The Genetics of Spinal Muscular Atrophy: Progress and Challenges

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.

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.

The impact of three SMN2 gene copies on clinical characteristics and effect of disease-modifying treatment in patients with spinal muscular atrophy: a systematic literature review

Objective

To review the clinical characteristics and effect of treatment in patients with spinal muscular atrophy (SMA) and three copies of the SMN2 gene.

Methods

We conducted a literature search in October 2022 to identify English-language clinical research on SMA that included SMN2 copy number according to PRISMA guidelines.

Results

Our search identified 44 studies examining the impact of three SMN2 copies on clinical characteristics (21 on phenotype, 13 on natural history, and 15 on functional status and other signs/symptoms). In children with type I SMA or presymptomatic infants with an SMN1 deletion, three SMN2 copies was associated with later symptom onset, slower decline in motor function and longer survival compared with two SMN2 copies. In patients with SMA type II or III, three SMN2 copies is associated with earlier symptom onset, loss of ambulation, and ventilator dependence compared with four SMN2 copies. Eleven studies examined treatment effects with nusinersen (nine studies), onasemnogene abeparvovec (one study), and a range of treatments (one study) in patients with three SMN2 copies. In presymptomatic infants, early treatment delayed the onset of symptoms and maintained motor function in those with three SMN2 copies. The impact of copy number on treatment response in symptomatic patients is still unclear.

Conclusion

SMN2 copy number is strongly correlated with SMA phenotype in patients with SMN1 deletion, while no correlation was found in patients with an SMN1 mutation. Patients with three SMN2 copies show a highly variable clinical phenotype. Early initiation of treatment is highly effective in presymptomatic patients with three SMN2 copies.

Genetic Myelopathies

OBJECTIVE

This article provides an overview of genetic myelopathies, a diverse group of inherited, degenerative conditions that may be broadly categorized as motor neuron disorders, disorders of spinocerebellar degeneration, leukodystrophies, and hereditary spastic paraplegia. Clinical examples from each category are provided to illustrate the spectrum of genetic myelopathies and their distinguishing features that aid in differentiating genetic myelopathies from potentially treatable acquired causes of myelopathy.

LATEST DEVELOPMENTS

Advances in genetic testing have vastly enhanced current knowledge of genetic myelopathies and the ability to diagnose and provide appropriate counseling to patients and their families. However, potential health care disparities in access to genetic testing is a topic that must be further explored. Although treatment for most of these conditions is typically supportive, there have been recent therapeutic breakthroughs in treatments for amyotrophic lateral sclerosis, spinal muscular atrophy, and Friedreich ataxia.

ESSENTIAL POINTS

Genetic myelopathies may present with chronic and progressive symptoms, a family history of similar symptoms, and involvement of other structures outside of the spinal cord. Imaging often shows spinal cord atrophy, but cord signal change is rare. Exclusion of reversible causes of myelopathy is a key step in the diagnosis. There are many different causes of genetic myelopathies, and in some cases, symptoms may overlap, which underscores the utility of genetic testing in confirming the precise underlying neurologic condition.

Design and Validation of a Clinical Outcome Measure for Adolescents and Adult Patients with Spinal Muscular Atrophy: SMA Life Study Protocol

INTRODUCTION

The objective of this study is to develop a clinical tool for the evaluation and follow-up of adolescent and adult patients with 5q spinal muscular atrophy (SMA) and to design its validation.

METHODS

This prospective, non-interventional study will be carried out at five centres in Spain and will include patients aged 16 years or older with a confirmed diagnosis of 5q SMA (biallelic mutation of the survival motor neuron 1 [SMN1] gene). A panel of experts made up of neurologists, physiatrists and Spanish patients' association (FundAME), participated in the design of the clinical tool. Physicians will administer the tool at three time points (baseline, 12 months and 24 months). Additionally, data from other questionnaires and scales will be collected. Once recruitment is achieved, an interim statistical analysis will be performed to assess its psychometric properties by applying Rasch analysis and classical statistical tests.

RESULTS

The tool will consist of up to 53 items to assess functional status from a clinical perspective in seven key dimensions (bulbar, respiratory, axial, lower, upper, fatigability and other symptoms), which will be collected together with objective clinical measures (body mass index, forced vital capacity, pinch strength and 6-minute walk test).

CONCLUSIONS

The validation of this tool will facilitate the clinical evaluation of adult and adolescent patients with SMA and the quantification of their response to new treatments in both clinical practice and research.

Autophagy in spinal muscular atrophy: from pathogenic mechanisms to therapeutic approaches

Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder caused by the depletion of the ubiquitously expressed survival motor neuron (SMN) protein. While the genetic cause of SMA has been well documented, the exact mechanism(s) by which SMN depletion results in disease progression remain elusive. A wide body of evidence has highlighted the involvement and dysregulation of autophagy in SMA. Autophagy is a highly conserved lysosomal degradation process which is necessary for cellular homeostasis; defects in the autophagic machinery have been linked with a wide range of neurodegenerative disorders, including amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. The pathway is particularly known to prevent neurodegeneration and has been suggested to act as a neuroprotective factor, thus presenting an attractive target for novel therapies for SMA patients. In this review, (a) we provide for the first time a comprehensive summary of the perturbations in the autophagic networks that characterize SMA development, (b) highlight the autophagic regulators which may play a key role in SMA pathogenesis and (c) propose decreased autophagic flux as the causative agent underlying the autophagic dysregulation observed in these patients.

Patient and Caregiver Outcomes After Onasemnogene Abeparvovec Treatment: Findings from the Cure SMA 2021 Membership Survey

INTRODUCTION

Onasemnogene abeparvovec (OA) is the only gene replacement therapy currently approved for spinal muscular atrophy (SMA) treatment. We sought to assess real-world patient and caregiver outcomes after OA treatment for SMA.

METHODS

Patients who received OA were identified from the 2021 Cure SMA Membership Survey. Those treated at 6-23 months of age were matched to non-patients treated with OA on the basis of age at the time of survey and survival motor neuron 2 gene copy number. Patient characteristics, motor milestones, and resource and supportive care use, as well as caregiver proxy-reported health-related quality of life (HRQOL), were described. Caregiver unmet needs and HRQOL were also assessed.

RESULTS

Of the 614 patients in the survey, 64 received OA, and 17 were matched with 28 non-OA-treated patients. In general, a greater percentage of OA-treated patients achieved various motor milestones, including 100% sitting without support and 58.8% walking with assistance. OA-treated patients also had numerically lower rates of hospitalization and surgery. None required tracheostomy with a ventilator. The rate of using oxygen or a breathing machine for more than 16 h was also lower for OA-treated patients. OA-treated patients had less frequent trouble swallowing. HRQOL was reported to be similar to non-OA-treated patients. Caregivers of OA-treated patients reported better patient mobility scores and less work impairment.

CONCLUSIONS

The study suggests that treatment with OA is associated with greater rates of motor milestone achievements and less resource and supportive care use for patients with SMA treated at 6-23 months of age in the real world. For caregivers, it may also potentially reduce unmet needs, improve HRQOL, and reduce work impairment.

Safety Concerns with Nusinersen, Risdiplam, and Onasemnogene Abeparvovec in Spinal Muscular Atrophy: A Real-World Pharmacovigilance Study

BACKGROUND AND OBJECTIVE

Spinal muscular atrophy (SMA) is a genetic disorder with limited treatment options. It is crucial to have a comprehensive understanding of drug safety in order to make informed clinical drug selections for patients with SMA. Assessing the safety profiles of therapeutic drugs for SMA has been challenging due to the limited number of patients included in clinical trials. This study aims to investigate and compare the potential safety concerns associated with three leading SMA therapeutic drugs: nusinersen, risdiplam, and onasemnogene abeparvovec.

METHODS

The FDA Adverse Event Reporting System database was used to analyze drug safety, and a case (SMA drug)/noncase (all other drugs in the database) approach was employed to estimate safety signals through disproportionality analysis and reporting odds ratio (ROR). Veen analysis was conducted to compare and select the idiosyncratic adverse events (AEs) associated with each drug.

