Pharmacokinetics, safety and tolerability of miglustat in the treatment of pediatric patients with GM2 gangliosidosis

Intrathecal delivery of a bicistronic AAV9 vector expressing β-hexosaminidase A corrects Sandhoff disease in a murine model: A dosage study

The pathological accumulation of GM2 ganglioside associated with Tay-Sachs disease (TSD) and Sandhoff disease (SD) occurs in individuals who possess mutant forms of the heterodimer β-hexosaminidase A (Hex A) because of mutation of the HEXA and HEXB genes, respectively. With a lack of approved therapies, patients experience rapid neurological decline resulting in early death. A novel bicistronic vector carrying both HEXA and HEXB previously demonstrated promising results in mouse models of SD following neonatal intravenous administration, including significant reduction in GM2 accumulation, increased levels of Hex A, and a 2-fold extension of survival. The aim of the present study was to identify an optimal dose of the bicistronic vector in 6-week-old SD mice by an intrathecal route of administration along with transient immunosuppression, to inform possible clinical translation. Three doses of the bicistronic vector were tested: 2.5e11, 1.25e11, and 0.625e11 vector genomes per mouse. The highest dose provided the greatest increase in biochemical and behavioral parameters, such that treated mice lived to a median age of 56 weeks (>3 times the lifespan of the SD controls). These results have direct implications in deciding a human equivalent dose for TSD/SD and have informed the approval of a clinical trial application (NCT04798235).

Efficacy and safety of miglustat in the treatment of GM2 gangliosidosis: A systematic review

BACKGROUND

Since the results of previous studies regarding the safety and efficacy of miglustat in GM2 gangliosidosis (GM2g) were inconsistent, we aimed to assess miglustat therapy in GM2g patients.

METHODS

This study followed the latest version of PRISMA. We included the observational or interventional studies reporting GM2g patients under miglustat therapy by searching PubMed, Web of Science, and Scopus. Data extracted included the natural history of individual patient data, as well as the safety and efficacy of miglustat in GM2g patients. The quality assessment was performed using the Joanna Briggs Institute Critical Appraisal checklist.

RESULTS

A total of 1023 records were identified and reduced to 621 after removing duplicates. After screening and applying the eligibility criteria, 10 articles and 2 abstracts met the inclusion criteria. Overall, the studies represented 54 patients with GM2g under treatment with miglustat and 22 patients with GM2g in the control group. Among patients with available data, 14 and 54 have been diagnosed with Sandhoff disease and Tay-Sachs disease, respectively. Patients included in this review consisted of 23 infantile, 4 late-infantile, 18 juvenile, and 31 adult-onset GM2g.

CONCLUSIONS

Although miglustat should not be considered a definite treatment for GM2g, it appears that patients, particularly those with infantile or late-infantile GM2g, could benefit from miglustat therapy to some extent. We also make some suggestions regarding future studies presenting their findings in a standard format to facilitate pooling the available data in such rare diseases for a more comprehensive conclusion.

Role of Globotriaosylceramide in Physiology and Pathology

At first glance, the biological function of globoside (Gb) clusters appears to be that of glycosphingolipid (GSL) receptors for bacterial toxins that mediate host-pathogen interaction. Indeed, certain bacterial toxin families have been evolutionarily arranged so that they can enter eukaryotic cells through GSL receptors. A closer look reveals this molecular arrangement allocated on a variety of eukaryotic cell membranes, with its role revolving around physiological regulation and pathological processes. What makes Gb such a ubiquitous functional arrangement? Perhaps its peculiarity is underpinned by the molecular structure itself, the nature of Gb-bound ligands, or the intracellular trafficking unleashed by those ligands. Moreover, Gb biological conspicuousness may not lie on intrinsic properties or on its enzymatic synthesis/degradation pathways. The present review traverses these biological aspects, focusing mainly on globotriaosylceramide (Gb3), a GSL molecule present in cell membranes of distinct cell types, and proposes a wrap-up discussion with a phylogenetic view and the physiological and pathological functional alternatives.

