JAK1 and rheumatoid arthritis: Among these drugs, some are classified as non-selective inhibitors, e.g., tofacitinib, which acts preferentially on JAK1 and 2, first approved for the treatment of rheumatoid arthritis (RA) and then for psoriasis and ulcerative colitis, and bariticinib, which also acts on JAK1 and 2 and has been approved for treating RA [11].