Outcome of type III Gaucher disease on enzyme replacement therapy: review of 55 cases

Host Restrictive Factors Are the Emerging Storm Troopers Against Enterovirus: A Mini-Review

Enterovirus infection continues to be a global health problem. The lack of specific drugs and broad-spectrum vaccines means an urgent need to develop effective strategies against enteroviruses. Host restrictive factors are a class of intrinsic host antiviral factors that have been broadly defined and investigated during HIV infections and have great significance for drug development and treatment design. In recent years, the essential role of host restrictive factors in regulating enteroviral infections has been gradually recognized and investigated. An increasing number of studies have shown that host-restrictive factors regulate multiple steps in the life cycle of enteroviruses. This mini-review discusses the restrictive factors against enteroviruses, their antiviral mechanism, and the arms race between them and enteroviruses. We also summarise the pathways that enteroviruses use to impair host antiviral signals. This mini-review characterizes the essential role of host restriction factors in enterovirus infections, which provides ideas and potential targets for antiviral drug design by regulating host restrictive factors. It also reveals potential future research on the interplay between host restrictive factors and enteroviruses.

Enzyme Replacement Therapy for Mucopolysaccharidosis IIID using Recombinant Human α-N-Acetylglucosamine-6-Sulfatase in Neonatal Mice

There is currently no cure or effective treatment available for mucopolysaccharidosis type IIID (MPS IIID, Sanfilippo syndrome type D), a lysosomal storage disorder (LSD) caused by the deficiency of α-N-acetylglucosamine-6-sulfatase (GNS). The clinical symptoms of MPS IIID, like other subtypes of Sanfilippo syndrome, are largely localized to the central nervous system (CNS), and any treatments aiming to ameliorate or reverse the catastrophic and fatal neurologic decline caused by this disease need to be delivered across the blood-brain barrier. Here, we report a proof-of-concept enzyme replacement therapy (ERT) for MPS IIID using recombinant human α-N-acetylglucosamine-6-sulfatase (rhGNS) via intracerebroventricular (ICV) delivery in a neonatal MPS IIID mouse model. We overexpressed and purified rhGNS from CHO cells with a specific activity of 3.9 × 10⁴ units/mg protein and a maximal enzymatic activity at lysosomal pH (pH 5.6), which was stable for over one month at 4 °C in artificial cerebrospinal fluid (CSF). We demonstrated that rhGNS was taken up by MPS IIID patient fibroblasts via the mannose 6-phosphate (M6P) receptor and reduced intracellular glycosaminoglycans to normal levels. The delivery of 5 μg of rhGNS into the lateral cerebral ventricle of neonatal MPS IIID mice resulted in normalization of the enzymatic activity in brain tissues; rhGNS was found to be enriched in lysosomes in MPS IIID-treated mice relative to the control. Furthermore, a single dose of rhGNS was able to reduce the accumulated heparan sulfate and β-hexosaminidase. Our results demonstrate that rhGNS delivered into CSF is a potential therapeutic option for MPS IIID that is worthy of further development.

Gaucher Disease in Bone: From Pathophysiology to Practice

Gaucher disease (GD) is a rare, genetic lysosomal disorder leading to lipid accumulation and dysfunction in multiple organs. Involvement of the skeleton is one of the most prevalent aspects of GD and a major cause of pain, disability, and reduced quality of life. Uniform recommendations for contemporary evaluation and management are needed. To develop practical clinical recommendations, an international group of experienced physicians conducted a comprehensive review of 20 years' of the literature, defining terms according to pathophysiological understanding and pointing out best practice and unmet needs related to the skeletal features of this disorder. Abnormalities of bone modeling, reduced bone density, bone infarction, and plasma cell dyscrasias accompany the displacement of healthy adipocytes in adult marrow. Exposure to excess bioactive glycosphingolipids appears to affect hematopoiesis and the balance of osteoblast and osteoclast numbers and activity. Imbalance between bone formation and breakdown induces disordered trabecular and cortical bone modeling, cortical bone thinning, fragility fractures, and osteolytic lesions. Regular assessment of bone mineral density, marrow infiltration, the axial skeleton and searching for potential malignancy are recommended. MRI is valuable for monitoring skeletal involvement: It provides semiquantitative assessment of marrow infiltration and the degree of bone infarction. When MRI is not available, monitoring of painful acute bone crises and osteonecrosis by plain X-ray has limited value. In adult patients, we recommend DXA of the lumbar spine and left and right hips, with careful protocols designed to exclude focal disease; serial follow-up should be done using the same standardized instrument. Skeletal health may be improved by common measures, including adequate calcium and vitamin D and management of pain and orthopedic complications. Prompt initiation of specific therapy for GD is crucial to optimizing outcomes and preventing irreversible skeletal complications. Investing in safe, clinically useful, and better predictive methods for determining bone integrity and fracture risk remains a need. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Ophthalmic manifestations of Gaucher disease: the most common lysosomal storage disorder

