Effects of an orally active non-peptide bradykinin B2 receptor antagonist,FR173657, on plasma exudation in rat carrageenin-induced pleurisy

1. Effects of an orally active non-peptide (BK) B₂ receptor antagonist, {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 ((E)-3-(6-acetamido-3-pyridyl)- N-[N-[2,4-dichloro-3-[(2-methyl-8-quinolinyl)oxymethyl]phenyl]-N-methylaminocarbonylmethyl] acrylamide) on the plasma exudation in rat carrageenin-induced pleurisy were investigated.
2. Plasma exudation induced by intrapleural injection of bradykinin (BK, 3 nmol per rat) into male SD strain rats (SPF, 8 weeks old) were significantly inhibited by oral administration of novel B₂ receptor antagonist {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 (3–30 mg kg⁻¹, 1 h before BK injection) in a dose-dependent manner, whereas that induced by histamine was not.
3. The inhibitory effect of 30 mg kg⁻¹ {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 persisted for more than 4 h.
4. Intrapleural injection of λ-carrageenin (2% (w/v), 0.1 ml per rat) caused marked plasma exudation and accumulation of exudates from 1 h after carrageenin injection. The maximum plasma exudation response was observed 5 h after carrageenin. The oral administration of {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 to rats (30 mg kg⁻¹, 1 h before carrageenin) significantly (by 50–77%) blunted the plasma exudation 1, 3, 5, and 7 h after carrageenin, causing a significant parallel reduction (by 42–57%) in the volume of exudates.
5. The anti-inflammatory effect of {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 on rat carrageenin-induced pleurisy was almost equipotent with that of the peptide B₂ antagonist Hoe140 (1 mg kg⁻¹, i.v.), a plasma kallikrein inhibitor, soy bean trypsin inhibitor (0.3 mg per rat, intrapleural injection) and bromelain (10 mg kg⁻¹, i.v.).
6. In pleurisy induced by intrapleural injection of a histamine releaser, compound 48/80, the plasma exudation was observed only within 20 min after the injection. This plasma exudation was not affected by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657, although it was completely inhibited by a mixture of pyrilamine (5 mg kg⁻¹, i.v.) and methysergide (3 mg kg⁻¹, i.v.).
7. These results indicate that {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 is an orally active, promising anti-inflammatory agent for kinin-dependent inflammation.

     

The identification of an orally active,nonpeptide bradykinin B2 receptor antagonist,FR173657

1. An orally active, nonpeptide bradykinin (BK) B₂ receptor antagonist, {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 (E)-3-(6-acetamido-3 - pyridyl) - N - [N - [2 - 4 -dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide) has been identified.
2. This compound displaced [³H]-BK binding to B₂ receptors present in guinea-pig ileum membranes with an IC₅₀ of 5.6×10⁻¹⁰ M and in rat uterus with an IC₅₀ of 1.5×10⁻⁹ M. It did not inhibit different specific radio-ligand binding to other receptor sites.
3. In human lung fibroblast IMR-90 cells, {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 displaced [³H]-BK binding to B₂ receptors with an IC₅₀ of 2.9×10⁻⁹ M and a K_i of 3.6×10⁻¹⁰ M, but did not reduce [³H]-des-Arg¹⁰-kallidin binding to B₁ receptors.
4. In guinea-pig isolated preparations, {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 antagonized BK-induced contractions with an IC₅₀ of 7.9×10⁻⁹ M, but did not antagonize acetylcholine or histamine-induced contractions even at a concentration of 10⁻⁶ M. {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 caused parallel rightward shifts of the concentration-response curves to BK at concentrations of 10⁻⁹ M and 3.2×10⁻⁹ M, and a little depression of the maximal response in addition to the parallel rightward shift of the concentration-response curve at a concentration of 10⁻⁸ M. Analysis of the data yield a pA₂ of 9.2±0.2 (n=5) and a slope of 1.5±0.2 (n=5).
5. In vivo, the oral administration of {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 inhibited BK-induced bronchoconstriction dose-dependently in guinea-pigs with an ED₅₀ of 0.075 mg kg⁻¹, but did not inhibit histamine-induced bronchoconstriction even at 1 mg kg⁻¹. {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 also inhibited carrageenin-induced paw oedema with an ED₅₀ of 6.8 mg kg⁻¹ 2 h after the carrageenin injection in rats.
6. These results show that {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 is a potent, selective, and orally active bradykinin B₂ receptor antagonist.

