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.

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

BACKGROUND AND OBJECTIVES

The French Pompe disease registry was created in 2004 for study of the natural course of the disease in patients. It rapidly became a major tool for assessing the long-term efficacy of enzyme replacement therapy (ERT) after the market release of alglucosidase-alfa.

METHODS

Approximately 10 years after publication of the baseline characteristics of the 126 initial patients of the French Late-Onset Pompe Disease registry, we provide here an update of the clinical and biological features of patients included in this registry.

RESULTS

We describe 210 patients followed at 31 hospital-based French neuromuscular or metabolic centers. The median age at inclusion was 48.67 ± 14.91 years. The first symptom was progressive lower limb muscle weakness, either isolated (50%) or associated with respiratory symptoms (18%), at a median age of 38 ± 14.9 years. At inclusion, 64% of the patients were able to walk independently and 14% needed a wheelchair. Positive associations were found between motor function measure, manual motor test, and 6-minute walk test (6MWT) results, and these parameters were inversely associated with the time taken to sit up from a lying position at inclusion. Seventy-two patients had been followed for at least 10 years in the registry. Thirty-three patients remained untreated a median of 12 years after symptom onset. The standard ERT dose was administered for 177 patients.

DISCUSSION

This update confirms previous findings for the adult population included in the French Pompe disease registry, but with a lower clinical severity at inclusion, suggesting that this rare disease is now diagnosed earlier; thanks to greater awareness among physicians. The 6MWT remains an important method for assessing motor performance and walking ability. The French Pompe disease registry provides an exhaustive, nationwide overview of Pompe disease and can be used to assess individual and global responses to future treatments.

Macroglossia: A potentially severe complication of late-onset POMPE disease

BACKGROUND

Pompe disease is a rare neuromuscular disorder caused by a deficiency of a lysosomal enzyme, acid α-glucosidase. Macroglossia is a classic clinical sign of several inherited myopathies and has also been reported to occur progressively in late-onset Pompe disease (LOPD).

METHODS

We describe patients with LOPD and macroglossia included in the French national Pompe disease registry. Clinical, functional, and radiological data have been collected during periodic follow-up and analyzed retrospectively. These cases have been compared with 15 previously reported cases.

RESULTS

5 patients, 3 female and 2 males, from 71 to 88 years old, have been included in this study. All but one of the patients suffered from symptoms related to macroglossia before the diagnosis of Pompe disease. Three had localized tongue atrophy and one had significant localized tongue hypertrophy which led to glossectomy 10 years before diagnosis. Two patients had severe dysphagia, one of whom underwent gastrostomised for enteral nutritional support. One patient experienced the persistence of numerous sleep apneas despite nocturnal BiPAP ventilation. All our patients had dysarthria, and two required speech therapy. Four patients had a tongue hypersignal on MRI T1 sequences.

CONCLUSIONS

Detection of macroglossia should be part of the clinical diagnosis and follow-up of patients with LOPD, with a careful evaluation of its main consequences. Macroglossia can have severe functional impacts on speech, swallowing and sleep. Whole-body MRI with facial sections may facilitate the early diagnosis of Pompe disease with the "bright tongue sign".

Motor and respiratory decline in patients with Late-onset Pompe disease after cessation of enzyme replacement therapy during COVID-19 pandemic

BACKGROUND

Data on interruption of enzyme replacement therapy are scarce in late-onset Pompe disease. Due to the COVID-19 crisis, 8 neuromuscular reference centers in France were obligated to stop the treatment for 31 patients.

METHOD

We collected the motor and respiratory data from our French registry, before COVID-19 and at treatment restart.

RESULTS

In 2.2 months (mean), patients showed a significant deterioration of 37 meters (mean) in the 6-minute walk test and a loss of 210 mL (mean) of forced vital capacity, without ad integrum restoration after 3 months of ERT restart.

CONCLUSION

This national study based on data from the French Pompe registry shows that the interruption of enzyme replacement therapy, even as short as only few months, worsens Pompe patients' motor and respiratory function.

