This is a dose finding study to determine the safety and tolerability, pharmacokinetics and pharmacodynamics, and clinical activity of escalating doses of BMF-219 administered orally (PO) either once daily (QD) or twice daily (BID) in 28-day cycles. After observing acceptable safety performance in these dosing regimens, additional subjects will be enrolled to assess efficacy in the determination of the OBD for use as a RP2D.