Five JAK inhibitors are currently marketed for RA: tofacitinib, a selective inhibitor of JAK1 and JAK3, upadacitinib and filgotinib, selective inhibitors of JAK1, peficitinib, an inhibitor of pan-JAK, and baricitinib, a selective inhibitor of JAK1 and JAK2 [109]. This evidence concerns the gene JAK1 and rheumatoid arthritis.