The computational design of test compounds with potentially specific biological activity: histamine-H2 agonists derived from 5-HT/H2 antagonists

8R-Lisuride Is a Potent Stereospecific Histamine H1-Receptor Partial Agonist

The human histamine H1 receptor (H1R) is an important, well characterized target for the development of antagonists to treat allergic conditions. Many neuropsychiatric drugs are known to potently antagonize the H1R, thereby producing some of their side effects. In contrast, the tolerability and potential therapeutic utility of H1R agonism is currently unclear. We have used a cell-based functional assay to evaluate known therapeutics and reference drugs for H1R agonist activity. Our initial functional screen identified three ergot-based compounds possessing heretofore-unknown H1R agonist activity. 8R-lisuride demonstrated potent agonist activity in various assays including receptor selection and amplification technology, inositol phosphate accumulation, and activation of nuclear factor-kappaB with pEC50 values of 8.1, 7.9, and 7.9, respectively, and with varying degrees of efficacy. Based on these assays, 8R-lisuride is the most potent stereospecific partial agonist for the human H1R yet reported. Investigation of the residues involved in histamine and lisuride binding, using H1R mutants and molecular modeling, have revealed that although these ligands are structurally different, the lisuride-binding pocket in the H1R closely corresponds to the histamine-binding pocket. The discovery of a potent stereospecific partial H1R agonist provides a valuable tool to further characterize this important therapeutic target in vitro.

Multiconformational composite molecular potential fields in the analysis of drug action. I. Methodology and first evaluation using 5-HT and histamine action as examples

The quality of molecular electrostatic maps generated by non-quantum mechanical methods has been improved using extended electron distributions. Further simplification has been achieved by distilling these maps down to their energy extrema. A new means of defining surface interaction has been added and the resulting composite map has been plotted for a limited number of low-lying conformers of a series of agonists and antagonists of the H2 and H3 receptors and 5-HT1A and 5-HT1D receptors. The results from the cross-comparison of these maps indicate their ability to distinguish the specific receptor. Interesting consequences of the method are that structural overlay is irrelevant, that several conformations may contribute to the overall binding pattern and that lesser pharmacological activities may be deduced from the results.