104-week efficacy and safety of cipaglucosidase alfa plus miglustat in adults with late-onset Pompe disease: a phase III open-label extension study (ATB200-07)

The phase III double-blind PROPEL study compared the novel two-component therapy cipaglucosidase alfa + miglustat (cipa + mig) with alglucosidase alfa + placebo (alg + pbo) in adults with late-onset Pompe disease (LOPD). This ongoing open-label extension (OLE; NCT04138277) evaluates long-term safety and efficacy of cipa + mig. Outcomes include 6-min walk distance (6MWD), forced vital capacity (FVC), creatine kinase (CK) and hexose tetrasaccharide (Hex4) levels, patient-reported outcomes and safety. Data are reported as change from PROPEL baseline to OLE week 52 (104 weeks post-PROPEL baseline). Of 118 patients treated in the OLE, 81 continued cipa + mig treatment from PROPEL (cipa + mig group; 61 enzyme replacement therapy [ERT] experienced prior to PROPEL; 20 ERT naïve) and 37 switched from alg + pbo to cipa + mig (switch group; 29 ERT experienced; 8 ERT naive). Mean (standard deviation [SD]) change in % predicted 6MWD from baseline to week 104 was + 3.1 (8.1) for cipa + mig and - 0.5 (7.8) for the ERT-experienced switch group, and + 8.6 (8.6) for cipa + mig and + 8.9 (11.7) for the ERT-naïve switch group. Mean (SD) change in % predicted FVC was - 0.6 (7.5) for cipa + mig and - 3.8 (6.2) for the ERT-experienced switch group, and - 4.8 (6.5) and - 3.1 (6.7), respectively, in ERT-naïve patients. CK and Hex4 levels improved in both treatment groups by week 104 with cipa + mig treatment. Three patients discontinued the OLE due to infusion-associated reactions. No new safety signals were identified. Cipa + mig treatment up to 104 weeks was associated with overall maintained improvements (6MWD, biomarkers) or stabilization (FVC) from baseline with continued durability, and was well tolerated, supporting long-term benefits for patients with LOPD.Trial registration number: NCT04138277; trial start date: December 18, 2019.

Longitudinal changes of swallowing safety and efficiency in infants with spinal muscular atrophy who received disease modifying therapies

BACKGROUND

Dysphagia is a common feature of the natural history of patients with spinal muscular atrophy (SMA). Literature regarding swallowing safety and efficiency is scarce in patients with SMA, particularly in the era of newborn screening programs and disease-modifying therapies.

OBJECTIVE

To describe the longitudinal changes of swallowing safety and efficiency in children with SMA who received one or more disease modifying therapies METHODS: Case series of patients with SMA followed at the University of Florida from 1 May 2019 to 31 December 2022 who had two or more videofluoroscopy swallowing studies (VFSS), with the first being within 30 days of their first treatment. Data extracted from the electronic health record included: neuromotor outcomes, VFSS penetration aspiration scores (PAS), presence of abrnormal oral or pharyngeal residue, clinical history, and timing of disease-modifying therapies administration.

RESULTS

Seven subjects were included (five male); three were diagnosed via newborn screen. Median age at diagnosis was 10 days (range: 4-250). Median age at initial VFSS was 29 days (range: 9-246), and age at the last VFSS was 26.1 months (range: 18.2-36.2). All subjects received onasemnogene-abeparvovec (OA); four received additional therapies. PAS at diagnosis was abnormal in four subjects. Six subjects required feeding modifications after VFSS results. Of these, three had silent aspiration (PAS 8) and three of them improved after treatment.

CONCLUSIONS

Swallowing safety and efficiency can be impaired in patients with SMA despite early treatment. Larger, prospective studies are needed to define optimal timiing of longitudinal instrumental evaluations.

Long-term safety and efficacy of cipaglucosidase alfa plus miglustat in individuals living with Pompe disease: an open-label phase I/II study (ATB200-02)

Cipaglucosidase alfa plus miglustat (cipa + mig) is a novel, two-component therapy for Pompe disease. We report data from the Phase I/II ATB200-02 study for up to 48 months of treatment. Four adult cohorts, including one non-ambulatory ERT-experienced (n = 6) and three ambulatory cohorts, (two enzyme replacement therapy [ERT]-experienced cohorts [2-6 years (n = 11) and ≥ 7 years (n = 6)]), one ERT-naïve cohort (n = 6), received 20 mg/kg intravenous-infused cipa plus 260 mg oral mig biweekly. Change from baseline (CFBL) for multiple efficacy endpoints at 12, 24, 36, and 48 months, pharmacodynamics, pharmacokinetics, safety, and immunogenicity data were assessed. Six-minute walking distance (% predicted) improved at 12, 24, 36, and 48 months: pooled ambulatory ERT-experienced cohorts, mean(± standard deviation [SD]) CFBL: 6.1(± 7.84), n = 16; 5.4(± 10.56), n = 13; 3.4(± 14.66), n = 12; 5.9(± 17.36), n = 9, respectively; ERT-naïve cohort: 10.7(± 3.93), n = 6; 11.0(± 5.06), n = 6; 9.0(± 7.98), n = 5; 11.7(± 7.69), n = 4, respectively. Percent predicted forced vital capacity was generally stable in ERT-experienced cohorts, mean(± SD) CFBL - 1.2(± 5.95), n = 16; 1.0(± 7.96), n = 13; - 0.3(± 6.68), n = 10; 1.0(± 6.42), n = 6, respectively, and improved in the ERT-naïve cohort: 3.2(± 8.42), n = 6; 4.7(± 5.09), n = 6; 6.2(± 3.35), n = 5; 8.3(± 4.50), n = 4, respectively. Over 48 months, CK and Hex4 biomarkers improved in ambulatory cohorts. Overall, cipa + mig was well tolerated with a safety profile like alglucosidase alfa. ATB200-02 results show the potential benefits of cipa + mig as a long-term treatment option for Pompe disease. Trial registration number: NCT02675465 January 26, 2016.

Perspectives of the Friedreich ataxia community on gene therapy clinical trials

Gene therapy is a potential treatment for Friedreich ataxia, with multiple programs on the horizon. The purpose of this study was to collect opinions about gene therapy from individuals 14 years or older with Friedreich ataxia or parents/caregivers of Friedreich ataxia patients who were diagnosed as children 17 or younger. Participants were asked to complete a survey after reading brief educational materials regarding gene therapy. Most of the patients captured in this survey have an early-onset (classical) presentation of the disease. Participants expressed urgency in participating in gene therapy clinical trials despite the associated risks. About half of the respondents believed that gene therapy would cease progression or minimize symptoms, whereas nearly one-fourth expected to be cured. The survey also revealed how participants perceive their symptom burden, because a substantial majority reported that balance/walking issues most interfere with their quality of life and would be the symptom they would prioritize treating. Although not statistically significant, more caregivers prioritized treating cardiomyopathy than patients. This study provides valuable information on priorities, beliefs, and expectations regarding gene therapy and serves to guide future gene therapy opinion studies and gene therapy trial design.

B cell focused transient immune suppression protocol for efficient AAV readministration to the liver

Adeno-associated virus (AAV) vectors are used for correcting multiple genetic disorders. Although the goal is to achieve lifelong correction with a single vector administration, the ability to redose would enable the extension of therapy in cases in which initial gene transfer is insufficient to achieve a lasting cure, episomal vector forms are lost in growing organs of pediatric patients, or transgene expression is diminished over time. However, AAV typically induces potent and long-lasting neutralizing antibodies (NAbs) against capsid that prevents re-administration. To prevent NAb formation in hepatic AAV8 gene transfer, we developed a transient B cell-targeting protocol using a combination of monoclonal Ab therapy against CD20 (for B cell depletion) and BAFF (to slow B cell repopulation). Initiation of immunosuppression before (rather than at the time of) vector administration and prolonged anti-BAFF treatment prevented immune responses against the transgene product and abrogated prolonged IgM formation. As a result, vector re-administration after immune reconstitution was highly effective. Interestingly, re-administration before the immune system had fully recovered achieved further elevated levels of transgene expression. Finally, this immunosuppression protocol reduced Ig-mediated AAV uptake by immune cell types with implications to reduce the risk of immunotoxicities in human gene therapy with AAV.

