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Journal of Neuromuscular Diseases 2023Duchenne muscular dystrophy (DMD) is caused by DMD gene mutations, resulting in absence of functional dystrophin protein. Viltolarsen, an exon 53 skipping therapy,...
BACKGROUND
Duchenne muscular dystrophy (DMD) is caused by DMD gene mutations, resulting in absence of functional dystrophin protein. Viltolarsen, an exon 53 skipping therapy, significantly increased dystrophin levels in patients with DMD. Presented here are completed study results of > 4 years of functional outcomes in viltolarsen-treated patients compared to a historical control group (Cooperative International Neuromuscular Research Group Duchenne Natural History Study [CINRG DNHS]).
OBJECTIVE
To evaluate the efficacy and safety of viltolarsen for an additional 192 weeks in boys with DMD.
METHODS
This phase 2, open-label, 192-week long-term extension (LTE) study (NCT03167255) evaluated the efficacy and safety of viltolarsen in participants aged 4 to < 10 years at baseline with DMD amenable to exon 53 skipping. All 16 participants from the initial 24-week study enrolled into this LTE. Timed function tests were compared to the CINRG DNHS group. All participants received glucocorticoid treatment. The primary efficacy outcome was time to stand from supine (TTSTAND). Secondary efficacy outcomes included additional timed function tests. Safety was continuously assessed.
RESULTS
For the primary efficacy outcome (TTSTAND), viltolarsen-treated patients showed stabilization of motor function over the first two years and significant slowing of disease progression over the following two years compared with the CINRG DNHS control group which declined. Viltolarsen was well tolerated, with most reported treatment-emergent adverse events being mild or moderate. No participants discontinued drug during the study.
CONCLUSIONS
Based on the results of this 4-year LTE, viltolarsen can be an important treatment strategy for DMD patients amenable to exon 53 skipping.
Topics: Male; Humans; Muscular Dystrophy, Duchenne; Dystrophin; Oligonucleotides; Glucocorticoids
PubMed: 37005891
DOI: 10.3233/JND-221656 -
Circulation Research Feb 2022
Topics: Dystrophin; Humans; Muscular Dystrophy, Duchenne; Stem Cell Transplantation
PubMed: 35113658
DOI: 10.1161/CIRCRESAHA.121.320663 -
Circulation. Genomic and Precision... Oct 2023Variants in the gene, that encodes the cytoskeletal protein, dystrophin, cause a severe form of dilated cardiomyopathy (DCM) associated with high rates of heart...
BACKGROUND
Variants in the gene, that encodes the cytoskeletal protein, dystrophin, cause a severe form of dilated cardiomyopathy (DCM) associated with high rates of heart failure, heart transplantation, and ventricular arrhythmias. Improved early detection of individuals at risk is needed.
METHODS
Genetic testing of 40 male probands with a potential X-linked genetic cause of primary DCM was undertaken using multi-gene panel sequencing, multiplex polymerase chain reaction, and array comparative genomic hybridization. Variant location was assessed with respect to dystrophin isoform patterns and exon usage. Telomere length was evaluated as a marker of myocardial dysfunction in left ventricular tissue and blood.
RESULTS
Four pathogenic/likely pathogenic variants were found in 5 probands (5/40: 12.5%). Only one rare variant was identified by gene panel testing with 3 additional multi-exon deletion/duplications found following targeted assays for structural variants. All of the pathogenic/likely pathogenic variants involved dystrophin exons that had percent spliced-in scores >90, indicating high levels of constitutive expression in the human adult heart. Fifteen variant-negative probands (15/40: 37.5%) had variants in autosomal genes including , , , and . Myocardial telomere length was reduced in patients with DCM irrespective of genotype. No differences in blood telomere length were observed between genotype-positive family members with/without DCM and controls.
CONCLUSIONS
Primary genetic testing using multi-gene panels has a low yield and specific assays for structural variants are required if -associated cardiomyopathy is suspected. Distinguishing X-linked causes of DCM from autosomal genes that show sex differences in clinical presentation is crucial for informed family management.
