Background <p>Long-term safety and efficacy data on enzyme replacement therapy, particularly switching between recombinant iduronate-2-sulfatase formulations, remain limited in mucopolysaccharidosis II (MPS II). This open-label extension study included male patients with MPS II who completed a 52-week, phase 3 trial and either continued idursulfase beta (maintenance group, <i>n</i> = 22) or switched from idursulfase (switch group, <i>n</i> = 6). Participants received weekly intravenous idursulfase beta (0.5&#xa0;mg/kg) for an additional 52 weeks. Safety, immunogenicity, six-minute walk test (6-MWT), and urinary glycosaminoglycan (GAG) levels were evaluated longitudinally for two years. Changes over time were analyzed using descriptive statistics and mixed models for repeated measures.</p> Results <p>Over the two-year treatment period, no new safety signals were identified in both groups. In the maintenance group, the incidence of adverse drug reactions decreased in the second year compared with the first year (from 54.5% to 13.6%); anti-drug antibody positivity peaked within the first six months and subsequently declined, with a low prevalence of neutralizing antibodies (4.5–22.7%). At Month 24, least-square mean changes from baseline demonstrated a 23.1% increase in 6-MWT distance and a 73.1% reduction in urinary total GAG levels in the maintenance group. Patients switching from idursulfase showed comparable safety profiles and sustained functional and biochemical improvements.</p> Conclusions <p>These results demonstrate that idursulfase beta is safe and efficacious in the long-term management of MPS II. Additionally, switching from idursulfase to idursulfase beta preserved therapeutic efficacy without additional safety or immunogenicity concerns, supporting idursulfase beta as a viable option following prior idursulfase therapy.</p> Registration <p>The study was registered at ClinicalTrials.gov (identifier, NCT07344376 date of registration, 7 January 2026).</p>

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Sustained clinical benefit of idursulfase beta in mucopolysaccharidosis II: two-year experience from a phase 3 extension study including patients switched from idursulfase

  • Minji Im,
  • Ari Song,
  • Hyojung Park,
  • Jiyeon Kim,
  • Chiwoo Kim,
  • Eu-Seon Noh,
  • Ga young Bae,
  • Juyoung Sung,
  • JiHoon Hwang,
  • Yoon Ji Ahn,
  • Haein Kim,
  • Youngsin Oh,
  • Bogyeong Kim,
  • Sung Yoon Cho

摘要

Background

Long-term safety and efficacy data on enzyme replacement therapy, particularly switching between recombinant iduronate-2-sulfatase formulations, remain limited in mucopolysaccharidosis II (MPS II). This open-label extension study included male patients with MPS II who completed a 52-week, phase 3 trial and either continued idursulfase beta (maintenance group, n = 22) or switched from idursulfase (switch group, n = 6). Participants received weekly intravenous idursulfase beta (0.5 mg/kg) for an additional 52 weeks. Safety, immunogenicity, six-minute walk test (6-MWT), and urinary glycosaminoglycan (GAG) levels were evaluated longitudinally for two years. Changes over time were analyzed using descriptive statistics and mixed models for repeated measures.

Results

Over the two-year treatment period, no new safety signals were identified in both groups. In the maintenance group, the incidence of adverse drug reactions decreased in the second year compared with the first year (from 54.5% to 13.6%); anti-drug antibody positivity peaked within the first six months and subsequently declined, with a low prevalence of neutralizing antibodies (4.5–22.7%). At Month 24, least-square mean changes from baseline demonstrated a 23.1% increase in 6-MWT distance and a 73.1% reduction in urinary total GAG levels in the maintenance group. Patients switching from idursulfase showed comparable safety profiles and sustained functional and biochemical improvements.

Conclusions

These results demonstrate that idursulfase beta is safe and efficacious in the long-term management of MPS II. Additionally, switching from idursulfase to idursulfase beta preserved therapeutic efficacy without additional safety or immunogenicity concerns, supporting idursulfase beta as a viable option following prior idursulfase therapy.

Registration

The study was registered at ClinicalTrials.gov (identifier, NCT07344376 date of registration, 7 January 2026).