Rapid metabolic inactivation of tipredane, a structurally novel topical steroid.

[3H]Tipredane ([3H]TP), [3H]triamcinolone acetonide ([ 3H]TAAC), [3H]hydrocortisone ([3H]HC), and [3H]betamethasone-17 alpha-valerate ([3H]BMV), each at a concentration of 1 microM, were separately incubated with the 10,000 g supernatant fraction of the liver and skin homogenates of humans, rats and mice (BMV was studied only in human liver). Sequential samples were taken for up to 1 h during each incubation. The radioactivity in each sample was extracted with methanol, and the methanolic extracts were analyzed by high performance liquid chromatography. Among the four compounds studied, [3H]TP was most rapidly biotransformed by the liver preparations of the three species. The rates of in vitro biotransformation of TP were 2.5-30 times faster than those of TAAC, HC and BMV. In the human liver preparation, the rates of biotransformation were in the order of: TP greater than TAAC greater than HC = BMV. In the mouse and rat liver preparations, the orders were: TP greater than TAAC greater than HC and TP greater than HC greater than TAAC, respectively. In the skin preparations, little, if any, biotransformation of [3H]TP and [3H]TAAC was observed in any of the species studied; however, [3H]HC underwent a slow, steady biotransformation in the skin preparations of humans and rats but not of mice. [3H]TP was biotransformed by the liver preparations of all three species to numerous metabolites, thirteen of which have been identified. The biotransformation reactions included: (1) sulfoxidation; (2) elimination of either one or both alkylthio groups; and (3) hydroxylation of the steroid nucleus. Some metabolites were synthesized and tested for glucocorticoid receptor binding and anti-inflammatory activities; all were found to be much less potent than TP. The observed separation of local anti-inflammatory activity from systemic side effects of TP is most probably due to its rapid metabolic inactivation; the liver, rather than the skin, is mainly responsible for the metabolic inactivation of TP.

Androstene-17-thioketals. 1st communication: glucocorticoid receptor binding, antiproliferative and antiinflammatory activities of some novel 20-thiasteroids (androstene-17-thioketals).

The unique replacements of the alpha-hydroxyl and beta-ketol groups of corticoids at C17 with selected, simple alkylthio or (2-fluoroalkyl)thio groups resulted in the structurally novel steroids, C17-alkylthioketals of 9 alpha-fluoro-11 beta-hydroxy-androsta-1,4-diene-3,17-dione. The described androstene-17-thioketals (20-thiasteroids) had high affinities for the glucocorticoid receptor protein of rat liver cytosol. Most were more potent than triamcinolone acetonide, a clinically moderately potent corticoid, in antiproliferative and antiinflammatory activities in mice. Specifically, (11 beta, 17 alpha)-17-(ethylthio)-9 alpha-fluoro-11 beta-hydroxy-17-(methylthio) androsta-1,4-dien-3-one (tipredane, SQ 27,239) and (11 beta, 17 alpha)-17-(ethylthio)-9 alpha-fluoro-17-[2-(fluoroethyl)thio] - 11 beta - hydroxy-androsta-1,4-dien-3-one (SQ 28,300), topically applied, were as potent as halcinonide, a clinically highly potent corticoid, in inhibition of croton oil-induced edema in the mouse. It is suggested that both thiasteroids could be moderately to highly potent topical antiinflammatory agents in man.

Androstene-17-thioketals. 2nd communication: pharmacological profiles of tipredane and (11 beta, 17 alpha)-17-(ethylthio)-9 alpha-fluoro-17-[2-(fluoroethyl)thio]-11 beta-hydroxy-androsta-1,4-dien-3-one, structurally novel 20-thiasteroids possessing potent and selective topical antiinflammatory activity.

Two structurally novel alkylthio-substituted steroids, (11 beta, 17 alpha)-17-(ethylthio)-9 alpha-fluoro-11 beta-hydroxy-17-(methylthio)andro-1,4-dien-3-one (tipredane, SQ 27,239) and (11 beta, 17 alpha)-(ethylthio)-9 alpha-fluoro-17-[2-(fluoroethyl) thio]-11 beta-hydroxy-androsta-1,4-dien-3-one (SQ 28,300) were compared to presently available topical corticosteroids for in vitro and in vivo glucocorticoid and antiinflammatory activities. Based upon results of in vitro assays, in vivo antiinflammatory tests in mice, and human vasoconstriction measurements, the thiasteroids most closely resemble moderately potent to highly potent corticoids. These compounds display more modest activity in topical antiinflammatory assays using rats. Both tipredane and SQ 28,300 exhibit favorable separation of local antiinflammatory activity from systemic effects on thymus and hypothalamic-pituitary-adrenal axis function, most probably due to rapid metabolic inactivation. As such, these compounds represent potentially safer therapy for topical treatment of corticoid-responsive skin diseases and bronchopulmonary conditions in humans.

Characterization of the anti-inflammatory activity and reduced potential for dermal atrophy of (11 beta, 16 beta)-9-fluoro-1',2',3', 4'-tetrahydro-11,21-dihydroxypregna-1,4-dieno[16,17-b]naph thalene-3, 20-dione hydrate (1 : 1) (SQ 26,490), a topically active corticoid.

