Longitudinal natural history of type I spinal muscular atrophy: a critical review

Intra-amniotic antisense oligonucleotide treatment improves phenotypes in preclinical models of spinal muscular atrophy

Neurological disorders with onset before or at birth are a leading cause of morbidity and mortality in infants and children. Prenatal treatment has the potential to reduce or prevent irreversible neuronal loss and facilitate normal neurodevelopment. We hypothesized that antisense oligonucleotides (ASOs) delivered to the amniotic fluid by intra-amniotic (IA) injection could safely distribute to the fetal central nervous system (CNS) and provide therapeutic benefit in the motor neuron disease spinal muscular atrophy (SMA), caused by mutations of the survival of motor neuron 1 gene (SMN1), leading to deficiency of SMN protein. Although the splice-switching ASO nusinersen ameliorates SMA when delivered postnatally, substantial deficits can remain in severely affected infants. Here, IA injection of ASOs into two mouse models of severe SMA increased SMN expression in the CNS. In SMAΔ7 mice, which manifest pathology in utero, prenatal treatment improved motor neuron numbers, motor axon development, motor behavioral tests, and survival when compared with those in mice treated postnatally (between P1 and P3). To assess the feasibility of prenatal treatment in a large-animal model, ASOs were delivered midgestation to fetal sheep by IA or intracranial injection. ASOs delivered by IA injection distributed to the spinal cord at therapeutic concentrations and to multiple peripheral tissues without evidence of substantial toxicity to the fetus or mother. These data demonstrated that IA delivery of ASOs holds potential as a minimally invasive approach for prenatal treatment of SMA and possibly other severe, early-onset neurological disorders.

High Expression of SMN circ4-2b-3 in SMA I Children Treated with Nusinersen is Associated with Improved Motor Outcomes

Spinal muscular atrophy (SMA) is a neuromuscular disorder resulting in the loss of α-motor neurons. Nusinersen is an antisense oligonucleotide administered intrathecally to SMA patients that corrects the splicing defect of SMN2. Not all SMA patients respond equally to the therapy and work is in progress to identify biomarkers that may help stratify to SMA patients. In this study, we evaluated the expression of SMN circular RNAs (circRNAs) as potential biomarkers of the disease. This monocentric study was conducted at Fondazione Policlinico A. Gemelli in collaboration with Catholic University of Sacred Heart between December 2019 and March 2023. The inclusion criteria comprised having a diagnosis of SMA I and being treated with Nusinersen. The quantitative analysis of SMN circ4-2b-3 was conducted analyzing patients' serum-derived exosomes. The study included 19 type I SMA patients. Among several SMN circRNAs expressed in SMA cells, only SMN circ4-2b-3 was also detected in exosomes isolated from both type I SMA cell lines and patient-derived serum. High copy number of SMN circ4-2b-3 occurred in a small subgroup of type I SMA patients who were defined as super-responders, based on their response to the Nusinersen therapy. The levels of this circRNA remained high over time. Our results suggest that SMN circ4-2b-3 is a potential biomarker to predict the therapeutic response of type I SMA patients to Nusinersen. However, since other super-responders had a lower number of SMN circ4-2b-3 copies, these findings should be confirmed in larger cohorts.

Pilocytic astrocytoma in a child with spinal muscular atrophy treated with onasemnogene abeparvovec

Spinal muscular atrophy (SMA) is a severe neuromuscular disease, leading to progressive muscle weakness and potentially early mortality if untreated. Onasemnogene abeparvovec is a recombinant adeno-associated virus serotype 9 (rAAV9)-based gene therapy that has demonstrated improvements in survival and motor function for SMA patients. Here, we present a case of a patient diagnosed with a grade 1 pilocytic astrocytoma at the age of 2 years, approximately 8 months after onasemnogene abeparvovec treatment. Although vector genomes delivered by rAAVs persist primarily as episomes, rare integration events have been linked to tumor formation in neonate murine models. Therefore, we investigated the presence and possible integration of onasemnogene abeparvovec in formalin-fixed paraffin embedded (FFPE) and frozen tumor samples. In situ hybridization demonstrated variable transduction levels in individual tumor cells, while droplet digital PCR measured an average vector copy number ranging from 0.7 to 4.9 vector genomes/diploid genome. Integration site analysis identified a low number of integration sites that were not conserved between technical replicates, nor between FFPE and frozen samples, indicating that cells hosting integrating vector genomes represented a minority in the overall cell population. Thus, molecular analysis of the tumor tissue suggests that tumorigenesis was causally independent of the administration of onasemnogene abeparvovec.

Scoliosis development in 5q-spinal muscular atrophy under disease modifying therapies

PURPOSE

5q-spinal muscular atrophy (SMA) is a treatable neuromuscular disorder associated with scoliosis in up to 90% of patients. New SMA therapies could mark a paradigm shift in scoliosis management, but their effects on scoliosis development remain unclear. This study aims to observe scoliosis progression in the current treatment landscape to inform management strategies.

METHODS

We conducted a cross-sectional retrospective analysis of 94 SMA patients treated at our center. Scoliosis development was evaluated in 75 patients using spine radiographs and electronic health records. Statistical analysis was performed using Python and GraphPad Prism. One-way ANOVA and Pearson correlation were used for group comparisons and correlation analysis, respectively.

RESULTS

Scoliosis parameters in 5q-SMA patients who had received either nusinersen, onasemnogene abeparvovec, risdiplam, or their combinations showed mean ages at scoliosis detection were 23.94, 55.52, and 168.11 months for SMA types 1, 2, and 3, respectively. Cobb angles at detection showed no significant intergroup differences. The mean ages at scoliosis surgery were 60, 88.43, and 124.8 months. Pelvic obliquity (PO) was highest in type 1 and lowest in type 3. A strong correlation (r = 0.9) was found between PO measurement techniques. HFMSE scores correlated moderately with scoliosis severity (r = -0.38), while CHOP-INTEND showed no correlation.

CONCLUSION

The observations made in this study suggest that the effects of SMA therapies do not prevent scoliosis development. The improved prognosis may lead to a growing cohort of SMA type 1 and 2 patients with early onset scoliosis who require early growth-friendly surgical interventions.

Lumbar Transforaminal Injections of Nusinersen in Spinal Muscular Atrophy Patients

Following a review of spinal muscular atrophy pathogenesis and current therapeutics, a comprehensive review of transforaminal lumbar injections is provided. Patient preparation, special considerations, procedural technique, complications, and alternative approaches are discussed.

Feature Engineering for the Prediction of Scoliosis in 5q-Spinal Muscular Atrophy

BACKGROUND

5q-Spinal muscular atrophy (SMA) is now one of the 5% treatable rare diseases worldwide. As disease-modifying therapies alter disease progression and patient phenotypes, paediatricians and consulting disciplines face new unknowns in their treatment decisions. Conclusions made from historical patient data sets are now mostly limited, and new approaches are needed to ensure our continued best standard-of-care practices for this exceptional patient group. Here, we present a data-driven machine learning approach to a rare disease data set to predict spinal muscular atrophy (SMA)-associated scoliosis.

METHODS

We collected data from 84 genetically confirmed 5q-SMA patients who have received novel SMA therapies. We performed expert domain knowledge-directed feature engineering, correlation and predictive power score (PPS) analyses for feature selection. To test the predictive performance of the selected features, we trained a Random Forest Classifier and evaluated model performance using standard metrics.

