Long-term effects of glucocorticoids on function, quality of life, and survival in patients with Duchenne muscular dystrophy: a prospective cohort study

Effectiveness of pharmacological treatments in Duchenne muscular dystrophy: a protocol for a systematic review and meta-analysis

INTRODUCTION

In recent years, important advances have been made in the treatment of Duchenne muscular dystrophy (DMD). This protocol proposes a methodology for carrying out a systematic review and meta-analysis that aims to: (1) improve the evidence of the benefits of different pharmacological treatments in boys with DMD, and (2) compare the benefit of treatments specifically aimed at delaying the progression of disease in the functional outcomes.

METHODS AND ANALYSIS

This protocol is guided by the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) and by the Cochrane Collaboration Handbook. A thorough selection of the literature will be done through the MEDLINE, EMBASE and Web of Science databases. The search will be conducted in English and Spanish. The Risk of Bias 2.0 tool from the Cochrane Collaboration will be used to assess the risk of bias. A narrative synthesis of the data will be performed. Meta-analysis will be conducted for effect of treatment on the 6 min walking distance (6MWD), North Star Ambulatory Assessment and Timed Functional Tests. Subgroup analyses will be performed by age or baseline values of the 6MWD, and overall bias.

ETHICS AND DISSEMINATION

The approval of an ethical committee is not required. All the included trials will comply with the current ethical standards and the Declaration of Helsinki. The results of this proposed systematic review and meta-analysis will provide a general overview and evidence concerning the effectiveness of pharmacological treatments in Duchenne muscular dystrophy. Findings will be disseminated to academic audiences through peer-reviewed publications, as well as to clinical audiences, patients' associations and policy makers, and may influence guideline developers in order to improve outcomes for these patients.

PROSPERO REGISTRATION NUMBER

CRD42018102207.

Duchenne muscular dystrophy: an historical treatment review

In this review, we discuss the therapies used in the treatment of patients with Duchenne muscular dystrophy since the first description of the disease. A short description is given of the various theories based on disease pathogenesis, which give the substrates for the many therapeutic interventions. A brief review of the methods of evaluation used in therapeutic trials is made. Of all the treatments, the only drugs that are still considered able to modify the course of the disease are the corticosteroids (prednisone/prednisolone/deflazacort). Other drugs (coenzyme Q10 and creatine) have had a little effect in a few functions without adverse reactions. Idebenone seems to improve the respiratory function in the long term. The trials with mRNA transcription, through nonsense mutations or exon 51 skipping, show some beneficial results in a few functional tests, but they are limited to a small set of DMD patients.

Categorising trajectories and individual item changes of the North Star Ambulatory Assessment in patients with Duchenne muscular dystrophy

Functional variability among boys with Duchenne muscular dystrophy (DMD) is well recognised and complicates interpretation of clinical studies. We hypothesised that boys with DMD could be clustered into groups sharing similar trajectories of ambulatory function over time, as measured by the North Star Ambulatory Assessment (NSAA) total score. We also explored associations with other variables such as age, functional abilities, and genotype. Using the NorthStar Clinical Network database, 395 patients with >1 NSAA assessment were identified. We utilised latent class trajectory analysis of longitudinal NSAA scores, which produced evidence for at least four clusters of boys sharing similar trajectories versus age in decreasing order of clinical severity: 25% of the boys were in cluster 1 (NSAA falling to ≤ 5 at age ~10y), 35% were in cluster 2 (NSAA ≤ 5 ~12y), 21% in were cluster 3 (NSAA≤ 5 ~14y), and 19% in cluster 4 (NSAA > 5 up to 15y). Mean ages at diagnosis of DMD were similar across clusters (4.2, 3.9, 4.3, and 4.8y, respectively). However, at the first NSAA assessment, a significant (p<0.05) association was observed between earlier declining clusters and younger age, worse NSAA, slower rise from supine, slower 10 metre walk/run times, and younger age of steroid initiation. In order to assess the probability of observing complete loss of function for individual NSAA items, we examined the proportion of patients who shifted from a score of 1 or 2 at baseline to a score of 0. We also assessed the probability of gain of function using the inverse assessment and stratified the probability of deterioration, improvement-or static behavior-by age ranges and using baseline functional status. Using this tool, our study provides a comprehensive assessment of the NSAA in a large population of patients with DMD and, for the first time, describes discrete clusters of disease progression; this will be invaluable for future DMD clinical trial design and interpretation of findings.

Vamorolone trial in Duchenne muscular dystrophy shows dose-related improvement of muscle function

Objective

To study vamorolone, a first-in-class steroidal anti-inflammatory drug, in Duchenne muscular dystrophy (DMD).

Methods

An open-label, multiple-ascending-dose study of vamorolone was conducted in 48 boys with DMD (age 4–<7 years, steroid-naive). Dose levels were 0.25, 0.75, 2.0, and 6.0 mg/kg/d in an oral suspension formulation (12 boys per dose level; one-third to 10 times the glucocorticoid dose in DMD). The primary goal was to define optimal doses of vamorolone. The primary outcome for clinical efficacy was time to stand from supine velocity.

