Br. J. Pharmacol. (1992), 107, 785-789 © Macmillan Press Ltd, 1992
`
`Pharmacological profile of a high affinity dipeptide NK,
`receptor antagonist, FK888
`
`' Takashi Fujii, Masako Murai, Hiroshi Morimoto, Yasue Maeda, Makiko Yamaoka, *Daijiro
`Hagiwara, *Hiroshi Miyake, *Norihiro Ikari & *Masaaki Matsuo
`
`Department of Pharmacology and *Department of Chemistry, New Drug Research Laboratories, Fujisawa Pharmaceutical
`Co., Ltd, 1- 6, 2-chome, Kashima, Yodogawa-ku, Osaka, 532, Japan
`
`1 In our search for compounds that inhibit the binding of [*H]-substance P (SP) to guinea-pig lung
`membranes, the dipeptide SP antagonist, FK888, was developed by chemical modification of the parent
`compound, (D-Pro®, D-Trp™*!°, Phe'")SP,._ ;.
`
`2 In a [*H}-SP binding assay using guinea-pig lung membranes and rat brain cortical synaptic
`membranes, FK888 displaced [*H]-SP binding with a K; value of 0.69 £ 0.13nM and 0.45 % 0.17 pMm,
`respectively, in a competitive manner.
`
`3 FKB888 inhibited the contraction of guinea-pig isolated ileum induced by SP in the presence of
`atropine and indomethacin (a NK, receptor bioassay) with a pA, value of 9.29 (8.60— 9.98).
`
`4 FK3888 inhibited contractions of rat vas deferens by NKA (a NK, receptor bioassay) and of rat
`portal vein by NKB (a NK; receptor bioassay) at concentrations at least 10,000 times greater than that
`required to inhibit contractions of guinea-pig ileum.
`
`5 FK3888 also inhibited SP-induced airway oedema in guinea-pig after both intravenous and oral
`administration.
`
`6 These data demonstrate that FK888 is a potent and selective NK, antagonist which is active both in
`
`vitro and in vivo.
`
`Keywords: Substance P; tachykinin; antagonist; NK-receptor; airway oedema
`
`Introduction
`
`The discovery of several highly selective tachykinin receptor
`antagonists has recently been reported. Snider et al. (1991)
`and Garret et al. (1991) described the NK, receptor selective
`antagonists, CP-96,345 and RP 67589, respectively, and
`Maggi et al. (1991) and Emonds-Alt et al. (1992) described
`NK, receptor selective antagonists, MEN-10376 and SR
`48968, respectively. Substance P (SP) and its related peptides
`(neurokinin A, neurokinin B) elicit a wide range of biological
`actions in mammals via three different receptors (NK,, NK,
`and NK;) (Guard & Watson, 1991). For example, they cause
`hypotension as a result of vasodilatation (NK,), increase
`vascular permeability (NK,) and contract smooth muscle
`(NK,, NK,, NK;). The involvement of tachykinins in the
`pathophysiology of many disease states has been suggested
`(Pernow, 1983). The discovery of novel, selective SP
`antagonists will be useful both experimentally and clinically
`because it will allow further studies aimed at clarifying the
`role of tachykinins in physiological and pathophysiological
`conditions. We have been undertaking research to discover
`new SP antagonists for several years and have previously
`described the cyclic peptide antagonist FK224, a NK, and
`NK, dual type antagonist isolated from fermentation prod-
`ucts (Morimoto et al., 1992b; Murai et al., 1992), and the
`synthetic tripeptide NK, receptor antagonist, FR113680,
`which was produced by chemical modification of the parent
`compound, (D-Pro*, D-Trp”*'°, Phe!!)SP,_,, (Hagiwara et al.,
`1991; Morimoto et al., 1992a). After further modification of
`FR113680, we have successfully produced a very potent
`dipeptide NK, receptor antagonist FK888, N>-[(4R)-4-
`hydroxy - | -(1-methyl-1H-indol-3-yl)carbonyl-L-prolyl]- N-
`methyl-N-phenylmethyl-3-(2-naphthyl)-L-alaninamide, (Figure
`1). In this paper, we describe the pharmacological properties
`of FK888 in both in vitro and in vivo experiments.
