Advances in the treatment of mucopolysaccharidosis type I

IgG Fusion Proteins for Brain Delivery of Biologics via Blood-Brain Barrier Receptor-Mediated Transport

The treatment of neurological disorders with large-molecule biotherapeutics requires that the therapeutic drug be transported across the blood–brain barrier (BBB). However, recombinant biotherapeutics, such as neurotrophins, enzymes, decoy receptors, and monoclonal antibodies (MAb), do not cross the BBB. These biotherapeutics can be re-engineered as brain-penetrating bifunctional IgG fusion proteins. These recombinant proteins comprise two domains, the transport domain and the therapeutic domain, respectively. The transport domain is an MAb that acts as a molecular Trojan horse by targeting a BBB-specific endogenous receptor that induces receptor-mediated transcytosis into the brain, such as the human insulin receptor (HIR) or the transferrin receptor (TfR). The therapeutic domain of the IgG fusion protein exerts its pharmacological effect in the brain once across the BBB. A generation of bifunctional IgG fusion proteins has been engineered using genetically engineered MAbs directed to either the BBB HIR or TfR as the transport domain. These IgG fusion proteins were validated in animal models of lysosomal storage disorders; acute brain conditions, such as stroke; or chronic neurodegeneration, such as Parkinson’s disease and Alzheimer’s disease. Human phase I–III clinical trials were also completed for Hurler MPSI and Hunter MPSII using brain-penetrating IgG-iduronidase and -iduronate-2-sulfatase fusion protein, respectively.

Mucopolysaccharidosis Type I-Associated Corneal Disease: A Clinicopathologic Study

PURPOSE

To report the anterior segment clinical features and histopathologic and histochemical characteristics of explanted corneas from the largest reported cohort of patients with Hurler syndrome and other variants of mucopolysaccharidosis (MPS) I undergoing corneal transplantation.

DESIGN

Retrospective observational case series.

METHODS

This institutional study reviewed 15 corneas from 9 patients with MPS I spectrum disease who underwent corneal transplant to treat corneal clouding between May 2011 and October 2020. We reviewed the clinical data, hematoxylin-eosin-stained sections, and histochemical stains, including those for mucopolysaccharides (Alcian blue and/or colloidal iron). The main outcome measures were pathology observed under light microscopy and postsurgical clinical outcomes.

RESULTS

Nine patients underwent 15 corneal transplants for corneal clouding (14/15 procedures were deep anterior lamellar keratoplasty). All corneas had mucopolysaccharide deposition visible on hematoxylin-eosin-stained sections, which was highlighted in blue with histochemical stains. All corneas also showed alterations in Bowman's layer and the majority also showed epithelial abnormalities.

CONCLUSION

MPS I shows significant corneal clouding that is successfully treated with deep anterior lamellar keratoplasty. The excised corneas show characteristic epithelial changes, disruption or breaks in Bowman's membrane, and amphophilic collections of stromal granular mucopolysaccharides which are visible on hematoxylin-eosin-stained sections and highlighted by special histochemical stains (Alcian blue and collodial iron). These changes, although subtle, should alert the pathologist to the possibility of an underlying lysosomal storage disorder.

Genome Editing for Mucopolysaccharidoses

Genome editing holds the promise of one-off and potentially curative therapies for many patients with genetic diseases. This is especially true for patients affected by mucopolysaccharidoses as the disease pathophysiology is amenable to correction using multiple approaches. Ex vivo and in vivo genome editing platforms have been tested primarily on MSPI and MPSII, with in vivo approaches having reached clinical testing in both diseases. Though we still await proof of efficacy in humans, the therapeutic tools established for these two diseases should pave the way for other mucopolysaccharidoses. Herein, we review the current preclinical and clinical development studies, using genome editing as a therapeutic approach for these diseases. The development of new genome editing platforms and the variety of genetic modifications possible with each tool provide potential applications of genome editing for mucopolysaccharidoses, which vastly exceed the potential of current approaches. We expect that in a not-so-distant future, more genome editing-based strategies will be established, and individual diseases will be treated through multiple approaches.

Bi-functional IgG-lysosomal enzyme fusion proteins for brain drug delivery

Most lysosomal storage disorders affect the central nervous system. However, lysosomal enzymes do not cross the blood-brain barrier (BBB), and intravenous enzyme infusion is not effective for the brain. Lysosomal enzymes can be re-engineered for BBB transport as IgG-enzyme fusion proteins, where the IgG domain is a monoclonal antibody (MAb) against an endogenous BBB receptor/transporter, and which acts as a molecular Trojan horse to deliver the enzyme to brain. However, the problem is retention of high enzyme activity following enzyme fusion to the IgG. The present investigation shows this is possible with a versatile approach that employs fusion of the enzyme to either the IgG heavy chain or light chain using a long flexible linker. The model IgG is a chimeric monoclonal antibody (MAb) against the human insulin receptor (HIR). The enzyme activity of the HIRMAb-enzyme fusion protein is preserved for hexosaminidase A, which is mutated in Tay Sachs disease, for protein palmitoylthioesterase-1, which is mutated in Batten disease type 1, acid sphingomyelinase, which is mutated in Niemann Pick disease type A, and beta galactosidase-1, which is mutated in GM1 gangliosidosis.

Obstructive sleep apnea and craniofacial appearance in MPS type I-Hurler children after hematopoietic stem cell transplantation

OBJECTIVES

Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal storage disorder characterized by severe multi-systemic organ manifestations including obstructive sleep apnea syndrome (OSAS). Hematopoietic stem cell transplantation (HSCT) is the treatment of choice in severe MPS I (MPS IH, Hurler syndrome). However, the effect of HSCT on OSAS in MPS IH still remains unclear. The purpose of this study was to analyze respiratory patterns during sleep following HSCT in MPS IH children and to relate these findings to craniofacial abnormalities.