     

Characterization of non-peptide bradykinin B2 receptor agonist (FR 190997) and antagonist (FR 173657)

Pharmacologic parameters for a novel non-peptide bradykinin (BK)-B2 receptor agonist, 8-[2,6-dichloro-3-[N-[(E)-4-(N-methylcarbamoylcinnamidoacetyl]-N-+ ++methylano] benzyloxy]-2-methyl-4-(2-pyridylmethoxy)quinoline (FR 190997) (pEC50, ED50 values) and for the antagonist (E)-3-(6-acetamido-3-pyridyl)-[N-[2,4-dichloro-3-[(2-methyl-8-quinolinyl ) oxymethyl] phenyl]-N-methylaminocarbonylmethyl] acrylamide (FR 173657) (pIC50, ID50 values) were measured using conventional contractile B2 receptor bioassays from rabbit, guinea pig and rat tissues and by mean of animal blood pressure models performed on anesthetized animals in the same species. In vitro assays (on the rabbit jugular vein and the guinea pig ileum) demonstrated that both the onset and duration of action of FR 190997 are prolonged compared to BK. These in vitro effects of FR 190997 strongly desensitized upon repeated tissue applications. Similar pEC50 values (7.7) were measured on the rabbit and the guinea pig tissues. In vivo, when injected intraarterially, FR 190997 produced hypotensive responses in rabbits and guinea pigs with ED50 values of 3.7 +/- 0.5 and 8.9 +/- 3.6 nmol/kg, respectively. Both the contractile and the hypotensive effects of FR 190997 were abolished by pretreating tissues (1 microM) or animals (0.1-0.5 micromol/kg) with D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]BK (HOE 140) or FR 173657. FR 173657 (pIC550 approximately 8.40), as well as other known antagonists (e.g., HOE 140, D-Arg-[Hyp3,D-Phe7,Leu8]BK), inhibited the in vitro myotropic effects of BK on the rabbit, guinea pig and rat tissues. FR 173657 also abrogated the in vivo hypotensive responses elicited by BK in the rabbit (ID50 57 +/- 9 nmol/kg), the guinea pig (ID50 215 +/- 56 nmol/kg) and the rat (ID50 187 +/- 50 nmol/kg). The in vivo duration of action of FR 173657 was significantly lower in the rabbit (= 20 min) than in the guinea pig and the rat (> 90 min). It is concluded that the non-peptides FR 190997 and FR 173657 enable efficient activation and antagonism of rabbit and guinea pig B2 receptors. These non-peptide molecules represent a marked progress in medicinal chemistry and may be useful to define the role played by the kallikrein/kinin system in vivo.     

Characterization of FR 172357, a new non-peptide bradykinin B(2) receptor antagonist, in human, pig and rabbit preparations

We examined the effect of tyramine on the production of adenosine in rat heart. A flexibly mounted microdialysis setup was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in in vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at a rate of 1.0 microl/min. The concentration of adenosine in the effluent (dialysate) was measured by high-performance liquid chromatography (HPLC). Dialysate adenosine obtained during perfusion with the AMP-containing solution through the probe originated from the hydrolysis of AMP by endogenous ecto-5'-nucleotidase, and the level of adenosine reflected the activity of ecto-5'-nucleotidase in the tissue. Tyramine (0-4 mM) increased the adenosine concentration measured during the perfusion of AMP (100 microM) in a concentration-dependent manner. Alpha,beta-methyleneadenosine 5'-diphosphate (alpha,beta-meADP, 100 microM), an inhibitor of ecto-5'-nucleotidase, abolished the AMP-induced increase in dialysate adenosine. Tyramine (1 mM) increased the adenosine concentration measured in the presence of 100 microM AMP (i.e., the activity of ecto-5'-nucleotidase) by 65.8 +/- 19.9% (n = 6, P < 0.05), an increase which was inhibited by an antagonist of the alpha1-adrenoceptor (prazosin, 50 microM) or of protein kinase C (chelerythrine, 10 microM). These data provide the first evidence that alpha1-adrenoceptor stimulation and the subsequent activation of protein kinase C can increase adenosine concentrations in the interstitial space of ventricular muscle in vivo, through activation of endogenous ecto-5'-nucleotidase. To examine the effect of tyramine on the production of adenosine by ischemia-reperfusion of the rat myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery. When the heart was reperfused, elevation of the level of adenosine in the ischemic zone was observed, but this change was not significant. However, when corresponding experiments were performed with a subsequent systemic administration of tyramine (1 mM), a marked elevation in the level of adenosine was observed. The results suggest that tyramine elevates adenosine via stimulation of alpha1-adrenoceptors and protein kinase C-mediated activation of ecto-5'-nucleotidase in rat heart.     

