Functional changes in Duchenne muscular dystrophy: a 12-month longitudinal cohort study

The 6 minute walk test and performance of upper limb in ambulant duchenne muscular dystrophy boys

The Performance of Upper Limb (PUL) test was specifically developed for the assessment of upper limbs in Duchenne muscular dystrophy (DMD). The first published data have shown that early signs of involvement can also be found in ambulant DMD boys. The aim of this longitudinal Italian multicentric study was to evaluate the correlation between the 6 Minute Walk Test (6MWT) and the PUL in ambulant DMD boys. Both 6MWT and PUL were administered to 164 ambulant DMD boys of age between 5.0 and 16.17 years (mean 8.82). The 6 minute walk distance (6MWD) ranged between 118 and 557 (mean: 376.38, SD: 90.59). The PUL total scores ranged between 52 and 74 (mean: 70.74, SD: 4.66). The correlation between the two measures was 0.499. The scores on the PUL largely reflect the overall impairment observed on the 6MWT but the correlation was not linear. The use of the PUL appeared to be less relevant in the very strong patients with 6MWD above 400 meters, who, with few exceptions had near full scores. In patients with lower 6MWD the severity of upper limb involvement was more variable and could not always be predicted by the 6MWD value or by the use of steroids. Our results confirm that upper limb involvement can already be found in DMD boys even in the ambulant phase.

Suitability of North Star Ambulatory Assessment in young boys with Duchenne muscular dystrophy

The aim of this study was to establish the suitability of the North Star Ambulatory Assessment for use in young boys with Duchenne muscular dystrophy. We studied 147 typically developing and 144 boys affected by Duchenne muscular dystrophy between the ages of 3 and 5 years. More than 85% of the typically developing boys by the age of 4 years had full scores on all the items with total scores ≥33/34. Before the age of 4 years more than 15% of the typically developing boys did not achieve full scores on all the items. Some items, such as standing on one leg, showed significant improvement with age. In contrast, other activities were rarely achieved even in the older boys. Even if there was a progressive increase in scores with age, both total and individual item scores in Duchenne were still far from those obtained in the typically developing children of the same age. Our findings suggest that the North Star Ambulatory Assessment can be reliably used at least from the age of 4 years. Longitudinal natural history data studies are needed to assess possible changes over time and the possible effect of early steroids.

Ataluren treatment of patients with nonsense mutation dystrophinopathy

INTRODUCTION

Dystrophinopathy is a rare, severe muscle disorder, and nonsense mutations are found in 13% of cases. Ataluren was developed to enable ribosomal readthrough of premature stop codons in nonsense mutation (nm) genetic disorders.

METHODS

Randomized, double-blind, placebo-controlled study; males ≥ 5 years with nm-dystrophinopathy received study drug orally 3 times daily, ataluren 10, 10, 20 mg/kg (N=57); ataluren 20, 20, 40 mg/kg (N=60); or placebo (N=57) for 48 weeks. The primary endpoint was change in 6-Minute Walk Distance (6MWD) at Week 48.

RESULTS

Ataluren was generally well tolerated. The primary endpoint favored ataluren 10, 10, 20 mg/kg versus placebo; the week 48 6MWD Δ=31.3 meters, post hoc P=0.056. Secondary endpoints (timed function tests) showed meaningful differences between ataluren 10, 10, 20 mg/kg, and placebo.

CONCLUSIONS

As the first investigational new drug targeting the underlying cause of nm-dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need.

Long term natural history data in ambulant boys with Duchenne muscular dystrophy: 36-month changes

The 6 minute walk test has been recently chosen as the primary outcome measure in international multicenter clinical trials in Duchenne muscular dystrophy ambulant patients. The aim of the study was to assess the spectrum of changes at 3 years in the individual measures, their correlation with steroid treatment, age and 6 minute walk test values at baseline. Ninety-six patients from 11 centers were assessed at baseline and 12, 24 and 36 months after baseline using the 6 minute walk test and the North Star Ambulatory Assessment. Three boys (3%) lost the ability to perform the 6 minute walk test within 12 months, another 13 between 12 and 24 months (14%) and 11 between 24 and 36 months (12%). The 6 minute walk test showed an average overall decline of -15.8 (SD 77.3) m at 12 months, of -58.9 (SD 125.7) m at 24 months and -104.22 (SD 146.2) m at 36 months. The changes were significantly different in the two baseline age groups and according to the baseline 6 minute walk test values (below and above 350 m) (p<0.001). The changes were also significantly different according to steroid treatment (p = 0.01). Similar findings were found for the North Star Ambulatory Assessment. These are the first 36 month longitudinal data using the 6 minute walk test and North Star Ambulatory Assessment in Duchenne muscular dystrophy. Our findings will help not only to have a better idea of the progression of the disorder but also provide reference data that can be used to compare with the results of the long term extension studies that are becoming available.

Compensatory movements during functional activities in ambulatory children with Duchenne muscular dystrophy

OBJECTIVE

During the transitional phase (ambulatory to non-ambulatory), synergies characterize the evolution of Duchenne muscular dystrophy (DMD). This study was performed to describe and quantify compensatory movements while sitting down on/rising from the floor and climbing up/down steps.

METHOD

Eighty videos (5 children × 4 assessments × 4 tasks) were recorded quarterly in the year prior to gait loss. Compensatory movements from the videos were registered based on the Functional Evaluation Scale for DMD.

RESULTS

The most frequently observed compensatory movements were upper limb support on lower limbs/floor/handrail during all the tasks and lumbar hyperlordosis, trunk support on handrail, equinus foot, increased base of support, non-alternated descent, and pauses while climbing up/down steps.

CONCLUSION

Climbing up/down steps showed a higher number of compensatory movements than sitting down on/rising from the floor, which seemed to be lost before climbing up/down steps in ambulatory children with DMD.

