An Extension Study of JR-141-BR21 in Patients With Mucopolysaccharidosis II

Inclusion Criteria: * Patients who will have completed clinical trial JR-141-BR21. * Capable of providing written consent by himself, unless the patient is under the age of 18 years at the time of informed consent process, or it is not possible to obtain consent from the patient himself due to his intellectual disabilities associated with MPS II. * In the case of a patient who is under the age of 18 years or from whom it is not possible to obtain consent due to his intellectual disabilities associated with MSP II, he may be included if written consent can be provided by legal representative; however written consent should be obtained from the patient himself too, wherever possible. Exclusion Criteria: * Refusal to sign the informed consent form. * Unable to perform the study procedures, except for neurocognitive testing. * Previous engrafted BMT/HSCT. * Judged by the investigator or subinvestigator as being unable to undergo lumbar puncture, including those who have difficulties in taking a position for lumber puncture due to joint contracture or those who are likely to experience difficulty breathing during the lumbar puncture process. * Judged by the investigator or subinvestigator to be ineligible to participate in the study due to a history of a serious drug allergy or sensitivity. * Otherwise judged by the investigator or subinvestigator to be ineligible to participate in the study out of consideration for the subject safety.