Gaucher disease (GD) results from a deficiency of glucocerebrosidase activity and the subsequent accumulation of the enzyme's metabolites, principally glucosylsphingosine and glucosylceramide. There are three principal forms: Type I, which is the most common, is usually considered non-neuronopathic. Type II, III and IIIc manifest earlier and have neurological sequelae due to markedly reduced enzyme activity. Gaucher's can be associated with ophthalmological sequelae but these have not been systematically reviewed. We therefore performed a comprehensive literature review of all such ophthalmic abnormalities associated with the different types of Gaucher disease. We systematically searched the literature (1950 - present) for functional and structural ocular abnormalities arising in patients with Gaucher disease and found that all subtypes can be associated with ophthalmic abnormalities; these range from recently described intraocular lesions to disease involving the adnexae, peripheral nerves and brain. In summary, Gaucher can affect most parts of the eye. Rarely is it sight-threatening; some but not all manifestations are amenable to treatment, including with enzyme replacement and substrate reduction therapy. Retinal involvement is rare but patients with ocular manifestations should be monitored and treated early to reduce the risk of progression and further complications. As Gaucher disease is also associated with Parkinsons disease and may also confer an increased risk of malignancy (particularly haematological forms and melanoma), any ocular abnormalities should be fully investigated to exclude these potential underlying conditions.

Enzyme immobilized millimeter-sized polyHIPE beads with easy separability and recyclability

Enzyme immobilized reusable millimeter-sized beads were prepared through covalently immobilizing Candida antarctica lipase B onto emulsion-templated porous beads.

Previously unrecognized behavioral phenotype in Gaucher disease type 3

OBJECTIVE

To provide a comprehensive description of abnormal behaviors in patients with Gaucher disease type 3 (GD3) and relate these behaviors to demographic, neurodevelopmental, and neurologic characteristics.

METHODS

Thirty-four Egyptian patients with GD3 (mean age of 7.9 years) were enrolled in the study. They were selected based on parent report and/or physician observation of one or more abnormal behaviors documented in 2 settings and by 2 different individuals and/or by video recording. Behaviors were grouped into 4 categories: Crying/Withdrawal, Impatience/Overactivity, Anger/Aggression, and Repetitive Acts. Baseline and follow-up 6-12 monthly neurologic evaluations included IQ assessment and an EEG. All patients were receiving enzyme replacement therapy (30-60 IU/kg every 2 weeks) and were followed for periods of 3-10 years.

RESULTS

Supranuclear palsy of horizontal gaze, and of both horizontal and vertical gaze, bulbar symptoms, seizures, convergent strabismus, abnormal gait, and neck retroflexion were present in 97.1%, 50%, 55.9%, 29.4%, 29.4%, 20.6%, and 4.4% of patients, respectively. The most abnormal behavioral features were excessive anger (88.2%) and aggression (64.7%), and both were significantly higher in males. Anger/Aggression scores were highly correlated with IQ but not with either EEG/Seizure status or neurologic signs.

CONCLUSIONS

We describe behavioral problems with a unique pattern of excessive anger and aggression in patients with GD3. Defining these components using quantitative behavioral scoring methods holds promise to provide a marker of neurologic disease progression and severity.

CNS-accessible Inhibitor of Glucosylceramide Synthase for Substrate Reduction Therapy of Neuronopathic Gaucher Disease

Gaucher disease (GD) is caused by a deficiency of glucocerebrosidase and the consequent lysosomal accumulation of unmetabolized glycolipid substrates. Enzyme-replacement therapy adequately manages the visceral manifestations of nonneuronopathic type-1 Gaucher patients, but not the brain disease in neuronopathic types 2 and 3 GD. Substrate reduction therapy through inhibition of glucosylceramide synthase (GCS) has also been shown to effectively treat the visceral disease. Here, we evaluated the efficacy of a novel small molecule inhibitor of GCS with central nervous system (CNS) access (Genz-682452) to treat the brain disease. Treatment of the conduritol β epoxide-induced mouse model of neuronopathic GD with Genz-682452 reduced the accumulation of liver and brain glycolipids (>70% and >20% respectively), extent of gliosis, and severity of ataxia. In the genetic 4L;C* mouse model, Genz-682452 reduced the levels of substrate in the brain by >40%, the extent of gliosis, and paresis. Importantly, Genz-682452-treated 4L;C* mice also exhibited an ~30% increase in lifespan. Together, these data indicate that an orally available antagonist of GCS that has CNS access is effective at attenuating several of the neuropathologic and behavioral manifestations associated with mouse models of neuronopathic GD. Therefore, Genz-682452 holds promise as a potential therapeutic approach for patients with type-3 GD.

