Abstract: A substrate for thioredoxin reductase which comprises a compound represented by the following general formula (I) or (I?): wherein R1 and R2 independently represent a hydrogen atom, a halogen atom, a trifluoromethyl group and the like; R3 represents an aryl group, an aromatic heterocyclic group and the like; R4 represents a hydrogen atom, a hydroxyl group, a —S-?-amino acid group and the like; R5 represents a hydrogen atom or a C1-C6 alkyl group; Y represents oxygen atom or sulfur atom; n represents an integer of from 0 to 5; and the selenium atom may be oxidized, whose example includes 2-phenyl-1,2-benzisoselenazol-3(2H)-one or a ring-opened form thereof. The substrate is reduced by thioredoxin reductase in the presence of NADPH and enhances peroxidase activity of thioredoxin reductase.

Abstract: The present invention is directed to a drug for preventing or remedying Alzheimer's disease. The drug contains as the active ingredient 2-phenyl-1,2-benzisoselenazol-3(2H)-one (referred as compound (A)), whose effect is based on the action of reducing neuron toxicity induced by .beta.-amyloid protein.

Abstract: An inhibitor for restenosis after percutaneous coronary arterioplasty, which comprises, as an active ingredient, a compound of the following formula (1), (1') or a pharmaceutically acceptable salt thereof: ##STR1## wherein R.sup.1 and R.sup.2 are independently a hydrogen atom, a halogen atom, a trifluoromethyl group, a nitro group, a C1-C6 alkyl group or a C1-C6 alkoxyl group, and R.sup.1 and R.sup.2 may be linked to form a methylenedioxy group; R.sup.3 is an optionally substituted aryl group, an optionally substituted aromatic heterocyclic group, an optionally substituted 5 to 7-membered cycloalkyl or cycloalkenyl group; R.sup.4 is a hydrogen atom, a hydroxyl group, an -S-glutathione residue, an -S-.alpha.-amino acid residue, or an aralkyl group optionally having substituent(s) in the aryl moiety; R.sup.5 is a hydrogen atom or a C1-C6 alkyl group, and R.sup.4 and R.sup.