Discovery of GSK143, a highly potent, selective and orally efficacious spleen tyrosine kinase inhibitor

The lead optimisation of the diaminopyrimidine carboxamide series of spleen tyrosine kinase inhibitors is described. The medicinal chemistry strategy was focused on optimising the human whole blood activity whilst achieving a sufficient margin over liability kinases and hERG activity. GSK143 is a potent and highly selective SYK inhibitor showing good efficacy in the rat Arthus model.

Thiazoles and thiopyridines: novel series of high affinity h5HT7 ligands

A series of thiazole based 5HT(7) ligands has been identified from screening. Optimisation of the pendent aryl group and modification of the core gave a related series of high affinity, selective thiopyridine based 5HT(7) ligands, the most active of which behaves as a partial agonist.

Novel N1-(benzyl)cinnamamidine derived NR2B subtype-selective NMDA receptor antagonists

Novel (E)-N(1)-(benzyl)cinnamamidines were prepared and evaluated as NR2B subtype NMDA receptor ligands. Excellent affinity was achieved by appropriate substitution of either phenyl ring. The 2-methoxybenzyl compound 1h had approximately 1,000-fold lower IC(50) in NR2B than NR2A-containing cells. Replacement of the styryl unit by 2-naphthyl was well tolerated.

Orally efficacious NR2B-selective NMDA receptor antagonists

A novel series of benzamidines was synthesized and shown to exhibit NR2B-subtype selective NMDA antagonist activity. Compound 31 is orally active in a carrageenan-induced rat hyperalgesia model of pain and shows no motor coordination side effects.

Stereocontrolled syntheses of epimeric 3-aryl-6-phenyl-1-oxa-7-azaspiro(4.5)decane NK-1 receptor antagonist precursors

[structure: see text]. Complementary stereoselective syntheses of individual C3 epimers of the NK-1 receptor antagonist precursor 1 have been developed. Both diastereomers were derived from the common intermediate 3; introduction of the 3S stereocenter in 1a was achieved through hydrogenation of an arylated dihydrofuran, whereas the corresponding stereogenic center in 1b was installed using a stereo- and regioselective alkene hydroarylation.

Synthesis and sar of 2- and 3-substituted 7-azaindoles as potential dopamine D4 ligands

7-azaindole compounds bearing a cyclic amine moiety linked by a one or two carbon chain attached at the 2- or 3-position were synthesised and evaluated as potential dopamine D4 ligands. Highest affinity and selectivity for the D4 receptor resided in the 3-aminomethyl-7-azaindole series.

Identification and pharmacological characterization of [125I]L-750,667, a novel radioligand for the dopamine D4 receptor

We identified a novel azaindole derivative, L-750,667, that has high affinity (Ki = 0.51 nM) and >2000-fold selectivity for D4 dopamine receptors compared with its activity at D2 and D3 dopamine receptors. L-750,667 had little affinity for rat D1/D5 dopamine receptors, sigma binding sites, or 5-hydroxytryptamine1A or 5-hydroxytryptamine2 receptors. In functional studies, L-750,667 exhibited high affinity antagonist activity at D4 receptors, reversing dopamine (1 microM)-induced inhibition of cAMP accumulation in human embryonic kidney (HEK) cells expressing the human D4 receptor (hD4 HEK) with an EC50 value of 80 nM. The radioiodinated form of L-750,667 bound specifically to the human dopamine D4 receptor expressed in HEK cells and saturation analysis revealed a single high affinity binding site for [125I]L-750,667 (Kd = 0.16 +/- 0.06 nM). The maximum number of binding sites (Bmax) estimated using [125I]L-750,667 in hD4 HEK cells was 251 +/- 71 fmol/mg, which correlated well with the Bmax value determined using [3H]spiperone (227 +/- 83 fmol/mg) in the same membrane preparations. The pharmacological profile of [125I]L-750,667 binding to hD4 HEK cells was evaluated using known dopamine receptor agonists and antagonists. The rank order of potencies for dopamine receptor agonists was dopamine > quinpirole > 6,7-aminodihydroxytetralin > 5,6-aminodihydroxytetralin. Dopamine receptor antagonists also showed high affinity, with a rank order of haloperidol > chlorpromazine > domperidone > (+)-butaclamol > (-)-sulpiride = (+)-sulpiride > (+)-SCH23390 > (-)-butaclamol. [125I]L-750,667, bound to D4 receptors in a stereoselective manner with (+)-butaclamol showing higher activity than its respective enantiomer (-)-butaclamol. These results show that [125I]L-750,667 is a novel, highly selective radioligand for dopamine D4 receptors and may be used to investigate the dopamine D4 receptor population in the central nervous system.

Cyclic peptides as selective tachykinin antagonists

Twenty homodetic cyclic peptides based on the C-terminal sequence of substance P were prepared (Table I) by a combination of solid-phase techniques and cyclizations using azide coupling procedures. Incorporation of dipeptide mimics based on substituted gamma-lactams were used in some cases to restrict their conformational mobility. Five of these cyclic peptides were shown to have high tachykinin antagonist activity (pA2 > 6) at NK-2 receptors (rat vas deferens). The two most potent of this series, XVII, cyclo(Gln-Trp-Phe-Gly-Leu-Met) (pA2 = 8.1), and I cyclo(Gln-Trp-Phe(R)Gly[ANC-2]Leu-Met) (pA2 = 6.7), were selective for NK-2 receptors compared with the other tachykinin receptors (Table II).

