Immune response to enzyme replacement therapies in lysosomal storage diseases and the role of immune tolerance induction

Dose-intensive therapy (DIT) for infantile Pompe disease: A pilot study

Background

The current standard of care for infantile-onset Pompe disease (IOPD), a severe form of acid α-glucosidase enzyme activity deficiency is: (1) detection by newborn screening, (2) early initiation of intravenous enzyme replacement therapy (ERT) using recombinant human acid alpha-glucosidase (rhGAA), with higher doses of rhGAA increasingly used to improve clinical outcomes, and (3) immune tolerization induction (ITI) using to prevent anti-rhGAA antibody formation, with methotrexate (MTX), rituximab, and IVIG used for patients who are cross-reactive immunologic material negative (CRIM-) and monotherapy with MTX used in patients who are cross-reactive immunologic material positive (CRIM+).

Objectives/methods

A pilot study evaluates a dose-intensive therapy (DIT) using high-dose ERT (40 mg/kg/week) and more frequent exposure to ERT (i.e., 3 times weekly administration) to mitigate anti-rhGAA antibody formation, as an alternative to the standard therapeutic approach for IOPD.

Results

In the first patient, DIT resulted in rapid normalization of the following: (1) bi-ventricular hypertrophy, (2) urine HEX-4, (3) CK, (4) liver transaminases. At 7 years of age, the patient continues the DIT regimen. To date, all pediatric developmental milestones have been met on time, anti-rhGAA antibodies have been negative and the patient is able to attend school and maintain normal activities of daily living.

Conclusions

Over a 7-year period, DIT for CRIM-positive IOPD was well tolerated in the first patient treated. Excellent clinical outcomes were achieved, and anti-rhGAA antibodies levels were consistently undetectable. Assessments of more patients, that includes patients with CRIM-, as well as CRIM+ IOPD, will determine if this approach consistently achieves improved clinical outcomes and immune tolerization.

Prenatal Delivery of Enzyme Replacement Therapy to Fetuses Affected by Early-Onset Lysosomal Storage Diseases

The expansion of prenatal genetic screening and diagnosis warrants the evaluation of approved postnatal therapies that may be safely and feasibly translated to prenatal administration to a fetus affected by monogenic disease. For lysosomal storage diseases (LSDs), enzyme replacement therapy (ERT) often represents the main therapeutic approach. In utero enzyme replacement therapy (IUERT) has several potential benefits compared to postnatal therapy, such as: (1) delivering enzyme before the onset of irreversible organ damage; (2) developing tolerance toward the recombinant enzyme; and (3) targeting the central nervous system through a more permeable blood-brain barrier. In this review, we examine the general and disease-specific rationale for IUERT, and provide an overview of the main elements of our current clinical trial for the prenatal treatment of early-onset lysosomal storage diseases. Trial Registration: IUERT clinical trial: NCT04532047; Alpha thalassemia clinical trial: NCT02986698.

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.

The European reference network for metabolic diseases (MetabERN) clinical pathway recommendations for Pompe disease (acid maltase deficiency, glycogen storage disease type II)

Clinical pathway recommendations (CPR) are based on existing guidelines and deliver a short overview on how to deal with a specific diagnosis, resulting therapy and follow-up. In this paper we propose a methodology for developing CPRs for Pompe disease, a metabolic myopathy caused by deficiency of lysosomal acid alpha-glucosidase. The CPR document was developed within the activities of the MetabERN, a non-profit European Reference Network for Metabolic Diseases established by the European Union. A working group was selected among members of the MetabERN lysosomal storage disease subnetwork, with specific expertise in the care of Pompe disease, and patient support group representatives. The working strategy was based on a systematic literature search to develop a database, followed by quality assessment of the studies selected from the literature, and by the development of the CPR document according to a matrix provided by MetabERN. Quality assessment of the literature and collection of citations was conducted according to the AGREE II criteria and Grading of Recommendations, Assessment, Development and Evaluation methodology. General aspects were addressed in the document, including pathophysiology, genetics, frequency, classification, manifestations and clinical approach, laboratory diagnosis and multidisciplinary evaluation, therapy and supportive measures, follow-up, monitoring, and pregnancy. The CPR document that was developed was intended to be a concise and easy-to-use tool for standardization of care for patients among the healthcare providers that are members of the network or are involved in the care for Pompe disease patients.

Desensitization of olipudase alfa-induced anaphylaxis in a child with chronic neurovisceral acid sphingomyelinase deficiency

Olipudase alfa is indicated for the non-central nervous system manifestations of Acid sphingomyelinase deficiency (ASMD). Anaphylaxis is a very rare and life-threatening adverse reaction described for this drug. Here, we report the case of a 2-year-old boy affected by chronic neurovisceral ASMD who experienced signs of hypersensitivity reactions to olipudase alfa since the administered dose of 1 mg/kg during dose escalation and a proper anaphylactic reaction during the second administration of the target therapeutic dose of 3 mg/kg. The treatment was stopped for 15 weeks and then a 7-step desensitization protocol with the infused dose of 0.03 mg/kg was applied. Subsequent gradual dose escalation was resumed, successfully reaching the dose of 0.3 mg/kg. Moreover, biochemical, and radiological disease indexes, which were increased during treatment discontinuation, have gradually improved since the restart of treatment. However, at the second administration of the dose of 0.6 mg/kg, the patient experienced another adverse drug reaction with facial urticarial rash and bronchospasm, requiring the administration of adrenaline, methylprednisolone, and inhaled salbutamol. This case report highlights the need to customize the olipudase alfa desensitization protocol according to individual tolerance and raises the issue of achieving the established therapeutic target in the most sensitive children.

Synopsis

We report a case of anaphylaxis to olipudase alfa in a child affected by chronic neurovisceral Acid sphingomyelinase deficiency (ASMD) and describe a 7-step desensitization procedure. This procedure, with the total administered dose of 0.03 mg/kg, followed by gradual dose escalation, allowed to reach the dose of 0.3 mg/kg without adverse reactions; however, at the second administration of the dose of 0.6 mg/kg our patient presented another adverse reaction suggesting the need of a different desensitization strategy.

Advances in Immune Tolerance Induction in Enzyme Replacement Therapy

Inborn errors of metabolism (IEMs) are a group of genetic diseases that occur due to the either deficiency of an enzyme involved in a metabolic/biochemical pathway or other disturbances in the metabolic pathway including transport protein or activator protein deficiencies, cofactor deficiencies, organelle biogenesis, maturation or trafficking problems. These disorders are collectively significant due to their substantial impact on both the well-being and survival of affected individuals. In the quest for effective treatments, enzyme replacement therapy (ERT) has emerged as a viable strategy for patients with many of the lysosomal storage disorders (LSD) and enzyme substitution therapy in the rare form of the other inborn errors of metabolism including phenylketonuria and hypophosphatasia. However, a major challenge associated with enzyme infusion in patients with these disorders, mainly LSD, is the development of high antibody titres. Strategies focusing on immunomodulation have shown promise in inducing immune tolerance to ERT, leading to improved overall survival rates. The implementation of immunomodulation concurrent with ERT administration has also resulted in a decreased occurrence of IgG antibody development compared with cases treated solely with ERT. By incorporating the knowledge gained from current approaches and analysing the outcomes of immune tolerance induction (ITI) modalities from clinical and preclinical trials have demonstrated significant improvement in the efficacy of ERT. In this comprehensive review, the progress in ITI modalities is assessed, drawing insights from both clinical and preclinical trials. The focus is on evaluating the advancements in ITI within the context of IEM, specifically addressing LSDs managed through ERT.

Current Concepts in the Management of Sanfilippo Syndrome (MPS III): A Narrative Review

Sanfilippo syndrome is a childhood-onset (1-4 years) autosomal recessive lysosomal storage disease that presents as a neurodegenerative disease by targeting the brain and spinal cord. It is also known as mucopolysaccharidosis III. Mucopolysaccharidosis III is divided into four subtypes (A, B, C, or D). It can cause delayed speech, behavior problems, and features of autism spectrum disorder. Sanfilippo syndrome is of a higher prevalence within consanguineous families that carry its gene alteration. If both parents have a nonfunctional copy of a gene linked to this condition, their children will have a 25% (1 in 4) chance of developing the disease. In Saudi Arabia, the incidence rate is estimated at 2 per 100,000 live births. Recent research focused on promising treatment approaches, such as gene therapy, modified enzyme replacement therapy, and stem cells. These approaches work by exogenous administration of the proper version of the mutant enzyme (enzyme replacement therapy), cleaning the defective enzyme in individuals with glycolipid storage disorders (substrate reduction therapy), or using a pharmacological chaperone to target improperly folded proteins. However, there is currently no approved curative medication for Sanfilippo syndrome that can effectively halt or reverse the disorder.

