Safety and efficacy of idursulfase in the treatment of mucopolysaccharidosis II (Hunter syndrome): a post-marketing study in Japan

Enzyme replacement therapy with idursulfase has been shown to improve somatic signs and symptoms of mucopolysaccharidosis type II (MPS II). Idursulfase is available in Japan (since 2007), based on the outcome of clinical trials conducted in the United States, but data from Japanese patients are limited.

This was a postmarketing study of Japanese MPS II patients treated with 0.5 mg/kg intravenous idursulfase weekly, conducted over a period of 8 years after initial administration. Assessments included the safety profile, survival rate, degree of clinical improvement, change in urinary uronic acid (UA) concentration, and 6-minute walk test (6MWT).

The safety and efficacy analysis populations included 145 and 143 patients, respectively. The incidence of serious adverse events was 42.8% and the incidence of adverse drug reactions was 48.3%. The 7-year survival rate was 82.7%. Improvements in the clinical features of hepatosplenomegaly, skin, joint, and respiratory disorders were reported (per investigator’s assessment). The mean change in urinary UA concentration was −128.39 mg/g creatinine, and that of 6MWT walking distance was +31.8 m.

Long-term idursulfase treatment was well tolerated, and effective in improving clinical features, reducing urinary UA, and slowing disease progression in Japanese MPS II patients.