Prevalence, incidence and carrier frequency of 5q-linked spinal muscular atrophy - a literature review

Thrombospondin-4 as potential cerebrospinal fluid biomarker for therapy response in pediatric spinal muscular atrophy

BACKGROUND AND PURPOSE

Spinal muscular atrophy (SMA) as the second most common neurodegenerative disorder in childhood is characterized by the deficiency of survival of motor neuron (SMN) protein leading predominantly to degeneration of alpha motor neurons and consequently to progressive muscle weakness and atrophy. Besides some biomarkers like SMN2 copy number therapeutic biomarkers for SMA with known relevance for neuromuscular transmission are lacking. Here, we examined the potential of Thrombospondin-4 (TSP4) to serve as a cerebrospinal fluid (CSF) biomarker, which may also indicate treatment response.

METHODS

We used untargeted proteomic analyses to determine biomarkers in CSF samples derived from pediatric pre-symptomatic (n = 6) and symptomatic (n = 4) SMA patients. The identified biomarker TSP4 was then validated in additional 68 CSF samples (9 adult and 24 pediatric SMA patients, 5 adult and 13 pediatric non-disease controls in addition to 17 pediatric disease controls) by enzyme-linked immunosorbent assay (ELISA) as an additional analytical approach.

RESULTS

Untargeted proteomic analyses of CSF identified a dysregulation of TSP4 and revealed a difference between pre-symptomatic SMA patients and patients identified after the onset of first symptoms. Subsequent ELISA-analyses showed that TSP4 is decreased in pediatric but not adult SMA patients. CSF of pediatric patients with other neurological disorders demonstrated no alteration of TSP4 levels. Furthermore, CSF TSP4 levels of pediatric SMA patients increased after first dose of Nusinersen.

CONCLUSIONS

We found that TSP4 levels are exclusively reduced in CSF of pediatric SMA patients and increase after treatment, leading us to the hypothesis that TSP4 could serve as a CSF biomarker with the potential to monitor treatment response in pediatric SMA patients. Moreover, TSP4 enable to distinguish pre-symptomatic and symptomatic patients suggesting a potential to serve as a stratification marker.

Macrostructural Brain Abnormalities in Spinal Muscular Atrophy: A Case-Control Study

Background and Objectives

Most individuals with spinal muscular atrophy (SMA) on disease-modifying therapies continue to have chronic motor impairment. Insights into brain involvement in SMA may open new pathways for adjunctive therapies to optimize outcomes. We aimed to characterize macrostructural brain abnormalities detected by MRI in individuals with SMA compared with peer controls.

Methods

We conducted a cross-sectional case-control study of children and adults with a confirmed genetic diagnosis of 5q SMA, and peer controls matched by age and sex. Brain MRIs acquired on a 3T MRI scanner through a standardized research protocol were reviewed to qualitatively assess the presence of macrostructural changes. The primary outcome was the presence of any structural brain anomaly on MRI. In addition, the total volume of each participant's lateral ventricles was quantified by volumetry using MRIcron. Genetic and clinical variables, including SMN2 copy number and motor function (Hammersmith Functional Motor Scale Expanded and Revised Upper Limb Module scores), were then correlated with neuroimaging findings.

Results

A total of 42 participants completed the study (mean age 17.4, range 7-40; 67% male). Of the 21 individuals with 5q SMA, 9 (43%) had macrostructural brain abnormalities identified on MRI compared with 2 of 21 (10%) peer controls (odds ratio 7.1, 95% confidence interval 1.4-34.0). In patients with SMA, the most common structural changes were widening of the arachnoid spaces (n = 4) and ventriculomegaly (n = 4). Individuals with SMA had larger median lateral ventricular volume than their normally developing peers (9.3 mL, interquartile range [IQR] 5.5-13.1 vs 5.3 mL, IQR 3.8-9.8; p = 0.034). Structural brain abnormalities were more frequent in those with 2 SMN2 copies (3/5, 60%) compared with 3 or 4 SMN2 copies (4/10, 40% and 2/6, 33% respectively), not reaching significance. We found no association between structural changes and motor function scores.

Discussion

Individuals with SMA have higher rates of macrostructural brain abnormalities than their neurotypical peers, suggesting CNS involvement in SMA. Understanding changes in the brain architecture of the SMA population can inform the development of adjunct therapies targeting the CNS and potentially guide rehabilitation strategies.

Evaluating the clinical efficacy of a long-read sequencing-based approach for carrier screening of spinal muscular atrophy

Spinal muscular atrophy (SMA) is the second most common fatal genetic disease in infancy. It is caused by deletion or intragenic pathogenic variants of the causative gene SMN1, which degenerates anterior horn motor neurons and leads to progressive myasthenia and muscle atrophy. Early treatment improves motor function and prognosis in patients with SMA, but drugs are expensive and do not cure the disease. Therefore, carrier screening seems to be the most effective way to prevent SMA birth defects. In this study, we genetically analyzed 1400 samples using multiplex ligation-dependent probe amplification (MLPA) and quantitative polymerase chain reaction (qPCR), and compared the consistency of the results. We randomly selected 44 samples with consistent MLPA and qPCR results for comprehensive SMA analysis (CASMA) using a long-read sequencing (LRS)-based approach. CASMA results showed 100% consistency, visually and intuitively explained the inconsistency between exons 7 and 8 copy numbers detected by MLPA in 13 samples. A total of 16 samples showed inconsistent MLPA and qPCR results for SMN1 exon 7. CASMA was performed on all samples and the results were consistent with those of resampling for MLPA and qPCR detection. CASMA also detected an additional intragenic variant c.-39A>G in a sample with two copies of SMN1 (RT02). Finally, we detected 23 SMA carriers, with an estimated carrier rate of 1/61 in this cohort. In addition, CASMA identified the "2 + 0" carrier status of SMN1 and SMN2 in a family by analyzing the genotypes of only three samples (parents and one sibling). CASMA has great advantages over MLPA and qPCR assays, and could become a powerful technical support for large-scale screening of SMA.

Onasemnogene Abeparvovec Gene Therapy and Risdiplam for the Treatment of Spinal Muscular Atrophy in Thailand: A Cost-Utility Analysis

OBJECTIVES

Caring for individuals with spinal muscular atrophy (SMA), a rare genetic disorder, poses tremendous challenges for the economy and healthcare system. This study evaluated the cost-utility of onasemnogene abeparvovec-xioi gene therapy and risdiplam for SMA in Thailand.

METHODS

A Markov model was used to analyze the lifetime costs and outcomes of these treatments compared with standard of care for symptomatic SMA types 1 and 2-3. SMA type 1 patients were treated with one of either onasemnogene or risdiplam, while SMA types 2-3 patients received risdiplam. Data on disease progression and medical costs were sourced from hospital databases, while treatment efficacy was based on clinical trials. Interviews with patients and caregivers provided data on non-medical costs and utilities. Base case cost-effectiveness and sensitivity analyses were conducted, with the incremental cost-effectiveness ratio (ICER) calculated in US dollars (USD) per quality-adjusted life year (QALY) gained, against a willingness-to-pay threshold of 4444 USD/QALY gained.

RESULTS

For SMA type 1, the ICERs for onasemnogene and risdiplam were 163,102 and 158,357 USD/QALY gained, respectively. For SMA types 2-3, the ICER for risdiplam was 496,704 USD/QALY gained.

CONCLUSIONS

While onasemnogene and risdiplam exceeded the value-for-money threshold of the Thai healthcare system, they yielded the highest QALY gains among all approved medications. Policy-makers should incorporate various pieces of evidence alongside the cost-effectiveness results for rare diseases with costly drugs. Additionally, cost-effectiveness findings are useful for price negotiations and alternative financial funding, which allows policy-makers to seek solutions to ensure patient access, aligning with universal health coverage principles in Thailand.

Molecular analysis of SMN2, NAIP, and GTF2H2 gene deletions and relationships with clinical subtypes of spinal muscular atrophy

SMA (spinal muscular atrophy) is an autosomal recessive neuromuscular disease that causes muscle atrophy and weakness. SMA is diagnosed by a homozygous deletion in exon 7 of the SMN1 gene. However, mutations in genes located in the SMA region, such as SMN2, NAIP, SERF1, and GTF2H2, may also contribute to the severity of the disease. Within our study's scope, 58 SMA patients who applied in 2018-2021 and 40 healthy controls were analyzed. The study retrospectively included the SMN1 and SMN2 copy numbers previously determined by the MLPA method. Then, NAIP gene analyses with the multiplex PCR method and GTF2H2 gene analyses with the RFLP method were performed. There was a significant correlation (p = 0.00001) between SMN2 copy numbers and SMA subtypes. Also, the NAIP gene (p = 0.01) and the GTF2H2 gene (p = 0.0049) revealed a significant difference between healthy and SMA subjects, whereas the SMA subtypes indicated no significant differences. We detected a significant correlation between clinical subtypes and HFMSE scores in 32 pediatric SMA patients compared (p = 0.01). While pediatric patients with GTF2H2 deletions demonstrated higher motor functions, and those with NAIP deletions demonstrated lower motor functions. In this study, we examined the relationship between NAIP and GTF2H2, called SMN region modifier genes, and the clinical severity of the disease in Turkish SMA patients. Despite its small scale, this research will benefit future investigations into the pathogenesis of SMA disease.

