Long-term therapy with agalsidase alfa for Fabry disease: safety and effects on renal function in a home infusion setting

Control of proteinuria with increased doses of agalsidase alfa in a patient with Fabry disease with atypical genotype-phenotype expression

Fabry disease is a rare X-linked lysosomal storage disorder of glycosphingolipids, caused by the partial or complete deficiency of the lysosomal enzyme alpha-galactosidase A (a-Gal A). The missense mutation pN215S usually causes a milder form of the disease with isolated cardiac involvement. We report a case of a male Fabry patient with the pN215S mutation and a generalized disease. He suffered a relapse in proteinuria which responded to increased doses of the administered recombinant enzyme. Individualization of enzyme replacement therapy must be considered in selected cases characterized by clinical deterioration.

Characterization of early disease status in treatment-naive male paediatric patients with Fabry disease enrolled in a randomized clinical trial

Trial Design

This analysis characterizes the degree of early organ involvement in a cohort of oligo-symptomatic untreated young patients with Fabry disease enrolled in an ongoing randomized, open-label, parallel-group, phase 3B clinical trial.

Methods

Males aged 5–18 years with complete α-galactosidase A deficiency, without symptoms of major organ damage, were enrolled in a phase 3B trial evaluating two doses of agalsidase beta. Baseline disease characteristics of 31 eligible patients (median age 12 years) were studied, including cellular globotriaosylceramide (GL-3) accumulation in skin (n = 31) and kidney biopsy (n = 6; median age 15 years; range 13–17 years), renal function, and glycolipid levels (plasma, urine).

Results

Plasma and urinary GL-3 levels were abnormal in 25 of 30 and 31 of 31 patients, respectively. Plasma lyso-GL-3 was elevated in all patients. GL-3 accumulation was documented in superficial skin capillary endothelial cells (23/31 patients) and deep vessel endothelial cells (23/29 patients). The mean glomerular filtration rate (GFR), measured by plasma disappearance of iohexol, was 118.1 mL/min/1.73 m² (range 90.4–161.0 mL/min/1.73 m²) and the median urinary albumin/creatinine ratio was 10 mg/g (range 4.0–27.0 mg/g). On electron microscopy, renal biopsy revealed GL-3 accumulation in all glomerular cell types (podocytes and parietal, endothelial, and mesangial cells), as well as in peritubular capillary and non-capillary endothelial, interstitial, vascular smooth muscle, and distal tubules/collecting duct cells. Lesions indicative of early Fabry arteriopathy and segmental effacement of podocyte foot processes were found in all 6 patients.

Conclusions

These data reveal that in this small cohort of children with Fabry disease, histological evidence of GL-3 accumulation, and cellular and vascular injury are present in renal tissues at very early stages of the disease, and are noted before onset of microalbuminuria and development of clinically significant renal events (e.g. reduced GFR). These data give additional support to the consideration of early initiation of enzyme replacement therapy, potentially improving long-term outcome.

Trial Registration

ClinicalTrials.gov NCT00701415

Efficacy of Enzyme and Substrate Reduction Therapy with a Novel Antagonist of Glucosylceramide Synthase for Fabry Disease

Fabry disease, an X-linked glycosphingolipid storage disorder, is caused by the deficient activity of α-galactosidase A (α-Gal A). This results in the lysosomal accumulation in various cell types of its glycolipid substrates, including globotriaosylceramide (GL-3) and lysoglobotriaosylceramide (globotriaosyl lysosphingolipid, lyso-GL-3), leading to kidney, heart, and cerebrovascular disease. To complement and potentially augment the current standard of care, biweekly infusions of recombinant α-Gal A, the merits of substrate reduction therapy (SRT) by selectively inhibiting glucosylceramide synthase (GCS) were examined. Here, we report the development of a novel, orally available GCS inhibitor (Genz-682452) with pharmacological and safety profiles that have potential for treating Fabry disease. Treating Fabry mice with Genz-682452 resulted in reduced tissue levels of GL-3 and lyso-GL-3 and a delayed loss of the thermal nociceptive response. Greatest improvements were realized when the therapeutic intervention was administered to younger mice before they developed overt pathology. Importantly, as the pharmacologic profiles of α-Gal A and Genz-682452 are different, treating animals with both drugs conferred the greatest efficacy. For example, because Genz-682452, but not α-Gal A, can traverse the blood-brain barrier, levels of accumulated glycosphingolipids were reduced in the brain of Genz-682452-treated but not α-Gal A-treated mice. These results suggest that combining substrate reduction and enzyme replacement may confer both complementary and additive therapeutic benefits in Fabry disease.

Long-term effectiveness of agalsidase alfa enzyme replacement in Fabry disease: A Fabry Outcome Survey analysis

Outcomes from 5 years of treatment with agalsidase alfa enzyme replacement therapy (ERT) for Fabry disease in patients enrolled in the Fabry Outcome Survey (FOS) were compared with published findings for untreated patients with Fabry disease. Data were extracted from FOS, a Shire-sponsored database, for comparison with data from three published studies. Outcomes evaluated were the annualized rate of change in estimated glomerular filtration rate (eGFR) and left ventricular mass indexed to height (LVMI) as well as time to and ages at a composite morbidity endpoint and at death. FOS data were extracted for 740 treated patients who were followed for a median of ~ 5 years. Compared with no treatment, patients treated with agalsidase alfa demonstrated slower decline in renal function and slower progression of left ventricular hypertrophy. Treated male patients with baseline eGFR < 60 mL/min/1.73 m² had a mean (standard error of the mean [SEM]) annualized change in eGFR of − 2.86 (0.53) mL/min/1.73 m²/y compared with − 6.8 (1.5) in the published untreated cohort. The mean (SEM) rate of LVMI increase with treatment was 0.33 (0.10) g/m^2.7/y in males and 0.48 (0.09) in females, compared with 4.07 (1.03) in untreated males and 2.31 (0.81) in untreated females. Morbidity occurred later in treated patients, with ~ 16% risk of a composite morbidity event (26% in males) after 24 months with ERT versus ~ 45% without treatment, with first events and deaths also occurring at older ages in patients administered ERT (e.g., estimated median survival in treated males was 77.5 years versus 60 years in untreated males). Findings from these retrospective comparisons of observational data and published literature support the long-term benefits of ERT with agalsidase alfa for Fabry disease in slowing the progression of renal impairment and cardiomyopathy. Treatment also appeared to delay the onset of morbidity and mortality. Interpretation of these findings should take into account that they are based on retrospective comparisons with previously published data.

The attenuated/late onset lysosomal storage disorders: Therapeutic goals and indications for enzyme replacement treatment in Gaucher and Fabry disease

Enzyme replacement therapies have been developed and authorized for commercial use for six different lysosomal storage disorders. For Gaucher disease, Fabry disease and mucopolysaccharidosis type 1, disease-specific treatments have been available for more than a decade. Although long term follow-up data are still sparse, therapeutic goals for patients with Gaucher disease and Fabry disease have been formulated and published for both adults and children. Without adaptation or modification, these goals are often applied in clinical research and in routine patient care across the entire phenotypic spectrum of disease, although in practice, patients commonly manifest high variability in clinical presentation and course of the illness. In this context, establishing goals for the follow-up and treatment of late onset/attenuated phenotypes is particularly challenging. In this chapter, we review current therapeutic goals for Gaucher disease and Fabry disease and discuss approaches for those with attenuated disease manifestations.

