Pulmonary function tests (maximum inspiratory pressure, maximum expiratory pressure, vital capacity, forced vital capacity) predict ventilator use in late-onset Pompe disease

Defining clinically meaningful thresholds for forced vital capacity in patients with neuromuscular disorders: Lessons learned from the COMET study in Pompe disease

BackgroundRespiratory impairment in neuromuscular disorders (NMDs) is generally assessed using forced vital capacity (FVC). Any improvement in FVC trajectory will delay ventilatory support; however, the change required for patients to perceive a noticeable clinical benefit, the clinically meaningful threshold (CMT), has not been defined in NMDs.ObjectiveTo derive the within-person and between-group CMTs for FVC (% predicted) in patients with late-onset Pompe disease (LOPD).MethodsThis analysis leverages data from the Phase 3 COMET trial (NCT02782741, registered 25 May 2016), which assessed the efficacy of avalglucosidase alfa (AVA) versus alglucosidase alfa (ALG) on upright FVC (% predicted) in LOPD. Anchor- and distribution-based methods were used to estimate the within-person and between-group CMTs for FVC at Weeks 49 and 97.ResultsCOMET enrolled 99 participants aged ≥18 years (52% male; mean age 48.0 years). The within-person CMT for absolute change in FVC expressed as % predicted was estimated as 3.0% [95% confidence interval (CI) 2.3, 3.8]. The proportion of patients with a meaningful increase in FVC was higher in the AVA versus ALG group across the CI of the estimated CMT (odds ratios: 2.3-2.6; nominal p-values: 0.026-0.058). The between-group CMT, needed to evaluate differences between treatment groups, was estimated as 2.1% predicted [95% CI 1.1, 3.1].ConclusionsWe identified a narrow range of within-person and between-group CMTs for upright FVC (% predicted) in LOPD. Post hoc application of these thresholds to COMET showed that a greater proportion of patients in the AVA group had clinically meaningful improvement in FVC versus ALG. These findings may aid in interpretation of data from studies in other NMDs.

Efficacy of avalglucosidase alfa on forced vital capacity percent predicted in treatment-naïve patients with late-onset Pompe disease: A pooled analysis of clinical trials

Background

The efficacy of avalglucosidase alfa (AVA) versus alglucosidase alfa (ALG) on forced vital capacity percent predicted (FVCpp) in patients with late-onset Pompe disease (LOPD) has been assessed in the Phase 3 COMET trial (NCT02782741). Due to the rarity of LOPD and thus small sample size in COMET, additional data were analyzed to gain further insights into the efficacy of AVA versus ALG.

Methods

Data from treatment-naive patients with LOPD were pooled from COMET and Phase 1/2 NEO1/NEO-EXT (NCT01898364/NCT02032524) trials for patients treated with AVA, and Phase 3 LOTS trial (NCT00158600) for patients treated with ALG. Regression analyses using mixed models with repeated measures consistent with those pre-specified in COMET were performed post-hoc. Analyses were adjusted for trials and differences in baseline characteristics. Four models were developed: Model 1 considered all trials; Model 2 included Phase 3 trials; Model 3 included Phase 3 trials and was adjusted for baseline ventilation use; Model 4 included COMET and NEO1/NEO-EXT (i.e., AVA trials only).

Results

Overall, 100 randomized patients from COMET (AVA, n = 51, ALG, n = 49), 60 from LOTS (ALG arm only), and three patients from NEO1/NEO-EXT (who received open-label AVA only) were considered for analysis. Mean age at enrollment was similar across trials (45.3-50.3 years); however, patients from LOTS had a longer mean duration of disease versus COMET and NEO1/NEO-EXT trials (9.0 years and 0.5-2.2 years, respectively) and younger mean age at diagnosis (36.2 years and 44.7-48.6 years, respectively). Least squares mean (95% confidence interval) improvement from baseline in FVCpp at Week 49-52 for AVA versus ALG was 2.43 (-0.13; 4.99) for COMET (n = 98); 2.31 (0.06; 4.57) for Model 1 (n = 160); 2.43 (0.21; 4.65) for Model 2 (n = 157); 2.80 (0.54; 5.05) for Model 3 (n = 154); and 2.27 (-0.30; 4.45) for Model 4 (n = 101).

Conclusions

Models 1 to 3, which had an increased sample size versus COMET, demonstrated a nominally significant effect on FVCpp favoring AVA versus ALG after 1 year of treatment, consistent with results from COMET.

Changes in forced vital capacity over ≤ 13 years among patients with late-onset Pompe disease treated with alglucosidase alfa: new modeling of real-world data from the Pompe Registry

BACKGROUND

Chronic respiratory insufficiency from progressive muscle weakness causes morbidity and mortality in late-onset Pompe disease (LOPD). Previous Pompe Registry (NCT00231400) analyses for ≤ 5 years' alglucosidase alfa treatment showed a single linear time trend of stable forced vital capacity (FVC) % predicted.

METHODS

To assess longer term Pompe Registry data, piecewise linear mixed model regression analyses estimated FVC% predicted trajectories in invasive-ventilator-free patients with LOPD aged ≥ 5 years. We estimated annual FVC change 0-6 months, > 6 months-5 years, and > 5-13 years from treatment initiation, adjusting for baseline age, sex, and non-invasive ventilation.

FINDINGS

Among 485 patients (4612 FVC measurements; 8.3 years median follow-up), median ages at symptom onset, diagnosis, and alglucosidase alfa initiation were 34.3, 41.1, and 44.9 years, respectively. FVC% increased during the first 6 months' treatment (slope 1.83%/year; 95% confidence interval: 0.66, 3.01; P = 0.0023), then modestly declined -0.54%/year (-0.79, -0.30; P < 0.0001) during > 6 months-5 years, and -1.00%/year (-1.36, -0.63; P < 0.0001) during > 5-13 years. The latter two periods' slopes were not significantly different from each other (Pdifference = 0.0654) and were less steep than published natural history slopes (-1% to -4.6%/year). Estimated individual slopes were ≥ 0%/year in 96.1%, 30.3%, and 13.2% of patients during the 0-6 month, > 6 month-5 year, and > 5-13 year periods, respectively.

