Establishment of the Effectiveness of Early Versus Late Stem Cell Gene Therapy in Mucopolysaccharidosis II for Treating Central Versus Peripheral Disease.

Mucopolysaccharidosis type II (MPSII) is a rare pediatric X-linked lysosomal storage disease, caused by heterogeneous mutations in the iduronate-2-sulfatase (IDS) gene, which result in accumulation of heparan sulfate (HS) and dermatan sulfate within cells. This leads to severe skeletal abnormalities, hepatosplenomegaly, and cognitive deterioration. The progressive nature of the disease is a huge obstacle to achieve full neurological correction. Although current therapies can only treat somatic symptoms, a lentivirus-based hematopoietic stem cell gene therapy (HSCGT) approach has recently achieved improved central nervous system (CNS) neuropathology in the MPSII mouse model following transplant at 2 months of age. In this study, we evaluate neuropathology progression in 2-, 4- and 9-month-old MPSII mice, and using the same HSCGT strategy, we investigated somatic and neurological disease attenuation following treatment at 4 months of age. Our results showed gradual accumulation of HS between 2 and 4 months of age, but full manifestation of microgliosis/astrogliosis as early as 2 months. Late HSCGT fully reversed the somatic symptoms, thus achieving the same degree of peripheral correction as early therapy. However, late treatment resulted in slightly decreased efficacy in the CNS, with poorer brain enzymatic activity, together with reduced normalization of HS oversulfation. Overall, our findings confirm significant lysosomal burden and neuropathology in 2-month-old MPSII mice. Peripheral disease is readily reversible by LV.IDS-HSCGT regardless of age of transplant, suggesting a viable treatment for somatic disease. However, in the brain, higher IDS enzyme levels are achievable with early HSCGT treatment, and later transplant seems to be less effective, supporting the view that the earlier patients are diagnosed and treated, the better the therapy outcome.

Multifaceted Approach for Quantification and Enzymatic Activity of Iduronate-2-Sulfatase to Support Developing Gene Therapy for Hunter Syndrome.

Mucopolysaccharidosis type II, commonly called Hunter syndrome, is a rare X-linked recessive disease caused by the deficiency of the lysosomal enzyme iduronate-2-sulphatase (I2S). A deficiency of I2S causes an abnormal glycosaminoglycans accumulation in the body's cells. Although enzyme replacement therapy is the standard therapy, adeno-associated viruses (AAV)-based gene therapy could provide a single-dose solution to achieve a prolonged and constant enzyme level to improve patient's quality of life. Currently, there is no integrated regulatory guidance to describe the bioanalytical assay strategy to support gene therapy products. Herein, we describe the streamlined strategy to validate/qualify the transgene protein and its enzymatic activity assays. The method validation for the I2S quantification in serum and method qualification in tissues was performed to support the mouse GLP toxicological study. Standard curves for I2S quantification ranged from 2.00 to 50.0 µg/mL in serum and 6.25 to 400 ng/mL in the surrogate matrix. Acceptable precision, accuracy, and parallelism in the tissues were demonstrated. To assess the function of the transgene protein, fit-for-purpose method qualification for the I2S enzyme activity in serum was performed. The observed data indicated that the enzymatic activity in serum increased dose-dependently in the lower I2S concentration range. The highest I2S transgene protein was observed in the liver among tissue measured, and its expression level was maintained up to 91 days after the administration of rAAV8 with a codon-optimized human I2S. In conclusion, the multifaceted bioanalytical method for I2S and its enzymatic activity were established to assess gene therapy products in Hunter syndrome.

Current and Future Treatment of Mucopolysaccharidosis (MPS) Type II: Is Brain-Targeted Stem Cell Gene Therapy the Solution for This Devastating Disorder?

Mucopolysaccharidosis type II (Hunter Syndrome) is a rare, x-linked recessive, progressive, multi-system, lysosomal storage disease caused by the deficiency of iduronate-2-sulfatase (IDS), which leads to the pathological storage of glycosaminoglycans in nearly all cell types, tissues and organs. The condition is clinically heterogeneous, and most patients present with a progressive, multi-system disease in their early years. This article outlines the pathology of the disorder and current treatment strategies, including a detailed review of haematopoietic stem cell transplant outcomes for MPSII. We then discuss haematopoietic stem cell gene therapy and how this can be employed for treatment of the disorder. We consider how preclinical innovations, including novel brain-targeted techniques, can be incorporated into stem cell gene therapy approaches to mitigate the neuropathological consequences of the condition.