Results

Oral administration of vamorolone at all doses tested was safe and well tolerated over the 24-week treatment period. The 2.0–mg/kg/d dose group met the primary efficacy outcome of improved muscle function (time to stand; 24 weeks of vamorolone treatment vs natural history controls), without evidence of most adverse effects of glucocorticoids. A biomarker of bone formation, osteocalcin, increased in vamorolone-treated boys, suggesting possible loss of bone morbidities seen with glucocorticoids. Biomarker outcomes for adrenal suppression and insulin resistance were also lower in vamorolone-treated patients with DMD relative to published studies of glucocorticoid therapy.

Conclusions

Daily vamorolone treatment suggested efficacy at doses of 2.0 and 6.0 mg/kg/d in an exploratory 24-week open-label study.

Classification of evidence

This study provides Class IV evidence that for boys with DMD, vamorolone demonstrated possible efficacy compared to a natural history cohort of glucocorticoid-naive patients and appeared to be tolerated.

Disease-specific and glucocorticoid-responsive serum biomarkers for Duchenne Muscular Dystrophy

Extensive biomarker discoveries for DMD have occurred in the past 7 years, and a vast array of these biomarkers were confirmed in independent cohorts and across different laboratories. In these previous studies, glucocorticoids and age were two major confounding variables. In this new study, using SomaScan technology and focusing on a subset of young DMD patients who were not yet treated with glucocorticoids, we identified 108 elevated and 70 decreased proteins in DMD relative to age matched healthy controls (p value < 0.05 after adjusting for multiple testing). The majority of the elevated proteins were muscle centric followed by cell adhesion, extracellular matrix proteins and a few pro-inflammatory proteins. The majority of decreased proteins were of cell adhesion, however, some had to do with cell differentiation and growth factors. Subsequent treatment of this group of DMD patients with glucocorticoids affected two major groups of pharmacodynamic biomarkers. The first group consisted of 80 serum proteins that were not associated with DMD and either decreased or increased following treatment with glucocorticoids, and therefore were reflective of a broader effect of glucocorticoids. The second group consisted of 17 serum proteins that were associated with DMD and these tended to normalize under treatment, thus reflecting physiologic effects of glucocorticoid treatment in DMD. In summary, we have identified a variety of circulating protein biomarkers that reflect the complex nature of DMD pathogenesis and response to glucocorticoids.

Identification of Hub Genes in Duchenne Muscular Dystrophy: Evidence from Bioinformatic Analysis

The hub genes and signaling pathways associated with Duchenne muscular dystrophy (DMD) were predicted by bioinformatic methods to improve the therapeutic effect and quality of life of patients. Microarray data sets GSE465, GSE1004, and GSE1007 were downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified by GEO2R, and function enrichment analyses were performed by DAVID. The protein-protein interaction (PPI) network was constructed and the module analysis was performed using STRING and Cytoscape. A total of 195 DEGs were identified. The enriched functions and pathways of the DEGs include extracellular exosome, focal adhesion, extracellular matrix (ECM), focal adhesion, PI3K-Akt signaling pathway, calcium signaling pathway, and ECM-receptor interaction. Fifteen hub genes were identified. DEGs and hub genes identified in the present study help us understand the molecular mechanisms underlying the pathogenesis and progression of DMD, and provide candidate targets for treatment of DMD.

Discovery of potential urine-accessible metabolite biomarkers associated with muscle disease and corticosteroid response in the mdx mouse model for Duchenne

Urine is increasingly being considered as a source of biomarker development in Duchenne Muscular Dystrophy (DMD), a severe, life-limiting disorder that affects approximately 1 in 4500 boys. In this study, we considered the mdx mice-a murine model of DMD-to discover biomarkers of disease, as well as pharmacodynamic biomarkers responsive to prednisolone, a corticosteroid commonly used to treat DMD. Longitudinal urine samples were analyzed from male age-matched mdx and wild-type mice randomized to prednisolone or vehicle control via liquid chromatography tandem mass spectrometry. A large number of metabolites (869 out of 6,334) were found to be significantly different between mdx and wild-type mice at baseline (Bonferroni-adjusted p-value < 0.05), thus being associated with disease status. These included a metabolite with m/z = 357 and creatine, which were also reported in a previous human study looking at serum. Novel observations in this study included peaks identified as biliverdin and hypusine. These four metabolites were significantly higher at baseline in the urine of mdx mice compared to wild-type, and significantly changed their levels over time after baseline. Creatine and biliverdin levels were also different between treated and control groups, but for creatine this may have been driven by an imbalance at baseline. In conclusion, our study reports a number of biomarkers, both known and novel, which may be related to either the mechanisms of muscle injury in DMD or prednisolone treatment.

