RecruitingPhase 3Drug trialA Study to Evaluate the Efficacy and Safety of Intravenous (IV) Prasinezumab in Participants With Early-Stage Parkinson's DiseaseThe purpose of this study is to evaluate the efficacy, safety, and pharmacokinetics (PK) of prasinezumab compared with placebo in participants with early-stage Parkinson's disease (PD) on stable symptomatic monotherapy with levodopa.