`
`! Author for correspondence.
`
`Methods
`
`Receptor binding
`
`Guinea-pig lung membranes were prepared according to the
`method described by Norman ez al. (1987) with the following
`modification. Male Hartley guinea-pigs weighing 300-400 g
`were killed, and whole lungs together with the airway tracts
`were removed. The isolated whole lung tissues were
`homogenized in 10 volumes of ice cold Tris-HCl buffer
`(pH 7.5) containing 0.25 M sucrose and 0.1 mM EDTA using
`a Polytron PT-10. The homogenate was centrifuged at
`1,000 g for 10 min and the supernatant was collected. The
`supernatant obtained was further centrifuged at 35,000 g for
`20 min. The pellet was washed twice with 9 vol of 5mM
`Tris-HCl buffer (pH7.5) and the final pellet was re-
`suspended in 50 mM Tris-HCI buffer (pH 7.5) and stored at
`— 70°C until use.
`
`Rat cerebral cortical synaptic membranes were prepared
`according to the methods described by Zukin et al. (1974).
`Male Sprague-Dawley rats weighing 250—300 g were killed,
`and the cerebral cortex was rapidly removed and homo-
`genized in 9 vol of ice cold 1 mM phosphate buffer (pH 7.5)
`
`CO—N CHs
`| CO—NH CO—N
`N
`
`|
`CH,3
`
`Q
`X
`
`Figure 1 Chemical structure of FK888.
`
`HELSINN EXHIBIT 2049
`Azurity Pharmaceuticals, Inc. v. Helsinn Healthcare S.A.
`
`Page 1 of 5 IPR2025-00945
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`786 T. FUJII et al.
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`containing 0.32M sucrose and 0.1 mM EDTA in a glass
`homogenizer fitted with a Teflon pestle. The homogenate was
`centrifuged at 1,000 g for 10 min and the supernatant was
`collected. The supernatant was then centrifuged at 20,000 g
`for 20 min. The crude synaptosomal pellet was resuspended
`in distilled water to lyse the synaptosomes. The suspension
`was then centrifuged at 8,000 g for 20 min. The supernatant
`was removed and the soft buffy uppercoat of the pellet was
`collected by careful rinsing with the supernatant. The com-
`bined supernatant and buffy coat layer was then centrifuged
`at 35,000 g for 20 min and the pellet was washed twice with 9
`vol of SmM Tris-HCI buffer (pH 7.5). The final pellet was
`stored at — 70°C until use.
`
`The radioligand binding experiments were performed ac-
`cording to the methods described by Lee et al. (1983) with a
`slight modification. Binding was initiated by adding 100 pl of
`the membrane preparations (final concentration, circa 0.6 mg
`protein/tube) in a final volume of 500 pl of 50 mM Tris-HCI
`buffer (pH 7.5) containing 1 mM MnCl,, 200 pg ml~! bovine
`serum albumin (BSA), Spgml-! chymostatin, 4pgml-!
`leupeptin, 40 pgml~! bacitracin, 10 pM phosphoramidon,
`1 oM [PH]-SP and various concentrations of FK888. Assays
`were performed in duplicate. The reaction mixtures were
`incubated at 25°C for 30 min. At the end of the incubation
`period, 5 ml of ice cold 50 mM Tris-HCI buffer was added to
`each tube and its content was filtered immediately under
`reduced pressure through Whatman GF/B glass filters
`pretreated with 0.1% polyethyleneimine solution for 3 h
`before use. Each of the filters was then washed three times
`with 5 ml of ice cold 50 mM Tris-HCI buffer and radioactivity
`measured by liquid scintillation spectrometry. Non-specific
`binding was defined as binding in the presence of 5uM SP.