Carboxyl-terminal truncations alter the activity of the human α-galactosidase A

Fabry disease is an X-linked inborn error of glycolipid metabolism caused by deficiency of the human lysosomal enzyme, α-galactosidase A (αGal), leading to strokes, myocardial infarctions, and terminal renal failure, often leading to death in the fourth or fifth decade of life. The enzyme is responsible for the hydrolysis of terminal α-galactoside linkages in various glycolipids. Enzyme replacement therapy (ERT) has been approved for the treatment of Fabry disease, but adverse reactions, including immune reactions, make it desirable to generate improved methods for ERT. One approach to circumvent these adverse reactions is the development of derivatives of the enzyme with more activity per mg. It was previously reported that carboxyl-terminal deletions of 2 to 10 amino acids led to increased activity of about 2 to 6-fold. However, this data was qualitative or semi-quantitative and relied on comparison of the amounts of mRNA present in Northern blots with αGal enzyme activity using a transient expression system in COS-1 cells. Here we follow up on this report by constructing and purifying mutant enzymes with deletions of 2, 4, 6, 8, and 10 C-terminal amino acids (Δ2, Δ4, Δ6, Δ8, Δ10) for unambiguous quantitative enzyme assays. The results reported here show that the k_cat/K_m approximately doubles with deletions of 2, 4, 6 and 10 amino acids (0.8 to 1.7-fold effect) while a deletion of 8 amino acids decreases the k_cat/K_m (7.2-fold effect). These results indicate that the mutated enzymes with increased activity constructed here would be expected to have a greater therapeutic effect on a per mg basis, and could therefore reduce the likelihood of adverse infusion related reactions in Fabry patients receiving ERT treatment. These results also illustrate the principle that in vitro mutagenesis can be used to generate αGal derivatives with improved enzyme activity.

Innate and Adaptive Immune Response in Fabry Disease

Fabry disease is an X-linked lysosomal storage disease in which mutations of the gene (GLA) cause a deficiency of the lysosomal hydrolase α-galactosidase A (α-Gal). This defect results in an accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3) which causes a multisystemic vasculopathy. Available since 2001 in Europe, enzyme replacement therapy consists in the administration of agalsidase, a recombinant form of α-galactosidase A. Enzyme replacement therapy was shown to improve the global prognosis but allowed partial success in preventing critical events such as strokes and cardiac arrests. As in most lysosomal storage diseases, frequent immune reactions have been described in naive Fabry disease patients. Humoral immune responses following enzyme replacement therapy have also been described, with unclear consequences on the progression of the disease. While cost-effectiveness of enzyme replacement therapy in Fabry disease begins to be questioned and new therapeutic strategies arise such as chaperone or gene therapy, it appears necessary to better understand the immune responses observed in the treatment of naive patients and during enzyme replacement therapy with agalsidase. We propose a comprehensive review of the available literature concerning both innate and adaptive responses observed in Fabry disease. We particularly highlight the probable role of the toll-like receptor 4 (TLR4) and CD1d pathways triggered by Gb3 accumulation in the development of local and systemic inflammation that could lead to irreversible organ damages. We propose an immunological point of view of Fabry disease pathogenesis involving immune cells notably the invariant natural killer T cells. We finally review anti-agalsidase antibodies, their development and impact on outcomes.

A symptomatic Fabry disease mouse model generated by inducing globotriaosylceramide synthesis

Fabry disease is a lysosomal storage disorder in which neutral glycosphingolipids, predominantly Gb3 (globotriaosylceramide), accumulate due to deficient α-Gal A (α-galactosidase A) activity. The GLAko (α-Gal A-knockout) mouse has been used as a model for Fabry disease, but it does not have any symptomatic abnormalities. In the present study, we generated a symptomatic mouse model (G3Stg/GLAko) by cross-breeding GLAko mice with transgenic mice expressing human Gb3 synthase. G3Stg/GLAko mice had high Gb3 levels in major organs, and their serum Gb3 level at 5-25 weeks of age was 6-10-fold higher than that in GLAko mice of the same age. G3Stg/GLAko mice showed progressive renal impairment, with albuminuria at 3 weeks of age, decreased urine osmolality at 5 weeks, polyuria at 10 weeks and increased blood urea nitrogen at 15 weeks. The urine volume and urinary albumin concentration were significantly reduced in the G3Stg/GLAko mice when human recombinant α-Gal A was administered intravenously. These data suggest that Gb3 accumulation is a primary pathogenic factor in the symptomatic phenotype of G3Stg/GLAko mice, and that this mouse line is suitable for studying the pathogenesis of Fabry disease and for preclinical studies of candidate therapies.

Fabry nephropathy: a review - how can we optimize the management of Fabry nephropathy?

Fabry disease is a rare, X-linked, lysosomal storage disease caused by mutations in the gene encoding the enzyme alpha-galactosidase A. Complete or partial deficiency in this enzyme leads to intracellular accumulation of globotriaosylceramide (Gb₃) and related glycosphingolipids in many cell types throughout the body, including the kidney. Progressive accumulation of Gb₃ in podocytes, epithelial cells and the tubular cells of the distal tubule and loop of Henle contribute to the renal symptoms of Fabry disease, which manifest as proteinuria and reduced glomerular filtration rate leading to chronic kidney disease and progression to end-stage renal disease. Early diagnosis and timely initiation of treatment of Fabry renal disease is an important facet of disease management. Initiating treatment with enzyme replacement therapy (ERT; agalsidase alfa, Replagal^®, Shire; agalsidase beta, Fabrazyme^®, Genzyme) as part of a comprehensive strategy to prevent complications of the disease, may be beneficial in stabilizing renal function or slowing its decline. Early initiation of ERT may also be more effective than initiating therapy in patients with more advanced disease. Several strategies are required to complement the use of ERT and treat the myriad of associated symptoms and organ involvements. In particular, patients with renal Fabry disease are at risk of cardiovascular events, such as high blood pressure, cardiac arrhythmias and stroke. This review discusses the management of renal involvement in Fabry disease, including diagnosis, treatments, and follow-up, and explores recent advances in the use of biomarkers to assist with diagnosis, monitoring disease progression and response to treatment.

Natural course of Fabry disease and the effectiveness of enzyme replacement therapy: a systematic review and meta-analysis: effectiveness of ERT in different disease stages

OBJECTIVE

Current available evidence on long-term effectiveness of enzyme replacement therapy (ERT) for Fabry disease is limited. More insight is needed whether ERT effectiveness differs in patients with and without baseline end-organ damage.

DESIGN

Through a systematic review, untreated and ERT treated males and females with Fabry disease were compared for main clinical outcomes: renal function, left ventricular mass (LVmass), cerebral white matter lesions (WMLs) and end-organ complications. Through a meta-analysis ERT effectiveness was estimated in different disease stages.

DATA EXTRACTION

Two reviewers assessed quality of the included studies according to guidelines for prognosis research. Data were synthesized using a random effects meta-analysis.