RESULTS

The SMA data set consisted of 1304 visits and over 360 variables. We performed feature engineering for variables related to 'interventions', 'devices', 'orthosis', 'ventilation', 'muscle contractures' and 'motor milestones'. Through correlation and PPS analysis paired with expert domain knowledge feature selection, we identified relevant features for scoliosis prediction in SMA that included disease progression markers: Hammersmith Functional Motor Scale Expanded 'HFMSE' (PPS = 0.27) and 6-Minute Walk Test '6MWT' scores (PPS = 0.44), 'age' (PPS = 0.41) and 'weight' (PPS = 0.49), 'contractures' (PPS = 0.17), the use of 'assistive devices' (PPS = 0.39, 'ventilation' (PPS = 0.16) and the presence of 'gastric tubes' (PPS = 0.35) in SMA patients. These features were validated using expert domain knowledge and used to train a Random Forest Classifier with an observed accuracy of 0.82 and an average receiver operating characteristic (ROC) area of 0.87.

CONCLUSION

The introduction of disease-modifying SMA therapies, followed by the implementation of SMA in newborn screenings, has presented physicians with never-seen patients. We used feature engineering tools to overcome one of the main challenges when using data-driven approaches in rare disease data sets. Through predictive modelling of this data, we defined disease progression markers, which are easily assessed during patient visits and can help anticipate scoliosis onset. This highlights the importance of progressive features in the drug-induced revolution of this rare disease and further supports the ongoing efforts to update the SMA classification. We advocate for the consistent documentation of relevant progression markers, which will serve as a basis for data-driven models that physicians can use to update their best standard-of-care practices.

Development of the SMA EFFORT: A new approach to characterize perceived physical fatigability in spinal muscular atrophy

BACKGROUND

Fatigue and fatigability are commonly reported in spinal muscular atrophy (SMA). Physical fatigability, proposed to be the most relevant to SMA pathophysiology, encompasses performance-based and perceived physical fatigability (PPF) assessments. While performance-based measures have highlighted physical fatigability as an SMA hallmark, PPF is not well characterized due to the lack of disease- and construct-specific scales.

OBJECTIVE

Our aim was to create a patient-reported outcome measure tailored for SMA, named the SMA EFFORT, to improve PPF assessment. Here, we describe the scale development process, assess scale properties, and discuss future research and application.

METHODS

SMA and scale development experts organized a comprehensive physical activity item bank, relevant across the SMA phenotypic spectrum. Activities were systematically categorized by varying intensities and durations. The SMA EFFORT was completed by an international cohort of individuals with all types of SMA. To compare PPF across demographic and clinical variables, SMA EFFORT PPF percent (PPF%) composite scoring was established.

RESULTS

One hundred eighteen participants completed the SMA EFFORT. Total PPF% scores were broadly distributed within functional groups, with differences between non-sitters (35.1 ± 21.0) and sitters (24.9 ± 15.1) (p = 0.006), and those with (34.4 ± 18.1) and without respiratory support (26.4 ± 17.8) (p = 0.02). Participants treated with disease modifying therapy (DMT) showed similar scores to those without treatment (p = 0.70). Further, no differences in scores were observed in participants with scoliosis surgery and those without (p = 0.71). Subscale analyses revealed differences in mean PPF% subscale scores by functional group.

CONCLUSIONS

The novel SMA EFFORT standardizes PPF ratings by anchoring activity to intensity and duration. Item and scale data insights will inform the next iteration, which will undergo additional investigation. The SMA EFFORT aims to improve upon current measures to better assess treatment impact on physical well-being across the SMA spectrum.

Evaluation of cardiac function in patients with SMA after treatment with onasemnogene abeparvovec

BACKGROUND

Spinal muscular atrophy (SMA) is a recessively inherited neurological disease resulting in motor neuron disorder. Onasemnogene abeparvovec is a gene replacement therapy used to treat patients with SMA. Cardiac toxicity was observed in animal studies on this therapy, and elevated cardiac troponin I levels were observed in clinical trials; however, the clinical importance of these findings is unknown. Therefore, this study aimed to reveal the cardiac toxicity of onasemnogene abeparvovec through careful investigation of cardiac function using cardiac strain analysis, which can detect early subtle abnormalities.

METHODS

This study included patients with SMA treated with onasemnogene abeparvovec between June 2020 and November 2020. Echocardiography, including peak global longitudinal strain (GLS), and other laboratory test results were evaluated.

RESULTS

Case 1 showed a relative GLS decrease of 14.5% compared with that at the baseline (GLS reduction from -22.1% to -18.9%), elevation of N-terminal prohormone B-type natriuretic peptide levels from 227 pg/mL to 494 pg/mL, and elevated liver enzyme concentrations after gene replacement therapy without reduction of the left ventricular ejection fraction.

CONCLUSIONS

Subclinical myocardial dysfunction after infusion of onasemnogene abeparvovec was suggested by careful investigation of cardiac function. Cardiac toxicity may correlate with liver impairment following gene replacement therapy. Long-term studies that allow for a higher number of patients and more extended observation periods should be conducted to confirm the cardiac toxicity of onasemnogene abeparvovec.

Type I spinal muscular atrophy and disease modifying treatments: a nationwide study in children born since 2016

Background

The advent of disease-modifying treatments (DMT) has changed natural history in 5q Spinal muscular atrophy (SMA). The aim of this study was to report survival and functional aspects in all the Italian type I children born since 2016.

Methods

The study included all symptomatic children with type I SMA born since January 1st, 2016, when DMTs became available in Italy. All the Italian SMA referral centers provided data on survival and motor, respiratory, and nutritional status. To compare survival rate pre and post DMTs approval, we also included similar data from SMA I patients born between January 1st, 2010, and December 31st, 2015. A two-proportion z-test was conducted to compare the two cohorts. The significance level was set at p < .05.

Findings

241 infants (98%) had type I SMA. Mean follow-up was 3.48 years (SD 2.33). Among type I patients, 42/241 did not survive (25 untreated), while 199 were alive at last follow-up (all treated; mean treatment age 0.6 years), with 25 needing >16 h/day ventilation or tracheostomy with continuous invasive ventilation. 130 of the 199 survivors (65%) achieved independent sitting, and 175 (87.9%) did not require tube feeding.

Interpretation

Our study provides a picture of the 'new natural history' of type I SMA, confirming the impact of the new therapies on the progression of type I with longer survival r and has better motor, respiratory and nutritional.

Funding

This research was partially funded by grants from the Italian Ministry of Health.

Type-1 spinal muscular atrophy cohort before and after disease-modifying therapies

BACKGROUND

 Spinal muscular atrophy (SMA-5q) is a neurodegenerative disease characterized by progressive muscle atrophy, hypotonia, and weakness, with SMA 1 presenting symptoms within the first 6 months of life. Disease-modifying therapies have been approved, with better outcomes with earlier treatment.

OBJECTIVE

 To describe the safety and clinical efficacy of disease-modifying therapies based on SMN1 and SMN2 gene strategies concerning motor, respiratory, and bulbar function. Patients with SMA 1 were divided into 2 groups: those exclusively on nusinersen (group 1) and those transitioning to onasemnogene abeparvovec (OA) (group 2).

METHODS

 Over 18 months, patients were assessed using the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) scale, developmental milestones, ventilation needs and duration, nutritional support needs, consistency of food, and signs of dysphagia. There were ten patients, divided between the groups; in group 1, the average age for starting nusinersen was 53.6 (12-115) months, and, in group 2, the age was 7 (1-12) months for nusinersen and 15.2 (10-19) months for OA.

