Naphthalen-1-yl-(4-pentyloxynaphthalen-1-yl)methanone: a potent, orally bioavailable human CB1/CB2 dual agonist with antihyperalgesic properties and restricted central nervous system penetration.

Selective activation of peripheral cannabinoid CB1 receptors has the potential to become a valuable therapy for chronic pain conditions as long as central nervous system effects are attenuated. A new class of cannabinoid ligands was rationally designed from known aminoalkylindole agonists and showed good binding and functional activities at human CB1 and CB2 receptors. This has led to the discovery of a novel CB1/CB2 dual agonist, naphthalen-1-yl-(4-pentyloxynaphthalen-1-yl)methanone (13), which displays good oral bioavailability, potent antihyperalgesic activity in animal models, and limited brain penetration.

Identification and biological characterization of 6-aryl-7-isopropylquinazolinones as novel TRPV1 antagonists that are effective in models of chronic pain.

Vanilloid receptor 1 (VR1, TRPV1) is a cation-selective ion channel that is expressed on primary afferent neurons and is upregulated following inflammation and nerve damage. Blockers of this channel may have utility in the treatment of chronic nociceptive and neuropathic pain. Here, we describe the optimization from a high throughput screening hit, of a series of 6-aryl-7-isopropylquinazolinones that are TRPV1 antagonists in vitro. We also demonstrate that one compound is active in vivo against capsaicin-induced hyperalgesia and in models of neuropathic and nociceptive pain in the rat.

A nonpeptide antagonist reveals a highly glycosylated state of the rabbit kinin B1 receptor.

The inducible kinin B1 receptor is emerging as an attractive therapeutic target for the treatment of pain and inflammation. Although many studies described its regulation at the transcriptional level, little is known about the maturation of the B1 receptor. Using two human embryonic kidney (HEK) 293 cell lines stably expressing rabbit B1 receptors tagged with the yellow fluorescent protein at the C terminus (B1R-YFP) or the N-terminal myc epitope (myc-B1R), we showed that receptors are mainly retained in a perinuclear compartment and detectable as low-glycosylated species under control conditions. Interference with the ubiquitin-proteasome pathway function (proteasome inhibitors, coexpression with dominant-negative ubiquitin) blocked B1 receptor degradation and amplified its intracellular accumulation. A potent nonpeptide antagonist specifically increased the abundance of highly glycosylated B1R-YFP forms at the cell surface (accessible to chymotrypsin digestion in intact cells); this compound augmented low-glycosylated receptors in brefeldin A-treated cells, supporting the hypothesis that it reaches a newly synthesized receptor in the endoplasmic reticulum. Cell-impermeant peptide or low-affinity nonpeptide B1 receptor antagonists failed to influence the level of highly glycosylated receptors. Chemical chaperones stabilized all B1R-YFP species and up-regulated endogenous B1 receptors expressed at the surface of rabbit smooth muscle cells. Although myc-B1Rs behaved similarly to B1R-YFP in most aspects, antibody-based detection assays failed to reveal highly glycosylated species of this construct. Taken together, these results show that B1 receptors overexpressed in HEK 293 cells are degraded by the proteasome. Furthermore, a pharmacological chaperone highlights the existence of a highly N-glycosylated form of the rabbit kinin B1 receptor at the cell surface.

Potent and orally bioavailable non-peptide antagonists at the human bradykinin B(1) receptor based on a 2-alkylamino-5-sulfamoylbenzamide core.

The bradykinin B(1) receptor is rapidly induced after inflammation or tissue trauma and appears to play an important role in the maintenance of hyperalgesia in inflammatory conditions. Here, we describe the optimization process to identify novel, potent non-peptide human B(1) receptor antagonists based on a 2-alkylamino-5-sulfamoylbenzamide core. Optimized derivatives are selective, functional B(1) antagonists with low nanomolar affinity and exhibit oral bioavailability in animals.

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.

Nonpeptide bradykinin B2 receptor antagonists: conversion of rodent-selective bradyzide analogues into potent, orally-active human bradykinin B2 receptor antagonists.

The 1-(2-nitrophenyl)thiosemicarbazide (TSC) derivative, (S)-1-[4-(4-benzhydrylthiosemicarbazido)-3-nitrobenzenesulfonyl]pyrrolidine-2-carboxylic acid [2-[(2-dimethylaminoethyl)methylamino]ethyl]amide (bradyzide; (S)-4), was recently disclosed as a novel, potent, orally active nonpeptide bradykinin (BK) B2 receptor antagonist. The compound inhibited the specific binding of [3H]BK to NG108-15 cell membrane preparations (rodent neuroblastoma-glioma) expressing B2 receptors with a K(i) of 0.5 +/- 0.2 nM. Compound (S)-4 also demonstrated oral efficacy against Freund's complete adjuvant (FCA)-induced mechanical hyperalgesia in rats with an ED50 value of 0.84 micromol/kg. After we optimized the terminal binding determinants projecting from the TSC framework, we found that it was possible to replace the potentially toxicophoric nitro and divalent sulfur moieties with only a 15-fold loss in binding affinity ((S)-14a). However, bradyzide and its congeners were found to have much lower affinities for cloned human B2 receptors, expressed in Cos-7 cells. The hitherto synthesized TSC series was screened against the human B2 receptor, and the dibenzosuberane (DBS) pharmacophore emerged as the key structural requirement for potency. Incorporation of this group resulted in a series of derivatives ((S)-14d,e and 19b-d) with K(i) ranges of 10.7-176 nM in NG108-15 cells (expressing the rodent B2 receptor) and 0.79-253 nM in Cos-7 cells (expressing the human B2 receptor). There was no evidence of agonist activity with any of the nonpeptides in any of the cell lines tested. In vivo, oral administration of compound 19c reversed FCA-induced and turpentine-induced mechanical hyperalgesia in rodents with ED50 values of 0.027 and 0.32 micromol/kg, respectively. The selectivity profiles of compounds (S)-14f and (S)-14g were also assessed to determine the conformational and/or steric preferences of the double-ring arrangement. The affinity of (S)-14 g for the human B2 receptor suggested that it may be a hydrophobic interaction with the ethane bridge of the DBS moiety that accounts for the increased potency of compounds (S)-14d,e and 19b,c at this receptor, by favoring a binding mode inaccessible to the unsubstituted diphenylmethyl derivative, (S)-4.