Discovery, optimization, and biological evaluation of 5-(2- (trifluoromethyl)phenyl)indazoles as a novel class of transient receptor potential A1 (TRPA1) antagonists

Rooney, Lisa,Vidal, Agnès,D'Souza, Anne-Marie,Devereux, Nick,Masick, Brian,Boissel, Valerie,West, Ryan,Head, Victoria,Stringer, Rowan,Lao, Jianmin,Petrus, Matt J.,Patapoutian, Ardem,Nash, Mark,Stoakley, Natalie,Panesar, Moh,Verkuyl, J. Martin,Schumacher, Andrew M.,Petrassi, H. Michael,Tully, David C.

, p. 5129 - 5140 (2014/07/08)

A high throughput screening campaign identified 5-(2-chlorophenyl)indazole compound 4 as an antagonist of the transient receptor potential A1 (TRPA1) ion channel with IC50 = 1.23 μM. Hit to lead medicinal chemistry optimization established the SAR around the indazole ring system, demonstrating that a trifluoromethyl group at the 2-position of the phenyl ring in combination with various substituents at the 6-position of the indazole ring greatly contributed to improvements in vitro activity. Further lead optimization resulted in the identification of compound 31, a potent and selective antagonist of TRPA1 in vitro (IC50 = 0.015 μM), which has moderate oral bioavailability in rodents and demonstrates robust activity in vivo in several rodent models of inflammatory pain.