Intrauterine enzyme replacement therapies for lysosomal storage disorders: Current developments and promising future prospects

Lysosomal storage disorders (LSDs) are a group of monogenic condition, with many characterized by an enzyme deficiency leading to the accumulation of an undegraded substrate within the lysosomes. For those LSDs, postnatal enzyme replacement therapy (ERT) represents the standard of care, but this treatment has limitations when administered only postnatally because, at that point, prenatal disease sequelae may be irreversible. Furthermore, most forms of ERT, specifically those administered systemically, are currently unable to access certain tissues, such as the central nervous system (CNS), and furthermore, may initiate an immune response. In utero enzyme replacement therapy (IUERT) is a novel approach to address these challenges evaluated in a first-in-human clinical trial for IUERT in LSDs (NCT04532047). IUERT has numerous advantages: in-utero intervention may prevent early pathology; the CNS can be accessed before the blood-brain barrier forms; and the unique fetal immune system enables exposure to new proteins with the potential to prevent an immune response and may induce sustained tolerance. However, there are challenges and limitations for any fetal procedure that involves two patients. This article reviews the current state of IUERT for LSDs, including its advantages, limitations, and potential future directions for definitive therapies.

Hydrogel Delivery Device for the In Vitro and In Vivo Sustained Release of Active rhGALNS Enzyme

Morquio A disease is a genetic disorder resulting in N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency, and patients are currently treated with enzyme replacement therapy via weekly intravenous enzyme infusions. A means of sustained enzyme delivery could improve patient quality of life by reducing the administration time, frequency of hospital visits, and treatment cost. In this study, we investigated poly(ethylene-glycol) (PEG) hydrogels as a tunable, hydrolytically degradable drug delivery system for the encapsulation and sustained release of recombinant human GALNS (rhGALNS). We evaluated hydrogel formulations that optimized hydrogel gelation and degradation time while retaining rhGALNS activity and sustaining rhGALNS release. We observed the release of active rhGALNS for up to 28 days in vitro from the optimized formulation. rhGALNS activity was preserved in the hydrogel relative to buffer over the release window, and encapsulation was found to have no impact on the rhGALNS structure when measured by intrinsic fluorescence, circular dichroism, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In vivo, we monitored the retention of fluorescently labeled rhGALNS in C57BL/6 albino mice when administered via subcutaneous injection and observed rhGALNS present for up to 20 days when delivered in a hydrogel versus 7 days in the buffer control. These results indicate that PEG hydrogels are suitable for the encapsulation, preservation, and sustained release of recombinant enzymes and may present an alternative method of delivering enzyme replacement therapies that improve patient quality of life.

Polymer-based drug delivery systems under investigation for enzyme replacement and other therapies of lysosomal storage disorders

Lysosomes play a central role in cellular homeostasis and alterations in this compartment associate with many diseases. The most studied example is that of lysosomal storage disorders (LSDs), a group of 60 + maladies due to genetic mutations affecting lysosomal components, mostly enzymes. This leads to aberrant intracellular storage of macromolecules, altering normal cell function and causing multiorgan syndromes, often fatal within the first years of life. Several treatment modalities are available for a dozen LSDs, mostly consisting of enzyme replacement therapy (ERT) strategies. Yet, poor biodistribution to main targets such as the central nervous system, musculoskeletal tissue, and others, as well as generation of blocking antibodies and adverse effects hinder effective LSD treatment. Drug delivery systems are being studied to surmount these obstacles, including polymeric constructs and nanoparticles that constitute the focus of this article. We provide an overview of the formulations being tested, the diseases they aim to treat, and the results observed from respective in vitro and in vivo studies. We also discuss the advantages and disadvantages of these strategies, the remaining gaps of knowledge regarding their performance, and important items to consider for their clinical translation. Overall, polymeric nanoconstructs hold considerable promise to advance treatment for LSDs.

Focal lesions following intracerebral gene therapy for mucopolysaccharidosis IIIA

OBJECTIVE

Mucopolysaccharidosis type IIIA (MPSIIIA) caused by recessive SGSH variants results in sulfamidase deficiency, leading to neurocognitive decline and death. No disease-modifying therapy is available. The AAVance gene therapy trial investigates AAVrh.10 overexpressing human sulfamidase (LYS-SAF302) delivered by intracerebral injection in children with MPSIIIA. Post-treatment MRI monitoring revealed lesions around injection sites. Investigations were initiated in one patient to determine the cause.

METHODS

Clinical and MRI details were reviewed. Stereotactic needle biopsies of a lesion were performed; blood and CSF were sampled. All samples were used for viral studies. Immunohistochemistry, electron microscopy, and transcriptome analysis were performed on brain tissue of the patient and various controls.

RESULTS

MRI revealed focal lesions around injection sites with onset from 3 months after therapy, progression until 7 months post therapy with subsequent stabilization and some regression. The patient had transient slight neurological signs and is following near-normal development. No evidence of viral or immunological/inflammatory cause was found. Immunohistochemistry showed immature oligodendrocytes and astrocytes, oligodendrocyte apoptosis, strong intracellular and extracellular sulfamidase expression and hardly detectable intracellular or extracellular heparan sulfate. No activation of the unfolded protein response was found.

INTERPRETATION

Results suggest that intracerebral gene therapy with local sulfamidase overexpression leads to dysfunction of transduced cells close to injection sites, with extracellular spilling of lysosomal enzymes. This alters extracellular matrix composition, depletes heparan sulfate, impairs astrocyte and oligodendrocyte function, and causes cystic white matter degeneration at the site of highest gene expression. The AAVance trial results will reveal the potential benefit-risk ratio of this therapy.

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.

Expert-opinion-based guidance for the care of children with lysosomal storage diseases during the COVID-19 pandemic: An experience-based Turkey perspective

This expert-opinion-based document was prepared by a group of specialists in pediatric inherited metabolic diseases and infectious diseases including administrative board members of Turkish Society for Pediatric Nutrition and Metabolism to provide guidance for the care of children with lysosomal storage disorders (LSDs) during the COVID-19 pandemic in Turkey. The experts reached consensus on key areas of focus regarding COVID-19-based risk status in relation to intersecting immune-inflammatory mechanisms and disease patterns in children with LSDs, diagnostic virus testing, particularly preventive measures and priorities during the pandemic, routine screening and diagnostic interventions for LSDs, psychological and socioeconomic impact of confinement measures and quarantines and optimal practice patterns in managing LSDs and/or COVID-19. The participating experts agreed on the intersecting characteristics of immune-inflammatory mechanisms, end-organ damage and prognostic biomarkers in LSD and COVID-19 populations, emphasizing the likelihood of enhanced clinical care when their interaction is clarified via further studies addressing certain aspects related to immunity, lysosomal dysfunction and disease pathogenesis. In the context of the current global COVID-19 pandemic, this expert-opinion-based document provides guidance for the care of children with LSDs during the COVID-19 pandemic based on the recent experience in Turkey.

