Prognostic factors for changes in the timed 4-stair climb in patients with Duchenne muscular dystrophy, and implications for measuring drug efficacy: A multi-institutional collaboration

Appendicular lean mass index and motor function in ambulatory patients with Duchenne muscular dystrophy

INTRODUCTION/AIMS

Appendicular lean mass index (ALMI) has been linked to motor function in patients with Duchenne muscular dystrophy (DMD). However, quantification of the relationship between ALMI and disease-specific clinical outcome assessment trajectories is needed. The purpose of this study was to determine associations between dual-energy x-ray absorptiometry (DXA) derived estimates of ALMI and motor function in ambulatory patients with DMD.

METHODS

A retrospective analysis of longitudinal clinical visit data from 137 glucocorticoid-treated patients with DMD collected via structured motor assessment protocol evaluated associations between ALMI and motor function indexed by the North Star Ambulatory Assessment (NSAA) and 10 Meter Walk/run Test (10MWT). Body composition was assessed using DXA. ALMI was calculated by dividing arm and leg lean mass by height in m2; fat mass index (FMI) was calculated by dividing whole body fat mass by height in m2. Linear mixed-effects models were used to estimate associations between ALMI and motor function, controlling for age and FMI.

RESULTS

The full prediction model (age, age,2 ALMI, and FMI) explained 57% of the variance in NSAA scores and 63% of the variance in 10MWT speed. A 1 kg/m2 higher ALMI value predicted a 5.4-point higher NSAA score (p < .001) and 0.45 m/s faster 10MWT speed (p < .001). A 1 kg/m2 higher FMI value predicted a 1.5-point lower NSAA score (p < .001) and 0.14 meters/second slower 10MWT speed (p < .001).

DISCUSSION

DXA-derived estimates of ALMI and FMI are associated with motor function in DMD and may explain variation in DMD disease progression.

Meaningful changes in motor function in Duchenne muscular dystrophy (DMD): A multi-center study

Evaluations of treatment efficacy in Duchenne muscular dystrophy (DMD), a rare genetic disease that results in progressive muscle wasting, require an understanding of the 'meaningfulness' of changes in functional measures. We estimated the minimal detectable change (MDC) for selected motor function measures in ambulatory DMD, i.e., the minimal degree of measured change needed to be confident that true underlying change has occurred rather than transient variation or measurement error. MDC estimates were compared across multiple data sources, representing >1000 DMD patients in clinical trials and real-world clinical practice settings. Included patients were ambulatory, aged ≥4 to <18 years and receiving steroids. Minimal clinically important differences (MCIDs) for worsening were also estimated. Estimated MDC thresholds for >80% confidence in true change were 2.8 units for the North Star Ambulatory Assessment (NSAA) total score, 1.3 seconds for the 4-stair climb (4SC) completion time, 0.36 stairs/second for 4SC velocity and 36.3 meters for the 6-minute walk distance (6MWD). MDC estimates were similar across clinical trial and real-world data sources, and tended to be slightly larger than MCIDs for these measures. The identified thresholds can be used to inform endpoint definitions, or as benchmarks for monitoring individual changes in motor function in ambulatory DMD.

Exploring caregivers' attitudes and beliefs about nutrition and weight management for young people with Duchenne muscular dystrophy

INTRODUCTION/AIMS

Obesity disproportionately affects children and adolescents with Duchenne muscular dystrophy (DMD) and with adverse consequences for disease progression. This study aims to: explore barriers, enablers, attitudes, and beliefs about nutrition and weight management; and to obtain caregiver preferences for the design of a weight management program for DMD.

METHODS

We surveyed caregivers of young people with DMD from four Australian pediatric neuromuscular clinics. Survey questions were informed by the Theoretical Domains Framework and purposefully designed to explore barriers and enablers to food and weight management. Caregivers were asked to identify their preferred features in a weight management program for families living with DMD.

RESULTS

Fifty-three caregivers completed the survey. Almost half (48%) perceived their son as above healthy weight. Consequences for those children were perceived to be self-consciousness (71%), a negative impact on self-esteem (64%) and movement (57%). Preventing weight gain was a common reason for providing healthy food and healthy eating was a high priority for families. Barriers to that intention included: time constraints, selective food preferences, and insufficient nutrition information. Caregivers preferred an intensive six-week weight management program addressing appetite management and screen time.