Safety and efficacy of drisapersen for the treatment of Duchenne muscular dystrophy (DEMAND II): an exploratory, randomised, placebo-controlled phase 2 study

BACKGROUND

Duchenne muscular dystrophy is caused by dystrophin deficiency and muscle deterioration and preferentially affects boys. Antisense-oligonucleotide-induced exon skipping allows synthesis of partially functional dystrophin. We investigated the efficacy and safety of drisapersen, a 2'-O-methyl-phosphorothioate antisense oligonucleotide, given for 48 weeks.

METHODS

In this exploratory, double-blind, placebo-controlled study we recruited male patients (≥5 years of age; time to rise from floor ≤7 s) with Duchenne muscular dystrophy from 13 specialist centres in nine countries between Sept 1, 2010, and Sept 12, 2012. By use of a computer-generated randomisation sequence, we randomly allocated patients (2:2:1:1; block size of six; no stratification) to drisapersen 6 mg/kg or placebo, each given subcutaneously and either continuously (once weekly) or intermittently (nine doses over 10 weeks). The primary endpoint was change in 6-min walk distance (6MWD) at week 25 in patients in the intention-to-treat population for whom data were available. Safety assessments included renal, hepatic, and haematological monitoring and recording of adverse events. This trial is registered with ClinicalTrials.gov, number NCT01153932.

FINDINGS

We recruited 53 patients: 18 were given continuous drisapersen, 17 were given intermittent drisapersen, and 18 were given placebo (continuous and intermittent groups combined). At week 25, mean 6MWD had increased by 31·5 m (SE 9·8) from baseline for continuous drisapersen, with a mean difference in change from baseline of 35·09 m (95% CI 7·59 to 62·60; p=0·014) versus placebo. We recorded no difference in 6MWD changes from baseline between intermittent drisapersen (mean change -0·1 [SE 10·3]) and placebo (mean difference 3·51 m [-24·34 to 31·35]) at week 25. The most common adverse events in drisapersen-treated patients were injection-site reactions (14 patients given continuous drisapersen, 15 patients given intermittent drisapersen, and six given placebo) and renal events (13 for continuous drisapersen, 12 for intermittent drisapersen, and seven for placebo), most of which were subclinical proteinuria. None of the serious adverse events reported (one for continuous, two for intermittent, and two for placebo) resulted in withdrawal from the study.

INTERPRETATION

Continuous drisapersen resulted in some benefit in 6MWD versus placebo at week 25. The safety findings are similar to those from previous studies. Ambulation improvements in this young population with early-stage Duchenne muscular dystrophy are encouraging but need to be confirmed in larger studies.

FUNDING

GlaxoSmithKline, Prosensa Therapeutics BV (a subsidiary of Prosensa Holding NV).

Examination of effects of corticosteroids on skeletal muscles of boys with DMD using MRI and MRS

OBJECTIVE

To evaluate the effects of corticosteroids on the lower extremity muscles in boys with Duchenne muscular dystrophy (DMD) using MRI and magnetic resonance spectroscopy (MRS).

METHODS

Transverse relaxation time (T2) and fat fraction were measured by MRI/MRS in lower extremity muscles of 15 boys with DMD (age 5.0-6.9 years) taking corticosteroids and 15 corticosteroid-naive boys. Subsequently, fat fraction was measured in a subset of these boys at 1 year. Finally, MRI/MRS data were collected from 16 corticosteroid-naive boys with DMD (age 5-8.9 years) at baseline, 3 months, and 6 months. Five boys were treated with corticosteroids after baseline and the remaining 11 served as corticosteroid-naive controls.

RESULTS

Cross-sectional comparisons demonstrated lower muscle T2 and less intramuscular (IM) fat deposition in boys with DMD on corticosteroids, suggesting reduced inflammation/damage and fat infiltration with treatment. Boys on corticosteroids demonstrated less increase in IM fat infiltration at 1 year. Finally, T2 by MRI/MRS detected effects of corticosteroids on leg muscles as early as 3 months after drug initiation.

CONCLUSIONS

These results demonstrate the ability of MRI/MRS to detect therapeutic effects of corticosteroids in reducing inflammatory processes in skeletal muscles of boys with DMD. Our work highlights the potential of MRI/MRS as a biomarker in evaluating therapeutic interventions in DMD.

Spectrum of muscular dystrophies associated with sarcolemmal-protein genetic defects

Muscular dystrophies are heterogeneous genetic disorders that share progressive muscle wasting. This may generate partial impairment of motility as well as a dramatic and fatal course. Less than 30 years ago, the identification of the genetic basis of Duchenne muscular dystrophy opened a new era. An explosion of new information on the mechanisms of disease was witnessed, with many thousands of publications and the characterization of dozens of other genetic forms. Genes mutated in muscular dystrophies encode proteins of the plasma membrane and extracellular matrix, several of which are part of the dystrophin-associated complex. Other gene products localize at the sarcomere and Z band, or are nuclear membrane components. In the present review, we focus on muscular dystrophies caused by defects that affect the sarcolemmal and sub-sarcolemmal proteins. We summarize the nature of each disease, the genetic cause, and the pathogenic pathways that may suggest future treatment options. We examine X-linked Duchenne and Becker muscular dystrophies and the autosomal recessive limb-girdle muscular dystrophies caused by mutations in genes encoding sarcolemmal proteins. The mechanism of muscle damage is reviewed starting from disarray of the shock-absorbing dystrophin-associated complex at the sarcolemma and activation of inflammatory response up to the final stages of fibrosis. We trace only a part of the biochemical, physiopathological and clinical aspects of muscular dystrophy to avoid a lengthy list of different and conflicting observations. We attempt to provide a critical synthesis of what we consider important aspects to better understand the disease. In our opinion, it is becoming ever more important to go back to the bedside to validate and then translate each proposed mechanism. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Electrical impedance myography for the in vivo and ex vivo assessment of muscular dystrophy (mdx) mouse muscle

INTRODUCTION

Sensitive, non-invasive techniques are needed that can provide biomarkers of disease status and the effects of therapy in muscular dystrophy.

