Safety profile of idursulfase administered at home in patients with mucopolysaccharidosis II enrolled in the Hunter Outcome Survey

The Hunter Outcome Survey (HOS) collected global, real-world data on the natural history of mucopolysaccharidosis II and its treatment with intravenous idursulfase. For eligible patients, home therapy offers a convenient alternative to in-clinic therapy. Using data in HOS as of January 2023, we provide an updated assessment of the safety/tolerability profile of home therapy with idursulfase. The analysis population comprised 333 patients who had received at least one home infusion and 708 patients who had never received home therapy. Median (10th percentile [P10], 90th percentile [P90]) age at home therapy start was 8.9 (2.9, 21.1) years. Median (P10, P90) ages at latest visit were 15.5 (7.7, 29.3) years in the home therapy group and 13.9 (5.2, 29.0) years in the no home therapy group. Patients received a median (P10, P90) of 6.0 (0.8, 12.0) years of home infusions after 1.8 (0.3, 8.7) years of in-clinic therapy, and these timings varied by geographic region. The infusion-related reaction (IRR) rate was 0.11/patient-year during home therapy, 0.13/patient-year for the in-clinic period for the same patients (first 6 months excluded), and 0.05/patient-year for patients who never received home therapy (first 6 months excluded). More than 60% of IRRs were categorized as mild. The adverse event (AE) rate was lower during home therapy (0.59 AEs/patient-year) than during the in-clinic period for the same patients (0.86 AEs/patient-year). Among patients who never received home therapy, the rate was 0.60 AEs/patient-year. Deaths occurred at a rate of 2.17 deaths/100 patient-years of home therapy and 3.60 deaths/100 patient-years among patients never treated with home therapy. No deaths were deemed related to treatment. The rate of missed infusions was 0.52/year during the home therapy period compared with 1.42/year during the in-clinic period for the same patients and 0.57/year for patients who never received home therapy. Our data indicate a similar safety/tolerability profile for intravenous idursulfase administered at home and in clinic in patients with mucopolysaccharidosis II.