Yoshitaka Satoh

SP600125, an anthrapyrazolone inhibitor of Jun N-terminal kinase

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 (Ki = 0.19 μM). SP600125 is a reversible ATP-competitive 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-γ, TNF-α, and prevented the activation and differentiation of primary human CD4 cell cultures. In animal studies, SP600125 blocked (bacterial) lipopolysaccharide-induced expression of tumor necrosis factor-α 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.

JNK: a new therapeutic target for diabetes

Jun N-terminal kinase (JNK) regulates the transcription factor AP-1, which is implicated in the controlled expression of many genes involved in the immune response. For this reason, drug discovery efforts have focused on the development of JNK inhibitors for chronic inflammatory diseases. However, recent genetic evidence and emerging pharmacological data indicate that activated JNK could be critical in causing diabetes, insulin resistance and obesity. Indeed, if JNK is considered as a stress-activated protein kinase, there appear to be multiple mechanisms through which it might promote diabetes.

Discovery of CC-930, an orally active anti-fibrotic JNK inhibitor.

In this Letter we describe the discovery of potent, selective, and orally active aminopurine JNK inhibitors. Improving the physico-chemical properties as well as increasing the potency and selectivity of a subseries with rat plasma exposure, led to the identification of four structurally diverse inhibitors. Differentiation based on PK profiles in multiple species as well as activity in a chronic efficacy model led to the identification of 1 (CC-930) as a development candidate, which is currently in Phase II clinical trial for IPF.

Aminopurine based JNK inhibitors for the prevention of ischemia reperfusion injury.

In this Letter we describe the optimization of an aminopurine lead (1) with modest potency and poor overall kinase selectivity which led to the identification of a series of potent, selective JNK inhibitors. Improvement in kinase selectivity was enabled by introduction of an aliphatic side chain at the C-2 position. CC-359 (2) was selected as a potential clinical candidate for diseases manifested by ischemia reperfusion injury.

Activation of c-Jun N-terminal kinase (JNK) signalling in experimentally induced gastric lesions in rats

The c‐Jun N‐terminal kinase (JNK) participates in intracellular signalling cascades that mediate inflammatory responses. Therefore, the JNK signalling may be involved in gastric injury and inhibition of this pathway may form the basis of a new strategy for the treatment of gastric injury. The aim of this study was to determine whether JNK participates in the formation of gastric lesions in an experimental model. Acute gastric injury was induced in Sprague‐Dawley rats by intragastric administration of 100% ethanol. The amount of phospho‐JNK in the rat stomach was determined using immunohistochemistry and Western analysis. Animals received subcutaneous injections of a specific JNK inhibitor SP600125 or vehicle and the extent of mucosal damage in the stomach was determined. Western analysis revealed early phosphorylation of JNK and, to a lesser extent, p38 as well as late phosphorylation of the p42/44 extracellular signal‐related kinases during the development of gastric lesions. JNK was phosphorylated in epithelial cells and in occasional mononuclear cells present at lesion sites. These cells were rarely found in samples from control specimens. Treatment with SP600125 significantly reduced the extent of gastric lesions. These findings indicate that experimental gastric injury is associated with activation of the JNK signalling pathway, and also suggest that JNK inhibitors may play a role in the treatment of gastric injury in humans.

A Cereblon Modulator (CC-220) with Improved Degradation of Ikaros and Aiolos

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.

Suppression of alloreactivity and allograft rejection by SP600125, a small molecule inhibitor of c-jun N-terminal kinase

Background. c-Jun N-terminal kinase (JNK) is reported to play crucial roles in T-cell activation and differentiation, and SP600125 is a small molecule that inhibits JNK. The aim of this study was to examine immunosuppressive action of this compound. Methods. Rat heterotopic heart transplantation, popliteal lymph node (PLN) hyperplasia bioassay and lymphocyte proliferation assay. Results. SP600125 treatment reduced histological rejection, and dose-dependently extended median survival time of cardiac allografts from 7 days (vehicle) up to 20 days (40 mg/kg/day). Alloantigen-induced PLN hyperplasia was also inhibited by SP600125 in a similar fashion. SP600125 suppressed mixed lymphocyte reaction and OX52-positive lymphocyte proliferation (IC50: 1.5–5.7 &mgr;M). Thus, SP600125 inhibits both T-lymphocyte expansion in vitro and T-cell–mediated alloimmune responses in vivo. In addition, SP600125 interacted with cyclosporine additively to prolong cardiac allograft survival. Conclusion. Our data provide the first evidence indicating the potential for JNK as a therapeutic target to inhibit the alloimmune response.

Drugs for the Treatment of Respiratory Diseases: Drugs targeting cell signalling

Introduction Cellular responses to external stimuli are coordinated by intracellular transducers, which rapidly relay a chemical signal from the cell membrane to specific effector sites inside the cell. The transducers are typically enzymes and adaptor proteins, such as kinases, phosphatases, lipases, and G-proteins, while the signal is frequently an allosteric activator such as Ca 2+ , cAMP, phospholipid, and phosphate. Response to external signals may occur in seconds, e.g. changes in ion channels and membrane structure, to minutes, e.g. trafficking of proteins to cell surface, to hours, e.g. changes in protein levels due to gene expression. The diversity and detail of these signalling pathways is both remarkable and only partly understood. The discovery of numerous proteins within decipherable biochemical pathways has provided novel approaches to controlling specific cell responses. For instance, the overexpression of multiple genes encoding inflammatory enzymes, cytokines, adhesion molecules, and proteases is responsible for diseases such as asthma, chronic obstructive pulmonary disease (COPD), rheumatoid arthritis, inflammatory bowel disease psoriasis and colitis. By targeting key signalling components of these pathways for therapeutic intervention, it is believed that a new generation of drugs will attack the underlying cause of disease and not just the disease symptoms. A sufficient description of all of the molecular drug targets available in cell signalling pathways is not possible within the confines of this chapter, when it is estimated that there are between 400 and 600 protein kinases alone encoded in the human genome.

Inhibitors of the MAPK pathway

The mitogen-activated protein kinase (MAPK) family of protein kinases is a series of three highly conserved protein kinases arrayed in a cascade. Members of this family are proline-directed serine/threonine kinases that are activated by dual-phosphorylation. MAPK belong to the rapidly growing family of mammalian protein kinases. Less than 200 mammalian protein kinases were known in 1994. As of 1998, more than 700 distinct mammalian protein kinases have been identified by genomic technologies and estimates are that the human genome encodes around 2000 protein kinases. MAPK impact many cellular processes such as proliferation, oncogenesis, development and differentiation, cell cycle and cell death [1—4],. Selective inhibition of signal transduction processes has been considered by many pharmaceutical companies as an approach to disease management [5]. Two of the best-characterized anti-inflammatory drugs in patients, rapamycin and cyclosporin, act by directly affecting protein phosphorylation. Multiple clinical trials are underway with specific kinase inhibitors, in particular PKC and tyrosine kinase inhibitors. Therefore, targeting MAPK with therapeutics may be an effective way for treating a large number of diseases. This chapter will review the current field of biological and small molecule inhibitors of MAPKs. The authors recommend as starting point the following reviews on inhibitors of protein kinases [6—15].