Spinal presentations in children with spinal muscular atrophy type 1 following gene therapy treatment with onasemnogene abeparvovec - The SMA REACH UK network experience

Spinal muscular atrophy (SMA) is a neuromuscular disorder of mainly early onset and variable severity. Prior to the introduction of disease modifying therapies (DMTs), children with SMA type 1 typically died before 2 years of age and management was primarily palliative. Onasemnogene abeparvovec (OA), nusinersen, and risdiplam are novel DMTs which ameliorate the effects of the underlying genetic defect at least partially making SMA a treatable condition. Survival and achievement of previously unmet developmental milestones result in treated SMA type 1 children spending more time upright than expected based on the natural history of the treatment-naïve condition. Consequently, spinal asymmetry and kyphosis, features not typically seen in untreated SMA type 1 children due to early mortality, are increasingly common complications. Precise data regarding their prevalence, severity, and management are currently limited. This study describes the spinal features and management in 75 children with SMA type 1 who received OA between March 2021 and December 2022. Retrospective analysis from SMA REACH UK data showed that 44/75 (59 %) clinically had spinal asymmetry and 37 (49 %) had kyphosis. This study aims to raise awareness of this important feature as part of the changed natural history of SMA type 1 post OA treatment.

Real-world multidisciplinary outcomes of onasemnogene abeparvovec monotherapy in patients with spinal muscular atrophy type 1: experience of the French cohort in the first three years of treatment

BACKGROUND

Spinal muscular atrophy type 1 (SMA1) is the most severe and early form of SMA, a genetic disease with motor neuron degeneration. Onasemnogene abeparvovec gene transfer therapy (GT) has changed the natural history of SMA1, but real-world data are scarce.

METHODS

A French national expert committee identified 95 newly diagnosed treatment-naive SMA1 patients between June 2019 and June 2022. We prospectively report on children treated with GT as the first and only therapy who had more than one-year of follow-up.

RESULTS

Forty-six SMA1 patients received GT. Twelve patients received other treatments. Patients with respiratory insufficiency were oriented toward palliative care after discussion with families. Twenty-nine of the treated patients with more than 12 months of follow-up were included in the follow-up analysis. Among them, 17 had 24 months of follow-up. The mean age at treatment was 7.5 (2.1-12.5) months. Twenty-two patients had two SMN2 copies, and seven had three copies. One infant died in the month following GT due to severe thrombotic microangiopathy, and another died due to respiratory distress. Among the 17 patients with 24 months of follow-up, 90% required spinal bracing (15/17), three patients required nocturnal noninvasive ventilation, and two needed gastrostomy. Concerning motor milestones at the 24-month follow-up, all patients held their head, 15/17 sat for 30 s unassisted, and 12/17 stood with aid. Motor scores (CHOPINTEND and HINE-2) and thoracic circumference significantly improved in all patients.

CONCLUSIONS

Our study shows favorable motor outcomes and preserved respiratory and feeding functions in treatment-naive SMA1 infants treated by GT as the first and only therapy before respiratory and bulbar dysfunctions occurred. Nevertheless, almost all patients developed spinal deformities.

A scoping review of the role of managed entry agreements in upcoming drugs for amyotrophic lateral sclerosis: learning from the case of spinal muscular atrophy

Introduction: The therapeutic options for spinal muscular atrophy (SMA) are encouraging. However, there is currently no cure for amyotrophic lateral sclerosis (ALS). The clinical and economic uncertainty surrounding innovative treatments for rare neurodegenerative diseases makes it necessary to understand managed entry agreements (MEAs). The aim of this study was to review whether models of MEAs in SMA could be extrapolated to ALS. Methods: We performed a scoping review with information on MEAs on SMA in Web of Science (WOS), PubMed, Lyfegen Library, the National Institute for Health and Care Excellence (NICE), and the Canadian Agency for Drugs and Technologies in Health (CADTH). Results: We found 45 results in WOS and PubMed. After an initial survey, 10 were reviewed to assess eligibility, and three were selected. We obtained 44 results from Lyfegen Library, and three results each from NICE and CADTH. Conclusion: The main objective of MEAs is to reduce uncertainty in the financing of drugs with a high budgetary impact and clinical concerns, as is the case with drugs for SMA and ALS. While the information available on MEAs in SMA is scarce, some conceptual models are publicly available. MEAs for long-term treatments for SMA could be used for the design of MEAs in ALS because of their similarities in economic and clinical uncertainty.

Association among biomarkers, phenotypes, and motor milestones in Chinese patients with 5q spinal muscular atrophy types 1-3

Background

Biomarkers can be used to assess the severity of spinal muscular atrophy (5q SMA; SMA). Despite their potential, the relationship between biomarkers and clinical outcomes in SMA remains underexplored. This study aimed to assess the association among biomarkers, phenotypes, and motor milestones in Chinese patients diagnosed with SMA.

Methods

We collected retrospective clinical and follow-up data of disease-modifying therapy (DMT)-naïve patients with SMA at our center from 2019 to 2021. Four biomarkers were included: survival motor neuron 2 (SMN2) copies, neuronal apoptosis inhibitory protein (NAIP) copies, full-length SMN2 (fl-SMN2), and F-actin bundling protein plastin 3 (PLS3) transcript levels. Data were analyzed and stratified according to SMA subtype.

Results

Of the 123 patients, 30 were diagnosed with Type 1 (24.3%), 56 with Type 2 (45.5%), and 37 with Type 3 (30.1%). The mortality rate for Type 1 was 50%, with median survival times of 2 and 8 months for types 1a and 1b, respectively. All four biomarkers were correlated with disease severity. Notably, fl-SMN2 transcript levels increased with SMN2 copies and were higher in Type 2b than those in Type 2a (p = 0.028). Motor milestone deterioration was correlated with SMN2 copies, NAIP copies, and fl-SMN2 levels, while PLS3 levels were correlated with standing and walking function.

Discussion

Our findings suggest that SMN2 copies contribute to survival and that fl-SMN2 may serve as a valuable biomarker for phenotypic variability in SMA Type 2 subtypes. These insights can guide future research and clinical management of SMA.

Newborn Screening for Spinal Muscular Atrophy: Variations in Practice and Early Management of Infants with Spinal Muscular Atrophy in the United States

In the United States (U.S.), newborn screening (NBS) for spinal muscular atrophy (SMA) is implemented by individual states. There is likely variation in the practice patterns of state NBS programs and among the providers caring for newborns with SMA. This is a prospective, descriptive, observational study that seeks to quantify and describe practice patterns and heterogeneities in state NBS programs and provider practices in the U.S. We surveyed U.S. state NBS programs and care providers of newborns with SMA. Thirty states and 41 practitioners responded. NBS program practices vary by state. Most (74%) state programs provide results to both primary care and specialist providers and also defer confirmatory SMA testing to those providers. Two states had relatively high rates of false-positive or inclusive results. The total birth prevalence of SMA was 1:13,862. Most providers were in tertiary care centers (90%) and were child neurologists (81%) and/or had fellowship training in Neuromuscular Medicine or Electromyography (76%). All providers see new referrals in less than a week, but many do not initiate treatment until >3 weeks of age (39%), with most commonly reported delays related to insurance processes. Most (81%) prefer onasemnogene abeparvovec-xioi (OA) as the treatment of choice, mainly due to perceived efficacy and the route/frequency of administration. NBS practice patterns in the U.S. vary by state but overall yielded the predicted birth prevalence of positive results. Providers evaluate these newborns urgently, but many do not initiate therapy until after 3 weeks of age. Treatment delays are mainly related to insurance processes.

Timing of SMN replacement therapies in mouse models of spinal muscular atrophy: a systematic review and meta-analysis

Mutations in the Survival of Motor Neuron 1 gene lead to a loss of survival motor neuron protein in patients with spinal muscular atrophy. Revolutionary advances in gene therapy have led to survival motor neuron-replacement therapies that significantly prolong life expectancy and improve neuromuscular function. However, accumulating evidence suggests that the timing of survival motor neuron-replacement therapies is a critical determinant of success. We performed a systematic review and meta-analysis of all pre-clinical studies testing survival motor neuron replacement therapies in mouse models of spinal muscular atrophy to assess the impact of timing of delivery on therapeutic effectiveness. We incorporated four databases in this pre-registered study (PROSPERO 2020 CRD42020200180): EMBASE, PubMed, Scopus and Web of Science. Inclusion criteria were; primary research article, a measure of survival analysis, use of survival motor neuron mouse model and evaluation of survival motor neuron-targeting therapy. Exclusion criteria included; use of therapies not known to directly target survival motor neuron, genetic manipulations and/or lack of appropriate controls. We screened papers using the SyRF platform. The main outcome we assessed was survival in treated groups compared to untreated groups. We performed meta-analysis of survival using median survival ratio and the random effects model and measured heterogeneity using the I 2 statistic. Subgroup analyses were performed to assess treatment efficacy based on timing of intervention (embryonic delivery, day of birth, postnatal day 2 and postnatal day 3 or later) and treatment type. If detailed in the studies, body weight compared to untreated spinal muscular atrophy models and motor neuron number were included as secondary outcomes for meta-analysis. 3469 studies were initially identified, with 78 ultimately included. Survival motor neuron-replacement therapies significantly affected survival in favour of treatment by a factor of 1.20 (95% CI 1.10-1.30, P < 0.001) with high heterogeneity (I 2 = 95%). Timing of treatment was a significant source of heterogeneity (P < 0.01), with earlier treatment having a greater impact on survival. When stratified by type of treatment, earlier treatment continued to have the strongest effect with viral vector replacement therapy and antisense oligonucleotide therapy. Secondary outcome measures of body weight and spinal motor neuron counts were also positively associated with early treatment. Earlier delivery of survival motor neuron replacement therapies is therefore a key determinant of treatment efficacy in spinal muscular atrophy.

