Identification of hub genes and therapeutic siRNAs to develop novel adjunctive therapy for Duchenne muscular dystrophy.

OBJECTIVE: Duchenne muscular dystrophy (DMD) is a devastating X-linked neuromuscular disorder caused by various defects in the dystrophin gene and still no universal therapy. This study aims to identify the hub genes unrelated to excessive immune response but responsible for DMD progression and explore therapeutic siRNAs, thereby providing a novel treatment. METHODS: Top ten hub genes for DMD were identified from GSE38417 dataset by using GEO2R and PPI networks based on Cytoscape analysis. The hub genes unrelated to excessive immune response were identified by GeneCards, and their expression was further verified in mdx and C57 mice at 2 and 4 months (M) by (RT-q) PCR and western blotting. Therapeutic siRNAs were deemed as those that could normalize the expression of the validated hub genes in transfected C2C12 cells. RESULTS: 855 up-regulated and 324 down-regulated DEGs were screened from GSE38417 dataset. Five of the top 10 hub genes were considered as the candidate genes unrelated to excessive immune response, and three of these candidates were consistently and significantly up-regulated in mdx mice at 2 M and 4 M when compared with age-matched C57 mice, including Col1a2, Fbn1 and Fn1. Furthermore, the three validated up-regulated candidate genes can be significantly down-regulated by three rational designed siRNA (p < 0.0001), respectively. CONCLUSION: COL1A2, FBN1 and FN1 may be novel biomarkers for DMD, and the siRNAs designed in our study were help to develop adjunctive therapy for Duchenne muscular dystrophy.

Circadian Clock in Muscle Disease Etiology and Therapeutic Potential for Duchenne Muscular Dystrophy.

Circadian clock and clock-controlled output pathways exert temporal control in diverse aspects of skeletal muscle physiology, including the maintenance of muscle mass, structure, function, and metabolism. They have emerged as significant players in understanding muscle disease etiology and potential therapeutic avenues, particularly in Duchenne muscular dystrophy (DMD). This review examines the intricate interplay between circadian rhythms and muscle physiology, highlighting how disruptions of circadian regulation may contribute to muscle pathophysiology and the specific mechanisms linking circadian clock dysregulation with DMD. Moreover, we discuss recent advancements in chronobiological research that have shed light on the circadian control of muscle function and its relevance to DMD. Understanding clock output pathways involved in muscle mass and function offers novel insights into the pathogenesis of DMD and unveils promising avenues for therapeutic interventions. We further explore potential chronotherapeutic strategies targeting the circadian clock to ameliorate muscle degeneration which may inform drug development efforts for muscular dystrophy.

Chimeric Cell Therapies as a Novel Approach for Duchenne Muscular Dystrophy (DMD) and Muscle Regeneration.

Chimerism-based strategies represent a pioneering concept which has led to groundbreaking advancements in regenerative medicine and transplantation. This new approach offers therapeutic potential for the treatment of various diseases, including inherited disorders. The ongoing studies on chimeric cells prompted the development of Dystrophin-Expressing Chimeric (DEC) cells which were introduced as a potential therapy for Duchenne Muscular Dystrophy (DMD). DMD is a genetic condition that leads to premature death in adolescent boys and remains incurable with current methods. DEC therapy, created via the fusion of human myoblasts derived from normal and DMD-affected donors, has proven to be safe and efficacious when tested in experimental models of DMD after systemic-intraosseous administration. These studies confirmed increased dystrophin expression, which correlated with functional and morphological improvements in DMD-affected muscles, including cardiac, respiratory, and skeletal muscles. Furthermore, the application of DEC therapy in a clinical study confirmed its long-term safety and efficacy in DMD patients. This review summarizes the development of chimeric cell technology tested in preclinical models and clinical studies, highlighting the potential of DEC therapy in muscle regeneration and repair, and introduces chimeric cell-based therapies as a promising, novel approach for muscle regeneration and the treatment of DMD and other neuromuscular disorders.

CRISPR-Based Gene Therapies: From Preclinical to Clinical Treatments.

