Assessment of cellular cobalamin metabolism in Gaucher disease.

BACKGROUND: Gaucher disease (GD) is a lysosomal disorder caused by biallelic pathogenic mutations in the GBA1 gene that encodes beta-glucosidase (GCase), and more rarely, by a deficiency in the GCase activator, saposin C. Clinically, GD manifests with heterogeneous multiorgan involvement mainly affecting hematological, hepatic and neurological axes. This disorder is divided into three types, based on the absence (type I) or presence and severity (types II and III) of involvement of the central nervous system. At the cellular level, deficiency of GBA1 disturbs lysosomal storage with buildup of glucocerebroside. The consequences of disturbed lysosomal metabolism on biochemical pathways that require lysosomal processing are unknown. Abnormal systemic markers of cobalamin (Cbl, B12) metabolism have been reported in patients with GD, suggesting impairments in lysosomal handling of Cbl or in its downstream utilization events. METHODS: Cultured skin fibroblasts from control humans (n = 3), from patients with GD types I (n = 1), II (n = 1) and III (n = 1) and an asymptomatic carrier of GD were examined for their GCase enzymatic activity and lysosomal compartment intactness. Control human and GD fibroblasts were cultured in growth medium with and without 500 nM hydroxocobalamin supplementation. Cellular cobalamin status was examined via determination of metabolomic markers in cell lysate (intracellular) and conditioned culture medium (extracellular). The presence of transcobalamin (TC) in whole cell lysates was examined by Western blot. RESULTS: Cultured skin fibroblasts from GD patients exhibited reduced GCase activity compared to healthy individuals and an asymptomatic carrier of GD, demonstrating a preserved disease phenotype in this cell type. The concentrations of total homocysteine (tHcy), methylmalonic acid (MMA), cysteine (Cys) and methionine (Met) in GD cells were comparable to control levels, except in one patient with GD III. The response of these metabolomic markers to supplementation with hydroxocobalamin (HOCbl) yielded variable results. The content of transcobalamin in whole cell lysates was comparable in control human and GD patients. CONCLUSIONS: Our results indicate that cobalamin transport and cellular processing pathways are overall protected from lysosomal storage damage in GD fibroblasts. Extending these studies to hepatocytes, macrophages and plasma will shed light on cell- and compartment-specific vitamin B12 metabolism in Gaucher disease.

Thalamic and dentate nucleus abnormalities in the brain of children with Gaucher disease.

Gaucher disease (GD) represents the most common lysosomal storage defect. It is classified into three phenotypes: type 1 non-neuronopathic, type 2 acute neuronopathic, and type 3 subacute/chronic neuronopathic. Although children affected by GD may present with a broad spectrum of neurological signs, brain magnetic resonance imaging (MRI) findings are usually normal or non-specific. We report three cases of GD with previously undescribed brain MRI changes mainly affecting the thalami and/or the dentate nuclei. We discuss the possible etiopathogenesis of these abnormalities. Correlation between brain MRI abnormalities, neurological symptoms, and treatment efficacy is still unclear.

Twelve years of experience with miglustat in the treatment of type 1 Gaucher disease: The Spanish ZAGAL project.

We report data from a prospective, observational study (ZAGAL) evaluating miglustat 100mg three times daily orally. in treatment-naïve patients and patients with type 1 Gaucher Disease (GD1) switched from previous enzyme replacement therapy (ERT). Clinical evolution, changes in organ size, blood counts, disease biomarkers, bone marrow infiltration (S-MRI), bone mineral density by broadband ultrasound densitometry (BMD), safety and tolerability annual reports were analysed. Between May 2004 and April 2016, 63 patients received miglustat therapy; 20 (32%) untreated and 43 (68%) switched. At the time of this report 39 patients (14 [36%] treatment-naïve; 25 [64%] switch) remain on miglustat. With over 12-year follow-up, hematologic counts, liver and spleen volumes remained stable. In total, 80% of patients achieved current GD1 therapeutic goals. Plasma chitotriosidase activity and CCL-18/PARC concentration showed a trend towards a slight increase. Reductions on S-MRI (p=0.042) with an increase in BMD (p<0.01) were registered. Gastrointestinal disturbances were reported in 25/63 (40%), causing miglustat suspension in 11/63 (17.5%) cases. Thirty-eight patients (60%) experienced a fine hand tremor and two a reversible peripheral neuropathy. Overall, miglustat was effective as a long-term therapy in mild to moderate naïve and ERT stabilized patients. No unexpected safety signals were identified during 12-years follow-up.