DISCUSSION

Managing weight is an important issue for caregivers of sons with DMD; yet several barriers exist. Individualized 6 week programs are preferred by caregivers to improve weight management for DMD.

Draft Guidance for Industry Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, and Related Dystrophinopathies - Developing Potential Treatments for the Entire Spectrum of Disease

Background

Duchenne muscular dystrophy (DMD) and related dystrophinopathies are neuromuscular conditions with great unmet medical needs that require the development of effective medical treatments.

Objective

To aid sponsors in clinical development of drugs and therapeutic biological products for treating DMD across the disease spectrum by integrating advancements, patient registries, natural history studies, and more into a comprehensive guidance.

Methods

This guidance emerged from collaboration between the FDA, the Duchenne community, and industry stakeholders. It entailed a structured approach, involving multiple committees and boards. From its inception in 2014, the guidance underwent revisions incorporating insights from gene therapy studies, cardiac function research, and innovative clinical trial designs.

Results

The guidance provides a deeper understanding of DMD and its variants, focusing on patient engagement, diagnostic criteria, natural history, biomarkers, and clinical trials. It underscores patient-focused drug development, the significance of dystrophin as a biomarker, and the pivotal role of magnetic resonance imaging in assessing disease progression. Additionally, the guidance addresses cardiomyopathy's prominence in DMD and the burgeoning field of gene therapy.

Conclusions

The updated guidance offers a comprehensive understanding of DMD, emphasizing patient-centric approaches, innovative trial designs, and the importance of biomarkers. The focus on cardiomyopathy and gene therapy signifies the evolving realm of DMD research. It acts as a crucial roadmap for sponsors, potentially leading to improved treatments for DMD.

Stride Velocity 95th Centile Detects Decline in Ambulatory Function Over Shorter Intervals than the 6-Minute Walk Test or North Star Ambulatory Assessment in Duchenne Muscular Dystrophy

Background

Stride Velocity 95th Centile (SV95C) is the first wearable device-derived clinical outcome assessment (COA) to receive European Medicines Agency (EMA) qualification as a primary endpoint in ambulant patients with Duchenne muscular dystrophy (DMD) aged ≥4 years.

Objective

To compare SV95C-in its first-ever clinical trial application as a secondary endpoint-with established motor function COAs used in the trial (Four-Stair Climb [4SC] velocity, North Star Ambulatory Assessment [NSAA], and Six-Minute Walk Distance [6MWD]).

Methods

SV95C was a secondary endpoint in a subset (n = 47) of participants in the SPITFIRE/WN40227 trial of taldefgrobep alfa, which was discontinued due to lack of clinical benefit. Participants in the ≤48-week SV95C sub-study were 6-11 years old and received corticosteroids for ≥6 months pre-treatment. Pearson correlations were used to compare SV95C with the other COAs. Responsiveness and changes over time were respectively assessed via standardized response means (SRMs) based on absolute changes and mixed models for repeated measures.

Results

SV95C change at Week 24 was -0.07 m/s, with limited variability (standard deviation: 0.16, n = 27). The SRM for SV95C indicated moderate responsiveness to clinical change at the earliest timepoint (Week 12, n = 46), while those of the other COAs did not indicate moderate responsiveness until Week 36 (6MWD, n = 33) or Week 48 (4SC velocity, n = 20; NSAA total score, n = 20). Baseline correlations between SV95C and other COAs were strong (r = 0.611-0.695). Correlations between SV95C change from baseline to Week 48 and changes in other COAs were moderate to strong (r = 0.443-0.678).∥.

Conclusions

Overall, SV95C demonstrated sensitivity to ambulatory decline over short intervals, low variability, and correlation with established COAs. Although the negative trial precluded demonstration of SV95C's sensitivity to drug effect, these findings support the continued use of SV95C in DMD clinical trials.