METHODS

We evaluated electrical impedance myography (EIM) to serve in this role by studying 2-month-old and 18-month-old mdx and wild-type (WT) animals (10 animals in each of 4 groups).

RESULTS

Marked differences were observed in EIM values between mdx and WT animals; the differences were more pronounced between the older age groups (e.g., reactance of 92.6 ± 4.3 Ω for mdx animals vs. 130 ± 4.1 Ω for WT animals, P<0.001). In addition, in vivo EIM parameters correlated significantly with the extent of connective tissue deposition in the mdx animals.

CONCLUSIONS

EIM has the potential to serve as a valuable non-invasive method for evaluating muscular dystrophy. It can be a useful biomarker to assist with therapeutic testing in both pre-clinical and clinical studies.

One year outcome of boys with Duchenne muscular dystrophy using the Bayley-III scales of infant and toddler development

BACKGROUND

The pathogenesis of Duchenne muscular dystrophy starts before birth. Despite this, clinical trials exclude young boys because traditional outcome measures rely on cooperation. We recently used the Bayley-III Scales of Infant and Toddler Development to study 24 infants and boys with Duchenne muscular dystrophy. Clinical evaluators at six centers were trained and certified to perform the Bayley-III. Here, we report 6- and 12-month follow-up of two subsets of these boys.

PATIENTS

Nineteen boys (1.9 ± 0.8 years) were assessed at baseline and 6 months. Twelve boys (1.5 ± 0.8 years) were assessed at baseline, 6, and 12 months.

RESULTS

Gross motor scores were lower at baseline compared with published controls (6.2 ± 1.7; normal 10 ± 3; P < 0.0001) and revealed a further declining trend to 5.7 ± 1.7 (P = 0.20) at 6 months. Repeated measures analysis of the 12 boys monitored for 12 months revealed that gross motor scores, again low at baseline (6.6 ± 1.7; P < 0.0001), declined at 6 months (5.9 ± 1.8) and further at 12 months (5.3 ± 2.0) (P = 0.11). Cognitive and language scores were lower at baseline compared with normal children (range, P = 0.002-<0.0001) and did not change significantly at 6 or 12 months (range, P = 0.89-0.09). Fine motor skills, also low at baseline, improved >1 year (P = 0.05).

CONCLUSION

Development can reliably be measured in infants and young boys with Duchenne muscular dystrophy across time using the Bayley-III. Power calculations using these data reveal that motor development may be used as an outcome measure.

Intra-erythrocyte infusion of dexamethasone reduces neurological symptoms in ataxia teleangiectasia patients: results of a phase 2 trial

Background

Ataxia Teleangiectasia [AT] is a rare neurodegenerative disease characterized by early onset ataxia, oculocutaneous teleangiectasias, immunodeficiency, recurrent infections, radiosensitivity and proneness to cancer. No therapies are available for this devastating disease. Recent observational studies in few patients showed beneficial effects of short term treatment with betamethasone. To avoid the characteristic side effects of long-term administration of steroids we developed a method for encapsulation of dexamethasone sodium phosphate (DSP) into autologous erythrocytes (EryDex) allowing slow release of dexamethasone for up to one month after dosing. Aims of the study were: the assessment of the effect of EryDex in improving neurological symptoms and adaptive behaviour of AT patients; the safety and tolerability of the therapy.

Methods

Twenty two patients (F:M = 1; mean age 11.2 ± 3.5) with a confirmed diagnosis of AT and a preserved or partially supported gait were enrolled for the study. The subjects underwent for six months a monthly infusion of EryDex. Ataxia was assessed by the International Cooperative Ataxia Rating Scale (ICARS) and the adaptive behavior by Vineland Adaptive Behavior Scales (VABS). Clinical evaluations were performed at baseline and 1, 3, and 6 months.

Results

An improvement in ICARS (reduction of the score) was detected in the intention-to-treat (ITT) population (n = 22; p = 0.02) as well as in patients completing the study (per protocol PP) (n = 18; p = 0.01), with a mean reduction of 4 points (ITT) or 5.2 points (PP). When compared to baseline, a significant improvement were also found in VABS (increase of the score) (p < 0.0001, ITT, RMANOVA), with statistically significant increases at 3 and 6 months (p < 0.0001). A large inter-patient variability in the incorporation of DSP into erythrocytes was observed, with an evident positive effect of higher infusion dose on ICARS score decline. Moreover a more marked improvement was found in less neurologically impaired patients. Finally, a 19 month-extension study involving a subgroup of patients suggested that Erydex treatment can possibly delay the natural progression of the disease.

EryDex was well tolerated; the most frequent side effects were common AT pathologies.

Conclusions

EryDex treatment led to a significant improvement in neurological symptoms, without association with the typical steroid side effects.

Trial registration

Current Controlled Trial 2010-022315-19SpA

6 Minute walk test in Duchenne MD patients with different mutations: 12 month changes

OBJECTIVE

In the last few years some of the therapeutical approaches for Duchenne muscular dystrophy (DMD) are specifically targeting distinct groups of mutations, such as deletions eligible for skipping of individual exons. The aim of this observational study was to establish whether patients with distinct groups of mutations have different profiles of changes on the 6 minute walk test (6MWT) over a 12 month period.

METHODS

The 6MWT was performed in 191 ambulant DMD boys at baseline and 12 months later. The results were analysed using a test for heterogeneity in order to establish possible differences among different types of mutations (deletions, duplications, point mutations) and among subgroups of deletions eligible to skip individual exons.

RESULTS

At baseline the 6MWD ranged between 180 and 560,80 metres (mean 378,06, SD 74,13). The 12 month changes ranged between -325 and 175 (mean -10.8 meters, SD 69.2). Although boys with duplications had better results than those with the other types of mutations, the difference was not significant. Similarly, boys eligible for skipping of the exon 44 had better baseline results and less drastic changes than those eligible for skipping exon 45 or 53, but the difference was not significant.

CONCLUSIONS

even if there are some differences among subgroups, the mean 12 month changes in each subgroup were all within a narrow Range: from the mean of the whole DMD cohort. This information will be of help at the time of designing clinical trials with small numbers of eligible patients.

