PIA for FLT3 plotted against plasma drug levels. Shown are the standard curves (solid black lines) for inhibition of FLT3 autophosphorylation in plasma by CEP-701 (A) and PKC412 (B). These are the same curves from Figure 1B,D. Superimposed over the curves are PIA assay results (○) for individual samples from patients treated with CEP-701 (A) and PKC412 (B). Each circle plots the level of FLT3 phosphorylation in the PIA assay against the measurement of the actual drug level from that plasma sample.