Long-term data with idebenone on respiratory function outcomes in patients with Duchenne muscular dystrophy

Tcap deficiency impedes striated muscle function and heart regeneration with elevated ROS and autophagy

Telethonin/titin-cap (TCAP) encodes a Z-disc protein that plays important roles in sarcomere/T-tubule interactions, stretch-sensing and signaling. Mutations in TCAP are associated with muscular dystrophy and cardiomyopathy; however, the complete etiology and its roles in myocardial infarction and regeneration are not fully understood. Here, we generated tcap gene knockout zebrafish with CRISPR/Cas9 technology and observed muscular dystrophy-like phenotypes and abnormal mitochondria in skeletal muscles. The stretch-sensing ability was inhibited in tcap-/- mutants. Moreover, Tcap deficiency led to alterations in cardiac morphology and function as well as increases in reactive oxygen species (ROS) and mitophagy. In addition, the cardiac regeneration and cardiomyocyte proliferation ability of tcap-/- mutants were impaired, but these impairments could be rescued by supplementation with ROS scavengers or autophagy inhibitors. Overall, our study demonstrates the essential roles of Tcap in striated muscle function and heart regeneration. Additionally, elevations in ROS and autophagy may account for the phenotypes resulting from Tcap deficiency and could serve as novel therapeutic targets for muscular dystrophy and cardiomyopathy.

Efficacy and Safety of Coenzyme Q10 Supplementation in Neonates, Infants and Children: An Overview

To date, there have been no review articles specifically relating to the general efficacy and safety of coenzyme Q10 (CoQ10) supplementation in younger subjects. In this article, we therefore reviewed the efficacy and safety of CoQ10 supplementation in neonates (less than 1 month of age), infants (up to 1 year of age) and children (up to 12 years of age). As there is no rationale for the supplementation of CoQ10 in normal younger subjects (as there is in otherwise healthy older subjects), all of the articles in the medical literature reviewed in the present article therefore refer to the supplementation of CoQ10 in younger subjects with a variety of clinical disorders; these include primary CoQ10 deficiency, acyl CoA dehydrogenase deficiency, Duchenne muscular dystrophy, migraine, Down syndrome, ADHD, idiopathic cardiomyopathy and Friedreich's ataxia.

Critical contribution of mitochondria in the development of cardiomyopathy linked to desmin mutation

BACKGROUND

Beyond the observed alterations in cellular structure and mitochondria, the mechanisms linking rare genetic mutations to the development of heart failure in patients affected by desmin mutations remain unclear due in part, to the lack of relevant human cardiomyocyte models.

METHODS

To shed light on the role of mitochondria in these mechanisms, we investigated cardiomyocytes derived from human induced pluripotent stem cells carrying the heterozygous DESE439K mutation that were either isolated from a patient or generated by gene editing. To increase physiological relevance, cardiomyocytes were either cultured on an anisotropic micropatterned surface to obtain elongated and aligned cardiomyocytes, or as a cardiac spheroid to create a micro-tissue. Moreover, when applicable, results from cardiomyocytes were confirmed with heart biopsies of suddenly died patient of the same family harboring DESE439K mutation, and post-mortem heart samples from five control healthy donors.

RESULTS

The heterozygous DESE439K mutation leads to dramatic changes in the overall cytoarchitecture of cardiomyocytes, including cell size and morphology. Most importantly, mutant cardiomyocytes display altered mitochondrial architecture, mitochondrial respiratory capacity and metabolic activity reminiscent of defects observed in patient's heart tissue. Finally, to challenge the pathological mechanism, we transferred normal mitochondria inside the mutant cardiomyocytes and demonstrated that this treatment was able to restore mitochondrial and contractile functions of cardiomyocytes.

CONCLUSIONS

This work highlights the deleterious effects of DESE439K mutation, demonstrates the crucial role of mitochondrial abnormalities in the pathophysiology of desmin-related cardiomyopathy, and opens up new potential therapeutic perspectives for this disease.

Protection of dystrophic muscle cells using Idebenone correlates with the interplay between calcium, oxidative stress and inflammation

There is strong cross-talk between abnormal intracellular calcium concentration, high levels of reactive oxygen species (ROS) and an exacerbated inflammatory process in the dystrophic muscles of mdx mice, the experimental model of Duchenne muscular dystrophy (DMD). In this study, we investigated effects of Idebenone, a potent anti-oxidant, on oxidative stress markers, the anti-oxidant defence system, intracellular calcium concentrations and the inflammatory process in primary dystrophic muscle cells from mdx mice. Dystrophic muscle cells were treated with Idebenone (0.05 μM) for 24 h. The untreated mdx muscle cells were used as controls. The MTT assay showed that Idebenone did not have a cytotoxic effect on the dystrophic muscle cells. The Idebenone treatment was able to reduce the levels of oxidative stress markers, such as H2 O2 and 4-HNE, as well as decreasing intracellular calcium influx in the dystrophic muscle cells. Regarding Idebenone effects on the anti-oxidant defence system, an up-regulation of catalase levels, glutathione reductase (GR), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity was observed in the dystrophic muscle cells. In addition, the Idebenone treatment was also associated with reduction in inflammatory molecules, such as nuclear factor kappa-B (NF-κB) and tumour necrosis factor (TNF) in mdx muscle cells. These outcomes supported the use of Idebenone as a protective agent against oxidative stress and related signalling mechanisms involved in dystrophinopathies, such as DMD.

