Amiloride does not protect retinal nerve fibre layer thickness in optic neuritis in a phase 2 randomised controlled trial

The neuropathobiology of multiple sclerosis

Chronic low-grade inflammation and neuronal deregulation are two components of a smoldering disease activity that drives the progression of disability in people with multiple sclerosis (MS). Although several therapies exist to dampen the acute inflammation that drives MS relapses, therapeutic options to halt chronic disability progression are a major unmet clinical need. The development of such therapies is hindered by our limited understanding of the neuron-intrinsic determinants of resilience or vulnerability to inflammation. In this Review, we provide a neuron-centric overview of recent advances in deciphering neuronal response patterns that drive the pathology of MS. We describe the inflammatory CNS environment that initiates neurotoxicity by imposing ion imbalance, excitotoxicity and oxidative stress, and by direct neuro-immune interactions, which collectively lead to mitochondrial dysfunction and epigenetic dysregulation. The neuronal demise is further amplified by breakdown of neuronal transport, accumulation of cytosolic proteins and activation of cell death pathways. Continuous neuronal damage perpetuates CNS inflammation by activating surrounding glia cells and by directly exerting toxicity on neighbouring neurons. Further, we explore strategies to overcome neuronal deregulation in MS and compile a selection of neuronal actuators shown to impact neurodegeneration in preclinical studies. We conclude by discussing the therapeutic potential of targeting such neuronal actuators in MS, including some that have already been tested in interventional clinical trials.

Early predictors of visual and axonal outcomes after acute optic neuritis

Background

Predicting long-term visual outcomes and axonal loss following acute optic neuritis (ON) is critical for choosing treatment. Predictive models including all clinical and paraclinical measures of optic nerve dysfunction following ON are lacking.

Objectives

Using a prospective study method, to identify 1 and 3 months predictors of 6 and 12 months visual outcome (low contrast letter acuity 2.5%) and axonal loss [retinal nerve fiber layer thickness and multifocal evoked potential (mfVEP) amplitude] following acute ON.

Methods

In total, 37 patients of acute ON onset were evaluated within 14 days using between-eye asymmetry of visual acuity, color vision (Ishihara plates), optical coherence tomography, mfVEP, and optic nerve magnetic resonance imaging [magnetic transfer ratio (MTR) and diffusion tensor imaging (DTI)].

Results

Visual outcome at 6 and 12 months was best predicted by Ishihara asymmetry at 1 and 3 months following ON onset. Axonal loss at 6 and 12 months was reliably predicted by Ishihara asymmetry at 1 month. Optic nerve MTR and DTI at 3 months post-acute ON could predict axonal loss at 6 and 12 months.

Conclusions

Simple Ishihara asymmetry testing 1 month after acute ON onset can best predict visual outcome and axonal loss at 6 and 12 months in a clinical or research setting.

Neuroprotective Effects of Novel Treatments on Acute Optic Neuritis—A Meta-Analysis

Optic neuritis, inflammation of the optic nerve, can cause visual impairment through retinal nerve fiber layer (RNFL) degeneration. Optical coherence tomography could serve as a sensitive noninvasive tool for measuring RNFL thickness and evaluating the neuroprotective effects of treatment. We conducted a meta-analysis to compare RNFL loss between novel add-on treatments and corticosteroid therapy at least 3 months after acute optic neuritis. The outcome measures were mean differences (MDs) in (1) RNFL thickness compared with the baseline in the affected and unaffected eye and (2) LogMAR visual acuity (VA). Seven studies involving five novel agents (memantine, erythropoietin, interferon-beta, phenytoin, and clemastine) were analyzed. When compared with the baseline RNFL thickness of the affected eye, the neuroprotective effects of novel add-on treatments could not be demonstrated. The difference in visual outcomes was also not significant between the two treatment groups. One study revealed that phenytoin has the potential to alleviate RNFL loss when the baseline thickness of the unaffected eye is considered. Larger randomized controlled trials with suitable outcome measures are warranted to evaluate the neuroprotective effects of novel treatments. Further studies should also tailor therapies to specific patient populations and investigate a more targeted treatment for acute optic neuritis.