Astaxanthin Ameliorates Worsened Muscle Dysfunction of MDX Mice Fed with a High-Fat Diet through Reducing Lipotoxicity and Regulating Gut Microbiota

Duchenne muscular dystrophy (DMD), a severe X-linked inherited neuromuscular disease, has a high prevalence of obesity. Obesity exacerbates muscle damage and results in adverse clinical outcomes. Preventing obesity helps DMD patients delay disease progression and improve quality of life. Astaxanthin (AX) is a kind of carotenoid which has antioxidant and anti-adipogenesis effects. In this study, male C57BL/10ScSnDmdmdx/J mice were fed with a normal diet, a high-fat diet (HFD), and an HFD containing AX for 16 weeks, respectively. The results showed that AX significantly increased gastrocnemius fiber cross-section area and grip strength, improved treadmill endurance test and mitochondrial morphology, and reduced muscle triglyceride and malonaldehyde levels compared to the HFD. Lipidomic analysis revealed that AX decreased high levels of triglyceride, diglyceride, ceramides, and wax ester induced by HFD. Gut microbiota analysis indicated that AX supplementation failed to alleviate abnormal microbiota diversity, but increased the relative abundances of Akkermansia, Bifidobacterium, Butyricicoccus, and Staphylococcus. In conclusion, AX was expected to alleviate disease progression associated with obesity in DMD patients by reducing lipotoxicity and increasing the abundance of beneficial bacteria.

Delandistrogene Moxeparvovec Gene Therapy in Ambulatory Patients (Aged ≥4 to <8 Years) with Duchenne Muscular Dystrophy: 1-Year Interim Results from Study SRP-9001-103 (ENDEAVOR)

OBJECTIVE

Delandistrogene moxeparvovec is approved in the USA for the treatment of ambulatory patients (4-5 years) with Duchenne muscular dystrophy. ENDEAVOR (SRP-9001-103; NCT04626674) is a single-arm, open-label study to evaluate delandistrogene moxeparvovec micro-dystrophin expression, safety, and functional outcomes following administration of commercial process delandistrogene moxeparvovec.

METHODS

In cohort 1 of ENDEAVOR (N = 20), eligible ambulatory males, aged ≥4 to <8 years, received a single intravenous infusion of delandistrogene moxeparvovec (1.33 × 1014  vg/kg). The primary endpoint was change from baseline (CFBL) to week 12 in delandistrogene moxeparvovec micro-dystrophin by western blot. Additional endpoints evaluated included: safety; vector genome copies; CFBL to week 12 in muscle fiber-localized micro-dystrophin by immunofluorescence; and functional assessments, including North Star Ambulatory Assessment, with comparison with a propensity score-weighted external natural history control.

RESULTS

The 1-year safety profile of commercial process delandistrogene moxeparvovec in ENDEAVOR was consistent with safety data reported in other delandistrogene moxeparvovec trials (NCT03375164 and NCT03769116). Delandistrogene moxeparvovec micro-dystrophin expression was robust, with sarcolemmal localization at week 12; mean (SD) CFBL in western blot, 54.2% (42.6); p < 0.0001. At 1 year, patients demonstrated stabilized or improved North Star Ambulatory Assessment total scores; mean (SD) CFBL, +4.0 (3.5). Treatment versus a propensity score-weighted external natural history control demonstrated a statistically significant difference in least squares mean (standard error) CFBL in North Star Ambulatory Assessment, +3.2 (0.6) points; p < 0.0001.

INTERPRETATION

Results confirm efficient transduction of muscle by delandistrogene moxeparvovec. One-year post-treatment, delandistrogene moxeparvovec was well tolerated, and demonstrated stabilized or improved motor function, suggesting a clinical benefit for patients with Duchenne muscular dystrophy. ANN NEUROL 2023;94:955-968.

269th ENMC international workshop: 10 years of clinical trials in Duchenne muscular dystrophy - What have we learned? 9-11 December 2022, Hoofddorp, The Netherlands

There are multiple avenues for therapeutic development in Duchenne muscular dystrophy (DMD), which are highlighted in the first section of this report for the "10 years of Clinical trials in DMD - What have we learned?" workshop. This report then provides an overview of the presentations made at the workshop grouped into the following core themes: trial outcomes, disease heterogeneity, meaningfulness of outcomes and the utility of real-world data in trials. Finally, we present the consensus that was achieved at the workshop on the learning points from 10 years of clinical trials in DMD, and possible action points from these. This includes further work in expanding the scope and range of trial outcomes and assessing the efficacy of new trial structures for DMD. We also highlight several points which should be addressed during future interactions with regulators, such as clinical meaningfulness and the use of real-world data.