Validation of an ambient measurement system (AMS) for physical activities in a paediatric population

Ambient measurement systems (AMSs) can enable continuous assessment of functional performance at home, increasing the availability of data for monitoring of neuromuscular disease. An AMS passively measures movement whenever someone is in range of the sensor, without the need for any wearable sensors. The current study evaluates the performance of an AMS for three metrics associated with functional assessments in Duchenne muscular dystrophy (DMD): ambulation speed, rise-to-stand speed and arm-raise speed. Healthy paediatric subjects performed a series of functional tasks and were graded by both a human rater and an AMS. Linear mixed-effect models were fit to calculate agreement between the two measurement methods. For all activities, the AMS and human rater supplied similar measurements of average speed, with correlation coefficients of 0.76-0.92 and systematic differences ranging in magnitude from 0 to 0.48 m per second. The largest systematic difference was for the 10-m run, which was likely due to human rater reaction time. Systematic differences in arm-raise measurements were due to incomplete execution of movements by test participants. These results are consistent with previous studies comparing automated and manual measurements of movement. This study demonstrates that an AMS device is able to measure ambulation speed, rise-to-stand speed and arm-raise speed in a paediatric population in a controlled setting without the need for complicated installation, calibration or worn sensors.

Long-term natural history data in Duchenne muscular dystrophy ambulant patients with mutations amenable to skip exons 44, 45, 51 and 53

INTRODUCTION

The aim of this international collaborative effort was to report 36-month longitudinal changes using the 6MWT in ambulant patients affected by Duchenne muscular dystrophy amenable to skip exons 44, 45, 51 or 53.

MATERIALS AND METHODS

Of the 92 patients included in the study, 24 had deletions amenable to skip exon 44, 27 exon 45, 18 exon 51, and 28 exon 53. Five patients with a single deletion of exon 52 were counted in both subgroups skipping exon 51 and 53.

RESULTS

The difference between subgroups amenable to skip different exons was not significant at 12 months but became significant at both 24 (p≤0.05) and 36 months (p≤0.01).

DISCUSSION

Mutations amenable to skip exon 53 had lower baseline values and more negative changes than the other subgroups while those amenable to skip exon 44 had better results both at baseline and at follow up. Deletions amenable to skip exon 45 were associated with a more variable pattern of progression. Single exon deletions were more often associated with less drastic changes but this was not always true in individual cases.

CONCLUSION

Our results confirm that the progression of disease can differ between patients with different deletions, although the changes only become significant from 24 months onwards. This information is relevant because there are current clinical trials specifically targeting patients with these subgroups of mutations.

Embryonic myosin is a regeneration marker to monitor utrophin-based therapies for DMD

Duchenne muscular dystrophy (DMD) is a lethal, X-linked muscle-wasting disease caused by lack of the cytoskeletal protein dystrophin. Constitutive utrophin expression, a structural and functional paralogue of dystrophin, can successfully prevent the dystrophic pathology in the dystrophin-deficient mdx mouse model. In dystrophic muscles, utrophin is increased as part of the repair process and localized at the sarcolemma of regenerating myofibers. The presence of developmental myosin such as embryonic myosin (MyHC-emb) and neonatal represents a useful marker of muscle regeneration and a meaningful indicator of muscle damage, which correlates with the clinical severity of milder Becker muscular dystrophy and DMD patients. In the present study, we demonstrate that MyHC-emb is a robust marker of regeneration at different ages and in different skeletal muscles. We also evaluate the correlation between utrophin, dystrophin and MyHC-emb in wild-type (wt) and regenerating dystrophic muscles. Restoration of dystrophin significantly reduced MyHC-emb levels. Similarly, overexpression of utrophin in the transgenic mdx-Fiona mice reduced the number of MyHC-emb positive fibers to wt level, prevented the regenerative process and rescued the muscle function. In contrast, the absence of utrophin in the dystrophin-deficient double-knockout mice resulted in a higher MyHC-emb content and in a more severe dystrophic pathophysiology than in mdx mice. These data illustrate the importance of monitoring utrophin and MyHC-emb levels in the preclinical evaluation of therapies and provide translational support for the use of developmental myosin as a disease biomarker in DMD clinical trials.

The "Usual Suspects": Genes for Inflammation, Fibrosis, Regeneration, and Muscle Strength Modify Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD), the most severe form of dystrophinopathy, is quite homogeneous with regards to its causative biochemical defect, i.e., complete dystrophin deficiency, but not so much with regards to its phenotype. For instance, muscle weakness progresses to the loss of independent ambulation at a variable age, starting from before 10 years, to even after 16 years (with glucocorticoid treatment). Identifying the bases of such variability is relevant for patient counseling, prognosis, stratification in trials, and identification of therapeutic targets. To date, variants in five loci have been associated with variability in human DMD sub-phenotypes: SPP1, LTBP4, CD40, ACTN3, and THBS1. Four of these genes (SPP1, LTBP4, CD40, and THBS1) are implicated in several interconnected molecular pathways regulating inflammatory response to muscle damage, regeneration, and fibrosis; while ACTN3 is known as “the gene for speed”, as it contains a common truncating polymorphism (18% of the general population), which reduces muscle power and sprint performance. Studies leading to the identification of these modifiers were mostly based on a “candidate gene” approach, hence the identification of modifiers in “usual suspect” pathways, which are already known to modify muscle in disease or health. Unbiased approaches that are based on genome mapping have so far been applied only initially, but they will probably represent the focus of future developments in this field, and will hopefully identify novel, “unsuspected” therapeutic targets. In this article, we summarize the state of the art of modifier loci of human dystrophin deficiency, and attempt to assess their relevance and implications on both clinical management and translational research.

