The purpose of this study is to assess whether there is a survival benefit with lintuzumab given in combination with low dose cytarabine versus low dose cytarabine and placebo in patients with AML.

Inclusion Criteria:

• Untreated AML that occurred de novo, after prior exposure to chemotherapy for a separate malignancy, or evolved from an antecedent hematologic disorder.
• After being informed of the potential benefits and risks of available treatment options, patients must have declined intensive chemotherapy for AML.
• At least 20% blasts in blood or marrow.
• Must have a minimum of 50% leukemic blasts that express CD33.
• ECOG performance status score of 0 to 2.
• WBC less than 30,000/µL

Exclusion Criteria:

• No known diagnosis of acute promyelocytic leukemia or chronic myeloid leukemia.
• No other active systemic malignancies treated with chemotherapy within the last 12 months.
• Must not have received previous chemotherapy (except hydroxyurea) for AML.
• Must not have significantly abnormal kidney or liver disease.
• Must not have known human immunodeficiency virus (HIV).