N-acetyl-L-leucine improves symptoms and functioning in GM2 Gangliosidosis (Tay-Sachs & Sandhoff)

Background and Objective: GM2 gangliosidosis (Tay-Sachs and Sandhoff diseases) are rare, inherited neurodegenerative disorders with no available symptomatic or disease modifying treatments. This clinical trial aimed to investigate the safety and efficacy of N-acetyl-L-leucine (NALL) on symptoms of pediatric (greater than or equal to 6 years) and adult patients with GM2 gangliosidosis. Methods: We conducted an 8-center, multi-national, open-label, rater-blinded Phase IIb study (IB1001-201). Patients with a genetically confirmed diagnosis of GM2 gangliosidosis were assessed during a baseline period, a 6-week treatment period (orally administered NALL 4 g/day in patients greater than or equal to 13 years, weight-tiered doses for patients 6-12 years), and a 6-week post-treatment washout period. The primary Clinical Impression of Change in Severity (CI-CS) endpoint (based on a 7-point Likert scale) was assessed by blinded, centralized raters who compared randomized video pairs of each patient performing a pre-defined primary anchor test (8-Meter Walk Test or 9Hole Peg Test) during each study periods. Secondary outcomes included cerebellar rating scales (namely Scale for the Assessment and Rating of Ataxia), clinical global impression, and quality of life assessments. Results: 30 patients aged 6 to 55 years with a confirmed diagnosis of GM2 gangliosidosis (TaySachs or Sandhoff's disease) were enrolled. 29 patients were included in the primary modified intention-to-treat analysis. NALL met the CI-CS primary endpoint (mean difference 0.71, SD=2.09, 90% CI 0.00, 1.50, p=0.044), as well as secondary endpoints. No treatment-related serious adverse events occurred. Conclusions: This study showed NALL led to a statistically significant improvement in symptoms, functioning, and quality of life in patients with GM2 gangliosidosis. It is a safe, well-tolerated, easily administered oral therapy, therefore offering a favorable risk/benefit profile for this serious, debilitating disorder. NALL is a new therapeutic option for the treatment of this rare disease that has no other approved therapies worldwide. Classification of Evidence: This study provides Class IV evidence NALL is safe, well-tolerated, and improves neurological symptoms and quality of life in patients with GM2 gangliosidosis. Trial Registration Information: The trial is registered with ClinicalTrials.gov (NCT03759665; registered 30-Nov-2018), EudraCT (2018-004406-25), and DRKS (DRKS00017539). The first patient was enrolled 07-June-2019.