Discovery of novel, orally active dual NK1/NK2 antagonists

Exploration of the SAR around selective NK2 antagonists, SR48968 and ZD7944, led to the discovery that naphth-1-amide analogues provide potent dual NK1 and NK2 antagonists. ZD6021 inhibited binding of [3H]-NKA or [3H]-SP to human NK1 and NK2 receptors, with high-affinity (K(i)=0.12 and 0.62nM, respectively). In functional assays ZD6021 had, at 10(-7)M, in human pulmonary artery pK(B)=8.9 and in human bronchus pK(B)=7.3, for NK1 and NK2, respectively. Oral administration of ZD6021 to guinea pigs dose-dependently attenuated ASMSP induced extravasation of plasma proteins, ED(50)=0.5mg/kg, and NK2 mediated bronchoconstriction, ED(50)=13mg/kg.     

Synthesis and NK(1)/NK(2) binding activities of a series of diacyl-substituted 2-arylpiperazines

The synthesis and binding affinity for hNK(1) and hNK(2) receptors of a series of diacyl substituted 2-aryl piperazines are described. SAR evaluation led to the racemic derivative 11g as an apparent dual inhibitor. Chiral chromatographic separation of 11g led to the observation that NK(1) activity was shown by one enantiomer (13a) and NK(2) activity was shown by the other enantiomer (13b). X-ray crystallographic analysis of the crystalline di-BOC derivative of the NK(2) active piperazine (15) showed that the 2R configuration was associated with NK(2) activity. Further derivatization indicated that dual NK(1)/NK(2) activity could be built into the 2R series.     

Preparation of oxime dual NK(1)/NK(2) antagonists with reduced NK(3) affinity

By employing a stereosimplification approach, a thorough SAR exploration of the piperidine region of Sch 206272 was possible through a practical and efficient synthesis of substituted cyclic ureas. This SAR study led to the identification of a benzimidazolinone series of compounds which display single digit nanomolar NK(1)/NK(2) affinity and near micromolar binding for the NK(3) receptor.     

Design and synthesis of 3,5-disubstituted benzamide analogues of DNK333 as dual NK1/NK2 receptor probes

N-[(R,R)-(E)-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (DNK333, 1b) has been reported to be a potent and balanced dual neurokinin (tachykinin) receptor antagonist. A recent clinical trial using DNK333 has shown that it blocks the NKA-induced bronchoconstriction in patients with asthma. A series of six analogues 3-8 derived from modification of 3,5-bis(trifluoromethyl)benzamide moiety of DNK333 has been synthesized to serve as the dual NK(1)/NK(2) receptor probes. The 3,5-dinitro substituted benzamide compound 3 was found to possess potent and balanced dual NK(1)/NK(2) receptor antagonist activities (pK(b)=8.4 for the NK(1) receptors, pK(b)=7.87 for the NK(2) receptors) in the functional assay using guinea pig trachea. Furthermore, SAR analysis suggests that steric, electronic, and lipophilic characteristics of substituents in the benzamide region of DNK333 have a crucial effect on both the NK(1) and NK(2) receptor antagonist activities.     

Interaction of Met297 in the seventh transmembrane segment of the tachykinin NK2 receptor with neurokinin A

We report the use of thiol chemistry to define specific and reversible disulfide interactions of Cys-substituted NK2 receptor mutants with analogues of neurokinin A (NKA) containing single cysteine substitutions. The NKA analogues were N-biotinylated to facilitate the rapid detection of covalent analogue-receptor interactions utilizing streptavidin reactivity. N-biotinyl-[Tyr1,Cys9]NKA, N-biotinyl-[Tyr1,Cys10]NKA were both found to reversibly disulfide bond to the NK2 receptor mutant Met297 --> Cys. This is consistent with the improved affinities of these particular analogues for the Met297 --> Cys receptor as compared with those for the wild-type and Met297 --> Leu receptors. In our three-dimensional model, Met297 occupies the equivalent position in helix 7 to the retinal binding Lys296 in rhodopsin. Binding of the NK2 receptor antagonist [3H]SR 48968 and of 125I-NKA was used to characterize additional receptor mutants. It seems that the aromatic residues Trp99 (helix 3), His198 (helix 5), Tyr266, His267, and Phe270 play an important role in NKA binding as structural determinants. The existence of overlapping SR 48968 and NKA binding sites is also evident. These data suggest that the peptide binding site of the NK2R is at least in part formed by residues buried deep within the transmembrane bundle and that this intramembranous binding domain may correspond to the binding sites for substantially smaller endogenous GPCR ligands.     

