ICI 204,219 (4-(5-cyclopentyloxycarbonylamino-1-methylindol-3-ylmethy l)-3- methoxy-N-o-tolylsulfonylbenzamide) was designed as a peptide leukotriene (LT) antagonist. The compound is a competitive antagonist of LTD4- and LTE4-induced contraction of guinea pig lung tracheal and parenchymal strips with an apparent negative log molar dissociation constant (KB) of approximately 9.6. ICI 204,219 did not antagonize LTC4-induced contractions of guinea pig trachea when the metabolism of LTC4 to LTD4 and, subsequently, to LTE4 was inhibited. The compound inhibited the binding of [3H]LTD4, [3H]LTE4, and [3H]ICI 198,615 (a potent LT antagonist from a different heterocyclic series) to guinea pig lung parenchymal membranes in a competitive manner, and also inhibited [3H]ICI 198,615 binding to human lung parenchymal membranes. ICI 204,219 did not bind to a variety of other receptors when evaluated at concentrations 1,000- to 10,000-fold higher than the apparent KB value for peptide LT receptors. When administered orally, intravenously, or by aerosol, the compound provided dose-related antagonism of the airway effects of aerosol LTD4 in conscious guinea pigs. ED50 values and pharmacodynamic t1/2 (min) for oral, intravenous and aerosol routes of administration were, respectively: 0.52 mumol/kg, greater than 816 min; 0.046 mumol/kg, 85 min; 5.1 x 10(-6) M, 109 min. ICI 204,219 also produced dose-related inhibition of the effects of LTC4 (aerosol or intravenous administration) on pulmonary mechanics in anesthetized guinea pigs when administered orally, intraduodenally, intravenously, or by aerosol. The compound also reversed bronchospasm produced by LTs. Aerosol ovalbumin antigen-induced bronchospasm in guinea pigs was both inhibited and reversed by ICI 204,219. Lastly, the compound inhibited LTD4-induced increases in cutaneous vascular permeability in guinea pigs, being 1,006- and 679-fold more potent than the first generation LT antagonists LY 171,883 and FPL 55712, respectively. ICI 204,219 is a potent, selective, orally active LT antagonist currently undergoing clinical trials.

X = Leu Val MeOCOCH(CHMe,)NHCO-X-Gly-X = Leu Val W( CH ,S)-D-L~U-OCH 2 Ph v(CH ,S)-D-Leu-OCH 2 Ph Modifications at position P, X-L~U-GI~-I~(CH,S)-L~U-OCH,P~ (24) X = MeOCOCH(CH,CHMe,)NHCO (22) MeOCOCH(CHMe,)NHCO (25) X = MeOCOCH(CH,CHMe,)NHCO (23) (29) X = MeOCOCH(CH,CHMe,)NHCO (30) MeOCOCH(CHMe,)NHCO (31) X = MeOCOCH(CH,CHMe,)NHCO (32) MeOCOCH(CHMe,)NHCO X-L~U-GI~-~(CH,S)-D-L~U-OCH,P~ M eOCOC H (C H Me , ) N H CO X-Val-Gly-~(CH2S)-~-Leu-0CH,Ph X-Leu-W(CH ,

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Substituted indole-5-carboxamides and indole-6-carboxamides have been found to be potent and selective antagonists of the peptidoleukotrienes. Initial derivatives of these series (4-[[5-[(cyclopentylmethyl)carbamoyl]-1-methylindol-3-yl] methyl]-3-methoxy-N-[(2-methylphenyl)sulfonyl]benzamide (5a) and 4-[[6-[(cyclopentylmethyl)carbamoyl]-3-methylindol-1-yl] methyl]-3-methoxy-N-[(2-methylphenyl)sulfonyl]benzamide (6a), respectively), when compared to the corresponding indole amides (e.g. 28 and 29), were found to be approximately 10-fold less potent in vitro and substantially less active when administered orally to guinea pigs. Efforts to improve the potency of the title series by variation of the amide, indole, or sulfonamide substituents led to compounds of comparable in vitro potency to ICI 204,219, but of somewhat lower oral activity. A trend which suggested that more lipophilic transposed amides were needed to increase oral activity was exploited with some success and has led to the discovery of 5q (4-[[5-[(2-ethylbutyl)-carbamoyl]-1-ethylindol-3-yl]methyl]- 3- methoxy-N-[(2-methylphenyl)sulfonyl]benzamide), a transposed amide with subnanomolar affinity for the leukotriene receptor and an oral ED50 of 5 mg/kg in a model of asthma in guinea pigs. In this model, ICI 204,219 was active at 0.4 mg/kg. The absolute bioavailability of 5q has been found to be 28% in the rat, as compared to 68% for ICI 204,219, with significant levels of 5q observed in the blood of rats up to 24 h postdose.

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