Inhibition of myostatin and related signaling pathways for the treatment of muscle atrophy in motor neuron diseases

Spinal Muscular Atrophy Scoliosis in the Era of Background Therapies-A Review of the Literature

Spinal deformities are considered an important complication of neuromuscular disorders such as spinal muscular atrophy (SMA). SMA patients typically develop progressive early-onset scoliosis, which is associated with increased functional decline, discomfort, and respiratory dysfunction. Over the second decade of the twenty-first century, a lot has changed in terms of the therapeutic options available to people with SMA. Specifically, the use of pharmaceutical agents such as nusinersen (Spinraza), onasemnogene abeparvovec (Zolgensma), and risdiplam (Evrysdi) has dramatically changed the landscape for SMA patients. These medications significantly alter motor- and respiratory functioning, as well as the natural progression of spinal deformities. When evaluating these agents and their impact on the development of scoliosis and motor functioning, it is important to consider the timing of treatment initiation. In patients treated after they had already developed symptoms, a shift of phenotype to a less severe subtype has been observed. This results in a delay in the onset of scoliosis for the less severe SMA types and an increase in early-onset scoliosis for the severe types in patients who would typically not live to develop scoliosis. Patients who receive treatment before they develop symptoms achieve almost normal motor functioning and will likely have a significant decrease in scoliosis prevalence or at least delay its onset.

Frontiers in sarcopenia: Advancements in diagnostics, molecular mechanisms, and therapeutic strategies

The onset of sarcopenia is intimately linked with aging, posing significant implications not only for individual patient quality of life but also for the broader societal healthcare framework. Early and accurate identification of sarcopenia and a comprehensive understanding of its mechanistic underpinnings and therapeutic targets paramount to addressing this condition effectively. This review endeavors to present a cohesive overview of recent advancements in sarcopenia research and diagnosis. We initially delve into the contemporary diagnostic criteria, specifically referencing the European Working Group on Sarcopenia in Older People (EWGSOP) 2 and Asian Working Group on Sarcopenia (AWGS) 2019 benchmarks. Additionally, we elucidate comprehensive assessment techniques for muscle strength, quantity, and physical performance, highlighting tools such as grip strength, chair stand test, dual-energy X-ray Absorptiometry (DEXA), bioelectrical impedance analysis (BIA), gait speed, and short physical performance battery (SPPB), while also discussing their inherent advantages and limitations. Such diagnostic advancements pave the way for early identification and unequivocal diagnosis of sarcopenia. Proceeding further, we provide a deep-dive into sarcopenia's pathogenesis, offering a thorough examination of associated signaling pathways like the Myostatin, AMP-activated protein kinase (AMPK), insulin/IGF-1 Signaling (IIS), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways. Each pathway's role in sarcopenia mediation is detailed, underscoring potential therapeutic target avenues. From a mechanistic perspective, the review also underscores the pivotal role of mitochondrial dysfunction in sarcopenia, emphasizing elements such as mitochondrial oxidative overload, mitochondrial biogenesis, and mitophagy, and highlighting their therapeutic significance. At last, we capture recent strides made in sarcopenia treatment, ranging from nutritional and exercise interventions to potential pharmacological and supplementation strategies. In sum, this review meticulously synthesizes the latest scientific developments in sarcopenia, aiming to enhance diagnostic precision in clinical practice and provide comprehensive insights into refined mechanistic targets and innovative therapeutic interventions, ultimately contributing to optimized patient care and advancements in the field.

TransNeT-CGP: A cluster-based comorbid gene prioritization by integrating transcriptomics and network-topological features

