Inclusion Criteria:

- Patients with MDS of any risk group who have, just immediately prior to being entered
into this study, already received at least six cycles of 5-azacytidine and have
failed, either due to no response or to disease relapse despite being still on
5-azacytidine, or patients whose MDS has progressed while on 5-azacytidine,
irrespective of the number of cycles the patient has received. We have specifically
chosen to be very stringent about our patient population in order to address our
question of whether clofarabine can be used to salvage patients who have failed
5-azacytidine with only a small patient population, i.e. 10 patients in each cohort.

- ECOG Performance status of 0 - 2

- Recombinant erythropoietin is allowed, if the patients are already receiving
erythropoietin. G-CSF can be given during the neutropenic stage following therapy
since this would not affect evaluation of response because the response will be made
based on CBC and bone marrow changes upon recovery from clofarabine.

- Patients must have been at least four weeks after the last course of 5-azacytidine

- Age over 18 years

- Have adequate renal and hepatic functions as indicated by the following laboratory
values:

- Serum creatinine 1.0 mg/dL; if serum creatinine 1.0 mg/dL, then the estimated
glomerular filtration rate (GFR) must be 60 mL/min/1.73 m2 as calculated by the
Modification of Diet in Renal Disease equation where Predicted GFR (ml/min/1.73
m2) = 186 x (Serum Creatinine)-1.154 x (age in years)-0.023 x (0.742 if patient
is female) x (1.212 if patient is black)

- Serum bilirubin ≤1.5 mg/dL × upper limit of normal (ULN)

- Aspartate transaminase (AST)/alanine transaminase (ALT) 2.5 × ULN

- Alkaline phosphatase 2.5 × ULN

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

- 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.

Exclusion Criteria:

- Nursing or pregnant women

- Prior clofarabine therapy

- Life expectancy of less than 3 months due to other intercurrent illness.

- Current concomitant chemotherapy, radiation therapy, or immunotherapy other than as
specified in the protocol.

- Use of investigational agents within 30 days or any anticancer therapy within 4 weeks
before study entry with the exception of hydroxyurea. The patient must have recovered
from all acute toxicities from any previous therapy.

- Have any other severe concurrent disease, or have a history of serious organ
dysfunction or disease involving the heart, kidney, liver, or other organ system that
may place the patient at undue risk to undergo treatment.

- Patients with a systemic fungal, bacterial, viral, or other infection not controlled
(defined as exhibiting ongoing signs/symptoms related to the infection and without
improvement, despite appropriate antibiotics or other treatment).

- 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.