A kaleidoscopic view of extracellular vesicles in lysosomal storage disorders

Extracellular vesicles (EVs) are a heterogeneous population of stable lipid membrane particles that play a critical role in the regulation of numerous physiological and pathological processes. EV cargo, which includes lipids, proteins, and RNAs including miRNAs, is affected by the metabolic status of the parental cell. Concordantly, abnormalities in the autophagic-endolysosomal pathway, as seen in lysosomal storage disorders (LSDs), can affect EV release as well as EV cargo. LSDs are a group of over 70 inheritable diseases, characterized by lysosomal dysfunction and gradual accumulation of undigested molecules. LSDs are caused by single gene mutations that lead to a deficiency of a lysosomal protein or lipid. Lysosomal dysfunction sets off a cascade of alterations in the endolysosomal pathway that can affect autophagy and alter calcium homeostasis, leading to energy imbalance, oxidative stress, and apoptosis. The pathophysiology of these diseases is very heterogenous, complex, and currently incompletely understood. LSDs lead to progressive multisystemic symptoms that often include neurological deficits. In this review, a kaleidoscopic overview will be given on the roles of EVs in LSDs, from their contribution to pathology and diagnostics to their role as drug delivery vehicles. Furthermore, EV cargo and surface engineering strategies will be discussed to show the potential of EVs in future LSD treatment, both in the context of enzyme replacement therapy, as well as future gene editing strategies like CRISPR/Cas. The use of engineered EVs as drug delivery vehicles may mask therapeutic cargo from the immune system and protect it from degradation, improving circulation time and targeted delivery.

In Utero Enzyme-Replacement Therapy for Infantile-Onset Pompe's Disease

Patients with early-onset lysosomal storage diseases are ideal candidates for prenatal therapy because organ damage starts in utero. We report the safety and efficacy results of in utero enzyme-replacement therapy (ERT) in a fetus with CRIM (cross-reactive immunologic material)-negative infantile-onset Pompe's disease. The family history was positive for infantile-onset Pompe's disease with cardiomyopathy in two previously affected deceased siblings. After receiving in utero ERT and standard postnatal therapy, the current patient had normal cardiac and age-appropriate motor function postnatally, was meeting developmental milestones, had normal biomarker levels, and was feeding and growing well at 13 months of age.

Targeting the Complement-Sphingolipid System in COVID-19 and Gaucher Diseases: Evidence for a New Treatment Strategy

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2)-induced disease (COVID-19) and Gaucher disease (GD) exhibit upregulation of complement 5a (C5a) and its C5aR1 receptor, and excess synthesis of glycosphingolipids that lead to increased infiltration and activation of innate and adaptive immune cells, resulting in massive generation of pro-inflammatory cytokines, chemokines and growth factors. This C5a-C5aR1-glycosphingolipid pathway- induced pro-inflammatory environment causes the tissue damage in COVID-19 and GD. Strikingly, pharmaceutically targeting the C5a-C5aR1 axis or the glycosphingolipid synthesis pathway led to a reduction in glycosphingolipid synthesis and innate and adaptive immune inflammation, and protection from the tissue destruction in both COVID-19 and GD. These results reveal a common involvement of the complement and glycosphingolipid systems driving immune inflammation and tissue damage in COVID-19 and GD, respectively. It is therefore expected that combined targeting of the complement and sphingolipid pathways could ameliorate the tissue destruction, organ failure, and death in patients at high-risk of developing severe cases of COVID-19.

Mucopolysaccharidoses and the blood-brain barrier

Mucopolysaccharidoses comprise a set of genetic diseases marked by an enzymatic dysfunction in the degradation of glycosaminoglycans in lysosomes. There are eight clinically distinct types of mucopolysaccharidosis, some with various subtypes, based on which lysosomal enzyme is deficient and symptom severity. Patients with mucopolysaccharidosis can present with a variety of symptoms, including cognitive dysfunction, hepatosplenomegaly, skeletal abnormalities, and cardiopulmonary issues. Additionally, the onset and severity of symptoms can vary depending on the specific disorder, with symptoms typically arising during early childhood. While there is currently no cure for mucopolysaccharidosis, there are clinically approved therapies for the management of clinical symptoms, such as enzyme replacement therapy. Enzyme replacement therapy is typically administered intravenously, which allows for the systemic delivery of the deficient enzymes to peripheral organ sites. However, crossing the blood-brain barrier (BBB) to ameliorate the neurological symptoms of mucopolysaccharidosis continues to remain a challenge for these large macromolecules. In this review, we discuss the transport mechanisms for the delivery of lysosomal enzymes across the BBB. Additionally, we discuss the several therapeutic approaches, both preclinical and clinical, for the treatment of mucopolysaccharidoses.

Therapeutic Strategies For Tay-Sachs Disease

Tay-Sachs disease (TSD) is an autosomal recessive disease that features progressive neurodegenerative presentations. It affects one in 100,000 live births. Currently, there is no approved therapy or cure. This review summarizes multiple drug development strategies for TSD, including enzyme replacement therapy, pharmaceutical chaperone therapy, substrate reduction therapy, gene therapy, and hematopoietic stem cell replacement therapy. In vitro and in vivo systems are described to assess the efficacy of the aforementioned therapeutic strategies. Furthermore, we discuss using MALDI mass spectrometry to perform a high throughput screen of compound libraries. This enables discovery of compounds that reduce GM2 and can lead to further development of a TSD therapy.

Treatment of Neuronopathic Mucopolysaccharidoses with Blood-Brain Barrier-Crossing Enzymes: Clinical Application of Receptor-Mediated Transcytosis

Enzyme replacement therapy (ERT) has paved the way for treating the somatic symptoms of lysosomal storage diseases (LSDs), but the inability of intravenously administered enzymes to cross the blood-brain barrier (BBB) has left the central nervous system (CNS)-related symptoms of LSDs largely impervious to the therapeutic benefits of ERT, although ERT via intrathecal and intracerebroventricular routes can be used for some neuronopathic LSDs (in particular, mucopolysaccharidoses). However, the considerable practical issues involved make these routes unsuitable for long-term treatment. Efforts have been made to modify enzymes (e.g., by fusing them with antibodies against innate receptors on the cerebrovascular endothelium) so that they can cross the BBB via receptor-mediated transcytosis (RMT) and address neuronopathy in the CNS. This review summarizes the various scientific and technological challenges of applying RMT to the development of safe and effective enzyme therapeutics for neuronopathic mucopolysaccharidoses; it then discusses the translational and methodological issues surrounding preclinical and clinical evaluation to establish RMT-applied ERT.

The diagnosis and management of Gaucher disease in pediatric patients: Where do we go from here?

Gaucher disease (GD) is an autosomal recessive inherited lysosomal storage disease that often presents in early childhood and is associated with damage to multiple organ systems. Many challenges associated with GD diagnosis and management arise from the considerable heterogeneity of disease presentations and natural history. Phenotypic classification has traditionally been based on the absence (in type 1 GD) or presence (in types 2 and 3 GD) of neurological involvement of varying severity. However, patient management and prediction of prognosis may be best served by a dynamic, evolving definition of individual phenotype rather than by a rigid system of classification. Patients may experience considerable delays in diagnosis, which can potentially be reduced by effective screening programs; however, program implementation can involve ethical and practical challenges. Variation in the clinical course of GD and an uncertain prognosis also complicate decisions concerning treatment initiation, with differing stakeholder perspectives around efficacy and acceptable cost/benefit ratio. We review the challenges faced by physicians in the diagnosis and management of GD in pediatric patients. We also consider future directions and goals, including acceleration of accurate diagnosis, improvements in the understanding of disease heterogeneity (natural history, response to treatment, and prognosis), the need for new treatments to address unmet needs for all forms of GD, and refinement of the tools for monitoring disease progression and treatment efficacy, such as specific biomarkers.

Immune responses to alglucosidase in infantile Pompe disease: recommendations from an Italian pediatric expert panel

Background

Classic infantile onset of Pompe disease (c-IOPD) leads to hypotonia and hypertrophic cardiomyopathy within the first days to weeks of life and, without treatment, patients die of cardiorespiratory failure in their first 1–2 years of life. Enzymatic replacement therapy (ERT) with alglucosidase alfa is the only available treatment, but adverse immune reactions can reduce ERT’s effectiveness and safety. It is therefore very important to identify strategies to prevent and manage these complications. Several articles have been written on this disease over the last 10 years, but no univocal indications have been established.

Methods

Our study presents a review of the current literature on management of immune responses to ERT in c-IOPD as considered by an Italian study group of pediatric metabolists and immunologists in light of our shared patient experience.

Results

We summarize the protocols for the management of adverse reactions to ERT, analyzing their advantages and disadvantages, and provide expert recommendations for their optimal management, to the best of current knowledge. However, further studies are needed to improve actual management protocols, which still have several limitations.