The local disruptions caused by the genes of one disease can influence the pathways associated with the other diseases resulting in comorbidity. For gene therapies, it is necessary to prioritize the key genes that regulate common biological mechanisms to tackle the issues caused by overlapping diseases. This work proposes a clustering-based computational approach for prioritising the comorbid genes within the overlapping disease modules by analyzing Protein-Protein Interaction networks. For this, a sub-network with gene interactions of the disease pair was extracted from the interactome. The edge weights are assigned by combining the pairwise gene expression correlation and betweenness centrality scores. Further, a weighted graph clustering algorithm is applied and dominant nodes of high-density clusters are ranked based on clustering coefficients and neighborhood connectivity. Case studies based on neurodegenerative diseases such as Amyotrophic Lateral Sclerosis- Spinal Muscular Atrophy (ALS-SMA) pair and cancers such as Ovarian Carcinoma-Invasive Ductal Breast Carcinoma (OC-IDBC) pair were conducted to examine the efficacy of the proposed method. To identify the mechanistic role of top-ranked genes, we used Functional and Pathway enrichment analysis, connectivity analysis with leave-one-out (LOO) method, analysis of associated disease-related protein complexes, and prioritization tools such as TOPPGENE and Heml2.0. From pathway analysis, it was observed that the top 10 genes obtained using the proposed method were associated with 10 pathways in ALS-SMA comorbidity and 15 in the case of OC-IDBC, while that in similar methods like SAPDSB and S2B were 4, 6 respectively for ALS-SMA and 9, 10 respectively for OC-IDBC. In both case studies, 70 % of the disease-specific benchmark protein complexes were linked to top-ranked genes of the proposed method while that of SAPDSB and S2B were 55 % and 60 % respectively. Additionally, it was found that the removal of the top 10 genes disconnect the network into 14 distinct components in the case of ALS-SMA and 9 in the case of OC-IDBC. The experimental results shows that the proposed method can be effectively used for identifying key genes in comorbidity and can offer insights about the intricate molecular relationship driving comorbid diseases.

Role of Myostatin in Rheumatoid Arthritis: A Review of the Clinical Impact

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects synovial joints and that frequently involves extra-articular organs. A multiplicity of interleukins (IL) participates in the pathogenesis of RA, including IL-6, IL-1β, transforming growth factor-beta (TGF-β), and tumor necrosis factor (TNF)-α; immune cells such as monocytes, T and B lymphocytes, and macrophages; and auto-antibodies, mainly rheumatoid factor and anti-citrullinated protein antibodies (ACPAs). Skeletal muscle is also involved in RA, with many patients developing muscle wasting and sarcopenia. Several mechanisms are involved in the myopenia observed in RA, and one of them includes the effects of some interleukins and myokines on myocytes. Myostatin is a myokine member of the TGF-β superfamily; the overproduction of myostatin acts as a negative regulator of growth and differentiates the muscle fibers, limiting their number and size. Recent studies have identified abnormalities in the serum myostatin levels of RA patients, and these have been found to be associated with muscle wasting and other manifestations of severe RA. This review analyzes recent information regarding the relationship between myostatin levels and clinical manifestations of RA and the relevance of myostatin as a therapeutic target for future research.

Licochalcone A and B enhance muscle proliferation and differentiation by regulating Myostatin

BACKGROUND

Myostatin (MSTN) inhibition has demonstrated promise for the treatment of diseases associated with muscle loss. In a previous study, we discovered that Glycyrrhiza uralensis (G. uralensis) crude water extract (CWE) inhibits MSTN expression while promoting myogenesis. Furthermore, three specific compounds of G. uralensis, namely liquiritigenin, tetrahydroxymethoxychalcone, and Licochalcone B (Lic B), were found to promote myoblast proliferation and differentiation, as well as accelerate the regeneration of injured muscle tissue.

PURPOSE

The purpose of this study was to build on our previous findings on G. uralensis and demonstrate the potential of its two components, Licochalcone A (Lic A) and Lic B, in muscle mass regulation (by inhibiting MSTN), aging and muscle formation.

METHODS

G. uralensis, Lic A, and Lic B were evaluated thoroughly using in silico, in vitro and in vivo approaches. In silico analyses included molecular docking, and dynamics simulations of these compounds with MSTN. Protein-protein docking was carried out for MSTN, as well as for the docked complex of MSTN-Lic with its receptor, activin type IIB receptor (ACVRIIB). Subsequent in vitro studies used C2C12 cell lines and primary mouse muscle stem cells to acess the cell proliferation and differentiation of normal and aged cells, levels of MSTN, Atrogin 1, and MuRF1, and plasma MSTN concentrations, employing techniques such as western blotting, immunohistochemistry, immunocytochemistry, cell proliferation and differentiation assays, and real-time RT-PCR. Furthermore, in vivo experiments using mouse models focused on measuring muscle fiber diameters.

