JAK3 and rheumatoid arthritis: The IC50 values determined in this study were consistent with the literature, with each JAK inhibitor demonstrating greater selectivity for JAK1 vs other isoforms.4, 5, 9, 10, 11 JAK1 is presumed to be a key target for RA and other inflammatory diseases since it associates with receptors for γc cytokines, interferons, type II cytokine receptors (eg, IL‐6), and other interleukins.5, 22 Also per the literature, tofacitinib showed comparative selectivity for JAK3, and baricitinib showed comparative selectivity for JAK2.4, 5, 9