Single Patient Investigational Treatment for Cree Leukoencephalopathy

Single Patient Investigational Treatment for Cree Leukoencephalopathy (Vanishing White Matter Disease)

Cree Leukoencephalopathy (CLE) is a very rare and severe brain disease that mainly affects members of the Cree communities in Northern Quebec. It causes the white matter of the brain-the part that helps nerves communicate-to slowly break down. As the disease progresses, children develop serious neurological problems that worsen over time and, sadly, lead to early death. At the moment, there are no effective treatments for CLE. The disease is caused by a single genetic change in the EIF2B5 gene, the same gene involved in another related condition called Vanishing White Matter (VWM).

A new medication called fosigotifator (FGT, ABBV-CLS-7262) is currently being tested in an international clinical trial for VWM.

The goal of this study is to provide access to this investigational medication (FGT) for a patient with CLE/VWM for whom no other treatment options exist. The study will also look at whether the potential benefits of FGT outweigh the risks, and whether the drug might slow down or stop the brain's white matter from deteriorating. By targeting the underlying cause of the disease, FGT may help reduce neurological symptoms and improve the patient's quality of life.

Study Overview

• Status: Active, not recruiting
• Conditions: Cree Leukoencephalopathy
• Intervention / Treatment: Drug: Fosigotifator

Detailed Description

Cree Leukoencephalopathy (CLE) is a rare and fatal neurodegenerative disorder predominantly affecting the Cree population in Northern Quebec. Characterized by progressive white matter degeneration, this condition leads to severe neurological impairment and decline, leading to premature death. Despite its significant impact on the affected population, there are currently no effective treatments for CLE. CLE is caused by a single founder pathogenic variant in the EIF2B5 gene and is therefore allelic to VWM.

Fosigotifator (FGT, ABBV-CLS-7262) has been developed and its safety and efficacy are currently being studied in a multi-center Phase 1b/2 clinical trial for Vanishing White Matter (VWM) by Calico.

This study aims to provide access to an investigational drug (FGT) for a patient diagnosed with CLE/VWM disease for whom there are no other treatment options available. The study will also evaluate the risk/benefit of FGT in slowing or halting the progression of white matter degeneration in this patient with CLE. By targeting the underlying pathophysiological mechanisms of white matter damage, FGT is expected to alleviate neurological symptoms and improve the quality of life for the patient.

• Study Type: Interventional
• Enrollment (Estimated): 1
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Quebec
    • Montreal, Quebec, Canada, H4A3J1
      • McGill University Health Centre

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• • Molecularly confirmed diagnosis of CLE

  • Pre-symptomatic or early symptomatic patient
  • Signed informed consent from the Legal Guardians/caregivers (parents)
  • Must not be eligible for any actively enrolling trial of fosigotifator in CLE/VWM
  • Must be at least 1 month of age at the Baseline visit
  • Must weigh at least 5kg at the Baseline visit

Exclusion Criteria:

• N/A

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Single patient trial; Fosigotifator	Drug: Fosigotifator; Fosigotifator

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Time to death or permanent ventilation	Time to death or permanent ventilation	From enrollment to 2 years

Collaborators and Investigators

• Sponsor: McGill University Health Centre/Research Institute of the McGill University Health Centre

Study record dates

Study Major Dates

• Study Start (Actual): December 3, 2025
• Primary Completion (Estimated): January 3, 2029
• Study Completion (Estimated): January 3, 2029

Study Registration Dates

• First Submitted: November 26, 2025
• First Submitted That Met QC Criteria: December 9, 2025
• First Posted (Estimated): December 23, 2025

Study Record Updates

• Last Update Posted (Estimated): January 16, 2026
• Last Update Submitted That Met QC Criteria: January 14, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: N=1; Fosigotifator; Cree Leukoencephalopathy
• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Leukoencephalopathies
• Other Study ID Numbers: CLE02-ABBV-CLS-7262

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