Safety and Treatment Effects of Nusinersen in Longstanding Adult 5q-SMA Type 3 - A Prospective Observational Study

Real-world Adherence to Nusinersen in Adults with Spinal Muscular Atrophy in the US: A Multi-site Chart Review Study

Limited evidence exists on real-world adherence to nusinersen for the treatment of spinal muscular atrophy (SMA). Data are presented from a multi-site retrospective chart review of 86 adults with SMA initiating nusinersen at nine US centers between January 2017 and February 2019. Seventy-nine (92%) adults remained on nusinersen during the study; 454 (92%) of 493 total nusinersen doses were received on time. Fifty-eight (67%) adults received all nusinersen doses on time. The majority of patients with at least one nonadherent dose resumed nusinersen on time. Most patients followed the dosing schedule across the loading and maintenance dose periods.

Prevalence of Anti-AAV9 Antibodies in Adult Patients with Spinal Muscular Atrophy

5q-associated spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder that leads to progressive muscle atrophy and weakness. The disease is caused by a homozygous deletion or mutation in the survival of motor neuron 1 gene (SMN1), resulting in insufficient levels of SMN protein. Onasemnogene abeparvovec-xioi (OA) is a non-replicating vector based on adeno-associated virus serotype 9 (AAV9) that contains the full-length human SMN1 gene. Recently, OA was approved for the treatment of SMA by the U.S. Food and Drug Administration and the European Medicines Agency. Since the presence of neutralizing antibodies caused by previous natural exposure to wild-type AAVs may impair the efficiency of AAV-mediated gene transfer, and thus reduce the therapeutic benefit of the gene therapy, an AAV9-binding antibody titer of >1:50 was defined as a surrogate exclusion criterion in pivotal OA clinical trials. However, these studies were exclusively conducted in infants and children. Since data on anti-AAV9 antibody titers in adults are generally sparse and not available for adult patients with SMA, we determined the prevalence of anti-AAV9 antibodies in sera of adult individuals with SMA to evaluate the feasibility of AAV9-mediated gene therapy in this cohort. In our study population of 69 adult patients with SMA type 2 and type 3 from four German academic sites, only three patients (4.3%) had an elevated anti-AAV9 antibody titer of >1:50. The prevalence of anti-AAV9 antibodies did not increase with age. The low and age-independent prevalence of anti-AAV9 antibodies in our cohort provides evidence that gene therapy with intravenous administered recombinant AAV9 vectors (rAAV9) might be feasible in adult patients with SMA, regardless of the patients' sex, SMA type, walking ability, or ventilatory status. This could also apply to the treatment of other inherited neurological diseases with rAAV9.

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.

Biochemical and clinical biomarkers in adult SMA 3-4 patients treated with nusinersen for 22 months

Objective

To investigate biomarkers of disease progression in cerebrospinal fluid (CSF) and serum in adult patients with spinal muscular atrophy (SMA). Furthermore, we assess the clinical response to nusinersen treatment in adults with SMA over a longer follow‐up period than the previously reported 6–14 months.

Methods

We included 16 adults with SMA type 3–4 for nusinersen treatment over 22 months in this prospective study. We evaluated chitotriosidase‐1 (CHIT1) and chitinase‐3‐like protein 1 (YKL‐40) as neuroinflammatory biomarkers in CSF, and neurofilament light chain (NfL) and heavy chain (pNfH) as neurodegenerative markers in CSF and serum at baseline, month 6, 14 and 22, together with a wide range of clinical outcome measures.

Results

Levels of CHIT1 increased significantly (p = 0.048) throughout the 22‐month treatment period and pNfH decreased significantly (p = 0.022) in CSF, but both did not correlate with clinical outcome measures. YKL‐40 correlated strongly with neurofilaments in CSF (rho = 0.76) and decreased significantly (p = 0.037) in patients with improvements in the revised upper limb module (RULM). Finally, patients showed significant improvements in hand grip strength, hand motor function, medical research council (MRC) sum score, and peak expiratory flow (PEF) after 22 months of treatment.

Interpretation

YKL‐40 in CSF correlated with clinical improvements during nusinersen treatment. In contrast, CHIT1 and pNfH in CSF changed significantly during treatment but did not correlate with clinical outcomes. Finally, we demonstrated a sustained clinical effect of nusinersen treatment in adults after 22 months.

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.

Disease Modifying Therapies for the Management of Children with Spinal Muscular Atrophy (5q SMA): An Update on the Emerging Evidence

SMA (5q SMA) is an autosomal recessive neuromuscular disease with an estimated incidence of approximately 1 in 11,000 live births, characterized by progressive degeneration and loss of α-motor neurons in the spinal cord and brain stem, resulting in progressive muscle weakness. The disease spectrum is wide, from a serious congenital to a mild adult-onset disease. SMA is caused by biallelic mutations in the SMN1 gene and disease severity is modified primarily by SMN2 copy number. Before the advent of specific disease altering treatments, SMA was the second most common fatal autosomal recessive disorder after cystic fibrosis and the most common genetic cause of infant mortality. Nusinersen, risdiplam, and onasemnogene abeparvovec are presently the only approved disease modifying therapies for SMA, and the aim of this review is to discuss their mode of action, effects, safety concerns, and results from real-world experience. All exert their action by increasing the level of SMN protein in lower motor neuron. Nusinersen and risdiplam by modifying the SMN2 gene product, and onasemnogene abeparvovec by delivering SMN1 gene copies into cells. All have an established clinical efficacy. An important feature shared by all three is that early intervention is associated with a better treatment outcome, such that in cases where treatment is initiated in an early pre-symptomatic period, it may result in normal – or almost normal – motor development. Thus, early diagnosis followed by swift initiation of treatment is fundamental for the treatment response and consequently long-term prognosis in SMA type 1, and probably SMA type 2. The same principle similarly applies to the milder phenotypes. All three therapies are relatively novel, with risdiplam being the latest addition. Except for nusinersen, real-world data are still scarce, and long-term data are quite naturally lacking.

[Gene-based treatment in spinal muscular atrophy]

BACKGROUND

The 5q-associated spinal muscular atrophy (SMA) affects ~ 80-120 newborns annually. The disease is characterized by progressive paresis involving the bulbar and respiratory musculatures. The phenotypes are very heterogeneous ranging from severe courses with early death in the first years of life to loss of gait in older age.

OBJECTIVE

There are now an increasing number of causally targeted therapies available that can either directly interfere with the transcription of the gene causing the disease or replace the homozygous loss of the SMN1 gene. This work aims to elucidate the current state of therapy in different groups of patients with SMA.

MATERIAL AND METHODS

Presentation of clinical trials and basic studies with a focus on patients with disease onset in adulthood.

RESULTS

The clinical studies all show improvement or stabilization of motor function; however, in individual cases, the burden of the therapy for severely immobilized patients must be considered in addition to the efficacy in the treatment decision. Even if the drugs show a good safety profile, observations on the long-term efficacy and safety of the new substance classes are still lacking.

CONCLUSION

The study landscape shows a good efficacy of the currently approved therapies across all degrees of severity and age groups. Due to the lack of comparative studies, the decision on the appropriate therapy should therefore be made according to an individual risk-benefit assessment.

Muscle microRNAs in the cerebrospinal fluid predict clinical response to nusinersen therapy in type II and type III spinal muscular atrophy patients

OBJECTIVE

The antisense oligonucleotide nusinersen (spinraza) regulates splicing of the survival motor neuron 2 (SMN2) messenger RNA to increase SMN protein expression and has improved ventilator free survival and motor function outcomes in infantile onset forms of SMA, treated early in the course of the disease. However, the response in later onset forms of SMA is highly variable and dependent on symptom severity and disease duration at treatment initiation. Therefore, we aimed to identify novel noninvasive biomarkers that could predict the response to nusinersen in type II and III SMA patients.

