FM-381 is a highly potent and JAK3-selective janus kinase (JAK) inhibitor (IC50 = 127 pM/JAK3, 52 nM/JAK1, 346 nM/JAK2, 459 nM/TYK2 by radiometric assay; [ATP] = 10 μM) that targets JAK3 gatekeeper (GK) Cys909 for a reversible covalent interaction, exhibiting much reduced or little potency against a panel of 409 other kinases. FM-381 is >3-fold more potent than the JAK1/3 inhibitor Tofacitinib (IC50 = 292 pM/JAK3, 496 pM/JAK1, 2.2 nM/JAK2, 8.9 nM/TYK2 by radiometric assay; [ATP] = 10 μM) in blocking JAK1/JAK3-mediated STAT5 phosphorylation in human CD4+ T-cells upon IL-2 stimulation (ECmax ∼100 nM with FM-381), while being ineffective (up to 1 μM) against JAK3-independent STAT1/3 phosphorylation following IL-6 or TNFα stimulation. For characterization details of FM-381, please visit the
FM-381 probe summary on the Structural Genomics Consortium (SGC) website.
FM-479 is the negative control for the active probe, FM-381. FM-479 is available from Sigma. To learn more about and purchase FM-479,
click here.
To learn about other SGC chemical probes, visit
sigma.com/sgc