Expression of SRP-9001 dystrophin and stabilization of motor function up to 2 years post-treatment with delandistrogene moxeparvovec gene therapy in individuals with Duchenne muscular dystrophy

Introduction: Delandistrogene moxeparvovec (SRP-9001) is an investigational gene transfer therapy designed for targeted expression of SRP-9001 dystrophin protein, a shortened dystrophin retaining key functional domains of the wild-type protein. Methods: This Phase 2, double-blind, two-part (48 weeks per part) crossover study (SRP-9001-102 [Study 102]; NCT03769116) evaluated delandistrogene moxeparvovec in patients, aged ≥4 to <8 years with Duchenne muscular dystrophy. Primary endpoints (Part 1) were change from baseline (CFBL) in SRP-9001 dystrophin expression (Week 12), by Western blot, and in North Star Ambulatory Assessment (NSAA) score (Week 48). Safety assessments included treatment-related adverse events (TRAEs). Patients were randomized and stratified by age to placebo (n = 21) or delandistrogene moxeparvovec (n = 20) and crossed over for Part 2. Results: SRP-9001 dystrophin expression was achieved in all patients: mean CFBL to Week 12 was 23.82% and 39.64% normal in Parts 1 and 2, respectively. In Part 1, CFBL to Week 48 in NSAA score (least-squares mean, LSM [standard error]) was +1.7 (0.6) with treatment versus +0.9 (0.6) for placebo; p = 0.37. Disparity in baseline motor function between groups likely confounded these results. In 4- to 5-year-olds with matched baseline motor function, CFBL to Week 48 in NSAA scores was significantly different (+2.5 points; p = 0.0172), but not significantly different in 6-to-7-year-olds with imbalanced baseline motor function (-0.7 points; p = 0.5384). For patients treated with delandistrogene moxeparvovec in Part 2, CFBL to Week 48 in NSAA score was +1.3 (2.7), whereas for those treated in Part 1, NSAA scores were maintained. As all patients in Part 2 were exposed to treatment, results were compared with a propensity-score-weighted external control (EC) cohort. The LSM difference in NSAA score between the Part 2 treated group and EC cohort was statistically significant (+2.0 points; p = 0.0009). The most common TRAEs were vomiting, decreased appetite, and nausea. Most occurred within the first 90 days and all resolved. Discussion: Results indicate robust expression of SRP-9001 dystrophin and overall stabilization in NSAA up to 2 years post-treatment. Differences in NSAA between groups in Part 1 were not significant for the overall population, likely because cohorts were stratified only by age, and other critical prognostic factors were not well matched at baseline.

Evolving regulatory perspectives on digital health technologies for medicinal product development

Digital health technology tools (DHTTs) present real opportunities for accelerating innovation, improving patient care, reducing clinical trial duration and minimising risk in medicines development. This review is comprised of four case studies of DHTTs used throughout the lifecycle of medicinal products, starting from their development. These cases illustrate how the regulatory requirements of DHTTs used in medicines development are based on two European regulatory frameworks (medical device and the medicinal product regulations) and highlight the need for increased collaboration between various stakeholders, including regulators (medicines regulators and device bodies), pharmaceutical sponsors, manufacturers of devices and software, and academia. As illustrated in the examples, the complexity of the interactions is further increased by unique challenges related to DHTTs. These case studies are the main examples of DHTTs with a regulatory assessment thus far, providing an insight into the applicable current regulatory approach; they were selected by a group of authors, including regulatory specialists from pharmaceutical sponsors, technology experts, academic researchers and employees of the European Medicines Agency. For each case study, the challenges faced by sponsors and proposed potential solutions are discussed, and the benefit of a structured interaction among the different stakeholders is also highlighted.

Longitudinal Assessment of Creatine Kinase, Creatine/Creatinineratio, and Myostatin as Monitoring Biomarkers in Becker Muscular Dystrophy

BACKGROUND AND OBJECTIVES

The slow and variable disease progression of Becker muscular dystrophy (BMD) urges the development of biomarkers to facilitate clinical trials. We explored changes in 3 muscle-enriched biomarkers in serum of patients with BMD over 4-year time and studied associations with disease severity, disease progression, and dystrophin levels in BMD.