Therapeutic Options for Mucopolysaccharidosis II (Hunter Disease).

BACKGROUND: Mucopolysaccharidosis type II (Hunter syndrome, or MPS II) is an X-linked lysosomal disorder caused by the deficiency of iduronate-2-sulfatase, which leads to the accumulation of glycosaminoglycans (GAGs) in a variety of tissues, resulting in a multisystemic disease that can also impair the central nervous system (CNS). OBJECTIVE: This review focuses on providing the latest information and expert opinion about the therapies available and under development for MPS II. METHODS: We have comprehensively revised the latest studies about hematopoietic stem cell transplantation (HSCT), enzyme replacement therapy (ERT - intravenous, intrathecal, intracerebroventricular, and intravenous with fusion proteins), small molecules, gene therapy/genome editing, and supportive management. RESULTS AND DISCUSSION: Intravenous ERT is a well-established specific therapy, which ameliorates the somatic features but not the CNS manifestations. Intrathecal or intracerebroventricular ERT and intravenous ERT with fusion proteins, presently under development, seem to be able to reduce the levels of GAGs in the CNS and have the potential of reducing the impact of the neurological burden of the disease. Gene therapy and/or genome editing have shown promising results in preclinical studies, bringing hope for a "one-time therapy" soon. Results with HSCT in MPS II are controversial, and small molecules could potentially address some disease manifestations. In addition to the specific therapeutic options, supportive care plays a major role in the management of these patients. CONCLUSION: At this time, the treatment of individuals with MPS II is mainly based on intravenous ERT, whereas HSCT can be a potential alternative in specific cases. In the coming years, several new therapy options that target the neurological phenotype of MPS II should be available.

Oxidative and nitrative stress and pro-inflammatory cytokines in Mucopolysaccharidosis type II patients: effect of long-term enzyme replacement therapy and relation with glycosaminoglycan accumulation.

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disease caused by a deficient activity of iduronate-2-sulfatase, leading to abnormal accumulation of glycosaminoglycans (GAG). The main treatment for MPS II is enzyme replacement therapy (ERT). Previous studies described potential benefits of six months of ERT against oxidative stress in patients. Thus, the aim of this study was to investigate oxidative, nitrative and inflammatory biomarkers in MPS II patients submitted to long term ERT. It were analyzed urine and blood samples from patients on ERT (mean time: 5.2years) and healthy controls. Patients presented increased levels of lipid peroxidation, assessed by urinary 15-F2t-isoprostane and plasmatic thiobarbituric acid-reactive substances. Concerning to protein damage, urinary di-tyrosine (di-Tyr) was increased in patients; however, sulfhydryl and carbonyl groups in plasma were not altered. It were also verified increased levels of urinary nitrate+nitrite and plasmatic nitric oxide (NO) in MPS II patients. Pro-inflammatory cytokines IL-1ß and TNF-α were increased in treated patients. GAG levels were correlated to di-Tyr and nitrate+nitrite. Furthermore, IL-1ß was positively correlated with TNF-α and NO. Contrastingly, we did not observed alterations in erythrocyte superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities, in reduced glutathione content and in the plasmatic antioxidant capacity. Although some parameters were still altered in MPS II patients, these results may suggest a protective role of long-term ERT against oxidative stress, especially upon oxidative damage to protein and enzymatic and non-enzymatic defenses. Moreover, the redox imbalance observed in treated patients seems to be GAG- and pro-inflammatory cytokine-related.