Variability and trends in corticosteroid use by male United States participants with Duchenne muscular dystrophy in the Duchenne Registry

Background

Treatment options for Duchenne muscular dystrophy remain limited, although consensus treatment guidelines recommend corticosteroid use.

Methods

This retrospective analysis assessed corticosteroid use in ambulatory and nonambulatory US males with Duchenne, age 35 and under, or Becker muscular dystrophy, who enrolled in The Duchenne Registry from 2007 to 2016 (formerly DuchenneConnect).

Results

The mean (SD) age of corticosteroid use initiation was 5.9 (2.5) years, and deflazacort use (54%) was slightly more common than prednisone/prednisolone (46%). Among all responses from those with Duchenne, 63% were currently on corticosteroids, 12% were no longer on corticosteroids, and 25% had never been on corticosteroids. Among those who were nonambulatory, 49% were currently on corticosteroids, 28% had discontinued corticosteroids, and 23% had never used corticosteroids. Primary reasons for never initiating therapy were that corticosteroids were not prescribed or recommended and concerns about side effects. Corticosteroid use was maximal at age 8 (84% on corticosteroids) and gradually declined from age 10 to 19. The primary reasons for corticosteroid discontinuation were problems with side effects (65%) or not enough benefit (28%). Average doses of corticosteroids were below recommended doses. In the 159 responses with Becker muscular dystrophy, 20% were currently using corticosteroids.

Conclusions

Recognizing the self-selected nature of participation, it appears that a considerable proportion of US participants registered with The Duchenne Registry were either not on corticosteroids or not on recommended doses despite consensus recommendations. Side effects were a consideration in initiating and discontinuing treatment.

These data reinforce the need for additional treatment options for those affected by Duchenne.

Targeting angiogenesis in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) represents one of the most devastating types of muscular dystrophies which affect boys already at early childhood. Despite the fact that the primary cause of the disease, namely the lack of functional dystrophin is known already for more than 30 years, DMD still remains an incurable disease. Thus, an enormous effort has been made during recent years to reveal novel mechanisms that could provide therapeutic targets for DMD, especially because glucocorticoids treatment acts mostly symptomatic and exerts many side effects, whereas the effectiveness of genetic approaches aiming at the restoration of functional dystrophin is under the constant debate. Taking into account that dystrophin expression is not restricted to muscle cells, but is present also in, e.g., endothelial cells, alterations in angiogenesis process have been proposed to have a significant impact on DMD progression. Indeed, already before the discovery of dystrophin, several abnormalities in blood vessels structure and function have been revealed, suggesting that targeting angiogenesis could be beneficial in DMD. In this review, we will summarize current knowledge about the angiogenesis status both in animal models of DMD as well as in DMD patients, focusing on different organs as well as age- and sex-dependent effects. Moreover, we will critically discuss some approaches such as modulation of vascular endothelial growth factor or nitric oxide related pathways, to enhance angiogenesis and attenuate the dystrophic phenotype. Additionally, we will suggest the potential role of other mediators, such as heme oxygenase-1 or statins in those processes.

Pulmonary function and clinical correlation in DMD

Duchenne muscular dystrophy [DMD] is the most common inherited myopathy and is caused by a defect in the dystrophin gene on the X chromosome causing production of a dysfunctional dystrophin protein. Over the last decade there have been advances in disease modifying pharmacotherapy beyond the widely used strategy of corticosteroids into products to impact both dystrophin production itself and also some of the downstream effects of absent of dysfunctional dystrophin. This manuscript will explore the respiratory progression of DMD including some proposed functional and clinical correlations and the overlap between loss of function in different muscle groups. Options for symptomatic treatment and support are presented and direction as to when the different options should be considered is provided. The manuscript will also review the currently available and late phase developmental pharmacotherapies for DMD.

