Developmental milestones in type I spinal muscular atrophy

Combination molecular therapies for type 1 spinal muscular atrophy

BACKGROUND

Data on combining molecular therapies that increase survival motor neuron protein for spinal muscular atrophy type 1 (SMA1) is lacking.

METHODS

This was a retrospective study describing our centers' experiences in treating SMA1 patients with combination therapy.

RESULTS

Five children received nusinersen and onasemnogene abeparvovec-xioi (onasemnogene). Four were receiving nusinersen prior to onasemnogene. Nusinersen was continued in three. Marked liver enzyme elevations resulted in prolonged corticosteroid treatment in two patients with hospitalization and liver biopsy in one; milder liver enzyme elevations were noted in the other two. One patient received onasemnogene first, and then nusinersen. No adverse effects were noted. All patients improved.

CONCLUSIONS

Combination molecular therapy is tolerated in SMA1 patients. Further studies are needed to determine whether there are circumstances in which combination therapy would be more efficacious than either monotherapy. Prolonged corticosteroid use and liver toxicity monitoring may be necessary with onasemnogene therapy.

Effects of nusinersen after one year of treatment in 123 children with SMA type 1 or 2: a French real-life observational study

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by degeneration of the anterior horn cells of the spinal cord. Nusinersen has been covered by public healthcare in France since May 2017. The aim of this article is to report results after 1 year of treatment with intrathecal nusinersen in children with SMA types 1 and 2 in France. Comparisons between treatment onset (T0) and after 1 year of treatment (Y1) were made in terms of motor function and need for nutritional and ventilatory support. Motor development milestone achievements were evaluated using the modified Hammersmith Infant Neurologic Examination-Part 2 (HINE-2) for patients under 2 years of age and Motor Function Measure (MFM) scores for patients over 2 years of age.

RESULTS

Data on 204 SMA patients (type 1 or 2) were retrospectively collected from the 23 French centers for neuromuscular diseases. One hundred and twenty three patients had been treated for at least 1 year and were included, 34 of whom were classified as type 1 (10 as type 1a/b and 24 as type 1c) and 89 as type 2. Survival motor Neuron 2 (SMN2) copy numbers were available for all but 6 patients. Patients under 2 years of age (n = 30), had significantly higher HINE-2 scores at year 1 than at treatment onset but used more nutritional and ventilatory support. The 68 patients over 2 years of age evaluated with the Motor Function Measure test had significantly higher overall scores after 1 year, indicating that their motor function had improved. The scores were higher in the axial and proximal motor function (D2) and distal motor function (D3) parts of the MFM scale, but there was no significant difference for standing and transfer scores (D1). No child in either of the two groups achieved walking.

CONCLUSION

Nusinersen offers life-changing benefits for children with SMA, particularly those with more severe forms of the disorder. Caregiver assessments are positive. Nevertheless, patients remain severely disabled and still require intensive support care. This new treatment raises new ethical challenges.

A National Spinal Muscular Atrophy Registry for Real-World Evidence

Background:

Spinal muscular atrophy (SMA) is a devastating rare disease that affects individuals regardless of ethnicity, gender, and age. The first-approved disease-modifying therapy for SMA, nusinursen, was approved by Health Canada, as well as by American and European regulatory agencies following positive clinical trial outcomes. The trials were conducted in a narrow pediatric population defined by age, severity, and genotype. Broad approval of therapy necessitates close follow-up of potential rare adverse events and effectiveness in the larger real-world population.

Methods:

The Canadian Neuromuscular Disease Registry (CNDR) undertook an iterative multi-stakeholder process to expand the existing SMA dataset to capture items relevant to patient outcomes in a post-marketing environment. The CNDR SMA expanded registry is a longitudinal, prospective, observational study of patients with SMA in Canada designed to evaluate the safety and effectiveness of novel therapies and provide practical information unattainable in trials.

Results:

The consensus expanded dataset includes items that address therapy effectiveness and safety and is collected in a multicenter, prospective, observational study, including SMA patients regardless of therapeutic status. The expanded dataset is aligned with global datasets to facilitate collaboration. Additionally, consensus dataset development aimed to standardize appropriate outcome measures across the network and broader Canadian community. Prospective outcome studies, data use, and analyses are independent of the funding partner.

Conclusion:

Prospective outcome data collected will provide results on safety and effectiveness in a post-therapy approval era. These data are essential to inform improvements in care and access to therapy for all SMA patients.

Choosing Life with Spinal Muscular Atrophy Type 1

This article is co-authored by the mother of a patient with spinal muscular atrophy (SMA), two pediatric pulmonologists and the pediatric neurologist in the team. It describes the patient and their family's experience of living with SMA. This commentary describes the mother's experience of the diagnosis and treatment process of her daughter's SMA in an era of emerging treatments for a disease which was until recently considered incurable. SMA diagnosis and management in the context of the patient mother's experiences is discussed.

Twenty-Five Years of Spinal Muscular Atrophy Research: From Phenotype to Genotype to Therapy, and What Comes Next

Twenty-five years ago, the underlying genetic cause for one of the most common and devastating inherited diseases in humans, spinal muscular atrophy (SMA), was identified. Homozygous deletions or, rarely, subtle mutations of SMN1 cause SMA, and the copy number of the nearly identical copy gene SMN2 inversely correlates with disease severity. SMA has become a paradigm and a prime example of a monogenic neurological disorder that can be efficiently ameliorated or nearly cured by novel therapeutic strategies, such as antisense oligonucleotide or gene replacement therapy. These therapies enable infants to survive who might otherwise have died before the age of two and allow individuals who have never been able to sit or walk to do both. The major milestones on the road to these therapies were to understand the genetic cause and splice regulation of SMN genes, the disease's phenotype-genotype variability, the function of the protein and the main affected cellular pathways and tissues, the disease's pathophysiology through research on animal models, the windows of opportunity for efficient treatment, and how and when to treat patients most effectively.This review aims to bridge our knowledge from phenotype to genotype to therapy, not only highlighting the significant advances so far but also speculating about the future of SMA screening and treatment.

