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

Establishing Treatment Effectiveness in Fabry Disease: Observation-Based Recommendations for Improvement

Fabry disease (FD, OMIM #301500) is caused by pathogenic GLA gene (OMIM #300644) variants, resulting in a deficiency of the α-galactosidase A enzyme with accumulation of its substrate globotriaosylceramide and its derivatives. The phenotype of FD is highly variable, with distinctive disease features and course in classical male patients but more diverse and often nonspecific features in non-classical and female patients. FD-specific therapies have been available for approximately two decades, yet establishing robust evidence for long-term effectiveness remains challenging. This review aims to identify the factors contributing to this lack of robust evidence for the treatment of FD with enzyme replacement therapy (ERT) (agalsidase-alfa and -beta and pegunigalsidase alfa) and chaperone therapy (migalastat). Major factors that have been identified are study population heterogeneity (concerning sex, age, phenotype, disease stage) and differences in study design (control groups, outcomes assessed), as well as the short duration of studies. To address these challenges, we advocate for patient matching to improve control group compatibility in future FD therapy studies. We recommend international collaboration and harmonization, facilitated by an independent FD registry. We propose a stepwise approach for evaluating the effectiveness of novel treatments, including recommendations for surrogate outcomes and required study duration.

Fabry Disease Rat Model Develops Age- and Sex-Dependent Anterior Segment Ocular Abnormalities

Purpose

Fabry disease is an X-linked lysosomal storage disorder that results in multi-systemic renal, cardiovascular, and neuropathological damage, including in the eyes. We evaluated anterior segment ocular abnormalities based on age, sex (male and female), and genotype (wild-type, knockout [KO] male, heterozygous [HET] female, and KO female) in a rat model of Fabry disease.

Methods

The α-Gal A KO and WT rats were divided into young (6-24 weeks), adult (25-60 weeks), and aged (61+ weeks) groups. Intraocular pressure (IOP) was measured. Eyes were clinically scored for corneal and lens opacity as well as evaluated for corneal epithelial integrity and tear break-up time (TBUT). Anterior chamber depth (ACD) and central corneal thickness (CCT) using anterior segment-optical coherence tomography (AS-OCT).

Results

The Fabry rats showed an age-dependent increase in IOP, predominantly in the male genotype. TBUT was decreased in both male and female groups with aging. Epithelial integrity was defective in KO males and HET females with age. However, it was highly compromised in KO females irrespective of age. Corneal and lens opacities were severely affected irrespective of sex or genotype in the aging Fabry rats. AS-OCT quantification of CCT and ACD also demonstrated age-dependent increases but were more pronounced in Fabry versus WT genotypes.

Conclusions

Epithelial integrity, corneal, and lens opacities worsened in Fabry rats, whereas IOP and TBUT changes were age-dependent. Similarly, CCT and ACD were age-related but more pronounced in Fabry rats, providing newer insights into the anterior segment ocular abnormalities with age, sex, and genotype in a rat model of Fabry disease.

Oxidative stress and its role in Fabry disease

Fabry disease is a rare X-linked disease characterized by deficient expression and activity of alpha-galactosidase A with consequent lysosomal accumulation of glycosphingolipids, particularly globotriaosylceramide in various organs. Currently, enzyme replacement therapy with recombinant human α-galactosidase is the cornerstone of the treatment of Fabry patients, although in the long term enzyme replacement therapy fails to halt disease progression, in particular in case of late diagnosis. This suggests that the adverse outcomes cannot be justified by the lysosomal accumulation of glycosphingolipids alone, and that additional therapies targeted at further pathophysiologic mechanisms might contribute to halting the progression of cardiac, cerebrovascular and kidney disease in Fabry patients. Recent evidence points toward the involvement of oxidative stress, oxidative stress signaling and inflammation in the pathophysiology of cardio cerebrovascular and kidney damage in Fabry patients. This review reports the current knowledge of the involvement of oxidative stress in Fabry disease, which clearly points toward the involvement of oxidative stress in the pathophysiology of the medium to long-term cardio-cerebrovascular-kidney damage of Fabry patients and summarizes the antioxidant therapeutic approaches currently available in the literature. This important role played by oxidative stress suggests potential novel additional therapeutic interventions by either pharmacologic or nutritional measures, on top of enzyme replacement therapy, aimed at improving/halting the progression of cardio-cerebrovascular disease and nephropathy that occur in Fabry patients.

The Effect of Fabry Disease Therapy on Bone Mineral Density

Fabry disease (FD) is an X-linked lysosomal storage disorder, characterised by the cellular accumulation of globotriaosylceramide due to impaired alpha-galactosidase A enzyme activity. FD may manifest with multisystem pathology, including reduced bone mineral density (BMD). Registry data suggest that the introduction of Fabry-specific therapies (enzyme replacement therapy or chaperone therapy) has led to significant improvements in overall patient outcomes; however, there are limited data on the impact on bone density. The aim of this study was to describe the effect of Fabry-specific therapies on longitudinal changes in bone mineral density (BMD) in FD. We performed a retrospective observational study analysing bone densitometry (DXA) in patients with genetically confirmed FD. Patients were grouped based on the use of Fabry-specific therapies. The between-group longitudinal change in BMD Z-score was analysed using linear mixed effects models. A total of 88 FD patients were analysed (50 untreated; 38 treated). The mean age at first DXA was 38.5 years in the untreated group (84% female) and 43.7 years in the treated group (34% female). There was no significant longitudinal between-group difference in the BMD Z-score at the lumbar spine. However, the Z-score per year at the total hip (β = -0.105, p < 0.001) and femoral neck (β = -0.081, p = 0.001) was significantly lower over time in the treated than the untreated group. This may reflect those receiving therapy having a more severe underlying disease. Nevertheless, this suggests that Fabry-specific therapies do not reverse all disease mechanisms and that the additional management of BMD may be required in this patient population.

Inflammation and Exosomes in Fabry Disease Pathogenesis

Fabry Disease (FD) is one of the most prevalent lysosomal storage disorders, resulting from mutations in the GLA gene located on the X chromosome. This genetic mutation triggers glo-botriaosylceramide (Gb-3) buildup within lysosomes, ultimately impairing cellular functions. Given the role of lysosomes in immune cell physiology, FD has been suggested to have a profound impact on immunological responses. During the past years, research has been focusing on this topic, and pooled evidence strengthens the hypothesis that Gb-3 accumulation potentiates the production of pro-inflammatory mediators, revealing the existence of an acute inflammatory process in FD that possibly develops to a chronic state due to stimulus persistency. In parallel, extracellular vesicles (EVs) have gained attention due to their function as intercellular communicators. Considering EVs' capacity to convey cargo from parent to distant cells, they emerge as potential inflammatory intermediaries capable of transporting cytokines and other immunomodulatory molecules. In this review, we revisit the evidence underlying the association between FD and altered immune responses and explore the potential of EVs to function as inflammatory vehicles.

Fabry Disease: Cardiac Implications and Molecular Mechanisms

PURPOSE OF REVIEW

This review explores the interplay among metabolic dysfunction, oxidative stress, inflammation, and fibrosis in Fabry disease, focusing on their potential implications for cardiac involvement. We aim to discuss the biochemical processes that operate in parallel to sphingolipid accumulation and contribute to disease pathogenesis, emphasizing the importance of a comprehensive understanding of these processes.

RECENT FINDINGS

Beyond sphingolipid accumulation, emerging studies have revealed that mitochondrial dysfunction, oxidative stress, and chronic inflammation could be significant contributors to Fabry disease and cardiac involvement. These factors promote cardiac remodeling and fibrosis and may predispose Fabry patients to conduction disturbances, ventricular arrhythmias, and heart failure. While current treatments, such as enzyme replacement therapy and pharmacological chaperones, address disease progression and symptoms, their effectiveness is limited. Our review uncovers the potential relationships among metabolic disturbances, oxidative stress, inflammation, and fibrosis in Fabry disease-related cardiac complications. Current findings suggest that beyond sphingolipid accumulation, other mechanisms may significantly contribute to disease pathogenesis. This prompts the exploration of innovative therapeutic strategies and underscores the importance of a holistic approach to understanding and managing Fabry disease.

