The discovery and SAR of a new series of substituted 8-arylquinoline PDE4 inhibitors are herein described. This work has led to the identification of several compounds with excellent in vitro and in vivo profiles, including a good therapeutic window of emesis to efficacy in several animal models. Typical optimized compounds from this series are potent inhibitors of PDE4 (IC(50)<1nM) and also of LPS-induced TNF-alpha release in human whole blood (IC(50)<0.5microM). The same compounds are potent inhibitors of ovalbumin-induced bronchoconstriction in conscious guinea pigs (EC(50)<0.1mg/kg ip) but require a dose of about 10mg/kg po in the squirrel monkey to produce an emetic response. From this series of compounds, 23a (L-454,560) was identified as an optimized compound.

A detailed SAR study directed toward the optimization of pharmacokinetic parameters for analogues of L-791,943 is reported. The introduction of a soft metabolic site on this structure permitted the identification of L-826,141 as a potent phosphodiesterase type 4 (PDE4) inhibitor that is well absorbed and that presents a shorter half-life than L-791,943 in a variety of animal species. The efficacy of L-826,141 is also demonstrated in different in vivo models.

The synthesis and the biological evaluation of new potent phosphodiesterase type 4 (PDE4) inhibitors are presented. This new series was elaborated by replacement of the metabolically resistant phenyl hexafluorocarbinol of L-791,943 (1) by a substituted aminopyridine residue. The structure-activity relationship of N-substitution on 3 led to the identification of (-)-3n which exhibited a good PDE4 inhibitor activity (HWB-TNFalpha=0.12 microM) and an improved pharmacokinetic profile over L-791,943 (rat t(1/2)=2 h). (-)-3n was well tolerated in ferret with an emetic threshold of 30 mg/kg (po) and was found to be active in the ovalbumin-induced bronchoconstriction model in guinea pig (54%, 0.1 mg/kg, ip) as well as the ascaris-induced bronchoconstriction model in sheep (64%/97%, early/late, 0.5 mg/kg, iv).

The synthesis and the phosphodiesterase-4 (PDE4) inhibitory activity of 2-pyridinemethanol derivatives is described. The evaluation of the structure-activity relationship (SAR) in this series of novel PDE4 inhibitors led to the identification of compound 9 which exhibits excellent in vitro activity, desirable pharmacokinetic parameters and good efficacy in animal models of bronchoconstriction.

Phosphodiesterase 4 (PDE4) inhibitors elevate cyclic adenosine 5′-monophosphate (cAMP), and this elevation has been shown to inhibit inflammatory cytokines such as tumor necrosis factor-α (TNF-α). Using TNF-α as a biomarker, we have developed transcription-based assays to examine inhibition of PDE4 activity in human and guinea pig whole blood. In vitro inhibition by PDE4 inhibitors was measured using quantitative PCR (qPCR) analysis of TNF-α mRNA levels in whole blood stimulated with lipopolysaccharide (LPS). The kinetics of human TNF-α mRNA production were analyzed and shown to be highest 4hr following LPS stimulation. The guinea pig displayed kinetics of TNF-α transcription similar to those of the human. Analysis of inhibition of human TNF-α protein production was performed by immunoassay and shown to correlate with inhibition of transcription for three of the four compounds tested. Roflumilast was found to be 9-fold more potent for TNF-α inhibition in the qPCR assay than in the protein assay. The potencies of L-826,141 and roflumilast were determined in human and guinea pig whole blood by qPCR, with ic50 values of 270 and 20nM, respectively, in humans and 100 and 10nM, respectively, in guinea pigs. These results show that the potency of PDE4 inhibitors can be monitored in whole blood using a transcription-based assay, and that this type of assay can be adapted to various species provided the TNF-α nucleotide sequence is known. The in vitro whole blood ic50 for TNF-α inhibition was compared to inhibition in the ovalbumin-challenged guinea pig model of bronchoconstriction. Obtaining plasma levels at the ic50 determined in vitro for L-826,141 and roflumilast provides significant inhibition of bronchoconstriction. This suggests that TNF-α can be used as a whole blood biomarker in the guinea pig for PDE4 inhibition in this inflammatory model.

