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

Diagnosis and follow-up of patients with Hunter syndrome in Spain: A Delphi consensus

Hunter syndrome or mucopolysaccharidosis type II (MPSII) is a progressive multisystem X-linked lysosomal storage disease caused by mutations in the IDS gene that shows a wide spectrum of clinical symptoms and severity. Idursulfase, a specific enzyme replacement therapy (ERT) for MPSII, has been available since 2007. ERT, along with symptomatic management of patients, is fundamental for improving patient prognosis and quality of life. The aims of this study were to investigate whether Spanish pediatricians who are experts in managing the disease agreed with current international guidelines regarding MPSII patient diagnosis and follow-up; and to reach a consensus regarding which items are essential for the diagnosis, follow-up, and treatment of these patients in Spain.An advisory panel of 5 experts from the Hunter Spanish Working Group reviewed key studies, developed a questionnaire based on a modified Delphi method, sent the questionnaire to selected experts, and reviewed the responses. The final questionnaire had 83 items in the following categories: diagnosis, ERT considerations after diagnosis, Periodic assessments, and ERT considerations during follow-up. A total of 85 experts were invited to participate; 28 (35%) responded and showed a strong consensus for most items. The advisory panel decided not to perform a second Delphi round. There was strong agreement (>3.1 median value; range, 1 to 4) for 43/56 items in Diagnosis, for 4/6 items in "ERT considerations after diagnosis," for 6/16 items in "Periodic assessments," and for 3/5 items in "ERT considerations during follow-up." Most responses were in agreement with international guidelines, and controversial items were discussed by the advisory panel. Based on the results, on the key studies, and on clinical experience and opinions, the panel developed and scheduled recommendations for the diagnosis and follow-up of patients with MPSII.An expert 5-person panel oversaw a Delphi survey of 28 pediatricians and reached a consensus on recommendations for the diagnosis and follow-up of MPSII patients. This document will help guide clinicians involved in the diagnosis, management, and treatment of MPSII.

Treatment of mucopolysaccharidosis type II (Hunter syndrome): results from a systematic evidence review

PurposeA pilot systematic evidence review to establish methodology utility in rare genetic diseases, support clinical recommendations, and identify important knowledge gaps.MethodsBroad-based published/gray-literature searches through December 2015 for studies of males with confirmed mucopolysaccharidosis type II (any age, phenotype, genotype, family history) treated with enzyme replacement therapy or hematopoietic stem cell transplantation. Preset inclusion criteria employed for abstract and full document selection, and standardized methods for data extraction and assessment of quality and strength of evidence.ResultsTwelve outcomes reported included benefits of urinary glycosaminoglycan and liver/spleen volume reductions and harms of immunoglobulin G/neutralizing antibody development (moderate strength of evidence). Less clear were benefits of improved 6-minute walk tests, height, early treatment, and harms of other adverse reactions (low strength of evidence). Benefits and harms of other outcomes were unclear (insufficient strength of evidence). Current benefits and harms of hematopoietic stem cell transplantation are unclear, based on dated, low-quality studies. A critical knowledge gap is long-term outcomes. Consensus on selection of critical outcomes and measures is needed to definitively evaluate treatment safety and effectiveness.ConclusionMinor methodology modifications and a focus on critical evidence can reduce review time and resources. Summarized evidence was sufficient to support guidance development and highlight important knowledge gaps.

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.

Characterization of knee alignment in children with mucopolysaccharidosis types I and II and outcome of treatment with guided growth

PURPOSE

To describe knee alignment in children of different ages with severe mucopolysaccharidosis (MPS) I and II and the outcome of treatment with guided growth in a patient subgroup.

METHODS

This is a retrospective observational study of 58 knees in 29 children with severe MPS I and II. Long-leg standing radiographs were evaluated to determine mechanical axis deviation, mechanical lateral distal femoral angle and medial proximal tibial angle at different ages throughout childhood. The change in deformity in individual children over time is reported. 20 knees in 10 patients were treated with guided growth using eight-plates. Radiographic measurements were recorded at the time of plate insertion, at plate removal and at 1 year following removal.

RESULTS

At 8 years of age, all MPS I children and three-quarters of MPS II children had valgus knee alignment. There was deformity progression in two-thirds of MPS I knees and half of MPS II knees. Guided growth corrected the deformities. There was recurrence in most cases 1 year after plate removal.

CONCLUSIONS

Knee deformity is common in children with severe MPS I and II. Guided growth can be considered where there is significant and/or or progressive deformity with the aim of halting progression and correcting existing deformity and thus minimizing the risk of gross deformity. Patients should be aware of the high rate of recurrence and the need for repeat surgery.

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

BACKGROUND

Hunter Syndrome is an X-linked lysosomal storage disorder due to the deficit of iduronate 2-sulfatase, an enzyme catalysing the degradation of the glycosaminoglycans (GAG) dermatan- and heparan-sulfate. Treatment of the disease is mainly performed by Enzyme Replacement Therapy (ERT) with idursulfase, in use since 2006. Clinical efficacy of ERT has been monitored mainly by the Hunter Outcome Survey (HOS) while very few independent studies have been so far conducted. The present study is a 3.5-years independent follow-up of 27 Hunter patients, starting ERT between 1.6 and 27 years of age, with the primary aim to evaluate efficacy of the therapy started at an early age (<12 years).

METHODS

In this study, we evaluated: urinary GAG content, hepato/splenomegaly, heart valvulopathies, otorinolaryngological symptoms, joint range of motion, growth, distance covered in the 6-minute walk test, neurological involvement. For data analysis, the 27 patients were divided into three groups according to the age at start of ERT: ≤5 years, >5 and ≤ 12 years and > 12 years. Patients were analysed both as 3 separate groups and also as one group; in addition, the 20 patients who started ERT up to 12 years of age were analysed as one group. Finally, patients presenting a "severe" phenotype were compared with "attenuated" ones.

RESULTS

Data analysis revealed a statistically significant reduction of the urinary GAG in patients ≤5 years and ≤ 12 years and of the hepatomegaly in the group aged >5 and ≤ 12 years. Although other clinical signs improved in some of the patients monitored, statistical analysis of their variation did not reveal any significant changes following enzyme administration. The evaluation of ERT efficacy in relation to the severity of the disease evidenced slightly higher improvements as for hepatomegaly, splenomegaly, otological disorders and adenotonsillar hypertrophy in severe vs attenuated patients.

CONCLUSIONS

Although the present protocol of idursulfase administration may result efficacious in delaying the MPS II somatic disease progression at some extent, in this study we observed that several signs and symptoms did not improve during the therapy. Therefore, a strict monitoring of the efficacy obtained in the patients under ERT is becoming mandatory for clinical, ethical and economic reasons.