Prolyl endopeptidases (PEPs) have been found in numerous species. Inhibitors of human enzyme could correct cognitive deficits in Alzheimer patients while inhibition of Trypanosoma cruzi PEP could prevent invasion phase in Chagas disease. A structure– activity relationship study carried out in a tetrahydroisoquinoline series allowed to obtain potent competitive inhibitors superior to SUAM-1221. Besides, inhibitors expected to act ...