Judicialization of Zolgensma in the Ministry of Health: costs and clinical profile of patients

OBJECTIVE

To investigate the costs and profile of patients who have filed a lawsuit against the Ministry of Health for the treatment of spinal muscular atrophy (SMA) with the onasemnogene abeparvovec (Zolgensma®).

METHODS

This is a cross-sectional, descriptive study with a census design, based on records of lawsuits filed against the Ministry of Health between January 2019 and September 2022. Data was requested from the Ministry of Health via the Access to Information Act. Information was extracted on the epidemiological profile of the beneficiaries of the lawsuits, as well as the expenses spent by the Ministry of Health in cases where the requests were granted.

RESULTS

136 lawsuits were identified, of which 113 (83%) were favorable to patients at a cost of R$ 944.8 million in the period analyzed. Demographic (gender and age), clinical (SMA subtypes, use of ventilatory or nutritional support), and lawsuit (type of legal service) characteristics were not associated with the granting of lawsuits. Prior use of medication (nusinersena or ridisplam) was associated with the dismissal of lawsuits. Of the 113 lawsuits granted in favor of patients, only six (5.3%) would meet the criteria currently established by the National Committee for Health Technology Incorporation - Conitec (children up to six months without ventilatory and nutritional support). R$ 146 million was spent on supplying Zolgensma to children over the age of two, which is outside the recommendation contained in the drug's package leaflet.

CONCLUSIONS

The Ministry of Health incurs a high cost with the judicialization of Zolgensma for SMA, representing 2.45% of total spending on medicines in the Unified Health System, including spending by the three administrative spheres. Some of the lawsuits have been granted in disagreement with the criteria established by health technology assessment agencies and the drug manufacturer's recommendations.

Clinical perspectives: Treating spinal muscular atrophy

Spinal muscular atrophy is a rare and progressive neuromuscular disease that, without treatment, leads to progressive weakness and often death. A plethora of studies have led to the approval of three high-cost and effective treatments since 2016. These treatments, nusinersen, onasemnogene abeparvovec, and risdiplam, have not been directly compared and have varying challenges in administration. In this review, we discuss the evidence supporting the use of these medications, the process of treatment selection, monitoring after treatment, the limited data comparing treatments, as well as future directions for investigation and therapy.

Clinical Evidence Supporting FDA Approval of Gene and RNA Therapies for Rare Inherited Conditions

BACKGROUND

Gene and RNA therapies have potential to transform the treatment of rare inherited diseases, but there are concerns about the evidence supporting their use and high costs.

OBJECTIVE

We analyze the evidence supporting Food and Drug Administration (FDA) approval of gene and RNA therapies for rare inherited diseases and discuss implications for clinical practice and policy.

METHODS

We conducted a qualitative analysis of FDA documents outlining the basis of approval for gene and RNA therapies approved for rare inherited diseases between 2016 and 2023. For each drug, we gathered five characteristics of the evidence supporting FDA approval (no phase 3 trial, nonrandomized, no clinical endpoint, lack of demonstrated benefit, and significant protocol deviation) and four characteristics of the FDA approval process (prior rejection or complete response, negative committee vote, discrepancy between label and trial population, and boxed warning). The main outcome was the number of drugs with each characteristic.

RESULTS

Between 2016 and 2023, 19 gene and RNA therapies received FDA approval to treat rare inherited diseases. The most common limitations in the evidence supporting approval of these drugs were nonrandomized studies (8/19, 42%), no clinical endpoint (7/19, 37%), lack of demonstrated benefit or inconsistent results (4/19, 21%), and no phase 3 trial (4/19, 21%). Half (3/6) of accelerated approvals and 57% (5/9) of drugs with breakthrough designation had nonrandomized trials, and gene therapies with one-time dosing were overrepresented (5/7, 71%) among the drugs with nonrandomized trials. Five of six accelerated approvals (83%) and five of nine pediatric drugs (56%), most of which were indicated for Duchenne muscular dystrophy, had no clinical endpoint. Four of nine (44%) pediatric drugs and four of six (67%) accelerated approvals failed to demonstrate benefit compared with none of the nonpediatric drugs and none of the traditional approvals. Five drugs, which all had different indications and represented a mix of RNA and gene therapies, did not have any of these evidence characteristics. Among drugs that received prior rejections or negative committee opinions, all four had nonrandomized trials and lacked a clinical endpoint, and 75% (3/4) lacked demonstrated benefit. Five of nine (56%) pediatric drugs were indicated for broader age groups according to the drug label compared with the trial populations. Of the three drugs with boxed warnings, two had pediatric indications and nonrandomized studies, and one had no phase 3 trial.

CONCLUSIONS

Issues related to trial design, outcome, and data integrity in the evidence supporting FDA approval of rare inherited disease gene and RNA therapies raise questions about whether this evidence is adequate to inform prescribing decisions. Gene and RNA therapies with accelerated approval and pediatric indications were overrepresented among drugs lacking clinical endpoints or demonstrated benefit and should be the focus of efforts to reduce uncertainty in the evidence.

Spinal Muscular Atrophy Update in Best Practices: Recommendations for Diagnosis Considerations

Background and Objectives

Spinal muscular atrophy (SMA) is an autosomal recessive progressive neurodegenerative primary motor neuron disorder caused by biallelic variants of the survival motor neuron 1 (SMN1) gene. The most recent SMA best practice recommendations were published in 2018 shortly after the approval of the first SMN-enhancing treatment. The availability of disease-modifying therapies for 5q SMA and implementation of SMA newborn screening (NBS) has led to urgency to update the SMA best practice recommendations for diagnosis and to reevaluate the current classification of SMA. In addition, the availability of disease-modifying therapies has opened the door to explore improved diagnosis of adult-onset SMA.

Methods

A systematic literature review was conducted on SMA NBS. An SMA working group of American and European health care providers developed recommendations through a modified Delphi technique with serial surveys and virtual meeting feedback on SMA diagnosis to fill information gaps for topics with limited evidence. A community working group of an individual with SMA and caregivers provided insight and perspective on SMA diagnosis and support through a virtual meeting to guide recommendations.

Results

The health care provider working group achieved consensus that SMA NBS is essential to include in the updated best practice for SMA diagnosis (100%). Recommendations for the following are described: characterizing NBS-identified infants before treatment; minimum recommendations for starting or offering SMA NBS in a state or country; recommendations for activities and services to be provided by an SMA specialty care center accepting SMA NBS referrals; and recommendations for partnership with individuals with SMA and caregivers to support NBS-identified infants and their caregivers. Limited data are available to advance efficient diagnosis of adult-onset SMA.

Discussion

Updating best practice recommendations for SMA diagnosis to include SMA NBS implementation is essential to advancing care for individuals with SMA. In addition to testing, processes for the efficient management of positive newborn screen with access to knowledgeable and skilled health care providers and access to treatment options is critical to successful early diagnosis. Additional evidence is required to improve adult-onset SMA diagnosis.

A Five-Year Review of Newborn Screening for Spinal Muscular Atrophy in the State of Utah: Lessons Learned

Spinal muscular atrophy (SMA) is an autosomal recessive condition characterized by alpha motor neuron degeneration in the spinal cord anterior horn. Clinical symptoms manifest in the first weeks to months of life in the most severe cases, resulting in progressive symmetrical weakness and atrophy of the proximal voluntary muscles. Approximately 95% of SMA patients present with homozygous deletion of the SMN1 gene. With multiple available therapies preventing symptom development and slowing disease progression, newborn screening for SMA is essential to identify at-risk individuals. From 2018 to 2023, a total of 239,844 infants were screened. 13 positive screens were confirmed to have SMA. An additional case was determined to be a false positive. We are not aware of any false-negative cases. All patients were seen promptly, with diagnosis confirmed within 1 week of the initial clinical visit. Patients were treated with nusinersen or onasemnogene abeparvovec. Treated patients with two copies of SMN2 are meeting important developmental milestones inconsistent with the natural history of type 1 SMA. Patients with 3-4 copies of SMN2 follow normal developmental timelines. Newborn screening is an effective tool for the early identification and treatment of patients with SMA. Presymptomatic treatment dramatically shifts the natural history of SMA, with most patients meeting appropriate developmental milestones. Patients with two copies of SMN2 identified through newborn screening constitute a neurogenetic emergency. Due to the complexities of follow-up, a multidisciplinary team, including close communication with the newborn screening program, is required to facilitate timely diagnosis and treatment.

