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

Onasemnogene abeparvovec for the treatment of spinal muscular atrophy

INTRODUCTION

Gene therapy for spinal muscular atrophy (SMA) represents a significant milestone in the treatment of neurologic diseases. SMA is a neurodegenerative disease that results in motor neuron loss because of mutations of the survival motor neuron 1 gene, which directs survival motor neuron (SMN) protein production. Onasemnogene abeparvovec, a one-time gene replacement therapy, delivers a functional transgene to restore SMN protein expression. Onasemnogene abeparvovec has demonstrated improved survival and motor milestone achievements for presymptomatic infants and patients with SMA type 1.

AREAS COVERED

This expert review describes the current state of gene therapy for SMA, reviews the mechanism of and clinical experience with onasemnogene abeparvovec, explains future efforts to expand applications of gene therapy for SMA, and provides context for developing gene therapy for other conditions.

EXPERT OPINION

Onasemnogene abeparvovec has demonstrated efficacy in clinical trials and, because of this, is a valuable treatment option for patients with symptomatic infantile SMA and those identified by newborn screening. Gene therapy is still in its infancy, and challenges and uncertainties associated with transgene delivery must be addressed. With ongoing development of vector technology, more specific tissue tropism, reduced "off-target" effects, and an enhanced safety profile will continue to evolve.

Systematic Literature Review to Assess the Cost and Resource Use Associated with Spinal Muscular Atrophy Management

BACKGROUND

Spinal muscular atrophy (SMA) is a severe neuromuscular disease that is inherited in an autosomal recessive manner with an estimated incidence of 1 in 10,000 live births. The traditional classification of SMA includes five types (Types 0-4 SMA) based on patient age at disease onset and the highest motor milestone achieved. Spinal muscular atrophy leads to progressive muscle denervation, skeletal muscle atrophy and loss of motor function and ambulation, though phenotypes vary along a disease continuum. Regardless of disease severity, or access to treatment, a multidisciplinary approach to care is required to ease the burden of disease. To date, limited global data exist regarding the cost and resource use associated with SMA management.

OBJECTIVE

We planned to perform a systematic literature review to identify studies on cost and healthcare resource use associated with SMA.

METHODS

A comprehensive search was conducted in 2019 using several electronic databases in addition to supplementary sources and updated in 2021 in order to capture recently published studies. Electronic searches performed in Embase, MEDLINE, Evidence-Based Medicine Reviews and EconLit via the Ovid platform were supplemented by searches of the grey literature (reference lists, conference proceedings, global Health Technology Assessment body websites and other relevant sources). Study eligibility criteria were based on the population, interventions, comparators and outcomes (PICO) framework. Quality assessment of full-text publications was evaluated with reference to a published checklist. To accommodate heterogeneity across studies including countries, currencies, populations, time units and methods of reporting used, costs were reported in Euros in 2019.

RESULTS

A total of 51 publications, comprising 49 unique studies of patients with SMA that met all eligibility criteria were included in the final selection. The publications comprised data from 14 countries and seven additional studies that reported multi-national data. Because of the heterogeneity between the different types of SMA, data were frequently reported separately for individuals with Type 1 or early-onset SMA and for Types 2, 3, and 4 SMA or later-onset SMA. Generally, direct medical costs and resource use were reported to be highest for patients with Type 1 SMA, decreasing incrementally for patients with Type 2 and Type 3 disease. Where cost categories were similar, direct costs were much lower in Europe than in the USA. Indirect costs were primarily associated with informal care, which was a substantial burden on patients and families in terms of both cost and time. Cost drivers were generally found to be dependent on SMA type.

CONCLUSIONS

Long-term robust studies are required to fully elucidate the economic burden of SMA. Considering that motor function can vary broadly, especially in Type 2 SMA, it would be beneficial to understand how costs and resource use are affected by different degrees of ambulation. Reporting data in terms of achieved motor function could also mitigate the challenges of comparing global data studies of small populations. Global, regional, and/or local data collection platforms and disease registry networks could play an important role in helping to address current data gaps.

Risdiplam: A Review in Spinal Muscular Atrophy

Risdiplam (Evrysdi^®) is the first oral drug developed to treat spinal muscular atrophy (SMA) and is approved in multiple countries worldwide. It is approved for the treatment of SMA in patients aged ≥ 2 months in the USA and the EU, with this approval further specified in the EU for the treatment of 5q-autosomal recessive SMA with a clinical diagnosis of SMA types 1, 2, or 3 or with one to four survival motor neuron 2 (SMN2) copies. As an SMN2 pre-mRNA splicing modifier, risdiplam increases the production of full-length SMN protein, the lack of which drives the pathophysiology of SMA. In phase 2/3 clinical trials, risdiplam significantly improved motor function in infants with SMA type 1 and in patients aged 2-25 years with SMA types 2 or 3. These motor improvements were maintained with up to 2 years of treatment with risdiplam. Risdiplam was generally well tolerated, with a favourable benefit to risk balance. As an oral drug, risdiplam provides a convenient and useful treatment option across a broad range of patient ages and subtypes of SMA.

Systematic Literature Review to Identify Utility Values in Patients with Spinal Muscular Atrophy (SMA) and Their Caregivers

BACKGROUND

Spinal muscular atrophy (SMA) is a progressive neuromuscular disorder that has a substantial impact on health-related quality of life for patients with SMA and their caregivers. Utility values ('utilities') are used in health economic analyses to incorporate individual or societal perspectives regarding the desirability of health outcomes such as a certain health state or change in health states over time.

OBJECTIVES

The primary objective of this systematic literature review (SLR) was to identify published utilities associated with patients with SMA and their caregivers and to determine the extent to which Health Technology Assessment (HTA) requirements of methods used to generate utilities are met. A secondary objective was to broaden the scope to identify utilities associated with other (non-SMA) neuromuscular disorders.

METHODS

A comprehensive search to capture published utilities associated with patients with SMA and their caregivers was performed in 2019 and updated in 2021 using several electronic databases in addition to supplementary sources. As we anticipated that few published utilities associated with SMA would be identified, the search also captured utilities for other (non-SMA) neuromuscular disorders that may serve as useful surrogate values for studies of SMA and other rare diseases. Electronic searches were performed in Embase, MEDLINE, Evidence-Based Medicine Reviews, and EconLit via the Ovid platform and were supplemented by searches of the grey literature (reference lists, conference proceedings, global HTA body websites, and other relevant sources). Study eligibility criteria were based on the population, interventions, comparators, and outcomes (PICO) framework. The quality of the full-text publications was assessed using a checklist based on UK National Institute for Health and Care Excellence technical support documents.

RESULTS

In total, 14 publications that reported SMA-related patient or caregiver utilities or disutilities met the eligibility criteria to be included in the SLR; the included studies demonstrate the substantial health-related quality-of-life burden of SMA on both patients with SMA and their caregivers. A variety of preference-based measures were used to derive utilities for patients with SMA and their caregivers. Different methods for collecting utility data included patient and proxy assessment of health states using questionnaires, vignette methodologies, structured forms of expert elicitation, and mapped data from results of clinical trials. A range of utilities was reported from both patient- and proxy-reported data, which reflects the degree of disability associated with early- and later-onset SMA. Methods for deriving utilities were assessed with respect to three reference cases from HTA bodies in the UK, the USA, and Canada. None of the 14 publications met the requirements of all three HTA bodies because of differing tariff requirements between countries; one study met the requirements of HTA bodies in Canada and the UK. Also, six studies did not report the method of valuation, which precluded analysis with respect to the HTA reference cases.

CONCLUSIONS

This SLR provides a comprehensive repository of the currently available utilities relevant to patients with SMA and their caregivers. This SLR provides recommendations for establishing consensus on the approach to generating utility values for the SMA patient population and their caregivers for health economic decisions.

