Characteristics of Patients With Late-Onset Pompe Disease in France: Insights From the French Pompe Registry in 2022

A model to predict the 6-Minute Walk Distance in Pompe disease

BACKGROUND

Pompe disease is a rare neuromuscular disorder caused by acid alpha-glucosidase deficiency, leading to glycogen accumulation and progressive striated muscle weakness. The 6-minute walk test (6MWT) is commonly used to assess functional capacity in neuromuscular diseases but can be challenging for severely affected ambulant patients.

OBJECTIVE

This study aimed to develop and validate predictive models for 6MWT performance using simpler, less demanding tests.

METHODS

This retrospective monocentric study included 74 patients with Pompe disease (712 visits) and a mean follow-up of 6.6 ± 3.8 years. Functional assessments included the 6MWT, 10-meter walk test (10mWT) which was specifically used to determine gait speed, timed tests, strength and respiratory measures, and the Motor Function Measure (MFM-32). Linear regression models were developed to predict 6MWT speed, with validation using an 80%-20% training-testing split.

RESULTS

The cohort had an equal male-to-female ratio, with a mean age of 54.4 ± 13.5 years. The 10mWT speed showed a strong correlation with 6MWT speed (R = 0.91, p < 0.0001), confirming its potential as a surrogate measure. The most practical predictive model included 10mWT speed, age, sex, height, and weight, achieving an adjusted R2 of 0.86. This model balances simplicity and accuracy, relying on easily measurable parameters suitable for routine clinical use. More complex models, including variables such as the MFM-32 or supine-to-sit time, offered only marginal improvements in accuracy.

CONCLUSION

The 10mWT offers a robust and less exhausting alternative to the 6MWT for assessing walking capacity in Pompe disease, particularly for ambulant patients with severe mobility limitations. Its strong correlation with the 6MWT and ease of implementation support its integration into clinical practice and trials.

Clinical insights in enzyme replacement therapy for metabolic storage disorders: lessons from Pompe disease

Metabolic storage disorders, including lysosomal storage disorders, pose complex challenges in management due to their progressive and life-threatening nature. Although enzyme replacement therapy has substantially improved outcomes for patients with lysosomal storage disorders, limitations of this therapy have become apparent throughout two decades of use. New clinical features of these diseases have emerged as patients live longer, leading to unresolved questions regarding ongoing treatment and long-term care. Innovative therapies are emerging that aim to improve targeting of tissues, particularly for previously inaccessible areas such as the CNS. These next-generation treatments hold promise for enhancing patient outcomes beyond what enzyme replacement therapy can do. Continued exploration of novel therapeutic strategies will be crucial for providing more effective and personalised care for these complex diseases.

Metabolic and proteomic profiles provide insights on mechanism of late onset Pompe disease

Late onset Pompe disease (LOPD) is caused by a deficiency of the enzyme acid α-glucosidase, resulting in glycogen accumulation in lysosomes. The mechanism of LOPD has been less explored. In this study, we used an integrative analysis of the proteomics and metabolomics of LOPD muscle samples to reveal the potential mechanisms. Proteomic analysis identified 635 upregulated proteins and 89 downregulated proteins in the LOPD group. Similarly, metabolomic analysis revealed 15 upregulated and 143 downregulated metabolites; notably, L-arginine levels were significantly decreased in the LOPD group. Lysosome-related GO terms were significantly upregulated, while GO terms related to neurofilament, cytoskeleton, axon ensheathment, and myelin sheath were significantly downregulated. KEGG pathway analysis demonstrated that the lysosome, autophagy, and mTOR pathways were distinctly upregulated. Correlation analysis indicated that CALML3 showed a potential correlation with LOPD severity. Our study highlighted the potential crosstalk among these LOPD-related pathways. Supplementation with L-arginine could represent a promising therapeutic approach for LOPD, and CALML3 could serve as a potential biomarker for LOPD severity. These findings provide valuable insights into the pathogenesis of LOPD and suggest avenues for future therapeutic development.

Real-world evidence for Pompe disease remains fragmented. Comment on "A rare partnership: patient community and industry collaboration to shape the impact of real-world evidence on the rare disease ecosystem" by Klein et al

In a recent publication by Klein et al., the need for real-world data on rare diseases is highlighted. We strongly support this need, and the collaboration with the patient community to collect data, as promoted in this publication. Our concern, however, is that this paper may be misunderstood as suggesting that the Sanofi-run Rare Disease Registries (RDRs) are sufficient to provide the datasets needed to evaluate current and future therapies. Industry-driven registries focus on their own product(s) and, therefore, do not provide the opportunity to compare products from different companies. Today, multiple companies produce treatments for all diseases included in the RDRs. Each company will have to run its own registry for regulatory purposes. This will lead to data fragmentation, which is prohibitive of truly understanding the effects of the various treatment options for these rare diseases. Therefore, independently funded and owned registries are essential to generate real-world evidence (RWE) unrelated to specific products. We discuss options for this for Pompe disease, including the International Pompe Survey, which has collected patient-reported outcomes independently from industry since 2002. This letter aims to raise awareness of the problem of siloed data and advocate for a new way forward where independent registries provide post-marketing surveillance data.