Structure-activity relationship studies directed toward improving the potency and metabolic stability of CDP-840 (3) resulted in the discovery of L-791,943 (11n) as a potent (HWB TNF-alpha = 0.67 microM) and orally active phosphodiesterase type 4 (PDE4) inhibitor. This compound, which bears a stable bis-difluoromethoxy catechol and a pendant hexafluorocarbinol, exhibited a long half-life in rat and in squirrel monkey. It is well tolerated in ferret with an emetic threshold greater than 30 mg/kg (po) and was found to be active in the ovalbumin-induced bronchoconstriction model in guinea pig and in the ascaris-induced bronchoconstriction models in sheep and squirrel monkey.

ADVERTISEMENT RETURN TO ISSUEPREVLetterNEXTHunting the Emesis and Efficacy Targets of PDE4 Inhibitors: Identification of the Photoaffinity Probe 8-(3-Azidophenyl)-6- [(4-iodo-1H-1-imidazolyl)methyl]quinoline (APIIMQ)Dwight Macdonald, Hélène Perrier, Susana Liu, France Laliberté,, Roberta Rasori, Annette Robichaud, Paul Masson, and Zheng HuangView Author Information Merck Frosst Centre for Therapeutic Research, P.O. Box 1005, Pointe Claire-Dorval, Québec, Canada, H9R 4P8 Cite this: J. Med. Chem. 2000, 43, 21, 3820–3823Publication Date (Web):September 30, 2000Publication History Received16 February 2000Published online30 September 2000Published inissue 1 October 2000https://doi.org/10.1021/jm000065cCopyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views757Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (64 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Inhibitors,Labeling,Peptides and proteins,Probes,Substituents Get e-Alerts

Montelukast sodium (Singulair), also known as MK-0476 (1-(((1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)(3-2-(1- hydroxy-1-methylethyl)phenyl)propyl)thio)methyl)cyclopropane) acetic acid sodium salt, is a potent and selective inhibitor of [3H]leukotriene D4 specific binding in guinea pig lung (Ki 0.18 +/- 0.03 nM), sheep lung (Ki 4 nM), and dimethylsulfoxide-differentiated U937 cell plasma membrane preparations (Ki 0.52 +/- 0.23 nM), but it was essentially inactive versus [3H]leukotriene C4 specific binding in dimethylsulfoxide-differentiated U937 cell membranes (IC50 10 microM) and [3H]leukotriene B4 specific binding in THP-1 cell membranes (IC50 40 microM). Montelukast also inhibited specific binding of [3H]leukotriene D4 to guinea pig lung in the presence of human serum albumin, human plasma, and squirrel monkey plasma with Ki values of 0.21 +/- 0.08, 0.19 +/- 0.02, and 0.26 +/- 0.02 nM, respectively. Functionally, montelukast antagonized contractions of guinea pig trachea induced by leukotriene D4 (pA2 value 9.3; slope 0.8). In contrast, montelukast (16 microM) failed to antagonize contractions of guinea pig trachea induced by leukotriene C4 (45 mM serine-borate), serotonin, acetylcholine, histamine, prostaglandin D2, or U-44069. Intravenous montelukast antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. leukotriene D4 but did not block bronchoconstriction to arachidonic acid, histamine, serotonin, or acetylcholine. Oral administration of montelukast blocked leukotriene D4 induced bronchoconstriction in conscious squirrel monkeys, ovalbumin-induced bronchoconstriction in conscious sensitized rats (ED50 0.03 +/- 0.001 mg/kg; 4 h pretreatment), and also ascaris-induced early and late phase bronchoconstriction in conscious squirrel monkeys (0.03-0.1 mg/kg; 4 h pretreatment). A continuous i.v. infusion of montelukast (8 micrograms.kg-1.min-1) resulted in a 70% decrease in the peak early response and a 75% reduction of the late response to ascaris aerosol in allergic conscious sheep. Montelukast, a potent and selective leukotriene D4 receptor antagonist with excellent in vivo activity is currently in clinical development for the treatment of asthma and related diseases.

