Spleen tyrosine kinase (Syk) is a non-receptor tyrosine kinase that upon phosphorylation binds to immunoreceptor tyrosine-based activation motifs (ITAMs) of FcRγ chains and mediates downstream signaling related to platelet function and inflammation. Syk inhibitor is an oxindole compound that potently blocks Syk activity with an IC50 value of 5 nM and inhibits FcεRI-mediated rat RBL-2H3 basophil cell degranulation (EC50 = 1.4 μM). At 2 μM, this compound completely abolishes convulxin-induced platelet aggregation and shape change.