The Clinical Development of Taldefgrobep Alfa: An Anti-Myostatin Adnectin for the Treatment of Duchenne Muscular Dystrophy

INTRODUCTION

Duchenne muscular dystrophy (DMD) is a genetic muscle disorder that manifests during early childhood and is ultimately fatal. Recently approved treatments targeting the genetic cause of DMD are limited to specific subpopulations of patients, highlighting the need for therapies with wider applications. Pharmacologic inhibition of myostatin, an endogenous inhibitor of muscle growth produced almost exclusively in skeletal muscle, has been shown to increase muscle mass in several species, including humans. Taldefgrobep alfa is an anti-myostatin recombinant protein engineered to bind to and block myostatin signaling. Preclinical studies of taldefgrobep alfa demonstrated significant decreases in myostatin and increased lower limb volume in three animal species, including dystrophic mice.

METHODS

This manuscript reports the cumulative data from three separate clinical trials of taldefgrobep alfa in DMD: a phase 1 study in healthy adult volunteers (NCT02145234), and two randomized, double-blind, placebo-controlled studies in ambulatory boys with DMD-a phase 1b/2 trial assessing safety (NCT02515669) and a phase 2/3 trial including the North Star Ambulatory Assessment (NSAA) as the primary endpoint (NCT03039686).

RESULTS

In healthy adult volunteers, taldefgrobep alfa was generally well tolerated and resulted in a significant increase in thigh muscle volume. Treatment with taldefgrobep alfa was associated with robust dose-dependent suppression of free myostatin. In the phase 1b/2 trial, myostatin suppression was associated with a positive effect on lean body mass, though effects on muscle mass were modest. The phase 2/3 trial found that the effects of treatment did not meet the primary endpoint pre-specified futility analysis threshold (change from baseline of ≥ 1.5 points on the NSAA total score).

CONCLUSIONS

The futility analysis demonstrated that taldefgrobep alfa did not result in functional change for boys with DMD. The program was subsequently terminated in 2019. Overall, there were no safety concerns, and no patients were withdrawn from treatment as a result of treatment-related adverse events or serious adverse events.

TRIAL REGISTRATION

NCT02145234, NCT02515669, NCT03039686.

Thrombotic microangiopathy following systemic AAV administration is dependent on anti-capsid antibodies

BACKGROUNDSystemic administration of adeno-associated virus (AAV) can trigger life-threatening inflammatory responses, including thrombotic microangiopathy (TMA), acute kidney injury due to atypical hemolytic uremic syndrome-like complement activation, immune-mediated myocardial inflammation, and hepatic toxicity.METHODSWe describe the kinetics of immune activation following systemic AAV serotype 9 (AAV9) administration in 38 individuals following 2 distinct prophylactic immunomodulation regimens. Group 1 received corticosteroids and Group 2 received rituximab plus sirolimus in addition to steroids to prevent anti-AAV antibody formation.RESULTSGroup 1 participants had a rapid increase in immunoglobulin M (IgM) and IgG. Increase in D-dimer, decline in platelet count, and complement activation are indicative of TMA. All Group 1 participants demonstrated activation of both classical and alternative complement pathways, as indicated by depleted C4 and elevated soluble C5b-9, Ba, and Bb antigens. Group 2 patients did not have a significant change in IgM or IgG and had minimal complement activation.CONCLUSIONSThis study demonstrates that TMA in the setting of AAV gene therapy is antibody dependent (classical pathway) and amplified by the alternative complement pathway. Critical time points and interventions are identified to allow for management of immune-mediated events that impact the safety and efficacy of systemic gene therapy.

Development of capsid- and genome-modified optimized AAVrh74 vectors for muscle gene therapy

The first generation of adeno-associated virus (AAV) vectors composed of the naturally occurring capsids and genomes, although effective in some instances, are unlikely to be optimal for gene therapy in humans. The use of the first generation of two different AAV serotype vectors (AAV9 and AAVrh74) in four separate clinical trials failed to be effective in patients with Duchenne muscular dystrophy, although some efficacy was observed in a subset of patients with AAVrh74 vectors leading to US Food and Drug Administration approval (Elevidys). In two trials with the first generation of AAV9 vectors, several serious adverse events were observed, including the death of a patient in one trial, and more recently, in the death of a second patient in an N-of-1 clinical trial. In a fourth trial with the first generation of AAVrh74 vectors, myositis and myocarditis were also observed. Here, we report that capsid- and genome-modified optimized AAVrh74 vectors are significantly more efficient in transducing primary human skeletal muscle cells in vitro and in all major muscle tissues in vivo following systemic administration in a murine model. The availability of optimized AAVrh74 vectors promises to be safe and effective in the potential gene therapy of muscle diseases in humans.

Evolving Horizons: Adenovirus Vectors' Timeless Influence on Cancer, Gene Therapy and Vaccines

Efficient and targeted delivery of a DNA payload is vital for developing safe gene therapy. Owing to the recent success of commercial oncolytic vector and multiple COVID-19 vaccines, adenovirus vectors are back in the spotlight. Adenovirus vectors can be used in gene therapy by altering the wild-type virus and making it replication-defective; specific viral genes can be removed and replaced with a segment that holds a therapeutic gene, and this vector can be used as delivery vehicle for tissue specific gene delivery. Modified conditionally replicative-oncolytic adenoviruses target tumors exclusively and have been studied in clinical trials extensively. This comprehensive review seeks to offer a summary of adenovirus vectors, exploring their characteristics, genetic enhancements, and diverse applications in clinical and preclinical settings. A significant emphasis is placed on their crucial role in advancing cancer therapy and the latest breakthroughs in vaccine clinical trials for various diseases. Additionally, we tackle current challenges and future avenues for optimizing adenovirus vectors, promising to open new frontiers in the fields of cell and gene therapies.

Current avenues of gene therapy in Pompe disease

PURPOSE OF REVIEW

Pompe disease is a rare, inherited, devastating condition that causes progressive weakness, cardiomyopathy and neuromotor disease due to the accumulation of glycogen in striated and smooth muscle, as well as neurons. While enzyme replacement therapy has dramatically changed the outcome of patients with the disease, this strategy has several limitations. Gene therapy in Pompe disease constitutes an attractive approach due to the multisystem aspects of the disease and need to address the central nervous system manifestations. This review highlights the recent work in this field, including methods, progress, shortcomings, and future directions.

RECENT FINDINGS

Recombinant adeno-associated virus (rAAV) and lentiviral vectors (LV) are well studied platforms for gene therapy in Pompe disease. These products can be further adapted for safe and efficient administration with concomitant immunosuppression, with the modification of specific receptors or codon optimization. rAAV has been studied in multiple clinical trials demonstrating safety and tolerability.

SUMMARY

Gene therapy for the treatment of patients with Pompe disease is feasible and offers an opportunity to fully correct the principal pathology leading to cellular glycogen accumulation. Further work is needed to overcome the limitations related to vector production, immunologic reactions and redosing.