Six-minute walk test: reference values and prediction equation in healthy boys aged 5 to 12 years

OBJECTIVE

This study aimed to (1) generate normative data in healthy boys aged 5-12 years for the six-minute walk test (6MWT), an outcome measure currently used in clinical trials in Duchenne muscular dystrophy (DMD), (2) to describe the relation with anthropometric variables and myometry, and (3) to compare our data with published equations.

METHODS

The 6MWT was conducted in 442 boys according to a standardized protocol, as currently used in clinical trials in DMD. Maximal voluntary isometric contractions for knee flexion and extension were recorded with a hand-held myometer.

RESULTS

The 6MWD increased significantly with age, from 478.0 ± 44.1 m at age 5, to 650.0 ± 76.8 m at age 12, with the steepest increase between 5 and 8 years. Age- and height related percentile curves of the 6MWD were developed. Correlations with anthropometric variables were fair to good (age r = 0.60, height r = 0.57, weight r = 0.44). Myometric variables (knee flexors and extensors) showed correlations of 0.46 and 0.50 respectively. When dividing into two age categories (5-8 years, 9-12 years), these magnitudes of correlations only applied to the younger age group. Additionally, predicted values were calculated according to available reference equations (Geiger and Ben Saad), indicating an overestimation by those equations. Finally, the Geiger equation was refitted to our population.

CONCLUSION

The percentile curves according to age and height provide a useful tool in the assessment of ambulatory capacity in boys aged 5 to 12 years. Significant correlations with anthropometric variables and myometry were only found in the 5-8 years age group. The Geiger prediction equation, currently used to assess ambulatory capacity in DMD was refitted to obtain a more accurate prediction model based on a large sample with a homogenous distribution across the age categories 5 to 12 years and applying the methodology as currently used in clinical trials in DMD.

Reliability of the walking energy cost test and the six-minute walk test in boys with Duchenne muscular dystrophy

The walking energy cost test (WECT) is a useful tool when measuring ambulatory function in children with motor disorders. However, data on the reliability of this test in Duchenne muscular dystrophy (DMD) is not available. In this study we established the reliability of the WECT and the commonly used six-minute walk test (6MWT) in 19 boys with DMD, aged 6-12years. Participants performed the WECT and 6MWT twice within three weeks. Reliability was determined for walking distance (D, m) and gross energy cost (EC, Jkg(-1)m(-1)), using the intraclass correlation coefficient (ICC2,1) and smallest detectable change (SDC). Reliability for walking distance was good, with an ICC of 0.92 [95% CI: 0.81-0.97] and 0.83 [CI: 0.53-0.94] for the 6MWT and WECT, respectively, and an ICC of 0.85 [CI: 0.64-0.94] for gross EC. SDCs were 12.2% for D6MWT, 12.7% for DWECT and 18.5% for gross EC. In conclusion, in young boys with DMD, the reliability of both the WECT and 6MWT for assessing walking distance is adequate. Gross EC, as assessed with the WECT is also reliable and sufficiently sensitive to detect change in walking strain following interventions at group level.

Ongoing therapeutic trials and outcome measures for Duchenne muscular dystrophy

Muscular dystrophy is a heterogeneous group of genetic disorders characterised by progressive muscle tissue degeneration. No effective treatment has been discovered for these diseases. Preclinical and clinical studies aimed at the development of new therapeutic approaches have been carried out, primarily in subjects affected with dystrophinopathies (Duchenne and Becker muscular dystrophy). In this review, we outline the current therapeutic approaches and past and ongoing clinical trials, highlighting both the advantages and limits of each one. The experimental designs of these trials were based on different rationales, including immunomodulation, readthrough strategies, exon skipping, gene therapy, and cell therapy. We also provide an overview of available outcome measures, focusing on their reliability in estimating meaningful clinical improvement in order to aid in the design of future trials. This perspective is extremely relevant to the field considering the recent development of novel therapeutic approaches that will result in an increasing number of clinical studies over the next few years.

Muscular dystrophy: new challenges and review of the current clinical trials

PURPOSE OF REVIEW

We provide a review of recent standards of care and therapeutic development in different forms of muscular dystrophies. This topic is relevant as the improved understanding of these disorders has not only led to a better definition of clinical course and to the development of standards of care for individual types of muscular dystrophies, but also culminated in different therapeutic approaches.

RECENT FINDINGS

Recent natural history studies have demonstrated the impact of new standards of care in different forms of muscular dystrophies, and identified areas of clinical management in which further developments are needed. The majority of the experimental studies are focused on Duchenne muscular dystrophy. Some of them target patients with specific mutations, such as antisense oligonucleotides, to induce exon skipping of specific mutations or drugs developed to allow read-through of nonsense mutations, whereas other therapies deal with secondary aspects of muscle degeneration, aiming, for example, at reducing inflammation or apoptosis, and may also be suitable for other forms of muscular dystrophies.

SUMMARY

The advances in the field of muscular dystrophy have resulted in improved clinical course and survival. The encouraging results of early experimental studies could further improve these outcomes in the future.

Detecting meaningful change using the North Star Ambulatory Assessment in Duchenne muscular dystrophy

AIM

Clinician-reported outcome instruments such as the North Star Ambulatory Assessment (NSAA) need to be able to detect clinically important change to be suitable for clinical trials. However, in Duchenne muscular dystrophy (DMD), identifying changes in function is not straightforward. In this study, we use Rasch-transformed data to examine the responsiveness and minimal important difference (MID) of the NSAA in males with DMD receiving different corticosteroid regimes.

METHOD

NSAA data were examined from 198 males (mean age at assessment was 8 y 6 mo [SD 2 y 6 mo] range 4 y-18 y; 805 assessments). Responsiveness was assessed using mean score changes (using Rasch-transformed data) between adjacent pairs of age groups, pairwise squared t-values from paired samples t-tests, and an effect size calculation. The MID was assessed using the effect size calculation and 0.5 standard deviation (SD) of mean score differences.

