Inhibition of Janus kinases [JAKs] in Crohn's disease [CD] patients has shown 
conflicting results in clinical trials. Tofacitinib, a pan-JAK inhibitor, showed 
efficacy in ulcerative colitis [UC] and has been approved for the treatment of 
patients with moderate to severe UC. In contrast, studies in CD patients were 
disappointing and the primary end point of clinical remission could not be met 
in the respective phase II induction and maintenance trials. Subsequently, the 
clinical development of tofacitinib was discontinued in CD. In contrast, 
efficacy of filgotinib, a selective JAK1 inhibitor, in CD patients was 
demonstrated in the randomized, double-blinded, placebo-controlled phase II 
FITZROY study. Upadacitinib also showed promising results in a phase II trial in 
moderate to severe CD. Subsequently, phase III programmes in CD have been 
initiated for both substances, which are still ongoing. Several newer molecules 
of this class of orally administrated immunosuppressants are being tested in 
clinical programmes. The concern of side effects of systemic JAK inhibition is 
addressed by either exclusively intestinal action or higher selectivity [Tyk2 
inhibitors]. In general, JAK inhibitors constitute a new promising class of 
drugs for the treatment of CD.