SD-OCT Imaging of Macular Changes in Fabry Disease: A Case Report

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder that can result in fatal end-stage renal disease, heart failure, and cerebro-occlusive events. Vague clinical symptoms and rarity often mean diagnosis and potential treatment is delayed. Ophthalmic findings in FD patients can be helpful in establishing an early diagnosis and timely treatment. Spectral domain optical coherence tomography (SD-OCT) imaging in FD patients shows hyper-reflective foci (HRF) in characteristic patterns within the inner retinal layers. We found that the HRF was localised in linear distributions at the deep and superficial borders of the retinal inner nuclear layer, likely reflecting anatomic vascular plexuses and FD-related sphingolipid deposition within the vessel walls. These results highlight the potential use of SD-OCT in FD and how it may aid diagnosis in undifferentiated patients, prognostication, and disease monitoring.

Disease-specific therapy for the treatment of the cardiovascular manifestations of Fabry disease: a systematic review

OBJECTIVE

The cardiovascular manifestations of Fabry disease are common and represent the leading cause of death. Disease-specific therapy, including enzyme replacement therapy (ERT) and chaperone therapy (migalastat), is recommended for patients exhibiting cardiovascular involvement, but its efficacy for modulating cardiovascular disease expression and optimal timing of initiation remains to be fully established. We therefore aimed to systematically review and evaluate the effectiveness of disease-specific therapy compared with placebo, and to no intervention, for the cardiovascular manifestations of Fabry disease.

METHODS

Eight databases were searched from inception using a combination of relevant medical subject headings and keywords. Randomised, non-randomised studies with a comparator group and non-randomised studies without a comparator group were included. Studies were screened for eligibility and assessed for bias by two independent authors. The primary outcome comprised clinical cardiovascular events. Secondary outcomes included myocardial histology and measurements of cardiovascular structure, function and tissue characteristics.

RESULTS

72 studies were included, comprising 7 randomised studies of intervention, 16 non-randomised studies of intervention with a comparator group and 49 non-randomised studies of intervention without a comparator group. Randomised studies were not at serious risk of bias, but the others were at serious risk. Studies were highly heterogeneous in their design, outcome measurements and findings, which made assessment of disease-specific therapy effectiveness difficult.

CONCLUSION

It remains unclear whether disease-specific therapy sufficiently impacts the cardiovascular manifestations of Fabry disease. Further work, ideally in larger cohorts, with more standardised clinical and phenotypic outcomes, the latter measured using contemporary techniques, are required to fully elucidate the cardiovascular impact of disease-specific therapy.

PROSPERO REGISTRATION NUMBER

CRD42022295989.

Genotype-Phenotype Correlations in 293 Russian Patients with Causal Fabry Disease Variants

BACKGROUND

Fabry disease (FD) is a rare hereditary multisystem disease caused by variants of the GLA gene. Determination of GLA gene variants and identification of genotype-phenotype correlations allow us to explain the features of FD associated with predominant damage of one or another system, both in the classical and atypical forms of FD, as well as in cases with late manifestation and involvement of one of the systems.

METHODS

The study included 293 Russian patients with pathogenic variants of the GLA gene, which were identified as a result of various selective screening programs. Screening was carried out for 48,428 high-risk patients using a two-step diagnostic algorithm, including the determination of the concentration of the biomarker lyso-Gb3 as a first-tier test. Screening of atypical FD among patients with HCM was carried out via high-throughput sequencing in another 2427 patients.

RESULTS

102 (0.20%) cases of FD were identified among unrelated patients as a result of the study of 50,855 patients. Molecular genetic testing allowed us to reveal the spectrum and frequencies of 104 different pathogenic variants of the GLA gene in 293 examined patients from 133 families. The spectrum and frequencies of clinical manifestations in patients with FD, including 20 pediatric patients, were described. Correlations between the concentration of the lyso-Gb3 biomarker and the type of pathogenic variants of the GLA gene have been established. Variants identified in patients with early stroke were described, and the association of certain variants with the development of stroke was established.

CONCLUSIONS

The results of a large-scale selective FD screening, as well as clinical and molecular genetic features, in a cohort of 293 Russian patients with FD are described.

Systems analyses of the Fabry kidney transcriptome and its response to enzyme replacement therapy identified and cross-validated enzyme replacement therapy-resistant targets amenable to drug repurposing

Fabry disease is a rare disorder caused by variations in the alpha-galactosidase gene. To a degree, Fabry disease is manageable via enzyme replacement therapy (ERT). By understanding the molecular basis of Fabry nephropathy (FN) and ERT's long-term impact, here we aimed to provide a framework for selection of potential disease biomarkers and drug targets. We obtained biopsies from eight control individuals and two independent FN cohorts comprising 16 individuals taken prior to and after up to ten years of ERT, and performed RNAseq analysis. Combining pathway-centered analyses with network-science allowed computation of transcriptional landscapes from four nephron compartments and their integration with existing proteome and drug-target interactome data. Comparing these transcriptional landscapes revealed high inter-cohort heterogeneity. Kidney compartment transcriptional landscapes comprehensively reflected differences in FN cohort characteristics. With exception of a few aspects, in particular arteries, early ERT in patients with classical Fabry could lastingly revert FN gene expression patterns to closely match that of control individuals. Pathways nonetheless consistently altered in both FN cohorts pre-ERT were mostly in glomeruli and arteries and related to the same biological themes. While keratinization-related processes in glomeruli were sensitive to ERT, a majority of alterations, such as transporter activity and responses to stimuli, remained dysregulated or reemerged despite ERT. Inferring an ERT-resistant genetic module of expressed genes identified 69 drugs for potential repurposing matching the proteins encoded by 12 genes. Thus, we identified and cross-validated ERT-resistant gene product modules that, when leveraged with external data, allowed estimating their suitability as biomarkers to potentially track disease course or treatment efficacy and potential targets for adjunct pharmaceutical treatment.

Circulating Anti-GB3 Antibody as a Biomarker of Myocardial Inflammation in Patients with Fabry Disease Cardiomyopathy

BACKGROUND

Fabry disease cardiomyopathy (FDCM) has manifested some resistance to enzyme replacement therapy (ERT), particularly in its advanced phase. Recently, myocardial inflammation of autoimmune origin has been demonstrated in FDCM.

AIMS

The objective of this study was the assessment of circulating anti-globotriaosylceramide (GB3) antibodies as potential biomarkers of myocardial inflammation in FDCM, defined by the additional presence of ≥CD3+ 7 T lymphocytes/low-power field associated with focal necrosis of adjacent myocytes. Its sensitivity was based on the evidence of overlapping myocarditis at left ventricular endomyocardial biopsy.

METHODS AND RESULTS

From January 1996 to December 2021, 85 patients received a histological diagnosis of FDCM in our department and 48 (56.5%) of them had an overlapping myocardial inflammation with negative PCR for common cardiotropic viruses, positive antiheart, and antimyosin abs. The presence of anti-GB3 antibodies was evaluated with an in-house ELISA assay (BioGeM scarl Medical Investigational Research, MIR-Ariano Irpino, Italy), along with antiheart and antimyosin abs, in the FDCM patients and compared with control healthy individuals. The correlation between levels of circulating anti-GB3 autoantibody myocardial inflammation and FDCM severity was assessed. Anti-Gb3 antibodies were above the positivity cut-off in 87.5% of FDCM subjects with myocarditis (42 out of 48), while 81.1% of FDCM patients without myocarditis were identified as negative for Gb3 antibodies. Positive anti-Gb3 abs correlated with positive antiheart and antimyosin abs.

CONCLUSIONS

The present study suggests a potential positive role of anti-GB3 antibodies as a marker of overlapping cardiac inflammation in patients with FDCM.

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.

