Intravenous Idursulfase for the Treatment of Mucopolysaccharidosis Type II: A Systematic Literature Review.

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is a rare, X-linked disorder caused by deficient activity of the enzyme iduronate-2-sulfatase. Signs and symptoms typically emerge at 1.5-4 years of age and may include cognitive impairment, depending on whether patients have the neuronopathic or non-neuronopathic form of the disease. Treatment is available in the form of enzyme replacement therapy (ERT) with recombinant iduronate-2-sulfatase (idursulfase). A systematic literature review was conducted to assess the evidence regarding efficacy, effectiveness, and safety of ERT with intravenous idursulfase for MPS II. Electronic databases were searched in January 2023, and 33 eligible articles were found. These were analyzed to evaluate the effects of intravenous idursulfase and the overall benefits and disadvantages in patient subgroups. Studies showed that intravenous idursulfase treatment resulted in improved short- and long-term clinical and patient-centered outcomes, accompanied by a favorable safety profile. Patients with non-neuronopathic MPS II had more pronounced improvements in clinical outcomes than those with neuronopathic MPS II. In addition, the review identified that improvements in clinical outcomes are particularly apparent if intravenous idursulfase is started early in life, strengthening previous recommendations for early ERT initiation to maximally benefit patients. This review provides a comprehensive summary of our current knowledge on the efficacy of ERT in different populations of patients with MPS II and will help to inform the overall management of the disease in an evolving treatment landscape.

A Phase 2/3 Trial of Pabinafusp Alfa, IDS Fused with Anti-Human Transferrin Receptor Antibody, Targeting Neurodegeneration in MPS-II.

Pabinafusp alfa (JR-141) is a novel enzyme drug that crosses the blood-brain barrier by transcytosis via transferrin receptors. In order to establish its efficacy and safety, a multicenter, single-arm, open-label phase 2/3 clinical trial was conducted in 28 Japanese patients with mucopolysaccharidosis II (MPS-II, Hunter syndrome) by intravenous administrations of 2.0 mg/kg of pabinafusp alfa for 52 weeks. The primary efficacy endpoint was changes in heparan sulfate (HS) concentrations in the cerebrospinal fluid (CSF). Secondary endpoints included assessments of neurocognitive development for central efficacy, and changes in plasma HS and dermatan sulfate (DS) concentrations for peripheral efficacy. HS concentrations in the CSF significantly decreased from baseline to week 52 (p < 0.001), suggesting continuous inhibition of substrate accumulations in the CNS, i.e., hitherto unaddressed progressive neurodegeneration. Evaluations of neurocognitive developments showed positive changes in 21 of the 28 patients. Serum HS and DS concentrations, liver and spleen volumes, and other assessments suggested the peripheral efficacy of pabinafusp alfa was comparable to that of idursulfase. Drug-related adverse events were mild or moderate in severity, transient, and manageable. The results establish delivery across the BBB of pabinafusp alfa as an effective therapeutic for treating both the CNS and peripheral symptoms of patients with MPS-II.

Iduronate-2-sulfatase fused with anti-hTfR antibody, pabinafusp alfa, for MPS-II: A phase 2 trial in Brazil.

In Hunter syndrome (mucopolysaccharidosis II [MPS-II]), systemic accumulation of glycosaminoglycans (GAGs) due to a deficiency of iduronate-2-sulfatase (IDS), caused by mutations in the IDS gene, leads to multiple somatic manifestations and in patients with the severe (neuronopathic) phenotype, also to central nervous system (CNS) involvement. These symptoms cannot be effectively treated with current enzyme-replacement therapies, as they are unable to cross the blood-brain barrier (BBB). Pabinafusp alfa, a novel IDS fused with an anti-human transferrin receptor antibody, was shown to penetrate the BBB and to address neurodegeneration in preclinical studies. Subsequent phase 1/2 and 2/3 clinical studies in Japan have shown marked reduction of GAG accumulation in the cerebrospinal fluid (CSF), along with favorable clinical responses. A 26-week, open-label, randomized, parallel-group phase 2 study was conducted in Brazil to further evaluate the safety and efficacy of intravenously administered pabinafusp alfa at 1.0, 2.0, and 4.0 mg/kg/week in MPS-II patients. The safety profiles in the three dosage groups were similar. Neurodevelopmental evaluation suggested positive neurocognitive signals despite a relatively short study period. The 2.0-mg/kg group, which demonstrated marked reductions in substrate concentrations in the CSF, serum, and urine, was considered to provide the best combination regarding safety and efficacy signals.