Topics: Adult; Humans; Male; Female; Dystrophin; Comparative Genomic Hybridization; Pedigree; Genotype; Phenotype; Adaptor Proteins, Signal Transducing; Apoptosis Regulatory Proteins
PubMed: 37671549
DOI: 10.1161/CIRCGEN.123.004221 -
Circulation Nov 2021Loss of dystrophin protein causes Duchenne muscular dystrophy (DMD), characterized by progressive degeneration of cardiac and skeletal muscles, and mortality in...
BACKGROUND
Loss of dystrophin protein causes Duchenne muscular dystrophy (DMD), characterized by progressive degeneration of cardiac and skeletal muscles, and mortality in adolescence or young adulthood. Although cardiac failure has risen as the leading cause of mortality in patients with DMD, effective therapeutic interventions remain underdeveloped, in part, because of the lack of a suitable preclinical model.
METHODS
We analyzed a novel murine model of DMD created by introducing a 4-bp deletion into exon 4, one of the exons encoding the actin-binding domain 1 of dystrophin (referred to as mice). Echocardiography, microcomputed tomography, muscle force measurement, and histological analysis were performed to determine cardiac and skeletal muscle defects in these mice. Using this model, we examined the feasibility of using a cytidine base editor to install exon skipping and rescue dystrophic cardiomyopathy in vivo. AAV9-based CRISPR/Cas9-AID (eTAM) together with AAV9-sgRNA was injected into neonatal mice, which were analyzed 2 or 12 months after treatment to evaluate the extent of exon skipping, dystrophin restoration, and phenotypic improvements of cardiac and skeletal muscles.
RESULTS
mice recapitulated many aspects of human DMD, including shortened life span (by ≈50%), progressive cardiomyopathy, kyphosis, profound loss of muscle strength, and myocyte degeneration. A single-dose administration of AAV9-eTAM instituted >50% targeted exon skipping in the transcripts and restored up to 90% dystrophin in the heart. As a result, early ventricular remodeling was prevented and cardiac and skeletal muscle functions were improved, leading to an increased life span of the mice. Despite gradual decline of AAV vector and base editor expression, dystrophin restoration and pathophysiological rescue of muscular dystrophy were long lasted for at least 1 year.
CONCLUSIONS
Our study demonstrates the feasibility and efficacy to institute exon skipping through an enhanced TAM (eTAM) for therapeutic application(s).
Topics: APOBEC Deaminases; Animals; CRISPR-Cas Systems; Cardiomyopathies; Dependovirus; Dystrophin; Exons; Genetic Vectors; Humans; Mice; Mice, Inbred mdx; Muscular Dystrophy, Duchenne
PubMed: 34698513
DOI: 10.1161/CIRCULATIONAHA.121.054628 -
Neurotherapeutics : the Journal of the... Oct 2023Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. It is caused by mutations in the DMD gene, leading to reduced or absent... (Review)
Review
Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. It is caused by mutations in the DMD gene, leading to reduced or absent expression of the dystrophin protein. Clinically, this results in loss of ambulation, cardiomyopathy, respiratory failure, and eventually death. In the past decades, the use of corticosteroids has slowed down the disease progression. More recently, the development of genetically mediated therapies has emerged as the most promising treatment for DMD. These strategies include exon skipping with antisense oligonucleotides, gene replacement therapy with adeno-associated virus, and gene editing with CRISPR (clustered regularly interspaced short palindromic repeats) technology. In this review, we highlight the most up-to-date therapeutic progresses in the field, with emphasis on past and recent experiences, as well as the latest clinical results of DMD micro-dystrophin gene therapy. Additionally, we discuss the lessons learned along the way and the challenges encountered, all of which have helped advance the field, with the potential to finally alleviate such a devastating disease.
Topics: Humans; Child; Muscular Dystrophy, Duchenne; Dystrophin; Gene Editing; Exons; Genetic Therapy
PubMed: 37673849
DOI: 10.1007/s13311-023-01423-y -
Nature Cell Biology Nov 2020Dystrophin proteomic regulation in muscular dystrophies (MDs) remains unclear. We report that a long noncoding RNA (lncRNA), H19, associates with dystrophin and inhibits...
