This study of SCH 900776 (MK-8776) will evaluate its safety and tolerability when given in combination with cytarabine to participants with acute leukemias. Participants in the Dose-Escalation Part will be enrolled in cohorts that will receive sequentially higher doses of MK-8776 in combination with standard doses of cytarabine. Only one combination treatment cycle of approximately 4 to 6 weeks is anticipated, but participants may receive additional cycles if clinically indicated after discussion between the Investigator and the Sponsor. The recommended combination doses for a Phase 2 trial (RP2D) will be determined based on safety and biological activity. Up to 10 to 15 additional participants will be studied at the combination RP2D.