Mutation-specific Fabry disease patient-derived cell model to evaluate the amenability to chaperone therapy

Anderson-Fabry disease management: role of the cardiologist

Anderson-Fabry disease (AFD) is a lysosomal storage disorder characterized by glycolipid accumulation in cardiac cells, associated with a peculiar form of hypertrophic cardiomyopathy (HCM). Up to 1% of patients with a diagnosis of HCM indeed have AFD. With the availability of targeted therapies for sarcomeric HCM and its genocopies, a timely differential diagnosis is essential. Specifically, the therapeutic landscape for AFD is rapidly evolving and offers increasingly effective, disease-modifying treatment options. However, diagnosing AFD may be difficult, particularly in the non-classic phenotype with prominent or isolated cardiac involvement and no systemic red flags. For many AFD patients, the clinical journey from initial clinical manifestations to diagnosis and appropriate treatment remains challenging, due to late recognition or utter neglect. Consequently, late initiation of treatment results in an exacerbation of cardiac involvement, representing the main cause of morbidity and mortality, irrespective of gender. Optimal management of AFD patients requires a dedicated multidisciplinary team, in which the cardiologist plays a decisive role, ranging from the differential diagnosis to the prevention of complications and the evaluation of timing for disease-specific therapies. The present review aims to redefine the role of cardiologists across the main decision nodes in contemporary AFD clinical care and drug discovery.

A review and recommendations for oral chaperone therapy in adult patients with Fabry disease

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder affecting both males and females caused by genetic abnormalities in the gene encoding the enzyme α-galactosidase A. FD-affected patients represent a highly variable clinical course with first symptoms already appearing in young age. The disease causes a progressive multiple organ dysfunction affecting mostly the heart, kidneys and nervous system, eventually leading to premature death. Disease-specific management of FD includes enzyme replacement therapy with agalsidase α and β or pharmacological oral chaperone migalastat. Migalastat is a low-molecular-mass iminosugar, that reversibly binds to active site of amenable enzyme variants, stabilizing their molecular structure and improving trafficking to the lysosome. Migalastat was approved in the EU in 2016 and is an effective therapy in the estimated 35-50% of all patients with FD with amenable GLA gene variants. This position statement is the first comprehensive review in Central and Eastern Europe of the current role of migalastat in the treatment of FD. The statement provides an overview of the pharmacology of migalastat and summarizes the current evidence from the clinical trial program regarding the safety and efficacy of the drug and its effects on organs typically involved in FD. The position paper also includes a practical guide for clinicians on the optimal selection of patients with FD who will benefit from migalastat treatment, recommendations on the optimal selection of diagnostic tests and the use of tools to identify patients with amenable GLA mutations. Areas for future migalastat clinical research have also been identified.

Fabry disease biomarkers in patients switched from enzyme-replacement therapy to migalastat oral chaperone therapy

Background: A biomarker profile was evaluated longitudinally in patients with Fabry disease switched from enzyme-replacement therapy (ERT) to migalastat. Methods: 16 Gb3 isoforms and eight lyso-Gb3 analogues were analyzed in plasma and urine by LC-MS/MS at baseline and at three different time points in naive participants and participants switching from either agalsidase α or β to migalastat. Results: 29 adult participants were recruited internationally (seven centers). The Mainz Severity Score Index and mean biomarker levels remained stable (p ≥ 0.05) over a minimum of 12 months compared with baseline following the treatment switch. Conclusion: In this cohort of patients with Fabry disease with amenable mutations, in the short term, a switch from ERT to migalastat did not have a marked effect on the average biomarker profile.

Mass Spectrometry Analysis of Globotriaosylsphingosine and Its Analogues in Dried Blood Spots

Fabry disease (FD) is an X-linked lysosomal storage disorder where impaired α-galactosidase A enzyme activity leads to the intracellular accumulation of undegraded glycosphingolipids, including globotriaosylsphingosine (lyso-Gb₃) and related analogues. Lyso-Gb₃ and related analogues are useful biomarkers for screening and should be routinely monitored for longitudinal patient evaluation. In recent years, a growing interest has emerged in the analysis of FD biomarkers in dried blood spots (DBSs), considering the several advantages compared to venipuncture as a technique for collecting whole-blood specimens. The focus of this study was to devise and validate a UHPLC-MS/MS method for the analysis of lyso-Gb₃ and related analogues in DBSs to facilitate sample collection and shipment to reference laboratories. The assay was devised in conventional DBS collection cards and in Capitainer^®B blood collection devices using both capillary and venous blood specimens from 12 healthy controls and 20 patients affected with FD. The measured biomarker concentrations were similar in capillary and venous blood specimens. The hematocrit (Hct) did not affect the correlation between plasma and DBS measurements in our cohort (Hct range: 34.3-52.2%). This UHPLC-MS/MS method using DBS would facilitate high-risk screening and the follow-up and monitoring of patients affected with FD.

Fabry Disease: Switch from Enzyme Replacement Therapy to Oral Chaperone Migalastat: What Do We Know Today?

Fabry disease is a lysosomal storage disorder caused by the deficiency of the α-galactosidase-A enzyme. The result is the progressive accumulation of complex glycosphingolipids and cellular dysfunction. Cardiac, renal, and neurological involvement significantly reduces life expectancy. Currently, there is increasing evidence that clinical response to treatment improves with early and timely initiation. Until a few years ago, treatment options for Fabry disease were limited to enzyme replacement therapy with agalsidase alfa or beta administered by intravenous infusion every 2 weeks. Migalastat (Galafold^®) is an oral pharmacological chaperone that increases the enzyme activity of "amenable" mutations. The safety and efficacy of migalastat were supported in the phase III FACETS and ATTRACT studies, compared to available enzyme replacement therapies, showing a reduction in left ventricular mass, and stabilization of kidney function and plasma Lyso-Gb3. Similar results were confirmed in subsequent extension publications, both in patients who started migalastat as their first treatment and in patients who were previously on enzyme replacement therapy and switched to migalastat. In this review we describe the safety and efficacy of switching from enzyme replacement therapy to migalastat in patients with Fabry disease and "amenable" mutations, referring to publications available to date.