CONCLUSION

These real-world data indicate an alglucosidase alfa benefit on FVC trajectory that persists at least 13 years compared with published natural history data. Nevertheless, unmet need remains since most individuals demonstrate lung function decline 5 years after initiating treatment. Whether altered FVC trajectory impacts respiratory failure incidence remains undetermined.

TRIAL REGISTRATION

This study was registered (NCT00231400) on ClinicalTrials.gov on September 30, 2005, retrospectively registered.

[Diagnosis and Management of Late-Onset Pompe Disease]

Pompe disease is a lysosomal storage disorder, with onset between the first weeks after birth and adulthood, depending on its phenotype. It can affect multiple organ systems and presents itself with a wide variety of symptoms. Thus, recognizing Pompe disease is difficult. Especially since enzyme replacement therapy for Pompe disease was introduced (in Germany in 2006), early diagnosis by means of enzyme activity determination from dried blood spot analysis and genetic verification has become important for outcome and quality of life. When facing an obscure muscular disorder, it is crucial to consider Pompe disease. This article provides an overview about Pompe disease and focuses on the diagnosis of the late onset type. The most important aspects of interdiciplinary care for patients with Pompe disease are presented. Additionally, it contains a section focusing on psychosocial challenges for children with Pompe disease and their families, which may include mental disorders and social retreat, and gives advice on how to support parents of affected children.

Enzyme replacement therapy for late-onset Pompe disease

BACKGROUND

Pompe disease is caused by a deficiency of the enzyme acid alpha-glucosidase (GAA). People with infantile-onset disease have either a complete or a near-complete enzyme deficiency; people with late-onset Pompe disease (LOPD) retain some residual enzyme activity. GAA deficiency is treated with an intravenous infusion of recombinant human acid alglucosidase alfa, an enzyme replacement therapy (ERT). Alglucosidase alfa and avalglucosidase alfa are approved treatments, but cipaglucosidase alfa with miglustat is not yet approved.

OBJECTIVES

To assess the effects of enzyme replacement therapies in people with late-onset Pompe disease.

SEARCH METHODS

We searched the Cochrane Inborn Errors of Metabolism Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched MEDLINE OvidSP, clinical trial registries, and the reference lists of relevant articles and reviews. Date of last search: 21 April 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of ERT in people with LOPD of any age.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, extracted data, assessed the risk of bias and the certainty of the evidence (using GRADE). We resolved disagreements through discussion and by consulting a third author.

MAIN RESULTS

We included six trials (358 randomised participants) lasting from 12 to 78 weeks. A single trial reported on each comparison listed below. None of the included trials assessed two of our secondary outcomes: need for respiratory support and use of a walking aid or wheelchair. Certainty of evidence was most commonly downgraded for selective reporting bias. Alglucosidase alfa versus placebo (90 participants) After 78 weeks, alglucosidase alfa probably improves the six-minute walk test (6MWT) distance compared to placebo (mean difference (MD) 30.95 metres, 95% confidence interval (CI) 7.98 to 53.92; moderate-certainty evidence) and probably improves respiratory function, measured as the change in per cent (%) predicted forced vital capacity (FVC) (MD 3.55, 95% CI 1.46 to 5.64; moderate-certainty evidence). There may be little or no difference between the groups in occurrence of infusion reactions (risk ratio (RR) 1.21, 95% CI 0.57 to 2.61; low-certainty evidence), quality of life physical component score (MD -1.36 points, 95% CI -5.59 to 2.87; low-certainty evidence), or adverse events (RR 0.94, 95% CI 0.64 to 1.39; low-certainty evidence). Alglucosidase alfa plus clenbuterol versus alglucosidase alfa plus placebo (13 participants) The evidence is very uncertain about the effect of alglucosidase alfa plus clenbuterol compared to alglucosidase alfa plus placebo on: change in 6MWT distance after 52 weeks (MD 34.55 metres, 95% CI-10.11 to 79.21; very low-certainty evidence) and change in % predicted FVC (MD -13.51%, 95% CI -32.44 to 5.41; very low-certainty evidence). This study did not measure infusion reactions, quality of life, and adverse events. Alglucosidase alfa plus albuterol versus alglucosidase alfa plus placebo (13 participants) The evidence is very uncertain about the effect of alglucosidase alfa plus albuterol compared to alglucosidase alfa plus placebo on: change in 6MWT distance after 52 weeks (MD 30.00 metres, 95% CI 0.55 to 59.45; very low-certainty evidence), change in % predicted FVC (MD -4.30%, 95% CI -14.87 to 6.27; very low-certainty evidence), and risk of adverse events (RR 0.67, 95% CI 0.38 to 1.18; very low-certainty evidence). This study did not measure infusion reactions and quality of life. VAL-1221 versus alglucosidase alfa (12 participants) Insufficient information was available about this trial to generate effect estimates measured at one year or later. Compared to alglucosidase alfa, VAL-1221 may increase or reduce infusion-associated reactions at three months, but the evidence is very uncertain (RR 2.80, 95% CI 0.18 to 42.80). This study did not measure quality of life and adverse events. Cipaglucosidase alfa plus miglustat versus alglucosidase alfa plus placebo (125 participants) Compared to alglucosidase alfa plus placebo, cipaglucosidase alfa plus miglustat may make little or no difference to: 6MWT distance at 52 weeks (MD 13.60 metres, 95% CI -2.26 to 29.46); infusion reactions (RR 0.94, 95% CI 0.49 to 1.80); quality of life scores for physical function (MD 1.70, 95% CI -2.13 to 5.53) and fatigue (MD -0.30, 95% CI -2.76 to 2.16); and adverse effects potentially related to treatment (RR 0.83, 95% CI 0.49 to 1.40) (all low-certainty evidence). Cipaglucosidase alfa plus miglustat probably improves % predicted FVC compared to alglucosidase alfa plus placebo (MD 3.10%, 95% CI 1.04 to 5.16; moderate-certainty evidence); however, it may make little or no change in % predicted sniff nasal inspiratory pressure (MD -0.06%, 95% CI -8.91 to 7.71; low-certainty evidence). Avalglucosidase alfa versus alglucosidase alfa (100 participants) After 49 weeks, avalglucosidase alfa probably improves 6MWT compared to alglucosidase alfa (MD 30.02 metres, 95% CI 1.84 to 58.20; moderate-certainty evidence). Avalglucosidase alfa probably makes little or no difference to % predicted FVC compared to alglucosidase alfa (MD 2.43%, 95% CI -0.08 to 4.94; moderate-certainty evidence). Avalglucosidase alfa may make little or no difference to infusion reactions (RR 0.78, 95% CI 0.42 to 1.45), quality of life (MD 0.77, 95% CI -2.09 to 3.63), or treatment-related adverse events (RR 0.92, 95% CI 0.61 to 1.40), all low-certainty evidence.

