Lestaurtinib inhibits STAT5 phosphorylation and other downstream effectors of JAK/STAT signaling. Lysates from cultured cells from a subject with CIMF (homozygous for the V617F mutation) exposed to various concentrations of lestaurtinib for 1 hour and 24 hours. Phosphorylation of JAK2, STAT5, STAT3, AKT, ERK, and SHP2 was assayed by Western blot from samples treated for 1 hour (left panel). Blots were stripped and reprobed with antibodies against total protein for controls. Right Panel: After a 24-hour exposure, phosphorylation of STAT5 and expression of STAT5, Bcl-xL, and cyclin D1 and D2 were assessed by Western blot. Cyclophilin and β-actin served as loading controls.