RESULTS

The study included 5324 cases of nusinersen, 1184 cases of risdiplam, and 1277 cases of onasemnogene abeparvovec. Venn analysis revealed 27 common AEs among the three drugs, including cardiac, gastrointestinal, metabolism, musculoskeletal, renal, respiratory disorders, and infections. Additionally, 196 AEs exclusively found in nusinersen included post lumbar puncture syndrome [ROR (95% CI) = 6120.91 (5057.01-7408.64), n = 372], procedural pain [ROR (95% CI) = 54.86 (48.13-62.54), n = 234], idiopathic intracranial hypertension [ROR (95% CI) = 6.12 (2.29-16.33), n = 4], and hypokalemia [ROR (95% CI) = 2.02 (1.24-3.31), n = 16]. Additionally, transient deafness was identified as an unexpected and rare, yet severe, AE for nusinersen [ROR (95% CI) = 23.32 (8.71-62.44), n = 4]. Risdiplam exhibited 50 AEs exclusively, with notable idiosyncratic AEs including diarrhea [ROR (95% CI) = 4.55 (3.79-5.46), n = 121], fatigue [ROR (95% CI) = 2.03 (1.6-2.57), n = 70], photosensitivity reaction [ROR (95% CI) = 9.50 (4.25-21.13), n = 6], rash [ROR (95% CI) = 1.90 (1.36-2.67), n = 34], and [ROR (95% CI) = 4.3 (1.93-9.58), n = 6] in comparison with the other two drugs. Moreover, ileus [ROR (95% CI) = 11.11 (4.14-29.51), n = 4], gastrointestinal hemorrhage [ROR (95% CI) = 2.55 (1.15-5.69), n = 6], and hypoglycemic unconsciousness [ROR (95% CI) = 153.58 (62.98-374.54), n = 5] were rare but severe AEs associated with risdiplam. Onasemnogene abeparvovec had 143 exclusively identified AEs, with significant high signals for troponin I increase [ROR (95% CI) = 627.1 (492.2-798.99), n = 78], troponin T increase [ROR (95% CI) = 233.98 (153.29-357.15), n = 23], blood lactate dehydrogenase increase [ROR (95% CI) = 39.81 (28.88-54.87), n = 38], and transaminases increase [ROR (95% CI) = 36.88 (29.24-46.52), n = 73].

CONCLUSIONS

This study highlights the importance of monitoring injection-related injuries and transient deafness events in patients treated with nusinersen. For onasemnogene abeparvovec, careful monitoring for renal impairment, liver injury, and myocardial damage is necessary. Risdiplam requires attention to the potential risk of rare but severe gastrointestinal damage events and hypoglycemia. Importantly, risdiplam exhibited lower liver and renal toxicity, making it a potential consideration for patients with liver or renal insufficiency or for combined use with other drugs that possess high liver or renal toxicity. These findings can be a reference for drug selection and further prospective studies.

Evaluating Perceived Fatigue within an Adult Spinal Muscular Atrophy Population

INTRODUCTION

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by progressive muscle weakness and atrophy. While chronic fatigue is a common manifestation of SMA, the field lacks comprehensive data to assess the extent of its impact. Cure SMA, an SMA patient advocacy organization, conducted an online survey of its adults with SMA community members to measure the impact of fatigue.

METHODS

All survey respondents were asked to complete questions on demographics, use of SMA treatment, and quality of life, but respondents were randomized to receive three of the following fatigue instruments: the Modified Fatigue Impact Scale (MFIS), Multidimensional Fatigue Inventory (MFI), Fatigue Severity Scale (FSS), PedsQL™ Multidimensional Fatigue (PedsQL MF) Scale, and Spinal Muscular Atrophy Health Index (SMA-HI) fatigue modules. Scales were evaluated for reliability and overall fatigue scores were evaluated by multivariate regression models to determine which variables were related to the final scores of each instrument.

RESULTS

A total of 253 adults completed the online survey. When measured against the general population, statistically significant differences were found among adults with SMA for certain variables within each measurement instrument. However, there did not appear to be differences in fatigue levels among key subgroups within the SMA population.

CONCLUSIONS

This was the first use of more than two fatigue questionnaires simultaneously in SMA. The lack of a consistent relationship between SMA severity and fatigue levels was surprising. This may be related to the lack of specificity of the instruments for this population. An SMA-specific scale is needed to evaluate differences in fatigue impact across the SMA population.

Cerebellar structural, astrocytic, and neuronal abnormalities in the SMNΔ7 mouse model of spinal muscular atrophy

Spinalmuscular atrophy (SMA) is a neuromuscular disease that affects as many as 1 in 6000 individuals at birth, making it the leading genetic cause of infant mortality. A growing number of studies indicate that SMA is a multi-system disease. The cerebellum has received little attention even though it plays an important role in motor function and widespread pathology has been reported in the cerebella of SMA patients. In this study, we assessed SMA pathology in the cerebellum using structural and diffusion magnetic resonance imaging, immunohistochemistry, and electrophysiology with the SMNΔ7 mouse model. We found a significant disproportionate loss in cerebellar volume, decrease in afferent cerebellar tracts, selective lobule-specific degeneration of Purkinje cells, abnormal lobule foliation and astrocyte integrity, and a decrease in spontaneous firing of cerebellar output neurons in the SMA mice compared to controls. Our data suggest that defects in cerebellar structure and function due to decreased survival motor neuron (SMN) levels impair the functional cerebellar output affecting motor control, and that cerebellar pathology should be addressed to achieve comprehensive treatment and therapy for SMA patients.

Brazilian version of the CHOP INTEND scale: cross-cultural adaptation and validation

BACKGROUND

Spinal muscular atrophy (SMA) is a rare genetic disease that causes progressive muscle weakness and impacts motor function. The type I is the most severe presentation and affects infants before 6 months old. In addition, the instruments available for assessing motor function have limitations when applied to infants with neuromuscular diseases and significant muscle weakness.

OBJECTIVE

To translate, cross-culturally adapt, and validate the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) to Brazilian Portuguese.

METHODS

The present study comprised the translation, synthesis of translations, backtranslation, consolidation by a committee of experts, and test of the final version of the CHOP INTEND in 13 patients with SMA type I. We also assessed the content validity and reliability of the translated version.

RESULTS

The scale was translated considering semantic, structural, idiomatic, and cultural aspects. All agreement rates were > 0.8, the overall content validity index of the instrument was 0.98, and inter-rater reliability using the intraclass correlation coefficient was 0.998.

CONCLUSION

The Brazilian version of the CHOP INTEND met semantic and technical equivalence criteria with the original version and was valid and reliable for patients with SMA type I.

Phenotype Presentation and Molecular Diagnostic Yield in Non-5q Spinal Muscular Atrophy

Background and Objectives

Spinal muscular atrophy (SMA) is mainly caused by homozygous SMN1 gene deletions on 5q13. Non-5q SMA patients' series are lacking, and the diagnostic yield of next-generation sequencing (NGS) is largely unknown. The aim of this study was to describe the clinical and genetic landscape of non-5q SMA and evaluate the performance of neuropathy gene panels in these disorders.

Methods

Description of patients with non-5q SMA followed in the different neuromuscular reference centers in France as well as in London, United Kingdom. Patients without a genetic diagnosis had undergone at least a neuropathy or large neuromuscular gene panel.

Results

Seventy-one patients from 65 different families were included, mostly sporadic cases (60.6%). At presentation, 21 patients (29.6%) showed exclusive proximal weakness (P-SMA), 35 (49.3%) showed associated distal weakness (PD-SMA), and 15 (21.1%) a scapuloperoneal phenotype (SP-SMA). Thirty-two patients (45.1%) had a genetic diagnosis: BICD2 (n = 9), DYNC1H1 (n = 7), TRPV4 (n = 4), VCP, HSBP1, AR (n = 2), VRK1, DNAJB2, MORC2, ASAH1, HEXB, and unexpectedly, COL6A3 (n = 1). The genetic diagnostic yield was lowest in P-SMA (6/21, 28.6%) compared with PD-SMA (16/35, 45.7%) and SP-SMA (10/15, 66.7%). An earlier disease onset and a family history of the disease or consanguinity were independent predictors of a positive genetic diagnosis. Neuropathy gene panels were performed in 59 patients with a 32.2% diagnostic yield (19/59). In 13 additional patients, a genetic diagnosis was achieved through individual gene sequencing or an alternative neuromuscular NGS.

Discussion

Non-5q SMA is genetically heterogeneous, and neuropathy gene panels achieve a molecular diagnosis in one-third of the patients. The diagnostic yield can be increased by sequencing of other neuromuscular and neurometabolic genes. Nevertheless, there is an unmet need to cluster these patients to aid in the identification of new genes.

Comparison of TRIBE and STAMP for identifying targets of RNA binding proteins in human and Drosophila cells

RNA binding proteins (RBPs) perform a myriad of functions and are implicated in numerous neurological diseases. To identify the targets of RBPs in small numbers of cells, we developed TRIBE, in which the catalytic domain of the RNA editing enzyme ADAR (ADARcd) is fused to an RBP. When the RBP binds to an mRNA, ADAR catalyzes A to G modifications in the target mRNA that can be easily identified in standard RNA sequencing. In STAMP, the concept is the same except the ADARcd is replaced by the RNA editing enzyme APOBEC. Here we compared TRIBE and STAMP side-by-side in human and Drosophila cells. The goal is to learn the pros and cons of each method so that researchers can choose the method best suited to their RBP and system. In human cells, TRIBE and STAMP were performed using the RBP TDP-43. Although they both identified TDP-43 target mRNAs, combining the two methods more successfully identified high-confidence targets. In Drosophila cells, RBP-APOBEC fusions generated only low numbers of editing sites, comparable to the level of control editing. This was true for two different RBPs, Hrp48 and Thor (Drosophila EIF4E-BP), indicating that STAMP does not work well in Drosophila.