AUTHORS' CONCLUSIONS

One trial compared the effect of ERT to placebo in LOPD, showing that alglucosidase alfa probably improves 6MWT and respiratory function (both moderate-certainty evidence). Avalglucosidase alfa probably improves 6MWT compared with alglucosidase alfa (moderate-certainty evidence). Cipaglucosidase plus miglustat probably improves FVC compared to alglucosidase alfa plus placebo (moderate-certainty evidence). Other trials studied the adjunct effect of clenbuterol and albuterol along with alglucosidase alfa, with little to no evidence of benefit. No significant rise in adverse events was noted with all ERTs. The impact of ERT on some outcomes remains unclear, and longer RCTs are needed to generate relevant information due to the progressive nature of LOPD. Alternative resources, such as post-marketing registries, could capture some of this information.

Monitoring and Management of Respiratory Function in Pompe Disease: Current Perspectives

Pompe disease (PD) is a neuromuscular disorder caused by a deficiency of acid alpha-glucosidase (GAA) - a lysosomal enzyme responsible for hydrolyzing glycogen. GAA deficiency leads to accumulation of glycogen in lysosomes, causing cellular disruption. The severity of PD is directly related to the extent of GAA deficiency - if no or minimal GAA is produced, symptoms are severe and manifest in infancy, known as infantile onset PD (IOPD). If left untreated, infants with IOPD experience muscle hypotonia and cardio-respiratory failure leading to significant morbidity and mortality in the first year of life. In contrast, late-onset PD (LOPD) patients have more GAA activity and present later in life, but also have significant respiratory function decline. Despite FDA-approved enzyme replacement therapy, respiratory insufficiency remains a major cause of morbidity and mortality, emphasizing the importance of early detection and management of respiratory complications. These complications include impaired cough and airway clearance, respiratory muscle weakness, sleep-related breathing issues, and pulmonary infections. This review aims to provide an overview of the respiratory pathology, monitoring, and management of PD patients. In addition, we discuss the impact of novel approaches and therapies on respiratory function in PD.

Prediction of respiratory impairment in myotonic dystrophies using the 'Respiratory involvement symptom checklist' (Respicheck)

Chronic hypoventilation due to involvement of respiratory muscles is a frequent symptom in autosomal dominant inherited myotonic dystrophies, especially in type 1 (DM1), leading to a severely reduced quality of life, an early need for ventilatory support, or premature death. Thus, early knowledge of respiratory muscle weakness is essential to initiate further diagnostic and therapeutic measures. To get early, simple, and reliable information about respiratory impairment in DM patients, we performed a prospective controlled cohort study with DM1 and DM2 patients analysing the suitability of 'Respiratory involvement symptom checklist (Respicheck) as a clinically meaningful screening questionnaire for ventilatory impairment in patients with DM1 or DM2. Clinical assessments included a one-time pulmonary function test (spirometry and manometry) and the completion of the Respicheck. 172 participants were enrolled in this study (74 DM1, 72 DM2, 26 healthy controls). With a cut-off RespicheckCAT score of 4, the Respicheck can distinguish between patients with and without respiratory impairment with higher sensitivity and positive predictive value for DM1 than DM2 patients (DM1: sensitivity 77-87; positive predictive value 50-94%; DM2: sensitivity 67-80%; positive predictive value 14-38). In summary, our results confirm a clinically meaningful use of the Respicheck to detect respiratory impairments predominantly in DM1 patients.

A multi-trial, retrospective analysis of the antihypertensive effects of high-resistance, low-volume inspiratory muscle strength training

Above-normal blood pressure (BP) is a primary risk factor for cardiovascular diseases. In a retrospective analysis of five pilot trials, we assessed the BP-lowering effects of high-resistance inspiratory muscle strength training (IMST) in adults aged 18-82 years and the impact of IMST on maximal inspiratory pressure (PIMAX), a gauge of inspiratory muscle strength and independent disease risk factor. Participants were randomized to high-resistance IMST (75% PIMAX) or low-resistance sham (15% PIMAX) training (30 breaths/day, 5-7 days/wk, 6 wk). IMST (n = 67) reduced systolic BP (SBP) by 9 ± 6 mmHg (P < 0.01) and diastolic BP (DBP) by 4 ± 4 mmHg (P < 0.01). IMST-related reductions in SBP and DBP emerged by week 2 of training (-4 ± 8 mmHg and -3 ± 6 mmHg; P ≤ 0.01, respectively) and continued across the 6-wk intervention. SBP and DBP were unchanged with sham training (n = 61, all P > 0.05). Select subject characteristics slightly modified the impact of IMST on BP. Greater reductions in SBP were associated with older age (β = -0.07 ± 0.03; P = 0.04) and greater reductions in DBP associated with medication-naïve BP (β = -3 ± 1; P = 0.02) and higher initial DBP (β = -0.12 ± 0.05; P = 0.04). PIMAX increased with high-resistance IMST and low-resistance sham training, with a greater increase from high-resistance IMST (+20 ± 17 vs. +6 ± 14 cmH2O; P < 0.01). Gains in PIMAX had a modest inverse relation with age (β = -0.20 ± 0.09; P = 0.03) and baseline PIMAX (β = -0.15 ± 0.07; P = 0.04) but not to reductions in SBP or DBP. These compiled findings from multiple independent trials provide the strongest evidence to date that high-resistance IMST evokes clinically significant reductions in SBP and DBP, and increases in PIMAX, in adult men and women.NEW & NOTEWORTHY In young-to-older adult men and women, 6 wk of high-resistance inspiratory muscle strength training lowers casual systolic and diastolic blood pressure by 9 mmHg and 4 mmHg, respectively, with initial reductions observed by week 2 of training. Given blood pressure outcomes with the intervention were only slightly altered by subject baseline characteristics (i.e., age, blood pressure medication, and health status), inspiratory muscle strength training is effective in lowering blood pressure in a broad range of adults.