Palliative Care in SMA Type 1: A Prospective Multicenter French Study Based on Parents' Reports

Spinal muscular atrophy type 1 (SMA-1) is a severe neurodegenerative disorder, which in the absence of curative treatment, leads to death before 1 year of age in most cases. Caring for these short-lived and severely impaired infants requires palliative management. New drugs (nusinersen) have recently been developed that may modify SMA-1 natural history and thus raise ethical concerns about the appropriate level of care for patients. The national Hospital Clinical Research Program (PHRC) called "Assessment of clinical practices of palliative care in children with Spinal Muscular Atrophy Type 1 (SMA-1)" was a multicenter prospective study conducted in France between 2012 and 2016 to report palliative practices in SMA-1 in real life through prospective caregivers' reports about their infants' management. Thirty-nine patients were included in the prospective PHRC (17 centers). We also studied retrospective data regarding management of 43 other SMA-1 patients (18 centers) over the same period, including seven treated with nusinersen, in comparison with historical data from 222 patients previously published over two periods of 10 years (1989-2009). In the latest period studied, median age at diagnosis was 3 months [0.6-10.4]. Seventy-seven patients died at a median 6 months of age[1-27]: 32% at home and 8% in an intensive care unit. Eighty-five percent of patients received enteral nutrition, some through a gastrostomy (6%). Sixteen percent had a non-invasive ventilation (NIV). Seventy-seven percent received sedative treatment at the time of death. Over time, palliative management occurred more frequently at home with increased levels of technical supportive care (enteral nutrition, oxygenotherapy, and analgesic and sedative treatments). No statistical difference was found between the prospective and retrospective patients for the last period. However, significant differences were found between patients treated with nusinersen vs. those untreated. Our data confirm that palliative care is essential in management of SMA-1 patients and that parents are extensively involved in everyday patient care. Our data suggest that nusinersen treatment was accompanied by significantly more invasive supportive care, indicating that a re-examination of standard clinical practices should explicitly consider what treatment pathways are in infants' and caregivers' best interest. This study was registered on clinicaltrials.gov under the reference NCT01862042 (https://clinicaltrials.gov/ct2/show/study/NCT01862042?cond=SMA1&rank=8).

From Clinical Trials to Clinical Practice: Practical Considerations for Gene Replacement Therapy in SMA Type 1

Spinal muscular atrophy is a devastating neurodegenerative autosomal recessive disease that results from survival of motor neuron 1 (SMN1) gene mutation or deletion. Patients with spinal muscular atrophy type 1 utilizing supportive care, which focuses on symptom management, never sit unassisted, and 75% die or require permanent ventilation by age 13.6 months. Onasemnogene abeparvovec (Zolgensma, formerly AVXS-101) is a gene replacement therapy comprising an adeno-associated viral vector containing the human SMN gene under control of the chicken beta-actin promoter. This therapy addresses the genetic root cause of the disease by increasing functional SMN protein in motor neurons and preventing neuronal cell death, resulting in improved neuronal and muscular function as previously demonstrated in transgenic animal models. In an open-label, one-arm, dose-escalation phase 1 trial, systemic administration of onasemnogene abeparvovec via a one-time infusion over one hour demonstrated improved motor function and survival in all infants symptomatic for spinal muscular atrophy type 1. Of the 12 patients who received the proposed therapeutic dose, 11 achieved independent sitting, two achieved independent standing, and two are able to walk. Most of these 12 patients remained free of respiratory supportive care. The only treatment-related adverse event observed was transient asymptomatic transaminasemia that resolved with a short course of prednisolone treatment. This review discusses the biological rationale underlying gene replacement therapy for spinal muscular atrophy, describes the onasemnogene abeparvovec clinical trial experience, and provides expert recommendations as a reference for the real-world use of onasemnogene abeparvovec in clinical practice. As of May 24, 2019, the Food and Drug Administration approved onasemnogene abeparvovec, the first gene therapy approved to treat children younger than two years with spinal muscular atrophy.

Estimation Of The Quality Of Life Benefits Associated With Treatment For Spinal Muscular Atrophy

Background

Spinal muscular atrophy (SMA) is a rare, genetic, progressive neuromuscular disorder characterized by severe muscle atrophy and weakness and is a leading genetic cause of death in infants and children. Nusinersen was the first treatment targeting the underlying cause of disease approved by the FDA, EMA and other countries for patients with SMA. There are currently very limited data available on the health-related quality of life (HRQoL) burden of SMA suitable for use in a cost-effectiveness analysis.

Objective

This study was designed to estimate quality of life weights or utilities for different SMA states.

Methods

SMA case studies were developed describing Type I (infantile onset) and Type II (later-onset) patients and different outcomes from treatment. These were developed so that quality of life weights or utilities (where the value of health ranges from 1 – full health to 0 – dead) could be estimated for cost-effectiveness analysis. Clinical experts (n=5) rated each of the case studies using standardized HRQoL instruments – the EQ-5D-Y and PedsQL-NMM (baseline states only).

Results

The SMA Type I utilities ranged from −0.33 (requires ventilation) to 0.71 (Type I patient reclassified as Type III following treatment), with quite substantial differences between some states. Most Type I states had a utility score below zero indicating the severity of the states. The SMA Type II utilities ranged from −0.13 (worsened) to 0.72 (stands/walks unaided). In general, the results showed HRQoL improved in line with better health states.

