The synthesis of NPTS, 6, a potent inhibitor of the type 1 glycine transporter (GlyT1) is described, as well as preparation of 6 in optically active and tritiated form for use as a radioligand for affinity displacement assay of GlyT1.

The synthesis and SAR of a series of 6-(4-(substituted)phenyl)-2-aminopyridines as inhibitors of nitric oxide synthase are described. Compound 3a from this series shows potent and selective inhibition of the human nNOS isoform, with pharmacokinetics sufficient to provide in vivo inhibition of nNOS activity.

The synthesis and SAR of benzylamine side chain analogs of the NK-1 receptor antagonist CP-99,994 are described. The 5-trifluoromethoxy analog, CP-122,721, shows superior in vivo blockade of NK-1 receptor mediated responses.

Ligand recognition of the NK1 receptor (substance P receptor) by peptide agonist and non-peptide antagonist has been investigated and compared by the use of fluorescent ligands and spectrofluorometric methods, Analogues of substance P (SP) labeled with the environment-sensitive fluorescent group 5-dimethylaminonaphthalene-1 sulfonyl (dansyl) at either position 3, 8, or 11 or with fluorescein at the N-alpha position were synthesized and characterized. Peptides modified at the alpha-amino group or at positions 3 or 11 conserved a relatively good affinity for NK1 and agonistic properties, Modification at position 8 resulted in an 18,000-fold decrease in affinity, A fluorescent dansyl analogue of the non-peptide antagonist CP96,345 was prepared and characterized. The quantum yield of fluorescence for dansyl-CP96,345 was much higher than for any of the dansyl-labeled peptides indicating that the micro-environment of the binding site is more hydrophobic for the nonpeptide antagonist than for the peptide agonists, Comparison of collisional quenching of fluorescence by the water-soluble hydroxy-Tempo compound showed that dansyl-CP96,345 is buried and virtually inaccessible to aqueous quenchers, whereas dansyl-or fluoresceinyl-labeled peptides were exposed to the solvent, Anisotropy of all fluorescent ligands increased upon binding to NK1 indicating a restricted motional freedom, However, this increase in anisotropy was more pronounced for the dansyl attached to the non-peptide antagonist CP96,345 than for the fluorescent probes attached to different positions of SP, In conclusion, our data indicate that the environment surrounding non-peptide antagonist and peptide agonists are vastly different when bound to the NK1 receptor. These results support recent observations by mutagenesis and cross-linking work suggesting that peptide agonists have their major interaction points in the N-terminal extension and the loops forming the extracellular face of the NK1 receptor, Our data also suggest that neither the C terminus nor the N terminus of SP appears to penetrate deeply below the extracellular surface in the transmembrane domain of the receptor.

An azido derivative of [3H2](2S, 3S)-cis-2-(diphenylmethyl)-N-((2-methoxyphenyl) methyl)-1-azabicyclo[2.2.2]octon-3-amine (CP-96,345), a potent nonpeptide antagonist of the substance P (SP) (neurokinin-1) receptor, was synthesized and shown to have an affinity for the human SP receptor similar to that of the parent compound, CP-96,345. When Chinese hamster ovary cells expressing the human SP receptor were photolabeled with this compound and analyzed with the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography, several radioactive bands were observed, including a major band centered at molecular mass 80 kDa, the expected value for the SP receptor expressed in Chinese hamster ovary cells. Only the labeling of the 80-kDa protein was specific: nonradiolabeled CP-96,345 but not its optical enantiomer, CP-96,344 was a potent inhibitor of photoincorporation. SP prevented photolabeling only at concentrations higher than expected from its binding affinity but similar to those shown in a competition binding assay to displace radioiodinated analogue of CP-96,345. Antiserum generated against a synthetic peptide corresponding to the carboxyl terminus of the human SP receptor immunoprecipitated only the 80-kDa photoaffinity labeled protein, confirming that it is the human SP receptor. Interestingly, a second antiserum that was generated against the third extracellular loop of the G protein-coupled receptor no longer immunoprecipitated the receptor when covalently labeled with [3H2]azido-CP-96,345. This result indicates either that attachment of the antagonist modified the antigenic region directly, suggesting involvement of this domain in the binding of CP-96,345, or that the loss of recognition by the antiserum is secondary to a change in conformation induced by the covalent attachment of the antagonist at a different site.

A structurally novel series of cholecystokinin-B (CCK-B) receptor ligands has been designed and synthesized based on the 'double-ring system' theory of receptor recognition. Compounds 2b-cis and 2g-cis from this 1-amino-2-benzyltetralin series show modest CCK-B receptor affinity, with IC50 values of 48.5 nM and 39.0 nM, respectively. The results are discussed in the context of ongoing efforts to identify the CCK-B receptor binding site for nonpeptide ligands.