In recent years, clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) protein have emerged as a revolutionary gene editing tool to treat inherited disorders affecting different organ systems, such as blood and muscles. Both hematological and neuromuscular genetic disorders benefit from genome editing approaches but face different challenges in their clinical translation. The ability of CRISPR/Cas9 technologies to modify hematopoietic stem cells ex vivo has greatly accelerated the development of genetic therapies for blood disorders. In the last decade, many clinical trials were initiated and are now delivering encouraging results. The recent FDA approval of Casgevy, the first CRISPR/Cas9-based drug for severe sickle cell disease and transfusion-dependent ß-thalassemia, represents a significant milestone in the field and highlights the great potential of this technology. Similar preclinical efforts are currently expanding CRISPR therapies to other hematologic disorders such as primary immunodeficiencies. In the neuromuscular field, the versatility of CRISPR/Cas9 has been instrumental for the generation of new cellular and animal models of Duchenne muscular dystrophy (DMD), offering innovative platforms to speed up preclinical development of therapeutic solutions. Several corrective interventions have been proposed to genetically restore dystrophin production using the CRISPR toolbox and have demonstrated promising results in different DMD animal models. Although these advances represent a significant step forward to the clinical translation of CRISPR/Cas9 therapies to DMD, there are still many hurdles to overcome, such as in vivo delivery methods associated with high viral vector doses, together with safety and immunological concerns. Collectively, the results obtained in the hematological and neuromuscular fields emphasize the transformative impact of CRISPR/Cas9 for patients affected by these debilitating conditions. As each field suffers from different and specific challenges, the clinical translation of CRISPR therapies may progress differentially depending on the genetic disorder. Ongoing investigations and clinical trials will address risks and limitations of these therapies, including long-term efficacy, potential genotoxicity, and adverse immune reactions. This review provides insights into the diverse applications of CRISPR-based technologies in both preclinical and clinical settings for monogenic blood disorders and muscular dystrophy and compare advances in both fields while highlighting current trends, difficulties, and challenges to overcome.

Barriers to diverse clinical trial participation in Duchenne muscular dystrophy: Engaging Hispanic/Latina caregivers and health professionals.

BACKGROUND: Despite the increasing availability of clinical trials in Duchenne muscular dystrophy, racial/ethnic minorities and other populations facing health disparities remain underrepresented in clinical trials evaluating products for Duchenne. We sought to understand the barriers faced by Hispanic/Latino families specifically and underrepresented groups more generally to clinical trial participation in Duchenne. METHODS: We engaged two participant groups: Hispanic/Latino caregivers of children with Duchenne in the US, including Puerto Rico, and health professionals within the broader US Duchenne community. Caregiver interviews explored attitudes towards and experiences with clinical trials, while professional interviews explored barriers to clinical trial participation among socio-demographically underrepresented families (e.g., low income, rural, racial/ethnic minority, etc.). Interviews were analyzed aggregately and using a thematic analysis approach. An advisory group was engaged throughout the course of the study to inform design, conduct, and interpretation of findings generated from interviews. RESULTS: Thirty interviews were conducted, including with 12 Hispanic/Latina caregivers and 18 professionals. We identified barriers to clinical trial participation at various stages of the enrollment process. In the initial identification of patients, barriers included lack of awareness about trials and clinical trial locations at clinics that were less likely to serve diverse patients. In the prescreening process, barriers included ineligibility, anticipated non-compliance in clinical trial protocols, and language discrimination. In screening, barriers included concerns about characteristics of the trial, as well as mistrust/lack of trust. In consent and recruitment, barriers included lack of timely decision support, logistical factors (distance, time, money), and lack of translated study materials. CONCLUSIONS: Numerous barriers hinder participation in Duchenne clinical trials for Hispanic/Latino families and other populations experiencing health disparities. Addressing these barriers necessitates interventions across multiple stages of the clinical trial enrollment process. Recommendations to enhance participation opportunities include developing clinical trial decision support tools, translating prominent clinical trials educational resources such as ClinicalTrials.gov, fostering trusting family-provider relationships, engaging families in clinical trial design, and establishing ethical guidelines for pre-screening potentially non-compliant patients.

[How safe is gene therapy? : Second death after Duchenne therapy]. / Wie sicher ist die Gentherapie? : Zweiter Todesfall nach Therapie der Duchenne-Muskeldystrophie.