RESULTS

CWE of G. uralensis and two of its components, namely Lic A and B, promote myoblast proliferation and differentiation by inhibiting MSTN and reducing Atrogin1 and MuRF1 expressions and MSTN protein concentration in serum. In silico interaction analysis revealed that Lic A (binding energy -6.9 Kcal/mol) and B (binding energy -5.9 Kcal/mol) bind to MSTN and reduce binding between it and ACVRIIB, thereby inhibiting downstream signaling. The experimental analysis, which involved both in vitro and in vivo studies, demonstrated that the levels of MSTN, Atrogin 1, and MuRF1 were decreased when G. uralensis CWE, Lic A, or Lic B were administered into mice or treated in the mouse primary muscle satellite cells (MSCs) and C2C12 myoblasts. The diameters of muscle fibers increased in orally treated mice, and the differentiation and proliferation of C2C12 cells were enhanced. G. uralensis CWE, Lic A, and Lic B also promoted cell proliferation in aged cells, suggesting that they may have anti-muslce aging properties. They also reduced the expression and phosphorylation of SMAD2 and SMAD3 (MSTN downstream effectors), adding to the evidence that MSTN is inhibited.

CONCLUSION

These findings suggest that CWE and its active constituents Lic A and Lic B have anti-mauscle aging potential. They also have the potential to be used as natural inhibitors of MSTN and as therapeutic options for disorders associated with muscle atrophy.

Serum myostatin as a candidate disease severity and progression biomarker of spinal muscular atrophy

The identification of biomarkers for spinal muscular atrophy is crucial for predicting disease progression, severity, and response to new disease-modifying therapies. This study aimed to investigate the role of serum levels of myostatin and follistatin as biomarkers for spinal muscular atrophy, considering muscle atrophy secondary to denervation as the main clinical manifestation of the disease. The study evaluated the differential gene expression of myostatin and follistatin in a lesional model of gastrocnemius denervation in mice, as well as in a meta-analysis of three datasets in transgenic mice models of spinal muscular atrophy, and in two studies involving humans with spinal muscular atrophy. Subsequently, a case-control study involving 27 spinal muscular atrophy patients and 27 controls was conducted, followed by a 12-month cohort study with 25 spinal muscular atrophy cases. Serum levels of myostatin and follistatin were analysed using enzyme-linked immunosorbent assay at a single centre in southern Brazil. Skeletal muscle gene expression of myostatin decreased and of follistatin increased following lesional muscle denervation in mice, consistent with findings in the spinal muscular atrophy transgenic mice meta-analysis and in the iliopsoas muscle of five patients with spinal muscular atrophy type 1. Median serum myostatin levels were significantly lower in spinal muscular atrophy patients (98 pg/mL; 5-157) compared to controls (412 pg/mL; 299-730) (P < 0.001). Lower myostatin levels were associated with greater disease severity based on clinician-rated outcomes (Rho = 0.493-0.812; P < 0.05). After 12 months, there was a further reduction in myostatin levels among spinal muscular atrophy cases (P = 0.021). Follistatin levels did not differ between cases and controls, and no significant changes were observed over time. The follistatin:myostatin ratio was significantly increased in spinal muscular atrophy subjects and inversely correlated with motor severity. Serum myostatin levels show promise as a novel biomarker for evaluating the severity and progression of spinal muscular atrophy. The decrease in myostatin levels and the subsequent favourable environment for muscle growth may be attributed to denervation caused by motor neuron dysfunction.

The function of previously unappreciated exerkines secreted by muscle in regulation of neurodegenerative diseases

The initiation and progression of neurodegenerative diseases (NDs), distinguished by compromised nervous system integrity, profoundly disrupt the quality of life of patients, concurrently exerting a considerable strain on both the economy and the social healthcare infrastructure. Exercise has demonstrated its potential as both an effective preventive intervention and a rehabilitation approach among the emerging therapeutics targeting NDs. As the largest secretory organ, skeletal muscle possesses the capacity to secrete myokines, and these myokines can partially improve the prognosis of NDs by mediating the muscle-brain axis. Besides the well-studied exerkines, which are secreted by skeletal muscle during exercise that pivotally exert their beneficial function, the physiological function of novel exerkines, e.g., apelin, kynurenic acid (KYNA), and lactate have been underappreciated previously. Herein, this review discusses the roles of these novel exerkines and their mechanisms in regulating the progression and improvement of NDs, especially the significance of their functions in improving NDs' prognoses through exercise. Furthermore, several myokines with potential implications in ameliorating ND progression are proposed as the future direction for investigation. Elucidation of the function of exerkines secreted by skeletal muscle in the regulation of NDs advances the understanding of its pathogenesis and facilitates the development of therapeutics that intervene in these processes to cure NDs.

