Synthesis and In Vitro Evaluation of Imidazo[1,2-b]pyridazines as Ligands for β-Amyloid Plaques

A series of imidazo[1,2-b]pyridazine derivatives were synthesized and evaluated for binding to amyloid plaques in vitro using synthetic aggregates of Aβ1-40. Binding affinities of these compounds were found to range from 11.0 to >1000 nM, depending on the various substitution patterns in the 6-position and 2-position. 2-(4'-Dimethylaminophenyl)-6-(methylthio)imidazo[1,2-b]pyridazine (4) showed high binding affinity (K i = 11.0 nM) and might be useful for the development of novel positron emission tomography radiotracers for imaging Aβ plaques.