The juvenile gangliosidoses: A timeline of clinical change

Background

The gangliosidoses are rare inherited diseases that result in pathologic accumulation of gangliosides in the central nervous system and other tissues, leading to severe and progressive neurological impairment and early death in the childhood forms. No treatments are currently approved for the gangliosidoses, and development of treatments is impaired by limited understanding of the natural history of these diseases.

Objective

The objective of this study is to improve understanding of the juvenile gangliosidoses phenotypes and the late-infantile phenotypic subtype.

Methods

Through a prospective natural history study of subjects with juvenile GM1- and GM2-gangliosidosis, a timeline of clinical changes was developed for the classic juvenile phenotypes and the late-infantile phenotypes and results of serial neurodevelopmental testing was analyzed.

Results

Several candidate ‘outcome measures’ were identified: changes in ambulation and verbalization skills, the communication domain from neurodevelopmental testing and the caregiver-reported socialization domain.

Conclusions

The most common symptoms leading caregivers to seek a genetic diagnosis were changes in ambulation and verbalization.

CNS-Targeting Therapies for Lysosomal Storage Diseases: Current Advances and Challenges

During the past decades, several therapeutic approaches have been developed and made rapidly available for many patients afflicted with lysosomal storage disorders (LSDs), inborn organelle disorders with broad clinical manifestations secondary to the progressive accumulation of undegraded macromolecules within lysosomes. These conditions are individually rare, but, collectively, their incidence ranges from 1 in 2,315 to 7,700 live-births. Most LSDs are manifested by neurological symptoms or signs, including developmental delay, seizures, acroparesthesia, motor weakness, and extrapyramidal signs. The chronic and later-onset clinical forms are at one end of the continuum spectrum and are characterized by a subtle and slow progression of neurological symptoms. Due to its inherent physiological properties, unfortunately, the blood-brain barrier (BBB) constitutes a significant obstacle for current and upcoming therapies to achieve the central nervous system (CNS) and treat neurological problems so prevalent in these conditions. To circumvent this limitation, several strategies have been developed to make the therapeutic agent achieve the CNS. This narrative will provide an overview of current therapeutic strategies under development to permeate the BBB, and address and unmet need for treatment of the progressive neurological manifestations, which are so prevalent in these inherited lysosomal disorders.

Differential Effects of 2-Hydroxypropyl-Cyclodextrins on Lipid Accumulation in Npc1-Null Cells

Niemann-Pick disease type C (NPC) is an autosomal recessive disorder characterized by abnormal accumulation of free cholesterol and sphingolipids in lysosomes. The iminosugar miglustat, which inhibits hexosylceramide synthesis, is used for NPC treatment, and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), a cyclic oligosaccharide derivative, is being developed to treat NPC. Moreover, therapeutic potential of 2-hydroxypropyl-γ-cyclodextrin (HP-γ-CD) was shown in NPC models, although its mechanism of action remains unclear. Here, we investigated the effects of HP-β-CD, HP-γ-CD, and their homolog 2-hydroxypropyl-α-cyclodextrin (HP-α-CD) on lipid accumulation in Npc1-null Chinese hamster ovary (CHO) cells compared with those of miglustat. HP-β-CD and HP-γ-CD, unlike HP-α-CD, reduced intracellular free cholesterol levels and normalized the lysosome changes in Npc1-null cells but not in wild-type CHO cells. In contrast, miglustat did not normalize intracellular free cholesterol accumulation or lysosome changes in Npc1-null cells. However, miglustat decreased the levels of hexosylceramide and tended to increase those of sphingomyelins in line with its action as a glucosylceramide synthase inhibitor in both Npc1-null and wild-type CHO cells. Interestingly, HP-β-CD and HP-γ-CD, unlike HP-α-CD, reduced sphingomyelins in Npc1-null, but not wild-type, cells. In conclusion, HP-β-CD and HP-γ-CD reduce the accumulation of sphingolipids, mainly sphingomyelins, and free cholesterol as well as lysosome changes in Npc1-null, but not in wild-type, CHO cells.

