[Significance and creation of novel cyclooxygenase-1 (COX-1) selective inhibitors].

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to relieve physical and mental pain, and to improve patients' quality of life. However, stomach irritation is a major side effect. Most NSAIDs inhibit cyclooxygenases (COXs), and inhibition of COX-1 on the stomach mucous membrane is thought to be responsible for the gastric disturb- ance. Consequently, development efforts have focused on COX-2-selective inhibitors, while COX-1-selective inhibitors have been rather neglected. Subsequently, however, it was shown that inhibition of either COX-1 or COX-2 alone does not induce gastric damage. Therefore, we have developed the COX-1-selective inhibitor N-(4-aminophenyl)-4-trifluoromethylbenzamide (TFAP), which shows analgesic activity without causing gastric damage. However, metabolism of TFAP generates a colored metabolite, resulting in red-purple coloration of urine after administration. In addition, the analgesic activity of TFAP is weaker than that of indomethacin. Thus, we designed a series of new COX-1-selective inhibitors, the 5-amino-2-ethoxy-N-(substituted)benzamide (ABEX) series, in order to avoid formation of the colored metabolite by modifying the diaminopyridine skeleton. As a result of structural modification and in vitro and in vivo testing of compounds in the ABEX series, we found a novel COX-1-selective inhibitor, 5-amino-2-ethoxy-N-(3-trifluoromethylphenyl)benzamide (ABEX-3TF), which shows better analgesic activity than indomethacin, and does not cause coloration of urine.

Identification of urine metabolites of TFAP, a cyclooxygenase-1 inhibitor.

Only a few COX-1-selective inhibitors are currently available, and the research on COX-1 selective inhibitors is not fully developed. The authors have produced several COX-1 selective inhibitors including N-(5-amino-2-pyridinyl)-4-trifluoromethylbenzamide: TFAP (3). Although 3 shows potent analgesic effect without gastric damage, the urine after administration of 3 becomes red-purple. Since the colored-urine should be avoided for clinical use, in this research we examined the cause of the colored-urine. UV-vis spectra and LC-MS/MS analyses of urine samples and metabolite candidates of 3 were performed to afford information that the main reason of the colored urine is a diaminopyridine (4), produced by metabolization of 3. This information is useful to design new COX-1 selective inhibitors without colored urine based on the chemical structure of 3.

Modification at the acidic domain of RXR agonists has little effect on permissive RXR-heterodimer activation.

Retinoid X receptors (RXRs) function as homo- or heterodimers with other nuclear receptors, such as peroxisome proliferator-activated receptors (PPARs), which are targets for treatment of hyperlipidemia and type 2 diabetes, or liver X receptors (LXRs), which are involved in glucose/lipid metabolism. PPAR/RXR or LXR/RXR are known as permissive RXR-heterodimers because they are activated by RXR agonists alone. Interestingly, the pattern of RXR-heterodimer activation is different depending on the RXR agonist structure, but the structure-activity relationship has not been reported. Here we show that modification or replacement of the carboxyl group in the acidic domain of RXR agonists has little or no effect on permissive RXR-heterodimer activation. Phosphonic acid (9), tetrazole (10), and hydroxamic acid (12) analogues were synthesized from the common bromo intermediate 7. Except for 9, these compounds showed RXR full-agonistic activities in the concentration range of 1-10 microM. The order of agonistic activity toward both PPARgamma/RXRalpha and LXRalpha/RXRalpha was the same as it was for RXR, that is, 11>10>12. These results should be useful for the development of RXR agonists with improved bioavailability.

Design and synthesis of novel cyclooxygenase-1 inhibitors as analgesics: 5-amino-2-ethoxy-N-(substituted-phenyl)benzamides.

We previously found that N-(4-aminophenyl)-4-trifluoromethylbenzamide (TFAP), a COX-1 inhibitor, exhibits an analgesic effect without causing gastric damage. Unfortunately, TFAP causes reddish purple coloration of urine, and its analgesic effect is less potent than that of indomethacin. Herein we describe our study focusing on the development of 4- and 5-amino-2-alkoxy-N-phenylbenzamide scaffolds, designed on the basis of the structures of TFAP and parsalmide, another known COX-1 inhibitory analgesic agent. 5-Amino-2-ethoxy-N-(2- or 3-substituted phenyl)benzamide derivatives exhibited analgesic activity in a murine acetic acid induced writhing test. Among these compounds, 5-amino-2-ethoxy-N-(2-methoxyphenyl)benzamide (9 v) possesses potent COX-1 inhibitory and analgesic activities, similar to those of indomethacin. In addition, 5-amino-2-ethoxy-N-(3-trifluoromethylphenyl)benzamide (9 g) showed a more potent analgesic effect than indomethacin or 9 v without causing apparent gastric damage or coloration of urine, although its COX-1 inhibitory activity was weaker than that of indomethacin or 9 v. Thus, 9 g and 9 v appear to be promising candidates for analgesic agents and are attractive lead compounds for further development of COX-1 inhibitors.