Long-term follow-up and sudden unexpected death in Gaucher disease type 3 in Egypt

Objective:

To describe the long-term follow-up and distinct phenotype of a large cohort of patients with Gaucher disease type 3 on enzyme replacement therapy (ERT) in Egypt.

Methods:

A prospective cohort study of 78 patients on ERT who were followed for up to 9 years with yearly evaluations that included EEG and cognitive testing.

Results:

Of the patients, 73% were homozygous for the L444P GBA1 mutation; all but 7 were neurologically symptomatic. Supranuclear gaze palsy with variable but stable cognitive function was present in 91% of patients. Convergent strabismus and bulbar dysfunction were noted in 22% and 37%, respectively. Features of oppositional defiant disorder were present in 54% of patients. Twenty-three patients (30%) developed seizures while on ERT for 1–9 years. Of those, 12 patients (15%) died suddenly and unexpectedly at a mean age of 6.7 ± 5.0 years (range 1.5–18). Sudden death was usually associated with a seizure disorder or a terminal seizure, but 7 of 12 patients had a preceding normal EEG. An additional 11% had background slowing or epileptogenic activity on EEG without clinical seizures. There were 3 familial cases of sudden unexpected death.

Conclusions:

Despite having the most common GBA1 genotype known to be associated with neuronopathic Gaucher disease, patients with Gaucher disease type 3 in Egypt have a phenotype and a clinical outcome on ERT that are very different from those observed in other populations. Identifying putative modifying genes of this ethnic group is likely to lead to better therapy for neuronopathic Gaucher disease generally.

Synthesis and biological evaluation of d-gluconhydroximo-1,5-lactam and its oxime-substituted derivatives as pharmacological chaperones for the treatment of Gaucher disease

38 was an efficient pharmacological chaperone for GCase-related cell line N370S, which can effectively promote the activity of the mutant protein by 1.93-fold at 12.5 μM.

Long-term treatment outcomes in Gaucher disease

Following the treatment of the first Gaucher disease patient with enzyme replacement therapy (ERT), it was clear that ERT had the potential to be transformative with dramatic improvements in systemic manifestations of the disease within 2 years. Following over 20 years existence of the International Collaborative Gaucher Group Gaucher Registry and evidence from ∼6000 patients, the long-term effects of therapy have been documented. It has been shown that ERT can result in improvements in all clinical and laboratory parameters of nonneuronopathic disease. However, different aspects of the disease, such as hematologic parameters, organ volumes and bone disease do not necessarily respond to therapy at the same rate or to the same extent, and this has had major implications for disease monitoring and for the establishment of therapeutic goals for ERT. Response may be affected by factors such as the timing of therapy initiation, the presence of irreversible complications such as osteonecrosis, and by enzyme dose. It is also apparent that ERT has no impact on neurological aspects of disease and highlights the need for additional or alternative treatment strategies able to meet the needs of patients with neuronopathic disease.

Long term effects of enzyme replacement therapy in an Italian cohort of type 3 Gaucher patients

BACKGROUND

The chronic neuropathic form of Gaucher disease (GD3) is characterised by hepatosplenomegaly, anaemia, thrombocytopenia, bone alterations and central neurological involvement. Enzyme replacement therapy (ERT) has been demonstrated to be effective in non neuropathic Gaucher disease, but long term results in patients with GD3 are still limited and contrasting. A possible role of genotype in determining the response to ERT has been hypothesised.

PATIENTS AND METHODS

All patients affected by GD3, treated with ERT, and followed-up in 4 different Italian centres (Udine, Catanzaro, Sassari and Florence) were included. Data on clinical conditions, laboratory values, neurological and neuropsychological examinations, radiological and electrophysiological features were collected retrospectively from clinical records.

RESULTS

Ten patients (6 females, 4 males) with four different genotypes (L444P/L444P, L444P/F231I, P159T/unknown, C.115+1G>A/N188S) were identified. They received ERT infusions from 3 to 21years. Haematological parameters and organomegaly improved/normalised in all patients. Three patients showed severe progressive skeletal deformities. 6/10 patients were neurologically asymptomatic when they started ERT for systemic symptoms. During the follow-up, 2/6 developed an important central nervous system disease; 2/6 developed mild central symptoms; and 2/6 did not show any neurological symptom after 5, and 20years of treatment respectively, despite the presence of epileptiform abnormalities at the electroencephalogram. Overall, neurological involvement worsened over time in 6/10 patients, 3 of whom developed progressive myoclonic encephalopathy and died.