Conclusion

The utility scores obtained in this study highlight the very substantial burden experienced by SMA patients. Despite the limitations in the methods used, this study produced data with face validity and is a useful starting point for understanding the burden of SMA Types I and II in cost-effectiveness analysis.

Neurofilament light chain in serum of adolescent and adult SMA patients under treatment with nusinersen

OBJECTIVE

To determine the diagnostic and monitoring value of serum neurofilament light chain (NfL) in spinal muscular atrophy (SMA).

METHODS

We measured serum NfL in 46 SMA patients at baseline and over 14 months of treatment with the antisense-oligonucleotide (ASO) nusinersen using the ultrasensitive single molecule array (Simoa) technology. Serum NfL levels of SMA patients were compared to controls and related to cerebrospinal fluid (CSF) NfL, blood-CSF barrier function quantified by the albumin blood/CSF ratio (Qalb) and motor scores (Hammersmith Functional Motor Scale Expanded, HFMSE; Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised, ALSFRS-R).

RESULTS

Serum NfL levels of SMA patients were in the range of controls (p = 0.316) and did not correlate with CSF NfL (ρ = 0.302, p = 0.142) or Qalb (ρ = - 0.160, p = 0.293). During therapy, serum NfL levels were relatively stable with notable concentration changes in single SMA patients, however, within the control range. Higher NfL levels were associated with worse motor performance in SMA (baseline: HFMSE ρ = - 0.330, p = 0.025, ALSFRS-R ρ = - 0.403, p = 0.005; after 10 months: HFMSE ρ = - 0.525, p = 0.008, ALSFRS-R ρ = - 0.537, p = 0.007), but changes in motor scores did not correlate with changes in serum NfL.

CONCLUSION

Diagnostic and monitoring performance of serum NfL measurement seems to differ between SMA subtypes. Unlike to SMA type 1, in adolescent and adult SMA type 2 and 3 patients, neurodegeneration is not reflected by increased NfL levels and short-term therapeutic effects cannot be observed. Long-term follow-up has to be performed to see if even low levels of NfL might be good prognostic markers.

Nusinersen in type 1 spinal muscular atrophy: Twelve-month real-world data

OBJECTIVE

The aim of the study was to report 12-month changes after treatment with nusinersen in a cohort of 85 type I spinal muscular atrophy patients of ages ranging from 2 months to 15 years and 11 months.

METHODS

All patients were assessed using the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) and the Hammersmith Infant Neurological Examination-Section 2 (HINE-2).

RESULTS

Two of the 85 patients had 1 SMN2 copy, 61 had 2 copies, and 18 had 3 copies. In 4 patients the SMN2 copy number was not available. At baseline, the mean CHOP INTEND scores ranged between 0 and 52 (mean = 15.66, standard deviation [SD] = ±13.48), and the mean HINE-2 score was between 0 and 5 (mean = 0.69, SD = ±1.23). There was a difference between baseline and the 12-month scores on both the CHOP INTEND and the HINE-2 for the whole group (p < 0.001), the subgroups with 2 SMN2 copies (p < 0.001), and those with 3 SMN2 copies (p < 0.001). The difference was found not only in patients younger than 210 days at baseline (p < 0.001) but also in those younger than 5 years on the CHOP INTEND and younger than 2 years on the HINE-2.

INTERPRETATION

Our results, expanding the age range and the severity of type I patients treated with nusinersen over 1 year, provide additional data on the range of efficacy of the drug that will be helpful in making an informed decision on whether to start treatment in patients of different ages and severity. ANN NEUROL 2019;86:443-451.

[Pharmacological and clinical profile of spinal muscular atrophy (SMA) therapeutic drug nusinersen (Spinraza®)]

Nusinersen (Spinraza^®) was approved as Japan's first antisense oligonucleotide (ASO) drug for treatment of SMA (spinal muscular atrophy) patients with a deletion or mutation of the survival motor neuron (SMN) 1 gene and ≥1 copy of the SMN2 gene. Nuseinersen is a fully modified 2'-O-(2-methoxyethyl) (2'-MOE) ASO designed to bind the SMN2 pre-mRNA and alter splicing, such that a mature mRNA is produced and is translated as full-length SMN protein. In 4 types of mouse SMA disease models, treatment with nusinersen improved the form of the neuromuscular junction, increased myofiber size, improved righting reflex and grip, and prolonged survival. The efficacy of nusinersen was verified in 2 multinational, randomized, double-blind, sham-controlled clinical studies in SMA patients with differing ages of onset and ages (ENDEAR study and CHERISH study), and improvement and maintenance of motor function by nusinersen were demonstrated regardless of the type of SMA. Moreover, both studies showed that greater efficacy may be obtained with early initiation of nusinersen treatment. Therefore, treatment with nusinersen should be started as early as possible to delay or halt progression of the disease and maximize therapeutic effect. As nusinersen is the only ASO currently available for SMA, it will be widely used, therefore we will expect that nusinersen will contribute to improve patients' QOL and reduce the burden of caregivers and the healthcare system by improving motor function of patients with SMA.

Cost Effectiveness of Nusinersen in the Treatment of Patients with Infantile-Onset and Later-Onset Spinal Muscular Atrophy in Sweden

BACKGROUND

Spinal muscular atrophy is a rare neuromuscular disorder with a spectrum of severity related to age at onset and the number of SMN2 gene copies. Infantile-onset (≤ 6 months of age) is the most severe spinal muscular atrophy and is the leading monogenetic cause of infant mortality; patients with later-onset (> 6 months of age) spinal muscular atrophy can survive into adulthood. Nusinersen is a new treatment for spinal muscular atrophy.

OBJECTIVE

The objective of this study was to evaluate the cost effectiveness of nusinersen for the treatment of patients with infantile-onset spinal muscular atrophy and later-onset spinal muscular atrophy in Sweden.

