This study will test SAGE-718 to evaluate cognitive effects in subject with early manifest HD. The subject will be on study drug or placebo for 84 days. At clinic visits, participants will take the IP under staff supervision, followed
by assessments of cognitive function, health-related function and quality of life, and neuropsychiatric symptoms.
This is a Phase 3, randomized, double-blind, placebo-controlled study to evaluate the efficacy, safety, and tolerability of valbenazine in subjects with Huntington's Disease (HD). The study includes a 4-week screening period, an 8-week dose-adjustment period, a 4-week maintenance period, and a final study visit 2 weeks following the final dose of study drug. Approximately 120 adult male and female subjects with motor manifest HD (a type of HD that causes uncontrolled movements and balance issues) and a genetic diagnosis of HD will be enrolled.
Study drug will be self-administered (in the presence of the subject's caregiver, if applicable) once daily (qd), preferably in the morning but before 1800 hours, beginning on Day 1. Study drug should be administered at approximately the same time each day during the study. Valbenazine will be supplied as orally administered capsules containing 20 or 40 mg of valbenazine. Subjects must swallow the capsules with approximately 4 ounces of water or other liquid, with or without food.