Genotype-related respiratory progression in Duchenne muscular dystrophy-A multicenter international study

Survival among patients receiving eteplirsen for up to 8 years for the treatment of Duchenne muscular dystrophy and contextualization with natural history controls

INTRODUCTION/AIMS

Eteplirsen, approved in the US for patients with Duchenne muscular dystrophy (DMD) with exon 51 skip-amenable variants, is associated with attenuated ambulatory/pulmonary decline versus DMD natural history (NH). We report overall survival in a US cohort receiving eteplirsen and contextualize these outcomes versus DMD NH.

METHODS

US patients with DMD receiving eteplirsen were followed through a patient support program, with data collected on ages at eteplirsen initiation and death/end of follow-up. Individual DMD NH data were extracted by digitizing Kaplan-Meier (KM) curves from published systematic and targeted literature reviews. Overall survival age was analyzed using KM curves and contextualized with DMD NH survival curves; subanalyses considered age groups and duration of eteplirsen exposure. Overall survival time from treatment initiation was also evaluated.

RESULTS

A total of 579 eteplirsen-treated patients were included. During a total follow-up of 2119 person-years, median survival age was 32.8 years. DMD NH survival curves extracted from four publications (follow-up for 1224 DMD NH controls) showed overall pooled median survival age of 27.4 years. Eteplirsen-treated patients had significantly longer survival from treatment initiation versus age-matched controls (age-adjusted hazard ratio [HR], 0.65; 95% confidence interval [CI], 0.44-0.98; p < .05). Longer treatment exposure was associated with improved survival (HR, 0.15; 95% CI, 0.05-0.41; p < .001). Comparisons using different DMD NH cohorts to address common risks of bias yielded consistent findings.

DISCUSSION

Data suggest eteplirsen may prolong survival in patients with DMD across a wide age range. As more data become available, the impact of eteplirsen on survival will be further elucidated.

Development of respiratory care guidelines for Duchenne muscular dystrophy in the UK: key recommendations for clinical practice

Significant inconsistencies in respiratory care provision for Duchenne muscular dystrophy (DMD) are reported across different specialist neuromuscular centres in the UK. The absence of robust clinical evidence and expert consensus is a barrier to the implementation of care recommendations in public healthcare systems as is the need to increase awareness of key aspects of care for those living with DMD. Here, we provide evidenced-based and/or consensus-based best practice for the respiratory care of children and adults living with DMD in the UK, both as part of routine care and in an emergency.

METHODOLOGY

Initiated by an expert working group of UK-based respiratory physicians (including British Thoracic Society (BTS) representatives), neuromuscular clinicians, physiotherapist and patient representatives, draft guidelines were created based on published evidence, current practice and expert opinion. After wider consultation with UK respiratory teams and neuromuscular services, consensus was achieved on these best practice recommendations for respiratory care in DMD.

RESULT

The resulting recommendations are presented in the form of a flow chart for assessment and monitoring, with additional guidance and a separate chart setting out key considerations for emergency management. The recommendations have been endorsed by the BTS.

CONCLUSIONS

These guidelines provide practical, reasoned recommendations for all those managing day-to-day and acute respiratory care in children and adults with DMD. The hope is that this will support patients and healthcare professionals in accessing high standards of care across the UK.

Factors Associated with Respiratory Health and Function in Duchenne Muscular Dystrophy: A Systematic Review and Evidence Grading

BACKGROUND

Despite advances in the medical management of the disease, respiratory involvement remains a significant source of morbidity and mortality in children and adults with Duchenne muscular dystrophy (DMD).

OBJECTIVE

The objective of this systematic literature review was to synthesize and grade published evidence of factors associated with respiratory health and function in DMD.

METHODS

We searched MEDLINE, Embase, and the Cochrane Library for records of studies published from January 1, 2000 (to ensure relevance to current care practices), up until and including December 31, 2022, reporting evidence of prognostic indicators and predictors of disease progression in DMD. The quality of evidence (i.e., very low to high) was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) framework.