METHODS

Overnight polysomnographies of nine MPS IH children (mean age: 8.2 years) previously treated with HSCT were retrospectively analyzed. Magnetic resonance images of the head were assessed with regard to soft and hard tissue abnormalities of the upper respiratory tract.

RESULTS

The mean apnea hypopnea index (AHI) was 5.3 events/h (range, 0.3-12.2), and the majority of apnea/hypopneas were obstructive. Whereas two patients had severe OSAS (AHI > 10) and two moderate OSAS (5 > AHI < 10), five patients had no evidence of OSAS (AHI < 2.0). Donor cell chimerism was significantly lower in MPS IH patients with OSAS as compared to patients without OSAS (p < 0.001). The upper airway space and the maxilla were significantly smaller and the adenoids larger in MPS IH patients with OSAS as compared to those of non-OSAS patients.

CONCLUSION

OSAS was only observed in MPS IH patients with graft failure or low donor cell chimerism. Conversely, successful HSCT seems to ameliorate adenoid hyperplasia and maxillary constriction in MPS IH patients and thereby minimizes the risk of OSAS at least at younger ages.

Alder-Reilly Anomaly in Hurler's Syndrome in a Neonate: A Rare Case Report

A 22-days-old male newborn baby presented with persistence of neonatal jaundice since birth. On clinical examination he had coarse facial features, a prominent forehead, enlarged tongue, icterus, hepatosplenomegaly, skeletal deformities and bilateral inguinal hernia. On investigation the peripheral smear revealed Alder-Reilly anomaly in the neutrophils suggesting mucopolysaccharidosis. Mucopolysaccharide excretion spot test of the urine was positive; and an assay for glycosaminoglycans in the urine was also high, which confirmed the clinical diagnosis of Hurler's syndrome. We present this rare case to highlight the association of Alder-Reilly anomaly and bilateral inguinal hernia in Hurler's syndrome even in neonates.

Craniovertebral junction pathological features and their management in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are multisystemic inherited metabolic diseases caused by the deficiency of the enzymes involved in the degradation of glycosaminoglycans (GAGs), which variably involve the central nervous system, heart, lungs, and bones.Undegraded or only partly degraded GAGs accumulate in the extracellular matrix, joint fluid, and connective tissue leading to widespread tissue and organ dysfunction.The introduction of hematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT) has positively affected the natural history of MPS patients and their life expectancy. However, the presence of spinal abnormalities and deposition of GAGs in soft tissues remains nearly unaltered.Abnormalities of the craniovertebral junction (CVJ) and GAG deposits can result in spinal cord compression with slowly progressive myelopathy or acute posttraumatic tetraplegia.The current paper discusses neuroimaging findings in a consecutive series of 42 MPS patients followed at our Center for Metabolic Diseases and their neurosurgical issues.Current recommendations for decompression and fusion will be discussed according to our experience and review of the literature.

Pharmacokinetics and brain uptake in the rhesus monkey of a fusion protein of arylsulfatase a and a monoclonal antibody against the human insulin receptor

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder of the brain caused by mutations in the gene encoding the lysosomal sulfatase, arylsulfatase A (ASA). It is not possible to treat the brain in MLD with recombinant ASA, because the enzyme does not cross the blood-brain barrier (BBB). In the present investigation, a BBB-penetrating IgG-ASA fusion protein is engineered and expressed, where the ASA monomer is fused to the carboxyl terminus of each heavy chain of an engineered monoclonal antibody (MAb) against the human insulin receptor (HIR). The HIRMAb crosses the BBB via receptor-mediated transport on the endogenous BBB insulin receptor, and acts as a molecular Trojan horse to ferry the ASA into brain from blood. The HIRMAb-ASA is expressed in stably transfected Chinese hamster ovary cells grown in serum free medium, and purified by protein A affinity chromatography. The fusion protein retains high affinity binding to the HIR, EC50 = 0.34 ± 0.11 nM, and retains high ASA enzyme activity, 20 ± 1 units/mg. The HIRMAb-ASA fusion protein is endocytosed and triaged to the lysosomal compartment in MLD fibroblasts. The fusion protein was radio-labeled with the Bolton-Hunter reagent, and the [(125) I]-HIRMAb-ASA rapidly penetrates the brain in the Rhesus monkey following intravenous administration. Film and emulsion autoradiography of primate brain shows global distribution of the fusion protein throughout the monkey brain. These studies describe a new biological entity that is designed to treat the brain of humans with MLD following non-invasive, intravenous infusion of an IgG-ASA fusion protein.

Prevalence and development of orthopaedic symptoms in the dutch hurler patient population after haematopoietic stem cell transplantation

Hurler syndrome (MPS-IH) is a rare autosomal recessive lysosomal storage disease. Besides a variety of other features, Hurler syndrome is characterized by a range of skeletal abnormalities known as dysostosis multiplex. Despite the successful effect of haematopoietic stem cell transplantation on the other features, dysostosis remains a disabling symptom of the disease. This study analyzed the status and development of the orthopaedic manifestations of 14 Dutch Hurler patients after stem cell transplantation.Data were obtained retrospectively by reviewing patients' charts, radiographs and MRIs. Existing methods to measure the deficiencies were modified to optimally address the dysostosis. These measurements were done by two of the authors independently. The odontoïd/body ratio, kyphotic angle, scoliotic angle and parameters for hip dysplasia and genu valgum were measured and plotted against age. The degree of progression was determined. The intraclass correlation coefficient (ICC) was calculated to determine the reliability of the measurements.All patients showed hypoplasia of the odontoïd, which significantly improved during growth. Kyphosis in the thoracolumbar area was present in 13 patients and proved to be progressive. Scoliosis was observed in eight patients. Hip dysplasia was present in all patients and showed no tendency of improvement. In all but one patient, knee valgus remained more than two standard deviations above normal.Dysostosis remains a major problem after haematopoietic stem cell transplantation in Hurler patients. Moreover, except for dens hypoplasia, it appears to be progressive and therefore surgical interventions may be necessary in the majority of these patients.