Frailties and critical issues in neuromuscular diseases highlighted by SARS-CoV-2 pandemic: how many patients are still "invisible"?

Almost 90% of neuromuscular diseases (NMDs) are classified as rare diseases, defined as conditions affecting less than 5 individuals in 10.000 (0.05%). Their rarity and diversity pose specific challenges for healthcare and research. Epidemiological data on NMDs are often lacking and incomplete. The COVID-19 pandemic has further highlighted the management difficulties of NMDs patients and the necessity to continue the program of implementation of standard of care. This article summarizes the Italian experience during pandemic.

Treatment of Adult Spinal Muscular Atrophy: Overview and Recent Developments

Spinal muscular atrophy (SMA) is a rare genetic neuromuscular disease leading to progressive and in many cases severe muscle weakness and atrophy in the natural disease course. An increasing number of gene-based treatment options have become available in recent years. Growing knowledge about the underlying genetic mechanisms makes the disease well amenable to this. Over the past few years, many data on new treatments, their mechanisms of action and therapeutic outcomes have been published, reflecting the current dynamics in this field. With the approval of the antisense oligonucleotide nusinersen, the vector-based therapy with onasemnogene abeparvovec and the small molecule splicing modifier risdiplam, three gene therapeutic drugs are available for the treatment of SMA showing improvement in motor function. But in the pivotal studies several relevant parameters have not been addressed. There is a data gap for the treatment outcome of adult individuals with SMA as well as for several other relevant outcome parameters like bulbary or ventilatory function. With increasing treatment options, additional individual therapies have become necessary. Studies on combination therapies or switch of therapy, e.g. the sequential administration of onasemnogen abeparvovec and nusinersen, are necessary. An overview of current developments in the field of therapeutic options for adult SMA is presented. Important characteristics of each therapeutic option will be discussed so that the reader can comprehend underlying pathophysiological mechanisms as well as advantages and disadvantages of each therapy. The focus is on gene-based treatment options, but options beyond this are also addressed.

Risdiplam: an investigational motor neuron-2 (SMN-2) splicing modifier for spinal muscular atrophy (SMA)

INTRODUCTION

Spinal muscular atrophy (SMA) is a rare autosomal recessive neuromuscular disease which is characterized by muscle atrophy and early death in most patients. Risdiplam is the third overall and first oral drug approved for SMA with disease-modifying potential. Risdiplam acts as a survival motor neuron 2 (SMN2) pre-mRNA splicing modifier with satisfactory safety and efficacy profile. This review aims to critically appraise the place of risdiplam in the map of SMA therapeutics.

AREAS COVERED

This review gives an overview of the current market for SMA and presents the mechanism of action and the pharmacological properties of risdiplam. It also outlines the development of risdiplam from early preclinical stages through to the most recently published results from phase 2/3 clinical trials. Risdiplam has proved its efficacy in pivotal trials for SMA Types 1, 2, and 3 with a satisfactory safety profile.

EXPERT OPINION

In the absence of comparative data with the other two approved drugs, the role of risdiplam in the treatment algorithm of affected individuals is examined in three different patient populations based on the age and diagnosis method (newborn screening or clinical, symptom-driven diagnosis). Long-term data and real-world data will play a fundamental role in its future.

Translation and validation of Indonesian version of Pediatric Quality of Life Inventory™ (PedsQL™) Neuromuscular Module

BACKGROUND

The Pediatric Quality of Life™ 3.0 Neuromuscular Module is an instrument to assess health-related quality of life (HRQoL) among children with neuromuscular diseases (NMDs) aged 2-18 years. This study aimed to determine whether the PedsQL™ 3.0 Neuromuscular Module Indonesian Version is valid and reliable.

METHODS

This study used the Indonesian translation of the PedsQL™ 3.0 Neuromuscular Module after getting formal permission from the inventor, and the translation process followed the Mapi linguistic translation guidelines. This study administered the PedsQL™ 3.0 Neuromuscular Module Indonesian Version to 84 parents and 71 children. In addition, we used the Rasch model to analyze the psychometric properties.

RESULTS

The reliability of the total scale of the PedsQL™ Neuromuscular Module Indonesian Version shows good to very good criteria. On the parent proxy-report, Cronbach alpha was 0.95, person reliability was 0.84, item reliability was 0.93, person separation was 2.32, item separation was 3.61, person strata separation was 4 levels, and item strata separation was 5 levels. On the child self-report, Cronbach alpha was 0.93, person reliability was 0.81, item reliability was 0.81, person separation was 2.08, item separation was 2.06, person strata separation was 3 levels, and item strata separation was 3 levels. The total scale of the PedsQL Neuromuscular Module Indonesian Version shows fair to good construct validity in parent proxy-report (explained variance 51.9%; unexplained variance 8.4%) and child self-report (explained variance 40.9%; unexplained variance 12.6%). There were no misfit items in the parent proxy-report (infit 0.66-1.49; outfit 0.51-1.81; point measure correlation 0.36-0.93) and child self-report (infit 0.53-1.65; outfit 0.50-1.73; point measure correlation 0.31-0.90) identified by the Rasch models.

CONCLUSIONS

The PedsQL™ 3.0 Neuromuscular Modul Indonesian Version is a valid and reliable instrument in measuring HRQoL in Indonesian children with neuromuscular diseases.

SMA carrier testing using Real-time PCR as a potential preconception screening tool

Background

SMA is a neuromuscular genetic disorder causing irreversible degeneration of the anterior horn cells of lower motor neurons. According to the age of onset and severity of the condition, it is classified into 5 subtypes. SMA carrier’s frequency worldwide is 1:40–80. We used quantitative real-time PCR to determine the copy number of the disease-determining SMN1 gene by rapid and reliable assays. We studied the SMN1 gene copy number in Egyptian sample of 115 individuals, as well as in 10 SMA families.

Results

Our results showed that 57.4% of the couples with the previous history of an affected family members were carriers. On the individual level, carriers of single SMN1 gene copy rate are much higher than the previously reported frequency rates. The effect of consanguineous marriages appears evident in SMA as an autosomal recessive disorder.

Conclusions

In conclusion, the carrier frequency detected in our cohort was high, which possibly corresponds with the worldwide report of SMA as a leading genetic cause of death among infants. Considering the high rate of consanguinity in developing countries confirms the importance of national SMA carrier screening in Egypt. The qPCR carrier screening test is a rapid-cost effective test that can detect approximately 90% of carriers. A population-based preconception prenatal screening for couples will also help reduce the disease burden.

Therapeutic decisions under uncertainty for spinal muscular atrophy: The DECISIONS-SMA study protocol

Background

The therapeutic landscape for spinal muscular atrophy has changed in the last few years, encompassing respiratory/motor function and life expectancy benefits. However, physicians still have the challenge of tailoring individuals’ treatment to therapeutic goals, disease progression, patient/caregiver’s preferences, and personal experience to achieve an optimal risk/benefit balance. This study aims to provide insight into the preferred treatment choices of pediatric neurologists managing spinal muscular atrophy in their daily practice and to recognize behavioral factors that may influence decision-making.

Methods

This is a noninterventional, cross-sectional pilot study involving 50 pediatric neurologists managing spinal muscular atrophy in Spain. We designed an online platform that contains 13 simulated case scenarios of common presentations of patients with spinal muscular atrophy. The primary study outcome will be treatment preferences according to the percentages of participants who select treatment initiation when recommended, switch therapies when there is evidence of disease progression, and select treatment discontinuation when disease progression puts patients outside treatment recommendation (11 case scenarios). Secondary outcomes include therapeutic inertia prevalence (11 case scenarios), herding phenomenon prevalence (2 case scenarios), care-related regret prevalence (specific questions) and intensity (10-item Regret Intensity Scale), occupational burnout prevalence (nonproprietary single-item measure), and risk preferences (uncertainty test and risk aversion assessment).