A new framework for evaluating the health impacts of treatment for Gaucher disease type 1.

BACKGROUND: The Disease Severity Scoring System (DS3) is a validated measure for evaluating Gaucher disease type 1 (GD1) severity. We developed a new framework, consisting of health states, transition probabilities between those states, and preferences for those states (utilities) based on the DS3 to predict long-term outcomes of patients starting treatment. We defined nine mutually exclusive (alive) health states based on three DS3 categories: mild (0 ≤ DS3 ≤ 3.5) without symptoms of bone disease; mild with bone pain, mild with severe skeletal complications (SSC) defined as lytic lesions, avascular necrosis, or fracture; moderate (3.5 < DS3 ≤ 6.5) without SSC; moderate with SSC; marked (6.5 < DS3 ≤ 9.5) without SSC; marked with SSC; severe (9.5 < DS3 ≤ 19) without SSC; and severe with SSC. Health-state transition probabilities and utilities were estimated from a longitudinal sample of patients with GD1 who started enzyme replacement therapy (the DS3 Score Study). Age dependent GD1-specific mortality was derived from published data. We used a Markov state-transition model to illustrate how to estimate time spent in each health state. RESULTS: The average predicted utilities for each health state ranged from 0.76 for mild disease with no clinical symptoms of bone disease to 0.52 with severe disease with SSC. Transition probabilities depended on disease severity (DS3 score) at treatment initiation and whether patients had undergone a total splenectomy or had an intact spleen/partial splenectomy prior to starting treatment. Patients who started treatment with intact or residual spleens spent more time in better health states than those who started treatment with total splenectomy. CONCLUSIONS: This new framework, which is based on the DS3, can be used to project the long-term outcomes of GD1 patients starting treatment. The framework could also be used to compare the long-term outcomes of different GD1 treatment options. TRIAL REGISTRATION: NCT01136304 . Registered: May 31, 2010 (retrospectively registered).

Successful switch from enzyme replacement therapy to miglustat in an adult patient with type 1 Gaucher disease: a case report.

BACKGROUND: Gaucher disease is one of the most common lipid-storage disorders, affecting approximately 1 in 75,000 births. Enzyme replacement therapy with recombinant glucocerebrosidase is currently considered the first-line treatment choice for patients with symptomatic Gaucher disease type 1. Oral substrate reduction therapy is generally considered a second-line treatment option for adult patients with mild to moderate Gaucher disease type 1 who are unable or unwilling to receive lifelong intravenous enzyme infusions. The efficacy and safety of the oral substrate reduction therapy miglustat (Zavesca®) in patients with Gaucher disease type 1 have been established in both short-term clinical trials and long-term, open-label extension studies. Published data indicate that miglustat can be used as maintenance therapy in patients with stable Gaucher disease type 1 switched from previous enzyme replacement therapy. CASE PRESENTATION: We report a case of a 44-year-old Caucasian man with Gaucher disease type 1 who was initially treated with enzyme replacement therapy but, owing to repeated cutaneous allergic reactions, had to be switched to miglustat after several attempts with enzyme replacement therapy. Despite many attempts, desensitization treatment did not result in improved toleration of imiglucerase infusions, and the patient became unwilling to continue with any intravenous enzyme replacement therapy. He subsequently agreed to switch to oral substrate reduction therapy with miglustat 100 mg twice daily titrated up to 100 mg three times daily over a short period. Long-term miglustat treatment maintained both hemoglobin and platelet levels within acceptable ranges over 8 years. The patient's spleen volume decreased, his plasma chitotriosidase levels stayed at reduced levels, and his bone mineral density findings have remained stable throughout follow-up. The patient's quality of life has remained satisfactory. Miglustat showed good gastrointestinal tolerability in this patient, and no adverse events have been reported. CONCLUSIONS: Oral miglustat therapy proved to be a valid alternative treatment to intravenous enzyme replacement therapy for long-term maintenance in this patient with Gaucher disease type 1, who showed persistent allergic intolerance to imiglucerase infusions. This report exemplifies the type of patient with Gaucher disease type 1 who can benefit from switching from enzyme replacement therapy to substrate reduction therapy.

