Axonal excitability changes in children with spinal muscular atrophy treated with nusinersen.

Spinal muscular atrophy (SMA) is associated with developmental disruption of motor axons in ventral roots of the spinal cord alongside motor axon degeneration. The pathogenesis of peripheral axonal change during development is pertinent to understand treatment response. Nerve excitability techniques, stimulating the median motor nerve at the wrist, were utilised to investigate axonal change during neurodevelopment in 24 children with SMA, compared with 71 age-matched controls. Longitudinal axonal response to nusinersen treatment in 18 children was also investigated. Significant differences in axonal development were noted in the youngest children with SMA, signified by reduced compound muscle action potential (CMAP) (P = 0.030), higher axonal threshold (P = 0.016), rheobase (minimal current amplitude of infinite duration, required to generate an action potential) (P = 0.012) and greater changes in depolarising and hyperpolarising threshold electrotonus. Subexcitability increased in all children with SMA, compared to controls. With treatment, nerve excitability changes were observed prominently in young children, with increases in CMAP, reduction in axonal threshold, fanning-in of threshold electrotonus, increase in resting current-threshold slope and reduction in subexcitability. Whilst motor axons continue to mature in SMA, developmental delays in passive and active membrane properties occur especially in early childhood. Concurrently, motor axons actively undergo degeneration. Nusinersen restores the developmental trajectory of motor axons reducing degeneration, especially in children with early treatment initiation. Our findings move the field forward in understanding the developmental aspect of childhood-onset motor neurone diseases and changes in axonal function associated with disease modification. KEY POINTS: Pathomechanisms in spinal muscular atrophy involve concurrent neurodevelopmental and neurodegenerative processes. The greatest delays in maturation of the passive and active properties of the peripheral motor axon are seen in early childhood. Nusinersen facilitates developmental recovery of the motor axon whilst also reducing neurodegeneration. Axonal dysfunction is reversed with SMN repletion particularly when intervention occurs early in development.

Integrating newborn screening for spinal muscular atrophy into health care systems: an Australian pilot programme.

AIM: This study dynamically designed, evaluated, and implemented the components of an Australian newborn bloodspot screening (NBS) pilot programme for spinal muscular atrophy (SMA). METHOD: We used an implementation-effectiveness study design and continuous interdisciplinary review to measure SMA NBS test protocol performance, identify and overcome laboratory and clinical barriers to implementation, and describe progress during the 2-year pilot study. RESULTS: The NBS programme screened 252 081 newborn infants from 1st August 2018 to 31st January 2021. Using an NBS pilot test protocol, 21 infants were diagnostically confirmed with SMA. The NBS pilot test protocol had a sensitivity of 100%, specificity greater than 99.9%, false-positive rate less than 0.001%, a false-negative rate of 0%, and positive predictive value of 95.5%. A severe phenotype was predicted on the basis of two copies of SMN2 in 57.2% of newborn infants screening positive for SMA. Clinical signs consistent with SMA were evident in 6 out of 21 screen-positive newborn infants within the first 4 weeks of life. A multidisciplinary team establishing strong partnerships across clinical and laboratory staff was key to implementation. INTERPRETATION: This pilot programme suggests that NBS is essential for early identification of newborn infants at risk of SMA and can be effectively translated into clinical practice.

First Trimester Protein Biomarkers for Risk of Spontaneous Preterm Birth: Identifying a Critical Need for More Rigorous Approaches to Biomarker Identification and Validation.

BACKGROUND: Spontaneous preterm birth is the leading cause of perinatal morbidity and mortality worldwide and continues to present a major clinical dilemma. We previously reported that a number of protein species were dysregulated in maternal serum collected at 11-13+6 weeks' gestation from pregnancies that continued to labour spontaneously and deliver preterm. OBJECTIVES AND METHODS: In this study, we aimed to validate changes seen in 4 candidate protein species: alpha-1-antitrypsin, vitamin D-binding protein (VDBP), alpha-1beta-glycoprotein and apolipoprotein A-1 in a larger cohort of women using a western blot approach. RESULTS: Serum levels of all 4 proteins were reduced in women who laboured spontaneously and delivered preterm. This reduction was significant for VDBP (p = 0.04), which has been shown to be involved in a plethora of essential biological functions, including actin scavenging, fatty acid transport, macrophage activation and chemotaxis. CONCLUSIONS: The decrease in select proteoforms of VDBP may result in an imbalance in the optimal intrauterine environment for the developing foetus as well as to a successful uncomplicated pregnancy. Thus, certain (phosphorylated) species of VDBP may be of value in developing a targeted approach to the early prediction of spontaneous preterm labour. Importantly, this study raises the importance of a focus on proteoforms and the need for any biomarker validation process to most effectively take these into account rather than the more widespread practice of simply focussing on the primary amino acid sequence of a protein.