Supporting the Diagnosis of Fabry Disease Using a Natural Language Processing-Based Approach

In clinical practice, the consideration of non-specific symptoms of rare diseases in order to make a correct and timely diagnosis is often challenging. To support physicians, we developed a decision-support scoring system on the basis of retrospective research. Based on the literature and expert knowledge, we identified clinical features typical for Fabry disease (FD). Natural language processing (NLP) was used to evaluate patients' electronic health records (EHRs) to obtain detailed information about FD-specific patient characteristics. The NLP-determined elements, laboratory test results, and ICD-10 codes were transformed and grouped into pre-defined FD-specific clinical features that were scored in the context of their significance in the FD signs. The sum of clinical feature scores constituted the FD risk score. Then, medical records of patients with the highest FD risk score were reviewed by physicians who decided whether to refer a patient for additional tests or not. One patient who obtained a high-FD risk score was referred for DBS assay and confirmed to have FD. The presented NLP-based, decision-support scoring system achieved AUC of 0.998, which demonstrates that the applied approach enables for accurate identification of FD-suspected patients, with a high discrimination power.

Could immune cells be associated with nephropathy in Fabry disease patients?

BACKGROUND

In Fabry Disease (FD), although the primary factor initiating kidney damage is glycosphingolipid accumulation, secondary conditions such as increased inflammation and fibrosis may cause this damage to progress. These processes may be induced by immune cells. Therefore, we aimed to investigate the peripheral lymphocyte subgroup analysis of the patients with FD and compare these results with healthy individuals. In addition, we performed T, B, NK, and plasma cell analyses in kidney biopsy materials and compared these kidney biopsy results with the biopsy results of patients whose kidney functions were impaired after 4 years of regular ERT.

MATERIALS AND METHODS

18 FD and 16 healthy individuals were included in the study. T-B lymphocyte and NK-cell populations were determined. We performed kidney biopsies (KBx) on 13 patients with FD prior to ERT. Of these, 4 patients had rebiopsy after 4 years of regular ERT. Immunohistochemical staining was performed to define immune cell infiltration.

RESULTS

There was no statistically significant difference in terms of total, helper and cytotoxic T-lymphocyte and CD3^-CD16⁺CD56⁺ natural killer (NK)-cell count (p = 0.20; p = 0.12; p = 0.76; p = 0.75, respectively).According to KBx findings prior to ERT, all patients had interstitial fibrosis (IF), podocyte vacuoles (PV), and podocyte inclusion (PI), CD3, CD4, CD8, CD16, and CD56 positivity at different levels. None of the patients had CD19, CD20, and CD138 positivity at the first biopsies. When we compared the first and the second KBx results of the two progressors, we also demonstrated that CD3⁺4⁺T-cells infiltration remained the same, whereas CD8⁺T cells, CD16⁺ and 56⁺NK-cells infiltration were significantly decreased. In contrast, CD20⁺B cells and CD138⁺plasma cell infiltration were significantly increased despite 4 years of ERT (15 fold and sixfold, respectively). The CD20⁺B and CD138⁺ plasma cells and IF were positively correlated with proteinuria.

CONCLUSIONS

The progression of FD nephropathy and proteinuria is increased despite a long-term ERT. Immune cells, primarily B and plasma cells, might cause these unwanted consequences.

The Benefits of Early versus Late Therapeutic Intervention in Fabry Disease

Background

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by pathogenic variants of the GLA gene. Heterozygous female patients may show much more variability in clinical manifestations, ranging from asymptomatic to full-blown disease. Because of this heterogeneous clinical picture in women, the diagnosis of FD has typically been delayed for more than a decade, and the optimal time to initiate treatment remains controversial. Case Presentation. Here, we present two unrelated female patients diagnosed with FD harbouring the same pathogenic GLA variant. We discuss the implications of initiating specific therapy at different stages of the disease, with and without organ involvement (early versus late therapeutic intervention).

Conclusions

These clinical cases suggest that initiating specific treatment at an earlier age in women with FD may prevent organ involvement and associated clinical events.

Emerging cellular themes in leukodystrophies

Leukodystrophies are a broad spectrum of neurological disorders that are characterized primarily by deficiencies in myelin formation. Clinical manifestations of leukodystrophies usually appear during childhood and common symptoms include lack of motor coordination, difficulty with or loss of ambulation, issues with vision and/or hearing, cognitive decline, regression in speech skills, and even seizures. Many cases of leukodystrophy can be attributed to genetic mutations, but they have diverse inheritance patterns (e.g., autosomal recessive, autosomal dominant, or X-linked) and some arise from de novo mutations. In this review, we provide an updated overview of 35 types of leukodystrophies and focus on cellular mechanisms that may underlie these disorders. We find common themes in specialized functions in oligodendrocytes, which are specialized producers of membranes and myelin lipids. These mechanisms include myelin protein defects, lipid processing and peroxisome dysfunction, transcriptional and translational dysregulation, disruptions in cytoskeletal organization, and cell junction defects. In addition, non-cell-autonomous factors in astrocytes and microglia, such as autoimmune reactivity, and intercellular communication, may also play a role in leukodystrophy onset. We hope that highlighting these themes in cellular dysfunction in leukodystrophies may yield conceptual insights on future therapeutic approaches.

Twenty years of the Fabry Outcome Survey (FOS): insights, achievements, and lessons learned from a global patient registry

Background

Patient registries provide long-term, real-world evidence that aids the understanding of the natural history and progression of disease, and the effects of treatment on large patient populations with rare diseases. The year 2021 marks the 20th anniversary of the Fabry Outcome Survey (FOS), an international, multicenter, observational registry (NCT03289065). The primary aims of FOS are to broaden the understanding of Fabry disease (FD), an X-linked lysosomal storage disorder, and to improve the clinical management of affected patients. Here, we review the history of FOS and the analyses and publications disseminated from the registry, and we discuss the contributions FOS studies have made in understanding FD.

Results

FOS was initiated in April 2001 and, as of January 2021, 4484 patients with a confirmed diagnosis and patient informed consent have been enrolled from 144 centers across 26 countries. Data from FOS have been published in nearly 60 manuscripts on a wide variety of topics relevant to FD. Analyses of FOS data have investigated the long-term effectiveness and safety of enzyme replacement therapy (ERT) with agalsidase alfa and its effects on morbidity and mortality, as well as the benefits of prompt and early treatment with agalsidase alfa on the progression of cardiomyopathy and the decline in renal function associated with FD. Based on analyses of FOS data, ERT with agalsidase alfa has also been shown to improve additional signs and symptoms of FD experienced by patients. FOS data analyses have provided a better understanding of the natural history of FD and the specific populations of women, children, and the elderly, and have provided practical tools for the study of FD. FOS has also provided methodology and criteria for assessing disease severity which contributed to the continuous development of medical practice in FD and has largely improved our understanding of the challenges and needs of long-term data collection in rare diseases, aiding in future rare disease real-world evidence studies.

Conclusion

FOS over the last 20 years has substantially increased the scientific knowledge around improved patient management of FD and continues to expand our understanding of this rare disease.

Echocardiography in Anderson-Fabry Disease

Echocardiography is the most common diagnostic tool to screen for Fabry cardiomyopathy as it is fast, non-invasive, low-cost, widely available, easily applicable and reproducible. Echocardiography is the first-line investigation, being useful in all the stages of the disease: (1) in gene-positive patients, to unveil signs of early cardiac involvement and allowing timely treatment; (2) in patients with overt cardiomyopathy to estimate the severity of cardiac involvement, the possible related complications, and the effect of treatment. Recently, advanced echocardiographic techniques, such as speckle tracking analysis, are offering new insights in the assessment of Fabry disease patients and in the differential diagnosis of cardiomyopathies with hypertrophic phenotype. The aim of this review is to provide a comprehensive overview on the cardiac structural and functional abnormalities described in Fabry disease by means of echocardiography.

Endocrine disorders in patients with Fabry disease: insights from a reference centre prospective study

CONTEXT

Fabry Disease (FD) is a rare X-linked storage disease characterised by a-galactosidase A deficiency and diffuse organ accumulation of glycosphingolipids. Enzyme replacement and chaperone therapies are only partially effective. It remains unclear if FD-related endocrine disorders contribute to the observed morbidity.

