Inclusion Criteria:

• All patients, 18 years of age or older, with a diagnosis of CML.
• Patients must have a life expectancy of at least 12 weeks.
• Patients must have an ECOG performance status of 0-2.
• Patients must sign an informed consent.
• Patients should have adequate hepatic function with a total bilirubin < 2 mg/dl and SGOT or SGPT < two times the upper limit of normal, and adequate renal function as defined by a serum creatinine < 1.5 x upper limit of normal.
• Patients with CML in chronic phase on imatinib as first line therapy who fulfill the following criteria:
• The patient has at least two tests for quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for bcr-abl (peripheral blood or bone marrow aspirate). The results of these tests should demonstrate a relative plateau in the effect of imatinib on the detected level of the transcript (i.e. there should less than a ½ log difference between the last two values). Note: Patients will be eligible if the more recent study is greater than the previous study by any value.
• The last two quantitative RT-PCR studies should be at least 3 months apart.
• The patient should have received at least 9 months of imatinib since the diagnosis of CML.
• The patient is tolerating imatinib without any grade 3 or greater toxicity.

Exclusion Criteria:

• Pregnant women or nursing mothers are not eligible for this trial. Patients of child bearing potential must use adequate contraception.
• Patients may receive no other concurrent chemotherapy or radiation therapy during this trial.
• Patients with severe medical problems such as uncontrolled diabetes mellitus or cardiovascular disease or active infections are not eligible for this trial.
• Patients who have a hypersensitivity to valproic acid, derivatives, or any component of the formulation. Patients with hepatic disease or significant impairment, or urea cycle disorders