An orally bioavailable, specific, broad spectrum JAK inhibitor (IC50s = 10, 18, 99, and 84 nM for JAK1, JAK2, JAK3, and JAK4, respectively); blocks cell-based JAK signaling induced by IL-2, IL-4, IL-6, IL-13, or IL-31 with IC50 values ranging from 36 to 249 nM