OBJECTIVE

To investigate the function of the endocrine system in patients with FD.

DESIGN

We conducted an observational prospective study from 2017 to 2020.

SETTING AND PATIENTS

We included 77 patients with genetically confirmed FD (27 men, 20/27 Classic, 7/26 Late Onset phenotype, 50 women, 41/50 and 9/50 respectively), who are systematically followed by our reference centre.

RESULTS

36/77 (46.8%) patients had VitD deficiency (25(0H)VitD <20 μg/L) despite the fact that 19/36 (52.8%) were substituted with cholecalciferol. Only 21/77 (27.3%) patients had normal VitD levels without VitD substitution. 11/77 (14.3%) had significant hypophosphatemia (p < 0.80 mmol/L). Three new cases (3.9%) of subclinical, two (2.6%) of overt and six (7.8%) of known hypothyroidism were identified. Of note, men had significantly higher renin levels than women [61.4 (26.1-219.6) vs.25.4 (10.9-48.0) mU/L, p = 0.003]. There were no major abnormalities in adrenal, growth and sex-hormone axes. Patients of Classic phenotype had significantly higher High-Density Lipoprotein Cholesterol (HDL-C) levels (p = 0.002) and in men those levels were positively correlated with globotriaosylsphingosin (Lyso-Gb3) values. 10/77 (13%) of the patients were underweight.

CONCLUSIONS

VitD supplementation should be considered for all patients with FD. Thyroid screening should be routinely performed. Malnutrition should be prevented or treated, particularly in Classic phenotype patients. Overall, our data suggest that FD specialists should actively seek and diagnose endocrine disorders in their patients.

Recommendations for the diagnosis and management of Fabry disease in pediatric patients: a document from the Rare Diseases Committee of the Brazilian Society of Nephrology (Comdora-SBN)

Abstract Fabry disease (FD) is a genetic disease, with X-chromosome linked inheritance, due to variants in the GLA gene that encodes the α-galactosidase A (α-GAL) enzyme. The purpose of the present study was to create a consensus aiming to standardize the recommendations regarding the renal involvement of FD with guidelines on the diagnosis, screening, and treatment of pediatric patients. This consensus is an initiative of the Rare Diseases Committee (Comdora) of the Brazilian Society of Nephrology (SBN). Randomized controlled clinical studies and studies with real-life data added to the authors' experience were considered for this review. The result of this consensus was to help manage patient and physician expectations regarding treatment outcomes. Thus, this consensus document recommends the investigation of the pediatric family members of an index case, as well as cases with suggestive clinical signs. From the diagnosis, assess all possible FD impairments and grade through scales. From an extensive review of the literature including pediatric protocols and particularly evaluating pediatric cases from general studies, it can be concluded that the benefits of early treatment are great, especially in terms of neuropathic pain and renal impairment parameters and outweigh the possible adverse effects that were mainly manifested by infusion reactions.

Brazilian consensus recommendations for the diagnosis, screening, and treatment of individuals with fabry disease: Committee for Rare Diseases - Brazilian Society of Nephrology/2021

Fabry disease (FD) is an X-linked inherited disorder caused by mutations in the GLA gene encoding enzyme alpha-galactosidase A (α-Gal A). The purpose of this study was to produce a consensus statement to standardize the recommendations concerning kidney involvement in FD and provide advice on the diagnosis, screening, and treatment of adult and pediatric patients. This consensus document was organized from an initiative led by the Committee for Rare Diseases (Comdora) of the Brazilian Society of Nephrology (SBN). The review considered randomized clinical trials, real-world data studies, and the expertise of its authors. The purpose of this consensus statement is to help manage patient and physician expectations concerning the outcomes of treatment. Our recommendations must be interpreted within the context of available evidence. The decisions pertaining to each individual case must be made with the involvement of patients and their families and take into account not only the potential cost of treatment, but also concurrent conditions and personal preferences. The Comdora intends to update these recommendations regularly so as to reflect recent literature evidence, real-world data, and appreciate the professional experience of those involved. This consensus document establishes clear criteria for the diagnosis of FD and for when to start or stop specific therapies or adjuvant measures, to thus advise the medical community and standardize clinical practice.

Gene therapy for Fabry disease: Progress, challenges, and outlooks on gene-editing

Gene therapy is the delivery of a therapeutic gene for endogenous cellular expression with the goal of rescuing a disease phenotype. It has been used to treat an increasing number of human diseases with many strategies proving safe and efficacious in clinical trials. Gene delivery may be viral or non-viral, performed in vivo or ex vivo, and relies on gene integration or transient expression; all of these techniques have been applied to the treatment of Fabry disease. Fabry disease is a genetic disorder of the α-galactosidase A gene, GLA, that causes an accumulation of glycosphingolipids in cells leading to cardiac, renal and cerebrovascular damage and eventually death. Currently, there are no curative treatments available, and the therapies that are used have significant drawbacks. These treatment concerns have led to the advent of gene therapies for Fabry disease. The first Fabry patients to receive gene therapy were treated with recombinant lentivirus targeting their hematopoietic stem/progenitor cells. Adeno-associated virus treatments have also begun. Alternatively, the field of gene-editing is a new and rapidly growing field. Gene-editing has been used to repair disease-causing mutations or insert genes into cellular DNA. These techniques have the potential to be applied to the treatment of Fabry disease provided the concerns of gene-editing technology, such as safety and efficiency, were addressed. This review focuses on the current state of gene therapy as it is being developed for Fabry disease, including progresses and challenges as well as an overview of gene-editing and how it may be applied to correct Fabry disease-causing mutations in the future.

Prompt Agalsidase Alfa Therapy Initiation is Associated with Improved Renal and Cardiovascular Outcomes in a Fabry Outcome Survey Analysis

Background

The timing of enzyme replacement therapy initiation in patients with Fabry disease is hypothesized to be critical. In this study, we used Fabry Outcome Survey data to assess the impact of prompt versus delayed initiation of treatment with agalsidase alfa on cardiovascular and renal events in patients with Fabry disease.

Methods

Available genetic data at baseline were used to define patients with mutations associated with classical versus late-onset Fabry disease. Time to cardiovascular or renal events, from treatment initiation until 120 months, was compared for patients in prompt versus delayed groups. "Prompt" was defined as treatment initiation <24 months from symptom onset (analysis A) or diagnosis (analysis B), and "delayed" was defined as ≥24 months from symptom onset (analysis A) or diagnosis (analysis B). Kaplan-Meier curves and Log rank tests compared event-free probabilities and time to first event. Multivariate Cox regression estimated hazard ratios (HRs).

Results

Analysis by time from symptom onset included 1374 patients (172 prompt, 1202 delayed). In a multivariate Cox regression analysis, prompt versus delayed treatment initiation significantly reduced the probability of cardiovascular (HR=0.62; P<0.001) and renal (HR=0.57; P=0.001) events. History of cardiovascular or renal events was associated with increased risk of respective events. Analysis by time from diagnosis included 2051 patients (1006 prompt, 1045 delayed). In a multivariate Cox regression analysis, prompt treatment initiation significantly reduced the probability of cardiovascular events (HR=0.83; P=0.003) after adjusting for history of cardiovascular events, sex, and age at treatment initiation. Univariate analysis showed that the probability of renal events was significantly lower in the prompt group (P=0.018); this finding was attenuated in the multivariate Cox regression analysis.

Conclusion

This analysis suggests that prompt treatment initiation with agalsidase alfa provided better renal and cardiovascular outcomes than delayed treatment in patients with Fabry disease.