An exploratory study of brain function and structure in mucopolysaccharidosis type I: long term observations following hematopoietic cell transplantation (HCT)

AIM

Although hematopoietic cell transplantation (HCT) arrests the cognitive decline in mucopolysaccharidosis type IH (Hurler syndrome, MPS IH), these children continue to have neuropsychological deficits as they age. Both compromised attention and effects on white matter have been observed in cancer patients who have had chemotherapy. Therefore, we explored the effects of disease and treatment on brain function in children with MPS I who have had HCT with those with attenuated MPS I treated with enzyme replacement therapy (ERT).

SUBJECTS

7 MPS IH participants at least 5 years post-HCT were compared with 7 attenuated participants who were treated with ERT.

MEASURES

IQ, attention, spatial ability, and memory were assessed. Medical history and an unsedated MRI scan using diffusion tensor imaging (DTI) were acquired.

RESULTS

Despite clinically equivalent IQ and memory, children with MPS IH had poorer attention span than those with attenuated MPS I as well as decreased fractional anisotropy (FA) of the corpus callosum. A relationship between attention scores and FA was found in the MPS IH group but not the attenuated group. FA was also related to the frequency of medical events.

INTERPRETATION

In children with MPS IH, both the treatment and the disease affect attention functions associated with poor white matter integrity.

A retrospective audit of anesthetic techniques and complications in children with mucopolysaccharidoses

OBJECTIVES AND AIMS

To document the incidence of difficult airway management and difficult intubation in the era of replacement therapy for Australian children with mucopolysaccharidosis (MPS).

BACKGROUND

Medical treatment for MPS has developed significantly since 1980's with a large number of patients now being offered either bone marrow transplant or enzyme replacement. The impact of these therapies on the incidence of difficult airway management has not been adequately documented. Similarly, anesthesia techniques and airway devices have been developed, which are thought to have greatly increased the safety of managing these patients under anesthesia but their role in children with MPS has not been systematically described.

METHODS

A retrospective chart review of 17 patients with MPS who had received anesthetics at the Royal Children's Hospital during the time frame January 1998-January 2011. The primary outcome was the incidence of difficult or failed intubation. Secondary outcomes were the relationship between the incidence of difficult intubation and treatment with enzyme replacement therapy (ERT) or bone marrow transplantation.

RESULTS

Seventeen patients received 141 anesthetics for 214 procedures. Difficult face mask ventilation occurred in 20 anesthetics (14.2%). Difficult intubation occurred in 40 anesthetics (25%). Failed intubation occurred in two cases (1.6%).The incidence of difficult intubation was 12% in MPS I, 35% MPS II, 86.7% in MPS VI, and 0% in MPS III and IV.

CONCLUSIONS

Hematopoietic stem cell transplantation prior to 2 years of age reduces the incidence of difficult mask ventilation and difficult intubation in children with MPS I. ERT was initiated late in the clinical course of MPS II and VI and induced improvements in upper airway patency but did not reduce the incidence of difficult airway management.

Enzyme replacement therapy improves joint motion and outcome of the 12-min walk test in a mucopolysaccharidosis type VI patient previously treated with bone marrow transplantation

Mucopolysaccharidosis type VI (MPS VI; Maroteaux-Lamy syndrome, OMIM #253200) is a rare disorder involving multiple organs and manifested particularly by severe skeletal abnormalities. Bone marrow transplantation (BMT) improves cardiopulmonary function and facial features, but has limited success in ameliorating skeletal abnormalities and short stature. Here, we report the outcome of enzyme replacement therapy (ERT) with recombinant human arylsulfatase-B (ASB, Naglazyme, BioMarin, Novato, CA) in an MPS VI patient who received BMT 10 years prior to ERT induction. Administration of weekly Naglazyme for 18 months was effective in improving range of motion in several joints [shoulders (improvement of flexion (Right/Left): 40°/55°; improvement of extension 30°/40°; improvement of abduction 10°/10°), elbows (improvement of flexion 25°/25°; improvement of extension 10°/15°), hips (improvement of flexion 25°/10°), and knees (improvement of flexion 45°/40°; improvement of extension 50°/60°)]. Improvement in the outcome of the 12-min walk test (70% increase) and 3-min stair-climbing test (29% increase) was also noted after ERT. Because ERT improved clinical features in an MPS VI patient who had undergone prior BMT, the role of ERT post successful BMT in MPS VI needs further investigation.

Hurler disease bone marrow stromal cells exhibit altered ability to support osteoclast formation

Mucopolysaccharidosis type I (MPS IH; Hurler syndrome) is a rare genetic disorder that is caused by mutations in the α-L-iduronidase (IDUA) gene, resulting in the deficiency of IDUA enzyme activity and intra-cellular accumulation of glycosaminoglycans. A characteristic skeletal phenotype is one of the many clinical manifestations in Hurler disease. Since the mechanism(s) underlying these skeletal defects are not completely understood, and bone and cartilage are mesenchymal lineages, we focused on the characterization of mesenchymal cells isolated from the bone marrow (BM) of 5 Hurler patients. IDUA-mutated BM stromal cells (BMSC) derived from MPS IH patients exhibited decreased IDUA activity, consistent with the disease genotype. The expansion rate, phenotype, telomerase activity, and differentiation capacity toward adipocytes, osteoblasts, chondrocytes, and smooth muscle cells in vitro of the MPS I BMSC lines were similar to those of BMSC from age-matched normal control donors. MPS I BMSC also had a similar in vivo osteogenic capacity as normal BMSC. However, MPS I BMSC displayed an increased capacity to support osteoclastogenesis, which may correlate with the up-regulation of the RANKL/RANK/OPG molecular pathway in MPS I BMSC compared with normal BMSC.