Protocolo de evaluación rápida de seguridad y efectividad del uso de Idursulfasa en el tratamiento de pacientes con síndrome de Hunter / Protocol of rapid evaluation of safety and effectiveness of the use of Idursulfase in the treatment of patients with Hunter syndrome

El Síndrome de Hunter o Mucopolisacaridosis tipo II (MPSII) es una enfermedad de almacenamiento lisosomal ocasionada por la deficiencia de la enzima iduronato 2 sulfatasa, su incidencia se calcula en aproximadamente 1 por cada 132 000 recién nacidos vivos varones de acuerdo al reporte de algunos estudios europeos, esta enfermedad es una entidad progresiva, incapacitante y con daños irreversibles. Las personas que padecen la forma de aparición temprana (severa) generalmente viven durante 10 a 20 años, mientras que las personas con la forma de aparición tardía (leve) viven de 20 a 60 años. El Fondo Intangible Solidario de Salud solicita la evaluación de la tecnología sanitaria idursulfasa como tratamiento síndrome de Hunter, la cual a su vez fue solicitada Instituto Nacional de Salud del Niño, a raíz de la aparición de un caso. Luego de una primera revisión, se determina que la tecnología idursulfasa, comercializada en el Perú como Elaprase 2 mg/mL, supera la tolerancia al riesgo para evaluación de tecnologías sanitarias en el Seguro Integral de Salud, por lo se consideró sea evaluada por el área de Evaluación de Tecnologías Sanitarias en el SIS Central.(AU)

Mucopolysaccharidosis type II, Hunter's syndrome.

Hunter syndrome is caused by deficiency of the lysososmal enzyme iduronate-2-sulphatase that cleaves O-linked sulphate moieties from dermatan sulphate and heparan sulphate and leads to accumulation of GAGs. The disease is a X-linked condition affecting males and rarely females, clinically divided into severe (2/3) and attenuated types. Children with severe form, diagnosed at 12-36 months, have coarse facial feature, short stature, joint stiffness, short neck, broad chest, large head circumference, watery diarrhea, skeletal changes, progressive and profound mental retardation, retinal degeneration' hearing loss, cardiomyopathy, valvular involvement, with progressive thickening and stiffening of the valve leaflets leading to mitral and aortic regurgitation and stenosis . Recurrent and prolonged rhinitis with persistent nasal discharge are the first symptoms of airway disease that manifests itself as noisy breathing and later sleep apnea. Some patients develop ivory-colored skin lesions on the upper back and sides of the upper arms, pathogenomic of Hunter syndrome. The scalp hair becomes coarse, straight and bristly. Inguinal and umbilical hernias occur caused by the disturbed structure of connective tissue and increased liver and spleen volume. Patients with attenuated form have normal intelligence and a milder phenotype. Physical features diagnosed later are similar but less pronounced but progress to severe disease. Sceening is by quantitative assessment of urinary GAGs excretion. Qualitative assessment of GAG by electrophoresis can distinguish the type of mucopolysaccharidosis. Definitive diagnosis is based on enzyme activity assay in leukocytes, fibroblasts or plasma. Molecular testing is recommended mainly for genetic counseling and carrier detection. Limited experience of Haematopoietic stem cell therapy in MPS II showed progressive neurodegeneration. Recombinant 125 Idursulfase, is indicated for long-term treatment. The response appears to depend on the severity of the disease and the age treatment is started, Improvements in a composite endpoint comprising: change in walking distance percentage of predicted forced vital capacity (%FVC) ,decrease in liver and spleen volume and urinary GAG levels were encouraging. Current research is focused on pharmacological chaperones, gene therapy and substrate reduction therapy and therapies that, unlike Idursulfase, do cross the blood-brain barrier.

Clinical efficacy of enzyme replacement therapy in paediatric Hunter patients, an independent study of 3.5 years.

