Compound R406 was initially reported to be a Syk inhibitor and its orally bioavailable prodrug, R788 (fostamatinib), was shown to ameliorate lupus-like disease in New Zealand black/white (NZB/W), MRL-lpr, and FcγRIIb-deficient C57BL/6 models of SLE, as well as serum-transferred and collagen-induced models of RA [22–26]. Here, SYK is linked to rheumatoid arthritis.