Long-term follow-up of renal function in patients treated with migalastat for Fabry disease

The effect of migalastat on long-term renal outcomes in enzyme replacement therapy (ERT)-naive and ERT-experienced patients with Fabry disease is not well defined. An integrated posthoc analysis of the phase 3 clinical trials and open-label extension studies was conducted to evaluate long-term changes in renal function in patients with Fabry disease and amenable GLA variants who were treated with migalastat for ≥2 years during these studies. The analysis included ERT-naive (n = 36 [23 females]; mean age 45 years; mean baseline estimated glomerular filtration rate (eGFR), 91.4 mL/min/mL/1.73 m²) and ERT-experienced (n = 42 [24 females]; mean age, 50 years; mean baseline eGFR, 89.2 mL/min/1.73m²) patients with amenable variants who received migalastat 123 mg every other day for ≥2 years. The annualized rate of change from baseline to last observation in estimated glomerular filtration rate using the Chronic Kidney Disease Epidemiology Collaboration equation (eGFR_CKD-EPI) was calculated by both simple linear regression and a random coefficient model. In ERT-naive patients, mean annualized rates of change from baseline in eGFR_CKD-EPI were - 1.6 mL/min/1.73 m² overall and - 1.8 mL/min/1.73 m² and - 1.4 mL/min/1.73 m² in male and female patients, respectively, as estimated by simple linear regression. In ERT-experienced patients, mean annualized rates of change from baseline in eGFR_CKD-EPI were - 1.6 mL/min/1.73 m² overall and - 2.6 mL/min/1.73 m² and - 0.8 mL/min/1.73 m² in male and female patients, respectively. Mean annualized rate of change in eGFR_CKD-EPI in ERT-naive patients with the classic phenotype (defined by white blood cell alpha galactosidase A [α-Gal A] activity of <3% of normal and multiorgan system involvement) was -1.7 mL/min/1.73 m². When calculated using the random coefficient model, which adjusted for sex, age, and baseline renal function, the annualized eGFR_CKD-EPI change was minimal (mean: -0.1 and 0.1 mL/min/1.73 m² in ERT-naive and ERT-experienced patients, respectively). In conclusion, patients with Fabry disease and amenable GLA variants receiving long-term migalastat treatment (≤8.6 years) maintained renal function irrespective of treatment status, sex, or phenotype.

Treatment for Lysosomal Storage Disorders

Lysosomal storage disorders comprise a group of approximately 70 types of inherited diseases resulting due to lysosomal gene defects. The outcome of the defect is a deficiency in either of the three: namely, lysosomal enzymes, activator protein, or transmembrane protein, as a result of which there is an unwanted accumulation of biomolecules inside the lysosomes. The pathophysiology of these conditions is complex affecting several organ systems and nervous system involvement in a majority of cases. Several research studies have well elucidated the mechanism underlying the disease condition leading to the development in devising the treatment strategies for the same. Currently, these approaches aim to reduce the severity of symptoms or delay the disease progression but do not provide a complete cure. The main treatment methods include Enzyme replacement therapy, Bone marrow transplantation, Substrate reduction therapy, use of molecular chaperones, and Gene therapy. This review article presents an elaborate description of these strategies and discusses the ongoing studies for the same.

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.

White matter integrity correlates with cognition and disease severity in Fabry disease

Cerebral white matter pathology is a common CNS manifestation of Fabry disease, visualized as white matter hyperintensities on MRI in 42-81% of patients. Diffusion tensor imaging (DTI) MRI is a sensitive technique to quantify microstructural damage within the white matter with potential value as a disease biomarker. We evaluated the pattern of DTI abnormalities in Fabry disease, and their correlations with cognitive impairment, mood, anxiety, disease severity and plasma lyso-Gb3 levels in 31 patients with genetically proven Fabry disease and 19 age-matched healthy control subjects. We obtained average values of fractional anisotropy and mean diffusivity within the white matter and performed voxelwise analysis with tract-based spatial statistics. Using a standardized neuropsychological test battery, we assessed processing speed, executive function, anxiety, depression and disease severity. The mean age (% male) was 44.1 (45%) for patients with Fabry disease and 37.4 (53%) for the healthy control group. In patients with Fabry disease, compared to healthy controls the mean average white matter fractional anisotropy was lower in [0.423 (standard deviation, SD 0.023) versus 0.446 (SD 0.016), P = 0.002] while mean average white matter mean diffusivity was higher (749 × 10-6 mm2/s (SD 32 × 10-6) versus 720 × 10-6 mm2/s (SD 21 × 10-6), P = 0.004]. Voxelwise statistics showed that the diffusion abnormalities for both fractional anisotropy and mean diffusivity were anatomically widespread. A lesion probability map showed that white matter hyperintensities also had a wide anatomical distribution with a predilection for the posterior centrum semiovale. However, diffusion abnormalities in Fabry disease were not restricted to lesional tissue; compared to healthy controls, the normal appearing white matter in patients with Fabry disease had reduced fractional anisotropy [0.422 (SD 0.022) versus 0.443 (SD 0.017) P = 0.003] and increased mean diffusivity [747 × 10-6 mm2/s (SD 26 × 10-6) versus 723 × 10-6 mm2/s (SD 22 × 10-6), P = 0.008]. Within patients, average white matter fractional anisotropy and white matter lesion volume showed statistically significant correlations with Digit Symbol Coding Test score (r = 0.558, P = 0.001; and r = -0.633, P ≤ 0.001, respectively). Average white matter fractional anisotropy correlated with the overall Mainz Severity Score Index (r = -0.661, P ≤ 0.001), while average white matter mean diffusivity showed a strong correlation with plasma lyso-Gb3 levels (r = 0.559, P = 0.001). Our findings using DTI confirm widespread areas of microstructural white matter disruption in Fabry disease, extending beyond white matter hyperintensities seen on conventional MRI. Moreover, diffusion measures show strong correlations with cognition (processing speed), clinical disease severity and a putative plasma biomarker of disease activity, making them promising quantitative biomarkers for monitoring Fabry disease severity and progression.

Sphingolipids as Regulators of Neuro-Inflammation and NADPH Oxidase 2

Neuro-inflammation accompanies numerous neurological disorders and conditions where it can be associated with a progressive neurodegenerative pathology. In a similar manner, alterations in sphingolipid metabolism often accompany or are causative features in degenerative neurological conditions. These include dementias, motor disorders, autoimmune conditions, inherited metabolic disorders, viral infection, traumatic brain and spinal cord injury, psychiatric conditions, and more. Sphingolipids are major regulators of cellular fate and function in addition to being important structural components of membranes. Their metabolism and signaling pathways can also be regulated by inflammatory mediators. Therefore, as certain sphingolipids exert distinct and opposing cellular roles, alterations in their metabolism can have major consequences. Recently, regulation of bioactive sphingolipids by neuro-inflammatory mediators has been shown to activate a neuronal NADPH oxidase 2 (NOX2) that can provoke damaging oxidation. Therefore, the sphingolipid-regulated neuronal NOX2 serves as a mechanistic link between neuro-inflammation and neurodegeneration. Moreover, therapeutics directed at sphingolipid metabolism or the sphingolipid-regulated NOX2 have the potential to alleviate neurodegeneration arising out of neuro-inflammation.

Lentivirus-mediated gene therapy for Fabry disease

Enzyme and chaperone therapies are used to treat Fabry disease. Such treatments are expensive and require intrusive biweekly infusions; they are also not particularly efficacious. In this pilot, single-arm study (NCT02800070), five adult males with Type 1 (classical) phenotype Fabry disease were infused with autologous lentivirus-transduced, CD34+-selected, hematopoietic stem/progenitor cells engineered to express alpha-galactosidase A (α-gal A). Safety and toxicity are the primary endpoints. The non-myeloablative preparative regimen consisted of intravenous melphalan. No serious adverse events (AEs) are attributable to the investigational product. All patients produced α-gal A to near normal levels within one week. Vector is detected in peripheral blood and bone marrow cells, plasma and leukocytes demonstrate α-gal A activity within or above the reference range, and reductions in plasma and urine globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) are seen. While the study and evaluations are still ongoing, the first patient is nearly three years post-infusion. Three patients have elected to discontinue enzyme therapy.

Renal Manifestations of Fabry Disease: A Narrative Review

Purpose of review

In this narrative review, we describe general aspects, histological alterations, treatment, and implications of Fabry disease (FD) nephropathy. This information should be used to guide physicians and patients in a shared decision-making process.

Source of information

Original peer-reviewed articles, review articles, and opinion pieces were identified from PubMed and Google Scholar databases. Only sources in English were accessed.