Conclusions

The study findings will contribute to better understand relevant factors associated with therapeutic decisions of pediatric neurologists in spinal muscular atrophy, identifying treatment preferences and evaluating the role of behavioral aspects such as therapeutic inertia, herding, regret, and workplace burnout.

New-Born Screening for Spinal Muscular Atrophy: Results of a Latvian Pilot Study

New disease-modifying treatments have recently been approved for 5q spinal muscular atrophy (SMA) and early treatment has been associated with a better clinical outcome. Accordingly, new-born screening (NBS) for SMA should be implemented to ensure early diagnosis of affected individuals. The aim of this study was to determine the feasibility and usefulness of NBS for SMA in Latvia. Between February and November of 2021, 10,411 parents consented to participation in the study. DNA testing for the SMN1 exon 7 homozygous deletion was conducted using qPCR with fluorescent locked nucleic acid primers. In the first month of testing, reporting of results took up to a maximum of 17 days after samples arrived in the laboratory. However, following familiarisation with the procedure, the median report time was reduced to 11 days after birth. Forty cases required samples to be taken again due to poor quality of the isolated DNA transpiring from either the quality of the blood punch or manual mistakes during DNA isolation. The SMN1 exon 7 homozygous deletion was identified in two individuals, which was subsequently confirmed by multiplex ligation-dependent probe amplification. When a NBS sample is taken 48 to 72 h after birth and transported to the laboratory within two working days after collection according to legal requirements, DNA test results can be reported to healthcare professionals before the 12th day of life. Expansion of our SMA 5q NBS procedure to the whole of Latvia is feasible and would facilitate early diagnosis and result in more effective treatment. We strongly advocate that SMA is added to the national Latvia Recommended Uniform Screening Panel.

Spinal muscular atrophy type 2 patient who survived 61 years: an autopsy case report

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by progressive muscle weakness due to degeneration of lower motor neurons in the anterior horn of the spinal cord. We analyzed autopsy findings of a male patient with SMA type 2 who survived until 61 years of age. Genetic analysis revealed a homozygous deletion of the survival motor neuron (SMN) gene 1 (SMN1) exon 7, confirming the diagnosis of SMA. Results of further analyses indicated that the patient had two copies of the genuine SMN gene 2 (SMN2) and one copy of a hybrid gene containing SMN2 exon 7 and SMN1 exon 8. Pathological examination revealed moderate neuronal loss of the anterior horn and appearance of heterotopic neurons in the lateral funiculus, whereas a few achromatic neurons were notably localized in the anterior horn of the lumbar segment. Microdysgenesis as a consequence of migration disturbance was found in the white matter of the frontal lobe, postulating the possibility of the maldevelopment of the nervous system.

Therapeutic promise of carotenoids as antioxidants and anti-inflammatory agents in neurodegenerative disorders

Neurodegenerative disorders (NDs) including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis have various disease-specific causal factors and pathological features. A very common characteristic of NDs is oxidative stress (OS), which takes place due to the elevated generation of reactive oxygen species during the progression of NDs. Furthermore, the pathological condition of NDs including an increased level of protein aggregates can further lead to chronic inflammation because of the microglial activation. Carotenoids (CTs) are naturally occurring pigments that play a significant role in averting brain disorders. More than 750 CTs are present in nature, and they are widely available in plants, microorganisms, and animals. CTs are accountable for the red, yellow, and orange pigments in several animals and plants, and these colors usually indicate various types of CTs. CTs exert various bioactive properties because of its characteristic structure, including anti-inflammatory and antioxidant properties. Due to the protective properties of CTs, levels of CTs in the human body have been markedly linked with the prevention and treatment of multiple diseases including NDs. In this review, we have summarized the relationship between OS, neuroinflammation, and NDs. In addition, we have also particularly focused on the antioxidants and anti-inflammatory properties of CTs in the management of NDs.

Assessment of Health-Related Quality of Life in Adult Spinal Muscular Atrophy Under Nusinersen Treatment—A Pilot Study

5q-Spinal muscular atrophy (SMA) is a severely disabling inherited neuromuscular disease that progressively reduces the motor abilities of affected individuals. The approval of the antisense oligonucleotide nusinersen, which has been shown to improve motor function in adult SMA patients, changed the treatment landscape. However, little is known about its impact on patients' quality of life (QoL), and there is still a need for adequate patient-reported outcome measures. In this study, we used the short form of the Neuro-QoL (Quality of Life in Neurological Disorders) for upper/lower extremity function to prospectively assess the health-related QoL of 17 adult SMA patients prior to initiation of nusinersen treatment and 2, 6, 10, and 14 months afterwards. At baseline, Neuro-QoL scores strongly correlated with motor function scores (Hammersmith Functional Motor Scale Expanded, HFMSE; Revised Upper Limb Module, RULM), but QoL did not increase significantly during the 14-month treatment period despite significant motor improvement as measured by HFMSE. Our results underline the need for novel, disease-specific assessments of QoL in SMA.

Stability and Oligomerization of Mutated SMN Protein Determine Clinical Severity of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disease characterized by defects of lower motor neurons. Approximately 95% of SMA patients are homozygous for survival motor neuron 1 (SMN1) gene deletion, while ~5% carry an intragenic SMN1 mutation. Here, we investigated the stability and oligomerization ability of mutated SMN1 proteins. Plasmids containing wild- and mutant-type SMN1 cDNA were constructed and transfected into HeLa cells. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated similar abundances of transcripts from the plasmids containing SMN cDNA, but Western blotting showed different expression levels of mutated SMN1 proteins, reflecting the degree of their instability. A mutated SMN1 protein with T274YfsX32 exhibited a much lower expression level than other mutated SMN1 proteins with E134K, Y276H, or Y277C. In immunoprecipitation analysis, the mutated SMN1 protein with T274YfsX32 did not bind to endogenous SMN1 protein in HeLa cells, suggesting that this mutation completely blocks the oligomerization with full-length SMN2 protein in the patient. The patient with T274YfsX32 showed a much more severe phenotype than the other patients with different mutations. In conclusion, the stability and oligomerization ability of mutated SMN1 protein may determine the protein stability and may be associated with the clinical severity of SMA caused by intragenic SMN1 mutation.

Assessing the Value of Nusinersen for Spinal Muscular Atrophy: A Comparative Analysis of Reimbursement Submission and Appraisal in European Countries

Background: Nusinersen is an orphan drug intended for the treatment of spinal muscular atrophy (SMA), a severe genetic neuromuscular disorder. Considering the very high costs of orphan drugs and the expected market entry of cell and gene therapies, there is increased interest in the use of health technology assessment (HTA) for orphan drugs. This study explores the role of the economic evaluation and budget impact analysis on the reimbursement of nusinersen. Methods: Appraisal reports for nusinersen were retrieved from reimbursement and HTA agencies in Belgium, Canada, France, England and Wales, Germany, Italy, Ireland, Scotland, Sweden, the Netherlands, and the United States. Detailed information was extracted on the economic evaluation, the budget impact, the overall reimbursement decision, and the managed entry agreement (MEA). Costs were adjusted for inflation and currency. Results: Overall, the reports included limited data on budget impact, excluding information on the sources of data for cost and patient estimates. Only three jurisdictions reported on total budget impact, estimated between 30 and 40 million euros per year. For early-onset SMA, the incremental cost-effectiveness threshold (ICER) ranged from €464,891 to €6,399,097 per quality-adjusted life year (QALY) gained for nusinersen versus standard of care. For later-onset SMA, the ICER varied from €493,756 to €10,611,936 per QALY. Although none of the jurisdictions found nusinersen to be cost-effective, reimbursement was granted in each jurisdiction. Remarkably, only four reports included arguments in favor of reimbursement. However, the majority of the jurisdictions set up an MEA, which may have promoted a positive reimbursement decision. Conclusion: There is a need for more transparency on the appraisal process and conditions included in the MEA. Additionally, by considering all relevant criteria explicitly during the appraisal process, decision-makers are in a better position to justify their allocation of funds among the rising number of orphan drugs that are coming to the market in the near future.