Preclinical evaluation of FLT190, a liver-directed AAV gene therapy for Fabry disease

Fabry disease is an X-linked lysosomal storage disorder caused by loss of alpha-galactosidase A (α-Gal A) activity and is characterized by progressive accumulation of glycosphingolipids in multiple cells and tissues. FLT190, an investigational gene therapy, is currently being evaluated in a Phase 1/2 clinical trial in patients with Fabry disease (NCT04040049). FLT190 consists of a potent, synthetic capsid (AAVS3) containing an expression cassette with a codon-optimized human GLA cDNA under the control of a liver-specific promoter FRE1 (AAV2/S3-FRE1-GLAco). For mouse studies FLT190 genome was pseudotyped with AAV8 for efficient transduction. Preclinical studies in a murine model of Fabry disease (Gla-deficient mice), and non-human primates (NHPs) showed dose-dependent increases in plasma α-Gal A with steady-state observed 2 weeks following a single intravenous dose. In Fabry mice, AAV8-FLT190 treatment resulted in clearance of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) in plasma, urine, kidney, and heart; electron microscopy analyses confirmed reductions in storage inclusion bodies in kidney and heart. In NHPs, α-Gal A expression was consistent with the levels of hGLA mRNA in liver, and no FLT190-related toxicities or adverse events were observed. Taken together, these studies demonstrate preclinical proof-of-concept of liver-directed gene therapy with FLT190 for the treatment of Fabry disease.

An expert consensus on practical clinical recommendations and guidance for patients with classic Fabry disease

Fabry disease is an X-linked inherited lysosomal disorder that causes accumulation of glycosphingolipids in body fluids and tissues, leading to progressive organ damage and reduced life expectancy. It can affect both males and females and can be classified into classic or later-onset phenotypes. In classic Fabry disease, α-galactosidase A (α-Gal A) activity is absent or severely reduced and disease manifestations have an early onset that can affect multiple organs. In contrast, in later-onset Fabry disease, patients have residual α-Gal A activity and clinical features are primarily confined to the heart. Individualized therapeutic goals in Fabry disease are required due to varying phenotypes and patient characteristics, and the wide spectrum of disease severity. An international group of expert physicians convened to discuss and develop practical clinical recommendations for disease- and organ-specific therapeutic goals in Fabry disease, based on expert consensus and evidence identified through a structured literature review. Biomarkers reflecting involvement of various organs in adult patients with classic Fabry disease are discussed and consensus recommendations for disease- and organ-specific therapeutic goals are provided. These consensus recommendations should support the establishment of individualized approaches to the management of patients with classic Fabry disease by considering identification, diagnosis, and initiation of disease-specific therapies before significant organ involvement, as well as routine monitoring, to reduce morbidity, optimize patient care, and improve patient health-related quality of life.

The 30-year Natural History of Non-classic Fabry Disease with an R112H Mutation

Fabry disease is a rare X-linked lysosomal storage disorder caused by mutations in the alpha-galactosidase A (GLA) gene that results in deficiency of the enzyme GLA and leads to the accumulation of globotriaosylceramide (GL-3) in cells. The accumulation of GL-3 may lead to life-threatening complications. Significant advances in genetic sequencing technology have led to a better understanding of genotype-phenotype interactions in Fabry disease. Fabry disease with an R112H mutation is known as the non-classic type. However, the long-term clinical course of the disease remains unknown. We herein report a patient with a 30-year natural history of non-classic Fabry disease with an R112H mutation.

Fabry disease - a multisystemic disease with gastrointestinal manifestations

Nonspecific gastrointestinal (GI) symptoms, such as postprandial cramping pain, diarrhea, nausea and vomiting are typical symptoms for irritable bowel syndrome or inflammatory bowel disease, but may also be the first symptoms of Fabry disease (FD). This review focus on GI manifestations in FD, by providing an overview of symptoms, a proper diagnosis, an appropriate management by FD-specific and concomitant medications and lifestyle interventions. We provide comprehensive literature-based data combined with personal experience in the management of FD patients. Since FD is rare and the clinical phenotype is heterogeneous, affected patients are often misdiagnosed. Consequently, physicians should consider FD as a possible differential diagnosis when assessing unspecific GI symptoms. Improved diagnostic tools, such as a modified GI symptom assessment scale can facilitate the diagnosis of FD in patients with GI symptoms of unknown cause and thus enable the timely initiation of a disease-specific therapy. Expansive intravenous enzyme replacement therapy with α-galactosidase A or oral chaperone therapy for patients with amenable mutations improve the disease burden including GI symptoms, but a timely start of therapy is crucial for the prognosis. A special diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) or pro- and prebiotics might improve FD-typical GI symptoms. Furthermore, preliminary success was reported with the oral administration of α-galactosidase A. In addition to a timely initiation of FD-specific therapy, affected patients with GI symptoms might benefit from a FODMAP-low diet, pro- and prebiotics and/or low-cost oral substitution with AGAL to support digestion and reduce dysbiosis.