Brain-penetrating IgG-iduronate 2-sulfatase fusion protein for the mouse

Mucopolysaccharidosis (MPS) type II (Hunter's syndrome) is caused by mutations in the iduronate 2-sulfatase (IDS) fusion protein. MPS-II affects the brain, and enzyme replacement therapy is not effective in the brain, because the enzyme does not cross the blood-brain barrier. To treat mouse models of MPS-II with brain-penetrating IDS, the lysosomal enzyme was reengineered as an IgG-IDS fusion protein. The mature human IDS was fused to the carboxyl terminus of both heavy chains of the chimeric monoclonal antibody (MAb) against the mouse transferrin receptor (TfR), and the fusion protein is designated cTfRMAb-IDS. The purity and identity of the fusion protein was confirmed by electrophoresis and Western blotting with antibodies to mouse IgG and human IDS. The EC₅₀ of binding of the cTfRMAb-IDS fusion protein to the mouse TfR (0.85 ± 0.15 nM) was comparable to the EC₅₀ of binding of the cTfRMAb (0.78 ± 0.05 nM). The IDS enzyme activity of the cTfRMAb-IDS fusion protein was 126 ± 1 nmol · h⁻¹ · μg⁻¹ protein. After intravenous injection in the mouse, the cTfRMAb-IDS fusion protein was rapidly removed from plasma and distributed to tissues, including brain and spinal cord. The uptake of the fusion protein by brain or spinal cord was 1.3 ± 0.1 and 2.2 ± 0.2% injected dose/g, respectively, which is 100-fold greater than the brain uptake of IDS alone. This work shows that a lysosomal sulfatase can be reengineered as an IgG-enzyme fusion protein that rapidly penetrates the brain after intravenous administration.

[Mental retardation revealing mucopolysaccharidosis type I in a child treated for cystic fibrosis: a case report]

Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease due to an α-L-iduronidase deficiency, which leads to an accumulation of glycosaminoglycans in the lysosomes of most cells, resulting in tissue and organ dysfunction. MPS I is inherited in an autosomal-recessive manner. This disorder has a chronic, progressive course and is characterized by mental retardation, dysmorphy, organomegaly, multisystem involvement, and multiple dysostosis. Early disease recognition is important for a prompt start of specific treatment, which improves many aspects of MPS I, and for the patient's overall management.

Therapeutic approaches to the challenge of neuronal ceroid lipofuscinoses

The Neuronal Ceroid Lipofuscinoses (NCLs) are lysosomal storage diseases (LSDs) affecting the central nervous system (CNS), with generally recessive inheritance. They are characterized by pathological lipofuscin-like material accumulating in cells. The clinical phenotypes at all onset ages show progressive loss of vision, decreasing cognitive and motor skills, epileptic seizures and premature death, with dementia without visual loss prominent in the rarer adult forms. Eight causal genes, CLN10/CTSD, CLN1/PPT1, CLN2/TPP1, CLN3, CLN5, CLN6, CLN7/MFSD8, CLN8, with more than 265 mutations and 38 polymorphisms (http://www.ucl.ac.uk/ncl) have been described. Other NCL genes are hypothesized, including CLN4 and CLN9; CLCN6, CLCN7 and possibly SGSH are under study. Some therapeutic strategies applied to other LSDs with significant systemic involvement would not be effective in NCLs due to the necessity of passing the blood brain barrier to prevent the neurodegeneration, repair or restore the CNS functionality. There are therapies for the NCLs currently at preclinical stages and under phase 1 trials to establish safety in affected children. These approaches involve enzyme replacement, gene therapy, neural stem cell replacement, immune therapy and other pharmacological approaches. In the next decade, progress in the understanding of the natural history and the biochemical and molecular cascade of events relevant to the pathogenesis of these diseases in humans and animal models will be required to achieve significant therapeutic advances.

Expression in CHO cells and pharmacokinetics and brain uptake in the Rhesus monkey of an IgG-iduronate-2-sulfatase fusion protein

Sulfatases are potential therapeutic biopharmaceuticals, as mutations in sulfatase genes leads to inherited disease. Mucopolysaccharidosis (MPS) Type II is caused by mutations in the lysosomal enzyme, iduronate-2-sulfatase (IDS). MPS-II affects the brain and enzyme replacement therapy is ineffective for the brain, because IDS does not cross the blood-brain barrier (BBB). To deliver IDS across the human BBB, the sulfatase has been re-engineered as an IgG-sulfatase fusion protein with a genetically engineered monoclonal antibody (MAb) against the human insulin receptor (HIR). The HIRMAb part of the HIRMAb-IDS fusion protein acts as a molecular Trojan horse to ferry the fused IDS across the BBB. Chinese hamster ovary (CHO) cells were stably transfected to produce the HIRMAb-IDS fusion protein. The fusion protein was triaged to the lysosomal compartment of MPS-II fibroblasts based on confocal microscopy, and 300 ng/mL medium concentrations normalized IDS enzyme activity in the cells. The HIRMAb-IDS fusion protein was tritiated and injected intravenously into the adult Rhesus monkey at a low dose of 0.1 mg/kg. The IDS enzyme activity in plasma was elevated 10-fold above the endogenous level, and therapeutic plasma concentrations were generated in vivo. The uptake of the HIRMAb-IDS fusion protein in the brain was sufficiently high to produce therapeutic concentrations of IDS in the brain following IV administration of the fusion protein.