BKCa Activator NS1619 Improves the Structure and Function of Skeletal Muscle Mitochondria in Duchenne Dystrophy

Duchenne muscular dystrophy (DMD) is a progressive hereditary disease caused by the absence of the dystrophin protein. This is secondarily accompanied by a dysregulation of ion homeostasis, in which mitochondria play an important role. In the present work, we show that mitochondrial dysfunction in the skeletal muscles of dystrophin-deficient mdx mice is accompanied by a reduction in K+ transport and a decrease in its content in the matrix. This is associated with a decrease in the expression of the mitochondrial large-conductance calcium-activated potassium channel (mitoBKCa) in the muscles of mdx mice, which play an important role in cytoprotection. We observed that the BKCa activator NS1619 caused a normalization of mitoBKCa expression and potassium homeostasis in the muscle mitochondria of these animals, which was accompanied by an increase in the calcium retention capacity, mitigation of oxidative stress, and improvement in mitochondrial ultrastructure. This effect of NS1619 contributed to the reduction of degeneration/regeneration cycles and fibrosis in the skeletal muscles of mdx mice as well as a normalization of sarcomere size, but had no effect on the leakage of muscle enzymes and muscle strength loss. In the case of wild-type mice, we noted the negative effect of NS1619 manifested in the inhibition of the functional activity of mitochondria and disruption of their structure, which, however, did not significantly affect the state of the skeletal muscles of the animals. This article discusses the role of mitoBKCa in the development of DMD and the prospects of the approach associated with the correction of its function in treatments of this secondary channelopathy.

Generating Evidence from Expanded Access Use of Rare Disease Medicines: Challenges and Recommendations

Patients with rare diseases often have limited or no options for approved treatments or participation in clinical trials. In such cases, expanded access (or “compassionate use”) provides a potential means of accessing unapproved investigational medicines. It is also possible to capture and analyze clinical data from such use, but doing so is controversial. In this perspective, we offer examples of evidence derived from expanded access programs for rare diseases to illustrate its potential value to the decision-making of regulators and payers in the European Union and the United States. We discuss ethical and regulatory aspects to the use of expanded access data, with a focus on rare disease medicines. The heterogeneous approach to expanded access among countries within the European Union leaves uncertainties to what extent data can be collected and analyzed. We recommend the issuance of new guidance on data collection during expanded access, harmonization of European pathways, and an update of existing European compassionate use guidance. We hereby aim to clarify the supportive role of expanded access in evidence generation. Harmonization across Europe of expanded access regulations could reduce manufacturer burdens, improve patient access, and yield better data. These changes would better balance the need to generate quality evidence with the desire for pre-approval access to investigational medicine.

Tcap Deficiency in Zebrafish Leads to ROS Production and Mitophagy, and Idebenone Improves its Phenotypes

Limb-girdle muscular dystrophy 2G (LGMD2G) is a subtype of limb-girdle muscular dystrophy. However, the disease’s mechanisms are still not fully understood, and no established therapeutic targets have been found. Using a morpholino-based knockdown approach, we established an LGMD2G zebrafish model. In this study, we found that the ROS level increased in LGMD2G zebrafish. The expression of the mitophagy-related protein BNIP3L, LC3A-II/LC3A-I, and LAMP1 were increased in LGMD2G zebrafish. The oxygen consumption rate and citrate synthase expression was significantly decreased. Thus, mitophagy was presumed to be involved in the LGMD2G to reduce ROS levels. Then, we administered vitamin C, coenzyme Q10, idebenone, metformin, or dexamethasone to rescue LGMD2G in zebrafish. Idebenone reduced the curly tail phenotype and ROS level. Also, it reduced BNIP3L expression in LGMD2G zebrafish models and improved their motor function. In conclusion, mitophagy might be involved in the LGMD2G, and idebenone ameliorated LGMD2G by downregulating ROS level.

