Pridopidine Phase 3 Study in Huntington's Disease

This Phase 3 study consists of two study periods, a randomized, double-blind, placebo-controlled 1-year study period and a 2-year open-label extension (OLE) period. The study assesses the effect of pridopidine 45 mg twice daily on HD in participants who are not using antidopaminergic medications (ADMs) at study start. Main objectives of the study will be to assess the effect of pridopidine on clinical progression of HD within 1 year and to evaluate the effect of pridopidine on functional capacity, cognition, motor function, quality of life (QoL), and speech in participants with HD within 1 year. The target population in this study are adult participants (age 23-65, inclusive) with adult-onset HD (onset of signs and symptoms and a diagnosis ≥21 years of age). Eligible participants have not been using ADMs for at least 6 months prior to the screening visit. In case ADM treatment is deemed necessary by the treating physician during the study, specific ADMs and doses may be initiated. Female participants who are pregnant, planning to become pregnant or breastfeeding are not allowed to enter the study. The treatment period will start with a 2-week titration period of once-daily treatment (1 capsule of pridopidine or placebo taken orally in the morning). From Day 15 onwards, all participants will take the study drug twice daily: in the morning and in the afternoon. Treatment will continue for an additional 50 weeks. The placebo-controlled study period includes 6 in-clinic visits and 5 telephone visits (safety calls) during the 1-year treatment period. The placebo-controlled study period will be followed by a 2-year OLE period. During the OLE period, all eligible participants will receive pridopidine. The OLE will consist of a 2-year treatment period, including an initial 2-week (re)titration period for all participants at pridopidine once daily and a maintenance period of 102 weeks with pridopidine twice daily. The blinding of the original treatment assignment will be maintained for all participants and study personnel during the OLE period. A total of 6 in-clinic visits and 6 telephone visits (safety calls) are planned during the 2-year OLE period.