Progression of Behavioral and CNS Deficits in a Viable Murine Model of Chronic Neuronopathic Gaucher Disease.

To study the neuronal deficits in neuronopathic Gaucher Disease (nGD), the chronological behavioral profiles and the age of onset of brain abnormalities were characterized in a chronic nGD mouse model (9V/null). Progressive accumulation of glucosylceramide (GC) and glucosylsphingosine (GS) in the brain of 9V/null mice were observed at as early as 6 and 3 months of age for GC and GS, respectively. Abnormal accumulation of α-synuclein was present in the 9V/null brain as detected by immunofluorescence and Western blot analysis. In a repeated open-field test, the 9V/null mice (9 months and older) displayed significantly less environmental habituation and spent more time exploring the open-field than age-matched WT group, indicating the onset of short-term spatial memory deficits. In the marble burying test, the 9V/null group had a shorter latency to initiate burying activity at 3 months of age, whereas the latency increased significantly at ≥12 months of age; 9V/null females buried significantly more marbles to completion than the WT group, suggesting an abnormal response to the instinctive behavior and an abnormal activity in non-associative anxiety-like behavior. In the conditional fear test, only the 9V/null males exhibited a significant decrease in response to contextual fear, but both genders showed less response to auditory-cued fear compared to age- and gender-matched WT at 12 months of age. These results indicate hippocampus-related emotional memory defects. Abnormal gait emerged in 9V/null mice with wider front-paw and hind-paw widths, as well as longer stride in a gender-dependent manner with different ages of onset. Significantly higher liver- and spleen-to-body weight ratios were detected in 9V/null mice with different ages of onsets. These data provide temporal evaluation of neurobehavioral dysfunctions and brain pathology in 9V/null mice that can be used for experimental designs to evaluate novel therapies for nGD.

Less Is More: Substrate Reduction Therapy for Lysosomal Storage Disorders.

Lysosomal storage diseases (LSDs) are a group of rare, life-threatening genetic disorders, usually caused by a dysfunction in one of the many enzymes responsible for intralysosomal digestion. Even though no cure is available for any LSD, a few treatment strategies do exist. Traditionally, efforts have been mainly targeting the functional loss of the enzyme, by injection of a recombinant formulation, in a process called enzyme replacement therapy (ERT), with no impact on neuropathology. This ineffectiveness, together with its high cost and lifelong dependence is amongst the main reasons why additional therapeutic approaches are being (and have to be) investigated: chaperone therapy; gene enhancement; gene therapy; and, alternatively, substrate reduction therapy (SRT), whose aim is to prevent storage not by correcting the original enzymatic defect but, instead, by decreasing the levels of biosynthesis of the accumulating substrate(s). Here we review the concept of substrate reduction, highlighting the major breakthroughs in the field and discussing the future of SRT, not only as a monotherapy but also, especially, as complementary approach for LSDs.

Taliglucerase alfa: an enzyme replacement therapy using plant cell expression technology.

Gaucher disease (GD) is a rare, genetic lysosomal storage disorder caused by functional defects of acid ß-glucosidase that results in multiple organ dysfunction. Glycosylation of recombinant acid human ß-glucosidase and exposure of terminal mannose residues are critical to the success of enzyme replacement therapy (ERT) for the treatment of visceral and hematologic manifestations in GD. Three commercially available ERT products for treatment of GD type 1 (GD1) include imiglucerase, velaglucerase alfa, and taliglucerase alfa. Imiglucerase and velaglucerase alfa are produced in different mammalian cell systems and require production glycosylation modifications to expose terminal α-mannose residues, which are needed for mannose receptor-mediated uptake by target macrophages. Such modifications add to production costs. Taliglucerase alfa is a plant cell-expressed acid ß-glucosidase approved in the United States and other countries for ERT in adults with GD1. A plant-based expression system, using carrot root cell cultures, was developed for production of taliglucerase alfa and does not require additional processing for postproduction glycosidic modifications. Clinical trials have demonstrated that taliglucerase alfa is efficacious, with a well-established safety profile in adult, ERT-naïve patients with symptomatic GD1, and for such patients previously treated with imiglucerase. These included significant improvements in organomegaly and hematologic parameters as early as 6months, and maintenance of achieved therapeutic values in previously treated patients. Ongoing clinical trials will further characterize the long-term efficacy and safety of taliglucerase alfa in more diverse patient populations, and may help to guide clinical decisions for achieving optimal outcomes for patients with GD1.