Cytoprotective Effect of Idebenone through Modulation of the Intrinsic Mitochondrial Pathway of Apoptosis in Human Retinal Pigment Epithelial Cells Exposed to Oxidative Stress Induced by Hydrogen Peroxide

Idebenone is a ubiquinone short-chain synthetic analog with antioxidant properties, which is believed to restore mitochondrial ATP synthesis. As such, idebenone is investigated in numerous clinical trials for diseases of mitochondrial aetiology and it is authorized as a drug for the treatment of Leber’s hereditary optic neuropathy. Mitochondria of retinal pigment epithelium (RPE) are particularly vulnerable to oxidative damage associated with cellular senescence. Therefore, the aim of this study was to explore idebenone’s cytoprotective effect and its underlying mechanism. We used a human-RPE cell line (ARPE-19) exposed to idebenone pre-treatment for 24 h followed by conditions inducing H₂O₂ oxidative damage for a further 24 h. We found that idebenone: (a) ameliorated H₂O₂-lowered cell viability in the RPE culture; (b) activated Nrf2 signaling pathway by promoting Nrf2 nuclear translocation; (c) increased Bcl-2 protein levels, leaving unmodified those of Bax, thereby reducing the Bax/Bcl-2 ratio; (d) maintained the mitochondrial membrane potential (ΔΨ_m) at physiological levels, preserving the functionality of mitochondrial respiratory complexes and counteracting the excessive production of ROS; and (e) reduced mitochondrial cytochrome C-mediated caspase-3 activity. Taken together, our findings show that idebenone protects RPE from oxidative damage by modulating the intrinsic mitochondrial pathway of apoptosis, suggesting its possible role in retinal epitheliopathies associated with mitochondrial dysfunction.

Therapeutic Application of Extracellular Vesicles-Capsulated Adeno-Associated Virus Vector via nSMase2/Smpd3, Satellite, and Immune Cells in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by loss-of-function mutations in the dystrophin gene on chromosome Xp21. Disruption of the dystrophin-glycoprotein complex (DGC) on the cell membrane causes cytosolic Ca2+ influx, resulting in protease activation, mitochondrial dysfunction, and progressive myofiber degeneration, leading to muscle wasting and fragility. In addition to the function of dystrophin in the structural integrity of myofibers, a novel function of asymmetric cell division in muscular stem cells (satellite cells) has been reported. Therefore, it has been suggested that myofiber instability may not be the only cause of dystrophic degeneration, but rather that the phenotype might be caused by multiple factors, including stem cell and myofiber functions. Furthermore, it has been focused functional regulation of satellite cells by intracellular communication of extracellular vesicles (EVs) in DMD pathology. Recently, a novel molecular mechanism of DMD pathogenesis-circulating RNA molecules-has been revealed through the study of target pathways modulated by the Neutral sphingomyelinase2/Neutral sphingomyelinase3 (nSMase2/Smpd3) protein. In addition, adeno-associated virus (AAV) has been clinically applied for DMD therapy owing to the safety and long-term expression of transduction genes. Furthermore, the EV-capsulated AAV vector (EV-AAV) has been shown to be a useful tool for the intervention of DMD, because of the high efficacy of the transgene and avoidance of neutralizing antibodies. Thus, we review application of AAV and EV-AAV vectors for DMD as novel therapeutic strategy.

Therapeutic approaches to preserve the musculature in Duchenne Muscular Dystrophy: The importance of the secondary therapies

Muscular dystrophies (MDs) are heterogeneous diseases, characterized by primary wasting of skeletal muscle, which in severe cases, such as Duchenne Muscular Dystrophy (DMD), leads to wheelchair dependency, respiratory failure, and premature death. Research is ongoing to develop efficacious therapies, particularly for DMD. Most of the efforts, currently focusing on correcting or restoring the primary defect of MDs, are based on gene-addition, exon-skipping, stop codon read-through, and genome-editing. Although promising, most of them revealed several practical limitations. Shared knowledge in the field is that, in order to be really successful, any therapeutic approach has to rely on spared functional muscle tissue, restricting the number of patients eligible for clinical trials to the youngest and less compromised individuals. In line with this, many therapeutic strategies aim to preserve muscle tissue and function. This Review outlines the most interesting and recent studies addressing the secondary outcomes of DMD and how to better deliver the therapeutic agents. In the future, the effective treatment of DMD will likely require combinations of therapies addressing both the primary genetic defect and its consequences.

Lessons Learned From Translational Research in Neuromuscular Diseases: Impact on Study Design, Outcome Measures and Managing Expectation

Spinal Muscular Atrophy (SMA) and Duchenne Muscular Dystrophy (DMD), two of the most common, child onset, rare neuromuscular disorders, present a case study for the translation of preclinical research into clinical work. Over the past decade, well-designed clinical trials and innovative methods have led to the approval of several novel therapies for SMA and DMD, with many more in the pipeline. This review discusses several features that must be considered during trial design for neuromuscular diseases, as well as other rare diseases, to maximise the possibility of trial success using historic examples. These features include well-defined inclusion criteria, matching criteria, alternatives to placebo-controlled trials and the selection of trial endpoints. These features will be particularly important in the coming years as the investigation into innovative therapy approaches for neuromuscular diseases continues.