Cyclobutane derivatives as potent NK1 selective antagonists

A series of novel cyclobutane derivatives as potent and selective NK1 receptor antagonists is described. Several compounds in this series exhibited high in vitro binding affinity (Ki 相似文献   

Localization of tachykinin binding sites (NK1, NK2, NK3 ligands) in the rat brain

A comparative autoradiographic analysis of the distribution of tachykinin binding sites was made on brain serial sections using several ligands. (1) 3H-SP, 125I-BHSP and 3H-physalaemin labeled identical binding sites (NK1 type). (2) 3H-NKB, 125I-BHE and 3H-eledoisin also labeled identical sites (NK3 type). (3) 125I-BHNKA preferentially labeled NK3 binding sites, the distribution of 125I-BHNKA binding sites being identical to that of 3H-NKB or 125I-BHE binding sites. (4) The distributions of 3H-SP and 3H-NKB binding sites were markedly different. (5) A very low density of labeling was found with 3H-NKA or 125I-NKA, and these binding sites were distributed only in areas rich in either 3H-SP or 3H-NKB binding sites. (6) Particular efforts were made to look for the presence of tachykinin binding sites in the substantia nigra, since this structure is particularly rich in SP and NKA and contains functional tachykinin receptors of the NK1 and NK2 types as suggested by physiological studies. Confirming previous reports, low or very low labeling was observed in the substantia nigra with 3H-SP or 125I-BHSP and 3H-NKB or 125I-BHE. Similar results were found with 3H-NKA, 125I-NKA or 125I-BHNKA. In conclusion, our data do not provide evidence yet for the existence of NK2 binding sites in the rat brain.     

Stable expression of high affinity NK1 (substance P) and NK2 (neurokinin A) receptors but low affinity NK3 (neurokinin B) receptors in transfected CHO cells.

Stable CHO cell clones which selectively express all three rat tachykinin receptors were established by transfection. The binding of radiolabled substance P and neurokinin A (substance K) to CHO clones expressing the NK1 and NK2 receptors, respectively, were saturatable and of high affinity (Kd = 0.17 nM (NK1); 3.4 nM (NK2)). Scatchard analysis of the binding data indicated for both receptors binding to a single population of binding sites, and competition binding studies showed that the binding specificities of the receptors corresponded to those of classical NK1 and NK2 receptors. In contrast, the binding of eledoisin to the NK3 receptor expressed in the transfected CHO cells was of low affinity (IC50 = 240 nM) compared to the high affinity of the receptor found when it was transiently expressed in COS-7 cells (IC50 = 8 nM). However, in both cases the receptor exhibited the specificity of a classical NK3 receptor. The established cell clones may provide an important tool for further analysis of the molecular mechanisms involved in binding, activation, and coupling of receptors for tachykinin peptides.     

4,4-Disubstituted cyclohexylamine NK(1) receptor antagonists II

A series of novel 4,4-disubstituted cyclohexylamines as NK(1) receptor antagonists is described: modifications to the amine moiety retain NK(1) receptor binding affinity whilst disrupting I(Kr) affinity.     

Interaction between human NK cells and bone marrow stromal cells induces NK cell triggering: role of NKp30 and NKG2D receptors

In this study we have analyzed the interaction between in vitro cultured bone marrow stromal cells (BMSC) and NK cells. Ex vivo-isolated NK cells neoexpressed the activation Ag CD69 and released IFN-gamma and TNF-alpha upon binding with BMSC. Production of these proinflammatory cytokines was dependent on ligation of ICAM1 expressed on BMSC and its receptor LFA1 on NK cells. Furthermore, the NKp30, among natural cytotoxicity receptors, appeared to be primarily involved in triggering NK cells upon interaction with BMSC. Unexpectedly, autologous IL-2-activated NK cells killed BMSC. Again, LFA1/ICAM1 interaction plays a key role in NK/BMSC interaction; this interaction is followed by a strong intracellular calcium increase in NK cells. More importantly, NKG2D/MHC-I-related stress-inducible molecule A and/or NKG2D/UL-16 binding protein 3 engagement is responsible for the delivery of a lethal hit. It appears that HLA-I molecules do not protect BMSC from NK cell-mediated injury. Thus, NK cells, activated upon binding with BMSC, may regulate BMSC survival.     

