Study of SCH 900776 (MK-8776) With and Without Cytarabine in Participants With Acute Leukemias (P05247)

Inclusion Criteria: * Must have a histologically or cytologically confirmed diagnosis of relapsed and/or refractory acute leukemia, including: * acute myelogenous leukemia (AML), including AML arising from myelodysplasia (MDS) or myeloproliferative disorder (MPD); * acute lymphocytic leukemia, including Philadelphia chromosome-positive (Ph+) ALL (Dose-Escalation Part only); * chronic myelogenous leukemia (CML) in accelerated phase (AP) or blast crisis (BC) of either myeloid or lymphoid origin (Dose-Escalation Part only); * treatment-related high-grade MDS (i.e. refractory anemia with excess blasts in transformation \[RAEBT\]); * MPD in transformation \[eg, CMMoL-T (5%-19% blasts)\]. * Must have recurred or progressed following standard therapy or failed standard therapy, or have disease for which no standard therapy currently exists. * Must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2. * Females of childbearing potential must have a negative pregnancy test within 5 days prior to first dose of cytarabine. * Females of childbearing potential and males whose sexual partner is of childbearing potential must agree to abstain from sexual intercourse or to use an acceptable method of contraception during the study and for 90 days following the last dose of study treatment. * Must have adequate renal function as evidenced by a serum creatinine level \<=1.5 x upper limit of normal (ULN) or a calculated creatinine clearance \>=60 mL/min. * Participants, except ones with known Gilbert's Syndrome, must have adequate hepatic function as evidenced by a serum bilirubin level \<=1.5 mg/dL AND serum levels of aspartate and alanine aminotransferase (AST/ALT) \<=5 x the ULN for the reference laboratory. * Must have adequate cardiac function with a left ventricular ejection fraction (LVEF) of \>=45% (echocardiogram or multiple-gated acquisition \[MUGA\] scan). * Must be recovered from the effects of any prior surgery, radiotherapy, or systemic antineoplastic therapy. * Participants who are refractory to or relapsed after prior allogeneic or autologous stem cell transplant are eligible. Exclusion Criteria: * Must not have known hypersensitivity to MK-8776 or cytarabine or to any of their excipients or have received therapy with another Checkpoint kinase 1 (CHK1) inhibitor. * Must not have persistent, unresolved Common Terminology Criteria for Adverse Events version 3.0 (CTCAE v 3.0) ≥ Grade 2 drug-related toxicity (except alopecia, erectile impotence, hot flashes, decreased libido, hematologic toxicity) associated with previous treatment. * Must not have known human immunodeficiency virus (HIV), hepatitis B or hepatitis C, or have a known history of liver cirrhosis or active alcohol abuse. * Must not be New York Heart Association (NYHA) Class III (has marked limitation in activity due to symptoms, even during less than ordinary activity \[e.g. walking short distances \>20-100 m\]; is comfortable only at rest) or Class IV (has severe limitations; experiences symptoms even while at rest; mostly bed bound). * Must not have undergone major surgery within 3 weeks prior to first study drug administration after enrollment. * Must not have known active central nervous system (CNS) or leptomeningeal leukemia. * Must not have received radiation therapy within 2 weeks prior to first study treatment administration after enrollment or radiation therapy to \>25% of bone marrow. * Must not have received more than 4 prior induction regimens. * Must not have a peripheral blast count ≥50,000/mm\^3. * Must not have active, uncontrolled graft versus host disease (GVHD) post-allogeneic stem cell transplant. * Must not have had any of the following within 6 months prior to first study treatment administration after enrollment: myocardial infarction, severe/unstable angina pectoris, coronary/peripheral artery bypass graft, symptomatic congestive heart failure, cerebrovascular accident or transient ischemic attack, or seizure disorder. * Must not have a known bleeding diathesis, e.g. hemophilia, or disseminated intravascular coagulation. * Must not have an active, uncontrolled infection. * Must not have a history of cytarabine-related neurotoxicity. * Must not have a baseline corrected QT (QTc) interval \>470 msec (i.e. CTCAE v 3.0 Grade ≥2). * Must not currently be a smoker and/or must not be likely to smoke during the study. * Females must not be breast-feeding, pregnant, or intend to become pregnant.