Pyrazole C-region analogues of 2-(3-fluoro-4-methylsulfonylaminophenyl)propanamides as potent TRPV1 antagonists.

A series of 1-substituted 3-(t-butyl/trifluoromethyl)pyrazole C-region analogues of 2-(3-fluoro-4-methylsulfonamidophenyl)propanamides were investigated for hTRPV1 antagonism. The structure activity relationship indicated that the 3-chlorophenyl group at the 1-position of pyrazole was the optimized hydrophobic group for antagonistic potency and the activity was stereospecific to the S-configuration, providing exceptionally potent antagonists 13S and 16S with Ki(CAP)=0.1nM. Particularly significant, 13S exhibited antagonism selective for capsaicin and NADA and not for low pH or elevated temperature. Both compounds also proved to be very potent antagonists for rTRPV1, blocking in vivo the hypothermic action of capsaicin, consistent with their in vitro mechanism. The docking study of compounds 13S and 16S in our hTRPV1 homology model indicated that the binding modes differed somewhat, with that of 13S more closely resembling that of GRT12360.