RESULTS

Thirty-one studies were systematically reviewed while six studies were included in the meta-analysis. In patients with a GFR > 60 ml/min/1.73 m(2), decline of renal function was similar for treated and untreated patients. Only ERT treated males with a GFR < 60 ml/min/1.73 m(2) had a slower rate of decline in renal function, possibly attributable to anti-proteinuric therapy. Regardless of left ventricular hypertrophy (LVH) at baseline, LVmass remained stable or increased in males despite ERT, however at a slower rate compared to untreated male patients. In ERT treated females with LVH LVmass decreased, and remained stable in females without LVH. WMLs can not be prevented by ERT. Stroke, cardiac and end-stage renal complications develop, though the incidence of new complications seems to be reduced during ERT.

CONCLUSION

ERT is effective in reducing LVH, but has a limited effect on renal function. Improved treatment options are needed for Fabry disease.

Successful management of enzyme replacement therapy in related fabry disease patients with severe adverse events by switching from agalsidase Beta (fabrazyme(®)) to agalsidase alfa (replagal (®))

BACKGROUND

Enzyme replacement therapy (ERT) is the only approved therapy for Fabry disease. In June 2009, there was a worldwide shortage of agalsidase beta, necessitating dose reductions or switching to agalsidase alfa in some patients.

CASE PRESENTATION

We present two cases of Fabry disease (a parent and a child) who received agalsidase beta for 27 months at the licensed dose and 10 months at a reduced dose, followed by a switch to agalsidase alfa for 28 months. Case 1, a 26-year-old male had severe coughing and fatigue during ERT with agalsidase beta requiring antitussive and asthmatic drug therapy. After switching to agalsidase alfa, the coughing gradually resolved completely. Case 2, a 62-year-old female had advanced cardiac manifestations at the time of diagnosis. Despite receiving ERT with the approved dose of agalsidase beta, she experienced aggravation of congestive heart failure and was hospitalized. After switching to agalsidase alfa with standard care in heart disease, BNP level, echocardiographic parameters, eGFR rate and lyso-Gb3 levels were improved or stabilized.

CONCLUSIONS

We report on two Fabry disease patients who experienced severe adverse events while on approved and/or reduced doses of agalsidase beta. Switching to agalsidase alfa associated with standard care in heart disease led to resolution or improvement in the cardiorespiratory status. And reduction in dose associated with standard care in respiratory disease was useful for decrease in cough and fatigue. Plasma BNP level was useful for monitoring heart failure and the effects of ERT.

Reduced glucosylceramide in the mouse model of Fabry disease: correction by successful enzyme replacement therapy

Fabry disease is an X-linked lysosomal storage disease (LSD) caused by deficient activity of α-Galactosidase A (α-Gal A). As a result, glycosphingolipids, mainly globotriaosylceramide (Gb3), progressively accumulate in body fluids and tissues. Studies aiming at the identification of secondary lipid alterations in Fabry disease may be potentially useful for the monitorization of the response to enzyme replacement therapy (ERT) and development of future therapies. The focus of this study was to evaluate if α-Gal A deficiency has an effect on two key groups of molecules of sphingolipids metabolism: glucosylceramides (GlucCers) and ceramides (Cers). Studies performed in a mouse model of Fabry disease showed reduced level of GlucCer and normal level of Cer in plasma, liver, spleen, kidney and heart. Moreover, analysis of GlucCer isoforms in Fabry knockout mice showed that GlucCer isoforms are unequally reduced in different tissues of these animals. ERT had a specific effect on the liver's GlucCer levels of Fabry knockout mice, increasing hepatic GlucCer to the levels observed in wild type mice. In contrast to Fabry knockout mice, plasma of Fabry patients had normal GlucCer and Cer but an increased GlucCer/Cer ratio. This alteration showed a positive correlation with plasma globotriaosylsphingosine (lyso-Gb3) concentration. In conclusion, this work reveals novel secondary lipid imbalances caused by α-Gal A deficiency.

Development of a highly sensitive immuno-PCR assay for the measurement of α-galactosidase A protein levels in serum and plasma

Fabry disease is an X-linked genetic disorder caused by defects in the α-galactosidase A (GLA) gene, and heterogeneous mutations lead to quantitative and/or qualitative defects in GLA protein in male patients with Fabry disease. Random X-chromosomal inactivation modifies the clinical and biochemical features of female patients with Fabry disease. Functional polymorphisms have been frequently reported in recent times, and these increase the difficulty of understanding the pathogenetic basis of the disease. To date, GLA protein level has been measured using an enzyme-linked immunosorbent assay (ELISA). However, ELISA is not highly sensitive due to the high background noise. In this paper, we introduce a novel application of the immuno-polymerase chain reaction (PCR) method (termed Multiple Simultaneous Tag [MUSTag]) for measurement of the GLA protein level in blood samples. We compared the sensitivities of the MUSTag method with plates or magnetic beads with those of ELISA for recombinant human GLA and found that the apparent maximal sensitivity was higher for the former than for the latter. We then measured the GLA concentrations in serum and plasma from male patients with classic Fabry disease (Male Fabry), females with Fabry disease (Female Fabry), male subjects harboring the functional polymorphism p.E66Q (E66Q), and control (Control) subjects. Our results revealed that compared to the MUSTag plate and ELISA, the MUSTag beads assay afforded a clearer estimation of the GLA protein levels in the serum and plasma with minimal or no background noise, although all the methods could differentiate between the Male Fabry, E66Q, and Control groups. The Female Fabry group showed characteristic heterogeneity, which was consistent with the X-linked inheritance. This novel method is expected to be useful for the sensitive determination of GLA level in blood and elucidation of the pathogenetic basis of Fabry disease.

Long-term enzyme replacement therapy is associated with reduced proteinuria and preserved proximal tubular function in women with Fabry disease

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene. Deficiency of α-galactosidase A (α-Gal A) causes intracellular accumulations of globotriaosylceramide (GL-3) and related glycosphingolipids in all organs, including the kidney, often leading to end-stage renal failure. In women with Fabry disease, accumulation of GL-3 in the glomerular podocytes and other renal cells induces progressive, proteinuric nephropathy, but not as severe as in men. Enzyme replacement therapy (ERT) with recombinant α-Gal A reduces cellular GL-3 deposits in podocytes and tubular epithelial cells. We have previously shown that α-Gal A is delivered to these cells by different pathways involving different receptors. This study investigated the long-term changes in albuminuria, estimated glomerular filtration rate (eGFR) and urinary markers of both glomerular and tubular dysfunction in women with Fabry disease treated with ERT.

METHODS

A retrospective, single centre, cohort study evaluated the long-term association between ERT, albuminuria and eGFR in 13 women with Fabry disease and mild renal involvement. In particular, we analysed the changes in the proteinuric profile, including the glomerular marker IgG, the tubular markers α1-microglobulin and retinol-binding protein (RBP), and the shared tubular and glomerular markers albumin and transferrin.

RESULTS

ERT was associated with a significant reduction in albuminuria and a relatively stable eGFR. The decrease in albuminuria was paralleled by a decrease in both glomerular and tubular urine protein markers.

CONCLUSIONS

The data indicate that long-term ERT is associated with a reduction in albuminuria and glomerular and tubular urinary protein markers in women with Fabry disease and mild renal manifestations.