RIPK3 as a potential therapeutic target for Gaucher's disease.

Gaucher's disease (GD), an inherited metabolic disorder caused by mutations in the glucocerebrosidase gene (GBA), is the most common lysosomal storage disease. Heterozygous mutations in GBA are a major risk factor for Parkinson's disease. GD is divided into three clinical subtypes based on the absence (type 1) or presence (types 2 and 3) of neurological signs. Type 1 GD was the first lysosomal storage disease (LSD) for which enzyme therapy became available, and although infusions of recombinant glucocerebrosidase (GCase) ameliorate the systemic effects of GD, the lack of efficacy for the neurological manifestations, along with the considerable expense and inconvenience of enzyme therapy for patients, renders the search for alternative or complementary therapies paramount. Glucosylceramide and glucosylsphingosine accumulation in the brain leads to massive neuronal loss in patients with neuronopathic GD (nGD) and in nGD mouse models. However, the mode of neuronal death is not known. Here, we show that modulating the receptor-interacting protein kinase-3 (Ripk3) pathway markedly improves neurological and systemic disease in a mouse model of GD. Notably, Ripk3 deficiency substantially improved the clinical course of GD mice, with increased survival and motor coordination and salutary effects on cerebral as well as hepatic injury.

Glucosylceramide modulates endolysosomal pH in Gaucher disease.

GlcCer accumulation causes Gaucher disease where GlcCer breakdown is inhibited due to a hereditary deficiency in glucocerebrosidase. Glycolipids are endocytosed and targeted to the Golgi apparatus in normal cells but in Gaucher disease they are mistargeted to lysosomes. To better understand the role of GlcCer in endocytic sorting RAW macrophages were treated with Conduritol B-epoxide to inhibit GlcCer breakdown. Lipid analysis found increases in GlcCer led to accumulation of both triacylglycerol and cholesterol consistent with increased lysosomal pH. Ratio imaging of macrophages using both acridine orange and lysosensor yellow/blue to measure endolysosomal pH revealed increases in Conduritol B-epoxide treated RAW macrophages and Gaucher patient lymphoblasts. Increased endolysosomal pH was restricted to Gaucher lymphoblasts as no significant increases in pH were seen in Fabry, Krabbe, Tay-Sachs and GM1-gangliosidosis lymphoblasts. Substrate reduction therapy utilises inhibitors of GlcCer synthase to reduce storage in Gaucher disease. The addition of inhibitors of GlcCer synthesis to RAW macrophages also led to increases in cholesterol and triacylglycerol and an endolysosomal pH increase of up to 1 pH unit. GlcCer modulation appears specific since glucosylsphingosine but not galactosylsphingosine reversed the effects of GlcCer depletion. Although no acute effects on glycolipid trafficking were observed using bafilomycin A the results are consistent with a multistep model whereby increases in pH lead to altered trafficking via cholesterol accumulation. GlcCer modulates endolysosomal pH in lymphocytes suggesting an important role in normal lysosomes which may be disrupted in Gaucher disease.

Neuronopathic Gaucher's disease: induced pluripotent stem cells for disease modelling and testing chaperone activity of small compounds.

Gaucher's disease (GD) is caused by mutations in the GBA1 gene, which encodes acid-ß-glucosidase, an enzyme involved in the degradation of complex sphingolipids. While the non-neuronopathic aspects of the disease can be treated with enzyme replacement therapy (ERT), the early-onset neuronopathic form currently lacks therapeutic options and is lethal. We have developed an induced pluripotent stem cell (iPSc) model of neuronopathic GD. Dermal fibroblasts of a patient with a P.[LEU444PRO];[GLY202ARG] genotype were transfected with a loxP-flanked polycistronic reprogramming cassette consisting of Oct4, Sox2, Klf4 and c-Myc and iPSc lines derived. A non-integrative lentiviral vector expressing Cre recombinase was used to eliminate the reprogramming cassette from the reprogrammed cells. Our GD iPSc express pluripotent markers, differentiate into the three germ layers, form teratomas, have a normal karyotype and show the same mutations and low acid-ß-glucosidase activity as the original fibroblasts they were derived from. We have differentiated them efficiently into neurons and also into macrophages without observing deleterious effects of the mutations on the differentiation process. Using our system as a platform to test chemical compounds capable of increasing acid-ß-glucosidase activity, we confirm that two nojirimycin analogues can rescue protein levels and enzyme activity in the cells affected by the disease.