Clearance of heparan sulfate in the brain prevents neurodegeneration and neurocognitive impairment in MPS II mice.

Mucopolysaccharidosis II (MPS II), a lysosomal storage disease caused by mutations in iduronate-2-sulfatase (IDS), is characterized by a wide variety of somatic and neurologic symptoms. The currently approved intravenous enzyme replacement therapy with recombinant IDS (idursulfase) is ineffective for CNS manifestations due to its inability to cross the blood-brain barrier (BBB). Here, we demonstrate that the clearance of heparan sulfate (HS) deposited in the brain by a BBB-penetrable antibody-enzyme fusion protein prevents neurodegeneration and neurocognitive dysfunctions in MPS II mice. The fusion protein pabinafusp alfa was chronically administered intravenously to MPS II mice. The drug reduced HS and attenuated histopathological changes in the brain, as well as in peripheral tissues. The loss of spatial learning abilities was completely suppressed by pabinafusp alfa, but not by idursulfase, indicating an association between HS deposition in the brain, neurodegeneration, and CNS manifestations in these mice. Furthermore, HS concentrations in the brain and reduction thereof by pabinafusp alpha correlated with those in the cerebrospinal fluid (CSF). Thus, repeated intravenous administration of pabinafusp alfa to MPS II mice decreased HS deposition in the brain, leading to prevention of neurodegeneration and maintenance of neurocognitive function, which may be predicted from HS concentrations in CSF.

Efficient engraftment of genetically modified cells is necessary to ameliorate central nervous system involvement of murine model of mucopolysaccharidosis type II by hematopoietic stem cell targeted gene therapy.

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disease (LSD) caused by a deficiency of the iduronate-2-sulfatase (IDS) that catabolizes glycosaminoglycans (GAGs). Abnormal accumulations of GAGs in somatic cells lead to various manifestations including central nervous system (CNS) disease. Enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are the currently available therapy for MPS II, but both therapies fail to improve CNS manifestations. We previously showed that hematopoietic stem cell targeted gene therapy (HSC-GT) with lethal irradiation improved CNS involvement in a murine model of MPS II which lacks the gene coding for IDS. However, the strong preconditioning, with lethal irradiation, would cause a high rate of morbidity and mortality. Therefore, we tested milder preconditioning procedures with either low dose irradiation or low dose irradiation plus an anti c-kit monoclonal antibody (ACK2) to assess CNS effects in mice with MPS II after HSC-GT. Mice from all the HSC-GT groups displayed super-physiological levels of IDS enzyme activity and robust reduction of abnormally accumulated GAGs to the wild type mice levels in peripheral organs. However, only the mice treated with lethal irradiation showed significant cognitive function improvement as well as IDS elevation and GAG reduction in the brain. These results suggest that an efficient engraftment of genetically modified cells for HSC-GT requires strong preconditioning to ameliorate CNS involvement in cases with MPS II.

Targeting Brain Disease in MPSII: Preclinical Evaluation of IDS-Loaded PLGA Nanoparticles.