Enzyme replacement therapy in two Japanese siblings with Fabry disease, and its effectiveness on angiokeratoma and neuropathic pain

Enzyme replacement therapy (ERT) for Fabry disease does not show a clear benefit in angiokeratoma. We describe two Japanese siblings with Fabry disease, who were diagnosed when angiokeratomas were found on the older sibling at the age of 13 years. Neither of the boys complained of pain, while both suffered from hypohidrosis. We evaluated the safety and efficacy of ERT with recombinant human agalsidase alfa (Replagal®, Dainippon-Sumitomo Pharma. Co., Osaka, Japan) in these siblings over a 5-year period. In both siblings, sweating was observed 3 months after the initiation of ERT, which motivated them to adhere to ERT. Pain sensation was regained after 12 to 36 months of ERT, followed by a decrease after 48 to 60 months. Angiokeratomas on the lateral side of the knee of the older sibling partially disappeared after 48 months of ERT. Although the height of both siblings at baseline was lower than the corresponding average age-related heights in the normal Japanese population, during ERT they were within, or close to, the average +1 standard deviation in the non-Fabry population. Their growth rate seemed to indicate catch-up growth. Other clinical symptoms were maintained at baseline levels. Immunoglobulin G anti-agalsidase alfa antibodies were not detected in both sibling during ERT, and no infusion-associated reaction was observed. The treatment was generally well tolerated. ERT was a safe and effective treatment for angiokeratoma and neuropathic pain for these two siblings with Fabry disease.

Long-term outcome of enzyme-replacement therapy in advanced Fabry disease: evidence for disease progression towards serious complications

OBJECTIVE

The long-term effects of enzyme-replacement therapy (ERT) in Fabry disease are unknown. Thus, the aim of this study was to determine whether ERT in patients with advanced Fabry disease affects progression towards 'hard' clinical end-points in comparison with the natural course of the disease.

METHODS

A total of 40 patients with genetically proven Fabry disease (mean age 40 ± 9 years; n = 9 women) were treated prospectively with ERT for 6 years. In addition, 40 subjects from the Fabry Registry, matched for age, sex, chronic kidney disease stage and previous transient ischaemic attack (TIA), served as a comparison group. The main outcome was a composite of stroke, end-stage renal disease (ESRD) and death. Secondary outcomes included changes in myocardial left ventricular (LV) wall thickness and replacement fibrosis, change in glomerular filtration rate (GFR), new TIA and change in neuropathic pain.

RESULTS

During a median follow-up of 6.0 years (bottom and top quartiles: 5.1, 7.2), 15 events occurred in 13 patients (n = 7 deaths, n = 4 cases of ESRD and n = 4 strokes). Sudden death occurred (n = 6) only in patients with documented ventricular tachycardia and myocardial replacement fibrosis. The annual progression of myocardial LV fibrosis in the entire cohort was 0.6 ± 0.7%. As a result, posterior end-diastolic wall thinning was observed (baseline, 13.2 ± 2.0 mm; follow-up, 11.4 ± 2.1 mm; P < 0.01). GFR decreased by 2.3 ± 4.6 mL min(-1) per year. Three patients experienced a TIA. The major clinical symptom was neuropathic pain (n = 37), and this symptom improved in 25 patients. The event rate was not different between the ERT group and the untreated (natural history) group of the Fabry Registry.

CONCLUSION

Despite ERT, clinically meaningful events including sudden cardiac death continue to develop in patients with advanced Fabry disease.

Renal complications of Fabry disease in children

Fabry disease is an X-linked α-galactosidase A deficiency, resulting in accumulation of glycosphingolipids, especially globotriaosylceramide, in cells in different organs in the body. Renal failure is a serious complication of this disease. Fabry nephropathy lesions are present and progress in childhood while the disease commonly remains silent by routine clinical measures. Early and timely diagnosis of Fabry nephropathy is crucial since late initiation of enzyme replacement therapy may not halt progressive renal dysfunction. This may be challenging due to difficulties in diagnosis of Fabry disease in children and absence of a sensitive non-invasive biomarker of early Fabry nephropathy. Accurate measurement of glomerular filtration rate and regular assessment for proteinuria and microalbuminuria are useful, though not sensitive enough to detect early lesions in the kidney. Recent studies support the value of renal biopsy in providing histological information relevant to kidney function and prognosis, and renal biopsy could potentially be used to guide treatment decisions in young Fabry patients. This review aims to provide an update of the current understanding, challenges, and needs to better approach renal complications of Fabry disease in children.

Long term enzyme replacement therapy for Fabry disease: effectiveness on kidney, heart and brain

Background

Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase A deficiency leading to renal, cardiac, cerebrovascular disease and premature death. Treatment with α-galactosidase A (enzyme replacement therapy, ERT) stabilises disease in some patients, but long term effectiveness is unclear.

Methods

Renal, cardiac, and cerebral outcomes were prospectively studied in males and females with Fabry disease treated with ERT. Additionally, the occurrence of major cardiac events, stroke, end-stage renal disease and death was compared to a natural history (NH) cohort meeting treatment criteria.

Results

Of 75 patients on ERT (median treatment duration 5.2 years, range 0.05-11.0), prospective follow-up was available for 57 adult patients (30 males) and 6 adolescents. Renal function declined in males (-3.4 ml/min/1.73 m² per year, SE 0.2; p < 0.001) despite ERT, but followed the normal course in females (-0.8 ml/min/1.73 m² per year, SE 0.3; p = 0.001). Cardiac mass increased during ERT in males (+ 1.2 gram/m^2.7, SE 0.3; p < 0.001), but remained stable in females (-0.3 gram/m^2.7 per year, SE 0.4; p = 0.52). ERT did not prevent the occurrence of cerebral white matter lesions. Comparison of ERT treated to untreated patients revealed that the odds to develop a first complication increased with age (OR 1.05 (95% CI: 1.0-1.1) per year, p = 0.012). For development of a first or second complication the odds declined with longer treatment duration (OR 0.81 (95% CI: 0.68-0.96) per year of ERT, p = 0.015;OR 0.52 (0.31-0.88), p = 0.014 respectively).

Conclusions

Long term ERT does not prevent disease progression, but the risk of developing a first or second complication declines with increasing treatment duration. ERT in advanced Fabry disease seems of doubtful benefit.

Agalsidase benefits renal histology in young patients with Fabry disease

The effect of early-onset enzyme replacement therapy on renal morphologic features in Fabry disease is largely unknown. Here, we evaluated the effect of 5 years of treatment with agalsidase alfa or agalsidase beta in 12 consecutive patients age 7-33 years (median age, 16.5 years). We performed renal biopsies at baseline and after 5 years of enzyme replacement therapy; 7 patients had additional biopsies after 1 and 3 years. After a median of 65 months, biopsy findings from all patients showed total clearance of glomerular endothelial and mesangial cell inclusions, and findings from 2 patients showed complete clearance of inclusions from epithelial cells of the distal tubule. The 4 patients who received the highest dose of agalsidase exhibited substantial clearance of podocyte inclusions, and the youngest patient had nearly complete clearance of these inclusions. Linear regression analysis showed a highly significant correlation between podocyte globotriaocylceramide clearance and cumulative agalsidase dose (r=0.804; P=0.002). Microalbuminuria normalized in five patients. In summary, long-term enzyme replacement therapy in young patients can result in complete globotriaocylceramide clearance of mesangial and glomerular endothelial cells across all dosage regimens, and clearance of podocyte inclusions is dose-dependent.

Enzyme replacement therapy for Anderson-Fabry disease

BACKGROUND

Anderson-Fabry disease is an X-linked defect of glycosphingolipid metabolism. Progressive renal insufficiency is a major source of morbidity, additional complications result from cardio- and cerebro-vascular involvement. Survival is reduced among affected males and symptomatic female carriers.