Structure-activity studies at the rat tachykinin NK2 receptor: effect of substitution at position 5 of neurokinin A.

A series of analogues of neurokinin A(4-10) was synthesized using solid phase techniques with Chiron pins, and purified by HPLC. The potencies of 10 peptides with substitution at Ser5 were assessed at rat fundus NK2 receptors. In membrane binding studies with [125I]-[Lys5,Tyr(I2)7,MeLeu9,Nle10]-NKA(4-10), all compounds except [Asp5]NKA(4-10) showed reasonable affinity, and analogues with Lys and Arg substitutions were five-fold more potent than NKA(4-10). In functional studies, all peptides were able to contract the rat isolated fundus strips. Analogues with Phe, His and Asn substitutions were substantially weaker in functional than in binding studies, whereas there was an excellent correlation (r = 0.95) between binding and functional potency for the remaining seven peptides. [Phe5]NKA(4-10) is in fact neurokinin B(4-10) and this residue may be critical in determining selectivity between NK2 and NK3 receptors. Analogues with a basic residue (Lys, Arg) at position 5 showed both increased affinity and functional potency, whereas the neutral [Asn5]NKA(4-10) was equally as weak in contractile studies as the acidic [Asp5]NKA(4-10). However, [Glu5]NKA(4-10) and [Gln5]NKA(4-10) were no different from NKA(4-10). Our results could indicate the presence of a negative charge on the NK2 receptor, close to position 5 of NKA. This would facilitate interaction with positively charged side chains and impede interaction with negatively charged side chains, particularly the inflexible side chain of aspartic acid. Thus, not only the charge, but also the length of the side chain of the residue at position 5, seems to be important for interaction with the rat NK2 receptor.     

Heparin induces dimerization and confers proliferative activity onto the hepatocyte growth factor antagonists NK1 and NK2

Hepatocyte growth factor (HGF) is a potent epithelial mitogen whose actions are mediated through its receptor, the proto-oncogene c-Met. Two truncated variants of HGF known as NK1 and NK2 have been reported to be competitive inhibitors of HGF binding to c-Met, and to function as HGF antagonists (Lokker, N.A., and P.J. Godowski. 1993. J. Biol. Chem. 268: 17145-17150; Chan, A.M., J.S. Rubin, D.P. Bottaro, D.W. Hirschfield, M. Chedid, and S.A. Aaronson. 1991. Science (Wash. DC). 254:1382-1387). We show here, however, that NK1 acts as a partial agonist in mink lung cells. Interestingly, NK1, which is an HGF antagonist in hepatocytes in normal conditions, was converted to a partial agonist by adding heparin to the culture medium. The interaction of NK1 and heparin was further studied in BaF3 cells, which express little or no cell surface heparan sulfate proteoglycans. In BaF3 cells transfected with a plasmid encoding human c-Met, heparin and NK1 synergized to stimulate DNA synthesis and cell proliferation. There was no effect of heparin on the IL-3 sensitivity of BaF3-hMet cells, and no effect of NK1 plus heparin in control BaF3 cells, indicating that the response was specific and mediated through c-Met. The naturally occurring HGF splice variant NK2 also stimulated DNA synthesis in mink lung cells and exerted a heparin-dependent effect on BaF3-hMet cells, but not on BaF3-neo cells. The activating effect of heparin was mimicked by a variety of sulfated glycosaminoglycans. Mechanistic studies revealed that heparin increased the binding of NK1 to BaF3-hMet cells, stabilized NK1, and induced dimerization of NK1. Based on these studies, we propose that the normal agonist activity of NK1 and NK2 in mink lung cells is due to an activating interaction with an endogenous glycosaminoglycan. Consistent with that model, a large portion of the NK1 binding to mink lung cells could be blocked by heparin. Moreover, a preparation of glycosaminoglycans from the surface of mink lung cells induced dimerization of NK1. These data show that the activity of NK1 and NK2 can be modulated by heparin and other related glycosaminoglycans to induce proliferation in cells expressing c-Met.     

