Crossover Study to Assess the Efficacy and Safety of UX007 in the Treatment of Movement Disorders Associated With Glucose Transporter Type 1 Deficiency Syndrome (Glut1 DS)

UX007G-CL301 is a randomized, double-blind, placebo-controlled, crossover study to assess the
efficacy and safety of UX007 in Glut1 DS. The study will enroll approximately 40 pediatric,
adolescent, and adult subjects who are not on KD and are having disabling paroxysmal movement
disorders. A movement disorder event is defined in this study as a period of time when the
subject experiences one or more movement disorder symptoms, including symptoms that are
experienced during a movement disorder event alone or significant worsening of continuous
movement disorders. In this study, movement disorder events are defined as disabling if they
affect or limit a subject's activities of daily living.

During the 6-week Run-in Period, subjects will record disabling paroxysmal movement disorder
events in a daily electronic Glut1 DS symptom diary; if the minimum criterion for number of
events is not met or subjects complete <80% of the daily electronic Glut1 DS symptom diary,
the subject will be considered a screen failure and will not be randomized. Individuals may
be allowed to rescreen, at the discretion of the Principal Investigator, subject to approval
by the Medical Monitor.

At the end of the Run-in Period, eligible subjects will be randomized (1:1 ratio) to one of
two treatment sequences (UX007/placebo or placebo/UX007). At Randomization, subjects will
begin a 10-week double-blind Treatment Period 1. Treatment Period 1 will consist of a 2-week
titration period and an 8-week Maintenance Period. At the end of Treatment Period 1, subjects
will discontinue treatment and begin a 2-week washout period to minimize any potential
carryover effect. Subjects will crossover to the second randomized, double-blind treatment
assignment (placebo to UX007, UX007 to placebo) for an additional 10 weeks during Treatment
Period 2. Treatment Period 2 will consist of a 2-week titration period and an 8-week
Maintenance Period. At the end of the blinded crossover period (Week 22), all active subjects
will have the option of rolling into the open-label Extension Period, to continue UX007
treatment for up to 3 years or until one of the following occurs: the subject withdraws
consent, the subject is discontinued from the study at the discretion of the Investigator,
the study is terminated, or until commercial availability of the study drug in a subject's
region, whichever occurs first. Long-term safety and maintenance of effect of UX007 will be
assessed during the open-label Extension Period. A Safety Follow-up Phone Call will be
conducted 30-35 days after the last dose of UX007G-CL301 study drug.

Inclusion Criteria:

1. Diagnosis of Glut1 DS confirmed by SLC2A1 mutation

2. Males and females, aged ≥6 years old at the time of informed consent

3. At least 8 disabling paroxysmal movement disorder events in the 12 weeks prior to the
Screening, by subject or caregiver report or At least 6 disabling paroxysmal movement
disorder events in any 6 consecutive week period, over the last 12 week period prior
to the Screening, by subject or caregiver report

4. At least 4 disabling paroxysmal movement disorder events in 6 week Run-in Period,
reported in the daily electronic Glut1 DS symptom diary

5. ≥80% compliance with daily electronic Glut1 DS symptom diary completion during the Run
in Period

6. Not on KD, modified KD, or ketosis-inducing modified-fat diet for at least 3 months
prior to Screening

7. Plasma level of beta-hydroxybutyrate (BHB) ≤ 1 mmol/L (non-fasting) at Screening

8. Provide written or verbal assent (if possible) and written informed consent by the
patient(if an adult), or by a legally authorized representative after the nature of
the study has been explained, and prior to any research-related procedures

9. Must, in the opinion of the Investigator, be willing and able to complete key aspects
of the study and be likely to complete the 22-week, placebo-controlled, treatment
period

10. Patient (or caregiver) must, in the opinion of the Investigator, be able to comply
with accurate completion of the study daily electronic Glut1 DS symptom diary

11. Females of child-bearing potential must have a negative urine pregnancy test at
Screening and Baseline and be willing to have additional pregnancy tests during the
study. Females considered not to be of childbearing potential include those who have
not experienced menarche, are post-menopausal (defined as having no menses for at
least 12 months without an alternative medical cause) or are permanently sterile due
to total hysterectomy, bilateral salpingectomy, or bilateral oophorectomy.

12. Participants of child‐bearing potential or fertile males with partners of
child-bearing potential who are sexually active must consent to use a highly effective
method of contraception as determined by the site Investigator from the period
following the signing of the informed consent through 30 days after last dose of study
drug

Exclusion Criteria:

1. Any known hypersensitivity to triheptanoin or safflower oil that, in the judgment of
the Investigator, places the subject at increased risk for adverse effects

2. Prior use of triheptanoin within 30 days prior to Screening

3. History of, or current suicidal ideation, behavior and/or attempts per C-SSRS at
Screening or Baseline

4. Pregnant and/or breastfeeding an infant at Screening or Baseline

5. Participants unwilling or unable to discontinue use of a prohibited medication or
other substance that may confound study objectives [MCT oil, barbiturates,pancreatic
lipase inhibitors, KetoCal or other KD supplements, and/or KD])

6. Glut1 DS treatment regimen, including AEDs, should be stable for at least 30 days
prior to Screening

7. Use of any investigational product (drug, medical food, or supplement, including
medium chain triglyceride [MCT] oil, including coconut oil) within 30 days prior to
Screening

8. Has a concurrent disease or condition, or laboratory abnormality that, in the view of
the Investigator, places the subject at high risk of poor treatment compliance or of
not completing the study, or would interfere with study participation or introduces
additional safety concerns

9. Feeding or nutrition that, in the opinion of the dietitian, potentially affects
consistent administration of study drug