A small, nonpeptidyl mimic of granulocyte-colony-stimulating factor [see commetns].

A nonpeptidyl small molecule SB 247464, capable of activating granulocyte-colony-stimulating factor (G-CSF) signal transduction pathways, was identified in a high-throughput assay in cultured cells. Like G-CSF, SB 247464 induced tyrosine phosphorylation of multiple signaling proteins and stimulated primary murine bone marrow cells to form granulocytic colonies in vitro. It also elevated peripheral blood neutrophil counts in mice. The extracellular domain of the murine G-CSF receptor was required for the activity of SB 247464, suggesting that the compound acts by oligomerizing receptor chains. The results indicate that a small molecule can activate a receptor that normally binds a relatively large protein ligand.

Synthesis and LTD4 antagonist activity of 2-norleukotriene analogues.

A series of structural analogues of 4(R)-hydroxy-5(S)-cysteinylglycyl-6(Z)-nonadecenoic acid [4R,5S,6Z)-2-nor-LTD1 (10b), SK&F 101132) has been synthesized and pharmacologically characterized. (4R,5S,6Z)-2-nor-LTD1 significantly antagonized LTD4-induced contractile responses on isolated guinea pig trachea. The cis double-bond geometry appears to be critical for antagonist activity, whereas the trans isomer 17 exhibited weak contractile activity. Replacement of the cysteinylglycyl moiety with cysteine afforded 20, which retained significant antagonist activity, while lengthening or shortening the lipid tail by five methylene groups resulted in complete loss of activity. The eicosanoid amide 15, glycinamide 14, and C-1 carbinol 18 analogues all possessed antagonist activity, whereas the diol derivative 19 exhibited increased intrinsic agonist activity.

Synthesis and LTB4 receptor antagonist activities of the naturally occurring LTB4 receptor antagonist Leucettamine A and related analogues.

The isolation and structure determination of the naturally occurring LTB4 receptor antagonist Leucettamine A (1) was recently reported. Herein we describe the synthesis of this natural product, the preparation of several analogues, and their effectiveness as antagonists of [3H]LTB4 binding to intact human U-937 cells. Total synthesis of Leucettamine A (1) is achieved by a convergent route which takes advantage of the elements of symmetry within the molecule. Syntheses of analogues of 1, which lacked the same degree of symmetry, are achieved by a different approach starting from alpha-amino acids. The natural product 1 inhibits [3H]LTB4 binding to its receptors on intact human U-937 cells with a Ki = 3.5 +/- 0.8 microM and is devoid of measurable agonist activity at the concentrations tested. 2-Amino imidazole analogues of 1 lacking the dioxolane groups were prepared. Generally these are significantly less potent than 1. However, one (26), designed on the basis of a putative structural overlay with LTB4, demonstrated potency comparable to that of the natural product (Ki = 2.4 +/- 0.2 microM).

Imidodisulfamides. 2. Substituted 1,2,3,4-tetrahydroisoquinolinylsulfonic imides as antagonists of slow-reacting substance of anaphylaxis.

As part of a study of the influence of structural modifications of N',N'-bis(aralkyl)imidodisulfamides on their ability to selectively antagonize SRS-A activity, a few conformationally constrained structures were examined. Among these derivatives having a conformationally restricted alkylene side chain, substituted 1,2,3,4-tetrahydroisoquinolinylsulfonic imides produced optimum SRS-A antagonist activity and selectivity. These compounds were tested for antagonism of partially purified SRS-A induced contractions of isolated guinea pig ileum. In this series of tetrahydroisoquinolines, the effect of aromatic ring substitution, as well as substitution and variation of the size of the heterocyclic ring on SRS-A antagonist activity and selectivity, was studied.

Imidodisulfamides. 1. A novel class of antagonists of slow-reacting substance of anaphylaxis.