Dystrophin proteomic regulation in muscular dystrophies (MDs) remains unclear. We report that a long noncoding RNA (lncRNA), H19, associates with dystrophin and inhibits E3-ligase-dependent polyubiquitination at Lys 3584 (referred to as Ub-DMD) and its subsequent protein degradation. In-frame deletions in BMD and a DMD non-silent mutation (C3340Y) resulted in defects in the ability of the protein to interact with H19, which caused elevated Ub-DMD levels and dystrophin degradation. Dmd C3333Y mice exhibited progressive MD, elevated serum creatine kinase, heart dilation, blood vessel irregularity and respiratory failure with concurrently reduced dystrophin and increased Ub-DMD status. H19 RNA oligonucleotides conjugated with agrin (AGR-H19) and nifenazone competed with or inhibited TRIM63. Dmd C3333Y animals, induced-pluripotent-stem-cell-derived skeletal muscle cells from patients with Becker MD and mdx mice subjected to exon skipping exhibited inhibited dystrophin degradation, preserved skeletal and cardiac muscle histology, and improved strength and heart function following AGR-H19 or nifenazone treatment. Our study paves the way for meaningful targeted therapeutics for Becker MD and for certain patients with Duchenne MD.
Topics: Animals; Antipyrine; Cardiomyopathies; Cell Line; Disease Models, Animal; Dystrophin; Enzyme Inhibitors; Female; Half-Life; Humans; Induced Pluripotent Stem Cells; Male; Mice, Inbred C57BL; Mice, Inbred mdx; Mice, Mutant Strains; Muscle Proteins; Muscle Strength; Muscle, Skeletal; Muscular Dystrophies; Mutation; Myocytes, Cardiac; Niacinamide; Oligonucleotides; Protein Stability; Proteolysis; RNA, Long Noncoding; Tripartite Motif Proteins; Ubiquitin-Protein Ligases; Ubiquitination
PubMed: 33106653
DOI: 10.1038/s41556-020-00595-5 -
Acta Neuropathologica Communications Oct 2023Duchenne muscular dystrophy (DMD) is a devastating X-linked muscular disease, caused by mutations in the DMD gene encoding Dystrophin and affecting 1:5000 boys...
Duchenne muscular dystrophy (DMD) is a devastating X-linked muscular disease, caused by mutations in the DMD gene encoding Dystrophin and affecting 1:5000 boys worldwide. Lack of Dystrophin leads to progressive muscle wasting and degeneration resulting in cardiorespiratory failure. Despite the absence of a definitive cure, innovative therapeutic avenues are emerging. Myopathologic studies are important to further understand the biological mechanisms of the disease and to identify histopathologic benchmarks for clinical evaluations. We conducted a myopathologic analysis on twenty-four muscle biopsies from DMD patients, with particular emphasis on regeneration, fibro-adipogenic progenitors and muscle stem cells behavior. We describe an increase in content of fibro-adipogenic progenitors, central orchestrators of fibrotic progression and lipid deposition, concurrently with a decline in muscle regenerative capacity. This regenerative impairment strongly correlates with compromised activation and expansion of muscle stem cells. Furthermore, our study uncovers an early acquisition of a senescence phenotype by DMD-afflicted muscle stem cells. Here we describe the myopathologic trajectory intrinsic to DMD and establish muscle stem cell senescence as a pivotal readout for future therapeutic interventions.
