FLT3 genotype analysis was performed in all patients on entry to the study. The observed incidence of FLT3-ITD (exon 14) mutations was 10.3% [3 of 29; VDFREYE (592–598), KYFYVDFRE (588–596), and DFREY (593–597) in patients 3, 4, and 10, respectively]….All patients who exhibited strong FLT3 inhibition at doses <200 mg were FLT3 mutant. SU11248 inhibited FLT3 phosphorylation in all five FLT3 mutant cases. IP/W analysis of FLT3 phosphorylation in ITD patients 3 and 10...

All patients with FLT3 mutations (n = 4) had morphologic or partial responses compared with 2 of 10 evaluable patients with wild-type FLT3. Responses, although longer in patients with mutated FLT3, were of short duration....Of the 16 enrolled patients, 2 presented with FLT3-ITD (patients 7 and 13) and 2 with FLT3-D835 (patients 3 and 8) mutated receptors at baseline. After 4 weeks of SU11248 treatment, 1 patient with D835 mutation (patient 3) achieved a MorphR and the other 3 achieved PRs...C indicates cycle; D, the day of the cycle when blood was drawn; and pY591, flt3 phosphorylated at tyrosine 591.