High-risk screening of late-onset Pompe disease: A different early portrait in China

Introduction

The lack of knowledge regarding the differences between Chinese and other ethnicities in the early manifestation of late-onset Pompe disease (LOPD) prohibits the development of an effective screening strategy. We conducted a multicenter screening study to determine LOPD prevalence in high-risk populations and define the early manifestation of LOPD in China.

Methods

Between August 2020 and April 2021, the participants were prospectively identified through medical examination at 20 centers from inpatient departments and outpatient neuromuscular clinics in China. The inclusion criteria were as follows: (1) age ≥ 1 year and (2) either one of the following conditions: (a) persistent hyperCKemia, (b) muscle weakness of the axial and/or limb-girdle muscles, or (c) unexplained restrictive respiratory insufficiency (RI). Enzymatic activity of acid α-glucosidase (GAA) was measured in a dried blood spot (DBS) using a tandem mass spectrometry (MS/MS) assay. Next-generation sequencing (NGS) was used to evaluate all samples with decreased GAA activity, searching for GAA mutations and pseudodeficiency alleles.

Results

Among the 492 cases, 26 positive samples (5.3%) were detected in the DBS test. Molecular studies confirmed a diagnosis of LOPD in eight cases (1.6%). Using MS/MS assay, GAA activities in individuals with pseudodeficiency could be distinguished from those in patients with LOPD. The median interval from the onset of symptoms to diagnosis was 5 years. All patients also showed RI, with a mean forced vital capacity (FVC) of 48%, in addition to axial/proximal muscle weakness. The creatine kinase (CK) level ranged from normal to no more than 5-fold the upper normal limit (UNL). LOPD with isolated hyperCKemia was not identified.

Conclusion

Less frequent hyperCKemia and predominant RI depict a different early portrait of adult Chinese patients with LOPD. A modified high-risk screening strategy should be proposed for the early diagnosis of Chinese patients with LOPD.

Effect of Test Interface on Respiratory Muscle Activity and Pulmonary Function During Respiratory Testing in Healthy Adults

Purpose

The mouthpiece is the standard interface for spirometry tests. Although the use of a mouthpiece can be challenging for patients with orofacial weakness, maintaining a proper seal with a facemask can be an issue for healthy individuals during forceful efforts. We compared respiratory muscle activity and tests using a mouthpiece and facemask in healthy adults to investigate whether they can be used interchangeably.

Methods

In this observational study, subjects (n=12) completed forced vital capacity, maximal respiratory pressure, and peak cough flow with a mouthpiece and facemask. Root mean square values of the genioglossus, diaphragm, scalene, and sternocleidomastoid were compared between conditions.

Results

When switching from a mouthpiece to a facemask, significantly higher values were seen for peak cough flow (average bias= -54.36 L/min, p<0.05) and the difference seen with MEP and MIP were clinically significant (average bias: MEP=27.33, MIP=-5.2). Additionally, submental activity was significantly greater when MIP was conducted with a mouthpiece. No significant differences were seen in respiratory muscle activity during resting breathing or spirometry.

Conclusion

There are clinically significant differences with cough and MEP tests and neck muscles are activated differently based on interface. Considering the small sample size, our findings suggest a facemask may be used to complete some PFTs.

Safety and efficacy of avalglucosidase alfa versus alglucosidase alfa in patients with late-onset Pompe disease (COMET): a phase 3, randomised, multicentre trial

BACKGROUND

Pompe disease is a rare, progressive neuromuscular disorder caused by deficiency of acid α-glucosidase (GAA) and accumulation of lysosomal glycogen. We assessed the safety and efficacy of avalglucosidase alfa, a recombinant human GAA enzyme replacement therapy specifically designed for enhanced mannose-6-phosphate-receptor targeting and enzyme uptake aimed at increased glycogen clearance, compared with the current approved standard of care, alglucosidase alfa, in patients with late-onset Pompe disease.

METHODS

We did a randomised, double-blind, phase 3 trial at 55 sites in 20 countries. We enrolled individuals (aged ≥3 years) with enzymatically confirmed late-onset Pompe disease who had never received treatment. We used a centralised treatment allocation system to randomly allocate participants to either avalglucosidase alfa or alglucosidase alfa. Participants and investigators were unaware of their treatment allocation. The primary outcome measure was change from baseline to week 49 in upright forced vital capacity percent (FVC%) predicted. We used a hierarchical fixed sequential testing strategy, whereby non-inferiority of avalglucosidase alfa compared with alglucosidase alfa was assessed first, with a non-inferiority margin of 1·1. If non-inferiority was seen, then superiority was tested with a 5% significance level. The key secondary objective was effect on functional endurance, measured by the 6-minute walk test (6MWT). Safety was assessed, including treatment-emergent adverse events and infusion-associated reactions. The modified intent-to-treat population was the primary analysis population for all efficacy analyses. The safety population was the analysis population for safety analyses. This trial is registered with ClinicalTrials.gov, NCT02782741. We report results of the 49-week primary analysis period.