Mucopolysaccharidosis type II (MPSII) is a lysosomal storage disorder due to the deficit of the enzyme iduronate 2-sulfatase (IDS), which leads to the accumulation of glycosaminoglycans in most organ-systems, including the brain, and resulting in neurological involvement in about two-thirds of the patients. The main treatment is represented by a weekly infusion of the functional enzyme, which cannot cross the blood-brain barrier and reach the central nervous system. In this study, a tailored nanomedicine approach based on brain-targeted polymeric nanoparticles (g7-NPs), loaded with the therapeutic enzyme, was exploited. Fibroblasts from MPSII patients were treated for 7 days with NPs loaded with the IDS enzyme; an induced IDS activity like the one detected in healthy cells was measured, together with a reduction of GAG content to non-pathological levels. An in vivo short-term study in MPSII mice was performed by weekly administration of g7-NPs-IDS. Biochemical, histological, and immunohistochemical evaluations of liver and brain were performed. The 6-weeks treatment produced a significant reduction of GAG deposits in liver and brain tissues, as well as a reduction of some neurological and inflammatory markers (i.e., LAMP2, CD68, GFAP), highlighting a general improvement of the brain pathology. The g7-NPs-IDS approach allowed a brain-targeted enzyme replacement therapy. Based on these positive results, the future aim will be to optimize NP formulation further to gain a higher efficacy of the proposed approach.

Efficacy of Idursulfase therapy in patients with Mucopolysaccharidosis type II who initiated enzyme replacement therapy in adult age. A systematic review of the literature.

BACKGROUND: Enzyme replacement therapy (ERT) has been shown to decrease urine glycosaminoglycans (uGAGs) and liver and spleen volumes, and to improve clinical symptoms in mucopolysaccharidosis type II (MPS-II) patients. METHODS: A systematic search of the literature, from inception to August 2017, was conducted to identify randomized trials or observational studies including ≥1 MPS-II patients with ERT initiated in adult age (≥16 years) and evaluating ERT efficacy. Evidence was rated according to GRADE criteria. Common efficacy outcomes of the clinical studies were analyzed. Case reports were separately evaluated. RESULTS: One randomized clinical trial, 4 observational studies and 5 case reports were selected. ERT decreased uGAG levels and liver and spleen size with moderate evidence level and led to anti-ERT antibody and IRRS development in a significant proportion of patients with moderate evidence level. There were no conclusive results for beneficial effects on 6MWT, respiratory, cardiac and neurological function, joint mobility, sleep disorders of respiratory origin, and quality of life. LIMITATIONS: Excluding one observational study, all others were not conducted specifically in the target population (ERT ≥16 years). Data were from subgroup analyses of selected studies. There was a great heterogeneity between study designs and clinical outcomes evaluated. CONCLUSIONS: ERT improves uGAGs and liver/spleen volume with a moderate evidence level in MPS-II patients initiating therapy as adults, although the putative associated clinical benefit is unclear.

Correlation between urinary GAG and anti-idursulfase ERT neutralizing antibodies during treatment with NICIT immune tolerance regimen: A case report.

INTRODUCTION: Antibodies to intravenous idursulfase enzyme replacement therapy (ERT) for patients with Hunter syndrome (mucopolysaccharidosis type II, MPS II) can have a harmful clinical impact, including both increasing risk of infusion reactions and inhibiting therapeutic activity. Thus, failure to monitor anti-idursulfase antibodies and neutralizing antibodies, and delays in reporting results, may postpone critical clinical decisions. HYPOTHESIS: Urinary glycosaminoglycan (GAG) levels may be used as a biomarker for anti-idursulfase antibodies and neutralizing antibodies to improve timeliness in monitoring and managing ERT. METHODS: This is a case report describing a patient with MPS II with high levels of neutralizing antibodies and worsened clinical status who was treated for five years with a non-immunosuppressive and non-cytotoxic immune tolerance (NICIT) regimen, consisting of intravenous immune globulin and frequent infusions of idursulfase. Neutralizing antibodies and total anti-idursulfase antibodies were measured by two different methods, the direct 1,9-dimethylmethylene blue (DMB) assay and cetylpyridinium chloride carbazole-borate (CPC) assay. RESULTS: Neutralizing antibodies, measured as percent inhibition of enzyme activity and also by total neutralizing antibody titer, were correlated with quantitative urinary GAG measured by DMB assay (p=0.026, p=0.0067), and quantitative urinary GAG by CPC assay with percent inhibition of enzyme activity by neutralizing antibodies (p=0.0475). The NICIT regimen showed a sustained immune tolerance after five years and was well-tolerated. CONCLUSIONS: Urinary GAG, measured by DMB assay, may be a biomarker for anti-idursulfase neutralizing antibodies and is useful for managing immune tolerance regimens for patients with MPS II who have high levels of anti-idursulfase neutralizing antibodies. This study highlights the importance of regular and frequent monitoring of urinary GAG in patients with MPS II who are receiving ERT. The NICIT regimen, with less drug toxicities, may be preferred in patients with MPS who have a high risk of infections and whose disease progresses less rapidly than some other lysosomal storage diseases, such as infantile Pompe disease.

