Developing standardized corticosteroid treatment for Duchenne muscular dystrophy

Despite corticosteroids being the only treatment documented to improve strength and function in boys with Duchenne muscular dystrophy (DMD) corticosteroid prescription is inconsistent and in some countries, corticosteroids are not prescribed. We are conducting a clinical trial that (1) compares the 3 most frequently prescribed corticosteroid regimes; (2) standardizes treatment of DMD complications; and (3) standardizes prevention of corticosteroid side effects. Investigators at 38 sites in 5 countries plan to recruit 300 boys aged 4-7 who are randomly assigned to one of three regimens: daily prednisone; daily deflazacort; or intermittent prednisone (10days on/10days off). Boys are followed for a minimum of 3years to assess the relative effectiveness and adverse event profiles of the different regimens. The primary outcome is a 3-dimensional variable consisting of log-transformed time to rise from the floor, forced vital capacity, and subject/parent satisfaction with treatment, each averaged over all post-baseline visits. The study protocol includes evidence- and consensus-based treatment of DMD complications and of corticosteroid side effects. This study seeks to establish a standard corticosteroid regimen for DMD. Since all new interventions for DMD are being developed as add-on therapies to corticosteroids, defining the optimum regimen is of importance for all new treatments.

General anesthesia with a native airway for patients with mucopolysaccharidosis type III

BACKGROUND

Mucopolysaccharidosis type III is a progressive disease with worsening airway, pulmonary, and cardiac involvement that may complicate anesthetic care.

AIM

To prospectively evaluate the incidence of airway issues and complications during magnetic resonance imaging (MRI) and lumbar puncture (LP) during general anesthesia with a native airway for patients with mucopolysaccharidosis type III.

METHOD

The study was a part of the natural history study. Anesthesia was induced with sevoflurane, which was discontinued after intravenous access was obtained. General anesthesia with a native airway was provided by dexmedetomidine and propofol. Dexmedetomidine (0.5 μg·kg^-1 ) was administered over 5 min followed by a continuous infusion at 0.5 μg·kg^-1 ·h^-1 . A continuous infusion of propofol was started at 150 μg·kg^-1 ·min^-1 . A bolus dose of propofol (1 mg·kg^-1 ) was administered and the propofol infusion was increased as needed. Airway management and vital signs were recorded for the entire procedure until discharge.

RESULTS

Twenty-five patients (6.9 ± 3.1 years) received total of 43 MRI and LP procedures in the cohort. No patient failed sedation. Although mask induction with sevoflurane was not clinically problematic, upper airway obstruction was noted during 14 procedures (33%). This required the application of continuous positive airway pressure, temporary oral airway placement, jaw thrust, or shoulder roll. Airway dynamics improved once the anesthesia was transitioned to intravenous anesthetic agents. Although a small shoulder roll was needed to improve airway patency for 11 cases (26%), a large shoulder roll tended to make the upper airway obstruction worse. Oxygen desaturation (≤90%) was noted during MRI in three cases (7%).

CONCLUSION

A combination of dexmedetomidine and propofol provided effective general anesthesia with a native airway during the procedures. Although upper airway obstruction was noted, it resolved with simple airway maneuvers without further airway intervention.

Follistatin Gene Therapy for Sporadic Inclusion Body Myositis Improves Functional Outcomes

Sporadic inclusion body myositis, a variant of inflammatory myopathy, has features distinct from polymyositis/dermatomyositis. The disease affects men more than women, most commonly after age 50. Clinical features include weakness of the quadriceps, finger flexors, ankle dorsiflexors, and dysphagia. The distribution of weakness is similar to Becker muscular dystrophy, where we previously reported improvement following intramuscular injection of an isoform of follistatin (FS344) by AAV1. For this clinical trial, rAAV1.CMV.huFS344, 6 × 10¹¹ vg/kg, was delivered to the quadriceps muscles of both legs of six sporadic inclusion body myositis subjects. The primary outcome for this trial was distance traveled for the 6-min walk test. The protocol included an exercise regimen for each participant. Performance, annualized to a median 1-year change, improved +56.0 m/year for treated subjects compared to a decline of -25.8 m/year (p = 0.01) in untreated subjects (n = 8), matched for age, gender, and baseline measures. Four of the six treated subjects showed increases ranging from 58-153 m, whereas two were minimally improved (5-23 m). Treatment effects included decreased fibrosis and improved regeneration. These findings show promise for follistatin gene therapy for mild to moderately affected, ambulatory sporadic inclusion body myositis patients. More advanced disease with discernible muscle loss poses challenges.

