Serum Glial Fibrillary Acidic Protein: A Neuromyelitis Optica Spectrum Disorder Biomarker

Biomarkers for neuromyelitis optica: a visual analysis of emerging research trends

Neuromyelitis optica is an inflammatory demyelinating disease of the central nervous system that differs from multiple sclerosis. Over the past 20 years, the search for biomarkers for neuromyelitis optica has been ongoing. Here, we used a bibliometric approach to analyze the main research focus in the field of biomarkers for neuromyelitis optica. Research in this area is consistently increasing, with China and the United States leading the way on the number of studies conducted. The Mayo Clinic is a highly reputable institution in the United States, and was identified as the most authoritative institution in this field. Furthermore, Professor Wingerchuk from the Mayo Clinic was the most authoritative expert in this field. Keyword analysis revealed that the terms "neuromyelitis optica" (261 times), "multiple sclerosis" (220 times), "neuromyelitis optica spectrum disorder" (132 times), "aquaporin 4" (99 times), and "optical neuritis" (87 times) were the most frequently used keywords in literature related to this field. Comprehensive analysis of the classical literature showed that the majority of publications provide conclusive research evidence supporting the use of aquaporin-4-IgG and neuromyelitis optica-IgG to effectively diagnose and differentiate neuromyelitis optica from multiple sclerosis. Furthermore, aquaporin-4-IgG has emerged as a highly specific diagnostic biomarker for neuromyelitis optica spectrum disorder. Myelin oligodendrocyte glycoprotein-IgG is a diagnostic biomarker for myelin oligodendrocyte glycoprotein antibody-associated disease. Recent biomarkers for neuromyelitis optica include cerebrospinal fluid immunological biomarkers such as glial fibrillary acidic protein, serum astrocyte damage biomarkers like FAM19A5, serum albumin, and gamma-aminobutyric acid. The latest prospective clinical trials are exploring the potential of these biomarkers. Preliminary results indicate that glial fibrillary acidic protein is emerging as a promising candidate biomarker for neuromyelitis optica spectrum disorder. The ultimate goal of future research is to identify non-invasive biomarkers with high sensitivity, specificity, and safety for the accurate diagnosis of neuromyelitis optica.

Matching proposed clinical and MRI criteria of aggressive multiple sclerosis to serum and cerebrospinal fluid markers of neuroaxonal and glial injury

BACKGROUND

Definitions of aggressive MS employ clinical and MR imaging criteria to identify highly active, rapidly progressing disease courses. However, the degree of overlap between clinical and radiological parameters and biochemical markers of CNS injury is not fully understood. Aim of this cross-sectional study was to match clinical and MR imaging hallmarks of aggressive MS to serum/CSF markers of neuroaxonal and astroglial injury (neurofilament light chain (sNfL, cNfL), and glial fibrillary acidic protein (sGFAP, cGFAP)).

METHODS

We recruited 77 patients with relapsing-remitting MS (RRMS) and 22 patients with clinically isolated syndrome. NfL and GFAP levels in serum and CSF were assessed using a single-molecule-array HD-1-analyzer. A general linear model with each biomarker as a dependent variable was computed. Clinical and imaging criteria of aggressive MS, as recently proposed by the ECTRIMS Consensus Group, were modeled as independent variables. Other demographic, clinical or laboratory parameters, were modeled as covariates. Analyses were repeated in a homogenous subgroup, consisting only of newly diagnosed, treatment-naïve RRMS patients presenting with an acute relapse.

RESULTS

After adjusting for covariates and multiplicity of testing, sNfL and cNfL concentrations were strongly associated with the presence of ≥2 gadolinium-enhancing lesions (psNfL = 0.00008; pcNfL = 0.004) as well as the presence of infratentorial lesions on MRI (psNfL = 0.0003; pcNfL < 0.004). No other clinical and imaging criteria of aggressive MS correlated significantly with NfL or GFAP in serum and CSF. In the more homogeneous subgroup, sNfL still was associated with the presence of ≥2 gadolinium-enhancing lesions (psNfL = 0.001), presence of more than 20 T2-lesions (psNfL = 0.049) as well as the presence of infratentorial lesions on MRI (psNfL = 0.034), while cNfL was associated with the presence of ≥2 gadolinium-enhancing lesions (psNfL = 0.011) and presence of more than 20 T2-lesions (psNfL = 0.029).

CONCLUSIONS

Among proposed risk factors for an aggressive disease course, MRI findings but not clinical characteristics correlated with sNfL and cNfL as a marker of neuroaxonal injury and should be given appropriate weight considering MS prognosis and therapy. No significant correlation was detected for GFAP alone.

Safety and efficacy of inebilizumab for the treatment of neuromyelitis optica spectrum disorder: end-of-study results from the open-label period of the N-MOmentum trial

BACKGROUND

Inebilizumab, an anti-CD19 B-cell-depleting antibody, demonstrated safety and efficacy in neuromyelitis optica spectrum disorder in the randomised controlled period of the N-MOmentum trial. Here, end-of-study data, including the randomised controlled period and open-label extension period, are reported.

METHODS

In the double-blind, randomised, placebo-controlled, phase 2/3 N-MOmentum trial, adults aged 18 years and older with an neuromyelitis optica spectrum disorder diagnosis, Expanded Disability Status Scale score of 8·0 or less, and history of either at least one acute inflammatory attack requiring rescue therapy in the past year or two attacks requiring rescue therapy in the past 2 years, were recruited from 81 outpatient specialty clinics or hospitals in 24 countries. Eligible participants were randomly assigned (3:1), using a central interactive voice system or interactive web response system, and a permuted block randomisation scheme (block size of 4), to receive intravenous inebilizumab (300 mg) or identical placebo on days 1 and 15 of the randomised period, which lasted up to 197 days. Participants and all study staff were masked to treatment assignment. The primary endpoint of the randomised period of the trial was time to onset of adjudicated neuromyelitis optica spectrum disorder attack on or before day 197. Participants in the randomised controlled period who had an adjudicated attack, completed 197 days in the study, or were in the randomised controlled period when enrolment stopped, could voluntarily enter the open-label period. In the open-label period, participants either initiated inebilizumab if assigned placebo (receiving 300 mg on days 1 and 15 of the open-label period) or continued treatment if assigned inebilizumab (receiving 300 mg on day 1 and placebo on day 15, to maintain B-cell depletion and masking of the randomised controlled period). All participants subsequently received inebilizumab 300 mg every 6 months for a minimum of 2 years. The end-of-study analysis endpoints were time to adjudicated attack and annualised attack rate (assessed in all participants who received inebilizumab at any point during the randomised controlled period or open-label period [any inebilizumab population] and the aquaporin-4 [AQP4]-IgG seropositive subgroup [any inebilizumab-AQP4-IgG seropositive population]) and safety outcomes (in all participants who were exposed to inebilizumab, analysed as-treated). This study is registered with ClinicalTrials.gov, NCT02200770, and is now complete.

FINDINGS

Between Jan 6, 2015, and Sept 24, 2018, 467 individuals were screened, 231 were randomly assigned, and 230 received at least one dose of inebilizumab (n=174) or placebo (n=56). Between May 19, 2015, and Nov 8, 2018, 165 (95%) of 174 participants in the inebilizumab group and 51 (91%) of 56 in the placebo group entered the open-label period (mean age 42·9 years [SD 12·4], 197 [91%] of 216 were female, 19 [9%] were male, 115 [53%] were White, 45 [21%] were Asian, 19 [9%] were American Indian or Alaskan Native, and 19 [9%] were Black or African American). As of data cutoff for this end of study analysis (Dec 18, 2020; median exposure 1178 days [IQR 856-1538], total exposure of 730 person-years) 225 participants formed the any inebilizumab population, and 208 (92%) participants were AQP4-IgG seropositive. Overall, 63 adjudicated neuromyelitis optica spectrum disorder attacks occurred in 47 (21%) of 225 treated participants (60 attacks occurred in 44 [21%] of 208 in the AQP4-IgG seropositive subgroup); 40 (63%) of 63 attacks occurred in 34 (15%) of 225 treated participants during the first year of treatment. Of individuals who had an adjudicated attack while receiving inebilizumab, 36 (77%) of 47 were subsequently attack-free at the end of 4 years. Annualised attack rates decreased year-on-year, with end-of-study adjusted annualised attack rates being similar in the any inebilizumab-AQP4-IgG seropositive subgroup (0·097 [95% CI 0·070-0·14]) and any inebilizumab populations (0·092 [0·067-0·13]). Overall, 208 (92%) of 225 participants who received any inebilizumab had at least one treatment-emergent adverse event, the most frequent of which were urinary tract infection (59 [26%]), nasopharyngitis (47 [21%]), and arthralgia (39 [17%]). Infection rates did not increase over 4 years. Three (1%) of 225 participants in the any inebilizumab population died during the open-label period (one each due to a CNS event of unknown cause and pneumonia, respiratory insufficiency resulting from an neuromyelitis optica spectrum disorder attack and viral pneumonia related to COVID-19), all of which were deemed to be unrelated to treatment.

