Inclusion Criteria:

- Patients of either sex aged 18-65 years of age

- Diagnosis of acute myeloid or lymphoblastic leukemia (second or subsequent remission,
if not in remission, then <20% bone marrow blasts), chronic myelogenous leukemia
resistant to or intolerant of tyrosine kinase inhibitor therapy (accelerated phase,
first chronic phase with TKI resistance, or second chronic phase), or myelodysplastic
syndrome (intermediate/high or high risk by International Prognostic Scoring System
(IPSS), lower risk by IPSS with patient having progressed after prior therapy.
Complete remission is defined as the absence of blasts in the peripheral circulation
at the time of enrollment and <5% blasts in the marrow within 28 days of enrollment.

- Life expectancy of at least 100 days

- Patients scheduled for allogeneic bone marrow transplant or peripheral blood stem
cell transplant (PBST) procedure

- Family-related or unrelated donors

- HLA matching should either be matched related or matched unrelated donors, 6/6 match
or 5/6 single allelic mismatch, with provision that the DRB1 is molecularly matched

- Performance status (ECOG ≤2)

- Signed informed consent

Exclusion Criteria:

- Active infection

- Known allergies to bovine or porcine products

- Renal function: Serum creatinine >2 mg/dL or creatinine clearance ≤50 mL/min

- Hepatic function: Screening ALT or AST ≥3x than the upper limit of normal for the
laboratory OR total bilirubin ≥2.0 mg/dL (Exception: acceptable if patient is
identified with pre-existing condition e.g., Gilbert's disease that will contribute
to baseline elevations of bilirubin)

- Pulmonary function: FEV1, FVC, DLCO ≤50% predicted

- Cardiac function: left ventricular ejection fraction ≤50%

- Patient received an investigational agent within 30 days prior to transplant

- The patient is pregnant, has a positive serum BhCG, or is lactating

- Patient on corticosteroids at a dose >0.25 mg/kg/day

- Planned non-myeloablative transplant

- Planned cord blood transplant

- Prior allogeneic myeloablative HSCT

- HIV seropositive, HTLV seropositive, hepatitis B or C seropositive, varicella virus
active infection, or syphilis active infection

- Other serious medical or psychiatric illness that, in the investigator's opinion,
would not permit the patient to be managed according to the protocol