To compare disease-free survival in patients 60 years or older with acute myeloid leukemia (AML) who are randomly assigned to receive either OCV-501 monotherapy or placebo.

Inclusion Criteria:

• Patients with AML who achieved first complete remission within one or two courses of standard induction therapy, and completed standard consolidation therapy (more than one course).
• Patients who are 60 years or older.
• Patients who have provided written informed consent within 90 days from the last dose of consolidation therapy on an informed consent form that has been approved by an institutional review board or independent ethics committee.

Exclusion Criteria:

• Patients who have acute promyelocytic leukemia (APL) with t(15;17) (q22;q12), (PML/RARA) karyotype abnormalities, and other variant types.
• Patients who are scheduled for hematopoietic stem cell transplantation.
• Patients who have received drugs potentially affecting the immune system within 4 weeks before starting IMP administration or who may receive such drugs after start of the trial.
• Patients who have a severe concurrent disease or psychiatric illness likely to interfere with participation in this trial.
• Patients who are HIV antibody positive, HBV-DNA positive or have unrecovered chronic hepatitis C with positive HCV antibody.
• Patients who have cirrhosis.
• Patients judged to be ineligible by the investigator (or subinvestigator) for any other reasons.