Correction of neurological disease of mucopolysaccharidosis IIIB in adult mice by rAAV9 trans-blood-brain barrier gene delivery

The greatest challenge in developing therapies for mucopolysaccharidosis (MPS) IIIB is to achieve efficient central nervous system (CNS) delivery across the blood-brain barrier (BBB). In this study, we used the novel ability of adeno-associated virus serotype 9 (AAV9) to cross the BBB from the vasculature to achieve long-term global CNS, and widespread somatic restoration of α-N-acetylglucosaminidase (NAGLU) activity. A single intravenous (IV) injection of rAAV9-CMV-hNAGLU, without extraneous treatment to disrupt the BBB, restored NAGLU activity to normal or above normal levels in adult MPS IIIB mice, leading to the correction of lysosomal storage pathology in the CNS and periphery, and correction of astrocytosis and neurodegeneration. The IV delivered rAAV9 vector also transduced abundant neurons in the myenteric and submucosal plexus, suggesting peripheral nervous system (PNS) targeting. While CNS entry did not depend on osmotic disruption of the BBB, it was significantly enhanced by pretreatment with an IV infusion of mannitol. Most important, we demonstrate that a single systemic rAAV9-NAGLU gene delivery provides long-term (>18 months) neurological benefits in MPS IIIB mice, resulting in significant improvement in behavioral performance, and extension of survival. These data suggest promising clinical potential using the trans-BBB neurotropic rAAV9 vector for treating MPS IIIB and other neurogenetic diseases.

α-Galactosidase A expressed in the salivary glands partially corrects organ biochemical deficits in the fabry mouse through endocrine trafficking

Fabry disease is caused by an X-linked deficiency of the lysosomal enzyme α-galactosidase A (GLA) and has been treated successfully with enzyme replacement therapy (ERT). Gene therapy has been proposed as an alternative to ERT due to the presumed advantages of continuous, endogenous production of the therapeutic enzyme. GLA production in the liver and its therapeutic efficacy in the Fabry mouse have been demonstrated previously with various viral vector systems. In consideration of the potential advantages of using the salivary glands as endogenous GLA biosynthesis sites, we explored the feasibility of this approach in the Fabry mouse. GLA -/0 or -/- mice received an adenoviral vector (2 × 10(10) or 1 × 10(9) viral particles) expressing GLA to the right submandibular gland via oral cannulation of the submandibular duct. Four days later, animals were sacrificed; saliva, plasma, kidney, liver, and brain were collected and assayed using ELISA, Western blot, and a GLA enzymatic activity assay using both traditional fluorescence methods and isotope dilution mass spectrometry by following the U.S. EPA Method 6800. GLA activity was significantly elevated in the serum and liver of both treatment groups, and improvement in the kidney was marginally significant (P < 0.069) in the high-dose group. Notably, we found that liver and salivary gland produce different glycoforms of the GLA transgene. Only small numbers of adenoviral genomes were observed in the livers of treated animals, but in four of 14 in the high-dose groups, liver levels of adenovirus exceeded 20 copies/μg, indicating that the sequestration in the salivary gland was imperfect at high doses. Taken together, these results indicate that the salivary gland-based gene therapy for Fabry disease is promising, and further studies with advanced viral vector gene delivery systems (e.g., adeno-associated virus) for long-term treatment appear to be warranted.

Gene therapy augments the efficacy of hematopoietic cell transplantation and fully corrects mucopolysaccharidosis type I phenotype in the mouse model

Type I mucopolysaccharidosis (MPS I) is a lysosomal storage disorder caused by the deficiency of α-L-iduronidase, which results in glycosaminoglycan accumulation in tissues. Clinical manifestations include skeletal dysplasia, joint stiffness, visual and auditory defects, cardiac insufficiency, hepatosplenomegaly, and mental retardation (the last being present exclusively in the severe Hurler variant). The available treatments, enzyme-replacement therapy and hematopoietic stem cell (HSC) transplantation, can ameliorate most disease manifestations, but their outcome on skeletal and brain disease could be further improved. We demonstrate here that HSC gene therapy, based on lentiviral vectors, completely corrects disease manifestations in the mouse model. Of note, the therapeutic benefit provided by gene therapy on critical MPS I manifestations, such as neurologic and skeletal disease, greatly exceeds that exerted by HSC transplantation, the standard of care treatment for Hurler patients. Interestingly, therapeutic efficacy of HSC gene therapy is strictly dependent on the achievement of supranormal enzyme activity in the hematopoietic system of transplanted mice, which allows enzyme delivery to the brain and skeleton for disease correction. Overall, our data provide evidence of an efficacious treatment for MPS I Hurler patients, warranting future development toward clinical testing.

Genetic engineering of a bifunctional IgG fusion protein with iduronate-2-sulfatase

Iduronate-2-sulfatase (IDS) is a lysosomal sulfatase that prevents the accumulation within the brain of glycosoaminoglycans. However, IDS does not cross the blood-brain barrier (BBB). To enable BBB transport, human IDS, minus its signal peptide, was fused to the carboxyl terminus of the heavy chain of a chimeric monoclonal antibody (mAb) to the human insulin receptor (HIR). The HIRMAb crosses the BBB on the endogenous insulin receptor and acts as a molecular Trojan horse to ferry the IDS into brain. The HIRMAb-IDS fusion protein was expressed in COS cells and purified with protein A affinity chromatography. The size of the fusion heavy chain, as measured with Western blotting and antibodies to either human IDS or human IgG, was increased about 80 kDa, relative to the size of the heavy chain of the parent HIRMAb. The HIRMAb-IDS fusion protein retained high-affinity binding for the HIR. The IDS enzyme specific activity of the fusion protein was 51 +/- 7 nmol/h per microgram of protein, which is comparable to the enzyme activity of recombinant IDS. The fusion protein was taken up by human fibroblasts, and the accumulation of glycosoaminoglycans in fibroblasts null for the sulfatase was decreased 84% by treatment with the fusion protein. The HIRMAb-IDS fusion protein is a bifunctional IgG-sulfatase fusion protein, which has been specifically engineered for targeted drug delivery across the human BBB.