2,4 Dinitrophenol as Medicine

In the sanctity of pure drug discovery, objective reasoning can become clouded when pursuing ideas that appear unorthodox, but are spot on physiologically. To put this into historical perspective, it was an unorthodox idea in the 1950’s to suggest that warfarin, a rat poison, could be repositioned into a breakthrough drug in humans to protect against strokes as a blood thinner. Yet it was approved in 1954 as Coumadin^® and has been prescribed to billions of patients as a standard of care. Similarly, no one can forget the horrific effects of thalidomide, prescribed or available without a prescription, as both a sleeping pill and “morning sickness” anti-nausea medication targeting pregnant women in the 1950’s. The “thalidomide babies” became the case-in-point for the need of strict guidelines by the U.S. Food & Drug Administration (FDA) or full multi-species teratogenicity testing before drug approval. More recently it was found that thalidomide is useful in graft versus host disease, leprosy and resistant tuberculosis treatment, and as an anti-angiogenesis agent as a breakthrough drug for multiple myeloma (except for pregnant female patients). Decades of diabetes drug discovery research has historically focused on every possible angle, except, the energy-out side of the equation, namely, raising mitochondrial energy expenditure with chemical uncouplers. The idea of “social responsibility” allowed energy-in agents to be explored and the portfolio is robust with medicines of insulin sensitizers, insulin analogues, secretagogues, SGLT2 inhibitors, etc., but not energy-out medicines. The primary reason? It appeared unorthodox, to return to exploring a drug platform used in the 1930s in over 100,000 obese patients used for weight loss. This is over 80-years ago and prior to Dr Peter Mitchell explaining the mechanism of how mitochondrial uncouplers, like 2,4-dinitrophenol (DNP) even worked by three decades later in 1961. Although there is a clear application for metabolic disease, it was not until recently that this platform was explored for its merit at very low, weight-neutral doses, for treating insidious human illnesses and completely unrelated to weight reduction. It is known that mitochondrial uncouplers specifically target the entire organelle’s physiology non-genomically. It has been known for years that many neuromuscular and neurodegenerative diseases are associated with overt production of reactive oxygen species (ROSs), a rise in isoprostanes (biomarker of mitochondrial ROSs in urine or blood) and poor calcium (Ca²⁺) handing. It has also been known that mitochondrial uncouplers lower ROS production and Ca²⁺ overload. There is evidence that elevation of isoprostanes precedes disease onset, in Alzheimer’s Disease (AD). It is also curious, why so many neurodegenerative diseases of known and unknown etiology start at mid-life or later, such as Multiple Sclerosis (MS), Huntington Disease (HD), AD, Parkinson Disease, and Amyotrophic Lateral Sclerosis (ALS). Is there a relationship to a buildup of mutations that are sequestered over time due to ROSs exceeding the rate of repair? If ROS production were managed, could disease onset due to aging be delayed or prevented? Is it possible that most, if not all neurodegenerative diseases are manifested through mitochondrial dysfunction? Although DNP, a historic mitochondrial uncoupler, was used in the 1930s at high doses for obesity in well over 100,000 humans, and so far, it has never been an FDA-approved drug. This review will focus on the application of using DNP, but now, repositioned as a potential disease-modifying drug for a legion of insidious diseases at much lower and paradoxically, weight neutral doses. DNP will be addressed as a treatment for “metabesity”, an emerging term related to the global comorbidities associated with the over-nutritional phenotype; obesity, diabetes, nonalcoholic steatohepatitis (NASH), metabolic syndrome, cardiovascular disease, but including neurodegenerative disorders and accelerated aging. Some unexpected drug findings will be discussed, such as DNP’s induction of neurotrophic growth factors involved in neuronal heath, learning and cognition. For the first time in 80’s years, the FDA has granted (to Mitochon Pharmaceutical, Inc., Blue Bell, PA, USA) an open Investigational New Drug (IND) approval to begin rigorous clinical testing of DNP for safety and tolerability, including for the first ever, pharmacokinetic profiling in humans. Successful completion of Phase I clinical trial will open the door to explore the merits of DNP as a possible treatment of people with many truly unmet medical needs, including those suffering from HD, MS, PD, AD, ALS, Duchenne Muscular Dystrophy (DMD), and Traumatic Brain Injury (TBI).

Titin fragment in urine: A noninvasive biomarker of muscle degradation

Titin/connectin, encoded by the TTN gene, is the largest protein in humans. It acts as a molecular spring in the sarcomere of striated muscles. Although titin is degraded in the skeletal muscles of patients with muscular dystrophies, studies of titin have been limited by its mammoth size. Mutations in the TTN gene have been detected not only in skeletal muscle diseases but in cardiac muscle diseases. TTN mutations result in a wide variety of phenotypes. Recent proteome analysis has found that titin fragments are excreted into the urine of patents with Duchenne muscular dystrophy (DMD). Enzyme-linked immunosorbent assays (ELISAs) have shown that urinary titin is a useful noninvasive biomarker for the diagnosis and screening of not only DMD, but also of neuromuscular diseases, for predicting the outcome of cardiomyopathy and for evaluating physical activities. The development of ELISA systems to measure urinary titin has opened a door to studying muscle degradation directly and noninvasively. This review provides current understanding of urinary titin and future prospects for measuring this protein.

Heart Transplantation Ameliorates Ambulation Capacity in Patients With Muscular Dystrophy - An Analysis of 9 Cases

BACKGROUND

Heart transplantation (HTx) is reported to have a comparable effect on the prognosis of heart failure patients without muscular disease and for those with muscular dystrophy (MD). However, little is known about the changes in muscular diseases in patients with MD after HTx. Methods and Results: We assessed the ambulatory capacity of 9 patients with MD who underwent HTx. All patients demonstrated improvement in ambulation to varying degrees and 1 patient successfully climbed Mount Fuji 3.8 years after HTx.

CONCLUSIONS

HTx potentially improves not only the prognosis but also the ambulatory capacity of patients with MD.

Population Pharmacokinetics of Vamorolone (VBP15) in Healthy Men and Boys With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an inherited neuromuscular disorder occurring in boys and caused by mutations in the dystrophin gene. Vamorolone is a first-generation delta-9,11 compound that has favorable efficacy and side effect profiles relative to classical glucocorticoids. The pharmacokinetics (PK) of oral vamorolone were assessed in parallel-group studies in healthy men (phase 1, n = 86) and boys with DMD (phase 2a, n = 48) during 14 days of once-daily dosing with a range of doses. Vamorolone exhibited moderate variability in PK, with the maximum plasma concentration usually occurring at 2-4 hours and a half-life of approximately 2 hours for all doses and days examined. Population PK modeling of all data together indicated that the PK of vamorolone can be well described by a 1-compartment model with zero-order absorption. Both men and boys showed a dose-linearity of PK parameters for the doses examined, with no accumulation of the drug during daily dosing. Ingestion with food resulted in markedly enhanced absorption of the drug, as tested in healthy men. There were similar PK of vamorolone in healthy men and DMD boys with apparent clearance averaging 2.0 L/h/kg in men and 1.7 L/h/kg in boys. Overall, vamorolone exhibited well-behaved linear PK, with similar profiles in healthy men and boys with DMD, moderate variability in PK parameters, and absorption and disposition profiles similar to those of classical glucocorticoids.