A series of N',N"-bis(aryl)- and N',N"-(aralkyl)imidodisulfamides was prepared and evaluated as antagonists of slow-reacting substance of anaphylaxis (SRS-A) induced contractions of isolated guinea pig ileum. Some of these compounds, notably N',N"-bis(4-phenylbutyl)-, N',N"-bis[2-(4-chlorophenyl)ethyl]-, and N',N"-bis[2-(4-bromophenyl)ethyl]imidodisulfamides (16, 22, and 26), were moderately potent and selective antagonists of SRS-A. The influence of lipophilic (pi) and electronic (sigma) factors on SRS-A antagonist activity appears to be of considerable importance to the derivation of potent and selective SRS-A antagonists.

Synthesis and structure-activity relationship studies of a series of 5-aryl-4,6-dithianonanedioic acids and related compounds: a novel class of leukotriene antagonists.

A series of 5-alkynyl- and 5-aryl-4,6-dithianonanedioic acids and related compounds has been prepared for evaluation of leukotriene antagonist activity. The alkynyl compounds were prepared by thioacetal exchange from the corresponding acetylenic acetals. The aryl derivatives were synthesized from the appropriate benzaldehydes, most of which were prepared by one of three general routes: Meyers' oxazolin method, a palladium coupling procedure, and a hydroxybenzaldehyde alkylation. The analogues were examined in vitro for their ability to antagonize an LTD4-induced contraction of isolated guinea pig tracheal smooth muscle and to compete with [3H]LTD4 for receptor sites on guinea pig lung membrane. A number of structure-activity relationships have emerged from this study. There is an optimal chain length of 10-12 atoms (or its equivalent) in the lipid tail and two methylenes in the polar region. In the aromatic series, the ortho- and meta-substituted compounds have comparable activity, whereas the para derivatives are inactive. Substitution in the aromatic ring and lipid tail is generally well tolerated, with the terminal phenyl (6) and acetylene (33) analogues having especially good activity. Conformational restriction of either the polar region or lipid tail produced compounds devoid of activity. A number of selected analogues were also evaluated in vivo as antagonists of LTD4-induced bronchoconstriction in the guinea pig. The data established these compounds as a novel class of leukotriene antagonists with potential utility for the treatment of asthma and other immediate hypersensitivity diseases.

Rational design, synthesis, and crystallographic analysis of a hydroxyethylene-based HIV-1 protease inhibitor containing a heterocyclic P1'--P2' amide bond isostere.

The rational design and synthesis of a highly potent inhibitor of HIV-1 protease have been accomplished. The inhibitor, SB 206343, is based on a model derived from the structure of the MVT-101/HIV-1 protease complex and contains a 4(5)-acylimidazole ring as an isosteric replacement for the P1'--P2' amide bond. It is a competitive inhibitor with an apparent inhibition constant of 0.6 nM at pH 6.0. The three-dimensional structure of SB 206343 bound in the active site of HIV-1 protease has been determined at 2.3 A resolution by X-ray diffraction techniques and refined to a crystallographic discrepancy factor, R (= sigma parallel Fo magnitude of/Fc parallel/sigma magnitude of), of 0.194. The inhibitor is held in the enzyme by a set of hydrophobic and polar interactions. N-3 of the imidazole ring participates in a novel hydrogen-bonding interaction with the bound water molecule, demonstrating the effectiveness of the imidazole ring as an isosteric replacement for the P1'--P2' amide bond in hydroxyethylene-based HIV-1 protease inhibitors. Also present are hydrogen-bonding interactions between N-1 of the imidazole ring and the carbonyl of Gly-127 as well as between the imidazole acyl carbonyl oxygen and the amide nitrogen of Asp-129, exemplifying the peptidomimetic nature of the 4(5)-acylimidazole isostere. All of these interactions are in qualitative agreement with those predicted by the model.

1,4-Cyclohexanecarboxylates: potent and selective inhibitors of phosophodiesterase 4 for the treatment of asthma.