A series of substituted phenethyl derivatives of 3-benzisothiazolylpiperazine incorporating potent D2 and 5-HT2A antagonist activity was investigated as an approach to a novel atypical antipsychotic agent. The in vitro profile of 8e from this series is a combination of D2 receptor affinity comparable to the typical antipsychotic agent haloperidol and a 5-HT2A/D2 ratio comparable to the atypical agent clozapine. In vivo 8e possesses activity consistent with an efficacious antipsychotic agent with less tendency to induce extrapyramidal side effects in man.

Ziprasidone (CP-88,059) is a combined 5-HT (serotonin) and dopamine receptor antagonist which exhibits potent effects in preclinical assays predictive of antipsychotic activity. Whereas the compound is a dopamine antagonist in vitro and in vivo, its most potent action is antagonism of 5-HT2A receptors, where its affinity is an order of magnitude greater than that observed for dopamine D2 sites. Laboratory and clinical findings have led to a hypothesis that antagonism of 5-HT2A receptors in the brain limits the undesirable motor side effects associated with dopamine receptor blockade and improves efficacy against the negative symptoms of schizophrenia. Ziprasidone possesses an in vitro 5-HT2A/dopamine D2 receptor affinity ratio higher than any clinically available antipsychotic agent. In vivo, ziprasidone antagonizes 5-HT2A receptor-induced head twitch with 6-fold higher potency than for blockade of d-amphetamine-induced hyperactivity, a measure of central dopamine D2 receptor antagonism. Ziprasidone also has high affinity for the 5-HT1A, 5-HT1D and 5-HT2C receptor subtypes, which may further enhance its therapeutic potential. The prediction of antipsychotic efficacy without severe motor side effects is supported by the relatively weak potency of ziprasidone to produce catalepsy in animals, contrasted with its potent antagonism of conditioned avoidance responding and dopamine agonist-induced locomotor activation and stereotypy. The compound is well tolerated in animals at doses producing effective dopamine antagonism in the brain. Ziprasidone should be a valuable addition to the treatment of psychotic disorders.

Conference Article| February 01 1995 Tachykinin non-peptide antagonists: binding domain and molecular mode of action U. Gether; U. Gether § *Howard Hughes Medical Institute, Beckman Center, B159, Stanford University Medical Center, CA 94305, U.S.A. §To whom correspondence should be addressed. Search for other works by this author on: This Site PubMed Google Scholar J. A. Lowe, III; J. A. Lowe, III †Department of Exploratory Medicinal Chemistry, Central Research Division, Pfizer Inc., Groton, CT 06340, U.S.A. Search for other works by this author on: This Site PubMed Google Scholar T. W. Schwartz T. W. Schwartz ‡Laboratory of Molecular Endocrinology, University Department of Clinical Biochemistry, Rigshospitalet 6321, Copenhagen DK-2100, Denmark Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1995) 23 (1): 96–102. https://doi.org/10.1042/bst0230096 Article history Received: August 31 1994 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation U. Gether, J. A. Lowe, T. W. Schwartz; Tachykinin non-peptide antagonists: binding domain and molecular mode of action. Biochem Soc Trans 1 February 1995; 23 (1): 96–102. doi: https://doi.org/10.1042/bst0230096 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search Keywords: NK, neurokinin, TM, transmembrane This content is only available as a PDF. © 1995 Biochemical Society1995 Article PDF first page preview Close Modal You do not currently have access to this content.

A series of 5-substituted-3-ureidobenzazepin-2-ones bearing ioizable functionality was synthesized as potential cholecystokinin-B (CCK-B) receptor antagonists. SAR of this series of compounds demonstrated the optimal combination of a carboxylic acid and 5-cyclohexyl group, providing the high affinity (CCK-B IC50 = 0.10 nM), water soluble CCK-B antagonist 2.

