Onasemnogene abeparvovec preserves bulbar function in infants with presymptomatic spinal muscular atrophy: a post-hoc analysis of the SPR1NT trial.

Bulbar function in spinal muscular atrophy has been defined as the ability to meet nutritional needs by mouth while maintaining airway protection and communicate verbally. The effects of disease-modifying treatment on bulbar function are not clear. A multidisciplinary team conducted post-hoc analyses of phase 3 SPR1NT trial data to evaluate bulbar function of infants at risk for spinal muscular atrophy who received one-time gene replacement therapy (onasemnogene abeparvovec) before symptom onset. Three endpoints represented adequate bulbar function in SPR1NT: (1) absence of physiologic swallowing impairment, (2) full oral nutrition, and (3) absence of adverse events indicating pulmonary instability. Communication was not assessed in SPR1NT. We descriptively assessed numbers/percentages of children who achieved each endpoint and all three collectively. SPR1NT included infants <6 postnatal weeks with two (n = 14) or three (n = 15) copies of the survival motor neuron 2 gene. At study end (18 [two-copy cohort] or 24 [three-copy cohort] months of age), 100% (29/29) of patients swallowed normally, achieved full oral nutrition, maintained pulmonary stability, and achieved the composite endpoint. When administered to infants before clinical symptom onset, onasemnogene abeparvovec allowed children at risk for spinal muscular atrophy to achieve milestones within published normal ranges of development and preserve bulbar function.

Patients with Spinal Muscular Atrophy Type 1 Achieve and Maintain Bulbar Function Following Onasemnogene Abeparvovec Treatment.

BACKGROUND: Improvement and maintenance of bulbar function are goals of disease-modifying treatments for spinal muscular atrophy (SMA). Lack of standardized measures and a widely accepted definition of bulbar function represents a gap in SMA care. OBJECTIVE: A multidisciplinary team conducted post-hoc analyses of pooled data from one phase 1 (START) and two phase 3 (STR1VE-US, STR1VE-EU) studies to define and evaluate bulbar function of infants with SMA type 1 after receiving one-time gene replacement therapy, onasemnogene abeparvovec. METHODS: We defined bulbar function as the ability to meet nutritional needs while maintaining airway protection and the ability to communicate verbally. Four endpoints represented adequate bulbar function: (1) absence of clinician-identified physiologic swallowing impairment, (2) receiving full oral nutrition, (3) absence of adverse events indicating pulmonary instability, and (4) the ability to vocalize at least two different, distinct vowel sounds. We descriptively assessed numbers/percentages of patients who achieved each endpoint and all four collectively. Patients were followed until 18 months old (STR1VE-US and STR1VE-EU) or 24 months (START) post-infusion. RESULTS: Overall, 65 patients were analyzed for swallowing, nutrition intake, and adverse events, and 20 were analyzed for communication. At study end, 92% (60/65) of patients had a normal swallow, 75% (49/65) achieved full oral nutrition, 92% (60/65) had no evidence of pulmonary instability, 95% (19/20) met the communication endpoint, and 75% (15/20) achieved all four bulbar function components in the composite endpoint. CONCLUSIONS: In these three clinical trials, patients with SMA type 1 who received onasemnogene abeparvovec achieved and maintained the bulbar function criteria utilized within this investigation.

Safety of Onasemnogene Abeparvovec for Patients With Spinal Muscular Atrophy 8.5 kg or Heavier in a Global Managed Access Program.