METHODS

34 SMA patients were included. We applied next-generation sequencing to identify microRNAs in the cerebrospinal fluid (CSF) as candidate biomarkers predicting response to nusinersen. Hammersmith Functional Motor Scale Expanded (HFMSE), was conducted at baseline and 6 months post initiation of nusinersen therapy to assess motor function. Patients changing by ≥ 3 or ≤0 points in the HFMSE total score were considered as responders or non-responders, respectively.

RESULTS

Lower baseline levels of two muscle microRNAs (miR-206 and miR-133), alone or in combination, predicted the pre-determined clinical response to nusinersen after 6 months therapy. Moreover, miR-206 levels were inversely correlated with the HFMSE score.

CONCLUSIONS

Lower miR-206 and miR-133 in the CSF predict more robust clinical response to nusinersen treatment in later onset SMA patients. These novel findings have high clinical relevance for identifying early treatment response to nusinsersen in later onset SMA patients and call to test the ability of miRNAs to predict more sustained long-term benefit.

Management of Spinal Muscular Atrophy in the Adult Population

Spinal muscular atrophy (SMA) is a group of neurodegenerative disorders resulting from the loss of spinal motor neurons. 95% of patients share a pathogenic mechanism of loss of survival motor neuron (SMN) 1 protein expression due to homozygous deletions or other mutations of the SMN1 gene, with the different phenotypes influenced by variable copy numbers of the SMN2 gene. Advances in supportive care, disease modifying treatment and novel gene therapies have led to an increase in the prevalence of SMA, with a third of SMA patients now represented by adults. Despite the growing number of adult patients, consensus on the management of SMA has focused primarily on the pediatric population. As the disease burden is vastly different in adult SMA, an approach to treatment must be tailored to their unique needs. This review will focus on the management of the adult SMA patient as they age and will discuss proper transition of care from a pediatric to adult center, including the need for continued monitoring for osteoporosis, scoliosis, malnutrition, and declining mobility and functioning. As in the pediatric population, multidisciplinary care remains the best approach to the management of adult SMA. Novel and emerging therapies such as nusinersen and risdiplam provide hope for these patients, though these medications are of uncertain efficacy in this population and require additional study.

Treatment of Adult Spinal Muscular Atrophy: Overview and Recent Developments

Spinal muscular atrophy (SMA) is a rare genetic neuromuscular disease leading to progressive and in many cases severe muscle weakness and atrophy in the natural disease course. An increasing number of gene-based treatment options have become available in recent years. Growing knowledge about the underlying genetic mechanisms makes the disease well amenable to this. Over the past few years, many data on new treatments, their mechanisms of action and therapeutic outcomes have been published, reflecting the current dynamics in this field. With the approval of the antisense oligonucleotide nusinersen, the vector-based therapy with onasemnogene abeparvovec and the small molecule splicing modifier risdiplam, three gene therapeutic drugs are available for the treatment of SMA showing improvement in motor function. But in the pivotal studies several relevant parameters have not been addressed. There is a data gap for the treatment outcome of adult individuals with SMA as well as for several other relevant outcome parameters like bulbary or ventilatory function. With increasing treatment options, additional individual therapies have become necessary. Studies on combination therapies or switch of therapy, e.g. the sequential administration of onasemnogen abeparvovec and nusinersen, are necessary. An overview of current developments in the field of therapeutic options for adult SMA is presented. Important characteristics of each therapeutic option will be discussed so that the reader can comprehend underlying pathophysiological mechanisms as well as advantages and disadvantages of each therapy. The focus is on gene-based treatment options, but options beyond this are also addressed.

Nusinersen in Adults with 5q Spinal Muscular Atrophy: a Systematic Review and Meta-analysis

Evidence for nusinersen administration in adult 5q spinal muscular atrophy (5q-SMA) patients is scarce and based on real-world observational data. The present systematic review and meta-analysis aimed to explore the efficacy and safety of nusinersen in patients older than 12 years of age with 5q-SMA. We searched MEDLINE, EMBASE, the Cochrane Library, and grey literature through April 2021. Cross-sectional studies, case reports, review articles, and studies with follow-up less than 6 months were excluded. We included 12 records (seven case-series, five cohorts) representing 11 population cohorts and enrolling 428 SMA patients. We observed statistically significant improvements on motor function Hammersmith Functional Motor Scale Expanded (HFMSE) and Revised Upper Limb Module (RULM) scores at the longest follow-up assessments [SMD = 0.17(95% CI 0.01-0.33), SMD = 0.22(95% CI 0.06-0.38), respectively]. HFMSE and RULM significant improvements were also detected at the subgroup analysis during 10 and 14 months. HFMSE and RULM amelioration occurred earlier in patients with SMA type 3 or 4 during short-term analysis (≤ 6 months). 6-min walk tests (6MWT) and pulmonary function tests did not change. Minimal clinically important differences in HFMSE and RULM were observed in 43.3% (95% CI 34.5-52.3) and 38.9% (95% CI 27.7-50.7), respectively. Severe adverse events were reported in 2% (95% CI 0-5.8). Treatment withdrawal rate was 3% (95% CI 0.5-6.6). Despite the low quality of evidence and the unmet need for randomized data to establish the safety and efficacy of nusinersen in adults, our meta-analysis confirms that nusinersen is a valuable treatment option for older patients with longer-disease duration.Trial registration: PROSPERO database CRD42020223109.

Validity and reliability of the German multidimensional fatigue inventory in spinal muscular atrophy

Objective

Fatigue is a common and burdensome symptom of spinal muscular atrophy. Given its complex interactions, different dimensions of fatigue need to be investigated. The Multidimensional Fatigue Inventory is a widely used instrument that captures five distinct dimensions. The aim of this study was to investigate the validity and reliability of the German Multidimensional Fatigue Inventory in spinal muscular atrophy and to evaluate the presence of clinically relevant fatigue.

Methods

One hundred and forty adult spinal muscular atrophy patients completed the Multidimensional Fatigue Inventory in a nationwide, multicenter, cross‐sectional study. Structural validity was explored using principal component analysis. Cronbach’s α was calculated to evaluate internal consistency. Convergent validity was assessed by correlation with a Visual Analog Scale for fatigue and the EuroQol‐Five Dimension‐Five Level Scale as a measure of quality of life.

Results

The original five‐component model of the questionnaire constituted an acceptable fit. Internal consistency and convergent validity of general, physical, mental fatigue, and reduced activity were good. We observed a floor effect for mental fatigue. While physical fatigue exceeded the cutoff for clinically relevant fatigue, all dimensions but reduced motivation correlated negatively with quality of life. Age, depression, and ≥4 copies of the survival motor neuron 2 gene were associated with higher general/physical fatigue; unemployed participants reported higher scores for reduced activity/motivation.

Interpretation

The Multidimensional Fatigue Inventory is a valid and reliable instrument to assess different dimensions of fatigue in spinal muscular atrophy. Fatigue is a relevant problem in spinal muscular atrophy and its assessment should be incorporated into standard care.

Natural history of 10-meter walk/run test performance in spinal muscular atrophy: A longitudinal analysis

As trials and treatments for spinal muscular atrophy (SMA) rapidly evolve, understanding the natural history and potential utility of the 10-meter walk/run test (10MWRT) in ambulant individuals is critical. Study aims were to: 1) establish change over time and across age for 10MWRT time in an untreated natural history cohort of young, ambulatory participants with SMA and 2) identify relations between 10MWRT time and age, SMA type, SMN2 copy number and anthropometrics. Untreated individuals (n = 56) age 2 to 21 years who were enrolled in a long-term natural history study between 2005 and 2014 and met inclusion criteria were included. Linear mixed effects models were used to assess changes in 10MWRT time with age and associations with SMA type, SMN2 copy number, and body mass. SMA type 3b (versus 3a), SMN2 copy number 4 (versus 3) and lower body mass were associated with faster 10MWRT. 10MWRT performance improved between 3 and 8 years of age, was stable between 9 and 10, and gradually declined from 11 to 18. Findings provide the first longitudinal natural history report of 10MWRT time in young individuals with SMA and offer a critical foundation for interpreting childhood change in short distance walking speed with pharmacologic treatment.