A phase I/II study of intrathecal idursulfase-IT in children with severe mucopolysaccharidosis II.

PURPOSE: Approximately two-thirds of patients with the lysosomal storage disease mucopolysaccharidosis II have progressive cognitive impairment. Intravenous (i.v.) enzyme replacement therapy does not affect cognitive impairment because recombinant iduronate-2-sulfatase (idursulfase) does not penetrate the blood-brain barrier at therapeutic concentrations. We examined the safety of idursulfase formulated for intrathecal administration (idursulfase-IT) via intrathecal drug delivery device (IDDD). A secondary endpoint was change in concentration of glycosaminoglycans in cerebrospinal fluid. METHODS: Sixteen cognitively impaired males with mucopolysaccharidosis II who were previously treated with weekly i.v. idursulfase 0.5 mg/kg for ≥6 months were enrolled. Patients were randomized to no treatment or 10-mg, 30-mg, or 1-mg idursulfase-IT monthly for 6 months (four patients per group) while continuing i.v. idursulfase weekly. RESULTS: No serious adverse events related to idursulfase-IT were observed. Surgical revision/removal of the IDDD was required in 6 of 12 patients. Twelve total doses were administrated by lumbar puncture. Mean cerebrospinal fluid glycosaminoglycan concentration was reduced by approximately 90% in the 10-mg and 30-mg groups and approximately 80% in the 1-mg group after 6 months. CONCLUSIONS: These preliminary data support further development of investigational idursulfase-IT in MPS II patients with the severe phenotype who have progressed only to a mild-to-moderate level of cognitive impairment.Genet Med 18 1, 73-81.

Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome).

BACKGROUND: Mucopolysaccharidosis II, also known as Hunter syndrome, is a rare, X-linked disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyses a step in the catabolism of glycosaminoglycans. The glycosaminoglycans accumulate within tissues affecting multiple organs and physiologic systems. The clinical manifestations include neurologic involvement, severe airways obstruction, skeletal deformities and cardiomyopathy. The disease has a variable age of onset and variable rate of progression. In those with severe disease, death usually occurs in the second decade of life, whereas those individuals with less severe disease may survive into adulthood. Enzyme replacement therapy with intravenous infusions of idursulfase has emerged as a new treatment for mucopolysaccharidosis type II. This is an update of a previously published version of this review. OBJECTIVES: To evaluate the effectiveness and safety of enzyme replacement therapy with idursulfase compared to other interventions, placebo or no intervention, for treating mucopolysaccharidosis type II. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register (date of last search 23 November 2015).We also searched Embase, PubMed and the Literature Latino-Americana e do Caribe em Ciências da Saúde (LILACS) (date of last search 28 November 2015). SELECTION CRITERIA: Randomised and quasi-randomised controlled trials of enzyme replacement therapy with idursulfase compared to no intervention, placebo or other options (e.g. behavioral strategies, transplantation). DATA COLLECTION AND ANALYSIS: Two authors independently screened the trials identified, appraised quality of papers and extracted data. MAIN RESULTS: One study (96 male participants) met the inclusion criteria, although the primary outcome of this review - z score for height and weight, was not assessed in the study. This trial was considered to be of overall good quality. Following 53 weeks of treatment, participants in the weekly idursulfase 0.5 mg/kg group demonstrated a significant improvement rate compared with placebo for the primary outcome: distance walked in six minutes on the basis of the sum of ranks of change from baseline, mean difference 37.00 (95% confidence interval 6.52 to 67.48). The every-other-week idursulfase 0.5 mg/kg group also showed an improvement, which was not significant compared with placebo, mean difference 23.00 (95% confidence interval -4.49 to 50.49). After 53 weeks, there was no statistical significance difference in per cent predicted forced vital capacity between the three groups and absolute forced vital capacity was significantly increased from baseline in the weekly dosing group compared to placebo, mean difference 0.16 (95% confidence interval CI 0.05 to 0.27). No difference was observed between the every-other-week idursulfase 0.5 mg/kg group and placebo.In addition, liver and spleen volumes and urine glycosaminoglycan excretion were significantly reduced from baseline by both idursulfase dosing regimens. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 31.7% of participants at the end of the study and they were related to a smaller reduction in urine glycosaminoglycan levels. AUTHORS' CONCLUSIONS: The current evidence is limited. While the randomised clinical trial identified was considered to be of good quality, it failed to describe important outcomes. It has been demonstrated that enzyme replacement therapy with idursulfase is effective in relation to functional capacity (distance walked in six minutes and forced vital capacity), liver and spleen volumes and urine glycosaminoglycan excretion in people with mucopolysaccharidosis type II compared with placebo. There is no available evidence in the included study and in the literature on outcomes such as improvement in growth, sleep apnoea, cardiac function, quality of life and mortality. More studies are needed to obtain more information on the long-term effectiveness and safety of enzyme replacement therapy.

