Treatment of Fabry disease with different dosing regimens of agalsidase: effects on antibody formation and GL-3

Reducing agalsidase beta infusion time in Fabry patients: low incidence of antibody formation and infusion-associated reactions in an Italian multicenter study

BACKGROUND

Fabry disease is a rare progressive X-linked lysosomal storage disease caused by mutations in the GLA gene that encodes α-galactosidase A. Agalsidase beta is a recombinant enzyme replacement therapy authorized in Europe at a standard dose of 1.0 mg/kg intravenously every other week at an initial infusion rate of ≤ 0.25 mg/min until patient tolerance is established, after which the infusion rate may be increased gradually. However, specific practical guidance regarding the progressive reduction in infusion time is lacking. This study investigated a new and specific protocol for reducing agalsidase beta infusion time in which a stable dosage of 15 mg/h is infused for the first four months, and the infusion rate is increased progressively from 15 to 35 mg/h for the subsequent four infusions. The shortest infusion time is reached after six months and maintained thereafter. The incidence of infusion-associated reactions (IARs) and the development of anti-drug antibodies were analyzed, and the disease burden and the clinical evolution of the disease at 12 months were evaluated.

RESULTS

Twenty-five of the 31 patients were naïve to enzyme or chaperone treatment at baseline and six patients had been switched from agalsidase alfa. The reduced infusion time protocol was well tolerated. Only one patient exhibited an IAR, with mild symptoms that resolved with low-dose steroids. Six patients globally seroconverted during treatment (4 with a classic phenotype and 2 with late-onset disease). All but three patients were seronegative at month 12. All patients were stable at the study's end (FAbry STabilization indEX value < 20%); reducing infusion time did not negatively impact clinical outcomes in any patient. The perceived medical assessment showed that the quality of life of all patients improved.

CONCLUSIONS

The study demonstrates that reducing agalsidase beta infusion time is possible and safe from both an immunogenic and clinical point of view. The use of a low infusion rate in the first months when the probability of onset of the development of antibodies is higher contributed to very limited seroconversion to antibody-positive status.

Complement activation and cellular inflammation in Fabry disease patients despite enzyme replacement therapy

Defective α-galactosidase A (AGAL/GLA) due to missense or nonsense mutations in the GLA gene results in accumulation of the glycosphingolipids globotriaosylceramide (Gb3) and its deacylated derivate globotriaosylsphingosine (lyso-Gb3) in cells and body fluids. The aberrant glycosphingolipid metabolism leads to a progressive lysosomal storage disorder, i. e. Fabry disease (FD), characterized by chronic inflammation leading to multiorgan damage. Enzyme replacement therapy (ERT) with agalsidase-alfa or -beta is one of the main treatment options facilitating cellular Gb3 clearance. Proteome studies have shown changes in complement proteins during ERT. However, the direct activation of the complement system during FD has not been explored. Here, we demonstrate strong activation of the complement system in 17 classical male FD patients with either missense or nonsense mutations before and after ERT as evidenced by high C3a and C5a serum levels. In contrast to the strong reduction of lyso-Gb3 under ERT, C3a and C5a markedly increased in FD patients with nonsense mutations, most of whom developed anti-drug antibodies (ADA), whereas FD patients with missense mutations, which were ADA-negative, showed heterogenous C3a and C5a serum levels under treatment. In addition to the complement activation, we found increased IL-6, IL-10 and TGF-ß1 serum levels in FD patients. This increase was most prominent in patients with missense mutations under ERT, most of whom developed mild nephropathy with decreased estimated glomerular filtration rate. Together, our findings demonstrate strong complement activation in FD independent of ERT therapy, especially in males with nonsense mutations and the development of ADAs. In addition, our data suggest kidney cell-associated production of cytokines, which have a strong potential to drive renal damage. Thus, chronic inflammation as a driver of organ damage in FD seems to proceed despite ERT and may prove useful as a target to cope with progressive organ damage.

Safety and efficacy of pegunigalsidase alfa in patients with Fabry disease who were previously treated with agalsidase alfa: results from BRIDGE, a phase 3 open-label study

BACKGROUND

Pegunigalsidase alfa is a novel, PEGylated α-galactosidase-A enzyme-replacement therapy approved in the EU and US to treat patients with Fabry disease (FD).

OBJECTIVE/METHODS

BRIDGE is a phase 3 open-label, switch-over study designed to assess safety and efficacy of 12 months of pegunigalsidase alfa (1 mg/kg every 2 weeks) treatment in adults with FD who had been previously treated with agalsidase alfa (0.2 mg/kg every 2 weeks) for ≥ 2 years.

RESULTS

Twenty-seven patients were screened; 22 met eligibility criteria; and 20 (13 men, 7 women) completed the study. Pegunigalsidase alfa was well-tolerated, with 97% of treatment-emergent adverse events (TEAEs) being of mild or moderate severity. The incidence of treatment-related TEAEs was low, with 2 (9%) discontinuations due to TEAEs. Five patients (23%) reported infusion-related reactions. Overall mean (SD; n = 22) baseline estimated glomerular filtration rate (eGFR) was 82.5 (23.4) mL/min/1.73 m2 and plasma lyso-Gb3 level was 38.3 (41.2) nmol/L (men: 49.7 [45.8] nmol/L; women: 13.8 [6.1] nmol/L). Before switching to pegunigalsidase alfa, mean (standard error [SE]) annualized eGFR slope was - 5.90 (1.34) mL/min/1.73 m2/year; 12 months post-switch, the mean eGFR slope was - 1.19 (1.77) mL/min/1.73 m2/year; and mean plasma lyso-Gb3 reduced by 31%. Seven (35%) out of 20 patients were positive for pegunigalsidase alfa antidrug antibodies (ADAs) at ≥ 1 study timepoint, two of whom had pre-existing ADAs at baseline. Mean (SE) changes in eGFR slope for ADA-positive and ADA-negative patients were + 5.47 (3.03) and + 4.29 (3.15) mL/min/1.73 m2/year, respectively, suggesting no negative impact of anti-pegunigalsidase alfa ADAs on eGFR slope.

CONCLUSION

Pegunigalsidase alfa may offer a safe and effective treatment option for patients with FD, including those previously treated with agalsidase alfa. TRN: NCT03018730. Date of registration: January 2017.

Enzyme replacement therapy in two patients with classic Fabry disease from the same family tree: Two case reports

BACKGROUND

The pathophysiology of Fabry disease (FD)-induced progressive vital organ damage is irreversible. Disease progression can be delayed using enzyme replacement therapy (ERT). In patients with classic FD, sporadic accumulation of globotriaosylceramide (GL-3) in the heart and kidney begins in utero; however, until childhood, GL-3 accumulation is mild and reversible and can be restored by ERT. The current consensus is that ERT initiation during early childhood is paramount. Nonetheless, complete recovery of organs in patients with advanced FD is challenging.

