The mechanism of the cytotoxic effects of CEP-701 on pediatric AML blasts is the induction of apoptosis. Dose-response curves showing correlation between MTT and annexin V binding (AVB) assays for CEP-701–responsive samples. MTT curves show the average of the mean OD for each sample at each dose level, normalized to untreated controls. AVB curves show the mean percentage of viable (ie, annexin V and 7-AAD negative) cells for each sample at each dose level, normalized to untreated controls. Error bars represent SEM. (A) FLT3/ITD samples (N = 10), (B) FLT3/PM samples (N = 3), (C) FLT3/WT samples (N = 3). (D) Correlation of MTT and AVB results at the CEP-701 100-nM dose level. r² = Pearson correlation coefficient. Solid line represents best-fit line by linear regression; dotted lines represent 95% confidence interval of best-fit line.