Molm14 cells were incubated for 48 hours with increasing concentrations of FLT3 inhibitors in the presence of increasing concentrations of FL and then assayed for cytotoxic effect using an MTT assay. The concentration of drug for which the optical density was reduced to 50% or 80% of its baseline was determined using linear regression analysis of the dose-response curves after linear transformation using an exponential model. All r values in these experiments were ≥ 0.99.