Developmental milestones in type I spinal muscular atrophy

Nusinersen effectiveness and safety in pediatric patients with 5q-spinal muscular atrophy: a multi-center disease registry in China

OBJECTIVE

To evaluate the effectiveness and safety of nusinersen for the treatment of 5q-spinal muscular atrophy (SMA) among Chinese pediatric patients.

METHODS

Using a longitudinal, multi-center registry, both prospective and retrospective data were collected from pediatric patients with 5q-SMA receiving nusinersen treatment across 18 centers in China. All patients fulfilling the eligibility criteria were included consecutively. Motor function outcomes were assessed post-treatment by SMA type. Safety profile was evaluated among patients starting nusinersen treatment post-enrollment. Descriptive analyses were used to report baseline characteristics, effectiveness, and safety results.

RESULTS

As of March 2nd, 2023, 385 patients were included. Most patients demonstrated improvements or stability in motor function across all SMA types. Type II patients demonstrated mean changes [95% confidence interval (CI)] of 4.4 (3.4-5.4) and 4.1 (2.8-5.4) in Hammersmith Functional Motor Scale-Expanded (HFMSE), and 2.4 (1.7-3.1) and 2.3 (1.2-3.4) in Revised Upper Limb Module (RULM) scores at months 6 and 10. Type III patients exhibited mean changes (95% CI) of 3.9 (2.5-5.3) and 4.3 (2.6-6.0) in HFMSE, and 2.1 (1.2-3.0) and 1.5 (0.0-3.0) in RULM scores at months 6 and 10. Of the 132 patients, 62.9% experienced adverse events (AEs). Two patients experienced mild AEs (aseptic meningitis and myalgia) considered to be related to nusinersen by the investigator, with no sequelae.

CONCLUSIONS

These data underscore the significance of nusinersen in Chinese pediatric patients with SMA regarding motor function improvement or stability, and support recommendations on nusinersen treatment by Chinese SMA guidelines and continuous coverage of nusinersen by basic medical insurance.

Functional and Structural Changes in Patients with Spinal Muscular Atrophy Treated in Poland during 12-Month Follow-Up: A Prospective Cohort Study

Background: In recent years, rapid advances in diagnosis and treatment have been observed in spinal muscular atrophy (SMA) patients. The introduction of modern therapies and screening tests has significantly changed the clinical picture of the disease. The previous classification has, therefore, been replaced by new phenotypes: non-sitters, sitters, and walkers, defined by the patient's functional level. However, despite the change in the clinical picture of the disease, patients still suffer from accompanying structural disorders such as scoliosis or joint contractures. Their presence also significantly affects the acquisition of subsequent motor skills. Due to this, monitoring structural changes and ensuring therapists are aware of improvements or declines in patient functionality are essential components of clinical practice. This study aims to compare the assessment of structural and functional changes after a 12-month follow-up in SMA patients who have already experienced the effects of the disease and are now receiving modern therapy. Methods: We present a study of 34 SMA patients being treated with modern therapies and tested twice 12 months apart. The participants were tested using structural measurements and validated scales such as The Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) and Hammersmith Functional Motor Scale-Expanded (HFMSE). Results: During the 12-month follow-up, patients showed deteriorating, non-statistically significant structural changes. We also proved that patients showed a trend toward functional improvement. Analyzing the individual scale items, we distinguished which participants obtained the maximum score for a given parameter and no longer had an opportunity to improve during the second examination. Conclusions: Our study proved that most patients improved overall motor function. The examination of structural measurements should become a standard in the evaluation of SMA patients.

Real-world safety and effectiveness of nusinersen, a treatment for spinal muscular atrophy, in 401 Japanese patients: results from an interim analysis of post-marketing surveillance

Purpose: Nusinersen is an antisense oligonucleotide for the treatment of spinal muscular atrophy (SMA). A post-marketing surveillance (PMS) has been ongoing (August 2017-August 2025) in all patients in Japan who received intrathecal nusinersen in real-world clinical settings. We report the interim analysis results of safety and effectiveness.Methods: This interim analysis was conducted using data collected from 401 patients whose case report forms were obtained at least once by 30 May 2020. Collected data included patient demographics and adverse events (AEs) for safety, and motor function assessments and Clinical Global Impressions of Improvement (CGI-I) for effectiveness.Results: All 401 patients were diagnosed with SMA and were included in the safety and effectiveness analysis (infantile-onset SMA [n = 126, 31.4%], later-onset SMA [n = 275, 68.6%]). The median duration of treatment was 330 days (range 1-823 days). The incidence proportion of AEs was 31.7% (37.3% in infantile-onset SMA and 29.1% in later-onset SMA). The most common AEs were headache (4.5%), pyrexia (4.2%), and pneumonia (3.7%). The incidence proportion of serious AEs was 11.5%. Nusinersen improved motor function scores and was assessed as 'effective' based on CGI-I in 99.7-100% of patients.Conclusions: This interim analysis of the PMS in Japanese patients treated with nusinersen found no new safety concerns, with the type of AEs consistent with the expected safety profile. The benefit-risk balance of nusinersen treatment remains favorable.

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

Introduction

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

Methods

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

Results and discussion

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

Real-World Outcomes in Patients with Spinal Muscular Atrophy Treated with Onasemnogene Abeparvovec Monotherapy: Findings from the RESTORE Registry

Background

Long-term, real-world effectiveness and safety data of disease-modifying treatments for spinal muscular atrophy (SMA) are important for assessing outcomes and providing information for a larger number and broader range of SMA patients than included in clinical trials.

Objective

We sought to describe patients with SMA treated with onasemnogene abeparvovec monotherapy in the real-world setting.

Methods

RESTORE is a prospective, multicenter, multinational, observational registry that captures data from a variety of sources.

Results

Recruitment started in September 2018. As of May 23, 2022, data were available for 168 patients treated with onasemnogene abeparvovec monotherapy. Median (IQR) age at initial SMA diagnosis was 1 (0-6) month and at onasemnogene abeparvovec infusion was 3 (1-10) months. Eighty patients (47.6%) had two and 70 (41.7%) had three copies of SMN2, and 98 (58.3%) were identified by newborn screening. Infants identified by newborn screening had a lower age at final assessment (mean age 11.5 months) and greater mean final (SD) CHOP INTEND score (57.0 [10.0] points) compared with clinically diagnosed patients (23.1 months; 52.1 [8.0] points). All patients maintained/achieved motor milestones. 48.5% (n = 81/167) experienced at least one treatment-emergent adverse event (AE), and 31/167 patients (18.6%) experienced at least one serious AE, of which 8/31 were considered treatment-related.

Conclusion

These real-world outcomes support findings from the interventional trial program and demonstrate effectiveness of onasemnogene abeparvovec over a large patient population, which was consistent with initial clinical data and published 5-year follow-up data. Observed AEs were consistent with the established safety profile of onasemnogene abeparvovec.

A Systematic Literature Review of the Natural History of Respiratory, Swallowing, Feeding, and Speech Functions in Spinal Muscular Atrophy (SMA)

Background

Respiratory and bulbar dysfunctions (including swallowing, feeding, and speech functions) are key symptoms of spinal muscular atrophy (SMA), especially in its most severe forms. Demonstrating the long-term efficacy of disease-modifying therapies (DMTs) necessitates an understanding of SMA natural history.

Objective

This study summarizes published natural history data on respiratory, swallowing, feeding, and speech functions in patients with SMA not receiving DMTs.

Methods

Electronic databases (Embase, MEDLINE, and Evidence-Based Medicine Reviews) were searched from database inception to June 27, 2022, for studies reporting data on respiratory and/or bulbar function outcomes in Types 1-3 SMA. Data were extracted into a predefined template and a descriptive summary of these data was provided.

Results

Ninety-one publications were included: 43 reported data on respiratory, swallowing, feeding, and/or speech function outcomes. Data highlighted early loss of respiratory function for patients with Type 1 SMA, with ventilatory support typically required by 12 months of age. Patients with Type 2 or 3 SMA were at risk of losing respiratory function over time, with ventilatory support initiated between the first and fifth decades of life. Swallowing and feeding difficulties, including choking, chewing problems, and aspiration, were reported in patients across the SMA spectrum. Swallowing and feeding difficulties, and a need for non-oral nutritional support, were reported before 1 year of age in Type 1 SMA, and before 10 years of age in Type 2 SMA. Limited data relating to other bulbar functions were collated.

Conclusions

Natural history data demonstrate that untreated patients with SMA experience respiratory and bulbar function deterioration, with a more rapid decline associated with greater disease severity. This study provides a comprehensive repository of natural history data on bulbar function in SMA, and it highlights that consistent assessment of outcomes in this area is necessary to benefit understanding and approval of new treatments.

