Topical anti-inflammatory activity of esters of steroid 21-oic acids

Nonclinical and human pharmacology of the potent and selective topical retinoic acid receptor-γ agonist trifarotene

BACKGROUND

First- and third-generation retinoids are the main treatment for acne. Even though efficacious, they lack full selectivity for retinoic acid receptor (RAR) γ, expressed in the epidermis and infundibulum.

OBJECTIVES

To characterize the in vitro metabolism and the pharmacology of the novel retinoid trifarotene.

MATERIALS AND METHODS

In vitro assays determined efficacy, potency and selectivity on RARs, as well as the activity on the expression of retinoid target genes in human keratinocytes and ex vivo cultured skin. In vivo studies investigated topical comedolytic, anti-inflammatory and depigmenting properties. The trifarotene-induced gene expression profile was investigated in nonlesional skin of patients with acne and compared with ex vivo and in vivo models. Finally, the metabolic stability in human keratinocytes and hepatic microsomes was established.

RESULTS

Trifarotene is a selective RARγ agonist with > 20-fold selectivity over RARα and RARβ. Trifarotene is active and stable in keratinocytes but rapidly metabolized by human hepatic microsomes, predicting improved safety. In vivo, trifarotene 0·01% applied topically is highly comedolytic and has anti-inflammatory and antipigmenting properties. Gene expression studies indicated potent activation of known retinoid-modulated processes (epidermal differentiation, proliferation, stress response, retinoic acid metabolism) and novel pathways (proteolysis, transport/skin hydration, cell adhesion) in ex vivo and in vivo models, as well as in human skin after 4 weeks of topical application of trifarotene 0·005% cream.

CONCLUSIONS

Based on its RARγ selectivity, rapid degradation in human hepatic microsomes and pharmacological properties including potent modulation of epidermal processes, topical treatment with trifarotene could result in good efficacy and may present a favourable safety profile in acne and ichthyotic disorders.

Anti-inflammatory agents from Sandoricum koetjape Merr

The anti-inflammatory activity of the stem extracts of Sandoricum koetjape was investigated on topical administration using the TPA (tetradecanoylphorbol acetate)-induced mouse ear inflammation model. Bioassay-guided chromatographic fractionation of active fractions led to the isolation 3-oxo-12-oleanen-29-oic acid and katonic acid as the bioactive principles responsible for the anti-inflammatory acitivity. The percentage of inhibition exhibited by 3-oxo-12-oleanen-29-oic acid was almost equivalent to indomethacin.

Effect of crystal form on in vivo topical anti-inflammatory activity of corticosteroids

The aim of this study was to gain information on the effects of the crystal form of corticosteroids on the topical anti-inflammatory activity. Two different crystal forms, Form A and Form B, of the drugs of prednicarbate, hydrocortisone, betamethasone 17-valerate, prednisolone, and methyl prednisolone were prepared and their topical anti-inflammatory activities were measured using arachidonic acid induced ear edema assay in mice. Two crystal forms of the drugs showed differences in anti-inflammatory activity. Among the drugs examined, Form B of prednicarbate and betamethasone 17-valerate showed significantly more potent anti-inflammatory activities as compared to their Form A.

Effect of chirality at C-20 of methyl 11beta,17alpha,20-trihydroxy-3-oxo-1,4-pregnadien-21-oate derivatives on antiinflammatory activity

In an effort to determine the C-20 chirality effect on the antiinflammatory activity of 17beta-glycolate esters, methyl 11beta,17alpha,20-trihydroxy-3-oxo-1,4-pregnadien-21-oate and its 9alpha-fluoro analog, their acetonide and their carbonate derivatives were synthesized and evaluated. The agents were tested for their binding potency to the macrophage glucocorticoid receptor, and their effect on LPS-induced nitric oxide generation in RAW 264.7 cells. The acetonide derivatives showed the highest binding affinity while the triols and carbonates bound rather poorly to the receptors. With the exception of the triols, the alpha-isomer in each pair of the agents exhibited higher binding affinity to the receptor than its corresponding beta-isomer, clearly indicating that C-20 chirality has a significant effect on antiinflammatory activity. In addition, the alpha-isomers of the acetonides showed substantially higher binding affinity than the parent compound, prednisolone. In contrast to the high binding activity exhibited by some of the acetonides, all of the agents showed weak inhibitory effect on NO generation. Metabolic inactivation during assessment of NO inhibition may play a role in the divergence noted between receptor affinity and the measured biologic activity resulting from the binding.

