Study to Investigate the Influence of Hepatic Insufficiency on the Pharmacokinetics of Tozadenant

Inclusion Criteria:

All subjects must fulfill the following to participate:

• Subject has given his/her written informed consent on an IEC or IRB approved consent form.
• Subject understands the study procedures in the informed consent form (ICF), and is willing and able to comply with the protocol.
• Be either male or female 18 years old
• Have a BMI ≥ 18.5 and ≤ 40.0 kg/m2 at screening
• Is a continuous non-smoker or a smoker who will consume up to 10 cigarettes/day
• Child bearing females should be sexually inactive (abstinent) prior to dosing
• Females subjects of non childbearing potential must have undergone one of the following sterilization or be postmenopausal

Subjects with mild, moderate, or severe hepatic impairment must:

• Have a medical history consistent with a diagnosis of hepatic impairment.
• Have a diagnosis of chronic (> 6 months), stable hepatic insufficiency

Healthy subjects must be:

• Medically healthy with no significant medical history

Exclusion Criteria:

Subjects must not be enrolled in the study if they:

• Previously participated in any study with tozadenant
• Has orthostatic hypotension, history or symptoms of cardiovascular disease, or hypertensive crisis.
• Currently participating in or has participated in another study and received drug (active or placebo)
• Have a known diagnosis of malignant melanoma
• Have a current episode of major depression
• Has a recent history of suicide attempt
• Has any other condition or clinically significant abnormal findings on the physical or neurological examination, psychiatric and medical history
• Had surgery or any medical condition within 6 months
• Unable to refrain from or anticipates the use of any drugs, vitamins, natural or herbal supplements
• Subject is currently lactating or pregnant or planning to become pregnant.
• Recent donation of blood, plasma or significant blood loss
• Has positive test for ethanol or drugs of abuse or a history of chronic alcohol or drug abuse
• Clinically significant medical history
• Positive results hepatitis B surface antigen (HBsAg) or hepatitis C virus (HCV) for Healthy Volunteers only.