Efficacy of risdiplam in spinal muscular atrophy: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to assess the efficacy and safety of risdiplam on motor and respiratory function in spinal muscular atrophy (SMA). We systematically searched Medline, Scopus, Web of Science, and the Cochrane Library from inception to March 2023. We included pre-post studies that determined the effect of risdiplam on the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), the 32-item Motor Function Measure (MFM32), the Revised Upper Limb Module (RULM), the Hammersmith Functional Motor Scale - Expanded (HFMSE), respiratory function, and the proportion of risdiplam-related adverse events in a population with SMA (phenotypes 1 and 2/3). Meta-analyses were also performed where possible. Eleven studies were included. After 12 months of treatment, 57% of participants with SMA1 achieved a CHOP-INTEND score ≥ 40 points, and more than half were able to feed orally and had head control. In SMA2/3, MFM32, RULM, and HFMSE increased by 2.09 (1.17, 3.01), 1.73 (1.25, 2.20), and 1.00 (0.40, 1.59) points, respectively. Efficacy on respiratory function in SMA2/3 was inconsistent. Finally, 16% of participants experienced adverse events, but serious adverse events could not be quantified due to a lack of cases. The limited available evidence suggests that risdiplam is an effective and safe drug for the treatment of SMA. In addition, long-term clinical benefit may be partly determined by the stage of disease at which treatment is initiated.

Structured Light Plethysmography for Non-Invasive Assessment of Respiratory Pattern in Spinal Muscular Atrophy Type 1

BACKGROUND

Spinal muscular atrophy (SMA) type 1 is a severe condition leading to early respiratory failure. Treatment options have become available, yet respiratory outcome measures in SMA type 1 are limited. The aim of this study was to assess the respiratory pattern in SMA type 1 patients via structured light plethysmography (SLP). SLP measures the thoraco-abdominal movements by projecting a light grid onto the anterior thoraco-abdominal surface.

METHODS

Cross-sectional study of consecutive children with SMA type 1. All children underwent motor assessment (CHOP-INTEND) and one-minute tidal breathing recording by SLP in supine position while self-ventilating in room air. The Respiratory rate, the abdominal vs. chest contribution to breath (Relative Expired Abdomen%, Relative Expired Chest%) and the severity of thoraco-abdominal paradox (Phase Angle) were acquired.

RESULTS

Nineteen patients were included, median (IQR) age 2.3 years (1.4-7.9). Their respiratory pattern captured via SLP showed a raised median (IQR) respiratory rate per age of 33.5 bpm (26.6-41.7), a prevalent abdominal contribution to tidal breathing with median (IQR) Relative Expired Abdomen 77% (68-90) vs. Chest 23% (10-32). Thoracoabdominal paradox was detected (median Phase Angle 48.70°) and its severity correlated negatively with CHOP-INTEND (r -0.8, p < 0.01).

CONCLUSIONS

SLP captured and quantified the respiratory features of infants and children with SMA type 1.

Assessing Prevalence and Characteristics of Oro-bulbar Involvement in Children and Adults with SMA Type 2 and 3 Using a Multimodal Approach

Bulbar and jaw muscles are impaired in patients with Spinal Muscular Atrophy (SMA) but the assessment of their severity and progression are limited by the lack of age-appropriate and disease-specific measures. We investigated mastication and swallowing in children and adults with SMA, sitters and walkers. In a 2-year multicentre cross-sectional prospective study, lip and tongue strength (Iowa Oral Performance Instrument), chewing and swallowing (Test of Masticating and Swallowing Solids), active mouth opening (aMMO) were compared to age-appropriate normative data. The perceived burden of oro-bulbar involvement (SMA-Health Index) was recorded. 78 patients were included, 45 children (median age 7.4 years),22 adults (median age 26.8 years) on nusinersen and 11 untreated (median age 32.7 years). Forty-three percent children had reduced mouth opening, 50% had prolonged total time to eat. These issues were more prominent in sitters than in walkers (p = 0.019, p = 0.014). Sixty-six percent needed increased swallows for bolus clearance. Nusinersen treated adults had median aMMO, tongue strength and total time at TOMASS values within normal range (z score: -1.40, -1.22, -1.32, respectively) whereas untreated adults had reduced aMMO (z score: -2.68) and tongue strength (z score: -2.20). Only a minority of children (2/17) and treated adults (5/21) reported burden in swallowing or mastication compared to all untreated adults (5/5). After 16 months, mastication and swallowing were stable in treated children and adults, whether sitters or walkers. The reported multimodal approach to assess oro-bulbar functions demonstrate that swallowing and mastication are impaired in SMA despite patients' perception. These results suggest a trend towards stabilization of oro-bulbar function in patients on long-term treatment with nusinersen.

Significant healthcare burden and life cost of spinal muscular atrophy: real-world data

OBJECTIVES

The aim of this study is to quantify the mortality rate, direct healthcare costs, and cumulative life costs of pediatric patients with spinal muscular atrophy (SMA) type 1, type 2, and type 3 born in Hong Kong.

METHODS

Data were collected from genetically confirmed SMA patients born in or after 2000 from the Hospital Authority medical database. Patients were followed up from birth until they died, left Hong Kong, reached 18 years, or initiated disease-modifying treatment. Study outcomes included incidence risks of mortality, cumulative direct medical costs-attendances of special outpatient clinics, emergency department, allied health services, and mean length of stay in hospitals over time. Total direct medical costs were calculated as unit costs multiplied by utilization frequencies of corresponding healthcare services at each age.

RESULTS

Seventy-one patients with SMA were included. Over a median follow-up period of 6 years, the overall incidence rate of death was 5.422/100 person-years (95%CI 3.542-7.945/100 person-years). 67.7% and 11% of deaths occurred in SMA1 and SMA2 groups, respectively. The median age of death was 0.8 years in SMA1 and 10.9 years in SMA2. The mean cumulative direct medical costs in overall SMA, SMA1, SMA2 and SMA3 groups per patient were US$935,570, US$2,393,250, US$413,165, and US$40,735, respectively.

INTERPRETATION

Our results confirmed a significantly raised mortality and extremely high healthcare burden for patients with SMA especially SMA type 1 and 2 without disease-modifying treatment. Study evaluating health and economic impact of newborn screening and early treatment is needed.

Cerebrospinal Fluid Proteomic Changes after Nusinersen in Patients with Spinal Muscular Atrophy

Disease-modifying treatments have transformed the natural history of spinal muscular atrophy (SMA), but the cellular pathways altered by SMN restoration remain undefined and biomarkers cannot yet precisely predict treatment response. We performed an exploratory cerebrospinal fluid (CSF) proteomic study in a diverse sample of SMA patients treated with nusinersen to elucidate therapeutic pathways and identify predictors of motor improvement. Proteomic analyses were performed on CSF samples collected before treatment (T0) and at 6 months (T6) using an Olink panel to quantify 1113 peptides. A supervised machine learning approach was used to identify proteins that discriminated patients who improved functionally from those who did not after 2 years of treatment. A total of 49 SMA patients were included (10 type 1, 18 type 2, and 21 type 3), ranging in age from 3 months to 65 years. Most proteins showed a decrease in CSF concentration at T6. The machine learning algorithm identified ARSB, ENTPD2, NEFL, and IFI30 as the proteins most predictive of improvement. The machine learning model was able to predict motor improvement at 2 years with 79.6% accuracy. The results highlight the potential application of CSF biomarkers to predict motor improvement following SMA treatment. Validation in larger datasets is needed.

Gene transfer therapy in children with spinal muscular atrophy: A single-center experience with a cohort of 25 children

INTRODUCTION/AIMS

New therapeutic strategies to increase survival motor neuron protein levels in spinal muscular atrophy (SMA) have focused on replacing the SMN1 gene. Onasemnogene abeparvovec was approved by the US Food and Drug Administration in 2019 for treatment of children with SMA less than 2 years of age. Postmarketing studies are limited, especially outside of Europe and the United States. Herein we describe a single-center experience with onasemnogene abeparvovec from the Middle East.

METHODS

Between November 17, 2020 and January 31, 2022, 25 children with SMA received onasemnogene abeparvovec at our center in the United Arab Emirates. Data were collected on patients' demographics, age at diagnosis, SMA type, genetic information, relevant medical history, laboratory investigations, and Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) functional assessment scores at baseline and 1 and 3 months after gene therapy.