BACKGROUND: Spinal muscular atrophy is a rare, neurodegenerative disorder caused by biallelic deletions in the survival motor neuron (SMN1) gene. Onasemnogene abeparvovec is a one-time, intravenous gene replacement therapy designed to deliver the SMN1 transgene. Although available in many geographies, it is not approved globally. The Global Managed Access Program (GMAP) expanded treatment access to patients in countries where treatment was not approved. Previous onasemnogene abeparvovec clinical trials included patients with body weight <8.5 kg. Through GMAP, children weighing ≥8.5 kg received onasemnogene abeparvovec. We describe safety data for heavier patients in GMAP. METHODS: GMAP records were reviewed to identify patients weighing ≥8.5 kg at onasemnogene abeparvovec dosing. To obtain corresponding adverse event (AE) data, the Novartis ARGUS safety database was searched using patient identification numbers and birth dates/dosing dates for any reported AE for GMAP patients. RESULTS: As of September 2, 2021, 102 patients weighing ≥8.5 kg at time of dosing were identified. Fifty-four (53%) had one or more reported AEs. Three patients were reported to be deceased. All three deaths were assessed to be secondary to acute respiratory events. Most (62%) AEs were non-serious. The most frequently reported AEs included increases in hepatic laboratory values, decreased platelets and thrombocytopenia, pyrexia, vomiting, and decreased appetite. CONCLUSIONS: Safety findings for patients weighing ≥8.5 kg administered onasemnogene abeparvovec through GMAP were consistent with those described in clinical trials and included hepatotoxicity, thrombotic microangiopathy, and thrombocytopenia.

Clinical Trial and Postmarketing Safety of Onasemnogene Abeparvovec Therapy.

INTRODUCTION: This is the first description of safety data for intravenous onasemnogene abeparvovec, the only approved systemically administered gene-replacement therapy for spinal muscular atrophy. OBJECTIVE: We comprehensively assessed the safety of intravenous onasemnogene abeparvovec from preclinical studies, clinical studies, and postmarketing data. METHODS: Single-dose toxicity studies were performed in neonatal mice and juvenile or neonatal cynomolgus nonhuman primates (NHPs). Data presented are from a composite of preclinical studies, seven clinical trials, and postmarketing sources (clinical trials, n = 102 patients; postmarketing surveillance, n = 665 reported adverse event [AE] cases). In clinical trials, safety was assessed through AE monitoring, vital-sign and cardiac assessments, laboratory evaluations, physical examinations, and concomitant medication use. AE reporting and available objective clinical data from postmarketing programs were evaluated. RESULTS: The main target organs of toxicity in mice were the heart and liver. Dorsal root ganglia (DRG) inflammation was observed in NHPs. Patients exhibited no evidence of sensory neuropathy upon clinical examination. In clinical trials, 101/102 patients experienced at least one treatment-emergent AE. In total, 50 patients experienced serious AEs, including 11 considered treatment related. AEs consistent with hepatotoxicity resolved with prednisolone in clinical trials. Transient decreases in mean platelet count were detected but were without bleeding complications. Thrombotic microangiopathy (TMA) was observed in the postmarketing setting. No evidence of intracardiac thrombi was observed for NHPs or patients. CONCLUSIONS: Risks associated with onasemnogene abeparvovec can be anticipated, monitored, and managed. Hepatotoxicity events resolved with prednisolone. Thrombocytopenia was transient. TMA may require medical intervention. Important potential risks include cardiac AEs and DRG toxicity.

The Cure SMA Membership Surveys: Highlights of Key Demographic and Clinical Characteristics of Individuals with Spinal Muscular Atrophy.

BACKGROUND: Cure SMA maintains the largest patient-reported database for people affected with spinal muscular atrophy (SMA). In 2017, Cure SMA initiated annual surveys with their membership to collect demographic and disease characteristics, healthcare, and burden of disease information from patients and caregivers. OBJECTIVE: To summarize results from two large-scale Cure SMA surveys in 2017 and 2018. METHODS: Cure SMA database members were invited to complete surveys; these were completed by caregivers for living or deceased individuals with SMA and/or affected adults. RESULTS: In 2017, 726 surveys were completed for 695 individuals with SMA; in 2018, 796 surveys were completed for 760 individuals with SMA. Data from both survey years are available for 313 affected individuals. Age at symptom onset, distribution of SMN2 gene copy number, and representation of each SMA type in the surveys were consistent with that expected in the SMA population. In the 2018 survey, the average age at diagnosis was 5.2 months for SMA type I and the reported mean age at death for this subgroup was 27.8 months. Between survey years, there was consistency in responses for factors that should not change within individuals over time (e.g., reported age at diagnosis). CONCLUSIONS: Results from the Cure SMA surveys advance the understanding of SMA and facilitate advocacy efforts and healthcare services planning. Longitudinal surveys are important for evaluating the impact of effective treatments on changing phenotypes, and burden of disease and care in individuals with SMA.