Safety and efficacy of enzyme replacement therapy with idursulfase beta in children aged younger than 6 years with Hunter syndrome.

Idursulfase beta (Hunterase®) has been used for enzyme replacement therapy (ERT) of patients with mucopolysaccharidosis II (MPS II, Hunter syndrome) aged 6 years or older since 2012 in Korea. The objective of this study was to evaluate the safety and efficacy of ERT with idursulfase beta in Hunter syndrome children younger than 6 years. This study was a 52-week, single center, single arm, open-label clinical trial (NCT01645189). Idursulfase beta (0.5mg/kg/week) was administered intravenously for 52 weeks. The primary endpoint was safety assessed by adverse events (AEs). Secondary endpoints included vital signs, physical examination, ECG, laboratory tests, anti-idursulfase antibodies, and efficacy represented by changes in urinary glycosaminoglycan (GAG) at week 53 from baseline. In addition, growth indices and developmental milestones (Denver II test) were evaluated as exploratory variables. All six patients experienced at least one AE. A total of 109 AEs were reported. One patient experienced a serious AE (hospitalization due to gastroenteritis) that was considered not to be treatment related. One patient (16.7%) experienced infusion-related adverse drug reactions (ADRs), developing urticaria six times and a cough five times. There were no serious ADRs and no clinically significant changes in vital signs, physical exam, laboratory parameters, or ECG. Of the six patients, four (66.7%) showed anti-idursulfase antibodies and neutralizing antibodies on at least one occasion during the study. At week 53, urinary GAG was significantly reduced by -35.1±30.6mgGAG/g creatine from baseline (P=0.038). This study indicates that the safety and efficacy of idursulfase beta are similar to those reported in Hunter syndrome patients aged 6 years or older.

A multicenter, open-label study evaluating safety and clinical outcomes in children (1.4-7.5 years) with Hunter syndrome receiving idursulfase enzyme replacement therapy.

PURPOSE: The primary objective of this study was to determine the safety of idursulfase in Hunter syndrome patients aged 5 years or younger. METHODS: Idursulfase (0.5 mg/kg) was administered intravenously on a weekly basis (52 infusions per patient) in an open-label study. Safety monitoring included adverse events, anti-idursulfase antibodies, vital signs, physical examination, 12-lead electrocardiogram, concomitant medications or procedures, and laboratory testing (clinical chemistry, hematology, and urinalysis). The following exploratory efficacy outcomes were assessed at baseline and at weeks 18 or 36 or 53: urinary glycosaminoglycan levels, liver or spleen size, developmental milestones, and growth indices. Pharmacokinetic parameters were assessed at week 27. RESULTS: Twenty-eight boys aged 1.4-7.5 years were enrolled (one discontinued for noncompliance) in the study. All the patients reported adverse events (16 patients (57%) reported possibly or probably treatment-related adverse events). The only severe adverse event was sleep apnea (two patients); others were mild or moderate. Sixteen patients had infusion-related adverse events, a similar proportion as previously reported. Thirteen patients (46%) experienced at least one serious adverse event: pyrexia and bronchopneumonia were the most common (three patients each). No clinically important drug-related changes in laboratory parameters or vital signs or electrocardiograms were reported. Nineteen patients (68%) developed anti-idursulfase immunoglobulin G antibodies. Growth rates remained within normal age-related ranges. Developmental quotients were lower than normal but remained stable. By week 18, organ size and urinary glycosaminoglycan levels decreased as compared with baseline and remained stable throughout the study. CONCLUSION: Idursulfase safety, tolerability, and efficacy were similar to that previously reported in males ≥5 years.