A novel approach to the discovery of non-systemic anti-inflammatory steroids; antedrug

Therapeutic use of anti-inflammatory steroids is limited due primarily to their systemic suppressive effects on pituitary function and the immune system. To overcome the clinical limitation, a new approach toward the discovery of non-systemic anti-inflammatory steroids is based upon the antedrug concept introduced by this laboratory. The new concept describes locally active agents which are designed to undergo a predictable biotransformation to inactive metabolites upon entry into systemic circulation from the applied site. Thus, true antedrugs are devoid of systemic adverse effects. In a continuing effort, 16alpha-carboxylate and isoxazoline derivatives of prednisolone have been synthesized and screened. In the croton oil-induced ear edema bioassay, the following relative potencies were obtained setting hydrocortisone=1.0; 3a, 1.5; 3b, 3.1; 4a, 4.0; 4b, 12.2; 5b, 8.2; 6b, 11.2; 7a, 1.9; 7b, 4.1; 8a, 3.3; 8b, 6.8; 9a, 0.7; 9b, 8.6; 10a, 2.6; 10b, 7.4. Results of the five-day bioassay indicated that, in contrast to the parent compound, the novel steroidal antedrugs did not significantly alter body weight gain, thymus weights, adrenal weights or plasma corticosterone levels. Taken together, the antedrug concept appears to be a fundamentally sound strategy for the separation of local anti-inflammatory activity from systemic adverse effects.

Effects of indole-3-acetic acid on croton oil- and arachidonic acid-induced mouse ear edema

The indole-3-acetic acid (IAA) is a plant growth hormone (auxin) being considered as a tryptophan metabolite in animals. The main purpose of this work was to verify IAA's topical anti-inflammatory action using croton oil- or arachidonic acid-induced mouse ear edema, in comparison to known anti-inflammatory agents. IAA antioxidant activity was also verified by measuring the inhibition of brain homogenate lipid peroxidation with the thiobarbituric acid reactive substances (TBARS) test. IAA inhibited the action of both croton oil-and arachidonic acid-induced edema in a dose-dependent manner (4.0 mumoles IAA inhibited 75.8% in croton oil and 82.5% in arachidonic acid induced ear edema). Both IAA (5.3 mM) and indomethacin (8.0 mM) inhibited TBARS formation. Data suggest that IAA exhibits antiinflammatory effect possibly by its anti-oxidant activity.

Pharmacological activities of water extracts of Umbelliferae plants

In order to evaluate the pharmacological activities of Chinese medicine, nine Umbelliferae plants were selected and their restoring activity against dexamethasone-induced disorders, liver protective activity, antimicrobial activity, anti-inflammatory activity and antimutagenic activity were tested and compared. Angelica dahurica. Angelica acutiloba and Ostericum koreanum showed various activities in these tests at the dose used in this study.

In vitro hydrolysis of steroid acid ester derivatives of prednisolone in plasma of different species

The in vitro hydrolysis of two new classes of steroid acid esters synthesized from prednisolone as local anti-inflammatory steroids was investigated in rat, rabbit, and human plasma. One class was synthesized by incorporating methoxycarbonyl groups at the 16 position of prednisolone to produce 16 alpha-methoxycarbonyl prednisolone (P16CM) and its 17-deoxy analogue (DP16CM). The other class was synthesized by modifying the ketol side chain of prednisolone to produce methyl 20 alpha- and methyl beta-dihydroprednisolonate (P4 alpha and P4 beta). The P16CM and P4 beta were rapidly and completely hydrolyzed within 1 h of incubation in rat and rabbit plasma and within 4 h in human plasma. There was a marked species difference in the hydrolysis of DP16CM which occurred in the following order: rat greater than human greater than rabbit. The in vitro hydrolysis of P4 alpha was much slower than that of P4 beta; the process continued over 24 h in rat plasma. As expected, no change in the initial concentration of prednisolone was found over 120 h of incubation in rat plasma. This marked species difference in the hydrolysis of these steroid acid esters is probably related to the differences in the amounts, types, and activities of the hydrolyzing enzymes (e.g., esterases) in the plasma of the three species. From this study it can be concluded that the existence of an hydroxyl group at C-17 and the orientation of hydroxyl groups at C-20 play an important role in the systemic hydrolysis rate of the carboxy ester group on the steroid nucleus.

