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.