Lentivirus-mediated gene therapy for Fabry disease

Progress and Challenges in the Treatment of Fabry Disease

Fabry disease is a rare but life-threatening, X-linked, inherited lysosomal storage disorder in which globotriaosylceramide is insufficiently metabolized because of reduced α-galactosidase A activity. Cellular globotriaosylceramide accumulation causes a multisystemic disease, which, if left untreated, reduces life expectancy in female and male individuals by around 10 and 20 years, respectively, leading to progressive renal failure, hypertrophic cardiomyopathy, cardiac arrhythmia, and premature cerebral infarction. The method of choice for confirming the diagnosis is the determination of reduced α-galactosidase A activity in leukocytes in male individuals and the molecular genetic detection of a disease-causing mutation in female individuals. Current approved treatment includes enzyme replacement therapy (agalsidase alfa [0.2 mg/kg body weight], agalsidase beta or pegunigalsidase alfa [both 1.0 mg/kg body weight]) every other week intravenously or, if a responding ('amenable') α-galactosidase A mutation is present, oral pharmacological chaperone therapy (migalastat 123 mg, every other day). Future therapeutic options may include substrate reduction therapy, gene therapy, messenger RNA therapy, and/or vesicle-packaged enzyme replacement therapy. This review presents current and future treatment options with advantages and disadvantages of the different treatment options.

Updated Gene Therapy for Renal Inborn Errors of Metabolism

Inborn errors of metabolism (IEMs) are a group of disorders resulting from defects in enzymes in metabolic pathways. These disorders impact the processing of metabolites, leading to a wide array of effects on each organ system. Advances in genetic screening have allowed for the early identification and intervention of IEMs, traditionally in the form of enzyme replacement or vitamin supplementation. However, many IEMs disrupt essential metabolic pathways where simple supplementation proves ineffective, resulting in substantial disease burden. In the case of renal IEMs, metabolic pathway disruption leads to the onset of chronic kidney disease (CKD). For these diseases, genetic therapy provides hope. Over the past few decades, the technology for genetic therapy has emerged as a promising solution to these disorders. These therapies aim to correct the source of the defect in the genetic code so that patients may live full, unencumbered lives. In this review, we searched a large database to identify IEMs that affect the kidney and investigated the current landscape and progression of gene therapy technology. Multiple promising genetic therapies were identified for IEMs affecting the kidney, including primary hyperoxaluria, argininemia, glycogen storage diseases Ia and Ib, and Fabry disease. Emerging gene therapy approaches using adeno-associated virus (AAV) vectors, lentiviral vectors, and CRISPR/Cas9 techniques hold promising potential to provide curative treatments for additional single-mutation disorders.

The use and performance of lyso-Gb3 for the diagnosis and monitoring of Fabry disease: A systematic literature review

BACKGROUND

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder in which a lack of alpha-galactosidase (α-Gal A) enzyme activity leads to intracellular accumulation of deacylated globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3), and their analogs. Lyso-Gb3, present in the blood and urine of affected patients, has been extensively investigated as a biomarker for FD. This systematic literature review (SLR) aimed to comprehensively assess the use of lyso-Gb3 as a biomarker for screening, monitoring, and diagnosis of FD in both real-world and clinical trial settings.

METHODS

An SLR was performed to identify the following outcomes in adult and pediatric patients with FD: lyso-Gb3 testing patterns, lyso-Gb3 levels in subpopulations, performance and accuracy of lyso-Gb3 testing for diagnosis, and lyso-Gb3 testing for monitoring of disease progression or treatment efficacy/effectiveness. Interventional and non-interventional studies published between 1 January 2017 and 3 November 2022 were included. Searches were primarily conducted in MEDLINE and Embase; pragmatic or hand searches were also performed. The methodological quality of included full-text studies was assessed using validated appraisal tools. Extracted data were synthesized qualitatively.

RESULTS

The SLR included 83 eligible publications, comprising 71 observational studies and 12 clinical trials. Differences in lyso-Gb3 levels were identified across subpopulations, with several studies reporting higher levels in males versus females. Lyso-Gb3 demonstrated good diagnostic performance in newborns and high-risk patients when used in combination with other markers (α-Gal A activity or GLA variants) but failed to diagnose females with late-onset FD. Reliability and stability across different methods used to measure lyso-Gb3 was high, with a coefficient of variation <10 % for inter- and intra-assay measurements. Several studies identified moderate to strong correlation between plasma lyso-Gb3 levels and cardiac measures, but association with renal measures needs further investigation.

CONCLUSIONS

Lyso-Gb3 testing demonstrated accuracy in screening, diagnosis, and monitoring of FD in certain subpopulations, particularly males, but considering its lower sensitivity in late-onset female patients, it should be used in conjunction with other tools. Given the reliability of the test, it can be considered a feasible method for monitoring disease progression in FD in individual patients. Several gaps in the literature were identified, warranting further investigation.

REGISTRATION

PROSPERO (CRD42022375141).

Improving the production of BaEV lentivirus by comprehensive optimization

With the rapid development of the cell and gene therapy industry, there is an increasing demand for lentiviral vectors that can efficiently infect cells of different purposes. BaEV lentiviruses have been shown to efficiently infect hematopoietic stem cells, primary B cells, and NK cells, which traditional VSV-G lentiviruses cannot infect. However, there is a problem of low virus yield in the production of BaEV lentivirus. The formation of syncytium and apoptosis occur after plasmid transfection, and resulting in a reduction in virus production. In this study, the issue of low production of BaEV lentivirus was comprehensively improved. By increasing the cell density of inoculation, reducing the amount of BaEV plasmid, and adjusting the harvest time, the maximum titer of BaEV lentivirus reached 4.43E+ 06 IU/ml, representing an increase of 369 times compared to the unoptimized condition. Further, the purification method of lentivirus solution was optimized, and the infection titer of lentivirus reached 1.00E+ 08 IU/ml, which is 10300 times higher than pre-optimization levels.

Progress in Gene Therapy for Hereditary Tyrosinemia Type 1

Hereditary Tyrosinemia Type-1 (HT1), an inherited error of metabolism caused by a mutation in the fumarylacetoacetate hydrolase gene, is associated with liver disease, severe morbidity, and early mortality. The use of NTBC (2-(2-nitro-4-fluoromethylbenzoyl)-1,3-cyclohexanedione) has almost eradicated the acute HT1 symptoms and childhood mortality. However, patient outcomes remain unsatisfactory due to the neurocognitive effects of NTBC and the requirement for a strict low-protein diet. Gene therapy (GT) offers a potential single-dose cure for HT1, and there is now abundant preclinical data showing how a range of vector-nucleotide payload combinations could be used with curative intent, rather than continued reliance on amelioration. Unfortunately, there have been no HT1-directed clinical trials reported, and so it is unclear which promising pre-clinical approach has the greatest chance of successful translation. Here, to fill this knowledge gap, available HT1 preclinical data and available clinical trial data pertaining to liver-directed GT for other diseases are reviewed. The aim is to establish which vector-payload combination has the most potential as a one-dose HT1 cure. Analysis provides a strong case for progressing lentiviral-based approaches into clinical trials. However, other vector-payload combinations may be more scientifically and commercially viable, but these options require additional investigation.