Enzyme augmentation therapy enhances the therapeutic efficacy of bone marrow transplantation in mucopolysaccharidosis type II mice.

Before the availability of an enzyme replacement therapy (ERT) for mucopolysaccharidosis type II (MPS II), patients were treated by bone marrow transplantation (BMT). However, the effectiveness of BMT for MPS II was equivocal, particularly at addressing the CNS manifestations. To study this further, we subjected a murine model of MPS II to BMT and evaluated the effect at correcting the biochemical and pathological aberrations in the viscera and CNS. Our results indicated that BMT reduced the accumulation of glycosaminoglycans (GAGs) in a variety of visceral organs, but not in the CNS. With the availability of an approved ERT for MPS II, we investigated and compared the relative merits of the two strategies either as a mono or combination therapy. We showed that the combination of BMT and ERT was additive at reducing tissue levels of GAGs in the heart, kidney and lung. Moreover, ERT conferred greater efficacy if the immunological response against the infused recombinant enzyme was low. Finally, we showed that pathologic GAGs might potentially represent a sensitive biomarker to monitor the therapeutic efficacy of therapies for MPS II.

Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome).

BACKGROUND: Mucopolysaccharidosis II, also known as Hunter syndrome, is a rare, X-linked disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyses a step in the catabolism of glycosaminoglycans. The glycosaminoglycans accumulate within tissues affecting multiple organs and physiologic systems. The clinical manifestations include neurologic involvement, severe airways obstruction, skeletal deformities and cardiomyopathy. The disease has a variable age of onset and variable rate of progression. In those with severe disease, death usually occurs in the second decade of life, whereas those patients with less severe disease may survive into adulthood. Enzyme replacement therapy with intravenous infusions of idursulfase has emerged as a new treatment for mucopolysaccharidosis type II. OBJECTIVES: To evaluate the effectiveness and safety of enzyme replacement therapy with idursulfase compared to other interventions, placebo or no intervention, for treating mucopolysaccharidosis type II. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register (date of last search 22 July 2013).We also searched EMBASE, PubMed and the Literature Latino-Americana e do Caribe em Ciências da Saúde (LILACS) (date of last search 09 July 2013). SELECTION CRITERIA: Randomised and quasi-randomised controlled trials of enzyme replacement therapy with idursulfase compared to no intervention, placebo or other options (e.g. behavioral strategies, transplantation). DATA COLLECTION AND ANALYSIS: Two authors independently screened the trials identified, appraised quality of papers and extracted data. MAIN RESULTS: One study (96 patients) met the inclusion criteria, although the primary outcome of this review - z score for height and weight, was not assessed in the study. This trial was considered to be of overall good quality. Following 53 weeks of treatment, patients in the weekly idursulfase 0.5 mg/kg group demonstrated a significant improvement rate compared with placebo for the primary outcome: distance walked in six minutes on the basis of the sum of ranks of change from baseline, mean difference 37.00 (95% confidence interval 6.52 to 67.48). The every-other-week idursulfase 0.5 mg/kg group also showed an improvement, which was not significant compared with placebo, mean difference 23.00 (95% confidence interval -4.49 to 50.49). After 53 weeks, there was no statistical significance difference in per cent predicted forced vital capacity between the three groups and absolute forced vital capacity was significantly increased from baseline in the weekly dosing group compared to placebo, mean difference 0.16 (95% confidence interval CI 0.05 to 0.27). No difference was observed between the every-other-week idursulfase 0.5 mg/kg group and placebo.In addition, liver and spleen volumes and urine glycosaminoglycan excretion were significantly reduced from baseline by both idursulfase dosing regimens. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 31.7% of patients at the end of the study and they were related to a smaller reduction in urine glycosaminoglycan levels. AUTHORS' CONCLUSIONS: The current evidence is limited. While the randomised clinical trial identified was considered to be of good quality, it failed to describe important outcomes. It has been demonstrated that enzyme replacement therapy with idursulfase is effective in relation to functional capacity (distance walked in six minutes and forced vital capacity), liver and spleen volumes and urine glycosaminoglycan excretion in patients with mucopolysaccharidosis type II compared with placebo. There is no available evidence in the included study and in the literature on outcomes such as improvement in growth, sleep apnoea, cardiac function, quality of life and mortality. More studies are needed to obtain more information on the long-term effectiveness and safety of enzyme replacement therapy.