RESULTS

Onasemnogene abeparvovec was well tolerated. Significant improvements in CHOP-INTEND scores were observed after the therapy. Elevation of liver enzymes and thrombocytopenia were the most common adverse events, but were transient and managed with high-dose corticosteroids. There were no life-threatening adverse events or deaths reported during the 3-month follow-up period.

DISCUSSION

The study findings concurred with those of previously published studies. Side effects of gene transfer therapy are well tolerated, although serious complications can arise. In such cases, persistent transaminitis for example, steroid dose escalation is warranted with close observation of the patient's clinical status and lab values. Combination therapy should be explored as an alternative to gene transfer therapy only.

Clinical and Functional Characteristics of a New Phenotype of SMA Type I among a National Sample of Spanish Children: A Cross-Sectional Study

Spinal Muscular Atrophy (SMA) type I has classically presented extremely severe clinical features. New pharmacological treatments have led to a new phenotype of SMA. The aim of this study was to describe the current health and functional status of children with SMA. A cross-sectional study was conducted based on the STROBE guidelines. Patient questionnaires and standardized tools were used. A descriptive analysis was conducted establishing the proportions of subjects for each of the characteristics of interest. In total, 51 genetically confirmed SMA type I subjects were included. Fifty-seven percent received oral feeding, 33% received tube feeding and 10% combined both. Moreover, 21.6% had tracheostomies, and 9.8% needed more than 16 h/d ventilatory support. Regarding orthopedic status, 66.7% had scoliosis, and 68.6% had hip subluxation or dislocation. Up to 67% were able to sit independently, 23.5% walked with support and one child walked independently. Current SMA type I is a different entity from the classic phenotype but also from types II and III. In addition, no differences were found between SMA type I subgroups. These findings may enable the professionals involved in the care of these patients to improve their interventions in terms of prevention and rehabilitation measures for these children.

Evaluation of sputum cultures in children with spinal Muscular atrophy

BACKGROUND

Spinal Muscular Atrophy (SMA) is a severe neuromuscular disorder. Despite increased survival due to novel therapies, morbidity from respiratory complications still persists. We aim to describe these patients' sputum cultures as an expression of chronic infectious airway disease.

METHODS

Retrospective review of medical records of all children with SMA followed at the multidisciplinary respiratory neuromuscular clinic at Schneider Childrens' Medical Center of Israel over a 16-year period. Sputum cultures were obtained during routine visits or pulmonary exacerbations.

RESULTS

Sixty-one SMA patients, aged 1 month to 21 years, were included in this cohort. Of these, sputum cultures were collected from 41 patients. Overall, 288 sputum cultures were obtained, and 98 (34%) were negative for bacterial growth. For the first culture taken from each patient, 12 out of 41 (29%) were sterile. The most common bacteria were pseudomonas aeruginosa (PSA) (38%) and staphylococcus aureus (19.6%). PSA was found in SMA type I patients more frequently than in type II patients (15/26 = 58% vs 4/13 = 31%, p < 0.001). PSA infection was positively associated with noninvasive ventilation, recurrent atelectasis, recurrent pneumonias, swallowing difficulties, but no significant association was found with cough assist machine usage. The incidence of positive cultures did not differ between those treated with Onasemnogene abeparvovec or Nusinersen compared to those without treatment, but the age of first PSA isolation was slightly older with Nusinersen treatment (p = 0.01).

CONCLUSIONS

Airway bacterial colonization is common in SMA type I patients and is not decreased by Onasemnogene abeparvovec or Nusinersen treatment.

Effect of nusinersen on motor, respiratory and bulbar function in early-onset spinal muscular atrophy

5q-associated spinal muscular atrophy is a rare neuromuscular disorder with the leading symptom of a proximal muscle weakness. Three different drugs have been approved by the European Medicines Agency and Food and Drug Administration for the treatment of spinal muscular atrophy patients, however, long-term experience is still scarce. In contrast to clinical trial data with restricted patient populations and short observation periods, we report here real-world evidence on a broad spectrum of patients with early-onset spinal muscular atrophy treated with nusinersen focusing on effects regarding motor milestones, and respiratory and bulbar insufficiency during the first years of treatment. Within the SMArtCARE registry, all patients under treatment with nusinersen who never had the ability to sit independently before the start of treatment were identified for data analysis. The primary outcome of this analysis was the change in motor function evaluated with the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders and motor milestones considering World Health Organization criteria. Further, we evaluated data on the need for ventilator support and tube feeding, and mortality. In total, 143 patients with early-onset spinal muscular atrophy were included in the data analysis with a follow-up period of up to 38 months. We observed major improvements in motor function evaluated with the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders. Improvements were greater in children >2 years of age at start of treatment than in older children. 24.5% of children gained the ability to sit independently. Major improvements were observed during the first 14 months of treatment. The need for intermittent ventilator support and tube feeding increased despite treatment with nusinersen. Our findings confirm the increasing real-world evidence that treatment with nusinersen has a dramatic influence on disease progression and survival in patients with early-onset spinal muscular atrophy. Major improvements in motor function are seen in children younger than 2 years at the start of treatment. Bulbar and respiratory function needs to be closely monitored, as these functions do not improve equivalent to motor function.

Onasemnogene Abeparvovec in Type 1 Spinal Muscular Atrophy: A Systematic Review and Meta-Analysis

One of the latest approved therapies for spinal muscular atrophy (SMA) is onasemnogene abeparvovec, which transduces motor neurons with the survival of motor neuron gene. The aim of this meta-analysis was to estimate the effect of onasemnogene abeparvovec on motor function in participants with type 1 SMA. Medline, Web of Science, Scopus, and Cochrane Library were searched for studies published from inception to August 2022. Pre-post clinical trials and observational studies determining the effect of onasemnogene abeparvovec on the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) score or motor milestones (i.e., head control, sit unassisted, feed orally, not use permanent ventilatory support, crawl, stand alone, and walk alone) in participants with type 1 SMA were included. Continuous outcomes (i.e., CHOP-INTEND score) were expressed as pre-post mean difference and 95% confidence interval (CI), while the proportion of participants who achieved >40, >50, and >58/60 points on the CHOP-INTEND and the achievement of the motor milestones were expressed as proportions and 95% CI. A random effects meta-analysis was conducted on each outcome, and the baseline CHOP-INTEND score was considered a covariate. Eleven studies were included in the systematic review, and four were included in the meta-analyses. Onasemnogene abeparvovec improved CHOP-INTEND scores by 11.06 (9.47 to 12.65) and 14.14 (12.42 to 15.86) points at 3 and 6 months postinfusion, respectively. Moreover, 87%, 51%, and 12% achieved CHOP-INTEND scores of >40, >50, and >58/60 points, respectively. However, this proportion increased to 100% in presymptomatic participants with greater baseline CHOP-INTEND. Motor milestones were also improved, especially in presymptomatic participants. Our systematic review not only showed a marked improvement in motor function in type 1 SMA but also showed that treatment in the presymptomatic stage improves the development of these children toward an evolution close to normal for their age.

The SMN Complex at the Crossroad between RNA Metabolism and Neurodegeneration

In the cell, RNA exists and functions in a complex with RNA binding proteins (RBPs) that regulate each step of the RNA life cycle from transcription to degradation. Central to this regulation is the role of several molecular chaperones that ensure the correct interactions between RNA and proteins, while aiding the biogenesis of large RNA-protein complexes (ribonucleoproteins or RNPs). Accurate formation of RNPs is fundamentally important to cellular development and function, and its impairment often leads to disease. The survival motor neuron (SMN) protein exemplifies this biological paradigm. SMN is part of a multi-protein complex essential for the biogenesis of various RNPs that function in RNA metabolism. Mutations leading to SMN deficiency cause the neurodegenerative disease spinal muscular atrophy (SMA). A fundamental question in SMA biology is how selective motor system dysfunction results from reduced levels of the ubiquitously expressed SMN protein. Recent clarification of the central role of the SMN complex in RNA metabolism and a thorough characterization of animal models of SMA have significantly advanced our knowledge of the molecular basis of the disease. Here we review the expanding role of SMN in the regulation of gene expression through its multiple functions in RNP biogenesis. We discuss developments in our understanding of SMN activity as a molecular chaperone of RNPs and how disruption of SMN-dependent RNA pathways can contribute to the SMA phenotype.

Comprehensive profile and natural history of pediatric patients with spinal muscular atrophy: A large retrospective study from China

Background

There is a large population of people with spinal muscular atrophy (SMA) in China, and new disease-modifying therapies have become available recently. However, comprehensive data on the management and profile of treatment-naive SMA patients in China are still lacking.

