Evaluating meaningful changes in physical functioning and cognitive declines in metachromatic leukodystrophy: a...

Area of Science:

• Neurology
• Genetics
• Lysosomal Storage Diseases

Background:

• Metachromatic leukodystrophy (MLD) is a rare genetic disorder affecting the nervous system due to arylsulfatase A (ASA) deficiency.
• Current MLD treatments are limited, with gene therapy via hematopoietic stem cell transplantation being the only approved option for specific subtypes.
• Assessing the clinical meaningfulness of therapeutic benefits from the patient and caregiver perspective is crucial for treatment evaluation.

Purpose of the Study:

• To evaluate the clinical meaningfulness of slowing gross motor function decline, measured by the Gross Motor Function Classification in MLD (GMFC-MLD), from the caregiver perspective.
• To assess the perceived significance of declines in communication abilities, measured by the Expressive Language Function Classification in MLD (ELFC-MLD).
• To inform the selection of endpoints for a Phase 2 clinical trial investigating intrathecal recombinant human ASA in MLD.

Main Methods:

• Semi-structured telephone interviews were conducted with caregivers of children diagnosed with late-infantile MLD.
• Caregivers reported on the motor and language progression of their children using the GMFC-MLD and ELFC-MLD scales.
• The study focused on understanding caregiver perceptions of meaningful delays in disease progression.

Main Results:

• Most caregivers (10/12) perceived delaying MLD progression as meaningful.
• A slowing of motor function decline (e.g., GMFC-MLD category 1 to 3 over 2 years) was considered meaningful by all caregivers asked.
• Caregivers found delaying expressive language decline meaningful, particularly when it did not indicate a complete loss of communication (ELFC-MLD categories 1-3).

Conclusions:

• Caregiver perspectives strongly support the meaningfulness of delaying gross motor function decline in MLD, validating GMFC-MLD as a key clinical trial endpoint.
• Communication abilities, assessed via ELFC-MLD, are also significant and should be considered in future clinical trial designs.
• These findings will help refine the endpoints for ongoing and future MLD clinical trials, ensuring therapeutic benefits align with patient and family priorities.