TAS05567 is a potent, highly selective, and ATP-competitive Syk inhibitor (IC50: 0.37 nM), showing >70% inhibition of Syk and four other kinases [FLT3 (IC50: 10 nM), JAK2 (IC50: 4.8 nM), KDR (IC50: 600 nM), RET (IC50: 29 nM)] in a panel of 192 kinases.