Status and frontiers of Fabre disease

Fabry disease is characterized by an X sex chromosome gene mutation caused by α-galactosidase A deficiency, resulting in the accumulation of globotriaosylceramide and globotriaosylsphingosine in various organs, which induces end-organ lesions. In Fabry disease, enzymes with lost or decreased activity in the body are replaced by exogenous supplementation of normal-function α-galactosidase A. Currently, agalsidase α and agalsidase β are widely used for ERT therapy. However, this therapy has limitations such as high cost, short half-life, and production of neutralizing drug antibodies. The use of Migalastat as chaperone therapy has been approved in many countries, and it plays a therapeutic role by enhancing enzyme activity. However, companion therapy drugs are only suitable for patients with decreased enzyme activity, so the scope of their application is limited. In addition, there are several therapeutic drugs in development, including a new generation of ERT therapies, drugs resistant to neutralizing anti-drug antibody drugs, and substrate reduction therapy drugs. Due to the limitations of existing therapeutic drugs, researchers have begun to explore new therapeutic drugs for Fabry disease, so new pathogenic mechanisms and adjuvant therapeutic drugs have been continuously discovered, and the development of related drugs will contribute to disease control and treatment. This article summarizes the existing and potential drugs for treating Fabry disease to facilitate the selection of suitable and effective drugs for treatment.

Fabry Disease: Insights into Pathophysiology and Novel Therapeutic Strategies

Fabry disease (FD) is an X-linked lysosomal storage disorder characterized by deficiency of α-galactosidase A (α-GalA), leading to the accumulation of glycosphingolipids and multi-organ dysfunction, particularly affecting the cardiovascular and renal systems. Disease-modifying treatments such as enzyme replacement therapy (ERT) and oral chaperone therapy (OCT) have limited efficacy, particularly in advanced disease, prompting a need for innovative therapeutic approaches targeting underlying molecular mechanisms beyond glycosphingolipid storage alone. Recent insights into the pathophysiology of FD highlights chronic inflammation and mitochondrial, lysosomal, and endothelial dysfunction as key mediators of disease progression. Adjunctive therapies such as sodium-glucose cotransporter-2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) agonists, and mineralocorticoid receptor antagonists (MRAs) demonstrate significant cardiovascular and renal benefits in conditions including heart failure and chronic kidney disease. These drugs also modulate pathways involved in the pathophysiology of FD, such as autophagy, oxidative stress, and pro-inflammatory cytokine signaling. While theoretical foundations support their utility, dedicated trials are necessary to confirm efficacy in the FD-specific population. This narrative review highlights the importance of expanding therapeutic strategies in FD, advocating for a multi-faceted approach involving evidence-based adjunctive treatments to improve outcomes. Tailored research focusing on diverse FD phenotypes, including females and non-classical variants of disease, will be critical to advancing care and improving outcomes in this complex disorder.

Lectin-Based Substrate Detection in Fabry Disease Using the Gb3-Binding Lectins StxB and LecA

Fabry disease, the second most common lysosomal storage disorder, is caused by a deficiency of α-galactosidase A (α-Gal A), which leads to an accumulation of glycosphingolipids (GSL), mainly globotriaosylceramide (also known as Gb3). This aberrant GSL metabolism subsequently causes cellular dysfunction; however, the underlying cellular and molecular mechanisms are still unknown. There is growing evidence that damage to organelles, including lysosomes, mitochondria, and plasma membranes, is associated with substrate accumulation. Current methods for the detection of Gb3 are based on anti-Gb3 antibodies, the specificity and sensitivity of which are problematic for glycan detection. This study presents a robust method using lectins, specifically the B-subunit of Shiga toxin (StxB) from Shigella dysenteriae and LecA from Pseudomonas aeruginosa, as alternatives for Gb3 detection in Fabry fibroblasts by flow cytometry and confocal microscopy. StxB and LecA showed superior sensitivity, specificity, and consistency in different cell types compared to all anti-Gb3 antibodies used in this study. In addition, sphingolipid metabolism was analyzed in primary Fabry fibroblasts and α-Gal A knockout podocytes using targeted tandem liquid chromatography-mass spectrometry. Our findings establish lectins as a robust tool for improved diagnostics and research of Fabry disease and provide evidence of SL changes in cultured human cells, filling a knowledge gap.

Natural History and Clinicopathological Associations of TRPC6-Associated Podocytopathy

KEY POINTS

We conducted a clinical, genetic, and pathological analysis on 64 cases from 39 families with TRPC6-associated podocytopathy (TRPC6-AP). Analysis of 37,542 individuals excluded a major contribution of loss-of-function variants to TRPC6-AP, legitimating current drug discovery approaches. This study identifies key features of disease that can help intervention studies design and suggests similarities between TRPC6-AP and primary FSGS.

BACKGROUND

Understanding the genetic basis of human diseases has become integral to drug development and precision medicine. Recent advancements have enabled the identification of molecular pathways driving diseases, leading to targeted treatment strategies. The increasing investment in rare diseases by the biotech industry underscores the importance of genetic evidence in drug discovery and approval processes. Here we studied a monogenic Mendelian kidney disease, TRPC6-associated podocytopathy (TRPC6-AP), to present its natural history, genetic spectrum, and clinicopathological associations in a large cohort of patients with causal variants in TRPC6 to help define the specific features of disease and further facilitate drug development and clinical trials design.

METHODS

The study involved 64 individuals from 39 families with TRPC6 causal missense variants. Clinical data, including age of onset, laboratory results, response to treatment, kidney biopsy findings, and genetic information, were collected from multiple centers nationally and internationally. Exome or targeted sequencing was performed, and variant classification was based on strict criteria. Structural and functional analyses of TRPC6 variants were conducted to understand their effect on protein function. In-depth reanalysis of light and electron microscopy specimens for nine available kidney biopsies was conducted to identify pathological features and correlates of TRPC6-AP.

RESULTS

Large-scale sequencing data did not support causality for TRPC6 protein-truncating variants. We identified 21 unique TRPC6 missense variants, clustering in three distinct regions of the protein, and with different effects on TRPC6 3D protein structure. Kidney biopsy analysis revealed FSGS patterns of injury in most cases, along with distinctive podocyte features including diffuse foot process effacement and swollen cell bodies. Most patients presented in adolescence or early adulthood but with ample variation (average 22, SD ±14 years), with frequent progression to kidney failure but with variability in time between presentation and kidney failure.

CONCLUSIONS

This study provides insights into the genetic spectrum, clinicopathological associations, and natural history of TRPC6-AP.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER:

A Study to Test BI 764198 in People With a Type of Kidney Disease Called Focal Segmental Glomerulosclerosis, NCT05213624.

Current and Emerging Therapies for Lysosomal Storage Disorders

Lysosomal storage disorders (LSDs) are rare inherited metabolic disorders characterized by defects in the function of specific enzymes responsible for breaking down substrates within cellular organelles (lysosomes) essential for the processing of macromolecules. Undigested substrate accumulates within lysosomes, leading to cellular dysfunction, tissue damage, and clinical manifestations. Clinical features vary depending on the degree and type of enzyme deficiency, the type and extent of substrate accumulated, and the tissues affected. The heterogeneous nature of LSDs results in a variety of treatment approaches, which must be tailored to patient presentation and characteristics. The treatment landscape for LSDs is rapidly evolving. An up-to-date discussion of current evidence is required to provide clinicians with an appropriate overview of treatment options. Therefore, we aimed to review current and ongoing trials pertaining to the treatment of common LSDs.

Plasmid Gene Therapy for Monogenic Disorders: Challenges and Perspectives

Monogenic disorders are a group of human diseases caused by mutations in single genes. While some disease-altering treatments offer relief and slow the progression of certain conditions, the majority of monogenic disorders still lack effective therapies. In recent years, gene therapy has appeared as a promising approach for addressing genetic disorders. However, despite advancements in gene manipulation tools and delivery systems, several challenges remain unresolved, including inefficient delivery, lack of sustained expression, immunogenicity, toxicity, capacity limitations, genomic integration risks, and limited tissue specificity. This review provides an overview of the plasmid-based gene therapy techniques and delivery methods currently employed for monogenic diseases, highlighting the challenges they face and exploring potential strategies to overcome these barriers.

