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Evaluation of the long-term treatment effects of intravenous idursulfase in patients with mucopolysaccharidosis II (MPS II) using statistical modeling: data from the Hunter Outcome Survey (HOS)

ABSTRACT:

Background

Mucopolysaccharidosis II (MPS II; Hunter syndrome) is a rare, life-limiting lysosomal storage disease caused by deficient iduronate-2-sulfatase activity. Enzyme replacement therapy (ERT) with intravenous (IV) idursulfase can stabilize or improve many somatic manifestations, but there remains a need for further analysis of long-term treatment outcomes. Using data from patients with MPS II enrolled in the Hunter Outcome Survey (HOS), mixed modeling was performed to evaluate and predict the effects of IV idursulfase treatment on selected clinical parameters for up to 8 years following treatment start. The modeling population comprised male patients followed prospectively in HOS who had received IV idursulfase for at least 5 years and who had data available for two or more time points (at least one post-ERT). Age at ERT start and time since ERT start were included as covariates.

Results

In total, 481 patients were eligible for inclusion in at least one model. At 8 years post-ERT start, improvement from baseline was predicted for each age group (< 18 months, 18 months to < 5 years and ≥ 5 years at treatment start) in the following parameters: mean urinary glycosaminoglycan levels (percentage changes of > –75% in each group), mean left ventricular mass index (decreases of ~ 1 g/m2) and mean palpable liver size (decreases of > 2 cm). Improvements in mean 6-min walk test distance (increase of > 50 m) and stabilization in percent predicted forced vital capacity and forced expiratory volume in 1 s (decreases of ~ 4 and ~ 9 percentage points, respectively) at 8 years post-ERT start were predicted for patients aged ≥ 5 years at ERT start (these assessments are unsuitable for patients aged < 5 years). Predicted changes over time were similar across the three age groups; however, overall outcomes were most favorable in children aged < 18 months at ERT start.

Conclusions

These findings suggest that the previously reported positive effects of IV idursulfase on the somatic manifestations of MPS II are predicted to be maintained for at least 8 years following ERT initiation and highlight the value of statistical modeling to predict long-term treatment outcomes in patients with rare diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02052-4.

SUBMITTER: Muenzer J

PROVIDER: S-EPMC8557006 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is a rare, X-linked disorder caused by deficient activity of the enzyme iduronate-2-sulfatase (I2S). Treatment is available in the form of enzyme replacement therapy (ERT) with recombinant I2S. Clinical outcomes following ?3 years of ERT with idursulfase were investigated in a broad population of patients with MPS II enrolled in the Hunter Outcome Survey (HOS). METHODS:As of January 2016, 639 patients (excluding female patients, individuals who had received a bone marrow transplant and those enrolled in the phase 1/2 [TKT018] or phase 2/3 [TKT024] clinical trial) followed prospectively in the registry had received idursulfase for ?6 months. These individuals all had data available for ?1 clinical parameter at baseline and ?1 additional time point following treatment initiation. Changes in clinical parameters were assessed in the subcohorts of patients with a measurement at baseline and at year 1, 2 or 3 of treatment. Safety data from patients who started treatment at or after enrollment in HOS (n = 233) were also assessed. RESULTS:Median (10th, 90th percentiles) age at first treatment was 6.2 (2.1, 18.2) years and median treatment duration was 56.3 (18.2, 97.6) months. Urinary glycosaminoglycan (uGAG) levels decreased from baseline to year 3 in patients with data available at this time point (median change from baseline: -201.0 [-591.4, -21.9] ?g/mg creatinine [n = 121]). Improvements in the following parameters were observed at year 3 in the subcohorts: 6-min walking test (6MWT) distance, 10.6 (-33.6, 50.8)% (n = 26); left ventricular mass index (LVMI), -9.3 (-31.5, 19.7)% (n = 52); absolute forced vital capacity (FVC), 29.7 (-13.4, 66.7)% (n = 23); absolute forced expiratory volume in 1 s (FEV1), 22.8 (-15.2, 62.1)% (n = 22); palpable liver size, -54.5 (-85.7, 50.0)% (n = 53); palpable spleen size, -33.3 (-80.0, 33.3)% (n = 17). No new or unexpected safety concerns were identified in this analysis. CONCLUSIONS:These findings suggest that idursulfase has a positive effect on uGAG levels, 6MWT results, LVMI, FVC, FEV1 and hepatosplenomegaly after 1, 2 and 3 years treatment.