Lipidomic Profiling Links the Fanconi Anemia Pathway to Glycosphingolipid Metabolism in Head and Neck Cancer Cells

Purpose: Mutations in Fanconi anemia (FA) genes are common in sporadic squamous cell carcinoma of the head and neck (HNSCC), and we have previously demonstrated that FA pathway depletion in HNSCC cell lines stimulates invasion. The goal of our studies was to use a systems approach in order to define FA pathway-dependent lipid metabolism and to extract lipid-based signatures and effectors of invasion in FA-deficient cells.Experimental Design: We subjected FA-isogenic HNSCC keratinocyte cell lines to untargeted and targeted lipidomics analyses to discover novel biomarkers and candidate therapeutic targets in FA-deficient cells. Cellular invasion assays were carried out in the presence and absence of N-butyldeoxynojirimycin (NB-DNJ), a biosynthetic inhibitor of the newly identified class of gangliosides, to investigate the requirement of ganglioside upregulation in FA-deficient HNSCC cells.Results: The most notable element of the lipid profiling results was a consistent elevation of glycosphingolipids, and particularly the accumulation of gangliosides. Conversely, repression of this same class of lipids was observed upon genetic correction of FA patient-derived HNSCC cells. Functional studies demonstrate that ganglioside upregulation is required for HNSCC cell invasion driven by FA pathway loss. The motility of nontransformed keratinocytes in response to FA loss displayed a similar dependence, thus supporting early and late roles for the FA pathway in controlling keratinocyte invasion through lipid regulation.Conclusions: Elevation of glycosphingolipids including the ganglioside GM3 in response to FA loss stimulates invasive characteristics of immortalized and transformed keratinocytes. An inhibitor of glycosphingolipid biosynthesis NB-DNJ attenuates invasive characteristics of FA-deficient HNSCC cells. Clin Cancer Res; 24(11); 2700-9. ©2018 AACR.

Infantile gangliosidoses: Mapping a timeline of clinical changes

BACKGROUND

Infantile gangliosidoses include GM1 gangliosidosis and GM2 gangliosidosis (Tay-Sachs disease, Sandhoff disease). To date, natural history studies in infantile GM2 (iGM2) have been retrospective and conducted through surveys. Compared to iGM2, there is even less natural history information available on infantile GM1 disease (iGM1). There are no approved treatments for infantile gangliosidoses. Substrate reduction therapy using miglustat has been tried, but is limited by gastrointestinal side effects. Development of effective treatments will require identification of meaningful outcomes in the setting of rapidly progressive and fatal diseases.

OBJECTIVES

This study aimed to establish a timeline of clinical changes occurring in infantile gangliosidoses, prospectively, to: 1) characterize the natural history of these diseases; 2) improve planning of clinical care; and 3) identify meaningful future treatment outcome measures.

METHODS

Patients were evaluated prospectively through ongoing clinical care.

RESULTS

Twenty-three patients were evaluated: 8 infantile GM1, 9 infantile Tay-Sachs disease, 6 infantile Sandhoff disease. Common patterns of clinical change included: hypotonia before 6months of age; severe motor skill impairment within first year of life; seizures; dysphagia and feeding-tube placement before 18months of age. Neurodevelopmental testing scores reached the floor of the testing scale by 20 to 28months of age. Vertebral beaking, kyphosis, and scoliosis were unique to patients with infantile GM1. Chest physiotherapy was associated with increased survival in iGM1 (p=0.0056). Miglustat combined with a low-carbohydrate ketogenic diet (the Syner-G regimen) in patients who received a feeding-tube was associated with increased survival in infantile GM1 (p=0.025).

CONCLUSIONS

This is the first prospective study of the natural history of infantile gangliosidoses and the very first natural history of infantile GM1. The homogeneity of the infantile gangliosidoses phenotype as demonstrated by the clinical events timeline in this study provides promising secondary outcome measure candidates. This study indicates that overall survival is a meaningful primary outcome measure for future clinical trials due to reliable timing and early occurrence of this event. Combination therapy approaches, instead of monotherapy approaches, will likely be the best way to optimize clinical outcomes. Combination therapy approaches include palliative therapies (e.g., chest physiotherapy) along with treatments that address the underlying disease pathology (e.g. miglustat or future gene therapies).

