A novel, highly selective, tight binding IkappaB kinase-2 (IKK-2) inhibitor: a tool to correlate IKK-2 activity to the fate and functions of the components of the nuclear factor-kappaB pathway in arthritis-relevant cells and animal models.
Nuclear factor (NF)-kappaB activation has been clearly linked to the pathogenesis of multiple inflammatory diseases including arthritis. The central role that IkappaB kinase-2 (IKK-2) plays in regulating NF-kappaB signaling in response to inflammatory stimuli has made this enzyme an attractive target for therapeutic intervention. Although diverse chemical classes of IKK-2 inhibitors have been identified, the binding kinetics of these inhibitors has limited the scope of their applications. In addition, safety assessments of IKK-2 inhibitors based on a comprehensive understanding of the pharmacokinetic/pharmacodynamic relationships have yet to be reported. Here, we describe a novel, potent, and highly selective IKK-2 inhibitor, PHA-408 [8-(5-chloro-2-(4-methylpiperazin-1-yl)isonicotinamido)-1-(4-fluorophenyl)-4,5-dihydro-1H-benzo[g]indazole-3-carboxamide]. PHA-408 is an ATP-competitive inhibitor, which binds IKK-2 tightly with a relatively slow off rate. In arthritis-relevant cells and animal models, PHA-408 suppresses inflammation-induced cellular events, including IkappaBalpha phosphorylation and degradation, p65 phosphorylation and DNA binding activity, the expression of inflammatory mediators, and joint pathology. PHA-408 was efficacious in a chronic model of arthritis with no adverse effects at maximally efficacious doses. Stemming from its ability to bind tightly to IKK-2, as a novelty, we demonstrated that PHA-408-mediated inhibition of IKK-2 activity correlated very well with its ability to modulate the fate of IKK-2 substrates and downstream transcriptional events. We ultimately directly linked IKK-2 activity ex vivo and in vivo to markers of inflammation with the inhibitor plasma concentrations. Thus, PHA-408 represents a powerful tool to further gain insight into the mechanisms by which IKK-2 regulates NF-kappaB signaling and validates IKK-2 as a therapeutic target.
Mbalaviele
Gabriel
G
Department of Inflammation, Pfizer St. Louis Laboratories, Chesterfield, MO 63017, USA. gabriel.mbalaviele@pfizer.com
Sommers
Cynthia D
CD
Bonar
Sheri L
SL
Mathialagan
Sumathy
S
Schindler
John F
JF
Guzova
Julia A
JA
Shaffer
Alexander F
AF
Melton
Michele A
MA
Christine
Lori J
LJ
Tripp
Catherine S
CS
Chiang
Po-Chang
PC
Thompson
David C
DC
Hu
Yiding
Y
Kishore
Nandini
N
D000818:Animals; D001168:Arthritis / Q000473:pathology*; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000473:pathology; D015153:Blotting, Western; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D024202:Electrophoretic Mobility Shift Assay; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007249:Inflammation / Q000139:chemically induced / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D016328:NF-kappa B / Q000187:drug effects*; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013291:Streptococcus / Q000276:immunology; D013582:Synovial Fluid / Q000166:cytology / Q000187:drug effects; D053719:Tandem Mass Spectrometry; D014057:Tomography, X-Ray Computed; D051996:Transcription Factor RelA / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D011994:Recombinant Proteins; D051996:Transcription Factor RelA; D051550:I-kappa B Kinase; D048051:p38 Mitogen-Activated Protein Kinases