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.

Clinical and Molecular Disease Spectrum and Outcomes in Patients with Infantile-Onset Pompe Disease

OBJECTIVES

To evaluate the clinical and molecular spectrum, and factors affecting clinical outcome of patients in India diagnosed with infantile-onset Pompe disease (IOPD).

STUDY DESIGN

In this multicenter, cross-sectional study, we evaluated the records of 77 patients with IOPD to analyze their clinical course, outcomes, and factors influencing the outcomes.

RESULTS

Of the 77 patients with IOPD, phenotype data were available in 59; 46 (78%) had the classic phenotype. Overall, 58 of 77 (75%) and 19 of 77 (25%) patients were symptomatic before and after age 6 months, respectively. Alpha-glucosidase gene variant analysis available for 48 patients (96 alleles) showed missense variants in 49 alleles. Cross-reactive immunologic material (CRIM) status could be determined or predicted in 44 of 48 patients. In total, 32 of 44 patients (72%) were CRIM-positive, and 12 of 44 patients (27%) were CRIM-negative. Thirty-nine cases received enzyme-replacement therapy (ERT), alglucosidase alfa, and 38 patients never received ERT. Median age at initiation of ERT was 6.5 months. Response to ERT was better in babies who had CRIM-positive, non-classic IOPD.

CONCLUSIONS

This study highlights the clinical spectrum of IOPD in India and provides an insight on various factors, such as undernutrition, feeding difficulties, and recurrent respiratory infection, as possible factors influencing clinical outcomes in these patients. The study also reiterates the importance of raising awareness among clinicians about the need for early diagnosis and timely treatment of IOPD.

Survival and long-term outcomes in late-onset Pompe disease following alglucosidase alfa treatment: a systematic review and meta-analysis

A number of studies have assessed the efficacy of alglucosidase alfa as an enzyme replacement therapy (ERT) on motor and respiratory endpoints in patients with late-onset Pompe disease (LOPD). A previous review evaluated the clinical efficacy and safety of alglucosidase alfa; however, it is difficult to draw inferences from individual studies due to small patient populations, particularly in evaluating the benefit on survival. To evaluate the current evidence on the long-term efficacy of alglucosidase alfa with regard to survival, motor, and respiratory function in patients with LOPD in relation to the natural progression of the disease, a new systematic literature review was performed identifying studies that assessed either mortality, percent predicted forced vital capacity (% FVC), or the 6-min walk test (6MWT) among treated and untreated LOPD patients. Patient overlap was avoided by removing smaller studies or ensuring the use of only one conflicting study per outcome. Mortality was modeled using Poisson models for each treatment group. Outcomes were modeled using first- and second-order fractional polynomial meta-analysis with fixed- and random-effects. Meta-regression was used to explore sources of heterogeneity. Twenty-two publications pertaining to 19 studies/trials were selected, including 438 patients when accounting for overlaps, with the average study duration being 45.7 months. Patients treated with alglucosidase alfa in these studies had a nearly five-fold lower mortality rate than untreated patients (rate ratio: 0.21; 95 % credible interval: 0.11, 0.41). On average, % FVC declined consistently among untreated patients, including a 2.3 % decline after 12 months follow-up and 6.2 % decline after 48 months. This is in contrast to alglucosidase alfa-treated patients, who, on average, improved rapidly, with an increase of 1.4 % FVC after 2 months, followed by a slow regression back to baseline over a three-year period. Nonetheless, the relative difference between those treated and not grew over time, from 4.5 % FVC after 12 months to 6 % FVC after 48 months. In the 6MWT, alglucosidase alfa-treated patients on average had the largest improvement over the first 20 months of treatment of approximately 50 meters increase over baseline, with its substantial stabilization in the following years. By comparison, untreated patients do not show 6MWT improvement over time. Alglucosidase alfa has a beneficial effect in LOPD patients as demonstrated by improvements in survival and ambulation maintained over time, as well as prevention of deterioration in respiratory function.

Response of 33 UK patients with infantile-onset Pompe disease to enzyme replacement therapy

BACKGROUND

Enzyme replacement therapy (ERT) for infantile-onset Pompe disease has been commercially available for almost 10 years. We report the experience of its use in a cohort treated at three specialist lysosomal treatment centres in the UK.

METHODS

A retrospective case-note review was performed, with additional data being gathered from two national audits on all such patients treated with ERT. The impact on the outcome of various characteristics, measured just prior to the initiation of ERT (baseline), was evaluated using logistic regression.