Comparison of Serum rAAV Serotype-Specific Antibodies in Patients with Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, Inclusion Body Myositis, or GNE Myopathy

Recombinant adeno-associated virus (rAAV) is a commonly used gene therapy vector for the delivery of therapeutic transgenes in a variety of human diseases, but pre-existing serum antibodies to viral capsid proteins can greatly inhibit rAAV transduction of tissues. Serum was assayed from patients with Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), inclusion body myositis (IBM), and GNE myopathy (GNE). These were compared to serum from otherwise normal human subjects to determine the extent of pre-existing serum antibodies to rAAVrh74, rAAV1, rAAV2, rAAV6, rAAV8, and rAAV9. In almost all cases, patients with measurable titers to one rAAV serotype showed titers to all other serotypes tested, with average titers to rAAV2 being highest in all instances. Twenty-six percent of all young normal subjects (<18 years old) had measurable rAAV titers to all serotypes tested, and this percentage increased to almost 50% in adult normal subjects (>18 years old). Fifty percent of all IBM and GNE patients also had antibody titers to all rAAV serotypes, while only 18% of DMD and 0% of BMD patients did. In addition, serum-naïve macaques treated systemically with rAAVrh74 could develop cross-reactive antibodies to all other serotypes tested at 24 weeks post treatment. These data demonstrate that most DMD and BMD patients should be amenable to vascular rAAV-mediated treatment without the concern of treatment blockage by pre-existing serum rAAV antibodies, and that serum antibodies to rAAVrh74 are no more common than those for rAAV6, rAAV8, or rAAV9.

Association Study of Exon Variants in the NF-κB and TGFβ Pathways Identifies CD40 as a Modifier of Duchenne Muscular Dystrophy

The expressivity of Mendelian diseases can be influenced by factors independent from the pathogenic mutation: in Duchenne muscular dystrophy (DMD), for instance, age at loss of ambulation (LoA) varies between individuals whose DMD mutations all abolish dystrophin expression. This suggests the existence of trans-acting variants in modifier genes. Common single nucleotide polymorphisms (SNPs) in candidate genes (SPP1, encoding osteopontin, and LTBP4, encoding latent transforming growth factor β [TGFβ]-binding protein 4) have been established as DMD modifiers. We performed a genome-wide association study of age at LoA in a sub-cohort of European or European American ancestry (n = 109) from the Cooperative International Research Group Duchenne Natural History Study (CINRG-DNHS). We focused on protein-altering variants (Exome Chip) and included glucocorticoid treatment as a covariate. As expected, due to the small population size, no SNPs displayed an exome-wide significant p value (< 1.8 × 10^-6). Subsequently, we prioritized 438 SNPs in the vicinities of 384 genes implicated in DMD-related pathways, i.e., the nuclear-factor-κB and TGFβ pathways. The minor allele at rs1883832, in the 5'-untranslated region of CD40, was associated with earlier LoA (p = 3.5 × 10^-5). This allele diminishes the expression of CD40, a co-stimulatory molecule for T cell polarization. We validated this association in multiple independent DMD cohorts (United Dystrophinopathy Project, Bio-NMD, and Padova, total n = 660), establishing this locus as a DMD modifier. This finding points to cell-mediated immunity as a relevant pathogenetic mechanism and potential therapeutic target in DMD.

A prospective one-year natural history study of mucopolysaccharidosis types IIIA and IIIB: Implications for clinical trial design