`Specific binding was calculated by subtracting non-specific
`binding from total binding. Specific binding corresponded to
`about 85% of total binding in all cases. The protein concent-
`ration was determined by the method of Lowry et al. (1951)
`with BSA used as a standard. ICs, values were determined by
`the data from three independent experiments. Scatchard
`analysis of saturation data was performed by the regression
`analysis using the data from three independent experiments.
`
`Functional assays
`
`In order to evaluate receptor selectivity, the following three
`experiments were performed: contraction of guinea-pig ileum
`by SP in the presence of atropine and indomethacin (a NK,
`receptor bioassay), contraction of rat vas deferens by NKA
`(a NK, receptor bioassay) and contraction of rat portal vein
`by NKB (a NK; receptor bioassay), (Lee et al., 1982; Mast-
`rangelo et al, 1986; Regoli et al., 1988). Tissues were
`obtained from male guinea-pigs (Hartley, 300—400g) and
`male rats (Sprague-Dawley, 250—350 g). Strips of guinea-pig
`ileum were suspended in 10 ml organ baths filled with warm
`(37°C), oxygenated (95% 0,/5% CO,) Tyrode solution con-
`taining 5.2 uM atropine sulphate and 4.1 pM indomethacin
`under a tension of 0.5 g. Strips of rat vas deferens and rat
`portal vein were suspended in Tyrode solution (not supp-
`lemented with atropine and indomethacin) under a tension of
`0.3 g and 0.5 g, respectively. Tension change was monitored
`isometrically with a force-displacement transducer connected
`to a polygraph system. The contraction of each tissue was
`induced by addition of a submaximal concentration of each
`agonist (SP 1nM, NKA 100nM and NKB 100 nM). Test
`drugs were applied 10 min before agonists. To obtain pA,
`values in the guinea-pig ileum, dose-response curves to SP
`(0.1 nM—100 uM) in the absence and the presence of FK888
`were obtained. Results were expressed as mean * s.e.mean
`from 5-6 preparations and the ICs, values were determined
`by the probit method. The pA, values and slopes were deter-
`mined by regression analysis of Schild plots as described by
`Arunlakshana & Schild (1959), using the data from 5-6
`experiments in each dose.
`
`Page 2 of 5
`
`Airway oedema in guinea-pig
`
`Male albino guinea-pigs weighing 260440 g were given a
`solution of SP (I nmol kg™') or capsaicin (320 nmol kg~!)
`containing Evans Blue dye (20mgkg~') and heparin
`(200 iu kg~') by i.v. administration. Ten min later animals
`were stunned, bled and perfused through the pulmonary
`artery with 50 ml saline. The trachea and main bronchi were
`removed, blotted dry and weighed. The trachea and main
`bronchi were then incubated at 37°C in 0.5ml of 1 N KOH
`overnight and Evans Blue dye was then extracted by addition
`of 4.5ml of 0.6 N H,PO,: acetone (5:13) solution. After
`centrifugation at 3,000 r.p.m. for 15 min, the concentration
`of extracted Evans Blue dye in the supernatant was
`quantified from light absorbance at 620 nm by interpolation
`on standard curve of dye concentrations in the range
`0-4pgml~!. Test drugs or control vehicles were admini-
`stered i.v. 2min before an agonist challenge. Increased
`amount of leaked Evans Blue dye was calculated by subtrac-
`ting the Evans Blue content obtained from animals injected
`with Evans Blue dye and heparin solution without agonist.
`Results were expressed as mean * s.e.mean and statistical
`analysis was performed by a Student’s ¢ test for unpaired
`data.