Ambroxol as a pharmacological chaperone for mutant glucocerebrosidase.

Gaucher disease (GD) is characterized by accumulation of glucosylceramide in lysosomes due to mutations in the GBA1 gene encoding the lysosomal hydrolase ß-glucocerebrosidase (GCase). The disease has a broad spectrum of phenotypes, which were divided into three different Types; Type 1 GD is not associated with primary neurological disease while Types 2 and 3 are associated with central nervous system disease. GCase molecules are synthesized on endoplasmic reticulum (ER)-bound polyribosomes, translocated into the ER and following modifications and correct folding, shuttle to the lysosomes. Mutant GCase molecules, which fail to fold correctly, undergo ER associated degradation (ERAD) in the proteasomes, the degree of which is one of the factors that determine GD severity. Several pharmacological chaperones have already been shown to assist correct folding of mutant GCase molecules in the ER, thus facilitating their trafficking to the lysosomes. Ambroxol, a known expectorant, is one such chaperone. Here we show that ambroxol increases both the lysosomal fraction and the enzymatic activity of several mutant GCase variants in skin fibroblasts derived from Type 1 and Type 2 GD patients.

Synthesis of N-substituted ε-hexonolactams as pharmacological chaperones for the treatment of N370S mutant Gaucher disease.

A series of N-substituted ε-hexonolactams have been designed and prepared by a concise route with a tandem ring-expansion reaction as the key step. Some of the N-substituted ε-hexonolactams show better enhancements to N370S mutant ß-glucocerebrosidase activity than NB-DNJ and NN-DNJ. Both the experimental results and computational studies highlight the importance of the carbonyl group for stabilizing protein folds in the mutant enzyme. The structure-activity relationships are also discussed. These novel N-alkylated iminosugars are promising pharmacological chaperones for the treatment of N370S mutant Gaucher disease.

Goal-oriented therapy with miglustat in Gaucher disease.

BACKGROUND: Gaucher disease (GD) is a highly heterogeneous disorder with multisystem involvement. Specific therapeutic goals for each manifestation of type 1 GD (GD1) were established in 2004 by an international panel of experts, to facilitate better management of GD1 patients. The goals were defined based on experience with enzyme replacement therapy (ERT) using imiglucerase. Miglustat, a small iminosugar, is the only commercially available substrate reduction therapy (SRT) for patients with GD1. Several clinical studies have demonstrated the beneficial effects of miglustat on cardinal disease manifestations of GD1. OBJECTIVE: To review the currently available data on miglustat, and provide guidance on the attainment of the GD therapeutic goals with miglustat therapy. METHODS: A literature search identified publications on miglustat using MEDLINE, HighWire Press, and Google Scholar databases. Articles were identified using the terms 'miglustat' and 'Gaucher disease type 1'. FINDINGS: Improvements in hematological manifestations and organomegaly can be expected with miglustat therapy, with disease stabilization achievable over the long term. Recent data suggest that miglustat can maintain stability in patients with mild to moderate GD1 who have been previously treated with ERT. Miglustat may be beneficial with regards to bone manifestations, with reduction in the incidence of patients reporting bone pain and improvements in bone mineral density seen within the first 24 months of therapy. CONCLUSIONS: Several of the therapeutic goals for patients with GD1 can be achieved with miglustat therapy. In select cases, miglustat can be considered an alternative to ERT for the treatment of patients with GD1. Long-term experience with the use of miglustat will help define its overall safety and efficacy; this information will be useful in determining the role of SRT using miglustat in the management of the general adult GD1 patient population.

Promising results of the chaperone effect caused by imino sugars and aminocyclitol derivatives on mutant glucocerebrosidases causing Gaucher disease.