Frailty in end-stage liver disease: Understanding pathophysiology, tools for assessment, and strategies for management

Frailty and sarcopenia are frequently observed in patients with end-stage liver disease. Frailty is a complex condition that arises from deteriorations across various physiological systems, including the musculoskeletal, cardiovascular, and immune systems, resulting in a reduced ability of the body to withstand stressors. This condition is associated with declined resilience and increased vulnerability to negative outcomes, including disability, hospitalization, and mortality. In cirrhotic patients, frailty is influenced by multiple factors, such as hyperammonemia, hormonal imbalance, malnutrition, ascites, hepatic encephalopathy, and alcohol intake. Assessing frailty is crucial in predicting morbidity and mortality in cirrhotic patients. It can aid in making critical decisions regarding patients' eligibility for critical care and transplantation. This, in turn, can guide the development of an individualized treatment plan for each patient with cirrhosis, with a focus on prioritizing exercise, proper nutrition, and appropriate treatment of hepatic complications as the primary lines of treatment. In this review, we aim to explore the topic of frailty in liver diseases, with a particular emphasis on pathophysiology, clinical assessment, and discuss strategies for preventing frailty through effective treatment of hepatic complications. Furthermore, we explore novel assessment and management strategies that have emerged in recent years, including the use of wearable technology and telemedicine.

Polyvalent passive vaccine candidates from egg yolk antibodies (IgY) of important outer membrane proteins (PF1380 and ExbB) of Pseudomonas fluorescens in fish

Polyvalent antibodies can resist multiple bacterial species, and immunoglobulin Y (IgY) antibody can be economically prepared in large quantities from egg yolk; further, IgY polyvalent antibodies have application value in aquaculture. The outer membrane proteins (OMPs) PF1380 and ExbB of Pseudomonas fluorescens were expressed and purified, and the corresponding IgY antibodies were prepared. PF1380, ExbB, and the corresponding IgY antibodies could activate the innate immune responses of chicken and Carassius auratus. The passive immunization to C. auratus showed that the IgY antibodies of PF1380 and ExbB had an immune protection rate, down-regulated the expression of antioxidant-related factors (MDA, SOD, GSH-Px, and CAT) to reduce the antioxidant reaction, down-regulated the expression of inflammation-related genes (IL-6, IL-8, TNF-α, and IL-1β) to reduce the inflammatory reaction, maintained the integrity of visceral tissue structure, and reduced apoptosis and damage of tissue cells in relation to P. fluorescens and Aeromonas hydrophila infections. Thus, the IgY antibodies of PF1380 and ExbB could be considered as passive polyvalent vaccine candidates in aquaculture.

Role of circulating biomarkers in spinal muscular atrophy: insights from a new treatment era

Spinal muscular atrophy (SMA) is a lower motor neuron disease due to biallelic mutations in the SMN1 gene on chromosome 5. It is characterized by progressive muscle weakness of limbs, bulbar and respiratory muscles. The disease is usually classified in four different phenotypes (1-4) according to age at symptoms onset and maximal motor milestones achieved. Recently, three disease modifying treatments have received approval from the Food and Drug Administration (FDA) and the European Medicines Agency (EMA), while several other innovative drugs are under study. New therapies have been game changing, improving survival and life quality for SMA patients. However, they have also intensified the need for accurate biomarkers to monitor disease progression and treatment efficacy. While clinical and neurophysiological biomarkers are well established and helpful in describing disease progression, there is a great need to develop more robust and sensitive circulating biomarkers, such as proteins, nucleic acids, and other small molecules. Used alone or in combination with clinical biomarkers, they will play a critical role in enhancing patients' stratification for clinical trials and access to approved treatments, as well as in tracking response to therapy, paving the way to the development of individualized therapeutic approaches. In this comprehensive review, we describe the foremost circulating biomarkers of current significance, analyzing existing literature on non-treated and treated patients with a special focus on neurofilaments and circulating miRNA, aiming to identify and examine their role in the follow-up of patients treated with innovative treatments, including gene therapy.

Combination disease-modifying treatment in spinal muscular atrophy: A proposed classification

We sought to devise a rational, systematic approach for defining/grouping survival motor neuron-targeted disease-modifying treatment (DMT) scenarios. The proposed classification is primarily based on a two-part differentiation: initial DMT, and persistence/discontinuation of subsequent DMT(s). Treatment categories were identified: monotherapy add-on, transient add-on, combination with onasemnogene abeparvovec, bridging to onasemnogene abeparvovec, and switching to onasemnogene abeparvovec. We validated this approach by applying the classification to the 443 patients currently in the RESTORE registry and explored the demographics of these different groups of patients. This work forms the basis to explore the safety and efficacy profile of the different combinations of DMT in SMA.

