Potent and selective JAK3 inhibitor (IC50 = 33.1 μM). Exhibits no significant activity against a panel of other kinases including JAK1, JAK2 and TYK2. Inhibits phosphorylation of STAT5, induced by IL-2, IL-4, IL-7 and IL-15. Suppresses Th1 and Th17 T-cell differentiation and function in vitro. Reduces paw swelling in a rat model of arthritis and reduces disease severity in a rat EAE model. Purity 98%. MW (observed): 389.41