METHODS

We quantitatively measured creatine kinase (CK) using the International Federation of Clinical Chemistry reference method, creatine/creatinine_ratio (Cr/Crn) using liquid chromatography-tandem mass spectrometry, and myostatin with ELISA in serum and assessed functional performance using the North Star Ambulatory Assessment (NSAA), 10-meter run velocity (TMRv), 6-Minute Walking Test (6MWT), and forced vital capacity in a 4-year prospective natural history study. Dystrophin levels were quantified in the tibialis anterior muscle using capillary Western immunoassay. The correlation between biomarkers, age, functional performance, mean annual change, and prediction of concurrent functional performance was analyzed using linear mixed models.

RESULTS

Thirty-four patients with 106 visits were included. Eight patients were nonambulant at baseline. Cr/Crn and myostatin were highly patient specific (intraclass correlation coefficient for both = 0.960). Cr/Crn was strongly negatively correlated, whereas myostatin was strongly positively correlated with the NSAA, TMRv, and 6MWT (Cr/Crn rho = -0.869 to -0.801 and myostatin rho = 0.792 to 0.842, all p < 0.001). CK showed a negative association with age (p = 0.0002) but was not associated with patients' performance. Cr/Crn and myostatin correlated moderately with the average annual change of the 6MWT (rho = -0.532 and 0.555, p = 0.02). Dystrophin levels did not correlate with the selected biomarkers nor with performance. Cr/Crn, myostatin, and age could explain up to 75% of the variance of concurrent functional performance of the NSAA, TMRv, and 6MWT.

DISCUSSION

Both Cr/Crn and myostatin could potentially serve as monitoring biomarkers in BMD, as higher Cr/Crn and lower myostatin were associated with lower motor performance and predictive of concurrent functional performance when combined with age. Future studies are needed to more precisely determine the context of use of these biomarkers.

Next steps for the optimization of exon therapy for Duchenne muscular dystrophy

INTRODUCTION

It is established that the exon-skipping approach can restore dystrophin in Duchenne muscular dystrophy (DMD) patients. However, dystrophin restoration levels are low, and the field is evolving to provide solutions for improved exon skipping. DMD is a neuromuscular disorder associated with chronic muscle tissue loss attributed to the lack of dystrophin, which causes muscle inflammation, fibrosis formation, and impaired regeneration. Currently, four antisense oligonucleotides (AONs) based on phosphorodiamidate morpholino oligomer (PMO) chemistry are approved by US Food and Drug Administration for exon skipping therapy of eligible DMD patients.

AREAS COVERED

This review describes a preclinical and clinical experience with approved and newly developed AONs for DMD, outlines efforts that have been done to enhance AON efficiency, reviews challenges of clinical trials, and summarizes the current state of the exon skipping approach in the DMD field.

EXPERT OPINION

The exon skipping approach for DMD is under development, and several chemical modifications with improved properties are under (pre)-clinical investigation. Despite existing advantages of these modifications, their safety and effectiveness have to be examined in clinical trials, which are planned or ongoing. Furthermore, we propose clinical settings using natural history controls to facilitate studying the functional effect of the therapy.

On the relevance of prognostic information for clinical trials: A theoretical quantification

The question of how individual patient data from cohort studies or historical clinical trials can be leveraged for designing more powerful, or smaller yet equally powerful, clinical trials becomes increasingly important in the era of digitalization. Today, the traditional statistical analyses approaches may seem questionable to practitioners in light of ubiquitous historical prognostic information. Several methodological developments aim at incorporating historical information in the design and analysis of future clinical trials, most importantly Bayesian information borrowing, propensity score methods, stratification, and covariate adjustment. Adjusting the analysis with respect to a prognostic score, which was obtained from some model applied to historical data, received renewed interest from a machine learning perspective, and we study the potential of this approach for randomized clinical trials. In an idealized situation of a normal outcome in a two-arm trial with 1:1 allocation, we derive a simple sample size reduction formula as a function of two criteria characterizing the prognostic score: (1) the coefficient of determination R² on historical data and (2) the correlation ρ between the estimated and the true unknown prognostic scores. While maintaining the same power, the original total sample size n planned for the unadjusted analysis reduces to ( 1 - R 2 ρ 2 ) × n $(1 - R^2 \rho ^2) \times n$ in an adjusted analysis. Robustness in less ideal situations was assessed empirically. We conclude that there is potential for substantially more powerful or smaller trials, but only when prognostic scores can be accurately estimated.

