Selective functional inhibition of JAK-3 is sufficient for efficacy in collagen-induced arthritis in mice.
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.


CONCLUSIONS
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.
Lin
Tsung H
TH
Ligand Pharmaceuticals, Inc., Cranbury, New Jersey, USA.
Hegen
Martin
M
Quadros
Elizabeth
E
Nickerson-Nutter
Cheryl L
CL
Appell
Kenneth C
KC
Cole
Andrew G
AG
Shao
Yuefei
Y
Tam
Steve
S
Ohlmeyer
Michael
M
Wang
Bojing
B
Goodwin
Debra G
DG
Kimble
Earl F
EF
Quintero
Jorge
J
Gao
Min
M
Symanowicz
Peter
P
Wrocklage
Christopher
C
Lussier
Jennifer
J
Schelling
Scott H
SH
Hewet
Amha G
AG
Xuan
Dejun
D
Krykbaev
Rustem
R
Togias
Jenny
J
Xu
Xin
X
Harrison
Richard
R
Mansour
Tarek
T
Collins
Mary
M
Clark
James D
JD
Webb
Maria L
ML
Seidl
Katherine J
KJ
D000704:Analysis of Variance; D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy* / Q000378:metabolism; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D053613:Janus Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D053616:Janus Kinase 3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects
D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053616:Janus Kinase 3