Mucopolysaccharidosis type III is a group of four autosomal recessive enzyme deficiencies leading to tissue accumulation of heparan sulfate. Central nervous system disease is prominent, with initial normal development followed by neurocognitive decline leading to death. In order to define outcome measures suitable for gene transfer trials, we prospectively assessed disease progression in MPS IIIA and IIIB subjects >2years old at three time points over one year (baseline, 6 and 12months). Fifteen IIIA (9 male, 6 female; age 5.0±1.9years) and ten IIIB subjects (8 male, 2 female; age 8.6±3years) were enrolled, and twenty subjects completed assessments at all time points. Cognitive function as assessed by Mullen Scales maximized at the 2.5 to 3year old developmental level, and showed a significant age-related decline over a 6month interval in three of five subdomains. Leiter nonverbal IQ (NVIQ) standard scores declined toward the test floor in the cohort by 6 to 8years of age, but showed significant mean declines over a 6month interval in those <7years old (p=0.0029) and in those with NVIQ score≥45 (p=0.0313). Parental report of adaptive behavior as assessed by the Vineland-II composite score inversely correlated with age and showed a significant mean decline over 6month intervals (p=0.0004). Abdominal MRI demonstrated increased volumes in liver (mean 2.2 times normal) and spleen (mean 1.9 times normal) without significant change over one year; brain MRI showed ventriculomegaly and loss of cortical volume in all subjects. Biochemical measures included urine glycosaminoglycan (GAG) levels, which although elevated showed a decline correlating with age (p<0.0001) and approached normal values in older subjects. CSF protein levels were elevated in 32% at enrollment, and elevations of AST and ALT were frequent. CSF enzyme activity levels for either SGSH (in MPS IIIA subjects) or NAGLU (in MPS IIIB) significantly differed from normal controls. Several other behavioral or functional measures were found to be uninformative in this population, including timed functional motor tests. Our results suggest that cognitive development as assessed by the Mullen and Leiter-R and adaptive behavior assessment by the Vineland parent interview are suitable functional outcomes for interventional trials in MPS IIIA or IIIB, and that CSF enzyme assay may be a useful biomarker to assess central nervous system transgene expression in gene transfer trials.

A GLP-Compliant Toxicology and Biodistribution Study: Systemic Delivery of an rAAV9 Vector for the Treatment of Mucopolysaccharidosis IIIB

No treatment is currently available for mucopolysaccharidosis (MPS) IIIB, a neuropathic lysosomal storage disease due to defect in α-N-acetylglucosaminidase (NAGLU). In preparation for a clinical trial, we performed an IND-enabling GLP-toxicology study to assess systemic rAAV9-CMV-hNAGLU gene delivery in WT C57BL/6 mice at 1 × 10(14) vg/kg and 2 × 10(14) vg/kg (n = 30/group, M:F = 1:1), and non-GLP testing in MPS IIIB mice at 2 × 10(14) vg/kg. Importantly, no adverse clinical signs or chronic toxicity were observed through the 6 month study duration. The rAAV9-mediated rNAGLU expression was rapid and persistent in virtually all tested CNS and somatic tissues. However, acute liver toxicity occurred in 33% (5/15) WT males in the 2 × 10(14) vg/kg cohort, which was dose-dependent, sex-associated, and genotype-specific, likely due to hepatic rNAGLU overexpression. Interestingly, a significant dose response was observed only in the brain and spinal cord, whereas in the liver at 24 weeks postinfection (pi), NAGLU activity was reduced to endogenous levels in the high dose cohort but remained at supranormal levels in the low dose group. The possibility of rAAV9 germline transmission appears to be minimal. The vector delivery resulted in transient T-cell responses and characteristic acute antibody responses to both AAV9 and rNAGLU in all rAAV9-treated animals, with no detectable impacts on tissue transgene expression. This study demonstrates a generally safe and effective profile, and may have identified the upper dosing limit of rAAV9-CMV-hNAGLU via systemic delivery for the treatment of MPS IIIB.

Reassessing carrier status for dystrophinopathies

The cloning of the DMD gene, and the identifications of mutations in it as the cause of Duchenne muscular dystrophy (DMD), makes a compelling story that is aptly told elsewhere.¹ The locus-the largest in the human genome-consists of 79 exons, distributed over 2.5 million nucleotides on the X chromosome, which are assembled into a complementary DNA (cDNA) of around 14 kb encoding the predominant muscle isoform of the dystrophin protein.² The size of the gene, and the number of exons, had historically made mutation analysis challenging. For more than a decade, the standard clinical assay was a multiplex PCR test that amplified sequences from a limited number of exons; nevertheless, because it included exons within the deletion hotspots of the gene, this method could confirm the presence of mutations in up to 98% of boys with exonic deletions.^3,4.

