Neurokinins are known to induce
neurogenic inflammation related to
respiratory diseases, though there is little information on triple neurokinin receptor antagonists. The pharmacological properties of the novel triple neurokinin 1, 2 and 3 receptor antagonist [1-(2-[(2R)-(3,4-dichlorophenyl)-4-(3,4,5-trimethoxybenzoyl)morpholin-2-yl]ethyl)spiro[benzo[c]
thiophene-1(3H),4'-
piperidine]-(2S)-
oxide hydrochloride] (CS-003) were evaluated in this study. The binding affinities of
CS-003 were evaluated with human and guinea pig neurokinin receptors. As well, the in vivo antagonism of
CS-003 against exogenous neurokinins and effects on
capsaicin-induced and
citric acid-induced responses were investigated in guinea pigs.
CS-003 exhibited high affinities for human neurokinin 1, neurokinin 2 and
neurokinin 3 receptors with Ki values (mean+/-S.E.M.) of 2.3+/-0.52, 0.54+/-0.11 and 0.74+/-0.17 nM, respectively, and for the guinea pig receptors with Ki values of 5.2+/-1.4, 0.47+/-0.075 and 0.71+/-0.27 nM, respectively. Competitive antagonism was indicated in a Schild analysis of
substance P-,
neurokinin A- and
neurokinin B-induced
inositol phosphate formation with pA2 values of 8.7, 9.4 and 9.5, respectively.
CS-003 inhibited
substance P-induced tracheal vascular hyperpermeability,
neurokinin A- and
neurokinin B-induced bronchoconstriction with ID50 values of 0.13, 0.040 and 0.063 mg/kg (i.v.), respectively.
CS-003 also inhibited
capsaicin-induced bronchoconstriction (ID50: 0.27 mg/kg, i.v.), which is caused by endogenous neurokinins.
CS-003 significantly inhibited
citric acid-induced
coughs and the effect was greater than those of other selective neurokinin receptor antagonists.
CS-003 is a potent antagonist of triple neurokinin receptors and may achieve the best therapeutic efficacy on
respiratory diseases associated with neurokinins compared to selective neurokinin receptor antagonists.