METHODS

One Markov cohort health-state transition model was developed for each population. The infantile-onset and later-onset models were based on the efficacy results from the ENDEAR phase III trial and the CHERISH phase III trial, respectively. The cost effectiveness of nusinersen in both models was compared with standard of care in Sweden.

RESULTS

For a time horizon of 40 years in the infantile-onset model and 80 years in the later-onset model, treatment with nusinersen resulted in 3.86 and 9.54 patient incremental quality-adjusted life-years and 0.02 and 2.39 caregiver incremental quality-adjusted life-years and an incremental cost of 21.9 and 38.0 million SEK (Swedish krona), respectively. These results translated into incremental cost-effectiveness ratios (including caregiver quality-adjusted life-years) of 5.64 million SEK (€551,300) and 3.19 million SEK (€311,800) per quality-adjusted life-year gained in the infantile-onset model and later-onset model, respectively.

CONCLUSIONS

Treatment with nusinersen resulted in overall survival and quality-adjusted life-year benefits but with incremental costs above 21 million SEK (€2 million) [mainly associated with maintenance treatment with nusinersen over a patient's lifespan]. Nusinersen was not cost effective when using a willingness-to-pay threshold of 2 million SEK (€195,600), which has been considered in a recent discussion by the Dental and Pharmaceutical Benefits Agency as a reasonable threshold for rare disease. Nonetheless, nusinersen gained reimbursement in Sweden in 2017 for paediatric patients (below 18 years old) with spinal muscular atrophy type I-IIIa.

High Healthcare Resource Use in Hospitalized Patients with a Diagnosis of Spinal Muscular Atrophy Type 1 (SMA1): Retrospective Analysis of the Kids' Inpatient Database (KID)

BACKGROUND

Patients with spinal muscular atrophy (SMA) have high healthcare resource use (HRU) due to respiratory and nutritional complications resulting from progressive muscle atrophy. While previous studies estimate the direct costs to be US$113,000 to US$121,682 per year in the US, they potentially understate costs for type 1 SMA (SMA1). This study analyzed HRU in hospitalizations with a diagnosis of SMA1 and compared it with hospitalizations with complex chronic conditions (CCC) other than SMA1 or those with no CCC.

METHODS

This retrospective analysis of a defined subset of the 2012 Kids' Inpatient Database (KID) compared a nationally estimated number of hospitalizations of children (aged < 3 years) categorized into three groups: (1) SMA1 (n = 237 admissions), (2) no CCC (n = 632,467 admissions), and (3) other CCC (n = 224,953 admissions).

RESULTS

Mean total charges were higher for SMA1 admissions compared with admissions with no CCC (US$150,921 vs US$19,261 per admission, respectively; costs: US$50,190 vs $5862 per admission, respectively; both p < 0.0001). A larger proportion of SMA1 admissions were billed for one or more procedure codes (81.9%) than in the no CCC group (39.4%) or other CCC group (70.1%; both p ≤ 0.0003). SMA1 admissions had a longer length of stay compared with admissions with no CCC (15.1 vs 3.4, respectively; p < 0.0001).

CONCLUSIONS

The average total charges for a single SMA1 admission were higher than those of the no CCC group. Because most infants with SMA1 require multiple hospitalizations per year, previous estimates may dramatically underestimate the direct costs associated with HRU. Further studies are required to determine the indirect costs and societal impacts of SMA1.

Perspectives in genetic counseling for spinal muscular atrophy in the new therapeutic era: early pre-symptomatic intervention and test in minors

Spinal muscular atrophy (SMA) is an autosomal-recessive neuromuscular disorder representing a continuous spectrum of muscular weakness ranging from compromised neonates to adults with minimal manifestations. Patients show homozygous absence or disease-causing variants of the SMN1 gene (−/− or 0/0) and in carriers only one copy is absent or mutated (1/0). Genetic diagnosis and counseling in SMA present several challenges, including the existence of carriers (2/0) that are undistinguishable of non-carriers (1/1) with current genetic testing methods and the report of patients (0/0) with very mild manifestations and even asymptomatic that are discovered when a full symptomatic case appears in the family. Younger asymptomatic siblings of symptomatic SMA patients are usually never tested until adolescence or adult life. However, following regulatory approval of the first tailored treatment for SMA, the prospects for care of these patients have changed. Early testing, including pre-symptomatic newborn screening and confirmation of diagnosis would change proactive measures and opportunities for therapy based in the actual landscape of new treatments. This review discusses the challenges and new perspectives of genetic counseling in SMA.

Nusinersen: A Novel Antisense Oligonucleotide for the Treatment of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) encompasses a group of autosomal recessively inherited degenerative neuromuscular disorders. They range in severity from neonatal onset with rapidly progressive weakness and early mortality (SMA-1), to onset in infancy (SMA-2), to adolescent/adult onset with indolent clinical course (SMA-3/-4). SMA patients share mutations in the survival motor neuron (SMN) gene; variations in clinical phenotypes are attributable to copy numbers of the closely related SMN2 gene. In December 2016, the US Food and Drug Administration (FDA) approved nusinersen (Spinraza, Biogen, Cambridge, MA) to treat SMA. Nusinersen, an antisense oligonucleotide, is administered directly into cerebrospinal fluid. It alters SMN2 pre-RNA splicing so exon 7 is included, increasing expression of functional SMN protein. Although nusinersen was FDA approved for treatment of all forms of SMA, the initial clinical trials were limited to patients up to age 14 years, diagnosed with SMA-1,-2, -3, not on mechanical ventilation support. Two subsequent phase 3 trials were completed for SMA-1 and SMA-2/-3 and demonstrated improved motor milestones and event-free survival, better than expected based on natural history studies. Efficacy assessments for patients receiving nusinersen are based on serial assessments of performance on age-appropriate standardized motor scales. Treatment requires complex financial and logistics because of the very high drug cost, intrathecal administration, and medical fragility of the patients. Treatment implementation also engenders ethical considerations related to cost, insurance coverage, limited clinical data on groups of patients not in clinical trials, and questions of duration of treatment. Nusinersen has been integrated into the treatment of many SMA patients.