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Project description:Mucopolysaccharidosis type II (MPS II; Hunter syndrome; OMIM 309900) is a rare, multisystemic, progressive lysosomal storage disease caused by deficient activity of the iduronate-2-sulfatase (I2S) enzyme. Accumulation of the glycosaminoglycans dermatan sulfate and heparan sulfate results in a broad range of disease manifestations that are highly variable in presentation and severity; notably, approximately two-thirds of individuals are affected by progressive central nervous system involvement. Historically, management of this disease was palliative; however, during the 1990s, I2S was purified to homogeneity for the first time, leading to cloning of the corresponding gene and offering a means of addressing the underlying cause of MPS II using enzyme replacement therapy (ERT). Recombinant I2S (idursulfase) was produced for ERT using a human cell line and was shown to be indistinguishable from endogenous I2S. Preclinical studies utilizing the intravenous route of administration provided valuable insights that informed the design of the subsequent clinical studies. The pivotal Phase II/III clinical trial of intravenous idursulfase (Elaprase®; Shire, Lexington, MA, USA) demonstrated improvements in a range of clinical parameters; based on these findings, intravenous idursulfase was approved for use in patients with MPS II in the USA in 2006 and in Europe and Japan in 2007. Evidence gained from post-approval programs has helped to improve our knowledge and understanding of management of patients with the disease; as a result, idursulfase is now available to young pediatric patients, and in some countries patients have the option to receive their infusions at home. Although ERT with idursulfase has been shown to improve somatic signs and symptoms of MPS II, the drug does not cross the blood-brain barrier and so treatment of neurological aspects of the disease remains challenging. A number of novel approaches are being investigated, and these may help to improve the care of patients with MPS II in the future.

Project description:BackgroundTwenty-eight treatment-naïve mucopolysaccharidosis II patients (16 months-7.5 years) received 0.5 mg/kg idursulfase weekly for one year in NCT00607386. Serum anti-idursulfase immunoglobulin G antibodies (Abs) were seen in 68% of patients.MethodsThis post hoc analysis examined the relationship between Ab status, genotype, adverse events (AEs), and efficacy. Event rate analyses, time-varying proportional hazards (Cox) modeling, and landmark analyses were performed to evaluate the relationship between Ab status and safety. We calculated the cumulative probability of AEs by genotype to evaluate the relationship between genotype and safety. Urinary glycosaminoglycan (uGAG) concentration, index of liver size, and spleen volume were compared by Ab status and genotype.Safety resultsThe overall infusion-related AE (IRAE) rate was higher in Ab+ patients than in Ab- ones. However, the rate was highest before Abs developed, then decreased over time, suggesting that Abs did not confer the risk. A landmark analysis of patients who were IRAE-naïve at the landmark point found that Ab+ patients were no more likely to experience post-landmark IRAEs than were Ab- patients. In the genotype analysis, all patients in the complete deletion/large rearrangement (CD/LR) and frame shift/splice site mutation (FS/SSM) groups seroconverted, compared with only one-third of patients in the missense mutation (MS) group (p < 0.001). The cumulative probability of having ≥1 IRAE was 87.5% in the CD/LR group and 46.2% in the MS group, with a shorter time to first IRAE in the CD/LR group (p = 0.004).Efficacy resultsAb+ patients had a reduced response to idursulfase for liver size and uGAG concentration, but not for spleen size. However, when percent change from baseline in liver size and in uGAG level at Week 53 were adjusted for genotype, the difference was significant only for neutralizing Ab+ groups. In the genotype analysis, the CD/LR and FS/SSM groups had a reduced response in liver size and uGAG concentration compared with the MS group.ConclusionsSafety outcomes and spleen size response on idursulfase treatment appeared to be associated with genotype, not Ab status. Liver size and uGAG response on idursulfase treatment at Week 53 appeared to be associated with both neutralizing Ab status and genotype.