NS 398 is a selective inhibitor of cyclooxygenase-2 with IC50 value of 3.8 μM [1].

Cyclooxygenase (COX) is an enzyme that is responsible for the formation of prostaglandins, prostacyclin and thromboxane. COX-2 converts arachidonic acid (AA) to prostaglandin endoperoxide H2.

NS 398 is a selective COX-2 inhibitor and a novel anti-inflammatory agent. NS 398 inhibited COX-2 with IC50 value of 3.8 μM in a concentration-dependent way [1]. In RG/C2, AA/C1 and RR/C1 pre-malignant human colorectal adenoma cell lines, NS-398 (20 ~ 100 μM) inhibited cell proliferation and induced apoptosis. In HT29 colorectal carcinoma cell lines, NS-398 induced apoptosis. Also, NS-398 increased COX-2 protein expression. In HT29 cultures, NS-398 inhibited prostaglandin E2 secretion and COX-2 activity [2].

In rats with trauma, NS-398 (0.3-5 mg/kg) exhibited anti-inflammatory and analgesic effects [1]. In Balb/C mice, NS-398 (10 mg/kg) reduced prostaglandin E2 (PGE2) production and also significantly decreased the production of NO, IL-6 and TNF-α. Also, NS-398 decreased the mRNA levels of COX-2 and inhibited NF-κB activation. These results suggested that NS-398 regulated the inflammatory response after trauma and improved survival [3].

References:
[1].  Futaki N, Takahashi S, Yokoyama M, et al. NS-398, a new anti-inflammatory agent, selectively inhibits prostaglandin G/H synthase/cyclooxygenase (COX-2) activity in vitro. Prostaglandins, 1994, 47(1): 55-59.
[2].  Elder DJ, Halton DE, Crew TE, et al. Apoptosis induction and cyclooxygenase-2 regulation in human colorectal adenoma and carcinoma cell lines by the cyclooxygenase-2-selective non-steroidal anti-inflammatory drug NS-398. Int J Cancer, 2000, 86(4): 553-560.
[3].  Mack Strong VE, Mackrell PJ, Concannon EM, et al. NS-398 treatment after trauma modifies NF-kappaB activation and improves survival. J Surg Res, 2001, 98(1): 40-46.