The primary purpose of the study is to assess the effect of hepatic impairment on the PK of tavapadon following administration of a single oral dose in participants with mild and moderate hepatic impairment relative to age, body weight, and sex-matched participants with normal hepatic function.

Key Inclusion Criteria:

1. Body mass index of ≥17.5 to 42.0 0 kilograms per meter square (kg/m^2), inclusive, and a total body weight >50 kilograms (kg) [110 pounds (lbs)].
2. Must meet the criteria for Class A or B of the modified Child-Pugh classification.
3. Stable hepatic disease defined as no clinically significant change in disease status in the last 28 days prior to the screening visit.
4. Previous alcohol abuse is permitted provided that the participant is willing and able to follow lifestyle guidelines and has a negative breath alcohol test at Screening and Check-in (Day -1).

Key Exclusion Criteria:

1. Receipt of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) vaccine or booster within 7 days of planned dosing.
2. Have recently been diagnosed with symptomatic Coronavirus Disease 2019 (COVID-19) or test positive for COVID-19 within 30 days prior to signing the informed consent form (ICF).
3. Taking any prohibited medication prior to randomization or likely to require prohibited concomitant therapy.
4. Has received study drug in a clinical trial of Tavapadon within 12 months of signing the ICF.
5. Acute hepatitis.
6. Grade ≥2 hepatic encephalopathy.
7. Participants who have received an organ transplant or are currently waiting for an organ transplant and are listed on the national transplant list.
8. Primary biliary cholangitis or primary sclerosing cholangitis.

Note: Other protocol-defined Inclusion/Exclusion criteria may apply.