BACKGROUND: Hunter Syndrome is an X-linked lysosomal storage disorder due to the deficit of iduronate 2-sulfatase, an enzyme catalysing the degradation of the glycosaminoglycans (GAG) dermatan- and heparan-sulfate. Treatment of the disease is mainly performed by Enzyme Replacement Therapy (ERT) with idursulfase, in use since 2006. Clinical efficacy of ERT has been monitored mainly by the Hunter Outcome Survey (HOS) while very few independent studies have been so far conducted. The present study is a 3.5-years independent follow-up of 27 Hunter patients, starting ERT between 1.6 and 27 years of age, with the primary aim to evaluate efficacy of the therapy started at an early age (<12 years). METHODS: In this study, we evaluated: urinary GAG content, hepato/splenomegaly, heart valvulopathies, otorinolaryngological symptoms, joint range of motion, growth, distance covered in the 6-minute walk test, neurological involvement. For data analysis, the 27 patients were divided into three groups according to the age at start of ERT: ≤5 years, >5 and ≤ 12 years and > 12 years. Patients were analysed both as 3 separate groups and also as one group; in addition, the 20 patients who started ERT up to 12 years of age were analysed as one group. Finally, patients presenting a "severe" phenotype were compared with "attenuated" ones. RESULTS: Data analysis revealed a statistically significant reduction of the urinary GAG in patients ≤5 years and ≤ 12 years and of the hepatomegaly in the group aged >5 and ≤ 12 years. Although other clinical signs improved in some of the patients monitored, statistical analysis of their variation did not reveal any significant changes following enzyme administration. The evaluation of ERT efficacy in relation to the severity of the disease evidenced slightly higher improvements as for hepatomegaly, splenomegaly, otological disorders and adenotonsillar hypertrophy in severe vs attenuated patients. CONCLUSIONS: Although the present protocol of idursulfase administration may result efficacious in delaying the MPS II somatic disease progression at some extent, in this study we observed that several signs and symptoms did not improve during the therapy. Therefore, a strict monitoring of the efficacy obtained in the patients under ERT is becoming mandatory for clinical, ethical and economic reasons.

Early initiation of enzyme replacement therapy for the mucopolysaccharidoses.

The mucopolysaccharidoses (MPS), a group of rare genetic disorders caused by defects in glycosaminoglycan (GAG) catabolism, are progressive, multi-systemic diseases with a high burden of morbidity. Enzyme replacement therapy (ERT) is available for MPS I, II, and VI, and may improve walking ability, endurance, and pulmonary function as evidenced by data from pivotal trials and extension studies. Despite these demonstrable benefits, cardiac valve disease, joint disease, and skeletal disease, all of which cause significant morbidity, do not generally improve with ERT if pathological changes are already established. Airway disease improves, but usually does not normalize. These limitations can be well understood by considering the varied functions of GAG in the body. Disruption of GAG catabolism has far-reaching effects due to the triggering of secondary pathogenic cascades. It appears that many of the consequences of these secondary pathogenic events, while they may improve on treatment, cannot be fully corrected even with long-term exposure to enzyme, thereby supporting the treatment of patients with MPS before the onset of clinical disease. This review examines the data from clinical trials and other studies in human patients to explore the limits of ERT as currently used, then discusses the pathophysiology, fetal tissue studies, animal studies, and sibling reports to explore the question of how early to treat an MPS patient with a firm diagnosis. The review is followed by an expert opinion on the rationale for and the benefits of early treatment.

Eficácia e segurança da terapia com idursulfase em pacientes com mucopolissacaridose tipo II, com e sem comparação com placebo: revisão sistemática e metanálise / Efficacy and safety of idursulfase therapy in patients with mucopolysaccharidosis type II with and without comparison to placebo: systematic review and meta-analysis / Eficacia y seguridad del tratamiento con idursulfasa en pacientes con mucopolisacaridosis tipo II con y sin comparación con el placebo: revisión sistemática y metaanálisis

A mucopolissacaridose tipo II (MPS II) é uma doença genética de amplo espectro clínico, caracterizada por deficiência da enzima iduronato-2sulfatase. Revisão sistemática avaliou a eficácia e segurança da terapia de reposição enzimática (TRE) com idursulfase (IDS) na MPS II. As bases de dados PubMed/MEDLINE, Embase, LILACS e Biblioteca Cochrane foram pesquisados até 30 de novembro de 2012. Apenas cinco estudos preencheram os critérios de inclusão (ensaios clínicos randomizados - ECRs, ECRs abertos ou séries de caso prospectivas, incluindo cinco ou mais pacientes e avaliando desfechos relevantes). Metanálise foi realizada para capacidade vital forçada (CVF; valores absolutos e em %) e para a distância percorrida no teste da caminhada dos seis minutos, com mudanças significativas em ambas as variáveis; também foi encontrado risco aumentado de reações leves relacionadas à infusão e de desenvolvimento de anticorpos IgG à IDS. Em face dos dados apresentados neste estudo, conclui-se que a TRE com IDS é segura e tem benefício potencial em MPS II, mas estudos adicionais são necessários.