A newly developed cannabinoid antagonist, SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1 H-pyrazole-3-carboxamide hydrochloride], binds to brain cannabinoid receptors and has been shown to block characteristic pharmacological effects of the aminoalkylindole cannabinoid agonist, WIN 55,212-2 {R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpho-linyl)methyl]pyrol-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl)methanone monomethanesulfonate). In the present study, the effects of this compound in an animal model of cannabis intoxication were investigated. Rats were trained to press one lever after being injected with 3 mg/kg of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and to press a second lever after injection with vehicle. Rhesus monkeys also were trained to discriminate between Delta(9)-THC and vehicle. Results of tests with various doses of SR141716A in combination with 3 mg/kg of Delta(9)-THC showed that SR141716A produced reversible, dose-dependent antagonism of the discriminative stimulus properties of Delta(9)-THC in rats, with recovery within 24 hr. SR141716A also blocked the discriminative stimulus effects of Delta(9)-THC in monkeys. Furthermore, in rats, 1 mg/kg of SR141716A produced a 12-fold rightward shift in the Delta(9)-THC dose-effect curve and a 43-fold rightward shift in the WIN 55,212-2 dose-effect curve. When SR141716A was administered alone, it did not substitute for Delta(9)-THC in rats. The present results suggest that SR141716A blocks the discriminative stimulus effects of Delta(9)-THC via a receptor-mediated mechanism. This drug is the first reliable antagonist of cannabinoid discrimination and would be predicted to block or reverse cannabis intoxication in humans.

Precipitated withdrawal in rats chronically exposed to Delta(9)-tetrahydrocannabinol, the major psychoactive principle of the marijuana plant, was unequivocally demonstrated for the first time using a selective antagonist, SR 141716A (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1(2,4-dichloro-phenyl)-4-methyl-1H-pyrazole carboxamide . HCl). This demonstration should provide a powerful stimulus for the systematic study of dependency on the psychoactive cannabinoids.

A series of 5-phenyl-3-ureidobenzazepin-2-one cholecystokinin-B (CCK-B) receptor antagonists was synthesized using Beckmann ring expansion of a suitable 4-phenyl-1-tetralone as a key step. Structure-activity relationship studies revealed the importance of the 5-phenyl group for potent and selective CCK-B affinity. Addition of an 8-methyl substituent and resolution provided the potent (CCK-B IC50 = 0.48 nM) CCK-B antagonist 4. The role of the 5-phenyl group as part of a "privileged structure" for high-affinity receptor antagonism is discussed.

The synthesis and SAR of a series of 2-aryl-1-azabicyclo[2.2.2]octanes structurally related to the nonpeptide substance P antagonists CP-96,345 and CP-99,994 are described. The novel SAR observed at the 2-position in these derivatives represents a hybrid between that seen in the two previous series.

Previously we have found that binding of the nonpeptide substance P antagonist, CP 96,345, to the neurokinin-1 (NK-1) receptor was critically dependent on two short segments adjacent to the top of transmembrane segments (TM) V and VI, called segments A (residues 183-195) and D (residues 271-276), respectively. In the present study we have systematically performed substitutions of nonconserved residues within these two segments with residues from the homologous NK-3 and/or NK-2 receptor. In segment A, deletion of residues Glu193 and Lys194, which are not present in the NK-3 receptor, or substituting them with leucines as in the NK-2 receptor, decreased the affinity of CP 96,345 10- and 22-fold, respectively. Surprisingly, switching the position of Glu193 and Lys194 did not affect the affinity of CP 96,345, suggesting that, rather than interacting directly with CP 96,345, an interaction of these residues with one another is important for CP 96,345 binding. In segment D substitution of Tyr272 with threonine as in the NK-2 receptor and with alanine as in the NK-3 receptor decreased the affinity of CP 96,345 7- and 24-fold, respectively. Mutation of the preceding Pro271 to glycine alone did not affect CP 96,345 binding, but, combined with the mutation of Tyr272 to threonine, the affinity decreased 28-fold. A series of CP 96,345 analogues with modifications of the major chemical moieties exhibited equally reduced affinity as that of CP 96,345 for the Tyr272- and Lys193-Glu194-substituted constructs, except CP 95,555, which lacks one of the phenyl rings in the benzhydryl group and which was almost unaffected by these mutations. In conclusion, our data indicate a direct interaction between CP 96,345 and Tyr272, which are located at the top of TM VI likely in close spatial proximity to the previously identified interaction point, His197, at the top of the adjacent TM V. Furthermore, the data demonstrated a critical involvement in CP 96,345 binding of Lys193 and Glu194 located one alpha-helical turn above His197.

The synthesis and structure-activity relationships of a series of aza-tricyclic analogs of the quinuclidine substance P (SP) antagonist 1 are described. The SP receptor affinity of these compounds was found to vary according to the size of the new ring fused to the quinuclidine and the mode of fusion. Correlations between receptor affinity and (1) the steric bulk of the newly introduced ring fusion and (2) the dihedral angle between the benzhydryl and benzylamino substituents of these aza-tricyclic compounds were explored.