A mini-review and implementation model for using ataluren to treat nonsense mutation Duchenne muscular dystrophy

AIM

Ataluren has been approved for treating nonsense mutation Duchenne muscular dystrophy (nmDMD), and there are currently discussions concerning drug access and applications beyond the development programme. This study provides an overview of nmDMD and ataluren, stipulates clinical rules for treatment initiation and discontinuation and proposes a model for the implementation of orphan drugs in clinical practice in Sweden.

METHODS

This was a targeted mini-review of the literature from 1995 to 2018, which included cohort studies, guidelines, randomised clinical trials, clinical commentaries and reviews. The review covered the pathophysiology, epidemiology and burden of nmDMD and the clinical programme for ataluren.

RESULTS

Based on the current evidence, and our experiences, we recommend that patients with nmDMD should be given ataluren as soon as possible after diagnosis and this treatment should continue until they reach a forced vital capacity of <30%, and, or, a score of at least six on the Brooke upper extremity scale. We propose an implementation model that comprises a coordinating specialist physician and a national expert committee responsible for providing clinical intelligence to ensure appropriate use.

CONCLUSION

Our clinical recommendations and proposed implementation model will inform the optimum medical management of nmDMD in Sweden and help ensure timely, equal access to ataluren and similar orphan drugs.

Growth, pubertal development, and skeletal health in boys with Duchenne Muscular Dystrophy

PURPOSE OF REVIEW

Glucocorticoid therapy is currently the most widely used treatment for Duchenne muscular dystrophy (DMD), having consistently shown to prolong ambulation by 2 years, reduce the frequency of scoliosis, and improve cardiorespiratory function. Among the most frequent side effects of glucocorticoids are fractures due to osteoporosis, linear growth retardation or arrest, and pubertal delay, the subjects of this review.

RECENT FINDINGS

The diagnosis of osteoporosis has shifted in recent years away from a bone mineral density-centric to a fracture-focused approach, with particular emphasis on early vertebral fracture identification (one of the key triggers for osteoporosis intervention). Delayed puberty should be addressed in an age-appropriate manner, with numerous options available for sex steroid replacement. Growth impairment, however, is a more challenging complication of glucocorticoid-treated DMD, one that is most likely best addressed through growth-sparing therapies that target the dystrophinopathy.

SUMMARY

With glucocorticoid prescription an increasingly prevalent component of DMD care, early attention to management of osteoporosis and delayed puberty are important components of multidisciplinary and anticipatory care. The treatment of short stature remains controversial, with no accepted therapy currently available to over-ride the toxic effects of glucocorticoids on the growth axis.

Use of bone age for evaluating bone density in patients with Duchenne muscular dystrophy: A preliminary report

INTRODUCTION

Patients with Duchenne muscular dystrophy (DMD) exhibit low bone mineral density and increased fracture risk. Because glucocorticoid therapy results in delayed puberty and short stature, it is important to account for delayed skeletal development when interpreting patients' bone mineral density.

METHODS

Twelve glucocorticoid-treated patients with DMD were evaluated by dual x-ray absorptiometry scans and wrist x-rays to estimate bone density and bone age, respectively. Z-scores were determined on the basis of chronological age. Each patient was assigned a "corrected" birth date that was calculated according to bone age, and a bone-age-corrected z-score was determined.

RESULTS

Z-scores adjusted for chronological age were lower than those adjusted for bone age.

DISCUSSION

We suggest the use of bone age as an alternative to chronological age for analysis of bone mineral density in glucocorticoid-treated patients with DMD. Additional research is required to determine the optimal method to predict fracture risk in this patient group. Muscle Nerve 59:422-425, 2019.

Urinary prostaglandin metabolites as Duchenne muscular dystrophy progression markers

BACKGROUND

Patients with Duchenne muscular dystrophy (DMD) exhibit increased prostaglandin D₂ (PGD₂) expression in necrotic muscle and increased PGD₂ metabolites in their urine. In mouse models, inhibiting PGD₂ production suppresses muscle necrosis, suggesting a possible intervention through PGD₂-mediated activities.

OBJECTIVE

We investigated the involvement of PGD₂ and its potential use as a marker of pathological progression in DMD.

METHODS

Sixty-one male children with DMD and thirty-five age-matched controls were enrolled in the study. DMD patients were divided into "ambulant" and "non-ambulant" groups, which were further subdivided into "steroid" and "non-steroid" therapy groups. Levels of the PGD₂ metabolite tetranor-PGDM (t-PGDM) and creatinine were measured in both spot and 24-hour urine samples, with comparisons between groups made according to geometric mean values.