The Carrier Frequency of Two SMN1 Genes in Parents of Symptomatic Children with SMA and the Significance of SMN1 Exon 8 in Carriers

BACKGROUND

Current carrier screening methods do not identify a proportion of carriers that may have children affected by spinal muscular atrophy (SMA). Additional genetic data is essential to inform accurate risk assessment and genetic counselling of SMA carriers. This study aims to quantify the various genotypes among parents of children with SMA.

METHOD

A retrospective cohort study was undertaken at Sydney Children's Hospital Network, the major SMA referral centre for New South Wales, Australia. Participants included children with genetically confirmed SMA born between 2005 and 2021. Data was collected on parent genotype inclusive of copy number of SMN1 exons 7 and 8. The number of SMN2 exon 7 copies were recorded for the affected children. Descriptive statistics were used to determine the proportion of carriers of 2+0 genotype classified as silent carriers. Chi-square test was used to correlate the association between parents with a heterozygous SMN1 exon 7 deletion and two copies of exon 8 and ≥3 SMN2 copy number in the proband.

RESULTS

SMA carrier testing was performed in 118/154 (76.6%) parents, incorporating 59 probands with homozygous SMN1 deletions and one proband with compound heterozygote pathogenic variants. Among parents with a child with SMA, 7.6% had two copies of SMN1 exon 7. When only probands with a homozygous SMN1 exon 7 deletion were included, 6.9% of parents had two copies of SMN1 exon 7. An association was observed between heterozygous deletion of SMN1 exon 7 with two copies of exon 8 in a parent and ≥3 SMN2 copy number in the affected proband (p = 0.07).

CONCLUSIONS

This study confirmed a small but substantial proportion of silent carriers not identified by conventional screening within an Australian context. Accordingly, the effectiveness of carrier screening for SMA is linked with genetic counselling to enable health literacy regarding high and low risk results and is complemented by new-born screening and maintaining clinical awareness for SMA. Gene conversion events may underpin the associations between parent carrier status and proband SMN2 copy number.

VRK1 variants at the cross road of Cajal body neuropathogenic mechanisms in distal neuropathies and motor neuron diseases

Distal hereditary neuropathies and neuro motor diseases are complex neurological phenotypes associated with pathogenic variants in a large number of genes, but in some the origin is unknown. Recently, rare pathogenic variants of the human VRK1 gene have been associated with these neurological phenotypes. All VRK1 pathogenic variants are recessive, and their clinical presentation occurs in either homozygous or compound heterozygous patients. The pathogenic VRK1 gene pathogenic variants are located in three clusters within the protein sequence. The main, and initial, shared clinical phenotype among VRK1 pathogenic variants is a distal progressive loss of motor and/or sensory function, which includes diseases such as spinal muscular atrophy, Charcot-Marie-Tooth, amyotrophic lateral sclerosis and hereditary spastic paraplegia. In most cases, symptoms start early in infancy, or in utero, and are slowly progressive. Additional neurological symptoms vary among non-related patients, probably because of their different VRK1 variants and their genetic background. The underlying common pathogenic mechanism, by its functional impairment, is a likely consequence of the roles that the VRK1 protein plays in the regulation on the stability and assembly of Cajal bodies, which affect RNA maturation and processing, neuronal migration of RNPs along axons, and DNA-damage responses. Alterations of these processes are associated with several neuro sensory or motor syndromes. The clinical heterogeneity of the neurological phenotypes associated with VRK1 is a likely consequence of the protein complexes in which VRK1 is integrated, which include several proteins known to be associated with Cajal bodies and DNA damage responses. Several hereditary distal neurological diseases are a consequence of pathogenic variants in genes that alter these cellular functions. We conclude that VRK1-related distal hereditary neuropathies and motor neuron diseases represent a novel subgroup of Cajal body related neurological syndromes.

Adherence and Persistence to Nusinersen for Spinal Muscular Atrophy: A US Claims-Based Analysis

INTRODUCTION

Spinal muscular atrophy (SMA) is a genetic, neuromuscular disease caused by deletions and/or mutations in the survival of motor neuron 1 (SMN1) gene leading to reduced SMN protein levels. Nusinersen, an intrathecally administered antisense oligonucleotide therapy that increases SMN protein levels, is approved for use in adult and pediatric patients with SMA. Data to inform real-world patient adherence and persistence to nusinersen are limited, with disparities in the population with SMA, study design, and results. The objective of this study is to characterize real-world nusinersen adherence and persistence in patients with SMA.

METHODS

This retrospective study examined nusinersen adherence and persistence over a 2-year period in patients with SMA in the USA from the IQVIA PharMetrics Plus claims database. Patients were followed from the date of first evidence of nusinersen treatment (occurring after 1 July 2017) until the end of the study period (31 December 2019) or end of continuous pharmacy and medical benefit enrollment, whichever came first. Subgroup analyses for nusinersen adherence and persistence were performed on the basis of age and presence or absence of spinal complications.

RESULTS

The final cohort consisted of 179 patients with SMA treated with nusinersen. Adherence to nusinersen treatment was 41% at 56 weeks and 39% at 104 weeks. In the base-case persistence analysis, there was a decrease in persistence before 6 months (67%) and further decline at 1 (57%) and 2 years (55%). Patients with spinal complication versus without had numerically higher persistence with nusinersen.

CONCLUSIONS

The findings suggest that adherence and persistence to nusinersen treatment appear low. Demographic (age ≥ 18 years) and clinical factors (no spinal complications) may contribute to nusinersen treatment discontinuation. Future research should explore possible reasons for low adherence and persistence to nusinersen treatment, such as clinical or logistical factors, patient preferences, and payer restrictions.

Strategies for targeting RNA with small molecule drugs

INTRODUCTION

Historically, therapeutic treatment of disease has been restricted to targeting proteins. Of the approximately 20,000 translated human proteins, approximately 1600 are associated with diseases. Strikingly, less than 15% of disease-associated proteins are predicted or known to be 'druggable.' While the concept and narrative of protein druggability continue to evolve with the development of novel technological and pharmacological advances, most of the human proteome remains undrugged. Recent genomic studies indicate that less than 2% of the human genome encodes for proteins, and while as much as 75% of the genome is transcribed, RNA has largely been ignored as a druggable target for therapeutic interventions.

AREAS COVERED

This review delineates the theory and techniques involved in the development of small molecule inhibitors of RNAs from brute force, high-throughput screening technologies to de novo molecular design using computational machine and deep learning. We will also highlight the potential pitfalls and limitations of targeting RNA with small molecules.

EXPERT OPINION

Although significant advances have recently been made in developing systems to identify small molecule inhibitors of RNAs, many challenges remain. Focusing on RNA structure and ligand binding sites may help bring drugging RNA in line with traditional protein drug targeting.

Disease Burden of Spinal Muscular Atrophy: A Comparative Cohort Study Using Insurance Claims Data in the USA

BACKGROUND

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by homozygous deletion or loss-of-function mutations of the survival of motor neuron 1 (SMN1) gene, resulting in reduced levels of SMN protein throughout the body. Patients with SMA may have multiple tissue defects, which could present prior to neuromuscular symptoms.

OBJECTIVE

To assess the signs, comorbidities and potential extraneural manifestations associated with SMA in treatment-naïve patients.

METHODS

This observational, retrospective and matched-cohort study used secondary insurance claims data from the US IBM® MarketScan® Commercial, Medicaid and Medicare Supplemental databases between 01/01/2000 and 12/31/2013. Treatment-naïve individuals aged≤65 years with≥2 International Classification of Diseases, Ninth Revision (ICD-9) SMA codes were stratified into four groups (A-D), according to age at index (date of first SMA code recorded) and type of ICD-9 code used, and matched with non-SMA controls. The occurrence of ICD-9 codes, which were converted to various classifications (phecodes and system classes), were compared between groups in pre- and post-index periods.

RESULTS

A total of 1,457 individuals with SMA were included and matched to 13,362 controls. Increasing numbers of SMA-associated phecodes and system classes were generally observed from pre- to post-index across all groups. The strongest associations were observed in the post-index period for the youngest age groups. Endocrine/metabolic disorders were associated with SMA in almost all groups and across time periods.

CONCLUSIONS

This exploratory study confirmed the considerable disease burden in patients with SMA and identified 305 unique phecodes associated with SMA, providing a rationale for further research into the natural history and progression of SMA, including extraneural manifestations of the disease.