FINDINGS

Between Nov 2, 2016, and March 29, 2019, 100 participants were randomly allocated avalglucosidase alfa (n=51) or alglucosidase alfa (n=49). Treatment with avalglucosidase alfa resulted in a least-squares mean improvement in upright FVC% predicted of 2·89% (SE 0·88) compared with 0·46% (0·93) with alglucosidase alfa at week 49 (difference 2·43% [95% CI -0·13 to 4·99]). Non-inferiority was shown because the lower bound of the 95% CI for the difference far exceeded the predefined non-inferiority margin but did not exclude 0 (p=0·0074). Superiority was not reached (p=0·063), so formal testing was stopped, as per the testing hierarchy. Improvements were also seen in the 6MWT with avalglucosidase alfa compared with alglucosidase alfa, with greater increases in distance covered (difference 30·01 m [95% CI 1·33 to 58·69]) and percent predicted (4·71% [0·25 to 9·17]). Treatment-emergent adverse events potentially related to treatment were reported in 23 (45%) of 51 participants in the avalglucosidase alfa group and in 24 (49%) of 49 in the alglucosidase alfa group, and infusion-associated reactions were reported in 13 (26%) participants in the avalglucosidase alfa group and 16 (33%) in the alglucosidase alfa group. Of the five trial withdrawals, all in the alglucosidase alfa group, four were due to adverse events, including two infusion-associated reactions. Serious treatment-emergent adverse events were reported in eight (16%) participants who received avalglucosidase alfa and in 12 (25%) who received alglucosidase alfa. One participant treated with alglucosidase alfa died because of acute myocardial infarction determined to be unrelated to treatment. Antidrug antibody responses were similar in both groups. High and persistent titres (≥12 800) and neutralising antibodies were more common with alglucosidase alfa (in 16 [33%] participants) than with avalglucosidase alfa (ten [20%]).

INTERPRETATION

We consider that this study provides evidence of clinically meaningful improvement with avalglucosidase alfa therapy over alglucosidase alfa in respiratory function, ambulation, and functional endurance, with no new safety signals reported. An open-label extended-treatment period is ongoing to confirm the long-term safety and efficacy of avalglucosidase alfa, with the aim for this therapy to become the new standard treatment in late-onset Pompe disease.

FUNDING

Sanofi Genzyme.

Chest MRI to diagnose early diaphragmatic weakness in Pompe disease

Background

In Pompe disease, an inherited metabolic muscle disorder, severe diaphragmatic weakness often occurs. Enzyme replacement treatment is relatively ineffective for respiratory function, possibly because of irreversible damage to the diaphragm early in the disease course. Mildly impaired diaphragmatic function may not be recognized by spirometry, which is commonly used to study respiratory function. In this cross-sectional study, we aimed to identify early signs of diaphragmatic weakness in Pompe patients using chest MRI.

Methods

Pompe patients covering the spectrum of disease severity, and sex and age matched healthy controls were prospectively included and studied using spirometry-controlled sagittal MR images of both mid-hemidiaphragms during forced inspiration. The motions of the diaphragm and thoracic wall were evaluated by measuring thoracic cranial-caudal and anterior–posterior distance ratios between inspiration and expiration. The diaphragm shape was evaluated by measuring the height of the diaphragm curvature. We used multiple linear regression analysis to compare different groups.

Results

We included 22 Pompe patients with decreased spirometry results (forced vital capacity in supine position < 80% predicted); 13 Pompe patients with normal spirometry results (forced vital capacity in supine position ≥ 80% predicted) and 18 healthy controls. The mean cranial-caudal ratio was only 1.32 in patients with decreased spirometry results, 1.60 in patients with normal spirometry results and 1.72 in healthy controls (p < 0.001). Anterior–posterior ratios showed no significant differences. The mean height ratios of the diaphragm curvature were 1.41 in patients with decreased spirometry results, 1.08 in patients with normal spirometry results and 0.82 in healthy controls (p = 0.001), indicating an increased curvature of the diaphragm during inspiration in Pompe patients.

Conclusions

Even in early-stage Pompe disease, when spirometry results are still within normal range, the motion of the diaphragm is already reduced and the shape is more curved during inspiration. MRI can be used to detect early signs of diaphragmatic weakness in patients with Pompe disease, which might help to select patients for early intervention to prevent possible irreversible damage to the diaphragm.

Deoxynucleoside therapy for respiratory involvement in adult patients with thymidine kinase 2-deficient myopathy

Background

Recessive mutations in the thymidine kinase 2 (TK2) gene cause a rare mitochondrial myopathy, frequently with severe respiratory involvement. Deoxynucleoside therapy is currently under investigation.

Research question

What is the impact of nucleosides in respiratory function in patients with TK2-deficient myopathy?

Study design and methods

Retrospective observational study of patients treated with deoxycytidine and deoxythymidine. Evaluations were performed every 3 to 4 months after treatment during approximately 30 months. Forced vital capacity (FVC), maximuminspiratory and expiratory pressures (MIP/MEP), sniff nasal inspiratory pressure (SNIP), cough peak flow (CPF), arterial blood gas and nocturnal pulse oximeter (SpO2) were collected.

Results

We studied six patients, five of which were women, with a median age at onset of symptoms was 35.8 (range 5 to 60) years old. Patients presented a restrictive ventilatory pattern (median FVC of 50 (26 to 71)%) and severe neuromuscular respiratory weakness (MIP 38 (12 to 47)% and SNIP 14 (8 to 19) cmH2O). Four patients required ventilatory support before starting the treatment. FVC improved by 6%, proportion of sleep time with SpO2 <90% diminished from 14% to 0%, CPF increased by 23%, MEP increased by 73%, production and management of bronchial secretions improved and respiratory infections diminished.