Effects of FR173657, a non-peptide B2 antagonist,on kinin-induced hypotension,visceral and peripheral oedema formation and bronchoconstriction

1. Kinins are believed to play a key role in many inflammatory conditions. Therefore, bradykinin antagonists are being developed for potential therapeutic applications. In the present investigation we describe the pharmacology, in vivo, of (E)-3-(6- acetamido- 3-pyridyl)- N-[N- [2,4- dichloro- 3-[(2- methyl-8- quinolinyl)oxymethyl]phenyl]- N-methylaminocarbonylmethyl]acrylamide ({"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657), a novel, non-peptide bradykinin antagonist.
2. The hypotensive effects of i.v. injections of bradykinin (50 pmol) in captopril-pre-treated anaesthetized rats were significantly inhibited by 100 nmol kg⁻¹ {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 s.c., and completely abolished by 300 nmol kg⁻¹. The full inhibitory effect developed within 60 min and remained unchanged for at least 4 h. However, the effect was reversible, since 24 h after an injection of 300 nmol kg⁻¹ {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 no inhibitory effect could be observed.
3. The plasma protein extravasation into the pancreas and duodenum induced by an i.v. infusion of bradykinin (11 nmol kg⁻¹ within 20 min) in captopril-treated anaesthetized rats was completely abolished by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 at doses of 30 nmol kg⁻¹ s.c. and above, given 60 min before bradykinin. {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 3 nmol kg⁻¹ was ineffective, while a dose of 10 nmol kg⁻¹ produced an intermediate effect.
4. The paw oedema induced by the subplantar injection of bradykinin (30 nmol) in anaesthetized rats was inhibited slightly by s.c. injection of {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 0.3 μmol kg⁻¹, whereas 1 and 3 μmol kg⁻¹ produced significant inhibition of the bradykinin-induced oedema. The maximum inhibition amounted to about 50% and could not be increased even when the dose of {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 was increased to 30 μmol kg⁻¹. {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 did not effect the oedema caused by histamine or 5-hydroxytryptamine.
5. Bradykinin (20 nmol kg⁻¹, i.v.) caused increases in pulmonary inflation pressure by 300–600 Pa in anaesthetized, respirated guinea-pigs. The effect was reduced to 58±9% of the initial value 60 min after the s.c. injection of {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 1 μmol kg⁻¹, whereas only 9±7% remained after 10 μmol kg⁻¹. The bronchoconstrictor actions of histamine remained unaffected by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657.
6. In summary, {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 is a highly potent and selective bradykinin antagonist. The inhibitory action in vivo lasts for longer than 4 h but is fully reversible. {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657, or similar compounds, will be a useful tool for the pharmacological investigation of pathophysiological states and may possess a therapeutic potential in diseases involving the endogenous release of kinins.

