Quizartinib (AC220)

AC220, a unique, potent and selective inhibitor of FLT3, has high affinity for FLT3 with a K_d value of 1.6 nM. AC220 inhibits the autophosphorylation of FLT3 in the human leukemia cell lines MV4-11 which harbor a homozygous FLT3-ITD mutation and is FLT3 dependent, and RS4;11 which expresses wild-type FLT3 with IC50 values of 1.1 nM and 4.2 nM, respectively. AC220 is the most potent cellular FLT3-ITD inhibitor, leading to the most significant inhibition of MV4-11 cell proliferation with IC50 of 0.56 nM compared to all other FLT3 inhibitors whose IC50 values range from 0.87 nM to 64 nM. AC220 has no inhibitory activity against the proliferation of A375 cells which harbor an activating mutation in BRAF and are not FLT3 dependent, indicating a large window between FLT3 inhibition and general cytotoxic effects. ^[1]