`
`Materials
`
`Tris; 2-amino-2-(hydroxymethyl)-1,3-propanediol, acid, BSA,
`chymostatin, leupeptin, bacitracin and capsaicin were pur-
`chased from Sigma Chemical Company (St. Louis, U.S.A.);
`polyethyleneimine, histamine and atropine sulphate were
`obtained from Nakarai Tesque Chemical Company (Kyoto,
`Japan). Phosphoramidon and substance P were from Peptide
`Institute Inc. (Osaka, Japan). Evans Blue dye was from E.
`Merck (Darmstadt, Germany). [’H]-SP (1.65 TBq mmol~!)
`was purchased from Amersham International plc (Amer-
`sham, U.K.). (% )-CP-96,345 was synthesized in our labora-
`tories as a racemic mixture according to the method
`described by Lowe et al. (1991).
`
`Results
`
`Effect of FK888 on tachykinin receptors
`
`FK888 inhibited [*H}-SP (1 nM) binding to guinea-pig lung
`membranes in a dose-dependent manner with an ICs, value
`of 6.9t13nM (K;=0.69%0.13nM). FK888 also dose-
`dependently inhibited [*H}-SP (1 nM) binding to rat brain
`cortical synaptic membranes but with a lower affinity
`(ICs=1.810.7uM, K;=0.45%0.17 uMm). The specificity of
`FK888 in the binding assay was tested in the following
`experiments: [*’H]-quinuclidinyl benzilate (1 nM), [’H]-leuko-
`triene D, (PH}-LTD,, 0.3 nM) and [’H]-bradykinin (0.1 nM)
`binding to guinea-pig lung membranes; ['*’I}-cholecystokinin
`('*1}-CCK, 50pM) binding to rat pancreas membranes
`(CCK, receptor) and guinea-pig brain cortical membranes
`(CCKjp receptor); [*H]-angiotensin II (1 nM) binding to rat
`lung membranes; [*H}-Arg-vasopressin (0.5 nM) binding to
`rat liver membranes (V, receptor) and rat kidney medullary
`membranes (V, receptor); ['*’I}-endothelin-1 (50 pM) binding
`to a membrane preparation from CHO cells transfected with
`bovine ET, receptor cDNA and rat ETy receptor cDNA.
`FK888 (10 uM) did not inhibit ligand binding in any of these
`assays (data not shown).
`
`Unlabelled tachykinins displaced [*H]-SP binding to
`guinea-pig lung membranes with the following order of pot-
`ency: SP> physalaemin> > eledoisin™>NKA>NKB, sug-
`gesting that binding was predominantly to the NK, receptor.
`(£ )-CP-96,345, which is reported to be an NK, antagonist
`(Snider et al., 1991), also inhibited [*H]-SP binding to guinea-
`pig lung membranes with an ICs value of 4.7*0.2nM
`
`
`
`
`
`
`
`
`(K;=0.47 £ 0.02 nM). The mechanism of FK888 inhibition
`was studied by Scatchard analysis (Figures 2 and 3). In
`guinea-pig lung membrane, FK888 (0, 1, 3.2, 10 nM) in-
`creased Kp values (0.11, 0.16, 0.34, 0.99 nM) without chang-
`ing the B, values (Figure 2). Similarly in rat brain cortical
`synaptic membranes, FK888 (0, 1, 3.2 uM) also increased Kp
`values (0.34, 0.51, 0.90 nM) without changing the B, values
`(Figure 3). These results suggest that the inhibition of [*H]-SP
`binding in guinea-pig lung membranes or rat brain cortical
`synaptic membranes by FK888 was competitive.
`
`0.5
`
`04
`
`0.3
`
`0.2
`
`B/F (pmol mg~" protein nm~")
`
`0.1
`
`a
`0.0 L 1 1 L ;
`0.00 '0.01 0.02 0.03 0.04 0.05
`
`B (pmol mg~"! protein)
`
`Figure 2 Scatchard analysis of specific *H]-substance P ([*H]-SP)
`binding to guinea-pig lung membranes in the absence (@) and in the
`presence of FK888 at 10~° M (O), 3.2 x 10~°M (A) and 10-3 M (O).
