for males ages 6 months to 65 years (full criteria)
at La Jolla, California and other locations
study started
estimated completion



With only limited prospective longitudinal data currently available on Creatine Transporter Deficiency (CTD), its natural history is at present incompletely understood. This international study is designed to provide additional insights into disease progression, to characterize how patients perform on clinical neurodevelopmental assessments, and to evaluate magnetic resonance spectroscopy (MRS) and event-related potentials (ERPs) in patients with CTD.


This is an observational study designed to determine an appropriate clinical assessment battery for males with CTD, and to evaluate MRS along with other potential biomarkers. It is designed to explore developmental domains of interest and to examine the feasibility and utility of various neuropsychological assessments to measure domains of interest, and to identify possible endpoints for interventional studies. Study will also explore genotype-phenotype correlations. This study will consist of a Screening Period, a Baseline period, and Ongoing Assessment Periods. During the Screening Period, subjects will be assessed for study eligibility including verification of existing laboratory evidence of a pathologic mutation at Solute Carrier Family 6 (Neurotransmitter Transporter), Member 8 (SLC6A8) gene. A comprehensive history and physical and neurological examination, including evaluation of growth and dysmorphic features, will be completed for all subjects. During the Baseline Period, the caregiver will be interviewed and study staff will administer scales/questionnaires at the study site. For purpose of this protocol, a duly authorized patient representative (e.g. parent, legal guardian) will be referred to as a caregiver. Biological, physiological and radiographic assessments, including ERP recordings, MRS, skin biopsy, cerebrospinal fluid, urine and blood will be obtained. During the Ongoing Assessment Period, growth assessments and limited physical and neurological examinations will be performed. All scales/questionnaires will be repeated every 6 months (± 2 weeks) for 48 months either at the study site or with instructions for completion at home. Clinical adverse events will be monitored throughout the study. This study was previously posted by Lumos Pharma, which has been transferred to Ultragenyx in June 2019.


Creatine Deficiency, X-linked Creatine transporter developmental delay intellectual disability X-linked language seizure observational brain spectroscopy


You can join if…

Open to males ages 6 months to 65 years

  1. Subject is male and between 6 months and 65 years of age, inclusive.
  2. Subject has genomic confirmation of a pathologic mutation in the SLC6A8 gene.
  3. Subject is able to complete study-related procedures.
  4. Subjects' parents/guardians/caregivers must provide written consent (informed consent) to study-related procedures, and if appropriate, the subject will provide an assent.

You CAN'T join if...

  1. Subject has had status epilepticus within 3 months of screening.
  2. Subject is unable to comply with the study procedures or with a clinical disease or laboratory abnormality that in the opinion of the investigator would potentially increase the risk of participation.


  • University of California San Diego accepting new patients
    La Jolla California 92037 United States
  • University of Utah accepting new patients
    Salt Lake City Utah 84108 United States


accepting new patients
Start Date
Completion Date
Ultragenyx Pharmaceutical Inc
Study Type
Last Updated