The primary objective of this study is to evaluate the safety, tolerability, and plasma pharmacokinetic (PK) of E2511 following multiple oral doses in healthy adult participants.

Inclusion Criteria:

1. Non-smoking, male, or female, non-Japanese participants age >=18 years and <55 years old (Cohorts 1 to 4) or age >=55 years and <=85 years old (Cohort 8); or Japanese participants age >=20 years and <55 years old (Cohorts 5 to 7) at the time of informed consent

2. Japanese participants must also satisfy the following requirements:

   • Must have been born in Japan of Japanese parents and Japanese grandparents
   • Must have lived no more than 5 years outside of Japan
   • Must not have changed their lifestyle or habits, including diet, while living outside of Japan

3. Weight of at least 50 kilogram (kg) and body mass index (BMI) >=18 and <30 kilogram per square meter (kg/m^2) (Cohorts 1 to 7) or BMI >=18 and <32 kg/m^2 (Cohort 8) at Screening

Exclusion Criteria:

1. Females who are breastfeeding or pregnant at Screening or Baseline

2. Females of childbearing potential who:

   • Within 28 days before study entry, did not use a highly effective method of contraception
   • Do not agree to use a highly effective method of contraception throughout the entire study period and for 28 days after study drug discontinuation.

3. Clinically significant illness that requires medical treatment within 8 weeks or a clinically significant infection that requires medical treatment within 4 weeks of dosing

4. Evidence of disease that may influence the outcome of the study within 4 weeks before dosing; example, psychiatric disorders and disorders of the gastrointestinal tract, liver, kidney, respiratory system, endocrine system, hematological system, neurological system, or cardiovascular system, or participants who have a congenital abnormality in metabolism

5. Evidence of disease within 4 weeks before dosing related to chronic headaches, migraines, joint pain, or other disorders or disease resulting in chronic or intermittent pain

6. Any personal or family history of seizures (including febrile seizures) or diagnosis of epilepsy or episode of unexplained loss of consciousness

7. Any history of neurological or other medical conditions which in the opinion of the investigator has the potential to reduce seizure threshold

8. Any history of gastrointestinal surgery that may affect PK profiles of E2511, example, hepatectomy, nephrectomy, digestive organ resection at Screening

9. Any clinically abnormal symptom or organ impairment found by medical history at Screening, and physical examinations, vital signs, ECG finding, or laboratory test results that require medical treatment at Screening or Baseline

10. A prolonged QT/QT interval corrected for heart rate (QTc) interval or a prolonged QT/QTc interval (QT interval corrected for heart rate using Fridericia's formula [QTcF] greater than [>] 450 milliseconds [ms]). A history of risk factors for torsade de pointes

11. HR <50 or more than 100 beats per minute at Screening or Baseline (Cohorts 1 through 7); or HR <55 or more than 100 beats per minute at Screening or Baseline (Cohort 8) NOTE: At Baseline, HR must meet the above criteria on 3 assessments (each separated by 15 minutes) to ensure eligibility

12. Left bundle branch block

13. History of myocardial infarction or active ischemic heart disease

14. History of clinically significant arrhythmia or uncontrolled arrhythmia

15. Any lifetime history of suicidal ideation or any lifetime history of suicidal behavior as indicated by the C-SSRS

16. Any lifetime history of psychiatric disease

Eisai's data sharing commitment and further information on how to request data can be found on our website http://eisaiclinicaltrials.com/.