CONCLUSIONS

ERT improved the systemic manifestations in patients with GD3, but was not able to counteract the progression of neurological symptoms in the long term.

Outcome of early-treated type III Gaucher disease patients

Recombinant human acid β-glucosidase GBA (rhGBA) infusion is an effective therapy for non-neuropathic (type I) Gaucher disease (GD), but its effect on subacute neuropathic (type III) GD is still controversial. The most common genotype for type III GD is homozygous c.1448T>C (p.L444P) mutation, and in this study, we treated seven such patients starting from an early age (median 2.1 years; range 1-2.9 years). Before the start of treatment, all patients presented hepatosplenomegaly, anemia, and thrombocytopenia, but with no neurological signs. Normalization of hemoglobin levels and platelet numbers was achieved in all patients in one year. However, after a median treatment period of 7.6 years (2.2-12.0 years), two patients developed horizontal gaze palsy, one had seizures, four demonstrated mental retardation, and five showed kyphosis. Moreover, lymphadenopathy in the neck, thorax, or abdomen was observed in four patients. Therefore, the progression of neurological symptoms in these patients probably reflected the neurologic natural history of type III GD. Residual somatic symptoms, including kyphosis and lymphadenopathy, may be more common than what we thought. An additional treatment will be necessary to improve the outcome of type III GD.

Niemann-Pick disease type C or Gaucher's disease type 3? A clinical conundrum

We describe a patient who presented with a neurovisceral syndrome characterised by ataxia, bulbar dysfunction, supranuclear gaze palsy, splenomegaly and foamy histiocytes in the bone marrow. This presentation was suggestive of a lysosomal storage disorder such as Niemann-Pick disease type C or Gaucher's disease type 3. We review the presentation of these disorders, with a focus on the neurological features. In addition, we briefly discuss the disease-modifying therapeutic options which have recently become available.

Glucocerebrosidase inhibitors for the treatment of Gaucher disease

Gaucher disease is a progressive lysosomal storage disorder caused by a deficiency in the activity of β-glucocerebrosidase and is characterized by the accumulation of the glycosphingolipid glucosylceramide in the lysosomes of macrophages that leads to dysfunction in multiple organ system. An emerging strategy for the treatment of Gaucher disease is pharmacological chaperone therapy, based on the use of β-glucocerebrosidase inhibitors that are capable of enhancing residual hydrolytic activity at subinhibitory concentrations. In this article, the most common lysosomal storage disorder, Gaucher disease, is introduced and the current therapeutic strategies based on the use of enzyme inhibitors to ameliorate this disease are discussed, with a focus on the efforts being made toward finding and optimizing novel molecules as pharmacological chaperones for Gaucher disease that offer the promise to remedy this malady.

Proton MR Spectroscopy of the brain in children with neuronopathic Gaucher's disease

OBJECTIVE

To assess the clinical usefulness of proton magnetic resonance spectroscopy ((1)H-MRS) in children with neuronopathic Gaucher's disease (NGD).

METHODS

A prospective study was conducted upon 21 consecutive children with acute (n = 7) and chronic (n = 14) forms of NGD (13 boys, 8 girls; mean age 37 months) and for a control group (n = 15). All patients and controls underwent (1)H-MRS of frontal white matter. The choline/creatine (Ch/Cr) and N-acetyl aspartate (NAA)/Cr ratios were calculated. A modified severity scoring tool (m-SST) of NGD was calculated and genotyping was performed for all patients. Metabolic ratios were correlated with clinical types, m-SST and genotyping.

RESULTS

There was a significant difference in Ch/Cr (P = 0.001) between patients with NGD and the control group. Lipid peak was detected in 15 patients with NGD. Patients with acute NGD revealed higher m-SST (P = 0.001) and Ch/Cr (P = 0.001) compared with the chronic form. Patients with homozygous gene mutation (L444P/L444P) had significantly higher m-SST (P = 0.001) and Ch/Cr (P = 0.013) than those with the heterozygous gene mutation (L444P/other). The Ch/Cr was negatively correlated with m-SST (r = -0.682; P = 0.001) CONCLUSION: (1)H-MRS can be used to detect brain abnormalities in children with NGD and Ch/Cr is well correlated with m-SST and genotyping.

KEY POINTS

• Proton magnetic resonance spectroscopy offers important information in some paediatric neurological conditions. • Significantly different choline/creatine ratios were found between neuronopathic Gaucher's disease and controls. • Lipid peak helps with the diagnosis of neuronopathic Gaucher's disease. • Ch/Cr correlated with the modified severity scoring tool of Gaucher's disease.