Methods

As a retrospective study, a large cohort of treatment-naive patients with clinical and genetic diagnoses of 5q SMA were enrolled, ranging from neonatal to 18 years old, from the Neurology Department of Children's Hospital of Fudan University between January 2013 and December 2020. The data regarding their clinical presentations, genetic defects, motor function assessment results, and follow ups were reviewed.

Results

We enrolled 392 SMA patients (male: female = 189: 203): 1a = 46, 1b = 44, 1c = 31, 2a = 119, 2b = 56, 3a = 52, 3b = 14, from 27 of the 34 administrative districts in China, and 389 patients harbored homozygous deletion of exon 7 in the SMN1 gene (99.2%). The median age of onset was 0.08 (range: 0-0.30), 0.25 (0.06-0.60), 0.42 (0.08-1.50), 0.67 (0.07-5.08), 1.0 (0.40-1.83), 1.5 (1.00-3.00), and 4.04 (1.80-12.00) years old for SMA 1a, 1b, 1c, 2a, 2b, 3a, and 3b patients, while the median age of first assessment was 0.25 (0.08-2.60), 0.42 (0.17-1.90), 0.80 (0.17-4.5), 2.50 (0.5-15.83), 2.92 (1.08-13.42), 4.25 (1.58-17.33), and 7.34 (3.67-14.00) years old, respectively. Patients were followed up with for up to 15.8 years. The median event-free survival time was 7 months, 15 months, and indeterminate in SMA 1a, 1b, and 1c patients (p < 0.0001), with a better survival situation for higher SMN2 copies (p = 0.0171). The median age of sitting loss was 5.75 years and 13.5 years in SMA 2a and 2b (p = 0.0214) and that of ambulation loss was 9.0 years and undefined in SMA 3a and 3b (p = 0.0072). Cox regression analysis showed that higher SMN2 copies indicated better remaining ambulation in SMA 3. The median time to develop orthopedic deformities was 4.5, 5.2, and 10.1 years in SMAs 1c, 2, and 3, respectively (p < 0.0001), with a possible trend of better preservation of joint function for patients under regular rehabilitation (p = 0.8668).

Conclusion

Our study elucidated insight into the comprehensive management and profile of different types of SMA patients in China, providing a clinical basis for assessing the efficacy of new therapies.

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.

Survival in patients diagnosed with SMA at less than 24 months of age in a population-based setting before, during and after introduction of nusinersen therapy. Experience from Sweden

INTRODUCTION

Clinical trials have demonstrated a positive effect of nusinersen therapy on survival of infants with SMA type 1. However, there is a lack of data outside clinical trials on how the introduction of nusinersen has affected the survival of patients with SMA. We therefore set out to analyse survival in patients diagnosed at less than 24 months before, during and after the introduction of nusinersen in a nationwide population-based real-world setting.

METHODS

SMA patients diagnosed before the age of 24 months in the time period between February 21, 2000 and December 19, 2019 were identified using ICD-codes, and medical procedures for identification of treatment utilizing information from the public available National Patient Registry held by the National Board of Health and Welfare. Data was divided into 3 different calendar periods (before, during, and after introduction of nusinersen treatment in Sweden). Time to Event analysis was then applied.

RESULTS

A total of 155 patients were enrolled in the study, and median follow-up was 1.14 years (inter-quartile range (IQR): 0.27-8.37 years). Data did not provide conclusive evidence that survival differed between the calendar periods (P-value from the log-rank test = 0.419) and while hazards were lower in the middle period, HR 0.70 (95% CI: 0.34-1.47), and 3, HR 0.71 (95% CI: 0.28-1.77) compared to the first period, all confidence intervals were wide., However, nusinersen treatment was associated with a decreased mortality rate, HR 0.05 (95% CI: 0.01-0.37).

CONCLUSION

SMA patients receiving nusinersen therapy had a dramatically increased overall survival compared to patients not receiving therapy. This indicates that nusinersen treatment has an effect on survival, in patients diagnosed with SMA, in a nationwide real-world setting. Larger studies are warranted.

Cost-effectiveness analysis of gene-based therapies for patients with spinal muscular atrophy type I in Australia

Introduction

Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder and regarded as one of the most frequent genetic causes of infant mortality. The aim of this study is to develop a cost-effectiveness analysis of AVXS-101 (Onasemnogene Abeparvovec/Zolgensma^®) and nusinersen (Spinraza^®) for SMA to inform decision-making on reimbursement policies in Australia.

Methods

A Markov model was developed with five health states to evaluate the costs and effects for patients with SMA Type I from a healthcare system perspective over a time-horizon of 100 years. The model parameters were based on clinical trials, parametric distributions, published literature, and Australian registries. One-way and probabilistic sensitivity analysis were performed to appraise the uncertainties of the parameters in the model. A threshold analysis was conducted to estimate the cost of AVXS-101 of being cost-effective.

Results

The incremental cost-effectiveness ratio (ICER) of AVXS-101 was $1,808,471 per quality-adjusted life year (QALY) and that of nusinersen was $2,772,798 per QALY, compared to standard of care, respectively. The ICER of AVXS-101 was $1,238,288 per QALY compared to nusinersen. The key drivers influencing on ICERs were costs of using treatments and utility values of sitting and walking independently.

Conclusion

Both nusinersen and AVXS-101 resulted in health benefits, but they were not cost-effective with a commonly used willingness-to-pay (WTP) threshold of $50,000 per QALY. Developing high-quality clinical data and exploring appropriate WTP thresholds are critical for decision-making on reimbursement policies in the treatment of rare diseases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11319-0.

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.

Systematic Review of Motor Function Scales and Patient-Reported Outcomes in Spinal Muscular Atrophy

ABSTRACT

Spinal muscular atrophy is a heterogeneous disease that results in loss of motor function. In an evolving treatment landscape, establishing the suitability and limitations of existing motor function scales and patient-reported outcomes used to monitor patients with this disease is important. A systematic review was conducted to examine utility of motor function scales and patient-reported outcomes in evaluating patients with spinal muscular atrophy. Published literature was reviewed up to June 2021 with no start date restriction. Of the reports screened, 122 were deemed appropriate for inclusion and are discussed in this review (including 24 validation studies for motor function scales or patient-reported outcomes). Fifteen motor function scales and patient-reported outcomes were identified to be commonly used (≥5 studies), of which 11 had available validation assessments. Each instrument has its strengths and limitations. It is imperative that the patient population (e.g., age, mobility), goals of treatment, and outcomes or endpoints of interest be considered when selecting the appropriate motor function scales and patient-reported outcomes for clinical studies.

Response of plasma microRNAs to nusinersen treatment in patients with SMA

OBJECTIVE

Spinal muscular atrophy (SMA) is a common genetic cause of infant mortality. Nusinersen treatment ameliorates the clinical outcome of SMA, however, some patients respond well, while others have limited response. We investigated microRNAs in blood samples from SMA patients and their response to nusinersen treatment evaluating the potential of circulating microRNAs as biomarkers for SMA.

METHODS

In a discovery cohort study, microRNA next-generation sequencing was performed in blood samples from SMA patients (SMA type 2, n = 10; SMA type 3, n = 10) and controls (n = 7). The dysregulated microRNAs were further analysed in the therapeutic response cohort comprised of SMA type 1 patients (n = 22) who had received nusinersen treatment, at three time points along the treatment course (baseline, 2 and 6 months of treatment). The levels of the studied microRNAs were correlated to the SMA clinical outcome measures.

RESULTS

In the discovery cohort, 69 microRNAs were dysregulated between SMA patients and controls. In the therapeutic response cohort, the baseline plasma levels of miR-107, miR-142-5p, miR-335-5p, miR-423-3p, miR-660-5p, miR-378a-3p and miR-23a-3p were associated with the 2 and 6 months response to nusinersen treatment. Furthermore, the levels of miR-107, miR-142-5p, miR-335-5p, miR-423-3p, miR-660-5p and miR-378-3p at 2 months of treatment were associated with the response after 6 months of nusinersen treatment.

INTERPRETATION

Blood microRNAs could be used as biomarkers to indicate SMA patients' response to nusinersen and to monitor the efficacy of the therapeutic intervention. In addition, some of these microRNAs provide insight into processes involved in SMA that could be exploited as novel therapeutic targets.

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.