Interpretation

Early detection of respiratory involvement requires an active search, even in asymptomatic patients. The nucleosides therapy may improve respiratory function, and stabilise the loss of respiratory capacity.

Respiratory failure and sleep-disordered breathing in late-onset Pompe disease: a narrative review

Late-onset Pompe disease (LOPD) is a rare autosomal recessive glycogen storage disease that results in accumulation of glycogen in muscle cells causing muscular weakness. It causes a progressive proximal myopathy, accompanied by respiratory muscle weakness, which can lead to ventilatory failure. In untreated LOPD, the most common cause of death is respiratory failure. Patients suffering from respiratory compromise may present with symptoms of sleep-disordered breathing (SDB) before overt signs of respiratory failure. Diaphragm weakness leads to nocturnal hypoventilation, which can result in sleep disruption. Both subjective and objective sleep quality can be impaired with associated excessive daytime sleepiness (EDS). Health-related quality of life worsens as sleep disturbance increases. The mainstay of treatment for SDB and respiratory failure in LOPD is non-invasive ventilation (NIV), which aims to ensure adequate ventilation, particularly during sleep, and prevent acute hypercapnic failure. These patients are at risk of acute deterioration due to lower respiratory tract infections; effective secretion clearance and vaccination against common pathogens is an important facet of care. Whilst disease-modifying enzyme replacement therapy (ERT) delays progression of locomotor dysfunction and prolongs life, its effect on respiratory function and SDB remains unclear. There are no data demonstrating the impact of ERT on sleep quality or SDB.

Respiratory function during enzyme replacement therapy in late-onset Pompe disease: longitudinal course, prognostic factors, and the impact of time from diagnosis to treatment start

OBJECTIVE

To examine respiratory muscle function among late-onset Pompe disease (LOPD) patients in the Pompe Registry (NCT00231400/Sanofi Genzyme) during enzyme replacement therapy (ERT) with alglucosidase alfa by assessing the longitudinal course of forced vital capacity (FVC), prognostic factors for FVC, and impact of time from diagnosis to ERT initiation.

METHODS

Longitudinal FVC data from LOPD (symptom onset > 12 months or ≤ 12 months without cardiomyopathy) patients were analyzed. Patients had to have baseline FVC (percent predicted upright) assessments at ERT start and ≥ 2 valid post-baseline assessments. Longitudinal analyses used linear mixed-regression models.

RESULTS

Among 396 eligible patients, median baseline FVC was 66.9% (range 9.3-126.0). FVC remained stable during the 5-year follow-up (slope = - 0.17%, p = 0.21). Baseline FVC was lower among various subgroups, including patients who were male; older at ERT initiation; had a longer duration from symptom onset to ERT initiation; and had more advanced disease at baseline (based on respiratory support use, inability to ambulate, ambulation device use). Age at symptom onset was not associated with baseline degree of respiratory dysfunction. Differences between subgroups observed at baseline remained during follow-up. Shorter time from diagnosis to ERT initiation was associated with higher FVC after 5 years in all patients and the above subgroups using a cut-off of 1.7 years.

CONCLUSION

FVC stability over 5 years suggests that respiratory function is preserved during long-term ERT in real-world settings. Early initiation of alglucosidase alfa was associated with preservation of FVC in LOPD patients with better respiratory function at the time of treatment initiation.

Utility of maximum inspiratory and expiratory pressures as a screening method for respiratory insufficiency in slowly progressive neuromuscular disorders

The aim of this study was to assess whether different cut-offs of maximum inspiratory and/or expiratory pressure (MIP/MEP) are valuable screening parameters to detect restrictive respiratory insufficiency. Spirometry, MIP, MEP and capillary blood gas analysis were obtained from patients with confirmed neuromuscular disorders. We calculated regression analysis, sensitivity, specificity and predictive values. We enrolled 29 patients with myotonic dystrophy type 1 (DM1), 19 with late-onset Pompe disease (LOPD), and 24 with spinal muscular atrophy type 3. Moderate to high reduction in manometry was exclusively found in LOPD and DM1 patients. Significant associations were found between manometry and spirometry. Highest adjusted r² was found for MIP % predicted and forced vital capacity (FVC) % predicted. Manometry predicted abnormal FVC and forced expiratory volume 1 s (FEV1). MEP > 80 cmH₂O predicted normal FVC and FEV1, regardless of cut-off values. MIP and MEP did not positively predict alterations in capillary blood gas analysis. Disease-specific cut-offs of manometry did not increase the prediction rate of patients with abnormal FVC and FEV1. Predicted values should be calculated for a more comprehensive interpretation of manometry results. MIP and MEP can serve as a screening parameter for patients with neuromuscular disorders, but parallel testing of both MIP and MEP needs to be performed to increase the positive prediction probability across disease groups.

Pulmonary outcome measures in long-term survivors of infantile Pompe disease on enzyme replacement therapy: A case series

OBJECTIVES

To report the respiratory function of school-aged children with infantile Pompe disease (IPD) who started enzyme replacement therapy (ERT) in infancy and early childhood.

STUDY DESIGN

This is a retrospective chart review of pulmonary function tests of: (a) patients with IPD 5 to 18 years of age, (b) who were not ventilator dependent, and (c) were able to perform upright and supine spirometry. Subjects were divided into a younger (5-9 years) and older cohort (10-18 years) for the analysis. Upright and supine forced vital capacity (FVC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were analyzed.

RESULTS

Fourteen patients, all cross-reactive immunologic material (CRIM)-positive, met the inclusion criteria and were included in this study. Mean upright and supine FVC were 70.3% and 64.9% predicted, respectively, in the 5- to 9-year-old cohort; and 61.5% and 52.5% predicted, respectively, in the 10- to 18-year-old group. Individual patient trends showed stability in FVC overtime in six of the 14 patients. MIPs and MEPs were consistent with inspiratory and expiratory muscle weakness in the younger and older age group but did not decline with age.