RESULTS

Our findings revealed a difference in change scores over time between the two corticosteroid regimes. Mean NSAA person estimates were higher in the daily prednisolone group. The mean MID (0.5 SD) was 8.8 and 6.9 for the daily group and intermittent group respectively.

INTERPRETATION

This study, based on Rasch-transformed NSAA data, provides an initial basis for the interpretation of clinical change in DMD over time and between corticosteroid regimes. Our proposed MIDs can be mapped back to differences in specific item content across the range of the NSAA.

Development of the Performance of the Upper Limb module for Duchenne muscular dystrophy

AIM

An international Clinical Outcomes Group consisting of clinicians, scientists, patient advocacy groups, and industries identified a need for a scale to measure motor performance of the upper limb. We report the steps leading to the development of the Performance of the Upper Limb (PUL), a tool specifically designed for assessing upper limb function in ambulant and non-ambulant patients with Duchenne muscular dystrophy (DMD).

METHOD

The development of the PUL followed a number of steps, from the systematic review and a preliminary study exploring the suitability of the existing measures, to the application of a pilot version in a multicentric setting, with Rasch analysis of the preliminary results, leading to a revised pro forma.

RESULTS

The PUL was specifically designed for DMD, with a conceptual framework reflecting the progression of weakness and natural history of functional decline in DMD. Modern psychometric methods were used to create a scale with robust internal reliability, validity, and hierarchical scalability; males with DMD and their families were involved iteratively throughout the process of the clinician-reported outcome assessment tool development to establish clinical meaningfulness and relevance of individual PUL items to activities of daily living.

INTERPRETATION

The module was developed using innovative approaches and will be useful for designing clinical trials.

Eteplirsen for the treatment of Duchenne muscular dystrophy

OBJECTIVE

In prior open-label studies, eteplirsen, a phosphorodiamidate morpholino oligomer, enabled dystrophin production in Duchenne muscular dystrophy (DMD) with genetic mutations amenable to skipping exon 51. The present study used a double-blind placebo-controlled protocol to test eteplirsen's ability to induce dystrophin production and improve distance walked on the 6-minute walk test (6MWT).

METHODS

DMD boys aged 7 to 13 years, with confirmed deletions correctable by skipping exon 51 and ability to walk 200 to 400 m on 6 MWT, were randomized to weekly intravenous infusions of 30 or 50 mg/kg/wk eteplirsen or placebo for 24 weeks (n = 4/group). Placebo patients switched to 30 or 50 mg/kg eteplirsen (n=2/group) at week 25; treatment was open label thereafter. All patients had muscle biopsies at baseline and week 48. Efficacy included dystrophin-positive fibers and distance walked on the 6MWT.

RESULTS

At week 24, the 30 mg/kg eteplirsen patients were biopsied, and percentage of dystrophin-positive fibers was increased to 23% of normal; no increases were detected in placebo-treated patients (p≤0.002). Even greater increases occurred at week 48 (52% and 43% in the 30 and 50 mg/kg cohorts, respectively), suggesting that dystrophin increases with longer treatment. Restoration of functional dystrophin was confirmed by detection of sarcoglycans and neuronal nitric oxide synthase at the sarcolemma. Ambulation-evaluable eteplirsen-treated patients experienced a 67.3 m benefit compared to placebo/delayed patients (p≤0.001).

INTERPRETATION

Eteplirsen restored dystrophin in the 30 and 50 mg/kg/wk cohorts, and in subsequently treated, placebo-controlled subjects. Duration, more than dose, accounted for dystrophin production, also resulting in ambulation stability. No severe adverse events were encountered.

New treatments for mitochondrial disease-no time to drop our standards

Mitochondrial dysfunction is a common cause of inherited multisystem disease that often involves the nervous system. Despite major advances in our understanding of the pathophysiology of mitochondrial diseases, clinical management of these conditions remains largely supportive. Using a systematic approach, we identified 1,039 publications on treatments for mitochondrial diseases, only 35 of which included observations on more than five patients. Reports of a positive outcome on the basis of a biomarker of unproven clinical significance were more common in nonrandomized and nonblinded studies, suggesting a publication bias toward positive but poorly executed studies. Although trial design is improving, there is a critical need to develop new biomarkers of mitochondrial disease. In this Perspectives article, we make recommendations for the design of future treatment trials in mitochondrial diseases. Patients and physicians should no longer rely on potentially biased data, with the associated costs and risks.

Six minute walk test in type III spinal muscular atrophy: a 12month longitudinal study

The aim of our longitudinal multicentric study was to establish the changes on the 6min walk test (6MWT) in ambulant SMA type III children and adults over a 12month period. Thirty-eight ambulant type III patients performed the 6MWT at baseline and 12months after baseline. The distance covered in 6min ranged between 75 and 510m (mean 294.91, SD 127) at baseline and between 50 and 611m (mean 293.41m, SD 141) at 12months. The mean change in distance between baseline and 12months was -1.46 (SD 50.1; range: -183 to 131.8m). The changes were not correlated with age or baseline values (p>.05) even though younger patients reaching puberty, had a relatively higher risk of showing deterioration of more than 30m compared to older patients. Our findings provide the first longitudinal data using the 6MWT in ambulant SMA patients.

The 6-minute walk test and other clinical endpoints in duchenne muscular dystrophy: reliability, concurrent validity, and minimal clinically important differences from a multicenter study

INTRODUCTION

An international clinical trial enrolled 174 ambulatory males ≥5 years old with nonsense mutation Duchenne muscular dystrophy (nmDMD). Pretreatment data provide insight into reliability, concurrent validity, and minimal clinically important differences (MCIDs) of the 6-minute walk test (6MWT) and other endpoints.

METHODS

Screening and baseline evaluations included the 6-minute walk distance (6MWD), timed function tests (TFTs), quantitative strength by myometry, the PedsQL, heart rate-determined energy expenditure index, and other exploratory endpoints.