Topics: Humans; Male; Dystrophin; Fibrosis; Muscle, Skeletal; Muscular Dystrophy, Duchenne; Regeneration; Satellite Cells, Skeletal Muscle; Cellular Senescence
PubMed: 37858263
DOI: 10.1186/s40478-023-01657-z -
Progress in Retinal and Eye Research Jul 2023Duchenne muscular dystrophy (DMD) is caused by X-linked inherited or de novo DMD gene mutations predominantly affecting males who develop early-onset muscle... (Review)
Review
Duchenne muscular dystrophy (DMD) is caused by X-linked inherited or de novo DMD gene mutations predominantly affecting males who develop early-onset muscle degeneration, severely affecting their quality of life and leading to reduced life expectancy. DMD patients may also develop proliferative retinopathy, cataract, ERG abnormalities, altered contrast sensitivity, color vision losses, and elevated flash detection thresholds during dark adaptation. Depending on the position of the genetic alteration in the large DMD gene, it is associated with a lack of the full-length dystrophin protein possibly with an additional loss of one or several other dystrophins, which are normally transcribed from internal promoters in retina and crystalline lens. During the last decades, the properties of the dystrophins have been characterized in patients with different genetic alterations and in genetic mouse models of DMD. The complex expression pattern of the dystrophins in photoreceptors, Müller glial cells and astrocytes, likely influences synaptic transmission, ionic balance and vascular integrity of the retina. However, the specific function of each retinal dystrophin remains largely unknown. This review describes the current knowledge on dystrophin expression, the putative molecular, structural, and physiological properties of retinal dystrophins, and the main clinical implications associated with the loss of dystrophins in DMD patients and mouse models. Current data and working hypotheses warrant future research on retinal dystrophins to increase our understanding of dystrophin function in the central nervous system in general and to unveil new retinal mechanisms and therapeutic avenues for retinal diseases.
Topics: Male; Mice; Animals; Dystrophin; Muscular Dystrophy, Duchenne; Quality of Life; Retina; Retinal Diseases
PubMed: 36404230
DOI: 10.1016/j.preteyeres.2022.101137 -
Journal of Neuromuscular Diseases 2020The DMD gene is the largest in the human genome, with a total intron content exceeding 2.2Mb. In the decades since DMD was discovered there have been numerous reported... (Review)
Review
The DMD gene is the largest in the human genome, with a total intron content exceeding 2.2Mb. In the decades since DMD was discovered there have been numerous reported cases of pseudoexons (PEs) arising in the mature DMD transcripts of some individuals, either as the result of mutations or as low-frequency errors of the spliceosome. In this review, I collate from the literature 58 examples of DMD PEs and examine the diversity and commonalities of their features. In particular, I note the high frequency of PEs that arise from deep intronic SNVs and discuss a possible link between PEs induced by distal mutations and the regulation of recursive splicing.
Topics: Dystrophin; Exons; Humans; Introns; Muscular Dystrophy, Duchenne; RNA Splicing
PubMed: 32176650
DOI: 10.3233/JND-190431 -
Cell Reports Nov 2023Duchenne muscular dystrophy (DMD) is a severe genetic disease caused by the loss of the dystrophin protein. Exon skipping is a promising strategy to treat DMD by...
Duchenne muscular dystrophy (DMD) is a severe genetic disease caused by the loss of the dystrophin protein. Exon skipping is a promising strategy to treat DMD by restoring truncated dystrophin. Here, we demonstrate that base editors (e.g., targeted AID-mediated mutagenesis [TAM]) are able to efficiently induce exon skipping by disrupting functional redundant exonic splicing enhancers (ESEs). By developing an unbiased and high-throughput screening to interrogate exonic sequences, we successfully identify novel ESEs in DMD exons 51 and 53. TAM-CBE (cytidine base editor) induces near-complete skipping of the respective exons by targeting these ESEs in patients' induced pluripotent stem cell (iPSC)-derived cardiomyocytes. Combined with strategies to disrupt splice sites, we identify suitable single guide RNAs (sgRNAs) with TAM-CBE to efficiently skip most DMD hotspot exons without substantial double-stranded breaks. Our study thus expands the repertoire of potential targets for CBE-mediated exon skipping in treating DMD and other RNA mis-splicing diseases.
Topics: Humans; Dystrophin; RNA, Guide, CRISPR-Cas Systems; Muscular Dystrophy, Duchenne; RNA Splicing; Exons
PubMed: 37906593
DOI: 10.1016/j.celrep.2023.113340