Viral-mediated gene therapy in pediatric neurological disorders

BACKGROUND

Due to the broad application of next-generation sequencing, the molecular diagnosis of genetic disorders in pediatric neurology is no longer an unachievable goal. However, treatments for neurological genetic disorders in children remain primarily symptomatic. On the other hand, with the continuous evolution of therapeutic viral vectors, gene therapy is becoming a clinical reality. From this perspective, we wrote this review to illustrate the current state regarding viral-mediated gene therapy in childhood neurological disorders.

DATA SOURCES

We searched databases, including PubMed and Google Scholar, using the keywords "adenovirus vector," "lentivirus vector," and "AAV" for gene therapy, and "immunoreaction induced by gene therapy vectors," "administration routes of gene therapy vectors," and "gene therapy" with "NCL," "SMA," "DMD," "congenital myopathy," "MPS" "leukodystrophy," or "pediatric metabolic disorders". We also screened the database of ClinicalTrials.gov using the keywords "gene therapy for children" and then filtered the results with the ones aimed at neurological disorders. The time range of the search procedure was from the inception of the databases to the present.

RESULTS

We presented the characteristics of commonly used viral vectors for gene therapy for pediatric neurological disorders and summarized their merits and drawbacks, the administration routes of each vector, the research progress, and the clinical application status of viral-mediated gene therapy on pediatric neurological disorders.

CONCLUSIONS

Viral-mediated gene therapy is on the brink of broad clinical application. Viral-mediated gene therapy will dramatically change the treatment pattern of childhood neurological disorders, and many children with incurable diseases will meet the dawn of a cure. Nevertheless, the vectors must be optimized for better safety and efficacy.

Patient Reported Outcome Measures in Adult Spinal Muscular Atrophy: A Scoping Review and Graphical Visualization of the Evidence

BACKGROUND

Spinal Muscular Atrophy (SMA) is a hereditary neuromuscular disease with an estimated prevalence of 1/10 000 births. SMA is increasingly recognized as a multi-system disease with a need to study additional under-recognized health domains such as quality of life, fatigue, bulbar function, respiratory function, and independence.

OBJECTIVE

Identify and assess reported evidence from the literature investigating Patient Reported Outcome Measures (PROMs) in adults with SMA. Develop a novel method drawing from network theory to graphically depict the literature, PROMs, and supporting psychometric evidence.

METHODS

A scoping review was completed following PRISM-ScR, COSMIN and JBI scoping review guidelines. Literature investigating PROMs in adult SMA or neuromuscular disease was identified from peer-reviewed and grey databases. A network graph was derived from extracted data.

RESULTS

5292 articles were retrieved, 81 articles met inclusion criteria; corresponding to 31 unique PROMs. Only two PROMs were developed specifically for SMA. Few PROMs covered multiple domains of health. Most PROMs were incompletely validated, focusing on concurrent validity, and few assessed responsiveness or internal consistency.

CONCLUSIONS

PROMs are emerging tools for monitoring and assessing adults with SMA. Despite their potential benefits, additional validation studies should be completed prior to their use for clinical decision-making. Network graphics may represent a technique to aid in the visualization of evidence supporting a scoping review.

The Japan Registry for Adult Subjects of Spinal Muscular Atrophy (jREACT-SMA): Protocol for a Longitudinal Observational Study

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive genetic neuromuscular disorder with progressive muscle weakness and atrophy, mainly caused by lower motor neuron degeneration resulting from decreased levels of the survival motor neuron protein. Recently, 3 disease-modifying therapies for SMA (nusinersen, onasemnogene abeparvovec, and risdiplam) were approved in Japan that are expected to improve the prognosis of patients with SMA. Long-term clinical follow-up of adult patients treated with disease-modifying therapies and the natural history of SMA are essential to assess the real-world effectiveness of available treatments. Until recently, nusinersen was the only treatment option for patients with SMA in Japan; however, because Japanese approval of nusinersen was based on global clinical trials in infants and children aged 0-15 years with SMA, the effectiveness of nusinersen in adult patients has not been fully assessed in Japan. In addition, longitudinal clinical data of adult patients have not been systematically collected in Japan.

OBJECTIVE

This longitudinal observational study of adult patients with SMA who have been diagnosed with 5q-SMA in Japan aims to gain a better understanding of the natural history of SMA, as well as the long-term effectiveness of disease-modifying therapies. Here, we describe the protocol for the study.

METHODS

The Japan Registry for Adult Subjects of Spinal Muscular Atrophy (jREACT-SMA) study is a longitudinal (prospective and retrospective) observational study with a 60-month prospective follow-up being conducted at 19 investigational sites using the newly established jREACT-SMA registry. Patients aged ≥18 years with genetically confirmed 5q-SMA were planned to be enrolled in the registry from December 2020 to May 2022. The planned enrollment was 100 patients. The protocol was approved on September 28, 2020 (approval 2020-0289) by the ethical review committee of Nagoya University. Registration, demographics, genetic diagnosis, motor functions, patient-reported outcomes/quality-of-life outcomes, and other clinical data have been or will be collected.

RESULTS

As of May 2022, 113 patients had been enrolled, and the completion of patient registration has been extended from May 2022 to December 2022. Data at registration and during the follow-up period were and will be prospectively collected at least once a year until November 2025 (maximum 60 months). Data analyses will be conducted when all data have been collected. Results are expected to be available in 2026 and the study is expected to be completed by March 2027.

CONCLUSIONS

This jREACT-SMA study will provide longitudinal prospective follow-up data in adult patients with SMA in Japan, including data on the natural history of the disease and data on the long-term effectiveness of disease-modifying therapies.

TRIAL REGISTRATION

University Hospital Medical Information Network Center Clinical Trials Registry UMIN000042015; https://rctportal.niph.go.jp/en/detail?trial_id=UMIN000042015.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/38878.

Early onset hereditary neuronopathies: an update on non-5q motor neuron diseases

Hereditary motor neuropathies (HMN) were first defined as a group of neuromuscular disorders characterized by lower motor neuron dysfunction, slowly progressive length-dependent distal muscle weakness and atrophy, without sensory involvement. Their cumulative estimated prevalence is 2.14/100 000 and, to date, around 30 causative genes have been identified with autosomal dominant, recessive,and X-linked inheritance. Despite the advances of next generation sequencing, more than 60% of patients with HMN remain genetically uncharacterized. Of note, we are increasingly aware of the broad range of phenotypes caused by pathogenic variants in the same gene and of the considerable clinical and genetic overlap between HMN and other conditions, such as Charcot-Marie-Tooth type 2 (axonal), spinal muscular atrophy with lower extremities predominance, neurogenic arthrogryposis multiplex congenita and juvenile amyotrophic lateral sclerosis. Considering that most HMN present during childhood, in this review we primarily aim to summarize key clinical features of paediatric forms, including recent data on novel phenotypes, to help guide differential diagnosis and genetic testing. Second, we describe newly identified causative genes and molecular mechanisms, and discuss how the discovery of these is changing the paradigm through which we approach this group of conditions.

Clinical and Electrophysiological Changes in Pediatric Spinal Muscular Atrophy after 2 Years of Nusinersen Treatment

In the new therapeutic era, disease-modifying treatment (nusinersen) has changed the natural evolution of spinal muscular atrophy (SMA), creating new phenotypes. The main purpose of the retrospective observational study was to explore changes in clinical evolution and electrophysiological data after 2 years of nusinersen treatment. We assessed distal compound motor action potential (CMAP) on the ulnar nerve and motor abilities in 34 SMA patients, aged between 1 and 16 years old, under nusinersen treatment, using specific motor scales for types 1, 2 and 3. The evaluations were performed at treatment initiation and 26 months later. There were registered increased values for CMAP amplitudes after 2 years of nusinersen, significantly correlated with motor function evolution in SMA type 1 patients (p < 0.005, r = 0.667). In total, 45% of non-sitters became sitters and 25% of sitters became walkers. For SMA types 1 and 2, the age at the treatment initialization is highly significant (p < 0.0001) and correlated with treatment yield. A strong negative correlation (r = −0.633) was observed for SMA type 1 and a very strong negative correlation (r = −0.813) for SMA type 2. In treated SMA cases, the distal amplitude of the CMAP and motor functional scales are important prognostic factors, and early diagnosis and treatment are essential for a better outcome.