Novel approaches to analysis of the North Star Ambulatory Assessment (NSAA) in Duchenne muscular dystrophy (DMD): Observations from a phase 2 trial

Introduction

The North Star Ambulatory Assessment (NSAA) tool is a key instrument for measuring clinical outcomes in patients with Duchenne muscular dystrophy (DMD). To gain a better understanding of the longitudinal utility of the NSAA, we evaluated NSAA data from a phase II trial of 120 patients with DMD treated with domagrozumab or placebo.

Methods

The NSAA exploratory analyses included assessment of individual skills gained/lost, total skills gained/lost, cumulative loss of function, and the impact of transient loss of function due to a temporary disability on NSAA total score (temporary zero score).

Results

There was no significant difference in the total number of NSAA skills gained (mean 1.41 and 1.04, respectively; p = 0.3314) or lost (3.90 vs. 5.0; p = 0.0998) between domagrozumab- vs. placebo-treated patients at week 49. However, domagrozumab-treated patients were less likely to lose the ability to perform a NSAA item (hazard ratio 0.80, 95% confidence interval [CI]: 0.65–0.98, p = 0.029) over 48-weeks vs. placebo-treated patients. When temporary zero scores were changed to “not obtainable” (8 values from 7 patients), domagrozumab-treated patients scored higher on the NSAA total score versus placebo-treated patients (difference at week 49: 2.0, 95% CI: 0.1–3.9, p = 0.0359).

Conclusions

These exploratory analyses reveal additional approaches to interpreting the NSAA data beyond just change in NSAA total score. These observations also highlight the importance of reporting items as “not obtainable” for a patient with a temporary/transient physical disability that impacts their ability to perform the NSAA test.

ClinicalTrials.gov identifier

NCT02310763.

The Relationship between Obesity and Clinical Outcomes in Young People with Duchenne Muscular Dystrophy

Background: Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular disorder. Young people with DMD have high rates of obesity. There is emerging evidence that a higher BMI may negatively affect clinical outcomes in DMD. This study aimed to explore the relationship between obesity and clinical outcomes in DMD. Methods: This was a retrospective clinical audit of young people (two–21 years) with DMD. Height and weight were collected to calculate BMI z-scores to classify obesity, overweight and no overweight or obesity (reference category). Cox proportional hazards models determined the impact of obesity at five to nine years on clinical milestones including time to: loss of ambulation, timed function test cut-offs, obstructive sleep apnoea (OSA) diagnosis and first fracture. Results: 158 young people with DMD were included; most (89.9%) were steroid-treated. Mean follow-up was 8.7 ± 4.7 years. Obesity prevalence increased from age five (16.7%) to 11 years (50.6%). Boys with obesity at nine years sustained a fracture earlier (hazard ratio, HR: 2.050; 95% CI: 1.038–4.046). Boys with obesity at six to nine years were diagnosed with OSA earlier (e.g., obesity nine years HR: 2.883; 95% CI: 1.481–5.612). Obesity at eight years was associated with a 10 m walk/run in 7–10 s occurring at an older age (HR: 0.428; 95% CI: 0.207–0.887), but did not impact other physical function milestones. Conclusions: Although 50% of boys with DMD developed early obesity, the impact of obesity on physical function remains unclear. Obesity puts boys with DMD at risk of OSA and fractures at a younger age. Early weight management interventions are therefore important.

Peak functional ability and age at loss of ambulation in Duchenne muscular dystrophy

AIM

To correlate the North Star Ambulatory Assessment (NSAA) and timed rise from floor (TRF) recorded at age of expected peak with age at loss of ambulation (LOA) in Duchenne muscular dystrophy (DMD).

