About the study

In this study, researchers will learn more about a study drug called BIIB122 in participants with early-stage Parkinson's disease (PD). In this study: - Participants will take 225 milligrams (mg) of BIIB122 or a placebo as tablets by mouth. A placebo looks like the study drug but has no real medicine in it. - Participants will take BIIB122 or placebo 1 time a day for up to a minimum of 48 weeks and a maximum of 144 weeks. - Certain medications for PD will be allowed at enrollment for a subset of participants. - The majority of clinic visits will be every 12 weeks. The main question researchers are trying to answer is if taking BIIB122 slows the worsening of symptoms more than placebo in the early stages of PD. To help answer this question, researchers will use a questionnaire called the Movement Disorder Society-Unified Parkinson's Disease Rating Scale, also known as the MDS-UPDRS. Researchers will use the MDS-UPDRS to learn about participant PD symptoms and how they affect their daily life. Researchers will also learn more about the safety of BIIB122.

Who can take part?

You may be eligible to participate in the study if you meet the following criteria:

Inclusion criteria

1. Clinical diagnosis of PD meeting the Movement Disorder Society Clinical Diagnostic Criteria within 2 years of the Screening Visit, inclusive, and at least 30 years of age at the time of diagnosis
2. Modified Hoehn and Yahr scale stages 1 to 2 (in OFF state), inclusive, at screening
3. MDS-UPDRS Parts II and III (in OFF state) combined score less than or equal to (≤)40 at screening
4. Screening genetic test results verifying the absence of a pathogenic leucine-rich repeat kinase 2 (LRRK2) variant. Confirmation of this eligibility requirement may come from an accredited genetic test that includes all exclusionary LRRK2 genetic variants. Key

Exclusion criteria

1. Clinically significant neurological disorder other than PD, including but not limited to stroke, dementia, or seizure, within 5 years of screening visit, in the opinion of the Investigator
2. Clinical evidence of atypical parkinsonism (e.g., multiple-system atrophy or progressive supranuclear palsy) or evidence of drug-induced parkinsonism.
3. Montreal Cognitive Assessment (MoCA) score <24 at the screening visit NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

For a full list of inclusion/exclusion criteria, please visit ClinicalTrials.gov

Study locations

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How to apply

Determine if a study site for this clinical trial is near you. Contact the study to apply.