The purpose of this study is to assess the safety and tolerability of E5555 in Japanese patients with acute coronary syndrome.

Inclusion Criteria:

1. 45 - 80 years old (at time of informed consent)
2. Male or female (females of childbearing potential must be contracepted)
3. Confirmed acute coronary syndrome

Exclusion Criteria:

1. Unwilling or unable to provide informed consent
2. History of acquired or congenital bleeding disorder, coagulopathy, or platelet disorder
3. Recent trauma or major surgery
4. Evidence of active pathological bleeding at screening or history of gastrointestinal or genitourinary bleeding with unknown cause within 24 weeks prior to screening
5. History of intracranial bleeding or history of hemorrhagic retinopathy
6. History of New York Heart Association (NYHA) class III or IV congestive heart failure
7. Pregnant or lactating women