New medicine for neuromuscular diseases: An evolving paradox for patient and family hopes and expectations

Recent developments in novel therapies for neuromuscular diseases offer parents new perspectives on their affected children's future. This article examines how the emergence of new therapies impacts the lives of parents of children with Duchenne muscular dystrophy or spinal muscular atrophy type 2, two genetic neuromuscular disorders characterized by progressive muscle degeneration. Aiming for a first-person perspective, fieldwork was conducted utilizing participant observation, semistructured interviews, and several internet sources. Six families with a total of 12 persons, all living in Denmark, were included in the interviews. Two types of parents were identified who were at opposite ends in dealing with the new therapies-the cure optimists and the cure pragmatists. Different hopes resulted in different narratives for their children's futures. The article raises questions about how and when children with chronic diseases should be involved in their parent's hopes for a cure and highlights the dilemmas facing health professionals working in the field of children with chronic diseases for which the prospects of a cure are improving. We conclude that health professionals must find a way to carefully balance guidance and information about experimental medicines, including the fact that experimental medicine sometimes fails, does not work as well as hoped for, or does not become available, with sustaining parental hopes for their children's future.

Spinal muscular atrophy carrier frequency in Saudi Arabia

BACKGROUND

Spinal Muscular Dystrophy (SMA) is one of the leading causes of death in infants and young children from heritable diseases. Although no large-scale popultion-based studies have been done in Saudi Arabia, it is reported that the incidence of SMA is higher in the Saudi population partly because of the high degree of consanguineous marriages.

METHODS

The final analysis included 4198 normal volunteers aged between 18 and 25 years old, 54.7% males, and 45.3% females. Whole blood was spotted directly from finger pricks onto IsoCode StixTM and genomic DNA was isolated using one triangle from the machine. To discern the SMN1 copy number independently from SMN2, Multiplex PCR with Dral restriction fragment analysis was completed. We used the carrier frequency and population-level data to estimate the prevalence of SMA in the population using the life-table method.

RESULTS

This data analysis showed the presence of one copy of the SMN1 gene in 108 samples and two copies in 4090 samples, which resulted from a carrier frequency of 2.6%. The carrier frequency was twofold in females reaching 3.7% compared to 1.6% in males. 27% of participants were children of first-cousin marriages. We estimated the birth incidence of SMA to be 32 per 100,000 birth and the total number of people living with SMA in the Kingdom of Saudi Arabia to be 2265 of which 188 are type I, 1213 are type II, and 8,64 are type III.

CONCLUSION

The SMA carrier rate of 2.6% in Saudi control subjects is slightly higher than the reported global frequency of 1.25 to 2% with links to the high degree of consanguinity.

Natural history of Type 1 spinal muscular atrophy: a retrospective, global, multicenter study

BACKGROUND

ANCHOVY was a global, multicenter, chart-review study that aimed to describe the natural history of Type 1 spinal muscular atrophy (SMA) from a broad geographical area and provide further contextualization of results from the FIREFISH (NCT02913482) interventional study of risdiplam treatment in Type 1 SMA.

METHODS

Data were extracted from medical records of patients with first symptoms attributable to Type 1 SMA between 28 days and 3 months of age, genetic confirmation of SMA, and confirmed survival of motor neuron 2 copy number of two or unknown. The study period started on 1 January 2008 for all sites; study end dates were site-specific due to local treatment availabilities. Primary endpoints were time to death and/or permanent ventilation and proportion of patients achieving motor milestones. Secondary endpoints included time to initiation of respiratory and feeding support.

RESULTS

Data for 60 patients from nine countries across Asia, Europe and North and South America were analyzed. The median age (interquartile range [IQR]) for reaching death or permanent ventilation was ~ 7.3 (5.9-10.5) months. The median age (IQR) at permanent ventilation was ~ 12.7 (6.9-16.4) months and at death was ~ 41.2 (7.3-not applicable) months. No patients were able to sit without support or achieved any level of crawling, standing or walking.

INTERPRETATION

Findings from ANCHOVY were consistent with published natural history data on Type 1 SMA demonstrating the disease's devastating course, which markedly differed from risdiplam-treated infants (FIREFISH Part 2). The results provide meaningful additions to the literature, including a broader geographical representation.

Respiratory management of spinal muscular atrophy type 1 patients treated with Nusinersen

INTRODUCTION

The recent development of disease-modifying treatments in spinal muscular atrophy (SMA) type 1 shifted these patients' management from palliative to proactive. The aim of this study was to assess patients' nocturnal gas exchanges before noninvasive ventilation (NIV) initiation and their clinical evolution to determine if capnia is a good criterion to decide when to introduce respiratory support.

PATIENTS AND METHODS

This multicentric retrospective study reports the respiratory management and evolution of 17 SMA type 1 children (10 females) for whom treatment with Nusinersen was initiated between 2016 and 2018.

RESULTS

Median [interquartile range-IQR] age at diagnosis and at first Nusinersen injection was of 4 [3;8] and 4 [3;9] months, respectively. Patients were followed during 38 [24;44] months. Thirteen (76%) patients were started on NIV at a median [IQR] age of 12 [9;18] months. Repeated hospitalizations and intensive care unit admissions were needed for 11 of them. Blood gas and nocturnal gas exchange recordings performed before NIV initiation were always normal. 9/13 X-ray performed before NIV showed atelectasis and/or acute lower respiratory tract infections. There was a significant decrease in the total number of hospital admissions between the first and second year of treatment (p = 0.04).

CONCLUSION

This study shows that patients do not present with nocturnal hypoventilation before respiratory decompensations and NIV initiation, and suggests that a delay in NIV initiation might result in respiratory complications. There is a need for disease-centered guidelines for the respiratory management of these patients, including NIV indications.

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.

A review of the genetic spectrum of hereditary spastic paraplegias, inherited neuropathies and spinal muscular atrophies in Africans

Background

Genetic investigations of inherited neuromuscular disorders in Africans, have been neglected. We aimed to summarise the published data and comment on the genetic evidence related to inherited neuropathies (Charcot-Marie-Tooth disease (CMT)), hereditary spastic paraplegias (HSP) and spinal muscular atrophy (SMA) in Africans.

Methods

PubMed was searched for relevant articles and manual checking of references and review publications were performed for African-ancestry participants with relevant phenotypes and identified genetic variants. For each case report we extracted phenotype information, inheritance pattern, variant segregation and variant frequency in population controls (including up to date frequencies from the gnomAD database).

Results

For HSP, 23 reports were found spanning the years 2000–2019 of which 19 related to North Africans, with high consanguinity, and six included sub-Saharan Africans. For CMT, 19 reports spanning years 2002–2021, of which 16 related to North Africans and 3 to sub-Saharan Africans. Most genetic variants had not been previously reported. There were 12 reports spanning years 1999–2020 related to SMN1-SMA caused by homozygous exon 7 ± 8 deletion. Interestingly, the population frequency of heterozygous SMN1-exon 7 deletion mutations appeared 2 × lower in Africans compared to Europeans, in addition to differences in the architecture of the SMN2 locus which may impact SMN1-SMA prognosis.

Conclusions

Overall, genetic data on inherited neuromuscular diseases in sub-Saharan Africa, are sparse. If African patients with rare neuromuscular diseases are to benefit from the expansion in genomics capabilities and therapeutic advancements, then it is critical to document the mutational spectrum of inherited neuromuscular disease in Africa.

Highlights

Review of genetic variants reported in hereditary spastic paraplegia in Africans

Review of genetic variants reported in genetic neuropathies in Africans

Review of genetic underpinnings of spinal muscular atrophies in Africans

Assessment of pathogenic evidence for candidate variants

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02280-2.

The Safety and Efficacy of Nusinersen in the Treatment of Spinal Muscular Atrophy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background and objectives: Spinal muscular atrophy (SMA) is a neurodegenerative disease that leads to progressive proximal muscle weakness and muscle atrophy. To assess the beneficial and adverse effects of nusinersen, a promising intervention for SMA, we conducted a systematic search and meta-analysis of the published randomized control trials (RCTs) of nusinersen for SMA. Materials and methods: Utilizing the Preferred Reporting for Systematic Review and Meta-Analysis (PRISMA), we searched PubMed, Scopus, Web of Science, Cochrane Central, and Clinicaltrials.gov from inception to 22 July 2021. Results: Three RCTs satisfying the inclusion and exclusion criteria covered 274 patients: 178 patients in the nusinersen group. Our results show a significant risk difference (RD) in the motor milestone response (RD: 0.51; 95% CI: 0.39, 0.62; p < 0.00001) and improvement in the HINE-2 score (RD: 0.26; 95% CI: 0.12, 0.40; p < 0.0003) in the nusinersen group compared to the control group. Moreover, a significant decrease in the risk ratio (RR) for severe adverse events (RR: 0.72; 95% CI: 0.57, 0.92; p = 0.007) and any adverse event leading to treatment discontinuation (RR: 0.40; 95% CI: 0.22, 0.74; p = 0.004) was observed. An insignificant result was found for any adverse effects (RR: 0.93; 95% CI: 0.97, 1.01; p = 0.14) and for serious adverse effects (RR: 0.81; 95% CI: 0.60, 1.07; p = 0.14). Conclusions: This review provides evidence that nusinersen treatment was effective in treatment for infants with SMA and was associated with fewer severe adverse events; however, more RCTs are needed to establish evidence.