How does risdiplam compare with other treatments for Types 1-3 spinal muscular atrophy: a systematic literature review and indirect treatment comparison

Aim: To conduct indirect treatment comparisons between risdiplam and other approved treatments for spinal muscular atrophy (SMA). Patients & methods: Individual patient data from risdiplam trials were compared with aggregated data from published studies of nusinersen and onasemnogene abeparvovec, accounting for heterogeneity across studies. Results: In Type 1 SMA, studies of risdiplam and nusinersen included similar populations. Indirect comparison results found improved survival and motor function with risdiplam versus nusinersen. Comparison with onasemnogene abeparvovec in Type 1 SMA and with nusinersen in Types 2/3 SMA was challenging due to substantial differences in study populations; no concrete conclusions could be drawn from the indirect comparison analyses. Conclusion: Indirect comparisons support risdiplam as a superior alternative to nusinersen in Type 1 SMA.

[Spinal muscular atrophy]

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused by biallelic mutations in the SMN1 (survival motor neuron 1) gene on chromosome 5q13.2, which leads to a progressive degeneration of alpha motor neurons in the spinal cord and in motor nerve nuclei in the caudal brainstem. It is characterized by progressive proximally accentuated muscle weakness with loss of already acquired motor skills, areflexia and, depending on the phenotype, varying degrees of weakness of the respiratory and bulbar muscles, although the facial muscles and eye muscles are not affected. The previously purely symptom-oriented treatment has undergone a significant expansion since 2017 with the approval of three drugs (nusinersen, onasemnogene abeparvovec and risdiplam) that modify the course of the disease at the gene expression level and have led to a change in the natural disease course of SMA. The effect of these new forms of treatment can only be fully assessed in the coming years. New aspects and challenges in this context are discussed in this article.

Case report of pregnancy management and genetic evaluation after negative carrier screening for spinal muscular atrophy in an affected family

Background

Screening for spinal muscular atrophy (SMA) is recommended for all pregnant women; however, interpreting the results of carrier screening in the context of family history can be challenging.

Case

We report the case of a 28-year-old woman (G4P3001) with two previous children affected with SMA and negative carrier screening via the Horizon 4 panel. SMN1/2 analysis was pursued to clarify risk for point mutations, carrier screening for her partner, and diagnostic testing for the fetus for SMA. Results of this testing confirmed her status as a silent carrier for SMA and the status of the fetus.

Conclusion

Carrier screening does not account for family history and can therefore generate results inconsistent with known inheritance patterns. In these situations, additional genetic testing and genetic counseling are indicated to clarify risk for SMA in pregnancy and guide prenatal and neonatal healthcare.

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A pregnant woman with two previous children with spinal muscular atrophy (SMA) presented to clinic with negative carrier screening for SMA.

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Additional screening and diagnostic testing of the fetus confirmed the mother's silent carrier status and the fetal status.

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Carrier screening for complex genetic conditions remains limited.

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Genetic testing and reproductive options should be discussed extensively with members of affected families.

The Birth Prevalence of Spinal Muscular Atrophy: A Population Specific Approach in Estonia

Background: Rare diseases are an important population health issue and many promising therapies have been developed in recent years. In light of novel genetic treatments expected to significantly improve spinal muscular atrophy (SMA) patients' quality of life and the urgent need for SMA newborn screening (NBS), new epidemiological data were needed to implement SMA NBS in Estonia. Objective: We aimed to describe the birth prevalence of SMA in the years 1996-2020 and to compare the results with previously published data. Methods: We retrospectively analyzed clinical and laboratory data of SMA patients referred to the Department of Clinical Genetics of Tartu University Hospital and its branch in Tallinn. Results: Fifty-seven patients were molecularly diagnosed with SMA. SMA birth prevalence was 1 per 8,286 (95% CI 1 per 6,130-11,494) in Estonia. Patients were classified as SMA type 0 (1.8%), SMA I (43.9%), SMA II (22.8%), SMA III (29.8%), and SMA IV (1.8%). Two patients were compound heterozygotes with an SMN1 deletion in trans with a novel single nucleotide variant NM_000344.3:c.410dup, p.(Asn137Lysfs*11). SMN2 copy number was assessed in 51 patients. Conclusion: In Estonia, the birth prevalence of SMA is similar to the median birth prevalence in Europe. This study gathered valuable information on the current epidemiology of SMA, which can guide the implementation of spinal muscular atrophy to the newborn screening program in Estonia.

Novel genome-editing-based approaches to treat motor neuron diseases: Promises and challenges

Motor neuron diseases are untreatable with common pharmacological approaches. Spinal muscular atrophy (SMA) is caused by SMN1 gene mutations leading to lowered SMN expression. Symptoms are alleviated in infants with a higher copy number of the SMN2 gene, which, however, displays a splicing defect resulting in low SMN levels. Amyotrophic lateral sclerosis (ALS) is caused by a number of mutations, with C9orf72 repeat expansions the most common genetic cause and SOD1 gain-of-function mutations the first genetic cause identified for this disease. Genetic therapies based on oligonucleotides that enhance SMN2 splicing and SMN production or lower SOD1 expression have shown promise in initial clinical trials for individuals with SMA and ALS harboring SOD1 mutations, respectively. Gene addition/silencing approaches using adeno-associated viruses (AAVs) are also currently under clinical investigation in trials for SMA and ALS. Here we provide a brief overview of these efforts and their advantages and challenges. We also review genome editing approaches aimed at correcting the disease-causing mutations or modulating the expression of genetic modifiers, e.g., by repairing SOD1 mutations or the SMN2 splicing defect or deleting C9orf72 expanded repeats. These studies have shown promising results to approach therapeutic trials that should significantly lower the progression of these deadly disorders.

Therapy development for spinal muscular atrophy: perspectives for muscular dystrophies and neurodegenerative disorders

BACKGROUND

Major efforts have been made in the last decade to develop and improve therapies for proximal spinal muscular atrophy (SMA). The introduction of Nusinersen/Spinraza™ as an antisense oligonucleotide therapy, Onasemnogene abeparvovec/Zolgensma™ as an AAV9-based gene therapy and Risdiplam/Evrysdi™ as a small molecule modifier of pre-mRNA splicing have set new standards for interference with neurodegeneration.

MAIN BODY

Therapies for SMA are designed to interfere with the cellular basis of the disease by modifying pre-mRNA splicing and enhancing expression of the Survival Motor Neuron (SMN) protein, which is only expressed at low levels in this disorder. The corresponding strategies also can be applied to other disease mechanisms caused by loss of function or toxic gain of function mutations. The development of therapies for SMA was based on the use of cell culture systems and mouse models, as well as innovative clinical trials that included readouts that had originally been introduced and optimized in preclinical studies. This is summarized in the first part of this review. The second part discusses current developments and perspectives for amyotrophic lateral sclerosis, muscular dystrophies, Parkinson's and Alzheimer's disease, as well as the obstacles that need to be overcome to introduce RNA-based therapies and gene therapies for these disorders.

CONCLUSION

RNA-based therapies offer chances for therapy development of complex neurodegenerative disorders such as amyotrophic lateral sclerosis, muscular dystrophies, Parkinson's and Alzheimer's disease. The experiences made with these new drugs for SMA, and also the experiences in AAV gene therapies could help to broaden the spectrum of current approaches to interfere with pathophysiological mechanisms in neurodegeneration.

