This study will evaluate MK0457 in combination with Dasatinib in patients with Chronic Myelogenous Leukemia and Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia. Efficacy and Safety will be evaluated.

Inclusion Criteria:

• Patients must have chronic myelogenous leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL)
• Patients must be at least 3 months from the start of dasatinib therapy and are currently receiving dasatinib therapy for CML or Ph+ ALL and be evaluable for hematologic response prior to entering the study
• Patient is able to be treated with a 70 mg bid dose of dasatinib without significant toxicity at the time of study entry
• Patients with active CNS disease are included and may be treated concurrently with intrathecal therapy as per institutional standards

Exclusion Criteria:

• Patient has had treatment with any anti-leukemia therapy (investigational or approved) other than dasatinib during the preceding 3 months. Pheresis or hydroxyurea treatment in the preceding 3 months will not exclude patients from eligibility
• Patient has unresolved more than or equal to grade 2 clinically significant toxicity attributed to dasatinib at the time of study entry
• Patient has known hypersensitivity to the components of study drug or its analogs
• Patient is pregnant or breastfeeding, or expecting to conceive within the projected duration of the study
• Patient has symptomatic ascites, pericardial or pleural effusion. A patient who is clinically stable following treatment for these conditions is eligible
• Patient has had prior radiation therapy to more than 10% of the bone marrow; patients must have recovered for at least 3 weeks from the hematologic toxicity of prior radiotherapy
• Patient has a LVEF <40% by multigated radionucleotide angiography (MUGA) or echocardiography