Safety and Pharmacodynamic Effects of BIIB122 in Participants With LRRK2-Associated Parkinson's Disease (LRRK2-PD)

Inclusion Criteria:

• For heterozygous pathogenic LRRK2 mutation carriers: ≥ 30 to ≤ 80 years

• For homozygous pathogenic LRRK2 mutation carriers: ≥ 30 years

• Have screening genetic test results verifying the presence of a pathogenic LRRK2variant.

• Have a clinical diagnosis of PD meeting the Movement Disorder Society ClinicalDiagnostic Criteria.

Exclusion Criteria:

• Have a history of any clinically significant neurological disorder other than PD,including, but not limited to, stroke and dementia, in the opinion of theinvestigator, within 5 years of the screening visit.

• Have clinical evidence of atypical parkinsonism (eg, multiple-system atrophy orprogressive supranuclear palsy) or evidence of drug-induced parkinsonism.

• Have previously participated or are currently participating in the BIIB122 LUMAstudy (Study 283PD201).

• Have previously participated or are currently participating in a gene therapy studyfor PD.

• Have a history of brain surgical intervention for PD (eg, deep-brain stimulation,pallidotomy).

• Have any physical condition that may confound the motor assessment (MDS-UPDRS) overtime (eg, severe arthritis, severe dyskinesias, traumatic injuries with permanentphysical disability).

• Abnormal vitals including Blood Pressure, Heart Rate, or Body Temperature

• Have abnormal PFT results at screening

Note: Other protocol defined Inclusion/Exclusion criteria may apply