E5501 (5 mg, 20 mg, and 40 mg) will be administered to healthy male adults in a single-center, randomized, open-label, cross-over manner. This study will consist of 2 phases including pre-randomization (before drug administration) and postrandomization (after drug administration).

Inclusion criteria;

1. Non-smokers aged 20-44 at the time of informed consent,
2. BMI is between 18.5 kg/m2 and below 25 kg/m2 at screening,
3. Platelet count is between 120,000/ microliter and below 300,000/ microliter at screening and baseline
4. Subjects and their partners can agree to use medically appropriate contraception through the study period
5. Voluntarily provided written informed consent
6. Willing and able to comply with the protocol

Exclusion criteria;

1. With a past or present history of arterial thrombosis, venous thrombosis or thrombophilia
2. With a past history of clinically significant disease within 8 weeks before study drug administration or clinically significant infection within 4 weeks before study drug administration
3. With a past surgical history that may affect the pharmacokinetics of E5501
4. Suspected to have a clinically abnormal symptom or organ dysfunction that requires treatment based on the past history, complications, subjective and objective symptoms, vital signs and body weight, electrocardiograms or clinical laboratory results at screening or baseline
5. QTcF greater than 450 ms (corrected for heart rate according to Fridericia's formula) category of the 12-lead electrocardiogram at screening or baseline