Lentivirus-mediated gene therapy for Fabry disease: 5-year End-of-Study results from the Canadian FACTs trial

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder due to a deficiency of α-galactosidase A (α-gal A) activity. Our goal was to correct the enzyme deficiency in Fabry patients by transferring the cDNA for α-gal A into their CD34+ hematopoietic stem/progenitor cells (HSPCs). Overexpression of α-gal A leads to secretion of the hydrolase; which can be taken up and used by uncorrected bystander cells. Gene-augmented HSPCs can circulate and thus provide sustained systemic correction. Interim results from this 'first-in-the-world' Canadian FACTs (Fabry Disease Clinical Research and Therapeutics) trial were published in 2021. Herein we report 5-year 'End-of-Study' results.

METHODS

Five males with classical Fabry disease were treated. Their HSPCs were mobilized, enriched, and transduced with a recombinant lentivirus engineering expression of α-gal A. Autologous transduced cells were infused after conditioning with a nonmyeloablative, reduced dose, melphalan regimen. Safety monitoring was performed. α-Gal A activity was measured in plasma and peripheral blood (PB) leucocytes. Globotriaosylceramide (Gb3) and lyso-Gb3 levels in urine and plasma were assessed by mass spectrometry. qPCR assays measured vector copy number in PB leucocytes. Antibody titers were measured by ELISA. Body weight, blood pressure, urinary protein levels, eGFR, troponin levels, and LVMI were tracked.

RESULTS

Four out of 5 patients went home the same day as their infusions; one was kept overnight for observation. Circulating α-gal A activity was observed at Day 6-8 in each patient following infusion and has remained durable for 5+ years. LV marking of peripheral blood cells has remained durable and polyclonal. All 5 patients were eligible to come off biweekly enzyme therapy; 3 patients did so. Plasma lyso-Gb3 was significantly lower in 4 of 5 patients. There was no sustained elevation of anti-α-gal A antibodies. Patient weight was stable in 4 of the 5 patients. All blood pressures were in the normal range. Kidney symptoms were stabilized in all patients.

CONCLUSIONS

This treatment was well tolerated as only two SAEs occurred (during the treatment phase) and only two AEs were reported since 2021. We demonstrate that this therapeutic approach has merit, is durable, and should be explored in a larger clinical trial.

HIGHLIGHTS

This was the first gene therapy clinical trial to be completed for Fabry disease. There were no adverse events of any grade attributable to the cellular gene therapy intervention or host conditioning throughout the follow-up interval of 5 years. After reduced-intensity melphalan treatment, all patients engrafted their autologous modified α-gal A expressing cells. All patients synthesized and secreted α-gal A throughout the course of the study. Expression of α-gal A resulted in a decrease in plasma lyso-Gb3 in four of five patients and stabilization of kidney symptoms in all patients.

UPLC-MS/MS High-Risk Screening for Sphingolipidoses Using Dried Urine Spots

BACKGROUND

Early detection of sphingolipidoses is crucial to prevent irreversible complications and improve patient outcomes. The use of urine samples dried on filter paper (DUS) is a non-invasive strategy that simplifies the collection, storage, and shipping of samples compared to using liquid urine specimens.

OBJECTIVES

(1) Develop and validate a multiplex ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) methodology using DUS to quantify twenty-one lysosphingolipids normalized to creatinine for eight different sphingolipidoses. (2) Establish normal reference values to evaluate the clinical utility of the methodology.

METHODS

Samples were eluted from a 5 cm filter paper disk (~1 mL of urine) and extracted on Oasis MCX solid-phase extraction cartridges prior to injection in the UPLC-MS/MS system.

RESULTS

Urinary lysosphingolipids were stable on DUS at -80 °C and -30 °C for 117 days, at 21.5 °C and 4 °C for at least 26 days, and at 35 °C for 3 days. Globotriaosylsphingosine, glucosylsphingosine, and their analogs were elevated in patients with Fabry disease and Gaucher disease, respectively, compared to controls (p-value < 0.0001). The analysis of related analog profiles suggests a better overall reliability in detecting patients early, especially for Fabry patients.

CONCLUSIONS

This approach is feasible and might be useful for the early detection, monitoring, and follow-up of patients with sphingolipidoses.

[What is confirmed in the treatment of Fabry's disease?]

Fabry's disease is a rare X chromosome-linked inherited lysosomal storage disease characterized by insufficient metabolism of the substrate globotriaosylceramide (Gb3) due to reduced alpha-galactosidase A (AGAL) activity. Lysosomal Gb3 accumulation causes a multisystemic disease which, if untreated, reduces the life expectancy in females and males by around 10 and 20 years, respectively, due to progressive renal dysfunction, hypertrophic cardiomyopathy, cardiac arrhythmia and early occurrence of cerebral infarction. The diagnosis is confirmed by determining the reduced AGAL activity in leukocytes in males and molecular genetic detection of a -mutation causing the disease in females. The treatment comprises enzyme replacement therapy (ERT), agalsidase alfa, 0.2 mg/kg body weight (BW), agalsidase beta 1.0 mg/kg BW or pegunigalsidase alfa 1.0 mg/kg BW every 2 weeks i.v. or oral chaperone therapy (one capsule of migalastat 123 mg every other day) in the presence of amenable mutations. This article summarizes the data on the treatment of Fabry's disease and on complications in practice. The current guideline recommendations are addressed and new study results that could expand the therapeutic repertoire in the future are discussed.

Targeted gene therapy for rare genetic kidney diseases

Chronic kidney disease is one of the leading causes of mortality worldwide because of kidney failure and the associated challenges of its treatment including dialysis and kidney transplantation. About one-third of chronic kidney disease cases are linked to inherited monogenic factors, making them suitable for potential gene therapy interventions. However, the intricate anatomical structure of the kidney poses a challenge, limiting the effectiveness of targeted gene delivery to the renal system. In this review, we explore the progress made in the field of targeted gene therapy approaches and their implications for rare genetic kidney disorders, examining preclinical studies and prospects for clinical application. In vivo gene therapy is most commonly used for kidney-targeted gene delivery and involves administering viral and nonviral vectors through various routes such as systemic, renal vein, and renal arterial injections. Small nucleic acids have also been used in preclinical and clinical studies for treating certain kidney disorders. Unexpectedly, hematopoietic stem and progenitor cells have been used as an ex vivo gene therapy vehicle for kidney gene delivery, highlighting their ability to differentiate into macrophages within the kidney, forming tunneling nanotubes that can deliver genetic material and organelles to adjacent kidney cells, even across the basement membrane to target the proximal tubular cells. As gene therapy technologies continue to advance and our understanding of kidney biology deepens, there is hope for patients with genetic kidney disorders to eventually avoid kidney transplantation.

Identification of c.146G > A mutation in a Fabry patient and its correction by customized Cas9 base editors in vitro

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the GLA gene, leading to reduced α-galactosidase (α-Gal A) activity. Current treatments, like enzyme replacement, have limitations affecting efficacy and patient outcomes. CRISPR/Cas9 genome editing tools may offer the potential to develop therapeutic strategy via correcting GLA mutations. In this study, we diagnosed a female FD patient with a missense mutation in exon 1 of the GLA gene (c.146G > A, p.R49H). Bioinformatic predictions and biochemical analyses in GLA-knockout cells revealed that this mutation significantly reduced α-Gal A stability and activity, confirming its pathogenicity. To correct this, we used adenine base editing. The mutation, along with a nearby bystander A, was efficiently edited by the traditional N-terminal adenine base editor. To avoid unwanted bystander editing, we developed a series of domain-inlaid base editors with the aim of narrowing editing window. The most effective variant, with deaminase inserted between the 947th and 948th residues of the RUVC3 domain, was further optimized by modifying linker rigidity. These adjustments shifted the editing window, eliminating bystander editing. Our findings clarify the pathogenic nature of a novel GLA mutation and demonstrate the potential of a customized base editor for therapeutic application in FD.

