Long-term impact of early initiation of enzyme replacement therapy in 34 MPS VI patients: A resurvey study.

Patients with mucopolysaccharidosis type VI (MPS VI) present with a wide range of disease severity and clinical manifestations, with significant functional impairment and shortened lifespan. Enzyme replacement therapy (ERT) with galsulfase has been shown to improve clinical and biochemical parameters including patient survival, quality of life and growth. The present study is a resurvey of 34 Brazilian MPS VI patients with rapidly progressive disease (classical phenotype) who initiated ERT with galsulfase under five years of age and had been on ERT until data collection in 2019, with few exceptions (n = 4 patients who died before 2019). Anthropometric measures, urinary glycosaminoglycans, and data regarding cardiac, orthopedic, neurologic, sleep apnea, hearing and ophthalmologic outcomes were filled in by specialists. Pubertal development, clinical complications, hospitalizations, and surgeries were also assessed. In this resurvey study, treatment with galsulfase has shown to be safe and well tolerated in MPS VI patients who initiated ERT under the age of 5 years and who have been undergoing ERT for approximately 10 years. Mortality rate suggests that early initiation of ERT may have a positive impact on patients' survival, improving but not preventing disease progression and death. MPS VI patients on ERT also showed improved growth velocity and the pubertal development was normal in all surviving patients. Follow-up data on pneumonia and hospitalization suggest that early ERT may have a protective effect against major respiratory complications. Cardiac valve disease progressed since their prior evaluation and spinal cord compression was observed in a large number of patients, suggesting that these disease complications were not modified by ERT.

Retrospective chart review of urinary glycosaminoglycan excretion and long-term clinical outcomes of enzyme replacement therapy in patients with mucopolysaccharidoses.

BACKGROUND: Mucopolysaccharidoses (MPS) are a group of rare, inherited metabolic diseases that result from a deficiency in one of several lysosomal enzymes essential for stepwise glycosaminoglycan (GAG) degradation, leading to GAG accumulation and widespread cellular pathology and clinical disease. Although disease presentation is heterogeneous, the clinical hallmarks are largely comparable across several MPS subtypes. Extensive data have shown that the level of urinary GAG (uGAG) excretion above normal is strongly correlated with disease severity and clinical outcomes in MPS diseases. Thus, change in uGAG excretion may have significant value as a potential primary endpoint in clinical trials of MPS diseases that are too rare to study using traditional clinical endpoints. METHODS: A retrospective medical chart review was undertaken of patients with MPS I, II, and VI who had been treated long term with enzyme replacement therapy (ERT). The relationship between uGAG reduction and clinical outcomes relevant to the major clinical manifestations of these MPS diseases was evaluated. A multi-domain responder index (MDRI) score was calculated, measuring the following 4 domains: 6-min walk test, pulmonary function, growth rate, and Clinician Global Impression of Change. For each domain, a minimal important difference (MID) was defined based on published information of these outcome measures in MPS and other diseases. RESULTS: Of the 50 patients evaluated, 18 (36%) had MPS I, 23 (46%) had MPS II, and 9 (18%) had MPS VI. Forty-two were clinical practice patients and 8 had participated in clinical trials. Across all MPS subtypes, the mean (± SD) uGAG level at baseline was 66.0 ± 51.5 mg/mmol creatinine (n = 48) and there was a mean reduction of 54.6% following ERT. Analysis of the MDRI score based on the MID defined for each domain showed a greater magnitude of improvement in patients with increased uGAG reduction when compared with those patients with lower uGAG reduction for all assessed uGAG thresholds, and a trend toward a higher likelihood of positive mean MDRI score in patients with a uGAG reduction ≥40%. CONCLUSIONS: In this retrospective study, uGAG reduction was associated with long-term clinical outcomes as assessed by a number of approaches, supporting the use of uGAG reduction as a biomarker primary endpoint.

Identification of arylsulfatase B gene mutations and clinical presentations of Iranian patients with Mucopolysaccharidosis VI.