Mitigating the pro-oxidant state and melanogenesis of Retinitis pigmentosa: by counteracting mitochondrial dysfunction

Retinitis pigmentosa (RP) is a group of mitochondrial diseases characterized by progressive degeneration of rods and cones leading to retinal loss of light sensitivity and, consequently, to blindness. To date, no cure is available according to the clinical literature. As a disease associated with pigmentation-related, pro-oxidant state, and mitochondrial dysfunction, RP may be viewed at the crossroads of different pathogenetic pathways involved in adverse health outcomes, where mitochondria play a preeminent role. RP has been investigated in a number of experimental and clinical studies aimed at delaying retinal hyperpigmentation by means of a number of natural and synthetic antioxidants, as well as mitochondrial cofactors, also termed mitochondrial nutrients (MNs), such as alpha-lipoic acid, coenzyme Q10 and carnitine. One should consider that each MN plays distinct-and indispensable-roles in mitochondrial function. Thus, a logical choice would imply the administration of MN combinations, instead of individual MNs, as performed in previous studies, and with limited, if any, positive outcomes. A rational study design aimed at comparing the protective effects of MNs, separately or in combinations, and in association with other antioxidants, might foresee the utilization of animal RP models. The results should verify a comparative optimization in preventing or effectively contrasting retinal oxidative stress in mouse RP models and, in prospect, in human RP cases.

Antioxidants to prevent respiratory decline in people with Duchenne muscular dystrophy and progressive respiratory decline

BACKGROUND

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterised by progressive muscle weakness beginning in early childhood. Respiratory failure and weak cough develop in all patients as a consequence of muscle weakness leading to a risk of atelectasis, pneumonia, or the need for ventilatory support. There is no curative treatment for DMD. Corticosteroids are the only pharmacological intervention proven to delay the onset and progression of muscle weakness and thus respiratory decline in DMD. Antioxidant treatment has been proposed to try to reduce muscle weakness in general, and respiratory decline in particular.  OBJECTIVES: To assess the effects of antioxidant agents on preventing respiratory decline in people with Duchenne muscular dystrophy during the respiratory decline phase of the condition.  SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, and two trials registers to 23 March 2021, together with reference checking, citation searching, and contact with study authors to identify additional studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that met our inclusion criteria. We included male patients with a diagnosis of DMD who had respiratory decline evidenced by a forced vital capacity (FVC%) less than 80% but greater than 30% of predicted values, receiving any antioxidant agent compared with other therapies for the management of DMD or placebo.  DATA COLLECTION AND ANALYSIS: Two review authors screened studies for eligibility, assessed risk of bias of studies, and extracted data. We used standard methods expected by Cochrane. We assessed the certainty of the evidence using the GRADE approach. The primary outcomes were FVC and hospitalisation due to respiratory infections. Secondary outcomes were quality of life, adverse events, change in muscle function, forced expiratory volume in the first second (FEV1), and peak expiratory flow (PEF).  MAIN RESULTS: We included one study with 66 participants who were not co-treated with corticosteroids, which was the only study to contribute data to our main analysis. We also included a study that enrolled 255 participants treated with corticosteroids, which was only available as a press release without numerical results. The studies were parallel-group RCTs that assessed the effect of idebenone on respiratory function compared to placebo. The trial that contributed numerical data included patients with a mean (standard deviation) age of 14.3 (2.7) years at the time of inclusion, with a documented diagnosis of DMD or severe dystrophinopathy with clinical features consistent with typical DMD. The overall risk of bias across most outcomes was similar and judged as 'low'.  Idebenone may result in a slightly less of a decline in FVC from baseline to one year compared to placebo (mean difference (MD) 3.28%, 95% confidence interval (CI) -0.41 to 6.97; 64 participants; low-certainty evidence), and probably has little or no effect on change in quality of life (MD -3.80, 95% CI -10.09 to 2.49; 63 participants; moderate-certainty evidence) (Pediatric Quality of Life Inventory (PedsQL), range 0 to 100, 0 = worst, 100 = best quality of life). As a related but secondary outcome, idebenone may result in less of a decline from baseline in FEV1 (MD 8.28%, 95% CI 0.89 to 15.67; 53 participants) and PEF (MD 6.27%, 95% CI 0.61 to 11.93; 1 trial, 64 participants) compared to placebo. Idebenone was associated with fewer serious adverse events (RR 0.42, 95% CI 0.09 to 2.04; 66 participants; low-certainty evidence) and little to no difference in non-serious adverse events (RR 1.00, 95% CI 0.88 to 1.13; 66 participants; low-certainty evidence) compared to placebo. Idebenone may result in little to no difference in change in arm muscle function (MD -2.45 N, 95% CI -8.60 to 3.70 for elbow flexors and MD -1.06 N, 95% CI -6.77 to 4.65 for elbow extensors; both 52 participants) compared to placebo. We found no studies evaluating the outcome hospitalisation due to respiratory infection.  The second trial, involving 255 participants, for which data were available only as a press release without numerical data, was prematurely discontinued due to futility after an interim efficacy analysis based on FVC. There were no safety concerns. The certainty of the evidence was low for most outcomes due to imprecision and publication bias (the lack of a full report of the larger trial, which was prematurely terminated).