CONCLUSION

Data from this cohort of CRIM-positive patients with IPD showed that ERT is able to maintain respiratory function in a subgroup of patients whereas others had a steady decline. There was a statistically significant decline in FVC from the upright to a supine position in both the younger and older age groups of CRIM-positive ERT-treated patients. Before ERT, patients with IPD were unable to maintain independent ventilation beyond the first few years of life.

The nature of respiratory muscle weakness in patients with late-onset Pompe disease

Late-onset Pompe disease (LOPD) causes myopathy of skeletal and respiratory muscles, and phrenic nerve pathology putatively contributes to diaphragm weakness. The aim of this study was to investigate neural contributions to diaphragm dysfunction, usefulness of diaphragm ultrasound, and involvement of expiratory abdominal muscles in LOPD. Thirteen patients with LOPD (7 male, 51±17 years) and 13 age- and gender-matched controls underwent respiratory muscle strength testing, ultrasound evaluation of diaphragm excursion and thickness, cortical and cervical magnetic stimulation (MS) of the diaphragm with simultaneous recording of surface electromyogram and twitch transdiaphragmatic pressure (twPdi; n = 6), and MS of the abdominal muscles with recording of twitch gastric pressure (twPgas; n = 6). The following parameters were significantly reduced in LOPD patients versus controls: forced vital capacity (p<0.01), maximum inspiratory and expiratory pressure (both p<0.001), diaphragm excursion velocity (p<0.05), diaphragm thickening ratio (1.8 ± 0.4 vs. 2.6 ± 0.6, p<0.01), twPdi following cervical MS (12.0 ± 6.2 vs. 19.4 ± 4.8 cmH₂O, p<0.05), and twPgas following abdominal muscle stimulation (8.8 ± 8.1 vs. 34.6 ± 17.1 cmH₂O, p<0.01). Diaphragm motor evoked potentials and compound muscle action potentials showed no between-group differences. In conclusion, phrenic nerve involvement in LOPD could not be electrophysiologically confirmed. Ultrasound supports assessment of diaphragm function. Abdominal expiratory muscles are functionally involved in LOPD.

ERS statement on respiratory muscle testing at rest and during exercise

Assessing respiratory mechanics and muscle function is critical for both clinical practice and research purposes. Several methodological developments over the past two decades have enhanced our understanding of respiratory muscle function and responses to interventions across the spectrum of health and disease. They are especially useful in diagnosing, phenotyping and assessing treatment efficacy in patients with respiratory symptoms and neuromuscular diseases. Considerable research has been undertaken over the past 17 years, since the publication of the previous American Thoracic Society (ATS)/European Respiratory Society (ERS) statement on respiratory muscle testing in 2002. Key advances have been made in the field of mechanics of breathing, respiratory muscle neurophysiology (electromyography, electroencephalography and transcranial magnetic stimulation) and on respiratory muscle imaging (ultrasound, optoelectronic plethysmography and structured light plethysmography). Accordingly, this ERS task force reviewed the field of respiratory muscle testing in health and disease, with particular reference to data obtained since the previous ATS/ERS statement. It summarises the most recent scientific and methodological developments regarding respiratory mechanics and respiratory muscle assessment by addressing the validity, precision, reproducibility, prognostic value and responsiveness to interventions of various methods. A particular emphasis is placed on assessment during exercise, which is a useful condition to stress the respiratory system.

Metabolic Myopathies and the Respiratory System

Metabolic myopathies are a heterogeneous group of disorders characterized by inherited defects of enzymatic pathways involved in muscle cellular energetics and adenosine triphosphate synthesis. Skeletal and respiratory muscles are most affected. There are multiple mechanisms of disease. The age of onset and prognosis vary. Metabolic myopathies cause exercise intolerance, myalgia, and increase in muscle breakdown products during exercise. Some affect smooth muscle like the diaphragm and cause respiratory failure. The pathophysiology is complex and the evidence in literature to guide diagnosis and management is sparse. Treatment is limited. This review discusses the pathophysiology and diagnostic evaluation of these disorders.

A case of unexplained dyspnoea: when lung function testing matters!

“Lung function corner” articles in Breathe present the results of a lung function test and the authors then debate the interpretation, including potential controversies and background from the literature. As section editors of this newly created section of Breathe, we felt it was important to write the first article, which highlights the usefulness of lung function testing in guiding clinical diagnosis especially in difficult cases such the one we discuss here.

Diverse methods are available for assessment of the respiratory muscles; the technique used should be tailored to the question posed.http://ow.ly/ChbX30m91bt

Pompe Disease: From Basic Science to Therapy

Pompe disease is a rare and deadly muscle disorder. As a clinical entity, the disease has been known for over 75 years. While an optimist might be excited about the advances made during this time, a pessimist would note that we have yet to find a cure. However, both sides would agree that many findings in basic science-such as the Nobel prize-winning discoveries of glycogen metabolism, the lysosome, and autophagy-have become the foundation of our understanding of Pompe disease. The disease is a glycogen storage disorder, a lysosomal disorder, and an autophagic myopathy. In this review, we will discuss how these past discoveries have guided Pompe research and impacted recent therapeutic developments.

[Clinical characteristics and GAA gene mutation in children with glycogen storage disease type II: an analysis of 3 cases]

Glycogen storage disease type II (GSD II) is an autosomal recessive disorder caused by a deficiency of the lysosomal glycogen-hydrolyzing enzyme acid α-glucosidase (GAA) and can affect multiple systems including the heart and skeletal muscle. The aim of this study was to investigate three children with GSD II confirmed by GAA gene analysis and to report their clinical characteristics and gene mutations. One case was classified as infantile-onset GSD II, and two cases as late-onset GSD II. The infantile-onset patient (aged 4 months) showed no weight increase and had dyspnea, muscle hypotonia, and increased alanine aminotransferase and creatine kinase; echocardiography showed hypertrophic cardiomyopathy. The late-onset patients (aged 8 years and 13 years respectively) showed persistently elevated liver enzymes; one of them had recurrent respiratory tract infection and restrictive ventilation disorder, and the other case showed significantly increased creatase but normal electromyographic findings. Peripheral blood genetic testing for GAA gene showed six pathogenic mutations in the three cases, and the mutations c.2738C>T and c.568C>T had not been reported. Therefore, peripheral blood genetic testing for GAA gene is an effective diagnostic method.

