Diphenoxylate, a well-known opioid agonist and anti-diarrhoeal agent, was recently found to block Kv1. 3 potassium channels, which have been proposed as potential therapeutic targets for a range of autoimmune diseases. The molecular basis for this Kv1. 3 blockade was assessed by the selective removal of functional groups from the structure of diphenoxylate as well as a number of other structural variations. Removal of the nitrile ...