Quality of life assessment in adult spinal muscular atrophy patients treated with nusinersen

OBJECTIVE

To retrospectively evaluate quality of life (QoL) in a large multicenter cohort of adult patients affected by spinal muscular atrophy (SMA) during nusinersen treatment.

METHODS

We included adult (≥ 18 years) patients clinically and genetically defined as SMA2, SMA3 and SMA4, who started nusinersen treatment in adulthood. QoL was rated by the Individualized Neuromuscular Quality of Life (INQoL) questionnaire. Concurrent motor function evaluation included the Hammersmith Functional Motor Scale Expanded (HFMSE), the Revised Upper Limb Module (RULM), the 6 min walking test (6MWT).

RESULTS

189 completed questionnaires were collected during a 14 months' treatment period. 78 patients were included (7 SMA2 and 69 SMA3 and 2 SMA4) with mean disease duration at first nusinersen administration of 33.2 years (± 12.5 years). All the scores for each INQoL domain (weakness, fatigue, activities, independence, social relationship, emotions, body images) and the derived QoL total score, significantly improved during the observation period, except the muscle locking and pain items. Exploratory analyses suggested that emotions and social relationships were more relevant issues for females compared to males. Social relationships were affected also by a longer disease duration (> 30 years). In SMA3 non-walker patients, activities ameliorate better compared to walkers. The HFMSE and RULM significantly improved from baseline; however, no associations with QoL total score and weakness, activities or independence were demonstrated.

CONCLUSION

In our cohort, adult SMA patients showed a global improvement at the INQoL assessment over 14 months of nusinersen treatment. QoL assessment is relevant to SMA multidisciplinary evaluation.

Epidemiological investigation of spinal muscular atrophy in Japan

BACKGROUND

International reporting of epidemiological surveys of spinal muscular atrophy (SMA) in Japan has been limited to Shikoku, despite the epidemiology of the disease in countries worldwide becoming clearer. Treatments of 5q-SMA have been developed, and epidemiological studies are needed.

PURPOSE

This study aimed to conduct a nationwide epidemiological survey of SMA in Japan to clarify the actual situation of SMA in Japan.

METHOD

Patients with all clinical types of SMA, including neonates and adults, were selected from 1,005 medical facilities in Japan.

RESULTS

As of December 2017, the actual number of reported patients with SMA was 658 and the genetic testing rate was 79.5%. The estimated number of patients was 1,478 (95% confidence interval (CI), 1,122-1,834), with a prevalence of 1.17 (95%CI, 0.89-1.45) per 100,000 people and an incidence of 0.51 (95%CI, 0.32-0.71) per 10,000 live births. Incidence rates of 5q-SMA by clinical type were 0.27 (95%CI, 0.17-0.38) and 0.08 (95%CI, 0.04-0.11) per 10,000 live births for type 1 and 2, respectively, in cases with a definitive diagnosis by genetic testing. We found that 363 cases (82.7%) occurred less than 2 years and 88 (20.0%) occurred age of 2 months old or under.

CONCLUSION

This study clarifies the prevalence and incidence of SMA in Japan. As infantile onset accounts for most cases of SMA, newborn screening and subsequent treatment are important to save lives.

Spinal Muscular Atrophy Patient iPSC-Derived Motor Neurons Display Altered Proteomes at Early Stages of Differentiation

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder characterized by loss of motor neurons (MN) in the spinal cord leading to progressive muscle atrophy and weakness. SMA is caused by mutations in the survival motor neuron 1 (SMN1) gene, resulting in reduced levels of survival motor neuron (SMN) protein. The mechanisms that link SMN deficiency to selective motor neuron dysfunction in SMA remain largely unknown. We present here, for the first time, a comprehensive quantitative TMT-10plex proteomics analysis that covers the development of induced pluripotent stem cell-derived MNs from both healthy individuals and SMA patients. We show that the proteomes of SMA samples segregate from controls already at early stages of neuronal differentiation. The altered proteomic signature in SMA MNs is associated with mRNA splicing, ribonucleoprotein biogenesis, organelle organization, cellular biogenesis, and metabolic processes. We highlight several known SMN-binding partners and evaluate their expression changes during MN differentiation. In addition, we compared our study to human and mouse in vivo proteomic studies revealing distinct and similar signatures. Altogether, our work provides a comprehensive resource of molecular events during early stages of MN differentiation, containing potentially therapeutically interesting protein expression profiles for SMA.

Genetic architecture of motor neuron diseases

Motor neuron diseases (MNDs) are rare and frequently fatal neurological disorders in which motor neurons within the brainstem and spinal cord regions slowly die. MNDs are primarily caused by genetic mutations, and > 100 different mutant genes in humans have been discovered thus far. Given the fact that many more MND-related genes have yet to be discovered, the growing body of genetic evidence has offered new insights into the diverse cellular and molecular mechanisms involved in the aetiology and pathogenesis of MNDs. This search may aid in the selection of potential candidate genes for future investigation and, eventually, may open the door to novel interventions to slow down disease progression. In this review paper, we have summarized detailed existing research findings of different MNDs, such as amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), spinal bulbar muscle atrophy (SBMA) and hereditary spastic paraplegia (HSP) in relation to their complex genetic architecture.

Antisense oligonucleotides targeting the SMN2 promoter region enhance SMN2 expression in spinal muscular atrophy cell lines and mouse model

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by homozygous deletions or mutations in survival motor neuron gene 1 (SMN1). Currently, the primary therapeutic strategy for SMA is to increase the level of SMN via correcting SMN2 splicing (nusinersen and risdiplam). However, some patients with SMA do not respond to such treatments, thereby warranting a need to develop new therapeutic strategies. We have previously reported that SMN2 expression is epigenetically regulated by DNA methylation levels of the SMN2 promoter region. In the present study, we determined that methyl-CpG-binding protein 2 (MeCP2) may bind to this critical promoter region (nt-167 to 43). Antisense oligonucleotides (ASO-P1 and ASO-P2) were designed to target the key methylation sites in the SMN2 promoter region, which enhanced the overall transcription and functional protein expression levels in the SMA cell lines. These results were similar to those observed in nusinersen-treated SMA cells. Moreover, a combined treatment of ASO-P1 and ASO-NUS in SMA cell lines further increases fl-SMN2 transcript and SMN protein levels. The delivery of ASO-P1 to the central nervous system of severe SMA mice corrected the molecular, pathological, and functional phenotypes of this disease and increased survival rates. Our findings suggest that the key methylation regions in the SMN2 promoter region may be a novel therapeutic target for SMA.

Combination Therapy with Nusinersen and Onasemnogene Abeparvovec-xioi in Spinal Muscular Atrophy Type I

Background: Spinal muscular atrophy (SMA) is a neuromuscular progressive disease, characterized by decreased amounts of survival motor neuron (SMN) protein, due to an autosomal recessive genetic defect. Despite recent research, there is still no cure. Nusinersen, an antisense oligonucleotide acting on the SMN2 gene, is intrathecally administered all life long, while onasemnogene abeparvovec-xioi, a gene therapy, is administered intravenously only once. Both therapies have proven efficacy, with best outcomes obtained when administered presymptomatically. In recent years, disease-modifying therapies such as nusinersen and onasemnogene abeparvovec-xioi have changed the natural history of SMA. Methods: We observed seven SMA type I patients, who received both therapies. We compared their motor function trajectories, ventilation hours and cough assist sessions to a control group of patients who received one therapy, in order to investigate whether combination therapy may be more effective than a single intervention alone. Results: Patients who received both therapies, compared to the monotherapy cohort, had the same motor function trajectory. Moreover, it was observed that the evolution of motor function was better in the 6 months following the first therapy than in the first 6 months after adding the second treatment. Conclusions: Our results suggest that early treatment is more important than combined therapy.

