Proof-of-Concept Safety Study of CPP-109 (Vigabatrin) for Treatment Refractory Tourette's Disorder

The aims of this study are to 1) explore proof of concept that CPP-109 will reduce tics, and
2) to obtain systematic data regarding dosing, safety and tolerability of CPP-109 in adults
with treatment refractory TD. We will obtain preliminary data on estimate of effect size for
tics using Cohen's d, calculating the difference between the two means (baseline and endpoint
scores on the YGTSS), divided by the standard deviation of the difference.

Inclusion Criteria:

1. Subjects must be between 18 and 35 years of age (inclusive) when informed consent is
obtained.

2. Subjects must meet full DSM-IV diagnostic criteria for TD by clinical interview on
examination by a physician investigator, and confirmed by the Structured Clinical
Interview for DSM (SCID-CT) for clinical trials.

3. Subjects will have failed to respond to an adequate trial, as determined by the
investigator, of clonidine, guanfacine, and a first generation (typical) and
second-generation (atypical) neuroleptic medication in the past.

4. Tics are causing significant distress or impairment, as determined by the subject and
principal investigator, on the current treatment regimen.

5. Laboratory results, including serum chemistries, hematology, and urinalysis, must show
no significant abnormalities (significant is defined as laboratory values requiring
acute medical intervention).

6. Subjects will not undergo formal IQ testing, but must be of normal intelligence in the
judgment of the investigator.

7. Subjects must possess an educational level, degree of understanding and command of the
English language to enable them to communicate suitably with the investigators and
study coordinator, and to understand the nature of the study.

8. Subjects must be considered reliable.

9. Written informed consent of subjects is obtained.

Exclusion Criteria:

1. Subjects with organic brain disease, for example, traumatic brain injury residua.

2. Subjects with a preexisting ophthalmologic condition.

3. Subjects with or at high risk of other types of irreversible vision loss or who
require other drugs associated with serious adverse ophthalmic effects such as
retinopathy or glaucoma.

4. Subjects meeting criteria for mental retardation as defined by the DSM-IV-TR.

5. Subjects with a history of seizure disorder (other than febrile seizure).

6. Subjects with history of Sydenham's Chorea.

7. Subjects with autism, schizophrenia, other psychotic disorder, or bipolar disorder.

8. Subjects with a primary diagnosis of a major mood disorder that requires ongoing
psychiatric treatment.

9. Subjects with a neurological disorder other than a tic disorder.

10. Subjects with a major medical illness.

11. Female subjects who are unwilling to use birth control or who are pregnant, as
determined by serum pregnancy test at baseline assessment, or lactating.

12. Subjects who have a past or current history of substance dependence and/or a current
history of substance abuse or who fail baseline toxicology screen.

13. Subjects who have any clinically significant abnormal laboratory result at baseline
screening including EKG, or blood tests.

14. Subjects who, in the opinion of the investigator, are unsuitable in any other way to
participate in this study.