Mechanisms of Neutralizing Anti-drug Antibody Formation and Clinical Relevance on Therapeutic Efficacy of Enzyme Replacement Therapies in Fabry Disease

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A (AGAL/GLA) gene. The lysosomal accumulation of the substrates globotriaosylceramide (Gb₃) and globotriaosylsphingosine (lyso-Gb₃) results in progressive renal failure, cardiomyopathy associated with cardiac arrhythmia, and recurrent strokes, significantly limiting life expectancy in affected patients. 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, facilitating 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 (ADAs) in ERT-treated males, leading to an attenuation of therapy efficacy and thus disease progression. In this narrative review, we provide a brief overview of the clinical picture of FD and diagnostic confirmation. The focus is on the biochemical and clinical significance of neutralizing ADAs as a humoral response to ERT. In addition, we provide an overview of different methods for ADA measurement and characterization, as well as potential therapeutic approaches to prevent or eliminate ADAs in affected patients, which is representative for other ERT-treated lysosomal storage diseases.

Long-term safety and efficacy of agalsidase beta in Japanese patients with Fabry disease: aggregate data from two post-authorization safety studies

BACKGROUND

Enzyme replacement therapy in Fabry disease has been available in Japan since 2004. Two post-authorization safety studies were conducted to evaluate agalsidase beta in Japanese patients with Fabry disease in real-world practice.

RESEARCH DESIGN AND METHODS

The Special Drug Use Investigation monitored the long-term safety and efficacy of agalsidase beta, and the Drug Use Investigation monitored safety in patients not participating in the Special Drug Use Investigation. Safety and efficacy evaluations included adverse drug reactions (ADRs), infusion-associated reactions and hypersensitivity reactions, and change in blood GL-3 level over time.

RESULTS

Of 396 patients in the aggregated data set, safety and efficacy analysis sets comprised 307 and 196 patients, respectively. ADRs occurred in 93 (30.3%) patients and serious ADRs occurred in 25 (8.1%) patients, with general disorders and administration site conditions (n=55, 17.9%), nervous system disorders (n=30, 9.8%) and skin and subcutaneous tissue disorders (n=23, 7.5%) the most common. Reductions in blood GL-3 levels occurred over the study, irrespective of age or disease phenotype.

CONCLUSIONS

Agalsidase beta demonstrated acceptable safety and tolerability, with sustained reductions in blood GL-3 levelsin Japanese patients with Fabry disease in real-world clinical practice.

CLINICAL TRIAL REGISTRATION

NCT00233870/AGAL03004 (Special Drug Use Investigation of Agalsidase beta).

Oral immunotherapy tolerizes mice to enzyme replacement therapy for Morquio A syndrome

Immune response to therapeutic enzymes poses a detriment to patient safety and treatment outcome. Enzyme replacement therapy (ERT) is a standard therapeutic option for some types of mucopolysaccharidoses, including Morquio A syndrome caused by N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency. Current protocols tolerize patients using cytotoxic immunosuppressives, which can cause adverse effects. Here we show development of tolerance in Morquio A mice via oral delivery of peptide or GALNS for 10 days prior to ERT. Our results show that using an immunodominant peptide (I10) or the complete GALNS enzyme to orally induce tolerance to GALNS prior to ERT resulted in several improvements to ERT in mice: (a) decreased splenocyte proliferation after in vitro GALNS stimulation, (b) modulation of the cytokine secretion profile, (c) decrease in GALNS-specific IgG or IgE in plasma, (d) decreased GAG storage in liver, and (e) fewer circulating immune complexes in plasma. This model could be extrapolated to other lysosomal storage disorders in which immune response hinders ERT.

Sanfilippo Syndrome: Molecular Basis, Disease Models and Therapeutic Approaches

Sanfilippo syndrome or mucopolysaccharidosis III is a lysosomal storage disorder caused by mutations in genes responsible for the degradation of heparan sulfate, a glycosaminoglycan located in the extracellular membrane. Undegraded heparan sulfate molecules accumulate within lysosomes leading to cellular dysfunction and pathology in several organs, with severe central nervous system degeneration as the main phenotypical feature. The exact molecular and cellular mechanisms by which impaired degradation and storage lead to cellular dysfunction and neuronal degeneration are still not fully understood. Here, we compile the knowledge on this issue and review all available animal and cellular models that can be used to contribute to increase our understanding of Sanfilippo syndrome disease mechanisms. Moreover, we provide an update in advances regarding the different and most successful therapeutic approaches that are currently under study to treat Sanfilippo syndrome patients and discuss the potential of new tools such as induced pluripotent stem cells to be used for disease modeling and therapy development.

Benefits of Prophylactic Short-Course Immune Tolerance Induction in Patients With Infantile Pompe Disease: Demonstration of Long-Term Safety and Efficacy in an Expanded Cohort

Immune tolerance induction (ITI) with a short-course of rituximab, methotrexate, and/or IVIG in the enzyme replacement therapy (ERT)-naïve setting has prolonged survival and improved clinical outcomes in patients with infantile Pompe disease (IPD) lacking endogenous acid-alpha glucosidase (GAA), known as cross-reactive immunologic material (CRIM)-negative. In the context of cancer therapy, rituximab administration results in sustained B-cell depletion in 83% of patients for up to 26–39 weeks with B-cell reconstitution beginning at approximately 26 weeks post-treatment. The impact of rituximab on serum immunoglobulin levels is not well studied, available data suggest that rituximab can cause persistently low immunoglobulin levels and adversely impact vaccine responses. Data on a cohort of IPD patients who received a short-course of ITI with rituximab, methotrexate, and IVIG in the ERT-naïve setting and had ≥6 months of follow-up were retrospectively studied. B-cell quantitation, ANC, AST, ALT, immunization history, and vaccine titers after B-cell reconstitution were reviewed. Data were collected for 34 IPD patients (25 CRIM-negative and 9 CRIM-positive) with a median age at ERT initiation of 3.5 months (0.1–11.0 months). B-cell reconstitution, as measured by normalization of CD19%, was seen in all patients (n = 33) at a median time of 17 weeks range (11–55 weeks) post-rituximab. All maintained normal CD19% with the longest follow-up being 248 weeks post-rituximab. 30/34 (88%) maintained negative/low anti-rhGAA antibody titers, even with complete B-cell reconstitution. Infections during immunosuppression were reported in five CRIM-negative IPD patients, all resolved satisfactorily on antibiotics. There were no serious sequelae or deaths. Of the 31 evaluable patients, 27 were up to date on age-appropriate immunizations. Vaccine titers were available for 12 patients after B-cell reconstitution and adequate humoral response was observed in all except an inadequate response to the Pneumococcal vaccine (n = 2). These data show the benefits of short-course prophylactic ITI in IPD both in terms of safety and efficacy. Data presented here are from the youngest cohort of patients treated with rituximab and expands the evidence of its safety in the pediatric population.

Management of hypersensitivity reactions to enzyme replacement therapy in children with lysosomal storage diseases

BACKGROUND

Intravenous recombinant enzyme replacement therapy (ERT) is currently available for 8 lysosomal diseases. Hypersensitivity reactions (HSRs) may be observed during this long-term treatment.

OBJECTIVE

To evaluate the frequency and clinical treatment features of ERT HSRs and the management of desensitizations in children.

METHODS

Medical records were reviewed retrospectively for patients who received ERT. Those who had experienced HSRs to ERT were included in the study. The demographic characteristics of the patients, culprit enzyme, signs and symptoms, diagnostic tests, management of the reaction, and the protocol employed for the maintenance of ERT were recorded.

RESULTS

During the study period, 54 patients received ERT in our institution. A total of 11 patients (20.4%) experienced HSR to ERT. All reactions were of immediate type. The most common symptoms were cutaneous manifestations. A total of 9 patients experienced urticaria, and 2 had anaphylaxis as initial reaction. Patients who had isolated cutaneous symptoms continued their treatments with antihistamines, corticosteroid premedication, slower infusion rate or both. Patients who had recurrent urticaria with these modalities or those who had anaphylaxis continued their ERT with desensitization (n = 8). A total of 3 patients required revisions in desensitization protocols because of recurrent anaphylaxis.

CONCLUSION

The reactions that develop during this long-term treatment may be treated by premedication-prolonged infusion, but in some patients, desensitization protocols are necessary for the continuation of therapy. Revisions in desensitization protocols may be required.

