Saredutant (SR 48968)

The effect of the NK2 tachykinin receptor antagonist SR 48968 (saredutant) on neurokinin A-induced bronchoconstriction in asthmatics

Inhalation of neurokinin (NK) A causes bronchoconstriction in patients with asthma. The NKA-induced bronchoconstriction in isolated human airways is mediated via the NK2 receptor and inhibited by SR 48968, a potent and specific nonpeptide tachykinin NK2 receptor antagonist. In the present study, the effect of orally administered SR 48968 on NKA-induced bronchoconstriction was examined in 12 mild asthmatics. On the screening day and during the study periods, increasing concentrations of NKA (3.3 x 10(-9) to 1.0 x 10(-6) mol x mL(-1)) were inhaled, until the forced expiratory volume in one second (FEV1) and specific airway conductance (sGaw) decreased by at least 20 and 50%, respectively. During the study periods, 100 mg SR 48968 or matched placebo was ingested in a double-blind, randomized, crossover fashion and NKA provocation was performed at 1.5 and 24 h after dosing. At 1.5 h, the mean (SEM) log10 provocative concentration of NKA causing a 20% fall in FEV1 (PC20 FEV1) was -6.25 (0.20) after SR 48968 and -6.75 (0.17) after placebo (p=0.05); the mean log10 provocative concentration of NKA causing a 35% fall in sGaw (PC35 sGaw) was -7.02 (0.28) after SR 48968 and -7.64 (0.19) after placebo (p=0.05). At 24 h, the mean log10 PC20 FEV1 was -6.21 (0.17) after SR 48968 and -6.65 (0.11) after placebo (p=0.05); the mean log10 PC35 sGaw was -6.85 (0.23) after SR 48968 and -7.17 (0.15) after placebo (nonsignificant). As PC20 FEV1 and/or PC35 sGaw were not reached in up to 4 patients per SR 48968 group, the differences between SR 48968 and placebo were underestimated. In conclusion, oral treatment with 100 mg SR 48968 caused a significant inhibition of neurokinin A-induced bronchoconstriction in asthmatics. This finding constitutes the first evidence of inhibition of sensory neuropeptide-induced bronchoconstriction by a selective tachykinin receptor antagonist in humans.

Effect of the two tachykinin antagonists, SR 48968 and SR 140333, on cough induced by citric acid in the unanaesthetized guinea pig

It is now well-established that sensory nerves stimulation in the airway induces bronchoconstriction and inflammation, but also protective reflexes, such as coughing. These effects are mediated through the release of tachykinins (substance P and neurokinin A) and we have recently shown that SR 48968, a tachykinin NK2-receptor antagonist, inhibited cough induced by citric acid. In this paper, we have studied the effects of SR 48968 administered by aerosol. We have also investigated the effects of SR 140333, a tachykinin NK1-receptor antagonist, and the combination of both SR 48968 and SR140333 to determine whether tachykinin NK1 receptors are involved in cough. Finally, we have studied the combined effects of SR 48968 and salbutamol to find out whether the antitussive effect of SR 48968 is a consequence of the inhibition of bronchoconstriction. Unanaesthetized guinea-pigs were placed in a transparent chamber and exposed to an aerosol of citric acid (0.4 M). The number of coughs was counted by visual inspection and by determination of sounds and pressure variations in the chamber. By the aerosol route, SR 48968 was an efficient antitussive and 16 times more potent than codeine. SR 140333 (0.1-1 mg.kg-1 i.p.) did not exert any antitussive effect but it potentiated the maximal effect induced by SR 48968. Finally, salbutamol, in a dose (0.3 mg.kg-1) which inhibits bronchoconstriction, but not cough induced by citric acid, did not modify the antitussive effect of SR 48968.(ABSTRACT TRUNCATED AT 250 WORDS)

SR 48968, a neurokinin A (NK2) receptor antagonist

Effects of SR 140333 and SR 48968 on antigen and substance P-induced activation of guinea-pig alveolar macrophages