BACKGROUND: Mucopolysaccharidosis (MPS) type VI, also known as Maroteaux-Lamy syndrome, is an autosomal recessive lysosomal storage disorder caused by a deficiency in arylsulfatase B (ARSB) enzyme. Our objectives were to investigate clinical phenotypes and performed molecular studies in Iranian patients with MPS VI, for the first time, in the southwestern Iran. METHODS: We studied 14 cases from 10 unrelated kindreds with MPS VI that were enrolled during 8 years. The mutational analysis of coding and flanking regions of ARSB gene was performed for the patients and their families using genomic DNA from whole blood by direct sequencing. RESULTS: All cases had parental consanguinity. Except one who had Fars ethnicity and presented with a very mild degree of coarse face, but normal otherwise, even near normal height, all were from Arab ethnicity with characteristic phenotypes including severe facial changes, cardiac involvement and dysostosis multiplex. Sequencing analysis of ARSB gene revealed four pathogenic homozygote mutations, including a novel nonsense mutation c.281C>A (p.Ser94X) in 9 patients, as well as, a known nonsense mutation c.753C>G (p.Try251X) in 3 cases, and two missense mutations c.904G>A (p.Gly302Arg) and c.454C>T (p.Arg152Trp) in two cases. The type of mutations affected the severity patient's phenotypes. CONCLUSIONS: These findings increased the genetic databases of Iranian patients with MPS VI and would be so much helpful for the high-risk families to speed the detection of carriers with accuracy and perform the prenatal test of disorder with cost-effective in this population.

Identification of eleven different mutations including six novel, in the arylsulfatase B gene in Iranian patients with mucopolysaccharidosis type VI.

Mucopolysaccharidosis VI is a rare autosomal recessive disorder caused by the deficiency of enzyme Arylsulfatase B. The enzyme deficiency leads to the accumulation of dermatan sulfate in connective tissue which causes manifestations related to MPS VI. Up to now, three different disease causing variants are reported in Iranian patients. In this study, we scanned ARSB gene of 13 Iranian patients from 12 families in whom all parents were consanguineous and from the same ethnicity except one family that were not consanguineous but co-ethnic. We found six not previously reported disease causing variants. We extracted DNA from peripheral blood samples of patients that were previously confirmed as MPS VI by clinical, biochemical and enzymatic assays including berry-spot test and fluorimetry, followed by PCR and direct sequencing. Computational approaches were used to analyze novel variants in terms of their impact on the protein structure. 11 disease causing variants and 15 polymorphisms were found. Six disease causing variants were novel and five were previously reported of which three were in Iranian population. Four of patients, who were unrelated, two by two had the same disease causing variant and polymorphisms, which indicates a possible founder effect. Our study also implicates genotype-phenotype correlation. Computational structural modeling indicated these disease causing variants might affect structural stability and function of the protein. Data of this study confirms the existence of mutational heterogeneity in the ARSB between Iranian patients. Disease causing variants with high frequency can be used in the prenatal diagnosis and genetic counseling. Also, the existence of the same variants and polymorphisms in some of the unrelated patients indicates a possible founder effect.

Genotypic-phenotypic features and enzyme replacement therapy outcome in patients with mucopolysaccharidosis VI from Turkey.

Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disorder (LSD) characterized by a chronic, progressive course with multiorgan involvement. In our study, clinical, biochemical, molecular findings, and response to enzyme replacement therapy (ERT) for at least 6 months were evaluated in 20 patients with MPS VI. Treatment effects on clinical findings such as liver and spleen sizes, cardiac and respiratory parameters, visual and auditory changes, joints' range of motions, endurance tests and changes in urinary glycosaminoglycan excretions, before and after ERT were analyzed. ERT caused increased physical endurance and decreased urinary dermatan sulfate/chondroitin sulfate ratios. Changes in growth parameters, cardiac, respiratory, visual, auditory findings, and joint mobility were not significant. All patients and parents reported out an increased quality of life, which were not correlated with clinical results. The most prevalent mutation was p.L321P, accounting for 58.8% of the mutant alleles and two novel mutations (p.G79E and p.E390 K) were found. ERT was a safe but expensive treatment for MPS VI, with mild benefits in severely affected patients. Early treatment with ERT is mandatory before many organs and systems are involved.

Functional characterization of arylsulfatase B mutations in Indian patients with Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI).