RESULTS

The bibliographic search strategy resulted in the inclusion of 29 articles. In total, evidence of 10 factors associated with respiratory health and function in patients with DMD was identified: glucocorticoid exposure (high- to very low-quality evidence), DMD mutations (low-quality evidence), DMD genetic modifiers (low-quality evidence), other pharmacological interventions (i.e., ataluren, eteplirsen, idebenone, and tamoxifen) (moderate- to very low-quality evidence), body mass index and weight (low-quality evidence), and functional ability (low-quality evidence).

CONCLUSIONS

In conclusion, we identified a total of 10 factors associated with respiratory health in function in DMD, encompassing both pharmacological therapies, genetic mutations and modifiers, and patient clinical characteristics. Yet, more research is needed to further delineate sources of respiratory heterogeneity, in particular the genotype-phenotype association and the impact of novel DMD therapies in a real-world setting. Our synthesis and grading should be helpful to inform clinical practice and future research of this heavily burdened patient population.

Safety and effectiveness of ataluren in patients with nonsense mutation DMD in the STRIDE Registry compared with the CINRG Duchenne Natural History Study (2015-2022): 2022 interim analysis

OBJECTIVE

Strategic Targeting of Registries and International Database of Excellence (STRIDE) is an ongoing, international, multicenter registry of real-world ataluren use in individuals with nonsense mutation Duchenne muscular dystrophy (nmDMD) in clinical practice. This updated interim report (data cut-off: January 31, 2022), describes STRIDE patient characteristics and ataluren safety data, as well as the effectiveness of ataluren plus standard of care (SoC) in STRIDE versus SoC alone in the Cooperative International Neuromuscular Research Group (CINRG) Duchenne Natural History Study (DNHS).

METHODS

Patients are followed up from enrollment for at least 5 years or until study withdrawal. Propensity score matching was performed to identify STRIDE and CINRG DNHS patients who were comparable in established predictors of disease progression.

RESULTS

As of January 31, 2022, 307 patients were enrolled from 14 countries. Mean (standard deviation [SD]) ages at first symptoms and at genetic diagnosis were 2.9 (1.7) years and 4.5 (3.7) years, respectively. Mean (SD) duration of ataluren exposure was 1671 (56.8) days. Ataluren had a favorable safety profile; most treatment-emergent adverse events were mild or moderate and unrelated to ataluren. Kaplan-Meier analyses demonstrated that ataluren plus SoC significantly delayed age at loss of ambulation by 4 years (p < 0.0001) and age at decline to %-predicted forced vital capacity of < 60% and < 50% by 1.8 years (p = 0.0021) and 2.3 years (p = 0.0207), respectively, compared with SoC alone.

CONCLUSION

Long-term, real-world treatment with ataluren plus SoC delays several disease progression milestones in individuals with nmDMD. NCT02369731; registration date: February 24, 2015.

Safety, tolerability and pharmacokinetics of eteplirsen in young boys aged 6–48 months with Duchenne muscular dystrophy amenable to exon 51 skipping

Eteplirsen is FDA-approved for the treatment of Duchenne muscular dystrophy (DMD) in exon 51 skip-amenable patients. Previous studies in boys > 4 years of age indicate eteplirsen is well tolerated and attenuates pulmonary and ambulatory decline compared with matched natural history cohorts. Here the safety, tolerability and pharmacokinetics of eteplirsen in boys aged 6-48 months is evaluated. In this open-label, multicenter, dose-escalation study (NCT03218995), boys with a confirmed mutation of the DMD gene amenable to exon 51 skipping (Cohort 1: aged 24-48 months, n = 9; Cohort 2: aged 6 to < 24 months, n = 6) received ascending doses (2, 4, 10, 20, 30 mg/kg) of once-weekly eteplirsen intravenously over 10 weeks, continuing at 30 mg/kg up to 96 weeks. Endpoints included safety (primary) and pharmacokinetics (secondary). All 15 participants completed the study. Eteplirsen was well tolerated with no treatment-related discontinuations, deaths or evidence of kidney toxicity. Most treatment-emergent adverse events were mild; most common were pyrexia, cough, nasopharyngitis, vomiting, and diarrhea. Eteplirsen pharmacokinetics were consistent between both cohorts and with previous clinical experience in boys with DMD > 4 years of age. These data support the safety and tolerability of eteplirsen at the approved 30-mg/kg dose in boys as young as 6 months old.