RESULTS

Thirty-three patients were identified; 13/29 (45%) were cross-reactive immunological material (CRIM) negative, and nine were immunomodulated. At baseline assessment, 79% were in heart failure, 66% had failure to thrive and 70% had radiological signs of focal pulmonary collapse. The overall survival rate was 60%, ventilation-free survival was 40% and 30% of patients were ambulatory. Median follow-up of survivors was 4 years, 1.5 months (range 6 months to 13.5 years). As with previous studies, the CRIM status impacted on all outcome measures. However, in this cohort, baseline failure to thrive was related to death and lack of ambulation, and left ventricular dilatation was a risk factor for non-ventilator-free survival.

CONCLUSION

The outcome of treated patients remains heterogeneous despite attempts at immunomodulation. Failure to thrive at baseline and left ventricular dilation appear to be associated with poorer outcomes.

Enzyme therapy and immune response in relation to CRIM status: the Dutch experience in classic infantile Pompe disease

BACKGROUND

Enzyme-replacement therapy (ERT) in Pompe disease--an inherited metabolic disorder caused by acid α-glucosidase deficiency and characterized in infants by generalized muscle weakness and cardiomyopathy--can be complicated by immune responses. Infants that do not produce any endogenous acid α-glucosidase, so-called CRIM-negative patients, reportedly develop a strong response. We report the clinical outcome of our Dutch infants in relation to their CRIM status and immune response.

METHODS

Eleven patients were genotyped and their CRIM status was determined. Antibody formation and clinical outcome were assessed for a minimum of 4 years.

RESULTS

ERT was commenced between 0.1 and 8.3 months of age, and patients were treated from 0.3 to 13.7 years. All patients developed antibodies. Those with a high antibody titer (above 1:31,250) had a poor response. The antibody titers varied substantially between patients and did not strictly correlate with the patients' CRIM status. Patients who started ERT beyond 2 months of age tended to develop higher titers than those who started earlier. All three CRIM-negative patients in our study succumbed by the age of 4 years seemingly unrelated to the height of their antibody titer.

CONCLUSION

Antibody formation is a common response to ERT in classic infantile Pompe disease and counteracts the effect of treatment. The counteracting effect seems determined by the antibody:enzyme molecular stoichiometry. The immune response may be minimized by early start of ERT and by immune modulation, as proposed by colleagues. The CRIM-negative status itself seems associated with poor outcome.

Antenatal diagnosis of pompe disease by fetal echocardiography: impact on outcome after early initiation of enzyme replacement therapy

Hypertrophic cardiomyopathy (HCM) affects most infants with Pompe disease (PD), and may serve as a marker for its antenatal diagnosis (ANDx) by fetal echocardiography (FE). Fetuses diagnosed with HCM between 2006 and 2009 were included in this study. HCM, defined as Z-score of mean left ventricular wall thickness (LVWT) and/or mass (LVM) above 2, was detected in 5/1,268 fetuses (0.39%) carried by 1,137 pregnant women referred for FE. Three fetuses (0.24%) had postnatal confirmation of PD. Their gestational age and fetal weight at diagnosis was (mean ± standard deviation) 31 ± 3.6 weeks and 1.9 ± 0.2 kg, respectively. Fetal Z-score of LVM and LVWT was 3.8 ± 0.9 and 3.1 ± 0.6, respectively. Postnatally, acid α-glucosidase (GAA) enzyme activity was nearly absent in all patients, 2 were homozygous for the mutation 1327-2A>G in the GAA gene, and 1 was homozygous for 340insT. Enzyme replacement therapy (ERT) was initiated 4.9 ± 7.8 days after birth (range 2 h-14 days), and continued every 2 weeks. Two infants are alive at 4 and 31 months, and one died of aspiration pneumonia at 19 months. Cardiac hypertrophy resolved after 10-12 weeks of ERT in all patients, and none required any respiratory support. One patient had normal neurodevelopmental assessment at 25 months, and one had severe global delay at 15 months before death. ANDx of PD by FE is feasible based on fetal HCM. It promotes early initiation of ERT which may improve outcome in some patients. However, larger studies and longer follow-ups are required.

