Selective functional inhibition of JAK-3 is sufficient for efficacy in collagen-induced arthritis in mice
Tsung H Lin1, Martin Hegen, Elizabeth Quadros
1Ligand Pharmaceuticals, Inc., Cranbury, New Jersey, USA.
Objective:
All gamma-chain cytokines signal through JAK-3 and JAK-1 acting in tandem. We undertook this study to determine whether the JAK-3 selective inhibitor WYE-151650 would be sufficient to disrupt cytokine signaling and to ameliorate autoimmune disease pathology without inhibiting other pathways mediated by JAK-1, JAK-2, and Tyk-2.
Methods:
JAK-3 kinase selective compounds were characterized by kinase assay and JAK-3-dependent (interleukin-2 [IL-2]) and -independent (IL-6, granulocyte-macrophage colony-stimulating factor [GM-CSF]) cell-based assays measuring proliferation or STAT phosphorylation. In vivo, off-target signaling was measured by IL-22- and erythropoietin (EPO)-mediated models, while on-target signaling was measured by IL-2-mediated signaling. Efficacy of JAK-3 inhibitors was determined using delayed-type hypersensitivity (DTH) and collagen-induced arthritis (CIA) models in mice.
Results:
In vitro, WYE-151650 potently suppressed IL-2-induced STAT-5 phosphorylation and cell proliferation, while exhibiting 10-29-fold less activity against JAK-3-independent IL-6- or GM-CSF-induced STAT phosphorylation. Ex vivo, WYE-151650 suppressed IL-2-induced STAT phosphorylation, but not IL-6-induced STAT phosphorylation, as measured in whole blood. In vivo, WYE-151650 inhibited JAK-3-mediated IL-2-induced interferon-gamma production and decreased the natural killer cell population in mice, while not affecting IL-22-induced serum amyloid A production or EPO-induced reticulocytosis. WYE-151650 was efficacious in mouse DTH and CIA models.
Conclusion:
In vitro, ex vivo, and in vivo assays demonstrate that WYE-151650 is efficacious in mouse CIA despite JAK-3 selectivity. These data question the need to broadly inhibit JAK-1-, JAK-2-, or Tyk-2-dependent cytokine pathways for efficacy.
Insights
A selective JAK-3 inhibitor, WYE-151650, effectively treated autoimmune disease models in mice. This suggests that targeting JAK-3 alone may be sufficient for therapeutic efficacy, questioning the need for broader JAK inhibition.
Area of Science:
- Immunology
- Pharmacology
- Molecular Biology
Background:
- Gamma-chain cytokines utilize Janus kinase-3 (JAK-3) and JAK-1.
- Targeting JAK-3 selectively could offer therapeutic benefits for autoimmune diseases by disrupting specific cytokine signaling pathways.
Purpose of the Study:
- To evaluate if the JAK-3 selective inhibitor WYE-151650 can disrupt cytokine signaling and ameliorate autoimmune disease pathology.
- To determine if WYE-151650 achieves efficacy without inhibiting JAK-1, JAK-2, and Tyk-2 mediated pathways.
Main Methods:
- In vitro kinase assays and cell-based assays (IL-2, IL-6, GM-CSF) assessed JAK-3 selectivity and activity.
- In vivo studies in mice evaluated on-target (IL-2) and off-target (IL-22, EPO) signaling.
- Efficacy was determined using delayed-type hypersensitivity (DTH) and collagen-induced arthritis (CIA) models.
Main Results:
- WYE-151650 potently inhibited IL-2-induced signaling while showing significantly less activity against IL-6 or GM-CSF.
- In vivo, WYE-151650 suppressed IL-2-mediated interferon-gamma production and reduced natural killer cells without affecting IL-22 or EPO pathways.
- The inhibitor demonstrated efficacy in mouse models of DTH and CIA.
Conclusions:
- WYE-151650 exhibits efficacy in mouse autoimmune models (CIA) due to its JAK-3 selectivity.
- These findings challenge the necessity of broadly inhibiting JAK-1, JAK-2, or Tyk-2 for achieving therapeutic effects in autoimmune diseases.
