Efficacy, Safety, Tolerability, Pharmacodynamics, and Pharmacokinetics of BIA 28-6156 in GBA-PD

This is a 2-part (Part A \[Genetic Screening\] and Part B \[Double-Blind Treatment\]), Phase 2, multicenter, randomized, double-blind, placebo-controlled study to evaluate the efficacy, safety, tolerability, pharmacodynamics, and pharmacokinetics of 2 fixed dose levels of BIA 28-6156 (10 and 60 mg/day) in approximately 237 subjects with genetically confirmed GBA-PD. Part A (Genetic Screening) will identify individuals with a PD risk-associated variant in the GBA1 gene for potential enrolment into Part B (Double-Blind Treatment) of the study. Part B will consist of a screening period to ensure that all protocol inclusion/exclusion criteria for Part B of the study are met (up to 5 weeks). After screening period, eligible subjects will be randomized into 1 of 3 treatment arms (BIA 28-6156 10 mg/day, BIA 28-6156 60 mg/day, or placebo) in a 1:1:1 ratio, and enter a double-blind treatment period up to 78 weeks, followed by a 30-day (4 weeks) of safety follow-up period. Subjects must be receiving a stable dose of PD medication for at least 30 days before screening (for Part B \[Double-Blind Treatment\]) and will continue to receive their usual PD medications throughout the study.