component 5, was shown to significantly reduce the risk of NMOSD relapse in a Phase III placebo-controlled trial. Based on this, eculizumab (Soliris^®) was the first drug to be formally approved for the treatment of anti-AQP4-antibody positive NMOSD in 2019.

Visualizing the Central Nervous System: Imaging Tools for Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are autoimmune central nervous system conditions with increasing incidence and prevalence. While MS is the most frequent inflammatory CNS disorder in young adults, NMOSD is a rare disease, that is pathogenetically distinct from MS, and accounts for approximately 1% of demyelinating disorders, with the relative proportion within the demyelinating CNS diseases varying widely among different races and regions. Most immunomodulatory drugs used in MS are inefficacious or even harmful in NMOSD, emphasizing the need for a timely and accurate diagnosis and distinction from MS. Despite distinct immunopathology and differences in disease course and severity there might be considerable overlap in clinical and imaging findings, posing a diagnostic challenge for managing neurologists. Differential diagnosis is facilitated by positive serology for AQP4-antibodies (AQP4-ab) in NMOSD, but might be difficult in seronegative cases. Imaging of the brain, optic nerve, retina and spinal cord is of paramount importance when managing patients with autoimmune CNS conditions. Once a diagnosis has been established, imaging techniques are often deployed at regular intervals over the disease course as surrogate measures for disease activity and progression and to surveil treatment effects. While the application of some imaging modalities for monitoring of disease course was established decades ago in MS, the situation is unclear in NMOSD where work on longitudinal imaging findings and their association with clinical disability is scant. Moreover, as long-term disability is mostly attack-related in NMOSD and does not stem from insidious progression as in MS, regular follow-up imaging might not be useful in the absence of clinical events. However, with accumulating evidence for covert tissue alteration in NMOSD and with the advent of approved immunotherapies the role of imaging in the management of NMOSD may be reconsidered. By contrast, MS management still faces the challenge of implementing imaging techniques that are capable of monitoring progressive tissue loss in clinical trials and cohort studies into treatment algorithms for individual patients. This article reviews the current status of imaging research in MS and NMOSD with an emphasis on emerging modalities that have the potential to be implemented in clinical practice.