Thrombotic Microangiopathy Following Onasemnogene Abeparvovec for Spinal Muscular Atrophy: A Case Series.

Spinal muscular atrophy is treated with onasemnogene abeparvovec, which replaces the missing survival motor neuron 1 gene via an adeno-associated virus vector. As of July 1, 2020, we had identified 3 infants who developed thrombotic microangiopathy following onasemnogene abeparvovec. Early recognition and treatment of drug-induced thrombotic microangiopathy may lessen mortality and morbidity.

Outcome measures in a cohort of ambulatory adults with spinal muscular atrophy.

INTRODUCTION: With the advent of disease-altering therapies for spinal muscular atrophy (SMA), there is a requirement to better characterize outcome measures, particularly in milder forms of disease. METHODS: Maximal voluntary isometric contraction testing and 6-minute walk test (6MWT) performed in ambulatory SMA adults as part of the SMA-VALIANT trial were analyzed. Test-retest reliability and correlation with other candidate biomarkers and outcomes were investigated. RESULTS: Maximal voluntary isometric contraction testing and 6MWT showed good test-retest reliability (intraclass correlation coefficient = 0.98 and 0.85, respectively). Maximal voluntary isometric contraction testing and 6MWT demonstrated very strong correlation (r = 0.83, P <. 0001), and each correlated with the SMA Functional Rating Scale (r = 0.7, P < .0001 and r = 0.65, P = .0001, respectively), lean muscle mass (r = 0.68, P < .0001 and r = 0.56, P = .001, respectively), and ulnar compound muscle action potential (r = 0.57, P = .0008 and r = 0.47, P = .008, respectively). DISCUSSION: Maximal voluntary isometric contraction testing and 6MWT are suitable outcomes for use in ambulatory adults with SMA. Maximal voluntary isometric contraction testing may be preferable because of superior test-retest reliability and closer associations with other outcomes and biomarkers of neuromuscular function.

Spinal Muscular Atrophy (SMA) Subtype Concordance in Siblings: Findings From the Cure SMA Cohort.

BACKGROUND: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by homozygous survival of motor neuron 1 (SMN1) gene disruption. Despite a genetic etiology, little is known about subtype concordance among siblings. OBJECTIVE: To investigate subtype concordance among siblings with SMA. METHODS: Cure SMA maintains a database of newly diagnosed patients with SMA, which was utilized for this research. RESULTS: Among 303 sibships identified between 1996 and 2016, 84.8% were subtype concordant. Of concordant sibships, subtype distribution was as follows: Type I, 54.5%; Type II, 31.9%; Type III, 13.2%; Type IV, 0.4%. Subtype and concordance/discordance association was significant (Fisher's exact test; p < 0.0001). Among discordant sibships (chi-square test, p < 0.0001), Types II/III (52.2%) and Types I/II (28.3%) were the most common pairs. No association was found between sibling sex and concordance. Our findings show that most siblings with SMA shared the same subtype concordance (most commonly Type I). CONCLUSIONS: These data are valuable for understanding familial occurrence of SMA subtypes, enabling better individual treatment and management planning in view of new treatment options and newborn screening initiatives.

Nusinersen initiated in infants during the presymptomatic stage of spinal muscular atrophy: Interim efficacy and safety results from the Phase 2 NURTURE study.

