An Extension Study to Assess the Long-term Safety and Efficacy of Hunterase (Idursulfase Beta)

An Extension Study to Assess the Long-term Safety and Efficacy of Hunterase (Idursulfase Beta) in Patients With Hunter Syndrome

The objective of this study is to assess the long-term safety and efficacy of Hunterase for approximately 1 year in subjects who completed the end of study (EOS) visit (Visit 54) tests in the Phase 3 Hunterase study and patients who received Hunterase for more than 6 months

Study Overview

• Status: Completed
• Conditions: Hunter Syndrome; MPS II; Hunter Syndrome (MPS II); Hunterase; GC1111
• Intervention / Treatment: Drug: Hunterase

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Phase 3

Contacts and Locations

Study Locations

• South Korea
  • Seoul, South Korea
    • Samsung Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Subject diagnosed with Hunter syndrome (MPS II) who completed activities at the EOS visit (Visit 54) in the GC1111_P3 study
2. (Subject who did not participate in the GC1111_P3 study) Subject diagnosed with Hunter syndrome (MPS II) who received Hunterase for more than 6 months
3. (Subjects who did not participate in the GC1111_P3 study) Males aged ≥ 5
4. Informed consent form voluntarily signed by the subject or by a legally acceptable representative
5. Subject who agrees to use contraception

Exclusion Criteria:

1. Subject with hypersensitivity to any of the ingredients of the investigational product
2. Subject impossible to perform follow-up observation of the safety
3. Subject who received the treatment with another investigational product within 14 days prior to the start of study drug
4. Subject who plans to be treated with another investigational product during the study period
5. Subject who has history of tracheostomy, bone marrow transplant, or cord blood transplant
6. Any other inappropriate conditions for study participation at the investigator's discretion

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Hunterase; Single arm	Drug: Hunterase; 0.5mg/kg weekly IV administration; Other Names: GC1111

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Laboratory tests (CBC, Chemistry, Urinanalysis)	Abnormality of Laboratory tests results	Every visit until 12months
Physical examination	Abnormality of physical examination	Every visit until 12months
Adverse Event	occurence, grade	Every visit until 12months
Electrocardiography	Abnormality of ECG results	Every 6 months until 12months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
6-minute walk test	Mean, Change and percent change of 6-minute walk test	Every 4months until 12months
Urine GAG (Heparan sulfate, Dermatan sulfate)	Mean, Change and percent change of Urine HS/DS	Every visit until 12months

Collaborators and Investigators

• Sponsor: GC Biopharma Corp
• Collaborators: Samsung Medical Center, Sungkyunkwan University School of Medicine

Study record dates

Study Major Dates

• Study Start (Actual): May 23, 2018
• Primary Completion (Actual): December 30, 2022
• Study Completion (Actual): December 30, 2022

Study Registration Dates

• First Submitted: November 17, 2025
• First Submitted That Met QC Criteria: January 7, 2026
• First Posted (Actual): January 15, 2026

Study Record Updates

• Last Update Posted (Actual): January 15, 2026
• Last Update Submitted That Met QC Criteria: January 7, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: extension study; GC1111; Long-term study; Hunterase; GC Biopharma
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Pathologic Processes; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Connective Tissue Diseases; Neurobehavioral Manifestations; Death; Heredodegenerative Disorders, Nervous System; Intellectual Disability; Genetic Diseases, X-Linked; Carbohydrate Metabolism, Inborn Errors; Lysosomal Storage Diseases; Mucinoses; Death, Sudden; Mucopolysaccharidoses; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Skin and Connective Tissue Diseases; X-Linked Intellectual Disability; Infant Death; Mucopolysaccharidosis II; Sudden Infant Death
• Other Study ID Numbers: GC1111_P3_Ex

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No