Inhibition of FLT3 in plasma. Molm14 cells were incubated for 1 hour in plasma containing increasing concentrations of KW-2449 (solid lines) and M1 (dashed lines). The cells were then lysed and analyzed for phosphorylated FLT3 (A) and STAT5 (C) as in Figure 1A and B. Densitometry was performed and the results plotted as percent untreated control in panels B and D. IC₅₀ values were calculated using linear regression analysis.