RESULTS

 Our results indicate that 70% of patients reached some motor milestones, with group 1 increasing by 10.2 points on the CHOP-INTEND scale, while group 2 increased by 33 points. Additionally, 90% of the patients experienced no respiratory decline, and 30% maintained oral feeding. No serious adverse effects or deaths were recorded.

CONCLUSION

 Both groups showed improvement in motor function and stabilization of respiratory and bulbar function, with the difference between the groups possibly being related to the earlier treatment initiation. Thus, the present study provides valuable insights into the real-world safety and clinical efficacy of disease-modifying therapies for SMA 1 patients.

Effects of nusinersen on motor function in children with spinal muscular atrophy: a retrospective study

Background

Spinal muscular atrophy (SMA) is a genetic progressive neuromuscular disease. Nusinersen is the first disease modifying drug approved to treat patients with SMA. Our study aimed to evaluate the efficacy of nusinersen treatment on motor function in children with SMA.

Methods

A retrospective analysis was conducted on the data of 52 genetically confirmed SMA patients from November 2020 to September 2023. Motor function was assessed based on standardized scales from baseline to 14 months of follow-up.

Results

Of patients in this study, the majority had SMA type 2 (40/52, 76.9%), 5 (9.6%) and 7 (13.5%) patients had SMA types 1 and 3, respectively. The median disease duration was 11 months (range 0-52), and the median age at initiation of treatment was 44.5 months (range 5-192). Motor function of all the patients with SMA improved from baseline to 14 months of follow-up. Mean increases of 4.6-point (p = 0.173), 4.7-point (p = 0.021) and 2.7-point (p = 0.013) were observed from baseline to 14 months of follow-up for the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scores, the Hammersmith Functional Motor Scale Expanded (HFMSE) and the Revised Upper Limb Module (RULM), respectively. Increased disease duration and age of treatment initiation were negatively correlated with the changes in HFMSE scores (r = -0.567, p = 0.043; r = -0.771 and p = 0.002, respectively). Similar results were observed for the RULM scores (r = -0.714, p = 0.014; r = -0.638 and p = 0.035, respectively).

Conclusion

Our study suggested that 14 months of treatment with nusinersen was effective and improved the motor function of children with SMA types 1, 2, or 3. In addition, disease duration and age at treatment initiation were negatively correlated with treatment outcome in the patients.

Gene replacement therapy for spinal muscular atrophy: safety and preliminary efficacy in a Brazilian cohort

Spinal muscular atrophy (SMA) is a motor neuron disease associated with progressive muscle weakness, ventilatory failure, and reduced survival. Onasemnogene abeparvovec is the first gene replacement therapy (GT) approved to treat this condition. An observational retrospective study was conducted to assess adverse events and efficacy of GT in SMA patients. Forty-one patients with SMA (58.5% females and 80.1% SMA type 1) were included. The mean age at GT dosing was 18 (±6.4) months. Thirty-six patients (87.8%) were under previous treatment with nusinersen, and 10 (24.4%) continued nusinersen after GT. Mean CHOP-INTEND increased 13 points after 6 months and this finding did not differ between groups according to nusinersen maintenance after GT (p = 0.949). Among SMA type 1 patients, 14 (46.6%) reached the ability to sit alone. Liver transaminases elevation at least two times higher than the upper limit of normal value occurred in 29 (70.7%) patients. Thrombocytopenia occurred in 13 (31.7%) patients, and one presented thrombotic microangiopathy. Older age (>2 years) was associated with more prolonged use of corticosteroids (p = 0.021). GT is effective in SMA patients, combined nusinersen after GT did not appear to add gain in motor function and older age is associated with prolonged corticosteroid use.

Nusinersen therapy changed the natural course of spinal muscular atrophy type 1: What about spine and hip?

Purpose

Spinal muscular atrophy type 1 has a devastating natural course and presents a severe course marked by scoliosis and hip subluxation in nonambulatory patients. Nusinersen, Food and Drug Administration-approved spinal muscular atrophy therapy, extends survival and enhances motor function. However, its influence on spinal and hip deformities remains unclear.

Methods

In a retrospective study, 29 spinal muscular atrophy type 1 patients born between 2017 and 2021, confirmed by genetic testing, treated with intrathecal nusinersen, and had registered to the national electronic health database were included. Demographics, age at the first nusinersen dose, total administrations, and Children's of Philadelphia Infant Test of Neuromuscular Disorders scores were collected. Radiological assessments included parasol rib deformity, scoliosis, pelvic obliquity, and hip subluxation.

Results

Mean age was 3.7 ± 1.1 (range, 2-6), and average number of intrathecal nusinersen administration was 8.9 ± 2.9 (range, 4-19). There was a significant correlation between Children's of Philadelphia Infant Test of Neuromuscular Disorders score and the number of nusinersen administration (r = 0.539, p = 0.05). The correlation between Children's of Philadelphia Infant Test of Neuromuscular Disorders score and patient age (r = 0.361) or the time of first nusinersen dose (r = 0.39) was not significant (p = 0.076 and p = 0.054, respectively). While 93.1% had scoliosis, 69% had pelvic obliquity, and 60.7% had hip subluxation, these conditions showed no significant association with patient age, total nusinersen administrations, age at the first dose, or Children's of Philadelphia Infant Test of Neuromuscular Disorders scores.

Conclusion

Disease-modifying therapy provides significant improvements in overall survival and motor function in spinal muscular atrophy type 1. However, progressive spine deformity and hip subluxation still remain significant problems in the majority of cases which would potentially need to be addressed.

Continued safety and long-term effectiveness of onasemnogene abeparvovec in Ohio

5q spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease caused by absence of the SMN1 gene with three FDA approved genetic therapies which significantly improve outcomes. The AAV9 mediated gene replacement therapy, onasemnogene abeparvovec, has the greatest potential for side effects. Here we report the safety and outcomes from 46 children treated with onasemnogene abeparvovec in the state of Ohio between December 2018 and January 2023. In our cohort, onasemnogene abeparvovec treatment remained safe and no child experienced any significant adverse events, including thrombotic microangiopathy, liver failure or death. All children experienced benefit, although the benefit in those with 2 copies of SMN2 was variable. 79 % of the children treated when symptomatic had a SMN2 modifying therapy added on. With careful screening and post treatment monitoring, onasemnogene abeparvovec is safe and effective for children with SMA in the state of Ohio, but more work needs to be done to ensure optimal outcomes for all children with 2 copies of SMN2.

Assessing the Assisted Six-Minute Cycling Test as a Measure of Endurance in Non-Ambulatory Patients with Spinal Muscular Atrophy (SMA)

Assessing endurance in non-ambulatory individuals with Spinal Muscular Atrophy (SMA) has been challenging due to limited evaluation tools. The Assisted 6-Minute Cycling Test (A6MCT) is an upper limb ergometer assessment used in other neurologic disorders to measure endurance. To study the performance of the A6MCT in the non-ambulatory SMA population, prospective data was collected on 38 individuals with SMA (13 sitters; 25 non-sitters), aged 5 to 74 years (mean = 30.3; SD = 14.1). The clinical measures used were A6MCT, Revised Upper Limb Module (RULM), Adapted Test of Neuromuscular Disorders (ATEND), and Egen Klassifikation Scale 2 (EK2). Perceived fatigue was assessed using the Fatigue Severity Scale (FSS), and effort was assessed using the Rate of Perceived Exertion (RPE). Data were analyzed for: (1) Feasibility, (2) Clinical discrimination, and (3) Associations between A6MCT with clinical characteristics and outcomes. Results showed the A6MCT was feasible for 95% of the tested subjects, discriminated between functional groups (p = 0.0086), and was significantly associated with results obtained from RULM, ATEND, EK2, and Brooke (p < 0.0001; p = 0.029; p < 0.001; p = 0.005). These findings indicate the A6MCT's potential to evaluate muscular endurance in non-ambulatory SMA individuals, complementing clinician-rated assessments. Nevertheless, further validation with a larger dataset is needed for broader application.