RESULTS

DMD patients had significantly higher levels of creatinine-corrected t-PGDM in spot urine samples as compared with the control group. Additionally, both ambulant and non-ambulant DMD groups had significantly higher levels of t-PGDM as compared with controls, with no significant difference in t-PGDM levels observed between steroid and non-steroid groups. Moreover, total creatinine excretion in 24-hour urine samples was significantly lower in DMD patients as compared with controls, and although DMD patients had lower muscle mass than controls, their overall levels of t-PGDM did not differ significantly from those in the non-ambulant and control groups.

CONCLUSION

PGD₂ might help explain the progression and symptomatic presentations (e.g., ambulatory difficulty) associated with DMD, suggesting it as a useful pathological marker and use of a selective PGD₂ inhibitor as a potential treatment modality.

Phase IIa trial in Duchenne muscular dystrophy shows vamorolone is a first-in-class dissociative steroidal anti-inflammatory drug

We report a first-in-patient study of vamorolone, a first-in-class dissociative steroidal anti-inflammatory drug, in Duchenne muscular dystrophy. This 2-week, open-label Phase IIa multiple ascending dose study (0.25, 0.75, 2.0, and 6.0 mg/kg/day) enrolled 48 boys with Duchenne muscular dystrophy (4 to <7 years), with outcomes including clinical safety, pharmacokinetics and pharmacodynamic biomarkers. The study design included pharmacodynamic biomarkers in three contexts of use: 1. Secondary outcomes for pharmacodynamic safety (insulin resistance, adrenal suppression, bone turnover); 2. Exploratory outcomes for drug mechanism of action; 3. Exploratory outcomes for expanded pharmacodynamic safety. Vamorolone was safe and well-tolerated through the highest dose tested (6.0 mg/kg/day) and pharmacokinetics of vamorolone were similar to prednisolone. Using pharmacodynamic biomarkers, the study demonstrated improved safety of vamorolone versus glucocorticoids as shown by reduction of insulin resistance, beneficial changes in bone turnover (loss of increased bone resorption and decreased bone formation only at the highest dose level), and a reduction in adrenal suppression. Exploratory biomarkers of pharmacodynamic efficacy showed an anti-inflammatory mechanism of action and a beneficial effect on plasma membrane stability, as demonstrated by a dose-responsive decrease in serum creatine kinase activity. With an array of pre-selected biomarkers in multiple contexts of use, we demonstrate the development of the first dissociative steroid that preserves anti-inflammatory efficacy and decreases steroid-associated safety concerns. Ongoing extension studies offer the potential to bridge exploratory efficacy biomarkers to clinical outcomes.

Deflazacort versus prednisone/prednisolone for maintaining motor function and delaying loss of ambulation: A post HOC analysis from the ACT DMD trial

Introduction: ACT DMD was a 48‐week trial of ataluren for nonsense mutation Duchenne muscular dystrophy (nmDMD). Patients received corticosteroids for ≥6 months at entry and stable regimens throughout study. This post hoc analysis compares efficacy and safety for deflazacort and prednisone/prednisolone in the placebo arm. Methods: Patients received deflazacort (n = 53) or prednisone/prednisolone (n = 61). Endpoints included change from baseline in 6‐minute walk distance (6MWD), timed function tests, estimated age at loss of ambulation (extrapolated from 6MWD). Results: Mean changes in 6MWD were ‐39.0 m (deflazacort; 95% confidence limit [CL], ‐68.85, ‐9.17) and ‐70.6 m (prednisone/prednisolone; 95% CL, ‐97.16, ‐44.02). Mean changes in 4‐stair climb were 3.79 s (deflazacort; 95% CL, 1.54, 6.03) and 6.67 s (prednisone/prednisolone; 95% CL, 4.69, 8.64). Conclusions: This analysis, limited by its post hoc nature, suggests greater preservation of 6MWD and 4‐stair climb with deflazacort vs. prednisone/prednisolone. A head‐to‐head comparison will better define these differences. Muscle Nerve58: 639–645, 2018

The effect of steroid treatment on weight in nonambulatory males with Duchenne muscular dystrophy

To describe the long-term effect of steroid treatment on weight in nonambulatory males with Duchenne Muscular Dystrophy (DMD), we identified 392 males age 7-29 years with 4,512 weights collected after ambulation loss (176 steroid-naïve and 216 treated with steroids ≥6 months) from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet). Comparisons were made between the weight growth curves for steroid-naïve males with DMD, steroid-treated males with DMD, and the US pediatric male population. Using linear mixed-effects models adjusted for race/ethnicity and birth year, we evaluated the association between weight-for-age and steroid treatment characteristics (age at initiation, dosing interval, cumulative duration, cumulative dose, type). The weight growth curves for steroid-naïve and steroid-treated nonambulatory males with DMD were wider than the US pediatric male growth curves. Mean weight-for-age z scores were lower in both steroid-naïve (mean = -1.3) and steroid-treated (mean = -0.02) nonambulatory males with DMD, compared to the US pediatric male population. Longer treatment duration and greater cumulative dose were significantly associated with lower mean weight-for-age z scores. Providers should consider the effect of steroid treatment on weight when making postambulation treatment decisions for males with DMD.

