A Study of the Structure and Function of the Retina in Adult Patients With Refractory Complex Partial Seizures Treated With Vigabatrin (Sabril®)

Multicenter, prospective open-label study with approximately 25 sites in the US that
specialize in caring for adult patients with refractory CPS

- Sites must have access to Humphrey static perimetry and to Spectralis SD-OCT.

- All vision test results will be sent to the central readers for evaluation.

- Additional study tests:

- The Columbia Suicide Severity Rating Scale (C-SSRS)

- The National Eye Institute Visual Field Questionnaire-39 (NEI VFQ-39)

- A whole blood sample for specific analysis of DNA characteristics

- An optional whole blood sample for exploratory analysis of DNA characteristics

- Plasma samples for bioanalytical analysis of vigabatrin and blood samples for
taurine biomarker analysis

Important Inclusion Criteria:

1. The patient speaks English or Spanish.

2. The patient has had no prior exposure to Sabril.

3. To begin Sabril therapy for the treatment of CPS.

4. Male or female ≥18 years of age.

5. The patient has refractory CPS:

1. The patient has complex partial epilepsy of more than 1 year duration and no
other seizure type within the past year except for partial seizures secondarily
generalized.

2. The patient has failed because of lack of efficacy 3 or more prior or concurrent
treatment trials including 3 or more anti-epileptic drugs (AEDs) of differing
pharmacologic mechanisms administered as monotherapy or polytherapy.

3. The patient is taking at least 1 AED. A vagal nerve stimulator is not counted as
an AED.

4. The patient reports an average of 2 or more seizures per month averaged over the
prior 3 months.

6. The patient is deemed by the treating neurologist and ophthalmologist to be able to
reliably complete perimetry testing.

7. The initial (Visit 1) SD-OCT and static perimetry readings tests must be performed
and assessed for technical adequacy by the SD-OCT and perimetry central readers prior
to the first dose of Sabril. The initial (Visit 1) tangent corner test must be
performed prior to the first dose of Sabril.

Exclusion Criteria:

1. Prior exposure to Sabril.

2. Pre-existing ocular or neurological disease that might affect bilateral visual fields
or interfere with perimetry (e.g., aphakia, visually significant cataract, glaucoma,
diabetes mellitus, ischemic optic neuropathy, multiple sclerosis). Patients with
stable visual field defects from CNS lesions (e.g., epilepsy surgery more than 6
months prior to receiving Sabril) may be enrolled.

3. Concurrent exposure to medications with known or suspected retinal or optic nerve
toxicity.

4. Concurrent use of an investigational agent or device or such use within 30 days of
entering the study.

5. Concurrent use of the ketogenic or similar diet.

6. For any reason, the patient is considered by the investigator to be an unsuitable
candidate for the study.