Inclusion Criteria:
1. Body Mass Index (BMI) greater than or equal to (≥) 18 and less than (<) 30 kilograms per square meter (kg/m2) at Screening
2. Non-smoking and non-vaping, healthy male or female, age ≥18 years and ≤55 years old at the time of informed consent (only Parts A and B).
3. Non-smoking and non-vaping, healthy female, age ≥18 years and ≤55 years old at the time of informed consent (only Part C).
Exclusion Criteria:
1. Females who are breastfeeding or pregnant at Screening or Baseline (as documented by a positive beta-human chorionic gonadotropin \[ß-hCG\] or human chorionic gonadotropin \[hCG\] test with a minimum sensitivity of 25 international units per liter (IU/L) or equivalent units of ß-hCG or hCG). A separate baseline assessment is required if a negative screening pregnancy test was obtained more than 72 hours before the first dose of study drug
2. Females of childbearing potential who did not use a highly effective method of contraception (as described below) within 28 days before study entry, or who do not agree to use an approved method of contraception from 28 days before study entry throughout the entire study period, and for 28 days after study drug discontinuation.
Approved (highly effective) methods of contraception for this study include at least 1 of the following:
- Total abstinence (if it is her preferred and usual lifestyle)
- Have a vasectomized partner with confirmed azoospermia
- Double-barrier method (such as condom plus diaphragm with spermicide) NOTE: All females will be considered of childbearing potential unless they are postmenopausal (amenorrheic for at least 12 consecutive months, in the appropriate age group, and without other known or suspected cause) or have been sterilized surgically (ie, bilateral tubal ligation, total hysterectomy, or bilateral oophorectomy, all with surgery at least 1 month before dosing).
3. Subjects who are using steroidal hormones including for contraceptives, implants and intrauterine system, or for any other indications from 4 weeks before informed consent until study discharge from the final period
4. Clinically significant illness that requires medical treatment within 8 weeks or a clinically significant infection that requires medical treatment within 4 weeks of dosing
5. Evidence of disease that may influence the outcome of the study within 4 weeks before dosing; eg, psychiatric disorders and disorders of the gastrointestinal tract, liver, kidney, respiratory system, endocrine system, hematological system, neurological system, or cardiovascular system
6. Any history of surgery that may affect pharmacokinetics (PK) profiles of E2086 (eg, hepatectomy, nephrectomy, digestive organ resection) or subjects who have a congenital abnormality in metabolism at Screening
7. Any clinically abnormal symptom or organ impairment found by medical history at Screening, including estimated glomerular filtration rate (eGFR) <90 milliliters per minute (ml/min), and physical examinations, vital signs, ECG findings, or laboratory test results that require medical treatment at Screening or Baseline
8. A prolonged QT/corrected (QTc) interval (QT interval corrected for heart rate using Fridericia's formula \[QTcF\] >450 millisecond \[ms\]) as demonstrated by the mean of triplicate ECGs (recorded at least 1 minute \[min\] apart) at Screening or Baseline
9. Systolic blood pressure >140 millimeters of mercury (mmHg) or diastolic blood pressure >90 mmHg at Screening or Baseline
10. Heart rate <50 beats per (/) min or >100 beats/min at Screening or Baseline
11. Any lifetime history of suicidal ideation or any lifetime history of suicidal behavior as indicated by the Columbia-Suicide Severity Rating Scale (C-SSRS).
12. Any lifetime history of psychiatric disease (including, but not limited to, depression or other mood disorders, bipolar disorder, psychotic disorders, including schizophrenia, panic attacks, and anxiety disorders \[if ever treated with medication\]).
13. Known history of clinically significant drug allergy at Screening
14. Known history of food allergies or presently experiencing significant seasonal or perennial allergy at Screening
15. Known to be human immunodeficiency virus (HIV) positive at Screening
16. History of drug or alcohol dependency or abuse within the 2 years before Screening, or those who have a positive urine drug test or breath alcohol test at Screening or Baseline.
17. Currently enrolled in another clinical study or used any investigational drug or device within 28 days (or 5 half-lives, whichever is longer) preceding informed consent
18. Use of illegal recreational drugs and marijuana
19. Receipt of blood products within 4 weeks, or donation of blood within 8 weeks, or donation of plasma within 1 week before dosing.
20. A history of noncompliance in any previous study or inability to comply with study conduct, as assessed by the investigator
21. Any other findings that the investigator feels would increase the risk of having an adverse outcome from participating in the study
22. Subjects carrying human leukocyte antigen (HLA)-B\*1502 or HLA-A\*3101 (only Part A -CBZ treatment group)
23. Genetically determined poor metabolizers of CYP2D6 substrates (only Part B - MDZ, DEX, and BUP)