Overcoming Resistance in Anderson-Fabry Disease: Current Therapeutic Challenges and Future Perspectives

Anderson-Fabry disease (AFD) remains a therapeutic challenge despite advances in early diagnosis and the availability of enzyme replacement therapies (ERTs). While early initiation of therapy can mitigate disease progression, resistance mechanisms-such as the development of anti-drug antibodies-limit the efficacy of current treatments, particularly in patients with severe genetic variants. Chaperone therapy provides a targeted option for a subset of patients, yet significant gaps remain in treating those with complete enzyme deficiency. This perspective article explores the existing therapeutic landscape and reflects on emerging treatments, such as mRNA and gene therapies, which hold promise for overcoming the resistance mechanisms. By addressing the limitations of current pharmacological options and considering future innovations, this article aims to outline the path forward for more effective and personalized treatment strategies in Anderson-Fabry disease.

Targeted therapeutic strategies for the kidney

INTRODUCTION

Kidney diseases impose a significant burden with high incidence and mortality rates. Current treatment options for kidney diseases are limited, necessitating urgent development of novel and effective therapeutic strategies to delay or reverse disease progression. Targeted therapies for the kidney hold promise in significantly enhancing treatment outcomes, offering hope to patients afflicted with renal disorders.

AREAS COVERED

This review summarized advances in kidney-targeted therapies including genes, peptides and proteins, cell-based, nanoparticles, and localized delivery routes. We also explored the potential clinical applications, prospects, and challenges of targeted therapies for renal disorders.

EXPERT OPINION

Advances in targeted therapies for renal conditions have enhanced therapeutic outcomes. Clinical application of kidney-targeted therapies is currently limited by renal structure and the scarcity of robust biomarkers. Bridging the gap from basic and pre-clinical research targeting the kidney to achieving clinical translation remains a formidable challenge.

Lentiviral Vector-Mediated Ex Vivo Hematopoietic Stem Cell Gene Therapy for Mucopolysaccharidosis IVA Murine Model

Mucopolysaccharidosis IVA (MPS IVA) is an autosomal recessive disease caused by a mutation in the N-acetylgalactosamine-6-sulfate-sulfatase (GALNS) gene resulting in progressive systemic skeletal dysplasia. There is currently no effective treatment available for this skeletal condition. Thus, the development of a new therapy stands as an unmet challenge in reversing or alleviating the progression of the disease. Our research, which could be a game-changer, hypothesizes that ex vivo lentiviral (LV) gene therapy (GT) could produce the supraphysiological level of active GALNS enzyme by hematopoietic stem cells (HSCs) transduced with LVs carrying the native GALNS gene under two different promoters (CBh and COL2A1), impacting bone and cartilage abnormalities in MPS IVA. We conditioned newborn knock-out (Galns-/-) MPS IVA mice with busulfan and intravenously transplanted LV-modified HSCs isolated from the bone marrow of Galns-/- donor mice. Transplanted mice were autopsied at 16 weeks, and tissues were collected to assess the therapeutic efficacy of modified HSCs in MPS IVA mice. Although HSC-LV-CBh-hGALNS provided a higher GALNS enzyme activity in plasma, HSC-LV-COL2A1-hGALNS stably corrected heart and bone abnormalities better under a low level of GALNS enzyme. Our findings suggest that ex vivo LV-GT may potentially treat MPS IVA.

Human in vitro models for Fabry disease: new paths for unravelling disease mechanisms and therapies

Fabry disease is a multi-organ disease, caused by mutations in the GLA gene and leading to a progressive accumulation of glycosphingolipids due to enzymatic absence or malfunction of the encoded alpha-galactosidase A. Since pathomechanisms are not yet fully understood and available treatments are not efficient for all mutation types and tissues, further research is highly needed. This research involves many different model types, with significant effort towards the establishment of an in vivo model. However, these models did not replicate the variety of symptoms observed in patients. As an alternative strategy, patient-derived somatic cells as well as patient-independent cell lines were used to model specific aspects of the disease in vitro. Fabry disease patients present different phenotypes according to the mutation and the level of residual enzyme activity, pointing to the necessity of personalized disease modeling. With the advent of induced pluripotent stem cells, the derivation of a multitude of disease-affected cell types became possible, even in a patient-specific and mutation-specific manner. Only recently, three-dimensional Fabry disease models were established that even more closely resemble the native tissue of investigated organs and will bring research closer to the in vivo situation. This review provides an overview of human in vitro models and their achievements in unravelling the Fabry disease pathomechanism as well as in elucidating current and future treatment strategies.

Different diseases, different needs: Patient preferences for gene therapy in lysosomal storage disorders, a probabilistic threshold technique survey

BACKGROUND

Gene therapy is currently in development for several monogenetic diseases including lysosomal storage disorders. Limited evidence is available on patient preferences for gene therapy in this population. In this study, we compare gene therapy-related risk tolerance between people affected by three lysosomal storage diseases currently faced with different therapeutic options and prognoses.

METHODS

A survey including the probabilistic threshold technique was developed in which respondents were asked to choose between gene therapy and the current standard of care. The attributes included to establish participants' risk tolerance were previously identified in focus groups of affected people or their representatives, namely: risk of mild side effects, severe side effects, the need for additional medication, and the likelihood of long-term effectiveness. The survey was distributed among people receiving outpatient care for type 1 Gaucher disease (good prognosis with current treatment options), Fabry disease (varying prognosis with current treatment options, XY-genotype on average more severely affected than XX), and parents representing people with severe forms of mucopolysaccharidosis type III A/B (poor prognosis, no disease-specific therapy available).

RESULTS

A total of 85 surveys were completed (15 Gaucher disease respondents, 62 Fabry disease respondents (17 self-identifying male), eight parents of ten people with mucopolysaccharidosis type III). Disease groups with higher disease severity trended towards higher risk tolerance: Gaucher disease respondents were most cautious and predominantly preferred the current standard of care as opposed to MPS III representatives who were more risk tolerant. Respondents with Fabry disease were most heterogeneous in their risk tolerance, with male participants being more risk tolerant than female participants. Long-term effectiveness was the attribute in which respondents tolerated the least risk.

CONCLUSIONS

People affected by a lysosomal storage disease associated with a poorer prognosis and less effective current treatment options trended towards more risk tolerance when choosing between gene therapy and the current standard of care. This study shows the importance of involvement of patient preferences before and during the development process of new treatment modalities such as gene therapy for rare diseases, to ensure that innovative therapies align with the wishes and needs of people affected by these diseases.

Biomarkers for gene therapy clinical trials of lysosomal storage disorders

Lysosomal storage disorders (LSDs) are multisystemic progressive disorders caused by defects in proteins involved in lysosomal function. Different gene therapy strategies are under clinical investigation in several LSDs to overcome the limitations of available treatments. However, LSDs are slowly progressive diseases that require long-term studies to establish the efficacy of experimental treatments. Biomarkers can be reliable substitutes for clinical responses and improve the efficiency of clinical trials, especially when long-term disease interventions are evaluated. In this review, we summarize both available and future biomarkers for LSDs and discuss their strengths and weaknesses.

Inflammatory cytokine expression in Fabry disease: impact of disease phenotype and alterations under enzyme replacement therapy

Objectives

The aim of this study is to explore the expression of inflammatory cytokines (ICs) in Fabry disease (FD), the correlation between ICs and FD phenotypes, and the impact of enzyme replacement therapy (ERT) on IC expression.

Methods

We recruited 67 FD patients and 44 healthy controls (HCs) and detected concentrations of the following ICs: interferon-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12P70, IL-17A, IL-17F, IL-22, tumor necrosis factor (TNF)-α, and TNF-β. We also analyzed the impact of ERT on IC expression in FD patients and the relationship between IC expression and sex, genotype, phenotype, disease burden, and biomarkers.

