Reduction from baseline to Week 8 in frequency of seizures (normalized to a 4-week rate): observable seizures measured for 6 weeks after 2-week titration by diary and absence seizures measured overnight by EEG. Observable seizures from the diary include generalized tonic-clonic, generalized tonic, generalized clonic, generalized atonic, partial/focal with secondary generalization, myoclonic, myoclonic (astatic) atonic, myoclonic tonic, complex partial/focal, simple partial/focal motor, simple partial/focal sensory, and simple partial/focal psychological. Absence seizures from EEG include absence awake (>=10 sec), absence sleep (>=10 sec), indeterminate absence awake (3-10 sec), and indeterminate absence sleep (3-10 sec). A negative value indicates an increase in frequency.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product.

An adverse event (AE) was defined as any untoward medical occurrence, whether or not considered drug related. A serious AE was defined as an AE or suspected adverse reaction that at any dose resulted in any of the following outcomes: death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, a congenital anomaly/birth defect, or an important medical event that may have jeopardized the subject and may have required medical or surgical intervention to prevent one of the outcomes listed in the definition. An AE was considered a TEAE if it occurred or worsened in severity on or after the date of the first dose of study drug. An AE was considered a UX007 emergent adverse event if it occurred or worsened in severity on or after the first date of first dose of UX007 during the study.

Safety Analysis Set: all participants who received at least one dose of investigational product.

An AE was defined as any untoward medical occurrence, whether or not considered drug related. A serious AE was defined as an AE or suspected adverse reaction that at any dose resulted in any of the following outcomes: death, a life-threatening AE, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, a congenital anomaly/birth defect, or an important medical event that may have jeopardized the subject and may have required medical or surgical intervention to prevent one of the outcomes listed in the definition. An AE was considered a TEAE if it occurred or worsened in severity on or after the date of the first dose of study drug. An AE was considered a UX007 emergent adverse event if it occurred or worsened in severity on or after the first date of first dose of UX007 during the study.

Safety Analysis Set: all participants who received at least one dose of investigational product.

Reduction from baseline to Week 8 in frequency of seizures (normalized to a 4-week rate): observable seizures measured for 6 weeks after 2-week titration by diary. Observable seizures from the diary include generalized tonic-clonic, generalized tonic, generalized clonic, generalized atonic, partial/focal with secondary generalization, myoclonic, myoclonic (astatic) atonic, myoclonic tonic, complex partial/focal, simple partial/focal motor, simple partial/focal sensory, and simple partial/focal psychological. A negative value indicates an increase in frequency.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with observable seizures.

Reduction from baseline to Week 8 in frequency of absence seizures measured overnight by EEG. Absence seizures from EEG include absence awake (>=10 sec), absence sleep (>=10 sec), indeterminate absence awake (3-10 sec), and indeterminate absence sleep (3-10 sec). A negative value indicates an increase in frequency.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with absence seizures.

Seizure response, defined as the percentage of participants with at least 50% reduction from randomization to Week 8 in frequency of total seizures. Includes observable generalized and partial-onset seizures measured for 6 weeks by diary and absence seizures measured overnight by EEG. Observable seizures from the diary include generalized tonic-clonic, generalized tonic, generalized clonic, generalized atonic, partial/focal with secondary generalization, myoclonic, myoclonic (astatic) atonic, myoclonic tonic, complex partial/focal, simple partial/focal motor, simple partial/focal sensory, and simple partial/focal psychological. Absence seizures from EEG include absence awake (>=10 sec), absence sleep (>=10 sec), indeterminate absence awake (3-10 sec), and indeterminate absence sleep (3-10 sec).

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product.

Observable seizure response, defined as the percentage of participants with at least 50% reduction from randomization to Week 8 in frequency of observable seizures. Observable seizures from the diary include generalized tonic-clonic, generalized tonic, generalized clonic, generalized atonic, partial/focal with secondary generalization, myoclonic, myoclonic (astatic) atonic, myoclonic tonic, complex partial/focal, simple partial/focal motor, simple partial/focal sensory, and simple partial/focal psychological.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with observable seizures.

Absence seizure response, defined as the percentage of participants with at least 50% reduction from randomization to Week 8 in frequency of absence seizures. Absence seizures from EEG include absence awake (>=10 sec), absence sleep (>=10 sec), indeterminate absence awake (3-10 sec), and indeterminate absence sleep (3-10 sec).

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with absence seizures.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. RTI Simple choice reaction time standard deviation (RTISRTSD) assesses the cognitive domain of attention, with scores on a continuous range from 0 to 5000; lower scores indicate better function. RTI median simple choice reaction time (RTIMDSRT) assesses the cognitive domain of reaction time, with scores on a continuous range from 100 to 5100; lower scores indicate better function. RTI median 5-choice reaction time (RTIMDFRT) assesses the cognitive domain of reaction time, with scores on a continuous range from 100 to 5100; lower scores indicate better function. GEE statistical model.