INTERPRETATION

Data from the end-of-study analysis of the N-MOmentum trial showed continued and sustained clinical benefits of long-term inebilizumab treatment in individuals with neuromyelitis optica spectrum disorder, which supports the role of inebilizumab as a CD19+ B-cell-depleting therapy in neuromyelitis optica spectrum disorder.

FUNDING

MedImmune and Viela Bio/Horizon Therapeutics, now part of Amgen.

Moving towards a new era for the treatment of neuromyelitis optica spectrum disorders

Neuromyelitis optica spectrum disorders (NMOSD) include a rare group of autoimmune conditions that primarily affect the central nervous system. They are characterized by inflammation and damage to the optic nerves, brain and spinal cord, leading to severe vision impairment, locomotor disability and sphynteric disturbances. In the majority of cases, NMOSD arises due to specific serum immunoglobulin G (IgG) autoantibodies targeting aquaporin 4 (AQP4-IgG), which is the most prevalent water-channel protein of the central nervous system. Early diagnosis and treatment are crucial to manage symptoms and prevent long-term disability in NMOSD patients. NMOSD were previously associated with a poor prognosis. However, recently, a number of randomized controlled trials have demonstrated that biological therapies acting on key elements of NMOSD pathogenesis, such as B cells, interleukin-6 (IL-6) pathway, and complement, have impressive efficacy in preventing the occurrence of clinical relapses. The approval of the initial drugs marks a revolutionary advancement in the treatment of NMOSD patients, significantly transforming therapeutic options and positively impacting their prognosis. In this review, we will provide an updated overview of the key immunopathological, clinical, laboratory, and neuroimaging aspects of NMOSD. Additionally, we will critically examine the latest advancements in NMOSD treatment approaches. Lastly, we will discuss key aspects regarding optimization of treatment strategies and their monitoring.

Soluble biomarkers for Neuromyelitis Optica Spectrum Disorders: a mini review

The Neuromyelitis Optica Spectrum Disorders (NMOSD) constitute a spectrum of rare autoimmune diseases of the central nervous system characterized by episodes of transverse myelitis, optic neuritis, and other demyelinating attacks. Previously thought to be a subtype of multiple sclerosis, NMOSD is now known to be a distinct disease with unique pathophysiology, clinical course, and treatment options. Although there have been significant recent advances in the diagnosis and treatment of NMOSD, the field still lacks clinically validated biomarkers that can be used to stratify disease severity, monitor disease activity, and inform treatment decisions. Here we review many emerging NMOSD biomarkers including markers of cellular damage, neutrophil-to-lymphocyte ratio, complement, and cytokines, with a focus on how each biomarker can potentially be used for initial diagnosis, relapse surveillance, disability prediction, and treatment monitoring.

Blood sphingolipid as a novel biomarker in patients with neuromyelitis optica spectrum disorder

BACKGROUND

Sphingolipids are signaling molecules and structural components of the axolemma and myelin sheath. Plasma sphingolipid levels may reflect disease status of neuromyelitis optica spectrum disorder (NMOSD). We aimed to examine plasma sphingolipids as disease severity biomarkers for NMOSD and compare their characteristics with those of serum neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP).

METHODS

We measured plasma sphingolipids, sNfL, and sGFAP levels in NMOSD cases with anti-aquaporin-4-antibody. An unbiased approach, partial least square discriminant analysis (PLS-DA), was utilized to determine whether sphingolipid profiles differ according to the disease state of NMOSD (presence, moderate-to-severe disability [Expanded Disease Severity Scale, (EDSS) > 3.0], and relapses).

RESULTS

We investigated 81 patients and 10 controls. PLS-DA models utilizing sphingolipids successfully differentiated patients with EDSS > 3.0, but failed to identify the presence of disease and relapses. Ceramide-C14-a significant contributor to differentiating EDSS > 3.0-positively correlated with EDSS, while its levels were independent of age and the presence of relapses. This characteristic was unique from those of sNfL and sGFAP, which were affected by age and relapses as well as EDSS.

CONCLUSION

Plasma sphingolipids may be useful NMOSD biomarkers for disability with distinct characteristics compared to sNfL and sGFAP.

The relationship between serum astroglial and neuronal markers and AQP4 and MOG autoantibodies

BACKGROUND

Certain demyelinating disorders, such as neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) exhibit serum autoantibodies against aquaporin-4 (αAQP4) and myelin oligodendrocyte glycoprotein (αMOG). The variability of the autoantibody presentation warrants further research into subtyping each case.

METHODS

To elucidate the relationship between astroglial and neuronal protein concentrations in the peripheral circulation with occurrence of these autoantibodies, 86 serum samples were analyzed using immunoassays. The protein concentration of glial fibrillary acidic protein (GFAP), neurofilament light chain (NFL) and tau protein was measured in 3 groups of subcategories of suspected NMOSD: αAQP4 positive (n = 20), αMOG positive (n = 32) and αMOG/αAQP4 seronegative (n = 34). Kruskal-Wallis analysis, univariate predictor analysis, and multivariate logistic regression with ROC curves were performed.

RESULTS

GFAP and NFL concentrations were significantly elevated in the αAQP4 positive group (p = 0.003; p = 0.042, respectively), and tau was elevated in the αMOG/αAQP4 seronegative group (p < 0.001). A logistic regression model to classify serostatus was able to separate αAQP4 seropositivity using GFAP + tau, and αMOG seropositivity using tau. The areas under the ROC curves (AUCs) were 0.77 and 0.72, respectively. Finally, a combined seropositivity versus negative status logistic regression model was generated, with AUC = 0.80.

CONCLUSION

The 3 markers can univariately and multivariately classify with moderate accuracy the samples with seropositivity and seronegativity for αAQP4 and αMOG.

Body fluid markers for multiple sclerosis and differential diagnosis from atypical demyelinating disorders

INTRODUCTION

Body fluid markers could be helpful to predict the conversion into clinically definite multiple sclerosis (MS) in people with a first demyelinating event of the central nervous system (CNS). Consequently, biomarkers such as oligoclonal bands, which are integrated in the current MS diagnostic criteria, could assist early MS diagnosis.

AREAS COVERED

This review examines existing knowledge on a broad spectrum of body fluid markers in people with a first CNS demyelinating event, explores their potential to predict conversion to MS, to assess MS disease activity, as well as their utility to differentiate MS from atypical demyelinating disorders such as neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein associated disease.

EXPERT OPINION

This field of research has shown a dramatic increase of evidence, especially in the last decade. Some biomarkers are already established in clinical routine (e.g. oligoclonal bands) while others are currently implemented (e.g. kappa free light chains) or considered as breakthroughs (e.g. neurofilament light). Determination of biomarkers poses challenges for continuous monitoring, especially if exclusively detectable in cerebrospinal fluid. A handful of biomarkers are measurable in blood which holds a significant potential.

Neuromyelitis Optica Spectrum Disorder Resembling Wernicke's Encephalopathy: A Case Report and Review of the Literature

We describe a case of Neuromyelitis Optica Spectrum Disorder (NMOSD) mimicking Wernicke's Encephalopathy (WE) to highlight an atypical presentation of NMOSD. A 39-year-old female presented with subacute encephalopathy and progressive ophthalmoplegia. Her MRI revealed T2 hyperintensities involving the mammillary bodies, periaqueductal grey matter, medial thalami, third ventricle, and area postrema. Whole blood thiamine levels were elevated and she did not improve with IV thiamine. CSF was notable for lymphocytic pleocytosis and elevated protein. She tested positive for serum Aquaporin-4 (AQP4) antibody. Subsequent imaging revealed multilevel lesions in the cervical and thoracic spinal cord. Her CSF GFAP antibody also came back positive. She steadily and significantly improved after high-dose IV steroids and plasmapheresis. She later started on chronic rituximab therapy. This represents a unique case of NMOSD presenting with the classical clinical and imaging features of WE, as opposed to the typical presenting symptoms of NMOSD. As such, demyelinating disorders should be considered when there is concern for diencephalic and midline pathologies, particularly without classic WE risk factors. Conversely, clinicians should be aware of secondary nutritional complications arising from severe area postrema syndrome.

