Inclusion Criteria:

- Patients must satisfy the following conditions listed below.

1. Patients who have been histologically documented or cytologically confirmed with
myelodysplastic syndrome (MDS), and who have been found to meet any of the following
criteria on the basis of the WHO classification or FAB classification.

- RA (< 5% myeloblasts, < 15% ringed sideroblasts)

- RARS (< 5% myeloblasts, ≥ 15% ringed sideroblasts)

- RAEB-1 (5% to 9% myeloblasts)

- RAEB-2 (10% to 19% myeloblasts)

- RAEB-t (20% to 29% myeloblasts or < 25,000/mm3 peripheral leukocytes)

- CMML (10% to 19% myeloblasts in marrow, ≥ 1,000/mm3 peripheral monocytes, <
13,000/mm3 leukocytes) However, RA patients must have score of Int-2 or higher
in IPSS

2. Patients with a low value in at least one blood cell lineage (having at least one of
the following cytopenias).

- Neutrophils : < 1,800/mm3

- Platelets : < 100,000/mm3

- Hemoglobin : < 10 g/dL

3. Patients with a previous history of chemotherapy (including lenalidomide) for the
target disease who meet any of the following criteria.

- Patients who have not achieved complete remission, partial remission, or
hematologic improvement*

- Patients with recurrence/relapse after complete remission, partial remission, or
hematologic improvement*

- Patients with intolerability that has led to discontinuation of treatment
because of the development of liver dysfunction, kidney dysfunction, etc., after
the start of treatment. * Proximate therapeutic efficacy judged under IWG2006
criteria

4. Patients who have not been treated for four weeks or longer after the end of the
previous therapy and who are judged to have no residual effects (antitumor effects)
from the previous therapy.

5. Patients who can be expected to survive at least three months or longer.

6. Patients at least 20 years old (when informed consent is obtained).

7. Patients who have score of 0 to 2 in ECOG Performance Status (P.S.).

8. Patients with adequate function in major organs (heart, lungs, liver, kidneys, etc.).

- AST (GOT): no greater than 3.0 times the upper boundary of the reference range
at each institution

- ALT (GPT): no greater than 3.0 times the upper boundary of the reference range
at each institution

- Total bilirubin: no more than 1.5 times the upper boundary of the reference
range at each institution

- Serum creatinine: no more than 1.5 times the upper boundary of the reference
range at each institution

- ECG: no abnormal findings requiring treatment

- Echocardiography: no abnormal findings requiring treatment

9. Patients who personally signed an informed consent document for participation in this
study.

Exclusion Criteria:

- Patients who satisfy any of the following conditions will not be enrolled in the study.

1. Patients with anemia caused by factors other than MDS (hemolytic anemia,
gastrointestinal (GI) bleeding, etc.).

2. Patients who have undergone treatment for an active malignant tumor within the past
year (except basal cell or squamous cell skin cancer or carcinoma in situ of the
cervix or breast).

3. Patients who have been administered a cytokine preparation such as G-CSF
(granulocyte-colony stimulating factor), erythropoietin, etc. within 14 days of
tests for enrollment of the study.

4. Patients with obvious infectious diseases (including viral infections).

5. Patients with serious complications (liver failure, renal failure, etc.).

6. Patients with a complicating or previous history of serious heart disease (myocardial
infarction, ischemic heart disease, etc.) within the past two years before
enrollment, and with cardiac arrhythmia requiring treatment.

7. Patients with a serious gastrointestinal condition (severe or significant
nausea/vomiting, diarrhea, etc.).

8. Patients who are positive for the HBs antigen or HIV antibodies.

9. Patients with serious bleeding tendencies (disseminated intravascular coagulation
(DIC), internal hemorrhage, etc.).

10. Ascites requiring active medical management including paracentesis, or hyponatremia
(defined as serum sodium value of <130 mEq/L).

11. Patients who have been administered a drug in a clinical trial or an unapproved drug
within three months before enrollment.

12. Patients with an addiction to a legal or illegal drug, or with alcohol dependency.

13. Patients who are pregnant or may become pregnant.

14. Patients who have not consented to the following contraceptive measures.

Patients will avoid sexual intercourse with sexual partners or should use the
following contraceptive methods in these time periods: for male patients during the
administration period of the trial and for six months after the end of
administration; female patients during the administration period of the trial, and
until a second menstrual period is confirmed after the end of administration (or in
the case of female patients with no menstrual period, for two months after the end of
administration).

•Male patients

The patient will always use a condom. For effective contraception, it is recommended
that the female partner also use the contraceptive methods for female patients.

•Female patients

Female patients who may become pregnant should use one or more types of the following
contraceptive methods. In addition, the male partner will always use a condom.

- Oral contraceptive (birth control pills)

- Intrauterine device (IUD)

- Tubal ligation

15. Other patients judged to be unsuitable by an investigator or sub-investigator.