`Data represent a typical experiment that was performed in duplicate
`and repeated three times with similar results.
`
`0.2
`
`0.1
`
`B/F (pmol mg~" protein nm~")
`
`0.0 L L 1
`0.00 0.01 0.02 0.03
`
`0.04 0.05 0.06 0.07
`B (pmol mg ™' protein)
`
`Figure 3 Scatchard analysis of specific [*H]-substance P (°H]-SP)
`binding to rat brain cortical synaptic membranes in the absence (@)
`and the presence of FK888 at 10~°m (O) and 3.2x 10-%M (A).
`Data represent a typical experiment that was performed in duplicate
`and repeated three times with similar results.
`
`Page 3 of 5
`
`A NOVEL NK,; ANTAGONIST, FK888 787
`
`The selectivity of FK888 for SP receptor subtypes (NK,,
`NK, and NK;) was tested in functional experiments using
`contraction of guinea-pig ileum by SP (1 nM) in the presence
`of atropine and indomethacin (NK; receptor), contraction of
`rat vas deferens by NKA (100 nM) (NK, receptor) and con-
`traction of rat portal vein by NKB (100 nM) (NK; receptor)
`(Lee et al., 1982; Mastrangelo et al., 1986; Regoli et al.,
`1988). FK888 dose-dependently inhibited the NK, receptor-
`mediated response with an ICs value of 0.64 nMm. Figure 4
`shows the dose-response curves for SP-induced contraction of
`guinea-pig isolated ileum in the absence and in the presence
`of FK888. FK888 dose-dependently shifted the dose-response
`curve of SP to the right without suppression of the maximum
`response. The Schild plot gave a slope of —0.78 (— 1.02—
`— 0.54), which was not significantly different from — 1 and a
`PA, value of 9.29 (8.60—9.98). In this experiment, the pD,
`value for SP was calculated as 8.34. On the other hand, NK,
`and NK,; receptor-mediated responses were inhibited only by
`very high concentrations of FK888, with ICs, values of 11 um
`and > 32 puM, respectively (data not shown).
`
`(£ )-CP-96,345 also showed selectivity for NK, receptors
`in these experimental systems with an ICs, value in guinea-
`pig isolated ileum of 1.5 nM. Higher concentrations of ( *)-
`CP-96,345 (1 uM—32 uM) also exhibited inhibitory actions in
`the NK, and NK; receptor assays. However, this was con-
`sidered to be non-specific because at the same concentrations
`(£ )-CP-96,345 inhibited contraction of rat vas-deferens and
`portal vein induced by noradrenaline. FK888, by itself, did
`not induce any change in the resting tension of the tissues
`used in the study at any of the concentrations tested,
`0.1 nM—10 uM.
`
`Effect of FK888 on airway oedema in guinea-pig
`
`The effect of FK888 on plasma extravasation in guinea-pig
`airway (airway oedema) was studied in vivo. As shown in
`Figure 5, FK888 given intravenously dose-dependently (i.v.)
`inhibited airway oedema induced by an i.v. injection of SP
`(1 nmol kg~') with an EDjs, value of 0.011 mgkg~'. The
`inhibitory activity of FK888 on airway oedema induced by
`SP was also observed after oral administration (p.o.) and the
`EDs, value was 4.2 mgkg~!. Airway oedema induced by
`histamine (320 nmol kg~!) was not affected by FK888 at the
`dose of 1 mgkg~! (i.v.) and 100 mgkg~' (p.0.), suggesting
`that the effect of FK888 was selective for SP induced-airway
`oedema.
`
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`
`Figure 4 Dose-response curves to substance P (SP) in guinea-pig
`isolated ileum in the absence (O) and the presence of FK888 at
`10~ M (@), 10-"M (A), 10-°M (A) and 10-°> M (O). The maximum
`contraction was induced by histamine (3.2 x 10~°M). Each point
`shows the mean of 5-6 experiments.