AUTHORS' CONCLUSIONS

Idebenone is the only antioxidant agent tested in RCTs for preventing respiratory decline in people with DMD for which evidence was available for assessment. Idebenone may result in slightly less of a decline in FVC and less of a decline in FEV1 and PEF, but probably has little to no measurable effect on change in quality of life. Idebenone is associated with fewer serious adverse events than placebo. Idebenone may result in little to no difference in change in muscle function. Discontinuation due to the futility of the SIDEROS trial and its expanded access programmes may indicate that idebenone research in this condition is no longer needed, but we await the trial data. Further research is needed to establish the effect of different antioxidant agents on preventing respiratory decline in people with DMD during the respiratory decline phase of the condition.

Antioxidants to prevent respiratory decline in people with Duchenne muscular dystrophy and progressive respiratory decline

BACKGROUND

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterised by progressive muscle weakness beginning in early childhood. Respiratory failure and weak cough develop in all patients as a consequence of muscle weakness leading to a risk of atelectasis, pneumonia, or the need for ventilatory support. There is no curative treatment for DMD. Corticosteroids are the only pharmacological intervention proven to delay the onset and progression of muscle weakness and thus respiratory decline in DMD. Antioxidant treatment has been proposed to try to reduce muscle weakness in general, and respiratory decline in particular.  OBJECTIVES: To assess the effects of antioxidant agents on preventing respiratory decline in people with Duchenne muscular dystrophy during the respiratory decline phase of the condition.  SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, and two trials registers to 23 March 2021, together with reference checking, citation searching, and contact with study authors to identify additional studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that met our inclusion criteria. We included male patients with a diagnosis of DMD who had respiratory decline evidenced by a forced vital capacity (FVC%) less than 80% but greater than 30% of predicted values, receiving any antioxidant agent compared with other therapies for the management of DMD or placebo.  DATA COLLECTION AND ANALYSIS: Two review authors screened studies for eligibility, assessed risk of bias of studies, and extracted data. We used standard methods expected by Cochrane. We assessed the certainty of the evidence using the GRADE approach. The primary outcomes were FVC and hospitalisation due to respiratory infections. Secondary outcomes were quality of life, adverse events, change in muscle function, forced expiratory volume in the first second (FEV1), and peak expiratory flow (PEF).  MAIN RESULTS: We included one study with 66 participants who were not co-treated with corticosteroids, which was the only study to contribute data to our main analysis. We also included a study that enrolled 255 participants treated with corticosteroids, which was only available as a press release without numerical results. The studies were parallel-group RCTs that assessed the effect of idebenone on respiratory function compared to placebo. The trial that contributed numerical data included patients with a mean (standard deviation) age of 14.3 (2.7) years at the time of inclusion, with a documented diagnosis of DMD or severe dystrophinopathy with clinical features consistent with typical DMD. The overall risk of bias across most outcomes was similar and judged as 'low'.  Idebenone may result in a slightly less of a decline in FVC from baseline to one year compared to placebo (mean difference (MD) 3.28%, 95% confidence interval (CI) -0.41 to 6.97; 64 participants; low-certainty evidence), and probably has little or no effect on change in quality of life (MD -3.80, 95% CI -10.09 to 2.49; 63 participants; moderate-certainty evidence) (Pediatric Quality of Life Inventory (PedsQL), range 0 to 100, 0 = worst, 100 = best quality of life). As a related but secondary outcome, idebenone may result in less of a decline from baseline in FEV1 (MD 8.28%, 95% CI 0.89 to 15.67; 53 participants) and PEF (MD 6.27%, 95% CI 0.61 to 11.93; 1 trial, 64 participants) compared to placebo. Idebenone was associated with fewer serious adverse events (RR 0.42, 95% CI 0.09 to 2.04; 66 participants; low-certainty evidence) and little to no difference in non-serious adverse events (RR 1.00, 95% CI 0.88 to 1.13; 66 participants; low-certainty evidence) compared to placebo. Idebenone may result in little to no difference in change in arm muscle function (MD -2.45 N, 95% CI -8.60 to 3.70 for elbow flexors and MD -1.06 N, 95% CI -6.77 to 4.65 for elbow extensors; both 52 participants) compared to placebo. We found no studies evaluating the outcome hospitalisation due to respiratory infection.  The second trial, involving 255 participants, for which data were available only as a press release without numerical data, was prematurely discontinued due to futility after an interim efficacy analysis based on FVC. There were no safety concerns. The certainty of the evidence was low for most outcomes due to imprecision and publication bias (the lack of a full report of the larger trial, which was prematurely terminated).