A novel CARM1-HuR axis involved in muscle differentiation and plasticity misregulated in spinal muscular atrophy

Spinal muscular atrophy (SMA) is characterized by the loss of alpha motor neurons in the spinal cord and a progressive muscle weakness and atrophy. SMA is caused by loss-of-function mutations and/or deletions in the survival of motor neuron (SMN) gene. The role of SMN in motor neurons has been extensively studied, but its function and the consequences of its loss in muscle has also emerged as a key aspect of SMA pathology. In this study, we explore the molecular mechanisms involved in muscle defects in SMA. First, we show in C2C12 myoblasts, that arginine methylation by CARM1 controls myogenic differentiation. More specifically, the methylation of HuR on K217 regulates HuR levels and subcellular localization during myogenic differentiation, and the formation of myotubes. Furthermore, we demonstrate that SMN and HuR interact in C2C12 myoblasts. Interestingly, the SMA-causing E134K point mutation within the SMN Tudor domain, and CARM1 depletion, modulate the SMN-HuR interaction. In addition, using the Smn2B/- mouse model, we report that CARM1 levels are markedly increased in SMA muscles and that HuR fails to properly respond to muscle denervation, thereby affecting the regulation of its mRNA targets. Altogether, our results show a novel CARM1-HuR axis in the regulation of muscle differentiation and plasticity as well as in the aberrant regulation of this axis caused by the absence of SMN in SMA muscle. With the recent developments of therapeutics targeting motor neurons, this study further indicates the need for more global therapeutic approaches for SMA.

The Antisense Oligonucleotide Nusinersen for Treatment of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, autosomal recessive neuromuscular degenerative disease characterized by loss of spinal cord motor neurons leading to progressive muscle wasting. The most common pathology results from a homozygous disruption in the survival motor neuron 1 (SMN1) gene on chromosome 5q13 via deletion, conversion, or mutation. SMN2 is a near duplicate of SMN1 that can produce full-length SMN mRNA transcripts, but its overall production capability of these mRNA transcripts is lower than that seen in SMN1. This leads to lower levels of functional SMN protein within motor neurons. The FDA approved nusinersen in December 2016 to treat SMA associated with SMN1 gene mutation. It is administered directly to the central nervous system by intrathecal injection. An antisense oligonucleotide (ASO) drug, nusinersen, provides an upcoming and promising treatment option for SMA and represents a novel pharmacological approach with a mechanism of action relevant for other neurodegenerative disorders. Nusinersen begins with four initial loading doses that are followed by three maintenance doses per year. Three major studies (CHERISH, ENDEAR, and NURTURE) have shown to improve motor function in early and late-onset individuals and reduce the chances of ventilator requirements in pre-symptomatic infants. Studies investigating the timing of drug delivery in mouse models of SMA report the best outcomes when drugs are delivered early before any significant motor function is lost. Nusinersen is a novel therapeutic approach with consistent results in all three studies and is proof of the novel concept for treating SMA and other neurodegenerative disorders in the future.

Epidemiology, healthcare resource utilization and healthcare costs for spinal muscular atrophy in Alberta, Canada

AIMS

Spinal muscular atrophy (SMA) is a progressive neuromuscular disease associated with the degeneration of motor neurons in the brainstem and spinal cord. Studies examining the epidemiology and economic impact of SMA are limited in Canada. This study aimed to estimate the epidemiology as well as healthcare resource utilization (HRU) and healthcare costs for children with SMA in Alberta, Canada.

MATERIALS AND METHODS

We conducted a retrospective study using anonymized data from administrative healthcare databases provided by Alberta Health. Data from 1 April 2010 to 31 March 2018, were extracted for patients <18 years of age identified with SMA. Five-year incidence and prevalence were calculated for cases identified between 1 April 2012 and 31 March 2017. HRU and healthcare costs were assessed one year after SMA diagnosis, including hospitalizations, physician visits, ambulatory care visits and long-term care admissions.

RESULTS

The five-year incidence and prevalence of pediatric onset SMA were 1.03 per 100,000 person-years and 9.97 per 100,000 persons, respectively. General practitioner, specialist, and ambulatory care visits were common among children with SMA in the first-year post-diagnosis. The mean (SD) total annual direct cost per patient in the first-year post-diagnosis was $29,774 ($38,407); hospitalizations accounted for 41.7% of these costs ($12,412 [$21,170]), followed by practitioner visits at 32.3% ($9,615 [$13,054]), and ambulatory care visits at 26.0% ($7,746 [$9,988]).

CONCLUSIONS

Children with SMA experience substantial HRU, particularly for hospitalizations and practitioner visits, following diagnosis. Given the high costs of SMA, timely access to effective treatment strategies, such as the novel survival motor neuron (SMN)-restoring treatments recently approved for use, are needed to improve health outcomes and HRU.

Dual SMN inducing therapies can rescue survival and motor unit function in symptomatic ∆7SMA mice

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by survival motor neuron (SMN) protein deficiency which results in motor neuron loss and muscle atrophy. SMA is caused by a mutation or deletion of the survival motor neuron 1 (SMN1) gene and retention of the nearly identical SMN2 gene. SMN2 contains a C to T change in exon 7 that results in exon 7 exclusion from 90% of transcripts. SMN protein lacking exon 7 is unstable and rapidly degraded. The remaining full-length transcripts from SMN2 are insufficient for normal motor neuron function leading to the development of SMA. Three different therapeutic approaches that increase full-length SMN (FL-SMN) protein production are approved for treatment of SMA patients. Studies in both animal models and humans have demonstrated increasing SMN levels prior to onset of symptoms provides the greatest therapeutic benefit. Treatment of SMA, after some motor neuron loss has occurred, is also effective but to a lesser degree. The SMN∆7 mouse model is a well characterized model of severe or type 1 SMA, dying at 14 days of age. Here we treated three groups of ∆7SMA mice starting before, roughly during, and after symptom onset to determine if combining two mechanistically distinct SMN inducing therapies could improve the therapeutic outcome both before and after motor neuron loss. We found, compared with individual therapies, that morpholino antisense oligonucleotide (ASO) directed against ISS-N1 combined with the small molecule compound RG7800 significantly increased FL-SMN transcript and protein production resulting in improved survival and weight of ∆7SMA mice. Moreover, when give late symptomatically, motor unit function was completely rescued with no loss in function at 100 days of age in the dual treatment group. We have therefore shown that this dual therapeutic approach successfully increases SMN protein and rescues motor function in symptomatic ∆7SMA mice.

Screening of Neonatal UK Dried Blood Spots Using a Duplex SMN1 Screening Assay

Spinal muscular atrophy (SMA) is an autosomal inherited neuromuscular genetic disease caused, in 95% of cases, by homozygous deletions involving the SMN1 gene exon 7. It remains the leading cause of death in children under 2 years of age. New treatments have been developed and adopted for use in many countries, including the UK. Success of these treatments depends on early diagnosis and intervention in newborn babies, and many countries have implemented a newborn screening (NBS) or pilot NBS program to detect SMN1 exon 7 deletions on dried blood spots. In the UK, there is no current NBS program for SMA, and no pilot studies have commenced. For consideration of adoption of NBS for a new condition, numerous criteria must be satisfied, including critical assessment of a working methodology. This study uses a commercially available real-time PCR assay to simultaneously detect two different DNA segments (SMN1 exon 7 and control gene RPP30) using DNA extracted from a dried blood spot. This study was carried out in a routine clinical laboratory to determine the specificity, sensitivity, and feasibility of SMA screening in a UK NBS lab setting. Just under 5000 normal DBSs were used alongside 43 known SMA positive DBSs. Study results demonstrate that NBS for SMA using real-time PCR is feasible within the current UK NBS Laboratory infrastructure using the proposed algorithm.

[Newborn screening program for spinal muscular atrophy]

BACKGROUND

The introduction of a comprehensive newborn screening program for spinal muscular atrophy (SMA), specifically for 5q-SMA, is planned for the end of 2021 in Germany. Several targeted treatment options have become available for all patients with SMA.

