Treatment with Nusinersen - Challenges Regarding the Indication for Children with SMA Type 1

Can the CHOP-INTEND be used as An Outcome Measure in the First Months of Age? Implications for Clinical Trials and Real World Data

BACKGROUND

The CHOP-INTEND is an established outcome measure used to assess motor function in young and weak SMA patients previously validated in type I infants older than 3 months.

OBJECTIVE

The aim of our study was to assess the maturation of the CHOP-INTEND scores in a group of healthy infants, establishing which items of the scale can be reliably used in individuals younger than 3 months.

METHODS

This is a prospective observational study. The whole cohort was divided into 5 age groups. Each of the 16 CHOP-INTEND items was analyzed looking at the frequency distribution of the scores in each age subgroup. An item was considered developmentally appropriate when > 85% of the infants achieved a full score.

RESULTS

our study includes 61 assessments collected < 2 weeks, 25 at 2-4 weeks, 20 at 5-8 weeks, 25 at 9-12 weeks and 20 at 13-17 weeks. Eight of the 16 items were developmentally appropriate already in the first week and another by the end of the first month. The remaining 7 items had more variable responses in the first three months and full scores were consistently achieved only after the third month.

CONCLUSIONS

Our findings suggest that the CHOP-INTEND can be used before the age of 3 months, but the results should be interpreted with caution, considering which items are developmentally appropriate at the time of testing. This will also help to establish whether the changes observed following early treatments are a sign of efficacy or at least partly reflect maturational aspects.

New therapies for spinal muscular atrophy: where we stand and what is next

The natural history of spinal muscular atrophy has been radically changed by the advent of improved standards of care and the availability of disease-modifying therapies. The aim of this paper is to provide the current therapeutic scenario including new perspectives and to report the challenges related to new phenotypes a few years after the therapies have become available. The paper also includes a review of real-world data that provides information on safety and efficacy in individuals that were not included in clinical trials. Special attention is paid to future perspectives both in terms of new drugs that are currently investigated in clinical trials or providing details on current developments in the use of the available drugs, including combination therapies or new modalities of dose or administration.  Conclusion: Clinical trials and real world data support the efficacy and safety profiles of the available drugs. At the moment there is not enough published evidence about the superiority of one product compared to the others. What is Known: • Safety and efficacy results of clinical trials have led in the last 6 years to the marketing of three drugs for spinal muscular atrophy, with different mechanisms of action. What is New: • Since the drug's approval, real-world data allow us to have data on bigger and heterogeneous groups of patients in contrast with those included in clinical trials. • In addition to the new molecules, combinations of therapies are currently being evaluated.

[Update on drug treatment of spinal muscular atrophy]

BACKGROUND

The 5q-associated spinal muscular atrophy (SMA) is a hereditary motor neuron disease leading to progressive tetraplegia, often involving the bulbopharyngeal and respiratory muscle groups. The disease usually manifests in early childhood and, if untreated, is progressive throughout life and associated with numerous complications depending on the severity. Since 2017, genetically based therapeutic mechanisms are now available that correct the causative deficiency of survival motor neuron (SMN) protein and lead to significant modifications in disease progression. As the number of treatment options increases, the question of which patient is suitable for which treatment also arises.

OBJECTIVE

This review article provides an update on the current treatment strategies for SMA in children and adults.

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.

Oral and Swallowing Abilities Tool (OrSAT) in nusinersen treated patients

INTRODUCTION

The aim of the study was to longitudinally assess swallowing abilities in nusinersen-treated patients with type 1 spinal muscular atrophy.

METHODS

Twenty infants with type 1 SMA (11 female and 9 male) treated with nusinersen between 3 weeks and 15 months of age, were assessed using the Oral and Swallowing Abilities Tool (OrSAT). The duration of the follow-up after treatment ranged between 12 months and 62 months.

RESULTS

Twelve of the 20 infants had normal swallowing and there was no need for tube feeding at the time treatment started. Ten of the 12 had consistently normal swallowing with no need for tube feeding on follow-up. The other two required tube feeding but they regained the ability to eat some food by mouth.The remaining 8 infants already had tube feeding inserted at the time treatment started: 4 of them also had tracheostomy and they showed no changes on the OrSAT Scale. The other 4 who had tube feeding but no tracheostomy had partial functional improvement.

CONCLUSION

Our results suggest that the degree of functional impairment at the time treatment is started can help to predict the progression of swallowing abilities. The use of a structured assessment also helped to detect partial improvements.

Spinal muscular atrophy

Spinal muscular atrophy (SMA) is a neurodegenerative disorder caused by mutations in SMN1 (encoding survival motor neuron protein (SMN)). Reduced expression of SMN leads to loss of α-motor neurons, severe muscle weakness and often early death. Standard-of-care recommendations for multidisciplinary supportive care of SMA were established in the past few decades. However, improved understanding of the pathogenetic mechanisms of SMA has led to the development of different therapeutic approaches. Three treatments that increase SMN expression by distinct molecular mechanisms, administration routes and tissue biodistributions have received regulatory approval with others in clinical development. The advent of the new therapies is redefining standards of care as in many countries most patients are treated with one of the new therapies, leading to the identification of emerging new phenotypes of SMA and a renewed characterization of demographics owing to improved patient survival.

Spinal muscular atrophy: from rags to riches

The aim of this paper is to provide a short history of spinal muscular atrophy, from the first descriptions of the disease to the impact of the most recent therapeutical advances on the disease course. The paper provides an overview of how the field has progressed over the years after the availability of care recommendations and, more recently of the new therapies. The paper also highlights the new challenges related to the interpretation of the efficacy of the new therapies and how these are likely to affect several aspects such as the classification of spinal muscular atrophy. We will also discuss the need for further work to better define possible new phenotypes and new methods of assessments and how these should be reflected in the care recommendations. The results in presymptomatic patients will finally highlight the need for neonatal screening.

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.

Nusinersen in type 0 spinal muscular atrophy: should we treat?

A male infant affected by type 0 SMA with one copy of SMN2 received early treatment with Nusinersen at the age of 13 days. He showed mild motor improvement 2 months after treatment started but despite also showing some minimal respiratory improvement, required tracheostomy at the age of 4 months and had increasing cardiac and autonomic dysfunction leading to exitus at 5 months. Our findings, expanding the results available on Nusinersen, confirm its relative efficacy in the most severely affected infants and provide clinical evidence to be used at the time requests for treating severe infants are discussed.

Spinal muscular atrophy - insights and challenges in the treatment era

Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron disease caused by deletion or mutation of SMN1. Four subtypes exist, characterized by different clinical severities. New therapeutic approaches have become available in the past few years, dramatically changing the natural history of all SMA subtypes, including substantial clinical improvement with the severe and advanced SMA type 1 variant. Trials have now demonstrated that phenotypic rescue is even more dramatic when pre-symptomatic patients are treated, and emerging real-world data are demonstrating the benefits of intervention even in the chronic phase of the condition. Here, we critically review how the field is rapidly evolving in response to the new therapies and questions that the new treatments have posed, including the effects of treatment at different ages and stages of disease, new phenotypes and long-term outcomes in patients who would not have survived without treatment, and decisions of who to treat and when. We also discuss how the outcomes associated with different timing of therapeutic intervention are contributing to our understanding of the biology and pathogenesis of SMA.