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

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

Epithelioid neoplasm of the spinal cord in a child with spinal muscular atrophy treated with onasemnogene abeparvovec

Spinal muscular atrophy is an autosomal recessive disease resulting in motor neuron degeneration and progressive life-limiting motor deficits when untreated. Onasemnogene abeparvovec is an adeno-associated virus serotype 9-based gene therapy that improves survival, motor function, and motor milestone achievement in symptomatic and presymptomatic patients. Although the adeno-associated virus genome is maintained as an episome, theoretical risk of tumorigenicity persists should genomic insertion occur. We present the case of a 16-month-old male with spinal muscular atrophy who was diagnosed with an epithelioid neoplasm of the spinal cord approximately 14 months after receiving onasemnogene abeparvovec. In situ hybridization analysis detected an onasemnogene abeparvovec nucleic acid signal broadly distributed in many but not all tumor cells. Integration site analysis on patient formalin-fixed, paraffin-embedded tumor samples failed to detect high-confidence integration sites of onasemnogene abeparvovec. The finding was considered inconclusive because of limited remaining tissue/DNA input. The improved life expectancy resulting from innovative spinal muscular atrophy therapies, including onasemnogene abeparvovec, has created an opportunity to analyze the long-term adverse events and durability of these therapies as well as identify potential disease associations that were previously unrecognized because of the premature death of these patients.

Spinal Muscular Atrophy: A (Now) Treatable Neurodegenerative Disease

Spinal muscular atrophy (SMA) is a progressive disease of the lower motor neurons associated with recessive loss of the SMN1 gene, and which leads to worsening weakness and disability, and is fatal in its most severe forms. Over the past six years, three treatments have emerged, two drugs that modify exon splicing and one gene therapy, which have transformed the management of this disease. When treated pre-symptomatically, many children show normal early motor development, and the benefits extend from the newborn period to adulthood. Similar treatment approaches are now under investigation for rare types of SMA associated with genes beyond SMN1.

Brazilian version of the CHOP INTEND scale: cross-cultural adaptation and validation

BACKGROUND

Spinal muscular atrophy (SMA) is a rare genetic disease that causes progressive muscle weakness and impacts motor function. The type I is the most severe presentation and affects infants before 6 months old. In addition, the instruments available for assessing motor function have limitations when applied to infants with neuromuscular diseases and significant muscle weakness.

OBJECTIVE

To translate, cross-culturally adapt, and validate the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) to Brazilian Portuguese.

METHODS

The present study comprised the translation, synthesis of translations, backtranslation, consolidation by a committee of experts, and test of the final version of the CHOP INTEND in 13 patients with SMA type I. We also assessed the content validity and reliability of the translated version.

RESULTS

The scale was translated considering semantic, structural, idiomatic, and cultural aspects. All agreement rates were > 0.8, the overall content validity index of the instrument was 0.98, and inter-rater reliability using the intraclass correlation coefficient was 0.998.

CONCLUSION

The Brazilian version of the CHOP INTEND met semantic and technical equivalence criteria with the original version and was valid and reliable for patients with SMA type I.

Treatment of spinal muscular atrophy with Onasemnogene Abeparvovec in Switzerland: a prospective observational case series study

BACKGROUND

Spinal muscular atrophy (SMA) is a rare neuromuscular disorder leading to early death in the majority of affected individuals without treatment. Recently, targeted treatment approaches including Onasemnogene Abeparvovec (OA) were introduced. This study describes the first real-world experience with OA in Switzerland.

METHODS

Prospective observational case series study using data collected within the Swiss Registry for Neuromuscular Disorders from SMA patients treated with OA. Development of motor, bulbar and respiratory function, appearance of scoliosis, and safety data (platelet count, liver function, and cardiotoxicity) were analyzed.

RESULTS

Nine individuals were treated with OA and followed for 383 ± 126 days: six SMA type 1 (of which two with nusinersen pretreatment), one SMA type 2, and two pre-symptomatic individuals. In SMA type 1, CHOP Intend score increased by 28.1 from a mean score of 20.5 ± 7.6 at baseline. At end of follow-up, 50% of SMA type 1 patients required nutritional support and 17% night-time ventilation; 67% developed scoliosis. The SMA type 2 patient and two pre-symptomatically treated individuals reached maximum CHOP Intend scores. No patient required adaptation of the concomitant prednisolone treatment, although transient decrease of platelet count and increase of transaminases were observed in all patients. Troponin-T was elevated prior to OA treatment in 100% and showed fluctuations in 57% thereafter.

CONCLUSIONS

OA is a potent treatment for SMA leading to significant motor function improvements. However, the need for respiratory and especially nutritional support as well as the development of scoliosis must be thoroughly evaluated in SMA type 1 patients even in the short term after OA treatment.

Spinal muscular atrophy with hypoplasia of the corpus callosum: a case report

BACKGROUND

Spinal Muscular Atrophy (SMA) is a severe neuromuscular disorder due to a defect in the survival motor neuron 1 (SMN1) gene. Hypoplasia of the corpus callosum is underdevelopment or thinness of the corpus callosum. SMA and callosal hypoplasia are relatively rare, and there is limited information sharing the diagnosis and treatment for SMA patients with callosal hypoplasia.

CASE DESCRIPTION

A boy with callosal hypoplasia, small penis, and small testes had been perceived with motor regression at 5 months. He was referred to the rehabilitation department and neurology department at 7 months. Physical examination showed absent deep tendon reflexes, proximal weakness and significant hypotonia. He was recommended to perform trio whole-exome sequencing (WES) and array comparative genomic hybridization (aCGH) for his complicated conditions. The subsequent nerve conduction study revealed some characteristics of motor neuron diseases. We identified a homozygous deletion in exon 7 of the SMN1 gene by multiplex ligation-dependent probe amplification and failed to find further pathogenic variations responsible for multiple malformations by trio WES and aCGH. He was diagnosed as SMA. Despite some concerns, he received the therapy of nusinersen for nearly 2 years. He gained the milestone of sitting without support, which he had never accomplished, after the seventh injection, and he continued to improve. During follow-up, there were no adverse events reported and no signs of hydrocephalus.

CONCLUSIONS

Some extra features which could not belong to neuromuscular manifestation made the diagnosis and treatment of SMA more complicated.

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

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

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

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

Assessment of motor function and nutritional status in children with spinal muscular atrophy treated with nusinersen after loading period in Western China: a retrospective study

BACKGROUND

Spinal muscular atrophy (SMA) is a progressive degenerative neuromuscular disease. Nusinersen, with its quick onset of action, can benefit patients early in the treatment course. However, there are currently no clinical studies regarding the improvement in motor function and nutritional status of patients after loading period treatment with nusinersen. Here, we aimed to determine the efficacy of nusinersen in improving motor function and nutritional status in children with SMA treated with nusinersen after loading period in Western China.