Targeted RNA editing: novel tools to study post-transcriptional regulation

RNA binding proteins (RBPs) regulate nearly all post-transcriptional processes within cells. To fully understand RBP function, it is essential to identify their in vivo targets. Standard techniques for profiling RBP targets, such as crosslinking immunoprecipitation (CLIP) and its variants, are limited or suboptimal in some situations, e.g. when compatible antibodies are not available and when dealing with small cell populations such as neuronal subtypes and primary stem cells. This review summarizes and compares several genetic approaches recently designed to identify RBP targets in such circumstances. TRIBE (targets of RNA binding proteins identified by editing), RNA tagging, and STAMP (surveying targets by APOBEC-mediated profiling) are new genetic tools useful for the study of post-transcriptional regulation and RBP identification. We describe the underlying RNA base editing technology, recent applications, and therapeutic implications.

A Compound Heterozygous Mutation in Calpain 1 Identifies a New Genetic Cause for Spinal Muscular Atrophy Type 4 (SMA4)

Spinal Muscular Atrophy (SMA) is a heterogeneous group of neuromuscular diseases characterized by degeneration of anterior horn cells of the spinal cord, leading to muscular atrophy and weakness. Although the major cause of SMA is autosomal recessive exon deletions or loss-of-function mutations of survival motor neuron 1 (SMN1) gene, next generation sequencing technologies are increasing the genetic heterogeneity of SMA. SMA type 4 (SMA4) is an adult onset, less severe form of SMA for which genetic and pathogenic causes remain elusive.Whole exome sequencing in a 30-year-old brother and sister with SMA4 identified a compound heterozygous mutation (p. G492R/p. F610C) in calpain-1 (CAPN1). Mutations in CAPN1 have been previously associated with cerebellar ataxia and hereditary spastic paraplegia. Using skin fibroblasts from a patient bearing the p. G492R/p. F610C mutation, we demonstrate reduced levels of CAPN1 protein and protease activity. Functional characterization of the SMA4 fibroblasts revealed no changes in SMN protein levels and subcellular distribution. Additional cellular pathways associated with SMA remain unaffected in the patient fibroblasts, highlighting the tissue specificity of CAPN1 dysfunction in SMA4 pathophysiology. This study provides genetic and functional evidence of CAPN1 as a novel gene for the SMA4 phenotype and expands the phenotype of CAPN1 mutation disorders.

Spinal muscular atrophy: Where are we now? Current challenges and high hopes

Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by muscle weakness. It causes movement issues and severe physical disability. SMA is classified into four types based on the level of function achieved, age of onset, and maximum function achieved. The deletion or point mutation in the Survival of Motor Neuron 1 (SMN1) gene causes SMA. As a result, no full-length protein is produced. A nearly identical paralog, SMN2, provides enough stable protein to prevent death but not enough to compensate for SMN1's loss. The difference between SMN1 and SMN2 is due to different exon 7 alternative splicing patterns. SMA molecular therapies currently focus on restoring functional SMN protein by splicing modification of SMN2 exon 7 or elevated SMN protein levels. Nusinersen, an antisense oligonucleotide targeting the ISS-N1 sequence in SMN2 intron 7, was the first drug approved by the Food and Drug Administration. Risdiplam, a novel therapeutic that acts as an SMN2 exon 7 splicing modifier, was recently approved. All of these drugs result in the inclusion of SMN2 exon 7, and thus the production of functional SMN protein. Onasemnogene abeparvovec is a gene therapy that uses a recombinant adeno-associated virus that encodes the SMN protein. There are also experimental therapies available, such as reldesemtiv and apitegromab (SRK-015), which focus on improving muscle function or increasing muscle tissue growth, respectively. Although approved therapies have been shown to be effective, not all SMA patients can benefit from them due to age or weight, but primarily due to their high cost. This demonstrates the significance of continuous treatment improvement in today's medical challenges.

Rare Neurological Diseases: an Overreview of Pathophysiology, Epidemiology, Clinical Features and Pharmacoeconomic Considerations in the Treating

Rare diseases (RD) are serious chronic diseases affecting small number of people compared to the general population. There are between 6000 and 8000 RDs, which affect about 400 million people worldwide. Drugs used for causal treatment of RDs are called orphan drugs. RDs bear great clinical and economic burden for patients, their families, healthcare systems and society overall. There are at least two reasons for the high cost of treatment of RDs. First, there is no causal therapy for majority of RDs, so exacerbations, complications, and hospitalizations in those patients are common. The second reason is high price of available orphan drugs, which are not cost-effective when traditional pharmacoeconomic evaluation is employed. The pharmacoeconomic aspect of the treatment of RDs is especially important in the field of neurology, since at least one fifth of all RDs is composed of neurological conditions. The aim of this paper was to provide a concise overview of the pathophysiological, epidemiological and clinical characteristics of some of the most important and common rare neurological diseases, with special reference to their impact on society and economy.

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.

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.

Adult-onset non-5q proximal spinal muscular atrophy: a comprehensive review

BACKGROUND

Adult-onset spinal muscular atrophy (SMA) represents an expanding group of inherited neurodegenerative disorders in clinical practice.

OBJECTIVE

This review aims to synthesize the main clinical, genetic, radiological, biochemical, and neurophysiological aspects related to the classical and recently described forms of proximal SMA.

METHODS

The authors performed a non-systematic critical review summarizing adult-onset proximal SMA presentations.

RESULTS

Previously limited to cases of SMN1-related SMA type 4 (adult form), this group has now more than 15 different clinical conditions that have in common the symmetrical and progressive compromise of lower motor neurons starting in adulthood or elderly stage. New clinical and genetic subtypes of adult-onset proximal SMA have been recognized and are currently target of wide neuroradiological, pathological, and genetic studies.

CONCLUSIONS

This new complex group of rare disorders typically present with lower motor neuron disease in association with other neurological or systemic signs of impairment, which are relatively specific and typical for each genetic subtype.

A Canadian Adult Spinal Muscular Atrophy Outcome Measures Toolkit: Results of a National Consensus using a Modified Delphi Method

Background:

Spinal Muscular Atrophy (SMA) is a rare disease that affects 1 in 11 000 live births. Recent developments in SMA treatments have included new disease-modifying therapies that require high quality data to inform decisions around initiation and continuation of therapy. In Canada, there are no nationally agreed upon outcome measures (OM) used in adult SMA. Standardization of OM is essential to obtain high quality data that is comparable among neuromuscular clinics.

Objective:

To develop a recommended toolkit and timing of OM for assessment of adults with SMA.

Methods:

A modified delphi method consisting of 2 virtual voting rounds followed by a virtual conference was utilized with a panel of expert clinicians treating adult SMA across Canada.

Results:

A consensus-derived toolkit of 8 OM was developed across three domains of function, with an additional 3 optional measures. Optimal assessment frequency is 12 months for most patients regardless of therapeutic access, while patients in their first year of receiving disease-modifying therapy should be assessed more frequently.

Conclusions:

The implementation of the consensus-derived OM toolkit will improve monitoring and assessment of adult SMA patients, and enrich the quality of real-world evidence. Regular updates to the toolkit must be considered as new evidence becomes available.

Onasemnogene Abeparvovec (AVXS-101) for the Treatment of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a debilitating disorder characterized by degeneration of large motor neurons. It is a heterogeneous group of disorders caused by a homozygous deletion in the survival motor neuron (SMN) gene on chromosome 5, resulting in a SMN protein deficiency. Small amounts of SMN protein are also produced by the SMN2 gene, which that differs from SMN1 by a single nucleotide. Spinal muscular atrophy types and phenotypic severity depend on the number of variations of the SMN2 gene and the amount of SMN2 protein produced. Because the SMN protein deficiency is the root cause of the disease, treatment strategies for SMA revolve around increasing SMN protein production. Nusinersen (Spinraza, Biogen, Cambridge, MA) was the only treatment option available for SMA until the FDA approved onasemnogene abeparvovec-xioi (Zolgensma, AveXis Inc, Bannockburn, IL), a one-time-administered adeno-associated viral vector-based gene therapy that delivers the SMN gene to the motor neuron cells. Data from clinical studies show significant improvement in motor milestone achievements and ventilator-free survival but are limited by approximately 5 years' worth of results. This one-time intravenous injection of this new gene therapy also bears a hefty price tag; however, it may be more cost effective in the long run versus the multiple intrathecal administrations needed with nusinersen. Drug access and use are hindered by drug cost, payer reimbursement issues, and lack of long-term data from clinical studies. Questions also remain regarding the safety and efficacy of repeated drug administration for patients with advanced disease.

