Overview
The primary goal of this study is to evaluate the long-term safety and pharmacodynamic effects of PTC518 in participants with HD.
Description
Participants who completed the Treatment Period in the parent Phase 2a Study PTC518-CNS-002-HD (NCT05358717), fulfilled the enrollment criteria, and chose to enroll in this extension study will undergo baseline evaluations and be assessed for 30 additional months.
All participants will receive active PTC518 in this extension study. Participants who received PTC518 in the parent Study PTC518-CNS-002-HD will continue at the same dose level they received in that study in a blinded fashion (5, 10, or 20 milligrams [mg]). Participants who received placebo in the parent Study PTC518-CNS-002-HD will be allocated to a PTC518 dose level according to the same dosing group in which they were previously randomized (5, 10, or 20 mg). The 20 mg dosing arm will be open for randomization only if and when the Data Safety and Monitoring Board from the parent Study PTC518-CNS-002-HD recommends initiating this dosing level based on an unblinded review of safety data from that study.
Eligibility
Inclusion Criteria:
- Participant who has completed the Treatment Period in Study PTC518-CNS-002-HD.
Exclusion Criteria:
- Participants who have not previously completed the Treatment Period in Study PTC518-CNS-002-HD.
Note: Other inclusion and exclusion criteria may apply.
