The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics (PK) of E8001 of single ascending dose intravenous infusions in healthy male participants.

Inclusion Criteria

1. Non-smoking, age greater than or equal to (>=) 20 years and less than or equal to (<=) 55 years old adult male at the time of informed consent. To be considered non-smokers, participants must have discontinued smoking for at least 4 weeks before dosing
2. Body mass index (BMI) >=18.5 and less than (<) 25.0 kilogram per square meter (kg/m˄2) at Screening

Exclusion Criteria:

1. Males who have not had a successful vasectomy (confirmed azoospermia) or they and their female partners do not meet the criteria (that is, not of childbearing potential or practicing highly effective contraception throughout the study period or for 5 times the half-life of the study drug plus 90 days after study drug discontinuation). No sperm donation is allowed during the study period and for 5 times the half-life of the study drug plus 90 days after study drug discontinuation

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

3. History of meningococcal infection or pneumococcal infection

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. Any history of gastrointestinal surgery that may affect PK profiles of E8001, example- hepatectomy, nephrectomy, and digestive organ resection at Screening

6. 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

7. History of prolonged QT/QTc interval

8. History of left bundle branch block (LBBB)

9. History of myocardial infarction (MI) or active ischemic heart disease (IHD)

10. History of clinically significant arrhythmia or uncontrolled arrhythmia

11. Active viral hepatitis (A, B or C) and syphilis as demonstrated by positive serology at Screening

12. History of drug or alcohol dependency or abuse, or those who have a positive drug test at Screening or Baseline

13. Liver function test with following values at Screening or Baseline:

    1. aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), or gamma glutamyl transpeptidase (GGT): greater than (>) upper limit of normal (ULN)
    2. direct bilirubin or total bilirubin: >1.5*ULN

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