Axl blockade exerts therapeutic potential in vivo. (A) Dose-dependent inhibition of MV4-11 tumor growth by BGB324 (n = 4/6/6; *P < .05). (B) OS benefit of Axl inhibition with BGB324 in vivo in the systemic Hoxa9/Meis1 BMT mouse model (median OS 31 days [control], 38 days [12.5 mg/kg BGB324], and 42 days [25 mg/kg BGB324], respectively; n = 7; *P < .05 vs control, respectively). (C) Immunoblots from MV4-11 tumor protein extracts indicated inhibition of Akt, Erk, and Axl phosphorylation and of Bcl2 expression as well as induction of cleavage of caspase 3 after treatment with 25 mg/kg BGB324. Densitometric quantification of (phosphorylated protein/β-actin)/(total protein expression/β-actin), (Bcl-2/β-actin) and (cleaved caspase 3/β-actin) was normalized to control-treated tumors (n = 4; *P < .05). (D) Anemia and (E) thrombocytopenia, 2 cardinal symptoms of AML, were improved by the treatment with 12.5 mg/kg BGB324 at endstage in the Hoxa9/Meis1 model compared with control-treated animals (n = 7; *P < .05). (D) This treatment also improved the leukemia burden determined by flow cytometric quantification of GFP⁺ leukemia cells at endstage (n = 7; *P < .05).