D835 mutations in native FLT3 cause resistance to quizartinib. (A) Normalized cell viability of Ba/F3 populations stably expressing FLT3-mutant isoforms after 48 hours in various concentrations of quizartinib (error bars represent standard deviation of triplicates from the same experiment). (B) Western blot analysis using the indicated antibodies performed on lysates from interleukin-3–independent Ba/F3 populations expressing the FLT3-mutant isoforms indicated. Cells were exposed to quizartinib at the noted concentrations for 90 minutes.