Mucopolysaccharidosis type II (MPS II) is a genetic disease of broad clinical spectrum, characterized by a deficiency of the enzyme iduronate2-sulfatase. The aim of this study was to assess whether enzyme replacement therapy (ERT) with idursulfase (IDS) for MPS II is effective and safe. PubMed/MEDLINE, Embase, LILACS, and Cochrane Library were searched until November 30, 2012. Only five articles met the inclusion criteria (randomized controlled trials - RCTs, or open-label trials/prospective case series including > 5 patients and evaluating relevant outcomes). A meta-analysis was performed for forced vital capacity (FVC; absolute and %) and for distance walked on the 6-minute walking test (6MWT). There was a statistically significant increase, but not clinically relevant, in both variables; an increased risk for development of mild infusion-related reactions and IgG antibodies to IDS were also found. The data suggest that ERT with IDS is safe and has a potential benefit for MPS II patients, but further studies are required.

La mucopolisacaridosis tipo II (MPS II) es una enfermedad genética de amplio espectro clínico, caracterizada por una deficiencia de la enzima iduronato-2-sulfatasa. El objetivo fue evaluar la seguridad y eficacia de la Terapia de Reemplazo Enzimático (TRE) con idursulfasa (IDS) en la MPS II. En las bases PubMed/MEDLINE, EMBASE, LILACS y Cochrane Library se inició la búsqueda hasta el 30 de noviembre de 2012. Sólo cinco estudios cumplieron los criterios de inclusión (ensayos controlados aleatorios -ECA, o ECA abiertos o series de casos prospectivo incluyendo > 5 pacientes y evaluación de los resultados pertinentes). El metaanálisis se realizó para la capacidad vital forzada (FVC; absoluta y %) y la distancia caminada en 6 minutos, con cambios significativos en ambas variables; el riesgo también se encuentra aumentado por reacciones leves y anticuerpos IgG, relacionados con la infusión con IDS. El TRE con IDS es seguro y tiene un beneficio potencial en la MPS II, pero se necesitan estudios adicionales.

Enzyme replacement therapy (ERT) procedure for mucopolysaccharidosis type II (MPS II) by intraventricular administration (IVA) in murine MPS II.

Mucopolysaccharidosis type II (MPS II), or Hunter syndrome, is a lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS) and is characterized by the accumulation of glycosaminoglycans (GAGs). MPS II has been treated by hematopoietic stem cell therapy (HSCT)/enzyme replacement therapy (ERT), but its effectiveness in the central nervous system (CNS) is limited because of poor enzyme uptake across the blood-brain barrier (BBB). To increase the efficacy of ERT in the brain, we tested an intraventricular ERT procedure consisting of repeated administrations of IDS (20 µg/mouse/3 weeks) in IDS-knockout, MPS II model mice. The IDS enzyme activity and the accumulation of total GAGs were measured in mouse brains. The IDS activity was significantly increased, and the accumulation of total GAGs was decreased in the MPS II mouse brains treated with multiple administrations of IDS via intraventricular ERT. Additionally, a high level of IDS enzyme activity was appreciated in other MPS II mouse tissues, such as the liver, spleen, testis and others. A Y-maze was used to test learning and memory after repeated intraventricular ERT with IDS. The IDS-treated mouse groups recovered the capacity for short-term memory and activity. Although large and small vacuoles were found at the margin of the cerebellar Purkinje cells in the disease-control mice, these vacuoles disappeared upon treated with IDS. Loss of vacuoles was also observed in other tissues (liver, kidney and testis). These results demonstrate the possible efficacy of an ERT procedure with intraventricular administration of IDS for the treatment of MPS II.

Mucopolysaccharidosis type II: European recommendations for the diagnosis and multidisciplinary management of a rare disease.