Montelukast sodium (Singulair(TM), also known as MK-0476 (1-(((1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)(3-2-( 1-hydroxy-1-methylethyl)phenyl)propyl)thio)methyl)cyclopropane) acetic acid sodium salt, is a potent and selective inhibitor of [H-3]leukotriene D-4, specific binding in guinea pig lung (K-i 0.18 +/- 0.03 nM), sheep lung (K-i 4 nM), and dimethylsulfoxide-differentiated U937 cell plasma membrane preparations (K-i 0.52 +/- 0.23 nM), but it was essentially inactive versus [H-3]leukotriene C-4 specific binding in dimethylsulfoxide-differentiated U937 cell membranes (IC50 10 mu M) and [H-3]leukotriene B-4, specific binding in THP-1 cell membranes (IC50 40 mu M). Montelukast also inhibited specific binding of [H-3]leukotriene D-4 to guinea pig lung in the presence of human serum albumin, human plasma, and squirrel monkey plasma with K-i values of 0.21 +/- 0.08, 0.19 +/- 0.02, and 0.26 +/- 0.02 nM, respectively. Functionally, montelukast antagonized contractions of guinea pig trachea induced by leukotriene D-4 (pA(2) value 9.3; slope 0.8). In contrast, montelukast (16 mu M) failed to antagonize contractions of guinea pig trachea induced by leukotriene C-4 (45 mM serine-borate), serotonin, acetylcholine, histamine, prostaglandin D-2, or U-44069. Intravenous montelukast antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. leukotriene D-4 but did not block bronchoconstriction to arachidonic acid, histamine, serotonin, or acetylcholine. Oral administration of montelukast blocked leukotriene D-4 induced bronchoconstriction in conscious squirrel monkeys, ovalbumin-induced bronchoconstriction in conscious sensitized rats (ED(50) 0.03 +/- 0.001 mg/kg; 4 h pretreatment), and also ascaris-induced early and late phase bronchoconstriction in conscious squirrel monkeys (0.03-0.1 mg/kg; 4 h pretreatment). A continuous i.v. infusion of montelukast (8 mu g . kg(-?1). min(-1)) resulted in a 70% decrease in the peak early response and a 75% reduction of the late response to ascaris aerosol in allergic conscious sheep. Montelukast, a potent and selective leukotriene Dq receptor antagonist with excellent in vivo activity is currently in clinical development for the treatment of asthma and related diseases.

The styryl quinoline thioether 5 (L-699,392) is a potent and orally active leukotriene D4 antagonist. The structure-activity studies leading to its discovery are described.

A new, potent, orally active leukotriene D4 receptor antagonist has been discovered. The structure-activity relationship leading to L-695,499 is described.

The peptide leukotrienes LTC4, D4 and E4 collectively account for the biological activity known as slow-reacting substance of anaphylaxis (SRS-A). These metabolites of arachidonic acid are thought to play a role in lung pathophysiology. A role in asthma is postulated as a result of their potent bronchoconstrictor activity both in vitro (Dahlén et al. 1980; Drazen et al. 1980; Hanna et al. 1981; Piper et al. 1981; Jones et al. 1982; Peters et al. 1984) and in vivo (Manning et al. 1990; Holroyde et al. 1981; Griffin et al. 1983; Weiss et al. 1982; Barnes et al. 1984). Increased production of leukotrienes has been demonstrated following antigen challenge of the airways of allergic patients in vivo (Creticos et al. 1984; Ishihara et al. 1985; Isono et al. 1985) and in vitro (Dalhén et al. 1983).

Based on LTD4 receptor antagonist activity of 3-(2-quinolinyl-(E)-ethenyl)pyridine (2) found in broad screening, structure-activity studies were carried out which led to the identification of 3-[[[3-[2-(7-chloro-2-quinolinyl)-(E)-ethenyl]phenyl][[3- (dimethylamino)-3-oxopropyl]thio]methyl]thio]propionic acid (1, MK-571) as a potent and orally active LTD4 receptor antagonist. These studies demonstrated that a phenyl ring could replace the pyridine in 2 without loss of activity, that 7-halogen substitution in the quinoline group was optimal for binding, that the (E)-ethenyl linkage was optimal, that binding was enhanced by incorporation of a polar acidic group or groups in the 3-position of the aryl ring, and that two acidic groups could be incorporated via a dithioacetal formed from thiopropionic acid and the corresponding styrylquinoline 3-aldehyde to yield compounds such as 20 (IC50 = 3 nM vs [3H]LTD4 binding to the guinea pig lung membrane). It was found that one of the acidic groups could be transformed into a variety of the amides without loss of potency and that the dimethylamide 1 embodied the optimal properties of intrinsic potency (IC50 = 0.8 nM on guinea pig lung LTD4 receptor) and oral in vivo potency in the guinea pig, hyperreactive rat, and squirrel monkey. The evolution of 2 to 1 involves the increase of > 6000-fold in competition for [3H]LTD4 binding to guinea pig lung membrane and a > 40-fold increase in oral activity as measured by inhibition of antigen-induced dyspnea in hyperreactive rats.

