Study to Evaluate Serum Free Thyroxine (FT4) and Free Triiodothyronine (FT3) Measurements for Subjects Treated With Eslicarbazeine Acetate (ESL)

Part 1 of the study will enroll a minimum of 30 male and female subjects who have received at
least 1200 mg once daily (QD) ESL over a minimum 6-week period (ESL-exposed subjects).
Subjects, who meet study eligibility requirements and provide written consent, will provide
blood samples for measurement of thyroid hormones, thyroxine binding globulins (TBG), serum
pregnancy (female subjects of childbearing potential 1only), thyroid peroxidase (TPO)
antibodies, and ESL metabolites (eslicarbazepine and (R)-licarbazepine).

Optional blood samples will be requested from subjects in Part 1 who provide genetic consent
and are eligible to participate (as controls) in a separate rash registry protocol. These
samples will be tested for HLA typing, genetic ancestry, and viral titers (including human
herpes virus [HHV]-6, HHV-7, and Epstein-Barr virus [EBV]).

ESL metabolites will be determined by a validated liquid chromatography- tandem mass
spectrometry (LC-MS/MS) assay. Levels of FT4 and FT3 in ESL-exposed serum will be assayed
using the automated kit assay (Roche Cobas ECLIA kits FT4 II and FT3 III) and Equilibrium
Dialysis (ED) method. FT4 and FT3 results measured by both methods will be compared to
evaluate potential assay differences. Serum TSH, TT4, TT3, and TBG in ESL treated subject
samples will also be measured using automated kit assays.

Part 2 of the study will enroll a minimum of 30 age (± 5 y) and gender-matched non-ESL
exposed volunteers. Subjects, who meet study eligibility requirements and provide written
consent, will provide a blood sample for measurement of thyroid hormones, TBG, serum
pregnancy (female subjects of childbearing potential only), and TPO antibodies. Serum samples
obtained from non-ESL exposed subjects will be split into 4 aliquots, one aliquot will be
used as the control blank (unspiked) and the rest spiked with 3 levels (high, low, and a
concentration representative of therapeutic levels also called middle) of eslicarbazepine
(range approximately 5 to 18 μg/mL) and (R)-licarbazepine (range approximately 0.5 to 1.8
μg/mL). The low concentration for spiking the non-ESL exposed samples will be approximately 1
standard deviation (SD) below Cavg associated with the 800 mg dose in chronic use in the
epilepsy population and the high concentration for spiking will be approximately 1 SD above
Cavg associated with the 1200 mg dose.

After sample is spiked with eslicarbazepine and (R)-licarbazepine, serum FT4 and FT3 will be
measured by the automated kit assay method, as well as ED method. FT4 and FT3 measured in
non-spiked and spiked volunteer samples will be compared to detect potential in vitro
artifacts. Serum TSH, TT4, TT3, and TBG in non-spiked and spiked volunteer samples will also
be measured using automated kit assays.

Inclusion Criteria:

- ESL-exposed Subjects

1. Subject must give written informed consent and privacy authorization prior to
participation in the study.

2. Male or female patient (≥ 18 years of age) who has received at least 1200 mg QD
ESL for at least 6 weeks and has not experienced any rash or other allergic
reaction at the time of blood draw.

- Non-ESL-exposed Subjects

1. Subject must give written informed consent and privacy authorization prior to
participation in the study.

2. Male or female healthy normal volunteer (≥ 18 years of age).

Exclusion Criteria:

- Both ESL-exposed and non-ESL exposed subjects

1. Subject who does not tolerate venipuncture or Has poor venous access that would
cause difficulty for collecting blood samples.

2. Subject with a history of thyroid disease or clinical condition (eg, renal
insufficiency, Sjogren's syndrome, lupus, rheumatoid arthritis, pernicious anemia
etc.) that in the opinion of the Investigator may effect levels of thyroid
hormones, TBG, and/or TPO antibodies.

3. Female subject who is pregnant.

4. Female subject with a positive urine pregnancy test at screening.

5. Subject who received any excluded medication for at least 30 days prior to blood
draw.

6. Subject has experienced significant blood loss and/or donated blood within last
60 days of blood draw.

7. Subject intends to donate blood or undergo elective surgery within next 30 days
following blood draw.

8. Subject has donated plasma within last 72 hours of blood draw or intends to
donate plasma during study participation.

9. Subject is, in the opinion of the Investigator, unsuitable in any other way to
participate in the study.