James Jakway

Pharmacological Characterization of Sch527123, a Potent Allosteric CXCR1/CXCR2 Antagonist

In neutrophils, growth-related protein-α (CXCL1) and interleukin-8 (CXCL8), are potent chemoattractants (Cytokine 14:27–36, 2001; Biochemistry 42:2874–2886, 2003) and can stimulate myeloperoxidase release via activation of the G protein-coupled receptors CXCR1 and CXCR2. The role of CXCR1 and CXCR2 in the pathogenesis of inflammatory responses has encouraged the development of small molecule antagonists for these receptors. The data presented herein describe the pharmacology of 2-hydroxy-N,N-dimethyl-3-{2-[[(R)-1-(5-methyl-furan-2-yl)-propyl]amino]-3,4-dioxo-cyclobut-1-enylamino}-benzamide (Sch527123), a novel antagonist of both CXCR1 and CXCR2. Sch527123 inhibited chemokine binding to (and activation of) these receptors in an insurmountable manner and, as such, is categorized as an allosteric antagonist. Sch527123 inhibited neutrophil chemotaxis and myeloperoxidase release in response to CXCL1 and CXCL8 but had no effect on the response of these cells to C5a or formyl-methionyl-leucyl-phenylalanine. The pharmacological specificity of Sch527123 was confirmed by testing in a diversity profile against a panel of enzymes, channels, and receptors. To measure compound affinity, we characterized [3H]Sch527123 in both equilibrium and nonequilibrium binding analyses. Sch527123 binding to CXCR1 and CXCR2 was both saturable and reversible. Although Sch527123 bound to CXCR1 with good affinity (Kd = 3.9 ± 0.3 nM), the compound is CXCR2-selective (Kd = 0.049 ± 0.004 nM). Taken together, our data show that Sch527123 represents a novel, potent, and specific CXCR2 antagonist with potential therapeutic utility in a variety of inflammatory conditions.

Receptor reserve analysis of the human CCR3 receptor in eosinophils and CCR3-transfected cells.

A novel pharmacological study of CCR3 receptor reserve in a CCR3‐transfected cell (CREM3) and human eosinophils was done; functional responses measured were increases in intracellular calcium and chemotaxis. Eotaxin, eotaxin‐2, monocyte chemoattractant protein‐4 (MCP‐4), RANTES, and MCP‐3 induced similar maximal eosinophil chemotaxis, whereas MCP‐3 and RANTES induced submaximal calcium responses in eosinophils compared to eotaxin, MCP‐4, and eotaxin‐2. This suggested a receptor reserve in the chemotaxis response. Receptor reserve was quantitated for eotaxin. Occupancy of all CCR3 receptors was required for a maximal calcium response in both CREM3 and eosinophils (reserve = 1.0 or 0.17, respectively); the stimulus‐calcium response relationship was linear, indicating no receptor reserve. In contrast, in eosinophils a large receptor reserve (6.5) was found for chemotaxis, where occupancy of 15% receptors drove half‐maximal responses. These studies indicate that CCR3 interacts with G‐proteins that are poorly coupled to the calcium response, whereas coupling efficiency and/or amplification to the chemotaxis apparatus in human eosinophils is significantly greater. J. Leukoc. Biol. 67: 441–447; 2000.

Synthesis and structure-activity relationships of heteroaryl substituted-3,4-diamino-3-cyclobut-3-ene-1,2-dione CXCR2/CXCR1 receptor antagonists.

Comprehensive SAR studies were undertaken in the 3,4-diaminocyclobut-3-ene-1,2-dione class of CXCR2/CXCR1 receptor antagonists to explore the role of the heterocycle on chemokine receptor binding affinities, functional activity, as well as oral exposure in rat. The nature of the heterocycle as well as the requisite substitution pattern around the heterocycle was shown to have a dramatic effect on the overall biological profile of this class of compounds. The furyl class, particularly the 4-halo adducts, was found to possess superior binding affinities for both the CXCR2 and CXCR1 receptors, functional activity, as well as oral exposure in rat versus other heterocyclic derivatives.

Postjunctional α2C-adrenoceptor contractility in human saphenous vein

Abstract The postjunctional α 2 -adrenoceptor-mediated contractility was characterized in human saphenous vein derived from coronary artery bypass graft surgery. Human saphenous vein contracted to α 2 -adrenoceptor selective agonists BHT-920 (5,6,7,8-Tetrahydro-6-(2-propenyl)-4 H -thiazolo[4,5-d]azepin-2-amine dihydrochloride; p D 2 =6.7±0.1) and UK 14,304 (5-Bromo-6-(2-imidazolin-2-ylamino)quinoxaline; p D 2 =7.2±0.1). BHT-920-induced contractions were inhibited by the α 2 -adrenoceptor antagonist yohimbine (17-Hydroxy-yohimban-16-carboxylic acid methyl ester hydrochloride; p A 2 =8.7±0.5), but not by the α 1 -adrenoceptor antagonist prazosin (1-[4-Amino-6,7-dimethoxy-2-quinazolinyl]-4-[2-furanylcarbonyl]-piperazine hydrochloride; 300 nM). In contrast, prazosin (p K b =7.9±0.2) potently antagonized contractions elicited by the α 1 -adrenoceptor agonist phenylephrine (( R )-3-Hydroxy-α-[(methylamino)methyl] benzenemethanol hydrochloride; p D 2 =4.9±0.1), indicating that both α 2 - and α 1 -adrenoceptor evoke human saphenous vein contractions. Functional antagonist activity estimates (p A 2 or p K b ) obtained for the α-adrenoceptor antagonists ARC 239 (2-[2-(4-(2-Methoxyphenyl)piperazin-1-yl)ethyl]-4,4-dimethyl-1,3-(2 H ,4 H )-isoquinolindione dihydrochloride), WB 4101 (2-(2,6-Dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane hydrochloride) and HV 723 (α-ethyl-3,4,5-trimethoxy-α-(3-((2-(2-methoxyphenoxy) ethyl)amino)propyl)benzeneacetonitrile) against BHT-920-induced human saphenous vein contractions were 7.0±0.6, 8.3±0.6 and 7.7±0.3, respectively. The α 2 -adrenoceptor subtype affinities (p K i ) obtained in recombinant human α 2A -, α 2B - and α 2C -adrenoceptor competition binding assays were 8.6, 8.3 and 8.6 for yohimbine; 6.3, 8.4 and 7.0 for ARC 239; 8.4, 7.5 and 8.4 for WB 4101 and 7.5, 7.4 and 7.9 for HV 723, respectively. Taken together, the binding and functional antagonist activity estimates obtained in these investigations indicate that α 2C -adrenoceptor is the predominant postjunctional α 2 -adrenoceptor subtype in human saphenous vein.

Synthesis of dibenzo[a,d]cycloheptanes as cytokine biosynthesis inhibitors

Abstract 2-[10,11-Dihydro-5-ethoxy-5 H -dibenzo[a,d]cyclohepten-5-yl]-N,N-dimethyl-ethanamine (1) has been found to possess anticytokine activity. The synthesis and structure-activity relationship study of a series of analogues are reported.