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

A Multicenter, Randomized, Double-Blind, Placebo-Controlled Study, With an Active-Treatment Dose-Blinded Period, to Evaluate the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of BIIB054 in Subjects 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.

Inclusion Criteria

• Diagnosed with Parkinson's disease (PD) within a maximum of 3 years prior to Screening.
• Score of ≤2.5 on the Modified Hoehn and Yahr Scale.
• Has not received any medication for the treatment of the motor symptoms of PD for at least 12 weeks prior to Day 1 and, in the opinion of the Investigator, is not expected to require PD treatment for at least 6 months following Day 1. Maximum total duration of prior PD regimens should not exceed 30 days. Stable (at least 8 weeks) dosages of medications that are used to treat conditions other than PD tremor are allowed. Further guidance will be provided by the study's Medical Monitor on a case by case basis.
• Screening dopamine transporter (DaT)/ single-photon emission computed tomography (SPECT) results consistent with neurodegenerative Parkinsonism (central reading).
• All women of childbearing potential and all men must practice highly effective contraception during the study and for 6 months after their last dose of study treatment.

Exclusion Criteria:

• Presence of freezing of gait.
• Montreal cognitive assessment (MOCA) score <23 or other significant cognitive impairment or clinical dementia that, in the opinion of the Investigator, would interfere with study evaluation.
• History of or screening brain magnetic resonance imaging (MRI) scan indicative of clinically significant abnormality, as read by central reader.
• History of severe allergic or anaphylactic reactions, or history of hypersensitivity to BIIB054 or any of the inactive ingredients in the drug product or to radioligands or iodine used in the study.
• Participation in any active immunotherapy study targeting alpha-synuclein.
• Use of allowed medications not previously specified at doses that have not been stable for at least 8 weeks before Day 1, and/or that are not expected to remain stable for the duration of the study.
• Clinically significant abnormal laboratory test values at Screening, as determined by the Investigator.
• Blood donation (1 unit or more) within 8 weeks before Day 1 (must also refrain from donating blood for the duration of the study).

NOTE : Other protocol defined Inclusion/Exclusion criteria may apply