Treatment of infantile Pompe disease with alglucosidase alpha: the UK experience

Treatment of infantile Pompe disease with recombinant human acid α-glucosidase has shown substantial improvement in survival, and in cardiac, motor and respiratory functions. We analyzed the outcome of all patients with infantile Pompe disease treated in the United Kingdom since the availability of the enzyme, using a questionnaire-based survey circulated to all treating centres. A total of 20 infants were treated from 2000 to 2009. Median ages at diagnosis and treatment were 5.75 months (range 0.25-31 months) and 6.5 months (0.5-32 months), respectively. Median duration of treatment was 31 months (1-102 months). Overall ventilator-free survival was 35% (7/20 infants), while 35% (7/20) died at a median age of 10 months (5.75-15 months) and 30% (6/20) were alive but ventilator-dependent. Endotracheal intubation for acute deterioration carried a high risk of failure of extubation and progression to long-term ventilation (LTV), but elective general anaesthesia, in contrast, was well tolerated. Overall outcome was worse than in the pivotal clinical trials; possible causes include later diagnosis and treatment in our patients and a higher incidence of infants at the severe end of the clinical spectrum. Careful consideration must be given to all possible outcomes, including LTV, before commencing enzyme replacement therapy in newly diagnosed infants.

Early treatment with alglucosidase alpha prolongs long-term survival of infants with Pompe disease

In a previous 52-wk trial, treatment with alglucosidase alpha markedly improved cardiomyopathy, ventilatory function, and overall survival among 18 children <7 mo old with infantile-onset Pompe disease. Sixteen of the 18 patients enrolled in an extension study, where they continued to receive alglucosidase alpha at either 20 mg/kg biweekly (n = 8) or 40 mg/kg biweekly (n = 8), for up to a total of 3 y. These children continued to exhibit the benefits of alglucosidase alpha at the age of 36 mo. Cox regression analyses showed that over the entire study period, alglucosidase alpha treatment reduced the risk of death by 95%, reduced the risk of invasive ventilation or death by 91%, and reduced the risk of any type of ventilation or death by 87%, compared with an untreated historical control group. Cardiomyopathy continued to improve and 11 patients learned and sustained substantial motor skills. No significant differences in either safety or efficacy parameters were observed between the 20 and 40 mg/kg biweekly doses. Overall, long-term alglucosidase alpha treatment markedly extended survival as well as ventilation-free survival and improved cardiomyopathy.

Alglucosidase alfa: new drug. Pompe disease: a short-term benefit

(1) Pompe disease is the early-onset form of type 2 glycogenosis, a rare enzyme deficiency. Onset occurs in early infancy, and most patients die from cardiorespiratory failure before their first birthday. (2) The missing enzyme, alglucosidase alfa is now produced through biotechnology and is approved as replacement therapy for infants with Pompe disease. (3) According to a dose-finding study involving 19 infants, and a somewhat shaky historical comparison, alglucosidase alfa has a positive impact on survival at the age of 18 months. (4) The main known adverse effects of alglucosidase alfa are potentially severe infusion reactions and the development of anti-alglucosidase antibodies. (5) Treatment requires an intravenous infusion every two weeks. In France, it costs 4200 euros for a child weighing 10 kg. (6) Alglucosidase alfa replacement therapy is the only treatment that seems to improve the short-term survival of infants with Pompe disease. However, it should only be used within a context of continued assessment.

Recombinant human acid [alpha]-glucosidase: major clinical benefits in infantile-onset Pompe disease

BACKGROUND

Pompe disease is a progressive metabolic neuromuscular disorder resulting from deficiency of lysosomal acid alpha-glucosidase (GAA). Infantile-onset Pompe disease is characterized by cardiomyopathy, respiratory and skeletal muscle weakness, and early death. The safety and efficacy of recombinant human (rh) GAA were evaluated in 18 patients with rapidly progressing infantile-onset Pompe disease.

METHODS

Patients were diagnosed at 6 months of age and younger and exhibited severe GAA deficiency and cardiomyopathy. Patients received IV infusions of rhGAA at 20 mg/kg (n = 9) or 40 mg/kg (n = 9) every other week. Analyses were performed 52 weeks after the last patient was randomized to treatment.

RESULTS

All patients (100%) survived to 18 months of age. A Cox proportional hazards analysis demonstrated that treatment reduced the risk of death by 99%, reduced the risk of death or invasive ventilation by 92%, and reduced the risk of death or any type of ventilation by 88%, as compared to an untreated historical control group. There was no clear advantage of the 40-mg/kg dose with regard to efficacy. Eleven of the 18 patients experienced 164 infusion-associated reactions; all were mild or moderate in intensity.

CONCLUSIONS

Recombinant human acid alpha-glucosidase is safe and effective for treatment of infantile-onset Pompe disease. Eleven patients experienced adverse events related to treatment, but none discontinued. The young age at which these patients initiated therapy may have contributed to their improved response compared to previous trials with recombinant human acid alpha-glucosidase in which patients were older.