The relationship between anti-idursulfase antibody status and safety and efficacy outcomes in attenuated mucopolysaccharidosis II patients aged 5 years and older treated with intravenous idursulfase.

In the pivotal phase II/III trial of idursulfase administered intravenously to treat mucopolysaccharidosis II, approximately half of the patients developed antibodies to idursulfase. This post-hoc analysis of data from the phase II/III trial and extension study examined the relationship between antibody status and outcomes. A total of 63 treatment-naïve patients received 0.5 mg/kg of intravenous idursulfase weekly for two years. Thirty-two patients (51%) were positive for anti-idursulfase IgG antibodies, 23 of whom (37%) became persistently positive. All patients who developed an antibody response did so by their scheduled Week 27 study visit. Positive antibody status appeared to have no statistically significant effect upon changes in six-minute walk test distance, percent predicted forced vital capacity, or liver and spleen volume. All patients showed significant decreases in urinary GAG levels, although the antibody positive group maintained somewhat higher urinary GAG levels than their antibody-negative counterparts at the end of study (138.7 vs. 94.7 µg/mg creatinine, p = 0.001). Antibody positivity was not associated with a higher event rate for serious adverse events. Among patients who had no prior infusion-related reactions, antibody positive patients were 2.3 times more likely to have a first infusion-related reaction than those who would remain negative (p = 0.017); the risk increased to 2.5 times more likely for those who were persistently positive (p = 0.009). These differences in risk disappeared among patients with a previous infusion-related reaction, likely because of preventive measures. A genotype analysis for the 36 patients with available data found that patients with nonsense or frameshift mutations may be more likely to develop antibodies, to experience infusion-related reactions, and to have a reduced uGAG response than those with missense mutations, suggesting the possibility that antibodies are not a driver of clinical outcomes but rather a marker for genotype.

Improvement of CNS defects via continuous intrathecal enzyme replacement by osmotic pump in mucopolysaccharidosis type II mice.

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome (OMIM 309900), is a rare, X-linked lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS; EC 3.1.6.13), which is involved in the lysosomal degradation of glycosaminoglycans (GAG). Although intermittent intrathecal (IT) injection of the enzyme has been introduced as a method to overcome the blood-brain barrier, continuous IT infusion of the enzyme would be more physiologic. This study was performed to investigate responses in the brain of MPS II mice to varying doses of continuous IT infusion of recombinant human IDS (rh-IDS) in MPS II mice by osmotic pump in three different doses (2.4, 4.8, and 12 µg/day) of rh-IDS for 3 weeks. The results showed that the group treated with 12 µg/day doses of rh-IDS demonstrated decreased GAG concentrations compared to the untreated KO mice group (P = 0.003). After 3 weeks of continuous IT ERT, the brain tissues of the high-dose IT-treated KO mice showed a reduction of vacuolation in the cerebral cortex, thalamus and cerebellar cortex, which was not observed in the low- and medium-dose KO mice groups. Moreover, the anti-NeuN signal representing intact neuron was restored in the cortexes of the high-dose group. In conclusion, continuous IT infusion of the deficient enzyme was effective in improving CNS defects in the MPS II mice, and could be a valuable therapeutic method for treating neurological deterioration in patients with MPS II.