Spinal Muscular Atrophy: Autopsy Based Neuropathological Demonstration

Spinal muscular atrophy (SMA) encompasses a group of disorders with loss of spinal motor neurons.The report describes the neuropathological findings including brain and spinal cord at autopsy in a five-and-half-month-old boy with suspected type 1 SMA. The anterior motor neurons, Clarke's column at all the levels of spinal cord showed neuronal loss and degeneration while neurons at all the deep grey nuclei were preserved apart from variable degree anoxic changes. Skeletal muscle biopsy revealed features of neurogenic atrophy consistent with SMA. A differential diagnosis like storage disorders was excluded using electron microscopy. No extra-neural manifestations were seen. Neuropathological features at autopsy have seldom been reported in the literature.

Ultrastructural characterization of peripheral denervation in a mouse model of Type III spinal muscular atrophy

Spinal muscular atrophy (SMA) is a heritable, autosomal recessive neuromuscular disorder characterized by a loss of the survival of motor neurons (SMN) protein, which leads to degeneration of lower motor neurons, and muscle atrophy. Despite SMA being nosographically classified as a motor neuron disease, recent advances indicate that peripheral alterations at the level of the neuromuscular junction (NMJ), involving the muscle, and axons of the sensory-motor system, occur early, and may even precede motor neuron loss. In the present study, we used a mouse model of slow progressive (type III) SMA, whereby the absence of the mouse SMN protein is compensated by the expression of two human genes (heterozygous SMN1A2G, and SMN2). This leads to late disease onset and prolonged survival, which allows for dissecting slow degenerative steps operating early in SMA pathogenesis. In this purely morphological study carried out at transmission electron microscopy, we extend the examination of motor neurons and proximal axons towards peripheral components, including distal axons, muscle fibers, and also muscle spindles. We document remarkable ultrastructural alterations being consistent with early peripheral denervation in SMA, which may shift the ultimate anatomical target in neuromuscular disease from the spinal cord towards the muscle. This concerns mostly mitochondrial alterations within distal axons and muscle, which are quantified here through ultrastructural morphometry. The present study is expected to provide a deeper knowledge of early pathogenic mechanisms in SMA.

Awareness screening and referral patterns among pediatricians in the United States related to early clinical features of spinal muscular atrophy (SMA)

Background

Spinal Muscular Atrophy (SMA), a leading genetic cause of death in infants, is an autosomal recessive neuromuscular disease characterized by progressive muscle weakness and atrophy. While early diagnosis of SMA is critical to modifying disease progression and improving outcomes, serious diagnostic delays persist. There is a need to improve SMA awareness, screening, and referral patterns.

Methods

Two online surveys, developed by Cure SMA for general pediatricians, were distributed by Medscape Education via email (September 2018, n = 300, December 2019, n = 600). The surveys asked about adherence to the American Academy of Pediatrics (AAP) developmental screening and surveillance guidelines, comfort with identification of early signs of neuromuscular disease (NMD), familiarity with SMA, and barriers to timely referral.

Results

In 2018, 70.3% of survey respondents indicated comfort in identifying early signs of NMD and 67.3% noted familiarity with SMA. 52.7% correctly indicated the need for genetic testing to make a definitive diagnosis of SMA, 74.0% meet or exceed developmental screening recommendations, and 52.0% said they would immediately refer to a specialist. In 2019, with a larger sample, 73.0% adhere to developmental screening guidelines, and awareness of the genetic testing requirement for SMA was significantly lower by 7.7% (p < 0.03). Specialist wait times emerged as a barrier to referral, with 64.2% of respondents citing wait times of 1–6 months.

Conclusions

Many pediatricians underutilize developmental screening tools and lack familiarity with diagnostic requirements for SMA. Continuing efforts to expand awareness and remove barriers to timely referral to SMA specialists, including reducing appointment wait times, are needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02692-2.

Prognostic Factors and Treatment-Effect Modifiers in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, progressive neuromuscular disease characterized by loss of motor neurons and muscle atrophy. Untreated infants with type 1 SMA do not achieve major motor milestones, and death from respiratory failure typically occurs before 2 years of age. Individuals with types 2 and 3 SMA exhibit milder phenotypes and have better functional and survival outcomes. Herein, a systematic literature review was conducted to identify factors that influence the prognosis of types 1, 2, and 3 SMA. In untreated infants with type 1 SMA, absence of symptoms at birth, a later symptom onset, and a higher survival of motor neuron 2 (SMN2) copy number are all associated with increased survival. Disease duration, age at treatment initiation, and, to a lesser extent, baseline function were identified as potential treatment‐modifying factors for survival, emphasizing that early treatment with disease‐modifying therapies (DMT) is essential in type 1 SMA. In patients with types 2 and 3 SMA, factors considered prognostic of changes in motor function were SMN2 copy number, age, and ambulatory status. Individuals aged 6–15 years were particularly vulnerable to developing complications (scoliosis and progressive joint contractures) which negatively influence functional outcomes and may also affect the therapeutic response in patients. Age at the time of treatment initiation emerged as a treatment‐effect modifier on the outcome of DMTs. Factors identified in this review should be considered prior to designing or analyzing studies in an SMA population, conducting population matching, or summarizing results from different studies on the treatments for SMA.

Comprehensive Mutation Analysis and Report of 12 Novel Mutations in a Cohort of Patients with Spinal Muscular Atrophy in Iran

Spinal muscular atrophies (SMAs) are a heterogeneous group of neuromuscular diseases characterized by loss of motor neurons, muscle weakness, hypotonia and muscle atrophy, with different modes of inheritance; however, the survival motor neuron 1 (SMN1) gene is predominantly involved. The aims of the current study were to clarify the genetic basis of SMA and determine the mutation spectrum of SMN1 and other associated genes, in order to provide molecular information for more accurate diagnosis and future prospects for treatment. We performed a comprehensive analysis of 5q SMA in 1765 individuals including 528 patients from 432 unrelated families with at least one child with suspected clinical presentation of SMA. Copy number variations of the SMN1 and SMN2 genes and linkage analysis were performed using multiplex ligation-dependent probe amplification (MLPA) and short tandem repeat (STR) markers linked to the SMN1 gene. Cases without mutation in the SMA locus on 5q were analyzed for the DNAJB2, IGHMBP2, SIGMAR1 and PLEKHG5 genes using linked STR markers. Sanger sequencing of whole genes was performed for cases with homozygous haplotypes. Whole-genome sequencing (WGS) and whole-exome analysis was conducted for some of the remaining cases. Mutations in the SMN1 gene were identified in 287 (66.43%) families including 269 patients (62.26%) with homozygous deletion of the entire SMN1 gene. Only one of the patients had a homozygous point mutation in the SMN1 gene. Among the remaining families, three families showed mutations in either the DNAJB2, SIGMAR1 or PLEKHG5 genes, which were linked using STR analysis and Sanger sequencing. From 10 families who underwent WGS, we found six homozygous point mutations in six families for either the TNNT1, TPM3, TTN, SACS or COL6A2 genes. Two mutations in the PLA2G6 gene were also found in another patient as compound heterozygous. This rather large cohort allowed us to identify genotype patterns in Iranian 5q SMA patients. The process of identifying 11 mutations (9 novel) in 9 different genes among non-5q SMA patients shows the diversity of genes involved in non-5q SMA in Iranians. Genotyping of patients with SMA is essential for prenatal and preimplantation genetic diagnosis (PGD), and may be very helpful for guiding treatment, with the advent of new, more effective, albeit very expensive, therapies. Also, combining linkage analysis was shown to be beneficial in many ways, including sample authenticity and segregation analysis, and for ruling out maternal cell contamination during prenatal diagnosis (PND).

Treatment preference among patients with spinal muscular atrophy (SMA): a discrete choice experiment

Objective

To examine patient/caregiver preference for key attributes of treatments for spinal muscular atrophy (SMA).

Background

In the rapidly evolving SMA treatment landscape, it is critically important to understand how attributes of potential treatments may impact patient/caregiver choices.

Design/methods

A discrete choice experiment survey was developed based on qualitative interviews. Patients with SMA (≥ 18 years) and caregivers of patients were recruited through a U.S. patient organization. Respondents made choices in each of 12 sets of hypothetical treatments. The relative importance of five treatment characteristics was compared (measured by regression coefficients [RC] of conditional logit models): (1) improvement or stabilization of motor function, (2) improvement or stabilization of breathing function, (3) indication for all ages or pediatric patients only, (4) route of administration [repeated intrathecal (IT) injections, one-time intravenous (IV) infusion, daily oral delivery] and (5) potential harm (mild, moderate, serious/life threatening).