New potent topical anti-inflammatory steroids with reduced side effects: derivatives of steroid-16-carboxy esters

Therapeutic use of anti-inflammatory steroids is limited due to their potential suppressive effects on pituitary-adrenal function and the immune system. Based on the antedrug concept, a new class of potent locally active compounds with reduced risk of side effects has been synthesized from prednisolone by introducing a metabolically labile methoxycarbonyl substituent at C-16. Results of topical application of the lead compound, methyl 11 beta,17 alpha,21-trihydroxy-3,20-dioxo-pregna-1,4-diene-16 alpha-carboxylate (P16CM;1), showed that it was 14 times more potent than prednisolone and that it had a greatly reduced tendency to cause systemic side effects. In the present investigations, we have demonstrated that chemical modifications such as 17- and/or 21-esterifications and 17,21-acetonidation of 1 further enhance topical activity in the croton oil ear edema model in rats. Following multiple topical ID50 applications of 1 or its derivatives, no thymolysis was noted. In the carrageenan-soaked sponge model of acute inflammation, all derivatives were potent inhibitors of leukocyte migration, generation of PGE2, and release of elastase. Taken together, these results indicate that esterification or acetonidation of hydroxyl groups at the 17 and/or 21 position, in combination with a labile C-16 methoxycarbonyl group, increases topical activity without concomitantly increasing the risk of side effects.

In vivo plaque-forming cell suppression by methyl 20 beta-dihydroprednisolonate

Methyl 20 beta-dihydroprednisolonate, a new local antiinflammatory steroid, and its ester hydrolysis product, 20 beta-dihydroprednisolonic acid, were evaluated for potential immunosuppressive actions as determined by the splenic plaque-forming cell response assay. The parent compound, prednisolone, was used as a comparative agent. All three corticosteroid agents, when administered intraperitoneally or subcutaneously by separate injections given at the same time as antigen, demonstrated significant dose-related suppression of this immunologic parameter. In a croton oil-induced inflammation test (ear challenge in mice), methyl 20 beta-dihydroprednisolonate demonstrated significant antiinflammatory effects, but only in the ear to which it was applied. The comparative drug, prednisolone, significantly reduced inflammation in the ear to which it was applied and in the contralateral ear as well. The methyl ester derivative demonstrated effective antiinflammatory activity when applied topically in the oxazolone delayed-type hypersensitivity test (ear challenge in mice). The results seen in the plaque-forming cell response are in contrast to the generally noted lack of systemic glucocorticoid actions of the steroid acid ester derivatives reported in other studies.

Modulation by glycyrrhetinic acid derivatives of TPA-induced mouse ear oedema

1. The anti-inflammatory effects of glycyrrhetinic acid and its derivatives on TPA (12-O-tetradecanoylphorbol-13-acetate)-induced mouse ear oedema were studied. The mechanisms of TPA-induced ear oedema were first investigated with respect to the chemical mediators. 2. The formation of ear oedema reached a maximum 5 h after TPA application (2 micrograms per ear) and the prostaglandin E2 (PGE2) production of mouse ear increased with the oedema formation. 3. TPA-induced ear oedema was prevented by actinomycin D and cycloheximide (0.1 mg per ear, respectively) when applied during 60 min after TPA treatment. 4. Of glycyrrhetinic acid derivatives examined, dihemiphthalate derivatives (IIe, IIe', IIIa, IIIa', IVa, IVa') most strongly inhibited ear oedema on both topical (ID50, 1.6 mg per ear for IIe, 2.0 mg per ear for IIIa and 1.6 mg per ear for IVa) and oral (ID50, 88 mg kg-1 for IIe', 130 mg kg-1 for IIIa' and 92 mg kg-1 for IVa') administration. 5. Glycyrrhetinic acid (Ia) and its derivatives applied 30 min before TPA treatment were much more effective in inhibiting oedema than when applied 30 min after TPA. A dihemiphthalate of triterpenoid compound IVa completely inhibited oedema, even when applied 3 h before TPA treatment. 6. Glycyrrhetinic acid (Ia) and deoxoglycyrrhetol (IIa), the parent compounds, produced little inhibition by oral administration at less than 200 mg kg-1. 7. These results suggest that the dihemiphthalate derivatives of triterpenes derived from glycyrrhetinic acid by chemical modification are useful for the treatment of skin inflammation by both topical and oral application.