Results

Most ICs were significantly higher in FD patients than in HCs. A number of ICs were positively correlated with clinical aspects, including disease burden (Mainz Severity Score Index [MSSI]) and cardiac and renal markers. IL-8 was higher in the high MSSI (P-adj=0.026*) than in the low MSSI.

Conclusions

ICs were upregulated in FD patients, indicating the role of the innate immune process in FD etiology. ERT ameliorated FD-related inflammatory activation, at least to some extent. IC expression was positively correlated with disease burden and clinical markers in FD. Our findings indicated that the inflammatory pathway may be a promising therapeutic target for FD.

Usefulness of antibody-drug conjugate as preconditioning for hematopoietic stem cell-targeted gene therapy in wild-type and Fabry disease mouse models

BACKGROUND

Fabry disease (FD) is characterized by deficient activity of α-galactosidase A (GLA). Consequently, globotriaosylceramide (Gb3) accumulates in various organs, causing cardiac, renal, and cerebrovascular damage. Gene therapies for FD have been investigated in humans. Strong conditioning is required for hematopoietic stem cell-targeted gene therapy (HSC-GT). However, strong conditioning leads to various side effects and should be avoided. In this study, we tested antibody-based conditioning for HSC-GT in wild-type and FD model mice.

METHODS

After preconditioning with an antibody-drug conjugate, HSC-GT using a lentiviral vector was performed in wild-type and Fabry model mice. In the wild-type experiment, the EGFP gene was introduced into HSCs and transplanted into preconditioned mice, and donor chimerism and EGFP expression were analyzed. In the FD mouse model, the GLA gene was introduced into HSCs and transplanted into preconditioned Fabry mice. GLA activity and Gb3 accumulation in the organs were analyzed.

RESULTS

In the wild-type mouse experiment, when anti-CD45 antibody-drug conjugate was used, the percentage of donor cells at 6 months was 64.5%, and 69.6% of engrafted donor peripheral blood expressed EGFP. When anti-CD117 antibody-drug conjugate and ATG were used, the percentage of donor cells at 6 months was 80.7%, and 73.4% of engrafted donor peripheral blood expressed EGFP. Although large variations in GLA activity among mice were observed in the FD mouse experiment for both preconditioning regimens, Gb3 was significantly reduced in many organs.

CONCLUSIONS

Antibody-based preconditioning may be an alternative preconditioning strategy for HSC-GT for treating FD.

Inflammation in Fabry disease: stages, molecular pathways, and therapeutic implications

Fabry disease, a multisystem X-linked disorder caused by mutations in the alpha-galactosidase gene. This leads to the accumulation of globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), culminating in various clinical signs and symptoms that significantly impact quality of life. Although treatments such as enzyme replacement, oral chaperone, and emerging therapies like gene therapy exist; delayed diagnosis often curtails their effectiveness. Our review highlights the importance of delineating the stages of inflammation in Fabry disease to enhance the timing and efficacy of diagnosis and interventions, particularly before the progression to fibrosis, where treatment options are less effective. Inflammation is emerging as an important aspect of the pathogenesis of Fabry disease. This is thought to be predominantly mediated by the innate immune response, with growing evidence pointing towards the potential involvement of adaptive immune mechanisms that remain poorly understood. Highlighted by the fact that Fabry disease shares immune profiles with systemic autoinflammatory diseases, blurring the distinctions between these disorders and highlighting the need for a nuanced understanding of immune dynamics. This insight is crucial for developing targeted therapies and improving the administration of current treatments like enzyme replacement. Moreover, our review discusses the complex interplay between these inflammatory processes and current treatments, such as the challenges posed by anti-drug antibodies. These antibodies can attenuate the effectiveness of therapies, necessitating more refined approaches to mitigate their impact. By advancing our understanding of the molecular changes, inflammatory mediators and causative factors that drive inflammation in Fabry disease, we aim to clarify their role in the disease's progression. This improved understanding will help us see how these processes fit into the current landscape of Fabry disease. Additionally, it will guide the development of more effective diagnostic and therapeutic approaches, ultimately improving patient care.

Chimeric Cell Therapies as a Novel Approach for Duchenne Muscular Dystrophy (DMD) and Muscle Regeneration

Chimerism-based strategies represent a pioneering concept which has led to groundbreaking advancements in regenerative medicine and transplantation. This new approach offers therapeutic potential for the treatment of various diseases, including inherited disorders. The ongoing studies on chimeric cells prompted the development of Dystrophin-Expressing Chimeric (DEC) cells which were introduced as a potential therapy for Duchenne Muscular Dystrophy (DMD). DMD is a genetic condition that leads to premature death in adolescent boys and remains incurable with current methods. DEC therapy, created via the fusion of human myoblasts derived from normal and DMD-affected donors, has proven to be safe and efficacious when tested in experimental models of DMD after systemic-intraosseous administration. These studies confirmed increased dystrophin expression, which correlated with functional and morphological improvements in DMD-affected muscles, including cardiac, respiratory, and skeletal muscles. Furthermore, the application of DEC therapy in a clinical study confirmed its long-term safety and efficacy in DMD patients. This review summarizes the development of chimeric cell technology tested in preclinical models and clinical studies, highlighting the potential of DEC therapy in muscle regeneration and repair, and introduces chimeric cell-based therapies as a promising, novel approach for muscle regeneration and the treatment of DMD and other neuromuscular disorders.

Outcomes and management of kidney transplant recipients with Fabry disease: a review

Fabry disease is an X-linked inheritable lysosomal storage disease caused by various mutations of the galactosidase α gene resulting in α-galactosidase deficiency. Chronic kidney disease (CKD) is one of the most significant consequences of Fabry disease, with risk of end-stage kidney disease (ESKD) in this population. Like for other patients with ESKD, kidney transplant is the optimal treatment for Fabry disease patients with ESKD. However, enzyme replacement therapy and newer Fabry disease treatments remain important to mitigate other end organ damage such as cardiomyopathy post transplantation. This review is a primer on Fabry disease, which examines the outcomes of disease in the context of kidney transplant prior to, and during, the enzyme replacement treatment era, medical treatment of kidney transplant recipients with Fabry disease, and progress in screening studies.

Integrome signatures of lentiviral gene therapy for SCID-X1 patients

Lentiviral vector (LV)-based gene therapy holds promise for a broad range of diseases. Analyzing more than 280,000 vector integration sites (VISs) in 273 samples from 10 patients with X-linked severe combined immunodeficiency (SCID-X1), we discovered shared LV integrome signatures in 9 of 10 patients in relation to the genomics, epigenomics, and 3D structure of the human genome. VISs were enriched in the nuclear subcompartment A1 and integrated into super-enhancers close to nuclear pore complexes. These signatures were validated in T cells transduced with an LV encoding a CD19-specific chimeric antigen receptor. Intriguingly, the one patient whose VISs deviated from the identified integrome signatures had a distinct clinical course. Comparison of LV and gamma retrovirus integromes regarding their 3D genome signatures identified differences that might explain the lower risk of insertional mutagenesis in LV-based gene therapy. Our findings suggest that LV integrome signatures, shaped by common features such as genome organization, may affect the efficacy of LV-based cellular therapies.