Bulbar muscle impairment in patients with late onset Pompe disease: Insight from the French Pompe registry

BACKGROUND AND PURPOSE

Late onset Pompe disease (LOPD) is a rare neuromuscular disorder caused by a deficit in acid alpha-glucosidase. Macroglossia and swallowing disorders have already been reported, but no study has focused yet on its frequency and functional impact on patients' daily life.

METHODS

We reviewed 100 adult LOPD patients followed in 17 hospitals in France included in the French national Pompe disease registry. The Swallowing Quality of Life Questionnaire and the Sydney Swallow Questionnaire were completed by patients, and a specialist carried out a medical examination focused on swallowing and assigned a Salassa score to each patient. Respiratory and motor functions were also recorded. Subgroup analysis compared patients with and without swallowing difficulties based on Salassa score.

RESULTS

Thirty-two percent of patients presented with swallowing difficulties, often mild but sometimes severe enough to require percutaneous endoscopic gastrostomy (1%). Daily dysphagia was reported for 20% of our patients and aspirations for 18%; 9.5% were unable to eat away from home. Macroglossia was described in 18% of our patients, and 11% had lingual atrophy. Only 15% of patients presenting with swallowing disorders were followed by a speech therapist. Swallowing difficulties were significantly associated with macroglossia (p = 0.015), longer duration of illness (p = 0.032), and a lower body mass index (p = 0.047).

CONCLUSIONS

Swallowing difficulties in LOPD are common and have significant functional impact. Increased awareness by physicians of these symptoms with systematic examination of the tongue and questions about swallowing can lead to appropriate multidisciplinary care with a speech therapist and dietitian if needed.

Real-life effectiveness 1 year after switching to avalglucosidase alfa in late-onset Pompe disease patients worsening on alglucosidase alfa therapy: A French cohort study

INTRODUCTION

Late-onset Pompe disease (LOPD) is characterized by a progressive myopathy resulting from a deficiency of acid α-glucosidase enzyme activity. Enzyme replacement therapy has been shown to be effective, but long-term treatment results vary. Avalglucosidase alfa demonstrated non-inferiority to alglucosidase alfa in a phase 3 study, allowing in France compassionate access for advanced LOPD patients unresponsive to alglucosidase alfa.

METHODS

Data from the French Pompe registry were analyzed for patients who benefited from a switch to avalglucosidase alfa with at least 1 year of follow-up. Respiratory (forced vital capacity [FVC]) and motor functions (Six-Minute Walk Test [6MWT]) were assessed before and 1 year after switching. Individual changes in FVC and 6MWT were expressed as slopes and statistical analyses were performed to compare values.

RESULTS

Twenty-nine patients were included (mean age 56 years, 11 years of prior treatment). The FVC and 6MWT values remained stable. The individual analyses showed a stabilization of motor worsening: -1 m/year on the 6MWT after the switch versus -63 m/year the year before the switch (i.e., a worsening of 33%/year before vs. an improvement of 3%/year later). Respiratory data were not statistically different.

DISCUSSION

At the group level, gait parameters improved slightly with a stabilization of previous worsening, but respiratory parameters showed limited changes. At the individual level, results were discordant, with some patients with a good motor or respiratory response and some with further worsening.

CONCLUSION

Switching to avalglucosidase alfa demonstrated varied responses in advanced LOPD patients with failing alglucosidase alfa therapy, with a general improvement in motor stabilization.

Characterization of neuromuscular performances in adults with late-onset Pompe disease: A control case cross-sectional study

Adults with late-onset Pompe disease (aLOPD) are characterized by muscular contractile tissue deterioration. However, their neuromuscular performances are poorly known. We aimed to compare maximal muscle strength, activation, explosive strength and neuromuscular fatigue between aLOPD and controls. We studied 20 aLOPD and 20 matched controls. Isometric maximum voluntary contraction (MVC) torque was obtained for the hip, knee and ankle muscles. The voluntary activation level (VAL) during knee extensor MVC was assessed using interpolated twitch technique. Explosive strength was evaluated for knee and ankle muscles through the rate of torque development (RTD) during fast contractions. Neuromuscular fatigue was measured during a 30-second contraction of knee flexors and extensors. All muscle MVC torques were significantly lower in aLOPD than controls (p <0.05). The weakest muscles were the hip extensors followed by hip abductors and abductors. Raw value of RTD was lower in aLOPD for the majority of muscles (p <0.05). No intergroup differences were reported for normalized RTD, VAL and neuromuscular fatigue (p-values> 0.05). Our study shows that maximal strength was the only neuromuscular characteristic affected in aLOPD with a proximal-distal intensity gradient. This suggests that the surviving muscle tissue of aLOPD is as functionally efficient as that of control individuals.