     

The nonpeptide B2 receptor antagonist FR173657: inhibition of effects of bradykinin related to its role in nociception

1. The nonpeptide bradykinin B₂ receptor antagonist, {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 ((E)-3-(6-acetamido-3-pyridyl)-N-[N-(2, 4-dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl] phenyl]-N-methylaminocarbonylmethyl] acrylamide), was tested in models involving bradykinin-induced activation of primary afferent neurones in vitro and in vivo.
2. Bradykinin-induced contractions of the rabbit isolated iris sphincter muscle mediated by tachykinin release from trigeminal afferent neurones were inhibited in a non-competitive manner by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657. A pK_B value of 7.9 was calculated. Effects of substance P were unaffected by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657.
3. Nociceptive behavioural responses following intraplantar injection of bradykinin in unanaesthetized rats were reduced by 0.3 μmol kg⁻¹ {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 s.c. (P<0.05), and completely abolished by 3 μmol kg⁻¹ (P<0.05). Peroral administration of 5 μmol kg⁻¹ {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 abolished the bradykinin effects (P<0.05); lower doses had no significant effect.
4. Shortening by intraplantar injection of bradykinin of the paw withdrawal latency in response to radiant heat was abolished by 3 μmol kg⁻¹ {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 s.c. (P<0.05), while 300 nmol kg⁻¹ had an intermediate effect. Hyperalgesia induced by prostaglandin E₂ remained unaffected by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657.
5. Blood pressure reflexes following i.p. instillation of bradykinin in anaesthetized rats were inhibited by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 s.c. with an ID₅₀ of 1.1 μmol kg⁻¹, while the peptidic B₂ antagonist icatibant (Hoe-140; D-Arg⁰-[Hyp³, Thi⁵, D-Tic⁷, Oic⁸]-bradykinin) caused inhibition at significantly lower doses (ID₅₀ 8.5 nmol kg⁻¹ P<0.001). Responses to hydrochloric acid i.p. remained unaffected by {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657.
6. {"type":"entrez-nucleotide","attrs":{"text":"FR173657","term_id":"257935500","term_text":"FR173657"}}FR173657 or similar nonpeptide compounds may be useful for the development of drugs for diseases involving pain induced by the release of endogenous kinins, i.e. especially in acute inflammatory conditions.

     

Discovery of orally active nonpeptide bradykinin B2 receptor antagonists

Orally active nonpeptide bradykinin (BK) B2 receptor antagonists have been discovered by using directed random screening and chemical modification. These compounds displaced [3H]BK binding to B2 receptors in guinea-pig ileum membranes, rat uterus membranes and human lung fibroblasts with nanomolar IC50s. They did not inhibit different specific radio-ligand bindings to other receptor sites including B2 receptors. In isolated guinea-pig ileum preparations, these compounds had no agonistic effect on smooth muscle contraction at 10(-6) M, and caused parallel rightward shifts of the concentration-response curves to BK on contraction with higher p A2 values. They also blocked human B2 receptor-mediated phosphatidylinositol hydrolysis without agonistic effect. In vivo, the oral administrations of these antagonists potently inhibited BK-induced bronchoconstriction in guinea-pigs. They also reduced carrageenin-induced paw edema and caerulein-induced pancreatitis in rats. Moreover, these compounds alleviated kaolin-induced pain in mice by oral administration. These results show that our compounds are potent, selective, and orally active BK B2 receptor antagonists and that they may have therapeutic potential against inflammatory diseases and pain.     

Pharmacological characterisation of the first non-peptide bradykinin B2 receptor agonist FR 190997: an in vitro study on human, rabbit and pig vascular B2 receptors

FR 190997, a new kinin B2 receptor agonist of non-peptide nature, has been studied in three isolated vessels: the human umbilical vein (hUV), the rabbit jugular vein (rbJV), and the pig coronary artery (pCA). Bradykinin (BK) contracts the hUV and rbJV through smooth muscle B2 receptors, while it relaxes the pCA through endothelial receptors of the B2 type. Contractions of the hUV and rbJV in response to FR 190997 show slow onset and are not reproducible compared to the rapid and reproducible effect of BK. They reach only 70% and 30% of the BK-induced maximal contractions in the hUV and rbJV, respectively. The effects of FR 190997 are antagonised by HOE 140 and this antagonist shows similar pK(B) values against BK and FR 190997, indicating that the non-peptide agent interacts with the kinin B2 receptor. FR 190997 is inactive as relaxant of the pCA; in this tissue, it acts as a pure and competitive antagonist, with a pK(B) value of 7.6, while HOE 140 acts as an insurmountable antagonist (pK(B) 9.3). When tested as an antagonist, FR 190997 inhibits also the contractile effects of BK in the hUV (pK(B) 7.8) and in the rbJV (pK(B) 7.6). FR 190997 is selective for the B2 receptor since it does not interact with the B1, and is specific since it does not affect the contraction evoked by 5-hydroxytryptamine, endothelin-1, and noradrenaline in the hUV, or the relaxation induced by substance P in the pCA. FR 190997 shows therefore different pharmacological profiles in various preparations, acting as a partial agonist in the hUV and especially in the rbJV and as a pure antagonist in the pCA. This new compound could be of interest in understanding how non-peptide agonists may activate receptors for peptides.     

