SB705498 is a TRPV1 antagonist for hTRPV1, antagonizes capsaicin, acid, and heat activation of TRPV1 with IC50 of 3 nM, 0.1 nM and 6 nM, shows a degree of voltage dependence, exhibits >100-fold selectivity for TRPV1 over TRPM8.

SB705498 potently inhibits capsaicin-induced activation of human TRPV1 expressed in 1321N1 cells or HEK293 cells with apparent pKi of 7.5 or 7.6, respectively. Coapplication of 100 nM SB705498 rapidly, completely and reversibly inhibits hTRPV1 expressed in HEK293 cells. Compared with placebo, SB705498 reduced the area of capsaicin-evoked flare (P=0.0047). The heat pain threshold on non-sensitised skin was elevated following SB705498 (estimated difference from placebo [95% confidence intervals]: 1.3 degrees C [0.07,2.53], P=0.019). Following capsaicin sensitisation, the heat pain threshold and tolerance were similar between SB705498 and placebo. However, SB705498 increased heat pain tolerance at the site of UVB-evoked inflammation (estimated difference from placebo: 0.93 degrees C [0.25,1.6], P=0.0054). The magnitude of the pharmacodynamic effects of SB705498 appeared to be related to plasma concentration. These results indicate that SB705498, at a clinically safe and well-tolerated dose, has target-specific pharmacodynamic activity in humans. These data provide the first clinical evidence that a TRPV1 antagonist may alleviate pain and hyperalgesia associated with inflammation and tissue injury.