Altered immune co-inhibitory receptor expression and correlation of LAG-3 expression to disease severity in NMOSD

Co-inhibitory receptors (CIR)s regulate T cell-mediated immune responses and growing evidence links co-inhibitory receptors to the progression of neuroimmunological diseases. We studied the expression levels of CIRs: TIM-3, TIGIT, PD-1 and LAG-3 in the peripheral blood mononuclear cells (PBMCs) of 30 patients with Neuromyelitis optica spectrum disorder (NMOSD), 11 Multiple sclerosis (MS) patients and 31 Healthy controls (HC). We found that the mRNA expression levels of TIM-3 were significantly increased in NMOSD compared with HC, and increased LAG-3 surface protein expression was also observed on T-cells of NMOSD patients. Moreover, we observed a negative correlation between LAG-3 expression and disease severity in NMOSD. Our findings suggest a protective effect of LAG-3 in the setting of NMOSD, and that the differential expression of CIRs observed in this study may play a role in the pathological process of NMOSD.

Recent Advances in Diagnostic, Prognostic, and Disease-Monitoring Biomarkers in Multiple Sclerosis

Multiple sclerosis (MS) is a highly heterogeneous disease. Currently, a combination of clinical features, MRI, and cerebrospinal fluid markers are used in clinical practice for diagnosis and treatment decisions. In recent years, there has been considerable effort to develop novel biomarkers that better reflect the pathologic substrates of the disease to aid in diagnosis and early prognosis, evaluation of ongoing inflammatory activity, detection and monitoring of disease progression, prediction of treatment response, and monitoring of disease-modifying treatment safety. In this review, the authors provide an overview of promising recent developments in diagnostic, prognostic, and disease-monitoring/treatment-response biomarkers in MS.

Serum Biomarker Profiles Discriminate AQP4 Seropositive and Double Seronegative Neuromyelitis Optica Spectrum Disorder

BACKGROUND AND OBJECTIVES

Glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) serum levels are useful to define disease activity in different neurologic conditions. These biomarkers are increased in patients with aquaporin-4 antibody-positive NMOSD (AQP4+NMOSD) during clinical attacks suggesting a concomitant axonal and glial damage. However, there are contradictory results in double seronegative NMOSD (DS-NMOSD). The aim of this study was to characterize the neuronal, axonal, and glial damage of DS-NMOSD in comparison with AQP4+NMOSD.

METHODS

Patients with DS-NMOSD (i.e., for AQP4 and myelin oligodendrocyte glycoprotein antibodies-MOG-Abs) and age-matched AQP4+NMOSD diagnosed according to the latest diagnostic criteria and with available serum samples obtained within 3 months from onset/relapse were retrospectively enrolled from 14 international centers. Clinical and radiologic data were collected. Serum NfL, GFAP, tau, and UCH-L1 levels were determined using an ultrasensitive paramagnetic bead-based ELISA (SIMOA). Statistical analysis was performed using nonparametric tests and receiver-operating characteristic (ROC) curve analysis.

RESULTS

We included 25 patients with AQP4+NMOSD and 26 with DS-NMOSD. The median age at disease onset (p = 0.611) and female sex predominance (p = 0.072) were similar in the 2 groups. The most common syndromes at sampling in both AQP4+NMOSD and DS-NMOSD were myelitis (56% vs 38.5%) and optic neuritis (34.6% vs 32%), with no statistical differences (p = 0.716). Median EDSS at sampling was 3.2 (interquartile range [IQR] 2-7.7) in the AQP4+NMOSD group and 4 (IQR [3-6]) in the DS-NMOSD group (p = 0.974). Serum GFAP, tau, and UCH-L1 levels were higher in patients with AQP4+NMOSD compared with those with DS-NMOSD (median 308.3 vs 103.4 pg/mL p = 0.001; median 1.2 vs 0.5 pg/mL, p = 0.001; and median 61.4 vs 35 pg/mL, p = 0.006, respectively). The ROC curve analysis showed that GFAP, tau, and UCH-L1, but not NfL, values were able to discriminate between AQP4+ and DS-NMOSD (area under the curve (AUC) tau: 0.782, p = 0.001, AUC GFAP: 0.762, p = 0.001, AUC UCH-L1: 0.723, p = 0.006). NfL levels were associated with EDSS at nadir only in patients with AQP4+NMOSD.

DISCUSSION

Serum GFAP, tau, and UCH-L1 levels discriminate between AQP4+NMOSD and DS-NMOSD. The different biomarker profile of AQP4+NMOSD vs DS-NMOSD suggests heterogeneity of diseases within the latter category and provides useful data to improve our understanding of this disease.

Update on the diagnosis and treatment of neuromyelitis optica spectrum disorders (NMOSD) - revised recommendations of the Neuromyelitis Optica Study Group (NEMOS). Part II: Attack therapy and long-term management

This manuscript presents practical recommendations for managing acute attacks and implementing preventive immunotherapies for neuromyelitis optica spectrum disorders (NMOSD), a rare autoimmune disease that causes severe inflammation in the central nervous system (CNS), primarily affecting the optic nerves, spinal cord, and brainstem. The pillars of NMOSD therapy are attack treatment and attack prevention to minimize the accrual of neurological disability. Aquaporin-4 immunoglobulin G antibodies (AQP4-IgG) are a diagnostic marker of the disease and play a significant role in its pathogenicity. Recent advances in understanding NMOSD have led to the development of new therapies and the completion of randomized controlled trials. Four preventive immunotherapies have now been approved for AQP4-IgG-positive NMOSD in many regions of the world: eculizumab, ravulizumab - most recently-, inebilizumab, and satralizumab. These new drugs may potentially substitute rituximab and classical immunosuppressive therapies, which were as yet the mainstay of treatment for both, AQP4-IgG-positive and -negative NMOSD. Here, the Neuromyelitis Optica Study Group (NEMOS) provides an overview of the current state of knowledge on NMOSD treatments and offers statements and practical recommendations on the therapy management and use of all available immunotherapies for this disease. Unmet needs and AQP4-IgG-negative NMOSD are also discussed. The recommendations were developed using a Delphi-based consensus method among the core author group and at expert discussions at NEMOS meetings.

Understanding the Pathophysiology and Magnetic Resonance Imaging of Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

Magnetic resonance imaging (MRI) has been extensively applied in the study of multiple sclerosis (MS), substantially contributing to diagnosis, differential diagnosis, and disease monitoring. MRI studies have significantly contributed to the understanding of MS through the characterization of typical radiological features and their clinical or prognostic implications using conventional MRI pulse sequences and further with the application of advanced imaging techniques sensitive to microstructural damage. Interpretation of results has often been validated by MRI-pathology studies. However, the application of MRI techniques in the study of neuromyelitis optica spectrum disorders (NMOSD) remains an emerging field, and MRI studies have focused on radiological correlates of NMOSD and its pathophysiology to aid in diagnosis, improve monitoring, and identify relevant prognostic factors. In this review, we discuss the main contributions of MRI to the understanding of MS and NMOSD, focusing on the most novel discoveries to clarify differences in the pathophysiology of focal inflammation initiation and perpetuation, involvement of normal-appearing tissue, potential entry routes of pathogenic elements into the CNS, and existence of primary or secondary mechanisms of neurodegeneration.

Reshaping neuroimmunology: diagnosis and treatment in the era of precision medicine

Precision medicine has revolutionized the field of neuroimmunology, with innovative approaches that characterize diseases based on their biology, deeper understanding of the factors leading to heterogeneity within the same disease, development of targeted therapies, and strategies to tailor therapies to each patient. This review explores the impact of precision medicine on various neuroimmunological conditions, including multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), optic neuritis, autoimmune encephalitis, and immune-mediated neuropathies. We discuss advances in disease subtyping, recognition of novel entities, promising biomarkers, and the development of more selective monoclonal antibodies and cutting-edge synthetic cell-based immunotherapies in neuroimmunological disorders. In addition, we analyze the challenges related to affordability and equity in the implementation of these emerging technologies, especially in situations with limited resources.

The relationship between serum astroglial and neuronal markers and AQP4 and MOG autoantibodies

Background

Certain demyelinating disorders, such as neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) exhibit serum autoantibodies against aquaporin-4 (αAQP4) and myelin oligodendrocyte glycoprotein (αMOG). The variability of the autoantibody presentation warrants further research into subtyping each case.

Methods

To elucidate the relationship between astroglial and neuronal protein concentrations in the peripheral circulation with occurrence of these autoantibodies, 86 serum samples were analyzed using immunoassays. The protein concentration of glial fibrillary acidic protein (GFAP), neurofilament light chain (NFL) and tau protein was measured in 3 groups of subcategories of suspected NMOSD: αAQP4 positive (n = 20), αMOG positive (n = 32) and αMOG/αAQP4 seronegative (n = 34). Kruskal-Wallis analysis, univariate predictor analysis, and multivariate logistic regression with ROC curves were performed.