Transplant outcomes in mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) are inherited metabolic disorders (IMDs) caused by single-gene defects leading to progressive cellular accumulation of glycosaminoglycans (GAGs) and damage to multiple organs, including the central nervous, musculoskeletal, cardiorespiratory, and other systems. Hurler syndrome (MPS IH), the most severe form, is the prototypical model. Enzyme replacement therapy (ERT), available for MPS I, II, and VI, is beneficial in some patients. However, ERT does not improve neurocognitive function because of its inability to cross the blood-brain barrier. In contrast, allogeneic hematopoietic stem cell transplantation (HSCT) allows donor-derived, enzyme-producing cells to migrate to the brain and other organs to provide permanent enzyme therapy and thus help somatic organs, improve neurocognitive function and quality of life, and prolong survival, particularly when performed early in the course of the disease. Bone marrow has been the graft source in the past. However, in the last 5 years many patients have been treated with unrelated donor (URD) umbilical cord blood transplant (UCBT), allowing rapid and increased access to transplantation with favorable outcomes. This review describes published and our institutional clinical experiences, discusses the current status of the field, and provides therapy guidelines for patients with MPS.

Cord blood and bone marrow transplantation in inherited metabolic diseases: scientific basis, current status and future directions

Progressive degeneration of the central nervous system leading to the loss of neuromotor, neurophysiological and cognitive abilities is the fundamental clinical problem in patients with many inherited metabolic diseases (IMD). Worldwide experience shows that morbidity, quality of life, and survival in these patients can be improved by allogeneic haematopoietic stem cell transplantation (HSCT), particularly when performed early in the course of the disease. At present, while available for some conditions, exogenous enzyme replacement therapy is unable to correct cognitive and central nervous system disease because of its inability to cross the blood-brain barrier. In contrast, HSCT allows donor-derived, enzyme-producing cells to migrate to the brain and other organs providing a permanent enzyme replacement therapy. HSCT may also mediate non-hematopoietic cell regeneration or repair. Traditionally, bone marrow has been the graft source for IMD patients. However, in the last 5 years many studies utilizing unrelated donor umbilical cord blood (UCB) as a graft source have demonstrated that UCB provides rapid and increased access to transplantation with favourable outcomes. This review describes preclinical studies and past and present clinical treatment approaches and discusses current controversies and future directions of this promising field.

Umbilical cord blood transplantation for non-malignant diseases

Many factors, including lower risk of GVHD, rapid availability of 4/6-6/6 matched cord blood (CB) units and incremental gains in the outcomes, have led to an increasing use of CB transplantation (CBT) to treat many patients who lack fully matched adult BM donors. A large electronically searchable worldwide inventory of publicly banked CB units allows for quicker donor identification and selection. In this review, we examine the current status and cumulative experience of related and unrelated donor CBT for the treatment of non-malignant diseases, including hemoglobinopathies, BM failure syndromes, primary immunodeficiency diseases (PIDs) and inherited metabolic disorders (IMDs), and conclude that CBT offers a promising and effective therapy for these diseases. Future strategies to facilitate earlier diagnosis and to decrease transplant-related risks should further improve the short- and long-term outcomes. Every effort should be made to perform transplantation early in the course of disease before extensive damage to various tissues and organs ensues.

AGT-181: expression in CHO cells and pharmacokinetics, safety, and plasma iduronidase enzyme activity in Rhesus monkeys

Enzyme replacement therapy is not effective for the brain, owing to the lack of transport of the enzyme across the blood-brain barrier (BBB). Recombinant proteins such as the lysosomal enzyme, iduronidase, can penetrate the human BBB, following the re-engineering of the protein as an IgG fusion protein, where the IgG moiety targets an endogenous BBB transport system. The IgG acts as a molecular Trojan horse to ferry the fused protein into brain. AGT-181 is a genetically engineered fusion protein of human iduronidase and a chimeric monoclonal antibody against the human insulin receptor. Adult Rhesus monkeys were administered repeat intravenous doses of AGT-181 ranging from 0.2 to 20 mg/kg. Chronic AGT-181 dosing resulted in no toxicity at any dose, no changes in organ histology, no change in plasma or cerebrospinal fluid glucose, and no significant immune response. AGT-181 was rapidly removed from plasma, based on measurements of either plasma immunoreactive AGT-181 or plasma iduronidase enzyme activity. Plasma pharmacokinetics analysis showed a high systemic volume of distribution, and a clearance rate comparable to a small molecule. The safety pharmacology studies provide the basis for future drug development of AGT-181 as a new therapeutic approach to treatment of the brain in Hurler's syndrome.

Gene therapy of Hunter syndrome: evaluation of the efficiency of muscle electro gene transfer for the production and release of recombinant iduronate-2-sulfatase (IDS)

Mucopolysaccharidosis type II (MPSII) is an inherited disorder due to a deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS). The disease is characterized by a considerable deposition of heparan- and dermatan-sulfate, causing a general impairment of physiological functions. Most of the therapeutic protocols proposed so far are mainly based upon enzyme replacement therapy which is very expensive. There is a requirement for an alternative approach, and to this aim, we evaluated the feasibility of muscle electro gene transfer (EGT) performed in the IDS-knockout (IDS-ko) mouse model. EGT is a highly efficient method of delivering exogenous molecules into different tissues. More recently, pre-treatment with bovine hyaluronidase has shown to further improve transfection efficiency of muscle EGT. We here show that, by applying such procedure, IDS was very efficiently produced inside the muscle. However, no induced IDS activity was measured in the IDS-ko mice plasma, in contrast to matched healthy controls. In the same samples, an anticipated and rapidly increasing immune response against the recombinant protein was observed in the IDS-ko vs control mice, although reaching the same levels at 5 weeks post-injection. Additional experiments performed on healthy mice showed a significant contribution of hyaluronidase pre-treatment in increasing the immune response.