A study on the safety and efficacy of reveglucosidase alfa in patients with late-onset Pompe disease

BACKGROUND

Late-onset Pompe disease is a rare genetic neuromuscular disorder caused by lysosomal acid alpha-glucosidase (GAA) deficiency that ultimately results in mobility loss and respiratory failure. Current enzyme replacement therapy with recombinant human (rh)GAA has demonstrated efficacy in subjects with late-onset Pompe disease. However, long-term effects of rhGAA on pulmonary function have not been observed, likely related to inefficient delivery of rhGAA to skeletal muscle lysosomes and associated deficits in the central nervous system. To address this limitation, reveglucosidase alfa, a novel insulin-like growth factor 2 (IGF2)-tagged GAA analogue with improved lysosomal uptake, was developed. This study evaluated the pharmacokinetics, safety, and exploratory efficacy of reveglucosidase alfa in 22 subjects with late-onset Pompe disease who were previously untreated with rhGAA.

RESULTS

Reveglucosidase alfa plasma concentrations increased linearly with dose, and the elimination half-life was <1.2 h. Eighteen of 22 subjects completed 72 weeks of treatment. The most common adverse events were hypoglycemia (63%), dizziness, fall, headache, and nausea (55% for each). Serious adverse events included hypersensitivity (n = 1), symptomatic hypoglycemia (n = 2), presyncope (n = 1), and acute cardiac failure (n = 1). In the dose-escalation study, all treated subjects tested positive for anti-reveglucosidase alfa, anti-rhGAA, anti-IGF1, and anti-IGF2 antibodies at least once. Subjects receiving 20 mg/kg of reveglucosidase alfa demonstrated increases in predicted maximum inspiratory pressure (13.9%), predicted maximum expiratory pressure (8.0%), forced vital capacity (-0.4%), maximum voluntary ventilation (7.4 L/min), and mean absolute walking distance (22.3 m on the 6-min walk test) at 72 weeks.

CONCLUSIONS

Additional studies are needed to further assess the safety and efficacy of this approach. Improvements in respiratory muscle strength, lung function, and walking endurance in subjects with LOPD may make up for the risk of hypersensitivity reactions and hypoglycemia. Reveglucosidase alfa may provide a new treatment option for patients with late-onset Pompe disease.

TRIAL REGISTRATION

ISRCTN01435772 and ISRCTN01230801 , registered 27 October 2011.

Sleep-Disordered Breathing and Effects of Noninvasive Ventilation in Patients with Late-Onset Pompe Disease

STUDY OBJECTIVES

In neuromuscular disease, non-invasive ventilation (NIV) is indicated if sleep-disordered breathing (SDB) or significant respiratory muscle weakness (RMW) is present. We investigated immediate and long-term effects of NIV on sleep and nocturnal ventilation in patients with late-onset Pompe disease (LOPD).

METHODS

Polysomnography and transcutaneous capnometry were performed in 22 adult patients. If indicated, NIV was initiated the subsequent night and follow-up sleep studies were scheduled. Sleep quality and health-related quality of life (HRQoL) were self-assessed using standard questionnaires.

RESULTS

Fourteen patients received enzyme replacement therapy (ERT), five patients were treatment-naÏve, and three individuals had previously stopped ERT. Fifteen patients reported symptoms of SDB, all showing abnormal sleep studies. Two patients had obstructive sleep apnea (OSA), three patients showed both OSA and nocturnal hypercapnia, four individuals had nocturnal hypercapnia, and two patients had both OSA and daytime hypercapnia. Four patients showed normal apnea-hypopnea index and CO₂ measures but nocturnal tachypnea, orthopnea, and significant RMW were present. Supine forced vital capacity (FVC) and positional drop of FVC were independent predictors of SDB. In patients with SDB, HRQoL was significantly reduced. NIV was initiated in 15 individuals and led to significant improvement of ventilation and oxygenation in the first night of treatment. Follow-up sleep studies revealed stable normoxia and normocapnia without deterioration of sleep outcomes for up to 40 months.

CONCLUSIONS

In LOPD, SDB is common and comprises both hypoventilation and OSA. NIV significantly improves respiration already in the first night of treatment. NIV warrants nocturnal long-term normoventilation without deterioration of sleep quality.

Practical Recommendations for Diagnosis and Management of Respiratory Muscle Weakness in Late-Onset Pompe Disease

Pompe disease is an autosomal-recessive lysosomal storage disorder characterized by progressive myopathy with proximal muscle weakness, respiratory muscle dysfunction, and cardiomyopathy (in infants only). In patients with juvenile or adult disease onset, respiratory muscle weakness may decline more rapidly than overall neurological disability. Sleep-disordered breathing, daytime hypercapnia, and the need for nocturnal ventilation eventually evolve in most patients. Additionally, respiratory muscle weakness leads to decreased cough and impaired airway clearance, increasing the risk of acute respiratory illness. Progressive respiratory muscle weakness is a major cause of morbidity and mortality in late-onset Pompe disease even if enzyme replacement therapy has been established. Practical knowledge of how to detect, monitor and manage respiratory muscle involvement is crucial for optimal patient care. A multidisciplinary approach combining the expertise of neurologists, pulmonologists, and intensive care specialists is needed. Based on the authors' own experience in over 200 patients, this article conveys expert recommendations for the diagnosis and management of respiratory muscle weakness and its sequelae in late-onset Pompe disease.