CASE SUMMARY

Two related male patients, an uncle (patient 1) and nephew (patient 2), presented with classic FD. Both patients were treated by us. Patient 1 was in his 50s, and ERT was initiated following end-organ damage; this was subsequently ineffective. He developed cerebral infarction and died of sudden cardiac arrest. Patient 2 was in his mid-30s, and ERT was initiated when the patient was diagnosed with FD, during which the damage to vital organs was not overtly apparent. Although he had left ventricular hypertrophy at the beginning of this treatment, the degree of hypertrophy progression was limited to a minimal range after > 18 years of ERT.

CONCLUSION

We obtained discouraging ERT outcomes for older patients but encouraging outcomes for younger adults with classic FD.

Assessment and impact of dose escalation on anti-drug antibodies in Fabry disease

Enzyme replacement therapy (ERT) with recombinant α-galactosidase A (AGAL) can lead to the formation of neutralizing anti-drug antibodies (ADA), which significantly limit treatment efficacy in patients with Fabry disease (FD). The effects of dose escalation on ADA titer and plasma globotriaosylsphingosine (lyso-Gb₃) level are unknown. We screened 250 FD patients (200 males, 50 females) under ERT for ADAs and assessed the impact of an approved dose escalation in affected patients, focusing on ADA titers and plasma lyso-Gb₃. ADA-positive patients were identified by serum-mediated inhibition assays, followed by titration assays to determine the individual inhibitory capacities of ADAs against agalsidase-alfa and agalsidase-beta. 70 (35%) of the male patients were ADA-positive, with a mean inhibitory capacity of 83.5 ± 113.7mg AGAL. Although patients receiving agalsidase-beta showed higher inhibitory capacities (84.7 ± 34.7mg) than patients under agalsidase-alfa (60.3 ± 126.7mg, p<0.001), the "theoretical deficit" to the infused dose was lower in patients receiving agalsidase-beta. In seven patients receiving agalsidase-alfa (0.2 mg/kg) ADAs were saturable by switching patients to agalsidase-beta (1.0 mg/kg). The switch resulted in increasing ADA titers within the first months. In 2 out of 7 (28.6%) therapy switchers, dose escalation could lead to durable ADA saturation. Independent of an increase in ADA titers, lyso-Gb₃ levels decrease and cardiac and renal parameters remained stable after dose escalation. Dose escalation results in a heterogeneous, unpredictable ADA response, with more than a quarter of all treatment switchers succeeding in ADA saturation. Longitudinal ADA measurements are required to assess the individual risk of affected patients.

Burden associated with Fabry disease and its treatment in 12-15 year olds: results from a European survey

Background

Fabry Disease (FD) is a rare X-linked metabolic lysosomal disorder. FD has a broad range of symptoms which vary markedly between patients. The heterogenous nature of the disease makes diagnosis difficult for health care professionals (HCPs), which in turn has a significant effect on the patient’s quality of life (QoL). As few adolescent patients are eligible for treatment, to date there has been little published data on the burden of disease and impact of treatment on these patients and their caregivers. This study was developed to provide some insight into these groups.

Methods

An online-based survey was performed to gather further insights on the burden of FD in 14 adolescents aged 12–15 years old across three European countries, from the perspective of the patients, caregivers and HCPs.

Results

Symptom burden was found to be high in the adolescent population, with ‘pain’ and ‘intolerance to heat or cold’ commonly reported symptoms, both by patients and to HCPs. Eleven of the 14 patients surveyed were receiving enzyme replacement therapy (ERT), with their post-ERT symptomology showing improvement when compared to symptoms before receiving ERT. The majority of caregivers believe their child’s overall health has improved since starting ERT. While there was a positive outlook towards ERT noted by the patients and caregivers, 4/5 HCPs believed there is ‘a need for more efficacious treatment options’ and all HCPs noted that there is ‘a need for more manageable treatment options’. FD was shown to place a burden on caregivers, who reported feelings of guilt and absences from work.

Conclusions

Data show there is a significant symptom burden for the adolescent, which affects their QoL and mental health, as well as placing a burden on the wider family. While ERT is an effective treatment and provides symptom relief for many of the respondents in the survey, they still reported symptom burden. Additionally, there was reporting of reluctance to engage in treatment or difficulties associated with the treatment. Heterogeneity in symptom presentation suggests that the treatment regimen needs to be tailored to the individual. Physicians therefore need to have a choice of treatment options available to help them manage symptoms and disease where the benefit to risk ratio is in favour of undergoing treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02417-3.

Multimodality imaging approach to Fabry cardiomyopathy: Any role for nuclear cardiology?

Anderson-Fabry disease (AFD) is a multisystem X-linked disorder of lipid metabolism frequently associated with progressive glycosphingolipid accumulation in cardiac, renal, and nervous cells. The diagnosis of AFD is usually assessed by enzyme assay and genetic tests, but advanced cardiac imaging can be useful in detecting early signs of the disease. Echocardiography and cardiac magnetic resonance are the first-line imaging modalities to investigate cardiac involvement in AFD, but the recent introduction of new molecular and hybrid imaging techniques opens to a wider range of diagnostic applications. This article aims to provide an overview of nuclear cardiology techniques in diagnosis and clinical management of AFD.

Fabry Cardiomyopathy: Current Treatment and Future Options

Fabry disease is a multisystem X-linked lysosomal storage disorder caused by a mutation in the alpha-galactosidase A gene. Deficiency or reduced activity of alpha-galactosidase A (GLA) is leading to progressive intracellular accumulation of globotriaosylceramide (GL3) in various organs, including the heart, kidney and nerve system. Cardiac involvement is frequent and is evident as concentric left ventricular hypertrophy. Currently, the standard treatment is enzyme replacement therapy or chaperone therapy. However, early starting of therapy, before myocardial fibrosis has developed, is essential for long-term improvement of myocardial function. For future treatment options, various therapeutic approaches including gene therapy are under development. This review describes the current and potential future therapy options for Fabry cardiomyopathy.

Human α-Galactosidase A Mutants: Priceless Tools to Develop Novel Therapies for Fabry Disease

Fabry disease (FD) is a lysosomal storage disease caused by mutations in the gene for the α-galactosidase A (GLA) enzyme. The absence of the enzyme or its activity results in the accumulation of glycosphingolipids, mainly globotriaosylceramide (Gb3), in different tissues, leading to a wide range of clinical manifestations. More than 1000 natural variants have been described in the GLA gene, most of them affecting proper protein folding and enzymatic activity. Currently, FD is treated by enzyme replacement therapy (ERT) or pharmacological chaperone therapy (PCT). However, as both approaches show specific drawbacks, new strategies (such as new forms of ERT, organ/cell transplant, substrate reduction therapy, or gene therapy) are under extensive study. In this review, we summarize GLA mutants described so far and discuss their putative application for the development of novel drugs for the treatment of FD. Unfavorable mutants with lower activities and stabilities than wild-type enzymes could serve as tools for the development of new pharmacological chaperones. On the other hand, GLA mutants showing improved enzymatic activity have been identified and produced in vitro. Such mutants could overcome several complications associated with current ERT, as lower-dose infusions of these mutants could achieve a therapeutic effect equivalent to that of the wild-type enzyme.