Chinese hamster ovary cell-derived recombinant human acid alpha-glucosidase in infantile-onset Pompe disease

OBJECTIVE

To conduct an open-label, multinational, multicenter study examining the safety and efficacy of recombinant human acid alpha-glucosidase (rhGAA) in treatment of infantile-onset Pompe disease.

STUDY DESIGN

We enrolled 8 infant patients who had Pompe disease with GAA activity <1% of normal, cardiomyopathy, and hypotonia. In the 52-week initial phase, rhGAA was infused intravenously at 10 mg/kg weekly; an extension phase continued survivors' treatment with 10 to 20 mg/kg of rhGAA weekly or 20 mg/kg every 2 weeks for as long as 153 weeks. Safety measurements included adverse events, laboratory tests, and anti-rhGAA antibody titers. Efficacy evaluations included survival, ventilator use, echocardiograms, growth, and motor and cognitive function.

RESULT

After 52 weeks of treatment, 6 of 8 patients were alive, and 5 patients were free of invasive ventilator support. Clinical improvements included ameliorated cardiomyopathy and improved growth and cognition. Five patients acquired new motor milestones; 3 patients walked independently. Four patients died after the initial study phase; the median age at death or treatment withdrawal for all patients was 21.7 months, significantly later than expected for patients who were not treated. Treatment was safe and well tolerated; no death was drug-related.

CONCLUSION

rhGAA improved ventilator-free survival, cardiomyopathy, growth, and motor function in patients with infantile-onset Pompe disease compared with outcomes expected for patients without treatment.

The natural course of infantile Pompe's disease: 20 original cases compared with 133 cases from the literature

OBJECTIVE

Infantile Pompe's disease is a lethal cardiac and muscular disorder. Current developments toward enzyme replacement therapy are promising. The aim of our study is to delineate the natural course of the disease to verify endpoints of clinical studies.

METHODS

A total of 20 infantile patients diagnosed by the collaborative Dutch centers and 133 cases reported in literature were included in the study. Information on clinical history, physical examination, and diagnostic parameters was collected.

RESULTS

The course of Pompe's disease is essentially the same in the Dutch and the general patient population. Symptoms start at a median age of 1.6 months in both groups. The median age of death is 7.7 and 6 months, respectively. Five percent of the Dutch patients and 8% of all reported patients survive beyond 1 year of age. Only 2 patients from literature became older than 18 months. A progressive cardiac hypertrophy is characteristic for infantile Pompe's disease. The diastolic thickness of the left ventricular posterior wall and cardiac weight at autopsy increase significantly with age. Motor development is severely delayed and major developmental milestones are generally not achieved. For the Dutch patient group, growth deviates significantly from normal despite start of nasogastric tube feeding. Levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase, or creatine kinase-myocardial band isoenzyme are typically elevated, although aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase increase significantly with age. The patients have fully deleterious mutations. Acid alpha-glucosidase activity is severely deficient.

CONCLUSIONS

Survival, decrease of the diastolic thickness of the left ventricular posterior wall, and achievement of major motor milestones are valid endpoints for therapeutic studies of infantile Pompe's disease. Mutation analysis and measurement of the alpha-glucosidase activity should be part of the enrollment program.

Secondary endocardial fibroelastosis associated with Pompe disease and multicystic dysplastic kidney

An infant with secondary endocardial fibroelastosis (EFE) associated with glycogen storage disease II (Pompe disease) and multicystic dysplastic kidney (MCDK) is described. She had had refractory heart and renal failure from the early neonatal period. In spite of administration of cathecholamines and diuretics, ventilator support, and peritoneal dialysis, her heart failure due to reduction of left ventricular contractility progressively worsened. She died on the 40th day after admission. Histological examination of a left ventricular autopsy specimen showed prominent thickening of the endocardium due to fibroelastosis, and a lacework-like structure due to accumulation of glycogen in the cardiomyocytes. The EFE was derived from degeneration of the smooth muscle in the endocardium and cardiomyocytes due to glycogen storage. In addition, we supposed that the renal failure due to MCDK made the preload for the ventricles increase and accelerated her heart failure.

Identification of two subtypes of infantile acid maltase deficiency

Infantile patients with acid maltase deficiency have severe hypertrophic cardiomyopathy, left ventricular outflow obstruction, and generalized muscle weakness and die before 1 year of age. We identified 12 infants with acid maltase deficiency who had a similar clinical presentation but less severe cardiomyopathy and absence of left ventricular outflow obstruction, and 9 of 12 had longer survival with assisted ventilation and supplemental intubation.