Gaucher disease

Gaucher disease is an autosomal recessive condition due to glucocerebrosidase deficiency responsible for the lysosomal accumulation of glucosylceramide, a complex lipid derived from cell membranes, mainly in macrophages. It is due to mutations mostly in the GBA gene, although saposine C deficiency is due to mutations in the PSAP gene. It encompasses an extremely heterogeneous spectrum of clinical involvement from the fetus to adulthood. Splenomegaly, blood cytopenia, and bone involvement are the main manifestations of Gaucher disease, but nervous system degeneration is observed in about 5-10% of patients. The accumulation in neurons of glucosylceramide and its derivative, psychosine, are thought to underlie neuronal dysfunction and death, although Gaucher cells that mostly accumulate such substances are mainly macrophages. Enzyme replacement therapy dramatically improves the outcome of patients because of its extreme efficacy in the treatment of the systemic involvement. However, it has only limited effects on most neurological signs.

Systemic delivery of a glucosylceramide synthase inhibitor reduces CNS substrates and increases lifespan in a mouse model of type 2 Gaucher disease

Neuropathic Gaucher disease (nGD), also known as type 2 or type 3 Gaucher disease, is caused by a deficiency of the enzyme glucocerebrosidase (GC). This deficiency impairs the degradation of glucosylceramide (GluCer) and glucosylsphingosine (GluSph), leading to their accumulation in the brains of patients and mouse models of the disease. These accumulated substrates have been thought to cause the severe neuropathology and early death observed in patients with nGD and mouse models. Substrate accumulation is evident at birth in both nGD mouse models and humans affected with the most severe type of the disease. Current treatment of non-nGD relies on the intravenous delivery of recombinant human glucocerebrosidase to replace the missing enzyme or the administration of glucosylceramide synthase inhibitors to attenuate GluCer production. However, the currently approved drugs that use these mechanisms do not cross the blood brain barrier, and thus are not expected to provide a benefit for the neurological complications in nGD patients. Here we report the successful reduction of substrate accumulation and CNS pathology together with a significant increase in lifespan after systemic administration of a novel glucosylceramide synthase inhibitor to a mouse model of nGD. To our knowledge this is the first compound shown to cross the blood brain barrier and reduce substrates in this animal model while significantly enhancing its lifespan. These results reinforce the concept that systemically administered glucosylceramide synthase inhibitors could hold enhanced therapeutic promise for patients afflicted with neuropathic lysosomal storage diseases.

[Clinical characteristics of the neurological forms of Gaucher's disease]

Gaucher's disease is the most prevalent disease of accumulation of glycosphingolipids. Neurological involvement is used to classify the different types of the disease. Type 1 affects approximately 90% of patients, and visceral manifestations and bone marrow, without affecting the nervous system. Type 2 is considered a severe form of disease with severe nervous system and death within two years. Type 3 is late, slowly progressive neurological symptoms and survival until the third decade. Besides these classical syndromes, the best knowledge of the disease related to the existence of national registries, the increased survival of patients resulting from replacement therapy, and demonstration of the behavior of glucocerebrosidase mutations as a risk factor of neurodegenerative diseases, has expanded the clinical phenotype and altered the traditional classification of the disease.

Four-year follow-up of chronic neuronopathic Gaucher disease in Europeans using a modified severity scoring tool

In 2007, the European Task Force for neuronopathic Gaucher disease (NGD) published a review of 55 patients across four countries. Although some observations were possible, analysis was difficult due to the absence of a systematic way of assessing patients. In response to this, a Severity Scoring Tool (SST) was devised to offer a systematic means of assessing the neurological presentation seen. The SST has been modified (mSST) and is a valid tool for monitoring neurological progression. This review describes disease status and progression of neurological manifestations in a cohort of 39 chronic NGD patients across three European countries over a period of 4 years, using the mSST.

Iminosugar-based inhibitors of glucosylceramide synthase increase brain glycosphingolipids and survival in a mouse model of Sandhoff disease

The neuropathic glycosphingolipidoses are a subgroup of lysosomal storage disorders for which there are no effective therapies. A potential approach is substrate reduction therapy using inhibitors of glucosylceramide synthase (GCS) to decrease the synthesis of glucosylceramide and related glycosphingolipids that accumulate in the lysosomes. Genz-529468, a blood-brain barrier-permeant iminosugar-based GCS inhibitor, was used to evaluate this concept in a mouse model of Sandhoff disease, which accumulates the glycosphingolipid GM2 in the visceral organs and CNS. As expected, oral administration of the drug inhibited hepatic GM2 accumulation. Paradoxically, in the brain, treatment resulted in a slight increase in GM2 levels and a 20-fold increase in glucosylceramide levels. The increase in brain glucosylceramide levels might be due to concurrent inhibition of the non-lysosomal glucosylceramidase, Gba2. Similar results were observed with NB-DNJ, another iminosugar-based GCS inhibitor. Despite these unanticipated increases in glycosphingolipids in the CNS, treatment nevertheless delayed the loss of motor function and coordination and extended the lifespan of the Sandhoff mice. These results suggest that the CNS benefits observed in the Sandhoff mice might not necessarily be due to substrate reduction therapy but rather to off-target effects.

