A Phase II Study With Exploratory Outcomes of Fucose Supplementation in GLUT1 Deficiency Syndrome

A Phase II Randomized, Double-blind, Placebo-controlled, Cross-over Study With Exploratory Outcomes of Fucose Supplementation in GLUT1 Deficiency Syndrome

This is a single-center, randomized, double-blind, placebo-controlled, cross-over study to evaluate the efficacy and safety of L-fucose supplementation in subjects with GLUT1 deficiency syndrome (GLUT1DS).

Study Overview

• Status: Recruiting
• Conditions: GLUT1DS1; Glut1 Deficiency
• Intervention / Treatment: Drug: L-fucose; Other: Placebo

• Study Type: Interventional
• Enrollment (Estimated): 16
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Celena Byerlee-Dixon; Phone Number: 503-494-7004; Email: byerlee@ohsu.edu

Study Locations

• United States
  • Oregon
    • Portland, Oregon, United States, 97239
      • Recruiting
      • Oregon Health and Science University
      • Principal Investigator: Rodrigo T. Starosta, MD, PhD
      • Contact: Celena Byerlee-Dixon, MS, CCRP; Phone Number: 971-334-1942; Email: byerlee@ohsu.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Age ≥ 18 years
2. Confirmed diagnosis of GLUT1DS, including at least 2 out of the following 3: molecular genetic testing showing a pathogenic or likely pathogenic variant in SLC2A1; documented hypoglycorrhachia with a CSF:blood glucose ratio ≤ 0.6; clinical features consistent with GLUT1DS (epilepsy, movement disorders, ataxia, intellectual disability, dysarthria)
3. Presence of ataxia

Exclusion Criteria:

1. Inability to swallow liquids
2. Change in neurological medications (either medication itself or medication dosages) in the past 90 days
3. Use of fucose- or mannose-containing supplements within one year of enrollment

4. Presence of hepatic, renal, hematological, or concomitant metabolic disorders, as assessed by the presence of a previous diagnosis of such disorders (for instance, chronic kidney disease, liver cirrhosis, diabetes mellitus) or by the following laboratory values, which will be considered if obtained clinically up to 90 days before enrollment (if this is not available, laboratory tests will be obtained prior to first study visit):

   1. Any degree of hepatic impairment based on the Child-Pugh classification
   2. eGFR (as measured by serum creatinine or cystatin C) < 60 mg/min/1.73m2
   3. Hemoglobin A1c > 6.5%
   4. Hemoglobin level below the lower limit of normal (LLN) for sex and age
   5. Platelet counts below the LLN for sex and age
5. Subjects who are pregnant, breastfeeding, or planning to become pregnant within one year of enrollment
6. Enrollment in an investigational new drug trial for G1DS within one year of enrollment

