TFAP (Okayama University)

Cyclooxygenase -1 (COX-1) selective inhibitors are anticipated to be potential therapeutic agents for thrombosis, tumorigenesis, atherosclerosis, neuroprotection, and oxidative stress. In this study, a 3D-QSAR pharmacophore model was developed for potent and selective COX-1 inhibition based on 44 compounds from four different scaffolds using Phase, Schrödinger. One (hydrogen-bond) acceptor, one hydrophobic, and two aromatic sites (AHRR) contribute to COX-1 inhibitory activity. Test and decoy sets were used to corroborate the best hypothesis and the validated hypothesis was used to screen the SPECS database. The resultant hits were filtered by standard precision (SP) and extra precision (XP) modes of docking using Glide, Schrödinger which yielded five hits. Free energy calculations were carried out to quantify the affinity differences of the hits towards COX enzymes. These five hits were subjected to in vitro COX (ovine) inhibitory activity studies. The hits displayed potent COX-1 inhibitory activity and good selectivity versus COX-2 enzyme. The compounds also protected the nitric oxide (NO) induced cell death mediated by COX-1 in mouse macrophages cell line. Hence, we hypothesize that these compounds could be promising leads for the design of superior COX-1 inhibitors and insights gained from further exploration of the same could provide pertinent clues for the treatment of the conditions mentioned above.

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.