To date, three JAK inhibitors have been tested in patients with moderate-to-severe CD: tofacitinib (pan-JAK inhibitor), filgotinib (JAK1 inhibitor) and upadacitinib (JAK1 inhibitor).
Tofacitinib, a JAK inhibitor targeting predominantly JAK1 and JAK3, has been approved for the treatment of ulcerative colitis (UC), and there are other specific JAK inhibitors under development that may be effective in Crohn's.
Tofacitinib, a non-selective oral Janus kinase (JAK) inhibitor, is effective in patients with UC and several other more or less selective Jak1, 2 and 3 inhibitors are being developed for the treatment of CD and UC (Sandborn et al. in N Engl J Med 376(18):1723-1736, 2017; Vermeire et al. in Lancet 389(10066):266-275, 2017; De Vries et al. in J Crohns Colitis 11(7):885-93, 2017).
Filgotinib (GS-6034, formerly GLPG0634) is an oral, selective Janus kinase 1 (JAK1) inhibitor that showed early response and sustained efficacy in patients with rheumatoid arthritis and with Crohn's disease.
For example, the JAK1 blocker filgotinib was tested in Crohn's disease, whereas the JAK1/3 inhibitor tofacitinib was tested in clinical trials for both Crohn's disease and ulcerative colitis.