Recurrent Fat Embolic Strokes in a Patient With Duchenne Muscular Dystrophy With Long Bone Fractures and a Patent Foramen Ovale

BACKGROUND

Individuals with Duchenne muscular dystrophy have an increased risk of long bone fractures. Such fractures are sometimes associated with brain dysfunction due to fat embolism syndrome, although this syndrome has seldom been documented in muscular dystrophy patients.

PATIENT DESCRIPTION

We describe a child with Duchenne muscular dystrophy who developed fat embolism syndrome with neurological dysfunction following multiple long bone fractures. He experienced recurrent cerebral infarctions that probably resulted from embolization through a patent foramen ovale. The patent foramen ovale was closed by an occluder device in the cardiac catheterization laboratory, and he did not experience further infarctions.

CONCLUSIONS

Fat embolism with ischemic cerebral infarction can occur in individuals with Duchenne muscular dystrophy following long bone fractures. In this setting it is important to identify and close atrial level shunts in order to prevent additional infarctions.

EPG5-related Vici syndrome: a paradigm of neurodevelopmental disorders with defective autophagy

Vici syndrome is a progressive neurodevelopmental multisystem disorder due to recessive mutations in the key autophagy gene EPG5. We report genetic, clinical, neuroradiological, and neuropathological features of 50 children from 30 families, as well as the neuronal phenotype of EPG5 knock-down in Drosophila melanogaster. We identified 39 different EPG5 mutations, most of them truncating and predicted to result in reduced EPG5 protein. Most mutations were private, but three recurrent mutations (p.Met2242Cysfs*5, p.Arg417*, and p.Gln336Arg) indicated possible founder effects. Presentation was mainly neonatal, with marked hypotonia and feeding difficulties. In addition to the five principal features (callosal agenesis, cataracts, hypopigmentation, cardiomyopathy, and immune dysfunction), we identified three equally consistent features (profound developmental delay, progressive microcephaly, and failure to thrive). The manifestation of all eight of these features has a specificity of 97%, and a sensitivity of 89% for the presence of an EPG5 mutation and will allow informed decisions about genetic testing. Clinical progression was relentless and many children died in infancy. Survival analysis demonstrated a median survival time of 24 months (95% confidence interval 0-49 months), with only a 10th of patients surviving to 5 years of age. Survival outcomes were significantly better in patients with compound heterozygous mutations (P = 0.046), as well as in patients with the recurrent p.Gln336Arg mutation. Acquired microcephaly and regression of skills in long-term survivors suggests a neurodegenerative component superimposed on the principal neurodevelopmental defect. Two-thirds of patients had a severe seizure disorder, placing EPG5 within the rapidly expanding group of genes associated with early-onset epileptic encephalopathies. Consistent neuroradiological features comprised structural abnormalities, in particular callosal agenesis and pontine hypoplasia, delayed myelination and, less frequently, thalamic signal intensity changes evolving over time. Typical muscle biopsy features included fibre size variability, central/internal nuclei, abnormal glycogen storage, presence of autophagic vacuoles and secondary mitochondrial abnormalities. Nerve biopsy performed in one case revealed subtotal absence of myelinated axons. Post-mortem examinations in three patients confirmed neurodevelopmental and neurodegenerative features and multisystem involvement. Finally, downregulation of epg5 (CG14299) in Drosophila resulted in autophagic abnormalities and progressive neurodegeneration. We conclude that EPG5-related Vici syndrome defines a novel group of neurodevelopmental disorders that should be considered in patients with suggestive features in whom mitochondrial, glycogen, or lysosomal storage disorders have been excluded. Neurological progression over time indicates an intriguing link between neurodevelopment and neurodegeneration, also supported by neurodegenerative features in epg5-deficient Drosophila, and recent implication of other autophagy regulators in late-onset neurodegenerative disease.

Dp412e: a novel human embryonic dystrophin isoform induced by BMP4 in early differentiated cells

Background

Duchenne muscular dystrophy (DMD) is a devastating X-linked recessive genetic myopathy. DMD physiopathology is still not fully understood and a prenatal onset is suspected but difficult to address.

