 This is an open-label repeat dose, multicenter, 2-part study to determine the maximum tolerated dose MTD and the recommended Phase 2 dose RP2D for GSK525762 given once-daily QD orally. Part 1 of the study is a dose escalation phase to select the recommended Part 2 dose RP2D based on the safety, PK, and PD profiles observed after oral administration of GSK525762. Eligible subjects with select relapsed refractory hematological malignancies acute myeloid leukemia AML, non-Hodgkins Lymphoma NHLand multiple myeloma MM, will be enrolled in the QD andor BID dosing cohorts until a MTD is established. Subjects may continue treatment in the study until disease progression, unacceptable toxicity, or withdrawal of consent. . Upon determination of the MTD, twice daily BID dosing cohorts may be opened to collect additional safety data and evaluate the preliminary efficacy of GSK525762 administered BID. Part 2 will explore clinical activity at the MTD or RP2D; separate expansion cohorts will be planned for acute myeloid leukemia AML, non-Hodgkins Lymphoma NHL, including an exploratory sub-cohort of subjects with myc and B-Cell Leukemia BCL2 andor BCL6 rearrangementsoverexpression double- and triple-hit lymphoma, and multiple myeloma MM. This is the first study of this agent to be conducted in subjects with these relapsed andor refractory hematological malignancies for which no standard therapies are anticipated to result in a durable remission. 