MPS VI is an autosomal recessive disorder which occurs due to the deficiency of N-acetyl galactosamine-4-sulfatase (Arylsulfatase B - ARSB) involved in catabolism of dermatan sulfate resulting from disease-causing variations in the ARSB gene. Human Gene Mutation Database (HGMD) search revealed 200 different mutations in ARSB worldwide. In the present study we carried out molecular and functional analyses to characterize the mutations reported by us in Indian population. Mutation analysis of 19 MPS VI patients revealed presence of a total of 15 different mutations of which twelve were novel [p.Asp53Asn (c.157G>A; p.D53N), p.Leu98Arg (c.293T>G; p.L98R), p.Tyr103Serfs*9 (c.306_312delCTACCAG+146del; p.Y103Sfs*9), p.Phe166Leufs*18 (c.496delT; p.F166Lfs*18), p.Ile220Serfs*5 (c.659_660delTA; p.I220Sfs*5), p.Ile350Phe (c.1048A>T; p.I350F), p.Trp353* (c.1059G>A; p.W353*), p.His393Arg (c.1178A>G; p.H393R), p.Ser403Tyrfs* (c.1208delC; p.S403Yfs*), p.Pro445Leu (c.1334C>T; p.P445L), p.Trp450Leu (c.1349G>T; p.W450L) and p.Trp450Cys (c.1350G>C; p.W450C)] and three were known mutations [p.Asp54Asn (c.160G>A; p.D54N), p.Ala237Asp (c.710C>A; p.A237D) and p.Ser320Arg (c.960C>G; p.S320R)]. Functional characterization using site-directed mutagenesis followed by cell transfection assays, immunoblot, reverse transcriptase PCR and immunofluorescence studies for the putative pathogenic variants detected in our MPS VI patient cohort helped us to confirm the pathogenic potential of the variants in ARSB.

Restriction of Aerobic Metabolism by Acquired or Innate Arylsulfatase B Deficiency: A New Approach to the Warburg Effect.

Aerobic respiration is required for optimal efficiency of metabolism in mammalian cells. Under circumstances when oxygen utilization is impaired, cells survive by anerobic metabolism. The malignant cell has cultivated the use of anerobic metabolism in an aerobic environment, the Warburg effect, but the explanation for this preference is not clear. This paper presents evidence that deficiency of the enzyme arylsulfatase B (ARSB; N-acetylgalactosamine 4-sulfatase), either innate or acquired, helps to explain the Warburg phenomenon. ARSB is the enzyme that removes 4-sulfate groups from the non-reducing end of chondroitin 4-sulfate and dermatan sulfate. Previous reports indicated reduced ARSB activity in malignancy and replication of the effects of hypoxia by decline in ARSB. Hypoxia reduced ARSB activity, since molecular oxygen is needed for post-translational modification of ARSB. In this report, studies were performed in human HepG2 cells and in hepatocytes from ARSB-deficient and normal C57BL/6J control mice. Decline of ARSB, in the presence of oxygen, profoundly reduced the oxygen consumption rate and increased the extracellular acidification rate, indicating preference for aerobic glycolysis. Specific study findings indicate that decline in ARSB activity enhanced aerobic glycolysis and impaired normal redox processes, consistent with a critical role of ARSB and sulfate reduction in mammalian metabolism.

A desensitization method to maintain enzyme replacement therapy in mucopolysaccharidosis type VI

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Deletion of exon 4 in the N-acetylgalactosamine-4-sulfatase gene in a Taiwanese patient with mucopolysaccharidosis type VI.

Mucopolysaccharidosis type VI (MPS VI) is a rare autosomal recessive disorder caused by a deficiency of N-acetylgalactosamine-4-sulfatase (ARSB), one of the enzymes required for the degradation of dermatan sulfate (DS). Accumulation of DS in connective tissue causes growth failure, resulting in short stature. Here, we observed a 5-year-old girl who was the only one affected member of her family and who presented with an exaggerated, convex curvature of the back at the age of one year. Abnormal excretion of DS in the urine and extremely low leukocyte ARSB activity were noted. The patient was suspected to have MPS VI. Direct DNA sequencing indicated that there was no mutation in the coding region of ARSB. However, RT-PCR analysis of RNA prepared from blood samples indicated the deletion of the entire exon 4. Further analysis of the genomic DNA by quantitative PCR confirmed a homozygous deletion of exon 4, an unusual intragenic deletion in ARSB. The deletion led to a truncated protein that lacks most of the catalytic domain. The patient received recombinant human ARSB as enzyme replacement therapy (ERT) at an early stage (2 years), and responded positively in terms of skeletal development and other developmental milestones. The early identification of type VI MPS patients and subsequent treatment with ERT may be beneficial for the clinical outcome of MPS VI patients. In addition, detailed gene analysis may enhance the ability to provide genetic counseling to families of patients affected by MPS VI.