OBJECTIVES

To evaluate the effectiveness and safety of enzyme replacement therapy compared to other interventions, placebo or no interventions, for treating Anderson-Fabry disease.

SEARCH METHODS

We searched 'Clinical Trials' on The Cochrane Library, MEDLINE, EMBASE, LILACS and the Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register (date of the most recent search: 11 September 2012). The original search was performed in September 2008.Date of the most recent search of the Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register: 11 September 2012.

SELECTION CRITERIA

Randomized controlled trials of agalsidase alfa or beta in participants diagnosed with Anderson-Fabry disease.

DATA COLLECTION AND ANALYSIS

Two authors selected relevant trials, assessed methodological quality and extracted data.

MAIN RESULTS

Six trials comparing either agalsidase alfa or beta in 223 participants fulfilled the selection criteria.Both trials comparing agalsidase alfa to placebo reported on globotriaosylceramide concentration in plasma and tissue; aggregate results were non-significant. One trial reported pain scores, there was a statistically significant improvement for participants receiving treatment at up to three months, mean difference -2.10 (95% confidence interval (CI) -3.79 to -0.41); at up to five months, mean difference -1.90 (95% CI -3.65 to -0.15); and at up to six months, mean difference -2.00 (95% CI -3.66 to -0.34). There was a significant difference in pain-related quality of life at over five months and up to six months, mean difference -2.10 (95% CI -3.92 to -0.28) but not at other time-points. Neither trial reported deaths.One of the three trials comparing agalsidase beta to placebo reported on globotriaosylceramide concentration in plasma and tissue and showed significant improvement: kidney, mean difference -1.70 (95% CI -2.09 to -1.31); heart, mean difference -0.90 (95% CI -1.18 to -0.62); and composite results (renal, cardiac, and cerebrovascular complications and death), mean difference -4.80 (95% CI -5.45 to -4.15). There was no significant difference between groups for death; no trials reported on pain.Only one trial compared agalsidase alfa to agalsidase beta. There was no significant difference between the groups for any adverse events, risk ratio 0.36 (95% CI 0.08 to 1.59), or any serious adverse events; risk ratio 0.30; 95% CI 0.03 to 2.57).

AUTHORS' CONCLUSIONS

Six small, poor quality randomised controlled trials provide no robust evidence for use of either agalsidase alfa and beta to treat Anderson-Fabry disease.

Fabry disease

Fabry disease results from deficient activity of the enzyme α-galactosidase A and progressive lysosomal deposition of globotriaosylceramide (GL-3) in cells throughout the body. The main neurological presentations of Fabry disease patients are painful neuropathy, hypohidrosis, and stroke. Fabry neuropathy is characterized as a length-dependent peripheral neuropathy affecting mainly the small myelinated (Aδ) fibers and unmyelinated (C) fibers. Enzyme replacement therapy (ERT) has been shown to have some positive effects on the reduction of neuropathic pain, the improvement of detection threshold for thermal sensation, and sweat function. On the contrary, the effect of ERT on the central nervous system has not been established. Early initiation of ERT before irreversible organ failure is extremely important, and alternative therapeutic approaches are currently being explored. Heterozygotes suffer from peripheral neuropathy at a higher rate than previously shown, significant multisystemic disease, and severely decreased quality of life. As well as being carriers, heterozygotes also display symptoms of Fabry disease, and should be carefully monitored and given adequate therapy.

Effects of enzyme replacement therapy for cardiac-type Fabry patients with a Chinese hotspot late-onset Fabry mutation (IVS4+919G>A)

OBJECTIVE

Current studies of newborn screening for Fabry disease in Taiwan have revealed a remarkably high prevalence of cardiac-type Fabry disease with a Chinese hotspot late-onset Fabry mutation (IVS4+919G>A).

DESIGN

Retrospective cohort study.

SETTING

Tertiary medical centre.

PARTICIPANTS

21 patients with cardiac-type Fabry disease (15 men and 6 women) as well as 15 patients with classic Fabry disease (4 men and 11 women) treated with biweekly intravenous infusions of agalsidase β (1 mg/kg) or agalsidase α (0.2 mg/kg) for at least 6 months.

OUTCOME MEASURES

These data were collected at the time before enzyme replacement therapy (ERT) began and followed up after ERT for at least 6 months, including patient demographics, medical history, parameter changes of cardiac status and renal functions, plasma globotriaosylsphingosine (lyso-Gb3) and Mainz Severity Score Index.

RESULTS

After 6-39 months of ERT, plasma lyso-Gb3 was found to be reduced in 89% (17/19) and 93% (14/15) of patients with cardiac-type and classic Fabry disease, respectively, which indicated an improvement of disease severity. For patients with cardiac-type Fabry disease, echocardiography revealed the reduction or stabilisation of left ventricular mass index (LVMI), the thicknesses of intraventricular septum (IVS) and left posterior wall (LPW) in 83% (15/18), 83% (15/18) and 67% (12/18) of patients, respectively, as well as 77% (10/13), 73% (11/15) and 60% (9/15) for those with classic type. Most patients showed stable renal function after ERT. There were statistically significant improvements (p<0.05) between the data at baseline and those after ERT for values of plasma lyso-Gb3, LVMI, IVS, LPW and Mainz Severity Score Index. No severe clinical events were reported during the treatment.

CONCLUSIONS

ERT is beneficial and appears to be safe for Taiwanese patients with cardiac-type Fabry disease, as well as for those with the classic type.

Fabry nephropathy: indications for screening and guidance for diagnosis and treatment by the European Renal Best Practice

Fabry disease (FD) is an X-linked disorder of glycosphingolipid catabolism resulting in the accumulation of glycolipids including globotriaosylceramide in cells of various tissues resulting in end-organ manifestations. Initially, FD is typically characterized by angiokeratoma and recurrent episodes of neuropathic pain in the extremities occurring during childhood or adolescence. Most affected patients also exhibit a decreased ability to sweat. Later in life, FD results in left ventricular hypertrophy, proteinuria, renal failure and stroke. These later disease manifestations are non-specific and also common in diabetes, hypertension and atheromatosis and thus for most practitioners do not point into the direction of FD. As a consequence, FD is under-diagnosed and screening of high-risk groups is important for case finding, as is a thorough pedigree analysis of affected patients. In the nephrology clinic, we suggest to screen patients for FD when there is unexplained chronic kidney disease in males younger than 50 years and females of any age. In men, this can be performed by measuring α-galactosidase A activity in plasma, white blood cells or dried blood spots. In women, mutation analysis is necessary, as enzyme measurement alone could miss over one-third of female Fabry patients. A multidisciplinary team should closely monitor all known Fabry patients, with the nephrologist screening kidney impairment (glomerular filtration rate and proteinuria) on a regular basis. Transplanted Fabry patients have a higher mortality than the regular transplant population, but have acceptable outcomes, compared with Fabry patients remaining on dialysis. It is unclear whether enzyme replacement therapy (ERT) prevents deterioration of kidney function. In view of the lack of compelling evidence for ERT, and the low likelihood that a sufficiently powered randomized controlled trial on this topic will be performed, data of all patients with FD should be collected in a central registry.

