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.