Nusinersen treatment in adults with severe spinal muscular atrophy: A real-life retrospective observational cohort study

BACKGROUND AND OBJECTIVES

Spinal muscular atrophy (SMA) is a progressive neurodegenerative disease due to homozygous loss-of-function of the survival motor neuron gene SMN1 with absence of the functional SMN protein. Nusinersen, a costly intrathecally administered drug approved in 2017 in Europe, induces alternative splicing of the SMN2 gene, which then produces functional SMN protein, whose amount generally increases with the number of SMN2 gene copies.

METHODS

We retrospectively collected data from consecutive wheelchair-bound adults with SMA managed at a single center in 2018-2020. The following were collected at each injection, on days 1, 14, 28, 63, 183, and 303: 32-item Motor Function Measurement (MFM) total score and D2 and D3 subscores; the Canadian Occupational Performance Measure (COPM) performance and satisfaction scores; and lung function tests. The patients were divided into two groups based on whether their MFM total score was<or≥the mean (15.6%). Adverse events were recorded.

RESULTS

We identified 18 patients who received 4 to 8 Nusinersen injections. No significant improvements occurred over time in any of the MFM scores or lung function test results, which did not differ between groups. The COPM performance score improved significantly from day 0 to day 303 in the high-MFM group and the COPM satisfaction score in the overall population from D0 to D183. Half the patients achieved the minimal clinically important difference for both COPM scores.

DISCUSSION

The overall stability of conventional motor assessment in this population with advanced disabilities is encouraging to use more sensitive tools based on self-perception and autonomy in daily life activities, such as COPM. Our finding of a significant COPM performance score improvement from days 0 to 303 only in the patients with initial MFM-32 scores above the mean in the population suggests that the severity of the baseline disabilities may affect treatment efficacy.

CLASSIFICATION OF EVIDENCE LEVEL

IV, retrospective observational cohort study.

Ethical Perspectives on Treatment Options with Spinal Muscular Atrophy Patients

Since 2016, 3 innovative therapies for spinal muscular atrophy (SMA) have changed the face of the disease. Although these therapies often result in remarkable improvements in infants and children, benefits in adults are modest and treatment is not curative. Concerns have been raised about the enormous costs of these medications, the ultimate burden to taxpayers, and the costs to society of withholding treatments and sacrificing or disadvantaging some individuals. Physicians are best positioned to serve our patients by carefully considering the costs, benefits, implications for quality of life (QOL), and the interplay of these factors within the framework of core ethical principles that guide clinical care. ANN NEUROL 2022;91:305–316

Restoration of Nusinersen Levels Following Treatment Interruption in People With Spinal Muscular Atrophy: Simulations Based on a Population Pharmacokinetic Model

BACKGROUND

Nusinersen is approved for the treatment of spinal muscular atrophy. The most common approved dosing regimen is four intrathecal loading doses of nusinersen 12 mg; the first three are administered at 14-day intervals followed by a fourth dose 30 days later, and then 12-mg maintenance doses are administered every 4 months thereafter. Interruption of nusinersen treatment in the maintenance dosing phase might occur for a number of clinical reasons.

OBJECTIVE

The objective of this report is to describe dosing regimens that allow for the most rapid restoration of steady-state concentrations of nusinersen in the cerebrospinal fluid (CSF) following a treatment interruption during maintenance dosing.

METHODS

Population pharmacokinetic models using integrated pharmacokinetic data from ten nusinersen clinical trials that included a broad range of participants with spinal muscular atrophy treated with intrathecal nusinersen were used to investigate different durations of treatment interruptions during maintenance treatment. Potential dosing regimens for re-initiation of nusinersen were evaluated, with the goal of achieving the quickest restoration of steady-state nusinersen CSF concentrations without exceeding maximal CSF exposures observed during the initial loading period.

RESULTS

Our pharmacokinetic modeling indicates the following regimen will lead to optimal restoration of nusinersen CSF levels after treatment interruption: two doses of nusinersen should be administered at 14-day intervals following treatment interruptions of ≥ 8 to < 16 months since the last dose, and three doses of nusinersen at 14-day intervals for treatment interruptions of ≥ 16 to < 40 months since the last maintenance dose, with subsequent maintenance dosing every 4 months in both instances. After treatment interruptions of ≥ 40 months, the full loading regimen will rapidly restore nusinersen CSF levels.

CONCLUSIONS

Prolonged treatment interruptions lead to suboptimal CSF levels of nusinersen. The optimal regimen to restore nusinersen CSF levels depends on the interval since the last maintenance dose was administered.

Magnetic resonance reveals mitochondrial dysfunction and muscle remodelling in spinal muscular atrophy

Genetic therapy has changed the prognosis of hereditary proximal spinal muscular atrophy, although treatment efficacy has been variable. There is a clear need for deeper understanding of underlying causes of muscle weakness and exercise intolerance in patients with this disease to further optimize treatment strategies. Animal models suggest that in addition to motor neuron and associated musculature degeneration, intrinsic abnormalities of muscle itself including mitochondrial dysfunction contribute to the disease aetiology.

To test this hypothesis in patients, we conducted the first in vivo clinical investigation of muscle bioenergetics. We recruited 15 patients and 15 healthy age and gender-matched control subjects in this cross-sectional clinico-radiological study. MRI and ³¹P magnetic resonance spectroscopy, the modality of choice to interrogate muscle energetics and phenotypic fibre-type makeup, was performed of the proximal arm musculature in combination with fatiguing arm-cycling exercise and blood lactate testing. We derived bioenergetic parameter estimates including: blood lactate, intramuscular pH and inorganic phosphate accumulation during exercise, and muscle dynamic recovery constants. A linear correlation was used to test for associations between muscle morphological and bioenergetic parameters and clinico-functional measures of muscle weakness.

MRI showed significant atrophy of triceps but not biceps muscles in patients. Maximal voluntary contraction force normalized to muscle cross-sectional area for both arm muscles was 1.4-fold lower in patients than in controls, indicating altered intrinsic muscle properties other than atrophy contributed to muscle weakness in this cohort. In vivo³¹P magnetic resonance spectroscopy identified white-to-red remodelling of residual proximal arm musculature in patients on the basis of altered intramuscular inorganic phosphate accumulation during arm-cycling in red versus white and intermediate myofibres. Blood lactate rise during arm-cycling was blunted in patients and correlated with muscle weakness and phenotypic muscle makeup. Post-exercise metabolic recovery was slower in residual intramuscular white myofibres in patients demonstrating mitochondrial ATP synthetic dysfunction in this particular fibre type.

This study provides the first in vivo evidence in patients that degeneration of motor neurons and associated musculature causing atrophy and muscle weakness in 5q spinal muscular atrophy type 3 and 4 is aggravated by disproportionate depletion of myofibres that contract fastest and strongest. Our finding of decreased mitochondrial ATP synthetic function selectively in residual white myofibres provides both a possible clue to understanding the apparent vulnerability of this particular fibre type in 5q spinal muscular atrophy types 3 and 4 as well as a new biomarker and target for therapy.

Revised upper limb module in type II and III spinal muscular atrophy: 24-month changes

The aim of the study was to establish 24-month changes in a large cohort of type II and III spinal muscular atrophy (SMA) patients assessed with the Revised Upper Limb Module (RULM), a tool specifically developed to assess upper limb function in SMA. We included 107 patients (54 type II and 53 type III) with at least 24-months follow up. The overall RULM 24-month changes showed a mean decline of -0.79 points. The difference between baseline and 24 months was significant in type II but not in type III patients. There was also a difference among functional subgroups but not in relation to age. Most patients had 24-month mean changes within 2 points, with 23% decreasing more than 2 points and 7% improving by >2 points. Our results suggest an overall progressive decline in upper limb function over 24 months. The negative changes were most notable in type II, in non-ambulant type III and with a different pattern of progression, also in non-sitter type II. In contrast, ambulant type III showed relative stability within the 24-month follow up. These findings will help in the interpretation of the real world data collected following the availability of new therapeutic approaches.

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.