Analysis of blood concentrations and clinical application of risdiplam in patients with spinal muscular atrophy using ultra-high performance liquid chromatography-tandem mass spectrometry

Risdiplam, the first oral therapy approved for spinal muscular atrophy and made globally available in 2021, necessitates a highly sensitive and straightforward assay for therapeutic drug monitoring. This is crucial to manage potential toxicities linked to drug concentrations and supervise dosing regimens. A cutting-edge ultra-high performance liquid chromatography-tandem mass spectrometry bioassay for risdiplam in human serum has been developed. In this method, analytes were separated on a Phenomenex Kinetex XB C18 column using a 6.5-min gradient elution after a single-step protein precipitation. MS detection was conducted via electrospray ionization in positive mode with selected reaction monitoring. The validated range for risdiplam was determined to be 1.95-125.00 ng/mL. The precision and accuracy of intra- and inter-batch analyses were within ±15%. The novel method met all other established criteria. This assay holds promise for monitoring drug concentrations and guiding clinical decisions in patients with spinal muscular atrophy.

Effects of nusinersen on motor function in children with spinal muscular atrophy: a retrospective study

Background

Spinal muscular atrophy (SMA) is a genetic progressive neuromuscular disease. Nusinersen is the first disease modifying drug approved to treat patients with SMA. Our study aimed to evaluate the efficacy of nusinersen treatment on motor function in children with SMA.

Methods

A retrospective analysis was conducted on the data of 52 genetically confirmed SMA patients from November 2020 to September 2023. Motor function was assessed based on standardized scales from baseline to 14 months of follow-up.

Results

Of patients in this study, the majority had SMA type 2 (40/52, 76.9%), 5 (9.6%) and 7 (13.5%) patients had SMA types 1 and 3, respectively. The median disease duration was 11 months (range 0-52), and the median age at initiation of treatment was 44.5 months (range 5-192). Motor function of all the patients with SMA improved from baseline to 14 months of follow-up. Mean increases of 4.6-point (p = 0.173), 4.7-point (p = 0.021) and 2.7-point (p = 0.013) were observed from baseline to 14 months of follow-up for the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scores, the Hammersmith Functional Motor Scale Expanded (HFMSE) and the Revised Upper Limb Module (RULM), respectively. Increased disease duration and age of treatment initiation were negatively correlated with the changes in HFMSE scores (r = -0.567, p = 0.043; r = -0.771 and p = 0.002, respectively). Similar results were observed for the RULM scores (r = -0.714, p = 0.014; r = -0.638 and p = 0.035, respectively).

Conclusion

Our study suggested that 14 months of treatment with nusinersen was effective and improved the motor function of children with SMA types 1, 2, or 3. In addition, disease duration and age at treatment initiation were negatively correlated with treatment outcome in the patients.

Spinal muscular atrophy caused by compound heterozygous SMN1 mutations: two cases and literature review

Spinal muscular atrophy (SMA) is a rare neuromuscular disease, which is characterized by the degeneration of motor neurons, leading to symmetrical muscle weakness and atrophy. Description of two novel SMN1 mutations (patient1: c.683T > A, p.Leu228Ter; patient2: c.347 T > C, p.Ile116 Thr). We reported two patients with SMN1 mutations with the clinical features, and provided a literature review of the previously reported 22 cases. Two SMA patients showed progressive proximal lower limb weakness and milder clinical symptom. In a total of 22 cases, the most commonly observed SMN1 gene alteration was missense mutation (55%), followed by splicing defect (27%), nonsense (9%) and frameshift (9%). We discuss the possible decisive role of these intragenic mutations in the phenotypic results, which enriched the SMN 1 fine mutation database.

Treatment Options in Spinal Muscular Atrophy: A Pragmatic Approach for Clinicians

Spinal muscular atrophy (SMA) is a rare neurodegenerative neuromuscular disorder with a wide phenotypic spectrum of severity. SMA was previously life limiting for patients with the most severe phenotype and resulted in progressive disability for those with less severe phenotypes. This has changed dramatically in the past few years with the approvals of three disease-modifying treatments. We review the evidence supporting the use of currently approved SMA treatments (nusinersen, onasemnogene abeparvovec, and risdiplam), focusing on mechanisms of action, side effect profiles, published clinical trial data, health economics, and pending questions. Whilst there is robust data from clinical trials of efficacy and side effect profile for individual drugs in select SMA populations, there are no comparative head-to-head clinical trials. This presents a challenge for clinicians who need to make recommendations on the best treatment option for an individual patient and we hope to provide a pragmatic approach for clinicians across each SMA profile based on current evidence.

Mass spectrometry for metabolomics analysis: Applications in neonatal and cancer screening

Chemical analysis by analytical instrumentation has played a major role in disease diagnosis, which is a necessary step for disease treatment. While the treatment process often targets specific organs or compounds, the diagnostic step can occur through various means, including physical or chemical examination. Chemically, the genome may be evaluated to give information about potential genetic outcomes, the transcriptome to provide information about expression actively occurring, the proteome to offer insight on functions causing metabolite expression, or the metabolome to provide a picture of both past and ongoing physiological function in the body. Mass spectrometry (MS) has been elevated among other analytical instrumentation because it can be used to evaluate all four biological machineries of the body. In addition, MS provides enhanced sensitivity, selectivity, versatility, and speed for rapid turnaround time, qualities that are important for instance in clinical procedures involving the diagnosis of a pediatric patient in intensive care or a cancer patient undergoing surgery. In this review, we provide a summary of the use of MS to evaluate biomarkers for newborn screening and cancer diagnosis. As many reviews have recently appeared focusing on MS methods and instrumentation for metabolite analysis, we sought to describe the biological basis for many metabolomic and additional omics biomarkers used in newborn screening and how tandem MS methods have recently been applied, in comparison to traditional methods. Similar comparison is done for cancer screening, with emphasis on emerging MS approaches that allow biological fluids, tissues, and breath to be analyzed for the presence of diagnostic metabolites yielding insight for treatment options based on the understanding of prior and current physiological functions of the body.

Epidemiology of Spinal Muscular Atrophy Based on the Results of a Large-Scale Pilot Project on 202,908 Newborns

BACKGROUND

This study presents the findings of a newborn screening (NBS) pilot project for 5q-spinal muscular atrophy (5q-SMA) in multiple regions across Russia for during the year 2022. The aim was to assess the feasibility and reproducibility of NBS for SMA5q in diverse populations and estimate the real prevalence of 5q-SMA in Russia as well as the distribution of patients with different number of SMN2 copies.

METHODS

The pilot project of NBS here was based on data, involving the analysis of 202,908 newborns. SMA screening assay was performed using a commercially available real-time polymerase chain reaction kit, the Eonis SCID-SMA.

RESULTS

In one year, 202,908 newborns were screened, identifying 26 infants with homozygous deletion of SMN1 exon 7, yielding an estimated 5q-SMA incidence of 1:7804 newborns. It was found that 38.46% had two SMN2 copies, 42.31% had three copies, 15.38% had four copies, and 3.85% had five copies of SMN2. Immediate treatment was proposed for patients with two or three SMN2 copies. Infants with four or more SMN2 copies warranted further investigation on management and treatment. Short-term monitoring after gene therapy showed motor function improvements. Delays in treatment initiation were observed, including the testing for adeno-associated virus 9 antibodies and nonmedical factors.

CONCLUSIONS

The study emphasizes the need for a standardized algorithm for early diagnosis and management through NBS to benefit affected families. Overall, the NBS program for 5q-SMA in Russia demonstrated the potential to improve outcomes and transform SMA from a devastating disease to a chronic condition with evolving medical requirements.

Integrated Approaches and Practical Recommendations in Patient Care Identified with 5q Spinal Muscular Atrophy through Newborn Screening

In recent years, significant progress has been made in 5q Spinal Muscular Atrophy therapeutics, emphasizing the importance of early diagnosis and intervention for better clinical outcomes. Characterized by spinal cord motor neuron degeneration, 5q-SMA leads to muscle weakness, swallowing difficulties, respiratory insufficiency, and skeletal deformities. Recognizing the pre-symptomatic phases supported by screening and confirmatory genetic tests is crucial for early diagnosis. This work addresses key considerations in implementing 5q-SMA screening within the Brazilian National Newborn Screening Program and explores Brazil's unique challenges and opportunities, including genetic tests, time-to-patient referral to specialized centers, program follow-up, and treatment algorithms. We aim to guide healthcare professionals and policymakers, facilitating global discussions, including Latin American countries, and knowledge-sharing on this critical subject to improve the care for newborns identified with 5q SMA.