Adeno-associated virus-mediated gene therapy in a patient with Canavan disease using dual routes of administration and immune modulation

Gene replacement therapy is a rational therapeutic strategy and clinical intervention for neurodegenerative disorders like Canavan disease, a leukodystrophy caused by biallelic mutations in the aspartoacylase (ASPA) gene. We aimed to investigate whether simultaneous intravenous (i.v.) and intracerebroventricular (i.c.v.) administration of rAAV9-CB6-ASPA provides a safe and effective therapeutic strategy in an open-label, individual-patient, expanded-access trial for Canavan disease. Immunomodulation was given prophylactically prior to adeno-associated virus (AAV) treatment to prevent an immune response to ASPA or the vector capsid. The patient served as his own control, and change from baseline was assessed by clinical pathology tests, vector genomes in the blood, antibodies against ASPA and AAV capsids, levels of cerebrospinal fluid (CSF) N-acetylaspartate (NAA), brain water content and morphology, clinical status, and motor function tests. Two years post treatment, the patient's white matter myelination had increased, motor function was improved, and he remained free of typical severe epilepsy. NAA level was reduced at 3 months and remained stable up to 4 years post treatment. Immunomodulation prior to AAV exposure enables repeat dosing and has prevented an anti-transgene immune response. Dual-route administration of gene therapy may improve treatment outcomes.

Elevated liver glycogenolysis mediates higher blood glucose during acute exercise in Barth syndrome

Barth syndrome (BTHS) is an X-linked recessive genetic disorder due to mutations in the Tafazzin (TAFAZZIN) gene that lead to cardiac and skeletal muscle mitochondrial dysfunction. Previous studies in humans with BTHS demonstrate that the defects in muscle mitochondrial oxidative metabolism result in an enhanced reliance on anaerobic metabolism during exercise to meet energy demands of muscular work. During exercise, the liver normally increases glucose production via glycogenolysis and gluconeogenesis to match the elevated rate of muscle glucose uptake and meet the ATP requirements of working muscle. However, the impact of Tafazzin deficiency on hepatic glucose production and the pathways contributing to hepatic glucose production during exercise is unknown. Therefore, the purpose of this study was to quantify in vivo liver gluconeogenesis and glycogenolysis in Tafazzin knockdown mice at rest and during acute exercise.

METHODS

Male TAFAZZIN shRNA transgenic (TG) and wild-type (WT) mice completed exhaustive treadmill running protocols to test exercise tolerance. Mice underwent 2H- and 13C-stable isotope infusions at rest and during a 30-minute treadmill running bout to quantify hepatic glucose production and associated nutrient fluxes under sedentary conditions and during acute exercise. Circulating and tissue (skeletal muscle and liver) samples were obtained during and following exercise to assess static metabolite levels.

RESULTS

TG mice reached exhaustion sooner during exhaustive treadmill running protocols and exhibited higher plasma lactate concentrations after exhaustive exercise compared to WT mice. Arterial glucose levels were comparable between genotypes at rest, but higher in TG mice compared to WT mice during exercise. Consistent with the higher blood glucose, TG mice showed increased endogenous glucose production owing to elevated glycogenolysis compared to WT mice during exercise. Total gluconeogenesis, gluconeogenesis from glycerol, gluconeogenesis from phosphoenolpyruvate, pyruvate cycling, total cataplerosis, and anaplerotic fluxes were similar between TG and WT mice at rest and during exercise. However, lactate dehydrogenase flux and TCA cycle fluxes trended higher in TG mice during exercise. Liver glycogen content in TG was higher in TG vs. controls.

CONCLUSION

Our data in the Tafazzin knockdown mouse suggest that elevated anaerobic metabolism during rest and exercise previously reported in humans with BTHS are supported by the finding of higher hepatic glycogenolysis.

The multifaceted roles of the brain glycogen

Glycogen is a biologically essential macromolecule that is directly involved in multiple human diseases. While its primary role in carbohydrate storage and energy metabolism in the liver and muscle is well characterized, recent research has highlighted critical metabolic and non-metabolic roles for glycogen in the brain. In this review, the emerging roles of glycogen homeostasis in the healthy and diseased brain are discussed with a focus on advancing our understanding of the role of glycogen in the brain. Innovative technologies that have led to novel insights into glycogen functions are detailed. Key insights into how cellular localization impacts neuronal and glial function are discussed. Perturbed glycogen functions are observed in multiple disorders of the brain, including where it serves as a disease driver in the emerging category of neurological glycogen storage diseases (n-GSDs). n-GSDs include Lafora disease (LD), adult polyglucosan body disease (APBD), Cori disease, Glucose transporter type 1 deficiency syndrome (G1D), GSD0b, and late-onset Pompe disease (PD). They are neurogenetic disorders characterized by aberrant glycogen which results in devastating neurological and systemic symptoms. In the most severe cases, rapid neurodegeneration coupled with dementia results in death soon after diagnosis. Finally, we discuss current treatment strategies that are currently being developed and have the potential to be of great benefit to patients with n-GSD. Taken together, novel technologies and biological insights have resulted in a renaissance in brain glycogen that dramatically advanced our understanding of both biology and disease. Future studies are needed to expand our understanding and the multifaceted roles of glycogen and effectively apply these insights to human disease.

Diaphragm pacing and independent breathing in individuals with severe Pompe disease

Introduction

Pompe disease is an inherited disease characterized by a deficit in acid-α-glucosidase (GAA), an enzyme which degrades lysosomal glycogen. The phrenic-diaphragm motor system is affected preferentially, and respiratory failure often occurs despite GAA enzyme replacement therapy. We hypothesized that the continued use of diaphragm pacing (DP) might improve ventilator-dependent subjects' respiratory outcomes and increase ventilator-free time tolerance.

Methods

Six patients (3 pediatric) underwent clinical DP implantation and started diaphragm conditioning, which involved progressively longer periods of daily, low intensity stimulation. Longitudinal respiratory breathing pattern, diaphragm electromyography, and pulmonary function tests were completed when possible, to assess feasibility of use, as well as diaphragm and ventilatory responses to conditioning.

Results

All subjects were eventually able to undergo full-time conditioning via DP and increase their maximal tolerated time off-ventilator, when compared to pre-implant function. Over time, 3 of 6 subjects also demonstrated increased or stable minute ventilation throughout the day, without positive-pressure ventilation assistance.

Discussion

Respiratory insufficiency is one of the main causes of death in patients with Pompe disease. Our results indicate that DP in Pompe disease was feasible, led to few adverse events and stabilized breathing for up to 7 years.

Optogenetic activation of the tongue in spontaneously breathing mice

Inadequate tongue muscle activation contributes to dysarthria, dysphagia, and obstructive sleep apnea. Thus, treatments which increase tongue muscle activity have potential clinical benefit. We hypothesized that lingual injection of an adeno-associated virus (AAV) encoding channelrhodopsin-2 (ChR2) would enable light-induced activation of tongue motor units during spontaneous breathing. An AAV serotype 9 vector (pACAGW-ChR2-Venus-AAV9, 8.29 × 1011 vg) was injected to the posterior tongue in adult C57BL/6J mice. After 12 weeks, mice were anesthetized and posterior tongue electromyographic (EMG) activity was recorded during spontaneous breathing; a light source was positioned near the injection site. Light-evoked EMG responses increased with the intensity and duration of pulses. Stimulus trains (250 ms) evoked EMG bursts that were comparable to endogenous (inspiratory) tongue muscle activation. Histology confirmed lingual myofiber transgene expression. We conclude that intralingual AAV9-ChR2 delivery enables light evoked lingual EMG activity. These proof-of-concept studies lay the groundwork for clinical application of this novel approach to lingual therapeutics.