A Highly Efficacious PS Gene Editing System Corrects Metabolic and Neurological Complications of Mucopolysaccharidosis Type I

Our previous study delivered zinc finger nucleases to treat mice with mucopolysaccharidosis type I (MPS I), resulting in a phase I/II clinical trial (ClinicalTrials.gov: NCT02702115). However, in the clinical trial, the efficacy needs to be improved due to the low transgene expression level. To this end, we designed a proprietary system (PS) gene editing approach with CRISPR to insert a promoterless α-l-iduronidase (IDUA) cDNA sequence into the albumin locus of hepatocytes. In this study, adeno-associated virus 8 (AAV8) vectors delivering the PS gene editing system were injected into neonatal and adult MPS I mice. IDUA enzyme activity in the brain significantly increased, while storage levels were normalized. Neurobehavioral tests showed that treated mice had better memory and learning ability. Also, histological analysis showed efficacy reflected by the absence of foam cells in the liver and vacuolation in neuronal cells. No vector-associated toxicity or increased tumorigenesis risk was observed. Moreover, no off-target effects were detected through the unbiased genome-wide unbiased identification of double-stranded breaks enabled by sequencing (GUIDE-seq) analysis. In summary, these results showed the safety and efficacy of the PS in treating MPS I and paved the way for clinical studies. Additionally, as a therapeutic platform, the PS has the potential to treat other lysosomal diseases.

Immune Modulation for Enzyme Replacement Therapy in A Female Patient With Hunter Syndrome

A 3.5 year old Hispanic female presented with signs and symptoms concerning for MPS II (Hunter Syndrome). The diagnosis of MPS II was confirmed by enzyme and molecular testing. Genetic evaluation revealed undetectable plasma iduronate-2-sulfatase enzyme activity and an inversion between intron 7 of the IDS gene and a region near exon 3 of IDS-2. This inversion is the molecular cause for ~8% of cases of MPS II and often results in a severe phenotype. X-inactivation studies revealed an inactivation ratio of 100:0. Given the patient's undetectable enzyme level, in combination with a severe IDS gene mutation, classic features at time of presentation, and the significantly skewed X inactivation, there was concern that she was at high risk of developing high and sustained antibody titers to idursulfase which would limit her benefit from enzyme replacement therapy (ERT). Anti-drug neutralizing antibodies to idursulfase have been associated with reduced systemic exposure to idursulfase and poorer clinical outcomes. Therefore, the decision was made to concurrently treat the patient with immune tolerance induction therapy during the first month of treatment with idursulfase in order to decrease the risk of developing high sustained antibody titers. The immune tolerance induction protocol consisted of rituximab weekly for 4 weeks, methotrexate three times a week for 3 weeks and monthly IVIG through B-cell and immunoglobulin recovery. Immune tolerance induction was initiated concurrently with the start of ERT. The patient had no significant adverse effects related to undergoing immune tolerance induction therapy and two and half years later is doing well with significantly reduced urine glycosaminoglycans and very low anti-drug antibody titers. This immune tolerance induction protocol could be considered for other patients with MPS II as well as patients with other lysosomal storage disorders who are starting on enzyme replacement therapy and are at high risk of developing neutralizing anti-drug antibodies.

Odiparcil, a potential glycosaminoglycans clearance therapy in mucopolysaccharidosis VI-Evidence from in vitro and in vivo models

Mucopolysaccharidoses are a class of lysosomal storage diseases, characterized by enzymatic deficiency in the degradation of specific glycosaminoglycans (GAG). Pathological accumulation of excess GAG leads to multiple clinical symptoms with systemic character, most severely affecting bones, muscles and connective tissues. Current therapies include periodic intravenous infusion of supplementary recombinant enzyme (Enzyme Replacement Therapy–ERT) or bone marrow transplantation. However, ERT has limited efficacy due to poor penetration in some organs and tissues. Here, we investigated the potential of the β-D-xyloside derivative odiparcil as an oral GAG clearance therapy for Maroteaux–Lamy syndrome (Mucopolysaccharidosis type VI, MPS VI). In vitro, in bovine aortic endothelial cells, odiparcil stimulated the secretion of sulphated GAG into culture media, mainly of chondroitin sulphate (CS) /dermatan sulphate (DS) type. Efficacy of odiparcil in reducing intracellular GAG content was investigated in skin fibroblasts from MPS VI patients where odiparcil was shown to reduce efficiently the accumulation of intracellular CS with an EC₅₀ in the range of 1 μM. In vivo, in wild type rats, after oral administrations, odiparcil was well distributed, achieving μM concentrations in MPS VI disease-relevant tissues and organs (bone, cartilage, heart and cornea). In MPS VI Arylsulphatase B deficient mice (Arsb^-), after chronic oral administration, odiparcil consistently stimulated the urinary excretion of sulphated GAG throughout the treatment period and significantly reduced tissue GAG accumulation in liver and kidney. Furthermore, odiparcil diminished the pathological cartilage thickening observed in trachea and femoral growth plates of MPS VI mice. The therapeutic efficacy of odiparcil was similar in models of early (treatment starting in juvenile, 4 weeks old mice) or established disease (treatment starting in adult, 3 months old mice). Our data demonstrate that odiparcil effectively diverts the synthesis of cellular glycosaminoglycans into secreted soluble species and this effect can be used for reducing cellular and tissue GAG accumulation in MPS VI models. Therefore, our data reveal the potential of odiparcil as an oral GAG clearance therapy for MPS VI patients.

Enzyme replacement therapy interruption in patients with Mucopolysaccharidoses: Recommendations for distinct scenarios in Latin America

Background

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders, leading to the progressive accumulation of glycosaminoglycans (GAGs) and the subsequent compromising of tissues and organ malfunction. Although incurable, most types of MPS can be treated with enzyme replacement therapy (ERT), an approach that has had positive effects on the natural clinical evolution and which impact has been extensively investigated. Unfortunately, to date, there is relatively little data regarding the effects of ERT interruption, especially in Latin America, where such interruption may be frequent due to a variety of issues (for instance, difficulties involving logistics, reimbursement and/or payment withdrawal).

Method

A group of medical professionals from Latin America with experience in Genetics, Pediatrics and Neurology held an Advisory Board Meeting in the city of São Paulo, in October 2018, to discuss the issue of ERT interruptions in the region and recommendations health care professionals on how to deal with these interruptions and better assess the therapeutic effects of ERT.

Conclusion

Recommendations provided by the experts may support physicians in dealing with the most common reasons for ERT interruptions in Latin America. Most importantly, recommendations for data collection at specific timepoints (at baseline, throughout the treatment and during the interruption period of ERT and after its resumption) can significantly improve the collection of real world evidence on the effects of ERT and its interruptions, supporting health care professionals and policy makers in the decision making regarding the provision of these therapies for MPS patients.

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Positive impact of ERT is reported in MPS patients, but the effects of its interruption is overlooked.

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In Latin America, ERT interruption is not infrequent. A systematic evaluation the worsening of MPS progression is vital.

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The proposed structured data collection would help to evaluate patients and generate real word data.

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We encourage studies and experts discussions for a better understand the value of ERT for MPS patients in Latin America.

Persistent dyslipidemia in treatment of lysosomal acid lipase deficiency

BACKGROUND

Lysosomal acid lipase deficiency (LALD) is an autosomal recessive inborn error of lipid metabolism characterized by impaired lysosomal hydrolysis and consequent accumulation of cholesteryl esters and triglycerides. The phenotypic spectrum is diverse, ranging from severe, neonatal onset failure to thrive, hepatomegaly, hepatic fibrosis, malabsorption and adrenal insufficiency to childhood-onset hyperlipidemia, hepatomegaly, and hepatic fibrosis. Sebelipase alfa enzyme replacement has been approved by the Food and Drug Administration for use in LALD after demonstrating dramatic improvement in transaminitis and dyslipidemia with initiation of enzyme replacement therapy.

METHODS

A chart review was performed on 2 patients with childhood-onset, symptomatic LALD with persistent dyslipidemia despite appropriate enzyme replacement therapy to identify biological pathways and risk factors for incomplete response to therapy.

RESULTS

Two patients with attenuated, symptomatic LALD had resolution of transaminitis on enzyme replacement therapy without concomitant effect on dyslipidemia despite dose escalation and no evidence of antibody response to enzyme.