Treatment of Anderson-Fabry Disease

Fabry disease is an X-linked disorder of glycosphingolipid metabolism that results in progressive accumulation of neutral glycosphingolipids, predominantly globotriaosylsphingosine (Gb3) in lysosomes, as well as other cellular compartments of several tissues, causing multi-organ manifestations (acroparesthesias, hypohidrosis, angiokeratomas, signs and symptoms of cardiac, renal, cerebrovascular involvement). Pathogenic mutations lead to a deficiency of the lysosomal enzyme alpha-galactosidase A (GLA). In the presence of high clinical suspicion, a careful physical examination and specific laboratory tests are required. Finally, the diagnosis of Fabry's disease is confirmed by the demonstration of the absence of or reduced alpha-galactosidase A enzyme activity in hemizygous men and gene typing in heterozygous females. Measurement of the biomarkers Gb3 and Lyso Gb3 in biological specimens may facilitate diagnosis. The current treatment of Anderson-Fabry disease is represented by enzyme replacement therapy (ERT) and oral pharmacological chaperone. Future treatments are based on new strategic approaches such as stem cell-based therapy, pharmacological approaches chaperones, mRNA therapy, and viral gene therapy. This review outlines the current therapeutic approaches and emerging treatment strategies for Anderson-Fabry disease.

Contemporary therapeutics and new drug developments for treatment of Fabry disease: a narrative review

Fabry disease (OMIM 301500) is an X-linked (Xq22.1) lysosomal storage disorder leading to a progressive multisystem disease with high variability in both genotype and phenotype expression. The pathophysiological origin is found in an enzyme deficiency of the α-galactosidase A (enzyme commission no. 3.2.1.22) leading to accumulation of globotriaosylceramides in all lysosome carrying tissue. Especially organ manifestations of the heart, kidneys and nervous system are of significant prognostic value and might complicate with Fabry-associated pain, young aged cryptogenic stroke, proteinuria, kidney failure, hypertrophic cardiomyopathy, heart failure, malign cardiac rhythm disturbances and eventually sudden cardiac death. Up to the introduction of the first enzyme replacement agent in 2001, patients faced the disease's natural course with no disease-specific therapies available. Today, two recombinant enzyme replacement agents (Fabrazyme^®, Sanofi Genzyme, Cambridge, MA, USA; Replagal^®, Takeda Pharmaceutical, Tokio, Japan) and one oral chaperone therapy (Migalastat^®, Amicus Therapeutics, USA) are available and well-established in daily clinical practice. Substrate reduction therapy, second-generation enzyme replacement agents and different gene therapy approaches are currently undergoing preclinical and clinical trial phases and aim to improve therapeutic success and long-term outcome of patients with Fabry disease. This narrative review summarizes the currently available therapeutic options and future perspectives in Fabry disease.

Generation and Characterization of a Polyclonal Human Reference Antibody to Measure Anti-Drug Antibody Titers in Patients with Fabry Disease

Male patients with Fabry disease (FD) are at high risk for the formation of antibodies to recombinant α-galactosidase A (AGAL), used for enzyme replacement therapy. Due to the rapid disease progression, the identification of patients at risk is highly warranted. However, currently suitable references and standardized protocols for anti-drug antibodies (ADA) determination do not exist. Here we generate a comprehensive patient-derived antibody mixture as a reference, allowing ELISA-based quantification of antibody titers from individual blood samples. Serum samples of 22 male patients with FD and ADAs against AGAL were pooled and purified by immune adsorption. ADA-affinities against agalsidase-α, agalsidase-β and Moss-AGAL were measured by quartz crystal microbalance with dissipation monitoring (QCM-D). AGAL-specific immune adsorption generated a polyclonal ADA mixture showing a concentration-dependent binding and inhibition of AGAL. Titers in raw sera and from purified total IgGs (r2 = 0.9063 and r2 = 0.8952, both p < 0.0001) correlated with the individual inhibitory capacities of ADAs. QCM-D measurements demonstrated comparable affinities of the reference antibody for agalsidase-α, agalsidase-β and Moss-AGAL (KD: 1.94 ± 0.11 µM, 2.46 ± 0.21 µM, and 1.33 ± 0.09 µM, respectively). The reference antibody allows the ELISA-based ADA titer determination and quantification of absolute concentrations. Furthermore, ADAs from patients with FD have comparable affinities to agalsidase-α, agalsidase-β and Moss-AGAL.

Biomarkers in Anderson-Fabry Disease

Fabry disease is a rare lysosomal storage disorder caused by a deficiency of α-galactosidase A, resulting in multisystemic involvement. Lyso-Gb3 (globotriaosylsphingosine), the deacylated form of Gb3, is currently measured in plasma as a biomarker of classic Fabry disease. Intensive research of biomarkers has been conducted over the years, in order to detect novel markers that may potentially be used in clinical practice as a screening tool, in the context of the diagnostic process and as an indicator of response to treatment. An interesting field of application of such biomarkers is the management of female heterozygotes who present difficulty in predictable clinical progression. This review aims to summarise the current evidence and knowledge about general and specific markers that are actually measured in subjects with confirmed or suspected Fabry disease; moreover, we report potential novel markers such as microRNAs. Recent proteomic or metabolomic studies are in progress bringing out plasma proteome profiles in Fabry patients: this assessment may be useful to characterize molecular pathology of the disease, to improve diagnostic process, and to monitor response to treatment. The management of Fabry disease may be improved by the identification of biomarkers that reflect clinical course, severity, and the progression of the disease.

Anti-drug antibody formation in Japanese Fabry patients following enzyme replacement therapy

Enzyme replacement therapy (ERT) for Fabry disease (deficiency of α-galactosidase A, α-Gal) with recombinant α-Gals (agalsidase alfa and agalsidase beta) is widely available and improves some of the clinical manifestations and biochemical findings. However, recent reports suggest that recurrent administration of recombinant enzymes often induces the formation of anti-drug antibodies, which may have a negative impact on the outcome of the therapy. We examined the formation of anti-drug antibodies using blood samples from 97 Japanese Fabry patients following ERT and tried to characterize them by means of enzyme-linked immunosorbent assay (ELISA), serum-mediated α-Gal inhibition, and immunochromatographic (IC) assay, followed by GLA gene analysis and measurement of plasma globotriaosylsphingosine (lyso-Gb3). ELISA revealed that 20/35 (57%) classic Fabry males were antibody (Immunoglobulin G, IgG) -positive (Ab+) at 6 months after the initiation of ERT, although only two of the seventeen (12%) later-onset Fabry males and none of the 45 Fabry females were. The Ab+ state was maintained at least until 24 months after the initiation of ERT in most of the cases, the exceptions being two patients who acquired immune tolerance during ERT. As many Ab+ patients have nonsense mutations, attention should be paid to the formation of anti-drug antibodies in Fabry patients harboring such gene mutations, who hardly produce α-Gal protein. Serum-mediated α-Gal inhibition was seen in most of the Ab+ patients and the antibodies affected the reduction of the plasma lyso-Gb3 level following ERT, suggesting that the antibodies inhibit the enzyme activity. There was a correlation between the results of the IC test and those of the ELISA. As the former is easy and rapid, it should be useful as a bed-side test.

