Quizartinib

Quizartinib (AC220) is an orally active, highly selective and potent second-generation type II FLT3 tyrosine kinase inhibitor, with a K_d of 1.6 nM. Quizartinib inhibits wild-type FLT3 and FLT3-ITD autophosphorylation in MV4-11 cells with IC₅₀s of 4.2 and 1.1 nM, respectively. Quizartinib can be linked to the VHL ligand via an optimized linker to form a PROTAC FLT3 degrader. Quizartinib induces apoptosis^[1]. IC50 & Target:Kd: 1.6±0.7 nM (Flt3)^[1] In Vitro:Quizartinib (AC220) is a novel compound expressly optimized as a FLT3 inhibitor for the treatment of acute myeloid leukemia (AML). Quizartinib inhibits FLT3-WT and FLT3-ITD autophosphorylation with IC₅₀ of 4.2±0.3 nM and 1.1±0.1 nM, respectively. Quizartinib inhibits MV4-11 and A375 cells with IC₅₀ of 0.56±0.3 nM and >10 000 nM, respectively. Quizartinib inhibits FLT3 with low nanomolar potency in cellular assays and is highly selective when screened against the majority of the human protein kinome^[1]. In Vivo:Quizartinib (AC220) inhibits FLT3 activity in vivo, significantly extends survival in a mouse model of FLT3-ITD AML at doses as low as 1 mg/kg when dosed orally once a day, eradicates tumors in a FLT3-dependent mouse xenograft model at 10 mg/kg, and potently inhibits FLT3 activity in primary patient cells. The oral bioavailability of Quizartinib, determined in rats by comparing oral and intravenous pharmacokinetics at 3 mg/kg, is approximately 40%. A single 10 mg/kg dose of Quizartinib is administered by oral gavage, and mice are killed at 2 time points after dosing, using groups of 4 animals each. Quantitation of total FLT3 and phospho-FLT3 in tumor samples revealed time-dependent inhibition of FLT3 autophosphorylation. FLT3 activity is inhibited by 90% at 2 hours, and 40% at 24 hours after administration. The extent of inhibition therefore correlated well with the expected free Quizartinib plasma levels, based on pharmacokinetic experiments^[1].