METHODS

In this retrospective study, data for all pediatric patients (aged < 18 years), with genetically confirmed diagnosis of SMA who were treated with nusinersen, were collected before initiation of treatment and after 2 months of treatment. We assessed motor function using standardized scales and nutritional status of patients with SMA as well as side effects of nusinersen.

RESULTS

Forty-six pediatric patients aged < 18 years were enrolled in this study. After 2 months of treatment, the motor function of patients with SMA type 1, 2, and 3 improved. The difference in Revised Upper Limb Module scores from M0 to M2 was significant in patients with SMA type 2 and 3 (P = 0.004, P = 0.042, respectively). The difference in Hammersmith Functional Motor Scale Expanded scores from M0 to M2 in patients with SMA type 2 was also significant (P = 0.000). No significant differences were found for Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorder (CHOP-INTEND), Hammersmith Infant Neurologic Examination-Part 2 (HINE-2), and 6-Minute Walking Test (6MWT) scores between M0 and M2, but the scores of CHOP-INTEND, HINE-2, and 6MWT were all increased after loading period treatment. The overall improvement in nutritional status was not statistically significant. No serious adverse effects were observed.

CONCLUSIONS

Our study provides evidence for the efficacy and safety of nusinersen and the nutritional status of pediatric patients with SMA after the loading period treatment. Motor function of all patients improved after 2 months of loading period nusinersen treatment. Patients with a shorter disease duration showed better response to treatment. Careful surveillance of nutritional status is needed in patients with SMA.

Gene Therapy in ALS and SMA: Advances, Challenges and Perspectives

Gene therapy is defined as the administration of genetic material to modify, manipulate gene expression or alter the properties of living cells for therapeutic purposes. Recent advances and improvements in this field have led to many breakthroughs in the treatment of various diseases. As a result, there has been an increasing interest in the use of these therapies to treat motor neuron diseases (MNDs), for which many potential molecular targets have been discovered. MNDs are neurodegenerative disorders that, in their most severe forms, can lead to respiratory failure and death, for instance, spinal muscular atrophy (SMA) or amyotrophic lateral sclerosis (ALS). Despite the fact that SMA has been known for many years, it is still one of the most common genetic diseases causing infant mortality. The introduction of drugs based on ASOs-nusinersen; small molecules-risdiplam; and replacement therapy (GRT)-Zolgensma has shown a significant improvement in both event-free survival and the quality of life of patients after using these therapies in the available trial results. Although there is still no drug that would effectively alleviate the course of the disease in ALS, the experience gained from SMA gene therapy gives hope for a positive outcome of the efforts to produce an effective and safe drug. The aim of this review is to present current progress and prospects for the use of gene therapy in the treatment of both SMA and ALS.

Identifying Biomarkers of Spinal Muscular Atrophy for Further Development

BACKGROUND

Spinal muscular atrophy (SMA) is caused by bi-allelic, recessive mutations of the survival motor neuron 1 (SMN1) gene and reduced expression levels of the survival motor neuron (SMN) protein. Degeneration of alpha motor neurons in the spinal cord causes progressive skeletal muscle weakness. The wide range of disease severities, variable rates of decline, and heterogenous clinical responses to approved disease-modifying treatment remain poorly understood and limit the ability to optimize treatment for patients. Validation of a reliable biomarker(s) with the potential to support early diagnosis, inform disease prognosis and therapeutic suitability, and/or confirm response to treatment(s) represents a significant unmet need in SMA.

OBJECTIVES

The SMA Multidisciplinary Biomarkers Working Group, comprising 11 experts in a variety of relevant fields, sought to determine the most promising candidate biomarker currently available, determine key knowledge gaps, and recommend next steps toward validating that biomarker for SMA.

METHODS

The Working Group engaged in a modified Delphi process to answer questions about candidate SMA biomarkers. Members participated in six rounds of reiterative surveys that were designed to build upon previous discussions.

RESULTS

The Working Group reached a consensus that neurofilament (NF) is the candidate biomarker best poised for further development. Several important knowledge gaps were identified, and the next steps toward filling these gaps were proposed.

CONCLUSIONS

NF is a promising SMA biomarker with the potential for prognostic, predictive, and pharmacodynamic capabilities. The Working Group has identified needed information to continue efforts toward the validation of NF as a biomarker for SMA.

Use of MFM-20 to monitor SMA types 1 and 2 patients treated with nusinersen

OBJECTIVE

To evaluate sensitivity to change and discriminant validity of the 20-item Motor Function Measure (MFM-20) in 2-7-year-old patients with spinal muscular atrophy types 1 (SMA1) or 2 (SMA2) treated with nusinersen.

METHODS

Children aged 2 to 7 years old with SMA1 or SMA2 treated with nusinersen were assessed at least three times using the MFM-20 over an average follow-up time of 17 months. Evolution of 4-month-standardized MFM-20 scores was calculated for each MFM-20 domain (D1 standing and transfers, D2 axial and proximal, D3 distal) and for the total score (TS).

RESULTS

Included in the study were 22 SMA1 subjects and 19 SMA2 subjects. Baseline MFM scores were significantly lower in patients with SMA1 than SMA2 (TS 29.5% vs. 48.3%, D1 4.5% vs. 10.6%, D2 43.6% vs. 72.6%, D3 51.2% vs. 75.0%). When considering the mean change during nusinersen treatment, standardized over a 4-month period, TS was improved for both SMA1 (+ 4.1%, SRM 1.5) and SMA2 (+ 2.8%, SRM 0.89) patients. For SMA1 patients, considerable changes were observed in D2 (+ 6.2%, SRM 0.89) and D3 (+ 6.0%, SRM 0.72), whereas the change in D1 was small (+ 0.5%, SRM 0.44). In SMA2 2 subjects, D3 was improved to a larger extent (+ 4.2%, SRM 0.53) than D1 (+ 1.8% SRM 0.63) or D2 (+ 3.2%, SRM 0.69).

CONCLUSION

Our results validate use of MFM-20 to monitor function of young SMA1 and SMA2 subjects treated with nusinersen. Significant motor function improvements following treatment were observed in both SMA1 and SMA2 patients.

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

Background

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

Methods

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

Results

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

Conclusion

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

Natural History and Real-World Data in Rare Diseases: Applications, Limitations, and Future Perspectives

Rare diseases represent a highly heterogeneous group of disorders with high phenotypic and genotypic diversity within individual conditions. Due to the small numbers of people affected, there are unique challenges in understanding rare diseases and drug development for these conditions, including patient identification and recruitment, trial design, and costs. Natural history data and real-world data (RWD) play significant roles in defining and characterizing disease progression, final patient populations, novel biomarkers, genetic relationships, and treatment effects. This review provides an introduction to rare diseases, natural history data, RWD, and real-world evidence, the respective sources and applications of these data in several rare diseases. Considerations for data quality and limitations when using natural history and RWD are also elaborated. Opportunities are highlighted for cross-sector collaboration, standardized and high-quality data collection using new technologies, and more comprehensive evidence generation using quantitative approaches such as disease progression modeling, artificial intelligence, and machine learning. Advanced statistical approaches to integrate natural history data and RWD to further disease understanding and guide more efficient clinical study design and data analysis in drug development in rare diseases are also discussed.