Neurofilament light protein as a biomarker for spinal muscular atrophy: a review and reference ranges

Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality, characterized by progressive neuromuscular degeneration resulting from mutations in the survival motor neuron (SMN1) gene. The availability of disease-modifying therapies for SMA therapies highlights the pressing need for easily accessible and cost-effective blood biomarkers to monitor treatment response and for better disease management. Additionally, the wide implementation of newborn genetic screening programs in Western countries enables presymptomatic diagnosis of SMA and immediate treatment administration. However, the absence of monitoring and prognostic blood biomarkers for neurodegeneration in SMA hinders effective disease management. Neurofilament light protein (NfL) is a promising biomarker of neuroaxonal damage in SMA and reflects disease progression in children with SMA undergoing treatment. Recently, the European Medicines Agency issued a letter of support endorsing the potential utilization of NfL as a biomarker of pediatric neurological diseases, including SMA. Within this review, we comprehensively assess the potential applications of NfL as a monitoring biomarker for disease severity and treatment response in pediatric-onset SMA. We provide reference ranges for normal levels of serum based NfL in neurologically healthy children aged 0-18 years. These reference ranges enable accurate interpretation of NfL levels in children and can accelerate the implementation of NfL into clinical practice.

[Carrier screening for 223 monogenic diseases in Chinese population: a multi-center study in 33 104 individuals]

OBJECTIVE

To investigate the epidemiological characteristics and mutation spectrum of monogenic diseases in Chinese population through a large-scale, multicenter carrier screening.

METHODS

This study was conducted among a total of 33 104 participants (16 610 females) from 12 clinical centers across China.Carrier status for 223 genes was analyzed using high-throughput sequencing and different PCR methods.

RESULTS

The overall combined carrier frequency was 55.58% for 197 autosomal genes and 1.84% for 26 X-linked genes in these participants.Among the 16 669 families, 874 at-risk couples (5.24%) were identified.Specifically, 584 couples (3.50%) were at risk for autosomal genes, 306(1.84%) for X-linked genes, and 16 for both autosomal and X-linked genes.The most frequently detected autosomal at-risk genes included GJB2(autosomal recessive deafness type 1A, 393 couples), HBA1/HBA2(α-thalassemia, 36 couples), PAH (phenylketonuria, 14 couples), and SMN1(spinal muscular atrophy, 14 couples).The most frequently detected X-linked at-risk genes were G6PD (G6PD deficiency, 236 couples), DMD (Duchenne muscular dystrophy, 23 couples), and FMR1(fragile X syndrome, 17 couples).After excluding GJB2 c.109G>A, the detection rate of at-risk couples was 3.91%(651/16 669), which was lowered to 1.72%(287/16 669) after further excluding G6PD.The theoretical incidence rate of severe monogenic birth defects was approximately 4.35‰(72.5/16 669).Screening for a battery of the top 22 most frequent genes in the at-risk couples could detect over 95% of at-risk couples, while screening for the top 54 genes further increased the detection rate to over 99%.

CONCLUSION

This study reveals the carrier frequencies of 223 monogenic genetic disorders in the Chinese population and provides evidence for carrier screening strategy development and panel design tailored to the Chinese population.In carrier testing, genetic counseling for specific genes or gene variants can be challenging, and the couples need to be informed of these difficulties before testing and provided with options for not screening these genes or gene variants.

Spinal muscular atrophy genetic epidemiology and the case for premarital genomic screening in Arab populations

BACKGROUND

Spinal muscular atrophy (SMA) is a fatal autosomal recessive disorder for which several treatment options, including a gene therapy, have become available. SMA incidence has not been well-characterized in most Arab countries where rates of consanguinity are high. Understanding SMA disease epidemiology has important implications for screening, prevention, and treatment in those populations.

METHODS

We perform SMA diagnostic testing in a clinical multi-national patient cohort (N = 171) referred for hypotonia and/or muscle weakness. In addition, we carry out genetic newborn screening for SMA on 1502 healthy Emirati newborns to estimate the carrier frequency and incidence of the disease in the United Arab Emirates.

RESULTS

Patients referred for SMA genetic testing are mostly Arabs (82%) representing 18 countries. The overall diagnostic yield is 33.9%, which is higher (>50%) for certain nationalities. Most patients (71%) has two SMN2 copies and earlier disease onset. For the first time, we estimate SMA carrier frequency (1.3%) and incidence of the disease (1 in 7122 live births) in the United Arab Emirates. Using birth and marriage rates in two Arab populations (United Arab Emirates and Saudi Arabia), as well as disease incidence in both countries, we show that, besides preventing new cases, premarital genetic screening could potentially result in around $8 to $324 million annual cost savings, respectively, relative to postnatal treatment.

CONCLUSIONS

The SMA carrier frequency and incidence we document suggests high potential benefit for universal implementation of premarital genomic screening for a wide range of recessive disorders in Arab populations.

Analytical validation of the amplification refractory mutation system polymerase chain reaction-capillary electrophoresis assay to diagnose spinal muscular atrophy

OBJECTIVES

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by homozygous deletion and compound heterozygous mutations in survival motor neuron 1 (SMN1), with severity tied to the copy number of survival motor neuron 2 (SMN2). This study aimed to develop a rapid and comprehensive method for the diagnosis of SMA.

METHODS

A total of 292 children with clinically suspected SMA and 394 family members were detected by the amplification refractory mutation system polymerase chain reaction-capillary electrophoresis (ARMS-PCR-CE) method, which targeted 19 reported mutations, and the results were compared with those in multiplex ligation-dependent probe amplification (MLPA). Individuals with identified point mutations were further confirmed by SMN1 long-range PCR and Sanger sequencing.

RESULTS

A total of 202 children with SMA, 272 carriers, and 212 normal individuals were identified in this study. No difference was found in the R-value distribution of exons 7 and 8 in SMN1 and SMN2 among these cohorts, with coefficients of variation consistently below 0.08. To detect exon 7 and 8 copy numbers in SMN1 and SMN2, the ARMS-PCR-CE results were concordant with those of MLPA. Approximately 4.95 % (10/202) of the study patients had compound heterozygous mutations.

CONCLUSIONS

The ARMS-PCR-CE assay is a comprehensive, rapid, and accurate diagnostic method for SMA that simultaneously detects copy numbers of exons 7 and 8 in SMN1/SMN2, as well as 19 point mutations in SMN1 and 2 enhancers in SMN2. This approach can effectively reduce the time frame for diagnosis, facilitating early intervention and preventing birth defects.

Nusinersen Treatment for Spinal Muscular Atrophy: Retrospective Multicenter Study of Pediatric and Adult Patients in Kuwait

Spinal muscular atrophy is a neuromuscular genetic condition associated with progressive muscle weakness and atrophy. Nusinersen is an antisense oligonucleotide therapy approved for the treatment of 5q spinal muscular atrophy in pediatric and adult patients. The objective of this clinical case series is to describe the efficacy and safety of nusinersen in treating spinal muscular atrophy in 20 pediatric and 18 adult patients across six treatment centers in Kuwait. Functional motor assessments (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders, Hammersmith Functional Motor Scale Expanded, and Revised Upper Limb Module) were used to assess changes in motor function following nusinersen treatment. The safety assessment involved clinical monitoring of adverse events. The results demonstrate clinically meaningful or considerable improvement in motor performance for nearly all patients, lasting over 4 years in some cases. A total of 70% of patients in the pediatric cohort and 72% of patients in the adult cohort achieved a clinically meaningful improvement in motor function following nusinersen treatment. Additionally, nusinersen was well-tolerated in both cohorts. These findings add to the growing body of evidence relating to the clinical efficacy and safety of nusinersen.

Assessment of Barriers to Referral and Appointment Wait Times for the Evaluation of Spinal Muscular Atrophy (SMA): Findings from a Web-Based Physician Survey

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by progressive muscle weakness and atrophy. Clinical trial data suggest early diagnosis and treatment are critical. The purpose of this study was to evaluate neurology appointment wait times for newborn screening identified infants, pediatric cases mirroring SMA symptomatology, and cases in which SMA is suspected by the referring physician. Approaches for triaging and expediting referrals in the US were also explored.

METHODS

Cure SMA surveyed healthcare professionals from two cohorts: (1) providers affiliated with SMA care centers and (2) other neurologists, pediatric neurologists, and neuromuscular specialists. Surveys were distributed directly and via Medscape Education, respectively, between July 9, 2020, and August 31, 2020.

RESULTS

Three hundred five total responses were obtained (9% from SMA care centers and 91% from the general recruitment sample). Diagnostic journeys were shorter for infants eventually diagnosed with SMA Type 1 if they were referred to SMA care centers versus general sample practices. Appointment wait times for infants exhibiting "hypotonia and motor delays" were significantly shorter at SMA care centers compared to general recruitment practices (p = 0.004). Furthermore, infants with SMA identified through newborn screening were also more likely to be seen sooner if referred to a SMA care center versus a general recruitment site. Lastly, the majority of both cohorts triaged incoming referrals. The average wait time for infants presenting at SMA care centers with "hypotonia and motor delay" was significantly shorter when initial referrals were triaged using a set of "key emergency words" (p = 0.036).

