Non-peptide δ opioid agonists and antagonists (Part II)

A continuing effort in the development of non-peptide δ opioid agonists and antagonists has been seen in the last two years. The first non-peptide δ opioid antagonist naltrindole has represented for years the starting point for the design of novel potent and selective δ opioid ligands. Several research groups are still working on the framework of this prototype and have produced a large number of new derivatives with different in vitro and in vivo pharmacological activities. The discovery of TAN-67, BW373U86 and SNC 80 stimulated other lines of research aimed at synthesising analogues with better δ opioid agonist profile and suitable in vivo activity. Chemically unrelated compounds have also been disclosed deriving from the structural comparison of previously identified ligands. These studies have given further insights about the key determinants for the selective interaction with the δ opioid receptor (DOR). The availability of these tool compounds has allowed significant progression in the understanding...