The frequency of paroxysmal movement disorders captured as disabling movement disorder events (normalized to a 4-week rate) observed during the Maintenance Phase in participants treated with UX007 versus placebo, as recorded by the subject/caregiver in an event-based daily Glut1 DS symptom diary.

Full Analysis Set: all randomized participants who received at least 1 dose of study drug.

An Adverse Event (AE) was defined as any untoward medical occurrence, whether or not considered drug related. Serious adverse events (SAE) was defined as an AE that at any dose, in the view of either the Investigator or Ultragenyx, results in any of the following outcomes: death; a life-threatening AE; inpatient hospitalization or prolongation of existing hospitalization; persistent or significant incapacity or disability (substantial disruption of the ability to conduct normal life functions); a congenital anomaly/birth defect; other important medical event. All reported AEs with with a start date that occurred or worsened in severity on or after the first dose of study drug in the corresponding treatment period and before the first dose of study drug in the next treatment period were defined as TEAEs. AEs were graded as 1=mild, 2=moderate, 3=severe, 4=life=threatening, 5=death.

Safety Analysis Set: all randomized participants who received at least 1 dose of study drug.

The C-SSRS is a participant-rated questionnaire to assess suicidal ideation, suicidal behavior, and self-injurious behavior with no suicidal intent (yes or no responses). Positive responses (i.e., 'Yes') to C-SSRS questions correspond to events in these categories with the exception of the category 'No events'. Suicidal ideation includes the following subcategories: passive; active-nonspecific; active-method/no intent/no plan; active-intent/with or without method/no plan; active-method/intent/plan. Suicidal behavior includes the following subcategories: suicide attempt; interrupted attempt; aborted attempt; preparatory actions toward immanent suicidal behaviors; completed suicide. Suicidal ideation and/or suicidal behavior category includes participants with positive responses in the category suicidal ideation and/or suicidal behavior.

Safety Analysis Set: all randomized participants who received at least 1 dose of study drug. Participants with a baseline (BL) and postbaseline (PB) assessment.

Walking capacity and endurance, as determined by the distance in meters walked in 12 minutes during the 12MWT.

Full Analysis Set: all randomized participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Physical Function Mobility Domain, increases in score indicate greater mobility.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Fatigue Domain, decreases in score indicate less fatigue.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Sleep Disturbance Domain, decreases in score indicate less sleep disturbance.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Pain Interference Domain, decreases in scores indicate less pain interference.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. The Cognitive Function Domain measures cognitive function impairment. Decreases in score indicate less cognitive function impairment.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Social Roles and Activities Domain, decreases in score indicate worse /less or decrease of performance in social roles and activities.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Anxiety Domain, decreases in scores indicate less anxiety.

Full Analysis Set: all randomized adult participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015) via parent/proxy. It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Mobility Domain, decreases in score indicate less mobility.

Full Analysis Set: all randomized pediatric participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015) via parent/proxy. It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Upper Extremity Domain, decreases in score indicate less upper extremity movement.

Full Analysis Set: all randomized pediatric participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015) via parent/proxy. It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Fatigue Domain, decreases in score indicate less fatigue.

Full Analysis Set: all randomized pediatric participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015) via parent/proxy. It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Pain Interference Domain, decreases in score indicate less pain interference.

Full Analysis Set: all randomized pediatric participants who received at least 1 dose of study drug. Participants who had an assessment.

The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013; NIH 2015) via parent/proxy. It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Peer Relationships Domain, decreases in score indicate worse functioning in peer relationships.

Full Analysis Set: all randomized pediatric participants who received at least 1 dose of study drug. Participants who had an assessment.

Participant/caregiver global impression of change in clinical status using the CGI-I. The CGI-I is a 7-point scale that assesses how much the participant's condition has improved or worsened relative to a baseline state at the beginning of the intervention and rated as: 1=very much better; 2=much better; 3=a little better; 4=no change; 5=a little worse; 6=much worse; 7=very much worse.

Full Analysis Set: all randomized participants who received at least 1 dose of study drug. Participants who had an assessment.

Duration of disabling paroxysmal movement disorder events observed during the Maintenance Period of treatment, as recorded by the subject/caregiver in an event-based daily electronic Glut1 DS symptom diary.

Full Analysis Set: all randomized participants (or parent/proxy) who received at least 1 dose of study drug.

Cognitive function as measured by the CANTAB. CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. SSP Span Length assesses the cognitive domain of sequential memory, with scores on a discrete, ordinal scale from 2 to 9; higher scores indicate better function.

Full Analysis Set: all randomized participants who received at least 1 dose of study drug. Participants who had an assessment.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. SWMBE assesses the cognitive domain of working memory, with scores on a discrete, ordinal scale from 0 to 360; lower scores indicate better function.

Full Analysis Set: all randomized participants who received at least 1 dose of study drug. Participants who had an assessment.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. SWMS assesses the cognitive domain of executive function/strategy, with scores on a discrete, ordinal scale from 4 to 28; lower scores indicate better function.

Full Analysis Set: all randomized participants who received at least 1 dose of study drug. Participants who had an assessment.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. PALTEA assesses the cognitive domain of episodic memory/new learning, with scores on a discrete, ordinal scale from 0 to 137; lower scores indicate better function.

Full Analysis Set: all randomized participants (or parent/proxy) who received at least 1 dose of study drug. Participants who had an assessment.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. PALFTMS assesses the cognitive domain of episodic memory, with scores on a discrete, ordinal scale from 0 to 27; higher scores indicate better function.

Full Analysis Set: all randomized participants (or parent/proxy) who received at least 1 dose of study drug. Participants who had an assessment.