This study will be an open-label, prospective, interventional feasibility pilot project to study the efficacy, safety, and tolerability of UX007 (triheptanoin) on reducing hypoglycemic events in patients with GSD I. Subjects will serve as their own control. Five (5) subjects who are treatment naïve to UX007 (triheptanoin) and are already on standard dietary therapy for GSDI will be enrolled.

The primary objective is to evaluate the efficacy, safety, and tolerability of UX007 (triheptanoin) in patients with GSD I. The secondary objectives include evaluating the effect of UX007 (triheptanoin) on maintaining the duration of normoglycemia between meals based on glucose monitoring (Preventing and reducing the frequency of hypoglycemia); reduction/stabilization of the dose of cornstarch; and the prevention of increased liver steatosis based on ultrasound with elastography.

Prior to first study appointment:

A medical record review will be done prior to the appointment to confirm the diagnosis of GSD I. For interested subjects who are not already known to the investigators (i.e., patients of the Duke University Medical Center), a release of protected health information will be signed by the potential subjects to obtain records that can be used to confirm diagnosis.

Baseline / Visit 1:

Study subjects will be instructed to come to the DUMC to review and sign the informed consent document. At that time, complete medical history and complete physical examination will be obtained. Blood and urine will be collected for laboratory assessments. Height, weight, and vital signs (blood pressure, pulse, respiration) will be collected.

A nutritional history and review of diet dairy collected three days prior to the visit will be reviewed by a study dietitian. The blood glucose monitoring log for the three days prior to the visit will also be reviewed the study dietitian and MD. Study staff will collect concomitant medications and adverse event collection will begin once dosing with UX007 is initiated. An ultrasound with elastography will be conducted at the DUMCs radiology department and reviewed and a report generated by a radiologist.

Safety Phone Contact:

Subjects will be called by study staff the day after they start the UX007 and again 4 weeks later to assess nutritional history, review of glucose diary, review of dosing compliance, and to obtain an updated weight. Study staff will also review adverse events (AE/SAE) and concomitant medications during these calls. If a subject experiences an AE/SAE they will be contacted every two weeks until the AE/SAE is resolved.

2, 4, and 6 Month/Early Termination Visits:

Same procedures will be conducted as at the baseline visit, with the exception of the ultrasound with elastography, which will only be collected again at the 6 Month/Early Termination Visit.

Post-termination Phone Contact:

2-6 weeks after the 6 month/early termination visit study staff will contact the subject to collect an interim medical history, evaluation of nutritional history, review of glucose diary as well as review of adverse events and concomitant medications. An updated weight will also be obtained.

Inclusion Criteria:

• Naive to UX007 (triheptanoin)
• Confirmed documented diagnosis of GSDI: confirmation may be based on mutation analysis, liver biopsy, or enzyme testing
• Willing and able to complete all aspects of the study through the end of the study, including visits and tests, documentation of symptoms, blood sugar and dietary log, and administration of UX007 (triheptanoin); minors in the study must have a parent/legally authorized representative who is willing and able to assist in all applicable study requirements

Exclusion Criteria:

• Have a history of severe inflammatory bowel disease, or severe chronic diarrhea per the PI discretion on conventional doses of cornstarch
• Patient is on any other form of medium chain triglyceride (MCT) during the time of the study. Patients will be asked to stop any nutritional compound that includes MCT oil one week (7 days) prior to baseline.
• Have any co-morbid conditions, including major organ-system disease(s) that in the opinion of the Investigator, places the subject at increased risk of complications, interferes with study participation or compliance, or confounds study objectives
• Pregnancy
• Patients on continuous feeds, with a diagnosis of diabetes, and/or a diagnosis of any other inborn error or metabolism