The primary purpose of this study is to evaluate the safety of a peptide-gene vaccine against CML in patients under Imatinib treatment.

We will also perform some laboratory tests suggesting biological response.

• Patients will continue to take their current dose of Imatinib.

• Patients will undergo HLA-typing to define the HLA A, B, and DR.

• One constant dose of ten bcr-abl peptides (100μg each) will be administered subcutaneously in all patients triweekly for 8 doses.

• Four different doses of IL-12 and GM-CSF plasmids will be tested in this trial. The plasmids will be administered subcutaneously near the vaccination site 24 hours before vaccination.

• The first three patients will receive the lower dose of both IL-12 and GM-CSF plasmids. If this is well tolerated, then the next three patients will receive the lower dose of IL-12 plasmid and higher dose of GM-CSF plasmid. If this is well tolerated, then the next three patients will receive the higher dose of IL-12 and lower dose of GM-CSF plasmids. If this is well tolerated, then the next three patients will receive the higher dose of both IL-12 and GM-CSF plasmids. Once assigned to a dose, the patient will receive the same dose throughout their participation in this trial.

• Each vaccination may consist of one to several shots placed under the skin on the forearm, thigh or trunk area, and the sites will rotate per vaccination.

• During the clinic visit for vaccinations, blood tests will be drawn. If, during the course of therapy, side effects develop that the doctor feels pose a threat to the patient, treatment will be stopped.

• Patients will also undergo DTH skin tests before and after vaccination to see if an immune reaction is occurring at the injection site.

• Patients' lymphocytes will be tested before and after vaccination regarding IFN-γ and IL-4 production to assess immune system activation.

• During the course of treatment we will measure the effect the vaccine is having on the patients CML every three months by:

  1. doing a bone marrow biopsy and aspirate analysis, and
  2. measuring the amount of BCR-ABL that is detectable by RT-PCR in the patients' peripheral blood and bone marrow aspirate.

Inclusion Criteria:

• Patients with Philadelphia chromosome positive CML who are:

  1. of subtype b3a2
  2. In first complete hematologic response;
  3. have received imatinib for > 12 months of which the last 3 months were at a stable dose of at least 400 mg/day;
  4. have PCR detectable BCR-ABL transcript by qRT-PCR, and
  5. with persistent disease, as defined by <1 log reduction in peripheral blood or bone marrow BCR-ABL transcripts levels compared with a standardized baseline.

• Greater than or equal to 18 years in age

• No known infection with human immunodeficiency virus

• Physician and patient willingness to maintain the baseline dose of imatinib throughout the study period

• Written informed consent obtained from the patient

Exclusion Criteria:

• Female patients who are pregnant or breast feeding or adults of childbearing age who are not using adequate birth control.
• Current use of systemic immunosuppressive medications
• ALT or AST >3X Upper limit Normal
• Prior allogeneic stem cell transplantation
• Other experimental therapy within the past two months
• Prior participation in vaccine studies within the past six months
• Oxygen saturation of less than 95% at room air
• History of recent acute myocardial infarction, unstable angina, or pulmonary decompensation requiring hospitalization within the past 3 months.
• Concurrent and or uncontrolled psychiatric or medical condition which may interfere with the study completion.