Spinal Muscular Atrophy: Huge Steps

Spinal muscular atrophy is the number one genetic cause of infant death. Until recently, half the babies born with it would die before their second birthdays, their hearts and lungs becoming too weak to continue. Medical care improved the odds somewhat, but new discoveries and therapeutic developments have improved survival rates significantly-and more good news may be on the horizon.

Neonatal hypotonia and neuromuscular conditions

The differential diagnosis of neonatal hypotonia is a complex task, as in newborns hypotonia can be the presenting sign of different underlying causes, including peripheral and central nervous system involvement and genetic and metabolic diseases. This chapter describes how a combined approach, based on the combination of clinical signs and new genetic techniques, can help not only to establish when the hypotonia is related to peripheral involvement but also to achieve an accurate and early diagnosis of the specific neuromuscular diseases with neonatal onset. The early identification of such disorders is important, as this allows early intervention with disease-specific standards of care and, more importantly, because of the possibility to treat some of them, such as spinal muscular atrophy, with therapeutic approaches that have recently become available.

Cost-effectiveness analysis of using onasemnogene abeparvocec (AVXS-101) in spinal muscular atrophy type 1 patients

Background: Spinal muscular atrophy type 1 (SMA1) is a devastating genetic disease for which gene-replacement therapy may bring substantial survival and quality of life benefits. Objective: This study investigated the cost-effectiveness of onasemnogene abeparvovec (AVXS-101) gene-replacement therapy for SMA1. Study design: A Markov model was used to estimate the incremental cost-effectiveness ratio (ICER), expressed as cost/quality-adjusted life year ($/QALY), of AVXS-101 versus nusinersen over a lifetime. Survival, healthcare costs and QALYs were estimated using natural history data for SMA patients who achieved motor milestones (sitting/walking). Health utility weights were obtained from the CHERISH trial. Setting: USA; commercial payer perspective Participants: SMA1 infants Interventions: AVXS-101 was compared to nusinersen. Main outcome measure: The primary outcome was the ICER. Results: Expected survival (undiscounted) over a lifetime predicted by the model was 37.20 life years for AVXS-101 and 9.68 for nusinersen (discounted QALYs, 15.65 and 5.29, respectively). Using a potential AVXS-101 price range ($2.5-5.0M/treatment), the average lifetime cost/patient was $4.2-6.6M for AVXS-101 and $6.3M for nusinersen. The ICER range was (-$203,072) to $31,379 per QALY gained for AVXS-101 versus nusinersen, indicating that AVXS-101 was cost-effective with prices of ≤$5M. Conclusion: Single-dose AVXS-101 was cost-effective compared to chronic nusinersen for SMA1 patients.

Evaluation of Children with SMA Type 1 Under Treatment with Nusinersen within the Expanded Access Program in Germany

Background:

Spinal muscular atrophy (SMA) is a neuromuscular disorder characterized by muscle weakness and muscle atrophy. Nusinersen acts as a splicing modifier and has recently been approved for intrathecal treatment of SMA.

Objective:

Prior to approval, nusinersen was provided to patients with SMA type 1 in Germany within an Expanded Access Program (EAP). In contrast to previous clinical trials, children of different age groups and different stages of the disease were treated with nusinersen.

Methods:

We conducted a prospective, longitudinal data collection of patients treated with nusinersen within the EAP in seven neuromuscular centers in Germany. Standardized assessments including CHOP-INTEND and HINE-2 motor milestones were performed at baseline and 60 and 180 days after start of treatment.

Results:

Data from 61 SMA type 1 patients (mean age 21.08 months, range 1–93) were available for analysis. After six months of treatment, 47 children (77.0%) improved by ≥4 points in CHOP INTEND score. Mean change in CHOP INTEND score was 9.0±8.0 points. Nineteen patients (31.1%) improved by ≥2 points in HINE-2 motor milestones. Regression analysis revealed age at onset of treatment as major determinant of change in CHOP INTEND from baseline.

Conclusion:

When analyzing a broad spectrum of SMA type 1 patients, many children showed an improvement of motor function after six months of treatment with nusinersen, which is generally not expected within the natural course of the disease. Long-term observation and follow-up of patients with later onset types of SMA are crucial to understand the clinical impact of treatment with nusinersen.

The role of sleep diagnostics and non-invasive ventilation in children with spinal muscular atrophy

Spinal muscular atrophy (SMA) is a degenerative motor neurone disorder causing progressive muscular weakness. Without assisted ventilation or novel therapies, most children with SMA type 1 die before the second year of life due to respiratory failure as the respiratory muscles and bulbar function are severely affected. Active respiratory treatment (mechanically assisted cough, invasive or non-invasive ventilation) has improved survival significantly in recent decades, but often at the cost of becoming ventilator dependent. The advent of a new oligonucleotide based therapy (Nusinersen) has created new optimism for improving motor function. However, the long-term effect on respiratory function is unclear and non-invasive respiratory support will remain an important part of medical management in patients with SMA. This review summarises the existing knowledge about sleep-disordered breathing and respiratory failure in patients with SMA, especially type 1, as well as the evidence of improved outcome and survival in patients treated with non-invasive or invasive ventilation. Practical considerations and ethical concerns are delineated with discussion on how these may be affected by the advent of new therapies such as Nusinersen.

