A Phase 1/2 Safety and Efficacy Study of Orally Administered PLX3397 in Adults With Relapsed or Refractory Flt3-ITD Positive Acute Myeloid Leukemia

The specific purpose of the study is to find out whether PLX3397 taken by mouth twice per day, daily in 28 day cycles is safe and effective as a treatment for AML.

Part I (Dose Escalation Phase) will look at the safety of increasing dose levels of PLX3397 in patients with relapsed or refractory acute myeloid leukemia (AML). Each dose group will include between 3-6 patients. The study doctor and Sponsor will review the safety data of each dose level of PLX3397 following 15 days of dosing, before the subjects in the next dose level are dosed. The highest dose level (maximum tolerated dose or MTD) tolerated by patients in Part I will be used as the dose level in Part 2 of this study.

Part 2 (Cohort Expansion Phase) - The dose will be the highest tolerated dose from Part 1. Part 2 will look at how the highest tolerated dose of PLX3397 affects your cancer and your body. Throughout both parts of the study, the amount of PLX3397 that is in your blood after taking the study drug and also how PLX3397 affects your body will be tracked.