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The anti-drug antibodies formed in Fabry patients during ERT were characterized.

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Serum-mediated α-Gal inhibition was seen in most of the antibody-positive patients.

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The immunochromatographic test is easy, rapid, and useful as a bed-side test.

Therapeutic advances in Fabry disease: The future awaits

Fabry disease (FD) is an X-linked disorder caused by mutations in GLA gene responsible for coding of the lysosomal enzyme alpha-galactosidase A(α-GAL). The resultant accumulation of globotriaosylceramide (Gb-3) leads to multisystemic disease including progressive chronic kidney disease, hypertrophic cardiomyopathy, stroke, angiokeratomas and corneal whorls. Current treatments include enzyme replacement therapy (ERT), along with recent advent of chaperone therapy. ERT has not shown to have dramatic improvement in outcomes for all organ systems, with benefit mostly seen in kidney disease and reduction in left ventricular hypertrophy. ERT, however, is associated with formation of anti-drug antibodies and requirement of long-term venous access, while chaperone therapy can only be used in amenable mutations. A multitude of therapies are now under investigation in various phases of clinical trials. These include pegylated form of α-GAL (pegunigalsidase alpha), gene therapy (both in-vivo and ex-vivo methods), mRNA therapy (inducing production of α-GAL) and substrate reduction therapy (inhibitors of glucosylceramide synthase leading to reduction of Gb-3). This review encapsulates literature pertaining to current and investigational therapies for FD.

Developments in the treatment of Fabry disease

Enzyme replacement therapy (ERT) with recombinant α-galactosidase A (r-αGAL A) for the treatment of Fabry disease has been available for over 15 years. Long-term treatment may slow down disease progression, but cardiac, renal, and cerebral complications still develop in most patients. In addition, lifelong intravenous treatment is burdensome. Therefore, several new treatment approaches have been explored over the past decade. Chaperone therapy (Migalastat; 1-deoxygalactonojirimycin) is the only other currently approved therapy for Fabry disease. This oral small molecule aims to improve enzyme activity of mutated α-galactosidase A and can only be used in patients with specific mutations. Treatments currently under evaluation in (pre)clinical trials are second generation enzyme replacement therapies (Pegunigalsidase-alfa, Moss-aGal), substrate reduction therapies (Venglustat and Lucerastat), mRNA- and gene-based therapy. This review summarises the knowledge on currently available and potential future options for the treatment of Fabry disease.

Detailed epitope mapping of neutralizing anti-drug antibodies against recombinant α-galactosidase A in patients with Fabry disease

BACKGROUND

Fabry disease (FD) is a lysosomal storage disease, treatable by enzyme replacement therapy (ERT) that substitutes deficient α-galactosidase A (AGAL). The formation of neutralizing anti-drug antibodies (ADA) inhibiting AGAL activity is associated with disease progression in affected male patients. In the current study, we performed a detailed epitope mapping of ADAs from antibody-positive males against infused AGAL.

METHODS

A detailed epitope mapping for 34 male FD patients with neutralizing ADAs against AGAL was performed. Based on this data, in silico analyses were used to identify potential epitope clusters and mapped surface-located or buried epitopes. ELISA-based assays against α-galactosidase B (NAGA) were performed to identify ADAs that potentially recognize shared epitopes of AGAL and NAGA. A subset of 20 patients was analyzed to assess if NAGA-recognizing ADAs against AGAL might affect long-term outcomes under ERT.

RESULTS

Thirty percent of the AGAL active site was recognized by patients' ADAs. No differences between buried and surface-located epitopes were observed. Dependent on the epitopes, ADAs against AGAL were also able to recognize human NAGA. Patients with NAGA recognizing anti-AGAL antibodies presented with lower plasma NAGA activities. The presence of NAGA-recognizing ADAs had no effect on disease progression.

CONCLUSION

In conclusion, our current data underline previous reports demonstrating a large variation of antibody epitopes against AGAL. Detailed epitope mapping in affected patients might be the first step for the generation of patient-specific blocking peptides and/or immune adsorption columns for an individually tailored anti-antibody strategy.

Neutralising anti-drug antibodies in Fabry disease can inhibit endothelial enzyme uptake and activity

Fabry disease (FD) is a lysosomal storage disease, treatable by enzyme replacement therapy (ERT) that substitutes deficient α-galactosidase A (AGAL). The formation of neutralising anti-drug antibodies (ADA) inhibiting AGAL activity during infusion is associated with disease progression in affected male patients. In this study we analysed if ADAs also inhibit endothelial enzyme uptake as well as intracellular enzyme activity. Therefore, fluorescence-labelled AGAL in combination with ADA-positive sera from FD patients (n = 8) was used to analyse enzyme uptake in endothelial and FD-specific cells. Furthermore, immune adsorption and a comprehensive ADA epitope mapping were performed. Pre-incubation of AGAL with ADAs significantly inhibited intracellular enzyme activity, which was rescued by immune adsorption (both P < .01). ADAs from some patients also inhibited enzyme uptake. ADA epitope mapping identified an epitope at position 121 to 140 aa potentially responsible for uptake inhibition for these patients. Further analyses revealed the presence of stable AGAL/ADA-immune complexes at pH 4.5 and decreased intracellular enzyme activity in endothelial cells (P < .001). Finally, the pre-incubation of AGAL with ADAs resulted in a reduced depletion of intracellular globotriaosylceramide in patient-derived AGAL-deficient cells, demonstrating a direct negative impact of ADAs on intracellular clearance. Neutralising ADAs may not only inhibit infused AGAL activity, but according to their epitopes can also inhibit endothelial AGAL uptake. Indeed, internalised AGAL/ADA-complexes may not dissociate, underlining the importance of novel therapeutic approaches for ADA reduction and prevention to increase therapy efficiency in affected patients.