Methods

We performed a focused narrative review assessing the main aspects of FD nephropathy. The literature was critically analyzed from a theoretical and contextual perspective, and thematic analysis was performed.

Key findings

FD nephropathy is related to the progressive accumulation of GL3, which occurs in all types of renal cells. It is more prominent in podocytes, which seem to play an important role in the pathogenesis of this nephropathy. A precise detection of renal disorders is of fundamental importance because the specific treatment of FD is usually delayed, making reversibility unlikely and leading to a worse prognosis.

Limitations

As no formal tool was applied to assess the quality of the included studies, selection bias may have occurred. Nonetheless, we have attempted to provide a comprehensive review on the topic using current studies from experts in FD and extensive review of the literature.

Ischemic Stroke in Young Adults

PURPOSE OF REVIEW

This article reviews current knowledge on epidemiology, risk factors and causes, diagnostic considerations, management, and prognosis of ischemic stroke in young adults (those 55 years old and younger).

RECENT FINDINGS

The incidence of ischemic stroke in young adults has been increasing since the 1980s, which has occurred in parallel with increasing prevalence of vascular risk factors and substance abuse among the younger population. Young adults have a considerably wider range of risk factors than older patients, including age-specific factors such as pregnancy/puerperium and oral contraceptive use. Behavioral risk factors such as low physical activity, excess alcohol consumption, and smoking are factors as well. More than 150 identified causes of early-onset ischemic stroke exist, including rare monogenic disorders. Several recent advances have been made in diagnosis and management of stroke in young adults, including molecular characterization of monogenic vasculitis due to deficiency of adenosine deaminase 2 and transcatheter closure of patent foramen ovale for secondary prevention. Compared with the background population of the same age and sex, long-term mortality in patients remains fourfold higher with cardiovascular causes underlying most of the deaths. The cumulative rate of recurrent stroke extends up to 15% at 10 years. Patients with atherosclerosis, high-risk sources of cardioembolism, and small vessel disease underlying their stroke seem to have the worst prognosis regarding survival and recurrent vascular events. Young stroke survivors also often have other adverse outcomes in the long term, including epilepsy, pain, cognitive problems, and depression.

SUMMARY

Systematic identification of risk factors and causes and the motivation of patients for long-term prevention and lifestyle changes are of utmost importance to improve the prognosis of early-onset ischemic stroke.

Fabry cardiomyopathy: Gb3-induced auto-reactive panmyocarditis requiring heart transplantation

Resistance to enzyme replacement therapy (ERT) is a major therapeutic challenge in Fabry disease (FD). Recent reports attribute to immune-mediated inflammation a main role in promoting disease progression and resistance to ERT. Aim of the study is to report a Gb3-induced auto-reactive panmyocarditis causing inefficacy of ERT and severe electrical instability, which required cardiac transplantation. Examining the explanted heart from a 57-year-old man with FD cardiomyopathy (CM) on 3-year ERT presenting incoming ventricular fibrillation, we documented a severe virus-negative myocarditis extended to cardiomyocytes, intramural coronary vessels, conduction tissue, and subepicardial ganglia. Serology was positive for anti-Gb3, anti-heart, and anti-myosin antibodies. In vitro Gb3 stimulation of patient's peripheral blood mononuclear cells (PBMC) induced high amount production of inflammatory cytokine IL1-β, IL-6, IL-8, and TNF-α. PBMC were stained using the monoclonal antibodies CD3-V500, CD4-V450, CD8-APCcy7, CD45RO-PerCPcy5.5 and CD27-FITC from BD Biosciences and CD56-PC7 from Bekman Coulter. The phenotypic analysis of PBMC showed a lower frequency of CD8 (9.2%) vs. 19.3% and NKT cells (1.6% vs. 2.4%) in Fabry patient respect to healthy donor, suggesting a possible homing to peripheral tissues. A Gb3-induced auto-reactive myocarditis is suggested as a possible cause of FDCM progression and ERT resistance. Immune-mediated inflammation of systemic Fabry cells may coexist and be controlled by implemental immunosuppressive therapy.

The GALA project: practical recommendations for the use of migalastat in clinical practice on the basis of a structured survey among Italian experts

Background

Oral migalastat has recently been approved for the treatment of Anderson-Fabry disease (FD) in patients aged ≥16 years with amenable mutations on the basis of two phase III trials, FACETS and ATTRACT. However, with the introduction of migalastat into clinical practice, it is important to correctly identify the patients who may gain the most benefits from this therapy. Due to the relatively recent availability of migalastat, its role in clinical practice still has to be included in guidelines or recommendations. On these bases, a multidisciplinary group of Italian Experts in the treatment of FD has run the GALA project, with the aim to collect the opinions of expert physicians and to propose some starting points for an experience-based use of migalastat.

Results

Overall, although studies and data from longer-term follow-up with migalastat are still emerging, available evidence is consistent in showing that this molecule does represent a suitable therapy for the treatment of FD, in patients aged ≥16 years and with amenable mutations. The use of migalastat as an oral option appears to be overall safe, and experience thus far indicates potential for improving quality of life, controlling GI symptoms, stabilizing renal function and reducing cardiac hypertrophy.

Conclusion

Migalastat can be considered either as a first-line therapy – given its efficacy, extensive tissue penetration, convenient oral regimen, and the current limited therapeutic options available – or in patients on enzyme-replacement therapy (ERT) who experience side effects, with poor compliance to chronic i.v. therapy, or with clinical evidence of progression of the disease.

The Role of Cardiac Imaging in the Diagnosis and Management of Anderson-Fabry Disease

Anderson-Fabry disease (AFD) is a rare X-linked inherited metabolic disorder which results in a deficiency or absence of the enzyme α-galactosidase A, leading to the accumulation of glycosphingolipids in various cells and organs including the heart. Cardiac involvement is common and results in increased myocardial inflammation, left ventricular hypertrophy (LVH), and myocardial fibrosis. Echocardiography and cardiovascular magnetic resonance (CMR) offer distinctive and often complementary use to assist in the diagnosis and monitoring pharmacologic therapy in AFD, including detection of the AFD cardiac phenotype, differentiation from other forms of LVH, and patient selection for therapeutic intervention. Advanced cardiac imaging holds promise in subclinical detection of AFD-related abnormalities as well as disease staging and prognostication.

Enhanced thrombospondin-1 causes dysfunction of vascular endothelial cells derived from Fabry disease-induced pluripotent stem cells

BACKGROUND

Fabry disease (FD) is a recessive X-linked lysosomal storage disorder caused by α-galactosidase A (GLA) deficiency. Although the mechanism is unclear, GLA deficiency causes an accumulation of globotriaosylceramide (Gb3), leading to vasculopathy.

METHODS

To explore the relationship between the accumulation of Gb3 and vasculopathy, induced pluripotent stem cells generated from four Fabry patients (FD-iPSCs) were differentiated into vascular endothelial cells (VECs). Genome editing using CRISPR-Cas9 system was carried out to correct the GLA mutation or to delete Thrombospondin-1 (TSP-1). Global transcriptomes were compared between wild-type (WT)- and FD-VECs by RNA-sequencing analysis.

FINDINGS

Here, we report that overexpression of TSP-1 contributes to the dysfunction of VECs in FD. VECs originating from FD-iPSCs (FD-VECs) showed aberrant angiogenic functionality even upon treatment with recombinant α-galactosidase. Intriguingly, FD-VECs produced more p-SMAD2 and TSP-1 than WT-VECs. We also found elevated TSP-1 in the peritubular capillaries of renal tissues biopsied from FD patients. Inhibition of SMAD2 signaling or knock out of TSP-1 (TSP-1-/-) rescues normal vascular functionality in FD-VECs, like in gene-corrected FD-VECs. In addition, the enhanced oxygen consumption rate is reduced in TSP-1-/- FD-VECs.

INTERPRETATION

The overexpression of TSP-1 secondary to Gb3 accumulation is primarily responsible for the observed FD-VEC dysfunction. Our findings implicate dysfunctional VEC angiogenesis in the peritubular capillaries in some of the complications of Fabry disease.