Methods

The bone morphogenetic protein 4 (BMP4) is a critical signaling molecule involved in mesoderm commitment. Human induced pluripotent stem cells (hiPSCs) from DMD and healthy individuals and human embryonic stem cells (hESCs) treated with BMP4 allowed us to model the early steps of myogenesis in normal and DMD contexts.

Results

Unexpectedly, 72h following BMP4 treatment, a new long DMD transcript was detected in all tested hiPSCs and hESCs, at levels similar to that found in adult skeletal muscle. This novel transcript named “Dp412e” has a specific untranslated first exon which is conserved only in a sub-group of anthropoids including human. The corresponding novel dystrophin protein of 412-kiloDalton (kDa), characterized by an N-terminal-truncated actin-binding domain, was detected in normal BMP4-treated hiPSCs/hESCs and in embryoid bodies. Finally, using a phosphorodiamidate morpholino oligomer (PMO) targeting the DMD exon 53, we demonstrated the feasibility of exon skipping validation with this BMP4-inducible hiPSCs model.

Conclusions

In this study, the use of hiPSCs to analyze early phases of human development in normal and DMD contexts has led to the discovery of an embryonic 412 kDa dystrophin isoform. Deciphering the regulation process(es) and the function(s) associated to this new isoform can contribute to a better understanding of the DMD physiopathology and potential developmental defects. Moreover, the simple and robust BMP4-inducible model highlighted here, providing large amount of a long DMD transcript and the corresponding protein in only 3 days, is already well-adapted to high-throughput and high-content screening approaches. Therefore, availability of this powerful cell platform can accelerate the development, validation and improvement of DMD genetic therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13395-015-0062-6) contains supplementary material, which is available to authorized users.

The first exon duplication mouse model of Duchenne muscular dystrophy: A tool for therapeutic development

Exon duplication mutations account for up to 11% of all cases of Duchenne muscular dystrophy (DMD), and a duplication of exon 2 is the most common duplication in patients. For use as a platform for testing of duplication-specific therapies, we developed a mouse model that carries a Dmd exon 2 duplication. By using homologous recombination we duplicated exon 2 within intron 2 at a location consistent with a human duplication hotspot. mRNA analysis confirms the inclusion of a duplicated exon 2 in mouse muscle. Dystrophin expression is essentially absent by immunofluorescent and immunoblot analysis, although some muscle specimens show very low-level trace dystrophin expression. Phenotypically, the mouse shows similarities to mdx, the standard laboratory model of DMD. In skeletal muscle, areas of necrosis and phagocytosis are seen at 3 weeks, with central nucleation prominent by four weeks, recapitulating the "crisis" period in mdx. Marked diaphragm fibrosis is noted by 6 months, and remains unchanged at 12 months. Our results show that the Dup2 mouse is both pathologically (in degree and distribution) and physiologically similar to mdx. As it recapitulates the most common single exon duplication found in DMD patients, this new model will be a useful tool to assess the potential of duplicated exon skipping.

Reliability and validity of active-seated: An outcome in dystrophinopathy

INTRODUCTION

Traditional upper extremity measures typically focus on distal abilities and do not quantify the unique progression of decline in dystrophinopathy. We designed ACTIVE-seated to meet this need. Our objective was to establish the tool's validity and reliability.

METHODS

ACTIVE-seated uses the Microsoft Kinect gaming interface to quantify functional reaching ability while playing a custom-designed game. A skeletal tracking algorithm was used to determine the furthest arm excursion in all planes in 61 subjects with dystrophinopathy and 16 controls.

RESULTS

Total reachable area was scaled based on arm length to standardize comparisons across subjects and accommodate growth. ACTIVE-seated discriminately ranked subjects from normal controls and by Brooke level (P < 0.001). Scores were highly correlated with parent reports of daily activities and mobility (P < 0.05). Test-retest reliability of ACTIVE-seated was excellent (ICC = 0.97, P < 0.0001).

CONCLUSIONS

Initial evaluation of reliability and validity suggests that ACTIVE-seated shows promise as a clinical and research outcome for individuals with dystrophinopathy.