Results

GFAP and NFL concentrations were significantly elevated in the αAQP4 positive group (p = 0.003; p = 0.042, respectively), and tau was elevated in the αMOG/αAQP4 seronegative group (p < 0.001). A logistic regression model to classify serostatus was able to separate αAQP4 seropositivity using GFAP + tau, and αMOG seropositivity using tau. The areas under the ROC curves (AUCs) were 0.77 and 0.72, respectively. Finally, a combined seropositivity versus negative status logistic regression model was generated, with AUC = 0.80.

Conclusion

The 3 markers can univariately and multivariately classify with moderate accuracy the samples with seropositivity and seronegativity for αAQP4 and αMOG.

Clinically relevant increases in serum neurofilament light chain and glial fibrillary acidic protein in patients with Susac syndrome

BACKGROUND AND PURPOSE

Serum levels of neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP) are promising neuro-axonal damage and astrocytic activation biomarkers. Susac syndrome (SS) is an increasingly recognized neurological condition and biomarkers that can help assess and monitor disease evolution are highly needed for the adequate management of these patients. sNfL and sGFAP levels were evaluated in patients with SS and their clinical relevance in the relapse and remission phase of the disease was assessed.

METHODS

As part of a multicentre study that enrolled patients diagnosed with SS from six international centres, sNfL and sGFAP levels were assessed in 22 SS patients (nine during a relapse and 13 in remission) and 59 age- and sex-matched healthy controls using SimoaTM assay Neurology 2-Plex B Kit.

RESULTS

Serum NfL levels were higher than those of healthy controls (p < 0.001) in SS patients and in both subgroups of patients in relapse and in remission (p < 0.001 for both), with significantly higher levels in relapse than in remission (p = 0.008). sNfL levels showed a negative correlation with time from the last relapse (r = -0.663; p = 0.001). sGFAP levels were slightly higher in the whole group of patients than in healthy controls (p = 0.046) and were more pronounced in relapse than in remission (p = 0.013).

CONCLUSION

In SS patients, both sNFL and sGFAP levels increased compared with healthy controls. Both biomarkers had higher levels during clinical relapse and much lower levels in remission. sNFL was shown to be time sensitive to clinical changes and can be useful to monitor neuro-axonal damage in SS.

Serum neurofilament light chain levels at attack predict post-attack disability worsening and are mitigated by inebilizumab: analysis of four potential biomarkers in neuromyelitis optica spectrum disorder

OBJECTIVE

To investigate relationships between serum neurofilament light chain (sNfL), ubiquitin C-terminal hydrolase L1 (sUCHL1), tau (sTau) and glial fibrillary acidic protein (sGFAP) levels and disease activity/disability in neuromyelitis optica spectrum disorder (NMOSD), and the effects of inebilizumab on these biomarkers in N-MOmentum.

METHODS

N-MOmentum randomised participants to receive inebilizumab or placebo with a randomised controlled period (RCP) of 28 weeks and an open-label follow-up period of ≥2 years. The sNfL, sUCHL1, sTau and sGFAP were measured using single-molecule arrays in 1260 scheduled and attack-related samples from N-MOmentum participants (immunoglobulin G (IgG) autoantibodies to aquaporin-4-positive, myelin oligodendrocyte glycoprotein-IgG-positive or double autoantibody-negative) and two control groups (healthy donors and patients with relapsing-remitting multiple sclerosis).

RESULTS

The concentration of all four biomarkers increased during NMOSD attacks. At attack, sNfL had the strongest correlation with disability worsening during attacks (Spearman R2=0.40; p=0.01) and prediction of disability worsening after attacks (sNfL cut-off 32 pg/mL; area under the curve 0.71 (95% CI 0.51 to 0.89); p=0.02), but only sGFAP predicted upcoming attacks. At RCP end, fewer inebilizumab-treated than placebo-treated participants had sNfL>16 pg/mL (22% vs 45%; OR 0.36 (95% CI 0.17 to 0.76); p=0.004).

CONCLUSIONS

Compared with sGFAP, sTau and sUCHL1, sNfL at attack was the strongest predictor of disability worsening at attack and follow-up, suggesting a role for identifying participants with NMOSD at risk of limited post-relapse recovery. Treatment with inebilizumab was associated with lower levels of sGFAP and sNfL than placebo.

TRIAL REGISTRATION NUMBER

NCT02200770.

Autoimmune encephalitis: recent clinical and biological advances

In 2015, we wrote a review in The Journal of Neurology summarizing the field of autoantibody-associated neurological diseases. Now, in 2023, we present an update of the subject which reflects the rapid expansion and refinement of associated clinical phenotypes, further autoantibody discoveries, and a more detailed understanding of immunological and neurobiological pathophysiological pathways which mediate these diseases. Increasing awareness around distinctive aspects of their clinical phenotypes has been a key driver in providing clinicians with a better understanding as to how these diseases are best recognized. In clinical practice, this recognition supports the administration of often effective immunotherapies, making these diseases 'not to miss' conditions. In parallel, there is a need to accurately assess patient responses to these drugs, another area of growing interest. Feeding into clinical care are the basic biological underpinnings of the diseases, which offer clear pathways to improved therapies toward enhanced patient outcomes. In this update, we aim to integrate the clinical diagnostic pathway with advances in patient management and biology to provide a cohesive view on how to care for these patients in 2023, and the future.

The neuro-ophthalmological manifestations of NMOSD and MOGAD-a comprehensive review

Optic neuritis (ON) is one of the most frequently seen neuro-ophthalmic causes of vision loss worldwide. Typical ON is often idiopathic or seen in patients with multiple sclerosis, which is well described in the landmark clinical trial, the Optic Neuritis Treatment Trial (ONTT). However, since the completion of the ONTT, there has been the discovery of aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) antibodies, which are biomarkers for neuromyelitis optica spectrum disorder (NMOSD) and MOG antibody-associated disease (MOGAD), respectively. These disorders are associated with atypical ON that was not well characterised in the ONTT. The severity, rate of recurrence and overall outcome differs in these two entities requiring prompt and accurate diagnosis and management. This review will summarise the characteristic neuro-ophthalmological signs in NMOSD and MOGAD, serological markers and radiographic findings, as well as acute and long-term therapies used for these disorders.

International Delphi Consensus on the Management of AQP4-IgG+ NMOSD: Recommendations for Eculizumab, Inebilizumab, and Satralizumab

BACKGROUND AND OBJECTIVES

Neuromyelitis optica spectrum disorder (NMOSD) is a rare debilitating autoimmune disease of the CNS. Three monoclonal antibodies were recently approved as maintenance therapies for aquaporin-4 immunoglobulin G (AQP4-IgG)-seropositive NMOSD (eculizumab, inebilizumab, and satralizumab), prompting the need to consider best practice therapeutic decision-making for this indication. Our objective was to develop validated statements for the management of AQP4-IgG-seropositive NMOSD, through an evidence-based Delphi consensus process, with a focus on recommendations for eculizumab, inebilizumab, and satralizumab.

METHODS

We recruited an international panel of clinical experts in NMOSD and asked them to complete a questionnaire on NMOSD management. Panel members received a summary of evidence identified through a targeted literature review and provided free-text responses to the questionnaire based on both the data provided and their clinical experience. Responses were used to generate draft statements on NMOSD-related themes. Statements were voted on over a maximum of 3 rounds; participation in at least 1 of the first 2 rounds was mandatory. Panel members anonymously provided their level of agreement (6-point Likert scale) on each statement. Statements that failed to reach a predefined consensus threshold (≥67%) were revised based on feedback and then voted on in the next round. Final statements were those that met the consensus threshold (≥67%).

RESULTS

The Delphi panel comprised 24 experts, who completed the Delphi process in November 2021 after 2 voting rounds. In round 1, 23/25 statements reached consensus and were accepted as final. The 2 statements that failed to reach consensus were revised. In round 2, both revised statements reached consensus. Twenty-five statements were agreed in total: 11 on initiation of or switching between eculizumab, inebilizumab, and satralizumab; 3 on monotherapy/combination therapy; 7 on safety and patient population considerations; 3 on biomarkers/patient-reported outcomes; and 1 on research gaps.

DISCUSSION

An established consensus method was used to develop statements relevant to the management of AQP4-IgG-seropositive NMOSD. These international statements will be valuable for informing individualized therapeutic decision-making and could form the basis for standardized practice guidelines.