Nusinersen in patients older than 7 months with spinal muscular atrophy type 1: A cohort study

OBJECTIVE

To evaluate the safety and clinical efficacy of nusinersen in patients older than 7 months with spinal muscular atrophy type 1 (SMA1).

METHODS

Patients with SMA1 were treated with nusinersen by intrathecal injections as a part of the Expanded Access Program (EAP; NCT02865109). We evaluated patients before treatment initiation (M0) and at 2 months (M2) and 6 months (M6) after treatment initiation. Survival, respiratory, and nutritional data were collected. Motor function was assessed with the modified Hammersmith Infant Neurologic Examination Part 2 (HINE-2) and physiotherapist scales adjusted to patient age (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders and the Motor Function Measure 20 or 32).

RESULTS

We treated 33 children ranging in age from 8.3 to 113.1 months between December 2016 and May 2017. All patients were alive and were continuing treatment at M6. Median progress on the modified HINE-2 score was 1.5 points after 6 months of treatment (p < 0.001). The need for respiratory support significantly increased over time. There were no statistically significant differences between patients presenting with 2 and those presenting with 3 copies of the survival motor neuron 2 (SMN2) gene.

CONCLUSIONS

Our results are in line with the phase 3 study for nusinersen in patients with SMA1 treated before 7 months of age and indicate that patients benefit from nusinersen even at a later stage of the disease.

CLINICALTRIALSGOV IDENTIFIER

NCT02865109.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for patients with SMA1 who are older than 7 months, nusinersen is beneficial.

An observational study of functional abilities in infants, children, and adults with type 1 SMA

OBJECTIVE

To report cross-sectional clinical findings in a large cohort of patients affected by type 1 spinal muscular atrophy.

METHODS

We included 122 patients, of age ranging between 3 months and 22 years, 1 month. More than 70% (85/122) were older than 2 years and 25% (31/122) older than 10 years. Patients were classified according to the severity of phenotype and to the number of SMN2 copies.

RESULTS

Patients with the more common and the most severe phenotype older than 2 years were, with few exceptions, on noninvasive ventilation and, with increasing age, more often had tracheostomy or >16-hour ventilation and a gastrostomy inserted. In contrast, 25 of the 28 patients with the mildest phenotype older than 2 years had no need for tracheostomy or other ventilatory or nutritional support. In patients older than 2 years, the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scores were generally lower compared to those found in younger patients and showed distinct levels of functional abilities according to the severity of the phenotype. Similar findings were also observed on the Hammersmith Infant Neurological Examination.

CONCLUSIONS

Our findings confirm that, after the age of 2 years, patients with type 1 spinal muscular atrophy generally survive only if they have gastrostomy and tracheostomy or noninvasive ventilation >16 hours and have low scores on the functional scales. More variability, however, can be expected in those with the mildest phenotype, who achieve head control. These data provide important baseline information at the time treatments are becoming available.

Two breakthrough gene-targeted treatments for spinal muscular atrophy: challenges remain

The motor neuron disease spinal muscular atrophy (SMA) is caused by recessive, loss-of-function mutations of the survival motor neuron 1 gene (SMN1). Alone, such mutations are embryonically lethal, but SMA patients retain a paralog gene, SMN2, that undergoes alternative pre-mRNA splicing, producing low levels of SMN protein. By mechanisms that are not well understood, reduced expression of the ubiquitously expressed SMN protein causes an early-onset motor neuron disease that often results in infantile or childhood mortality. Recently, striking clinical improvements have resulted from two novel treatment strategies to increase SMN protein by (a) modulating the splicing of existing SMN2 pre-mRNAs using antisense oligonucleotides, and (b) transducing motor neurons with self-complementary adeno-associated virus 9 (scAAV9) expressing exogenous SMN1 cDNA. We review the recently published clinical trial results and discuss the differing administration, tissue targeting, and potential toxicities of these two therapies. We also focus on the challenges that remain, emphasizing the many clinical and biologic questions that remain open. Answers to these questions will enable further optimization of these remarkable SMA treatments as well as provide insights that may well be useful in application of these therapeutic platforms to other diseases.

Mathematical Disease Progression Modeling in Type 2/3 Spinal Muscular Atrophy

INTRODUCTION

We propose a mathematical model to empirically describe spinal muscular atrophy (SMA) progression assessed by the 3 domains of the motor function measure (MFM) scale. The model implements development and deterioration of muscle function.

METHODS

Nonlinear mixed-effects modeling was applied to data from 2 observational studies and 1 prospective clinical efficacy study comprising 190 healthy participants and 277 patients with type 2/3 SMA.

RESULTS

The model evidenced correlations between parameter estimates for different MFM domains. Slower development in MFM domain D1 (standing and transfers) was associated with faster deterioration for MFM domains D2 (proximal and axial motricity) and D3 (distal motor function).

DISCUSSION

The model describes all individual data well, although sparseness and variability of observational data prevented numerically stable estimation of parameters. Treatment duration in clinical studies was too limited to determine a proper drug-effect model that could differentiate between symptomatic and disease modifying effects. Muscle Nerve 58: 528-535, 2018.

c.835-5T>G Variant in SMN1 Gene Causes Transcript Exclusion of Exon 7 and Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder caused by survival motor neuron (SMN) protein deficiency leading the loss of motor neurons in the anterior horns of the spinal cord and brainstem. More than 95% of SMA patients are attributed to the homozygous deletion of survival motor neuron 1 (SMN1) gene, and approximately 5% are caused by compound heterozygous with a SMN1 deletion and a subtle mutation. Here, we identified a rare variant c.835-5T>G in intron 6 of SMN1 in a patient affected with type I SMA. We analyzed the functional consequences of this mutation on mRNA splicing in vitro. After transfecting pCI-SMN1, pCI-SMN2, and pCI-SMN1 c.835-5T>G minigenes into HEK293, Neuro-2a, and SHSY5Y cells, reverse transcription polymerase chain reaction (RT-PCR) was performed to compare the splicing effects of these minigenes. Finally, we found that this mutation resulted in the skipping of exon 7 in SMN1, which confirmed the genetic diagnosis of SMA.