Lessons Learned From Translational Research in Neuromuscular Diseases: Impact on Study Design, Outcome Measures and Managing Expectation

Spinal Muscular Atrophy (SMA) and Duchenne Muscular Dystrophy (DMD), two of the most common, child onset, rare neuromuscular disorders, present a case study for the translation of preclinical research into clinical work. Over the past decade, well-designed clinical trials and innovative methods have led to the approval of several novel therapies for SMA and DMD, with many more in the pipeline. This review discusses several features that must be considered during trial design for neuromuscular diseases, as well as other rare diseases, to maximise the possibility of trial success using historic examples. These features include well-defined inclusion criteria, matching criteria, alternatives to placebo-controlled trials and the selection of trial endpoints. These features will be particularly important in the coming years as the investigation into innovative therapy approaches for neuromuscular diseases continues.

Neurofilament Levels in CSF and Serum in an Adult SMA Cohort Treated with Nusinersen

OBJECTIVE

To retrospectively evaluate the utility of serum and cerebrospinal fluid (CSF) levels of neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH) as biomarkers for spinal muscular atrophy (SMA) progression and response to nusinersen treatment.

METHODS

NfL and pNfH levels were quantified using single molecular array (SIMOA) in CSF of 33 adult SMA patients (SMN copy number 3-5) before and in response to nusinersen treatment. In 11 of the patients, blood serum samples were also collected. CSF NfL and pNfH from patients were compared to CSF Nfs from age-matched controls without neurological disease (n = 6). For patients, pearson correlation coefficients (r) were calculated to investigate associations between Nf levels and other functional outcome measures.

RESULTS

Nf levels were similar between SMA and control adults and showed no change in response to nusinersen treatment in CSF or serum. Cross-sectional analyses showed an increase in CSF NfL and pNfH with age in patients (NfL p = 0.0013; pNfH p = 0.0035) and an increase in CSF NfL in controls (p = 0.002). In non-ambulatory patients, baseline serum pNfH showed a negative correlation with multiple strength and functional assessment metrics including Revised Upper Limb Module (r = -0.822, p = 0.04), upper extremity strength (r = -0.828, p = 0.042), lower extremity strength (r = -0.860, p = 0.028), and total strength (r = -0.870, p = 0.024).

CONCLUSIONS

Nf levels did not change in response to nusinersen in adults with SMA and were not different from controls. In patients and controls, we detected an age-related increase in baseline CSF NfL and pNfH levels. Though some associations were identified, our results suggest Nf levels are not preditive or prognostic biomarkers in this population.

Implications of circulating neurofilaments for spinal muscular atrophy treatment early in life: A case series

This longitudinal cohort study aimed to determine whether circulating neurofilaments (NFs) can monitor response to molecular therapies in newborns with spinal muscular atrophy (SMA; NCT02831296). We applied a mixed-effect model to examine differences in serum NF levels among healthy control infants (n = 13), untreated SMA infants (n = 68), and SMA infants who received the genetic therapies nusinersen and/or onasemnogene abeparvovec (n = 22). Increased NF levels were inversely associated with SMN2 copy number. SMA infants treated with either nusinersen or onasemnogene abeparvovec achieved important motor milestones not observed in the untreated cohort. NF levels declined more rapidly in the nusinersen cohort as compared with the untreated cohort. Unexpectedly, those receiving onasemnogene abeparvovec monotherapy showed a significant rise in NF levels regardless of SMN2 copy number. In contrast, symptomatic SMA infants who received nusinersen, followed by onasemnogene abeparvovec within a short interval after, did not show an elevation in NF levels. While NF cannot be used as the single marker to predict outcomes, the elevated NF levels observed with onasemnogene abeparvovec and its absence in infants treated first with nusinersen may indicate a protective effect of co-therapy during a critical period of vulnerability to acute denervation.

Motor function in type 2 and 3 SMA patients treated with Nusinersen: a critical review and meta-analysis

Background

There is an increasing number of papers reporting the real world use of Nusinersen in different cohorts of SMA patients.

Main body

The aim of this paper was to critically review the literature reporting real world data on motor function in type 2 and 3 patients treated with Nusinersen, subdividing the results according to SMA type, age and type of assessment and performing a meta-analysis of the available results. We also report the available data collected in untreated patients using the same measures. Of the 400 papers identified searching for Nusinersen and spinal muscular atrophy, 19 reported motor function in types 2 and 3: 13 in adults, 4 in children and 2 included both. Twelve papers reported untreated patients’ data. All studies reported positive changes on at least one of the functional measures and at every time point while all-untreated cohorts showed negative changes.

Conclusion

Our review suggests that Nusinersen provides a favorable benefit in motor function across a wide range of SMA type 2 and 3 patients over a 10–14 month observation period. Although a direct comparison with studies reporting data from untreated patients cannot be made, the longitudinal changes in the treated cohorts (consistently positive) are divergent from those observed in the untreated cohorts (consistently negative). The difference could be observed both in the global cohorts and in smaller groups subdivided according to age, type or functional status.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02065-z.

Onasemnogene abeparvovec gene therapy for symptomatic infantile-onset spinal muscular atrophy type 1 (STR1VE-EU): an open-label, single-arm, multicentre, phase 3 trial

BACKGROUND

Spinal muscular atrophy is a rare, autosomal recessive, neuromuscular disease caused by biallelic loss of the survival motor neuron 1 (SMN1) gene, resulting in motor neuron dysfunction. In this STR1VE-EU study, we aimed to evaluate the safety and efficacy of onasemnogene abeparvovec gene replacement therapy in infants with spinal muscular atrophy type 1, using broader eligibility criteria than those used in STR1VE-US.

METHODS

STR1VE-EU was a multicentre, single-arm, single-dose, open-label phase 3 trial done at nine sites (hospitals and universities) in Italy (n=4), the UK (n=2), Belgium (n=2), and France (n=1). We enrolled patients younger than 6 months (180 days) with spinal muscular atrophy type 1 and the common biallelic pathogenic SMN1 exon 7-8 deletion or point mutations, and one or two copies of SMN2. Patients received a one-time intravenous infusion of onasemnogene abeparvovec (1·1 × 10¹⁴ vector genomes [vg]/kg). The outpatient follow-up consisted of assessments once per week starting at day 7 post-infusion for 4 weeks and then once per month until the end of the study (at age 18 months or early termination). The primary outcome was independent sitting for at least 10 s, as defined by the WHO Multicentre Growth Reference Study, at any visit up to the 18 months of age study visit, measured in the intention-to-treat population. Efficacy was compared with the Pediatric Neuromuscular Clinical Research (PNCR) natural history cohort. This trial is registered with ClinicalTrials.gov, NCT03461289 (completed).

FINDINGS

From Aug 16, 2018, to Sept 11, 2020, 41 patients with spinal muscular atrophy were assessed for eligibility. The median age at onasemnogene abeparvovec dosing was 4·1 months (IQR 3·0-5·2). 32 (97%) of 33 patients completed the study and were included in the ITT population (one patient was excluded despite completing the study because of dosing at 181 days). 14 (44%, 97·5% CI 26-100) of 32 patients achieved the primary endpoint of functional independent sitting for at least 10 s at any visit up to the 18 months of age study visit (vs 0 of 23 untreated patients in the PNCR cohort; p<0·0001). 31 (97%, 95% CI 91-100) of 32 patients in the ITT population survived free from permanent ventilatory support at 14 months compared with six (26%, 8-44) of 23 patients in the PNCR natural history cohort (p<0·0001). 32 (97%) of 33 patients had at least one adverse event and six (18%) had adverse events that were considered serious and related to onasemnogene abeparvovec. The most common adverse events were pyrexia (22 [67%] of 33), upper respiratory infection (11 [33%]), and increased alanine aminotransferase (nine [27%]). One death, unrelated to the study drug, occurred from hypoxic-ischaemic brain damage because of a respiratory tract infection during the study.

INTERPRETATION

STR1VE-EU showed efficacy of onasemnogene abeparvovec in infants with symptomatic spinal muscular atrophy type 1. No new safety signals were identified, but further studies are needed to show long-term safety. The benefit-risk profile of onasemnogene abeparvovec seems favourable for this patient population, including those with severe disease at baseline.

FUNDING

Novartis Gene Therapies.

Walking onset: a poor predictor for motor and cognitive skills in healthy preschool children

Background

The onset of walking is thought to be an indicator of early development. However, evidence is mixed and clear data on this relationship at preschool age is missing. The study aimed at investigating if walking onset and motor and cognitive development in preschool children are related.

Methods

A total of 555 children (mean age 3.86 years) of the Swiss Preschoolers’ Health Study SPLASHY were tested twice at their childcare center (at baseline and one year later). Motor skills and cognitive skills were assessed by standardized testing procedures and parents were asked to provide information on walking onset of their child.