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 by subcutaneous intrathecal catheter for symptomatic spinal muscular atrophy patients with complex spine anatomy

INTRODUCTION/AIMS

Intrathecal administration of nusinersen is challenging in patients with spinal muscular atrophy (SMA) who have spine deformities or fusions. We prospectively studied the safety and efficacy of nusinersen administration via an indwelling subcutaneous intrathecal catheter (SIC) for SMA patients with advanced disease.

METHODS

Seventeen participants commenced nusinersen therapy between 2.7 and 31.5 years of age and received 9 to 12 doses via SIC. Safety was assessed in all participants. A separate efficacy analysis comprised 11 nonambulatory, treatment-naive SMA patients (18.1 ± 6.8 years) with three SMN2 copies and complex spine anatomy.

RESULTS

In the safety analysis, 14 treatment-related adverse events (AEs) occurred among 12 (71%) participants; all were related to the SIC and not nusinersen. Device-related AEs interfered with 2.5% of nusinersen doses. Four SICs (24%) required surgical revision due to mechanical malfunction with or without cerebrospinal fluid leak (n = 2), and one (6%) was removed due to Staphylococcus epidermidis meningitis. In the efficacy analysis, mean performance on the nine-hole peg test improved in dominant (15.9%, P = 0.012) and nondominant (19.0%, P = 0.008) hands and grip strength increased by 44.9% (P = 0.031). We observed no significant changes in motor scales, muscle force, pulmonary function, or SMA biomarkers. All participants in the efficacy cohort reported one or more subjective improvement(s) in endurance, purposeful hand use, arm strength, head control, and/or speech.

DISCUSSION

For SMA patients with complex spine anatomy, the SIC allows for reliable outpatient administration of nusinersen that results in meaningful improvements in upper limb function, but introduces risks of technical malfunction and iatrogenic infection.

Assessment of Bulbar Function in Adult Patients with 5q-SMA Type 2 and 3 under Treatment with Nusinersen

The antisense oligonucleotide nusinersen has been shown to improve trunk and limb motor function in patients with spinal muscular atrophy (SMA). Bulbar dysfunction, which is regularly present in SMA, is not captured by standard motor scores, and validated measurement instruments to assess it have not yet been established. Data on whether and how bulbar function changes under gene-based therapies in adult SMA patients are also unavailable. Here, we present data on the course of bulbar dysfunction assessed prospectively before nusinersen treatment initiation and 6 and 14 months later in 23 adult SMA patients using the Sydney Swallow Questionnaire (SSQ) and the bulbar subscore of the Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R). While no improvement in bulbar scores was observed under treatment with nusinersen, the absence of a decline still implies a therapeutic effect of nusinersen on bulbar dysfunction. The results of this study aim to contribute to a standardized assessment of bulbar function in adult SMA patients, which may show therapeutic effects of gene-based therapies that are not evident from standard motor scores.

Nusinersen Treatment in Adults With Spinal Muscular Atrophy

Objective

To determine changes in motor and respiratory function after treatment with nusinersen in adults with spinal muscular atrophy (SMA) during the first two years of commercial availability in the USA.

Methods

Data were collected prospectively on adult (age >17 years at treatment initiation) SMA participants in the Pediatric Neuromuscular Clinical Research (PNCR) Network. Baseline assessments of SMA outcomes including the Expanded Hammersmith Functional Rating Scale (HFMSE), Revised Upper Limb Module (RULM), and 6-Minute Walk Test (6MWT) occurred <5 months before treatment, and post-treatment assessments were made up to 24 months after nusinersen initation. Patient-reported experiences, safety laboratory tests and adverse events were monitored. The mean annual rate of change over time was determined for outcome measures using linear mixed effects models.

Results

Forty-two adult SMA participants (mean age: 34 years, range 17-66) receiving nusinersen for a mean of 12.5 months (range 3-24 months) were assessed. Several motor and respiratory measures showed improvement distinct from the progressive decline typically seen in untreated adults. Participants also reported qualitative improvements including muscle strength, stamina, breathing and bulbar related outcomes. All participants tolerated nusinersen with normal surveillance labs and no significant adverse events.

Conclusions

Trends of improvement emerged in functional motor, patient-reported, and respiratory measures, suggesting nusinersen may be efficacious in adults with SMA. Larger well-controlled studies and additional outcome measures are needed to firmly establish the efficacy of nusinersen in adults with SMA.

Classification of Evidence

This study provides Class IV evidence regarding nusinersen tolerability and efficacy based on reported side effects and pulmonary and physical therapy assessments in an adult SMA cohort.

Persistent neuromuscular junction transmission defects in adults with spinal muscular atrophy treated with nusinersen

Objective

Spinal muscular atrophy (SMA) is a motor neuron disease caused by low levels of survival motor neuron (SMN) protein. Prior work in models and patients has demonstrated electrophysiological and morphological defects at the neuromuscular junction (NMJ). Therapeutic development has resulted in clinically available therapies to increase SMN protein levels in patients and improve muscle function. Here we aimed to investigate the effect of SMN restoration (via nusinersen) on NMJ transmission in adults with SMA.

Methods

Participants undergoing nusinersen treatment underwent 3 Hz repetitive nerve stimulation (RNS) of the spinal accessory nerve to assess compound muscle action potential amplitude decrement. Maximum voluntary isometric contraction (MVICT), Revised Upper Limb Module (RULM), and 6 min walk test (6MWT) were assessed for correlations with decrement.

Results

Data from 13 ambulatory (7 men/6 women, mean age 40±11 years) and 11 non-ambulatory (3 men/8 women, mean age 38±12 years) participants were analysed. Cross-sectional analyses of RNS decrement were similar at 14 months of nusinersen (−14.2%±11.5%, n=17) vs baseline (−11.9%±8.3%, n=15) (unpaired t-test, p=0.5202). Longitudinal comparison of decrement in eight participants showed no change at 14 months (−13.9%±6.7%) vs baseline (−16.9%±13.4%) (paired t-test, p=0.5863). Decrement showed strong correlations with measures of MVICT, RULM and 6MWT but not age or disease duration.

Conclusion

Adults with SMA had significant NMJ transmission defects that were not corrected with 14 months of nusinersen treatment. NMJ defects were negatively associated with physical function, and thus may represent a promising target for additive or combinatorial treatments.

Cerebrospinal Fluid and Clinical Profiles in Adult Type 2-3 Spinal Muscular Atrophy Patients Treated with Nusinersen: An 18-Month Single-Centre Experience

BACKGROUND AND OBJECTIVES

Nusinersen was approved as the first disease-modifying therapy in spinal muscular atrophy (SMA). Our aim was to analyse therapy-related changes in cerebrospinal fluid (CSF) and serum parameters of adult type 2-3 SMA and to correlate biochemical data with motor functional status.

METHODS

Nine adult SMA type 2-3 patients and ten control subjects without neurodegenerative diseases were included in our single-centre study. Cross-sectional analysis of CSF routine parameters, CSF neurofilament light chain, CSF Tau, CSF phospho-Tau and serum creatinine was performed between SMA patients at baseline (T0) and control subjects. The above-mentioned fluid parameters were longitudinally analysed in the SMA cohort after loading dose (T1) and after four maintenance doses (T2, T3, T4, T5). Hammersmith Functional Motor Scale Expanded (HFMSE), Revised Upper Limb Module (RULM) and the 6-minute walking test (6MWT) were used to evaluate motor outcomes.

RESULTS

Improvements in HFMSE, RULM and 6MWT were observed only after the loading dose of nusinersen. No significant differences in routine CSF parameters and CSF markers of neurodegeneration were found between SMA patients and control subjects. Serum creatinine levels were significantly lower in SMA patients than in control subjects. CSF/serum albumin ratio (Qalb) significantly increased from T0 to each time point, without any further increase after the maintenance doses. Persistent systemic oligoclonal bands (OCBs) were found in five patients from baseline. Three more patients developed persistent systemic OCBs from T1; one patient showed intrathecal OCBSs from baseline to T5. Markers of neurodegeneration did not change during the follow-up and did not correlate with motor scores at baseline and at each timepoint. Serum creatinine levels significantly correlated with HFMSE and RULM at each time point.