[Analysis of clinical features and arylsulfatase B gene mutation in thirteen Chinese children with mucopolysaccharidosis type VI].

OBJECTIVE: Mucopolysaccharidosis type VI (MPS VI) or Maroteaux-Lamy syndrome is an autosomal recessive lysosomal storage disease caused by a deficiency of arylsulfatase B(ARSB), which is required in the degradation of dermatan sulfate and chondroitin sulfate. The deficiency of ARSB leads to an accumulation of dermatan sulfate and chondroitin sulfate in lysosomes and gross excretion in the urine.Few articles about clinical study and ARSB gene mutation analysis of Chinese MPS VI patients were published. This study aimed to explore the clinical features and characteristics of ARSB gene in Chinese children with MPS VI. METHOD: Thirteen children were diagnosed as MPS VI by ARSB enzyme activity determination during the period from 2009 to 2013. Their clinical features, radiological findings and urine glycosaminoglycan (GAG) levels were retrospectively reviewed. Direct sequencing was used to identify any mutation in the ARSB gene. RESULT: Thirteen children were diagnosed at the average age of (3.9 ± 2.2) years with 6 male and 7 female. All of these children presented with severe form and onset at an early age of (1.5 ± 0.8) years.Other clinical features included coarse facies, short stature, skeleton deformity, corneal clouding, hepatosplenomegaly with normal intelligence. The radiological findings in all children were characteristic of dysostosis multiplex, like abnormal development of vertebral bodies of the spine, campylorrhachia and paddle-shaped widened ribs. The MRI in case 2 showed cervical cord compression and multiple cysts degeneration in the corona radiate, cella lateralis and callosum.High urine GAG levels were detected, (307.10 ± 112.14) mg/L (Normally below 70 mg/L) and (722.28 ± 245.68) µg/mg creatinine. The ARSB enzyme activity in leukocytes was low, (13.29 ± 6.22) nmol/(mg×h) [Normal range (47-169) nmol/(mg×h)] by fluorogenic assay and (0.24 ± 0.18) U/g [Normal range (1.01-11.47) U/g] by colorimetric assay. A total of 11 mutations were identified by molecular analysis, including seven previously reported mutations (p.L72R, p.G167R, p.G303E, p.F399L, p. T442M, p.Y255X and p.R327X) and four novel mutations (p.Y175D, p.S403X, p.S464X and large deletion including ex. 2, 3). The c.1197C>G (p.F399L) mutation was the most common mutation in this study (31%). CONCLUSION: The severe form of MPS VI is characterized by early onset and rapid illness progression. Both the radiological findings and increased urine GAG are important clues to diagnose MPS VI.Large decrease or absence of ARSB activity is diagnostic for MPS VI.Four novel mutations of ARSB gene were identified. The reported mutation c.1197C>G (p.F399L) was the hot-spot mutation in this study.

Development of nanoparticle-bound arylsulfatase B for enzyme replacement therapy of mucopolysaccharidosis VI.

Lysosomal storage disorders like mucopolysaccharidosis (MPS) VI are rare diseases with a lack of well-suited treatments. Even though an enzyme replacement therapy (ERT) of recombinant arylsulfatase B (ASB) is available for MPS VI, the administration cannot positively affect the neurologic manifestations such as spinal cord compression. Since nanoparticles (NP) have shown to be effective drug carriers, the feasibility of arylsulfatase B adsorption onto poly(butyl cyanoacrylate) (PBCA) nanoparticles was investigated in this study. In order to advance the ERT of ASB, the adsorption of the latter on the surface of PBCA NP as well as in vitro release in serum was investigated. With alteration of parameters like temperature, incubation time, pH, and enzyme amount, the adsorption process revealed to be stable with a maximum capacity of 67 microg/mg NP at a pH of 6.3. In vitro release experiments demonstrated that the adsorption is stable for at least 60 minutes in human blood serum, indicating that the ASB-loaded PBCA nanoparticles represent a promising candidate for ERT of MPS VI.