Evaluation of a variety of PDE4 inhibitors in a series of cellular and in vivo assays suggested a strategy to improve the therapeutic index of PDE4 inhibitors by increasing their selectivity for the ability to inhibit PDE4 catalytic activity versus the ability to compete for high affinity [3H]rolipram-binding sites in the central nervous system. Use of this strategy led ultimately to the identification of cis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxyl ic acid (1, SB 207499, Ariflo), a potent second-generation inhibitor of PDE4 with a decreased potential for side effects versus the archetypic first generation inhibitor, (R)-rolipram.

Characterization of the conjunctival vasopermeability response to leukotrienes and their involvement in immediate hypersensitivity.

The microvascular permeability response of the guinea pig conjunctiva to sulfidopeptide leukotrienes (LTs) was quantified as extravasation of radiolabeled bovine serum albumin. The LTs were potent inducers of increased microvascular permeability, with relative potencies LTE4 greater than or equal to LTD4 greater than LTC4. The response to LTs was unaffected by indomethacin or a pyrilamine/cimetidine combination, but the LT antagonists FPL 55712 and SKF 102922 significantly inhibited the response to LTC4, LTD4 and LTE4. In guinea pigs actively sensitized to ovalbumin, topical ocular administration of ovalbumin markedly increased conjunctival microvascular permeability; this response was reduced by approximately 50% following histaminergic blockade by pyrilamine/cimetidine. FPL 55712 and SKF 102922 and the 5-lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) had no effect on the response to antigen when used alone. However, each agent significantly reduced the non-histaminergic component of the response when given in conjunction with pyrilamine/cimetidine. Thus, it appears that the immediate hypersensitivity response in guinea pig conjunctiva has a possible non-histaminergic component which is at least partly mediated by LTs.

SK&F 86002: a structurally novel anti-inflammatory agent that inhibits lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid.

The effects of SK&F 86002 [5-(4-pyridyl)-6 (4-fluorophenyl)-2,3-dihydroimidazo (2,1-b) thiazole] on the generation of eicosanoids in vitro and on inflammatory responses in vivo are described and compared to other non-steroidal anti-inflammatory drugs. SK&F 86002 inhibited prostaglandin H2 (PGH2) synthase activity (IC50 120 microM) as well as prostanoid production by rat basophilic leukemia (RBL-1) cells (IC50 70 microM) and its sonicate (IC50 100 microM) and human monocytes (IC50 1 microM). In addition, SK&F 86002 inhibited the generation of dihydroxyeicosatetraenoic acid (diHETE) and 5-hydroxyeicosatetraenoic acid (5-HETE) by a high speed supernatant fraction of RBL-1 cells (IC50 10 microM). Cellular production of 5-lipoxygenase products was inhibited by SK&F 86002 as measured by leukotriene B4 (LTB4) generation from human neutrophils (IC50 20 microM), leukotriene C4 (LTC4) generation by human monocytes (IC50 20 microM), and 5-HETE production by RBL-1 cells (IC50 40 microM). The in vivo profile of anti-inflammatory activity of SK&F 86002 supports the dual inhibition of arachidonate metabolism as indicated by its activity in inflammation models that are insensitive to selective cyclooxygenase inhibitors. The responses of arachidonic-acid-induced edema in the mouse ear and rat paw, as well as the cell infiltration induced by carrageenan in the mouse peritoneum and by arachidonic acid in the rat air pouch, were inhibited by SK&F 86002 and phenidone but not by the selective cyclooxygenase inhibitors naproxen and indomethacin.

Interactive effects of peptidoleukotrienes and histamine on microvascular permeability and their involvement in experimental cutaneous and conjunctival immediate hypersensitivity.

