An Observational Study Evaluating Anti-Idursulfase Serum Antibody Response in Hunter Syndrome Patients

This study is being conducted to satisfy post-marketing commitments to monitor anti-idursulfase antibody development in Hunter syndrome patients after long-term idursulfase enzyme replacement therapy. The study will be conducted as a sub-study within the Hunter Outcome Survey (HOS). Hunter syndrome patients in the HOS who have previously received idursulfase as well as treatment-naive patients who will begin idursulfase treatment within 30 days of study enrollment will be included.

Inclusion criteria

Patients must meet all of the following criteria to be considered eligible for enrollment:

• The patient is male and enrolled in the HOS (i.e., meets the entry criteria of a documented diagnosis of Hunter syndrome)
• The patient is ≥ 5 years-old
• The patient is on idursulfase treatment or scheduled to begin idursulfase treatment within 30 days of study enrollment
• The patient, patient's parent(s), or patient's legally authorized guardian must have voluntarily signed an Institutional Review Board (IRB)/Independent Ethics Committee (IEC)-approved informed consent form after all relevant aspects of the study have been explained and discussed with the patient, patient's parent(s), or patient's legally authorized guardian.

Exclusion criteria

Patients who meet any of the following criteria are not eligible for this study:

• The patient has received biologic/ERT products other than idursulfase, or other investigational product(s) for any reason within 30 days prior to study entry.
• The patient has a life expectancy of < 2 years
• The patient is unable to comply with the protocol, e.g., has a clinically relevant medical condition making implementation of the protocol difficult; has an uncooperative attitude; is unable to return for safety evaluations; or is otherwise unlikely to complete the study, as determined by the Investigator.