FUNDING

This study was supported by grant 2018M3A9H1078330 from the National Research Foundation of the Republic of Korea.

Treating lysosomal storage disorders: What have we learnt?

The first enzyme replacement therapy (ERT) for a lysosomal storage disorder (LSD) was approved in 1991 and we now have more than 25 years of experience of treating patients with type 1 Gaucher disease. Because of the remarkable success of this therapy, enormous effort and resource has gone into developing other ERTs, for Gaucher (where three different enzyme preparations have now been approved) and for other LSDs. We now have more than 10 years of clinical experience in using ERT to treat Gaucher, Fabry, Pompe and MPS I, II, and VI. This article aims to assess the real-life experience of a selection of these innovative and expensive treatments to see if they have met the high expectations which were set for them when they launched.

Novel mRNA-Based Therapy Reduces Toxic Galactose Metabolites and Overcomes Galactose Sensitivity in a Mouse Model of Classic Galactosemia

Classic galactosemia (CG) is a potentially lethal inborn error of galactose metabolism that results from deleterious mutations in the human galactose-1 phosphate uridylyltransferase (GALT) gene. Previously, we constructed a GalT^-/- (GalT-deficient) mouse model that exhibits galactose sensitivity in the newborn mutant pups, reduced fertility in adult females, impaired motor functions, and growth restriction in both sexes. In this study, we tested whether restoration of hepatic GALT activity alone could decrease galactose-1 phosphate (gal-1P) and plasma galactose in the mouse model. The administration of different doses of mouse GalT (mGalT) mRNA resulted in a dose-dependent increase in mGalT protein expression and enzyme activity in the liver of GalT-deficient mice. Single intravenous (i.v.) dose of human GALT (hGALT) mRNA decreased gal-1P in mutant mouse liver and red blood cells (RBCs) within 24 h with low levels maintained for over a week. Repeated i.v. injections increased hepatic GalT expression, nearly normalized gal-1P levels in liver, and decreased gal-1P levels in RBCs and peripheral tissues throughout all doses. Moreover, repeated dosing reduced plasma galactose by 60% or more throughout all four doses. Additionally, a single intraperitoneal dose of hGALT mRNA overcame the galactose sensitivity and promoted the growth in a GalT^-/- newborn pup.

Inhibition of Mitochondrial Complex I Impairs Release of α-Galactosidase by Jurkat Cells

Fabry disease (FD) is caused by mutations in the GLA gene that encodes lysosomal α-galactosidase-A (α-gal-A). A number of pathogenic mechanisms have been proposed and these include loss of mitochondrial respiratory chain activity. For FD, gene therapy is beginning to be applied as a treatment. In view of the loss of mitochondrial function reported in FD, we have considered here the impact of loss of mitochondrial respiratory chain activity on the ability of a GLA lentiviral vector to increase cellular α-gal-A activity and participate in cross correction. Jurkat cells were used in this study and were exposed to increasing viral copies. Intracellular and extracellular enzyme activities were then determined; this in the presence or absence of the mitochondrial complex I inhibitor, rotenone. The ability of cells to take up released enzyme was also evaluated. Increasing transgene copies was associated with increasing intracellular α-gal-A activity but this was associated with an increase in Km. Release of enzyme and cellular uptake was also demonstrated. However, in the presence of rotenone, enzyme release was inhibited by 37%. Excessive enzyme generation may result in a protein with inferior kinetic properties and a background of compromised mitochondrial function may impair the cross correction process.

Why systematic literature reviews in Fabry disease should include all published evidence

Fabry disease is an X-linked inherited, progressive disorder of lipid metabolism resulting from the deficient activity of the enzyme α-galactosidase. Enzyme replacement therapy (ERT) with recombinant agalsidase, with intravenous infusions of either agalsidase beta or agalsidase alfa, is available and clinical experience now exceeds 15 years. There are very few randomised, placebo-controlled clinical trials evaluating the outcomes of ERT. Data are often derived from observational, registry-based studies and case reports. Pooled analysis of data from different sources may be limited by the heterogeneity of the patient populations, outcomes and treatment. Therefore, comprehensive systematic literature reviews of unpooled data are needed to determine the effects of ERT on disease outcomes. A systematic literature search was conducted in the Embase and PubMed (MEDLINE) databases to retrieve original articles that evaluated outcomes of ERT in patients with Fabry disease; the outcome data were analysed unpooled. The literature analysis included the full range of published literature including observational studies and case series/case reports. Considerable heterogeneity was found among the studies, with differences in sample size, statistical methods, ERT regimens and patient demographic and clinical characteristics. We have demonstrated the value of performing an unpooled systematic literature review of all published evidence of ERT outcomes in Fabry disease, highlighting that in a rare genetic disorder like Fabry disease, which is phenotypically diverse, different patient populations can require different disease management and therapeutic goals depending on age, genotype, and disease severity/level of organ involvement. In addition, these findings are valuable to guide the design and reporting of new clinical studies.

Lysosomal Leukodystrophies Lysosomal Storage Diseases Associated With White Matter Abnormalities

The leukodystrophies are a group of genetic metabolic diseases characterized by an abnormal development or progressive degeneration of the myelin sheath. The myelin is a complex sheath composed of several macromolecules covering axons as an insulator. Each of the leukodystrophies is caused by mutations in genes encoding enzymes that are involved in myelin production and maintenance. The lysosomal storage diseases are inborn disorders of compartmentalized cellular organelles with broad clinical manifestations secondary to the progressive accumulation of undegraded macromolecules within lysosomes and related organelles. The more than 60 different lysosomal storage diseases are rare diseases; however, collectively, the incidence of lysosomal storage diseases ranges just over 1 in 2500 live births. The majority of lysosomal storage diseases are associated with neurologic manifestations including developmental delay, seizures, acroparesthesia, motor weakness, and extrapyramidal signs. These inborn organelle disorders show wide clinical variability affecting individuals from all age groups. In addition, several of neurologic, also known as neuronopathic, lysosomal storage diseases are associated with some level of white matter disease, which often triggers the diagnostic investigation. Most lysosomal storage diseases are autosomal recessively inherited and few are X-linked, with females being at risk of presenting with mild, but clinically relevant neurologic manifestations. Biochemical assays are the basis of the diagnosis and are usually confirmed by molecular genetic testing. Novel therapies have emerged. However, most affected patients with lysosomal storage diseases have only supportive management to rely on. A better understanding of the mechanisms resulting in the leukodystrophy will certainly result in innovative and efficacious disease-modifying therapies.

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

BACKGROUND

Heterozygous females with Fabry disease have a wide range of clinical phenotypes depending on the nature of their mutation and their X-chromosome inactivation pattern; it is therefore important to examine outcomes of enzyme replacement therapy (ERT) in the female patient population specifically. This paper presents the findings of a systematic literature review of treatment outcomes with ERT in adult female patients.

METHODS

A comprehensive systematic literature review was conducted through January 2017 to retrieve published papers with original data on ERT in the treatment of Fabry disease. The review included all original articles that presented ERT outcomes data on patients with Fabry disease, irrespective of the study type.

RESULTS

Clinical evidence for the efficacy of ERT in female patients was available from 67 publications including six clinical trial publications, and indicates significant reductions in plasma and urine globotriaosylceramide (GL-3) accumulation (in female patients with elevated pre-treatment levels) and improvements in cardiac parameters and quality of life (QoL). To date, data are insufficient to conclude on the effects of ERT on the nervous system, gastrointestinal manifestations, and pain in female patients with Fabry disease.

CONCLUSIONS

This review of available literature data demonstrates that ERT in adult female patients with Fabry disease has a beneficial effect on GL-3 levels and cardiac outcomes. The current evidence also suggests that ERT may improve QoL in this patient population, though further studies are needed to examine these results.