A French experience of type 3 Gaucher disease: Phenotypic diversity and neurological outcome of 10 patients

OBJECTIVE

To describe the clinical presentation of 10 patients with type 3 Gaucher disease and the clinical evolution of nine of them following specific therapy regimes.

METHODS

The follow-up of these 10 patients was between 2 and 15 years. The clinical history was provided by each patient's general practitioner and a final clinical evaluation was made by two different physicians including a neurologist. One patient received no treatment, eight received enzyme replacement therapy (ERT) and one received ERT combined with substrate reduction therapy (SRT, miglustat).

RESULTS

The clinical presentations were heterogeneous and most phenotypes reported for type 3 Gaucher disease were represented. The neurological involvement stabilized or improved in six patients under ERT with a follow-up of 2-15 years. Four of them showed isolated oculomotor signs only that improved or remained unchanged during the follow-up. Of two patients with progressive myoclonic epilepsy, the outcome was clearly unfavorable in one receiving ERT and disputable for the other receiving ERT+SRT. An unfavorable neurological outcome was observed in another patient in whom the ERT dose had been reduced before clinical decline.

CONCLUSION

The stabilization of the clinical course in most patients is noteworthy. Though further evidence is needed from a larger series in order to draw any definite conclusions, our data suggest that ERT may be effective in preventing the evolution of neurological disturbances associated with type 3 Gaucher disease in some patients. However, the clinical course of the two patients with progressive myoclonic epilepsy was not influenced by ERT, as previously reported. In accordance with that reported in the literature, data from our series suggest that the outcome of patients undergoing ERT depends on the type of clinical involvement, treatment onset and dose. Genotype may also be an important factor, with p.L444P/p.L444P possibly indicating a better outcome.

Gaucher disease: clinical profile and therapeutic developments

Gaucher disease is a rare inborn error of glycosphingolipid metabolism due to deficiency of lysosomal acid β-glucocerebrosidase; the condition has totemic significance for the development of orphan drugs. A designer therapy, which harnesses the mannose receptor to complement the functional defect in macrophages, ameliorates the principal clinical manifestations in hematopoietic bone marrow and viscera. While several aspects of Gaucher disease (particularly those affecting the skeleton and brain) are refractory to treatment, enzyme (replacement) therapy has become a pharmaceutical blockbuster. Human β-glucocerebrosidase was originally obtained from placenta and the Genzyme Corporation (Allston, MA) subsequently developed a recombinant product. After purification, the enzyme is modified to reveal terminal mannose residues which facilitate selective uptake of the protein, imiglucerase (Cerezyme^®), in macrophage-rich tissues. The unprecedented success of Cerezyme has attracted fierce competition: two biosimilar agents, velaglucerase-alfa, VPRIV^® (Shire Human Genetic Therapies, Dublin, Ireland) and taliglucerase-alfa (Protalix, Carmiel, Israel), are now approved or in late-phase clinical development as potential ‘niche busters’. Oral treatments have advantages over biological agents for disorders requiring lifelong therapy and additional stratagems which utilize small, orally active molecules have been introduced; these include two chemically distinct compounds which inhibit uridine diphosphate glucose: N-acylsphingosine glucosyltransferase, the first step in the biosynthesis of glucosylceramide – a key molecular target in Gaucher disease and other glycosphingolipidoses. Academic and commercial enterprises in biotechnology have combined strategically to expand the therapeutic repertoire in Gaucher disease. The innovative potential of orphan drug legislation has been realized – with prodigious rewards for companies embracing its humanitarian precepts. In the era before enzyme therapy, bone marrow transplantation was shown to correct systemic disease in Gaucher patients by supplying a source of competent donor macrophages. As a radical advance on cell- or protein-replacement techniques, contemporary methods for transferring genes to autologous hematopoietic stem cells, and to the brain, merit further exploration. At present, the inflated pharmaceutical niche of Gaucher disease appears to be resilient, but if the remaining unmet needs of patients are to be convincingly addressed and commercial development sustained, courageous scientific investment and clinical experimentation will be needed.