Sphingosine-1-Phosphate Levels Are Higher in Male Patients with Non-Classic Fabry Disease

Fabry disease is an X-linked lysosomal disease in which defects in the alpha-galactosidase A enzyme activity lead to the ubiquitous accumulation of glycosphingolipids. Whereas the classic disease is characterized by neuropathic pain, progressive renal failure, white matter lesions, cerebral stroke, and hypertrophic cardiomyopathy (HCM), the non-classic phenotype, also known as cardiac variant, is almost exclusively characterized by HCM. Circulating sphingosine-1-phosphate (S1P) has controversially been associated with the Fabry cardiomyopathy. We measured serum S1P levels in 41 patients of the FFABRY cohort. S1P levels were higher in patients with a non-classic phenotype compared to those with a classic phenotype (200.3 [189.6−227.9] vs. 169.4 ng/mL [121.1−203.3], p = 0.02). In a multivariate logistic regression model, elevated S1P concentration remained statistically associated with the non-classic phenotype (OR = 1.03; p < 0.02), and elevated lysoGb3 concentration with the classic phenotype (OR = 0.95; p < 0.03). S1P levels were correlated with interventricular septum thickness (r = 0.46; p = 0.02). In a logistic regression model including S1P serum levels, phenotype, and age, age remained the only variable significantly associated with the risk of HCM (OR = 1.25; p = 0.001). S1P alone was not associated with cardiac hypertrophy but with the cardiac variant. The significantly higher S1P levels in patients with the cardiac variant compared to those with classic Fabry suggest the involvement of distinct pathophysiological pathways in the two phenotypes. S1P dosage could allow the personalization of patient management.

Chaperone Therapy in Fabry Disease

Fabry disease is an X-linked lysosomal multisystem storage disorder induced by a mutation in the alpha-galactosidase A (GLA) gene. Reduced activity or deficiency of alpha-galactosidase A (AGAL) leads to escalating storage of intracellular globotriaosylceramide (GL-3) in numerous organs, including the kidneys, heart and nerve system. The established treatment for 20 years is intravenous enzyme replacement therapy. Lately, oral chaperone therapy was introduced and is a therapeutic alternative in patients with amenable mutations. Early starting of therapy is essential for long-term improvement. This review describes chaperone therapy in Fabry disease.

How Genetics Can Improve Clinical Practice in Chronic Kidney Disease: From Bench to Bedside

Chronic kidney disease (CKD) is considered a major global health problem with high socio-economic costs: the risk of CKD in individuals with an affected first degree relative has been found to be three times higher than in the general population. Genetic factors are known to be involved in CKD pathogenesis, both due to the possible presence of monogenic pathologies as causes of CKD, and to the role of numerous gene variants in determining susceptibility to the development of CKD. The genetic study of CKD patients can represent a useful tool in the hands of the clinician; not only in the diagnostic and prognostic field, but potentially also in guiding therapeutic choices and in designing clinical trials. In this review we discuss the various aspects of the role of genetic analysis on clinical management of patients with CKD with a focus on clinical applications. Several topics are discussed in an effort to provide useful information for daily clinical practice: definition of susceptibility to the development of CKD, identification of unrecognized monogenic diseases, reclassification of the etiological diagnosis, role of pharmacogenetics.

Endothelial Dysfunction in Fabry Disease Is Related to Glycocalyx Degradation

Fabry disease (FD) is an X-linked multisystemic lysosomal storage disease due to a deficiency of α-galactosidase A (GLA/AGAL). Progressive cellular accumulation of the AGAL substrate globotriaosylceramide (Gb₃) leads to endothelial dysfunction. Here, we analyzed endothelial function in vivo and in vitro in an AGAL-deficient genetic background to identify the processes underlying this small vessel disease. Arterial stiffness and endothelial function was prospectively measured in five males carrying GLA variants (control) and 22 FD patients under therapy. AGAL-deficient endothelial cells (EA.hy926) and monocytes (THP1) were used to analyze endothelial glycocalyx structure, function, and underlying inflammatory signals. Glycocalyx thickness and small vessel function improved significantly over time (p<0.05) in patients treated with enzyme replacement therapy (ERT, n=16) and chaperones (n=6). AGAL-deficient endothelial cells showed reduced glycocalyx and increased monocyte adhesion (p<0.05). In addition, increased expression of angiopoietin-2, heparanase and NF-κB was detected (all p<0.05). Incubation of wild-type endothelial cells with pathological globotriaosylsphingosine concentrations resulted in comparable findings. Treatment of AGAL-deficient cells with recombinant AGAL (p<0.01), heparin (p<0.01), anti-inflammatory (p<0.001) and antioxidant drugs (p<0.05), and a specific inhibitor (razuprotafib) of angiopoietin-1 receptor (Tie2) (p<0.05) improved glycocalyx structure and endothelial function in vitro. We conclude that chronic inflammation, including the release of heparanases, appears to be responsible for the degradation of the endothelial glycocalyx and may explain the endothelial dysfunction in FD. This process is partially reversible by FD-specific and anti-inflammatory treatment, such as targeted protective Tie2 treatment.

α-Galactosidase a Deficiency in Fabry Disease Leads to Extensive Dysregulated Cellular Signaling Pathways in Human Podocytes

Fabry disease (FD) is caused by mutations in the α-galactosidase A (GLA) gene encoding the lysosomal AGAL enzyme. Loss of enzymatic AGAL activity and cellular accumulation of sphingolipids (mainly globotriaosylcermide) may lead to podocyturia and renal loss of function with increased cardiovascular morbidity and mortality in affected patients. To identify dysregulated cellular pathways in FD, we established a stable AGAL-deficient podocyte cell line to perform a comprehensive proteome analysis. Imbalanced protein expression and function were analyzed in additional FD cell lines including endothelial, epithelial kidney, patient-derived urinary cells and kidney biopsies. AGAL-deficient podocytes showed dysregulated proteins involved in thermogenesis, lysosomal trafficking and function, metabolic activity, cell-cell interactions and cell cycle. Proteins associated with neurological diseases were upregulated in AGAL-deficient podocytes. Rescues with inducible AGAL expression only partially normalized protein expression. A disturbed protein expression was confirmed in endothelial, epithelial and patient-specific cells, pointing toward fundamental pathway disturbances rather than to cell type-specific alterations in FD. We conclude that a loss of AGAL function results in profound changes of cellular pathways, which are ubiquitously in different cell types. Due to these profound alterations, current approved FD-specific therapies may not be sufficient to completely reverse all dysregulated pathways.

