Marginal effect of RO9021 in the JAK–STAT pathway. Human peripheral blood mononuclear cells were pretreated with RO9021 or the janus kinase (JAK) inhibitor tofacitinib and then stimulated with IL-2 to induce STAT5 phosphorylation in CD3+ T cells (A) or IFNγ to induce STAT1 phosphorylation in CD14+ monocytes/macrophages (B). Left panels, representative overlaid histograms of flow cytometric analysis. Filled gray, unstimulated; filled red, stimulated with IL-2 or IFNγ. Blue line, treatment with 1 μM RO9021; green line, treatment with 1 μM JAK inhibitor (tofacitinib). Right panels: concentration-dependent inhibition curves of RO9021 (dots) and tofacitinib (squares).