Clobenpropit analogs as dual activity ligands for the histamine H3 and H4 receptors: Synthesis, pharmacological evaluation, and cross-target QSAR studies

Previous studies have demonstrated that clobenpropit (N-(4-chlorobenzyl)-S-[3-(4(5)-imidazolyl)propyl] isothiourea) binds to both the human histamine H-3 receptor (H3R) and H-4 receptor (H4R). In this paper, we describe the synthesis and pharmacological characterization of a series of clobenpropit analogs, which vary in the functional group adjacent to the isothiourea moiety in order to study structural requirements for H3R and H4R ligands. The compounds show moderate to high affinity for both the human H3R and H4R. Furthermore, the changes in the functional group attached to the isothiourea moiety modulate the intrinsic activity of the ligands at the H4R, ranging from neutral antagonism to full agonism. QSAR models have been generated in order to explain the H3R and H4R affinities. (C) 2009 Published by Elsevier Ltd.