Tifluadom, a kappa-opiate agonist, acts as a peripheral cholecystokinin receptor antagonist

Medicinal chemistry of target family-directed masterkeys

The majority of pharmaceutically relevant drug targets cluster into densely populated target families, thus offering a novel approach that complements the currently favoured screening paradigm in medicinal chemistry. This approach uses a privileged structure concept whereby molecular masterkeys are developed that account for a target family wide structural or functional commonality. Numerous lead compounds, based on multipurpose privileged structures, can be generated that address a variety of targets from a gene family of interest, irrespective of therapeutic area. Several different interpretations of the privileged structure concept will be highlighted, with a strong emphasis on the most stringent application: the optimization of a molecular masterkey for a distinct target family of interest.

Development and evaluation of pharmacological agents targeting chemokine receptors

Chemokine receptors belong to one of the most pharmacologically exploited proteins, the G-protein-coupled receptors. Drugs that target these receptors make up greater than 45% of all known marketed medicines. Several excellent reviews published recently have concentrated on the biology, pathophysiology, and molecular mechanisms of action of the chemokines [C. Gerard, B.J. Rollins, Nat. Immunol. 2 (2001) 108; C.R. Mackay, Nat. Immunol. 2 (2001) 95; M. Thelen, Nat. Immunol. 2 (2001) 129] and the reader is directed toward them to gain a thorough understanding of the importance of this growing family of proteins. Although some background will be given here to aid in an understanding of the medical importance of chemokines, this review will focus on the rapid advances that have been made in identifying and characterizing chemokine receptor antagonists, by discussing their efficacy in animal models of disease as well as detailing their progression through human clinical trials. This approach is exemplified by specific reference to CCR1 and CCR5, which are the most advanced chemokine receptor programs.

Enantiomers of 2-[(Acylamino)ethyl]-1,4-benzodiazepines, potent ligands of kappa-opioid receptor: chiral chromatographic resolution, configurational assignment and biological activity

Compounds 2a and 3a-e are racemic 2-[(acylamino)ethyl]-1,4-benzodiazepines, tifluadom analogs, with high affinity and selectivity towards the kappa-opioid receptor. We describe the enantiomeric separation of all compounds through liquid chromatography with chiral stationary phases, as well as the resolution of the enantiomers of the most interesting compounds, 2a and 3a, by the semipreparative column Chiralpak AD. The configuration of the resolved enantiomers was investigated: the comparative study of CD and (1)H NMR spectra shows that compounds (-)-2a and (-)-3a have the same absolute configuration of (+)-(S)-tifluadom. A study on the stereoselective interaction with opiate receptors is reported.

Opioid peptide receptor studies. 10. Nor-BNI differentially inhibits kappa receptor agonist-induced G-protein activation in the guinea pig caudate: further evidence of kappa receptor heterogeneity

There is strong evidence supporting the existence of multiple kappa receptors. Previous studies proposed that U69,593 and (+)-tifluadom act on different kappa receptor subtypes, kappa(1) (kappa(1)) and kappa(2) (kappa(2)), respectively. In this study, we investigated the effects of the kappa selective antagonist nor-binaltorphimine (Nor-BNI) on U69,593- and (+)-tifluadom-induced receptor-mediated stimulation of [(35)S]-GTP-gamma-S binding in the guinea pig caudate. The IC(50) value of Nor-BNI in the presence of a stimulating concentration of U69,593 (1 microM) was 0.19+/-0.02; while the IC(50) for Nor-BNI in the presence of (+)-tifluadom (1 microM) was 13.9+/- 1.62 nM. The mu-opioid receptor antagonist CTAP (10,000 nM) significantly reduced (+)-tifluadom-stimulated [(35)S]-GTP-gamma-S binding in rat brain sections and guinea pig brain membranes, indicating that (+)-tifluadom has mu agonist activity. Under conditions in which the mu agonist activity of (+)-tifluadom was blocked by 1000 nM CTAP the Ki value for Nor-BNI for inhibition of U69,593-stimulated [(35)S]-GTP-gamma-S binding was 0.036+/-.004 nM, whereas, its Ki value for the (+)-tifluadom-stimulated [(35)S]-GTP-gamma-S binding was 0.27+/-.015 nM. These results suggest that (+)-tifluadom and U69,593 activate pharmacologically different receptors. This study provides functional evidence in support of kappa receptor heterogeneity.

[3H]-SR 27897B: a selective probe for autoradiographic labelling of CCK-A receptors in the brain

The binding and distribution of radiolabelled SR27897B, a potent CCK-A antagonist, was characterized using in vitro receptor autoradiography. Rapid imaging and quantitative analysis of [3H]SR27897B binding was obtained in a very short period of time (5 days) with a highly sensitive radioimager ensuring very short exposure times for isotopes such as tritium. Tritiated SR27897B binding sites are localized almost exclusively in the area postrema and the medical part of the nucleus tractus solitarius and in this nucleus the rostral-caudal distribution of CCK-A sites differed from that of sulphated CCK8 receptors. Receptor binding properties analyzed on 15 microns serial coronal sections showed on site receptor occupancy in these two regions with high affinity and selectivity characteristic of the CCK-A receptor. These results precisely locate the SR27897B binding sites and provide further support for the absence of heterogeneity of the CCK-A receptors in the rat brain.

Localization of peripheral cholecystokinin receptors in vivo using the cholecystokinin antagonist [3H](+/-)-MK-329

Cholecystokinin (CCK) regulates various gastrointestinal functions through specific receptors. The mechanisms responsible for disorders of these functions could be elucidated by non-invasively localizing CCK receptors and quantifying their number in vivo. MK-329 is a highly selective and very high affinity antagonist at the peripheral CCK receptor. We investigated the in vivo binding of [3H](+/-)-MK-329 in mice to determine if binding to CCK receptors could be detected after systemic administration of the tracer. The uptake of [3H](+/-)-MK-329 increased in the pancreas from 5 min to 4 h after administration. The binding was saturable, stereospecific, and more than 80% specific. A total/non-specific binding ratio of 43 was reached at 8 h post-injection. The pancreas was the only organ where specific binding could be detected. Our results suggest that MK-329 labeled with a positron emitter such as C-11 could be used with positron emission tomography to image and quantify peripheral CCK receptors in man.

The influence of tifluadom on cholecystokinin-induced antinociception

The effects of tifluadom, a benzodiazepine-kappa-opioid-receptor agonist, on cholecystokinin-octapeptide (CCK-8)-induced antinociception were investigated in the mouse writhing test. When given alone, tifluadom produced pronounced, dose-dependent analgesia. The antinociceptive effect of intracerebroventricularly injected CCK-8 was potentiated by high doses of tifluadom. In contrast, when tifluadom was applied at low doses which did not induce antinociception, the antinociceptive effect of CCK-8 was completely antagonized. It is concluded that tifluadom acts both as kappa-opioid receptor agonist and as an antagonist at CCK receptors mediating CCK-induced antinociception.