Safety and Efficacy of Intravenous Trappsol Cyclo (HPBCD) in Niemann-Pick Type C Patients

The planned study has been designed as a Phase I/II, double-blind, randomised, multi-centre, parallel group study based on information and data available from the administration of Trappsol Cyclo via compassionate/named patient use in patients with NPC-1, and data on other cyclodextrin products in the scientific literature.

The study is comprised of two stages. The primary objective of Stage 1 is to compare the plasma pharmacokinetics of three different doses of IV Trappsol Cyclo in the prevention /delay of NPC-1 progression.Secondary objectives include investigation of the Hydroxypropyl Beta Cyclodextrin (HP-β-CD) effect of three different doses of IV Trappsol Cyclo upon serum and lymphocytic markers of cholesterol metabolism (Stages 1 and 2) and evaluation of concentrations in the cerebrospinal fluid (CSF) following intravenous (IV) administration (Stage 1), evaluation of the impact of treatment upon measures of neurological function including ataxia, aphasia and saccadic eye movements, and the impact of treatment upon behavioural aspects of NPC-1 (Stage 2).

It is planned to recruit a total of 12 patients to the study. Patients will be randomised 1:1:1 to one of the three dose levels (1500 mg/kg, 2000 mg/kg or 2500 mg/kg; four patients per dose level). Treatment will be administered every two weeks by slow IV infusion at a concentration of 250 mg/mL over 8 hours. Patients completing Stage 1 of the study will continue into Stage 2 and receive treatment for 48 weeks. Patients who withdraw prior to completion of the initial pharmacokinetic (PK) and pharmacodynamics (PD) assessments will be replaced.

The design of the proposed study thus enables early assessment of biochemical markers of response but allows for a sufficient dosing duration to enable the effectiveness of Trappsol in NPC-1 to be assessed.

As miglustat is an approved treatment for NPC-1 in the EU, with an established efficacy and safety profile, it would be unethical to exclude patients receiving miglustat therapy from the study, given that the study itself will also be conducted at sites in Europe. However, it is planned to balance randomisation across the treatment groups for its use.

The maximum dose proposed for this study is below the maximum dose for which long term clinical data is available in 2 patients (2800 mg/kg weekly for 3-5 years). Although individual clinicians have not always utilised an escalating rate of infusion, the reports of infusion related reactions in three patients suggest that this is an appropriate clinical strategy to mitigate the risk of such events and is consistent with dosing administration for other therapeutic agents. In the proposed study, treatment will be administered less frequently than has been undertaken in compassionate use. This longer dosing interval is supported by nonclinical data comparing the metabolism of cholesterol in non-human species with that in man; although a once weekly dosing interval was initially studied in man based on data in the mouse, HP-β-CD cholesterol metabolism/turnover in the mouse is 13-fold higher than in man which, in NPC-1, likely translates into a 13-fold slower accumulation of cholesterol in human cells compared with those of the mouse.Therefore, it is theorised that, given the slower cholesterol metabolism in humans, the dosing interval could be much less frequent in man than in mouse; however, based on what is known about cholesterol metabolism in humans and the pharmacokinetic and pharmacodynamic effect of HP-β-CD in the mouse, a dosing interval of 2 weeks in man is likely to be well within the therapeutic dosing interval and also minimises the amount of infusions required to be administered.