The development and use of small molecule inhibitors of glycosphingolipid metabolism for lysosomal storage diseases

Glycosphingolipid (GSL) storage diseases have been the focus of efforts to develop small molecule therapeutics from design, experimental proof of concept studies, and clinical trials. Two primary alternative strategies that have been pursued include pharmacological chaperones and GSL synthase inhibitors. There are theoretical advantages and disadvantages to each of these approaches. Pharmacological chaperones are specific for an individual glycoside hydrolase and for the specific mutation present, but no candidate chaperone has been demonstrated to be effective for all mutations leading to a given disorder. Synthase inhibitors target single enzymes such as glucosylceramide synthase and inhibit the formation of multiple GSLs. A glycolipid synthase inhibitor could potentially be used to treat multiple diseases, but at the risk of lowering nontargeted cellular GSLs that are important for normal health. The basis for these strategies and specific examples of compounds that have led to clinical trials is the focus of this review.

Developing therapeutic approaches for metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal disorder caused by the deficiency of arylsulfatase A (ASA), resulting in impaired degradation of sulfatide, an essential sphingolipid of myelin. The clinical manifestations of MLD are characterized by progressive demyelination and subsequent neurological symptoms resulting in severe debilitation. The availability of therapeutic options for treating MLD is limited but expanding with a number of early stage clinical trials already in progress. In the development of therapeutic approaches for MLD, scientists have been facing a number of challenges including blood–brain barrier (BBB) penetration, safety issues concerning therapies targeting the central nervous system, uncertainty regarding the ideal timing for intervention in the disease course, and the lack of more in-depth understanding of the molecular pathogenesis of MLD. Here, we discuss the current status of the different approaches to developing therapies for MLD. Hematopoietic stem cell transplantation has been used to treat MLD patients, utilizing both umbilical cord blood and bone marrow sources. Intrathecal enzyme replacement therapy and gene therapies, administered locally into the brain or by generating genetically modified hematopoietic stem cells, are emerging as novel strategies. In pre-clinical studies, different cell delivery systems including microencapsulated cells or selectively neural cells have shown encouraging results. Small molecules that are more likely to cross the BBB can be used as enzyme enhancers of diverse ASA mutants, either as pharmacological chaperones, or proteostasis regulators. Specific small molecules may also be used to reduce the biosynthesis of sulfatides, or target different affected downstream pathways secondary to the primary ASA deficiency. Given the progressive neurodegenerative aspects of MLD, also seen in other lysosomal diseases, current and future therapeutic strategies will be complementary, whether used in combination or separately at specific stages of the disease course, to produce better outcomes for patients afflicted with this devastating inherited disorder.

Scalable syntheses of both enantiomers of DNJNAc and DGJNAc from glucuronolactone: the effect of N-alkylation on hexosaminidase inhibition

The efficient scalable syntheses of 2-acetamido-1,2-dideoxy-D-galacto-nojirimycin (DGJNAc) and 2-acetamido-1,2-dideoxy-D-gluco-nojirimycin (DNJNAc) from D-glucuronolactone, as well as of their enantiomers from L-glucuronolactone, are reported. The evaluation of both enantiomers of DNJNAc and DGJNAc, along with their N-alkyl derivatives, as glycosidase inhibitors showed that DGJNAc and its N-alkyl derivatives were all inhibitors of α-GalNAcase but that none of the epimeric DNJNAc derivatives inhibited this enzyme. In contrast, both DGJNAc and DNJNAc, as well as their alkyl derivatives, were potent inhibitors of β-GlcNAcases and β-GalNAcases. Neither of the L-enantiomers showed any significant inhibition of any of the enzymes tested. Correlation of the in vitro inhibition with the cellular data, by using a free oligosaccharide analysis of the lysosomal enzyme inhibition, revealed the following structure-property relationship: hydrophobic side-chains preferentially promoted the intracellular access of iminosugars to those inhibitors with more-hydrophilic side-chain characteristics.