The involvement of peptidoleukotrienes (LTs) in mediating the increase in microvascular permeability associated with experimental cutaneous immediate hypersensitivity was studied by examining the effect of SK&F 104353, a potent and selective LT-antagonist, on the response evoked by graded, intradermal injections of antigen. SK&F 104353, employed at doses that profoundly blocked LTC4, LTD4 and LTE4 responses, significantly reduced the response produced by experimental cutaneous immediate hypersensitivity. The response to the lowest antigen dose (0.1 microgram) was, however, entirely insusceptible to SK&F 104353. The effect of SK&F 104353 was also examined in combination with a pyrilamine-cimetidine dosing regimen sufficient to remove the histaminergic component of cutaneous immediate hypersensitivity. The non-histaminergic component associated with higher antigen doses (10 and 100 micrograms) was significantly reduced but not abolished by SK&F 104353; the non-histaminergic component associated with low antigen doses (0.1 and 1 microgram) was not susceptible to SK&F 104353. Thus, the increase in cutaneous microvascular permeability evoked by immediate hypersensitivity appears to comprise three components: (1) A histaminergic response apparent for all antigen doses; (2) a LT-mediated component which is manifest in response to high antigen doses; (3) a third, unidentified component that is present for the entire antigen dose-range but contributes less to the overall response when high antigen doses are used. A distinct non-histaminergic, non-leukotriene mediated component was not a feature of conjunctival immediate hypersensitivity. SK&F 104353 administered in combinatio with pyrilamine-cimetidine virtually abolished the response with a small residual remaining only for the highest antigen dose. In further contrast to cutaneous immediate hypersensitivity, SK&F 104353 alone was comparatively ineffective in type 1 allergic conjunctivitis. This difference in susceptibility to SK&F 104353 appears to reflect the type of histamine-LTD4 interactive effect on microvascular permeability. Histamine and LTD4 were additive in terms of cutaneous microvascular permeability. In the conjunctiva, histamine and LTD4 appeared mutually exclusive in that the level of response produced by the combination tended not to exceed that of the single component which caused the greater effect.

SK&F 88046: a unique pharmacologic antagonist of bronchoconstriction induced by leukotriene D4, thromboxane and prostaglandins F2 alpha and D2 in vitro.

SK&F 88046, an imidodisulfamide initially reported as an end organ leukotriene (LT)D4 antagonist on guinea-pig lung parenchyma (Gleason et al., 1982), was studied further in order to elucidate its mechanism of action. The LTD4-induced contraction of the guinea-pig lung parenchyma, which occurs via both a direct action and an indirect, thromboxane (Tx)-dependent pathway (Weichman et al., 1982), was antagonized by SK&F 88046 and FPL 55712. SK&F 88046 was not acting on the lung parenchyma as a result of antagonism of cyclooxygenase or Tx synthetase, as SK&F 88046 did not block the LTD4-induced generation of TxB2 from the parenchyma. In contrast, the LTD4-induced contraction of the guinea-pig trachea, which is only directly mediated, was antagonized by FPL 55712 but not by SK&F 88046. However, SK&F 88046 did antagonize the contractions elicited by carbocyclic TxA2, a stable Tx analog, as well as those elicited by prostaglandins F2 alpha and D2, but not those elicited by histamine, carbachol or KCI. FPL 55712 weakly antagonized the actions of carbocyclic TxA2, but not the contractions induced by the other agonists. These results demonstrate that SK&F 88046 is an antagonist of the indirect, Tx-dependent component of LTD4 action in the guinea pig, presumably via antagonism of Tx on the end organ. These results provide additional evidence that LTD4 can exert its bronchoconstrictive actions via two mechanisms, a direct pathway and an indirect, Tx-dependent pathway.

Antagonism of the cardiac effects of leukotriene C4 by compound SKF 88046: dissociation of effects on contractility and coronary flow.

In the present study, we evaluated the properties of an imidodisulfamide derivative, compound SKF 88046, as an antagonist of the cardiac effects of leukotrienes (LTs). LTC4 (0.1-100 ng) caused dose-related decreases in the contractile force and coronary flow rate of the isolated guinea pig heart. SKF 88046 and the prototypic anti-SRS (anti-slow reacting substance) compound FPL 55712 (4.8 X 10(-7) M) were equieffective in antagonizing the LTC4-induced decrease in coronary flow. On the other hand, SKF 88046 was more potent than FPL 55712 in antagonizing the negative inotropic effect of LTC4. Our findings demonstrate that SKF 88046 is an effective antagonist of the coronary constricting and myocardial depressant effects of LTC4, but that SKF 88046 preferentially antagonizes the negative inotropic effect of LTC4. This favors the hypothesis formulated by others that LT effects may be mediated by multiple receptors.