Spinal muscular atrophy (SMA) is a neurodegenerative disease associated with severe muscle atrophy and weakness in the limbs and trunk. We report interim efficacy and safety outcomes as of March 29, 2019 in 25 children with genetically diagnosed SMA who first received nusinersen in infancy while presymptomatic in the ongoing Phase 2, multisite, open-label, single-arm NURTURE trial. Fifteen children have two SMN2 copies and 10 have three SMN2 copies. At last visit, children were median (range) 34.8 [25.7-45.4] months of age and past the expected age of symptom onset for SMA Types I or II; all were alive and none required tracheostomy or permanent ventilation. Four (16%) participants with two SMN2 copies utilized respiratory support for ≥6 h/day for ≥7 consecutive days that was initiated during acute, reversible illnesses. All 25 participants achieved the ability to sit without support, 23/25 (92%) achieved walking with assistance, and 22/25 (88%) achieved walking independently. Eight infants had adverse events considered possibly related to nusinersen by the study investigators. These results, representing a median 2.9 years of follow up, emphasize the importance of proactive treatment with nusinersen immediately after establishing the genetic diagnosis of SMA in presymptomatic infants and emerging newborn screening efforts.

Recruitment & retention program for the NeuroNEXT SMA Biomarker Study: Super Babies for SMA!

BACKGROUND/AIMS: Recruitment and retention of research participants are challenging and critical components of successful clinical trials and natural history studies. Infants with spinal muscular atrophy (SMA) have been a particularly challenging population to study due to their fragile and complex medical issues, poor prognosis and, until 2016, a lack of effective therapies. Recruitment of healthy infants into clinical trials and natural history studies is also challenging and sometimes assumed to not be feasible. METHODS: In 2011, our group initiated a two-year, longitudinal natural history study of infants with SMA and healthy infant controls to provide data to assist in the analysis and interpretation of planned clinical trials in infants with SMA. The recruitment goal was to enroll 27 infants less than 6 months of age with SMA and 27 age-matched healthy infants within the two-year enrollment period. A detailed recruitment and retention plan was developed for this purpose. In addition, a survey was administered to participant families to understand the determinants of participation in the study. RESULTS: All healthy infants were recruited within the study's first year and 26 SMA infants were recruited within the two-year recruitment period. Thirty-eight participant families responded to the recruitment determinants survey. Nearly half of respondents (18/38, 48%) reported that they first heard of the study from their physician or neurologist. The most common reason to decide to enroll their infant (22/38, 58%) and to remain in the study (28/38, 74%) was their understanding of the importance of the study. Thematic recruitment tools such as a study brochure, video on social media, and presentations at advocacy meetings were reported to positively influence the decision to enroll. CONCLUSIONS: A proactive, thematic and inclusive recruitment and retention plan that effectively communicates the rationale of a clinical study and partners with patients, advocacy groups and the local communities can effectively recruit participants in vulnerable populations. Recommendations for the proactive integration of recruitment and retention plans into clinical trial protocol development are provided.

Clinical trial of L-Carnitine and valproic acid in spinal muscular atrophy type I.

INTRODUCTION: The aim of this study was to determine the safety and therapeutic potential of L-carnitine and valproic acid (VPA) in infants with spinal muscular atrophy (SMA). METHODS: Our investigation was an open-label phase 2 multicenter trial of L-carnitine and VPA in infants with SMA type I with retrospective comparison to an untreated, matched cohort. Primary outcomes were: safety and adverse events; secondary outcomes were survival, time to death/>16 hours/day of ventilator support; motor outcomes; and maximum ulnar compound motor action potential amplitude. RESULTS: A total of 245 AEs were observed in 35 of the 37 treated subjects (95%). Respiratory events accounted for 49% of all adverse events, resulting in 14 deaths. Survival was not significantly different between treated and untreated cohorts. DISCUSSION: This trial provides evidence that, in infants with SMA type I, L-carnitine/VPA is ineffective at altering survival. The substantial proportion of infants reaching end-points within 6 months of enrollment underscores the urgent need for pre-symptomatic treatment in SMA type I. Muscle Nerve 57: 193-199, 2018.

Indirect estimation of the prevalence of spinal muscular atrophy Type I, II, and III in the United States.

