Akio Murase

CJ-023,423, a Novel, Potent and Selective Prostaglandin EP4 Receptor Antagonist with Antihyperalgesic Properties

The prostaglandin (PG) EP4 receptor subtype is expressed by peripheral sensory neurons. Although a potential role of EP4 receptor in pain has been suggested, a limited number of selective ligands have made it difficult to explore the physiological functions of EP4 or its potential as a new analgesic target. Here, we describe the in vitro and in vivo pharmacology of a novel EP4 receptor antagonist, N-[({2-[4-(2-ethyl-4,6-dimethyl-1H-imidazo [4,5-c] pyridin-1-yl) phenyl]ethyl}amino) carbonyl]-4-methylbenzenesulfonamide (CJ-023,423). In vitro, CJ-023,423 inhibits [3H]PGE2 binding to both human and rat EP4 receptors with Ki of 13 ± 4 and 20 ± 1 nM, respectively. CJ-023,423 is highly selective for the human EP4 receptor over other human prostanoid receptor subtypes. It also inhibits PGE2-evoked elevation in intracellular cAMP at the human and rat EP4 receptors with pA2 of 8.3 ± 0.03 and 8.2 ± 0.2 nM, respectively. In vivo, oral administration of CJ-023,423 significantly reduces thermal hyperalgesia induced by intraplantar injection of PGE2 (ED50 = 12.8 mg/kg). CJ-023,423 is also effective in models of acute and chronic inflammatory pain. CJ-023,423 significantly reduces mechanical hyperalgesia in the carrageenan model. Furthermore, CJ-023,423 significantly reverses complete Freunds adjuvant-induced chronic inflammatory pain response. Taken together, the present data indicate that CJ-023,423, a highly potent and selective antagonist of both human and rat EP4 receptors, produces antihyperalgesic effects in animal models of inflammatory pain. Thus, specific blockade of the EP4 receptor signaling may represent a novel therapeutic approach for the treatment of inflammatory pain.

Non-specific activity of (+/-)-CP-96,345 in models of pain and inflammation.

The non‐peptide NK1 receptor antagonist, CP‐96,345, and its 2R,3R enantiomer CP‐96,344, which is not an NK1 receptor antagonist (IC50 > 10 μm), were evaluated for antinociceptive and anti‐inflammatory activities in several classical models of pain and inflammation in the rat. Both CP‐96,345 and CP‐96,344 reduced carrageenin‐induced paw oedema and hyperalgesia, and attenuated the second phase of formalin‐induced paw licking with equal potency. These results indicate that NK1 antagonism is not responsible for the activity of (±)‐CP‐96,345 in the above animal models.

Effects of the selective EP4 antagonist, CJ‐023,423 on chronic inflammation and bone destruction in rat adjuvant‐induced arthritis

Prostaglandin E2 (PGE2) produced by cyclooxygenase (COX) is a potent pro‐inflammatory mediator. We have recently discovered CJ‐023,423, a highly selective antagonist of EP4 receptors, one of the PGE2 receptors. This agent is suitable for exploring the effects of blocking EP4 receptors following oral administration in rats. In this study, CJ‐023,423 was used in rats with adjuvant‐induced arthritis (AIA) to investigate the role of the EP4 receptor in chronic inflammation and bone destruction. These effects were compared with those of rofecoxib, a selective COX‐2 inhibitor. CJ‐023,423 had significant inhibitory effects on paw swelling, inflammatory biomarkers, synovial inflammation and bone destruction in AIA rats. In particular, the inhibitory effect on paw swelling in AIA rats was comparable to that of rofecoxib. These results suggest that PGE2 acting via the EP4 receptor is involved in the development of chronic inflammation and bone destruction, particularly with respect to oedema in AIA rats. This is the first study to confirm the in‐vivo effects of EP4 receptor blockade on inflammation and bone destruction in AIA rats with a small‐molecule compound.

Discovery of a novel COX-2 inhibitor as an orally potent anti-pyretic and anti-inflammatory drug: design, synthesis, and structure-activity relationship.