Results

Patient ages ranged from less than 1 to 67 years (n = 101, 65 self-reported and 36 caregiver-reported) and 64 were female. Total SMA subtypes included: type 1 (n = 21), type 2 (n = 48), type 3 (n = 29), other (n = 3). Prior spinal surgery was reported in 47 patients. Nusinersen and onasemnogene abeparvovec-xioi use were reported in 59 and 10 patients, respectively. Improvement in motor and breathing function was highly valued [RC: 0.65, 95% confidence interval (CI): 0.47–0.83 and RC: 0.79, 95% CI: 0.60–0.98, respectively]. Oral medication and one-time infusion were strongly preferred over repeated IT injections (RC: 0.80, 95% CI: 0.60–0.98 and RC: 0.51, 95% CI: 0.30–0.73, respectively). Patients least preferred an age-restricted label/approved use (≤ 2 years of age) (RC: − 1.28, 95% CI: − 1.47 to − 1.09). Cross-attributes trade-off decision suggested a lower willingness for a high-risk therapy despite additional efficacy gain. For some patients, there may be willingness to trade off additional gains in efficacy for a change in route of administration from repeated intrathecal administration to oral medication.

Conclusions

Improvements in motor/breathing function, broad indication, oral or one-time infusion, and minimal risk were preferred treatment attributes. Treatment decisions should be made in clinical context and be tailored to patient needs.

Modulating the endoplasmic reticulum stress response attenuates neurodegeneration in a Caenorhabditis elegans model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating autosomal recessive neuromuscular disease resulting in muscle atrophy and neurodegeneration, and is the leading genetic cause of infant death. SMA arises when there are homozygous deletion mutations in the human SMN1 gene, leading to a decrease in corresponding SMN1 protein. Although SMN1 is expressed across multiple tissue types, much of the previous research into SMA focused on the neuronal aspect of the disease, overlooking many of the potential non-neuronal aspects of the disease. Therefore, we sought to address this gap in knowledge by modeling SMA in the nematode Caenorhabditis elegans. We mutated a previously uncharacterized allele, which resulted in the onset of mild SMA-like phenotypes, allowing us to monitor the onset of phenotypes at different stages. We observed that these mutant animals recapitulated many key features of the human disease, and most importantly, we observed that muscle dysfunction preceded neurodegeneration. Furthermore, we tested the therapeutic efficacy of targeting endoplasmic reticulum (ER) stress in non-neuronal cells and found it to be more effective than targeting ER stress in neuronal cells. We also found that the most potent therapeutic potential came from a combination of ER- and neuromuscular junction-targeted drugs. Together, our results suggest an important non-neuronal component of SMA pathology and highlight new considerations for therapeutic intervention.

Summary: A new non-larval-lethal C. elegans model of spinal muscular atrophy shows mild phenotypes, such as muscle cell and neuronal degeneration, and is therefore useful for testing potential drug treatments.

Novel variants broaden the phenotypic spectrum of PLEKHG5-associated neuropathies

BACKGROUND AND PURPOSE

Pathogenic variants in PLEKHG5 have been reported to date to be causative in three unrelated families with autosomal recessive intermediate Charcot-Marie-Tooth disease (CMT) and in one consanguineous family with spinal muscular atrophy (SMA). PLEKHG5 is known to be expressed in the human peripheral nervous system, and previous studies have shown its function in axon terminal autophagy of synaptic vesicles, lending support to its underlying pathogenetic mechanism. Despite this, there is limited knowledge of the clinical and genetic spectrum of disease.

METHODS

We leverage the diagnostic utility of exome and genome sequencing and describe novel biallelic variants in PLEKHG5 in 13 individuals from nine unrelated families originating from four different countries. We compare our phenotypic and genotypic findings with a comprehensive review of cases previously described in the literature.

RESULTS

We found that patients presented with variable disease severity at different ages of onset (8-25 years). In our cases, weakness usually started proximally, progressing distally, and can be associated with intermediate slow conduction velocities and minor clinical sensory involvement. We report three novel nonsense and four novel missense pathogenic variants associated with these PLEKHG5-associated neuropathies, which are phenotypically spinal muscular atrophy (SMA) or intermediate Charcot-Marie-Tooth disease.

CONCLUSIONS

PLEKHG5-associated neuropathies should be considered as an important differential in non-5q SMAs even in the presence of mild sensory impairment and a candidate causative gene for a wide range of hereditary neuropathies. We present this series of cases to further the understanding of the phenotypic and molecular spectrum of PLEKHG5-associated diseases.

Risdiplam treatment has not led to retinal toxicity in patients with spinal muscular atrophy

OBJECTIVE

Evaluation of ophthalmologic safety with focus on retinal safety in patients with spinal muscular atrophy (SMA) treated with risdiplam (EVRYSDI®), a survival of motor neuron 2 splicing modifier associated with retinal toxicity in monkeys. Risdiplam was approved recently for the treatment of patients with SMA, aged ≥ 2 months in the United States, and is currently under Health Authority review in the EU.

METHODS

Subjects included patients with SMA aged 2 months-60 years enrolled in the FIREFISH, SUNFISH, and JEWELFISH clinical trials for risdiplam. Ophthalmologic assessments, including functional assessments (age-appropriate visual acuity and visual field) and imaging (spectral domain optical coherence tomography [SD-OCT], fundus photography, and fundus autofluorescence [FAF]), were conducted at baseline and every 2-6 months depending on study and assessment. SD-OCT, FAF, fundus photography, and threshold perimetry were evaluated by an independent, masked reading center. Adverse events (AEs) were reported throughout the study.

RESULTS

A total of 245 patients receiving risdiplam were assessed. Comprehensive, high-quality, ophthalmologic monitoring assessing retinal structure and visual function showed no retinal structural or functional changes. In the youngest patients, SD-OCT findings of normal retinal maturation were observed. AEs involving eye disorders were not suggestive of risdiplam-induced toxicity and resolved with ongoing treatment.

INTERPRETATION

Extensive ophthalmologic monitoring conducted in studies in patients with SMA confirmed that risdiplam does not induce ophthalmologic toxicity in pediatric or adult patients with SMA at the therapeutic dose. These results suggest that safety ophthalmologic monitoring is not needed in patients receiving risdiplam, as also reflected in the United States Prescribing Information for risdiplam.

Long-term follow-up of patients with type 2 and non-ambulant type 3 spinal muscular atrophy (SMA) treated with olesoxime in the OLEOS trial

In a previous Phase 2 study, olesoxime had a favorable safety profile. Although the primary endpoint was not met, analyses suggested that olesoxime might help in the maintenance of motor function in patients with Types 2/3 SMA. This open-label extension study (OLEOS) further characterizes the safety, tolerability and efficacy of olesoxime over longer therapy durations. In OLEOS, no new safety risks were identified. Compared to matched natural history data, patients treated with olesoxime demonstrated small, non-significant changes in motor function over 52 weeks. Motor function scores were stable for 52 weeks but declined over the remainder of the study. The greatest decline in motor function was seen in patients ≤15 years old, and those with Type 2 SMA had faster motor function decline versus those with Type 3 SMA. Previous treatment with olesoxime in the Phase 2 study was not protective of motor function in OLEOS. Respiratory outcomes were stable in patients with Type 3 SMA >15 years old but declined in patients with Type 2 SMA and in patients with Type 3 SMA ≤15 years old. Overall, with no stabilization of functional measures observed over 130 weeks, OLEOS did not support significant benefit of olesoxime in patients with SMA.

The Cure SMA Membership Surveys: Highlights of Key Demographic and Clinical Characteristics of Individuals with Spinal Muscular Atrophy

Background:

Cure SMA maintains the largest patient-reported database for people affected with spinal muscular atrophy (SMA). In 2017, Cure SMA initiated annual surveys with their membership to collect demographic and disease characteristics, healthcare, and burden of disease information from patients and caregivers.

Objective:

To summarize results from two large-scale Cure SMA surveys in 2017 and 2018.

Methods:

Cure SMA database members were invited to complete surveys; these were completed by caregivers for living or deceased individuals with SMA and/or affected adults.

Results:

In 2017, 726 surveys were completed for 695 individuals with SMA; in 2018, 796 surveys were completed for 760 individuals with SMA. Data from both survey years are available for 313 affected individuals. Age at symptom onset, distribution of SMN2 gene copy number, and representation of each SMA type in the surveys were consistent with that expected in the SMA population. In the 2018 survey, the average age at diagnosis was 5.2 months for SMA type I and the reported mean age at death for this subgroup was 27.8 months. Between survey years, there was consistency in responses for factors that should not change within individuals over time (e.g., reported age at diagnosis).

Conclusions:

Results from the Cure SMA surveys advance the understanding of SMA and facilitate advocacy efforts and healthcare services planning. Longitudinal surveys are important for evaluating the impact of effective treatments on changing phenotypes, and burden of disease and care in individuals with SMA.