This study is an open-label, single-arm, Phase II, PK and pharmacodynamic (PD) trial of CPX-351 in patients with documented acute leukemia (AML or ALL) or MDS (IPSS score ≥ 1.5) and suitable for treatment with intensive chemotherapy. Each patient will be screened for hepatic impairment. Hepatic impairment will be assessed using the Child-Pugh system and only patients with a Child-Pugh score <7 points will be eligible for this study. Patients will receive up to two inductions and four consolidation courses. Patients will be monitored for safety (early deaths, adverse events, metabolic changes, etc.) and efficacy (response for AML, ALL, and MDS) while on the study.