Development of a new class of nonimidazole histamine H(3) receptor ligands with combined inhibitory histamine N-methyltransferase activity

A new class of diamine-based human histamine H3 receptor antagonists: 4-(aminoalkoxy)benzylamines

4-(Aminoalkoxy)benzylamines were prepared and screened for in vitro activity at the human histamine H(3) receptor. Some members of this series exhibited subnanomolar binding affinities. Analogues in which one nitrogen atom was replaced with a methine group showed greatly reduced binding affinities. Six members of this series were found to be antagonists in a cell-based model of human histamine H(3) receptor activation. One member of this series, 1-[4-(3-piperidin-1-ylpropoxy)benzyl]piperidine (7b), was found to be a selective and potent human H(3) receptor antagonist.

A new class of histamine H(3)-receptor antagonists: synthesis and structure-activity relationships of 7,8,9,10-tetrahydro-6H-cyclohepta[b]quinolines

The synthesis and biological evaluation of novel cycloheptaquinoline antagonists of the human H(3) receptor are described. Two series of compounds, bearing either an amino substituent or an alkyne linker at the 11-position, were investigated. Modifications of the amino substituents, optimization of chain length and the effect of conformational restraints are described. Several compounds with high affinity and selectivity for the H(3) receptor were discovered.

Imidazole derivatives as a novel class of hybrid compounds with inhibitory histamine N-methyltransferase potencies and histamine hH3 receptor affinities

In this study, a novel series of imidazole-containing compounds with dual properties, that is, inhibitory potency at the enzyme histamine N(tau)-methyltransferase (HMT) and antagonist potency at histamine H(3) receptors was designed and synthesized. Pharmacologically, these new hybrid drugs were evaluated in functional assays for their inhibitory potencies at rat kidney HMT and for their antagonist activities on synaptosomes of rat cerebral cortex. For selected compounds, binding affinities at recombinant human histamine H(3) receptors were determined. The first compounds (1-10) of the series proved to be H(3) receptor ligands of high potency at rat synaptosomes or of high binding affinity at human H(3) receptors, respectively, but of only moderate activity as inhibitors of rat kidney HMT. In contrast, aminoquinoline- or tetrahydroacridine-containing derivatives 11-17 also displayed HMT inhibitory potency in the nanomolar concentration range. Preliminary data from molecular modeling investigations showed that the imidazole derivative 15 and the HMT inhibitor quinacrine possess identical binding areas. The most interesting compound (14) is simultaneously a highly potent H(3) receptor ligand (K(i)=4.1nM) and a highly potent HMT inhibitor (IC(50)=24nM), which makes this derivative a valuable pharmacological tool for further development.

Novel nonimidazole histamine H3 receptor antagonists: 1-(4-(phenoxymethyl)benzyl)piperidines and related compounds

In an extension of very recently published studies on successful imidazole replacements in some series of histamine H(3) receptor antagonists, we report on a new class of lipophilic nonimidazole antagonist having an aliphatic tertiary amino moiety connected to a benzyl template substituted in the 4-position by a phenoxymethyl group. The structural modifications were performed with the intention to avoid possible negative side effects reported for other series of antagonists. The novel compounds combine different characteristics of recently developed histamine H(3) receptor antagonists. The compounds were screened for their affinity in a binding assay for the human histamine H(3) receptor stably expressed in CHO-K1 cells and tested for their in vivo potency in the central nervous system of mice after oral administration. Different substitution patterns on the phenoxy group were used to optimize in vitro and/or in vivo potency leading to some compounds with low nanomolar affinity and high oral in vivo potency. Modifications of the basic piperidino moiety were performed by ring expansion, contraction, and opening. Selected compounds exhibited selectivity in functional assays on isolated organs of guinea-pig for H(3) vs H(1) and H(2) receptors. Unexpectedly, some of the novel antagonists also showed a slight preference for the human histamine H(3) receptor compared to their affinities for the guinea-pig H(3) receptor.

Synthesis and SAR of aminoalkoxy-biaryl-4-carboxamides: novel and selective histamine H3 receptor antagonists

Novel 4'-[(NR1R2-1-yl)]-propoxy-biaryl-4-carboxamides were designed and synthesized. All compounds were tested for affinity at histamine H(3)receptors. Most compounds were highly potent and selective for human and rat H(3) receptors and selected examples such as A-349821 showed functional antagonism of H(3) receptors in vitro and in a mouse dipsogenia model.