Pharmacological Inhibition of Myostatin in a Mouse Model of Typical Nemaline Myopathy Increases Muscle Size and Force

Nemaline myopathy is one of the most common non-dystrophic congenital myopathies. Individuals affected by this condition experience muscle weakness and muscle smallness, often requiring supportive measures like wheelchairs or respiratory support. A significant proportion of patients, approximately one-third, exhibit compound heterozygous nebulin mutations, which usually give rise to the typical form of the disease. Currently, there are no approved treatments available for nemaline myopathy. Our research explored the modulation of myostatin, a negative regulator of muscle mass, in combating the muscle smallness associated with the disease. To investigate the effect of myostatin inhibition, we employed a mouse model with compound heterozygous nebulin mutations that mimic the typical form of the disease. The mice were treated with mRK35, a myostatin antibody, through weekly intraperitoneal injections of 10 mg/kg mRK35, commencing at two weeks of age and continuing until the mice reached four months of age. The treatment resulted in an increase in body weight and an approximate 20% muscle weight gain across most skeletal muscles, without affecting the heart. The minimum Feret diameter of type IIA and IIB fibers exhibited an increase in compound heterozygous mice, while only type IIB fibers demonstrated an increase in wild-type mice. In vitro mechanical experiments conducted on intact extensor digitorum longus muscle revealed that mRK35 augmented the physiological cross-sectional area of muscle fibers and enhanced absolute tetanic force in both wild-type and compound heterozygous mice. Furthermore, mRK35 administration improved grip strength in treated mice. Collectively, these findings indicate that inhibiting myostatin can mitigate the muscle deficits in nebulin-based typical nemaline myopathy, potentially serving as a much-needed therapeutic option.

Insight on sarcopenic obesity and epicatechin as a promising treatment option

BACKGROUND AND AIM

Sarcopenic Obesity (SO) in the elderly population is a complex and multifactorial condition which refers to the loss of skeletal muscle mass, strength, and function associated with aging, while obesity involves excessive adipose tissue accumulation. The simultaneous occurrence of these two conditions presents a unique set of challenges to public health and clinical management. This narrative review aims to provide an overview of the use of epicatechin (EC) in the treatment of SO and its related complications.

METHOD

A survey of studies related to preclinical and clinical evidence of Epicatechin in sarcopenic obesity and its complications was performed in the following database Medline, Scopus, ProQuest, Embase, Web of Science, and Google scholar. Followed by structural activity relationship and pharmacokinetic profile of Epicatechin was discussed in this paper.

RESULTS

The main pharmacological effect of Epicatechin is myostatin inhibition activity which has been described by both in vitro and in vivo studies earlier. The SO is directly correlated with the alteration of Myostatin. The pre-clinical and clinical studies suggest that epicatechin can be a potential candidate in the management of SO and its related complication.

CONCLUSION

The present review describes the pharmacokinetic profile and structural activity of epicatechin respective to SO and its related complications. The goal of this review is to update the scientific community on the therapeutic potential of epicatechin in SO and age-related factors. Conduction of clinical and pre-clinical trials, also drug dosage optimization may provide with insights on the use of epicatechin in SO.

Oxidative stress: roles in skeletal muscle atrophy

Oxidative stress, inflammation, mitochondrial dysfunction, reduced protein synthesis, and increased proteolysis are all critical factors in the process of muscle atrophy. In particular, oxidative stress is the key factor that triggers skeletal muscle atrophy. It is activated in the early stages of muscle atrophy and can be regulated by various factors. The mechanisms of oxidative stress in the development of muscle atrophy have not been completely elucidated. This review provides an overview of the sources of oxidative stress in skeletal muscle and the correlation of oxidative stress with inflammation, mitochondrial dysfunction, autophagy, protein synthesis, proteolysis, and muscle regeneration in muscle atrophy. Additionally, the role of oxidative stress in skeletal muscle atrophy caused by several pathological conditions, including denervation, unloading, chronic inflammatory diseases (diabetes mellitus, chronic kidney disease, chronic heart failure, and chronic obstructive pulmonary disease), sarcopenia, hereditary neuromuscular diseases (spinal muscular atrophy, amyotrophic lateral sclerosis, and Duchenne muscular dystrophy), and cancer cachexia, have been discussed. Finally, this review proposes the alleviation oxidative stress using antioxidants, Chinese herbal extracts, stem cell and extracellular vesicles as a promising therapeutic strategy for muscle atrophy. This review will aid in the development of novel therapeutic strategies and drugs for muscle atrophy.