Enzyme replacement therapy in patients with Fabry disease: state of the art and review of the literature

Anderson-Fabry disease is an X-linked lysosomal storage disorder resulting from the deficiency of the hydrolytic enzyme alpha galactosidase A, with consequent accumulation of globotrioasoyl ceramide in cells and tissues of the body, resulting in a multi-system pathology including end organ failure. In the classical phenotype, cardiac failure, renal failure and stroke result in a reduced median life expectancy. The current causal treatment for Fabry disease is the enzyme replacement therapy (ERT): two different products, Replagal (agalsidase alfa) and Fabrazyme (agalsidase beta), have been commercially available in Europe for almost 10 years and they are both indicated for long-term treatment. In fact, clinical trials, observational studies and registry data have provided many evidences for safety and efficacy of ERT in improving symptoms of pain, gastrointestinal disturbances, hypohidrosis, left ventricular mass index, glomerular filtration rate and quality of life. Few data are available on comparison of the two treatments and on the clinical course of the disease. This article reviews the published evidence for clinical efficacy of the two available enzyme preparations.

Recommendations on reintroduction of agalsidase Beta for patients with fabry disease in europe, following a period of shortage

The interruption of the manufacturing process of agalsidase beta has led to a worldwide shortage of this drug. In the EU, nearly all patients initially reduced their agalsidase beta dose, and many of these switched to agalsidase alfa (Replagal Shire HGT). The clinical consequences of this period of drug shortage need to be further evaluated. A gradual increase of agalsidase beta supply is now expected. This implies that patients could resume or even commence agalsidase beta treatment. Guidance for prioritization of patients is needed to support equitable distribution of agalsidase beta to EU member states. To achieve this, in absence of level I clinical evidence, a draft consensus proposal was initiated and distributed. No full consensus was achieved, as there is disagreement regarding the indications for switching patients from agalsidase alfa to agalsidase beta. Some physicians support the concept that the 1.0 mg/kg EOW dose of agalsidase beta is more effective than agalsidase alfa at 0.2 mg/kg EOW, while others believe that at recommended dose, the preparations are equivalent. In light of these difficulties and the uncertainties with respect to supply of agalsidase beta, recommendations were agreed upon by a subgroup of physicians. These current recommendations focus on prioritization of criteria indicative of disease progression.

High-throughput screening identified disease-causing mutants and functional variants of α-galactosidase A gene in Japanese male hemodialysis patients

Fabry disease is a genetic disorder caused by deficient activity of lysosomal enzyme α-galactosidase A (GLA) and end-stage renal disease (ESRD) will be present after accumulation of glycosphingolipids within the kidney. Undiagnosed atypical variants of Fabry disease, which are limited to renal involvement, were found in several ESRD patient populations. On the other hand, unexpectedly high frequencies of male subjects having the c.196G>C nucleotide change (p.E66Q) showing low α-GLA activity have been reported on Japanese and Korean screening for Fabry disease. However, several evidences indicate the c.196G>C is not a pathogenic mutation but is a functional polymorphism. In the present study, high-throughput screening of serum GLA could successfully indentify two Fabry disease patients in a cohort consisted of 1080 male hemodialysis patients. Moreover, our serum assay was able to distinguish two patients with disease-causing genetic mutations (p.G195V and p.M296I) from eight functional variants that showed relatively decreased enzyme activity (p.E66Q). In conclusion, high-throughput serum enzyme assay distinctly identified disease-causing mutants and functional variants of GLA gene in Japanese male hemodialysis patients. In addition, our results underscore the high prevalence of not only undiagnosed Fabry patients but functional variants of p.E66Q among the ESRD population.

Fabry disease: biochemical, pathological and structural studies of the α-galactosidase A with E66Q amino acid substitution

Recently, male subjects harboring the c.196G>C nucleotide change which leads to the E66Q enzyme having low α-galactosidase A (GLA) activity have been identified at an unexpectedly high frequency on Japanese and Korean screening for Fabry disease involving dry blood spots and plasma/serum samples. Individuals with the E66Q enzyme have been suspected to have the later-onset Fabry disease phenotype leading to renal and cardiac disease. However, there has been no convincing evidence for this. To determine whether c.196G>C (E66Q) is disease-causing or not, we performed biochemical, pathological and structural studies. It was predicted that the E66Q amino acid substitution causes a small conformational change on the molecular surface of GLA, which leads to instability of the enzyme protein. However, biochemical studies revealed that subjects harboring the E66Q enzyme exhibited relatively high residual enzyme activity in white blood cells, and that there was no accumulation of globotriaosylceramide in cultured fibroblasts or an increased level of plasma globotriaosylsphingosine in these subjects. An electron microscopic examination did not reveal any pathological changes specific to Fabry disease in biopsied skin tissues from a male subject with the E66Q enzyme. These results strongly suggest that the c.196G>C is not a pathogenic mutation but is a functional polymorphism.

Fabry disease, enzyme replacement therapy and the significance of antibody responses

Fabry disease is an X-linked disorder caused by a deficiency of α-galactosidase A. This leads to a progressive accumulation of globotriaosylceramide in tissues throughout the body. Cardiac, renal and neurological manifestations are common and life expectancy is significantly reduced relative to the general population. Management of Fabry disease involves the administration of intravenous enzyme replacement therapy (ERT). Two forms - agalsidase alfa and agalsidase beta - have been licensed in certain jurisdictions and are generally well tolerated; however, some patients develop antibodies to the infused enzyme, which may impair the efficacy and safety of treatment. Agalsidase alfa and agalsidase beta are produced in different systems; this leads to certain differences in post-translational modification that may affect immunogenicity. Immunoglobulin (Ig) G antibodies have frequently been reported in patients with Fabry disease receiving ERT; IgG responses are reported in a greater proportion of patients receiving agalsidase beta than in patients receiving agalsidase alfa. IgE antibodies are less common than IgG antibodies, and have not been observed in patients receiving agalsidase alfa. However, these data are difficult to interpret due to methodological differences in the assessment of seropositivity, and in the doses of enzyme used. The clinical impact of the development of IgG antibodies to ERT in patients with Fabry disease remains unclear, due to lack of data and to the marked heterogeneity of patients both in terms of disease manifestations and response to therapy. Further studies that examine the development of antibodies in patients with Fabry disease and the potential impact of such antibodies on the outcome of ERT are necessary.

Fabry disease

PURPOSE OF REVIEW

This review discusses the literature on Fabry disease mainly in the domain of neurology with special attention to recent advancement.

RECENT FINDINGS

Fabry neuropathy is known as a length-dependent peripheral neuropathy affecting mainly the small myelinated (Aδ) fibers and unmyelinated (C) fibers. Recently, concerning heterozygotes, it seems that they suffer from peripheral neuropathy at a higher rate than previously shown, significant multisystemic disease, and severely decreased quality of life. The existence of an atypical variant of Fabry disease with late-onset cerebrovascular disease (cerebrovascular variant) is now suggested, like the cardiac and renal variants of Fabry disease. Although enzyme replacement therapy (ERT) has been shown to have some positive effects on reduction of neuropathic pain, the improvement of detection threshold for thermal sensation and sweat function, the effect of ERT on the central nervous system has not been established. Gene replacement therapy, chemical chaperone therapy, and ERT using modified α-N-acetylgalactosaminidase are in progress, and induced pluripotent stem cells were generated from mouse models of Fabry disease.