CONCLUSIONS

Infants directly referred to a SMA care center versus a general sample practice were more likely to experience shorter SMA diagnostic journeys and appointment wait times. Triage guidelines for referrals specific to "hypotonia and motor delay" including use of "key emergency words" may shorten wait times and support early diagnosis and treatment of SMA.

Non-Invasive Spinal Cord Stimulation for Motor Rehabilitation of Patients with Spinal Muscular Atrophy Treated with Orphan Drugs

Spinal muscular atrophy (SMA) is an orphan disease characterized by the progressive degeneration of spinal alpha motor neurons. In recent years, nusinersen and several other drugs have been approved for the treatment of this disease. Transcutaneous spinal cord stimulation (tSCS) modulates spinal neuronal networks, resulting in changes in locomotion and posture in patients with severe spinal cord injury and stroke. We hypothesize that tSCS can activate motor neurons that are intact and restored by medication, slow the decline in motor activity, and contribute to the development of motor skills in SMA patients. Thirty-seven children and adults with SMA types 2 and 3 participated in this study. The median duration of drug treatment was over 20 months. The application of tSCS was performed during physical therapy for 20-40 min per day for ~12 days. Outcome measures were specific SMA motor scales, goniometry of contractured joints, and forced vital capacity. Significant increases in motor function, improved respiratory function, and decreased contracture were observed in both type 2 and 3 SMA participants. The magnitude of functional changes was not associated with participant age. Further studies are needed to elucidate the reasons for the beneficial effects of spinal cord electrical stimulation on SMA.

Monitoring spinal muscular atrophy with three-dimensional optoacoustic imaging

BACKGROUND

Spinal muscular atrophy is a progressive neuromuscular disorder and among the most frequent genetic causes of infant mortality. While recent advancements in gene therapy provide the potential to ameliorate the disease severity, there is currently no modality in clinical use to visualize dynamic pathophysiological changes in disease progression and regression after therapy.

METHODS

In this prospective diagnostic clinical study, ten pediatric patients with spinal muscular atrophy and ten age- and sex-matched controls have been examined with three-dimensional optoacoustic imaging and clinical standard examinations to compare the spectral profile of muscle tissue and correlate it with motor function (ClinicalTrials.gov: NCT04115475).

FINDINGS

We observed a reduced optoacoustic signal in muscle tissue of pediatric patients with spinal muscular atrophy. The reduction in signal intensity correlated with disease severity as assessed by grayscale ultrasound and standard motor function tests. In a cohort of patients who received disease-modifying therapy prior to the study, the optoacoustic signal intensity was similar to healthy controls.

CONCLUSIONS

This translational study provides early evidence that three-dimensional optoacoustic imaging could have clinical implications in monitoring disease activity in spinal muscular atrophy. By visualizing and quantifying molecular changes in muscle tissue, disease progression and effects of gene therapy can be assessed in real time.

FUNDING

The project was funded by ELAN Fonds (P055) at the University Hospital of the Friedrich-Alexander-Universität (FAU) Erlangen-Nurnberg to A.P.R.

Hepatocyte-intrinsic SMN deficiency drives metabolic dysfunction and liver steatosis in spinal muscular atrophy

Spinal Muscular Atrophy (SMA) is typically characterized as a motor neuron disease, but extra-neuronal phenotypes are present in almost every organ in severely affected patients and animal models. Extra-neuronal phenotypes were previously underappreciated as patients with severe SMA phenotypes usually died in infancy; however, with current treatments for motor neurons increasing patient lifespan, impaired function of peripheral organs may develop into significant future comorbidities and lead to new treatment-modified phenotypes. Fatty liver is seen in SMA animal models , but generalizability to patients and whether this is due to hepatocyte-intrinsic Survival Motor Neuron (SMN) protein deficiency and/or subsequent to skeletal muscle denervation is unknown. If liver pathology in SMA is SMN-dependent and hepatocyte-intrinsic, this suggests SMN repleting therapies must target extra-neuronal tissues and motor neurons for optimal patient outcome. Here we showed that fatty liver is present in SMA and that SMA patient-specific iHeps were susceptible to steatosis. Using proteomics, functional studies and CRISPR/Cas9 gene editing, we confirmed that fatty liver in SMA is a primary SMN-dependent hepatocyte-intrinsic liver defect associated with mitochondrial and other hepatic metabolism implications. These pathologies require monitoring and indicate need for systematic clinical surveillance and additional and/or combinatorial therapies to ensure continued SMA patient health.

Efficacy and safety of onasemnogene abeparvovec for the treatment of patients with spinal muscular atrophy type 1: A systematic review with meta-analysis

BACKGROUND

Onasemnogene abeparvovec has been approved for the treatment of spinal muscular atrophy 5q type 1 in several countries, which calls for an independent assessment of the evidence regarding efficacy and safety.

OBJECTIVE

Conduct a meta-analysis to assess the efficacy and safety of onasemnogene abeparvovec in patients diagnosed with SMA type 1, based on the available evidence.

METHODS

This article results from searches conducted on databases up to November 2022. Outcomes of interest were global survival and event-free survival, improvement in motor function and treatment-related adverse events. Risk of bias assessment and certainty of evidence were performed for each outcome. Proportional meta-analysis models were performed when applicable.

RESULTS

Four reports of three open-label, non-comparative clinical trials covering 67 patients were included. Meta-analyses of data available in a 12-month follow-up estimate a global survival of 97.56% (95%CI: 92.55 to 99.86, I2 = 0%, n = 67), an event-free survival of 96.5% (95%CI: 90.76 to 99.54, I2 = 32%, n = 66) and a CHOP-INTEND score ≥ 40 points proportion of 87.28% (95%CI: 69.81 to 97.83, I2 = 69%, n = 67). Proportion of 52.64% (95%CI: 27.11 to 77.45, I2 = 78%, n = 67) of treatment-related adverse events was estimated.

CONCLUSION

The results indicate a potential change in the natural history of type 1 SMA, but the methodological limitations of the studies make the real extent of the technology's long-term benefits uncertain.

5qSMA: standardised retrospective natural history assessment in 268 patients with four copies of SMN2

Newborn screening for 5qSMA offers the potential for early, ideally pre-symptomatic, therapeutic intervention. However, limited data exist on the outcomes of individuals with 4 copies of SMN2, and there is no consensus within the SMA treatment community regarding early treatment initiation in this subgroup. To provide evidence-based insights into disease progression, we performed a retrospective analysis of 268 patients with 4 copies of SMN2 from the SMArtCARE registry in Germany, Austria and Switzerland. Inclusion criteria required comprehensive baseline data and diagnosis outside of newborn screening. Only data prior to initiation of disease-modifying treatment were included. The median age at disease onset was 3.0 years, with a mean of 6.4 years. Significantly, 55% of patients experienced symptoms before the age of 36 months. 3% never learned to sit unaided, a further 13% never gained the ability to walk independently and 33% of ambulatory patients lost this ability during the course of the disease. 43% developed scoliosis, 6.3% required non-invasive ventilation and 1.1% required tube feeding. In conclusion, our study, in line with previous observations, highlights the substantial phenotypic heterogeneity in SMA. Importantly, this study provides novel insights: the median age of disease onset in patients with 4 SMN2 copies typically occurs before school age, and in half of the patients even before the age of three years. These findings support a proactive approach, particularly early treatment initiation, in this subset of SMA patients diagnosed pre-symptomatically. However, it is important to recognize that the register will not include asymptomatic individuals.

Early spinal muscular atrophy treatment following newborn screening: A 20-month review of the first Italian regional experience

OBJECTIVES

Mandatory newborn screening (NBS) for spinal muscular atrophy (SMA) was implemented for the first time in Italy at the end of 2021, allowing the identification and treatment of patients at an asymptomatic stage.

METHODS

DNA samples extracted from dried blood spot (DBS) from newborns in Apulia region were analysed for SMA screening by using a real-time PCR-based assay. Infants harbouring homozygous deletion of SMN1 exon 7 confirmed by diagnostic molecular tests underwent clinical and neurophysiological assessment and received a timely treatment.

RESULTS

Over the first 20 months since regional NBS introduction, four out of 42,492 (0.009%) screened children were found to carry a homozygous deletion in the exon 7 of SMN1 gene, with an annual incidence of 1:10,623. No false negatives were present. Median age at diagnosis was 7 days and median age at treatment was 20.5 days. Three of them had two copies of SMN2 and received gene therapy, while the one with three SMN2 copies was treated with nusinersen. All but one were asymptomatic at birth, showed no clinical signs of disease after a maximum follow-up of 16 months and reached motor milestones appropriate with their age. The minimum interval between diagnosis and the treatment initiation was 9 days.

INTERPRETATION

The timely administration of disease-modifying therapies prevented presymptomatic subjects to develop disease symptoms. Mandatory NBS for SMA should be implemented on a national scale.