Intracerebroventricular delivery of glucocerebrosidase reduces substrates and increases lifespan in a mouse model of neuronopathic Gaucher disease

Gaucher disease is caused by a deficit in the enzyme glucocerebrosidase. As a consequence, degradation of the glycolipids glucosylceramide (GluCer) and glucosylsphingosine (GluSph) is impaired, and their subsequent buildup can lead to significant pathology and early death. Type 1 Gaucher patients can be treated successfully with intravenous replacement enzyme, but this enzyme does not reach the CNS and thus does not ameliorate the neurological involvement in types 2 and 3 Gaucher disease. As one potential approach to treating these latter patients, we have evaluated intracerebroventricular (ICV) administration of recombinant human glucocerebrosidase (rhGC) in a mouse model of neuronopathic Gaucher disease. ICV administration resulted in enzyme distribution throughout the brain and alleviated neuropathology in multiple brain regions of this mouse model. Treatment also resulted in dose-dependent decreases in GluCer and GluSph and significantly extended survival. To evaluate the potential of continuous enzyme delivery, a group of animals was treated ICV with an adeno-associated viral vector encoding hGC and resulted in a further extension of survival. These data suggest that ICV administration of rhGC may represent a potential therapeutic approach for type 2/3 Gaucher patients. Preclinical evaluation in larger animals will be needed to ascertain the translatability of this approach to the clinic.

Therapy for lysosomal storage disorders

In the last years, much progress has been achieved in the field of lysosomal storage disorders. In the past, no specific treatment was available for the affected patients; management mainly consisted of supportive care and treatment of complications. As orphan drug regulations, however, encouraged development of drugs for these disorders by granting marketing exclusivity for 10 years and other commercial benefits, enzyme replacement therapy became available for lysosomal storage disorders, such as Gaucher disease, Fabry disease, mucopolysaccharidoses type I, II, and VI, and Pompe disease. This review will summarize the efficacy and clinical status of hematopoietic stem cell transplantation, enzyme replacement, and substrate deprivation therapy, and describe new therapeutic perspectives currently under preclinical investigations such as chaperone-mediated therapy, stop-codon read-through therapy, and gene therapy.

Management of neuronopathic Gaucher disease: revised recommendations

The original guidelines drawn up for the management of the neuronopathic forms of Gaucher disease were felt to be in need of revision; in particular, the role of high-dose enzyme replacement therapy (120 IU/kg of body weight every 2 weeks) in stabilizing neurological disease. The existing published evidence was analysed; it was concluded that it did not support the role of high-dose ERT, although this might be required to treat severe visceral disease.

Review of the safety and efficacy of imiglucerase treatment of Gaucher disease

Most patients who suffer from symptomatic Gaucher disease will benefit from enzyme replacement therapy (ERT) with imiglucerase. The safety profile is excellent, only a small percentage of those exposed developing antibodies; similarly, very few patients require pre-medication for allergic reactions. Within 3 to 5 years of imiglucerase therapy, best documented at doses of 30 to 60 units/kg/infusion, hepatosplenomegaly can be expected to be reduced so that the liver volume will be maintained at 1 to 1.5 times normal (30% to 40% reduction from advent of ERT) and spleen volume to </= 2 to 8 times normal (50% to 60% reduction from advent of ERT). For anemic and thrombocytopenic patients, with 2 to 5 years of imiglucerase, hemoglobin levels are expected to be >/= 11 g/dL for women and children and >/= 12 g/dL for men; and platelet counts in patients with an intact spleen, depending on the baseline value, should approximately be doubled. Bone crises and bone pain but not irreversible skeletal damage will improve in most patients. Nonetheless, some features and some symptomatic patients apparently do not respond equally well and/or perhaps inadequately. The benefit for patients with the neuronopathic forms is primarily in improved visceral and hematological signs and symptoms. There are still several unresolved issues, the high per-unit cost being an important one, which have spurred the development of biosimilar enzymes as well as chaperone therapies currently in clinical trials.

Review of the safety and efficacy of imiglucerase treatment of Gaucher disease

Most patients who suffer from symptomatic Gaucher disease will benefit from enzyme replacement therapy (ERT) with imiglucerase. The safety profile is excellent, only a small percentage of those exposed developing antibodies; similarly, very few patients require pre-medication for allergic reactions. Within 3 to 5 years of imiglucerase therapy, best documented at doses of 30 to 60 units/kg/infusion, hepatosplenomegaly can be expected to be reduced so that the liver volume will be maintained at 1 to 1.5 times normal (30% to 40% reduction from advent of ERT) and spleen volume to </= 2 to 8 times normal (50% to 60% reduction from advent of ERT). For anemic and thrombocytopenic patients, with 2 to 5 years of imiglucerase, hemoglobin levels are expected to be >/= 11 g/dL for women and children and >/= 12 g/dL for men; and platelet counts in patients with an intact spleen, depending on the baseline value, should approximately be doubled. Bone crises and bone pain but not irreversible skeletal damage will improve in most patients. Nonetheless, some features and some symptomatic patients apparently do not respond equally well and/or perhaps inadequately. The benefit for patients with the neuronopathic forms is primarily in improved visceral and hematological signs and symptoms. There are still several unresolved issues, the high per-unit cost being an important one, which have spurred the development of biosimilar enzymes as well as chaperone therapies currently in clinical trials.