The changing landscape of optic neuritis: a narrative review

Optic neuritis (ON) is an inflammatory optic neuropathy that is often a harbinger of central nervous system (CNS) demyelinating disorders. ON is frequently misdiagnosed in the clinical arena, leading to either inappropriate management or diagnostic delays. As a result, patients may fail to achieve optimal recovery. The treatment response to corticosteroids and long term risk of multiple sclerosis was established in the first clinical trials conducted roughly 30 years ago. Spontaneous resolution was observed in the vast majority of patients and intravenous high-dose corticosteroids hastened recovery; half of the patients eventually developed multiple sclerosis. Over the ensuing decades, the number of inflammatory conditions associated with ON has significantly expanded exposing substantial variability in the prognosis, treatment, and management of ON patients. ON subtypes can frequently be distinguished by distinct clinical, serological, and radiological profiles allowing expedited and specialized treatment. Guided by an increased understanding of the immunopathology underlying optic nerve and associated CNS injuries, novel disease management strategies are emerging to minimize vision loss, improve long-term surveillance strategies, and minimize CNS injury and disability. Knowledge regarding the clinical signs and symptoms of different ON subtypes is essential to guide acute therapy, prognosticate recovery, accurately identify underlying CNS inflammatory disorders, and facilitate study design for the next generation of clinical and translational trials.

Failed, Interrupted, or Inconclusive Trials on Neuroprotective and Neuroregenerative Treatment Strategies in Multiple Sclerosis: Update 2015-2020

In the recent past, a plethora of drugs have been approved for the treatment of multiple sclerosis (MS). These therapeutics are mainly confined to immunomodulatory or immunosuppressive strategies but do not sufficiently address remyelination and neuroprotection. However, several neuroregenerative agents have shown potential in pre-clinical research and entered Phase I to III clinical trials. Although none of these compounds have yet proceeded to approval, understanding the causes of failure can broaden our knowledge about neuroprotection and neuroregeneration in MS. Moreover, most of the investigated approaches are characterised by consistent mechanisms of action and proved convincing efficacy in animal studies. Therefore, learning from their failure will help us to enforce the translation of findings acquired in pre-clinical studies into clinical application. Here, we summarise trials on MS treatment published since 2015 that have either failed or were interrupted due to a lack of efficacy, adverse events, or for other reasons. We further outline the rationale underlying these drugs and analyse the background of failure to gather new insights into MS pathophysiology and optimise future study designs. For conciseness, this review focuses on agents promoting remyelination and medications with primarily neuroprotective properties or unconventional approaches. Failed clinical trials that pursue immunomodulation are presented in a separate article.

Systematic review and meta-analysis of the development of multiple sclerosis in clinically isolated syndrome

Clinically isolated syndrome (CIS) usually describes a first clinical episode that suggest multiple sclerosis. One of the signs and symptoms of CIS is Optic neuritis (ON). Several early intervention drugs are being tested in clinical trials for the early intervention in CIS patients which may lead to multiple sclerosis (MS). This study aim (1) early intervention of the CIS progression to MS delay slow down the MS progression, (2) since that ON affects 30%-70% of MS patients, the available ON intervention delay the MS progression. PubMed was used as a search engine. Summary relative risks (RRs) and 95 % confidence intervals (CIs) were estimated using a random-effect model. For aim 1, it showed lower risk of progression to MS compared to non-treated group (Risk Ratio (RR) 0.64; 95%CI: 0.58, 0.69; p < 0.001). For aim 2, drug treated group showed lower risk of progression compared to non-treated group (RR 0.19, 95%CI: 0.06, 0.54, p < 0.002. Statistical heterogeneity was not significant in both outcomes and bias of publication was not found using inspection of funnel plot and Egger's statistical test in both outcomes. In conclusion, early treatment should be considered in CIS patients to prevent the progression of MS. Moreover, this data shows that early intervention (Erythropoietin, Ery) of ON decreases the conversion risk to MS.

Using Acute Optic Neuritis Trials to Assess Neuroprotective and Remyelinating Therapies in Multiple Sclerosis

Importance

Neuroprotective and remyelinating therapies are required for multiple sclerosis (MS), and acute optic neuritis (AON) is a potential condition to evaluate such treatments.

Objective

To comprehensively assess key biological and methodological aspects of AON trials for testing neuroprotection and remyelination in MS.

Design, Setting, and Participants

The AON-VisualPath prospective cohort study was conducted from February 2011 to November 2018 at the Hospital Clinic of University of Barcelona, Barcelona, Spain. Consecutive patients with AON were prospectively enrolled in the cohort and followed up for 18 months. Data analyses occurred from November 2018 to February 2019.

Exposures

Participants were followed up for 18 months using optical coherence tomography, visual acuity tests, and in a subset of 25 participants, multifocal visual evoked potentials.

Main Outcomes and Measures

Dynamic models of retinal changes and nerve conduction and their associations with visual end points; and eligibility criteria, stratification, and sample-size estimation for future trials.

