SCH 727965 in Patients With Acute Myelogenous Leukemia and Acute Lymphoblastic Leukemia (P04717AM2)(TERMINATED)

Inclusion Criteria: * For participants with AML: * Age \>=60 years, either sex, any race. * Diagnosis of CD33-positive AML by World Health Organization criteria. * Must be in first or second relapse, or have primary refractory or refractory disease at first salvage, and not be considered a candidate for transplant. * Acute promyelocytic leukemia who has relapsed following treatment with both all trans retinoic acid (tretinoin) and arsenic trioxide-based therapy is eligible. * For participants with ALL: * Age \>=18 years, either sex, any race. * Diagnosis of ALL by World Health Organization criteria. * Must be in first or second relapse, or have primary refractory or refractory disease at first salvage, and not be considered a candidate for potentially curative therapy. * Eastern Cooperative Oncology group performance status of 0 or 1. * Adequate hematologic, renal, and hepatic organ function and laboratory parameters. * Receiving treatment with hydroxyurea or leukapheresis to reduce elevated white blood cell count to \<=30 x 10\^9 is eligible, provided hydroxyurea and leukapheresis are discontinued at least 24 hours before initiation of study drug. Exclusion Criteria: * Known central nervous system leukemia. * Previous hematopoietic stem cell transplantation. * Previous treatment with SCH 727965 or other cyclin-dependent kinase inhibitors. * For AML, previous treatment with gemtuzumab ozogamicin. * Known HIV infection. * Known active hepatitis B or C.