BACKGROUND: Duchenne muscular dystrophy (DMD) is a severe monogenic hereditary disease with early manifestation and a progressive course. Treatment options have so far been limited. Gene therapy opens up new options for DMD patients. OBJECTIVES: Against the background of a further death following DMD gene therapy, the side effects and risks of the gene therapeutics already approved or undergoing clinical trials will be evaluated and alternative gene therapeutics will be described. Based thereon, the future of DMD gene therapy will be discussed. CURRENT DATA: For the first time, in June 2023, delandistrogene moxeparvovec (SRP-9001), a gene replacement therapy based on an adeno-associated virus (AAV) vector, was approved in the USA for children aged 4-5 years with DMD. Other promising gene therapies are in preclinical development or clinical trials, including CRISPR/Cas9-mediated strategies to restore dystrophin expression. Two deaths following DMD gene therapy with high-dose AAV vectors were attributed to AAV-mediated immune responses. The pre-existing disease underlying the therapy is most likely involved in the fatal AAV toxicity. CONCLUSIONS: Although gene therapy applications of AAV vectors are generally considered safe, the systemic administration of high vector doses can lead to severe side effects with a potentially fatal outcome in individual patients, especially after activation of the immune system. In the future, new methods for immunosuppression, reduction of AAV dose and alternative vectors will therefore increasingly come to the fore.

The FDA and Gene Therapy for Duchenne Muscular Dystrophy.

This Viewpoint examines the appropriateness of FDA accelerated approval of novel gene therapies to treat boys with Duchenne muscular dystrophy following clinical trials with surrogate outcomes that did not demonstrate net benefits.

Treatment with ataluren in four symptomatic Duchenne carriers. A pilot study.

Duchenne muscular dystrophy (DMD) is a devastating X-linked neuromuscular disorder caused by dystrophin gene deletions (75%), duplications (15-20%) and point mutations (5-10%), a small portion of which are nonsense mutations. Women carrying dystrophin gene mutations are commonly unaffected because the wild X allele may produce a sufficient amount of the dystrophin protein. However, approximately 8-10% of them may experience muscle symptoms and 50% of those over 40 years develop cardiomyopathy. The presence of symptoms defines the individual as an affected "symptomatic or manifesting carrier". Though there is no effective cure for DMD, therapies are available to slow the decline of muscle strength and delay the onset and progression of cardiac and respiratory impairment. These include ataluren for patients with nonsense mutations, and antisense oligonucleotides therapies, for patients with specific deletions. Symptomatic DMD female carriers are not included in these indications and little data documenting their management, often entrusted to the discretion of individual doctors, is present in the literature. In this article, we report the clinical and instrumental outcomes of four symptomatic DMD carriers, aged between 26 and 45 years, who were treated with ataluren for 21 to 73 months (average 47.3), and annually evaluated for muscle strength, respiratory and cardiological function. Two patients retain independent ambulation at ages 33 and 45, respectively. None of them developed respiratory involvement or cardiomyopathy. No clinical adverse effects or relevant abnormalities in routine laboratory values, were observed.

Management of Select Adverse Events Following Delandistrogene Moxeparvovec Gene Therapy for Patients With Duchenne Muscular Dystrophy.

BACKGROUND: Duchenne muscular dystrophy (DMD) is a rare, degenerative, recessive X-linked neuromuscular disease. Mutations in the gene encoding dystrophin lead to the absence of functional dystrophin protein. Individuals living with DMD exhibit progressive muscle weakness resulting in loss of ambulation and limb function, respiratory insufficiency, and cardiomyopathy, with multiorgan involvement. Adeno-associated virus vector-mediated gene therapy designed to enable production of functional dystrophin protein is a new therapeutic strategy. Delandistrogene moxeparvovec (Sarepta Therapeutics, Cambridge, MA) is indicated for treatment of ambulatory pediatric patients aged 4 through 5 years with DMD who have an indicated mutation in the DMD gene. OBJECTIVE: Evidence-based considerations for management of potential adverse events following gene therapy treatment for DMD are lacking in clinical literature. Our goal was to provide interdisciplinary consensus considerations for selected treatment-related adverse events (TRAEs) (vomiting, acute liver injury, myocarditis, and immune-mediated myositis) that may arise following gene therapy dosing with delandistrogene moxeparvovec. METHODS: An interdisciplinary panel of 12 specialists utilized a modified Delphi process to develop consensus considerations for the evaluation and management of TRAEs reported in delandistrogene moxeparvovec clinical studies. Panelists completed 2 Questionnaires prior to gathering for an in-person discussion. Consensus was defined as a majority (≥58% ; 7/12) of panelists either agreeing or disagreeing. RESULTS: Panelists agreed that the choice of baseline assessments should be informed by individual clinical indications, the treating provider's judgment, and prescribing information. Corticosteroid dosing for treatment of TRAEs should be optimized by considering individual risk versus benefit for each indication. In all cases involving patients with a confirmed TRAE, consultations with appropriate specialists were suggested. CONCLUSIONS: The Delphi Panel established consensus considerations for the evaluation and management of potential TRAEs for patients receiving delandistrogene moxeparvovec, including vomiting, acute liver injury, myocarditis, and immune-mediated myositis.