Results

A total of 60 patients (50 women [83%]; median age, 34 years) with AON were included. The patients studied displayed early and intense inner retinal thinning, with a thinning rate of approximately 2.38 μm per week in the ganglion cell plus inner plexiform layer (GCIPL) during the first 4 weeks. Eyes with AON displayed a 6-month change in latency of about 20 milliseconds, while the expected change in the eyes of healthy participants by random variability was 0.13 (95% CI, -0.80 to 1.06) milliseconds. The strongest associations with visual end points were for the 6-month intereye difference in 2.5% low-contrast letter acuity, which was correlated with the peripapillary retinal nerve fiber layer thinning (adjusted R2, 0.57), GCIPL thinning (adjusted R2, 0.50), and changes in mfVEP latency (adjusted R2, 0.26). A 5-letter increment in high-contrast visual acuity at presentation (but not sex or age) was associated with 6-month retinal thinning (1.41 [95% CI, 0.60-2.23] μm less peripapillary retinal nerve fiber layer thinning thinning; P = .001; adjusted R2, 0.20; 0.86 [95% CI, 0.35-1.37] μm less GCIPL thinning; P = .001; adjusted R2, 0.19) but not any change in multifocal visual evoked potential latency. To demonstrate 50% efficacy in GCIPL thinning or change in multifocal visual evoked potential latency, a 6-month, 2-arm, parallel-group trial would need 37 or 50 participants per group to test a neuroprotective or remyelinating drug, respectively (power, 80%; α, .05).

Conclusions and Relevance

Acute optic neuritis is a suitable condition to test neuroprotective and remyelinating therapies after acute inflammation, providing sensitive markers to assess the effects on both processes and prospective visual recovery within a manageable timeframe and with a relatively small sample size.

Basics on the use of acid-sensing ion channels' inhibitors as therapeutics

Since the discovery of acid-sensing ion channels in 1997, their importance in the health of neurons and other non-neuronal cells has gained significant importance. Acid-sensing ion channels play important roles in mediating pain sensation during diseases such as stroke, inflammation, arthritis, cancer, and recently migraine. More interestingly, acid-sensing ion channels may explain the sex differences in pain between males and females. Also, the ability of acid-sensing ion channel blockers to exert neuroprotective effects in a number of neurodegenerative diseases has added a new dimension to their therapeutic value. The current failure rate of ~45% of new drugs (due to toxicity issues) and saving of up to 7 years in the life span of drug approval makes drug repurposing a high priority. If acid-sensing ion channels’ blockers undergo what is known as “drug repurposing”, there is a great potential to bring them as medications with known safety profiles to new patient populations. However, the route of administration remains a big challenge due to their poor penetration of the blood brain and retinal barriers. In this review, the promise of using acid-sensing ion channel blockers as neuroprotective drugs is discussed.

Pharmacotherapy in Secondary Progressive Multiple Sclerosis: An Overview

Multiple sclerosis is an immune-mediated inflammatory disease of the central nervous system characterised by demyelination, neuroaxonal loss and a heterogeneous clinical course. Multiple sclerosis presents with different phenotypes, most commonly a relapsing-remitting course and, less frequently, a progressive accumulation of disability from disease onset (primary progressive multiple sclerosis). The majority of people with relapsing-remitting multiple sclerosis, after a variable time, switch to a stage characterised by gradual neurological worsening known as secondary progressive multiple sclerosis. We have a limited understanding of the mechanisms underlying multiple sclerosis, and it is believed that multiple genetic, environmental and endogenous factors are elements driving inflammation and ultimately neurodegeneration. Axonal loss and grey matter damage have been regarded as amongst the leading causes of irreversible neurological disability in the progressive stages. There are over a dozen disease-modifying therapies currently licenced for relapsing-remitting multiple sclerosis, but none of these has provided evidence of effectiveness in secondary progressive multiple sclerosis. Recently, there has been some early modest success with siponimod in secondary progressive multiple sclerosis and ocrelizumab in primary progressive multiple sclerosis. Finding treatments to delay or prevent the courses of secondary progressive multiple sclerosis is an unmet and essential goal of the research in multiple sclerosis. In this review, we discuss new findings regarding drugs with immunomodulatory, neuroprotective or regenerative properties and possible treatment strategies for secondary progressive multiple sclerosis. We examine the field broadly to include trials where participants have progressive or relapsing phenotypes. We summarise the most relevant results from newer investigations from phase II and III randomised controlled trials over the past decade, with particular attention to the last 5 years.