SCF levels are not significantly affected by AC220 dosing and Flt3 ligand levels return to normal within 12 days after AC220 dosing is discontinued. Eight-month-old c-Cbl^A/− mice were dosed daily with AC220 or vehicle and bled from the tail vein at the indicated times. In the experiment shown in panel B, mice were dosed daily for 42 days and then left untreated for 12 days. The levels of (A) SCF and (B) Flt3 ligand were measured by ELISA. Four vehicle- and 4 AC220-treated c-Cbl^A/− mice were followed for the length of the experiment. Serum levels (pg/mL) are shown as means ± SEM.