Long-term benefit of enzyme replacement therapy with alglucosidase alfa in adults with Pompe disease: Prospective analysis from the French Pompe Registry

Despite a wide clinical spectrum, the adult form of Pompe disease is the most common one, and represents more than 90% of diagnosed patients in France. Since the marketing of enzyme replacement therapy (alglucosidase alfa, Myozyme), all reports to date in adults demonstrated an improvement of the walking distance, and a trend toward stabilization of respiratory function, but the majority of these studies were less than 5 years of duration. We report here the findings from 158 treated patients included in the French Pompe Registry, who underwent regular clinical assessments based on commonly used standardized tests (6-minute walking test, MFM scale, sitting vital capacity, MIP and MEP). For longitudinal analyses, the linear mixed effects models were used to assess trends in primary endpoints over time under ERT. A two-phase model better described the changes in distance traveled in the 6-minute walk test and MFM. 6MWT showed an initial significant increase (1.4% ± 0.5/year) followed by a progressive decline (-2.3%/year), with a cut-off point at 2.2 years. A similar pattern was observed in total MFM score (6.6% ± 2.3/year followed by a - 1.1%/year decline after 0.5 years). A single-phase decline with a slope of -0.9 ± 0.1%/year (P < .001) was observed for FVC, and MEP remained stable over the all duration of follow-up. This study provides further evidence that ERT improves walking abilities and likely stabilizes respiratory function in adult patients with Pompe disease, with a ceiling effect for the 6MWT in the first 3 years of treatment.

Large variation in effects during 10 years of enzyme therapy in adults with Pompe disease

Objective

To determine the effects of 10 years of enzyme replacement therapy (ERT) in adult patients with Pompe disease, focusing on individual variability in treatment response.

Methods

In this prospective, multicenter cohort study, we studied 30 patients from the Netherlands and France who had started ERT during the only randomized placebo-controlled clinical trial with ERT in late-onset Pompe disease (NCT00158600) or its extension (NCT00455195) in 2005 to 2008. Main outcomes were walking ability (6-minute walk test [6MWT]), muscle strength (manual muscle testing using Medical Research Council [MRC] grading), and pulmonary function (forced vital capacity [FVC] in the upright and supine positions), assessed at 3- to 6-month intervals before and after the start of ERT. Data were analyzed with linear mixed-effects models for repeated measurements.

Results

Median follow-up duration on ERT was 9.8 years (interquartile range [IQR] 8.3–10.2 years). At the group level, baseline 6MWT was 49% of predicted (IQR 41%–60%) and had deteriorated by 22.2 percentage points (pp) at the 10-year treatment point (p < 0.001). Baseline FVC upright was 54% of predicted (IQR 47%–68%) and decreased by 11 pp over 10 years (p < 0.001). Effects of ERT on MRC sum score and FVC supine were similar. At the individual level, 93% of patients had initial benefit of ERT. Depending on the outcome measured, 35% to 63% of patients had a secondary decline after ≈3 to 5 years. Still, at 10 years of ERT, 52% had equal or better 6MWT and/or FVC upright compared to baseline.

Conclusions

The majority of patients with Pompe disease benefit from long-term ERT, but many patients experience some secondary decline after ≈3 to 5 years. Individual variation, however, is considerable.

Classification of evidence

This study provides Class IV evidence that for the majority of adults with Pompe disease, long-term ERT positively affects, or slows deterioration in, muscle strength, walking ability, and/or pulmonary function.

Late-onset Pompe disease in France: molecular features and epidemiology from a nationwide study

Pompe disease (PD) is caused by a deficiency of lysosomal acid α-glucosidase resulting from mutations in the GAA gene. The clinical spectrum ranges from a rapidly fatal multisystemic disorder (classic PD, onset < 1 year) to a milder adult onset myopathy. The aims of this study were to characterize the GAA mutations, to establish the disease epidemiology, and to identify potential genotype-phenotype correlations in French late-onset PD patients (onset ≥ 2 years) diagnosed since the 1970s. Data were collected from the two main laboratories involved in PD diagnosis and from the French Pompe registry. Two hundred forty-six patients (130 females and 116 males) were included, with a mean age at diagnosis of 43 years. Eighty-three different mutations were identified in the GAA gene, among which 28 were novel. These variants were spread all over the sequence and included 42 missense (one affecting start codon), 8 nonsense, 15 frameshift, 14 splice mutations, 3 small in-frame deletions, and one large deletion. The common c.-32-13T>G mutation was detected in 151/170 index cases. Other frequent mutations included the exon 18 deletion, the c.525del, and the missense mutations c.1927G>A (p.Gly643Arg) and c.655G>A (p.Gly219Arg). Patients carrying the c.-32-13T>G mutation had an older mean age at onset than patients non-exhibiting this mutation (36 versus 25 years). Patients with the same genotype had a highly variable age at onset. We estimated the frequency of late-onset PD in France around 1/69,927 newborns. In conclusion, we characterized the French cohort of late-onset PD patients through a nationwide study covering more than 40 years.