Up to five years experience with 11 mucopolysaccharidosis type VI patients.

Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a rare progressive metabolic disorder characterized by coarse facial features, hepatosplenomegaly, restrictive pulmonary function, cardiac abnormalities and stiff joints. The disease is caused by a deficiency of the lysosomal enzyme N-acetyl galactosamine 4-sulfatase which leads to glycosaminoglycan (GAG) storage in various tissues. It presents as a clinical spectrum with varying disease progressions and severities. While the phases I/II/III studies proved the effectiveness of enzyme-replacement therapy (ERT) with recombinant human arylsulfatase B, long-term data are still scarce. Over treatment periods ranging from 1.3 to 5.4 years, this prospective open-label follow-up study in 11 Dutch mucopolysaccharidosis type VI patients (age 2-18 years) showed that ERT had significant positive effects on cardiac-wall diameters (IVSd and LVMI), left and right shoulder flexions (p<0.001), liver size and spleen size (p<0.001), urinary GAG excretion (p<0.001), and the scales of quality of life (motor functioning and body functioning). ERT did not affect cardiac valve regurgitation or hearing function; HRQoL decreased slightly in two domains ('anxiety' and 'negative emotions'), and patients with the rapid and slow progressive forms of the disease differed with regard to baseline GAG excretion and GAG decrease during treatment. In conclusion, ERT had an effect on several clinical parameters. This effect was established in an open cohort of young mucopolysaccharidosis type VI patients.

Enzyme replacement therapy with galsulfase in 34 children younger than five years of age with MPS VI.

BACKGROUND: Mucopolysaccharidosis type VI (MPS VI) is a progressive, chronic and multisystem lysosomal storage disease with a wide disease spectrum. Clinical and biochemical improvements have been reported for MPS VI patients on enzyme replacement therapy (ERT) with rhASB (recombinant human arylsulfatase B; galsulfase, Naglazyme®, BioMarin Pharmaceutical Inc.), making early diagnosis and intervention imperative for optimal patient outcomes. Few studies have included children younger than five years of age. This report describes 34 MPS VI patients that started treatment with galsulfase before five years of age. METHODS: Data from patients who initiated treatment at <5 years of age were collected from patients' medical records. Baseline and follow-up assessments of common symptoms that led to diagnosis and that were used to evaluate disease progression and treatment efficacy were evaluated. RESULTS: A significant negative correlation was seen with treatment with ERT and urinary GAG levels. Of those with baseline and follow-up growth data, 47% remained on their pre-treatment growth curve or moved to a higher percentile after treatment. Of the 9 patients with baseline and follow-up sleep studies, 5 remained unaffected and 1 patient initially with mild sleep apnea showed improvement. Data regarding cardiac, ophthalmic, central nervous system, hearing, surgical interventions and development are also reported. No patient discontinued treatment due to an adverse event and all that were treatment-emergent resolved. CONCLUSIONS: The prescribed dosage of 1mg/kg IV weekly with galsulfase ERT is shown to be safe and effective in slowing and/or improving certain aspects of the disease, although patients should be closely monitored for complications associated with the natural history of the disease, especially cardiac valve involvement and spinal cord compression. A long-term follow-up investigation of this group of children will provide further information on the benefits of early treatment as well as disease progression and treatment efficacy and safety in this young patient population.

Pharmacological read-through of nonsense ARSB mutations as a potential therapeutic approach for mucopolysaccharidosis VI.