Mobility in Hurler syndrome

Hurler syndrome is an autosomal recessive metabolic storage disease. Hematopoietic stem cell transplant increases life expectancy, but the effects on associated musculoskeletal abnormalities remains unclear, and long-term data are limited. We detail the follow-up of 23 patients at a mean of 8.5 years after successful hematopoietic stem cell transplant. All patients underwent clinical examination at an annual multidisciplinary clinic. Serial radiological studies were reviewed to assess development and management of hip dysplasia and genu valgum. All patients demonstrated characteristic acetabular dysplasia and failure of ossification of the superolateral femoral head. Eight patients underwent bilateral pelvic and femoral derotation (mean age at surgery, 4.4 years); 4 patients had pelvic osteotomy only. Mean preoperative acetabular angle was 34 degrees. Genu valgum of variable severity due to failure of ossification of the lateral aspect of the proximal tibial metaphysis was observed early, and 6 patients underwent medial epiphyseal stapling, decreasing tibiofemoral angle by a mean of 8 degrees. Clinically, all patients were independently mobile, with restriction of internal hip rotation being the most significant clinical finding. Valgus knees and pronated feet were a typical finding. This cohort represents one of the largest available for study, and ongoing review will clarify the progression of musculoskeletal problems and determine the effectiveness of orthopaedic intervention.

Central corneal thickness and its relationship to intraocular pressure in mucopolysaccararidoses-1 following bone marrow transplantation

PURPOSE

To examine the ocular findings in mucopolysaccaridoses-1 (MPS-1) and the relationship between intraocular pressure (IOP) and central corneal thickness following bone marrow transplantation.

SETTING

clinical practice.

SUBJECTS

23 subjects with MPS-1 following bone marrow transplantation were examined.

OBSERVATION PROCEDURES

age, sex, visual acuity, presence of strabismus, refractive error, fundus examination, intraocular pressure, and central corneal thickness were assessed for each individual.

MAIN OUTCOME MEASURE

correlation of central corneal thickness with intraocular pressure. Only the right eye was used in correlations.

RESULTS

Forty-six eyes of 23 subjects were examined. All subjects had been treated with successful bone marrow transplantation with mean follow-up of 8.5 years. Ages ranged from 17 months to 19 years (SD 5.03). Of the subjects, 60.8% were female; 85.5% were hyperopic; 8.6% had best-corrected visual acuity of >/=6/12; 34.5% had best-corrected visual acuity of <6/12 and >6/36 with 56.9% <6/36; 30% had strabismus. IOP ranged from 13 to 41 mm Hg with four children on antiglaucoma therapy. Central corneal thickness ranged from 484 microm to 705 microm and was moderately correlated with measured IOP in the right eye (r = 0.56). Corneal opacification moderately correlated with central corneal thickness (r = 0.57). Seventy percent had a normal disk evaluation; 30% had abnormal disk cupping.

CONCLUSION

This is the first large case series of MPS-1 subjects demonstrating a correlation between measured IOP and central corneal thickness. All subjects had corneal opacification moderately correlating with corneal pachymetry.

[Hurler syndrome. Early diagnosis and successful enzyme replacement therapy: a new therapeutic approach. Case report]

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder due to alpha-L-iduronidase deficiency. Its severe prognosis has been significantly improved by enzyme replacement therapy using recombinant human alpha-L-iduronidase (laronidase). We report the case of a boy who was diagnosed at 19 months of age with Hurler's disease, the most severe form of MPS I, and received thereafter a treatment by laronidase, resulting in clinical and biological improvement. The aim of this case report is to draw physicians' attention on the presenting signs of Hurler's disease, in order to enable an earlier diagnosis, increasing the treatment's benefits.

Enzyme replacement therapy in patients who have mucopolysaccharidosis I and are younger than 5 years: results of a multinational study of recombinant human alpha-L-iduronidase (laronidase)

OBJECTIVE

Our objective was to evaluate the safety, pharmacokinetics, and efficacy of laronidase in young, severely affected children with mucopolysaccharidosis I.

METHODS

This was a prospective, open-label, multinational study of 20 patients who had mucopolysaccharidosis I and were <5 years old (16 with Hurler syndrome, 4 with Hurler-Scheie syndrome) and were scheduled to receive intravenous laronidase at 100 U/kg (0.58 mg/kg) weekly for 52 weeks. Four patients underwent dosage increases to 200 U/kg for the last 26 weeks because of elevated urinary glycosaminoglycan levels at week 22.

RESULTS

Laronidase was well tolerated at both dosages. Investigators reported improved clinical status in 94% of patients at week 52. The mean urinary glycosaminoglycan level declined by approximately 50% at week 13 and was sustained thereafter. A more robust decrease in urinary glycosaminoglycan was observed in patients with low antibody levels and those who were receiving the 200 U/kg dosage. On examination, the liver edge was reduced by 69.5% in patients with a palpable liver at baseline and week 52 (n = 10). The proportion of patients with left ventricular hypertrophy decreased from 53% to 17%. Global assessment of sleep studies showed improvement or stabilization in 67% of patients, and the apnea/hypopnea index decreased by 5.8 events per hour (-8.5%) in those with abnormal baseline values. The younger patients with Hurler syndrome (<2.5 years) and all 4 patients with Hurler-Scheie syndrome showed normal mental development trajectories during the 1-year treatment period.

CONCLUSIONS

Laronidase seems to be well tolerated and to provide clinical benefit in patients who have severe mucopolysaccharidosis I and are <5 years old. Enzyme replacement therapy is not curative and may not improve all affected organs and systems in individuals when irreversible changes have developed. The long-term clinical outcome and effects of antibodies and laronidase dosing on glycosaminoglycan reduction warrant additional investigation.

When is enlargement of the subarachnoid spaces not benign? A genetic perspective

Enlargement of the subarachnoid spaces is occasionally encountered during neuroimaging of children. This enlargement is generally regarded as a nonpathologic process that resolves uneventfully. However, there are several genetic disorders in which enlargement of the subarachnoid spaces can be an early sign, or the feature of an associated syndrome, that may aid in the underlying diagnosis. Recognizing subarachnoid space enlargement in these circumstances requires an understanding of the normal physiology of the subarachnoid space at different time points in a child's neurodevelopment. This article reviews the events shaping the subarachnoid space, both during normal physiologic maturation and in specific genetic disorders.