From bradykinin B2 receptor antagonists to orally active and selective bradykinin B1 receptor antagonists

The bradykinin (BK) B1 receptor is an attractive target for the treatment of chronic pain and inflammation. Starting from a dual B1 and B2 antagonist, novel antagonists were designed that display low-nanomolar affinity for human B1 receptor and selectivity over B2. Initially, potent imidazoline derivatives were studied, but these compounds suffered from low bioavailability. This issue could be overcome by the use of less basic amino derivatives leading to orally active compounds.     

Pharmacological characterization of a nonpeptide bradykinin B2 receptor antagonist,FR165649, and agonist,FR190997

1. The nonpeptide bradykinin (BK) B₂ receptor antagonist, {"type":"entrez-nucleotide","attrs":{"text":"FR165649","term_id":"258310103","term_text":"FR165649"}}FR165649 (8-[2,6-dichloro-3-[N-[(E)-4-(N- methylcarbamoyl)cinnamidoacetyl] -N-methylamino] benzyloxy] -2 - methylquinoline), and agonist, {"type":"entrez-nucleotide","attrs":{"text":"FR190997","term_id":"257934014","term_text":"FR190997"}}FR190997 (8-[2,6-dichloro-3-[N-[(E)-4-(N-methylcarbamoyl) cinnamidoacetyl]-N-methylamino]benzyloxy]-2-methyl-4-(2-pyridylmethoxy)quinoline) have been identified. These compounds have a common chemical structure, and the 2-pyridylmethoxy group is the only structural difference between them.
2. Both {"type":"entrez-nucleotide","attrs":{"text":"FR165649","term_id":"258310103","term_text":"FR165649"}}FR165649 and {"type":"entrez-nucleotide","attrs":{"text":"FR190997","term_id":"257934014","term_text":"FR190997"}}FR190997 displaced [³H]-BK binding to B₂ receptors in guinea-pig ileum membranes, with an IC₅₀ of 4.7×10⁻¹⁰ M and 1.5×10⁻⁹ M, respectively. They also displaced [³H]-BK binding to B₂ receptors in human lung fibroblast IMR-90 cells, with an IC₅₀ of 1.6×10⁻⁹ M and 9.8×10⁻¹⁰ M, respectively.
3. In guinea-pig isolated ileum-preparations, {"type":"entrez-nucleotide","attrs":{"text":"FR165649","term_id":"258310103","term_text":"FR165649"}}FR165649 had no agonistic effect on contraction and caused parallel rightward shifts of the concentration-response curves to BK on contraction. Analysis of the data produced a nominal pA₂ value of 9.2±0.1 (n=5) and a slope of 1.4±0.1 (n=5). On the other hand, {"type":"entrez-nucleotide","attrs":{"text":"FR190997","term_id":"257934014","term_text":"FR190997"}}FR190997 induced concentration-dependent contraction of guinea-pig ilea with a pD₂ of 7.9±0.2 and the contraction was inhibited by a specific peptide bradykinin B₂ receptor antagonist, Hoe 140 (D-Arg-[Hyp³, Thi⁵, D-Tic⁷, Oic⁸]BK) in a non-competitive manner.
4. In IMR-90 cells, {"type":"entrez-nucleotide","attrs":{"text":"FR165649","term_id":"258310103","term_text":"FR165649"}}FR165649 had no agonistic effect on phosphatidyl inositol (PI) hydrolysis and caused parallel rightward shifts (approximately 200 fold shift at 10⁻⁷ M) of the concentration-response curves to BK on PI hydrolysis. {"type":"entrez-nucleotide","attrs":{"text":"FR190997","term_id":"257934014","term_text":"FR190997"}}FR190997 induced concentration-dependent PI hydrolysis in IMR-90 cells with a pD₂ of 8.4±0.1, and this effect was inhibited by Hoe 140.
5. These results indicate that {"type":"entrez-nucleotide","attrs":{"text":"FR165649","term_id":"258310103","term_text":"FR165649"}}FR165649 and {"type":"entrez-nucleotide","attrs":{"text":"FR190997","term_id":"257934014","term_text":"FR190997"}}FR190997 are, respectively, a potent bradykinin B₂ receptor antagonist and agonist, and that the agonistic activity depends on the small part of the nonpeptide ligand. {"type":"entrez-nucleotide","attrs":{"text":"FR165649","term_id":"258310103","term_text":"FR165649"}}FR165649 and {"type":"entrez-nucleotide","attrs":{"text":"FR190997","term_id":"257934014","term_text":"FR190997"}}FR190997 may be useful tools for studying the relationship between ligands and receptors.