Fabry disease - current data and therapeutic approaches

Fabry disease represents an X-linked inherited disorder resulting in the accumulation of globotriaosylceramide (Gb3). This review explains the clinical manifestations and the possible therapies for this condition. Fabry disease is considered the second most frequent lysosomal storage disease. More than 1000 mutations of the galactosidase alpha (GLA) gene associated with this disorder have been identified. Pain, either episodic crises or chronic pain, is one of the earliest symptoms in Fabry disease. Gastrointestinal, ocular, ear or skeletal manifestations may complete the clinical picture. Cardiac and renal involvements are the most severe complications leading to organ failure and death. The cerebrovascular lesions may result in severe symptoms including stroke at younger ages. The diagnosis of Fabry disease may be put by enzymatic assays of the α-galactosidase A (AGAL-A) activity in plasma or leukocytes but genetic analysis remains the “gold standard” in identifying the precise mutation and even guiding the treatment. Enzyme replacement therapy (ERT) was the first step in treating subjects with Fabry disease. It proved important decrease of the number of sever clinical events and reduction of symptoms. Chemical chaperone therapy has many advantages including oral administration and was already approved in Europe and US, but it is suitable only for subjects with amenable mutations. Gene therapies (either ex vivo or in vivo) promise to represent a new era for many disorders including Fabry disease, the preliminary data being encouraging. Although many steps were taken in understanding the pathogeny of Fabry disease, future research is needed especially in the field of therapeutic approaches.

A molecular genetics view on Mucopolysaccharidosis Type II

Mucopolysaccharidosis Type II (MPS II) is an X-linked recessive genetic disorder that primarily affects male patients. With an incidence of 1 in 100,000 male live births, the disease is one of the orphan diseases. MPS II symptoms are caused by mutations in the lysosomal iduronate-2-sulfatase (IDS) gene. The mutations cause a loss of enzymatic performance and result in the accumulation of glycosaminoglycans (GAGs), heparan sulfate and dermatan sulfate, which are no longer degradable. This inadvertent accumulation causes damage in multiple organs and leads either to a severe neurological course or to an attenuated course of the disease, although the exact relationship between mutation, extent of GAG accumulation and disease progression is not yet fully understood. This review is intended to present current diagnostic procedures and therapeutic interventions. In times when the genetic profile of patients plays an increasingly important role in the assessment of therapeutic success and future drug design, we chose to further elucidate the impact of genetic diversity within the IDS gene on disease phenotype and potential implications in current diagnosis, prognosis and therapy. We report recent advances in the structural biological elucidation of I2S enzyme that that promises to improve our future understanding of the molecular damage of the hundreds of IDS gene variants and will aid damage prediction of novel mutations in the future.

Precision medicine in Fabry disease

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A (GLA) gene, leading to a deficiency in α-galactosidase A. The lysosomal accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3) and its deacylated form, globotriaosylsphingosine (lyso-Gb3), results in progressive renal failure, cardiomyopathy associated with cardiac arrhythmia and recurrent cerebrovascular events, significantly limiting life expectancy in affected patients. In male patients, a definitive diagnosis of FD involves demonstrating a GLA deficiency in leucocytes. In females, because of the potential high residual enzymatic activity, the diagnostic gold standard requires molecular genetic analyses. The current treatment options for FD include recombinant enzyme replacement therapies (ERTs) with intravenous agalsidase-α (0.2 mg/kg body weight) or agalsidase-β (1 mg/kg body weight) every 2 weeks as well as an oral pharmacological chaperone (migalastat 123 mg every other day) that selectively and reversibly binds to the active sites of amenable mutant forms of the GLA enzyme. These therapies facilitate cellular Gb3 clearance and an overall improvement of disease burden. However, ERT can lead to infusion-associated reactions, as well as the formation of neutralizing anti-drug antibodies in ∼40% of all ERT-treated males, leading to an attenuation of therapy efficacy. This article reviews the clinical presentation, diagnosis and interdisciplinary clinical management of FD and discusses the therapeutic options, with a special focus on precision medicine, accounting for individual variability in genetic mutations, Gb3 and lyso-Gb3 levels, allowing physicians to predict more accurately which prevention and treatment strategy is best for which patient.

Current and experimental therapeutics for Fabry disease

Fabry (or Anderson‐Fabry) is a rare pan‐ethnic disease affecting males and females. Fabry is an X‐linked lysosomal storage disease, affecting glycosphingolipid metabolism, that is caused by mutations of the GLA gene that codes for α‐galactosidase A. Fabry disease (FD) can be classified into a severe, classical phenotype, most often seen in men with no residual enzyme activity, that usually appear before 18 years and a usually milder, nonclassical (later‐onset) phenotype that usually appear above 18 years. Affected patients show multifactorial complications, including renal failure, cardiovascular problems, and neuropathy. In this review, we briefly report the clinical trials so far performed with the available therapies, and then we focus on the in vitro and the in vivo experimental models of the disease, to highlight the relevance in improving the existing therapeutics and understand the mechanism of this rare disorder. Current available in vivo and in vitro models can assist in better comprehension of the pathogenesis and underlying mechanisms of FD, thus the existing therapeutic approaches can be optimized, and new options can be developed.

Case Report: First Two Identified Cases of Fabry Disease in Central Asia

Background: Fabry disease (FD, OMIM #301500) is a rare, progressive, X-linked inherited, genetic disease due to the functional deficiency of lysosomal α-galactosidase (α-GAL) that leads to the accumulation of glycosphingolipids (mainly globotriaosylceramide or Gb₃) and its derivative globotriaosylsphingosine or lyso-Gb₃. Classic FD is a multisystem disorder which initially presents in childhood with neuropathic pain and dermatological, gastrointestinal, ocular, and cochleo-vestibular manifestations. Over time, end-organ damage such as renal failure, cardiac arrhythmia and early stroke may develop leading to reduced life expectancy in the absence of specific treatment. Case presentation: We describe two Kazakh patients who presented in adulthood with a delayed diagnosis. We conducted also a family screening through cascade genotyping. Conclusion: This is the first description of cases of Fabry disease in Central Asia. An extensive family pedigree enabled the identification of ten additional family members. Patients with rare genetic diseases often experience substantial delays in diagnosis due to their rarity and non-specific symptoms, which can negatively impact their management and delay treatment. FD may be difficult to diagnose because of the non-specificity of its early and later-onset symptoms and its X-linked inheritance. Raising awareness of clinicians is important for earlier diagnosis and optimal outcome of specific therapies.