Clinical and genetic study of Japanese patients with type 3 Gaucher disease

Information on the phenotypic variations seen in patients with type 3 (chronic neuronopathic) Gaucher disease (GD) is still limited compared with type 1 GD. We retrospectively investigated the clinical features of 42 Japanese patients with type 3 GD. The 42 patients classified as type 3 fell into two groups: those diagnosed as having type 3 GD at diagnosis (group A; n = 24) and those thought to have type 1 at diagnosis but who later developed neurological symptoms (group B; n = 18). The genotype of group A patients varied widely; however, L444P/L444P and L444P/F213I genotypes accounted for 83% in group B. All the patients who did not receive enzyme replacement with alglucerase or imiglucerase (4 in group A, 2 in group B) died. Nineteen patients received enzyme replacement in group A; however, 7 of these died despite the therapy. On the other hand, 14 patients received enzyme replacement alone in group B and 13 of them survived. Among the ERT-treated patients who survived, only one of 12 in group A and 12 out of 13 in group B can walk unaided. In conclusion, some Japanese GD patients who are thought to have type 1 at diagnosis develop neurological symptoms during their clinical course, and careful observation is essential for patients with characteristic genotypes. Moreover, enzyme replacement alone might not have a sufficient effect on the early onset neurological symptoms in type 3 patients. A different treatment strategy is needed to improve the prognosis of these patients.

Substrate-reduction therapy with miglustat for glycosphingolipid storage disorders affecting the brain

A number of lysosomal storage disorders (LSDs) are characterized by glycosphingolipid (GSL) storage in the brain. Although enzyme-replacement therapy is an effective treatment for the visceral manifestations of some of these disorders, this approach has not, to date, been useful in CNS disease. Substrate reduction therapy (SRT) is an alternative approach to treatment in which the aim is to reduce the rate of synthesis of GSL to a level where the residual enzyme activity in the affected cell can prevent lysosomal storage. Miglustat, an iminosugar, is an inhibitor of the first step of GSL synthesis and has been used successfully for SRT in Gaucher disease. Miglustat is a small molecule and can enter the brain. It has been shown to delay symptom onset and prolong life in a number of animal models of GSL LSDs. This review describes the current progress in the clinical development of SRT with miglustat for these disorders.

Enzyme replacement therapy for Gaucher disease

Gaucher disease is the most common lysosomal storage disease, and the first lysosomal storage disease for which a specific therapy has been developed. Enzyme replacement therapy, with glucocerebrosidase purified from human placentae, was introduced in 1991. Recombinant human glucocerebrosidase, produced by Chinese hamster ovary cells in tissue culture, became available in 1994 and has replaced the placenta-derived product. These therapies have revolutionized the care of patients with type 1 Gaucher disease, reversing many of the pathological consequences of this disease, and preventing further progression. Furthermore, they have served as a model for the treatment of other lysosomal storage diseases and inborn errors of metabolism.

Potential efficacy of enzyme replacement and substrate reduction therapy in three siblings with Gaucher disease type III

We report three siblings with Gaucher disease type III, born between 1992 and 2004. During this period, new developments resulted in different potential therapies, changing clinical practice. The two eldest siblings received enzyme replacement therapy (ERT) from the age of 24 and 5 months respectively, later followed by an increase in dosage. ERT was combined with substrate reduction therapy (SRT) from the ages of 12 and 8 years, respectively. In the youngest sibling the combination of high-dose ERT and SRT was given from the age of 5 months. The two eldest siblings showed significant neurological impairment from the age of 1.5 years, starting with a convergent strabismus and partial oculomotor apraxia, followed by cognitive decline and an abnormal EEG and BAER. In contrast, the neurological development in the youngest sibling is almost completely normal. At the age of 3 years, cognitive development, EEG and BAER are all normal. Disturbed saccadic eye movements, which were already present at the start of therapy, remained stable. In addition to the clinical efficacy, we report on the biochemical response to therapy. Based on our results, the combination of high-dose ERT and SRT should be considered as a possible therapeutic approach for GD III, especially if started at a young age. Further follow-up studies are necessary to explore the long-term therapeutic effects.