     

Discovery of an orally active non-peptide fibrinogen receptor antagonist based on the hydantoin scaffold

Antagonists of the platelet fibrinogen receptor (GP IIb/IIIa receptor) are expected to be a promising new class of antithrombotic agents. The binding of fibrinogen to the fibrinogen receptor depends on an Arg-Gly-Asp-Ser (RGDS) tetrapeptide recognition motif. Structural modifications of the RGDS lead have led to the discovery of a non-peptide RGD mimetic GP IIb/IIIa antagonist 44 (S 1197). Compound 44 inhibited, in a dose dependent and reversible manner, human and dog platelet aggregation as well as 125I-fibrinogen binding to ADP-activated human gel filtered platelets and isolated GP IIb/IIIa with K(i) values of 9 nM and 0.17 nM, respectively. A pharmacophore mapping procedure with QXP and a 3D-QSAR analysis applying the GRID/GOLPE methodology yielded a stable, rather predictive model and revealed structural features which are important for binding. Hydrophobic substitutions both at the hydantoin nucleus and at the C-terminus increase the affinity toward the fibrinogen receptor. The crystalline ethyl ester prodrug 48 (HMR 1794) is an orally active antithrombotic agent which is a promising drug candidate for the treatment of thrombotic diseases in humans.     

A non-peptide antagonist unusually selective for the human form of the bradykinin B2 receptor

Analgesic and anti-inflammatory applications for non-peptide bradykinin (BK) B2 receptor antagonists have been documented in rats. However, very large species differences in affinity were also noted within this class of drugs, making the preclinical development of relevant drugs difficult. Bradyzide is a potent antagonist at the rat B2 receptor, but a weak one at the human receptor; a series of analogues in which the diphenylmethyl moiety of this drug has been substituted with dibenzosuberane have been reported to gain potency at the human B2 receptor, with some loss of affinity at the rat receptor. The present experiments have been performed in order to verify that the novel series of dibenzosuberane B2 receptor antagonist optimized for affinity in the human species are effective in the isolated human umbilical vein contractility assay. Bradyzide, its analog compound (S)-14c and the dibenzosuberane compounds (S)-14d and 19c surmountably antagonized BK-induced contraction (pA2 values of 5.42, 6.48, 7.42 and 7.53, respectively). In the rabbit jugular vein contractility assay, the pA2 of compound 19c was smaller than 5. Potency at the recombinant rabbit B2 receptor was generally decreasing in the series of four drugs (Ki in a [3H]BK competition assay to recombinant receptors of 0.78, 0.77, 10.2 and 44.4 nM, respectively); these four compounds did not displace [3H]Lys-des-Arg(9)-BK binding from human B1 receptors expressed by smooth muscle cells. The dibenzosuberane compound 19c, verified to functionally antagonize the vascular B2 receptor, is an example of a drug unusually specific for the human form of the receptor.     