Effects of the leukotrienes on the vasculature and blood pressure of different species.

We have examined in these studies the contractile activity of leukotrienes (LTs) C4, D4 and E4 on vascular ring segments obtained from several species and demonstrated that the distal segment of the guinea-pig pulmonary artery is a useful and convenient preparation for the study of LT vascular pharmacology. In vitro, LTs had no effect on aortic rings from rats, rabbits or guinea pigs. In contrast, LTs produced significant contraction of the distal portion of the pulmonary artery of the guinea pig. The rank of the contractile effects of LT was LTD4 = LTC4, greater than LTE4, with ED40 (molar) values of 6.1 X 10(-9), 1 X 10(-8) and 1.4 X 10(-6), respectively. Norepinephrine, serotonin and histamine were at least 50- to 100-fold less potent. Partial tolerance developed to the contractile action of LT in vitro. Vascular contraction produced by LTD4 was antagonized by a selective LT antagonist. No evidence for a relaxant action of LT was obtained as LTD4 and LTC4 failed to relax rabbit aorta or guinea-pig pulmonary arterial rings. The effects of LTD4 on hemodynamics in vivo were studied in anesthetized guinea pigs. LTD4 (0.1-10 micrograms/kg) significantly decreased cardiac output but increased pulmonary vascular resistance. To assess the activity of LTs in another species, the in vitro contractile response of monkey pulmonary artery was determined. LTD4 was also a potent contractile agent in this species with significant contraction obtained at 1 X 10(-9) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukotriene D4 receptor-mediated synthesis and release of arachidonic acid metabolites in guinea pig lung: induction of thromboxane and prostacyclin biosynthesis by leukotriene D4.

The effects of the peptidoleukotrienes C4 (LTC4), D4 (LTD4), E4 (LTE4) and a series agonists and antagonists on arachidonic acid metabolism were characterized in minced guinea pig lung. In response to LTD4, guinea pig lung utilized and converted the endogenous arachidonic acid into a variety of cyclooxygenase metabolites [prostaglandins (PGs) E2, F2 alpha, 6-keto-F1 alpha and thromboxane (Tx) B2] and lipoxygenase metabolites (5,12-dihydroxy-6,8,11,14-eicosatetraneoic acid and 5,15-dihydroxy-5,9,11,13-eicosatetraneoic acid). Using radioimmunoassays, the stable, pharmacologically important metabolites of the cyclooxygenase pathway, 6-keto-PGF1 alpha and TxB2, were quantitated. LTD4, LTE4 and several synthetic agonists induced dose-dependent synthesis and release of TxB2 and 6-keto-PGF1 alpha. Agonist-induced synthesis and release of 6-keto-PGF1 alpha and TxB2 was time-dependent and was maximal after 10 to 12 min of incubation. The slow-reacting substance of anaphylaxis antagonist, FPL 55712, and the newly reported dithioacetal LTD4 receptor antagonists (SKF 102922 and SKF 102081) did not induce synthesis and release of TxB2 and 6-keto-PGF1 alpha in concentrations that blocked the agonist-induced smooth muscle contraction. Preincubation with these antagonists inhibited the synthesis and release of prostanoids induced by LTD4 in the guinea pig lung. Islet activating protein, which inactivates the inhibitory guanine nucleotide binding protein (Gi protein), partially inhibited the agonist-induced synthesis and release of prostanoids. Furthermore, the receptor binding affinities and/or the myotonic activities of the LTD4 agonists correlated linearly with the agonist-induced prostanoid synthesis and release effect.(ABSTRACT TRUNCATED AT 250 WORDS)