BACKGROUND: Spinal muscular atrophy (SMA) is a progressive, devastating disease and a leading inherited cause of infant mortality. The limited population-based literature is confined to small regional studies. Estimates of prevalence are needed to characterize the burden of SMA and to understand trends in prevalence by disease type as new treatments become available. The reported estimates of SMA genotype prevalence at birth consistently range from 8.5-10.3 per 100,000 live births, with a mid-range estimate of 9.4 per 100,000. Among infants born with an SMA genotype, it is reported that ~58% will develop SMA Type I, 29% will develop Type II, and 13% will develop Type III, respectively. RESULTS: Using evidence from peer-reviewed literature for SMA birth prevalence, age at symptom onset, and SMA type-specific survival, and incorporating United States vital statistics, we constructed life tables to estimate prevalence for SMA Types I, II, and III in the United States. We estimated the number of prevalent cases in the US to be 8526, 9429, and 10,333 based on a birth prevalence of 8.5, 9.4, and 10.3, respectively (the lower, midpoint, and upper ends of the reported range). Assuming the midpoint of 9.4 and US-reported survival, the type-specific population prevalence estimates were 1610 for SMA Type I, 3944 for SMA Type II, and 3875 for SMA Type III. Evidence-based estimates of the number of people living with SMA in the United States in the published literature were previously unavailable. CONCLUSIONS: In the absence of a survey or other means to directly estimate prevalence in the US population, estimates can be calculated indirectly using a life table.

Natural history of infantile-onset spinal muscular atrophy.

OBJECTIVE: Infantile-onset spinal muscular atrophy (SMA) is the most common genetic cause of infant mortality, typically resulting in death preceding age 2. Clinical trials in this population require an understanding of disease progression and identification of meaningful biomarkers to hasten therapeutic development and predict outcomes. METHODS: A longitudinal, multicenter, prospective natural history study enrolled 26 SMA infants and 27 control infants aged <6 months. Recruitment occurred at 14 centers over 21 months within the NINDS-sponsored NeuroNEXT (National Network for Excellence in Neuroscience Clinical Trials) Network. Infant motor function scales (Test of Infant Motor Performance Screening Items [TIMPSI], The Children's Hospital of Philadelphia Infant Test for Neuromuscular Disorders, and Alberta Infant Motor Score) and putative physiological and molecular biomarkers were assessed preceding age 6 months and at 6, 9, 12, 18, and 24 months with progression, correlations between motor function and biomarkers, and hazard ratios analyzed. RESULTS: Motor function scores (MFS) and compound muscle action potential (CMAP) decreased rapidly in SMA infants, whereas MFS in all healthy infants rapidly increased. Correlations were identified between TIMPSI and CMAP in SMA infants. TIMPSI at first study visit was associated with risk of combined endpoint of death or permanent invasive ventilation in SMA infants. Post-hoc analysis of survival to combined endpoint in SMA infants with 2 copies of SMN2 indicated a median age of 8 months at death (95% confidence interval, 6, 17). INTERPRETATION: These data of SMA and control outcome measures delineates meaningful change in clinical trials in infantile-onset SMA. The power and utility of NeuroNEXT to provide "real-world," prospective natural history data sets to accelerate public and private drug development programs for rare disease is demonstrated. Ann Neurol 2017;82:883-891.

Pregnancy and delivery in women with spinal muscular atrophy.

OBJECTIVES: To expand the limited available knowledge about pregnancy and delivery in women with spinal muscular atrophy (SMA) using a cohort of genetically proven SMA patients from USA. METHODS: This was a cross-sectional questionnaire-based study. We mailed questionnaires to 58 women with confirmed SMA. RESULTS: Thirty-two women responded, reporting 35 pregnancies, including 19 women with at least one pregnancy. In this cohort, preterm labor and delivery by cesarean section were more common in mothers with SMA particularly SMA type 2. Seventy-four percent of mothers reported increased weakness during pregnancy that persisted after delivery in 42%. SMA mothers generally had a positive experience and good outcomes and elected to have more than one pregnancy. CONCLUSION: This information regarding pregnancy in women with genetically confirmed 5q SMA will prove useful in guiding future research and in providing counseling to women with SMA.

Baseline results of the NeuroNEXT spinal muscular atrophy infant biomarker study.

