Inclusion Criteria:

1. Age > 50 years.

2. ECOG Performance Status of 0, 1 or 2

3. Life expectancy of at least 12 weeks.

4. Subjects in relapse or refractory after any kinds of chemotherapy for acute myeloid
leukemia expressing CD33 antigen on ≥ 50% of myeloblasts.

5. Adequate liver and renal function as assessed by the following laboratory
requirements to be conducted within 7 days and adequate bone marrow within 14 days
prior to screening:

1. Total bilirubin < 1.5 times the upper limit of normal

2. ALT and AST < 2.5 x upper limit of normal

3. Alkaline phosphatase < 4 x ULN

6. PT-INR/PTT < 1.5 x upper limit of normal [Patients who are being therapeutically
anticoagulated with an agent such as coumadin or heparin will be allowed to
participate provided that no prior evidence of underlying abnormality in these
parameters exists.]

7. Serum creatinine < 1.5 x upper limit of normal.

8. Signed and dated informed consent before the start of specific protocol procedures.

Exclusion Criteria:

1. History of cardiac disease: congestive heart failure >NYHA class 3 or 4; active CAD
(MI more than 6 mo prior to study entry is allowed); cardiac arrythmias requiring
anti-arrhythmic therapy (beta blockers or digoxin are permitted) or uncontrolled
hypertension.

2. History of HIV infection or chronic hepatitis B or C (except the case receiving
Lamivudine or entecavir and in control of HBV infection)

3. Active clinically serious infections (> grade 2 NCI-CTC version 3.0)

4. Patients with seizure disorder requiring medication (such as anti-epileptics)

5. Patients with evidence or history of bleeding diasthesis before diagnosis of acute
myeloid leukemia

6. Patients undergoing renal dialysis

7. Anticancer chemotherapy or immunotherapy during the study or within 4 weeks of study
entry.

8. Radiotherapy during study or within 3 weeks of start of study drug. (Palliative
radiotherapy will be allowed). Major surgery within 4 weeks of start of study

9. Investigational drug therapy outside of this trial during or within 4 weeks of study
entry

10. Substance abuse, medical, psychological or social conditions that may interfere with
the patient's participation in the study or evaluation of the study results

11. Any condition that is unstable or could jeopardize the safety of the patient and
their compliance in the study, such as Alzheimer's disease or dementia

12. Patients unable to swallow oral medications.