Proteomics and relationship with axonal pathology in multiple sclerosis: 5-year diffusion tensor imaging study

Blood-based biomarkers can be economic and easily accessible tools for monitoring and predicting disease activity in multiple sclerosis. The objective of this study was to determine the predictive value of a multivariate proteomic assay for concurrent and future microstructural/axonal brain pathology in a longitudinal study of a heterogeneous group of people with multiple sclerosis. A proteomic analysis was obtained on serum samples from 202 people with multiple sclerosis (148 relapsing-remitting and 54 progressive) at baseline and 5-year follow-up. The concentration of 21 proteins related to multiple pathways of multiple sclerosis pathophysiology was derived using Proximity Extension Assay on the Olink platform. Patients were imaged on the same 3T MRI scanner at both timepoints. Тhe rate of whole brain, white matter and grey matter atrophy over the 5-year follow-up was determined using the multi-timepoint Structural Image Evaluation, using Normalisation, of Atrophy algorithms. Lesion burden measures were also assessed. The severity of microstructural axonal brain pathology was quantified using diffusion tensor imaging. Fractional anisotropy and mean diffusivity of normal-appearing brain tissue, normal-appearing white matter, grey matter, T2 and T1 lesions were calculated. Age, sex and body mass index-adjusted step-wise regression models were used. Glial fibrillary acidic protein was the most common and highest-ranked proteomic biomarker associated with greater concurrent microstructural central nervous system alterations (P < 0.001). The rate of whole brain atrophy was associated with baseline levels of glial fibrillary acidic protein, protogenin precursor, neurofilament light chain and myelin oligodendrocyte (P < 0.009), whereas grey matter atrophy was associated with higher baseline neurofilament light chain, higher osteopontin and lower protogenin precursor levels (P < 0.016). Higher baseline glial fibrillary acidic protein level was a significant predictor of future severity of the microstructural CNS alterations as measured by normal-appearing brain tissue fractional anisotropy and mean diffusivity (standardized β = -0.397/0.327, P < 0.001), normal-appearing white matter fractional anisotropy (standardized β = -0.466, P < 0.0012), grey matter mean diffusivity (standardized β = 0.346, P < 0.011) and T2 lesion mean diffusivity (standardized β = 0.416, P < 0.001) at the 5-year follow-up. Serum levels of myelin-oligodendrocyte glycoprotein, neurofilament light chain, contactin-2 and osteopontin proteins were additionally and independently associated with worse concomitant and future axonal pathology. Higher glial fibrillary acidic protein levels were associated with future disability progression (Exp(B) = 8.65, P = 0.004). Multiple proteomic biomarkers are independently associated with greater severity of axonal brain pathology as measured by diffusion tensor imaging in multiple sclerosis. Baseline serum glial fibrillary acidic protein levels can predict future disability progression.

Profile and potential role of novel metabolite biomarkers, especially indoleacrylic acid, in pathogenesis of neuromyelitis optica spectrum disorders

Background: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune central nervous system (CNS) inflammatory and demyelinating disorder that can lead to serious disability and mortality. Humoral fluid biomarkers with specific, convenient, and efficient profiles that could characterize and monitor disease activity or severity are very useful. We aimed to develop a sensitive and high-throughput liquid chromatography-tandem mass spectrometry (LC-MS)/MS-based analytical method for novel biomarkers finding in NMOSD patients and verified its function tentatively. Methods: Serum samples were collected from 47 NMOSD patients, 18 patients with other neurological disorders (ONDs), and 35 healthy controls (HC). Cerebrospinal fluid (CSF) samples were collected from 18 NMOSD and 17 OND patients. Three aromatic amino acids (phenylalanine, tyrosine, and tryptophan) and nine important metabolites that included phenylacetylglutamine (PAGln), indoleacrylic acid (IA), 3-indole acetic acid (IAA), 5-hydroxyindoleacetic acid (HIAA), hippuric acid (HA), I-3-carboxylic acid (I-3-CA), kynurenine (KYN), kynurenic acid (KYNA), and quinine (QUIN) were analyzed by using the liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method. The profile of IA was further analyzed, and its function was verified in an astrocyte injury model stimulated by NMO-IgG, which represents important events in NMOSD pathogenesis. Results: In the serum, tyrosine and some of the tryptophan metabolites IA and I-3-CA decreased, and HIAA increased significantly in NMOSD patients. The CSF levels of phenylalanine and tyrosine showed a significant increase exactly during the relapse stage, and IA in the CSF was also increased markedly during the relapse and remission phases. All conversion ratios had similar profiles with their level fluctuations. In addition, the serum IA levels negatively correlated with glial fibrillary acidic protein (GFAP), and neurofilament light (NfL) levels in the serum of NMOSD patients were measured by using ultra-sensitive single-molecule arrays (Simoa). IA showed an anti-inflammatory effect in an in vitro astrocyte injury model. Conclusion: Our data suggest that essential aromatic amino acid tryptophan metabolites IA in the serum or CSF may serve as a novel promising biomarker to monitor and predict the activity and severity of NMOSD disease. Supplying or enhancing IA function can promote anti-inflammatory responses and may have therapeutic benefits.

Update on the diagnosis and treatment of neuromyelits optica spectrum disorders (NMOSD) - revised recommendations of the Neuromyelitis Optica Study Group (NEMOS). Part I: Diagnosis and differential diagnosis

The term 'neuromyelitis optica spectrum disorders' (NMOSD) is used as an umbrella term that refers to aquaporin-4 immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica (NMO) and its formes frustes and to a number of closely related clinical syndromes without AQP4-IgG. NMOSD were originally considered subvariants of multiple sclerosis (MS) but are now widely recognized as disorders in their own right that are distinct from MS with regard to immunopathogenesis, clinical presentation, optimum treatment, and prognosis. In part 1 of this two-part article series, which ties in with our 2014 recommendations, the neuromyelitis optica study group (NEMOS) gives updated recommendations on the diagnosis and differential diagnosis of NMOSD. A key focus is on differentiating NMOSD from MS and from myelin oligodendrocyte glycoprotein antibody-associated encephalomyelitis (MOG-EM; also termed MOG antibody-associated disease, MOGAD), which shares significant similarity with NMOSD with regard to clinical and, partly, radiological presentation, but is a pathogenetically distinct disease. In part 2, we provide updated recommendations on the treatment of NMOSD, covering all newly approved drugs as well as established treatment options.

Serum proteins for monitoring and predicting visual function in patients with recent optic neuritis

It is unclear whether serum proteins can serve as biomarkers to reflect pathological changes and predict recovery in inflammation of optic nerve. We evaluated whether serum proteins could monitor and prognosticate optic neuritis (ON). We prospectively recruited consecutive patients with recent ON, classified as ON with anti-aquaporin-4 antibody (AQP4-ON), ON with anti-myelin oligodendrocyte glycoprotein antibody (MOG-ON), and double-seronegative ON (DSN-ON). Using ultrasensitive single-molecule array assays, we measured serum neurofilament light chain and glial fibrillary acidic protein (GFAP), and brain-derived neurotrophic factor (BDNF). We analyzed the markers according to disease group, state, severity, and prognosis. We enrolled 60 patients with recent ON (15 AQP4-ON; 14 MOG-ON; 31 DSN-ON). At baseline, AQP4-ON group had significantly higher serum GFAP levels than did other groups. In AQP4-ON group, serum GFAP levels were significantly higher in the attack state than in the remission state and correlated with poor visual acuity. As a prognostic indicator, serum BDNF levels were positively correlated with follow-up visual function in the AQP4-ON group (r = 0.726, p = 0.027). Serum GFAP reflected disease status and severity, while serum BDNF was identified as a prognostic biomarker in AQP4-ON. Serum biomarkers are potentially helpful for patients with ON, particularly those with AQP4-ON.

Biomarkers in autoimmune diseases of the central nervous system

The autoimmune diseases of the central nervous system (CNS) represent individual heterogeneity with different disease entities. Although clinical and imaging features make it possible to characterize larger patient cohorts, they may not provide sufficient evidence to detect disease activity and response to disease modifying drugs. Biomarkers are becoming a powerful tool due to their objectivity and easy access. Biomarkers may indicate various aspects of biological processes in healthy and/or pathological states, or as a response to drug therapy. According to the clinical features described, biomarkers are usually classified into predictive, diagnostic, monitoring and safety biomarkers. Some nerve injury markers, humoral markers, cytokines and immune cells in serum or cerebrospinal fluid have potential roles in disease severity and prognosis in autoimmune diseases occurring in the CNS, which provides a promising approach for clinicians to early intervention and prevention of future disability. Therefore, this review mainly summarizes the potential biomarkers indicated in autoimmune disorders of the CNS.

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.