Background: Tachykinins, such as substance P, might be involved in the development of airway hyperresponsiveness and airway inflammation.
Objective: This study was designed to investigate the effects of the tachykinin NK1 receptor antagonist SR 140333 (Nolpitantium) and the NK2 receptor antagonist SR 48968 (Saredutant) on the activation of alveolar macrophages in the guinea-pig.
Methods: Guinea-pigs sensitized and challenged by ovalbumin administered by aerosol or naive guinea-pigs were exposed by aerosol to the neutral endopeptidase, phosphoramidon and, 15 min later, to substance P. Twenty-four hours later, bronchoalveolar lavages were performed and the cell composition of bronchoalveolar lavage fluids and the arachidonate release from alveolar macrophages stimulated in vitro with fMLP were evaluated.
Results: Antigen challenge in sensitized guinea-pigs induced an increase in the total number of cells and granulocytes in the bronchoalveolar lavage fluids that was not reduced by pre-treatment of guinea-pigs with a single dose of SR 140333 or SR 48968 (1 mg/kg). Substance P exposure in phosphoramidon-pretreated guinea-pigs did not induce an increase in the total number of cells. In contrast, antigen or substance P exposure induced a significant increase in the in vitro fMLP-induced arachidonate release from alveolar macrophages. Pre-treatment of the guinea pigs with SR 140333 or SR 48968 did not reduce the increase in arachidonate release from fMLP-stimulated alveolar macrophages from sensitized and challenged guinea-pigs. Pre-treatment of the animals by SR 140333 and SR 48968 reduced the enhanced arachidonate release induced by fMLP from substance P-exposed guinea-pigs.
Conclusion: The present data demonstrate the importance of NK1- and NK2-receptor stimulation in the development of substance P-induced increased reactivity of alveolar macrophages.

Central antitussive activity of the NK1 and NK2 tachykinin receptor antagonists, CP-99,994 and SR 48968, in the guinea-pig and cat

1. The purpose of this study was to investigate the antitussive activity and sites of action of the NK1 and NK2 tachykinin receptor antagonists, CP-99,994, SR 48968, and the racemate of SR 48968, SR 48212A in the cat and guinea-pig. 2. Guinea-pigs were dosed subcutaneously (s.c.) with CP-99,994, SR 48212A or SR 48968 one hour before exposure to aerosols of capsaicin (0.3 mM) to elicit coughing. Coughs were detected with a microphone and counted. 3. Intracerebroventricular (i.c.v.) cannulae were placed in the lateral cerebral ventricles of anaesthetized guinea-pigs. Approximately one week later, the animals were dosed with CP-99,994 or SR 48212A (i.c.v.) and exposed to aerosols of capsaicin (0.3 mM) to elicit coughing. 4. Cough was produced in anaesthetized cats by mechanical stimulation of the intrathoracic trachea and was monitored from electromyograms of respiratory muscle activity. Cannulae were placed for intravenous (i.v.) or, in separate groups of animals, intravertebral arterial (i.a.) administration of CP-99,994, SR 48212A or SR 48968. Dose-response relationships for i.v. and i.a. administration of each drug were generated to determine a ratio of i.v. ED50 to i.a. ED50, known as the effective dose ratio (EDR). The EDR will be 20 or greater for a centrally active drug and less than 20 for a peripherally active drug. 5. In the guinea-pig, CP-99,994 (0.1-30 mg kg-1, s.c.), SR 48212A (1.0-30 mg kg-1, s.c.), and SR 48968 (0.3-3.0 mg kg-1, s.c.) inhibited capsaicin-induced cough in a dose-dependent manner. Capsaicin-induced cough was also inhibited by i.c.v. administration of CP-99,994 (10 and 100 micrograms) or SR 48212A (100 micrograms). 6. In the cat, both CP-99,994 (0.0001-0.3 mg kg-1, i.a., n = 5; 0.003-3.0 mg kg-1, i.v., n = 5) and SR 48212A (0.003-1.0 mg kg-1, i.a., n = 5; 0.01-3.0 mg kg-1, i.v., n = 5) inhibited mechanically induced cough by either the i.v. or i.a. routes in a dose-dependent manner. SR 48968 (0.001-0.3 mg kg-1, i.a., n = 5; 0.03-1.0 mg kg-1, i.v., n = 5) inhibited cough when administered by the i.a. route in a dose-dependent manner, but had no effect by the i.v. route up to a dose of 1.0 mg kg-1. Intravenous antitussive potencies (ED50, 95% confidence interval (CI) of these compounds were: CP-99,994 (0.082 mg kg-1, 95% CI 0.047-0.126), SR 48212A (2.3 mg kg-1, 95% CI 0.5-20), and SR 48968 (> 1.0 mg kg-1, 95% CI not determined). The intra-arterial potencies of these compounds were: CP-99,994 (1.0 microgram kg-1, 95% CI 0.4-1.8), SR 48212A (25 micrograms kg-1, 95% CI 13-52), and SR 48968 (8.0 micrograms kg-1, 95% CI 1-32). The derived EDRs for each compound were: CP-99,994, 82; SR 48212A, 92; and SR 48968, > 125. 7. We concluded that CP-99,994 and SR 48968 inhibit cough in the guinea-pig and cat by a central site of action. In the cat, the antitussive action of these compounds appears to be solely by a central site.