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

Prevalence and incidence rates of 17 neuromuscular disorders: An updated review of the literature

BACKGROUND

Epidemiological frequency measures serve as reference point for patients, clinicians, researchers, and policymakers. Previously, we published a comprehensive review of the literature with prevalence and incidence rates for thirty neuromuscular disorders frequently encountered in the neuromuscular clinic. No meta-analyses were available at the time.

OBJECTIVE

We included various new studies and meta-analyses that have been published since 2014, we aim to update our previous review.

METHODS

Pubmed was searched for 'incidence' and 'prevalence' in combination with seventeen acquired and inherited neuromuscular disorders to identify peer-reviewed literature from 1990 to 2023. If multiple prevalence and incidence rates were found, these were summarized by providing the mean, the number of the estimates on which the mean was based and the range of these estimates. Additionally, we searched for meta-analyses to compare the found mean prevalence rates based on the summary of individual studies with the pooled prevalence rates based on the meta-analyses.

RESULTS

The mean prevalence estimates for 17 disorders ranged from 0.3/100,000 population for Lambert-Eaton myasthenic syndrome, glycogenosis type V and nemaline myopathy to 20/100,000 for Charcot-Marie-Tooth disease type I. We found annual incidence rates for eight disorders, ranging from 0.3/100,000 population for progressive (spinal) muscular atrophy and facioscapulohumeral muscular atrophy to 1/100,000 for Charcot-Marie-Tooth disease type 1 and myotonic dystrophy type 1. Plotting the mean prevalence estimates from the current study against the pooled prevalence estimates from eight meta-analyses showed reasonable agreement.

CONCLUSIONS

Epidemiological frequencies about neuromuscular diseases- and in particular data on incidence are scarce. The mean prevalence estimates based on recently published studies on individual cohorts correspond well with the findings from the sparingly performed meta-analyses.

Common complications in spinal muscular atrophy (SMA) type 1 after nusinersen treatment

BACKGROUND

Spinal muscular atrophy (SMA) is an inherited disease with progressive muscle weakness and atrophy. Despite the new treatments developed recently, primary and secondary effects of muscle weakness in patients with SMA cause mortality and morbidity. The aim of this study is to identify common problems in the follow-up of patients after new treatment modalities and to examine the difficulties in management of these problems.

METHODS

The study included 16 patients diagnosed with SMA type 1 according to clinical findings and genetic results between 2017 and 2022. The patients were divided into two groups as living and deceased, and complications were examined and compared between the groups.

RESULTS

The patients comprised 8 (50%) females and 8 (50%) males with a median age at diagnosis of 3 months. The patients had a history of gastrointestinal problems, orthopedic problems, infection and sepsis, and especially respiratory distress. Death occurred in 8 (50%) patients during follow-up (median age 38 months). Mortality was higher in patients who needed tracheostomy and had gastroesophageal reflux. The survival rate was better in patients who received more nusinersen treatment and had a higher CHOP-INTEND score.

CONCLUSIONS

Despite new-generation treatments for SMA type 1, morbidity and mortality rates remain very high. As the survival rate in SMA type 1 increases, the incidence of complications similar to those frequently seen in SMA type 2 and type 3 patients also increases. The follow-up and treatment of patients with SMA should be undertaken by a multidisciplinary team.

An updated systematic review on spinal muscular atrophy patients treated with nusinersen, onasemnogene abeparvovec (at least 24 months), risdiplam (at least 12 months) or combination therapies

OBJECTIVE

This systematic review provides an update on outcomes for patients with spinal muscular atrophy (SMA) type 1 to 4 treated with approved therapeutics, including the most recent, risdiplam, for an observation period of up to 48 months.

METHODS

A systematic literature search was conducted in July 2023 in four databases. Selected publications were assessed for internal validity and risk of bias by two authors and relevant data were extracted into standardised tables. Results were summarised narratively as substantial heterogeneity of studies prevents meaningful quantitative analysis.