CONCLUSION

Enzyme replacement therapy does not universally resolve all complications of LALD. Persistent dyslipidemia remains a clinically significant issue, likely related to the complex metabolic pathways implicated in LALD pathogenesis. We discuss the possible mechanistic basis for this unexpected finding and the implications for curative LALD therapy.

Autophagy in the Central Nervous System and Effects of Chloroquine in Mucopolysaccharidosis Type II Mice

Mucopolysaccharidosis type II (MPS II) is a rare lysosomal storage disease (LSD) involving a genetic error in iduronic acid-2-sulfatase (IDS) metabolism that leads to accumulation of glycosaminoglycans within intracellular lysosomes. The primary treatment for MPS II, enzyme replacement therapy, is not effective for central nervous system (CNS) symptoms, such as intellectual disability, because the drugs do not cross the blood-brain barrier. Recently, autophagy has been associated with LSDs. In this study, we examined the morphologic relationship between neuronal damage and autophagy in IDS knockout mice using antibodies against subunit c of mitochondrial adenosine triphosphate (ATP) synthetase and p62. Immunohistological changes suggesting autophagy, such as vacuolation, were observed in neurons, microglia, and pericytes throughout the CNS, and the numbers increased over postnatal development. Oral administration of chloroquine, which inhibits autophagy, did not suppress damage to microglia and pericytes, but greatly reduced neuronal vacuolation and eliminated neuronal cells with abnormal inclusions. Thus, decreasing autophagy appears to prevent neuronal degeneration. These results suggest that an autophagy modulator could be used in addition to conventional enzyme replacement therapy to preserve the CNS in patients with MPS II.

Targeted enzyme delivery systems in lysosomal disorders: an innovative form of therapy for mucopolysaccharidosis

Mucopolysaccharidoses (MPSs), which are inherited lysosomal storage disorders caused by the accumulation of undegraded glycosaminoglycans, can affect the central nervous system (CNS) and elicit cognitive and behavioral issues. Currently used enzyme replacement therapy methodologies often fail to adequately treat the manifestations of the disease in the CNS and other organs such as bone, cartilage, cornea, and heart. Targeted enzyme delivery systems (EDSs) can efficiently cross biological barriers such as blood-brain barrier and provide maximal therapeutic effects with minimal side effects, and hence, offer great clinical benefits over the currently used conventional enzyme replacement therapies. In this review, we provide comprehensive insights into MPSs and explore the clinical impacts of multimodal targeted EDSs.

Strategies for the Induction of Immune Tolerance to Enzyme Replacement Therapy in Mucopolysaccharidosis Type I

Enzyme replacement therapy with laronidase is an established treatment for Mucopolysaccharidosis type I (MPS I), but its efficacy may be limited by the development of anti-drug antibodies, which inhibit cellular uptake of the enzyme. In a related disorder, infantile Pompe disease, immune tolerance induction with low-dose, short-course methotrexate appears to reduce antibody formation. We investigated a similar regimen using oral methotrexate in three MPS I patients. All patients developed anti-laronidase immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies, and they had clinically relevant levels of cellular uptake inhibition. We then explored several immune tolerance induction strategies in MPS I mice: (1) methotrexate, (2) combination of non-depleting anti-CD4 and anti-CD8 monoclonal antibodies, (3) methotrexate with anti-CD4 and anti-CD8 monoclonals, (4) anti-CD4 monoclonal, and (5) anti-CD8 monoclonal. Treated mice received 10 weekly laronidase injections, and laronidase was delivered with adjuvant on day 49 to further challenge the immune system. Most regimens were only partially effective at reducing antibody responses, but two courses of non-depleting anti-CD4 monoclonal antibody (mAb) ablated immune responses to laronidase in seven of eight MPS I mice (87.5%), even after adjuvant stimulation. Immune tolerance induction with methotrexate does not appear to be effective in MPS I patients, but use of non-depleting anti-CD4 monoclonal is a promising strategy.

Characterization of immune response in Cross-Reactive Immunological Material (CRIM)-positive infantile Pompe disease patients treated with enzyme replacement therapy

Enzyme replacement therapy (ERT) with rhGAA has improved clinical outcomes in infantile Pompe disease (IPD). A subset of CRIM-positive IPD patients develop high and sustained antibody titers (HSAT; ≥51,200) and/or sustained intermediate titer (SIT; ≥12,800 and <51,200), similar to CRIM-negative patients. To date there has been no systematic study to analyze the extent of IgG antibody response in CRIM-positive IPD. Such data would be critical and could serve as a comparator group for potential immune modulation approaches. A retrospective analysis of the dataset from the original rhGAA clinical trials final reports was conducted. CRIM-positive patients who received ERT monotherapy and had >6 months of antibody titer data available, were included in the study. Patients were classified based on their longitudinal antibody titers into HSAT, SIT, and low titer (LT; <12,800) groups. Of the 37 patients that met inclusion criteria, five (13%), seven (19%), and 25 (68%) developed HSAT, SIT, and LT, respectively. Median peak titers were 204,800 (51,200-409,600), 25,600 (12,800-51,200), and 800 (200-12,800) for HSAT, SIT, and LT groups, respectively. Median last titers were 102,400 (51,200-409,600), 1600 (200-25,600), and 400 (0-12,800) at median time since ERT initiation of 94 weeks (64-155 weeks), 104 weeks (86-144 weeks), and 130 weeks (38-182 weeks) for HSAT, SIT, and LT groups, respectively. 32% (12/37) of CRIM-positive IPD patients developed HSAT/SIT which may lead to limited ERT response and clinical decline. Further Studies are needed to identify CRIM-positive IPD patients at risk of developing HSAT/SIT, especially with the addition of Pompe disease to the newborn screening.

Targeting a Pre-existing Anti-transgene T Cell Response for Effective Gene Therapy of MPS-I in the Mouse Model of the Disease

Mucopolysaccharidosis type I (MPS-I) is a severe genetic disease caused by a deficiency of the alpha-L-iduronidase (IDUA) enzyme. Ex vivo hematopoietic stem cell (HSC) gene therapy is a promising therapeutic approach for MPS-I, as demonstrated by preclinical studies performed in naive MPS-I mice. However, after enzyme replacement therapy (ERT), several MPS-I patients develop anti-IDUA immunity that may jeopardize ex vivo gene therapy efficacy. Here we treat MPS-I mice with an artificial immunization protocol to mimic the ERT effect in patients, and we demonstrate that IDUA-corrected HSC engraftment is impaired in pre-immunized animals by IDUA-specific CD8⁺ T cells spared by pre-transplant irradiation. Conversely, humoral anti-IDUA immunity does not impact on IDUA-corrected HSC engraftment. The inclusion of lympho-depleting agents in pre-transplant conditioning of pre-immunized hosts allowes rescue of IDUA-corrected HSC engraftment, which is proportional to CD8⁺ T cell eradication. Overall, these data demonstrate the relevance of pre-existing anti-transgene T cell immunity on ex vivo HSC gene therapy, and they suggest the application of tailored immune-depleting treatments, as well as a deeper immunological characterization of patients, to safeguard the therapeutic effects of ex vivo HSC gene therapy in immunocompetent hosts.

Validation of an Immunoassay for Anti-thymidine Phosphorylase Antibodies in Patients with MNGIE Treated with Enzyme Replacement Therapy

Erythrocyte encapsulated thymidine phosphorylase is recombinant Escherichia coli thymidine phosphorylase encapsulated within human autologous erythrocytes and is under development as an enzyme replacement therapy for the ultra-rare inherited metabolic disorder mitochondrial neurogastrointestinal encephalomyopathy. This study describes the method validation of a two-step bridging electrochemiluminescence immunoassay for the detection of anti-thymidine phosphorylase antibodies in human serum according to current industry practice and regulatory guidelines. The analytical method was assessed for screening cut point, specificity, selectivity, precision, prozone effect, drug tolerance, and stability. Key findings were a correction factor of 129 relative light units for the cut-point determination; a specificity cut point of 93% inhibition; confirmed intra-assay and inter-assay precision; assay sensitivity of 356 ng/mL; no matrix or prozone effects up to 25,900 ng/mL; a drug tolerance of 156 ng/mL; and stability at room temperature for 24 hr and up to five freeze-thaws. Immunogenicity evaluations of serum from three patients who received erythrocyte encapsulated thymidine phosphorylase under a compassionate treatment program showed specific anti-thymidine phosphorylase antibodies in one patient. To conclude, a sensitive, specific, and selective immunoassay has been validated for the measurement of anti-thymidine phosphorylase antibodies; this will be utilized in a phase II pivotal clinical trial of erythrocyte encapsulated thymidine phosphorylase.

