A master protocol to investigate a novel therapy acetyl-L-leucine for three ultra-rare neurodegenerative diseases: Niemann-Pick type C, the GM2 gangliosidoses, and ataxia telangiectasia

Abstract

Background: The lack of approved treatments for the majority of rare diseases is reflective of the unique challenges of orphan drug development. Novel methodologies, including new functionally relevant endpoints, are needed to render the development process more feasible and appropriate for these rare populations and thereby expedite the approval of promising treatments to address patients' high unmet medical need. Here, we describe the development of an innovative master protocol and primary outcome assessment to investigate the modified amino acid N-acetyl-L-leucine (Sponsor Code: IB1001) in three separate, multinational, phase II trials for three ultra-rare, autosomal-recessive, neurodegenerative disorders: Niemann-Pick disease type C (NPC), GM2 gangliosidoses (Tay-Sachs and Sandhoff disease; "GM2"), and ataxia telangiectasia (A-T).

Methods/design: The innovative IB1001 master protocol and novel CI-CS primary endpoints were developed through a close collaboration between the Industry Sponsor, Key Opinion Leaders, representatives of the Patient Communities, and National Regulatory Authorities. As a result, the open-label, rater-blinded study design is considerate of the practical limitations of recruitment and retention of subjects in these ultra-orphan populations. The novel primary endpoint, the Clinical Impression of Change in Severity© (CI-CS), accommodates the heterogenous clinical presentation of NPC, GM2, and A-T: at screening, the principal investigator appoints for each patient a primary anchor test (either the 8-m walk test (8MWT) or 9-hole peg test of the dominant hand (9HPT-D)) based on his/her unique clinical symptoms. The anchor tests are videoed in a standardized manner at each visit to capture all aspects related to the patient's functional performance. The CI-CS assessment is ultimately performed by independent, blinded raters who compare videos of the primary anchor test from three periods: baseline, the end of treatment, and the end of a post-treatment washout. Blinded to the time point of each video, the raters make an objective comparison scored on a 7-point Likert scale of the change in the severity of the patient's neurological signs and symptoms from video A to video B. To investigate both the symptomatic and disease-modifying effects of treatment, N-acetyl-L-leucine is assessed during two treatment sequences: a 6-week parent study and 1-year extension phase.

Discussion: The novel CI-CS assessment, developed through a collaboration of all stakeholders, is advantageous in that it better ensures the primary endpoint is functionally relevant for each patient, is able to capture small but meaningful clinical changes critical to the patients' quality of life (fine-motor skills; gait), and blinds the primary outcome assessment. The results of these three trials will inform whether N-acetyl-L-leucine is an effective treatment for NPC, GM2, and A-T and can also serve as a new therapeutic paradigm for the development of future treatments for other orphan diseases.

Trial registration: The three trials (IB1001-201 for Niemann-Pick disease type C (NPC), IB1001-202 for GM2 gangliosidoses (Tay-Sachs and Sandhoff), IB1001-203 for ataxia telangiectasia (A-T)) have been registered at www.clinicaltrials.gov (NCT03759639; NCT03759665; NCT03759678), www.clinicaltrialsregister.eu (EudraCT: 2018-004331-71; 2018-004406-25; 2018-004407-39), and https://www.germanctr.de (DR KS-ID: DRKS00016567; DRKS00017539; DRKS00020511).

Keywords: Ataxia telangiectasia; Cerebellar ataxia; GM2 gangliosidosis; Lysosomal storage disease; N-acetyl-L-leucine; Niemann-Pick disease type C (NPC); Pharmaceutical intervention; Sandhoff disease; Single-blinded trial; Symptomatic treatment; Tay-Sachs disease (TSD).

Fig. 1

Parent study schema. During the treatment period, all patients will receive N-acetyl-l-leucine for 42 days (+ 7 days). Visit 3 (treatment 1) will occur at day 28 (+ 7 days) of the treatment period and visit 4 (treatment 2) will occur after the full 42 days (+ 7 days) of treatment. A 42-day (+ 7 days) washout period will be performed following treatment with N-acetyl-l-leucine. Visit 5 (washout 1) will occur on day 28 (+ 7 days) of the washout period and visit 6 (washout 2) will occur after the full 42 days (+ 7 days) of washout. a Naïve patients screening pathway: patients who have not used any prohibited medications within 42 days of screening are “naïve.” Their initial screening visit is treated as visit 1 (baseline 1). b Non-naïve patient screening pathway: patients who have used or are unable to confirm or deny if they have used any prohibited medication within the past 42 days are “non-naïve.” Patient will be given the opportunity to undergo a minimum of 42 days washout before returning for a repeat visit 1 (baseline 1)

Fig. 2

Extension phase schema. Patients will be assessed approximately 4 times over a 64-week period: at the start of the extension phase, after 6 months of treatment, 1 year of treatment, and after a 42-day (+ 14 day) post-extension-phase treatment washout