Respiratory Function and Sleep Disordered Breathing in Pediatric Duchenne Muscular Dystrophy

BACKGROUND

The decline of respiratory function in Duchenne muscular dystrophy (DMD) is associated with sleep disordered breathing (SDB) and alteration of nocturnal gas exchange, first manifesting as nocturnal hypoventilation (NH). However, the correlation between pulmonary function measured by spirometry (PFT) and the onset of SDB with or without NH is unclear.

AIM

To identify the prevalence and features of SDB and to investigate the relationship between lung function determined by forced vital capacity (FVC) and sleep abnormalities in a large paediatric DMD population.

METHODS

Retrospective, single-center cohort study. FVC% predicted (FVC%) was calculated using predicted equations from the Global Lung Function Initiative. NH was defined by transcutaneous (tc) CO2 >50 mmHg for >25% of total sleep time (TST); borderline NH by a mean tcCO2 between 45-50mmHg or tcCO2>50mmHg for ≤25% of TST; Clinically meaningful obstructive sleep apnea (OSA) by obstructive Apnea-Hypopnea Index >5. The sensitivity, specificity, positive and negative predictive value of FVC<50% to indicate presence of nocturnal hypoventilation were calculated.

RESULTS

134 patients underwent 284 sleep studies and 1222 PFT. Mean (SD) age at first and last sleep study was 12.9 (2.7) and 14.3 (2.6) years. Borderline NH (n=31) was detected in both ambulant and early-non ambulant subjects, while 100% of NH cases (n=14) were non-ambulant. NH was detected in 4/14 patients despite an FVC>50%. Seventeen/26 patients with OSA presented with concomitant NH or borderline NH. FVC<50% was associated with NH indicating a sensitivity and specificity of 73% and 86%, respectively. Positive and negative predictive value were 32% and 97% respectively. PFT showed a non-linear, sudden FVC% decline in 18% of cases.

CONCLUSIONS

FVC% <50 was associated with NH in close to a third of patients. CO2 elevation can be associated with obstructive/pseudo-obstructive events and was also observed in early non-ambulant cases or in the presence of FVC>50%. These results are relevant for the clinical management of SDB.

Delays in pulmonary decline in eteplirsen-treated patients with Duchenne muscular dystrophy

INTRODUCTION/AIMS

Pulmonary decline is an important issue in patients with Duchenne muscular dystrophy (DMD). Eteplirsen is a US-approved treatment for patients with DMD and exon 51 skip-amenable mutations. Previous analyses have shown that eteplirsen is associated with statistically significant attenuation of pulmonary decline. This study evaluates the effect of eteplirsen treatment from newly available data sources on pulmonary function over time in patients with DMD.

METHODS

This study uses a post hoc pooled analysis to compare the percentage of predicted forced vital capacity (FVC%p) and projected time to pulmonary function milestones in patients with DMD and exon 51 skip-amenable mutations receiving eteplirsen (Studies 204 and 301) or standard of care (SoC; Cooperative International Neuromuscular Research Group Duchenne Natural History Study). A mixed model for repeated measures framework was applied to evaluate the impact of eteplirsen.

RESULTS

An average annual rate of FVC%p decline for eteplirsen-treated patients was estimated to be 3.47%, which was a statistically significant attenuation from the 5.95% rate of decline estimated in SoC patients (P = 0.0001). Using linear extrapolations of the model-estimated decline in FVC%p, the attenuation in FVC%p decline for eteplirsen-treated patients corresponded to a delay of 5.72 years in time to needing continuous ventilation, 3.31 years in time to needing nighttime ventilation, and 2.11 years in time to needing a cough assist device compared with SoC patients.

DISCUSSION

The attenuation of FVC%p decline suggests that eteplirsen-treated patients experienced statistically significant and clinically meaningful attenuations in pulmonary decline compared with SoC patients. This article is protected by copyright. All rights reserved.