Genetic therapies and respiratory outcomes in patients with neuromuscular disease.

PURPOSE OF REVIEW: Genetic therapies made a significant impact to the clinical course of patients with spinal muscular atrophy and Duchenne muscular dystrophy. Clinicians and therapists who care for these patients want to know the changes in respiratory sequelae and implications for clinical care for treated patients. RECENT FINDINGS: Different genetic therapy approaches have been developed to replace the deficient protein product in spinal muscular atrophy and Duchenne muscular dystrophy. The natural history of these conditions needed to be understood in order to design clinical trials. Respiratory parameters were not the primary outcome measures for the clinical trials. The impact of these therapies is described in subsequent clinical trial reports or real-world data. SUMMARY: Genetic therapies are able to stabilize or improve the respiratory sequelae in patients with spinal muscular atrophy and Duchenne muscular dystrophy. Standardized reporting of these outcomes is needed to help inform the future revisions of clinical standards of care and practice guidelines.

Social difficulties and care burden of adult Duchenne muscular dystrophy in Japan: a questionnaire survey based on the Japanese Registry of Muscular Dystrophy (Remudy).

BACKGROUND: Little is known about the social difficulties and health care needs of adult Duchenne muscular dystrophy (DMD) patients in Japan, as well as the financial and physical stress experienced by their caregivers. This study aimed to clarify the social circumstances surrounding adult DMD patients and assess the degree of involvement of family members in their care and the associated economic burden of the disorder in Japan. METHODS: Adult DMD patients were identified through the Registry of Muscular Dystrophy (Remudy) in Japan and invited to complete a questionnaire together with a caregiver. Data on health care use, quality of life, work status, informal care, and household expenses were collected to estimate the costs associated with DMD from social and caregiver household perspectives. RESULTS: In total, 234 (63.7%) of 367 adult DMD patients (mean age, 27.4 ± 6.0; range, 20-48 years) completed the questionnaire. Of these, 38 (21%) had developmental disorders (mental retardation, autism, and learning disorders), 57 (33%) experienced bullying in school, and 44 (77%) indicated the reason for bullying to be their physical handicap. Employment histories were noted by 72 (31%), although 23 (10%) lost their jobs mainly due to physical difficulties. Of the 234 patients, 164 (74%) lived with their relatives, and 78% of care time was supplied by family members, in particular, their mothers. The mean rate of care work provided by family members was 81%. Household income of families with an adult DMD patient was lower, whereas the rate of living with parent(s) and grandparent(s) was higher, in comparison with the general Japanese population. CONCLUSIONS: Adult DMD patients in Japan experience many social difficulties from childhood up to adulthood. As adults, many DMD patients experience bullying and workplace difficulties. Families were found to provide most of the care and financial support for DMD patients. Our results suggest the need to improve public patient care systems, including financial support, to address the physical and economic burdens of care for adult DMD patients in Japan.

AAV-Mediated Restoration of Dystrophin-Dp71 in the Brain of Dp71-Null Mice: Molecular, Cellular and Behavioral Outcomes.

A deficiency in the shortest dystrophin-gene product, Dp71, is a pivotal aggravating factor for intellectual disabilities in Duchenne muscular dystrophy (DMD). Recent advances in preclinical research have achieved some success in compensating both muscle and brain dysfunctions associated with DMD, notably using exon skipping strategies. However, this has not been studied for distal mutations in the DMD gene leading to Dp71 loss. In this study, we aimed to restore brain Dp71 expression in the Dp71-null transgenic mouse using an adeno-associated virus (AAV) administrated either by intracardiac injections at P4 (ICP4) or by bilateral intracerebroventricular (ICV) injections in adults. ICP4 delivery of the AAV9-Dp71 vector enabled the expression of 2 to 14% of brain Dp71, while ICV delivery enabled the overexpression of Dp71 in the hippocampus and cortex of adult mice, with anecdotal expression in the cerebellum. The restoration of Dp71 was mostly located in the glial endfeet that surround capillaries, and it was associated with partial localization of Dp71-associated proteins, α1-syntrophin and AQP4 water channels, suggesting proper restoration of a scaffold of proteins involved in blood-brain barrier function and water homeostasis. However, this did not result in significant improvements in behavioral disturbances displayed by Dp71-null mice. The potential and limitations of this AAV-mediated strategy are discussed. This proof-of-concept study identifies key molecular markers to estimate the efficiencies of Dp71 rescue strategies and opens new avenues for enhancing gene therapy targeting cognitive disorders associated with a subgroup of severely affected DMD patients.

