Cytokines are involved in intestinal homeostasis and pathological processes associated with inflammatory bowel disease (IBD). The biological effects of cytokines, including several involved in the pathology of Crohn’s disease and ulcerative colitis, occur as a result of receptor-mediated signalling through the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) DNA-binding families of proteins. Although therapies targeting cytokines have revolutionized IBD therapy, they have historically targeted individual cytokines, and an unmet medical need exists for patients who do not respond to or lose response to these treatments. Several small-molecule inhibitors of JAKs that have the potential to affect multiple pro-inflammatory cytokine-dependent pathways are in clinical development for the treatment of IBD, with one agent, tofacitinib, already approved for ulcerative colitis and several other agents with demonstrated efficacy in early phase trials. This Review describes the current understanding of JAK–STAT signalling in intestinal homeostasis and disease and the rationale for targeting this pathway as a treatment for IBD. The available evidence for the efficacy, safety and pharmacokinetics of JAK inhibitors in IBD as well as the potential approaches to optimize treatment with these agents, such as localized delivery or combination therapy, are also discussed. The biological effects of cytokines in intestinal homeostasis and disease occur as a result of JAK–STAT signalling. This Review describes the current understanding of JAK–STAT signalling in intestinal homeostasis and inflammatory bowel disease as well as the rationale for therapeutically targeting this pathway.

JAK-STAT pathway targeting for the treatment of inflammatory bowel disease.

Properties of FDA-approved small molecule protein kinase inhibitors: A 2021 update.

Background Atopic dermatitis is a chronic inflammatory skin disease characterized by pruritic skin lesions. Objective We sought to evaluate the safety and efficacy of multiple doses of the selective Janus kinase 1 inhibitor upadacitinib in patients with moderate to severe atopic dermatitis. Methods In the 16-week, double-blind, placebo-controlled, parallel-group, dose-ranging portion of this 88-week trial in 8 countries ( ClinicalTrials.gov , NCT02925117 ; ongoing, not recruiting), adults with moderate to severe disease and inadequate control by topical treatment were randomized 1:1:1:1, using an interactive response system and stratified geographically, to once-daily upadacitinib oral monotherapy 7.5, 15, or 30 mg or placebo. The primary end point was percentage improvement in Eczema Area and Severity Index from baseline at week 16. Efficacy was analyzed by intention-to-treat in all randomized patients. Safety was analyzed in all randomized patients who received study medication, based on actual treatment. Results Patients (N = 167) enrolled from November 21, 2016, to April 20, 2017. All were randomized and analyzed for efficacy (each upadacitinib group, n = 42; placebo, n = 41); 166 were analyzed for safety (each upadacitinib group, n = 42; placebo, n = 40). The mean (SE) primary efficacy end point was 39% (6.2%), 62% (6.1%), and 74% (6.1%) for the upadacitinib 7.5-, 15-, and 30-mg groups, respectively, versus 23% (6.4%) for placebo (P = .03, Conclusions A dose-response relationship was observed for upadacitinib efficacy; the 30-mg once-daily dose showed the greatest clinical benefit. Dose-limiting toxicity was not observed.

Upadacitinib in adults with moderate to severe atopic dermatitis: 16-week results from a randomized, placebo-controlled trial

Anti-cytokine therapies such as adalimumab, tocilizumab, and the small molecule JAK inhibitor tofacitinib have proven that cytokines and their subsequent downstream signaling processes are important in the pathogenesis of rheumatoid arthritis. Tofacitinib, a pan-JAK inhibitor, is the first approved JAK inhibitor for the treatment of RA and has been shown to be effective in managing disease. However, in phase 2 dose-ranging studies tofacitinib was associated with dose-limiting tolerability and safety issues such as anemia. Upadacitinib (ABT-494) is a selective JAK1 inhibitor that was engineered to address the hypothesis that greater JAK1 selectivity over other JAK family members will translate into a more favorable benefit:risk profile. Upadacitinib selectively targets JAK1 dependent disease drivers such as IL-6 and IFNγ, while reducing effects on reticulocytes and natural killer (NK) cells, which potentially contributed to the tolerability issues of tofacitinib. Structure-based hypotheses were used to design the JAK1 selective inhibitor upadacitinib. JAK family selectivity was defined with in vitro assays including biochemical assessments, engineered cell lines, and cytokine stimulation. In vivo selectivity was defined by the efficacy of upadacitinib and tofacitinib in a rat adjuvant induced arthritis model, activity on reticulocyte deployment, and effect on circulating NK cells. The translation of the preclinical JAK1 selectivity was assessed in healthy volunteers using ex vivo stimulation with JAK-dependent cytokines. Here, we show the structural basis for the JAK1 selectivity of upadacitinib, along with the in vitro JAK family selectivity profile and subsequent in vivo physiological consequences. Upadacitinib is ~ 60 fold selective for JAK1 over JAK2, and > 100 fold selective over JAK3 in cellular assays. While both upadacitinib and tofacitinib demonstrated efficacy in a rat model of arthritis, the increased selectivity of upadacitinib for JAK1 resulted in a reduced effect on reticulocyte deployment and NK cell depletion relative to efficacy. Ex vivo pharmacodynamic data obtained from Phase I healthy volunteers confirmed the JAK1 selectivity of upadactinib in a clinical setting. The data presented here highlight the JAK1 selectivity of upadacinitinib and supports its use as an effective therapy for the treatment of RA with the potential for an improved benefit:risk profile.