Results

Late onset of walking was related to poorer motor skills (fine motor skills, static and dynamic balance (all p < 0.003)) and poorer cognitive skills (selective attention and visual perception (p = 0.02; p = 0.001) in late preschool age.

Conclusions

For children with late walking onset a close monitoring of their development in the regular pediatric child health visits may be reasonable.

Trial registration: ISRCTN41045021.

Clinical outcome assessments in Duchenne muscular dystrophy and spinal muscular atrophy: past, present and future

Scores and scales used in pediatric motor development for neuromuscular disorders have evolved greatly since the beginning of their development. In this review we provide a brief history of scales used in pediatric patients with neuromuscular disorders and an update regarding the advancement of the scales commonly used in patients with spinal muscular atrophy and Duchenne muscular dystrophy. We focus on the collaborative effort that has led to the development of outcomes and speak to the possible future of Clinical Outcome Assessments.

Oral and Swallowing Abilities Tool (OrSAT) for Type 1 SMA Patients: Development of a New Module

We describe the development of a new tool specifically designed to record oral abilities, swallowing and, more generally, feeding in young type 1 SMA patients, to be used during the first 24 months of life.The tool is composed by a checklist and a separate section summarizing the functional abilities into levels of feeding/swallowing impairment. The checklist includes 12 questions assessing aspects thought to be clinically meaningful for a type 1 SMA population and developmentally appropriate for infants during the first months of life. Each item is graded with a score of 0 or 1, depending on the child's ability to perform the activity. As some items are age-dependent, the number of items to be used, and therefore the maximum score, changes with increasing age. The levels of feeding/swallowing impairment include four levels that can be identified using easily identifiable clinical criteria.In an attempt to validate the tool in an untreated population we applied it to 24 type 1 SMA patients (age range: 2.3-24.1 months, mean: 10.8) in whom the same information collected by the new tool had been previously recorded using a less-structured format.When patients were classified in three groups according to the Dubowitz decimal classification, there was a significant difference both at baseline and at follow-up (p < 0.001). The items assessing fatigue during the nursing sessions were the most frequently impaired even in infants who did not have any other obvious clinical sign of swallowing difficulties.

Risdiplam-Treated Infants with Type 1 Spinal Muscular Atrophy versus Historical Controls

BACKGROUND

Type 1 spinal muscular atrophy (SMA) is a progressive neuromuscular disease characterized by an onset at 6 months of age or younger, an inability to sit without support, and deficient levels of survival of motor neuron (SMN) protein. Risdiplam is an orally administered small molecule that modifies SMN2 pre-messenger RNA splicing and increases levels of functional SMN protein in blood.

METHODS

We conducted an open-label study of risdiplam in infants with type 1 SMA who were 1 to 7 months of age at enrollment. Part 1 of the study (published previously) determined the dose to be used in part 2 (reported here), which assessed the efficacy and safety of daily risdiplam as compared with no treatment in historical controls. The primary end point was the ability to sit without support for at least 5 seconds after 12 months of treatment. Key secondary end points were a score of 40 or higher on the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND; range, 0 to 64, with higher scores indicating better motor function), an increase of at least 4 points from baseline in the CHOP-INTEND score, a motor-milestone response as measured by Section 2 of the Hammersmith Infant Neurological Examination (HINE-2), and survival without permanent ventilation. For the secondary end points, comparisons were made with the upper boundary of 90% confidence intervals for natural-history data from 40 infants with type 1 SMA.

RESULTS

A total of 41 infants were enrolled. After 12 months of treatment, 12 infants (29%) were able to sit without support for at least 5 seconds, a milestone not attained in this disorder. The percentages of infants in whom the key secondary end points were met as compared with the upper boundary of confidence intervals from historical controls were 56% as compared with 17% for a CHOP-INTEND score of 40 or higher, 90% as compared with 17% for an increase of at least 4 points from baseline in the CHOP-INTEND score, 78% as compared with 12% for a HINE-2 motor-milestone response, and 85% as compared with 42% for survival without permanent ventilation (P<0.001 for all comparisons). The most common serious adverse events were pneumonia, bronchiolitis, hypotonia, and respiratory failure.

CONCLUSIONS

In this study involving infants with type 1 SMA, risdiplam resulted in higher percentages of infants who met motor milestones and who showed improvements in motor function than the percentages observed in historical cohorts. Longer and larger trials are required to determine the long-term safety and efficacy of risdiplam in infants with type 1 SMA. (Funded by F. Hoffmann-La Roche; FIREFISH ClinicalTrials.gov number, NCT02913482.).

Spinal Muscular Atrophy

PURPOSE OF REVIEW

This article provides an overview of the pathophysiology and clinical presentations of spinal muscular atrophy (SMA) and reviews therapeutic developments, including US Food and Drug Administration (FDA)-approved gene-targeted therapies and mainstays of supportive SMA care.

RECENT FINDINGS

Over the past decades, an understanding of the role of SMN protein in the development and maintenance of the motor unit and the intricate genetics underlying SMA has led to striking developments in therapeutics with three FDA-approved treatments for SMA, one targeting SMN1 gene replacement (onasemnogene abeparvovec-xioi) and two others enhancing SMN protein production from the SMN2 gene (nusinersen and risdiplam). These therapies are most effective in infants treated at younger ages, and improvement is most striking in babies treated as neonates. Despite improvements in motor function, patients (especially those treated at older ages) continue to experience significant weakness and require continued close monitoring of respiratory and orthopedic symptoms.

SUMMARY

Striking therapeutic advancements have changed the clinical course of SMA dramatically, although supportive care continues to play an important role in patient care.

Neck and Trunk Muscle Strength in Children With Spinal Muscular Atrophy Is Lower Than in Healthy Controls and Depends on Disease Type

Background: Neck and trunk muscle strength and relationship with motor function in individuals with spinal muscular atrophy (SMA) is not investigated well. Information on maximum muscle strength that children with SMA may develop considerably expands the possibilities of assessing the effectiveness of pharmacological treatment methods and therapeutic procedures. This study sought to assess neck and trunk muscle strength in patients with SMA and to compare it with values noted in healthy children.

Methods: The study involved 56 individuals with SMA aged 5–16 not treated pharmacologically, including 9 patients with SMA type 1 (SMA1), 27 with SMA type 2 (SMA2), and 20 with SMA type 3 (SMA3). The control group included 111 healthy individuals aged 5–16. Neck and trunk muscle strength was assessed by means of a maximum voluntary isometric contraction method with the use of a handheld digital muscle tester MICROFET2. Moreover, relative strength was also calculated by standardising the maximum voluntary isometric contraction according to body mass. The Kruskal–Wallis test, Mann–Whitney U-test, and Spearman's rank correlation were used for statistical analysis.

Results: The reliability of the neck and trunk muscle strength measurements with the handheld digital muscle tester was excellent with ICC > 0.9. The values of muscle strength in SMA groups were significantly lower than in the control group. The values of relative torque of the neck muscles expressed in percentage values calculated with regard to the control group were at the level of 47.6–51.6% in SMA1 group, 54.8–58.1% in SMA2 group and 80.6–90.3% in SMA3 group. The percentage values for upper and lower trunk muscle strength were at the level of 42.6–68.4% in SMA1 group, 56.9–75.4% in SMA2 group and 76.7–94.8% in SMA3 group.

Conclusion: Handheld dynamometry provides reliable measures of neck and trunk muscle strength in SMA children. Neck and trunk muscle strength in children with SMA is lower than in healthy controls and depends on disease type, which confirms the theory based on clinical observations. Further, study is needed to investigate the effect of pharmacological treatment on the strength of the neck/trunk muscles, and relationship between neck and trunk muscle strength and motor capabilities.

A new respiratory scoring system for evaluation of respiratory outcomes in children with spinal muscular atrophy type1 (SMA1) on SMN enhancing drugs

Nusinersen (NUS), the first treatment approved for Spinal Muscular Atrophy type 1 (SMA1), was made available in the UK for SMA1 through the Expanded Access Program (EAP) in 2017. The Great Ormond Street Respiratory (GSR) score was developed as an objective respiratory assessment for children with SMA1 during their treatment. Aims: Track respiratory status of SMA1 children over the course of Nusinersen treatment and compare GSR scores amongst SMA1 sub-types. Single centre study on SMA1 patients using the GSR score at set time points: prior to first NUS dose; 2 weeks post end of loading doses; 2 weeks post-subsequent doses. GSR score ranges 1-28, being 1-9 = Stable minimal support, thorough to 23-28 = Poor reserve with maximum support. 20 SMA1 children underwent NUS treatment between January 2017 - November 2018. Median age of diagnosis was 5.0 months. NUS started at median of 9.57 months. From 5th dose onwards, GSR scores were significantly lower for Type 1C patients compared to Type 1B By month 18, irrespective of subtypes, the whole cohort appears to stabilise GSR Scores. As treatment duration increases, an overall stabilisation of respiratory status across the cohort was observed. Further longitudinal studies are needed to validate the GSR.

