Inclusion Criteria:

- Subjects with AML with the FLT3-ITD mutation who have undergone allogeneic HSCT

- Peripheral blood chimerism studies showing >/= 70% of all cells are of donor origin

- Adequate hematologic and hepatic function

- ECOG performance status 0-2

- Able to swallow whole pills

Exclusion Criteria:

- Evidence of relapsed/recurrent/residual disease as assessed by bone marrow aspirate
and biopsy performed between days 30-60 after HSCT

- Active acute graft vs host disease requiring an equivalent dose of > 0.5 mg/kg/day of
prednisone or equivalent or those patients which necessitated the addition of another
agent for the treatment of GVHD beyond corticosteroids

- Ongoing uncontrolled infection

- Cardiac disease: congestive heart failure > class II NYHA, unstable angina or new
onset angina (began within the last 3 months) or myocardial infarction within the
past 6 months

- Cardiac ventricular arrhythmias requiring anti-arrhythmic therapy

- Uncontrolled hypertension

- Known HIV infection or chronic hepatitis B or C

- Thrombotic or embolic events such as cerebrovascular accident including transient
ischemic attacks within the past 6 months

- Pulmonary hemorrhage/bleeding event > CTCAE v 4.0 Grade 2 within 4 weeks of starting
study drug

- Any other hemorrhage/bleeding event > CTCAE v. 4.0 Grade 3 within 4 weeks of starting
study drug

- Serious non-healing wound, non-healing ulcer, or bone fracture

- Evidence or history of bleeding diathesis or coagulopathy

- Major surgery or significant traumatic injury within 4 weeks of starting study drug

- Use of St. John's Wort or rifampin (rifampicin)

- Known or suspected allergy to sorafenib

- Pregnant or breast-feeding

- Receiving any other investigational agents