CONCLUSIONS

The increase of the Qalb values and the development of systemic OCBs in some SMA patients could be due to repeated lumbar puncture and to the immunogenic effect of nusinersen. On the other hand, the presence of OCBs in serum and/or CSF at baseline should be further investigated. Furthermore, biomarkers of neurodegeneration did not play a prognostic role in our cohort of adult SMA patients.

Survival motor neuron deficiency slows myoblast fusion through reduced myomaker and myomixer expression

BACKGROUND

Spinal muscular atrophy is an inherited neurodegenerative disease caused by insufficient levels of the survival motor neuron (SMN) protein. Recently approved treatments aimed at increasing SMN protein levels have dramatically improved patient survival and have altered the disease landscape. While restoring SMN levels slows motor neuron loss, many patients continue to have smaller muscles and do not achieve normal motor milestones. While timing of treatment is important, it remains unclear why SMN restoration is insufficient to fully restore muscle size and function. We and others have shown that SMN-deficient muscle precursor cells fail to efficiently fuse into myotubes. However, the role of SMN in myoblast fusion is not known.

METHODS

In this study, we show that SMN-deficient myoblasts readily fuse with wild-type myoblasts, demonstrating fusion competency. Conditioned media from wild type differentiating myoblasts do not rescue the fusion deficit of SMN-deficient cells, suggesting that compromised fusion may primarily be a result of altered membrane dynamics at the cell surface. Transcriptome profiling of skeletal muscle from SMN-deficient mice revealed altered expression of cell surface fusion molecules. Finally, using cell and mouse models, we investigate if myoblast fusion can be rescued in SMN-deficient myoblast and improve the muscle pathology in SMA mice.

RESULTS

We found reduced expression of the muscle fusion proteins myomaker (P = 0.0060) and myomixer (P = 0.0051) in the muscle of SMA mice. Suppressing SMN expression in C2C12 myoblast cells reduces expression of myomaker (35% reduction; P < 0.0001) and myomixer, also known as myomerger and minion, (30% reduction; P < 0.0001) and restoring SMN levels only partially restores myomaker and myomixer expression. Ectopic expression of myomixer improves myofibre number (55% increase; P = 0.0006) and motor function (35% decrease in righting time; P = 0.0089) in SMA model mice and enhances motor function (82% decrease in righting time; P < 0.0001) and extends survival (28% increase; P < 0.01) when administered in combination with an antisense oligonucleotide that increases SMN protein levels.

CONCLUSIONS

Here, we identified reduced expression of muscle fusion proteins as a key factor in the fusion deficits of SMN-deficient myoblasts. This discovery provides a novel target to improve SMA muscle pathology and motor function, which in combination with SMN increasing therapy could enhance clinical outcomes for SMA patients.

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

Background:

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

Objective:

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

Methods:

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

Results:

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

Conclusions:

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

Spinal muscular atrophy: From approved therapies to future therapeutic targets for personalized medicine

Spinal muscular atrophy (SMA) is a devastating childhood motor neuron disease that, in the most severe cases and when left untreated, leads to death within the first two years of life. Recent therapeutic advances have given hope to families and patients by compensating for the deficiency in survival motor neuron (SMN) protein via gene therapy or other genetic manipulation. However, it is now apparent that none of these therapies will cure SMA alone. In this review, we discuss the three currently licensed therapies for SMA, briefly highlighting their respective advantages and disadvantages, before considering alternative approaches to increasing SMN protein levels. We then explore recent preclinical research that is identifying and targeting dysregulated pathways secondary to, or independent of, SMN deficiency that may provide adjunctive opportunities for SMA. These additional therapies are likely to be key for the development of treatments that are effective across the lifespan of SMA patients.

Three licensed SMA therapies increase SMN levels, but are not a cure

Other strategies to increase SMN levels are still under development

Alternatives target the correction of dysregulated pathways following SMN loss

Ultimately, a range of therapies may allow for a tailored treatment

Motor unit number estimation in adult patients with spinal muscular atrophy treated with nusinersen

BACKGROUND AND PURPOSE

The aim was to assess the organization and short-term changes of motor units in adult patients with spinal muscular atrophy (SMA) treated with nusinersen.

METHODS

In this single-centre cross-sectional and longitudinal study 15 adult patients with SMA type 3 were assessed and compared to 15 age-matched healthy controls and nine patients with amyotrophic lateral sclerosis. Moreover, 10 patients with SMA were followed up after 4-8 months. All patients were investigated clinically and by the motor unit number estimation method MScanFit of the abductor pollicis brevis muscle.

RESULTS

The number of motor units (p < 0.001) was significantly lower in patients with SMA compared to healthy controls at study entry. Mean unit amplitude, median amplitude and largest unit (p < 0.001) were significantly increased in patients with SMA. Patients with amyotrophic lateral sclerosis showed a significant reduction of compound muscle action potential (p = 0.005) and number of motor units (p = 0.03) compared to patients with SMA, accompanied by a larger median amplitude (p = 0.03). A prospective analysis identified patients with the ability to walk to improve the number of motor units (p = 0.046) accompanied by a decreased median amplitude (p = 0.03). Electrophysiological measures showed a moderate to strong correlation with clinical scores.

CONCLUSION

Patients with SMA show loss of motor units in distal muscles. MScanFit variables indicate that compound muscle action potential amplitudes are maintained by collateral sprouting. Prospective analyses suggest that milder affected adult patients with SMA preferentially benefit from nusinersen treatment through recovery of smaller motor units. Correlations with clinical scores underline the potential of MScanFit as a surrogate marker.

Motor unit number index: A potential electrophysiological biomarker for pediatric spinal muscular atrophy

INTRODUCTION/AIMS

In adult spinal muscular atrophy (SMA), the motor unit number index (MUNIX) has been shown to be an useful electrophysiological biomarker. This study evaluated the feasibility and the clinical relevance of using the MUNIX technique for patients with pediatric SMA (Ped-SMA) and correlated MUNIX results with clinical scores.

METHODS

Fourteen patients with type II Ped-SMA (11 females; median age 11 y [interquartile range (IQR), 4.8-17 y]) and 14 controls (nine females; median age 10.75 y [IQR, 6.5-13.4 y]) were enrolled and matched by sex, age, height, weight, and body mass index. Clinical examination included manual muscle testing, dynamometry (grasp and pinch), and motor function measure (MFM). The MUNIX technique was evaluated in the abductor digiti minimi (ADM) and abductor pollicis brevis (APB) on two sides when possible.

RESULTS

In the patients with Ped-SMA, the MUNIX and compound muscle action potential (CMAP) amplitudes were significantly decreased and the motor size unit index (MUSIX) was significantly increased in the ADM and APB when compared to controls. The intraclass correlation coefficient was good for the intrarater variability of the CMAP amplitude, MUNIX, and MUSIX in the ADM (0.95, 0.83, and 0.89, respectively) and the APB (0.98, 0.96, and 0.94, respectively). The total CMAP amplitude correlated with the grasp and pinch scores (P < .05), and the MUNIX measurements correlated with the MFM scores.

DISCUSSION

The MUNIX technique, which accurately estimated lower motor neuron loss and the number of remaining functional motor units, was shown to be a useful electrophysiological biomarker for disease progression and a potential biomarker for treatment response.

Hypoventilation syndrome in neuromuscular disorders

PURPOSE OF REVIEW

Hypoventilation syndrome in neuromuscular disorders (NMDs) is primarily due to respiratory muscle weakness and results in increased morbidity and mortality. This article highlights current aspects of neuromuscular hypoventilation syndrome, including pathophysiology, clinical symptoms, assessment, respiratory involvement in various NMD, and causal and symptomatic treatments with an emphasis on recent research and advances.

RECENT FINDINGS AND SUMMARY

New therapeutic agents have been developed within the last years, proving a positive effect on respiratory system. Symptomatic therapies, including mechanical ventilation and cough assistance approaches, are important in NMD and respiratory muscle training may have benefit in strengthening respiratory muscles and should be offered patients with respiratory muscle weakness the same way as physiotherapy. Correct respiratory assessments and their correct interpretation are hallmarks for early diagnosis of hypoventilation syndrome and treatment.