MATERIAL AND METHODS

Newborn screening for 5q-SMA is based on the detection of a homozygous deletion of exon 7 in the SMN1 gene by molecular genetic analysis from the dried blood card. In all cases a second blood sample must be drawn as a part of confirmation diagnostics including the determination of the SMN2 copy numbers.

RESULTS

Insights from pilot projects performed in parts of Germany are presented. Advantages and disadvantages of the screening project are discussed.

CONCLUSION

Consultation and treatment should be carried out in a department of neuropediatrics with experience in the treatment of children with 5q-SMA, which is able to provide all current treatment options for the child, so that, when necessary, the treatment can be started within the first month of life.

Effect of the COVID-19 Pandemic on Children With SMA Receiving Nusinersen: What Is Missed and What Is Gained?

Nusinersen is the first oligonucleotide-based drug that is approved for the treatment of spinal muscular atrophy. In January 2020, the WHO declared COVID-19 a pandemic and nusinersen-provider centers had to postpone planned infusions for some children along with other related interventions. Considering the important contribution that the intrathecal infusions and other support activities could have on the quality of life of spinal muscular atrophy patients and their families, this emergency could have a relevant impact on the course of the pathology. The present work aims to assess the clinical and social issues that arise for spinal muscular atrophy children in care at the referral pediatric palliative care Centre of Padua (Veneto) from a delay in nusinersen infusions, resulting from the contingent COVID-19 restrictions. This evaluation has been carried out in both the short and long term after the first lockdown period and can be considered as a "proxy" of a situation of a possible delay in administration or management of infusions, due to other different causes.

Newborn screening of neuromuscular diseases

Neuromuscular diseases represent an heterogenous group of more than 400 diseases, with a very broad phenotypic spectrum. Given their rarity and complexity, neuromuscular diseases are often diagnosed with a very significant delay after which irreversible muscle damage may limit the efficacy of treatments when available. In this context, neonatal screening could constitute a solution for early detection and treatment. A systematic review of the literature in PubMed up to May 1, 2021, was conducted according to PRISMA guidelines, including classical neuromuscular diseases and diseases with a clear peripheral nervous system involvement (including central nervous system disease with severe neuropathy). We found seven diseases for which newborn screening data were reported: spinal muscular atrophy (9), Duchenne muscular dystrophy (9), Pompe disease (8), X-linked adrenoleukodystrophy (5), Krabbe disease (4), myotonic dystrophy type 1 (1), metachromatic leukodystrophy (1). The future of newborn screening for neuromuscular disorders pass through a global technological switch, from a biochemical to a genetic-based approach. The rapid development of therapy also requires the possibility to quickly adapt the list of treated conditions, to allow innovative therapies to achieve their best efficacy.

A 20-year Clinical and Genetic Neuromuscular Cohort Analysis in Lebanon: An International Effort

BACKGROUND

Clinical and molecular data on the occurrence and frequency of inherited neuromuscular disorders (NMD) in the Lebanese population is scarce.

OBJECTIVE

This study aims to provide a retrospective overview of hereditary NMDs based on our clinical consultations in Lebanon.

METHODS

Clinical and molecular data of patients referred to a multi-disciplinary consultation for neuromuscular disorders over a 20-year period (1999-2019) was reviewed.

RESULTS

A total of 506 patients were diagnosed with 62 different disorders encompassing 10 classes of NMDs. 103 variants in 49 genes were identified. In this cohort, 81.4%of patients were diagnosed with motor neuron diseases and muscular dystrophies, with almost half of these described with spinal muscular atrophy (SMA) (40.3%of patients). We estimate a high SMA incidence of 1 in 7,500 births in Lebanon. Duchenne and Becker muscular dystrophy were the second most frequently diagnosed NMDs (17%of patients). The latter disorders were associated with the highest number of variants (39) identified in this study. A highly heterogeneous presentation of Limb Girdle Muscular Dystrophy and Charcot-Marie-Tooth disease was notably identified. The least common disorders (5.5%of patients) involved congenital, metabolic, and mitochondrial myopathies, congenital myasthenic syndromes, and myotonic dystrophies. A review of the literature for selected NMDs in Lebanon is provided.

CONCLUSIONS

Our study indicates a high prevalence and underreporting of heterogeneous forms of NMDs in Lebanon- a major challenge with many novel NMD treatments in the pipeline. This report calls for a regional NMD patient registry.

Nusinersen injections in adults and children with spinal muscular atrophy: a single-center experience

PURPOSE

Nusinersen is a drug approved in December 2016 for treatment of spinal muscular atrophy (SMA). We want to share our initial experience with image-guided, non-image-guided, and port-delivered nusinersen injections in a large single-center SMA patient cohort, treating both pediatric and adult patients with focus on technical considerations and other patient concerns from a combined perspective of patient, neurologist, and radiologist.

METHODS

All nusinersen injections between February 2017 and September 2018 were retrospectively reviewed. We obtained age, sex, SMA type and technical details of the injections and postprocedure complications for each procedure.

RESULTS

A total of 52 patients (24 women [46%]; 4 patients with SMA-1 [7.6%]; 30 patients with SMA-2 [57.8%]; 18 patients with SMA-3 [34.6%]; mean age, 25.5 years [7 months to 62 years]) with a total of 265 injections were included. Of the 265 injections, 206 (77.9%) were performed with local anesthetic, 25 (9.4%) with moderate sedation, and 23 (8.6%) under general anesthesia. We performed 65 CT-guided transforaminal injections in 13 patients, 106 fluoroscopy-guided lumbar punctures in 24 patients and 83 lumbar punctures in 16 patients using conventional technique. Only 6 of 265 injections (2.2%) ended up with a post-lumbar puncture headache (PLPH) requiring medical treatment. None required an epidural blood patch. Fourteen PLPH (5.2%) occurred and resolved at the same day without any treatment. After 6 of 265 injections (2.2%), patients reported soreness at the injection site which resolved spontaneously. Three elected to have an intrathecal reservoir placement (2 lumbar, 1 intraventricular) with a total of 11 injections. One patient with lumbar catheter developed infection after surgery with subsequent meningitis and treatment delay. After the resolution of meningitis, a new intraventricular reservoir was placed without any complication in the following injections.

CONCLUSION

With the introduction of nusinersen treatment, neurologists and radiologists play an important role in treatment of SMA patients and therefore should be familiar with different techniques and complications of drug administration. Using good technique, it is possible to have very low complication rates even in this complex patient population, and various image-guided procedures can be a safe alternative to surgical approach, even in the most difficult cases.

Cognitive Impairment in Adult Patients with 5q-Associated Spinal Muscular Atrophy

In previous studies, a below-average, average, or above-average intelligence quotient (IQ) in children with SMA was detected but, aside from a severe physical disability, the cognitive performance of adult SMA patients has not yet been evaluated. The intelligence test used in this study, the Wechsler Adult Intelligence Scale, fourth edition (WAIS-IV), was used to measure major intelligence components of adult SMA patients. The WAIS-IV determines four index scores representing verbal comprehension, perceptual reasoning, working memory, and processing speed. Due to time-dependent demands on motor function, the processing speed index score was excluded. IQ index scores of 33 adult SMA patients did not differ from IQ index scores of the normal population. In SMA type-3 patients, the index scores for verbal comprehension, perceptual reasoning, and working memory did not differ from the normal population but showed a trend of IQ scores towards lower points. Patients with SMA type 2 had lower IQ index scores for working memory (90.33 ± 12.95; p = 0.012) and perceptual reasoning (90.73 ± 12.58; p = 0.013) than the normal population. This study provided further evidence that SMA is a multi-systemic disease and may refute the widespread hypothesis that SMA patients might improve their cognitive skills to compensate for their physical impairment.