RNA-Targeted Therapeutics

RNA-targeted therapies represent a platform for drug discovery involving chemically modified oligonucleotides, a wide range of cellular RNAs, and a novel target-binding motif, Watson-Crick base pairing. Numerous hurdles considered by many to be impassable have been overcome. Today, four RNA-targeted therapies are approved for commercial use for indications as diverse as Spinal Muscular Atrophy (SMA) and reduction of low-density lipoprotein cholesterol (LDL-C) and by routes of administration including subcutaneous, intravitreal, and intrathecal delivery. The technology is efficient and supports approaching "undruggable" targets. Three additional agents are progressing through registration, and more are in clinical development, representing several chemical and structural classes. Moreover, progress in understanding the molecular mechanisms by which these drugs work has led to steadily better clinical performance and a wide range of mechanisms that may be exploited for therapeutic purposes. Here we summarize the progress, future challenges, and opportunities for this drug discovery platform.

Functional outcome measures for infantile Charcot-Marie-Tooth disease: a systematic review

A functional outcome measure for infants (aged 0-3 years) with Charcot-Marie-Tooth (CMT) disease is needed for upcoming disease-modifying trials. A systematic review of outcome measures for infants with neuromuscular disorders was completed to determine if validated measures were available for the CMT infant population. We assessed 20,375 papers and identified seven functional outcome measures for infants with neuromuscular disorders. Six were developed and validated for spinal muscular atrophy (SMA). There were no CMT-specific outcome measures identified; however, one (motor function measure) assessed a range of neuromuscular disorders including 13 infants and children with CMT. The included studies exhibited "good" face, discriminant, convergent and concurrent validity, and reported excellent intra- and inter-rater reliability. No outcome measure was subjected to item response theory. Studies reported outcome measures comprising of 51 different items assessing six domains of function: reflexive movement, axial movement, limb movement, positioning, gross motor, and fine-motor skills. Scoring of items ranged from 2- to 7-point rating scales; and none were scaled to normative reference values to account for changes in growth and development. The SMA focus of most items is likely to produce ceiling effects and lack sensitivity and responsiveness for within and between types of CMT in infants. Nevertheless, several items across scales assessing distal strength, gross- and fine-motor function, could be included in the development of a composite functional outcome measure for infants with CMT to assess disease-modifying interventions.

Natural history of infantile-onset spinal muscular atrophy

OBJECTIVE

Infantile-onset spinal muscular atrophy (SMA) is the most common genetic cause of infant mortality, typically resulting in death preceding age 2. Clinical trials in this population require an understanding of disease progression and identification of meaningful biomarkers to hasten therapeutic development and predict outcomes.

METHODS

A longitudinal, multicenter, prospective natural history study enrolled 26 SMA infants and 27 control infants aged <6 months. Recruitment occurred at 14 centers over 21 months within the NINDS-sponsored NeuroNEXT (National Network for Excellence in Neuroscience Clinical Trials) Network. Infant motor function scales (Test of Infant Motor Performance Screening Items [TIMPSI], The Children's Hospital of Philadelphia Infant Test for Neuromuscular Disorders, and Alberta Infant Motor Score) and putative physiological and molecular biomarkers were assessed preceding age 6 months and at 6, 9, 12, 18, and 24 months with progression, correlations between motor function and biomarkers, and hazard ratios analyzed.

RESULTS

Motor function scores (MFS) and compound muscle action potential (CMAP) decreased rapidly in SMA infants, whereas MFS in all healthy infants rapidly increased. Correlations were identified between TIMPSI and CMAP in SMA infants. TIMPSI at first study visit was associated with risk of combined endpoint of death or permanent invasive ventilation in SMA infants. Post-hoc analysis of survival to combined endpoint in SMA infants with 2 copies of SMN2 indicated a median age of 8 months at death (95% confidence interval, 6, 17).

INTERPRETATION

These data of SMA and control outcome measures delineates meaningful change in clinical trials in infantile-onset SMA. The power and utility of NeuroNEXT to provide "real-world," prospective natural history data sets to accelerate public and private drug development programs for rare disease is demonstrated. Ann Neurol 2017;82:883-891.

Single-Dose Gene-Replacement Therapy for Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy type 1 (SMA1) is a progressive, monogenic motor neuron disease with an onset during infancy that results in failure to achieve motor milestones and in death or the need for mechanical ventilation by 2 years of age. We studied functional replacement of the mutated gene encoding survival motor neuron 1 (SMN1) in this disease.

METHODS

Fifteen patients with SMA1 received a single dose of intravenous adeno-associated virus serotype 9 carrying SMN complementary DNA encoding the missing SMN protein. Three of the patients received a low dose (6.7×10¹³ vg per kilogram of body weight), and 12 received a high dose (2.0×10¹⁴ vg per kilogram). The primary outcome was safety. The secondary outcome was the time until death or the need for permanent ventilatory assistance. In exploratory analyses, we compared scores on the CHOP INTEND (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders) scale of motor function (ranging from 0 to 64, with higher scores indicating better function) in the two cohorts and motor milestones in the high-dose cohort with scores in studies of the natural history of the disease (historical cohorts).

RESULTS

As of the data cutoff on August 7, 2017, all 15 patients were alive and event-free at 20 months of age, as compared with a rate of survival of 8% in a historical cohort. In the high-dose cohort, a rapid increase from baseline in the score on the CHOP INTEND scale followed gene delivery, with an increase of 9.8 points at 1 month and 15.4 points at 3 months, as compared with a decline in this score in a historical cohort. Of the 12 patients who had received the high dose, 11 sat unassisted, 9 rolled over, 11 fed orally and could speak, and 2 walked independently. Elevated serum aminotransferase levels occurred in 4 patients and were attenuated by prednisolone.

