A 5-substituted-3-oxadiazolyl-1,6-naphthyridin-2(1H)-one derivative of the formula (I): CHEM wherein Het is oxadiazolyl, R1 is H, lower alkyl, cyclo-lower alkyl, trifluoromethyl, lower alkenyl, lower alkynyl, lower alkoxy, lower alkoxy-lower alkyl, hydroxy-lower alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaromatic group, and R2 is H, lower alkyl, cyclo-lower alkyl, cyclo-lower alkylmethyl, lower alkenyl, cyclo-lower alkenyl, lower alkynyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaromatic group, or a pharmaceutically acceptable acid addition salt thereof, which has high selective affinity to benzodiazepine receptor and is useful particularly as a benzodiazepine inverse agonist, for example, as psychoanaleptic drug or a drug for the treatment of dysmnesia in senile dementia or Alzheimer's disease.
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