Evaluating the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of BIIB054 in Participants With Parkinson's Disease

The primary objective of the study is to evaluate the clinical efficacy of BIIB054 via dose response using the change from baseline in Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Total Score. The secondary objectives of the study are to evaluate the dose-related safety of BIIB054, to evaluate the clinical efficacy of BIIB054 via MDS-UPDRS total score, to assess the pharmacokinetic (PK) profile of BIIB054, to evaluate the clinical efficacy of BIIB054 based on MDS-UPDRS subparts, to evaluate the pharmacodynamic effects of BIIB054 on the integrity of nigrostriatal dopaminergic nerve terminals and to evaluate the immunogenicity of BIIB054.