Evaluation of the Anti-CD-33 Immunotoxin Hum-195/rGel in Patients With Advanced Myeloid Malignancies

Before therapy, all patients will be asked about their medical history, and a physical exam (with measurement of vital signs) will be performed. A chest X-ray and an electrocardiogram (ECG - a test to measure the electrical activity of the heart) will be performed. Blood (about 4 teaspoons) will be drawn for routine tests and blood clotting tests. Women who are able to become pregnant will have a urine pregnancy test done. A test will be done to measure the amount of oxygen in your blood by placing a monitoring device on your finger. Blood (about 1 teaspoon) will be taken to measure the amount of a protein that is present on the diseased cells. During the study period, the study staff will draw blood samples for routine tests, pharmacokinetic (PK) tests, and anti-drug antibody tests. Blood (about 1 teaspoon) will be drawn to measure the amount of a protein that is present on the diseased cells. A bone marrow sample will also be obtained before treatment and on Study Day 28. Patients will receive four injections of the immunotoxin. The immunotoxin is designed to selectively destroy myeloid leukemia cells. The injections will be given through a vein twice weekly for two weeks. Patients will then be evaluated twice weekly for the next two weeks. If there has been improvement in the leukemia, or if the leukemia has remained stable and there have been no serious side effects of treatment, patients will then receive a second course of immunotoxin injections. These will again be given twice weekly for two weeks. Depending on the effectiveness against leukemia and the side effects, patients may receive maintenance treatment. This would also consist of two weekly injections given for two weeks followed by two weeks of observation. Maintenance therapy may continue for up to four months for partial response and up to two months for complete response. This is an investigational study. Up to 36 patients will take part in this study.