Efficacy Analysis Set, CANTAB: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) CANTAB assessment performed.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. PAL total errors adjusted (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. PAL first trial memory score (PALFTMS) assesses the cognitive domain of episodic memory, with scores on a discrete, ordinal scale from 0 to 27; higher scores indicate better function. GEE statistical model.

Efficacy Analysis Set, CANTAB: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) CANTAB assessment performed.

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 (SSPSLF) assesses the cognitive domain of sequential memory, with scores on a discrete, ordinal scale from 2 to 9; higher scores indicate better function. GEE statistical model.

Efficacy Analysis Set, CANTAB: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) CANTAB assessment performed.

CANTAB measures neuropsychological function using a standardized, computerized battery of tests designed to assess visual memory, working memory, new learning and reaction time. SWM between errors (SWMBE48) assesses the cognitive domain of working memory, with scores on a discrete, ordinal scale from 0 to 360; lower scores indicate better function. SWM strategy (SWMS68) assesses the cognitive domain of executive function/strategy, with scores on a discrete, ordinal scale from 4 to 28; lower scores indicate better function. GEE statistical model.

Efficacy Analysis Set, CANTAB: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) CANTAB assessment performed.

Participants were instructed to walk the length of a pre-measured 20-30 meter course in a hallway for 6 consecutive minutes. The total distance walked (meters) in a 6 minute period was recorded.

Efficacy Analysis Set - 6MWT: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) 6MWT assessment performed.

Participants were instructed to walk the length of a pre-measured 20-30 meter course in a hallway for 6 consecutive minutes. The total distance walked (meters) in a 6 minute period was recorded. The percent of predicted normal distance walked was determined based on published normative data.

Efficacy Analysis Set - 6MWT: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) 6MWT assessment performed.

For the 6MWT, subjects were instructed to walk the length of a pre-measured 20-30 meter course in a hallway for 6 consecutive minutes. The total distance walked (meters) in a 6 minute period was recorded. PED occurring during the 6MWT was assessed. (PED is characterized by transient abnormal, involuntary movements primarily affecting the legs and feet, and typically precipitated by prolonged exertion.)

Efficacy Analysis Set - 6MWT: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) 6MWT assessment performed. Participants with at least 1 PED.

The GMFM-88 is a standardized observational measure of abilities that includes the following 5 domains: lying/rolling, sitting, crawling/kneeling, standing, and walking/running/jumping. The GMFM-88 scores include the following:

• Lying & Rolling Score, Range 0-100%, higher is better
• Sitting Score, Range 0-100%, higher is better
• Crawling & Kneeling Score, Range 0-100%, higher is better
• Standing Score, Range 0-100%, higher is better
• Walking, Running & Jumping Score, Range 0-100%, higher is better
• Total Score = (Sum of 5 Above Scores) / 5, Range 0-100%, higher is better.

Efficacy Analysis Set - GMFM-88: Subset of participants taking UX007 during the treatment period in the efficacy analysis set who had a baseline and at least 1 post baseline (Week 4 or Week 8) GMFM-88 assessment performed.

Reduction from baseline over time in frequency of seizures (normalized to a 4-week rate): observable seizures measured for 6 weeks after 2-week titration by diary and absence seizures measured overnight by EEG. Observable seizures from the diary include generalized tonic-clonic, generalized tonic, generalized clonic, generalized atonic, partial/focal with secondary generalization, myoclonic, myoclonic (astatic) atonic, myoclonic tonic, complex partial/focal, simple partial/focal motor, simple partial/focal sensory, and simple partial/focal psychological. Absence seizures from EEG include absence awake (>=10 sec), absence sleep (>=10 sec), indeterminate absence awake (3-10 sec), and indeterminate absence sleep (3-10 sec). A negative value indicates an increase in frequency.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with an assessment at given time point.

Reduction from baseline over time in frequency of seizures (normalized to a 4-week rate): observable seizures measured for 6 weeks after 2-week titration by diary. Observable seizures from the diary include generalized tonic-clonic, generalized tonic, generalized clonic, generalized atonic, partial/focal with secondary generalization, myoclonic, myoclonic (astatic) atonic, myoclonic tonic, complex partial/focal, simple partial/focal motor, simple partial/focal sensory, and simple partial/focal psychological. A negative value indicates an increase in frequency.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with observable seizures and an assessment at given time point.

Reduction from baseline to Week 8 in frequency of absence seizures measured overnight by EEG. Absence seizures from EEG include absence awake (>=10 sec), absence sleep (>=10 sec), indeterminate absence awake (3-10 sec), and indeterminate absence sleep (3-10 sec). A negative value indicates an increase in frequency.

Efficacy Analysis Set: all randomized participants who received at least one dose of investigational product. Participants with absence seizures and an assessment at given time point.