CONCLUSIONS

In patients with SMA1, a single intravenous infusion of adeno-associated viral vector containing DNA coding for SMN resulted in longer survival, superior achievement of motor milestones, and better motor function than in historical cohorts. Further studies are necessary to confirm the safety and efficacy of this gene therapy. (Funded by AveXis and others; ClinicalTrials.gov number, NCT02122952 .).

Nusinersen versus Sham Control in Infantile-Onset Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy is an autosomal recessive neuromuscular disorder that is caused by an insufficient level of survival motor neuron (SMN) protein. Nusinersen is an antisense oligonucleotide drug that modifies pre-messenger RNA splicing of the SMN2 gene and thus promotes increased production of full-length SMN protein.

METHODS

We conducted a randomized, double-blind, sham-controlled, phase 3 efficacy and safety trial of nusinersen in infants with spinal muscular atrophy. The primary end points were a motor-milestone response (defined according to results on the Hammersmith Infant Neurological Examination) and event-free survival (time to death or the use of permanent assisted ventilation). Secondary end points included overall survival and subgroup analyses of event-free survival according to disease duration at screening. Only the first primary end point was tested in a prespecified interim analysis. To control the overall type I error rate at 0.05, a hierarchical testing strategy was used for the second primary end point and the secondary end points in the final analysis.

RESULTS

In the interim analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (21 of 51 infants [41%] vs. 0 of 27 [0%], P<0.001), and this result prompted early termination of the trial. In the final analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (37 of 73 infants [51%] vs. 0 of 37 [0%]), and the likelihood of event-free survival was higher in the nusinersen group than in the control group (hazard ratio for death or the use of permanent assisted ventilation, 0.53; P=0.005). The likelihood of overall survival was higher in the nusinersen group than in the control group (hazard ratio for death, 0.37; P=0.004), and infants with a shorter disease duration at screening were more likely than those with a longer disease duration to benefit from nusinersen. The incidence and severity of adverse events were similar in the two groups.

CONCLUSIONS

Among infants with spinal muscular atrophy, those who received nusinersen were more likely to be alive and have improvements in motor function than those in the control group. Early treatment may be necessary to maximize the benefit of the drug. (Funded by Biogen and Ionis Pharmaceuticals; ENDEAR ClinicalTrials.gov number, NCT02193074 .).

Clinical phenotypes and trajectories of disease progression in type 1 spinal muscular atrophy

The advent of clinical trials has highlighted the need for natural history studies reporting disease progression in type 1 spinal muscular atrophy. The aim of this study was to assess functional changes using the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) scale in a cohort of type 1 infants. Nutritional and respiratory longitudinal data were also recorded. Patients were classified according to the severity of the phenotype and age of onset. SMN2 copies were also assessed. Twenty patients were included, eight with early onset most severe phenotype, eight with the more typical type 1 phenotype and 4, who achieved some head control, with a milder phenotype. Both baseline values and trajectories of progression were different in the three subgroups (p = 0.0001). Infants with the most severe phenotype had the lowest scores (below 20) on their first assessment and had the most rapid decline. Those with the typical phenotype had scores generally between 20 and 40 and also had a fast decline. The infants with the milder phenotype had the highest scores, generally above 35, and a much slower deterioration. Infants with three SMN2 copies had an overall milder phenotype and milder progression while two SMN2 copies were found in all three subgroups.

Motor milestone assessment of infants with spinal muscular atrophy using the hammersmith infant neurological Exam-Part 2: Experience from a nusinersen clinical study

INTRODUCTION

In this study we examined the feasibility of assessing motor milestone performance of infants with spinal muscular atrophy (SMA) using the Hammersmith Infant Neurological Exam-Part 2 (HINE-2) in a phase 2 study of nusinersen.

METHODS

Nineteen SMA infants were assessed using the HINE-2 at baseline (≤7 months of age), and periodically up to 39 months of age. We evaluated whether the HINE-2 was feasible, reliable, and sensitive to change.

RESULTS

Motor milestone assessments in SMA infants were feasible using the HINE-2. Baseline test-retest reliability was excellent (R = 0.987; P < 0.0001). SMA infants were extremely low functioning at baseline and the HINE-2 was able to detect changes over time in 16 of 19 infants within all 8 domains. HINE-2 improvements were correlated with changes in other neuromuscular outcome measures.

CONCLUSION

Results support the use of the HINE-2 motor milestone assessment in clinical trials of SMA infants. Muscle Nerve 57: 143-146, 2017.

Spinal muscular atrophy: A changing phenotype beyond the clinical trials

Spinal muscular atrophy is a monogenic, progressive motor neuron disorder caused by deletion or mutation in the SMN1 gene. A broad range of phenotypic severity, from very weak infants (Type 1) to ambulant children (type 3), is modified mainly by the number of copies of the "backup" SMN2 gene. Since the discovery of the role of both genes, basic research into the pathobiology of SMA, with in vitro and animal model studies, has identified therapeutic targets. Development of clinical outcome measures, natural history studies and standard of care guidelines have contributed to the development of protocols for therapeutic drugs now under clinical investigation. Following regulatory approval of the first drug treatment for SMA in the US (December, 2016) and marketing authorization in Europe (June, 2017), the prospects for care of these patients have changed. The evolution of the phenotype of SMA now needs to be considered beyond the clinical trials. This perspective review discusses potential new trajectories in the phenotype of SMA and the need for multidisciplinary teams to prepare for this changing landscape.