Safety and effectiveness of enzyme replacement therapy with agalsidase alfa in patients with Fabry disease: Post-marketing surveillance in Japan

Fabry disease is a rare X-linked inherited multisystem disorder resulting from deficiency of the lysosomal enzyme alpha-galactosidase A. Currently, specific therapies, including enzyme replacement therapies, are available for Fabry disease, but clinical trials provide limited information on long-term safety and effectiveness. Agalsidase alfa was approved in Japan in 2006. The post-marketing surveillance study of all patients receiving agalsidase alfa to evaluate its long-term safety and effectiveness as a mandatory condition for its approval had been conducted for 8 years (from February 2007 to March 2015). A total of 493 patients were included in this analysis of safety and effectiveness. The overall mean follow-up period was 3.5 years (range, 0.0-7.9 years). The percentage of patients with adverse drug reactions was 24.5% (121/493) and 12.6% had infusion-related reactions (62/493). In the 256 patients without prior enzyme replacement therapy whose IgG antibody data were available, 17 were IgG antibody positive (6.6%). However, the chronological correlation between seroconversion and the incidence of infusion-related reactions was not clear. The mean brief pain inventory score of the worst pain decreased in patients with moderate and severe pain at baseline. Plasma Gb₃ and urine sediment Gb₃ in males with classical Fabry disease without prior enzyme replacement therapy significantly decreased. The mean yearly changes in eGFR (mL/min/1.73 m²) ranged from -2.88 to +1.00 in males with classical Fabry disease, from -2.04 to -0.95 in males with non-typical variant and from -2.64 to -1.02 in females. The lower eGFR or the more proteinuria at baseline, the faster the decrease in eGFR of the patients was observed. There was no substantial difference in cardiac parameters (left ventricular mass index, E/A wave ratio, ejection fraction, and QRS duration). In conclusion, agalsidase alfa, 0.2 mg/kg every other week, was well tolerated and controlled the progression of symptoms (especially renal and cardiac) of Fabry disease in adults. Enzyme replacement therapy should be started in Japanese patients before cardiac and/or renal symptoms of Fabry disease develop.

The effect of enzyme replacement therapy on clinical outcomes in male patients with Fabry disease: A systematic literature review by a European panel of experts

Background

Enzyme replacement therapy (ERT) with recombinant human α-galactosidase has been available for the treatment of Fabry disease since 2001 in Europe and 2003 in the USA. Treatment outcomes with ERT are dependent on baseline patient characteristics, and published data are derived from heterogeneous study populations.

Methods

We conducted a comprehensive systematic literature review of all original articles on ERT in the treatment of Fabry disease published up until January 2017. This article presents the findings in adult male patients.

Results

Clinical evidence for the efficacy of ERT in adult male patients was available from 166 publications including 36 clinical trial publications. ERT significantly decreases globotriaosylceramide levels in plasma, urine, and in different kidney, heart, and skin cell types, slows the decline in estimated glomerular filtration rate, and reduces/stabilizes left ventricular mass and cardiac wall thickness. ERT also improves nervous system, gastrointestinal, pain, and quality of life outcomes.

Conclusions

ERT is a disease-specific treatment for patients with Fabry disease that may provide clinical benefits on several outcomes and organ systems. Better outcomes may be observed when treatment is started at an early age prior to the development of organ damage such as chronic kidney disease or cardiac fibrosis. Consolidated evidence suggests a dose effect. Data described in male patients, together with female and paediatric data, informs clinical practice and therapeutic goals for individualized treatment.

Dose-Dependent Effect of Enzyme Replacement Therapy on Neutralizing Antidrug Antibody Titers and Clinical Outcome in Patients with Fabry Disease

BACKGROUND

Use of enzyme replacement therapy (ERT) to treat Fabry disease, caused by deficient lysosomal α-galactosidase A activity, can lead to formation of neutralizing antidrug antibodies (ADAs). These antibodies are associated with increased accumulation of plasma globotriaosylceramide (Gb3) and disease progression. Because agalsidase ERT can saturate ADA-binding sites during infusions (achieving agalsidase/antibody equilibrium), we investigated in this open cohort study whether saturated patients (who have excess agalsidase after infusions) experience better clinical outcomes compared with not saturated patients (who have excess ADAs after infusions).

METHODS

We isolated ADAs from sera of 26 men with Fabry disease receiving ERT (for a median of 94 months) and determined the amount of agalsidase necessary for antibody saturation. Clinical and biochemical outcomes included measurements of eGFR, interventricular septum thickness, and lyso-Gb3.

RESULTS

ADA titers decreased significantly in all patients during infusion. Agalsidase-α and agalsidase-β had similar ADA-binding capacity and comparable ADA saturation frequency. Fourteen patients with saturated ADAs presented with mild (but significant) loss of eGFR, stable septum thickness, and significantly decreased lyso-Gb3 levels. The 12 not saturated patients had a more pronounced and significant loss of eGFR, increased septum thickness, and a smaller, nonsignificant reduction in lyso-Gb3, over time. In three patients, dose escalation resulted in partially elevated ADA titers, but importantly, also in reduced lyso-Gb3 levels.

CONCLUSIONS

A not saturated ADA status during infusion is associated with progressive loss of eGFR and ongoing cardiac hypertrophy. Dose escalation can result in saturation of ADAs and decreasing lyso-Gb3 levels, but may lead to increased ADA titers.

European expert consensus statement on therapeutic goals in Fabry disease

BACKGROUND

Fabry disease, an inherited lysosomal storage disorder, causes multi-organ pathology resulting in substantial morbidity and a reduced life expectancy. Although Fabry disease is an X-linked disorder, both genders may be affected, but generally to a lesser extent in females. The disease spectrum ranges from classic early-onset disease to non-classic later-onset phenotypes, with complications occurring in multiple organs or being confined to a single organ system depending on the stage of the disease. The impact of therapy depends upon patient- and disease-specific factors and timing of initiation.

METHODS

A European panel of experts collaborated to develop a set of organ-specific therapeutic goals for Fabry disease, based on evidence identified in a recent systematic literature review and consensus opinion.

RESULTS

A series of organ-specific treatment goals were developed. For each organ system, optimal treatment strategies accounted for inter-patient differences in disease severity, natural history, and treatment responses as well as the negative burden of therapy and the importance of multidisciplinary care. The consensus therapeutic goals and proposed patient management algorithm take into account the need for early disease-specific therapy to delay or slow the progression of disease as well as non-specific adjunctive therapies that prevent or treat the effects of organ damage on quality of life and long-term prognosis.

CONCLUSIONS

These consensus recommendations help advance Fabry disease management by considering the balance between anticipated clinical benefits and potential therapy-related challenges in order to facilitate individualized treatment, optimize patient care and improve quality of life.

