The purpose of this study is to investigate the safety of Lu AF28996, how well it is tolerated and what the body does to the drug in participants with Parkinson's disease.

Key Inclusion Criteria:

• The participant is Chinese, defined as having four Chinese grandparents being born in China.
• The participant is diagnosed with idiopathic Parkinson's disease (consistent with the United Kingdom PD Society Brain Bank Criteria for the Diagnosis of PD).
• The participant's Modified Hoehn and Yahr score is ≥2 and ≤4 (in OFF) and ≤3 in the ON state.
• The participant experiences well recognizable and predictable motor fluctuations in the awake time including predictable morning OFF episodes causing clinically significant disability during the last 3 months prior to screening, as evaluated by the investigator.

Key Exclusion Criteria:

• The participant has received oral or transdermal dopamine agonist treatment ≤4 weeks prior to screening.
• The participant has undergone a neurosurgical intervention for Parkinson's disease (such as pallidotomy, thalamotomy, foetal or stem cell transplantation or deep brain stimulation).
• The participant has any other disorder for which the treatment takes priority over treatment of Parkinson's disease or is likely to interfere with trial treatment or impair treatment compliance.
• The participant has received Traditional Chinese Medicine treatment ≤4 weeks prior to screening.

Note: Other protocol-defined inclusion and exclusion criteria may apply.