Decision-making and challenges within the evolving treatment algorithm in spinal muscular atrophy: a clinical perspective.

INTRODUCTION: The clinical application of disease modifying therapies has dramatically changed the paradigm of the management of people with spinal muscular atrophy (SMA), from sole reliance on symptomatic care directed toward the downstream consequences of muscle weakness, to proactive intervention and even preventative care. AREAS COVERED: In this perspective, the authors evaluate the contemporary therapeutic landscape of SMA and discuss the evolution of novel phenotypes and the treatment algorithm, including the key factors that define individual treatment choice and treatment response. The benefits achieved by early diagnosis and treatment through newborn screening are highlighted, alongside an appraisal of emerging prognostic methods and classification frameworks to inform clinicians, patients, and families about disease course, manage expectations, and improve care planning. A future perspective of unmet needs and challenges is provided, emphasizing the key role of research. EXPERT OPINION: SMN-augmenting therapies have improved health outcomes for people with SMA and powered the practice of personalized medicine. Within this new proactive diagnostic and treatment paradigm, new phenotypes and different disease trajectories are emerging. Ongoing collaborative research efforts to understand the biology of SMA and define optimal response are critical to refining future approaches.

The outlook for individuals with Spinal Muscular Atrophy (SMA) has transformed with the approval of three effective disease modifying therapies in the past seven years. This group of genetic diseases that cause progressive muscle weakness and present as a broad range of severity ­ from mild disease with near normal lifespan to severe with abbreviated lifespan and comorbidities ­ now have gene-based therapies that have shown (motor) functional gains, ameliorated comorbidities, and improved overall quality of life of patients and prolonged survival. With the rapid translation of early diagnostic paradigms through newborn screening and the acceleration of a therapeutic pipeline, uncertainties within clinical practice arise including the optimal time to treat, the changing clinical characteristics of the treated population, monitoring of disease progression and therapeutic response in the post-treatment era. In this article, we review the evidence base to address these challenges. The key factors that determine individual treatment choice and response are discussed. The changed clinical characteristics in treated children that need early identification and appropriate management are discussed in depth. A new classification system in keeping with the changed paradigm is provided. In these early times of the treatment era, the evidence from clinical trials and real world is combined to generate evidence base to guide management. The reader would be apprised of the recent therapeutic developments, their applications, and outcomes. Finally, the challenges to be expected along the uncharted path of prolonged lifespan are discussed and care guidelines provided.

Identification of Novel CSF-Derived miRNAs in Treated Paediatric Onset Spinal Muscular Atrophy: An Exploratory Study.

The availability of disease modifying therapies for spinal muscular atrophy (SMA) have created an urgent need to identify clinically meaningful biomarkers that provide insight into disease progression and therapeutic response. microRNAs (miRNA) have been shown to be involved in the pathogenesis of SMA and have the potential to provide insight within the field of SMA. miRNA-sequencing was utilized to identify differential miRNA expression in the cerebrospinal fluid (CSF) in six children with SMA treated with nusinersen in this exploratory study. Fourteen differentially expressed miRNAs were significantly altered in CSF from baseline to follow-up during treatment with nusinersen. The greatest magnitude of change was noted in miR-7-5p, miR-15a-5p, miR-15b-3p/5p, miR-126-5p, miR-128-2-5p and miR-130a-3p which encompassed a spectrum of functions predominantly in neurogenesis, neuronal differentiation and growth. The dominant signaling pathways identified in this study were the mammalian target of rapamycin and the mitogen-activated protein kinase signaling pathways. This study identified multiple miRNAs that were involved in the complex interplay between neurodevelopment and neurodegeneration.

Newborn screening for spinal muscular atrophy in Australia: a non-randomised cohort study.