Disease characteristics of idiopathic transverse myelitis with serum neuronal and astroglial damage biomarkers

Despite its close association with CNS inflammatory demyelinating disorders (CIDDs), pathogenic characteristics of idiopathic transverse myelitis (ITM) remain largely unknown. Here, we investigated serum levels of neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP) in patients with ITM to unravel the disease characteristics of ITM. We prospectively recruited 70 patients with ITM, 62 with AQP4 + NMOSD and 85 with RRMS-including 31 patients with acute TM attacks-along with 30 HCs. We measured sNfL and sGFAP levels using single-molecular arrays and compared these levels per lesion volume between the disease groups during attacks. Compared to HCs, ITM patients showed higher sNfL and sGFAP during acute attacks (sNfL: p < 0.001, sGFAP: p = 0.024), while those in remission (sNfL: p = 0.944, sGFAP: p > 0.999) did not, regardless of lesion extents and presence of multiple attacks. ITM patients demonstrated lower sGFAP/volume (p = 0.011) during acute attacks and lower sGFAP (p < 0.001) in remission compared to AQP4 + NMOSD patients. These findings suggest that both neuronal and astroglial damages occur in patients with acute ITM attacks at a similar level to those with RRMS, distinct from AQP4 + NMOSD. However, active neuroinflammatory process was not remarkable during remission in this cohort.

Decipher potential biomarkers of diagnosis and disease activity for NMOSD with AQP4 using LC-MS/MS and Simoa

BACKGROUND

Neuromyelitis optica spectrum disorders (NMOSD) is an autoimmune demyelinating disease, leading recurrently relapses and severe disability. There is a need for new biomarkers to meet clinical needs in diagnosis and monitoring.

METHODS

Through liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis, brain lesions from NMO animal models were analyzed to identify potential biomarkers. Then, we assessed the levels of serum glial fibrillary acidic protein (sGFAP), neurofilament light chain (sNfL), Tau protein (sTau) and Ubiquitin C-terminal hydrolase L1 (sUCHL1) using an ultrasensitive single molecule array (Simoa) of AQP4-IgG + NMOSD patients, myelin oligodendrocyte glycoprotein antibody-associated disorder (MOGAD) patients, multiple sclerosis (MS) patients and healthy controls (HCs). Additionally, we further explored the early diagnosis value of these proteins.

RESULTS

There were 72 differentially expressed proteins between the NMO and control groups. NfL abundance was elevated when GFAP, UCHL1, and Tau abundance was decreased in the NMO group. Then, we observed that the sGFAP and sUCHL1 levels in patients with NMOSD in the early stage were significantly increased compared to those in control participants. Combined ROCs of the sGFAP, sNfL, and sUCHL1 levels to better predict NMOSD with relapse stages was optimal. Notably, univariate and multivariate analyses demonstrated that the sGFAP and sNfL levels were higher in patients with brain lesions, while the sUCHL1 levels were higher in those with spinal cord lesions during recent relapse.

CONCLUSIONS

These findings suggested that sGFAP, sNfL, and sUCHL1 displayed good diagnostic performance in AQP4-IgG + NMOSD and could be novel candidates for early discrimination.

A unified classification approach rating clinical utility of protein biomarkers across neurologic diseases

A major evolution from purely clinical diagnoses to biomarker supported clinical diagnosing has been occurring over the past years in neurology. High-throughput methods, such as next-generation sequencing and mass spectrometry-based proteomics along with improved neuroimaging methods, are accelerating this development. This calls for a consensus framework that is broadly applicable and provides a spot-on overview of the clinical validity of novel biomarkers. We propose a harmonized terminology and a uniform concept that stratifies biomarkers according to clinical context of use and evidence levels, adapted from existing frameworks in oncology with a strong focus on (epi)genetic markers and treatment context. We demonstrate that this framework allows for a consistent assessment of clinical validity across disease entities and that sufficient evidence for many clinical applications of protein biomarkers is lacking. Our framework may help to identify promising biomarker candidates and classify their applications by clinical context, aiming for routine clinical use of (protein) biomarkers in neurology.

SAkuraBONSAI: Protocol design of a novel, prospective study to explore clinical, imaging, and biomarker outcomes in patients with AQP4-IgG-seropositive neuromyelitis optica spectrum disorder receiving open-label satralizumab

Background

Neuromyelitis optica spectrum disorder (NMOSD) is a rare, autoimmune disease of the central nervous system that produces acute, unpredictable relapses causing cumulative neurological disability. Satralizumab, a humanized, monoclonal recycling antibody that targets the interleukin-6 receptor, reduced NMOSD relapse risk vs. placebo in two Phase 3 trials: SAkuraSky (satralizumab ± immunosuppressive therapy; NCT02028884) and SAkuraStar (satralizumab monotherapy; NCT02073279). Satralizumab is approved to treat aquaporin-4 IgG-seropositive (AQP4-IgG+) NMOSD. SAkuraBONSAI (NCT05269667) will explore fluid and imaging biomarkers to better understand the mechanism of action of satralizumab and the neuronal and immunological changes following treatment in AQP4-IgG+ NMOSD.

Objectives

SAkuraBONSAI will evaluate clinical disease activity measures, patient-reported outcomes (PROs), pharmacokinetics, and safety of satralizumab in AQP4-IgG+ NMOSD. Correlations between imaging markers (magnetic resonance imaging [MRI] and optical coherence tomography [OCT]) and blood and cerebrospinal fluid (CSF) biomarkers will be investigated.

Study design

SAkuraBONSAI is a prospective, open-label, multicenter, international, Phase 4 study that will enroll approximately 100 adults (18-74 years) with AQP4-IgG+ NMOSD. This study includes two patient cohorts: newly diagnosed, treatment-naïve patients (Cohort 1; n = 60); and inadequate responders to recent (<6 months) rituximab infusion (Cohort 2; n = 40). Satralizumab monotherapy (120 mg) will be administered subcutaneously at Weeks 0, 2, 4, and Q4W thereafter for a total of 92 weeks.

Endpoints

Disease activity related to relapses (proportion relapse-free, annualized relapse rate, time to relapse, and relapse severity), disability progression (Expanded Disability Status Scale), cognition (Symbol Digit Modalities Test), and ophthalmological changes (visual acuity; National Eye Institute Visual Function Questionnaire-25) will all be assessed. Peri-papillary retinal nerve fiber layer and ganglion cell complex thickness will be monitored using advanced OCT (retinal nerve fiber layer and ganglion cell plus inner plexiform layer thickness). Lesion activity and atrophy will be monitored by MRI. Pharmacokinetics, PROs, and blood and CSF mechanistic biomarkers will be assessed regularly. Safety outcomes include the incidence and severity of adverse events.

Conclusions

SAkuraBONSAI will incorporate comprehensive imaging, fluid biomarker, and clinical assessments in patients with AQP4-IgG+ NMOSD. SAkuraBONSAI will provide new insights into the mechanism of action of satralizumab in NMOSD, while offering the opportunity to identify clinically relevant neurological, immunological, and imaging markers.

Serum GFAP and NfL Levels Differentiate Subsequent Progression and Disease Activity in Patients With Progressive Multiple Sclerosis

Background and Objectives

Neurodegeneration and astrocytic activation are pathologic hallmarks of progressive multiple sclerosis (MS) and can be quantified by serum neurofilament light chain (sNfL) and glial fibrillary acidic protein (sGFAP). We investigated sNfL and sGFAP as tools for stratifying patients with progressive MS based on progression and disease activity status.

Methods

We leveraged our Comprehensive Longitudinal Investigation of MS at the Brigham and Women's Hospital (CLIMB) natural history study, which includes clinical, MRI data and serum samples collected over more than 20 years. We included patients with MS with a confirmed Expanded Disability Status Scale (EDSS) score ≥3 that corresponds with our classifier for patients at high risk of underlying progressive pathology. We analyzed sNfL and sGFAP within 6 months from the confirmed EDSS score ≥3 corresponding with our baseline visit. Patients who further developed 6-month confirmed disability progression (6mCDP) were classified as progressors. We further stratified our patients into active/nonactive based on new brain/spinal cord lesions or relapses in the 2 years before baseline or during follow-up. Statistical analysis on log-transformed sGFAP/sNfL assessed the baseline association with demographic, clinical, and MRI features and associations with future disability.

Results

We included 257 patients with MS who had an average EDSS score of 4.0 and a median follow-up after baseline of 7.6 years. sNfL was higher in patients with disease activity in the 2 years before baseline (adjusted β = 1.21; 95% CI 1.04–1.42;p= 0.016), during the first 2 years of follow-up (adjusted β = 1.17; 95% CI = 1.01–1.36;p= 0.042). sGFAP was not increased in the presence of disease activity. Higher sGFAP levels, but not sNfL levels, were associated with higher risk of 6mCDP (adjusted hazard ratio [HR] = 1.71; 95% CI = 1.19–2.45;p= 0.004). The association was stronger in patients with low sNfL (adjusted HR = 2.44; 95% CI 1.32–4.52;p= 0.005) and patients who were nonactive in the 2 years prior or after the sample.

