Indeed, second‐generation JAK inhibitors, preferentially selective for one JAK isoform, are being developed.6 For example, BMS‐986165 is a TYK2‐selective inhibitor under investigation for psoriasis44; and PF‐06651600 is a dual JAK3/TEC kinase‐selective inhibitor45 under investigation for alopecia (NCT02974868), Crohn's disease (NCT03395184), non‐segmental vitiligo (NCT03715829), RA (NCT02969044), and ulcerative colitis (NCT02958865). Here, JAK3 is linked to ulcerative colitis.