Development and Analytical Characterization of Pegunigalsidase Alfa, a Chemically Cross-Linked Plant Recombinant Human α-Galactosidase-A for Treatment of Fabry Disease

The current treatment of Fabry disease by enzyme replacement therapy with commercially available recombinant human α-Galactosidase A shows a continuous deterioration of the disease patients. Human recombinant α-Galactosidase A is a homodimer with noncovalently bound subunits and is expressed in the ProCellEx plant cell-based protein expression platform to produce pegunigalsidase alfa. The effect of covalent bonding between two α-Galactosidase A subunits by PEG-based cross-linkers of various lengths was evaluated in this study. The results show that cross-linking by a bifunctional PEG polymer of 2000 Da produces a more stable protein with improved pharmacokinetic and biodistribution properties. The chemical modification did not influence the tertiary protein structure but led to an increased thermal stability and showed partial masking of immune epitopes. The developed pegunigalsidase alfa is currently tested in phase III clinical trials and has a potential to show superior efficacy versus the currently used enzyme replacement therapies in the treatment of Fabry disease patients.

Pulmonary involvement in Fabry disease: effect of plasma globotriaosylsphingosine and time to initiation of enzyme replacement therapy

Introduction

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder caused by mutations of GLA gene leading to reduced α-galactosidase activity and resulting in a progressive accumulation of globotriaosylceramide (Gb3) and its deacylated derivative, globotriaosyl-sphingosine (Lyso-Gb3). Plasma Lyso-Gb3 levels serve as a disease severity and treatment monitoring marker during enzyme replacement therapy (ERT).

Methods

Adult patients with AFD who had yearly pulmonary function tests between 1999 and 2015 were eligible for this observational study. Primary outcome measures were the change in z-score of forced expiratory volume in the first second (FEV₁) and FEV₁/FVC over time. Plasma Lyso-Gb3 levels and the age of ERT initiation were investigated for their association with lung function decline.

Results

Fifty-three patients (42% male, median (range) age at diagnosis of AFD 34 (6–61) years in men, 34 (13–67) in women) were included. The greatest decrease of FEV₁/FVC z-scores was observed in Classic men (−0.048 per year, 95% CI −0.081 to –0.014), compared with the Later-Onset men (+0.013,95% CI −0.055 to 0.082), Classic women (−0.008, 95% CI −0.035 to +0.020) and Later-Onset women (−0.013, 95% CI −0.084 to +0.058). Cigarette smoking (P=0.022) and late ERT initiation (P=0.041) were independently associated with faster FEV₁ decline. FEV₁/FVC z-score decrease was significantly reduced after initiation of ERT initiation (−0.045 compared with −0.015, P=0.014). Furthermore, there was a trend towards a relevant influence of Lyso-Gb3 (P=0.098) on airflow limitation with age.

Conclusion

Early ERT initiation seems to preserve pulmonary function. Plasma Lyso-Gb3 is maybe a useful predictor for airflow limitation. Classic men need a closer monitoring of the lung function.

Agalsidase alfa versus agalsidase beta for the treatment of Fabry disease: an international cohort study

Background

Two recombinant enzymes (agalsidase alfa 0.2 mg/kg/every other week and agalsidase beta 1.0 mg/kg/every other week) have been registered for the treatment of Fabry disease (FD), at equal high costs. An independent international initiative compared clinical and biochemical outcomes of the two enzymes.

Methods

In this multicentre retrospective cohort study, clinical event rate, left ventricular mass index (LVMI), estimated glomerular filtration rate (eGFR), antibody formation and globotriaosylsphingosine (lysoGb3) levels were compared between patients with FD treated with agalsidase alfa and beta at their registered dose after correction for phenotype and sex.

Results

387 patients (192 women) were included, 248 patients received agalsidase alfa. Mean age at start of enzyme replacement therapy was 46 (±15) years. Propensity score matched analysis revealed a similar event rate for both enzymes (HR 0.96, P=0.87). The decrease in plasma lysoGb3 was more robust following treatment with agalsidase beta, specifically in men with classical FD (β: −18 nmol/L, P<0.001), persisting in the presence of antibodies. The risk to develop antibodies was higher for patients treated with agalsidase beta (OR 2.8, P=0.04). LVMI decreased in a higher proportion following the first year of agalsidase beta treatment (OR 2.27, P=0.03), while eGFR slopes were similar.

Conclusions

Treatment with agalsidase beta at higher dose compared with agalsidase alfa does not result in a difference in clinical events, which occurred especially in those with more advanced disease. A greater biochemical response, also in the presence of antibodies, and better reduction in left ventricular mass was observed with agalsidase beta.

Enzyme replacement therapy for Anderson-Fabry disease: A complementary overview of a Cochrane publication through a linear regression and a pooled analysis of proportions from cohort studies

BACKGROUND

Anderson-Fabry disease (AFD) is an X-linked recessive inborn error of glycosphingolipid metabolism caused by a deficiency of alpha-galactosidase A. Renal failure, heart and cerebrovascular involvement reduce survival. A Cochrane review provided little evidence on the use of enzyme replacement therapy (ERT). We now complement this review through a linear regression and a pooled analysis of proportions from cohort studies.

OBJECTIVES

To evaluate the efficacy and safety of ERT for AFD.

MATERIALS AND METHODS

For the systematic review, a literature search was performed, from inception to March 2016, using Medline, EMBASE and LILACS. Inclusion criteria were cohort studies, patients with AFD on ERT or natural history, and at least one patient-important outcome (all-cause mortality, renal, cardiovascular or cerebrovascular events, and adverse events) reported. The pooled proportion and the confidence interval (CI) are shown for each outcome. Simple linear regressions for composite endpoints were performed.

RESULTS

77 cohort studies involving 15,305 participants proved eligible. The pooled proportions were as follows: a) for renal complications, agalsidase alfa 15.3% [95% CI 0.048, 0.303; I2 = 77.2%, p = 0.0005]; agalsidase beta 6% [95% CI 0.04, 0.07; I2 = not applicable]; and untreated patients 21.4% [95% CI 0.1522, 0.2835; I2 = 89.6%, p<0.0001]. Effect differences favored agalsidase beta compared to untreated patients; b) for cardiovascular complications, agalsidase alfa 28% [95% CI 0.07, 0.55; I2 = 96.7%, p<0.0001]; agalsidase beta 7% [95% CI 0.05, 0.08; I2 = not applicable]; and untreated patients 26.2% [95% CI 0.149, 0.394; I2 = 98.8%, p<0.0001]. Effect differences favored agalsidase beta compared to untreated patients; and c) for cerebrovascular complications, agalsidase alfa 11.1% [95% CI 0.058, 0.179; I2 = 70.5%, p = 0.0024]; agalsidase beta 3.5% [95% CI 0.024, 0.046; I2 = 0%, p = 0.4209]; and untreated patients 18.3% [95% CI 0.129, 0.245; I2 = 95% p < 0.0001]. Effect differences favored agalsidase beta over agalsidase alfa or untreated patients. A linear regression showed that Fabry patients receiving agalsidase alfa are more likely to have higher rates of composite endpoints compared to those receiving agalsidase beta.

