FLT3 and acute myeloid leukemia: As early as 2008, phase I trials of sorafenib administered as a single agent n patients with FLT3-ITD-positive relapsed or refractory (r/r) AML demonstrated significant reductions in the number of leukemic cells both in the peripheral blood and bone marrow, achieving CR in several patients.71, 72, 73, 74 In a phase II trial of 13 patients with r/r FLT3-ITD-positive AML, single-agent sorafenib at doses of 200–400 mg twice daily established CR (including CR with insufficient hematologic recovery) in over 90% of cases.