Myospreader improves gene editing in skeletal muscle by myonuclear propagation.

Successful CRISPR/Cas9-based gene editing in skeletal muscle is dependent on efficient propagation of Cas9 to all myonuclei in the myofiber. However, nuclear-targeted gene therapy cargos are strongly restricted to their myonuclear domain of origin. By screening nuclear localization signals and nuclear export signals, we identify "Myospreader," a combination of short peptide sequences that promotes myonuclear propagation. Appending Myospreader to Cas9 enhances protein stability and myonuclear propagation in myoblasts and myofibers. AAV-delivered Myospreader dCas9 better inhibits transcription of toxic RNA in a myotonic dystrophy mouse model. Furthermore, Myospreader Cas9 achieves higher rates of gene editing in CRISPR reporter and Duchenne muscular dystrophy mouse models. Myospreader reveals design principles relevant to all nuclear-targeted gene therapies and highlights the importance of the spatial dimension in therapeutic development.

Comparison of energy expenditure of individuals with Duchenne muscular dystrophy in the sitting posture on the ground and in water.

Duchenne Muscular Dystrophy (DMD) is one of the most frequent childhood dystrophies, affecting cardiopulmonary functions and walking ability. One of the main symptoms is fatigue, which is caused by altered muscle metabolism related to energy expenditure (EE). Aquatic physiotherapy is a therapeutic modality that facilitates the maintenance of this posture because of immersion on the body. This cross-sectional observational study aimed to compare the EE on the ground and water of individuals with DMD through oxygen consumption in the maintenance of sitting posture. The individuals were in a sitting position on the ground and in the water for 20 min for the assessments. The variables peripheral oxygen saturation, heart rate, maximum expiratory pressure, maximum inspiratory pressure, forced vital capacity, respiratory quotient (RQ), and oxygen consumption per kilogram of body weight (VO2 /kg) were compared, adopting a significance of 5 %. No difference was found between medians and quartiles of RQ when comparing the two environments. The same was observed for VO2 /Kg values on the ground and in water. The data from this study demonstrate that the EE of individuals with DMD did not change when maintaining a sitting posture on the ground and in water.

Cell-mediated exon skipping normalizes dystrophin expression and muscle function in a new mouse model of Duchenne Muscular Dystrophy.

Cell therapy for muscular dystrophy has met with limited success, mainly due to the poor engraftment of donor cells, especially in fibrotic muscle at an advanced stage of the disease. We developed a cell-mediated exon skipping that exploits the multinucleated nature of myofibers to achieve cross-correction of resident, dystrophic nuclei by the U7 small nuclear RNA engineered to skip exon 51 of the dystrophin gene. We observed that co-culture of genetically corrected human DMD myogenic cells (but not of WT cells) with their dystrophic counterparts at a ratio of either 1:10 or 1:30 leads to dystrophin production at a level several folds higher than what predicted by simple dilution. This is due to diffusion of U7 snRNA to neighbouring dystrophic resident nuclei. When transplanted into NSG-mdx-Δ51mice carrying a mutation of exon 51, genetically corrected human myogenic cells produce dystrophin at much higher level than WT cells, well in the therapeutic range, and lead to force recovery even with an engraftment of only 3-5%. This level of dystrophin production is an important step towards clinical efficacy for cell therapy.

Trunk-oriented Exercises Versus Whole-body Vibration on Abdominal Thickness and Balance in Children with Duchene Muscular Dystrophy.

OBJECTIVES: Progressive proximal muscle weakening in children with Duchenne muscular dystrophy (DMD) impairs postural adjustments by impairing motor function and preventing ambulation. During daily activities, for gait and dynamic balance, certain postural modifications are required. The objective was to compare the impact of trunk-oriented exercises versus whole-body vibration on abdominal muscle thickness and balance in children with DMD. METHODS: Participants in this study were 30 boys with DMD, aged 6 to 10 years old. Children were divided into two groups (A and B) randomly. Children in group (A) underwent a prescribed regimen of physical therapy along with trunk-oriented exercises, whereas group (B) received the same regimen as group (A) together with whole-body vibration three times per week for three consecutive months. Balance and the thickness of the abdominal muscles were measured using the Biodex balance system and ultrasonography, respectively, before and after therapy. RESULTS: When compared to the pre-treatment results in both groups, the post-treatment results showed a significant difference in all measured variables (p<0.05). Post-treatment values showed that all of the measured variables significantly differed in favor of group A. CONCLUSIONS: Trunk-oriented exercises can improve abdominal thickness and balance more effectively than whole-body vibration in children with DMD. CLINICALTRIALS: gov ID: NCT05688072.