AUTHORS' CONCLUSIONS

Idebenone is the only antioxidant agent tested in RCTs for preventing respiratory decline in people with DMD for which evidence was available for assessment. Idebenone may result in slightly less of a decline in FVC and less of a decline in FEV1 and PEF, but probably has little to no measurable effect on change in quality of life. Idebenone is associated with fewer serious adverse events than placebo. Idebenone may result in little to no difference in change in muscle function. Discontinuation due to the futility of the SIDEROS trial and its expanded access programmes may indicate that idebenone research in this condition is no longer needed, but we await the trial data. Further research is needed to establish the effect of different antioxidant agents on preventing respiratory decline in people with DMD during the respiratory decline phase of the condition.

Lessons Learned from Discontinued Clinical Developments in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked condition caused by a deficiency of functional dystrophin protein. Patients experience progressive muscle weakness, cardiomyopathy and have a decreased life expectancy. Standards of care, including treatment with steroids, and multidisciplinary approaches have extended the life expectancy and improved the quality of life of patients. In the last 30 years, several compounds have been assessed in preclinical and clinical studies for their ability to restore functional dystrophin levels or to modify pathways involved in DMD pathophysiology. However, there is still an unmet need with regards to a disease-modifying treatment for DMD and the attrition rate between early-phase and late-phase clinical development remains high. Currently, there are 40 compounds in clinical development for DMD, including gene therapy and antisense oligonucleotides for exon skipping. Only five of them have received conditional approval in one jurisdiction subject to further proof of efficacy. In this review, we present data of another 16 compounds that failed to complete clinical development, despite positive results in early phases of development in some cases. We examine the reasons for the high attrition rate and we suggest solutions to avoid similar mistakes in the future.

Non-Invasive Respiratory Assessment in Duchenne Muscular Dystrophy: From Clinical Research to Outcome Measures

Ventilatory failure, due to the progressive wasting of respiratory muscles, is the main cause of death in patients with Duchenne muscular dystrophy (DMD). Reliable measures of lung function and respiratory muscle action are important to monitor disease progression, to identify early signs of ventilatory insufficiency and to plan individual respiratory management. Moreover, the current development of novel gene-modifying and pharmacological therapies highlighted the urgent need of respiratory outcomes to quantify the effects of these therapies. Pulmonary function tests represent the standard of care for lung function evaluation in DMD, but provide a global evaluation of respiratory involvement, which results from the interaction between different respiratory muscles. Currently, research studies have focused on finding novel outcome measures able to describe the behavior of individual respiratory muscles. This review overviews the measures currently identified in clinical research to follow the progressive respiratory decline in patients with DMD, from a global assessment to an individual structure–function muscle characterization. We aim to discuss their strengths and limitations, in relation to their current development and suitability as outcome measures for use in a clinical setting and as in upcoming drug trials in DMD.

[Update on Duchenne muscular dystrophy]

Duchenne muscular dystrophy, DMD*(ICD-9-C: 359.1; ICD-10-ES: G71.01, ORPHA: 98896) is a dystrophic type, autosomal recessive myopathy linked to the X chromosome, low incidence 1/3300, with full penetrance and multi-organ involvement (neuro-muscular, respiratory, digestive and metabolic). It has great clinical variability. Symptoms begin in pediatric age (mobility limitation and early respiratory complications). Respiratory complications reduce the life expectancy of those affected. There is no treatment that modifies its evolution, although corticosteroids and new gene therapies are increasing the half-life of this disease. The role of the Primary Care Physician (PCP) is decisive in the monitoring and control of the complications of DMD, either coordinating the different specialties involved in it.

Current Pharmacological Strategies for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a lethal, X-linked neuromuscular disorder caused by the absence of dystrophin protein, which is essential for muscle fiber integrity. Loss of dystrophin protein leads to recurrent myofiber damage, chronic inflammation, progressive fibrosis, and dysfunction of muscle stem cells. There is still no cure for DMD so far and the standard of care is principally limited to symptom relief through glucocorticoids treatments. Current therapeutic strategies could be divided into two lines. Dystrophin-targeted therapeutic strategies that aim at restoring the expression and/or function of dystrophin, including gene-based, cell-based and protein replacement therapies. The other line of therapeutic strategies aims to improve muscle function and quality by targeting the downstream pathological changes, including inflammation, fibrosis, and muscle atrophy. This review introduces the important developments in these two lines of strategies, especially those that have entered the clinical phase and/or have great potential for clinical translation. The rationale and efficacy of each agent in pre-clinical or clinical studies are presented. Furthermore, a meta-analysis of gene profiling in DMD patients has been performed to understand the molecular mechanisms of DMD.

Effect of Yoga and Physiotherapy on Pulmonary Functions in Children with Duchenne Muscular Dystrophy - A Comparative Study

Context:

Abnormal respiratory function is known to be detectable almost as soon as it can be measured reliably. Studies have identified the effect of respiratory muscle training as well as breathing exercises in improving pulmonary functions in children with Duchenne muscular dystrophy (DMD).

Aims:

This study aims to identify the add-on effect of yoga over physiotherapy on pulmonary functions in children with DMD.

Settings and Design:

One hundred and twenty-four patients with DMD were randomized to two groups. Group I received home-based physiotherapy and Group II received physiotherapy along with yoga intervention.

