Inclusion Criteria:

1. Patients with relapsed or refractory acute myelogenous leukemia (AML), Refractory
anemia with excess blasts in transformation (RAEB-t), Refractory Anemia with Excess
Blasts (RAEB), or chronic myelomonocytic leukaemia (CMML) who failed at least one
previous chemotherapy course. Patients with accelerated CML Ph+ or myeloid blastic
crisis are eligible. Patients in accelerated phase of non-Philadelphia chromosome +
myeloproliferative disorders are also eligible:

- P. vera,

- myelofibrosis

- essential thrombocytopenia with >5% blasts in the blood or bone marrow.

2. Male or female 18 yrs of age or older who have provided written informed consent

3. Tumor cells must be = or > 80% CD33 positive by flow cytometry

4. For women of childbearing potential (i.e. exclude post-menopausal women, women who
have been surgically sterilized), adequate birth control methods must be used.
Acceptable birth control methods are limited to oral contraceptives, implants,
diaphragm, IUD or spermicide used with a condom

5. White blood count (WBC) count <10,000/ml for AML, MDS, and myeloproliferative
disorders and up to 30,000 for accelerated CML

6. No cytotoxic chemotherapy for the two weeks prior to entering the study

7. No evidence of residual toxic effects grade 2 or higher from prior chemotherapy

8. Patients with proven bacterial infection are not eligible until resolution of the
infection (patient afebrile, not on steroids). Patients with active fungal infections
are eligible only if evidence of response to antifungal medications is documented and
they do not have fever exceeding 38°C

9. Creatinine - Patients should have values = or < 1.5 times the upper limit of
laboratory normal values

10. Liver function - Patients should have serum bilirubin values = or < 2.0 times the
upper limit of laboratory normal values. Patients should have SGOT and/or SGPT levels
= or < 2.5 times the upper limit of laboratory normal values

11. Cardiac function - Patients with cardiovascular disease should be < New York Heart
Association (NYHA) classification III

12. Pulmonary function - O2 saturation should be = or > 92% without exogenous O2
administered.

13. Neurologic function - Patients should have normal central nervous system function as
well as normal motor function consistent with = or < Grade 1 toxicity. Patients
should have peripheral sensory function damage (neuropathy) not exceeding Grade 1
toxicity

Exclusion Criteria:

Women who are pregnant or lactating