An orally available disodium salt of the Syk kinase inhibitor fostamatinib with potential anti-inflammatory and immunomodulating activities. Fostamatinib inhibits Syk kinase-mediated IgG Fc gamma receptor signaling, resulting in inhibition of the activation of mast cells, macrophages, and B-cells and related inflammatory responses and tissue damage. Syk kinase, widely expressed in hematopoietic cells, is a nonreceptor tyrosine kinase that is involved in coupling activated immunoreceptors to signal downstream events that mediate diverse cellular responses, including proliferation, differentiation, and phagocytosis. or A substance being studied in the treatment of cancer and certain other diseases, such as rheumatoid arthritis. It may block tumor cell signaling and growth. It is a type of tyrosine kinase inhibitor. Also called R788 sodium and Syk kinase inhibitor R-935788.