Spinal muscular atrophy: state of the art and new therapeutic strategies

Spinal muscular atrophy (SMA) is a severe disorder of motor neurons and the most frequent cause of genetic mortality, due to respiratory complications. We are facing an exciting era with three available therapeutic options in a disease considered incurable for more than a century. However, the availability of effective approaches has raised up ethical, medical, and financial issues that are routinely faced by the SMA community. Each therapeutic strategy has its weaknesses and strengths and clinicians need to know them to optimize clinical care. In this review, the state of the art and the results and challenges of the new SMA therapeutic strategies are highlighted.

The Effect of Nusinersen Therapy on Laboratory Parameters of Patients with Spinal Muscular Atrophy

INTRODUCTION

We evaluated the effect of nusinersen on clinical and laboratory parameters and presented its safety and effect on laboratory parameters.

METHODS

Two groups were formed from among patients with spinal muscular atrophy (SMA) followed up between September 2017 and June 2021: group 1, SMA type 1; group 2, SMA type 2 and 3. The laboratory parameters were evaluated in groups 1 and 2 between doses. Motor scale tests were performed on patients before each dose of nusinersen.

RESULTS

Twenty seven patients (group 1; n = 13, group 2; n = 14) were included. The mean age (±standard deviation) at the onset of symptoms was 3 ± 1.21 (range, 1.5-6) months in group 1 and 12 ± 4.27 (range, 8-24) months in group 2. No significant laboratory treatment-related abnormalities and adverse effects were observed. The cerebrospinal fluid protein levels and the frequency of conventional LP were higher in group 1. Serum creatinine (Cr) levels were higher in group 1 before the first dose and higher in group 2 before the fifth dose (p < 0.05). With treatment, the Cr levels of group 1 decreased and group 2 remained constant or increased. We observed that the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders and Hammersmith Functional Motor Scale-Expand scores increased as our patients received treatment (p < 0.05).

CONCLUSION

Our results support the safety and efficacy of nusinersen. However, changes in Cr levels according to the clinical type and treatment suggested that serum Cr could be a candidate marker for treatment follow-up.

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.

Caracterización clínica y funcional de pacientes con atrofia muscular espinal en el centro-occidente colombiano

Introducción.

La atrofia muscular espinal es una enfermedad neurodegenerativa huérfana de origen genético que afecta las neuronas motoras del asta anterior de la médula espinal, y produce atrofia y debilidad muscular. En Colombia, son pocos los estudios publicados sobre la enfermedad y no hay ninguno con análisis funcional.

Objetivo.

Caracterizar clínica y funcionalmente una serie de casos de atrofia muscular espinal del centro-occidente colombiano.

Materiales y métodos.

Se hizo un estudio descriptivo transversal, entre el 2007 y el 2020, de pacientes con diagnóstico clínico y molecular de atrofia muscular espinal que consultaron en el centro de atención. La evaluación funcional se realizó con las escalas Hammersmith y Chop Intend. En la sistematización de los datos, se empleó el programa Epi-Info, versión 7.0.

Resultados.

Se analizaron 14 pacientes: 8 mujeres y 6 hombres. La atrofia muscular espinal más prevalente fue la de tipo II, la cual se presentó en 10 casos. Se encontró variabilidad fenotípica en términos de funcionalidad en algunos pacientes con atrofia muscular espinal de tipo II, cinco de los cuales lograron alcanzar la marcha. La estimación de la supervivencia fue de 28,6 años.

Conclusiones.

Los hallazgos en el grupo de pacientes analizados evidenciaron que los puntajes de la escala de Hammersmith revisada y expandida, concordaron con la gravedad de la enfermedad.

Onasemnogene abeparvovec for the treatment of spinal muscular atrophy

INTRODUCTION

Gene therapy for spinal muscular atrophy (SMA) represents a significant milestone in the treatment of neurologic diseases. SMA is a neurodegenerative disease that results in motor neuron loss because of mutations of the survival motor neuron 1 gene, which directs survival motor neuron (SMN) protein production. Onasemnogene abeparvovec, a one-time gene replacement therapy, delivers a functional transgene to restore SMN protein expression. Onasemnogene abeparvovec has demonstrated improved survival and motor milestone achievements for presymptomatic infants and patients with SMA type 1.

AREAS COVERED

This expert review describes the current state of gene therapy for SMA, reviews the mechanism of and clinical experience with onasemnogene abeparvovec, explains future efforts to expand applications of gene therapy for SMA, and provides context for developing gene therapy for other conditions.

EXPERT OPINION

Onasemnogene abeparvovec has demonstrated efficacy in clinical trials and, because of this, is a valuable treatment option for patients with symptomatic infantile SMA and those identified by newborn screening. Gene therapy is still in its infancy, and challenges and uncertainties associated with transgene delivery must be addressed. With ongoing development of vector technology, more specific tissue tropism, reduced "off-target" effects, and an enhanced safety profile will continue to evolve.

Single-Dose Intrathecal Dorsal Root Ganglia Toxicity of Onasemnogene Abeparvovec in Cynomolgus Monkeys

Intravenous onasemnogene abeparvovec is approved for the treatment of spinal muscular atrophy in children < 2 years. For later-onset patients, intrathecal onasemnogene abeparvovec may be advantageous over intravenous administration. Recently, microscopic dorsal root ganglion (DRG) changes were observed in nonhuman primates (NHPs) following intrathecal onasemnogene abeparvovec administration. To characterize these DRG findings, two NHP studies evaluating intrathecal onasemnogene abeparvovec administration were conducted: a 12-month study with a 6-week interim cohort and a 13-week study with a 2-week interim cohort. The latter investigated the potential impact of prednisolone or rituximab plus everolimus on DRG toxicity. An additional 6-month, single-dose, intravenous NHP study conducted in parallel evaluated onasemnogene abeparvovec safety (including DRG toxicity) with or without prednisolone coadministration. Intrathecal onasemnogene abeparvovec administration was well tolerated and not associated with clinical observations. Microscopic onasemnogene abeparvovec-related changes were observed in the DRG and trigeminal ganglion (TG) and included mononuclear cell inflammation and/or neuronal degeneration, which was colocalized with high vector transcript expression at 6 weeks postdose. Incidence and severity of DRG changes were generally decreased after 52 weeks compared with 6 weeks postdose. Other onasemnogene abeparvovec-related microscopic findings of axonal degeneration, mononuclear cell infiltrates and/or gliosis in the spinal cord, dorsal spinal nerve root/spinal nerves, and/or peripheral nerves were absent or found at decreased incidences and/or severities after 52 weeks. DRG and/or TG microscopic findings following intravenous onasemnogene abeparvovec dosing included minimal to slight neuronal degeneration and mononuclear cell inflammation at 6 weeks and 6 months postdose. Nervous system microscopic findings following intrathecal onasemnogene abeparvovec (≥1.2 × 10¹³ vg/animal) trended toward resolution after 52 weeks, supporting nonprogression of changes, including in the DRG. Onasemnogene abeparvovec-related DRG findings were not associated with electrophysiology changes and were not ameliorated by prednisolone or rituximab plus everolimus coadministration. The pathogenesis is possibly a consequence of increased vector genome transduction and/or transgene expression.