CONCLUSIONS

Agalsidase beta is associated to a significantly lower incidence of renal, cardiovascular and cerebrovascular events than no ERT, and to a significantly lower incidence of cerebrovascular events than agalsidase alfa. In view of these results, the use of agalsidase beta for preventing major organ complications related to AFD can be recommended.

Screening, diagnosis, and management of patients with Fabry disease: conclusions from a "Kidney Disease: Improving Global Outcomes" (KDIGO) Controversies Conference

Patients with Fabry disease (FD) are at a high risk for developing chronic kidney disease and cardiovascular disease. The availability of specific but costly therapy has elevated the profile of this rare condition. This KDIGO conference addressed controversial areas in the diagnosis, screening, and management of FD, and included enzyme replacement therapy and nonspecific standard-of-care therapy for the various manifestations of FD. Despite marked advances in patient care and improved overall outlook, there is a need to better understand the pathogenesis of this glycosphingolipidosis and to determine the appropriate age to initiate therapy in all types of patients. The need to develop more effective specific therapies was also emphasized.

Pompe disease in adulthood: effects of antibody formation on enzyme replacement therapy

PURPOSE

To determine the effect of antibodies against recombinant human acid α-glucosidase (rhGAA) on treatment efficacy and safety, and to test whether the GAA genotype is involved in antibody formation.

METHODS

We used enzyme-linked immunosorbent assay (ELISA) to determine anti-rhGAA antibody titers at baseline and at 6, 12, and 36 months of rhGAA treatment. We measured the capacity of antibodies to neutralize rhGAA enzymatic activity or cellular uptake and the effects on infusion-associated reactions (IARs), muscle strength, and pulmonary function.

RESULTS

Of 73 patients, 45 developed antibodies. Maximal titers were high (≥1:31,250) in 22% of patients, intermediate (1:1,250-1:31,250) in 40%, and none or low (0-1:1,250) in 38%. The common IVS1/delex18 GAA genotype was absent only in the high-titer group. The height of the titer positively correlated with the occurrence and number of IARs (P ≤ 0.001). On the group level, antibody titers did not correlate with treatment efficacy. Eight patients (11%) developed very high maximal titers (≥156,250), but only one patient showed high sustained neutralizing antibodies that probably interfered with treatment efficacy.

CONCLUSIONS

In adults with Pompe disease, antibody formation does not interfere with rhGAA efficacy in the majority of patients, is associated with IARs, and may be attenuated by the IVS1/delex18 GAA genotype.Genet Med 19 1, 90-97.

Enzymes approved for human therapy: indications, mechanisms and adverse effects

Research and drug developments fostered under orphan drug product development programs have greatly assisted the introduction of efficient and safe enzyme-based therapies for a range of rare disorders. The introduction and regulatory approval of 20 different recombinant enzymes has enabled, often for the first time, effective enzyme-replacement therapy for some lysosomal storage disorders, including Gaucher (imiglucerase, taliglucerase, and velaglucerase), Fabry (agalsidase alfa and beta), and Pompe (alglucosidase alfa) diseases and mucopolysaccharidoses I (laronidase), II (idursulfase), IVA (elosulfase), and VI (galsulfase). Approved recombinant enzymes are also now used as therapy for myocardial infarction (alteplase, reteplase, and tenecteplase), cystic fibrosis (dornase alfa), chronic gout (pegloticase), tumor lysis syndrome (rasburicase), leukemia (L-asparaginase), some collagen-based disorders such as Dupuytren's contracture (collagenase), severe combined immunodeficiency disease (pegademase bovine), detoxification of methotrexate (glucarpidase), and vitreomacular adhesion (ocriplasmin). The development of these efficacious and safe enzyme-based therapies has occurred hand in hand with some remarkable advances in the preparation of the often specifically designed recombinant enzymes; the manufacturing expertise necessary for commercial production; our understanding of underlying mechanisms operative in the different diseases; and the mechanisms of action of the relevant recombinant enzymes. Together with information on these mechanisms, safety findings recorded so far on the various adverse events and problems of immunogenicity of the recombinant enzymes used for therapy are presented.

Unravelling the mechanism of action of enzyme replacement therapy in Fabry disease

Fabry disease (FD) is a rare X-linked recessive glycosphingolipid-storage disorder caused by deficient activity of the lysosomal enzyme alpha-galactosidase A. Intravenous enzyme replacement therapy (ERT) has been used to supplement deficient enzyme activity in patients with FD. Despite its clinical effect and manifestations, clear criteria for the clinical effectiveness and cost-effectiveness of ERT have not been well established. In this study, we investigated the pharmacodynamic actions and short-term effects of ERT in patients with FD through direct molecular profiling from blood samples of patients before and after ERT. Based on this comparison, we observed that immune/inflammation-related pathways and growth factor-related pathways such as innate/adaptive immune pathway, lymphocyte proliferation and leukocyte proliferation were actively regulated under ERT. We also found that TINAGL1, DAAM2, CDK5R1 and MYO5B known to be related with clinical symptoms of FD showed increased levels after ERT, leading to the amelioration of clinical manifestations. Especially the catabolic process-related genes, including USP15 and ERUN1, showed direct increasing after ERT in vivo in male patients. These results suggest that male patients with FD respond more actively to ERT than do female patients with FD. Pathway analysis revealed that oxidative phosphorylation pathway-related genes are downregulated under ERT. ERT has a role to protect the proteins from oxidative damage and such deactivation of oxidative phosphorylation is one of direct pharmacodynamic actions of ERT. These results extended our understanding of the pathophysiology of ERT. To our knowledge, this is the first study to observe the molecular basis for the mechanism of ERT in vivo through the comprehensive comparison of transcriptome study with next-generation sequencing data.

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.

Rapid Immunochromatographic Detection of Serum Anti-α-Galactosidase A Antibodies in Fabry Patients after Enzyme Replacement Therapy

We developed an immunochromatography-based assay for detecting antibodies against recombinant α-galactosidase A proteins in serum. The evaluation of 29 serum samples from Fabry patients, who had received enzyme replacement therapy with agalsidase alpha and/or agalsidase beta, was performed by means of this assay method, and the results clearly revealed that the patients exhibited the same level of antibodies against both agalsidase alpha and agalsidase beta, regardless of the species of recombinant α-galactosidase A used for enzyme replacement therapy. A conventional enzyme-linked immunosorbent assay supported the results. Considering these, enzyme replacement therapy with agalsidase alpha or agalsidase beta would generate antibodies against the common epitopes in both agalsidase alpha and agalsidase beta. Most of the patients who showed immunopositive reaction exhibited classic Fabry phenotype and harbored gene mutations affecting biosynthesis of α-galactosidase A. As immunochromatography is a handy and simple assay system which can be available at bedside, this assay method would be extremely useful for quick evaluation or first screening of serum antibodies against agalsidase alpha or agalsidase beta in Fabry disease with enzyme replacement therapy.