Gene therapy of the brain in the dog model of Hurler's syndrome

OBJECTIVE

A defect of the lysosomal enzyme alpha-L-iduronidase (IDUA) interrupts the degradation of glycosaminoglycans in mucopolysaccharidosis type I, causing severe neurological manifestations in children with Hurler's syndrome. Delivery of the missing enzyme through stereotactic injection of adeno-associated virus vectors coding for IDUA prevents neuropathology in affected mice. We examined the efficacy and the safety of this approach in enzyme-deficient dogs.

METHODS

Because deficient dogs raise antibodies against IDUA in response to infusion, intracerebral vector injections were combined with an immunosuppressive regimen.

RESULTS

Treatment was tolerated well. We observed broad dispersion of vector genomes in the brain of efficiently immunosuppressed dogs. The delivery of IDUA to large areas, which could encompass the entire brain, prevented glycosaminoglycan and secondary ganglioside accumulations. This condition was associated with drastic reduction of neuropathology throughout the encephalon. In contrast, vector injection combined with partial immunosuppression was associated with subacute encephalitis, production of antibodies against IDUA in brain tissues, and elimination of genetically modified cells.

INTERPRETATION

Gene therapy directed to the entire brain is feasible and may be beneficial to children with Hurler's syndrome. The possibility of subacute encephalitis emphasizes the importance of preventing immune response against IDUA, a problem that needs to be considered in similar therapies for other genetic defects.

Hurler's syndrome: dental findings in a case treated with bone marrow transplantation in infancy

Hurler's syndrome, also known as mucopolysaccharidosis I (MPS I-H), is a rare condition inherited as an autosomal recessive trait. It is caused by a deficiency in alpha-L-iduronidase, an enzyme that participates in the degradation of the glycosaminoglycans (GAGs) heparin sulphate and dermatan sulphate. Children with Hurler's syndrome appear nearly normal at birth but, left untreated, show a progressive mental and physical deterioration caused by a build-up of GAGs in all organs of the body. Death is often caused by cardiac or respiratory failure and usually occurs before the second decade of life. In recent years, bone marrow transplantation (BMT) has been employed in the management of patients with Hurler's syndrome. However, the dental findings observed in these cases have not previously been reported in the dental literature. Here we report a patient aged 11 years and 6 months, presented to a Specialist Paediatric Dentistry Unit, who was successfully treated by BMT at 18 months of age.

Reduction of GAG storage in MPS II mouse model following implantation of encapsulated recombinant myoblasts

BACKGROUND

Hunter syndrome, mucopolysaccharidosis type II (MPS II), is a X-linked inherited disorder caused by the deficiency of the enzyme iduronate-2-sulfatase (IDS), involved in the lysosomal catabolism of the glycosaminoglycans (GAG) dermatan and heparan sulfate. Such a deficiency leads to the intracellular accumulation of undegraded GAG and eventually to a progressive severe clinical pattern. Many attempts have been made in the last two to three decades to identify possible therapeutic strategies for the disorder, including gene therapy and somatic cell therapy.

METHODS

In this study we evaluated the intraperitoneal implantation of allogeneic myoblasts over-expressing IDS, enclosed in alginate microcapsules, in the MPS II mouse model. Animals were monitored for 8 weeks post-implantation, during which plasma and tissue IDS levels, as well as tissue and urinary GAG contents, were measured.

RESULTS AND CONCLUSIONS

Induced enzyme activity occurred both in the plasma and in the different tissues analyzed. A significant decrease in urinary undegraded GAG between the fourth and the sixth week of treatment was observed. Moreover, a biochemical reduction of GAG deposits was measured 8 weeks after treatment in the liver and kidney, on average 30 and 38%, respectively, while in the spleen GAG levels were almost normalized. Finally, the therapeutic effect was confirmed by histolochemical examination of the same tissues. Such effects were obtained following implantation of about 1.5 x 10(6) recombinant cells/animal. Taken together, these results represent a clear evidence of the therapeutic efficacy of this strategy in the MPS II mouse model, and encourage further evaluation of this approach for potential treatment of human beings.

Heparan sulfate levels in mucopolysaccharidoses and mucolipidoses

Glycosaminoglycans are accumulated in both mucopolysaccharidoses (MPS) and mucolipidoses (ML). MPS I, II, III and VII and ML II and ML III patients cannot properly degrade heparan sulphate (HS). In spite of the importance of HS storage in the metabolic pathway in these diseases, blood and urine HS levels have not been determined systematically using a simple and economical method. Using a new ELISA method using anti-HS antibodies, HS concentrations in blood and urine were determined in MPS and ML II and ML III patients. HS concentrations were determined in 156 plasma samples from MPS I (n = 23), MPS II (n = 26), MPS III (n = 24), MPS IV (n = 62), MPS VI (n = 5), MPS VII (n = 5), ML II (n = 8) and ML III (n = 3), and 205 urine samples from MPS I (n = 33), MPS II (n = 33), MPS III (n = 30), MPS IV (n = 82), MPS VI (n = 7), MPS VII (n = 9), ML II (n = 8) and ML III (n = 3). The ELISA method used monoclonal antibodies against HS. MPS I, II, III and VII and ML II and III patients had significant elevation in plasma HS, compared to the age-matched controls (p < 0.0001). Eighty-three out of 89 (93.3%) of individual values in the above MPS types and ML were above the mean +2SD of the controls. In urine samples, 75% of individual values in patients with those types were above the mean +2SD of the controls. In contrast to the previous understanding of the HS metabolic pathway, plasma HS levels in all five MPS VI and 15% of MPS IV patients were elevated above the mean +2SD of the controls. These findings suggest that HS concentration determined by ELISA, especially in plasma, could be a helpful marker for detection of the most severe MPS I, II, III, VI and VII and ML II, distinguishing them from normal populations.