ER-27319, an acridone derivative, serves as a potent and selective inhibitor of spleen tyrosine kinase (SYK), effectively impeding both the tyrosine phosphorylation and enzymatic activity of SYK. With an inhibitory concentration (IC50) of 10 µM, this compound suppresses the release of allergic mediators from human and rat mast cells triggered by antigens, making it useful for allergy research [1] [2].

ER-27319 (24 h) inhibits antigen-induced myo-inositol phosphate generation, arachidonic acid release, and histamine and tumor necrosis factor α secretion in RBL-2H3 cells, rat peritoneal, and human cultured mast cells, with an IC50 value of approximately 10 μM [1]. ER-27319 (10-30 μM, 10 min) selectively inhibits the tyrosine phosphorylation of SYK induced by immunoreceptor tyrosine activation motif upon FcεRI γ phosphorylation [1]. ER-27319 (up to 100 μM, 60 min) does not inhibit ZAP-70 tyrosine phosphorylation triggered by CD3 stimulation in Jurkat cells [1]. ER-27319 (100 μM, 10 min) suppresses the tyrosine phosphorylation of two proteins (38, 70 kD) and reduces the tyrosine phosphorylation of two other proteins (62, 80 kD) in canine cutaneous mastocytoma cells challenged with anti-IgG [2].