Binding and neutralizing anti-AAV antibodies: Detection and implications for rAAV-mediated gene therapy

Assessment of anti-adeno-associated virus (AAV) antibodies in patients prior to systemic gene therapy administration is an important consideration regarding efficacy and safety of the therapy. Approximately 30%-60% of individuals have pre-existing anti-AAV antibodies. Seroprevalence is impacted by multiple factors, including geography, age, capsid serotype, and assay type. Anti-AAV antibody assays typically measure (1) transduction inhibition by detecting the neutralizing capacity of antibodies and non-antibody neutralizing factors, or (2) total anti-capsid binding antibodies, regardless of neutralizing activity. Presently, there is a paucity of head-to-head data and standardized approaches associating assay results with clinical outcomes. In addition, establishing clinically relevant screening titer cutoffs is complex. Thus, meaningful comparisons across assays are nearly impossible. Although complex, establishing screening assays in routine clinical practice to identify patients with antibody levels that may impact favorable treatment outcomes is achievable for both transduction inhibition and total antibody assays. Formal regulatory approval of such assays as companion diagnostic tests will confirm their suitability for specific recombinant AAV gene therapies. This review covers current approaches to measure anti-AAV antibodies in patient plasma or serum, their potential impact on therapeutic safety and efficacy, and investigative strategies to mitigate the effects of pre-existing anti-AAV antibodies in patients.

Meeting Report: 2022 Muscular Dystrophy Association Summit on 'Safety and Challenges in Gene Transfer Therapy'

Muscular Dystrophy Association (MDA) has invested over $125M in the development of gene therapy for neuromuscular diseases (NMDs) over the past 20 years. As a lead initiator of progress in this important field of medicine and to help ensure continued progress towards therapies for patients, MDA organized a dedicated summit in January 2022 to address emerging challenges in safely delivering AAV gene therapies with a focus on their application in NMD. In this meeting, chaired by Carsten Bönnemann (NINDS, NIH) and Barry Byrne (University of Florida), academic and industry experts and stakeholders convened to openly discuss adverse events linked to clinical trials, as well as other challenges emerging in preclinical studies associated with difficulties in the translation of AAV gene therapies.

Assessment of systemic AAV-microdystrophin gene therapy in the GRMD model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease caused by the absence of dystrophin, a membrane-stabilizing protein encoded by the DMD gene. Although mouse models of DMD provide insight into the potential of a corrective therapy, data from genetically homologous large animals, such as the dystrophin-deficient golden retriever muscular dystrophy (GRMD) model, may more readily translate to humans. To evaluate the clinical translatability of an adeno-associated virus serotype 9 vector (AAV9)-microdystrophin (μDys5) construct, we performed a blinded, placebo-controlled study in which 12 GRMD dogs were divided among four dose groups [control, 1 × 1013 vector genomes per kilogram (vg/kg), 1 × 1014 vg/kg, and 2 × 1014 vg/kg; n = 3 each], treated intravenously at 3 months of age with a canine codon-optimized microdystrophin construct, rAAV9-CK8e-c-μDys5, and followed for 90 days after dosing. All dogs received prednisone (1 milligram/kilogram) for a total of 5 weeks from day -7 through day 28. We observed dose-dependent increases in tissue vector genome copy numbers; μDys5 protein in multiple appendicular muscles, the diaphragm, and heart; limb and respiratory muscle functional improvement; and reduction of histopathologic lesions. As expected, given that a truncated dystrophin protein was generated, phenotypic test results and histopathologic lesions did not fully normalize. All administrations were well tolerated, and adverse events were not seen. These data suggest that systemically administered AAV-microdystrophin may be dosed safely and could provide therapeutic benefit for patients with DMD.

Polysomnography findings in children with spinal muscular atrophy after onasemnogene-abeparvovec

BACKGROUND

Sleep disordered breathing (SDB) is common in patients with neuromuscular diseases, including spinal muscular atrophy (SMA). While polysomnography (PSG) findings have been described in natural history studies of patients with SMA, reports regarding PSG in treated children are limited to nusinersen. We aim to describe the sleep characteristics in a cohort of children treated with Onasemnogene-abeparvovec.

METHODS

We conducted a cross-sectional cohort study of children with SMA followed at the University of Florida Center for neuromuscular and rare diseases and had a diagnostic or split night PSG after SMA treatment.

RESULTS

Eight children were included in the cohort (four female), aged 5-250 days at diagnosis. Five children had two survival motor neuron 2 (SMN2) copies, two had three SMN2 copies and one subject had four SMN2 copies. Median age at the time of treatment was 46.5 days (range 20-257). All children received onasemnogene-abeparvovec (OA) before their PSG; in addition to OA, one received nusinersen and one received risdiplam. Apnea hypopnea index (AHI) ranged from 3.6 to 24.1/h. REM AHI was higher than NREM AHI. Median Children's Hospital of Philadelphia Infant test of neuromuscular disorders (CHOP-Intend) score at the time of PSG was 55 (range 33-64). There was no correlation between age at treatment, CHOP-Intend score and AHI.

CONCLUSION

SDB is common in treated children with SMA, regardless of age at diagnosis, treatment and neuromotor scores. While AHI may not be the only indicator of SDB in this population, indications, timing of PSG in this cohort remain unknown.

Addressing the implementation gap in advanced therapeutics for spinal muscular atrophy in the era of newborn screening programs

Spinal muscular atrophy (SMA) is a rare genetic disease that results in progressive neuromuscular weakness. Without therapy, the most common form of the disease, type 1, typically results in death or chronic respiratory failure in the first 2 years of life. Thanks to the recent introduction of newborn screening programs and the discovery of three disease-modifying therapies in the last decade, the outcomes of children with SMA have dramatically improved. Patients are able to achieve many, if not all, of the typical neuromotor milestones, such as sitting, standing and walking, as well as safe oral intake. As the natural history of treated patients is continuously evolving, children with SMA continue to require complex and multidisciplinary care, posing implementation and sustainability challenges. Accordingly, there is a significant need for the application and evaluation of implementation science to address the steps involved in the diagnosis and treatment of patients with SMA, ensuring that all pertinent stakeholders and systems are working effectively to deliver timely and appropriate care. In this manuscript, we discuss the current challenges and gaps in the care for children with SMA, as well as how implementation science can advance this field. In addition, we provide an adapted implementation science framework that includes the main domains and subdomains involved in the care of patients with SMA.

Chemogenetic activation of hypoglossal motoneurons in a mouse model of Pompe disease

Pompe disease is a lysosomal storage disease resulting from absence or deficiency of acid α-glucosidase (GAA). Tongue-related disorders including dysarthria, dysphagia, and obstructive sleep apnea are common in Pompe disease. Our purpose was to determine if designer receptors exclusively activated by designer drugs (DREADDs) could be used to stimulate tongue motor output in a mouse model of Pompe disease. An adeno-associated virus serotype 9 (AAV9) encoding an excitatory DREADD (AAV9-hSyn-hM3D(Gq)-mCherry, 2.44 × 1010 vg) was administered to the posterior tongue of 5-7-wk-old Gaa null (Gaa-/-) mice. Lingual EMG responses to intraperitoneal injection of saline or a DREADD ligand (JHU37160-dihydrochloride, J60) were assessed 12 wk later during spontaneous breathing. Saline injection produced no consistent changes in lingual EMG. Following the DREADD ligand, there were statistically significant (P < 0.05) increases in both tonic and phasic inspiratory EMG activity recorded from the posterior tongue. Brainstem histology confirmed mCherry expression in hypoglossal (XII) motoneurons in all mice, thus verifying retrograde movement of the AAV9 vector. Morphologically, Gaa-/- XII motoneurons showed histological characteristics that are typical of Pompe disease, including an enlarged soma and vacuolization. We conclude that lingual delivery of AAV9 can be used to drive functional expression of DREADD in XII motoneurons in a mouse model of Pompe disease.NEW & NOTEWORTHY In a mouse model of Pompe disease, lingual injection of adeno-associated virus (AAV) serotype 9 encoding DREADD was histologically verified to produce transgene expression in hypoglossal motoneurons. Subsequent intraperitoneal delivery of a DREADD ligand stimulated tonic and phase tongue motor output.In a mouse model of Pompe disease, lingual injection of adeno-associated virus (AAV) serotype 9 encoding DREADD was histologically verified to produce transgene expression in hypoglossal motoneurons. Subsequent intravenous delivery of a DREADD ligand stimulated tonic and phase tongue motor output.