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: L-fucose followed by placebo; L-fucose for 12 weeks, followed by placebo for 12 weeks.	Drug: L-fucose; L-fucose will be administered as 500 mg/kg to a maximum of 10 g three times per day by mouth.; Other Names: fucose; Other: Placebo; Placebo will be composed of micro-cellulose powder with a small amount of Stevia for taste mimicking, to be taken at 500 mg/kg for a maximum of 10 g three times per day by mouth.
Placebo Comparator: Placebo followed by L-fucose; Placebo for 12 weeks, followed by L-fucose for 12 weeks.	Drug: L-fucose; L-fucose will be administered as 500 mg/kg to a maximum of 10 g three times per day by mouth.; Other Names: fucose; Other: Placebo; Placebo will be composed of micro-cellulose powder with a small amount of Stevia for taste mimicking, to be taken at 500 mg/kg for a maximum of 10 g three times per day by mouth.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
SARA (Scale for the Assessment and Rating of Ataxia) Score	Severity of ataxia and cerebellar involvement as measured by the SARA clinical scales. This score ranges from 0 (no ataxia) to 40 (most severe ataxia)	24 weeks
Modified SARA (Scale for the Assessment and Rating of Ataxia) score	This modified score suggested by the FDA rates severity of ataxia from 0 (no ataxia) to 16 (most severe ataxia)	24 weeks
ICARS (International Cooperative Ataxia Rating Scale) Score	This scale score the severity of ataxia and other cerebellar findings from 0 (no compromise) to 100 (maximal impairment)	24 weeks
Safety labs: hemoglobin	Changes in levels of hemoglobin in g/dL	24 weeks
Safety labs: white blood cell count	Changes in white blood cell counts as measured in cells/mm3	24 weeks
Safety labs: platelet count	Changes in platelet counts measured as cells/mm3	24 weeks
Safety labs: lactate dehydrogenase	Changes in lactate dehydrogenase (LDH) levels measured as U/L	24 weeks
Safety labs: alanine-aminotransferase	Changes in alanine-aminotransferase (ALT) measured as U/L	24 weeks
Safety labs: aspartate-aminotransferase	Changes in aspartate-aminotransferase (AST) measured as U/L	24 weeks
Safety labs: gamma-glutamyltransferase	Changes in gamma-glutamyltransferase (GGT) measured as U/L	24 weeks
Safety labs: serum creatinine	Changes in serum creatinine measured as mg/dL	24 weeks
Safety labs: blood urea nitrogen	Changes in blood urea nitrogen (BUN) measured as mg/dL	24 weeks
Safety labs: serum sodium	Changes in serum sodium (Na) as measured in mmol/L	24 weeks
Safety labs: serum potassium	Changes in serum potassium (K) measured as mmol/L	24 weeks
Safety labs: serum chloride	Changes in serum chloride (Cl) measured as mmol/L	24 weeks
Safety labs: serum calcium	Changes in serum calcium (Ca) measured as mmol/L	24 weeks
Safety labs: serum bicarbonate	Changes in serum bicarbonate/carbonate measured as mmol/L	24 weeks
Subject-reported adverse events	Rate and character (including standardized severity) of adverse events as reported by the study subjects	24 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Severity of dysarthria	Number of "PA-TA" repetitions over 10 seconds ("PATA Rate Test")	24 weeks
Frequency and severity of migraines	Frequency and severity of migraines captured at a diary for 1 week, at the last week of each study arm.	24 weeks
Frequency of paroxysmal exercise-induced dystonia	Frequency of paroxysmal exercise-induced dystonic episodes, captured at a diary for 1 week, at the last week of each study arm.	24 weeks
Frequency of seizures	Frequency and duration of seizures captured at a diary for 1 week, at the last week of each study arm.	24 weeks
World Health Organization Quality of Life (WHO-QoL) scale	Objective scoring of global and domain-specific quality of life with the World Health Organization Quality of Life (WHO-QoL) scale.	24 weeks
Patient-Reported Outcomes Measurement Information System (PROMIS) score	Objective and quantitative measurement of quality of life using the PROMIS Fatigue, Mobility, and Physical Function tool	24 weeks

Collaborators and Investigators

• Sponsor: Oregon Health and Science University
• Collaborators: Glut1 Deficiency Foundation
• Investigators: Study Director: Rodrigo T. Starosta, MD, PhD, Oregon Health and Science University

Study record dates

Study Major Dates

• Study Start (Actual): May 5, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): August 1, 2027

Study Registration Dates

• First Submitted: February 14, 2026
• First Submitted That Met QC Criteria: February 19, 2026
• First Posted (Actual): February 25, 2026

Study Record Updates

• Last Update Posted (Actual): May 13, 2026
• Last Update Submitted That Met QC Criteria: May 8, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: SLC2A1; GLUT1 Deficiency; GLUT1 Deficiency Syndrome; GLUT1DS; Fucose; L-fucose
• Additional Relevant MeSH Terms: Glut1 Deficiency Syndrome; Carbohydrates; Deoxy Sugars; Fucose
• Other Study ID Numbers: 00028024

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No