Discussion

Higher levels of sGFAP correlated with subsequent progression, particularly in nonactive patients, whereas sNfL reflected acute disease activity in patients with MS at high risk of underlying progressive pathology. Thus, sGFAP and sNfL levels may be used to stratify patients with progressive MS for clinical research studies and clinical trials and may inform clinical care.

Inebilizumab: A Review in Neuromyelitis Optica Spectrum Disorder

Inebilizumab (Uplizna®) is a recently approved monoclonal antibody for use in adults with neuromyelitis optica spectrum disorder (NMOSD) who are anti-aquaporin-4 (AQP4) antibody seropositive. Inebilizumab targets the B cell antigen CD19 and effectively depletes circulating B cells, thus suppressing inflammatory NMOSD attacks that are potentially disabling or life-threatening. It is approved as an intravenous infusion in several countries. In the pivotal phase 2/3 N-MOmentum trial, inebilizumab reduced the risk of NMOSD attacks compared with placebo, including in AQP4-antibody seropositive patients. Inebilizumab also significantly reduced the risk of disability score worsening, the number of NMOSD-related hospitalisations and MRI lesion count, but had no significant effect on low-contrast binocular vision. The treatment effect on relapse risk and disability scores was sustained in inebilizumab-treated patients for ≥ 4 years during the open-label extension. Inebilizumab was generally well tolerated, with the most common adverse events being urinary tract infection and arthralgia. Thus, inebilizumab is an effective treatment option for adults with AQP4-antibody seropositive NMOSD.

Serum glial fibrillary acidic protein and neurofilament light chain in patients with early treated phenylketonuria

To pave the way for healthy aging in early treated phenylketonuria (ETPKU) patients, a better understanding of the neurological course in this population is needed, requiring easy accessible biomarkers to monitor neurological disease progression in large cohorts. The objective of this pilot study was to investigate the potential of glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) as blood biomarkers to indicate changes of the central nervous system in ETPKU. In this single-center cross-sectional study, GFAP and NfL concentrations in serum were quantified using the Simoa^® multiplex technology in 56 ETPKU patients aged 6–36 years and 16 age matched healthy controls. Correlation analysis and hierarchical linear regression analysis were performed to investigate an association with disease-related biochemical parameters and retinal layers assessed by optical coherence tomography. ETPKU patients did not show significantly higher GFAP concentrations (mean 73 pg/ml) compared to healthy controls (mean 60 pg/ml, p = 0.140). However, individual pediatric and adult ETPKU patients had GFAP concentrations above the healthy control range. In addition, there was a significant association of GFAP concentrations with current plasma tyrosine concentrations (r = −0.482, p = 0.036), a biochemical marker in phenylketonuria, and the retinal inner nuclear layer volume (r = 0.451, p = 0.04). There was no evidence of NfL alterations in our ETPKU cohort. These pilot results encourage multicenter longitudinal studies to further investigate serum GFAP as a complementary tool to better understand and monitor neurological disease progression in ETPKU. Follow-up investigations on aging ETPKU patients are required to elucidate the potential of serum NfL as biomarker.

Serum GFAP - reference interval and preanalytical properties in Danish adults

OBJECTIVES

Glial fibrillary acidic protein (GFAP) is a promising biomarker that could potentially contribute to diagnosis and prognosis in neurological diseases. The biomarker is approaching clinical use but the reference interval for serum GFAP remains to be established, and knowledge about the effect of preanalytical factors is also limited.

METHODS

Serum samples from 371 apparently healthy reference subjects, 21-90 years of age, were measured by a single-molecule array (Simoa) assay. Continuous reference intervals were modelled using non-parametric quantile regression and compared with traditional age-partitioned non-parametric reference intervals established according to the Clinical and Laboratory Standards Institute (CLSI) guideline C28-A3. The following preanalytical conditions were also examined: stability in whole blood at room temperature (RT), stability in serum at RT and -20 °C, repeated freeze-thaw cycles, and haemolysis.

RESULTS

The continuous reference interval showed good overall agreement with the traditional age-partitioned reference intervals of 25-136 ng/L, 34-242 ng/L, and 5-438 ng/L for the age groups 20-39, 40-64, and 65-90 years, respectively. Both types of reference intervals showed increasing levels and variability of serum GFAP with age. In the preanalytical tests, the mean changes from baseline were 2.3% (95% CI: -2.4%, 6.9%) in whole blood after 9 h at RT, 3.1% (95% CI: -4.5%, 10.7%) in serum after 7 days at RT, 10.4% (95% CI: -6.0%, 26.8%) in serum after 133 days at -20 °C, and 10.4% (95% CI: 9.5%, 11.4%) after three freeze-thaw cycles.

CONCLUSIONS

The study establishes age-dependent reference ranges for serum GFAP in adults and demonstrates overall good stability of the biomarker.

Serum glial fibrillary acidic protein correlates with retinal structural damage in aquaporin-4 antibody positive neuromyelitis optica spectrum disorder

BACKGROUND

Aquaporin-4 immunoglobulin-G positive (AQP4-IgG⁺) neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathy associated with optic neuritis (ON). Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is an oligodendrocytopathy with a similar phenotype. Serum glial fibrillary acidic protein (sGFAP), an astrocyte-derived protein, is associated with disease severity in AQP4-IgG⁺ NMOSD. Serum neurofilament light (sNfL) indicates neuroaxonal damage. The objective was to investigate the association of sGFAP and sNfL with subclinical afferent visual system damage in clinically stable AQP4-IgG⁺ NMOSD and MOGAD patients.

METHODS

In this cross-sectional study, clinically stable patients with AQP4-IgG⁺ NMOSD (N = 33) and MOGAD (N = 16), as diseased controls, underwent sGFAP and sNfL measurements by single molecule array, retinal optical coherence tomography and visually evoked potentials.

RESULTS

Higher sGFAP concentrations were associated with thinner ganglion cell-inner plexiform layer (β (95% confidence interval (CI)) = -0.75 (-1.23 to -0.27), p = 0.007) and shallower fovea (average pit depth: β (95%CI) = -0.59 (-0.63 to -0.55), p = 0.020) in NMOSD non-ON eyes. Participants with pathological P100 latency had higher sGFAP (median [interquartile range]: 131.32 [81.10-179.34] vs. 89.50 [53.46-121.91] pg/ml, p = 0.024). In MOGAD, sGFAP was not associated with retinal structural or visual functional measures.

CONCLUSIONS

The association of sGFAP with structural and functional markers of afferent visual system damage in absence of ON suggests that sGFAP may be a sensitive biomarker for chronic disease severity in clinically stable AQP4-IgG⁺ NMOSD.

Association of Serum GFAP with Functional and Neurocognitive Outcome in Sporadic Small Vessel Disease

Cerebrospinal fluid (CSF) and serum biomarkers are critical for clinical decision making in neurological diseases. In cerebral small vessel disease (CSVD), white matter hyperintensities (WMH) are an important neuroimaging biomarker, but more blood-based biomarkers capturing different aspects of CSVD pathology are needed. In 42 sporadic CSVD patients, we prospectively analysed WMH on magnetic resonance imaging (MRI) and the biomarkers neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), chitinase3-like protein 1 (CHI3L1), Tau and Aβ1-42 in CSF and NfL and GFAP in serum. GFAP and CHI3L1 expression was studied in post-mortem brain tissue in additional cases. CSVD cases with higher serum NfL and GFAP levels had a higher modified Rankin Scale (mRS) and NIHSS score and lower CSF Aβ1-42 levels, whereas the CSF NfL and CHI3L1 levels were positively correlated with the WMH load. Moreover, the serum GFAP levels significantly correlated with the neurocognitive functions. Pathological analyses in CSVD revealed a high density of GFAP-immunoreactive fibrillary astrocytic processes in the periventricular white matter and clusters of CHI3L1-immunoreactive astrocytes in the basal ganglia and thalamus. Thus, besides NfL, serum GFAP is a highly promising fluid biomarker of sporadic CSVD, because it does not only correlate with the clinical severity but also correlates with the cognitive function in patients.