Kynurenic acid derivatives. Structure-activity relationships for excitatory amino acid antagonism and identification of potent and selective antagonists at the glycine site on the N-methyl-D-aspartate receptor

Derivatives of the nonselective excitatory amino acid antagonist kynurenic acid (4-oxo-1,4-dihydroquinoline-2-carboxylic acid, 1) have been synthesized and evaluated for in vitro antagonist activity at the excitatory amino acid receptors sensitive to N-methyl-D-aspartic acid (NMDA), quisqualic acid (QUIS or AMPA), and kainic acid (KA). Introduction of substituents at the 5-, 7-, and 5,7-positions resulted in analogues having selective NMDA antagonist action, as a result of blockade of the glycine modulatory (or coagonist) site on the NMDA receptor. Regression analysis suggested a requirement for optimally sized, hydrophobic 5- and 7-substituents, with bulk tolerance being greater at the 5-position. Optimization led to the 5-iodo-7-chloro derivative (53), which is the most potent and selective glycine/NMDA antagonist to date (IC50 vs [3H]glycine binding, 32 nM; IC50's for other excitatory amino acid receptor sites, greater than 100 microM). Substitution of 1 at the 6-position resulted in compounds having selective non-NMDA antagonism and 8-substituted compounds were inactive at all receptors. The retention of glycine/NMDA antagonist activity in heterocyclic ring modified analogues, such as the oxanilide 69 and the 2-carboxybenzimidazole 70, suggests that the 4-oxo tautomer of 1 and its derivatives is required for activity. Structurally related quinoxaline-2,3-diones are also glycine/NMDA antagonists, but are not selective and are less potent than the 1 derivatives, and additionally show different structure-activity requirements for aromatic ring substitution. On the basis of these results, a model accounting for glycine receptor binding of the 1 derived antagonists is proposed, comprising (a) size-limited, hydrophobic binding of the benzene ring, (b) hydrogen-bond acceptance by the 4-oxo group, (c) hydrogen-bond donation by the 1-amino group, and (d) a Coulombic attraction of the 2-carboxylate. The model can also account for the binding of quinoxaline-2,3-diones, quinoxalic acids, and 2-carboxybenzimidazoles.

Effects of tachykinins on inositol phospholipid hydrolysis in slices of hamster urinary bladder

Tachykinin-stimulated inositol phospholipid hydrolysis was examined in slices of hamster urinary bladder. In the presence of lithium, to inhibit inositol monophosphatase activity, substance P, eledoisin and related tachykinins induced large, dose-dependent increases in [3H]-inositol monophosphate accumulation. The responses to substance P and eledoisin were not antagonized by the cholinoceptor antagonist, atropine. The rank order of potency for various tachykinins was kassinin greater than neurokinin A greater than neurokinin B greater than eledoisin greater than physaelamin greater than substance P greater than substance P methyl ester. The synthetic analogue [p-Glu6, D-Pro9]SP (6-11) was considerably more potent than its L-prolyl stereoisomer at stimulating inositol phospholipid hydrolysis. These results suggest that in the hamster urinary bladder, tachykinin-induced inositol phospholipid breakdown is mediated via tachykinin receptors of the SP-E type, as opposed to the SP-P type.

Conformationally constrained tachykinin analogs which are selective ligands for the eledoisin binding site

We have prepared a series of conformationally constrained hexapeptide analogs of substance P which are 500-1500-fold more potent as inhibitors of 125I-labeled Bolton Hunter-conjugated eledoisin binding to rat brain cortex membranes than as inhibitors of 125I-labeled Bolton Hunter-conjugated substance P binding. These analogs stimulate guinea pig ileum contraction (ED50 1-16 nM) and stimulate rat vas deferens contraction (ED50 2-4 microM). However, these peptides are poor stimulators of rat salivation (greater than 40 nmol/100 g body weight). Thus, based on both their receptor potency and pharmacological potency, these peptides are potent and selective tachykinin analogs. These data indicate that a specific carboxyl-terminal conformation is recognized by the 125I-labeled Bolton Hunter-conjugated eledoisin binding site and that this conformation is different from the conformation recognized by the 125I-labeled Bolton Hunter-conjugated substance P binding site. Hexapeptides containing phenylalanine, isoleucine, and valine identical with the carboxyl-terminal sequences of substance P, eledoisin, and neurokinin B, respectively, were nearly equipotent as inhibitors of 125I-labeled Bolton Hunter-conjugated eledoisin binding. The valine analog was only approximately 5-fold less potent than the isoleucine and phenylalanine analogs as an inhibitor of 125I-labeled Bolton Hunter-conjugated substance P binding. Thus, unknown determinants in the amino-terminal sequences of substance P must strongly contribute to the carboxyl-terminal peptide selectivity and conformation. The contraction of guinea pig ileum induced by one of the conformationally constrained analogs is attenuated by pretreatment of the tissue with atropine (2 microM), while that induced by substance P methyl ester, a selective inhibitor of 125I-labeled Bolton Hunter-conjugated substance P binding, is not. Thus, the constrained analog has a higher affinity for the tachykinin receptors in the guinea pig myenteric plexus which are responsible for acetylcholine release than for the tachykinin receptors present on the smooth muscle cells.