`
`
`
`
`
`
`
`
`788 T. FUJI et al.
`
`a b
`100 * 100
`4
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`
`Figure § Effect of FK888 on substance P (SP)- and histamine-
`induced airway oedema in guinea-pigs after intravenous (a) and oral
`(b) administration. In (a), Hl 0.003 mgkg~'; 0.0l mgkg™';
`E0.03mgkg"; 0.lmgkg'; CJ 1mgkg ' In (b), HN
`1 mgkg™"; 32mgkg™"; E= 10mgkg™; 32mgkg;
`[J 100 mgkg~'. Results are expressed % inhibition [(1-mean of
`treated group/mean of control group) x 100], from experiments using
`5-6 animals in each group. Significantly different from the control,
`*P<0.01.
`
`Discussion
`
`We have attempted to discover novel antagonists at the SP
`receptor using [PH]-SP receptor binding in guinea-pig lung
`membranes as the primary screening system. We have taken
`two different approaches in our research: one involving ran-
`dom screening of fermentation products and the other one
`involving a drug design study based on chemical modification
`of the parent compound, octapeptide (D-Pro*, D-Trp"*',
`Phe'')SP,_,; (Mizrahi et al., 1984). The first approach
`identified actinomycin D as a SP antagonist (Fujii et al.,
`1991) followed by the cyclic peptide SP antagonist,
`WS119326A. The catalytic hydrogenation of WS119326A
`produced FK224 which was about 10 times more potent than
`the original compound (Morimoto e al., 1992b; Murai et al.,
`1992). The second approach has produced a tripeptide
`antagonist, FR113680 (Hagiwara et al., 1991; Morimoto et
`al., 1992a), and a dipeptide antagonist, FK888, which is
`described in this paper. The ICs values for (D-Pro*, D-
`Trp’*"°, Phe'')SP,_,;,, FR113680 and FK888 in the [*H]-SP
`binding assay using guinea-pig lung membranes are 600 nM,
`85nM and 6.9 nM, respectively, indicating that the drug
`design study has achieved a 100 fold increase in potency
`following chemical modification of the original octapeptide
`antagonist to the dipeptide antagonist, FK888.
`
`To evaluate the selectivity of FK888 for the three distinct
`SP receptors (NK;, NK, and NK3), we tested FK888 in three
`bioassays. In the NK, receptor bioassay (contraction of
`guinea-pig ileum by SP), FK888 exhibited high affinity with a
`
`References
`
`ARUNLAKSHANA, O. & SCHILD, H.O. (1959). Some quantitative uses
`of drug antagonists. Br. J. Pharmacol. Chemother., 14, 48-58.
`
`BERESFORD, LJ.M. BIRCH, PJ.,, HAGAN, RM. & IRELAND, S.J.
`(1991). Investigation into species variants in tachykinin NK,
`receptors by use of the non-peptide antagonist, CP-96,345. Br. J.
`Pharmacol., 104, 292-293.
`
`EMONDS-ALT, X., VILAIN, P., GOULAOUIC, P., PROIETTO, V., VAN
`GROECK, D., ADVENIER, C., NALINE, E., NALIAT, G., LE FUR,
`G. & BRELIERE, J.C. (1992). A potent and selective non-peptide
`antagonist of the neurokinin A (NK;) receptor. Life Sci., 50,
`101-106.
`
`FARDIN, V. & GARRET, C. (1991). Species differences between [°H]
`substance P binding in rat and guinea-pig shown by the use of
`peptide agonists and antagonists. Ewr. J. Pharmacol., 201,
`231-234.