BACKGROUND: In light of a new therapeutic era for spinal muscular atrophy (SMA), newborn screening has been proposed as a gateway to facilitate expedient diagnosis and access to therapeutics. However, there is paucity of evidence on health outcomes outside the homogenous populations in clinical trials to justify broader implementation of newborn screening for SMA. In this real-world study, we aimed to investigate the effectiveness of newborn screening coupled with access to disease-modifying therapeutics, as an intervention for SMA. METHODS: In this prospective, non-randomised cohort study done at Sydney Children's Hospital Network (NSW, Australia), we included children younger than 16 years with homozygous exon 7 deletions of survival motor neuron 1 gene (SMN1) mutations, non-selectively assigned to a screening group (incident population diagnosed by newborn screening) from Aug 1, 2018, to Aug 1, 2020, or a comparator group (incident population diagnosed by clinical referral) from Aug 1, 2016, to July 31, 2018. We excluded infants with compound heterozygous SMN1 mutations and those participating in ongoing and unpublished clinical trials. Effectiveness of newborn screening for SMA was compared using motor development milestone attainment defined by WHO Multicentre Growth Reference Study at 2 years post diagnosis. Secondary outcome measures included mortality and change in Hammersmith Infant Neurological Examination-2 (HINE-2) score, ventilation requirements, and enteral requirements 2 years from the time of diagnosis. FINDINGS: 34 children met the study inclusion criteria, but 33 children were included in the study population after one neonate was excluded due to participation in an ongoing unpublished clinical trial. 15 children were included in the screening group (seven [47%] male and eight [53%] female; median age 2·1 weeks [IQR 1·9-2·7]) and 18 children (nine [50%] male and nine [50%] female) were included in the comparator group (median age 47·8 weeks [13·0-99·9]). The 2-year survival rate was 93% (14 of 15 children) in the screening group and 89% (16 of 18) in the comparator group. Among survivors, 11 (79%) of 14 walked independently or with assistance in the screening group, compared with one (6%) of 16 children in the comparator group (χ2=16·27; p<0·0001). A significantly greater change in motor function was observed in the screening group compared with the comparator group over 2 years (HINE-2 score group difference, 12·32; p<0·0001). The requirement for non-intensive ventilation or feeding support at follow-up was higher in the comparator group than in the screening group (odds ratio 7·1 [95% CI 0·7-70·2]). Significant predictors of functional motor outcomes as determined by HINE-2 score at 2 years post diagnosis were HINE-2 score (p=0·0022), CHOP-INTEND (p=0·0001), compound muscle action potential (CMAP; p=0·0006), and disease status (p=0·023) at diagnosis. INTERPRETATION: Newborn screening for SMA, coupled with early access to disease-modifying therapies, effectively ameliorates the functional burden and associated comorbidities for affected children. For children diagnosed through newborn screening, motor score, CMAP, and disease status at diagnosis has clinical utility to determine functional independence. FUNDING: Brain Foundation and National Health and Medical Research Council.

Characterizing Common Phenotypes Across the Childhood Dementia Disorders: A Cross-sectional Study From Two Australian Centers.

BACKGROUND: Childhood dementias are a group of rare pediatric conditions characterized by progressive neurocognitive decline. Quantifying and characterising phenotypes to identify similarities between specific conditions is critical to inform opportunities to optimize care and advance research. METHODS: This cross-sectional study recruited primary caregivers of children (<18 years) living with a dementia syndrome from neurology and metabolic clinics in Sydney and Adelaide, Australia. Sociodemographic and clinical data were collated. Behavior, eating, sleep, pain, and neurological disability were assessed using validated tools, including Strengths and Difficulties, Child Eating Behaviour, and Children's Sleep Habits questionnaires and visual analog of pain and modified Rankin scales. Data were analyzed with descriptive statistics. RESULTS: Among 45 children with 23 different dementia syndromes, the modified Rankin Scale demonstrated at least moderate neurological disability and functional dependence in 82% (37/45). Families reported delays in receiving an accurate diagnosis following initial symptoms (mean: 1.6 ± 1.4 years, range: 0-5 years). The most prevalent phenotypes included communication, comprehension, or recall difficulties (87%, 39/45); disturbances in sleep (80%, 36/45); appetite changes (74%, 29/39); mobility issues (53%, 24/45); and hyperactive behavior (53%, 21/40). Behavioral problems had a "high" or "very high" impact on everyday family life in 73% (24/33). CONCLUSIONS: Childhood dementia disorders share substantial behavioral, motor, sensory, and socioemotional symptoms, resulting in high care needs, despite their vast heterogeneity in age of onset and progression. Considering their unifying characteristics under one collective term is an opportunity to improve treatment, provide quality care, and accelerate research.