Verlukast (MK-679) (3-[(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)[3-(dimethylamino)- 3- oxopropyl)thio)methyl)-thio)propionic acid) is a potent and selective inhibitor of [3H]leukotriene D4 binding in guinea-pig (IC50 = 3.1 +/- 0.5 nM) and human (IC50 = 8.0 +/- 3.0 nM) lung homogenates and dimethyl sulfoxide differentiated U937 cell membrane preparations (IC50 = 10.7 +/- 1.6 nM) but is essentially inactive versus [3H]leukotriene C4 binding in guinea-pig lung homogenates (IC50 values of 19 and 33 microM). Functionally, when tested at 60 nM, it antagonized contractions of guinea-pig trachea (GPT) induced by leukotriene C4, leukotriene D4, and leukotriene E4 (respective-log KB values of 8.6, 8.8, and 8.9) and contractions of human trachea (HT) induced by leukotriene D4 (-log KB value 8.3 +/- 0.2). In contrast, verlukast (20-200 nM) failed to antagonize contractions of GPT induced by leukotriene C4 in the presence of 45 mM L-serine borate. Intravenous (i.v.) and aerosol verlukast antagonized bronchoconstriction (BC) induced in anaesthetized guinea pigs by i.v. leukotriene D4 but did not block BC to arachidonic acid or histamine. Intraduodenal verlukast (0.25 mg/kg) antagonized leukotriene D4 (0.2 micrograms/kg) induced BC in guinea pigs. Oral and aerosol administration blocked leukotriene D4-induced BC in conscious squirrel monkeys. Orally administered compound also blocked ovalbumin-induced BC in conscious sensitized rats treated with methysergide (3 micrograms/kg). The pharmacological profile for verlukast is similar to that of the racemic compound, MK-571. Verlukast is currently in clinical development for the treatment of asthma and related diseases.

The enantiomers of the leukotriene D4 antagonist 3-[[[3-[2-(7-chloroquinolin-2-yl)-(E)-ethenyl]phenyl] [[3-(dimethylamino)-3-oxopropyl]thio]methyl]thio]propionic acid (L-660,711)(MK-571) have been prepared, their absolute stereochemistry has been assigned as S for (+)-1 and R for (-)-1 by X-ray analysis of a synthetic intermediate (5), and the biological activity of the enantiomers has been explored. Unexpectedly, the enantiomers are both comparably biologically active with (+)-1 slightly more intrinsically active at the LTD4 receptor in vitro.

L-670,596 ((-)6,8-difluoro-9-rho-methylsulfonyl benzyl-1,2,3,4- tetrahydrocarbazol-1-yl-acetic acid) has been shown to be a potent receptor antagonist as evidenced by the inhibition of the binding of 125I-labeled PTA-OH to human platelets (IC50, 5.5 x 10(-9) M), inhibition of U-44069 induced aggregation of human platelet rich plasma (IC50, 1.1 x 10(-7) M), and competitive inhibition of contractions of the guinea pig tracheal chain induced by U-44069 (pA2,9.0). The compound was also active in vivo as shown by inhibition of arachidonic acid and U-44069 induced bronchoconstriction in the guinea pig (ED50 values, 0.04 and 0.03 mg/kg i.v., respectively), U44069 induced renal vasoconstriction in the pig (ED50, 0.02 mg/kg i.v.), and inhibition of ex vivo aggregation of rhesus monkey platelets to U-44069 (active 1-5 mg/kg p.o.). The selectivity of the compound was indicated by the failure to inhibit, first, ADP-induced human or primate platelet aggregation and, second, bronchoconstriction in the guinea pig in vivo and contraction of the guinea pig tracheal chain in vitro to a variety of agonists. It is concluded that L-670,596 is a potent, selective, orally active thromboxane A2/prostaglandin endoperoxide receptor antagonist.