RESULTS

The 6MWT proved feasible and reliable in a multicenter context. Concurrent validity with other endpoints was excellent. The MCID for 6MWD was 28.5 and 31.7 meters based on 2 statistical distribution methods.

CONCLUSIONS

The ratio of MCID to baseline mean is lower for 6MWD than for other endpoints. The 6MWD is an optimal primary endpoint for Duchenne muscular dystrophy (DMD) clinical trials that are focused therapeutically on preservation of ambulation and slowing of disease progression.

The cooperative international neuromuscular research group Duchenne natural history study--a longitudinal investigation in the era of glucocorticoid therapy: design of protocol and the methods used

Contemporary natural history data in Duchenne muscular dystrophy (DMD) is needed to assess care recommendations and aid in planning future trials.

METHODS

The Cooperative International Neuromuscular Research Group (CINRG) DMD Natural History Study (DMD-NHS) enrolled 340 individuals, aged 2-28 years, with DMD in a longitudinal, observational study at 20 centers. Assessments obtained every 3 months for 1 year, at 18 months, and annually thereafter included: clinical history; anthropometrics; goniometry; manual muscle testing; quantitative muscle strength; timed function tests; pulmonary function; and patient-reported outcomes/health-related quality-of-life instruments.

RESULTS

Glucocorticoid (GC) use at baseline was 62% present, 14% past, and 24% GC-naive. In those ≥6 years of age, 16% lost ambulation over the first 12 months (mean age 10.8 years).

CONCLUSIONS

Detailed information on the study methodology of the CINRG DMD-NHS lays the groundwork for future analyses of prospective longitudinal natural history data. These data will assist investigators in designing clinical trials of novel therapeutics.

The 6-minute walk test and other endpoints in Duchenne muscular dystrophy: longitudinal natural history observations over 48 weeks from a multicenter study

Introduction: Duchenne muscular dystrophy (DMD) subjects ≥5 years with nonsense mutations were followed for 48 weeks in a multicenter, randomized, double-blind, placebo-controlled trial of ataluren. Placebo arm data (N = 57) provided insight into the natural history of the 6-minute walk test (6MWT) and other endpoints. Methods: Evaluations performed every 6 weeks included the 6-minute walk distance (6MWD), timed function tests (TFTs), and quantitative strength using hand-held myometry. Results: Baseline age (≥7 years), 6MWD, and selected TFT performance are strong predictors of decline in ambulation (Δ6MWD) and time to 10% worsening in 6MWD. A baseline 6MWD of <350 meters was associated with greater functional decline, and loss of ambulation was only seen in those with baseline 6MWD <325 meters. Only 1 of 42 (2.3%) subjects able to stand from supine lost ambulation. Conclusion: Findings confirm the clinical meaningfulness of the 6MWD as the most accepted primary clinical endpoint in ambulatory DMD trials.

Motor and cognitive assessment of infants and young boys with Duchenne Muscular Dystrophy: results from the Muscular Dystrophy Association DMD Clinical Research Network

Therapeutic trials in Duchenne Muscular Dystrophy (DMD) exclude young boys because traditional outcome measures rely on cooperation. The Bayley III Scales of Infant and Toddler Development (Bayley III) have been validated in developing children and those with developmental disorders but have not been studied in DMD. Expanded Hammersmith Functional Motor Scale (HFMSE) and North Star Ambulatory Assessment (NSAA) may also be useful in this young DMD population. Clinical evaluators from the MDA-DMD Clinical Research Network were trained in these assessment tools. Infants and boys with DMD (n = 24; 1.9 ± 0.7 years) were assessed. The mean Bayley III motor composite score was low (82.8 ± 8; p ≤ .0001) (normal = 100 ± 15). Mean gross motor and fine motor function scaled scores were low (both p ≤ .0001). The mean cognitive comprehensive (p=.0002), receptive language (p ≤ .0001), and expressive language (p = .0001) were also low compared to normal children. Age was negatively associated with Bayley III gross motor (r = -0.44; p = .02) but not with fine motor, cognitive, or language scores. HFMSE (n=23) showed a mean score of 31 ± 13. NSAA (n = 18 boys; 2.2 ± 0.4 years) showed a mean score of 12 ± 5. Outcome assessments of young boys with DMD are feasible and in this multicenter study were best demonstrated using the Bayley III.

The six-minute walk test in chronic pediatric conditions: a systematic review of measurement properties

BACKGROUND

The Six-Minute Walk Test (6MWT) is increasingly being used as a functional outcome measure for chronic pediatric conditions. Knowledge about its measurement properties is needed to determine whether it is an appropriate test to use.

PURPOSE

The purpose of this study was to systematically review all published clinimetric studies on the 6MWT in chronic pediatric conditions.

DATA SOURCES

The databases MEDLINE, EMBASE, CINAHL, PEDro, and SPORTDiscus were searched up to February 2012.

STUDY SELECTION

Studies designed to evaluate measurement properties of the 6MWT in a chronic pediatric condition were included in the systematic review.

DATA EXTRACTION

The methodological quality of the included studies and the measurement properties of the 6MWT were examined.

DATA SYNTHESIS

A best evidence synthesis was performed on 15 studies, including 9 different chronic pediatric conditions. Limited evidence to strong evidence was found for reliability in various chronic conditions. Strong evidence was found for positive criterion validity of the 6MWT with peak oxygen uptake in some populations, but negative criterion validity was found in other populations. Construct validity remained unclear in most patient groups because of methodological flaws. Little evidence was available for responsiveness and measurement error. Studies showed large variability in test procedures despite existing guidelines for the performance of the 6MWT.

LIMITATIONS

Unavailability of a specific checklist to evaluate the methodological quality of clinimetric studies on performance measures was a limitation of the study.

CONCLUSIONS

Evidence for measurement properties of the 6MWT varies largely among chronic pediatric conditions. Further research is needed in all patient groups to explore the ability of the 6MWT to measure significant and clinically important changes. Until then, changes measured with the 6MWT should be interpreted with caution. Future studies or consensus regarding modified test procedures in the pediatric population is recommended.

