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.



Eligible Ages
Between 30 Years and 80 Years
Eligible Genders
Accepts Healthy Volunteers

Inclusion Criteria

  • 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 - Modified Hoehn and Yahr scale stages 1 to 2 (in OFF state), inclusive, at screening - MDS-UPDRS Parts II and III (in OFF state) combined score less than or equal to (≤)40 at screening - 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.

Exclusion Criteria

  • 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 - Clinical evidence of atypical parkinsonism (e.g., multiple-system atrophy or progressive supranuclear palsy) or evidence of drug-induced parkinsonism. - Montreal Cognitive Assessment (MoCA) score <24 at the screening visit NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Study Design

Phase 2
Study Type
Intervention Model
Parallel Assignment
Primary Purpose
Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)

Arm Groups

ArmDescriptionAssigned Intervention
BIIB122 225 mg
Participants will receive BIIB122, 225 mg tablets, by mouth, once daily (QD) for up to a minimum of 48 weeks and a maximum of 144 weeks.
  • Drug: BIIB122
    Administered as specified in the treatment arm
    Other names:
    • DNL151
  • Drug: BIIB122-Matching Placebo
    Administered as specified in the treatment arm
Placebo Comparator
BIIB122 225 mg-Matching Placebo
Participants will receive BIIB122, 225 mg-matching placebo tablets, by mouth, QD for up to a minimum of 48 weeks and a maximum of 144 weeks.
  • Drug: BIIB122-Matching Placebo
    Administered as specified in the treatment arm

Recruiting Locations

Boston University Medical Center
Boston, Massachusetts 02118

More Details


Study Contact

US Biogen Clinical Trial Center

Detailed Description

BIIB122 is an investigational central nervous system-penetrant small molecule inhibitor of LRRK2 kinase.


Study information shown on this site is derived from ClinicalTrials.gov (a public registry operated by the National Institutes of Health). The listing of studies provided is not certain to be all studies for which you might be eligible. Furthermore, study eligibility requirements can be difficult to understand and may change over time, so it is wise to speak with your medical care provider and individual research study teams when making decisions related to participation.