The blood biomarkers puzzle - A review of protein biomarkers in neurodegenerative diseases

Neurodegenerative diseases are heterogeneous in their cause and clinical presentation making clinical assessment and disease monitoring challenging. Because of this, there is an urgent need for objective tools such as fluid biomarkers able to quantitate different aspects of the disease. In the last decade, technological improvements and awareness of the importance of biorepositories led to the discovery of an evolving number of fluid biomarkers covering the main characteristics of neurodegenerative diseases such as neurodegeneration, protein aggregates and inflammation. The ability to quantitate each aspect of the disease at a high definition enables a more precise stratification of the patients at inclusion in clinical trials, hence reducing the noise that may hamper the detection of therapeutical efficacy and allowing for smaller but likewise powered studies, which particularly improves the ability to start clinical trials for rare neurological diseases. Moreover, the use of fluid biomarkers has the potential to support a targeted therapeutical intervention, as it is now emerging for the treatment of amyloid-beta deposition in patients suffering from Alzheimer's disease. Here we review the knowledge that evolved from the measurement of fluid biomarker proteins in neurodegenerative conditions.

Spinal Muscular Atrophy Treatments, Newborn Screening, and the Creation of a Neurogenetics Urgency

Spinal muscular atrophy (SMA) is a progressive neuromuscular disorder characterized by loss of motor neurons leading to muscle weakness and atrophy. The United States' Food and Drug Administration's (FDA) approval of nusinersen, onasemnogene abeparvovec, and risdiplam for SMA has challenged existing treatment paradigms with multiple treatment options, a new natural history of the disease, and an emerging understanding of the importance of early and pre-symptomatic treatment. The profound impact of early, pre-symptomatic treatment has led to the creation of a neurogenetics urgency for newly identified patients with SMA, a novel problem for neurologists more accustomed to a more methodical approach to diagnosis and care. Implementation of newborn screening programs has helped facilitate early diagnosis and treatment, but challenges remain in overcoming administrative and procedural hurdles that can lead to treatment delays. Herein I discuss 2 cases that highlight the importance of early treatment, as well as gaps in our understanding of the progression of SMA in pre-symptomatic infants.

Nusinersen in pediatric and adult patients with type III spinal muscular atrophy

Objective

We report longitudinal data from 144 type III SMA pediatric and adult patients treated with nusinersen as part of an international effort.

Methods

Patients were assessed using Hammersmith Functional Motor Scale Expanded (HFMSE), Revised Upper Limb Module (RULM), and 6‐Minute Walk Test (6MWT) with a mean follow‐up of 1.83 years after nusinersen treatment.

Results

Over 75% of the 144 patients had a 12‐month follow‐up. There was an increase in the mean scores from baseline to 12 months on both HFMSE (1.18 points, p = 0.004) and RULM scores (0.58 points, p = 0.014) but not on the 6MWT (mean difference = 6.65 m, p = 0.33).

When the 12‐month HFMSE changes in the treated cohort were compared to an external cohort of untreated patients, in all untreated patients older than 7 years, the mean changes were always negative, while always positive in the treated ones. To reduce a selection bias, we also used a multivariable analysis. On the HFMSE scale, age, gender, baseline value, and functional status contributed significantly to the changes, while the number of SMN2 copies did not contribute. The effect of these variables was less obvious on the RULM and 6MWT.

Interpretation

Our results expand the available data on the effect of Nusinersen on type III patients, so far mostly limited to data from adult type III patients.

Treatment expectations and perception of therapy in adult patients with spinal muscular atrophy receiving nusinersen

BACKGROUND AND PURPOSE

This was an investigation of treatment expectations and of the perception of therapy in adult patients with 5q-associated spinal muscular atrophy (5q-SMA) receiving nusinersen.

METHODS

A prospective, non-interventional observational study of nusinersen treatment in adult 5q-SMA patients was conducted at nine SMA centers in Germany. The functional status, treatment expectations and perceived outcomes were assessed using the Amyotrophic Lateral Sclerosis Functional Rating Scale-extended (ALS-FRS-ex), the Measure Yourself Medical Outcome Profile (MYMOP2), the Treatment Satisfaction Questionnaire for Medication (TSQM-9) and the Net Promoter Score (NPS).

RESULTS

In all, 151 patients were included with a median age of 36 years (15-69 years). SMA type 3 (n = 90, 59.6%) prevailed, followed by type 2 (33.8%) and type 1 (6.6%). In SMA types 1-3, median ALS-FRS-ex scores were 25, 33 and 46 (of 60 scale points), respectively. MYMOP2 identified distinct treatment expectations: head verticalization (n = 13), bulbar function (n = 16), arm function (n = 65), respiration (n = 15), trunk function (n = 34), leg function (n = 76) and generalized symptoms (n = 77). Median symptom severity decreased during nusinersen treatment (median observational period 6.1 months, 0.5-16 months) from 3.7 to 3.3 MYMOP2 score points (p < 0.001). The convenience of drug administration was critical (49.7 of 100 TSQM-9 points, SD 22); however, the overall treatment satisfaction was high (74.3, SD 18) and the recommendation rating very positive (NPS +66).

CONCLUSIONS

Nusinersen was administered across a broad range of ages, disease durations and motor function deficits. Treatment expectations were highly differentiated and related to SMA type and functional status. Patient-reported outcomes demonstrated a positive perception of nusinersen therapy in adult patients with 5q-SMA.

Safety, Tolerability, and Effect of Nusinersen Treatment in Ambulatory Adults With 5q-SMA

Objective: To determine the safety and tolerability of nusinersen treatment in ambulatory adults with spinal muscular atrophy (SMA) and investigate the treatment effect on muscle strength, physical function, and motor unit physiology.

Methods: Individuals aged 18 years or older with genetically confirmed 5q SMA, three or more copies of the SMN2 gene, and the ability to ambulate 30 feet were enrolled. Safety outcomes included the number of adverse events and serious adverse events, clinically significant vital sign or laboratory parameter abnormalities. Outcome assessments occurred at baseline (prior to the first dose of nusinersen) and then 2, 6, 10, and 14 months post-treatment.

Results: Six women, seven men (mean age: 37 ± 11, range: 18–59 years) were included for analyses. The most common side effects were headache and back pain, but overall procedures and treatments were well-tolerated. No serious adverse events were reported. Maximal Voluntary Isometric Muscle Contraction Testing (MVICT) and 6-min walk test (6MWT) both showed overall stability with significant increases at 2, 6, and 10 months for the 6MWT. More consistent significant treatment effects were noted on the Hammersmith Functional Motor Scale Expanded, SMA-Functional Rating Scale, and forced vital capacity. Treatment resulted in progressively increased ulnar compound muscle action potential and average single motor unit potential amplitudes, but motor unit number estimation remained stable.

Conclusions: Nusinersen treatment is safe and well-tolerated in ambulatory adults with SMA. Treatment resulted in improved motor function and electrophysiological findings suggest that this improvement may be occurring via improved motor unit reinnervation capacity.

Nusinersen treatment in adult patients with spinal muscular atrophy: a safety analysis of laboratory parameters

Background

Nusinersen is an intrathecally administered antisense oligonucleotide (ASO) that improves motor function in patients with spinal muscular atrophy (SMA). In addition to efficacy, the safety of a therapy is the decisive factor for the success of the treatment. For some ASOs, various organ toxicities have been described, such as thrombocytopenia, renal and liver impairment, or coagulation abnormalities. However, systematic data on laboratory parameters under treatment with nusinersen are mainly available from studies in infants and children. Therefore, our aim was to assess the safety of nusinersen therapy in adult SMA patients.

Methods

Laboratory data from 404 nusinersen injections performed in 50 adult patients with SMA type 2 and type 3 were retrospectively analyzed.