Corneal alterations during combined therapy with cyclodextrin/allopregnanolone and miglustat in a knock-out mouse model of NPC1 disease

Background

Niemann Pick disease type C1 is a neurodegenerative disease caused by mutations in the NPC1 gene, which result in accumulation of unesterified cholesterol and glycosphingolipids in the endosomal-lysosomal system as well as limiting membranes. We have previously shown the corneal involvement in NPC1 pathology in form of intracellular inclusions in epithelial cells and keratocytes. The purpose of the present study was to clarify if these inclusions regress during combined substrate reduction- and by-product therapy (SRT and BPT).

Methodology/Principal Findings

Starting at postnatal day 7 (P7) and thereafter, NPC1 knock-out mice (NPC1^−/−) and wild type controls (NPC1^+/+) were injected with cyclodextrin/allopregnanolone weekly. Additionally, a daily miglustat injection started at P10 until P23. Starting at P23 the mice were fed powdered chow with daily addition of miglustat. The sham group was injected with 0.9% NaCl at P7, thereafter daily starting at P10 until P23, and fed powdered chow starting at P23. For corneal examination, in vivo confocal laser-scanning microscopy (CLSM) was performed one day before experiment was terminated. Excised corneas were harvested for lipid analysis (HPLC/MS) and electron microscopy.

In vivo CLSM demonstrated a regression of hyperreflective inclusions in all treated NPC1^−/−mice. The findings varied between individual mice, demonstrating a regression, ranging from complete absence to pronounced depositions. The reflectivity of inclusions, however, was significantly lower when compared to untreated and sham-injected NPC1^−/− mice. These confocal findings were confirmed by lipid analysis and electron microscopy. Another important CLSM finding revealed a distinct increase of mature dendritic cell number in corneas of all treated mice (NPC1^−/− and NPC1^+/+), including sham-treated ones.

Conclusions/Significance

The combined substrate reduction- and by-product therapy revealed beneficial effects on the cornea. In vivo CLSM is a non-invasive tool to monitor disease progression and treatment effects in NPC1 disorder.

Evaluation of miglustat treatment in patients with type III mucopolysaccharidosis: a randomized, double-blind, placebo-controlled study

OBJECTIVE

To evaluate the efficacy and safety of oral miglustat treatment in patients with mucopolysaccharidosis type III. The primary outcome was efficacy with improvement or stabilization in at least two domains of Vineland Adaptative Behavior Scales at 6 months. The secondary outcome measured the evolution of other cognitive tests at 12 months. The safety and tolerability were assessed throughout the study.

STUDY DESIGN

This was a randomized, double-blind, placebo-controlled, monocenter, institutional, phase IIb to III study. In case of efficacy at 6 months, the study would go on for another 6 months on an open design with all patients receiving miglustat. In the absence of efficacy at 6 months, the trial had to be continued for 6 more months with the initial design.

RESULTS

After 6 months, efficacy was not superior in patients with miglustat. The independent review board confirmed continuing the study until 12 months.

CONCLUSION

Miglustat treatment was not associated with any improvement/stabilization in behavior problems in patients with mucopolysaccharidosis type III. Miglustat has an acceptable safety profile. However, the study has confirmed that miglustat is able to pass through the blood-brain barrier without significantly decreasing ganglioside levels.

Emerging therapies for neurodegenerative lysosomal storage disorders - from concept to reality

Lysosomal storage disorders are inherited metabolic diseases in which a mutation in a gene encoding a lysosomal enzyme or lysosome-related protein results in the intra-cellular accumulation of substrate and reduced cell/tissue function. Few patients with neurodegenerative lysosomal storage disorders have access to safe and effective treatments although many therapeutic strategies have been or are presently being studied in vivo thanks to the availability of a large number of animal models. This review will describe the comparative advancement of a variety of therapeutic strategies through the 'research pipeline'. Our goal is to provide information for clinicians, researchers and patients/families alike on the leading therapeutic candidates at this point in time, and also to provide information on emerging approaches that may provide a safe and effective treatment in the future. The length of the pipeline represents the significant and sustained effort required to move a novel concept from the laboratory into the clinic.

