Jun N-terminal kinase (JNK) is a stress-activated protein kinase that can be induced by inflammatory cytokines, bacterial endotoxin, osmotic shock, UV radiation, and hypoxia. We report the identification of an anthrapyrazolone series with significant inhibition of JNK1, -2, and -3 (K i ‫؍‬ 0.19 M). SP600125 is a reversible ATPcompetitive inhibitor with >20-fold selectivity vs. a range of kinases and enzymes tested. In cells, SP600125 dose dependently inhibited the phosphorylation of c-Jun, the expression of inflammatory genes COX-2, IL-2, IFN-␥, TNF-␣, and prevented the activation and differentiation of primary human CD4 cell cultures. In animal studies, SP600125 blocked (bacterial) lipopolysaccharideinduced expression of tumor necrosis factor-␣ and inhibited anti-CD3-induced apoptosis of CD4 ؉ CD8 ؉ thymocytes. Our study supports targeting JNK as an important strategy in inflammatory disease, apoptotic cell death, and cancer.

The drugs lenalidomide and pomalidomide bind to the protein cereblon, directing the CRL4-CRBN E3 ligase toward the transcription factors Ikaros and Aiolos to cause their ubiquitination and degradation. Here we describe CC-220 (compound 6), a cereblon modulator in clinical development for systemic lupus erythematosis and relapsed/refractory multiple myeloma. Compound 6 binds cereblon with a higher affinity than lenalidomide or pomalidomide. Consistent with this, the cellular degradation of Ikaros and Aiolos is more potent and the extent of substrate depletion is greater. The crystal structure of cereblon in complex with DDB1 and compound 6 reveals that the increase in potency correlates with increased contacts between compound 6 and cereblon away from the modeled binding site for Ikaros/Aiolos. These results describe a new cereblon modulator which achieves greater substrate degradation via tighter binding to the cereblon E3 ligase and provides an example of the effect of E3 ligase binding affinity with relevance to other drug discovery efforts in targeted protein degradation.

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Since Jun-N-terminal kinase participates in intracellular signaling cascades resulting in inflammatory responses, inhibiting this pathway may represent a new treatment for inflammatory bowel disease including ulcerative colitis and Crohn's disease. However, the functional significance of the activation of this kinase in inflammatory bowel disease remains unclear. We investigated whether Jun-N-terminal kinase activation is increased in inflammatory bowel disease and analyzed the effects of SP600125, which decreases inflammatory cytokine synthesis by inhibiting the phosphorylation of this kinase. Phosphorylation of the kinase was examined in affected human colon using an enzyme-linked immunosorbent assay and immunohistochemistry. The effect of SP600125 on cytokine production was examined in cultures of patients' leukocytes and colonic tissue. Finally, rats received injection of SP600125 (30 mg/kg, s.c.) or vehicle twice daily 2 h before the induction of colitis with dextran sulfate sodium. SP600125 effects were determined observationally and histologically. Colonic tissue contained increased phosphorylated kinase in patients with inflammatory bowel disease with expression localized to the nucleus of epithelial and lamina propria mononuclear cells in lesions. Culturing mononuclear cells or colonic tissue with SP600125 down-regulated inflammatory cytokine production. Prophylactic treatment with SP600125 significantly reduced clinical and pathological scores in dextran sulfate sodium-treated rats. This first demonstration of the pathogenetic role of Jun-N-terminal kinase in the development of intestinal inflammation suggests that inhibiting its phosphorylation could benefit patients with inflammatory bowel disease.

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