A Trial Investigating Lu AF28996 in Adult Japanese Participants With Parkinson's Disease (PD)

Inclusion Criteria: * The participant is diagnosed with idiopathic PD (consistent with the United Kingdom Parkinson's Disease Society Brain Bank Criteria for the Diagnosis of Parkinson's Disease) and should not have more than 1 first-degree relative with PD. * The participant's Modified Hoehn and Yahr score is ≤3 in the ON state and ≤4 in the OFF state. * The participant experiences well-recognizable and predictable motor fluctuations (≥1.5 hours of OFF-periods in the awake time, predictable morning OFF episodes included) causing clinically significant disability during the 7-week Screening Period. * The participant currently has a good response to levodopa and has been receiving a stable dose of levodopa (≥3 doses per day of levodopa/dopa decarboxylase inhibitor therapy) ≥4 weeks prior to screening. * The participant is Japanese, defined as having four Japanese grandparents and being born in Japan. Exclusion Criteria: * The participant has or had one or more of the following conditions that are considered clinically relevant in the context of the study; other neurological disorder, psychiatric disorder, seizure disorder or encephalopathy, respiratory disease, hepatic impairment or renal insufficiency, metabolic disorder, endocrinological disorder, hematological disorder, infectious disorder, any clinically significant immunological condition, or a history of narrow-angle glaucoma. * The participant has a positive test result for SARS-CoV-2 at the Baseline Visit. * The participant has undergone a neurosurgical intervention for PD (such as pallidotomy, thalamotomy, fetal or stem cell transplantation or deep brain stimulation). Note: Other inclusion and exclusion criteria may apply.