Parental experience of enzyme replacement therapy for Hunter syndrome.

We aimed to establish the profile of Irish patients with Hunter Syndrome (Mucopolysaccharidosis type II, MPS II) receiving weekly intravenous Enzyme Replacement Therapy (ERT) with recombinant iduronate-2-sulfatase and to assess the social impact and parental opinion of ERT through the use of a parental questionnaire. Nine patients aged 3.5- 14 years have received a mean of 2 (range 0.5-3.5) years of ERT. Treatment was associated with clinical improvements from baseline in hepatosplenomegaly in 6/7 (85%) respiratory manifestations in 4/6 (67%) and a mean reduction in urinary glycosaminoglycan excretion of 62%. Changes noted by parents included increased energy 3/9 (33%) and softening of skin, hair and facial features 8/9 (89%). Parents report that seven hours weekly were spent on hospitalizations for ERT. Parental employment was adversely affected in 8 (89%) families. One day of school/preschool (20%) was lost every week for 8 (89%) children. All parents believed the benefits of ERT out-weigh the difficulties involved. All families would welcome the introduction of home based therapy. In conclusion the social and educational burden of hospital-based ERT on these children and their families is significant. The introduction of home-based therapy is likely to improve overall quality of life for MPSII patients and their families.

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.

Idursulfase treatment of Hunter syndrome in children younger than 6 years: results from the Hunter Outcome Survey.

PURPOSE: To use the Hunter Outcome Survey, an international database, to assess the safety and effectiveness of enzyme replacement therapy with idursulfase in patients with Hunter syndrome who started treatment before 6 years of age. METHODS: The study population included all patients enrolled in the Hunter Outcome Survey who started idursulfase infusions (0.5 mg/kg every other week) before 6 years of age and who had at least one follow-up examination recorded. RESULTS: The study population included 124 patients, younger than 6 years, who had a mean age at start of idursulfase of 3.6 ± 1.6 years (mean ± SD). The mean duration of treatment was 22.9 ± 14.6 months. A total of 69 infusion-related reactions occurred in 33 (26.6%) patients, including three serious infusion-related reactions occurring in a single patient. After at least 6 months of idursulfase, urine glycosaminoglycan levels decreased from 592 ± 188 to 218 ± 115 µg/mg creatinine (P < 0.0001, n = 34). Liver size, estimated by palpation, was also significantly decreased (P = 0.005, n = 23). Similar safety and effectiveness results were seen in patients who were aged 6 years or older when initiating idursulfase. CONCLUSION: No new safety concerns were identified in patients younger than 6 years, and clinical benefit was suggested by the reduction in liver size.

Long-term, open-labeled extension study of idursulfase in the treatment of Hunter syndrome.

PURPOSE: This study evaluated the safety and effectiveness of long-term enzyme replacement therapy with idursulfase (recombinant human iduronate-2-sulfatase) in patients with Hunter syndrome. METHODS: All 94 patients who completed a 53-week double-blinded study of idursulfase enrolled in this open-labeled extension study and received intravenous idursulfase at a dose of 0.5 mg/kg weekly for 2 years, and clinical outcomes and safety were assessed. RESULTS: No change in percent predicted forced vital capacity was seen, but absolute forced vital capacity demonstrated sustained improvement and was increased 25.1% at the end of the study. Statistically significant increases in 6-minute walking test distance were observed at most time points. Mean liver and spleen volumes remained reduced throughout the 2-year extension study. Mean joint range of motion improved for the shoulder and remained stable in other joints. Both the parent- and child-assessed Child Health Assessment Questionnaire Disability Index Score demonstrated significant improvement. Infusion-related adverse events occurred in 53% of patients and peaked at Month 3 of treatment and declined thereafter. Neutralizing IgG antibodies were detected in 23% of patients and seemed to attenuate the improvement in pulmonary function. CONCLUSIONS: Weekly infusions of idursulfase result in sustained clinical improvement during 3 years of treatment.