GLA-modified RNA treatment lowers GB3 levels in iPSC-derived cardiomyocytes from Fabry-affected individuals

Recent studies in non-human model systems have shown therapeutic potential of nucleoside-modified messenger RNA (modRNA) treatments for lysosomal storage diseases. Here, we assessed the efficacy of a modRNA treatment to restore the expression of the galactosidase alpha (GLA), which codes for α-Galactosidase A (α-GAL) enzyme, in a human cardiac model generated from induced pluripotent stem cells (iPSCs) derived from two individuals with Fabry disease. Consistent with the clinical phenotype, cardiomyocytes from iPSCs derived from Fabry-affected individuals showed accumulation of the glycosphingolipid Globotriaosylceramide (GB3), which is an α-galactosidase substrate. Furthermore, the Fabry cardiomyocytes displayed significant upregulation of lysosomal-associated proteins. Upon GLA modRNA treatment, a subset of lysosomal proteins were partially restored to wild-type levels, implying the rescue of the molecular phenotype associated with the Fabry genotype. Importantly, a significant reduction of GB3 levels was observed in GLA modRNA-treated cardiomyocytes, demonstrating that α-GAL enzymatic activity was restored. Together, our results validate the utility of iPSC-derived cardiomyocytes from affected individuals as a model to study disease processes in Fabry disease and the therapeutic potential of GLA modRNA treatment to reduce GB3 accumulation in the heart.

Proteomic analysis unveils Gb3-independent alterations and mitochondrial dysfunction in a gla-/- zebrafish model of Fabry disease

BACKGROUND

Fabry disease (FD) is a rare lysosomal storage disorder caused by mutations in the GLA gene, resulting in reduced or lack of α-galactosidase A activity. This results in the accumulation of globotriaosylceramide (Gb3) and other glycosphingolipids in lysosomes causing cellular impairment and organ failures. While current therapies focus on reversing Gb3 accumulation, they do not address the altered cellular signaling in FD. Therefore, this study aims to explore Gb3-independent mechanisms of kidney damage in Fabry disease and identify potential biomarkers.

METHODS

To investigate these mechanisms, we utilized a zebrafish (ZF) gla-/- mutant (MU) model. ZF naturally lack A4GALT gene and, therefore, cannot synthesize Gb3. We obtained kidney samples from both wild-type (WT) (n = 8) and MU (n = 8) ZF and conducted proteome profiling using untargeted mass spectrometry. Additionally, we examined mitochondria morphology and cristae morphology using electron microscopy. To assess oxidative stress, we measured total antioxidant activity. Finally, immunohistochemistry was conducted on kidney samples to validate specific proteins.

RESULTS

Our proteomics analysis of renal tissues from zebrafish revealed downregulation of lysosome and mitochondrial-related proteins in gla-/- MU renal tissues, while energy-related pathways including carbon, glycolysis, and galactose metabolisms were disturbed. Moreover, we observed abnormal mitochondrial shape, disrupted cristae morphology, altered mitochondrial volume and lower antioxidant activity in gla-/- MU ZF.

CONCLUSIONS

These results suggest that the alterations observed at the proteome and mitochondrial level closely resemble well-known GLA mutation-related alterations in humans. Importantly, they also unveil novel Gb3-independent pathogenic mechanisms in Fabry disease. Understanding these mechanisms could potentially lead to the development of innovative drug screening approaches. Furthermore, the findings pave the way for identifying new clinical targets, offering new avenues for therapeutic interventions in Fabry disease. The zebrafish gla-/- mutant model proves valuable in elucidating these mechanisms and may contribute significantly to advancing our knowledge of this disorder.

Hypertrophic Cardiomyopathy versus Storage Diseases with Myocardial Involvement

One of the main causes of heart failure is cardiomyopathies. Among them, the most common is hypertrophic cardiomyopathy (HCM), characterized by thickening of the left ventricular muscle. This article focuses on HCM and other cardiomyopathies with myocardial hypertrophy, including Fabry disease, Pompe disease, and Danon disease. The genetics and pathogenesis of these diseases are described, as well as current and experimental treatment options, such as pharmacological intervention and the potential of gene therapies. Although genetic approaches are promising and have the potential to become the best treatments for these diseases, further research is needed to evaluate their efficacy and safety. This article describes current knowledge and advances in the treatment of the aforementioned cardiomyopathies.

Cardiovascular Involvement in Fabry's Disease: New Advances in Diagnostic Strategies, Outcome Prediction and Management

Cardiovascular involvement is common in Fabry's disease and is the leading cause of morbidity and mortality. The research is focused on identifying diagnostic clues suggestive of cardiovascular involvement in the preclinical stage of the disease through clinical and imaging markers. Different pathophysiologically driven therapies are currently or will soon be available for the treatment of Fabry's disease, with the most significant benefit observed in the early stages of the disease. Thus, early diagnosis and risk stratification for adverse outcomes are crucial to determine when to start an aetiological treatment. This review describes the cardiovascular involvement in Fabry's disease, focusing on the advances in diagnostic strategies, outcome prediction and disease management.

Investigation of bone mineral density and the changes by enzyme replacement therapy in patients with Fabry disease

BACKGROUND

Fabry disease (FD) is an inherited disorder that causes organ dysfunction. However, only a few studies have reported on bone mineral density (BMD) in FD patients, and the relationship between BMD and clinical factors such as globotriaosylsphingosine (lyso-Gb3) remains unclear. Therefore, the current study sought to investigate BMD in FD patients, the relationship between BMD and lyso-Gb3, and the effects of enzyme replacement therapy (ERT) on changes in BMD and lyso-Gb3.

METHODS

This single-center, observational study included 15 patients who visited our facility for FD between January 2008 and June 2021. We assessed BMD and clinical characteristics in study patients, including plasma lyso-Gb3 levels, and examined the relationship between BMD and plasma lyso-Gb3 levels, and changes in BMD after starting ERT.

RESULTS

Male patients' BMD had reduced, whereas female patients' BMD was preserved. Male patients had significantly higher plasma lyso-Gb3 levels than female patients. Moreover, plasma lyso-Gb3 levels were found to be significantly related to the lumbar spine and femoral BMD. These were strongly linked with plasma lyso-Gb3 levels in male patients, whereas no strong link was observed in female patients. Furthermore, BMD significantly increased only in male patients although plasma lyso-Gb3 levels significantly decreased by ERT in all patients.

CONCLUSION

BMD decreased possibly due to Gb3 accumulation, and ERT could increase BMD in male FD patients.

Anderson-Fabry disease cardiomyopathy: an update on epidemiology, diagnostic approach, management and monitoring strategies

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder caused by deficient activity of the enzyme alpha-galactosidase. While AFD is recognized as a progressive multi-system disorder, infiltrative cardiomyopathy causing a number of cardiovascular manifestations is recognized as an important complication of this disease. AFD affects both men and women, although the clinical presentation typically varies by sex, with men presenting at a younger age with more neurologic and renal phenotype and women developing a later onset variant with more cardiovascular manifestations. AFD is an important cause of increased myocardial wall thickness, and advances in imaging, in particular cardiac magnetic resonance imaging and T1 mapping techniques, have improved the ability to identify this disease non-invasively. Diagnosis is confirmed by the presence of low alpha-galactosidase activity and identification of a mutation in the GLA gene. Enzyme replacement therapy remains the mainstay of disease modifying therapy, with two formulations currently approved. In addition, newer treatments such as oral chaperone therapy are now available for select patients, with a number of other investigational therapies in development. The availability of these therapies has significantly improved outcomes for AFD patients. Improved survival and the availability of multiple agents has presented new clinical dilemmas regarding disease monitoring and surveillance using clinical, imaging and laboratory biomarkers, in addition to improved approaches to managing cardiovascular risk factors and AFD complications. This review will provide an update on clinical recognition and diagnostic approaches including differentiation from other causes of increased ventricular wall thickness, in addition to modern strategies for management and follow-up.