Mucopolysaccharidosis type VI (MPS VI) is a severe lysosomal storage disorder without central nervous system involvement caused by arylsulfatase B (ARSB) deficiency. MPS VI is characterized by dysostosis multiplex, corneal clouding, heart valve defects and urinary excretion of glycosaminoglycans (GAGs). The current treatment for MPS VI is enzyme replacement therapy (ERT) which has limited efficacy on bone, joints and heart valve disease, as well as high costs. A potential therapeutic approach for the subgroup of MPS VI patients that carry nonsense mutations is to enhance stop-codon read-through, using small molecules, to restore production of the full-length ARSB protein. In this study we investigated whether two compounds known to induce stop codon read-through, the aminoglycoside gentamicin and PTC124, can promote read-through of four different ARSB nonsense mutations (p.R315X, p.R327X, p.Q456X and p.Q503X) associated with MPS VI and enable the synthesis of full-length functional ARSB protein in patients fibroblast cell lines. Our study demonstrates that PTC124 but not gentamicin, increases the level of ARSB activity in three MPS VI patient fibroblast cell lines. In two of them the levels of ARSB activity obtained were significantly higher than in untreated cells, reaching ≤2.5 % of those detected in wild-type fibroblasts and resulting in significant reduction of lysosomal size. Since even small increases in enzyme activity can dramatically influence the clinical phenotype of MPS VI, our study suggests that pharmacological read-through may be combined with ERT potentially increasing therapeutic efficacy in those patients bearing nonsense ARSB mutations.

Identification of a novel arylsulfatase B gene mutation in three unrelated Iranian mucopolysaccharidosis type-VI patients with different phenotype severity.

BACKGROUND: Mucopolysaccharidosis type-VI (MPS-VI), which is inherited as an autosomal recessive trait, results from the deficiency of N-acetylgalactosamine 4-sulfatase (arylsulfatase B) activity and the lysosomal accumulation of dermatan sulfate. In this study, ARSB mutation analysis was performed on three unrelated patients who were originally from the West Azerbaijan province of Iran. METHODS: After PCR and direct DNA sequencing, DNA extraction was performed. RESULTS: Sequencing analysis revealed a novel homozygous missense mutation in the ARSB gene at c.1457A

Ethical and economic considerations of rare diseases in ethnic minorities: the case of mucopolysaccharidosis VI in Colombia.

Mucopolysaccharidosis VI is an autosomal recessive lysosomal storage disorder associated with severe disability and premature death. The presence of a mucopolysaccharidosis-like disease in indigenous ethnic groups in Colombia can be inferred from archaeological findings. There are several indigenous patients with mucopolysaccharidosis VI currently receiving enzyme replacement therapy. We discuss the ethical and economic considerations, regarding both direct and indirect costs, of a high-cost orphan disease in a marginalised minority population in a developing country.

Expert recommendations for the laboratory diagnosis of MPS VI.

Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease caused by a deficiency of N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). This enzyme is required for the degradation of dermatan sulfate. In its absence, dermatan sulfate accumulates in cells and is excreted in large quantities in urine. Specific therapeutic intervention is available; however, accurate and timely diagnosis is crucial for maximal benefit. To better understand the current practices for diagnosis and to establish diagnostic guidelines, an international MPS VI laboratory diagnostics scientific summit was held in February of 2011 in Miami, Florida. The various steps in the diagnosis of MPS VI were discussed including urinary glycosaminoglycan (uGAG) analysis, enzyme activity analysis, and molecular analysis. The following conclusions were reached. Dilute urine samples pose a significant problem for uGAG analysis and MPS VI patients can be missed by quantitative uGAG testing alone as dermatan sulfate may not always be excreted in large quantities. Enzyme activity analysis is universally acknowledged as a key component of diagnosis; however, several caveats must be considered and the appropriate use of reference enzymes is essential. Molecular analysis supports enzyme activity test results and is essential for carrier testing, subsequent genetic counseling, and prenatal testing. Overall the expert panel recommends caution in the use of uGAG screening alone to rule out or confirm the diagnosis of MPS VI and acknowledges enzyme activity analysis as a critical component of diagnosis. Measurement of another sulfatase enzyme to exclude multiple sulfatase deficiency was recommended prior to the initiation of therapy. When feasible, the use of molecular testing as part of the diagnosis is encouraged. A diagnostic algorithm for MPS VI is provided.

Neonatal gene therapy with a gamma retroviral vector in mucopolysaccharidosis VI cats.