Treatment of fabry disease with migalastat-outcome from a prospective 24 months observational multicenter study (FAMOUS)

AIMS

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a deficiency of the lysosomal enzyme α-galactosidase A (GLA/AGAL) resulting in lysosomal accumulation of globotriaosylceramide (Gb3). Patients with amenable GLA mutations can be treated with migalastat, an oral pharmacologic chaperone increasing endogenous AGAL activity. In this prospective observational multicenter study safety as well as cardiovascular, renal, and patient-reported outcomes and disease biomarkers were assessed after 12 and 24 months of migalastat treatment under "real world" conditions.

METHODS AND RESULTS

54 patients (26 females) (33 of these [61.1%] pre-treated with enzyme replacement therapy) with amenable mutations were analyzed. Treatment was generally safe and well tolerated. 153 events per 1,000 patient-years were detected. Overall left ventricular mass index decreased after 24 months (all: -7.5 ± 17.4 g/m2, p = 0.0118; females: -4.6 ± 9.1 g/m2, p = 0.0554; males: -9.9 ± 22.2 g/m2, p = 0.0699). After 24 months, females and males presented with a moderate yearly loss of eGFR (-2.6 and -4.4 ml/min/1.73 m2 per year; p = 0.0317 and p = 0.0028, respectively). FD-specific manifestations/symptoms remained stable (all p > 0.05). 76.9% of females and 50% of males suffered from pain, which has not improved under treatment. FD-specific disease scores (DS3 and MSSI) remained stable during treatment. AGAL activities and plasma lyso-Gb3 values remained stable, although some male patients presented with increasing lyso-Gb3 levels over time.

CONCLUSIONS

Treatment with migalastat was generally safe and resulted in most patients in an amelioration of left ventricular mass. However, due to the heterogeneity of FD phenotypes, it is advisable that the treating physician monitors the clinical response regularly.

Fabry Disease: The Current Treatment Landscape

Fabry disease (FD) is a rare X-linked lysosomal storage disease based on a deficiency of α-galactosidase A (AGAL) caused by mutations in the α-galactosidase A gene (GLA). The lysosomal accumulation of glycosphingolipids, especially globotriaosylceramide (Gb₃) and globotriaosylsphingosine (lyso-Gb₃, deacylated form), leads to a multisystemic disease with progressive renal failure, cardiomyopathy with potentially malignant cardiac arrhythmias, and strokes, which considerably limits the life expectancy of affected patients. Diagnostic confirmation in male patients is based on the detection of AGAL deficiency in blood leukocytes, whereas in women, due to the potentially high residual enzymatic activity, molecular genetic detection of a causal mutation is required. Current treatment options for FD include recombinant enzyme replacement therapy (ERT) with intravenous agalsidase-alfa (0.2 mg/kg body weight) or agalsidase-beta (1 mg/kg body weight) every 2 weeks and oral chaperone therapy with migalastat (123 mg every other day), which selectively and reversibly binds to the active site of AGAL, thereby correcting the misfolding of the enzyme and allowing it to traffic to the lysosome. These therapies enable cellular Gb₃ clearance and improve the burden of disease. However, in about 40% of all ERT-treated men, ERT can lead to infusion-associated reactions and the formation of neutralizing antidrug antibodies, which reduces the efficacy of therapy. In chaperone therapy, there are carriers of amenable mutations that show limited clinical success. This article provides a brief overview of the clinical picture in FD patients, diagnostic confirmation, and interdisciplinary clinical management of FD. The focus is on current and future therapeutic options.

Ion channels and pain in Fabry disease

Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A (α-Gal A) activity which results in progressive accumulation of globotriaosylceramide (Gb3) and related metabolites. One prominent feature of Fabry disease is neuropathic pain. Accumulation of Gb3 has been documented in dorsal root ganglia (DRG) as well as other neurons, and has lately been associated with the mechanism of pain though the pathophysiology is still unclear. Small fiber (SF) neuropathy in FD differs from other entities in several aspects related to the perception of pain, alteration of fibers as well as drug therapies used in the practice with patients, with therapies far from satisfying. In order to develop better treatments, more information on the underlying mechanisms of pain is needed. Research in neuropathy has gained momentum from the development of preclinical models where different aspects of pain can be modelled and further analyzed. This review aims at describing the different in vitro and FD animal models that have been used so far, as well as some of the insights gained from their use. We focus especially in recent findings associated with ion channel alterations -that apart from the vascular alterations-, could provide targets for improved therapies in pain.

Fabry Disease Therapy: State-of-the-Art and Current Challenges

Fabry disease (FD) is a lysosomal storage disorder caused by mutations of the GLA gene that lead to a deficiency of the enzymatic activity of α-galactosidase A. Available therapies for FD include enzyme replacement therapy (ERT) (agalsidase alfa and agalsidase beta) and the chaperone migalastat. Despite the large body of literature published about ERT over the years, many issues remain unresolved, such as the optimal dose, the best timing to start therapy, and the clinical impact of anti-drug antibodies. Migalastat was recently approved for FD patients with amenable GLA mutations; however, recent studies have raised concerns that "in vitro" amenability may not always reflect "in vivo" amenability, and some findings on real-life studies have contrasted with the results of the pivotal clinical trials. Moreover, both FD specific therapies present limitations, and the attempt to correct the enzymatic deficiency, either by enzyme exogenous administration or enzyme stabilization with a chaperone, has not shown to be able to fully revert FD pathology and clinical manifestations. Therefore, several new therapies are under research, including new forms of ERT, substrate reduction therapy, mRNA therapy, and gene therapy. In this review, we provide an overview of the state-of-the-art on the currently approved and emerging new therapies for adult patients with FD.

