Inclusion Criteria:

- Patients aged 18 years or more with MDS according to FAB classification and
intermediate-2 or high IPSS risk scores, or CMML (with WBC < 13 x 109/L and bone
marrow blasts > 10 %) according to WHO classification, or AML according to WHO
classification if less than 30 % bone marrow blasts (RAEB-T according to FAB MDS
classification or AML according to WHO classification with more than 30 % with bone
marrow blasts only if preceded by a proven MDS phase.

- Patients previously treated by azacitidine (Vidaza®) in proven progression, or stable
after 6 courses with ongoing transfusion dependent anemia (> 4 RBC units in the 8
weeks preceding inclusion (as erythroid response in IWG 2006 criteria is reduction
of at least 4 RBC units in 8 weeks).

- Previous biological and or targeted therapies of MDS or AML are allowed if stopped
more than 1 month before inclusion.

- ECOG PS ≤ 2.

- Adequate renal and liver function :

i.e. Serum creatinine < 110 microM in men or 90 microM in women. If plasma creatinine
level < 90 - 110 microM, then the estimated glomerular filtration rate (GFR) must be
< 50 mL/min/1.73 m2 as calculated by the Modification of Diet in Renal Disease (MDRD)
equation where Predicted GFR (mL/min/1.73 m2) = 32788 x (plasma creatinine level
(microM)-1.154 x (age in years)-0.023 x (0.742 if patient is female) x (1.212 if
patient is African American)

- Bilirubin < 1.5 x ULN, (except increased unconjugated bilirubin due to
dyserythropoiesis).

- Aspartate transaminase (AST)/alanine transaminase (ALT) < 2.5 × ULN and Alkaline
phosphatase < 2.5 × ULN.

- Absence of pregnancy or lactation in female patients (Female patients of childbearing
potential must have a negative serum pregnancy test within 2 weeks prior to
enrollment).

- Male and female patients must use an effective contraceptive method during the study
and for a minimum of 6 months after study treatment.

- Provided signed written informed consent.

- Capable of understanding the investigational nature, potential risks and benefits of
the study, and able to provide valid informed consent.

Exclusion Criteria:

- Patients with AML and bone marrow blasts count of 20-30%, if candidates to intensive
AML type chemotherapy.

- Known hypersensitivity to clofarabine or excipients.

- Concomitant malignant disease.

- Active uncontrolled infection (defined as exhibiting ongoing signs/symptoms related
to the infection and without improvement, despite appropriate antibiotics or other
treatment).

- Concomitant severe cardiovascular disease, i.e. congestive heart failure (NYHA grade
> 3).

- Any significant concurrent disease, illness, or psychiatric disorder that would
compromise patient safety or compliance, interfere with consent, study participation,
follow up, or interpretation of study results.

- No affiliation to a national insurance scheme directly or to an equivalent system.

- Chemotherapy, radiation therapy, or immunotherapy other than as specified in the
protocol.

- Use of investigational agents within 30 days or any anticancer therapy within 2 weeks
before study entry with the exception of hydroxyurea. The patient must have recovered
from all acute toxicities from any previous therapy.