Search for histamine H(3) receptor ligands with combined inhibitory potency at histamine N-methyltransferase: omega-piperidinoalkanamine derivatives.

In an effort to design new hybrid compounds with dual properties, i.e. binding affinity at histamine H(3) receptors and inhibitory potency at the catabolic enzyme histamine N(tau)-methyltransferase (HMT), a novel series of 1-substituted piperidine derivatives was synthesized. This alicyclic heterocycle is structurally linked via aminoalkyl spacers of variable lengths to additional aromatic carbo- or hetero-cycles. These new hybrid drugs were pharmacologically evaluated regarding their binding affinities at recombinant human H(3) receptors, stably expressed in CHO cells, and in a functional assay for their inhibitory potencies at rat kidney HMT. All compounds investigated proved to be H(3) receptor ligands with binding affinities in the micro- to nanomolar concentration range despite significant differences in the type of the aromatic moiety introduced. The most potent compound in this series was the quinoline derivative 20 (K(i) = 5.6 nM). Likewise, all new ligands studied showed impressive HMT inhibitory activities. Here, compounds 5, 10, 14 and 18-20 exhibited submicromolar potencies (IC(50) = 0.061-0.56 microM). The aminomethylated quinoline 19 showed almost the same, well balanced nanomolar activities on both targets. In this study, new hybrid compounds with a dual mode biological action were developed. These pharmacological agents are valuable leads for further development and candidates for treatment of histamine-dependent disorders.