`
`Page 4 of 5
`
`pPA, value of 9.29. FK888 has at least 10,000 times higher
`affinity at the guinea-pig ileum NK, receptor compared to rat
`NK, (contraction of vas-deferens by NKA) and rat NK;
`(contraction of portal vein by NKB) receptors. In contrast,
`in the same experimental systems, the cyclic peptide
`antagonist FK224 exhibited similar inhibitory effects on NK;
`and NK, receptor-mediated responses with pA, values of
`6.88 and 7.52, respectively (Morimoto et al., 1992b). There is
`therefore a critical difference in receptor selectivity between
`FK888 and FK224. This difference is also observed between
`FK888 and the original parent octapeptide which inhibited
`NK, and NK, receptor-mediated responses [contraction of
`guinea-pig ileum by SP (1 nM) and contraction of rat vas
`deferens by NKB (100 nM)] with ICs, values of 0.27 uM and
`1.34 uM, respectively, suggesting that only NK, antagonist
`potency has been potentiated by a large degree during the
`course of drug design.
`
`Recently, the existence of species differences in NK; recep-
`tors has been proposed. CP-96,345 was reported to displace
`PH]-SP binding to brain cerebral cortical membranes
`prepared from rabbit, guinea-pig, human, bovine, hamster
`and gerbil with an approximately 100 fold greater affinity
`than from rat and mouse membrane preparations (Beresford
`et al., 1991; Gitter et al., 1991). In contrast, unlabelled SP
`and physalaemin displace [PH}-SP binding to the same
`preparation with similar affinity. The peptide SP antagonist
`(D-Pro*, D-Trp”®)SP,_,; has also been reported to exhibit a
`higher affinity for [*’H]}-SP binding sites on guinea-pig brain
`and ileum membranes than for binding sites on rat mem-
`branes (Fardin & Garret, 1991). FK888 showed a similar
`species difference in its affinity for the NK, receptor to that
`seen with CP-96,345, and inhibited [*H]-SP binding to
`guinea-pig lung membrane with an approximately 100 fold
`higher affinity than to rat brain cortical membranes. On the
`other hand, the recently described NK, antagonist, RP 67580
`(Garret et al., 1991), is considered to have a distinct receptor
`selectivity when compared with FK888 and CP-96,345. RP
`67580 has been reported to be a potent inhibitor of [*H]-SP
`binding to rat brain membrane preparations (K; = 4.16 nM)
`whereas activity in the SP-induced guinea-pig ileum contrac-
`tion bioassay is relatively weak (pA,;=7.16).
`
`The pharmacological profile of FK888 as an NK, selective
`antagonist was also studied in in vivo experiments. FK888
`given i.v. or by oral administration significantly inhibited
`airway oedema induced by SP in guinea-pigs. SP-induced
`plasma extravasation is considered to be an NK, receptor-
`mediated response because SP is the most potent agonist of
`the tachykinin peptide family. FK888 also inhibited another
`vascular reaction mediated by the NK, receptor, SP-induced
`systemic hypotension in guinea-pigs, with a similar potency
`to SP-induced airway oedema (data not shown).
`
`FK888 is therefore a selective NK, receptor antagonist
`both in vitro and in vivo, and will be a useful tool for
`clarifying the role of SP in physiological and patho-
`physiological conditions.
`
`FUIJII, T., MURAI, M., MORIMOTO, H., NISHIKAWA, M. & KIYOTOH,
`S. (1991). Effects of actinomycin D on airway constriction
`induced by tachykinins and capsaicin in guinea-pigs. Eur. J.
`Pharmacol., 194, 183-188.
`
`GARRET, C., CARRUETTE, A, FARDIN, V., MOUSSAOUI, §,
`PEYRONEL, J.F., BLANCHARD, J.C. & LADURON, P.M. (1991).
`Pharmacological properties of a potent and selective nonpeptide
`substance P antagonist. Proc. Natl. Acad. Sci. U.S.A., 88,
`10208-10212.
`
`GITTER, B.D., WATERS, D.C.,, BRUNS, R.F., MASON, N.R., NIXON,
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`(Received March 3, 1992
`Revised June 8, 1992
`Accepted July 16, 1992)
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