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

The purpose of this research study is to determine if the blood tests used to measure free thyroid hormone levels are affected by a drug called eslicarbazepine acetate. To determine if eslicarbazepine acetate interferes with these blood tests, blood samples will be analysed so that researchers can compare different types of lab tests that measure these thyroid hormones. Half of the people who participate in this study will already be taking eslicarbazepine acetate either as a study drug or as a prescription (Part 1) and the other half will be people who do not take eslicarbazepine acetate (Part 2).

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.

Eligibility Criteria:
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.