Muscular dystrophies

Muscular dystrophies are a heterogeneous group of inherited disorders that share similar clinical features and dystrophic changes on muscle biopsy. An improved understanding of their molecular bases has led to more accurate definitions of the clinical features associated with known subtypes. Knowledge of disease-specific complications, implementation of anticipatory care, and medical advances have changed the standard of care, with an overall improvement in the clinical course, survival, and quality of life of affected people. A better understanding of the mechanisms underlying the molecular pathogenesis of several disorders and the availability of preclinical models are leading to several new experimental approaches, some of which are already in clinical trials. In this Seminar, we provide a comprehensive review that integrates clinical manifestations, molecular pathogenesis, diagnostic strategy, and therapeutic developments.

T₂ mapping provides multiple approaches for the characterization of muscle involvement in neuromuscular diseases: a cross-sectional study of lower leg muscles in 5-15-year-old boys with Duchenne muscular dystrophy

Skeletal muscles of children with Duchenne muscular dystrophy (DMD) show enhanced susceptibility to damage and progressive lipid infiltration, which contribute to an increase in the MR proton transverse relaxation time (T₂). Therefore, the examination of T₂ changes in individual muscles may be useful for the monitoring of disease progression in DMD. In this study, we used the mean T₂, percentage of elevated pixels and T₂ heterogeneity to assess changes in the composition of dystrophic muscles. In addition, we used fat saturation to distinguish T₂ changes caused by edema and inflammation from fat infiltration in muscles. Thirty subjects with DMD and 15 age-matched controls underwent T₂ -weighted imaging of their lower leg using a 3-T MR system. T₂ maps were developed and four lower leg muscles were manually traced (soleus, medial gastrocnemius, peroneal and tibialis anterior). The mean T₂ of the traced regions of interest, width of the T₂ histograms and percentage of elevated pixels were calculated. We found that, even in young children with DMD, lower leg muscles showed elevated mean T₂, were more heterogeneous and had a greater percentage of elevated pixels than in controls. T₂ measures decreased with fat saturation, but were still higher (P < 0.05) in dystrophic muscles than in controls. Further, T₂ measures showed positive correlations with timed functional tests (r = 0.23-0.79). The elevated T₂ measures with and without fat saturation at all ages of DMD examined (5-15 years) compared with unaffected controls indicate that the dystrophic muscles have increased regions of damage, edema and fat infiltration. This study shows that T₂ mapping provides multiple approaches that can be used effectively to characterize muscle tissue in children with DMD, even in the early stages of the disease. Therefore, T₂ mapping may prove to be clinically useful in the monitoring of muscle changes caused by the disease process or by therapeutic interventions in DMD.

Epigallocatechin-3-gallate: a useful, effective and safe clinical approach for targeted prevention and individualised treatment of neurological diseases?

Neurodegenerative disorders show an increasing prevalence in a number of highly developed countries. Often, these diseases require life-long treatment mostly with drugs which are costly and mostly accompanied by more or less serious side-effects. Their heterogeneous manifestation, severity and outcome pose the need for individualised treatment options. There is an intensive search for new strategies not only for treating but also for preventing these diseases. Green tea and green tea extracts seem to be such a promising and safe alternative. However, data regarding the beneficial effects and possible underlying mechanism, specifically in clinical trials, are rare and rather controversial or non-conclusive. This review outlines the existing evidence from preclinical studies (cell and tissue cultures and animal models) and clinical trials regarding preventive and therapeutic effects of epigallcatechin-3-gallate in neurodegenerative diseases and considers antioxidative vs. pro-oxidative properties of the tea catechin important for dosage recommendations.

Gene therapy for Duchenne muscular dystrophy

PURPOSE OF REVIEW

Duchenne muscular dystrophy is a severe neuromuscular disorder for which there is currently no cure. Years of research have come to fruition during the past 18 months with publications on clinical trials for several gene therapy approaches for Duchenne muscular dystrophy. This review covers the present status of these approaches.

RECENT FINDINGS

The exon skipping approach is most advanced in the process of clinical application. Encouraging results have been obtained in two systemic clinical trials and further optimization has increased delivery to the heart in animal models. Limitations of the approach are the mutation-specificity and the anticipated requirement for lifelong treatment. Gene therapy by means of gene transfer holds the promise of more long-lasting effects. Results of a first, early-stage gene therapy trial, using viral vectors to deliver a minidystrophin gene, were reported. Animal studies suggest that it may be possible to overcome the main challenges currently facing gene therapy (immunogenicity of the vector and systemic body-wide delivery).

SUMMARY

Significant steps have been made in the development of gene therapy approaches for Duchenne muscular dystrophy. These approaches aim to slow down disease progression, requiring robust outcome measures to assess efficacy.

24 month longitudinal data in ambulant boys with Duchenne muscular dystrophy

Objectives

The aim of the study was i) to assess the spectrum of changes over 24 months in ambulant boys affected by Duchenne muscular dystrophy, ii) to establish the difference between the first and the second year results and iii) to identify possible early markers of loss of ambulation.

Methods

One hundred and thirteen patients (age range 4.1–17, mean 8.2) fulfilled the inclusion criteria, 67 of the 113 were on daily and 40 on intermittent steroids, while 6 were not on steroids. All were assessed using the 6 Minute Walk Test (6MWT), the North Star Ambulatory Assessment (NSAA) and timed test.

Results

On the 6MWT there was an average overall decline of −22.7 (SD 81.0) in the first year and of −64.7 (SD 123.1) in the second year. On the NSAA the average overall decline was of −1.86 (SD 4.21) in the first year and of −2.98 (SD 5.19) in the second year. Fourteen children lost ambulation, one in the first year and the other 13 in the second year of the study. A distance of at least 330 meters on the 6MWT, or a NSAA score of 18 at baseline reduced significantly the risk of losing ambulation within 2 years.

Conclusions

These results can be of help at the time of using inclusion criteria for a study in ambulant patients in order to minimize the risk of patients who may lose ambulation within the time of the trial.