Genome Editing for Rare Diseases

PURPOSE OF THE REVIEW

Significant numbers of patients worldwide are affected by various rare diseases, but the effective treatment options to these individuals are limited. Rare diseases remain underfunded compared to more common diseases, leading to significant delays in research progress and ultimately, to finding an effective cure. Here, we review the use of genome-editing tools to understand the pathogenesis of rare diseases and develop additional therapeutic approaches with a high degree of precision.

RECENT FINDINGS

Several genome-editing approaches, including CRISPR/Cas9, TALEN and ZFN, have been used to generate animal models of rare diseases, understand the disease pathogenesis, correct pathogenic mutations in patient-derived somatic cells and iPSCs, and develop new therapies for rare diseases. The CRISPR/Cas9 system stands out as the most extensively used method for genome editing due to its relative simplicity and superior efficiency compared to TALEN and ZFN. CRISPR/Cas9 is emerging as a feasible gene-editing option to treat rare monogenic and other genetically defined human diseases.

SUMMARY

Less than 5% of ~7000 known rare diseases have FDA-approved therapies, providing a compelling need for additional research and clinical trials to identify efficient treatment options for patients with rare diseases. Development of efficient genome-editing tools capable to correct or replace dysfunctional genes will lead to novel therapeutic approaches in these diseases.

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.

Diurnal Variation of Urinary Fabry Disease Biomarkers during Enzyme Replacement Therapy Cycles

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene encoding the α-galactosidase A enzyme. This enzyme cleaves the last sugar unit of glycosphingolipids, including globotriaosylceramide (Gb₃), globotriaosylsphingosine (lyso-Gb₃), and galabiosylceramide (Ga₂). Enzyme impairment leads to substrate accumulation in different organs, vascular endothelia, and biological fluids. Enzyme replacement therapy (ERT) is a commonly used treatment. Urinary analysis of Gb₃ isoforms (different fatty acid moieties), as well as lyso-Gb₃ and its analogues, is a reliable way to monitor treatment. These analogues correspond to lyso-Gb₃ with chemical modifications on the sphingosine moiety (−C₂H₄, −C₂H₄+O, −H₂, −H₂+O, +O, +H₂O₂, and +H₂O₃). The effects of sample collection time on urinary biomarker levels between ERT cycles were not previously documented. The main objective of this project was to analyze the aforementioned biomarkers in urine samples from seven Fabry disease patients (three treated males, three treated females, and one ERT-naïve male) collected twice a day (morning and evening) for 42 days (three ERT cycles). Except for one participant, our results show that the biomarker levels were generally more elevated in the evening. However, there was less variability in samples collected in the morning. No cyclic variations in biomarker levels were observed between ERT infusions.

In Vitro and In Vivo Amenability to Migalastat in Fabry Disease

Migalastat (1-deoxygalactonojirimycin) is approved for the treatment of Fabry disease (FD) in patients with an amenable mutation. Currently, there are at least 367 amenable and 711 non-amenable mutations known, based on an in vitro good laboratory practice (GLP) assay. Recent studies demonstrated that in vitro amenability of mutations did not necessarily correspond to in vivo amenability of migalastat-treated patients. This discrepancy might be due to (methodological) limitations of the current GLP-HEK assay. Currently, there are several published comparable cell-based amenability assays, with partially different outcomes for the same tested mutation, leading to concerns in FD-treating physicians. The aim of this review is to elucidate the idea of amenability assays from their beginning, starting with patient-specific primary cells to high-throughput assays based on overexpression. Consequently, we compare methods of current assays, highlighting their similarities, as well as their pros and cons. Finally, we provide a literature-based list of α-galactosidase A mutations, tested by different assays to provide a comprehensive overview of amenable mutations as a good basis for the decision-making by treating physicians. Since in vitro amenability does not always correspond with in vivo amenability, the treating clinician has the responsibility to monitor clinical and laboratory features to verify clinical response.

Proteostasis regulators modulate proteasomal activity and gene expression to attenuate multiple phenotypes in Fabry disease

The lysosomal storage disorder Fabry disease is characterized by a deficiency of the lysosomal enzyme α-Galactosidase A. The observation that missense variants in the encoding GLA gene often lead to structural destabilization, endoplasmic reticulum retention and proteasomal degradation of the misfolded, but otherwise catalytically functional enzyme has resulted in the exploration of alternative therapeutic approaches. In this context, we have investigated proteostasis regulators (PRs) for their potential to increase cellular enzyme activity, and to reduce the disease-specific accumulation of the biomarker globotriaosylsphingosine in patient-derived cell culture. The PRs also acted synergistically with the clinically approved 1-deoxygalactonojirimycine, demonstrating the potential of combination treatment in a therapeutic application. Extensive characterization of the effective PRs revealed inhibition of the proteasome and elevation of GLA gene expression as paramount effects. Further analysis of transcriptional patterns of the PRs exposed a variety of genes involved in proteostasis as potential modulators. We propose that addressing proteostasis is an effective approach to discover new therapeutic targets for diseases involving folding and trafficking-deficient protein mutants.