Effect of FK3657, a non-peptide bradykinin B2 receptor antagonist,on allergic airway disease models

Bradykinin has been suggested to be involved in allergic diseases. In this study, we tested the effect of FK3657 ((E)-3-(6-acetamido-3-pyridyl)-N-[N-[2,4-dichloro-3-[(2-methyl-8-quinolinyl)-oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide), an orally active non-peptide bradykinin B(2) receptor antagonist, on allergic airway disease models in guinea pigs. FK3657 given orally inhibited bradykinin-induced or dextran sulfate (an activator of kinin-kallikrein cascade)-induced bronchoconstriction and plasma extravasation in the lower airways (trachea and main bronchi) and nasal mucosa of guinea pigs with ED(50) of 0.04-0.23 mg/kg. In the antigen-induced dual asthmatic response model of guinea pigs, FK3657 significantly attenuated the late phase asthmatic response, but not the immediate asthmatic response. FK3657 also significantly inhibited the 2,4-tolylene diisocyanate (TDI)-induced plasma extravasation in nasal mucosa of TDI-sensitized guinea pigs. These results suggest that oral FK3657 may be useful for asthma or allergic rhinitis as a therapeutic drug.     

Pharmacological profile of LF 16-0687, a new potent non-peptide bradykinin B2 receptor antagonist

LF 16-0687 (1-[[2,4-dichloro-3-[[(2,4-dimethylquinolin-8-yl)oxy] methyl]phenyl]sulfonyl]-N-[3-[[4-(aminoimethyl) phenyl] carbonylamino]propyl]-2(S)-pyrrolidinecarboxamide) has been selected from a large-scale medicinal chemistry program for further development. In competition binding studies using [3H]bradykinin (BK), LF 16-0687 bound to the human, rat and guinea-pig recombinant B2 receptor expressed in CHO cells giving K(i) values of 0.67 nM, 1.74 nM and 1.37 nM, respectively. It also bound to the native BK B2 receptor from human umbilical vein (HUV), rat uterus (RU) and guinea-pig ileum (GPI) giving K(i) values of 0.89 nM, 0.28 nM and 0.98 nM, respectively. It inhibited BK-induced IP1, IP2 and IP3 formation in INT407 cells yielding pK(B) values of 8.5, 8.6 and 8.7, respectively. In isolated organs experiments, LF 16-0687 behaved as a competitive antagonist of BK-mediated contractions giving pA2 values of 9.1 in HUV, 7.7 in RU and 9.1 in GPI. Binding and functional studies performed over 40 different receptors revealed that LF 16-0687 was selective for the BK B2 receptor. A continuous intravenous infusion of LF 16-0687 antagonized in a dose-dependent manner and with a rapid onset of action BK-induced hypotensive response. Subcutaneous administration of LF 16-0687 at 1.1 micromol/kg to rats markedly reduced BK-induced edema of the stomach (- 69%), duodenum (-65%) and pancreas (-56%).     

MEN16132, a kinin B2 receptor antagonist, prevents the endogenous bradykinin effects in guinea-pig airways

Kinins have been suggested to be involved in human airway diseases such as asthma and rhinitis. MEN16132 is a non-peptide kinin B(2) receptor antagonist able to inhibit the responses produced by intravenous bradykinin into the airways, as bronchoconstriction and microvascular leakage; we tested the effect of MEN16132 on endogenously generated bradykinin through the dextran sulfate-induced contact activation of kinin-kallikrein cascade in guinea-pigs. After dextran sulfate administration (1.5 mg/kg i.v.), the pulmonary insufflation pressure was monitored and the microvascular leakage of upper and lower airways was assessed using Evans blue as tracer of plasma protein extravasation. Our results demonstrated that topical MEN16132 strongly inhibited the dextran sulfate-induced bronchoconstriction (0.3 mM solution aerosol for 5 min) and plasma protein extravasation in both lower airways (3-10 microM solution aerosol for 5 min) and nasal mucosa (0.3 nmol/nostril); Icatibant, the peptide antagonist of kinin B(2) receptor, exerted a 3-30-fold less potent inhibitory effect than MEN16132. We conclude that local application of MEN16132 into the airways abolishes the responses produced by the endogenous generation of bradykinin and it can be useful as new pharmacological tool to check the role of kinins in human diseases.     

