Radequinil (also known as AC-3933 ) is a oxadiazolylnaphthyridinone derivative patented by Dainippon Pharmaceutical Co., Ltd. as an inverse agonist of benzodiazepine receptors useful for the treatment of cognitive disorders including Alzheimer's disease. In preclinical trials, Radequinil enhances acetylcholine release in the rat hippocampus and ameliorates scopolamine-induced memory impairment and age-related cognitive decline in both rats and mice. Unlike the acetylcholinesterase inhibitor donepezil and the benzodiazepine receptor inverse agonist FG-7142, oral administration of Radequinil significantly ameliorated MK-801-induced memory impairment in the Y-maze test and in the object location test. Interestingly, the procognitive effects of Radequinil on MK-801-induced memory impairment were not affected by the benzodiazepine receptor antagonist flumazenil, although this was not the case for the beneficial effects of Radequinil on scopolamine-induced memory deficit. Moreover, the onset of Radequinil ameliorating effect on scopolamine- or MK-801-induced memory impairment was different in the Y-maze test. Unfortunately, in clinical trials, Radequinil failed to demonstrate efficacy and further development was discontinued.