Combined tachykinin receptor antagonist: synthesis and stereochemical structure-activity relationships of novel morpholine analogues

We report herein the synthesis and stereochemical structure-activity relationships of novel morpholine analogues 12 and 13 with regards to NK1, NK2 and NK3 tachykinin receptor binding affinity. An essential requirement for more potent binding affinities was controlled by absolute configuration. (S,R)-12 and (S,R)-13 exhibited high binding affinities for NK1, NK2 and NK3 receptors.     

Characterization of tachykinin NK2 receptor in the anterior pituitary gland

Tachykinins are a family of bioactive peptides that interact with three subtypes of receptors: NK1, NK2 and NK3. Substance P has greater affinity for NK1, and neurokinin A (NKA) for NK2 receptor subtype. Although only NK1 receptor has been characterized in the anterior pituitary gland, some evidence suggests the existence of NK2 receptors in this gland. Therefore, we investigated the presence of NK2 receptors in the anterior pituitary gland of male rats by radioligand binding studies using labeled SR48968, a non peptidic specific antagonist. [3H]SR48968 specific binding to cultured anterior pituitary cells was time-dependent and saturable, but with a lower affinity than previously reported values for cells expressing NK2 receptors. Unlabeled NKA inhibited only partially [(3)H]SR48968 specific binding to whole anterior pituitary cells. Since SR48968 is a non polar molecule, we performed experiments to discriminate surface from intracellular binding sites. SR48968 exhibited both surface and intracellular specific binding. Analysis of the surface-bound ligand indicated that [3H]SR48968 binds to one class of receptor with high affinity. Neurokinin A completely displaced [3H]SR48968 surface specific binding fitting to a two-site/two-state model with high and low affinity. Additionally, immunocytochemical studies showed that the NK2 receptor is expressed at least in a subset of lactotropes. These results demonstrate the presence of NK2 receptors in the anterior pituitary gland and suggest that NKA actions in this gland are mediated, at least in part, by the NK2 receptor subtype.     

Biphenyl derivatives as novel dual NK(1)/NK(2)-receptor antagonists

In a continuation of our efforts to simplify the structure of our neurokinin antagonists, a series of substituted biphenyl derivatives has been prepared. Several compounds exhibit potent affinities for both the NK(1) receptor (<10nM) and for the NK(2) receptor (<50 nM). Details on the design, synthesis, biological activities, SAR and conformational analysis of this new class of dual NK(1)/NK(2) receptor antagonists are presented.     

Different subtypes of tachykinin NK(1) receptor binding sites are present in the rat brain

(2-[(125)I]iodohistidyl(1))Neurokinin A ([(125)I]NKA), which labels "septide-sensitive" but not classic NK(1) binding sites in peripheral tissues, was used to determine whether septide-sensitive binding sites are also present in the rat brain. Binding studies were performed in the presence of SR 48968 (NK(2) antagonist) and senktide (NK(3) agonist) because [(125)I]NKA also labels peripheral NK(2) binding sites and, as shown in this study, central NK(3) binding sites. [(125)I]NKA was found to label not only septide-sensitive binding sites but also a new subtype of NK(1) binding site distinct from classic NK(1) binding sites. Both subtypes of [(125)I]NKA binding sites were sensitive to tachykinin NK(1) antagonists and agonists but also to the endogenous tachykinins NKA, neuropeptide K (NPK), and neuropeptide gamma (NPgamma). However, compounds of the septide family such as substance P(6-11) [SP(6-11)] and propionyl-[Met(O(2))(11)]SP(7-11) and some NK(1) antagonists, GR 82334, RP 67580, and CP 96345, had a much lower affinity for the new NK(1)-sensitive sites than for the septide-sensitive sites. The hypothalamus and colliculi possess only this new subtype of NK(1) site, whereas both types of [(125)I]NKA binding sites were found in the amygdala and some other brain structures. These results not only explain the central effects of septide or SP(6-11), but also those of NKA, NPK, and NPgamma, which can be selectively blocked by NK(1) receptor antagonists.     