Gaucher disease is an autosomal recessive disorder. It is characterized by the accumulation of glucosylceramide in lysosomes of mononuclear phagocyte system, attributable to acid beta-glucosidase deficiency. The main consequences of this disease are hepatosplenomegaly, skeletal lesions and, sometimes, neurological manifestations. At sub-inhibitory concentrations, several competitive inhibitors act as chemical chaperones by inducing protein stabilization and increasing enzymatic activity. Here we tested two iminosugars (NB-DNJ and NN-DNJ) and four aminocyclitols with distinct degrees of lipophilicity as pharmacological chaperones for glucocerebrosidase (GBA). We report an increase in the activity of GBA using NN-DNJ, NB-DNJ and aminocyclitol 1 in stably transfected cell lines, and an increment with NN-DNJ and aminocyclitol 4 in patient fibroblasts. These results on specific mutations validate the use of chemical chaperones as a therapeutic approach for Gaucher disease. However, the development and analysis of new compounds is required in order to find more effective therapeutic agents that are active on a broader range of mutations.

Identification of pharmacological chaperones for Gaucher disease and characterization of their effects on beta-glucocerebrosidase by hydrogen/deuterium exchange mass spectrometry.

Point mutations in beta-glucocerebrosidase (GCase) can result in a deficiency of both GCase activity and protein in lysosomes thereby causing Gaucher Disease (GD). Enzyme inhibitors such as isofagomine, acting as pharmacological chaperones (PCs), increase these levels by binding and stabilizing the native form of the enzyme in the endoplasmic reticulum (ER), and allow increased lysosomal transport of the enzyme. A high-throughput screen of the 50,000-compound Maybridge library identified two, non-carbohydrate-based inhibitory molecules, a 2,4-diamino-5-substituted quinazoline (IC(50) 5 microM) and a 5-substituted pyridinyl-2-furamide (IC(50) 8 microM). They raised the levels of functional GCase 1.5-2.5-fold in N370S or F213I GD fibroblasts. Immunofluorescence confirmed that treated GD fibroblasts had decreased levels of GCase in their ER and increased levels in lysosomes. Changes in protein dynamics, monitored by hydrogen/deuterium-exchange mass spectrometry, identified a domain III active-site loop (residues 243-249) as being significantly stabilized upon binding of isofagomine or either of these two new compounds; this suggests a common mechanism for PC enhancement of intracellular transport.

Oral maintenance clinical trial with miglustat for type I Gaucher disease: switch from or combination with intravenous enzyme replacement.

Enzyme replacement therapy (ERT) with imiglucerase reduces hepatosplenomegaly and improves hematologic parameters in Gaucher disease type 1 within 6-24 months. Miglustat reduces organomegaly, improves hematologic parameters, and reverses bone marrow infiltration. This trial evaluates miglustat in patients clinically stable on ERT. Tolerability of miglustat and imiglucerase, alone and in combination, pharmacokinetic profile, organ reduction, and chitotriosidase activity were assessed. Thirty-six patients stable on imiglucerase were randomized into this phase II, open-label trial. Statistically significant changes from baseline were assessed (paired t test) on primary objectives with secondary analyses on biochemical and safety parameters. Liver and spleen volume were unchanged in switched patients. No significant differences were seen between groups regarding mean change in hemoglobin. Mean change in platelet counts was only significant between miglustat and imiglucerase groups (P = .035). Chitotriosidase activity remained stable. In trial extension, clinical endpoints were generally maintained. Miglustat was well tolerated alone or in combination. Miglustat's safety profile was consistent with previous trials; moreover, no new cases of peripheral neuropathy were observed. Gaucher disease type 1 (GD1) parameters were stable in most switched patients. Combination therapy did not show benefit. Findings suggest miglustat could be an effective maintenance therapy in stabilized patients with GD1.

Conditional expression of human acid beta-glucosidase improves the visceral phenotype in a Gaucher disease mouse model.