Cyclooxygenase (COX) has been considered as a significant pharmacological target because of its pivotal roles in the prostaglandin biosynthesis and following cascades that lead to various (patho)physiological effects. Non-steroidal anti-inflammatory drugs (NSAIDs) that suppress COX activities have been used clinically for the treatment of fever, inflammation, and pain; however, nonselective COX inhibitors exhibit serious side-effects such as gastrointestinal damage because of their inhibitory activities against COX-1. Thus, COX-1 is constitutive and expressed ubiquitously and serves a housekeeping role, while COX-2 is inducible or upregulated by inflammatory/injury stimuli such as interleukin-1β, tumor necrosis factor-α, and lipopolysaccharide in macrophage, monocyte, synovial, liver, and lung, and is associated with prostaglandin E₂ and prostacyclin production that evokes or sustains systemic/peripheral inflammatory symptoms. Also, hypersensitivity of aspirin is a significant concern clinically. Hence, design, synthesis, and structure-activity relationship of [2-{[(4-substituted)-pyridin-2-yl]carbonyl}-(6- or 5-substituted)-1H-indol-3-yl]acetic acid analogues were investigated to discover novel acid-type COX-2 inhibitor as an orally potent new-class anti-pyretic and anti-inflammatory drug. As significant findings, compounds 1-3 demonstrated potent COX-2 inhibitory activities with high selectivities for COX-2 over COX-1 in human cells or whole-blood in vitro, and demonstrated orally potent anti-pyretic activity against lipopolysaccharide-induced systemic-inflammatory fever model in F344 rats. Also compound 1 demonstrated orally potent anti-inflammatory activity against edema formation and a suppressive effect against PGE₂ production in carrageenan-induced peripheral-inflammation model on the paw of SD rats. These results suggest that compounds 1-3 are potential agents for the treatment of inflammatory disease and are useful for further pharmacological COX-2 inhibitor investigations.

Non-specific activity of (±)CP-96,345 in models of pain and inflammation

The non-peptide NK1 receptor antagonist, CP-96,345, and its 2R,3R enantiomer CP-96,344, which is not an NK1 receptor antagonist (IC50 > 10 microM), were evaluated for antinociceptive and anti-inflammatory activities in several classical models of pain and inflammation in the rat. Both CP-96,345 and CP-96,344 reduced carrageenin-induced paw oedema and hyperalgesia, and attenuated the second phase of formalin-induced paw licking with equal potency. These results indicate that NK1 antagonism is not responsible for the activity of (+/-)-CP-96,345 in the above animal models.

Characterization of binding affinity of CJ-023,423 for human prostanoid EP4 receptor.

In order to characterize the receptor binding pharmacology of CJ-023,423, a potent and selective EP4 antagonist, we performed a radioligand receptor binding assay under various assay conditions. An acidic (pH 6) and hypotonic buffer is a conventional, well-known buffer for prostaglandin E2 receptor binding assays. CJ-023,423 showed moderate binding affinity for human EP4 receptor under conventional buffer conditions. However, its binding affinity was greatly increased under neutral (pH 7.4) and isotonic buffer conditions. In this report, the binding mechanism between CJ-023,423 and human EP4 receptor is discussed based on the binding affinities determined under various assay conditions.

Design, synthesis and structure-activity relationship studies of novel and diverse cyclooxygenase-2 inhibitors as anti-inflammatory drugs.

Abstract Because of the pivotal role of cyclooxygenase (COX) in the inflammatory processes, non-steroidal anti-inflammatory drugs (NSAIDs) that suppress COX activities have been used clinically for the treatment of inflammatory diseases/syndromes; however, traditional NSAIDs exhibit serious side-effects such as gastrointestinal damage and hyper sensitivity owing to their COX-1 inhibition. Also, COX-2 inhibition-derived suppressive or preventive effects against initiation/proliferation/invasion/motility/recurrence/metastasis of various cancers/tumours such as colon, gastric, skin, lung, liver, pancreas, breast, prostate, cervical and ovarian cancers are significant. In this study, design, synthesis and structure–activity relationship (SAR) of various novel {2-[(2-, 3- and/or 4-substituted)-benzoyl, (bicyclic heterocycloalkanophenyl)carbonyl or cycloalkanecarbonyl]-(5- or 6-substituted)-1H-indol-3-yl}acetic acid analogues were investigated to seek and identify various chemotypes of potent and selective COX-2 inhibitors for the treatment of inflammatory diseases, resulting in the discovery of orally potent agents in the peripheral-inflammation model rats. The SARs and physicochemical properties for the analogues are described as significant findings. For graphical abstract: see Supplementary Material. (www.informahealthcare.com/enz)