Mucopolysaccharidosis (MPS) VI is due to a deficiency in the activity of N-acetylgalactosamine 4-sulfatase (4S), also known as arylsulfatase B. Previously, retroviral vector (RV)-mediated neonatal gene therapy reduced the clinical manifestations of MPS I and MPS VII in mice and dogs. However, sulfatases require post-translational modification by sulfatase-modifying factors. MPS VI cats were injected intravenously (i.v.) with a gamma RV-expressing feline 4S, resulting in 5 ± 3 copies of RV per 100 cells in liver. Liver and serum 4S activity were 1,450 ± 1,720 U/mg (26-fold normal) and 107 ± 60 U/ml (13-fold normal), respectively, and were directly proportional to the liver 4S protein levels for individual cats. This study suggests that sulfatase-modifying factor (SUMF) activity in liver was sufficient to result in active enzyme despite overexpression of 4S. RV-treated MPS VI cats achieved higher body weights and longer appendicular skeleton lengths, had reduced articular cartilage erosion, and reduced aortic valve thickening and aortic dilatation compared with untreated MPS VI cats, although cervical vertebral bone lengths were not improved. This demonstrates that therapeutic expression of a functional sulfatase protein can be achieved with neonatal gene therapy using a gamma RV, but some aspects of bone disease remain difficult to treat.

Intrathecal recombinant human 4-sulfatase reduces accumulation of glycosaminoglycans in dura of mucopolysaccharidosis VI cats.

INTRODUCTION: Mucopolysaccharidosis VI (MPS-VI) is caused by a deficiency in N-acetylgalactosamine-4-sulfatase activity, resulting in lysosomal accumulation of partially degraded glycosaminoglycans (GAGs). Compressive myelopathy in early-onset MPS-VI patients has been partly attributed to thickening of the dura mater following engorgement with GAG. In this study, we therefore tested whether the dural abnormalities could be prevented in a feline model of the disorder. RESULTS: All intrathecal injections (IT-INJs) were well tolerated. MPS-VI cats treated with IT-INJ of recombinant human N-acetylgalactosamine-4-sulfatase (rhASB) exhibited reduced vacuolation in the dural fibroblasts, diminished levels of sulfated-N-acetylhexosamine (HNAc(+S)) in the cerebrospinal fluid (CSF) and no hind-limb paresis. Serum anti-rhASB antibodies remained low in MPS-VI cats treated with intravenous enzyme replacement therapy (IV-ERT) and increased slightly in normal cats treated with IT-INJ of rhASB alone. Anti-rhASB antibodies in CSF remained undetectable. DISCUSSION: These data indicate that repeated IT-INJ of rhASB can safely prevent GAG storage in MPS-VI dura. METHODS: Cats were assigned to three groups: (i) receiving weekly IV-ERT of rhASB from birth plus six monthly IT-INJs of rhASB from age 2 months; (ii) receiving six monthly IT-INJs of vehicle; or (iii) untreated. Additional normal cats received five fortnightly IT-INJs of rhASB or vehicle alone.

Long-term amelioration of feline Mucopolysaccharidosis VI after AAV-mediated liver gene transfer.

Mucopolysaccharidosis VI (MPS VI) is caused by deficient arylsulfatase B (ARSB) activity resulting in lysosomal storage of glycosaminoglycans (GAGs). MPS VI is characterized by dysostosis multiplex, organomegaly, corneal clouding, and heart valve thickening. Gene transfer to a factory organ like liver may provide a lifetime source of secreted ARSB. We show that intravascular administration of adeno-associated viral vectors (AAV) 2/8-TBG-felineARSB in MPS VI cats resulted in ARSB expression up to 1 year, the last time point of the study. In newborn cats, normal circulating ARSB activity was achieved following delivery of high vector doses (6 × 10(13) genome copies (gc)/kg) whereas delivery of AAV2/8 vector doses as low as 2 × 10(12) gc/kg resulted in higher than normal serum ARSB levels in juvenile MPS VI cats. In MPS VI cats showing high serum ARSB levels, independent of the age at treatment, we observed: (i) clearance of GAG storage, (ii) improvement of long bone length, (iii) reduction of heart valve thickness, and (iv) improvement in spontaneous mobility. Thus, AAV2/ 8-mediated liver gene transfer represents a promising therapeutic strategy for MPS VI patients.