How does risdiplam compare with other treatments for Types 1-3 spinal muscular atrophy: a systematic literature review and indirect treatment comparison

Aim: To conduct indirect treatment comparisons between risdiplam and other approved treatments for spinal muscular atrophy (SMA). Patients & methods: Individual patient data from risdiplam trials were compared with aggregated data from published studies of nusinersen and onasemnogene abeparvovec, accounting for heterogeneity across studies. Results: In Type 1 SMA, studies of risdiplam and nusinersen included similar populations. Indirect comparison results found improved survival and motor function with risdiplam versus nusinersen. Comparison with onasemnogene abeparvovec in Type 1 SMA and with nusinersen in Types 2/3 SMA was challenging due to substantial differences in study populations; no concrete conclusions could be drawn from the indirect comparison analyses. Conclusion: Indirect comparisons support risdiplam as a superior alternative to nusinersen in Type 1 SMA.

Assessment of cerebral spinal fluid biomarkers and microRNA-mediated disease mechanisms in spinal muscular atrophy patient samples

Cerebral spinal fluid (CSF) is a promising biospecimen for the detection of central nervous system biomarkers to monitor therapeutic efficacy at the cellular level in neurological diseases. Spinal muscular atrophy (SMA) patients receiving intrathecal antisense oligonucleotide (nusinersen) therapy tend to show improved motor function, but the treatment effect on cellular health remains unknown. The objective of this study was to assess the potential of extracellular RNAs and microRNAs in SMA patient CSF as indicators of neuron and glial health following nusinersen treatment. Extracellular RNA analysis of CSF samples revealed ongoing cellular stress related to inflammation and glial differentiation, even after treatment administration. Downregulated microRNA expression associated with SMA-specific or general motor neuron dysfunction in animal and cellular models, tended to increase in nusinersen treated patient CSF samples and correlated with SMA Type 1 and 2 motor functioning improvements. However, miR-146a, known to be upregulated in SMA induced pluripotent stem cell (iPSC)-derived astrocytes, showed increased expression in nusinersen treated CSF samples. We then used mRNA sequencing and multi-electrode arrays to assess the transcriptional and functional effects of miR-146a on healthy and SMA iPSC-derived motor neurons. miR-146a treatment on iPSC-derived motor neurons led to a downregulation of extracellular matrix genes associated with synaptic perineuronal net and alterations in spontaneous electrophysiological activity. Together, this study suggests that extracellular RNAs and microRNAs may serve as useful biomarkers to monitor cellular health during nusinersen treatment. Moreover, these data highlight the importance of addressing astrocyte health and response to nusinersen in SMA pathogenesis and treatment strategies.

Intrathecal catheter and port placement for nusinersen infusion in children with spinal muscular atrophy and spinal fusion

BACKGROUND

Spinal administration of medications is challenging in patients with complete posterior spinal fusion. We describe percutaneous image-guided intrathecal port placement for administration of the antisense oligonucleotide nusinersen for children and young adults with spinal muscular atrophy.

OBJECTIVE

To describe and present our initial experience with a new technique for administering nusinersen in patients with spinal muscular atrophy and posterior spinal fusion.

MATERIALS AND METHODS

We reviewed medical records of 13 patients who received intrathecal ports using DynaCT, biplane fluoroscopy and iGuide from April 2018 through June 2019, and we describe the clinical course over 1 year.

RESULTS

Image-guided catheter and port implantation was successful in all cases. Two ports were subsequently removed, one for persistent cerebrospinal fluid leak and one for superficial infection. The other 11 have functioned successfully for a minimum of 23 months.

CONCLUSION

We report our experience with image-guided intrathecal port placement in children with complete posterior spine fusion. The implanted port permits dosing in an outpatient setting and avoids the need for multiple future radiologic procedures, and it reduces discomfort, procedural costs and potential risks and sequelae of multiple anesthetics and radiation exposures. Further studies are needed to define the relative risks and benefits of intrathecal ports compared to other approaches such as repeated transforaminal lumbar punctures.

Recombinant Adeno-Associated Virus Serotype 9 Gene Therapy in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by deletion or mutation of the SMN1 gene. It is characterized by a progressive loss of motor neurons resulting in muscle weakness. The disease affects 1 in 11,000 live births and before the era of treatment SMA was a leading genetic cause of mortality in infants. Recently, disease modifying therapies have been introduced in clinical practice. They include intrathecal and oral antisense oligonucleotides binding to pre-mRNA of SMN2 gene and increasing the translation of fully functional SMN protein as well as SMN1 gene replacement therapy. Onasemnogene abeparvovec uses the adeno-associated virus 9 (AAV9) vector to deliver the SMN1 gene. Phase 1 and phase 3 clinical trials showed that a single administration of onasemnogene abeparvovec resulted in improvement of motor functions in the majority of infants with SMA. Currently, phase 3 trials in SMA1 and SMA2 patients, as well as presymptomatic infants diagnosed with SMA, are ongoing. The drug was approved for medical use in the US in 2019, and in Japan and the European Union in 2020. Thus, first real-world data on efficacy and safety of onasemnogene abeparvovec in SMA patients are available.

Gene replacement therapy with onasemnogene abeparvovec in children with spinal muscular atrophy aged 24 months or younger and bodyweight up to 15 kg: an observational cohort study

BACKGROUND

Given the novelty of gene replacement therapy with onasemnogene abeparvovec in spinal muscular atrophy, efficacy and safety data are limited, especially for children older than 24 months, those weighing more than 8·5 kg, and those who have received nusinersen. We aimed to provide real-world data on motor function and safety after gene replacement therapy in different patient subgroups.

METHODS

We did a protocol-based, multicentre prospective observational study between Sept 21, 2019, and April 20, 2021, in 18 paediatric neuromuscular centres in Germany and Austria. All children with spinal muscular atrophy types 1 and 2 receiving onasemnogene abeparvovec were included in our cohort, and there were no specific exclusion criteria. Motor function was assessed at the time of gene replacement therapy and 6 months afterwards, using the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) and Hammersmith Functional Motor Scale-Expanded (HFMSE) scores. Additionally, in children pretreated with nusinersen, motor function was assessed before and after treatment switch. Off-target adverse events were analysed with a focus on liver function, thrombocytopaenia, and potential cardiotoxicity.

FINDINGS

76 children (58 pretreated with nusinersen and 18 who were nusinersen naive) with spinal muscular atrophy were treated with onasemnogene abeparvovec at a mean age of 16·8 months (range 0·8-59·0, IQR 9-23) and a mean weight of 9·1 kg (range 4·0-15·0, IQR 7·4-10·6). In 60 patients with available data, 49 had a significant improvement on the CHOP-INTEND score (≥4 points) and HFMSE score (≥3 points). Mean CHOP INTEND scores increased significantly in the 6 months after therapy in children younger than 8 months (n=16; mean change 13·8 [SD 8·5]; p<0·0001) and children aged between 8 and 24 months (n=34; 7·7 [SD 5·2]; p<0·0001), but not in children older than 24 months (n=6; 2·5 [SD 5·2]; p=1·00). In the 45 children pretreated with nusinersen and had available data, CHOP INTEND score increased by 8·8 points (p=0·0003) at 6 months after gene replacement therapy. No acute complications occurred during infusion of onasemnogene abeparvovec, but 56 (74%) patients had treatment-related side-effects. Serious adverse events occurred in eight (11%) children. Liver enzyme elevation significantly increased with age and weight at treatment. Six (8%) patients developed acute liver dysfunction. Other adverse events included pyrexia (n=47 [62%]), vomiting or loss of appetite (41 [54%]), and thrombocytopenia (n=59 [78%]). Prednisolone treatment was significantly prolonged with a mean duration of 15·7 weeks (IQR 9-19), mainly due to liver enzyme elevation. Cardiac adverse events were rare; only two patients had abnormal echocardiogram and echocardiography findings.