Effect of enzyme replacement therapy with alglucosidase alfa (Myozyme®) in 12 patients with advanced late-onset Pompe disease

BACKGROUND

The efficacy of enzyme replacement therapy (ERT) in patients at an advanced stage of Pompe disease has only been addressed in a few studies. Our objective was to assess the long term effects of ERT in a cohort of patients with severe Pompe disease.

METHODS

We identified patients from the French Pompe Registry with severe respiratory failure and permanent wheelchair use (assisted walk for a few meters was allowed) when starting ERT. Patients' medical records were collected and reviewed and respiratory and motor functions, before ERT initiation and upon last evaluation were compared.

RESULTS

Twelve patients (7 males) were identified. Median age at symptom onset was 24years [IQR=15.5; 36.0]. At baseline ventilation was invasive in 11 patients and noninvasive in one, with a median ventilation time of 24h [IQR=21.88; 24.00] (min 20; max 24). ERT was initiated at a median age of 52.5years [IQR=35.75; 66.50]. Median treatment duration was 55months [IQR=39.5; 81.0]. During observational period no adverse reaction to ERT was recorded, five patients (41.67%) died, three decreased their ventilation time by 30, 60 and 90min and two increased their assisted walking distance, by 80 and 20m.

CONCLUSION

Some patients at a very advanced stage of Pompe disease may show a mild benefit from ERT, in terms of increased time of autonomous ventilation and of enlarged distance in assisted walk. ERT can be initiated in these patients in order to retain their current level of independence and ability to perform daily life activities.

Long-term exposure to Myozyme results in a decrease of anti-drug antibodies in late-onset Pompe disease patients

Immunogenicity of recombinant human acid-alpha glucosidase (rhGAA) in enzyme replacement therapy (ERT) is a safety and efficacy concern in the management of late-onset Pompe disease (LOPD). However, long-term effects of ERT on humoral and cellular responses to rhGAA are still poorly understood. To better understand the impact of immunogenicity of rhGAA on the efficacy of ERT, clinical data and blood samples from LOPD patients undergoing ERT for >4 years (n = 28) or untreated (n = 10) were collected and analyzed. In treated LOPD patients, anti-rhGAA antibodies peaked within the first 1000 days of ERT, while long-term exposure to rhGAA resulted in clearance of antibodies with residual production of non-neutralizing IgG. Analysis of  T cell responses to rhGAA showed detectable T cell reactivity only after in vitro restimulation. Upregulation of several cytokines and chemokines was detectable in both treated and untreated LOPD subjects, while IL2 secretion was detectable only in subjects who received ERT. These results indicate that long-term ERT in LOPD patients results in a decrease in antibody titers and residual production of non-inhibitory IgGs. Immune responses to GAA following long-term ERT do not seem to affect efficacy of ERT and are consistent with an immunomodulatory effect possibly mediated by regulatory T cells.

The French Pompe registry. Baseline characteristics of a cohort of 126 patients with adult Pompe disease

Pompe disease is a rare autosomal recessive muscle lysosomal glycogenosis, characterised by limb-girdle muscle weakness and frequent respiratory involvement. The French Pompe registry was created in 2004 with the initial aim of studying the natural history of French patients with adult Pompe disease. Since the marketing in 2006 of enzyme replacement therapy (alglucosidase alfa, Myozyme(®)), the French Pompe registry has also been used to prospectively gather the biological and clinical follow-up data of all adult patients currently treated in France. This report describes the main clinical and molecular features, at the time of inclusion in the French registry, of 126 patients followed up in 21 hospital-based neuromuscular or metabolic centres. Sixty-five men and 61 women have been included in the registry. Median age at inclusion was 49 years, and the median age at onset of progressive limb weakness was 35 years. Fifty-five percent of the patients were walking without assistance, 24% were using a stick or a walking frame, and 21% were using a wheelchair. Forty-six percent of the patients needed ventilatory assistance, which was non-invasive in 35% of the cases. When performed, muscle biopsies showed specific features of Pompe disease in less than two-thirds of the cases, confirming the importance of acid alpha-glucosidase enzymatic assessment to establish the diagnosis. Molecular analysis detected the common c.-32-13T>G mutation, in at least one allele, in 90% of patients. The French Pompe registry is so far the largest country-based prospective study of patients with Pompe disease, and further analysis will be performed to study the impact of enzyme replacement therapy on the progression of the disease.