Evidence Synthesis of Gene Therapy and Gene Editing from Different Disorders-Implications for Individuals with Rett Syndrome: A Systematic Review

This systematic review and thematic analysis critically evaluated gene therapy trials in amyotrophic lateral sclerosis, haemoglobinopathies, immunodeficiencies, leukodystrophies, lysosomal storage disorders and retinal dystrophies and extrapolated the key clinical findings to individuals with Rett syndrome (RTT). The PRISMA guidelines were used to search six databases during the last decade, followed by a thematic analysis to identify the emerging themes. Thematic analysis across the different disorders revealed four themes: (I) Therapeutic time window of gene therapy; (II) Administration and dosing strategies for gene therapy; (III) Methods of gene therapeutics and (IV) Future areas of clinical interest. Our synthesis of information has further enriched the current clinical evidence base and can assist in optimising gene therapy and gene editing studies in individuals with RTT, but it would also benefit when applied to other disorders. The findings suggest that gene therapies have better outcomes when the brain is not the primary target. Across different disorders, early intervention appears to be more critical, and targeting the pre-symptomatic stage might prevent symptom pathology. Intervention at later stages of disease progression may benefit by helping to clinically stabilise patients and preventing disease-related symptoms from worsening. If gene therapy or editing has the desired outcome, older patients would need concerted rehabilitation efforts to reverse their impairments. The timing of intervention and the administration route would be critical parameters for successful outcomes of gene therapy/editing trials in individuals with RTT. Current approaches also need to overcome the challenges of MeCP2 dosing, genotoxicity, transduction efficiencies and biodistribution.

Cell and gene therapy for kidney disease

Kidney disease is a leading cause of morbidity and mortality across the globe. Current interventions for kidney disease include dialysis and renal transplantation, which have limited efficacy or availability and are often associated with complications such as cardiovascular disease and immunosuppression. There is therefore a pressing need for novel therapies for kidney disease. Notably, as many as 30% of kidney disease cases are caused by monogenic disease and are thus potentially amenable to genetic medicine, such as cell and gene therapy. Systemic disease that affects the kidney, such as diabetes and hypertension, might also be targetable by cell and gene therapy. However, although there are now several approved gene and cell therapies for inherited diseases that affect other organs, none targets the kidney. Promising recent advances in cell and gene therapy have been made, including in the kidney research field, suggesting that this form of therapy might represent a potential solution for kidney disease in the future. In this Review, we describe the potential for cell and gene therapy in treating kidney disease, focusing on recent genetic studies, key advances and emerging technologies, and we describe several crucial considerations for renal genetic and cell therapies.

Optimizing human α-galactosidase for treatment of Fabry disease

Fabry disease is caused by a deficiency of α-galactosidase A (GLA) leading to the lysosomal accumulation of globotriaosylceramide (Gb3) and other glycosphingolipids. Fabry patients experience significant damage to the heart, kidney, and blood vessels that can be fatal. Here we apply directed evolution to generate more stable GLA variants as potential next generation treatments for Fabry disease. GLAv05 and GLAv09 were identified after screening more than 12,000 GLA variants through 8 rounds of directed evolution. Both GLAv05 and GLAv09 exhibit increased stability at both lysosomal and blood pH, stability to serum, and elevated enzyme activity in treated Fabry fibroblasts (19-fold) and GLA^-/- podocytes (10-fold). GLAv05 and GLAv09 show improved pharmacokinetics in mouse and non-human primates. In a Fabry mouse model, the optimized variants showed prolonged half-lives in serum and relevant tissues, and a decrease of accumulated Gb3 in heart and kidney. To explore the possibility of diminishing the immunogenic potential of rhGLA, amino acid residues in sequences predicted to bind MHC II were targeted in late rounds of GLAv09 directed evolution. An MHC II-associated peptide proteomics assay confirmed a reduction in displayed peptides for GLAv09. Collectively, our findings highlight the promise of using directed evolution to generate enzyme variants for more effective treatment of lysosomal storage diseases.

Ex vivo gene therapy for lysosomal storage disorders: future perspectives

INTRODUCTION

Lysosomal storage disorders (LSD) are a group of monogenic rare diseases caused by pathogenic variants in genes that encode proteins related to lysosomal function. These disorders are good candidates for gene therapy for different reasons: they are monogenic, most of lysosomal proteins are enzymes that can be secreted and cross-correct neighboring cells, and small quantities of these proteins are able to produce clinical benefits in many cases. Ex vivo gene therapy allows for autologous transplant of modified cells from different sources, including stem cells and hematopoietic precursors.

AREAS COVERED

Here, we summarize the main gene therapy and genome editing strategies that are currently being used as ex vivo gene therapy approaches for lysosomal disorders, highlighting important characteristics, such as vectors used, strategies, types of cells that are modified and main results in different disorders.

EXPERT OPINION

Clinical trials are already ongoing, and soon approved therapies for LSD based on ex vivo gene therapy approaches should reach the market.

Treatment of Fabry Disease: Established and Emerging Therapies

Fabry disease (FD) is a rare, X-linked inherited disorder of glycosphingolipid metabolism. It leads to the progressive accumulation of globotriaosylceramide within lysosomes due to a deficiency of α-galactosidase A enzyme. It involves multiple organs, predominantly the renal, cardiac, and cerebrovascular systems. Early diagnosis and treatment are critical to prevent progression to irreversible tissue damage and organ failure, and to halt life-threatening complications that can significantly reduce life expectancy. This review will focus on the established and emerging treatment options for FD.

Gene Therapy of Sphingolipid Metabolic Disorders

Sphingolipidoses are defined as a group of rare hereditary diseases resulting from mutations in the genes encoding lysosomal enzymes. This group of lysosomal storage diseases includes more than 10 genetic disorders, including GM1-gangliosidosis, Tay-Sachs disease, Sandhoff disease, the AB variant of GM2-gangliosidosis, Fabry disease, Gaucher disease, metachromatic leukodystrophy, Krabbe disease, Niemann-Pick disease, Farber disease, etc. Enzyme deficiency results in accumulation of sphingolipids in various cell types, and the nervous system is also usually affected. There are currently no known effective methods for the treatment of sphingolipidoses; however, gene therapy seems to be a promising therapeutic variant for this group of diseases. In this review, we discuss gene therapy approaches for sphingolipidoses that are currently being investigated in clinical trials, among which adeno-associated viral vector-based approaches and transplantation of hematopoietic stem cells genetically modified with lentiviral vectors seem to be the most effective.

Cardiac MRI in Fabry disease

Fabry disease is a rare, progressive X-linked inherited disorder of glycosphingolipid metabolism due to a deficiency of α-galactosidase A enzyme. It leads to the accumulation of globotriaosylceramide within lysosomes of multiple organs, predominantly the vascular, renal, cardiac, and nervous systems. Fabry cardiomyopathy is characterized by increased left ventricular wall thickness/mass, functional abnormalities, valvular heart disease, arrhythmias, and heart failure. Early diagnosis and treatment are critical to avoid cardiac or renal complications that can significantly reduce life expectancy in untreated FD. This review will focus on the role of cardiovascular magnetic resonance imaging in the diagnosis, clinical decision-making, and monitoring of treatment efficacy.

Acid Ceramidase Deficiency: Bridging Gaps between Clinical Presentation, Mouse Models, and Future Therapeutic Interventions

Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME) are ultra-rare, autosomal-recessive, acid ceramidase (ACDase) deficiency disorders caused by ASAH1 gene mutations. Currently, 73 different mutations in the ASAH1 gene have been described in humans. These mutations lead to reduced ACDase activity and ceramide (Cer) accumulation in many tissues. Presenting as divergent clinical phenotypes, the symptoms of FD vary depending on central nervous system (CNS) involvement and severity. Classic signs of FD include, but are not limited to, a hoarse voice, distended joints, and lipogranulomas found subcutaneously and in other tissues. Patients with SMA-PME lack the most prominent clinical signs seen in FD. Instead, they demonstrate muscle weakness, tremors, and myoclonic epilepsy. Several ACDase-deficient mouse models have been developed to help elucidate the complex consequences of Cer accumulation. In this review, we compare clinical reports on FD patients and experimental descriptions of ACDase-deficient mouse models. We also discuss clinical presentations, potential therapeutic strategies, and future directions for the study of FD and SMA-PME.