INTERPRETATION

This study provides class IV evidence that children with spinal muscular atrophy aged 24 months or younger and patients pretreated with nusinersen significantly benefit from gene replacement therapy, but adverse events can be severe and need to be closely monitored.

FUNDING

None.

TRANSLATION

For the German translation of the abstract see Supplementary Materials section.

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

Background

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

Main body

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

Conclusion

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

Supplementary Information

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

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

BACKGROUND

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

METHODS

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

FINDINGS

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

INTERPRETATION

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

FUNDING

Novartis Gene Therapies.

Matching-adjusted indirect treatment comparison of onasemnogene abeparvovec and nusinersen for the treatment of symptomatic patients with spinal muscular atrophy type 1

OBJECTIVE

Onasemnogene abeparvovec, a one-time intravenous gene replacement therapy, and nusinersen, an antisense oligonucleotide that requires ongoing intrathecal administration, have been evaluated as treatments for spinal muscular atrophy (SMA) type 1 in separate Phase III trials, but no head-to-head comparison studies have been conducted. Onasemnogene abeparvovec was compared with nusinersen using a matching-adjusted indirect comparison (MAIC) to estimate the treatment effect of onasemnogene abeparvovec relative to nusinersen for the treatment of symptomatic patients with SMA type 1 for up to 24 months of follow-up.

METHODS

In the absence of studies for both onasemnogene abeparvovec and nusinersen with a common comparator, a Bayesian naïve indirect treatment comparison (ITC) and MAIC between onasemnogene abeparvovec and nusinersen were conducted to compare efficacy and safety of onasemnogene abeparvovec with nusinersen. Outcomes of interest were event-free survival (EFS), overall survival (OS), and motor milestone achievements (independent sitting and independent walking). Relative treatment effects were expressed as relative risk (RR) and risk difference.

RESULTS

Pooled and weighted patient-level data illustrated a favorable effect toward onasemnogene abeparvovec, suggesting longer EFS for patients compared with nusinersen (HR of onasemnogene abeparvovec vs. nusinersen: 0.19 [95% CI: 0.07-0.54; 99% CI: 0.05-0.74]). At 24 months of follow-up, patients receiving onasemnogene abeparvovec were statistically significantly more likely to achieve the motor milestone of sitting independently compared with patients treated with nusinersen. Although statistically significant differences were not observed at 6 to 18 months between treatment options, the likelihood of sitting independently at 12 and 18 months numerically favored onasemnogene abeparvovec. A numerically greater likelihood of walking by 18 and 24 months was also observed for patients treated with onasemnogene abeparvovec compared with nusinersen. Onasemnogene abeparvovec therapy was also associated with a favorable (but statistically nonsignificant) outcome for OS and may be associated with prolonged survival compared with nusinersen (HR of onasemnogene abeparvovec vs. nusinersen: 0.35 [95% CI: 0.09-1.32; 99% CI: 0.06-2.01]). Bayesian naïve ITC results were similar to the MAIC analysis for EFS, OS, and motor milestone achievements. Small sample size limited covariate matching to baseline CHOP INTEND and nutritional support requirement, leading to wider CIs and statistically inconclusive outcomes for some of the results.

CONCLUSIONS

Despite limitations of the current MAIC analysis (mainly a small sample size for statistical testing, even for the pooled onasemnogene abeparvovec trials, and potential differences in prognostic and predictive factors between studies), the relative treatment effects in EFS, OS, and motor milestone achievement indicate that onasemnogene abeparvovec may offer continued benefit compared with nusinersen through 24 months of follow-up.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Understanding European patient expectations towards current therapeutic development in spinal muscular atrophy

Following the 2017 approval of a first spinal muscular atrophy (SMA) treatment by the European Medicines Agency, SMA Europe launched a Europe-wide survey with the goal of understanding patients' treatment expectations, realities of daily living and access to clinical trials and therapy, and how this varied according to parameters such as age and disease severity. A response rate of 31% yielded 1474 completed surveys from 26 European countries. In line with findings from a 2015 SMA Europe-led survey, participants considered stabilization of their condition to be progress. Notably, responses indicated that the current classification of SMA at diagnosis by 'type' often does not reflect current mobility level. Large gaps in treatment access were identified that varied in particular between age and disease severity groups, yet there was high interest in clinical trial participation. In addition, alternative treatment options, including combination therapies, are now expectations. These perspectives should be central considerations through the research and development processes of new SMA therapies, through data generation and discussions on access to therapies. Results from this survey indicate that collaboration between stakeholders is essential to the foundation upon which innovative approaches for SMA treatments and access can be explored.

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

BACKGROUND

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

METHODS

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

FINDINGS

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

INTERPRETATION

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

FUNDING

Novartis Gene Therapies.

Combination molecular therapies for spinal muscular atrophy: How much is enough?

See article on Issue MUS 62:4 pages 550–554.

In Search of a Cure: The Development of Therapeutics to Alter the Progression of Spinal Muscular Atrophy

Until the recent development of disease-modifying therapeutics, spinal muscular atrophy (SMA) was considered a devastating neuromuscular disease with a poor prognosis for most affected individuals. Symptoms generally present during early childhood and manifest as muscle weakness and progressive paralysis, severely compromising the affected individual’s quality of life, independence, and lifespan. SMA is most commonly caused by the inheritance of homozygously deleted SMN1 alleles with retention of one or more copies of a paralog gene, SMN2, which inversely correlates with disease severity. The recent advent and use of genetically targeted therapies have transformed SMA into a prototype for monogenic disease treatment in the era of genetic medicine. Many SMA-affected individuals receiving these therapies achieve traditionally unobtainable motor milestones and survival rates as medicines drastically alter the natural progression of this disease. This review discusses historical SMA progression and underlying disease mechanisms, highlights advances made in therapeutic research, clinical trials, and FDA-approved medicines, and discusses possible second-generation and complementary medicines as well as optimal temporal intervention windows in order to optimize motor function and improve quality of life for all SMA-affected individuals.

Clinical Outcomes in Patients with Spinal Muscular Atrophy Type 1 Treated with Nusinersen

BackgroundSpinal muscular atrophy type 1 (SMA1) is a motor neuron disease associated with progressive muscle weakness, ventilatory failure, and reduced survival.Objective:To report the evaluation of the nusinersen, an antisense oligonucleotide, on the motor function of SMA1.MethodsThis was a longitudinal and observational study to assess the outcomes of nusinersen therapy in SMA1 patients using the HINE-2 and CHOP-INTEND scales.ResultsTwenty-one SMA1 patients (52.4% males) were included; the mean age at first symptoms was 2.7 months (SD =±1.5), and the mean disease duration at first dose was 34.1 (SD =±36.0) months. During posttreatment, the mean gain on the CHOP-INTEND was 4.9, 5.9, 6.6, and 14 points after 6, 12, 18, and 24 months, respectively. Starting medication with a disease duration of less than 12 months and/or without invasive ventilation were predictors of response on CHOP-INTEND. Of the patients, 28.6% acquired a motor milestone or gained at least three points on the HINE-2. The daily time for ventilatory support was reduced after treatment in most of the patients with noninvasive ventilation at baseline. No change in the daytime use of ventilation was observed in most of the patients using invasive ventilation at baseline.ConclusionsNusinersen produces improvements in motor and respiratory functions, even in long-term SMA1 patients. However, patients under invasive ventilation at the beginning of the treatment experience little benefit.