Nolpitantium (SR-140333) is a highly selective nonpeptide antagonist of neurokinin-1 (NK1) receptor. Nolpitantium potently, selectively and competitively inhibited substance P binding to NK1 receptors from various animal species, including humans. In vitro, it was a potent antagonist in functional assays for NK1 receptors such as [Sar9, Met(O2)11]substance P-induced endothelium-dependent relaxation of rabbit pulmonary artery and contraction of guinea-pig ileum. Up to 1 mkM, Nolpitantium had no effect in bioassays for NK2 and NK3 receptors. The antagonism exerted by Nolpitantium toward NK1 receptors was apparently non-competitive, with pD2' values between 9.65 and 10.16 in the different assays. Nolpitantium also blocked in vitro [Sar9, Met(O2)11]substance P-induced release of acetylcholine from rat striatum. In vivo, Nolpitantium exerted highly potent antagonism toward [Sar9, Met(O2)11]substance P-induced hypotension in dogs, bronchoconstriction in guinea-pig) and plasma extravasation in rats. Nolpitantium was found to be effective in the modulation of the inflammatory response and airway remodeling in mice. Nolpitantium is reported to cause antagonism of the SP-induced relaxations of human isolated intralobar pulmonary arterial rings. Nolpitantium also blocked the activation of rat thalamic neurons after nociceptive stimulation. Nolpitantium has been shown to reduce the severity of inflammation in trinitrobenzene sulfonic acid-induced colitis in the rat colon. Nolpitantium inhibited mustard oil-induced plasma protein extravasations in the dorsal skin of the rat hind paw. Nolpitantium had been in some phase II clinical trials but further studies were discontinued.