Longitudinal Observational Study of Cardiac Outcome Risk Factor Prediction in Children, Adolescents, and Adults with Barth Syndrome

Barth Syndrome (BTHS) is an X-linked mitochondrial cardioskeletal myopathy caused by defects in TAFAZZIN, a gene responsible for cardiolipin remodeling. Altered mitochondrial levels of cardiolipin lead to cardiomyopathy (CM), muscle weakness, exercise intolerance, and mortality. Cardiac risk factors predicting outcome are unknown. Therefore, we conducted a longitudinal observational study to determine risk factors for outcome in BTHS. Subjects with minimum two evaluations (or one followed by death or transplant) were included. Cardiac size, function, and QTc data were measured by echocardiography and electrocardiography at 7 time points from 2002 to 2018. Analysis included baseline, continuous, and categorical variables. Categorical risk factors included prolonged QTc, abnormal right ventricle fractional area change (RV FAC), left ventricle (LV) or RV non-compaction, and restrictive CM phenotype. The association between variables and cardiac death or transplant (CD/TX) was assessed. Median enrollment age was 7 years (range 0.5-22; n = 44). Transplant-free survival (TFS) was 74.4% at 15 years from first evaluation. The cohort demonstrated longitudinal declines in LV size and stroke volume z-scores (end-diastolic volume, p = 0.0002; stroke volume p < 0.0001), worsening RV FAC (p = 0.0405), and global longitudinal strain (GLS) (p = 0.0001) with stable ejection (EF) and shortening (FS) fraction. CD/TX subjects (n = 9) displayed worsening LV dilation (p = 0.0066), EF (p ≤ 0.0001), FS (p = 0.0028), and RV FAC (p = .0032) versus stability in TFS. Having ≥ 2 categorical risk factors predicted CD/TX (p = 0.0073). Over 15 years, 25% of BTHS subjects progressed to CD/TX. Those with progressive LV enlargement, dysfunction, and multiple cardiac risk factors warrant increased surveillance and intense therapy.

Longitudinal changes in cardiac function in Duchenne muscular dystrophy population as measured by magnetic resonance imaging

BACKGROUND

The lack of dystrophin in cardiomyocytes in Duchenne muscular dystrophy (DMD) is associated with progressive decline in cardiac function eventually leading to death by 20-40 years of age. The aim of this prospective study was to determine rate of progressive decline in left ventricular (LV) function in Duchenne muscular dystrophy (DMD) over 5 years.

METHODS

Short axis cine and grid tagged images of the LV were acquired in individuals with DMD (n = 59; age = 5.3-18.0 years) yearly, and healthy controls at baseline (n = 16, age = 6.0-18.3 years) on a 3 T MRI scanner. Grid-tagged images were analyzed for composite circumferential strain (ℇcc%) and ℇcc% in six mid LV segments. Cine images were analyzed for left ventricular ejection fraction (LVEF), LV mass (LVM), end-diastolic volume (EDV), end-systolic volume (ESV), LV atrioventricular plane displacement (LVAPD), and circumferential uniformity ratio estimate (CURE). LVM, EDV, and ESV were normalized to body surface area for a normalized index of LVM (LVMI), EDV (EDVI) and ESV (ESVI).

RESULTS

At baseline, LV ℇcc% was significantly worse in DMD compared to controls and five of the six mid LV segments demonstrated abnormal strain in DMD. Longitudinal measurements revealed that ℇcc% consistently declined in individuals with DMD with the inferior segments being more affected. LVEF progressively declined between 3 to 5 years post baseline visit. In a multivariate analysis, the use of cardioprotective drugs trended towards positively impacting cardiac measures while loss of ambulation and baseline age were associated with negative impact. Eight out of 17 cardiac parameters reached a minimal clinically important difference with a threshold of 1/3 standard deviation.

CONCLUSION

The study shows a worsening of circumferential strain in dystrophic myocardium. The findings emphasize the significance of early and longitudinal assessment of cardiac function in DMD and identify early biomarkers of cardiac dysfunction to help design clinical trials to mitigate cardiac pathology. This study provides valuable non-invasive and non-contrast based natural history data of cardiac changes which can be used to design clinical trials or interpret the results of current trials aimed at mitigating the effects of decreased cardiac function in DMD.

Comparison of highly pure rAAV9 vector stocks produced in suspension by PEI transfection or HSV infection reveals striking quantitative and qualitative differences

Recent clinical successes have propelled recombinant adeno-associated virus vectors (rAAV) to the center stage for human gene therapy applications. However, the exploding demand for high titers of highly pure rAAV vectors for clinical applications and market needs remains hindered by challenges met at the manufacturing stage. The production of rAAV by transfection in suspension cells remains one of the most commonly used production platforms. In this study, we describe our optimized protocol to produce rAAV by polyethyleneimine (PEI)-mediated transfection in suspension HEK293 cells, along with a side-by-side comparison to our high-performing system using the herpes simplex virus (HSV). Further, we detail a new, robust, and highly efficient downstream purification protocol compatible with both transfection and infection-based harvests that generated rAAV9 stocks of high purity. Our in-depth comparison revealed quantitative, qualitative, and biological differences between PEI-mediated transfection and HSV infection. The HSV production system yielded to higher rAAV vector titers, higher specific yields, and a higher percentage of full capsids than transfection. Furthermore, HSV-produced stocks had a significantly lower concentration of residual host cell proteins and helper DNA impurities, but contained detectable levels of HSV DNA. Importantly, the potency of PEI-produced and HSV-produced rAAV stocks were identical. Analyses of AAV Rep and Cap expression levels and replication showed that HSV-mediated production led to a lower expression of Rep and Cap, but increased levels of AAV genome replication. Our methodology enables high-yield, high purity rAAV production and a biological framework to improve transfection quality and yields by mimicking HSV-induced biological outcomes.

Long-term efficacy and safety of eladocagene exuparvovec in patients with AADC deficiency

Aromatic L-amino acid decarboxylase deficiency results in decreased neurotransmitter levels and severe motor dysfunction. Twenty-six patients without head control received bilateral intraputaminal infusions of a recombinant adeno-associated virus type 2 vector containing the human aromatic L-amino acid decarboxylase gene (eladocagene exuparvovec) and have completed 1-year evaluations. Rapid improvements in motor and cognitive function occurred within 12 months after gene therapy and were sustained during follow-up for >5 years. An increase in dopamine production was demonstrated by positron emission tomography and neurotransmitter analysis. Patient symptoms (mood, sweating, temperature, and oculogyric crises), patient growth, and patient caretaker quality of life improved. Although improvements were observed in all treated participants, younger age was associated with greater improvement. There were no treatment-associated brain injuries, and most adverse events were related to underlying disease. Post-surgery complications such as cerebrospinal fluid leakage were managed with standard of care. Most patients experienced mild to moderate dyskinesia that resolved in a few months. These observations suggest that eladocagene exuparvovec treatment for aromatic L-amino acid decarboxylase deficiency provides durable and meaningful benefits with a favorable safety profile.

