R406, an orally available spleen tyrosine kinase inhibitor blocks fc receptor signaling and reduces immune complex-mediated inflammation.
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Braselmann S, Taylor V, Zhao H, Wang S, Sylvain C, Baluom M, Qu K, Herlaar E, Lau A, Young C, Wong BR, Lovell S, Sun T, Park G, Argade A, Jurcevic S, Pine P, Singh R, Grossbard EB, Payan DG, Masuda ES
R406, an orally available spleen tyrosine kinase inhibitor blocks fc receptor signaling and reduces immune complex-mediated inflammation.
J Pharmacol Exp Ther. 2006 Dec;319(3):998-1008. doi: 10.1124/jpet.106.109058. Epub 2006 Aug 31.
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- 16946104 [ View in PubMed]
- Abstract
Recent compelling evidence has lead to renewed interest in the role of antibodies and immune complexes in the pathogenesis of several autoimmune disorders, such as rheumatoid arthritis. These immune complexes, consisting of autoantibodies to self-antigens, can mediate inflammatory responses largely through binding and activating the immunoglobulin Fc receptors (FcRs). Using cell-based structure activity relationships with cultured human mast cells, we have identified the small molecule R406 [N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyph enyl)-2,4-pyrimidinediamine] as a potent inhibitor of immunoglobulin E (IgE)- and IgG-mediated activation of Fc receptor signaling (EC(50) for degranulation = 56-64 nM). Here we show that the primary target for R406 is the spleen tyrosine kinase (Syk), which plays a key role in the signaling of activating Fc receptors and the B-cell receptor (BCR). R406 inhibited phosphorylation of Syk substrate linker for activation of T cells in mast cells and B-cell linker protein/SLP65 in B cells. R406 bound to the ATP binding pocket of Syk and inhibited its kinase activity as an ATP-competitive inhibitor (K(i) = 30 nM). Furthermore, R406 blocked Syk-dependent FcR-mediated activation of monocytes/macrophages and neutrophils and BCR-mediated activation of B lymphocytes. R406 was selective as assessed using a large panel of Syk-independent cell-based assays representing both specific and general signaling pathways. Consistent with Syk inhibition, oral administration of R406 to mice reduced immune complex-mediated inflammation in a reverse-passive Arthus reaction and two antibody-induced arthritis models. Finally, we report a first-inhuman study showing that R406 is orally bioavailable, achieving exposures capable of inhibiting Syk-dependent IgE-mediated basophil activation. Collectively, the results show R406 potential for modulating Syk activity in human disease.
DrugBank Data that Cites this Article
- Drugs
- Drug Targets
Drug Target Kind Organism Pharmacological Action Actions Fostamatinib Adenosine receptor A3 Protein Humans UnknownAntagonistDetails Fostamatinib Equilibrative nucleoside transporter 1 Protein Humans UnknownInhibitorDetails Fostamatinib Synaptic vesicular amine transporter Protein Humans UnknownInhibitorDetails Fostamatinib Tyrosine-protein kinase SYK Protein Humans YesInhibitorDetails