METHOD

Male children with DMD enrolled in the UK North Start Network database were included according to the following criteria: follow-up longer than 3 years, one NSAA record between 6 years and 7 years 6 months (baseline), at least one visit when older than 8 years. Data about corticosteroid treatment, LOA, genotype, NSAA, and TRF were analysed. Age at LOA among the different groups based on NSAA and TRF was determined by log-rank tests. Cox proportional hazard models were used for multivariable analysis.

RESULTS

A total of 293 patients from 13 different centres were included. Mean (SD) age at first and last visit was 5 years 6 months (1 year 2 months) and 12 years 8 months (2 years 11 months) (median follow-up 7 years 4 months). Higher NSAA and lower TRF at baseline were associated with older age at LOA (p<0.001). Patients scoring NSAA 32 to 34 had a probability of 0.61 of being ambulant when older than 13 years compared with 0.34 for those scoring 26 to 31. In multivariable analysis, NSAA, TRF, and corticosteroid daily regimen (vs intermittent) were all independently associated with outcome (p=0.01).

INTERPRETATION

Higher functional abilities at peak are associated with older age at LOA in DMD. This information is important for counselling families. These baseline measures should also be considered when designing clinical trials.

Disease Progression Stages and Burden in Patients with Duchenne Muscular Dystrophy Using Administrative Claims Supplemented by Electronic Medical Records

INTRODUCTION

This study aims to identify stages of Duchenne muscular dystrophy (DMD) and assess the disease burden by progression stage using real-world administrative claims supplemented by relevant electronic medical record (EMR) data.

METHODS

Claims and EMR data from the Decision Resources Group's Real World Data Repository (2011-2020) were used to identify patients with DMD by diagnosis code and to stratify them into four disease stages by diagnosis and procedure markers reflective of DMD progression. Clinical and medical history data from the Cooperative International Neuromuscular Research Group (CINRG) were used to validate the developed claims-based staging algorithm. The distribution and drivers by disease stage, as well as disease burden, were examined.

RESULTS

A total of 938 (94%) of patients with DMD identified in claims/EMR data had sufficient information for stage classification. Patients were classified by stage based on patient characteristics and the presence or absence of progression markers such as genetic testing, wheelchair usage, scoliosis treatment, or ventilation assistance. Average ages at stages 1-4 are 7, 13, 18, and 23 years, respectively. Using natural history data, the claims-based staging algorithm was validated with high sensitivity and specificity rates. Both healthcare resource utilization and medical charges increased by stage. For example, the average annualized total charges were $17,688 (stage 1), $36,868 (stage 2), $72,801 (stage 3), and $167,285 (stage 4).

CONCLUSIONS

Large-scale claims data supplemented by EMR data can be used to characterize DMD progression and evaluate disease burden which may inform the design of future real-world studies about DMD.

Predictive models in SMA II natural history trajectories using machine learning: A proof of concept study

It is known from previous literature that type II Spinal Muscular Atrophy (SMA) patients generally, after the age of 5 years, presents a steep deterioration until puberty followed by a relative stability, as most abilities have been lost. Although it is possible to identify points of slope indicating early improvement, steep decline and relative stabilizations, there is still a lot of variability within each age group and it’s not always possible to predict individual trajectories of progression from age only. The aim of the study was to develop a predictive model based on machine learning using an XGBoost algorithm for regression and report, explore and quantify, in a single centre longitudinal natural history study, the influence of clinical variables on the 6/12-months Hammersmith Motor Functional Scale Expanded score prediction (HFMSE). This study represents the first approach to artificial intelligence and trained models for the prediction of individualized trajectories of HFMSE disease progression using individual characteristics of the patient. The application of this method to larger cohorts may allow to identify different classes of progression, a crucial information at the time of the new commercially available therapies.

Prognostic indicators of disease progression in Duchenne muscular dystrophy: A literature review and evidence synthesis

BACKGROUND

Duchenne muscular dystrophy (DMD) is a rare, severely debilitating, and fatal neuromuscular disease characterized by progressive muscle degeneration. Like in many orphan diseases, randomized controlled trials are uncommon in DMD, resulting in the need to indirectly compare treatment effects, for example by pooling individual patient-level data from multiple sources. However, to derive reliable estimates, it is necessary to ensure that the samples considered are comparable with respect to factors significantly affecting the clinical progression of the disease. To help inform such analyses, the objective of this study was to review and synthesise published evidence of prognostic indicators of disease progression in DMD. We searched MEDLINE (via Ovid), Embase (via Ovid) and the Cochrane Library (via Wiley) for records published from inception up until April 23 2021, reporting evidence of prognostic indicators of disease progression in DMD. Risk of bias was established with the grading system of the Centre for Evidence-Based Medicine (CEBM).