Neuromyelitis Optica Spectrum Disorder: From Basic Research to Clinical Perspectives

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system characterized by relapses and autoimmunity caused by antibodies against the astrocyte water channel protein aquaporin-4. Over the past decade, there have been significant advances in the biologic knowledge of NMOSD, which resulted in the IDENTIFICATION of variable disease phenotypes, biomarkers, and complex inflammatory cascades involved in disease pathogenesis. Ongoing clinical trials are looking at new treatments targeting NMOSD relapses. This review aims to provide an update on recent studies regarding issues related to NMOSD, including the pathophysiology of the disease, the potential use of serum and cerebrospinal fluid cytokines as disease biomarkers, the clinical utilization of ocular coherence tomography, and the comparison of different animal models of NMOSD.

Contemporary management challenges in seropositive NMOSD

Neuromyelitis optica spectrum disorders (NMOSD) is an inflammatory disorder of the central nervous system that presents unique management challenges. Neurologic disability in NMOSD is directly linked to acute attacks, therefore, relapse prevention is an overarching goal of care. To this end, identifying effective biomarkers that predict relapse onset and severity is of critical importance. As treatment becomes more precision-based and patient-centred, clinicians will need to be familiar with managing circumstances of particular vulnerability for patients with NMOSD, including infection, pregnancy, and the post-partum phase. The discovery of the pathogenic aquaporin-4 Immunoglobulin G (AQP4 IgG) autoantibody almost 20 years ago ultimately distinguished NMOSD as an autoimmune astrocytopathy and helped spearhead recent therapeutic advancements. Targeted therapies, including eculizumab, satralizumab, and inebilizumab, approved for use in aquaporin-4 immunoglobulin G (AQP4 IgG) seropositive patients with NMOSD will likely improve outcomes, but there are formidable costs involved. Importantly, seronegative patients continue to have limited therapeutic options. Moving forward, areas of research exploration should include relapse prevention, restorative therapies, and initiatives that promote equitable access to approved therapies for all people living with NMOSD.

Distribution of five clinically important neuroglial proteins in the human brain

Glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), neurofilament light chain (NFL), tau and ubiquitin carboxy-terminal hydrolase L1 (UCHL1) are five neuroglial proteins that are used as CSF or blood biomarkers of tissue damage in the nervous system. There is incomplete knowledge of how the concentration of these proteins differs between anatomical regions in the CNS as previous studies have focused on gene expression or non-quantitative protein analyses, limiting the interpretability of these biomarkers. The purpose of this study was to create a map of the tissue content of these proteins in different regions of the CNS. The concentrations of the investigated proteins were determined with ELISA in post mortem tissue homogenates from 17 selected anatomical regions in the CNS from ten deceased donors aged 24 to 50 years. When appropriate, the protein concentrations were adjusted for post-mortem interval. In total, 168 tissue samples were analysed. There was a substantial variation in the concentrations of GFAP, MBP, NFL, tau and UCHL1 between different CNS regions. Highly myelinated areas of the CNS had tenfold higher MBP concentration than cerebral cortex, whereas tau showed an inverse pattern. GFAP, NFL and tau displayed an anteroposterior gradient in cerebral white matter. The cerebellum had low concentrations of all the investigated proteins. In conclusion, the tissue concentrations of GFAP, MBP, NFL, tau and UCHL1 were determined throughout the CNS. This information can be used as a reference when interpreting circulating levels of these biomarkers in relation to the extent and localisation of CNS-damaging processes.

Pathomechanisms in demyelination and astrocytopathy: autoantibodies to AQP4, MOG, GFAP, GRP78 and beyond

PURPOSE OF REVIEW

The purpose of this review is to highlight the recently emerging pathomechanisms of diseases associated with autoantibodies to AQP4, MOG, GFAP, GRP78 and further novel targets. We discuss novel biomarkers and therapeutic approaches.

RECENT FINDINGS

Although complement-mediated cytotoxicity (CDC) is regarded as the major effector mechanism for AQP4-IgG in neuromyelitis optica spectrum disorders (NMOSD), recent studies helped to understand the relevance of complement-independent effector mechanisms. For MOG-IgG mediated diseases the role of CDC is less clear. MOG-IgG may trigger a tightly controlled FcR and BTK-driven microglia proliferative response in MOG-antibody-associated diseases. Differences of antibody-mediated tissue damage may reflect differential response to therapy. In addition, antibodies to GFAP, GRP78 and further novel targets have been implicated in demyelination and astrocytopathy.

SUMMARY

Elucidating the whole spectrum of effector functions in diseases mediated by AQP4-IgG and MOG-IgG and understanding the role of additional novel autoantibodies involved in demyelination and astrocytopathy may guide further novel treatment decisions.

Chronic Cognitive Impairment in AQP4+ NMOSD With Improvement in Cognition on Eculizumab: A Report of Two Cases

Cognitive impairment may be associated with aquaporin-4 antibody positive (AQP4+) NMOSD, particularly where there is prominent cerebral, corpus callosum, or thalamic involvement. It is unclear to what extent this phenomenon may be treatable after months to years. We describe two cases of AQP4+ NMOSD with cognitive impairment persisting over more than 6 months, where cognition improved after eculizumab was initiated. In the first case, a 51-year-old woman presented with a 2-month history of cognitive decline and ataxia, and diffuse involvement of the corpus callosum on MRI. AQP4 antibody testing returned positive. Cognitive impairment persisted on therapy with mycophenolate, then rituximab. She was switched to eculizumab from rituximab 18 months after disease onset because of breakthrough optic neuritis; memory and cognitive function improved on eculizumab. In the second case, a 26-year-old woman initially presented with visual, auditory and tactile hallucinations, and impairment in activities of daily living, and was given a diagnosis of schizophrenia. Nine months later she was hospitalized for increasing confusion. MRI showed leukoencephalopathy and diffuse involvement of the corpus callosum with multiple enhancing callosal lesions. AQP4 antibody testing was positive and CSF testing for other antibodies of autoimmune encephalitis was negative. She had some improvement in cognition with high dose corticosteroids but remained significantly impaired. On follow-up, her repeat MRI showed a small new right inferomedial frontal enhancing lesion although she did not complain of any new cognitive issues, her MOCA score was 21/30, and she was started on eculizumab. Two months after eculizumab initiation she and her family reported cognitive improvement and MOCA score was 25/30. Common features of these two cases included extensive callosal involvement and an element of ongoing gadolinium enhancement on MRI. Our experience suggests the possibility that cognitive impairment may be amenable to immunotherapy in certain cases of NMOSD.

Differential diagnosis of demyelinating diseases: what's new?

BACKGROUND

Acquired demyelinating disorders lead to overlapping visual, pyramidal, sensory, autonomic, and cerebellar deficits and may lead to severe disability. Early diagnosis and start of treatment are fundamental towards preventing further attacks and halting disability.

OBJECTIVE

In this paper we provide an updated overview of the differential diagnoses of acquired demyelinating disorders.

METHODS

We performed a critical targeted review of the diagnoses of the most prevalent demyelinating disorders: multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody disease (MOGAD).

RESULTS

We discuss the workup, diagnostic criteria and new biomarkers currently being used for the diagnosis of these disease entities taking into account the particularities of the Brazilian population and healthcare system.

CONCLUSION

A comprehensive analysis of medical history, physical examination, biomedical and imaging data should be performed to obtain differential diagnosis. Diagnostic criteria should be mindfully employed considering ethnic and environmental particularities of each patient.

MR T2-relaxation time as an indirect measure of brain water content and disease activity in NMOSD

OBJECTIVE

Since astrocytes at the blood-brain barrier are targeted by neuromyelitis optica spectrum disorder (NMOSD), this study aims to assess whether patients with NMOSD have a subclinical accumulation of brain water and if it differs according to disease activity.

METHODS

Seventy-seven aquaporin-4-positive patients with NMOSD and 105 healthy controls were enrolled at two European centres. Brain dual-echo turbo spin-echo MR images were evaluated and maps of T2 relaxation time (T2rt) in the normal-appearing white matter (NAWM), grey matter and basal ganglia were obtained. Patients with a clinical relapse within 1 month before or after MRI acquisition were defined 'active'. Differences between patients and controls were assessed using z-scores of T2rt obtained with age-adjusted and sex-adjusted linear models from each site. A stepwise binary logistic regression was run on clinical and MRI variables to identify independent predictors of disease activity.

RESULTS

Patients had increased T2rt in both white and grey matter structures (p range: 0.014 to <0.0001). Twenty patients with NMOSD were defined active. Despite similar clinical and MRI features, active patients had a significantly increased T2rt in the NAWM and grey matter compared with those clinically stable (p range: 0.010-0.002). The stepwise binary logistic regression selected the NAWM as independently associated with disease activity (beta=2.06, SE=0.58, Nagelkerke R2=0.46, p<0.001).

CONCLUSIONS

In line with the research hypothesis, patients with NMOSD have increased brain T2rt. The magnitude of this alteration might be useful for identifying those patients with active disease.