Treatment of Fabry's Disease With Migalastat: Outcome From a Prospective Observational Multicenter Study (FAMOUS)

Fabry's disease (FD) is an X-linked lysosomal storage disorder caused by the deficient activity of the lysosomal enzyme α-galactosidase A (α-Gal A) leading to intracellular accumulation of globotriaosylceramide (Gb3). Patients with amenable mutations can be treated with migalastat, a recently approved oral pharmacologic chaperone to increase endogenous α-Gal A activity. We assessed safety along with cardiovascular, renal, and patient-reported outcomes and disease biomarkers in a prospective observational multicenter study after 12 months of migalastat treatment under "real-world" conditions. Fifty-nine (28 females) patients (34 (57.6%) pretreated with enzyme replacement therapy) with amenable mutations were recruited. Migalastat was generally safe and well tolerated. Females and males presented with a reduction of left ventricular mass index (primary end point) (-7.2 and -13.7 g/m² , P = 0.0050 and P = 0.0061). FD-specific manifestations and symptoms remained stable (all P > 0.05). Both sexes presented with a reduction of estimated glomerular filtration rate (secondary end point) (-6.9 and -5.0 mL/minute/1.73 m² ; P = 0.0020 and P = 0.0004, respectively), which was most prominent in patients with low blood pressure (P = 0.0271). α-Gal A activity increased in male patients by 15% from 29% to 44% of the normal wild-type activity (P = 0.0106) and plasma lyso-Gb3 levels were stable in females and males (P = 0.3490 and P = 0.2009). Reevaluation of mutations with poor biochemical response revealed no marked activity increase in a zero activity background. We conclude that therapy with migalastat was generally safe and resulted in an amelioration of left ventricular mass. In terms of impaired renal function, blood pressure control seems to be an unattended important goal.

The pharmacological chaperone N-n-butyl-deoxygalactonojirimycin enhances β-galactosidase processing and activity in fibroblasts of a patient with infantile GM1-gangliosidosis

GM1-gangliosidosis, a lysosomal storage disorder, is associated with ~ 161 missense variants in the GLB1 gene. Affected patients present with β-galactosidase (β-Gal) deficiency in lysosomes. Loss of function in ER-retained misfolded enzymes with missense variants is often due to subcellular mislocalization. Deoxygalactonojirimycin (DGJ) and its derivatives are pharmaceutical chaperones that directly bind to mutated β-Gal in the ER promoting its folding and trafficking to lysosomes and thus enhancing its activity. An Emirati child has been diagnosed with infantile GM1-gangliosidosis carrying the reported p.D151Y variant. We show that p.D151Y β-Gal in patient's fibroblasts retained < 1% residual activity due to impaired processing and trafficking. The amino acid substitution significantly affected the enzyme conformation; however, p.D151Y β-Gal was amenable for partial rescue in the presence of glycerol or at reduced temperature where activity was enhanced with ~ 2.3 and 7 folds, respectively. The butyl (NB-DGJ) and nonyl (NN-DGJ) derivatives of DGJ chaperoning function were evaluated by measuring their IC₅₀s and ability to stabilize the wild-type β-Gal against thermal degradation. Although NN-DGJ showed higher affinity to β-Gal, it did not show a significant enhancement in p.D151Y β-Gal activity. However, NB-DGJ promoted p.D151Y β-Gal maturation and enhanced its activity up to ~ 4.5% of control activity within 24 h which was significantly increased to ~ 10% within 6 days. NB-DGJ enhancement effect was sustained over 3 days after washing it out from culture media. We therefore conclude that NB-DGJ might be a promising therapeutic chemical chaperone in infantile GM1 amenable variants and therefore warrants further analysis for its clinical applications.

New drugs for the treatment of Anderson-Fabry disease

Enzyme replacement therapy (ERT) of the Anderson-Fabry disease (AFD) has changed the outcome of patients. However, ERT has some limitations: a restricted volume of distribution, requirement for intravenous access, and stimulation of the production of anti-drug antibodies. Studies of new drugs aiming to improve the clinical effectiveness and convenience of therapy have been reported. Migalastat, a pharmacological chaperone, increases available enzymate activity in patients with mutations amenable to the therapy, is now available for clinical practice. It is orally administered, and while clinical trial results are promising, long term real world follow up is awaited. PEGylated enzyme has a longer half-life and potentially reduced antigenicity, compared with standard preparations; investigation of whether a longer dosing interval is viable is under way. Moss-derived enzyme has a higher affinity for mannose receptors, and appears to have access to renal tissue. Substrate reduction therapy is based on reducing the catabolism processes of the glycosphingolipids, and is currently under investigation as monotherapy. Gene therapy has now been initiated in clinical trail of in vivo and ex vivo technologies with early results are emerging. ERT represents a certain milestone of therapy for AFD with Migalastat now a newly available option. Other agents in clinical trial prevent further potential opportunities to improve outcomes in AFD.

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.

FAbry STabilization indEX (FASTEX): Clinical evaluation of disease progression in Fabry patients

BACKGROUND

Two established scores, the Mainz Severity Score Index (MSSI) and Fabry Disease Severity Scoring System (DS3), quantify the disease burden in Fabry disease (FD), while the recent developed FAbry STabilization indEX (FASTEX) aims to detect disease progression.

OBJECTIVE

MSSI, DS3 and FASTEX were compared to evaluate disease stability or progression in a prospective cohort of Fabry patients under enzyme replacement therapy (ERT).

METHODS

Disease load of 62 patients (28 [45%] females) treated with ERT (26 [42%] under agalsidase-alfa) was assessed using the current scores and re-assessed after 12 months of treatment. Fifteen (24%) patients were ERT-naïve at baseline.

RESULTS

All scores showed a correlation with each other, while MSSI and DS3 showed the strongest (Pearson r: 0.81, p < .0001). Plasma lyso-Gb3 levels in naïve patients correlated with increasing DS3 and MSSI scores (Pearson r: 0.60, p < .05; Pearson r: 0.64, p < .01; respectively), but not with the total weighted FASTEX score. Longitudinal analysis suggested a stable disease course using DS3 and MSSI. Only males long-term-treated with agalsidase-alfa presented with a slight increase of the general MSSI score (p = .0084). By contrast, the FASTEX score demonstrates that only 21 patients (33.9%) were stable, all other patients presented a disease progression. Patients with an unstable FASTEX mainly suffered from a significant loss of renal function (eGFR_creat: -2.7 ± 7.3 ml/min/1.73 m², p = .0298).

CONCLUSION

We conclude that the FASTEX seems to be a simple and user friendly, valuable tool to assess early changes in disease progression even in smaller patient cohorts and short term surveillance.

