Long-Term Effects of Atidarsagene Autotemcel for Metachromatic Leukodystrophy

Area of Science:

• Genetics and Gene Therapy
• Neurology
• Rare Diseases

Background:

• Metachromatic leukodystrophy (MLD) is a severe, ultrarare lysosomal storage disorder.
• MLD results from a deficiency in the enzyme arylsulfatase A (ARSA).
• Early diagnosis and intervention are critical for managing MLD progression.

Purpose of the Study:

• To evaluate the efficacy and safety of atidarsagene autotemcel (arsa-cel) gene therapy for MLD.
• To compare outcomes of treated patients with a natural history cohort of untreated MLD patients.
• To assess survival free from severe motor impairment as a primary endpoint.

Main Methods:

• Prospective, open-label clinical studies and expanded-access programs involving arsa-cel treatment.
• Comparison of outcomes between 39 treated patients and 49 untreated patients (natural history cohort).
• Primary endpoint: survival free from severe motor impairment (loss of locomotion, sitting without support, or death).

Main Results:

• Arsa-cel significantly lowered the risk of severe motor impairment or death in presymptomatic and early-symptomatic MLD patients.
• At 6 years, 100% of treated presymptomatic late-infantile MLD patients survived without severe motor impairment vs. 0% untreated.
• At 10 years, treated early-juvenile MLD patients showed significantly higher survival without severe motor impairment (87.5% and 80.0%) compared to untreated (11.2%).
• No evidence of insertional oncogenesis; febrile neutropenia was the most common severe adverse event.
• Three deaths occurred, deemed unrelated to arsa-cel treatment.

Conclusions:

• Atidarsagene autotemcel (arsa-cel) gene therapy significantly reduces the risk of severe motor impairment or death in specific MLD patient groups.
• The study demonstrates a substantial survival benefit for treated patients compared to natural history data.
• Arsa-cel represents a promising therapeutic option for presymptomatic and early-symptomatic metachromatic leukodystrophy.