Diagnosis of Challenging Spinal Muscular Atrophy Cases with Long-Read Sequencing

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder primarily caused by the deletion or mutation of the survival motor neuron 1 (SMN1) gene. This study assesses the diagnostic potential of long-read sequencing (LRS) in three patients with SMA. For Patient 1, who has a heterozygous SMN1 deletion, LRS unveiled a missense mutation in SMN1 exon 5. In Patient 2, an Alu/Alu-mediated rearrangement covering the SMN1 promoter and exon 1 was identified through a blend of multiplex ligation-dependent probe amplification, LRS, and PCR across the breakpoint. The third patient, born to a consanguineous family, bore four copies of hybrid SMN genes. LRS determined the genomic structures, indicating two distinct hybrids of SMN2 exon 7 and SMN1 exon 8. However, a discrepancy was found between the SMN1/SMN2 ratio interpretations by LRS (0:2) and multiplex ligation-dependent probe amplification (0:4), which suggested a limitation of LRS in SMA diagnosis. In conclusion, this newly adapted long PCR-based third-generation sequencing introduces an additional avenue for SMA diagnosis.

Molecular Biomarkers of Neurodegenerative Disorders: A Practical Guide to Their Appropriate Use and Interpretation in Clinical Practice

Neurodegenerative disorders (NDs) represent a group of different diseases characterized by the progressive degeneration and death of the nervous system's cells. The diagnosis is challenging, especially in the early stages, due to no specific clinical signs and symptoms. In this context, laboratory medicine could support clinicians in detecting and differentiating NDs. Indeed, biomarkers could indicate the pathological mechanisms underpinning NDs. The ideal biofluid for detecting the biomarkers of NDs is cerebrospinal fluid (CSF), which has limitations, hampering its widespread use in clinical practice. However, intensive efforts are underway to introduce high-sensitivity analytical methods to detect ND biomarkers in alternative nonivasive biofluid, such as blood or saliva. This study presents an overview of the ND molecular biomarkers currently used in clinical practice. For some diseases, such as Alzheimer's disease or multiple sclerosis, biomarkers are well established and recommended by guidelines. However, for most NDs, intensive research is ongoing to identify reliable and specific biomarkers, and no consensus has yet been achieved.

Adeno-associated virus as a delivery vector for gene therapy of human diseases

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

Administration of adipose-derived stem cells extracellular vesicles in a murine model of spinal muscular atrophy: effects of a new potential therapeutic strategy

BACKGROUND

Spinal Muscular Atrophy (SMA) is an autosomal-recessive neuromuscular disease affecting children. It is caused by the mutation or deletion of the survival motor neuron 1 (SMN1) gene resulting in lower motor neuron (MN) degeneration followed by motor impairment, progressive skeletal muscle paralysis and respiratory failure. In addition to the already existing therapies, a possible combinatorial strategy could be represented by the use of adipose-derived mesenchymal stem cells (ASCs) that can be obtained easily and in large amounts from adipose tissue. Their efficacy seems to be correlated to their paracrine activity and the production of soluble factors released through extracellular vesicles (EVs). EVs are important mediators of intercellular communication with a diameter between 30 and 100 nm. Their use in other neurodegenerative disorders showed a neuroprotective effect thanks to the release of their content, especially proteins, miRNAs and mRNAs.

METHODS

In this study, we evaluated the effect of EVs isolated from ASCs (ASC-EVs) in the SMNΔ7 mice, a severe SMA model. With this purpose, we performed two administrations of ASC-EVs (0.5 µg) in SMA pups via intracerebroventricular injections at post-natal day 3 (P3) and P6. We then assessed the treatment efficacy by behavioural test from P2 to P10 and histological analyses at P10.

RESULTS

The results showed positive effects of ASC-EVs on the disease progression, with improved motor performance and a significant delay in spinal MN degeneration of treated animals. ASC-EVs could also reduce the apoptotic activation (cleaved Caspase-3) and modulate the neuroinflammation with an observed decreased glial activation in lumbar spinal cord, while at peripheral level ASC-EVs could only partially limit the muscular atrophy and fiber denervation.

CONCLUSIONS

Our results could encourage the use of ASC-EVs as a therapeutic combinatorial treatment for SMA, bypassing the controversial use of stem cells.

Utility of exome sequencing for the diagnosis of pediatric-onset neuromuscular diseases beyond diagnostic yield: a narrative review

Diagnosis of neuromuscular diseases (NMD) can be challenging because of the heterogeneity of this group of diseases. This review aimed to describe the diagnostic yield of whole exome sequencing (WES) for pediatric-onset neuromuscular disease diagnosis, as well as other benefits of this approach in patient management since WES can contribute to appropriate treatment selection in NMD patients. WES increases the possibility of reaching a conclusive genetic diagnosis when other technologies have failed and even exploring new genes not previously associated with a specific NMD. Moreover, this strategy can be useful when a dual diagnosis is suspected in complex congenital anomalies and undiagnosed cases.

No significant sex differences in incidence or phenotype for the SMNΔ7 mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive disease that affects 1 out of every 6,000-10,000 individuals at birth, making it the leading genetic cause of infant mortality. In recent years, reports of sex differences in SMA patients have become noticeable. The SMNΔ7 mouse model is commonly used to investigate pathologies and treatments in SMA. However, studies on sex as a contributing biological variable are few and dated. Here, we rigorously investigated the effect of sex on a series of characteristics in SMA mice of the SMNΔ7 model. Incidence and lifespan of 23 mouse litters were tracked and phenotypic assessments were performed at 2-day intervals starting at postnatal day 6 for every pup until the death of the SMA pup(s) in each litter. Brain weights were also collected post-mortem. We found that male and female SMA incidence does not differ significantly, survival periods are the same across sexes, and there was no phenotypic difference between male and female SMA pups, other than for females exhibiting lesser body weights at early ages. Overall, this study ensures that sex is not a biological variable that contributes to the incidence ratio or disease severity in the SMNΔ7 mouse model.

Development of a low-cost and accurate carrier screening method for spinal muscular atrophy in developing countries

Heterozygous carriers of the survival of motor neuron 1 (SMN1) gene deletion in parents account for approximately 95% of neonatal spinal muscular atrophy cases. Given the severity of the disease, professional organizations have recommended periconceptional spinal muscular atrophy carrier screening to all couples, regardless of race or ethnicity. However, the prevalence of screening activities in mainland China remains suboptimal, mainly attributed to the limitations of the existing carrier screening methods. Herein, we aimed to develop a low-cost, accessible, and accurate carrier screening method based on duplex droplet digital PCR (ddPCR), to cover a wider population in developing countries, including China. The receiver operating characteristic curve was used to determine the cut-off value of SMN1 copy numbers. Performance validation was conducted for linearity, precision, and accuracy. In total, 482 cases were considered to validate the concordance between the developed ddPCR assay and multiplex ligation-dependent probe amplification. Linear correlations were excellent between the expected concentration of the reference gene and the observed values (R2 > 0.99). Both the intra- and inter-assay precision of our ddPCR assays were less than 6.0%. The multiplex ligation-dependent probe amplification and ddPCR results were consistent in 480 of the 482 cases (99.6%). Two cases with multiplex ligation-dependent probe amplification, suggestive of two copies of SMN1 exon 7, were classified into three copies by ddPCR analysis. The overall correct classification of the samples included in our ddPCR assay was 100%. This study demonstrates that an appropriate cut-off value is an important prerequisite for establishing a semi-quantitative method to determine the SMN1 copy numbers. Compared to conventional methods, our ddPCR assay is low-cost, highly accurate, and has full potential for application in population spinal muscular atrophy carriers screening.

Neurodegeneration Biomarkers in Adult Spinal Muscular Atrophy (SMA) Patients Treated with Nusinersen

The objective of this study is to evaluate biomarkers for neurodegenerative disorders in adult SMA patients and their potential for monitoring the response to nusinersen. Biomarkers for neurodegenerative disorders were assessed in plasma and CSF samples obtained from a total of 30 healthy older adult controls and 31 patients with adult SMA type 2 and 3. The samples were collected before and during nusinersen treatment at various time points, approximately at 2, 6, 10, and 22 months. Using ELISA technology, the levels of total tau, pNF-H, NF-L, sAPPβ, Aβ40, Aβ42, and YKL-40 were evaluated in CSF samples. Additionally, plasma samples were used to measure NF-L and total tau levels using SIMOA technology. SMA patients showed improvements in clinical outcomes after nusinersen treatment, which were statistically significant only in walkers, in RULM (p = 0.04) and HFMSE (p = 0.05) at 24 months. A reduction in sAPPβ levels was found after nusinersen treatment, but these levels did not correlate with clinical outcomes. Other neurodegeneration biomarkers (NF-L, pNF-H, total tau, YKL-40, Aβ40, and Aβ42) were not found consistently changed with nusinersen treatment. The slow progression rate and mild treatment response of adult SMA types 2 and 3 may not lead to detectable changes in common markers of axonal degradation, inflammation, or neurodegeneration, since it does not involve large pools of damaged neurons as observed in pediatric forms. However, changes in biomarkers associated with the APP processing pathway might be linked to treatment administration. Further studies are warranted to better understand these findings.

