Inclusion Criteria:

- Able to understand and willing to sign a written informed consent document

- Received less than or equal to 3 induction/re-induction regimens for disease(s)
defined by the protocol

- Must have relapsed or refractory leukemia for which no standard therapies are
expected to result in a durable remission; patients who have not received prior
treatment who have either refused or, in the opinion of the Investigator, are not
able to tolerate, standard therapy may be included.

Exclusion Criteria:

- Prior exposure to SNS-595

- Pregnant or breastfeeding

- Women of childbearing potential or male partners of women of childbearing potential
unwilling to use an approved, effective means of contraception according to the
institution's standards

- Any evidence of active central nervous system (CNS) leukemia

- Any evidence of acute or chronic graft-versus-host disease

- Has active cancer (other than that which is defined by the inclusion criteria for
this protocol), except for skin cancer (excluding melanoma)

- Laboratory values outside normal or reasonable reference range specified by the
protocol

- Liver function and kidney function outside limits specified by the protocol

- Not yet recovered from side effects of previous cancer therapy

- Myocardial infarction, cerebrovascular accident/transient ischemic attack (TIA) or
thromboembolic event (deep vein thrombosis or pulmonary embolus) within 6 months
before the first SNS-595 dose

- Requires kidney dialysis (hemodialysis or peritoneal)

- Received an investigational agent within 14 days before Cycle 1, Day 1

- Prior pelvic radiation therapy or radiation to greater than or equal to 25% of bone
marrow reserve (palliative radiation is not excluded as long as it does not exceed
greater than or equal to 25% of bone marrow reserve)

- Any other medical (uncontrolled intercurrent illness including, but not limited to,
ongoing or active infection, symptomatic congestive heart failure, unstable angina
pectoris, cardiac arrhythmia), psychological, or social condition that, in the
opinion of the Principal Investigator, would contraindicate the patient's
participation in the clinical trial due to safety or compliance with study procedures