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

Julie M Parmentier,Jeff Voss,Lisa Olson,Heidi S Camp,Candace Graff,Matthew Rosebraugh,Michael Friedman,Annette Schwartz,Neil Wishart,Robert J Padley,Andrew J Long,Maria Argiriadi,Deborah Hyland,Jonathan S George

doi:10.1186/s41927-018-0031-x

Abstract

BackgroundAnti-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.MethodsStructure-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.ResultsHere, 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.ConclusionsThe 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.

Highlights

Anti-cytokine therapies such as adalimumab, tocilizumab, and the small molecule Janus kinase (JAK) inhibitor tofacitinib have proven that cytokines and their subsequent downstream signaling processes are important in the pathogenesis of rheumatoid arthritis
We explored the hypothesis that compounds with increased JAK1 selectivity within the JAK family could provide similar or even increased efficacy while sparing some of the dose-limiting side effects associated with tofacitinib
Design of selective JAK1 inhibitors We developed structural hypotheses for obtaining JAK1 selectivity using internal and external JAK protein crystal structures as described previously [14]

Summary

Introduction

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. Even with the significant improvement in care, there are limitations to the maximal benefit achieved by these therapies, which may be a function of targeting a single cytokine or cell type Based on this clinical understanding, medicines that target multiple pro-inflammatory mechanisms, such as the Janus kinase (JAK) family of intracellular signaling enzymes, are being developed for the treatment of RA. JAK3 in conjuction with JAK1 is an important component of signaling transduction for cytokine receptors that utilize the common gamma chain (γc) such as IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21 [9] These cytokines are involved in a range of physiologic processes including T cell survival, Th2 responses, and natural killer (NK) cell survival. Autosomal recessive JAK3 deficiency manifests in a lack of T cells and NK cells, resulting in a severe combined immunodeficiency (SCID) phenotype [10]

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Conclusion