A Real-World Study of Nusinersen Effects in Adults with Spinal Muscular Atrophy Type 2 and 3

BACKGROUND

Spinal muscular atrophy (SMA) is a progressive genetic disorder characterized by muscle weakness ultimately leading to pulmonary impairments that can be fatal. The recent approval of nusinersen, a disease-modifying therapy, substantially changed the prognosis for patients, particularly in children. However, real-world evidence about its long-term effectiveness in adults remains limited. This study aimed to document longitudinal data on motor function, pulmonary function and patient-reported outcome measures of Canadian adults with SMA type 2 and 3 treated with nusinersen.

METHODS

Outcomes from 17 patients were collected at the Institut de réadaptation en déficience physique de Québec during routine clinical visits over 36 months post nusinersen treatment, using the Hammersmith Functional Motor Scale Expanded for SMA (HFMSE), Revised Upper Limb Module (RULM), 6-Minute Walk Test (6MWT), Children's Hospital of Philadelphia Adult Test of Neuromuscular Disorders (CHOP-ATEND), SMA functional rating scale (SMAFRS), pulmonary function testing and subjective changes reported by patients.

RESULTS

After 36 months, 9 patients showed motor function improvement. Changes beyond the minimal clinically important difference were seen for four patients on the HFMSE, four patients on the RULM and five patients on the 6MWT. Pulmonary function remained stable for most subjects. Subjective positive changes were reported in 88% of patients and five patients showed improvement in the SMAFRS.

CONCLUSION

This real-world study demonstrates the positive effects of nusinersen in adults with SMA types 2 and 3. Although stabilizing the patient's condition is considered therapeutic success, this study shows an improvement in motor function and subjective gains in several patients.

Vaccination proposal for patients on onasemnogene abeparvovec therapy

The approval of disease-modifying treatment in spinal muscular atrophy made the condition less severe. The course of the disease changed, but some new concerns occurred with the different new therapies. The side effects of onasemnogene aboparvovec therapy can raise differential diagnostic challenges and necessitate immune therapy, leading to immunosuppression affecting response to vaccines. We provide a pretherapy screening proposal from an infectological point of view separately for newborns treated presymptomatically and children diagnosed with symptoms at any age. Furthermore, we summarise the guidelines on the vaccination before, during, and after immune therapy (steroids) in onasemnogene aboparvovec-treated patients.

Cost-Effectiveness of Onasemnogene Abeparvovec Compared With Nusinersen and Risdiplam in Patients With Spinal Muscular Atrophy Type 1 in Brazil: Custo-Efetividade do Onasemnogeno Abeparvoveque (AVXS-101) em Comparação ao Nusinersena e Risdiplam em Pacientes com Atrofia Muscular Espinhal Tipo 1 no Brasil

OBJECTIVES

This study aimed to evaluate the cost-effectiveness of the onasemnogene abeparvovec in relation to nusinersen and risdiplam in the treatment of spinal muscular atrophy type 1 from the perspective of the Brazilian Unified Health System.

METHODS

A Markov model was built on a lifetime horizon. Short-term data were obtained from clinical trials of the technologies and from published cohort survival curves (long term). Costs were measured in current 2022 local currency (R$) values and benefits in quality-adjusted life-years (QALYs). Utility values were derived from type 1 spinal muscular atrophy literature, whereas costs related to technologies and maintenance care in each health state were obtained from official sources of reimbursement in Brazil. Deterministic and probabilistic, as well as scenario, sensitivity analyses were performed.

RESULTS

Compared with the less costly strategy (nusinersen), the use of onasemnogene abeparvovec resulted in an incremental cost of R$2.468.448,06 ($975 671.169 - purchasing power parity [PPP]) and a 3-QALY increment and incremental cost-effectiveness ratio of R$742.890,92 ($293 632.774 - PPP)/QALY. Risdiplam had an extended dominance from other strategies, resulting in an incremental cost-effectiveness ratio of R$926.586,22 ($366 239.612 - PPP)/QALY compared with nusinersen. Sensitivity analysis showed a significant impact of the follow-up time of the cohort and the cost of acquiring onasemnogene abeparvovec.

CONCLUSIONS

Over a lifetime horizon, onasemnogene abeparvovec seems to be a potentially more effective option than nusinersen and risdiplam, albeit with an incremental cost. Such a trade-off should be weighed in efficiency criteria during decision making and outcome monitoring from the perspective of the Brazilian Unified Health System.

Variability in Newborn Screening Across Canada: Spinal Muscular Atrophy and Beyond

BACKGROUND

Newborn screening (NBS) identifies infants with severe, early-onset diseases, enabling early diagnosis and treatment. In Canada, decisions regarding disease inclusion in NBS programs occur at the provincial level, which leads to variability in patient care. We aimed to determine whether important differences exist in NBS programs across provinces and territories. Given that spinal muscular atrophy (SMA) is the most recent disease added to NBS programs, we hypothesized that its inclusion would show interprovincial variability and be more likely in provinces already screening for a greater number of diseases.

METHODS

We conducted a cross-sectional survey of all NBS labs in Canada to understand: 1) what conditions were included in their program; 2) what genetic-based testing was performed and; 3) if SMA was included.

RESULTS

All NBS programs (N = 8) responded to this survey by June 2022. There was a 2.5-fold difference in the number of conditions screened (N = 14 vs N = 36) and a 9-fold difference in the number of conditions screened by gene-based testing. Only nine conditions were common to all provincial NBS programs. NBS for SMA was performed in four provinces at the time of our survey, with BC recently becoming the fifth province to add SMA to their NBS on October 1, 2022. Currently, 72% of Canadian newborns are screened for SMA at birth.

CONCLUSION

Although healthcare in Canada is universal, its decentralization gives rise to regional differences in NBS programs which creates inequity in the treatment, care, and potential outcomes of affected children across provincial jurisdictions.

Multiplex Real-Time PCR-Based Newborn Screening for Severe Primary Immunodeficiency and Spinal Muscular Atrophy in Osaka, Japan: Our Results after 3 Years

In newborn screening (NBS), it is important to consider the availability of multiplex assays or other tests that can be integrated into existing systems when attempting to implement NBS for new target diseases. Recent developments in innovative testing technology have made it possible to simultaneously screen for severe primary immunodeficiency (PID) and spinal muscular atrophy (SMA) using quantitative real-time polymerase chain reaction (qPCR) assays. We describe our experience of optional NBS for severe PID and SMA in Osaka, Japan. A multiplex TaqMan qPCR assay was used for the optional NBS program. The assay was able to quantify the levels of T-cell receptor excision circles and kappa-deleting recombination excision circles, which is useful for severe combined immunodeficiency and B-cell deficiency screening, and can simultaneously detect the homozygous deletion of SMN1 exon 7, which is useful for NBS for SMA. In total, 105,419 newborns were eligible for the optional NBS program between 1 August 2020 and 31 August 2023. A case each of X-linked agammaglobulinemia and SMA were diagnosed through the optional NBS and treated at early stages (before symptoms appeared). Our results show how multiplex PCR-based NBS can benefit large-scale NBS implementation projects for new target diseases.

Motor and neurocognitive profiles of children with symptomatic spinal muscular atrophy type 1 with two copies of SMN2 before and after treatment: a longitudinal observational study

Introduction

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by mutations in the survival motor neuron 1 (SMN1) gene. In clinical studies, gene replacement therapy with onasemnogene abeparvovec (formerly AVXS-101, Zolgensma®, Novartis) was efficacious in improving motor functioning in children with SMA. However, its effects on cognitive and language skills are largely unknown.

Methods

This longitudinal observational study evaluated changes in motor and neurocognitive functioning over a 1-year period after administration of onasemnogene abeparvovec in 12 symptomatic SMA type 1 patients with two copies of SMN2 aged 1.7-52.6 months at administration. Motor functioning was measured using the Children's Hospital of Philadelphia Infant Test for Neuromuscular Disorders (CHOP-INTEND) while neurocognitive assessment was measured using Griffiths III. Motor milestones and language ability were also assessed at each timepoint.

Results and discussion

Statistically significant increases in median CHOP-INTEND scores from baseline were observed at 1, 3, 6, and 12 months after onasemnogene abeparvovec administration (all p ≤ 0.005). Most (91.7%) patients were able to roll over or sit independently for >1 min at 12 months. Significant increases in the Griffiths III Foundations of Learning, Language and Communication, Eye and Hand Coordination, and Personal-Social-Emotional subscale scores were observed at 12-months, but not in the Gross Motor subscale. Speech and language abilities progressed in most patients. Overall, most patients showed some improvement in cognitive and communication performance after treatment with onasemnogene abeparvovec in addition to significant improvement in motor functioning and motor milestones. Evaluation of neurocognitive function should be considered when assessing the global functioning of patients with SMA.