SQ 26,490, (11 beta, 16 beta)-9-fluoro-1',2',3',4'-tetrahydro-11, 21-dihydroxypregna-1,4-dieno[16,17-b]naphthalene 3,20-dione hydrate (1 : 1), was a moderately potent inhibitor of edema formation in the rat. After extended topical application, SQ 26,490 totally inhibited edema formation without appreciable production of skin atrophy, measured under identical conditions. This atrophy was maintained at a low plateau level of 15-20% at doses beyond those necessary to achieve optimal anti-inflammatory activity. In contrast, the potent corticoids, fluocinolone acetonide and halcinonide, and the moderately potent corticoid, clobetasone butyrate, produced inhibition of edema with a concomitant dose-related atrophy. Hydrocortisone, a weakly potent corticoid, totally inhibited edema and produced at high doses a low atrophy. SQ 26,490 possesses the property for a greater separation of anti-inflammatory and atrophogenic activities than comparative corticoids.

Characterization of augmentation of allergic and non-allergic histamine release by non-steroidal anti-inflammatory/analgesic agents.

Augmentation of allergic histamine release from human leukocytes previously was shown to be produced by numerous acidic anti-inflammatory/analgesic agents. In the present study, cicloprofen or diclofenac, representative of the arylalkanoic and anthranilic acids, respectively, augmented the antigen-dependent first stage and the calcium-dependent second stage of allergic histamine release. Both agents enhanced the rate and total amount of histamine release in the whole reaction. Further, it was demonstrated that augmentation could occur in a specific, non-cytolytic manner. In extended studies, cicloprofen and diclofenac augmented ionophore (A23187)- and concanavalin A-induced histamine release from human leukocytes and ionophore-induced release from rat mast cells. Concanavalin A- and ovalbumin-induced release from rat mast cells were inhibited by cicloprofen and diclofenac. These findings define systems useful for the study of the mechanisms of action of the acidic anti-inflammatory agents.

Augmentation of allergic histamine release from human leukocytes by nonsteroidal anti-inflammatory-analgesic agents.

Augmentation of allergic histamine release in vitro with human leukocytes was produced by numerous nonsteroidal anti-inflammatory--analgesic agents, primarily the arylalkanoic and anthranilic acids. Augmentation occurred without release of histamine by the agents in the absence of the allergen (ragweed) and only under conditions of an accompanying release by the allergen. As a consequence of augmentation, less allergen was necessary to produce a given response in the presence of these agents. It is suggested that some of these agents might enhance mediator release in immediate-type hypersensitivity reactions. The same agents reported to exacerbate chronic urticaria, i.e., indomethacin, mefenamic acid, sodium salicylate, aspirin, sodium benzoate, and tartrazine, also augmented allergic histamine release. Pharmacologically mediated augmentation of mediator release from stimulated cells is suggested to be involved in the exacerbation of existing chronic urticaria by the acidic nonsteroidal anti-inflammatory-analgesic agents.

Effect of nonsteroidal anti-inflammatory and other pharmacological agents on tuberculin reaction.

Nonsteroidal anti-inflammatory and other pharmacological agents were tested in the efferent arc of the tuberculin skin reaction in the guinea pig. A low but significant inhibition was produced by the acidic anti-inflammatory agents, including the arylalkanoic acids, the anthranilic acids, indomethacin, and phenylbutazone. Some nonacidic anti-inflammatory agents also were inhibitory; benzydamine caused a high inhibition. Except for methotrexate, the antineoplastic--antimetabolite agents were not potent inhibitors. Inhibition without toxicity was produced by the coumarin anticoagulants, the diuretics, chloroquine, tilorone, and the following immunoregulators: antithymocyte gamma-globulin, cyclophosphamide, and penicillamine. Levamisole, colchicine, heparin, and niridazole were inhibitory but produced lethality either at or above the effective dose.

Structure-activity profile of substituted purines and inflammation in the delayed hypersensitivity skin reaction.

Substituted purines were tested for their effectiveness in inhibiting the delayed hypersensitivity skin reaction (DHSR) caused by tuberculin in the guinea-pig. Among the tested purines were naturally occurring derivatives of guanine and adenine, including cyclic AMP. Based on the structure-activity profile, a class of purines was identified, the members of which were very effective inhibitors of inflammatory aspects of the DHSR and are characterized by a benzyl group in position 9, an amino or alkylamino group in position 6, and various substituents in position 2. This class of 2-substituted-9-benzyladenines was more effective in the DHSR than some antimetabolites, particularly the structurally related mercaptopurines.

Substituted 9-benzyladenines: inhibitors of inflammation associated with the delayed hypersensitivity skin reaction.

Members of a group of substituted 9-benzyladenines have been identified as effective inhibitors of inflammatory aspects of the delayed hypersensitivity skin reaction in the guinea-pig. Inhibitory activity was demonstrable in the efferent arc of the cell-mediated tuberculin and contact dermatitis (2,4-dinitrochlorobenzene) reactions. One of the compounds, 2-amino-9-benzyladenine, inhibited both turpentine-induced and histamine-induced inflammation in the skin. The toxicity and inhibitory activities of some of these compounds are discussed, and reference is made to the structurally related mercaptopurines.