Safety and efficacy of cipaglucosidase alfa plus miglustat versus alglucosidase alfa plus placebo in late-onset Pompe disease (PROPEL): an international, randomised, double-blind, parallel-group, phase 3 trial

BACKGROUND

Pompe disease is a rare disorder characterised by progressive loss of muscle and respiratory function due to acid α-glucosidase deficiency. Enzyme replacement therapy with recombinant human acid α-glucosidase, alglucosidase alfa, is the first approved treatment for the disease, but some patients do not respond, and many do not show a sustained benefit. We aimed to assess the safety and efficacy of an investigational two-component therapy (cipaglucosidase alfa, a novel recombinant human acid α-glucosidase, plus miglustat, an enzyme stabiliser) for late-onset Pompe disease.

METHODS

We did a randomised, double-blind, parallel-group, phase 3 trial at 62 neuromuscular and metabolic medical centres in 24 countries in the Americas, Asia-Pacific, and Europe. Eligible participants were aged 18 years or older with late-onset Pompe disease, and had either been receiving alglucosidase alfa for at least 2 years or were enzyme replacement therapy-naive. Participants were randomly assigned (2:1) using interactive response technology software, stratified by 6-min walk distance and previous enzyme replacement therapy status, to intravenous cipaglucosidase alfa (20 mg/kg) plus oral miglustat or to intravenous alglucosidase alfa (20 mg/kg) plus oral placebo once every 2 weeks for 52 weeks. Patients, investigators, and outcome assessors were masked to treatment assignment. The primary endpoint was change from baseline to week 52 in 6-min walk distance, assessed using a mixed-effect model for repeated measures analysis for comparison of superiority in the intention-to-treat population (all patients who received at least one dose of study drug). This study is now complete and is registered with ClinicalTrials.gov, NCT03729362.

FINDINGS

Between Dec 3, 2018, and Nov 26, 2019, 130 patients were screened for eligibility and 125 were enrolled and randomly assigned to receive cipaglucosidase alfa plus miglustat (n=85) or alglucosidase alfa plus placebo (n=40). Two patients in the alglucosidase alfa plus placebo group did not receive any dose due to absence of genotype confirmation of late-onset Pompe disease and were excluded from analysis. Six patients discontinued (one in the alglucosidase alfa plus placebo group, five in the cipaglucosidase alfa plus miglustat group), and 117 completed the study. At week 52, mean change from baseline in 6-min walk distance was 20·8 m (SE 4·6) in the cipaglucosidase alfa plus miglustat group versus 7·2 m (6·6) in the alglucosidase alfa plus placebo group using last observation carried forward (between-group difference 13·6 m [95% CI -2·8 to 29·9]). 118 (96%) of 123 patients experienced at least one treatment-emergent adverse event during the study; the incidence was similar between the cipaglucosidase alfa plus miglustat group (n=81 [95%]) and the alglucosidase alfa plus placebo group (n=37 [97%]). The most frequently reported treatment-emergent adverse events were fall (25 [29%] patients in the cipaglucosidase alfa plus miglustat group vs 15 [39%] in the alglucosidase alfa plus placebo group), headache (20 [24%] vs 9 [24%]), nasopharyngitis (19 [22%] vs 3 [8%]), myalgia (14 [16%] vs 5 [13%]), and arthralgia (13 [15%]) vs 5 [13%]). 12 serious adverse events occurred in eight patients in the cipaglucosidase alfa plus miglustat group; only one event (anaphylaxis) was deemed related to study drug. One serious adverse event (stroke) occurred in the alglucosidase alfa plus placebo group, which was deemed unrelated to study drug. There were no deaths.

INTERPRETATION

Cipaglucosidase alfa plus miglustat did not achieve statistical superiority to alglucosidase alfa plus placebo for improving 6-min walk distance in our overall population of patients with late-onset Pompe disease. Further studies should investigate the longer-term safety and efficacy of cipaglucosidase alfa plus miglustat and whether this investigational two-component therapy might provide benefits, particularly in respiratory function and in patients who have been receiving enzyme replacement therapy for more than 2 years, as suggested by our secondary and subgroup analyses.

FUNDING

Amicus Therapeutics.

Resistance exercise training with protein supplementation improves skeletal muscle strength and improves quality of life in late adolescents and young adults with Barth syndrome: A pilot study

BACKGROUND

Muscle weakness and exercise intolerance contribute to reduced quality of life (QOL) in Barth syndrome (BTHS). Our group previously found that 12 weeks of resistance exercise training (RET) improved muscle strength, however, did not increase muscle (lean) mass or QOL in n = 3 young adults with BTHS. The overall objective of this pilot study was to examine the safety and effectiveness of RET plus daily protein supplementation (RET + protein) on muscle strength, skeletal muscle mass, exercise tolerance, cardiac function, and QOL in late adolescents/young adults with BTHS.

METHODS

Participants with BTHS (n = 5, age 27 ± 7) performed 12 weeks of supervised RET (60 minutes per session, three sessions/week) and consumed 42 g/day of whey protein. Muscle strength, muscle mass, exercise capacity, cardiac function, and health-related QOL were assessed pre-post intervention.

RESULTS

RET + protein was safe, increased muscle strength and quality of life, and tended to increase lean mass.

CONCLUSIONS

RET + protein appears safe, increases muscle strength and quality of life and tends to increase lean mass. Larger studies are needed to confirm these findings and to fully determine the effects of RET + protein in individuals with BTHS.

A Combined Prospective and Retrospective Comparison of Long-Term Functional Outcomes Suggests Delayed Loss of Ambulation and Pulmonary Decline with Long-Term Eteplirsen Treatment

Background:

Studies 4658-201/202 (201/202) evaluated treatment effects of eteplirsen over 4 years in patients with Duchenne muscular dystrophy and confirmed exon-51 amenable genetic mutations. Chart review Study 4658-405 (405) further followed these patients while receiving eteplirsen during usual clinical care.

Objective:

To compare long-term clinical outcomes of eteplirsen-treated patients from Studies 201/202/405 with those of external controls.

Methods:

Median total follow-up time was approximately 6 years of eteplirsen treatment. Outcomes included loss of ambulation (LOA) and percent-predicted forced vital capacity (FVC%p). Time to LOA was compared between eteplirsen-treated patients and standard of care (SOC) external controls and was measured from eteplirsen initiation in 201/202 or, in the SOC group, from the first study visit. Comparisons were conducted using univariate Kaplan-Meier analyses and log-rank tests, and multivariate Cox proportional hazards models with regression adjustment for baseline characteristics. Annual change in FVC%p was compared between eteplirsen-treated patients and natural history study patients using linear mixed models with repeated measures.

Results:

Data were included from all 12 patients in Studies 201/202 and the 10 patients with available data from 405. Median age at LOA was 15.16 years. Eteplirsen-treated patients experienced a statistically significant longer median time to LOA by 2.09 years (5.09 vs. 3.00 years, p < 0.01) and significantly attenuated rates of pulmonary decline vs. natural history patients (FVC%p change: –3.3 vs. –6.0 percentage points annually, p < 0.0001).

Conclusions:

Study 405 highlights the functional benefits of eteplirsen on ambulatory and pulmonary function outcomes up to 7 years of follow-up in comparison to external controls.