The role of antibodies in enzyme treatments and therapeutic strategies

Substitution of the defective lysosomal enzyme in lysosomal storage disorders (LSDs) often elicits antibody formation towards the infused protein. Aside from Gaucher disease, antibodies often lead to infusion associated reactions and a reduced biochemical response. In Pompe disease, antibody titer is predictive of clinical outcome, but this is less apparent in other LSDs and warrants further study. Few laboratories are capable of enzyme-antibody determination: often physicians need to rely on the enzyme manufacturer for analysis. Currently, laboratories employ different antibody assays which hamper comparisons between cohorts or treatment regimens. Assay standardisation, including measurement of antibody-related enzyme inhibition, is therefore urgently needed. Successful immunomodulation has been reported in Pompe and in Gaucher disease, with variable success. Immunomodulation regimens that contain temporary depletion of B-cells (anti-CD20) are most used. Bone marrow transplantation in MPS-I results in disappearance of antibodies. No other clinical studies have been conducted in humans with immunomodulation in other LSDs.

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.

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.

A randomised, double-blind, placebo-controlled, crossover study to assess the efficacy and safety of three dosing schedules of agalsidase alfa enzyme replacement therapy for Fabry disease

Anecdotal reports suggest that the currently approved dosing interval of agalsidase alfa (0.2 mg/kg/2 weeks) for Fabry disease treatment is too long. This randomised, double-blind, placebo-controlled, crossover study investigated three altered dosing intervals. 18 Fabry patients received three agalsidase alfa dosing schedules, each for four weeks (A: 0.2 mg/kg∗2 weeks, B: 0.1 mg/kg/week, C: 0.2 mg/kg/week). Health state, pain levels, sweat volume and latency and plasma and urinary globotriaosylceramide levels were recorded throughout the study. No significant differences were found among the schedules for the primary efficacy outcome of self-assessed health state, or for pain scores. A trend toward increased sweat volume on QSART testing, and reduced urine globotriaosylceramide concentration were seen with treatment schedule C. Agalsidase alfa was safe and well tolerated with all schedules. In conclusion, the primary analyses did not find weekly infusions of agalsidase alfa to be statistically better than the approved dosing schedule however the data indicates that further studies with more patients over a longer period are required to more accurately determine the optimum dose and schedule.

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.

A revised home treatment algorithm for Fabry disease: influence of antibody formation

BACKGROUND

Enzyme replacement therapy for Fabry disease, consisting of biweekly infusions, interferes daily life. Home treatment proved beneficial. We evaluated a previously reported home treatment algorithm aiming to shorten the period of in-hospital infusions, while ascertaining patient safety.

METHODS

Retrospective analysis on clinical records of treated Fabry patients. Potentially predictive factors for infusion associated reactions (IARs) were studied: agalsidase antibodies, agalsidase product and dose, FOS-SSI scores, and GLA activity and mutation. A questionnaire evaluated patient satisfaction and compliance.

RESULTS

Seventy-nine patients were included (41 males, 46% agalsidase antibody positive (AB+)). 85% received home treatment. Home treatment complications were erroneous fast infusion rates (n=4) causing IARs and, rarely, venous access problems. The single SAE was unrelated to home treatment. IgG antibody status was significantly associated with IARs (89% vs. 26% p-value<0.01). Negative antibody status did not preclude IARs. Except for three AB+ patients, all first IARs occurred within 13 infusions. IARs occurred more frequently in patients using agalsidase beta 1.0 mg/kg/eow than agalsidase alpha or beta 0.2 mg/kg/eow, but the time to first IAR did not differ between groups. Four AB+ males experienced IARs after a dose increase. Compliance between home and in-hospital treatment was similar. Most patients preferred home treatment.

CONCLUSION

In this study home therapy for Fabry disease was safe and improved patient satisfaction. We propose a revised algorithm which allows safe home-treatment in all male patients after 13 instead of 26 infusions, irrespective of ERT preparation or dose. Furthermore, AB+ patients with dosage increase may experience new or increased IARs, necessitating in-hospital observations.

Enzyme replacement therapy for lysosomal diseases: lessons from 20 years of experience and remaining challenges

In 1964, Christian de Duve first suggested that enzyme replacement might prove therapeutic for lysosomal storage diseases (LSDs). Early efforts identified the major obstacles, including the inability to produce large quantities of the normal enzymes, the lack of animal models for proof-of-concept studies, and the potentially harmful immune responses to the "foreign" normal enzymes. Subsequently, the identification of receptor-mediated targeting of lysosomal enzymes, the cloning and overexpression of human lysosomal genes, and the generation of murine models markedly facilitated the development of enzyme replacement therapy (ERT). However, ERT did not become a reality until the early 1990s, when its safety and effectiveness were demonstrated for the treatment of type 1 Gaucher disease. Today, ERT is approved for six LSDs, and clinical trials with recombinant human enzymes are ongoing in several others. Here, we review the lessons learned from 20 years of experience, with an emphasis on the general principles for effective ERT and the remaining challenges.

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.

Effects of switching from agalsidase Beta to agalsidase alfa in 10 patients with anderson-fabry disease

Anderson-Fabry disease (AFD) is a multiorgan X-linked lysosomal storage disease that particularly affects the heart, kidneys, and cerebrovascular system. Current treatment is enzyme replacement therapy (ERT) with agalsidase beta (Fabrazyme(®), Genzyme Corporation, Cambridge, MA, USA) or agalsidase alfa (Replagal(®), Shire Human Genetic Therapies AB, Lund, Sweden). It was recommended that patients switch to agalsidase alfa due to a manufacturing shortage of agalsidase beta beginning in June 2009. This study assessed the effect of switching to agalsidase alfa on clinical outcomes in patients with AFD previously treated with agalsidase beta. Ten patients (seven male, three female) with genetically confirmed AFD and at least 48 months' continuous data collected during treatment with agalsidase beta 1 mg/kg every other week were switched to agalsidase alfa 0.2 mg/kg every other week for at least 20 months, with prospective clinical evaluations every 6 months. Pre-switch data was collected retrospectively from patient charts. Cardiac functional parameters were assessed using magnetic resonance imaging. Results showed that renal function was normal (estimated glomerular filtration rate ≥90 mL/min/1.73 m(2)) in 8 of 10 patients prior to agalsidase alfa and generally remained stable after the switch. Cardiac mass decreased significantly (p < 0.05 vs pre-ERT) after agalsidase beta and remained unchanged after switching to agalsidase alfa. Symptoms of pain and health status scores did not deteriorate during agalsidase alfa therapy. Adverse events were mostly mild and infusion related. In conclusion, switching to agalsidase alfa was relatively well tolerated and associated with stable clinical status and preserved renal and cardiac function.