Acetyl-L-leucine for Niemann-Pick type C – a multi-national, rater-blinded phase II trial

BackgroundNiemann-Pick disease type C (NPC) is a rare autosomal recessive neurodegenerative disorder characterized by symptoms such as progressive cerebellar ataxia and cognitive decline. The modified amino acid N-acetyl-leucine has been associated with positive symptomatic and neuroprotective, disease-modifying effects in observational case studies and animal and cellular models of NPC. Therefore, the effects of the active L-enantiomer, N-acetyl-L-leucine (NALL, Sponsor Code IB1001) were evaluated in paediatric and adult patients with NPC.MethodsWe conducted a 9-center, multinational, open-label, rater-blinded Phase 2 study to assess the safety and efficacy of NALL for the treatment of pediatric (≥ 6 years) and adult patients with NPC (IB1001-201 clinical trial). Eligible patients were assessed during three study phases: a baseline period (with or without a study run-in), a 6-week treatment period (dosage of NALL 4 g/d in patients aged ≥13 years; weight tiered doses for patients aged 6-12 years based on approximately 0.1 g/kg/day), and a 6-week post-treatment washout period. The primary outcome was based on the Clinical Impression of Change in Severity (CI-CS) assessment (assessed on a 7-point Likert scale) performed by blinded, centralized raters who compared videos of patients performing a pre-defined primary anchor test (either the 8-Meter Walk Test (8MWT) or 9-Hole Peg Test of the Dominant Hand (9HPT-D)) at different study periods. Secondary outcomes included the cerebellar function evaluations, namely the Scale for Assessment and Rating of Ataxia (SARA), the Spinocerebellar Ataxia Functional Index (SCAFI), and the Clinical Global Impression Scales (CGI) as well as the EuroQol-5D/VAS.ResultsThirty-three subjects aged 7 to 64 years with a confirmed diagnosis of NPC were enrolled according to the trial protocol between 04 September 2019 and 30 January 2020. Thirty-two patients were included in the modified intention-to-treat analysis. IB1001 met its CI-CS primary endpoint (mean difference 0.86 ((90% CI 0.25,1.75, p=0.029). IB1001 also met secondary endpoints, including improvement during treatment on the SARA scale (mean difference −1.19 (90% CI −1.8, −0.5, p=0.001)), investigator’s CGI-C assessment (mean difference from baseline to the end of treatment 0.6 (90% CI 0.5, 1.0, pp=0.002)) and investigator’s CGI-C assessment (washout mean difference −0.5 (90% CI −1.0, 0.0, p=0.006). IB1001 was well-tolerated with no treatment related serious adverse reactions occurring.ConclusionsConsistent with its pharmacological action, IB1001 rapidly improved symptoms, functioning, and quality of life in 6-weeks, the clinical effect of which was lost after the 6-week, post-treatment washout period. High consistency and statistical significance between the primary and secondary endpoints demonstrate a clear, clinically meaningful improvement with IB1001. IB1001 was well-tolerated and no drug-related serious adverse events were reported, demonstrating a favorable risk/benefit profile for the treatment of NPC (Funded by IntraBio; ClinicalTrials.gov number, NCT03759639; EudraCT number 2018-004331-71).