title: The active metabolite of spleen tyrosine kinase inhibitor fostamatinib abrogates the CD4⁺ T cell-priming capacity of dendritic cells.
abstract: OBJECTIVE
  Spleen tyrosine kinase (SYK) is a core signalling protein that drives inflammatory responses and is fundamental to the propagation of signals via numerous immune receptors, including the B cell receptor and Fc receptors (FcRs). Fostamatinib, a small molecule SYK inhibitor, has shown evidence of ameliorating inflammation in RA patients. We sought to understand how the active metabolite of fostamatinib, R406, affects the inflammatory response at the cellular level.
  
  
  METHODS
  Antigen-specific in vivo systems and in vitro fluorescence microscopy were combined to investigate the effects of fostamatinib on antigen-specific interactions between dendritic cells (DCs) and CD4(+) T cells.
  
  
  RESULTS
  Although it has previously been shown that R406 reduces the response of DCs to immune complexes (ICs), we found that fostamatinib failed to reduce specific CD4(+) T cell proliferation in mice after immunization with ICs. However, we observed in vitro that R406 reduces both the area and duration of cellular interactions between IC-activated DCs and specific CD4(+) T cells during the initial phase of cellular crosstalk. This led to diminished proliferation of antigen-specific CD4(+) T cells after R406 treatment compared with vehicle controls. This decreased proliferative capacity of CD4(+) T cells was accompanied by reduced expression of the co-stimulatory molecules, inducible T cell co-stimulator (ICOS) and PD-1, and abrogation of the production of inflammatory cytokines such as IFN-γ and IL-17.
  
  
  CONCLUSIONS
  Our findings indicate a potential mechanism by which this compound may be effective in inhibiting FcR-driven CD4(+) T cell responses.
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: Andrew M
authors: AM
authors: Platt
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: Robert A
authors: RA
authors: Benson
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: Ross
authors: R
authors: McQueenie
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: John P
authors: JP
authors: Butcher
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: Martin
authors: M
authors: Braddock
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: James M
authors: JM
authors: Brewer
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK.
authors: Iain B
authors: IB
authors: McInnes
authors: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow and Inflammation, Neuroscience and Respiratory Global Medicines Development, AstraZeneca Research and Development, Macclesfield, UK. paul.garside@glasgow.ac.uk.
authors: Paul
authors: P
authors: Garside
mesh_terms: D000284:Administration, Oral; D000631:Aminopyridines; D000818:Animals; D000936:Antigen-Antibody Complex / Q000494:pharmacology; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D002450:Cell Communication / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D023421:Models, Animal; D009025:Morpholines; D010078:Oxazines / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D011743:Pyrimidines; D000072377:Syk Kinase
chemical_list: D000631:Aminopyridines; D000936:Antigen-Antibody Complex; D018925:Chemokines; D016207:Cytokines; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D009025:Morpholines; C510788:N4-(2,2-dimethyl-3-oxo-4H-pyrid(1,4)oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine; D010078:Oxazines; D011725:Pyridines; D011743:Pyrimidines; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C523665:fostamatinib
keywords: SYK kinase; T cells; autoimmunity; dendritic cells; rheumatoid arthritis