TY - JOUR T1 - DOT1L Inhibitor EPZ-5676 Displays Synergistic Antiproliferative Activity in Combination with Standard of Care Drugs and Hypomethylating Agents in <em>MLL</em>-Rearranged Leukemia Cells JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 646 LP - 656 DO - 10.1124/jpet.114.214577 VL - 350 IS - 3 AU - Christine R. Klaus AU - Dorothy Iwanowicz AU - Danielle Johnston AU - Carly A. Campbell AU - Jesse J. Smith AU - Mikel P. Moyer AU - Robert A. Copeland AU - Edward J. Olhava AU - Margaret Porter Scott AU - Roy M. Pollock AU - Scott R. Daigle AU - Alejandra Raimondi Y1 - 2014/09/01 UR - http://jpet.aspetjournals.org/content/350/3/646.abstract N2 - EPZ-5676 [(2R,3R,4S,5R)-2-(6-amino-9H-purin-9-yl)-5-((((1r,3S)-3-(2-(5-(tert-butyl)-1H-benzo[d]imidazol-2-yl)ethyl)cyclobutyl)(isopropyl)amino)methyl)tetrahydrofuran-3,4-diol], a small-molecule inhibitor of the protein methyltransferase DOT1L, is currently under clinical investigation for acute leukemias bearing MLL-rearrangements (MLL-r). In this study, we evaluated EPZ-5676 in combination with standard of care (SOC) agents for acute leukemias as well as other chromatin-modifying drugs in cellular assays with three human acute leukemia cell lines: MOLM-13 (MLL-AF9), MV4-11 (MLL-AF4), and SKM-1 (non–MLL-r). Studies were performed to evaluate the antiproliferative effects of EPZ-5676 combinations in a cotreatment model in which the second agent was added simultaneously with EPZ-5676 at the beginning of the assay, or in a pretreatment model in which cells were incubated for several days in the presence of EPZ-5676 prior to the addition of the second agent. EPZ-5676 was found to act synergistically with the acute myeloid leukemia (AML) SOC agents cytarabine or daunorubicin in MOLM-13 and MV4-11 MLL-r cell lines. EPZ-5676 is selective for MLL-r cell lines as demonstrated by its lack of effect either alone or in combination in the nonrearranged SKM-1 cell line. In MLL-r cells, the combination benefit was observed even when EPZ-5676 was washed out prior to the addition of the chemotherapeutic agents, suggesting that EPZ-5676 sets up a durable, altered chromatin state that enhances the chemotherapeutic effects. Our evaluation of EPZ-5676 in conjunction with other chromatin-modifying drugs also revealed a consistent combination benefit, including synergy with DNA hypomethylating agents. These results indicate that EPZ-5676 is highly efficacious as a single agent and synergistically acts with other chemotherapeutics, including AML SOC drugs and DNA hypomethylating agents in MLL-r cells. ER -