This invention relates to methods and compositions for treatment of inv (16) leukemia and particularly to treatment of acute myeloid leukemia. Disclosed is a method of treating inv (16) leukemia comprising the step of administering to a subject in in need thereof a therapeutically effective combination of a) a compound of the formula (1) (1) and b) a BRD4 inhibitor selected from the group consisting of JQ1, CeMMECZ, 1-BET 151 (or GSK1210151A), 1-BET 762 (or GSK525762), PFI-1, bromosporine, OTX-015 (or MK-8628), TEN-010, CPI-203, CPI-0610, RVX-208, BI2536, TG101348, LY294002, ABBV-075 (or mivebresib), FT-1101, ZEN003694, pharmaceutically acceptable salts and mixtures thereof. The therapeutically effective combination synergistically inhibits proliferation of inv (16) leukemia cells. This invention also relates to pharmaceutical compositions comprising a therapeutically effective combination of the compound of formula (1) and the BRD4 inhibitor and a pharmaceutically acceptable excipient.