Myocardial glucose and fatty acid metabolism is altered and associated with lower cardiac function in young adults with Barth syndrome

BACKGROUND

Barth syndrome (BTHS) is a rare X-linked condition resulting in cardiomyopathy, however; the effects of BTHS on myocardial substrate metabolism and its relationships with cardiac high-energy phosphate metabolism and left ventricular (LV) function are unknown. We sought to characterize myocardial glucose, fatty acid (FA), and leucine metabolism in BTHS and unaffected controls and examine their relationships with cardiac high-energy phosphate metabolism and LV function.

METHODS/RESULTS

Young adults with BTHS (n = 14) and unaffected controls (n = 11, Control, total n = 25) underwent bolus injections of 15O-water and 1-11C-glucose, palmitate, and leucine and concurrent positron emission tomography imaging. LV function and cardiac high-energy phosphate metabolism were examined via echocardiography and 31P magnetic resonance spectroscopy, respectively. Myocardial glucose extraction fraction (21 ± 14% vs 10 ± 8%, P = .03) and glucose utilization (828.0 ± 470.0 vs 393.2 ± 361.0 μmol·g-1·min-1, P = .02) were significantly higher in BTHS vs Control. Myocardial FA extraction fraction (31 ± 7% vs 41 ± 6%, P < .002) and uptake (0.25 ± 0.04 vs 0.29 ± 0.03 mL·g-1·min-1, P < .002) were significantly lower in BTHS vs Control. Altered myocardial metabolism was associated with lower cardiac function in BTHS.

CONCLUSIONS

Myocardial substrate metabolism is altered and may contribute to LV dysfunction in BTHS. Clinical Trials #: NCT01625663.

Case Studies in Neuroscience: Neuropathology and diaphragm dysfunction in ventilatory failure from late-onset Pompe disease

Pompe disease (PD) is a neuromuscular disorder caused by a mutation in the acid alpha-glucosidase (GAA) gene. Patients with late-onset PD retain some GAA activity and present symptoms later in life, with fatality mainly associated with respiratory failure. This case study presents diaphragm electrophysiology and a histological analysis of the brainstem, spinal cord, and diaphragm, from a male PD patient diagnosed with late-onset PD at age 35. The patient was wheelchair dependent by age 38, required nocturnal ventilation at age 40, 24-h noninvasive ventilation by age 43, and passed away from respiratory failure at age 54. Diaphragm electromyography recorded using indwelling "pacing" wires showed asynchronous bursting between the left and right diaphragm during brief periods of independent breathing. The synchrony declined over a 4-yr period preceding respiratory failure. Histological assessment indicated motoneuron atrophy in the medulla and rostral spinal cord. Hypoglossal (soma size: 421 ± 159 µm²) and cervical motoneurons (soma size: 487 ± 189 µm²) had an atrophied, elongated appearance. In contrast, lumbar (soma size: 1,363 ± 677 µm²) and sacral motoneurons (soma size: 1,411 ± 633 µm²) had the ballooned morphology typical of early-onset PD. Diaphragm histology indicated loss of myofibers. These results are consistent with neuromuscular degeneration and the concept that effective PD therapy will need to target the central nervous system, in addition to skeletal and cardiac muscle.NEW & NOTEWORTHY This case study offered a unique opportunity to investigate longitudinal changes in phrenic neurophysiology in an individual with severe, ventilator-dependent, late-onset Pompe disease. Additional diaphragm and neural tissue histology upon autopsy confirmed significant neuromuscular degeneration, and it provided novel insights regarding rostral to caudal variability in the neuropathology. These findings suggest that a successful treatment approach for ventilator-dependent Pompe disease should target the central nervous system, in addition to skeletal muscle.

NaCl and KCl mediate log increase in AAV vector particles and infectious titers in a specific/timely manner with the HSV platform

The increasing demand for adeno-associated virus (AAV) vectors, a result from the surging interest for their potential to cure human genetic diseases by gene transfer, tumbled on low-performing production systems. Innovative improvements to increase both yield and quality of the vector produced have become a priority undertaking in the field. In a previous study, we showed that adding a specific concentration of sodium chloride (NaCl) to the production medium resulted in a dramatic increase of AAV vector particle and infectious titers when using the herpes simplex virus (HSV) production system, both in adherent or suspension platforms. In this work, we studied additional salts and their impact on AAV vector production. We found that potassium chloride (KCl), or a combination of KCl and NaCl, resulted in the highest increase in AAV vector production. We determined that the salt-mediated effect was the most impactful when the salt was present between 8 and approximately 16 h post-infection, with the highest rate increase occurring within the first 24 h of the production cycle. We showed that the AAV vector yield increase did not result from an increase in cell growth, size, or viability. Furthermore, we demonstrated that the impact on AAV vector production was specifically mediated by NaCl and KCl independently of their impact on the osmolality of the production media. Our findings convincingly showed that NaCl and KCl were uniquely efficacious to promote up to a 10-fold increase in the production of highly infectious AAV vectors when produced in the presence of HSV. We think that this study will provide unique and important new insights in AAV biology toward the establishment of more successful production protocols.

Gene delivery to the hypoglossal motor system: preclinical studies and translational potential

Dysfunction and/or reduced activity in the tongue muscles contributes to conditions such as dysphagia, dysarthria, and sleep disordered breathing. Current treatments are often inadequate, and the tongue is a readily accessible target for therapeutic gene delivery. In this regard, gene therapy specifically targeting the tongue motor system offers two general strategies for treating lingual disorders. First, correcting tongue myofiber and/or hypoglossal (XII) motoneuron pathology in genetic neuromuscular disorders may be readily achieved by intralingual delivery of viral vectors. The retrograde movement of viral vectors such as adeno-associated virus (AAV) enables targeted distribution to XII motoneurons via intralingual viral delivery. Second, conditions with impaired or reduced tongue muscle activation can potentially be treated using viral-driven chemo- or optogenetic approaches to activate or inhibit XII motoneurons and/or tongue myofibers. Further considerations that are highly relevant to lingual gene therapy include (1) the diversity of the motoneurons which control the tongue, (2) the patterns of XII nerve branching, and (3) the complexity of tongue muscle anatomy and biomechanics. Preclinical studies show considerable promise for lingual directed gene therapy in neuromuscular disease, but the potential of such approaches is largely untapped.

Safety, feasibility, and efficacy of strengthening exercise in Duchenne muscular dystrophy

BACKGROUND

This two-part study explored the safety, feasibility, and efficacy of a mild-moderate resistance isometric leg exercise program in ambulatory boys with Duchenne muscular dystrophy (DMD).

METHODS

First, we used a dose escalation paradigm with varying intensity and frequency of leg isometric exercise to determine the dose response and safety in 10 boys. Second, we examined safety and feasibility of a 12-wk in-home, remotely supervised, mild-moderate intensity strengthening program in eight boys. Safety measures included T₂ MRI, creatine kinase levels, and pain. Peak strength and function (time to ascend/descend four stairs) were also measured.

RESULTS

Dose-escalation revealed no signs of muscle damage. Seven of the eight boys completed the 12-wk in-home program with a compliance of 84.9%, no signs of muscle damage, and improvements in strength (knee extensors P < .01; knee flexors P < .05) and function (descending steps P < .05).

CONCLUSIONS

An in-home, mild-moderate intensity leg exercise program is safe with potential to positively impact both strength and function in ambulatory boys with DMD.