Test-retest reliability and developmental evolution of the 6-min walk test in Caucasian boys aged 5-12 years

The 6-min walk test (6MWT) assesses functional capacity and has been used as outcome measure in therapeutic studies in childhood neuromuscular disorders. The objectives were to evaluate test-retest reliability of the 6MWT and to generate normative data for healthy boys aged 5-12 years. Ninety boys (mean age 8 years 10 months) were recruited over four age subcategories (5-6, 7-8, 9-10, 11-12 years). Mean 6MWT distance and velocity (±standard deviation) for the total group were 555.5±93 m and 92.6±16.6 m/min. The 6MWT distance increased significantly with age. Test-retest reliability (mean interval 12 days) was very high for the total group (ICC>0.95) and for all age subcategories (ICC>0.80) a moderately high reliability (ICC>0.75) was found from 3 min onwards for each age subcategory. There was a mean difference of 5.2 m between test and retest without systematic bias. The standard error of measurement and smallest detectable difference were 20.7 and 57.4 m, respectively. These findings demonstrate the reliability of the 6MWT in young children, underscore its evolution with age, and indicate that a shorter version of the test is also reliable.

A critical review of functional assessment tools for upper limbs in Duchenne muscular dystrophy

The recent development of therapeutic approaches for Duchenne muscular dystrophy (DMD) has highlighted the need to identify clinical outcome measures for planned efficacy studies. Although several studies have reported the value of functional scales, timed tests, and measures of endurance aimed at ambulant individuals, less has been done to identify reliable measures of function in individuals who have lost ambulation. The aim of this paper is to provide a critical review of the existing literature on functional measures assessing upper extremity function in DMD. Four observer-rated, performance-based measures and four self-reported scales have been previously used in DMD. Each scale provides useful information but none reflects all the different levels of functional ability in activities of daily living observed in individuals with DMD at different ages.

Lung function monitoring in patients with duchenne muscular dystrophy on steroid therapy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a sex-linked inherited muscle disease characterized by a progressive loss in muscle strength and respiratory muscle involvement. After 12 years of age, lung function declines at a rate of 6 % to 10.7 % per year in patients with DMD. Steroid therapy has been proposed to delay the loss of motor function and also the respiratory involvement.

METHOD

In 21 patients with DMD aged between seven and 16 years, the forced vital capacity (FVC) and the forced expiratory volume in one second (FEV1) were evaluated at three different times during a period of two years.

RESULTS

We observed in this period of evaluation the maintenance of the FVC and the FEV1 in this group of patients independently of chronological age, age at onset of steroid therapy, and walking capacity.

CONCLUSION

The steroid therapy has the potential to stabilize or delay the loss of lung function in DMD patients even if they are non-ambulant or older than 10 years, and in those in whom the medication was started after 7 years of age.

The role of the neuromuscular medicine and physiatry specialists in the multidisciplinary management of neuromuscular disease

The neuromuscular medicine and physiatry specialists are key health care providers who work cooperatively with a multidisciplinary team to provide coordinated care for individuals with neuromuscular diseases (NMDs). The director or coordinator of the team must be aware of the potential issues specific to NMDs and be able to access the interventions that are the foundations for proper care in NMD. Ultimate goals include maximizing health and functional capacities, performing medical monitoring and surveillance to inhibit and prevent complications, and promoting access and full integration into the community to optimize quality of life.

Importance of SPP1 genotype as a covariate in clinical trials in Duchenne muscular dystrophy

OBJECTIVE

To test the effect of the single nucleotide polymorphism -66 T>G (rs28357094) in the osteopontin gene (SPP1) on functional measures over 12 months in Duchenne muscular dystrophy (DMD).

METHODS

This study was conducted on a cohort of ambulatory patients with DMD from a network of Italian neuromuscular centers, evaluated longitudinally with the north star ambulatory assessment (NSAA) and the 6-minute walk test (6MWT) at study entry and after 12 months. Genotype at rs28357094 was determined after completion of the clinical evaluations. Patients were stratified in 2 groups according to a dominant model (TT homozygotes vs TG heterozygotes and GG homozygotes) and clinical data were retrospectively compared between groups.

RESULTS

Eighty patients were selected (age 4.1-19.3 years; mean 8.3 ± 2.7 SD). There were no differences in age or steroid treatment between the 2 subgroups. Paired t test showed a significant difference in both NSAA (p = 0.013) and 6MWT (p = 0.03) between baseline and follow-up after 12 months in patients with DMD carrying the G allele. The difference was not significant in the T subgroup. The analysis of covariance using age and baseline values as covariate and SPP1 genotype as fixed effect showed that these parameters are significantly correlated with the 12-month values.

CONCLUSIONS

These data provide evidence of the role of SPP1 genotype as a disease modifier in DMD and support its relevance in the selection of homogeneous groups of patients for future clinical trials.

Percent-predicted 6-minute walk distance in duchenne muscular dystrophy to account for maturational influences

We recently described a modified version of the 6-minute walk test (6MWT) for Duchenne muscular dystrophy (DMD) based partly on the American Thoracic Society (ATS) guidelines. This measure has shown reliability, validity and utility as a primary outcome measure in DMD clinical trials. Because loss of muscle function in DMD occurs against the background of normal childhood growth and development, younger children with DMD can show increase in distance walked during 6MWT over ~1 year despite progressive muscular impairment. In this study, we compare 6-minute walk distance (6MWD) data from DMD boys (n=17) and typically developing control subjects (n=22) to existing normative data from age- and sex-matched children and adolescents. An age- and height-based equation fitted to normative data by Geiger and colleagues was used to convert 6MWD to a percent-predicted (%-predicted) value in boys with DMD. Analysis of %-predicted 6MWD data represents a method to account for normal growth and development, and shows that gains in function at early ages represents stable rather than improving abilities in boys with DMD. Boys with DMD from 4-7 years of age maintain a stable 6MWD approximately 80% of that of typically developing peers, with the deficit progressing at a variable rate thereafter.