for males ages up to 6 years (full criteria)
at Oakland, California and other locations
study started
completion around
Principal Investigator
by Paul Harmatz
Headshot of Paul Harmatz
Paul Harmatz



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).

Official Title

An Open-label, Multicenter, Phase 4 Study to Assess the Effects of a Prophylactic Immune Tolerizing Regimen in MPS II Treatment-Naïve Patients Planned to Receive ELAPRASE Who Are at Risk of Developing Persistent Neutralizing Antibodies


Mucopolysaccharidosis (MPS), Hunter Syndrome, Mucopolysaccharidosis II, Mucopolysaccharidoses, Syndrome, Rituximab, Methotrexate, Immunoglobulins, Intravenous Immunoglobulins, Antibodies, gamma-Globulins, Rho(D) Immune Globulin, ELAPRASE, Intravenous Immunoglobulin (IVIG), ITR + ELAPRASE


You can join if…

Open to males ages up to 6 years

  • Participant is male.
  • Participant is ELAPRASE-naïve at study entry.
  • Participant must have a documented diagnosis of MPS II. The following combination will be accepted as diagnostic of MPS II:
    • Participant has a deficiency in iduronate-2-sulfatase (I2S) enzyme activity of less than or equal to (<=) 10 percent (%) of the lower limit of the normal range as measured in plasma, fibroblasts, or leukocytes (based on the reference laboratory's normal range). The participant has a normal enzyme activity level of at least 1 other sulfatase as measured in plasma, fibroblasts, or leukocytes (based on the reference laboratory's normal range).
    • Participant has a documented mutation in the IDS gene; additionally, participants must have a severe mutation (example, large deletion or complex gene rearrangement), which is predicted to lead to development of a persistent anti-idursulfase antibody response.
  • Participant will be less than (<) 6 years of age at enrollment.
  • Participant has a negative test result for serum anti-idursulfase antibodies.

You CAN'T join if...

  • Participant has received treatment with any investigational drug within the 30 days prior to study entry.
  • Participant has received or is receiving treatment with idursulfase-IT.
  • Participant has received growth hormones, a cord blood infusion, or a bone marrow transplant at any time.
  • Participant has received blood product transfusions within 90 days prior to screening.
  • Participant is unable to comply with the protocol as determined by the investigator.
  • Participant has known or suspected intolerance or hypersensitivity to the investigational product(s), closely related compounds, or any of the stated ingredients, including the prophylactic ITR.
  • Participant has current or recurrent disease that could affect the action, absorption, or disposition of the investigational product, or clinical or laboratory assessments.
  • Participant has current or relevant history of physical or psychiatric illness, or any medical disorder that may require treatment or make the participant unlikely to fully complete the study, or any condition that presents undue risk from the investigational product or procedures.
  • Participant has current use of any medication (including over-the-counter, herbal, or homeopathic preparations) that could affect (improve or worsen) the condition being studied, or could affect the action, absorption, or disposition of the investigational product(s), or clinical or laboratory assessment (Current use is defined as use within 30 days).
  • Within 30 days prior to the first dose of investigational product, the participant has been enrolled in a clinical study (including vaccine studies) that, in the investigator's opinion, may impact this study.


  • Children's Hospital and Research Center at Oakland accepting new patients
    Oakland California 94609 United States
  • UC Davis Medical Center not yet accepting patients
    Sacramento California 95817 United States
  • The Lundquist Institute for BioMedical Innovation at Harbor-UCLA Medical Center accepting new patients
    Torrance California 90502 United States

Lead Scientist at UCSF

  • Paul Harmatz
    Dr. Paul Harmatz is a gastroenterologist who specializes in mucopolysaccharidoses (MPS) and other lysosomal storage diseases (genetic disorders in which a lack of certain enzymes results in progressive damage to cells and organ systems). He leads a team of specialists who diagnose and care for patients with these rare diseases, offering therapies such as weekly enzyme infusion.


accepting new patients
Start Date
Completion Date
More about this study
Phase 4 research study
Study Type
Expecting 5 study participants
Last Updated