Onasemnogene abeparvovec in spinal muscular atrophy: an Australian experience of safety and efficacy.

OBJECTIVE: To provide a greater understanding of the tolerability, safety and clinical outcomes of onasemnogene abeparvovec in real-world practice, in a broad population of infants with spinal muscular atrophy (SMA). METHODS: A prospective cohort study of children with SMA treated with onasemnogene abeparvovec at Sydney Children's Hospital Network, Australia was conducted from August 2019 to November 2021. Safety outcomes included clinical and laboratory evaluations. Efficacy assessments included World Health Organisation (WHO) motor milestones, oral and swallowing abilities, and requirements for respiratory support. The implementation of a model of care for onasemnogene abeparvovec administration in health practice is described. RESULTS: 21 children were treated (age range, 0.65-24 months; body weight range, 2.5-12.5 kg) and 19/21 (90.4%) had previous nusinersen. Transient treatment-related side effects occurred in all children; vomiting (100%), transaminitis (57%) and thrombocytopaenia (33%). Incidence of moderate/severe transaminitis was significantly greater in infants weighing ≥8 kg compared with <8 kg (p < 0.05). Duration of prednisolone following treatment was prolonged (mean 87.5 days, range 57-274 days). 16/21 (76%) children gained at least one WHO motor milestone. Stabilisation or improvement in bulbar or respiratory function was observed in 20/21 (95.2%) patients. Implementation challenges were mitigated by developing standard operating procedures and facilitating exchange of knowledge. INTERPRETATION: This study provides real-world evidence to inform treatment decisions and guide therapeutic expectations for onasemnogene abeparvovec and combination therapy for SMA in health practice, especially for children weighing ≥8 kg receiving higher vector loads. Proactive clinical and laboratory surveillance is essential to facilitate individualised management of risks.

Growth and nutrition in pediatric neuromuscular disorders.

BACKGROUND & AIMS: Little is currently known about the nutrition and growth outcomes in children with neuromuscular disorders (NMDs), and these are likely disease dependent. The aim of this study was to describe the range of nutritional issues in pediatric NMDs and identify similarities and differences in growth outcomes and nutritional needs in children with a variety of NMDs at different ages, with the goal of informing future services. METHODS: In this cross-sectional study we collected data on growth, dietetic interventions and nutrition-related issues in 160 children who attended a multidisciplinary clinic in a tertiary children's hospital, from February to December 2019. Children with significant weakness affecting mobility before the age of 3 years were clinically grouped into 'early-onset NMDs'. RESULTS: Across our clinic, 42.5% children had a history of chronic gastrointestinal issues, and 34.4% received dietetic care on the day of clinical visit. Children with early-onset NMDs had significantly higher prevalence of swallowing issues, gastroesophageal reflux, and vomiting, as well as higher frequency of dietetic consultations, high energy diet, swallowing assessment and tube-feeding, compared to later-onset NMDs (p < 0.05). In total, 49.2% children with NMDs had an abnormal weight, in which the prevalence of underweight (n = 24, 19.2%) was significantly higher compared to normal Australian children (8.2%) (p < 0.05). In Duchenne muscular dystrophy, over 50% children were overweight/obese. CONCLUSION: Among children with NMDs, there were many disease-specific nutrition-related symptoms, growth issues, and dietetic practices that were tailored to individual needs. Future studies should focus on measuring the impact of specific dietetic practices on growth and nutritional outcomes, as well as developing a precision medicine approach tailored to the individual nutritional needs of children with NMDs.

"We needed this": perspectives of parents and healthcare professionals involved in a pilot newborn screening program for spinal muscular atrophy.