How a patient advocacy group developed the first proposed draft guidance document for industry for submission to the U.S. Food and Drug Administration

Among the challenges confronting patients with rare diseases is a dearth of treatment options. The development of safe and effective new therapies is hampered by challenges associated with conducting clinical trials in small populations. In this article, we describe how the Duchenne muscular dystrophy community–led by Parent Project Muscular Dystrophy–created a proposed draft guidance document for industry for submission to the U.S. Food and Drug Administration. This unprecedented undertaking involved a broad coalition of more than 80 stakeholders collaborating across nine time zones to produce a document in only 6 months. We hope that other rare disease communities and advocacy organizations can use our experience as a model for developing their own draft guidance documents.

Genetics and emerging treatments for Duchenne and Becker muscular dystrophy

Mutations in the DMD gene result in Duchenne or Becker muscular dystrophy due to absent or altered expression of the dystrophin protein. The more severe Duchenne muscular dystrophy typically presents around ages 2 to 5 with gait disturbance, and historically has led to the loss of ambulation by age 12. It is important for the practicing pediatrician, however, to be aware of other presenting signs, such as delayed motor or cognitive milestones, or elevated serum transaminases. Becker muscular dystrophy is milder, often presenting after age 5, with ambulation frequently preserved past 20 years and sometimes into late decades.

The TREAT-NMD advisory committee for therapeutics (TACT): an innovative de-risking model to foster orphan drug development

Despite multiple publications on potential therapies for neuromuscular diseases (NMD) in cell and animal models only a handful reach clinical trials. The ability to prioritise drug development according to objective criteria is particularly critical in rare diseases with large unmet needs and a limited numbers of patients who can be enrolled into clinical trials. TREAT-NMD Advisory Committee for Therapeutics (TACT) was established to provide independent and objective guidance on the preclinical and development pathway of potential therapies (whether novel or repurposed) for NMD.

We present our experience in the establishment and operation of the TACT. TACT provides a unique resource of recognized experts from multiple disciplines. The goal of each TACT review is to help the sponsor to position the candidate compound along a realistic and well-informed plan to clinical trials, and eventual registration. The reviews and subsequent recommendations are focused on generating meaningful and rigorous data that can enable clear go/no-go decisions and facilitate longer term funding or partnering opportunities. The review process thereby acts to comment on viability, de-risking the process of proceeding on a development programme.

To date TACT has held 10 review meeting and reviewed 29 program applications in several rare neuromuscular diseases: Of the 29 programs reviewed, 19 were from industry and 10 were from academia; 15 were for novel compounds and 14 were for repurposed drugs; 16 were small molecules and 13 were biologics; 14 were preclinical stage applications and 15 were clinical stage applications. 3 had received Orphan drug designation from European Medicines Agency and 3 from Food and Drug Administration. A number of recurrent themes emerged over the course of the reviews and we found that applicants frequently require advice and education on issues concerned with preclinical standard operating procedures, interactions with regulatory agencies, formulation, repurposing, clinical trial design, manufacturing and ethics.

Over the 5 years since its establishment TACT has amassed a body of experience that can be extrapolated to other groups of rare diseases to improve the community’s chances of successfully bringing new rare disease drugs to registration and ultimately to market.

The TREAT-NMD DMD Global Database: analysis of more than 7,000 Duchenne muscular dystrophy mutations

Analyzing the type and frequency of patient-specific mutations that give rise to Duchenne muscular dystrophy (DMD) is an invaluable tool for diagnostics, basic scientific research, trial planning, and improved clinical care. Locus-specific databases allow for the collection, organization, storage, and analysis of genetic variants of disease. Here, we describe the development and analysis of the TREAT-NMD DMD Global database (http://umd.be/TREAT_DMD/). We analyzed genetic data for 7,149 DMD mutations held within the database. A total of 5,682 large mutations were observed (80% of total mutations), of which 4,894 (86%) were deletions (1 exon or larger) and 784 (14%) were duplications (1 exon or larger). There were 1,445 small mutations (smaller than 1 exon, 20% of all mutations), of which 358 (25%) were small deletions and 132 (9%) small insertions and 199 (14%) affected the splice sites. Point mutations totalled 756 (52% of small mutations) with 726 (50%) nonsense mutations and 30 (2%) missense mutations. Finally, 22 (0.3%) mid-intronic mutations were observed. In addition, mutations were identified within the database that would potentially benefit from novel genetic therapies for DMD including stop codon read-through therapies (10% of total mutations) and exon skipping therapy (80% of deletions and 55% of total mutations).