Increasing Skeletal Muscle Mass in Mice by Non-Invasive Intramuscular Delivery of Myostatin Inhibitory Peptide by Iontophoresis

Sarcopenia is a major public health issue that affects older adults. Myostatin inhibitory-D-peptide-35 (MID-35) can increase skeletal muscle and is a candidate therapeutic agent, but a non-invasive and accessible technology for the intramuscular delivery of MID-35 is required. Recently, we succeeded in the intradermal delivery of various macromolecules, such as siRNA and antibodies, by iontophoresis (ItP), a non-invasive transdermal drug delivery technology that uses weak electricity. Thus, we expected that ItP could deliver MID-35 non-invasively from the skin surface to skeletal muscle. In the present study, ItP was performed with a fluorescently labeled peptide on mouse hind leg skin. Fluorescent signal was observed in both skin and skeletal muscle. This result suggested that the peptide was effectively delivered to skeletal muscle from skin surface by ItP. Then, the effect of MID-35/ItP on skeletal muscle mass was evaluated. The skeletal muscle mass increased 1.25 times with ItP of MID-35. In addition, the percentage of new and mature muscle fibers tended to increase, and ItP delivery of MID-35 showed a tendency to induce alterations in the levels of mRNA of genes downstream of myostatin. In conclusion, ItP of myostatin inhibitory peptide is a potentially useful strategy for treating sarcopenia.

Chronic kidney disease-induced muscle atrophy: Molecular mechanisms and promising therapies

Chronic kidney disease (CKD) is a high-risk chronic catabolic disease due to its high morbidity and mortality. CKD is accompanied by many complications, leading to a poor quality of life, and serious complications may even threaten the life of CKD patients. Muscle atrophy is a common complication of CKD. Muscle atrophy and sarcopenia in CKD patients have complex pathways that are related to multiple mechanisms and related factors. This review not only discusses the mechanisms by which inflammation, oxidative stress, mitochondrial dysfunction promote CKD-induced muscle atrophy but also explores other CKD-related complications, such as metabolic acidosis, vitamin D deficiency, anorexia, and excess angiotensin II, as well as other related factors that play a role in CKD muscle atrophy, such as insulin resistance, hormones, hemodialysis, uremic toxins, intestinal flora imbalance, and miRNA. We highlight potential treatments and drugs that can effectively treat CKD-induced muscle atrophy in terms of complication treatment, nutritional supplementation, physical exercise, and drug intervention, thereby helping to improve the prognosis and quality of life of CKD patients.

Identifying Biomarkers of Spinal Muscular Atrophy for Further Development

BACKGROUND

Spinal muscular atrophy (SMA) is caused by bi-allelic, recessive mutations of the survival motor neuron 1 (SMN1) gene and reduced expression levels of the survival motor neuron (SMN) protein. Degeneration of alpha motor neurons in the spinal cord causes progressive skeletal muscle weakness. The wide range of disease severities, variable rates of decline, and heterogenous clinical responses to approved disease-modifying treatment remain poorly understood and limit the ability to optimize treatment for patients. Validation of a reliable biomarker(s) with the potential to support early diagnosis, inform disease prognosis and therapeutic suitability, and/or confirm response to treatment(s) represents a significant unmet need in SMA.

OBJECTIVES

The SMA Multidisciplinary Biomarkers Working Group, comprising 11 experts in a variety of relevant fields, sought to determine the most promising candidate biomarker currently available, determine key knowledge gaps, and recommend next steps toward validating that biomarker for SMA.

METHODS

The Working Group engaged in a modified Delphi process to answer questions about candidate SMA biomarkers. Members participated in six rounds of reiterative surveys that were designed to build upon previous discussions.

RESULTS

The Working Group reached a consensus that neurofilament (NF) is the candidate biomarker best poised for further development. Several important knowledge gaps were identified, and the next steps toward filling these gaps were proposed.

CONCLUSIONS

NF is a promising SMA biomarker with the potential for prognostic, predictive, and pharmacodynamic capabilities. The Working Group has identified needed information to continue efforts toward the validation of NF as a biomarker for SMA.