BACKGROUND: Newborn screening (NBS) for spinal muscular atrophy (SMA) is a recognised model through which health outcomes can be improved. However, perspectives of parents and healthcare professionals (HCPs) involved in such programs are largely unknown. METHODS: A pilot program for SMA ran from August 2018-July 2020. Using a mixed-methods convergent methodology, we used a self-administered questionnaire to understand parents' perceptions and psychological impact of the program from diagnosis to treatment. We thematically analysed successes/challenges encountered by HCPs and recommendations for service improvement from both participant groups. FINDINGS: 202,388 infants were screened for SMA and the perceptions of 44 parents and HCPs affected by a positive result in eighteen newborns was ascertained. Parents (n=29, 100%) were satisfied with NBS for SMA. Although screen-positive result was distressing for all parents, quality of life improved over time [CarerQoL-7D baseline median score 4 (SD=1.4) vs six-month median score 8 (SD=1.3), p<0.001)]. Challenges for HCPs included managing the time-critical nature of the pathway whilst remaining cognisant of limitations associated with the predictive screening test. INTERPRETATION: Interpretation: NBS for SMA fulfils criteria for population-wide screening. Net benefits are acknowledged by stakeholders to optimise lifelong outcomes. Harms including psychological distress associated with a screen-positive result may be managed by targeted psychosocial support, information provision and a personalised model of care together strengthening healthcare systems. FUNDING: The NSW Pilot NBS study was funded by Luminesce Alliance. Dr Kariyawasam received funding from the RTP Scholarship, University of New South Wales and The Freedman Family Foundation Scholarship, Sydney Children's Hospital Foundation.

Proteomic analysis of first trimester maternal serum to identify candidate biomarkers potentially predictive of spontaneous preterm birth.

Spontaneous preterm birth (sPTB) remains a major clinical dilemma; current diagnostics and interventions have not reduced the rate of this serious healthcare burden. This study characterizes differential protein profiles and post-translational modifications (PTMs) in first trimester maternal serum using a refined top-down approach coupling two-dimensional gel electrophoresis (2DE) and mass spectrometry (MS) to directly compare subsequent term and preterm labour events and identify marked protein differences. 30 proteoforms were found to be significantly increased or decreased in the sPTB group including 9 phosphoproteins and 11 glycoproteins. Changes occurred in proteins associated with immune and defence responses. We identified protein species that are associated with several clinically relevant biological processes, including interrelated biological networks linked to regulation of the complement cascade and coagulation pathways, immune modulation, metabolic processes and cell signalling. The finding of altered proteoforms in maternal serum from pregnancies that delivered preterm suggests these as potential early biomarkers of sPTB and also possible mediators of the disorder. BIOLOGICAL SIGNIFICANCE: Identifying changes in protein profiles is critical in the study of cell biology, and disease treatment and prevention. Identifying consistent changes in the maternal serum proteome during early pregnancy, including specific protein PTMs (e.g. phosphorylation, glycosylation), is likely to provide better opportunities for prediction, intervention and prevention of preterm birth. This is the first study to examine first trimester maternal serum using a highly refined top-down proteomic analytical approach based on high resolution 2DE coupled with mass spectrometry to directly compare preterm (<37 weeks) and preterm (≥37 weeks) events and identify select protein differences between these conditions. As such, the data present a promising avenue for translation of biomarker discovery to a clinical setting as well as for future investigation of underlying aetiological processes.

A Routine 'Top-Down' Approach to Analysis of the Human Serum Proteome.

Serum provides a rich source of potential biomarker proteoforms. One of the major obstacles in analysing serum proteomes is detecting lower abundance proteins owing to the presence of hyper-abundant species (e.g., serum albumin and immunoglobulins). Although depletion methods have been used to address this, these can lead to the concomitant removal of non-targeted protein species, and thus raise issues of specificity, reproducibility, and the capacity for meaningful quantitative analyses. Altering the native stoichiometry of the proteome components may thus yield a more complex series of issues than dealing directly with the inherent complexity of the sample. Hence, here we targeted method refinements so as to ensure optimum resolution of serum proteomes via a top down two-dimensional gel electrophoresis (2DE) approach that enables the routine assessment of proteoforms and is fully compatible with subsequent mass spectrometric analyses. Testing included various fractionation and non-fractionation approaches. The data show that resolving 500 µg protein on 17 cm 3-10 non-linear immobilised pH gradient strips in the first dimension followed by second dimension resolution on 7-20% gradient gels with a combination of lithium dodecyl sulfate (LDS) and sodium dodecyl sulfate (SDS) detergents markedly improves the resolution and detection of proteoforms in serum. In addition, well established third dimension electrophoretic separations in combination with deep imaging further contributed to the best available resolution, detection, and thus quantitative top-down analysis of serum proteomes.