Materials and Methods:

Pulmonary function test (PFT) was assessed before the intervention (baseline data) and at regular intervals of 3 months for a period of 1 year.

Statistical Analysis Used:

Normality was assessed using Shapiro–Wilk normality test. The baseline data were analyzed using Mann–Whitney U-test to identify the homogeneity. Repeated measures analysis of variance was used to assess significant changes in study parameters during the assessment of every 3 months, both within and between the two groups of patients.

Results:

A total of 88 participants completed all the 5 assessments, with a mean age of 7.9 ± 1.5 years. PFT parameters such as forced vital capacity (FVC), peak expiratory flow rate, maximum voluntary ventilation (MVV), and tidal volume during maximum voluntary ventilation (MVt) demonstrated significant improvements in Group I. In Group II, FVC and MVt significantly improved from baseline up to 1 year, whereas MVV improved from baseline up to 9 months. Tidal volume did not show any changes in both the groups.

Conclusions:

The findings suggest that introduction of yoga with physiotherapy intervention at an early age can be considered as one of the therapeutic strategies in improving pulmonary functions in patients with DMD.

Cardiopulmonary phenotypic variability and discordance in Duchenne muscular dystrophy: Implications for new therapies

Neuromuscular respiratory medicine has traditionally focused on assisted lung ventilation and mucus clearance. These therapies have prolonged survival for patients with Duchenne muscular dystrophy (DMD). However, the field is rapidly evolving in a new direction: it is being revolutionized by molecular and genetic therapies. A good correlation between a patient's dystrophin mutation and his cardiopulmonary phenotype would allow accurate prediction of patient prognosis and would facilitate the design of studies that assess new DMD therapies. Instead, patient prognosis and the design of valid therapeutic studies are complicated by cardiopulmonary phenotypic discordance and variability, by which a notable proportion of DMD patients have unexpectedly good or poor cardiopulmonary function. The likely cause of phenotypic variability and discordance is genetic modifiers. Once the modifiers that affect cardiopulmonary function are better understood, it should be possible to create a personalized genetic profile that accurately predicts the prognosis of each individual DMD patient. This would allow investigators to assess the effect of new therapies in the context of each patient's particular cardiopulmonary natural history. Amplification of beneficial cardiopulmonary genetic modifiers and blocking of detrimental modifiers is a promising strategy for creating new DMD therapies. When patients with chronic respiratory failure are treated with assisted ventilation, cardiac function determines their survival. Therefore, prioritizing new cardiac therapies is most likely to prolong patient survival. By focusing on these topics we aim to move neuromuscular respiratory medicine beyond assisted ventilation and coughing and into the age of translational medicine.

Pharmacological advances in mitochondrial therapy

Mitochondria play a vital role in cellular metabolism and are central mediator of intracellular signalling, cell differentiation, morphogenesis and demise. An increasingly higher number of pathologies is linked with mitochondrial dysfunction, which can arise from either genetic defects affecting core mitochondrial components or malfunctioning pathways impairing mitochondrial homeostasis. As such, mitochondria are considered an important target in several pathologies spanning from neoplastic to neurodegenerative diseases as well as metabolic syndromes. In this review we provide an overview of the state-of-the-art in mitochondrial pharmacology, focusing on the novel compounds that have been generated in the bid to correct mitochondrial aberrations. Our work aims to serve the scientific community working on translational medical science by highlighting the most promising pharmacological approaches to target mitochondrial dysfunction in disease.

Newborn screening of duchenne muscular dystrophy specifically targeting deletions amenable to exon-skipping therapy

Duchenne Muscular Dystrophy (DMD) is a lethal progressive muscle-wasting disease. New treatment strategies relying on DMD gene exon-skipping therapy have recently been approved and about 30% of patients could be amenable to exon 51, 53 or 45 skipping. We evaluated the spectrum of deletions reported in DMD registries, and designed a method to screen newborns and identify DMD deletions amenable to exon 51, 53 and 45 skipping. We developed a multiplex qPCR assay identifying hemi(homo)-zygotic deletions of the flanking exons of these therapeutic targets in DMD exons (i.e. exons 44, 46, 50, 52 and 54). We conducted an evaluation of our new method in 51 male patients with a DMD phenotype, 50 female carriers of a DMD deletion and 19 controls. Studies were performed on dried blood spots with patient's consent. We analyzed qPCR amplification curves of controls, carriers, and DMD patients to discern the presence or the absence of the target exons. Analysis of the exons flanking the exon-skipping targets permitted the identification of patients that could benefit from exon-skipping. All samples were correctly genotyped, with either presence or absence of amplification of the target exon. This proof-of-concept study demonstrates that this new assay is a highly sensitive method to identify DMD patients carrying deletions that are rescuable by exon-skipping treatment. The method is easily scalable to population-based screening. This targeted screening approach could address the new management paradigm in DMD, and could help to optimize the beneficial therapeutic effect of DMD therapies by permitting pre-symptomatic care.