OBJECTIVE: This study prospectively assessed putative promising biomarkers for use in assessing infants with spinal muscular atrophy (SMA). METHODS: This prospective, multi-center natural history study targeted the enrollment of SMA infants and healthy control infants less than 6 months of age. Recruitment occurred at 14 centers within the NINDS National Network for Excellence in Neuroscience Clinical Trials (NeuroNEXT) Network. Infant motor function scales and putative electrophysiological, protein and molecular biomarkers were assessed at baseline and subsequent visits. RESULTS: Enrollment began November, 2012 and ended September, 2014 with 26 SMA infants and 27 healthy infants enrolled. Baseline demographic characteristics of the SMA and control infant cohorts aligned well. Motor function as assessed by the Test for Infant Motor Performance Items (TIMPSI) and the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) revealed significant differences between the SMA and control infants at baseline. Ulnar compound muscle action potential amplitude (CMAP) in SMA infants (1.4 ± 2.2 mV) was significantly reduced compared to controls (5.5 ± 2.0 mV). Electrical impedance myography (EIM) high-frequency reactance slope (Ohms/MHz) was significantly higher in SMA infants than controls SMA infants had lower survival motor neuron (SMN) mRNA levels in blood than controls, and several serum protein analytes were altered between cohorts. INTERPRETATION: By the time infants were recruited and presented for the baseline visit, SMA infants had reduced motor function compared to controls. Ulnar CMAP, EIM, blood SMN mRNA levels, and serum protein analytes were able to distinguish between cohorts at the enrollment visit.

Alternating Hemiplegia of Childhood: Retrospective Genetic Study and Genotype-Phenotype Correlations in 187 Subjects from the US AHCF Registry.

Mutations in ATP1A3 cause Alternating Hemiplegia of Childhood (AHC) by disrupting function of the neuronal Na+/K+ ATPase. Published studies to date indicate 2 recurrent mutations, D801N and E815K, and a more severe phenotype in the E815K cohort. We performed mutation analysis and retrospective genotype-phenotype correlations in all eligible patients with AHC enrolled in the US AHC Foundation registry from 1997-2012. Clinical data were abstracted from standardized caregivers' questionnaires and medical records and confirmed by expert clinicians. We identified ATP1A3 mutations by Sanger and whole genome sequencing, and compared phenotypes within and between 4 groups of subjects, those with D801N, E815K, other ATP1A3 or no ATP1A3 mutations. We identified heterozygous ATP1A3 mutations in 154 of 187 (82%) AHC patients. Of 34 unique mutations, 31 (91%) are missense, and 16 (47%) had not been previously reported. Concordant with prior studies, more than 2/3 of all mutations are clusteredin exons 17 and 18. Of 143 simplex occurrences, 58 had D801N (40%), 38 had E815K(26%) and 11 had G947R (8%) mutations [corrected].Patients with an E815K mutation demonstrate an earlier age of onset, more severe motor impairment and a higher prevalence of status epilepticus. This study further expands the number and spectrum of ATP1A3 mutations associated with AHC and confirms a more deleterious effect of the E815K mutation on selected neurologic outcomes. However, the complexity of the disorder and the extensive phenotypic variability among subgroups merits caution and emphasizes the need for further studies.

SMA valiant trial: a prospective, double-blind, placebo-controlled trial of valproic acid in ambulatory adults with spinal muscular atrophy.

INTRODUCTION: An open-label trial suggested that valproic acid (VPA) improved strength in adults with spinal muscular atrophy (SMA). We report a 12-month, double-blind, cross-over study of VPA in ambulatory SMA adults. METHODS: There were 33 subjects, aged 20­55 years, included in this investigation. After baseline assessment, subjects were randomized to receive VPA (10­20 mg/kg/day) or placebo. At 6 months, patients were switched to the other group. Assessments were performed at 3, 6, and 12 months. The primary outcome was the 6-month change in maximum voluntary isometric contraction testing with pulmonary, electrophysiological, and functional secondary outcomes. RESULTS: Thirty subjects completed the study. VPA was well tolerated, and compliance was good. There was no change in primary or secondary outcomes at 6 or 12 months. CONCLUSIONS: VPA did not improve strength or function in SMA adults. The outcomes used are feasible and reliable and can be employed in future trials in SMA adults.