Infantile-onset Pompe disease: A case series highlighting early clinical features, spectrum of disease severity and treatment response

AIM

Pompe disease is a rare, autosomal, recessive disorder. Alterations in the gene encoding lysosomal acid alpha-glucosidase cause impaired glycogen degradation and resultant lysosomal glycogen accumulation. Classic infantile-onset Pompe disease (IPD) manifests soon after birth, severe cases have complete/near complete enzyme deficiency. IPD is associated with a broad spectrum of non-specific clinical features, and diagnostic delays are common. Without treatment, death typically occurs within the first 2 years of life. We present case experiences to help expand paediatricians' understanding of factors contributing to diagnostic delay, clinical decline and to highlight the need for timely therapy.

METHODS

Data were extracted from IPD cases managed at our hospital. Key aspects of clinical presentation, diagnosis, genetic variations, management and overall outcomes were collated then compared with what is already known in the literature.

RESULTS

We report four IPD cases (three female). Two patients were cross-reactive immunological material negative. Age at symptom onset was 3-9 months, presenting clinical features were varied, and confirmatory diagnosis was significantly delayed in one patient. In concert with the literature, cardiomegaly, ventricular hypertrophy and delayed developmental milestones were seen in all four cases. Our cases demonstrate a range of disease severity, response to enzyme replacement therapy and antibody development. Significant immune responses were seen in two cases (one cross-reactive immunological material positive); despite immunomodulation therapy, both were associated with fatal outcomes.

CONCLUSION

Timely diagnosis and initiation of enzyme replacement therapy is critical to patient outcomes as IPD progresses rapidly and irreversible changes in clinical status may occur during the delay.

An immune tolerance approach using transient low-dose methotrexate in the ERT-naïve setting of patients treated with a therapeutic protein: experience in infantile-onset Pompe disease

PURPOSE

To investigate immune tolerance induction with transient low-dose methotrexate (TLD-MTX) initiated with recombinant human acid α-glucosidase (rhGAA), in treatment-naïve cross-reactive immunologic material (CRIM)-positive infantile-onset Pompe disease (IOPD) patients.

METHODS

Newly diagnosed IOPD patients received subcutaneous or oral 0.4 mg/kg TLD-MTX for 3 cycles (3 doses/cycle) with the first 3 rhGAA infusions. Anti-rhGAA IgG titers, classified as high-sustained (HSAT; ≥51,200, ≥2 times after 6 months), sustained intermediate (SIT; ≥12,800 and <51,200 within 12 months), or low (LT; ≤6400 within 12 months), were compared with those of 37 CRIM-positive IOPD historic comparators receiving rhGAA alone.

RESULTS

Fourteen IOPD TLD-MTX recipients at the median age of 3.8 months (range, 0.7-13.5 months) had a median last titer of 150 (range, 0-51,200) at median rhGAA duration ~83 weeks (range, 36-122 weeks). One IOPD patient (7.1%) developed titers in the SIT range and one patient (7.1%) developed titers in the HSAT range. Twelve of the 14 patients (85.7%) that received TLD-MTX remained LT, versus 5/37 HSAT (peak 51,200-409,600), 7/37 SIT (12,800-51,000), and 23/37 LT (200-12,800) among comparators.

CONCLUSION

Results of TLD-MTX coinitiated with rhGAA are encouraging and merit a larger longitudinal study.

Deep characterization of the anti-drug antibodies developed in Fabry disease patients, a prospective analysis from the French multicenter cohort FFABRY

BACKGROUND

Fabry disease (OMIM #301500) is an X-linked disorder caused by alpha-galactosidase A deficiency with two major clinical phenotypes: classic and non-classic of different prognosis. From 2001, enzyme replacement therapies (ERT) have been available. We aimed to determine the epidemiology and the functional characteristics of anti-drug antibodies. Patients from the French multicenter cohort FFABRY (n = 103 patients, 53 males) were prospectively screened for total anti-agalsidase IgG and IgG subclasses with a home-made enzyme-linked immunosorbent assay (ELISA), enzyme-inhibition assessed with neutralization assays and lysoGb3 plasma levels, and compared for clinical outcomes.

RESULTS

Among the patients exposed to agalsidase, 40% of men (n = 18/45) and 8% of women (n = 2/25) had antibodies with a complete cross-reactivity towards both ERTs. Antibodies developed preferentially in men with non-missense GLA mutations (relative risk 2.88, p = 0.006) and classic phenotype (58.6% (17/29) vs 6.7% (1/16), p = 0.0005). Specific anti-agalsidase IgG1 were the most frequently observed (16/18 men), but the highest concentrations were observed for IgG4 (median 1.89 μg/ml, interquartile range (IQR) [0.41-12.24]). In the men exposed to agalsidase, inhibition was correlated with the total IgG titer (r = 0.67, p < 0.0001), especially IgG4 (r = 0.75, p = 0.0005) and IgG2 (r = 0.72, p = 0.001). Inhibition was confirmed intracellularly in Fabry patient leucocytes cultured with IgG-positive versus negative serum (median: 42.0 vs 75.6%, p = 0.04), which was correlated with IgG2 (r = 0.67, p = 0.017, n = 12) and IgG4 levels (r = 0.59, p = 0.041, n = 12). Plasma LysoGb3 levels were correlated with total IgG (r = 0.66, p = 0.001), IgG2 (r = 0.72, p = 0.004), IgG4 (r = 0.58, p = 0.03) and IgG1 (r = 0.55, p = 0.04) titers. Within the classic group, no clinical difference was observed but lysoGb3 levels were higher in antibody-positive patients (median 33.2 ng/ml [IQR 20.6-55.6] vs 12.5 [10.1-24.0], p = 0.005).

CONCLUSION

Anti-agalsidase antibodies preferentially develop in the severe classic Fabry phenotype. They are frequently associated with enzyme inhibition and higher lysoGb3 levels. As such, they could be considered as a hallmark of severity associated with the classic phenotype. The distinction of the clinical phenotypes should now be mandatory in studies dealing with Fabry disease and its current and future therapies.

Safety of Intradiaphragmatic Delivery of Adeno-Associated Virus-Mediated Alpha-Glucosidase (rAAV1-CMV-hGAA) Gene Therapy in Children Affected by Pompe Disease

A first-in-human trial of diaphragmatic gene therapy (AAV1-CMV-GAA) to treat respiratory and neural dysfunction in early-onset Pompe disease was conducted. The primary objective of this study was to assess the safety of rAAV1-CMV-hGAA vector delivered to the diaphragm muscle of Pompe disease subjects with ventilatory insufficiency. Safety was assessed by measurement of change in serum chemistries and hematology, urinalysis, and immune response to GAA and AAV, as well as change in level of health. The data demonstrate that the AAV treatment was safe and there were no adverse events related to the study agent. Adverse events related to the study procedure were observed in subjects with lower baseline neuromuscular function. All adverse events were resolved before the end of the study, except for one severe adverse event determined not to be related to either the study agent or the study procedure. In addition, an anti-capsid and anti-transgene antibody response was observed in all subjects who received rAAV1-CMV-hGAA, except for subjects who received concomitant immunomodulation to manage reaction to enzyme replacement therapy, as per their standard of care. This observation is significant for future gene therapy studies and serves to establish a clinically relevant approach to blocking immune responses to both the AAV capsid protein and transgene product.

Enzyme replacement therapies: what is the best option?

