A Study to Evaluate the Safety, Tolerability, PK and PD of Intracerebroventricular GC1123 in Patients with MPS Ⅱ

Inclusion Criteria: 1. Patient who has been diagnosed with severe MPS Ⅱ (Hunter syndrome) 2. Patient, aged 1.5 years (18 months) to 18 years at the time of the screening 3. Patient who has received and tolerated a minimum of 12 weeks of treatment with weekly intravenous treatment, and who has received 80% of the total planned infusions within that time frame. 4. Patient who is capable of undergoing neurosurgery, which has been confirmed by neurosurgeons and anesthesiologist. 5. Patient eligible to execute patient evaluation activities during the clinical trial period, as assessed by the investigator 6. Patient whose parents or legal representative are willing to participate in this clinical trial and provide written informed consent form Exclusion Criteria: 1. Patient who has been administered with intrathecal Idursulfase in the past 2. Patient with a history of bone marrow transplantation or cord blood transplant 3. Patient with a history of ventriculoperitoneal shunt or other intracranial surgeries 4. Patient with end-stage multiple organ dysfunction syndrome or other severe diseases 5. Patient who is exposed to malignant neoplasm 6. Patient who has received treatment with any investigational drug or device within 30 days prior to study entry 7. Patient who have experience of hypersensitivity or anaphylaxis to ingredients of the investigational product at the time of screening 8. Patient with a history of bronchotomy/tracheostomy, or patient with acute respiratory disease at the time of screening 9. Patient who is ineligible to participate in the clinical trial due to laboratory test results or other reasons, as determined by the investigator