Mitochondrial Transplantation Therapy Ameliorates Muscular Dystrophy in mdx Mouse Model.

Duchenne muscular dystrophy is caused by loss of the dystrophin protein. This pathology is accompanied by mitochondrial dysfunction contributing to muscle fiber instability. It is known that mitochondria-targeted in vivo therapy mitigates pathology and improves the quality of life of model animals. In the present work, we applied mitochondrial transplantation therapy (MTT) to correct the pathology in dystrophin-deficient mdx mice. Intramuscular injections of allogeneic mitochondria obtained from healthy animals into the hind limbs of mdx mice alleviated skeletal muscle injury, reduced calcium deposits in muscles and serum creatine kinase levels, and improved the grip strength of the hind limbs and motor activity of recipient mdx mice. We noted normalization of the mitochondrial ultrastructure and sarcoplasmic reticulum/mitochondria interactions in mdx muscles. At the same time, we revealed a decrease in the efficiency of oxidative phosphorylation in the skeletal muscle mitochondria of recipient mdx mice accompanied by a reduction in lipid peroxidation products (MDA products) and reduced calcium overloading. We found no effect of MTT on the expression of mitochondrial signature genes (Drp1, Mfn2, Ppargc1a, Pink1, Parkin) and on the level of mtDNA. Our results show that systemic MTT mitigates the development of destructive processes in the quadriceps muscle of mdx mice.

A review on mechanistic insights into structure and function of dystrophin protein in pathophysiology and therapeutic targeting of Duchenne muscular dystrophy.

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive genetic disorder characterized by progressive and severe muscle weakening and degeneration. Among the various forms of muscular dystrophy, it stands out as one of the most common and impactful, predominantly affecting boys. The condition arises due to mutations in the dystrophin gene, a key player in maintaining the structure and function of muscle fibers. The manuscript explores the structural features of dystrophin protein and their pivotal roles in DMD. We present an in-depth analysis of promising therapeutic approaches targeting dystrophin and their implications for the therapeutic management of DMD. Several therapies aiming to restore dystrophin protein or address secondary pathology have obtained regulatory approval, and many others are ongoing clinical development. Notably, recent advancements in genetic approaches have demonstrated the potential to restore partially functional dystrophin forms. The review also provides a comprehensive overview of the status of clinical trials for major therapeutic genetic approaches for DMD. In addition, we have summarized the ongoing therapeutic approaches and advanced mechanisms of action for dystrophin restoration and the challenges associated with DMD therapeutics.

The role of ataluren in the treatment of ambulatory and non-ambulatory children with nonsense mutation duchenne muscular dystrophy - a consensus derived using a modified Delphi methodology in Eastern Europe, Greece, Israel and Sweden.

BACKGROUND: This paper details the results of an evaluation of the level of consensus amongst clinicians on the use of ataluren in both ambulatory and non-ambulatory patients with nonsense mutation Duchenne muscular dystrophy (nmDMD). The consensus was derived using a modified Delphi methodology that involved an exploration phase and then an evaluation phase. METHODS: The exploration phase involved 90-minute virtual 1:1 interviews of 12 paediatric neurologists who cared for 30-120 DMD patients each and had patient contact every one or two weeks. The respondents managed one to ten nmDMD patients taking ataluren. The Discussion Guide for the interviews can be viewed as Appendix A. Following the exploration phase interviews, the interview transcripts were analysed by an independent party to identify common themes, views and opinions and developed 43 draft statements that the Steering Group (authors) reviewed, refined and endorsed a final list of 42 statements. Details of the recruitment of participants for the exploration and evaluation phases can be found under the Methods section. RESULTS: A consensus was agreed (> 66% of respondents agreeing) for 41 of the 42 statements using results from a consensus survey of healthcare professionals (n = 20) experienced in the treatment of nmDMD. CONCLUSIONS: The statements with a high consensus suggest that treatment with ataluren should be initiated as soon as possible to delay disease progression and allow patients to remain ambulatory for as long as possible. Ataluren is indicated for the treatment of Duchenne muscular dystrophy that results from a nonsense mutation in the dystrophin gene, in ambulatory patients aged 2 years and older (see Summary of Product Characteristics for each country).