Assessment of Gene Variant Amenability for Pharmacological Chaperone Therapy with 1-Deoxygalactonojirimycin in Fabry Disease

Fabry disease is one of the most common lysosomal storage disorders caused by mutations in the gene encoding lysosomal α-galactosidase A (α-Gal A) and resultant accumulation of glycosphingolipids. The sugar mimetic 1-deoxygalactonojirimycin (DGJ), an orally available pharmacological chaperone, was clinically approved as an alternative to intravenous enzyme replacement therapy. The decision as to whether a patient should be treated with DGJ depends on the genetic variant within the α-galactosidase A encoding gene (GLA). A good laboratory practice (GLP)-validated cell culture-based assay to investigate the biochemical responsiveness of the variants is currently the only source available to obtain pivotal information about susceptibility to treatment. Herein, variants were defined amenable when an absolute increase in enzyme activity of ≥3% of wild type enzyme activity and a relative increase in enzyme activity of ≥1.2-fold was achieved following DGJ treatment. Efficacy testing was carried out for over 1000 identified GLA variants in cell culture. Recent data suggest that about one-third of the variants comply with the amenability criteria. A recent study highlighted the impact of inter-assay variability on DGJ amenability, thereby reducing the power of the assay to predict eligible patients. This prompted us to compare our own α-galactosidase A enzyme activity data in a very similar in-house developed assay with those from the GLP assay. In an essentially retrospective approach, we reviewed 148 GLA gene variants from our former studies for which enzyme data from the GLP study were available and added novel data for 30 variants. We also present data for 18 GLA gene variants for which no data from the GLP assay are currently available. We found that both differences in experimental biochemical data and the criteria for the classification of amenability cause inter-assay discrepancy. We conclude that low baseline activity, borderline biochemical responsiveness, and inter-assay discrepancy are alarm signals for misclassifying a variant that must not be ignored. Furthermore, there is no solid basis for setting a minimum response threshold on which a clinical indication with DGJ can be justified.

Current and Investigational Therapeutics for Fabry Disease

Fabry disease (FD) is an X-linked lysosomal storage disease caused by a deficiency in the lysosomal enzyme α-galactosidase (α-GAL). This in turn leads to the buildup of globotriaosylceramide, resulting classically in progressive kidney disease, peripheral neuropathy, early-onset cerebrovascular disease, gastrointestinal symptoms, hypertrophic cardiomyopathy, arrhythmias, corneal whorls, and angiokeratomas. The diagnosis of FD relies on identification of a low α-GAL enzyme activity, identification of a genetic mutation, or histologic evidence of disease. With more than 900 mutations identified, there is phenotypic variability deriving from both mutational effects as well as the effect of skewed X-inactivation in females. Treatment of this disease has relied on intravenous replacement of the deficient enzyme with agalsidase α or agalsidase β. However, treatment options for some patients with FD have recently expanded, with the approval of migalastat, an oral molecular chaperone. In addition to chaperone-based therapies, there are several additional therapies under development that could substantially reshape treatment options for patients with FD. Four approaches to gene therapy, through both ex vivo and in vivo methods, are under development. Another approach is through the administration of α-GAL mRNA to help stimulate production of α-GAL, which is another unique form of therapy. Finally, substrate reduction therapies act as inhibitors of glucosylceramide synthase, thus inhibiting the production of GB-3, promise another oral option to treat FD. This article will review the literature around current therapies as well as these newer therapeutics agents in the pipeline for FD.

Advances in Sphingolipidoses: CRISPR-Cas9 Editing as an Option for Modelling and Therapy

Sphingolipidoses are inherited genetic diseases characterized by the accumulation of glycosphingolipids. Sphingolipidoses (SP), which usually involve the loss of sphingolipid hydrolase function, are of lysosomal origin, and represent an important group of rare diseases among lysosomal storage disorders. Initial treatments consisted of enzyme replacement therapy, but, in recent decades, various therapeutic approaches have been developed. However, these commonly used treatments for SP fail to be fully effective and do not penetrate the blood-brain barrier. New approaches, such as genome editing, have great potential for both the treatment and study of sphingolipidoses. Here, we review the most recent advances in the treatment and modelling of SP through the application of CRISPR-Cas9 genome editing. CRISPR-Cas9 is currently the most widely used method for genome editing. This technique is versatile; it can be used for altering the regulation of genes involved in sphingolipid degradation and synthesis pathways, interrogating gene function, generating knock out models, or knocking in mutations. CRISPR-Cas9 genome editing is being used as an approach to disease treatment, but more frequently it is utilized to create models of disease. New CRISPR-Cas9-based tools of gene editing with diminished off-targeting effects are evolving and seem to be more promising for the correction of individual mutations. Emerging Prime results and CRISPR-Cas9 difficulties are also discussed.

Design and optimization strategies for the development of new drugs that treat chronic kidney disease

Introduction: Chronic kidney disease (CKD) is characterized by increased risks of progression to end-stage kidney disease requiring dialysis and cardiovascular mortality, predicted to be among the five top causes of death by 2040. Only the design and optimization of novel strategies to develop new drugs to treat CKD will contain this trend. Current therapy for CKD includes nonspecific therapy targeting proteinuria and/or hypertension and cause-specific therapies for diabetic kidney disease, autosomal dominant polycystic kidney disease, glomerulonephritides, Fabry nephropathy, hemolytic uremic syndrome and others.Areas covered: Herein, the authors review the literature on new drugs under development for CKD as well as novel design and development strategies.Expert opinion: New therapies for CKD have become a healthcare priority. Emerging therapies undergoing clinical trials are testing expanded renin-angiotensin system blockade with double angiotensin receptor/endothelin receptor blockers, SGLT2 inhibition, and targeting inflammation, the immune response, fibrosis and the Nrf2 transcription factor. Emerging therapeutic targets include cell senescence, complement activation, Klotho expression preservation and microbiota. Novel approaches include novel model systems that can be personalized (e.g. organoids), unbiased systems biology-based identification of new therapeutic targets, drug databases that speed up drug identification and repurposing, nanomedicines that improve drug delivery and RNA targeting to expand the number of targetable proteins.