Current Clinical Applications of In Vivo Gene Therapy with AAVs

Hereditary diseases are caused by mutations in genes, and more than 7,000 rare diseases affect over 30 million Americans. For more than 30 years, hundreds of researchers have maintained that genetic modifications would provide effective treatments for many inherited human diseases, offering durable and possibly curative clinical benefit with a single treatment. This review is limited to gene therapy using adeno-associated virus (AAV) because the gene delivered by this vector does not integrate into the patient genome and has a low immunogenicity. There are now five treatments approved for commercialization and currently available, i.e., Luxturna, Zolgensma, the two chimeric antigen receptor T cell (CAR-T) therapies (Yescarta and Kymriah), and Strimvelis (the gammaretrovirus approved for adenosine deaminase-severe combined immunodeficiency [ADA-SCID] in Europe). Dozens of other treatments are under clinical trials. The review article presents a broad overview of the field of therapy by in vivo gene transfer. We review gene therapy for neuromuscular disorders (spinal muscular atrophy [SMA]; Duchenne muscular dystrophy [DMD]; X-linked myotubular myopathy [XLMTM]; and diseases of the central nervous system, including Alzheimer’s disease, Parkinson’s disease, Canavan disease, aromatic l-amino acid decarboxylase [AADC] deficiency, and giant axonal neuropathy), ocular disorders (Leber congenital amaurosis, age-related macular degeneration [AMD], choroideremia, achromatopsia, retinitis pigmentosa, and X-linked retinoschisis), the bleeding disorder hemophilia, and lysosomal storage disorders.

Arginine kinetics are altered in a pilot sample of adolescents and young adults with Barth syndrome

Barth syndrome (BTHS) is a rare, X-linked cardiomyopathy that is characterized by abnormalities in glucose and lipid metabolism, with less known regarding amino acid metabolism. This pilot study characterized whole-body arginine kinetics and found lower arginine rate of appearance into plasma (0.69 ± 0.09 vs. 0.88 ± 0.06 μmol/kgFFM/min, p < 0.01) and arginine non-oxidative disposal rate (0.64 ± 0.11 vs. 0.80 ± 0.03 μmol/kgFFM/min, p < 0.02) in adolescents and young adults with BTHS compared to Controls. This study provides a foundation for more in-depth studies on how arginine and potentially other amino acid abnormalities contribute to the pathology and clinical manifestations of BTHS.

Advancements in AAV-mediated Gene Therapy for Pompe Disease

Pompe disease (glycogen storage disease type II) is caused by mutations in acid α-glucosidase (GAA) resulting in lysosomal pathology and impairment of the muscular and cardio-pulmonary systems. Enzyme replacement therapy (ERT), the only approved therapy for Pompe disease, improves muscle function by reducing glycogen accumulation but this approach entails several limitations including a short drug half-life and an antibody response that results in reduced efficacy. To address these limitations, new treatments such as gene therapy are under development to increase the intrinsic ability of the affected cells to produce GAA. Key components to gene therapy strategies include the choice of vector, promoter, and the route of administration. The efficacy of gene therapy depends on the ability of the vector to drive gene expression in the target tissue and also on the recipient's immune tolerance to the transgene protein. In this review, we discuss the preclinical and clinical studies that are paving the way for the development of a gene therapy strategy for patients with early and late onset Pompe disease as well as some of the challenges for advancing gene therapy.

Micro-dystrophin AAV Vectors Made by Transient Transfection and Herpesvirus System Are Equally Potent in Treating mdx Mouse Muscle Disease

Vector production scale-up is a major barrier in systemic adeno-associated virus (AAV) gene therapy. Many scalable manufacturing methods have been developed. However, the potency of the vectors generated by these methods has rarely been compared with vectors made by transient transfection (TT), the most commonly used method in preclinical studies. In this study, we blindly compared therapeutic efficacy of an AAV9 micro-dystrophin vector generated by the TT method and scalable herpes simplex virus (HSV) system in a Duchenne muscular dystrophy mouse model. AAV was injected intravenously at 5 × 1014 (high), 5 × 1013 (medium), or 5 × 1012 (low) viral genomes (vg)/kg. Comparable levels of micro-dystrophin expression were observed at each dose in a dose-dependent manner irrespective of the manufacturing method. Vector biodistribution was similar in mice injected with either the TT or the HSV method AAV. Evaluation of muscle degeneration/regeneration showed equivalent protection by vectors made by either method in a dose-dependent manner. Muscle function was similarly improved in a dose-dependent manner irrespective of the vector production method. No apparent toxicity was observed in any mouse. Collectively, our results suggest that the biological potency of the AAV micro-dystrophin vector made by the scalable HSV method is comparable to that made by the TT method.

Respiratory function during enzyme replacement therapy in late-onset Pompe disease: longitudinal course, prognostic factors, and the impact of time from diagnosis to treatment start

Objective

To examine respiratory muscle function among late-onset Pompe disease (LOPD) patients in the Pompe Registry (NCT00231400/Sanofi Genzyme) during enzyme replacement therapy (ERT) with alglucosidase alfa by assessing the longitudinal course of forced vital capacity (FVC), prognostic factors for FVC, and impact of time from diagnosis to ERT initiation.

Methods

Longitudinal FVC data from LOPD (symptom onset > 12 months or ≤ 12 months without cardiomyopathy) patients were analyzed. Patients had to have baseline FVC (percent predicted upright) assessments at ERT start and ≥ 2 valid post-baseline assessments. Longitudinal analyses used linear mixed-regression models.

Results

Among 396 eligible patients, median baseline FVC was 66.9% (range 9.3–126.0). FVC remained stable during the 5-year follow-up (slope = − 0.17%, p = 0.21). Baseline FVC was lower among various subgroups, including patients who were male; older at ERT initiation; had a longer duration from symptom onset to ERT initiation; and had more advanced disease at baseline (based on respiratory support use, inability to ambulate, ambulation device use). Age at symptom onset was not associated with baseline degree of respiratory dysfunction. Differences between subgroups observed at baseline remained during follow-up. Shorter time from diagnosis to ERT initiation was associated with higher FVC after 5 years in all patients and the above subgroups using a cut-off of 1.7 years.

Conclusion

FVC stability over 5 years suggests that respiratory function is preserved during long-term ERT in real-world settings. Early initiation of alglucosidase alfa was associated with preservation of FVC in LOPD patients with better respiratory function at the time of treatment initiation.

Mortality and respiratory support in X-linked myotubular myopathy: a RECENSUS retrospective analysis

PURPOSE

Individuals with X-linked myotubular myopathy (XLMTM) who survive infancy require extensive supportive care, including ventilator assistance, wheelchairs and feeding tubes. Half die before 18 months of age. We explored respiratory support and associated mortality risk in RECENSUS, particularly among patients ≤5 years old who received respiratory support at birth; this subgroup closely matches patients in the ASPIRO trial of gene therapy for XLMTM.

DESIGN

RECENSUS is an international, retrospective study of patients with XLMTM. Descriptive and time-to-event analyses examined survival on the basis of age, respiratory support, tracheostomy use, predicted mutational effects and life-sustaining care.

RESULTS

Outcomes for 145 patients were evaluated. Among 126 patients with respiratory support at birth, mortality was 47% overall and 59% among those ≤5 years old. Median survival time was shorter for patients ≤5 years old than for those >5 years old (2.2 years (IQR 0.7-5.6) vs 30.2 years (IQR 19.4-30.2)). The most common cause of death was respiratory failure (66.7%). Median survival time was longer for patients with a tracheostomy than for those without (22.8 years (IQR 8.7-30.2) vs 1.8 years (IQR 0.2-not estimable)). The proportion of patients living without a tracheostomy was 50% at age 6 months and 28% at age 2 years. Median survival time was longer with provision of life-sustaining care than without (19.4 years (IQR 3.1-not estimable) vs 0.2 years (IQR 0.1-2.1)).

CONCLUSIONS

High mortality, principally due to respiratory failure, among patients with XLMTM ≤5 years old despite respiratory support underscores the need for early diagnosis, informed decision-making and disease-modifying therapies.

TRIAL REGISTRATION NUMBER

NCT02231697.