Onasemnogene abeparvovec gene therapy for symptomatic infantile-onset spinal muscular atrophy in patients with two copies of SMN2 (STR1VE): an open-label, single-arm, multicentre, phase 3 trial

BACKGROUND

Spinal muscular atrophy type 1 is a motor neuron disorder resulting in death or the need for permanent ventilation by age 2 years. We aimed to evaluate the safety and efficacy of onasemnogene abeparvovec (previously known as AVXS-101), a gene therapy delivering the survival motor neuron gene (SMN), in symptomatic patients (identified through clinical examination) with infantile-onset spinal muscular atrophy.

METHODS

STR1VE was an open-label, single-arm, single-dose, phase 3 trial done at 12 hospitals and universities in the USA. Eligible patients had to be younger than 6 months and have spinal muscular atrophy with biallelic SMN1 mutations (deletion or point mutations) and one or two copies of SMN2. Patients received a one-time intravenous infusion of onasemnogene abeparvovec (1·1 × 10¹⁴ vector genomes per kg) for 30-60 min. During the outpatient follow-up, patients were assessed once per week, beginning at day 7 post-infusion for 4 weeks and then once per month until the end of the study (age 18 months or early termination). Coprimary efficacy outcomes were independent sitting for 30 s or longer (Bayley-III item 26) at the 18 month of age study visit and survival (absence of death or permanent ventilation) at age 14 months. Safety was assessed through evaluation of adverse events, concomitant medication usage, physical examinations, vital sign assessments, cardiac assessments, and laboratory evaluation. Primary efficacy endpoints for the intention-to-treat population were compared with untreated infants aged 6 months or younger (n=23) with spinal muscular atrophy type 1 (biallelic deletion of SMN1 and two copies of SMN2) from the Pediatric Neuromuscular Clinical Research (PNCR) dataset. This trial is registered with ClinicalTrials.gov, NCT03306277 (completed).

FINDINGS

From Oct 24, 2017, to Nov 12, 2019, 22 patients with spinal muscular atrophy type 1 were eligible and received onasemnogene abeparvovec. 13 (59%, 97·5% CI 36-100) of 22 patients achieved functional independent sitting for 30 s or longer at the 18 month of age study visit (vs 0 of 23 patients in the untreated PNCR cohort; p<0·0001). 20 patients (91%, 79-100]) survived free from permanent ventilation at age 14 months (vs 6 [26%], 8-44; p<0·0001 in the untreated PNCR cohort). All patients who received onasemnogene abeparvovec had at least one adverse event (most common was pyrexia). The most frequently reported serious adverse events were bronchiolitis, pneumonia, respiratory distress, and respiratory syncytial virus bronchiolitis. Three serious adverse events were related or possibly related to the treatment (two patients had elevated hepatic aminotransferases, and one had hydrocephalus).

INTERPRETATION

Results from this multicentre trial build on findings from the phase 1 START study by showing safety and efficacy of commercial grade onasemnogene abeparvovec. Onasemnogene abeparvovec showed statistical superiority and clinically meaningful responses when compared with observations from the PNCR natural history cohort. The favourable benefit-risk profile shown in this study supports the use of onasemnogene abeparvovec for treatment of symptomatic patients with genetic or clinical characteristics predictive of infantile-onset spinal muscular atrophy type 1.

FUNDING

Novartis Gene Therapies.

Risdiplam in Type 1 Spinal Muscular Atrophy

BACKGROUND

Type 1 spinal muscular atrophy is a rare, progressive neuromuscular disease that is caused by low levels of functional survival of motor neuron (SMN) protein. Risdiplam is an orally administered, small molecule that modifies SMN2 pre-messenger RNA splicing and increases levels of functional SMN protein.

METHODS

We report the results of part 1 of a two-part, phase 2-3, open-label study of risdiplam in infants 1 to 7 months of age who had type 1 spinal muscular atrophy, which is characterized by the infant not attaining the ability to sit without support. Primary outcomes were safety, pharmacokinetics, pharmacodynamics (including the blood SMN protein concentration), and the selection of the risdiplam dose for part 2 of the study. Exploratory outcomes included the ability to sit without support for at least 5 seconds.

RESULTS

A total of 21 infants were enrolled. Four infants were in a low-dose cohort and were treated with a final dose at month 12 of 0.08 mg of risdiplam per kilogram of body weight per day, and 17 were in a high-dose cohort and were treated with a final dose at month 12 of 0.2 mg per kilogram per day. The baseline median SMN protein concentrations in blood were 1.31 ng per milliliter in the low-dose cohort and 2.54 ng per milliliter in the high-dose cohort; at 12 months, the median values increased to 3.05 ng per milliliter and 5.66 ng per milliliter, respectively, which represented a median of 3.0 times and 1.9 times the baseline values in the low-dose and high-dose cohorts, respectively. Serious adverse events included pneumonia, respiratory tract infection, and acute respiratory failure. At the time of this publication, 4 infants had died of respiratory complications. Seven infants in the high-dose cohort and no infants in the low-dose cohort were able to sit without support for at least 5 seconds. The higher dose of risdiplam (0.2 mg per kilogram per day) was selected for part 2 of the study.

CONCLUSIONS

In infants with type 1 spinal muscular atrophy, treatment with oral risdiplam led to an increased expression of functional SMN protein in the blood. (Funded by F. Hoffmann-La Roche; ClinicalTrials.gov number, NCT02913482.).

Clinical Experience of Nusinersen in a Broad Spectrum of Spinal Muscular Atrophy: A Retrospective Study

Background:

Nusinersen has recently been approved and more widely used as first-line treatment of spinal muscular atrophy (SMA). This study aimed to evaluate the real-world experience of nusinersen use for patients with a broad spectrum of SMA.

Methods:

We reviewed consecutive patients with SMA treated with nusinersen from April 2018 to April 2020. Data collected included clinical and diagnostic characteristics, molecular genetics, functional motor outcomes, and adverse events.

Results:

Seven patients including four with SMA type 1 and three with SMA type 2 were treated with nusinersen. The median disease duration at the time of the first dose and the median follow-up duration were 37 months (range: 0.5–254 months) and 6.1 months (range: 2.1–22.1 months), respectively. Of the 41 lumbar punctures (LPs), seven fluoroscopy-guided LPs were successfully performed for two patients without sedation. All patients showed improvement in motor function even though the current tools for motor assessment seemed unable to detect subtle subjective improvement. All patients maintained a stable respiratory status. No patient has experienced a severe adverse event or discontinued treatment so far.

Conclusion:

Although the number of patients in this study was small, our results suggest that nusinersen is effective even in patients with a later stage of the disease. Additional long-term prospective studies with more number of patients having a broad spectrum of diseases are needed to identify meaningful improvement in the motor function and quality of life after nusinersen treatment.

Gene-Targeting Therapeutics for Neurological Disease: Lessons Learned from Spinal Muscular Atrophy

The last few decades have seen an explosion in identification of genes that cause monogenetic neurological diseases, as well as advances in gene-targeting therapeutics. Neurological conditions that were once considered incurable are now increasingly tractable. At the forefront is the motor neuron disease spinal muscular atrophy (SMA), historically the leading inherited cause of infant mortality. In the last 5 years, three SMA treatments have been approved by the US Food and Drug Administration (FDA): intrathecally delivered splice-switching antisense oligonucleotide (nusinersen), systemically delivered AAV9-based gene replacement therapy (onasemnogene abeparvovec), and an orally bioavailable, small-molecule, splice-switching drug (risdiplam). Despite this remarkable progress, clinical outcomes in patients are variable. Therapeutic optimization will require improved understanding of drug pharmacokinetics and target engagement in neurons, potential toxicities, and long-term effects. We review current progress in SMA therapeutics, clinical trials, shortcomings of current treatments, and implications for the treatment of other neurogenetic diseases.