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In vitro and in vivo characterization of the JAK1 selectivity of upadacitinib (ABT-494)

Importance Atopic dermatitis (AD) is a chronic, recurrent, inflammatory skin disease with an unmet need for treatments that provide rapid and high levels of skin clearance and itch improvement. Objective To assess the safety and efficacy of upadacitinib vs dupilumab in adults with moderate-to-severe AD. Design, Setting, and Participants Heads Up was a 24-week, head-to-head, phase 3b, multicenter, randomized, double-blinded, double-dummy, active-controlled clinical trial comparing the safety and efficacy of upadacitinib with dupilumab among 692 adults with moderate-to-severe AD who were candidates for systemic therapy. The study was conducted from February 21, 2019, to December 9, 2020, at 129 centers located in 22 countries across Europe, North and South America, Oceania, and the Asia-Pacific region. Efficacy analyses were conducted in the intent-to-treat population. Interventions Patients were randomized 1:1 and treated with oral upadacitinib, 30 mg once daily, or subcutaneous dupilumab, 300 mg every other week. Main Outcomes and Measures The primary end point was achievement of 75% improvement in the Eczema Area and Severity Index (EASI75) at week 16. Secondary end points were percentage change from baseline in the Worst Pruritus Numerical Rating Scale (NRS) (weekly average), proportion of patients achieving EASI100 and EASI90 at week 16, percentage change from baseline in Worst Pruritus NRS at week 4, proportion of patients achieving EASI75 at week 2, percentage change from baseline in Worst Pruritus NRS (weekly average) at week 1, and Worst Pruritus NRS (weekly average) improvement of 4 points or more at week 16. End points at week 24 included EASI75, EASI90, EASI100, and improvement of 4 points or more in Worst Pruritus NRS from baseline (weekly average). Safety was assessed as treatment-emergent adverse events in all patients receiving 1 or more dose of either drug. Results Of 924 patients screened, 348 (183 men [52.6%]; mean [SD] age, 36.6 [14.6] years) were randomized to receive upadacitinib and 344 were randomized to receive dupilumab (194 men [56.4%]; mean [SD] age, 36.9 [14.1] years); demographic and disease characteristics were balanced among treatment groups. At week 16, 247 patients receiving upadacitinib (71.0%) and 210 patients receiving dupilumab (61.1%) achieved EASI75 (P = .006). All ranked secondary end points also demonstrated the superiority of upadacitinib vs dupilumab, including improvement in Worst Pruritus NRS as early as week 1 (mean [SE], 31.4% [1.7%] vs 8.8% [1.8%]; P < .001), achievement of EASI75 as early as week 2 (152 [43.7%] vs 60 [17.4%]; P < .001), and achievement of EASI100 at week 16 (97 [27.9%] vs 26 [7.6%]; P < .001). Rates of serious infection, eczema herpeticum, herpes zoster, and laboratory-related adverse events were higher for patients who received upadacitinib, whereas rates of conjunctivitis and injection-site reactions were higher for patients who received dupilumab. Conclusions and Relevance During 16 weeks of treatment, upadacitinib demonstrated superior efficacy vs dupilumab in patients with moderate-to-severe AD, with no new safety signals. Trial Registration ClinicalTrials.gov Identifier: NCT03738397.

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Deborah Hyland

Papers

In vitro and in vivo characterization of the JAK1 selectivity of upadacitinib (ABT-494)

Structure activity optimization of 6H-pyrrolo[2,3-e][1,2,4]triazolo[4,3-a]pyrazines as Jak1 kinase inhibitors