Bardet-Biedl Syndrome: Current Perspectives and Clinical Outlook

The Bardet Biedl syndrome (BBS) is a rare inherited disorder considered a model of non-motile ciliopathy. It is in fact caused by mutations of genes encoding for proteins mainly localized to the base of the cilium. Clinical features of BBS patients are widely shared with patients suffering from other ciliopathies, especially autosomal recessive syndromic disorders; moreover, mutations in cilia-related genes can cause different clinical ciliopathy entities. Besides the best-known clinical features, as retinal degeneration, learning disabilities, polydactyly, obesity and renal defects, several additional clinical signs have been reported in BBS, expanding our understanding of the complexity of its clinical spectrum. The present review aims to describe the current knowledge of BBS i) pathophysiology, ii) clinical manifestations, highlighting both the most common and the less described features, iii) current and future perspective for treatment.

Genetics of Kidney Disease: The Unexpected Role of Rare Disorders

Hundreds of different genetic causes of chronic kidney disease are now recognized, and while individually rare, taken together they are significant contributors to both adult and pediatric diseases. Traditional genetics approaches relied heavily on the identification of large families with multiple affected members and have been fundamental to the identification of genetic kidney diseases. With the increased utilization of massively parallel sequencing and improvements to genotype imputation, we can analyze rare variants in large cohorts of unrelated individuals, leading to personalized care for patients and significant research advancements. This review evaluates the contribution of rare disorders to patient care and the study of genetic kidney diseases and highlights key advancements that utilize new techniques to improve our ability to identify new gene-disease associations.

Persistent hematopoietic polyclonality after lentivirus-mediated gene therapy for Fabry disease

The safety and efficacy of lentivirus-mediated gene therapy was recently demonstrated in five male patients with Fabry disease-a rare X-linked lysosomal storage disorder caused by GLA gene mutations that result in multiple end-organ complications. To evaluate the risks of clonal dominance and leukemogenesis, which have been reported in multiple gene therapy trials, we conducted a comprehensive DNA insertion site analysis of peripheral blood samples from the five patients in our gene therapy trial. We found that patients had a polyclonal integration site spectrum and did not find evidence of a dominant clone in any patient. Although we identified vector integrations near proto-oncogenes, these had low percentages of contributions to the overall pool of integrations and did not persist over time. Overall, we show that our trial of lentivirus-mediated gene therapy for Fabry disease did not lead to hematopoietic clonal dominance and likely did not elevate the risk of leukemogenic transformation.

Gene therapy for lysosomal storage diseases: Current clinical trial prospects

Lysosomal storage diseases (LSDs) are a group of metabolic inborn errors caused by defective enzymes in the lysosome, resulting in the accumulation of undegraded substrates. LSDs are progressive diseases that exhibit variable rates of progression depending on the disease and the patient. The availability of effective treatment options, including substrate reduction therapy, pharmacological chaperone therapy, enzyme replacement therapy, and bone marrow transplantation, has increased survival time and improved the quality of life in many patients with LSDs. However, these therapies are not sufficiently effective, especially against central nerve system abnormalities and corresponding neurological and psychiatric symptoms because of the blood-brain barrier that prevents the entry of drugs into the brain or limiting features of specific treatments. Gene therapy is a promising tool for the treatment of neurological pathologies associated with LSDs. Here, we review the current state of gene therapy for several LSDs for which clinical trials have been conducted or are planned. Several clinical trials using gene therapy for LSDs are underway as phase 1/2 studies; no adverse events have not been reported in most of these studies. The administration of viral vectors has achieved good therapeutic outcomes in animal models of LSDs, and subsequent human clinical trials are expected to promote the practical application of gene therapy for LSDs.

Fabry Disease: Current and Novel Therapeutic Strategies. A Narrative Review

BACKGROUND

Fabry disease (FD) is an inherited lysosomal storage disorder, leading to multisystemic manifestations and causing significant morbidity and mortality.

OBJECTIVE

The aim of this narrative review is to present the current and novel therapeutic strategies in FD, including symptomatic and specific treatment options.

METHODS

A systematic literature search was conducted to identify relevant studies, including completed and ongoing randomized-controlled clinical trials (RCTs), prospective or retrospective cohort studies, case series and case reports that provided clinical data regarding FD treatment.

RESULTS

A multidisciplinary symptomatic treatment is recommended for FD patients, personalized according to disease manifestations and their severity. During the last two decades, FD-specific treatments, including two enzyme-replacement-therapies (agalsidase alfa and agalsidase beta) and chaperone treatment with migalastat have been approved for use and allowed for symptoms' stabilization or even disease burden reduction. More therapeutic agents are currently under investigation. Substrate reduction therapies, including lucerastat and venglustat, have shown promising results in RCTs and may be used either as monotherapy or as complementary therapy to established enzymereplacement- therapies. More stable enzyme-replacement-therapy molecules that are associated with less adverse events and lower likelihood of neutralizing antibodies formation have also been developed. Ex-vivo and in-vivo gene therapy is being tested in animal models and pilot human clinical trials, with preliminary results showing a favorable safety and efficacy profile.

CONCLUSION

The therapeutic landscape in FD appears to be actively expanding with more treatment options expected to become available in the near future, allowing for a more personalized approach in FD patients.

Screening chimeric GAA variants in preclinical study results in hematopoietic stem cell gene therapy candidate vectors for Pompe disease

Pompe disease is a rare genetic neuromuscular disorder caused by acid α-glucosidase (GAA) deficiency resulting in lysosomal glycogen accumulation and progressive myopathy. Enzyme replacement therapy, the current standard of care, penetrates poorly into the skeletal muscles and the peripheral and central nervous system (CNS), risks recombinant enzyme immunogenicity, and requires high doses and frequent infusions. Lentiviral vector-mediated hematopoietic stem and progenitor cell (HSPC) gene therapy was investigated in a Pompe mouse model using a clinically relevant promoter driving nine engineered GAA coding sequences incorporating distinct peptide tags and codon optimizations. Vectors solely including glycosylation-independent lysosomal targeting tags enhanced secretion and improved reduction of glycogen, myofiber, and CNS vacuolation in key tissues, although GAA enzyme activity and protein was consistently lower compared with native GAA. Genetically modified microglial cells in brains were detected at low levels but provided robust phenotypic correction. Furthermore, an amino acid substitution introduced in the tag reduced insulin receptor-mediated signaling with no evidence of an effect on blood glucose levels in Pompe mice. This study demonstrated the therapeutic potential of lentiviral HSPC gene therapy exploiting optimized GAA tagged coding sequences to reverse Pompe disease pathology in a preclinical mouse model, providing promising vector candidates for further investigation.

Fabry disease: Mechanism and therapeutics strategies

Fabry disease is a monogenic disease characterized by a deficiency or loss of the α-galactosidase A (GLA). The resulting impairment in lysosomal GLA enzymatic activity leads to the pathogenic accumulation of enzymatic substrate and, consequently, the progressive appearance of clinical symptoms in target organs, including the heart, kidney, and brain. However, the mechanisms involved in Fabry disease-mediated organ damage are largely ambiguous and poorly understood, which hinders the development of therapeutic strategies for the treatment of this disorder. Although currently available clinical approaches have shown some efficiency in the treatment of Fabry disease, they all exhibit limitations that need to be overcome. In this review, we first introduce current mechanistic knowledge of Fabry disease and discuss potential therapeutic strategies for its treatment. We then systemically summarize and discuss advances in research on therapeutic approaches, including enzyme replacement therapy (ERT), gene therapy, and chaperone therapy, as well as strategies targeting subcellular compartments, such as lysosomes, the endoplasmic reticulum, and the nucleus. Finally, the future development of potential therapeutic strategies is discussed based on the results of mechanistic studies and the limitations associated with these therapeutic approaches.