Spinal Muscular Atrophy: The Use of Functional Motor Scales in the Era of Disease-Modifying Treatment

Spinal muscular atrophy (SMA) is a genetic condition characterized by progressive motoneuron loss. Infants affected by SMA type 1 do not gain developmental milestones and acutely decline, requiring ventilatory support. Several scales are used to assess motor disability and its progression in SMA. Recently, 3 disease-modifying therapies have been approved for SMA patients: nusinersen, an intrathecal antisense oligonucleotide enhancing SMN protein production by the SMN2 gene, risdiplam, also influencing the SMN2 gene to stimulate SMN production but administered orally, and onasemnogene abeparvovec-xioi, an SMN1 gene replacement therapy. Thus, the functional scales should now be applicable for patients improving their motor function over time to assess treatment efficacy. In this paper, we compare different functional scales used in SMA patients. Their usefulness in different SMA types, age groups, and feasibility in daily clinical practice is described below. Some changes in motor function assessments in SMA are also suggested.

Psychometric properties of the PEDI-CAT for children and youth with spinal muscular atrophy

PURPOSE

The purpose of this study was to examine the psychometric properties of the Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (PEDI-CAT) in children and youth with Spinal Muscular Atrophy (SMA).

METHODS

In this prospective cross-sectional study, caregivers of children and youth with SMA completed the PEDI-CAT Daily Activities and Mobility domains. A subset of caregivers completed a questionnaire about the measure.

RESULTS

Mean ranks of scaled scores for Daily Activities (n = 96) and Mobility (n = 95) domains were significantly different across the three SMA types and across the three motor classifications. Normative scores indicated that 85 participants (89.5%) had limitations in Mobility and 51 in Daily Activities (53.1%). Floor effects were observed in≤10.4% of the sample for Daily Activities and Mobility. On average, caregivers completed the Mobility domain in 5.4 minutes and the Daily Activities domain in 3.3 minutes. Most caregivers reported that they provided meaningful information (92.1%), were willing to use the PEDI-CAT format again (79%), and suggested adding content including power wheelchair mobility items.

CONCLUSION

Convergent validity was demonstrated for the Daily Activities and Mobility domains. Normative scores detected limitations in Mobility and Daily Activity performance for most participants with SMA. The PEDI-CATwas feasible to administer and caregivers expressed willingness to complete the PEDI-CAT in the future.

Nusinersen for spinal muscular atrophy type 1: Real-world respiratory experience

BACKGROUND

The emergence of new treatments for spinal muscular atrophy (SMA) is revolutionary, especially for SMA type 1 (SMA1). Data on respiratory outcomes remain sparse and rely mostly on randomized clinical trials. We report our experience of Nusinersen-treated SMA1 patients in real-world settings.

METHODS

Data from SMA1 patients treated with Nusinersen were prospectively collected between 1/2017 and 1/2020. Respiratory variables included the use of assisted ventilation, the use of mechanical insufflation-exsufflation (MIE), respiratory complications, and death or treatment cessation due to respiratory reasons.

RESULTS

Twenty SMA1 patients were assessed before and after 2 years of Nusinersen treatment which was initiated at a median age of 13.5 months (range, 1-184). At baseline, 16 patients were using assisted ventilation, eight noninvasive and eight invasive. Twelve patients were using permanent ventilation and four partial ventilation. After 2 years of treatment, there was no change in respiratory support among ventilated patients. All four patients who were free from respiratory support at baseline required the initiation of assisted ventilation during the study period. All 20 patients used MIE after 2 years of treatment. Two patients died from acute respiratory failure and one sustained severe brain injury. Four patients had chronic and/or recurrent atelectasis.

CONCLUSION

Most of our patients were stable in their need for assisted ventilation and did not worsen as expected in SMA1, nor did they improve as might be hoped. Future studies are needed to determine if earlier treatment with Nusinersen might result in respiratory outcomes superior to those reported in this real-life study.

Emerging Oligonucleotide Therapeutics for Rare Neuromuscular Diseases

Research and drug development concerning rare diseases are at the cutting edge of scientific technology. To date, over 7,000 rare diseases have been identified. Despite their individual rarity, 1 in 10 individuals worldwide is affected by a rare condition. For the majority of these diseases, there is no treatment, much less cure; therefore, there is an urgent need for new therapies to extend and improve quality of life for persons who suffer from them. Here we focus specifically on rare neuromuscular diseases. Currently, genetic medicines using short antisense oligonucleotides (ASO) or small interfering ribonucleic acids that target RNA transcripts are achieving spectacular success in treating these diseases. For Duchenne muscular dystrophy (DMD), the state-of-the-art is an exon skipping therapy using an antisense oligonucleotide, which is prototypical of advanced precision medicines. Very recently, golodirsen and viltolarsen, for treatment of DMD patients amenable to skipping exon 53, have been approved by regulatory agencies in the USA and Japan, respectively. Here, we review scientific and clinical progress in developing new oligonucleotide therapeutics for selected rare neuromuscular diseases, discussing their efficacy and limitations.

Nusinersen treatment of older children and adults with spinal muscular atrophy

The purpose of this study was to determine how effective administration of nusinersen was at improving motor function in older adolescent and adult patients with spinal muscular atrophy, using standardized motor outcome measures. Data were gathered through a retrospective chart review of older spinal muscular atrophy patients (ages 5-58) being treated at Rady Children's Hospital and the University of California, San Diego with nusinersen from April 2017-June 2019. Linear mixed effects analyses found that, for older children and adult patients with SMA 1, 2, and 3, motor scores as measured by the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders for non-sitters improved by 6 points (p = .01) and the Hammersmith Infant Neurological Examination-2 by 2.6% (p = .008) over the 22-month study period. Over the same period, sitters improved on the Revised Upper Limb Module by 4.4 points (p = .02) and on the Hammersmith Functional Motor Scale-Expanded by 3.3% (p = .00005) post treatment with nusinersen. Older spinal muscular atrophy patients (5-58 years) being treated with nusinersen at our institutions are improving. Not only have symptoms stabilized, but their motor function has shown incremental improvements. Based on the results of this study, we suggested that nusinersen is well-tolerated and efficacious when treating older children and adult patients with spinal muscular atrophy 1, 2, and 3.

Development of a proxy-reported scale to assess motor function in infants and young children with early-onset neuromuscular disorders

AIM

To develop a novel proxy-reported scale of motor function in infants and young children with early-onset neuromuscular disorders (NMD), entitled the Proxy Motor Outcome Measure (PMOM).

DESIGN

A mixed method design was employed, applying both qualitative and quantitative research.

METHODS

A framework technique using sensitivity analyses guided the development of the most appropriate and relevant subset of items, modelled after 30 neuromuscular disease instruments/scales. The PMOM was designed based on semi-structured interviews with 16 proxies; a focus group of 11 experts in neuromuscular diseases and scale development, 10 of whom also gave quantitative data using a two-round Delphi method survey; and cognitive interviews with five proxies. These processes were conducted between January 2014-March 2019.

RESULTS

Nine themes and 32 subthemes were derived from the semi-structured interviews. Five domains and three subdomains of potential items were identified by the focus group. An initial version of the PMOM scale was created with 121 items. Using the two-round Delphi method, 43 items met agreement on pre-defined requirements. The second version of the PMOM scale included these 43 and two additional items based on expert feedback. Proxies gave 114 suggestions on cognitive interviews, 99 of which were successfully addressed by the research team. The final version of the PMOM scale included 43 items.

CONCLUSION

We developed a preliminary proxy-reported instrument, the PMOM, to evaluate motor function in infants and young children with early-onset NMD.

IMPACT

Proxies hold a wealth of knowledge on their child's motor function during early development, which may complement clinic-based motor function testing. However, there is no validated measure of motor function that incorporates the observation of proxies of infants and young children with NMD. Future work will be focused on assessing the reliability, validity and responsiveness of the PMOM scale and implementing this tool in clinical studies.

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.

Graphical Analyses in the Regulatory Evaluation of Gene Therapy Applications

The Center for Biologics Evaluation and Research (CBER) at the US Food and Drug Administration (FDA) regulates gene therapies, among other products. The approval of four gene therapy products since 2017 represents a significant milestone for a new class of treatments with the potential to treat or cure diseases, particularly rare diseases, that were previously considered incurable. Several factors have contributed to the recent rapid development of gene therapies including advances in genetics to facilitate target-detection, advances in vectors, and regulatory incentives such as breakthrough therapy designation, priority review and market exclusivity. The patient population affected by a rare disease is typically small, heterogeneous and geographically dispersed. As a result, clinical trials on a rare disease have unique features in terms of study design, subject enrollment, data analyses and interpretation of study results. Given that the patient population affected is small for rare diseases, providing substantial evidence of effectiveness and evidence of safety in trials for rare disease presents challenges. In this paper, we share our experiences in the statistical review of three gene therapy products that have been approved by FDA CBER. Our motivation in writing this paper is to encourage the use of appropriate analysis strategies for other similar small trials, with a focus on data visualization strategies.