Tenidap inhibits 5-lipoxygenase product formation in vitro, but this activity is not observed in three animal models.

OBJECTIVE AND DESIGN: The effect of tenidap on the metabolism of arachidonic acid via the 5-lipoxygenase (5-LO) pathway was investigated in vitro and in vivo. MATERIALS AND TREATMENT: In vitro (cells). Arachidonic acid (AA) stimulated rat basophilic leukemia, (RBL) cells; A23817 activated neutrophils (human rat, and rabbit), macrophages (rat), and blood (human). In vitro (enzyme activity). RBL-cell homogenate; purified human recombinant 5-LO. In vivo: Rat (Sprague-Dawley) models in which peritoneal leukotriene products were measured after challenge with zymosan (3 animals per group), A23187 (11 animals per group), and immune complexes (3-5 animals per group), respectively. METHODS: 5-Hydroxyeicosatetraenoic acid (5-HETE) and dihydroxyeicosatetraenoic acids (diHETEs, including LTB4) were measured as radiolabeled products (derived from [14C]-AA) or by absorbance at 235 or 280 nm, respectively, after separation by HPLC. Radiolabeled 5-HPETE was measured by a radio-TLC analyser after separation by thin layer chromatography (TLC). Deacylation of membrane bound [14C]-AA was determined by measuring radiolabel released into the extracellular medium. 5-LO translocation from cytosol to membrane was assessed by western analysis. Rat peritoneal fluid was assayed for PGE, 6-keto-PGF1 alpha, LTE4 or LTB4 content by EIA and for TXB2 by RIA. RESULTS: Tenidap suppressed 5-LO mediated product production in cultured rat basophilic leukemia (RBL-1) cells from exogenously supplied AA, and in human and rat neutrophils, and rat peritoneal macrophages stimulated with A23187 (IC50, 5-15 microM). In addition, tenidap was less potent in inhibiting the release of radiolabeled AA from RBL-1 cells (IC50, 180 microM), suggesting that the decrease in 5-LO derived products could not be explained by an effect on cellular mobilization of AA (i.e., phospholipase). Tenidap blocked 5-hydroxyeicosatetraenoic acid (5-HETE) production by dissociated RBL-1 cell preparations (IC50, 7 microM), as well as by a 100000 x g supernatant of 5-LO/hydroperoxidase activity, suggesting a direct effect on the 5-LO enzyme itself. In addition, tenidap impaired 5-LO translocation from cytosol to its membrane-bound docking protein (FLAP) which occurs when human neutrophils are stimulated with calcium ionophore, indicating a second mechanism for inhibiting the 5-LO pathway. Surprisingly, tenidap did not block the binding of radiolabeled MK-0591, an indole ligand of FLAP, to neutrophil membranes. Although its ability to inhibit the cyclooxygenase pathway was readily observed in whole blood and in vivo, tenidap's 5-LO blockade could not be demonstrated by ionophore stimulated human blood, nor after oral dosing in rat models in which peritoneal leukotriene products were measured after challenge with three different stimuli. The presence of extracellular proteins greatly reduced the potency of tenidap as a 5-LO inhibitor in vitro, suggesting that protein binding is responsible for loss of activity in animal models. CONCLUSIONS: Tenidap inhibits 5-lipoxygenase activity in vitro both directly and indirectly by interfering with its translocation from cytosol to the membrane compartment in neutrophils. A potential mechanism for the latter effect is discussed with reference to tenidap's ability to lower intracellular pH. Tenidap did not inhibit 5-LO pathway activity in three animal models.

Tenidap, a structurally novel drug for the treatment of arthritis: antiinflammatory and analgesic properties.