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

BACKGROUND

Fabry disease is caused by a deficiency of the lysosomal enzyme α-galactosidase, resulting in progressive accumulation of globotriaosylceramide (GL-3). The disease can manifest early during childhood and adolescence. Enzyme replacement therapy (ERT) with recombinant human α-galactosidase is the first specific treatment for Fabry disease and has been available in Europe since 2001. This paper presents the findings of a systematic literature review of clinical outcomes with ERT in paediatric patients with Fabry disease.

METHODS

A comprehensive systematic review of published literature on ERT in Fabry disease was conducted in January 2017. The literature analysis included all original articles reporting outcomes of ERT in paediatric patients.

RESULTS

Treatment-related outcomes in the paediatric population were reported in six publications derived from open-label clinical trials and in 10 publications derived from observational or registry-based studies. ERT was shown to significantly reduce plasma and urine GL-3 levels in paediatric patients with Fabry disease. The effect of ERT on GL-3 clearance from renal podocytes appeared to be agalsidase dose-dependent. ERT relieved pain and improved gastrointestinal symptoms and quality of life.

CONCLUSIONS

Based on the published literature, the use of ERT in paediatric patients can significantly clear GL-3 accumulation, ameliorate the early symptoms of Fabry disease, and improve quality of life. Treatment with ERT in paediatric patients with Fabry disease may be important to prevent further disease progression and overt organ damage.

Efficacy of the pharmacologic chaperone migalastat in a subset of male patients with the classic phenotype of Fabry disease and migalastat-amenable variants: data from the phase 3 randomized, multicenter, double-blind clinical trial and extension study

PURPOSE

Outcomes in patients with Fabry disease receiving migalastat during the phase 3 FACETS trial (NCT00925301) were evaluated by phenotype.

METHODS

Data were evaluated in two subgroups of patients with migalastat-amenable GLA variants: "classic phenotype" (n = 14; males with residual peripheral blood mononuclear cell α-galactosidase A <3% normal and multiorgan system involvement) and "other patients" (n = 36; males not meeting classic phenotype criteria and all females). Endpoints included estimated glomerular filtration rate (eGFR), left ventricular mass index (LVMi), Gastrointestinal Symptoms Rating Scale diarrhea subscale (GSRS-D), renal peritubular capillary (PTC) globotriaosylceramide (GL-3) inclusions, and plasma globotriaosylsphingosine (lyso-Gb₃).

RESULTS

Baseline measures in the classic phenotype patients suggested a more severe phenotype. At month 24, mean (SD) annualized change in eGFR_CKD-EPI with migalastat was -0.3 (3.76) mL/min/1.73 m² in the classic phenotype subgroup; changes in LVMi, GSRS-D, and lyso-Gb₃ were -16.7 (18.64) g/m², -0.9 (1.66), and -36.8 (35.78) nmol/L, respectively. At month 6, mean PTC GL-3 inclusions decreased with migalastat (-0.8) and increased with placebo (0.3); switching from placebo to migalastat, PTC inclusions decreased by -0.7. Numerically smaller changes in these endpoints were observed in the other patients.

CONCLUSION

Migalastat provided clinical benefit to patients with Fabry disease and amenable variants, regardless of disease severity.

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.

Challenging popular tools for the annotation of genetic variations with a real case, pathogenic mutations of lysosomal alpha-galactosidase

Background

Severity gradation of missense mutations is a big challenge for exome annotation. Predictors of deleteriousness that are most frequently used to filter variants found by next generation sequencing, produce qualitative predictions, but also numerical scores. It has never been tested if these scores correlate with disease severity.

Results

wANNOVAR, a popular tool that can generate several different types of deleteriousness-prediction scores, was tested on Fabry disease. This pathology, which is caused by a deficit of lysosomal alpha-galactosidase, has a very large genotypic and phenotypic spectrum and offers the possibility of associating a quantitative measure of the damage caused by mutations to the functioning of the enzyme in the cells. Some predictors, and in particular VEST3 and PolyPhen2 provide scores that correlate with the severity of lysosomal alpha-galactosidase mutations in a statistically significant way.

Conclusions

Sorting disease mutations by severity is possible and offers advantages over binary classification. Dataset for testing and training in silico predictors can be obtained by transient transfection and evaluation of residual activity of mutants in cell extracts. This approach consents to quantitative data for severe, mild and non pathological variants.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2416-7) contains supplementary material, which is available to authorized users.

α-galactosidase A deficiency promotes von Willebrand factor secretion in models of Fabry disease

Fabry disease results from loss of activity of the lysosomal enzyme α-galactosidase A (GLA), leading to the accumulation of globoseries glycosphingolipids in vascular endothelial cells. Thrombosis and stroke are life-threatening complications of Fabry disease; however, the mechanism of the vasculopathy remains unclear. We explored the relationship between GLA deficiency and endothelial cell von Willebrand factor (VWF) secretion in in vivo and in vitro models of Fabry disease. Plasma VWF was significantly higher at two months and increased with age in Gla-null compared to wild-type mice. Disruption of GLA in a human endothelial cell line by siRNA and CRISPR/Cas9 resulted in a 3-fold and 5-fold increase in VWF secretion, respectively. The increase in VWF levels was associated with decreased endothelial nitric oxide synthase (eNOS) activity in both in vitro models. Pharmacological approaches that increase nitric oxide bioavailability or decrease reactive oxygen species completely normalized the elevated VWF secretion in GLA deficient cells. In contrast, the abnormality was not readily reversed by recombinant human GLA or by inhibition of glycosphingolipid synthesis with eliglustat. These results suggest that GLA deficiency promotes VWF secretion through eNOS dysregulation, which may contribute to the vasculopathy of Fabry disease.

Oxidative Stress and Cardiovascular-Renal Damage in Fabry Disease: Is There Room for a Pathophysiological Involvement?

Fabry disease is an X-linked lysosomal storage disease caused by mutations in the GLA gene that lead to a reduction or an absence of the enzyme α-galactosidase A, resulting in the progressive and multisystemic accumulation of globotriaosylceramide. Clinical manifestation varies from mild to severe, depending on the phenotype. The main clinical manifestations are cutaneous (angiokeratomas), neurological (acroparesthesias), gastrointestinal (nausea, diarrhea abdominal pain), renal (proteinuria and kidney failure), cardiovascular (cardiomyopathy and arrhythmias), and cerebrovascular (stroke). A diagnosis of Fabry disease can be made with an enzymatic assay showing absent or reduced α-galactosidase A in male patients, while in heterozygous female patients, molecular genetic testing is needed. Enzyme replacement therapy (ERT) with recombinant human α-galactosidase is nowadays the most-used disease-specific therapeutic option. Despite ERT, cardiocerebrovascular-renal irreversible organ injury occurs, therefore additional knowledge and a deeper understanding of further pathophysiological mechanisms leading to end organ damage in Fabry disease are needed. Recent data point toward oxidative stress, oxidative stress signaling, and inflammation as some such mechanisms. In this short review, the current knowledge on the involvement of oxidative stress in cardiovascular-renal remodeling is summarized and related to the most recent evidence of oxidative stress activation in Fabry disease, and clearly points toward the involvement of oxidative stress in the pathophysiology of the medium- to long-term cardiovascular-renal damage of Fabry disease.

Neuroimaging in Fabry disease: current knowledge and future directions

Abstract

Fabry disease (FD) is a rare X-linked disorder characterised by abnormal progressive lysosomal deposition of globotriaosylceramide in a large variety of cell types. The central nervous system (CNS) is often involved in FD, with a wide spectrum of manifestations ranging from mild symptoms to more severe courses related to acute cerebrovascular events. In this review we present the current knowledge on brain imaging for this condition, with a comprehensive and critical description of its most common neuroradiological imaging findings. Moreover, we report results from studies that investigated brain physiopathology underlying this disorder by using advanced imaging techniques, suggesting possible future directions to further explore CNS involvement in FD patients.

Teaching Points

• Conventional neuroradiological findings in FD are aspecific.

• White matter hyperintensities represent the more consistent brain imaging feature of FD

• Abnormalities of the vasculature wall of posterior circulation are also consistent features.

• The pulvinar sign is not reliable as a finding pathognomonic for FD.

• Advanced imaging techniques have increased our knowledge about brain involvement in FD.