Drug Repurposing for Duchenne Muscular Dystrophy: The Monoamine Oxidase B Inhibitor Safinamide Ameliorates the Pathological Phenotype in mdx Mice and in Myogenic Cultures From DMD Patients

Oxidative stress and mitochondrial dysfunction play a crucial role in the pathophysiology of muscular dystrophies. We previously reported that the mitochondrial enzyme monoamine oxidase (MAO) is a relevant source of reactive oxygen species (ROS) not only in murine models of muscular dystrophy, in which it directly contributes to contractile impairment, but also in muscle cells from collagen VI-deficient patients. Here, we now assessed the efficacy of a novel MAO-B inhibitor, safinamide, using in vivo and in vitro models of Duchenne muscular dystrophy (DMD). Specifically, we found that administration of safinamide in 3-month-old mdx mice reduced myofiber damage and oxidative stress and improved muscle functionality. In vitro studies with myogenic cultures from mdx mice and DMD patients showed that even cultured dystrophic myoblasts were more susceptible to oxidative stress than matching cells from healthy donors. Indeed, upon exposure to the MAO substrate tyramine or to hydrogen peroxide, DMD muscle cells displayed a rise in ROS levels and a consequent mitochondrial depolarization. Remarkably, both phenotypes normalized when cultures were treated with safinamide. Given that safinamide is already in clinical use for neurological disorders, our findings could pave the way toward a promising translation into clinical trials for DMD patients as a classic case of drug repurposing.

Health profile of a cohort of adults with Duchenne muscular dystrophy

INTRODUCTION

As the Duchenne muscular dystrophy (DMD) population ages, it is essential that we understand the late-stage health profile and provide the appropriate care for this emerging population.

METHODS

We undertook a descriptive study to document the health profile of a cohort of adults with DMD using data from the Muscular Dystrophy Surveillance Tracking and Research network (MD STARnet). Data included information collected from Arizona, Colorado, Iowa, Georgia, and 12 counties in western New York on individuals born since January 1982 and followed through December 2012.

RESULTS

In 208 adults with DMD, the number of individuals (N) and median ages (years) at which certain critical milestones were crossed and interventions initiated were as follows: development of cardiomyopathy, N = 145 (16.7); initiation of non-invasive ventilation, N = 99 (18.0); gastrostomy, N = 47 (19.0); and death, N = 59 (21.8).

DISCUSSION

These population-based data provide critical information about late-stage health profiles among adults with DMD for developing appropriate models of care. Muscle Nerve 58: 219-223, 2018.

The Relationship Between Bone Mineral Density and Cardiovascular Function in Duchenne Muscular Dystrophy: A Retrospective Cohort Study

INTRODUCTION:

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder that causes progressive skeletal and cardiac muscle weakness in boys. Cardiac dysfunction is a frequent cause of death in DMD. Glucocorticoids are the standard of care in DMD. The long-term use of oral glucocorticoids in DMD is complicated by poor bone health. Epidemiological studies suggest a biological link between the loss of bone mineral density (BMD) and cardiovascular disease, including coronary artery and cerebrovascular diseases. Whether an association between low BMD and cardiac dysfunction occurs in DMD boys has not yet been studied. The objective of this retrospective cohort study was to examine the relationship between BMD and cardiovascular health in DMD.

METHODS:

Retrospective data analyses was performed from de-identified medical records from a tertiary academic medical center. Whole body BMD was measured using dual-energy xray absorptiometry (DEXA) scan and left ventricular ejection fraction (LVEF) was measured using echocardiogram. Linear regression was used to evaluate the relationship between BMD and LVEF.

RESULTS:

Data was analyzed from a total of 32 boys with DMD. The mean age at which baseline BMD measurements was obtained of 11±3 (SD) years. The worst LVEF was measured at a mean of 23.7±21.8 (SD) months after the baseline BMD measurement. The final adjusted linear regression of the relationship between baseline BMD z-score and worst LVEF was not statistically significant (ß=0.41, p‑value=0.6455).

DISCUSSION:

In this cohort of boys with DMD, BMD was not associated with LVEF dysfunction up to 79 months later. Future research with a longer longitudinal follow-up period is warranted to evaluate the relationship between BMD and cardiovascular disease in DMD.

Downregulation of miRNA-29, -23 and -21 in urine of Duchenne muscular dystrophy patients

AIM

To study the signature of 87 urinary miRNAs in Duchenne muscular dystrophy (DMD) patients, select the most dysregulated and determine statistically significant differences in their expression between controls, ambulant (A) and nonambulant (NA) DMD patients, and patients on different corticosteroid regimens. Patients/materials & methods: Urine was collected from control (n = 20), A (n = 31) and NA (n = 23) DMD patients. miRNA expression was measured by reverse transcription-quantitative PCR.

RESULTS

miR-29c-3p was significantly downregulated in A DMD patients while miR-23b-3p and miR-21-5p were significantly downregulated in NA DMD patients compared with age-matched controls.

CONCLUSION

miR-29c-3p, miR-23b-3p and miR-21-5p are promising novel noninvasive biomarkers for DMD, and miR-29c-3p levels are differentially affected by different steroid regimens, supporting the antifibrotic effect of steroid therapy.