Growth patterns in children with spinal muscular atrophy

Background

Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by muscle atrophy and weakness. SMA type 1 (SMA1) is the most severe form: affected infants are unable to sit unaided; SMA type 2 (SMA2) children can sit, but are not able to walk independently. The Standards of Care has improved quality of life and the increasing availability of disease-modifying treatments is progressively changing the natural history; so, the clinical assessment of nutritional status has become even more crucial. Aims of this multicenter study were to present the growth pattern of treatment-naïve SMA1 and SMA2, and to compare it with the general growth standards.

Results

Body Weight (BW, kg) and Supine Length (SL, cm) were collected using a published standardized procedure. SMA-specific growth percentiles curves were developed and compared to the WHO reference data. We recruited 133 SMA1 and 82 SMA2 (48.8% females). Mean ages were 0.6 (0.4–1.6) and 4.1 (2.1–6.7) years, respectively. We present here a set of disease-specific percentiles curves of BW, SL, and BMI-for-age for girls and boys with SMA1 and SMA2. These curves show that BW is significantly lower in SMA than healthy peers, while SL is more variable. BMI is also typically lower in both sexes and at all ages.

Conclusions

These data on treatment-naïve patients point toward a better understanding of growth in SMA and could be useful to improve the clinical management and to assess the efficacy of the available and forthcoming therapies not only on motor function, but also on growth.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02015-9.

Alternative Splicing Role in New Therapies of Spinal Muscular Atrophy

It has been estimated that 80% of the pre-mRNA undergoes alternative splicing, which exponentially increases the flow of biological information in cellular processes and can be an attractive therapeutic target. It is a crucial mechanism to increase genetic diversity. Disturbed alternative splicing is observed in many disorders, including neuromuscular diseases and carcinomas. Spinal Muscular Atrophy (SMA) is an autosomal recessive neurodegenerative disease. Homozygous deletion in 5q13 (the region coding for the motor neuron survival gene (SMN1)) is responsible for 95% of SMA cases. The nearly identical SMN2 gene does not compensate for SMN loss caused by SMN1 gene mutation due to different splicing of exon 7. A pathologically low level of survival motor neuron protein (SMN) causes degeneration of the anterior horn cells in the spinal cord with associated destruction of α-motor cells and manifested by muscle weakness and loss. Understanding the regulation of the SMN2 pre-mRNA splicing process has allowed for innovative treatment and the introduction of new medicines for SMA. After describing the concept of splicing modulation, this review will cover the progress achieved in this field, by highlighting the breakthrough accomplished recently for the treatment of SMA using the mechanism of alternative splicing.

Bone mineral density and its influencing factors in Chinese children with spinal muscular atrophy types 2 and 3

Background

Patients with spinal muscular atrophy (SMA) are at risk of decreased bone mineral density (BMD). The bone health status of Chinese patients with SMA has been poorly studied. We aimed to evaluate the BMD of children with SMA types 2 and 3 in mainland China and investigate its influencing factors.

Methods

Forty patients with a mean age of 5.5 years affected by SMA types 2 and 3 (n = 22 and n = 18, respectively) were enrolled between September 2017 and May 2019. Total body less head (TBLH) BMD, lumbar spine (LS) BMD, and body composition were measured using dual-energy X-ray absorptiometry (DXA). Serum bone metabolism markers and complete spinal radiographs were assessed. We utilized a linear regression model to explore the correlations between BMD and its related factors.

Results

A total of 67.5% (27/40) of patients were diagnosed with low BMD and 2.5% (1/40) were diagnosed with osteoporosis. The TBLH BMD and LS BMD Z-scores in children with SMA type 2 were significantly lower than those with SMA type 3. Both TBLH and LS BMD Z-scores tended to increase with the change of SMA subtypes from 2a-3b. Vitamin D insufficiency and deficiency were found in 37.5% (15/40) of the patients. Serum Ca, phosphorus (P), alkaline phosphatase (ALP) and parathormone (PTH) levels were normal. There were no significant differences among the four subtypes in terms of all the serum bone metabolism markers. Phenotype was significantly associated with TBLH BMD and LS BMD Z-scores, and serum PTH levels were significantly associated with TBLH BMD Z-scores.

Conclusions

Low BMD and osteoporosis were highly prevalent in mainland Chinese children with SMA types 2 and 3. Phenotype and serum PTH level might be the influencing factors of BMD. Regular monitoring of BMD by DXA scan and taking active interventions aim to SMA children with different types are important.

Drug Discovery of Spinal Muscular Atrophy (SMA) from the Computational Perspective: A Comprehensive Review

Spinal muscular atrophy (SMA), one of the leading inherited causes of child mortality, is a rare neuromuscular disease arising from loss-of-function mutations of the survival motor neuron 1 (SMN1) gene, which encodes the SMN protein. When lacking the SMN protein in neurons, patients suffer from muscle weakness and atrophy, and in the severe cases, respiratory failure and death. Several therapeutic approaches show promise with human testing and three medications have been approved by the U.S. Food and Drug Administration (FDA) to date. Despite the shown promise of these approved therapies, there are some crucial limitations, one of the most important being the cost. The FDA-approved drugs are high-priced and are shortlisted among the most expensive treatments in the world. The price is still far beyond affordable and may serve as a burden for patients. The blooming of the biomedical data and advancement of computational approaches have opened new possibilities for SMA therapeutic development. This article highlights the present status of computationally aided approaches, including in silico drug repurposing, network driven drug discovery as well as artificial intelligence (AI)-assisted drug discovery, and discusses the future prospects.

Sagittal Plane Deformities in Children with SMA2 following Posterior Spinal Instrumentation

This is a retrospective radiographic review to assess post-operative sagittal plane deformities in patients with Spinal Muscular Atrophy type 2 that had been treated with posterior spinal instrumentation. Thirty-two patients with a history of either spinal fusion (N = 20) or growing rods (N = 12) were identified with an average of 7.6 (2.1-16.6) years post-operative follow-up. Forty percent (13/32) of the patients were identified as having obvious "tucked chin" (N = 4), "tipped trunk" (N = 9), or both (N = 3). Sacral incidence was the only parameter that was statistically significant change between pre-operative or immediate post-operative measurements (66.9° vs. 55.2° p = 0.03). However, at final follow-up, the post-operative thoracic kyphosis had decreased over time in those that developed a subsequent sagittal deformity (24.2°) whereas it increased in those that did not (44.7°, p = 0.008). This decrease in thoracic kyphosis throughout the instrumented levels, resulted in a greater lordotic imbalance (30.4° vs. 5.6°, p = 0.001) throughout the instrumented levels in the group that developed the subsequent cervical or pelvic sagittal deformities. In conclusion, sagittal plane deformities commonly develop outside the instrumented levels in children with SMA type 2 following posterior spinal instrumentation and may be the result of lordotic imbalance that occurs through continued anterior growth following posterior instrumentation.

Views of the General Population on Newborn Screening for Spinal Muscular Atrophy in Japan

Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder that results in progressive muscle atrophy and weakness. As new therapies for SMA have been developed, newborn screening for SMA can lead to early diagnosis and treatment. The objective of this study was to gather the general population’s view on screening of SMA in newborns in Japan. A questionnaire survey was conducted on two general population groups in Japan. A total of 269 valid responses were obtained. In the general population, about half of the participants had no knowledge about SMA, and more than 90% did not know about new therapies for SMA. Conversely, more than 95% of the general population agreed with screening newborns for SMA because they believed that early diagnosis was important, and treatments were available. This study revealed that the general population in Japan mostly agreed with screening for SMA in newborns even though they did not know much about SMA. Newborn screening for SMA is promising, but it is in very early stages. Therefore, SMA newborn screening should be performed with sufficient preparation and consideration in order to have a positive impact on SMA patients and their families.