The reversibility and regression of histological and biochemical findings in a mouse model of Gaucher disease (4L/PS-NA) was evaluated using a liver-enriched activator protein promoter control of a tetracycline-controlled transcriptional activation-responsive human acid beta-glucosidase (hGCase) transgenic system. 4L/PS-NA has the acid beta-glucosidase (GCase) V394L/V394L (4L) point mutation combined with hypomorphic ( approximately 6% wild-type) expression of the mouse prosaposin transgene (PS-NA). The hGCase/4L/PS-NA had exclusive liver expression of hGCase controlled by doxycycline (DOX). In the absence of DOX, hGCase was secreted from liver at levels of approximately 120 microg/ml serum with only approximately 8% of full activity, following exposure to pH 7.4 in serum. The hGCase activity and protein were detected in cells of the liver (massive), lung, and spleen, but not the brain. The visceral tissue storage cells and glucosylceramide (GC) accumulation in hGCase/4L/PS-NA were decreased from that in 4L/PS-NA mice. Turning off hGCase expression with dietary DOX led to reaccumulation of storage cells and of GC in liver, lung, and spleen, and macrophage activation in those tissues. This study demonstrates that conditionally expressed hGCase supplemented the existing mutant mouse GCase to control visceral substrate accumulation in vivo.

Sustained therapeutic effects of oral miglustat (Zavesca, N-butyldeoxynojirimycin, OGT 918) in type I Gaucher disease.

It has been shown that treatment with miglustat (Zavesca, N-butyldeoxynojirimycin, OGT 918) improves key clinical features of type I Gaucher disease after 1 year of treatment. This study reports longer-term efficacy and safety data. Patients who had completed 12 months of treatment with open-label miglustat (100-300 mg three times daily) were enrolled to continue with therapy in an extension study. Data are presented up to month 36. Liver and spleen volumes measured by CT or MRI were scheduled every 6 months. Biochemical and haematological parameters, including chitotriosidase activity (a sensitive marker of Gaucher disease activity) were monitored every 3 months. Safety data were also collected every 3 months. Eighteen of 22 eligible patients at four centres entered the extension phase and 14 of these completed 36 months of treatment with miglustat. After 36 months, there were statistically significant improvements in all major efficacy endpoints. Liver and spleen organ volumes were reduced by 18% and 30%, respectively. In patients whose haemoglobin value had been below 11.5 g/dl at baseline, mean haemoglobin increased progressively from baseline by 0.55 g/dl at month 12 (NS), 1.28 g/dl at month 24 (p =0.007), and 1.30 g/dl at month 36 (p =0.013). The mean platelet count at month 36 increased from baseline by 22 x 10(9)/L. No new cases of peripheral neuropathy occurred since previously reported. Diarrhoea and weight loss, which were frequently reported during the initial 12-month study, decreased in magnitude and prevalence during the second and third years. Patients treated with miglustat for 3 years show significant improvements in organ volumes and haematological parameters. In conclusion, miglustat was increasingly effective over time and showed acceptable tolerability in patients who continued with treatment for 3 years.

Chemical chaperones increase the cellular activity of N370S beta -glucosidase: a therapeutic strategy for Gaucher disease.

Gaucher disease is a lysosomal storage disorder caused by deficient lysosomal beta-glucosidase (beta-Glu) activity. A marked decrease in enzyme activity results in progressive accumulation of the substrate (glucosylceramide) in macrophages, leading to hepatosplenomegaly, anemia, skeletal lesions, and sometimes CNS involvement. Enzyme replacement therapy for Gaucher disease is costly and relatively ineffective for CNS involvement. Chemical chaperones have been shown to stabilize various proteins against misfolding, increasing proper trafficking from the endoplasmic reticulum. We report herein that the addition of subinhibitory concentrations (10 microM) of N-(n-nonyl)deoxynojirimycin (NN-DNJ) to a fibroblast culture medium for 9 days leads to a 2-fold increase in the activity of N370S beta-Glu, the most common mutation causing Gaucher disease. Moreover, the increased activity persists for at least 6 days after the withdrawal of the putative chaperone. The NN-DNJ chaperone also increases WT beta-Glu activity, but not that of L444P, a less prevalent Gaucher disease variant. Incubation of isolated soluble WT enzyme with NN-DNJ reveals that beta-Glu is stabilized against heat denaturation in a dose-dependent fashion. We propose that NN-DNJ chaperones beta-Glu folding at neutral pH, thus allowing the stabilized enzyme to transit from the endoplasmic reticulum to the Golgi, enabling proper trafficking to the lysosome. Clinical data suggest that a modest increase in beta-Glu activity may be sufficient to achieve a therapeutic effect.