SUMMARY

Heterozygotes should be carefully monitored for precise estimation and adequate therapy. Early initiation of ERT before irreversible organ failure is most important, and alternative therapeutic approaches are currently being explored.

Pharmacological chaperone therapy for Fabry disease

Fabry disease is an inherited lysosomal storage disorder caused by deficient α-galactosidase A activity. Many missense mutations in Fabry disease often cause misfolded gene products, which leads to their retention in the endoplasmic reticulum by the quality control system; they are then removed by endoplasmic reticulum-associated degradation. We discovered that a potent α-galactosidase A inhibitor, 1-deoxygalactonojirimycin, acts as a pharmacological chaperone to facilitate the proper folding of the mutant enzyme by binding to its active site, thereby improving its stability and trafficking to the lysosomes in mammalian cells. The oral administration of 1-deoxygalactonojirimycin to transgenic mice expressing human mutant α-galactosidase A resulted in significant increases in α-galactosidase A activity in various organs, with concomitant reductions in globotriaosylceramide, which contributes to the pathology of Fabry disease. Seventy-eight missense mutations were found to be responsive to 1-deoxygalactonojirimycin. These data indicate that many patients with Fabry disease could potentially benefit from pharmacological chaperone therapy.

The effectiveness of long-term agalsidase alfa therapy in the treatment of Fabry nephropathy

BACKGROUND AND OBJECTIVES

Fabry disease is a rare X-linked disease with multisystemic manifestations. This study investigated the effectiveness of long-term enzyme replacement therapy with agalsidase alfa in Fabry nephropathy treatment.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this observational study, data on patients receiving agalsidase alfa (0.2 mg/kg every other week) were extracted from the Fabry Outcome Survey, an international registry of patients with Fabry disease. Serum creatinine and estimated GFR (eGFR) at baseline and after ≥5 years of treatment were assessed; 24-hour urinary protein excretion and BP measurements were also reviewed. The eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration formula. Patients with an eGFR <30 ml/min per 1.73 m(2) were excluded.

RESULTS

Renal function was assessed in 208 patients (mean enzyme replacement therapy, 7.4 years; range, 5.0-11.2 years). Mean yearly change in eGFR was -2.2 ml/min per 1.73 m(2) in men and -0.7 ml/min per 1.73 m(2) in women (95% confidence limits, -2.8; -1.7 and -1.4; 0.0, respectively). Patients with 24-hour protein excretion >1 g/24 h had poorer renal function at baseline and follow-up compared with patients with protein excretion of 500-1000 mg/24 h or with proteinuria <500 mg/24 h. Renal function was worse in patients with baseline arterial hypertension, and there was a more rapid yearly decline compared with normotensive patients.

CONCLUSIONS

This study suggests that long-term agalsidase alfa therapy is able to stabilize the rate of Fabry nephropathy progression in women and is associated with a mild to moderate decline of renal function in men.

Consequences of a global enzyme shortage of agalsidase beta in adult Dutch Fabry patients

Background

Enzyme replacement therapy is currently the only approved therapy for Fabry disease. From June 2009 on, viral contamination of Genzyme's production facility resulted in a worldwide shortage of agalsidase beta leading to involuntary dose reductions (approved dose 1 mg/kg/eow, reduced dose 0.5 mg/kg/m), or switch to agalsidase alpha (administered dose 0.2 mg/kg/eow). An assessment report from the European Medicines Agency (EMA) raised serious concerns about an increase in adverse events at lower dosages of agalsidase beta. We determined the influence of the shortage on clinical event incidence and the most sensitive biochemical marker (lysoGb3) in Dutch Fabry patients.

Methods

The incidence of clinical events per person per year was calculated from start of agalsidase beta treatment until the shortage, and was compared to the incidence of clinical events during the shortage period. In addition, plasma lysoGb3, eGFR, quality of life (SF-36) and brief pain inventory (BPI) questionnaires were analysed.

Results

All thirty-five Dutch Fabry patients using agalsidase beta (17 males) were included. Mean clinical event incidence was unchanged: 0.15 events per person per year before versus 0.15 during the shortage (p = 0.68). In total 28 clinical events occurred in 14 patients during 4.6 treatment years, compared to 7 events in 6 patients during the 1.3 year shortage period. eGFR and BPI scores were not significantly altered. Two SF-36 subscales were significantly but minimally reduced in females. In males, lysoGb3 increased with a median of 8.1 nM (range 2.5 - 29.2) after 1 year of shortage (p = 0.001). Increases in lysoGb3 were found in both patients switching to agalsidase alpha and on a reduced agalsidase beta dose. Antibody status, treatment duration or clinical event incidence showed no clear correlation to lysoGb3 increases.

Conclusions

No increase in clinical event incidence was found in the adult Dutch Fabry cohort during the agalsidase beta shortage. Increases in lysoGb3, however, suggest recurrence of disease activity.

Minimum requirement of donor cells to reduce the glycolipid storage following bone marrow transplantation in a murine model of Fabry disease

BACKGROUND

Fabry disease (FD) is a lysosomal storage disorders characterized by a deficiency of the lysosomal enzyme, α-galactosidase A. This results in the accumulation of glycolipids, mainly globotriaosylceramide (GL-3), in the lysosomes of various organs. Although bone marrow transplantation and hematopoietic stem cell-based gene therapy can offer the potential of a curative therapeutic outcome for FD, the minimum requirement of donor cells or gene-corrected cells to reduce GL-3 levels is not known.

METHODS

Lethally-irradiated FD mice were transplanted intravenously with normal bone marrow cells (Ly5.1 positive) mixed with those of FD mice (Ly5.2 positive) at various ratios to investigate the level of engraftment and enzyme activity necessary to effect a reduction in GL-3 storage.

RESULTS

Chimerism of whole white blood cells of recipients' peripheral blood remained stable at 8 weeks after transplantation, and chimerism of granulocytes, monocytes, B cells and T cells was equal to that of white blood cells. GL-3 levels were significantly reduced in the lung and heart of animals with a 30% and 50% chimera, respectively. The extent of reduction in these mice was almost identical to that with 100% chimera.

CONCLUSIONS

In FD mice, reconstitution with 100% donor cells is not required to obtain a therapeutic effect following bone marrow transplantation. These results suggest that a 30% gene correction might be sufficient to reverse disease manifestations in FD.

Receptor-mediated endocytosis of α-galactosidase A in human podocytes in Fabry disease

Injury to the glomerular podocyte is a key mechanism in human glomerular disease and podocyte repair is an important therapeutic target. In Fabry disease, podocyte injury is caused by the intracellular accumulation of globotriaosylceramide. This study identifies in the human podocyte three endocytic receptors, mannose 6-phosphate/insulin-like growth II receptor, megalin, and sortilin and demonstrates their drug delivery capabilities for enzyme replacement therapy. Sortilin, a novel α-galactosidase A binding protein, reveals a predominant intracellular expression but also surface expression in the podocyte. The present study provides the rationale for the renal effect of treatment with α-galactosidase A and identifies potential pathways for future non-carbohydrate based drug delivery to the kidney podocyte and other potential affected organs.