Results

The total observation period was 76.9 patient-years, and patients received up to 12 injections. Our data provides no new safety concerns. In cerebrospinal fluid (CSF), the mean white blood cell count and lactate remained stable over time. Total CSF protein increased by 2.9 mg/dL. No change in mean platelet count was observed under therapy. Only one patient showed sporadic mild thrombocytopenia. Coagulation parameters and inflammatory markers were stable. The mean creatinine level decreased by 0.09 mg/dL. Analysis of mean liver enzyme levels revealed no relevant changes during treatment.

Conclusion

Our data demonstrate a favorable safety profile of nusinersen therapy in adult SMA patients under longer-term “real-world” conditions. In particular, we found no evidence of clinically relevant platelet declines, coagulopathies, or renal or hepatic organ toxicities, which are common concerns with the use of ASOs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10569-8.

Safety, Tolerability, and Effect of Nusinersen in Non-ambulatory Adults With Spinal Muscular Atrophy

Objective: Investigation of the safety, tolerability, and treatment effect of nusinersen treatment in non-ambulatory adults with spinal muscular atrophy (SMA).

Methods: Non-ambulatory individuals, aged 18 years or older with genetically confirmed 5q SMA were enrolled. In participants with spinal fusion, fluoroscopy guided cervical C1–C2 lateral approach was used. Outcomes at 2, 6, 10, and 14 months post-treatment were compared with baseline assessment. Forced vital capacity (FVC) was the primary outcome, and RULM, HFMSE, the modified SMA-FRS, and ulnar nerve electrophysiology [compound muscle action potential (CMAP), single motor unit size, and motor unit number] were secondary. Adverse and serious adverse events and clinically significant vital sign or lab abnormalities were recorded.

Results: Results from 12 women and 7 men (mean age: 39.7 ± 13.9, range: 21–64 years) were analyzed. No clinically significant changes of vital signs or laboratory parameters were observed. Five participants were hospitalized for pneumonia. Other adverse events included headache, back pain, cervical injection site pain, and upper respiratory and urinary tract infections. High baseline protein/creatinine ratio without significant change on treatment noted in 4 participants. FVC was feasible in all participants. HFMSE and RULM were not feasible in the majority of participants. FVC and functional outcomes were stable without improvement. CMAP and single motor unit potential sizes showed enlargement while motor unit numbers were stable.

Conclusions: Nusinersen, including C1/C2 delivery, was safe overall and well-tolerated. Several outcome measures were limited by floor effect. Overall, treatment resulted in stability of motor outcomes, but motor unit and CMAP size were increased.

Age related treatment effect in type II Spinal Muscular Atrophy pediatric patients treated with nusinersen

Previous natural history studies suggest that type II SMA patients remain stable over one year but show some progression over two years. Since nusinersen approval, there has been increasing attention to identify more specific age-related changes. The aim of the study was to establish 12-month changes in a cohort of pediatric type II SMA treated with nusinersen and to establish possible patterns of treatment effect in relation to different variables such as age, baseline value and SMN2 copy number. The Hammersmith Functional Motor Scale Expanded and the Revised Upper Limb Module were performed at T0 and 12 months after treatment (T12). Data in treated patients were compared to available data in untreated patients collected by the same evaluators.Seventy-seven patients of age between 2.64 and 17.88 years (mean:7.47, SD:3.79) were included. On t-test there was an improvement, with increased mean scores between T0 and T12 on both scales (p < 0.001). Using multivariate linear regression analysis, age and baseline scores were predictive of changes on both scales (p < 0.05) while SMN2 copy number was not. Differences were also found between study cohort and untreated data on both scales (p < 0.001). At 12 months, an increase in scores was observed in all the age subgroups at variance with natural history data. Our real-world data confirm the treatment effect of nusinersen in pediatric type II SMA patients and that the data interpretation should take into account different variables. These data confirm and expand the ones already reported in the Cherish study.

Reldesemtiv in Patients with Spinal Muscular Atrophy: a Phase 2 Hypothesis-Generating Study

This phase 2, double-blind, placebo-controlled, hypothesis-generating study evaluated the effects of oral reldesemtiv, a fast skeletal muscle troponin activator, in patients with spinal muscular atrophy (SMA). Patients ≥ 12 years of age with type II, III, or IV SMA were randomized into 2 sequential, ascending reldesemtiv dosing cohorts (cohort 1: 150 mg bid or placebo [2:1]; cohort 2: 450 mg bid or placebo [2:1]). The primary objective was to determine potential pharmacodynamic effects of reldesemtiv on 8 outcome measures in SMA, including 6-minute walk distance (6MWD) and maximum expiratory pressure (MEP). Changes from baseline to weeks 4 and 8 were determined. Pharmacokinetics and safety were also evaluated. Patients were randomized to reldesemtiv 150 mg, 450 mg, or placebo (24, 20, and 26, respectively). The change from baseline in 6MWD was greater for reldesemtiv 450 mg than for placebo at weeks 4 and 8 (least squares [LS] mean difference, 35.6 m [p = 0.0037] and 24.9 m [p = 0.058], respectively). Changes from baseline in MEP at week 8 on reldesemtiv 150 and 450 mg were significantly greater than those on placebo (LS mean differences, 11.7 [p = 0.038] and 13.2 cm H2O [p = 0.03], respectively). For 6MWD and MEP, significant changes from placebo were seen in the highest reldesemtiv peak plasma concentration quartile (Cmax > 3.29 μg/mL; LS mean differences, 43.3 m [p = 0.010] and 28.8 cm H2O [p = 0.0002], respectively). Both dose levels of reldesemtiv were well tolerated. Results suggest reldesemtiv may offer clinical benefit and support evaluation in larger SMA patient populations.

Overview of gene therapy in spinal muscular atrophy and Duchenne muscular dystrophy

Both 5q-linked spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD) are fatal monogenic neuromuscular disorders caused by loss-of-function mutations. SMA is an autosomal recessive disorder affecting motor neurons that is typically caused by homozygous whole-gene deletions of SMN1. DMD is an X-linked recessive muscle disease most often due to exon deletions, but also duplications and smaller sized variants within the DMD gene. Gene replacement therapy offers the opportunity to correct the underlying genetic defect by the introduction of a functional gene. We review the transformative work from clinical trials to United States Food and Drug Administration approval of onasemnogene abeparvovec-xioi in SMA and its application in clinical practice and the early results of microdystrophin delivery in DMD. We also review the introduction of antisense oligonucleotides to alter pre-messenger RNA splicing to promote exon inclusion (as in nusinersen in SMA) or exclusion (as in eteplirsen in DMD) into neuromuscular therapeutics. There are multiple promising novel genetically mediated therapies on the horizon, which in aggregate point towards a hopeful future for individuals with SMA and DMD.

Serum creatine kinase and creatinine in adult spinal muscular atrophy under nusinersen treatment

OBJECTIVE

To determine whether serum creatine kinase activity (CK) and serum creatinine concentration (Crn) are prognostic and predictive biomarkers for disease severity, disease progression, and nusinersen treatment effects in adult patients with 5q-associated spinal muscular atrophy (SMA).

METHODS

Within this retrospective, multicenter observational study in 206 adult patients with SMA, we determined clinical subtypes (SMA types, ambulatory ability) and repeatedly measured CK and Crn and examined disease severity scores (Hammersmith Functional Motor Scale Expanded, Revised Upper Limb Module, and revised Amyotrophic Lateral Sclerosis Functional Rating Scale). Patients were followed under nusinersen treatment for 18 months.

RESULTS

CK and Crn differed between clinical subtypes and correlated strongly with disease severity scores (e.g., for Hammersmith Functional Motor Scale Expanded: (CK) ρ = 0.786/ (Crn) ρ = 0.558). During the 18 months of nusinersen treatment, CK decreased (∆CK = -17.56%, p < 0.0001), whereas Crn slightly increased (∆Crn = +4.75%, p < 0.05).

INTERPRETATION

Serum creatine kinase activity and serum creatinine concentration reflect disease severity of spinal muscular atrophy and are promising biomarkers to assess patients with spinal muscular atrophy during disease course and to predict treatment response. The decrease of creatine kinase activity, combined with the tendency of creatinine concentration to increase during nusinersen treatment, suggests reduced muscle mass wasting with improved muscle energy metabolism.