Effects of CP-96,345, a novel non-peptide antagonist of NK1 receptor, on the peristalsis in isolated guinea pig ileum.

CP-96,345, a novel non-peptide antagonist of the NK1 receptor, at 10(-8)-10(-6) M decreased the frequency of peristalsis and reduced peristalsis-associated longitudinal muscle contractions in isolated guinea pig ileum. In the presence of 10(-6) M CP-96,345, further addition of 10(-6) M atropine blocked the peristalsis. When 10(-6) M atropine was first applied, more than half of the preparations developed atropine-resistant peristalsis. CP-96,345 at 10(-6) M blocked the atropine-resistant peristalsis. These results are consistent with the view that substance P is involved in the peristalsis in guinea pig ileum.     

Bradykinin B2 antagonist HOE 140 inhibits late allergic microvascular leakage in guinea pig airways

Because bradykinin has potent inflammatory actions, this molecule may be involved in the late allergic response (LAR). We investigated the role of the molecule in airway microvascular hyperpermeability during the LAR. Three weeks after ovalbumin (OVA) sensitization, animals were pretreated with bradykinin B2 receptor antagonist HOE 140 or vehicle for 30 min before the OVA inhalation challenge. The occurrence of LAR was judged by a two-fold increase in transpulmonary pressure (Ptp) from the baseline values. The microvascular permeability in the trachea was assessed by an index defined as the ratio of the area of vasculature labeled by the Monastral blue dye (area density percent). Significant microvascular hyperpermeability were observed during the LAR. The bradykinin concentrations in the bronchoalveolar lavage-fluid (BAL-f) were increased during the LAR. HOE 140 (0.1-10 mg/kg, s.c.) inhibited the airway microvascular hyperpermeability during the LAR dose-dependently. These findings suggest that bradykinin may play an important role in microvascular hyperpermeability during the LAR.     

The non-peptide neurokinin1 receptor antagonist, RP 67580, blocks neurogenic plasma extravasation in the dura mater of rats.

A non-peptide neurokinin1 (NK1) receptor antagonist, RP 67580, that is selective for the rodent subtype of the NK1 receptor, dose-dependently reduced plasma extravasation in the dura mater produced by electrical stimulation of the trigeminal ganglion in rats, with an ID50 of 0.6 micrograms kg-1. Its enantiomer RP 68651 was some 400 fold less active. The results indicate that neurogenic plasma extravasation within the dura mater is NK1 receptor-mediated and suggest that NK1 receptor antagonists may have a role as antimigraine agents.     

In vitro antiplatelet profile of FR171113, a novel non-peptide thrombin receptor antagonist

We have examined the potency of several adenosine receptor antagonists at adenosine A₁ and A_2A receptors using quantitative autoradiography and have compared the results with those of previous studies using the same radioligands in membrane preparations. The agonists [³H]cyclohexyladenosine and [³H]2-[p-(2-carbonylethyl)-phenylethylamino]-5′-N-ethylcarboxamido adenosine ([³H]CGS 21680) were used as radioligands for the two receptors. The results show that 1,3-dipropyl-8-cyclopentyl xanthine (DPCPX) is almost 1000-fold and 8-chloro-4-cyclohexyl-amino-1-(trifluoromethyl)[1,2,4]triazolo[4,3-a] quinoxaline (CP-68,247) about 300-fold more potent at adenosine A₁ receptors in cortex and striatum than at striatal adenosine A_2A receptors. Conversely, 5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo [1,5-c]pyrimidine (SCH 58261) is approximately 1000-fold and 4-(2-[7-amino-2-(2-furyl) [1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-yl amino]ethyl)phenol (ZM 241,385) about 400-fold more potent at adenosine A_2A than at A₁ receptors. Caffeine and its metabolites did not show any selectivity. Other studied antagonists were non-selective or showed a modest (20- to 40-fold) adenosine A_2A receptor selectivity. Thus, only a few of the antagonists show such high selectivity that it is not offset by differences in drug distribution and levels of receptor subtype expression.