Awareness of Fabry disease among rheumatologists--current status and perspectives

Fabry disease is an inherited disorder of lipid metabolism caused by deficient activity of the lysosomal enzyme α-galactosidase A. Burning peripheral pain with triggered crises of excruciating pain and gastrointestinal dysmotility point to Fabry small fiber neuropathy; angiokeratoma, corneal deposits, and hypohidrosis are other common early manifestations. Progressive dysfunction of the kidneys, heart, and/or brain develops in adulthood. Diagnosis is often delayed which is of great concern, as therapeutic outcomes with enzyme replacement therapy are generally more favorable in early stages of Fabry disease. Results of a survey among 360 rheumatologists and pediatricians clinically managing patients with rheumatologic conditions demonstrate that Fabry manifestations are generally poorly recognized and that awareness of appropriate diagnostic tests is low. To raise awareness about the musculoskeletal aspects of Fabry disease among rheumatologists, the International Musculoskeletal Working Group on Lysosomal Storage Disorders has reviewed the current knowledge. We propose a diagnostic algorithm with burning pain in hands and feet and triggered attacks of excruciating pain as keystones. Evidence of autonomic nerve dysfunction and simple temperature sensitivity testing can provide important diagnostic clues. Multi-systemic involvement should be explored by taking a detailed medical history, including family history, and performing a thorough physical examination and appropriate laboratory workup. Confirmatory tests include the α-Gal A enzyme activity assay (males) and genetic testing (females). We propose that medical specialists use our diagnostic algorithm when evaluating individuals with peripheral neuropathic pain.

Modelling the resource implications of managing adults with Fabry disease in Italy

AIMS

This study estimated the resource implications and budget impact of managing adults with Fabry disease in Italy, from the perspective of the Servizio Sanitario Nazionale (SSN).

METHODS

A decision model was constructed using published clinical outcomes and clinician-derived resource utilisation estimates depicting the management of adults with Fabry disease in Italy.

RESULTS

The expected annual cost of managing 220 existing and 20 new Fabry patients in Italy was estimated to be €28·3 million. In an average year, patients receiving enzyme replacement therapy (ERT) with 0·2 mg kg(-1) agalsidase alfa (Replagal; Shire Human Genetic Therapies, Basingstoke, Hampshire, UK) or 1·0 mg kg(-1) agalsidase beta (Fabrazyme; Genzyme Europe BV, Naarden, The Netherlands) are collectively expected to make 4500 hospital attendances to a day ward for infusions, which equates to 2000 eight-h days on the day ward associated with ERT. If all ERT-treated patients received their infusions at home, there would be a marginal reduction in the annual health care cost to manage these patients, and the total annual number of days on the day ward associated with ERT in the second year could potentially be reduced from a mean 2000 to zero, thereby releasing substantial hospital resources for use by non-Fabry patients. Currently, only agalsidase alfa is licensed for home treatment in Italy; hence, only patients receiving this enzyme could be offered home treatment.

CONCLUSION

Use of agalsidase alfa (0·2 mg kg(-1) ) instead of agalsidase beta (1·0 mg kg(-1)) has the potential to reduce health care costs and release hospital resources in different specialities for alternative use by non-Fabry patients, thereby improving the efficiency of the public health care system in Italy.

Response of women with Fabry disease to enzyme replacement therapy: comparison with men, using data from FOS--the Fabry Outcome Survey

Fabry disease (α-galactosidase A deficiency) is an X-linked disorder. Women who are heterozygous for disease-causing mutations often manifest signs and symptoms of Fabry disease, but most studies of the effects of enzyme replacement therapy (ERT) have included only men. To date, no direct comparison has been made of the relative effectiveness of long-term ERT between men and women. The aim of this analysis was to report the effectiveness of agalsidase alfa in a cohort of 78 women treated for 4 years and to compare outcomes with those of 172 men. All data were obtained from the Fabry Outcome Survey--an international database of patients with Fabry disease sponsored by Shire Human Genetic Therapies. Quantifiable clinical parameters were assessed at baseline and the 4-year time point. Measures of pain, health-related quality of life, cardiac structure and function, and renal function changed to a similar extent in women and men during treatment, with the exception of left ventricular mass, which only reduced significantly in women. Changes in the presence of each of 27 clinical features after 4 years of ERT were evaluated in two subpopulations: patients with and patients without clinical features at baseline. It was clear for most types of clinical features that a number of women with a feature at baseline were no longer reported to have it at the 4-year time point, and that clinical features were observed in only a small percentage of women in whom they had been absent at baseline. The percentage of patients who were symptomatic at the 4-year time point was calculated for each type of clinical feature. The results showed no significant differences between men and women for most clinical features evaluated. Overall, both sexes responded to agalsidase alfa in a similar way, suggesting there should be no difference in the criteria for assessment of treatment in women and men.

[Renal lesions in patients with Fabry's disease]

Kidney involvement is one of the main manifestations of Fabry's disease. In the absence of enzyme replacement therapy, hemizygous males and some heterozygous females progress to end stage renal failure. In hemizygous males, diffuse glycolipid accumulation is observed in all glomerular and vascular cells whereas distal tubular cells are focally involved. In heterozygous females, the glycolipid storage is irregular in glomeruli and vessels, some cells being massively involved, others being normal. In both sexes, degenerative changes occur, linked to the necrosis of overloaded mesangial and vascular smooth muscle cells. Their progression leads to unspecific arteriopathy and glomerulosclerosis not prone to reverse under enzymotherapy. Kidney biopsy is useful for confirming the diagnosis if clinical presentation of Fabry's disease is atypical. Moreover, histological analysis of renal tissue allows to assess the severity of degenerative changes and to evaluate the beneficial impact of enzyme replacement therapy.

Safety of agalsidase alfa in patients with Fabry disease under 7 years

AIM

To evaluate the safety and explore the efficacy of enzyme replacement therapy (ERT) for Fabry disease with agalsidase alfa in young children enrolled in the Fabry Outcome Survey (FOS).

METHODS

This retrospective chart review identified eight children (mean age= 5.0±1.6 [mean ±SD]) in FOS who began treatment with agalsidase alfa (0.2 mg/kg, i.v., every other week) when <7 years old. Vital signs and adverse events were monitored throughout the study period. Glomerular filtration rate (GFR) was estimated, and left ventricular mass indexed to height(2.7) (LVMi) was assessed with echocardiography. Patients received 1.2-6.7 years of treatment (mean=4.2 years).

RESULTS

Infusion reactions occurred in three patients and were of mild or moderate severity. IgG antibodies to agalsidase alfa were found in one patient who experienced two mild and one moderate infusion reactions. Mean GFR was within the normal range at baseline and remained normal. LVMi was above the 75th percentile of age-matched children in 5 of 6 patients evaluated at baseline. Only two patients exceeded this threshold at their last assessment.

CONCLUSION

Long-term observation will be needed to determine whether early initiation of ERT will prevent major organ dysfunction in these patients.

Update on role of agalsidase alfa in management of Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder that affects both men and women. The manifestations of this heterogeneous disease are multisystemic and progressive. Prior to the development of enzyme replacement therapy, the management and treatment for Fabry disease was largely nonspecific and supportive. Because enzyme replacement therapy became commercially available in 2001, a variety of clinical benefits in Fabry patients have been consistently reported, including improved renal pathology and cardiac function, and reduced severity of neuropathic pain and improved pain-related quality of life. This update focuses on published data on the efficacy and tolerability of enzyme replacement therapy with agalsidase alfa, and gives a brief overview on some of the outstanding management issues in the treatment of this complex disease.