A Study of ELAPRASE in Treatment-naïve Participants With Hunter Syndrome (Mucopolysaccharidosis [MPS] II)

Conditions

• Hunter Syndrome
• Mucopolysaccharidosis (MPS)

Eligibility Criteria

Sex

MALE

Age

N/A - 6 Years

Healthy Volunteers

Not accepted

Interventions

• ELAPRASE — DRUG
  Participants will receive 0.5 milligram per kilogram (mg/kg) of body weight of ELAPRASE, intravenous, infusion for 104 weeks.
• Rituximab — DRUG
  Participants will receive 375 milligram per square meter per dose (mg/m\^2/dose) of intravenous rituximab weekly for 4 weeks in 5-week cycle.
• Methotrexate — DRUG
  Participants will receive 0.4 mg/kg of methotrexate by mouth (PO) 3 times per week for 5 weeks in each cycle.
• Intravenous Immunoglobulin (IVIG) — DRUG
  Participants will receive 500 mg/kg of IVIG every 4 weeks in 5-week cycle.

Study Details

The main aim of this study is to evaluate the ability of a prophylactic immune tolerizing regimen (ITR) to prevent or reduce the development of high titer anti-idursulfase antibodies in treatment-naïve participants with Hunter syndrome. In this open label, single arm study, all participants will receive ELAPRASE treatment and a prophylactic ITR. Participants will be treated with ELAPRASE for up to 104 weeks. The prophylactic ITR will start 1 day prior to the start of ELAPRASE. The prophylactic ITR will consist of a 5-week cycle of: Rituximab (intravenously \[IV\], weekly for 4 weeks); Methotrexate (oral, 3 times per week for 5 weeks) and intravenous immunoglobulin (IVIG) (IV, every 4 weeks of the cycle). Following the completion of 1 cycle, an assessment will be made at Month 6, 12, and 18 regarding the need for administering another 5-week cycle of the ITR. Participants will be in the study for approximately 112 weeks (including 6 weeks for screening, up to 104 weeks for treatment, and 2 weeks for follow-up).

Key Dates

Start date

Feb 28, 2023

Status verified

Dec 2025

Primary completion

Aug 29, 2025

Completion

Aug 29, 2025

Study Design

Enrollment

0 participants (actual)

Allocation

NA

Intervention model

SINGLE_GROUP

Primary purpose

TREATMENT

Arms

• Experimental: ITR + ELAPRASE
  Participants will receive prophylactic ITR which consist of rituximab, methotrexate and IVIG in a 5-week cycle. Following the completion of 1 cycle and at the Month 6, 12, and 18 study visits, an assessment will be made regarding the need for administering another 5-week cycle of the ITR depending on the trend of the participants anti-idursulfase antibody titers and lymphocyte quantitation and CD19 percent (%) recovery. Elaprase treatment (IV, weekly) will start 1 day after the initiation of the first cycle of ITR and continue for 104 weeks. The dose of ELAPRASE will be calculated based on the participant's weight at each visit.

Primary Outcome Measure

Rate of Anti-Idursulfase Antibodies Formation, Including Anti-Idursulfase Antibodies That Have Enzyme Neutralizing Activity [ Time Frame: Up to 24 months ]

Locations (8)

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