UNLABELLED: Mucopolysaccharidosis type II (MPS II) is a rare, life-limiting, X-linked recessive disease characterised by deficiency of the lysosomal enzyme iduronate-2-sulfatase. Consequent accumulation of glycosaminoglycans leads to pathological changes in multiple body systems. Age at onset, signs and symptoms, and disease progression are heterogeneous, and patients may present with many different manifestations to a wide range of specialists. Expertise in diagnosing and managing MPS II varies widely between countries, and substantial delays between disease onset and diagnosis can occur. In recent years, disease-specific treatments such as enzyme replacement therapy and stem cell transplantation have helped to address the underlying enzyme deficiency in patients with MPS II. However, the multisystem nature of this disorder and the irreversibility of some manifestations mean that most patients require substantial medical support from many different specialists, even if they are receiving treatment. This article presents an overview of how to recognise, diagnose, and care for patients with MPS II. Particular focus is given to the multidisciplinary nature of patient management, which requires input from paediatricians, specialist nurses, otorhinolaryngologists, orthopaedic surgeons, ophthalmologists, cardiologists, pneumologists, anaesthesiologists, neurologists, physiotherapists, occupational therapists, speech therapists, psychologists, social workers, homecare companies and patient societies. TAKE-HOME MESSAGE: Expertise in recognising and treating patients with MPS II varies widely between countries. This article presents pan-European recommendations for the diagnosis and management of this life-limiting disease.

Therapy for the mucopolysaccharidoses.

Better understanding of disease pathophysiology, improved supportive care and availability of disease-specific treatments for some of the mucopolysaccharidosis (MPS) disorders have greatly improved the outlook for patients with MPS disorders. Optimal management of these multisystemic disorders involves a multidisciplinary team and regular, comprehensive follow-up. Enzyme replacement therapy (ERT) is now available for MPS I (Hurler, Hurler-Scheie and Scheie syndromes) (laronidase), MPS II (Hunter syndrome) (idursulfase) and MPS VI Maroteaux-Lamy (galsulfase), and is in development for MPS IV (Morquio syndrome) and MPS VII (Sly syndrome). Benefits of ERT can include improved walking ability, improved respiration and enhanced quality of life. Haematopoietic stem cell transplantation (HSCT) can preserve cognition and prolong survival in very young children with the most severe form of MPS I, and is under investigation for several other MPS disorders. Better tissue matching techniques, improved graft-vs-host prophylaxis and more targeted conditioning regimens have improved morbidity and mortality associated with HSCT.

Hunter syndrome in an 11-year old girl on enzyme replacement therapy with idursulfase: brain magnetic resonance imaging features and evolution.

Mucopolysaccharidosis type II (MPS-II, Hunter disease) is a X-linked recessive disorder. Affected females are extremely rare, mostly due to skewed X chromosome inactivation. A few papers outline MPS-II brain magnetic resonance imaging (MRI) "gestalt" in males, but neuroradiological reports on females are still lacking. We present an 11-year-old girl affected by the severe form of MPS-II who was followed up over a time span of 8 years, focusing on clinical and brain MRI evolution. In the last 2.5 years, the patient has been treated with enzyme replacement therapy (ERT) with idursulfase (Elaprase™, Shire Human Genetic Therapies AB, Sweden). On brain and cervical MRI examination, abnormalities in our patient did not differ from those detected in male patients: J-shaped pituitary sella, enlargement of perivascular spaces, brain atrophy, mild T2-hyperintensity in the paratrigonal white matter, diffuse platyspondylia, and mild odontoid dysplasia with odontoid cup. Brain atrophy progressed despite ERT introduction, whereas perivascular space enlargement did not change significantly before and after ERT. Cognitive impairment worsened independently from the course of white matter abnormality. Despite a profound knowledge of genetic and biochemical aspects in MPS-II, neuroradiology is still poorly characterized, especially in female patients. Spinal and brain involvement and its natural course and evolution after ERT introduction still need to be clarified.

[Enzyme replacement therapy of lysosomal storage diseases]. / Thérapies enzymatiques substitutives des maladies lysosomales.

