RO9021 is an orally bioavailable, novel ATP-competitive inhibitor of SYK, with an average IC₅₀ of 5.6 nM.

RO9021 is a highly selective SYK inhibitor with low S-scores of 0.003 for S(99) and 0.015 for S(90), indicating that SYK is the only kinase with 99% competition with RO9021 in a total of 392 tested kinases. RO9021 inhibits anti-IgM induced phosphorylation of BTK, PLCγ2, AKT and ERK, indicating that blockade of SYK kinase activity by RO9021 results in attenuation of BCR downstream signaling cascade. RO9021 selectively suppresses B-cell receptor signaling. RO9021 also displays a similar inhibitory potency (IC₅₀=22.8±1.7 nM) in a FcεR-mediated mast cell activation and degranulation assay.

西域 has not independently confirmed the accuracy of these methods. They are for reference only.

• . Liao C, et al. Selective inhibition of spleen tyrosine kinase (SYK) with a novel orally bioavailable small molecule inhibitor, RO9021, impinges on various innate and adaptive immune responses: implications for SYK inhibitors in autoimmune disease therapy.