RESULTS

Our search included 135 studies involving 25,610 patients from 18 countries across six continents (Africa, Asia, Australia, Europe, North America and South America). We identified a total of 23 prognostic indicators of disease progression in DMD, namely age at diagnosis, age at onset of symptoms, ataluren treatment, ATL1102, BMI, cardiac medication, DMD genetic modifiers, DMD mutation type, drisapersen, edasalonexent, eteplirsen, glucocorticoid exposure, height, idebenone, lower limb surgery, orthoses, oxandrolone, spinal surgery, TAS-205, vamorolone, vitlolarsen, ventilation support, and weight. Of these, cardiac medication, DMD genetic modifiers, DMD mutation type, and glucocorticoid exposure were designated core prognostic indicators, each supported by a high level of evidence and significantly affecting a wide range of clinical outcomes.

CONCLUSION

This study provides a current summary of prognostic indicators of disease progression in DMD, which will help inform the design of comparative analyses and future data collection initiatives in this patient population.

The association between dietary factors and body weight and composition in boys with Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a X-linked neuromuscular disorder. Boys with DMD have high rates of obesity, but little is known about dietary factors that may contribute to weight gain in this population. This study aimedto explore the relationship between dietary factors, body mass index (BMI) z-score, body composition and motor function and to describe dietary intake in boys with DMD.

METHODOLOGY

A cross-sectional analysis of 3-day food diaries from ambulant and steroid treated boys with DMD aged 5-13 years was conducted. Correlation analysis explored the relationship between dietary factors, BMI z-score, fat mass % (FM%) and lean mass (LM%).

RESULTS

Themedian agewas 8.5 years [interquartile range (IQR) 7.2, 10.5]. Median energy/kg/day in those within a healthy weight range (n=11) was316 kJ/kg/day [IQR 276, 355] and greater than estimated requirements; and forthose above a healthy weight (n=26) energy intake was 185kJ/kg/day [IQR 143, 214] and lower than estimated requirements. Energy/kg/day was negatively associatedwith BMI z-score (r=-0. 650) and FM% (r=-0.817)but positively associated with LM% (r=0.805, all analyses p =<0.01). Younger age was associated (r=-0.609 p=<0.01) with a higher energy/kg/day. For all participants vegetable, grains, meat/alternatives and dairy intake was sub-optimal.

PRINCIPAL CONCLUSIONS

Younger boys with DMD within a healthy weight range are overconsuming energy dense nutrient poor foods. A focus on improving diet quality during early childhood may prove a useful strategy to reduce excess weight gain and support healthier eating habits in this vulnerable clinical population. This article is protected by copyright. All rights reserved.

Lessons Learned from Discontinued Clinical Developments in Duchenne Muscular Dystrophy

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

Developments in reading frame restoring therapy approaches for Duchenne muscular dystrophy

INTRODUCTION

Exon skipping compounds restoring the dystrophin transcript reading frame have received regulatory approval for Duchenne muscular dystrophy (DMD). Recently, focus shifted to developing compounds to skip additional exons, improving delivery to skeletal muscle, and to genome editing, to restore the reading frame on DNA level.

AREAS COVERED

We outline developments for reading frame restoring approaches, challenges of mutation specificity, and optimizing delivery. Also, we highlight ongoing efforts to better detect exon skipping therapeutic effects in clinical trials. Searches on relevant terms were performed, focusing on recent publications (<3 years).

EXPERT OPINION

Currently, 3 AONS are approved. Whether dystrophin levels are sufficient to slowdown disease progression needs to be confirmed. Enhancing AON uptake by muscles is currently under investigation. Gene editing is an alternative, but one that involves practical and ethical concerns. Given the field's momentum, we believe the efficiency of frame-restoring approaches will improve.