Genome editing for Duchenne muscular dystrophy: a glimpse of the future?

Mutations in Dystrophin, one of the largest proteins in the mammalian body, are causative for a severe form of muscle disease, Duchenne Muscular Dystrophy (DMD), affecting not only skeletal muscle, but also the heart. In particular, exons 45–52 constitute a hotspot for DMD mutations. A variety of molecular therapies have been developed, comprising vectors encoding micro- and minidystrophins as well as utrophin, a protein with partially overlapping functions. With the advent of the CRISPR-Cas9-nuclease, genome editing offers a novel option of correction of the disease-cuasing mutations. Full restoration of the healthy gene by homology directed repair is a rare event. However, non-homologous end-joining (NHEJ) may restore the reading frame by causing exon excision. This approach has first been demonstrated in mice and then translated to large animals (dogs, pigs). This review discusses the potential opportunities and limitations of genome editing in DMD, including the generation of appropriate animal models as well as new developments in genome editing tools.

New Therapeutics Options for Pediatric Neuromuscular Disorders

Neuromuscular disorders (NMDs) of Childhood onset are a genetically heterogeneous group of diseases affecting the anterior horn cell, the peripheral nerve, the neuromuscular junction, or the muscle. For many decades, treatment of NMDs has been exclusively symptomatic. But this has changed fundamentally in recent years due to the development of new drugs attempting either to ameliorate secondary pathophysiologic consequences or to modify the underlying genetic defect itself. While the effects on the course of disease are still modest in some NMDs (e.g., Duchenne muscular dystrophy), new therapies have substantially prolonged life expectancy and improved motor function in others (e.g., spinal muscular atrophy and infantile onset Pompe disease). This review summarizes recently approved medicaments and provides an outlook for new therapies that are on the horizon in this field.

[Expert recommendation: treatment of nonambulatory patients with Duchenne muscular dystrophy]

BACKGROUND

Duchenne muscular dystrophy (DMD) is the most frequent genetic neuromuscular disease in childhood with loss of ambulation usually occurring around the age of 9-11 years.

OBJECTIVE, MATERIAL AND METHODS

Based on current guidelines and clinical trials, neuropediatric and neurological experts developed recommendations for the treatment of nonambulatory DMD patients focusing on drug treatment of adults. This advisory board was sponsored by PTC Therapeutics, the distributers of the substance ataluren.

RESULTS AND CONCLUSION

Loss of ambulation is heterogeneously defined across clinical trials. Among others, the need of a wheelchair, ambulation without mobility aids or maximum walking distance can be suitable parameters for assessment. Treatment of DMD patients at any stage of the disease is based on supportive and symptomatic measures, which should be continued after loss of ambulation. In addition, disease-modifying drugs are available for the treatment of DMD and glucocorticoids are the usual standard of care treatment even beyond the loss of ambulation. Ataluren, a potentially dystrophin restorative, disease-modifying treatment, has been approved for patients with DMD due to a nonsense mutation (nmDMD), which applies to approximately 13% of DMD patients and is usually combined with steroids. Clinical data from the STRIDE registry demonstrated a delayed disease progression even after loss of ambulation. Currently, no reliable data are available for exon skipping approaches in adult DMD patients. The antioxidant idebenone could be an option in nonambulant adolescent patients not treated with glucocorticoids and without other therapeutic options. A combination treatment of idebenone and glucocorticoids is currently being investigated in a clinical trial. Add-on treatment with idebenone in addition to ataluren may be considered for nonambulant nmDMD patients. Some of the discussed treatment options are still in clinical trials or there are not enough data for older DMD patients; therefore, these expert recommendations correspond to evidence class IV.

"Betwixt Mine Eye and Heart a League Is Took": The Progress of Induced Pluripotent Stem-Cell-Based Models of Dystrophin-Associated Cardiomyopathy

The ultimate goal of precision disease modeling is to artificially recreate the disease of affected people in a highly controllable and adaptable external environment. This field has rapidly advanced which is evident from the application of patient-specific pluripotent stem-cell-derived precision therapies in numerous clinical trials aimed at a diverse set of diseases such as macular degeneration, heart disease, spinal cord injury, graft-versus-host disease, and muscular dystrophy. Despite the existence of semi-adequate treatments for tempering skeletal muscle degeneration in dystrophic patients, nonischemic cardiomyopathy remains one of the primary causes of death. Therefore, cardiovascular cells derived from muscular dystrophy patients' induced pluripotent stem cells are well suited to mimic dystrophin-associated cardiomyopathy and hold great promise for the development of future fully effective therapies. The purpose of this article is to convey the realities of employing precision disease models of dystrophin-associated cardiomyopathy. This is achieved by discussing, as suggested in the title echoing William Shakespeare's words, the settlements (or "leagues") made by researchers to manage the constraints ("betwixt mine eye and heart") distancing them from achieving a perfect precision disease model.