Despite many beneficial outcomes of the conventional enzyme replacement therapy (ERT), several limitations such as the high-cost of the treatment and various inadvertent side effects including the occurrence of an immunological response against the infused enzyme and development of resistance to enzymes persist. These issues may limit the desired therapeutic outcomes of a majority of the lysosomal storage diseases (LSDs). Furthermore, the biodistribution of the recombinant enzymes into the target cells within the central nervous system (CNS), bone, cartilage, cornea, and heart still remain unresolved. All these shortcomings necessitate the development of more effective diagnosis and treatment modalities against LSDs. Taken all, maximizing the therapeutic response with minimal undesired side effects might be attainable by the development of targeted enzyme delivery systems (EDSs) as a promising alternative to the LSDs treatments, including different types of mucopolysaccharidoses ( MPSs ) as well as Fabry, Krabbe, Gaucher and Pompe diseases.

Cryo-EM structure of a fungal mitochondrial calcium uniporter

The mitochondrial calcium uniporter (MCU) is a highly selective calcium channel localized to the inner mitochondrial membrane. Here, we describe the structure of an MCU orthologue from the fungus Neosartorya fischeri (NfMCU) determined to 3.8 Å resolution by phase-plate cryo-electron microscopy. The channel is a homotetramer with two-fold symmetry in its amino-terminal domain (NTD) that adopts a similar structure to that of human MCU. The NTD assembles as a dimer of dimers to form a tetrameric ring that connects to the transmembrane domain through an elongated coiled-coil domain. The ion-conducting pore domain maintains four-fold symmetry, with the selectivity filter positioned at the start of the pore-forming TM2 helix. The aspartate and glutamate sidechains of the conserved DIME motif are oriented towards the central axis and separated by one helical turn. The structure of NfMCU offers insights into channel assembly, selective calcium permeation, and inhibitor binding.

Study of Intraventricular Cerliponase Alfa for CLN2 Disease

BACKGROUND

Recombinant human tripeptidyl peptidase 1 (cerliponase alfa) is an enzyme-replacement therapy that has been developed to treat neuronal ceroid lipofuscinosis type 2 (CLN2) disease, a rare lysosomal disorder that causes progressive dementia in children.

METHODS

In a multicenter, open-label study, we evaluated the effect of intraventricular infusion of cerliponase alfa every 2 weeks in children with CLN2 disease who were between the ages of 3 and 16 years. Treatment was initiated at a dose of 30 mg, 100 mg, or 300 mg; all the patients then received the 300-mg dose for at least 96 weeks. The primary outcome was the time until a 2-point decline in the score on the motor and language domains of the CLN2 Clinical Rating Scale (which ranges from 0 to 6, with 0 representing no function and 3 representing normal function in each of the two domains), which was compared with the time until a 2-point decline in 42 historical controls. We also compared the rate of decline in the motor-language score between the two groups, using data from baseline to the last assessment with a score of more than 0, divided by the length of follow-up (in units of 48 weeks).

RESULTS

Twenty-four patients were enrolled, 23 of whom constituted the efficacy population. The median time until a 2-point decline in the motor-language score was not reached for treated patients and was 345 days for historical controls. The mean (±SD) unadjusted rate of decline in the motor-language score per 48-week period was 0.27±0.35 points in treated patients and 2.12±0.98 points in 42 historical controls (mean difference, 1.85; P<0.001). Common adverse events included convulsions, pyrexia, vomiting, hypersensitivity reactions, and failure of the intraventricular device. In 2 patients, infections developed in the intraventricular device that was used to administer the infusion, which required antibiotic treatment and device replacement.

CONCLUSIONS

Intraventricular infusion of cerliponase alfa in patients with CLN2 disease resulted in less decline in motor and language function than that in historical controls. Serious adverse events included failure of the intraventricular device and device-related infections. (Funded by BioMarin Pharmaceutical and others; CLN2 ClinicalTrials.gov numbers, NCT01907087 and NCT02485899 .).

A Humoral Immune Response Alters the Distribution of Enzyme Replacement Therapy in Murine Mucopolysaccharidosis Type I

Antibodies against recombinant proteins can significantly reduce their effectiveness in unanticipated ways. We evaluated the humoral response of mice with the lysosomal storage disease mucopolysaccharidosis type I treated with weekly intravenous recombinant human alpha-l-iduronidase (rhIDU). Unlike patients, the majority of whom develop antibodies to recombinant human alpha-l-iduronidase, only approximately half of the treated mice developed antibodies against recombinant human alpha-l-iduronidase and levels were low. Serum from antibody-positive mice inhibited uptake of recombinant human alpha-l-iduronidase into human fibroblasts by partial inhibition compared to control serum. Tissue and cellular distributions of rhIDU were altered in antibody-positive mice compared to either antibody-negative or naive mice, with significantly less recombinant human alpha-l-iduronidase activity in the heart and kidney in antibody-positive mice. In the liver, recombinant human alpha-l-iduronidase was preferentially found in sinusoidal cells rather than in hepatocytes in antibody-positive mice. Antibodies against recombinant human alpha-l-iduronidase enhanced uptake of recombinant human alpha-l-iduronidase into macrophages obtained from MPS I mice. Collectively, these results imply that a humoral immune response against a therapeutic protein can shift its distribution preferentially into macrophage-lineage cells, causing decreased availability of the protein to the cells that are its therapeutic targets.

Ten-year-long enzyme replacement therapy shows a poor effect in alleviating giant leg ulcers in a male with Fabry disease

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency of α-galactosidase A (α-gal A), leading to the progressive accumulation of glycosphingolipids. Classical hemizygous males usually present symptoms, including pain and paresthesia in the extremities, angiokeratoma, hypo- or anhidrosis, abdominal pain, cornea verticillata, early stroke, tinnitus, and/or hearing loss, during early childhood or adolescence. Moreover, proteinuria, renal impairment, and cardiac hypertrophy can appear with age. Enzyme replacement is the most common therapy for Fabry disease at present which has been approved in Japan since 2004. We report a case involving a 27-year-old male with extreme terminal pain, anhidrosis, abdominal pain, tinnitus, hearing impairment, cornea verticillata, and recurrent huge ulcers in the lower extremities. At the age of 16 years, he was diagnosed with Fabry disease with a positive family history and very low α-gal A activity. He then received enzyme replacement therapy (ERT) with recombinant human agalsidase beta at 1 mg/kg every 2 weeks for 10 years. Throughout the course of ERT, his leg ulcers recurred, and massive excretion of urinary globotriaosylceramide and plasma globotriaosylsphingosine was observed. Electron microscopy of the venous tissue in the regions of the ulcer showed massive typical zebra bodies in the vascular wall smooth muscle cells.

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A classical hemizygous male with Fabry disease presented with massive intractable leg ulcer.

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10 years' enzyme replacement therapy showed huge excretion of urinary Gb3 and plasma lyso-Gb3.

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Excessive zebra bodies in vascular wall smooth muscle cells caused venous reflux and varices on saphenous veins.

Modulating the immune system through nanotechnology

Nowadays, nanotechnology-based modulation of the immune system is presented as a cutting-edge strategy, which may lead to significant improvements in the treatment of severe diseases. In particular, efforts have been focused on the development of nanotechnology-based vaccines, which could be used for immunization or generation of tolerance. In this review, we highlight how different immune responses can be elicited by tuning nanosystems properties. In addition, we discuss specific formulation approaches designed for the development of anti-infectious and anti-autoimmune vaccines, as well as those intended to prevent the formation of antibodies against biologicals.

Immunogenicity of glycans on biotherapeutic drugs produced in plant expression systems-The taliglucerase alfa story

Plants are a promising alternative for the production of biotherapeutics. Manufacturing in-planta adds plant specific glycans. To understand immunogenic potential of these glycans, we developed a validated method to detect plant specific glycan antibodies in human serum. Using this assay, low prevalence of pre-existing anti-plant glycan antibodies was found in healthy humans (13.5%) and in glucocerebrosidase-deficient Gaucher disease (GD) patients (5%). A low incidence (9% in naïve patient and none in treatment experienced patients) of induced anti-plant glycan antibodies was observed in GD patients after up to 30 months replacement therapy treatment with taliglucerase alfa, a version of human glucocerebrosidase produced in plant cells. Detailed evaluation of clinical safety and efficacy endpoints indicated that anti-plant glycan antibodies did not affect the safety or efficacy of taliglucerase alfa in patients. This study shows the benefit of using large scale human trials to evaluate the immunogenicity risk of plant derived glycans, and indicates no apparent risk related to anti-plant glycan antibodies.