Laboratory monitoring of nusinersen safety

INTRODUCTION

This retrospective study reports our tertiary care center's experience with intrathecal nusinersen administration in children and adults with spinal muscular atrophy (SMA).

METHODS

We reviewed safety monitoring laboratory results and need for procedural sedation and fluoroscopy-guidance in all SMA patients receiving nusinersen between February 2017 and March 2020.

RESULTS

Fifty-eight patients ages 1 mo- 56 y received 494 nusinersen doses. There were 166 laboratory abnormalities in 45 patients. Most were either mild (145 [87.3%]) or were transient proteinuria (18 [10.8%]). None altered nusinersen treatment. Twenty-eight patients required either general anesthesia (75 doses) or anxiolysis with oral midazolam (133 doses, including 6 patients [23 doses] with SMA type I). Eight patients with complicated spines (45 doses) required fluoroscopic guidance. One treatment-related serious adverse event (emesis leading to intubation) occurred during general anesthesia. Two children had asymptomatic increased intracranial pressure. No patients discontinued treatment due to adverse events.

DISCUSSION

Intrathecal nusinersen is generally safe and well-tolerated, including in patients requiring oral anxiolysis, general sedation, and fluoroscopic guidance. Frequent serial laboratory monitoring did not identify any persistent significantly abnormal findings or alter treatment.

Is cerebrospinal fluid amyloid-β42 a promising biomarker of response to nusinersen in adult spinal muscular atrophy patients?

Introduction

Nusinersen was approved as the first treatment for all types of spinal muscular atrophy (SMA), including adults with SMA types 2 and 3. Robust biomarkers of treatment response in SMA adults are lacking. Our aim was to examine cerebrospinal fluid (CSF) amyloid‐β40 (Aβ40) and amyloid‐β42 (Aβ42) peptides as biomarkers of treatment response.

Methods

Eight patients with SMA types 2 and 3 were recruited consecutively in a single‐center study. CSF was sampled at baseline, after a loading dose, and after three maintenance doses. Levels of Aβ42 and Aβ40 were evaluated for each CSF sampling. Wilcoxon matched‐pairs signed‐rank test was used to detect longitudinal changes.

Results

CSF levels of Aβ42 increased from baseline to day 420 (95% confidence interval, P = .018), with a significant increase at days 180 and 420 compared with days 0 and 300, respectively (95% confidence interval, P = .012 and P = .018).

Discussion

The maintenance and promotion of wellness of residual motor neurons mediated by the restored level of SMN protein due to nusinersen could result in an increased level of amyloid peptides.

Effect of Discontinuation of Nusinersen Treatment in Long-Standing SMA3

BACKGROUND

Spinal muscular atrophy is an autosomal recessive neuromuscular disease leading to ongoing degeneration of anterior horn cells in the spinal cord. Nusinersen is the first approved treatment for the condition, an intrathecally administered antisense oligonucleotide. It modulates pre-RNA splicing of the SMN2 gene and increases full-length SMN protein expression, thereby increasing SMN protein levels. The benefit of Nusinersen for patients with spinal muscular atrophy type 3 (SMA3) has recently been shown in several real-world cohorts.

OBJECTIVE

We aim to elucidate not only the effect of therapy with Nusinersen, but the development of the disease course after discontinuation of treatment. To our knowledge, there are so far no reports on the effects of Nusinersen discontinuation.

METHODS

We report on a 45-year-old female patient with genetically confirmed SMA3 and a disease duration of 40 years prior to treatment onset.

RESULTS

The patient was non-ambulantory, best motor function at treatment onset was holding arms with support, reflected in MRC of 3/5 in upper limbs. After having received Nusinersen for 11 months without complications, the patient showed improvement in motor functions, as measured by hand grip measurement (HGS), Hammersmith Functional Rating Scale Expanded (HFMSE), and Revised Upper Limb Module (RULM). Due to worsening of a pre-existing anxiety disorder, treatment was discontinued after six injections. Sixteen months later, progression of the disease became evident with worsening of HFMSE and RULM scores, while hand strength remained stable.

CONCLUSION

Treatment with Nusinersen in SMA3 improves motor function in longstanding disease even in clinically advanced stages; however, after discontinuation of treatment, further progression mirroring the natural history of the disease is anticipated.

Prospective Cohort Study of Nusinersen Treatment in Adults with Spinal Muscular Atrophy

BACKGROUND

The impact of nusinersen therapy on outcomes in adults with Spinal Muscular Atrophy (SMA) remains uncertain.

OBJECTIVE

To demonstrate whether nusinersen therapy, at currently prescribed doses, can stabilize or improve motor function in adults with SMA using existing outcome measures.

METHODS

A single-center prospective cohort study of 6 adults with SMA type 3, with inclusion/exclusion criteria intended to optimize the ability to demonstrate change using established outcome measures. Primary outcomes were the Hammersmith Functional Motor Scale-Expanded (HFMSE) and the Revised Upper Limb Measure (RULM). Secondary outcomes were the PedsQL Fatigue scale, the SMA Functional Rating Scale (SMAFRS), and the 6-minute and 10-meter walk tests (6 MWT and 10 MWT). Estimates of change in HFMSE and RULM mean scores across visits were calculated using a linear mixed effects model. Change from baseline was used for other outcome measures.

RESULTS

HFMSE and RULM scores over 12 months were stable or improved in all participants, with a mean increase of 2 points in each. Other measures showed high intra-individual variability. Adverse events related to the primary diagnosis, including injury and infection, significantly impacted the ability to reliably perform walk tests in the four ambulatory participants.

CONCLUSIONS

HFMSE and RULM show potential as responsive outcome measures of motor function in ambulatory and non-ambulatory adults with SMA type 3. A time-dependent accrual of benefit of nusinersen on motor function was apparent in this cohort. More sensitive alternative measures of quality of life, fatigue, exercise tolerance, stability and ADLs are clearly needed for adults with SMA.

Treatment satisfaction in 5q-spinal muscular atrophy under nusinersen therapy

Background:

Nusinersen was the first approved disease-modifying therapy for all 5q-spinal muscular atrophy (SMA) patients regardless of age or disease severity. Its efficacy in adults has recently been demonstrated in a large cohort by motor outcome measures, which were only partially suitable to detect changes in very mildly or severely affected patients. Patient-reported outcome measures (PROs) have been suggested as a valuable addition. Here, we aimed to assess treatment satisfaction and investigate whether it may be a useful PRO to monitor SMA patients.

Methods:

We enrolled 91 mainly adult 5q-SMA patients treated with nusinersen in a national, multicenter, cross-sectional observational study. 21 patients underwent longitudinal follow up. Patients’ satisfaction with treatment in four dimensions (global, effectiveness, convenience, side effects) was assessed by the Treatment Satisfaction Questionnaire for Medication German version 1.4 (TSQM-1.4^©) and related to clinical parameters, motor scores, and treatment duration.

Results:

More than 90% of SMA patients were consistently satisfied over a median treatment duration of 10 months. Highest mean scores were observed in the dimensions ‘side effects,’ ‘global satisfaction,’ and ‘effectiveness’ (93.5 ± 14.8 versus 73.1 ± 21.0 and 64.8 ± 20.6, respectively). Patients’ satisfaction with the convenience of treatment was considerably lower (43.6 ± 20.2). Interestingly, satisfaction with the effectiveness was higher in ambulatory (p = 0.014) compared with non-ambulatory patients and directly correlated to motor outcome measures. Five non-ambulatory patients withdrew from therapy. All of them presented with a deterioration of motor outcome measures and reported dissatisfaction with treatment effectiveness and convenience.

Conclusion:

Most patients were satisfied with nusinersen treatment effectiveness. Less severely affected patients indicated higher satisfaction. The TSQM-1.4^© helped to identify therapy non-responders, who mainly addressed dissatisfaction with effectiveness and convenience. We suggest introducing the TSQM-1.4^© as an additional PRO in SMA into clinical practice.