GTP 14564 is an inhibitor of class III receptor tyrosine kinases (IC50s = 0.3 μM for c-Fms, c-Kit, ITD-FLT3 and 1 μM for PDGFRβ). It is without effect against a panel of non-receptor tyrosine and serine/threonine kinases. GTP 14564 blocks the proliferation of leukemia cells stimulated with FLT3 ligand by preventing the activation of STAT5.