Spatial requirements of the antagonist binding site of the NK2 receptor

Computer-aided modelling has been used to identify a putative antagonist binding site in the tachykinin NK2 receptor. In order to validate the implied spatial requirements for this region, a series of compounds, based on the potent antagonist GR 149861 have been synthesised and their binding affinities established. Our findings suggest the presence of a large hydrophobic cavity in the putative binding crevice of GR 149861.     

Identification of a new series of non-peptidic NK3 receptor antagonists

The identification and structure-activity relationships of 2-aminomethyl-1-aryl cyclopropane carboxamides as novel NK₃ receptor antagonists are reported. The compound series was optimized to give analogues with low nanomolar binding to the NK₃ receptor and brain exposure, leading to activity in vivo in the senktide-induced hypoactivity model in gerbils.     

Multiple cytokines regulate the NK gene complex-encoded receptor repertoire of mature NK cells and T cells

Mature NK cells comprise a highly diverse population of lymphocytes that express different permutations of receptors to facilitate recognition of diseased cells and perhaps pathogens themselves. Many of these receptors, such as those belonging to the NKRP1, NKG2, and Ly49 families are encoded in the NK gene complex (NKC). It is generally thought that these NKC-encoded receptors are acquired by a poorly understood stochastic mechanism, which operates exclusively during NK cell development, and that following maturation the repertoire is fixed. However, we report a series of observations that demonstrates that the mature NK cell repertoire in mice can in fact be radically remodeled by multiple cytokines. Thus, both IL-2 and IL-15 selectively induce the de novo expression of Ly49E on the majority of mature NK cells. By contrast, IL-4 not only blocks this IL-2-induced acquisition of Ly49E, but reduces the proportion of mature NK cells that expresses pre-existing Ly49 receptors and abrogates the expression of NKG2 receptors while leaving the expression of several NKRP1 receptors unaltered. IL-21 also abrogates NKG2 expression on mature NK cells and selectively down-regulates Ly49F. IL-4 and IL-21 additionally cause dramatic and selective alterations in the NKC-encoded receptor repertoire of IL-2-activated T cells but these are quite different to the changes induced on NK cells. Collectively these findings reveal an unexpected aspect of NKC receptor expression that has important implications for our understanding of the function of these receptors and of the genetic mechanisms that control their expression.     

NK lytic-associated molecule, involved in NK cytotoxic function, is an E3 ligase

NK lytic-associated molecule (NKLAM) is a protein involved in the cytolytic function of NK cells and CTLs. It has been localized to the cytolytic granules in NK cells and is up-regulated when cells are exposed to cytokines IL-2 or IFN-beta. We report in this study that NKLAM contains a cysteine-rich really interesting new gene (RING) in between RING-RING domain, and that this domain possesses strong homology to the RING domain of the known E3 ubiquitin ligase, Dorfin. To determine whether NKLAM functions as an E3 ligase, we performed coimmunoprecipitation binding assays with ubiquitin conjugates (Ubcs) UbcH7, UbcH8, and UbcH10. We demonstrated that both UbcH7 and UbcH8 bind to full-length NKLAM. We then performed a similar binding assay using endogenous NKLAM and UbcH8 expressed by human NK clone NK3.3 to show that the protein interaction occurs in vivo. Using the yeast two-hybrid system, we identified uridine kinase like-1 (URKL-1) protein as a substrate for NKLAM. We confirmed that NKLAM and URKL-1 interact in mammalian cells by using both immunoprecipitation and confocal microscopy. We demonstrated decreased protein expression and enhanced ubiquitination of URKL-1 in the presence of NKLAM. These data indicate that NKLAM is a RING finger protein that binds Ubcs and has as one of its substrates, URKL-1, thus defining this cytolytic protein as an E3 ubiquitin ligase.