Fostamatinib (R788) disodium hexahydrate is the oral proagent of the active compound R406[1]. R406 is an orally available and competitive Syk/FLT3 inhibitor with a Ki of 30 nM and an IC50 of 41 nM[2]. R406 also inhibits Lyn (IC50=63 nM) and Lck (IC50=37 nM) [3].