Pathology and current treatment of neurodegenerative sphingolipidoses

Sphingolipidoses constitute a large subgroup of lysosomal storage disorders (LSDs). Many of them are associated with a progressive neurodegeneration. As is the case for LSDs in general, most sphingolipidoses are caused by deficiencies in lysosomal hydrolases. However, accumulation of sphingolipids can also result from deficiencies in proteins involved in the transport or posttranslational modification of lysosomal enzymes, transport of lipids, or lysosomal membrane proteins required for transport of lysosomal degradation end products. The accumulation of sphingolipids in the lysosome together with secondary changes in the concentration and localization of other lipids may cause trafficking defects of membrane lipids and proteins, affect calcium homeostasis, induce the unfolded protein response, activate apoptotic cascades, and affect various signal transduction pathways. To what extent, however, these changes contribute to the pathogenesis of the diseases is not fully understood. Currently, there is no cure for sphingolipidoses. Therapies like enzyme replacement, pharmacological chaperone, and substrate reduction therapy, which have been shown to be efficient in non-neuronopathic LSDs, are currently evaluated in clinical trials of neuronopathic sphingolipidoses. In the future, neural stem cell therapy and gene therapy may become an option for these disorders.

Substrate deprivation therapy in juvenile Sandhoff disease

Substrate deprivation therapy has been successfully applied in a number of lysosomal storage diseases, such as Gaucher disease. So far only limited experience is available in Sandhoff disease. We initiated substrate deprivation therapy in one male patient, who initially presented at the age of 3.5 years with epilepsy and regression in motor skills and speech development. Juvenile Sandhoff disease was diagnosed on the basis of a decreased hexosaminidase activity in leukocytes and a homozygous HEXB gene mutation. After the epilepsy was controlled, the clinical course remained stable for years, defined by a mild proximal myopathy and stable mental retardation. At 14 years of age the patient experienced a second episode with progressively worsening general condition with diminishing muscle power and progressive ataxia. Treatment was started with the N-alkylated imino sugar miglustat, inhibiting the glucosylceramide synthase, an essential enzyme for the synthesis of glycosphingolipids. Diarrhoea was treated with lactose restriction. We performed detailed biochemical investigations, motor and mental development analysis, brain imaging, organ function studies and quality of life score prior to and at different time points after start of the treatment. Two years after the initiation of therapy the patient has a stable neurological picture without further regression in his motor development, ataxia or intelligence. There is a subjective improvement in the fine motor skills and walking up the stairs but no change in the quality of life score. Under treatment with miglustat the clinical course in our patient with Sandhoff disease did not further deteriorate.

Miglustat therapy in juvenile Sandhoff disease

GM(2)-gangliosidosis is a rare and heterogeneous inherited metabolic disorder caused by autosomal recessive mutations in genes encoding the lysosomal enzyme β-hexosaminidase, resulting in the accumulation of ganglioside GM(2) in various tissues, particularly the central nervous system. It is characterized by progressive neurological deterioration that mainly affects motor and spinocerebellar function. Several forms of GM(2)-gangliosidosis exist, including the Sandhoff variant. Currently there is no treatment for these conditions, except for palliative care. Miglustat (Zavesca) is a reversible inhibitor of glucosylceramide synthase, which catalyses the first committed step in the synthesis of glucose-based glycolipids. Miglustat has pharmacokinetic properties that allow it to cross the blood-brain barrier, and preclinical data suggest that it may benefit neuronopathic lysosomal storage diseases. Here we present a case report of a Norwegian patient with Sandhoff disease treated with miglustat at our centre in Norway. The patient initially presented with ataxia and dysarthria at 2-3 years of age, which progressed slowly during childhood. At age 14, he experienced episodes of depression and apathy, leading to weight loss. He was diagnosed with Sandhoff disease at age 16. Following 2.5 years of treatment with miglustat, his body weight was stabilized and disease progression appeared to have slowed, as evidenced by the lack of progressive brain atrophy. His depressive symptoms were managed using electroconvulsive treatment (ECT), which improved general functioning. These findings suggest that miglustat may provide beneficial effects in patients with juvenile Sandhoff disease, and that ECT may alleviate depressive symptoms.