Tenidap is a new anti-rheumatic agent which has clinical properties characteristic of a disease modifying drug combined with acute antiinflammatory and analgesic activity. This paper details tenidap's cyclooxygenase (COX) inhibitory activity and the resulting pharmacological properties in experimental animals. Tenidap inhibited calcium ionophore-stimulated prostaglandin D2 synthesis by rat basophilic leukemia cells (COX-1) with an IC50 of 20 nM. In two different in vitro human test systems, tenidap inhibited COX-1 activity more potently than COX-2, although the relative potency ratio (COX-1/COX-2) differed markedly between the two systems. Tenidap inhibited the COX pathway when added to human blood in vitro (IC50, 7.8 mu M) and when administered orally to monkeys, rats and dogs (at 5, 2.5 and 10 mg/kg p.o., respectively) and COX activity measured ex vivo in blood collected 2 to 4 hours post dose. After oral administration to rats, tenidap inhibited carrageenan-induced paw edema with an ED50 of 14 mg/kg and inhibited the glucocorticoid-resistant UV erythema in guinea pigs with an ED50 of 1.4 mg/kg. It retained antiinflammatory activity in adrenalectomized rats indicating that this property is independent of adrenal stimulation. Oral administration of tenidap inhibited the development of adjuvant-induced polyarthritis in the rat and exhibited antinociceptive activity in the murine phenylbenzoquinone and rat acetic acid abdominal constriction tests. These data indicate that tenidap is an effective antiinflammatory and analgesic agent in animal models. These cyclooxygenase-dependent pharmacologic activities do not explain tenidap's disease modifying anti-arthritic properties but add a useful symptom modifying component to its clinical profile.

Inhibition of IgE-mediated N-acetylglucosaminidase and serotonin release from rat basophilic leukemia cells (RBL-2H3) by tenidap: a novel anti-inflammatory agent.

Tenidap [(Z)-5-chloro-2,3-dihydro-3-(hydroxy-2-thienylmethylene)-2-oxo-1H- indole-1-carboxamide] is a novel anti-inflammatory compound of the oxindole class that currently is undergoing clinical evaluation in man. Here we demonstrate that tenidap inhibits (IC50 = approximately 10 microM) IgE-mediated secretion of granule constituents from the rat mast cell tumor line RBL-2H3. The inhibitory effect is rapid in onset, readily reversible, and appears to be unique when compared to a representative selection of other acidic (carboxylic acids, pyrazoles and oxicams) nonsteroidal anti-inflammatory compounds.

Structure--activity relationships in a series of novel 3,4-dihydro-4-oxopyrimido[4,5-b]quinoline-2-carboxylic acid antiallergy agents.

A series of more than 50 new 3,4-dihydro-4-oxopyrimido[4,5-b]quinoline-2-carboxylic acid derivatives and related compounds with substituent variations at the 2, 3, and 5--9 positions was prepared and evaluated for antiallergy activity using the rat PCA assay. These compounds were obtained by the condensation of the appropriately substituted 2-aminoquinoline-3-carboxamides with dialkyl oxalates, followed by further chemical transformations. More than two-thirds of the compounds prepared exhibited intravenous activity ranging from 1 to 400 times disodium cromoglycate (DSCG). Structure--activity data suggest that the presence of a carboxylic acid moiety at the 2 position affords optimal potency and that esters are preferred for good oral absorption. Best oral activity, with ED50 values ranging from 0.3 to 3.0 mg/kg, was displayed by ethyl esters with methoxy and/or ethoxy groups at the 7 and 8 positions.

Synthesis and antiinflammatory properties of N-substituted 4,5-dioxopyrrolidine-3-carboxanilides.

The synthesis and physical properties of a series of N-methyl- and N-phenyl-4,5-dioxopyrrolidine-3-carboxanilides are described. Unlike previously reported carboxanilides derived from 1,3(2H,4H)-dioxoisoquinoline and 2-oxobenzofuran, the currently described agents exist solely as the enol tautomers and, as a result, do not display comparable acidic properties. None of the newly reported compounds exhibited activity equal to that of aspirin in the carrageenin-induced rat foot edema assay.