RESULTS

Twenty observational studies and one RCT were included in the analysis, fifteen studies on nusinersen, one on onasemnogene abeparvovec and two on risdiplam. Evidence supports the effectiveness of the therapies in motor function improvement for up to 48 months of follow-up in the SMA types specified in their respective indications. Better results were observed with earlier treatment initiation and higher baseline function. Whilst motor improvement was consistently observed, regardless of SMA type or treatment used, we noted no significant improvements in respiratory and nutritional outcomes. Quality of life endpoints were rarely investigated. Adverse events were common but seldom classified as treatment-related except for post-lumbar puncture syndrome, which was frequently reported across nusinersen studies.

CONCLUSION

The treatment of SMA with the new therapies changes the disease phenotype with changes in motor function far exceeding any improvement in respiratory and nutritional function. Questions persist on long-term efficacy, potential regressions, impact on quality of life and social functioning, therapy duration, and discontinuation indicators.

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.

Nusinersen demonstrates effectiveness in treating spinal muscular atrophy: findings from a three-year nationwide study in Korea

Introduction

Nusinersen is the first drug approved for spinal muscular atrophy (SMA) treatment. In this study, we aimed to evaluate the long-term safety and efficacy of nusinersen, assess the therapeutic effects based on the treatment initiation timing and baseline motor function, and explore the perception of functional improvement from either parents or patients, utilizing 3-year nationwide follow-up data in South Korea.

Methods

We enrolled patients with SMA who were treated with nusinersen under the National Health Insurance coverage, with complete motor score records available and a minimum treatment duration of 6 months. To evaluate the motor function of patients, the Hammersmith Infant Neurological Examination-2 (HINE-2) was used for type 1 and the Expanded Hammersmith Functional Motor Scale (HFMSE) was used for types 2 and 3 patients. A significant improvement was defined as a HINE-2 score gain ≥5 for patients with type 1 and an HFMSE score ≥ 3 for patients with types 2 and 3 SMA. Effects of treatment timing were assessed. Patients with type 2 were further categorized based on baseline motor scores for outcome analysis. We also analyzed a second dataset from five tertiary hospitals with the information on parents/patients-reported impressions of improvement.

Results

The study comprised 137 patients, with 21, 103, and 13 patients representing type 1, 2, and 3 SMA, respectively. At the 3-year follow-up, the analysis encompassed 7 patients with type 1, 12 patients with type 2, and none with type 3. Nearly half of all enrolled patients across SMA types (42.8, 59.2 and 46.2%, respectively) reached the 2-year follow-up for analysis. Patients with type 1 SMA exhibited gradual motor function improvement over 1-, 2-, and 3-year follow-ups (16, 9, and 7 patients, respectively). Patients with type 2 SMA demonstrated improvement over 1-, 2-, and 3-year follow-ups (96, 61 and 12 patients, respectively). Early treatment from symptom onset resulted in better outcomes for patients with type 1 and 2 SMA. In the second dataset, 90.7% of 108 patients reported subjective improvement at the 1-year follow-up.

Conclusion

Nusinersen treatment for types 1-3 SMA is safe and effective in long-term follow-up. Early treatment initiation was a significant factor affecting long-term motor outcome.

Estimating mortality in rare diseases using a population-based registry, 2002 through 2019

BACKGROUND

Rare diseases (RD) are a heterogeneous group of diseases, sharing aspects of complexity. Prognosis is variable, even in individuals with the same disease. Real-world data on RD as a whole are scarce. The aim of this study is to provide data on mortality and survival for a substantial group of RD deriving from a population-based registry, which covers the Veneto region in Italy (4.9 million inhabitants).

RESULTS

During the study period, 3367 deaths occurred, mainly in males (53.9%), elderly patients (63.5%) and patients with diseases having a reported prevalence of 1-9/100000 (65.6%). When standardizing by age, the mortality ratio was higher in RD patients than in the general population, SMR = 1.93 (95% CI 1.84-2.11), with an observed gender difference, 2.01 (95% CI 1.88-2.29) in females and 1.86 (95% CI 1.73-2.10) in males. The lowest survival rates are experienced by patients with rare neurologic diseases, rare skin diseases and rare systemic or rheumatologic diseases, 58%, 68% and 81%, respectively, after a 15-year observation period. It should be noted that only 18% of patients diagnosed with motor neuron diseases were alive after 15 years from diagnosis.

CONCLUSIONS

Despite progress in diagnosis, treatment and care in recent years, RD patients globally have higher mortality rates and reduced survival compared to the general population, with specific variations according to gender, age and disease group.