Extraction and purification of an acid ß-glucosidase from human placenta (alglucerase) for the treatment of Gaucher disease, replaced a few years later by a recombinant enzyme (imiglucérase, Cerezyme(®)), has paved the way to the development of enzyme replacement therapies (ERT) for the treatment of lysosomal storage diseases (LSD) among which Fabry disease for which the long-term efficacy of the two currently available preparations (agalsidase alfa, Replagal(®) and Fabrazyme(®)) is still being investigated. Mucopolysaccharidosis (MPS) type I (Hurler and Scheie diseases), II (Hunter syndrome) and VI (Maroteaux-Lamy disease) also benefit from ERT using laronidase (Aldurazyme(®)), idursulfase (Elaprase(®)) and galsulfase (Naglazyme(®)), respectively. ERT reduces the hepatosplenomegaly and improves the physical and respiratory capacities of MPS patients with a globally acceptable safety profile although the possibility of infusion-associated should always be kept in mind. Alglucosidase alpha (Myozyme(®)) improves the cardiomyopathy and life expectancy of infants suffering from Pompe disease and is under evaluation for the treatment of the juvenile and adult forms of the disease. CNS involvement remains a major challenge for many LSD and innovative research and approaches are needed to address the fact that recombinant enzymes do not cross the blood-brain barrier and therefore are not expected to lead to any improvement in CNS damages, except if alternative routes such as intrathecal administration would be developed. Molecular chaperones (e.g. migalastat for Fabry disease) and inhibitors of glucosylceramide synthesis (e.g. eliglustat tartrate for Gaucher disease) are currently under investigation in various clinical trials.

Enzyme replacement therapy for the management of the mucopolysaccharidoses.

Enzyme replacement therapy (ERT) is now available for several of the mucopolysaccharidosis disorders. This brief review summarizes the role of ERT in reducing the burden of peripheral disease in many patients with mucopolysaccharidosis disorders, and describes the challenges that remain in treating the neurological manifestations of these conditions.

Enzyme reconstitution/replacement therapy for lysosomal storage diseases.

PURPOSE OF REVIEW: Over the past 15 years, the lysosomal storage diseases have become paradigms for the specific treatment of monogenic disorders, particularly those affecting children. This review summarizes the phenotypes and recent literature regarding enzyme reconstitution (replacement) therapy and outcomes for such treatable lysosomal storage diseases: Gaucher disease, Fabry disease, Pompe disease and the mucopolysaccharidoses. RECENT FINDINGS: Recent clinical trials have shown that enzyme reconstitution therapy effectively treats many of the manifestations of the lysosomal storage diseases. When initiated early in the disease course, enzyme reconstitution therapy can reverse some disease manifestations, but may not completely alleviate the disease progression. Enzyme reconstitution therapy is generally well tolerated. Many adverse events are antibody-related, but can be managed without requiring cessation of enzyme reconstitution therapy. Documented IgE reactions, i.e. anaphylactoid, are quite rare (fewer than 1%). SUMMARY: Enzyme reconstitution therapy is a safe and effective treatment modality available for several of the lysosomal storage diseases. Owing to the short history of enzyme reconstitution therapy, the long-term outcomes of enzyme reconstitution therapy-treated individuals are unknown and require further investigation. Medical professionals must learn to identify patients likely to benefit from these life-changing therapies so as to prevent many of the devastating, irreversible complications of the lysosomal storage diseases.

Recombinant human iduronate-2-sulphatase: correction of mucopolysaccharidosis-type II fibroblasts and characterization of the purified enzyme.

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is an X-chromosome-linked recessive lysosomal storage disorder that results from a deficiency of iduronate-2-sulphatase (12S). Patients with MPS II store and excrete large amounts of partially degraded heparan sulphate and dermatan sulphate. In order to evaluate enzyme-replacement therapy for MPS II we have expressed a chimaeric I2S cDNA in CHO (Chinese-hamster ovary)-K1 cells utilizing a plasmid vector that places the cDNA under the transcriptional control of the human polypeptide-chain-elongation factor-1 alpha gene promoter. A clonal cell line that accumulated recombinant I2S at greater than 10 mg/ml in conditioned medium was identified. Enzyme secreted from this cell line grown in the presence of NH4Cl was shown to be endocytosed into MPS II fibroblasts via the mannose 6-phosphate receptor and localized to the lysosomal compartment, resulting in correction of the storage phenotype of these cells. Milligram quantities of the recombinant I2S were purified, and the enzyme was shown to have a pH optimum and kinetic parameters similar to those for the mature form of I2S purified from human liver. The recombinant I2S had a molecular mass of approx. 90 kDa; this was reduced to 60 kDa by endoglycosidase treatment.